OFDM in Emerging Wireless Networks: Synchronization Algorithms and Physical Layer Security

In the last decade, orthogonal frequency division multiplexing (OFDM) has been chosen as the physical layer solution for a large variety of wireless, high data rates communication standards. The reasons for this success are found in the possibility of coping with frequency selective channels with simple and efficiently implemented transceivers, and achieving high spectral efficiency. In order to push the performance of these systems close to their limit, emerging wireless networks need efficient methods for time and frequency synchronization, since an erroneous choice of the symbol timing and residual offsets in the clock and carrier frequencies at the transmitter and the receiver can highly impair transmissions due to the effects of intersymbol interference (ISI) and interchannel interference (ICI). In the first part of this thesis we focus on time and frequency synchronization algorithms for ultrawide band (UWB) multiband (MB) OFDM systems. First, we consider the time synchronization problem and we analyze the case when the channel delay spread is larger than the cyclic prefix length determined by the standard, that is when ISI and ICI can not be completely avoided with a proper symbol timing. In this case, we identify as an appropriate target for synchronization the maximization of the ratio of the total useful received power over all subcarriers to the total power of ISI and ICI for a given channel realization. We also present a practical low-complexity synchronization scheme and show that its performance tops the results obtained by the best existing correlation-based timing estimators. Moreover, the very high transmission rate of MB-OFDM architectures asks for carrier and clock frequency offset estimators with moderate complexity and fast acquisition times. Then, we formulate algorithms that are based upon the received frequency domain symbols, where the effects of both offsets can be observed, and jointly estimate them with either a linear least squares or a maximum likelihood approach. The performance of the algorithms is assessed through simulation in a realistic UWB channel scenario and compared with previous literature results. v

[1]  Jean Cardinal,et al.  Reconciliation of a quantum-distributed Gaussian key , 2001, IEEE Transactions on Information Theory.

[2]  F.J. Block.  Comparison of jamming robustness of airborne networking waveforms , 2005, MILCOM 2005 - 2005 IEEE Military Communications Conference.

[3]  Lajos Hanzo,et al.  OFDM and MC-CDMA for Broadband Multi-User Communications, WLANs and Broadcasting , 2003 .

[4]  Robert M. Gray,et al.  Toeplitz and Circulant Matrices: A Review , 2005, Found. Trends Commun. Inf. Theory.

[5]  Tamer Basar,et al.  A complete characterization of minimax and maximin encoder- decoder policies for communication channels with incomplete statistical description , 1985, IEEE Trans. Inf. Theory.

[6]  R. Srikant,et al.  Correlated Jamming on MIMO Gaussian Fading Channels , 2004, IEEE Trans. Inf. Theory.

[7]  Shlomo Shamai,et al.  Secured Communication over Frequency-Selective Fading Channels: A Practical Vandermonde Precoding , 2009, EURASIP J. Wirel. Commun. Netw..

[8]  Muriel Médard,et al.  On Jamming in the Wideband Regime , 2006, 2006 IEEE International Symposium on Information Theory.

[9]  Shlomo Shamai,et al.  A Note on the Secrecy Capacity of the Multiple-Antenna Wiretap Channel , 2007, IEEE Transactions on Information Theory.

[10]  Andrew Thangaraj,et al.  LDPC-based Gaussian key reconciliation , 2006, 2006 IEEE Information Theory Workshop - ITW '06 Punta del Este.

[11]  Mustafa Cenk Gursoy.  Secure communication in the low-SNR regime: A Characterization of the energy-secrecy tradeoff , 2009, 2009 IEEE International Symposium on Information Theory.

[12]  A. D. Wyner,et al.  The wire-tap channel , 1975, The Bell System Technical Journal.

[13]  S. Weinstein,et al.  Data Transmission by Frequency-Division Multiplexing Using the Discrete Fourier Transform , 1971 .

