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BreezeMAX Modular Base Station System Manual 201
Access Concentrator behind the Base Station. In a PPPoE Forwarding Rule,
Unicast and Multicast Relaying are always disabled, packets with Unknown
Address are always rejected. The frames are forwarded only between the
Subscribers' PCs and the PPPoE Access Concentrator. Frames that are not PPPoE
Ethertype are discarded.
4.11.1.2.3 VoIP 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. Appropriate
connections are established to satisfy to actual demand, according to session
status and required bandwidth. In a VoIP Forwarding Rule, Unicast and Multicast
Relaying are always enabled, packets with Unknown Address are always
forwarded.
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. Bandwidth is allocated
according to actual requirements of each call, taking into account the Codec’s
type and sampling rate being used.
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.