CN1099774C - Mobile communication equipment - Google Patents

Abstract

When CDMA/TDD is used for data communication between the base station device and the mobile station device, VOX control is performed on the base station device and the mobile station device to perform or stop the transmission operation according to the presence or absence of data transmission, and the transmission is stopped on the base station transmission side When the mobile station receives and receives the channel usually sent by the base station device, it performs open-loop transmission power control. Receive empty time slots for transmit space diversity.

Description

Mobile station device and transmission power control method thereof in wireless communication system

technical field

The present invention relates to mobile station devices used in cellular wireless communication systems such as digital car phones and mobile phones, and particularly relates to open-loop transmission power control and mobile station devices for preventing deterioration of transmission diversity performance during VOX (Voice Operated Transmission) control.

Background technique

In cellular wireless communication systems such as automobile phones and mobile phones, the CDMA (Code Division Multiple Access) method is known as a multiple access technology capable of simultaneously communicating with multiple mobile stations on the same frequency band. In the multiple access technology, it is already known that there are other methods such as FDMA (Frequency Division Multiple Access: Frequency Division Multiple Access) and TDMA (Time Division Multiple Access: Time Division Multiple Access). Compared with these technologies, the CDMA method can achieve higher frequency utilization efficiency and include more users, and has a good effect in this respect.

In order to distinguish multiple users who share the same frequency band, the CDMA method uses the user's inherent spreading code, multiplies the spreading code and the information signal, and spreads the spectrum of the information signal into a frequency band much wider than the original information bandwidth for transmission. A spread spectrum communication for multiple access connections. In particular, a method of multiplying an information signal by a spreading code as it is is called a direct spreading method. In the direct spread CDMA mode, the signals of multiple mobile stations are multiplexed in the same frequency band and the same time period.

In addition, there is TDD (Time Division Duplex: Time Division Duplex) method as a wireless communication method that uses the same frequency band for reception and transmission. The TDD method is also called a two-way method, and is a method of time-sharing communication using the same radio frequency when receiving and sending. Compared with the TDD method, there is also the FDD (Frequency Division Duplex: Frequency Division Duplex) method. The FDD method is a method of performing communication using different frequencies for reception and transmission.

FIG. 5A is a conceptual diagram of the TDD method, and FIG. 5B is a conceptual diagram of the FDD method. In FIG. 5A, the base station transmits and the mobile station receives at time T1. At the next time T2, the mobile station transmits and the base station receives. By repeating this process, communication using a single frequency band is realized.

In FIG. 5B, the base station transmits at frequency f1 and the mobile station receives, while the mobile station transmits at frequency f2 and the base station receives. The time unit for this transmission or reception is called a slot (Slot).

In the direct spread CDMA method, when a desired transmitting station is far away and an undesired transmitting station (interfering station) is close, a so-called "near-far problem" occurs. In this case, the received power of the signal from the interfering station is higher than that of the received signal from the desired transmitting station. This causes a problem that the cross-correlation between spreading codes cannot be completely suppressed only by the processing gain (spreading gain), and it becomes Cannot communicate.

For this reason, in a cellular radio communication system employing the direct spread CDMA scheme, it is necessary to control the transmission power in the uplink path from the mobile station to the base station according to the state of each transmission path.

In addition, in land mobile communications, fading is a cause of path quality deterioration. As a countermeasure against fading, a method of compensating for changes in the instantaneous value of received power by controlling the transmitted power can be considered.

Papers "Discussion on Transmitting Power Control in CDMA/TDD Transmission" (Miya, Lin, Kato, 1994 Spring National Conference of Electronic Information and Communication Society, B-418) and "POWER CONTROL IN PACKETS SWITCHED TIMEDIVISION DUPLES SEQUENSE SPREAD SPECTRUM COMMUNICATIONS" (R .ESMAILZADEH, M.NAKAGAWA, A.KAJIWARA, proc.of VTC'92.pp.989-992, 1992) gives the method of the transmission power control in the CDMA/TDD scheme.

