JP4962473B2 - Wireless communication terminal - Google Patents

Description

  The present invention relates to a wireless communication terminal that performs bidirectional wireless communication using a time division multiplexing method.

  For example, Patent Document 1 describes wireless communication for making an emergency call using a conventional time division multiplex communication line. The emergency call method described in Patent Document 1 is a method in which a radiotelephone device used in a base station and a mobile station has means for grasping the radio wave state of each time slot of a time division multiplex line, The slots allocated for use are assigned to the slots with the best radio wave conditions when the radio wave condition of each slot is ascertained. It was supposed to be able to make an emergency call without decreasing.

JP-A-2005-057643

  This conventional emergency communication system has a problem in that normal communication capacity is reduced because it is necessary to arrange a large number of slots for emergency communication in order to shorten the propagation time for emergency communication. In addition, once a slot for emergency communication is set, normal communication is limited to slots other than the emergency communication slot, and there is a problem that normal communication is restricted. Furthermore, since an emergency call is transmitted from each terminal using a time slot, data cannot be exchanged by an emergency call at an interval shorter than the timing cycle. In this case, there is also a problem that time responsiveness cannot be improved as compared with a case where an emergency call is superimposed on a communication signal in communication by frequency division multiplexing or code division multiplexing.

  The present invention has been made to solve the above-described problems, and performs communication by time division multiplexing using a limited frequency band to perform emergency communication with good time responsiveness. An object is to obtain a wireless communication terminal that can be used.

According to a first aspect of the present invention, there is provided a radio communication terminal comprising: a data transmission processing unit that generates a transmission signal to be transmitted in a payload area of a transmission time slot assigned by a time division multiplexing method from communication data; An emergency transmission processing unit that generates a transmission signal to be transmitted from the emergency notification signal, a signal generated by the data transmission processing unit in the payload area of the transmission time slot, and a signal generated by the emergency transmission processing unit in the transmission time TDMA multiplexing means for storing in the guard time of the slot, a data reception processing unit for demodulating the received signal stored in the payload area of the reception time slot assigned by time division multiplexing, and reproducing the communication data, and the reception Demodulate the received signal stored in the guard time of the time slot A emergency reception processing unit for reproducing an emergency notification signal, the emergency transmission processing section has a lower power level than the signal generated by the data transmission unit, the transmission signal to be transmitted in the guard time of the transmission time slot Is generated at a power level within a range that can be received by other wireless communication terminals existing within a distance that can be received within the transmission time slot .

According to a second aspect of the present invention, there is provided a radio communication terminal comprising : a data transmission processing unit that generates a transmission signal to be transmitted in a payload area of a transmission time slot assigned by a time division multiplexing method from communication data; An emergency transmission processing unit that generates a transmission signal to be transmitted from the emergency notification signal, a signal generated by the data transmission processing unit in the payload area of the transmission time slot, and a signal generated by the emergency transmission processing unit in the transmission time TDMA multiplexing means for storing in the guard time of the slot, a data reception processing unit for demodulating the received signal stored in the payload area of the reception time slot assigned by time division multiplexing, and reproducing the communication data, and the reception Demodulate the received signal stored in the guard time of the time slot An emergency reception processing unit that reproduces an emergency call signal, the emergency transmission processing unit spread-modulates the emergency call signal, and transmits the transmission signal to be transmitted at the guard time of the transmission time slot by spreading the power density by spreading. A transmission signal within a range that can be received by other wireless communication terminals existing within a distance that can be received within a time slot is generated, and the emergency reception processing unit despreads and demodulates the reception signal to reproduce an emergency notification signal. It is a feature .

According to the first or second aspect of the invention, the wireless communication terminal transmits an emergency call signal at the guard time of the time slot, and is within a distance that can be received within the transmission time slot in which the emergency call signal is transmitted. since other wireless communication terminal is present, it receives the emergency notification signal, it is possible to increase the immediacy of the emergency notification, by lowering the power level of the emergency notification signal, or by spreading modulation of the emergency notification signal In this way, it is possible to suppress reception wave interference in a remote radio communication terminal.

