C. Et, PERSPECTIVES deux métriques ontétéévaluéesontétéontétéévaluées par simulations et ont montré de bonnes performances dans le cadre des applications visées. La seconde métrique, relative au taux d'allocation temps-fréquence, peut s'avérer non informative dans le cas ou toute la bande passante disponible est allouéè a un seul utilisateur, il est ainsi nécessaire d'orienter de futurs travaux sur l'estimation d'une métrique complémentaire qui tendraitàtendrait

C. Pour-les-réseaux and . Ca, estimer le taux de charge du canal et le taux de collisions sur un point d'accès. Les techniques proposées ont montré des performances acceptables sur les gammes de RSB compatibles avec des applications en radio opportuniste . Ces deux métriques combinées sont totalement informatives sur l'´ etat du canal CSMA/CA De plus, la technique d'estimation du taux de charge proposée dans le chapitre 4-section 3 a ´ eté validée sur un banc d'essais mettant en jeux des signaux WiFi réels. Il est utile de noter que cet algorithme a ´ eté utilisé pour développer une approche cross layer dédiéè a la découverte de point d'accès WiFi. Ces travaux ontété ontété mené en collaboration avec le département Réseaux et Systèmes Multimédia de TELECOM Bretagne. Cet algorithme a ´ eté validé expérimentalement et a fait l, il serait judicieux de penseràpenserà une approche qui permettrait de mettrè a jour ces probabilités au fil des observations

F. Socheleau, S. Houcke, and A. Aissa-el-bey, Estimation aveugle du taux d'activité temps-fréquence des signaux OFDMA, XXII colloque GRETSI, 2009.

F. Socheleau, S. Houcke, P. Ciblat, and A. A¨?ssaa¨?ssa-el-bey, Signal Metrics for Vertical Handoff Towards (Cognitive) WiMAX, WiMAX New Developments, 2009.
DOI : 10.5772/8279
URL : http://www.intechopen.com/articles/show/title/signal-metrics-for-vertical-handoff-towards-cognitive-wimax

Q. Zhang, C. Guo, Z. Guo, and W. Zhu, Integration of wireless LAN and 3G wireless - Efficient mobility management for vertical handoff between wwan and wlan, IEEE Communications Magazine, vol.41, issue.11, pp.102-108, 2003.
DOI : 10.1109/MCOM.2003.1244929

K. Park, CS 536 : Data Communication and Computer Networks, 2004.

J. Mitola and G. Q. Maguire, Cognitive radio: making software radios more personal, IEEE Personal Communications, vol.6, issue.4, pp.13-18, 1999.
DOI : 10.1109/98.788210

I. Mitola and J. , Cognitive radio for flexible mobile multimedia communications, 1999 IEEE International Workshop on Mobile Multimedia Communications (MoMuC'99) (Cat. No.99EX384), pp.3-10, 1999.
DOI : 10.1109/MOMUC.1999.819467

U. S. Fcc, Notice of Proposed Rulemaking, in the Matter of Unlicensed Operation in the TV Broadcast Bands (ET Docket no. 04-186) and Additional Spectrum for Unlicensed Devices below 900 MHz and in the 3 GHz Band, 2004.

U. S. Fcc, Second Report and Order and Memorandum Opinion and Order, in the Matter of Unlicensed Operation in the TV Broadcast Bands Additional Spectrum for Unlicensed Devices Below 900 MHz and in the 3 GHz Band, Tech. Rep, 2008.

C. Stevenson, G. Chouinard, Z. Lei, W. Hu, S. Shellhammer et al., The First Cognitive Radio Wireless Regional Area Network Standard, Communications Magazine IEEE, vol.80222, issue.47 1, pp.130-138, 2009.

D. Birru, S. Shankar, C. Cordeiro, and K. Challapali, IEEE 802.22 : An Introduction to the First Wireless Standard Based on Cognitive Radios, Journal of Communications, vol.1, issue.1, pp.38-47, 2006.

E. Gustafsson and A. Jonsson, Always best connected, IEEE Wireless Communications, vol.10, issue.1, pp.49-55, 2003.
DOI : 10.1109/MWC.2003.1182111

M. Oularbi, S. Gazor, S. Houcke, and A. Aissa-el-bey, OFDM system identification using pilot tone signature, International Workshop on Systems, Signal Processing and their Applications, WOSSPA, 2011.
DOI : 10.1109/WOSSPA.2011.5931422
URL : https://hal.archives-ouvertes.fr/hal-00609305

M. Oularbi, S. Gazor, S. Houcke, and A. Aissa-el-bey, GLR Test for OFDM System Identification Usning Pilot Tones Pattern, 2011.