[14]  S. Kay.  Fundamentals of statistical signal processing: estimation theory , 1993 .

[15]  Rohit Negi,et al.  Guaranteeing Secrecy using Artificial Noise , 2008, IEEE Transactions on Wireless Communications.

[16]  Miguel R. D. Rodrigues,et al.  Filter Design with Secrecy Constraints: The Degraded Parallel Gaussian Wiretap Channel , 2008, IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference.

[17]  Eduard Axel Jorswieck,et al.  Optimal transmitter and jamming strategies in Gaussian MIMO channels , 2005, 2005 IEEE 61st Vehicular Technology Conference.

[18]  Shuangqing Wei,et al.  Jamming and counter-measure strategies in parallel Gaussian fading channels with channel state information , 2008, MILCOM 2008 - 2008 IEEE Military Communications Conference.

[19]  Rudolf Ahlswede,et al.  Common randomness in information theory and cryptography - I: Secret sharing , 1993, IEEE Trans. Inf. Theory.

[20]  George T. Amariucai,et al.  Jamming Games in Fast-Fading Wireless Channels , 2008, IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference.

[21]  Hesham El Gamal,et al.  On the Secrecy Capacity of Fading Channels , 2007, ISIT.

[22]  Donald C. Cox,et al.  Robust frequency and timing synchronization for OFDM , 1997, IEEE Trans. Commun..

[23]  Roy D. Yates,et al.  Secrecy capacity of independent parallel channels , 2009 .

[24]  Frédérique E. Oggier,et al.  The secrecy capacity of the MIMO wiretap channel , 2008, ISIT.

[25]  George T. Amariucai,et al.  Jamming in Fixed-Rate Wireless Systems with Power Constraints - Part I: Fast Fading Channels , 2008, ArXiv.

[26]  Sennur Ulukus,et al.  Correlated Jamming in Multiple Access Channels 1 , 2005 .

[27]  Zhongding Lei,et al.  Maximum Likelihood Frequency Offset Estimation & Cramer Rao Bound for Ultra-Wideband (UWB) Multi-Band OFDM Systems , 2006, 2006 IEEE 63rd Vehicular Technology Conference.

[28]  Tamer Basar,et al.  With the Capacity 0.461(bits) and the Optimal Opd Being 'q = , 1998 .

[29]  André Bourdoux,et al.  A performance and complexity comparison of auto-correlation and cross-correlation for OFDM burst synchronization , 2003, 2003 IEEE International Conference on Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP '03)..

[30]  Martin E. Hellman,et al.  The Gaussian wire-tap channel , 1978, IEEE Trans. Inf. Theory.

[31]  Samel Çelebi.  Interblock interference (IBI) and time of reference (TOR) computation in OFDM systems , 2001, IEEE Trans. Commun..

[32]  Miguel R. D. Rodrigues,et al.  Secrecy Capacity of Wireless Channels , 2006, 2006 IEEE International Symposium on Information Theory.

[33]  Matthieu Bloch,et al.  Secret Sharing over Fast-Fading MIMO Wiretap Channels , 2009, EURASIP J. Wirel. Commun. Netw..

[34]  U. Maurer,et al.  Secret key agreement by public discussion from common information , 1993, IEEE Trans. Inf. Theory.

[35]  O. Edfors,et al.  Time and frequency synchronization for OFDM using PN-sequence preambles , 1999, Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324).

[36]  B. Krongold.  A method for minimum-interference OFDM time synchronization , 2003, 2003 4th IEEE Workshop on Signal Processing Advances in Wireless Communications - SPAWC 2003 (IEEE Cat. No.03EX689).

[37]  M. Batariere,et al.  Cyclic prefix length analysis for 4G OFDM systems , 2004, IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004.

[38]  Nevio Benvenuto,et al.  Equalization methods in OFDM and FMT systems for broadband wireless communications , 2002, IEEE Trans. Commun..

[39]  Francois P. S. Chin,et al.  Two-Dimensional Iterative Sampling Frequency Offset Estimation for MB-OFDM System , 2006, 2006 IEEE 63rd Vehicular Technology Conference.

[40]  Shlomo Shamai,et al.  Secure Communication Over Fading Channels , 2007, IEEE Transactions on Information Theory.

[41]  Moe Z. Win,et al.  Frequency offset estimation for MB-OFDM-based UWB systems , 2008, IEEE Trans. Commun..

[42]  M. El-Tanany,et al.  Synchronization of OFDM systems over frequency selective fading channels , 1997, 1997 IEEE 47th Vehicular Technology Conference. Technology in Motion.

[43]  Yuhong Yang.  Elements of Information Theory (2nd ed.). Thomas M. Cover and Joy A. Thomas , 2008 .

[44]  Heidi Steendam,et al.  Analysis and optimization of the performance of OFDM on frequency-selective time-selective fading channels , 1999, IEEE Trans. Commun..

[45]  Claude E. Shannon,et al.  Communication theory of secrecy systems , 1949, Bell Syst. Tech. J..

[46]  D. Reilly,et al.  Noise-enhanced encryption for physical layer security in an OFDM radio , 2009, 2009 IEEE Radio and Wireless Symposium.

[47]  Jaehong Park,et al.  An MMSE fine carrier frequency synchronization algorithm for OFDM systems , 1997 .

[48]  Chia-Chin Chong,et al.  A Comprehensive Standardized Model for Ultrawideband Propagation Channels , 2006, IEEE Transactions on Antennas and Propagation.

[49]  Gilles Brassard,et al.  Secret-Key Reconciliation by Public Discussion , 1994, EUROCRYPT.

[50]  Evangelos Eleftheriou,et al.  Filtered multitone modulation for very high-speed digital subscriber lines , 2002, IEEE J. Sel. Areas Commun..

[51]  R. Chang.  Synthesis of band-limited orthogonal signals for multichannel data transmission , 1966 .

[52]  Charles R. Johnson,et al.  Matrix analysis , 1985, Statistical Inference for Engineers and Data Scientists.

[53]  D. C. Cox,et al.  Low-overhead, low-complexity [burst] synchronization for OFDM , 1996, Proceedings of ICC/SUPERCOMM '96 - International Conference on Communications.

[54]  Per Ola Börjesson,et al.  ML estimation of time and frequency offset in OFDM systems , 1997, IEEE Trans. Signal Process..

[55]  Georgios B. Giannakis,et al.  Cyclic prefixing or zero padding for wireless multicarrier transmissions? , 2002, IEEE Trans. Commun..

[56]  Matthieu R. Bloch,et al.  Wireless Information-Theoretic Security , 2008, IEEE Transactions on Information Theory.

[57]  John Hamilton,et al.  An elliptical cryptographic algorithm for rf wireless devices , 2007, 2007 Winter Simulation Conference.

[58]  Thomas M. Cover,et al.  Elements of Information Theory , 2005 .

[59]  R. V. Churchill,et al.  Lectures on Fourier Integrals , 1959 .

[60]  Eduard A. Jorswieck,et al.  Resource allocation for the wire-tap multi-carrier broadcast channel , 2008, 2008 International Conference on Telecommunications.

[61]  Ueli Maurer,et al.  Information-Theoretic Key Agreement: From Weak to Strong Secrecy for Free , 2000, EUROCRYPT.

[62]  Venkat Anantharam,et al.  Information-Theoretic Key Agreement of Multiple Terminals—Part I , 2010, IEEE Transactions on Information Theory.

[63]  David H. Bailey,et al.  The Fractional Fourier Transform and Applications , 1991, SIAM Rev..

[64]  Imre Csiszár,et al.  Broadcast channels with confidential messages , 1978, IEEE Trans. Inf. Theory.

