SYSTEM AND METHOD PROVIDING SECURE DATA
TRANSMISSION VIA SPECTRAL FRAGMENTS
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Patent Application
Serial No. 13/040,458, filed March 4, 201 1, entitled VIRTUAL
AGGREGATION OF FRAGMENTED WIRELESS SPECTRUM (Attorney
Docket No. 809125) which application is incorporated herein by reference in
its entirety. This application is a also continuation-in-part of U.S. Patent
Application Serial No. 13/449,170, filed April 17, 2012, entitled SYSTEM AND
METHOD PROVIDING RESILIENT DATA TRANSMISSION VIA SPECTRAL
FRAGMENTS (Attorney Docket No. 80961 5), which application is a
continuation-in-part of U.S. Patent Application Serial No. 13/040,458, filed
March 4, 201 1, entitled VIRTUAL AGGREGATION OF FRAGMENTED
WIRELESS SPECTRUM (Attorney Docket No. 809125), which applications
are incorporated herein by reference in their entireties.
This application claims the benefit of U.S. Provisional Patent
Applications Serial No. 61/486,489, filed on May 16, 201 1, entitled
ENHANCED SECURITY USING AGGREGATION OF WIRELESS SIGNALS
(Attorney Docket No. 809662L), Serial No. 61/486,597, filed May 16, 201 1,
entitled EFFICIENT FAILOVER SUPPORT USING AGGREGATION OF
WIRELESS SIGNALS (Attorney Docket No. 809663L); and Serial No.
61/523,678, filed August 15, 201 1, entitled DISJOINT REPLICATED SPREAD
SPECTRUM (Attorney Docket No. 810305L), which applications are
incorporated herein by reference in their entireties.
TECHNICAL FIELD
The invention relates generally to communication networks and, more
specifically, but not exclusively, to point-to-point and point-to-multipoint
communication networks and backhaul links.
BACKGROUND
Traditional wireless systems assume the availability of a contiguous
block of spectrum with bandwidth proportional to the amount of data to be
transmitted. Transmission systems are thus frequently designed for worstcase
bandwidth requirements with the typical or average use-case, in some
instances, requiring much less bandwidth (i.e., spectrum).
Within the context of satellite communications systems and other pointto-
point communications systems, available spectrum allocated to customers
may become fragmented over time, which leads to unused blocks between
allocated blocks of spectrum. When the blocks of unused spectrum are too
small, it is necessary to reallocate spectrum among customers or "move" a
customer from existing spectral allocation to a new spectral allocation so that
the unused blocks of spectrum may be coalesced into a single spectral
region. Unfortunately, such reallocation is very disruptive..
SUMMARY
Various deficiencies of the prior art are addressed by the present
invention of systems, methods and apparatus for improving security,
resiliency to interference, and bandwidth utilization in data transmission
systems. In particular, various embodiments provide for systems, methods
and/or apparatus for securely transmitting a data stream by dividing a data
stream into a plurality of sub-streams; associating each substream with a
respective spectral fragment; encrypting at least some of the sub-streams;
and modulating each sub-stream to provide a respective modulated signal
adapted for transmission via a respective spectral fragment.
In various embodiments, each encrypted substream is associated with
a respective encryption key. In various embodiments, at least some of the
encrypted substreams are associated with a common encryption key. In
various embodiments, the encryption key used to encrypt a substream is
changed each session. In various embodiments, encrypting comprises
selecting an encryption key from a table of encryption keys according to a
generated index value.
BRIEF DESCRIPTION OF THE DRAWINGS
The teachings of the present invention can be readily understood by
considering the following detailed description in conjunction with the
accompanying drawings, in which:
FIG. 1 depicts a block diagram of a communication system according
to one embodiment;
FIG. 2 depicts a graphical representation of a spectral allocation useful
in understanding the present embodiments;
FIG. 3 depicts a high-level block diagram of a general purpose
computing device suitable for use in various embodiments;
FIGS. 4-6 depicts flow diagrams of methods according to various
embodiments;
FIGS. 7-9 depicts block diagrams of communication systems according
to various embodiments;
FIG. 10 depicts a high-level block diagram of a slicer/de-multiplexer
suitable for use in various embodiments;
FIG. 1 depicts a flow diagram of a method according to one
embodiment;
FIG. 12 depicts a high level block diagram of a system benefiting from
various embodiments;
FIG. 13 depicts a flow diagram of a method according to an
embodiment;
FIGS. 14A-14B depict a graphical representation of a spectral
allocation useful in understanding various embodiments; and
FIG. 15 depicts a flow diagram of a method according to an
embodiment.
To facilitate understanding, identical reference numerals have been
used, where possible, to designate identical elements that are common to the
figures.
DETAILED DESCRIPTION
The invention will be primarily described within the context of a satellite
communications system. However, those skilled in the art and informed by the
teachings herein will realize that the invention is also applicable to any system
benefiting from flexible spectral allocation, such as microwave
communications systems, wireless communications systems and the like.
One embodiment provides an efficient and general-purpose technique
for aggregating multiple, fragmented blocks of wireless spectrum into one
contiguous virtual block such that the cumulative bandwidth is almost equal to
the sum of the bandwidths of the constituent blocks. The fragmented blocks
are optionally separated from each other by blocks of spectrum, such as
guard blocks, blocks owned by other parties, blocks prohibited by the wireless
spectrum regulatory authority of a region or country and so on.
FIG. 1 depicts a block diagram of a communication system benefiting
from various embodiments. The communication system 100 of FIG. 1
comprises a point-to-point link including a virtual spectrum aggregator
transmitter 110, a power amplifier 120, a satellite uplink 130, a satellite 140, a
satellite downlink 150, a virtual spectrum aggregator receiver 160 and,
optionally, a control module 170. Data to be transmitted over the point-to-point
link is provided as a stream of data packets D, such as 188-byte transport
stream (TS) packets, 64-1 500 bytes Ethernet packets and so on. The specific
packet structure, data conveyed within a packet structure and so on is readily
adapted to the various embodiments described herein.
The input data stream D is received by the virtual spectrum aggregated
transmitter 110, where it is processed by a slicer/demultiplexer 111 to provide
N sub-streams (D0 ...D - ) , where N corresponds to a number of spectral
fragments denoted as So, S and so on up to S - .
As depicted in FIG. 1, N = 3 such that the slicer/demultiplexer 111
slices, the multiplexes and/or divides the input data stream D into
(illustratively) three sub-streams denoted as D0, D and D2.
Each of the sub-streams D0 , D and D2 is coupled to a respective
modulator 112 (i.e., modulators 1120, and 1122) . Each of the modulators
1120, 1 2 and 112 modulates its respective sub-stream D0, and D2 to
provide corresponding modulated signals to be carried by respective spectral
fragments So, S and S2.
The modulators 12 may comprise modulators having the same
characteristics or having different characteristics, such as the characteristics
of waveform type, constellation maps, forward error correction (FEC) settings
and so on. Each modulator may be optimized according to a specific type of
traffic (e.g., streaming media, non-streaming data and the like), the specific
channel conditions associated with its corresponding spectral fragment S ,
and/or other criteria.
Generally speaking, the amount of data allocated by the
slicer/demultiplexer 111 to any sub-stream D is proportional to the data
carrying capacity of the corresponding spectral fragment S,. In various
embodiments, each of the sub-streams D, comprises the same amount of
data, while in other embodiments the various sub-streams D, may comprise
different amounts of data.
As depicted in FIG. 1, the first modulator 1120 provides a 6 MHz signal
associated with a first spectral fragment So; the second modulator 1 2
provides a 1 MHz signal associated with a second spectral fragment S ; and
third modulator 122 provides a 1 MHz signal associated with a third spectral
fragment S2.
A frequency multiplexer (i.e., signal combiner) 113 operates to combine
the modulated signals to produce a combined modulated signal Sc, which is
modulated onto a carrier signal by up-converter 114 to provide a modulated
carrier signal C. It is noted that multiple frequency multiplexers / signal
combiners 113 may be used to multiplex respective groups of modulated
signals to be transported via common transponders, microwave links, wireless
channels and the like.
In the embodiment of FIG. 1, the spectrum associated with the
modulated carrier signal C is logically or virtually divided into the plurality of
spectral fragments used to convey the modulated data sub-streams. The
spectral fragment allocation table or other data structure is used to keep track
of which spectral fragments have been defined, which spectral fragments are
in use (and by which data sub-streams), and which spectra! fragments are
available. Generally speaking, each transponder/transmission channel may
be divided into a plurality of spectral fragments or regions. Each of these
spectral fragments or regions may be assigned to a particular data substream.
Each of the data sub-streams may be modulated according to a
unique or common modulation technique.
As depicted in FIG. 1, a single satellite transponder is used and,
therefore, all of the modulated signals may be combined by frequency
multiplexer 3 prior to up-conversion and transmission via a single satellite
channel. In various embodiments, multiple transponders within one or more
satellites may be used. In these embodiments, only those modulated signals
to be transmitted via a common transponder within a satellite are combined
and then converted together. In various embodiments, modulate waveforms
are transmitted independently.
The modulated carrier signal C produced by up-converter 114 is
amplified by power amplifier 120 and transmitted to satellite 140 via satellite
uplink 130. Satellite 140 transmits a modulated carrier signal including the
modulated sub-streams D0, D and D to satellite downlink 150, which
propagates the signal to the virtual spectrum aggregator receiver 160.
