1 Introduction
2 System model
Symbol
|
Explanation
|
---|---|
y
j
| Received signal at the jth node |
h
i
j
| Channel coefficient from ith to jth node |
P
ij
| Transmitting power per bandwidth from the ith node to the |
jth node | |
x
i
| Transmitting signal at the ith node |
W | Transmission bandwidth |
N
o
| Spectral density height of thermal noise |
n
j
| Thermal noise |
λ
ij
| Rate parameter of exponential distribution |
d
ij
| Distance between the ith and jth nodes |
R
d
| Direct transmission data rate |
γ
d
| Transmitting SINR of direct transmission |
h
d
| Channel coefficient of direct transmission |
R
c
| Data rate of PR |
\(R_{p{s_{k}}}\phantom {\dot {i}\!}\)
| Data rate of the link of PT-SR
k
|
R
MRC
| Data rate of MRC |
γ
p
| Ratio between the transmission signal power over the noise |
variance for PU | |
\(h_{p{s_{k}}}\phantom {\dot {i}\!}\)
| Channel coefficient of the link PT-SR
k
|
\(\gamma _{{s_{k}}d}\phantom {\dot {i}\!}\)
| Ratio between the transmission signal power over the noise |
variance between ST
k
and PR | |
\(h_{{s_{k}}d}\phantom {\dot {i}\!}\)
| Channel coefficient of the link ST
k
-PR |
\(R_{{su}_{k}}\phantom {\dot {i}\!}\)
| Data rate of the kth SU |
\(\gamma _{{su}_{k}}\phantom {\dot {i}\!}\)
| Ratio between the transmission signal power over the noise |
variance for the kth SU | |
\(h_{{su}_{k}}\phantom {\dot {i}\!}\)
| Channel coefficient of the link ST-SR |
R
N
| Cooperative network throughput |
T | Time for the 1st and 2nd phase transmission |
t
k
| Time for the third phase transmission |
P
p
| Transmitting power of PT |
P
d
| Transmitting power of non-cooperative scheme |
\(P_{{s_{k}}d}\phantom {\dot {i}\!}\)
| Transmitting power of the ST
k
|
\({P_{s{u_{k}}}}\phantom {\dot {i}\!}\)
| Transmitting power of the third phase |
w
k
| Beamforming weight of the ST
k
|
P
OV
| Circuit power |
P
SR
| Overheads of cooperative beamforming |
P
TR
| Overheads of message sharing |
P
c
| Circuit power |
M | Number of cooperative SUs |
b
RD
| Number of bits per symbol for cooperative beamforming |
b
SR
| Number of bits per symbol for message sharing |
ρ
| Amplifier efficiency |
N
TR
| Number of symbols of training period |
N
RD
| Number of symbols of cooperative beamforming |
P
b
| Power consumption per throughput |
β
k
| Time allocation ratio of the kth SU |
Q
p
| QoS of PU |
Q
s
| QoS of SU |
\(P_{\mathrm {d}}^{\text {out}}\)
| Outage probability of direct transmission |
\(C_{\text {d}}^{\text {out}}\)
| Outage capacity of direct transmission |
Csuout | Outage capacity of SU |
ε
| Outage probability threshold |
\(C_{\text {cb}}^{{\text {out}}}\)
| Outage capacity of cooperative beamforming |
η
| Energy efficiency |
θ
1
| SNR threshold for decoding |
θ
2
| SNR of the worst link between ST
k
and PR |
d
p
| Distance between PT and PR |
\({d_{{s_{k}}d}}\phantom {\dot {i}\!}\)
| Distance between PT and PR |
d
su
| Distance between ST and SR |
\({d_{p{s_{k}}}}\phantom {\dot {i}\!}\)
| Distance between PT and ST |
P
max
| Maximum transmitting power |
γ
d
| Ratio between the direct transmission signal power over the |
noise variance | |
ζ
| Network energy consumption for unit bit of throughput |
L
s
| Number of SUs |
v
| Moving speed of users |
3 An algorithm for energy consumption minimization and cooperative beamforming
3.1 Optimal power allocation for cooperative beamforming
3.2 Energy efficiency of the cooperative beamforming scheme
4 Simulation results for performance evaluation
Description
|
Value
|
---|---|
Amplifier efficiency ρ
| 38%
|
Circuit power p
C
| 1 mw |
Power for training signals P
TR
| 1 mw |
Bits per symbol of MS b
RD
| 6 |
Bits per symbol of CB b
SR
| 4 |
Number of training symbols N
TR
| 1 |
Number of symbols for CB N
RD
| 99 |
Outage probability threshold ε
| 0.01 |
Required QoS of PU/SU | 1/0.5 bps/Hz |
Pathloss exponent α
| 3.5 |
PT-PR distance d
p
| 0<d
p
≤1,000 m |
PT-ST distance \({d_{p{s_{k}}}}\phantom {\dot {i}\!}\)
|
\({{\mathrm {d}}_{{\mathrm {p}}{{\mathrm {s}}_{\mathrm {k}}}}} \le 800 m \phantom {\dot {i}\!}\)
|
ST-PR distance \({d_{{s_{k}}d}}\phantom {\dot {i}\!}\)
|
\({d_{{s_{k}}d}} = 300\) m |
ST-SR distance d
su
|
d
su=200 m |
Maximum transmission power P
max
| 40 mw |
Noise spectral density N
o
| 0.5 |
Number of snapshots per meter | 20 |
SNR threshold for decoding θ
1
| 0.01 |
SNR of the worst link between ST
k
and PR θ
2
| 0.0001 |