JP2002057601A - Cdma receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CDMA system and a demodulation system which are simple in structure and high in performance by using channel estimation that takes advantage of pilot channels as to the demodulation system in spread spectrum communication that keeps data communication in a fading environment or a CDMA system. SOLUTION: Channel estimation used for compensating information symbols is made by taking advantage of the pilot symbols of the pilot channels located just before they overlap temporally with information signal symbols that make channel estimation in this CDMA receiving system, in a CDMA system composed of a transmitter which transmits pilot channels and information channels as CDMA transmission signals and a receiver which receives the CDMA signals and demodulates them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CDMA (Code D)
The present invention relates to a CDMA receiver that performs data communication in a fading environment in an ivision Multiplex Access (ivision Multiplex Access) system.

[0002]

2. Description of the Related Art Conventionally, spread spectrum communication and a CDMA system using spread spectrum communication technology are resistant to multipath fading, capable of high-speed data, have good communication quality, and have good frequency use efficiency. It is a promising communication method for mobile communication and multimedia wireless communication.

A transmission signal in the CDMA system and the spread spectrum communication is transmitted by being spread over a band much wider than the bandwidth of the information signal to be transmitted on the transmission side. On the other hand, the receiving side is required to have a function of restoring the spread CDMA signal to the original signal bandwidth and demodulating the information signal. The operation of restoring the original signal bandwidth is called despreading, and for despreading, a method using a matched filter and a method using sliding correlation are known.

In a radio environment such as mobile communication, there is fading such as multipath between a base station and a mobile station. When a CDMA signal transmitted from the base station is received by the mobile station, the received signal has an amplitude and a phase. Subject to fluctuations. For this reason,
Conventionally, in order to estimate this fading distortion,
A known pilot symbol is inserted into a part of the information data (symbol) transmitted by the base station at a fixed time interval and transmitted. The mobile station receives and demodulates this pilot symbol, and transmits a known pilot symbol to be received. By making the comparison, it is possible to estimate the amplitude / phase fluctuation (fading distortion) of the transmission signal received on the propagation path.

For example, “Fading distortion compensation method of 16QAM for land mobile communication, Sanbe: Transactions of the Institute of Electronics, Information and Communication Engineers, Vol. J72-B-II No. 1 pp7-15.
In “January 1989”, known frame symbols (pilot symbols) for transmission path characteristic measurement are periodically inserted into information symbols. Fading distortion is estimated by receiving and demodulating this periodic pilot symbol and comparing it with the known frame symbol (pilot symbol). That is, a scheme has been proposed in which information symbols between pilot symbols are compensated for by interpolation based on channel estimation using pilot symbols.

FIG. 7 shows a method for estimating fading distortion according to the above document. In FIG. 7, a signal 790 has information information 700, 720, 7 consisting of a plurality of one pilot symbols 710, 730 for one slot length.
It is periodically inserted between 40. So, for example,
The fading distortion compensation of the information symbol 720 is executed by estimating fading distortion using the pilot symbols 710 and 730 at both ends thereof and performing interpolation.

As a method of estimating fading distortion with high accuracy and performing interpolation, there is a method of “high accuracy channel estimation using a plurality of pilot blocks in DS-CDMA, Ando, Sawahashi: IEICE RCS-96-72 1996-
08 "proposes a channel estimation method using pilot symbols spanning a plurality of slots and weighting and averaging the pilot symbols.

In addition to the traffic channel (information channel) for transmitting an information signal shown in the above-mentioned conventional example, a pilot channel for transmitting only known pilot symbols orthogonalized by orthogonal codes is transmitted simultaneously (in parallel) and the pilot channel is transmitted. A method of estimating and compensating fading distortion using a channel is described in "DS / CDMA Synchronous Detection Method Using Suppressed Pilot Channel, Abeda: IEICE Journal Vol. J77-B-II pp641-648.
November 1994 ". In this method, a fading distortion is estimated between one slot using a pilot channel, and an information symbol of an information channel is compensated using the estimated value.

[0009]

However, in the above-mentioned "fading distortion compensation method of 16QAM for land mobile communication", information symbols between pilot symbols are compensated for by interpolating to compensate for information symbols between pilot symbols. , 720, and 740 need to be temporarily stored in the memory. When handling multimedia data, the data rate (symbol rate) is increased, so that the amount of information in one slot stored in the memory becomes very large. Therefore, there is a problem that the memory capacity is increased, the difficulty of LSI integration and the cost are increased. Was.

