Resource Allocation in OFDM Based Wireless Relay Networks ...

2.5 Simulation Results
Rate (bits/s/Hz)
4
3.5
3
2.5
2
1.5
Dual Solution (D(ν,λ)/K)
JntSol
SubOpt
JSP−(with matching)
EP−ECarr
EP−RndCarr
1
0.5
0
0 5 10 15 20
SNR (dB)
Figure 2.5: Throughput versus SNR for M = 10 and N = 5.
almost constant, which shows the robustness of the proposed sub-optimal algorithm.
Moreover, the JntSol also performs much better than JSP-(with matching) due to
the same reasons.
To make the comparison complete, we show the throughput performance versus
the number of relays in Fig. 2.7. The number of users is taken as M = 6 and SNR
is set as 10 dB. The key observation is that the gap between JntSol and JSP-(with
matching) increases when the number of relay becomes large. This is due to the fact
that in JSP-(with matching) a user can use at most one RS so the difference from
the proposed JntSol becomes large. Other observations are similar to those in Fig.
2.7.
It is then of interest to check the performance of the proposed method when
simultaneously varying the number of both users and relays. The curves for N =
1, 2, 3, 4 relays versus M are shown in Fig. 2.8 for SNR = 10 dB. We numerically
draw the conclusion that in order to increase the data throughput, both the number
of the users and the number of relays should be increased simultaneously. It is
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