Method and apparatus for exchanging data signals over a
plurality of domains in a home network
Field of the Invention
The present invention pertains to improved communication in
networks comprising multiple domains, in particular in
(home) networks according to the G.hn standards family
comprising domains using different physical media.
Background
The "G.hn" standards family of the International
Telecommunication Union (ITU) (i.e., ITU-T Recommendations
G.996x) was defined to enable the in-house broadband data
communication required by high data rate (i.e., broadband)
applications. In G.hn, different domains are available for
the in-house network access over different media, in
particular copper twisted-pairs as traditionally used for
telephony, coaxial lines as traditionally used for
transmitting television signals, power line cables, and
wireless .
The available network resources and the achievable data
rates are limited by the characteristics of the medium and
the structure of the network. It is therefore challenging to
obtain decent data rates over these media, most of which
were not originally designed to carry high-speed digital
data transmissions.
Summary
Accordingly, it is an object of embodiments of the present
invention to obtain higher data rates between certain nodes
in a multi -domain network.
According to a first aspect of the present invention, there
is provided a method for receiving data signals transmitted
over a plurality of domains in a network, the apparatus
comprising: receiving a first data signal at a first
physical interface connected to a first domain from among
said plurality of domains; receiving a second data signal at
a second physical interface connected to a second domain
from among said plurality of domains; combining said first
data signal and said second data signal to produce a
combined signal; and extracting transmitted data from said
combined signal; wherein said first data signal and said
second data signal are instances of a common original data
signal, transmitted over said first domain and said second
domain respectively, and having undergone physical signal
degradation associated with said first domain and said
second domain respectively.
It is an advantage of the present invention that an improved
version of the data signal can be produced at the receiver
side by recombining independently received copies of a
common original data signal . The invention thus takes
advantage of multiple available transmission paths between
end points in a multi -domain network.
In an embodiment, the method according to the present
invention further comprises receiving said common original
data signal transmitted over said first domain at a first
domain manager as a first intermediate signal;
retransmitting said first intermediate signal from said
first domain manager; and receiving said retransmitted
common original data signal at said first interface as said
first data signal .
In an embodiment, the method according to the present
invention further comprises receiving said common original
data signal transmitted over said second domain at a second
domain manager as a second intermediate signal;
retransmitting said second intermediate signal from said
second domain manager; and receiving said retransmitted
second intermediate signal at said second interface as said
second data signal .
According to an aspect of the present invention, there is
provided a method for transmitting data signals over a
plurality of domains in a network, said method comprising at
a network node: receiving data for transmission over said
network at a service interface; producing a data signal
representative of said data; transmitting a first instance
of said data signal over a first physical interface,
connected to a first domain from among said plurality of
domains; and transmitting a second instance of said data
signal over a second physical interface, connected to a
second domain from among said plurality of domains.
In an embodiment of the method according to the present
invention, said first instance and said second instance are
shifted relative to each other in the frequency domain.
In an embodiment, the method according to the present
invention further comprises selecting said first domain and
said second domain from among said plurality of domains on
the basis of one or more of a priority list and transmission
queue status .
According to an aspect of the present invention, there is
provided an apparatus for receiving data signals over a
plurality of domains in a network, said apparatus
comprising: a multiplexer having a service interface and a
lower-layer interface, said service interface being adapted
to present data received over said network; a first physical
interface, operatively connected to said lower- layer
interface, said first physical interface being adapted to
receive data signals over a first domain from among said
plurality of domains; a second physical interface,
operatively connected to said lower-layer interface, said
second physical interface being adapted to receive data
signals over a second domain from among said plurality of
domains; wherein said multiplexer is adapted to combine
respective instances of a physical layer signal received
from said first physical interface and said second physical
interface, and to decode said data from said combined
instances .
In an embodiment of the apparatus according to the present
invention, said network is a G.hn network, and said
plurality of domains are taken from the set of a coaxial
cable domain, a twisted-pair domain, and a power-line
communication domain.
In an embodiment of the apparatus according to the present
invention, said instances are corresponding versions of one
or more OFDM modulation symbols.
In an embodiment of the apparatus according to the present
invention, said corresponding versions are shifted relative
to each other in the frequency domain.
