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- Unified propagation model for Wi-Fi, UMTS and WiMAX planning in mixed scenariosPublication . Varela, Frederico; Sebastião, Pedro; Correia, Americo; Cercas, Francisco; Rodrigues, António; Velez, Fernando J.; Robalo, DanielThis paper presents an unified and empirical propagation model to obtain the received power in mixed scenarios, with outdoor and indoor environments, or in a scenario with only one kind of environment, either for an urban, sub-urban or rural scenario, with or without vegetation. This unified model is called the Lisbon University Institute (LUI) one and can be included into planning tools for wireless communication systems. The developed model is suitable for Path Loss prediction in mobile, as well as fixed wireless network systems, e.g., Wireless Fidelity, Universal Mobile Telecommunications System and Worldwide Interoperability for Microwave Access, considering Line-of-Sight or Non-Line-of-Sight propagation conditions.
- System CapacityPublication . Velez, Fernando J.; Nazir, Muhammad Kashif; Aghvami, A. Hamid; Holland, Oliver; Robalo, DanielIn Fixed WiMAX, the contribution from each transmission mode can be incorporated into an implicit formulation to obtain the supported throughput as a function of the carrier-to-interference ratio. This is done by weighting the physical throughput in each concentric coverage ring by the size of the ring. In this paper, multi-hop cells are formed by a central coverage zone and three outer coverage zones served by cheaper low-complexity relays. It is assumed that line of sight propagation to the bases station is achieved in a high percentage of the cell, reducing the impact of selective fading, through allowing dimensioning to be done by GIS cellular planning tools. By using tri-sectorised equipment there is a need for three times more bandwidth, while hardware costs are higher. In our proposal for relays, the FDD mode is considered and the frames need to guarantee resources for BS-to-MS communications but also for BS-to-RS and RS-to-MS communications. These requirements leads to a 1/5 asymmetry factor between the UL and DL in the omnidirectional BS case and to a 3/7 asymmetry factor in the case of tri-sectored BSs. Although the reuse distance is augmented by a factor, we show that with the use of relays in FDD mode only the consideration of tri-sectored BSs with reuse pattern K = 3 (at the cost of extra channels, corresponding to 9 channels) enables to obtain values for the throughput comparable to cases without the use of relays. The presence of sub-channelisation only improves the results for the highest values of R. The consideration of tri-sectored BS antennas with K = 1 (whilst keeping the number of required channels – equal to 3) did not enable to obtain values of the throughput comparable to the ones without using relays, although frame format is more favourable. Relays can be cheaper than BS with full functionalities. As the use of relays may lead to lower costs it is worthwhile to analyse the impact of using them on costs and revenues.
- Validation of the unified propagation model for Wi-Fi, UMTS and WiMAX planningPublication . Varela, Frederico; Sebastião, Pedro; Correia, Americo; Cercas, Francisco; Rodrigues, Antonio; Velez, Fernando J.; Robalo, DanielThis paper presents the validation of the unified propagation model, the Lisbon University Institute (LUI) model, which is valid for three wireless technologies: Wireless Fidelity, Universal Mobile Telecommunications System and Worldwide Interoperability for Microwave Access. With this purpose in mind, several experimental trials for those technologies were performed in different scenarios, where mixed environments (outdoor and indoor) were included. This generalized and unified propagation model was tuned by adjusting specific parameters for each different technology, based on the achieved results from the field experiments.
