JPH03182134A - Error detecting device and method thereof - Google Patents

Abstract

PURPOSE: To prevent sound from being muted in error by detecting the increment of bit error distribution and executing correction processing in response to the detection of the increment. CONSTITUTION: The symmetry of error distribution over adjacent time intervals is detected and a radio telephone set is muted in response to the detection of loss in the symmetry except a case that an error is caused by effective and alternative detection. For instance, an error exceeding an allowable threshold value in two continuous intervals (A/B) requires the generation of sound path muting, and when a signal other than DSAT is received in the period of intervals B1/A2 (the same 150ms interval) and B2/A2 (the same 150ms interval), a sound pass is muted. Consequently the sound path can be correctly and reliably muted.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an error detection apparatus and method.

More particularly, the present invention relates to muting a radiotelephone due to asymmetries in detected errors.

[Prior Art] Analog cellular radio telephone systems are
h) and subaudible (Su) for network management.
b-audible) signal. In this way,
While any given radiotelephone user is busy, secondary audible data messages are exchanged between that radiotelephone and the network, allowing cell-to-cell handoffs.
f f ), power level change, etc. This secondary audio signal is also used to maintain continuity of the radio link between the cell station and the radiotelephone.

Traditional analog cellular radiotelephone systems use pseudo-continuously relayed supervisory audio tones (SATs), i.e., specific sub-audible tones assigned to each cell, that can be heard from surrounding cells. Determine the desired cell and maintain continuity of the radio link between the cell and the wireless telephone. This loss of relayed and returned tones causes both the radiotelephone and the network to mute the audio, preventing the noise from being heard by either party. Split (Spl
it) channel In analog cellular, these 5A Th-ons interfere with each other and create a digital SAT (D
SAT) or its references are U.S. Patent Application No. 228.071, filed Aug. 4, 1988, by Pine (CE00408H). The problem is that a duly chosen DSAT (which, according to its incorporated disclosures, has the minimum Hamming distance and is insensitive to falsing) is shorter than many data messages. be.

Therefore, interleaved sub-audible data messages required for network management will initially be detected as a loss of DSAT, resulting in false audio muting.

Therefore, the challenge is to avoid mistaking audio mute processing for data messages.

The present invention aims to overcome these deficiencies and realize certain advantages as follows.

[Problem to be solved by the invention]

The solution provided by the present invention is to provide the detection of distributed DSAT losses and to provide a mute decision based on the asymmetry of the errors in that distribution.

[Means to solve the problem]

That is, the error detection mechanism detects symmetry in the error distribution over adjacent time intervals and avoids any substantial loss of symmetry unless the error can be due to effective selective detection. consisting of muting the radiotelephone in response to the detection. More particularly, detecting symmetry in the error distribution over adjacent time intervals, resulting in asymmetry or substantial symmetry (unless the error can be due to selective detection of valid synchronization words) muting the radiotelephone as a corrective response to the detection of a loss of synchronization, and canceling any such corrective response upon subsequent selective detection of a valid synchronization word.

[Summary of the invention]

The error detection mechanism detects the symmetry of the error distribution over adjacent time intervals and avoids any substantial loss of symmetry unless the error can be due to effective alternative detection. muting the wireless telephone in response to the detection of the radiotelephone. More particularly, detecting symmetry in the error distribution over adjacent time intervals, resulting in asymmetry or substantial symmetry (unless the error can be due to selective detection of valid synchronization words) muting the radiotelephone as a corrective response to the detection of loss of synchronization, and subsequent selective (alt) activation of a valid sync word.
any such corrective response in the native) detection.

[Detailed explanation of examples]

FIG. 1 is an event diagram of a network in which a preferred embodiment of the present invention operates.

FIG. 1 illustrates the sub-audible transmission of a voice link between a cell of a cellular network and a radiotelephone, as well as their simultaneous (albeit asynchronous) detection in successive intervals A and B; is the latest 30
A contains the previous 30 bits.

The actual received bits during each interval A/B of 150m5 (30 bits in 2008PS) and the circular shift of the expected DSAT pattern
5hift) is counted.

However, if the error count for the current interval (B) increases unacceptably, a loss of DSAT is detected (requiring audio muting) or
Either the ATA arrival has started (preempted by sync word 5YNC) and there is no need to mute the voice path.