Virtual spectrum aggregator receiver 160 includes a downconverter
(165) which downconverts a combined spectral fragment signal Sc' from a
received carrier signal , and a frequency demultiplexer (164) which operates
to separate the spectral fragments So', S-T and S2' from the combined
spectral fragment signal Sc'.
Each of the spectral fragments So', S ' and S2' is coupled to a
separate demodulator (i.e., demodulators 1620, 162- and 1622 ). Each of the
demodulators 1620, 162 and 1622 demodulates its respective spectral
fragments So', S-T and S2' to provide corresponding demodulated substreams
D0' , D - ' and D ' .
The demodulated sub-streams Do', D ' and D2' are processed by a
combiner 161 to produce an output data stream D' representative of the input
data stream D initially processed by the virtual spectrum aggregator
transmitter 110. It is noted that each of the demodulators 162 operates in a
manner compatible with its corresponding modulator 112.
Optionally, virtual spectrum aggregator receiver 160 includes buffers
1660, 166 and 1662 which provide an elastic buffering function for the
various demodulated sub-streams such that alignment errors induced by
different propagation delays associated with the various sub-streams may be
avoided prior to combining the sub-streams. The buffers in 166 are depicted
as functional elements disposed between the demodulators (162) and
combiner 161 . In various embodiments, the buffers 166 or their functional
equivalent are included within the combiner 161 . For example, combiner 161
may include a single buffer which receives data from all of the demodulators
(162) and subsequently rearranges that data as output stream D'. Packet D
and/or other information within the sub-streams may be used for this purpose.
Optional control module 170 interacts with an element management
system (EMS), a network management system (NMS) and/or other
management or control system suitable for use in managing network
elements implementing the functions described herein with respect to FIG. 1.
The control module 170 may be used to configure various modulators,
demodulators and/or other circuitry within the elements described herein with
respect FIG. 1. Moreover, the control module 170 may be remotely located
with respect to the elements controlled thereby, located proximate
transmission circuitry, located proximate receiver circuitry and so on. The
control module 170 may be implemented as a general purpose computer
programmed to perform specific control functions such as described herein. In
one embodiment, control module 170 adapts the configuration and/or
operation of the virtual spectrum aggregator transmitter 110 and the virtual
spectrum aggregator receiver 160 via, respectively, a first control signal
TXCONF and a second control signal RXCONF. In this embodiment, multiple
control signals may be provided in the case of multiple transmitters and
receivers.
FIG. 2 depicts a graphical representation of a spectral allocation useful
in understanding the present embodiments. Specifically, FIG. 2 graphically
depicts a 36 MHz spectral allocation in which a first customer is allocated a
first portion 210 of the spectrum, illustratively a single 10 MHz block; a second
customer is allocated a second portion 220 of the spectrum, illustratively
single 8 MHz block; a third customer is allocated a third portion 230 of the
spectrum, illustratively single 10 MHz block; and a fourth customer is
allocated is allocated a fourth portion 240 of the spectrum, illustratively three
noncontiguous spectrum blocks comprising a first 1 MHz block 240 , a
second 1 MHz block 240 and a 6 MHz block 240 3.
Within the context of the various embodiments discussed herein, the
data stream associated with the fourth customer is divided into two different 1
MHz spectral fragments in a single 6 MHz spectral fragment, each of which is
processed in substantially the same manner as described above with respect
to FIG. 1.
FIG. 3 depicts a high-level block diagram of a general purpose
computing device 300 suitable for use in various embodiments described
herein. For example, the computing device 300 depicted in FIG. 3 may be
used to execute programs suitable for implementing various transmitter
processing functions, receiver processing functions and/or management
processing functions as will be described herein.
As depicted in FIG. 3, the computing device 300 includes input/output
(I/O) circuitry 310, a processor 320 and memory 330. The processor 320 is
coupled to each of the /O circuitry 310 and memory 330.
The memory 330 is depicted as including buffers 332, transmitter (TX)
programs 334, receiver (RX) programs 336 and or management programs
338. The specific programs stored in memory 330 depend upon the function
implemented using the computing device 300.
In one embodiment, the slicer/demultiplexer 111 described above with
respect to FIG. 1 is implemented using a computing device such as the
computing device 300 of FIG. 3. Specifically, the processor 320 executes the
various functions described above with respect to the slicer/demultiplexer 111.
In this embodiment the I/O circuits 310 receive the input data stream D from a
data source (not shown) and provide the N sub-streams (D0...D - ) to the
demodulators 112.
In one embodiment, the combiner 161 described above with respect to
FIG. 1 is implemented using a computing device such as the computing
device 300 of FIG. 3 . Specifically, the processor 320 executes the various
functions described above with respect to the combiner 161 . In this
embodiment the /O circuits 310 receive the demodulated sub-streams D0' ,
Di' and D2' from the demodulators 162 (optionally via buffers 166) and
provide the output data stream D' representative of the input data stream D
initially processed by the virtual spectrum aggregator transmitter 110.
In one embodiment, the optional control module 170 described above
with respect to FIG. 1 is implemented using a computing device such as the
computing device 300 of FIG. 3.
Although primarily depicted and described as having specific types and
arrangements of components, it will be appreciated that any other suitable
types and/or arrangements of components may be used for computing device
300. The computing device 300 may be implemented in any manner suitable
for implementing the various functions described herein.
It will be appreciated that computer 300 depicted in FIG. 3 provides a
general architecture and functionality suitable for implementing functional
elements described herein and/or portions of functional elements described
herein. Functions depicted and described herein may be implemented in
software and/or hardware, e.g., using a general purpose computer, one or
more application specific integrated circuits (ASIC), and/or any other
hardware equivalents.
It is contemplated that some of the steps discussed herein as software
methods may be implemented within hardware, for example, as circuitry that
cooperates with the processor to perform various method steps. Portions of
the functions/elements described herein may be implemented as a computer
program product wherein computer instructions, when processed by a
computer, adapt the operation of the computer such that the methods and/or
techniques described herein are invoked or otherwise provided. Instructions
for invoking the inventive methods may be stored in fixed or removable media,
transmitted via a data stream in a broadcast or other signal bearing medium,
transmitted via tangible media and/or stored within a memory within a
computing device operating according to the instructions.
FIG. 4 depicts a flow diagram of a method according to one
embodiment. Specifically, the method 400 of FIG. 4 is suitable for processing
a data stream D for transmission, such as described above with respect to
FIG. 1.
At step 410, the data stream including data from one or more
customers is received, such as by the virtual spectrum aggregated transmitter
110.
At step 420, the received data stream is sliced into N sub-streams,
where each sub-streams is associated with a respective spectral fragment.
Referring to box 425, the slicing of data streams into sub-streams may be
performed using any of the following criteria, alone or in any combination: per
customer, per fragment, for data type, fixed size, variable size, combination of
various slicing methods and/or other criteria.
At step 430, each of the sub-streams is modulated using a respective
modulator. Referring to box 435, demodulators may be optimized for data
type, optimized for channel conditions, they share common characteristics,
they have various/different characteristics and so on.
At optional step 440, where one or more modulated sub-streams are to
be transmitted using the same transponder or transmission channel, these
modulated sub-streams are combined.
At step 450, the modulated sub-streams are up converted and
transmitted. Referring to box 455, the up conversion/transmission process
may be within the context of a satellite communication system, microwave
communication system, wireless communication system/channel or other
medium.
FIG. 5 depicts a flow diagram of a method according to one
embodiment. Specifically, the method 500 of FIG. 5 is suitable for processing
one or more received sub-streams, such as described above with respect to
FIG. 1.
At step 510, one or more modulated sub-streams are received and
down converted. Referring to box 515, one or more modulated sub-streams
may be received via a satellite communication system, wireless
communication system, wireless communication system/channel or other
medium.
At step 520, any sub-streams previously combined at the transmitter
are separated to provide individual sub-streams, and at step 530 each of the
individual sub-streams is demodulated using a respective appropriate
demodulator.
At step 540, one or more of the demodulated sub-streams are
selectively delayed so that the resulting demodulated data streams may be
temporally aligned.
At step 550, the demodulated and selectively delayed sub-streams are
combined to provide a resulting data stream such as a data stream D'
representative of an input data stream D initially processed by the virtual
spectrum aggregator transmitter.
FIG. 6 depicts a flow diagram of a method according to one
embodiment. Specifically, the method 600 of FIG. 6 is suitable for configuring
various transmitter and receiver parameters in accordance with the various
embodiments.
At step 610, a request is received for the transmission of customer
data. Referring to box 615, the request may provide a specified bandwidth, a
specified data rate, a specified data type, specified modulation type and/or
other information describing the bandwidth and/or service requirements
associated with the customer data transmission request.
At step 620, a determination is made as to the spectrum allocation
suitable for satisfying the customer data transmission request.
At step 630, an optional determination is made as to whether any
specific spectrum related criteria is suitable for satisfying the customer data
transmission request. Referring to box 635, such spectrum related criteria
may include a minimum bandwidth block size, a requirement for contiguous
bandwidth blocks and/or other criteria.
