Reduce Transmission Delay for Caching-Aided Two-Layer Networks

Abstract

In this paper, we consider a two-layer caching-aided network, where a single server consisting a library of N files connects with multiple relays through a shared noiseless link, and each relay connects with multiple users through a shared noiseless link. Each relay and user are equipped with a cache memory of M1 and M2 files, respectively. We design a caching scheme that exploits the spared transmission time resource by allowing the concurrent transmission between the two layers. It is shown that the caching scheme is order optimal and can further reduce the transmission delay compared to the previously known caching scheme. Also, we show that for the two-relay case, if each relay's caching size M1 equals to 0.382N , our scheme achieves the same delay as M1 = N , which implies that increasing M1 will not always reduce the transmission delay.

Centralized Hierarchical Coded Caching Scheme Over Two-Layer Networks

“…Due to the complexity of the above hierarchical caching system, there are only a few studies in [9]- [11]. In fact, all the existing schemes consist of two-subsystem model controlled by two parameters α, β ∈ [0, 1], where the first subsystem includes the whole cache memory size of each mirror sites, an α fraction of each file and a β fraction of users' cache memory size, and the second subsystem includes the rest 1 − α fraction of each file and a 1 − β fraction of users' cache memory size.…”

“…However, the ZWXWL scheme ignores the usefulness of users' cache in the second layer when decoding the messages sent from the server. The author in [11] proposed an improved scheme (the WWCY scheme) by utilize two MN schemes. the WWCY scheme also achieves the minimum load of R 2 under uncoded placement, while the load of the first layer R 1 is smaller than the ZWXWL scheme.…”

“…From the introduction in the above subsection, the existing schemes already have a good performance on R 2 , while designing a scheme aiming at decreasing R 1 still remains open. Further, [9]- [11] all utilize the MN scheme or MN decentralized scheme, whose subpacketization increases exponentially with the growing on user number, so it is meaningful to design the scheme with minimizing the transmission load for the first layer R 1 or reducing the subpacketization. According to the above points, in this paper we obtain the following main results.…”

“…So we can get a scheme with flexible subpacketiztion when we choose the base PDAs with low subpacketiziations. In addition if the base PDAs are MN PDAs, then the scheme realized by our HPDA is exactly the scheme in [11].…”

Coded Caching for Broadcast Networks with User Cooperation

“…Besides, other researches also studied the application of decentralized coded caching for hierarchical tree topologies where the server communicates with the users through some intermediate cache-aided relays [23]- [25]. [24] investigated the two-layer network considered in [23] and allows the relays to send signals during the servers transmission. The proposed caching scheme is proved to be order optimal and achieves an additive parallel gain by fully exploiting the opportunity of concurrent transmission at the server and relays.…”