Channel state feedback schemes for multiuser MIMO-OFDM downlink

Abstract

Channel state feedback schemes for the MIMO broadcast downlink have been widely studied in the frequency-flat case. This work focuses on the more relevant frequency selective case, where some important new aspects emerge. We consider a MIMO-OFDM broadcast channel and compare achievable ergodic rates under three channel state feedback schemes: analog feedback, direction quantized feedback and "time-domain" channel quantized feedback. The first two schemes are direct extensions of previously proposed schemes. The third scheme is novel, and it is directly inspired by rate-distortion theory of Gaussian correlated sources. For each scheme we derive the conditions under which the system achieves full multiplexing gain. The key difference with respect to the widely treated frequency-flat case is that in MIMO-OFDM the frequency-domain channel transfer function is a Gaussian correlated source. The new time-domain quantization scheme takes advantage of the channel frequency correlation structure and outperforms the other schemes. Furthermore, it is by far simpler to implement than complicated spherical vector quantization. In particular, we observe that no structured codebook design and vector quantization is actually needed for efficient channel state information feedback. Index TermsMIMO Broadcast Channel, OFDM, Channel State Feedback, Quantization.H. Shirani-Mehr and G. Caire are with the Ming Hsieh

A limited feedback scheme based on spatially correlated channels for coordinated multipoint systems

“…In this scheme, B G bits are used by each UE to quantize the real and imaginary part of each coefficient of the CIR. A similar scheme but using uniform quantization instead of Gaussian quantization is proposed in [18]. It is important to notice that the optimizations applied to the scheme in [18], such as different bit allocation across the different paths, could be also applied to the DQ and GQ schemes.…”

“…A similar scheme but using uniform quantization instead of Gaussian quantization is proposed in [18]. It is important to notice that the optimizations applied to the scheme in [18], such as different bit allocation across the different paths, could be also applied to the DQ and GQ schemes. However, our comparison has been performed with equal bit allocation across the different paths.…”

“…Limited feedback schemes for MIMO-OFDM systems have been widely proposed in the literature, and we will comment the most representative as in [16][17][18][19]. A frequency-domain limited feedback scheme is presented in [16].…”

“…However, correlation between subcarriers can be difficult to exploit and computationally expensive. In order to avoid complex frequency interpolation operations, a time-domain channel quantized feedback scheme is presented in [18], comparing it with two different frequencydomain channel quantization schemes: an analog feedback scheme and a direction quantized feedback scheme. It is shown that the scheme based on time-domain channel quantization outperforms frequency-domain schemes in terms of system sum-rate, requiring lower complexity.…”

Joint Scheduling and ARQ for MU-MIMO Downlink in the Presence of Inter-Cell Interference

“…This can be accurately obtained using open and closed loop channel estimation and feedback schemes (the literature on this subject is overwhelming, for example, see [13]- [17] and references therein).…”