Low Earth Orbit (LEO) Satellites have been considered to expand the coverage of terrestrial networks, especially for collecting data from remote ground users unable to communicate directly with base stations (BSs). However, for reliable connectivity at specific data rates, a network over ground users with multiple LEO-Satellites is essential. To this end, in this paper, we study a LEO-Satellite network for integrated access and backhaul (IAB) in fifth generation (5G) and beyond systems, where a LEO-Satellite becomes an IAB node that is connected to other IAB nodes for backhaul transmissions and acts like a BS to ground users. Both the access network and backhaul are assume to be affected by large scale fading. Thus, terrestrial source transmits packets to the terrestrial destination via LEO-Satellite network. The proposed model is evaluated by analyzing the end-to-end packet transmission delay and propagation delay. Analytical formulas for transmission delay in both the access and backhaul networks are derived, and simulation results illustrate the system’s dependency to various parameters.

This paper examines the preferences of undergraduate students for two distinct laboratory formats in a computer networks course. The laboratory activities require students to construct various network scenarios to develop their abilities in designing, developing, and assessing computer networks. In each assignment, students construct and evaluate a specific network scenario using a simulation tool, Cisco Packet Tracer, followed by physically executing the same work with network equipment such as PCs, switches, and routers. Through a survey, this study evaluates the students' learning experiences and preferences for the two lab formats. The results indicate that computer simulations are as effective as hands-on work in comprehending the concepts taught in the course. Additionally, the students expressed no particular preference between the two lab formats and found that the formats complemented each other.

In order to develop students to be effective engineers upon graduation, it is important to bridge the gap between theory and reality. This is usually achieved through hands-on laboratory experiments. Hands-on laboratories form an integral and important part of engineering courses, and especially, the electronic circuits related courses within the undergraduate level of education. Hence, it is important to develop well outlined laboratory manuals that reflect the theoretical part of the course, with complete embodiment of simulation and hands-on experimental parts. Moreover, it is important to compare simulation and measurement data to appreciate the merits of hands-on experiments. This work presents an integrated simulation and hands-on experiments in teaching electronics instrumentation and measurement laboratory course using low-cost off-the-shelf components. A no-cost circuit simulator software (LTSPICE) and low-cost breadboard with readily available off-the-shelf circuit components can be used both at home (self-paced) and in the laboratory to motivate students and align results for an improved learning approach. The advantage of this integrated laboratory is that no specialized or expensive teaching kit is required, which improves accessibility and delivery of the course. In addition, students are satisfied with this simplified and low-cost integrated laboratory.

The growing interest in drone swarms and their applications using wireless communication has resulted in the necessity for innovative network architectures. Drone swarms are subject to highly dynamic network topology, and the low drone density may constrain connectivity and overall network performance. The Delay Tolerant Network (DTN) architecture, which is based on dynamic discovery of neighbouring nodes and relay of data via store-and-forward mechanism, overcomes these challenges. In this study, we develop a DTN simulator for drone swarms using web technologies that operate within the web browser. We employ two commonly used DTN routing algorithms, namely epidemic routing and spray-and-wait routing, for varying numbers of nodes, simulation durations, and maximum allowed copies in the network. We compare these protocols by evaluating performance metrics such as delivery probability, number of hops/copies, and delivery time, through a case study. Additionally, we investigate the influence of the outage probability of the air-to-air channel between nodes.

In this work, we evaluate the two most common routing protocols of Delay Tolerant Networks (DTNs), opportunistic and scheduled routing, for vehicular networks. We compare the feasibility of these routing protocols in terms of packet delivery ratio, delivery time, and network load using a miniature vehicular network. The mobile nodes in the network are equipped with a radio transceiver such that they exchange the data packets according to the chosen routing protocol. We observe that scheduled routing can decrease the traffic load significantly as compared to opportunistic routing, however, this comes at the cost of requiring nodes to have a contact plan.

Visible light communication (VLC) has the potential to serve as a high-speed underwater wireless connectivity solution to support real-time image and video transmission. Underwater propagation medium imposes additional challenges on the design of VLC systems which were originally proposed for indoor applications. Temperature and salinity fluctuations result in fluctuations of the refractive index of seawater and eventually introduce turbulence-induced fading. In this paper, to mitigate the effects of fading, we propose transmit laser selection for a diver-to-diver underwater VLC link where the transmitter has multiple laser sources and the receiver has one photodetector. The source with the highest received instantaneous signal-to-noise ratio is selected for transmission while the remaining sources remain idle. We derive a closed-form expression for asymptotical bit error rate over log-normal distributed underwater turbulence channels and derive the achievable diversity order. We further present simulation results to confirm our derivations and diversity gain analysis.

