Browsing by Author "Prasad, Ramjee"
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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.
- Cost-benefit aware routing protocol for wireless sensor networks with Hybrid Energy Storage SystemPublication . Pais, Nuno Miguel Esteves; Cetin, Bilge Karta; Pratas, Nuno; Velez, Fernando J.; Prasad, Neeli R.; Prasad, RamjeeAt the eve of a new decade, when energy concerns are at the top of the research priorities, this work presents a new cost-benefit function for wireless sensor networks (WSNs) powered by harvesting energy sources. The models rely on a Hybrid Energy Storage System (HESS) that combines a super-capacitor (SC) with a Rechargeable Battery (RB). While the SC has low energy storage capability but is capable of providing high level of energy throughput and frequent charge cycles, the RB has higher energy storage capability but limited charge cycles. Our proposal for the protocol associated with HESS assigns different weights to the residual energy in both energy storage systems whilst favouring routes with more SC energy and harvesting rates. The main innovation is the application of a new routing cost metric to prolong the network lifetime. An energy model framework has been developed in MATLAB with different application scenarios to test the proposed cost metric. The simulation results show that, by using the HESS flexible energy-aware cost-benefit function, significant extension of the network lifetime is achieved by means a balance between the energy consumption and the reliable delivery of data packets.
- 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.
- Dynamic Resource Block Allocation in Network SlicingPublication . Nidhi; Khan, Bahram; Mihovska, Albena; Prasad, Ramjee; Poulkov, Vladimir K.; Velez, Fernando J.Network slicing is crucial in 5G and its evolution concerning user-centric services. By allocating independent resources, like link bandwidth, computing/processing capabilities and spectrum, to address users’ requests, slicing serves the end-to-end verticals or services. gNodeB (gNB) allocates the bandwidth resources to transmit/receive data to User Equipments (UEs). Resources Blocks (RBs) are the smallest resource entities assigned to a single user. In 5G New Radio (NR), the timedomain resource allocation defines the allocated symbols (OFDM symbols), while the frequency-domain allocation illustrates the RBs (sub-carriers) allocation to the UE. RB comprehends 12 subcarriers in the frequency domain with a flexible RB bandwidth, unlike LTE-A. It is critical to provide enhanced services to different users. There have been several works on challenges to enable a multi-tenant and service RAN while providing isolation to the slices. This work proposes a detailed approach for creating slices based on the demanded services, resource virtualization and isolation. The focus is on resource sharing algorithms at the Slice Orchestrator (SO) level. These virtual network slices support a wide range of services and applications categorized into the Enhanced Mobile Broadband, Ultra-Reliable and Low-Latency Communications and Massive Machine-Type Communications megatrends. The paper also provides an overview of standardization activities and evolving requirements to support use cases and services like Holographic Telepresence, Automotives, among other.
- 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.
- Overview of Network Slicing: Business and Standards Perspective for Beyond 5G NetworksPublication . Khan, Bahram; Nidhi; Mihovska, Albena; Prasad, Ramjee; Velez, Fernando J.The deployment of fifth-generation wireless communications (5G) networks brought a significant difference in the data rate and throughput to the wireless systems. It ensures ultra-low latency and high reliability. In particular, Network Slicing (NS), one of the enablers for the 5G phase-II and beyond, has opened enormous opportunities for the Communications Service Provider (CSPs). NS allows CSPs to create independent virtual networks in the same physical network to guarantee high service levels. This paper provides an overview of the advances in NS from the perspective of the business opportunities and associated standardization activities. Standardization is critical in research as it intends to maintain interoperability among multi-vendor scenarios in telcos. We emphasize highlighting the technical facets of slicing within the business implementation and industry standardization process. Additionally, we address the application of Artificial Intelligence (AI) and Machine Learning (ML) to NS-enabled future networks deployments. A set of use cases and the underlying specific requirements challenges are discussed as well. Finally, future research directions are addressed in detail.
- A Study on Cross-Carrier Scheduler for Carrier Aggregation in Beyond 5G NetworksPublication . Nidhi; Khan, Bahram; Mihovska, Albena; Prasad, Ramjee; Velez, Fernando J.Carrier Aggregation (CA) allows the network and User Equipment (UE) to aggregate carrier frequencies in licensed, unlicensed, or Shared Access (SA) bands of the same or different spectrum bands to boost the achieved data rates. This work aims to provide a detailed study on CA techniques for 5G New Radio (5G NR) networks while elaborating on CA deployment scenarios, CA-enabled 5G networks, and radio resource management and scheduling techniques. We analyze cross-carrier scheduling schemes in CA-enabled 5G networks for Downlink (DL) resource allocation. The requirements, challenges, and opportunities in allocating Resource Blocks (RBs) and Component Carriers (CCs) are addressed. The study and analysis of various multi-band scheduling techniques are made while maintaining that high throughput and reduced power usage must be achieved at the UE. Finally, we present CA as the critical enabler to advanced systems while discussing how it meets the demands and holds the potential to support beyond 5G networks, followed by discussing open issues in resource allocation and scheduling techniques.
- Trends in Standardization Towards 6GPublication . Nidhi; Khan, Bahram; Mihovska, Albena; Prasad, Ramjee; Velez, Fernando J.Mobile networks have always been an indispensable part of a fully connected digital society. The industry and academia have joined hands to develop technologies for the anticipated future wireless communication. The predicted Key Performance Indicators (KPIs) and use cases for the 6G networks have raised the bar high. 6G networks are developing to provide the required infrastructure for many new devices and services. The 6G networks are conceptualized to partially inherit 5G technologies and standards but they will open the ground for innovations. This study provides the vision and requirements for beyond 5G (B5G) networks and emphasizes our vision on the required standards to reach a fully functional and interoperable 6G era in general. We highlight various KPIs and enabling technologies for the B5G networks. In addition, standardization activities and initiatives concerning challenges in the se of spectrum are diuscussed in detail.