Part 101 frequencies have been used by businesses and others for some time. But not until 2011, when the FCC abolished the so-called “last link rule” precluding broadcasters from using these bands, did broadcasters have access to these frequencies for wireless IP STLs.
Licensed IP wireless systems (Part 101 6 GHz or 11 GHz) are useful as a main STL, such as when a station is moving and re-upping their STL in a market where 950 MHz frequencies are hard to get.
By putting up an IP link from the studio to the transmitter, your transmitter site immediately becomes part of your Ethernet network. “It’s almost like from an IP standpoint, that tower is sitting as part of your building now,” said Jeff Holdenrid, who specializes in wireless IP for broadcast and other emerging markets for DoubleRadius engineering firm. Jeff has installed dozens of wireless IP microwave systems with our WheatNet-IP audio network in the past five years, most averaging in the 20 to 25 mile range.
A WheatNet-IP IP88D BLADE into an IP wireless radio can run 8 stereo channels across a wireless IP link and still have enough bandwidth left over for video surveillance, VoIP, remote control and other periphery functions.
A licensed-frequency system is likely to be full duplex and its throughput consistent. A 100 Mbps IP wireless radio on a licensed frequency will operate at 100 Mbps whether its range is six miles or 20 miles.
One of the reasons licensed-frequency IP wireless radios are able to maintain throughput is because of adaptive modulation. “Whereas most Part 74 radios are on or off, they work or don’t, in the IP world they work at a slower speed. They’ll slow down to stay alive. That’s another advantage of what they do. If you have a 100 meg radio, and only need 50 megs, you have room to step down,” explains Jeff.
Planning for Throughput
But while greater output power doesn’t necessarily mean that you can go farther, it does often mean better signal strength and subsequently, being able to drop down in dish size to put less load on the tower. “If you’re renting space on a tower, and you can get away with a 4’ dish instead of a 6’, you’ve just saved thousands a month in rental fees for tower space,” says Jeff.
To determine how much throughput you’ll need for a licensed or unlicensed system, Jeff suggests you start with 100 Mbps per station and then add on current requirements such as whether or not you’ll need VoIP capability or video surveillance transmitted back from the transmitter site. He recommends planning for another 20 to 40 percent above that for any new requirements bound to pop up in the next several years.
Some of the unlicensed IP wireless radios and all of the licensed radios provide software upgrades that let you scale up in throughput, starting at 250 Mbps and scaling up to as much as 1 gigabit.
Licensing for Part 101
Applying for Part 101 licensed frequency for your wireless IP STL is fairly straightforward and quick. “We do a PCN – power coordination notice – just like they traditionally do with 7 gig, 13 or 950. We find channels available and issue a PCN. Once the PCN is clear, which usually takes two to four weeks, then you file. Once you file, as long as you’re not within 10 miles of a U.S. border, meaning Canada or Mexico, you have conditional approval to start operating,” comments Jeff, who says in most markets, frequencies are readily available.
Installing Part 101 Systems
For Part 101 systems, there are three different setups: all indoors, where 100 percent of the electronics and radio components are indoors and you run flexible waveguide cable up the tower to the antennas. These installs are a lot like traditional Part 74s, and can get somewhat pricey. A step down is the split system, where the radio is located up near the antenna, but the connections – Ethernet, fiber and T1 connections - are on the ground, which brings down your cost. All-outdoor installations are when 100 percent of the equipment is on the tower, which lowers costs even more.