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Indoor layout with two operators (operator A and operator B) with 4 cells per operator and 5 STAs/UEs per cell.
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![Fig. 1. Cat 4 LBT algorithm [3].](profile/Moawiah-Alhulayil/publication/342454976/figure/fig1/AS:1087131229388802@1636203691371/Cat-4-LBT-algorithm-3_Q320.jpg)
With the rapid proliferation of smart devices, the demand for more licensed spectrum bands arises. Due to the scarcity of the licensed spectrum, the 3rd Generation Partnership (3GPP) has recently deployed Long Term Evolution (LTE) networks using the Licensed Assisted Access (LAA) scheme over unlicensed bands. On the other hand, the Wi-Fi technology...
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... this study, the coexistence performance of LTE-LAA and Wi-Fi networks following the simulation conditions in [3] is evaluated by considering the static TxOP period scheme, then by using the proposed dynamic TxOP period scheme. The performance of LTE-LAA and Wi-Fi networks is evaluated using NS-3 simulator with LAA extension [20]. As shown in Fig. 2, we consider an indoor scenario in a single floor building with two operators using the same 20 MHz channel in the unlicensed 5 GHz band. Operator A (Wi-Fi) deploys four Access Points (AP) while operator B (LAA) deploys four eNBs. All the base stations (i.e., APs and eNBs) are equally spaced and centred along the shorter dimension of ...
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Citations
... The Medium Access Control (MAC) mechanisms [18,19] of Wi-Fi and BLE are designed to optimize their specific wireless environments and usage models. Wi-Fi utilizes Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), optionally enhanced with Request to Send/Clear to Send (RTS/CTS) protocols and acknowledgments (ACKs) to manage data traffic in dense and potentially congested environments, ensuring robust high-speed data transmission by avoiding collisions. ...
Indoor wireless positioning has long been a dynamic field of research due to its broad application range. While many commercial products have been developed, they often are not open source or require substantial and costly infrastructure. Academically, research has extensively explored Bluetooth Low Energy (BLE) for positioning, yet there are a noticeable lack of studies that comprehensively compare traditional algorithms under these conditions. This research aims to fill this gap by evaluating classical positioning algorithms such as K-Nearest Neighbor (KNN), Weighted K-Nearest Neighbor (WKNN), Naïve Bayes (NB), and a Received Signal Strength-based Neural Network (RSS-NN) using BLE technology. We also introduce a novel method using Convolutional Neural Networks (CNN), specifically tailored to process RSS data structured in an image-like format. This approach helps overcome the limitations of traditional RSS fingerprinting by effectively managing the environmental dynamics within indoor settings. In our tests, all algorithms performed well, consistently achieving an average accuracy of less than two meters. Remarkably, the CNN method outperformed others, achieving an accuracy of 1.22 m. These results establish a solid basis for future research, particularly towards enhancing the precision of indoor positioning systems using deep learning for cost-effective, easy to set up applications.
... In fact, the OP, symbol error rate (SER), and the closed-form expression for the ergodic capacity were derived under different constraint scenarios. In [31][32][33][34][35][36], the exact OP of the AF relaying under imperfect channel state information (CSI) was derived for independent and identically distributed (i.i.d) Rayleigh fading channels. The effects of some parameters (i.e. ...
Cognitive relay network is a spectrum dynamic paradigm that exploits the unused portions of the licensed spectrum. This is based on merging both cooperative relaying techniques and cognitive radio network to achieve spectrum efficiency and enhance the overall system performance. In this paper, the presence of mobile users at the destination node is considered. Here, the end users can navigate at relatively fast vehicular velocities causing dynamic multipath fading and high Doppler shift. which can be fairly modelled using Nakagami‐m$m\;$fading channel (i.e. m<1$\;m < 1$). In a spectrum scarcity environment, a secondary user must deploy an optimal power allocation policy to get higher transmission rates while the overall interference affecting the primary user (PU) is kept below a certain threshold value. In particular, the outage probability (OP) performance is studied over the mixed Rayleigh and Nakagami‐m fading channels for different scenarios and a tight closed‐form expressions are derived for the system OP of underlay dual‐hop cognitive relay networks with a single amplifiy‐and‐forward (AF) relay with and without the use of the direct link transmission and selection diversity at the destination with interference power constraints for the primary network over independent and non‐identical (i.n.i.d) Rayleigh and Nakagami‐m fading channels when m<1$m < 1$ based on the statistical characteristics of signal‐to‐noise ratio. Numerical results are presented to evaluate the impact of the fading parameter, m, the maximum aggregated intrusion constraint, and the locations of the primary users (PUs) on different channel scenarios at high vehicular speeds. Monte Carlo simulations are presented to verify and validate analytical results.
