KR19990026455A - CAS signal detection method of sender-ID receiver - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a caller-ID receiver, and more particularly, to a method for detecting a Customer Pramises Equipment (CPE) alerting signal containing information of a sender from a signal received by the sender-ID receiver. In the case of CAS, the CAS detects the energy level of the received signal and detects CAS by operating the bandpass filter or correlator suitable for the energy level. can do

Description

CAS DETECTING METHOD OF CALLER-ID RECEIVER

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a caller-ID receiver, and more particularly, to a method for detecting a Customer Pramises Equipment (CPE) alerting signal containing information of a sender from a signal received by the sender-ID receiver. It is about.

Currently, there is a telephone service called Caller-ID or Calling Number Delivery in the telephone service provided by the telephone station. This is a service that provides the receiver with information of the sender, that is, information such as subscriber number and subscriber name. In order to receive these services, the user must apply for the service to the telephone company in advance. The telephone station then provides the sender-ID providing service to registered users only. In order to receive these services, the user must have a sender-ID receiver telephone. The sender-ID receiving telephone is provided with an LCD (Liquid Crystal Display) as a display device for displaying received information and a sender-ID receiver which is usually provided as a semiconductor chip in addition to the telephone circuit generally configured.

The overall operation in which the sender-ID is provided proceeds as follows.

First, when the called party is not busy, that is, when the called party's telephone is in an on-hook state, the telephone company sends the sender-ID information to the idle period between the first ring signal and the second ring signal. Is sent to the receiver. The sender ID information is a signal generally called a CAS and contains information of a sender (CPE; Customer Pramises Equipment).

When the receiver is busy, i.e., when the receiver's telephone is off hook, the telephone company transmits the CAS along with the sender's voice signal. The transmitted CAS is detected by a CAS detector provided in the sender-ID receiver. The detected CAS is restored to the corresponding data through a demodulation process and displayed on the LCD. In order to receive these services, a call waiting service must be subscribed to the telephone company in addition to the sender-ID service. The call waiting service is a service that notifies a called party when a third party makes a call to a busy subscriber. When a third party makes a call, the called party detects the call request of the third party through a ring signal and can confirm the third party's information through the third party's sender-ID information displayed on the LCD.

In the on-hook state, the CAS detects and restores the CAS after the first ring signal is detected. In this case, since only CAS is received, it is easy to detect CAS. In the case of off-hook, the CAS detector determines whether the CAS is included in the received signal, and when CAS is received, restores data through a demodulator so that sender-ID information is displayed on the LCD.

However, in the conventional CAS detection method, since a band pass filter is used, when the signal-to-noise ratio (SNR) is low, it does not operate well, and thus CAS cannot be detected normally.

Accordingly, it is an object of the present invention to provide a CAS detection method that can normally detect CAS even when the SNR is low as proposed to solve the above-mentioned problems.

1 is a flowchart showing a procedure of a CAS signal detection method of a sender-ID receiver according to an embodiment of the present invention.

According to a feature of the present invention for achieving the object of the present invention as described above, the CAS detection method of the sender-ID receiver comprises: determining the energy level of the received signal; Dropping out of a CAS detector when it is determined that an energy level of the received signal is an energy level in which only a voice signal exists; Operating one of a band pass filter or a correlator according to the corresponding energy level when it is determined that the energy level of the received signal is an energy level in which CAS may exist; Either the band pass filter or the correlator is operated to detect the CAS.

In this embodiment, the energy level of the received signal includes: a first section of -9 dBm or more, a second section of -15.5 dBm to -9 dBm, a third section of -25 dBm to -15.5 dBm, and -25 dBm or less It divides into a 4th section.

In this embodiment, when the received signal is present in the first section, the energy level of the received signal is determined to be an energy level in which only a voice signal exists and is dropped out of the CAS detector; When the received signal is present in the second section, the band pass filter is operated to detect a CAS; When the received signal is present in the third and fourth sections, the correlator is operated to detect the CAS.

In this embodiment, when the received signal transitions from the second section to the third section, the band pass filter is operated to detect a CAS; When the received signal transitions from the third section to the second section, the correlator is operated to detect the CAS.

In this embodiment, the threshold voltage of the correlator is reduced by half when the received signal transitions from the third section to the fourth section.

According to the present invention as described above, if CAS is present by determining the energy level of the received signal, the CAS is detected by operating a bandpass filter or correlator suitable for the energy level of the received signal. Can detect CAS correctly

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart illustrating a procedure of a CAS signal detection method of a sender-ID receiver according to an embodiment of the present invention.

