Intelligent transportation systems (ITS) are designed to enhance road safety and traffic efficiency. Connected autonomous vehicles are a critical component of ITS, and platooning among vehicles can enhance close coordination and improve driving efficiency. This requires high-capacity links, which can be facilitated by light communication. However, due to the small area of optical photodiodes, the light communication link can suffer misalignment, leading to reduced reliability during maneuvering on-road curvatures. Solar panels present a potential solution having a larger receiver area and the ability to convert the optical signal to its electrical equivalent. However, solar panel 3-dB bandwidth for communication is limited to only a few tens of kHz range, resulting in low data throughput. In this work, we develop an analog circuit to enhance the 3-dB bandwidth of solar panel receivers, effectively mitigating misalignment issues by maintaining connectivity even at high orientation. Experimental results demonstrate that the solar receiver can maintain communication despite extreme misalignment of the order of ±50°. Furthermore, the results indicate that the solar panel can still provide connectivity even when 90% of its area is in blockage. Specifically, on the transmitter side, we have employed near-infrared light-emitting diodes (LEDs) to mitigate the glare effect caused by white LEDs. Also, IR LEDs cause less attenuation loss in outdoor environments, thus consuming less power than white LEDs to transmit information. Analytical expressions for designed analog circuitry and the impact of using solar panels in the dead zone are derived, and the comparison results with conventional photodiode is presented. The findings indicate that solar panels, when used as optical receivers, meet the communication requirements for the connected vehicles and effectively address issues such as loss of communication links.

Solar panels, traditionally used for energy harvesting, are emerging as viable optical receivers for visible light communication (VLC). This work investigates the impact of different solar panel configurations—series, parallel, and standalone (single panel)—on their performance as VLC receivers. A series configuration reduces junction capacitance, enhancing bandwidth and response time and making it ideal for high-speed optical communication. However, the increased impedance may affect signal reception efficiency. In contrast, a parallel configuration increases overall capacitance, which can limit bandwidth and slow response time but provide better signal strength. The single-panel configuration offers a balanced approach, ensuring efficient signal reception without additional circuit complexities. Experimental evaluations focus on key communication metrics such as bandwidth and solar panel time response. While the impact on energy harvesting is acknowledged, the primary emphasis is on optimizing signal reception for high-speed VLC applications. Solar panel enabled long distance communication links can enhance mid-haul and front-haul networking, extending connectivity to rural and remote areas.

To fulfil the demand for high energy and spectral efficiency (SE) while serving multiple users concurrently for next-generation 6G systems, both non-orthogonal multiple access (NOMA) and orthogonal frequency division multiplexing (OFDM) aided index modulation (IM) endorse the requirements. NOMA serves several users concurrently while sharing the frequency and time resources. In addition, the single-mode OFDM-IM system improves the SE by broadcasting the additional bits of active subcarrier selection. Meanwhile, dual-mode OFDM-IM relatively enhances the SE via transmitting different constellation sets over a subblock OFDM vector. Furthermore, broadcasting the baseband NOMA symbols over a dual-mode OFDM-IM scheme improves the SE compared to the conventional IM schemes. This paper describes a dual-mode aided cooperative relaying OFDM-IM-based downlink hybrid NOMA system serving multiple users simultaneously. The Monte Carlo simulation results demonstrate that the bit error rate (BER) performance of the proposed system accessed using the maximum likelihood (ML) detector for different modulation schemes is significantly better as compared to the existing cooperative relaying OFDM-IM-aided NOMA systems, including single-mode and hybrid systems.

The future intelligent transport systems (ITSs) promise to improve traffic safety and security along with reducing the driver workload. In this article, we consider a pre-emptive emergency situation, wherein we design a safe-driving maneuver problem for transportation Metaverse (TransVerse) to compensate for driver reaction delay. The proposed scheme balances the risk of collision, and the spectral and computation resources required by the network. This combination of the spectral and computation resources required is also known as utility of the vehicular network. Further, an emergency maneuver is proposed to suggest a lane-changing maneuver based on the safe lane quality index for vehicles in vicinity of the emergency vehicle, also known as collision risk vehicles (CRVs). Moreover, based on the current position of the vehicles and the proposed safe maneuver, we propose a driving mode advisory to the drivers to provide a speed profile and a real-time high-level driving modes advice on acceleration, cruise, and engine brake. We evaluate the performance of the proposed safe-maneuver planning for CRVs in terms of collision probability, velocity, driving mode, and end-to-end lane changing delay. It can be observed that with the use of the proposed scheme, there is no effect on the performance of the high-CRV (HCRV). However, for the second following vehicle (HCRV2), the probability of collision decreases by 34.78%, and the velocity of the vehicle increases by 61.70% with the use of TransVerse. Moreover, a tradeoff between resource allocation and end-to-end delay of the network is also analyzed with and without TransVerse scenario.

The efficacy of a reconfigurable intelligent surface (RIS)-aided network for enhanced connectivity in skip zones is demonstrated through real-time video streaming. The demonstration is carried out with the help of National Instruments universal software radio peripheral (NI-USRP) devices integrated with an RIS prototype. The RIS prototype is designed and fabricated using a 16 × 10 metasurface operating at 5.3 GHz carrier frequency. Utilizing LabVIEW’s long-term evolution (LTE) application framework module, good connectivity between the transmitter and receiver in an otherwise skip zone is exhibited. Various modulation and coding schemes have been applied to the streamed data to observe the throughput, SINR, and constellation diagrams with respect to different positions of the receiver in the non-line of sight (NLOS) skip zone. The demonstration ratifies the potential of RIS system in practical applications related to future wireless communications.