[0010] DS / using a suppressed pilot channel
Similarly, the "CDMA synchronous detection method" also needs to store information for one slot, and has the same problem.

In the above-mentioned “high-precision channel estimation method using a plurality of pilot blocks in DS-CDMA”, it is necessary to store information for a plurality of slots in a memory.
There is a problem that the memory capacity further increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has high performance and requires a minimum memory by using channel estimation using a pilot channel. C with easy configuration
It is intended to provide a DMA receiver.

[0013]

The present invention has the following configuration to achieve the above object. According to a first aspect of the present invention, an information signal including a pilot channel in which pilot symbols are spread using a spreading code, and an information symbol and a pilot symbol periodically inserted between the information symbols, is provided. In a CDMA receiver for receiving and demodulating a CDMA signal having a spreading code and an information channel spread by using a spreading code orthogonal to the spreading code, a receiver includes a despreading unit for despreading the received CDMA signal, A channel estimator for estimating fading characteristics using the pilot channel despread by the unit and outputting first channel estimation information; and a despreading unit using the first channel estimation information. And a compensator for compensating for the information symbols of the despread information channel and outputting a first compensation information symbol. In CDMA receiver and performing a first channel estimation using pilot symbols positioned immediately before that does not overlap the broadcast signal symbol temporally.

According to a first aspect of the present invention, an information signal symbol is stored in a memory for extrapolation using the first channel estimation information using the pilot symbol immediately before the information signal symbol to be compensated. No need to do. With the increase in multimedia, as the data rate (symbol rate) increases, the number of information symbols included in one slot of the information channel increases, so that the effect is further enhanced.

A second gist of the present invention is that the channel estimating section uses a pilot symbol located immediately before that does not temporally overlap with an information signal symbol and a pilot symbol temporally identical to the information symbol. CDMA according to the first aspect, wherein the first channel estimation is performed.
In the receiver.

According to the second aspect of the present invention, since the pilot symbol time length for performing the first channel estimation is an integral multiple of the information signal symbol time length, the accuracy of CH estimation is improved.

According to a third aspect of the present invention, there is provided an information signal comprising a pilot channel in which pilot symbols are spread using a spreading code, and an information symbol and a pilot symbol periodically inserted between the information symbols. Receives and demodulates a CDMA signal having the spreading code and an information channel spread using an orthogonal spreading code, the receiver comprising:
Channel estimation for estimating fading characteristics using a despreading unit for despreading an MA signal and a pilot channel despread by the despreading unit, and outputting first channel estimation information And a compensating unit that compensates for the information symbol of the information channel despread by the despreading unit using the first channel estimation information and outputs a first compensated information symbol. , A pilot symbol that is temporally identical to an information symbol and a pilot symbol that is positioned immediately after the pilot symbol.

According to the third aspect of the present invention, the pilot symbol time length for estimation is an integral multiple of the information symbol time length to be compensated, so that the accuracy of channel estimation is improved. Further, since there is no missing information symbol to be compensated, efficient channel estimation becomes possible. In this case, C
This is effective at the initial stage when the power of the DMA receiver is turned on and the channel estimation / information demodulation is started, or when a paging signal is received in the sleep mode to reduce power consumption.

A fourth aspect of the present invention is characterized in that the channel estimating section performs the process using a pilot symbol temporally identical to the information symbol and pilot symbols located before and after the pilot symbol. In the CDMA receiver described in the above.

According to the fourth aspect of the present invention, the pilot symbol time length for performing channel estimation is an integral multiple of the information symbol time length to be compensated, so that the accuracy of channel estimation is improved. Further, the pilot symbol used for compensating the information symbol temporally includes the information symbol to be compensated, and thus has a characteristic of interpolation. Further, since there is no missing information symbol to be compensated, efficient channel estimation becomes possible.

According to a fifth aspect of the present invention, the channel estimating unit uses the information channel despread by the despreading unit to perform the second
, And obtains second channel estimation information. The compensating unit compensates for the information symbol of the information channel despread by the despreading unit using the second channel estimation information, and performs second compensation. An information symbol is calculated, and the amplitude of the first compensation information symbol is corrected by an amplitude correction value obtained using the first compensation information symbol and the second compensation information symbol. Or the CD according to 3
In the MA receiver.

