JPH0955974A - Mobile communication device - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the utilization efficiency of spreading codes, increase the channel capacity for communication, and determine the location and base station during shadowing in a short time. [Structure] Direct spread CDMA / as a multiple access method
In the cellular mobile communication device that uses the FDD system or the direct spread CDMA / TDD system and performs the in-area determination using the perch channel spread with a specific spreading code for each base station, divides time into a plurality of time slots, The same number of base stations as the time slot period transmits the perch channel in a time division manner using the same spreading code and different time slots. The mobile station measures the reception levels in all spreading codes and all time slots, and identifies the base station with the highest level as the nearest base station.

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 in a cellular radio communication system such as a digital car phone and a mobile phone.

[0002]

2. Description of the Related Art CDMA (Code Division Multiple Acc)
The ess: code division multiple access) method is one of multiple access method technologies when a plurality of stations simultaneously communicate in the same frequency band in a cellular radio communication system such as a car phone and a mobile phone. Another technique is FDMA (Fr
frequency division multiple access: TDMA (Time Division Multiple Access)
s: Time-division multiple access) system is known, but CDM
The A method is a method capable of achieving higher frequency utilization efficiency as compared with these techniques and accommodating more users.

In the CDMA system, multiple access is performed by spread spectrum communication in which the spectrum of an information signal is spread and transmitted in a band sufficiently wider than the original information bandwidth. The direct spreading method is a method of multiplying an information signal by a spreading code as it is in spreading, and signals of a plurality of mobile stations are multiplexed in the same frequency domain and the same time domain.

TDD (Time Division Duplex) is a transmission / reception same-band system, also called a ping-pong system,
This is a method of performing communication by dividing the same radio frequency into transmission / reception. Compared to TDD, FDD (Frequency Divis
The ion duplex) method is a method in which transmission / reception is performed using different frequencies. FIG. 8A is a conceptual diagram of the TDD system, and FIG. 8B is a conceptual diagram of the FDD system. In FIG. 8A, the base station transmits and the mobile station receives at time T1, and the mobile station transmits and the base station receives at next time T2. By repeating this,
It realizes communication using a single frequency band. Figure 8
In (b), base station transmission / mobile station reception is performed at frequency f1, and mobile station transmission / base station reception is performed at frequency f2.

In the CDMA system using direct spreading, when a desired transmitting station is distant and an undesired transmitting station (interfering station) is nearby, the interfering station receives more than the received signal from the desired transmitting station. There is a "far-and-far problem" in which the received power of the signal becomes larger, the cross-correlation between the spread codes cannot be suppressed only by the processing gain (spreading gain), and communication becomes impossible. For this reason, in the cellular system using the direct spread CDMA system, transmission power control according to the state of each transmission line is essential in the uplink from the mobile station to the 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 an instantaneous value fluctuation of received power by controlling transmission power has been considered.

Paper "A study of transmission power control in CDMA / TDD transmission" (Miya, Hayashi, Kato, 1994 Shin-Gaku Spring semester, B
-418) and "POWER CONTROL IN PACKETS SWITCHED TIM
E DIVISION DUPLEX SEQUENSE SPREAD SPECTRUM COMMUNI
CATIONS ”(R.ESMAILZADEH, M.NAKAGAWA, A.KAJIWARA,
proc. of VTC'92.pp.989-992,1992), CDMA
A method of performing transmission power control in the / TDD system is shown. Fading has the symmetry that variations in transmission and reception are the same in the same frequency band. Therefore, in the CDMA / TDD system, by detecting the power of the received signal, grasping the propagation state by this, determining the transmission power level and using the open loop transmission power control for transmission, high-speed and highly accurate transmission power is obtained. Control can be performed.

The fluctuations in the propagation loss due to the fluctuations in the position of the mobile station include fading and fluctuations in the distance between the base station and the mobile station, as well as shadowing fluctuations. What is shadowing?
This is fluctuation due to factors such as the mobile station appearing in the line-of-sight position from the base station due to the shadow of the building, which causes the propagation loss between the mobile station and the base station to fluctuate rapidly over the entire frequency band. The variation in propagation loss due to shadowing is shown in FIG.
As shown in (a), the mobile station 52 communicating with the base station 51.
Is within the line-of-sight range 54 of the base station 51 from the shadow of the building 53, and as shown in FIG. 9B, a mobile station 56 that is in communication with the base station 55 and is under the transmission power control of the base station 55 ,
It may be behind a building 58 with respect to another base station 57 from which it may be within the line-of-sight range 59 of the base station 57. At this time, the received power from the mobile station 52 reaching the base station 51 and the received power from the mobile station 56 reaching the base station 57 increase, and the other mobile stations communicating with the base station 51 and the base station 57. The interference given to all increases, and the communication quality deteriorates.

