JPH11191896A - Receiver for cdma cellular system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a time required for cell search without increasing the scale of a circuit in a receiver for a code division multiple access(CDMA) cellular system that distinguishes cells based on types of spread codes. SOLUTION: A base band signal obtained by applying base band frequency conversion to a CDMA signal is given to a plurality of correlation devices 100, where each signal is correlated with a reference code generated from each code generating section 101, and a resulting output is given to a selector section 103. At the selector section 103, the output signal is given to a plurality of notification channel demodulation sections 104 or a plurality of demodulation sections 105 for a speech channel are selected based on a control signal from a control section 102. The output of the notification channel demodulation section is processed by a signal processing section 107 and its result is given to the control section 102. An output of the demodulation section for a speech channel is given to a symbol synthesis section 106, where rake synthesis is conducted, with its resulting signal processed. Part or all of the correlation devices are used for collecting notification channel information or used for path demodulation for rake synthesis is selected properly by the control section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a cellular system using CDMA, and more particularly, to a receiving device on a mobile station side of the system.

[0002]

2. Description of the Related Art Personal communication such as "anytime, anywhere, with anyone, and with any media" is a field that is expected to be most developed now along with multimedia. Personal communication is a concept that has been universalized through wired and wireless communication, but expectations for wireless communication are particularly high. In wireless communication, portable telephones have been rapidly expanding in recent years, mainly in developed countries, and the conventional analog system is not being able to cover the rapidly increasing demand. For this reason, digital systems that are excellent in subscriber capacity, communication cost, confidentiality, and communication diversity are becoming mainstream. Digital systems include TDMA (Time Division Multiple Acc)
ess: Time division multiple access (CDMA) and CDMA (Code Division)
Multiple Access: Code Division Multiple Access)
Since the DMA system is superior to the TDMA system in terms of subscriber capacity, it is the technology that has received the most attention now.

In the CDMA system, a spread spectrum technique is usually used. Spread spectrum is a method of transmitting a signal by spreading the occupied frequency bandwidth of a signal to a bandwidth much wider than the occupied frequency bandwidth of information using a code sequence called a spread code. The spread spectrum technology includes a direct spread (DS) system and a frequency hopping (FH) system. In a cellular telephone system, the direct spread system is exclusively used. DS
In the CDMA system using CDMA, each mobile station performs spectrum spreading using a different spreading code, and multiplexes the signal of each code channel into the same frequency band and transmits the multiplexed signal. On the other hand, on the receiving side, by performing despreading with the same spreading code as that of the desired receiving channel, only the spectrum of the desired signal is demodulated in a narrow band, and other interference waves become wideband noise. A CDMA system using such a spread spectrum technique is as follows.
Large subscriber capacity, asynchronous access possible, RAKE
By providing a receiver, it has excellent features such as being resistant to multipath fading, capable of soft handover, resistant to mutual interference with other systems, and highly confidential.

[0004] The conventional US standard CDMA digital cellular system (Interim Standard (IS) -9)
5), a signal transmitted on the downlink is a signal obtained by multiplying a certain short-period spreading code PN1 and a long-period spreading code PN2 having the same chip rate as PN1 and a sufficiently longer period than PN1. Spreading. The communication channel of each user can be multiplexed by distinguishing PN1, and PN2 is a code common to each user.
Further, between the base stations (cells), the phase of PN2 is made different to realize the distinction between the base stations. in this way,
In order to make the phase of PN2 different between each base, a GPS (Global Positioning System) receiver is mounted on each base station, and synchronization is established between the base stations. IS-95 system CD
About MA, "CDMA system and next-generation mobile communication system" (Trickeps Monographs, pp. 158-163)
Is described in The PN1 code described above represents a Walsh sequence in the above-mentioned reference, and the PN2 code represents a short-period PN.

FIG. 7 is a block diagram showing a configuration example of a baseband signal processing section in a receiving apparatus for receiving such a CDMA signal. The baseband signal processing unit shown in FIG. 7 includes a signal search unit 1001, a control unit 1002, and a despreading unit 100.
3-1 to 3, symbol combining section 1004, signal processing section 10
It consists of 05. Here, the signal search unit 1001 and the despreading units 1003-1 to 1003-3 are correlators that perform correlation processing and despreading with a received signal. The configuration of this receiving apparatus is described in “Nikkei Electronics” No. 579 (April 26, 1993)
Day) pp. 169-170.

Hereinafter, the operation of the baseband signal processing section will be described. A CDMA baseband signal obtained by frequency-converting a received signal into a baseband is input to the baseband signal processing unit. As described above, the baseband signal is a signal spread by the combined signal of the short-period spreading code PN1 and the long-period spreading code PN2. The signal spread by the synthesized signal is input to the signal search unit 1001, and the direct wave,
The reception timing of each path such as a reflected wave is searched. In this conventional system, a signal (pilot channel) spread only with the PN2 code is transmitted for signal level and reception timing detection, and the signal search unit 1001 despreads this signal. Therefore, in order to perform despreading using the PN2 code, a despreading method using a sliding correlation is generally used because the period of the PN2 code is very long.

FIG. 8 shows a signal search section 1001 in FIG.
FIG. 2 is a block diagram showing an internal configuration of the device. Signal search unit 100
1 is a PN2 code generator 1101, DLL (Delay Lock
(ed Loop) unit 1102 and an amplitude detection unit 1103 that obtains correlation amplitude information from the output of the DLL unit 1102. DLL section 1102 includes PN2 code generation section 11
The PN2 code includes a synchronization acquisition unit that slides the PN2 code generated at 01 and finds a synchronization point with the input received signal.

The operation of the DLL unit 1102 is described in “Spread Spectrum Communication System” (Mitsuo Yokoyama, Science and Technology Publishing Co., Ltd.), p. 290-pp. 311 describes in detail. The PN2 code obtained by the PN2 code generation unit 1101 is input to the DLL unit 1102. DL
L section 1102 performs correlation with the received signal using the spread code obtained from PN2 code generation section 1101 as a reference code. Using this correlation output, the amplitude detector 1
103 gives the correlation amplitude.

