VIRTUAL AGGREGATION OF FRAGMENTED WIRELESS SPECTRUM
FIELD OF THE INVENTION
The invention relates generally to communication networks and, more
specifically, but not exclusively, to satellite- and microwave-based point-to-point
communication 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 worst-case 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 point-topoint
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.
BRIEF SUMMARY
Various deficiencies of the prior art are addressed by the present invention
of systems, methods and apparatus aggregating spectrum in which multiple
disjoint blocks of spectrum may be configured as one virtual contiguous block of
spectrum by modulating onto each disjoint blocks of spectrum a respective
portion of a data stream in which the data rate associated with the modulated
portion is compatible with the available bandwidth of the disjoint spectrum block
upon which is modulated.
A method according to one embodiment comprises dividing a data stream
into a plurality of sub-streams, each of the sub-streams associated a respective
spectral fragment and having a data rate compatible with a bandwidth of the
respective spectral fragment; modulating each of the sub-streams to provide a
modulated signal adapted for transmission via the respective spectral fragment;
and upconverting the 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 data stream.
An apparatus according to one embodiment comprises a splitter, for
dividing a data stream into a plurality of sub-streams, each of the 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;
and at least one upconverter, for upconverting the modulated signals onto
respective spectral fragments of at least one carrier signal; wherein the substreams
included within the upconverted modulated signals are adapted to be
demodulated and combined at a receiver to recover thereby data stream.
The splitting function of the method or apparatus may include
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 selectively routing
encapsulated packets towards demodulators.
The selective routing may be based on routing encapsulating packets
according any of a random routing algorithm, a round robin routing algorithm, a
customer preference algorithm, a service provider preference algorithm and so
on where each sub-stream is associated with a respective weight.
The various sub-streams may be modulated and up converted onto a
carrier signal for transmission via one or more transponders within a satellite
medication system, one or more microwave links within a microwave
communications system and/or one or more wireless channels within a wireless
communication system.
In various embodiments, encapsulated packets are routed multiple times
to add resiliency/redundancy.
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; and
FIG. 11 depicts a flow diagram of a method according to one embodiment.
To facilitate understanding, identical reference numerals have been used,
where possible, to designate identical elements that are common to the figures.
DETAILED DESCRIPTION OF THE INVENTION
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, 64-1500 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 -i), where N corresponds to a number of spectral fragments
denoted as S0, S and so on up to SN- i .
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, 1 12-1 and 1122) . Each of the modulators
1120, 1 12-1 and 1122 modulates its respective sub-stream D0, D and D2 to
provide corresponding modulated signals to be carried by respective spectral
fragments S0, S and S2.
The modulators 112 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 S0; the second modulator 112-i provides
a 1 MHz signal associated with a second spectral fragment S ; and third
modulator 1122 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 spectral 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 sub-stream. Each of the data substreams
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 113 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 substreams
D0, D and D2 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 S0' , S ' and S2' from the combined spectral fragment
signal Sc ' .
Each of the spectral fragments S0 S-i' and S2' is coupled to a separate
demodulator (i.e., demodulators 1620, 162-1 and 1622) . Each of the demodulators
1620, 162 and 1622 demodulates its respective spectral fragments So', S-i' and
S2' to provide corresponding demodulated sub-streams D0 Di' and D2' .
The demodulated sub-streams D0 Di' 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,
166-1 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 ID 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 2403.
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 I/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 I/O
circuits 310 receive the demodulated sub-streams D0' , D ' 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 110, where it is processed by a slicer/de-multiplexer x 11 to provide N
sub-streams (D0... D -i), where each of the N sub-streams is modulated by
respective modulator x 12 . 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 - i) 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 S0, Si and S2. The
corresponding modulated signals are combined by a second signal combiner
7 132 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 de
multiplexer 764 to recover the modulated signals and then demodulated by
respective demodulators 752.
The DDD signal components are separated by a third frequency demultiplexer
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 112.
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 - i ) which are then modulated by respective modulators 712
(i.e., modulators 7120, 712-1 and 7122) to provide corresponding modulated
signals to be carried by respective spectral fragments S 0 , S and S 2 .
The modulated signals associated with data streams A, B and C are
combined by a first signal combiner 8 3 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 2 .
The combined modulated signals produced by the first 8 3 and second
8 132 signal combiners are then combined by a third signal combiner 8 133 and
converted by a first upconverter 814i 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,
8 13 , 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 downconverter
865. The down-converted signal is separated into its two carrier signals
by frequency demultiplexer 864 . 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 (940i) 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 (9402) 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 (920 I and 9202) and transmitted to
satellites 940-I and 9402, respectively, using uplinks 930-I and 9302.
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 10 10 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 1030
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, encapsulates 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 sub-stream.
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.
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 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 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.
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:
1. A method, comprising:
dividing a data stream into a plurality of sub-streams, each of said substreams
associated a respective spectral fragment and having a data rate
compatible with a bandwidth of the respective spectral fragment;
modulating each of the sub-streams to provide a modulated signal
adapted for transmission via the respective spectral fragment; and
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 data stream.
2 . The method of claim 1, further comprising combining two or more of the
modulated sub-streams to form respective combined sub-streams, each of said
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 sub-streams.
3 . The method of claim 1.further comprising transmitting said carrier signals
via respective channels within a communications system, wherein each of said
one or more carrier signals is supported by a respective transponder within a
satellite communications system, a respective microwave link within a microwave
communications system, or a respective wireless channel within a wireless
communications system.
4 . The method of claim 1, wherein said dividing a data stream into a plurality
of sub-streams comprises:
encapsulating sequential portions of said data stream into payload
portions of respective encapsulating packets, each of said sequential portions of
said 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 one or more of said substreams.
5 . The method of claim 1, further comprising:
receiving each of the modulated sub-streams via respective spectral
fragments;
demodulating each of the modulated sub-streams;
ordering encapsulating packets received via one or more sub-streams
according to their respective sequence numbers; and
extracting sequential portions of said data stream from said ordered
encapsulating packets to recover thereby said data stream.
6 . 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; and
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 data stream.
7 . The apparatus of claim 6 , wherein said splitter comprises:
an encapsulate^ for encapsulating sequential portions of said data stream
into payload portions of respective encapsulating packets, each of said
sequential portions of said data stream being associated with a respective
sequence number included within a header portion of the respective
encapsulating packet;
a master scheduler, for selectively routing encapsulated packets towards
the demodulators; and
a plurality of sub schedulers, each of said sub schedulers adapted to route
packets received from the master scheduler toward a respective modulator.
8 . The apparatus of claim 7 , wherein said master scheduler routes packets
according to one of a random routing algorithm, a round robin routing algorithm.
9 . The apparatus of claim 7 , wherein:
said master scheduler routes packets according to one of a customer
preference algorithm and a service provider preference algorithm, wherein each
sub-stream is associated with a respective weight; and
the respective weight of a sub-stream is defined by one or more of a
preferred spectral fragment, a preferred spectral fragment type, the preferred
communication channel, a preferred communication channel type, a preferred
traffic type and a preferred customer.
10. A computer readable medium including software instructions which, when
executed by a processer, perform a method comprising:
dividing a data stream into a plurality of sub-streams, each of said substreams
associated a respective spectral fragment and having a data rate
compatible with a bandwidth of the respective spectral fragment;
modulating each of the sub-streams to provide a modulated signal
adapted for transmission via the respective spectral fragment; and
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 data stream.