JPH09307597A - Automatic frequency controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a large error from being caused in AFC information by outputting an AFC information latch inhibit control signal to an AFC register when an error is detected in the AFC information based on reception state information. SOLUTION: An automatic frequency controller(AFC) 10 is made up of a frequency difference detection section 11, a frequency difference correction section 12, an AFC information error detection section 13, and an AFC information register 14. Then the AFC information acquired by a synchronization burst is latched by an AFC information register 14 after the end of the burst and it is used for an initial value of the AFC information in a TCH. When the AFC information error detection section 13 detects an error, the AFC information register 14 does not make latching but stores the AFC information detected for the preceding synchronization burst where no fault was detected. Since the synchronization burst is sent/received between a base station and a mobile station for several number of times, the transition to the TCH is successful with higher probability than that the case with absence of an AFC protection circuit 15 consisting of the AFC information error detection section 13 and the register 14.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to RCR-STD2.
Automatic frequency control (AF
C: Automatic Frequency Control) device, for example, used in PHS and the like based on RCR-STD28,
The present invention relates to an automatic frequency control device used in a π / 4 shift QPSK system demodulator.

[0002]

2. Description of the Related Art A current digital wireless mobile terminal device such as a PHS (Personal Handy phone System) uses a 1.9 GHz band as a frequency band to be used, a carrier interval is 300 kHz, and an access method is 4-channel multi-carrier TDMA ( Time Division Multiple Acces
s: Time division multiple access), the transmission method is TDD (Time Di
vision Duplex: Time-division replication). In this access method and transmission method, a signal on one frequency is divided into, for example, 8 slots per 5 milliseconds, and 4 slots are provided for downlink (base station → terminal) and 4 slots for uplink (terminal → base station). Assign That is, four bidirectional communication channels can be simultaneously set on one carrier.

Data between the terminal and the base station is π / 4.
Shift QPSK (Quadrature Phase Shift Keying) is used, and the voice coding method is ADPC.
32 PCM audio signals of 64 kbit / sec by M (Adaptive Differential PCM)
It is compressed and encoded to k bits / second and transmitted.

The carrier frequency is divided into one for control and one for communication, and the control carrier is always shared by each terminal. The communication carrier confirms and uses a vacant carrier and slot at each communication at each terminal, and when receiving a radio wave interference, moves to another carrier or slot to avoid the interference.

The PHS radio section protocol basically complies with RCR-STD28. RCR-STD2
Automatic frequency control (AFC: Automa) used for a π / 4 shift QPSK demodulator used for PHS-8
tic Frequency Control) is as follows.

In the RCR-STD 28, as a sequence for communication, first, communication of the control channel is performed in the link channel probability phase. When the service channel establishment phase and the communication phase are entered, communication on the communication channel is performed. Therefore, control channel communication must first be enabled.

The basic physical slot structure of the control channel is as shown in FIG.

FIG. 3 is a diagram showing the structure of a control physical slot. A preamble pattern of 32 symbol width (consecutive of "1001") peculiar to the control physical slot, UW (Uniq).
ue Word: Sync word), ID, etc.

[0009]

As described above, RC
When shifting to the communication channel in the communication protocol defined in R-STD28, the preamble pattern is set to 3
Synchronous verses arranged for 1 symbol are transmitted and received every frame (5 msec cycle) between the base station and the mobile station. In the device of Appendix 1, the ACH information detected at the end of this synchronization burst is used as the initial value for the TCH (Channel code).
ng format: information channel signal) starts AFC operation.

Here, in mobile communication, fading of up to several tens of dB may occur, and this must be premised. As shown in FIG. 4, when the last synchronization burst, which is the initial value of the AFC information, just overlaps with deep fading, the AFC information obtained there may have a larger error than the allowable range of the AFC detection capability in TCH. .

The present invention provides an automatic frequency control device capable of preventing a large error from occurring in AFC information even when the last synchronization burst as an initial value of AFC information overlaps deep fading. The purpose is to provide.

