G S Kok, Hytera's vice-president for subscriber terminals, talks to ...

Tier III trunkingcomed by the firefighters is its digital voice encryptioncapability. “Hytera has one of the bestencryption protocols in the market becauseyou can have, on DMR, three scenarios: 16bits, 128 and 256 bits”, comments Mr Scott.“We’ve given them the capacity to change theirown keys by themselves. This way, the clienthimself is able to control the privacy in theircommunications.”Traffic loadingA conventional, one-slot trunking system cansupport up to 45 radios and three or four companyfleets, Mr Scott finds, although even thatmodest level of loading can lead to contention.“On pseudo-trunking, you can actually pumpthe system up to 75 units and have about 6–7companies operating with almost no collisionswhatsoever”, he says. “But here is one of thefactors that made a big difference with Hytera.Pseudo-trunking gave us an edge on loading capabilitieswith our clients.“Obviously you have to be very efficient inchoosing, because you cannot choose two taxicompanies on the same system, because theyare going to flood it! But you have to mix andmatch and be very comprehensive upon thetype of client you are going to use with thepseudo-trunking system.”Connecting with IPAnother Hytera system feature he values is theability to interconnect repeaters using IP datalinks, enabling wide-area coverage to be providedsimply. “Once you operate pseudo-trunkingDMR Tier III: new network equipmentdelivered to Guatemala by HyteraDriver’s radio in a Transurbano bus, a harsh environment for mobile communications.But dust and vibration are not the only hazard in Central America: Crelosa reportsthat a number of Hytera radios were inundated in flood waters after a recent tropicalstorm, some of them to a depth of more than one metre, but all of them survivedsingle-site, the first thing that your client wantsthen is more coverage”, he explains. “Thatmeans that you have to install repeaters.“The interesting part here is that the Hyteraproduct has the automatic roaming capabilityinstalled into the system, without an extra option.When we buy from the factory, it comesin with all the bells and whistles, so it’s easierfor us just to program whatever we need.“But the scenario of roaming works reallywell. Here’s an interesting hint: there is somethingcalled beacon programming on the repeater.It means that if no one is speaking – ifthere’s no traffic flowing through that repeater– the repeater has to have a beacon to tell anyradio scanning on DMR that the repeater ison, and it’s working and it’s ready to receivesignals. This way, the radio can actually do theroaming into that site.“That is a big tip”, he laughs. “Either youhave a client who actually uses a repeater sothat the radio can find it, or you do your beaconvery often.”But he continues: “DMR wide-area networkinghas a wonderful capacity for managementand administration, simply because youare able to program all the repeaters on the radio.You can even tell it that, for example, yourradio can only access Repeaters 1, 2 and 3 – not4, 5 and 6. We can do that. And if you want 1,5, 6 – not a problem.“If the radio gets stolen, we can turn it off,or radio-kill. We can take that ID off the system,so he will not be able to get into the systemand communicate.Split affectionsFor Crelosa, a very special feature of Hytera’sDMR radios is their support for unconventionaltransmit/receive frequency splits. These are commonlyrequired in Guatemala and other CentralAmerican countries, in place of the tidy 10 MHzor 5 MHz splits usual in Europe. “Specifically,for Guatemala, you’d sometimes get 1 MHzwhile sometimes you get 3 MHz and sometimesyou get 10 MHz”, Mr Scott observes. “Well, myfriend, welcome to Guatemala.”The solution to this problem, he continues,is simple enough: you approach your radiomanufacturer and you ask them to changetheir entire programming scheme.“Well, Hytera did it”, he adds. “And Hytera,in version 2.0, will have that difficult channelsplit. For that, with humility, I have to thankthe people at Hytera, because they have beenlistening to me.”And he ends: “I have fallen in love withHytera because of the way Hytera works – theybring you into a family. That’s very difficult forme to explain, but it’s a family feeling thatreally pushes you forward into much, muchmore than a business relationship. I have hadG S Kok here, the head of engineering, askingpersonally what would I prefer to have inour next radio. And everything that Hytera haspromised to me, it has come true.”Sponsored by11