According to an aspect of the present invention, there is
provided an apparatus for transmitting data signals over a
plurality of domains in a network, said apparatus
comprising: a demultiplexer having a service interface and a
lower-layer interface, said service interface being adapted
to receive data for transmission over said network; a first
physical interface, operatively connected to said lowerlayer
interface, said first physical interface being adapted
to transmit data signals over a first domain from among said
plurality of domains; a second physical interface,
operatively connected to said lower-layer interface, said
second physical interface being adapted to transmit data
signals over a second domain from among said plurality of
domains; wherein said demultiplexer is adapted to provide
instances of a physical layer signal to said first physical
interface and said second physical interface, said physical
layer signal representing said data.
In an embodiment of the apparatus according to the present
invention, said network is a G.hn network, and wherein said
plurality of domains are taken from the set of a coaxial
cable domain, a twisted-pair domain, and a power-line
communication domain.
In an embodiment of the apparatus according to the present
invention, said instances are corresponding versions of one
or more OFDM modulation symbols.
In an embodiment of the apparatus according to the present
invention, said corresponding versions are shifted relative
to each other in the frequency domain.
The advantages of the methods for transmitting information
according to the present invention, and of the various
apparatus according to the invention, correspond mutatis
mutandis to those of the method for receiving information
according to the present invention.
Brief Description of the Figures
Some embodiments of apparatus and/or methods in accordance
with embodiments of the present invention are now described,
by way of example only, and with reference to the
accompanying drawings, in which:
Figure 1 presents a flow chart of a method according to an
embodiment of the present invention;
Figure 2 presents a flow chart of a method according to
another embodiment of the present invention;
Figure 3 provides a block diagram of an apparatus according
to an embodiment of the present invention;
Figure 4 provides a block diagram of an apparatus according
to another embodiment of the present invention;
Figures 5 and 6 illustrate an exemplary multi -domain network
according to the G.hn standards family, presenting loops
which may be exploited by embodiments of the present
invention; and
Figure 7 presents a schematic illustrating the relationship
between various functions carried out in the context of the
present invention.
The same reference numerals have been used throughout the
figures to designate the same elements.
Detailed Description of Embodiments
Power line and wireless channels can be characterized as
multipath propagation environments. Upon the multipath
signal transmission, different signal copies undergo
different attenuation, distortion, delays and phase shifts.
Due to this effect, the overall system performance (e.g.,
BER, throughput, etc.) may be severely degraded, because the
channel response is a superposition of the different copies
of the signals with their different channel -induced
modifications, leading to a decrease in signal-to-noise
ratio .
Diversity techniques can be used to improve system
performance (e.g., BER, throughput) in multipath channels.
The idea behind diversity is that it is possible to combine
several copies of the transmitted signal, which will be
independently affected by the particular channel they
experienced, and which together provide enough information
to reconstruct the transmitted symbol. This will increase
the overall received power and make the correct decision on
the transmitted symbol .
Currently, multiple-input multiple-output (MIMO)
transmission is used in certain communication systems,
including wireless and vectored digital subscriber lines
(DSL) . In the context of G.hn, MIMO may be applied between
two devices linked by a power line communication (PLC)
domain, to achieve spatial multiplexing or diversity within
the power line domain in G.hn. Moreover, MIMO antenna
diversity is also available for wireless domains operating
according to certain wireless LAN standards.
The implementation of diversity solutions within individual
G.hn domains involves hardware changes to the devices, such
as an increase in the number of antennas, the number of PHY
interfaces, etc. This is both impractical and expensive to
the vendors and the end users .
Furthermore, in the case of a multi -domain scenario such as
the one illustrated in Figure 5 , the initiation of a
communication session between two devices is not
straightforward to implement. The problem is worsened by the
fact that different domains can use different media types
(e.g., copper twisted-pairs, coax, power line cables,
wireless) . Consequently, straightforward
transitions/interfaces between different mediums are not
feasible when MIMO is implemented. For example, a power line
medium has 3 available degrees of freedom (3 conductors) for
MIMO, while the coax medium has only 1 level of freedom (1
central conductor) .
Embodiments of the present invention enable multi -domain
(spatial) diversity for broadband home network data
transmission by exploiting the physical characteristics of
the home network environment. According to the insight of
the inventor, copies of the transmitted signal are
transmitted over multiple independent media (i.e., multiple
domains) and combined at the receiver end to increase the
overall received power and make the correct decision on the
transmitted symbol .
Combining of the analog signals is possible at the PHY layer
or at the packet level (similar to packet combining in
Hybrid ARQ) . Without loss of generality, the invention will
be described here with regard to recombination at the
physical level .