At step 640, available spectrum fragments are identified. Referring to
box 645, the identification of available spectrum fragments may be made with
respect to an allocation table, a management system and/or other source of
such information. In one embodiment, an allocation table defines the spectral
allocation associated with each customer served by a satellite
communications system; namely, the bandwidth allocation of each customer,
the transponder(s) supporting the bandwidth, the satellite(s) supporting the
transponder(s) and so on. Additionally, available spectrum fragments are
defined in terms of size and spectral region for each transponder of each
satellite.
At step 650, available spectrum fragments are allocated to satisfy the
customer data transmission request. Referring to box 655, the available
spectrum fragments may be allocated as available, optimized for the
customer, optimized for the carrier, optimized to reduce spectrum fragment
count, optimized to provide resiliency or redundancy, and/or optimized based
on other criteria.
At step 660, transmitter/receiver systems are configured to provide the
correct number and type of modulators/demodulators to support the customer
data transmission request and adapt to any changes to spectrum fragment
allocations for the requesting customer and/or other customers. That is, based
upon optimization and/or other criteria, it may be appropriate to modify the
spectral fragment allocations of multiple customers to optimize in favor of a
particular customer, service provider and the like.
At step 670, billing data, service agreements and the like are updated
as appropriate. At step 680, system configuration, provisioning and/or other
management data is updated.
In various embodiments, spectral fragment available on different
satellite transponders and/or different satellites are aggregated to form a
virtual contiguous block. In other embodiments, the entire bandwidth of
multiple transponders is used to support high data-rate pipes (e.g., OC-3/12c)
over satellite links.
FIGS. 7-9 depict block diagrams of communication systems according
to various embodiments. Each of the various components within the
communication systems depicted in FIGS. 7-9 operates in substantially the
same manner as described above with respect to corresponding components
within the communication system of FIG. 1. For example, in each of the
embodiments of FIGS. 7-9, an input data stream D is received by a virtual
spectrum aggregated transmitter 10, where it is processed by a slicer/demultiplexer
x 11 to provide N sub-streams (D0 ...D -i), where each of the N
sub-streams is modulated by respective modulator x12. Other differences and
similarities between the various figures will now be described more detail.
FIG. 7 depicts a single transponder embodiment in which a single
transponder is used to transport each of a plurality of data streams denoted
as streams A, B, C and D. FIG. 7A depicts an uplink portion of the system,
while FIG. 7B depicts a downlink portion of the system.
Referring to FIG. 7A, data streams A, B and C are modulated by
respective modulators 712 to produce respective modulated streams which
are then combined by a first signal combiner 1 3 to provide a combined
modulated signal ABC.
Data stream D is processed by a slicer/de-multiplexer 7 11 to provide N
sub-streams (D0 ...D - ) which are then modulated by respective modulators
712 (i.e., modulators 7120, 712 and 7122) to provide corresponding
modulated signals to be carried by respective spectral fragments So, S and
S2. The corresponding modulated signals are combined by a second signal
combiner 7 13 to provide a combined modulated signal DDD, which is
combined with modulated signal ABC by a third signal combiner 7 133. The
resulting combined modulated signals are converted by an up converter 714
to produce a carrier signal C which is amplified by a power amplifier 720 and
transmitted towards a satellite 740 via a satellite uplink 730.
Referring to FIG. 7B, satellite 740 transmits a modulated carrier signal
including the modulated streams A through D to satellite downlink 750, which
propagates the signal to a down-converter, 765. The down-converted signal is
processed by a frequency de-multiplexer 1643 which operates to separate the
signal into the ABC and DDD signal components.
The ABC signal components are separated by a second frequency demultiplexer
764 to recover the modulated signals and then demodulated by
respective demodulators 752.
The DDD signal components are separated by a third frequency de
multiplexer 7642 to recover the modulated signals which are demodulated by
respective demodulators 752.
The demodulated sub-streams D0 D and D2' are processed by a
combiner 761 to produce an output data stream D' representative of the input
data stream D. It is noted that each of the demodulators 162 operates in a
manner compatible with its corresponding modulator 1 2.
FIG. 8 depicts a dual transponder embodiment in which a first
transponder is used to transport each of a plurality of data streams denoted
as streams A, B, and C, as well as two of three sub-streams associated with a
data stream D, while a second transponder is used to transport each of a
plurality of data stream denoted as E and F, as well as the third sub-stream
associated with the data stream D. FIG. 8A depicts an uplink portion of the
system, while FIG. 8B depicts a downlink portion of the system.
Referring to FIG. 8A, data streams A, B, C, E and F are modulated by
respective modulators 812 to produce respective modulated streams.
Data streams E and F are modulated by respective modulators 812 to
produce respective modulated signals.
Data stream D is processed by a slicer/de-multiplexer 7 11 to provide N
sub-streams (D0 ...D - ) which are then modulated by respective modulators
712 (i.e., modulators 7120, 712i and 7122) to provide corresponding
modulated signals to be carried by respective spectral fragments So, S and
S2.
The modulated signals associated with data streams A, B and C are
combined by a first signal combiner 8 1 to provide a combined modulated
signal ABC.
The modulated signals associated with sub-streams D0 and D are
combined by a second signal combiner 8 132 to provide a combined
modulated signal D .
The combined modulated signals produced by the first 8 13 - and
second 8 132 signal combiners are then combined by a third signal combiner
8 133 and converted by a first upconverter 8 14 to produce a first carrier signal
C 1.
The modulated signals associated with sub-stream D3 and streams E
and F are combined by a fourth signal combiner 8 133 and converted by a
second upconverter 8 142 to produce a second carrier signal C2.
The C 1 and C2 carrier signals are combined by a fourth signal
combiner, 8134, amplified by a power amplifier, 820, and transmitted towards
a satellite, 840, via respective transponders (A and B) of a satellite uplink 830.
Referring to FIG. 8B, satellite 840 transmits the two modulated carrier
signals including the modulated streams A through F via respective
transponders (A and B) to satellite downlink 850, which propagates the signal
to a down-converter 865. The down-converted signal is separated into its two
carrier signals by frequency demultiplexer 8644. The two carrier signals are
processed using various demultiplexers in 864, demodulators in 862 and
combiner 861 to produce the various output data streams A' through F'
representative of the input data stream A through F.
FIG. 9 depicts a dual satellite embodiment in which one satellite (940 )
is used to transport a plurality of data streams denoted as streams A, B, and
C, as well as two of the three sub-streams associated with data stream D.A
second satellite (940 ) is used to transport a plurality of data streams denoted
E and F as well as the third sub-stream associated with data-stream D. FIG.
9A depicts an uplink portion of the system while FIG. 9B depicts a downlink
portion of the system.
Referring to FIG. 9A, data streams A, B, C, E and F are processed in
substantially the same manner as described above with respect to FIG. 8A,
except that the two carrier signals are not combined for transport via
respective transponders of a single satellite. Rather, FIG. 9 shows two carrier
signals amplified by separate power amplifiers (920i and 920 2) and
transmitted to satellites 940 and 940 2, respectively, using uplinks 930 and
930 2.
Referring to FIG. 9B, the two satellites 940 transmit their respective
modulated carrier signals including modulated streams A through F via
respective downlinks 950, which are then fed to respective down-converters
965. The two down-converted carrier signals are processed using de
multiplexers (964), demodulators (962) and a combiner (961 ) to produce the
output data streams A' through F' representative of the input data streams A
through F.
FIG. 10 depicts a high-level block diagram of a slicer/de-multiplexer
suitable for use in the various embodiments described herein. Specifically, the
slicer/de-multiplexer 1000 of FIG. 10 comprises a packet encapsulator 1010,
a master scheduler 1020 including a buffer memory 1022, and a plurality of
slave schedulers 1030 including buffer memories 1032.
The packet encapsulator 1010 operates to encapsulate packets
received from data-stream D into a packet structure having a predefined or
normalized format. While various encapsulating packet formats may be used,
it is important that the combiner at a downlink side of a system be configured
to combine packets according to the encapsulating format used by the
slicer/de-multiplexer at an uplink side of the system.
In one embodiment, encapsulating packets comprise 188 byte packets
having a 185-byte payload section and a three-byte header section. The
packet encapsulator 1010 extracts a sequence of 185 byte portions from the
original data stream D, and encapsulates each extracted portion to form
encapsulating packet (EP). The header portion of each encapsulating packet
stores a user sequence number associated with payload data such that the
sequence of 185 byte portions of the data stream may be reconstructed by a
combiner, such as described above with respect to the various figures.
In one embodiment, the user sequence number comprises a 14-bit
number that is continually incremented and used to stamp encapsulated
packets provided by the packet encapsulator 1010. In one embodiment, the
header portion of the packet provided by the packet encapsulator 010
comprises a first byte storing 47 hexadecimal (i.e. 47h), followed by 2 zero
bits, followed by 14 bits associated with the user sequence number.
A larger sequence number field (e.g., 24 or 32 bits) may be used when
the aggregate data rate being transported is higher. The size of the sequence
number field is related to the amount of buffering that takes place at the
receiving combiner element described in various figures above. The size of
the buffer, in turn, is related to the ratio of the largest sub-stream bandwidth to
the smallest sub-stream bandwidth. Thus, various embodiments may adjust
the sequence number field size (and the resulting overhead) based on total
aggregate bandwidth and/or the ratio of the highest to smallest bandwidth
sub-streams.
