Cooperative multi-user MIMO based on limited feedback in downlink OFDM systems

Abstract

Abstract-Multi-cellular radio systems are often limited due to the presence of cochannel interference. Physical layer concepts as e.g. interference rejection combining, optimize the receiver side and thus strengthen the signal while combating the interference at the terminal side only. It is well known that joint transceiver optimization, i.e. coordinated joint transmission from several base stations, yields large capacity improvement for downlink transmission. However, the performance highly depends on the available channel knowledge. We focus on how to realize a decentralized and limited cooperative downlink transmission in a multi-cellular network. This yields the crucial question: Is an efficient cooperative transmission possible by using simple channel quality identifiers, or is channel state information at the transmitter mandatory? Further, we use minimum mean square error equalization at the terminal side to combat residual cochannel interference. For baseline we apply receiver optimization only and compare these results with those obtained from cooperative transmission. We demonstrate potential capacity gains in a cellular orthogonal frequency division multiplexing system and their scaling with the number of cooperating antenna arrays.

A Scalable Limited Feedback Design for Network MIMO Using Per-Cell Product Codebook

“…Note that, the first statement of Lemma 1 in turn suggests that the codewords in the joint-cell codebook shall have the same structure as the aggregate-codeword defined in (15) almost surely for sufficiently large n T and finite N . As a result, the second statement of Lemma 1 can be derived from the definition of average distortion associated with joint-cell codebooks and per-cell product codebooks given in equation (22) and (23), respectively.…”

“…In the joint-cell codebook based CSI feedback schemes [14], [15], the cooperating BSs are treated as one composite BS (super BS), and the codebooks are designed for the aggregate CSI matrix H k in a standard way. Moreover, authors of [15] has also considered the heterogeneous path loss effects and the effects of increasing cluster size with a variable number of cooperating BSs.…”

“…In the joint-cell codebook based CSI feedback schemes [14], [15], the cooperating BSs are treated as one composite BS (super BS), and the codebooks are designed for the aggregate CSI matrix H k in a standard way. Moreover, authors of [15] has also considered the heterogeneous path loss effects and the effects of increasing cluster size with a variable number of cooperating BSs. While the joint-cell codebook approaches provide some preliminary solutions for network MIMO systems, two important issues, namely the dynamic number of cooperating BSs and the heterogeneous path loss effects, are ignored.…”

“…However, perfect CSI is difficult to obtain at the transmitter side in practice and there are lots of literatures discussing SDMA with limited CSI feedback in single-cell MU-MIMO systems [7]- [13]. Recently, the authors of [14], [15] have extended the single-cell limited feedback designs to network MIMO systems by treating the cooperating BSs as a composite MIMO transmitter (i.e., one super BS), and this refers to the joint-cell codebook approach. While the existing work [14], [15] provide some preliminary solutions for CSI feedback in network MIMO systems, there are still a number of important issues to be addressed.…”

Incorporating Stiefel Geometry in Codebook Design and Selection for Improved Base Station Cooperation

“…Preliminary work considered transposing pointto-point limited feedback design to cooperative systems [1], [4]. However, as described in [5], the aggregate channel matrix is a specific feature that cannot be addressed by directly applying point-to-point codebook based precoding.…”