System information

221 02-FGB 101 544 Uen A – September 2008 35
7.4 Timers
The following fax related timers can be configured in the Ericsson W35.
7.4.1 SIP Timers
Since the delay in the radio network is a little bit longer than in a wired
network, it might be needed to adjust the SIP timers (T1, T2, T4 and
transaction timeout) to better fit the network. The default values are
adjusted for the radio network, but might need some fine tuning.
7.4.2 Registration Timers
The registration timers are used when the Ericsson W35 sends a SIP
registration message to the SIP server/registrar.
7.4.3 VoIP Session Timeout
To avoid that the “Phone/Fax” port is used as a telephony port using VoIP it
is possible to restrict for how long a voice call is allowed. If no fax tones are
detected, i.e. switching over to T.38, within a certain time, the call is teared
down by the Ericsson W35.
7.5 Security
The Ericsson W35 authenticates towards the VoIP system using the HTTP
Digest Authentication mechanism.
7.6 Media Stream
Due to the procedure of setting up a fax call both G.711 and T.38 is
supported by the Ericsson W35. First a call is setup as a normal voice
connection (using G.711) before a switchover to T.38 is done (using SIP
Re-INVITE practices).
7.6.1 Jitter Buffer
To handle latency and jitter in the IP network the Ericsson W35 has a jitter
buffer. The access network contributes with most of the latency and jitter,
so to reduce this a HSPA connection is recommended.
7.6.2 Echo Canceller
To improve the fax transfer, the Ericsson W35 has an echo canceller in
accordance with G.168.
7.6.3 QoS
The outgoing VoIP related traffic will be prioritized before other traffic from
the Ericsson W35 to reduce the uplink delay and jitter.
7.7 Interoperability
The Ericsson W35 is interoperable with e.g. Broadsoft, which is included in
Ericsson’s IMT (IMS Multimedia Telephony). Other SIP servers and Media
Gateways should also work as long as they support SIP v2 (RFC 3261) and
T.38, but interoperability testing needs to be done to verify this.