Traffic congestion at road intersections is one of the critical challenges for vehicular traffic systems. In the urban environment, this traffic congestion results in an increase in the travel time, more driver fatigue, higher pollution, etc. Consequently, traffic congestion not only exacerbates travel delays but also impacts the environment and human health. As a consequence, the implementation of adaptive traffic signal cycle control to alleviate traffic congestion is of paramount importance. In this work, we use Simulation of Urban MObility (SUMO) based traffic simulation to control traffic signal cycle for smart cities. We propose a deep reinforcement learning (DRL)-based adaptive traffic signal cycle control that aims to minimize carbon dioxide (CO2) emissions while simultaneously decreasing the waiting time of the drivers. The results showcase that with the use of a DRL-based adaptive traffic signal control cycle, specifically, the average waiting time of the vehicles increases by 15.58% as the number of vehicles increases from 1750 to 2000. Furthermore, the average CO2emissions of the vehicles increase by 25% as the number of vehicles increases from 1750 to 2000.

Terahertz (THz) communication and visible light communication (VLC) are promising technologies for rapidly de-veloping next-generation wireless communication systems. This work focuses on THz and VLC performance analysis under two challenging scenarios: atmospheric weather impact and human blockages. Under these two challenges, we thoroughly compare the sum rate with multiple access techniques using orthogonal multiple access (OMA), power domain non-orthogonal multiple access (PD-NOMA), and rate splitting multiple access (RSMA) and analyzing the impact of misalignment errors in THz and semi-angles in VLC. By examining the strengths and weaknesses of both technologies, the simulation results show how different weather impacts and human blockages affect the sum rate per-formance of the THz and VLC systems. Also, it shows that THz outperforms VLC in both challenging scenarios. Consequently, the proposed comparison study will be useful to system designers in an outdoor communication system based on THz and VLC.

In recent years, LiFi has become increasingly pop-ular as an indoor communication technology that utilizes the unlicensed visible light and infra-red spectrum to transmit data. A major challenge of utilizing LiFi is that its area of coverage is limited. Thus, a large number of LiFi access points (APs) is often complemented by deploying a WiFi AP to form a hybrid WiFilLiFi network. However, such deployment does not lead to any additional improvement in the performance of WiFi or LiFi APs. Recent WiFi APs are known to have high overhead due to the requirement of channel state information (CSI), which is essential for utilizing spatial multiplexing. Thus, in this work, we propose a system called WiLiConnect (WiFi-LiFi Connectivity with CSI), which communicates the CSI requirement of the WiFi channel through the LiFi APs, thereby reducing the overhead of WiFi APs. We formulate this problem of load-balancing the overhead of CSI sharing across the LiFi APs, and show that the general problem is NP-Hard. We then propose a round-robin algorithm to solve a special case of the problem, where all the users are assumed to have a single antenna. We further utilize extensive simulation to show that WiLiConnect significantly reduces the overhead of sending CSI. Specifically, WiLiConnect incurs only 0.06% overhead on a WiFi AP having 8 antennas on the total sum rate.

We study the handover (HO) rate and user performance in a large-scale three-dimensional (3-D) unmanned-aerial vehicle (UAV) network, where the UAVs are deployed to provide access to the ground mobile users in a disaster scenario. The 3-D network is modeled as a two-dimensional (2-D) homogeneous marked poisson point process (PPP), in which the marks represent the altitude of the UAVs. Due to the different altitudes marked for the UAVs, irregularly shaped Voronoi cells are formed, which is challenging to analyze. Leveraging the HO rate, we derive the signal-to-interference-plus-noise ratio (SINR) coverage probability and the average throughput experienced by mobile users. Based on the derived framework, we investigate the impact of the intensity of deployment and user speeds on the HO rate and throughput, which enables us to present several key system-design insights for such networks.

Future autonomous driving would require a plethora of networking resources and high-quality vehicular communication links. As these mobile devices are resource-constrained, thus, offloading computer-intensive operations to the mobile edge servers has been a crucial strategy to meet the stringent quality of service (QoS) requirements. However, various types of smart vehicles with distinct capabilities, dynamic demands, and unpredictable topology pose significant challenges in realizing efficient edge computing services. To cope with these challenges, we incorporate a digital twin (DT)-enabled con-nected vehicular network which can facilitate automated resource management to enhance QoS of vehicular users. Specifically, we aim to allocate computation and spectrum resources for a DT-enabled vehicular network along with designing an optimal offloading policy. In addition, a problem to optimize the vehicular network's utility-cost ratio (UCR) is formulated in order to reduce the overall latency, energy consumption, and to improve the throughput. Further, to obtain an optimal resource allocation framework, we propose a three-step iterative algorithm to optimize the bandwidth, prices for latency, energy consumption, and offloading factor iteratively until convergence. The simulations demonstrate that the suggested approach efficiently reduces the task offloading latency as well as decreases the average energy usage for vehicular network, in addition to improving the throughput. Specifically, the utility-to-cost ratio decreases by 85 % and 12.5 % for sparse and dense traffic scenarios, respectively for a vehicle density of 0.137 vehicle/m.

