Protocoles coopératifs pour réseaux sans fil

La technique MIMO (Multiple-Input Multiple-Output) est l’une des techniques de base qui offre une diversité spatiale. Elle associe plusieurs antennes à l’émission et à la réception. En plus de la diversité spatiale, le système MIMO permet d’augmenter le gain de multiplexage sans avoir besoin de plus de bande passante ou de puissance d’émission. Cependant, la technique MIMO a des limites liées au coût d’installation de plusieurs antennes sur un terminal, et a l’écart minimal exigé entre les antennes. La communication coopérative a été proposée comme une technologie alternative, dans laquelle la diversité spatiale peut être réalisée en coordonnant plusieurs nœuds qui sont proches géographiquement pour former des réseaux d’antennes virtuelles. La coopération permet de lutter contre l’instabilité du canal radio et de faire face aux phénomènes qui le perturbent comme les évanouissements, les bruits, ou les interférences. Elle permet aussi d’améliorer les performances du système en termes de débit global, d’énergie consommée et d’interférences, etc. Dans le cadre des communications coopératives, nous avons proposé deux protocoles MAC coopératifs dans le contexte des réseaux ad hoc. La première proposition est le protocole RACT (Rate Adaptation with Cooperative Transmission). Ce protocole combine la coopération avec un mécanisme d’adaptation de débit. Lorsqu’un lien entre une source et une destination subit de mauvaises conditions de canal, une station relais est sélectionnée dans le voisinage des deux nœuds de sorte que la liaison directe à faible débit de transmission soit remplacée par un lien à deux sauts avec un débit de données plus élevé. La sélection du meilleur relais est fondée sur un processus de contention distribué. La procédure ne nécessite aucune connaissance de la topologie et aucune communication entre les relais potentiels. Lorsque la qualité de la liaison directe est bonne et que la transmission coopérative n’est pas nécessaire, le protocole fonctionne comme un mécanisme d’adaptation de débit. L’adaptation de débit de données est également réalisée sans aucune signalisation supplémentaire. La sélection du meilleur relais et l’adaptation de débit sont fondés sur des mesures instantanées du canal pour s’adapter aux conditions dynamiques du canal radio. Dans le but d’améliorer davantage les performances du système, nous avons proposé notre deuxième protocole MAC coopératif PRACT (Power and Rate Adaptation with Cooperative Transmission). Ce protocole combine un mécanisme d’adaptation de puissance et de débit (TPRC : Transmit Power and Rate Control) avec un mécanisme de coopération. C’est en cela que cette contribution se distingue des solutions proposées dans la littérature. Notre objectif avec cette contribution est d’atteindre une efficacité d’énergie pour la transmission des données tout en augmentant le débit global du réseau. PRACT propose d’ajuster dynamiquement la puissance et le débit de transmission en s’adaptant aux variations de la qualité du canal radio. Cela permet de gagner davantage dans l’énergie économisée. En outre, le contrôle de puissance, réduit les interférences et augmente la réutilisation spatiale entre cellules ad hoc adjacentes en utilisant la même fréquence de transmission. L’idée de base du protocole est de permettre à chaque nœud dans le réseau ad hoc de créer une table avec les combinaisons puissance-débit optimales, en se fondant seulement sur les spécifications de la carte réseau, à savoir, les débits de transmission possible et la consommation en énergie de la carte. Avec la connaissance des qualités des liens obtenue grâce à l’échange des trames de contrôle et en recherchant dans la table puissance-débit, les nœuds choisissent la stratégie de transmission la plus adaptée pour chaque transmission de trames de données, ainsi que le mode de transmission (direct ou coopératif). ABSTRACT : MIMO (Multiple-Input Multiple-Output) technology is one of the basic techniques that offer a spatial diversity. It combines multiple antennas for transmission and reception. In addition to spatial diversity, MIMO can increase the multiplexing gain without requiring more bandwidth or transmit power. However, the MIMO technology has limitations related to the cost of installing multiple antennas on a terminal, and to the minimum distance required between antennas. The cooperative communication has been proposed as an alternative technology, in which the spatial diversity can be achieved by coordinating multiple nodes that are geographically close to form virtual antenna arrays. Cooperation helps to fight against the instability of the radio channel and deal with phenomena that disturb this channel like fading, noise or interference. It also improves