JPH11313008A - Diffusion code generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a restriction that the code length of a producible diffusion code is limited to exponentiations of two by producing plural delay outputs whose delay times are different from one anther from a reference diffusion code series and producing a new diffusion code series having a code length which is an integer multiple to the reference diffusion code series by means of time division multiplexing. SOLUTION: A reference PN code generator 1 generates a reference pseudo- random (reference PN) code series. A branching device 2 branches a reference PN code series which is produced and outputted by the generator 1 into n pieces of code series. (N-1) pieces of delaying devices (3 (0), 3 (1),...3 (n-2)) whose number is smaller than a branch number (n) by one are provided. A time division multiplexer 4 performs time division multiplexing of inputs which are given from the device 2 and the devices 3 and are n pieces in all within one symbol section of the reference PN code series. That is, a new PN code series that is n times as long as the code length of the reference PN code series is outputted by performing n multiplexing within one symbol section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread code generator suitable for use in, for example, a code division multiple access (CDMA) type mobile communication system (personal communication system (PCS), digital cellular system, etc.).

[0002]

2. Description of the Related Art The following documents describe a CDMA mobile communication system.

Reference: "Mobile Station-Base Station Co
mpatibility Standard for Dual-Mode Wideband Spread
Spectrum Cellular System ", IS-95. In this document, a mobile station and a base station are provided with three types of spreading code generating means, respectively, and communicate with the three types of spreading codes generated by the respective spreading code generating means. In the communication system described in this document, four frames are allocated to three periods of the spreading code, and the synchronization acquisition of the mobile station and the base station is performed. A similar spreading code is used for a pilot channel to be used.

[0004]

However, in the case of the communication system disclosed in the above document, it is necessary to separately provide a spreading code generator for generating a spreading code required for communication for each required spreading code. This is a major obstacle in hardware design and configuration.

This is based on the following reasons. Generally, CD
In the MA communication system, a call is established between a base station and a mobile station using a spreading code. That is, the mobile station selects an optimal base station for communication, and the base station allocates a channel to the mobile station. At this time, the channels are distinguished by the mobile station spreading codes, and the number of mobile station spreading codes corresponds to the number of channels. Therefore, in consideration of interference from a mobile terminal connected to another base station in an adjacent relationship, it is necessary to prepare more spreading codes and secure the number of channels. However, when the number of spreading codes is increased, the number of spreading code generators provided in each of the mobile station and the base station is also increased, which causes the above-described problem.

Further, in the case of the communication system disclosed in the above-mentioned document, the length of a generated code sequence is defined by a power of two. Since it cannot be set freely, it is a great restriction on the design of the communication system and the system.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and comprises: (1) a reference spreading code generating means for generating a reference spreading code sequence;
(2) Mutual delay time (delay time 0
including. And (3) time-division multiplexing of the plurality of delayed outputs to generate a new spread code sequence having a code length that is an integer multiple of the reference spread code sequence. And time-division multiplexing means for generation.

As described above, the spread code generation apparatus according to the present invention can generate a new spread code sequence having a code length that is an integral multiple of one reference spread code sequence. That is, it is possible to eliminate the restriction that the code length of the spread code that can be generated is limited to a power of 2, unlike the conventional system. This also significantly increases the number of spread codes that can be generated within a limited code length.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a configuration example of a spread code generation apparatus according to the present invention and a form example of an application system thereof will be described.

(A) Configuration of Spreading Code Generation Apparatus The spreading code generation apparatus described below is characterized in that a plurality of reference PNs having different phases from one pseudo-random code sequence (hereinafter referred to as a “reference PN code sequence”). A code sequence is generated, and the code sequence length is time-division multiplexed to generate a plurality of reference PN code sequences having an arbitrary spreading code length.

Hereinafter, the configuration of such a spread code generating apparatus will be described.
Two embodiments will be described.

