WO2002019560A1

WO2002019560A1 - Cdma based transmitter for producing particular pilot signal for changing call mode and wireless communication terminals corresponding to the same

Info

Publication number: WO2002019560A1
Application number: PCT/KR2001/001429
Authority: WO
Inventors: Sook-Hyeon Chang
Original assignee: Comtrue Technologies Co., Ltd.
Priority date: 2000-08-30
Filing date: 2001-08-24
Publication date: 2002-03-07
Also published as: KR20000072355A; KR100313311B1; AU2001282636A1

Abstract

Provided are a transmitter which generates pilot signals having particular pseudo-random number (PN) offset for changing a call mode and a wireless communication terminal which receives the pilot signal and automatically changes the call mode into an environment-adaptive call mode. The transmitter includes a unit for receiving a CDMA forward channel signal from neighbor base stations, a unit for acquiring system time for system synchronization from the forward channel signal, a unit for generating a pilot channel signal having a particular PN offset which is not absolutely received from the neighbor base stations, in synchronization with the system time, and a unit for transmitting the pilot signal through the overall CDMA frequency bands to be received by all CDMA terminals present within a coverage, whereby the transmitter commands all CDMA terminals present in the receivable area of the pilot signal to change a call mode.

Description

CDMA BASED TRANSMITTER FOR PRODUCING PARTICULAR

PILOT SIGNAL FOR CHANGING CALL MODE AND WIRELESS

COMMUNICATION TERMINALS CORRESPONDING TO THE SAME

Technical Field

The present invention relates to a wireless communication system of code division multiple access (CDMA), and more particularly, to a transmitter which produces pilot signals having particular pseudo- random number (PN) sequence offset for changing a call mode and a wireless communication terminal which receives the pilot signal and automatically changes a call mode into an environment-adaptive call mode.

Background of the Art

With the advent of wireless communication terminals such as cellular phones and PCS phones as necessaries of life, a calling sound originated from the wireless communication terminal became a serious noise problem, and particularly the problem gets severer where it should be quiet.

The present inventor suggested a system that changes a call mode of a wireless telephone into an environment-adaptive call mode, i.e., a vibration mode, a light mode or a low-volume mode, at the silence- requested place, as disclosed in Korean Patent Application Nos. 98-34681 and 98-50736. However, a specific technology applicable to the wireless communication terminal of CDMA is not provided in t e above-described system. The mobile communication system of CDMA has developed in its applicable standard from a standard for transmitting and receiving a voice signal to a standard of IMT-2000 enabling high-speed data transmission as well as voice transmission. The standard of IMT-2000 is defined for the purposes of rendering services of high-quality voice, moving pictures of high definition, Internet retrieval and so on.

The industrial standard of CDMA will now be described briefly, for a better understanding of the present invention.

In a CDMA based wireless communication system, such as a cellular system, a Portable Communication System (PCS) system, an International Mobile Telecommunication 2000 (IMT-2000) system and the like, the pilot channel is a sub-channel in an up-link of CDMA, that is, a link from a base station to a mobile station. The pilot channel helps the mobile station to establish initial synchronization with the base station, and is utilized by a base station (often called a cell site) to provide information on time, frequency and phase tracing of a signal transmitted from the cell site. In order for the mobile station to utilize the pilot channel for synchronization, first, the mobile station should receive the pilot channel. Whenever power is turned on and the tracing of the pilot channel results in a failure, the mobile station will try to receive the pilot channel. In a CDMA system, base stations communicate with all mobile stations by PN binary code sequences. At this time, -the respective base stations transmit the same binary code sequences of the pilot channel having different timing offsets so that the mobile stations can distinguish the base stations from one another while utilizing the same PN binary code sequence with respect to the pilot channel.