The received signal amplitude information at each path timing obtained in this way is sent to control section 1102,
Using this result, the paths having the highest received power are selected by the number of the despreading units, and PN code phase information is sent to each of the despreading units 1003-1 to 1003-3 so as to be synchronized with the PN2 reception timing. By performing such an operation, in each of the despreading units 1003-1 to 1003-3, the received signal is not only a direct wave,
When multipath waves are included, RAKE combining that separates and demodulates each path and performs maximum ratio combining can be realized.

FIG. 9 shows each despreading unit 1003 in FIG.
It is a block diagram which shows the internal structure of -1 to 3. The despreading units 1003-1 to 1003-3 are different from the signal search unit 1001 in that the PN1 code generation units 12
02 and an PN2 code generator 1201, and an EX-OR unit 1203 that performs an exclusive OR operation on the output of the PN1 code generator 1202 and the output of the PN1 code generator 1202.

In each of the despreading units 1003-1 to 1003-3, a reference code is generated at a different timing (phase), and despreading of each path used for RAKE reception is realized. The operation of the DLL unit 1204 is the same as that of the DLL unit 1102 in the signal search unit 1001, so the above description will be referred to. Thus, each despreading unit 10
The despread signal outputs obtained from 03-3 to 03-3 are input to the symbol combining section 1004, respectively, where timing adjustment,
After being weighted, they are combined to achieve an ideal path diversity maximum ratio combination.

FIG. 10 shows a flow of a rough processing operation of the receiving unit when actually making a call. In general,
When the power of the receiving terminal is turned on (step S130)
1) First, the system is initialized (step S)
1302). Thereafter, an initial cell search operation is performed (step S1303). Here, the initial cell search is an operation of first determining which base station to communicate with.

In the present cellular telephone system, the types of PN2 codes used by each base station are common as described above, and are distinguished only by the code phase. Therefore, the initial cell search uses one type of PN code. This can be realized only by identifying the reception timing (code phase) having the largest correlation amplitude. After the base station (cell) with which the call is made is determined in this way, RAKE reception of the above-described call channel is performed (step S1304), and at the end of the call, the power is turned off (step S1305). Call can be realized.

However, in such a system, it is necessary to give an accurate offset to the PN2 between the base stations, so that it is necessary to achieve time synchronization between the base stations. Must be installed. As a result, the base station system becomes larger and more expensive, and a system for synchronizing between base stations is required. Therefore, there are problems such as expansion of the system by adding base stations and the accompanying complexity of the system. is there.

In view of these problems, a CDMA cellular system in which the type of the PN2 code is made different for each base station is being studied. Also, in order to enable high-quality mobile communication, the same information is transmitted from two base stations to one terminal, and the terminals perform despreading of soft handover by despreading different base station signals in despreading sections 1003-1 and 1003-1. ,
Antenna diversity for despreading signals from a plurality of receiving antennas has been studied.

[0016]

In the above-mentioned conventional system, it is necessary to demodulate the broadcast channel information and the speech channel information at the same time. This is called "DS-CDM".
A Study of Radio Channel Configuration Method in A "(1996 IEICE Communications Society Conference B-347). For this reason, in the receiver, a correlator and a demodulator dedicated to each channel are required.
Further, particularly at the time of cell search, it is necessary to simultaneously demodulate broadcast channels of several cells (sectors) in order to increase the speed. Therefore, a plurality of correlators and demodulators used for broadcast channel demodulation are provided. In addition, in order to realize soft handover and RAKE reception, which are features of the CDMA system, it is necessary to provide a plurality of correlating devices and demodulating units for demodulating a traffic channel, and there is a problem that the circuit scale becomes large.

The present invention has been made in view of the above-mentioned problems in the prior art, and effectively uses a small number of correlators and code generators to change the type of the PN2 code for each cell (sector). It is necessary to solve the problem of providing a cellular phone system of a CDMA system which allows a cell search to be performed without increasing the circuit scale in a receiver as a component of the system. Make it an issue.

[0018]

According to the first aspect of the present invention, multiplexing is performed by using a predetermined spreading code and discriminating a type of a spreading signal and a spreading code transmitted through a common broadcast channel to all mobile stations. A plurality of correlation devices that receive a transmission spread signal transmitted through a speech channel and take a correlation between the obtained reception spread signals using a spreading code, and broadcast information of the broadcast channel from a correlation output of the correlation device. A broadcast channel demodulation unit for demodulating, and a communication channel demodulation unit for demodulating speech information of the speech channel from a correlation output of the correlator, a receiving device for a CDMA cellular system, wherein: A part or all of the correlating devices can be selected and connected to the plurality of broadcast channel demodulators or the traffic channel demodulators. A switching unit, and a control unit that controls the switching unit to connect a part or all of the plurality of correlation devices to an arbitrary number of the plurality of broadcast channel demodulation units. is there.

In this manner, in a situation where simultaneous reception of a plurality of broadcast channels is given the highest priority, for example, after a cell (sector) candidate to be connected is determined in an initial cell search process, each candidate is determined. When collecting information of the broadcast channel of the cell, a part of a plurality of correlating devices,
Alternatively, the switching unit is controlled by the control unit so that all of them are connected to the broadcast channel demodulation unit. When the cell search process is completed and information of a channel other than the broadcast channel (traffic channel) is demodulated, a part or all of a plurality of correlators are provided in order to optimally perform RAKE reception. The switching unit is controlled by the control unit so as to be used by connecting to the demodulation unit.

According to a second aspect of the present invention, there is provided a transmission spread signal transmitted through a common broadcast channel to all mobile stations using a predetermined spreading code and a transmission transmitted through a communication channel multiplexed by discriminating the type of the spreading code. A plurality of correlator units for receiving the spread signal and taking a correlation between them using a spread code for the obtained received spread signal; and a plurality of demodulators respectively connected to the plurality of correlator devices. C
In the receiving device of the DMA cellular system, a part or all of the plurality of correlators and the plurality of demodulation units are switched so as to be selectively used for demodulation of the broadcast channel symbol or the communication channel symbol. A switching unit, and a control unit that controls the switching unit to use a part or all of the plurality of correlation devices and the plurality of demodulation units in an arbitrary number of the broadcast channels. is there.

