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13th International Symposium on Communications and Information Technologies: Communication and Information Technology for New Life Style Beyond the Cloud, ISCIT 2013 | Year: 2013

This paper investigates the issue of determining an appropriate utility function to model the Secondary User (SU) preference toward spectrum holes on the basis of their duration. A Sigmoid shaped utility function is proposed and a proper tuning is discussed to improve the representation of SU preference and to involve the radio quality on the access decision process. The performance and the suitability of the proposed utility function is investigated within an access model whose purpose is to reduce handoff process related to PU activity. © 2013 IEEE. Source

13th International Symposium on Communications and Information Technologies: Communication and Information Technology for New Life Style Beyond the Cloud, ISCIT 2013 | Year: 2013

Spectrum handoff (HO) is one of the main issues in cognitive radio networks. Spectrum handoff occurs when the owner of the spectrum or the primary user (PU) reclaims a channel already used opportunistically by a secondary user (SU). In this case, the SU has to vacate this channel and select another free one. This process has a negative impact on the performance of SU transmission in terms of delay and link maintenance, specially because of the unpredictable PU behavior. In this paper, the problem of minimizing the secondary user (SU) handoff process because of primary user activity is underlined. A mixed Integer non Linear Programming formulation of the problem is detailed and a channel selection strategy is proposed. The main idea of this access model is to select channels maximizing the preference of the secondary user towards the holding time and the achievable throughput. The SU preference is expressed using a microeconomic concept of Sigmoid utility. The performance and the suitability of the proposed access model is investigated through numerical simulations. © 2013 IEEE. Source

2013 9th International Wireless Communications and Mobile Computing Conference, IWCMC 2013 | Year: 2013

The specificity of overlay spectrum sharing in cognitive radio network, is that the secondary user has to handoff and vacate immediately the channel once the Primary User appears and reclaims it. Such handoff becomes more frequent specially in case of multichannel access since that in a wider band, a PU is likely to reclaim a part of the band more quickly, and the SU has to switch to a different set of channels. However, a frequent handoff may alter the quality of the communication and generate an additional delay since that for each channel switching a sensing phase has to take place, additionally to channel evacuation and link set up times. In this paper we propose a Holding Time based access model in order to avoid such handoff. The effectiveness of this model is investigated within a Common Pilot Channel framework. © 2013 IEEE. Source

GSCIT 2015 - Global Summit on Computer and Information Technology - Proceedings | Year: 2015

Wireless communications markets present rapidly changing technology, evolving customer demands, and the emergence of new products and services. Within spectral limitations, wireless standards end up competing for optimal network performance and better client satisfaction, especially for residential scenarios and hotspots. In actual wireless networks, the main issue of resource management concerns the one-to-one link constraint. In fact, each station is connected to one Access Point (AP) at once, where several are reachable. Therefore, wireless clients should be able to use every available resource within range. In this context, stands the idea of AP backhaul bandwidth aggregation. This paper introduces an enhanced solution, Centralized- HeavyAP, for backhaul resource aggregation. Our solution focuses on symmetric AP-to-AP level and proposes several upgrades for optimal allocation of available backhaul resource. Within an adequate optimization method, namely the Newton method, we succeeded to establish weighted throughput and load balance among APs in the same network. © 2015 IEEE. Source

Ben Rejeb S.,MEDIATRON | Nasser N.,Alfaisal University | Tabbane S.,MEDIATRON
Journal of Network and Computer Applications | Year: 2014

Mobile communication systems have evolved considerably in recent years, encouraging the deployment of multiple systems or multi-cellular technology, and improving the quality of service (QoS) offered to mobile users. For example 4G systems offers better quality of service than that offered by 3G and 3.5G. Furthermore, 4G systems, such as Long Term Evolution (LTE) also offers expanded cellular coverage and provides higher throughput. Such emerging systems certainly enhance the overall accessibility Internet, and enabling such networks to handle both new and migrating fixed users becomes a challenge. This paper evaluates system performance by developing a new LTE mechanism for allocating resources in the downlink based on call admission control (CAC) taking into account mobility within and between cellular users. The proposed mechanism uses adaptive modulation and coding (AMC) that divides the geographical area into several concentric regions. With this mechanism each call accepted by the system maintains its initial throughput regardless of the position of the user in the cell. © 2014 Elsevier Ltd. All rights reserved. Source

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