chekker

Trunked radio technology is suitable for mobile communications in a limited area of around 15 km in diameter. Under the service name Chekker, Deutsche Telekom offers trunked radio services in Germany in competition with private companies. Chekker is structured in cellular city networks.

Unlike private mobile radio, in which a group of subscribers is allocated a radio channel, trunked radio provides a bundle of radio channels for transmission. The trunked radio service Chekker assigns the subscriber his own radio channel if required, which is provided exclusively for the maximum connection duration of 60 seconds. The switched transmission channel method makes much more effective use of the limited radio frequencies available.

The frequency range between 410 MHz and 430 MHz is available for the Chekker networks. In public trunked radio networks, transmission from the mobile station to the network, known as the lower band, takes place in the frequency range from 410 MHz to 418 MHz; the return channel, known as the upper band, for transmission from the network to the mobile station takes place in the frequency range from 420 MHz to 428 MHz. At the same time, this defined a frequency spacing of 10 MHz between the transmit and receive channels. For private, local trunked radio networks, the frequency ranges from 418 MHz to 420 MHz and 428 MHz to 430 MHz are provided. The channel width is 12.5 kHz. In trunked radio networks, traffic is controlled via a so-called organization channel. Signaling between terminal and network takes place via this channel; in addition, status messages can also be transmitted from terminal to terminal via this channel. The transmission in the organization channel takes place with a transmission speed of 1.2 kbit/s. The information transmission is analog and half- duplex. Information transmission is analog and half-duplex.

The central control and switching unit is the Main SystemController( MSC). Each radio cell of the network supports up to 20 radio channels; each radio channel bundle contains an organization channel for control purposes. The user channels operate in analog mode, unlike the signaling channel, which is designed for digital transmission speeds of 1200 bps.

Chekker is best suited for transport companies, courier services, service companies, government agencies and field workers.