Study On Key Techniques For Uplink Transmission In LTE Trunking Communications System

Trunking communication system is a wireless dispatching system, which provides communication services under the special circumstances. Although from a technical point of view, it is conform to public mobile communication, trunking communication system has some special features, such as high customized requirements, identifying the user priority, extremely fast access etc., which cannot be implemented by public communication. Trunking communication system system is independent of the public network communication system, it has its own separate evolutionary path. It undergoes a three stages network evolution:analog trunking communication system system, digital trunking communication system system and broadband digital trunking communication system system. As a global standard, LTE has high spectral efficiency, high speed, low latency and industry strength. Thus LTE trunking communication system has incomparable advantages than other broadband communication technologies. Currently broadband trunking communication system based on LTE technology has become the consensus of trunking development. Relevant firms such as Hytera are earring out the research of the LTE trunking communication system.This paper is to carry out research work in this industry background. It focuses on research and improvement of uplink key technology in LTE trunking communication system, including two aspects:uplink random access, unlink scheduling and resource allocation.As a key technology in the media access control (MAC) layer of wireless communication system, the pros and cons of random access performance has a negligible impact on the performance of the whole system. Trunking system has special requirements on access delay and identification of user priority. So random access technology will inevitably become the focus in research of uplink of LTE trunking communication system. The core research question in LTE random access is how to reduce the probability of collisions among users in access procedure, thereby reducing the access delay. In this paper, the research takes collision and priority access into account in order to ensure high-priority access. The main work of this paper about uplink random access include the following aspects:(1) Having a study of commonly used random access protocol in communication systems. Analyzing the performance based on the corresponding mathematical models. There is also some work done to classify LTE random access scene classification and analyze the trigger conditions under different scenarios of random access.(2) Studying the preamble sequence in LTE and the common back-off algorithms. For the different characteristics between the trunking communication system and the public network communication, an improved scheme in random access is proposed. In order to verify the performance improvement compared with the LTE random access, two random access simulation models are bulided separately. At the same amount of access services and scenarios to verify the effectiveness and practicality of the new random access scheme.As another important part of MAC, unlink scheduling and resource allocation plays a significance role in the whole system. In some scenario involves public safety, trunking communication system has high requirements on data transmission delay. And in some scenario involves a huge number of data transmission, throughput is also an important performance indicator. The main work of this paper about unlink scheduling and resource allocation include the following aspects:(1) Having a study of commonly used uplink schedule algorithms and a simple comparison and analysis is given. Analyzing the uplink reference signal and the buffer status report related to the uplink schedule. Analyzing the principle and function of the scheduler and general process of uplink scheduling.(2) On the basis of predecessors’work and the characteristics of trunking communication system, a three-dimensional dynamic resources allocation method which can reduce the uplink transmission delay is proposed. Simulation is carried out to verify the effectiveness and practicality of the new method.