Research On Wireless Transmission Technology Based On Interleaved Iterative Multi - Source Interference Cancellation

With the fast development of mobile network, the demands of high-speed wireless communication are increasing gradually. In order to meet the growing requirements, the wireless standards organization3GPP is working on the new network access technology. Therefore, LTE-A (Long Term Evolution-Advanced), the next version of LTE, has been regarded as the new standards for future mobile communication in2011in Release10. OFDMA (Orthogonal Frequency Division Multiple Access) is designed as the access technology for LTE-A downlink. OFDMA transmits data signal in multi-carrier; and it enjoys robustness for multipath fading channel and high frequency efficiency.The traditional access schemes, TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access) and etc. take advantage of separate wireless resources in time and frequency domain to combat inter-cell interference. While in OFDM, the transmission of signal is combined in both time and frequency domains. Therefore, OFDM suffers frequency reuse, which causes interference directly. The solution of decreasing ICI (inter-cell interference) is a key point in celluar-communication system.With the advantage of combating multipath fading and multi-user interference, IDMA (Interleave-Division Multiple-Access) allocates the same interleaver for each user in both transmitter and receiver to randomize the interference including noise. Channel estimation is essential in IDMA, and the accuracy of estimation will influence system to a large degree. EM (Expectation Maximization) estimation algorithm performs well in IDMA with the combining of iterative receiver. On another hand, traditional IDMA only using BPSK modulation, the modification of ESE will help IDMA work for higher modulation scenario based on each signal bit.The IDMA receiver scheme in OFDM and FSO (Free Space Optical) are studied in the first part of the thesis, and then channel estimation methods in wireless and FSO scenarios are analysised in the following part. We introduce two inter-cell interference mode which can be applied in uplink and downlink communication separately. With the modification of ESE for higher-modulation IDMA, we discussed the gray and nongray code modulation in QPSK (Quadrature Phase Shift Keying) and16QAM (Quadrature amplitude modulation) in detail. The BER performance of16QAM and64QAM of the iterative receiver is also illustrated. The performance in the inter-cell interference mode is analysised in the final part.