Study On Scheme For Uplink And Downlink Wireless Transmission In Generalized Multi Carrier System And It's Implementation

The next generation communications wireless system beyond 3 generation should support high efficient packet data transmission with peak data rate no less than 20 Mbps. According to the research of new generation cellular mobile communications system around the world, National Mobile Communications Research Laboratory (NCRL) of Southeast University is investigating Generalized Multi Carrier (GMC) cellular mobile communications transmission technique. And the first stage of demo system based on GMC system has been almost completed yet.According to the demand of the whole system, based on characteristics of the system structures, we deal with each sub-carrier of multi-carrier system and two different transmission blocks using pipeline technology. And we design and implement encapsulation frame structure module , dual-circular transmission block module in transmitter and de-encapsulation frame structure in receiver which consume few resources based on field programmable gate array (FPGA). At last, on simulating of the logic circuit, the designed module is tested roundly on an integrated hardware platform.The automatic gain control (AGC) loops are usually used in communication systems to stabilize the performance. Based on the requirements to digital IF receiver on their gain tuning range, step width and accuracy, frequency range as well as response speed of AGC circuits, the article analyses the draw backs of three kinds of typical variable gain amplifiers for the AGC system, and designs a digital AGC system,using a new digital VGA IC. The article provides a signal processing circuit and algorithm based on FPGA. The digital AGC system has its virtues in having fast and exact stable state response. It can easily realize very complex AGC. Finally, the article discuss several key problems of the IF digital receiver designing.In wireless communication system, there is a large frequency bias between carrier frequency and local oscillating frequency. A traditional AFC adopts analog loop filter that must work consecutively. However, in GMC system, the pilot parts are discontinuous. According to the definition of GMC system, an automatic frequency correction scheme is presented, which get the estimation of frequency off set while the channel parameters are obtained from pilot channel. The design of automatic frequency correction loop is given. Computer simulation results show that in the same case, the receiver using automatic frequency correction provides higher signal-to-noise ratio and lower error probability compared without automatic frequency correction.