RADIO TELEMETRY OVERVIEW

Radio telemetry offers a cost-effective, robust means for government agencies and commercial entities to transmit environmental monitoring data. Constant advances in transmitter size and reliability make deployment easy, and data can be collected in flexible formats by websites, laptops and PDAs.

In every country, the use of the radio spectrum is regulated by certain organizations. The FCC regulates North America and ETSI (European Telecommunications Standards Institute) regulates Europe. These regulators define the allocation of each radio frequency bandwidth: for TV and radio broadcasting, for telecommunication operators, for the military, for data transmissions, etc. The VHF or UHF frequency bands are commonly used. Usually, to transmit over a frequency band, you must obtain a communication license from one of these bodies, register your architecture and buy the right to use the frequency.

Wireless communication options include a modem that provides a defined radio frequency (RF) and an antenna. Radio waves (signals) exhibit very different propagation characteristics depending on their frequency band. Consequently, engineers design radio systems to take advantage of the unique propagation characteristics of a given frequency band. The following are the definitions of different frequency bands:

Environmental monitoring data are typically transmitted in packets through radio signals using VHF and UHF frequencies. In the United States, there are up to 50 different frequencies available in the VHF spectrum and as many as 1600 frequencies in the UHF spectrum. However, many of these frequencies are allocated for specific forms of wireless communication. For example, certain reserved data communications modes within the VHF/UHF frequency range include:

Commonly used VHF/UHF Frequencies in radio modems for environmental monitoring or SCADA include:

66 MHz-79 MHz
132 MHz-174 MHz
216 MHZ-266 MHz
380 MHz-512 MHz
928 MHz-960 MHz

A typical VHF or UHF radio (good for up to 30 miles) is an electromagnetic transmission received by special antennas. A license from the FCC must be obtained and coverage is limited to special geographical boundaries. The regulation, licensing, and governing of the radio transmission spectrum varies from country to country. Many countries, for various purposes, provide license-free radio data transmission spectrums. Check with the spectrum management authority in your country for license-free data transmission regulations.

A limited number of unallocated operating frequencies remain available in the US and other jurisdictions to carry wireless telemetric data among machines. Among these are unregulated 'spread spectrum' and frequencies designated for carrying voice and digital traffic. Click for more information on Spread Spectrum.

ADVANTAGES TO RADIO TELEMETRY  

Cost-Effective: There is no cost for time, no roaming and no long distance charges - i.e. no direct monthly communication fees. A licensing fee is paid to the regulator authority responsible for controlling the frequency bands.

Reliable, Error-Free Transmission : The data packets sent are error-checked and corrected. If the transmission was incorrect, the same packet is sent again, until confirmation of successful communication.

Secure: Encryption provides privacy of data, it can be installed on the receiver or at both ends.

Time-Sensitive: You can be constantly connected and receive the messages right after they are sent or receive them later if you chose to.

Fast: there is no time spent waiting for a network connection . The network is always on.

Enhances productivity: Wireless communications offers real-time data to improve decision making. It also provides great employees safety conditions, and allows the existence of virtual offices.

Low interference (especially compared to spread spectrum radios): Users of these VHF or UHF bands benefit by not having interference from other radios.

Communication range: Compared to spread spectrum radios, the allowed output power of the VHF or UHF transmitter is higher, resulting in a a longer transmission range.

Mobility: Allows users to get the advantages of these products from anywhere.


DISADVANTAGES TO RADIO TELEMETRY

Set-up considerations: Deploying radio communications requires a certain amount of study and planning of your needs and limitations. This typically requires an engineering firm to do a propagation study to determine the configuration for the system and if additional repeater sites are required.

Testing: The system has to be installed and tested to ensure its efficiency.

Employee training: Employees must be trained in order for the company to effectively benefit from wireless communications.

Cost of licensing : There are additional costs for licensing in the VHF and UHF bands when used for environmental monitoring.

Capital expenditures : Antenna towers and repeater sites (if required) could significantly increase the overall cost of a radio telemetry system.

Line-of-sight considerations : Wireless communications have still a limitation on the amount of miles that separate a transmitter from a receiver. This concept is called "Line-of-Sight", meaning one antenna must see the other antenna without obstruction. The distance between antennas can be up to 30 miles line-of-sight, and this distance depends on the number of antennas (repeaters) used, the type of antenna and the terrain.

Advantages of VHF over UHF : Commercial telemetric applications that have been tried in the UHF spectrum but have not proven commercially viable may prove viable when implemented using the VHF spectrum. This is due to three fundamental advantages: