JamLab: Augmenting Sensornet Testbeds with Realistic and Controlled Interference Generation

Radio interference drastically affects the performance of sensor-net communications, leading to packet loss and reduced energy-efficiency. As an increasing number of wireless devices operates on the same ISM frequencies, there is a strong need for understanding and debugging the performance of existing sensornet protocols under interference. Doing so requires a low-cost flexible testbed infrastructure that allows the repeatable generation of a wide range of interference patterns. Unfortunately, to date, existing sensornet testbeds lack such capabilities, and do not permit to study easily the coexistence problems between devices sharing the same frequencies. This paper addresses the current lack of such an infrastructure by using off-the-shelf sensor motes to record and playback interference patterns as well as to generate customizable and repeat-able interference in real-time. We propose and develop JamLab: a low-cost infrastructure to augment existing sensornet testbeds with accurate interference generation while limiting the overhead to a simple upload of the appropriate software. We explain how we tackle the hardware limitations and get an accurate measurement and regeneration of interference, and we experimentally evaluate the accuracy of JamLab with respect to time, space, and intensity. We further use JamLab to characterize the impact of interference on sensornet MAC protocols

Implementing and Evaluating a Wireless Body Sensor System for Automated Physiological Data Acquisition at Home

Advances in embedded devices and wireless sensor networks have resulted in new and inexpensive health care solutions. This paper describes the implementation and the evaluation of a wireless body sensor system that monitors human physiological data at home. Specifically, a waist-mounted triaxial accelerometer unit is used to record human movements. Sampled data are transmitted using an IEEE 802.15.4 wireless transceiver to a data logger unit. The wearable sensor unit is light, small, and consumes low energy, which allows for inexpensive and unobtrusive monitoring during normal daily activities at home. The acceleration measurement tests show that it is possible to classify different human motion through the acceleration reading. The 802.15.4 wireless signal quality is also tested in typical home scenarios. Measurement results show that even with interference from nearby IEEE 802.11 signals and microwave ovens, the data delivery performance is satisfactory and can be improved by selecting an appropriate channel. Moreover, we found that the wireless signal can be attenuated by housing materials, home appliances, and even plants. Therefore, the deployment of wireless body sensor systems at home needs to take all these factors into consideration.Comment: 15 page

Factors affecting the bit error rate performance of the indoor radio propagation channel for 2.3-2.5 GHz frequency band

The use of wireless in buildings based on microwave radio technology has recently become a viable alternative to the traditional wired transmission media. Because of the portable nature of radio transceivers, the need for extensive cabling of buildings with either twisted pair, coaxial, or optical fibre cable is eliminated. This is particularly desirable where high user mobility occurs and existing wiring is not in place, or buildings are heritage in nature and extensive cabling is seen as intrusive. Economic analysis bas also shown that significant labour cost savings can result by using a radio system or a hybrid mix of cable and radio for personal communication. The use of wireless systems within buildings introduces a new physical radio wave propagation medium, namely the indoor radio propagation channel. This physical medium has significantly different characteristics to some of the other forms of radio channels where elevated antennas, longer propagation path distances, and often minimally obstructed paths between transmit and receive antenna are common. Radio waves transmitted over the indoor channel at microwave frequencies behave much like light rays, they are blocked, scattered, and reflected by objects in the environment. As a direct result of this several phenomena unique to this form of physical medium become apparent, and they must be accounted for in the design and modelling of the indoor radio propagation channel transmission performance. In this thesis we analyse and characterise the indoor radio channel as a physical medium for data transmission. The research focuses on the influence of the radio physics aspects of an indoor microwave channel on the data transmission quality. We identify the associated statistical error performance for both time varying and temporally stationary indoor channels. Together with the theoretical analysis of the channel, a series of propagation measurements within buildings are completed to permit empirical validation of the theoretical predictions of how the indoor microwave channel should perform. The measurements are performed in the frequency range 2.3-2.5 GHz, which includes the 2.4-2.4835 GHz band allocated by spectrum management authorities for industrial scientific and medical radio use, (ISM band). As a direct result of our measurements, statistics related to channel noise, fading, and impulse response for the indoor microwave channel are obtained. The relationship between data transmission error statistics and the aforementioned phenomena is quantified and statistically analysed for the indoor radio channel and phase shift keyed (PSK) modulation. The results obtained from this research provide input data for the development of a simulation model of an indoor wireless mobile channel. Our measurements identify microwave ovens as a channel noise source of sufficient magnitude to corrupt data transmission in the ISM band, and an in depth analysis of the effect of noise emissions from operational microwave ovens on PSK modulation is presented in this thesis. As a result of this analysis, the estimated data error rates are calculated. Channel fading measurements provide results that will be used as the input data for the design of antennas for use on the indoor microwave channel. We also show that a data rate of eight megabits/second is possible over the typical indoor radio channel, with no requirement for adaptive delay equalisation to counter multipath signal delay spread

