摘要
本文研究了OFDM通信技术在无线移动环境中的应用,主要是针对OFDM通信系统中高效传输技术的研究。
本文首先介绍了OFDM技术的基本概念,并且与单载波以及其它多载波技术比较,阐明了其技术特征以及主要的优缺点。由于其它多载波技术都能够通过OFDM技术来实现,因此对于移动通信中的OFDM技术进行重点研究具有很强的现实意义,且研究结论可以推广到其它一些多载波通信方式中。本文主要是研究无线移动环境中OFDM系统的高效接收方法,包括高效的时频同步算法、高效内插导频的信道估计算法以及高效的自适应信道估计算法。
为了阐述在无线移动环境中进行高效通信必要性,本文分析了时间同步以及频率同步误差对OFDM系统的影响,详细介绍了现有的时频同步算法的基本原理以及其主要的优缺点:分析了OFDM系统无线移动信道的特点,总结了现有的OFDM信道估计算法,详细的介绍了基于导频内插的信道估计方法以及其主要的优缺点。
在高效时间同步与频偏估计算法的研究中,本文针对现有OFDM时频同步技术存在的问题,提出了一种新的用于无线移动信道下OFDM系统的高效时频同步算法。该算法利用频域相关以及最大似然的原理,设计了一个长为一个OFDM信元的前缀信元,能够同时实现初始时间同步与频偏估计,并且能够将初始频偏估计的估计范围扩展到整个OFDM的系统带宽以及能够有效地克服小数倍频偏为±0.5倍子载波间隔附近时的相位模糊问题。针对该算法实现过程中的逐点FFT运算,提出了一种迭代实现逐点FFT的快速算法,使得该时频同步算法在实际系统中更为可行。仿真结果表明,该算法在高斯信道以及多径衰落信道环境下具有良好的初始时间同步以及频偏估计性能。
在基于内插导频的高效信道估计算法的研究中,本文提出了一种基于内插导频的高效OFDM时频二维信道估计算法。该算法利用OFDM系统无线信道在多普勒展宽域进行滤波可以大大减少算法复杂度的原理,使用改进最大径选择(MST)与多项式滤波的方法,对已经得到的导频(Pilot)信号最小二乘(LS)信道估计进行时频二维滤波。该算法不需要预先知道信道的相关矩阵以及信噪比等信道信息,简单且易于实现,并且能够适用于高效导频利用率的矩形内插的导频内插方式。仿真结果表明,在梳状内插方式下,该算法的MSE性能有了显著的提高;在高效导频利用的矩形内插方式下,该算法的BER性能逼近于理想信道估计的性能。
在高效的自适应信道估计算法的研究中,本文提出了一种高效的基于多项式预测滤波OFDM自适应信道估计算法。该算法能够使用少量内插导频的OFDM信元对多项式滤波器系数进行初始化,利用多项式预测以及迭代接收的原理,对承载纯数据的OFDM信元进行信道估计以及信道跟踪。本文还将该算法应用于基于Turbo接收的OFDM系统中,通过信道编码的纠错能力来提高承载纯数据OFDM信元的信道估计以及信道跟踪的准确度。该算法不需要预先知道信道的自相关矩阵以及信噪比等信道信息,简单且易于实现。仿真结果表明,在信噪比较高的多径衰落信道下,该算法有良好的信道估计以及信道跟踪的性能,从而大大的减少了系统的导频利用率,提高了系统的频谱利用率。
This dissertation is devoted to the research on the OFDM communication techniques in the wireless mobile communication environments, including some high-efficient transmission techniques.
This dissertation begins with the basic introduction of OFDM techniques and a summary of single carrier technique and several existing multicarrier techniques in order to clarify the difference between the OFDM and the other multicarrier techniques. The research on the OFDM system is of great practical values since many of the existing multicarrier techniques can be fulfilled through OFDM module and many useful results in OFDM system are also applicable to other multicarrier systems. This dissertation mainly focuses on some high-efficient transmission techniques, including the high-efficient time-frequency synchronization algorithm, the high-efficient channel estimation algorithm based on pilot arrangement and the high-efficient adaptive channel estimation algorithm, in OFDM systems.