[0012]

An automatic frequency control device according to the present invention detects a frequency difference in phase information and outputs it as AFC information, and phase information based on AFC information from the frequency difference detection section. In the automatic frequency control device including a frequency difference correction unit that corrects A and outputs the corrected output as an AFC output,
When the AFC information abnormality detecting means for detecting an abnormality in the FC information and the AFC information from the frequency difference detecting section are latched and output to the frequency difference correcting section, and the abnormality detecting signal is received from the AFC information abnormality detecting means. , And AFC information holding means for prohibiting the latch.

Further, the automatic frequency control device according to the present invention detects the frequency difference of the phase information and outputs it as AFC information, and the AFC from the frequency difference detecting section.
In the automatic frequency control device including the frequency difference correction unit that corrects the phase information based on the information and outputs the corrected output as the AFC output, the AFC acquired through a predetermined number of transmissions and receptions.
A plurality of AFC information holding means for latching information, a plurality of reception state holding means installed corresponding to the plurality of AFC information holding means, for latching reception state information acquired by a predetermined number of transmissions and receptions, and a plurality of reception states Compare the reception status information from the holding means, select the series with the best reception status,
And a selecting unit that outputs the AFC information of the selected AFC information holding unit to the frequency difference correcting unit.

Further, the AFC information holding means may hold the AFC information acquired in each synchronization burst when transmission and reception are performed a predetermined number of times between the base station and the mobile station, and the reception state For the information, the received electric field strength in the slot may be compared with a reference value, and the reception state information may be detected based on the result of comparison between the received electric field strength and the reference value.

Further, the reception status information may be detected by a unique word pattern mismatch detection that represents a bit string in the slot configuration data, and the reception status information is handled inside the automatic phase shift circuit. A value PW in which the number of hits in the specified symbol section is emphasized by the emphasizing circuit using PW (dMAX)
(D) The maximum value PW (dMAX) of (d is 0 to 15) may be compared with a reference value, and the reception state information may be detected based on the comparison result of the PW (dMAX) and the reference value.

The automatic frequency control (AFC) device may be an AFC based on a communication protocol defined in RCR-STD28, and the automatic frequency control (AFC)
The FC) device may be an AFC used for a π / 4 shift QPSK demodulator used for RHS-based PHS.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Automatic frequency control (A
The FC) device can be applied to an automatic frequency control (AFC) device that uses a preamble pattern conforming to RCR STD-28.

FIG. 1 is a diagram showing the configuration of an automatic frequency control (AFC) device according to a first embodiment of the present invention, where RC
This is an example applied to an automatic frequency control (AFC) device used in a demodulator that digitally processes phase information in accordance with RSTD-28.

In FIG. 1, automatic frequency control (AFC)
The device 10 includes a frequency difference detection unit 11 and a frequency difference correction unit 1.
2, AFC information abnormality detection unit 13 (AFC information abnormality detection means), AFC information register 14 (AFC information holding means)
Consists of

The frequency difference detecting section 11 detects the frequency difference from the input phase information and outputs the AFC as AFC information.
Output to the information register 14.

The frequency difference correction unit 12 corrects the input phase information by the output of the AFC information register 14 and outputs the corrected output after the AFC control output signal (hereinafter, simply referred to as AF
It is called C output. ).

The AFC information abnormality detecting section 13 detects that there is an abnormality in the AFC information based on the reception state information, and when it detects an abnormality, it outputs a latch inhibition control signal to the AFC information.
Output to the information register 14.

The AFC information register 14 latches the AFC information from the frequency difference detection unit 11 and outputs it to the frequency difference correction unit 12, and also the AFC information abnormality detection unit 13
When the latch prohibition control signal is received from, the latching of the AFC information when receiving the latch prohibition control signal is prohibited.

The AFC information abnormality detection unit 13 and the AFC
The information register 14 constitutes the AFC protection circuit 15 as a whole.

