M. Arif Khan

A Synopsis of Simulation and Mobility Modeling in Vehicular Ad-hoc Networks (VANETs)

Vehicular communication is considered to be a backbone for many critical safety applications. In order to achieve a better implementation of any vehicular communication scenario, an efficient, accurate and reliable simulator is essential. Various open source and commercial simulating tools are available for this purpose. One of the key issues in this regard is the selection of a reliable simulator which implements all standard algorithms and paradigms giving accurate results. In this paper, we first present IEEE standard and protocols for vehicular communication, IEEE 802.11p and IEEE 1609.x, also known as WAVE protocol stack. The paper then discusses the necessary requirements for a generic discrete event simulator which can be used to simulate Vehicular Ad-hoc Networks. Since not all the network simulators can be used in the scenario of vehicular communication, we highlight the key features of some network simulators in the context of vehicular ad-hoc networks. The paper also highlights some of the implementation limitations in these simulators. Furthermore, the paper presents a discussion on traffic simulators by emphasizing on the underlying mobility models used in order to generate the realistic traffic patterns. A comparative study of both network and traffic simulators show the pros and cons of these simulation tools. The paper suggests the appropriate choice of a network simulator to be used as a VANET simulator.

Alpha-Rule Scheduling for MIMO Broadcast Wireless Channels with Linear Receivers

This paper considers a multi-user MIMO broadcast wireless channel where a MAC layer scheduler is used to improve system efficiency and provide quality of service improvements (fairness) to users. In particular, an alpha-rule scheduler is considered that uses rate estimates from users to make user selection decisions. The main challenge faced by the scheduler is that users need to estimate the interference caused by other users before transmit antenna allocation has been done. The paper examines two techniques for estimating data rates. The first technique assumes no interfering signals are present and the second technique includes the dominant interfering signal. We show that the scheduler can be tuned to significantly increase fairness with little reduction in mean sum rate to users and we show that both mean sum rate and fairness can be increased by including the dominant interfering signal to estimate data rates.

A Multiple Ring Slots Ultra Wide-Band antenna (MRS-UWB) for biomedical applications

These days, breast tumor is a second leading cause of cancer in women after the lung cancer. Early detection tests for breast cancer save thousands of lives each year. One popular way to detect the tumor is microwave imaging because of its non-ionizing and low cost process. Also, an antenna is a key component of microwave imaging. In this paper, a study of Multiple Ring Slots Ultra-WideBand (MRS-UWB) patch antenna is presented for breast cancer detection. The proposed antenna design is capable to detect the breast tumor with the improved characteristics compared to the other available designs in the literature. The proposed antenna with the ring slots is designed on FR-4 substrate and is fed through a microstrip line by optimizing the width and the position of the feed along with the width of the partial ground structure. According to −10dB bandwidth criteria, the proposed antenna offers promising performance of UWB design ranging from 2–12 GHz. From the results, it is shown that the maximum Return Loss (RL) occurred at 4.3 GHz, 5.8 GHz, 8 GHz and 11.6 GHz. For the entire UWB range, the VSWR is ≤ 2 that is one of the desired characteristic of an efficient design. It is worth noting that our proposed design is of low cost and easy to fabricate that makes it a favorable choice for medical applications. The proposed antenna is simulated and then fabricated to demonstrate the desired characteristics.

Cross layer routing for VANETs

Routing is an important and critical issue for successful transmission in Vehicular Ad-hoc Networks (VANETs). Most of the traditionally designed routing schemes are based on optimising their parameters individually in the existing VANET architecture. Such approaches may not result in an overall efficient system. Therefore, it is important to consider various parameters from multiple layers such as PHY and MAC, to optimise routing. In this paper while presenting a new cross-layer routing scheme, we subdivide the existing OSI model in three main layers. The routing scheme presented in this paper considers parameters from multiple layers simultaneously to achieve the routing objectives. We argue that the proposed routing scheme results in less packet drops and comparatively smaller delay in packet transmission.

Wireless transmission modeling for Vehicular Ad-hoc Networks

Modeling wireless transmission in stringent networks such as VANETs is a challenging task. This requires mathematically incorporating all the environmental effects present within such a dynamics atmosphere. The key attributes to model the wireless channel are physical constraints inherent to such networks such as lack of permanent infrastructure, limited knowledge in relation to the position of vehicles as well as interference that effects the strength of receive signal at each position of vehicles. The selection of an appropriate transmission model plays a key role in the routing decisions for VANET. This paper investigates such wireless transmission models for vehicular communication. It identifies the situations where a particular model can be beneficial. The paper also provides an insight into the use of practical parameters in theoretical transmission models. An analysis of the proposed transmission model is presented. The performance of different transmission models in terms of receive signal strength (RSS) is also presented. These results help to select a transmission model that suits best to a particular VANET communication scenario.