In general, the reception of the pilot channel is conducted by a searcher circuit in a CDMA modem circuit in the mobile station. Specifically, the reception of the pilot channel comprises the steps of converting a received signal into a digital signal, and comparing the received signal with a generation signal with respect to the PN sequence of the pilot channel using serial and initial conjecture (hypothesis) for the accurate timing of the PN sequence of the pilot channel. If such a hypothesis corresponds to the timing of the PN sequence of the pilot channel, the accumulated value over the predetermined value is produced by comparing the generated PN sequence with the PN sequence of the pilot channel. Then, the hypothesis on the PN sequence of the pilot channel is regarded as appropriate and recorded for the next evaluation. In the case that the mobile station is positioned out of the effective area of one base station, the base stations transmit the list of other base stations taking the connection control.

Once the mobile station gets out of the effective area under the present base station after the mobile station is synchronized with the base station, the base stations transmit the list of other base stations taking the connection control. The searcher circuit is converted into a search mode after synchronization with the base station to thereby search the PN sequence from other base station. When the PN sequence signal having the predetermined intensity is detected, the searcher circuit records the PN timing offset of the signal received from the base station. The mobile station begins to call the handoff process when the intensity of the signal from the present base station decreases while that of signals from one or more base stations considerably increases.

The above-described standards of CDMA are adopted for the next generation mobile communication system, e.g., IMT-2000. Thus, it is necessary to develop a transmitter and a wireless communication system for changing a call mode, which can be suitable to the standards of CDMA.

Disclosure of the Invention

The present invention is primarily directed to production of a mode changing signal that automatically changes the call mode of the existing wireless communication terminals without any modification in hardware of the terminals.

To this end, an object of the present invention is to provide a transmitter of the CDMA standard for producing a pilot signal having a PN sequence offset for mode change.

Also, another object of the present invention is to provide a wireless communication terminal having software algorithm determining the mode change signal from the received pilot signal. The above and other objects and advantages of the present invention will now be described and become more apparent by describing in detail a preferred embodiment thereof.

To accomplish the above object, according to an embodiment of the present invention, there is provided a code division multiple access (CDMA) transmitter for generating a particular pilot signal for changing a call mode, including means for receiving a CDMA forward channel signal from a plurality of neighbor base stations, means for acquiring system time for system synchronization from the forward channel signal, means for generating a pilot channel signal having a particular pseudo-random number (PN) sequence offset which is not absolutely received from the neighbor base stations, in synchronization with the system time, and means for transmitting the pilot signal through the overall CDMA frequency bands so as to be received by all CDMA terminals present within a coverage. Therefore, the transmitter can command all CDMA terminals present in the receivable area of the pilot signal to change a call mode.

The CDMA transmitter may further include means for acquiring a frequency band used by the present base station and neighbor base station, a PN sequence offset value of the pilot channel used in the corresponding frequency band and a received signal level, from the forward channel received from the receiving means, and storing the same. Also, the CDMA transmitter may further include means for storing the particular PN sequence offset, wherein the particular PN sequence offset is one of 512 PN sequence offsets. Here, the particular PN sequence offset is not used by the base station and is particularly allocated only for changing the call mode. In another embodiment of the present invention, the CDMA transmitter may further include means for performing an operation on the particular PN sequence offset value. Here, the particular PN sequence offset value is a predetermined value shifted from a PN sequence offset used by the present base station, and is calculated so that it does not overlap with PN sequence offset values of all pilot channels.

Also, the transmitting means is constructed so as to sequentially transmit the pilot signal for all frequency bands of the CDMA forward channel periodically according to the frequency band. The CDMA transmitter may further include means for manually setting from the outside the power intensity of the pilot signal.

To accomplish the other object of the present invention, there is provided a portable wireless communication terminal including means for receiving a CDMA forward signal transmitted from a base station and a pilot signal having a particular PN sequence offset for changing a call mode, means for storing the particular PN offset, means for periodically searching the PN sequence offset in an idle state, means for comparing a energy value of the searched pilot signal with a threshold value and determining presence or absence of a mode changing signal, and means for changing a current call mode into an environment-adaptive call mode when the mode changing signal is present.

Here, the storing means may further include PN sequence offset values of an active sector, a neighbor sector and a candidate sector. In this case, the portable wireless communication terminal may further include means for performing an operation on the particular PN sequence offset value and recording the operation result in the storing means.

