JPH11215098A - Apparatus and system for spread spectrum communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To substantially satisfy communication quality and transmission efficiency by transmitting/receiving head length in a frame which has different frame head in accordance with a communication environment. SOLUTION: A header inverse diffusion part 34 opens a switch 33 during a frame header period and closes it during a frame data period. An information demodulation part 38 demodulates information against a signal from the switch 33. An error correction decoding part 39 executes error correction/decoding, based on an encoding rate on the type of a radio frame adopted at that time against the demodulated signal. A frame decomposition part 41 decomposes the signal of a frame unit, which has the number of data corresponding to the type of the radio frame adopted at that time, by using the count value of a frame length counter 42 and restores user information which a facing transmitter is to transmit. Thus, a frame length can be changed in accordance with the communication environment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication apparatus and system, for example, a code division multiple access (CDMA) for transmitting and receiving a known reference signal (header) by time-multiplexing transmission data.
The present invention can be applied to a mobile communication system (hereinafter, referred to as a CDMA mobile communication system) according to a Multiple Access) communication system.

[0002]

2. Description of the Related Art In recent years, CDs to which wireless packet communication is applied
Research and development of the MA mobile communication system are underway.

In the CDMA communication system, a method has been proposed in which a sequence that has been spread once is spread again in order to reduce the synchronization detection time of a long-period sequence. For example, a method has been proposed in which a header is added to transmission data, and only the header portion is double-spread. The added header is used for packet detection and coherent detection at the receiver. Further, in the CDMA communication system, by increasing the processing gain of the header, it is possible to improve the estimation accuracy of the channel used for packet detection and coherent detection.

[0004] Hereinafter, processing in a conventional CDMA mobile communication system will be briefly described using a downlink traffic channel as an example.

[0005] After the user information generated in the base station is framed, it is subjected to error correction coding and information modulation. After that, spreading is performed using a spreading code, and a header that has been multiplexed and spread by applying a spreading code for a header is added. Then, the baseband signal obtained in this way is up-converted to a radio frequency (RF) band and emitted to space (wireless line).

On the other hand, on the mobile station (reception) side, the baseband signal obtained by down-converting the received signal is despread, and the despread signal is despread using a spreading code for header. To detect the beginning of the frame. When the head of the frame is detected, information demodulation and error correction decoding are performed on the despread signal for the baseband signal in a period other than the header period, and the decoded frame data is decomposed to be transmitted by the base station. Restores the user information.

[0007]

The method of adding a header has the advantage that the synchronization pull-in is fast, but has the characteristic that the ratio of the header length to the frame length affects the transmission efficiency.

For example, in order to cope with a high-speed movement of a mobile station, it is preferable to shorten the frame length so that a header is frequently generated.
The transmission efficiency of the original transmission data deteriorates. On the other hand, if the frame length is increased in order to improve the transmission efficiency of the transmission data, the header period is also increased, the synchronization acquisition accuracy and the like are reduced, and the communication quality is reduced.

Therefore, there is a need for a spread spectrum communication apparatus and system capable of satisfying both transmission efficiency and communication quality.

[0010]

According to a first aspect of the present invention, there is provided a spread spectrum communication apparatus for performing transmission to an opposing spread spectrum communication apparatus in units of a frame including a header period and a data period. Spread signal forming means for forming a spread signal per frame having a length corresponding to the currently adopted frame length from the information, and (2) a header corresponding to the currently adopted frame length. A header adding means for forming a spread header signal relating to the length and preceding the spread signal formed by the spread signal forming means; and (3) a frame length of a currently adopted frame length from a plurality of frame lengths. A frame control means for instructing the spread signal forming means and the header adding means with information is provided.