Errors exceeding the tolerance threshold value in two consecutive intervals (A/B) will require muting of the audio path to occur. Normally, intervals Bl/A2 (same 150m5 interval) and B2
/A3 (same 150m5 interval) reception of anything other than DSAT will mute the audio path. However, detection of DSAT during the AI period prevents muting during the Bl period (two successive error thresholds must be exceeded);
The asymmetric distribution of unacceptable errors from AI to Bl/A2 makes the 5YNC pattern potentially treated as an erroneous signal, and the distribution of unacceptable errors from DATA
Unless the detection of NC (a selectively valid detection criterion) keeps the audio path completely open during that same interval (B2/A3), i.e. the continuity of the speech is lost. , mute is performed during interval B2/A3.

It is this preserved asymmetric distribution of unacceptable errors that improves mute sensitivity and error rate.
This is the reason for the decrease in interval is 3
00m5 (or other length) window
ow), the sync word entering the window will have many errors, which will cause a mute unless an unreasonably high threshold is chosen.

The distribution of unacceptable error symmetry in two consecutive intervals (and the lack of valid 5YNC detection (a
loss of link integrity can only be concluded from (bsence)) and can confidently mute the audio path.

A mechanism for implementing the invention is described below.

DSAT acquisition DS
AT is acquired whenever the mobile changes voice channels (eg, after a call or hand-off) or after the radio is muted for 4.5 seconds. DSAT is 200B
It is transmitted in the PS to yield the maximum number of uncorrelated samples for better noise-error performance, and also yields the maximum distance characteristics during the DSAT sequence over the shortest time interval. There is a minimum distance between every cycle shift of a DSAT sequence. This means that the DSAT data flow is not just at the DSAT r-word boundary;
Allows analysis at the beginning of any bit. This is because the DSAT acquisition algorithm continuously
T can be checked and an increased number of valid and S
Provides faster acquisition and greater sensitivity with AT phase. The price is DSAT error (error: fals)
ing).

Multidimensional 7-Aze DSAT Acquisition Algorithm (MPDAA)
(used by mobile and base site) are:

The received bits from the PLL (2008PS) go into a 24-bit register. The 24-bit DSAT sequence assigned to the current cell is compared with the received bits, and if there is one or no errors, an initial DSAT Detect
(Initial DSAT detection: n1tial DSAT De
tect) is occurring. For later reference, this is the first 24 bits of the B window register. If one or more errors have occurred, the DSAT sequence is rotated and compared again to the receiving 24-bit register.

This is repeated until an initial detection occurs or all 24 cyclic rotations of the DSAT sequence have been compared. If the latter case, the next received bit is shifted into the 24-bit receive register. Once initial detection occurs, the current DSAT phase is determined and the acquisition routine begins comparing only the expected DSAT phase. This reduces both the DSAT error probability and the processing load.

At the one-error threshold, the probability of an error due to random noise is 3.576 per received bit.
It is E-5. The move expects DSAT to appear when it arrives on the voice channel.

Its D for setting up the synthesizer and locking the PLL.
By delaying SAT acquisition, the amount of noise that can cause DSAT errors is greatly minimized. However, the possibility of arrival of a mobile on the channel during a slow fade is such that the next 6 bits of DSAT after SAT Detect (initial DSAT detection) are shifted into the B register and
The DSAT phase of the decision is used to compare to the expected DSAT bits. This DSAT Qnalif(ng
If check (DSAT test check) is correct,
ConfiredDSAT Detect
AT detection) occurs. Confirmed DSAT
The error probability of Detect (confirmation DSAT detection) is 5.5875E-7 or 2.5875E-7 per received bit.
One mistake per 49 hours.

If an error occurs within the 6 test bits, the next bit is shifted into the B receive window register and the DSAT acquisition is
n1tial DSAT Detect
It starts again with MPDAA (Polyphase DSAT Acquisition Algorithm) looking for detection).

Mute Algorithm FIG. 2 is a state diagram of the method of the preferred embodiment of the present invention.