M. Oularbi, S. Gazor, S. Houcke, and A. Aissa-el-bey, Identification de systèmes OFDMàOFDMà partir de la signature des pilotes, XXIIIe colloque GRETSI : traitement du signal et des images, 2011.

M. Oularbi, F. Socheleau, S. Houcke, and A. Aissa-el-bey, Blind estimation of the time-frequency activity rate of OFDMA signals, International Congress on Ultra Modern Telecommunications and Control Systems, 2010.
DOI : 10.1109/ICUMT.2010.5676666
URL : https://hal.archives-ouvertes.fr/hal-00565928

M. Oularbi, F. Socheleau, S. Houcke, and A. Aissa-el-bey, Estimation du taux d'activité temps-fréquence d'un signal OFDMA pour des applications en radio-cognitive, XXIIIe colloque GRETSI : traitement du signal et des images, 2011.

M. Oularbi, S. Houcke, and A. Aissa-el-bey, Base Station Number of Antennas Detection Using Pilot Tones sencond order cyclostationnarity, Letter en cours de pr´partionpr´partion, 2011.

M. Oularbi, F. Socheleau, S. Houcke, and A. Aissa-el-bey, Vertical Handover Metrics Estimation for OFDM Based Systems, EURASIP Journal On Wireless Communication and Networking, 2011.

M. Oularbi, A. Aissa-el-bey, and S. Houcke, Two vertical handcover metrics toward an IEEE 802.11N network, COGIS 2009 : Cognitive systems with Interactive Sensors, 2009.
URL : https://hal.archives-ouvertes.fr/hal-00472054

M. Oularbi, A. Aissa-el-bey, and S. Houcke, Physical layer IEEE 802.11 channel occupancy rate estimation, 2010 5th International Symposium On I/V Communications and Mobile Network, 2010.
DOI : 10.1109/ISVC.2010.5656158
URL : https://hal.archives-ouvertes.fr/hal-00527537

M. Oularbi, S. Gazor, S. Houcke, and A. Aissa-el-bey, Markov Chain Modelling for Channel Occupancy Rate and Collision Rate estimation for CSMA/CA based systems Article en préparation, 2011.

M. Stemm and R. H. Katz, Vertical handoffs in wireless overlay networks, Mobile Networks and Applications, vol.3, issue.4, pp.335-350, 1998.
DOI : 10.1023/A:1019197320544

W. Zhang, J. Jaehnert, and K. Dolzer, Design and evaluation of a handover decision strategy for 4th generation mobile networks, The 57th Semiannual Vehicular Technology Conference VTC 2003-Spring, pp.22-25, 2003.

K. Friedrich and . Jondral, Software-defined radio : basics and evolution to cognitive radio, EURASIP J. Wirel. Commun. Netw, vol.2005, issue.3, pp.275-283, 2005.

H. Urkowitz, Energy detection of unknown deterministic signals, Proceedings of the IEEE, vol.55, issue.4, pp.523-531, 1967.
DOI : 10.1109/PROC.1967.5573

D. Cabric, S. M. Mishra, and R. W. Brodersen, Implementation Issues in Spectrum Sensing for Cognitive Radios Conference Record of the Thirty-Eighth Asilomar, nov, Conference on Signals, Systems and Computers, pp.772-776, 2004.

A. Bouzegzi, P. Ciblat, and P. Jallon, New algorithms for blind recognition of OFDM based systems, Signal Processing, vol.90, issue.3, pp.900-913, 2010.
DOI : 10.1016/j.sigpro.2009.09.017

A. Bouzegzi, P. Jallon, and P. Ciblat, A fourth-order algorithm for blind characterization of OFDM signals, 2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications, pp.411-415, 2008.
DOI : 10.1109/SPAWC.2008.4641640

A. Bouzegzi, P. Jallon, and P. Ciblat, A Second Order Statistics Based Algorithm for Blind Recognition of OFDM Based Systems, IEEE GLOBECOM 2008, 2008 IEEE Global Telecommunications Conference, pp.1-5, 2008.
DOI : 10.1109/GLOCOM.2008.ECP.625