The current regulations on CAS detection (proposed by Bellcore, USA) are the first, CAS detection in the absence of voice signal, the second, talk-off test and the third talk-down test. The talk-off test is a test performed when there is no CAS and only a voice signal, that is, a call, thereby preventing an incorrect ring signal from being generated due to malfunction of CAS detection. The talk-down test is a test to detect this in the section where the CAS exists.

In the present invention, as a method for satisfying all three cases as described above, the received signal is classified into four energy levels as shown in Table 1 below, and the CAS is detected through this.

Classification section Energy level of the received signal characteristic First section -9 dBm or more Voice signal only Dropout 2nd section -15.5 dBm to -9 dBm CAS can exist CAS detection with band pass filter 3rd section -25 dBm to -15.5 dBm CAS can exist CAS detection with correlator 4th section -25dBm or less CAS can exist CAS detection with correlator

As shown in FIG. 1, the detection of the CAS signal of the sender-ID receiver is as follows.

First, in step S100 it is determined the energy level of the received signal. In this case, the energy level is determined by dividing the energy level into four sections as shown in Table 1 above.

When the energy level of the received signal exists in the first section, the process proceeds to step S210. In the case of the received signal existing in the first section, only a voice signal exists, and there is no possibility of CAS. Therefore, if the energy of the received signal is present in this section, it is dropped out from the CAS detector.

If the energy level of the received signal exists in the second section, the flow proceeds to step S220. There is a possibility that CAS exists in the second section, and since the CAS will have a large energy (about -24 dBm), the CAS can be detected by a band pass filter having a performance of about -10 dB. In this case, the band pass filter is advantageous in preventing a false ring signal, which is also advantageous in a talk-off test.

When the received signal is present in the third section or the fourth section, the process proceeds to step S230 and step S240, respectively. In the third section or the fourth section, when the CAS is present, a very small energy (about -32 dBm) is present, so that the CAS can be detected by a correlator having a performance of about -17 dB. When the transition from the third section to the fourth section occurs, the detection voltage is increased by reducing the threshold voltage of the correlator by half.

When the received signal crosses the second section and the third section, the process proceeds to step S250. In this step, a predetermined time (approximately 60 msec) is maintained by using one of the band pass filter or the correlator based on the value before crossing the boundary. That is, when the transition from the second section to the third section, the CAS is detected using the band pass filter, and when the transition from the third section to the second section, the CAS is detected using the correlator. Detect. In this case, the threshold voltage of the correlator is reset so that the hybrid loss in the telephone conversation has attenuation of 8 dB or more.

As described above, a corresponding step is performed according to the energy level of the received signal. When CAS is received, the CAS is detected using a band pass filter or a correlator in step S300. The detected CAS is restored to the sender-ID information through the demodulation process and displayed on the LCD.

According to the present invention as described above, unlike the conventional CAS detection of the sender-ID, CAS can be detected normally even when the SNR has a low SNR of about -23 dB.

Claims (5)

In the method for detecting a CAS (CPE Alerting Signal) of the sender-ID receiver, Determining an energy level of the received signal; Dropping out of a CAS detector when it is determined that an energy level of the received signal is an energy level in which only a voice signal exists; Operating one of a band pass filter or a correlator according to the corresponding energy level when it is determined that the energy level of the received signal is an energy level in which CAS may exist; Any one of the bandpass filter or the correlator is operated to detect a CAS. The method of claim 1, The energy level of the received signal is, A sender-ID receiver characterized by being divided into a first section of -9 dBm or more, a second section of -15.5 dBm to -9 dBm, a third section of -25 dBm to -15.5 dBm, and a fourth section of -25 dBm or less. CAS detection method. The method of claim 2, When the received signal is present in the first section, when it is determined that the energy level of the received signal is an energy level in which only a voice signal exists, it is dropped out from the CAS detector; When the received signal is present in the second section, the band pass filter is operated to detect a CAS; And detecting a CAS by operating a correlator when the received signal exists in the third and fourth sections. The method of claim 2, Detect the CAS by operating the band pass filter when the received signal transitions from the second section to the third section; And detecting the CAS by operating the correlator when the received signal transitions from the third section to the second section. The method of claim 2, And the threshold voltage of the correlator is reduced by half when the received signal transitions from the third section to the fourth section.