Highly dynamic geographical topology, two-direction mobility, and varying traffic density can lead to fairness issues in Vehicular Ad-hoc Networks (VANETs). The Medium Access Control (MAC) protocol plays a vital role in sharing the common wireless channel efficiently between vehicles in a VANET system. However, ensuring fairness between vehicles can be a challenge in designing MAC protocols for VANET systems. The existing protocol, IEEE 802.11 DCF, ensures that the packet transmission rate for a particular vehicle is directly proportional to the amount of time a vehicle spends within a service area, but it does not guarantee that faster vehicles will be able to send the minimum number of packets. Other existing MAC protocols based on IEEE 802.11 are able to provide a minimum amount of data transmission regardless of velocity, but are unable to provide an amount of data transmission that is more proportionate to the time a vehicle spends in the service area. To address the above limitations, we propose a Speed Aware Fairness Enabled MAC (SAFE-MAC) protocol that calculates the residence time of a vehicle in a service area by using mobility metrics such as position, direction, and speed to synthesize the transmission probability of each individual vehicle with respect to its residence time. This is achieved by dynamically altering the values of parameters such as minimum contention window, maximum backoff stage, and retransmission limit in the MAC protocol. We then develop an analytical model to compare the performance of our proposed protocol with contemporary MAC protocols. Numerical analysis results show that our proposed protocol significantly improves fairness among the speed-varying vehicles in VANET.
This article presents a comparative analysis of the properties of cotton yarn spun on aerodynamic compact spinning and open-end rotor spinning systems. Yarn samples with a linear density of 50 Tex, 37 Tex, 30 Tex, 25 Tex, and 20 Tex were spun both on the aerodynamic compact and rotor spinning systems using the same finisher drawn sliver of medium staple cotton which were produced by a specific mixing. The quality parameters such as mass variation, imperfection index, hairiness, and tensile behavior (strength in count strength product, elongation percentage) of the yarn samples were assessed and analyzed. The results revealed that aerodynamic compact spun yarn had a lower unevenness and mass variation, a higher imperfection in case of a finer count, less hairiness, higher tensile strength, and lower elonga-tion% compared to the open-end rotor spun yarn samples. Finally, pairedsamples t-test and regression analysis were carried out by using IBM SPSS 25 to check the significance of yarn quality parameters and correlation among them.
The recently released IEEE 802.15.6 standard specifies several physical (PHY) layers and medium access control (MAC) layer protocols for variety of medical and non-medical applications of Wireless Body Area Networks (WBAN). The medical applications of WBAN has several obligatory requirements and constrains viz. high reliability, strict delay deadlines and low power consumption. The standard IEEE 802.15.6 MAC scheme is not able to fulfil the all requirements of medical applications of WBAN. To address this issue we propose an IEEE 802.15.6-based MAC scheme that is the modification of superframe structure, user priorities and access mechanism of standard IEEE 802.15.6 MAC scheme. The proposed superframe has three access phases: random access phases (RAP), manage access phases (MAP) and contention access phase (CAP). The proposed four user priorities nodes access the channel during RAP using CAMA/CA mechanism with a large value of contention window. The proposed MAC scheme uses RTS/CTS access mechanism instead of basic access mechanism to mitigate the effect of hidden and expose terminal problem. Moreover, we develop an analytical model to evaluate the performance of proposed MAC scheme and solve the analytical model using Maple. The results show that the modified IEEE 802.15.6 MAC scheme achieve the better performance in terms of reliability, throughput, average access delay, energy consumption, channel utilization and fairness compared to standard IEEE 802.15.6 MAC scheme in E-health applications.
The field experiment was carried out during the period from July to November, 2013 at the research farm of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh to investigate the influence of nitrogen and phosphorus on the growth and yield of BRRI dhan57. The two factorial experiments were laid out in a Randomized Complete Block Design (RCBD) with three replications. Four levels of nitrogen N0: 0 kg N ha ) and treatment combination N2P2 (120 kg N and 35 kg P ha -1 ) whereas, the treatments N0, P0 and treatment combination N0P0 (without N and P) showed the smallest plant height in each case, respectively. Side by side, N2, P2 treatments and N2P2 treatment combination gave the maximum effective tillers hill -1 , highest length of panicle and the maximum filled grains panicle -1 . The highest 1000 grain weight (20.85 g), grain yield (4.95 t ha -1 ), straw yield (5.39 t ha -1 ) and biological yield (10.34 t ha -1 ) were found in the treatment combination N2P2 and also found highest in each individual under N2 and P2 treatments.
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