On the other hand, in the case of FIG. 9A, the mobile station 52 can cope with this by performing the conventional transmission power control to lower the transmission power of the mobile station 52. However, in the case of FIG. 9B, the conventional transmission power control method is
Since the control is based on the reception level from the mobile station 56 in the base station 55, appropriate control cannot be performed and interference with all mobile stations in communication with the base station 57 cannot be reduced. Therefore, in this case, the mobile station 56 needs to promptly switch the communication destination to the base station 57 and perform transmission power control with the base station 57. This base station switching process is called handover. In order to realize this handover processing,
The mobile station needs to quickly identify with which base station the shadowing has occurred.

Also, when the mobile station is turned on or when communication with the base station is cut off, which base station is the mobile station currently closest to and which is the best for communication? Need to be identified. This is called presence determination.

In a cellular radio communication system using the CDMA system, a method conventionally considered for identifying a base station and determining a location in a handover is that the base station is
The nearest base station is specified by transmitting a perch channel for base station identification to which a different spreading code is assigned to each base station, and receiving the perch channel of all base stations by the mobile station and measuring the reception level. Is to do. FIG. 10 shows an example of a specific spreading code allocation method. A circle 60 in the figure is a communication area in which each base station communicates, and the number in the circle is the number of the spreading code for the perch channel used by each base station. When six spreading codes 0 to 5 are allocated to the perch channel, one of the six spreading codes prepared is allocated to each base station. If the total number of base stations is greater than 6, the spreading code will be used repeatedly. In that case, the base stations using the same spreading code (spreading codes 0 and 2 in the figure) are the perch channels. However, since the mobile stations receiving one of the perch channels interfere with each other, the distance is set as large as possible so as to suppress the interference due to the distance attenuation.

[0012]

However, the conventional method has a problem that the number of spreading codes assigned to the perch channel is large because different spreading codes are used for each base station. Also, at the time of the presence determination, the mobile station measures the spread code level of all base stations, but in that case, it is necessary to switch the code to be measured for each base station, and the code switching process is frequently performed. In particular, there is a problem that it takes time to identify a base station during shadowing. Furthermore, since each base station transmits a perch channel, there is a problem that the channel capacity for communication is reduced accordingly.

The present invention solves the above-mentioned conventional problems, and uses mobile codes for perch channels, which are less in number than the conventional ones, to enable base station identification at high speed and to increase channel capacity. The purpose is to provide a device.

[0014]

In order to achieve the above-mentioned object, the present invention uses a CDMA system as a multiple access system, and uses a perch channel spread by a spreading code specific to each base station to determine a presence area. In the mobile communication device to be performed, the time is divided into a plurality of time slots, and the same number of adjacent base stations as the time slot period is used to transmit the perch channel in a time division manner by using different time slots with the same spreading code. It is a thing.

[0015]

Therefore, according to the present invention, the time is divided into a plurality of time slots, and the same number of adjacent base stations as the time slot period divides the perch channel into time divisions by using different time slots with the same spreading code. Since the transmission is performed, if the time slot period is N, the number of spreading codes assigned to the perch channel can be reduced to 1 / N. In addition, when determining the presence of a service area, the mobile station measures the spread code levels of all base stations. In this case, the level of N base station perch channels can be measured without switching the codes to be measured. Further, since each base station transmits perch channels in a time division manner, the perch channels transmitted from all the base stations at the same time become 1 / N, and the channel capacity for communication increases accordingly.

[0016]

【Example】

(Embodiment 1) FIG. 1 shows the configuration of a base station apparatus in Embodiment 1 of the present invention. This embodiment is an embodiment in the case of using a direct sequence CDMA / FDD system as an access system. In FIG. 1, 1 is the entire base station side device, 2 is transmission data for a mobile station, and 3 is a baseband processing unit. The baseband processing unit 3 is composed of a transmission baseband processing unit 4 and a reception baseband processing unit 5, and is controlled by a control signal from the control unit 6. 7 is an adder for adding the signal from the perch channel generation unit 8 and the signals from the baseband processing unit 3 and the baseband processing unit 9 for other mobile stations to perform digital / analog conversion, and 10 is digitized A transmission RF unit for transmitting transmission data through the antenna 11. 1
On the contrary, 2 is a reception baseband processing unit 5 by frequency-converting a signal received by the antenna 11 and performing analog / digital conversion.
The reception RF section 13 to be passed to is reception data which has been subjected to reception processing.

