Optical Radio Convergence Infrastructure for Communications and Power Delivering

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Publications

Block acknowledgment in IEEE 802.15.4 by employing DSSS and CSS PHY layers

Publication . Barroca, Norberto; Borges, Luís M.; Velez, Fernando J.; Chatzimisios, Periklis

The IEEE 802.15.4 standard has been widely accepted as the de facto standard for Wireless Sensor Networks (WSNs), since it provides ultra-low complexity, cost and energy consumption for low-data rate wireless connectivity. However, one of the fundamental reasons for the IEEE 802.15.4 Medium Access Control (MAC) inefficiency is overhead. In the context of our research, we demonstrate that WSNs may benefit from packet concatenation. In this paper we introduce and study the employment of a block acknowledgment mechanisms in order to achieve enhanced channel efficiency in IEEE 802.15.4 nonbeacon-enabled networks for both the Chirp Spread Spectrum (CSS) and Direct Sequence Spread Spectrum (DSSS) Physical (PHY) layers for the 2.4 Industrial, Scientific and Medical (ISM) frequency band. The proposal of the two new innovative MAC sublayer mechanisms can also be considered as a future possible contribution to the standard itself. The throughput and delay performance is mathematically derived under ideal conditions, (i.e., a channel environment without transmission errors). The performance of the proposed schemes is compared against the IEEE 802.15.4 standard through extensive simulations by employing the OMNeT++ simulator. We demonstrate that, for both PHY layers, the network performance is significantly improved in terms of throughput, end-to-end delay and bandwidth efficiency.

2014-12Conference object

Open access

Service Quality of the Urban Microcellular Scenario in the Sub-6 GHz Frequency Bands

Publication . Paulo, Rui R.; Teixeira, Emanuel; Velez, Fernando J.

This paper compares the service quality between 4G and 5G New Radio (NR) among different sub-6 GHz frequency bands in an urban micro-cellular outdoor setting. An updated version of LTE-Sim is considered to obtain the exponential effective signal-to-interference-plus-noise ratio in 4G while determining the modulation and coding scheme. System capacity is obtained by considering a video application at 3.1 Mb/s and the proportional fair (PF) scheduler while comparing 4G and 5G NR through system-level simulations (the 5G-air-simulator is considered for 5G NR). The modified largest weighted delay first (MLWDF) scheduler is compared with the PF, though only in 4G. Optimal system performance is reached both in 4G and 5G NR for cell radii longer than two times the breakpoint distance (or beyond), which are preferable compared to the shortest values for the cell radius. We have learned that the packet loss ratio (PLR) is higher for the cell radii, R, shorter than breakpoint distance, d′ BP. For d′BP ≤ R ≤ 1000 m, the PLR first decreases and then increases. For a target PLR < 2%, in 4G, the highest maximum average goodput is obtained with the M-LWDF scheduler (10-25% increase). This maximum occurs at the 2.6 GHz and 3.5 GHz frequency bands for 300 ≤ R ≤ 500 m, while at 5.62 GHz the highest goodput occurs for the longest Rs. With 5G NR and the PF, the maximum average goodput increases, in our simulations, from ≈ 14.1 (in 4G) to 26.1 Mb/s (20 MHz bandwidth).

2024Journal article

Open access

Fundamental Limits for LTE Radio and Network Planning

Publication . Velez, Fernando J.; Acevedo Flores, Jessica; Robalo, Daniel

A comprehensive study on the variation of the carrier-to-noise-plus-interference ratio (CNIR) with different system parameters is of fundamental importance in the context of LTE planning. For cellular planning purposes, the UL and DL CNIRs from/at the mobile station are very important parameters, although we are only considering DL in this work. From a detailed analysis of its variation with the coverage and reuse distances for different modulation and coding schemes (MCS) and given empirical propagation models, an evaluation of the possible range for the reuse pattern is performed. By considering the CQI and reference CNIR requirements recommended by 3GPP. DL peak bit rates along with the Transport Block Size (TBS) assumed for single stream and bandwidth of 5 MHz, physical and supported throughputs are analysed. These formulations shows the clear decrease of the supported throughput for the longest coverage distances in the LTE 2.6 GHz band, a behaviour that is not so clear at 800 MHz, and gives hints to the optimization of the use of different frequency bands in the optimization of carrier aggregation between two different bands in LTE-A scenarios.

2015-09Conference object

Open access

LTE-Advanced Radio and Network Optimization: Basic Coverage and Interference Constraints

Publication . Velez, Fernando J.; Sousa, Sofia; Acevedo Flores, Jessica; Robalo, Daniel; Mihovska, Albena; Prasad, Ramjee

In 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.

2015-12Conference object

Open access

Basic limits for LTE-Advanced radio and HetNet optimization in the outdoor-to-indoor scenario

Publication . Velez, Fernando J.; Sousa, Sofia; Mihovska, Albena; Prasad, Ramjee

The 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.

2016-06Conference object

Open access