We study the problem of cache-aided communication for cellular networks with multi-user and multiple antennas at finite signal-to-noise ratio. Users are assumed to have non-symmetric links, modeled by wideband fading channels. We show that the problem can be formulated as a linear program, whose solution provides a joint cache allocation along with pre-fetching and fetching schemes that minimize the duration of the communication in the delivery phase. The suggested scheme uses zero-forcing and cached interference subtraction, and hence, allows each user to be served at the rate of its own channel. Thus, this scheme is better than the previously published schemes that are compromised by the poorest user in the communication group. We also consider a special case of the parameters for which we can derive a closed form solution and formulate the optimal power, rate, and cache optimization. This special case shows that the gain of MIMO coded caching goes beyond the throughput. In particular, it is shown that in this case, the cache is used to balance the users such that fairness and throughput are no longer contradicting. More specifically, in this case, strict fairness is achieved jointly with maximizing the network throughput.
Bibliographical noteFunding Information:
Manuscript received December 11, 2017; revised May 25, 2018; accepted May 25, 2018. Date of publication June 6, 2018; date of current version October 30, 2018. The work of S. Mohajer was supported by the National Science Foundation under Grant CCF-1749981. (Corresponding author: Itsik Bergel.) I. Bergel is with the Faculty of Engineering, Bar-Ilan University, Ramat Gan 52900, Israel (e-mail: email@example.com).
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- Cache-aided communication
- cache and power allocation
- finite SNR regime
- linear optimization