700 MHz challenges far from over

Two months ago, President George W. Bush signed budget-reconciliation legislation that included a firm date for TV broadcasters to finally vacate the 700 MHz band — a chunk of which will be reallocated to first responders — and $1.2 billion in funding earmarked for public-safety communications. Now the question becomes: how will public safety use these vital airwaves?

Public-safety users have clamored to get their hands on the 24 MHz portion of the 700 MHz band that was allocated to them in 1997 to ease the overcrowding of spectrum that plagues the country’s top markets. Under previous law, TV broadcasters didn’t have to leave the band until Jan. 1, 2007, provided 85% of the homes in their license areas could receive digital signals. But it was unclear when, if ever, the 85% penetration necessary to force broadcasters out of the band would be achieved.

The new law requires broadcasters to clear the 700 MHz airwaves on Feb. 17, 2009, after which the aforementioned 24 MHz of frequencies will be allocated nationwide to public safety, nearly doubling the spectrum holdings that first responders have today. Other airwaves in the band will be auctioned to commercial operators in a bidding process expected to generate $10 billion or more in additional revenue for the government.

So, what does public safety plan to do with the 700 MHz band? Since the frequencies were allocated nearly a decade ago, the FCC already has configured half of the spectrum for voice and the other half for broadband data services. Motorola already offers infrastructure, mobiles and portables that include both 800 MHz and 700 MHz capabilities, meaning public-safety operators can hit the ground running with Project 25-compliant voice equipment once the spectrum is cleared.

But the bigger unknown is how data services will be deployed in the band. The Spectrum Coalition for Public Safety had been trying to secure an additional 10 MHz for broadband data services, but enactment of the budget-reconciliation measure effectively ends such discussion, said Harlin McEwen, chairman of the International Association of Chiefs of Police communications and technology committee.

“All the spectrum that is not going to public safety is ready to be auctioned, so it is highly unlikely [that more frequencies would be dedicated to public safety],” McEwen said.

In light of this, the public-safety community recently asked the FCC to modify its rules to allow for additional broadband data in the 700 MHz band and to let public safety choose how to divide the band, rather than being limited to a rigid 12 MHz voice/12 MHz broadband data split.

“Public safety wants the flexibility to choose,” said Stu Overby director of global spectrum strategy for Motorola. “The higher the data rate you go, the less coverage you get per site. Not every public-safety entity wants to choose the same thing.”

According to Dave Buchanan, chair of the National Public Safety Telecommunications Council’s spectrum management committee, NPSTC has proposed to the FCC that the commission reallocate public safety’s resources on a regional basis by allowing 1.25 MHz operations with a larger guard band. This would allow public safety to leverage commercial technologies such as CDMA 1× EV-DO — which is designed to deliver wireless broadband data services within 1.25 MHz of spectrum.

The next generation of 1× EV-DO, known as EV-DO Rev. A, will be able to support real-time push-to-talk, or P2T, services with quality-of-service assurances and latency below 100 milliseconds. Commercial mobile services are playing an increasingly important role in the public-safety communications arena as they evolve to support first-responder features such as advanced P2T and high-speed data transmission.

Other possibilities include proposed platforms, based on the IEEE 802.20 standard, that incorporate orthogonal frequency division multiplexing (OFDM) technology, as well as mobile WiMAX, which could provide advanced applications such as video surveillance applications and critical data transmission.

For example, the District of Columbia in September 2004 launched a pilot high-speed wireless broadband network, known as the Wireless Accelerated Responder Network (WARN), for public safety using an experimental 700 MHz license. Motorola and Flarion Technologies provided the technology that leveraged Flarion’s proprietary Flash-OFDM technology, which is now owned by Qualcomm and likely will be a candidate for the 802.20 standard. WARN was first used in January 2005 for President Bush’s second inauguration and subsequently for his 2005 State of the Union address.

WARN is supported, managed and operated by the district’s Office of the Chief Technology Officer’s (OCTO) Wireless Programs Office (WPO) and consists of 12 radio sites and 200 network devices (i.e., PC cards) that enable wireless interconnection of local and federal public-safety mobile devices throughout 95% of the district. The OCTO has been making the case for a nationwide Flash-OFDM network in the 700 MHz band to provide critical high-speed data services.