Next, the operation of the base station apparatus 1 will be described. The transmission data 2 input to the baseband processing unit 3 is subjected to channel coding, modulation processing, and spreading processing by superimposing a spreading code in the transmission baseband processing unit 4, and is input to the adder 7. . Control unit 6
Outputs a control signal to the perch channel generation unit 8, and the perch channel generation unit 8 outputs the perch channel signal spread by the spreading code assigned to the base station apparatus 1 according to the input control signal. , Is output to the adder 7 only in the allocated time slot section. The adder 7 adds the output of the transmission baseband processing unit 3 and the outputs of the other mobile station baseband processing units 9 and the output of the perch channel generation unit 8 to perform digital / analog conversion, and then transmit RF. Output to the unit 10. In the transmission RF unit 10, the input from the adder 7 is subjected to waveform shaping, frequency conversion into a carrier frequency, and amplification processing, and is transmitted from the antenna 11 to the mobile station side device.

On the other hand, the receiving RF section 12 receives the received signals from all mobile stations from the antenna 11, performs waveform shaping, frequency conversion to baseband, analog / digital conversion, and outputs to the baseband processing section 3. The received signal input to the baseband processing unit 3 is subjected to correlation detection processing, demodulation processing using the same code as the spreading code used in the mobile station side device in the reception baseband processing unit 5,
The received data 13 is obtained by performing the decoding process.

FIG. 2 shows the configuration of spreading codes and time slots assigned to the perch channels of a plurality of base stations when the time slot period is set to 8 in the first embodiment. A circle 14 in FIG. 2A is a communication area in which each base station communicates. The vertical axis of FIG. 2B is the spreading code number, the horizontal axis is time, and the cycle is divided into eight time slots 15. The method of determining the spreading code and time slot to be assigned when transmitting the perch channel of each base station will be described below. First, all base stations are divided into groups of 8 stations that are close to each other, and the same code is used as the spreading code of the perch channel within the group. In the figure, the base stations A to H forming the group 0 use the code of code number 0, and the base stations I to P forming the group 1 use the code of code number 1 as the spreading code of the perch channel. One of eight time slots is assigned to each base station, the perch channel is transmitted in bursts, and the base stations in the group are assigned so that the time slots for transmitting the perch channel are not the same. In group 0 of FIG. 2, time slots 0 to 7 are allocated to base stations A to H, and a perch channel is transmitted.

By configuring the perch channel as described above, the number of spreading codes assigned to the perch channel can be reduced to 1/8 and the spreading code utilization efficiency can be improved. Furthermore, since each base station transmits perch channels in a time division manner, the number of perch channels transmitted from all base stations at the same time is reduced to 1/8, and the number of channels for communication can be increased by that amount, and the subscriber capacity can be increased. You can increase.

FIG. 3 shows the configuration of the mobile station side apparatus in the first embodiment. In the mobile station device 16, the signal from the base station received from the antenna 17 is received by the reception RF unit 18.
Is input to The reception RF section 18 performs waveform shaping, frequency conversion to baseband, analog / digital conversion, and outputs the result to the reception baseband processing section 19 and reception level measurement circuit 20. The reception baseband processing unit 19 performs a correlation detection process on the input reception signal using the same code as the spreading code used in the base station, and the received signal is addressed to the own mobile station from the signal multiplexed in the base station. The desired wave signal of 1 is separated, and further the synchronization processing, the demodulation processing, and the decoding processing are performed to obtain the reception data 21. The reception level measuring circuit 20 measures the desired wave signal component of the reception power level from the reception signals multiplexed in the base station, and inputs the measurement result to the control unit 22.

On the other hand, the transmission data 23 to the base station is input to the transmission baseband processing unit 24. The transmission baseband processing section 24 performs transmission path coding, modulation processing, spreading processing by superimposing a spreading code on the transmission data 23, and digital / analog conversion, and then outputs the data to the transmission RF section 25. The transmission RF unit 25 performs waveform shaping, frequency conversion to carrier frequency, and amplification processing, and transmits from the antenna 17 to the base station side device.

The operation of the mobile station in the above-mentioned configuration at the time of determining the presence area will be described. It is assumed that the mobile station stores the perch channel spreading codes used in all the base stations in the system, and the reception level measuring circuit 20 measures the reception levels of the spreading codes of all the perch channels in all time slots. The measurement result is input to the control unit 22. The control unit 22 creates a table in the order of reception levels as shown in FIG. 4 using the reception level in each spreading code and each time slot, and identifies the base station with the highest level as the nearest base station. , Communicate with the base station. In the case of FIG. 4, the mobile station is within the range of the base station H of group 0, and the base station F is determined to be an adjacent base station.

