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Replacing the traditional day/night switches, the system will prevent lamps from remaining lit wastefully during the daytime. So far the system has been implemented only along major roads and highways, but next it will be extended to all parts of the city via TETRA. And there are plans to bring in other city agencies and functions – for example, the traffic lights (known in South Africa as robots) at main road junctions. GSM modems have been used to control and synchronize these, but theft of the SIM cards has left many of them operating out of phase or not functioning at all, contributing further to Johannesburg’s traffic jams. City Power’s network is working successfully and delivering the communications benefits seen by other TETRA users around the world. Based on infrastructure from Rohill, the system is being implemented and maintained under a service level agreement by Ikwezi Maintenance & Communications. Ikwezi has also been asked to complete the original network deployment plan by installing the remaining base stations. The company is an offshoot of Global Communications, a radio supplier and system integrator established in the Johannesburg-Pretoria area for some 35 years. But for other TETRA networks in Southern Africa, the journey has been more difficult. An example is a system for the municipality of Tshwane (Pretoria). Initially the contract went to an office automation company which seems to have lacked the radio knowhow and TETRA experience to implement the technology successfully. Installation errors and an incorrect choice of antennas at the base station sites led to disappointing radio coverage. But after many difficulties and delays, the project was eventually placed in Ikwezi’s hands, and today the system is working well and achieving its original goals. “It was a disaster”, declares Errol Baker, of Global Communications, candidly. “But we’ve been given this opportunity to recover and try to get TETRA back and give it a good name – and that’s what we’re doing at the moment. So far it is working like a dream. We’ve really got it up and running properly.” Elsewhere, Ikwezi’s drive to restore the reputation of TETRA in Africa has concentrated on an expanding municipal network in Mbombela (formerly Nelspruit), and a system serving a key centre of South Africa’s mining industry, at the Rustenburg mines of Anglo American Platinum. Remote control “We have remote access into all our networks, which gives us the capability to interrogate the system and pick up a fault before it becomes a serious issue”, says engineer Jon-Pierre Booysen, at a screen display on his PC terminal in Global Communications’ headquarters. “We do this via our own VPN access, though some clients prefer using their own VPN access. In this instance we’re looking at the Mbombela system, which is close to the Mozambique border.” Clicking his mouse, he continues: “Over here we have different sites, with the Civic Centre being our main site that does all the switching. So we go to Civic – and then you have subdivisions for microwave going in and out, ethernet switches, and then all the TETRA devices. With TETRA devices we can have a look at the amount of subscribers currently on the network. “Every five minutes we take a grab of the system to see the amount of active calls. You can clearly see that round about two o’clock in the afternoon, when they do a shift change, there’s a peak, and from midnight to about 5 a.m. it’s the lowest. We can gather historic data from this.” The remote access system can also be used to upload software upgrades and updates. But besides reporting the overall health of the radio equipment, it monitors details such as the temperature in the radio cabinets and the state of the incoming electricity supply. In case of a failure at a site, there is a battery back-up supply which will last for up to two days. But the monitoring system does not rely only on human vigilance. “Should a breaker fail at a site, the intelligent system that we have will indicate a fault and raise an alarm in the system”, Mr Booysen explains. “We have some reporting rules, and it will send it out by e-mail or SMS, and we can have distribution lists on that. “This system has eight sites, one carrier each, so it’s quite a small system. We are planning an upgrade now and the order for that is imminent. We would add another five sites and upgrade all sites to two-carrier.” Supporting around 280 users at any one time, all equipped with Sepura terminals, the Mbombela network is used by the emergency services and public utilities, roads and transport, bus services, and staff at the town’s large football stadium. “During the 2010 World Cup, we ran call detail recording and with 600 Sepura terminals they performed a little bit over 25?000 calls within one month”, Mr Booysen remembers. “The call setup time was just over 100 milliseconds. We were using quite a fast microwave backbone.”
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