Nera WILINK I System Manual page 140

designed for 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.
NOTE
The DRAP-based Voice Service is also available when an L2 Service is provisioned.
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.
Automatic support of Codec changing in a VoIP call – the DRAP messages
update the WILINK I equipment on any Codec change or subsequent
bandwidth allocation change during the call, hence the exact required
bandwidth is always provided. This is essential in fax transmissions where the
call might begin with one Codec and switch to another to accommodate the
fax transmission.
VoIP stack is always in synch with the wireless transport – as the DRAP is
integrated into the VoIP stack all calls are terminated according to the VoIP
standard. Even if no resources are available, the voice gateway receives an
appropriate message from the WILINK I system and sends the required
signaling message according to the VoIP standard used.
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