Evaluating the Impact of Transmission Range on the Performance of VANET

Recently, interest in the field of Vehicular Ad-hoc Networks (VANETs) has grown among research community to improve traffic safety and efficiency on the roads. Despite the many advantages, the transmission range in vehicular network remains one of the major challenges due to the unique characteristics of VANETs such as various communication environments, highly dynamic topology, high node mobility and traffic density. The network would suffer from a broadcast-storm in high vehicular density when a fixed transmission range in VANET is used, while in sparse vehicular density the network could be disconnected frequently. In this paper, we evaluated the impact of different transmission ranges and number of flows formed between vehicles in a highway scenario using AODV as routing protocol. In order to validate the simulation of VANET, traffic and network simulators (SUMO & NS-2) have been used. The performance was evaluated in terms of packet delivery ratio and end-to-end delay. The simulation results have shown that better performance was achieved in term of higher PDR and lower end-to-end delay for less than 500 meters transmission range. On the contrary, the PDR started to decrease and end-to-end delay increased when the transmission range exceeded 500 meters. The performance degraded as the number of flows increased

Adaptive spatial mode of space-time and spacefrequency OFDM system over fading channels

In this paper we present a 2 transmit 1 receive (1 Tx : 1 Rx) adaptive spatial mode (ASM) of space-time (ST) and space-frequency (SF) orthogonal frequency division multiplexing (OFDM). At low signal to noise ratio (SNR) we employ ST-OFDM and switch to SF-OFDM at a certain SNR threshold. We determine this threshold from the intersection of individual performance curves. Results show a gain of 9 dB (at a bit error rate of 10-3) is achieved by employing adaptive spatial mode compared to a fixed ST-OFDM, almost 6 dB to fixed SF-OFDM, 4 dB to Coded ST-OFDM and 2 dB to a fixed coded SF-OFDM, at a delay spread of 700 ns

A Comprehensive Performance Analysis of IEEE 802.11p based MAC for Vehicular Communications Under Non-saturated Conditions

Reliable and efficient data broadcasting is essential in vehicular networks to provide safety-critical and commercial service messages on the road. There is still no comprehensive analysis of IEEE 802.11p based MAC that portrays the presence of buffer memory in vehicular networks. Besides, most of the analytical works do not fulfill some of the IEEE 802.11p specifications, such as short retry limit and back-off timer freezing. This paper proposes a 1-D and 2-D Markov model to analyze mathematically IEEE 802.11p based MAC for safety and non-safety messages respectively. The work presented in this paper takes into account the traffic arrival along with the first-order buffer memory and freezing of the back-off timer as well, to utilize the channel efficiently and provide higher accuracy in estimation of channel access, yielding more precise results of the system throughput for non-safety messages and lower delay for safety messages. Furthermore, back-off stages with a short retry limit were applied for non-safety messages in order to meet the IEEE 802.11p specifications, guaranteeing that no packet is served indefinitely, avoiding the overestimation of system throughput. A simulation was carried out to validate the analytical results of our model

An Accurate Performance Analysis of Hybrid Efficient and Reliable MAC Protocol in VANET under Non-saturated Conditions

Vehicular Ad Hoc Networks (VANETs) is a technology supporting two types of applications, safety and service applications with higher and lower priorities respectively. Thereby, Medium Access Control (MAC) protocol is designed to provide reliable and efficient data broadcasting based on prioritization. Different from the IEEE 1609.4 (legacy), HER-MAC protocol is a new multi-channel MAC proposed for VANETs, offering remarkable performance with regards to safety applications transmission. This paper focuses on the analysis of packet delivery ratio of the HER-MAC protocol under non-saturated conditions. 1-D and 2-D Markov chains have been developed for safety and non-safety applications respectively, to evaluate mathematically the performance of HER-MAC protocol. The presented work has taken into account the freezing of the backoff timer for both applications and the backoff stages along with short retry limit for non-safety applications in order to meet the IEEE 802.11p specifications. It highlights that taking these elements into consideration are important in modeling the system, to provide an accurate estimation of the channel access, and guarantees that no packet is served indefinitely. More precise results of the system packet delivery ratio have been yield. The probability of successful transmission and collisions were derived and used to compute the packet delivery ratio. The simulation results validate the analytical results of our models and indicate that the performance of our models outperformed the existing models in terms of the packet delivery ratio under different number of vehicles and contention window

