ZigBee-assisted ad-hoc networking of multi-interface mobile devices

Wireless ad hoc network is decentralized wireless network, which does not rely on a preexisting infrastructure, such as routers in wired networks or access points in managed (infrastructure) wireless networks. Instead, each node participates in routing by forwarding data for other nodes. The determination of which nodes forward data is made dynamically based on the network connectivity. Node density has a great impact on the performance and efficiency of wireless ad hoc networks by influencing some factors such as capacity, network contention, routing efficiency, delay, and connectivity. On one hand, maintaining stable connectivity is a big challenge for sparsely deployed and highly dynamic ad hoc wireless network. Vehicle ad hoc network (VANET) which consists of highly mobile vehicles with wireless interfaces is one type of such network, especially in rural areas where vehicles traffic are very sparse. One of the most important applications built on top of VANET is the safety application. In VANET safety applications, source vehicles that observe accidents or some other unsafe conditions of the roads generate warning messages about the conditions, and propagate the warning messages to the following vehicles. In this way, the following drivers have the opportunity to do some necessary action before they reach the potential danger zone to avoid accident. The safety application requires timely and accurate warning message detection and delivery. However, recent researches have shown that sparse and highly dynamic vehicle traffic leads network fragmentation, which poses a crucial research challenge for VANET safety application. On the other hand, reducing contention and thus maximizing the network throughput is also a big challenge for densely deployed ad hoc wireless network, especially when many devices are located in a small area and each device has heavy duty message to transmit. The WiFi interface perhaps is the most common interface found in mobile devices for data transfer as it provides good combination of throughout, range and power efficiency. However, the WiFi interface may have to consume a large amount of bandwidth and energy for contention and combating collision, especially when mobile devices located in a small area all have heavy traffic to transmit. Meanwhile, ZigBee is an emerging wireless communication technology which supports low-cost, low-power and short-range wireless communication. Nowadays, it has been common for a mobile device, such as smart phone, PDA and laptop, to have both WiFi and Bluetooth interfaces. As the ZigBee technology becomes more and more mature, it will not be surprising to see the ZigBee interface commonly embedded in mobile devices together with WiFi and Bluetooth interfaces in the near future. The co-existence of the ZigBee and the WiFi interfaces in the same mobile device inspires us to develop new techniques to address the above two issues. Specifically, this thesis presents two systems built based on ZigBee-assisted ad-hoc networking of multi-interface mobile devices. In order to achieve stable connectivity in a sparse and dynamic VANET, the first system integrates a network of static roadside sensors and highly mobile vehicles to improve driving safety. In order to reduce contention in a densely deployed ad hoc wireless network, the second system assists WiFi transmission with ZigBee interface for multi-interface mobile devices. Extensive implementations and experiments have been conducted to demonstrate the effectiveness of our proposed systems

The Impact of Transmission Range Over Node Density in Vehicular Ad Hoc Network (Vanet) With Obstruction of Road Infrastructure

Vehicular ad hoc networks have the characteristic to of experiencing rapid change of network topology and mobility. Importantly, vehicular networks are required to deal with different network densities in order to provide efficient routing and data dissemination. These are some of the main characteristic that can affect the performance of the network immensely. The main issue that became the driving factor in implementing this project is the need to fill these gaps of understanding the behavioral of vehicular network performance when they are restrained by certain network condition which in this case, dealing with an obstruction of road infrastructure with varying transmission range and node density. In order to understand this problem, we identify the objectives of this project to integrate SUMO/MOVE (a vehicular traffic generator) into NS-2 to simulate a realistic vehicular ad hoc network environment and to study the performance of the network when the being conditioned into varying settings of transmission range and node density. In this project, we evaluate the network performance of VANETs in a highway environment using SUMO traffic simulator and network simulator, NS-2 which specifically focusing at the toll booths by studying the effect of varying transmission range over node density. From the simulation results, we found out that the smaller transmission range will produce less throughput, higher end to end delay and also higher normalized routing load. Particularly in vehicular ad hoc network, a constant or a fixed transmission range is not efficient enough in maintaining the connectivity in the network. This is due to the unpredictable of traffic conditions in the network. In addition to this, by dynamically changing the transmission range according to its need, will offer the advantage of power saving and increase capacity

Performance enhancement of safety message communication via designing dynamic power control mechanisms in vehicular ad hoc networks

