Cities and towns are attempting to improve public safety by using special software that creates one big virtual wireless network out of incompatible wireless net infrastructures.Addison, Texas, as well as Tempe and Chandler, Ariz., for example, are melding newer 802.11 Wi-Fi mesh networks with their legacy wireless networks using Padcom TotalRoam software. The software enables automatic switchover from one network type to another, thereby increasing coverage and, thus, network availability.This is appealing to the Town of Addison, which wants redundant, multiple wireless layers to ensure that emergency responders always remain connected, says Hamid Khaleghipour, director of IT. The newest tier is an 802.11g mesh network service from RedMoon based on Tropos mesh gear.Unlike the low-speed 800 MHz public safety network Addison shares with the neighboring community of Farmers Branch, Texas, the multimegabit Wi-Fi network allows the transfer of photographs and video from police cruisers at crime scenes and supports business applications. Sprint 1XRTT CDMA service was also added to the Addison wireless network mix a few years back to plug a 10% to 15% coverage gap in the 800 MHz network. Any one network service can fail over to another in the event of an outage.Khaleghipour says he deployed the Padcom software because it was the only solution that enabled roaming among all wireless nets, including non-IP, modem-based 800 MHz networks.He anticipates a payback of seven months with the roaming software, which runs on emergency responders\u2019 mobile data devices and in a gateway server in the data center. He has figured a cumulative, five-year ROI of 957%, or $275,000 benefit, derived from increased productivity and from merging existing nets rather than rebuilding them.Meanwhile, the Strix-based mesh network used by Tempe municipal workers, which you read about here last summer, is being extended into the neighboring city of Chandler. The move, to begin in February by operator NeoReach Wireless, will create one contiguous network covering about 112 square miles.Tempe muni workers also use Padcom TotalRoam to integrate access to the 802.11 mesh network and a low-speed 800 MHz public safety dispatch network. Now Tempe workers will also be able to roam into Chandler and vice versa.In addition to supporting municipal workers, the Wi-Fi net services in Addison, Tempe and Chandler are available to business and residential customers.