Modeling and analysis of IEEE 1609.4 MAC in the presence of error-prone channels

Vehicular Ad Hoc Networks (VANETs) have been developed to improve the safety, comfort and efficiency of driving on the road. The IEEE 1609.4 is a standard intended to support multi-channel in VANETs. These channels include one control channel for safety applications and six service channels for service applications. However, there is still no comprehensive analysis for the average delay and system throughput of IEEE 1609.4 MAC in VANETs considering error-prone channel under non-saturated conditions. In this paper, we propose an analytical models based on 1-D and 2-D Markov chain to evaluate the performance analysis of IEEE 1609.4 MAC in the presence of error-prone channels. Besides, freezing of the back-off timer is taken into consideration to provide an accurate estimation of access to the channel. The simulation results have been carried out to validate the analytical results of our model. The results show that the performance of our model outperforms the existing model in terms of packet delivery ratio and average delay of safety packets over CCH, and system throughput of service packets over SCHs

Competitive anxiety levels of track and field athletes in rural area of Sabah

The purpose of the study was to examine the competitive anxiety level of track and field athletes in remote areas of Sabah. A total of 213 male athletic athletes aged between sixteen to eighteen years have participated in this study. The participants' competitive anxiety levels before competition were assessed and classified into three categories: cognitive anxiety, somatic anxiety, and self-confidence. The Competitive State Anxiety Inventory (CSAI-2) was utilized in this study, and participants completed the questionnaire 60 minutes before the competition began. The data were analyzed by using a one-way analysis of variance (ANOVA). The results showed that field athletes were significantly better compared to track athletes in cognitive anxiety and self-confidence, (p 0.05). The study found that field events athletes can cope with anxiety better than track events athletes. Hence, it was essential for track and field athletes to get a proper training program regarding their psychological demands before the competition. Low anxiety and high confidence levels can contribute to improved performance in athletes

Competitive anxiety levels of track and field athletes in rural area of Sabah

The purpose of the study was to examine the competitive anxiety level of track and field athletes in remote areas of Sabah. A total of 213 male athletic athletes aged between sixteen to eighteen years have participated in this study. The participants' competitive anxiety levels before competition were assessed and classified into three categories: cognitive anxiety, somatic anxiety, and self-confidence. The Competitive State Anxiety Inventory (CSAI-2) was utilized in this study, and participants completed the questionnaire 60 minutes before the competition began. The data were analyzed by using a one-way analysis of variance (ANOVA). The results showed that field athletes were significantly better compared to track athletes in cognitive anxiety and self confidence, (p 0.05). The study found that field events athletes can cope with anxiety better than track events athletes. Hence, it was essential for track and field athletes to get a proper training program regarding their psychological demands before the competition. Low anxiety and high confidence levels can contribute to improved performance in athletes

Relative age effect in U-16 Asian Championship Soccer Tournament

Athletes born at the beginning of the year may present advantages in terms of physical characteristics, motor ability or cognitive knowledge that could increase their chances for selection against their peers. This circumstance could lead to the over-representation of older athletes in an age-defined competition, a phenomenon commonly referred to as relative age effect (RAE). Although, a number of studies have demonstrated that RAE is apparent in youth soccer, such studies rarely investigate the performance advantage that likely exists across the birth month of the athletes. The current study aims to determine the presence of RAE in the under 16 Asian Football Confederation Championship (AFC); investigate the effect of RAE on the team qualification success; as well as ascertain the existence of RAE in choice of playing position amongst the soccer players. Data for the 2018 AFC under 16 qualifications matches were obtained from the AFC. A total of 719 players from 32 countries participated in the qualification competitions. Chi-square for goodness fit is used to determine the existence of the RAE across the players’ month of birth while logistic regression is applied to analyze the differences of the quartiles’ distribution with respect to the quartile, qualification status (qualifier or non-qualifier) as well as the playing position of the players. The results demonstrate the presence of RAE in the AFC under 16 soccer tournaments [χ2(4) = 21.53; p < 0.001] with the largest number of older players dominating the qualified team. Likewise, a substantial difference is observed with regards to the quartile and various playing positions of the players at p < 0.05

Gross motor development among 7 – 9 years old children in Sabah

The aim of the study was to examine the gross motor development of children between 7-9 years old in Sabah. A total of 240 children (134 boys, 104 girls) participated in this study from 2 different location; rural and urban area. The children’s proficiency in motor skills was assessed with the Test of Gross Motor Development-2 (TGMD-2). The children performed two trials for each gross motor skill which has been divided into two subtests, locomotor and object control. The results showed that there was no significant difference between boys and girls in locomotor skills (p>0.05) but there was a significant difference in one of the object control skills (overarm throw) between boys and girls (p<0.05). There were significant differences between rural and urban children in locomotor skills (run, gallop, and slide) and object control (catch and underarm roll) (p<0.05). The current study demonstrated that children in rural schools displayed better fundamental motor skills development compared to children in urban schools