On Lookahead Strategy for Movement-based Location Update. A General Formulation

Abstract. Location management deals with the procedure to update the current location of a mobile terminal (MT) and with the procedure to deliver incoming calls to that called MT. Basically, the performance evaluation of location management procedures are dependent on the MT's mobility behavior, on the MT's cell residence time and on the call arrival process to the MT. In the open literature, the typical analysis for location management has been addressed under the assumptions of a random walk mobility model, the exponential cell sojourn time of the MT -some times relaxed to a general probability distribution functionand the exponential inter-arrival time distribution for incoming calls. However, the random walk model seems not to be valid as many mobile users follow some daily trajectories, such as from home to the working place, from the working place to the shopping center, etc. To reflect a more realistic movement pattern, we propose a directional oriented mobility model. And as a consequence of that, we also propose a lookahead procedure combined with the movement-based location update scheme, with the main idea of saving signaling traffic through the air interface. In the lookahead strategy we analytically derive closed form expressions for the mean number of location update (LU) messages triggered by the MT between two consecutive call arrivals and the paging probabilities to evaluate the paging cost under some selective paging strategies. The analysis has been carried out assuming a general cell residence time and a renewal point process for call arrivals to the MT

Performance model for two-tier mobile wireless networks with macrocells and small cells

[EN] A new analytical model is proposed to evaluate the performance of two-tier cellular networks composed of macrocells (MCs) and small cells (SCs), where terminals roam across the service area. Calls being serviced by MCs may retain their channel when entering a SC service area, if no free SC channels are available. Also, newly offered SC calls can overflow to the MC. However, in both situations channels may be repacked to vacate MC channels. The cardinality of the state space of the continuous-time Markov chain (CTMC) that models the system dynamics makes the exact system analysis unfeasible. We propose an approximation based on constructing an equivalent CTMC for which a product-form solution exist that can be obtained with very low computational complexity. We determine performance parameters such as the call blocking probabilities for the MC and SCs, the probability of forced termination, and the carried traffic. We validate the analytical model by simulation. Numerical results show that the proposed analytical model achieves very good precision in scenarios with diverse mobility rates and MCs and SCs loads, as well as when MCs overlay a large number of SCs.Authors would like to thank you the anonymous reviewers for the review comments provided to our work that have decisively contributed to improve the paper. Most of the contribution of V. Casares-Giner was done while visiting the Huazhong University of Science and Technolgy (HUST), Whuhan, China. This visit was supported by the European Commission, 7FP, S2EuNet project. The authors from the Universitat Politecnica de Valencia are partially supported by the Ministry of Economy and Competitiveness of Spain under grant TIN2013-47272-C2-1-R and TEC2015-71932-REDT. The research of Xiaohu Ge was supported by the National Natural Science Foundation of China (NSFC) grant 61210002, the Fundamental Research Funds for the Central Universities grant 2015XJGH011, and China International Joint Research Center of Green Communications and Networking grant 2015B01008.Casares-Giner, V.; Martínez Bauset, J.; Ge, X. (2018). Performance model for two-tier mobile wireless networks with macrocells and small cells. Wireless Networks. 