In order to illustrate the necessary of OFDM high-efficient communication techniques in the wireless mobile communication environments, this dissertation analyses the performance influence of OFDM systems due to the time and frequency synchronization errors and detailedly introdues the existing time and frequency synchronization algorithms and their corresponding merits and demerits. This dissertation also clarifies the characteristics of wireless mobile communication environments in OFDM systems, summarizes the existing channel estimation algorithms and detailedly describes the channel estimation algorithms based on pilot arrangement and their corresponding merits and demerits.
In the research of high-efficient time-frequency synchronization algorithms of OFDM systems, this dissertation presents a new time and frequency synchronization method used in wireless mobile communication environments. This method is based on the frequency domain correlation and the maximum likelihood theories and can solve the problems in the existing time and frequency synchronization algorithms. This method uses one training sequence of just one symbol and the design of the symbol is presented. The time synchronization and carrier frequency offset estimation can be achieved simultaneously and the frequency synchronization algorithm can extend the frequency acquisition range to nearly the whole useful OFDM signal bandwidth. The frequency synchronization algorithm can also overcome the ambiguity problem existing in carrier frequency offset estimation. A fast realizing algorithm is presented in the dissertation to reduce the calculating complexity in order to make the method easier to be implemented. The simulation results demonstrate the efficacy of the method.
In the research of the high-efficient channel estimation algorithm based on pilot arrangement, this dissertation proposes a robust pilot-assisted channel estimation method for OFDM signals in Rayleigh fading channel. The method is based on the theory that the calculating complexity can be greatly reduced when the filter for channel estimation is performed in Dopler spreading domain of wireless mobile communication environments in OFDM systems. Using the way of Most Significant Tap (MST) selection and polynomial filtering, the method conducts the time-frequency filtering for the Least Square (LS) estimation results of pilot symbols. The method is simple and need not know the statistic characteristic of the practical channel, such as the channel correlation matrix and signal-to-noise rate(SNR). The method can be used in rectangular pilot-assisted geometry and can be easily realized in practical OFDM systems. The simulation results show that the mean square error(MSE) performance of the method is greatly improved when the method is compared with LS and MST estimation method in comb pilot-assisted geometry and the bit error rate(BER) performance of the method approaches that of the ideal channel estimation in rectangular pilot-assisted geometry.
引文
[1] K. Yungsoo, J. B. Jang, C. Jaehak, H. Chan-Soo, R. J. S., K. Ki-Ho, and K. Y. Kyun, "Beyond 3G: Vision, requirements, and enabling technologies," IEEE Communications Magazine, vol. 41, pp. 120-124, 2003.
[2] T.S. Rappaport, A. Annamalai, R. M. Buehrer, and W. H. Tranter, "Wireless communications: past events and a future perspective," Communications Magazine, IEEE, vol. 40, pp. 148-161, 2002.
[3] R. C. Qiu, Z. Wenwu, and Z. Ya-Qin, "Third-generation and beyond (3.5G) wireless networks and its applications," presented at ISCAS 2002, IEEE International Symposium on Circuits and Systems (ISCS), 2002, 2002.
[4] S. Hara and R. Prasad, "Overview of multicarrier CDMA," IEEE Communications Magazine, vol. 35, pp. 126-133, 1997.
[5] S. D. Blostein and H. Leib, "Multiple antenna systems: their role and impact in future wireless access," Communications Magazine, IEEE, vol. 41, pp. 94-101, 2003.
[6] D.J.C. MacKay, "Good error-correcting codes based on very sparse matrices," Information Theory, IEEE Transactions on, vol. 45, pp. 399-431, 1999.
[7] E. Biglieri, POLITECNICO DI TORINO, "Digital transmission in the 21st century: conflating modulation and coding," Communications Magazine, IEEE, vol. 40, pp. 128-137, May 2002.
[8] FCC, "New Public Safety Applications and Broadband Internet Access among Uses Envisioned by FCC Authorization of Ultra-Wideband Technology, CC First Report and Order," Feb. 14, 2002.
[9] Z.J. Haas, "Design methodologies for adaptive and multimedia networks," Communications Magazine, IEEE, vol. 39, pp. 106-107, 2001.
[10] J.L.-V. a. C. Anton-Haro, "Throughput Optimization for MIMO Systems via Cross-Layer Designs," 9th WWRF meeting, 2003.
[11] R. Ramanathan and J. Redi, "A brief overview of ad hoc networks: challenges and directions," Communications Magazine, IEEE, vol. 40, pp. 20-22, 2002.
