Abstract: A noncoherent receiver based on Semidefinite Relaxation（SDR） approach is proposed for Decode and Forward（DF） cooperative system with distributed orthogonal space-time codes. In the scheme, noncoherent detection is simplified to a Boolean Quadratic Program（BQP）, and then, using the SDR approach, the Nondeterministic Polynomial-time hard（NP-hard） BQP problem is transformed into the optimization of a Semidefinite Program（SDP） of polynomial-time hard. Furthermore, a relaying protocol with a combination of channel estimation and detection at relays is also proposed. Compared with the coherent detection, the channel state information is not a necessary in the proposed algorithm at destination and the system complexity is reduced, although there is acceptable performance loss. The proposed relaying scheme further reduces the requirements of source-relay channel state information. In addition, the performance of the noncoherent detection scheme with different number of receiving antennas at the destination is compared.

Key words: cooperative communications, decode-and-forward, distributed space-time block codes, noncoherent detection, semidefinite relaxation

摘要： 针对译码转发（DF）协议下分布式空时编码（DSTBC）的多中继协作系统，提出了基于半定松弛（SDR）算法的协作系统非相干检测方案。将协作系统的非相干检测转化为布尔二次方程（BQP）形式，采用SDR算法，把NP难的BQP问题转换为多项式时间复杂度的半定规划问题。进一步结合SDR算法的特点，提出了一种中继加入信道信息估计的协作方案。与相干检测相比，SDR非相干检测虽然存在一定的性能损失，但目的节点无需任何信道信息，降低了系统的复杂度；提出的协作方案进一步降低了中继节点对源到中继间信道信息的要求。另外，比较了不同接收天线数目对系统检测性能的影响。

关键词: 协作通信, 译码转发, 分布式空时编码, 非相干检测, 半定松弛