[65]  Shlomo Shamai,et al.  Multiple-Input Multiple-Output Gaussian Broadcast Channels With Confidential Messages , 2009, IEEE Transactions on Information Theory.

[66]  S.H. Muller-Weinfurtner.  On the optimality of metrics for coarse frame synchronization in OFDM: a comparison , 1998, Ninth IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (Cat. No.98TH8361).

[67]  Paul H. Moose,et al.  A technique for orthogonal frequency division multiplexing frequency offset correction , 1994, IEEE Trans. Commun..

[68]  J.A.C. Bingham,et al.  Multicarrier modulation for data transmission: an idea whose time has come , 1990, IEEE Communications Magazine.

[69]  Helmut Bölcskei,et al.  Blind estimation of symbol timing and carrier frequency offset in wireless OFDM systems , 2001, IEEE Trans. Commun..

[70]  Daniel Pérez Palomar,et al.  Gradient of mutual information in linear vector Gaussian channels , 2005, ISIT.

[71]  Balasubramaniam Natarajan,et al.  The effect of jamming on the performance of carrier interferometry/OFDM , 2005, WiMob'2005), IEEE International Conference on Wireless And Mobile Computing, Networking And Communications, 2005..

[72]  Wei-Jian Lin,et al.  An integrating channel coding and cryptography design for OFDM based WLANs , 2009, 2009 IEEE 13th International Symposium on Consumer Electronics.

[73]  Gregory W. Wornell,et al.  The MIMOME Channel , 2007, ArXiv.

[74]  John G. Proakis,et al.  Digital Communications , 1983 .

[75]  Umberto Mengali,et al.  An improved frequency offset estimator for OFDM applications , 1999, 1999 IEEE Communications Theory Mini-Conference (Cat. No.99EX352).

[76]  Gregory W. Wornell,et al.  Secure Transmission With Multiple Antennas I: The MISOME Wiretap Channel , 2010, IEEE Transactions on Information Theory.

[77]  Eduard Axel Jorswieck.  Unified approach for optimisation of single-user and multi-user multiple-input multiple-output wireless systems , 2004 .

[78]  Shlomo Shamai,et al.  An MMSE Approach to the Secrecy Capacity of the MIMO Gaussian Wiretap Channel , 2009, 2009 IEEE International Symposium on Information Theory.

[79]  Venkat Anantharam,et al.  Information-Theoretic Key Agreement of Multiple Terminals—Part II: Channel Model , 2010, IEEE Transactions on Information Theory.

[80]  Dov Wulich,et al.  Securing OFDM over Wireless Time-Varying Channels Using Subcarrier Overloading with Joint Signal Constellations , 2009, EURASIP J. Wirel. Commun. Netw..

[81]  J. D. Martin,et al.  Statistical performance of the first order phase difference digital instantaneous frequency estimator , 1996 .

[82]  Ami Wiesel,et al.  On the Gaussian MIMO Wiretap Channel , 2007, 2007 IEEE International Symposium on Information Theory.

[83]  Chunjie Duan,et al.  A Low-Complexity Synchronization Design for MB-OFDM Ultra-Wideband Systems , 2008, 2008 IEEE International Conference on Communications.

[84]  Lajos Hanzo,et al.  Orthogonal frequency division multiplex synchronisation techniques for wireless local area networks , 1996, Proceedings of PIMRC '96 - 7th International Symposium on Personal, Indoor, and Mobile Communications.

[85]  Antti Toskala,et al.  LTE for UMTS - OFDMA and SC-FDMA Based Radio Access , 2009 .

[86]  Alan V. Oppenheim,et al.  Discrete-time Signal Processing. Vol.2 , 2001 .

[87]  Ramjee Prasad,et al.  OFDM for Wireless Multimedia Communications , 1999 .

[88]  Alex Reznik,et al.  Extracting Secrecy from Jointly Gaussian Random Variables , 2006, 2006 IEEE International Symposium on Information Theory.