Research And Improvement Of QoS Technologies In 3GPP LTE System

To ensure competitive edge over other cellular technologies such as WiMAX, 3GPP started work on the LTE and SAE research project with a workshop that was held in Toronto Canada in November 2004. LTE-Advanced meets or exceeds all IMT-Advanced requirements. LTE is expected to substantially improve end-user throughputs, sector capacity and reduce user plane latency, bringing significantly improved user experience with full mobility. LTE-Advanced have been supported by almost all the major operating companies and telecommunications manufacturers.Providing strict end-to-end Quality of Service (QoS) guarantee of data, voice, image, video and other multimedia services is the major challenges. From view of user, QoS is the satisfaction with services; and from services point, it is the performance parameter such as bandwidth, delay, packet loss rate and so on. After gives a briefly introduction about LTE system and the MAC protocol, this paper focus on the QoS related technologies.Firstly, this paper introduces the 3GPP LTE system including the development process, system architecture, key technology, TD-LTE technology and the Structure and function of MAC protocol. Then an OFDM communication system including transmitter and receiver was designed and the performance of the system was analyzed. This paper analyses the possibility and necessity of the cooperation of the LTE and the internet of things, and then an architectural of the internet of things based on LTE system is proposed.Secondly, the QoS mechanism of LTE system had been studied and improved. This paper introduces the roadmap of QoS and the existing QoS mechanism including EPS bearer, bearer structure and QoS parameters. And then this paper proposed an enhanced QoS architecture, which is based on the existing QoS architecture and the buffer module, traffic policing module, competitive regional distribution module added. In addition, the uplink packet scheduling module and the admission control module were designed. Thirdly, this paper proposes an efficient adaptive uplink scheduling algorithm for voice over Internet protocol (VoIP) services with adaptive multi-rate (AMR) speech codec in LTE systems. In our proposed algorithm, the eNode B adapts uplink resources assignment according to the two reserved bits in the generic MAC header, which is utilized to indicate the mode transition of next frame. This paper gives a generally introduction of the conventional algorithms (UGS, rtPS, Lee, Oh) as well as the proposed one. The performances of the proposed strategy in terms of system capacity, throughput, delay of system are analyzed. The theoretical analysis and simulation results show that the average access delay increases but still meet the VoIP real-time requirements and our algorithm can support much more voice users than the conventional algorithms.Fourthly, to minimize the UE power consumption, a discontinuous reception (DRX) mechanism has been adopted in LTE, but the LTE DRX only has long DRX cycle and short DRX cycle, and it cannot dynamically adjusts the cycle length according to the QoS of various kinds of services. In order to overcome the shortcomings above, this paper presents an improved algorithm which can adjust the cycle length and adjust the initial sleep interval according to the last cycle length. Then the performances of the proposed strategy in terms of energy consumption and delay are analyzed. The simulation results show that the proposed algorithm has better performances.Finally, according to the proposed algorithm, this paper designed and invented a DRX device and its control methods based on LTE system. The device includes data buffer, control module, the initial sleep interval algorithm module and the sleep interval algorithm module, and the control methods of DRX cycle control device are given. The device can achieve a variable sleep cycle multiples, and adjust the initial sleep interval according to the last cycle length.