The network load is increasing due to the spread of content distribution services. Caching is recognized as a technique to reduce the peak network load by storing popular content into memories of users. Coded caching is a new caching approach based on a carefully designed content placement to create coded multicasting opportunities. Coded caching schemes in single-rate networks are evaluated by the tradeoff between the size of memory and that of delivered data. For considering the network with multiple transmission rates, it is crucial how to operate multicast. In multicast delivery, a sender must communicate to intended receivers at a rate that is available to all receivers. Multicast scheduling method of determining rates to deliver are evaluated by throughput and delay in multi-rate wireless networks. In this paper, we discuss coded caching in the multi-rate wireless networks. We newly define a measure for evaluating the coded caching scheme as coded caching delay and propose a new coded caching scheme. Also, we compare the proposed coded caching scheme with conventional coded caching schemes and show that the proposed scheme is suitable for multi-rate wireless networks.

In wireless networks, the mechanism to adaptively select a link transmission rate based on channel variations is referred to as RA (rate adaptation). The operation may have a critical impact on the upper-layer application, specifically video streaming which has strict QoS requirements. Thus, RA should consider the QoS requirements and radio conditions at the same time. In this paper, we present a CV-RA (cross-layer video-oriented rate adaptation) scheme for video transmission over multi-rate wireless networks. The transmission rate is switched in a cross-layer optimized way, by simultaneously considering video R-D (rate-distortion) characteristics as well as wireless conditions. At the radio link layer, transmission rate selection is made using cross-layer optimization. As a result of RA, the effective link throughput dynamically changes. At the application layer, video source rate is adaptively controlled using cross-layer adaptation. CV-RA is compared to three traditional RA schemes. It can realize the highest possible visual communications for any channel condition. For the previous schemes, the variations of visual quality is high due to dynamic packet error rates. In contrast, for CV-RA, visual quality improves with the channel condition.