U.S. patent application number 15/483429 was filed with the patent office on 2018-03-08 for method and apparatus for full-duplex operation in a multipoint-to-multipoint network.
The applicant listed for this patent is Marvell World Trade Ltd.. Invention is credited to Antonio Arregui De La Cruz, Agustin Badenes Corella, Salvador Iranzo Molinero.
Application Number | 20180069687 15/483429 |
Document ID | / |
Family ID | 60190898 |
Filed Date | 2018-03-08 |
United States Patent
Application |
20180069687 |
Kind Code |
A1 |
Iranzo Molinero; Salvador ;
et al. |
March 8, 2018 |
METHOD AND APPARATUS FOR FULL-DUPLEX OPERATION IN A
MULTIPOINT-TO-MULTIPOINT NETWORK
Abstract
A method of conducting full-duplex transmission between first
and second nodes in a communications system having more than two
nodes includes the issuing of a start signal on a channel by the
first node, wherein the start signal signals that full-duplex
transmission is to begin, and identifies the second node as a node
with which full-duplex communication is to occur. The method also
includes, following the issuing of the start signal, the beginning
of full-duplex transmission by the first and second nodes. A node,
for use in a network including at least two nodes, is configured to
initiate full-duplex communication with any other node by issuing a
start signal, where the start signal signals that full-duplex
transmission is to begin, and identifies a second node as a node
with which full-duplex communication is to occur, and by, following
the issuing of the start signal, beginning full-duplex
communication.
Inventors: |
Iranzo Molinero; Salvador;
(Betera, ES) ; Arregui De La Cruz; Antonio;
(Castellon, ES) ; Badenes Corella; Agustin;
(Valencia, ES) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Marvell World Trade Ltd. |
St. Michael |
|
BB |
|
|
Family ID: |
60190898 |
Appl. No.: |
15/483429 |
Filed: |
April 10, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62382908 |
Sep 2, 2016 |
|
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|
62382913 |
Sep 2, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/1469 20130101;
H04L 5/0048 20130101; H04L 25/0202 20130101; H04L 5/143 20130101;
H04W 56/0015 20130101; H04B 17/364 20150115; H04L 5/0053 20130101;
H04L 5/0091 20130101; H04L 5/1461 20130101; H04L 5/16 20130101;
H04L 5/14 20130101; H04L 69/22 20130101; H04B 3/20 20130101; H04L
5/0007 20130101 |
International
Class: |
H04L 5/14 20060101
H04L005/14; H04B 3/20 20060101 H04B003/20; H04L 5/00 20060101
H04L005/00 |
Claims
1. A method of conducting full-duplex transmission between first
and second nodes in a communications system having more than two
nodes, the method comprising: issuing of a start signal on a
channel by the first node, wherein the start signal signals that
full-duplex transmission is to begin, and identifies the second
node as a node with which full-duplex communication is to occur;
and following the issuing of the start signal, beginning
full-duplex transmission by the first node and by the second
node.
2. The method of claim 1 wherein: each node of the first and second
nodes signals a respective duration of its respective transmission;
and duration of the full-duplex transmission between the first and
second nodes is determined by whichever respective duration is
longer.
3. The method of claim 2 further comprising the one of the first
and second nodes whose respective transmission has a shorter
duration transmitting additional symbols to extend its transmission
to match the duration of the transmission of the other of the first
and second nodes.
4. The method of claim 1 further comprising: the first node
signaling a required transmission duration based on its data to be
transmitted; and the second node adjusting its transmission to fit
the required transmission duration.
5. The method of claim 4 wherein the second node adjusting its
transmission comprises the second node shortening its transmission
by decreasing the amount of data to be sent.
6. The method of claim 4 wherein the second node adjusting its
transmission comprises the second node transmitting additional
symbols to extend its transmission to match the duration of the
transmission of first a node.
7. The method of claim 1 further comprising performing echo
cancellation on the full-duplex transmission to remove, from a
transmission in one direction, an echo of a transmission in another
direction.
8. The method of claim 1 wherein: the full-duplex transmission is
performed using orthogonal frequency division modulation (OFDM);
the first node transmits on a first set of OFDM subcarriers; and
the second node transmits on a second set of OFDM subcarriers.
