Analysis and design of efficient massive device communication for heterogeneous networks.

With the exponential increase in high rate traffic in today’s mobile cellular networks, wireless communication system is facing a enormous change. Wireless cellular networks have to provide full coverage of wireless access anywhere and anytime and have enough capacity to serve user equipments (UEs). In order to satisfy the high rate traffic and consider the sustainability of our society, 5G networks will need to face big challenges. In this dissertation, analysis and design of efficient massive device communication schemes are considered for Heterogeneous Networks (HetNets). The contributions of this study are two-fold. One is to overcome random access bottleneck for massive device in HetNets, the other is to overcome bandwidth bottleneck for massive device in HetNets. First, two different strategies to overcome random access bottleneck for massive device in small cells have been proposed. One strategy is model-based load estimation and dynamic p-persistence random access scheme. Performance shows that proposed load estimation and p-persistence random access help to reduce contention when a massive number of UEs simultaneously accessing a small cell. Another strategy is hash preamble random access scheme, which used some information based on the load estimation developed in the Chapter 3. The hash preamble random access scheme includes the multiway-tree coding virtual preamble space and Fibonacci hash preamble mapping. Multiway-tree coding virtual preamble increases orthogonal preamble space and reduced ambiguities by coding. Fibonacci hash preamble further reduces ambiguities by the hash function. These two random access schemes are proposed to support massive devices in small cells. The results in proposed model-based load estimation and dynamic p-persistence random access scheme are 5 times as high as the LTE system. The results in proposed hash preamble random access scheme are 16 times as high as the LTE system. Second, a technique to overcome bandwidth bottleneck for massive device accessing a small cell in HetNets is introduced. To overcome the bandwidth bottleneck, we propose using cognitive-based small cells. The main feature of cognitive-based approach is the elimination of message exchanges to achieve spectrum sharing. We model our proposed solution using into a Continuous-Time Markov Chain model and demonstrate improvement of the system performance in terms of system throughput, collision rate load balancing and delay for HetNets