Figure 1 illustrates an exemplary embodiment of a method for
receiving data signals transmitted over plurality of domains
in a network such as a G.hn network. Without loss of
generality this embodiment and the further embodiments will
be described with reference to two domains generally
designated by reference numerals 1 and 2 , but the skilled
person will understand that the principles of the invention
also hold for greater numbers of domains. Although the steps
shown in Figure 1 and subsequent Figures are illustrated and
described in a particular order, this is done only for
exemplary purposes and is not intended to limit the
invention to that particular order unless where it is clear
from the description that a particular step cannot take
place before another step has been completed or vice versa.
Figure 1 shows a preparatory step 100 which consists of the
transmission of common original data signals over the first
and the second domain, and which will be explained in more
detail with reference to Figure 2 . The further steps
illustrated in Figure 1 assume that the original data signal
has been transmitted over the first and second domain 1 , 2
and is available for reception at a first and second
receiver interface.
The embodiment of the method according to the invention as
illustrated in Figure 1 further assumes that the
transmission of the original data signal over the first and
second domain 1 , 2 takes place via a first and second domain
manager. Block 110 illustrates how the original data signal
is received at the first domain manager at step 111 and
retransmitted after an optional digital regeneration of the
signal by the first domain manager at step 112 . In the
substantially simultaneous block 120 another copy of the
original data signal is received at the second domain
manager in step 121 and retransmitted after optional digital
regeneration of the signal in step 122 . The skilled person
will understand that blocks 110 and 120 are optional and
that the invention would operate according to the same
general principles if transmission were to take place
immediately from the common data signal generator 400 to the
joint receiver 300.
The operation of the receiver 300 will now be described in
connection with block 130. Block 130 illustrates how the
first data signal, optionally regenerated by the first
domain manager, is received at a common receiver in step
131, and how the second data signal, optionally regenerated
by the second domain manager, is received by the common
receiver at step 132. Both received data signals, which will
have undergone different respective degradations by the
respective domains through which they have travelled, are
then combined at step 133 in order to reconstruct an optimal
copy of the originally transmitted data signal. The
recombination may take place according to MIMO techniques
that are known in the art .
The transmitted data is extracted from this combined signal
at step 134. The combination of data signals received over
physically distinct paths or domains has the technical
effect that impairments of either one of the domains can be
compensated by means of the other received copy of the
signal and vice versa. In this way, transmission path
diversity is exploited to obtain a better signal quality at
the joint receiver, i.e. a better signal to noise ratio
which results in lower error rates and/or higher bit rates.
Figure 2 illustrates the complementary embodiment of the
present invention which consists of a method to transmit
data signals over plurality of domains in a network such as
a G.hn network. The steps illustrated in Figure 2 correspond
to the abstract block 100 already mentioned in connection
with Figure 1 .
In a first step 101, data to be transmitted over the network
is received by the transmitter 400 via any suitable service
interface such as a logical link control (LLC) service
interface or any other hardware or software entry point into
the protocol stack. The transmitter 400 selects the target
domains 1 , 2 for the transmission of the received data
according to suitable criteria, which may include the
instantaneous load on the various domains, the priority of
the data to be transmitted and any information regarding the
network topology. The skilled person will understand that
only those domains that actually provide a pathway between
the transmitter 400 and the intended receiver 300 should be
selected for the application of the transmission method
according to the present invention.
At the third step 103, the transmitter 400 generates the
data signals corresponding to the received data for
transmission in accordance with the physical requirements on
the selected target domains 1 , 2 . Although it is assumed
that the various domains generally employ the same
modulation techniques for the transmission of data, it will
be understood that this is not a strict prerequisite and
that various degrees of deviation from this assumption may
occur without disrupting the operation of the inventive
concept. In particular, the data signal generated for one
domain may be a frequency- shifted version of the data signal
generated for another domain. At the transmission steps 104
and 105, the generated data signals are transmitted over the
respective selected target domains 1 , 2 .
Although known MIMO techniques may generally be applied to
the present invention, certain additional aspects are
specific to embodiments of the present invention.
In embodiments of the present invention, participating
domains may be selected on the basis of the quality of the
medium of each of the respective domains. Such a selection
requires an assessment of the quality of these media, which
preferably takes place in the course of other (non-MIMO)
communications conducted over these domains, or
alternatively in a separate medium quality assessment step.
