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A method to reserve channel for call sesion in TDMA direct mode Disclosure Number: IPCOM000239131D
Original Publication Date: 2014-Oct-14
Included in the Prior Art Database: 2014-Oct-14
Document File: 2 page(s) / 40K

Publishing Venue


Related People

Chung, Angela: INVENTOR [+3]


The transmitter radio shall transmit VT in alternate slot to reserve the channel from other radio.

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A method to reserve channel for call session in TDMA direct mode

By Angela Chung, Teh Teik Choon, Khoo Hun Weng, Wiatrowski Dave

Motorola Solutions, Inc.



 Under a shared frequency environment, radios from different talk group may initiate voice call transmission at any one time.

In repeater mode, there is a hang-time mechanism to make sure the talk group call is reserved for certain duration before other talk group call is allowed to start.

In direct mode, however, no hang-time reserved.  It may cause current talk group call get interrupted by others talk group call, which may cause dissatisfaction among the users.

This paper attempts to address the solution by providing a method to reserve channel for a call session in direct mode system.


In a shared frequency environment, any radio can access the channel when the channel is free. After a call is started, when the transmitter radio de-keys, the channel may be taken over by other group of radio. So the user that wishes to talk back to the call may not be able to get through. In repeater mode, the repeater reserves the channel for a call session by sending Voice Terminator (VT). During this time, only the radios in the same call are allowed to access the channel. In direct mode, there is no such infrastructure that does the reservation for the channel for the call.



To reserve the channel for a call session, the last transmitter shall transmit additional voice terminator after the user de-key. The additional voice terminator serves the purpose to keep the channel busy. The transmitter shall transmit the voice terminator in alternative slot, to allow other radio in the call session to talk back in the drop burst. More details in next section.