9. The method of claim 1 wherein: the full-duplex transmission is
performed using orthogonal frequency division modulation (OFDM);
and at least one of the first node and the second node transmits a
signal on at least one OFDM subcarrier to signal other nodes that
the channel is in use.
10. A method of conducting full-duplex transmission between nodes
in a communications system having more than two nodes, the method
comprising: establishing a medium access plan assigning respective
temporal slots to respective pairs of nodes; and on opening of a
respective temporal slot, initiating full-duplex transmission
between nodes in the respective pair of nodes to which the
respective temporal slot is assigned; wherein: any node in the
communications system is capable of full-duplex communication with
any other node according to the medium access plan.
11. The method of claim 10 wherein the initiating full-duplex
transmission comprises: issuing of a start signal on a channel by
one of the nodes in the respective pair of nodes, signaling that
full-duplex transmission is to begin; and following the issuing of
the start signal, beginning full-duplex transmission by both of the
nodes in the respective pair of nodes.
12. The method of claim 10 wherein: each node in the respective
pair of nodes signals a respective duration of its respective
transmission; and duration of the full-duplex transmission between
the nodes in the respective pair of nodes is determined by
whichever respective duration is longer.
13. The method of claim 12 wherein the one of the nodes in the
respective pair of nodes whose respective transmission has a
shorter duration transmits additional symbols to extend its
transmission to match the duration of the transmission of the other
of the first and second nodes.
14. The method of claim 10 further comprising: a first one of the
nodes in the respective pair of nodes signaling a required
transmission duration based on its data to be transmitted; and a
second one of the nodes in the respective pair of nodes adjusting
its transmission to fit the required transmission duration.
15. The method of claim 10 further comprising performing echo
cancellation on the full-duplex transmission to remove, from a
transmission in one direction, an echo of a transmission in another
direction.
16. The method of claim 10 wherein: the full-duplex transmission is
performed using orthogonal frequency division modulation; a first
set of subcarriers is used for transmission by a first node in the
respective pair of nodes; and a second set of subcarriers is used
for transmission by a second node in the respective pair of
nodes.
17. A node for use in a communications network including at least
two nodes; wherein: the node is configured to initiate full-duplex
communication with any other node by: issuing a start signal on a
channel, wherein the start signal signals that full-duplex
transmission is to begin, and identifies a second node as a node
with which full-duplex communication is to occur; and following the
issuing of the start signal, beginning full-duplex
communication.
18. A communications system comprising a plurality of the node of
claim 17.
19. The communications system of claim 18 wherein: each node
signals a respective duration of its respective transmission; and
duration of the full-duplex transmission is determined by whichever
respective duration is longer.
20. The communications system of claim 19 further comprising the
node whose respective transmission has shorter duration
transmitting additional symbols to extend its transmission to match
the duration of the transmission of the node whose respective
transmission has a longer duration.
21. The communications system of claim 18 further comprising: one
node signaling a required transmission duration based on its data
to be transmitted; and the other node adjusting its transmission to
fit the required transmission duration.
22. The communications system of claim 18 wherein: the full-duplex
transmission is performed using orthogonal frequency division
modulation (OFDM); one node transmits on a first set of OFDM
subcarriers; and the other node transmits on a second set of OFDM
subcarriers.
23. The communications system of claim 18 wherein: the full-duplex
transmission is performed using orthogonal frequency division
modulation (OFDM); and at least one of the nodes transmits a signal
on at least one OFDM subcarrier to signal other nodes that the
channel is in use.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This claims the benefit of copending, commonly-assigned
United States Provisional Patent Applications Nos. 62/382,908 and
62/382,913, both filed Sep. 2, 2016, each of which is hereby
incorporated by reference herein in its respective entirety.
FIELD OF USE
[0002] This disclosure relates to a method and apparatus for
providing full-duplex operation in a multipoint-to-multipoint
network.
BACKGROUND
[0003] The background description provided herein is for the
purpose of generally presenting the context of the disclosure. Work
of the inventors hereof, to the extent the work is described in
this background section, as well as aspects of the description that
may not otherwise qualify as prior art at the time of filing, are
neither expressly nor impliedly admitted to be prior art against
the present disclosure.
