Alireza Babaei

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Papers by Alireza Babaei

Wi-Fi Coexistence with Duty Cycled LTE-U

Coexistence of Wi-Fi and LTE-Unlicensed (LTE-U) technologies has drawn significant concern in ind... more Coexistence of Wi-Fi and LTE-Unlicensed (LTE-U) technologies has drawn significant concern in industry. In this paper, we investigate the Wi-Fi performance in the presence of duty cycle based LTE-U transmission on the same channel. More specifically, one LTE-U cell and one Wi-Fi basic service set (BSS) coexist by allowing LTE-U devices transmit their signals only in predetermined duty cycles. Wi-Fi stations, on the other hand, simply contend the shared channel using the distributed coordination function (DCF) protocol without cooperation with the LTE-U system or prior knowledge about the duty cycle period or duty cycle of LTE-U transmission. We define the fairness of the above scheme as the difference between Wi-Fi performance loss ratio (considering a defined reference performance) and the LTE-U duty cycle (or function of LTE-U duty cycle). Depending on the interference to noise ratio (INR) being above or below -62dbm, we classify the LTE-U interference as strong or weak and establ...

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Chapter 10 On the Performance of Transport Control Protocol in Cognitive Radio Networks

Transmission Control Protocol (TCP) is the most commonly used transport protocol on the Internet.... more Transmission Control Protocol (TCP) is the most commonly used transport protocol on the Internet. All indications assure that it will be an integral part of the future Internetworks. In this chapter, the authors present how regular TCP, which was designed for wired networks, is not suitable for dynamic spectrum access networks. They develop an analytical model to estimate the TCP throughput of dynamic spectrum access networks. Dynamic spectrum access networks deal with opportunistic spectrum access leading to greater utilization of the spectrum. The extent of utilization depends on the primary user’s traffic and also on the way the spectrum is accessed by the primary and secondary users. The proposed model considers primary and secondary user traffic in estimating the TCP throughput by modeling the spectrum access using continuous-time Markov chains, thus providing more insight on effect of dynamic spectrum access on TCP performance than the existing models.

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A Cutting Plane Optimization Algorithm for Intra-cell Link Adaptation Problem

2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications

On the Impact of LTE-U on Wi-Fi Performance

International Journal of Wireless Information Networks, 2015

With the exponential growth in mobile data traffic taking place currently and projected into the ... more With the exponential growth in mobile data traffic taking place currently and projected into the future, mobile operators need cost effective ways to manage the load of their networks. Traditionally, this has been achieved by offloading mobile traffic onto Wi-Fi networks due to their low cost and increasingly ubiquitous deployment. Recently, LTE operating in the unlicensed spectrum has drawn significant interests from mobile operators due to the availability of the unlicensed spectrum. Using this technology, the unlicensed spectrum is directly utilized by LTE without the need to offload traffic to an alternative radio access technology such as Wi-Fi. However, the deployment of LTE networks in the unlicensed band poses significant challenges to the performance of current and future Wi-Fi networks. We discuss the LTE and Wi-Fi coexistence challenges and present analysis on performance degradation of the Wi-Fi networks at the presence of LTE.

On the impact of LTE-U on Wi-Fi performance

2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC), 2014

An efficient cluster update model in MANET

Proceedings of the 2012 44th Southeastern Symposium on System Theory (SSST), 2012

In hierarchical networks, the efficient choices of cluster-head as well as the cluster update int... more In hierarchical networks, the efficient choices of cluster-head as well as the cluster update interval is important to keep the established cluster structure stable and improve the communication quality. In this paper, we establish a cluster update interval model and use this model to determine a reliable update interval for the cluster structures in MANETs. This update interval is affected by two main factors: nodes' relative mobility and transmission range. We establish a cluster update interval model which uses the expected link lifetime with respect to the cluster-head (CH) as the update interval. The proposed model takes all of the above mentioned factors into consideration and no weights combination is needed. Simulation results shows that our proposed model can help to determine a dynamic cluster update interval adapting to various scenarios and achieve better stability in the cluster structure.

SCL: A cross-layer protocol for wireless sensor networks

Proceedings of the 2012 44th Southeastern Symposium on System Theory (SSST), 2012

Wireless Sensor Networks are a new class of distributed systems that are used to collect informat... more Wireless Sensor Networks are a new class of distributed systems that are used to collect information from the physical area they inhabit. They usually consist of a large number of lowpower wireless sensor nodes or motes with limited computation power and memory for sensing of the environment. Energy efficiency and real-time response are important features in the design of sensor networks. Many communication protocols at different layers have been proposed to reduce the energy consumption of wireless sensor networks. In this thesis, the main objective is to present a method to improve the performance of wireless sensor networks in terms of throughput and latency. We use a hybrid access protocol based on a clustering routing scheme, named SCL (Sigma Cross-Layer) protocol. The main idea is to use a hybrid access protocol to deal with the intra-cluster communications after partitioning the whole network into several clusters. The access scheme incorporates both contention-based (e.g., CSMA) and contention-free (e.g., TDMA) medium access schemes. TDMA is used when the networks are under high traffic load or congestion, and CSMA is used during the clusters' setup phase as well as low contention scenarios. In summary, the results provided by NS-2 simulations showed the proposed scheme, compared to other scheme which uses TDMA stand-alone, improves the throughput and reduces the latency of sensor networks.

