Research On The Capacity Algorithm In The Wireless Ad-Hoc Networks

Wireless Mobile Ad-hoc Networks(MANETs)which consist of a number of sensor nodes in the way of multi-hop and self-organization have many advantages,such as networking flexibility and eliminating the constraints of wired devices.MANETs have been widely used in practical applications like emergency rescue,military exercises and medical treatment and gradually become the most promising technologies with rising concerns in the 21 st.How to calculate the overall channel characteristics of the MANETs and the maximum information flow the transmission protocol can be supported is the main problem of the wireless network capacity.Due to the time-varied topology structure and the multi-path fading effects,the throughput of the MANET is far less than the wired networks and can't be obtained by applying the Shannon formula directly.Therefore,it remains an unsolved problem how to calculate and improve the capacity of the wireless networks,which has been much studied in the literature.In 2000,the network's transport capacity put forward by Gupta and Kumar was widely adopted,which was regarded as the foundation of the capacity calculation.After investigating capacity algorithms based on the physics SINR model,we found that the quality of service was not considered in the classical capacity algorithms.This thesis developed the closed-form expressions of the upper bound and lower bound of the multi-hop capacity based on the Gupta physics models for the random networks.Then,we proposed the residual capacity algorithm and total capacity algorithm based on the lifetime of network in the given network topology.Finally,we proposed the power distribution strategy and multi relay cooperative system to improve the capacity.The main contribution of this thesis includes:1.This thesis analyzed the connectivity of the network to form the hops-distribution formula between the source node and the destination node;then developed the closed-form expressions of the upper bound and lower bound of the multi-hop capacity based on the Gupta physics models;first-order energy model was built for computing the bounds of the lifetime of the networks.This thesis defined capacity as the amount of traffic in the lifetime of the networks.The numerical simulation shows: multi-hops network capacity with the node number showed a trend of first increasing and then decreasing;and when the number of nodes increasing,single-hop network capacity is higher than that of multi-hops network capacity.2.This thesis investigated capacity algorithms based on the physics SINR model by using the integer linear programming to formulate the routing problem.We proposed the residual capacity algorithm and total traffic algorithm based on the lifetime of network.The numerical results showed the capacity would be improved with the increase of the nodes in networks and the dynamic capacity was a time-varied function which will decrease with time.Finally,this thesis pointed out that routing strategies and mobility would improve the capacity.3.Channel bandwidth and signal to interference plus noise ratio(SINR)were the main factors that limit the network capacity.This paper proposed an improved wireless network capacity algorithm based on power distribution strategy optimization in multi relay cooperative system.Firstly,the thesis used the multi relay cooperative scheme to improve the network transmission rate and established the network maximum flow model.Under the limitation of network power,we optimized the power distribution of relay notes and established the network maximum flow model.Finally,we compared the interrupt probability and network capacity performances under two different strategies,which were relay coordination and energy optimization allocation and non-relay coordination and equal energy allocation.The results showed that with the increase of the number of nodes,the network capacity increases firstly and then decrease,and the multi relay cooperation and energy optimization allocation strategy was more beneficial to improve the capacity of wireless network.