According to a fifth aspect of the present invention, in mobile communication, a pilot channel which is affected by a propagation path characteristic when a mobile station is located near a base station and when a mobile station is located far away is considered. The influence on the compensation information symbol amplitude can be reduced.

According to a sixth aspect of the present invention, the channel estimating unit uses the information channel despread by the despreading unit to perform the second
, And obtains second channel estimation information. The compensating unit compensates for the pilot symbols of the information channel despread by the despreading unit, and calculates the first channel estimation information and the second channel estimation information. A reliability measuring unit for determining the reliability of the first channel estimation information and the second channel estimation information by executing each of the used channel estimations, and based on the reliability result of the reliability measurement unit,
The CDMA receiver according to Summary 1 or 3, wherein the information symbol is compensated by selecting one of the first channel estimation information and the second channel estimation information.

According to a seventh aspect of the present invention, a reliability measuring section comprises:
Compensation for the pilot symbol of the information channel is performed using both the channel estimation information of the first channel estimation information and the second channel estimation information, and the compensation between the pilot symbol after compensation based on the both channel estimation information and the known pilot symbol is performed. The CDMA receiver according to the Summary 6, wherein the reliability result is obtained by comparing the errors.

According to an eighth aspect of the present invention, a reliability measuring section comprises:
Compensating the pilot symbols of the information channel by using both the channel estimation information of the first channel estimation information and the second channel estimation information, and comparing the amplitude values of the compensated pilot symbols based on the both channel estimation information. Summary 6 of finding reliability results by
In the CDMA receiver described in the above.

According to the fifth to eighth aspects of the present invention, in mobile communication, a pilot channel which is affected by a propagation path characteristic when a mobile station is located near a base station and when a mobile station is located far away is considered. However, the influence on the compensation information symbol amplitude can be reduced.

According to a ninth aspect of the present invention, the compensator uses the second channel estimation information for the phase term used for compensating the information symbol, and uses the first channel estimation information for the compensation of the amplitude term. And the amplitude of the first compensation information symbol is corrected by the amplitude correction value.
In the MA receiver.

According to a tenth aspect of the present invention, a pilot symbol of an information channel is composed of a plurality of pilot symbols, and a channel estimation of an information channel is performed by averaging a plurality of pilot symbols and then performing channel estimation.
Alternatively, in the CDMA receiver according to the fifth to ninth aspects, channel estimation is performed by averaging after channel estimation using each of a plurality of pilot symbols.

According to an eleventh aspect of the present invention, the second channel estimation of the information channel is performed by averaging the pilot symbols of the information channel over a plurality of slots. In a CDMA receiver. According to a twelfth aspect of the present invention, in the second channel estimation of the information channel, channel estimation is performed using pilot symbols including at least pilot symbols of the information channel located at both ends of the information symbol to be compensated. The CDMA receiver according to any one of the fifth to ninth aspects.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of a CDMA receiving unit according to an embodiment of the present invention.
Here, the CDMA signal transmitted from the base station is composed of a pilot channel in which pilot symbols are spread using a spreading code, and an information symbol composed of information symbols and pilot symbols periodically inserted between the information symbols. The signal comprises the spreading code and an information channel spread using an orthogonal spreading code.

This CDMA signal is received by the antenna 1 and amplified by the RF amplifier 2,
Is converted from a radio frequency to an intermediate frequency or a baseband frequency, and a despreading unit 4 for an information channel, a channel estimating unit for estimating fading characteristics determined from a radio channel environment between a base station and a mobile station (hereinafter referred to as a “CH estimating unit”). 9), the amplitude / phase compensator 5 for the information symbol of the information channel using the CH estimation information 15 obtained by the channel estimator 9, and the Rake for combining the amplitude / phase compensated information symbol of each path. The combining unit 6, the despreading unit 7 of the pilot channel, and the multipath component of the propagation path are identified,
It is composed of a path search unit 8 that defines an effective path for combining.

The information channel despreading unit 4, the CH estimating unit 9, the amplitude / phase compensating unit 5, and the pilot channel despreading unit 7 are arranged in parallel as many as the number of paths required for the Rake combining unit.

FIG. 2 shows the signal structure of pilot channel 30 and information channel 40. The pilot channels are all composed of known pilot symbols 31 to 38, while the information channels are similar to the known pilot symbols 41, 42, and 43 with respect to the information symbols 58 and 59, as in FIG. It is inserted periodically for each slot.

