AU3912999A

AU3912999A - Transmission power control for use in a radio base station apparatus n a TDMA-TDD system

Info

Publication number: AU3912999A
Application number: AU39129/99A
Authority: AU
Inventors: Tomohiro Azuma
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1998-07-10
Filing date: 1999-07-09
Publication date: 2000-02-03
Anticipated expiration: 2019-07-09
Also published as: CN1101121C; CN1241887A; JP2000032529A; AU757900B2; SE0601408L; JP3039637B2

Description

4 S F Ref: 471760

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD

PATENT

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ORIGINAL

1 Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: NEC Corporation 7-1, Shiba Minato-ku Tokyo

JAPAN

Tomohiro Azuma Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Transmission Power Control For Use in a Radio Base Station Apparatus in a TDMA-TDD System The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845 TRANSMISSION POWER CONTROL FOR USE IN A RADIO BASE STATION APPARATUS IN A TDMA-TDD SYSTEM Background of the Invention: This invention relates to a transmission power control ".method for controlling transmission power by a transmission diversity gain and a radio base station apparatus using the transmission power control method.

e° a In prior art, in order to satisfy a service in radio mobile stations such as portable telephone sets or a personal handyphone sets for use in a personal handyphone system (PHS), transmission diversity is adopted by providing a radio base station with a plurality of antennas. Transmitted from the radio base station, electric waves arrive in a portable mobile station via complicated paths with the electric waves reflected by walls of buildings or the like. If the radio mobile station communicates with the radio base station which is visible to the radio mobile station, there is both an electric wave which directly arrives to the radio mobile station and another electric wave which arrives to the radio mobile station after it reflects to the buildings. Inasmuch as a plurality of electric waves pass through different transmission paths, the transmission paths have different propagation distances.

Attention will be directed to the personal handyphone system. The personal handyphone system uses an electric wave Shaving a wavelength of about twenty centimeters. It will be assumed that first and second electric waves arrive from the radio base station to the radio mobile station via first and second transmission paths having first and second propagation distances, respectively. If a difference between the first and the second propagation distances is equal to a multiple of the wavelength of about twenty centimeters, the first and the second electric waves are added in the radio mobile station. If a difference between the first and the second propagation distances is equal to an odd multiple of half-wavelength, the first and the second electric wave are cancelled with each other in the radio mobile station. Accordingly, a strength of a total electric wave in the radio mobile station changes with movement of the radio mobile station. Accordingly, reception performance is improved by providing the radio base station with o the plurality of antennas and by using an electric wave received by one of the antennas that has the best condition with respect 0 to the reception performance. This improvement is called a diversity effect.

In addition, the personal handyphone system adopts a time division duplex (TDD) system where electric waves having the same frequency are used in both forward and reverse links.

Accordingly, if the radio base station determines, as a selected antenna, one of the antennas in accordance with a reverse electric wave and transmits a forward electric wave from the selected antenna, it may be possible for the radio mobile station to receive the forward electric wave on the forward link at a good condition. This is called a transmission diversity.

However, if a condition changes for a duration of milliseconds from a time instant when a reverse burst arrives in the radio base station to a time instant when the radio base station transmits a forward burst, the transmission diversity is of no effect. As a result, the transmission diversity produces a main cause where the radio mobile station has a moving speed which is limited.

A transmission power control method in the radio base station using the transmission diversity is disclosed in Japanese Unexamined Patent Publication of Tokkai No. Hei 10-32,527 or JP-A 10-032527 under the title of "Radio base station apparatus." JP-A 10-03257 realizes a radio base station apparatus that adopts the transmission diversity system •in which interference on the same adjacent system or other system is reduced in the case of transmission and power consumption is reduced. According to JP-A 10-03257, in the case of making call connection to a mobile station by the radio base station apparatus, a speech channel setup detection section detects a time instant when a speech channel is set up after a control channel. A speech channel setup signal is supplied to a transmission power control section. A transmission section, which executes transmission of transmission data, reduces the power consumption on transmission by the transmission diversity gain. Thus, the size of a control area for the control channel and the size of a speech area for the speech channel in a direction of the mobile station are the same.

It is possible to prevent production of interference due to the extended speech area for the speech channel and the increase in the power consumption.

Attention will be directed to a "reception diversity gain" and a "transmission diversity gain." It will be assumed that two antennas are arranged in a radio base station with no correlation state or no correlation rear state. In this event, the radio base station receives two received signals via two electric wave propagation paths. By selecting, as a selected electric wave propagation path, one of the two electric wave propagation paths that has a small electric wave propagation %fe: loss, there is an apparent gain or the radio base station has o a good reception sensitivity. This is called a "reception diversity." If the reception sensitivity is improved by the magnitude of 2dB, the magnitude of 2dB is defined as the "reception diversity gain." In addition, if the selected V460 electric wave propagation path is also selected on transmission, an apparent transmission power is higher by the magnitude of 2dB. The magnitude of 2dB is defined as the "transmission S diversity gain." The more the number of the antennas having no correlation becomes, the larger the reception diversity gain and the transmission diversity gain become. This is because selective branches in the electric wave propagation paths increase.

The radio base station apparatus according to JP-A 10-03257 suppresses or controls the transmission power by a fixed transmission diversity gain initialized on transmission of a speech or a communication signal via the speech channel although an antenna's abnormality is detected or the number of receiving sections which normally operates decreases.

Accordingly, the speech area for the speech channel is smaller than the control area for the control channel and degradation of a reception sensitivity in the mobile station occurs in the manner which will later described in conjunction with Figs. 1 through 3.

