Cooperative communication fully leverages the broadcast nature of the wireless channel and spatial diversity, thereby achieving tremendous improvements in system capacity and delay. A cross-layer implementation approach has been pursued in this demonstration, in order to confirm the viability and efficacy of cooperation at the MAC layer, in conjunction with the routing layer, in multi-hop ad-hoc networks. In the cooperative MAC protocol [1], a station would use a neighboring helper station for MAC layer forwarding, if the two-hop relaying yields to a better performance than a direct single-hop transmission. In this cross layer scheme, the DSDV routing protocol [2] defines a multihop path from the source to the destination, while the cooperative MAC scheme, eventually selects two hop forwarding for each routing layer hop, in order to boost the performance of the routing protocol. The Cooperative MAC scheme has been implemented in the MadWiFi [3] driver, while the DSDV routing protocol has been implemented in the Click modular router [4]. In the demo, a video clip is streamed from a server to a remote client, where the received video is played out in real time. The basic route is discovered by the DSDV routing protocol that runs on every station. The underlying MAC implementation would dynamically alternate between IEEE 802.11g and the cooperative MAC protocol, for each route hop. In the multi-hop, ad-hoc network, the cooperative cross-layer scheme delivers a smooth user experience while the video playout over the legacy IEEE 802.11g has noticeable freezes and frequent distortions. The demo verifies the extensibility of the cooperative MAC protocol into multi-hop ad-hoc networks, where in conjunction with the routing protocol, can achieve superior performance, compared to the legacy IEEE 802.11g.
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