TETRA to bring trunked radio into broadband era

With the commercial telecoms sectors pushing broadband services at ever-growing data speeds - and the mobile industry in particular increasingly data-centric thanks to smartphones, dongles and migration to 4G - it should be no surprise that the vertical and public comms sector is also setting its sights on broadband.

The need for speed in the public and vertical space has been highlighted in the last couple of years via interest in municipal Wi-Fi mesh networks that public safety agencies can access for transmitting photos and video streams. But such solutions aren't without drawbacks, chief among them the capex and opex involved, coverage requirements and security and reliability issues.
However, one thing driving interest in such solutions was the fact that dedicated digital trunked radio systems like TETRA, TETRAPOL and P25 - which public safety agencies and vertical industries like transport and energy have been using for one-to-many comms for years - do not support fast data speeds.

Not right now, anyway. That's set to change in the TETRA community with the arrival of TEDS (TETRA Enhanced Data Services), an upgrade feature included in TETRA 2, the next-gen version of the original TETRA trunked radio standard developed by ETSI.
Indeed, broadband data was high on the agenda at this year's TETRA World Congress in Singapore in May. Several vendors at the event, including Motorola and EADS Defence & Security, unveiled the first new TEDS products. The same month, EADS also announced the world's first TEDS pilot with VIRVE, Finland's nationwide TETRA network run by State Security Networks.

While first-gen TETRA supports low-speed data apps (less than 5 kbps) in a 25 kHz channel, TEDS offers considerably faster speeds, albeit more on par with first-wave 3G networks like UMTS and cdma2000. Speeds depend on modulation schemes and spectrum availability, but TEDS can support channels as wide as 150 kHz and, with 64 QAM modulation and four slots, can hit data speeds of close to 540 kbps.

However, TETRA customers hungry for broadband face a number of challenges in implementing TEDS. And the biggest one is a lack of spectrum to support it.

Spectrum problems

In fact, despite its potential 540-kbps capabilities, the first wave of TEDS gear coming out now will be limited to between 50 kbps and 100 kbps via four slots in a 50 kHz channel primarily due to limited spectrum availability for existing TETRA systems, says Kevin Graham, Asia-Pacific regional director for Sepura.

"Public safety agencies were never allocated much spectrum for TETRA because it used 25 kHz channels and didn't generate high-volume traffic," Graham told Wireless Asia. "Now in Asia we're seeing a lot of effort in spectrum reform, but everyone wants more - not just TETRA users, but mobile operators and broadcasters as well."

David Chater-Lea, fellow of the Technical Staff at Motorola and chairman of ETSI WG4, says that competition for spectrum is also forcing TETRA users to set more realistic goals for spectrum lobbying, which in turn will limit TEDS' data performance.

"We're trying for 2 x 3 MHz for voice and 2 x 3 MHz for TEDS. Ideally we'd like 2 x 10 MHz for true broadband, but that's probably pushing it," he says. "We're looking at the digital dividend from analog broadcast spectrum as a possibility as well."

Even if competition for new spectrum wasn't already fierce, another problem is that TETRA users themselves aren't sure just how much spectrum they need, Chater-Lea says.

"Despite all the interest in higher-bandwidth apps, the public safety sector is still learning what they can do with data with the spectrum they have," he says. "The more they use it, the more they'll see the need for additional spectrum, but it will take a long time to get that moving."

Complicating matters further, says Peter Goulding, chief superintendent of  London's Metropolitan Police Service (MPS), is that different users will have different data requirements even within the same TETRA network.

"Everyone needs to assess what we really need and where we need it and who we're delivering it to, because whatever we do, it has to cover the entire population - we can't pick and choose where we deploy these capabilities," he says. "We have to get away from the idea that everyone wants video everywhere, because that won't always be the case."

Also missing is a lack of organized regulator lobbying on behalf of TETRA users. In May, the TETRA Association signed a formal agreement with public safety communications forum PSC Europe to cooperate in lobbying the EU government for more spectrum. But in Asia - which at 25% global market share is the second largest TETRA region after Western Europe, and the faster growing of the two - no such centralized spectrum allocation body exists.

"There's no easy answer for Asia because it's country-specific with no centralized management of the process for the region," Chater-Lea says. "We've organized seminars in places like China to explain the situation to government agencies. The best thing to do may be to let Europe serve as an example for frequency management."

The fragmented approach to spectrum acquisition could also create harmonization issues down the line, says Graham of Sepura. "For voice it's harmonized in the EU, but for TEDS it isn't, and that's a problem if you have terminals going across borders."

Nevertheless, EADS CTO Eric Davalo advises TETRA users to take action in their home markets to make their voices heard and acquire whatever additional spectrum they can.

"You're going to need more spectrum to get more data capability, so it's up to you to go back to your national regulators and ask for it," he said. "You have to demonstrate a real need for it, because mobile operators and broadcasters already have their lawyers pushing for more spectrum. We need to do the same thing. It won't be solved in two days or even two years, but you need to start pushing now and keep pushing if you want to succeed."

The 4G option

In the meantime, Sepura's Graham says TEDS - and TETRA 2 in general - is still likely a couple of years away in terms of live deployments.

"Users still need to get the spectrum for it, and once they get it they'll have to go through a test and trial phase," he says.

Given the delays in TEDS deployments, however, some trunked radio users, particularly in the public-safety sector, are pondering an alternative solution - utilizing wireless broadband technologies like Wimax and LTE.

A December 2009 report from Frost & Sullivan pegged both technologies as potential enablers of broadband data apps for public safety networks. Wimax operators in particular have been looking for whatever niche markets they can target to differentiate themselves from HSPA and LTE and tout their all-IP credentials.

That said, however, several public safety agencies in the US have endorsed LTE as the preferred technology for a proposed national broadband network for first responders in the 700 MHz band. In July, Motorola won the first contract under that endorsement - it will supply San Francisco's public safety agencies with a 700-MHz LTE network that will serve as a broadband data overlay for the city's existing P25 trunked radio network.

Perhaps unsurprisingly, the TETRA community is quick to point out the downsides of using commercial LTE or Wimax networks as data solutions in a public-safety context.

"In the case of LTE, for example, there would be no coverage in rural areas," says Phil Godfrey, chair of the TETRA Association. "Also, in emergency situations, cellular networks tend to collapse under the weight of demand. Emergency networks need full coverage and redundancy."

Motorola's Chater-Lea says that TETRA users may turn to LTE and Wimax as short-term measures, "but in the future we want to see something integrated with the TETRA standard, so we can have a single terminal."