Research On Multicast Radio Resource Management In Mimo-ofdm System

The next generation mobile network will integrate several communication manners, including unicasst, multicast and broadcast, and support different levels for wideband multimedia service. Using the feature of multiple users participating the same service, wireless multicast is an effective technology to improve radio resource efficiency by making the subscribers form a group and for them to share the common spectrum, time and power resource for receiving plentiful datas transmitted from base station. In multi-path fading channel, besides channel varying with time in mobile users, there are two distinct contradictions in wireless multicast, one is the transmitting contradiction among member users with different channel conditions, and the other is the tradeoff between multi-users diversity gain and multicast gain. MIMO-OFDM has been one key measure in next generation wireless communication systems for the strong anti-fading, resisting interference and relaxing diversity/multiplexing in space, time and frequency domain. In multicast radio resource management (RRM) of MIMO-OFDM system, how to utilize the limited radio resource to provide efficient and reliable multicast service is a hot topic.Based on integrating the current research activities, some key technologies of multicast RRM are studied to guarantee multicast QoS and channel capacity, and improve fairness in MIMI-OFDM system. In the thesis, the primary researched contents and results are listed as bellows.(1) Based on correlation modeling algorithm, the channel space correlation array can be obtained easily for MIMO-OFDM cellular system used in Rayleigh fading condition by setting a coherence value between the elements of antenna according to actuality in transmitter and receiver. Based on this, a multicast transmitting simulation platform is performed for a MIMO-OFDM cellular system, in which unicast users and multicast groups are integrated, and the radio resource can be configured in cells or sectors.(2) An optimization problem to guarantee multicast QoS with SINR threshold through beamforming in MIMO-OFDM system is researched. Choosing the maximum MIMO diversity strategy under limited power is suggested, and an optimization model satisfying SINR of QoS beamforming is extended against the problem of transmitting performance limited by the worst multicast users, deduce the optimized received beamforming algorithm. The solution is obtained by SDR algorithm, and the solution can minimize the transimitting power while the SINR of QoS is guaranteed.(3) In order to overcome the unfair property of SINR among the multicast users with different channel conditions, an optimization model is established based on Max-Min SINR strategy under choosing the maximum MIMO diversity with the limited power in MIMO-OFDM system. The solution is obtained by SDR algorithm, and the corresponding vectors of transmitting beamforming and receiving beamforming could be also obtained. With the upper boundary power, Max-Min and QoS beamforming integrated optimization is proposed to minimize transmitting power while the QoS is ensured simultaneously. In order to make the optimization model has solution when several service modes are integrated in a system, a priority strategy of sub-channel scheduled for multicast is introduced. Simulating result appears that the std of multicast users SINR is suppressed and the fair performance is improved distinctly.(4) For the sake of determination SINR threshold and supporting QoS adaptive transmitting, a link layer mapping algorithm is introduced for multicast based on EESM with proposed maximizing diversity strategy. An inverse link layer mapping method is suggested for estimating MCS and its SINR threshold with given error probability. The maximal throughput can be obtained with QoS guaranteed under the proposed method.(5) Considering the problem of that multicast users may be refused because of their bad channel conditions when spectrum band resource is not enough, a multicast bandwidth dynamic borrowed scheduling algorithm with smoothly upgrading or downgrading QoS level is proposed based on that multimedia bandwidth can be varied. The algorithm can maximize the number of serviced multicast users at the cost of downgrading acceptable QoS level of unicast users. Furthermore, a strategy for multicast users to access system with the priority is proposed, a preserved bandwidth threshold based on user mobility model is suggested, and finally, the optimal threshold for GoS is obtained based on Markov model.