In this manner, in a situation where simultaneous reception of a plurality of broadcast channels is given the highest priority, for example, after a cell (sector) candidate to be connected is determined in the initial cell search process, each candidate is determined. When collecting the broadcast channel information of the cell, the control unit controls so that part or all of the plurality of demodulation units respectively connected to the plurality of correlators are used for broadcast channel demodulation. Also, when the cell search process is completed and other channel information is demodulated, to perform RAKE reception optimally,
The control unit controls the apparatus to use a plurality of correlations and a part or all of a plurality of demodulation units respectively connected to the correlating apparatuses to channels other than the broadcast channel (communication channels). .

According to a third aspect of the present invention, a transmission signal transmitted through a communication channel multiplexed by discriminating a type of a transmission signal and a diffusion code to be transmitted to all mobile stations through a common broadcast channel using a predetermined spreading code. A correlator for receiving a signal by an antenna diversity function and using a spreading code to obtain a received spread signal, and a demodulator for demodulating the broadcast channel and the speech channel from a correlation output of the correlator; A receiving apparatus for a CDMA cellular system having a unit, further comprising a sample and hold circuit for sampling and holding the received spread signal input from each antenna branch by the antenna diversity function in correspondence with each antenna branch, Apparatus for selectively using said sample and hold circuit Switching means, and a plurality of correlation operation units for performing a correlation operation on the received spread signal selected by the switching means by the spreading codes of the broadcast channel and the speech channel, and selecting and using a path for diversity combining And a control unit for controlling the switching means so as to select the sample and hold circuit of the antenna branch that can receive the path to be switched.

In this manner, a plurality of S / Hs for sampling and holding the detection signals from each antenna branch are provided.
A plurality of S / H circuit groups, a plurality of S / H circuit groups, and a plurality of S / H circuit groups. A correlation operation is performed using a reference code, and antenna diversity can be applied to correlation processing of a broadcast channel and a channel other than the broadcast channel (communication channel).

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a block diagram showing a configuration example of a baseband signal processing section according to a first embodiment of the present invention. As shown in FIG. 1, the baseband signal processing unit includes the correlation devices 100-1 to 100-4,
Code generation units 101-1 to 4-1, control unit 102, selector unit 103, broadcast channel demodulation units 104-1 to 104-2, demodulation unit 1
05-1 to 3, symbol synthesizing section 106, signal processing section 10
7-1 to 7-1. Here, the correlation devices 100-1 to 100-4
Performs despreading by performing a correlation process between the replica code generated by the code generation units 101-1 to 101-4 and the received signal. Means for performing despreading include, for example, a sliding correlation method and a matched filter method.

An input signal to the baseband signal processing unit is a CD obtained by frequency-converting a received signal into a baseband.
This is the MA baseband signal. This baseband signal is supplied to a short-period spreading code PN1 (hereinafter referred to as PN) as in the conventional example.
1 code) and a long-cycle spreading code PN2 (hereinafter referred to as a PN2 code) having a sufficiently longer period than the PN1 code. However, as a difference from the above conventional example, here, the PN2 code is a cell (sector).
A different code is used for each. The PN1 code is a code assigned to each channel in each cell, and a code common to each base station (hereinafter, referred to as a common PN1 code) is assigned to the broadcast channel.

In the baseband signal processing section, some or all of the correlation devices 100-1 to 100-4 are used,
First, identification of the PN2 code and identification of the code phase are performed.
Here, the identification of the PN2 code and the PN2 code phase means:
Although any method may be used, for example, the correlation device 10
The signal generation units 101-1 to 10-4 connected to 0-1 to 0-4 generate a composite code of the PN2 code and the common PN1 code allocated to each cell (sector), correlate with the input signal, and obtain the correlation. Perform using the level.

The control unit 102 selects a cell (sector) candidate to be connected based on the identification result thus obtained. As a method of selecting a cell (sector) candidate, for example,
A correlation signal having an intensity corresponding to the reception electric field intensity obtained from the correlation device 100 is compared with a predetermined reception electric field intensity threshold value. If the reception electric field intensity is larger than the threshold value, a cell (sector) to be connected is connected. )
A technique of making it a candidate can be used.

Thereafter, the baseband signal processing section collects broadcast channel information for each cell (sector) candidate determined as described above. This broadcast channel generally requires several frames. For this reason, if there are a plurality of cell (sector) candidates, there is a problem that it takes an enormous amount of time to collect broadcast channel information of all the candidate cells.

In view of such a problem, in this embodiment, as a countermeasure, in the present embodiment, a plurality of correlators, which are a part of the plurality of correlators 100-1 to 100-4, are allocated to the broadcast channel demodulators 104-1 and 104-2. . In the present embodiment, for example, two broadcast channel demodulation units 100-1 to 100-4 are provided, so that a maximum of two of the correlation devices 100-1 to 100-4 are provided.
Will be assigned.

For example, the correlator 100-1 and the correlator 100-2 are each provided with a broadcast channel demodulator 104-1.
And a broadcast channel demodulation unit 104-2. In this case, the code generation unit 101-1 sets a PN1 code, a PN2 code, and a code phase corresponding to a certain candidate cell (sector), and the code generation unit 101-2 differs from the candidate cell (sector). P of candidate cell (sector)
The N1 code, the PN2 code, and the code phase are set. Then, in the correlation devices 100-1 and 100-2, the input signal is correlated with the set code, and despreading is performed. This despread signal is subjected to synchronous detection in the connected broadcast channel information demodulators 104-1 and 104-2. In the broadcast channel information demodulation units 104-1 and 104-2,
For example, an interpolation synchronous detection method to which a pilot symbol is added is used. This pilot symbol is a known symbol, and is used for each radio slot (for example, 1.25 m).
For each s), several known symbols are inserted.

The pilot interpolation synchronous detection method is described in "Wideband CDMA Field Transmission Experiment Results" (RC
It is described in S97-3). Broadcast channel information demodulation sections 104-1 and 104-2 compare the phase of the pilot symbol with the demodulated result to calculate a phase error. In the next slot, the phase error in the pilot symbol is similarly calculated. From these two phase error calculation results,
An information symbol phase between two pilot symbols is interpolated and interpolated to perform synchronous detection. Thereafter, the signal processing unit 1
07-1 and the signal processing unit 107-2 perform channel decoding (interleave, error correction, etc.) and input to the control unit 102. By simultaneously processing the demodulated information in the control unit 102, simultaneous information collection of two candidate cells can be realized.

