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3.3.2 Pitch detection
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3.3.3 Tone detection
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3.3.4 Correlated Complex Signal Analysis (and detection)
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3.3.5 VAD decision
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3.3.5.1 Hangover addition
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3.3.5.2 Background noise estimation
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4 Technical Description of VAD Option 2
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4.1 Definitions, symbols and abbreviations
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4.1.1 Definitions
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4.1.2 Symbols
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4.1.2.1 Variables
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4.1.2.2 Constants
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4.1.2.3 Functions
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4.1.3 Abbreviations
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4.2 General
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4.3 Functional description
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4.3.1 Frequency Domain Conversion
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4.3.2 Channel Energy Estimator
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4.3.3 Channel SNR Estimator
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4.3.4 Voice Metric Calculation
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4.3.5 Frame SNR and Long-Term Peak SNR Calculation
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4.3.6 Negative SNR Sensitivity Bias
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4.3.7 VAD Decision
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4.3.8 Spectral Deviation Estimator
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4.3.10 Background Noise Update Decision
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4.3.10 Background Noise Estimate Update
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5 Computational details
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............................................................................................................................27 Annex A (informative) : Change history...............................................................................................28 History..............................................................................................................................................................29 (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 4 3G TS 26.094 version 3.0.0 Foreword This Technical Specification has been produced by the 3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Working Group 4 (Codec). The contents of this informal TS may be subject to continuing work within the 3GPP and may change following formal TSG-S4 approval. Should TSG-S4 modify the contents of this TS, it will be re-released with an identifying change of release date and an increase in version number as follows: - Version m.t.e - where: m indicates [major version number] x the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc. y the third digit is incremented when editorial only changes have been incorporated into the specification. (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 5 3G TS 26.094 version 3.0.0 1 Scope This document specifies two alternatives for the Voice Activity Detector (VAD) to be used in the Discontinuous Transmission (DTX) as described in [3]. Implementors of mobile station and infrastructure equipment conforming to the AMR specifications can choose which of the two VAD options to implement. There are no interoperability factors associated with this choice. The requirements are mandatory on any VAD to be used either in User Equipment (UE) or Base Station Systems (BSS)s that utilize the AMR speech codec. 2 Normative References This TS incorporates by dated and undated reference, provisions from other publications. These normative references are cited in the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this TS only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to applies. [1] TS 26.73: "ANSI-C code for the Adaptive Multi Rate speech codec" . [2] TS 26.90: "AMR Speech Codec Speech Transcoding Functions" . [3] TS 26.93: "AMR Speech codec; Source Controlled Rate Operation". [4] ITU, The International Telecommunications Union, Blue Book, Vol. III, Telephone Transmission Quality, IXth Plenary Assembly, Melbourne, 14-25 November, 1988, Recommendation G.711, Pulse code modulation (PCM) of voice frequencies. 3 Technical Description of VAD Option 1 3.1 Definitions, symbols and abbreviations 3.1.1 Definitions For the purposes of this TS, the following definitions apply: frame: Time interval of 20 ms corresponding to the time segmentation of the speech transcoder. 3.1.2 Symbols For the purposes of this TS, the following symbols apply. 3.1.2.1 Variables bckr_est[n] background noise estimate burst_count counts length of a speech burst, used by VAD hangover addition hang_count hangover counter, used by VAD hangover addition complex_hang_count hangover counter, used by CAD hangover addition complex_hang_timer hangover initator, used fo Complex Activity Estimation (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 6 3G TS 26.094 version 3.0.0 lagcount pitch detection counter level[n] signal level new_speech pointer of the speech encoder, points a buffer containing last received samples of a speech frame [2] noise_level average level of the background noise estimate oldlagcount lagcount of the previous frame pitch flag indicating presence of a periodic signal complex_warningflag indicating the presence of a complex signal. best_corr_hp normalized and limited value from maximum HP filtered correlation vector corr_hp filtered best_corr_hp values pow_sum power of the input frame s(i) samples of the input framer snr_sum measure between input frame and noise estimate stat_count stationarity counter stat_rat measure indicating stationary T_op[n] open-loop lags [2] t0 autocorrelation maxima calculated by the open-loop pitch analysis [2] t1 signal power related to the autocorrelation maxima t0 [2] tone flag indicating the presence of a tone vad_thr VAD threshold VAD_flag boolean VAD flag vadreg intermediate VAD decision complex_low intermediate complex signal decisions complex_high intermediate complex signal decisions 3.1.2.2 Constants ALPHA_UP1 constant for updating noise estimate (see subclause 3.3.5.2) ALPHA_DOWN1 constant for updating noise estimate (see subclause 3.3.5.2) ALPHA_UP2 constant for updating noise estimate (see subclause 3.3.5.2) ALPHA_DOWN2 constant for updating noise estimate (see subclause 3.3.5.2) ALPHA3 constant for updating noise estimate (see subclause 3.3.5.2) ALPHA4 constant for updating average signal level (see subclause 3.3.5.2) ALPHA5 constant for updating average signal level (see subclause 3.3.5.2) BURST_LEN_HIGH_NOISE constant for controlling VAD hangover addition (see subclause 3.3.5.1) (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 7 3G TS 26.094 version 3.0.0 BURST_LEN_LOW_NOISE constant for controlling VAD hangover addition (see subclause 3.3.5.1) COEFF3 coefficient for the filter bank (see subclause 3.3.1) COEFF5_1 coefficient for the filter bank (see subclause 3.3.1) COEFF5_2 coefficient for the filter bank (see subclause 3.3.1) HANG_LEN_HIGH_NOISE constant for controlling VAD hangover addition (see subclause 3.3.5.1) HANG_LEN_LOW_NOISE constant for controlling VAD hangover addition (see subclause 3.3.5.2) HANG_NOISE_THR constant for controlling VAD hangover addition (see subclause 3.3.5.2) L_FRAME size of a speech frame, 160 L_NEXT length for the lookahead of the speech encoder, 40 LTHRESH threshold for pitch detection (see subclause 3.3.2) NOISE_MAX maximum value for noise estimate (see subclause 3.3.5.2) NOISE_MIN minimum value for noise estimate (see subclause 3.3.5.2) NTHRESH threshold for pitch detection (see subclause 3.3.2) POW_PITCH_THR threshold for pitch detection (see subclause 3.3.5) POW_COMPLEX_THR threshold for complex detection (see subclause 3.3.5) STAT_COUNT threshold for stationary detection (see subclause 3.3.5.2) CAD_MIN_STAT_COUNT minimum threshold after complex warning STAT_THR threshold for stationary detection (see subclause 3.3.5.2) STAT_THR_LEVEL threshold for stationary detection (see subclause 3.3.5.2) TONE_THR threshold for tone detection (see subclause 3.3.3) VAD_P1 constant of computation for VAD threshold (see subclause 3.3.5.2) VAD_POW_LOW constant for controlling VAD hangover addition (see subclause 3.3.5.1) VAD_SLOPE constant of computation for VAD threshold (see subclause 3.3.5) VAD_THR_HIGH constant of computation for VAD threshold (see subclause 3.3.5) CVAD_THRESH_ADAPT_HIGH constant for updating complex_high CVAD_THRESH_ADAPT_LOW constant for updating complex_low CVAD_THRESH_HANG constant for updating complex_hang_timer CVAD_HANG_LIMIT constant for initiating complex_hang_count CVAD_HANG_LENGTH constant for resetting complex_hang_count 3.1.2.3 Functions + addition - subtraction * multiplication / division (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 8 3G TS 26.094 version 3.0.0 | x | absolute value of x AND Boolean AND OR Boolean OR x n n a b ( ) =∑ ( ) ( ) ( ) ( ) = + + + + − + x a x a x b x b 1 1 MIN(x,y) = < ≤ x y y y x x , , MAX(x,y) = > ≥ x y y y x x , , 3.1.3 Abbreviations ANSI American National Standards Institute DTX Discontinuous Transmission VAD Voice Activity Detector CAD Complex Activity Detection CNG Comfort Noise Generation 3.2 General The function of the VAD algorithm is to indicate whether each 20 ms frame contains signals that should be transmitted, i.e. speech, music or information tones. The output of the VAD algorithm is a Boolean flag (VAD_flag) indicating presence of such signals. 