(A-1) First Embodiment FIG. 1 shows a functional block configuration of a spread code generating apparatus according to a first embodiment. The spread code generation device according to this embodiment includes a reference PN code generator 1, a branching device 2, a variable delay device 3, a time division multiplexing device 4, and a control device 5.

The reference PN code generator 1 is a means for generating a reference PN code sequence. For example, an M-sequence code generator is used.

The branching device 2 is means for branching the reference PN code sequence generated and output by the reference PN code generator 1 into n code sequences. Here, the number n of branches depends on the multiplicity n of the reference PN code sequence. Note that the maximum value that the number of branches n can take is given by an integer value smaller than the code length N of the reference PN code sequence by one.

The delay units 3 (3 (0), 3 (1)... 3 (n−
2)) is a value that is one less than the number of branches n, that is, n
-1 are provided. This is for this embodiment,
This is because one of the code sequences to be multiplexed by the time division multiplexing device 4 is the reference PN code sequence with a delay time of 0 itself. Therefore, in the case of a configuration in which all delayed signals are multiplexed, the number of the delay devices 3 may be n.

The delay units 3 are configured so that the delay times can be freely and variably set. The delay time of each delay unit 3 is provided from the control device 5 and is set individually. Here, the delay time is given as an integral multiple of one symbol section T of the reference PN code sequence output from the reference PN code generator 1. Therefore, assuming that the delay time is 3 symbols, 1 symbol, and 0 symbols (no delay), the phase relationship of the reference PN code sequence output from each delay unit 3 is, for example, as shown in FIGS. ).

The time-division multiplexing device 4 time-division-multiplexes a total of n inputs provided from the branching device 2 and the delay unit 3 into one symbol section of the reference PN code sequence, ie, 1
This is a means for outputting by multiplexing n within a symbol section. The time division multiplexing device 4 cyclically multiplexes each input according to a predetermined order. In the case of this embodiment, the time-division multiplexing device 4 performs the multiplexing in the descending order of the delay. FIGS. 2B to 2D show this state. Thus,
As shown in FIG. 2E, the time-division multiplexing device 4 generates a new PN code sequence n times the code length N of the original reference PN code sequence.

The control device 5 responds to the generated spreading code by
This is means for individually controlling the delay time set by each delay unit 3. Here, the control device 5 sets such that any two of the delay times set at the time of communication have different values. For example, assuming that the code length of the reference PN code sequence is N, the control device 5 sets the delay time of each delay unit 3 to 0 <N
(N-2) <... <N1 <N0 <N. In addition to this function, the control device 5 is provided with a function of controlling the combination of time-division multiplexed delay outputs in accordance with the generated spreading code.

FIG. 3 shows an embodiment of the spread code generator. FIG. 3 is an example of a configuration in which an M-sequence code generator is used as the reference PN code generator 1 and the number of multiplexes n is three. In the case of FIG. 3, a time T holding circuit 41 is used as an output stage of the time division multiplexing device 4 to control the output timing.

Next, an example of the operation of the spread code generator having the above configuration will be described. Note that this operation example is a case where the spreading code generation device is applied to a CDMA mobile communication system.

At the time of synchronization acquisition, the control device 5
Each of the delay times N0 and N1 of (0) and 3 (1) is set to no delay (that is, N0 = 0 and N1 = 0).

At this time, the time-division multiplexing device 4 is provided with three code sequences having the same phase, for example, as shown in FIGS. Therefore, from the time division multiplexer 4,
As shown in FIG. 4 (D), three identical symbol values are successively output for each symbol section, and as a result, as shown in FIG. 4 (E), the original reference PN code sequence itself is output. It will be the same.

This is because the shorter the code length of the spread code sequence output from the time-division multiplexing device 4, the earlier the correlation detection by a matched filter or the like can be performed, and the faster the synchronization acquisition. .

On the other hand, at the time of communication, since synchronization is already secured, it is important to spread the communication band over a wide band and increase the number of multiplexed communication channels.