system performance in terms of overall throughput, energy consumption and interference, etc. In the context of cooperative communications, we proposed two MAC protocols in the context of cooperative ad-hoc networks. The first proposal is the RACT (Rate Adaptation with Cooperative Transmission) protocol. This protocol combines cooperation with a rate adaptation mechanism. When a link between a source and a destination suffers from poor channel conditions, a relay station is selected in the neighborhood of the two nodes so that the direct low data-rate link is replaced by a two-hop link with a higher data-rate. Selecting the best relay is based on a distributed contention process. The procedure requires no knowledge of the topology and no communication between the potential relay. When the quality of the direct link is good enough and the cooperative transmission is not necessary, the protocol operates as a rate adaptation mechanism. The data rate adaptation is also performed without any additional signaling. Both the best relay selection and the rate adaptation is based only on the instantaneous channel measurements to adapt to the dynamic conditions of the radio channel. In order to further improve the system performance, we proposed our second cooperative MAC protocol PRACT (Power and Rate Adaptation with Cooperative Transmission). This protocol combines a power and rate control mechanism (TPRC: Transmit Power and Rate Control) with a mechanism for cooperation, this feature distinguishes this contribution from the solutions proposed in the literature. Our objective with this contribution is to achieve energy efficiency for data transmission while increasing the overall throughput of the network. PRACT proposes to dynamically adjust dynamically the power and the transmission rate to adapt to the radio channel quality variations. This way more energy can be saved. In addition, the power control reduces interference and increases the spatial reuse between adjacent ad-hoc cells using the same channel transmission frequency. The basic idea of the protocol is to allow each node in the network to create a table with the best power-rate combinations, based only on the specifications of the network card, namely the possible transmission rates, transmit power levels and the power consumption of the card. With the knowledge of the qualities of links obtained through the exchange of the control frames and looking up in the power-rate table, the nodes choose the most suitable transmission strategy, for each data frame transmission, and the transmission mode (direct or cooperative)

Busy tone-based channel access control for cooperative communication

Cooperative communication has attracted many research interests in recent years because it can take advantage of the broadcast nature of wireless communications and spatial diversity to improve the network performance. Although relay nodes in cooperative communications can help improve the performance, relay nodes may cause the serious competition on wireless channel accessing, which makes the channel access problem in cooperative communications challenging. To solve this problem, based on cooperative triple busy tone multiple access, this paper proposes a media access control scheme that concurrently combines the request to send/clear to send and busy tone with a proper tone duration timer. In the scheme, three busy tones are proposed to coordinate the nodes in the network to transmit packets, which is further utilised to solve the hidden terminal and exposed terminal problems in cooperative communications. Among the three busy tones, the cooperative busy tone is set according to the relay's signal-to-noise ratio. Based on the busy tone, this paper also proposes a bandwidth efficient relay selection algorithm, in which the source node can select the best relay in a distributed way by monitoring the busy tone. The simulation results demonstrate that the proposed scheme can largely reduce the blocking time and improve the channel utilisation in wireless cooperative networks. Copyright (c) 2014 John Wiley & Sons, Ltd.The work is supported by the National Key Technology R&D Program of China under grant no. 2012BAD35B06, the open Foundation of State Key Laboratory of Networking and Switching Technology (Beijing University of Posts and Telecommunications) under grant no. SKLNST-2013-1-04, the Prospective Research Project on Future Networks (Jiangsu Future Networks Innovation Institute) under grant no. BY2013095-4-06, and the National Natural Science Foundation of China under grant nos. 6113305, 61173167 and 61103182, the Fok Ying Tung Education Foundation (No. 142006), and Fundamental Research Funds for the Central Universities (No. 2100219043).Xie, K.; Xie, K.; He, S.; Zhang, D.; Wen, J.; Lloret, J. (2015). Busy tone-based channel access control for cooperative communication. Transactions on Emerging Telecommunications Technologies. 26(10):1173-1188. doi:10.1002/ett.2856S117311882610Boche, H., & Jorswieck, E. A. (2007). On the performance optimization in multiuser MIMO systems. European Transactions on Telecommunications, 18(3), 287-304. doi:10.1002/ett.1155Laneman, J. N., Tse, D. N. C., & Wornell, G. W. (2004). Cooperative Diversity in Wireless Networks: Efficient Protocols and Outage Behavior. IEEE Transactions on Information Theory, 50(12), 3062-3080. doi:10.1109/tit.2004.838089Manhas EB Brante G Souza RD Pellenz ME Energy-efficient cooperative image transmission over wireless sensor networks WCNC, Paris, France 2012 2014 2019Ghelber, B., & Dabora, R. (2012). The value of cooperation between relays in the multiple-access channel with multiple relays. Transactions on Emerging Telecommunications Technologies, 23(4), 341-359. doi:10.1002/ett.1543Zimmermann, E., Herhold, P., & Fettweis, G. (2005). On the performance of cooperative relaying protocols in wireless networks. European Transactions on Telecommunications, 16(1), 5-16. doi:10.1002/ett.1028Sergi, S., Pancaldi, F., & Vitetta, G. M. (2011). Cross-layer design for double-string cooperative communications in wireless ad-hoc networks. European Transactions on Telecommunications, 22(8), 471-486. doi:10.1002/ett.1497Moualeu JM Hamouda W Xu H Takawira F Cross-layer relay selection criterion for cooperative-diversity networks ICC, Ottawa, ON, Canada 2012 5075 5079Hasan Z Jamalipour A Bhargava VK Cooperative communication and relay selection under asymmetric information WCNC, Paris, France 2012 2373 2378Wang B Han Z Liu KJR Distributed relay selection and power control for multiuser cooperative communication networks using buyer/seller game INFOCOM, Anchorage, AK, United states 2007 544 552Chen D Ji H Li X An energy-efficient distributed relay selection and power allocation optimization scheme over wireless cooperative networks ICC, Kyoto, Japan 2011 1 5Feng J Zhang R Ng SX Hanzo L Relay selection for energy-efficient cooperative media access control WCNC, IEEE Cancun, Mexico 2011 287 292Zhang G Cong L Ding E Yang K Yang X Fair and efficient resource sharing for selfish cooperative communication networks using cooperative game theory ICC, IEEE, Kyoto, Japan 2011 1 5Liu, P., Tao, Z., Narayanan, S., Korakis, T., & Panwar, S. (2007). CoopMAC: A Cooperative MAC for Wireless LANs. IEEE Journal on Selected Areas in Communications, 25(2), 340-354. doi:10.1109/jsac.2007.070210Khalid, M., Wang, Y., Ra, I., & Sankar, R. (2011). Two-Relay-Based Cooperative MAC Protocol for Wireless Ad hoc Networks. IEEE Transactions on Vehicular Technology, 60(7), 3361-3373. doi:10.1109/tvt.2011.2159872Sayed, S. G., Yang, Y., & Xu, J. (2010). BTAC: A Busy Tone Based Cooperative MAC Protocol for Wireless Local Area Networks. Mobile Networks and Applications, 16(1), 4-16. doi:10.1007/s11036-010-0267-1Sayed S Yang Y Guo H Hu H Analysis of energy efficiency of a busy tone based cooperative MAC protocol for multi-rate WLANs WCNC, IEEE, Sydney, NSW, Australia 2010 1 6Shan H Wang P Zhuang W Wang Z Cross-layer cooperative triple busy tone multiple access for wireless networks GLOBECOM, IEEE New Orleans, LA, United states 2008 1 5Liu Y Liu K Zeng F A relay-contention-free cooperative MAC protocol for wireless networks CCNC, IEEE, Las Vegas, NV, United states 2011 203 207Abramson N The ALOHA system: another alternative for computer communications Proceedings of the November 17-19, 1970, Fall Joint Computer Conference, ACM, Houston, TX 1970 281 285Bianchi G Fratta L Oliveri M Performance evaluation and enhancement of the CSMA/CA MAC protocol for 802.11 wireless LANs PIMRC Taipei, Taiwan 1996 392 396Haas, Z. J., & Jing Deng. (2002). Dual busy tone multiple access (DBTMA)-a multiple access control scheme for ad hoc networks. IEEE Transactions on Communications, 50(6), 975-985. doi:10.1109/tcomm.2002.1010617Rajeswari, A., & P.T, K. (2011). A Novel Energy Efficient Routing Protocols for Wireless Sensor Networks Using Spatial Correlation Based Collaborative Medium Access Control Combined with Hybrid MAC. Network Protocols and Algorithms, 3(4). doi:10.5296/npa.v3i4.1296Chen Y Li B HCRBT: a dual-busy-tone-assisted MAC protocol with channel reservation for ad hoc networks WICOM, IEEE, Wuhan, China 2011 1 4Li Z Liu K A multiple-recipient-based cooperative MAC protocol for wireless ad hoc networks 2013 IEEE 5th International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications (MAPE), Chengdu, China 2013 59 64Sklar, B. (1997). Rayleigh fading channels in mobile digital communication systems. I. Characterization. IEEE Communications Magazine, 35(9), 136-146. doi:10.1109/35.62053