Mobile Solutions
Page 58 7705 SAR OS Services Guide
Figure 8 shows a typical example of HSDPA offload.
A 3G Node B is connected to a 7705 SAR-F (or 7705 SAR-8) over an ATM/IMA access
port (SAP endpoint). An ATM SAP-to-SAP connection is set up in the 7705 SAR and a
pseudowire is configured between the two endpoints to emulate local ATM switching.
Traffic from the Node B enters an ATM/IMA port, the VCs transporting mission-critical
traffic are locally switched (SAP-to-SAP) to another ATM/IMA port (SAP endpoint), and
then switched over the leased lines to the MTSO.
For non-mission-critical traffic, for example, HSDPA traffic, an Ethernet interface on the
7705 SAR is connected to an external DSL modem. HSDPA traffic is interworked to ATM
pseudowires and transported over the DSL network to the BRAS, then forwarded to the
service router at the MTSO.
Figure 8: HSDPA Offload Example
19872
Node B
ATM PW
Ethernet
IP/GRE Tunnel
Cell Site
Owned by Mobile Operator
MTSO
Owned by Mobile Operator
ATM
IP
DSL
ATM NW
RNC
DSL
modem
BRAS
ATM
DSLAM
77x0 SR
L1
SONET/SDH NW
or L2 ATM NW
7705 SAR
Legend:
Note: ATM SAP-to-SAP connections are supported between any T1/E1 ASAP port that is in
access mode with ATM/IMA encapsulation and another port with the same encapsulation
configuration. One endpoint of a SAP connection can be an IMA group, while the other
endpoint can be on a single ATM port.
ATM SAP-to-SAP connections are also supported between any two OC3/STM1 ports and
between any T1/E1 ASAP port and OC3/STM1 port, as long as both SAPs support ATM.
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