There is various systems in speech communication of the amateur radio. AM, the SSB and FM were used for the amateur radio so far even among them, it is system of typical analog speech communication.
It does the typical irregularity system which is used for AM, the SSB and FM mode with those as in the chart below. With the D-STAR digital speech communication is adopted for speech communication.
It does with those like the well which enters with this digital speech communication the \u3087 \u3046? There is the difference of occupied bandwidth as an analog speech communication system and the difference of feature of the digital speech communication of the D-STAR which are used for the amateur radio.

Communication method		Irregularity system	Occupied bandwidth
Analog	AM system	Electrical irregularity	6kHz
Analog	SSB system	Equilibrium irregularity	3kHz
Analog	FM system	Reactance irregularity	16kHz (possession frequency zone of current FM tranceiver)
Digital	D-STAR	Frequency-modulated (GMSK) (AMBE CODEC)	6kHz

It is utilized well in the V/U/SHF band, analog FM system being to be high does, the articulation of sound but, per 1 wave frequency of the 16kHz is possessed.
The HF band focusing on, the analog SSB system which is used at various frequencies does, it meaning that also utilization efficiency of electric power flies also radio wave well well, but, zero in of frequency are difficult, either articulation is not good excessively.
In addition AM system is not almost used in the frequency band which is higher than the 50MHz band.
On one hand, as for the digital speech communication of the D-STAR, the sound where the articulation which is a match to analog FM system at occupied bandwidth of the 6kHz is high sends, furthermore, it is simultaneously attachment the small digital data of the picture and the like also possible with sound to attach.

< Feature of digital speech communication > Among digital speech communication, change degree of modulation there is analog speech communication very is little, furthermore almost there is no noise and, clearing it can enjoy communication in the sound. In the D-STAR tranceiver, setting the information of call sign and the like, it meaning that the kind of function which it transmits simultaneously with the voice data is attached, appointed communication partner bureau call sign " the comfortable expecting reception which does not have noise " is possible. In addition, as introduced even before, with the digital speech communication of the D-STAR, attaching the small data of the static image and the like simultaneously with sound, also it is possible to transmit. This way it is the digital speech communication of the D-STAR which had splendid feature but, it is very delicate in change of signal strength of radio wave such as one side and phasing. This is remarkable at signal strength of the especially reception limit. " To noise mixture finally to hear is possible the fact that you take ", when it is change of the signal kind of strength where, with analog system fragmentarily it can receive, but, the aural signal which is encoded not be able to receive with digital communication method, completely, it seems that the case where it cannot recover sound is many.

With digital speech communication, sending and receiving of sound is done with digital irregularity system.
The upper figure, is the outline figure of operation of the tranceiver when it is digital speech communication. The biggest difference of constitution of the former analog wireless radio and the D-STAR tranceiver is block of the CODEC.
With former analog speech communication, because each it modulates with the aural signal of analog, there is no block of this CODEC.
In case of digital speech communication, correcting the analog aural signal once in the digital signal, using that digital signal, being to modulate, it does.
For example transmission of the speech communication of the D-STAR, with block of the AMP after the expanding, sound encodes the aural signal which is inputted from the microphone with block of the CODEC and converts to the digital signal. The GMSK it modulates that digital signal with block of the Transmitter and expands to necessary electric power and outputs.
As for reception of speech communication, the reception signal which is inputted from the antenna the GMSK recovers with block of the Receiver, the digital signal which recovers, is reconstructed to the original analog signal with block of the CODEC, with block of the AMP after the expanding, sound is outputted from the speaker.

- How doing, you send the sound which is encoded?

Modulating the aural signal which is encoded with AMBE system with GMSK system, it transmits the D-STAR tranceiver. The packet of audio type communication has become as in the figure under.

Radio section header

Data

Bit Same period

Hurray \u30e0 Same period

Flag 1

Flag 2

Flag 3

ID

PFCS

Sound Frame

Data Frame

Sound Frame

Data Frame

\u2026\u2026

Sound Frame

Rust Frame

Ahead sending Repeater Call Sign

Sending origin Repeater Call Sign

Partner bureau Call Sign

Our bureau Call Sign 1

Our bureau Call Sign 2

64bit

15bit

1byte

1byte

1byte

8byte

8byte

8byte

8byte

4byte

2byte

72bit

24bit

72bit

24bit

\u2026

72bit

48bit

The packet referred to here with thing of the parcel, became also origin of a word " of packet transmission " of the amateur radio. How collecting the consecutive data of digital speech communication with some kind of order, it has shown this figure, whether it transmits.
As for the radio header section it is the information which is used in order to connect with the partners with radio communication.
The radio header section has become as follows.

- Bit synchronization	To take the same period of the input signal bit synchronization signal
- Frame same period	From this displays the fact that it is the signal the frame synchronization signal
- Flag 1	It causes to mean this header. Communication / direct communication by way of the repeater, Such as repeater control
- You send, tip repeater call sign	When relaying at assist bureau, repeater call sign of last
- You send, original repeater call sign	The D-STAR tranceiver is generic call sign
- Partner bureau call sign	\u3000\u3000
- Our bureau call sign	\u3000\u3000
- Flag 2	Such as version information of communication
- P-FCS	Whether or not this radio header section validity the frame check sequence

The data division after the radio header section is the audio frame of the 48bit which with the AMBE is digitalized in every 20ms. After that as for the data frame of the 48bit, the small still picture and memo et cetera it has become the constitution which can send simultaneously with sound. Lastly of transmission, the rust frame being added, it has reached the point where end of transmission is recognized.
In the frame of the data division, in the repetition 20 time " of the audio frame and the data frame " 1 time, it has meant to insert the synchronization signal. This does in the middle of communicating when the signal breaks off with phasing and the like, same period becoming unable to come off on receiving end, being something which prevents the fact that it becomes playback impossible.

< CODEC (audio coded system) with > ACELP (Algebraic Code Excited Linear Prediction) (ITU G723.1) AMBE (Advanced Multi-Band Excitation) VSELP (Vector Sum Exited Linear Prediction) CELP (Code Exited Linear Prediction) RELP (Residual Excited Linear Prediction) MOS appraisal of each audio coded system As shown in the figure above the CODEC which digitalizes sound (audio coded system) concerning, there is various systems. With the digital speech communication of the D-STAR, at the beginning the ITU advice G723.1 (the ACELP) adoption was examined, but, finally the AMBE standard which was developed at the American DVSI corporation which can designate occupied bandwidth very as the narrow band is adopted. The AMBE CODEC, dividing the segment of the respective sound into the clear frequency band, the sound for the respective frequency band / decides non- sound and making use of the technology of speech synthesis, mixes the \u30a8\u30ad\u30b5\u30a4\u30c6\u30fc\u30b7\u30e7\u30f3 signal for the audio segment of specification to sound and noise when encoding and reconstructing and reconstructs sound. The CODEC of the AMBE system which was developed at the DVSI corporation is very, 2.4kbps low conversion rate, but, bit rate being low, the sound quality is satisfactory. It has meant to send the short data 2.4kbps where you can send with the D-STAR simultaneously with the 2.4kbps of sound together with the 4.8kbps. The photograph IC is of the AMBE CODEC which has been used for the D-STAR tranceiver for processing. Furthermore when this CODEC is used, at the time of bit rate of the conversion rate 2.4kbps, occupied bandwidth it can do approximately 2.6kHz and to make the narrow band like the SSB even with GMSK irregularity digital speech communication is possible even in the HF band.