[0004] Many full-duplex systems operate in a point-to-point mode in
which two nodes communicate between themselves. In such a case,
Medium Access Control (MAC) is not required given that each of the
two nodes can always transmit while simultaneously receiving from
the other node. Examples of full-duplex point-to-point systems are
Ethernet 1000BASE-T and 10GBASE-T systems.
[0005] Some full-duplex systems operate in a point-to-multipoint
mode in which one node (sometimes referred to as a "master node" or
"access point") transmits to multiple other nodes and receives
transmission from the other nodes. There is no direct communication
between the other nodes. The master node or access point transmits
in the downstream direction, and the other nodes share the upstream
transmissions. The master node or access point is thus the only
node that can initiate a full-duplex transmission.
SUMMARY
[0006] A method of conducting full-duplex transmission between
first and second nodes in a communications system having more than
two nodes includes the issuing of a start signal on a channel by
the first node, wherein the start signal signals that full-duplex
transmission is to begin, and identifies the second node as a node
with which full-duplex communication is to occur. The method also
includes, following the issuing of the start signal, beginning
full-duplex transmission by the first node and by the second
node.
[0007] In such a method, each node of the first and second nodes
signals a respective duration of its respective transmission, and
duration of the full-duplex transmission between the first and
second nodes is determined by whichever respective duration is
longer.
[0008] The method further includes the one of the first and second
nodes whose respective transmission has a shorter duration
transmitting additional symbols to extend its transmission to match
the duration of the transmission of the other of the first and
second nodes. Alternatively, the method includes the first node
signaling a required transmission duration based on its data to be
transmitted, and the second node adjusting its transmission to fit
the required transmission duration. In such a method, the second
node adjusting its transmission includes the second node shortening
its transmission by decreasing the amount of data to be sent, or
the second node adjusting its transmission includes the second node
transmitting additional symbols to extend its transmission to match
the duration of the transmission of first a node.
[0009] The method further includes performing echo cancellation on
the full-duplex transmission to remove, from a transmission in one
direction, an echo of a transmission in another direction.
[0010] In the method, the full-duplex transmission may be performed
using orthogonal frequency division modulation (OFDM), the first
node transmits on a first set of OFDM subcarriers, and the second
node transmits on a second set of OFDM subcarriers.
[0011] In the method, the full-duplex transmission is performed
using orthogonal frequency division modulation (OFDM), and at least
one of the first node and the second node transmits a signal on at
least one OFDM subcarrier to signal other nodes that the channel is
in use.
[0012] A method of conducting full-duplex transmission between
nodes in a communications system having more than two nodes
includes establishing a medium access plan assigning respective
temporal slots to respective pairs of nodes, and on opening of a
respective temporal slot, initiating full-duplex transmission
between nodes in the respective pair of nodes to which the
respective temporal slot is assigned, wherein any node in the
communications system is capable of full-duplex communication with
any other node according to the medium access plan.
[0013] In the method, the initiating full-duplex transmission
includes issuing of a start signal on a channel by one of the nodes
in the respective pair of nodes, signaling that full-duplex
transmission is to begin, and following the issuing of the start
signal, beginning full-duplex transmission by both of the nodes in
the respective pair of nodes.
[0014] In the method, each node in the respective pair of nodes
signals a respective duration of its respective transmission, and
duration of the full-duplex transmission between the nodes in the
respective pair of nodes is determined by whichever respective
duration is longer. The one of the nodes in the respective pair of
nodes whose respective transmission has a shorter duration may
transmit additional symbols to extend its transmission to match the
duration of the transmission of the other of the first and second
nodes.
[0015] The method also includes a first one of the nodes in the
respective pair of nodes signaling a required transmission duration
based on its data to be transmitted, and a second one of the nodes
in the respective pair of nodes adjusting its transmission to fit
the required transmission duration.
[0016] The method also includes performing echo cancellation on the
full-duplex transmission to remove, from a transmission in one
direction, an echo of a transmission in another direction.
[0017] In the method, the full-duplex transmission is performed
using orthogonal frequency division modulation, a first set of
subcarriers is used for transmission by a first node in the
respective pair of nodes, and a second set of subcarriers is used
for transmission by a second node in the respective pair of
nodes.
