Wireless ATM-based multicode CDMA transport architecture for MPEG-2 video transmission

Abstract

In this paper, we present a genetic ATM-based multicode code division multiple access (CDMA) transport architecture for the Motion Picture Experts Group phase 2 (MPEG-2) compressed video sen ices over a bandlimited mobile channel with the emphasis of wireless asynchronous transfer mode (ATM) cell design, spreading code management, and the impact of CDMA systems on the video services. Such services allow users to share novel MPEG-2 video applications without any geographical restrictions. The ATM technique is especially well suited for variable bit rate (VBR) MPEG-2 video because of its ability to allocate bandwidth on demand to these services. However, since the mobile radio has a limited channel capacity, the over-all capacity of the traditional ATM-based CDMA system may not be sufficient to accommodate the MPEG-2 video services requested by the multiple mobile users simultaneously. To tackle this difficulty, a multicode CDMA technique is proposed to provide multiple VER MPEG-2 video services by varying the number of spreading codes assigned to each MPEG-2 video in order to meet its dynamic throughput requirement. Moreover, both the multipath fading and interference CDMA radio channels tend to cause significant transmission error and IMPEG-2 bit streams are very vulnerable to these errors. Powerful forward error correction (FEC) codes are therefore necessary to protect the video data so that it can be successfully transmitted at acceptable signal power levels. Two separate FEC code schemes are applied to the header and payload of an ATM cell containing MPEG-2 video data, respectively. The ATM cell header is protected by a relatively powerful FEC code to ensure the low average cell loss I are (CLR). On the other hand, the ATM cell payload is encoded for varying degrees of error protection according to bath the priority and statistical behavior of the payload data in MPEG-2 videos. An adaptive FEC code combining scheme is proposed to provide the good protection for payload data with the maximization of its code rate in order to minimize the extra bandwidth for FEC overhead. Two typical MPEG-2 test sequences are conducted to evaluate the effectiveness of our system.