Dissertation
Dissertation > Industrial Technology > Radio electronics, telecommunications technology > Wireless communications

The Research on Power Allocation Is Based on OFDM Technology for Wireless Communication Systems.

Author YeCheng
Tutor LiuChen
School Nanjing University of Posts and Telecommunications
Course Circuits and Systems
Keywords Orthogonal frequency division multiplexing (OFDM) Channel estimation Adaptive modulation technology Subcarrier grouping Bits allocation
CLC TN92
Type Master's thesis
Year 2012
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Orthogonal Frequency Division Multiplexing (OFDM) can effectively inhibit the adverse effects of multipath fading in wireless communications. The orthogonal properties of the technology can save spectrum resources to improve the spectrum utilization rate. Currently, OFDM has been considered as a key technology for future wireless communications. In addition, because of the unstable characteristics of wireless channel, and in order to guarantee the signal transmission quality, we must make an appropriate adjustment to the system resources to have the system to be a best match with the transmission conditions. Therefore, how to make more effective use of system resources has become one of the concerned topics.As a sub-topic of the National Natural Science Foundation (project No.: 61071089), the thesis combines with the adaptive technology and makes an in-depth research on power optimization for the communication system on the basis of the OFDM system. First, it has a brief introduction of the development of wireless communications and some factors that affect the signal transmission. Then, the system model, the working principle, the technical characteristics and the advantages of OFDM are detailed. After that, it elaborates channel estimation and adaptive technologies of the OFDM system. Finally, on the basis of several classical adaptive optimization algorithms, including: Hughes-Hartogs algorithm, Chow algorithm, Fischer-Huber algorithm and SBLA algorithm,it proposes an improved adaptive optimization algorithm, which is core of the thesis. The improved adaptive algorithm in this thesis integrates the subcarrier grouping theory and adaptive modulation technology. Subcarrier grouping is a dynamic grouping by using the logarithmic relationship of channel frequency response, then it selects appropriate modulation mode by using the Signal to Noise Ratio and Bit Error Rate of each subcarrier group, and finally, bits are distributed for each subcarrier. This approach greatly reduces the complexity of the optimization algorithm, and its performance is also very reliable, these can be seen by the simulation results, so it is suitable for the requirements of wireless communication transmission.

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