Multichannel cross-layer routing for sensor networks

This paper proposes a new decentralised multi-channel tree building protocol with a centralised controller for the Internet of Things. The protocol alleviates the effect of interference which results in improved network efficiency and stability, and link reliability. The proposal takes into account all available channels to utilise the spectrum and aims to use the spectrum efficiently by transmitting on several channels. The protocol detects which channels suffer interference and changes away from those channels. The algorithm for channel selection is a two-hop colouring protocol that reduces the chances of nearby nodes to transmit on the same channel. All nodes are battery operated except for the low power border router (LPBR). This enables a centralised channel switching process at the LPBR. The protocol is built based on the routing protocol for low power and lossy networks (RPL). In its initial phase, the protocol uses RPL's standard topology formation to create an initial working topology and then seeks to improve this topology by switching channels. The implementation and evaluation of the protocol is performed using the Contiki framework. The experimental results demonstrate an increased resilience to interference and significantly higher throughput making better use of the total available spectrum and link stability

Radio Network Planning and Propagation Models for Urban and Indoor Wireless Communication Networks

As the growing demand for mobile communications is constantly increasing, the need for better coverage, improved capacity, and higher transmission quality rises. Thus, a more efficient use of the radio spectrum and communication systems availability are required. This chapter presents EM propagation models most commonly used for the design of wireless communication systems, computer networks WLAN and WPAN for urban and/or in indoor environments. The review of commercial or University computer codes to assist design of WLAN and WPAN networks were done. An example of computer design and simulation of indoor Bluetooth and WLAN communication systems, in the building of Wroclaw University of Science and Technology, Wroclaw, Poland is shown in Chapter 8

Ultra-wideband systems exploiting orthonormal waveforms

textElectrical and Computer Engineerin

Sub-optimal Ultra-wide Band Receivers

Ultra-wide Band (UWB) has sparked a lot of interest lately from the industry and academia. The growing capacity of the wireless industry is requires a new communication system that satisfies the high data rate which does not interfere with existing RF systems. UWB promises to be this new technology. UWB also promises low power, low cost and flexibility. The UWB Channel opens up a huge new wireless channel with Giga Hertz Capacities as well as the highest spatial capacities measured in bits per hertz per square meter. When properly implemented UWB channel can share spectrum with traditional radio systems without causing harmful interference. In this thesis we studied and compared several reduced complexity sub-optimal Ultra-Wide Band receivers. These receivers include auto correlation receiver, the square value detector and the absolute value detector are studied. We consider OOK and PPM modulation schemes. We examine these schemes and the receivers on Gaussian and UWB indoor channels. We compare the performance with optimal receivers. A transmitter receiver system using 0.1us pulses implemented using existing hardware. A packet consisting of 24 bits were transmitted and the received signal could be verified in real time using a vector signal analyzer. The results show sub-optimal receivers provide a better trade off between robust, complexity and performance

Effective Scheduling Algorithms for Cross-Interference Mitigation in Heterogeneous Wireless Networks

Wireless networks are making life easier, smarter and more convenient. However, the well-known Carrier-sense multiple access with collision avoidance (CSMA/CA) mechanism is powerless when dealing with Cross-Technology Interference (CTI) between Wi-Fi and Low-Rate Wireless Personal Area Network (LR-WPAN), because of asymmetric transmission power, incompatible Clear Channel Assessment (CCA) and different timing parameters. Plenty of studies have shown that WiFi always has a higher priority to access the wireless medium and even block LR-WPAN transmission in the worst case. Our experiments confirm this point and conclude that Wi-Fi can interrupt LR-WPAN severely even block LR-WPAN traffic, while the interference from LR-WPAN to Wi-Fi is negligible. Different from other studies, this thesis presents a novel centralized scheduling mechanism in the time domain to harmonize coexistence of Wi-Fi and LR-WPAN, also refer to as time-slot based scheduling mechanism. The mechanism is achieved by introducing a new command frame, named Access Notification (AN), into the IEEE802.15.4 Medium Access Control (MAC) layer. Based on this mechanism, a static time-slot based scheduling algorithm is designed and evaluated on both real hardware-based system and NS-3 simulator. The result shows the algorithm improves LR-WPAN Packet Loss Rate (PLR) significantly but at the cost of reducing Wi-Fi throughput. In order to maximize performance, based on slot-based congestion indicator (CI) that is proposed and defined to tell whether an allocated time slot is adequate for data transmission or not, we further design an adaptive time-slot based scheduling algorithm. The evaluation shows that the adaptive algorithm covers the shortage of the static algorithm and offers a distinct improvement on LR-WPAN Packet Transmission Rate (PTR)