In various embodiments, more or fewer than 188 bytes are used to
construct encapsulating packets. In various embodiments, more or fewer than
three bytes are used to construct encapsulating packet headers. For example,
by allocating additional header bits to the user sequence number a larger user
sequence number may be used. In this case, the likelihood of processing at a
receiver two encapsulating packets having the same sequence is reduced.
In the embodiments described herein, the fixed packet size of 188
bytes is used for the encapsulating packets. However, in various alternate
embodiments different fixed-sized packets and/or different variable sized
packets may be used for different sub-streams as long as such packet sizes
are compatible with the input interfaces of the respective modulators used for
those sub-streams.
The master scheduler 1020 routes encapsulated packets to the various
slave schedulers 1030. The slave schedulers 1030 in turn route their packets
to respective output ports of the slicer/demultiplexer, thereby providing
respective sub-streams to, illustratively, modulators or other components.
Generally speaking, each slave scheduler 1030 accepts packets
conforming to the bandwidth of the spectral fragment assigned to that
scheduler. Thus, the slave scheduler servicing a 1 MHz spectral fragment
channel accepts packets at a data rate approximately 1/10 that of a slave
scheduler serving a 10 MHz spectral fragment or region.
The master scheduler 1020 communicates with the slave schedulers
030 to identify which slave scheduler 1030 is (or should be) capable of
receiving the next encapsulated packet. Optionally, the master scheduler
1020 receives status and other management information from the slave
schedulers 1030, and some of this status information may be propagated to
various management entities (not shown).
In one embodiment, the slave schedulers 1030 provide a control signal
to the master scheduler 1020 indicative of an ability to accept the packet. In
one embodiment, the master scheduler 1020 allocates packets to the slave
schedulers 1030 in a round robin fashion. In one embodiment, where certain
transmission channels or spectral regions are preferred based upon customer
and/or service provider requirements, the allocation of encapsulated packet
by the master scheduler 1020 is weighted in favor of providing more
encapsulated packets to those slave schedulers 1030 servicing the preferred
transmission channels.
In one embodiment, each of the slave schedulers is associated with a
predefined bandwidth or other indicators of channel capacity associated with
the corresponding spectral fragment. In this embodiment, the master
scheduler 1020 routes packets according to a weighting assignment for each
slave scheduler 1030.
Generally speaking, the master scheduler routes packets according to
one or more of a random routing algorithm, a round robin routing algorithm, a
customer preference algorithm and a service provider preference algorithm.
Such routing may be accommodated by associating a weighting factor with
each modulator, spectral fragment, communications channel (e.g.,
transponder, microwave links, wireless channel etc.) and so on. For example,
a preferred spectral fragment may comprise a fragment having a minimum or
maximum size, a fragment associated with a relatively low error or relatively
high error channel, a fragment associated with a preferred communications
type (e.g., satellite, microwave link, wireless network and so on), a fragment
associated with a preferred customer and the like. Other means of weighting
channels, communication systems, spectral regions and so on may also be
used within the context of the various embodiments.
FIG. 11 depicts a flow diagram of a method according to one
embodiment. At step 1110, packets are received from data stream D. At step
1120, received packets are encapsulated. Referring to box 1125, the packet
may comprise 185 byte payload and three byte header packets. Other header
formats with a different sequence number field size and/or additional control
information may be used within the context of the present embodiments.
At step 1130 the encapsulated packets are buffered by, illustratively,
the master scheduler 1020, a separate buffer (not shown) within the packet
encapsulator 1010 and so on.
At step 1140, encapsulator packets are forwarded (or caused to be
forwarded) to the slave schedulers 1030 by the master scheduler 1020.
In the various embodiments described herein, each encapsulated
packet is coupled to a respective modulator as part of a respective substream.
However, in embodiments adapted to provide increased data
resiliency and/or backup, encapsulated packets may be coupled to multiple
modulators as part of multiple respective sub-streams. In these embodiments,
the sequence number associated with the encapsulated packet remains the
same.
In these embodiments, a receiver will process the first encapsulated
packet (or error-free encapsulated packet) having the appropriate sequence
number and ignore other packets having the same sequence number. That
is, when re-ordering encapsulating packets at the receiver, those
encapsulating packets having a sequence number matching a sequence
number of a recently ordered encapsulating packet are discarded. Since
sequence numbers are cyclical or repeated (e.g., every 16,384 encapsulating
packets in the case of a 14-bit sequence number), an encapsulating packet
having the same sequence number of encapsulating packet processed
several thousand packets ago is likely a duplicate of that previously
processed encapsulating packet and, therefore, should be dropped or
discarded as being redundant.
Various embodiments described herein provide dynamic spectrum
aggregation of disjoint blocks of spectrum such that spectrum may be added
to or subtracted from existing spectrum allocations as customer bandwidth
requirements change. Additionally, small or orphaned spectrum blocks (i.e.,
those spectrum blocks too small to generally be useful) may be virtually
combined to form larger blocks of bandwidth.
The above-described embodiments provide a number of advantages,
including improved system resiliency since the loss of any one spectral
fragment will likely not cause a complete loss of service. In addition, when
spectral fragments are mapped across multiple transponders, the loss of any
one transponder does not result in a complete loss of service; rather, a
graceful degradation of service is provided. Older/existing schemes utilizing
contiguous spectrum are capable of using only one transponder which
becomes a potential single point of failure.
Interference Mitigation and Improved Resiliency
For purposes of the following discussion, assume that a transmission
mechanism utilizes four carriers, SO...S3 (though different numbers of carriers
may be used). Further, that the carriers are separated (not adjacent) in the
frequency domain such that any signal interference potentially affects only a
subset (and not all) of the slices. Finally, assume that a control channel
available (either in-band or out-of-band) for the receiver to provide feedback
about the status of the signals to the transmitter. These assumptions may be
also by imputed to various other embodiments discussed herein with respect
to the various figures.
When a slice, Si, (0 <= i <= 3) is affected by interference, the receiving
site notices a degradation in the C/N (Carrier to Noise) of that slice. It informs
the transmit side about the degradation using a control channel. The
transmitter then decreases the FEC rate (makes the FEC stronger, by
changing to rate 2/3 from 3/4, for e.g.) to enable the receiver the combat the
added noise. This scheme is called Adaptive Coding and Modulation (ACM).
Various embodiments discussed herein may be used to enhance the
effectiveness of ACM by providing a capability to change the FEC rate of only
a specific slice or portion of a data stream (rather than the traditional
approach of changing the FEC rate of the entire carrier or data stream). In this
manner, higher through put is maintained in the various embodiments vs.
traditional techniques.
Various embodiments discussed herein provide that if an interferer is
too strong for any available FEC rate to mitigate its effects, then the receiver
loses lock on that carrier (e.g., carrier S2) and informs transmitter about the
loss. The transmitter re-routes data over carriers S 1, S3 and S4. In effect, it is
"bypassing" spectral slice S2 and maintains service albeit at a lower
throughput. Contrast this with traditional single-carrier schemes where a
strong interferer would have completely impaired that carrier causing a
complete loss of service.
Various embodiments discussed herein provide different carrier
arrangements than previously known. Specifically, rather than the traditional
OFDM systems where a signal is comprised of a large number of subcarriers
that are adjacent to each other, the various embodiments provide separated
and spectrally disjoint carriers. In this manner, front end saturation or passband
impact of a strong interferer is greatly attenuated in the various slices.
Various embodiments discussed herein enable slices to be
transplanted or rerouted to different parts of the spectrum to combat
interference, resulting in a complete restoration of service with little
degradation in throughput.
Various embodiments discussed herein enable hitless delivery in the
presence of strong interference. For example, some embodiments configure a
subset of carriers, such as SO and S 1, as a protection group such that
impairment of either SO or S 1, but not both simultaneously, results in no loss
of data. Under that scenario S2 and S3 may continue to operate as
independent carriers without being members of any protection groups.
Alternately, they may be grouped into a second protection group to protect
each other. As a third alternative, more than two carriers, say S0.. .S2, may
form a protection group and S3 stays independent. Taken to its extreme, all
four carriers may be part of a protection group for combating widespread
interference, and so on. The degree of flexibility is enormous and
configurations can be fine-tuned to most effectively deal with the particular
type of interference.
Various embodiments discussed herein enable the addition and
deletion of carriers dynamically to further improve resiliency such as caused
by equipment failures and/or interference. For example, a system may employ
two carriers, SO and S 1, acting independently (i.e., not constituting a
protection group) while a third carrier, S2, may be added later in a region of
available spectrum if either SO or S 1 are impaired. In one embodiment, the
third or spare carrier (e.g., S2) may be configured as a substitute carrier, part
of a temporary protection group, part of a dynamically formed protection
group.
As a substitute carrier, the spare carrier (e.g., S2) may be configured to
act as a "substitute" carrier for either SO or S 1 thus effectively taking over the
purpose of the impaired carrier.
As part of a temporary protection group, the spare carrier (e.g., S2)
may be configured to form a temporary protection group in alliance or
association with the impaired carrier. For example, if S 1 is impaired then a
protection group between S 1 and S2 may be formed. SO stays independent.
When the cause of the impairment is addressed restoring S 1, then S2 may be
removed.