Thereafter, the code generation units 101-1 and 101-2 input the PN1 code of the candidate cell different from the previous one,
The N2 code and the code phase are set, and the above operation is repeated to collect information. In this way, the broadcast channel information of all the candidate cells is collected, and the cell (sector) to be connected is determined from the result. Also, when other wireless channel information is being collected (such as a call state), it is necessary to collect the broadcast channel information. This is the case, for example, when the broadcast channel information of the currently connected cell (sector) is updated, or when searching for a cell (sector) that is a candidate for handover.

In a case where only broadcast channel information of one cell (sector) is collected, a plurality of correlators 100
Of the -1 to -4, only the correlator 100-1 is assigned to the broadcast channel demodulator 104-1.
-2 to 4 are allocated for demodulation of channels other than the broadcast channel. Then, as described above, the PN1 code, the PN2 code, and the code phase corresponding to the desired cell (sector) are set by the code generation unit 101-1 and the correlation between the input signal and the set code is set in the correlation device 100-1. Is taken and despreading is performed. This despread signal is subjected to synchronous detection in the connected broadcast channel information demodulator 104-1. Thereafter, channel decoding (interleave, error correction, etc.) is performed in the signal processing unit 107-1, and the result is input to the control unit 102.

Further, the remaining correlation devices 100-2 to 100-4
Assigned to demodulation sections 105-1 to 105-1. Thereby, when demodulating a channel other than the broadcast channel, high-performance RAKE combining for combining three multipaths can be realized.
That is, the PN1 code, the PN2 code, and the code phase of the wireless channel to be demodulated are set in the code generation units 101-2 to 4 connected to the correlation devices 100-2 to 100-4, respectively. Here, the PN1 code and the PN2 code information are common to the three code generators 101-2 to 10-4, and only the code phases are different corresponding to the respective propagation delays.

The code thus set and the input signal are correlated by the correlators 100-2 to 100-4, despreading is performed, and then the despread signals are connected to the demodulated signal. Synchronous detection is performed in units 105-1 to 105-3. Here, the demodulation units 105-1 to 35-1 perform interpolation synchronous detection in the same manner as the broadcast channel demodulation units 104-1 and 104-2.

However, unlike the broadcast channel, the symbol rate may be different for channels other than the broadcast channel. Further, the CDMA digital cellular system currently under consideration supports multimedia communication, so that a communication channel can support a plurality of symbol rates. When the symbol rates are different, the number of symbols in the radio slot and the pilot symbols are different.
Therefore, the demodulation units 105-1 to 105-3 need to have a configuration that can be set by the control unit 102 so as to realize the interpolation synchronous detection according to the symbol rate. Note that the broadcast channel demodulation sections 104-1 and 104-2 do not need to have the above configuration since the information symbol rate is fixed.

The signal thus synchronously detected is input to the symbol combining section 106. Symbol combining section 106
In, each detected signal is weighted and combined (added). The signal synthesized in this way is input to the signal processing unit 107-3, subjected to channel decoding (interleave, error correction, etc.), and input to the control unit 102. Here, this channel codec also needs to have a different configuration for each different symbol rate.

As described above, the broadcast channel information and other radio channel information (for example, an individual traffic channel) are simultaneously input to the control unit 102 and can be processed simultaneously. Also, for individual traffic channels, three-path RAKE combining is possible, and high-performance wireless channel demodulation is possible. In a case where broadcast channel information of a plurality of cells (sectors) is collected and only two paths effective for RAKE reception exist due to propagation path characteristics, the correlation device 1
Two correlators among 00-1 to 00-4 are allocated to broadcast channel information collection, and the remaining two correlators 100 are allocated to radio channel information collection other than the broadcast channel.

Such control is performed by the control unit 102 by the selector unit 1 provided at the output stage of the correlation devices 100-1 to 100-4.
03 and setting each of the correlators 1
This can be easily realized by setting the code information of the channel to be demodulated and the code phase information in the code generation units 101-1 to 101-4 connected to 00-1 to 00-4. Here, the selector unit 10
3 can be easily realized simply by installing one-input multi-output selector circuits corresponding to the number of correlators (four in FIG. 1). Therefore, when the control unit 102 determines the operation state of the baseband signal processing unit, the control unit 102 sets the select setting information to appropriately assign the plurality of correlators 100-1 to 100-4 according to the operation state. The control unit 102 that performs such control is generally realized by a CPU, a DSP, or the like, but may be realized by any available means.

In this embodiment, the four correlator devices 1
00-1 to 4, two broadcast channel information demodulators 104-
1, 2, and 3 other wireless channel information demodulators 105
The example shown in FIG. However, since there are four correlators, it is apparent that by configuring the system with four broadcast channel information demodulators, broadcast channel information of four candidate cells (sectors) can be simultaneously collected. It is. Also, by having four other wireless channel information demodulation units, RAKE reception using a four-wave multi-bus signal is also possible. Furthermore, the number of correlators, the number of demodulators, etc. can be arbitrarily determined,
These combinations are not specified,
It can be arbitrarily selected.

(Second Embodiment) FIG. 2 is a block diagram of a configuration example of a baseband signal processing unit according to a second embodiment of the present invention. This baseband signal processing unit is shown in FIG.
As shown in the figure, the correlation devices 100-1 to 100-4, the code generation unit 1
01-1 to 4, a control unit 102, a selector unit 103-1 to 103-1
4, the demodulation units 105-1 to 105-4, the symbol combining unit 106, and the signal processing units 107-1 to 107-5. Here, the correlation device 1
00-1 to 4 perform inverse processing by performing a correlation process between the replica code generated by the code generation units 101-1 to 10-4 and the received signal, and are, for example, like a sliding correlator. . The difference from the first embodiment is that each of the correlators 100-1 to 100-4 already has a demodulation unit 105-
1 to 4 are connected, and selector circuits 103-1 to 103-4 are inserted in the output stages of the respective demodulation units 105-1 to 104-1.

An input signal in the baseband signal processing similar to that of the first embodiment is first processed by the control unit 102 in the same processing as that of the first embodiment. Select a candidate. Thereafter, the baseband signal processing unit collects broadcast channel information for each cell (sector) candidate. However, as in the first embodiment, when there are a plurality of cell (sector) candidates, high-speed transmission is performed. To collect broadcast channel information, a plurality of correlators 10
0-1 to 0-4 and the demodulation unit 105- connected to each of them.
A plurality corresponding to a part of 1 to 4 is allocated for broadcast channel demodulation.