The particular PN sequence offset value is a predetermined value shifted from a PN sequence offset used by the present base station, and is calculated so that it does not overlap with PN sequence offset values of all pilot channels.

Also, according to another aspect of the present invention, the particular PN sequence offset stored in the storing means may be one of 512 PN offsets, which is not used by the base station and is particularly allocated only for changing the call mode.

The portable wireless communication terminal may further include means for storing the current call mode state. Here, the call changing means restores the environment-adaptive call mode into the current call mode state if the mode changing signal is not received for a predetermined time.

Brief description of the drawings

FIG. 1 illustrates the state in which a call mode of a wireless communication terminal is changed using a transmitter installed in a silence requested place;

FIG. 2 is a block diagram illustrating a CDMA based transmitter according to an embodiment of the present invention;

FIG. 3 is a flow chart illustrating the process of producing a pilot signal having a particular PN sequence offset by the transmitter of FIG. 2 and transmitting the same;

FIG. 4 is a block diagram illustrating a CDMA based wireless communication terminal according to an embodiment of the present invention;

FIG. 5 is a detailed block diagram of a searcher unit in a CDMA modem circuit (CMC) shown in FIG. 4; and

FIG. 6 is a flow chart illustrating the process of automatically changing a call mode into an environment-adaptive call mode by the wireless communication terminal, which has received a pilot signal having a particular PN sequence offset. Best mode for carrying out the Invention

FIG. 1 shows an entrance door 100 of the place where it should be quiet, such as a library, a theater, a lecture room, an office, a lab, a conference room, a church, a temple, a music hall, a gallery, an emergency room and a mortuary (hereinafter referred as a silent place), and a wireless communication terminal 300 held by a user entering the silent place.

A transmitter 200a described later is installed on the wall of the entrance. A transmitter 200b may be installed on the ceiling of the silent place.

Here, the wireless communication terminal 300 entering the place where the transmitters 200a and 200b of the present embodiment are provided, receives a mode change signal from the transmitters 200a and 200b to thereby automatically change a call mode into an environment- adaptive call mode, i.e., a vibration mode or a light mode.

A. Transmitters

The configuration of the transmitters according to an embodiment of the present invention will now be described in detail with reference to FIG. 2.

As shown in FIG. 2, a transmitter 200 of the present embodiment comprises a plurality of antennas 210a and 210b, a RF switching portion 220, RF/IF receiving block 230, RF/IF transmitting block 270, a demodulation portion 240, a controller 250, a memory 260, a pilot channel generator 280, a power setup portion 291, and a liquid crystal display (LCD) 292.

The antennas 210a and 210b receive a forward channel signal of CDMA, particularly a pilot channel, a synchronization channel and a phasing channel from the base station that is placed in the sector or cell where the transmitter 200 is positioned. Accordingly, the antennas 210a and 210b may receive all the frequency band signal allocated to mobile communication service providers as well as all the frequency band signal of mobile communication system, such as a cellular system, a PCS system and a IMT-2000 system, transmitted from the base stations.

The transmitter 200 of FIG. 2 is provided with antennas 210a and 210b receiving a forward signal of 800 MHz of the cellular system and a forward signal of 1.8 GHz of the PCS system, respectively. The transmitters are not limited to this embodiment and may include single antenna, which can receive the above signals together.

The RF switching portion 220 selects a receiving mode or a transmitting mode according to a switch control signal from the controller 250. The receiving mode indicates the state in which the forward channel signal received by the antenna 210a and 210b from the base station is transferred to the RF/IF receiving block 230, and the transmitting mode indicates the state in which a pilot channel signal for mode change transferred from the RF/IF transmitting block 270 is emitted by antenna 210a and 210b. The RF switching portion 220 should be configured separately corresponding to each mobile communication system.

The RF/IF receiving block 230 converts the forward channel signal which is received through the antenna 210a and 210b in the receiving mode of the switching portion into a base band signal.