As part of a dynamically formed protection group, the spare carrier
(e.g., S2) may be configured as part of a dynamic formation of Protection
Groups among existing carriers, which is effective for combating transient
interference that affects multiple carriers for durations long enough to cause
packet loss and other impairments, but is not long enough to mandate a
complete re-routing of traffic as described above. For example, assume that
SO...S3 constitute a four-carrier transmission system, and S2 and S3
experience transient interference that neither per-carrier ACM nor re-routing
can effectively address. In this embodiment, S2 and S3 are temporarily paired
to constitute a DSS Protection Group while SO and S 1 stay independent. The
net result is a robust way of dealing with interference with a temporary
reduction in throughput. Once the root cause of the impairments affecting S2
and S3 are addressed, they can be reconfigured to act independently.
Disjoint Replicated Spread Spectrum (DRSS)
The various techniques and embodiments described herein may be
adapted to provide Disjoint Replicated Spread Spectrum (DRSS)
embodiments which provide "hitless" delivery of payload data in the presence
of strong Radio Frequency (RF) interference in wireless communication
channels. For example, traditional techniques for wireless communications
involves use of single-carrier RF signals that have error-protection code rates
designed to deliver Quasi Error Free (QEF) data given the Carrier-to-Noise
(C/N) ratio of the communications channel. In the presence of increased
interference, the error-protection code rate is reduced (made stronger) to help
negate the effects of degradation of the signal at the receiver. A problem with
this approach is that a sufficiently strong interferer that is in-band with the
received signal and which results in a C/N ratio being lower than the QEF
threshold can result in complete loss of data, no matter how strong the code
rate. This may be due to (among other reasons) complete saturation of the
receiver's front-end RF down-conversion circuitry involving components such
as LNAs, mixers and sampling circuits using Analog-to-Digital Converters
(ADC). Thus, even the best error-coding technique based on single-carrier
systems cannot combat interference that is in-band and greater than the
carrier power by the QEF C/N threshold.
DRSS utilizes multiple spectrally-disjoint carriers. In the DRSS
technique, the original payload (P) is transmitted over N (N>=2) carriers, each
coded and modulated, in the general case, with different physical layer
schemes suitable for their respective channel conditions. In a simple
embodiment, all carriers are constructed using the same physical-layer
parameters but transmitted in spectral blocks that are disjoint (separated)
from each other. Carriers, in general, do not have to be of the same spectral
bandwidth. However, the information carrying capacity (as determined by the
symbol rate, code rate, constellation map, roll-off and other relevant
modulation parameters) of each carrier is required to be sufficient to carry the
required payload.
At the transmit end, the payload (P) is first pre-processed and broken
up into a sequence of fixed-size packets (p,, /=0, 1, 2, ...) using the virtual
spectrum aggregation (VSA) techniques described above. Each packet at
the output of the VSA pre-processor is then replicated N times, and each copy
is transmitted over all N carriers.
At the receive end, the receiver demodulates data from each carrier.
When all carriers have good C/N, the receiver will recover N error-free copies
of each packet, p,. N-1 copies are discarded and one retained for packet p,
for each . All selected copies are provided to the VSA processor at the
receive end where the original payload, P, is reconstructed and delivered to
its intended recipient again as described above.
In the presence of strong interference, a subset of the N carriers may
experience complete loss of data. However, as long as at least one carrier
has its C/N above its QEF threshold at any given time, the receiver will have
access to at least one good copy (out of the N copies transmitted) of each
packet, p,. This enables the VSA processor at the receiver to reconstruct the
payload error-free.
In the above scheme, multiple spectrally-disjoint carriers are less likely
to be simultaneously affected by the same interfering signal unless it happens
to be extremely broadband. Strong interference may result in a complete loss
of data in up to N-1 carriers, but complete recovery of the desired payload is
still possible as long as for each packet, p, , there's at least one carrier that is
able to deliver that packet error-free. For interference that moves rapidly in
the spectral domain, this may imply that consecutive packets are derived from
different carriers due to the possibility that a carrier that delivered packet p
may experience interference thereafter and may not be the most suitable
carrier for delivering packet p + .
Use of the VSA techniques described with respect to Figures 1-1 1 and
their associated description allow aggregation of multiple, disjoint spectral
slices. When DRSS is used in conjunction with spectral aggregation, a
powerful new capability is enabled. For instance, selective use of DRSS
enables mapping of carriers to portions of spectrum (such as unlicensed
bands) that may be prone to interference. In other words, use of DRSS
enables a service provider to start to use noisy or unlicensed bands by
mapping either the entire set or a subset of the carriers being aggregated to
potentially noisy bands while still delivering the constituent payloads with a
high degree of resiliency.
FIG. 12 depicts a high level block diagram of a system benefiting from
various embodiments. Specifically, FIG. 12 depicts a high level block diagram
of a system 1200 that uses the above-described VSA techniques to
aggregate, illustratively, four spectral slices S1-S4 including redundant
payload communicated over spectral slices S2 and S3. The exemplary
system 1200 is a hybrid VSA/DRSS system that transports a payload P using
carriers SO, S 1, S2 and S3. The exemplary system 1200 is depicted as
utilizing a satellite communications link 1260, though other and additional
types of communications links may be employed.
The system 1200 generally contemplates a VSA preprocessor, a
modulator/transmitter, a communications link, a demodulator/receiver and a
VSA postprocessor.
The VSA preprocessor 1210 performs the various slicer functions
1212, parity codes functions 1214, control header insertion functions 1216
and scheduler functions 1218 as discussed herein. The VSA preprocessor
1210 is adapted to process or slice an input signal or stream payload P into,
illustratively, four stream portions or segments denoted as P'0 through P'3. As
previously noted, each of the four stream portions or segments will be
modulated in a manner conforming to a respective spectral slice of a carrier
signal, such as a transmitted via a communications link.
The modulator/transmitter comprises, illustratively, four modulators
1220-1 through 1220-4 adapted to respectively modulate payload stream
portions or segments as P'0 through P'3 to produce modulated signals S0
through S3, which modulated signals are combined by single
combiner/multiplexer 1230. The resulting combined signal is processed by
upconverter 1240 and amplifier 1250 to provide, illustratively, a signal suitable
for transmission via a communications link 1260.
The communications link 1260 is depicted as a satellite
communications link including a transmitter 1260-T which sends the
transmission signal to a receiver 1260-R via a satellite 1260-S.
The demodulator/receiver comprises, illustratively, a signal
separator/demultiplexer 1270 which extracts the modulated signals So
through S3 from the received satellite signal, and four demodulators 1280-1
through 1280-4 adapted to demodulate the modulated signals S0 through S3
and retrieve therefrom payload stream portions or segments P'0 through P'3.
The VSA postprocessor 1290 performs various buffer manager
functions 1291 , buffer functions 1292, no packet deletion functions 1293,
parity code processor functions 1294, re-sync and alignment functions 1295,
control header removal functions 1296 and combiner functions 1297 as
discussed herein. The VSA postprocessor 1290 is adapted to process the
illustratively, four stream portions or segments denoted as P'0 through P'3 to
reassemble the input signal or stream payload P.
In various embodiments, Spectral Slices SO and S 1 that are
independent carriers do not use DRSS. These carrier are assumed to be
mapped to "clean" spectrum where strong interference is not usually a
problem and standard code rates (such as LDPC 3/4, 5/6 and the like, along
with a block code such Reed Solomon or BCH) is sufficient for each carrier.
In various embodiments, Spectral Slices S2 and S3 use DRSS. In
other words, the payload carried in S2 is replicated and sent over carrier S3.
Both S2 and S3 use standard coding techniques (such as LDPC 3/4 or 5/6,
etc. along with a block code such as BCH or Reed Solomon). This example
assumes that carriers S2 and S3 will be mapped to spectrum that may have
strong interferers (e.g., malicious or unintentional) capable of causing
complete loss of data loss in either S2 or S3. By ensuring a spectral gap
between S2 and S3, the probability of interference simultaneously affecting
S2 and S3 is minimized. Thus, the aggregated signal may be recovered so
long as both S2 and S3 are not affected by interference above a threshold.
In various embodiments, the system is configured such that aggregate
capacity of SO, S and S2 is sufficient to transport payload P. A similar
assumption is made for the aggregate capacity of SO, S 1 and S3.
The payload P is sliced into small fixed-size packets, and a control
header is inserted at the beginning of each packet conformant to the VSA
technique described above. Additional parity codes are appended to allow
the receiver to check for header integrity. Three separate schedulers, one
each for SO and S , and one for the combined set of S2 and S3, are used for
allocating the packets to three separate streams denoted P0' , P ' and P 0' .
2 ' is a replica of P2o'. The schedulers ensure that the amount of data
allocated to each carrier does not exceed its information-bearing capacity.
In various embodiments, 0' , , P20' and P21 ' are fed to separate
modulators ( odO, Modi , Mod2 and Mod3, respectively) to generate carriers
SO, S 1, S2 and S3. In various other embodiments, composite modulators are
used.
The four carriers are combined using a standard RF combiner, upconverted
to the desired frequency band, amplified using a Power Amplifier
(PA) and then radiated using an antenna. A bent-pipe satellite sends the
signal to potentially multiple receiving sites.
