# A Low-Complexity Cache-Aided Multi-antenna Content Delivery Scheme

## TL;DR

This paper proposes a low-complexity cache-aided multi-antenna content delivery scheme that efficiently manages beamforming in multi-user systems, balancing performance and computational complexity.

## Contribution

It introduces a time-sharing approach to reduce complexity in multi-antenna beamforming for cache-enabled networks, maintaining near-optimal performance.

## Key findings

- Low-complexity scheme outperforms existing methods across SNR and rate regimes.
- The proposed approach achieves minimal performance loss compared to full joint subfile transmission.
- Numerical results confirm effectiveness in high SNR and limited spatial degrees of freedom scenarios.

## Abstract

We study downlink beamforming in a single-cell network with a multi-antenna base station (BS) serving cache-enabled users. For a given common rate of the files in the system, we first formulate the minimum transmit power with beamforming at the BS as a non-convex optimization problem. This corresponds to a multiple multicast problem, to which a stationary solution can be efficiently obtained through successive convex approximation (SCA). It is observed that the complexity of the problem grows exponentially with the number of subfiles delivered to each user in each time slot, which itself grows exponentially with the number of users in the system. Therefore, we introduce a low-complexity alternative through time-sharing that limits the number of subfiles that can be received by a user in each time slot. It is shown through numerical simulations that, the reduced-complexity beamforming scheme has minimal performance gap compared to transmitting all the subfiles jointly, and outperforms the state-of-the-art low-complexity scheme at all SNR and rate values with sufficient spatial degrees of freedom, and in the high SNR/high rate regime when the number of spatial degrees of freedom is limited.