A wideband slot-coupled inverted microstrip patch antenna for wireless communications

A wideband slot-coupled superstrate based microstrip patch antenna is presented for wireless communications. The antenna is designed by employing a stacked geometry and inverted configuration of patch antenna. The circular patch antenna design is used for the particular design. The proposed antenna is able to operate for a wide range of frequencies, i.e., 19.5-22.6 GHz. Through simulation, the impedance bandwidth is achieved up to 15% having VSWR less than 2. By employing a technique of thicker substrate and stacked geometry, maximum peak gain of 8.5 dBi of the antenna is achieved. The paper also presents a parametric study showing that the impedance of patch decreases with the change in patch dimension which also effects VSWR and gain of the antenna.

Quality of service based cross layer routing protocol for VANETs

Achieving high Quality of Service (QoS) in routing is one of the major issues to be tackled in VANET. This is primarily due to the interference among vehicles and the objects present within the transmission environment. This also causes rapid degradation in transmitted signal and affects the overall system throughput. As a result, the system performance parameters such as delay, packet drop ratio and efficiency are highly effected. This paper proposes a Cross-Layer Decision Based (CLDB) routing protocol that necessitates to choose the best path for routing the packets to meet promised QoS requirements. The protocol considers the parameters from both PHY and MAC layers to optimise the routing objective. Performance of the proposed algorithm is evaluated using extensive computer simulations.

A multi-hop cross layer decision based routing for VANETs

Abstract In recent years, vehicular ad-hoc networks have emerged as a key wireless technology offering countless new services and applications for the transport community. Along with many interesting and useful applications, there have been a number of design challenges to create an efficient and reliable routing scheme. A conventional design approach only optimizes routing schemes without considering the constraints from other network layers. This may result in an under-performing routing mechanism. In this paper we present the design of a multi-hop cross-layer routing scheme that utilises beaconing information at the physical layer as well as queue buffer information at medium access control layer to optimise routing objectives. In particular, the proposed scheme integrates channel quality information and queuing information from other layers to transmit data. Using simulations as well as analytical studies we have presented results of our proposed scheme and have done a thorough comparison with existing approaches in this area. The results highlight better performance of the proposed cross-layer structure as compared to other conventional single layer approaches.

Optimizing Broadcasting Scheme for VANETs Using Genetic Algorithm

Broadcasting is one of the communication mechanism utilised in VANET architecture through which an up-to-date traffic data can be disseminated among the commuters and this can help reduce traffic jams/congestions. Broadcasting storm (broadcasting) is considered to be an NP-hard problem consisting of multiple objectives. Conventional techniques use Multi-Objective Genetic Algorithms (MOGAs) to solve such optimization problems. Performance of such algorithms depend on fitness function. In this paper, we propose a novel and improved fitness function for MOGA to solve the broadcasting problem in VANETs. The proposed fitness function has enhanced the rate of evolution, resulting in more generations and producing better optimization results. We consider a highway scenario for simulation to evaluate performance of the proposed solutions. We compare the results of the proposed algorithm with existing state-of-the-art technique [1]. Our results show improvement in reduction of the propagation time and the number of retransmissions compared to the previous solution.

A practical miniature antenna design for future internet of things enabled smart devices

Internet of Things (IoT) will play an important role in the contemporary communication networks. In this modern and future communication paradigm hundreds of different smart Internet enabled devices will communicate with each other continuously. For such communication networks and smart devices, apart from the sophisticated communication protocols, efficient hardware will also play a very crucial role. Antennas being at the front end of communication, are one of the important components of such a hardware. The antennas for IoT applications are required to exhibit three important characteristics, namely; (i) small size, (ii) energy efficiency and (iii) ability to operate in multi antenna environment. In this paper, we propose an antenna design that fulfils these important requirements. We propose an ultra-wideband antenna that is small in size compared to other existing designs, with dimensions 24 × 28 mm2, that can easily fit in hand-held mobile devices. Measured results indicate that the antenna not only has a very small power return loss but also exhibits a low mutual coupling that highlights that the proposed design is capable to operate in multiple-input multiple-output (MIMO) configurations.