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In electrical engineering, the utilization of infrared thermography has been traditionally confined to the periodic inspection of electric installations, distribution lines and power transformers, among other applications. Over recent years, this technique is being increasingly incorporated in electric motors predictive maintenance programs. This is due to the fact that it has been reported its suitability...
We consider cellular base stations (BSs) equipped with a large number of antennas and operating in the unlicensed band. We denote such system as massive MIMO unlicensed (mMIMO-U). We design the key procedures required to guarantee coexistence between a cellular BS and nearby Wi-Fi devices. These include: neighboring Wi-Fi channel covariance estimation, allocation of spatial degrees of freedom for...
In this paper, we conduct performance evaluation for Ultra-Dense Networks (UDNs), and identify which modelling factors play major roles and minor roles. From our study, we draw the following conclusions. First, there are 3 factors/models that have a major impact on the performance of UDNs, and they should be considered when performing theoretical analyses: i) a multi-piece path loss model with line-of-sight...
3GPP LWIP Release 13 technology and its pre- standard version Wi-Fi Boost have recently emerged as an efficient LTE and Wi-Fi integration at the IP layer, allowing the combined use of LTE and Wi-Fi radio resources by the user. This solves the contention problems of Wi-Fi cell by routing uplink traffic over LTE, thus enabling an optimum usage of the unlicensed band for downlink. In this paper, we present...
In this paper, we present a new and significant theoretical discovery. If the absolute height difference between base station (BS) antenna and user equipment (UE) antenna is larger than zero, then the network capacity performance in terms of the area spectral efficiency (ASE) will continuously decrease as the BS density increases for ultra-dense (UD) small cell networks (SCNs). This performance behavior...
Heterogeneous networks (HetNets) with a multi-tier structure have been considered as a promising method to provide high quality of service to mobile users. The dense deployment of small-cell base stations (BSs) implies short distances between BSs and users. It is therefore likely that users will see line-of- sight (LoS) links from its serving BS and even nearby interfering BSs, which has not been...
Optimization of resource allocation is fundamental to implement orthogonal frequency division multiple access (OFDMA), which energy efficiency (EE) is very much desired. Wireless network virtualization recently emerges to flexibly enable high data rate services, but optimal cross-layer design with OFDMA remains open. While energy efficiency (EE) is a critical issue for OFDMA systems, the appropriate...
This paper analyses the performance benefits of a user-centric scheduling approach, exploiting the flexibility of both dynamic time division duplex (TDD) and a variable transmission time interval (TTI), where the downlink to uplink ratio and TTI duration can be adapted to the traffic load. The formulation of the joint optimisation problem takes into consideration the individual requirements of each...
In this paper, we study the impact of the base station (BS) idle mode capability (IMC) on the network performance in dense small cell networks (SCNs). Different from existing works, we consider a sophisticated path loss model incorporating both line-of-sight (LoS) and non- line-of-sight (NLoS) transmissions. Analytical results are obtained for the coverage probability and the area spectral efficiency...
Wireless fidelity (Wi-Fi) benefits from large downlink bandwidth but suffers from inefficient uplink contention, while long term evolution (LTE) benefits from efficient scheduling in the uplink but suffers from bandwidth scarcity in the downlink. In this paper, we quantify the performance gain of Boost, a new technology that blends the advantages of Wi-Fi and LTE in an efficient manner to overcome...
Spatial multiplexing (SM) gains in multiple input multiple output (MIMO) cellular networks are limited when used in combination with ultra-dense small cell networks. This limitation is due to large spatial correlation among channel pairs. More specifically, it is due to i) line-of-sight (LOS) communication between user equipment (UE) and base station (BS) and ii) insufficient spacing between antenna...
In this paper, we propose a new approach of network performance analysis, which is based on our previous works on the deterministic network analysis using the Gaussian approximation (DNA-GA). First, we extend our previous works to a signal-to-interference ratio (SIR) analysis, which makes our DNA-GA analysis a formal microscopic analysis tool. Second, we show two approaches for upgrading the DNA-GA...
In this paper, we analyse the coverage probability and the area spectral efficiency (ASE) in the uplink (UL) of dense small cell networks (SCNs) considering a piecewise linear path loss model incorporating both line-of-sight (LoS) and non-line-of-sight (NLoS) transmissions. The performance impact of LoS and NLoS transmissions in the ASE of the UL of dense SCNs is shown to be significant, both quantitatively...
Self-configuration of network parameters is a desired network management feature, especially in dense small cell deployments. One of the key parameters that requires such autonomous set up is the cell ID. Its configuration to a large extent influences the network performance affecting such mechanisms as network access, decoding, handover, and is therefore of a very high importance. In this paper a...
The most promising approach to enhance network capacity for the next generation of wireless cellular networks (5G) is densification, which benefits from the extensive spatial reuse of the spectrum and the reduced distance between transmitters and receivers. In this paper, we examine the performance of different schedulers in ultra dense small cell deployments. Due to the stronger line of sight (LOS)...
In heterogeneous cellular networks for mobile communications, small cells are deployed within the coverage range of primary macro cells to provide for a localized capacity boost in traffic hotspots. The sharing of communication channels among the small-cell and macro-cell tiers is spectrally efficient, but causes failures of control signaling and data channels due to unmitigated co-channel interference...
In system-level simulations, it is vital to appropriately model spatially correlated shadow fading, especially the auto-correlation, so as to emulate realistic scenarios. However, as the size of the network increases, the complexity of the straightforward approach involving the Cholesky decomposition grows exponentially. Alternatively, low-complexity oriented schemes to generate correlated shadow...
Handover decisions and mobility management in modern communication networks are carried out using signal measurements taken at user equipment (UE), obtained from neighboring base stations. Therefore, time and frequency selective characteristics of the radio propagation channel can seriously degrade the handover performance. In this paper, we investigate the impact of channel fading on the handover...
Small cells are envisioned to embrace dynamic time division duplexing (TDD) in order to tailor downlink (DL)/uplink (UL) subframe resources to the quick variations and burstiness of their DL/UL traffic. In this paper, and for the first time, we perform a theoretical analysis on the signal-to-interference-plus-noise ratio performance of dynamic TDD transmissions in homogeneous small cell networks....
In this paper, we introduce a sophisticated path loss model into the stochastic geometry analysis incorporating both line-of-sight (LoS) and non- line-of-sight (NLoS) transmissions to study their performance impact in small cell networks (SCNs). Analytical results are obtained on the coverage probability and the area spectral efficiency (ASE) assuming both a general path loss model and a special case...
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