RTX 8630 User's Guide download pdf (Page 115)

SME VoIP System Guide, Version 1.9

Proprietary and Confidential

Chapter: Appendix E: Network Operations

115

14.6 Handover

14.6.1 RTP Stream Remains at Initial Base Station

When the call is set up, the handset is located at base station 1. Thus, the DECT communication takes place

between the handset and station 1, and the SIP signalling as well as the RTP stream takes place between

base station 1 and the SIP server/media gateway. The figure below illustrates this application:

SIP Server/Media Gateway

Base station 1

DECT Connection

RTP Stream

SIP Signaling

Base station 2 Base station n

Stage 1: Before handover the handset is located at BS 1.

After handover, the handset is located at base station 2, and hence the DECT communication goes on

between the handset and base station 2. However, to avoid disruption of the audio, the RTP stream is

relayed via the initial base station, since a transfer of the RTP stream to another base station may cause the

media gateway (or whatever the remote endpoint is) to re-initialize the RTP stream with a small disruption

of the RTP stream as consequence. Thus, from the point of view of the remote endpoint, the RTP stream is

not affected by the handover, and since the call control also remains at base station 1 the SIP signalling is

also unaffected, as shown below:

Stage 2: After handover to BS 2, the HS is located at BS 2, and the RTP stream is relayed via BS 1.

Since the call control and hence the SIP User Agent remains at the initial base station, the SIP registration is

also unaffected by the handover.

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RTX 8630 User's Guide Page 115