单载波超宽带（SC-UWB）系统存在长时延密集多径，严重影响系统性能。传统信道均衡方法的均衡效果不够理想，而传统分集方法的硬件复杂度高且数据冗余量大。该文提出一种单载波频域均衡（SC-FDE）与时域分数级分集联合设计方法，以对抗超宽带（UWB）系统的复杂密集多径。该方法在发端为两个或多个信息支路配备一个分集支路；收端先进行SC-FDE，然后将信息支路和分集支路得到的均衡结果进行基于后验概率的分集合并或低复杂度的等增益分集合并，最终恢复出原始数据。该方法具有单天线、低冗余的特点，仅需1.5倍或更低倍数的分集，即可取得良好的分集增益。仿真结果表明：在误码率为10-3下，该方法与SC-FDE相比有3 dB的分集增益。
Long delays and dense paths seriously affect the performance of single-carrier ultra-wideband (SC-UWB) systems. Traditional channel equalization methods are not sufficient for these systems and the traditional diversity methods are very complex with excessive data redundancy. This paper presents a joint design method for single-carrier frequency domain equalization (SC-FDE) with time domain fractional diversity to improve the complex multipath characteristics of ultra-wideband (UWB) systems. At the transmitting end, this method uses one diversity branch for two or more information branches. At the receiving end, the system first performs the SC-FDE and then combines operations based on the posterior probabilities combination or the low complexity equal gain combination of the equalization results obtained by the information branches and the diversity branch. The system then finally recovers the original information. This time domain fractional diversity method has outstanding performance with a single antenna and low redundancy. The system needs only 1.5 or less applications of the diversity mode and obtains excellent diversity gains. Simulations show that this scheme has a 3 dB diversity gain over the SC-FDE scheme for a bit error rate of 10-3.
[1] ROY S, FOERSTER J R, SOMAYAZULU V S, et al. Ultrawideband radio design:The promise of high-speed, short-range wireless connectivity[J]. Proceedings of the IEEE, 2004, 92(2):295-311.
[2] DI BENEDETTO M G. UWB communication systems:A comprehensive overview[M]. London, UK:Hindawi Publishing Corporation, 2006.
[3] 栾志斌, 裴玉奎, 葛宁. 联合载波恢复的高速均衡器设计及ASIC实现[J]. 清华大学学报(自然科学版), 2012, 52(12):1698-1702. LUAN Z B, PEI Y K, GE N. Design and ASIC realization of high speed equalization combining carrier recovery[J]. Journal of Tsinghua University (Science and Technology), 2012, 52(12):1698-1702. (in Chinese)
[4] THOMESSE J P. Fieldbus technology in industrial automation[J]. Proceedings of the IEEE, 2005, 93(6):1073-1101.
[5] WILLIG A, MATHEUS K, WOLISZ A. Wireless technology in industrial networks[J]. Proceedings of the IEEE, 2005, 93(6):1130-1151.
[6] MOLISCH A F, FOERSTER J R, PENDERGRASS M. Channel models for ultrawideband personal area networks[J]. IEEE Wireless Communications, 2003, 10(6):14-21.
[7] SHENOY S P, NEGRO F, GHAURI I, et al. Low-complexity linear equalization for block transmission in multipath channels[C]//Proceedings of the IEEE Wireless Communications and Networking Conference. Piscataway, USA:IEEE Press, 2009:1-4.
[8] 闻武杰, 裴玉奎, 葛宁. 单载波超宽带下判决反馈均衡器芯片优化设计[J]. 清华大学学报(自然科学版), 2010, 50(4):577-580.WEN W J, PEI Y K, GE N. ASIC design optimization of a decision feedback equalizer at single-carrier ultra-wide band[J]. Journal of Tsinghua University (Science and Technology), 2010, 50(4):577-580. (in Chinese)
[9] FORNEY G. Maximum-likelihood sequence estimation of digital sequences in the presence of intersymbol interference[J]. IEEE Transactions on Information Theory, 1972, 18(3):363-378.
[10] PANCALDI F, VITETTA G M, KALBASI R, et al. Single-carrier frequency domain equalization[J]. IEEE Signal Processing Magazine, 2008, 25(5):37-56.
[11] GUSMAO A, DINIS R, ESTEVES N. On frequency-domain equalization and diversity combining for broadband wireless communications[J]. IEEE Transactions on Communications, 2003, 51(7):1029-1033.
[12] ZHU L, PEI Y K, GE N, et al. A time-frequency interleave structure of single carrier FDE over deep fading wireless channels[J]. IEICE Transactions on Communications, 2010, 93(10):2800-2803.
[13] AHLSWEDE R, CAI N, LI S Y R, et al. Network information flow[J]. IEEE Transactions on Information Theory, 2000, 46(4):1204-1216.
[14] ZHANG S, LIEW S C, LAM P P. Hot topic:Physical-layer network coding[C]//Proceedings of the 12th Annual International Conference on Mobile Computing and Networking. New York, USA:ACM Press, 2006:358-365.
[15] CHEN Z, YUAN J, VUCETIC B. Analysis of transmit antenna selection/maximal-ratio combining in Rayleigh fading channels[J]. IEEE Transactions on Vehicular Technology, 2005, 54(4):1312-1321.
[16] IKKI S S, AHMED M H. Performance of cooperative diversity using equal gain combining (EGC) over Nakagami-m fading channels[J]. IEEE Transactions on Wireless Communications, 2009, 8(2):557-562.
