Editor:
Nice article about TETRA. Thanks. I have a question: In the sentence, “TETRA radios display signal strength and signal quality,” what does the author mean by signal quality, and what are the parameters to determine the signal quality?
Edwin Nettleton, P.E.
Communications Engineer
AECOM – Technology Solutions
Lynchburg, Va.
Author’s Response: The radios have an engineering mode that shows multiple parameters. They show signal strength along with signal quality. Signal quality is a combination of strength and bit error rate (BER) among other parameters.
The engineering mode on the Sepura radios includes several pieces of information:
• Received Signal Strength Indication (RSSI) — The radio will give the received signal strength of the base station that it is using, so the operator knows what base station the radio is using.
• C Value — A formula that uses both uplink and downlink signal strength, as well as minimum thresholds to compute a value. The higher the C value the better the link, both up and down. In the engineering mode, you can see this value for the base station the radio is using, as well as the neighboring base station.
• GPS — The coordinates of the radio at its current location.
• Accelerometer — This is built in and is used to calculate tilt, motion and force for man-down applications.
• Unit Information — Retrieve information about the radio such as electronic serial number.
Editor:
We installed three TETRA systems using the Sepura terminals, and they work brilliantly. We are now repairing a system another company installed with Hytera terminals and backbone.
We are fortunate because the one client now wants to expand its system considerably. We are looking at a few thousand modems and terminals combined. The client wants to run all traffic lights and electrical substations on modems.
Leon van der Linde
Global Communications
Editor:
We recently had our FCC station license modified. When it came back to us, it had a stipulation that we must be narrowbanded by the first of the year with the narrowband modulation code already granted on the license. As far as I can tell, there was no stipulation on our part to notify anyone upon the completion of this task even though we just completed the task this month. In the end, for all those that had their licenses recently modified for any other reason than narrowbanding, there is an assumption that this will happen automatically without further notice.
So my second question is: Were we on the list of those 60 percent in compliance?
Reid Ashbaucher
Radio Technician/Phone Admin
Toledo Area Regional Transit Authority
Toledo, Ohio
Editor:
If it will help Motorola lose money and customers, they will oppose it. When they cause severe interference then there is nothing wrong. Icom's system is not even discernable. You don't even know it's there.
Leon van der Linde
Global Communications
In response to “U.S. UCAN: A National Broadband Backbone” from the June issue of MissionCritical Communications
Editor:
I have been reading this article and Puerto Rico and the U.S. Virgin Islands are not included in the backbone. As you know, we are the Caribbean support for the nation in the eastern part of the Atlantic. Also we have participated in events like Hurricane Katrina and others.
Ferdinand Cedeño, P.E.
Bayamón Gardens Station
Bayamón, Puerto Rico
Editor:
What is interesting about the article is the dollar figure doesn’t provide for more than the urban areas. As Minnesota has 79,626 square miles and a Long Term Evolution (LTE) cell can only provide reliable coverage across 11.8 square miles, that means 6,748 sites need to be built to cover the entire state. At the average price of an LTE cell that includes installation cost of $150,000 that means $1.012 billion in costs without the interconnecting infrastructure for a true statewide system.
At $332 million, that means only one-third of the state will be covered if the cost of interconnection is ignored. Realistically, $332 million probably will only cover the larger towns and cities.
Mark Pride
Newfield Design
Editor:
It’s nice to see the Pennsylvania Game Commission is moving forward with technology. Meanwhile the Pennsylvania State Police have had software like this for eight years, but they are moving backward in time. They will close their consolidated dispatch centers this summer, do away with all the software from InterAct, and put the dispatchers back at a station or barracks using pen and paper — the old fashioned way.
Randy Minninger
Editor:
There is an aspect that it seems few are considering. Some of us were in mid-project and were caught unawares. I have hundreds of thousands invested in delivered equipment, some installed, with licensing now stalled. The National Public Safety Telecommunications Council (NPSTC) and others are now beginning to consider this and advocate with FCC. While I agree the long-term implications are important, don’t neglect the plight of those caught in the freeze with licenses now in limbo. We are hopeful some waiver process may be added so that at least these stuck projects may be completed without disrespecting the legislative intent of the eventual sunset.
Michael Guerin
California State University
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