Optimal cognitive transmission exploiting redundancy in the primary ARQ process
Optimal cognitive transmission exploiting redundancy in the primary ARQ process
复制标题
利用主 ARQ 过程中的冗余实现最佳认知传输
DOI：
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发表时间：
2011
期刊：
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通讯作者：
M. Zorzi
中科院分区：
文献类型：
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作者：
Nicolò Michelusi;O. Simeone;M. Levorato;P. Popovski;M. Zorzi
认知无线电技术（Cognitive radio）是指在同一频谱范围内可以同时存在主用户（Primary user）和从用户（Secondary user）。在这项工作中，假设PU实现了基于重传的错误控制技术（ARQ）。这在主传输到SU产生的干扰中产生了固有的冗余。我们研究了利用这种冗余的二次传输策略。其基本思想是，如果辅助接收器（SR）在给定的主重传中学习到主消息（PM），那么它可以在主重传的情况下使用该知识来取消后续时隙中的主要干扰，从而实现更大的辅助吞吐量。这在二级策略的设计中产生了有趣的权衡。事实上，一方面，二次传输可能会增加二次吞吐量，但另一方面，对主接收器（PR）和sr接收PM造成干扰。这种干扰可能会导致相同PM的重发，这对辅助用户有利。同时，在SR处对PM进行解码也变得更加困难，并减少了在PR处给定干扰约束下的可用裕度。证明了最优辅助策略优先考虑SR知道PM的状态，因为后者能够执行干扰缓解并获得更大的辅助吞吐量。此外，在主约束足够宽松的情况下，当PM对sr未知时，副发射器也应进行传输。找到了最优策略的结构，并通过数值结果显示了所提技术的吞吐量效益。
Cognitive radio technology enables the coexistence of Primary (PUs) and Secondary Users (SUs) in the same spectrum. In this work, it is assumed that the PU implements a retransmission-based error control technique (ARQ). This creates an inherent redundancy in the interference created by primary transmissions to the SU. We investigate secondary transmission policies that take advantage of this redundancy. The basic idea is that, if a Secondary Receiver (SR) learns the Primary Message (PM) in a given primary retransmission, then it can use this knowledge to cancel the primary interference in the subsequent slots in case of primary retransmissions, thus achieving a larger secondary throughput. This gives rise to interesting trade-offs in the design of the secondary policy. In fact, on the one hand, a secondary transmission potentially increases the secondary throughput but, on the other, causes interference to the reception of the PM at the Primary Receiver (PR) and SR. Such interference may induce retransmissions of the same PM, which plays to the advantage of the secondary user, while at the same time making decoding of the PM more difficult also at the SR and reducing the available margin on the given interference constraint at the PR. It is proved that the optimal secondary strategy prioritizes transmissions in the states where the PM is known to the SR, due to the ability of the latter to perform interference mitigation and obtain a larger secondary throughput. Moreover, when the primary constraint is sufficiently loose, the Secondary Transmitter should also trasmit when the PM is unknown to the SR. The structure of the optimal policy is found, and the throughput benefit of the proposed technique is shown by numerical results.