In embodiments of the present invention, communication
channels, made up of one or more domains that are being
combined for MIMO communication according to the invention,
are classified, compared with a threshold based on a
particular desired quality of service level, and selectively
activated on the basis of that comparison. The threshold may
pertain to a desired bitrate. For example, the threshold may
pertain to the bitrate that is required to accommodate the
transmission of an HDTV signal, and a system according to an
embodiment of the invention may be configured to activate
only channels that meet this target bitrate.
Figure 3 schematically illustrates an apparatus 300 for
receiving data signals over a plurality of domains in a
network, such as a G.hn network. The apparatus 300 comprises
a multiplexer 320 having a service interface (illustrated
here as the arrow between multiplexer 320 and the LLC
sublayer 310) , which is adapted to present the data received
over the network to the higher layers. The multiplexer 320
further comprises a lower layer interface, i.e. an interface
to connect to one or more physical layer entities that are
designed to interact with interactive physical media (the
lower layer interface is schematically represented by the
arrows interconnecting respective layer entities 331 and 332
with the multiplexer 320) .
The various physical layer entities 331, 332 (only two of
them are illustrated without loss of generality) are
designed to be connected with respective physical domains 1
and 2 according to any of the various physical layer
technologies listed above.
The multiplexer 320 is illustrated here as a modified media
access control (MAC) layer with diversity support
encompassing the MAC functions required for the respective
physical layer entities 331 and 332. The skilled person will
understand that this particular architecture with boundaries
between the various functions provided at the MAC service
interface and at the physical layer interface was chosen
just for illustrative purposes and does not limit the scope
of the invention to implementations following this
particular division of functions.
The multiplexer 320 is adapted to combine the respective
instances of a received physical layer signal received at
the first physical layer entity 331 and the second physical
layer entity 332 respectively, and to decode received data
from the combined instances, for instance by using
conventional MIMO techniques as known in the art.
Figure 4 illustrates the complementary apparatus for
transmitting data signals over a plurality of domains in a
network such as a G.hn network. The apparatus 400 comprises
a demultiplexer 420 having a service interface and a lower
layer interface. The service interface is schematically
represented as the arrow interconnecting the logical link
control sublayer 410 and demultiplexer 420 while the lower
layer interface is schematically represented as the
respective arrows interconnecting the demultiplexer 420 with
the physical layer entities 431 and 432.
The service interface is adapted to receive data for
transmission over said network from an LLC client such as an
Internet Protocol (IP) layer or another network layer
instance (not shown) . Physical layer entities 431 and 432,
operatively connected to respective domains 1 and 2 , and
operate in an analogous way as described for Figure 3 . They
are configured to transmit data received from the
demultiplexer 420 over their respective associated domain.
The demultiplexer 420 is adapted to provide instances of a
physical layer signal to the physical layer entities 431 and
432 wherein the physical layer signal represents the data
provided by the LLC sublayer 410.
The skilled person will understand that the transmitter of
Figure 4 and the received of Figure 3 are functional
descriptions of various roles that may be performed by the
same physical apparatus. Clearly, in a practical embodiment,
an apparatus will comprise a single LLC layer 310/410, logic
for multiplexing and demultiplexing physical layer signals
320/420 and a set of physical layer entities 331/431,
332/432, operatively connected to the respective available
domains 1 , 2 , Each performing the various functions
described above in relation to transmitted data and received
data .
Figures 5 and 6 illustrate an exemplary network architecture
in which the methods and apparatus previously described may
be deployed. The illustrated deployment assumes the presence
of multi-port device functionality that can be exploited to
enable efficient multi-domain diversity. Without loss of
generality, two devices from different domains (Ai and Di,
from domains A and D respectively) establish the
communication session. Note that different domains can use
the same or different mediums (e.g., copper twisted-pairs,
coax, power line cables, wireless) . The transmitter 400 of
Figure 4 may be assumed to be present at domain manager DM-A
and the receiver 300 of Figure 3 may be assumed to be
present at domain manager DM-D, wherein data is transmitted
between DM-A and DM-D over selected target domains B and C
in such a way that DM-D receives separate copies of the same
data signal from respective domains B and C via the
respective domain managers DM-B and DM -C . The receiver DM-D
will then be capable of reconstructing a combined signal
from which it will be able to extract the data transmitted
by DM-A thereby compensati for any impairments introduced
in either domain by means the other copy of a signal .
With respect to the role of the division of functions
between the end points A i and Di, and the intervening domain
managers DM-A, DM-B, DM-C, and DM-D, several alternative
models are within the scope of the present invention.
