Leveraging coherent distributed space-time codes for noncoherent communication in relay networks via training
View Patent ↗In a training cycle, a source node transmits at least one pilot symbol to relay nodes in a training cycle. The relay nodes each amplifies and forwards the pilot symbol to a destination node in an assigned time slot in the training cycle. The destination node sequentially receives multiple versions of the pilot symbol from the relay nodes and estimates channel information based on the multiple versions of the pilot symbol. In data transmission cycles that follow the training cycle, the nodes apply coherent distributed space-time block code (DSTBC) with the estimated channel information to communicate data symbols. The power allocation between training and data cycles may be adjusted to improve the error performance. The nodes may also apply orthogonal frequency division multiplexing (OFDM) based DSTBC when timing errors are not known.
1. A method for one of a plurality of relay nodes in a relay network to amplify and forward data from a source node to a destination node, the method comprising:
receiving a version of at least one pilot symbol from the source node, the at least one pilot symbol being known to the destination node in a training cycle;
amplifying and forwarding the version of the at least one pilot symbol to the destination node in a time slot in the training cycle, wherein the relay nodes have respective time slots to transmit their versions of the at least one pilot symbol;
receiving a version of data symbols from the source node in a data transmission cycle that follows the training cycle;
generating a new version of the data symbols according to a coherent distributed space-time block code (DSTBC) in the data transmission cycle; and
amplifying and forwarding the new version of the data symbols to the destination node in the data transmission cycle.
2. The method of claim 1 , wherein the at least one pilot symbol consists of a complex number 1.
3. The method of claim 1 , wherein the at least one pilot symbol comprises multiple complex number 1s.
4. The method of claim 1 , further comprising determining an allocation of a first power for training and a second power for data transmission that improves error performance.
5. The method of claim 4 , wherein the first power is greater than the second power by a percentage that ranges up to and including 40%.
6. A method for a destination node in a relay network to communicate with a source node through relay nodes, the method comprising:
sequentially receiving multiple versions of at least one pilot symbol from the relay nodes, the at least one pilot symbol being transmitted from the source node to the relay nodes, the at least one pilot symbol being known to the destination node;
estimating channel information based on the multiple versions of the at least one pilot symbol;
receiving multiple versions of data symbols from the relay nodes at substantially the same time, the data symbols being transmitted from the source node to the relay nodes, the multiple versions of the data symbols being generated by the relay nodes according to a coherent distributed space-time block code (DSTBC); and
decoding the multiple versions of the data symbols to determine data from the source node according to the coherent DSTBC using estimated channel information.
7. The method of claim 6 , wherein the at least one pilot symbol consists of a complex number of 1.
8. The method of claim 7 , wherein said estimating channel information comprises determining an estimated equivalent channel matrix as follows:
h
^
=
π
1
π
2
P
t
2
R
π
1
P
t
+
1
(
π
2
P
t
R
+
π
1
π
2
P
t
2
R
π
1
P
t
+
1
+
1
)
-
1
y
^
,
where P t is the total power dedicated to training, π 1 is a fraction of the total power P t for the source node to transmit to the relay nodes, π 2 is a fraction of the total power P t for the relay nodes to transmit to the source node, R is the number of relay nodes, and ŷ is the multiple versions of the at least one pilot symbol received at the destination node.
9. The method of claim 8 , wherein said decoding the multiple versions of the data symbols comprises:
X
^
=
arg
min
X
∈
Λ
y
-
π
1
π
2
P
d
2
π
1
P
d
+
1
Xh
F
2
.
where {circumflex over (X)} is the decoded data at the destination node, P d is the total power dedicated to data transmission, Λ denotes the set of all possible codeword matrices X, y is the multiple versions of the data symbols received at the destination node, h is the equivalent channel matrix to be replaced with the estimated equivalent channel matrix, and F is the total number of data transmission cycle that can be accommodated in a channel quasi-static duration.
10. The method of claim 6 , wherein:
the at least one pilot symbol comprises multiple complex number 1s;
said sequentially receiving multiple version of the at least one pilot symbol comprises applying orthogonal frequency division multiplexing (OFDM) decoding to the multiple complex number 1s;
said estimating channel information comprises estimating the channel information for OFDM subcarriers; and
said decoding the multiple versions of the data symbols comprises applying OFDM based coherent DSTBC using the estimated channel information for the OFDM subcarriers.
11. A non-transitory computer-readable storage medium encoded with computer-executable instructions for execution by one of a plurality of relay nodes in a relay network to amplify and forward data from a source node to a destination node, the instructions comprising:
receiving a version of at least one pilot symbol from the source node, the at least one pilot symbol being known to the destination node;
amplifying and forwarding the version of the at least one pilot symbol to the destination node in a time slot, wherein the relay nodes are assigned respective time slots to transmit their versions of the at least one pilot symbol;
receiving a version of data symbols from the source node in a data transmission cycle that follows the training cycle;
generating a new version of the data symbols according to a coherent distributed space-time block code (DSTBC); and
amplifying and forwarding the new version of the data symbols to the destination node.
