宽带MIMO CDMA系统的频域混合ARQ Chase合并
Frequency Domain Hybrid-ARQ Chase Combining for Broadband MIMO CDMA Systems
摘要：
在本文中，我们考虑使用码分多址（CDMA）和多输入多输出（MIMO）的高速无线分组接入。诸如高速分组接入（HSPA）的当前无线标准已经采用多码传输和混合自动重传请求（ARQ）作为用于递送高数据率的主要技术。混合ARQ的关键技术是在接收端保留错误的数据包以检测/解码重传的数据包。这种策略被称为分组合并。在基于CDMA MIMO的无线分组接入中，由于码片间干扰（ICI）和共天线干扰（CAI）导致的码正交性损失，多码传输遭受严重的性能下降。当在链路层中使用ARQ机制时，这种限制导致大的传输延迟。在本文中，我们研究了有效的最小均方误差（MMSE）频域均衡（FDE）为基础的迭代（turbo）分组合并循环前缀（CP）-CDMA MIMO与追逐型ARQ。我们介绍了两种Turbo分组合并方案：i）在第一种方案中，即“码片级Turbo分组合并”，MMSE FDE和分组合并在码片级联合执行。ii）在第二种方案中，即“符号级turbo分组组合”，针对每次传输单独执行码片级MMSE FDE和解扩，然后在软解映射器的级别执行分组组合。这两种技术的计算复杂性和存储器要求对ARQ延迟非常不敏感，即，最大ARQ轮数。一些代表性的天线配置和负载因素的吞吐量进行评估，以显示所提出的技术提供的增益。
英文摘要：
In this paper, we consider high-speed wireless packet access using code division multiple access (CDMA) and multiple-input multiple-output (MIMO). Current wireless standards, such as high speed packet access (HSPA), have adopted multi-code transmission and hybrid-automatic repeat request (ARQ) as major technologies for delivering high data rates. The key technique in hybrid-ARQ, is that erroneous data packets are kept in the receiver to detect/decode retransmitted ones. This strategy is refereed to as packet combining. In CDMA MIMO-based wireless packet access, multi-code transmission suffers from severe performance degradation due to the loss of code orthogonality caused by both interchip interference (ICI) and co-antenna interference (CAI). This limitation results in large transmission delays when an ARQ mechanism is used in the link layer. In this paper, we investigate efficient minimum mean square error (MMSE) frequency domain equalization (FDE)-based iterative (turbo) packet combining for cyclic prefix (CP)-CDMA MIMO with Chase-type ARQ. We introduce two turbo packet combining schemes: i) In the first scheme, namely "chip-level turbo packet combining", MMSE FDE and packet combining are jointly performed at the chip-level. ii) In the second scheme, namely "symbol-level turbo packet combining", chip-level MMSE FDE and despreading are separately carried out for each transmission, then packet combining is performed at the level of the soft demapper. The computational complexity and memory requirements of both techniques are quite insensitive to the ARQ delay, i.e., maximum number of ARQ rounds. The throughput is evaluated for some representative antenna configurations and load factors to show the gains offered by the proposed techniques.
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