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Achievable throughput in power-constrained cognitive wireless networks

2012 IEEE International Conference on Communications (ICC), 2012

ABSTRACT

Statistical inference modeling and

Cognitive radio is a novel approach for better utilization of the scarce, already packed but high... more Cognitive radio is a novel approach for better utilization of the scarce, already packed but highly underutilized radio spectrum. To this end, environment-aware unlicensed secondary wireless devices are envisioned to share the spectrum with the primary licensed network, provided that their operation does not impose unmanageable interference on the primary nodes. To achieve this coexistence goal, interference modeling is of great significance. Interference, in general, has a stochastic nature not only due to randomness in the propagation channel, but also due to the random geographic dispersion of nodes. A statistical representation for interference, in which the power levels of the secondary nodes influence the parameters of the model, is, thus, of considerable interest in analysis and design of cognitive wireless network. Stochastic geometry and spatial point processes are used for modeling the coexisting primary and secondary networks. In particular, we model these networks using spatial bivariate Poisson processes. We obtain statistical properties of the distances in these

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Wi-Fi Coexistence with Duty Cycled LTE-U

Wireless Communications and Mobile Computing, 2017

Coexistence of Wi-Fi and LTE-Unlicensed (LTE-U) technologies has drawn significant concern in ind... more Coexistence of Wi-Fi and LTE-Unlicensed (LTE-U) technologies has drawn significant concern in industry. In this paper, we investigate the Wi-Fi performance in the presence of duty cycle based LTE-U transmission on the same channel. More specifically, one LTE-U cell and one Wi-Fi basic service set (BSS) coexist by allowing LTE-U devices to transmit their signals only in predetermined duty cycles. Wi-Fi stations, on the other hand, simply contend the shared channel using the distributed coordination function (DCF) protocol without cooperation with the LTE-U system or prior knowledge about the duty cycle period or duty cycle of LTE-U transmission. We define the fairness of the above scheme as the difference between Wi-Fi performance loss ratio (considering a defined reference performance) and the LTE-U duty cycle (or function of LTE-U duty cycle). Depending on the interference to noise ratio (INR) being above or below −62 dbm, we classify the LTE-U interference as strong or weak and es...

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Throughput Optimization in Cognitive Random Wireless Ad hoc Networks

2010 Ieee Global Telecommunications Conference Globecom 2010, Dec 1, 2010

Abstract We consider coexistence of overlapping but distinct primary and secondary random ad hoc ... more

Internodal Distance Distribution and Power Control for Coexisting Radio Networks

Ieee Globecom 2008 2008 Ieee Global Telecommunications Conference, Nov 1, 2008

Abstract In cognitive radio networks, we assume that primary and secondary nodes form a bivariate... more

Statistical interference modeling and coexistence strategies in cognitive wireless networks

Interference Modeling, Shaping and Avoidance in Cognitive Wireless Networks

Lecture Notes in Electrical Engineering, 2012

Interference and throughput in spectrum sensing cognitive radio networks using point processes

Journal of Communications and Networks, 2014

Spectrum sensing is vital for Secondary unlicensed nodes to coexist and avoid interference with t... more Spectrum sensing is vital for Secondary unlicensed nodes to coexist and avoid interference with the Primary licensed users in cognitive wireless networks. In this paper, we develop models for bounding interference levels from Secondary network to the Primary nodes within a spectrum sensing framework. Instead of classical stochastic approaches where Poisson point processes are used to model transmitters, we consider a more practical model which takes into account the medium access control regulations and where the Secondary Poisson process is judiciously thinned in two phases to avoid interference with the Secondary as well as the Primary nodes. The resulting process will be a modified version of the Matèrn point process. For this model, we obtain bounds for the complementary cumulative distribution function (CCDF) of interference and present simulation results which show the developed analytical bounds are quite tight. Moreover, we use these bounds to find the operation regions of the Secondary network such that the interference constraint is satisfied on receiving Primary nodes. We then obtain theoretical results on the Primary and Secondary throughputs and find the throughput limits under the interference constraint.

