JPH10164652A - Mobile communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the transmission power of a cellular system using a CDMA/ TDD system when VOX control is made and suppress the performance deterioration of the transmission space diversity of the system. SOLUTION: When a mobile station is in a 'transmission-off' state, the mobile station transmits a control signal by using a leading slot A and and another B by transmitting the state informing bit of the slot A as 'transmission off'. A base station selects the transmission antennas in slots B-E from signals received in the slot A and the transmission antennas in slots F, G, H and the next frame slot from signals received in the slot E. When the base station is in a 'transmission-off' state, the base station transmits a control signal by using the slots A and E by transmitting the state informing bit of the leading slot A as 'transmission off'. When the mobile station is informed that no data exist in a received frame from the received state informing bit, the station controls the transmission power to the slots A-D by detecting the power of the signal desired for the slot A and the transmission power to the slots E-H by detecting the power of the signal desired to the slot E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication device used for a cellular radio communication system such as a digital car telephone and a portable telephone, and more particularly to a control of open loop transmission power and a reduction in performance of transmission diversity when performing VOX control. Mobile communication device.

[0002]

2. Description of the Related Art CDMA (Code Division Multiple Acc)
The ess (code division multiple access) system is one of multiple access system technologies when a plurality of stations simultaneously communicate in the same frequency band in a cellular system such as a car phone or a mobile phone. Other technologies include FDMA (Frequenc
y Division Multiple Access)
Systems, a TDMA (Time Division Multiple Access) system and the like are known, but the CDMA system can achieve higher frequency use efficiency as compared with these technologies,
This is a system that can accommodate more users.

[0003] In the CDMA system, multiple access is performed by spread spectrum communication in which the spectrum of an information signal is spread over a band sufficiently larger than the original information bandwidth and transmitted. The direct spreading system is a system in which an information signal is directly multiplied by a spreading code in spreading, and signals of a plurality of mobile stations are multiplexed in the same frequency domain and the same time domain.

[0004] TDD (Time Division Duplex) is a transmission / reception same band system, also called a ping-pong system, which is a system in which the same radio frequency is time-divided into transmission / reception for communication. FDD (Frequency Divis
The ion duplex method is a method of performing communication using different frequencies for transmission / reception.

FIG. 6A is a conceptual diagram of the TDD system, and FIG.
2 shows a conceptual diagram of the FDD system. In FIG. 6A, at time T1, the base station performs transmission and the mobile station performs reception. At the next time T2, the mobile station performs transmission and the base station performs reception. By repeating this, communication using a single frequency band is realized. In FIG. 6 (2), base station transmission and mobile station reception are performed at frequency f1, and mobile station transmission and base station reception are performed at frequency f2. This transmission or reception time unit is called a slot.

[0006] In the CDMA system using direct spreading, when a desired transmitting station is located far away and an undesired transmitting station (interfering station) is nearby, a signal transmitted from the interfering station is reduced by a received signal from the desired transmitting station. The signal (2) has a higher received power, and the processing gain (spreading gain) alone cannot suppress the cross-correlation between spreading codes. For this reason, in a cellular system using the direct spread CDMA system, transmission power control according to the state of each transmission path is essential in an uplink from a mobile station to a base station.

As a countermeasure against fading, which is a cause of deterioration of channel quality in land mobile communication, a method of compensating for instantaneous fluctuations in received power by controlling transmission power has been considered.

[0008] Dissertation "Study of Transmission Power Control in CDMA / TDD Transmission" (Miya, Hayashi, Kato, 1994, IEICE Spring,
B-418) and “POWER CONTROL IN PACKETS SWITCHED TI
ME DIVISION DUPLEX SEQUENSE SPREAD SPECTRUM COMMUN
ICATIONS "(R.ESMAILZADEH, M.NAKAGAWA, A.KAJIWARA, pro
c. of VTC'92. pp. 989-992, 1992), CDMA / TD
A method for performing transmission power control in the D system is shown.