According to a second aspect of the present invention, in a spread spectrum communication apparatus in which a signal in units of a frame including a header period and a data period arrives from an opposite spread spectrum communication apparatus, (1) the signal is adopted at that time. Transmission information restoring means for despreading the signal in the data period of the received signal determined according to the type of the frame length, and restoring the information which the opposed spread spectrum communication apparatus has attempted to transmit, (2) employed at that time Header reception processing means for performing synchronization acquisition and synchronization continuation processing while despreading the signal of the header period in the reception signal determined according to the set frame length, and (3) a plurality of frame lengths. Frame control means for instructing the information on the adopted frame length to the transmission information restoring means and the header reception processing means. The features.

A third spread spectrum communication system according to the present invention comprises a first spread spectrum communication apparatus on the transmitting side.
The spread spectrum communication apparatus of the present invention is applied, and the spread spectrum communication apparatus of the second present invention is applied as a receiving-side spread spectrum communication apparatus.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a spread spectrum communication apparatus and system according to the present invention is applied to a system according to a CDMA communication system will be described below in detail with reference to the drawings.

FIG. 1 is a functional block diagram showing a configuration of a transmitter of a traffic channel in this embodiment.
Note that the configuration shown in FIG. 1 is mounted on a base station for a downlink traffic channel and mounted on a mobile station for an uplink traffic channel.

In FIG. 1, a transmitter 10 includes a framing unit 11, a frame length counter 12, an error correction encoding unit 1
3, coding rate control unit 14, information modulation unit 15, spreading unit 1
6, spreading code generator 17, header adding unit 18, header spreading code generator 19, header register 20, header length counter 21, frequency converter 22, and frame controller 23
have.

[0016] The framing section 11 is for framing the user information and providing it to the error correction coding section 13. The framing unit 11 performs framing based on the count value of the frame length counter 12 so that the amount of user information per frame becomes the upper limit count value set in the frame length counter 12 at that time. An upper limit count value (user information amount per frame) is set in the frame length counter 12 from a frame control unit 23 described later.

The error correction coding unit 13 performs error correction coding on the frame of the input user information and supplies the frame to the information modulation unit 15. Here, for example, a convolutional coding method is applied as the error correction coding method, and the error correction coding unit 13 can change the coding rate. Error correction coding unit 13
Performs error correction coding at the coding rate specified by the coding rate control unit 14. The coding rate control unit 14 instructs the error correction coding unit 13 on the coding rate set by the frame control unit 23 described later.

The information modulation section 15 performs information modulation (for example, BPSK modulation, QPSK modulation, etc.) on an input signal and supplies the signal to a spreading section 16.

The spreading section 16 spreads and modulates the information-modulated signal using a spreading code (for example, a PN code) provided from a spreading code generation section 17 and supplies the resulting signal to a header adding section 18.

The header adding unit 18 includes a header register 20
Is extracted until the header length counter 21 counts the upper limit count value, and the header pattern is spread by the spreading code for the header given from the spreading code generator 19 for the header. And is provided to the frequency conversion unit 22 before the frame signal.

In the case of this embodiment, the header spreading code (sequence) output from the header spreading code generator 18 is:
If this is represented by PN # 2 and the spreading code (sequence) from the spreading code generator 16 is represented by PN # 1, PN # 2 = PN # 1
* PN # X, which has a larger spreading gain than the spreading code PN # 1 by the spreading gain of the spreading code PN # X, and also includes a component of the spreading code PN # 1. It is a thing.

A header pattern is set in the header register 20 by a frame control unit 23 described later.
The upper limit count value of the header length counter 21 is also set by the frame control unit 23 described later.

Although the illustration of the signal lines is omitted, the activation (initial phase) of the spreading code generator 17 and the spreading code generator 19 for the header is also controlled by the frame controller 23.

The frequency conversion unit 22 up-converts the frequency of the output signal from the header addition unit 18 to a radio frequency band (RF band). The up-converted RF signal is controlled in transmission power, applied to a shared transmission / reception antenna via an unillustrated antenna transmission / reception unit, and radiated to space (wireless line).

The frame control unit 23 determines which of the three types of radio frame configuration is to be applied based on the communication environment at that time, and based on the determined radio frame configuration,
As described above, the frame length counter 12, the coding rate control unit 14, the header register 20, and the header length counter 2
Control 1

FIG. 2 shows a header period (header length) and a data period (data length) of three types of frames in a wireless line.
FIG. 4 is an explanatory diagram showing a relationship with the above.

