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Denver Public Schools Adopt VoIP for Stability and Effectiveness

January 1, 2006

In his 1997 book The Innovator's Dilemma, Harvard Business School professor Clayton M. Christensen introduced us to the "disruptive technology" concept, which describes an innovation that challenges and ultimately replaces the conventional way of doing things. The car was a disruptive technology that replaced the horse-and-buggy, minicomputers supplanted mainframes and digital photography has all but made film obsolete.

While disruptive technologies may be slow out of the gate and are generally characterized by poor initial performance, ultimately they become "cheaper, simpler, smaller, and, frequently, more convenient to use," according to Christensen.

Many believe VoIP is a disruptive technology for the communications industry. Two-way radio users that have long relied on an extensive network of repeaters to provide coverage over wide areas and expensive radio consoles to operate the system are finding VoIP to be a stable and cost-effective alternative to their wide-area networking, radio control and interoperability requirements.

Though it hasn't yet replaced conventional two-way communications, VoIP is no longer a fledgling platform. Equipment developers continue to perfect applications and are racking up customers that can attest to its performance and capabilities.


Denver Public Schools (DPS) is one of these early adopters. Skeptical at first, DPS took a chance on VoIP because of its emerging reputation as a stable and cost-effective networking platform. The technology didn't disappoint, and by the time DPS completed a VoIP implementation at the main school bus dispatch facility, it was already developing plans to deploy VoIP throughout the entire district for security and administrative communications.

When Good isn't Good Enough

DPS is no slouch when it comes to two-way communications. Over the past decade, the school system built its UHF network up from a single frequency supporting communications for one dispatcher and 100 school busses into a three-channel system with three dispatch positions that monitor and control two-way communications for the 425-bus fleet.

In addition, DPS operates an extensive 800 MHz network for security and maintenance personnel with several hundred mobile and portable radios deployed in the field. And each individual school has its own in-house two-way system operating on a split talkaround frequency, which adds an additional 1,200 radios to DPS' cache. But with the safety of 70,000 students in hand, DPS wasn't content to sit back and admire its two-way radio networks - things could always be done better. DPS needed a disruptive technology to help it improve its communications capabilities.

One critical limitation of its wireless strategy was the lack of interoperability between the disparate networks. If a school bus were in an accident, for instance, a number of people would need to get involved. But security personnel and administrators operating on the 800 MHz network had no way to communicate with the bus driver or dispatcher who operated on the UHF network except by tracking down a UHF radio and finding the appropriate channel to talk on.

DPS sought to build greater efficiencies into the system by not only standardizing on a single radio network but also the consolidating the various communications methods employed by dispatchers and other personnel such as landline telephones, iDEN phones and pagers on a common platform.

If that weren't enough, DPS wanted to add redundancy to the network with a backup system in case the district's central dispatch center went down. And it required a system that could grow with their future communications plans, such as integrating with the Denver Police Department's 800 MHz radio network and even linking each individual school over a wide-area network for improved security.

The time was right for DPS to consider a new communications strategy that could meet all of its requirements. It was planning a complete renovation of the main Hilltop bus terminal and dispatch facility just outside downtown Denver. It also was building a second bus terminal that would serve as the 800 MHz network's base of operations.

But the most obvious solution to its interoperability needs-converting the UHF school bus dispatch system over to 800 MHz (or vice versa)-was quickly eliminated as an option. DPS had already invested a significant amount of money into these networks and simply could not abandon any network infrastructure it had built over the last 10 years. DPS needed an entirely new approach to interoperability and wide-area networking-one that could only be served by VoIP.


Making the Case for VoIP

In 2004, DPS was introduced to IP technology with a trial run of three Telex C-6200 Radio/Telephone Desktop Consoles. It wasn't long before Jim Bailey, who manages DPS' radio system, realized that an IP-based solution was the answer for DPS' interoperability and wide-area networking requirements.

The ability to control the radio network-patching disparate systems and creating talkgroups at the touch of a button-was a major selling point for Bailey. "At first, I didn't understand how powerful VoIP could be," he says. "But once we put it to use, I was convinced" (See sidebar, "What is RoIP?").

Bailey spent the next six months touting the benefits of VoIP to DPS administrators, hoping to get the go-ahead on a complete IP-based implementation. For starters, he outlined VoIP's inherent characteristic as an interoperability tool. Each radio on the network is assigned an IP address, which identifies the radio and connects it to designated ports and addresses. Since the system doesn't care what kind of radio is connected to it, equipment the district had already deployed would be easily interfaced through crosspatches created by the dispatcher. And interoperability is not limited to two-way radios; telephone systems, iDEN phones, satellite phones and intercom systems can all be interlinked.