Other prior arts related to this invention are already known. By way of example, Japanese Unexamined Patent Publication of Tokkai No. Hei 9-107,579 or JP-A 9-107579 discloses an idle channel forward transmission power control system in which proper antenna diversity is selected with a required minimum idle channel forward transmission power.

According to JP-A 9-107579, a base station informs prescribed threshold level information through a forward control channel to a mobile station. The mobile station determines an idle channel forward transmission power value of the base station based on a level difference between the informed threshold level information and a reception level of the forward control channel and informs it to the base station through a reverse control channel. The base station uses the informed idle channel forward transmission power value as its own idle channel forward transmission power. Preferably, the base station energizes the forward transmission power of the idle channel by the level measurement slot for antenna diversity selection by mobile station to which the speech channel is allocated.

Alternatively, the base station energizes the forward transmission power of the idle speech channel by the level measurement slot level measurement time.

Japanese Unexamined Patent Publication of Tokkai No. Hei 9-9,344 or JP-A 9-009344 discloses an idle channel transmission power control method in a mobile communication system and a transmission power controller for a base station in the mobile communication system which are capable of avoiding the effect onto other mobile station and a base station and of saving power consumption of the base station by using only one slot among idle channels other than the slot assigned as a speech channel so as to conduct transmission with required transmission power.

•.:According to JP-A 9-009344, the base station is provided with a speech channel transmission power control section controlling transmission power as to a slot assigned as a speech channel S° and with an idle channel transmission power control section to S.select antenna changeover diversity antennas in a mobile station by controlling transmission power to be required transmission power as to only one slot among other slots being idle channels than the slot assigned as the speech channel.

Summary of the Invention: It is therefore an object of the present invention to provide a radio base station apparatus which is capable of equating a control area for a control channel with a speech area for a speech channel on communication by always suppressing a transmission power by a transmission diversity gain corresponding to the number of normal antennas although the radio base station apparatus has antenna trouble.

It is another object of the present invention to provide a radio base station apparatus which is capable of equating a control area for a control channel with a speech area for a speech

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channel on communication although a malfunction occurs in any receiving sections.

Other objects of this invention will become clear as the description proceeds.

According to a first aspect of this invention, a radio base station apparatus carries out a transmission diversity for use in a time division multiple access-time division duplex (TDMA-TDD) mobile communication system. The radio base astation apparatus comprises an actual transmission diversity gain determining arrangement for determining an actual a.l transmission diversity gain. Connected to the actual a. *a transmission diversity gain determining arrangement, a S' transmission power control section controls transmission power S" by the actual transmission diversity gain.

According to a second aspect of this invention, a method S"..is controlling transmission power in a radio base station apparatus carrying out a transmission diversity for use in a time division multiple access-time division duplex

(TDMA-TDD)

mobile communication system. The method comprises the steps of determining an actual transmission diversity gain, and of controlling the transmission power by the actual transmission diversity gain.

Brief Description of the Drawing: Fig. 1 is a block diagram of a conventional radio base station apparatus for carrying out a conventional transmission power control for use in a time division multiple access-time division duplex (TDMA-TDD) mobile communication system; 8 Fig. 2 is a schematic view showing a forward signal area in the radio base station apparatus illustrated in Fig. 1; Fig. 3 is a schematic view showing a forward signal area for use in describing problems of the radio base station apparatus illustrated in Fig. 1; Fig. 4 is a block diagram of a radio base station apparatus according to a first embodiment of this invention for use in the TDMA-TDD mobile communication system; :Fig. 5 is a schematic view showing a forward signal area in the radio base station apparatus illustrated in Fig. 2.

Fig. 6 is a block diagram of a radio base station S* apparatus according to a second embodiment of this invention for use in the TDMA-TDD mobile communication system; and S" •Fig. 7 is a block diagram of a radio base station apparatus according to a third embodiment of this invention for use in the TDMA-TDD mobile communication system.

Description of the Preferred Embodiments: Referring to Fig. i, description will proceed to a conventional radio base station apparatus 10' will be described at first in order to facilitate an understanding of the present invention. The illustrated radio base station apparatus is for use in a time division multiple access-time division duplex (TDMA-TDD) mobile communication system and is disclosed in the above-mentioned JP-A 10-32527.

The radio base station apparatus 10' comprises first through N-th transmission/reception antennas 11-1, and 11-N, where N represents a positive integer which is not less than two, a switch section 13, first through N-th receiving

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9 sections 15-1, 15-2, and 15-N, a control section 17, a transmission section 19, a speech channel setup detection section 21, and a transmission power control section 23'.

The first through the N-th transmission/reception antennas 11-1 to 11-N are connected to the switch section 13.

In the manner which will later be described, the switch section 13 selects one of the through the N-th transmission/reception antennas 11-1 to 11-N as a selected transmission antenna. The switch section 13 is connected to the first through the N-th receiving sections 15-1 to 15-N and the transmission section

**SS

19. Received by the first through the N-th transmission/reception antennas 11-1 to 11-N, first through N-th received signals are supplied through the switch section 13 to the first through the N-th receiving sections 15-1 to respectively. The first through the N-th receiving sections 15-1 to 15-N demodulate the first through the N-th received signals into first through N-th received data RDI, RD 2 and RDN, respectively. The first through the N-th received data RD1 to RDN are supplied to the control section 17. In addition, the first through the N-th receiving sections 15-1 to measure received electric field strengths in the first through the N-th received signals to produce first through N-th received electric field strength signals

RS

1

RS

2 and RSN indicative of the received electric field strengths of the first through the N-th received signals, respectively. The first through the N-th received electric field strength signals RS 1 to RSN are supplied to the control section 17.

