Matters are slowly improving now as the authorities gain a grip on the favelas; but, with a series of detailed graphs and tables of casualty figures, Lt-Col Cajueiro shows dramatically that it has been more dangerous to join Rio’s military police department during the past 14 years than the United States Army through all the wars of the 20th Century. In those 14 years, over 2000 PMERJ officers have been killed on duty.

As well as law enforcement, there can be natural events to deal with. In January this year came exceptionally heavy rains, causing flooding and devastating mud slides which swept through several cities in a mountainous region of Rio de Janeiro State. This disaster, almost without precedent in Brazil, cost more than 900 lives.

With this experience, DETEL is currently reviewing its emergency communications readiness. Some new emergency communications vehicles are part of these plans.

Communications studies

The state’s first practical experience of TETRA came in 2007, with a small installation to support the Pan American Games in Rio in that year. “Since 2003 we had studied many communications protocols”, says Lt-Col Cajueiro. “We studied APCO 25, we studied Tetrapol, we studied TETRA – and we understood that the TETRA was the best. So we were waiting for the chance to go to TETRA. Then the Pan American Games came and we began to use TETRA.”

Since then, the network – an IP-based Nebula system from Teltronic – has been extended. Today, DETEL operates 61 radio sites, of which 31 supply TETRA coverage across the city region. The remainder carry the old analogue service. Digital coverage could therefore be wider than it is, and the communications team would like to have more TETRA sites, extending coverage to the interior of the state – but back in 2007 it was decided to remain with the existing government radio sites.

Nonetheless, Lt-Col Cajueiro is enthusiastic about the TETRA system, not least because of the high traffic capacity it provides and the dependable performance offered by an independently-managed system. “One of the best properties of TETRA is because when you are in trouble, or a crime area, or a big problem, you can operate with four people calling”, he says. “You have the best spectral efficiency. Many people can talk. It’s very important when you are in a very terrible situation and all the cellular systems are down.

“When we have here Carnival and we have Reveillon [New Year’s Eve], Fathers’ Day, Mothers’ Day, many people talk at the same time and we have the cellphones shutting down. Then we understand that the spectral efficiency is very important. If you have spectral efficiency, like 4 × 1, like TETRA, it’s very important for us and for everybody.”

Frequency switch

But another legacy of the 2007 network plan is that it was for vehicle radios only, not handportable coverage. “But the policeman on the ground, in some places he wants to use portable radios”, Lt-Col Cajueiro points out. “In Rio nowadays we understand this, and in our plans we intend (but it’s not possible, because we don’t have money for this!) to put our state on portable, mobile radios. We are studying where we can put the coverage and the extra sites, and maybe some mobile units to put coverage on the site during events.”

Now DETEL is buying radio planning software so that, at the same time, its technicians can plan the best radio sites in readiness for one further evolution – this time imposed by Anatel, Brazil’s national telecoms regulator. Anatel plans to move the emergency services out of their 450?MHz band by the end of 2018, to clear it for future rural broadband Internet services. DETEL will migrate to 380–400?MHz, the frequencies used by public safety organizations in Europe. “For us that’s good, because we see that it’s not only in Brazil”, comments Lt-Col Cajueiro. “When you buy something that is international, you get a good price.”

One factor which could help close the system’s performance gap would be the new generation of higher-powered handportables, which are allowable in Brazil. “Maybe it’s better with 3 watts, because we have a network designed for analogue and we have problems with coverage”, he says. “If we can use more power, it’s better.... We will plan the future network for 3 watts, 1·8 watts or 1 watt. We understand the inverse correlation between power and the number of sites and the coverage.”

Another facility he is looking for in new radios is ‘man down’ alerting. “Some of the officers go into places which are quite dangerous, so this is very important”, he says.

Narcotics sweep

For some operations, the force makes use of the full range of TETRA capabilities. Lt-Col Cajueiro describes a major multi-agency anti-narcotics operation which took place in Rio one Sunday last November, a long-planned, armed invasion of a group of shanty-towns known as the Complexo do Alemão (German Complex). He likens this place to the caves of Afghanistan – a drug traffickers’ fortress with tunnels into the hillside and arsenals, run by a kind of army.
(中国集群通信网 | 责任编辑：陈晓亮)