Wireless Multihop Device-to-Device Caching Networks

Abstract

We consider a wireless device-to-device (D2D) network where n nodes are uniformly distributed at random over the network area. We let each node with storage capacity M cache files from a library of size m ≥ M . Each node in the network requests a file from the library independently at random, according to a popularity distribution, and is served by other nodes having the requested file in their local cache via (possibly) multihop transmissions. Under the classical "protocol model" of wireless networks, we characterize the optimal per-node capacity scaling law for a broad class of heavy-tailed popularity distributions including Zipf distributions with exponent less than one. In the parameter regimes of interest, we show that a decentralized random caching strategy with uniform probability over the library yields the optimal per-node capacity scaling of Θ( M/m), which is constant with n, thus yielding throughput scalability with the network size. Furthermore, the multihop capacity scaling can be significantly better than for the case of single-hop caching networks, for which the per-node capacity is Θ(M/m). The multihop capacity scaling law can be further improved for a Zipf distribution with exponent larger than some threshold > 1, by using a decentralized random caching uniformly across a subset of most popular files in the library. Namely, ignoring a subset of less popular files (i.e., effectively reducing the size of the library) can significantly improve the throughput scaling while guaranteeing that all nodes will be served with high probability as n increases.

How Much Can D2D Communication Reduce Content Delivery Latency in Fog Networks With Edge Caching?

“…To the best of our knowledge, F-RANs with D2D communication have not yet been considered, apart from the conference versions of this work [25], [26]. Content delivery in a multi-hop D2D caching network was instead studied in [27], where the per-node capacity scaling law was derived. In [28], it was shown that in-band transmitter or receiver cooperation cannot increase the sum DoF of an interference channel.…”

“…Next, for M < K and r F ≥ 1, the achievable NDT (23) satisfies 27 where (a) follows from δ ach (µ, r F , r D ) being a monotonically decreasing function of µ and since µ > 0, whereas (b) is due to r F ≥ 1. Dividing (72) by (60) gives…”

The Design of Dynamic Probabilistic Caching with Time-Varying Content Popularity

“…Fig. 10b shows the cache hit ratio of the three schemes as well as the number of replacements of LRU and the (simplified) proposed dynamic caching versus the cache size N c in the range of [10,100]. The popularity skewness parameter s is 0.8, and the average content lifetime for the 100 most popular files is 32.7 minutes.…”

Information- Theoretic Analysis of D2D-Aided Pipelined Content Delivery in Fog-RAN

“…A cache-aided interference channel where both ENs and users have caching capabilities was studied in [9], and lower and upper bound on the sum degrees-of-freedom were presented under the constraint of linear precoders at the ENs. Content delivery in a D2D caching network, i.e., without ENs, was studied in [10], where the per-node capacity scaling law was characterized for multi-hop D2D communication.…”