Technology choices

Next on the programme came presentations from four of the major wireless technology providers. First to speak were Pedro Schmid and Markus Schwab, from the network infrastructure maker Nokia Siemens Networks, with an introduction to LTE and its growing success among wireless carriers.

Focusing on the requirement for spectrum, Mr Schwab explained that a small slot would be not be enough. “A radio broadband experience starts with a bandwidth of 5?MHz”, he said. “Below, it’s not really broadband. An optimum would be something like 10?MHz, or even more.” 

With LTE, it would be possible to have a full range of cell types, from femtocells up to countrywide services, and even communication with high-speed trains, with full handovers. Measurements in China had shown that uplink and downlinks worked at speeds up to 230–240 km/h.

To integrate TETRA with the 3GPP programme, the next opportunity would be in the coming Release 12 of the 3GPP standards. “In Release 12 they will start to talk about the requirements of critical voice and data communication and we are supporting this very strongly”, Mr Schwab said. “Now it’s time to get the requirements for 3GPP concerning critical voice communications. And then, in something like 2014, standards are fixed. If things are done today, we benefit from them tomorrow.

He added: “The US will do it anyway. The P25 community will do it – so it’s now a matter of to participate or to be out.”

And Mr Schwab’s colleague, Pedro Schmid, emphasized: “Our statement to the audience from Nokia Siemens is that the TCCA should participate in 3GPP Release 12, which is starting now. That’s our clear message.”

The promise of LTE

Francesco Pasquale, of Selex Elsag, was the next speaker, and his company’s outlook turned out to be closely similar. “In our mind, LTE is the choice”, he said. “LTE is the most promising technology to answer broadband needs in the PMR sector.”

Asking himself who was pushing for broadband, and why, he said: “The users are realizing that video transmission – high-resolution, full-motion video transmission – is passing from being just a future nice-to-have application, as it was a few years ago, to being a future mission-critical application.”

Enlarging on this, he went on: “We are convinced that, once broadband solutions adequate for PMR use are available, this will not just enable video transmission but will totally reinvent the operational routine.” For example, consumer products might be adapted to the PMR environment; and professional users might find a use for Skype-like chat applications. “I’m thinking about, for example, the use of devices such as tablet PCs. Of course, they will have to be ruggedized, not usual tablet PCs. But we are convinced that we will go in that direction.”

Any PMR technology based on LTE would need to be integrated with existing digital technologies (TETRA, Tetrapol, DMR, P25) and adapted to meet users’ needs. “TETRA has been so successful because it has not remained limited to national, PSS networks but has spread across all sectors and sizes of systems”, Mr Pasquale argued. “But to do the same, scalable, low-cost platforms should be conceived – whereas for the moment it’s quite likely that LTE industries are focusing on providing quite expensive and big solutions for large public networks.”

However, he added: “Whatever the technology mix is, the network needs to be perceived by the users and applications as if it was a single technology network... TETRA for voice and basic applications, but complemented by a TEDS or LTE data overlay for more demanding applications.

“A mixed approach with LTE hotspots in metropolitan areas and other locations of interest, such as airports or sports stadiums, and TEDS elsewhere in rural and isolated areas will be the choice for the future, to provide enough coverage everywhere. Of course, as it was for TETRA, a rapidly deployable solution will also be needed to cover the limited areas in case of disaster incidents or special events.”

But the major difficulty continues to lie in obtaining suitable spectrum. “As Selex Elsag, we have people within TCCA and CEPT fully supporting the request for PPDR broadband spectrum below 1?GHz”, Mr Pasquale continued. Ruling out the 400?MHz range currently used by many PMR systems (“We don’t think it would be a good idea at all to destroy PMR services in other sectors to find spectrum to give to PPDR users”) and the possibility of narrow LTE bands of 1·4 or 3?MHz (TEDS would be a better use of the space), he concluded: “We are really convinced that the 700–800?MHz bands would be much more viable option.”
(中国集群通信网 | 责任编辑：陈晓亮)