Research On Systematic RaptorQ Codes Decoding Algorithms For Mobile Multimedia Broadcast

Mobile multimedia services appeared in the third generation mobile communi-cations. Facing to the fourth and the fifth generation mobile communications, it needs to improve the quality and the rate of its transmission. So solving the problems of multimedia's transmission speed and transmission quality are lmminent.For the reasons of the network structure of mobile network is specific and the requirements of multimedia services that multiple users can simultaneously receive the same data. However, the network resources can not be shared by the existing IP multicast and it can not satisfy the features of mobile network, the Multimedia Broadcast Multicast Service(MBMS) protocol architecture, which is put forworded by the 3GPP MBMS, is the best way to solve the multimedia's transmission. Reliablity of MBMS's data transmission is depended on the FLUTE protocol, which using the systematic Raptor codes to solve the data packet lossion. Although trad-itional TCP protocol can ensure reliable data transmission, TCP protocol uses an automatic feedback mechanism retransmission ARQ, which needs of feedback channel, When the channel environment is bad, one or more users will send the retrans-mission information, which will increase mobile multimedia servic es transmission delay, and at the same time cause the data congestion. Compared with ARQ, the forward error correction code, which without the feedback channel, is more suitable for mobile multimedia services background.First, this paper looks the Raptor codes, which is belonging to the forward error correction code, as the research objection. To satisfy the conditions of the rapid of transmission rate and the higher quality of the forth and fifth mobile communication system, we need to research about the improvement of the systematic Raptor codes decoding methods, such as based on the form of the generated matrix, by changing the columns of it, we call this method as IM1; then using the method called Maximum Likelihood to select row, which called IM2; at last combine IM1 and IM2, which called IM3. Making some simulation comparations on these methods, the results prove that these three methods all can achieve the goals of reducing of decoding time and the decoding complexity, and IM3 is the best method to o ptimize the systematic Raptor codes.Secondly, this paper also looks the new research result—the systematic Raptor Q codes as the research objection. Although using the systematic Raptor Q code s replaces the systematic Raptor codes can improve the performance of transmission, it is at the expensive of increasing the time of encoding and decoding and the complexity of it, so we also need to optimize it to achieve the goal. First, we use the methods which used in the systematic Raptor codes, then reduce the decoding steps of system Raptor Q codes, according to the system Raptor decoding steps, and combine the methods refered to, we call them Nocopy-IM1-Raptor Q, Nocopy-IM2-Raptor Q, Nocopy-IM3-Raptor Q. At last, making some comparations on them, and the results prove that Nocopy- IM3-Raptor Q is the best mehod.Finally, based on the above knowledge and according to the research on the FLUTE protocol, we making some implements on the protocol process. First, using the systematic Raptor Q codes replaces the systematic Raptor codes to transmit the satatic picture to improve the quality of transmission. Then making some simulations and the results prove that when the block code is small, we can change the FEC encoding method, using the systematic Raptor Q codes replaces the system- atic Raptor codes for transmitting data. Although the systematic Raptor Q codes can increase the timing consume of the coding and decoding, its performance is better than the systematic Raptor codes, then we can using the Nocopy-IM3-Raptor Q to reduce the time that consumed in the data transmission and the complexity of it. At last, using Nocopy-IM3-Raptor Q replaces the systematic Raptor Q codes to transmit the static picture.In order to satisfy the index requirements of the forth generation mobile communication, this paper makes a optimization on the decoding of the systematic Raptor codes, which is used in the FLUTE protocol, to reduce the decoding time and the complexity of decoding; facing to the fifth generation mobile communication, using the systematic Raptor Q codes replaces the systematic Raptor codes to improve the quality of data transmission, and using the method Nocopy-IM3-Raptor Q, which is proposed by this paper, to a certain extent solves the higher complexity and decoding time.