As the radio frame, a standard frame having a standard radio frame length shown in FIG. 2A, a long frame having a longer radio frame length as shown in FIG. 2B, and a radio frame length longer than the standard frame are shown. Fig. 2 (C)
There are three types of short frames. Both the header length and the data length increase in the order of the short frame, the standard frame, and the long frame. The header patterns for the header periods of the long frame, the standard frame, and the short frame are independent from each other. That is, the length of the same header pattern used is not changed, but is a separate pattern.

FIG. 2 shows an example in which a standard frame has twice the length of a short frame and a long frame has a length four times that of a standard frame.

The frame control unit 23 controls the frame length counter 12, the coding rate control unit 14, the header register 20, and the header length counter 21 based on one of the radio frame configurations determined at that time.

The frame controller 23 determines a radio frame to be applied, for example, as follows.

The radio frame at the start of communication is a standard frame. It receives one or more parameters or communication environment evaluation values that define the communication environment and are transmitted from the opposing receiver (see FIG. 3) through the control channel. The one or more parameters that define the communication environment include a moving speed, a BER (bit error rate), and the like. For example, if the receiver has an AFC (automatic frequency control) function, the moving speed is obtained from the change in the AFC signal and the Doppler frequency from the change in the tap coefficient of the channel estimator. It is obtained by converting it into speed information. If one or a plurality of parameters are transmitted, they are converted into communication environment evaluation values by a predetermined operation such as weighted addition. The necessity of switching to another wireless frame configuration is determined by comparing the communication environment evaluation value obtained in this way or the received communication environment evaluation value with a threshold.

The long frame is used when the communication environment is good, the short frame is used when the communication environment is bad, and the standard frame is used when the communication environment is intermediate. Things.

In this embodiment, the coding rate in error correction coding is increased in the order of a short frame, a standard frame, and a long frame.
That is, in this order, the ratio of the number of bits increased for error correction decreases.

The above-described review of the radio frame configuration is performed, for example, every period that is an integral multiple of the long frame period.

When it is determined that the radio frame is to be switched, the frame controller 23 notifies the frame controller (see FIG. 3) of the opposing receiver of the type of the radio frame through the control channel.

If the same radio frame is used for the upstream and downstream traffic channels, one or more parameters defining the communication environment are not transmitted from the receiver of the opposite station, but the transmitter is mounted. It may be obtained from the receiver of the own station.

Further, a radio frame to be applied by the frame control unit (see FIG. 3) on the receiver side is determined, and the type of the determined radio frame is notified to the frame control unit 23 of the transmitter 10 through a control channel. There may be.

Next, the operation of the traffic channel transmitter 10 shown in FIG. 1 will be briefly described with reference to FIG.

As the user information, the count value of the frame length counter 12 is used by the framing unit 11,
The frame is divided into frames each corresponding to the type of the radio frame determined at that time, and is provided to the error correction encoding unit 13. The error correction coding unit 13 applies an error to the frame of the input user information at the coding rate specified by the coding rate control unit 14 and according to the wireless frame type determined at that time. Correction encoding is performed. The signal after error correction coding is subjected to information modulation by information modulating section 15 and applied to spreading section 16, where the signal is spread using the spreading code given from spreading code generating section 17. To the header adding unit 18.

The header adding unit 18 uses the count value of the header length counter 21 to determine the header pattern corresponding to the radio frame type set in the header register 20 at that time. Only the length corresponding to the determined header length of the radio frame type is extracted, and the header pattern of the predetermined header length is spread by the spreading code for the header given from the spreading code generator 19 for the header. To the frequency converter 22.

In the frequency conversion section 22, the frequency of the output signal from the header addition section 18 is changed to a radio frequency band (RF
The RF signal is up-converted into a band, the transmission power of the up-converted RF signal is controlled, and the RF signal is given to a shared antenna via a shared antenna (not shown) and radiated to a space (wireless line).