In this embodiment, up to four channels can be allocated for broadcast channel demodulation. For example, it is assumed that all of the plurality of correlation devices 100-1 to 100-4 and demodulation units 105-1 to 105-4 are allocated for broadcast channel demodulation.
In this case, a PN1 code, a PN2 code, and a code phase corresponding to different candidate cells (sectors) are set in the code generation units 101-1 to 101-4. And the correlation device 10
In 0-1 to 4-4, the input signal is correlated with the set code, and despreading is performed. The despread signal is subjected to synchronous detection in the connected demodulation units 105-1 to 105-4. Here, as described in the first embodiment, the control unit 102 sets symbol rate information and the like in the demodulation units 105-1 to 105-4 so that interpolated synchronous detection of the broadcast channel can be realized. Interpolated synchronous detection using symbols is performed.

Thereafter, the respective demodulated outputs are input to the selectors 103-1 to 103-4. Here, this selector unit 1
Numerals 03-1 to 4-4 are realized by the correlator 100-1 to 100-4 at the preceding stage and a one-input two-output multiplexer circuit for selecting an output depending on which channel demodulation unit 105-1 to 105-4 is used for. This selection is made by the control unit 102.
The setting is performed according to the setting contents of the correlators 100-1 to 100-4 and the demodulation units 105-1 to 105-4. For example, when performing broadcast channel demodulation, the outputs of selector sections 103-1 to 103-1 are connected to signal processing sections 107-1 to 107-4, and when demodulating other communication channels and the like, selector section 103-1 is used.
The outputs of 3-1 to 4 are connected to the symbol combining section 106. Here, since the broadcast channel is demodulated, the selector units 103-1 to 103-4 are set to be connected to the signal processing units 107-1 to 107-4.

Channel decoding (interleaving, error correction, etc.) is performed in the signal processing units 107-1 to 107-4, and is input to the control unit 102. By simultaneously processing the demodulated information, the control unit 102 can realize information collection at high speed. Further, as described in the first embodiment, in a state where radio channel information other than the broadcast channel is being collected (such as a call state), only the broadcast channel information of one cell (sector) is collected. In this case, of the plurality of correlation devices and the plurality of demodulation units, only one system (for example, the correlation device 100-1 and the demodulation unit 105-1) is allocated for broadcast channel demodulation. That is, in the example in which the correlation device 100-1 and the demodulation unit 105-1 are allocated for broadcast channel demodulation, the PN1 code, PN2 code,
And the symbol phase, and also set symbol rate information and the like in the demodulation unit 105, and further in the selector unit 103-1.
The output of the demodulation unit is selected and connected to the signal processing unit 107-1. In this manner, broadcast channel information collection can be realized by the same processing as described above.

The remaining correlators 100-2 to 100-4 and demodulators 105-2 to 4 are allocated to demodulation of radio channels such as speech. As a result, high-performance RAKE combining of three passes can be realized. That is, the PN1 code, the PN2 code, and the code phase of the wireless channel to be demodulated are set in the code generation units 101-2 to 104-2 connected to the correlation devices 100-2 to 100-4, respectively. Here, the PN1 code and the PN2 code information are common to the three code generation units 101-2 to 10-4, and differ from each other only in the code phase corresponding to the propagation delay. The code thus set and the input signal are correlated by the correlating devices 100-2 to 100-4, and despreading is performed. After that, the despread signals are respectively demodulated by the demodulation units 105-2 to 105-2. At 4, synchronous detection is performed.

Here, as described in the first embodiment, the control unit 102 causes the demodulation units 105-2 to 10-4 to output symbol rate information and the like so that interpolation and synchronous detection of other radio channels can be realized. Is set, and interpolation synchronous detection to which a pilot symbol is added is performed. The signal demodulated in this way is input to selector sections 103-2 to 103-4. The selectors 103-2 to 103-4 are set by the controller 102 so that outputs are input to the symbol synthesizer 106. As described above, the signals input to the symbol combining section 106 are subjected to appropriate weighting for each detected signal and combined (added). Weighting and multiplexing here are based on general RA
This is a method used for KE synthesis, and may be performed by any applicable method. The signal synthesized in this way is input to the signal processing unit 107-5, subjected to channel decoding (interleave, error correction, etc.), and input to the control unit 102.

As described above, the broadcast channel information and other radio channel information (for example, individual traffic channels) are simultaneously input to the control unit 102 and can be processed simultaneously. Also, for individual traffic channels, three-path RAKE combining is possible, and high-performance wireless channel demodulation is possible. Of course, if it is not necessary to collect broadcast channel information, the 4-path RA
It is possible to perform KE reception. In the case of collecting broadcast channel information of a plurality of cells (sectors),
If there are only two paths effective for RAKE reception due to propagation path characteristics, two correlators are allocated to broadcast channel information collection, and the remaining two correlators are used to collect radio channel information other than the broadcast channel. Assign to Thus, the number of broadcast channel demodulated cells and RAK
The number of paths used for E can be arbitrarily set within the range of the number of correlating devices and the number of demodulation units.

For such control, the control unit 102 sets a select signal to the selector units 103-1 to 10-4 provided in the output stages of the demodulation units 105-1 to 10-4 as in the first embodiment. And setting code information and code phase information of a channel to be demodulated in code generation sections 101-1 to 101-4 connected to correlation apparatuses 100-1 to 100-4, and synchronous detection in demodulation sections 105-1 to 10-4. It can be easily realized by setting the necessary information for. Here, the selector units 103-1 to 103-1
4 can be easily realized simply by installing a 1-input 2-output selector circuit corresponding to each correlator. Therefore, the control unit 1
02, when the operation state of the baseband signal processing unit is determined, the plurality of correlation devices 100-
Select setting information is set so as to appropriately assign the demodulators 1 to 4 and the plurality of demodulators 105-1 to 105-4. The control unit 102 that performs such control is generally realized by a CPU, a DSP, or the like, but may be realized by any applicable means. In the present embodiment, four correlation devices 100-1 to 100-4 and four demodulation units 105-1 to 105-4 are used.
An example of such a configuration is shown. Obviously, the same effect can be obtained with a smaller number of demodulators than in the first embodiment, and the circuit size can be reduced. The number of such correlators, the number of demodulators, and the like can be arbitrarily determined, and the combination thereof is not specified but can be arbitrarily selected.