The RF/IF transmitting block 270 converts the pilot signal of base band, which is transferred from the pilot channel generator 280 in the transmitting mode of the switching portion into a communication frequency band signal capable of emitting through the antenna. The controller 250 controls a frequency synthesizer (not shown) in the RF/IF receiving block 230 so that frequency band signals of cellular systems, PCS systems and IMT-2000 systems can be converted into base band signals, respectively.

The demodulator 240 converts the base band signals transferred from the RF/IF receiving block 230 into digital data to transmit the same to the controller 250, and acquires a system time from the base band signal to transmit the acquired system time to the pilot channel generator

280. Here, the " system time" means synchronization time information required for synchronization between base stations or between a base station and a mobile station.

A CDMA protocol prescribed in IS-95/IS-95A/B/C is stored in the memory 260. Thus, the controller 250 controls the RF switching portion 220, the RF/IF receiving block 230 and the demodulator 240 according to the CDMA protocol stored in the memory 260 to perform sync acquisition through a pilot channel, acquires system configuration and time information through a sync channel, and processes a paging channel message through a paging channel. Also, information including a particular PN sequence offset value for changing a call mode, frequency bands used by a presently positioned base station and a neighboring base station, a PN sequence offset value of a pilot channel in use in the corresponding frequency band, a received signal level and the like, is stored in an internal memory of the controller 250. The information is acquired from a pilot channel signal, a sync channel signal and a paging channel signal transmitted from the base station of a sector or cell at which a transmitting apparatus is presently positioned.

The particular PN sequence offset is preferably a mode changing PN sequence offset among 512 offsets, which is particularly allocated only for changing a call mode, rather than being used by base stations.

Also, the particular PN sequence offset value may be a value stored in the internal memory after being calculated by an arithmetic means provided in the controller 250. In other words, the particular PN sequence offset is a predetermined value shifted from a PN sequence offset used by the present base station, and can be calculated so that it may not overlap with PN sequence offset values of all pilot channels. In other words, assuming that a PN sequence offset used by the present base station is denoted by PN1, and PN offsets of pilot channels receivable by the transmitter according to the present invention are denoted by PN2, PN3, ... PNf, the particular PN sequence offset (PNs) for changing modes can be calculated to satisfy the equation (1) below:

PNs = PNl+n ≠ PN2 ≠ PN3 ... ≠ PNf ... (1) where n is an integer.

The pilot channel generator 280 receives a control signal for periodically generating signals from the controller 250 and generates a pilot channel signal having the PN sequence offset in synchronization with the system time from the demodulator 240 to transmit the same to the RF/IF transmitting block 270. The mode changing pilot signal transmitted to the RF/IF transmitting block 270 in such a manner is made into an RF signal based on the frequency band of a cellular system, PCS system or IMT-2000 system to then be radiated over the air through the antennas 210a and 210b via the RF switching portion 220. Here, before the pilot channel signal reaches the RF switching portion 220, the controller 250 must control the RF switching portion 220 to be switched from a receiving mode to a transmitting mode.

The power setup portion 291 is for manually adjusting from the outside the power intensity of the mode changing pilot signal emitted through the antennas 210a and 210b. Thus, the user can easily manipulate the radiation range of the pilot signal.

Also, the LCD 292 is for displaying the malfunction of the transmitter to the outside.

A process of transmitting the mode changing signal having the particular PN sequence offset using the aforementioned transmitter will now be described in detail with reference to FIG. 3. First, when power is applied to the transmitter according to the present invention (step S300), the controller disables the driving of a power amplifier in the RF/IF transmitting block (step S301).

Also, the controller disables SYNC80M which is a synchronization signal between base stations, transmitted form the demodulator to the pilot channel generator, that is, system time (step S302).

If disabling of the power setup portion and the synchronization signal is completed, the RF switching portion is set to a receiving mode so as to receive a forward channel signal transmitted from the base station (step S303). In a state in which the receiving mode is set, the controller controls the RF/IF receiving block and the demodulator in accordance with the CDMA protocol prescribed in IS-95/IS-95A/B/C, thereby acquiring pilot channel synchronization from a primary channel operated by a specific mobile communication service prpvider (step S304). Also, the controller acquires system configuration and time information from a following sync channel (step S305) and acquires a paging channel message from paging channels (step S306).