3.3 Functional description The block diagram of the VAD algorithm is depicted in figure 1. The VAD algorithm uses parameters of the speech encoder to compute the Boolean VAD flag (VAD_flag). Samples of the Input frame (s(i)) are divided into sub-bands and level of the signal in each band (level[n]) is calculated. Input for the pitch detection function are open-loop lags (T_op[n]), which are calculated by open-loop pitch analysis of the speech encoder. The pitch detection function computes a flag (pitch) which indicates presence of pitch. Tone detection function calculates a flag (tone), which indicates presence of an information tone. Tones are detected based on pitch gain of the open-loop pitch analysis The pitch gain is estimated using autocorrelation values (t0 and t1) received from the pitch analysis. Complex Signal Detection function calculates a flag (complex_warning), which indicates presence of a correlated complex signal such as music. Correlate complex signals are detected based on analysis of the correlation vector available in the open- loop pitch analysis.The VAD decision function estimates background noise levels. Intermediate VAD decision is calculated based on the comparison of the background noise estimate and levels of the input frame (level[n]). Finally, the VAD flag is calculated by adding hangover to the intermediate VAD decision. (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 9 3G TS 26.094 version 3.0.0 Filter bank and computation of sub-band levels VAD decision Pitch detection Tone detection T_op[n] t0,t1 VAD_flag level[n] pitch tone s(i) Complex signal analysis OL-LTP correlation vector complex_warning Tone detection t0,t1 complex_timer Figure 3.1. Simplified block diagram of the VAD algorithm: Option 1 3.3.1 Filter bank and computation of sub-band levels The input signal is divided into frequency bands using a 9-band filter bank (figure 3.2). Cut-off frequencies for the filter bank are shown in table 3.1. (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 10 3G TS 26.094 version 3.0.0 Table 3.1. Cut-off frequencies for the filter bank Band number Frequencies 1 0 - 250 Hz 2 250 - 500 Hz 3 500 - 750 Hz 4 750 - 1000 Hz 5 1000 - 1500 Hz 6 1500 - 2000 Hz 7 2000 - 2500 Hz 8 2500 - 3000 Hz 9 3000 - 4000 Hz Input for the filter bank is the speech frame pointed by the new_speech pointer of the speech encoder [1]. Input values for the filter bank are scaled down by one bit. This ensures safe scaling, i.e. saturation can not occur during calculation of the filter bank. 5th order filter block 5th order filter block 5th order filter block 3rd order filter block 3rd order filter block 3rd order filter block 3rd order filter block 3rd order filter block 0 - 250 Hz 250 - 500 Hz 500 - 750 Hz 750 - 1000 Hz 3k - 4 kHz 2.5 - 3 kHz 2 - 2.5 kHz 1.5 - 2 kHz 1 - 1.5 kHz Figure 3.2. Filter bank The filter bank consists of 5th and 3rd order filter blocks. Each filter block divides the input into high-pass and low-pass parts and decimates the sampling frequency by 2. The 5th order filter block is calculated as follows: ))) ( ( )) 1 ( ( ( * 5.0 ) ( 2 1 i x A i x A i xlp + − = (3.1a) ))) ( ( )) 1 ( ( ( * 5.0 ) ( 2 1 i x A i x A i xhp − − = (3.1b) where x(i) input signal for a filter block (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 11 3G TS 26.094 version 3.0.0 ) (i xlp low-pass component ) (i xhp high-pass component The 3rd order filter block is calculated as follows: ))) 1 ( ( ) ( ( * 5.0 ) ( 3 − + = i x A i x i xlp (3.2a) ))) 1 ( ( ) ( ( * 5.0 ) ( 3 − − = i x A i x i xhp (3.2b) The filters () 1A , () 2 A , and () 3 A are first order direct form all-pass filters, whose transfer function is given by: 1 1 * 1 ) ( − − + + = z C z C z A , (3.3) where C is the filter coefficient. Coefficients for the all-pass filters () 1A , () 2 A , and () 3 A are COEFF5_1, COEFF5_2, and COEFF3, respectively. Signal level is calculated at the ouput of the filter bank at each frequency band as follows: ∑ = = n n END START i n i x n level ) ( ) ( , (3.4) where: n index for the frequency band ) (i xn sample i at the output of the filter bank at frequency band n n START = = − ≤ ≤ − ≤ − 9 n 8, 8 n 5 4, 4 n 2, n END = = ≤ ≤ ≤ 9 n , 39 8 n 5 19, 4 n ,9 Negative indices of ) (i xn refer to the previous frame. 3.3.2 Pitch detection The purpose of the pitch detection function is to detect vowel sounds and other periodic signals. The pitch detection is based on comparison of open-loop lags (T_op[n]), which are calculated by the speech encoder [2]. If the difference of consecutive open-loop lags (T_op[n]) is smaller than a threshold, lagcount is incremented. If the sum of the lagcounts of two consecutive frames is high enough, the pitch flag is set. For 5.15 and 4.75 kbit/s rates, only one open-loop lag is calculated, and therfore only the first lag-comparison is made every frame. The pitch flag is calculated as follows: (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 12 3G TS 26.094 version 3.0.0 Lagcount = 0; If ( | T_op[-1] - T_op[0] | < LTHRESH) Lagcount = Lagcount + 1 If ( | T_op[0] - T_op[1] | < LTHRESH) Lagcount = Lagcount + 1 If (Lagcount + oldlagcount > NTHRESH) pitch = 1 else pitch = 0 oldlagcount = Lagcount T_op[-1] refers to the open-loop lag of the previous frame. 3.3.3 Tone detection Tone detection is used to detect information tones, since the pitch detection function can not always detect these signals. Also, other signals which contain very strong periodic component are detected, because it may sound annoying if these signals are replaced by comfort noise. If the open-loop pitch gain is higher than the constant TONE_THR, tone is detected and tone flag is set. The pitch gain can be tested by comparing variables t0 and t1 as follows: if (t0 > TONE_THR * t1) tone = 1 The speech encoder calculates the pitch in three delay ranges, except for mode 10.2 kbit/s, where only one range is used. The above comparison is made once for each delay range and the tone flag should be set if the condition is true at least in one range. Otherwise, the tone flag should be set to zero. The variables t0 and t1 are calculated by the open-loop pitch analysis of the speech encoder [2]. The variable t0 is autocorrelation maxima given by: ∑ − = n w w k n s n s t ) ( ) ( 0 (3.5) The variable t1 is the signal power related to the autocorrelation maxima t0 at the delay value k: ∑ − = n w k n s t ) ( 1 2 (3.6) The open-loop pitch search and correspondingly the tone flag is computed twice in each frame, except for modes 5.15 kbit/s and 4.75 kbit/s, where it is computed only once. 3.3.4 Correlated Complex Signal Analysis (and detection) Correlated complex signal detection is used to detect correlated signals in the highpass filtered weighted speech domain, since the pitch and tone detection functions can not always detect these signals. Signals which contain very strong correlation values in the high pass filtered domain are taken care of, because it may sound really annoying if these signals are replaced by comfort noise. If the statistics of the maximum normalized correlation value of a high pass filtered input signal indicates the presence of a correlated complex signal a flag complex_warning is set. To reduce complexity the high band correlation analysis is (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 13 3G TS 26.094 version 3.0.0 performed in a simplified manner by analysing the high pass filtered fullband correlation vector which is available from the OL-LTP analysis performed by the speech encoder at least once in each frame. best_corr_hpm is the maximum normalized value of the high pass filtered correlation in the range 19-146 limited to be in the range [1.0, 0.0]. (Note that the best_corr_hp value is delayed one frame). The high pass filter is a simple first order filter with coefficients [1, -1] The best_corr_hp value is filtered according to : m m m hp corr best alpha hp corr alpha hp corr _ _ * ) 1( _ * ) ( _ 1 − + = + , where alpha is varied between 0.98 and 0.8 as a function of corr_hpm and best_corr_hpm The corr_hp output value is thresholded into two to registers complex_high, complex_low and one counter complex_hang_timer. complex_low is set to 1 if the corr_hp value is greater than CVAD_THRESH_ADAPT_LOW. complex_high is set to 1 if the corr_hp value is greater than CVAD_THRESH_ADAPT_HIGH. complex_hang_timer is increased by 1 if the corr_hp value is greater than CVAD_THRESH_HANG. If the corr_hp value is lower than or equal to CVAD_THRESH_HANG the complex_hang_timer value is set to 0. The flag complex_warning is set if complex_low have been set for 15 consecutive frames or complex_high has been set for 8 consecutive frames. The open-loop pitch search and correspondingly the tone flag is computed twice in each frame, except for modes 5.15 kbit/s and 4.75 kbit/s, where it is computed only once. The computation of the corr_hp value is however always done only once per frame using the newest correlation vector available. 3.3.5 VAD decision Power of the input frame is calculated as follows: ∑ − − − = = 1 _ _ _ ) ( * ) ( _ NEXT L FRAME L NEXT L i i s i s sum pow , (3.7) where samples s(i) of the input frame are pointed by the new_speech pointer of the speech encoder. If the power of the input frame (pow_sum) is lower than the constant POW_PITCH_THR, last pitch flag is set to zero. If the power of the input frame (pow_sum) is lower than the constant POW_COMPLEX_THR, last complex_low flag is set to zero. The difference between the signal levels of the input frame and background noise estimate is calculated as follows: [ ] [ ] ∑ = = 9 1 2) _ ,0.1( _ n n est bckr n level MAX sum snr , (3.8) where: level[n] signal level at band n bckr_est[n] level of background noise estimate at band n VAD decision is made by comparing the variable snr_sum to a threshold. The threshold (vad_thr) is tuned to get desired sensitivity at each background noise level. The higher the noise level the lower is the threshold. Specially, a low threshold at high-level background noise is needed to detect speech reliably enough, although probability of detecting noise as speech also increases. Average level of background noise is calculated by adding noise estimates at each band: (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 14 3G TS 26.094 version 3.0.0 [ ] ∑ = = 9 1 _ _ n n est bckr level noise (3.9) Threshold is calculated using average noise level as follows: HIGH THR VAD PI VAD level noise SLOPE VAD thr vad _ _ ) _ _ ( * _ _ + − = , (3.10) where VAD_SLOPE, VAD_P1, and VAD_THR_HIGH are constants. The variable vadreg indicates intermediate VAD decision and it is calculated as follows: if (snr_sum > vad_thr) vadreg = 1 else vadreg = 0 3.3.5.1 Hangover addition Before the final VAD flag is given, a hangover is added. The hangover addition helps to detect low power endings of speech bursts, which are subjectively important but difficult to detect. Also a long hangover is added if the signal has been found to be of very complex nature for a long time (2 seconds) since the VAD is not likely to work reliably for such a complex signal. VAD flag is set to “1” if less that hang_len frames with “0” decision have been elapsed since burst_len