Responsive to the first through the N-th received electric field strength signals RS 1 to RSN, the control section 17 selects, as a selected received datum RDs, one of the first through the N-th received data RD 1 to RDN that corresponds to the largest one among the electric field strengths indicated by the first through the N-th received electric field strength signals RS 1 to RSN. The control section 17 produces the selected received datum RD s In addition, the control section 17 supplies the switch section 13 with a switch switching signal SS indicative of selection of one of the first through the N-th •transmission/reception antennas 11-1 to 11-N that corresponds to the selected received datum RD s Responsive to the switch switching signal SS, the switch section 13 selects one of the first through the N-th transmission/reception antennas 11-1 to 11-N as the selected transmission antenna for use in °*o0 transmitting a transmission signal.

Furthermore, the control section 17 supplies the transmission section 19 and the speech channel setup detection section 21 with a transmission datum TD. Responsive to the transmission datum TD, the speech channel setup detection section 21 detects a timing when a control channel is switched to a speech channel to produce a speech channel setup signal CS when the control channel is switched to the speech channel.

The speech channel setup signal CS is supplied to the transmission power control section 23'. Responsive to the speech channel setup signal CS, the transmission power control section 23' produces an output control signal OC for controlling a transmission power for the transmission signal. The output control signal OC indicates that the transmission power should be controlled by a transmission diversity gain Gdt. It is noted that the transmission diversity gain Gdt is initialized to a fixed value in the radio base station apparatus 10'. In other words, the radio base station apparatus 10' has a fixed transmission diversity gain Gdtf as the transmission diversity gain Gdt.

The output control signal OC is supplied to the transmission section 19. Responsive to the output control *o 00:- signal OC, the transmission section 19 modulates a carrier 000:0 e signal by the transmission datum TD into a modulated signal and ON 0 S0 power amplifies the modulated signal with the transmission S Cpower controlled by the output control signal OC into an ON amplified signal. The transmission section 19 produces the amplified signal as the transmission signal which is S. transmitted via the switch section 13 from the selected transmission antenna.

With this structure, the control section 17 supplies the switch section 13 with the switch switching signal SS for switching the first through the N-th transmission/reception antennas 11-1 to 11-N by selecting, as the selected transmission antenna, one of the first through the N-th transmission/reception antennas 11-1 to 11-N that receives the received signal having the largest reception electric field strength in order to guarantee a speech service of high quality.

In order to cope with movement of the portable mobile station, on communication with the portable mobile station using a control signal on a control channel, the control section 17 12 determines which transmission/reception antenna has the largest reception electric field strength signal to select the most suitable antenna as initialization. Subsequently, the control section 17 switches the first through the N-th transmission/reception antennas 11-1 to 11-N in a speech channel for every predetermined time interval to detect the first through the N-th received electric field strength signals

RS

1 to RSN and selects one of the first through the N-th transmission/reception antennas 11-1 to 11-N that receive the received signal having the electric field strength of a maximum level to continue the communication of the high quality.

Turning to Fig. 2, description will be made as regards operation of the radio base station apparatus (CS) 10' In Fig.

4 2, a reference symbol of 30 represents a radio mobile station The control area for the control channel is depicted at 0000 goo* 32 and the control area has a spherical shape.

In order to equate the control area 32 for the control eo Schannel with a speech area for the speech channel on communication, equality between the control area 32 for the control channel and the speech area for the speech channel is achieved by degrading the transmission power by the fixed transmission diversity gain Gdtf. Specifically, when no degradation of the transmission power by the fixed transmission diversity gain Gdtf is made, the speech area for the speech channel is depicted at 34 illustrated in a broken line of Fig.

2. This speech area 34 has a spheroidal shape which extends towards the radio base station 30 in comparison with the control area 32. When degradation of the transmission power by the 13 fixed transmission diversity gain Gdtf is made, the speech area for the speech channel is depicted at 36 illustrated in a solid line of Fig. 2. That is, the speech area 36 is shifted from the speech area 34 along an arrow depicted at A and is smaller than the speech area 34. Accordingly, equality between the control area 32 and the speech area 36 is achieved.

The fixed transmission diversity gain Gdtf is determined by the number N of the transmission/reception antennas 11-i to 11I-N and the number N of the receiving sections 15-1 to *e a N. In other words, the fixed transmission diversity gain Gdtf in the conventional radio base station apparatus 10' is based upon the assumption that all of the first through the N-th 5005 S9* transmission/reception antennas 11-1 to 11-N normally operate •and all of the first through the N-th receiving sections 15-1 to 15-N normally operate.

*oo However, the above-mentioned radio base station apparatus 10 has problems in the manner which will presently be described in conjunction with Fig. 3.

A first problem will first be described. It will be assumed that abnormality in any transmission/reception antenna is detected. In this event, an actual transmission diversity gain Gdta decreases or is smaller than the fixed transmission diversity gain Gdtf because the number of the transmission/reception antennas enable to be selected as the transmission antennas decreases on transmission of a speech or a communication signal on the speech channel. Nevertheless, inasmuch as the transmission power is controlled or suppressed by the fixed transmission diversity gain Gdtf which is 14 initialized, the speech area of the speech channel is shifted from the speech area 36 along an arrow depicted at B in Fig.