[0018] A node, for use in a communications network including at
least two nodes, is configured to initiate full-duplex
communication with any other node by issuing a start signal on a
channel, wherein the start signal signals that full-duplex
transmission is to begin, and identifies a second node as a node
with which full-duplex communication is to occur, and following the
issuing of the start signal, beginning full-duplex communication. A
communications system includes a plurality of that node.
[0019] In such a communications system, each node signals a
respective duration of its respective transmission, and duration of
the full-duplex transmission is determined by whichever respective
duration is longer.
[0020] The communications system further includes the node whose
respective transmission has shorter duration transmitting
additional symbols to extend its transmission to match the duration
of the transmission of the node whose respective transmission has a
longer duration.
[0021] The communications system further includes one node
signaling a required transmission duration based on its data to be
transmitted, and the other node adjusting its transmission to fit
the required transmission duration.
[0022] In the communications system, the full-duplex transmission
is performed using orthogonal frequency division modulation (OFDM),
one node transmits on a first set of OFDM subcarriers, and the
other node transmits on a second set of OFDM subcarriers.
[0023] In the communications system, the full-duplex transmission
is performed using orthogonal frequency division modulation (OFDM),
and at least one of the nodes transmits a signal on at least one
OFDM subcarrier to signal other nodes that the channel is in
use.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Further features of the disclosure, its nature and various
advantages, will be apparent upon consideration of the following
detailed description, taken in conjunction with the accompanying
drawings, in which like reference characters refer to like parts
throughout, and in which:
[0025] FIG. 1 is a schematic representation of a system operating
in accordance with an implementation of the subject matter of this
disclosure;
[0026] FIG. 2 is a flow diagram of an implementation of a first
method according to the subject matter of this disclosure;
[0027] FIG. 3 is a representation of one variant of a signaling
format used in accordance with the subject matter of this
disclosure;
[0028] FIG. 4 is a representation of another variant of a signaling
format used in accordance with the subject matter of this
disclosure;
[0029] FIG. 5 is a flow diagram of an implementation of a second
method according to the subject matter of this disclosure;
[0030] FIG. 6 is a schematic representation of a node used in
implementations of the subject matter of this disclosure.
DETAILED DESCRIPTION
[0031] For purposes of this disclosure, "full-duplex" communication
should be considered to mean communication in which nodes transmit
and receive at the same time, using at least some overlapping
frequencies. Because there is usually some residual echo of the
transmit signal in the receive path, each node has to perform echo
cancellation. The received signal is:
r(t)=y(t)+a(t)+n(t)
where r(t) is the received signal, y(t) is the desired signal
received from a distant transmitter, a(t) is the echo of the node's
own transmit signal, and n(t) is noise. In receive mode, the node
estimates a(t) and subtracts it from r(t). The echo signal is
obtained via the convolution of the echo channel with the
transmitted signal:
a(t)=x(t)*h(t)
where x(t) is the transmitted signal and h(t) is the echo channel.
The echo channel may be estimated by the node by using a sounding
signal and/or adaptive filtering techniques.
[0032] As noted above, many full-duplex systems operate in a
point-to-point mode in which two nodes communicate between
themselves. In such a case, Medium Access Control (MAC) is not
required given that each of the two nodes can always transmit while
simultaneously receiving from the other node. Examples of
full-duplex point-to-point systems are Ethernet 1000BASE-T and
10GBASE-T systems.
[0033] Some full-duplex systems operate in a point-to-multipoint
mode in which one node (sometimes referred to as a "master node" or
"access point") transmits to the other nodes and receives
transmission from the other nodes. There is no direct communication
between the other nodes. The master node or access point transmits
in the downstream direction, and the other nodes share the upstream
transmissions. The master node or access point is thus the only
node that can initiate a full-duplex transmission.
[0034] In accordance with implementations of the subject matter of
this disclosure, in a full-duplex system, each node in a plurality
of nodes (which may include all nodes) is configured to initiate
full-duplex communication with each other node. In effect, each
node in the plurality of nodes can be a master node. A system in
accordance with the subject matter of this disclosure typically
includes up to 32 nodes. Such a system may be a home network, a
small office network, or an access system.
