Random Access for Massive Machine-Type Communications

Abstract

As a key enabler for the Internet-of-Things (IoT), machine-type communications (MTC) has emerged to be an essential part for future communications. In MTC, a number of machines (called users or devices) ubiquitously communicate to a base station or among themselves with no or minimal human interventions. It is envisioned that the number of machines to be connected will reach tens of billions in the near future. In order to accommodate such a massive connectivity, random access schemes are deemed as a natural and efficient way. Different from scheduled multiple access schemes in existing cellular networks, users with transmission demands will access the channel in an uncoordinated manner via random access schemes, which can substantially reduce the signalling overhead. However, the reduction in signalling overhead may sacrifice the system reliability and efficiency, due to the unknown user activity and the inevitable interference from contending users. This seriously hinders the application of random access schemes in MTC.Therefore, this thesis is dedicated to studying methods to improve the efficiency of random access schemes and to facilitate their deployment in MTC. Rank(•)Rank of a matrix mod(x, y) Modulo operation of x and y lim Limit