Previously, the authors have shown that linear precoding with only private streams can have unbounded gap to the sum capacity of the two-user multi-input single-output (MISO) broadcast channel (BC), and that rate-splitting (RS) combined with zero-forcing (ZF) can reduce the gap to a constant number of bits per channel use. In this paper, we extend the investigation to the general K-user multiple-input multiple-output (MIMO) channel. We propose a RS scheme with minimum mean square error (MMSE) precoding. First, we show that the proposed scheme achieves the whole capacity region to within a constant gap in the two-user case. Second, we prove that the proposed scheme does not enjoy the same optimality in the three-user case in general. Third, we provide a simple pathological example showing why RS with linear precoding does not work beyond the two-user case. The current study reveals a fundamental gap between the transmitter-side and the receiver-side interference mitigation.
A Linearly Precoded Rate Splitting Approach and Its Optimality for MIMO Broadcast Channels
Published 2018 in Information Theory Workshop
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- Publication year
2018
- Venue
Information Theory Workshop
- Publication date
2018-11-01
- Fields of study
Computer Science, Engineering
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