[0009] Fading has a symmetry that fluctuations in transmission and reception are the same in the same frequency band. Therefore, the CDMA / TDD scheme is simpler than the FDD scheme by detecting the power of the received signal, grasping the propagation state by this, determining the transmission power level, and using open loop transmission power control for transmission. It is characterized in that high-speed and high-accuracy transmission power control can be performed by a simple method.

As a countermeasure against fading, a space diversity technique is also effective. This is to receive using a plurality of antennas at different positions, combine and demodulate, and since the fading fluctuation of the received signal is uncorrelated for each propagation path, the probability that the received power level drops due to fading This is a technique for reducing the degradation of reception quality by reducing noise. In the TDD system, a plurality of antennas are installed in a base station again using the transmission / reception symmetry of fading fluctuation in a radio channel, and in the base station reception, diversity reception is performed on the base station side to detect a propagation environment for each antenna. However, by using the best antenna at the time of base station transmission, space diversity can be performed in the downlink even with one mobile station antenna, and communication quality can be improved without increasing the hardware scale of the mobile station. Thesis "C
"Proposal of base station transmission / reception diversity scheme in DMA / TDD scheme" (Miya et al., RCS94-73, p.25-30, 1994-09) discloses a transmission space diversity scheme in the CDMA / TDD scheme.

VOX (Voice Operated Transmitter) is a technique for transmitting power only when there is voice to be transmitted in a mobile phone or the like, and turning off the transmission when there is no voice to transmit. In, VOX is an important technology in increasing system capacity. In TDMA and FDMA, the system capacity is fixedly determined, whereas in CDMA, the system capacity is determined by the amount of interference from users simultaneously communicating. This is called soft capacity. Therefore, the capacity can be increased by reducing the interference. Stopping transmission by VOX reduces interference with other users as it is, which leads to an increase in system capacity. For example, the voice / silence rate of all users is 5
At 0%, the number of simultaneously transmitting users is halved, resulting in doubling the capacity.

[0012]

SUMMARY OF THE INVENTION However, CDM
When VOX control is performed in the A / TDD method,
When there is no sound, there is a slot that does not transmit.
Along with this, in a slot that is not transmitted on the receiving side, the state of the propagation path cannot be estimated from the signal at the time of reception, open-loop transmission power control and transmission space diversity cannot be performed, and the speed of fading fluctuation that control can follow And the speed performance deteriorates.

[0013] The present invention solves the above-mentioned problems, and VO
An object of the present invention is to provide a mobile communication device that suppresses performance degradation of open-loop transmission power control and transmission diversity when performing X control.

[0014]

According to the present invention, in order to achieve the above object, in VOX control, a mobile station is arranged so that a transmission cycle of a fixed signal section such as a control signal constantly transmitted from a base station is minimized. The mobile station performs open loop transmission power control using the reception level in the fixed signal section, and the base station performs transmission space diversity using the reception level in the fixed signal section.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a direct access CDMA / TDD as a multiple access system.
It has a plurality of base stations and a plurality of mobile stations provided with a communication means of the (code division multiple access / time division duplex) system, and the base station and the mobile stations turn on / off transmission according to the presence or absence of transmission data during communication. A VOX function for turning off the power, a function for arranging a fixed transmission signal to be transmitted constantly even in a channel for which the transmission is off, so that the transmission cycle is minimized, and further, in the base station, a plurality of antennas and a reception time of TDD are provided. , A reception diversity function of combining signals received by the plurality of antennas, and a TDD using an antenna having a maximum received power at a TDD reception time.
A mobile communication apparatus characterized by having a transmission diversity function of performing transmission at a transmission time of DD, wherein a fixed signal arranged so as to have a minimum period even when a mobile station is off in VOX control. The slot has an effect that deterioration of transmission space diversity performance in the base station can be suppressed.

According to a second aspect of the present invention, in the mobile station, a function of detecting a power level of a received signal at a TDD reception time, and a transmission power at a TDD transmission time using the received signal level are used. The mobile communication apparatus according to claim 1, further comprising: a transmission power control function for controlling the transmission power, and a function for performing transmission power control using a reception signal level of only the fixed transmission signal when the transmission of the base station is turned off. In addition to the function of the first aspect of the present invention, in the VOX control, even if the base station is in the transmission off state, the fixed signal slot can suppress the performance degradation of the open loop transmission power control.