[0035] As seen in FIG. 1, a system 100 operating in accordance with
an implementation of the subject matter of this disclosure,
includes at least four nodes A, B, C, D. In this implementation,
the aforementioned plurality of nodes includes all nodes in system
100. Either of nodes A and B can initiate full-duplex communication
with the other of nodes A and B over path 101. Either of nodes A
and C can initiate full-duplex communication with the other of
nodes A and C over path 102. Either of nodes A and D can initiate
full-duplex communication with the other of nodes A and D over path
103. Either of nodes B and C can initiate full-duplex communication
with the other of nodes B and C over path 104. Either of nodes B
and D can initiate full-duplex communication with the other of
nodes B and D over path 105. Either of nodes C and D can initiate
full-duplex communication with the other of nodes C and D over path
106. If there are additional nodes in system 100, then any one of
those other nodes can initiate full-duplex communication with any
other node in system 100 over a path between them.
[0036] Although paths 101-106 are shown in FIG. 1 as being
individual paths, paths 101-106 are only logical representations of
communication paths. System 100 could be a wired system in which
paths 101-106 are actual physical paths, or a wired system in which
paths 101-106 are logical paths on a single multi-channel physical
path (e.g., a bus to which all nodes are connected). Alternatively,
system 100 could be a wireless system in which paths 101-106 are
wireless connections.
[0037] In order to avoid collisions, and to allow each node to
estimate the echo channel for echo cancellation (i.e., as noted
above, to cancel from a transmission in one direction echoes
remaining from a transmission in the other direction), a control
protocol, such as a Medium Access Control (MAC) protocol, for
system 100 should control when and how a node may initiate
full-duplex communication on a channel. In one implementation, a
MAC protocol such as, e.g., a CSMA/CA (Carrier Sense Multiple
Access with Collision Avoidance) protocol is used to access a
channel. A node, which may be referred to as a "primary
transmitter," that is initiating a full-duplex communication
broadcasts a signal to access the communications medium. This
signal, which may be referred to as a Full-Duplex Start (FDS)
signal, reserves the channel and identifies the other node that
will form the full-duplex pair. All other nodes in system 100 also
receive this signal.
[0038] Once the other node that is identified in the FDS (also
referred to as the "secondary transmitter") receives the FDS, the
secondary transmitter knows that it is the other member of the
full-duplex pair and can also transmit. From that point on, the
other nodes in system 100, which also process the FDS (see below in
connection with FIG. 6), refrain from attempting to access the
channel being used by the primary transmitter node and the
secondary transmitter node. Both the primary transmitter node and
the secondary transmitter node can start a full-duplex
communication (with both nodes transmitting and receiving
simultaneously) once a predetermined time, as discussed below, has
elapsed from the transmission of the FDS by the primary
transmitter.
[0039] In a variation, a similar scheme could be used to implement
three-way full-duplex communication among three nodes, in which
Node A transmits to node B, and node C transmits back to node A.
This is a less common case than two-way full duplex, but it is
possible in some scenarios. In such a scheme, the FDS identifies
node C as the secondary transmitter, but the header of messages
transmitted by the primary transmitter indicates that node B is the
intended receiver of data transmitted by node A. In order for such
an arrangement to work, node B must not receive the signal
transmitted by node C. That is, node B and node C must be selected
and configured so that they do not interfere each other. For
example, in a frequency-division multiplexing environment, they
could be configured to use different subcarriers.
[0040] A method 200 for initiating a full-duplex transmission
between nodes in a network system, according to an implementation
of the subject matter of this disclosure using an FDS signal, is
diagrammed in FIG. 2. At 201, a primary transmitter node sends an
FDS signal. At 202, all other nodes in system 100 receive the FDS
signal. At 203, nodes other than the secondary transmitter node
designated in the FDS signal remove themselves from the channel (by
refraining from attempting to access the channel) for a duration
derived from a signal from the primary transmitter (see below). At
204, both the primary transmitter node and the secondary
transmitter node wait for a predetermined duration. Normally the
predetermined duration is of zero length. However, there may be a
short wait, such as the time needed for the secondary node to
change from receive mode to transmit mode, which may be, e.g., one
or a small number of clock cycles. At 205, both the primary
transmitter node and the secondary transmitter node begin
full-duplex transmission, ending the initiation phase.