If the fading is in the same frequency band, the changes in transmission and reception are the same and have this symmetry. Therefore, the CDMA/TDD method adopts open-loop transmission power control, that is, detects the power of the received signal, and grasps the transmission status accordingly, and then determines the transmission power level for transmission according to the transmission status. In this way, in the CDMA/TDD method, compared with the FDD method, it is possible to perform simple, high-speed and high-accuracy transmission power control.

As a countermeasure against fading, another space diversity technique is also effective. Space diversity technology is a technology that uses multiple antennas at different positions to receive radio waves, and then synthesizes and demodulates the received signals. Since the fading variation of the received signal has no correlation with each transmission path, it is possible to reduce the probability of a sharp drop in the received power level due to fading, and to suppress the deterioration of the received quality.

In the TDD method, the transmission and reception symmetry of the fading change of the wireless transmission path is still used, and multiple antennas are installed in the base station. In the reception of the base station, diversity reception is performed on the base station side, and the transmission environment of each antenna is analyzed. Detect, when transmitting from the base station, use the best antenna. In this way, even if the mobile station has only one antenna, spatial diversity can be performed on the downlink, and communication quality can be improved without increasing the hardware scale of the mobile station.

The paper "Scheme of Base Station Transceiver Diversity in CDMA/TDD Transmission" (Gong et al., BCS 94-73, p25-30, 1994-09) provides a method of transmitting space diversity in CDMA/TDD.

The VOX control of mobile phones, etc. is to transmit only when there is sound to be transmitted, and to stop transmission when there is no sound to be transmitted. This is a technology aimed at saving energy. In the CDMA way, VOX control technology is the main technology to increase the system capacity.

Unlike TDMA and FDMA, where the system capacity is fixed, in CDMA, the system capacity is determined based on the amount of interference from users communicating at the same time. This is called soft capacity (SoftCapacity). The system capacity in the CDMA way can increase capacity by reducing interference.

Using VOX to stop sending means reducing interference to other users in this state, which is related to increasing system capacity. For example, when the voiced/non-voiced ratio of all users is 50%, statistically speaking, the number of users who transmit at the same time is half, and as a result, the capacity is doubled.

However, in the case of performing VOX control in the CDMA/TDD system, when there is no sound, there are slots for non-transmission. Accordingly, the state of the transmission path cannot be estimated from the signal at the time of reception in the non-transmission time slot on the receiving side. As a result, there is a problem that open-loop transmission power control and transmission space diversity cannot be performed, and the speed of fading change that can be tracked by the control is slow, and the speed performance is deteriorated.

invention disclosure

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mobile station apparatus that does not degrade open-loop transmission power control and transmission diversity performance even when VOX control is performed.

In order to achieve the aforementioned object, in the VOX control of the present invention, when the base station transmission side stops sending, the mobile station receives the channel that the base station usually sends all the time, and performs open-loop transmission power control. When the mobile station stops sending, the transmission power is reduced The empty time slots are used for transmission, and the base station receives empty time slots for transmission space diversity.

The communication system of the present invention has a plurality of base stations and a plurality of mobile stations, and the plurality of base stations and the plurality of mobile stations have a direct spread CDMA/TDD (Code Division Multiple Access/Time Division Duplex) method as a multiple access method. The communication means has a VOX function that transmits or stops transmission according to the presence or absence of transmission data in the base station and the mobile station, and has a plurality of antennas in the base station, and has signals to be received by the aforementioned plurality of antennas at the time of TDD reception Combined receive diversity function and transmit diversity function for transmitting at TDD transmit time using the antenna with the maximum receive power at TDD receive time, when the mobile station has a null signal with lower than normal transmit power when transmission is stopped function to send.

According to such a communication system, even when the mobile station stops transmission during VOX control, it is possible to suppress deterioration of transmission space diversity performance in the base station by using a null signal.

In another communication system of the present invention, the base station has a control channel transmission function for transmitting and receiving control information that is commonly connected to a plurality of mobile stations, and the mobile station has a function of detecting the power level of the received signal at the time of TDD reception. It includes the transmission power control function of controlling the transmission power at the time of TDD transmission, and the function of receiving the aforementioned control channel to perform transmission power control when the base station stops transmitting.

According to this communication system, even when the base station stops transmission during VOX control, the mobile station receives the control channel and uses it for transmission power control, thereby suppressing performance deterioration of open-loop transmission power control.