- Economic trade-off in the optimization of carrier aggregation with enhanced multi-band scheduling in LTE-Advanced scenariosPublication . Robalo, Daniel; Velez, FernandoThis work proposes Long Term Evolution-Advanced (LTE-A) integrated Common Radio Resource Management (iCRRM) for inter-band carrier aggregation (CA) between band 7 (2.6 GHz) and band 20 (800 MHz), considering bandwidths of 5 and 20 MHz. The iCRRM entity performs component carrier (CC) scheduling and increases user’s quality of service and experience while considering mobile video traffic. The performance from a new enhanced multi-band scheduling (EMBS) algorithm is compared to the one from a basic multi-band scheduler (BMBS), an integer programming-based general multi-band scheduling (GMBS) and the case without CA. EMBS involves reduced optimization scheduling complexity and allows the allocation of UEs to one or both CCs simultaneously, whereas both BMBS and GMBS only support one CC per UE. Simulations results have shown that, for 5 MHz CCs and cell radius equal to 1,000 m, with EMBS and GMBS, the 3GPP and ITU-T’s 1% packet loss ratio (PLR) threshold is only exceeded above 58 UEs (goodputs of 7.48 and 7.40 Mbps, respectively), while with BMBS only 54 UEs (6.9 Mbps) are supported. Without CA, the minimum obtained PLR is approximately 2%. For CCs with bandwidth of 20 MHz, only EMBS has been considered. The PLR threshold is not exceeded up to 40 users and the value of QoE raises from 2.86 (for 5-MHz bandwidth) to 3.96, while a gain of 9.56 occurs in supported goodput, increasing from 7.48 to 71.53 Mbps. Results from the cost/revenue trade-off have shown substantial improvements by using CA. Although the profit increases as the price per megabyte increases, it is verified that prices can be much lower if a bandwidth of 20 MHz is available. Assuming values for the supported goodput under the PLR ≤1% range and 20 MHz CCs, it has been shown that the percentage of profit decreases at a considerably higher rate (compared to 5-MHz bandwidth), due to the lower rate of decrease from the curve for costs. Considering PLR ≤1%, the profit curve for 20 MHz CCs at 0.001 € /MByte is similar to the one for 5 MHz CCs and price of 0.01 € /MByte for the smallest cell sizes (few hundreds of meters) but starts to decrease faster for larger cells.
- Planning and Deployment of WiMAX NetworksPublication . Sebastião, Pedro; Velez, Fernando; Costa, Rui; Robalo, Daniel; Rodrigues, AntónioIncorporation of measurement based techniques in Worldwide Interoperability for Microwave Access (WiMAX) are required to improve IEEE 802.16 engineering methodologies. Wireless planning methodologies are presented, supported by a planning tool which facilitates the design and implementation of WiMAX networks. Propagation models available for WiMAX still need to be tuned and further validated. By comparing IEEE 802.16-2004 measurement results at 3.5GHz with computed values using the modified Friis and the Stanford University Interim (SUI) models, for a suburban area, we found that the use of the modified Friis equation with a propagation exponent ∼3 is more appropriate than the use of the SUI model, although, for coverage distances between 275 and 475 m, the SUI-B and mainly SUI-C models may still be used. From the analysis of the carrier-to-noise-plusinterference ratio, it is clear that both noise and interference present a strong limitation to the cellular reuse performance of fixedWiMAX mainly for higher order modulation and codingschemes.With a reuse pattern K = 7, cell throughputs near the maximum are only achieved in the uplink if sub-channelisation is used together with sectorization. The planning tool provides planners with practical and useful information through quick coverage/capacity based procedures, and outputs the number and position of the base stations and an estimation of the total cost of implementation, based on data provided by different equipment manufacturers. WiMAX cellular planning exercises are presented for the zone of Covilhã, Portugal, where Geographic Information Systems are used for representation of rural and sparse urban areas. One of the main conclusions is the strong need to use sector antennas in order to guarantee an adequate coverage, and higher system capacity whilst mitigating interference for several terrain types and environments, including hilly terrain.
- 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.
- Radio and Network PlanningPublication . Velez, Fernando J.; Sebastião, Pedro; Costa, Rui; Robalo, Daniel; Comissário, Cláudio; Rodrigues, António; Aghvami, A. HamidThis chapter starts by presenting the Stanford University Interim (SUI) and modified Friis propagation models. Although the SUI model is being recommended for WiMAX, the comparison between the model and experimental results show that, in our environment, at 3.5 GHz, the modified Friis model with gama = 3 fits better the measurement values. From the analyses of the signal-to-noise-plusinterference ratio, SNIR, interference-to-noise ratio and reuse pattern, it is found that both noise and interference present a strong limitation to the performance of fixed WiMAX, mainly for higher order modulation and coding schemes (MCSs). In general terms, the use of sectorization in fixed WiMAX enables to reduce the reuse pattern while considering sub-channelisation allows for improvement on the coverage. The reduction of the reuse pattern directly corresponds to an increase in the system capacity but the improvement in the coverage range (through subchannelisation) can also allow for an improvement in UL system capacity, as adaptive MCS are used. Two different approaches are considered for graphical cellular planning, and the district of Covilha˜ is considered as a case study. On the one hand, one considered a GIS based WiMAX planning tool conceived by considering coverage issues, frequency reuse, and the impact of the different classes of service. On the other, WinpropTM is used as it distinguishes among different MCS in the graphical presentation of the results. Both tools consider the information coming from the digital terrain profile. The GIS functionalities allow for appropriately adjusting azimuth and tilt of antennas. This cellular planning exercises confirm the results of theoretical analysis, where different crowns are achieved for the coverage with each MCS (corresponding to a given range of values for SNIR), for the maximum physical throughput, and for the “best server” cells. The frequency radio resources should be considered as the most valuable resourceduring the planning of wireless broadband access networks. As a rule, spectral efficiency needs to be optimized by using several advanced techniques, corresponding to an optimization from the cost-benefit point of view.