By the above processing, when measuring the level of the perch channel, the same spreading code is used for the perch channels of the same group and they are transmitted in time division. Therefore, the spreading code to be measured is set in the reception level measuring circuit. The frequency of switching can be reduced, and the time required for determining the presence area can be shortened. Further, even during shadowing, the base station can be identified at high speed.

(Embodiment 2) FIG. 5 shows the configuration of a base station apparatus in Embodiment 2 of the present invention. This embodiment is an embodiment in the case of using a direct sequence CDMA / TDD system as an access system. Since the TDD system is used, the base station apparatus repeats the operations of transmission (T1) and reception (T2) for transmission and reception, as shown in FIG. In FIG. 5, reference numeral 25 is a base station side device, 26 is transmission data, and 27 is a baseband processing unit, which includes a transmission baseband processing unit 28 and a reception baseband processing unit 29. Reference numeral 30 is a control unit, 31 is an adder, 32 is a perch channel generation unit, and 33 is another mobile station baseband processing unit. Reference numeral 34 is a transmission RF unit, 35 is a switch, 36 is an antenna, 37 is a reception RF unit, and 38 is reception data.

Next, the base station side device 25 in this embodiment
The operation of will be described. First, at the time of transmission, it operates as follows. The transmission data 26 for a certain mobile station is input to the baseband processing unit 27, and by the control signal from the control unit 30, the transmission baseband processing unit 28 superimposes channel coding, modulation processing, and spreading code. Diffusion processing is performed and input to the adder 31. The control unit 30 also outputs a control signal to the perch channel generation unit 32, and the perch channel generation unit 32 is spread by the spreading code assigned to this base station side device 25 according to the input control signal. The perch channel signal is output to the adder 31 only in the assigned time slot section. In the adder 31, the output of the transmission baseband processing unit 28, the output of the other mobile station baseband processing unit 33, and the output of the perch channel generation unit 32 are added, and after performing digital / analog conversion,
Output to the transmission RF unit 34. The transmission RF unit 34 performs waveform shaping, frequency conversion into a carrier frequency, and amplification processing on the input from the adder 31, and outputs it to the switch 35.
In the transmission operation, the switch 35 connects the transmission RF unit 34 and the antenna 36, and the output of the transmission RF unit 34 is transmitted from the antenna 36 to the mobile station side device.

On the other hand, when receiving, it operates as follows. In the receiving operation, the switch 35 includes the receiving RF unit 37 and the antenna 3
6 are connected, and the received signals from all mobile stations are received from the antenna and input to the reception RF section 37. Receive R
In the F section 37, waveform shaping, frequency conversion to baseband,
Then, analog / digital conversion is performed and the result is output to the baseband processing unit 27 of each mobile station. The reception signal input to the baseband processing unit 27 is processed by the reception baseband processing unit 29 in a correlation detection process, a demodulation process using the same code as the spreading code used in the mobile station side device,
Decryption processing is performed to obtain received data 38.

FIG. 6 shows the configuration of spreading codes and time slots assigned to perch channels of a plurality of base stations when the time slot period is set to 8 in the second embodiment, as in the first embodiment. In the second embodiment, TD
The transmission / reception unit time of D and the time slot length are matched. The area for grouping the base stations and performing communication is the same as in FIG. The vertical axis of FIG. 6 is the spreading code number,
The horizontal axis represents time, and the cycle is divided into eight time slots 39. Furthermore, the length of one time slot is made to match the TDD unit. The spreading code and time slot allocation method to each base station is the same as in the first embodiment. Similar to the first embodiment, even when the CDMA / TDD method is used as the access method, by configuring the perch channel as described above, the number of spreading codes assigned to the perch channel can be reduced to 1/8, and the spreading code can be reduced. The utilization efficiency of can be improved. Furthermore, since each base station transmits perch channels in a time division manner, the number of perch channels transmitted from all base stations at the same time is reduced to 1/8, and the number of channels for communication can be increased by that amount, and the subscriber capacity can be increased. You can increase.

FIG. 7 shows the configuration of the mobile station side apparatus in the second embodiment. Similarly to the base station side apparatus, the mobile station side apparatus in the present embodiment also repeats the transmission operation and the reception operation in time. However, when the base station side device is in the transmitting operation, the mobile station side device is in the receiving operation, and conversely, when the base station side device is in the receiving operation, the mobile station side device is in the transmitting operation.

