GERAN Voice and Data Multiplexing (OS2) Proposal

1. GERAN Voice and Data Multiplexing (OS2) Proposal Source: AT&T For: 3GPP TSG GERAN Adhoc #2 9 -13 October 2000 Munich, Germany

2. Introduction • Operational Scenario 2 is a fundamental service requirement for R00 • OS2 multiplex single user’s voice and (E)GPRS data on to single time slot • Objectives are: • support delay sensitive interactive data • improve channel utilization by sending data between talk spurts • Voice quality should not be impacted by best effort data

3. Basic Requirements • Support single user’s voice and data multiplexing on single time slot • Support time critical interactive data with limited interruption of speech that is similar to FACCH • No degradation of the speech quality with BED • No major degradation in the stealing bit performance • No changes to existing channel coding • No or minor change on current stealing bit design • BED performance is secondary to that of speech • Should not preclude legacy transceiver support.

4. Background Information • State-based multiplexing • using the information from previously received and current data blocks for multiplexing • higher reliability with stealing bits in current data block • Stateless multiplexing • solely based on SB contained in current data block • reliability fully depends on SB performance • A lot of work has been carried out by vendors on stateless approach, such as tdoc 080/00, 118/00, 254/00 • This proposal is a sate-based approach

5. OS2 Proposal with AMR Procedures • Use the already defined AMR procedures for DTX operation to place the receiver in one of three states, ‘Speech’, ‘No Speech’ or ‘Possible Speech’. • Stealing bits pattern is used in combination with ‘state’ for multiplexing • Other information can also be used for state recovery when a state transition message is lost • Limited extra processing power is required for error recovery

6. AMR DTX State Transition Identifiers Identifier types defined for AMR full and half-rate speech • SID_FIRST Marker to define end of speech • SID_UPDATE Used to convey comfort noise parameters during DTX • ONSET Used to signal the Codec mode for the first speech frame after DTX Identifier types defined for half-rate speech • SID_FIRST_P1 First part of marker to define end of speech • SID_FIRST_P2 Second part of marker to define end of speech • SID_FIRST_INH Used to inhibit the second part of a SID_FIRST_P1 frame if there is a speech onset • SID_UPDATE_INH Used to inhibit the second part of a SID_UPDATE frame if there is a speech onset

7. AMR RX Speech Identifiers • SPEECH_GOOD Speech frame with CRC OK, Channel Decoder soft values also OK • SPEECH_DEGRADED Speech frame with CRC OK, but 1B bits and class2 bits may be corrupted • SPEECH_BAD (likely) speech frame, bad CRC (or very bad Channel Decoder measures) • NO_DATA Nothing useable (for the speech decoder) was received.

8. States Description • SPEECH State Exactly the same as for AMR full-rate and half-rate circuit voice with one difference: the receiver transitions to the Data state upon reception of a SID_FIRST frame. • NO_SPEECH State PDTCH/PACCH block is handled in exactly the same manner as for (E)GPRS. Except, it transits to Speech State after ONSET message is received or a Speech State is declared by VAD. Thus, SACCH and FACCH operation follow normal AMR TCH procedure. • SPEECH_POSSIBLE State Follows DTX comfort noise procedures and go to the Speech state upon reception of a speech frame or returns to the No Speech state upon reception of a SID frame. Data and stealing bits are treated as diagonally interleaved

9. AMR Based OS2 State Transition

10. Example of OS2 Operation

11. State Transition Reliability Issue • State transition reliability requires error recovery e.g. when state transition messages are lost • It is an implementation dependent issue • With existing SB or minor change of SB pattern, SB can be used to assist/verify state transition (need standardization) • SID_UPDATE, SID_BAD, USF bits, EGPRS Header CRC, SPEECH_GOOD, SPEECH_BAD and SPEECH_ DEGRADED can also trigger and verify the state transition • Blind detection could potentially assist to improve state transition reliability if speech and FACCH use the same modulation

12. Speech to No Speech State Transition • Use SID_UPDATE, SID_BAD to recover If SID_FIRST missing, wait for SID_UPDATE, SID_BAD to transit to NO_SPEECH state. Probability of missing two consecutive SID frame is very small. Penalty: Loss of some data throughput • Predefined USF bit pattern In dedicated mode, this is an additional downlink indicator of possible state transition • Check stealing bits to assist state transition Check SB before state transition or introduce minor SB pattern change to help state identification. E.g. make speech SB not be used in (E)GPRS at all

13. Transition to Speech/Speech Possible state • Use speech decoder output identifier SPEECH_GOOD and SPEECH_DEGRADED can be used to trigger transition from SPEECH_POSSIBLE to SPEECH state • Predefined USF bit pattern In dedicated mode, USF bits can be predefined to expand stealing bits on downlink to assist the No Speech to Speech Possible state transition when SID_FIRST or ONSET is not detected • Check data header CRC In NO_SPEECH state, ONSET or data block header CRC failure triggers the transition to SPEECH_POSSIBLE state

14. Legacy Transceivers Support The proposed scheme is independent of any schemes being contemplated that include support for legacy transceivers. This is because the TCH operation is being retained as is in its entirety. In particular, SIP signaling on a TCH using FACCH or using DTM-like approach (2 half-rate channels on a single slot) is possible.

15. Enhancements to Support Delay Critical Date • Proposed scheme could be enhanced to support time critical data, such as SIP by forcing interrupt speech for a short period • Maximum interruption to speech should be limited by the tolerance of speech quality degradation • Available bandwidth for time critical data is limited by maximum interruption rate and speech activity factor

16. Conclusions • A mechanism to support OS2 multiplexing has been presented that meets the speech quality performance and design simplicity requirements • There are no changes to the existing channel coding or stealing bits. • The scheme only requires that the (E)GPRS-related procedures during DTX periods, be slightly modified. • The procedures could be enhanced to support call control signalling by forcing interruption of speech activity to transmit (E)GPRS data