(Third Embodiment) FIG. 3 is a block diagram showing a baseband signal processing unit according to a third embodiment of the present invention. The present embodiment is an example of a configuration for realizing antenna diversity combining. As shown in FIG. 3, the baseband signal processing unit includes a matched filter unit 801, path selector units 301-1 to 301-4, and a demodulation unit 105
-1 to 4, symbol combining sections 106-1 to 5-5, selector sections 103-1 to 4-4, signal processing sections 107-1 to 5-5, control section 1
02, a diversity selector unit 802. In the present embodiment, an example is shown in which the correlation devices 100-1 to 100-4 described in the first embodiment and the second embodiment are realized by a configuration using a matched filter. FIG. 4 shows the configuration of the matched filter unit 801 used here. As shown in FIG. 4, the matched filter unit 801 includes a plurality of correlation operation units 903-1 to 903-4, a sample and hold circuit (hereinafter, referred to as an S / H circuit) unit 901, and an S / H circuit unit 9.
02.

In the matched filter section 801, the input signal is input to the S / H circuit section 901 and the S / H circuit section 902, and the detection signal obtained from each antenna branch is input, and the S / H circuits 901-1 to 901-1 are input by a sampling clock. The data is sequentially shifted over n. If the input signal is quantized when it is digitized (A / D converted), an S / H circuit is provided in parallel for the quantization bit. The correlation value between the signal subjected to S / H and the reference code in this manner is calculated by the EX-OR circuit unit 404.
Is calculated by the adder 405. The configuration up to this point is the configuration of a general matched filter.

A case will be described below in which a composite code of a long-period code such as the PN2 code and a short-period code such as the PN1 code is despread. In this case, it is necessary to switch the reference code every period of the PN1 code, but the present invention does not specify a method for realizing such an operation. For example, it may be realized by the following method using the configuration as shown in FIG. 4, the reference code generated by the code generation unit 703 is sequentially input to the S / H circuits 402-1 to 40-n of the S / H circuit unit 402 in FIG. Then, the S / H circuit unit 403 uses the latch pulse input at the same timing as the reception signal.
This reference code is input to the receiver, and a correlation with the received signal is obtained in accordance with the above-described operation. That is, the code set in the S / H circuit unit 403 becomes the reference code for which the correlation operation is actually performed. For example, when this latch pulse is not input, the previously set sign remains unchanged.

Hereinafter, the operation of the baseband signal processing will be described with reference to FIG. The input signal in the baseband signal processing unit is a CDMA baseband signal obtained by frequency-converting a received signal into a baseband, as in the first embodiment. It is assumed that these two signals are input. FIG. 5 is a diagram showing a radio frame configuration of a broadcast channel used for cell search.

The radio frame configuration shown in FIG. 5 uses a PN common to all cells (sectors) in a broadcast channel frame which is currently being studied in order to speed up PN2 code phase identification.
It is composed of a portion spread with only one code, and a portion spread twice with different PN2 and PN1 codes (which may be different from the PN1 code) for each cell (sector). In addition, about such a radio frame structure,
"Two-Step High-Speed Cell Search Method in DS-CDMA Base Station Asynchronous Cellular System Using Long Code" (RCS
96-73).

Hereinafter, the operation of the baseband processing unit according to the above-described frame configuration will be described. First, identification of the PN2 code and identification of the code phase are performed. In the case of such a radio frame configuration, since the PN1 code of the portion spread only by the PN1 code is common to each cell (sector), the correlation processing is performed by the PN1 code. , It is possible to easily identify the phase timing of the PN2 code.

In this case, a plurality of matched filters 903
The code generator 703 sets a common PN1 code for each cell in the matched filter 903-1 of -1 to -4, and performs a correlation process for one radio frame in a fixed state, thereby achieving a high-speed code phase. Identification can be realized. That is,
In FIG. 4, the above operation can be easily realized by setting the reference code input by the code generation unit 703 to one period of the PN1 code and inputting the latch pulse only once. Utilizing the correlation timing with the PN1 code, the PN2 code is identified thereafter, whereby the code can be executed at high speed.
And identification of the code phase can be realized. In the control unit 102,
Based on the identification result thus obtained, a cell (sector) candidate to be connected is selected. Thereafter, the baseband signal processing unit collects broadcast channel information for each determined cell (sector) candidate.

As in the second embodiment, in this embodiment,
The plurality of matched filter units 903-1 to 4 and the plurality of demodulation units 105-1 to 105-4 are assigned to broadcast channel demodulation. For example, when the matched filter units 903-1 and 903-2 are used for broadcast channel demodulation,
The code generation unit 703 in the matched filter unit 903-1 stores a PN1 code corresponding to a certain candidate cell (sector), P
The N2 code and the code phase are set, and the code generation unit 703 in the matched filter unit 903-2 stores the PN1 code, PN2 code, and code phase of a candidate cell (sector) different from the candidate cell (sector). Is set.

The input signals are input to the matched filter unit 903-1 and the matched filter unit 903-2.
Correlation with each set code is taken, and despreading is performed. FIG. 6 is a diagram for explaining the code update timing based on the relationship between the reception timing of each reception path, the generation timing of the reference PN code, and the correlation output. As shown in FIG. 6, a code update timing (the latch pulse input timing) in the matched filter unit 903-1 and the matched filter unit 903-2 is selected between a maximum delay multipath wave and a minimum delay multipath wave. As a result, a correlation signal output is obtained for all multipaths.

The correlation signals thus obtained are respectively supplied to the path selector 301-1 and the path selector 30.
1-2. The path selectors 301-1 to 301-4 have a function of selecting from correlation outputs obtained from the matched filter unit 801 to output only correlation values at timings at which a multipath effective for RAKE combining exists. As an example of realizing this selection function, first, a method of calculating reception electric field strength at each reception timing from a correlation output obtained from the matched filter unit 801 will be described. This means that a threshold value for the received electric field strength is prepared in advance, and if the received electric field strength is larger than the received electric field strength threshold value, a correlation output by a matched filter is output to the subsequent stage, and if not, Performs an operation of not outputting to the subsequent stage.

