Equivalent Signal-Alignment-Based Frequency-Domain Equalization for MC-CDMA Two-Way Relay Systems
Equivalent Signal-Alignment-Based Frequency-Domain Equalization for MC-CDMA Two-Way Relay Systems
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DOI：
10.1109/tvt.2011.2175952
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发表时间：
2012
影响因子：
6.8
通讯作者：
Tingting Liu;Chenyang Yang
中科院分区：
文献类型：
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作者：
Tingting Liu;Chenyang Yang
在多用户中继系统中，如果中继没有足够的自由度来消除多用户干扰，双向中继传输的频谱效率增益可能会消失。信号对准（SA）信令可以恢复该增益，但是可能遭受信号功率损失。为了提高多载波码分多址（MC-CDMA）TWR系统的频谱效率，我们开发了一个等效的SA（ESA）信令过程。简单地通过在解扩之后对准接收到的符号而不是如SA信令中那样对准接收到的信号，ESA信令具有比SA信令更可行的解决方案，并且其性能和复杂度取决于扩频序列。这使得我们能够通过优化ESA信令来提高系统性能，并通过设计扩频序列来降低其复杂度。具体来说，我们开发最佳的ESA信令，以最大限度地提高信号噪声比（SNR）下的无干扰约束。然后，我们设计扩展序列以获得低复杂度的基于ESA的频域均衡器（FDE），即，基于ESA的单抽头FDE，并为单抽头FDE提供最大分集增益。理论分析和仿真结果表明，在MC-CDMA TWR系统中，ESA信令比SA信令具有更高的频谱效率。
In multiuser relay systems, if the relay does not have sufficient degrees of freedom to eliminate multiuser interference, the spectral efficiency gain of two-way relay (TWR) transmission may vanish. Signal alignment (SA) signaling is possible to recover this gain but may suffer from a signal power loss. To improve the spectral efficiency of multicarrier code-division multiple-access (MC-CDMA) TWR systems, we develop an equivalent SA (ESA) signaling procedure. Simply by aligning the received symbols after despreading instead of aligning the received signals as in SA signaling, ESA signaling has more feasible solutions than SA signaling, and its performance and complexity depend on the spreading sequences. This allows us to improve the system performance by optimizing ESA signaling and to reduce its complexity by designing the spreading sequences. Specifically, we develop optimal ESA signaling to maximize the signal-to-noise-ratio (SNR) under the interference-free constraint. Then, we design the spreading sequence to obtain a low-complexity ESA-based frequency-domain equalizer (FDE), i.e., ESA-based one-tap FDE, and to provide the maximal diversity gain for the one-tap FDE. Both theoretical analysis and simulation results demonstrate that ESA signaling is more spectral efficient than SA signaling for MC-CDMA TWR systems.