Browsing by Author "Mihovska, Albena Dimitrova"
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- 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.
- Energy-Aware Wireless Sensor Networks MAC Modelling and Simulation with Efficient TransceiversPublication . Barroca, Norberto; Velez, Fernando J.; Ferro, João Miguel; Mihovska, Albena Dimitrova; Lebres, António S.This paper addresses an analytical model that may be applied to different Wireless Sensor Networks (WSNs) Medium Access Control (MAC) protocols using different efficient transceivers. Our model accounts for the impact of several simultaneous factors, including periodic receive/transmit and sleep cycles, the length of the transmitted packet and data rate. The Sensor Block Acknowledgement MAC, a new innovative WSNs MAC protocol that uses a Block Acknowledgement scheme to achieve energy efficiency, is proposed as well. Our implementation takes into account the average delay, which can be clearly reduced when a Block Acknowledgement Scheme is used. In terms of energy consumption and average delay the efficient radio transceivers that operate in the 2.4GHz band have better results that the ones that use the 900MHz band. Adaptive listening (AL) enables radio transceivers to stay alert after the communication between two neighbour nodes before going to sleep, allowing for energy saving when synchronisation is involved.
- Optimization of Multi-Service IEEE 802.11e Block AcknowledgementPublication . Cabral, Orlando; Velez, Fernando José; Mihovska, Albena Dimitrova; Prasad, NeeliOptimization of IEEE 802.11e MAC protocol performance is addressed by modifying several parameters left open in the standard, like block size and acknowledgement policies in order to improve the channel efficiency. The use of small block sizes leads to a high overhead caused by the negotiation on the other hand, the use of large block sizes causes long delays, which can affect negatively real-time applications (or delay sensitive applications). An event driven simulator was developed, and results with a single service and several services running simultaneously were extracted. By using the Block Acknowledgement (BA) procedure, for video and background traffics in a single service situation, the capacity was improved in the case when the number of stations is equal or higher than 16 and 12, respectively. However, for lower values of the number of stations, the use of BA leads to a slightly worst system performance. In a scenario with mixture of services the most advised block size is 12 (less delay in a highly loaded scenario). The number of supported user (total) increases from 30 to 35.
- Spectrum Aggregation with Optimal Multi-Band SchedulingPublication . Meucci, Filippo; Cabral, Orlando Manuel Brito; Velez, Fernando J.; Mihovska, Albena Dimitrova; Prasad, Neeli RashmiThis paper seeks to explore the integration of spectrum and network resource management functionalities to the benefit of achieving higher performance and capacity gains in an International Mobile Telecommunications-Advanced (IMT-A) scenario. In particular, we investigate the allocation of users over two frequency bands (i.e., 2 GHz and 5 GHz) for a single operator scenario. The same type of Radio Access Technology (RAT) is considered for both frequency bands. It is assumed that the operator has gained access to a non-shared 2 GHz band and to part (or all) of the frequency pool band at 5 GHz. The performance gain is analyzed in terms of higher data throughput. The performance is heavily dependent on the channel quality for each user in the considered bands which, in turn, is a function of the path loss and the distance from the Base Station (BS). The operator will have relevant improvements when Mobile Stations are heterogeneously distributed on the cell, with variable distances from the BS. A gain up to 500 kbps (20%) was obtained with the proposed optimal solution.
- Survey on 5G Second Phase RAN Architectures and Functional SplitsPublication . Bahram, Khan; Nidhi, Nidhi; OdetAlla, Hatem; Flizikowski, Adam; Mihovska, Albena Dimitrova; Wagen, Jean-Frédéric; Velez, FernandoThe Radio Access Network (RAN) architecture evolves with different generations of mobile communication technologies and forms an indispensable component of the mobile network architecture. The main component of the RAN infrastructure is the base station, which includes a Radio Frequency unit and a baseband unit. The RAN is a collection of base stations connected to the core network to provide coverage through one or more radio access technologies. The advancement towards cloud native networks has led to centralizing the baseband processing of radio signals. There is a trade-off between the advantages of RAN centralization (energy efficiency, power cost reduction, and the cost of the fronthaul) and the complexity of carrying traffic between the data processing unit and distributed antennas. 5G networks hold high potential for adopting the centralized architecture to reduce maintenance costs while reducing deployment costs and improving resilience, reliability, and coordination. Incorporating the concept of virtualization and centralized RAN architecture enables to meet the overall requirements for both the customer and Mobile Network Operator. Functional splitting is one of the key enablers for 5G networks. It supports Centralized RAN, virtualized Radio Access Network, and the recent Open Radio Access Networks. This survey provides a comprehensive tutorial on the paradigms of the RAN architecture evolution, its key features, and implementation challenges. It provides a thorough review of the 3rd Generation Partnership Project functional splitting complemented by associated challenges and potential solutions. The survey also presents an overview of the fronthaul and its requirements and possible solutions for implementation, algorithms, and required tools whilst providing a vision of the evaluation beyond 5G second phase.