“This is a major step toward delivering critical information to police, fire and emergency medical services workers, wherever they need it to safeguard our lives,” said Suzanne Peck, district chief technology officer, when OCTO launched WARN. “The applications our first responders have asked to support wirelessly are only the tip of the iceberg. Just as the Internet has matured into a powerful communications tool, this network will serve as a catalyst for innovation.”

Possible 700 MHz public-safety reallocation: Less channels, wider guard bands

Large guard bands allow for commercial equipment deployments

Source: National Public Safety Telecommunications Council

Offers three paired 1.25 MHz channels, with 1 MHz and 1.25 MHz guard bands between broadband and narrowband operations

Supportable technologies:

• CDMA EV-DO
• IEEE 802.20a proposals
• Mobile WiMAX (IEEE 802.16e) may be possible

All with frequency reuse of 100%

• Three simultaneous independent, full-coverage and overlapping broadband deployments

Possible 700 MHz public-safety reallocation: More channels, smaller guard band

Smaller guard bands require more expensive filtering

Source: National Public Safety Telecommunications Council

Offers four paired 1.25 MHz channels, with 500 kHz guard bands between broadband and narrowband operation

Supportable technologies:

• CDMA EV-DO
• IEEE 802.20a proposals
• Mobile WiMAX (IEEE 802.16e) may be possible

All with frequency reuse of 100%

• Four simultaneous independent, full-coverage and overlapping broadband deployments

Help is on the way

Public safety’s hope of attracting vendors willing to adapt commercial offerings to the 4.9 GHz sector is coming to fruition.

A host of vendors with mesh-networking capabilities are tuning their existing products to the 4.9 GHz band while giving public-safety entities 2.4 GHz public access as well.

Motorola recently announced general availability of its quad-radio product, MotoMesh, which operates in both the 2.4 GHz and 4.9 GHz bands.

Now being deployed in 12 U.S. cities, MotoMesh uses two standard 802.11 radios and two proprietary Mesh Enabled Architecture radios in one solution. The four radios can be turned up as needed and configured either as access or backhaul on a link-by-link basis. Other notable MotoMesh features include a seamless handoff between nodes with session persistence.

“Other vendors may support session persistence, but not seamless connectivity with no interruption,” said Roberta Wiggins, Yankee Group analyst.

In addition, Alvarion last month released a commercial version of its BreezeAccess line of broadband wireless infrastructure targeting the 4.9 GHz frequencies. Although BreezeAccess is Alvarion’s legacy equipment line — which is being replaced by the BreezeMax WiMAX portfolio — the vendor has tweaked its older technology by adding orthogonal frequency division multiplexing (OFDM) and greater range to its standard package. The result is a system Alvarion believes will supply voice over IP and broadband data connections that could be used for public-safety tasks ranging from traffic signal management to remote video and voice surveillance.

Alvarion said pre-commercial trials of the system already have been launched with several agencies, and one such system helped uncover a drug-smuggling operation in an unnamed jurisdiction, resulting in narcotics seizures and several arrests. The base station supports encrypted non-line-of-sight connections to sensors, cameras and traffic-control equipment with premise radios. It is designed to work with Alvarion’s other public-safety system, the BreezeAccess 900, which supplies mobile data and voice communications to vehicles.

Other mesh-networking vendors planning to jump into the public-safety broadband data arena include BelAir Networks, which is planning to offer a 4.9 GHz option later this year, according to the Yankee Group, and SkyPilot Networks, which is planning to re-tune 5.8 GHz radios to work in the 4.9 GHz band. Also, Strix Systems’ Access/One platform supports 4.9 GHz — while providing metro-scale Wi-Fi at 2.4 GHz — but at lower power levels, according to the Yankee Group. For higher power applications, a new module is required to meet FCC requirements. However, neither SkyPilot nor Strix have demonstrated such a capability so far.
— Lynnette Luna