24(4):1327-1342. https://doi.org/10.1007/s11276-016-1407-8S13271342244ABIresearch. (2016). In-building mobile data traffic forecast. ABIreseach, Technical Report.NGMN Alliance. (2015). Recommendations for small cell development and deployment. NGMN Alliance, Technical Report.Chandrasekhar, V., Andrews, J., & Gatherer, A. (2008). Femtocell networks: A survey. IEEE Communications Magazine, 46(9), 59–67.Yamamoto, T., & Konishi, S. (2013). Impact of small cell deployments on mobility performance in LTE-Advanced systems. In IEEE PIMRC workshops (pp. 189–193).Balakrishnan, R., & Akyildiz, I. (2016). Local anchor schemes for seamless and low-cost handover in coordinated small cells. IEEE Transactions on Mobile Computing, 15(5), 1182–1196.Zahir, T., Arshad, K., Nakata, A., & Moessner, K. (2013). Interference management in femtocells. IEEE Communications Surveys & Tutorials, 15(1), 293–311.Yassin, M., AboulHassan, M. A., Lahoud, S., Ibrahim, M., Mezher, D., Cousin, B., & Sourour, E. A. (2015). Survey of ICIC techniques in LTE networks under various mobile environment parameters. Wireless Networks, 1–16.Andrews, M., & Zhang, L. (2015). Utility optimization in heterogeneous networks via CSMA-based algorithms. Wireless Networks, 1–14.El-atty, S. M. A., & Gharsseldien, Z. M. (2016). Performance analysis of an advanced heterogeneous mobile network architecture with multiple small cell layers. Wireless Networks, 1–22.Huang, Q., Huang, Y.-C., Ko, K.-T., & Iversen, V. B. (2011). Loss performance modeling for hierarchical heterogeneous wireless networks with speed-sensitive call admission control. IEEE Transactions on Vehicular Technology, 60(5), 2209–2223.Bonald, T., & Roberts, J. W. (2003). Congestion at flow level and the impact of user behaviour. Computer Networks, 42, 521–536.Lee, Y. L., Chuah, T. C., Loo, J., & Vinel, A. (2014). Recent advances in radio resource management for heterogeneous LTE/LTE-A networks. IEEE Communications Surveys & Tutorials, 16(4), 2142–2180.Rappaport, S. S., & Hu, L.-R. (1994). Microcellular communication systems with hierarchical macrocell overlays: Traffic performance models and analysis. Proceedings of the IEEE, 82(9), 1383–1397.Ge, X., Han, T., Zhang, Y., Mao, G., Wang, C.-X., Zhang, J., et al. (2014). Spectrum and energy efficiency evaluation of two-tier femtocell networks with partially open channels. IEEE Transactions on Vehicular Technology, 63(3), 1306–1319.Song, W., Jiang, H., & Zhuang, W. (2007). Performance analysis of the WLAN-first scheme in cellular/WLAN interworking. IEEE Transactions on Wireless Communications, 6(5), 1932–1952.Ge, X., Martinez-Bauset, J., Gasares-Giner, V., Yang, B., Ye, J., & Chen, M. (2013). Modeling and performance analysis of different access schemes in two-tier wireless networks. In IEEE Globecom (pp. 4402–4407).Tsai, H.-M., Pang, A.-C., Lin, Y.-C., & Lin, Y.-B. (2005). Repacking on demand for hierarchical cellular networks. Wireless Networks, 11(6), 719–728.Maheshwari, K., & Kumar, A. (2000). Performance analysis of microcellization for supporting two mobility classes in cellular wireless networks. IEEE Transactions on Vehicular Technology, 49(2), 321–333.Whiting, P., & McMillan, D. (1990). Modeling for repacking in cellular radio. In 7th UK Teletraffic Symposium, IEE, Durham.Kelly, F. (1989). Fixed point models of loss networks. The Journal of the Australian Mathematical Society. Series B. Applied Mathematics, 31(02), 204–218.McMillan, D. (1991). Traffic modelling and analysis for cellular mobile networks. In A. Jensen & V. Iversen (Eds.), Proceedigs of ITC-13 (pp. 627–632). IAC. Copenhaguen: Elsevier Science.Fu, H.-L., Lin, P., & Lin, Y.-B. (2012). Reducing signaling overhead for femtocell/macrocell networks. IEEE Transactions on Mobile Computing, 12(8), 1587–1597.Eklundh, B. (1986). Channel utilization and blocking probability in a cellular mobile telephone system with directed retry. IEEE Transactions on Communications, 37, 329–337.Karlsson, J., & Eklundh, B. (1989). A cellular telephone system with load sharing—An enhancement of directed retry. IEEE Transactions on Communications, 37(5), 530–535.Nelson, R. (1995). Probability, stochastic processes and queueing theory. New York: Springer.Iversen, V.B. (Aug. 1987). The exact evaluation of multi-service loss systems with access control. In Proceedings of the Seventh Nordic Teletraffic Seminar (NTS-7) (Vol. 31, pp. 56–61) Lund, (Sweden).Ross, K. W. (1995). Multiservice loss models for broadband telecommunication networks. New York: Springer.Lin, Y.-B., & Mak, V. W. (1994). Eliminating the boundary effect of a large-scale personal communication service network simulation. ACM Transactions on Modeling and Computer Simulation (TOMACS), 4(2), 165–190.Karray, M.K. (2010). Evaluation of the blocking probability and the throughput in the uplink of wireless cellular networks. In IEEE ComNet (pp. 1–8)

