非同分布衰落环境下最大链路选择方案及性能研究

A max link selection scheme over independent and non-identically distributed fading channel

通过对Nakagami-m衰落环境下缓冲中继协作最大链路选择方案(MLS)的中断和延迟性能的研究,得到了中断概率和平均分组延迟的闭式解析解以及相应的分集增益和编码增益。基于所得结果,给出了中断概率和平均分组延迟的数值分析,结果表明,非同分布衰落环境不仅严重地影响了MLS方案的分集增益和编码增益,而且使得各个中继节点处的平均分组延迟也不相同,系统极不稳定。为此提出了一种新颖的基于加权的MLS(W-MLS)方案,该方案一方面使信源-中继和中继-信宿链路等效功率分别相同;另一方面使中继-信宿链路等效功率略大于信源-中继链路等效功率,这样,不仅可以保证系统获得足够的分集增益,而且可以显著地降低平均分组延迟,使得各个中继节点处的平均分组延迟完全相同,提高了系统的稳定性。

We focus on the buffer-aided max link selection （MLS） relaying system in term of outage and delay performance over independent and non-identically distributed Nakagami-m fading channels. By using appropriate mathematical manipulation, the exact closed-form expressions of outage probability and average packet delay are achieved firstly, as well as the diversity and coding gains. The presented numerical results show that the non-identically distributed fading channels impose great loss in diversity gain for the MLS schemes. Moreover, the buffer-aided relaying systems are also unstable due to the fact that the average packet delays at all relays are different under this condition. Therefore, to improve the diversity and delay performance, we propose a novel weighted-based MLS （W-MLS） scheme. By emplo- ying weight vectors, the W-MLS scheme on one hand makes the equivalent powers of source-relay and relay-destination links equal. On the other hand, the W-MLS scheme also ensures that the equivalent power of relay-destination links is greater than the one of source-relay links. As a result, comparing with the traditional MLS, the proposed W-MLS scheme can not only provide enough diversity and cod- ing gains, but also enhance the stability of buffer-aided relaying systems due to that the average packet delays at all relays are entirely the same.