Therefore, the control device 5 sets the delay times N0 and N1 of the delay units 3 (0) and 3 (1) to be different values. Thus, the time division multiplexer 4
Thus, a new PN code sequence having a spreading factor three times that of the original reference PN code sequence is generated and output.

As described above, according to the configuration of the first embodiment, only by providing one reference PN code generator 1, a PN code sequence having a code length that is an integral multiple of that can be freely generated. . In addition, it is possible to eliminate the restriction of being limited to a power of 2 unlike the conventional device, and it is possible to remarkably improve the degree of freedom in designing a communication system.

In this embodiment, if the number of branches n or the number of inputs used for time division multiplexing is selected and the multiplexing rate is changed accordingly, a plurality of PN code sequences can be changed from one reference PN code sequence. Can be generated. Therefore, it is not necessary to use as many generators as the number of necessary PN code sequences as in the conventional device, and the circuit scale can be reduced and the degree of freedom in designing can be greatly improved.

(A-2) Second Configuration Example FIG. 5 shows a functional block configuration of a spread code generation device according to the second embodiment. Here, in FIG. 5, the same corresponding parts as those in FIG. 1 are denoted by the same corresponding reference numerals.

The second embodiment is different from the first embodiment in the method of realizing a PN code sequence. That is, in the first embodiment, the delay time of the delay unit 3 is individually controlled. However, in the second embodiment, the delay time of the delay unit 3 is fixed, and the time-division multiplexing device 4 'is used.
The difference is that the same function is realized by controlling the multiplexing operation of. Hereinafter, only different components will be described.

One difference is that a fixed delay unit 3 'is used as a delay unit used for delaying the reference PN code sequence. Here, the condition required for the delay time of each delay unit 3 ′ is that any two of the delay times have different values as described in the first embodiment. Also in this embodiment, the number of delay units 3 'is set to n-1 which is one less than the multiplexing number n, but one of the multiplexing inputs is the same as the original reference PN code itself. To do that.
Therefore, in the case of multiplexing all signals that have undergone some delay, the number of delay units 3 'may be set to the same number as the multiplex number n.

Another difference is that a multiplexing means having a structure capable of switching the operation between the time of synchronization acquisition and the time of communication is used as the time division multiplexing device 4 '. That is, the time-division multiplexing device 4 ′ stops the time-division multiplexing operation at the time of synchronization acquisition and outputs the original reference PN code itself, while the communication device provides a total of n given from the branching device 2 and the delay unit 3 at the time of communication The number of inputs is time-division multiplexed within one symbol section of the reference PN code sequence. Accordingly, the control target of the control device 5 'is also the time-division multiplexing device 4'.

The control device 5 'controls the number of multiplexes and the order of multiplexing in accordance with the generated spreading code.

As described above, in the second embodiment,
Although a part of the configuration is different from that of the first embodiment, the basic operation itself is the same. That is,
From one reference PN code sequence, a PN code sequence having a code length that is an integral multiple of the reference PN code sequence can be freely generated. In addition, it is possible to eliminate the restriction of being limited to a power of 2 unlike the conventional device, and it is possible to remarkably improve the degree of freedom in designing a communication system.

Also in the case of this embodiment, if the number of branches n or the number of inputs to be time-division multiplexed is selected and the multiplexing speed is changed accordingly, a plurality of PN codes can be obtained from one reference PN code sequence.
A code sequence can be generated. Therefore, it is not necessary to use as many generators as the number of necessary PN code sequences as in the conventional device, and the circuit scale can be reduced and the degree of freedom in designing can be greatly improved.

(B) Example of Applied System (B-1) Example of First System FIG. 6 shows a first example of application of the spread code generation apparatus according to the present invention.
The following shows an example of the system. The first system example is an example in which the present invention is applied to a system using a spreading code for communication between a fixed station (base station) 100 and a mobile station 110.