In a first model, the MIMO transmission is terminated (i.e.,
the multiple signal copies are recombined) at the receiving
domain manager DM-D, while the respective broadcast signals
are pre-processed (i.e. digitally regenerated) by the domain
managers DM-B and DM-C in their respective domains to cope
with the negative effects of the corresponding media. In
this case the receiving device D i does not require any
processing, as it receives a substantially clean copy of the
signal. This case is a combination of joint MIMO processing
at the DM transceivers. It can advantageously be applied to
G.hn networks, because we can rely on the assumption that
all G.hn DM devices are permanently plugged into the
electricity grid. Hence, the power consumption that comes
with the added computational complexity is not an issue.
In a second model, the entire processing (removal of MIMO
channels as well as removal of corresponding medium) is done
at the device D i. Thus, the receiving DM-D is only used as a
relay. Channel information is provided to the device D i
before the processing is carried out. This model comes with
higher complexity at the receiving device D i.
In a third model, the removal of MIMO channels is done at
receiving domain manager DM-D, which then broadcasts the
reconstructed signal into the domain D of the targeted
receiver device D i. The device D i only removes the negati^
effect of its corresponding medium, i.e. the medium of its
domain D . This case provides optimum balance between the
processing complexity and delay at the device Di and DM- D .
The skilled person will understand that a minimum of
interaction will be required between the demultiplexer of
DM-A and the multiplexer of DM-D in order to coordinate the
diversity based transmission according to the present
invention .
DM-A and DM-D are assumed to comprise a "diversity manager"
for that purpose, each of which communicates with its
counterpart using conventional single domain communication.
The diversity manager is a logical function, which enables
the logical "connection" between different DMs, allowing the
sender and the receiver in the MIMO transmission to
coordinate their respective actions. The communication
between the domain managers is schematically illustrated in
Figure 7 as the arrow interconnecting stage 1 with stage 3
where joint communication about rules, priority lists,
queuing and domain selection is exchanged between the
diversity managers of the respective end points. Without
loss of generality, the diversity manager is assumed to be
present in the logical link control (LLC) sublayer 310, 410
of the respective end points.
Hence, unlike traditional MIMO systems, where the end points
have no knowledge of system/network parameters, the
processing algorithm used in embodiments of the present
invention take into consideration different home network
parameters such as domain ID, device ID, queries, QoS,
service/system-wise rules, etc. The MIMO processing requires
coordination between the end points, preferably under the
direction of a "global master" , which may be one of the
diversity managers under consideration.
An exemplary procedure flow is shown in Figure 7 . In this
example the device Ai from domain A transmits its signal to
the device Di from domain D or vice versa. The proposed
concept is divided into three stages:
[Stage 1 ] In the first stage, the diversity manager of
the domain master A (DM-A) sends the signal from device
A l to different domains B and C , selected on the basis
of input parameters (i.e., priority list, rules, queue
and domain selection criteria) among all available
domains (no other domains are shown in Figures 5 and
6 ) . Communication takes place using existing multi-port
functionality or the logical link control (LLC)
function .
[Stage 2 ] Then, the signal from Ai is propagated over
the selected domains.
[Stage 3 ] At the receiver end, the diversity manager of
the domain master D (DM-D) executes the signal
combining step on the basis of the parameters (i.e.,
priority list, rules, queue, and domain selection
criteria) from the "feedback" channel to exploit the
multi -domain diversity. Thus, substantially the same
copies of the transmitted signal are sent over multiple
independent media (i.e., multiple domains), to be
recombined at the receiver end in order to increase the
overall received power. Combining of the analog signals
is possible at the PHY layer or at the packet level
(similar to packet combining in Hybrid ARQ) .
Note that the proposed multi -domain diversity concept does
not require any hardware modification at the end user home
network devices (Ai , Di ) .
The functions of the various elements shown in the FIGs .,
including any functional blocks labeled as "processors" ,
"sublayers", or "entities" may be provided through the use
of dedicated hardware as well as hardware capable of
executing software in association with appropriate software.
When provided by a processor, the functions may be provided
by a single dedicated processor, by a single shared
processor, or by a plurality of individual processors, some
of which may be shared. Moreover, explicit use of the term
"processor" or "controller" should not be construed to refer
exclusively to hardware capable of executing software, and
may implicitly include, without limitation, digital signal
processor (DSP) hardware, network processor, application
specific integrated circuit (ASIC) , field programmable gate
array (FPGA) , read only memory (ROM) for storing software,
random access memory (RAM), and non volatile storage. Other
hardware, conventional and/or custom, may also be included.