Visible light communication (VLC) has enabled the inception of a novel communication technique due to its high bandwidth and resistance to interference from various electromagnetic sources. However, in an indoor VLC system, other users (static as well as dynamic) can act as blockages to the communication link for the desired user. In this paper, we analyze the performance of an indoor VLC system with dynamic human blockages. Specifically, we use the random waypoint (RWP) model to characterize the movement of the blockages. The system performance is analyzed for a 4-LED configuration, where the blockages can pause during the movement for a specific pause time. Further, we developed a model to calculate the blockage probability in a typical indoor space, which is consequently used to calculate the power at the VLC receiver. Additionally, the analysis is extended for multiple blockage scenarios with different pause times. The second-order statistics such as level crossing rate (LCR) and average fade duration (AFD) have been examined to demonstrate the impact of both pause time and the number of blockages on this dynamic time-varying indoor VLC channel. It is observed that a blockage with a longer pause time will have a longer average outage duration (AOD). Finally, the effect of the velocity of blockages on LCR and AFD is also analyzed. We believe that the insights obtained in this paper will be useful to the operator while deploying an indoor VLC communication system in the presence of dynamic blockages.

In view of recent developments in underwater wireless technology and the continuous demand for deep ocean exploration, this study investigates the underwater optical wireless communication system. Underwater wireless optical communication (UWOC) has several benefits over short-distance wireless connectivity due to its significantly higher bandwidth and data rate compared to acoustic communication. This paper presents an analysis of a non-line-of-sight (NLOS) UWOC system configuration using a submerged optical intelligent reflecting surface (OIRS) that is used to support multiple users by allocating different OIRS elements to various users at the receiver end. To increase the average sum rate and preserve user fairness, techniques based on equal mirror assignment (EMA) and distance-based mirror assignment (DMA) are presented. The outcomes are evaluated against conventional orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) schemes for underwater communications.

This paper studies an unmanned aerial vehicle (UAV)-aided downlink sparse code multiple access (SCMA) sys-tem to serve multiple users under finite resources. The objective of this work is to maximize the average sum-rate of UAV-SCMA system by optimizing the three-dimensional (3D) UAV trajectory within the UAV energy and mobility constraints, and the inter-user interference in SCMA. The formulated problem is non-convex in nature, we reformulate it using logarithmic approximation and solve it iteratively. The simulation results validates that the proposed UAV 3D trajectory outperforms the benchmark schemes with around a 20% increase in the overall sum-rate under the available energy budget.

Optical intelligent reflective surface (OIRS) is one of the promising solutions to address the ‘skip-zone’ problem between the base stations and the mobile users. The performance of OIRS can be further complemented by mounting them on unmanned aerial vehicles (UAVs), which are known for their flexibility and maneuverability. The proposed work aims to utilize the OIRS-assisted UAV to improve the performance of optical wireless communication (OWC) systems. In this work, multiple mirror elements of the OIRS are grouped and assigned to the user. Specifically, a novel mirror element assignment scheme is proposed, namely a signal-to-noise ratio (SNR) based mirror assignment (SMA) to achieve maximum user throughput with proportional fairness for each user. The performance of the proposed SMA scheme is compared against the equal mirror assignment (EMA) scheme and well-known conventional bench-mark approaches, e.g., time-division multiple-access (TDMA) and non-orthogonal multiple access (NOMA). The results are reported in terms of average sum rate, fairness, and capacity outage probability. The obtained results show that the proposed SMA scheme outperforms EMA, TDMA, and NOMA schemes.

In order to facilitate low latency vehicle-to-infrastructure (V2I) communication, latency sensitive solutions for resource allocation should be explored. In our paper, we propose a novel wavelength allocation algorithm for a fiber-wireless (FiWi) based V2I communication network. Specifically, we propose a novel approach for wavelength allocation in a time and wavelength division multiplexed passive optical network (TWDM-PON) by utilizing a first-fit bin packing algorithm. The TWDN-PON forms the optical backhaul of our FiWi network. The proposed algorithm is hybrid in nature, i.e., it utilizes both static and dynamic wavelength allocation. Further, the proposed algorithm enables an hourly allocation of wavelength to each optical network unit (ONU), connected to a roadside unit (RSU), whilst reducing the switching between the wavelengths and hence, consequently reducing the latency in the optical link. The proposed bin packing algorithm has been compared with conventional first-fit bin packing algorithm. It has been shown that by utilizing the proposed algorithm, the total number of wavelength switches reduces by 65 in 12 hours duration as well as the latency of the optical network reduces by 40% per ONU when compared with the conventional bin packing algorithm.

This paper presents a bandwidth enhancement circuit that enhances the 3 dB bandwidth of an off-the-shelf solar panel based receiver system for optical wireless communication. Experiment results show enhancement of the 3 dB bandwidth from 163 kHz to 1.62 MHz. A data rate of 1.5 Mbps is achieved with the OOK modulation scheme over the VLC link of 1 m. To the best of our knowledge, this is the highest data rate using solar panel as a receiver with OOK modulation. Low-cost, larger receiving area, ease of integration with other devices make the proposed system an environment-friendly and energy-efficient solution for optical wireless communication.

