Browsing by Author "Prasad, Neeli R."
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- Cost-benefit aware routing protocol for wireless sensor networks with Hybrid Energy Storage SystemPublication . Pais, Nuno Miguel Esteves; Cetin, Bilge Karta; Pratas, Nuno; Velez, Fernando J.; Prasad, Neeli R.; Prasad, RamjeeAt the eve of a new decade, when energy concerns are at the top of the research priorities, this work presents a new cost-benefit function for wireless sensor networks (WSNs) powered by harvesting energy sources. The models rely on a Hybrid Energy Storage System (HESS) that combines a super-capacitor (SC) with a Rechargeable Battery (RB). While the SC has low energy storage capability but is capable of providing high level of energy throughput and frequent charge cycles, the RB has higher energy storage capability but limited charge cycles. Our proposal for the protocol associated with HESS assigns different weights to the residual energy in both energy storage systems whilst favouring routes with more SC energy and harvesting rates. The main innovation is the application of a new routing cost metric to prolong the network lifetime. An energy model framework has been developed in MATLAB with different application scenarios to test the proposed cost metric. The simulation results show that, by using the HESS flexible energy-aware cost-benefit function, significant extension of the network lifetime is achieved by means a balance between the energy consumption and the reliable delivery of data packets.
- Cost/revenue performance in an IMT-Advanced scenario with Spectrum Aggregation over non-contiguous frequency bandsPublication . Acevedo Flores, Jessica Elizabeth; Velez, Fernando J.; Cabral, Orlando; Robalo, Daniel Luís Silveira; Holland, Oliver; Aghvami, A. Hamid; Meucci, Filippo; Mihovska, Albena Dimitrova; Prasad, Neeli R.; Prasad, RamjeeThis paper determines the cost/revenue performance of a mobile communication system in an IMT-Advanced scenario with integrated Common Radio Resource Management (iCRRM). The iCRRM performs classic CRRM functionalities jointly with Spectrum Aggregation (SA), being able to switch users between non-contiguous frequency bands. The SA scheduling is obtained with an optimized General Multi-Band Scheduling (GMBS) algorithm with the aim of cell throughput maximization. In particular, we investigate the dependence of the throughput on the cell coverage distance for the allocation of users over the 2 and 5 GHz bands for a single operator scenario under a constant average Signal to Interference-plus-Noise Ratio (SINR), for the same type of Radio Access Technology and both frequency bands. The operator has the availability of a non-shared 2 GHz band and has access to part (or all) of a shared frequency band at 5 GHz. An almost constant gain near 30 % was obtained with the proposed optimal solution compared to a system where users are first allocated in one of the two bands and later not able to handover between the bands. It is shown that the profit in percentage terms decreases as the cell radius increases. These results allow for evaluating the impact of the revenue from the channel in the total revenue and in the profit, defined as the difference between revenues and costs, in percentage. Maximum profits of about 1270, 585 and 240 % have been obtained for prices of 0.10, 0.05 and 0.025 €/MByte, respectively, when iCRRM is employed, while profits of 990, 440, and 170 % have been reached with no iCRRM, i.e., simple CRRM. Finally, an energy efficiency strategy is proposed and analyzed, showing that there is significant transmission power saving potential through the opportunistic reallocation scheme.
- Multi-operator resource sharing scenario in the context of IMT-Advanced systemsPublication . Mihovska, Albena; Meucci, Filippo; Prasad, Neeli R.; Velez, Fernando J.; Cabral, Orlando Manuel BritoThis paper investigates and proposes a framework for the efficient integration of functionalities for dynamic spectrum use (e.g., spectrum aggregation) and cooperative radio resource management (RRM) in the scope of IMT-Advanced (IMT-A) candidate systems. The envisaged technical solution is based on a joint centralized and distributed approach for both intra-and inter-operator scenarios. Spectrum assignment decisions benefit from a distributed approach that can be realized by the pooling of resources at higher layers together. The paper investigates the possible interworking between the two techniques for the benefits of achieving higher performance and capacity gains. Based on the proposed framework, operators will be able to demand portions of the spectrum for a certain time period and coordinate this action with the actual network loads. The framework is described in terms of functionalities, physical entities, and mutual interactions. The proposed integrated framework can reduce the CAPEX and OPEX during the deployment of IMT-A systems.
- Optimal load suitability based RAT selection for HSDPA and IEEE 802.11ePublication . Cabral, Orlando; Velez, Fernando J.; Rodriguez, Jonathan; Monteiro, Valdemar; Gameiro, Atilio; Prasad, Neeli R.Networks of the future envisage a network-of-wireless networks that provide the end user the means to connect to the best available network at anytime and at any place. However, equally challenging for the operators is to provide these services at low cost in an era where spectral resources are a premium. This paper investigates cooperation between networks based Radio Access Technology (RAT) selection algorithm that uses suitability to optimize the choice between WiFi and High Speed Downlink Packet Access (HSDPA). It has been shown that this approach has the potential to provide gain by allocating a user terminal to the most preferred network based on traffic type and network load. Optimal load threshold values that maximise the total QoS throughput for the given interworking scenario are 0.6 and 0.53 for HSDPA and WiFi, respectively. This corresponds to a CRRM gain on throughput of 80% with 60 users.