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D-STAR
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Im Folgenden Informationen zu D-STAR:
(Für eine vergrößerte Version bitte aufs Bild klicken.)

 

 

Folie 1

D-STAR is a multi-media communications system that utilizes Amateur radio data and voice communications that have been digitalized, for the purpose of communication.

Folie 2

D-STAR, the result of the development by the Japanese Amateur Radio League (JARL) of the combination of data and voice communications, is a complete digital communications system connected by a backbone relay that connects the respective repeater sites.
This is an open system that anyone can participate in and use to communicate with. Also, as this is Amateur radio, there is no special encryption preventing use of or communication on the system.

Folie 3

D-STAR has been made according to the concepts listed below, to best match the needs for Amateur radio.

  • The terminal is not heavily restricted by the system
    A system like a cellular phone where if immediate registration is not made, the phone cannot be used, is not suitable for D-STAR. Other than the necessary components required for communication, the condition where frequencies etc. can be freely chosen is left unchanged.
  • Compatibility with the Internet
    In a world where the Internet is now a daily necessity in any country around the world, it is convenient for Amateur radio to have compatibility with the Internet. The application sources available for use are numerous, and data communication protocol is the same as that of the Internet, TCP/IP.
  • Necessity for user’s to be able to make by themselves
    As this is an Amateur radio system, it is not suitable for the system to be able to be made only by a manufacturer’s Engineers. It is necessary for general user’s with a certain amount of electrical knowledge, to be able to make it also.
  • Operation as a single system with sequential expansion possible via infrastructure maintenance
    A system like a cellular phone where the system does not work unless the infrastructure is complete is not suitable for Amateur radio. It is necessary that the system can operate with only one data repeater, and that the system can be expanded as required anytime after that.
  • Necessity for communication with existing analog systems
    It is not suitable to have just a new digital communication system, but it is also necessary to be able to use existing analog systems via an appropriate interface. In principal, this form of operation has been tested and confirmed.

Folie 4

The D-STAR system can utilize 128kbps high-speed data communication and 8kbps digital voice communication, and direct communication with the other station is possible via communication through the respective data and voice repeaters.
Data communication is relayed by the alternation between transmit and receive (simplex), and voice communication is relayed in the same way as existing analog FM, by semi-duplex.
In D-STAR, there is a broadband backbone that links the respective repeater sites, and it is possible to send the data and voice communication signals by multiplexing. Because of this, it is possible to communicate digitally with another station in a different area.
I.e. Communication between stations in separate repeater areas is possible.

Folie 5

It is possible to communicate with another station by digital data communication via a digital data repeater. As mentioned earlier, data communication is carried out using the same TCP/IP protocol as the Internet.
In actuality, the digital transceiver ID-1 is connected to a computer via its 10 Base-T connecter, and communication is carried out using the TCP/IP protocol of the computer. Therefore, it is possible to be able to communicate the same images, text, and voice etc. that is handled on the Internet.
Naturally, direct communication with another station is possible without being relayed through the repeater.


 

 

 

 

Folie 6

Digital voice communication works in the same way as data communication, by using one digital voice repeater, it is possible to communicate with another station. However, voice communication differs from data communication in the fact that it is necessary to have real-time communication. In data communication, even if there is a slight time delay in the response, there is almost no effect in the communication quality. However, for voice communication, if there is a long delay against the initial call made from this end, or the delay is erratic, smooth communication is not possible. For this reason, in D-STAR the data and voice communication is separated into separate systems.
For VoIP voice communication by data communication, actual use is permitted, but in Amateur radio due to the limit in the number or capacity of lines available, it is likely that smooth VoIP voice communication would be difficult.
Direct communication with another station is possible without being relayed through the repeater.

Folie 7

The accumulation of data or voice repeaters in a place is typically called a repeater site, and it is the backbone that links multiple repeater sites. In D-STAR, this backbone communication is carried out in the 10 GHz band, at a transfer rate of 10 Mbps. This 10 Mbps transfer rate was decided on by an analysis of the frequency of use of data and voice communications, and by what types of 10 Base-T components etc. were most easily acquired in the market.
The frequency used (10 GHz) is the frequency that had the spectrum to be able to transmit a 10 Mbps signal. At present, the 10 GHz band and the 5.6 GHz band metes this requirement. There are many frequencies above 10 GHz that have the broadband for this, however, by using these high frequencies, the communication distance becomes shorter, and is not suitable as a relay for the backbone.