On the receive side, the four carriers are demodulated by four separate
demodulators. Packets from the demodulators are queued in separate
buffers (one per demodulator). This is necessary because propagation delays
of the four carriers may be quite different and may vary over time. Null
packets (e.g., introduced by modulators if using DVB-S or DVB-S2 as the
physical layer standard) are removed and parity codes are checked to detect
and correct control header information vital for the correct processing of the
four packet streams. Packets with incorrect parity codes are dropped. A
Resynchronization and Alignment block ensures that packets from all
available streams are properly sequenced, and duplicate packets received
over carriers S2 or S3 (e.g., as would happen when both signals have a good
C/N) are dropped. Control headers are stripped and the payload sections of
the packets are merged to generate the final payload P.
Interference in S2 and S3 may be localized to specific receive sites or,
if present at the transmit side, would impact those signals at all receive sites.
In case of localized interference, certain sites may experience a partial or
complete loss of data in, say, S2. In those cases, the packets received over
S3 are chosen. At other receiver sites, S3 may be impaired in which case
packets received over S2 are chosen. If the interference is a sweeper type
that may alternately affect S2 and S3, then receivers resort to switching
between those two carriers on a per-packet basis.
The system 1200 is depicted as using a bent-pipe satellite
communications link 1260. However, in various other embodiments, other
types of wireless networks such as a point-to-multipoint terrestrial broadcast
system or a point-to-point microwave system for cellular backhaul may be
used. More generally, the system can be effectively applied for transport of
any data payload (whether synchronous or packetized) over a wireless
channel.
In still other embodiments, one or more of the modulated signals is
conveyed via an alternate network 1265, such as an optical network, IP
network or other wireline network.
Various benefits of the embodiments include significantly higher
spectral usage efficiency as well as the ability to use orphaned spectral
fragments that are too small to use otherwise. The various embodiments are
applicable to satellite applications, point-to-point wireless links such as those
used in bent-pipe SatCom applications, wireless backhaul infrastructure such
as provided using microwave towers and so on.
The various embodiments provide a mechanism wherein bandwidth
may be allocated by "appending" additional blocks of bandwidth to those
bandwidth blocks already in use, thereby facilitating a "pay-as-you-grow"
business model for service providers and consumers.
In various embodiments, a single transponder in a satellite system is
used to propagate a carrier signal including a plurality of modulated substreams,
each of the modulated sub-streams occupying its respective spectral
fragment region. In other embodiments, multiple carrier signals are
propagated via respective transponders.
In various embodiments, a single microwave link within a microwave
communication system is used to propagate a carrier signal including a
plurality of modulated sub-streams, each modulated sub-stream occupying its
respective spectral fragment region. In other embodiments, multiple carrier
signals are propagated via respective microwave links.
In various embodiments, a single wireless channel within a wireless
communication system is used to propagate a carrier signal including a
plurality of modulated sub-streams, each modulated sub-stream occupying its
respective spectral fragment region. In other embodiments, multiple carrier
signals are propagated via respective wireless channels.
Efficient Failover Support Using Protection Groups
By segmenting a stream into a plurality of stream segments and
transmitting these stream segments via respective spectral portions, resiliency
to interferers such as from malicious sweepers, leaky equipment and the like
may be improved.
Various embodiments further improve resiliency by replicating stream
segments and modulating/transmitting the replicated stream segments via a
different spectral region, optionally using a different modulation technique. In
some embodiments, an original or replicated stream segment may be
conveyed by a wireline communications link, as discussed above.
Various embodiments further improve resiliency by providing segmentlevel
protection groups in which a stream segment modulated/transmitted
within a first spectral region is modulated/transmitted within a backup spectral
region in response to channel impairments within the first spectral region
exceeding a threshold level. In various embodiments, the backup spectral
region comprises a spectral region associated with a lower priority data
stream segment. In various embodiments, priority is assigned according to
type of data, customer, service level agreement (SLA) profile and/or other
criteria.
In various embodiments, rather than allocating a block of active
spectrum and another equally large block of backup spectrum that remains
unused, several smaller blocks of spectrum are utilized. The spectrum blocks
may be allocated to the same or different satellites (or other wireless
communications mechanisms), the same or different transponders and so on.
For exemplary purposes, it is assumed that the bandwidth capacity of each of
the smaller spectral blocks is the same, though this is not a requirement of the
various embodiments. Within the context of a backup spectral block or region,
the backup spectral block or region should be at least as large as the largest
spectral block or region. Where the spectral blocks or regions are of similar
size, the backup spectral block or region will also be of the similar size.
In various embodiments, information such as channel status feedback
is received at the transmitter. Referring to FIG. 12, optional status feedback
(SF) may be received via the alternate network 1265 or any other mechanism.
For example, in the typical satellite system a back channel exists which may
be used by the receiver to convey information to the transmitter indicative of
transmission quality, error rate, buffer back pressure, receiver status and so
on. In the various embodiments discussed herein, any of the known
mechanisms for providing feedback or status information from a receiver to
transmitter may be employed.
FIG. 13 depicts a flow diagram according to one embodiment.
Specifically, FIG. 13 depicts a flow diagram of a mechanism for providing
enhanced channel resiliency with optional prioritization according to the
various embodiments. The methodology discussed herein with respect to FIG.
13 may be provided at one or more VSA transmitters such as discussed
above.
At step 1310, one or more data streams are received from one or more
customers. Referring to box 1315, the one or more data streams may be
received via satellite link, microwave link, wireless channel, wireline channel
and/or other means.
At step 1320, each of the data streams is sliced into a plurality of
stream segments and/or sub-streams, each of the stream segments and/or
sub-streams being associated with a respective spectral fragment as
discussed above with respect to the various embodiments. Referring to box
1325, the stream segments and/or sub-streams may defined according to
customer, available spectral fragments of fixed size or variable size, data
type, signal type and/or other parameters.
At step 1330, the various modulation parameters, bandwidth
allocations, priority levels and/or other parameters are selected for the stream
segments and/or sub-streams and their respective spectral fragments. The
various stream segments and/or sub-streams are accordingly modulated and
transmitted within their respective spectral fragments.
At step 1340, the various channels associated with the spectral
fragments are monitored to identify suboptimal channel behavior, such as
channel interference, channel impairments and the like. Referring to box
1345, such monitoring may occur at predetermined intervals, after each
relevant subscriber event, after a predetermined number of subscriber events
or according to some other schedule. For example, in various embodiments
interrupt-driven monitoring is provided wherein receivers only convey
information to respective transmitters when a channel is impaired beyond one
or more threshold levels, such as one or more levels correctable by adapting
forward error correction (FEC) parameters, a level beyond FEC correction
ability, a level indicative of channel failure and so on.
At step 1350, suboptimal channels are processed according to channel
performance and/or priority level of channel data. Referring to box 1355, the
forward error correction (FEC) and/or other parameters associated with the
channel may be adapted. Such adaptation may be based upon various
thresholds, such as one or more of interference thresholds, one or more
impairment thresholds and so on. Within the context of priority level
processing (such as where a channel is effectively nonfunctioning), the
stream segments and/or sub-streams associated with the channel may be
modulated and transmitted via a backup channel(s) or channel(s) associated
with lower priority data. That is, a scheduler may adapt the various schedules
to accommodate priority segments and/or sub-streams preferentially over
lower priority segments and/or sub-streams.
At step 1360, segments and/or sub-streams are optionally aggregated
over multiple spectral fragments such that they are transported via multiple
communications channels. Additionally, the multiple communications
channels may be supported via different communications networks or links.
Referring to box 1365, various links include one or more of a point to point
links such as satellite links or microwave links, point to multipoint links such as
provided by various wireless channels, wireline channels and/or other
mechanisms.
The above-described steps contemplate, in response to channel quality
degradation or failure, one or both of individual processing of channels to
adapt FEC and/or other parameters and channel reallocation based upon
priority of data. These steps are implemented in a substantially automatic
manner in response to service level agreement (SLA), profile data, default
carrier preferences and/or other criteria. Generally speaking, the systems
operate in a substantially automated manner to ensure that prioritized data
channels are used as efficiently as possible. Different data streams may be
associated with different priority levels. Different customers may be
associated with different priority levels.
Various embodiments operate to provide automatic rerouting of data by
a VSA transmitter over available spectral blocks to bypass one or more failed
spectral blocks. Various embodiments operate to provide automatic rerouting
of data by the VSA transmitter to provide load balancing functions or
otherwise utilize available spectral blocks as efficiently as possible.
As previously discussed, various prioritization techniques may be
employed to ensure that high-priority traffic is guaranteed delivery, while lowpriority
traffic is delivered using spare bandwidth left over from servicing the
higher priority traffic or opportunistically inserted data.
Various embodiments support multiple prioritization levels such as by
using a Weighted Fair Queuing (WFQ) scheduler for allocation to the various
traffic classes.
Various embodiments provide interference mitigation using spectral
aggregation. That is, when an interferer (whether CW or complex in nature)
degrades a particular channel, only the FEC rate of that particular channel is
adapted to compensate for this degradation. If the interferer is too strong to be
overcome with better FEC code rates alone (or so strong that the adapted
FEC code rate may drop the throughput to unacceptably low levels), then the
channel must be reallocated to a different spectral fragment. In particular, the
various embodiments provide interference mitigation per-slice FEC rate
adjustment (FEC rate of each slice is adjusted depending upon the degree of
interference specific to each slice) and spectral slice reallocation (IF
interference within a specific slice is too strong and cannot be mitigated with a
higher FEC rate, that slice rather than the entire set of slices is relocated to
another region of the transponder or another transponder entirely without
affecting the other slices).
