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Most localization algorithms in wireless sensor networks rely on a few reference nodes with known locations to estimate the locations of unknown nodes. The locations of reference nodes can be either manually configured or, more practically, obtained by means of some satellite-based positioning system(s). However, satellite-based locations may be inaccurate and imprecise, which results in reduced location accuracy of localization algorithms. This paper proposes a peer-to-peer cooperative GNSS-based localization algorithm for stationary reference nodes to improve their relative location accuracy and precision. The algorithm applies simple statistical methods and GNSS-based information from multiple reference nodes within a WSN in a peer-to-peer fashion to achieve the improvement. The results of the experiments indicate that both location precision and relative location accuracy are clearly increased due to the algorithm. peerReviewed

Environmental noise is considered as one of the big issues in environmental pollutions. Typical noise sources like traffic can have great influence on wellbeing and healthy. In this paper, we report the sensor function design and implementation of a wireless sensor network application for measuring environmental acoustic noise. The sensing system is built on Atmega128 and CC2420 platform. The protocol stack is based on CiNet stack with a global synchronization scheme and supports multi-hop communications. Strict filtering function specified by ITU-R 468 (namely A-weighting) is followed. Both the indoor and outdoor test results were compared with a standard sound level meter and showed a less than ± 2.1 dB mean differences in both short-term and long-term measurement. Power consumption has been measured that a single AA-type battery can sustain the application. Comparing to the traditional noise measurement method, the designed wireless sensor network solution is much lower in cost.

Many wireless sensor networks operating outdoors are exposed to changing weather conditions, which may cause severe degradation in system performance. Therefore, it is essential to explore the factors affecting radio link quality in order to mitigate their impact and to adapt to varying conditions. In this paper, we study the effects of temperature and humidity on radio signal strength in outdoor wireless sensor networks. Experimental measurements were performed using Atmel ZigBit 2.4GHz wireless modules, both in summer and wintertime. We employed all the radio channels specified by IEEE 802.15.4 for 2.4GHz ISM frequency band with two transmit power levels. The results show that changes in weather conditions affect received signal strength. Of the studied weather variables, variation in signal strength can be best explained by the variation in temperature. We also show that frequency diversity can reduce the effects of channel-specific variation, and the difference between the transmit power levels. peerReviewed

In this paper, we report the sensor function design and implementation of a wireless sensor network application for measuring environmental acoustic noise. The system is built on ATmega128 and CC2420 platform. The protocol stack is based on CiNet stack with a global synchronization scheme and supports multi-hop communications. Strict filtering function specified by ITU-R 468 (namely A-weighting) is followed. Both the indoor and outdoor test results were compared with standard sound level meters (CESVA SC-20c and Pulsar94) and showed a less than ±2dB error in both short-term and longterm measurement. Power consumption has been measured that a single AA-type battery can sustain the application. Comparing to the traditional noise measurement method, our wireless sensor network solution is much lower in cost, able to offer real-time data with sensed data timely coherent, and requests least attention after deployment.

Reliable communication is crucial for successful deployment of a wireless sensor network. Many environmental factors can affect the performance of radio links, and the deployment of a network without real-time information about link qualities can be a demanding task. This paper describes the CiNetView application that is intended to support the deployment and monitoring of wireless sensor network. CiNetView is based on diagnostic information collected by sensor nodes, and it allows the user to see a graphical presentation of the network topology and to monitor the network diagnostic information in real time.