3 and is smaller than the control area 32 of the control channel as shown at 38 in Fig. 3 and it results in giving rise to degradation of reception sensitivity in the radio mobile station 30. Accordingly, when trouble in the antenna occurs actually, degradation of the reception sensitivity in the radio mobile station 30 occurs. This is because the control area 32 .o for the control channel does not equate with the speech area 000:oi 38 for the speech channel on communication.

o Subsequently, a second problem will be described. If S0 the number of the receiving sections which normally operate is decreased, a reception diversity gain Gdr decreases. Although S the actual transmission diversity gain Gdta also decreases in comparison with the fixed transmission diversity gain Gdtf, the 0 speech area 38 for the speech channel is smaller than the control area 32 for the control channel as shown in Fig. 3 because the e. Ctransmission power is controlled or suppressed by the fixed transmission diversity gain Gdtf which is initialized and it results in giving rise to degradation of reception sensitivity in the radio mobile station 30. Accordingly, when disorder occurs in any receiving section connected to the antenna, degradation of the reception sensitivity in the radio mobile station 30 occurs in the similar manner in the above-mentioned first problem. This is because the actual transmission diversity gain Gdta decreases in comparison with the fixed transmission diversity gain Gdtf.

Referring to Fig. 4, description will proceed to a radio base station apparatus 10 according to a first embodiment of the present invention. The illustrated radio base station apparatus 10 is similar in structure and operation to the conventional radio base station apparatus 10' illustrated in Fig. 1 except that the radio base station apparatus 10 further comprises first through N-th antenna defect detection sections 25-1, 25-2, and 25-N, an antenna monitoring section 27, *qe .and a receiving section abnormality detection section 29 and the transmission power control section is modified from that illustrated in Fig. 1 as will later become clear. The transmission power control section is therefore depicted at 23.

"".More specifically, the first through the N-th transmission/reception antennas 11-1 to 11-N are antennas which o are arranged so as to make no correlation with each other. The switch section 13 is a switch which enable to switch transmission and reception. Arranged so as to correspond to °o o.

the first through the N-th transmission/reception antennas 11-1 to 11-N, respectively, the first through the N-th receiving sections 15-1 to 15-N demodulate the first through the N-th received signals supplied from the first through the N-th transmission/reception antennas 11-1 to 11-N through the switch section 13 to produce the first through the N-th received data RDI to RD

N

respectively. In addition, the first through the N-th receiving sections 15-1 to 15-N produce the first through the N-th received electric field strength signals RS 1 to RSN indicative of the received electric field strengths in the first through the N-th received signals, respectively.

Responsive to the first through the N-th received electric field strength signals RS 1 to RSN, the control section 17 determines the largest one of the first through the N-th received electric field strength signals RS 1 to RSN and selects, as the selected received datum RDs, one of the first through the N-th received data RD 1 to RDN that corresponds to the largest one of the first through the N-th received electric field strength signals

RS

1 to RSN.

4qt* .4e In addition, on transmission of the speech or the

S..

communication signal via the speech channel, the control 4444 section 17 supplies the switch section 13 with the switch switching signal SS for selecting one of the first through the N-th transmission/reception antennas 11-1 to 11-N as the selected transmission antenna so as to transmit the transmission signal from the selected transmission antenna o connected to one of the first through the N-th receiving sections 15-1 to 15-N that produces the largest one of the first

S.

4 through the N-th received electric field strength signals RS 1 to RSN. This selection is effective in a case of the TDMA- TDD mobile communication system where a transmission frequency and a reception frequency coincide with each other and transmission/reception is separated by a difference of transmission/reception slot.

Disposed between the control section 17 and the switch section 13, the transmission section 19 can control the transmission power in response to the output control signal OC supplied from the transmission power control section 23.

Supplied with the transmission datum DT, the speech channel 17 setup detection section 21 monitors a time instant when the control channel is switched to the speech channel to supply the speech channel setup signal CS to the transmission power control section 23 after the speech channel is established.

Specifically, the transmission datum TD includes a signal control channel (SCCH) field indicative of the time instant when the control channel is switched to the speech channel. The speech channel setup detection section 21 monitors the SCCH field in the transmission datum DT to produce the speech channel asetup signal when the speech channel setup detection section 21 detects the SCCH field in the transmission datum DT.

The first antenna defect detection section 25-1 is disposed between the first transmission/reception antenna 11-1 and the switch section 13. Likewise, the second antenna defect .detection section 25-2 is disposed between the second transmission/reception antenna 11-2 and the switch section 13.

The N-th antenna defect detection section 25-N is disposed between the N-th transmission/reception antenna 11-N and the switch section 13. In general, an n-th antenna defect detection section 25-n is disposed between an n-th transmission/reception antenna 11-n and the switch section 13, where n represents each of 1 through N.

The n-th antenna defect detection section determines whether or not an n-th received signal has an n-th received electric field strength which is less than a predetermined threshold value to produce an n-th antenna'alarm signal AAn when the n-th received electric field strength of the n-th received signal is less than the predetermined i 18 threshold value. That is, the n-th antenna defect detection section 25-n determines whether or not the n-th transmission/reception antenna 11-n is defective. Various antenna defect detection methods may be adopted in determination of any defect in the n-th transmission/reception antenna 11-n as follows. A first antenna defect detection method is a method of detecting reflected power of a transmission wave at an end of the n-th transmission/reception S. antenna 11-n. A second antenna defect detection method is a method of measuring a voltage standing wave ratio (VSWR) in the n-th transmission/reception antenna 11-n and of detecting a 0 defect in the n-th transmission/reception antenna 11-n when the VSWR has a large value. A third antenna defect detection method S. is a method of making a direct current flow through the n-th transmission/reception antenna 11-n which is grounded and of detecting a defect in the n-th transmission/reception antenna 11-n using an open collector circuit where a current does not flow on malfunction of the n-th transmission/reception antenna 11-n.