Embodiment 1

  A radio communication terminal according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a block diagram showing the overall configuration of a communication system including a radio communication terminal according to Embodiment 1 of the present invention, and FIG. 2 is a functional block diagram of the radio communication terminal according to Embodiment 1 of the present invention. . In FIG. 1, reference numeral 1 is a reference station that supervises a time division multiplexing system line in a communication system, and 2 (reference numerals 2a to 2c in FIG. 1) is subordinate to the reference station 1 for communication between terminals. It is a wireless communication terminal to perform. The reference station 1 defines the frame timing and time slot of the time division multiplexing line, and manages the time slot used by the radio communication terminals 2a to 2c. For example, a frame timing signal (burst signal having a minute time length) that is a delimiter signal is transmitted from the reference station 1 for each frame length, and is received by the wireless communication terminals 2a to 2c. Frame synchronization is measured, and a preassigned time slot position can be specified according to the frame synchronization. Also, by transmitting a slot timing signal that divides time slots from the reference station 1, the slot timing signals can be received by the radio communication terminals 2a to 2c, and the time slot position can be specified. There are various situations regarding the positional relationship between the reference station 1 and the wireless communication terminals 2a to 2c. In FIG. 1, for example, the wireless communication terminals 2a and 2b in communication are at a short distance and the reference station 1 shows that the wireless communication terminal 2c is at a long distance and the wireless communication terminal 2c is at a long distance from the wireless communication terminals 2a and 2b.

In FIG. 2, 3 is a data transmission processing unit that performs signal processing on communication data (hereinafter referred to as TDMA data; TDMA is an abbreviation of Time Division Multiple Access) to be transmitted in the payload area of the time slot. An emergency transmission processing unit 4 generates a transmission signal by performing signal processing on an emergency call signal and an emergency call response signal transmitted outside the payload area (guard time) of the time slot. In the data transmission processing unit 3, reference numeral 5 denotes a transmission data processing unit that reads TDMA data, performs processing such as framing and outputs the data, and an output signal from the transmission data processing unit 5 is encoded by the encoding circuit 6. Modulated by the modulator 7. In the emergency transmission processing unit 4, 8 is a transmission emergency notification processing unit that reads an emergency notification signal and an emergency notification response signal transmitted outside the payload area of the time slot, performs processing such as framing, and outputs it. An output signal from the processing unit 8 is encoded by the encoding circuit 9, modulated by the modulator 10, and attenuated to a predetermined signal level by the attenuator 11. When spreading the emergency call signal and the emergency call response signal, the emergency call signal and the emergency call response signal are spread and modulated using the spread modulator 12 instead of the modulator 10 and the attenuator 11. 13 normally allocates a transmission signal of TDMA data output from the modulator 7 to the payload area in the time slot, and when there is an emergency report, the emergency report from the attenuator 11 (or spread modulator 12) It is a TDMA multiplexing circuit that inserts a signal and an emergency call response signal outside the payload area (guard time) in the time slot. A transmission signal assigned to a time slot and appropriately multiplexed with an emergency call signal and an emergency call response signal is transmitted from an antenna (not shown) after adjusting the transmission signal level by an attenuator 14.

On the other hand, the modulated wave from the counterpart terminal received by the antenna is distributed by the distributor 15. Reference numeral 16 denotes a data reception processing unit that receives and reproduces TDMA data from one output signal of the distributor 15, and reference numeral 17 denotes an emergency reception process that receives and reproduces an emergency notification signal and an emergency notification response signal from the other output signal of the distributor 15. Part. Reference numeral 18 denotes a TDMA demodulator that demodulates one output signal of the distributor 15, and reference numeral 19 denotes a TDMA synchronization circuit that outputs a synchronization signal synchronized with the time slot position. As described above, a frame timing signal and a slot timing signal are received, and a timing signal synchronized therewith is input from the TDMA synchronization circuit 19 to a TDMA demodulator 18 and a demodulator 22 (or despread demodulator 23) described later, Based on the input timing signal, demodulation and despread demodulation processes are performed. The TDMA data demodulated by the TDMA demodulator 18 is decoded by the decoding circuit 20, deframed by the reception data processing unit 21, and data is reproduced. Reference numeral 22 denotes a demodulator that demodulates the other output of the distributor 15. The received signal demodulated by the demodulator 22 is decoded by the decoding circuit 24, deframed by the reception emergency notification processing unit 25, and urgent. The notification signal and the emergency call response signal are reproduced. When the emergency call signal and the emergency call response signal are spread-modulated and transmitted, a despreading demodulator 23 is used instead of the demodulator 22, and the received signal is despread-modulated and output to the decoding circuit 24. To do. The TDMA demodulator 18 demodulates the received signal in the payload area in the time slot based on the timing signal from the TDMA synchronization circuit 19, while the demodulator 22 and the despreading demodulator 23 are supplied from the TDMA synchronization circuit 19. Based on the timing signal, the received signal outside the payload area (guard time) in the time slot is demodulated.

