Caching and Coded Multicasting in Slow Fading Environment
Mingyue Ji, Rong‐Rong Chen · 2017
We study the delay-outage tradeoff in a shared link caching network formed by one source node and n users over a wireless slow fading channel. Each user requests an arbitrary file from a library of m files, each of entropy F bits. The users can locally cache up to MF information bits. Under a single-input single-output (SISO) multi-user system, we present a closed form expression of the delay-outage tradeoff under any i.i.d. channel distributions by using the classical caching and coded multicasting scheme presented by Maddah-Ali and Niesen in [1], where outage probability is regarded as the probability that a user cannot decode the requested file. In addition, when the channel gains follow a Gaussian distribution, we show that for a large range of vanishing outage probability p, the average delay scales as Ω (min {n2-ε1, n1-ε2/p}), where ε1, ε2> 0 are some arbitrarily small constants. This means that the multiplicative caching gain introduced by Maddah-Ali and Niesen is lost. To overcome this problem, we modify the network to a single-input multiple-output system (SIMO) system and find the required number of receive antennas per user such that the promised multiplicative caching gain can be preserved.