W. J. FENG ET AL.
342
From Figure 7, we can draw the following conclu-
sions:
In Case Random_UE, the throughput of eNB, D2D
and overall system is all lower than Case 10_RB_Sep,
and the throughput of cell-edge users also lower than
Case 10_RB_Sep. So Case Random_UE is not an appro-
priate case to further optimize the performance.
In Case Worst_UE, th e throughput of eNB and over all
system increases a lot, but the throughput of D2D com-
munication fall sharply. And worst yet, the throughput of
cell-edge UEs is the lowest so that cell-edge users canno t
communicate normally. So Case Worst_UE is still not an
appropriate case to further optimize the performance.
In Case Best_UE, comparing with Case 10_RB_Sep,
the average throughput of eNB is reduced by 0.8%, and
the overall system throughput is reduced by 1.1%. At the
same time, the throughput o f cell-edge users is increased
by 7.1%. So in this case, we giv e up a little th roughp ut of
eNB and overall system, for the purpose of cell-edge
users’ throughput improvement. Case Best_UE is an ap-
propriate case to further optimize the performance.
Figure 8 shows the cellular UEs SINR of 4 optimized
cases.
From this figure, we can obviously see that the cellular
UEs of Case Worst_UE has the worst SINR. In Case
Best_UE, due to choosing the highest transmission rate
in current slot, the SINR is not as good as Case 10_
RB_Sep. But the improvement of cell-edge users’
throughput is what we want.
5. Conclusions
Based on the simulation and analysis above, we can rec-
ognize that after introducing D2D communication into
LTE-Advanced uplink system, the performance of over-
all system gains dramatically increase and it also im-
prove the system spectrum efficiency. At the same time,
when D2D communication reuses frequency resource
-40 -30 -20 -10010 2030
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
SINR(dB)
CDF
Last10Sep
OneBestMS
OneRanMS
OneWorstMS
Figure 8. Cellular UEs SINR of optimized cases.
with cellular users, cellular UEs will be interfered
strongly. It leads to the unable transmission of cell-edge
users. Therefore, proposing an appropriate resource allo-
cation method for D2D communication is a key factor to
improve the performance of the overall system. This pa-
per firstly consider different kinds of D2D communica-
tion resource allocation methods and choose the case that
D2D communication uses 10 RB of uplink frequency
resource and the cellular UEs only use another 36 RB of
uplink frequency resource, which has the best perform-
ance. On the basis of Case 10_RB_Sep, we consider
choosing one cellular UE, which has the highest trans-
mission rate in current slot, to reuse 10 RB with D2D
UEs. This optimized simulation case sacrifice a little
throughput of overall system in order to improve the
performance of cell-edge users. After verification and
analysis, Case Best_UE has the ability to improve overall
system performance and limit inference for cellular
communication, especially for cell-edge cellular users.
6. Acknowledgements
This paper is supported by National Key Technology
R&D Program of China under grant No.
2012ZX03003011.
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