Here, the spread code generation device is a modulation / demodulation device 1 constituting the fixed station (base station) 100 and the mobile station 110.
01, 102 and 111 and 112 respectively. In the figure, the existence of this spreading code generation device is indicated by 101.
A, 102A, 111A and 112A.

In the first system, a predetermined communication operation is performed by the following operation. Each base station 100 periodically generates and transmits an original reference PN code sequence for establishing synchronization in order to establish synchronization with the mobile station 110 in its service area. Here, the spreading code generator 101A of the base station 100 outputs the original reference PN code sequence output from the reference PN code generator 1 as it is. This behavior is
The operation is the same as the operation at the time of synchronization acquisition described above. The generated spreading code (reference PN code sequence) is transmitted to the mobile station as a pilot signal.

However, if the transmission phase of such a pilot signal is the same as that of another base station, mobile station 110
Since the spreading code sequences from the respective stations interfere with each other, neighboring base stations 100 transmit the signals with shifted phases so that the transmission timings of the pilot signals do not coincide with each other.

When the mobile station 110 specifies the base station 100 including its own station in the service area based on the reception status of the pilot signal and other information, the mobile station 110 registers itself in the base station 100 and continues to register this base station. Monitor 100. Thereafter, an access request is issued from the mobile station 110 to the base station 100, or a call is issued from the base station 100 to the mobile station 110, and the operation shifts to a communication operation.

Prior to communication, the base station 100 notifies the mobile station 110 of the setting of the spreading code used for communication between the two stations. Here, the base station 100 notifies the number of delay units 3 (or 3 ′) used for generating the spreading code and the delay time of each delay unit 3 (or 3 ′) as the setting of the spreading code used for communication. I do.

After the above setting operation, communication is started in both the base station 100 and the mobile station 110 using the spread code generated under the conditions determined in the setting operation. Incidentally, the mobile station 110 of this communication system
By transmitting the transmission frame in synchronization with the phase of the reception frame received from the STA, the time required for uplink synchronization is reduced.

An advantage of applying the spread code generation device according to the present invention to such a communication system is that the configuration of the device for generating a spread code can be the same between the base station 100 and the mobile station 110. This is a very effective effect in designing hardware.

The spreading codes used in this system have a relationship given by an integral multiple of the code length of the reference PN code sequence. Therefore, if there is a certain relationship between the period of the reference PN code sequence and the frame period, the period of the spread code sequence can be easily adjusted to the frame period.

Since the code length of the spread code is not limited to a power of 2, the design of the communication system and system can be simplified.

(B-2) Second System Example FIG. 7 shows a second system to which the spreading code generation apparatus according to the present invention is applied.
The following shows an example of the system. The second system example is different from the first system example in that a fixed station (wireless switching device 200)
This is an example of a case where the present invention is applied to a system using a spreading code for communication between devices. However, the wireless switching device 200 may be movable.

When a request for communication is generated between the terminal devices 201 accommodated in the wireless switching device 200, the wireless switching device 200 executes a connection operation via a switching function (not shown), while the other wireless switching device 200 When a connection to any of the terminal devices 201 accommodated in the terminal is requested, a connection operation is performed via a wireless propagation path. In the figure, each terminal device 201
A relay station between the wireless switching device 200 and the wireless switching device 200 is omitted.

Here, the spread code generation device is a line modulation / demodulation device 202 (2) provided corresponding to each terminal device 201.
02A, 202B, 202C).
05 and the despreading devices 209 and 210, respectively. In the figure, the existence of this spread code generation device is indicated by 204
A, 205A, 209A, and 210A.

Spreading devices 204 and 205 perform an operation of spreading and modulating user data input from each terminal device 201 by using a spreading code generated internally. That is, spread modulation processing is executed using a spread code assigned in advance for discriminating the line path on the receiving side.
Each of the spread code generation devices 204A and 205A performs a delay setting operation based on the address given from the address conversion and error correction device 203. Here, a set of delay times and a multiplex number used for generating a spreading code are set.

