Municipal and private utilities, water and waste water among them, have communications and physical security requirements that are often challenging to address. Interconnecting multiple sites at wire-like speeds is a daunting proposition for many, when fiber or leased lines are too costly or impractical. The needs are pressing, with a single act of theft or vandalism potentially costing six figures to mitigate.
With that in mind, Southern California’s Otay Water District is a great example in utilizing the flexibility, capacity and reliability of wireless mesh in an extremely challenging environment of hills, mesas and canyons of the eastern part of San Diego County.
Real-time communications at an affordable cost
The Otay Water District has a 125 square mile service area and more than 200,000 customers. Many of its 50+ remote facilities, such as reservoirs and pump/hydro stations, are in geographically isolated and non-densely populated areas. Options for getting land method communications to these sites (T1, DSL, or cable) were cost prohibitive, with some bids coming in as high as $100,000 a month.
The wireless mesh network offered Otay an economical and easy way to provide reliable connections and video surveillance between its headquarters and remote facilities. Besides the cost savings, the system delivers real-time security feeds rather than dial on alarm and real-time access control information rather than daily dial-up. The high-capacity network also provides the ability to use multiple cameras at a site. In the past, much of Otay’s SCADA infrastructure was periodic dial-up or dial on alarms situations. Having the real-time SCADA information is critical during main breaks, valve closures and other pressure monitoring situations. Finally, the district can now have Wi-Fi access at their sites rather than relying on cellular broadband connections.
100 Mbps performance across MIMO mesh backbone
The initial phase of the deployment, to prove the performance of the MIMO wireless mesh backbone, connected four sites as shown below. Otay’s headquarters, recycled water treatment plant, and two nearby water storage reservoirs are separated by a high ridge line. Because of line of sight issues, the network uses linear mesh topology (‘daisy-chaining’) and loops back to connect the final site, with the longest link of 2.3 miles and shortest link of .5 miles. This initial network uses dual-radio Firetide HotPort 7000 MIMO mesh nodes operating in a combination of 5 GHz and 4.9 GHz frequency bands. The overall capacity end-to-end is 100 Mbps.
Design with flexibility in mind
Twelve sites have been completed and the entire proposed network will connect more than 50 sites. The system uses a redundant mesh design for the WAN backbone with MIMO mesh technology, and point-to-point design using 900 MHz frequency band for non-line-of-sight and near-line-of-site links. Link distances in the overall deployment will range from .3 mile to 3+ miles.
For some of its well and booster stations, where trees make it impossible to use the frequencies in 5 GHz, the system will use the Firetide HotPort 6200-900 non-line-of-sight mesh. These dual-radio units have one radio at 900 MHz and one radio at the higher frequencies. The 900 MHz links connect well sites and reservoirs at lower elevations to ‘hub’ nodes located at higher elevations. Once the 900 MHz link reaches the reservoirs, the second radio on the mesh node uses the 5 GHz frequency to send the data back to the control center.
The combination of 900 MHz and line-of-sight 5 GHz bands is often the best solution for utilities, which must deal with vegetation and a variety of topographies. Also note that many utilities have access to 4.9 GHz public safety band, so 4.9 GHz communications can be incorporated into the design.
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