MAC Designs for Uplink Multiuser MIMO Systems
| Autor: | Wei-Liang Shen, 沈威良 |
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| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 103 With the popularity of mobile devices and data-intensive applications, the amount of traffic generated by existing wireless networks has been tremendously increasing. This phenomenon introduces the urgent requirement for high speed wireless transmissions. One predominate approach is Multiuser MIMO (MU-MIMO) systems, which exploit multiple antennas equipped at a phyiscal access point or a virtual access point connected by backhaul networks to enable several users to communicate simultaneously. These strategies introduce several new challenges: 1) The optimal ransmission bitrate of a user will change with the concurrent transmitters on a per packet basis.Therefore, traditional historical-based bitrate selection algorithms cannot work in MU-MIMO systems. 2) In a uplink MU-MIMO system, every single error caused by hidden terminals or collisions will corrupt the whole packets.Therefore, MU-MIMO systems are especially more vulnerable to errors than single-user networks. Simply retransmitting collided packets will take away the performance gains provided by multiple concurrent transmissions. 3) A system can further combine multiple access points as a multi-antenna virtual access point. However, in such a ``network MU-MIMO system'', arbitrarily forming several antennas as an access point could increase the probability of inter-cell interference and further decrease channel utilization. How to form practically-sized virtual access points becomes a critical problem in network MIMO systems. This dissertation tries to solve the above problems. First, this dissertation focuses on a single access point scenario, and proposes a MAC protocol for each user to properly select their bitrates based on the channels of concurrent transmitters such that the performance gain provided by MU-MIMO can be fully utilized. To address the error vulnerability problem of MU-MIMO,this dissertation proposes a packet recovery strategy for MU-MIMO systems to repair collided packets without significant overhead. Finally, this dissertation introduces a new structure for network MIMO systems, which adaptively forms practically-size virtual access points based on dynamic client distributions and traffic demands to reduce inter-cell interference and enhance antenna utilization. The above designs have been implemented on software defined radio platforms and analyzed through simulations. In both testbed experiments and simulations, the proposed systems can achieve a significant performance gain, as compared to the traditional wireless network and existing MU-MIMO systems. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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