On The Timing Synchronization For MB-OFDM UWB Systems

Ultra-wide Bandwidth (UWB) technology has become an interesting research area in wireless communication, meanwhile orthogonal frequency division multiplexing (OFDM) technology is also considered the next generation of wireless communications technology after the third generation mobile communication. In 2004 the federal communications commission (FCC) released a new UWB spectrum standard, and after the UWB group IEEE 802.15.3 stipulated a related standard, UWB wireless communication system is divided into two options:non-carrier modulation UWB system and carrier modulation UWB system. Non-carrier modulation system takes direct sequence code division multiple access (DS-UWB, Direct Sequence-UWB) technical solution for the standard. Carrier modulation system takes orthogonal frequency division multiplexing (MB-OFDM, Multi-Band OFDM) scheme for standard.Orthogonal frequency division multiplexing (OFDM) technology,with high frequency spectrum efficiency, strong anti-multipath ability and relatively simple equalization etc, is especially suitable for Ultra-wide Bandwidth wireless communication system. This paper focuses on the UWB wireless communication system based on OFDM modulation technology, the key is the system of timing synchronization technology research. Following the introduction of the basic principle of OFDM system and the background of UWB technology, timing synchronization technology of MB-OFDM UWB system is analyzed in more detail, meanwhile influence of performance by various kinds of synchronous factors of synchronization technology on MB-OFDM system of is discussed, and several typical time and frequency synchronization schemes of MB-OFDM systems are given.By the research and analysis on all kinds of existing synchronization schemes, a set of UWB wireless communication system synchronization scheme based on OFDM technology is designed in this paper. First, after studying and analyzing on various parameters of MB-OFDM UWB system carefully, according to the parameters of system, signal emission of MB-OFDM UWB system is simulated. Then, according to the U.S. federal communications commission standards for UWB and to a spectrum standard of UWB indoor channel developed by IEEE 802.15.3 UWB group, do an earnest study on MB-OFDM UWB system. MB-OFDM UWB system channel model is divided into four, which is within 4m line-of-sight (LOS) signal channel model, within 4m non line-of-sight (NLOS) signal channel model, 4~10m NLOS signal channel model and the extreme multipath channel with 25ns RMS delay. According to the channel parameters of four channel models do the simulation respectively, and present the corresponding impulse response. Finally, according to the research and analysis on the auxiliary type synchronization algorithms Schmidl & Cox typical algorithms, the optimal algorithm is proposed. Based on the simulation results, signal emission is simulated, and through a radio channel, receiving signal synchronous simulation. Experimental results show that the system synchronous precision has a certain degree of improvement. The system performance has been further ascent. On the basis of synchronization of system, this paper also focuses on the frequency offset. With the optimization of CAZAC sequence, the frequency offset estimation precision for MB-OFDM UWB system has a degree of improvement. The simulation results also prove the improved frequency offset estimation method has good robustness, and system has almost no influence by channel characteristics.