Compact feedback for MIMO-OFDM systems over frequency selective channels
Compact feedback for MIMO-OFDM systems over frequency selective channels
复制标题
频率选择性信道上 MIMO-OFDM 系统的紧凑反馈
DOI：
10.1109/vetecs.2005.1543275
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
X.E. Lin
中科院分区：
文献类型：
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作者：
Qinghua Li;X.E. Lin
发射波束形成可以提高多输入多输出（MIMO）天线系统的性能。然而，波束形成矩阵的反馈开销可能会显著降低FDD系统的吞吐量。最近报道了有效的反馈技术。然而，对于具有大量发射天线（M/sub t/）和空间流（M/sub s/）的系统，它们的复杂性可能高得令人望而却步，因为需要大量的Grassman流形包装G（M/sub f/,M/sub s/）的大型矩阵码本。Roh et al.（2004）表明，波束形成矩阵可以用独立的单位向量参数化。这意味着联合量化矩阵等同于分别量化向量。首先，我们证明了单位矢量在单位球上的分布是各向同性的。其次，推导了一种低复杂度、可扩展的量化方案。关键的创新在于大维单位向量的量化。每个大维单位向量被分割成更小的维向量，并通过为低维单位向量设计的小尺寸码本进行量化，分割本身由一个3位码本进行量化。最后，提出了一种在频域下采样波束形成矩阵的插值方案，大大降低了MIMO-OFDM系统的开销。缺失的波束形成矢量沿单位球上两个反馈矢量连接的测地线插值。仿真结果表明，采用该方案可以将IEEE 802.16d/e草案的开销降低三倍。
Transmit beamforming can improve the performance of multiple-input multiple-output (MIMO) antenna systems. However, the feedback overhead of beamforming matrixes may significantly reduce the FDD system throughput. Efficient feedback techniques were reported recently. However, their complexities can be prohibitively high for systems with large numbers of transmit antennas (M/sub t/) and spatial streams (M/sub s/) since numerous large matrix codebooks of Grassman manifold packing G(M/sub f/,M/sub s/) are required. In Roh et al. (2004), it is shown that the beamforming matrix can be parameterized by independent unit vectors. This implies that quantizing the matrix jointly is equivalent to quantizing the vectors separately. Firsts we show that the distributions of the unit vectors are isotropic on unit spheres. Secondly, a low-complexity, scalable quantization scheme is derived. The key innovation lies in the quantization of the large dimension unit vectors. Each large dimension unit vector is partitioned into smaller dimension vectors and quantized by small size codebooks designed for low dimension unit vectors, and the partition itself is quantized by a 3-bit codebook. Finally, an interpolation scheme is proposed for beamforming matrixes downsampled in frequency domain, which significantly reduces overhead for MIMO-OFDM systems. The missing beamforming vectors are interpolated along the geodesic connecting two fed back vectors on a unit sphere. Simulations demonstrate that the overhead in IEEE 802.16d/e draft can be reduced by a factor of three using the proposed scheme.