Self-organizing Network Voice Broadcast Protocol Study

IP phone becomes more and more popular, and it develops quickly with its high bandwidth utilizing rate. IP phone can be applied anywhere, especially in Ad Hoc network which develops recently.The main goal of this subject is researching voice broadcasting in Ad Hoc network, analyzing whether it is possible to realize voice broadcasting and how far the broadcast can be reached with the voice broadcasting performance characteristic, and proposing a new protocol PDP-3CTS to improve the communication quality for the voice broadcasting problem.Firstly,this paper analyzes the performance of voice broadcasting under BF and PDP protocol. The voice broadcasting in Ad Hoc network is limited by hops which can only get good communication quality within some hops. Voice broadcasting is not affected by voice coding when the data interval after encoded is the same. The voice communication is getting worse when the background traffic is getting more. Although BF can get high packet receiving rate, it can result broadcast redundancy, wasting channel utilizing rate and bringing more contention and collision, and its performance varies by node's density. PDP reduces broadcasting redundancy by reducing rebroadcast nodes but get lower receiving rate. Ad Hoc network brings voice broadcasting hidden terminal problem because of its multi-hop sharing channel, so voice communication quality gets worse. Based on PDP,this paper proposed a broadcast protocol which adopts RTS-CTS to reduce hidden terminal problems.Although RTS-CTS can reduce hidden terminal problem, it brings CTS packet collision. This paper proposed that CTS could be sent in different time slots which have been allocated already. By this mean we can not only reduce CTS collision but also improve receiving rate. We adopt CTS to reduce hidden terminal problem if potential hidden terminal can receive CTS packet then it will be prevented sending packet. We only permit no more than three time slots to send CTS as too many CTS will cause long delay and delay jitter.I programmed in OPNET and realized the new protocol. After simulating I conclude that the new protocol has higher receiving rate and has steady performance but higher delay and delay jitter than BF and PDP. Because voice broadcasting is not interactive communication, it requires delay not much and within a certain delay jitter the more packet it received the better voice quality it will get. The new protocol increases the packet receiving rate by considering the delay and delay jitter not so much, and it results in wider broadcasting communication area and improves the quality of voice communication.