Folie 8

ID-1 is the terminal used for this digital communication. To compare between digital data communication, digital voice communication and existing analog, an analog FM communication function is included.
The transceiver RF unit and controller a separate units, and digital data/voice communication is possible even without connection to a computer.

Folie 9

This diagram shows the basic block diagram of the ID-1. For digital voice communication, the CODEC converts the voice signal input from the mic to a digital signal after amplification. That digital signal is GMSK modulated, and is amplified to the required voltage and output.
The received signal input from the antenna is GMSK demodulation, is converted back to the original analog signal, and after amplification, is output from the speaker.
A data signal is input to the 10 Base-T connector from the connected computer, and after passing through the interface is GMSK modulated and out put in the same way as voice communication. For the reception of a data signal, the same GMSK demodulation as a voice signal is carried out, and then it passes through the interface and is input to the computer by the 10 Base-T.
The USB connected to the controller is used in the control of the ID-1, and is not directly related to communication. It is possible to control the operation by using only the RC-24 controller, but it is even more convenient to operate using the USB connected to a computer. (This will be explained later)
The existing analog FM in included in this set-up, but it has not been indicated in this block diagram.

Folie 10

This panel shows the characteristics of the ID-1. As mentioned, the modulation is GMSK, and the interference to adjacent channels is minimal, and also like existing analog it is possible to be able to use a C grade amp.
The data transfer rate is 128 kbps, and voice communication is 8 kbps.


 

 

 

 

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.


 

 

 

 

Folie 16

The software and protocol shown here is related in the ID-1.
The protocol is the D-STAR system protocol. What ID-1 USB terminal uses is not called the protocol, but is expressed as the control command. In this way, the communication via the ID-1 USB is not the original communication protocol, so care is needed regarding this point.
Also, communication from the computer connected to the ID-1, in this manner is simply connected to the local repeater or backbone only, thus in reality various applications are necessary. Connection to a wired line and access to the Internet and access to an added server is a part of this application, how this is used is a point of interest, and we look forward to seeing the introduction of applications from user’s.

Folie 17

The structure of the packet used in the data communication of the D-STAR protocol is shown in this diagram. The Radio Header part is the part used to connect to the station you are communicating with. The parts other than the Radio Header will be explained later in the structure of the Ethernet packet.
The Radio Header part is as follows:

  • Bit Sync
    The bit synchronization signal that obtains synchronization in the input signal.
  • Frame Sync
    The frame synchronization signal that indicates that this is a signal from here on.
  • Flag
    This distinguishes this header’s attributes. If it’s a repeater relay/direct communication, repeatr control signal etc.
  • Destination Repeater Callsign
    Indicates the final repeater destination callsign when relayed through the backbone
  • Departure Repeater Callsign
    Indicates the repeater callsign of that, that terminal belongs to.
  • Companion Callsign
    Indicates the called station’s callsign
  • Own Callsign
    Indicates your callsign
  • P-FCS
    The frame check sequence indicating the validity of this Radio Header part.

Folie 18

This diagram indicates the process of how a message is sent by digital data communication. The left side ‘s User A sends a message to the right side’s User B. The respective TCP, IP and Ethernet headers are attached in the wired part in the message made. The computer that is connected automatically processes this.
The Radio Header explained in the previous page is attached to the Ethernet packet that comes from the 10 Base-T. On the receive side, this Radio Header is decoded, then the header is removed and is passed as an Ethernet packet to the connected computer from the 10 Base-T. After that the computer automatically carries out the processing, and the message is displayed on User B’s screen.

