STBCs with Reduced Sphere Decoding Complexity for Two-User MIMO-MAC
STBCs with Reduced Sphere Decoding Complexity for Two-User MIMO-MAC
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DOI：
10.1109/glocom.2009.5425864
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发表时间：
2009-08
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影响因子：
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通讯作者：
J. Harshan;B. Rajan
中科院分区：
文献类型：
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作者：
J. Harshan;B. Rajan
在本文中，为两用户多输入多输出（MIMO）衰落多址信道构建了具有降低的球解码复杂度（SDC）的空时分组码（STBC）。在此设置中，两个用户都使用相同的 STBC，并且目的地对两个用户的符号执行球形解码。首先，我们确定由点阵生成器的 Q-R 分解产生的 R 矩阵中的零位置，从而减少 (i) 最坏情况 SDC (WSDC) 和 (ii) 平均 SDC (ASDC)。然后，提供晶格生成器上的一组充分必要条件，使得 R 矩阵在所识别的位置处具有零。随后，提出了导致 ASDC 减少的 STBC 的显式构造。所提出的设计的速率（以每个信道使用的复杂符号为单位）最多为2/Nt，其中Nt表示每个用户的发射天线的数量。我们还表明，来自复杂正交设计（Alamouti 设计除外）的 STBC 类会降低 WSDC，但不会降低 ASDC。
In this paper, Space-Time Block Codes (STBCs) with reduced Sphere Decoding Complexity (SDC) are constructed for two-user Multiple-Input Multiple-Output (MIMO) fading multiple access channels. In this set-up, both the users employ identical STBCs and the destination performs sphere decoding for the symbols of the two users. First, we identify the positions of the zeros in the R matrix arising out of the Q-R decomposition of the lattice generator such that (i) the worst case SDC (WSDC) and (ii) the average SDC (ASDC) are reduced. Then, a set of necessary and sufficient conditions on the lattice generator is provided such that the R matrix has zeros at the identified positions. Subsequently, explicit constructions of STBCs which results in the reduced ASDC are presented. The rate (in complex symbols per channel use) of the proposed designs is at most 2/Nt where Nt denotes the number of transmit antennas for each user. We also show that the class of STBCs from complex orthogonal designs (other than the Alamouti design) reduce the WSDC but not the ASDC.