QoS Guaranteed Wireless Broadcast Scheduling with Network Coding and Rate Adaptation in NS2

Network coding is critical to wireless broadcast for real-time applications. Most of the existing approaches make strong assumptions either on application requirements (e.g., single constraint type or the same constraint level) or on data transmission (e.g., ideal channel, fixed transmission rate, or packet length) in order to facilitate formalization and solution. Those assumptions limit the applicability of previous approaches. This work studies quality-of-service-guaranteed broadcast scheduling over wireless networks with network coding and rate selection capabilities, focusing on reducing broadcast completion delay while maximizing the number of packet receptions that satisfy heterogeneous deadline and reliability requirements. To begin with, a multirate graph model is constructed to formulate the optimal broadcast scheduling problem, which is proved to be NP-hard. Then, an adaptive graph compression policy is proposed to reduce the computational burden significantly without sacrificing performance. Furthermore, an approximation framework is presented for each propagation. In the framework, the coding strategy and rate selection can be formulated as a complexity-adjustable clique problem. Finally, a progressive clique search algorithm is designed to make decision on each broadcast. Simulation results demonstrate that compared with typical heuristic algorithms, the proposed algorithm achieves significant performance improvement with lower complexity.