consecutive “1” decisions have been detected. The variables hang_len and burst_len are set depending on the average noise level (noise_level). The vad_flag is also controlled by the complex_hang_count which indicates that the signal is too complex for the VAD and should not be used with a Comfort noise generation algorithm. The filtered correlation value corr_hp is also used as an activity indication after the VAD has indicated noise for a while (during 200 ms), this will aid in situations where the VAD noise estimate has adapted to a rather stationary but still all to complex signal to make it sound well with CNG. The power of the input frame is compared to a threshold (VAD_POW_LOW). If the power is lower, the VAD flag is set to “0” and no hangover is added. The VAD_flag is calculated as follows: if (noise_level > HANG_NOISE_THR) burst_len = BURST_LEN_HIGH_NOISE hang_len = HANG_LEN_HIGH_NOISE else burst_len = BURST_LEN_LOW_NOISE hang_len = HANG_LEN_LOW_NOISE if(complex_hang_timer > CVAD_HANG_LIMIT) { if(complex_hang_count < CVAD_HANG_LENGTH { complex_hang_count = CVAD_HANG_LENGTH; } } if (powsum < VAD_POW_LOW){ burst_count = 0 (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 15 3G TS 26.094 version 3.0.0 hang_count = 0 complex_hang_count = 0; complex_hang_timer = 0; Vad_flag=0; Goto Exit; } VAD_flag=0; if(complex_hang_count != 0){ burst_count = BURST_LEN_HIGH_NOISE; complex_hang_count = complex_hang_count – 1 ; VAD_flag=1; goto Exit } else { if ( (the 10 last out of 11 vadreg values all are zero) AND (corr_hp > CVAD_THRESH_IN_NOISE ) ) { VAD_flag = 1; Goto Exit } } if (vadreg = 1){ burst_count = burst_count + 1} if (burst_count >= burst_len){ hang_count = hang_len } VAD_flag = 1 } else { burst_count = 0 if (hang_count > 0){ hang_count = hang_count - 1 VAD_flag=1 } } Label Exit (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 16 3G TS 26.094 version 3.0.0 3.3.5.2 Background noise estimation Background noise estimate (bckr_est[n]) is updated using amplitude levels of the previous frame. Thus, the update is delayed by one frame to avoid undetected start of speech bursts to corrupt the noise estimate. If the internal VAD decision is “1” or if pitch has been detected, the noise estimate is not updated upwards. The update speed for the current frame is selected as follows: if ((vadreg for the last 4 frames has been zero) AND (pitch for the last 4 frames has been zero) AND (we are not in complex signal hangover)) alpha_up = ALPHA_UP1 alpha_down = ALPHA_DOWN1 else if ((stat_count = 0 ) AND (not in complex_signal hangover)) alpha_up = ALPHA_UP2 alpha_down = ALPHA_DOWN2 else alpha_up = 0 alpha_down = ALPHA3 The variable stat_count indicates stationary and its propose is explained later in this subclause. The variables alpha_up and alpha_down define the update speed to upwards and downwards. The update speed for each band n is selected as follows: if ( [ ] n est bckr m _ < [ ] n levelm 1 − ) alpha = alpha_up else alpha = alpha_down Finally, noise estimate is updated as follows: [ ] [ ] [ ] n level alpha n est bckr alpha n est bckr m m m 1 1 * _ * ) 0.1( _ − + + − = , (3.11) where: n index of the frequency band m index of the frame Level of the background estimate (bckr_est[n]) is limited between constants NOISE_MIN and NOISE_MAX. If level of background noise increases suddenly, vadreg will be set to "1" and background noise is not updated upwards. To recover from this situation, update of the background noise estimate is enabled if the intermediate VAD decision (vadreg) is “1” for enough long time and spectrum is stationary. Stationary (stat_rat) is estimated using following equation: [ ] [ ] [ ] [ ] ∑ = = 9 1 )) , _ MIN( EVEL, STAT_THR_L ( )) , _ MAX( EVEL, STAT_THR_L ( _ n m m m m n level n level ave MAX n level n level ave MAX rat stat (3.12) (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 17 3G TS 26.094 version 3.0.0 If the stationary estimate (stat_rat) is higher than a threshold, the stationary counter (stat_count) is set to the initial value defined by constant STAT_COUNT. The stationary counter (stat_count) is also initialised if pitch or tone or a complex_warning is detected. If the signal is not stationary but speech has been detected (VAD decision is “1”), stat_count is decreased by one in each frame until it is zero. if (complex_warning){ If(stat_count < CAD_MIN_STAT_COUNT) stat_count = < CAD_MIN_STAT_COUNT } if ( (8 last vadreg flags have been zero) OR (2 last pitch flags have been one) OR (5 last tone flags have been one) ) stat_count = STAT_COUNT else if (stat_rat > STAT_THR) stat_count = STAT_COUNT else if ((vadreg) AND (stat_count ≠ 0)) stat_count = stat_count - 1 The average signal levels (ave_level[n]) are calculated as follows: [ ] [ ] [ ] n level alpha n level ave alpha n level ave m m m * _ * ) 0.1( _ 1 + − = + (3.13) The update speed (alpha) for the previous equation is selected as follows: if (stat_count = STAT_COUNT) alpha = 1.0 else if (vadreg = 1) alpha=ALPHA5 else alpha = ALPHA4 (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 18 3G TS 26.094 version 3.0.0 4 Technical Description of VAD Option 2 4.1 Definitions, symbols and abbreviations 4.1.1 Definitions For the purposes of the present document, the following definitions apply: codec: The combination of an encoder and decoder in series (encoder/decoder). compand: The process of compressing and expanding a signal. In this text, the process is described in terms of PCM [4]. Decoder: Generally, a device for the translation of a signal from a digital representation into an analog format. For this standard, a device which converts speech encoded in the format specified in this standard to analog or an equivalent PCM representation. DFT: See Discrete Fourier Transform. Discrete Fourier Transform (DFT): A method of transforming a time domain sequence into a corresponding frequency domain sequence. Encoder: Generally, a device for the translation of a signal into a digital representation. For this standard, a device which converts speech from an analog or its equivalent PCM representation to the digital representation described in this standard. Fast Fourier Transform (FFT): An efficient implementation of the Discrete Fourier Transform. FFT: See Fast Fourier Transform. Vocoder: Voice coder. frame: Time interval of 20 ms corresponding to the time segmentation of the speech transcoder. 4.1.2 Symbols For the purposes of this TS, the following symbols apply. 4.1.2.1 Variables αch(m) channel energy smoothing factor α(m) exponential windowing factor ∆Ε(m) estimated spectral deviation between current power spectrum and average long term power spectral estimate φ(m) spectral peak-to-average ratio σq(i) quantized channel SNR indices b(m) burst count bth burst count threshold {d(m)} overlapped portion of the frame buffer of input samples (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 19 3G TS 26.094 version 3.0.0 Ech(m,i) channel energy estimate; channel i, subframe m Ech(m) vector of channel energy estimates, 0 ≤ i < Nc EdB(m,i) estimated log power spectrum EdB(m) vector of log power spectrum estimates, 0 ≤ i < Nc EdBm,i ( ) average long term power spectral estimate EdBm ( ) vector of average long term power spectral estimates, 0 ≤ i < Nc En(m,i) channel noise estimate En(m) vector of channel noise estimates, 0 ≤ i < Nc Etn(m) total estimated noise energy Etot(m) total channel energy E ' tot(m) modified total channel energy h(m) hysteresis counter hcnt hangover count ho(n) overlap-and-add buffer of samples hyster_cnt hysteresis counter to avoid long term creeping of update_cnt last_update_cntprevious value of update_cnt shp(n) sample at the output of the speech encoder high pass filter sinewave_flag boolean flag, set TRUE when spectral peak-to-average ratio is greater than 10dB and the spectral deviation is less than DEV_THLD SNR Signal to Noise ratio SNRp(m) long-term peak SNR SNRq(m) quantized version of SNRp(m) update_cnt counter gating noise estimate update process update_flag flag controlling noise estimate updating VAD(m) boolean VAD flag for subframe m VAD_flag boolean VAD Flag v(m) sum of voice metrics vth voice metric threshold 4.1.2.2 Constants αH upper limit for values of α(m) αL lower limit for values of α(m) αn channel noise smoothing factor ζp pre-emphasis factor (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 20 3G TS 26.094 version 3.0.0 btable table to generate bth D overlap (delay) in sample intervals DEV_THLD threshold for setting sinewave_flag Efloor low threshold for Etot(m) EH high energy endpoint for linear interpolation of Etot(m) Einit minimum allowable channel noise initialisation energy EL low energy endpoint for linear interpolation of Etot(m) Emin minimum allowable channel energy fH high channel combining table fL low channel combining table g(n) trapezoidal window, n = 0 to M G(k) frequency domain transformation of g(n) htable table to generate hcnt HYSTER_CNT_THLD threshold for hyster_cnt L subframe length in samples M DFT sequence length Nc number of combined channels NOISE_FLOOR_D low threshold for Etot(m) in dB UPDATE_CNT_THLD threshold for update_cnt UPDATE_THLD threshold for v(m) V voice metric table vtable table to generate vth 4.1.2.3 Functions + addition - subtraction * multiplication / division x largest integer ≤ x AND Boolean AND OR Boolean OR x n n a b ( ) =∑ ( ) ( ) ( ) ( ) = + + + + − + x a x a x b x b 1 1 (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 21 3G TS 26.094 version 3.0.0 4.1.3 Abbreviations ANSI American National Standards Institute DTX Discontinuous Transmission VAD Voice Activity Detector CAD Complex Activity Detection CNG Comfort Noise Generation 4.2 General The function of the VAD algorithm is to indicate whether each 20 ms frame contains signals that should be transmitted, i.e. speech, music or information tones. The output of the VAD algorithm is a Boolean flag (VAD_flag) indicating presence of such signals. 