  Next, time slots for time division multiplex communication between the wireless communication terminals 2 will be described. FIG. 3 is a schematic diagram showing a time slot structure of communication by the radio communication terminal according to Embodiment 1 of the present invention. As shown in FIG. 3A, one time slot includes a payload area 26 and a guard time outside the area. The guard time is a non-transmission time zone provided to prevent radio waves from the radio communication terminal 2 that are far away from interfering with each other due to propagation delay, and the maximum propagation distance based on the transmission power of the radio communication terminal Is systematically set in consideration of On the other hand, when viewed only between the wireless communication terminals 2 at a short distance, even if a signal is transmitted at a guard time with a small propagation delay, as long as the signal is received within a time slot including the guard time, Interference between the communication terminals 2 does not occur. Therefore, as shown in FIG. 3B, the emergency call signal 27 is assigned to the guard time. However, in the radio communication terminal 2 located far away, the emergency call signal interferes with the payload area in the time slot. It is preferable to reduce the transmission power of the emergency call signal and the emergency call response signal, and transmit the emergency call signal and the emergency Tsukata response signal after being spread-modulated so that the power is reduced. That is, referring to FIG. 1, when communication is performed between two wireless communication terminals 2a and 2b at a short distance, the payload area of the time slot normally assigned to the wireless communication terminals 2a and 2b is set. A wireless communication terminal that performs the data transmission used, but allows the emergency call signal and the emergency call response signal to be transmitted at the guard time, and the emergency call signal and the emergency call response signal assigned to the guard time are located at a distance. Although it is also received by 2c, it is transmitted at the minimum necessary transmission level, or transmitted by spreading modulation so that the reception level becomes sufficiently small.

  FIG. 4 is a timing chart showing transmission / reception timings by the radio communication terminal according to Embodiment 1 of the present invention. As shown in FIG. 1, the radio communication terminals 2a and 2b are located at a short distance, and the radio communication terminals 2a and 2b, the reference station 1 and the radio communication terminal 2c are at a long distance, and the reference station 1 and the radio It is assumed that the communication terminal 2c is located at a short distance. Communication is performed between the wireless communication terminals 2a and 2b, and between the reference station 1 as a terminal and the wireless communication terminal 2c, and the time slots TS1, TS2, TS3, and TS4 are sequentially referenced. It is assumed that it is used by the station 1, the wireless communication terminal 2c, the wireless communication terminal 2a, and the wireless communication terminal 2b. A transmission signal TX1 transmitted from the reference station 1 through TS1 is received by the wireless communication terminal 2c. A transmission signal TX2 transmitted from the wireless communication terminal 2c by TS2 is received by the reference station 1. These transmission signals TX1 and TX2 also reach the radio communication terminals 2a and 2b, but the reception level is low because the propagation distance is long. Next, the transmission signal TX3 transmitted from the wireless communication terminal 2a by TS3 is received by the wireless communication terminal 2b, and TX4 transmitted by TS4 from the wireless communication terminal 2b is received by the wireless communication terminal 2a. These transmission signals TX3 and TX4 reach the reference station 1 and the wireless communication terminal 2c, but the reception level is low because the propagation distance is long. The wireless communication terminal 2b transmits the emergency call signal 28 in the time slot TS4 following the transmission signal TX4, and the wireless communication terminal 2a in a short distance receives this in the same time slot TS4. In the example shown in FIG. 4, the case where the emergency call signal 28 is received in the time slot TS4 also in the reference station 1 and the radio communication terminal 2c that are sufficiently short in time and in the reference station 1 and the radio communication terminal 2c at a long distance. This emergency call signal 28 does not interfere with other time slots. The wireless communication terminal 2a may transmit the emergency call response signal 29 to the wireless communication terminal 2b after receiving the emergency call signal 28 from the wireless communication terminal 2b. The emergency call response signal 29 is a signal assigned outside the payload area 20 (guard time) in the time slot as with the emergency call signal 28, and is not a time slot assigned for the radio communication terminal 2a as shown in FIG. Transmission in time slot TS1 is allowed. In the example shown in FIG. 4, the emergency call response signal 29 is received by the wireless communication terminal 2b at a short distance in the same time slot TS1, the emergency call response signal length is sufficiently short in time, and at a long distance. The reference station 1 and the wireless communication terminal 2c also receive in the time slot TS1, and do not interfere with other time slots.