The output signals from the path selectors 301-1 and 301-2 are subjected to synchronous detection in the connected demodulators 105-1 and 105-2. Here, the demodulation units 105-1 to 105-4 include a path selector unit 301-1 and a path selector unit 301-2.
It is configured so that synchronous detection can be performed for all paths selected in. This may simply have a configuration having a plurality of demodulation units 105-1 or 105-2 used in the first embodiment. The method of realization is not specified, and any possible method may be used.

The signal subjected to the correlation processing and demodulation in this way is input to the symbol combining sections 106-1 to 106-4 via the diversity selector section 802 shown in FIG. In the diversity selector unit 802, for example, in the matched filter unit 801 in the preceding stage, the correlation operation units 903-1 and 903-2 illustrated in FIG. 4 use different antenna branches to transmit signals of the same base station. When demodulation is performed, the outputs of these two correlation operation units are selected so as to be input to the same symbol combining unit. here,
Since different information from different base stations is demodulated, different symbol combining units (in this embodiment, symbol combining unit 1
06-1 to the symbol combining section 106-2).

The symbol combining section 106-1 and the symbol combining section 106-2 perform timing adjustment and weighting of each multipath component, combine them, realize RAKE combining, and output a signal. After that, the selector section 103-1,
When the signal is input to the selector 103-2 and is used for demodulation of broadcast channel information, the signal is directly transmitted to the signal processing units 107-1 and 107-2 instead of the symbol combining unit 106-5 at the subsequent stage. The control unit 10
2 is controlled. In the signal processing units 107-1 and 107-2, channel decoding (interleaving, error correction, and the like) is performed, and the result is input to the control unit 102. The operations of the selectors 103-1 to 103-4 and the control by the controller 102 are the same as in the second embodiment. Here, since the broadcast channel demodulation is performed, the direct signal processing unit 107-1 and the direct signal processing unit 107 are respectively provided.
-2, and the channel-decoded signal is then input to the control unit 102.

In this way, a plurality of broadcast channel information items are simultaneously and individually RAKE-received, and highly accurate information collection can be realized at high speed. Also, when a cell other than a broadcast channel is demodulated after a cell (sector) to be connected is determined, high-performance information demodulation that achieves antenna diversity can be realized. Hereinafter, a detailed operation in this case will be described with reference to FIG. In this case, in order to determine the antenna diversity switching control and determine the reception timing of the multipath component used for demodulation, first acquire the timing corresponding to the number of valid paths and information indicating which antenna branch is the input signal from which antenna branch. .

Although there is no particular limitation on this method,
For example, after a cell (sector) to be connected is determined, a common PN1 code is again used for each antenna branch for several μs before and after a known reception timing (with a time width in which a multipath is expected to exist). (Determined by propagation path characteristics and frequency) to obtain information indicating the timing of the number of valid paths from the one with the highest received electric field strength and information indicating which antenna branch is the input signal. We will take a method. As a result, when there is a valid path in the input signals from both antenna branches, two matched filters are used for demodulating the same channel, and S / H circuits of different antenna branches are selectively used. ,
Control is performed (for example, the matched filter 903-3 is controlled to select and use the antenna branch 1 and the matched filter 903-4 is controlled to select and use the antenna branch 2).

In this way, the correlation processing is performed on the received signal, and the despread signal is input to the path selector 301-1 and the path selector 301-4, respectively.
The timing of the path to be used in the antenna branch selected by the matched filter unit 801 is also set by the control unit 102 in the path selector unit. The demodulators 105-3 and 105-4 perform synchronous detection on the paths selected by the path selectors 301-3 and 301-4 and input the results to the diversity selector 802. This demodulation unit is configured to be able to demodulate all the paths selected by the path selector unit as described above. Since diversity selector section 802 demodulates the signal of the same base station using different antenna branches, the outputs of these two demodulation sections are selected to be input to the same symbol combining section. Here, the symbol combining unit 10
It is assumed that the input is made to 6-3.

In the symbol combining section 106-3, the multipath components are subjected to timing adjustment and weighting, and then combined to realize RAKE combining. In this embodiment, antenna diversity can also be achieved. Thereafter, the selector unit 103
-3 and the selector 103-4 and input to the symbol synthesizer 106-5. Unless it is in the handover state, the symbol combining section 106-5 does not perform any processing, and inputs the signal to the signal processing section 107-5. Here, channel decoding (interleave, error correction, etc.)
Is input to the control unit 102. The operations of the selectors 103-1 to 103-4 and the control by the controller 102 are the same as in the second embodiment. By performing the control in this manner, each of the correlation calculators 903-1 to 903-4 can perform a correlation calculation with an arbitrary code and a signal of an antenna branch. As a result, an ideal diversity reception can be realized by effectively using a small number of correlation calculation units.

When performing soft handover, signals transmitted from each cell (sector) are common information signals, but the PN1 code, PN2 code and code phase may be different. Therefore, the correlation operation unit 903-2 using a matched filter, the path selector unit 301-2, and the demodulation unit 1
05-2 is allocated for demodulation of a signal transmitted from a cell (sector) of a handover destination. That is, the code generation unit 70 in the correlation operation unit 903-2 using the matched filter
3, the PN1 code and PN of the cell (sector) of the handover destination
Two codes and a code phase are set. In this manner, synchronous detection including multipath is performed in the same manner as described above, and input to the diversity selector unit 802. Diversity selector section 802 demodulates a different base station, so that a different symbol combining section (eg, symbol combining section 106-4) from symbol combining section 106-3 used for symbol combining of the handover source base station is used. Input in the same way.

In symbol combining section 106-4, RAKE
The signals are combined and input to the symbol combining unit 106-5 via the selector unit 103-4. Here, the demodulated signal from the handover source base station and the demodulated signal from the handover destination base station are similarly synthesized after appropriate timing adjustment and weighting, and soft handover can be realized. By making the correlator have a matched filter configuration as described above, the generation timing in the code generation units 101-1 to 10-4 (see FIG. 2) can be changed to the maximum delay multipath wave as described with reference to FIG. From the reception timing, it is only necessary to update during the minimum delay multipath wave, there is no need to make it so strict, there is no need to have a plurality of code generators for multipath demodulation, and the circuit size can be reduced. can get.