The setting contents are stored in the wireless switching device 2 on the transmitting side.
00 is notified to the wireless switching device 200 on the receiving side, and according to the contents, conditions for generating the spreading code generated by the despreading devices 209 and 210 of the wireless switching device 200 on the receiving side are set. On the receiving side, the despreading devices 209 and 2
When the output of 10 exceeds a certain threshold, it is determined that the line is connected, and the physical layer is operated.

The address conversion and error correction device 203 that performs the operation of the upper layer analyzes and converts the address of the terminal device 201 as the transmission destination from the data input from the terminal device 201 as a function of the network layer, and performs the conversion as described above. Then, the translated address is sent to the spreading devices 204 and 205. The converted address is given to the spreading code generators 204A and 205A, and is used, for example, for setting a register initial value at a certain time.

The address translation and error correction device 20
3 executes an error correction process as a function of the data link layer. Here, this error correction function is connected to both the uplink and downlink lines in order to execute error retransmission, to eliminate transmission errors caused by the radio circuit, and to guarantee the order of the data sequence.

The wireless switching device 200 on the transmitting side uses, for example, a slotted Aloha method as its access method. This is because by matching the period of the spreading code to the slot, it becomes easy to match the spreading period at the time of transmission with the despreading period at the time of reception, and the transmission efficiency is higher than in the pure Aloha system.

In order to increase the transmission efficiency, a channel for transmitting a control signal for switching connection is secured, the status of the receiving circuit is broadcast, or the connection is controlled by giving a connection instruction to the partner station. . This is called flow control.

The station desiring transmission transmits a transmission request message to the receiving station in the form of a packet. For this packet transmission, the slotted Aloha system is used, but by shortening the packet length, the probability of collision can be reduced.

When the transmission request message reaches the receiving station, the receiving side secures the transmission channel as requested in the transmission request message, and transmits a transmission permission message to the transmitting station. The transmitting side performs transmission according to the transmission permission message. By performing the schedule, the transmission efficiency can be increased.

Thus, even when the spreading code generation device according to the present invention is applied to such a communication system, the configuration of the device for generating the spreading code can be made identical in each of the wireless switching devices 200, and the hardware Design is easy.

Further, since the code length of the spreading code is not limited to a power of two, it is easy to add wireless switching device 200.

(B-3) Third System Example FIG. 8 shows a third system to which the spreading code generation apparatus according to the present invention is applied.
The following shows an example of the system.

The third example of the system is different from the above-mentioned two examples of systems in that it is applied to spread coding or decoding of a digital watermark to be embedded in original information.

On the other hand, advances in recording technology today have increased the risk of unauthorized copying / duplication of works (music, video, etc.) owned by the copyright holder. In order to protect the copyright holder from such unauthorized copying, a method of embedding digital watermark information spread with a spreading code such as a PN code in original information has been proposed. Note that an ID number that can be distinguished for each distribution is given to the digital watermark information.

The digital watermark information is regarded as pseudo noise from the original information, and its intensity level is set so as not to impair the quality of the original information. For this reason, even if such a digital watermark is embedded in the information purchased by the user from the copyright holder, it cannot be determined.

On the other hand, when the copyright holder obtains the illegally copied information existing in the city, if the information is despread using the PN code used for embedding the digital watermark information in the information, the copyright holder is embedded in the information. Since the ID number can be obtained, fraudulent acts of the user can be detected. In addition,
Since it is very difficult for the user to generate the PN code, it is almost impossible to remove the watermark information.

The configuration of the device used for such a purpose is the configuration of the digital watermark embedding and extracting device 300 shown in FIG. Here, the PN code generation device 301 is a device corresponding to the spread code generation device according to the present invention. In particular, in this type of apparatus, it is important to be able to use the PN code as much as possible and to be able to generate the PN code simply. Therefore, by using the above-described spread code generation device, the length and initial value of the generated code sequence can be determined flexibly, and all code sequences can be generated from the same PN code generation device. it can. Therefore, the design of the system becomes easy.