Since the pilot channel 30 functions as a pilot, its symbol rate is generally lower than the information symbol rate. In FIG. 2, the symbol rate of the pilot channel 30 is, for example, 1/4 of the information symbol rate.

The channel estimation using the pilot channel 30 according to the present embodiment will be described below. The receiver receives pilot symbols 31 to 38 of pilot channel 30 transmitted from the base station and despreads signal 14 in pilot channel despreading unit 7. Is executed. The channel estimation is obtained by calculating the despread signal 14 (code “P” in the following equation) and a known pilot symbol (code “P ₀ ” in the following equation). Expression code “C”) can be expressed by Expression (1).

C = P · P ₀ ^* = A · A ₀ ^* expj (θ−θ ₀ ) (1) where P = Aexp (jθ) = P _i + jPq P ₀ = A ₀ exp (jθ ₀ ) = P _{0i + jP 0 q (2)} *: complex conjugate j: complex number imaginary part a: amplitude a _0: amplitude

Here, the real part of the symbol represents the in-phase component, and the imaginary part represents the quadrature component. The amplitude / phase compensator 5 uses the channel estimation value C calculated by the CH estimator 9 and the received information symbol 11 (code “D” in the following equation) obtained by despreading the information signal of the information channel, and performs fading of the propagation path. Compensate for the amplitude and phase distortion caused by The information symbol Da compensated by the correction value H can be expressed as in Expression (3). Da = DH = DC ^* (3)

This compensation method will be specifically described with reference to FIG. For example, CH estimation is performed using the received pilot symbol 31 of the pilot channel 30, and based on the CH estimation value, the information symbol 52 of the nearest information channel 40 that does not overlap in time and exists at the nearest position is calculated by the above equation (1). ) ~
Compensate according to (3). In the example of FIG. 2, one symbol of pilot symbol 31 compensates for four information symbols 52 of information channel 40. The symbol time length used for performing the CH estimation is the same as the compensated symbol time length. Similarly, CH estimation is performed using the received pilot symbols 32 of the pilot channel 30, and based on the CH estimation values, the information symbols 53 of the nearest information channel 40 that does not overlap in time and are compensated are compensated for. , It is possible to compensate all the information symbols of the information channel by repeating the CH estimation and the compensation sequentially.

Since extrapolation using the CH estimation value C of the immediately preceding pilot symbol for the information symbol to be compensated for in this way, there is no need to store information symbols. Practically, even if the delay due to the processing time of the CH estimation is taken into account, the required information symbol memory size of about several symbols is sufficient.

In FIG. 2, the information symbol rate is four times the symbol rate of the pilot channel. However, if the information symbol rate is eight times, the CH estimation using pilot symbols 31
The information symbol 52 consisting of eight symbols is compensated.

As the data rate (symbol rate) increases with multimedia, the number of information symbols 58 and 59 included in one slot of the information channel 40 increases. In this case, in the conventional interpolation, the number of information symbols in one slot is greatly increased, so that the feature of the present invention is more effective.

Although the pilot channel symbols 31, 32 and the like used for CH estimation are composed of only one symbol, CH estimation is performed based on the result of averaging using a plurality of pilot symbols to compensate for information symbols. If C
An improvement in H estimation accuracy can be expected. Information channel 4
Although the example in which each of the 0 pilot symbols 41, 42, and 43 is composed of one symbol has been described, the pilot symbol 41, 42, and 43 may be composed of a plurality of pilot symbols, but it is apparent that the present invention can be applied.

A second embodiment of the present invention will be described with reference to FIG. Note that the present embodiment differs from the above-described embodiment in the CH estimation method. The following description focuses on such a CH estimation method, and the same contents as in FIG. 2 are denoted by the same symbols. The CH estimation method according to the present embodiment performs CH estimation using a pilot symbol 61 including a plurality of pilot symbols 31 and 32 of the pilot channel 30, and compensates for an information symbol 52 that partially overlaps the pilot symbol 61. That is, in order to compensate for the information symbol 52, CH estimation is performed using a pilot symbol 61 composed of the pilot symbol 32 temporally identical to the information symbol 52 and the pilot symbol 31 immediately before it.