At any rate, the first through the N-th antenna defect detection sections 25-1 to 25-N produce first through N-th antenna alarm signals AA 1

AA

2 and AAN, respectively, which are supplied to the antenna monitoring section 27 for monitoring whether or not the first through the N-th transmission/reception antennas 11-1 to 11-N normally carry out transmission/reception. When any one of the first through the N-th antenna alarm signals AA 1 to AAN is present, the antenna monitoring section 27 produces an antenna abnormality detected 19 signal AAD indicative of a monitored result that is supplied to the transmission power control section 23. In other words, the antenna abnormality detected signal AAD indicates the number of the transmission/reception antennas which normally operate. In addition, the actual transmission diversity gain Gdta is determined by the number of the transmission/reception antennas which normally operate.

_Produced by the first through the N-th receiving sections to o 15-1 to 15-N, the first through the N-th received electric field 0 strength signals RS 1 to RSN are also supplied to the receiving 0 °section abnormality detection section 29 for determining whether or not the first through the N-th receiving sections *000 0 15-1 to 15-N normally carry out reception operation. When any eoe• one of the first through the N-th receiving sections 15-1 to iO• 15-N does not normally carry out reception operation, the o receiving section abnormality detection section 29 produces a receiving section abnormality detected signal RAD which is OO Ssupplied to the transmission power control section 23. In other words, the receiving section abnormality detected signal RAD indicates the number of the receiving sections which normally operate. In addition, the actual transmission diversity gain Gdta is also determined by the number of the receiving sections which normally operate.

Responsive to the speech channel setup signal CS and on the basis of the antenna abnormality detected signal AAD and the receiving section abnormality detected signal RAD, the transmission power control section 23 produces the output control signal OC in the manner which will later become clear.

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Referring to Fig. 5 in addition to Fig. 4, the description will be made as regards operation of the radio base station apparatus 10 illustrated in Fig. 4. A control signal is transmitted via the control channel from a particular transmission/reception antenna of the radio base station apparatus 10 that is arbitrarily determined. In the example being illustrated, it will be assumed that the control signal is transmitted from the first transmission/reception antenna 11-1 and the control channel has a control area 32 as illustrated in Fig. oo e. Attention will be directed to the personal handyphone 0e'." system (PHS) which adopts the time division multiple ooo• OSS access-time division duplex (TDMA-TDD) mobile communication •system. The personal handyphone system uses a carrier frequency band of 1.9 GHz in common for transmi s s ion/reception .and divides the transmission/reception into four slots. In the 0•personal handyphone system, service of speech or data o communication is carried out using the control channel for position registration and outgoing/incoming call control and a plurality of speech channels which are assigned to communication apparatuses, individually.

In a case where communication is carried out by specifying any one of the first though the N-th transmission/reception antennas 11-1 to 11-N, the control signal is transmitted via the control channel from another transmission/reception antenna when the radio base station apparatus 10 detects that the particular transmission/ reception antenna is abnormal. It will be presumed that the

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21 control channel has a fixed area or the control area 32 in spite of a selected transmission/reception antenna.

Now, the description will proceed to operation on transmission of a speech or a communication signal via the speech channels from the radio base station apparatus Received in the first transmis s ion/reception antenna 11-1 from the radio mobile station 30 to the radio base station apparatus 10, a first reverse signal is supplied to the first receiving section 15-1 through the switch section 13 as the first received ooooo signal. The first receiving section 15-1 demodulates the first :received signal to produce the first received datum RS 1 and the first received electric field strength signal RS 1 which are supplied to the control section 17.

Likewise, second through N-th reverse signals, which are received in the second through the N-th transmission/reception antennas 11-2 to 11-N from the radio mobile station 30 to the radio base station apparatus 10, are supplied to the second through the N-th receiving sections 15-2 to 15-N through the switch section 13 as the second through the N-th received signals, respectively. The second through the N-th receiving sections 15-2 to 15-N demodulate the second through the N-th received signals to produce the second through the N-th received data RD 2 to RDN and the second through the N-th received electric field strength signals RS 2 to RSN, respectively. The second through the N-th received data RD 2 to RDN and the second through the N-th received electric field strength signals RS 2 to RSN are supplied to the control section 17.

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Supplied with the first through the N-th received data

RD

1 to RDN and with the first through the N-th received electric field strength signals RS 1 to RSN, the control section 17 selects, as the selected received datum RDs, one of the first through the N-th received data RD 1 to RDN that corresponds to the largest one of the first through the N-th received electric field strength signals RS 1 to RSN. As a result, it is possible for the radio base station apparatus 10 to obtain the selected received datum RD, having the least code error rate. Although S: selection of the received datum or selection of the *oe V'oOO transmission/reception antenna is carried out using the received electric field strength signal as an index, a data error rate may be used as the index by detecting the data error rate in each receiving section. In addition, both of the received electric field strength signal and the data error rate oooo .o may be used as the index for selecting the transmission/ reception antenna.

