Method for transmitting packets in relay networks
View Patent ↗A method transmits an L bit packet in a relay network including a source node, a relay node and a destination node. The source node partitions the packet into first fragment of βL bits and a second fragment of (1−β) bits. The first fragment is transmitted from the source node to the relay node at a first data rate during a first phase. The second fragment is transmitted from the source node to the destination node at a second data rate during a second phase while the first fragment is retransmitted from the relay node to the destination node at a third data rate.
1. A method for transmitting a packet in a relay network including a source node, a relay node and a destination node, comprising:
partitioning, in a source node of a relay network, a packet into a first fragment and a second fragment, wherein the packet has L bits and the first fragment has βL and the second fragment has (1−β)L bits, where β is a splitting ratio;
transmitting the first fragment from the source node to a relay node of the relay network at a first data rate during a first phase;
transmitting the second fragment from the source node to a destination node in the relay network at a second data rate during a second phase;
combining the first fragments and the second fragment in the destination node;
retransmitting the first fragment from the relay node to the destination node at a third data rate during the second phase; and
optimizing the first, second and third data rates so that a total energy consumption in the network is minimized, wherein P 0 is a power used by the source node during the first phase, p s is the power used by the source during the second phase, and p r is the power used by the relay node during the second phase and wherein a power gain between the source node s and the relay node r is |h sr | 2 , and the power gain between the relay node s and the destination node d is |h rd | 2 , and the combining is according to h sd and h rd , and wherein the energy consumption is minimized according to
β
LP
r
R
rd
-
mpr
+
(
1
-
β
)
LP
s
R
sd
-
mpr
,
where R rd-mpr is the third data rate and R sd-mpr is the second data rate.
2. The method of claim 1 , further comprising:
retransmitting a fraction of the first fragment from the source node to the destination node at the second data rate during the second phase.
3. The method of claim 2 , wherein the retransmitting of the fraction of the first fragment uses Slepian-Wolf coding.
4. The method of claim 1 , wherein P 0 is a power used by the source node during the first phase, p s is the power used by the source during the second phase, and p r is the power used by the relay node during the second phase.
5. The method of claim 1 , wherein the second data rate R sd from the source to the destination satisfies R sd ≦C(|h sd | 2 P s ), where
C
(
x
)
=
W
2
log
(
1
+
x
σ
2
)
,
(
1
)
where C is a channel capacity, W is an available bandwidth in the network, σ 2 is a receiver noise power of a transmitted signal x, and log denotes the logarithm in base 2.
6. The method claim 5 , in which the transmitting of the second fragment and the retransmitting of the first fragment use multiple-packet reception (mpr), and packets are received successfully if and only if the second data rate R sd-mpr and the third data rate R rd-mpr , satisfy an information theoretic bounds for a multiple access channel according to
R
sd
-
mpr
≤
C
(
h
sd
2
P
s
)
R
rd
-
mpr
≤
C
(
h
rd
2
P
r
)
R
sd
-
mpr
+
R
rd
-
mpr
≤
C
(
h
sd
2
P
s
+
h
rd
2
P
r
)
.
7. The method of claim 5 , wherein bounds on the split ratio β are
1
-
C
(
h
sd
2
P
s
)
C
(
h
sd
2
P
s
+
h
rd
2
P
r
)
≤
β
≤
C
(
h
rd
2
P
r
)
C
(
h
sd
2
P
s
+
h
rd
2
P
r
)
,
and
optimal data rates in the second phase at the source and relay are respectively
R sd-mpr =(1−β) C (| h sd | 2 P s +|h rd | 2 P r )
R rd-mpr =βC (| h sd | 2 P s +|h rd | 2 P r ).
8. The method of claim 7 , further comprising:
selecting the powers P 0 , P s and P r , as a function of |h sr | 2 , |h rd | 2 , |h sd | 2 , and an objective overall transmission data rate R optimizes:
min
P
0
,
P
s
,
P
r
β
LP
0
C
(
h
sr
2
P
0
)
+
L
(
P
s
+
P
r
)
C
(
h
sd
2
P
s
+
h
rd
2
P
r
)
subject to P 0 , P s , P r >0 and
β
=
1
-
log
(
1
+
h
sd
2
P
s
σ
2
)
log
(
1
+
h
sd
2
P
s
+
h
rd
2
P
r
σ
2
)
,
and
R
=
C
(
h
sr
2
P
0
)
β
+
C
(
h
sd
2
P
s
+
h
rd
2
P
r
)
.
9. The method of claim 1 , wherein a transmission delay and a retransmission delay during the second phase are equal.
10. The method of claim 1 , wherein the first and second segments are respectively transmitted and retransmitted concurrently during the second phase.
11. The method of claim 1 , wherein the second and third data rates are different.
12. The method of claim 1 , wherein all nodes have a single antenna, one transceiver radio frequency chain.
13. The method of claim 1 , wherein the nodes use the same frequency band.