Fast Localization Using Robust UWB Coding in Wireless Sensor Networks

Abstract—Localization has many important applications in wireless sensor networks. A variety of wireless technologies, such as acoustic, infrared, and ultra-wide band (UWB) media have been applied for localization purposes. This paper consists of two parts. The first part presents new UWB-based communication protocols for received signal strength (RSS) information collection, namely, a robust UWB coding method called U-BOTH (UWB based on Orthogonal Variable Spreading Factor and Time Hopping), an ALOHA-type channel access method and a message exchange protocol to collect location information. The second part presents the localization algorithm, which is applied in coal mine environments. The localization algorithm first derives the corresponding UWB path loss model, then applies the maximum likelihood estimation (MLE) method to compute the distances to the reference sensors using the RSS information, and to estimate the coordinate of the moving sensor using least squares (LS) method. The performance of the system is validated using theoretic analysis and simulations. Results show that U-BOTH transmission technique can effectively reduce the bit error rate under the path loss model, and the corresponding ranging and localization algorithms can accurately compute object locations in coal mine environments. Keywords-Coal mine channel modeling; orthogonal variable spreading factor (OVSF); time hopping (TH); ultra-wide band (UWB); localization; ranging; I

Enhancing the energy efficiency of ultra wideband (UWB) based media access control (MAC) protocols in mobile ad-hoc networks (MANETs) through the use of steerable directional antenna

Energy efficiency contributes to the survival of nodes in Mobile Ad Hoc Networks (MANETs). The use of directional antennas can conserve energy due to the increased gain and directed transmission towards specific point in space. Directional antennas also resolve many issues associated with interference from different points within the network. Despite the vast body of work in this area, research on the way directional antennas access the wireless medium specific to Ultra-WideBand (UWB) systems have not gained wide attention. The aim of this research is to design, implement and test an improved Medium Access Control (MAC) protocol for UWB systems in order to minimise energy consumption in MANET’s through the application of directional antenna. Building on initial testing in the QualNet Simulator; a new MAC protocol design was modelled on the IEEE 802.15.3 standard using directional antennas. Specific simulation parameters were changed based on the antenna angle of transmission and reception, with a view to optimising power consumption in the network. Both analytical and simulation techniques were then used for testing and validating the improved protocol design. Initial testing of the proposed model was completed analytically using numerical values from justifiable literature in order to validate the protocol. A comparative analysis was then conducted which considered omni-directional antenna, the Ultra-wideband Concepts for Ad hoc Networks (UCANs) approach, and the proposed MAC design. The results show that the proposed MAC protocol design outperforms other approaches in both energy conservation and data throughput in MANETs. Final testing then considered a descriptive framework which was used to highlight the difference between the proposed MAC protocol and existing designs. A physical (PHY) layer was implemented in MATLAB prior to integrating it within the ns-3 simulator. The simulated results showed that by combining the proposed UWB-MAC protocol, with directional antenna, a significant amount of energy can be conserved to a level better than existing UWB MAC protocols. This work offers a contribution to knowledge by providing a proof-of-concept approach for optimising energy consumption, through modifying existing MAC protocols in comparison to other UCANs using directional antenna techniques