Brief description of the drawings

FIG. 1 is a functional block diagram of a base station side device of a cellular wireless communication system according to an embodiment of the present invention.

Fig. 2 is a functional block diagram of a mobile station side device in a cellular wireless communication system according to an embodiment of the present invention.

FIG. 3 is a frame diagram of the embodiment of the present invention.

FIG. 4A is a frame structure diagram in the case where only the mobile station stops sending according to the embodiment of the present invention.

FIG. 4B is a frame structure diagram when both the base station and the mobile station stop transmitting according to an embodiment of the present invention.

FIG. 5A is a conceptual diagram showing the concept of the TDD method.

FIG. 5B is a conceptual diagram showing the concept of the FDD method.

The best form for carrying out the invention

A cellular wireless communication system with a base station side device and a plurality of mobile station side devices using an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the base station side device in the cellular wireless communication system related to this embodiment, and FIG. 2 shows the mobile station side device in the same cellular wireless communication system. In the cellular wireless communication system of this embodiment, it is assumed that data communication is performed between the base station and the mobile station using CDMA/TDD.

In the base station device 1, a plurality of baseband processing units 2-1 to 2-n are arranged side by side. In a cellular radio communication system, since a base station communicates with a plurality of mobile stations simultaneously, the number of baseband processing units 2-1 to 2-n corresponds to the maximum number of mobile stations capable of simultaneous communication. In the following, baseband processing units 2-1 to 2-n are only described as the baseband processing unit 2 without distinguishing each one.

The base station side apparatus 1 transmits the transmission data 3 of the mobile station in the TDD base station transmission slot. In the TDD scheme, each slot constituting a frame is time-divided into a base station transmission slot and a mobile station transmission slot. When the base station is in the transmit slot, the mobile station is in the receive slot. Also, when the mobile station is in the transmitting slot, the base station is in the receiving slot.

The transmission data 3 is input to the baseband processing unit 2 . The transmission data 3 is sent to the encoder 4 in the baseband processing unit 2 . The encoder 4 encodes the transmitted data 3 to form a frame structure and outputs it to the expander 5 . The spreader 5 in the baseband processing unit 2 assigns a different spreading code to each mobile station. The spreader 5 spreads the transmission data constituting the frame structure with a spreading code unique to the mobile station of the transmission source. The spectrum spread transmission data is supplied to the switch 6 . The switch 6 outputs the transmission data to either the first adder 7-1 or the second adder 7-2 using a signal supplied from a diversity combiner described later. Also, the control channel generator 8 outputs the control channel signal spread with the dedicated spreading code to the first adder 7-1. The first adder 7-1 and the second adder 7-2 add the outputs of the plurality of baseband processing units 2-1 to 2-n and the control channel generator 8. Each output of the first adder 7-1 and the second adder 7-2 is output to the corresponding first transmission RF unit 9-1 and second transmission RF unit 9-2, respectively. The first transmission RF unit 9-1 and the second transmission RF unit 9-2 perform modulation, frequency conversion and amplification processing on the input transmission data, respectively, through the first switch 10-1 and the second switch 10-2 respectively from the first switch 10-1 and the second switch 10-2 The antenna 11-1 and the second antenna 11-2 transmit to the wireless transmission path.

Also, the base station side apparatus 1 receives multiplexed signals from a plurality of mobile stations in a TDD base station reception slot. The first antenna 11-1 and the second antenna 11-2 receive signals sent from multiplexed signals of multiple mobile stations through different wireless transmission paths, and output them to the first receiving RF unit 12-1 and the second receiving RF unit 12-1, respectively. Receive RF unit 12-2.

The first receiving RF unit 12-1 and the second receiving RF unit 12-2 perform frequency conversion, automatic gain control processing, and demodulation processing on the multiplexed received signals, and output them to a plurality of baseband processing units 2-1 to 2- n. The outputs of the first receiving RF unit 12 - 1 and the second receiving RF unit 12 - 2 are input in parallel to correlators 13 - 1 and 13 - 2 provided in the baseband processing unit 2 . The correlators 13-1 and 13-2 perform correlation processing on the output of the first receiving RF unit 12-1 and the second receiving RF unit 12-2 with the mobile station-specific spreading code of the transmission source, and separate the signal for the own station. . The separated signals are RAKE-combined by RAKE (rake) combiners 14-1 and 14-2, and then output to diversity combiner 15.

