Resource Allocation in OFDM Based Wireless Relay Networks ...

5.5 Simulation Results
150
OPT−SOL
(a)
Lifetime (S)
100
50
end−to−end rate (bits/s/Hz)
0
0 50 100 150 200 250 300
iteration no.
(b)
300
200
100
HOP1
HOP5
R−Req
0
0 50 100 150 200 250 300
iteration no.
Figure 5.4: Lifetime convergence
5.5 Simulation Results
In this section, we present simulation results to evaluate the performance of our
proposed algorithm. We consider a network with 10 relay nodes such that there
are 5 virtual sub-hops. We assume that all the transmitting nodes, i.e., source and
relay nodes, have same initial energy and each node can provide equal amount of
maximum power. We consider an OFDM system with K = 32 sub-carriers. Further
we assume σn,a 2 = σn,d 2 , ∀ n. The SNR is defined as the ratio between the transmitted
signal power and the additive noise power. We compare the performance of proposed
algorithm (OPT-SOL) with the equal power allocation solution (EP-SOL), where
the available power on each node is evenly distributed among the K sub-carriers.
Fig. 5.4 shows the convergence of the proposed algorithm at SNR=30 dB. The
initial energy of each node is taken as E AF
n
= E DF
n
= 50 and the maximum power per
transmission is taken as P n = Q n = 2. The minimum end-to-end rate requirement
(R-Req) over complete OFDM block is 64 bits/s/Hz. Obviously the system with
EP-SOL has lifetime equal to 25 seconds. Fig. 5.4 (a) shows that lifetime t converges
92