Energy efficiency in cellular wireless networks

Energy efficiency of Long Term Evolution (LTE) cellular communication networks has become a major concern for network operators, not only to reduce the operational costs, but also to reduce their environmental effects. Within LTE cellular networks, base stations are responsible for most of the energy consumption, consuming 70-95% or more of the network power depending on the network topology, configuration, radio technology and data rates that are used. Power control is an important function in cellular wireless networks and refers to setting the output power levels of transmitters, termed eNodeB in the downlink and user equipment (UEs) in the uplink. LTE utilizes two different mechanisms for uplink power control: Open Loop Power Control (OLPC) and Closed Loop Power Control (CLPC). Uplink OLPC is performed by the UE following eNodeB configuration and can compensate for long term channel variation such as path loss and shadowing. The uplink CLPC mechanism attempts to improve power control performance by compensating fast channel variations due to multipath fading. In CLPC the eNodeB sends Transmit Power Control (TPC) commands to the UE to adjust the UE’s transmit power. This thesis focuses on an Open Loop Power Control (OLPC) scheme for LTE uplink by using the Okumura-Hata propagation path loss model to set the User Equipment (UE) uplink transmit power control parameters in order to reduce the UE energy consumption. In general, the UE requires more power to connect to distant base stations than closer base stations and therefore this thesis analyses the required power levels using the Okumura-Hata propagation path loss model. Estimation of path loss is very important in initial deployment of wireless network and cell planning. This thesis analyses the Okumura-Hata propagation path loss in different receiver antenna heights (

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. 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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. 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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