The Research On The System Of Adaptive Multi-service Transmission Of OFDM Based On Smart Antenna

With the high requirement of the transmission of services in quality and the scarcity of frequency resources, OFDM become a key technology for next generation mobile communication system because of its high spectrum efficiency and good capability of decreasing multipath interference. The paper is supported by the Nature Science Foundation of China "Research on joint source-channel allocation of WPDM system oriented graded multi-service"( No.60372084).In this paper a method is put forward which combine Adaptive Antenna Array (AAA) with OFDM. Adaptive antenna array is employed in the receiver side. This paper proposes a modified Sample Matrix Inversion(SMI) algorithm, a windowed subcarrier-grouping method is used to estimate the most optimum weight of the antenna array. Simulation results show compared to the conventional OFDM system , the system BER performance is improved by using adaptive antenna array. Based on the modified system, a adaptive bit assignment algorithm is proposed. The Signal-to-Noise Ratio (SNR) of the subcarriers, which can be derived from the SMI algorithm's weight, is used to control the modulation mode adaptation. In OFDM system we can realize the channel's dynamic allocation. This trait offers a method of raising the spectrum efficiency further for transmission system oriented multimedia service. This paper puts away the traditional coarse service classify according to difference of application, and proposes a new concept of fine grading for data service. Data service is classified to different quality based on delay time. Then ,bit/channel/width is adaptive assigned based on the condition of channel. This method will realize to use all limited channel recourse to transmit all service.