In order to use the plurality of pilot symbols 31 and 32, the above equations (1) and (2) are calculated for each of the plurality of symbols, and the results are averaged.
The estimated CH value C of the pilot symbol 61 is obtained.

Similarly, in order to compensate for the next information symbol 53, CH estimation is performed using a pilot symbol 62 composed of a pilot symbol 33 temporally identical to the information symbol 53 and a pilot symbol 32 immediately before.

As described above, in the second embodiment, in order to compensate for the continuous information symbols 52, 53, etc., the pilot symbols 61, 62, etc. used for CH estimation are temporally different from the information symbols 52, 53, etc. The same and immediately preceding pilot symbols (32, 31), (33, 32) and the like are used. Therefore, the pilot symbol time length for performing CH estimation is an integral multiple of the information symbol time length to be compensated (FIG. 2).
This is twice as long in the example of FIG. 1), and thus has the advantage of improving the accuracy of CH estimation. Further, the pilot symbol used for compensating the information symbol temporally includes the information symbol to be compensated, and thus has a characteristic of interpolation. FIG.
The number of memories required in the second embodiment is only a few symbols because of the information symbols 52 and 53 to be compensated.

Next, a third embodiment of the present invention will be described with reference to FIG. Note that this embodiment is different from the above-described embodiment in C
The method for estimating H is different, and the method for estimating CH will be mainly described. In FIG. 4, the same contents as those in FIG. 2 are indicated by the same symbols. The CH estimation method according to the present embodiment performs CH estimation using a pilot symbol 61 including a plurality of pilot symbols 31 and 32 of the pilot channel 30, and compensates for the information symbol 51 that partially overlaps the pilot symbol 61. That is, in order to compensate for the information symbol 51, CH estimation is performed using the pilot symbol 61 including the pilot symbol 31 temporally identical to the information symbol 51 and the pilot symbol 32 immediately after the pilot symbol 31.

Similarly, in order to compensate for the next information symbol 52, CH estimation is performed using a pilot symbol 62 composed of the pilot symbol 32 temporally identical to the information symbol 52 and the pilot symbol 33 immediately after.

As described above, in the third embodiment, in order to compensate for the continuous information symbols 51, 52, etc., the pilot symbols 61, 62, etc. used for CH estimation are time-varying with the information symbols 51, 52, etc. Pilot symbols (31, 32) and (32, 3)
3) is used. Therefore, similarly to the second embodiment, the pilot symbol time length for performing CH estimation is an integral multiple of the information symbol time length to be compensated (twice in the example of FIG. 2).
Since it is long, there is an advantage that the accuracy of CH estimation is improved. Further, the pilot symbol used for compensating the information symbol temporally includes the information symbol to be compensated, and thus has a characteristic of interpolation.

In the first and second embodiments, when the CH estimation is started from the pilot symbol 31, the information symbol 51 cannot be compensated, and cannot be compensated until the next cycle (frame time length). However, in the third embodiment, unlike the first and second embodiments, as shown in FIG. 4, the information symbol to be compensated, for example, the temporal position of the symbol 51 is different from that of the pilot symbol 61 for performing the CH estimation. , The same position symbol 31 and the rear position symbol 32
, There is no missing information symbol to be compensated for, efficient CH estimation, information demodulation, Rake
Compositing becomes possible. This phenomenon is important at the initial stage when the power of the CDMA receiver is turned on to start the CH estimation / information demodulation, or when a paging signal is received in the sleep mode to reduce power consumption.

Next, a fourth embodiment of the present invention will be described with reference to FIG. Note that the present embodiment differs from the above-described embodiment in the CH estimation method. The following description focuses on the CH estimation method, and in FIG. 5, the same contents as those in FIG. 2 are indicated by the same symbols. The CH estimation method according to the present embodiment employs a pilot symbol 71 including a plurality of pilot symbols 31, 32, and 33 of the pilot channel 30.
Is used to perform CH estimation, and the information symbol 52 temporally included in the pilot symbol 71 is compensated. That is, the pilot symbol 32 temporally identical to the information symbol 52 and the pilot symbols 31
CH estimation is performed using a pilot symbol 71 composed of three symbols.

Similarly, compensation for the next information symbol 53 is also performed on pilot symbol 3 temporally identical to information symbol 53.
CH estimation is performed by using a pilot symbol 72 including 3 and pilot symbols 32 and 34 before and after the channel 3.

