BICM-ID系统低复杂度解映射算法研究

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"BICM-ID系统的降低复杂度的解映射算法" 本文主要探讨的是在无线通信领域中，一种用于Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID)系统的降低复杂度的解映射算法。BICM-ID是一种高效的编码调制技术，它结合了编码和迭代解码的优势，提高了通信系统的误码率性能。在传统的BICM-ID系统中，解映射和解码过程通常具有较高的计算复杂度，这对于资源有限的移动设备来说可能成为瓶颈。在给定的部分内容中，虽然没有具体列出降低复杂度的解映射算法细节，但我们可以推测，该文可能涉及以下几个方面： 1. **BICM-ID原理**：BICM-ID系统首先将信息比特进行交织，然后进行调制，接着在接收端通过联合解映射和迭代解码来恢复原始信息。这种联合处理允许错误信息在解调和解码之间传播，从而改善系统性能。 2. **复杂度优化**：由于BICM-ID的高复杂度主要源于多次迭代和大量的计算，研究可能提出了新的算法或方法，如简化解映射规则、减少迭代次数或采用更有效的数据结构，以降低计算负担，同时保持良好的系统性能。 3. **参考文献分析**： - `[14]` 3GPP规范引用可能涉及物理信道和调制方式，这是无线通信系统的基础，可能为理解BICM-ID在实际网络中的应用提供背景。 - `[15]` 论文讨论了多用户MIMO系统的发射机设计和信道量化，这与BICM-ID在多用户环境下的应用相关，可能涉及到如何处理多用户干扰问题。 - `[16]` 提到的低复杂度用户选择算法适用于多用户MIMO系统，这可能为优化BICM-ID系统中的资源分配提供启示。 - `[17]` 随机矩阵理论在无线通信中的应用，可能被用来分析BICM-ID系统的统计特性，帮助设计更高效的算法。 4. **算法设计**：文章可能详细介绍了一个新的解映射算法，该算法可能基于概率模型、信噪比估计或其他统计方法，旨在降低计算复杂度，同时保持与全复杂度解映射相当的性能。 5. **性能评估**：通常，任何新的算法都需要通过仿真或实验来验证其性能，文章可能包含对新算法的误码率(BER)、吞吐量等关键性能指标的比较，以证明其优势。这篇研究论文致力于解决BICM-ID系统中计算复杂度高的问题，提出了一种降低复杂度的解映射算法，对于提高无线通信效率和适应未来高速、大容量的移动通信网络具有重要意义。

4350 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 64, NO. 9, SEPTEMBER 2015

[14] 3rd Generation Partnership Project (3GPP), “Physical channels and

modulation,” Sophia Antipolis, France, 3GPP TS36.211, Dec. 2009.

[15] M. Trivellato, F. Boccardi, and H. Huang, “On transceiver design and

channel quantization for downlink multiuser MIMO systems with limited

feedback,” IEEE J. Sel. Areas Commun., vol. 26, no. 8, pp. 1494–1504,

Oct. 2008.

[16] Z. Shen, R. Chen, J. G. Andrews, R. W. Heath, Jr., and B. L. Evans,

“Low complexity user selection algorithms for multiuser MIMO systems

with block diagonalization,” IEEE Trans. Signal Process., vol. 54, no. 9,

pp. 3658–3663, Sep. 2006.

[17] A. M. Tulino and S. Verdu, “Random matrix theory and wireless

communications,” in Foundations and Trends in Communications and

Information Theory. Delft, The Netherlands: Now, 2004.

A Reduced-Complexity Demapping Algorithm for

BICM-ID Systems

Jiandong Tan, Qi Wang, Chen Qian,

Zhaocheng Wang, Senior Member, IEEE,

Sheng Chen, Fellow, IEEE, and Lajos Hanzo, Fellow, IEEE

Abstract—As a highly efﬁcient decoding and demodulation scheme,

bit-interleaved coded modulation (BICM) is widely adopted in modern

communication systems. In order to enhance the attainable spectral

efﬁciency, usually, high-order modulation schemes are used for BICM

systems. When BICM is combined with iterative decoding (BICM-ID),

it is capable of further improving the achievable receiver performance.

However, the complexity of the standard max-sum approximation of the

maximum a posteriori probability in log-domain (Max-Log-MAP) invoked

by the iterative demapper is on the order of 2

or O





for a 2

-ary

modulation constellation having m bits per symbol, which may become

excessive for high-order BICM-ID systems. The existing simpliﬁed algo-

rithms employed for noniterative demappers are based on exploiting the

constellation’s symmetry, which is no longer retained upon the introduc-

tion of the aprioriinformation in BICM-ID systems. Hence, in this paper,

a simpliﬁed iterative demapping algorithm is proposed to substantially

reduce the demapping complexity for a binary-reﬂected Gray-labeled

constellation. Our detailed analysis shows that the simpliﬁed demapping

scheme proposed for BICM-ID reduces the computational complexity

to O(m). We demonstrate that this dramatic computational complexity

only imposes modest performance degradation with respect to that of the

optimal high-complexity Max-Log-MAP scheme.