The following explanation describes how the subaudible signal (
Two mute algorithms (MUTE-1 and MUTE-1 and MU
TE-2). Cellular radio telephone land line (l
and 1ine: land line) or to prevent long noise bursts from being heard by mobile users.
Audio is muted when the received signal is disturbed due to interference or noise. The next mute algorithm is DSA
The continuous reception of T-sequences is used as a continuous bit stream rather than as a word sequence.

Mute algorithm is Confirmed DSAT
Started only after Detect (confirm DSAT detection). Since the DSAT phase is known, from this point
Only the scheduled DSAT phase is checked. The check procedure for only a single expected DSAT phase is performed by a single Funny's DSAT detection algorithm.

Mute algorithm MUTE-2 is used during conversation mode, while MUTE-1 is used briefly only after a confirmation DSAT is detected. An example of the exact point in time of use of these algorithms is explained in the ALERT protocol below.

All references to DSAT in MUTE-2ALGORITHM (algorithm) are inverted (in
(verted)DSAT also applies.

Mute operating principle: Two 30-bit mutes with independent thresholds.
The use of windows protects the mute algorithm from errors on the data message. The data message synchronization word is
Having a minimum distance of 10 bits from all phases of the AT sequence, the first reception of the synchronization word
This will be perceived as many errors in the flow of T. Up to the point where sync word detection occurs, parts (b) and (C) in step 5 of MUTE-2 are satisfied, but part (a) is not, protecting the sync word from muting the audio. After the sync word enters register B, step (C) protects the audio from being muted. In this regard, mute is also
Sync word and data messages muted A and B
is held until it is flushed from the receive window. During a fade or incorrect DSAT interference, the error distribution is even larger than the sync word, and (a), (b) and (c) are satisfied to mute the audio.

MUTE-2 algorithm! , each stream of received bits is 15
into two registers (or windows) A and B, 0m5 or 30DSAT bits long.

The received bit leaves register A and enters register B.

2. The 30 received bits in register B are the expected DS
The number of DSAT errors is counted (Bent) compared to the AT flow.

3. The B register (which can be a holding register for the synchronization correlator) is compared with the data message 30-bit synchronization word (195A99A6) and the number of errors is counted (Scnt).

4. The 30 received bits in register A are the expected DSA
The number of DSAT errors is counted (
Acnt) will be performed.

5. If (a) (A cnt > A th) and (b) (B cnt > 8 th) and (c)
If (S cnt > 8 th) (ie, there was no synchronization detection during the B window), go to step 10.

6. If the sync word detection occurs in the B window (S
ent <8th+ 1 ), go to step 7; otherwise go to step 8.

? , 110 bits for FVC messages, RV
For C messages, shift 126 bits. (Mute is in addition to the channel message
It is invalidated for the 30-bit period that fills the register. ) Go to step 2.

8. If 5cnt > (30-8th -1),
That is, if an inverted sync word is detected, shift in 30 bits to flush out the B register and go to step 2.

9. The received DSAT stream is shifted one bit through the A and B registers and the algorithm returns to step 2.

Mute the lO1 receive audio and set the PLL bandwidth to zero (
Set PLL to self-propelled. This ensures that bit slips cannot occur during the mute period.

11. The received DSAT stream is shifted one bit through the A and B registers.

12. Errors in the 30-bit B window are counted, and if B cnt < U th), the received audio is unmuted and the PLL bandwidth is set to IHz;
The algorithm returns to step 2.

13. Sync word errors in window B are counted and if 5ent < 8th+ 1), the received audio is unmuted and the PLL bandwidth is set to 1 Hz, 110 bits for FVC or 126 bits for RVC. One of the bit messages is shifted in. Go to step 2.

14. If 5ent > (30-8th -1)
That is, when the inverted sync word is detected, the received audio is unmuted, the PLL bandwidth is set to IHz, and either the 110-bit message for FVC or the 126-bit message for RVC is shifted. The algorithm returns to step 2.

! 56 The algorithm loops back from step 11 to step 14 until it reaches a timeout of 4.5 seconds, after which it leaves the MUTE-2 algorithm and returns to the multi-phase DSAT acquisition algorithm. Returning to the multi-phase DSAT acquisition algorithm results in a last attempt to ensure DSAT synchronization before the call is discarded.

Reference parameters: 8 th=4 A th=8 th=3 Uth=2 All references to DSAT in the MUTE-1 algorithm shall also apply to the inverted DSAT when this algorithm is applied at the base site. .

