| Wireless communication technology is one of the fastest growing technologies in recent years. The series of wireless access protocols of IEEE 802.16 which made by WiMAX (Worldwide Interoperability for Microwave Access) play an important role in it. These protocols are applied to achieve low-delay, high-quality, high-mobility services such as sound, video, data services, etc. IEEE 802.16 protocols have been committed and put to publish for years. Among them, IEEE 802.16m is a wireless wideband access protocol which is being studying out. It support high speed up to 300km/h, and is compatible with IEEE 802.16e protocol. It is a protocol that makes wireless transmission speed high up to another level.HARQ (Hybrid Automatic Repeat reQuest) technology is an important technology in wireless communication. It is indispensable for improving of data correctness, throughput, spectral efficiency, and quality of service. HARQ technology is one of the key technologies in IEEE 802.16 protocols. It is specified in details in IEEE 802.16e. IEEE 802.16m follow the instructions in IEEE 802.16e, and add up new elements in it.Basing on the compatibility to IEEE 802.16e, this thesis constructs a HARQ system. An improvement method of system throughput, spectral efficiency and transmission delay is put forward. Starting with changing the method of transmission, parameters control, queue control, and reallocation, three important method is given. Evaluation methods are taken, and the methods are proved to be right and useful.Starting with IEEE 802.16e and IEEE 802.16m, this thesis discuss about the differences and associations between them. The theorem of HARQ system is analyzed, and the research depth and direction is expounded. Based on the regulations that are described in IEEE 802.16e and IEEE 802.16m, the structures of HARQ system and their corresponding algorithms are analyzed.Then, the HARQ system is analyzed in theory. The relation among maximum retransmission times, power in every transmission, sub-packet length, modulation bits, coding rate in hybrid automatic repeat request (HARQ) transmission mode and the system throughput is studied. Aimed at enhancing the throughput of wireless transmission system, a feed-back mode with channel parameters is proposed based on IEEE 802.16e protocol, and the constraint of power allocation and packet error rate in the proposed mode is given, which is different from that of transmission mode with fixed parameters. A model under Gaussian channel is established for the analysis of the influence on the throughput caused by different parameters and the corresponding optimization dependent on certain parameter. Then, a sub-optimal iterative algorithm is proposed.Thereafter, using the theory that gets before, the queueing problem in HARQ system is studied in the direction of queueing theorem. In the limitation of system packet error rate, a multi-parameter joint control which gets maximal spectral efficiency is proposed. To get this system work, the minimal queueing buffer and maximal packet arrival rate is given.Last, combining all the conclusions together, the effect made by HARQ transmission mode to the transmission queue is studied. To improve spectral efficiency more and decrease packet transmission delay, a new transmission queueing reallocation method is proposed. This method has never been studied before. After a system simulation to the reallocation method and algorithm complexity estimation, it can be proved that this reallotion method is effective and practical. |
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