[0041] In one variant of a signaling format 300 used in accordance
with the subject matter of this disclosure, shown in FIG. 3, after
sending the FDS 301, the primary transmitter node sends a header
signal portion 311 specifying the total duration of the full-duplex
transmission. Following header signal portion 311, the primary
transmitter node sends a training signal portion 321 and one or
more data symbols 331. At the same time, following header signal
portion 311, the secondary transmitter node, advised of the total
duration of the full-duplex transmission, sends a header/training
signal portion 322, followed by one or more data symbols 332. The
amount of data sent in data symbols 332 is adjusted by the
secondary transmitter node to fit the duration set by the primary
transmitter node in header signal portion 311.
[0042] In another variant of a signaling format 400 used in
accordance with the subject matter of this disclosure, shown in
FIG. 4, after the primary transmitter node sends the FDS 401, both
the primary transmitter node and the secondary transmitter node
wait for the aforementioned predetermined duration (which normally
is of zero length, as discussed above) to elapse. Both the primary
transmitter node and the secondary transmitter node then send a
respective header/training signal portion 411, 412 specifying the
respective duration required to send the total amount of data that
the respective node has to send in one or more symbols 431, 432.
Because those durations could be, and likely are, different for
each node, the total duration will be the longer of the two
durations. The node with the shorter duration will extend its frame
with dummy or silence symbols. In any case the node with the
shorter duration may transmit acknowledgments for the data it
receives from the other node.
[0043] In a second implementation of the subject matter of this
disclosure, based on time-division multiplexing, different nodes
are assigned temporal slots during which they can engage in
full-duplex communication. The assignments may be referred to as a
"Medium Access Plan" (MAP), which may be promulgated by one of the
nodes that is tasked with that function. In one variant of such an
implementation, nodes are assigned to slots by pairs, and in each
slot, the pairs assigned to that slot engage in full-duplex
communication (unless neither node has information to transmit, in
which case the slot remains unused). The assigning of temporal
slots is made according to an analysis of which nodes are likely to
need to transmit to which other nodes. Such an analysis may include
review of previous resource reservation requests.
[0044] Normally, the MAP remains in effect until a new MAP is sent.
Therefore, in order to ensure that every possible pair of nodes
that may need to communicate can communicate, then unless the
system includes a resource request mechanism, the MAP should
include a slot for all possible pairings. However, in all but the
smallest systems, assigning a temporal slot for every possible pair
of nodes is impractical. One solution may be for the MAP to include
a repeating pattern of slots that does not include every possible
pairing, but on every nth repetition, where n is determined by the
system design, the pattern is expanded to include all possible
pairings.
[0045] In a second variant of a time-division multiplexing
implementation, the MAP assigns temporal slots to individual nodes
as primary transmitters. Upon the opening of any temporal slot, the
primary transmitter assigned to that temporal slot begins
full-duplex communication with a desired other node by sending an
FDS identifying that other node. The full-duplex communication
session lasts only until the temporal slot closes, unless both of
the participating nodes require less than the full duration of the
temporal slot to transmit whatever information they have to
transmit. If the full-duplex communication session does not occupy
the full duration of the temporal slot, the channel remains
inactive for the balance of the temporal slot.
[0046] Returning to the first variant of a time-division
multiplexing implementation in which each temporal slot is assigned
to a particular pair of nodes, in one version of such a variant of
a time-division multiplexing implementation, the two nodes assigned
to a temporal slot begin transmitting immediately upon opening of
that temporal slot. In a second version of such a variant of a
time-division multiplexing implementation, upon opening of a
temporal slot, even though the temporal slot is assigned
exclusively to a particular pair of nodes, no transmission occurs
until one of the nodes assigned to that temporal slot sends an FDS
signal as in the first implementation, as discussed above. In this
version of such a variant, if no FDS signal is sent by either node
in a particular temporal slot, no transmission occurs during that
temporal slot.
[0047] A method 500 for initiating a full-duplex transmission
according to a time-division multiplexing implementation of the
subject matter of this disclosure is diagrammed in FIG. 5. At 501,
a MAP is promulgated from one of the nodes to all nodes. At 502 a
next temporal slot is opened (i.e., a system clock reaches that
temporal slot). At 503 it is determined whether FDS signaling is in
use. If FDS signaling is not in use, then at 504 the two nodes
assigned to that temporal slot begin transmitting for the duration
of the temporal slot. At the conclusion of the temporal slot at
505, the two nodes stop transmitting and flow returns to 502 for
the next temporal slot.