In the example being illustrated, it will be assumed that the second received electric field strength signal RS 2 has the largest electric field strength. In this event, the second received datum RD 2 is supplied from the control section 17 to a signal processing section (not shown) as the selected received datum RD s In addition, the control section 17 supplies the switch section 13 with the switch switching signal SS so that the transmission signal is transmitted from the second transmission/reception antenna 11-2 connected to the second receiving section 15-2 which produces the largest received electric field strength and which has the best reception quality.

23 Responsive to the switch switching signal SS, the switch section 13 selects the second transmission/reception antenna 11-2 as a selected transmission antenna for transmitting the transmission signal sent from the transmission section 19.

The transmission section 19 is supplied with the transmission datum TD from the control section 17. The transmission section 19 modulates a carrier signal by the transmission datum TD to produce the transmission signal. The transmission signal is transmitted from the selected oooeo transmission antenna 11-2 via the switch section 13.

o• SIn the radio base station apparatus 10 in which a transmission diversity is carried out in the manner as described above, the transmission datum TD is supplied to the speech channel setup detection section 21 for monitoring a timing when the control channel is switched to the speech channel. After the speech channel is established, the speech channel setup detection section 21 produces the speech channel setup signal CS which is supplied to the transmission power control section 23. Responsive to the speech channel setup signal CS, the transmission power control section 23 produces the output control signal OC for controlling the transmission power by the actual transmission diversity gain Gdta in the manner which will later become clear.

In addition, a changing from the control channel to the speech channel is carried out as follows. When an incoming call is received from the radio mobile station 30 or when the radio base station apparatus 10 generates an outgoing call to the radio mobile station 30, exchange of the control signal is first 1 24 carried out between the radio mobile station 30 and the radio base station apparatus 10 using a predetermined control channel.

Thereafter, the radio base station apparatus 10 designates the speech channel specifying an idle speech frequency and a speech slot and continues communication using the speech channel.

Responsive to the output control signal OC from the transmission power control section 23, the transmission section 19 controls the transmission power by the actual transmission diversity gain Gdta with respect to the speech channel.

.:oo.i The first through the N-th antenna defect detection sections 25-1 to 25-N have functions for detecting abnormality in the first through the N-th transmission/reception antennas 11-1 to 11-N, respectively. When abnormality in the n-th transmission/reception antenna 11-n is detected, the n-th Santenna defect detection section 25-n produces the n-th antenna alarm signal AA n which is supplied to the antenna monitoring section 27. The first through the N-th transmission/reception antennas 11-1 to 11-N are assigned with first through N-th antenna numbers for identifying the first through the N-th transmission/reception antennas 11-1 to 11-N, respectively.

The antenna monitoring section 27 supplies the transmission power control section 23 with the antenna abnormality detected signal AAD indicative of the antenna number(s) for identifying the transmission/reception antenna(s) where any abnormality occur(s). In other words, the antenna abnormality detected signal AAD indicates the number of transmission/reception antennas which normally operate.

For example, it will be presumed that the abnormality occurs in the second transmission/reception antenna 11-2. In this event, the second antenna defect detection section 2 produces the second antenna alarm signal AA 2 Responsive to the second antenna alarm signal AA 2 the antenna monitoring section 27 supplies the transmission power control section 23 with the antenna abnormality detected signal AAD indicative of the second antenna number.

.9 Inasmuch as the antenna abnormality detected signal AAD *99999 9oo is supplied from the antenna monitoring section 27 to the *'."otransmission power control section 23, the transmission power control section 23 can always grasp the transmission/reception 9999 oantennas which enable to use as the transmission antennas on *e 9 transmission.

99• Each of the first through the N-th transmission/reception antennas 11-1 to 11-N may use various types, for example, a type where two antennas are horizontally cocked as diversity, a type butt together up and down, a small-sized printed antenna type, a beam zone antenna type having directivity, and so on. In addition, each of the first through the N-th antenna defect detection sections 25-1 to may use a mechanism sensor for detecting mechanical damage in the antenna or a directional coupler for detecting the presence or absence of a transmission/reception signal.

In addition, produced by the first through the N-th receiving sections 15-1 to 15-N, the first through the N-th received electric field strength signals RS 1 to RSN are supplied to the receiving section abnormality detection section 29. The 26 receiving section abnormality detection section 29 detects abnormality in the first through the N-th receiving sections 15-1 to 15-N to produce the receiving section abnormality detected signal RAD indicative of the abnormality in the first through the N-th receiving sections 15-1 to 15-N. In other words, the receiving section abnormality detected signal

RAD

indicates the number of the receiving sections which normally ""@"operate. 9* 9 A decision basis of abnormality detection in the receiving section abnormality detection section 29 is as 9follows. The first through the N-th receiving sections 1 to 15-N are assigned with first through N-th receiving section numbers for identifying the first through the N-th receiving sections 15-1 to 15-N, respectively. For example, it will be e assumed that the first received electric field strength signal

RS

1 alone is lower than a threshold value by 10dB or more for 9 -a predetermined time interval (for instance, two minutes) or more. In addition, the first antenna defect detection section 25-1 detects no abnormality in the first transmission/reception antenna 11-i. In this event, the receiving section abnormality detection section 29 produces the receiving section abnormality detected signal RAD indicative of the first receiving section number.

