Research Of Pilot Design In The Future Wireless Communication Systems

The next generation mobile communication systems will have higher spectrum efficiency, higher transmission rate, and provide multimedia services to the users. In order to achieve above targets, new wireless air interface technologies must be applied. Orthogonal Frequency Division Multiplexing is one of the candidate technologies in B3G systems. This thesis focuses on the channel estimation and pilot design technology in OFDM-based B3G systems under multi-cell environment.For deeper understanding of the simulation-design in our considered environment, this thesis first describes the wireless channel characteristics and models, cellular cell and multi-cell model with co-frequency interferences. And then, this thesis introduces the principle and structure of OFDM systems and the issue of optimal pilot design, summarizes several common channel estimation techniques and interpolation algorithms in OFDM system, and evaluates the performance of LS, MMSE, DFT channel estimation algorithms, and discusses the influence of cyclic prefix interception on channel estimation performance in the actual system.Based on above works, this thesis pays attention to the issue of pilot design technologies to suppress the co-frequency interferences from other cells in the process of channel estimation in multi-cell environments. This thesis presents a pilot design proposal based on constant amplitude and zero autocorrelation (CAZAC) sequence. The proposal breaks the sequence length limit of prime number in long term evolution (LTE) system. Instead, the length is expanded to a broader scope. This proposal also proposes a method by mixed use the optimal pilot sequences and sub-optimal pilot sequences, so that improves the original design of pilot in the uplink of LTE system. It is found that this method can significantly inhibit the intra-cell multi-user interference and the inter-cell co-frequency interference.Furthermore, this thesis investigates how to make use of the channel information at the transmitter and the receiver after we get knowledge of channel through channel estimation. This thesis describes an adaptive algorithm in multi-cell environment, which uses partial channel information feedback from closed-loop link to suppress inter-cell interference and intra-cell Gaussian noise. This adaptive algorithm is shown to enhance the signal-to-interference ratio in multi-cell environment and make use of the channel state information more efficiently.