Design And Implementation Of A Handover Scheme For Seamless Multicasting In Video Service

With the development of the wireless network and the popularity of the IP-enabled portable mobile devices, people have more opportunity to access the multimedia service in daily life.As the range of one AP(access point) is limited, a handover process is inevitable during the mobile node moving around.In addition,the handover process belongs to the hard handover.Once no measures taken to reduce the damage,the mobile node will be faced with unignorable time delay and packet loss.Two main aspects have done to release the problems caused by the handover process.On the one hand,a comprehensive and realizable scheme for multicast handover has been put forward.The proposed scheme is based on the existing schemes. And some points for realize the scheme have been further explained in this thesis. On the other hand,on the basis of sufficient investigation and research,some theoretical improvements have been present for multicast service handover in PMIPv6 network. The main achievements in this paper are as follows:(1) The design and implementation of a handover scheme for seamless multicasting in video service are studied.The schemes for resolving the handover problems mainly focus on two directions: the one is to decrease handover delay, and the other one is to decrease the packet loss by storing packets.At first, comparisions among the existing schemes have been made to study the advantages and disadvantages of the exsiting schemes.And then, a relatively much more comprehensive scheme has been proposed.The "background scanning" method to reduce the handover delay and seamless handover method with caching packets are combined in the proposed scheme.In addition,a number of important parameters and steps have been further researched in this paper.The points to realize the proposed scheme are mianly about the predicted handover time,the buffer data in MH and AP,the identification of some wireless events and the configuration of the Raspberry Pi.(2) Some improvements on the handover scheme for seamless multicasting in PMIPv6 wireless networks are studied.Because many redundancy signals and steps are still consist in the existing schemes,many aspects need to improve.An added Neighbour List Entry in MAG and a modified set of probably new LMAs can contribute to low handover latency and nearly zero packet loss.Also,the time in p-MAG or p-LMA for stopping bufferring packets has been redefined.In exsiting schemes,to find the n-LMA, the p-LMA would broadcast query messages to all of its neighbour LMAs.However, in the proposed scheme,the p-LMA multicasts the query messages to only the neighbour LMAs in the nLMA-set.In this way,a number of unnessary signal and delay can be left out on the p-LMA.In addition,the proposed scheme put forward a NMLE(The Neighbour MAGs List Entry) message in MAG.By using the added NMLE message,the p-MAG can judge the type of handover. And thus,the task of judging the handover type is handed over from the LMA to MAG. In addition,the signal and processing steps in local and gloabl mobility are explained in detail.At last,the simulation result indicates that the proposed scheme performs a faster binding and group joining procedure.