摘要
超宽带通信技术是一种新兴的短距离无线通信技术,它利用纳秒至皮秒级的非正弦波窄脉冲传输数据,具有传输速率高、功耗低、安全性好、抗多径能力强以及成本低廉等许多优点,特别是它不需要占用额外的频谱资源,可与现有的无线通信系统在同一频带内共存这一特点,使它在频谱资源日益紧张的今天受到了广泛的注意。目前,超宽带通信技术已成为无线通信技术研究的热点之一。本文主要从多径信道下的Rake接收机和多用户干扰这两方面研究了基于截短平衡Gold码的超宽带通信系统,并且得到了一些有意义的结果,主要工作概括如下:
1.分析了截短平衡Gold码的生成原理,给出了截短平衡Gold码的生成方法,并且验证了该方法的可行性。介绍了超宽带信道模型,对超宽带无线通信信道模型的一般建模过程进行了讨论。重点介绍了S-V信道模型和Intel信道模型,并对仿真的Intel信道模型进行了分析,通过分析对超宽带无线信道传播特性进行了总结。
2.给出了多径信道下Rake接收机发送端和接收端的模型,用截短平衡Gold码代替传统的跳时码,分析了在脉冲位置调制(PPM)和脉冲幅度调制(PAM)两种调制方式下理想型接收机(A-Rake),部分Rake接收机(P-Rake)和选择性Rake接收机(S-Rake)这三种Rake接收方式的误码性能,并进行了仿真。仿真结果表明,在多径信道情况下截短码的误码性能要优于传统码的误码性能;在相同条件下,采用PAM调制方式的接收机的误码性能要好于采用PPM调制方式的误码性能。
3.详细分析了多用户干扰下的超宽带通信系统的原理,建立了多用户干扰下的超宽带通信系统的模型。在PPM和PAM两种不同的调制方式下,对受到不同用户数目干扰的超宽带通信系统进行了误码性能分析,通过仿真实验表明:在多用户干扰的情况下,采用相同调制方式时,使用截短码的通信系统的误码性能要优于传统通信系统的误码性能。
Ultra-wideband (UWB) communication is a novel short-distance wireless communication technique, in which data are transferred using non-sinusoidal pulses with very short duration. It has many advantages, such as high transmission rate, low power consumption, good security, robustness to multi-path and low cost. Especially, it does not need extra frequency spectrum, and can coexist with the existing wireless communication systems at the same frequency band, which makes it attract much attention nowadays when the frequency spectrum resource has become more and more precious. In this paper, the UWB communications system based on truncated balanced Gold codes was researched from multi-path channel of the Rake receiver and multi-user interference, and get some meaningful results, the principal tasks summarized as follows:
1. Analysis of truncated balanced Gold code generation principle, given truncated balanced Gold code generation methods, and verify the feasibility of the method. Introduced the UWB channel model, and discussed the general builds model process of UWB wireless communication channel model. Second, highlight introduced the S-V channel model and Intel channel model, and analyzed the Intel channel model. Finally, summarized the UWB wireless channel characteristics.
2. Given the send and receive terminal model of multi-path channel Rake receiver, using truncated balanced Gold codes instead of the traditional time-hopping code, analyzed the All Rake receiver (A-Rake,), Partial Rake receiver (P-Rake) and selective Rake receiver (S-Rake) of these three Rake receivers performance which under the PPM and PAM two kinds of modulation, and make a lot of simulation. The results show that the performance of truncated code is superior to the traditional code’s performance; under the same conditions, the receiver's error performance which using PAM modulation is better than using PPM modulation’s performance.
3. The UWB communication system’s principle which under the multi-user interference was detailed analyzed, and established the communication system model. Under the PPM and PAM two kinds of modulation, analyzed the system’s performances which have multi-user interference. Through a large number of simulation experiments, the results show that: in the same modulation mode, the system’s performance which using truncated code is superior to the traditional system’s performance.
引文
[1] Fontana J. Robert. A brief history of UWB communications [EB/OL]. http://www.jacksons.net/tac/First%20Term/A_Brief_History_of_UWB_Communications.pdf.
[2] Morey R.N. Geophysical survey system employing electromagnetic impulses [J]. US Patent 3,806, 795, Apr.1974.
[3] Scholtz R.A. Multiple access with time-hopping impulse modulation [J]. Invited paper, In Proc. IEEE MILCOM, 1993: 447-450.
[4]上海无线电管理局.UWB:值得关注的无线通信新技术[EB/OL]. http://www.shrc.gov.cn/zsc/ShowArticle.asp?ArticleID=144.
[5] FCC. Revision of part 15 of the commission’s rules regarding ultra-wideband transmission systems [EB/OL]. http://www.naic.edu/~astro/RXstatus/Lnarrow/fcc_UWB.pdf.
[6] FCC. The updated part 15-radio frequency devices [EB/OL]. http://www.tscm.com/47cfr15.pdf.
[7] Win M.Z, Scholtz R.A. Ultra-Wide Bandwidth Signal Propagation for Indoor Wireless Communications [J]. In Proc. IEEE ICC. 1997, Vol.1:56-60.
