ZyXEL Communications LTE5121, User Manual

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Chapter 17 VoIP
LTE-5121 User’s Guide
164
SIP
SIP stands for Session Initiation Protocol. SIP is a signalling standard that lets one network device
(like a computer or the LTE Device) send messages to another. In VoIP, these messages are about
phone calls over the network. For example, when you dial a number on your LTE Device, it sends a
SIP message over the network asking the other device (the number you dialed) to take part in the
call.
SIP Accounts
A SIP account is a type of VoIP account. It is an arrangement with a service provider that lets you
make phone calls over the Internet. When you set the LTE Device to use your SIP account to make
calls, the LTE Device is able to send all the information about the phone call to your service provider
on the Internet.
Strictly speaking, you don’t need a SIP account. It is possible for one SIP device (like the LTE
Device) to call another without involving a SIP service provider. However, the networking difficulties
involved in doing this make it tremendously impractical under normal circumstances. Your SIP
account provider removes these difficulties by taking care of the call routing and setup - figuring
out how to get your call to the right place in a way that you and the other person can talk to one
another.
Voice Activity Detection/Silence Suppression
Voice Activity Detection (VAD) detects whether or not speech is present. This lets the LTE Device
reduce the bandwidth that a call uses by not transmitting “silent packets” when you are not
speaking.
Comfort Noise Generation
When using VAD, the LTE Device generates comfort noise when the other party is not speaking. The
comfort noise lets you know that the line is still connected as total silence could easily be mistaken
for a lost connection.
Echo Cancellation
G.168 is an ITU-T standard for eliminating the echo caused by the sound of your voice
reverberating in the telephone receiver while you talk.
Use this screen to maintain basic information about each SIP account. You can also enable and
disable each SIP account, configure the volume, echo cancellation and VAD (Voice Activity
Detection) settings for each individual phone port on the LTE Device.
How to Find Out More
See page 178 for advanced technical information on SIP.
17.1.3 Before You Begin
• Before you can use these screens, you need to have a VoIP account already set up. If you don’t
have one yet, you can sign up with a VoIP service provider over the Internet.