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BreezeMAX Modular Base Station System Manual 175
Access Concentrator behind the Base Station. The frames are forwarded only
between the Subscribers' PCs and the PPPoE Access Concentrator. Frames that
are not PPPoE Ethertype are discarded. In the uplink, frames are never relayed
but only forwarded to the Access Concentrator. In the downlink, broadcasts are
allowed only in cases of unknown addresses.
4.10.1.2.3 Voice Service
The Voice over IP (VoIP) service provides telephony services through an external
Voice Gateway connected to the Subscriber Unit's data port. The VoIP service is
designed for Alvarion's Voice Gateways, using the proprietary DRAP signaling
protocol to identify VoIP sessions and to verify optimal handling of these sessions.
Upon provisioning of such a service, the system automatically handles Signaling
and RTP connections establishment, including QoS issues.
DRAP (Dynamic Resources Allocation Protocol) is a protocol between the Gateway
(installed behind the Subscriber Unit) and the base station. The protocol provides
an auto-discovery mechanism for the Gateway, so that no specific configuration is
needed and the Gateway can automatically locate and register with the base
station. The protocol uses a few simple messages enabling a Voice Gateway to
request resources when calls are made, and the base station to dynamically
allocate them.
Using the DRAP solution has the following advantages:
Maintain telephony toll quality over the wireless network - dynamically
allocate Continuous Grant (CG) connections for active calls, maintaining the
QoS and low jitter needed for toll-quality voice services.
Allocate CG bandwidth only for the duration of the call - the air resources are
allocated and released according to the DRAP messages, which are based on
the VoIP signaling. This dynamic allocation ensures efficient use of the air
resources.
Prevent callers from placing calls if a sector is overloaded - the operator can
control and limit the maximum number of concurrent calls per wireless sector
and per end user voice gateway. Thus, the operator has complete control of its
network and the resources in it.
NOTE
The DRAP-based Voice Service is also available when an L2 Service is provisioned.