Publishing Venue
Motorola
Related People
Authors:
Joseph Phillips
•
Randy Ekl
•
Michael Retzer
Abstract
In a WLAN system used for voice communication, bandwidth could
become limited because of the loading of many users. Users may experience
degraded one-to-many dispatch performance if the bandwidth is no longer
available to enable continuity of conversation. In particular, a first
user would key up and transmit to his user group. The first user then
de-keys. A second user wants to reply. The response could be delayed or
may not be completed in a timely manner. This problem is further
complicated when a wide area dispatch system is added that has wide area
subscriber components that are also members of the dispatch group. The
real problem here is how to initiate and manage dispatch hang time in such a
system.
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CENTRALIZED
HETEROGENEOUS SYSTEM HANG TIME DETERMINATION AND DISTRIBUTION BETWEEN A
WLAN SYSTEM AND A LEGACY WIDE AREA SYSTEM
By:
Joseph Phillips, Randy Ekl and Michael Retzer
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THE PROBLEM
In a WLAN system used for voice
communication, bandwidth could become limited because of the loading of many
users. Users may experience
degraded one-to-many dispatch performance if the bandwidth is no longer
available to enable continuity of conversation. In particular, a first user would key up and transmit
to his user group. The first user
then de-keys. A second user
wants to reply. The response
could be delayed or may not be completed in a timely manner. This problem is further
complicated when a wide area dispatch system is added that has wide area
subscriber components that are also members of the dispatch group. The real problem here is how to
initiate and manage dispatch hang time in such a system.
THE SOLUTION
One possible
solution to this problem would be to have the last talker, upon PTT release,
send hang time to the central controller that also functions as a gateway to a
foreign system with members of the group. If another user takes up the conversation floor, the
user terminal must send in a hang time cancel message to the gateway. If the hang time expires, the
central gateway sends an end of call to all users on both systems. If a wide area member of the
group keys up, the gateway device routes the call to the LAN embodiment of the
group. This may be a VOIP
conference ID, or simply an RTP session with a unique session ID for the
group. Either way, the call
is routed to members of the group on the multi-access LAN and to the WLAN as
required by group membership.
When the wide area member de-keys, the gateway detects it and creates a
hang timer for the group.
The gateway also sends out idle messages or voice prompts to members of
the group on the LAN/WLAN side of the system. The hang timer selected matches the hang timer used by the
wide area system. This could
either be Radio Service Software programmed elements in the wide area
subscriber units or system wide parameters programmed into the Wide Area System
component. If the hang timer
expires, the Gateway sends a hang timer expire message to LAN/WLAN members of
the group. A
message may not be sent to the wide area system since it is maintaining a hang
timer by traditional means.
If provisions exist for external hang timer input into the Wide Area
System, an appropriate hang timer expire message will be sent from the Gateway
to the Wide Area System for completeness and to ensure against race conditions.
The system
controller function on the LAN side of the system could be a different
component. In this case, the
Gateway only functions as the interface between the Wide Area System group
member and the LAN portion of the system.
Figure 1 depicts
a system (100) that contains one or more wired segment (101), WLAN segments
(150, 151) and one or more traditional wireless wide area segments (320). Th...