MUTE-1 algorithm 1, the receive bit stream is divided into two registers (or windows), A and B each for 50 ms or 3
Enter 0DSAT bit length. The received bit leaves register A and enters register B.

2. 30 received bits in register B is the expected DS
Compared to the AT flow, the number of DSAT errors is counted (Bent).

The 3,8 register (which can be a holding register for the sync correlator) is compared with the data message 30-bit sync word (195A99A6) and the number of DSAT errors is counted (Sent).

4. 30 received bits in register A are expected DS
It is compared to the AT flow and the number of DSAT errors is counted (Sent).

5. If (a) (Acnt > Ath) and (
b) (Bent > 8th) and (c) (S ant > 8th) (i.e., B
If there is no synchronization detection in the window), go to step IO, leave the MUTE-1 algorithm and return to the multi-phase DSAT acquisition algorithm.

6. If the sync word detection occurs within the B window (S
cnt <8th+1), return to step 7 of the MUTE-2 algorithm.

7. The received DSAT stream is shifted one bit through the A and B registers and the algorithm returns to step 2.

ALERT As an example of how the mute algorithm is used, the ALERT protocol is listed below.

When a mobile receives a valid PAGE message and is assigned to a voice channel, the following sequence of events defines an ALERT.

PROTOCOL (protocol) 1. Base site sends DSAT.

2. The mobile unit tunes to the audio channel and sets the PLL to 10.
) tz, wait until 24 bits are received,
Begin the multi-phase DSAT acquisition algorithm.

3. Mobile object is In1tiaH early) and confirmation DSAT
Has detection. The PLL bandwidth is reduced to lHz.

PLL bandwidth is never 10 during activity on this channel.
It does not return to Hz.

4. The mobile relays DSAT to the base site and
Start checking for C messages and start the MUTE-1 algorithm using the single Funny's DSAT detection algorithm. MUTE-1 keeps the PLL operating at IHz bandwidth and mute (possibly illegal or SAT
phase), it is MUTE-2
Returning to the multi-phase DSAT acquisition algorithm much faster than

5. After starting MUTE-1, the mobile starts counting DSAT bits. After receiving 30 DSAT bits without muting (correctly or incorrectly), the mobile
Switch to TE-2 algorithm.

If a mute occurs during MUTE-1, the mobile is reverted to the multi-phase DSAT acquisition algorithm.

The 30 bit count provides further confirmation for the correct DSAT phase and initiates MUTE-2. M
The advantage of the UTE-2 algorithm is that once In1ti
al DSAT Detect (initial DSAT detection),
Confirm DSAT detection, and once MUTE-1 is satisfied,
Bit-slips cannot occur, so a multi-phase DSAT acquisition algorithm is not required. This is D
Improve SAT errors and reduce processor load.

The use of a mute algorithm before the call is put through, of course, does not provide the user with any voice noise protection since the voice is already muted at this point. However, these algorithms
It provides a useful application for monitoring the channel return to the multi-phase DSAT acquisition algorithm, or free-running the PLL to protect against bit-slips during noise (after initiation of MUTE-2).

(If the confirmation DSAT false detection protection for 2,49 hours is taken into account, the use of MUTE-1 can be stopped and started immediately after the confirmation DSAT detection.

) 6. Once the base site has initial and confirmed DSAT detections, it begins to send FVCALERT continuously. The PLL is reduced to IHz bandwidth.

The PLL bandwidth is never returned to 1 OHZ while active on this channel. The base is a single Funnies DSAT
Start the MUTEl algorithm using the detection algorithm. The base also begins checking the inverse DSAT from the mobile. (The base continues to detect the non-inverted DSAT until the inverted DSAT arrives.) Neither an ARQ nor a NAK is requested from the mobile before repeating the ALERT message.

It is not necessary to increment DSAT between ALERT messages.

MUTE-1 keeps the PLL running at 1 Hz and if mute (probably due to incorrect SAT phase)
When this happens, it returns to the multi-phase DSAT acquisition algorithm much faster than MUTE-2.