4.3 Functional description The block diagram of the VAD algorithm is depicted in figure 4.1. The VAD algorithm uses parameters of the speech encoder to compute the Boolean VAD flag (VAD_flag). s hp (n ) G (k ) F r eq u e n cy D om a in C o n v er si on C h a n n e l E n er gy E s tim a t or S p e ct r a l D ev ia tio n E s ti m a t or B a c k gr ou n d N o is e E s tim a t or V oic e M e tr ic C a lc u la t ion C h a n n e l S N R E s tim a t or N o is e U p d a te D ec is io n E ch (m ) E t o t(m ), ∆E(m ) {σ q } u p d a te _f la g E n(m ) VAD fupdate_flag Etn(m) Etot(m) VAD_flag v(m) Peak-to- Average Ratio Figure 4.1. Block Diagram of the VAD algorithm: Option 2 Input: _ The output of the High-Pass Filter, {shp(n)} - LTP_flag is generated by the comparison of the long-term prediction gain to a constant threshold LTP_THLD, where the long-term prediction gain β is derived from the speech encoder[2] open-loop pitch predictor. Output: (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 22 3G TS 26.094 version 3.0.0 _ The output of the vad is designated as VAD_flag Initialization: The following variables shall be set to zero at initialization (frame m = 0): _ The pre-emphasis memory The following shall be initialized to a startup value other than zero: _ The channel energy estimate, Ech(m), (see Section 4.3.2) _ The long-term power spectral estimate, EdB m ( ) , (see Section 4.3.5) _ The channel noise estimate, En(m), (see Section 4.3.8) Processing: The following procedures shall be executed two times per 20 ms speech frame and the current 10 ms subframe shall be denoted m. 4.3.1 Frequency Domain Conversion The input signal is pre-emphasised and windowed prior to frequency domain conversion. This process is defined as L n n s n s n d hp p hp < ≤ − + = 0 ), 1 ( ) ( ) ( ζ , (4.1) where d(n) is the pre-emphasised speech buffer, ζp is the pre-emphasis factor, and L is the subframe length. A rectangular window is then used to frame the speech prior to frequency domain conversion, which is expressed as: + < ≤ − < ≤ + < ≤ = D L n D D n d M n D L D n n g ), ( , 0 ,0 ) ( , (4.2) where D is the zero-padding offset into the DFT buffer, and M is the DFT length. The transformation of g(n) to the frequency domain is performed using the Discrete Fourier Transform (DFT) defined1 as: ∑ − = − < ≤ = 1 0 / 2 0 , ) ( 2 ) ( M n M nk j M k e n g M k G π (4.3) where ejω is a unit amplitude complex phasor with instantaneous radial position ω. 1 This atypical definition is used to exploit the efficiencies of the complex Fast Fourier Transform (FFT). The 2/M scale factor results from preconditioning the M point real sequence to form an M/2 point complex sequence that is transformed using an M/2 point complex FFT. Details on this technique can be found in Proakis, J. G. and Manolakis, D. G., Introduction to Digital Signal Processing, New York, Macmillan, 1988, pp. 721-722. (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 23 3G TS 26.094 version 3.0.0 4.3.2 Channel Energy Estimator Calculate the channel energy estimate Ech(m) for the current subframe, m, as: ( ) c i f i f k L H ch ch ch ch N i k G i f i f m i m E m E i m E H L < ≤ + − − + − = ∑ = 0 , ) ( 1 ) ( ) ( 1 ) ( 1 ) ,1 ( ) ( , max ) , ( ) ( ) ( 2 min α α (4.4) where Emin is the minimum allowable channel energy, αch(m) is the channel energy smoothing factor (defined below), Nc is the number of combined channels, and fL(i) and fH(i) are the i-th elements of the respective low and high channel combining tables. The channel energy smoothing factor, αch(m), is defined as: > ≤ = 1 , 45 .0 1 ,0 ) ( m m m ch α (4.5) So, this means that αch(m) assumes a value of zero for the first frame (m = 1) and a value of 0.45 for all subsequent frames. This allows the channel energy estimate to be initialized to the unfiltered channel energy of the first frame. 4.3.3 Channel SNR Estimator Estimate the channel SNR vector { σ } as: c n ch N i i m E i m E i < ≤ = 0 , ) , ( ) , ( log 10 ) ( 10 σ (4.6) where En(m) is the current channel noise energy estimate (see Section 4.3.8), and then quantify the channel SNR estimate in 3/8 dB steps to yield the channel SNR indices { σq } given as: { } { } { } c q N i i i < ≤ = 0 , 375 .0 /) ( round , 89 min ,0 max ) ( σ σ (4.7) where the values of { σq } are constrained to be between 0 and 89, inclusive. 4.3.4 Voice Metric Calculation Next, calculate the sum of voice metrics as: ( ) ∑ − = = 1 0 ) ( ) ( c N i q i V m v σ , (4.8) where V(k) is the k th value of the 90 element voice metric table V. 4.3.5 Frame SNR and Long-Term Peak SNR Calculation The instantaneous frame SNR, SNR, and long-term peak SNR, SNRp(m), are used to calibrate the responsiveness of the VAD decision. When the frame count is less than or equal to four (m ≤ 4) or the forced update flag (sec 4.3.10) is set (fupdate_flag == TRUE), then the SNR’s are initialized as: (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 24 3G TS 26.094 version 3.0.0 − = = ∑ − = 1 0 10 ) , ( log 10 56 ) ( c N i n p i m E SNR m SNR . (4.9) Otherwise, the instantaneous frame SNR is generated by: = ∑ − = 1 0 10 /) ( 10 10 1 log 10 c N i i c N SNR σ (4.10) and the long-term peak SNR is derived by the following expression: − − ≤ < − + − − > + − = otherwise m SNR m SNR SNR m SNR SNR m SNR m SNR SNR SNR m SNR m SNR p p p p p p p ), 1 ( )1 ( )1 ( 625 .0 , 002 .0 )1 ( 998 .0 )1 ( , 1.0 )1 ( 9.0 ) ( . (4.11) The long-term peak SNR is then quantized in 3 dB steps and limited to be between 0 and 19, as follows: { } { } 0 , 19 , 3 /) ( min max m SNR SNR p q = (4.12) where x is the largest integer ≤ x (floor function). 4.3.6 Negative SNR Sensitivity Bias In order for the VAD decision to overcome the problem of being over-sensitive to fluctuating, non-stationary background noise conditions, a bias factor is used to increase the threshold on which the VAD decision is based. This bias factor is derived from an estimate of the variablility of the background noise estimate. The variability estimate is further based on negative values of the instantaneous SNR. It is presumed that a negative SNR can only occur as a result of fluctuating background noise, and not from the presence of voice. Therefore, the bias factor µ(m) is derived by first calculating the variability factor ψ(m) as: − < + − = otherwise m SNR SNR m m )1 ( 0 , 01 .0 )1 ( 99 .0 ) ( 2 ψ ψ ψ (4.13) which is then clamped in magnitude to 0.4 ) ( 0 ≤ ≤ m ψ . In addition, the variability factor is reset to zero when the frame count is less than or equal to four (m ≤ 4) or the forced update flag (sec 4.3.10) is set (fupdate_flag == TRUE). The bias factor µ(m) is then calculated as: ( ) { } 0 , 65 .0 ) ( 0. 12 max ) ( − = m m ψ µ (4.14) 4.3.7 VAD Decision The quantized SNR SNRq is used to determine the respective voice metric threshold vth, hangover count hcnt, and burst count threshold bth parameters: ( ) ( ) ( ) q table th q table cnt q table th SNR b b SNR h h SNR v v = = = , , (4.15) (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 25 3G TS 26.094 version 3.0.0 where SNRQ is the index of the respective table elements. The VAD decision can then be made according to the following pseudocode: if ( v(m) > vth + µ(m)) { /* if the voice metric > voice metric threshold*/ VAD(m) = ON b(m) = b(m-1) + 1 /* increment burst counter */ if ( b(m) > bth ) { /* compare counter with threshold */ h(m) = hcnt /* set hangover */ } } else { b(m) = 0 /* clear burst counter */ h(m) = h(m-1) -1 /* decrement hangover / if ( h(m) <= 0 ) { /* check for expired hangover / VAD(m) = OFF h(m) = 0 } else { VAD(m) = ON /* hangover not yet expired */ } } Note that two 10 ms subframes are required to determine one VAD decision. The final decision is determined by the maximum of two subframe decisions, i.e. if(VAD(m) == ON OR VAD(m-1) == ON) { VAD_flag = TRUE } else { VAD_flag = FALSE } 4.3.8 Spectral Deviation Estimator The spectral deviation estimator is used as a safeguard against erroneous updates of the background noise estimate. If the spectral deviation of the input signal is too high, then the background noise estimate update may not be permitted. Calculate the estimated log power spectrum as: ( ) c ch dB N i i m E i m E < ≤ = 0 , ) , ( log 10 ) , ( 10 (4.16) Then, calculate the estimated spectral deviation between the current power spectrum and the average long- term power spectral estimate: ∑ − = − = ∆ 1 0 ) , ( ) , ( ) ( c N i dB dB E i m E i m E m (4.17) where ) (m dB E is the average long-term power spectral estimate calculated during the previous subframe, as defined in Equation 4.20. The initial value of ) (m dB E , however, is defined to be the estimated log power spectrum of subframe 1, or: 1 ), ( ) ( = = m m m dB dB E E (4.18) The exponential windowing factor, α(m), is then calculated as a function of the instantaneous frame SNR SNR and the long-term peak SNR SNRp(m), as: (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 26 3G TS 26.094 version 3.0.0 ( ) − − − = ) ( ) ( ) ( m SNR SNR m SNR m p p L H H α α α α , (4.19) which is then limited to H L m α α α ≤ ≤ ) ( . The average long-term power spectral estimate is then updated for the next frame by: c dB dB dB N i i m E m i m E m i m E < ≤ − + = + 0 ), , ( )) ( 1( ) , ( ) ( ) ,1 ( α α (4.20) where all the variables are previously defined. 4.3.9 Sinewave Detection Next the sinewave_flag is set TRUE when the spectral peak-to-average ratio φ(m) is greater than 10, i.e. > = otherwise m lag sinewave_f FALSE, 10 ) ( , TRUE φ (4.21) where: { } c N j c ch ch N i N j m E i m E m c < ≤ = ∑ − = 2 , /) , ( ) , ( max log 10 ) ( 1 0 10 φ (4.22) 4.3.10 Background Noise Update Decision The following logic, as shown in pseudo-code, demonstrates how the noise estimate update decision is ultimately made: /* Normal update logic */ update_flag = fupdate_flag = FALSE if ( v(m) ≤ UPDATE_THLD and b(m) == 0 ) { update_flag = TRUE update_cnt = 0 } /* Forced update logic (for over-riding the normal update logic)*/ else if (( Etot > NOISE_FLOOR) and ( ∆E(m) < DEV_THLD ) and ( sinewave_flag == FALSE ) and (LTP_flag == FALSE)) { update_cnt = update_cnt + 1 if ( update_cnt ≥ UPDATE_CNT_THLD ) update_flag = fupdate_flag = TRUE } /* “Hysteresis” logic to prevent long-term creeping of update_cnt */ (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 27 3G TS 26.094 version 3.0.0 if ( update_cnt == last_update_cnt ) hyster_cnt = hyster_cnt + 1 else hyster_cnt = 0 last_update_cnt = update_cnt if ( hyster_cnt > HYSTER_CNT_THLD ) update_cnt = 0 where Etot is the total channel energy defined as: ∑ − = = 1 0 ) , ( c N i ch tot i m E E (4.23) and LTP_flag is generated by the comparison of the long-term prediction gain to a constant threshold LTP_THLD, i.e.: > = otherwise flag LTP , FALSE LTP_THLD , TRUE _ β (4.24) where the long-term prediction gain β is derived from the speech encoder [2] open-loop pitch predictor, and can be expressed as: ∑ ∑ − = − = − = 1 0 2 1 0 ) ( ) ( ) ( N n w N n w w n s k n s n s p β (4.25) where sw(n) is the weighted speech, k is the optimal open-loop lag, and Np is the pitch analysis frame length. This expression is calculated in the speech encoder on the previous frame. 4.3.10 Background Noise Estimate Update If (and only if) the update flag is set (update_flag == TRUE), then update the channel noise estimate for the next subframe by: { } c ch n n n n N i i m E i m E E i m E < ≤ − + = + 0 , ) , ( ) 1( ) , ( , max ) ,1 ( min α α (4.26) where Emin is the minimum allowable channel energy, and αn is the channel noise smoothing factor. The channel noise estimate shall be initialized for each of the first four frames to the estimated channel energy, i.e.: { } c ch init n N i m i m E E i m E < ≤ ≤ = 0 ,4 , ) , ( , max ) , ( , (4.27) where Einit is the minimum allowable channel noise initialization energy. A low level description has been prepared in form of ANSI C source code [1]. (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 3GPP 3G TS 26.094 V3.0.0 (1999-10) 28 3G TS 26.094 version 3.0.0 Annex A (informative) : Change history Change history (3G TS 26.094 version 3.0.0 Release 1999) ETSI TS 126 094 V3.0.0 (2000-01) ETSI 29 ETSI ETSI TS 126 094 V3.0.0 (2000-01) (3G TS 26.094 version 3.0.0 Release 1999) History Document history V3.0.0 January 2000 Publication
