Case Study: City of Sioux Falls relies on Exalt microwave backhaul when other solutions fail

Sioux Falls is the largest city in South Dakota, with a population of more than 150,000 according to a 2008 U.S. Census Bureau estimate. Like most American cities, Sioux Falls provides a host of public services for its residents, including parks, libraries, fire and police services, community centers, and utilities. The city uses modern computer networks and applications to deliver these services more efficiently. Unlike many cities, however, Sioux Falls must provide these services in temperatures ranging from 110 degrees in the summer to -35 degrees in the winter. As these severe weather conditions have rendered some technologies useless, the City of Sioux Falls has now upgraded to Exalt microwave backhaul systems for reliable performance under all conditions.
A commitment to wireless
City of Sioux Falls network administrator Kim Hansen has always been a believer in wireless communications. “We have about 20 sites around the city, and we have used point-to-point and point-to-multipoint wireless systems for several years,” he says.
In some cases, wireless has been the only way to connect a fire station or other facility to the backbone network since there is no fiber available at those locations. But in other cases the city has used wireless as a less expensive alternative to leased lines. Several years ago, the city began using point-to-point wireless systems to link its buildings to aggregation points that were connected to a fiber backbone.
Over the past two years, the city’s use of networked applications has grown to include computerized utility billing, remote backup storage for its data center, IP voice, and other mission-critical systems. Since then, Hansen has recognized that he would need more bandwidth in the wireless side of the network.
Initially, Hansen tried using a millimeter wave wireless system to deliver more bandwidth on five backhaul links. The 75 and 80 GHz radios could deliver up to 1 gigabit of data, but when the link distances exceeded two miles, it proved to be more than the technology could handle under adverse weather conditions. “We found that the links weren’t very reliable during moderate to heavy rainstorms or snowstorms, even the shorter links of one mile or less,” says Hansen. “We needed something we could really count on.”
Another challenge facing the city was that its harsh winters meant frozen ground, and with it frozen fiber optic lines. “Every winter the ground freezes and we have some fiber that breaks,” says Hansen, “so we have to dig it up when the ground thaws in the spring and repair it.”
Microwave makes the connection
On a recommendation from Sioux Falls wireless systems consultant Calhoun Communications, Hansen decided to try an Exalt microwave backhaul system on one link in the network during the spring of 2009. Calhoun Communications deployed all-outdoor Exalt microwave radios configured for the 5.8 GHz frequency band between the Utilities Department building and the City Hall, which houses the data center. The link was provisioned for 100 Mbps Ethernet, as compared to the 15 Mbps that the old wireless technology was providing.
“Once we put in the first microwave link, we were very impressed not only with its performance but also its resilience under adverse conditions like driving rain, snow and fog,” says Hansen.
After deploying one more 5.8 GHz link at a remote fire station, Hansen decided to build out the entire wireless backhaul system using Exalt radios. For the rest of the build-out, he standardized on Exalt radios configured for the 18 GHz frequency band. “There are some ISPs and other vendors using microwave in our market area, and we were starting to see some interference from their systems,” says Hansen. “We went with the 18 GHz Exalt systems so we could have our own protected frequency.”
Today, most of the offices in the city are connected via wireless, and the backhaul network uses Exalt radios exclusively. At some remote sites, the microwave system is both a backhaul node as well as that site’s connection to the network, while other sites continue to use the old point-to-multipoint system as a link with backhaul aggregation points. The network is configured as a fault-tolerant ring to further boost its resilience.
Fiber takes a back seat
Since their deployment in 2009, the Exalt microwave backhaul systems have been exposed to extremes of hot and cold temperatures as well as rain, sleet, fog and snow, and nothing has interrupted their service. Hansen can’t say the same for his legacy fiber backbone. “Our fiber network is one gigabit, but a lot of our connections went down this winter when it got to almost 30 below zero,” he says. “We cut over to the 100-megabit microwave network and we have been using that exclusively with no impact on application performance.”
If bandwidth does become an issue in the future, Hansen can always increase it by simply purchasing additional license keys for the radio systems, or he can use Exalt’s capacity aggregation capability to connect additional radios and scale up to 1 gigabit per second or more on any link.
Thanks to the microwave systems’ proven reliability, the City of Sioux Falls may even reconsider whether to continue spending money ever spring to repair its fiber plant. “We might forego repairing some of the fiber links and just use wireless because it’s been totally reliable,” says Hansen. “What we’re seeing that microwave survives whatever the weather throws at it, and when we do have an issue we can realign an antenna or replace a radio even during the depths of winter.”
Although it once considered fiber to be the gold standard for reliable connectivity, the City of Sioux Falls has learned that Exalt’s advanced microwave backhaul systems are an even better solution.
Challenges:
–Increase available bandwidth in city-wide wireless data network.
–Ensure complete reliability in extreme weather conditions.
–Provide scalability for future bandwidth upgrades, if needed.
Solutions:
–Deploy Exalt split-mount and all-outdoor microwave backhaul systems to support 100 Mbps aggregate Ethernet capacity with field-upgradability to 200 Mbps.
–Ensure 99.999% reliability and throughput availability in all weather conditions.
–Scale up bandwidth easily with license upgrades and capacity aggregation.