In this paper, we have determined the optimum pair of light-emitting diode (LED) semiangle and the receiver field-of-view (FOV) in the presence of human blockages for indoor visible light communication (VLC) system. Firstly, we have calculated the optimum value of LED semiangle and the receiver FOV independently, keeping others constant. Secondly, we have jointly optimized both the LED semiangle and the receiver FOV. In the analysis, both LoS and NLoS up to the second-order have been considered. We have also incorporated the reflections from the human body, essentially the skin and the clothes, in the analysis as it impacts the received power. In order to obtain the optimum value of the LED semiangle and the receiver FOV, we have used the quality factor (Q) as a performance metric. In addition, the analytical expression for the achieved quality factor is derived for both single variable and joint optimization formulation. Results shows that with 2 and 5 blockages, the optimum pair using single and joint optimization is (63°, 65°) and (63°, 70°) for a separation distance of $D_{1}=40~{\mathrm cm}$ and (65°, 70°) and (65°, 75°) for $D_{2}=20~{\mathrm cm}$ respectively which provide the highest quality factor with minimum delay spread shown. Furthermore, the optimization analysis can also be mapped to different room sizes and LED placement, with static and dynamic blockages inside the room.

The Light Fidelity (LiFi) and Wireless Fidelity (WiFi) technologies operate in non-overlapping spectrum, thus, a user is capable of receiving data concurrently from both LiFi and WiFi Access points (APs). Therefore, facilitating a link aggregation (LA) enabled heterogeneous LiFi-WiFi network (HLWN). In this paper, we have analysed the performance of LA enabled HLWN by utilizing an LA based on SINR (LA-SINR) algorithm and compared it with the conventional indoor access networks like the hybrid LiFi-WiFi, standalone WiFi and standalone LiFi. Additionally, an intuitive LA for enhancement of QoS (LA-EQoS) algorithm has been proposed to further improve the quality of service (QoS) and average data rate performance of LA enabled HLWN. The simulation results validate that for a predefined QoS requirement, proposed LA-EQoS provides 80% to 100% coverage for more number of users as compared to other networks. Moreover, for a given outage constraint, the maximum QoS offered by LA-EQoS is 1.5 times higher than other networks. 16

Reconfigurable intelligent surfaces (RISs) have recently been envisioned to provide an adaptable channel for futuristic wireless communication networks. In this work, we investigate a downlink RIS-aided non-orthogonal multiple access (NOMA) wireless networks, where a RIS is deployed to enhance users’ performance communicating with the base station (BS) in the presence of a non-ideal transceiver. Specifically, closed-form expressions for the outage, spectral efficiency (SE) and energy efficiency (EE) are derived. The results demonstrate that the non-ideal transceiver has a detrimental impact on the performance of the RIS-aided NOMA system. The proposed analysis also shows that for a RIS-aided NOMA system with a non-ideal transceiver, there exists an upper bound on SE that is independent of the transmit power and the number of reflecting elements in the RIS. Additionally, the performance of the NOMA system is compared with its OMA counterpart, where the results show that for a non-ideal transceiver-based system, the RIS-aided NOMA outperforms OMA.

Visible light communication (VLC) has recently emerged as an affordable and scalable technology supporting very high data rates for short range vehicle-to-vehicle (V2V) communication. In this work, we advocate the use of vehicular-VLC (V-VLC) for basic safety messages (BSMs) dissemination in lieu of conventional vehicular radio frequency (V-RF) communication in road intersection applications, where the reception performance is affected by interference from the concurrent transmissions of other vehicles. We make use of stochastic geometry to characterize the interference from the same lane as well as the perpendicular lane for various network configurations, i.e., standalone V-VLC, stand-alone V-RF and hybrid V-VLC/V-RF network. Specifically, by modelling the interfering vehicles’ locations as a spatial Poisson point process (PPP), we are able to capture a static two-dimensional road geometry as well as the impact of interference due to vehicles clustering in the vicinity of road intersection in terms of outage probability and throughput. In addition to above, the performance of spatial ALOHA and carrier sense multiple access with collision avoidance medium access control (CSMA/CA MAC) protocol for standalone V-VLC, standalone V-RF and hybrid V-VLC/V-RF network configuration for relaying BSMs at road intersection is also compared. The performance metrics such as delay outage rate (DOR) and information outage rate (IOR) are utilized to investigate the impact of latency associated with various network configurations. Our numerical results reveal that our proposed hybrid V-VLC/V-RF leads to significant improvement in terms of outage performance, throughput and latency as compared to stand-alone V-VLC or stand-alone V-RF network.

In this paper, we consider a fiber-wireless (FiWi) network consisting of 10-Gigabit-capable passive optical network (XG-PON) and wireless fidelity (WiFi). In order to mitigate the conventional limitations of grid-power supply, an off-grid FiWi network is considered, where the components of the network such as optical network units (ONUs) and IEEE 802.11 access points (APs) are powered using renewable sources of energy such as photovoltaic (PV) panels and wind turbines along with batteries. Depending on the availability of renewable power at different locations, the energy resources available to power ONU-AP may vary. Consequently, we propose a joint energy resource allocation framework to minimize the number of PV panels and batteries required by ONU-AP based on its location as well as throughput requirement of the users. An analytical framework is derived to justify the accuracy of the proposed joint energy resource allocation framework. Further, a socio-economic analysis and trade-off analysis between allocation efficiency and cost is also presented. The results show a good agreement between the analytical and the proposed approach. It has also been observed that location with high renewable energy sources contributes to a significant reduction in the number of PV panels and batteries requirement and, therefore, has lower cost and carbon dioxide (CO2) emissions.