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Reliable link lifetime-based cluster-head election in wireless ad hoc networks

Proceedings of the thirteenth ACM international symposium on Mobile Ad Hoc Networking and Computing - MobiHoc '12, 2012

ABSTRACT

A nullspace-based precoder with subspace expansion for radar/communications coexistence

2013 IEEE Global Communications Conference (GLOBECOM), 2013

ABSTRACT

A Practical Precoding Approach for Radar/Communications Spectrum Sharing

Proceedings of the 8th International Conference on Cognitive Radio Oriented Wireless Networks, 2013

Interference Modeling and Avoidance in Spectrum Underlay Cognitive Wireless Networks

2010 IEEE International Conference on Communications, 2010

Abstract In spectrum underlay cognitive wireless networks, secondary nodes need to limit their ag... more

GC12 CSSM: Globecom 2012-Communications Software, Services and Multimedia Symposium-Committees and Welcome

Wi-Fi Coexistence with Duty Cycled LTE-U

Download

Chapter 10 On the Performance of Transport Control Protocol in Cognitive Radio Networks

Download

A Cutting Plane Optimization Algorithm for Intra-cell Link Adaptation Problem

2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications

On the Impact of LTE-U on Wi-Fi Performance

International Journal of Wireless Information Networks, 2015

On the impact of LTE-U on Wi-Fi performance

2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC), 2014

An efficient cluster update model in MANET

Proceedings of the 2012 44th Southeastern Symposium on System Theory (SSST), 2012

SCL: A cross-layer protocol for wireless sensor networks

Proceedings of the 2012 44th Southeastern Symposium on System Theory (SSST), 2012

Download

Achievable throughput in power-constrained cognitive wireless networks

2012 IEEE International Conference on Communications (ICC), 2012

ABSTRACT

Statistical inference modeling and

Download

Wi-Fi Coexistence with Duty Cycled LTE-U

Wireless Communications and Mobile Computing, 2017

Coexistence of Wi-Fi and LTE-Unlicensed (LTE-U) technologies has drawn significant concern in ind... more Coexistence of Wi-Fi and LTE-Unlicensed (LTE-U) technologies has drawn significant concern in industry. In this paper, we investigate the Wi-Fi performance in the presence of duty cycle based LTE-U transmission on the same channel. More specifically, one LTE-U cell and one Wi-Fi basic service set (BSS) coexist by allowing LTE-U devices to transmit their signals only in predetermined duty cycles. Wi-Fi stations, on the other hand, simply contend the shared channel using the distributed coordination function (DCF) protocol without cooperation with the LTE-U system or prior knowledge about the duty cycle period or duty cycle of LTE-U transmission. We define the fairness of the above scheme as the difference between Wi-Fi performance loss ratio (considering a defined reference performance) and the LTE-U duty cycle (or function of LTE-U duty cycle). Depending on the interference to noise ratio (INR) being above or below −62 dbm, we classify the LTE-U interference as strong or weak and es...

Download

Throughput Optimization in Cognitive Random Wireless Ad hoc Networks

2010 Ieee Global Telecommunications Conference Globecom 2010, Dec 1, 2010

Abstract We consider coexistence of overlapping but distinct primary and secondary random ad hoc ... more

Internodal Distance Distribution and Power Control for Coexisting Radio Networks

Ieee Globecom 2008 2008 Ieee Global Telecommunications Conference, Nov 1, 2008

Abstract In cognitive radio networks, we assume that primary and secondary nodes form a bivariate... more

Statistical interference modeling and coexistence strategies in cognitive wireless networks

Interference Modeling, Shaping and Avoidance in Cognitive Wireless Networks

Lecture Notes in Electrical Engineering, 2012

Interference and throughput in spectrum sensing cognitive radio networks using point processes

Journal of Communications and Networks, 2014

Download

Reliable link lifetime-based cluster-head election in wireless ad hoc networks

Proceedings of the thirteenth ACM international symposium on Mobile Ad Hoc Networking and Computing - MobiHoc '12, 2012

ABSTRACT

A nullspace-based precoder with subspace expansion for radar/communications coexistence

2013 IEEE Global Communications Conference (GLOBECOM), 2013

ABSTRACT

A Practical Precoding Approach for Radar/Communications Spectrum Sharing

Proceedings of the 8th International Conference on Cognitive Radio Oriented Wireless Networks, 2013

Interference Modeling and Avoidance in Spectrum Underlay Cognitive Wireless Networks

2010 IEEE International Conference on Communications, 2010

Abstract In spectrum underlay cognitive wireless networks, secondary nodes need to limit their ag... more

GC12 CSSM: Globecom 2012-Communications Software, Services and Multimedia Symposium-Committees and Welcome

Alireza Babaei

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