[12] R.R.M.a.R.G.C. Kineplex, "A bandwidth-efficient binary transmission system," AIEE Transactions, pp. 76:723-728, Jan. 1958.
[13] R.Chang, "Synthesis of band-limited orthogonal signals for multicharmel data transmission," The Bell System Technical Journal, pp. 1775-1796, Dec. 1966.
[14] R.Chang, "Orthogonal Frequency Division Multiplexing," US. Patent 3,488445, filed November 14, 1966, issued January 6, 1970.
[15] J.W.C.a.O.W.Tukey, "An algorithm for the machine calculation of complex Fourier series. Math. Comput," Math. Comput, pp. 19:297-301, 1965.
[16] S. Weinstein and P. Ebert, "Data Transmission by Frequency-Division Multiplexing Using the Discrete Fourier Transform," Communications, IEEE Transactions on[legacy, pre-1988], vol. 19, pp.628-634, 1971.
[17] L. J .Cimini, "Analysis and simulation of a digital mobile channel using Ortlaogonal Frequency Division Multiplexing," IEEE Trans. Comm., pp. 33(7): 665—675, Jul. 1985.
[18] K. F.a.L.Papke., "On the performance of convolutionally-coded CDMA/OFDM for mobile communication system," In Proc. Of IEEE PIMRC'93, pp. 468-472, Sept. 1993.
[19] V. DaSilva and E. S. Sousa, "Performance of orthogonal CDMA codes for quasi-synchronous communication systems," presented at Proc. of IEEE ICUPC'93, Oct. 1993.
[20] V.M. DaSilva and E. S. Sousa, "Multicarrier orthogonal CDMA signals for quasi-synchronous communication systems," Selected Areas in Communications, IEEE Journal on, vol. 12, pp. 842-852, 1994.
[21] L.Vandendorpe., "Multitone direct sequence CDMA system in an indoor wireless environment," In Proc. of IEEE First Symposium of Communications and Vehicular Technology, pp. 4.1.1-4.1.8, Oct. 1993.
[22] R. Prasad and S. Hara, "An overview of multi-carrier CDMA," presented at Proc. of IEEE 4th International Symposium on Spread Spectrum Techniques and Applications, Sept. 1996.
[23] N.S.J.Chuang, "Beyond 3G: Wireless Wideband Data Access based on OFDM and Dynamic Packet Assignment," IEEE Communications Magazine, pp. 78-87, July 2000.
[24] S. Hara and R. Prasad, "DS-CDMA, MC-CDMA and MT-CDMA for mobile multi-media communications," presented at IEEE 46th Vehicular Technology Conference, 1996.
[25] A. Chouly, A. Brajal, and S. Jourdan, "Orthogonal multicarrier techniques applied to direct sequence spread spectrum CDMA systems," presented at IEEE GLOBECOM '93, 29 Nov.-2 Dec. 1993.
[26] T. Muller, H. Rohling, and R. Grunheid, "Comparison of different detection algorithms for OFDM-CDMA in broadband Rayleigh fading," presented at IEEE 45th Vehicular Technology Conference, July 1995.
[27] M. Schnell, "Interference calculations for MC-SSMA systems in mobile communications," presented at Proc. ofIEEE PIMRC'95, Sept. 1995.
[28] N. Yee and J. P. Linnartz, "Wiener filtering of multi-carrier CDMA in Rayleigh fading channel," presented at Proc. ofIEEE PIMRC'94, Sept. 1994.
[29] K. Fazel, "Performance of convolutionally coded CDMA/OFDM in a frequency-time selective fading channel and its near-far resistance," presented at Proc. of IEEE ICC'94, May 1994.
[30] K. Fazel, "Narrow-band interference rejection in orthogonal multi-career spread-spectrum communications," presented at Proc. ofIEEE ICUPC'94, 27 Sept.-1 Oct. 1994.
[31] S. Kaiser, "OFDM-CDMA versus DS-CDMA: performance evaluation for fading channels," presented at Proc. of IEEE ICC'95, June 1995.
[32] Y. Bar-Ness, J. P. Linnartz, and L. Xiangqun, "Synchronous multi-user multi-carrier CDMA communication system with decorrelating interference canceler," presented at Proc. ofIEEE PIMRC'94,Sept. 1994.
[33] A. Haimovich, Y. Bar-Ness, and R. Manzo, "A stochastic gradient-based decorrelation algorithm with applications to multicarrier CDMA," presented at Proc. of IEEE 45th Vehicular Technology Conference, July 1995.
