Browsing by Author "Cabral, Orlando"
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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.
- HSDPA/WiFi RAT Selection Based on Load SuitabilityPublication . Monteiro, Valdemar; Cabral, Orlando; Rodriguez, Jonathan; Velez, Fernando José; Gameiro, AtílioRadio access technologies (RATs) selection algorithms have been studied in the literature and nowadays equipment with several RATs incorporated into it is already common. The major goal of this work is to measure the gain obtained by using WiFi as a backup network for HSDPA, allowing for preventing from quality of service (QoS) deterioration when in a low mobility scenario. Since IEEE 802.11e already supports QoS, it was the natural choice. The proposed RAT selection algorithm is based on the load of each system, and the results show a gain of 60% on supported network load with QoS over the HSDPA-alone system. As a consequence, when there is heavy load for the IEEE 802.11e network, acceptance of high priority services will affect the delay in low priority services, like FTP.
- Implementation of IEEE 802.11e Block Acknowledgement PoliciesPublication . Cabral, Orlando; Segarra, Alberto; Velez, Fernando JoséOptimisation of IEEE 802.11e MAC protocol performance can be performed by modifying several parameters left open in the standard, like buffer size and acknowledgement policies. In this work, an event driven simulator was developed, and a comparison of the results between the case of standalone services and several services supported simultaneously was addressed. With only a single service, higher values for the goodput are obtained for video and background (BK) traffics, while the lowest is found for the voice application. The number of supported users is higher for voice. With mixtures of traffic, when the number of station is small the goodput is lower for voice. However, for higher number of station, the lowest values of the goodput occur for background traffic. By using the Block Acknowledgement (ACK) procedure, for video and BK traffics, the capacity is improved when the number of station is equal or higher than 16 and 12, respectively. From a detailed analysis of the video application, a reduction of more than 40% was achieved in the delay.
- Implementation of IEEE 802.11e block acknowledgement policies based on the buffer sizePublication . Cabral, Orlando; Segarra, Alberto; Velez, Fernando J.Optimization of IEEE 802.11e MAC protocol performance is done by modifying several parameters left open in the standard, like buffer size and acknowledgement policies. By using the developed event-driven simulator, results were extracted with single and multi-service. With only a single service, higher values for the goodput are obtained for video and background (BK) traffics in comparison with the voice (VO) application. Besides, the number of supported user is higher for voice. With mixtures of traffic, when the number of station is small the goodput is lower for VO. However, for higher number of station, the lowest values for the goodput occur for background traffic. By using the Block Acknowledgement (ACK) procedure, for video and BK traffics, the capacity is improved when the number of station is equal or higher than 16 and 12, respectively. From a detailed analysis of the video application, a reduction of more than 40% was achieved in the delay. However, a clear trend is not identified for the optimum block size.
- Opportunistic load and spectrum management for mobile communications energy efficiencyPublication . Holland, Oliver; Cabral, Orlando; Velez, Fernando; Aijaz, Adnan; Pangalos, Paul; Aghvami, A. HamidDynamic load and spectrum usage management techniques can significantly improve the energy efficiency of mobile communications systems. This paper considers: (i) the opportunistic reallocation of traffic loads between bands to allow radio network equipment in the bands that the traffic is originated from to be powered down, and (ii) the opportunistic selection of more appropriate spectrum based on propagation characteristics to minimize necessary transmission power through improving propagation and/or reducing power leaking into co-channel cells in frequency reuse cases. This paper addresses the simulation of video, FTP and HTTP (web browsing) traffic sources for configurations representing LTE and HSDPA telecommunications networks, and shows that the opportunistic reallocation of users between bands to power down radio equipment achieves a significant saving of 50% or more in from-the-socket power. Furthermore, it shows that the opportunistic reallocation of users/links to minimize transmission power through using more appropriate propagation spectrum leads to a further modest reduction in from-the-socket power consumption.
- 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.
- 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.
- Simulation of IEEE 802.11e in the context of interoperabilityPublication . Cabral, Orlando; Segarra, Alberto; Velez, Fernando JoséThis work provides the specification of a MAC layer simulator that evaluates the service quality in WiFi, and presents initial results as a stand-alone simulator. The simulator will account for inter-working with WiMAX and HSDPA in the context of the IT-MOTION tool. Higher throughputs are found for the FTP service and for the video service, mainly because the frames transmitted in these services are longer than the ones for the voice application. However, the number of supported users is higher for voice. This simulator will allow for tuning-up several parameters like the ones related to how to use BlockACK, normal ACK, and NO ACK policies.