? , After the start of MUTE-1, the base starts counting DSAT bits. After receiving 30 DSAT bits (correctly or incorrectly) without mute, the base
Switch to UTE-2 algorithm. If mute is M
Occurs during UTE-1, the base is in multiple phase D
Return to SAT acquisition algorithm. The 30 bit count provides further confirmation of the correct DSAT phase and initiates MUTE-2. The advantage of the MUTE-2 algorithm is that once the In1tial DSAT D
etect (initial DSAT detection), confirmation DSAT detection,
and MUTE-1 are satisfied, bit slips may occur, therefore a multi-phase DSAT acquisition algorithm is not required. This improves DSAT error protection and reduces processor load.

8. After receiving a valid error detection FVCALERT, the mobile begins relaying an inverted DSAT to the base indicating that the mobile is receiving an ALERT FVC message.

9. If the base site detects an inverted DSAT (over a 30-bit interval with zero or one error), it ceases sending FVCALERT (alert) messages and sends a DSAT.

10. If the mobile detects DSAT (over a 30-bit interval with 0 or 1 error),
The mobile plays a sound to the mobile user.

Il, mobile user goes off-hook
, the mobile relays the non-inverted DSAT.

+2. The base site is (3 with 0 to 1 errors)
If it detects a non-inverted DSAT (over a 0 bit interval), the base site connects the call.

Ancillary advantages of the present invention include improved mute sensitivity, protection against mistakes, individually adjustable thresholds for balancing mute sensitivity and speech quality, and provision of bit-slip protection during high noise conditions. including.

In this way, a mechanism for error detection is provided, including the detection of symmetry in the error distribution over adjacent time intervals, and the detection of full-fledged loss of symmetry, unless the error is due to effective selective detection. including muting the radiotelephone in response to.

More specifically, detecting symmetries in the error distribution over adjacent times; corrective for subsequent asymmetries or full-blown symmetry losses (unless the errors are due to valid synchronization word selection detection); muting the radiotelephone in response, and canceling any such corrective response upon subsequent selective detection of a valid synchronization word.

Means for carrying out the invention are readily available;
It is recognized by those of ordinary skill in the art that their operation is well understood. Many digitally operated squelch radios, such as the Revine (U.S.
4.649.543) or no pull (
Figures 1 to 5 of US 4.450.573) are
This forms the subject of the device claim of the invention. Although preferred embodiments of this invention have been described, those skilled in the art will recognize that the invention may be practiced with other changes and modifications. For example, to change mute sensitivity, the thresholds of two windows do not need to be equal. This would be a trade-off between error protection and mute sensitivity.

These and all other variations and adaptations are expected to be within the scope of the appended claims.

[Brief explanation of drawings]

FIG. 1 is an event diagram of a network in which a preferred embodiment of the present invention operates. FIG. 2 is a state diagram of a method according to a preferred embodiment of the invention.

Claims (1)

Claims: 1. A method of error detection comprising the steps of: detecting an increase in a bit error distribution; and taking corrective action in response to detecting the increase. 2. The error detection method according to claim 1, further comprising the step of causing the detection to occur over time. 3. An error detection method as claimed in claim 1, comprising the step of detecting the symmetry of the error distribution occurring over adjacent time intervals. 4. The error detection method according to claim 1, wherein the step of taking corrective action comprises the step of initiating mute on the radiotelephone. 5. An error detection method according to claim 1, which comprises the step of denying the step of taking corrective action based on another valid detection. 6. An error detection method according to claim 1, which comprises the step of canceling the step of taking corrective action due to another valid detection occurring subsequently. 7. An error detection method according to claim 1, which comprises negating the step of taking corrective action upon detection of the synchronization word. 8. Error detection comprising the steps of: detecting an increasing bit error distribution over adjacent time intervals; and muting the radiotelephone in response to the detection of the increase, unless the error is due to another valid detection. Method. 9. detecting an increasing bit error distribution over adjacent time intervals; muting the radiotelephone as a corrective response to the detection of the increase, unless the error is due to another detection of a valid synchronization word; canceling any such corrective response by subsequent detection of another synchronization word. 10. An error detection apparatus comprising means for detecting an increasing bit error distribution and means for taking corrective action in response to detecting the increase. 11. means for detecting an increasing bit error distribution over adjacent time intervals; means for muting the radiotelephone in response to the detection of the increase unless the error is due to another valid detection;
An error detection device comprising: