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D2D通信允许终端用户之间通过复用蜂窝小区频谱直接进行短距离通信[1],具有提高频谱利用率、降低发射功率以及增强网络覆盖等诸多优点,目前已引起广泛关注。文献[2-3]中指出,采用网络编码技术同样能提高无线蜂窝网络的频谱效率,提高无线传播传输的可靠性。然而,D2D用户与蜂窝用户共享无线频谱的同时,不可避免地两者之间存在相互干扰[4-6]。当D2D用户复用蜂窝下行链路频谱,D2D通信用户所处的小区位置对D2D用户的发送功率影响不大,而复用上行链路频谱要比复用下行链路频谱敏感得多。考虑D2D用户复用频谱资源较为丰富的蜂窝下行链路[7],此时D2D发送端会对蜂窝用户产生干扰,同时基站对D2D接收端也会产生干扰。消除蜂窝网络中D2D通信与蜂窝通信之间的干扰,已经成为D2D通信研究中的热点问题。
现有文献主要从资源管理和功率控制的角度来考虑避免D2D通信与蜂窝通信之间的干扰。文献[8]把D2D共享蜂窝小区无线资源分配问题归结为混合整数非线性规划问题,通过遍历小区资源找到满足最大吞吐量的复用资源,时间开销比较大,在计算复杂度上还有待改进。文献[9]基于小区位置管理分配离D2D终端远的蜂窝用户资源给D2D通信使用,通过计算得到蜂窝用户的抗干扰程度和D2D用户对蜂窝用户的干扰情况。文献[10]基于信道干扰值计算,尽量给D2D通信分配受干扰较小的和抗干扰程度高的用户资源,通过资源分配有效控制干扰。
文献[11-13]通过功率控制来减少D2D用户和蜂窝用户之间的干扰,该方法基于所有用户的信干噪比(signal to interference plus noise ratio,SINR)统计提出了一种D2D通信简单功率控制方案,降低了蜂窝用户和D2D用户之间的干扰,但是该方案限制了小区的传输速率,在通信业务量较大时,一定程度上限制了D2D通信的优势。文献[14]进一步提出了一种D2D通信系统的功率控制方案,通过基站控制D2D发射端的发射功率,使得D2D用户与蜂窝用户之间的干扰控制在一个可接受的水平。
无论是资源管理还是功率控制,在避免D2D通信与蜂窝通信之间干扰的过程中,都限定了D2D通信和蜂窝通信的通信范围,限制了D2D通信在LTE-A中的进一步推广。为此,本文提出一种基于复数域网络编码的D2D传输方案,将基站和D2D发送端作为两个信源,蜂窝用户作为中继节点,在该蜂窝中继节点上采用复数域网络编码并将复数域编码信号转发给D2D接收端,D2D接收端采用最大似然多用户检测恢复出D2D信号,利用蜂窝干扰实现D2D通信。理论分析与实验仿真表明,基于复数域网络编码的D2D传输方案较传统的D2D传输方案,可获得更高的系统可达速率,进一步降低D2D接收端的符号错误概率(symbol error probability,SEP)。
Design of D2D Transmission Scheme Based on Complex Field Network Coding
doi: 10.3969/j.issn.1001-0548.2016.05.005
- Received Date: 2015-08-04
- Rev Recd Date: 2016-03-01
- Publish Date: 2016-09-01
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Key words:
- complex field network coding /
- D2D communication /
- signal interference /
- system achievable rate /
- symbol error probability
Abstract: Terminal users of device-to-device (D2D) communication inevitably will be interfered by cellular users while using multiplexing cellular network spectrum to improve spectrum efficiency. A D2D transmission scheme based on complex field network coding is proposed in this paper. Specifically, as the D2D user multiplexes cellular downlink spectrum, the cellular base station and D2D sender can be regarded as two independent sources, and meanwhile the cellular user as relay node. Moreover, the cellular user encodes the detected cellular signals and D2D signals by complex field network coding, and the D2D receiver can recover D2D signals by adopting maximum likelihood multiuser detection to eliminate cellular signal interference. Theoretical analysis and simulation results show that, compared with traditional D2D transmission schemes, the proposed scheme can improve system achievable rate evidently and reduce symbol error probability, simultaneously ensuring the elimination of cellular signal interference.
Citation: | WANG Jing, OUYANG Ming-sheng, LUO Wei, WANG Xin-mei. Design of D2D Transmission Scheme Based on Complex Field Network Coding[J]. Journal of University of Electronic Science and Technology of China, 2016, 45(5): 738-743. doi: 10.3969/j.issn.1001-0548.2016.05.005 |