Various embodiments are adapted to provide improved security via
encryption of some or all of the data segments associated with a data stream.
That is, in various embodiments channel modulation circuitry is adapted to
include encryption functionality, while channel demodulation circuitry is
adapted to include decryption functionality. Such encryption/decryption
functionality may be based on the use of large encryption keys, frequently
changed encryption keys or some combination thereof. Techniques such as
AES may also be utilized within the context of the various embodiments. The
use of the VSA techniques described herein provide additional layers of
security even without encryption. With encryption security becomes extremely
robust.
In one embodiment, each data segment and/or channel is encrypted
with a common encryption key or technique. In other embodiments, each data
segment and/or channel is encrypted with a respective encryption key or
technique.
Various embodiments contemplate a system, method, apparatus,
computing device and the like operable to perform the various steps and
functions discussed herein, such as dividing a data stream into a plurality of
sub-streams; modulating each sub-stream to provide a respective modulated
signal adapted for transmission via a respective spectral fragment or block;
monitoring data indicative of channel performance for each of the spectral
fragments to identify degraded channels; and adapting, for each degraded
channel, one or more respective modulation parameters to compensate for
respective identified channel degradation.
In various embodiments, the one or more modulation parameters are
adapted to compensate for identified channel degradation up to a threshold
level of degradation. FEC rate and/or other parameters may be adjusted to
accomplish this. A spectral gap may be maintained between various spectral
fragments or blocks.
In the case of the degradation of an identified channel exceeding a
threshold level (e.g., too many errors to correct, too many errors to correct
and have sufficient bandwidth etc.) or the channel simply failing, then various
embodiments operate to select a backup spectral fragment for use by the
modulated signal associated with the identified degraded channel. The substream
may need to be remodulated or modulated in a different manner for
the newly selected spectral fragment or block. Prioritization among data
stream and/or sub-streams may be provided in the case of a limited number
of spectral fragments or blocks.
Various embodiments contemplate compound or multiple sub-streams
within at least some of the spectral fragments or blocks, such as by combining
two or more modulated sub-streams to form respective combined substreams,
each of the combined sub-streams being modulated onto a
modulated signal adapted for transmission via a spectral fragment having a
bandwidth compatible with the total effective data rate of combined substreams.
Various embodiments contemplate transmitting carrier signals via
respective channels within a communications system. For example, each of
one or more carrier signals may be supported by a respective transponder
within a satellite communications system, a respective microwave link within a
microwave communications system, and/or a respective wireless channel
within a wireless communications system.
Various embodiments contemplate dividing a data stream into a
plurality of sub-streams by encapsulating sequential portions of the data
stream into payload portions of respective encapsulating packets, each of the
sequential portions of the data stream being associated with a respective
sequence number included within a header portion of the respective
encapsulating packet; and including each encapsulating packet within a
respective sub-stream. Alternatively, each encapsulating packet may be
included within one or more of the sub-streams. The sequence number may
be represented by a field having at least 14 bits. The encapsulating packet
header may includes a hexadecimal 47 in a first byte.
Various embodiments contemplate a receiver for receiving each of the
modulated sub-streams via respective spectral fragments; demodulating each
of the modulated sub-streams; and combining a plurality of the demodulated
sub-streams to recover the data stream. Combining the demodulated substreams
to recover the data stream may be provided via ordering
encapsulating packets received via one or more sub-streams according to
their respective sequence numbers; and extracting sequential portions of the
data stream from the ordered encapsulating packets to recover thereby the
data stream. Discarding of encapsulating packets having a sequence number
matching the sequence number of a recently received encapsulating packet
may also be provided.
Encryption and Secured Communications
The use of Virtual Spectrum Aggregation (VSA) techniques as
described above allows a payload to be transmitted over multiple carriers
each of which may potentially be dispersed in the frequency domain. Each
carrier may be encrypted with a different key, and the bandwidth associated
with each carrier may also be randomly assigned such that the aggregate
bandwidth of the constituent carriers equals the desired bandwidth necessary
for transport of the payload.
Various embodiments contemplate the use of multiple carriers
encrypted with separate encryption keys, randomly assigned bandwidth, and
dispersed in the frequency domain makes the problem significantly more
complex for an eavesdropper. The keys can be changed continuously for
each spectral slice with only minimal overhead necessary for the receiver to
stay synchronized with the transmitter. These embodiments increases the
overall security strength by several orders of magnitude. The security of the
communications channel is increased by a factor of (N power M) where N is
the number of keys in the lookup tables maintained by the transmitter and the
receiver, and M is the number of spectral slices used for virtual aggregation.
For example, the use of four carriers and 128 keys per carrier increases
computational complexity by a factor of 128 * * 4 or roughly 268 million.
Various embodiments provide an efficient and general-purpose
technique for aggregating multiple, fragmented blocks of wireless spectrum
into one contiguous virtual block such that the cumulative bandwidth is almost
equal to the sum of the bandwidths of the constituent blocks. Various
embodiments provide that the fragmented blocks or spectral slices are
dynamically and continuously relocated for enhanced security.
Various embodiments provide that each of a plurality of substreams are
encrypted using different encryption keys from one session to the next. In
one embodiment, the encryption keys are periodically relocated along with the
various spectral fragments. In other embodiments, either the encryption keys
or the various spectral fragments are relocated.
Generally speaking, each transponder/transmission channel discussed
above with respect to the various figures may be divided into a plurality of
spectral fragments or regions. Each of these spectral fragments or regions
may be assigned to a particular data sub-stream. Each of the data substreams
may be modulated according to a unique or common modulation
technique. In various embodiments, multiple transponders within one or more
satellites may be used. In these embodiments, only those modulated signals
to be transmitted via a common transponder within a satellite are combined
and then converted together. In various embodiments, a dual transponder
arrangement (e.g., an uplink portion of the system and a downlink portion of
the system) is provided in which a first transponder is used to transport a first
portion of a plurality of data streams associated with a data stream D, while a
second transponder is used to transport a second portion of a plurality of data
streams associated with the data stream D. Although described herein as a
dual transponder embodiment, it will be appreciated that exemplary
communications systems may include any suitable number and/or
combination of uplink/downlink transponders.
In another embodiment, one transponder of a dual transponder
arrangement is used as a separate out-of-band secure channel to
communicate changing parameters, e.g., aggregate bandwidth, to configure
the VSA receiver. In various embodiments, modulated waveforms are
transmitted independently.
In various embodiments, a slicer/demultiplexer such as described
above with respect to the various figures is modified to further include an
encryption function. In various embodiments, a modulator such as described
above with respect to the various figures is modified to further include an
encryption function in any of these embodiments, the various functions may
be implemented using a computing device such as the computing device 300
of FIG. 3 wherein a processor cooperating with memory and input/output
circuitry executes software adapted to implement the various functions
described herein.
In various embodiments, a slicer/demultiplexer, VSA pre-processor
and/or modulator function such as described above with respect to the various
embodiments is modified to further include an encryption function. In any of
these embodiments, the various functions may be implemented using a
computing device such as the computing device of FIG. 3 wherein a
processor cooperating with memory and input/output circuitry executes
software adapted to implement the various functions described herein.
In various embodiments, a demodulator, combiner and/or VSA post
processor function such as described above with respect to the various
embodiments is modified to further include a decryption function. In any of
these embodiments, the various functions may be implemented using a
computing device such as the computing device of FIG. 3 wherein a
processor cooperating with memory and input/output circuitry executes
software adapted to implement the various functions described herein.
FIGS. 14A-14B depict a graphical representation of a spectral
allocation useful in understanding various embodiments. Specifically, FIG.
14A graphically depicts a 12 MHz carrier, which is sliced into four carriers,
illustratively four noncontiguous spectrum blocks comprising a first 3 MHz
block 1405, a second 3 MHz block 1410, a third 2 MHz block 141 5 and a 4
MHz block 1420. Each spectral slice may be encrypted with a different key.
Additional security is obtained by virtue of the following features; namely, ( 1 )
at the start of a communications session, each slice is assigned a randomly
chosen spectral bandwidth such that the sum total is equal to the desired
aggregate bandwidth. A potential eavesdropper would then face the added
burden of acquiring knowledge of the spectral bandwidth of each slice in order
to reconstruct the original signal; and (2) the use of N slices makes the
eavesdropping task that much more computationally intensive. For example,
if N along with the set of keys used for the N slices is varied from one session
to the next, the level of security is enhanced considerably.
FIG. 14B graphically depicts an example progression over time of the
use of four active spectral slices and one unused spectral block. Illustratively,
at time TOfive noncontiguous spectrum blocks comprising a first 3 MHz block
1425 (key= K 1) , a second 3 MHz block 1426 (key= K2), a third 3 MHz block
1427 (key= K3), a fourth unused 3 MHz block 1428 (key= unused) and a 3
MHz block 1429 (key= K4). At time T 1, carrier at block 1426 is relocated to
block 1428 making block 1426 unused. At time T2, carrier at block 1427 is
relocated to block 1426 making bloc 1427 unused. Note that at time T2, the
key used by carrier at block 1425 changes from K 1 to K ' . Key changes also
occur in time slots T3 and T4 where the slice transition by one carrier is
accompanied with a key change in the same or another carrier. At time T3,
carrier at block 1429 is relocated to block 1427 making block 1429 unused.
