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The adaptive modulation and coding of the OFDM system,

Author: ShiLiJun
Tutor: KongJinZuoï¼›DuYang
School: Zhejiang University
Course: Electromagnetic Field and Microwave Technology
Keywords: OFDM Adaptive modulation Adaptive Modulation and Coding Threshold Modulation and coding scheme Grouping
CLC: TN919.3
Type: Master's thesis
Year: 2006
Downloads: 338
Quote: 3
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Abstract


Orthogonal frequency division multiplexing (OFDM) technique using an orthogonal superimposed subcarrier of the transmitted signal is modulated , can be effective against the multipath channel due to inter-code interference is considered to be one of the key technologies for the future wireless communication . Adaptive modulation and coding techniques can greatly improve the spectrum efficiency of the system , to ensure that the BER or FER performance requirements , is the inevitable trend of development of the next generation of communication systems . The adaptive modulation and coding the main mechanism that is: when the channel condition is good , using a higher order modulation scheme and a higher code rate of the channel coding , in order to improve the system throughput performance ; in poor channel conditions , the use of the low - level modulation manner and lower bit rate , channel coding, in order to guarantee the quality of each transmission . In this paper, starting from the adaptive modulation algorithm , the introduction of the concept of OFDM subcarrier grouping , elaborated the principle and implementation of the five fixed threshold algorithm and subband BER estimate calculations , based on adaptive coding adaptive modulation and coding . Algorithm , this paper focuses on the fixed threshold algorithm and optimization and sub ??threshold with a signal-to-noise ratio calculated both to optimize the performance of the algorithm . Different calculation method based on the sub-band signal-to-noise ratio , the fixed threshold method is divided into five categories : worst subcarriers instead of the law , the best sub-carriers instead of law , means method , cross - correlation correction means method and with subcarriers variance amendment Act . Finally, through the comparison and analysis of the performance of various adaptive systems and fixed modulation and coding system , we found that both the BER ( AM systems ) or FER ( AMC system ) performance , throughput performance , AM or AMC system performance should be significantly superior to a fixed modulation and coding system . In addition , the paper also the performance of the adaptive algorithm simulation, comparative analysis of their impact on system performance and application of occasions .

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