A. Bouzegzi, P. Ciblat, and P. Jallon, Matched Filter Based Algorithm for Blind Recognition of OFDM Systems, 2008 IEEE 68th Vehicular Technology Conference, pp.1-5, 2008.
DOI : 10.1109/VETECF.2008.285

A. Bouzegzi, P. Ciblat, and P. Jallon, Maximum likelihood based methods for OFDM intercarrier spacing characterization, 2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications, pp.1-5, 2008.
DOI : 10.1109/PIMRC.2008.4699444

N. Han, G. Zheng, S. H. Sohn, and J. Kim, Cyclic Autocorrelation Based Blind OFDM Detection and Identification for Cognitive Radio, 2008 4th International Conference on Wireless Communications, Networking and Mobile Computing, pp.1-5, 2008.
DOI : 10.1109/WiCom.2008.313

A. Punchihewa, V. K. Bhargava, and C. Despins, Blind Estimation of OFDM Parameters in Cognitive Radio Networks, IEEE Transactions on Wireless Communications, vol.10, issue.3, pp.733-738, 2011.
DOI : 10.1109/TWC.2010.010411.100276

M. Oner and F. Jondral, On the extraction of the channel allocation information in spectrum pooling systems, IEEE Journal on Selected Areas in Communications, vol.25, issue.3, pp.558-565, 2007.
DOI : 10.1109/JSAC.2007.070406

T. Yucek and H. Arslan, OFDM Signal Identification and Transmission Parameter Estimation for Cognitive Radio Applications, IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference, pp.4056-4060, 2007.
DOI : 10.1109/GLOCOM.2007.771

H. Li, Y. Bar-ness, A. Abdi, O. S. Somekh, and W. Su, OFDM Modulation Classification and Parameters Extraction, 2006 1st International Conference on Cognitive Radio Oriented Wireless Networks and Communications, pp.1-6, 2006.
DOI : 10.1109/CROWNCOM.2006.363474

P. D. Sutton, K. E. Nolan, and L. E. Doyle, Cyclostationary Signatures in Practical Cognitive Radio Applications, Selected Areas in Communications, pp.13-24, 2008.
DOI : 10.1109/JSAC.2008.080103

K. Maeda, A. Benjebbour, T. Asai, T. Furuno, and T. Ohya, Recognition Among OFDM-Based Systems Utilizing Cyclostationarity-Inducing Transmission, 2007 2nd IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks, pp.516-523, 2007.
DOI : 10.1109/DYSPAN.2007.74

F. Socheleau, S. Houcke, P. Ciblat, and A. Aissa-el-bey, Cognitive OFDM system detection using pilot tones second and third-order cyclostationarity, Signal Processing, vol.91, issue.2, 2011.
DOI : 10.1016/j.sigpro.2010.07.003
URL : https://hal.archives-ouvertes.fr/hal-00632790

Y. Jung and Y. H. Lee, Use of periodic pilot tones for identifying base stations of FH-OFDMA systems, IEEE Communications Letters, vol.10, issue.3, pp.192-194, 2006.
DOI : 10.1109/LCOMM.2006.1603381

Y. Li, Pilot-symbol-aided channel estimation for OFDM in wireless systems, IEEE Transactions on Vehicular Technology, vol.49, issue.4, pp.1207-1215, 2000.
DOI : 10.1109/25.875230

S. Colieri, M. Ergen, A. Puri, and A. Bahai, A study of channel estimation in OFDM systems, Proceedings IEEE 56th Vehicular Technology Conference, pp.894-898, 2002.
DOI : 10.1109/VETECF.2002.1040729

S. Colieri, M. Ergen, A. Puri, and A. Bahai, Channel estimation techniques based on pilot arrangement in OFDM systems, IEEE Transactions on Broadcasting, vol.48, issue.3, pp.223-229, 2002.
DOI : 10.1109/TBC.2002.804034

A. J. Coulson, Maximum likelihood synchronization for OFDM using a pilot symbol : algorithms, " Selected Areas in Communications, IEEE Journal on, vol.19, issue.12, pp.2486-2494, 2001.

