19-05-2012, 01:23 PM
DESIGN OF WIRELESS COMMUNICATION SENSING NETWORKS FOR TUNNELS, TRAINS AND BUILDINGS
[attachment=22449]
INTRODUCTION
It has been found from the recent literature survey [1- 13] that no proper design tools have yet been developed for indoor wireless communications. As cellular systems are operated today, in-building communication is provided by transmitting radio signals from cell sites to portable handsets inside buildings which requires the transmitted power to be about 20 dB stronger than that for the ground mobile communications in order to penetrate into or out from a building. The coverage of the portable units is not two-dimensional but three-dimensional.
Rayleigh fading and Doppler Shift
Different paths may exist between a base station (BS) and a mobile set (MS) giving rise to a number of partial waves arriving with different amplitudes and delays. Since the MS will be moving, a Doppler shift is also associated with each partial wave, depending on the MS’s velocity and the angle of incidence. The delayed and Doppler shifted partial waves interfere at the receiver causing frequency and time selective fading on the transmitted signal.
TETRA Dynamic Sensitivity Model
The TETRA standard caters for the two main cases of stationary users and moving vehicles at speeds up to 200 km/h through various terrains. The dynamic sensitivity model is typical of built-up areas for situations where there is no LOS path but some reflections from large buildings. For our system design, users are assumed to be moving and therefore the dynamic sensitivity limits apply. It is assumed that the received signal is at least 5 dB higher than the TETRA dynamic sensitivity limit as shown in the Table I.
Noise
It is assumed that our in-building mobile coverage system has 25 kHz channel spacing. The noise floor of a receiver is calculated as the thermal noise plus the receiver noise figure. The 3 dB bandwidth is assumed as the reference bandwidth for the receiver IF stages. For special services such as Police, Ambulance, Security systems this bandwidth can safely be assumed to be 18 kHz. This results in a thermal noise figure of -131.44 dBm. When considering digital radio systems, symbol-energy-to-noise ratio (Eb/No) is equivalent to carrier–to-noise ratio (C/N) but only when the receiver filter’s equivalent noise bandwidth has the same value as the bit/symbol rate.
[attachment=22449]
INTRODUCTION
It has been found from the recent literature survey [1- 13] that no proper design tools have yet been developed for indoor wireless communications. As cellular systems are operated today, in-building communication is provided by transmitting radio signals from cell sites to portable handsets inside buildings which requires the transmitted power to be about 20 dB stronger than that for the ground mobile communications in order to penetrate into or out from a building. The coverage of the portable units is not two-dimensional but three-dimensional.
Rayleigh fading and Doppler Shift
Different paths may exist between a base station (BS) and a mobile set (MS) giving rise to a number of partial waves arriving with different amplitudes and delays. Since the MS will be moving, a Doppler shift is also associated with each partial wave, depending on the MS’s velocity and the angle of incidence. The delayed and Doppler shifted partial waves interfere at the receiver causing frequency and time selective fading on the transmitted signal.
TETRA Dynamic Sensitivity Model
The TETRA standard caters for the two main cases of stationary users and moving vehicles at speeds up to 200 km/h through various terrains. The dynamic sensitivity model is typical of built-up areas for situations where there is no LOS path but some reflections from large buildings. For our system design, users are assumed to be moving and therefore the dynamic sensitivity limits apply. It is assumed that the received signal is at least 5 dB higher than the TETRA dynamic sensitivity limit as shown in the Table I.
Noise
It is assumed that our in-building mobile coverage system has 25 kHz channel spacing. The noise floor of a receiver is calculated as the thermal noise plus the receiver noise figure. The 3 dB bandwidth is assumed as the reference bandwidth for the receiver IF stages. For special services such as Police, Ambulance, Security systems this bandwidth can safely be assumed to be 18 kHz. This results in a thermal noise figure of -131.44 dBm. When considering digital radio systems, symbol-energy-to-noise ratio (Eb/No) is equivalent to carrier–to-noise ratio (C/N) but only when the receiver filter’s equivalent noise bandwidth has the same value as the bit/symbol rate.