As described above, the transmission power control section 23 can grasp the receiving sections which enable to normally carry out reception operation. In other words, on the basis of the antenna abnormality detected signal AAD supplied from the antenna monitoring section 27 and of the receiving 27 section abnormality detected signal RAD supplied from the receiving section abnormality detection section 29, the transmission power control section 23 always holds information indicative of a combination of the transmission/reception antennas enable to normally obtain the reception diversity gain and the transmission diversity gain and the receiving sections connected to the transmission/reception antennas in question.

At any rate, a combination of the first through the N-th antenna defect detection sections 25-1 to 25-N, the antenna monitoring 9**9*9 o* 9• 9*9* section 27, and the receiving section abnormality detection section 29 serves as an actual transmission diversity gain determining arrangement for determining the actual 9**9 *o 9@ transmission diversity gain Gdta.

On the basis of the above-mentioned information, the transmission power control section 23 supplies the transmission @999 section 19 with the output control signal OC so as to lower the transmission power by the actual transmission diversity gain Gdta. By this control method, although malfunction occurs in any transmission/reception antenna and any receiving section, the speech area 36 for the speech channel equates with the control area 32 for the control channel as illustrated in Fig.

That is, the speech area 36 for the speech channel is shifted from the speech area 38 for the speech channel along an arrow depicted at C in Fig. 5. It is possible to avoid degradation in reception sensitivity of the radio base station 30 as shown in the speech area 36 of Fig. Referring to Fig. 6, the description will proceed to a radio base station apparatus 10A according to a second 28 embodiment of this invention. The illustrated radio base station apparatus 10A is similar in structure and operation to the radio base station apparatus 10 illustrated in Fig. 4 except that the receiving section abnormality detection section 29 is omitted from that illustrated in Fig. 4 and the transmission power control section is modified from that illustrated in Fig.

4 as will later become clear. The transmission power control section is therefore depicted at 23A.

Responsive to the speech channel setup signal CS and on the basis of the antenna abnormality detected signal AAD, the a. ."atransmission power control section 23A supplies the output control signal OC to the transmission section 19. At any rate, a combination of the first through the N-th antenna defect detection sections 15-1 to 15-N and the antenna monitoring section 27 serves as an actual transmission diversity gain 0040 determining arrangement for determining the actual transmission diversity gain Gdta. Inasmuch as the radio base station apparatus 10A has a similar effect or merit in the radio base station apparatus 10 illustrated in Fig. 4, description thereof is therefore omitted because of simplification of description.

Referring to Fig. 7, the description will proceed to a radio base station apparatus 10B according to a third embodiment of this invention. The illustrated radio base station apparatus 10B is similar in structure and operation to the radio base station apparatus 10 illustrated in Fig. 4 except that the first through the N-th antenna defect detection sections 25-1 to 25-N and the antenna monitoring section 27 are omitted from that illustrated in Fig. 4 and the transmission power control section is modified from that illustrated in Fig. 4 as will later become clear. The transmission power control section is therefore depicted at 23B.

Responsive to the speech channel setup signal CS and on the basis of the receiving section abnormality detected signal RAD, the transmission power control section 23B supplies the output control signal OC to the transmission section 19. At any rate, the receiving section abnormality detection section o 29 serves as an actual transmission diversity gain determining .e arrangement for determining the actual transmission diversity gain Gdta Inasmuch as the radio base station apparatus S.e has a similar effect or merit in the radio base station apparatus illustrated in Fig. 4, description thereof is therefore omitted because of simplification of description.

5555 While this invention has thus far been described in conjunction with preferred embodiments thereof, it will now be readily possible for those skilled in the art to put this invention into various other manners.

Claims

1. A radio base station apparatus carrying out a transmission diversity for use in a time division multiple access-time division duplex (TDMA-TDD) mobile communication system, said radio base station apparatus comprising: actual transmission diversity gain determining means for determining an actual transmission diversity gain; and a transmission power control section, connected to said actual transmission diversity gain determining means, for controlling a transmission power by the actual transmission diversity gain.

2. A radio base station apparatus as claimed in claim 1, said radio base station apparatus comprising first through 0.e. S* N-th transmission/reception antennas where N represents a positive integer which is not less than two, wherein said actual transmission diversity gain determining means comprises: first through N-th antenna defect detection sections, connected to said first through said N-th transmission/reception antennas, respectively, for detecting defects in said first through said N-th transmission/reception antennas to produce first through N-th alarm signals when the defects in said first through said N-the transmission/reception antennas are detected, respectively; and an antenna monitoring section, connected to said first through said N-th antenna defect detection sections, for monitoring the first through the N-th antenna alarm signals to produce an antenna abnormality detected signal indicative of 31 the number of the transmission/reception antennas which normally operate, said actual transmission diversity gain being determined by the number of the transmission/reception antennas which normally operate, whereby said transmission power control section controls the transmission power by the actual transmission diversity gain corresponding to the number of the transmission/reception antennas which normally operate.

3. A radio base station apparatus as claimed in claim S1i, said radio base station apparatus comprising first through N-th transmission/reception antennas where N represents a U. S positive integer which is not less than two, said radio base °°station apparatus further comprising first through N-th receiving sections, connected to said first through said N-th transmission/reception antennas, respectively, for :oo receiving first through N-th received signals to produce first through N-th received electric field strength signals indicative of received electric field strengths in the first through the N-th received signals, respectively, wherein said actual transmission diversity gain determining means comprises: a receiving section abnormality detection section, connected to said first through said N-th receiving sections, for detecting abnormality in said first through said N-th receiving sections on the basis of the first through the N-th received electric field strength signals to produce a receiving section abnormality detected signal indicative of the number of the receiving sections which normally operate, said actual transmission diversity gain being determined by the 32 number of the receiving sections which normally operate, whereby said transmission power control section controls the transmission power by the actual transmission diversity gain corresponding to the number of the receiving sections which normally operate.

