本项目针对M2M通信系统中MTC设备密度高、短数据包传输、时延需求多样化等特点，在有限长编码约束下，研究适用于M2M通信的联合spinal码传输-随机接入理论，以降低MTC设备的接入碰撞概率和接入时延，提高接入吞吐量和数据传输效率。为此，将首先基于Spinal码的基本原理，设计一类适用于M2M通信系统的双向Spinal编码方案，研究其有限长性能和渐近性能，给出双向Spinal码的优化设计方法，在此基础上设计具有不等错误保护特性的双向Spinal码；然后，研究基于双向Spinal码的联合物理层传输-随机接入(即联合Spinal码传输-随机接入)理论，在有限长编码和限定最大接入用户数的约束下，分析所设计方案的接入吞吐量，并以最大化接入吞吐量为目标，研究接入控制、接入资源分配和双向Spinal码等参数的优化，最终给出适用于M2M通信系统的有限长编码约束下的联合物理层传输-随机接入方案与方法。

Considering the characteristics of the M2M communication systems, such as high density of machine type communication (MTC) devices, usually a small amount of data to be transmitted or received, various delay requirements and so on, this project will study on the theory of joint spinal coding and random accessing scheme to decrease the probability of access collision and the access delay, as well as to increase the access throughput and the data transmission efficiency. To achieve this objective, a kind of two-spinal codes, which are obtained by modifying the basic structure of the initial spinal codes, for M2M communication systems will be designed first. The performance of the finite length two-way spinal codes, as well as the asymotic performance, will be analyzed, based on which the optimization of the two-way spinal codes will be discussed. A kind of two-way spinal code with unequal error protection capability will also be designed for some special applications in M2M communication systems. Another theory that needs to be studied is the design of joint physical-layer transmission and random accessing scheme. In this project, we will discuss the design and optimization of a kind of joint two-way spinal coding and random accessing scheme. Specifically, the access throughput of the designed scheme will be discussed first under the assumptation that the codeword length of the error-correcting code employed by MTC device is finite and the maximal number of access users employ the same resource blocks is limited. Then, to maximize the access throughput, the optimization of the access controlling parameters (i.e. access barring), the access resource allocation parameters and the encoding parameters of the two-way spinal codes will be studied. The results of this project will give a systematic theory on the design and optimization of joint physical-layer transmission and random accessing theory.