As described above, in the fourth embodiment, in order to compensate for continuous information symbols 52, 53, etc., pilot symbols 71, 72, etc., used for CH estimation are time-varying with each information symbol 52, 53, etc. Pilot symbols (32, 31, 33) before and after the same, (3
2, 33, 34). Therefore, as in the second embodiment, the pilot symbol time length for performing CH estimation is an integral multiple (three times in the example of FIG. 5) of the information symbol time length to be compensated, and the accuracy of CH estimation is improved. Further, the pilot symbol used for compensating the information symbol temporally includes the information symbol to be compensated, and thus has a characteristic of interpolation.

Next, a fifth embodiment will be described with reference to FIG. The pilot channel 30 is commonly used by all mobile stations existing within the service area of the base station. The local information channel 40 is transmitted from the base station as a signal spread by each spreading code to each mobile station existing within the service area of the base station. Further, the amplitude and phase of the information channel signal 40 are adjusted by, for example, power control, transmission diversity, and the like performed by the base station depending on the propagation path conditions between each mobile station and the base station. Therefore, the received signal amplitudes of pilot channel 30 and information channel 40 received by the mobile device may be different. As an example, when power control is performed as shown in FIG.
And the received powers 90 and 91 of the information channel 40 are schematically shown. The received power 91 of the information channel 40 is a constant received power independent of the distance from the base station if the power control is performed, while the received power 90 of the pilot channel 30 is dependent on the distance from the base station. Attenuate. In addition, since the pilot channel 30 is used by all mobile stations located in the base station area, the pilot channel 30 is generally transmitted with high power.

As described above, in FIG. 2, the information channel 40 periodically includes pilot symbols 41, 42,
43 is inserted. From the equations (1) to (3), the amplitude of the compensated information symbol Da is not only the amplitude | D | of the received information symbol before compensation (||
It depends on the received pilot symbol amplitude A used for H estimation. Accordingly, in channel estimation using pilot channel 30, as shown in FIG. 6, the information symbol amplitude after compensation may be greatly affected when the mobile station is located near the base station and when the mobile station is located far away. . Also,
Since the power of the pilot channel is not controlled, phenomena 92 and 93 may be attenuated in mobile communication due to propagation path characteristics. In the CH estimation using the attenuated pilot channel, since the amplitude of the compensated information symbol Da is also attenuated, the result may be inconsistent with the power control operation.

The fifth embodiment is a channel estimation method in consideration of the above situation, and performs CH estimation using both pilot symbols of pilot channel 30 and information channel 40. The CH estimation using the pilot symbols of the information channel 40 is performed on the signal 13 despread by the information channel despreading unit 4 by the pilot symbol using CH estimating unit 21 of the channel estimating unit 9 to output the channel estimation value 16. .

For the received information symbol D to be corrected,
CH estimation value 15 using pilot channel (“C
1 "), the information symbol Da after compensation using the estimated value
And CH using information channel pilot symbols
The estimated value 16 (the following symbol “C10”), the information symbol Db after compensation using the estimated value, and the amplitude ratio M after both compensations are as follows from the above equations (1), (2) and (3). Become. Da = D · C1 ^* (4) Db = D · C10 ^* (5) M = | Db / Da | = | C10 / C1 | (6) From the equation (6), the amplitude ratio M is equal to the reception amplitude of the information channel. It becomes the ratio of the received signal amplitude of the pilot channel.

As described above, the above problem can be solved by performing CH estimation using the pilot channel 30 and calculating the amplitude correction value M represented by the equation (6) for the compensated information symbol Da.

Next, in the sixth embodiment, both the CH estimation using the pilot channel 30 and the CH estimation using the pilot symbol of the information channel 40 are executed, and the CH estimation or the compensated information channel is performed. A pilot symbol reliability measuring means is installed. Here, the reliability measuring means is a means for measuring which of the two CH estimations can be used to perform more accurate symbol compensation for the information channel. Based on the reliability result measured by the reliability measuring means, one of the CH estimation values is selected to compensate for the information channel symbol.

As an example of the reliability measuring means, a method of measuring the reliability of the compensated information channel pilot symbol will be described. Since the information channel 40 has the pilot symbols 41, 42, and 43, the CH estimation for the pilot symbols is performed by both the CH estimation using the pilot channel and the CH estimation using the information channel pilot symbols. . The compensated pilot symbol Pa based on the CH estimation using the pilot channel 30 and the information channel 40
Is compared with the pilot symbol Pb after compensation based on the CH estimation using the known pilot symbol P10. For example, as shown in Expressions (7) and (8), the errors E1 and E2 between the pilot symbols of the compensated information channel and the known pilot symbols are used as a criterion, and the higher reliability CH estimation value is selected. To compensate for the information channel symbol. E1 = | Pa-P10 | (7) E2 = | Pb-P10 | (8)

As another example of the reliability measuring means,
Compensation for the information channel and the pilot symbol can be realized by performing both the CH estimation using the pilot channel and the CH estimation using the pilot symbol of the information channel, and comparing the amplitude values of the pilot symbols after both compensation. . That is, the amplitude value of the CH estimation or the compensated amplitude value is compared, and the larger amplitude value is determined to be more reliable, and any one of the CH estimations is selected.

Next, as a seventh embodiment, a CH estimation method corresponding to a case where there is a phase difference between a pilot channel signal and an information channel signal transmitted by a base station will be described.
As in the sixth embodiment, both CH estimation using a pilot channel and CH estimation using a pilot symbol of an information channel are performed. Furthermore, in order to hold the phase information of the information channel, the phase term used for information symbol compensation uses CH estimation using the information channel. On the other hand, as for the compensation of the amplitude term, as shown in the fifth embodiment, CH estimation using a pilot channel is performed, and the amplitude correction value M shown in Expression (6) is calculated for the compensated information symbol Da. .

Information channel 4 in the above embodiment
The channel estimation using 0 is performed, for example, by using the pilot symbols 41, 42, 43, etc. of the information channel 40 in FIG. 2 or averaging them. For example, pilot symbol 4 of information channel 40 in FIG.
When each of 1, 2, and 43 is composed of a plurality of pilot symbols, CH estimation is performed after averaging the plurality of received pilot symbols, or CH estimation is performed on each symbol. This is done by averaging the results.

As other CH estimation of the information channel,
In the information channel 40 of FIG. 2, using pilot symbols 41, 42 and 43 over a plurality of slots,
By averaging, a method of performing CH estimation of the information channel can be performed. By averaging a plurality of pilot symbols of an information channel or averaging over a plurality of slots, pilot symbols of a limited information channel can be effectively used as CH estimation.

The CH estimation using the information channel in the above embodiment is performed, for example, by using the information symbol 5 in FIG.
9, the pilot symbols 42 and 43 located at both ends of the information symbol 59 to be compensated, that is, the pilot symbol 43 existing in the slot including the information symbol to be compensated and the pilot symbol 43 CH estimation can be performed using a pilot symbol including at least the symbol 42.

[0066]

As described above, according to the present invention, in order to perform CH estimation and symbol compensation using the pilot channel, it is not necessary to store one slot of the information symbol, and the pilot channel and the pilot symbol need not be stored. Since at least one is used, fading generated in the propagation path can be compensated with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram of a CDMA receiving unit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a received information symbol compensation method according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a received information symbol compensation method according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a method for compensating received information symbols according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a received information symbol compensation method according to a fourth embodiment of the present invention.

FIG. 6 is an explanatory diagram of received power with respect to a distance between an information channel and a pilot channel from a base station.

FIG. 7 is an explanatory diagram of a conventional received information symbol compensation method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Antenna 2 RF amplifier 3 Frequency converter 4 Information channel despreading part 5 Amplitude / phase compensation part 6 Rake combining part 7 Pilot channel despreading part 8 Path search part 9 Channel estimation part 10 Received baseband signal 11, 13, 14 Reverse Spread signal 12 Signal after amplitude / phase compensation 20 Channel estimation unit using pilot channel 21 Channel estimation unit using pilot symbol 30 Pilot channel 40 Information channel 31, 32, 33, 34, 35, 36 Pilot symbol of pilot channel 41, 42, 43 Pilot symbols of information channel 51, 52, 53, 54, 55, 56, 57 Symbols to be compensated 61, 62, 63, 64, 71, 72, 73 Pilot symbols used for channel estimation

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Tatsumi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 5K022 EE01 EE23 EE24 EE32

Claims (12)

