Slice of the spectrum
- By William Jackson
- Jul 30, 2004
D.C.'s fledgling network for first responders underscores the bandwidth battles
'We're concerned about the future of the spectrum.'
J. Adam Fenster
The District of Columbia is ready to launch a 10-site, citywide broadband mobile network that will give first responders high-speed access to video and data.
'This is a pilot network,' Robert LeGrande, the district's deputy chief technology officer, said last month. 'We have one transceiver site up and working. The other nine sites will be operational [in August].'
The IP network will be the first of its kind in the nation. Police, fire and rescue personnel will have up to 1.5 Mbps of bandwidth to access video feeds and remote applications on notebook computers, personal digital assistants and, eventually, cell phones.
The one-year, $2.7 million pilot is more than a test of technology. The city is part of a coalition hoping to demonstrate the value of the applications'and the need for additional radio spectrum.Not available
'We need to have 1 Mbps throughput,' LeGrande said, and right now public safety agencies do not have the spectrum available.
A chunk of bandwidth in the 700-MHz band now used by television broadcasters is scheduled to come on the market soon, and the Federal Communications Commission is planning to auction it to commercial users. The Spectrum Coalition for Public Safety wants 10 MHz of that band set aside for public safety.
Broadcasters will be giving up the band as they move to digital broadcasting, expected by the end of 2006. FCC plans to auction the bandwidth currently are on hold.
'We're concerned about the future of the spectrum,' LeGrande said.
Washington's network has an experimental license issued in March by the FCC. The commission wants to make 12 licenses in the 700-MHz band available to commercial users in each of six geographic regions. That includes six licenses in the 10-MHz-wide C block and six in the 20-MHz-wide D block. A 10-MHz swath in the middle of the band already has been set aside for public safety use, but the coalition is lobbying for an additional 10 MHz in the C block.
Contracts were awarded in December to Motorola Inc. as the systems integrator and to Flarion Technologies Inc. of Bedminster, N.J., for equipment.
Flarion is providing mobile air interface technology called FLASH-OFDM (Fast Low-latency Access with Seamless Handoff-Orthogonal Frequency Division Multiplexing). The system's heart is the RadioRouter, a packet-switched base station that will route signals to the city's DC-Net, an OC-48 Synchronous Optical Network. Base stations will be linked to DC-Net edge routers by T1 lines.
The system will provide on-street coverage initially, with some in-building coverage later.
FLASH-OFDM wireless network cards are available now for notebook computers and handhelds, and chip sets for cellular phones are expected by next year, said Ronny Haraldsvik, Flarion's vice president of global marketing and communications. Because the system is IP, users will be able to access legacy databases and applications without modification.
Maximum download speed would be 1.5 Mbps, but the average user experience is about 1 Mbps, Haraldsvik said. Uplink speed is 300 Kbps to 500 Kbps, with bursts up to 900 Kbps possible. Uplink and downlink use channels of 1.25 MHz each.
Quality-of-service provisions let administrators prioritize applications or access by individual user, department or other criteria.
Latency typically is a problem in IP over cellular networks. Haraldsvik said latency in the Flarion system is no more than 50 milliseconds, which can support streaming video and voice over IP.
'We want to start with the things we are at risk for in this city and enhance our response to these,' LeGrande said. 'We want to work with our bomb squad to get them remote video ca-
pability.' The hazardous material team will have remote access to sensors around the city to detect chemical, biological or radiological threats.
The network also will beta test Motorola's Greenhouse Project, a high-speed public safety data application that enables wireless video, voice and data transmissions over IP at speeds of up to 468 Kbps.Limited applications
LeGrande said the city does not anticipate moving its traditional voice communications to the new wireless network. He said initial applications on the network would be limited.
'We just completed a $40 million upgrade of that,' he said. The upgraded system improved coverage inside the District's buildings and Metrorail tunnels, and added 63 vehicle repeater systems. 'It's my belief the District of Columbia has one of the best, if not the best, communications systems in the country.'
William Jackson is freelance writer and the author of the CyberEye blog.