That is, the automatic frequency control (AFC) device 10 according to the first embodiment detects a frequency difference of phase information and outputs it as AFC information.
And the AFC device including the frequency difference correction unit 12 that corrects the phase information based on the AFC information from the frequency difference detection unit 11 and outputs the corrected output as the AFC output. AFC information abnormality detection unit 13 for detecting an abnormality, and frequency difference detection unit 11
AFC information register 1 that latches the AFC information from the device and outputs it to the frequency difference correction unit 12 and also inhibits the latch by the latch inhibition control signal from the AFC information abnormality detection unit
4 is added to the AFC protection circuit 15.

The operation of the automatic frequency control (AFC) device 10 configured as described above will be described below.

The AFC information acquired in the synchronous burst is latched in the AFC information register 14 after the burst is completed,
It becomes the initial value of AFC information in CH. When the AFC information abnormality detection unit 13 detects an abnormality, the AFC information register 14 does not perform latching and holds the AFC information detected in the synchronization burst in which the previous abnormality was not detected.

Since the synchronization burst is transmitted and received between the base station and the mobile station several times, there is a higher probability that the transition to the TCH will be successful than in the case without the AFC protection circuit 15.

Here, in the present embodiment, the following methods a) to c) are adopted as a method for realizing the AFC protection method, depending on the type of the reception status information.

A) Carrier sense method The RCR-STD 28 defines a carrier sense function. The received electric field strength in the slot (particularly, the range in which the preamble pattern is arranged) is compared with the reference value, and when the received electric field strength is lower than the reference value, the AFC information register 14 prohibits latching. This reference value is
A value is arbitrarily selected so that the probability that the AFC information will be abnormal becomes higher than a certain level.

B) Unique word error method In the PHS, a match / mismatch detection of a unique word pattern (bit string in slot configuration data) is performed in order to establish synchronization of the physical layer in a block that normally performs baseband processing. . Therefore, latching is prohibited when a unique word mismatch (unique word error) is detected.

C) Phase distribution detection method PW (d) handled inside the automatic phase shift circuit
MAX) is used. The value obtained by emphasizing the number of hits in the specified symbol section by the emphasizing circuit is PW (d) (d is 0 to 15), and the one having the largest PW (d) value is PW (dMAX). . The better the reception condition, the larger the C / N and the larger PW (dMAX).
The smaller is, the smaller is PW (dMAX). This PW
(DMAX) is compared with the reference value, and when PW (dMAX) is smaller than the reference value, the AFC information register 14 inhibits latching.

As described above, the automatic frequency control (AFC) device 10 according to the first embodiment detects the frequency difference of the phase information and outputs it as AFC information, and the frequency difference detection unit 11. The frequency difference correction unit 12 that corrects the phase information based on the AFC information from the unit 11 and outputs the corrected output as the AFC output, and the AFC information abnormality detection that detects that the AFC information is abnormal based on the reception state information While latching the AFC information from the unit 13 and the frequency difference detection unit 11 and outputting it to the frequency difference correction unit 12,
Since the AFC information register 14 configured to inhibit the latch by the latch inhibition control signal from the AFC information abnormality detection unit is provided, fading of several tens of dB occurs in mobile communication, and the AFC information register 14 has an initial value of the AFC information. Even when the last synchronization burst to be performed exactly overlaps deep fading, it is possible to prevent a large error from occurring in the AFC information.

Therefore, an automatic frequency control (AFC) device having such excellent features is installed in the RCR-STD2.
If it is used in a π / 4 shift QPSK system demodulator such as PHS based on 8, the mobile communication terminal device can perform information transmission with higher quality without quality deterioration.

FIG. 2 is a block diagram showing the configuration of an automatic frequency control (AFC) device according to the second embodiment of the present invention. The automatic frequency control (AFC) device shown in FIG.
It can be applied to a mobile communication device such as PHS based on R-STD28. In the description of the automatic frequency control (AFC) device according to this embodiment, the same components as those of the automatic frequency control (AFC) device shown in FIG. 1 are designated by the same reference numerals.

In FIG. 2, automatic frequency control (AFC)
The device 10 includes a frequency difference detection unit 11 and a frequency difference correction unit 1.
2. An AFC information register 21 (a plurality of AFC information holding means), a reception status register 22 (a plurality of reception status holding means), a comparator 23 and a selector 24.

The frequency difference detecting section 11 detects the frequency difference from the input phase information and outputs it as AFC information for each AF.
Output to the C information register 21.

The frequency difference correction unit 12 corrects the input phase information by the output of the AFC information register 21 selected by the selector 24 and outputs the corrected output as the AFC output.

The AFC information register 21 latches the AFC information acquired in each synchronization burst when transmission and reception are performed several times between the base station and the mobile station.

The reception status register 22 is installed corresponding to the plurality of AFC information registers 21, and the reception status acquired in each synchronization burst when transmission and reception are performed several times between the base station and the mobile station. Latch information directly.

The comparator 23 compares the reception status information from the plurality of reception status registers 22 and outputs a selection switching signal for selecting the register series having the best reception status to the selector 24.

The selector 24 has the AFC information register 21 which has the best reception state according to the reception state information when shifting to TCH based on the selection switching signal from the comparator 23.
Of the selected AFC information register 21
The FC information is output to the frequency difference correction unit 12.

The AFC information register 21, the reception status register 22, the comparator 23 and the selector 24 constitute an AFC protection circuit 25 as a whole, and the comparator 23 and the selector 24 constitute a selecting means 26 as a whole. To do.

As described above, the automatic frequency control (AFC) device 20 according to the second embodiment detects the frequency difference of the phase information and outputs it as AFC information.
And the AFC device including the frequency difference correction unit 12 that corrects the phase information based on the AFC information from the frequency difference detection unit 11 and outputs the corrected output as the AFC output, between the base station and the mobile station. AF that latches the AFC information acquired in each synchronization burst when transmission and reception are performed several times
C information register 21 and reception status register 2 that directly latches the reception status information acquired in each synchronization burst
2 and the reception status information from the plurality of reception status registers 22, and outputs a selection switching signal for selecting the register series having the best reception status, and shifts to TCH based on the selection switching signal. When selecting the AFC information register 21 series with the best reception status,
An AFC protection circuit 25 including a selector 24 that outputs FC information to the frequency difference correction unit 12 is added.

The operation of the automatic frequency control (AFC) device 20 configured as described above will be described below.

In the second embodiment, the reception status information is directly latched in each reception status register 22. Since the synchronization burst is transmitted and received several times between the base station and the mobile station, the AFC information acquired in each synchronization burst is stored in the AFC information register 21 and the reception state information is also stored. When shifting to the TCH, the selector 24 selects the AFC information register 21 and the receiving condition register 22 having the best receiving state according to the receiving state information, and the AFC information of the AFC information register 21 is set to the AFC information in the TCH. Use as initial value of information.

The synchronization burst is normally performed several times in a cycle of 5 msec, and the fluctuation amount of the frequency difference until the transition to TCH can be considered to be extremely small, so this method is possible.

The reception status information can be obtained by the same method as in the first embodiment described above. That is: a) Carrier sense method The carrier sense function is defined in the RCR-STD 28. To select the system that sends the AFC information to the frequency difference correction unit 12 by latching the received electric field strength in the slot (in particular, the range where the preamble pattern is arranged) as the reception state information and comparing the received electric field strength. You can

B) Baseband Data Detection Method In the PHS, the unique word pattern (bit string in the slot configuration data) is detected for matching / mismatching in order to establish physical layer synchronization in a block that normally performs baseband processing. There is. In addition, a CRC (cyclic redundancy check code) operation is performed in a specified section within the slot, and a CRC bit is added to the end of the slot. Furthermore, there is also channel type information that can determine whether the slot information is a synchronization burst.

Therefore, a system for sending AFC information to the frequency difference correction unit 12 by latching and comparing the match / mismatch of unique word patterns, the match / mismatch of CRC calculation results, and the match / mismatch of channel type information as reception status information. Can be selected. In this case, the conversion logic from the above three pieces of matching / non-matching information to the reception state information is arbitrary.

C) Phase distribution detection method PW (d) handled inside the automatic phase shift circuit
MAX) is used. The value obtained by emphasizing the number of hits in the specified symbol section by the emphasizing circuit is PW (d) (d is 0 to 15), and the one having the largest PW (d) value is PW (dMAX). . C in receiving state
The larger the / N, the larger the PW (dMAX), and the C / N
The smaller is, the smaller is PW (dMAX). This PW
(DMAX) as reception state information
It is possible to select the system that sends the optimum AFC information to the frequency difference correction unit 12 by latching and comparing at.

As described above, the automatic frequency control (AFC) device 20 according to the second embodiment detects the frequency difference of the phase information and outputs it as AFC information, and the frequency difference detection unit 11. The frequency difference correction unit 12 that corrects the phase information based on the AFC information from the unit 11 and outputs the corrected output as the AFC output, and the synchronization between the base station and the mobile station when transmission and reception are performed several times. AFC information register 2 that latches AFC information acquired by burst
1, the reception status register 22 that directly latches the reception status information acquired in each synchronization burst, and the reception status information from a plurality of reception status registers 22 are compared, and the register series with the best reception status is selected. A comparator 23 that outputs a selection switching signal, and TCH based on the selection switching signal
Since it is configured to include the selector 24 that selects the series of the AFC information register 21 having the best reception state when shifting to the step 1 and outputs the selected AFC information to the frequency difference correction unit 12, Similar to the embodiment described above, even when fading reaching several tens of dB occurs and the last synchronization burst as the initial value of AFC information exactly overlaps deep fading, a large error occurs in AFC information. Can be prevented.

The automatic frequency control (AFC) device according to each of the above-described embodiments is used in the RCR-STD2 as described above.
The present invention is applied to a π / 4 shift QPSK system demodulator (synchronous detection system) used for PHS based on 8 but is not limited to this, and for example, automatic frequency control used in a delay detection system demodulation unit in PHS. It can also be applied to the department (AFC). Further, it goes without saying that it can be applied to all devices (for example, mobile communication terminals) as long as they are devices that perform automatic frequency control.

Needless to say, the types of registers, comparators, selectors, etc. constituting the automatic frequency control (AFC) device, the number of them, and the method of detecting the reception state are not limited to those in the above-described embodiment. .

[0055]

According to the automatic frequency control device of the present invention,
AFC information abnormality detecting means for detecting an abnormality in the AFC information based on the reception status information, and latching the AFC information from the frequency difference detecting section and outputting the latched AFC information to the frequency difference correcting section. When the abnormal detection signal is received, since the AFC information holding means for prohibiting the latch is provided, fading of several tens of dB occurs, and the last synchronization burst as the initial value of the AFC information is just Even if it overlaps with deep fading, it is possible to prevent a large error from occurring in the AFC information.

Further, the automatic frequency control device according to the present invention is installed corresponding to a plurality of AFC information holding means for latching the AFC information acquired by transmitting and receiving a predetermined number of times and a plurality of AFC information holding means. A plurality of receiving state holding means for latching the receiving state information acquired by transmitting and receiving
Compare the reception status information from a plurality of reception status holding means,
Since a sequence having the best reception state is selected and a selection unit that outputs the AFC information of the AFC information holding unit of the selected sequence to the frequency difference correction unit is provided, several tens of dB are provided.
It is possible to prevent a large error from occurring in the AFC information even when fading that extends over a long period of time occurs and the last synchronization burst that is the initial value of the AFC information just overlaps the deep fading.