[34] C. Qingxin, E. S. Sousa, and S. Pasupathy, "Multi-carrier DS-CDMA with adaptive sub-carrier hopping for fading channels," presented at Proc. of PIMRC'95, Sept. 1995.
[35] L. Vandendorpe, "Multitone spread spectrum multiple access communications system in a multipath Rician fading channel," Vehicular Technology, IEEE Transactions on, vol. 44, pp. 327-337,1995.
[36] O. van de Wiel and L. Vandendorpe, "Analysis of residual interference after DFE equalization of multitone DS/SS systems over multipath channels," presented at IEEE 45th Vehicular Technology Conference,, 1995.
[37] O. van de Wiel and L. Vandendorpe, "A comparison of bidimensional RLS and LMS equalizers for OFDM/DS transmission in an indoor environment," presented at Proc. of IEEE GLOBECOM'94, Dec. 1994.
[38] L. Vandendorpe and O. van de Wiel, "Analysis of residual interference after MSE linear equalization of multitone spread spectrum signals," presented at Proc. of IEEE ICC'95, 1995.
[39] L. Vandendorpe and O. van de Wiel, "Performance analysis of linear joint multiple access interference cancellation-equalization for asynchronous multitone CDMA," presented at Proc. of PIMRC'95, 1995.
[40] C. Byoung-Jo and L. Hanzo, "Crest factors of complementary-sequence-based multicode MCCDMA signals," Wireless Communications, IEEE Transactions on, vol. 2, pp. 1114-1119, 2003.
[41] R. Kimura and E. Adachi, "Comparison of OFDM and multicode MC-CDMA in frequency selective fading channel," Electronics Letters, vol. 39, pp. 317-318, 2003.
[42] T. Mizhou and Y. Bar-Ness, "Equal BER power distribution control for multicode MC-CDMA with MMSE successive interference cancellation," presented at IEEE International Conference on Communications 2004, June 2004.
[43] Y. Lie-Liang and L. Hanzo, "Performance of generalized multicarrier DS-CDMA over Nakagami-m fading channels," Communications, IEEE Transactions on, vol. 50, pp. 956-966, 2002.
[44] G.B. Giannakis, P. A. Anghel, and W. Zhengdao, "Wideband generalized multicarrier CDMA over frequency-selective wireless channels," presented at Proc. of IEEE ICASSP '00, June,2000.
[45] W. Zhengdao and G. B. Giannakis, "Block precoding for MUI/ISI-resilient generalized multicarrier CDMA with multirate capabilities," Communications, IEEE Transactions on, vol. 49, pp. 2016-2027, 2001.
[46] G.B. Giannakis, Z. Wang, A. Scaglione, and S. Barbarossa, "AMOUR-generalized multicarrier transceivers for blind CDMA regardless of multipath," Communications, IEEE Transactions on, vol. 48, pp. 2064-2076, 2000.
[47] 罗.佟学俭,“OFDM移动通信技术原理与应用,”人民邮电出版社,北京,2003.
[48] W.Y. Zou and W. Yiyan, "COFDM: an overview," Broadcasting, IEEE Transactions on, vol. 41, pp. 1-8, 1995.
[49] H. Chien-Fang, H. Yuan-Hao, and C. Tzi-Dar, "Design of an OFDM receiver for high-speed wireless LAN," presented at Proc. ofIEEE ISCAS'2001, May 2001.
[50] J.Proakis, "Digital Communications," Prentice-Hall, 3rd edition, 1995.
[51] ETSI, "Radio Broadcasting Systems: Digital Audio Broadcasting to Mobile, Portable and Fixed Receivers," European Telecommunication Standard, ETS 300-401, Feb. 1995.
[52] ETSI, "Digital Video Broadcasting: Framing Structure, Channel Coding and Modulation for Digital Terrestrial Television," European Telecommunication Standard, EN 300-744, Aug 1997.
[53] L Mikkonen, J. Aldis, G. Awater, A. Lunn, and D. Hutchison, "The Magic WAND-functional overview," Selected Areas in Communications, IEEE Journal on, vol. 16, pp. 953-972, 1998.
[54] ETSI, "Broadcasting radio access networks (BRAN); HIPERLAN Type2 technical specification part Ⅰ- Physical layer," DTS/BRAN030003-1, Oct. 1999.
