Throughput Computation And Optimization Of CSMA Wireless Networks With Finite Offered-load

WLAN has been widely adopted in our daily life due to its advantages of high data rate, low cost and so on. With the widespread deployment of CSMA wireless networks, the analysis and optimization of CSMA networks have become a hot topic among researchers. For the throughput maximization problem of a CSMA wireless network, this dissertation proposes a model of achieving the maximal aggregate link throughputs through proper offered-load control. Furthermore, to tackle the high complexity of throughput optimization, this dissertation proposes a quick computation method based on the Artificial Bee Colony (ABC) algorithm. Simulation results bore out the accuracy of our optimization model as well as the effectiveness of the quick computation method. The main contents and innovations of this dissertation are as follows.(1) Different from prior works in which saturated networks are considered, this dissertation considers a CSMA wireless network with general offered-load. We build up an analytical model, "contention graph combination (CGC)", to describe the relationship between the offered-load and the output link throughputs. Based on CGC, a linear optimization model is then developed in which the aggregated link throughputs are maximized through optimal offered-load control.(2) To tackle the high complexity of the throughput optimization problem based on CGC, we propose a quick computation method based on ABC algorithm. By carefully designing the objective function and the neighbor-operation strategy, we enable the ABC algorithm to effectively solve the throughput maximization problem within a reasonable time. Simulation results show that the proposed quick computation method based on the ABC algorithm costs much less time while keeps high accuracy.It is worthwhile to note that this dissertation proposes to achieve maximal link throughputs by adjusting the rates of the traffic pumped into the source nodes of links, which runs in a software manner and is more practical to be implemented in real networks, compared with in prior works the CSMA protocol parameters are adaptively adjusted to achieve better performance.