Sioux Falls, South Dakota has just deployed a microwave backhaul system to link together 20 public buildings. The project caught my eye because it challenges one of the assumptions most of us make – that fiber is always more reliable and faster than wireless. Apparently, not in Sioux Falls. Yesterday, I spoke to Kim Hansen, Network Administrator of the IT department of Sioux Falls, which has approximately 1000 city employees, 20 of whom work in IT.
The big problem: Sioux Falls is a very cold place and winter temperatures of -30 Fahrenheit (-34 Celsius) knocked out the city’s fiber optic links. They thought about repairing the fiber links but the ground is mostly granite, therefore it is very difficult and expensive to dig. In many places, they have to use dynamite!
Before they deployed the new microwave network, they already had a point to multi-point wireless network for the last mile, with fiber as backhaul. Then, they began to install point to point links to bring more bandwidth to certain departments like the public utility. Initially they used the 75 – 85 GHz spectrum bands but that spectrum does not work well for links over one mile. They are sensitive to weather conditions (fog, rain). They used a mix of millimeter wave wireless and fiber optic links to connect facilities such as fire stations, libraries, public works, parks and the utility billing department. But the millimeter wave radios failed during moderate to severe rainstorms.
When they had enough in their budget to do an upgrade, they asked Calhoun Communications to assist them in building out the network. Calhoun and the city chose microwave base stations from Exalt Communications. In the beginning, they deployed the Exalt microwave backhaul systems to upgrade bandwidth on the connection between City Hall and the public utility. The 100-megabit Ethernet links proved so reliable that they replaced the millimeter wave links and built out a complete 100-megabit Exalt microwave backhaul network to support utility billing, VoIP, fire dispatch and administrative applications. Now, they have two 5GHz Exalt microwave radios for point-to-point links and 18 GHz radios for four point to multipoint links. Hansen says the Exalt systems are very easy to use and administer. Ease of use is critical for their IT department because there are only 20 employees supporting the entire city’s tech needs. Sioux Falls was planning to get more two to three more Exalt microwave radios, but because of budget issues, they have to delay the purchase.
“We had initially thought of the Exalt microwave systems as something we needed for higher bandwidth at specific locations or as a backup to our fiber network, but this winter it has become our primary production network,” said Hansen. “The resilience of these new microwave systems is really causing us to consider whether we will even spend the money to repair the fiber links once the ground thaws in the spring, because it’s something we end up having to do every year.” Hansen also says that the departments with the greatest need for bandwidth – the utility billing office- sees a dramatic increase in performance from the new point to point links created by the Exact microwave radios. Note that Sioux Falls is using licensed spectrum (they file with the FCC each year and pay a fee). The license is good for 10 years.
As for the cost of laying fiber versus deploying wireless, Hansen says it’s much cheaper to roll out the wireless network because there is no digging required. They do have to send people up to towers to install the radios. He estimates that two-thirds of cost of deployment is labour.
In addition to the Exalt microwave system, Sioux Falls has been using Proxim’s point to multipoint wireless base stations. They also have twelve 802.11n Wi-Fi hotspots using Cisco equipment. Police officers drive to these hotspots (which are not open to public use) to write reports and check databases. The fire stations are also equipped with Wi-Fi networks so that fire department personnel can obtain information right before leaving the fire house. There is a an outdoor wireless network that is run by a local Internet provider for the city’s nomadic employees, but that is not open to the public either.
In summary, Sioux Falls, South Dakota’s extremely cold weather and granite foundations make wireless a more attractive option than fiber in providing fast, reliable connections between municipal departments across the city. Because the cost of microwave equipment has come down in the past few years, cities are looking increasingly to deploy microwave over fiber.