Frequency bands used by the present base station and neighbor base station, a PN sequence offset value of a pilot channel used in the corresponding frequency band and a received signal channel are extracted from a neighbor list message and a CDMA channel list message among the paging channel messages and then stored in the interval memory of the controller (step S307).

Also, the controller calculates an operation with respect to a PN sequence offset value transferred from the outside and another PN sequence offset for changing modes and then stores the operation result in the internal memory with the frequency band information (Otherwise, among 521 PN sequence offsets, a single offset particularly allocated for changing modes might have already been stored in the internal memory).

The controller checks whether or not the above-described routine has been performed with respect to the primary channels or the secondary channels of all mobile communication service providers (step S308). Here, if the above-described routine (steps S304~S307) has not been performed for all mobile communication service providers, the routine returns to the step S304 to then repeat the above-described process.

On the other hand, if the above-described routine (steps S304~S307) has been performed for all mobile communication service providers, the pilot, sync and paging channels are acquired for the primary frequency band currently in use by a specific provider of a sector or cell at which the transmitter is positioned (step S310). After acquiring the pilot channel, it is checked whether the pre- stored information, that is, the number of frequency bands used by the present base station and neighbor base station, PN sequence offset values of pilot channels used in the corresponding frequency band and received signal levels, has been updated or not, and then the updated information is stored (step S311).

Here, if the CDMA channel number or particular PN sequence offset value has changed, or a new frequency band has been added, the pre-stored CDMA channel number or particular PN sequence offset value is updated to then be automatically edited.

The controller controls the demodulator to transfer to the pilot channel generator the system time SYNC80M which is a synchronization

signal between base stations (step S312). Here, the "synchronization

signal" means a synchronization signal between base stations, required for a mobile station to perform handoff with a base station.

The synchronization signal (i.e., system time) is used as a base time of a mode changing pilot signal emitted from the pilot channel generator.

In a state in which the synchronization standard for the mode changing signal is established, the controller changes the receiving mode of the RF switching portion to the transmitting mode (step S313). After the changing to the transmitting mode is done, the pilot channel generator generates a pilot signal having a particular PN sequence offset value for changing modes and transfers the signal to the RF/IF transmitting block. The RF/IF transmitting block transfers the mode changing signal to the antenna for emission over the atmosphere (step S314). Here, the RF/IF transmitting block is provided in each system so that the mode changing signal is sequentially emitted periodically for the frequency band of each system provider.

On the contrary, it is also possible that the RF/IF transmitting block is constructed alone and the RF switching portion is constructed by each system, thereby sequentially emitting the mode changing signal periodically with respect to the frequency band by each system provider.

If the emission of the mode changing signal is completed for all frequency bands of the corresponding mobile communication service provider, the routine returns to the step S310 to obtain updated information for the second mobile communication service provider to repeat the same routine (step S314)

B. Mobile communication terminal

The configuration of a wireless communication terminal according to the present invention, for automatically changing a electronic tone call mode into an environment-adaptive call mode by receiving a mode changing pilot channel signal from the transmitter according to this embodiment of the present invention, will now be described in detail.

The wireless communication terminal according to the present invention is preferably a CDMA based mobile communication system such as a cellular phone, a PCS phone or an IMT-2000 phone.

FIG. 4 is a block diagram of a CDMA based wireless telephone according to an embodiment of the present invention, and is further applied to various wireless telephones according to another embodiments of the present invention, including PCS phones and IMT-2000 phones.

According to the wireless communication terminal of this embodiment, a forward channel signal is received from a base station through an antenna 310, analog-to-digital (A/D) converted by an A/D converter 330 to then be filtered by an RF transmitting/ receiving portion 320, mixed with a lower frequency, automatic-gain controlled while separating the mixed received signal into an in-phase (I) and quadrature- phase (Q) components, and then I- and Q-demodulated, prior to being transmitted to a CDMA modem circuit (CMC) 340. The CMC 340, controlled by a central processing unit (CPU) 350, demodulates the I- and Q-channel signals into interleaved signal streams. The interleaved signal streams are deinterleaved, Viterbi-decoded and digitally audio-decoded by a digital signal processor (DSP) 370 according to an embodiment of the present invention, decoded into an acoustic signal by a coder/ decoder (380) and then controllably amplified by an interface circuit 390 to then

be output through a phone speaker 393. Similarly, if user's voice is

detected via a microphone 394, the process is performed by a wireless telephone in the reverse order of the above-described process. A display portion 391 and a key input portion 392 provide user's input and output

in conventional manners.

The mode changing pilot signal transmitted through the transmitter according to the present invention is received through the antenna 310, analog- to-digital (A/D) converted by the A/D converter 330 to then be filtered by the RF transmitting/receiving portion 320, mixed with a lower frequency, and then automatic-gain controlled, prior to being transmitted to the CMC 340. The mode changing pilot signal transmitted to the CMC 340, is searched by a searcher unit incorporated in the CMC shown in FIG. 5. As the result of search, if it is determined that the searched signal is a mode changing signal, the CPU 350 commands a mode switching portion 360 to change a call mode. In other words, if a mode changing signal is detected, the CPU 350 reads a current call mode stored in the internal memory. Here, if the current call mode is a electronic tone call mode or a melody mode, the CPU 350 commands the mode switching portion 360 to change a call mode to a vibration mode. On the other hand, if the current call mode is a vibration mode, the CPU 350 commands the mode switching portion 360 to maintain the current call mode. In FIG. 4, undefined reference numeral 361 denotes a vibration motor and 362 is a ringer.

The detailed configuration of the searcher unit shown in FIG. 4 will now be described with reference to FIG. 5. A controller 347 controls the overall operation of a PN sequence phase searcher. Also, the controller 347 adjusts various parameters such as integration period range, window size or asynchronous accumulation period, and controls phase shift of mobile station PN sequences generated by a PN generator 342. Also, a received signal may be received by a mobile station, RF processed, such as down conversion, and digitally converted to be input to a modem chip. Here, the received signal includes PN sequences generated by a predetermined base station and a mode changing pilot signal transmitted from the transmitter according to the present invention.

An inverse diffuser 341 multiplies PN sequence values from the PN generator 342 with the received signal input at an arbitrary timing to then inversely diffuse the same. Here, a phase search starting point of PN sequences generated from the mobile station is previously set. For example, the phase search starting point may be from a PN sequence offset "0".

A synchronization accumulator 343 accumulates outputs of the inverse diffuser 341 for the corresponding integration period. An energy calculator 344 calculates detection energy based on the correlation of the received PN sequences by the accumulated value of the accumulator 343. Also, a comparator 345 compares the calculated energy with threshold energy. The threshold energy may be arbitrarily set by the controller 347. Also, a reliable PN sequence phase which satisfies predetermined conditions may be captured, which is reported to an upper-level processor by the controller 347. Then, the mobile station performs demodulation of a received signal such as sync channel, paging channel and the like, for the next step.

A memory 346 stores an active set for storing a PN sequence offset value used by a base station that transmits and receives messages to /from a present wireless communication terminal, a neighbor set for storing PN sequence offset values used by a base station to be possibly used for handoff in the future, a candidate set for storing PN sequence offset values of a base station, which are not currently used for data demodulation but which have energy sufficiently large enough for data demodulation, and other sets for storing particular PN sequence offset values for changing modes. The particular PN sequence offset is preferably a mode changing

PN sequence offset among 512 offsets, which is not used by base stations but is particularly allocated only for changing a call mode.

Also, the particular PN sequence offset value may be a value stored in the internal memory after being calculated by an arithmetic means provided in the controller (that is, CPU). In other words, the particular PN sequence offset is a predetermined value shifted from a PN sequence offset used by the present base station, and can be calculated so that it may not overlap with PN sequence offset values of all pilot channels. In other words, assuming that a PN sequence offset used by the active set is denoted by PN1, and PN offsets in the data set and candidate set are denoted by PN2, PN3, ... PNf, the particular PN sequence offset (PNs) for changing modes can be calculated to satisfy the equation (1) below:

PNs = PNl+n ≠ PN2 ≠ PN3 ... ≠ PNf ... (1) where n is an integer.