According to a third aspect of the present invention, in the transmission-off channel of the base station and the mobile station, a fixed transmission signal to be constantly transmitted is uniformly distributed to all slots, and a TDD transmission time 3. The mobile communication device according to claim 1, further comprising a function of shifting the transmission position of the fixed transmission signal to a different position for each channel in the mobile communication device. Since the transmission signal exists, the control delay does not deteriorate as compared with the case where the transmission signal exists.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a mobile communication device according to the embodiment.

In a cellular system, the base station communicates with a plurality of mobile stations at the same time, so the base station side device 1 is provided with the baseband processing units 2 for the maximum number of mobile stations that can communicate simultaneously. In a TDD base station transmission slot, transmission data 3 and a transmission control signal 4 to a certain mobile station are input to a baseband processing unit 2, and are encoded by an encoder 5, frame-assembled, and differ from one mobile station to a spreader 6. A spreading process using a spreading code is performed, and a switch 7 outputs the result to either the first adder 8 or the second adder 9.

A first adder 8 and a second adder 9 add the outputs of the plurality of baseband processing units, and
To the transmission RF unit 10 and the second transmission RF unit 11.
The first transmission RF unit 10 and the second transmission RF unit 11 perform modulation, frequency conversion, and amplification processing on the input, and perform a first transmission / reception switch 12 and a second transmission / reception switch, respectively.
The signal is transmitted from the first antenna 14 and the second antenna 15 to the radio channel through the respective antennas 13.

In the TDD base station reception slot,
The first antenna 14 and the second antenna 15 receive multiplexed signals from a plurality of mobile stations that have passed through different radio propagation paths, and respectively receive a first reception RF unit 16 and a second reception RF unit 17. Output to First reception RF section 16 and second reception RF section 16
The receiving RF section 17 performs frequency conversion, AGC processing, and demodulation processing on the multiplexed received signal, and outputs the result to a plurality of baseband processing sections.

In the baseband processing unit 2, the first reception R
The outputs of the F section 16 and the second receiving RF section 17 are respectively the first
In the correlator 18 and the second correlator 19, a signal addressed to itself is separated by a correlation process using a spreading code different for each mobile station, RAKE combining is performed by the RAKE combiners 20 and 21, and output to the diversity combiner 22. Diversity combiner 22 includes a first RAKE combining output and a second RAKE combining output.
The combined output is combined and output to the decoder 23.

Further, the first RAKE combining output and the second RAKE combining output
Are compared to determine whether to transmit with the first antenna 14 or the second antenna 15 in the next TDD transmission slot, and output a selection signal to the switch 7. The decoder 23 decodes the input, and
24 and a reception control signal 25 are obtained.

In the mobile station side apparatus 26, in the TDD mobile station transmission slot, the transmission data 27 and the transmission control signal output from the control unit 28 are encoded and frame-assembled in the encoder 29, and transmitted to the spreader 30. Is entered. Diffuser 30
Performs a spreading process on the input using a different spreading code for each mobile station, and outputs the result to the transmission RF unit 31. Transmission RF unit 31
Then, modulation, frequency conversion, and amplification are performed on the input.
The signal is transmitted from the antenna 33 to the radio channel through the transmission / reception switch 32.

In the TDD mobile station reception slot, the antenna 33 receives a signal from the base station and outputs it to the reception RF section 34. The reception RF section 34 performs frequency conversion, AGC processing, and demodulation processing on the multiplexed reception signal, and
Output to 35. The correlator 35 separates a signal addressed to itself from the output of the received RF unit by a correlation process using a spreading code different for each mobile station, performs RAKE combining by the RAKE combiner 36, decodes the signal by the decoder 37, and decodes the received data 38 And a reception control signal. The reception control signal is input to the control unit 28.

As shown in FIG. 2, the transmission data forms a frame, and the presence or absence of the transmission data is switched on a frame basis. The frame is composed of a plurality of slots, and the transmission slot of the base station is set at the top in the frame.