In this paper, we study the trade-offs between two network configurations employed in a heterogeneous network setup wherein unmanned aerial vehicle (UAV) base stations (UBS) coexist with a macro base station (MBS). Specifically, two network configurations are investigated: (i) Heterogeneous network with MBS and UAV-Cellular base station (UAV-CBS) and (ii) Heterogeneous network with MBS and visible light communication (VLC) enabled UAV-Optical base station (UAV-OBS). A framework has been developed to compare the average spectral efficiency of the proposed network configurations. In the developed framework, the average spectral efficiency has been analyzed by taking into account the user’s association and user’s quality of service (QoS) requirement and location. To gain more concrete insights, we compare the above configurations for (i) one UBS and one MBS network, and (ii) two UBSs and one MBS network. We infer, from the simulation results, that as the number of UBSs in use increases, the network with VLC enabled UAV-OBS outperforms the cellular-enabled UAV-CBS.

An intelligent reflecting surface (IRS) comprises of an array of discrete reflective elements (REs) possessing re-configurable scattering properties. IRS has the capability to beamform and relays the received radio signal from the transmitter to the desired receiver. This has made the IRS a promising candidate technology for the beyond fifth-generation (5G) cellular standards. In this work, the performance of an IRS-assisted wireless communication system is investigated and compared with the full-duplex (FD) relay-assisted system in the presence of non-ideal transmitters. Specifically, the performance is compared in terms of channel capacity and energy efficiency (EE). The results show that the IRS can never achieve more capacity than the ideal FD relaying, in the presence of a non-ideal transmitter, irrespective of the placement of IRS and relay. Further increasing the number of REs, the capacity saturates with an upper bound that equals to the capacity provided by the relay-assisted system. However, increasing the number of REs results in the reduction of the EE for IRS-assisted systems, which are otherwise known to be highly energy-efficient.

This paper proposes orthogonal frequency division multiple access (OFDMA) based multiuser hybrid cooperative- D2D (C-D2D) communication system with the best user selection. In the proposed model, the listen-before-talk (LBT) algorithm with an energy detection method has been used to check the WiFi spectrum availability. Based on the spectrum availability, the system adapts to any one of the two modes, namely in-band C- D2D or out-band C-D2D. Further, the best user selection scheme is applied to a system wherein multiple D2D users coexist with a cellular user in the same cell. In particular, among the M available D2D pairs, selected D2D user helps the cellular user by relaying D out of N subcarriers to the base station (BS). Based on the availability of Wi-Fi, either N-D subcarriers of the cellular spectrum or N subcarriers of the Wi-Fi spectrum will be shared among M D2D users for D2D transmission. Closedform expressions of outage probability for cellular and D2D users are derived. Results show that the proposed hybrid C-D2D communication system with the best user selection outperforms the conventional C-D2D framework.

Unmanned aerial vehicles (UAVs) have the potential of being used as flying base stations to facilitate a disaster-resilient communication network. However, the optimal placement of UAVs over a disaster-affected area must be aware of the mobility of the ground users. Hence, in this paper, we propose a ground user mobility aware multi-UAV placement strategy for disaster-resilient communication network. We formulate an optimization problem to maximize the number of ground users covered by the UAVs, while also taking into account the UAV flight time constraint. Specifically, in this work, the emergency first responders (EFRs) are considered as the ground users and their mobility is modeled in the disaster-affected area. We analyze single-UAV and multi-UAV scenarios in terms of average covered users and average coverage time. We observe that there exists a trade-off between the average number of covered users and average coverage time.

Wireless sensor network (WSN) data is prone to huge losses and corruption. Hence, the existing matrix completion algorithms experience high estimation errors in such scenarios. Therefore, a robust matrix completion algorithm is required for WSN data to meet the above challenges. This paper proposes a robust "two stage matrix completion (TS-MC)" algorithm to recover data from missing and corrupted values. The proposed TS-MC algorithm consists of two stages. For the first stage, two different methods have been proposed for recovering the incomplete data that exploit the double DCT sparsity as WSN data varies smoothly in both time and spatial domain. In the second stage, the recovered data of the first stage is de-noised in the matrix factorization framework, wherein the rank of the data is estimated from the data recovered from the first stage. Simulations are performed on two real datasets of Intel Lab and Data Sensing Lab. Results demonstrate that the proposed TS-MC algorithm achieves high accuracy even when 90% of the data is missing.

Energy efficiency (EE) and spectral efficiency (SE) are among the key performance metrics for any wireless standards. In this work, we study the trade-off between EE-SE for supporting the downlink data rate as well as opportunistically harvesting the ambient radio frequency (RF) energy. The goal is to maximize EE while maintaining the requisite data rate for the downlink. We consider a case of downlink full duplex multi-input single-output (MISO) system where the transmitter having multiple antennas is transmitting to a user equipped with single antenna. At the transmitter, few antennas are reserved for selfenergy recycling (S-ER) while the remaining antennas are utilized for information transmission. S-ER enhances the EE of the system at the expense of SE due to loss in the array gain. In order to improve the SE, we incorporate the adaptive S-ER scheme which utilizes selection of antennas corresponding to higher gains for information transmission. This compensates the loss in the SE along with the increase in EE of the system. Both linear and nonlinear transmitter cases have been considered for analyzing the trade-off and the simulation results are shown by obtaining the outage probability.