[Claims] An information signal composed of a pilot channel in which pilot symbols are spread using a spreading code and an information symbol and pilot symbols periodically inserted between the information symbols is orthogonal to the spreading code. In a CDMA receiver that receives and demodulates a CDMA signal having an information channel spread using the spread code obtained, the receiver includes: a despreading unit that despreads the received CDMA signal; Using the despread pilot channel to perform channel estimation to estimate the fading characteristics,
A channel estimating unit that outputs first channel estimation information; and using the first channel estimation information, compensating for information symbols of the information channel despread by the despreading unit. A CDMA receiver, comprising: a compensating unit that outputs a signal; and wherein the channel estimating unit performs the first channel estimation using a pilot symbol located immediately before the information signal symbol and not temporally overlapping. 2. The channel estimation section according to claim 1, wherein the first channel estimation is performed using a pilot symbol located immediately before and not temporally overlapping with the information signal symbol and a pilot symbol temporally identical to the information symbol. The CDMA receiver according to claim 1, wherein the CDMA receiver performs the operation. 3. An information signal composed of a pilot channel in which pilot symbols are spread using a spreading code and information symbols and pilot symbols periodically inserted between the information symbols is orthogonal to the spreading code. In a CDMA receiver that receives and demodulates a CDMA signal having an information channel spread using the spread code obtained, the receiver includes: a despreading unit that despreads the received CDMA signal; Using the despread pilot channel to perform first channel estimation for estimating fading characteristics and outputting first channel estimation information, using the first channel estimation information, A compensating unit that compensates for the information symbol of the information channel despread by the despreading unit and outputs a first compensated information symbol. The channel estimation unit, CDMA receiver for the information symbols and temporally same pilot symbols, and pilot symbols positioned immediately thereafter, and performing with. 4. The CDMA reception apparatus according to claim 1, wherein the channel estimator performs using a pilot symbol temporally identical to the information symbol and pilot symbols located before and after the pilot symbol. Machine. 5. The channel estimating unit performs second channel estimation by using the information channel despread by the despreading unit to obtain second channel estimation information. Using the channel estimation information of
Compensating the information symbol of the information channel despread by the despreading unit, calculating a second compensated information symbol, and
4. The CDMA according to claim 1, wherein the amplitude of the first compensation information symbol is corrected by an amplitude correction value obtained using the first compensation information symbol and the second compensation information symbol. Receiving machine. 6. The channel estimating unit performs second channel estimation using an information channel despread by the despreading unit to obtain second channel estimation information. The first channel estimation information and the second channel estimation information are each compensated for the pilot symbol of the information channel despread by the unit by performing the channel estimation using the first channel estimation information and the second channel estimation information. A reliability measurement unit for determining the reliability of the second channel estimation information, wherein the first channel estimation information and the second channel estimation information are determined based on a reliability result of the reliability measurement unit.
4. The method according to claim 1, wherein one of the channel estimation information is selected to compensate for the information symbol.
DMA receiver. 7. The reliability measurement unit performs compensation on pilot symbols of an information channel based on both channel estimation information of the first channel estimation information and the second channel estimation information. The CDMA receiver according to claim 6, wherein a reliability result is obtained by comparing an error between a pilot symbol after compensation based on the pilot symbol and a known pilot symbol. 8. The reliability measurement unit executes compensation for pilot symbols of an information channel based on both channel estimation information of the first channel estimation information and the second channel estimation information. The CDMA receiver according to claim 6, wherein the reliability result is obtained by comparing the amplitude values of the pilot symbols after compensation based on the CDMA receiver. 9. The compensator uses the second channel estimation information for a phase term used for information symbol compensation, uses the first channel estimation information for an amplitude term compensation, and 6. The CD according to claim 5, wherein the amplitude of the first compensation information symbol is corrected by the amplitude correction value.
MA receiver. 10. The pilot symbol of the information channel is composed of a plurality of pilot symbols, and the channel estimation of the information channel is performed by averaging the plurality of pilot symbols and then performing channel estimation;
10. The CDMA receiver according to claim 5, wherein channel estimation is performed by averaging after channel estimation using each of a plurality of pilot symbols. 11. The CDMA receiver according to claim 5, wherein the second channel estimation of the information channel is performed by averaging pilot symbols of the information channel over a plurality of slots. 12. The second channel estimation of the information channel is performed using a pilot symbol including at least pilot symbols of the information channel located at both ends of the information symbol to be compensated. Item 10. A CDMA receiver according to items 5 to 9.