Browse Prior Art Database

VOICE CHANNEL SITE SWITCHING

IP.com Disclosure Number: IPCOM000007847D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2002-Apr-29
Document File: 2 page(s) / 99K

Publishing Venue

Motorola

Related People

Steve Van Swol: AUTHOR

Abstract

Currently this process to determine when to switch between sites is only done when the radio is on the control channel. When a subscriber receives a voice channel grant, the subscriber will transition to the voice channel and suspend the sampling proc- ess. The subscriber will remain on the voice chan- nel until a terminator data packet is received or until the radio fails frame sync for 750 msec. If the radio is moving from an area of good RF coverage to an area of poor RF coverage during a voice call, the process of losing frame sync, trying to find a new control channel, alliliating on the new site and receiv- ing a grant for the call on the new site will cause an audio hole of approximately two seconds in the voice call. This will result in a significant amount ofaudio missed during this transition.

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M-LA Technical Developments

VOICE CHANNEL SITE SWITCHING

by Steve Van Swol

subscriber will sample the active adjacent voice chan- nels according to the priority of the adjacent control channel list. If the sampled signal strength level exceeds an acceptable threshold, the subscriber will consider the voice channel acceptable. Otherwise if the signal strength level is below the acceptable threshold, the subscriber will sample the other active adjacent voice channels. This process will continue until either an acceptable voice channel is found or all of the active adjacent voice channels have been sampled.

  If an acceptable voice channel is found the subscriber unit will move to that voice channel and unmute on the call. The subscriber will affiliate on the new site after the voice call has ended.

  If no acceptable voice channel is found, the subscriber unit will start normal control channel acquisition procedures. Aher finding a new control channel, the lixed network equipment will send a voice channel grant ifthe call is still active.

This method will provide seamless voice chan- nel coverage in wide area systems.

  In current trunking SmartZone radio systems, a radio may switch from site to site to improve cover- age due to degrading RF conditions. Switching to the new site may be beneficial due to better signal strength received from an adjacent site. Currently the radio maintains a list of adjacent sites and the signal strength level of the adjacent sites. If the sig- nal strength ofan adjacent site is significantly better than the site the radio is currently on the radio will switch to the new site.

PROBLEM:

  Currently this process to determine when to switch between sites is only done when the radio is on the control channel. When a subscriber receives a voice channel grant, the subscriber will transition to the voice channel and suspend the sampling proc- ess. The subscriber will remain on the voice chan- nel until a terminator data packet is received or until the radio fails frame sync for 750 msec. If the radio is moving from an area...