FIG. 5 is a timing chart showing another example of transmission / reception timings by the radio communication terminal according to Embodiment 1 of the present invention. Transmission and reception in the first time slots TS1 to TS3 shown in FIG. 5 are the same as those shown in FIG. TX4 transmitted from the wireless communication terminal 2b by TS4 is received by the wireless communication terminal 2a. The transmission signal TX4 also reaches the reference station 1 and the wireless communication terminal 2c, but the reception level is low because of the long propagation distance, and is within the payload area and guard time of the time slot TS4. The wireless communication terminal 2b transmits the emergency call signal 28 in the time slot TS4 following the transmission signal TX4, and the wireless communication terminal 2a in a short distance receives this in the same time slot TS4. In the example shown in FIG. 5, the emergency call signal length is long in time (in addition to meaning that the ratio of the emergency call signal occupying the guard band is large, it takes the next time slot used by the radio communication terminal located far away Therefore, the emergency call signal 28 is shown in the case where the reference station 1 and the wireless communication terminal 2c located at a long distance receive in the next time slot TS1. The transmission power is lowered by the attenuator 11 so as to prevent interference. The transmission power level attenuated by the attenuator 11 can be lowered to a minimum level that can be received by the wireless communication terminal 2a at a short distance. Although the emergency call signal 28 is received by the reference station 1 and the wireless communication terminal 2c, the influence of interference is reduced because the received power is small, and the time slot TS1 between the reference station 1 and the wireless communication terminal 2 is reduced. Communication with can be performed. The wireless communication terminal 2a may transmit the emergency call response signal 29 to the wireless communication terminal 2b after receiving the emergency call signal 28 from the wireless communication terminal 2b. The emergency call response signal 29 is a signal assigned to the outside of the payload area 26 in the time slot in the same manner as the emergency call signal 28. It is allowed to send. In the example shown in FIG. 5, the emergency call response signal 29 is received in the same time slot TS1 by the wireless communication terminal 2b at a short distance. At this time, the transmission level of the emergency call response signal 29 is reduced by the attenuator 11 , and although the reference station 1 and the radio communication terminal 2c are received in the time slot TS2, the influence of interference is reduced. Communication between the reference station 1 and the wireless communication terminal 2 can be performed in the time slot TS2.

FIG. 6 is a timing chart showing still another example of transmission / reception timings by the radio communication terminal according to Embodiment 1 of the present invention. Transmission / reception in the first time slots TS1 to TS3 shown in FIG. 6 is the same as that shown in FIG. TX4 transmitted from the wireless communication terminal 2b by TS4 is received by the wireless communication terminal 2a. The transmission signal TX4 also reaches the reference station 1 and the wireless communication terminal 2c, but the reception level is low because of the long propagation distance, and is within the payload area and guard time of the time slot TS4. The wireless communication terminal 2b transmits the emergency call signal 28 in the time slot TS4 following the transmission signal TX4, and the wireless communication terminal 2a in a short distance receives this in the same time slot TS4. In the example shown in FIG. 6 , the emergency call signal length is long in time (in addition to the meaning that the ratio of the emergency call signal occupying the guard band is large, it takes the next time slot used by a radio communication terminal located far away Therefore, the emergency call signal 28 is shown in the case where the reference station 1 and the wireless communication terminal 2c located at a long distance receive in the next time slot TS1. Is spread modulated by the spread modulator 12 so as to prevent interference. The wireless communication terminal 2a at a short distance can receive the emergency call signal by despreading and demodulating the received signal. The spread-modulated emergency call signal 28 is received by the reference station 1 and the wireless communication terminal 2c. However, since the power spectrum density is small, the influence of interference is reduced. Communication in the time slot TS1 can be performed. The wireless communication terminal 2a may transmit the emergency call response signal 29 to the wireless communication terminal 2b after receiving the emergency call signal 28 from the wireless communication terminal 2b. The emergency call response signal 29 is a signal assigned to the outside of the payload area 26 in the time slot in the same manner as the emergency call signal 28. In the time slot TS1 that is not the time slot assigned for the wireless communication terminal 2a as shown in FIG. It is allowed to send. In the example shown in FIG. 6, the emergency call response signal 29 is received by despreading and demodulating the received signal in the same time slot TS1 by the wireless communication terminal 2b at a short distance. At this time, the emergency call response signal 29 is spread and modulated by the spread modulator 12, and the reference station 1 and the radio communication terminal 2c are also received in the time slot TS2, but the power spectrum density is small and the influence of interference is reduced. Thus, communication in the time slot TS2 between the reference station 1 and the wireless communication terminal 2 can be performed.