Then he pointed out how VoIP is a cost-effective solution. Since it utilizes an Ethernet data network as its backbone, communications is possible to and from anywhere a user has access to an IP network. Like most organizations, DPS already had an Ethernet WAN in place; thus, there would be no need to add additional infrastructure to its existing radio networks. But this raised an additional set of concerns for DPS' Department of Technology Services (DoTS), which was resistant to any technology that would add traffic to their data network. DoTS reluctantly agreed to test the Telex IP dispatch system, and after several months they found it to be a stable and easy to use platform that ran at very modest data rates.

Finally, Bailey explained how VoIP networks are easily expanded to grow with users' needs. With support from those knowledgeable in IT to maintain the data network, assign IP addresses and program routers and other network equipment, the number of end users that can be added to the network is virtually unlimited. In addition, Bailey would have the ability to build additional redundancy into the system. IP is by nature a distributed network, meaning an operator can ensure that there is no single point of failure. If a dispatch center were to lose power or a connection to the data network, dispatchers at another location could access the radio system via the data network and take over radio control.

Taking Bailey's advice, the school district set its sights on VoIP. "DPS started out cautiously, but once they found out what they could do with VoIP, enthusiasm spread," says Steve Crout, president of Triple C Communications, a local radio dealer who has been working with DPS for the past seven years.

In April 2005, DPS ordered a complete lineup of IP dispatch equipment, and by August-the start of the school year-Triple C Communications and DPS had created an entirely new IP-based dispatch center at the Hilltop bus terminal using Telex equipment. Dispatchers control the traffic for the entire transportation department using C-Soft console software and IP-223 Dual IP Remote Adapters, with the C-6200 dispatch console serving as back-up dispatch positions and an interface to the phone system.

The IP-223 remote adapter panel converts analog signals transmitted by two-way radio into digital packets that are sent as data over the Ethernet network. It can control up to two base radios and has accessory equipment that allows for connectivity to iDEN (Nextel) phones and standard analog telephone lines.

The C-Soft VoIP software dispatch console controls the radio network. A Microsoft Windows-based application, C-Soft enables a PC with a full-duplex sound card and network connection to monitor and control all two-way radios on the network. The software is compatible with popular touch-screen monitors, offering dispatchers a simple user interface by which to create talk groups and crosspatch other communications networks and equipment to the system.

The C-6200 is a multiline, full-featured desktop control console designed with VoIP technology for use with conventional radio systems. The C-6200 console controls up to 18 lines, contains two-tone paging, three concurrent crosspatches and other standard analog console features.


The Verdict

To say that Bailey is pleased with his new system six months after deployment is an understatement. "I have been working with two-way radios for DPS going on 25 years now, and VoIP is the neatest technology I have seen in communications yet," he proclaims.

But the system has proven to be more than just a nifty technology. They were able to implement it at a fraction of what it would have cost to outfit their dispatch center with traditional radio consoles. According to Crout, "It's opened up some doors they've never had before." For instance, they deployed the C-Soft dispatch software not only on dispatcher computers but also in the terminal manager's office, the program routing office, the radio room and the IT department, which would have been economically impossible without VoIP.

Since the system operates over the school district's wide-area Ethernet data network, DPS did not have to add radio infrastructure to extend the network. In addition, the school district was able to use two-way radios already in their possession, regardless of manufacturer or operating frequency.

DPS now has the capability to control up to eight radio frequencies and three telephone lines from the new dispatch facility with the VoIP equipment, which provides a level of interoperability between DPS' UHF school bus dispatch radio system and the 800 MHz security network they never had before.

"This sped up their accident reporting immensely," Crout says. Now if a school bus is in an accident, the dispatcher can connect the bus driver operating on UHF with a security official for direct two-way communications over the network. Eventually, they will link with the Denver Police Department's 800 MHz network, enabling DPS employees to communicate directly with police during an emergency.

DPS has also built redundancy into the network, which is made much easier with VoIP. Bailey has duplicated the Hilltop dispatch center setup at DPS' brand new Northeast bus terminal near site of the old Stapleton Airport. It's also here that the new 800 MHz security network will be dispatched from.

The school district now plans to network each school via the Telex IP-based platform, a process that will evolve over the next several years. This will enable each school to communicate directly with the security dispatch facility using the district's Ethernet WAN. Every facility will have an IP-223 connected to a base radio operating on their own frequency and will deploy the C-Soft dispatch software, which will allow administrators to use their computers as a two-way radio.

Bailey credits the system's success to VoIP, and particularly its multicast functionality, which gives the network its wide-area characteristics. "The ability to multicast over Ethernet is a powerful tool." With multicasting, he envisions the day when his radio network will also be used in the education process-sending a video feed from a classroom in one school to another classroom in a school across town, for instance.

"VoIP has created endless possibilities for our two-way applications," Bailey says. "We can design and add on to the system in many different ways. It's a great platform to grow with."


Related products

Dual IP Remote Adapter Panel
Flexible, reliable Dual IP Remote Adapter Panel connects C-6200 IP console or C-Soft Windows console by WAN connection and offers numerous dispatch configurations in a variety of modes. The IP-223 remote adapter provides a reliable means of remotely controlling up to two, two-way radio base stations.

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