VMS Parking Systems using UHF Wireless Networks
Implementing a car parking control system over a large area inevitably means using wireless to communicate between the vehicle detectors, variable message signs and the central server. Either a broadband WiFi network or a narrow band UHF network can be used in this application.
Broadband WiFi wireless networks can be easily interfaced to a Server but they have the considerable disadvantage of a limited range of up to 500m and rely on line of sight communications. In addition parked vehicles give rise to RF multi-path reflections which affect the overall data speed. However narrow band radio modems operating on UHF frequencies provide a very robust wireless network with ranges of up to 1Km to 3Km through buildings and can achieve 6Km to 10Km in free space. They have the disadvantage of low data through put of typical 9600 Baud which in this application will be acceptable.
A typical installation would consist of inductive loops or Inferred detectors being installed at strategic position around the site to count vehicles entering and exiting different areas. An X8100 XNET Telemetry Transceiver can be connected directly to each vehicle detector. These use narrow band UHF radios to transmit the accumulated total of each vehicle counted to a central X8100 XNET Telemetry Transceiver. A Web Relay can be used to interface the base station X8100 XNET to the Ethernet Network where the vehicle counts are then forwarded to a Server.
Messages directing the vehicles are initiated by the Server and sent to an Ethernet to Serial Converter. This is then connected to an X8200 Radio Modem operating on narrow band UHF frequency bands which forwards the messages onto X8200 Radio modems in each of the Variable Message Signs.
Both the X8100 XNET Telemetry Transceivers and the X8200 Radio Modems can be quickly and easily installed and make a much more cost effective solution than cabling a large site and provide a more robust communication network than wireless WiFi.