  Next, the distance between wireless communication terminals and the presence or absence of interference will be described. FIG. 7 is a characteristic diagram showing the relationship between the distance between terminals and the received power of the wireless communication terminal according to Embodiment 1 of the present invention. FIG. 7 shows whether interference occurs in a remote radio communication terminal when an emergency call is made between radio communication terminals in a short distance. In FIG. 7, a straight line 30 (including a thick line segment 31 and a line segment 32) indicates the received power at the receiving radio communication terminals (2a, 2c) with respect to the distance from the radio communication terminal 2b that transmits the emergency call signal. The received power decreases as the distance increases. In FIG. 7, the wireless communication terminal 2 a located at a distance A or less can receive an emergency call signal because the received power is on the thick line segment 31 and exceeds the reception power limit. The wireless communication terminal 2c (terminal 2c surrounded by a solid line) located at a distance B or more has the power of receiving the emergency call signal on the thick line segment 32 and is below the power level causing interference, so that it is not affected by the interference. Communication is possible. However, the radio communication terminal 2c (terminal 2c surrounded by a dotted line) located at a distance A or more and a distance B or less has a large reception level of the emergency call signal, and this radio communication terminal 2c has an emergency call signal transmitted at the guard time. Interference prevents communication.

  A case where the control for reducing the transmission power of the emergency call signal is performed to eliminate this interference will be described with reference to FIG. FIG. 8 is a characteristic diagram showing characteristics when the transmission power of the emergency call signal is lowered with respect to the relationship between the distance between terminals and the reception power of the radio communication terminal according to Embodiment 1 of the present invention. The emergency call signal at the radio communication terminal 2c indicated by the solid line and the radio communication terminal 2c indicated by the dotted line whose distance from the radio communication terminal 2b that transmits the emergency call signal with the transmission power level lowered is equal to or greater than the distance B1 (<B). Since the received power is lower than the power level causing interference, communication can be performed without being affected by the interference. On the other hand, since the transmission power level of the emergency call signal is lowered, the distance at which the emergency call signal can be received is equal to or less than the distance A1 (<A).

  FIG. 9 is a characteristic diagram showing characteristics when the emergency call signal is spread-modulated with respect to the relationship between the distance between terminals of the wireless communication terminal according to Embodiment 1 of the present invention and the received power. The power spectrum density of the emergency call signal is reduced by the spread modulation, and the reception level of the emergency call signal at the wireless communication terminal 2c that does not perform despread demodulation is on the straight line 30 (including the thick line segment 32). Accordingly, the reception power of the emergency call signal at the wireless communication terminal 2c indicated by the solid line and the wireless communication terminal 2c indicated by the dotted line, where the distance from the wireless communication terminal 2b that transmits the emergency call signal is equal to or greater than the distance B1 (<B), is Since the power level is lower than the interference level, communication is possible without being affected by the interference. On the other hand, since the reception level of the emergency call signal at the radio communication terminal 2a that performs despread demodulation is on the thick line segment 31 due to the effect of despreading and exceeds the reception power limit, the radio communication terminal 2a located below the distance A Can receive emergency call signals.