Therefore, if it is used in a π / 4 shift QPSK system demodulator such as PHS based on RCR-STD28, this mobile communication terminal device can carry out more sensitive information transmission without quality deterioration. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an automatic frequency control device according to a first embodiment to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration of an automatic frequency control device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a control physical slot in mobile communication.

FIG. 4 is a diagram showing an example of burst reception during fading in mobile communication.

[Explanation of symbols]

10, 20 Automatic frequency control (AFC) device, 11 Frequency difference detection unit, 12 Frequency difference correction unit, 13 AFC information abnormality detection unit (AFC information abnormality detection means), 14 AFC
Information register (AFC information holding means), 15, 25 A
FC protection circuit, 21 AFC information register (multiple AF
C information holding means), 22 reception status register (plurality of reception status holding means), 23 comparator, 24 selector, 26
Selection means

Claims (9)

[Claims] 1. A frequency difference detection unit that detects a frequency difference of phase information and outputs it as AFC information; and a phase difference is corrected by AFC information from the frequency difference detection unit and the corrected output is used as an AFC output. In an automatic frequency control (AFC) device provided with a frequency difference correction unit for outputting, an AFC information abnormality detection unit for detecting abnormality in the AFC information based on reception state information, and an AFC information abnormality detection unit from the frequency difference detection unit. An automatic frequency control device, comprising: AFC information latching means for latching AFC information and outputting it to the frequency difference correcting section; and AFC information holding means for inhibiting latching when the abnormality detection signal is received from the AFC information abnormality detecting means. Control device. 2. A frequency difference detection unit that detects a frequency difference of phase information and outputs it as AFC information, and the phase information is corrected by AFC information from the frequency difference detection unit, and the corrected output is an AFC output. In an automatic frequency control (AFC) device equipped with a frequency difference correction unit for outputting, a plurality of AFC information holding means for latching AFC information acquired by transmitting and receiving a predetermined number of times, and a plurality of AFC information holding means corresponding to the plurality of AFC information holding means A plurality of reception state holding means that is installed and latches the reception state information acquired by transmitting and receiving a predetermined number of times is compared with the reception state information from the plurality of reception state holding means, and the series with the best reception state is selected. And a selecting means for outputting the AFC information of the selected AFC information holding means to the frequency difference correction section. 3. The AFC information holding means holds the AFC information acquired in each synchronization burst when transmission and reception are performed a predetermined number of times between a base station and a mobile station. Item 2. The automatic frequency control device according to item 2. 4. The selecting means compares the receiving status information from the plurality of receiving status holding means, and selects the series of the AFC information holding means having the best receiving status when shifting to TCH, 3. The automatic frequency control device according to claim 2, wherein the AFC information of the selected AFC information holding unit is output to the frequency difference correction unit. 5. The reception status information is characterized in that the reception electric field strength in a slot is compared with a reference value, and the reception status information is detected based on a comparison result of the reception electric field strength and the reference value. The automatic frequency control device according to claim 1. 6. The reception status information is detected by detecting a unique word pattern mismatch indicating a bit string in the slot configuration data. Automatic frequency control device. 7. The reception state information uses PW (dMAX) handled in the automatic phase shift circuit, and a value PW (d) (d is 0 to 15) obtained by emphasizing the number of hits in a specified symbol period by an emphasis circuit. ) Maximum value PW (dMA
X) is compared with a reference value, and the reception status information is detected based on the result of comparison between the PW (dMAX) and the reference value. Control device. 8. The automatic frequency control device according to claim 1 or 2, wherein the automatic frequency control device is an AFC based on a communication protocol defined in RCR-STD28. 9. The automatic frequency control device according to claim 1 or 2, further comprising: π / 4 used for PHS based on RCR-STD28.
An automatic frequency control device, which is an AFC used for a shift QPSK demodulator.