Performance evaluation of framed slotted ALOHA with reservation packets and succesive interference cancelation for M2M networks

[EN] Random access protocols like ALOHA have been considered for machine-to-machine (M2M) communication in future networks for their simplicity of operation. This paper evaluates the performance of a Frame Slotted-ALOHA protocol that uses reservation and data packets (FSA-RDP), in a scenario where a controller collects data packets transmitted by a finite number of M2M devices. In FSA-RDP, frames of variable duration are divided in two parts, the reservation and data subframes. During the reservation subframe, active devices send short reservation packets to the controller. The controller assigns reserved slots in the data subframe to those devices that succeeded with the reservation. At devices, the FIFO service discipline and two queue management schemes, tail drop and push-out, have been considered. When the queue size is of one packet, we develop a discrete-time Markov chain to evaluate the protocol performance, including the cumulative distribution function of the delay of data packets that are successfully transmitted. Analytical results are validated by extensive simulations. The simulation model is also used to evaluate the system performance when larger queues are used. In addition, we study the impact that implementing Successive Interference Cancellation (SIC) at the controller has on the system performance. We also evaluate the performance of implementing SIC at the controller together with Irregular Repetition Slotted ALOHA (IRSA) to send the reservation packets. Numerical results show that the protocol efficiency of FSA-RDP is between one and two orders of magnitude larger than the efficiency of conventional Frame Slotted ALOHA, when a perfect channel is assumed. In more realistic channel environments, the use of SIC brings an important performance boost.This work has been supported by the Ministry of Economy and Competitiveness of Spain through projects TIN2013-47272-C2-1-R and TEC2015-71932-REDT. The authors would like to thank the support received from the Institute ITACA (Instituto Universitario de Tecnologias de la Informacion y Comunicaciones) at the Universitat Politecnica de Valencia, Spain. C. Portillo acknowledges the funding received from the European Union under the program Erasmus Mundus Partnerships, project EuroinkaNet, GRANT AGREEMENT NUMBER -2014 -0870/001/001, and the support received from SEP-SES (DSA/103.5/15/6629).Casares-Giner, V.; Martínez Bauset, J.; Portillo, C. (2019). Performance evaluation of framed slotted ALOHA with reservation packets and succesive interference cancelation for M2M networks. Computer Networks. 155:15-30. https://doi.org/10.1016/j.comnet.2019.02.021S153015

XIII Jornadas de ingeniería telemática (JITEL 2017)

Las Jornadas de Ingeniería Telemática (JITEL), organizadas por la Asociación de Telemática (ATEL), constituyen un foro propicio de reunión, debate y divulgación para los grupos que imparten docencia e investigan en temas relacionados con las redes y los servicios telemáticos. Con la organización de este evento se pretende fomentar, por un lado el intercambio de experiencias y resultados, además de la comunicación y cooperación entre los grupos de investigación que trabajan en temas relacionados con la telemática. En paralelo a las tradicionales sesiones que caracterizan los congresos científicos, se desea potenciar actividades más abiertas, que estimulen el intercambio de ideas entre los investigadores experimentados y los noveles, así como la creación de vínculos y puntos de encuentro entre los diferentes grupos o equipos de investigación. Para ello, además de invitar a personas relevantes en los campos correspondientes, se van a incluir sesiones de presentación y debate de las líneas y proyectos activos de los mencionados equiposLloret Mauri, J.; Casares Giner, V. (2018). XIII Jornadas de ingeniería telemática (JITEL 2017). Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/97612EDITORIA

SERVICIOS PORTADORES EN REDES CELULARES 2,5G Y 3G Y SU DIMENSIONADO

RESUMEN Las redes celulares 2,5G y 3G están evolucionando hacia una red totalmente IP. Una de las ventajas principales de estas redes es que ofrecen diferentes grados de calidad de servicio (QoS), mientras que una de las principales desventajas es la complejidad que supone su dimensionado. Las aportaciones más relevantes de este trabajo son dos: Primera, el estudio de la evolución de los servicios portadores en la Internet y el impacto que ello puede tener en los servicios portadores que se han definido para las redes celulares. Y segunda, el análisis de los modelos de tráfico más comunes y la identificación de las características de los modelos de tráfico que deberían ser utilizados para dimensionar las redes de acceso 2,5Gy3G. La principal conclusión del estudio es que la creciente complejidad del proceso de dimensionado de las redes celulares posiblemente requerirá del uso de herramientas automáticas, como las redes de Petri. PALABRAS RELEVANTES·      Redes celulares 2,5G y 3G.·      Servicios portadores.·      Arquitectura Diffserv.·      Modelos de tráfico.·      Dimensionado. 

SERVICIOS PORTADORES EN REDES CELULARES 2,5G Y 3G Y SU DIMENSIONADO

RESUMEN Las redes celulares 2,5G y 3G están evolucionando hacia una red totalmente IP. Una de las ventajas principales de estas redes es que ofrecen diferentes grados de calidad de servicio (QoS), mientras que una de las principales desventajas es la complejidad que supone su dimensionado. Las aportaciones más relevantes de este trabajo son dos: Primera, el estudio de la evolución de los servicios portadores en la Internet y el impacto que ello puede tener en los servicios portadores que se han definido para las redes celulares. Y segunda, el análisis de los modelos de tráfico más comunes y la identificación de las características de los modelos de tráfico que deberían ser utilizados para dimensionar las redes de acceso 2,5Gy3G. La principal conclusión del estudio es que la creciente complejidad del proceso de dimensionado de las redes celulares posiblemente requerirá del uso de herramientas automáticas, como las redes de Petri. PALABRAS RELEVANTES·      Redes celulares 2,5G y 3G.·      Servicios portadores.·      Arquitectura Diffserv.·      Modelos de tráfico.·      Dimensionado. 

Modulation and Coding Techniques in Wireless Communications

This is a timely book on wireless communications, with twelve chapters covering theoretical results and material of standards. The first nine chapters, some 380 pages, are devoted to basic concepts on channel models, modulation, coding, equalization, MIMO techniques, and multiple access methods. The last three chapters extend up to 274 pages and cover the modern wireless communication standardsCasares Giner, V.; Martínez Zaldívar, FJ. (2012). Modulation and Coding Techniques in Wireless Communications. IEEE Communications Magazine. 50(6):13-14. doi:10.1109/MCOM.2012.6211478S131450

Local Anchor Based Location Management Schemes for Small Cells in HetNets

(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.[EN] Existing location management (LM) methods for macrocells in LTE-Advanced have tracking area list (TAL) granularity. Therefore, a user equipment (UE) triggers a location update (LU) whenever it leaves its current TAL, and it is searched through paging (PG) with TAL accuracy. However, these procedures are not well-suited for small cells (SCs). The reasons are twofold. First, dense deployments of SCs imply that paging has a low probability to be successful in the first attempt, increasing the signaling overhead in the core network (CN). Second, smaller coverage areas lead to a higher mobility among cells, increasing the signaling overhead in the CN due to LUs. In this work, two LM schemes with fine granularity are proposed. These schemes update UE's location to a local anchor (LA) in a SC or tracking area (TA) basis, respectively. By increasing the accuracy of UE's location, a significant reduction of signaling overhead in the CN due to PG is achieved. Moreover, LUs to the LA are performed through direct X2-interface links to avoid signaling overhead in the CN. A versatile mobility model is developed and closed-form expressions for UEs' mobility metrics are found to validate the proposed schemes through variations of critical parameters such as TA/TAL configuration, UE's mobility patterns and cell residence times.This work has been supported by European Commission under the FP7 S2EuNet project and the Spanish Government through project TIN2013-47272-C2-1-RPacheco-Paramo, DF.; Akyildiz, IF.; Casares Giner, V. (2016). Local Anchor Based Location Management Schemes for Small Cells in HetNets. IEEE Transactions on Mobile Computing. 15(4):883-894. https://doi.org/10.1109/TMC.2015.2431717S88389415

Modeling of Duty-Cycled MAC Protocols for Heterogeneous WSN with Priorities

[EN] Wireless Sensor Networks (WSN) have experienced an important revitalization, particularly with the arrival of Internet of Things applications. In a general sense, a WSN can be composed of different classes of nodes, having different characteristics or requirements (heterogeneity). Duty-cycling is a popular technique used in WSN, that allows nodes to sleep and wake up periodically in order to save energy. We believe that the modeling and performance evaluation of heterogeneous WSN with priorities operating in duty-cycling, being of capital importance for their correct design and successful deployment, have not been sufficiently explored. The present work presents a performance evaluation study of a WSN with these features. For a scenario with two classes of nodes composing the network, each with a different channel access priority, an approximate analytical model is developed with a pair of two-dimensional discrete-time Markov chains. Note that the same modeling approach can be used to analyze networks with a larger number of classes. Performance parameters such as average packet delay, throughput and average energy consumption are obtained. Analytical results are validated by simulation, showing accurate results. Furthermore, a new procedure to determine the energy consumption of nodes is proposed that significantly improves the accuracy of previous proposals. We provide quantitative evidence showing that the energy consumption accuracy improvement can be up to two orders of magnitudeThis work is part of the project PGC2018-094151-B-I00, which is financed by the Ministerio de Ciencia, Innovacion y Universidades (MCIU), Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) (MCIU/AEI/FEDER.UE). C. Portillo acknowledges the funding received from the European Union under the program Erasmus Mundus Partnerships, project EuroinkaNet, GRANT AGREEMENT NUMBER -2014 -0870/001/001, and the support received from SEP-SES (DSA/103.5/15/6629)Portillo, C.; Martínez Bauset, J.; Pla, V.; Casares-Giner, V. (2020). Modeling of Duty-Cycled MAC Protocols for Heterogeneous WSN with Priorities. Electronics. 9(3):1-16. https://doi.org/10.3390/electronics9030467S11693Gomes, D. A., & Bianchini, D. (2016). Interconnecting Wireless Sensor Networks with the Internet Using Web Services. IEEE Latin America Transactions, 14(4), 1937-1942. doi:10.1109/tla.2016.7483537Libo, Z., Tian, H., & Chunyun, G. (2019). Wireless multimedia sensor network for rape disease detections. EURASIP Journal on Wireless Communications and Networking, 2019(1). doi:10.1186/s13638-019-1468-3Shi, X., An, X., Zhao, Q., Liu, H., Xia, L., Sun, X., & Guo, Y. (2019). State-of-the-Art Internet of Things in Protected Agriculture. Sensors, 19(8), 1833. doi:10.3390/s19081833Rajandekar, A., & Sikdar, B. (2015). A Survey of MAC Layer Issues and Protocols for Machine-to-Machine Communications. IEEE Internet of Things Journal, 2(2), 175-186. doi:10.1109/jiot.2015.2394438Dai, H.-N., Ng, K.-W., & Wu, M.-Y. (2013). On Busy-Tone Based MAC Protocol for Wireless Networks with Directional Antennas. Wireless Personal Communications, 73(3), 611-636. doi:10.1007/s11277-013-1206-9Padilla, P., Padilla, J. L., Valenzuela-Valdés, J. F., Serrán-González, J.-V., & López-Gordo, M. A. (2015). Performance Analysis of Different Link Layer Protocols in Wireless Sensor Networks (WSN). Wireless Personal Communications, 84(4), 3075-3089. doi:10.1007/s11277-015-2783-6Ye, W., Heidemann, J., & Estrin, D. (2004). Medium Access Control With Coordinated Adaptive Sleeping for Wireless Sensor Networks. IEEE/ACM Transactions on Networking, 12(3), 493-506. doi:10.1109/tnet.2004.828953Kuo, Y.-W., Li, C.-L., Jhang, J.-H., & Lin, S. (2018). Design of a Wireless Sensor Network-Based IoT Platform for Wide Area and Heterogeneous Applications. IEEE Sensors Journal, 18(12), 5187-5197. doi:10.1109/jsen.2018.2832664He, X., Liu, S., Yang, G., & Xiong, N. (2018). Achieving Efficient Data Collection in Heterogeneous Sensing WSNs. IEEE Access, 6, 63187-63199. doi:10.1109/access.2018.2876552Ortin, J., Cesana, M., Redondi, A. E. C., Canales, M., & Gallego, J. R. (2019). Analysis of Unslotted IEEE 802.15.4 Networks With Heterogeneous Traffic Classes. IEEE Wireless Communications Letters, 8(2), 380-383. doi:10.1109/lwc.2018.2873347Bianchi, G. (2000). Performance analysis of the IEEE 802.11 distributed coordination function. IEEE Journal on Selected Areas in Communications, 18(3), 535-547. doi:10.1109/49.840210Liu, R. P., Sutton, G. J., & Collings, I. B. (2010). A New Queueing Model for QoS Analysis of IEEE 802.11 DCF with Finite Buffer and Load. IEEE Transactions on Wireless Communications, 9(8), 2664-2675. doi:10.1109/twc.2010.061010.091803Ou Yang, & Heinzelman, W. (2012). Modeling and Performance Analysis for Duty-Cycled MAC Protocols with Applications to S-MAC and X-MAC. IEEE Transactions on Mobile Computing, 11(6), 905-921. doi:10.1109/tmc.2011.121Martinez-Bauset, J., Guntupalli, L., & Li, F. Y. (2015). Performance Analysis of Synchronous Duty-Cycled MAC Protocols. IEEE Wireless Communications Letters, 4(5), 469-472. doi:10.1109/lwc.2015.2439267Guntupalli, L., Martinez-Bauset, J., Li, F. Y., & Weitnauer, M. A. (2017). Aggregated Packet Transmission in Duty-Cycled WSNs: Modeling and Performance Evaluation. IEEE Transactions on Vehicular Technology, 66(1), 563-579. doi:10.1109/tvt.2016.2536686Zhang, R., Moungla, H., Yu, J., & Mehaoua, A. (2017). Medium Access for Concurrent Traffic in Wireless Body Area Networks: Protocol Design and Analysis. IEEE Transactions on Vehicular Technology, 66(3), 2586-2599. doi:10.1109/tvt.2016.2573718Guntupalli, L., Martinez-Bauset, J., & Li, F. Y. (2018). Performance of frame transmissions and event-triggered sleeping in duty-cycled WSNs with error-prone wireless links. Computer Networks, 134, 215-227. doi:10.1016/j.comnet.2018.01.047(July, 2019). The State Transition Probabilities of the Two 2D-DTMC. Technical Report http://personales.upv.es/jmartine/public/2DDTMC.pdfCrossbow Technology Incorporated, San Jose, CA, USA http://www.openautomation.net/uploadsproductos/micaz-datasheet.pd

