Make UHF trunking profitable
How does a commercial service provider integrate newly available UHF spectrum and technologies into a profit center?
Here’s the view from the inside.
UHF trunking presents a unique set of issues that determine whether the system will operate efficiently, effectively and profitably. My company, based in Denver for the last 27 years, put up a trunked UHF system about four years ago using narrowband technology. This was added to our portfolio of community repeaters, cellular, paging and communications consulting services in the Denver and Colorado Front Range areas.
There are four main areas that the prospective UHF trunking operator should be aware of: licensing, equipment, technology and infrastructure.
Licensing issues The FCC has basically issued two types of licenses in the UHF bands: an IG (decentralized) license and a YG (centralized) license. The commission is licensing both the 461MHz and the 451MHz parts of the band. (This split presents some challenges that will be covered later in the section on technology.)
The frequencies to which a licensee is assigned may be mixed. You may be assigned a 461MHz and a 451MHz frequency. They may also be mixed by type, IG and YG, depending on how densely populated and licensed your geographic area is.
Another issue, for IG licensees, is looking at co-channel users. When you interact with your co-channel users, or interfere with them, you are going to have issues that you will have to work out. One of the nice things about the YG license is that you do not have co-channel users – it’s an exclusive license.
Equipment issues The 10MHz split in the band assignments presents a unique set of challenges for the equipment. The transmitters will split with no problem, and combining is not a problem. On the receive side, however, it is much more difficult if you are installing a master antenna/multicoupler type of system. This will require splitting and creates problems such as losses incurred from that splitting.
Another challenge is channel monitoring. If you are an IG licensee, whether in the 461MHz region or the 451MHz region (or the 466MHz region, for that matter), you will still have to monitor the channel. YG licensees do not need to monitor. Most of the current trunking technologies use a data burst that is transmitted on the channel every ten seconds. If you are an IG licensee, you are going to have to hold off and monitor before those data bursts occur, which will hinder efficient functioning of the system.
IG and YG channels can be used together. When they are mixed, the home channels are placed on the YG assignments because there is no monitoring requirement, and then users can be trunked off onto the IG channels. Some of the current technology allows the equipment to look at busy channels, skip them if they are in use, and go on to assign other free channels.
Another challenge is that wide-area trunking requires that the system either be linked via a landline, microwave or some other means. We chose to use a microwave link, the 2.4GHz unlicensed spectrum (See “Unlicensed Microwave: A Blessing or a Curse?” page 40) and run a T1 between sites to link them.
(c) Centralized and decentralized trunking – Centralized trunking seems to be the most popular and most appropriate technology for these bands, and that’s what we’re using in Denver. Everything is done at one site, everything is controlled from that one site, and the repeaters are assigned from that singular point of view. If you use decentralized trunking, then the radio makes the decision, and it’s a much slower system. Centralized trunking does work more efficiently.
Technology issues Available technology for UHF trunking has been slow to turn out. For a long time, there was no technology available to allow handoffs. The big problem with multisite systems (we have three sites in the Denver area, for example), has been the requirement of the user to select which site he is going to use. The radio is not capable of making that determination. There is some technology, exhibited at the IWCE last March, for the next generation of UHF trunking that will allow automatic handoffs and will also allow automatic registration and unique user ID codes.
We are using the E.F. Johnson LTR format. We are examining going on to the Net-LTR system, which is an enhanced, more robust system with automatic handoffs and unique user ID. The standard LTR system seems to work as well as the 800MHz LTR has for the last 10 to 15 years.
The situation of having the users select the site has been a drawback because the users are often unsophisticated regarding propagation, and they are generally unfamiliar with system operations. Unless you make it extremely simple for them, they may have a difficult time.
We are using compandered audio on our system, and we encourage those who come onto the system to use it. Most of the newer radios have this function available. It gives a much more intelligible system, giving users the feel of a wideband radio in a narrowband environment.
We have not found any problem going from wideband repeaters to the narrowband technology. Of course, we’re running a hot preamp, using a multicoupler system and sitting on good, quiet sites. We try to keep our transmitter noise levels low. It’s just a matter of engineering the system right. In terms of the audio recovery difference between wideband and narrowband, customers have not complained about volume or audio quality.
Infrastructure issues (c) The dynamics of interconnect – New trunking technologies, unlike those for the old 800MHz trunking systems, allow interconnect on any channel at any time in any place. That capability can be dynamic across the system. For example, in our area, if a user wants to use a site in Colorado Springs, which is 70 miles away from us, and wants to interconnect to a Denver telco line, we can allow that over the network – again, via microwave, T1 or some other system link. The system is no longer dependent on the interconnect being at the particular channel and at the site. Now the interconnects can be at any location in the system.
For interconnects we use USWest in the Denver, Colorado Springs and Boulder markets. We do run a T1 through a separate carrier, Qwest, from Denver to Colorado Springs to link the two cities, as well as for other applications. The hardware connects easily – all two-wire, standard signaling equipment that looks like a POTS line. In our system we use an overdial. Dial into the seven-digit number and then add either a two-digit or three-digit overdial, which is programmable. To access an outside line, the mobile unit keys up, gets dial tone, dials the number, and makes the connection. Timers can be customized to restrict time of day, time of week or day of week. The system is robust in terms of programming capability.
(c) Coverage issues – Our operation uses multiple sites in the Denver area: a downtown site that is on a tall building, a mountaintop site on Lookout Mountain and a third site in Boulder, a suburb 30 miles away. All three of these sites are linked, and this gives us the best of both worlds. The mountaintop gives us nice coverage up and down the Front Range, about a 30-mile radius up and down the north-south Interstate 25 corridor. However, it doesn’t give us good coverage downtown, amongst the buildings or down in their sub-basements and so forth. What we have done is marry the two systems together. Now we can have a mobile operating 20 miles south of Denver that is communicating with a portable in the second sub-basement of a downtown office building. Linking the systems, and again having that microwave or landline backbone link, allows us to do that because the system is programmable and it’s all software-driven.
The repeaters in most metro areas do have dead spots, and so we try to add locations to them. And, as we build the system, we’re starting to build it as a cellular-looking system. As technology improves, it will look and feel more like a cellular system with automatic handoffs, and the technology will have caught up with what the customers want.
Good planning makes for a successful system. Know the issues of your system, and it will be a reliable and profitable system with a minimum of hassle.
Selling the system We’ve tried going out to the other mobile shops in town because we’re the only service provider in Denver, presently, that has a UHF trunked system. We’ve gone to these other shops and offered them service on our system. That seems to be the best way to sell because, like many small telecom businesses, we don’t have a huge sales force, and we’re not out selling individual radios. Making the system available to other shops and users makes it much more profitable.
Only a handful of manufacturers support LTR for UHF. We use about three different brands. We are not restricting shops. If they’re selling “Brand X,” we don’t care, as long as they service and support it. This eliminates finger pointing when trying to distinguish between a system fault vs. an equipment fault.
To provide service to other shops, we basically offer an unlimited amount of airtime for dispatch for a flat rate. We sell to the shop at a wholesale rate of, say, $5 to $7. They turn around and sell it to the end user for $8 to $10.
Interconnect is a separate issue; we sell that for quite a bit more, in the $35 range. The shop does its own billing, and they pay us for the number of units. Right now, we are not keeping track of airtime. It is too difficult at this point, but as both we and the system become more sophisticated, we’ll start keeping track.
We’re also migrating a lot of our customers from our conventional over to the trunked channels because of the efficiencies. Finally, we are selling directly to end users as well.