T. M. Schmidl and D. C. Cox, Robust frequency and timing synchronization for OFDM, IEEE Transactions on Communications, vol.45, issue.12, pp.1613-1621, 1997.
DOI : 10.1109/26.650240

S. Gazor, M. Derakhtian, and A. A. Tadaion, Computationally Efficient Maximum Likelihood Sequence Estimation and Activity Detection for <formula formulatype="inline"><tex Notation="TeX">$M$</tex> </formula>-PSK Signals in Unknown Flat Fading Channels, IEEE Signal Processing Letters, vol.17, issue.10, pp.871-874, 2010.
DOI : 10.1109/LSP.2010.2062891

W. C. Jakes, Microwave Mobile Communications, 1975.
DOI : 10.1109/9780470545287

R. E. Glaser, The Ratio of the Geometric Mean to the Arithmetic Mean for a Random Sample from a Gamma Distribution, Journal of the American Statistical Association, vol.36, issue.354, pp.480-487, 1976.
DOI : 10.1080/01621459.1976.10480374

J. Mcnair and F. Zhu, Migration toward 4G wireless communications - Vertical handoffs in fourth-generation multinetwork environments, IEEE Wireless Communications, vol.11, issue.3, pp.8-15, 2004.
DOI : 10.1109/MWC.2004.1308935

W. Chen, J. Liu, and H. Huang, An adaptive scheme for vertical handoff in wireless overlay networks, Parallel and Distributed Systems, International Conference on, p.541, 2004.

F. Zhu and J. Mcnair, Optimizations for vertical handoff decision algorithms, Wireless Communications and Networking Conference, pp.867-872, 2004.

W. Zhang, Handover decision using fuzzy MADM in heterogeneous networks, Wireless Communications and Networking Conference, pp.653-658, 2004.

Q. Song and A. Jamalipour, A network selection mechanism for next generation networks, Communications, 2005. ICC 2005. 2005 IEEE International Conference on, pp.1418-1422, 2005.

Z. Dai, R. Fracchia, J. Gosteau, P. Pellati, and G. Vivier, Vertical handover criteria and algorithm in IEEE 802.11 and 802.16 hybrid networks, IEEE International Conference on Communications, pp.2480-2484, 2008.

H. Bolcskei, D. Gesbert, and A. J. Paulraj, On the capacity of OFDM-based spatial multiplexing systems, IEEE Transactions on Communications, vol.50, issue.2, pp.225-234, 2002.
DOI : 10.1109/26.983319

O. Somekh, O. Simeone, Y. Bar-ness, and W. Su, Detecting the Number of Transmit Antennas with Unauthorized or Cognitive Receivers in MIMO Systems, MILCOM 2007, IEEE Military Communications Conference, 2007.
DOI : 10.1109/MILCOM.2007.4455298

M. Shi, Y. Bar-ness, and W. Su, Adaptive estimation of the number of transmit antennas, MILCOM 2007, IEEE Military Communications Conference, 2007.
DOI : 10.1109/MILCOM.2007.4454817

E. Ohlmer, T. Liang, and G. Fettweis, Algorithm for Detecting the Number of Transmit Antennas in MIMO-OFDM Systems, VTC Spring 2008, IEEE Vehicular Technology Conference, pp.478-482, 2008.
DOI : 10.1109/VETECS.2008.111

E. Ohlmer, T. Liang, and G. Fettweis, Algorithm for Detecting the Number of Transmit Antennas in MIMO-OFDM Systems: Receiver Integration, 2008 IEEE 68th Vehicular Technology Conference, pp.1-5, 2008.
DOI : 10.1109/VETECF.2008.203

E. T. Jaynes, Probability Theory : The Logic of Science, 2000.
DOI : 10.1017/CBO9780511790423

F. Socheleau, A. Aissa-el-bey, and S. Houcke, Non data-aided SNR estimation of OFDM signals, IEEE Communications Letters, vol.12, issue.11, 2008.
DOI : 10.1109/LCOMM.2008.081134
URL : https://hal.archives-ouvertes.fr/hal-00656640

C. Guo, Z. Guo, Q. Zhang, and W. Zhu, A Seamless and Proactive End-to-End Mobility Solution for Roaming Across Heterogeneous Wireless Networks, IEEE Journal on Selected Areas in Communications, vol.22, issue.5, pp.834-848, 2004.
DOI : 10.1109/JSAC.2004.826921

B. Zayen, A. Hayar, and K. Kansanen, Blind Spectrum Sensing for Cognitive Radio Based on Signal Space Dimension Estimation, 2009 IEEE International Conference on Communications, pp.1-5, 2009.
DOI : 10.1109/ICC.2009.5198794

M. Haddad, A. Hayar, F. M. Hedi, and M. Debbah, Cognitive Radio Sensing Information-Theoretic Criteria Based, 2007 2nd International Conference on Cognitive Radio Oriented Wireless Networks and Communications, pp.241-244, 2007.
DOI : 10.1109/CROWNCOM.2007.4549803
URL : https://hal.archives-ouvertes.fr/hal-00280767

D. W. Scott, Multivariate density estimation : theory, practice, and visualization, Wiley series in probability and mathematical statistics : applied probability and statistic section, 1992.

B. W. Silverman, Density Estimation for Statistics and Data Analysis, 1992.
DOI : 10.1007/978-1-4899-3324-9

L. Scharf, Statistical Signal Processing : Detection, Estimation, and Time Series Analysis

. Iperf and . Fr, IPERF, la référence pour les tests de débits TCP / UDP, PHPSESSID=q6m1u31f5od97egdhgnv5hgpj2, [Online ; accessed 05, 2010.

J. Yun and S. Seo, Collision Detection based on RE Energy Duration in IEEE 802.11 Wireless LAN, Communication System Software and Middleware First International Conference on, 2006.

J. Yun and S. Seo, Novel collision detection scheme and its applications for IEEE 802.11 wireless LANs, Computer Communications, vol.30, issue.6, pp.1350-1366, 2007.
DOI : 10.1016/j.comcom.2006.12.022

M. Wax, T. Kailath, and J. Geier, Detection of signals by information theoretic criteria ASSP-33 WiFi Planet Tutorials : SNR Cutoff Recommendations, SNR-Cutoff-Recommendations.htm, pp.387-392, 1985.

G. Bianchi, Performance analysis of the ieee 802.11 distributed coordination function Selected Areas in Communications, IEEE Journal on, vol.18, issue.3, pp.535-547, 2000.

J. Mcdougall and S. Miller, Sensitivity of wireless network simulations to a two-state markov model channel approximation, GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489), pp.697-701, 2003.
DOI : 10.1109/GLOCOM.2003.1258328

T. Vercauteren, A. L. Toledo, and X. Wang, Online Bayesian Estimation of Hidden Markov Models with Unknown Transition Matrix and Applications to IEEE 802.11 Networks, Proceedings. (ICASSP '05). IEEE International Conference on Acoustics, Speech, and Signal Processing, 2005., pp.13-16, 2005.
DOI : 10.1109/ICASSP.2005.1415933

A. Kavcic and B. Yang, Adaptive rank estimation for spherical subspace trackers, IEEE Transactions on Signal Processing, vol.44, issue.6, pp.1573-1579, 1996.
DOI : 10.1109/78.506625

B. Champagne, W. Kang, and H. C. Tam, Improved strategy for adaptive rank estimation with spherical subspace trackers, CCECE 2003, Canadian Conference on Electrical and Computer Engineering. Toward a Caring and Humane Technology (Cat. No.03CH37436), pp.2029-2034, 2003.
DOI : 10.1109/CCECE.2003.1226314

D. J. Rabideau, Fast, rank adaptive subspace tracking and applications, IEEE Transactions on Signal Processing, vol.44, issue.9, pp.2229-2244, 1996.
DOI : 10.1109/78.536680

P. O. Perry and P. J. Wolfe, Minimax rank estimation for subspace tracking Selected Topics in Signal Processing, IEEE Journal, vol.4, issue.3, pp.504-513, 2010.

A. Taherpour, S. Gazor, and A. Taherpour, Adaptive spectrum sensing and learning in cognitive radio networks, 18th European Signal Processing Conference, pp.860-864, 2010.

B. Champagne and Q. G. Liu, Plane rotation-based EVD updating schemes for efficient subspace tracking, IEEE Transactions on Signal Processing, vol.46, issue.7, pp.1886-1900, 1998.
DOI : 10.1109/78.700961

G. Castignani, N. Montavont, A. Emilio-arcia-moret, S. Houcke, and M. Oularbi, Cross-layer adaptive scanning algorithms for IEEE 802, WCNC 2011 : IEEE Wireless Communications and Networking Conference, 2011.
DOI : 10.1109/wcnc.2011.5779152
URL : https://hal.archives-ouvertes.fr/hal-00725670