The Research Of AMC And HARQ Technology In Wide-band Mobile Communication

Mobile communication is developing toward wideband and personalizing. Some new wireless technologies spring up in quantities and standardization is accelerated. As the enhanced version of WCDMA, HSDPA highly boosts the downlink data rate with peak value lOMbps. As the evolution of 3G standard, LTE adopts OFDM/MIMO as core technologies. Its upload speed can reach 50Mbps and download speed is up to lOOMbps. As to the time-varying characteristics of wireless channel, HSDPA and LTE system adopt adaptive modulation and coding (AMC) and hybrid ARQ as two main link adaptive technologies. They can fully use the spectrum resource and boost data rate in the precondition that QoS is guaranteed.Chapter 2 studies wireless channel modeling. Firstly channel characteristics of single-carrier and OFDM system are analyzed, and then the corresponding simulation modeling is presented. Three kinds of SOS simulation method for flat fading channel as follows are compared: straight simulation, Jakes modeling and improved Jakes modeling. And simulation result shows that statistical characteristic of improved Jakes modeling is much closer to the ideal value. Based on the discussion above, A tapped-delay-line model and three kinds of simulation method for OFDM channel are exhibited.Chapter 3 studies the key technologies in AMC and HARQ system. Based on the construction method of RC-LDPC, six kinds of MCS are abtained. PHY abstraction theory is deeply researched and RBIR, EESM as well as mean value methods are evaluated by simulation. It can be concluded that RBIR and EESM have good estimation accuracy, while mean value method only adapts to flat slow fading channel. Besides, the fixed threshold and outer loop method for MCS selection rule are showed. Simulation comparison of three kinds of fixed threshold method in flat slow fading channel is presented. Outer loop can make up for the deficiency of fixed threshold method, such as sensitivity to channel estimation and prediction inaccuracy. Thus the combination of fixed and outer loop method is the best choice. After that, two kinds of adaptive scheme based on HARQ technology are analyzed by simulation. The result shows that these adaptive schemes bring performance gain.Chapter 4 analyzes AMC-HARQ system in the two conditions of retransmission-combined and non-combined with the assumption of retransmission channel unchanged or FSMC model. The correlation of noise in combined data and pre-combined data is also considered according to channel-combined BLER rule and maximum throughput rate rule. We deduce the expression of throughput rate and FER, get the optimal threshold for AMC-HARQ system and verify them by simulation.Chapter 5 studies channel prediction in AMC system. The performance and application of four kinds of channel predictor for flat fading channel are compared by simulation. And four existing algorithms for OFDM channel prediction are elaborated. Based on ESPRIT algorithm, IDFT+ESPRIT algorithm is proposed, which can reduce complexity without causing performance loss. In the end, three kinds of adaptive prediction algorithm as follows are analyzed by simulation: LMS, RLS, adaptive ESPRIT.