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2.1.4 Alternate from one call to the other
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2.1.5 Auxiliary states for hold and retrieve
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2.1.6 An example of dimensioned state space
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2.2 Activation and deactivation
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2.3 Registration, erasure and interrogation
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............................................................................................................ 16 Annex A: Change history......................................................................................................................17 History..............................................................................................................................................................18 ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 4 3G TS 24.083 version 3.0.0 Foreword This Technical Specification has been produced by the 3GPP. This TS specifies the procedures used at the radio interface for normal operation, registration, erasure, activation, deactivation, invocation and interrogation of call completion supplementary services within the 3GPP system. The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of this TS, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows: Version 3.y.z where: x the first digit: 1 presented to TSG for information; 2 presented to TSG for approval; 3 Indicates TSG approved document under change control. y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc. z the third digit is incremented when editorial only changes have been incorporated in the specification; ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 5 3G TS 24.083 version 3.0.0
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0 Scope
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The present document specifies the procedures used at the radio interface (Reference point Um as defined in GSM 04.02) for normal operation, registration, erasure, activation, deactivation, invocation and interrogation of call completion supplementary services. Provision and withdrawal of supplementary services is an administrative matter between the mobile subscriber and the service provider and cause no signalling on the radio interface. In GSM 04.10 the general aspects of the specification of supplementary services at the layer 3 radio interface are given. GSM 04.80 specifies the formats and coding for the supplementary services. Definitions and descriptions of supplementary services are given in GSM 02.04 and GSM 02.8x and GSM 02.9x-series. GSM 02.83 is related specially to call completion supplementary services. Technical realization of supplementary services is described in GSM 03.11 and GSM 03.8x and GSM 03.9x-series. GSM 03.83 is related specially to call completion supplementary services. The procedures for Call Control, Mobility Management and Radio Resource management at the layer 3 radio interface are defined in GSM 04.07 and GSM 04.08. The following supplementary services belong to the call completion supplementary services and are described in the present document: - Call waiting (CW) (clause 1); - Call hold (HOLD) (clause 2). 0.1 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. • References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific. • For a specific reference, subsequent revisions do not apply. • For a non-specific reference, the latest version applies. • A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number. [1] GSM 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms". [2] GSM 02.04: "Digital cellular telecommunications system (Phase 2+); General on supplementary services". [3] GSM 02.81: "Digital cellular telecommunications system (Phase 2+); Line identification supplementary services - Stage 1". [4] GSM 02.82: "Digital cellular telecommunications system (Phase 2+); Call Forwarding (CF) supplementary services - Stage 1". [5] GSM 02.83: "Digital cellular telecommunications system (Phase 2+); Call Waiting (CW) and Call Hold (HOLD) supplementary services - Stage 1". [6] GSM 02.84: "Digital cellular telecommunications system (Phase 2+); MultiParty (MPTY) supplementary services - Stage 1". [7] GSM 02.85: "Digital cellular telecommunications system (Phase 2+); Closed User Group (CUG) supplementary services - Stage 1". ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 6 3G TS 24.083 version 3.0.0 [8] GSM 02.86: "Digital cellular telecommunications system (Phase 2+); Advice of charge (AoC) supplementary services - Stage 1". [9] GSM 02.88: "Digital cellular telecommunications system (Phase 2+); Call Barring (CB) supplementary services - Stage 1". [10] GSM 02.90: "Digital cellular telecommunications system (Phase 2+); Unstructured Supplementary Services Data (USSD) - Stage 1". [11] GSM 02.91: "Digital cellular telecommunications system (Phase 2+); ECT supplementary services operation - Stage 1". [12] GSM 03.11: "Digital cellular telecommunications system (Phase 2+); Technical realization of supplementary services". [13] GSM 03.81: "Digital cellular telecommunications system (Phase 2+); Line identification supplementary services - Stage 2". [14] GSM 03.82: "Digital cellular telecommunications system (Phase 2+); Call Forwarding (CF) supplementary services - Stage 2". [15] GSM 03.83: "Digital cellular telecommunications system (Phase 2+); Call Waiting (CW) and Call Hold (HOLD) supplementary services - Stage 2". [16] GSM 03.84: "Digital cellular telecommunications system (Phase 2+); MultiParty (MPTY) supplementary services - Stage 2". [17] GSM 03.85: "Digital cellular telecommunications system (Phase 2+); Closed User Group (CUG) supplementary services - Stage 2". [18] GSM 03.86: "Digital cellular telecommunications system (Phase 2+); Advice of Charge (AoC) supplementary services - Stage 2". [19] GSM 03.88: "Digital cellular telecommunications system (Phase 2+); Call Barring (CB) supplementary services - Stage 2". [20] GSM 03.90: "Digital cellular telecommunications system (Phase 2+); Unstructured supplementary services operation - Stage 2". [21] GSM 03.91: "Digital cellular telecommunications system (Phase 2+); Explicit Call Transfer (ECT) supplementary service - Stage 2". [22] GSM 04.02: "Digital cellular telecommunications system (Phase 2+); GSM Public Land Mobile Network (PLMN) access reference configuration". [23] GSM 04.07: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface signalling layer 3; General aspects". [24] GSM 04.08: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3 specification". [25] GSM 04.10: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3; Supplementary services specification; General aspects". [26] GSM 04.80: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3 supplementary services specification; Formats and coding". [27] GSM 04.82: "Digital cellular telecommunications system (Phase 2+); Call Forwarding (CF) supplementary services - Stage 3". 0.2 Abbreviations Abbreviations used in the present document are listed in GSM 01.04. ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 7 3G TS 24.083 version 3.0.0 1 Call Waiting (CW) 1.1 Waiting call indication and confirmation When this service is activated for the controlling subscriber B and the B-subscriber has calls only in states U10 (Active) or U26 (MO Modify) as defined in GSM 04.08, the arrival of an incoming call from subscriber C shall, if no other call is waiting be signalled to the mobile station B by a normal call indication. In that case the network and the mobile station shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (C-B) allocated to the waiting call and must not be the same as the transaction identifier (A-B) for the already existing call (see figure 1.1). In the CALL CONFIRMED message sent to the network the Cause information element shall be included with cause #17 "user busy" (see figure 1.1). When the ALERTING message is received by the network the call waiting timer T2 shall be started or if call forwarding on no reply is activated for the B-subscriber the no reply condition timer T3 shall be started. If the network received a non-zero SS Screening indicator from the calling users mobile station the ALERTING/FACILITY message sent to a calling mobile user shall include the Facility information element with an invoke of the Notification operation indicating that the call is waiting (see figure 1.2). If the network did not receive a non-zero SS Screening indicator from the calling users mobile station it shall not send a notification, i.e. either the ALERTING message does not include the Notification operation or the FACILITY message is omitted. MS Network SETUP <------------------------------------------------------------------------------------------------------------------------ .....Transaction identifier(C-B)..... CALL CONFIRMED ------------------------------------------------------------------------------------------------------------------------> .....Transaction identifier(C-B)..... .....Cause #17 (user busy)..... ALERTING ------------------------------------------------------------------------------------------------------------------------> .....Transaction identifier(C-B)..... start T2/T3 NOTE: The SETUP message shall include a "Signal Information" element with value #7 (call waiting tone on). This shall be used by the MS to generate an appropriate call waiting indication. Figure 1.1: Call indication to the mobile station on arrival of an incoming call and call confirmation from the mobile