Device-to-Device (D2D) communication, an influential addition to long term evolution- advanced (LTE-A) standards, enables direct communication between closely located cellular users to improve the throughput, latency and spectral efficiency of a cellular network. In this paper, we augment the development of D2D by proposing an orthogonal frequency division multiple access (OFDMA) based cooperative D2D (C-D2D) framework wherein multiple D2D pairs exist with a cellular user. Among M available D2D pairs, a D2D transmitter (DT) that can achieve the largest quality-of-service (QoS) improvement of uplink cellular transmission is selected to serve as a user relay for the cellular transmission. In addition, a novel round robin process with priority cube method is proposed to facilitate the fair distribution of available resources among M DTs. A generic mathematical probability model is developed to analyze the performance of the proposed scheme. In particular, the closed-form expression of the outage probability for the best D2D user selection for C-D2D framework is derived. Results show that the proposed scheme improves the QoS of the cellular user as compared to the conventional C-D2D framework.

In this paper, we evaluate the performance of carrier aggregated dual band (DB) multi- user (MU) multi-input-multi- output (MIMO) orthogonal frequency division multiplexing (OFDM) system in the presence of transmitter nonlinearity and frequency-selective fading channels. As a benchmark, the performance has been compared with a linear DB MU-MIMO-OFDM system which employs a conventional transmit preprocessing technique to mitigate the inter-user interference. A two-dimensional (2D) memory polynomial (MP) is considered to model the transmitter nonlinearity. We show that transmitter nonlinearity leads to nonlinear interference in a DB MU-MIMO- OFDM system which can not be eliminated by the conventional transmit preprocessing techniques. As a consequence, there is an irreducible error floor which degrades the performance of the nonlinear DB MU-MIMO-OFDM systems. We have also shown that the irreducible error floor is the function of number of aggregated bands as well as number of users present in the system. The impact of number of bands and users has been shown by comparing the symbol error rates of a nonlinear single band (SB) MU- MIMO-OFDM system vis-a-vis nonlinear DB MU-MIMO-OFDM system for a multi-path frequency selective Rayleigh fading channel.

In this paper, a new protocol for simultaneous wireless information and power transfer (SWIPT) has been proposed, which randomly switches the signal for information decoding (ID) and energy harvesting (EH). However, the information decoder recovers the complete data by utilizing the sparse behaviour of the real world signal, thus not compromising the system performance, unlike the conventional SWIPT protocols such as time switching and power splitting.

Device to Device (D2D) communication is one of the key enhancement of Long-Term Evolution (LTE) Advanced standard which is a precursor to fifth generation (5G) cellular standard. D2D has gained considerable attention due to several drawbacks associated with the existing mobile networks such as multi-hop transmission, higher latency, high power consumption and significant path loss. In an underlay D2D communication, both cellular and D2D users coexist by simultaneously sharing the licensed cellular spectrum. However, the performance of an underlay D2D communication is limited by the amount of interference from the cellular user(CU) to the D2D user and vice versa. In this paper, we design and develop a test-bed to evaluate the real-world performance of the underlay D2D communication framework. We demonstrate the impact of interference caused by CU on D2D receiver's throughput at different cellular angles and position with respect to the base station (BS). The demonstration has been performed on National Instruments Universal Software Radio Peripheral (USRP) RIO platform with LTE application framework module of LabVIEW communication system design suite as a supportive Application programming interface (API).

This paper presents the theoretical characterization of the impact of nonlinear amplification on the spectral content of a carrier aggregated orthogonal frequency division multiplexing (CA-OFDM) system. Specifically, we derive a simplified mathematical expression of power spectral density (PSD) at the output of a nonlinearly amplified dual band CA-OFDM system. We show that nonlinear distortions caused due to nonlinear amplification severely affects the spectral content of dual band CA-OFDM signal, thus considerably increasing the adjacent channel power ratio (ACPR) at the output. Further, through the obtained results, we also demonstrate that the nonlinear amplification has far more adverse impact on a CA-OFDM system vis-a-vis non-aggregated OFDM system. A two-dimensional (2D) enhanced Hammerstein (EH) model is used to model the nonlinear behavior of the transmitter due to high power amplifier (HPA). A good agreement between the theoretical and simulation results demonstrates the accuracy of our analysis.

Cooperative device to device (C-D2D) communication framework can be exploited for offloading cellular data as well as to combat congestion in a crowded cellular network. In C-D2D, a D2D transmitter (DT) acts as an in-band relay to satisfy the quality of service (QoS) requirements of a cellular user (CU). In this paper, we present the measurement results for orthogonal frequency division multiple access (OFDMA) based adaptive C-D2D communication framework. The measurements are conducted on a software re-configurable National Instruments (NI) Universal Software Radio Peripheral (USRP) platform. The on-field trials are carried out for both line of sight (LOS) and non-line of sight (N-LOS) measurement scenarios. Further, an adaptive subcarrier sharing scheme is also proposed to facilitate in-band D2D communication within a cellular network. The measurement results show that the adaptive and C-D2D framework significantly improves the bit error rate (BER) and spectral efficiency (SE) performance of the cellular network.

In this study, the authors consider an energy‐constrained secondary user which harvests energy from the primary signal and forwards this latter with the guarantee of spectrum access. Two key protocols are proposed, namely time‐splitting cooperative spectrum sharing (TS‐CSS) and power‐sharing cooperative spectrum sharing (PS‐CSS), based on time splitting and power sharing at the relay, respectively. Assuming a Nakagami‐ m fading model, exact closed‐form expressions for the outage probabilities of the primary and secondary users are derived in decode‐and‐forward and amplify‐and‐forward relaying modes. From the obtained results, it is shown that the secondary user can carry its own transmission without any adverse impact on the performance of the primary user and that the PS‐CSS protocol outperforms the TS‐PSS protocol in terms of outage probability over a wide range of signal‐to‐noise ratio. Furthermore, the effect of various system parameters, such as splitting ratio, distance between nodes and harvesting efficiency, on the system outage performance on employing the proposed protocols is investigated and several insights are drawn.