Index Terms—Bit-interleaved coded modulation with iterative decod-

ing (BICM-ID), iterative demapper, maximum a posteriori probability in

log-domain demapping, pulse amplitude modulation (PAM), quadrature

amplitude modulation (QAM).

Manuscript received May 26, 2014; revised September 13, 2014; accepted

October 29, 2014. Date of publication October 31, 2014; date of current

version September 15, 2015. This work was supported in part by the National

Key Basic Research Program of China under Grant 2013CB329203, by the

National Natural Science Foundation of China under Grant 61271266, by the

National High Technology Research and Development Program of China under

Grant 2014AA01A704, and by Beijing Natural Science Foundation under Grant

4142027. The review of this paper was coordinated by Dr. S. K. Jayaweera.

J. Tan, Q. Wang, C. Qian, and Z. Wang are with Tsinghua National

Laboratory for Information Science and Technology (TNList), Department of

Electronic Engineering, Tsinghua University, Beijing 100084, China.

S. Chen is with the School of Electronics and Computer Science, University

of Southampton, Southampton SO17 1BJ, U.K., and also with King Abdulaziz

University, Jeddah 21589, Saudi Arabia.

L. Hanzo is with the School of Electronics and Computer Science, University

of Southampton, Southampton SO17 1BJ, U.K.

Color versions of one or more of the ﬁgures in this paper are available online

at http://ieeexplore.ieee.org.

Digital Object Identiﬁer 10.1109/TVT.2014.2366195

I. INTRODUCTION

The original concept of bit-interleaved coded modulation (BICM)

was presented by Zehavi [1], who found that the performance of

coded modulation over Rayleigh fading channels can be considerably

improved by adopting bit interleaving. Based on his work, a set of

theoretical modeling and analysis tools has been developed for BICM

for other applications as well [2]. In 1998, Li and Ritcey [3] improved

BICM with the aid of iterative decoding (BICM-ID). In the same

year, ten Brink et al. [4] provided further insights on enhancing the

performance of BICM-ID at reduced complexity. Therefore, state-

of-the-art communication systems often employ BICM to improve

the attainable performance, as exempliﬁed by the second-generation

digital terrestrial television broadcasting standard (DVB-T2) system

[5]. For the sake of achieving high bandwidth efﬁciency, typically

high-order quadrature amplitude modulation (QAM) [6] is recom-

mended for both noniterative BICM and BICM-ID systems. The Gray-

labeled mapping is also widely applied to high-order modulation

constellation schemes to reduce the bit errors since two adjacent Gray-

labeled constellation points differ in only one bit [7]. The DVB-T2

standard [5], for example, supports binary-reﬂected Gray-labeled mod-

ulation. However, high-order BICM and BICM-ID systems impose

high-complexity when adopting the optimal log-domain maximum

a posteriori probability (Log-MAP) demapping algorithm [8]. Al-

though the max-sum approximation of the Log-MAP (Max-Log-MAP)

algorithm [9] is capable of substantially reducing the associated com-

putational complexity, it is still on the order of O





,where2

the size of the modulation constellation employed that contains m bits

per symbol.

Several simpliﬁcations of the Max-Log-MAP algorithm have been

proposed for high-order constellations. Tosato and Bisaglia [10] found

that 2

-QAM symbols relying on Gray labeling can be divided

into two independent 2

m/2

-ary pulse amplitude modulation (PAM)

constellations, and with the aid of this partitioning, the complexity of

the noniterative demapper can be reduced to O



m/2



without any

performance degradation. In [10], the complexity of the simpliﬁed

QAM demapper is further reduced to O





by adopting a piece-

wise linear approximation, but this simpliﬁcation results in modest

performance degradation. Since the aprioriinformation necessary

for iterative demapping is not included in the simpliﬁed algorithms in

[10], it cannot be readily applied to BICM-ID systems. The simpliﬁed

demapping algorithm in [11] was conceived for universal Gray-labeled

constellations, which reduces the complexity to O





by exploiting

the symmetry of Gray-labeled constellations while attaining exactly

the same performance as the Max-Log-MAP algorithm for QAM,

PAM, and phase-shift keying (PSK) constellations. However, this algo-

rithm cannot be applied to the iterative demapper since the symmetry

of Gray-labeled constellations is no longer satisﬁed after taking into

account the input aprioriinformation. Further efforts invested in

reducing the complexity of BICM-ID systems were reported in [12],

where hard-feedback-based iterative decoding was used to reduce the

complexity of BICM-ID combined with frequency-shift keying modu-

lation, whereas in [13], a mapping scheme combined with low-density

parity-check (LDPC) coding is proposed to merge the demapping

operation into the process of LDPC decoding. However, the methods

in [12] and [13] are only applicable to orthogonal modulation schemes.

By only allowing the extrinsic information for systematic bits to be fed

back to the demodulator, the scheme proposed in [14] was shown to

reduce the complexity of BICM-ID schemes, but the objective of this

scheme is to reduce the decoding complexity of turbo coding rather

than to simplify the demapping algorithm conceived for universal

modulation and coding schemes.

IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.

See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

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