Key 3 for carrier at block 1427 is replaced with K4'. At time T4, carrier at
block 1425 is relocated to block 1429 making block 1425 unused. Key 4 for
carrier 1429 is replaced with key K 1' and key 3 for carrier 1426 is replaced
with K3
Within the context of various embodiments discussed herein, the VSA
scheme described above utilizes multiple carriers and unlike traditional
frequency hopping scheme requiring a large number of unused spectrum
blocks, the instant VSA scheme requires only a small number (e.g., one in the
above example) of extra spectral blocks.
FIG. 15 depicts a flow diagram according to one embodiment.
Specifically, FIG. 15 depicts a flow diagram of a mechanism for providing
enhanced channel resiliency and security with optional prioritization according
to the various embodiments. The methodology discussed herein with respect
to FIG. 15 may be provided at one or more VSA transmitters such as
discussed above with respect to the various figures, and/or transmitters for
other communications channels or links such as satellite link, microwave link,
wireless channel, wireline channel and/or other means. In particular, in
various embodiments the functional elements supporting modulator and
demodulator functions such as described above with respect to the various
figures are modified to further include encryption and decryption functions.
Further, encryption functionality may be provided within the context of VSA
pre-processing functional elements, while decryption functionality may be
provided within the context of VSA post-processing functional elements.
At step 1510, one or more data streams are received from one or more
customers. Referring to box 1515, the one or more data streams may be
received via satellite link, microwave link, wireless channel, wireline channel
and/or other means.
At step 1520, each of the data streams is sliced into a plurality of
stream segments and/or sub-streams (illustratively N), each of the stream
segments and/or sub-streams being associated with a respective spectral
fragment and/or link as discussed above with respect to the various
embodiments. Referring to box 1525, the stream segments and/or substreams
may defined according to customer, available spectral fragments of
fixed size or variable size, data type or signal type, fragment or link capacity,
fragment or link parameters and/or other parameters or criteria.
At step 1530, the various modulation parameters, bandwidth
allocations, priority levels and/or other parameters are selected for the stream
segments and/or sub-streams and their respective spectral fragments or links.
The various stream segments and/or sub-streams are accordingly modulated
and transmitted within their respective spectral fragments or links.
Further at step 1530, at least some of the slices are also encrypted.
Referring to box 1535, the same encryption key may be used for all encrypted
slices, a respective encryption key may be used for each encrypted slice,
some of the cryptic slices may use the same encryption key while others use
one or more other encryption keys and so on. Further, in various
embodiments the encryption key to be used for a particular slice is selected
from a key table. In other embodiments, the encryption key to be used for a
particular slice is generated at encryption time for that slice. Various other
combinations of respective and/or shared encryption keys are contemplated,
as are various other mechanisms for generating encryption keys.
At step 1540, the encrypted/modulated slices, as well as any
unencrypted/modulated slices are transmitted via their respective spectral
fragments or links toward one or more receivers. In addition, decryption key
information is also transmitted as necessary. Referring to box 1545,
decryption key information may be transmitted via in-band transmission
channel, out-of-band transmission channel and the like. The decryption key
information may comprise specific decryption keys, updated tables associated
with encryption/decryption keys and so on.
At step 1550, optional adaptations are made to substream transmission
channel associations, channel bandwidth allocations, encryption key table
entries, encryption key transmission means and/or other parameters.
Referring to box 1555, these adjustments may be made in response to an
expiration of a predefined time, an occurrence of a threshold number of uses
of a particular key, a response to a particular event, or some other factor.
Specifically, the various adaptations discussed above with respect to
step 1550 enable the use of channel-hopping and other mechanisms adapted
to enhance security by increasing the amount of resources necessary to
extract coherent data from one or more of the encrypted data slices.
The above-described steps contemplate various methodologies
adapted to providing secure and resilient transmission of a data stream by
slicing the stream into a plurality of segments, encrypting some or all of those
segments, modulating the various segments and transmitting the segments
via respective transmission channels. The various encryption techniques
described above with respect to FIG. 15 may also be used within the context
of the techniques described with respect to any of the other figures described
herein.
In one embodiment, both transmitters and receivers maintain a lookup
table including a number of encryption keys where a pseudorandom number
generator is used to index into the table and extract therefrom a particular
encryption key to be used for encrypting or decrypting a data slicer segment.
Encrypted slices are appended with the unencrypted index of the table to
enable receiver to successfully decrypt the slice. Thus, in one embodiment,
management programs or other programs within a computing device suitable
for use in the various embodiments is used to provide the necessary
functionality to establish encryption key lookup table, updates to the
encryption key lookup table as necessary, generate table index data via
pseudorandom number generators or other means, and utilize the encryption
keys indexed therefrom to encrypt and/or decrypt the data slice of interest.
Various embodiments described herein provide dynamic spectrum
fragmentation of an input stream such that each fragment is encrypted using a
separate key and randomly allocated a bandwidth.
The above-described embodiments provide a number of advantages,
including enhanced security because ( ) a potential eavesdropper is then
faced with the added burden of acquiring knowledge of the spectral bandwidth
of each slice in order to reconstruct the original signal; and (2) the use of N
slices makes the eavesdropping task that much more computationally
intensive. In addition, spectral slices are deliberately and periodically
relocated to new center frequencies making that much harder for a potential
eavesdropper to track and decode the constituent carriers.
Various benefits of the embodiments include significantly higher
spectral usage efficiency as well as enhanced security. The various
embodiments are applicable to satellite applications, point-to-point wireless
links such as those used in bent-pipe SatCom applications, wireless backhaul
infrastructure such as provided using microwave towers and so on.
In various embodiments, a single transponder in a satellite system is
used to propagate multiple carrier signals including a plurality of modulated
sub-streams, each of the modulated sub-streams occupying its respective
spectral fragment region. In other embodiments, multiple carrier signals are
propagated via respective transponders in dual transponder or dual satellite
arrangement.
In various embodiments, a single microwave link within a microwave
communication system is used to propagate multiple carrier signals including
a plurality of modulated sub-streams, each modulated sub-stream occupying
its respective spectral fragment region. In other embodiments, multiple carrier
signals are propagated via respective microwave links.
In various embodiments, a single wireless channel within a wireless
communication system is used to propagate multiple carrier signal including a
plurality of modulated sub-streams, each modulated sub-stream occupying its
respective spectral fragment region. In other embodiments, multiple carrier
signals are propagated via respective wireless channels.
Methodologies or techniques associated with various embodiments
may be implemented using a computer program product comprising a nontransitory
computer-readable storage medium having computer readable
instructions stored thereon, the computer readable instructions being
executable by a computerized device to cause the computerized device to
perform the methodologies or techniques.
While the foregoing is directed to various embodiments of the present
invention, other and further embodiments of the invention may be devised
without departing from the basic scope thereof and those skilled in the art can
readily devise many other varied embodiments that still incorporate these
teachings. As such, the appropriate scope of the invention is to be
determined according to the claims, which follow.
What is claimed is:
. A method comprising:
dividing a data stream into a plurality of sub-streams;
associating each substream with a respective spectral fragment;
encrypting at least some of the sub-streams; and
modulating each sub-stream to provide a respective modulated signal
adapted for transmission via a respective spectral fragment.
2 . The method of claim 1, wherein each encrypted substream is
associated with a respective encryption key.
3 . The method of claim , wherein at least some of the encrypted
substreams are associated with a common encryption key.
4. The method of claim , wherein the encryption key used to encrypt a
substream is changed each session.
5. The method of claim 1, wherein said encrypting comprises selecting an
encryption key from a table of encryption keys according to a generated index
value generated via a pseudorandom number generator.
6. The method of claim 5, wherein said table of encryption keys is
periodically updated.
7 . The method of claim , further comprising adjusting substream spectral
fragment associations in response to at least one of an expiration of a
predefined time period, an occurrence of a threshold number of encryption
key uses and an occurrence of a predefined event.
8. The method of claim , wherein some of the spectral fragments are
associated with respective portions of a first upconverted carrier signal, and
some of the spectral fragments are associated with respective portions of a
second upconverted carrier signal, wherein the first and second carrier signals
are conveyed using different point-to-point links.
9. A computer program product comprising a non-transitory computerreadable
storage medium having computer readable instructions stored
thereon, the computer readable instructions being executable by a
computerized device to cause the computerized device to perform a method
comprising:
dividing a data stream into a plurality of sub-streams;
associating each substream with a respective spectral fragment;
encrypting at least some of the sub-streams; and
modulating each sub-stream to provide a respective modulated signal
adapted for transmission via a respective spectral fragment.
10. An apparatus, comprising:
a splitter, for dividing a data stream into a plurality of sub-streams,
each of said sub-streams associated a respective spectral fragment and
having a data rate compatible with a bandwidth of the respective spectral
fragment;
a plurality of modulators, each modulator configured to modulate a
respective sub-stream to provide a modulated signal adapted for transmission
via the respective spectral fragment, wherein at least some of said modulators
are configured to encrypt respective substreams;
at least one upconverter, for upconverting said modulated signals onto
respective spectral fragments of at least one carrier signal;
wherein the sub-streams included within the upconverted modulated
signals are adapted to be demodulated and combined at a receiver to recover
thereby the data stream.