In Intelligent Transportation Systems, visible light communication (VLC) has emerged as a powerful candidate to enable wireless connectivity in vehicle-to-vehicle (V2V) and vehicle-to- infrastructure (V2I) links. While VLC has been studied intensively in the context of indoor communications, its application to vehicular networking is relatively new. In this paper, we carry out a comprehensive channel modeling study to quantify the effect of rain and fog on a V2V link with a high-beam headlamp acting as the transmitter. Taking advantage of advanced ray tracing features, we first develop a path loss model for V2V link as a function of distance under different weather conditions. Then, we use this expression to determine the maximum achievable distance to ensure a given bit error rate. We further investigate the deployment of relay- assisted systems to extend transmission ranges. Extensive numerical results are presented to corroborate our findings.

In this paper, we propose a multiple-input multiple-output (MIMO) uplink transmission scheme for optical wireless communication applications. The transmission is based on optical single-carrier frequency domain equalization (SC-FDE) due to its low complexity where the signal is transmitted over infrared communication channels. Based on non-sequential ray tracing, we first obtained realistic infrared MIMO channel impulse responses including low-pass filter effect of infrared light-emitting-diodes. We then investigate the performance of bit-error-rate (BER) and peak to average power ratio (PAPR) with respect to different modulation orders using spatial multiplexing.

Estimation of the time-varying optical wireless channel response is crucial in order to decode received signals coherently. In this work, we investigate symbol-error-rate and mean absolute error performance of different interpolation techniques including linear, nearest, spline, and piece-wise cubic Hermite interpolating polynomial (pchip), which are used in pilot-aided channel estimation process for visible light communication. The performance of interpolators is evaluated in realistic time-varying channel model, generated on Zemax software and compared with each other under the consideration of different modulation orders, different pilot symbol periods, and different user equipment (UE) speeds through Monte Carlo simulations. The results reveal that spline and pchip techniques are more robust to low pilot symbol transmission rate and fast time-varying channel conditions as a consequence of high UE speeds. However, low complex linear interpolation technique can be chosen for highly rated pilot signal transmission cases or when optical channel varies slowly over the time.

In this study, we investigate a relay-assisted visible light communication (VLC) system where an intermediate light source cooperates with the main light source. Specifically, we consider two light sources in an office space: one is the information source employed on the ceiling and the other one is a task light. Our system uses dc biased optical orthogonal frequency division multiplexing (DCO-OFDM) where the task light performs relaying to assist the communication and operates in half-duplex mode for both amplify-and-forward and decode-and-forward relaying. We investigate the bit error rate (BER) performance of the relay-assisted VLC system and optimize the performance through optimal ac/dc power allocation under illumination constraints. The dc power allocation is determined by sharing the number of LED chips between the terminals to satisfy a desired luminance ratio. The ac power allocation decides the fraction of the information signal power to be consumed at the terminals in order to minimize the BER. Numerical results reveal that cooperation brings significant performance gains over direct transmission. We further provide comparisons of two relaying techniques under consideration and discuss the effect of clipping noise on the error rate performance.

In this report, an adaptive modulated orthogonal frequency division multiplexing (OFDM) scheme that provides efficient data transmission for correlated receiver antenna arrays is proposed. Previously reported adaptive modulation schemes generally select the modulation scheme based on the estimated carrier-to-noise ratio (CNR) on each subcarrier. However, in antenna array communication in addition to the CNR, the spatial fading correlation should also be considered to evaluate the system performance. Especially, when the Time Shifted Sampling (TSS) technique is applied which overcomes the spatial correlation for some subchannels of an OFDM symbol, the spatial correlation varies dramatically through subcarriers. In this work, modulation scheme is selected based on the CNR and the spatial correlation coefficient for each subcarrier when the TSS technique is employed at the receiver. Numerical results through computer simulation show that the proposed scheme outperforms the conventional systems in achieving a target BER and establishing reliable communication while having almost the same transmission rate.

In this paper, an interference suppression scheme by MMSE combining in OFDM-antenna array with time shifted sampling (TSS) is proposed. An array antenna at a base station has been thoroughly investigated to increase the uplink capacity. The performance of the uplink is not only limited by the correlation between the antenna elements, which strongly depends on the spatial aspects of the channel, as well as the interference from the terminals. Numerical results through computer simulation show that the proposed scheme improves bit error rate performance because of interference suppression by MMSE combining and diversity reception by TSS at the same time.

An essential condition for diversity reception is that the fading distributions between the individual received signals of an antenna array are uncorrelated. In this paper, a new technique to improve the performance of transmission with the correlated Rayleigh-fading signals is proposed. In conventional array systems, individual receivers start sampling the received signals at the same time with the same sampling rate. On the other hand, in the proposed scheme, the received signals are again sampled with the same rate, however the sampling points are shifted in each receiver. Numerical results through computer simulation show that with the correlated received signals, by applying the proposed technique the correlation can be reduced to a sufficient level for diversity reception.