In the example of FIG. 2, one frame is composed of eight slots. A status notification bit 39 is inserted into the first slot of the frame to notify the presence or absence of data in the frame.
Therefore, even if there is no transmission data, the slot at the head of the frame needs to be transmitted. Further, even when there is no transmission data, the control signal 40 needs to be constantly transmitted. In the example of FIG. 2, the control signal occupies two slots.

The operation at the time of VOX control will be described on the premise of the above configuration. When the mobile station is off, the mobile station transmits the status notification bit 39 of the first slot A with transmission off and transmits the control signal 40 using slots A and E, as shown in FIG. Therefore, the base station uses the signals received by the first antenna 14 and the second antenna 15 in slot A from the correlators 18, 19 and the RAKE combiner 20,
At 21, transmission antennas in slots B to E are selected according to the power of the signal obtained by separating the desired signal, and the correlators 18 and 19 and the RAKE combiner are obtained from the signals received by the first antenna 14 and the second antenna 15 in slot E. The slots F, 20 and 21 are separated by the power of the signal obtained by separating the desired signal.
By selecting transmission antennas in G, H and the next frame slot A, even if there is no transmission data of the mobile station, the period for performing transmission space diversity is reduced to half of the case where control signals are packed in slots A and B. be able to.

(Second Embodiment) The configuration of a base station-side device according to a second embodiment of the present invention is the same as that of the first embodiment, except for the configuration of the mobile station-side device. FIG. 4 is a block diagram showing a configuration of the mobile station side device of the mobile communication device according to the second embodiment of the present invention.

In the mobile station side device 41, in the TDD mobile station transmission slot, the transmission data 42 and the transmission control signal 44 output from the control unit 43 are encoded and frame-assembled in the encoder 45, and the spreader 46 is transmitted. Is input to Diffuser
The input unit 46 performs a spreading process on the input using a different spreading code for each mobile station, and outputs the result to the transmission RF unit 47. Transmission RF section
47 performs modulation, frequency conversion and amplification processing on the input,
The signal is transmitted from the antenna 49 to the wireless propagation path through the transmission / reception switch 48.

In the TDD mobile station reception slot, the antenna 49 receives a signal from the base station and outputs it to the reception RF section 50. The reception RF section 50 performs frequency conversion, AGC processing, and demodulation processing on the multiplexed reception signal, and
Output to 51. The correlator 51 separates a signal addressed to itself from the output of the reception RF unit 50 by a correlation process using a spreading code different for each mobile station, performs RAKE combining by a RAKE combiner 52, decodes by a decoder 53, 54
And a reception control signal 55. The reception control signal 55 is a control unit
Entered in 43.

On the other hand, the output of the correlator 51 is input to the reception level detection circuit 56. The reception level detection circuit 56 detects the average power of the correlation output in the mobile station transmission slot, uses this to determine the transmission power of the next transmission slot after TDD, and outputs a control signal to the transmission RF section 47.

On the premise of the above configuration, the base station is a VOX
The operation when the transmission is turned off by the control will be described with reference to FIG. The base station transmits the status notification bit 39 of the first slot A with transmission off, and transmits the control signal 40 using slots A and E. The mobile station receives the status notification bit 39 and is notified that there is no data in the received frame, the reception level detection circuit 56 detects the power of the desired signal for slot A, and performs transmission power control for slots A to D, For slot E, reception level detection circuit 56 detects the power of the desired signal and performs transmission power control for slots E to H. Therefore, even when there is no transmission signal from the base station, it is possible to minimize the control interval of transmission power control.

(Third Embodiment) The configurations of a base station-side device and a mobile station-side device according to a third embodiment of the present invention are the same as those of the second embodiment, except for the operations. The operation of the third embodiment of the present invention will be described with reference to FIG.

FIG. 5 (1) shows a case where transmission is turned off at the mobile station.
As shown in (1), the control signal 40 is uniformly distributed to all slots and transmitted. Therefore, the base station can perform transmission diversity without deterioration of control delay as compared with the case where there is a transmission signal by using the reception level of the control signal reception section in all slots. Further, by arranging the transmission position of the control signal 40 in the slot at different positions as in the case of the mobile station 1 and the mobile station 2 in the figure, mutual interference is reduced,
System capacity can be increased.

