Browse Prior Art Database

Scheduling Priority/FER Reduction Immediately after Reselection

IP.com Disclosure Number: IPCOM000126203D
Original Publication Date: 2005-Jul-07
Included in the Prior Art Database: 2005-Jul-07
Document File: 3 page(s) / 77K

Publishing Venue

Motorola

Related People

John M. Harris: INVENTOR

Abstract

In current systems, when a cell reselection within a streaming /PTT (push to talk)/POTs (plain old telephone service) call occurs, typically the mobile cannot send and/or receive any audio data for a significant interval of time. This can cause significant audio gaps/audio quality degradation. This is the problem addressed by this publication. A cell reselection is when a mobile is operating within a system where there is a delay when switching between communicating with one base transceiver station in another base transceiver station. When this type of reselection occurs, audio builds up at the transmitter, and the playout buffer at the receiver shrinks and may even run completely dry. In this case, it may take the target hundreds of milliseconds to refill its playout buffer. During this interval, while the playout buffer is refilling, the playout buffer is not deep enough to tolerate the delay resulting from ARQ (automatic repeat request) or retransmissions over the wireless link. For this reason, further audio quality degradation can occur during this interval. Additionally, it is not feasible to avoid this retransmission delay by simply using more system resources, e.g. power, to avoid retransmissions during the entire call as this would be prohibitive from a system capacity perspective. For this reason, we need a mechanism to minimize audio quality degradation, while maximizing capacity for streaming calls, which can experience reselections.

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Scheduling Priority/FER Reduction Immediately after Reselection

John M. Harris

Performance Analysis Department

Network Advanced Technology

Motorola

I.                   Problem

                          In current systems, when a cell reselection within a streaming /PTT (push to talk)/POTs (plain old telephone service) call occurs, typically the mobile cannot send and/or receive any audio data for a significant interval of time.  This can cause significant audio gaps/audio quality degradation.  This is the problem addressed by this publication.  A cell reselection is when a mobile is operating within a system where there is a delay when switching between communicating with one base transceiver station in another base transceiver station.

                          When this type of reselection occurs, audio builds up at the transmitter, and the playout buffer at the receiver shrinks and may even run completely dry.  In this case, it may take the target hundreds of milliseconds to refill its playout buffer. During this interval, while the playout buffer is refilling, the playout buffer is not deep enough to tolerate the delay resulting from ARQ (automatic repeat request) or retransmissions over the wireless link.  For this reason, further audio quality degradation can occur during this interval.  Additionally, it is not feasible to avoid this retransmission delay by simply using more system resources, e.g. power, to avoid retransmissions during the entire call as this would be prohibitive from a system capacity perspective.

                          For this reason, we need a mechanism to minimize audio quality degradation, while maximizing capacity for streaming calls, which can experience reselections.

II.                Solution Proposed

The proposal is:

•                       If RAN (radio access network) or MS (mobile station) detects that reselection has occurred for a MS which is currently sending or receiving PTT/streaming/VoIP (voice-over-IP) audio, then:

–        Allocate that mobile,

•         Higher data rate/higher priority for higher data rate

•        

Lower FER

(frame erasure rate)

–        until the target playout buffer depth has been reached

•         RAN can calculate target play out buffer depth/when it has been reached, using:

–        Length of reselection interval

–        Knowledge of target and original playout buffer depth

–        Knowledge of service bit rate, based on QoS class parameters /observed bit rate

–        Bit rate provided to MS since reselect

In this way, the target mobile station audio quality is protected immediately after a reselection through the use of lower FER, while the playout buffer is being reestablished.  However, the RF capacity impact of the call is not significantly increased because the FER is only...