The exclusive OR circuit (XOR) 303
And 304 are watermark information 30 prepared for each user.
2 and 303 are means for spread-encoding each of them, and the output is used as digital watermark information.
The addition circuits 304 and 307 are means for embedding digital watermark information in the original information, and the output thereof is information provided to users A and B.

An exclusive OR circuit (XOR) 308
Is a means provided for identifying from which user illegally copied information existing in the market has leaked. In this exclusive OR circuit (XOR) 308, the digital watermark information 309 embedded in the information can be extracted by multiplying the information with the digital watermark by the PN code sequence.

(C) Other Embodiments (C-1) In the above embodiment, n multiplexing is performed within one symbol period, that is, the period (time) of the spread code sequence output after time division multiplexing. Has been described as being equal to the period (time) of the original reference PN code sequence.
The time division multiplexing speed is not limited to this.

(C-2) In the above-described embodiment, a plurality of delay outputs having different delay times (including a delay time of 0) from one reference PN code sequence are transmitted to the branching device 2. Although the case of generation using the delay unit 3 or 3 'has been described, the generation means is not limited to this. For example, a multistage shift register may be used, and a plurality of delay outputs output from all or some of the stages may be extracted.

(C-3) In the first and second system examples described above, the case where the present invention is applied to the wireless communication between the base station and the mobile station and the wireless communication between the wireless switching devices has been described. Can be applied to the spread code communication system.

(C-4) Also, in the third system example described above, the case where the present invention is applied to embedding and extracting digital watermark information into a work is described. Can be widely applied to a system in which spread-encoding (encryption) is performed by embedding and extracting.

[0070]

As described above, according to the spread code generation apparatus of the present invention, a new spread code sequence having a code length that is an integral multiple of one reference spread code sequence can be generated from one reference spread code sequence. Furthermore, it is possible to eliminate the restriction that the code length of the generated spread code is limited to a power of 2, and to remarkably increase the number of spread codes that can be generated within the limited code length.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a first embodiment of a spread code generation device.

FIG. 2 is a diagram showing a spread code generation procedure during communication.

FIG. 3 is a block diagram illustrating an embodiment of a spread code generation device.

FIG. 4 is a diagram showing a spread code generation procedure during synchronization acquisition.

FIG. 5 is a block diagram showing a second embodiment of the spread code generating apparatus.

FIG. 6 is a block diagram showing a first application system example.

FIG. 7 is a block diagram illustrating a second applied system example.

FIG. 8 is a block diagram illustrating a third applied system example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reference PN code generator, 2 ... Branch device, 3 3 '... Variable delay device, 4,4' ... Time-division multiplexing device, 5,5 '... Control device, 100 ... Base station, 110 ... Mobile station, 101A, 1
02A, 111A, 112A, 204, 205, 20
9, 210, 301: spread code generating device, 200: wireless switching device, 300: digital watermark embedding and extracting device.

Claims (4)

[Claims] 1. A reference spreading code generating means for generating a reference spreading code sequence, and a delay time (delay time 0
including. A delay output generating means for generating a plurality of delay outputs different from each other, and time-division multiplexing of the plurality of delay outputs to generate a new spread code sequence having a code length that is an integral multiple of the reference spread code sequence. A spread code generation device comprising: division multiplexing means. 2. The spreading code generating apparatus according to claim 1, wherein the delay output generating means is different from a splitting means for splitting the reference spreading code sequence into a plurality of sequences, and each of the split sequences. And a delay unit for adding a delay time (including a delay time of 0). 3. A spread code generation apparatus according to claim 2, wherein a set of delay times to be given to the branched sequence and a set of delay outputs used for time division multiplexing are controlled in accordance with the generated spread code sequence. A spread code generator, further comprising a control unit. 4. The spread code generation apparatus according to claim 2, further comprising control means for switching the code length of the generated spread code between the time of synchronization acquisition and the time of normal operation. apparatus.