Recent studies have shown that carrier-aggregated multi-user (MU) multi-input-multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems can deliver unprecedented improvements in network throughput and capacity when compared with existing systems. However, most of these studies fail to take into account the nonlinear constraints that limit the performance of such systems. This paper proposes an analytical framework to evaluate the end-to-end performance of a carrier-aggregated dual-band (DB) MU-MIMO-OFDM system in the presence of transmitter nonlinearity. Specifically, we derive the closed-form expression for signal-to-interference-plus-noise ratio (SINR) and further utilize this expression to evaluate the average capacity and symbol error rate of a nonlinear DB MU-MIMO-OFDM system in a multi-path Rayleigh fading channel. We show that the transmit preprocessing technique conventionally used to mitigate inter-user interference in a linear DB MU-MIMO-OFDM system fails to eliminate inter-user interference in a nonlinear DB MU-MIMO-OFDM system. As a consequence, there is an irreducible error floor which is function of number of aggregated bands as well as number of users present in the system. The irreducible error floor has been shown to considerably deteriorate the performance of nonlinear DB MU-MIMO-OFDM system. Simulation results are also reported to validate the efficacy of the proposed analysis.

Device-to-Device (D2D) communication, an influential addition to long term evolution-advanced (LTE-A) standards enables direct communication between the closely located cellular users to improve the throughput, latency, and spectral efficiency of a cellular network. In this paper, we augment the development of D2D by proposing the orthogonal frequency division multiple access (OFDMA) based underlay and overlay D2D frameworks wherein multiple D2D users coexist with the cellular users in the same cell. A general mathematical probability model is developed to analyze the performance of both frameworks. Specifically, closed form expression to find minimum angle θ (an angle between the cellular link and D2D interference link) is derived for which the target rate and outage probability constraint of both cellular and D2D users are satisfied. By deducing the value of θ, BS can select an optimal cellular user to facilitate D2D communication in a cellular network.

This paper proposes a framework to analyze the viability of network-assisted Device-to-Device (D2D) communication in an indoor propagation environment using location awareness. Based on the past location information of the users a probability model is developed. The model helps to evaluate the probability of a user's location on a specific indoor site at a given time of the day. Further, leveraging this location information, a heterogeneous framework is considered where user devices are capable of supporting cellular, as well as D2D communication. In order to quantify the performance, the proposed D2D+cellular framework is compared with the conventional cellular framework, and the gains are measured in terms of spectral efficiency and amount of energy saved. It is shown, on opting D2D over cellular for indoor communication it is possible to achieve an average spectral efficiency gain of 10.45 bits/s/Hz as well as an average energy saving of 59%. Further, it is also observed that there exists a critical point beyond which D2D ceases to be beneficial over conventional cellular communication.

This paper analyzes the impact of nonlinear distortion caused by high power amplifier (HPA) on a dual band carrier aggregated multi input multi output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. A two dimensional (2D) general memory polynomial (GMP) has been used to characterize the behavioural model of HPA. The inband and cross modulation distortion, caused by nonlinear HPA on the carrier aggregated MIMO-OFDM system can be modelled in terms of complex phase shift and Gaussian nonlinear noise that distorted the received data symbol. The mathematical expressions for the complex phase shift and variance of Gaussian nonlinear noise have been formulated. Furthermore, this analysis is also augmented to evaluate the overall performance of aggregated MIMO-OFDM system in terms of probability of symbol error for Mary quadrature amplitude modulation (M-QAM) in presence of multi-path Rayleigh fading channel. Simulation results demonstrate the validity of analytically derived expressions.

In this study, an overlay spectrum sharing scheme has been proposed for a cognitive radio system. To achieve the desired quality of service for the licenced (i.e. primary) system and spectrum access for unlicenced (i.e. secondary) system, a three‐phase cooperative decode and forward relaying is used. Furthermore, space–time block coding is used in order to cancel the interference at primary as well as secondary receiver. It has been shown that the proposed scheme helps in achieving diversity gain of three and two for primary and secondary systems, respectively. The performance of both primary and cognitive (secondary) system is appraised by deriving closed‐form expression for bit error rate and outage probability. The theoretical and simulation results validate that the proposed scheme improves the performance of both systems as compared with the earlier proposed schemes.

IEEE 802.11p standard is a wireless vehicular communication standard meant for outdoor applications. This standard suffers from the challenge of robust channel estimation due to rapid time-varying nature of the channel This paper proposes a novel scheme of channel estimation by utilizing the guard interval of every orthogonal frequency division multiplexing (OFDM) symbol. For a typical vehicular wireless communication where the channel fades quite rapidly, inter-symbol-interference (ISI) may not be as significant a problem as time varying nature of the channel due to Doppler effect. Hence, the proposed scheme utilizes the redundant space of guard interval (GI) (other than that required for cyclic prefix (CP) to combat ISI) to insert pseudo-random sequence (PRS)for channel estimation. A decision-directed time-domain least squares channel estimation method is proposed using the inserted PRS with CP. Simulation results show that the proposed scheme can considerably improve the bit error rate (BER) performance compared to the existing techniques.