Discrete time analysis of cognitive radio networks with imperfect sensing and saturated source of secondary users, Computer Communications

Sensing is one of the most challenging issues in cognitive radio networks. Selection of sensing parameters raises several tradeoffs between spectral efficiency, energy efficiency and interference caused to primary users (PUs). In this paper we provide representative mathematical models that can be used to analyze sensing strategies under a wide range of conditions. The activity of PUs in a licensed channel is modeled as a sequence of busy and idle periods, which is represented as an alternating Markov phase renewal process. The representation of the secondary users (SUs) behavior is also largely general: the duration of transmissions, sensing periods and the intervals between consecutive sensing periods are modeled by phase type distributions, which constitute a very versatile class of distributions. Expressions for several key performance measures in cognitive radio networks are obtained from the analysis of the model. Most notably, we derive the distribution of the length of an effective white space; the distributions of the waiting times until the SU transmits a given amount of data, through several transmission epochs uninterruptedly; and the goodput when an interrupted SU transmission has to be restarted from the beginning due to the presence of a PU. (C) 2015 Elsevier B.V. All rights reserved.The research of A. S. Alfa was partially supported by the NSERC (Natural Sciences and Engineering Research Council) of Canada under Grant G00315156. Most of the contribution of V. Pla was done while visiting the University of Manitoba. This visit was supported by the Ministerio de Educacion of Spain under Grant PR2011-0055, and by the UPV through the Programa de Apoyo a la Investigacion y Desarrollo (PAID-00-12). The research of the authors from the Universitat Politecnica de Valencia was partially supported by the Ministry of Economy and Competitiveness of Spain under Grant TIN2013-47272-C2-1-R.Alfa, AS.; Pla, V.; Martínez Bauset, J.; Casares Giner, V. (2016). Discrete time analysis of cognitive radio networks with imperfect sensing and saturated source of secondary users, Computer Communications. Computer Communications. 79:53-65. https://doi.org/10.1016/j.comcom.2015.11.012S53657