Browsing by Author "Sousa, Sofia"
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- Basic limits for LTE-Advanced radio and HetNet optimization in the outdoor-to-indoor scenarioPublication . Velez, Fernando J.; Sousa, Sofia; Mihovska, Albena; Prasad, RamjeeThe unplanned deployment of small cells is leading to high levels of intra- and inter-tier interference. An insight on how to manage the interference is vital to reach a significant capacity improvement through ultra-dense networks. This paper considers heterogeneous networks with carrier aggregation, where the macro cells operate at 800 MHz to provide coverage and the small cells operate at 2.6 GHz to provide throughput enhancement at hotspots, including an outdoor-to-indoor scenario. We analyze in detail the values of the carrier-to-noise-plus-interference ratio (CNIR) from/at the user equipment (UE) for bandwidths of 10 and 20 MHz. A rapid decay is observed in the throughput for the small cells at a distance <; 300m. Broader bandwidths allow for doubling the capacity only for R>dBP/rcc. For R>250m, the capacity is similar for reuse pattern, K=3 and 7, showing no advantages for higher K. A clear decrease of the supported throughput is verified for the highest coverage distances in non-line-of-sight propagation conditions. Besides, one concludes that outdoor-to-indoor coverage corresponds to slightly worst coverage with less interference.
- Impact of considering the ITU-R two slope propagation model in the system capacity trade-off for LTE-A HetNets with small cellsPublication . Sousa, Sofia; Velez, Fernando; Peha, JonThis work aims at understanding and evaluating the impact of using different path loss models in the optimization trade-off of small cell (SC) networks. In LTE-A, the more realistic propagation models are the more efficient the radio and network optimization becomes. In this work we compare four urban path loss models: the urban/vehicular and pedestrian test environment from the ITU-R M. 1255 Report as well as the two slope Micro Urban Line-of-Sight (LoS) and Non-Line-of-Sight (NLoS) from the ITU-R 2135 Report. The two-slope model considers the existence of a breakpoint in the behaviour of the path loss and yields a significantly lower throughput per square km than a traditional one-slope model if and only if cell radius is small (coverage distances, R, up to breakpoint distance divided by the reuse pattern).
- Impact of propagation model on capacity in small-cell networksPublication . Sousa, Sofia; Velez, Fernando; Peha, JonThis work evaluates the impact of different path loss models on capacity of small cell (SC) networks, including the relationship between cell size and capacity. We compare four urban path loss models: the urban/vehicular and pedestrian test environment from the ITU-R M. 1255 Report, and the two-slope Micro Urban Line-of-Sight (LoS) and Non-Line-of-Sight (NLoS) models from the ITU-R 2135 Report. We show that when using the ITU-R two-slope model that considers the existence of a break-point in the behaviour of path loss, for coverage distances, R, up to break-point distance divided by reuse factor, supported cell throughput, Rb-sup, is much lower than expected when traditional single-slope models are assumed. For Rs longer than dBP/rcc the results for Rb-sup increase with R, whereas they are steady or decrease with R when using the traditional single-slope propagation models. We conclude that the two-slope propagation model yields a significantly lower throughput per square km than a traditional one-slope model if and only if cell radius is small.
- Impact of the propagation model on the capacity in small‐cell networks: comparison between the UHF/SHF and the millimetre wavebandsPublication . Teixeira, Emanuel; Sousa, Sofia; Velez, Fernando J.; Peha, JonThis work shows how both frequency and the election of path loss model affect estimated spectral efficiency. Six different frequency bands are considered, ranging from 2.6 GHz in the Ultra High Frequency (UHF) band to 73 GHz in the millimetre wave bands (mmWaves), using both single-slope and two-slope path-loss models. We start by comparing four ur ban path loss models for UHF: the urban/vehicular and pedestrian test environment from the ITU-R M. 1255 Report, which includes the two-slope urban micro line-of-sight (LoS) and NLoS, from the ITU-R 2135 Report. Then, we consider mmWaves taking into con26 sideration the modified Friis propagation model, followed by an analysis of the through put for the 2.6, 3.5, 28, 38, 60 and 73 GHz frequency bands. We have found that the signal to-interference-plus-noise ratio, as estimated with the more realistic two-slope model, is lower for devices that are within the break-point of the transmitter, which is a small dis tance in the UHF/SHF band. As a result, spectral efficiency is higher with mmWaves than with UHF/SHF spectrum when cell radius is under 40 meters but not when cells are larger. Consequently, mmWaves spectrum will be more valuable as cells get small. We also find that capacity as estimated with the two-slope model is considerably smaller than one would obtain with the one-slope model when cells are small but there is little difference in the models when cells are larger. Thus, as cells get smaller, the use of one slope models may underestimate the number of cells that must be deployed.
- LTE-Advanced Radio and Network Optimization: Basic Coverage and Interference ConstraintsPublication . Velez, Fernando J.; Sousa, Sofia; Acevedo Flores, Jessica; Robalo, Daniel; Mihovska, Albena; Prasad, RamjeeIn cellular optimization, the UL and DL the values from carrier-to-noise-plus-interference ratio (CNIR) from/at the mobile station are very important parameters. From a detailed analysis of its variation with the coverage and reuse distances for different values of the Channel Quality Indicator (CQI) and given ITU-R propagation models, an evaluation of the possible range for the reuse factor of LTE-A is performed for the DL. By considering CQI and reference CNIR requirements recommended by 3GPP, DL peak bit rates along with the Transport Block Size assumed for single stream and bandwidths of 10 and 20 MHz, PHY and supported throughputs are analysed. HetNets with Carrier Aggregation are considered, where macro cells operating at 800 MHz provide coverage and small cells (SCs) operating at 2.6 GHz provide throughput enhancement at hotspots. A clear decrease is shown for the supported throughput for the longest coverage distances in NLoS propagation conditions. In the given range of coverage distances, the same maximum value occurs for the supported throughput for K=3 and 7, both for macro and SCs.