station MS Network SETUP ------------------------------------------------------------------------------------------------------------------------> CALL PROCEEDING <------------------------------------------------------------------------------------------------------------------------ ALERTING/FACILITY <------------------------------------------------------------------------------------------------------------------------ Facility (Invoke = NotifySS (CW, CallIsWaiting-Indicator)) NOTE: If possible, the ALERTING message shall be used as the carrier message for the Call Waiting notification. Otherwise the FACILITY message shall be used. Figure 1.2: Notification to a calling mobile station that the call is in the waiting state ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 8 3G TS 24.083 version 3.0.0 1.2 Normal operation with successful outcome 1.2.1 Waiting call accepted; existing call released If the mobile user B before expiry of timer T2 determines to accept the waiting call and release the existing call the mobile station shall release the existing call firstly and accept the waiting call secondly. For the release of the existing call the mobile station and the network shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (A-B) of the already existing call. The Cause information element in the first clearing message shall indicate cause #16 "normal clearing". For the acceptance of the waiting call the mobile station and the network shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (C-B) of the waiting call. When the network receives the CONNECT message the timer T2 or if applicable the timer T3 shall be stopped. 1.2.2 Waiting call accepted; existing call on hold If the mobile user B before expiry of timer T2 or if applicable timer T3 determines to accept the waiting call and put the existing call on hold the mobile station shall put the existing call on hold firstly and accept the waiting call secondly. In case there is one active call (A-B) and another call (D-B) on hold and call (C-B) waiting, and the mobile user B wants to accept the waiting call (C-B) and put the active call (A-B) on hold, the held call (D-B) has to be released first, either by user B or user D, in accordance with GSM 04.08. To put the existing call on hold the mobile station and the network shall act in accordance with clause 2. The hold function shall be initiated by the mobile station and the transaction identifier shall be the transaction identifier (A-B) of the existing call (see figure 1.3). For the acceptance of the waiting call the mobile station and the network shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (C-B) of the waiting call (see figure 1.3). When the network receives the CONNECT message the timer T2 or if applicable the timer T3 shall be stopped. MS Network HOLD ------------------------------------------------------------------------------------------------------------------------> .....Transaction identifier(A-B)..... HOLD ACKNOWLEDGE <------------------------------------------------------------------------------------------------------------------------ .....Transaction identifier(A-B)..... HOLD REJECT <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - .....Transaction identifier(A-B)..... .....Cause #29 (facility rejected)..... or #50 (requested facility not subscribed) or #69 (requested facility not implemented) CONNECT ------------------------------------------------------------------------------------------------------------------------> .....Transaction identifier(C-B)..... stop T2/T3 CONNECT ACKNOWLEDGE <------------------------------------------------------------------------------------------------------------------------ .....Transaction identifier(C-B)..... Figure 1.3: Existing call on hold and acceptance of waiting call by the mobile station ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 9 3G TS 24.083 version 3.0.0 1.2.3 Existing call released by user A; waiting call accepted If user A before the expiry of timer T2 or if applicable timer T3 determines to release the existing call then the existing call shall by released by the network firstly and the waiting call may be accepted by the mobile station secondly. For the release of the existing call the network and the mobile station shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (A-B) of the existing call. For the acceptance of the waiting call the mobile station and the network shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (C-B) of the waiting call. When the network receives the CONNECT message the timer T2 or if applicable the timer T3 shall be stopped. 1.3 Normal operation with unsuccessful outcome 1.3.1 Waiting call released by subscriber B For the release of the waiting call the mobile station and the network shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (C-B) of the waiting call. * If the B subscriber indicates UDUB by the sending of the first clearing message with cause information element #17 (User Busy), and call forwarding on mobile subscriber busy is activated for the B subscriber the call shall be forwarded by the network. If call forwarding is not active the call will be cleared. * If any other causes are given in the first clearing message the call will be released. 1.3.2 Waiting call released by calling user C If the calling user C, before the expiry of timer T2 or timer T3 (if applicable), releases the waiting call then the network shall release the waiting call against the mobile station. For the release of the waiting call the network and the mobile station shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (C-B) of the waiting call. When the network initiates clearing by sending a clearing message to the mobile station the timer T2 or, if applicable, the timer T3 shall be stopped. 1.3.3 Waiting call times out If the timer T2 expires the network shall release the waiting call. The network and the mobile station shall act in accordance with GSM 04.08. The transaction identifier shall be the transaction identifier (C-B) of the waiting call. The Cause information element in the first clearing message shall indicate cause #102 "recovery on timer expiry". 1.3.4 No reply condition timer expires If call forwarding on no reply is activated for the B-subscriber and the no reply condition timer expires the waiting call shall be forwarded in accordance with GSM 04.82. The network shall clear the waiting call towards the B-subscriber as in subclause 1.3.3. ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 10 3G TS 24.083 version 3.0.0 1.4 Activation Activation of the supplementary service call waiting will be performed by the subscriber. The network will send a return result indication of acceptance of the request (see figure 1.4). If the network cannot accept an activation request, an error indication is returned to the served mobile subscriber. Error values are specified in GSM 04.80 (see figure 1.4). If the mobile subscriber does not indicate a specific basic service group the activation of call waiting is valid for all applicable basic services (see figure 1.4). Normal outgoing call procedures apply when this service is activated. MS Network REGISTER ------------------------------------------------------------------------------------------------------------------------> Facility (Invoke = ActivateSS (CW, BasicServiceCode)) RELEASE COMPLETE <------------------------------------------------------------------------------------------------------------------------ Facility (Return result = ActivateSS (BasicServiceCode)) RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Facility (Return error (Error)) RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Facility (Reject (Invoke_problem)) NOTE: If the BasicServiceCode is not included the activation is valid for all applicable basic services. Figure 1.4: Activation of call waiting 1.5 Deactivation Deactivation of the supplementary service call waiting will be performed by the subscriber. The network will send a return result indication of acceptance of the request (see figure 1.5). If the network cannot accept a deactivation request, an error indication is returned to the served mobile subscriber. Error values are specified in GSM 04.80 (see figure 1.5). If the subscriber does not indicate a specific basic service group the deactivation of call waiting is valid for all applicable basic services (see figure 1.5). ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 11 3G TS 24.083 version 3.0.0 MS Network REGISTER ------------------------------------------------------------------------------------------------------------------------> Facility (Invoke = DeactivateSS (CW, BasicServiceCode)) RELEASE COMPLETE <------------------------------------------------------------------------------------------------------------------------ Facility (Return result = DeactivateSS (BasicServiceCode)) RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Facility (Return error (Error)) RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Facility (Reject (Invoke_problem)) NOTE: If the BasicServiceCode is not included the deactivation is valid for all applicable basic services. Figure 1.5: Deactivation of call waiting 1.6 Interrogation Status check The mobile subscriber can request the status of the supplementary service call waiting and be informed whether the service is supported in the network and if so, a list of all basic service groups to which the call waiting supplementary service is active (see figure 1.6). If a mobile subscriber interrogates the network on the status of call waiting, and the network supports call waiting but the service is not active for any basic service groups then an SS-Status parameter shall be returned indicating "deactivated" (see figure 1.6). If a mobile subscriber interrogates the network on the status of call waiting, whilst the network does not support call waiting, the network shall return an error indication (see figure 1.6). MS Network REGISTER ------------------------------------------------------------------------------------------------------------------------> Facility (Invoke = InterrogateSS (CW)) RELEASE COMPLETE <------------------------------------------------------------------------------------------------------------------------ Facility (Return result = InterrogateSS (BasicServiceCode(s)) or RELEASE COMPLETE <------------------------------------------------------------------------------------------------------------------------ Facility (Return result = InterrogateSS (SS-Status) RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Facility (Return error (Error)) RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Facility (Reject (Invoke_problem)) Figure 1.6: Interrogation of call waiting ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 12 3G TS 24.083 version 3.0.0 1.7 Invocation Invocation of call waiting causes no signalling on the radio path. 1.8 Registration and erasure Registration and erasure of the supplementary service call waiting are not applicable. 