Paper Title
Success Rate Maximization with Code-Expanded Random Access for M2M Communication

Many researchers expect that Internet of Things (IoT) era will arrive. As a result huge amount of machine-tomachine (M2M) devices will appear. However, current LTE system is not suitable for this massive amount of M2M devices. Preamble is a kind of resource that is used for random access of devices. The problem is that while expected number of M2M devices in the future is so large, the number of preamble is restricted to 64. What is worse, 64 preambles cannot be used for M2M communications because some of them are reserved for (human-to-human) H2H communications. Among studies to solve this kind of problem, code-expansion can be a powerful method. In this paper, we propose an optimization problem for efficient use of code-expanded. Code-expansion is investigated to maximize the success probability of random access while satisfying the code utility ratio and the access delay threshold. Our simulation shows that the length of a virtual frame which is equal to two is enough to cover up to 120,000 devices for 10seconds. Keywords - Random Access, Success Rate, Code-Expanded, Preamble, M2M Communications