Sub-linear capacity scaling for multi-path channel models

TL;DR

This paper demonstrates that the theoretical capacity of multi-antenna communication systems is limited to grow at a sub-linear rate with the number of antennas, contrasting with idealized models suggesting linear growth.

Contribution

The paper establishes that, under certain assumptions, the capacity of multi-path channel models is upper bounded by a sub-linear function of system size, challenging previous linear growth assumptions.

Findings

Capacity scales sub-linearly with system size.

Theoretical upper bounds on capacity are derived.

Contrasts with idealized i.i.d. channel models.

Abstract

The theoretic capacity of a communication system constituted of several transmitting/receiving elements is determined by the singular values of its transfer matrix. Results based on an independent identically distributed channel model, representing an idealized rich propagation environment, state that the capacity is directly proportional to the number of antennas. Nevertheless there is growing experimental evidence that the capacity gain can at best scale at a sub-linear rate with the system size. In this paper, we show under appropriate assumptions on the transfer matrix of the system, that the theoretic information-capacity of multi-antenna systems is upper bounded by a sub-linear function of the number of transmitting/receiving links.