2 Call Hold (HOLD) 2.1 Normal operation 2.1.1 Hold and retrieve functions The hold and retrieve functions are performed on the same MM-connection. The hold function is used to put an existing call which is in the active phase in the Call held auxiliary state. By default, it retains the MM-connection in use and the transaction identifier of the held call for possible subsequent call retrieval. On receipt of a HOLD message the network shall return a HOLD ACKNOWLEDGE message, provided that the requested function can be performed. The network disconnects any user information path allocated to the active call when putting that call in the Call held auxiliary state. The mobile station disconnects any user information path to the active call and retains the transaction identifier and the MM-connection when putting that call in the Call held auxiliary state. The HOLD ACKNOWLEDGE message puts the call in the Call held auxiliary state and indicates that the hold function has been performed. The HOLD REJECT message indicates that the hold request was denied and returns the call to the condition it was in prior to the hold request. The HOLD REJECT message contains the Cause information element with e.g.: - cause #29 "Facility rejected"; - cause #50 "Requested facility not subscribed"; - cause #69 "Requested facility not implemented". The retrieve function reconnects the mobile station to the requested user information path. The RETRIEVE message requests that a call be retrieved. The RETRIEVE ACKNOWLEDGE message indicates that the retrieve function has been performed. The RETRIEVE REJECT message indicates that the retrieve request was denied. The RETRIEVE REJECT message contains the Cause information element with e.g.: - cause #34 "No channel available". 2.1.2 Hold invocation The served mobile subscriber indicates to the network that communication on the interface is to be interrupted. The hold function should be invoked in association with an existing active call. The invocation of the hold function does not affect the existing GSM 04.08 call states, but does affect the auxiliary state. The request for placing a call on hold places the auxiliary state in the hold request state. The responding entity will acknowledge this request with a HOLD ACKNOWLEDGE message if this operation was successful (see figure 2.1). This will result in the auxiliary state being put in the Call held state. If the requested hold function cannot be obtained, then a HOLD REJECT message will be returned with the appropriate cause (see figure 2.1). This will result in the auxiliary state returning to the Idle state. The traffic channel is now available to originate another call or to accept a waiting call (see call waiting). If at any time a call is in the held state, either party may clear the call according to the normal release procedure. Before to originate another call the MS will request the establishment of an MM-connection first, see GSM 04.08. ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 13 3G TS 24.083 version 3.0.0 MS Network HOLD ------------------------------------------------------------------------------------------------------------------------> HOLD ACKNOWLEDGE <------------------------------------------------------------------------------------------------------------------------ HOLD REJECT <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - .....Cause..... Figure 2.1: Invocation of call hold If the network received a non-zero SS Screening indicator from the remote party's mobile station the network shall send a notification to the remote party indicating that the call has been placed on hold (see figure 2.2). If the network did not receive a non-zero SS Screening indicator from the remote party's mobile station it shall not send a notification. MS Network FACILITY <------------------------------------------------------------------------------------------------------------------------ Facility (Invoke = NotifySS (HOLD, CallOnHold-Indicator)) Figure 2.2: Notification to the held mobile party that the existing call being put on hold If the served mobile subscriber clears the current call and another call is still on hold, the normal call clearing procedure is used. 2.1.3 Retrieve procedure When the mobile subscriber that invoked the call hold service indicates that the call is to be retrieved, the network shall re-establish communication and send an acknowledgement to the served mobile subscriber (see figure 2.3). If the network received a non-zero SS Screening indicator from the remote party's mobile station the network shall send a notification to the remote party indicating that the call has been retrieved (see figure 2.4). If the network did not receive a non-zero SS Screening indicator from the remote party's mobile station it shall not send a notification. The retrieve function is requested by sending a RETRIEVE message. This message may be sent while the auxiliary state is in the Call held state. Upon the sending of the RETRIEVE message the auxiliary state of the initiator's terminal would be the retrieve request state. If the retrieve request is successful, the RETRIEVE ACKNOWLEDGE message will be returned. The initiator should not assume that call retrieval has occurred until it receives this message. The auxiliary state would then return to the Idle state. If the retrieve request is not successful, the RETRIEVE REJECT message will be returned with an appropriate cause. The auxiliary state machine would then remain to the Call held state. ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 14 3G TS 24.083 version 3.0.0 MS Network RETRIEVE ------------------------------------------------------------------------------------------------------------------------> RETRIEVE ACKNOWLEDGE <------------------------------------------------------------------------------------------------------------------------ RETRIEVE REJECT <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - .....Cause..... Figure 2.3: Notification that the held call is to be retrieved (using the transaction identifier of the held call), by the served mobile subscriber MS Network FACILITY <------------------------------------------------------------------------------------------------------------------------ Facility (Invoke = NotifySS (HOLD, CallOnHold-Indicator)) Figure 2.4: Notification to the held mobile party that the held call has been retrieved 2.1.4 Alternate from one call to the other If the served mobile subscriber is connected to an active call and a call on hold, he can alternate from one call to the other. This results in the previously active call being held and the previously held call becoming retrieved. This is achieved by sending a HOLD message for the active call, followed by a RETRIEVE message for the held call (see figure 2.5). These requests place the auxiliary state for the held and active calls in the retrieve request and hold request states respectively. If this alternate procedure is successful the HOLD ACKNOWLEDGE message will be returned, followed by the RETRIEVE ACKNOWLEDGE message. The initiator should not assume that the held call is retrieved and the active call is held until it receives both these messages. If the alternate procedure is not successful the HOLD REJECT message will be returned followed by the RETRIEVE REJECT message. This will result in the auxiliary state for the held and active calls returning to the previous states. If the network received a non-zero SS Screening indicator from the remote party's mobile station the network shall send a notification towards the previously held party that the call has been retrieved (see figure 2.4) and towards the previously active party that the call has been on hold (see figure 2.2). If the network did not receive a non-zero SS Screening indicator from the remote party's mobile station it shall not send a notification. ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 15 3G TS 24.083 version 3.0.0 MS Network HOLD (TI A-B) ------------------------------------------------------------------------------------------------------------------------> RETRIEVE (TI A-C) ------------------------------------------------------------------------------------------------------------------------> HOLD ACKNOWLEDGE (TI A-B) <------------------------------------------------------------------------------------------------------------------------ RETRIEVE ACKNOWLEDGE (TI A-C) <------------------------------------------------------------------------------------------------------------------------ HOLD REJECT (TI A-B) <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - .....Cause..... RETRIEVE REJECT (TI A-C) <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - .....Cause..... NOTE: TI A-B indicates the transaction identifier allocated to the original active call and TI A-C indicates the transaction identifier allocated to the original held call. Figure 2.5: Alternate procedure 2.1.5 Auxiliary states for hold and retrieve It is possible to place a call on hold in the Active state. The concept of dimensioned state space is being introduced to ensure state synchronization between the mobile station and the network. This concept suggests dimensioning the call state machine into two dimensions. In other words, there would be two states associated with each call. The first would be a GSM 04.08 call state and the second would be an auxiliary state associated with hold. Suppose the dimensioned state space is represented by two co-ordinates: one is a GSM 04.08 call state co-ordinate and the other is a hold co- ordinate. If a GSM 04.08 call state transition occurs, the former co-ordinate is updated. If a call is put on hold, the hold co-ordinate is updated. When the held call is reconnected, the hold co-ordinate is again updated. There are four auxiliary states associated with the hold and retrieve functions: - Idle; - Hold request; A request has been made for the hold function. - Call held; The call is held and the user information path has been reserved. - Retrieve request; A request has been made for the retrieve function. ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 16 3G TS 24.083 version 3.0.0 2.1.6 An example of dimensioned state space Suppose a call is in the Active state. The dimensioned state space would be: (Active, Idle). Now the mobile station requests the hold function. The dimensioned state space would become: (Active, Hold request). The call is then put on hold. The mobile station becomes aware of this upon receiving the HOLD ACKNOWLEDGE message from the network. The dimensioned state space would now be: (Active, Call held). Now the mobile station requests the retrieve function. The dimensioned state space would become: (Active, Retrieve request). When a call is reconnected, the dimensioned state space would be: (Active, Idle). 2.2 Activation and deactivation Activation and deactivation of the supplementary service call hold cause no signalling on the radio path. 2.3 Registration, erasure and interrogation Registration, erasure and interrogation of the supplementary service call hold are not applicable. ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 3GPP 3G TS 24.083 V3.0.0 (1999-05) 17 3G TS 24.083 version 3.0.0 Annex A: Change history Change history TSG CN# Spec Version CR <Phase> New Version Subject/Comment Apr 1999 GSM 04.83 6.0.0 Transferred to 3GPP CN1 CN#03 24.083 3.0.0 Approved at CN#03 ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) ETSI ETSI 18 ETSI ETSI TS 124 083 V3.0.0 (2000-01) (3G TS 24.083 version 3.0.0 Release 1999) History Document history V3.0.0 January 2000 Publication
