Not the Same Old STL
In larger radio markets, or even markets where many FM stations are gathered at one mountaintop or tall tower farm, obtaining a new 950MHz license for STL purposes can be difficult at best and impossible at worst. Fortunately, there are alternatives, and we'll explore some of them.
The FCC has recognized this frequency congestion issue and responded by eliminating what was called the final link rule from Part 101 of the Rules. Previously, broadcasters could use certain Part 101 bands for transmission of programs in the direction of the transmitter, from the studio, except for the very last link. (It was possible to get a waiver of this rule in certain circumstances.) In the Commission's own words, "With increasing adoption of digital technologies, the final link rule has become an outdated regulation that imposes unnecessary costs on broadcasters." And further: "Eliminating the rule will provide tangible benefits to broadcasters by reducing unnecessary duplication of systems and facilities and enabling them to operate more efficiently. We therefore find the benefits of eliminating the final link rule to be significant."
Before the elimination of the final link, an alternative to the 950MHz band was using an ISM band (928MHz, 2.4GHz, 5.8GHz) radio link, and of course all those options are still available. For example, Moseley offers its system called the Event 5800, which operates in the 5.8GHz ISM band (or the 5.3GHz UNII band). It can handle up to nine T1s, or alternatively 27Mb/s Ethernet. This is a system that makes use of an indoor unit and outdoor unit. Control is via a built-in Web server or SNMP.
But if you want to go with a licensed channel, you have many options. Radio Systems offers the IPC100 series of point-to-point microwave radio systems. The IPC100 operates in frequency ranges from 7 to 38GHz (licensed frequency bands), and its payload bandwidth can be allocated in various ways, including 4, 8, 16, 32 T1/E1 Interface, or 100base-T Ethernet. It uses indoor and outdoor units, which can be separated by as much as 300 meters (using LMR-400). Control is accomplished via an NMS GUI or via SNMP.
I've written in prior articles about how the explosion in the use of Ethernet has substantially affected how we assemble radio stations. I want to point out that the dramatic increase in smartphone usage is having a similar effect. Cell telephone companies are scrambling to rebuild and upgrade their own infrastructure - in particular the way they backhaul data from cell sites - and this has made a huge market for Ethernet radios, such as those described below. This market has brought new manufacturers into the game, which lowers the prices of the equipment.
IP in play again
Ceragon has an extensive product line, but in particular take a look at the FibeAir IP-10 E series. This radio hauls Ethernet, and it's scalable up to 2Gb/s of throughput (don't laugh - who knows what might go at the transmitter?). This radio uses an indoor unit and outdoor unit, and you can use coax (LMR-400 for example) to connect the two ends together. Comprehensive QoS mechanisms are specified.
Another brand with which you may be familiar is DragonWave. The Horizon series also has an indoor/outdoor configuration and is scalable up to 2Gb/s of throughput (Ethernet of course). QoS packet prioritization is specified as a feature.
- continued on page 2
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