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Sonntag, den 29. Juli 2007 um 20:14 Uhr
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D-STAR
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Folie 11

The local repeater used for date and voice communication is for the 1.2 GHz band. The transfer rate for data communication of 128 kbps requires a occupied bandwidth of about 130 kHz, therefore is it not possible to communicate (with data) on the occupied bandwidths of low frequencies such as 144 MHz etc. The transfer rate for voice communication is 8 kbps in an occupied bandwidth of 8.5 kHz which is narrower than existing analog FM, therefore as far as bandwidth is concerned, it is possible to use voice on frequencies used for existing analog FM.
The simultaneous use of data and voice communication is common, so for the antenna, to reduce the respective interaction, the antenna is an all in one type.

Folie 12

The backbone repeater that sends the multiplexed data and voice communication is an encased unit operating in the 10 GHz band, and the transmit output power is 1W/2W.
In the backbone field tests that have been carried out so far, the limit for communication distance at 10 GHz of a 90cm parabola antenna with 36dB gain, output of 1W and taking into consideration the weather conditions, is about 20 km (12.5 miles). Because the frequency is so high, it is affected by heavy rain or fog, so when more than 30mm (12 inches) of rain per hour falls, there is a possibility that the communication will be interrupted or will stop. Details on the multiplexing method will be explained later.
By using this antenna for analog FM voice communication at 10 GHz, communication distances of up to 100 km (62.5 miles) is possible, however in the backbone, the data transfer rate becomes 10 Mbps in an occupied bandwidth of 10.5 MHz, so the communication distance becomes drastically shortened when compared to voice in narrow bandwidth communication.

Folie 13

A representation of an actual repeater site structure is shown in this diagram. Data communication and voice communication operate in separate repeaters respectively, and connection of a conventional repeater like an analog FM repeater, as shown in the diagram is also possible.
As shown in the diagram, a modem is placed at the repeater site, so when connected to a wired line, access to the Internet is possible. Also, if a server is connected, each respective terminal can access the server.

Folie 14

This diagram shows even more specific details of a repeater site. The yellow boxes indicate an existing analog system, and shows that it is possible to connect it to this digital system. The bit-rate conversion or the protocol conversion systems for the analog system has not been prepared yet, but it is possible for these systems to be developed in the future.

Folie 15

This diagram shows the part indicating D-STAR’s digital data communication, digital voice communication and the backbone structure and connection. At each repeater site a controller is necessary, but this controller is included in the digital data repeater. The data signal and voice signal is multiplexed and sent from this repeater to the backbone repeater. Conversely, the data from the backbone repeater is separated by this controller, and is sent to the data repeater and voice repeater, respectively.
The green box indicates the minimum system, but as the yellow boxes indicate, it is possible to expand the data/voice repeaters to a total of 4, and also it is possible to add one more backbone repeater. For the data/voice repeaters that have been added, the controller is not need, and thus not included.



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