This paper proposes a Service Differentiated-Dynamic Slotted Multiple Access （SD-DSMA） protocol with QoS guarantee. The Media Access Control （MAC） frame format is variable according to the traffic of uplink and downlink and the traffic of control and data. In addition, the services are divided into two categories, Guaranteed Bandwidth （GB） and Best Effort （BE）. Uplink control message slots are designed for the GB users to reduce contention. Taking into consideration the techniques in physical layer, a two-Dimensional Radio Resource Allocation （2-D RRA） method is proposed. The 2-D RRA is an efficient way to allocate radio resources for multi-cell, multi-user OFDM/TDMA system as it takes into consideration both the channel condition and the co-channel interference. The piggyback mechanism and fair scheduling algorithm are adopted for GB services, and the max C/I scheduling algorithm is used for BE services. The simulation results show that the proposed MAC protocol has better performance in terms of delay, probability of successful access request.
This article proposes a simple pilot-aided channel estimation method based on correlation in time domain for multiple-input and multiple-output olthogonal frequency division multiplexing （MIMO-OFDM） systems. Pilot symbols in all transmit antennas are generated from different circular shifting of a certain sequence. Through once correlation, the receiver can obtain time-domain pulse responses for channel fading from all transmit antennas to a certain receive antenna, from which channel estimation in frequency domain can be obtained. Beyond 3G time-division duplex （B3G-TDD） uplink is introduced, and the channel estimation method is used in it. Theoretical analysis and simulation are both carried out. Mean square error （MSE） performance shows that the method can exhibit precise estimation. Complexity analysis proves it requires very low complexity. System simulation result shows that it guarantees the performance of B3G-TDD uplink very well.
ZHOU Ming-yu LI Li-hua JIANG Jun ZHONG Ming-hua TAO Xiao-feng