[55] B. P. Crow, I. Widjaja, L. G. Kim, and P. T. Sakai, "IEEE 802.11 Wireless Local Area Networks," Communications Magazine, IEEE, vol. 35, pp. 116-126, 1997.
[56] J.M.Cioffi, "A multicarrier primer," T1E1.4/91-157, Nov. 1991.
[57] F. B. Frederiksen and R. Prasad, "An overview of OFDM and related techniques towards development of future wireless multimedia communications," presented at IEEE Radio and Wireless Conference 2002, Aug. 2002.
[58] P. H. Moose, "A technique for orthogonal frequency division multiplexing frequency offset correction," Communications, IEEE Transactions on, vol. 42, pp. 2908-2914, 1994.
[59] F. Classen and H. Meyr, "Frequency synchronization algorithms for OFDM systems suitable for communication over frequency selective fading channels," presented at vehicular technology conference, 1994.
[60] T.M. Schmidl and D. C. Cox, "Robust frequency and timing synchronization for OFDM," Communications, IEEE Transactions on, vol. 45, pp. 1613-1621, 1997.
[61] M. Morelli and U. Mengali, "An improved frequency offset estimator for OFDM applications," Communications Letters, IEEE, vol. 3, pp. 75-77, 1999.
[62] J.J. van de Beek, M. Sandell, and P. O. Borjesson, "ML estimation of time and frequency offset in OFDM systems," Signal Processing, IEEE Transactions on[see also Acoustics, Speech, and Signal Processing, IEEE Transactions on, vol. 45, pp. 1800-1805, 1997.
[63] J. J. van de Beek, M. Sandell, M. Isaksson, and P. Ola Borjesson, "Low-complex frame synchronization in OFDM systems," presented at Fourth IEEE International Conference, 6-10 Nov 1995.
[64] L. Wen, L. Jianhua, and G. Jun, "A new pilot assisted frequency synchronization for wireless OFDM systems," presented at Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP '03). 2003 IEEE International Conference on, 2003.
[65] H. Dong-Seog, S. Jae-Hyun, and K. Jung-Jin, "Fast carrier frequency offset compensation in OFDM systems," Consumer Electronics, IEEE Transactions on, vol. 47, pp. 364-369, 2001.
[66] R.P., "Effects of synchronization errors on multi-carrier digital transmission systems," DLR internal report, April 1994.
[67] M. Speth, D. Daecke, and H. Meyr, "Minimum overhead burst synchronization for OFDM based broadband transmission," 1998.
[68] X. Zhongzhe and D. Zaiwang, "Improved GIB synchronization method for OFDM systems," presented at Telecommunications, 2003. ICT 2003. 10th International Conference on, 2003.
[69] Z. Xiaobo and W. Xiaodong, "Channel estimation for OFDM systems using adaptive radial basis function networks," Vehicular Technology, IEEE Transactions on, vol. 52, pp. 48-59, 2003.
[70] C. Ming-Xian and Y. T. Su, "Performance analysis of equalized OFDM systems in Rayleigh fading," Wireless Communications, IEEE Transactions on, vol. 1, pp. 721-732, 2002.
[71] X. Yongzhe and C. N. Georghiades, "Two EM-type channel estimation algorithms for OFDM with transmitter diversity," Communications, IEEE Transactions on, vol. 51, pp. 106-115, 2003.
[72] C. Ming-Xian and Y. T. Su, "Model-based channel estimation for OFDM signals in Rayleigh fading," Communications, IEEE Transactions on, vol. 50, pp. 540-544, 2002.
[73] Y. Che-Shen, L. Yinyi, and W. Yiyan, "OFDM system channel estimation using time-domain training sequence for mobile reception of digital terrestrial broadcasting," Broadcasting, IEEE Transactions on, vol. 46, pp. 215-220, 2000.
[74] L. Ye, "Pilot-symbol-aided channel estimation for OFDM in wireless systems," Vehicular Technology, IEEE Transactions on, vol. 49, pp. 1207-1215, 2000.
[75] S. Won-Gyu and L. Jong-Tae, "Pilot-symbol aided channel estimation for OFDM with fast fading channels," Broadcasting, IEEE Transactions on, vol. 49, pp. 398-402, 2003.