In a cooperative spectrum sharing (CSS) protocol, two wireless systems operate over the same frequency band albeit with different priorities. The secondary (or cognitive) system which has a lower priority, helps the higher priority primary system to achieve its target rate by acting as a relay and allocating a fraction of its power to forward the primary signal. The secondary system in return is benefited by transmitting its own data on primary system's spectrum. In this paper, we have analyzed the performance of multiple antenna cooperative spectrum sharing protocol under Nakagami-m Fading. Closed form expressions for outage probability have been obtained by varying the parameters m and Ω of the Nakagami-m fading channels. Apart from above, we have shown the impact of power allocation factor (α) and parameter m on the region of secondary spectrum access, conventionally defined as critical radius for the secondary system. A comparison between theoretical and simulated results is also presented to corroborate the theoretical results obtained in this paper.

Although there has been significant research and development on automation devices for assisted living, there has always been trade-offs in terms of the cost, complexity, design and efficiency. In this pap er, a state-of-the-art simple and efficient yet cost effective reconfigurable assisted living system is proposed and implemented which will cater for the needs of bed-ridden patients, people with disability and senior citizens. The distinct fea tu re which makes this implementation unique is its low cost, low power consuming hard ware and user-friendly control, hence the user can operate the system without any external assistance. Additionally, the proposed work is a good head-start towards Internet of Things (IoT) concept and provides multitude of input options to the user by integrating cellular communication and Zigbee protocol based wireless devices with internet.

In this paper, we propose a multi-stage indirect learning architecture (ILA) for digital predistortion. Unlike the conventional ILA, in multi-stage ILA the digital predistorter (PD) is implemented in two or more stages. We demonstrate that depending on the power amplifier (PA), multi-stage ILA can achieve same or even better performance than the conventional ILA but with significantly lower PD identification complexity. The identification complexity is measured by computing the number of multipliers needed for identification of PD. In addition to above, we also propose two algorithms for the identification of the multi-stage ILA coefficients. The performance of the multi-stage ILA is evaluated in terms of improvement in adjacent channel power ratio (ACPR) and error vector magnitude (EVM) at the output of PA when a Long Term Evolution-Advanced (LTE-Advanced) signal is applied at the input. The reference PA models used for simulation are the Wiener model and Wiener-Hammerstein model.

In this paper, we have designed and developed a testbed for proof-of-concept demonstration and performance assessment of cooperative spectrum sharing (CSS) protocols. The performance of the testbed has been validated by obtaining both quantitative as well as qualitative results. Quantitative results are obtained by measuring the packet error rates for both primary and secondary systems during different times of the day whereas qualitative results are shown by utilizing a CSS protocol to successfully transmit two different images from primary transmitter (PT) to primary receiver (PR) and secondary transmitter (ST) to secondary receiver (SR) respectively. A parameter known as spectrum access probability which quantifies the probability of spectrum access for the secondary system is also measured.

Although much research has been devoted to the theoretical performance evaluation of cognitive spectrum sharing (CSS) protocols, there are few measurement results available to demonstrate the practical performance of such protocols. In this paper, we have designed and developed a testbed for proof-of-concept demonstration and performance assessment of our proposed CSS protocol. The packet error rate (PER) for both primary and secondary systems are measured to quantify their respective performance. Spectrum access probability for the secondary system is also measured. Measurement results proved that the proposed CSS protocol is able to assist the primary system to achieve a better PER and at the same time allows spectrum access for the secondary system.

The performance of modern communication transmitters utilising multi-carrier modulation techniques is highly sensitive to non-linear distortions arising mainly from the high-power amplifier (HPA). In addition, the wideband characteristics of multi-carrier signals result in frequency-dependent distortions, typically known as memory effects. This study aims to analytically evaluate the impact of the distortion induced by non-linear HPA with memory on a multi-carrier signal exemplified by orthogonal frequency division multiplexing (OFDM). The behavioural model of HPA considered for theoretical analysis is a memory polynomial model, which is a truncated form of the Volterra series. In the theoretical framework developed, this study shows that memory in HPA considerably degrades the performance of OFDM in terms of symbol error rate (SER), and the distortion itself can be canonically characterised by a complex attenuation component and a non-linear noise component. Closed-form expressions for SER in additive white Gaussian noise channel are derived and the SER for fading channel is approximated by the adaptive Gauss–Kronrod quadrature method. Simulation results are shown for a realistic HPA, based on the Wiener–Hammerstein model, and compared with the analytical results to validate the proposed analysis.

This paper analyzes the effects of nonlinear high power amplifier (HPA) with memory on an orthogonal frequency division multiplexing (OFDM) signal, by modeling the nonlinear HPA as a memory polynomial model with sparse delay taps. In the theoretical framework developed, we show that the in-band distortion due to nonlinear HPA with memory affects each subcarrier differently and the distortion itself can be canonically characterized by a complex attenuation component and nonlinear noise component. Analytical expressions for the complex attenuation and nonlinear noise are derived. From the expressions, a complete analytical approach to evaluate signal to noise ratio and probability of error for each subcarrier in an additive white Gaussian noise (AWGN) channel is obtained and illustrated using a M-QAM OFDM system. A comparison between theoretical and simulated results is also presented to verify the accuracy of our analysis.