Abstract-This paper compares, through analysis and simulation, a number of multichannel MAC protocols. We first classify these protocols into four categories based on their principles of operation: Dedicated Control Channel, Common Hopping, Split Phase, and Parallel Rendezvous protocols. We then examine the effects of the number of channels and devices, channel switching times, and traffic patterns on the throughput and delay of the protocols. Here are some of the conclusions of our study: 1) Parallel Rendezvous protocols generally perform better than Single Rendezvous protocols, 2) the Dedicated Control Channel protocol can be a good approach with its simplicity when the number of channels is high and the packets are long, and 3) the Split Phase protocol is very sensitive to the durations of the control and data phases. Our study focuses on a single collision domain.
Abstract-Many multiple channel MAC protocols for wireless networks have been proposed to make efficient use of multiple channels where each node has a single radio which allows it to send or receive on one channel at a time. However, most of the proposed protocols are single rendezvous protocols that are subject to the congestion of the control channel. We propose a new parallel rendezvous protocol, McMAC, to avoid control channel congestion so that it can scale to use a large number of channels efficiently. We validate our protocol design using simulation and implementation.
Recent advancements in video and audio codec technologies (e.g., RealVideo [18]) make multimedia streaming possible across a wide range of network conditions. With an increasing trend of ubiquitous connectivity, more and more areas have overlapping coverage of multiple wired and wireless networks. Because the best network service changes as the user moves, to provide good multimedia application performance, the service needs to adapt to user movement as well as network and computational resource variations. For wireless multimedia applications, one must ensure smooth transitions when network connectivity changes. We argue that network adaptations for multimedia applications should be provided at the application layer with help from proxies in the network. The reasons are ease of programming, ease of deployment, better faulttolerance, and greater scalability.We propose a self-adaptive distributed proxy system that provides streaming multimedia service to mobile wireless clients. Our system intelligently adapts to the real-time network variations and hides handoff artifacts using application protocol specific knowledge whenever possible. It also uses application-independent techniques such as dynamic relocation of transcoders and automatic insertion of forward error correction and compression into the data transcoding path. We advocate a composable, relocatable transcoding data path consisting of a directed acyclic graph of stronglytyped operators to bridge any data format mismatch between the client and the data source. In this paper, we present the design, implementation, and evaluation of our system in the context of streaming video playback involving a series of transcoding proxies and a mobile client.
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