Design of interfering mobile device in the band Wi-Fi with magnetron

The aim of this article is to design an interfering mobile device with a magnetron for the interference in Wi-fi signal in the band 2.4-2.5GHz. Propulsion of the interfering mobile device will be implemented using system of the stepper motor, which will be controlled with the help of the microcontroller ATmega 16. In order to deal with the interfering part, it is necessary to design an inverter 12V/4000V and 50-60Hz. The inverter is a supply of the high-powered vacuum tube that generates microwaves; magnetron. Magnetron is used as a source of electromagnetic interference high-frequency acting on targets, which operates in the band of Wi-Fi signal. For example, waves of high-frequency radio damage on-board electronic devices of the UAV, and by the way, we can disable fly of UAV in demarcated areas. The interfering mobile device will be used as a preparation interference and measurement electromagnetic compatibility of electronic military equipment

An initial examination of the occupancy and use of the wireless-radio bands

Data on the occupancy and use of the license-exempt wireless-radio bands collected over a 10 year period is summarized. Numerous examples of measured results are presented in a time-history format. The time- and frequency-varying properties of radio noise and radio interference are visually portrayed where the noise and interference is usually highly impulsive and highly changeable. Of primary concern is that the interference could not be effectively described in standard statistical terms such as peak power, average power, root-mean-square power, amplitude probability plots, or other such conventional measures. The noise and interference was nonstationary in nature with time and frequency variations comparable to message lengths.Approved for public release; distribution is unlimited

The effects of microwave oven over the IEEE 802.11 FHSS wireless LAN card

[[abstract]]We have investigated the effects of microwave ovens over the IEEE 802.11 FHSS wireless LAN card. The measured MAC frame error rate (FER) is affected by the microwave ovens. The signal spectrum radiated from the microwave oven can be used to verify the measured FER data. The performance of the specific bands assigned to some geographic locations in the IEEE 802.11 standard have been discussed in the paper. From these measurement results we can obtain that the performance of some channels within the IEEE 802.11 FHSS wireless LAN card can be seriously deteriorated. Therefore, the location of the microwave oven and the specific channels for the wireless LAN card should be pre-determined according to the experience guideline.[[conferencetype]]國際[[conferencedate]]19991018~19991022[[booktype]]紙本[[conferencelocation]]Beijing, Chin

Analysis of Background Noise for Wireless Microwave LAN Channels

Perusal of the details within, should provide the reader with an insight into general wireless indoor communications within the microwave spectrum, with respect to the problems laced, specific to noise corruption of the transmitted signal. Indoor communication systems are difficult to model, due to the largely random nature of the relevant environment, and the compounding factors that degrade system performance. These factors are many and varied, in accordance with the operational topologies of possible application area. However, there exists a common and increasing need to effectively model the communication links in question. Part of this strategy involves having an understanding of what levels of background noise exist within the operational area involved, and to what degree it is variable in accordance with application and link topologies. It is this requirement that provided the catalyst for my investigations. This study investigates the various noise sources evident on the two frequency bands allocated for wireless LAN applications, and considers the relative importance of the findings. As further perusal will reveal, the major disturbance likely to affect such technologies, are microwave ovens, both on a domestic and commercial scale. A lull statistical analysis is presented for the spectrum distribution and corresponding power levels for microwave ovens, with the results being utilised to present an examination of the possible influence that they may have upon the system, and the significance of such claims

PLFC: the packet length fuzzy controller to improve the performance of WLAN under the interference of microwave oven

[[abstract]]We design a novel fuzzy controller to dynamically adjust the packet length to protect against the interference from microwave oven over the IEEE 802.11 FHSS (frequency hopping spread spectrum) wireless LAN card. The idea of adjusting the packet length under the noise environment from the measurement results about the effects of microwave ovens over the wireless LAN card is referred by Lee, Sheu, Chen, Yu and Huaung (see APCC/OECC'99, p.817-820, 1999). Simulation results show that the designed fuzzy controller can effectively improve the transmission performance in terms of network throughput[[abstract]]In this paper, we have investigated the effects of microwave ovens over the IEEE 802.11 FHSS (Frequency Hopping Spread Spectrum) wireless LAN card. The measured MAC Frame Error Rate (FER) and UDP Packet Error Rate (PER) are affected by the microwave ovens. From these measurement results we know that the performance of some channels within the IEEE 802.11 FHSS wireless LAN card can be seriously deteriorated. Furthermore, decreasing the packet length would improve the transmission performance from the PER measurement results. Therefore, we design a novel fuzzy controller to dynamically adjust the packet length to against the interference from microwave oven. Simulation results show that the designed fuzzy controller can effectively improve the transmission performance in terms of throughput.[[sponsorship]]教育部; 淡江大學 資訊工程系; 行政院國家學委員會工程處[[conferencetype]]國內[[conferencetkucampus]]淡水校園[[conferencedate]]19991220~19991221[[booktype]]紙本[[conferencelocation]]臺北縣, 臺