Cognitive radio network in vehicular ad hoc network (VANET): a survey

Cognitive radio network and vehicular ad hoc network (VANET) are recent emerging concepts in wireless networking. Cognitive radio network obtains knowledge of its operational geographical environment to manage sharing of spectrum between primary and secondary users, while VANET shares emergency safety messages among vehicles to ensure safety of users on the road. Cognitive radio network is employed in VANET to ensure the efficient use of spectrum, as well as to support VANET’s deployment. Random increase and decrease of spectrum users, unpredictable nature of VANET, high mobility, varying interference, security, packet scheduling, and priority assignment are the challenges encountered in a typical cognitive VANET environment. This paper provides survey and critical analysis on different challenges of cognitive radio VANET, with discussion on the open issues, challenges, and performance metrics for different cognitive radio VANET applications

Performance modelling of adaptive VANET with enhanced priority scheme

In this paper, we present an analytical and simulated study on the performance of adaptive vehicular ad hoc networks (VANET) priority based on Transmission Distance Reliability Range (TDRR) and data type. VANET topology changes rapidly due to its inherent nature of high mobility nodes and unpredictable environments. Therefore, nodes in VANET must be able to adapt to the ever changing environment and optimize parameters to enhance performance. However, there is a lack of adaptability in the current VANET scheme. Existing VANET IEEE802.11p’s Enhanced Distributed Channel Access; EDCA assigns priority solely based on data type. In this paper, we propose a new priority scheme which utilizes Markov model to perform TDRR prediction and assign priorities based on the proposed Markov TDRR Prediction with Enhanced Priority VANET Scheme (MarPVS). Subsequently, we performed an analytical study on MarPVS performance modeling. In particular, considering five different priority levels defined in MarPVS, we derived the probability of successful transmission, the number of low priority messages in back off process and concurrent low priority transmission. Finally, the results are used to derive the average transmission delay for data types defined in MarPVS. Numerical results are provided along with simulation results which confirm the accuracy of the proposed analysis. Simulation results demonstrate that the proposed MarPVS results in lower transmission latency and higher packet success rate in comparison with the default IEEE802.11p scheme and greedy scheduler scheme

European polygenic risk score for prediction of breast cancer shows similar performance in Asian women

Abstract: Polygenic risk scores (PRS) have been shown to predict breast cancer risk in European women, but their utility in Asian women is unclear. Here we evaluate the best performing PRSs for European-ancestry women using data from 17,262 breast cancer cases and 17,695 controls of Asian ancestry from 13 case-control studies, and 10,255 Chinese women from a prospective cohort (413 incident breast cancers). Compared to women in the middle quintile of the risk distribution, women in the highest 1% of PRS distribution have a ~2.7-fold risk and women in the lowest 1% of PRS distribution has ~0.4-fold risk of developing breast cancer. There is no evidence of heterogeneity in PRS performance in Chinese, Malay and Indian women. A PRS developed for European-ancestry women is also predictive of breast cancer risk in Asian women and can help in developing risk-stratified screening programmes in Asia

Adaptive and Optimised Vehicular Ad Hoc Network with Cognitive Medium Access Control Layer

Vehicular Ad Hoc Network (VANET) technology is emerging as an ideal solution to enhance road driving experience through information sharing. The main purpose of VANET is to ensure road safety through efficient communication network between vehicles. However, VANET suffers from its inherent high mobility, ever changing nature of environment and communication interference which degrade the performance of the communication network and prevents successful data transmission. The current VANET employs mostly static parameters to improve data transmission. Despite the current efforts so far, VANET with static parameters are not adapted to the ever changing VANET environment, which makes VANET less adaptable and not optimized. Therefore the goal of this thesis is to propose solutions and techniques to optimize and adapt the VANET MAC to better suit VANET applications in the ever changing environment. All the proposed schemes presented in this thesis namely HaFL, MarPVS and MACVS, have been simulated in an urban area with the use of Omnet-4.2.2, Vehicles Network Simulation (Veins), Simulation of Urban Mobility (SUMO) and open google map application. Results show that the proposed schemes result in improvement in terms of latency, throughput and packet success rate, as compared to the default IEEE802.11p scheme and the current scheme in the literature. In summary, the thesis contribution includes derivation of new theorem, proofs and formula with the development of new techniques, algorithm and framework for VANET MAC. This research contributes to the improvement of VANET MAC performance through better adaptability and optimization