Mobility support in wimax networks

• Main Author: Lu, Qi.
• Other Authors: Ma Maode
• Format: Theses and Dissertations
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Wireless communication systems
• Online Access: http://hdl.handle.net/10356/40350
• Institution: Nanyang Technological University

The IEEE 802.16e WiMAX system is a potential candidate for the next generation wireless communication systems. It can provide the broadband wireless communication services with wide coverage for mobile devices moving at vehicular speed. With the relatively strong Quality-of-Service (QoS) support and good bandwidth utilization efficiency, it appears to be a suitable technology to build up command and control systems within the military field. However, to meet the very specific requirements in this specific usage, some research work is needed to make certain enhancements to the standard WiMAX system. In the research work, military-specific development efforts are supposed to be carried out to enable the mobility support for the desired scenarios in the military command and control systems. Firstly, the objective of the work in the research is to improve the existing handover schemes to achieve faster handovers with the handover latency reduction. The location-based scanning algorithm is proposed to reduce the number of neighbor base stations (BSs) to be scanned. It can reduce the time required for the target BS selection. On the network re-entry, based on the previous work, the early transport connection identifier (CID) update mechanism is developed to realize the fast resumption of the data transmissions while make full use of the transport CID resources. The improvement makes the fast service resuming more generic and possible for all types of applications. By utilizing the proposed location-based scanning algorithm and the enhanced network re-entry, the latency during the handover can be significantly reduced. Secondly, the QoS affected by the delay during the handover is considered. To improvement the performance, we proposed to equip each mobile station (MS) with an extra receiver that would be used to provide QoS maintenance of ongoing applications during handovers. The scanning and the channel synchronization are performed using the installed receiver. The data transmissions of the real-time applications and the normal system operation via the primary transceiver would not be affected during the handover procedure. Besides, the handover procedure is rearranged to allow handovers to be carried out seamlessly. The proposed scheme provides the faster and smoother handovers without obvious delay and it improves QoS of the ongoing applications during handovers. Thirdly, the issue of group mobility is investigated. By adopting some ideas in the relay technique, the network structure and the handover procedure are developed for the specific scenarios in military situations. To realize the fast handover for a group of MSs in the group mobility scenarios, we proposed a group handover scheme to execute a single handover procedure with the assistance of a special MS which has an extra transceiver and the enhanced functionality. The special MS, called Bridge MS is suggested and placed in the group of MSs and the rest of MSs will be temporarily connected to the Bridge MS during the handover process to achieve the faster transfer of the connections for the group of MSs from one BS to another BS. The proposed scheme can use an improved single handover process to complete the handovers of all MSs in the group. It eliminates the collision of the ranging requests from the multiple MSs within the group and the corresponding backoff. The short latency during the handover for the group mobility scenarios in the military situations is achieved. Finally, the research works, including the tasks on the fast handover scheme, the QoS support during handovers and the group mobility support, are concluded. Recommendations for the future work are made, such as the handover and mobility support in more complicated scenarios like mesh networks, the group mobility in vertical handover scenarios, the security issue in the group mobility and etc.