[76] M.C. Necker and G. L. Stuber, "Totally blind channel estimation for OFDM on fast varying mobile radio channels," Wireless Communications, IEEE Transactions on, vol. 3, pp. 1514-1525, 2004.
[77] B. Muquet, M. de Courville, and P. Duhamel, "Subspace-based blind and semi-blind channel estimation for OFDM systems," Signal Processing, IEEE Transactions on[see also Acoustics, Speech, and Signal Processing, IEEE Transactions on], vol. 50, pp. 1699-1712, 2002.
[78] X. Huang and H. Bi, "Blind channel identification and equalization in OFDM system without cyclic prefix," 2003.
[79] J.J. van de Beck, O. Edfors, M. Sandell, S. K. Wilson, and P. O. Borjesson, "On channel estimation in OFDM systems," presented at Vehicular Technology Conference, 1995 IEEE 45th, July 1995.
[80] H. Minn and V. K. Bhargava, "An investigation into time-domain approach for OFDM channel estimation," Broadcasting, IEEE Transactions on, vol. 46, pp. 240-248, 2000.
[81] S. Coleri, M. Ergen, A. Puri, and A. Bahai, "Channel estimation techniques based on pilot arrangement in OFDM systems," Broadcasting, IEEE Transactions on, vol. 48, pp. 223-229, 2002.
[82] O. Edfors, M. Sandell, J. J. van de Beck, S. K. Wilson, and P. O. Borjesson, "OFDM channel estimation by singular value decomposition," Communications, IEEE Transactions on, vol. 46, pp. 931-939, 1998.
[83] J. K. Cavers, "An analysis of pilot symbol assisted modulation for Rayleigh fading channels[mobile radio]," Vehicular Technology, IEEE Transactions on, vol. 40, pp. 686-693, 1991.
[84] K. Yun Hee, S. Iickho, Y. Seokho, and P. So Ryonng, "An efficient frequency offset estimator for OFDM systems and its performance characteristics," Vehicular Technology, IEEE Transactions on, vol. 50, pp. 1307-1312, 2001.
[85] R. Heejin, C. Kyungwhoon, and P. Jaehong, "An MMSE fine carder frequency synchronization algorithm for OFDM systems," Consumer Electronics, IEEE Transactions on, vol. 43, pp. 761-766,1997.
[86] A. J. Coulson, "Maximum likelihood synchronization for OFDM using a pilot symbol: analysis," Selected Areas in Communications, IEEE Journal on, vol. 19, pp. 2495-2503, 2001.
[87] A.J. Coulson, "Maximum likelihood synchronization for OFDM using a pilot symbol: algorithms," Selected Areas in Communications, IEEE Journal on, vol. 19, pp. 2486-2494, 2001.
[88] A. P. A. Mammela, and P.Jarvensivu, "Data and channel estimators: A systematic classification," available on web.
[89] A.V.奥本海姆,“信号与系统”西安, 1985.
[90] H. Meng-Han and W. Che-Ho, "Channel estimation for OFDM systems based on comb-type pilot arrangement in frequency selective fading channels," Consumer Electronics, IEEE Transactions on, vol. 44, pp. 217-225, 1998.
[91] R. Mersereau and T. Speake, "The processing of periodically sampled multidimensional signals," Acoustics, Speech, and Signal Processing[see also IEEE Transactions on Signal Processing], IEEE Transactions on, vol. 31, pp. 188-194, 1983.
[92] R. M. Mersereau, "The processing of hexagonally sampled two-dimensional signals," Proceedings of the IEEE, vol. 67, pp. 930-949, 1979.
[93] R. Nilsson, O. Edfors, M. Sandell, and P. O. Borjesson, "An analysis of two-dimensional pilot-symbol assisted modulation for OFDM," presented at Personal Wireless Communications, 1997 IEEE International Conference on, 1997.
[94] M. J. F. G. Garcia, S. Zazo, and J. M. Paez-Borrallo, "Pilot patterns for channel estimation in OFDM," Electronics Letters, vol. 36, pp. 1049-1050, 2000.
[95] R. Negi and J. Cioffi, "Pilot tone selection for channel estimation in a mobile OFDM system," Consumer Electronics, IEEE Transactions on, vol. 44, pp. 1122-1128,1998.
[96] P. Hoeher, S. Kaiser, and P. Robertson, "Two-dimensional pilot-symbol-aided channel estimation by Wiener filtering," 1997.