[8] Win M.Z, F. Ramirez-Mireles, Scholtz R.A, etc. Ultra-Wide Bandwidth Signal Propagation for Outdoor Wireless Communications [J]. In Proc. IEEE VTC, 1997, Vol.3:251-255.
[9] Win M.Z, Scholtz R.A. On the robustness of Ultra-wide bandwidth signals in dense multipath environments [J]. IEEE Communications Letters, 1998, Vol.2:51-53.
[10] H.Lee,B.Han,Y.Shin, etc. Multipath characteristics of impulse radio channels [J]. In Proc. IEEE VTC, 2000, Vol.23:2487-2491.
[11]周廷显.伪噪声编码技术[M].哈尔滨:哈尔滨工业大学出版社,1982.
[12]查光明.熊贤祚.扩频通信[M].西安:电子科技大学出版社,1992.
[13]朱近康.CDMA通信技术[M].北京:人民邮电出版社,2001.
[14] J.K.霍姆斯.相干扩展频谱系统[M].北京:国防工业出版社,1991.
[15]沈允春.扩谱技术[M].北京:国防工业出版社,1995.
[16]文海霞,孙娇燕.截短平衡Gold码的特性分析[J].信息技术,2008(1):47-51.
[17] J. Proakis. Digital Communications [M]. New York: McGraw-Hill, 1994.
[18] Alamouti S.M. A simple transmit diversity technique for wireless communications [J]. IEEE J. Select. Areas Comm, 1998, Vol.16:1451-1458.
[19] Liuqing Yang, Giannakis, G.B. Ultra-wideband communications: an idea whose time has come [J].IEEE Signal Processing Magazine, 2004, Vol. 21(6): 26-56.
[20] Chao Y, Scholtz R.A. Optimal and suboptimal receivers for Ultra-wideband transmitted reference systems [J].Global Telecommunications Conf, 2003, Vol.2: 759-763.
[21] Win M.Z, Scholtz R.A. On the energy capture of Ultrawide bandwidth signals in dense multipath environments [J]. IEEE Communications Letters, 1998, Vol. 2(9): 245-247.
[22] Ravi K.V. Comparison of multiple-accessing schemes for mobile communications systems [J]. IEEE International Conference on Personal Wireless Communications, 1994, 152-156.
[23] Scholtz R.A. Multiple access with time-hopping impulse modulation [J]. IEEE Military Communications Conference, 1993, Vol.2: 447-450.
[24] Win M.Z, Scholtz R.A. Ultra-wide bandwidth time-hopping spread-spectrum impulse radio for wireless multiple access communications [J]. IEEE Transactions on Communications, 2000, Vol. 48(4): 679-691.
[25]葛利嘉,朱林,袁晓芳等.超宽带无线电基础[M].电子工业出版社,2005.
[26]崔文韬.超宽带无线通信系统中关键技术的研究[D].山东:山东大学,2006.
[27]王立华.超宽带无线通信中接收技术的研究[D].南京:东南大学,2004.
[28]苗剑.超宽带(UWB)无线通信技术[D].西安:西安电子科技大学,2004.
[29] Scholtz R.A. Impulse Radio: How it works [EB/OL]. http://www.ifi.uio.no/forskning/grupper/mes/Research/UWB/IMPRADIO.pdf.
[30] Durisi G, Tarable A, J.Romme etc. A general method for error probability computation of UWB systems for indoor multiuser communications [J]. Journal of Communication and Networks, 2003, Vol. 5(4):354-364.
[31]李振玉,卢玉民.扩频选址通信[M].北京:国防工业出版社,1988.
[32]王秉均,居谧,孙学军等.扩频通信[M].天津:天津大学出版社,1993.
[33]黄剑明,施志勇,保铮.截短平衡Gold码的统计特性分析[J].系统工程与电子技术,2006(5):646-649.
[34]李川.超宽带通信Rake接收技术研究[D].成都:电子科技大学,2004.
[35]侯萌.基于Rake接收机的超宽带无线通信系统的性能研究[D].山东:山东大学,2006.
[36] Fourouzan, A.R, M. Nasir-Kenari, and J.A. Salehi. Performance analysis of time-hopping spread-spectrum multiple-access systems: uncoded and coded schemes [J]. IEEE Transactions on Communications, 2002, Vol. 30:671-681.
[37] Hu B, Beaulieu N.C. Precise bit error rate of TH-PPM UWB systems in the presence of multiple access interference [J]. IEEE Conference on Ultra Wideband Systems and Technologies, 2003, 106-110.
[38] Win M.Z. Spectral density of random UWB signals [J]. IEEE letters, 2002,Vol.6(12):526-528.
[39] Yao R, Gao Z. Chen, and W. Zhu etc. UWB multipath channel model based on time-domain UTD technique [J]. IEEE Global Telecommunications Conference, 2003, 1205-1210.
[40] Maggio, G.M, D. Laney, F. Lehmann, and L.Larson. A multi-access scheme for UWB radio using pseudo-chaotic time hopping [J]. IEEE Conference on Ultra-wideband Systems and Technologies, 2002, 225-229.