In vehicular ad hoc networks (VANETs), transmission power is a key factor in several performance measures, such as throughput, delay, and energy efficiency. Vehicle mobility in VANETs creates a highly dynamic topology that leads to a nontrivial task of maintaining connectivity due to rapid topology changes. Therefore, using fixed transmission power adversely affects VANET connectivity and leads to network performance degradation. New cross-layer power control algorithms called (BL-TPC 802.11MAC and DTPC 802.11 MAC) are designed, modeled, and evaluated in this paper. The designed algorithms can be deployed in smart cities, highway, and urban city roads. The designed algorithms improve VANET performance by adapting transmission power dynamically to improve network connectivity. The power adaptation is based on inspecting some network parameters, such as node density, network load, and media access control (MAC) queue state, and then deciding on the required power level. Obtained results indicate that the designed power control algorithm outperforms the traditional 802.11p MAC considering the number of received safety messages, network connectivity, network throughput, and the number of dropped safety messages. Consequently, improving network performance means enhancing the safety of vehicle drivers in smart cities, highway, and urban city. © 2020 Wiley Periodicals LLC

On Capacity and Delay of Multi-channel Wireless Networks with Infrastructure Support

In this paper, we propose a novel multi-channel network with infrastructure support, called an MC-IS network, which has not been studied in the literature. To the best of our knowledge, we are the first to study such an MC-IS network. Our proposed MC-IS network has a number of advantages over three existing conventional networks, namely a single-channel wireless ad hoc network (called an SC-AH network), a multi-channel wireless ad hoc network (called an MC-AH network) and a single-channel network with infrastructure support (called an SC-IS network). In particular, the network capacity of our proposed MC-IS network is $\sqrt{n \log n}$ times higher than that of an SC-AH network and an MC-AH network and the same as that of an SC-IS network, where $n$ is the number of nodes in the network. The average delay of our MC-IS network is $\sqrt{\log n/n}$ times lower than that of an SC-AH network and an MC-AH network, and $\min\{C_I,m\}$ times lower than the average delay of an SC-IS network, where $C_I$ and $m$ denote the number of channels dedicated for infrastructure communications and the number of interfaces mounted at each infrastructure node, respectively. Our analysis on an MC-IS network equipped with omni-directional antennas only has been extended to an MC-IS network equipped with directional antennas only, which are named as an MC-IS-DA network. We show that an MC-IS-DA network has an even lower delay of $\frac{c}{\lfloor \frac{2\pi}{\theta}\rfloor \cdot C_I}$ compared with an SC-IS network and our MC-IS network. For example, when $C_I=12$ and $\theta=\frac{\pi}{12}$, an MC-IS-DA network can further reduce the delay by 24 times lower that of an MC-IS network and reduce the delay by 288 times lower than that of an SC-IS network.Comment: accepted, IEEE Transactions on Vehicular Technology, 201

Multi-channel Wireless Networks with Infrastructure Support: Capacity and Delay

In this paper, we propose a novel multi-channel network with infrastructure support, called an \textit{MC-IS} network, which has not been studied in the literature. To the best of our knowledge, we are the first to study such an \textit{MC-IS} network. Our \textit{MC-IS} network is equipped with a number of infrastructure nodes which can communicate with common nodes using a number of channels where a communication between a common node and an infrastructure node is called an infrastructure communication and a communication between two common nodes is called an ad-hoc communication. Our proposed \textit{MC-IS} network has a number of advantages over three existing conventional networks, namely a single-channel wireless ad hoc network (called an \textit{SC-AH} network), a multi-channel wireless ad hoc network (called an \textit{MC-AH} network) and a single-channel network with infrastructure support (called an \textit{SC-IS} network). In particular, the \textit{network capacity} of our proposed \textit{MC-IS} network is $\sqrt{n \log n}$ times higher than that of an \textit{SC-AH} network and an \textit{MC-AH} network and the same as that of an \textit{SC-IS} network, where $n$ is the number of nodes in the network. The \textit{average delay} of our \textit{MC-IS} network is $\sqrt{\log n/n}$ times lower than that of an \textit{SC-AH} network and an \textit{MC-AH} network, and $\min(C_I,m)$ times lower than the average delay of an \textit{SC-IS} network, where $C_I$ and $m$ denote the number of channels dedicated for infrastructure communications and the number of interfaces mounted at each infrastructure node, respectively.Comment: 12 pages, 6 figures, 3 table

Optimizing the beacon exchange rate for proactive autonomic configuration in ubiquitous MANETs

Proactive self-configuration is indispensable for MANETs like ubiquitous sensor networks (USNs), as component devices of the network are usually exposed to natural or man-made disasters due to the hostile deployment and ad hoc nature of the USNs. Network state beacons (NSBs) are exchanged among the key nodes of the network for crucial and effective monitoring of the network for steady state operation. The rate of beacon exchange (F/sub E/) and its contents, define the time and nature of the proactive action. Therefore it is very important to optimize these parameters to tune the functional response of the USN. This paper presents a comprehensive model for monitoring and proactively reconfiguring the network by optimizing the F/sub E/. The results confirm the improved throughput while maintaining QoS over longer periods of network operation