| Various applications, such as battlefield surveillance, industrial process monitoring and control, civil infrastructure monitoring, etc. are enabled by multihop wireless networking technology. Many wireless multihop networks carry streams of data with time-critical information (e.g., video streams in surveillance networks, sensor streams in monitoring and actuating applications, or command and control streams in factory automation applications). Such data must reach their destinations in a predictable and timely manner. Providing real-time communications in such a multihop wireless network is critical to their success. However, providing timeliness support is challenging, mainly due to (i) the inherently unreliable nature of the wireless medium, (ii) the distributed nature of multihop wireless networks, and (iii) the resource-constrained (mainly bandwidth and energy) environments. As a result, the design of an effective and efficient medium access control layer is especially important since it lays the foundation to provide actual timeliness support for all upper layers.;However, existing solutions are either over-coordinated (fixed-schedule-based schemes) or under-coordinated (prioritized contention-based schemes), failing to address this problem efficiently. This thesis introduces DRAMA, a new distributed, progressive, dynamic slot reservation mechanism, aiming to provide timeliness support at the medium access control layer. In DRAMA, each node progressively and dynamically makes short-term slot reservations according to the timeliness and bandwidth requirements of its outgoing traffic, thereby quickly adapting to traffic and link dynamics. Potentially interfering nodes reserve slots in a serialized and orthogonal manner, which ensures fast, contention-free slot reservations with high bandwidth utilization and low bandwidth overhead. Similar to fixed-schedule-based approaches, nodes in DRAMA can enter a low-power sleep mode when they do not transmit or receive data.;To validate the design, we implemented a prototype and deployed it for extensive experiments. Our experimental results show that DRAMA is able to meet end-to-end latencies under various traffic and link dynamics when other schemes may not be able to do so, while incurring little energy and bandwidth overhead. |