- Dynamic Configuration and Optimization of WiMAX Networks with Relay Power Saving Modes: Measurement-Based Scenario in a Hilly RegionPublication . Robalo, Daniel; Oliveira, João R.; Velez, Fernando J.; Holland, Oliver; Aghvami, A. HamidThis paper investigates the performances achievable by WiMAX networks deployed in various sectorization configurations, with and without relay stations (RSs). Further, it studies the dynamic adjustment of the configuration to serve traffic loads at different times of the day while maximising the use of opportunistic sleep modes by relays in conjunction with cell zooming, thereby saving energy. The configuration changes and invocation of opportunistic sleep modes also take into account coverage constraints. This paper first reports extensive propagation measurements that have been undertaken in Covilha˜, a hilly area of Portugal which presents a realistic and challenging propagation scenario. Using this scenario as the topographical basis, practical cellular planning results are then obtained and compared, using the dominant path and ray tracing (RT) functionalities of WinpropTM. It is shown that without RSs present, the supported throughput is lower in practice because coverage is not 100 %. Further, for the case with omnidirectional cells, coverage reduces to only approximately 60 % if RSs go into sleep mode, and for the tri-sectored cells case coverage drops from 95.75 to 81.90 % (based on RT calculations) if RSs go into sleep mode. There is, however, still a reasonable economic performance in all cases. Additional results demonstrate that savings typically of 47.6 % in RSs’ average power consumption can be achieved. These savings are shown to result in a financial saving for the operator of 10 % of the combined operational and maintenance cost. However, it is observed that such solutions have to be used cautiously in hilly regions due to challenges in maintaining coverage.
- Characterization of WiMAX propagation in microcellular and picocellular environmentsPublication . Barbiroli, Marina; Carciofi, Claudia; Degli-Esposti, Vittorio; Fuschini, Franco; Grazioso, Paolo; Guiducci, Doriana; Robalo, Daniel Luís Silveira; Velez, FernandoIn this paper different propagation models for coverage prediction of WiMAX microcellular and picocellular urban environments and for WiMAX indoor femtocells at 3.5 GHz are compared with experimental data. Results obtained for different urban and indoor environments show that statistical models are quite far from good agreement with experimental data while deterministic ray-tracing models provide appropriate prediction in all different complex analyzed environments.
- WLAN planning tool: a techno-economic perspectivePublication . Sebastião, Pedro; Tomé, Ricardo; Velez, Fernando J.; Grilo, António; Cercas, Francisco; Robalo, Daniel; Rodrigues, António; Varela, Frederico F.A simple wireless local area network (WLAN) planning tool was developed to optimize the position and number of access points (APs), as well as the total cost of the required equipment, according to different WLAN suppliers, in indoor and outdoor environments. This planning tool can be distinguished in two mains scopes: technical (defining the number and position of APs) and economic (generating a budget according to all planned equipment and its suppliers). The proposed planning tool enables manual and automatic planning modes. It only needs some inputs, like the digital format of the floor plan, the obstacle types and their positions, the areas to be covered, the user’s most probable position and the applications used by them. The propagation model used in this tool was validated using experimental results for some scenarios. In the manual mode, the APs positions are defined by the network designer. The output of the tool is the received power or the throughput, depending on the chosen option. However, in the automatic mode the tool defines the AP position and minimizes the total amount of APs in a given area. For the implementation of the latter mode, two hot spots position planning algorithms were developed and implemented; they depend on the values of the received power or throughput, while guaranteeing the total coverage or service supply for all users, respectively. This tool also provides an estimation of the budget for the required implementation, and can avoid several days of tedious site-survey work. Except for the lowest distances, experimental values for the received power generally agree with the DP model for the range of distances considered, from the terminal station to the AP, both for outdoor and indoor environments. The differences near the AP are due to different antenna radiation patterns between the tool (omnidirectional isotropic) and the experimental setup (dipole antenna). In the indoor paths, the slight differences between the results of two floors may be due to the interaction of the direct ray with the floor direction itself.
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