@article {Simula.win.6,
	title = {Downlink Spectrum Sharing for Cognitive Radio Femtocell Networks},
	journal = {IEEE Systems Journal},
	volume = {4},
	number = {4},
	year = {2010},
	note = {Special issue on Broadband Access Networks},
	month = {December},
	pages = {524-534},
	abstract = {Femtocell is envisioned as a highly promising solution for indoor wireless communications. The spectrum allocated to femtocells is traditionally from the same licensed spectrum bands of macrocells. In this case, the capacity of femtocell networks is highly limited due to the finite number of licensed spectrum bands and also the interference with macrocells and other femtocells. In this paper, we propose a radically new communication paradigm by incorporating cognitive radio in femtocell networks. The cognitive radio enabled femtocells are able to access spectrum bands not only from macrocells but also from other licensed systems (e.g. TV systems) provided the interference from femtocells to the existing systems is not harmful. It results in more channel opportunities for femtocells. Thus, the co-channel interference in femtocells can be greatly reduced and the network capacity can be significantly improved. Because of the difference from other traditional wireless networks, we argue the traditional spectrum sharing schemes such as coloring methods are not efficient to femtocell networks especially for dense deployment scenarios. We formulate the downlink spectrum sharing problem in cognitive radio femtocell networks, and employ decomposition theories to solve the problem. Simulation results indicate that cognitive radio enabled femtocells could achieve much higher capacity than the femtocell networks which do not employ agile spectrum access. Simulation results also show that our proposed scheme without any iteration can achieve almost twice of the average capacity by coloring method when the number of available channels is less than five. Moreover, our proposed scheme can converge very fast with a typical value of only five iterations, and it can achieve around two percent extra average capacity than the fixed power control scheme.},
	doi = {10.1109/JSYST.2010.2083230},
	author = {Xiang, Jie and Zhang, Yan and Skeie, Tor and Xie, Lang}
}
@inproceedings {Simula.netsys.20,
	title = {Reliable Channel Selection and Routing for Real-Time Services Over Cognitive Radio Mesh Networks},
	journal = {Qshine 2010},
	year = {2010},
	publisher = {ACM},
	type = {Conference},
	abstract = {In Cognitive Radio Mesh Networks (CogMesh), Secondary Mesh Routers (SMRs) can opportunistically utilize the licensed spectrums for the traffic of the Secondary Mesh Users (SMUs). How to guarantee Quality of Service (QoS) for real-time services over CogMesh is still an opening issue. In this paper, we present a discrete-time vacation queueing system to abstract the Primary User (PU) interruption to SMR data transmission. Moreover, we formulate the optimization problem of joint channel selection and routing, to achieve minimum end-to-end delay for SMR while guaranteeing the channel unavailability. A heuristic method is proposed to solve this problem and results show our proposed method performs the most close to the optimal scheme, and outperforms the minimal unavailability scheme and minimal delay scheme in terms of end-to-end delay and solution rate.},
	author = {Xie, Lang and Poul E. {Heegaard} and Zhang, Yan and Xiang, Jie},
	editor = {Zhang, Xi}
}
@inproceedings {Simula.win.2,
	title = {System State Aware Admission Control Scheme for IEEE 802.16 WiMAX-Based Healthcare System},
	journal = {Proceedings of the 6th International Wireless Communications and Mobile Computing Conference (IWCMC {\textquoteright}10)},
	year = {2010},
	publisher = {ACM},
	type = {Conference},
	abstract = {Wireless healthcare is an evolutionary concept which is able to provide pervasive healthcare services to anyone, anytime and anywhere. IEEE 802.16e WiMAX, well known as the novel broadband wireless access technology, seems to be a feasible solution to implement wireless healthcare functionalities. In this paper, we consider wireless healthcare scenario using IEEE 802.16e WiMAX systems. After analyzing the characteristics of WiMAX technology and its application in healthcare service, we focus on the Quality of Service (QoS) guaranteeing issues and present a system state aware connection admission control scheme. In the proposed scheme, the resource utilization is modeled as a finite state machine (FSM) with three states and different admission control strategies is adopted adaptively. Our aim is to achieve a trade-off between satisfying Quality of Service (QoS), fairness and system bandwidth load. Simulation results are presented to demonstrate the performance of the proposed scheme.},
	isbn = {978-1-4503-0062-9},
	doi = {10.1145/1815396.1815608},
	author = {Xie, Lang and Poul E. {Heegaard} and Zhang, Jin and Xiang, Jie},
	editor = {Helmy, Ahmed and Mueller, Peter}
}
@inproceedings {Simula.ND.253,
	title = {Joint Bandwidth Reservation and Admission Control in IEEE 802.16e Based Networks},
	journal = {the IEEE International Conference on Communications (ICC 2009)},
	year = {2009},
	month = {June},
	pages = {1-6},
	publisher = {IEEE},
	type = {Conference},
	abstract = {The IEEE 802.16e is a compatible and reasonable technology to solve the last mile access problem. Since the multiple services in the system are connection-oriented, it is crucial to provide effective admission control and resource allocation mechanisms to guarantee the Quality of Service (QoS) of the system. In this paper, we investigate the joint bandwidth reservation and admission control in the IEEE 802.16e networks. Foremost, we consider two system models: model without buffer and model with buffer. Then two optimization problems are formulated for the two models separately. To solve the two min-max optimization problems, we propose a bandwidth reservation algorithm. In addition, the bandwidth reservation thus obtained can be used with admission control jointly. Our aim is to enhance fairness while satisfying QoS requirement. Numerical results are presented to demonstrate the performance of the proposed scheme in terms of maximal call blocking probability and fairness.},
	keywords = {Conference},
	isbn = {978-1-4244-3435-0},
	doi = {10.1109/ICC.2009.5199109},
	author = {Xie, Lang and Xiang, Jie and Zhang, Yan and Zhang, Jin},
	editor = {Akhavan, Hamid}
}
@inproceedings {Simula.ND.149,
	title = {A Novel Bandwidth Degradation Scheme for Admission Control in IEEE 802.16e Networks},
	journal = {the 4th IEEE International Conference on Wireless Communications, Networking and Mobile Computing (WiCOM 2008)},
	year = {2008},
	pages = {1-4},
	publisher = {IEEE},
	type = {Conference},
	abstract = {IEEE 802.16e networks can be widely applied in broadband wireless access scenarios. Admission control is an essential mechanism in IEEE 802.16e networks to guarantee the QoS of different subscribers. In this paper, we propose a novel bandwidth degradation scheme for the admission control in IEEE 802.16e networks. Simulation results are presented to demonstrate the performance of the proposed scheme in terms of service flow blocking rate and system bandwidth utilization.},
	isbn = {978-1-4244-2107-7},
	doi = {10.1109/WiCom.2008.18},
	author = {Xie, Lang and Xiang, Jie},
	editor = {Cuthbert, L.}
}
@inproceedings {Simula.ND.145,
	title = {Revenue-Based Admission Control for Cognitive Radio Cellular Systems},
	journal = {2008 International Workshop on Cognitive Networks and Communications (COGCOM 2008), in conjunction with CHINACOM 2008},
	year = {2008},
	publisher = {IEEE VTS},
	type = {Workshop},
	isbn = {978-1-4244-2373-6},
	author = {Xie, Lang and Xiang, Jie and Zhang, Yan},
	editor = {IEEE, }
}
