A General Rate Duality of the MIMO Multiple Access Channel and the MIMO Broadcast Channel

TL;DR

This paper introduces a versatile filter-based rate duality between the MIMO MAC and BC that simplifies computation, reduces complexity, and enables efficient rate-based optimization in wireless communication systems.

Contribution

It proposes a novel filter-based rate duality applicable to systems with nonlinear interference cancellation and multi-antenna terminals, improving computational efficiency and parallelizability.

Findings

Allows noncooperative stream-wise decoding reducing complexity.

Enables parallel implementation of the duality conversion.

Facilitates more efficient rate-based optimization in the dual domain.

Abstract

We present a general rate duality between the multiple access channel (MAC) and the broadcast channel (BC) which is applicable to systems with and without nonlinear interference cancellation. Different to the state-of-the-art rate duality with interference subtraction from Vishwanath et al., the proposed duality is filter-based instead of covariance-based and exploits the arising unitary degree of freedom to decorrelate every point-to-point link. Therefore, it allows for noncooperative stream-wise decoding which reduces complexity and latency. Moreover, the conversion from one domain to the other does not exhibit any dependencies during its computation making it accessible to a parallel implementation instead of a serial one. We additionally derive a rate duality for systems with multi-antenna terminals when linear filtering without interference (pre-)subtraction is applied and the different streams of a single user are not treated as self-interference. Both dualities are based on a framework already applied to a mean-square-error duality between the MAC and the BC. Thanks to this novel rate duality, any rate-based optimization with linear filtering in the BC can now be handled in the dual MAC where the arising expressions lead to more efficient algorithmic solutions than in the BC due to the alignment of the channel and precoder indices.