The controller transfers a particular PN sequence offset value of the other set to the PN generator once for every predetermined period and inversely diffuses the same with the received signal. The inversely diffused received signal is accumulated on the synchronization accumulator for the corresponding integration period. Also, the energy calculator 344 calculates detection energy based on the correlation of the received PN sequences by the accumulated value of the accumulator 343. Also, the comparator 345 compares the calculated energy with threshold energy and transfers the comparison result to the controller.

Here, if the calculated detection energy is greater than the threshold energy, the controller determines that the mode changing signal is received, and commands the mode switching portion to change a call mode to a vibration mode when the call mode is an electronic tone call mode. On the other hand, if the calculated detection energy is smaller than the threshold energy, the controller determines that the mode changing signal is not received, and commands the mode switching portion to restore the call mode to the original mode. In other words, when the call mode to be restored is a mode, the controller commands the mode switching portion to be changed to the electronic tone call mode. When the call mode to be restored is a vibration mode, the current call mode is retained.

Therefore, the non-changed call mode state and mode changing coefficients are stored in the internal memory of the controller. In other words, the non-changed call mode state means a call mode state immediately before the call mode is changed, and the mode changing coefficients mean indicators for identifying whether the call mode is a changed mode or a non-changed mode. The non-changed call mode

state, for example, may be set to "0" for an electronic tone call mode and

"0" for an environment-adaptive call mode.

Also, the mode changing coefficients are identifiers for determining whether the mode of a wireless communication terminal is changed or not.

A process of automatically changing a call mode to an environment-adaptive call mode by a wireless communication terminal according to the present invention and a process of restoring the call mode into the original mode, will now be described in detail with reference to FIG. 6.

A searcher unit of the wireless communication terminal searches a particular PN sequence offset value for changing modes from a received signal (step S401).

Here, if the energy of the searched signal is greater than threshold energy, the controller determines whether the mode changing coefficient

of the internal memory is set to "X" or not (The mode changing coefficient

is set to "0" when power is applied.) (steps S401 and S402).

When the mode changing coefficient of the internal memory is set

to "1", indicating a state in which the mode changing signal has already been detected, that is, the call mode has already been changed, one among expected PN sequence offset management sets, that is, the active set, neighbor set and candidate set, is searched again (step S411).

On the other hand, when the mode changing coefficient of the

internal memory is not set to "1", it is determined whether the non-

changed call mode of the internal memory is an electronic tone call mode or not (step S404). When the non-changed call mode of the internal memory is an electronic tone call mode, the controller sets the mode

changing coefficient is newly set to "1" and changes the call mode to an environment- adaptive call mode such as a vibration mode (step S405). Then, the LCD displays that the call mode is a manner mode (i.e., an etiquette mode) (step S406). If it is determined in step S404 that the non-changed call mode of the internal memory is a vibration mode, the controller commands the mode changing portion to maintain the current call mode and controls the searcher unit to search again one among expected PN sequence offset management sets, that is, the active set, neighbor set and candidate set (step S411).

When the energy searched in step S402 is smaller than the threshold energy, the controller determines whether the mode changing

coefficient of the internal memory is set to "1" or not (step S407). Here, when the mode changing coefficient of the internal memory is not set to

"1", one among expected PN sequence offset management sets, that is, the active set, neighbor set and candidate set, is searched again (steps S407 and S411). On the other hand, when the mode changing coefficient of the

internal memory is set to "1" in step S407, it is checked whether the number of restoration cycles has been reached or not (step S408). When the number of restoration cycles has not been reached, the existing number of restoration cycles is increased and one among expected PN sequence offset management sets, that is, the active set, neighbor set and candidate set, is searched again (step S411).

Here, the number of restoration cycles is determined in advance when power is applied to the wireless communication terminal. When the number of restoration cycles has been reached, the controller cancels the set mode changing coefficient and restores the call mode from the

vibration mode to a user's original call mode (step S409).

