The expansion of telecommunication providers and their efforts to expand network coverage in Sri Lanka has led to an alarming increase in Radio Frequency (RF) radiation exposure. This heightened exposure has raised concerns about its potential adverse effects on human health. Despite the country's growing number of cancer cases, no apparent cause has been identified. This research aims to identify areas exposed to harmful RF radiation levels through the innovative application of blockchain technology. The methodology involves measuring RF radiation in densely populated locations and implementing a blockchain-based spectral power misuse detection system via mobile networks. This system notifies users of harmful RF radiation exposure through an Android app. In this system, the collected data is first clustered and then aggregated after removing potential “outlier” data points, before adding the data to the blockchain. These two steps are important to increase the performance of the blockchain network, which is evaluated based on performance metrics, including success rate, latency, throughput, and memory usage of the blockchain. The data is analyzed in the blockchain network to detect if there are harmful signal levels in the country and to alert the users if there are any.

Prioritization of data streams in cellular vehicle-to-everything (C-V2X) may lead to unfavorable packet delays in low-priority streams. This paper studies allocating multiple candidate single-subframe resources (CSRs) per vehicle as a solution. It proposes a methodology to determine the number of CSRs for each vehicle based on the total number of neighboring vehicles, and to assign the multiple data streams among them for simultaneous transmission. The numerical results highlight the achievable delay gains of the proposed approach, and its negligible impact on packet collisions.

Supporting parallel multi-priority data streams is vital for maintaining the quality of service (QoS) in vehicle-to-everything (V2X) communication. Hence, the European telecommunications standard institute (ETSI) has defined four packet types, with varying priority levels, to be used as broadcast packets in such communication. This paper studies the medium access control (MAC) layer performance of IEEE 802.11p and cellular-V2X (C-V2X) Mode 4 using discrete-time Markov chain (DTMC) based models, while considering parallel multi-priority data streams. The overall model consists of four queue models with their respective traffic generators, which are appropriately linked with the DTMCs modeling the MAC layer operations of IEEE 802.11p and C-V2X Mode 4. Closed-form solutions for the steady-state probabilities of the models are obtained, which are then utilized to derive expressions for key performance indicators at the MAC layer. Numerical results are provided to draw insights on the MAC layer performance of the two technologies. IEEE 802.11p is comparatively superior in average delay, and at maintaining fairness among multi-priority data streams, whereas C-V2X Mode 4 exhibits better collision resolution, which leads to its higher throughput. The paper also includes design insights on possible performance enhancements for future releases.

Vehicle-to-vehicle (V2V) communication plays a pivotal role in intelligent transport systems (ITS) with cellular-vehicle to everything (C-V2X) and IEEE 802.11p being the two competing enabling technologies. This paper presents multi-dimensional discrete-time Markov chain (DTMC) based models to study the medium access control (MAC) layer performance of the IEEE 802.11p standard and C-V2X Mode 4, considering periodic cooperative awareness messages (CAMs) and event-driven decentralized environmental notification messages (DENMs). Closed-form solutions for the steady-state probabilities of the models are obtained, which are then utilized to derive expressions for several key performance metrics. Numerical results are provided to draw insights on the performance. In particular, a performance comparison between IEEE 802.11p and C-V2X Mode 4 in terms of the average delay, the collision probability, and the channel utilization is presented. The results show that IEEE 802.11p is superior in terms of average delay, whereas C-V2X Mode 4 excels in collision resolution. The paper also includes design insights on possible future MAC layer performance enhancements of both standards.

The enhanced distributed channel access (EDCA) mechanism enables IEEE 802.11p to accommodate differential quality of service (QoS) levels in vehicle-to-vehicle (V2V) communications, through four access categories (ACs). This paper presents multi-dimensional discrete-time Markov chain (DTMC) based model to study the effect of parallel operation of the ACs on the medium access control (MAC) layer performance of ITS-G5 IEEE 802.11p. The overall model consists of four queue models with their respective traffic generators, which are appropriately linked with the DTMCs modeling the operation of each AC. Closed-form solutions for the steady-state probabilities of the models are obtained, which are then utilized to derive expressions for key performance indicators at the MAC layer. An application for a highway scenario is presented to draw insights on the performance. The results show how the performance measures vary among ACs according to their priority levels, and emphasize the importance of analytical modeling of the parallel operation of all four ACs.

This paper proposes a multi-dimensional Markov model to evaluate the medium access control (MAC) layer performance of 3GPP cellular vehicle to everything (V2X) Mode 4. The Mode 4 specifications enable quality of service guarantees in a decentralized manner, without the connectivity of a cellular base station, and therefore, ideal for V2X messaging in intelligent transportation systems (ITS). To this end, periodic cooperative aware messages (CAMs) and event triggered decentralized environmental notification messages (DENMs) are considered in the paper. The discrete time Markov model consists of a node model, a queue model, and traffic generators for CAM and DENM packets that are dependent and solved in closed form and iteratively. The model is applied to a highway scenario to provide insights on the average delay, the collision probability, and the channel utilization in Mode 4. The results show that Mode 4 has been partially over-specified for ITS applications and able to serve CAMs and DENMs conveniently. However, there exists locally optimal combinations of CAM and DENM intervals that can lead to lower average delay.

To address the challenge of ever-growing data rate demand and benefit from the popularity of WiFi capability in mobile phones, 3GPP is studying techniques which enable the coexistence of WiFi and LTE in the unlicensed band, known as LTEU. Two flavors of the listen before talk (LBT) principle, referred to as load based equipment (LBE) and frame based equipment (FBE), are recommended by 3GPP. In this paper, we investigate two enhanced FBE mechanisms, i.e., 1) enhanced FBE (E-FBE); and 2) backoff and idle time reduction FBE (BITR-FBE) for the purpose of improving FBE. After presenting the idea of E-FBE, we propose BITR-FBE which can further improve throughput, shorten delay and reduce energy consumption of LTE-U or WiFi devices. The performance of these both mechanisms is evaluated through Markov modeling and simulations with respect to throughput, delay, energy consumption as well as transmission opportunities under both homogeneous and heterogeneous network scenarios.

To address the burgeoning demand for mobile data, 3GPP is actively studying the capability of operating LTE in the unlicensed band, referred to as LTE-U. One of the main challenges of this approach is to maintain better coexistence between WiFi and LTE-U devices. To enable the coexistence, the listen before talk (LBT) principle has been adopted for LTE-U medium access with two flavors of mechanisms, i.e., load based equipment (LBE) and frame based equipment (FBE) access. In this paper, we consider the FBE mechanism and enhance its performance by introducing a backoff procedure for LTE devices. We investigate the original FBE mechanism defined by 3GPP and the enhanced FBE (E- FBE) mechanism from our earlier work. Then we propose a novel FBE mechanism by both enabling a backoff approach for access contention and eliminating the unnecessary waiting time for nodes which failed in previous transmission contention. Furthermore, we compare the performance of these three mechanisms with respect to four parameters. Numerical results based on simulations demonstrate that the proposed mechanism outperforms the other two in terms offairnessindex,transmissionopportunities,collisio nprobability, as well as transmission delay.

Due to limited energy capacity in mobile devices, energy harvesting is regarded as a promising technology for lifetime extension in device-to-device (D2D) communication. However, medium access control (MAC) protocols designed for D2D communication intrinsically do not consider the existence of harvested energy. In this paper we study four backoff (BO) algorithms, among which one algorithm is proposed to enhance the BO selection based on energy harvesting rate and residual energy of devices. Simulations are performed in order to assess how the proposed algorithm can extend the lifetime of a D2D communication network as well as to provide fair channel access opportunities among devices.