FIG. 3 is a functional block diagram showing a configuration of a receiver of a traffic channel in this embodiment.
Note that the configuration shown in FIG. 3 is installed in a mobile station if it is a downlink traffic channel, and is installed in a base station if it is an uplink traffic channel.

The receiver 30 includes a despreading section 31, a spreading code generating section 32, a switch section 33, a header despreading section (header searcher) 34, a header spreading code generating section 35, a header register 36, a header length counter 37, Information demodulation unit 3
8, an error correction decoding unit 39, a coding rate control unit 40, a frame decomposition unit 41, a frame length counter 42, and a frame control unit 43.

A reception signal in the RF band, which is captured by a transmission / reception antenna (not shown) and input via an antenna transmission / reception device (not shown), is amplified by a radio reception unit (not shown).
The signal is down-converted, converted into a baseband frequency band, and provided to the despreading unit 31. Note that the AFC signal generated in the processing of the wireless reception unit is provided to, for example, a Doppler frequency detection unit (not shown).

The despreading section 31 performs despreading, which is the reverse processing of the processing in the spreading section 16, on such a baseband signal using the spreading code given from the spreading code generating section 32. It is. Here, the spreading code generation unit 32
It incorporates a matched filter or a sliding correlator, etc., and estimates (synchronously captures) a spreading code phase in a baseband signal to generate a spreading code. If the initial phase is set for each radio frame, the timing information of the initial phase is instructed by the frame control unit 43.

Since the frame header is also spread by a code having the same sequence as the spreading code generated by the spreading code generating unit 17, even if the despreading unit 31 is provided before the header despreading unit 34, there is a problem. Never.

In the header register 36, a header according to the type of the radio frame employed at that time is set by the frame control unit 43, and is taken out by the header despreading unit 34.

In the header length counter 37, an upper limit count value which defines a header period according to the type of radio frame employed at that time is set by the frame control unit 43, and the count value is set by the header despreading unit 34. It is used when confirming the header period (header pattern).

The header spreading code generator 35 generates a header spreading code for the header despreading unit 34 to despread. If the initial phase is set for each radio frame, the timing information of the initial phase is instructed by the frame control unit 43.

The header despreading unit 34 has a built-in matched filter or sliding correlator, and captures the frame header of the input signal to control the on / off of the switch 33.

The header despreading unit 34 is set with a header spreading code in the header spreading code generating unit 35, obtains a correlation value between the input signal and the header spreading code, and obtains a pattern when the correlation value is large. Is matched with the header pattern stored in the header register 36 and the header pattern of the length specified by the header length counter 37, the presence of the frame header is notified to the frame control unit 43, and the switch 33 is Leave open. The switch 33 is closed during such a frame data period in which a large correlation value cannot be obtained.

The switch 33 allows only the signal (frame data) from the despreading unit 31 arriving during the period designated by the header despreading unit 34 to pass therethrough and gives it to the information demodulation unit 38.

The information demodulation unit 38 subjects the output signal of the switch 33 to information demodulation processing, which is the inverse processing of information modulation in the transmitter 10, and gives the result to the error correction decoding unit 39.

The error correction decoding unit 39 includes the coding rate control unit 4
According to the coding rate information set to 0, error correction decoding which is a reverse process of the process in the error correction coding unit 13 is performed, and the result is given to the frame decomposition unit 41. In the coding rate control unit 40, the frame control unit 43 sets the coding rate according to the type of the radio frame employed at that time. For example, information such as BER detected by the error correction decoding unit 39 is provided to the opposing transmitter 10 or the frame control unit 23 of the transmitter 10 of the own station if necessary.

The frame decomposing unit 41 uses the count value of the frame length counter 42 to generate the error
9 is to decompose the signal in frame units given from 9 and restore the user information that the opposing transmitter 10 tried to transmit. Since the number of valid data for each wireless frame differs depending on the type of wireless frame, the count value of the frame length counter 42 is used. Frame length counter 4
The upper limit count value is set to 2 by the frame control unit 43.

As described above, the frame control unit 43
By transmitting and receiving information using the control channel to and from the frame control unit 23 of the transmitter 10, the type of the radio frame employed at that time is grasped. As shown in the header register 3
6, a control operation for the header length counter 37, the coding rate control unit 40, and the frame length counter 42. Further, based on a detection signal of a header pattern from the header despreading unit 34, a timing signal is given to each unit.

Although not shown, the receiver 30 includes a propagation path estimator (for example, provided in connection with a header despreading unit). Is used to control the switching of the radio frame type, if necessary, with the opposing transmitter 10 or its own transmitter 10.
Is provided to the frame control unit 23.

Next, the operation of the receiver 30 composed of the units having the above functions will be briefly described.

A reception signal in the RF band, which is captured by a transmitting / receiving antenna (not shown) and input to the receiving configuration through the antenna transmitting / receiving device, is amplified by a radio receiver (not shown).
The signal is down-converted, converted into a baseband frequency band, and provided to the despreading unit 31.

The despreading unit 31 is provided with a spreading code from the spreading code generation unit 32, and the despreading unit 31 is provided with the baseband signal from the radio reception unit from the spreading code generation unit 32. Despreading is performed using a spreading code. The despread signal is provided to the switch 33 and the header despreading unit 34.

Under the control of the frame header control unit 43, the header despreading unit 34 sends a predetermined value corresponding to the type of the radio frame at that time from the header register 36, the header length counter 37 and the header spreading code generation unit 35. The information is provided, the detection of the frame header and the continuous synchronization management are performed, and the header despreading unit 34 opens the switch 33 during the frame header period and closes the switch 33 during the frame data period.

In the information demodulation unit 38, the switch 33
Demodulates the information from the signal from
9, the signal after the information demodulation is subjected to error correction decoding based on the coding rate according to the radio frame type adopted at that time. Using the count value, a signal in a frame unit having the number of data according to the type of the radio frame employed at that time is decomposed, and user information that the opposing transmitter 10 attempts to transmit is restored.

As described above, according to the above-described embodiment, the frame length is changed according to the communication environment. Therefore, the transmission efficiency is enhanced when the communication environment is good, and the transmission efficiency is improved when the communication environment is poor. Even if efficiency is sacrificed, communication quality can be ensured, and both transmission efficiency and communication quality can be almost satisfied.

For example, when moving at high speed, a short frame is used to ensure that the propagation path estimation result in the header is correct over the frame length. That is,
At the time of high-speed movement, the result of the propagation path estimation changes rapidly. Therefore, by shortening the frame length, the next header arrives before the estimation result changes, and high quality can be maintained. Also, for example, when a low BER is desired to be realized, the error correction capability can be increased by similarly setting a short frame (and reducing the coding rate). Further, for example, when it is desired to increase transmission efficiency, a long frame is used. Also,
For services that allow a relatively high BER, such as packet data, a method of increasing the coding rate can be used together.

Here, it is conceivable to make the header length the same even if the frame length changes, but in this embodiment, the header length is also changed. For short frames,
When the header length is the same as in other frame configurations, the transmission efficiency is further deteriorated. On the other hand, in the case of a long frame, since the header interval is considerably long, it is required to improve the propagation path estimation accuracy using the header. By changing the header length, the above-described problems and requirements can be satisfied.

Further, according to the above embodiment, the header pattern is clearly changed for each type of frame configuration, so that the receiver can surely check the header pattern.

Furthermore, according to the above embodiment, the coding rate in the error correction processing is changed according to the type of the frame configuration. That is, the transmission efficiency in a state where the communication quality is good can be further improved.

In the above embodiment, the present invention is applied to transmission / reception of a traffic channel for transmitting user information. However, the invention can be applied to transmission / reception of another channel.

In the above embodiment, the header is double-spread, but the header may be single-spread.

