电信科学 ›› 2012, Vol. 28 ›› Issue (3): 57-61.doi: 10.3969/j.issn.1000-0801.2012.3.016

• 研究与开发 • 上一篇    下一篇

一种改善频谱利用率的新式混合非对称喷泉映射策略

张小弟,樊平毅   

  1. 清华大学电子工程系 北京 100084
  • 出版日期:2012-03-15 发布日期:2012-03-15
  • 基金资助:
    国家“973”重点基础研究基金资助项目;国家“973”重点基础研究基金资助项目

A Novel Hybrid Asymmetric Mapping Scheme to Improve the Spectrum Efficiency for Fountain Codes

Cheong Siotai,Pingyi Fan   

  1. Electronic Engineering Department of Tsinghua University,Beijing 100084,China
  • Online:2012-03-15 Published:2012-03-15

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摘要：

喷泉码的原理是利用传送端产生无限多个编码数据分组，直至接收端正确地接收足够数量的编码数据分组，便可以恢复出原来的未编码信息。这种特性说明，在解出原有未编码的信息过程中，所有编码数据分组具有几乎相等的重要性。本文利用这个特性，提出了一种应用于喷泉码中的新式BPSK/QPSK混合非对称映射策略。此策略可以显著地提高系统的频谱使用率，尤其在信道具有较低信噪比的情况下。本文首先给出了AWGN信道中各种映射方式符号错误率的理论结果，并利用不同的仿真结果，证明了本文提出的BPSK/QPSK混合非对称映射策略在较低信噪比的AWGN信道下，系统性能优于传统的QPSK调制策略。上述结果提供了如下启示：当传输信道为衰落信道或受到多普勒效应影响时，由于它们的瞬时信噪比较低的可能性较高，本文提出的新的混合调制策略在此类环境具有较好的性能。

关键词: 喷泉码, ；混合映射, LT码

Abstract:

The idea of fountain code is,the transmitter transmits unlimited numbers of coded packets until the receiver correctly receive enough number of coded packets to decode the original uncoded information.This characteristic implies that during the decoding of original information,almost all the coded packets have equally importance.In this paper,we propose a novel hybrid asymmetric BPSK/QPSK mapping modulation scheme for fountain codes.This scheme can increase system spectrum efficiency sharply,especially when the channels have relatively low signal-to-noise ratios（SNR）.Firstly,we calculated the symbol error probability of different mapping methods in AWGN channels,and used different simulation results to prove our novel hybrid asymmetric BPSK/QPSK mapping modulation scheme is better than the classic QPSK modulation in low SNR scenarios.From the results above we can be inspired that,when the channels are fading or affected by Doppler effect,our novel scheme can have better performance because they will most likely to have high probability of relatively low instant SNR values.

Key words: fountain code, hybrid mapping, LT code

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