The diversity combiner 15 combines the output of the first RAKE combiner 14 - 1 and the output of the second RAKE combiner 14 - 2 , and outputs the combined result to the decoder 16 . On the other hand, the diversity combiner 15 compares the output of the first RAKE combiner 14-1 and the output of the second RAKE combiner 14-2, and determines the antenna to be used for transmission in the next transmission slot in TDD. It is judged whether to transmit by the first antenna 11-1 or by the second antenna 11-2. A selection signal indicating the antenna used for transmission is output from the diversity combiner 15 to the switch 6 . Decoder 16 decodes the input to obtain received data 17 .

In addition, the mobile station side device 18 transmits the transmission data 19 addressed to the base station in the TDD mobile station transmission slot. Transmit data 19 is input to encoder 20 . The encoder 20 encodes the transmission data 19 to form a frame structure. The transmission data constituting the frame structure is input to the spreader 21 . At this time, the null signal generator 22 outputs a null signal to the expander 21 at a predetermined timing described later. The spreader 21 spreads the input signal with a different spreading code for each mobile station, and outputs the spread signal to the transmitting RF unit 23 . The transmitting RF unit 23 performs modulation, frequency conversion and amplification processing on the input signal. The output of the transmission RF unit 23 is transmitted from the antenna 25 to the wireless transmission path through the switch 24 .

In addition, the mobile station side device 18 receives a transmission signal from the base station in a TDD mobile station reception slot. The signal from the base station received by the antenna 25 is output to the receiving RF unit 26 . The receiving RF unit 26 performs frequency conversion, automatic gain control processing, and demodulation processing on the multiplexed received signal, and outputs it to the correlator 27 . The correlator 27 performs correlation processing using different spreading codes for each mobile station, and separates the signal for itself from the output of the receiving RF unit 26 . The separated signals are RAKE-combined by a RAKE combiner 28 , decoded by a decoder 29 , and output as received data 30 .

In addition, the output of the correlator 27 is input to the reception level detection circuit 31 . The reception level detection circuit 31 detects the average output power of the mobile station in the transmission slot, and uses this value to determine the transmission power of the next transmission slot for time division multiplexing, and outputs a control signal to the transmission RF unit 23 .

Figure 3 shows the frame structure for sending data. As shown in FIG. 3 , one frame is composed of a plurality of time slots, and the frame is determined so that the transmission time slot of the base station comes first. In the example shown in the figure, one frame is composed of eight slots. Each frame transmits a status notification bit 32 indicating whether there is data in the frame in the first slot of the frame. Therefore, even when no data is to be transmitted, the first slot of the frame must be transmitted, and the presence or absence of transmission data is switched in units of frames.

Next, the operation at the time of VOX control in the cellular radio communication system constructed as above will be described. Three cases are described in which only the base station stops transmission, only the mobile station stops transmission, and both the base station and the mobile station stop transmission.

This is only the case where the base station side device stops the transmission operation.

The base station side apparatus 1 transmits the status notification bit 32 indicating that the transmission operation is stopped in the first slot of the frame, and stops transmission in the following 7 slots.

The first slot is received by the mobile station side apparatus 18, and the status notification bit 32 indicating that the transmission operation is stopped is transmitted in this first slot. The mobile station side device 18 knows that there is actually no data in the received frame by checking the content of the status notification bit 32 received in the first slot of the received frame.

In the case where the status notification bit 32 is received at the top slot of the received frame, the correlator 27 separates a signal for itself only for the status notification bit 32 of the top slot using a spreading code assigned to each mobile station. The reception level detection circuit 31 detects the power of its own signal from the reception signal of the first slot in order to perform transmission power control. The correlator 27 performs correlation processing on the last 7 slots of the received frame to which the status notification bit 32 is transmitted in the first slot, using the spreading code of the control channel normally transmitted in the receiving slot. The reception level detection circuit 31 detects the power of the correlation value related to the control channel for the last seven slots, and performs transmission power control based on the detection result.