Furthermore, in the above embodiment, the type of the radio frame configuration is selected according to the communication environment. However, the type may be changed according to the required communication quality such as the type of user information. For example, simple data may employ a short frame configuration, audio data may employ a standard frame configuration, and image data may employ a long frame configuration. Further, the above may be an initial frame configuration, and thereafter, the type of the wireless frame configuration may be switched according to the communication environment. Also, the type of radio frame configuration may be changed according to the number of users communicating with the base station at that time.

Further, the present invention is not directly related to the gist of the present invention, such as omitting information modulation and information demodulation configurations, and changing the positions of a despreading unit and a switch in a main signal processing system in a receiver. The part is not limited to the above embodiment.

The structure of the transmitter and the receiver of the present invention is as follows.
It may be realized not only by hardware such as an ASIC, but also by a software configuration using one or a plurality of DSPs, or may be realized by combining ASICs and DSPs.

[0073]

As described above, according to the present invention, when transmitting and receiving a frame composed of a header period and a data period in units, any one of the frame lengths having different header lengths according to the communication environment and the like is used. Since transmission / reception is performed in the frames having the data, both the communication quality and the transmission efficiency can be almost satisfied.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a transmitter according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a wireless frame configuration according to the embodiment;

FIG. 3 is a block diagram illustrating a configuration of a receiver according to the embodiment.

[Explanation of symbols]

10: transmitter, 11: framing unit, 12: frame length counter, 13: error correction coding unit, 14: coding rate control unit, 16: spreading unit, 17: spreading code generation unit, 18: header adding unit 19, a header spread code generator, 20 a header register, 21 a header length counter, 23 a frame controller, 30 a receiver, 31 a despreader, 32 a spread code generator, 34 a header despreader Unit, 35: header spreading code generator, 36: header register, 37: header length counter, 39: error correction decoder, 40: coding rate controller, 41: frame decomposer, 42: frame length counter, 43 ... Frame control unit.

Claims (7)

[Claims] 1. A spread spectrum communication apparatus for performing transmission to an opposing spread spectrum communication apparatus in units of a frame including a header period and a data period, according to a frame length employed at that time from transmission information. Spread signal forming means for forming a spread signal per frame having a predetermined length, and a spread header signal relating to a header length corresponding to the frame length employed at that time, thereby forming the spread signal forming means. And a frame control means for instructing the spread signal forming means and the header adding means of information on a frame length employed at that time from among a plurality of frame lengths. A spread spectrum communication device, comprising: 2. The spread signal forming means includes an error correction coding unit for performing error correction coding, and a coding rate of the error correction coding unit according to a frame length employed at that time. 2. The spread spectrum communication apparatus according to claim 1, wherein: 3. The header pattern according to claim 1, wherein a header pattern from which the header adding means forms a spread header signal differs depending on a frame length adopted at that time. Spread spectrum communication equipment. 4. A spread spectrum communication apparatus in which a signal in units of a frame including a header period and a data period arrives from an opposite spread spectrum communication apparatus, according to the type of frame length employed at that time. Transmission information restoring means for despreading the signal of the data period in the determined reception signal and restoring information which the opposed spread spectrum communication device has attempted to transmit, and a reception signal determined according to the frame length employed at that time Header reception processing means for performing synchronization acquisition and synchronization continuation processing while despreading the signal of the header period in the above, and information on the frame length employed at that time from among a plurality of frame lengths as the transmission information restoring means And a frame control means for instructing the header reception processing means. Communication device. 5. The transmission information restoring means includes an error correction decoding unit for performing error correction decoding, and changes a coding rate in the error correction decoding unit according to a frame length employed at that time. The spread-spectrum communication device according to claim 4, characterized in that: 6. The spread spectrum communication according to claim 4, wherein a header pattern used by said header reception processing means for processing is different depending on a frame length adopted at that time. apparatus. 7. The spread spectrum communication apparatus according to claim 1, wherein the spread spectrum communication apparatus on the transmission side is applied, and the spread spectrum communication apparatus on the reception side is applied.
A spread spectrum communication system, characterized by applying the spread spectrum communication device described in (1).