12. The non-transitory computer-readable storage medium of claim 11 , wherein the at least one pilot symbol consists of a complex number 1.
13. The non-transitory computer-readable storage medium of claim 11 , wherein:
the at least one pilot symbol comprises multiple complex number 1s;
said amplifying and forwarding the version of the at least one pilot symbol comprises applying orthogonal frequency division multiplexing (OFDM) encoding to the multiple complex number 1s; and
the coherent DSTBC comprises an OFDM based coherent DSTBC.
14. The non-transitory computer-readable storage medium of claim 11 , wherein the instructions further comprise determining an allocation of a first power for training and a second power for data transmission that improves error performance.
15. The non-transitory computer-readable storage medium of claim 14 , wherein the first power is greater than the second power by a percentage that ranges up to and including 40%.
16. A non-transitory computer-readable storage medium encoded with computer-executable instructions for execution by a destination node in a relay network to communicate with a source node through relay nodes, the instructions comprising:
sequentially receiving multiple versions of at least one pilot symbol from the relay nodes, the at least one pilot symbol being transmitted from the source node to the relay nodes, the at least one pilot symbol being known to the destination node;
estimating channel information based on the multiple versions of the at least one pilot symbol;
receiving multiple versions of data symbols from the relay nodes at substantially the same time, the data symbols being transmitted from the source node to the relay nodes, the multiple versions of the data symbols being generated by the relay nodes according to a coherent distributed space-time block code (DSTBC); and
decoding the multiple versions of the data symbols to determine data from the source node according to the coherent DSTBC using estimated channel information.
17. The non-transitory computer-readable storage medium of claim 16 , wherein the at least one pilot symbol consists of a complex number of 1.
18. The non-transitory computer-readable storage medium of claim 17 , wherein said estimating channel information comprises determining an estimated equivalent channel matrix as follows:
h
^
=
π
1
π
2
P
t
2
R
π
1
P
t
+
1
(
π
2
P
t
R
+
π
1
π
2
P
t
2
R
π
1
P
t
+
1
+
1
)
-
1
y
^
,
where P t is the total power dedicated to training, π 1 is a fraction of the total power P t for the source node to transmit to the relay nodes, π 2 is a fraction of the total power P t for the relay nodes to transmit to the source node, R is the number of relay nodes, and ŷ is the multiple versions of the at least one pilot symbol received at the destination node.
19. The non-transitory computer-readable storage medium of claim 18 , wherein said decoding the multiple versions of the data symbols comprises:
X
^
=
arg
min
X
∈
Λ
y
-
π
1
π
2
P
d
2
π
1
P
d
+
1
Xh
F
2
.
where {circumflex over (X)} is the decoded data at the destination node, P d is the total power dedicated to data transmission, Λ otes the set of all possible codeword matrices X, y is the multiple versions of the at least one pilot symbol received at the destination node, h is the equivalent channel matrix to be replaced with the estimated equivalent channel matrix, and F is the total number of data transmission cycle that can be accommodated in a channel quasi-static duration.
20. The non-transitory computer-readable storage medium of claim 16 , wherein:
the at least one pilot symbol comprises multiple complex number 1s;
said sequentially receiving multiple version of the at least one pilot symbol comprises applying orthogonal frequency division multiplexing (OFDM) decoding to the multiple complex number 1s;
said estimating channel information comprises estimating the channel information for OFDM subcarriers; and
said decoding the multiple versions of the data symbols comprises applying OFDM based coherent DSTBC using the estimated channel information for the OFDM subcarriers.
21. A relay network, comprising
a source node for:
transmitting at least one pilot symbol to relay nodes in a training cycle; and
transmitting data symbols to the relay nodes in a data transmission cycle, wherein the data symbols represent data;
the relay nodes each for:
receiving a version of the at least one pilot symbol from the source node in the training cycle;
amplifying and forwarding the version of the at least one pilot symbol to a destination node in a time slot in the training cycle, wherein the relay nodes are assigned respective time slots to transmit the at least one pilot symbol;
receiving a version of the data symbol from the source node in the data transmission cycle that follows the training cycle;
generating a new version of the data symbols according to a coherent distributed space-time block code (DSTBC) in the data transmission cycle;
amplifying and forwarding the new version of the data symbols to the destination node in the data transmission cycle; and
the destination node for:
sequentially receiving multiple versions of the at least one pilot symbol from the relay nodes in the training cycle, wherein the at least one pilot symbol is known to the destination node;
estimating channel information based on the multiple versions of the at least one pilot symbol in the training cycle;
receiving multiple versions of the data symbols from the relay nodes at substantially the same time in the data transmission cycle; and
decoding the multiple versions of the data symbols to determine the data from the source node according to the coherent DSTBC using the estimated channel information in the data transmission cycle.