[0048] If at 503 it is determined that FDS signaling is in use,
then at 506, one of the nodes assigned to the temporal slot, which
has been designated "primary," sends an FDS signal. At 507, both
the primary node assigned to the temporal slot and the other node
with which the primary nodes is communicating (the other node may
or may not also be assigned to the temporal slot, depending on the
particular variant that is implemented as discussed above) wait for
a predetermined duration. At 508, both of the nodes that are
communicating in the temporal slot node begin full-duplex
transmission for a duration determined by signaling. At the
conclusion of the temporal slot at 505, the two nodes stop
transmitting (if the transmission has not concluded earlier) and
flow returns to 502 for the next temporal slot.
[0049] In some variants of the first implementation based on FDS
signaling, nodes not participating in the full-duplex transmission
also need to know its duration, so they can contend for access to
the channel when the full-duplex transmission is finished. Where
transmission duration is not known ahead of time, because it is
based on the duration of the longest of both transmissions, each of
the two nodes that are participating in the full-duplex
transmission has to signal the duration in an orthogonal way that
can be understood by all nodes, including nodes that cannot
separate the two transmitted signals. According to one mechanism,
where the communication uses orthogonal frequency-division
multiplexing (OFDM), each of the two nodes involved in a
full-duplex transmission could transmit the duration information in
a subcarrier that is not used by the other of the two nodes. If
duration is determined solely by one of the nodes, then only that
one node need signal the duration to other nodes. The use of such
orthogonal transmissions to signal channel availability allows any
half-duplex nodes (not shown) that may be present in the system to
participate in the same MAC scheme along with full-duplex
nodes.
[0050] Another situation that may be addressed by the use of OFDM
signaling is a situation where echo cancellation cannot be
performed, either because of low signal strength or where one node
does not have much or any data to transmit to the other node. If
OFDM is used, then rather than assigning all subcarriers in a
channel to both nodes using the channel, the subcarriers in the
channel can be divided up between the two nodes, so that there is
no echo of transmissions by one node in the transmissions of the
other node. Although such an arrangement would not be in-band
full-duplex, it is still full-duplex in the sense defined above.
Specifically, it is full duplex, in the sense of simultaneous
bidirectional communication. And although different frequencies are
used, in an OFDM context, and the gap between the subcarriers used
in the different directions would not be large enough to allow use
of external filters (e.g., diplexers). Therefore, there still
should be precise time synchronization and coordination of
transmissions between primary and secondary nodes, as provided
using the FDS signaling described above.
[0051] G.hn OFDM communication implementations of the subject
matter of this disclosure are described in concurrently-filed,
commonly-assigned U.S. patent application Ser. No. ______, entitled
"METHODS AND APPARATUS FOR PERFORMING FULL DUPLEX COMMUNICATIONS
USING A G.hn PROTOCOL" (Attorney Docket No.
MP10138/004048-0477-101), which is hereby incorporated by reference
herein in its entirety.
[0052] As shown in FIG. 6, a node 600 that may be used in a system
implemented according to the subject matter of this disclosure
includes transceiver circuitry 601, memory 602 for storing
parameters of a MAC scheme, possibly including a MAP, and a
controller 603 configured to operate transceiver circuitry 601 in
accordance the MAC scheme and/or MAP stored in memory 602.
Controller 603 may include detection hardware (not shown) that
determines whether a signal is intended for node 600 by computing
the phase difference between consecutively-received carriers, and
compares that phase difference with the phase difference that would
be expected if the signal was formed with a known sequence of
phases. When there is a good match of the expected phase
differences across a sufficient number of preamble carriers,
controller 603 declares that it has found a signal that matches the
known sequence of phases it was looking for.
[0053] Thus it is seen that a MAC scheme, and a system implementing
that scheme, in which any node can initiate full-duplex
transmission with any other node, have been provided.
[0054] As used herein and in the claims which follow, the
construction "one of A and B" shall mean "A or B."
[0055] It is noted that the foregoing is only illustrative of the
principles of the invention, and that the invention can be
practiced by other than the described embodiments, which are
presented for purposes of illustration and not of limitation, and
the present invention is limited only by the claims which
follow.
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