Folie 19

Next, we will explain the voice communication protocol. The voice communication packet is as shown in the diagram, and the Radio Header part is exactly the same as data communication.
The data part after the Radio Header is the Voice Frame, which is a 160-bit signal that is, digitalized every 30mS in the Codec. It is possible to send small still pictures and memos etc, with the 80-bit data frame after that. In the ID-1, this function is not available as it is difficult to change the whole CPU capacity etc. at a later stage. However, this function is planned for implementation in the second-generation model.
At the end of the transmission, the Last Frame is added to indicate that this is the end of the transmission. Also, a synchronous signal is input 1 time out of every 20. This is to prevent the occurrence of non-reproduction because of the loss of synchronization on the receiver side when the signal is interrupted, which is caused by phasing etc., during communication.

Folie 20

The backbone protocol that connects between repeater sites is sent as multiplexed data and voice signals according to the ATM (Asynchronous transfer Mode) method. The ATM packet is made up of a short 53-byte packet that consists of a 5-byte header part and a 48-byte payload, as shown in the diagram.
Because the designation of priority level can be done in this header part, the priority level is added to the voice signal that requires real time processing, and is sent so that when it arrives, the real time condition is kept. The ATM method is such that the ATM packet is sent to the required destination according to the preset list that is set by the ATM switch set at each repeater site. For more details, please refer to technical material on Asynchronous Transfer Mode.


 

 

 

 

Folie 21

The way the packet is sent was described on the previous page. In the case that the voice signal and data signal arrive randomly, because the voice signal keeps to real time, the priority level is set and sent every 30mS. The data signal is sent between this voice signal. This diagram shows one voice signal, but when multiple voice signals are involved, the addition of 30mS priority level setting and the sending timing becomes multiple, so this diagram becomes more complicated.

Folie 22

When the ID-1 USB is connected to a computer and the supplied software is booted, the control screen shown above appears. By following the User Manual to operate the various buttons by the computer, the respective functions can be operated. The supplied RC-24 controller can also perform the operations, using the computer is easier and more convenient.
The signal used by this USB as has already been explained, is not directly related to the communication protocol, but rather is just the control command to be able to operate the ID-1 via the computer. Various applications utilizing this control command will likely appear in the future.

Folie 23

This diagram shows as an assumed application, accessing the ARRL homepage using the ID-1 connected to a repeater site and also connection to a wired line by modem. In this way, it is possible to think of applications like access to the Internet, or for example access to mail on a particular server, or access to an Amateur radio database archive etc.

Folie 24

We explained that it is still not possible for the ID-1 to handle a voice communication data frame, in future versions, it will be possible to sent small still pictures and voice simultaneously, as shown in the diagram. The miniature cameras used in cellular phones recently are about 96 x 96 pixels, i.e. less than 10,000-bits, so this picture could be sent in about 4~5 seconds.
Also, an application that sends GPS position data simultaneously with voice would be interesting. There are many possibilities available from now on.

Folie 25

Finally, we will explain about the Codec used to digitalize the D-STAR voice. The ID-1 uses the Codec based on the ITU G723.1 standard. This is the type that has conformity with the Internet. As shown, there are many types of Codec available, however the D-STAR utilizes one other ultra-narrow AMBE type Codec.


 

 

 

 

Folie 26

The ITU G723.1 Codec possesses the characteristics shown in the diagram. The standard specifies two conversion speeds of 6.3 kbps and 5.3 kbps, however to achieve the narrowest occupied bandwidth possible, 5.3 kbps is used.
With an algorithm delay of 37mS, the total wireless communication throughput is a little over 100mS, but there is no distinct difference felt in the communication.

Folie 27

Although not used in the current ID-1, AMBE is 2.4 kbps, ultra-low bit rate Codec developed by the US company DVSI, and it is included in the D-STAR standard. Even though the bit rate is low, the audio quality is good, and we are considering using it in the next generation model.
By using this Codec, even GMSK modulation in an occupied bandwidth of 2.6 kHz, equivalent to that of narrow band SSB, can be done so that digital voice communication in HF bands is possible.

Folie 28

As we have shown, D-STAR is still just getting started, but we have carried out basic experimentation for over three years, and have acquired a lot of data, therefore we are very expectant that practical use is possible. Particularly, then from now on, users will likely develop many forms of applications, and we look forward to being introduced to these upon their realization.

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