  As described above, the wireless communication terminal 2 according to the first embodiment of the present invention transmits an emergency call signal and an emergency call response signal to other wireless communication terminals 2 in communication at a short distance in the time slot. Transmitting outside the payload area (guard time area), and in transmitting these, a technique for attenuating the emergency call signal and the emergency response signal (the technique described in FIG. 5 and the above explanation for this figure), and an emergency call signal And a method of reducing the power spectrum density by spreading modulation (a method described with reference to FIG. 6 and the above explanation for this figure). In this way, by giving attenuation or spread modulation to the emergency call signal and the emergency call response signal, reception by other wireless communication terminals 2 in communication at a short distance (in the case of spread modulation, despread demodulation at the time of reception) On the other hand, in the other wireless communication terminals 2 located far away, the signal levels of the emergency call signal and the emergency call response signal can be made low so as not to interfere. In addition, since the emergency call signal and the emergency call response signal can be inserted into the guard time in the time slot, the system standby time from the occurrence of the emergency call to the transmission is short, and the immediacy of the emergency call can be improved. Furthermore, since the wireless communication terminal 2 that has received the emergency call signal can generate the emergency call response signal, it can transmit the generated emergency call response signal in the guard time of the time slot that continues to the received time slot. Immediate emergency response can also be improved. 4 to 6, the wireless communication terminal 2a transmits the emergency call response signal 29 in the time slot TS1, but it may be transmitted in the subsequent TS2, TS3, and the like.

It is a block diagram which shows the whole structure of the communication system containing the radio | wireless communication terminal which concerns on Embodiment 1 of this invention. It is a functional block diagram of the radio | wireless communication terminal which concerns on Embodiment 1 of this invention. It is a schematic diagram showing the time slot structure of communication by the radio | wireless communication terminal which concerns on Embodiment 1 of this invention. It is a timing chart figure showing the transmission / reception timing by the radio | wireless communication terminal which concerns on Embodiment 1 of this invention. It is a timing chart figure showing another example of the timing of transmission / reception by the radio | wireless communication terminal which concerns on Embodiment 1 of this invention. It is a timing chart figure showing another example of the timing of transmission / reception by the radio | wireless communication terminal which concerns on Embodiment 1 of this invention. It is a characteristic view showing the relationship between the distance between terminals of the radio | wireless communication terminal which concerns on Embodiment 1 of this invention, and received power. These are the characteristic views showing the characteristic at the time of reducing the transmission power of an emergency call signal regarding the relationship between the distance between terminals of the radio | wireless communication terminal which concerns on Embodiment 1 of this invention, and received power. These are the characteristic views showing the characteristic at the time of carrying out the spread modulation of the emergency call signal regarding the relationship between the distance between terminals of the radio | wireless communication terminal which concerns on Embodiment 1 of this invention, and received power.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reference station 2a, 2b, 2c Wireless communication terminal 3 Data transmission process part 4 Emergency transmission process part 13 TDMA multiplexing circuit 16 Data reception process part 17 Emergency reception process part

Claims (2)

A data transmission processing unit that generates from a communication data a transmission signal to be transmitted in a payload area of a transmission time slot assigned by time division multiplexing, and a transmission signal to be transmitted at a guard time of the transmission time slot from an emergency notification signal An emergency transmission processing unit; TDMA multiplexing means for storing a signal generated by the data transmission processing unit in a payload area of the transmission time slot and a signal generated by the emergency transmission processing unit in a guard time of the transmission time slot; A data reception processing unit for demodulating a reception signal stored in a payload area of a reception time slot assigned by a time division multiplexing method and reproducing communication data; and a reception signal stored in a guard time of the reception time slot. Emergency reception processing that demodulates and reproduces emergency call signals It equipped with a door,
The emergency transmission processing unit has a lower power level than the signal generated by the data transmission processing unit,
A radio signal that generates a transmission signal having a power level within a range that can be received by another radio communication terminal existing at a distance that can be received within the transmission time slot. Communication terminal. A data transmission processing unit that generates from a communication data a transmission signal to be transmitted in a payload area of a transmission time slot assigned by time division multiplexing, and a transmission signal to be transmitted at a guard time of the transmission time slot from an emergency notification signal An emergency transmission processing unit; TDMA multiplexing means for storing a signal generated by the data transmission processing unit in a payload area of the transmission time slot and a signal generated by the emergency transmission processing unit in a guard time of the transmission time slot; A data reception processing unit for demodulating a reception signal stored in a payload area of a reception time slot assigned by a time division multiplexing method and reproducing communication data; and a reception signal stored in a guard time of the reception time slot. Emergency reception processing that demodulates and reproduces emergency call signals It equipped with a door,
The emergency transmission processing unit spread-modulates the emergency call signal, and the power density is determined by spreading.
Generating a transmission signal within a range that can be received by other wireless communication terminals existing at a distance where the transmission signal transmitted at the guard time of the transmission time slot can be received within the transmission time slot;
The wireless communication terminal , wherein the emergency reception processing unit despreads and demodulates a received signal to reproduce an emergency notification signal .

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