Then, the user's call mode is displayed on the LCD of the wireless

communication terminal and one among expected PN sequence offset management sets, that is, the active set, neighbor set and candidate set, is searched again (step S410).

Also, in order to reduce battery power consumption, the wireless communication terminal according to the present invention is operated in a sleep mode. When the wireless communication terminal is operated in a sleep mode, the particular PN sequence offset for changing modes follows the same process as described above once a pilot channel having a PN sequence offset value of the previous active set or neighbor set is searched and the signal is allocated to a finger. As described above, the present invention is not intended to be limited to the embodiment herein, but various modifications and changes will be readily apparent to those skilled in the art within the scope of the present invention, which is set forth in the appended claims.

Industrial Applicability

As described above, according to the present invention, since call modes of all wireless communication terminals used at places where noise is not allowed, are automatically changed from a electronic tone call mode or a melody mode to a vibration mode or a light mode, unpleasant feeling, which may be caused to people due to the calling sound, can be prevented.

Also, the call mode can be changed in a software manner without modifying the hardware of existing portable wireless communication terminals, which is quite cost-efficient.

Claims

What is claimed is:

1. A code division multiple access (CDMA) transmitter for generating a particular pilot signal for changing modes, comprising: means for receiving a CDMA forward channel signal from a plurality of neighbor base stations; means for acquiring system time for system synchronization from the forward channel signal; means for generating a pilot channel signal having a particular pseudo-random number (PN) offset which is not absolutely received from the neighbor base stations, in synchronization with the system time; and means for transmitting the pilot signal through the overall CDMA frequency bands so as to be received by all CDMA terminals present within a coverage, whereby the transmitter commands all CDMA terminals present in the receivable area of the pilot signal to change a call mode.

2. The CDMA transmitter according to claim 1, further comprising means for acquiring a frequency band used by the present base station and neighbor base station, a PN sequence offset value of the pilot channel used in the corresponding frequency band and a received signal level, from the forward channel received from the receiving means, and storing the same.

3. The CDMA transmitter according to claim 2, further comprising means for storing the particular PN offset, wherein the particular PN sequence offset is one of 512 PN offsets, which is not used by the base station and is particularly allocated only for changing the call mode.

4. The CDMA transmitter according to claim 2, further comprising means for performing an operation on the particular PN sequence offset value, wherein the particular PN sequence offset value is a predetermined value shifted from a PN sequence offset used by the present base station, and is calculated so that it does not overlap with PN sequence offset values of all pilot channels.

5. The CDMA transmitter according to claim 3 or 4, wherein the transmitting means sequentially transmits the pilot signal for all frequency bands of the CDMA forward channel periodically according to the frequency band.

6. The CDMA transmitter according to claim 5, further comprising means for manually setting from the outside the power intensity of the pilot signal.

7. A portable wireless communication terminal comprising: means for receiving a CDMA forward signal transmitted from a base station and a pilot signal having a particular PN sequence offset for changing a call mode; means for storing the particular PN offset; means for periodically searching the PN sequence offset in an idle state; means for comparing a energy value of the searched pilot signal with a threshold value and determining presence or absence of a mode changing signal; and means for changing a current call mode into an environment- adaptive call mode when the mode changing signal is present.

8. The portable wireless communication terminal according to claim 7, further comprising means for performing an operation on the particular PN sequence offset value and recording the operation result in the storing means, wherein the storing means further comprises PN sequence offset values of an active sector, a neighbor sector and a candidate sector; and wherein the particular PN sequence offset value is a predetermined value shifted from a PN sequence offset used by the present base station, and is calculated so that it does not overlap with PN sequence offset values of all pilot channels.

9. The portable wireless communication terminal according to claim 7, wherein the particular PN sequence offset stored in the storing means is one of 512 PN offsets, which is not used by the base station and is particularly allocated only for changing the call mode.

10. The portable wireless communication terminal according to claim 8 or 9, further comprising means for storing the current call mode state, wherein the call changing means restores the environment- adaptive call mode into the current call mode state if the mode changing signal is not received for a predetermined time.