In FIG. 7, the mobile station side device 40 uses the switching device 41 to receive RF section 42 and antenna 4 when receiving.
3 is connected, and the signal from the base station received from the antenna 43 is input to the reception RF unit 42. In the reception RF unit 42, waveform shaping, frequency conversion to baseband, analog /
The digital conversion is performed and output to the reception baseband processing unit 44 and the reception level measuring circuit 45. The reception baseband processing unit 44 performs correlation detection processing on the input reception signal using the same code as the spreading code used in the base station, and the target signal is addressed to the own mobile station from the signal multiplexed in the base station. The desired wave signal of 1 is separated, and the synchronization process, the demodulation process, and the decoding process are further performed to obtain the reception data 46. The reception level measuring circuit 45 measures the desired wave signal component of the reception power level from the reception signals multiplexed in the base station, and inputs the measurement result to the control unit 47.

On the other hand, at the time of transmission from the mobile station side device 40, the transmission data 48 to the base station is transmitted by the transmission baseband processing unit 49.
Is input to The transmission baseband processing unit 49 performs transmission path coding, modulation processing, spreading processing by superimposing a spreading code, and digital / analog conversion on the transmission data 48, and then outputs it to the transmission RF unit 50. In the transmission RF unit 50, waveform shaping, frequency conversion to carrier frequency, and amplification processing are performed, and the result is input to the switch 41. Since the switch 41 connects the transmission RF unit 50 and the antenna 43, the output of the transmission RF unit 50 is transmitted from the antenna 43 to the base station side device.

The operation of the mobile station at the time of determining the presence is the same as that of the first embodiment. Therefore, as in the first embodiment, when the level of the perch channel is measured, the same spreading code is used for the perch channels of the same group and they are transmitted in time division. Therefore, the spreading code to be measured by the reception level measuring circuit. It is possible to reduce the frequency of switching between, and it is possible to shorten the time required to determine the location and speed up the identification of the base station during shadowing.

[0033]

As is apparent from the above embodiment, the present invention is a direct access CDMA / FDD as a multiple access system.
In the mobile communication device that uses the perch channel or the direct spread CDMA / TDD system to perform the area determination using the perch channel, the time is divided into a plurality of time slots, and the same number of adjacent base stations as the time slot period spreads the same. Since the perch channels are transmitted in time division by using different time slots in the code, it is possible to improve the utilization efficiency of the spreading code assigned to the perch channels, increase the channel capacity for communication, and determine the location within a short time. A cellular mobile communication device that identifies a base station during shadowing can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a base station side device according to a first embodiment of the present invention.

FIG. 2A is a diagram showing allocation of spreading codes for perch channels according to the first embodiment of the present invention. FIG. 2B is a configuration diagram of spreading codes for perch channels and time slots according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a mobile station side apparatus in Embodiment 1 of the present invention.

FIG. 4 is a list view of reception level measurement results of a perch channel of a mobile station according to the first embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a base station side device according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of spreading codes and time slots of a perch channel according to the second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a mobile station side device in Embodiment 2 of the present invention.

FIG. 8 is a conceptual diagram of the TDD method and the FDD method.

[Figure 9] Conceptual diagram of shadowing

FIG. 10 is a diagram showing allocation of spreading codes for perch channels in a conventional example.

[Explanation of symbols]

 1 base station side device 2 transmission data 3 baseband processing unit 4 transmission baseband processing unit 5 reception baseband processing unit 6 control unit 7 adder 8 perch channel generation unit 9 baseband processing unit for other mobile stations 10 transmission RF unit 11 antenna 12 reception RF section 13 reception data 14 communication area in which base station communicates 15 time slot 16 mobile station side device 17 antenna 18 reception RF section 19 reception baseband processing section 20 reception level measurement circuit 21 reception data 22 control section 23 Transmission data 24 Transmission baseband processing unit 25 Transmission RF unit

Claims (2)

[Claims] 1. A direct spread CDM as a multiple access method
It has a plurality of base stations and a plurality of mobile stations equipped with A / FDD communication means, the base station divides time into a plurality of time slots, and the same number of base stations as the time slot period has the same spreading code. In a perch channel transmitting means for transmitting time-division perch channels using different time slots, the mobile station is provided with a perch channel receiving means and a reception level measuring means, and receives the perch channels of all base stations A mobile communication device characterized in that the closest base station is specified by measuring a reception level. 2. Direct spread CDM as a multiple access method
2. The mobile communication device according to claim 1, which has a plurality of base stations and a plurality of mobile stations equipped with a communication means based on a direct spread CDMA / TDD system instead of the A / FDD system.