Huawei B2368 Series User Manual page 128

LTE CPE B2368 User's
Guide
Pulse Code Modulation
Pulse Code Modulation (PCM from English Pulse-code modulation) is a modulation method of converting
analog audio signal into a digital signal.
Workflow SIP call
The following chart describes the basic steps to initiate, conduct and termination of SIP call. Device A calling
device B.
Figure 15-10 Workflow SIP call Figure 15-10 Workflow SIP call
Step 1 Device A sends a SIP INVITE request device B. This requirement is an invitation for Step 1 Device A sends a SIP INVITE request device B. This requirement is an invitation for
B device to initiate a phone call SIP.
step 2 B sends a response that indicates that the phone is ringing. step 2 B sends a response that indicates that the phone is ringing.
step 3 B sends after receiving a call answer OK step 3 B sends after receiving a call answer OK
step 4 A then sends a message ACK, which confirms that the B call accepted. step 4 A then sends a message ACK, which confirms that the B call accepted.
step 5 Now the data exchange between devices A and B (phone call). step 5 Now the data exchange between devices A and B (phone call).
step 6 After the call and hangs up and sends a request BYE. step 6 After the call and hangs up and sends a request BYE.
step 7 B responds with OK, which acknowledges the BYE request. The call is terminated. step 7 B responds with OK, which acknowledges the BYE request. The call is terminated.
- - - - End
Coding for voice transmission
Codec (resp. The process of encoding and decoding) are used to convert the analog signal (voice) signals to
digital and vice versa. The LTE modem supports the following transfer codecs.
•
•
Issue 01
5. Dialogue (phone call)
G.711 codec is based on pulse code modulation (PCM). Pulse Code Modulation is a modulation method of
converting analog audio signal into a digital signal. Codec
G.711 offers very good sound quality, but requires a bit rate of 64 Kbps.
G.726 is based on the variation of pulse code modulation adaptive differential (ADPCM), which is less
demanding in terms of bandwidth than standard PCM. ADPCM converts analog sound into digital signals
based on the difference between each sound
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