Study On Uplink Wireless Access Technology In LTE Private Network System

Private trunking communication is a wireless dispatching system, which provides communication services in exceptional relief, security service and other similar special circumstances for outdoor users. Although from a technical point of view, it is conform to public mobile communication, private trunking communication has some special features, such as high customized requirements, identifying the user priority, which cannot be realized by public communication. Private network trunking communication system is independent of the public network communication system, it has its own separate evolutionary path. It undergoes a three stages network evolution:analog private network trunking communication system, digital private network trunking communication system and broadband digital network trunking communication system.4G LTE, as a global standard, has high spectral efficiency, high speed, low latency and industry strength. Thus LTE network trunking communication has other broadband communication technologies incomparable advantages. Currently broadband private network trunking communication based on LTE technology has become the consensus of private network trunking development.This paper is to carry out research work in this industry background. The research focuses on QoS assurance of random access in LTE TDD private trunking communication. As a key technology in the media access control (MAC) of wireless communication system, the pros and cons of random access performance has a negligible impact on the performance of the whole system. Private network trunking system has requirements on access delay and identification of user priority. So random access technology will inevitably become the focus in research of uplink of LTE private network. 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 include the following aspects:1) Having a study of three 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. Two different LTE random access procedures are analyzed too.2) Studying the frame structure and the preamble sequence in LTE TDD. Analyzing the typical business model of trunking communication and the mathematical model of access. A further study of TD-LTE random access channel model compared with multi-channel slotted ALOHA follows. There is also a TD-LTE random access performance analysis.3) For the different characteristics of private network communication with the public network communication, proposing an improved preamble allocation scheme (APL-RA) in random access based on the original TD-LTE. In order to verify the performance improvement compared with the TD-LTE random access, building two random access simulation models separately. At the same amount of access services and scenarios to verify the effectiveness and practicality of the new random access scheme.