Similarly, any switches shown in the FIGS are conceptual
only. Their function may be carried out through the
operation of program logic, through dedicated logic, through
the interaction of program control and dedicated logic, or
even manually, the particular technique being selectable by
the implementer as more specifically understood from the
context .
Claims
1 . A method for receiving data signals transmitted over a
plurality of domains in a network, said apparatus
comprising:
receiving a first data signal at a first physical
interface connected to a first domain from among said
plurality of domains;
receiving a second data signal at a second physical
interface connected to a second domain from among said
plurality of domains;
combining said first data signal and said second data
signal to produce a combined signal; and
extracting transmitted data from said combined signal;
wherein said first data signal and said second data signal
are instances of a common original data signal,
transmitted over said first domain and said second domain
respectively, and having undergone physical signal
degradation associated with said first domain and said
second domain respectively.
The method according to claim 1 , further comprising:
receiving said common original data signal transmitted
over said first domain at a first domain manager as a
first intermediate signal;
retransmitting said first intermediate signal from sa i
first domain manager; and
receiving said retransmitted common original data
signal at said first interface as said first data
signal .
3 . The method according to claim 1 or 2 , further
comprising :
receiving said common original data signal transmitted
over said second domain at a second domain manager as a
second intermediate signal;
retransmitting said second intermediate signal from
said second domain manager; and
receiving said retransmitted second intermediate signal
at said second interface as said second data signal .
4 . A method for transmitting data signals over a plurality
of domains in a network, said method comprising at a network
node :
receiving data for transmission over said network at a
service interface;
producing a data signal representative of said data;
transmitting a first instance of said data signal over
a first physical interface, connected to a first domain
from among said plurality of domains; and
transmitting a second instance of said data signal over
a second physical interface, connected to a second
domain from among said plurality of domains.
5 . The method according to claim 4 , wherein said first
instance and said second instance are shifted relative to
each other in the frequency domain.
6 . The method according to claim 4 or claim 5 , further
comprising selecting said first domain and said second
domain from among said plurality of domains on the basis of
one or more of a priority list and transmission queue
status .
7 . An apparatus for receiving data signals over a
plurality of domains in a network, said apparatus
comprising :
a multiplexer having a service interface and a lowerlayer
interface, said service interface being adapted
to present data received over said network;
a first physical interface, operatively connected to
said lower-layer interface, said first physical
interface being adapted to receive data signals over a
first domain from among said plurality of domains;
a second physical interface, operatively connected to
said lower-layer interface, said second physical
interface being adapted to receive data signals over a
second domain from among said plurality of domains;
wherein said multiplexer is adapted to combine respective
instances of a physical layer signal received from said
first physical interface and said second physical
interface, and to decode said data from said combined
instances ..
8 . The apparatus according to claim 7 , wherein said
network is a G.hn network, and wherein said plurality of
domains are taken from the set of a coaxial cable domain, a
twisted-pair domain, and a power- line communication domain.
9 . The apparatus of claim 7 or claim 8 , wherein said
instances are corresponding versions of one or more OFDM
modulation symbols.
10. The apparatus of claim 9 , wherein said corresponding
versions are shifted relative to each other in the frequency
domain .
11. An apparatus for transmitting data signals over a
plurality of domains in a network, said apparatus
comprising :
a demultiplexer having a service interface and a lowerlayer
interface, said service interface being adapted
to receive data for transmission over said network;
a first physical interface, operatively connected to
said lower-layer interface, said first physical
interface being adapted to transmit data signals over a
first domain from among said plurality of domains;
a second physical interface, operatively connected to
said lower-layer interface, said second physical
interface being adapted to transmit data signals over a
second domain from among said plurality of domains;
wherein said demultiplexer is adapted to provide instances
of a physical layer signal to said first physical
interface and said second physical interface, said
physical layer signal representing said data.
12. The apparatus according to claim 1 , wherein said
network is a G.hn network, and wherein said plurality of
domains are taken from the set of a coaxial cable domain, a
twisted-pair domain, and a power- line communication domain.
13. The apparatus of any of the preceding claims, wherein
said instances are corresponding versions of one or more
OFDM modulation symbols.
14. The apparatus of claim 3 , wherein said corresponding
versions are shifted relative to each other in the frequency
domain .