[0069]

According to the first aspect of the present invention, in a receiving apparatus for receiving a multiplexed CDMA signal by distinguishing the type of spreading code, a broadcast channel arbitrarily set according to the situation (common to all mobile stations) The use of all or some of the plurality of correlators for broadcast channel demodulation and demodulation of other communication channels in accordance with the demodulation number of Thus, high-speed broadcast channel collection can be realized without performing, and high-speed cell search can be realized.

According to a second aspect of the present invention, in a receiver for receiving a multiplexed CDMA signal by distinguishing the type of spreading code, a broadcast channel arbitrarily set according to the situation (a spreading channel common to all mobile stations). And a part of the correlator / demodulator group, which is composed of a correlator and a demodulator connected to the correlator in accordance with the number of demodulators, is used in accordance with the number of demodulations. In this case, high-speed broadcast channel collection can be realized and high-speed cell search can be realized without significantly increasing the circuit scale. Further, compared to the first aspect, the same effect can be obtained with a smaller number of demodulators.

According to a third aspect of the present invention, in a receiving apparatus for receiving a multiplexed CDMA signal by discriminating the type of spreading code, a broadcast channel arbitrarily set according to the situation (a spreading channel common to all mobile stations). (Using a code), it is possible to apply antenna diversity to the correlation processing of the broadcast channel and the communication channel according to the demodulation number, and also to select and use a reception signal S / H circuit corresponding to each antenna branch as a circuit configuration. Thus, the antenna diversity function can be realized with a relatively easy configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an embodiment of a first baseband signal processing unit according to the present invention.

FIG. 2 is a block diagram illustrating a configuration example of an embodiment of a second baseband signal processing unit according to the present invention.

FIG. 3 is a block diagram illustrating a configuration example of an embodiment of a third baseband signal processing unit according to the present invention.

FIG. 4 shows a configuration example of a matched filter unit used in the baseband signal processing unit of FIG.

FIG. 5 is a diagram illustrating a configuration of a radio frame of a broadcast channel used for cell search.

FIG. 6 is a diagram for explaining a code update timing based on a relationship between a reception timing of each reception path, a generation timing of a reference PN code, and a correlation output.

FIG. 7 is a block diagram of a conventional example of a baseband signal processing unit in a receiving device that receives a CDMA signal.

FIG. 8 is a block diagram illustrating an internal configuration of a signal search unit in FIG. 7;

FIG. 9 is a block diagram showing an internal configuration of a despreading unit in FIG. 7;

FIG. 10 is a diagram showing a flow of a rough processing operation of a receiving unit when making a call;

[Explanation of symbols]

100-1 to 4 ... Correlation device, 101-1 to 4 ... Code generation unit, 102 ... Control unit, 103, 103-1 to 4 ... Selector unit, 104-1 and 2 ... Broadcast channel demodulation unit, 105-
1-4, demodulators, 106, 106-1-5, symbol combiners, 107-1-5, signal processors, 301-1-4, ...
Path selector section, 402... S / H circuit section, 402-1 to 402-1
n: S / H circuit, 403: S / H circuit section, 404: EX
-OR circuit section, 405 addition section, 703 code generation section,
801: matched filter unit, 802: diversity selector unit, 901-1 to n: sample and hold circuit,
901, 902: sample and hold circuit section, 903-1
.About.4 ... Correlation calculation unit, 1001 ... Signal search unit, 1002 ...
Control unit, 1003-1 to 3 ... despreading unit, 1004 ... symbol combining unit, 1005 ... signal processing unit, 1101 ... PN2
Code generator, 1102 DLL section, 1103 Amplitude detection section, 1201 PN2 code generation section, 1202 PN1 code generation section, 1203 EX-OR section, 1204 DLL
Department.

Claims (3)

[Claims] A mobile station receives a spread signal transmitted through a communication channel multiplexed by discriminating a type of spread code and a type of spread code by using a predetermined spreading code and a common broadcast channel to all mobile stations. A plurality of correlator devices that take a correlation between them using a spreading code with respect to the obtained received spread signal; a broadcast channel demodulator that demodulates broadcast information of the broadcast channel from a correlation output of the correlator device; A communication channel demodulation unit that demodulates the communication information of the communication channel from the correlation output of the CDMA cellular system, wherein a plurality of broadcast channel demodulation units, a part or all of the plurality of correlation devices, Switching means capable of selecting and connecting to the plurality of broadcast channel demodulation units or the communication channel demodulation unit; Some of the plurality of correlator to any number in the channel demodulator or receiver of a CDMA cellular system characterized by a control unit for controlling said switching means so as to connect the whole. 2. A transmission spreading signal transmitted through a common broadcast channel to all mobile stations using a predetermined spreading code and a transmission spreading signal transmitted through a communication channel multiplexed by discriminating the type of the spreading code. Receiving a CDMA cellular system comprising: a plurality of correlator devices that take a correlation between the obtained received spread signals using a spreading code; and a plurality of demodulators respectively connected to the plurality of correlator devices. In the device, switching means for switching a part or all of the plurality of correlation devices and the plurality of demodulation units so as to be selectively used for demodulation of the broadcast channel symbol or the demodulation of the speech channel symbol, The switching means is controlled to use a part or all of the plurality of correlators and the plurality of demodulators for an arbitrary number of broadcast channels. A receiving device for a CDMA cellular system, comprising: a control unit that performs control. 3. An antenna diversity function for transmitting a transmission signal transmitted through a common broadcast channel to all mobile stations using a predetermined spreading code and a transmission spread signal transmitted through a communication channel multiplexed by discriminating the type of the spreading code. A CDMA cellular system comprising: a correlator for taking a correlation between them using a spreading code with respect to the received spread signal obtained; and a demodulator for demodulating the broadcast channel and the communication channel from a correlation output of the correlator. In the receiving apparatus of the system, the reception diversity signal input from each antenna branch by the antenna diversity function is sampled and held in correspondence with each antenna branch.
The correlation device further includes a switching unit for selecting and using the sample-and-hold circuit, and the received spread signal selected by the switching unit is determined by a spreading code of the broadcast channel and the communication channel. A plurality of correlation operation units for performing a correlation operation, and a control unit for controlling the switching unit to select a path to be combined for diversity and to select the sample and hold circuit of an antenna branch that can receive a path to be used. A receiving device for a CDMA cellular system.