... The new proposed method selects the TxOP for LAA based on the current size of the CW for LAA, which is a parameter readily available in any practical implementation of LAA [46]. The 3GPP Cat 4 LBT algorithm adapts the size of the CW for LAA based on the HARQ feedbacks, which reflect incorrect data transmission due to a congestion or a collision in the channel. ...
Long Term Evolution-Licensed Assisted Access (LTE-LAA) has been pointed out as a key solution to cope with the increasing amounts of data traffic and the scarcity of the licensed spectrum. The 3rd Generation Partnership Project (3GPP) has standardised LAA to operate over the 5 GHz unlicensed spectrum which is mainly occupied by Wi-Fi. It is a challenging problem to ensure a fair coexistence between these technologies. Several studies have been proposed in the literature to allow a fair LAA/Wi-Fi coexistence. In this work, various methods are proposed to adapt/select the waiting times for LAA based on the activity statistics of the existing Wi-Fi network. The main novelty is that the knowledge of the existing Wi-Fi activities is exploited to tune the boundaries of the Contention Window (CW) for LAA and to select fixed waiting times for LAA. Moreover, a dynamic method is proposed to adapt the Transmission Opportunity (TxOP) times for LAA based on the Hybrid Automatic Repeat Request (HARQ) feedbacks. The methods are evaluated using ns-3 network simulator based on the 3GPP fairness definition. We show that selecting fixed waiting times for LAA based on the existing Wi-Fi activities is more friendly to the existing Wi-Fi and provides better total aggregated throughputs for both coexisting networks compared to the 3GPP Category 4 Listen Before Talk (Cat 4 LBT) algorithm. Moreover, the proposed dynamic TxOP method is more friendly to the existing Wi-Fi and provides better total aggregated throughputs compared to the fixed TxOP period approach of the 3GPP Cat 4 LBT scheme.
In this work, a cognitive relay network (CRN) with interference constraint from the primary user (PU) with a mobile end user is studied. The proposed system model employs a half-duplex transmission between a single PU and a single secondary user (SU). In addition, an amplify and forward (AF) relaying technique is employed between the SU source and SU destination. In this context, the mobile end user (SU destination) is assumed to move at high vehicular speeds, whereas other nodes (SU Source, SU relays and PU) are assumed to be stationary. The proposed scheme dynamically determines the best relay for transmission based on the highest signal-to-noise (SNR) ratio by deploying selection combiner at the SU destination, thereby achieving diversity. All channels connected with the stationary nodes are modelled using Rayleigh distribution, whereas all other links connected with the mobile end user are modelled using Nakagami-m fading distribution (m<1). The outage probabilities (OPs) are obtained considering several scenarios and Monte Carlo simulation is used to verify the numerical results. The obtained results show that a variety of factors, including the number of SU relays, the severity of the fading channels, the position of the PU, the fading model, and the mobile end user speed, might influence the CRN’s performance.
In this paper, a dual-hop underlay cognitive relay network (CRN) with a best-relay selection (BRS) scheme under spectrum-sharing constraints from the primary user (PU) is investigated. The system model in this work consists of one PU, one secondary user (SU) and a few SU relays. Both users exchange the information using a half-duplex mode through amplify-and-forward (AF) SU relays. Moreover, all channels are modelled using the Nakagami-m fading model. In this work, the outage probabilities (OPs) are derived for the proposed system model under several scenarios to investigate the network performance under interference power constraint Ip at the PU receiver. In addition, the impacts of the number of relays and the channel fading severity parameters are
investigated as well. Furthermore, the system performance is investigated for several PU locations. The various numerical results are verified using a Monte Carlo simulation. Overall, the obtained results show that several factors such as the number of relays, channel fading severity parameters and PU location have a major impact on the outage performance of the SU. The simulation and analytical results are perfectly matched, confirming the accuracy of the analytical derivations.