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0.1 References
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0.2 Abbreviations
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.................................................................................................................................. 8
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1 Call Forwarding Unconditional (CFU)
|
....................................................................................................8
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.1 Normal operation
|
............................................................................................................................................... 8
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.1.1 Served mobile subscriber side
|
...................................................................................................................... 8
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.1.2 Forwarded-to mobile subscriber side
|
........................................................................................................... 8
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.1.3 Calling mobile subscriber side
|
..................................................................................................................... 9
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.2 Registration
|
........................................................................................................................................................ 9
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.2.1 Registration by the served mobile subscriber
|
............................................................................................... 9
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.3 Erasure
|
............................................................................................................................................................. 10
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.3.1 Erasure by the served mobile subscriber
|
.................................................................................................... 10
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.4 Activation
|
........................................................................................................................................................ 11
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.5 Deactivation
|
..................................................................................................................................................... 12
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.6 Interrogation
|
.................................................................................................................................................... 12
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.7 Cross phase compatibility
|
................................................................................................................................ 14
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.7.1 Network only supports protocol version 1 control of SS by the subscriber
|
............................................... 14
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
1.7.2 MS only supports protocol version 1 control of SS by the subscriber
|
....................................................... 14
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2 Call Forwarding on mobile subscriber Busy (CFB)
|
..............................................................................14
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.1 Normal operation
|
............................................................................................................................................. 14
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.1.1 Served mobile subscriber side
|
.................................................................................................................... 14 2.1.2 Forwarded-to mobile subscriber side ......................................................................................................... 15
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.1.3 Calling mobile subscriber side
|
................................................................................................................... 16
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.2 Registration
|
...................................................................................................................................................... 16
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.2.1 Registration by the served mobile subscriber
|
............................................................................................. 16
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.3 Erasure
|
............................................................................................................................................................. 17
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.3.1 Erasure by the served mobile subscriber
|
.................................................................................................... 17
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.4 Activation
|
........................................................................................................................................................ 18
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.5 Deactivation
|
..................................................................................................................................................... 18
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.6 Interrogation
|
.................................................................................................................................................... 19
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.7 Cross phase compatibility
|
................................................................................................................................ 21
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.7.1 Network only supports protocol version 1 control of SS by the subscriber
|
............................................... 21
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
2.7.2 MS only supports protocol version 1 control of SS by the subscriber
|
....................................................... 21
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3 Call Forwarding on No Reply (CFNRy)
|
................................................................................................21
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.1 Normal operation
|
............................................................................................................................................. 21
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.1.1 Served mobile subscriber side
|
.................................................................................................................... 21 3.1.2 Forwarded-to mobile subscriber side ......................................................................................................... 22
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.1.3 Calling mobile subscriber side
|
................................................................................................................... 22
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.2 Registration
|
...................................................................................................................................................... 23
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.2.1 Registration by the served mobile subscriber
|
............................................................................................. 23
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.3 Erasure
|
............................................................................................................................................................. 24
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.3.1 Erasure by the served mobile subscriber
|
.................................................................................................... 24
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.4 Activation
|
........................................................................................................................................................ 25
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.5 Deactivation
|
..................................................................................................................................................... 25
|
df81caf795659f2ed71f5bfcc461b22d
|
124 082
|
3.6 Interrogation
|
.................................................................................................................................................... 26
|
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