Research Of Maximum Weight Packet Scheduling Scheme With Retransmission In Ad Hoc Networks

Nowadays,wireless devices such as sensors,PDA,wireless base stations are becoming more and more popular while its price is decreasing.Therefore,the development of wireless networks is essential.Due to the popularity of wireless local area network(WLAN)based on IEEE 802.11,people's interest in Ad Hoc network is increasing.Because of the instability of wireless network and the interference susceptible nature,Wireless networks are prone to transmission errors.Transmission failure can easily lead to queue backlog or head of line problem,that's why we introduce retransmission to solve the problem of transmission failure.The retransmissions is the basic building block that communication protocols use it to realize reliable transmission of data packet.However,the origin immediate retransmission of 802.11,the continuous possible interference may cause the following multiple retransmissions failed.Most traffic in multi-hop wireless networks is elastic,and minor delay is expected and tolerable in packet transmissions.To reduce data loss,retransmission scheme has been applied,as we metioned before,however,uncontrolled retransmission may increase network overhead significantly and data loss probability defeating the retransmission purpose.Therefore,we propose a packet scheduling scheme with retransmission.the retransmission of the scheduling is added to the scheduling considerations in order to achieve higher throughput and better service.Most retransmission schemes are studies in single base station networks,in this paper,we propose a maximum weight packet scheduling scheme with probability retransmission in multihop wireless networks,which integrates packet scheduling and retransmission in a unified manner at the MAC layer in order to minimize the negative effect of transmission errors to network performance.The main features of the proposed scheme are as follows:(1)the existing maximum weight scheduling algorithm does not consider the case of queue overflow,that the queue is infinite,it is unrealistic,in the proposed algorithm we add the queue usage to the scheduling decision.(2)An improved link prediction method is used to predict the status of the link.(3)The transmission priority of the flow is determined by the congestion degree of the queue and the delay of the transmitted packets to ensure the throughput of the network.(4)The retransmission priority of the flow is determined by the potential reliability of the transmission link,the congestion degree of the queue,and the delay of the packet.(5)In addition,the retransmission of the packet is deferred to the next service time of the flow,the purpose is to eliminate the additional delay to the other flows due to the immediate retransmission and to protect the allocation of the expected service resources.