![]() ![]() ![]() Therefore, the TETRA MoU does special compatibility tests. ISI or open channel) which makes the combination of devices made by several suppliers difficult. But not all the features that are supported are specified (e.g. There are three important specifications: Voice plus Data (V+D), Packet Data Optimized (PDO) and Direct Mode ( DMO). In the DMO only one frequency and the simplex mode is used.Īll the specifications can be downloaded from the ETSI web-page after registration. It uses two frequencies for the up- and downlink and use full duplex (a device can send and receive simultaneously) and half duplex (a device can send and receive only alternatingly) use. TETRA is based on TDMA and uses four timeslots with a bandwidth of 25 kHz per carrier. In 1990 proposals for the standard were investigated and around 1995 one of the proposals, TETRA-25, was chosen by the ETSI. TETRA is an open trunked radio standard that was started in 1988 by the European Commission and the ETSI for the special needs of professional mobile radio needs including not only speech but later also data. The operators try to minimize the costs GSM networks cause and try to maximize the services and prices for the end users, for instance with dial tones for € 1.99. These consumer care less about security and quality of service. Several technologies are available for public safety and security ( PSS) networks : TETRA and Tetrapol have been developed for advanced mobile radio requirements whereas GSM and UMTS have been developed for end consumers. ![]()
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