[97] V. Rajendran, K. Sundaresan, and S. Subramanian, "A power-efficient resource allocation scheme for multiuser OFDM," presented at Personal Wireless Communications, 2002 IEEE International Conference on, 15-17 Dec. 2002
[98] G. Song and Y. Li, "Adaptive resource allocation based on utility optimization in OFDM," presented at Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE, 1-5 Dec. 2003
[99] X. Liang, W. Anchun, Z. Shidong, and Y. Yan, "A dynamic resource scheduling algorithm for OFDM system," presented at Communications, 2003. APCC 2003. The 9th Asia-Pacific Conference on, 21-24 Sept. 2003
[100] R. Novak and W. A. Krzymien, "An adaptive downlink spread spectrum OFDM packet data system with two-dimensional radio resource allocation: performance in low-mobility cellular environments," presented at Wireless Personal Multimedia Communications, 2002. The 5th International Symposium on, 27-30 Oct. 2002.
[101] J. Tong, Y. Gong, and S. Sun, "An adaptive channel tracking method for MIMO-OFDM systems," presented at Communications, Circuits and Systems, 2004. ICCCAS 2004. 2004 International Conference on, 27-29 June 2004
[102] T. Tai-Lai, Y. Kung, and R. E. Hudson, "Channel estimation and adaptive power allocation for performance and capacity improvement of multiple-antenna OFDM systems," presented at Wireless Communications, 2001. (SPAWC '01). 2001 IEEE Third Workshop on Signal Processing Advances in, 2001.
[103] M. Stemad and D. Aronsson, "Channel estimation and prediction for adaptive OFDM downlinks [vehicular applications]," presented at Vehicular Technology Conference, 2003. VTC 2003-Fall. 2003 IEEE 58th, 6-9 Oct. 2003.
[104] H. S. Rad and S. Gazor, "Transmission diversity ambiguities and adaptive channel tracking," presented at Signal Processing and Its Applications, 2003. Proceedings. Seventh International Symposium on, 1-4 July 2003.
[105] V. Mignone and A. Morello, "CD3-OFDM: a novel demodulation scheme for fixed and mobile receivers," Communications, IEEE Transactions on, vol. 44, pp. 1144-1151, 1996.
[106] T. Onizawa, M. Mizoguchi, T. Sakata, and M. Morikura, "A simple adaptive channel estimation scheme for OFDM systems," presented at Vehicular Technology Conference, 1999. VTC 1999 - Fall. IEEE VTS 50th, 1999.
[107] X. G. Doukopoulos and G. V. Moustakides, "Adaptive algorithms for blind channel estimation in OFDM systems," presented at Communications, 2004 IEEE International Conference on, 20-24 June 2004.
[108] S. Takaoka and F. Adachi, "Adaptive prediction iterative channel estimation for OFDM signal reception in a frequency selective fading channel," presented at Vehicular Technology Conference, 2003. VTC 2003-Spring. The 57th IEEE Semiannual, 22-25 April 2003
[109] K. Y. Kuan, S. Suthaharan, and A. Nallanathan, "An adaptive channel estimation scheme for OFDM system with transmitter diversity," presented at Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE, 1-5 Dec. 2003.
[110] K. JoonBeom, G. L. Stuber, and L. Ye, "Iterative joint channel estimation and detection combined with pilot-tone symbols in convolutionally coded OFDM systems," 7-10 Sept. 2003.
[111] M. Flament, B. Mielczarek, and A. Svensson, "Joint channel estimation and turbo decoding for OFDM-based systems," presented at Wireless Personal Multimedia Communications, 2002. The 5th International Symposium on, 27-30 Oct. 2002
[112] E. Jaffrot and M. Siala, "Turbo channel estimation for OFDM systems on highly time and frequency selective channels," presented at Acoustics, Speech, and Signal Processing, 2000. ICASSP '00. Proceedings. 2000 IEEE International Conference on, 2000.
[113] B. Lu, W. Xiaodong, and L. Ye, "Iterative receivers for space-time block-coded OFDM systems in dispersive fading channels," Wireless Communications, IEEE Transactions on, vol. 1, pp.213-225, 2002.
[114] B. Lu, W. Xiaodong, and K. R. Narayanan, "LDPC-based space-time coded OFDM systems over correlated fading channels: Performance analysis and receiver design," Communications, IEEE Transactions on, vol. 50, pp. 74-88, 2002.