4. A radio base station apparatus as claimed in claim 1, said radio base station apparatus comprising first through N-th transmission/reception antennas where N represents a S.o positive integer which is not less than two, said radio base station apparatus further comprising first through N-th receiving sections, connected to said first through said N-th transmission/reception antennas, respectively, for o: receiving first through N-th received signals to produce first through N-th received electric field strength signals 5e** indicative of received electric field strengths in the first 0**S So through the N-th received signals, respectively, wherein said 5*95 Sactual transmission diversity gain determining means comprises: first through N-th antenna defect detection sections, connected to said first through said N-th transmission/reception antennas, respectively, for detecting defects in said first through said N-th transmission/reception antennas to produce first through N-th alarm signals when the defects in said first through said N-the transmission/reception antennas are detected, respectively; an antenna monitoring section, connected to said first through said N-th antenna defect detection sections, for monitoring the first through the N-th antenna alarm signals to 33 produce an antenna abnormality detected signal indicative of the number of the transmission/reception antennas which normally operate, said actual transmission diversity gain being determined by the number of the transmission/reception antennas which normally operate; and a receiving section abnormality detection section, connected to said first through said N-th receiving sections, for detecting abnormality in said first through said N-th S"receiving sections on the basis of the first through the N-th received electric field strength signals to produce a receiving section abnormality detected signal indicative of the number of the receiving sections which normally operate, said actual transmission diversity gain being also determined by the O 9 number of the receiving sections which normally operate, o whereby said transmission power control section controls the

9..transmission power by the actual transmission diversity gain o o corresponding to a combination of the number of the transmission/reception antennas which normally operate and the number of the receiving sections which normally operate. A method of controlling transmission power in a radio base station apparatus carrying out a transmission diversity for use in a time division multiple access-time division duplex (TDMA-TDD) mobile communication system, said method comprising the steps of: determining an actual transmission diversity gain; and controlling the transmission power by the actual transmission diversity gain. 4 34 6. A method as claimed in claim 5, said radio base station apparatus comprising first through N-th transmission/ reception antennas where N represents a positive integer which is not less than two, wherein said determining step comprises the step of: detecting defects in said first through said N-th transmission/reception antennas to produce first through N-th alarm signals when the defects in said first through said S"N-th transmission/reception antennas are detected, 9**99* respectively; and o• monitoring the first through the N-th antenna alarm signals to produce an antenna abnormality detected signal indicative of the number of the transmission/reception antennas which normally operate, said actual transmission diversity gain being determined by the number of the transmission/reception antennas which normally operate, whereby said controlling step *controls the transmission power by the actual transmission diversity gain corresponding to the number of the transmission/reception antennas which normally operate. 7. A method as claimed in claim 5, said radio base station apparatus comprising first through N-th transmission/ reception antennas where N represents a positive integer which is not less than two, said radio base station apparatus further comprising first through N-th receiving sections, connected to said first through said N-th transmission/reception antennas, respectively, for receiving first through N-th received signals to produce first through N-th received electric field strength signals indicative of received electric field strengths in the 4 first through the N-th received signals, respectively, wherein said determining step comprises the step of: detecting abnormality in said first through said N-th receiving sections on the basis of the first through the N-th received electric field strength signals to produce a receiving section abnormality detected signal indicative of the number of the receiving sections which normally operate, said actual transmission diversity gain being determined by the number of the receiving sections which normally operate, o D whereby said controlling step controls the transmission power by the actual transmission diversity gain corresponding to the number of the receiving sections which normally operate. e 8. A method as claimed in claim 5, said radio base station apparatus comprising first through N-th see*. transmission/reception antennas where N represents a positive integer which is not less than two, said radio base station apparatus further comprising first through N-th receiving sections, connected to said first through said N-th transmission/reception antennas, respectively, for receiving first through N-th received signals to produce first through N-th received electric field strength signals indicative of received electric field strengths in the first through the N-th received signals, respectively, wherein said determining steps comprises the steps of: detecting defects in said first through said N-th transmission/reception antennas to produce first through N-th alarm signals when the defects in said first through said N-the transmission/reception antennas are detected, A -36- respectively; monitoring the first through the N-th antenna alarm signals to produce an antenna abnormality detected signal indicative of the number of the transmission/reception antennas which normally operate, said actual transmission diversity gain being determined by the number of the transmission/reception antennas which normally operate; and detecting abnormality in said first through said N-th receiving sections on the basis of the first through the N-th received electric field strength signals to produce a receiving section abnormality detected signal indicative of the number of the receiving o 1 0 sections which normally operate, said actual transmission diversity gain being also -o determined by the number of the receiving sections which normally operate, whereby said controlling step controls the transmission power by the actual transmission diversity gain corresponding to a combination of the number of the transmission/reception antennas which normally operate and the number of the receiving sections which normally operate. S° 015 0 9. A radio base station apparatus substantially as herein described with reference to any one of the embodiments as illustrated in Figs. 4 to 7. oe*" *10. A method of controlling transmission power in a radio base station 20 apparatus substantially as herein described with reference to any one of the embodiments as illustrated in Figs. 4 to 7. DATED this Ninth Day of July, 1999 NEC Corporation Patent Attorneys for the Applicant SPRUSON FERGUSON [R:\LIBIF]05387.doc:IAD