Therefore, even when no signal is transmitted from the base station side apparatus 1, the control interval of the transmission power control does not change in the mobile station side apparatus 18, and performance degradation can be suppressed.

Only when the mobile station side device stops the transmission operation

The mobile station side device 18 transmits the state notification bit 32 indicating that the transmission operation is stopped in the first slot of the transmission frame, and transmits a null signal in the last seven slots of the transmission frame. FIG. 4A shows the transmission state of each slot when only the mobile station side device stops the transmission operation. The null signal is formed by expanding the null signal generated by the null signal generator 22 by the expander 21 .

In the first time slot of the frame, the base station side device 1 utilizes the correlators 13-1 and 13-2 and the RAKE combiners 14-1 and 14-2 in the same way as in the usual case to transmit the data from the first antenna 11-1 and the second antenna 11-2 The power of the hoped signal of the received signal separation selects the transmitting antenna for the next transmission, and utilizes the correlators 13-1 and 13-2 and the RAKE synthesizer 14-1 and 14-2 The power of the null signal separated from the signals received by the first antenna 11-1 and the second antenna 11-2 selects the transmission antenna for the next transmission.

In this way, similar to the case where the mobile station side apparatus 18 has transmission data, transmission space diversity can be performed.

Also, for the purpose of antenna selection on the base station side, a null signal is transmitted from the mobile station side. When the null signal is used only for antenna selection on the base station side, it is sufficient to transmit the null signal at a lower transmission power than a normal slot. Therefore, the mobile station side apparatus 18 performs control so that the transmission power of the null signal is lower than the transmission power of the normal slot. In this way, interference with other users can be reduced.

The case where both the base station side device and the mobile station side device stop the transmission operation.

The open-loop transmission power control of the mobile station side device 18 is controlled in the same manner as when only the base station side device 1 stops transmission.

The base station side apparatus 1 transmits only the first slot in the frame. In order for the base station side device 1 to select a transmission antenna when transmitting the transmission data of the first slot, it is only necessary that there is a received signal in the previous reception slot, that is, the last slot of the previous frame. Therefore, the mobile station side device 18 transmits a null signal only in the last slot of one frame. Therefore, there is a time slot in which the mobile station side apparatus 18 completely stops transmission, and the effect of reducing interference to other users can be further enhanced.

Possibility of industrial use

As described above, the mobile station apparatus according to the present invention is useful for VOX control in a cellular radio communication system employing the CDMA/TDD scheme, and is suitable for open-loop transmission power control and suppressing degradation of transmission diversity performance during VOX control.

Claims (6)

1. A mobile station device, characterized in that it comprises: a checking part that checks whether the data is sent from the base device; and a control section, if data is transmitted from the base station apparatus, the control section controls the transmission power of the time slot transmitted to the base station apparatus according to the reception power of the data, and if no data is transmitted from the base station apparatus, the control section controls the transmission power of the time slot according to the control channel signal The receive power of controls the power of the time slot sent to the base station device, and the control channel signal is always sent from the base station device. 2. The mobile station device according to claim 1, wherein the checking section checks whether the data is transmitted from the base station device by referring to a status notification bit included in the received frame in the first time slot of . 3. The mobile station device according to claim 1, further comprising: In the sending part, if no data is sent to the base station device, another status notification bit is sent in the first time slot of the sending frame, and a null bit is also sent in at least one other time slot except the first time slot of the sending frame. The other status notification bit indicates that no data is sent to the base station device, and the null signal is used to select a transmitting antenna at the base station device. 4. The mobile station apparatus according to claim 3, wherein said transmission section transmits said null signal in at least one slot of a transmission frame. 5. The mobile station apparatus according to claim 3, wherein said transmission unit transmits lower power for a slot containing a null signal than for a slot not containing the null signal. 6. A transmission power control method for a mobile station device, characterized in that the transmission power control method comprises the following steps: check if data is sent from the base device; and If data is transmitted from the base station device, the time slot transmission power to the base station device is controlled according to the received power of the data, and if no data is transmitted from the base station device, the transmission to the base station device is controlled according to the received power of the control channel signal The time slot transmission power of , the control channel signal is always transmitted from the base station device.

Images