Even when the transmission is turned off at the base station, the transmission is performed as shown in FIG. 5 (2), so that the control interval of the transmission power control of the mobile station is performed without deterioration compared to the case where there is a transmission signal. In addition, interference can be reduced by arranging the transmission positions of the control signal 40 in the slots for a plurality of mobile stations at different positions.

[0038]

As described above, the present invention provides a CDMA / TD
In a cellular system using the D system, in VOX control, a mobile station is arranged to minimize the transmission cycle of a fixed signal section such as a control signal constantly transmitted from a base station, and the mobile station receives the fixed signal section. The base station performs transmission space diversity using the reception level in the fixed signal section, and performs open-loop transmission power control and transmission even when performing VOX control. The effect of suppressing the deterioration of the diversity performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a mobile communication device according to a first embodiment of the present invention;

FIG. 2 is a diagram showing a frame configuration according to the first embodiment of the present invention;

FIG. 3 is a diagram (1) showing a frame configuration when mobile station transmission is off in the first embodiment of the present invention, and (2) a frame configuration when base station transmission is off in the second embodiment of the present invention. Diagram showing a frame configuration,

FIG. 4 is a block diagram showing a configuration of a mobile station side device according to a second embodiment of the present invention;

FIG. 5 is a diagram (1) showing a frame configuration when mobile station transmission is off in the third embodiment of the present invention, and (2) a frame configuration when base station transmission is off in the third embodiment of the present invention. Diagram showing a frame configuration,

FIG. 6 is a diagram (1) showing the concept of the TDD system, and (2) FD.
It is a figure showing the concept of the D system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base station apparatus 2 Baseband processing part 3, 27, 42 Transmission data 4, 44 Transmission control signal 5, 29, 45 Encoder 6, 30, 46 Spreader 7 Switch 8 First adder 9 Second addition Device 10 First transmission RF section 11 Second transmission RF section 12 First transmission / reception switch 13 Second transmission / reception switch 14 First antenna 15 Second antenna 16 First reception RF section 17 Second Receive RF section 18 First correlator 19 Second correlator 20 First RAKE combiner 21 Second RAKE combiner 22 Diversity combiner 23, 37, 53 Decoder 24, 38, 54 Received data 25, 55 Reception control signal 26, 41 Mobile station side device 28, 43 Control unit 31, 47 Transmit RF unit 32, 48 Transmit / receive switch 33, 49 Antenna 34, 50 Receive RF unit 35, 51 Correlator 36, 52 RAKE combiner 39 Status Notification bit 40 Control signal 56 Receive level detection circuit

Claims (3)

[Claims] 1. A direct spread CDM as a multiple access method
It has multiple base stations and multiple mobile stations equipped with A / TDD (code division multiple access / time division duplex) communication means. The base station and mobile stations transmit according to the presence or absence of transmission data during communication. A VOX function of turning on / off the power supply, and a function of arranging a fixed transmission signal that is always transmitted even in a transmission-off channel such that a slot transmission cycle is minimized. TDD
At the reception time, using the reception diversity function of combining the signals received by the plurality of antennas and the antenna having the maximum reception power at the TDD reception time,
A mobile communication device comprising: a transmission diversity function of performing transmission at a TDD transmission time. 2. A mobile station, comprising: a function for detecting a power level of a received signal at a TDD reception time; a transmission power control function for controlling transmission power at a TDD transmission time using the received signal level; 2. A function for performing transmission power control using a reception signal level of only the fixed transmission signal when the station is turned off.
A mobile communication device as described. 3. In a transmission-off channel of the base station and the mobile station, a fixed transmission signal to be constantly transmitted is uniformly distributed to all slots, and a transmission position of the fixed transmission signal within a TDD transmission time is determined. 3. The mobile communication device according to claim 1, wherein the mobile communication device has a function of displacing each channel at a different position.