| In recent years, mobile communication technology is facing the development of 2G to 3G/LTE. With the enhancement of the rate of the air interface, mobile communications services has also developed rapidly from voice service only to many multimedia services, such as MSM(Multimedia Messaging Service), VoD(Video-on-Demand ), live broadcast, file download and so on. Because of the ability of meeting users'demand for video immediately, the VoD service has got more and more attention and may grow to be a new killer service. However, due to the limited wireless resource and the time-varying characteristics of wireless channel, the enhancement level of the air interface rate can't catch up with the growth rate of the mobile services, so many users applied VoD service can't be served alone and provided QoS promise. To popular videos, full use of the broadcast nature of the wireless channel and providing satisfactory service for users using multicast/broadcast have become one of the hot researches. For an example, Multimedia Broadcast Multicast Service(MBMS) has been defined in 3GPP R6 protocol.Considering the sequence of arrival of the mobile VoD users'requests, this paper used periodic broadcasting protocols. FGS (fine-granular-scalability) layered video coding was used to encode videos. The object is to use limited bandwidth resources fully to improve user's video quality and the utilization of the bandwidth. According to the object, this paper did the research of bandwidth allocation while considering the heterogeneity of the users and differences and time-varying characteristics of the wireless subchannels.Based on periodic broadcasting and FGS layered video coding protocols, the research content of this paper contained: (1) the scheme of bandwidth allocation while considering the heterogeneity of the users; (2) the scheme of subcarriers allocation while considering the differences and time-varying characteristics of the wireless subchannels in wireless OFDM systems. The contributions of this paper are listed as follows: (1) because of the differences of the users'terminal equipments and the received bandwidth, users receive videos from periodic broadcasting protocol with different rules. The paper classified the users and provided a scheme of wireless bandwidth resource allocation, according to transmission rule of the periodic broadcasting protocol and the receiving rule of the users. The scheme allocated bandwidth to many enhancement channels to improve the users'perceived video quality. (2) in wireless OFDM systems, users'channel quality is different to the same subcarrier, in addition, the channel is time-varying.. This paper provide a scheme of subcarriers allocation while considering wireless channel characteristics. The scheme allocated subcarriers to many base video layers and enhancement video layers to enhance the utilization of the subcarriers while promised users'base video quality. |
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