JP2002185392A - Site diversity receiving method in mobile communication system and host unit of base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a site diversity receiving method in mobile communication system and a host unit of base station in which error rate is improved without increasing the flow rate of signal on the transmission line between a base station and the host unit of base station. SOLUTION: A turbo code signal from a mobile terminal station is received at a plurality of base stations and each base station turbo decodes the received signal before being transmitted to the host unit of base station. When turbo decoding is performed at the base station, the element decoder being used in the last decoding is differentiated among respective base stations. In the host unit of base, a discriminating section 37 distributes the signal from each base station depending on the type of element decoder used last, only element encoders 34B1-34Bk or 34C1-34Cm corresponding to the last element decoders perform encoding, and signals encoded by the same type of element encoders are synthesized, respectively, at synthesizing sections 35B and 35C and decoded by a turbo decoder 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a site diversity receiving method and a base station host device in a mobile communication system, and more particularly, to a cellular type mobile telephone system and a mobile telephone employing a turbo code for site diversity reception and error correction. The present invention relates to a site diversity reception method and a base station host device in a mobile communication system that can be suitably applied to a mobile communication system such as a system.

[0002] A preferred application example of the present invention is W-Wave, which is one of the next-generation mobile telephone systems (IMT-2000).
A CDMA system is applicable. In the W-CDMA system, not only voice but also large capacity and high quality multimedia data transmission is realized. It has been determined in a standardization process that a turbo code having a high coding gain is adopted in order to perform large-capacity and high-quality data transmission. Also, application of site diversity under the name of DHO (diversity handover) has been determined as a standardized system.

[0003]

2. Description of the Related Art Generally, in mobile communication systems such as a cellular type mobile telephone system and a cellular telephone system,
Since the terminal station performs communication while moving, the propagation environment between the base station and the terminal station constantly changes. For example, the propagation environment changes due to fading or the like in a short period, and the communication quality between the base station and the terminal station deteriorates.

As a typical countermeasure, there is a space (antenna) diversity for improving a received signal quality by combining (or selecting) a plurality of signals received from one base station through different propagation paths. . However,
In this space (antenna) diversity, if a terminal station enters a shadow of an obstacle such as a building for a relatively long period of time and it becomes difficult to transmit / receive a signal to / from one base station, the effect is expected. No, it is not a valid solution.

[0005] In recent years, site diversity reception for simultaneously receiving signals from a plurality of base stations has been adopted in mobile communication systems. In this site diversity reception, a radio signal from one terminal station is received by a plurality of base stations, each base station processes the received signal and transmits the processed signal to a base station host device such as an exchange. The host device selects or combines signals received from a plurality of base stations to improve the quality of the received signals.

FIG. 13 is an explanatory diagram of a mobile communication system to which site diversity reception is applied. In FIG. 1A, reference numeral 10 denotes a mobile terminal station (hereinafter referred to as “terminal station”);
0-1 and 20-2 are base stations, and 40 is a base station 20-.
An obstacle for radio wave propagation such as a building existing in the first communication area.

Here, for example, the terminal station 10 is connected to the base station 2
If the terminal station 10 moves while transmitting and receiving signals to and from 0-1 and falls behind an obstacle 40 such as a building, the terminal station 10
0, and the signal transmission / reception with the base station 20-1 cannot be performed smoothly.

However, in the site diversity reception, the base station 20-2 adjacent to the communication area of the base station 20-1 also receives the signal from the terminal station 10, and the base station 20-2 replaces the base station 20-1. By transmitting and receiving signals to and from the terminal station 10, the terminal station 10 can perform high-quality communication without being affected by obstacles (buildings such as buildings) 40 in the propagation environment.

[0009] In this site diversity system,
By receiving a signal from the terminal station 10 at a plurality of base stations, the terminal station 1 which is at least necessary to maintain the communication quality on the network side.
The transmission level (power) of 0 is reduced, and low power consumption of the terminal station 10 can be realized.

[0010] Therefore, when this site diversity system is applied to a mobile communication system employing a CDMA (Code Division Multiple Access) system, interference power can be reduced due to a decrease in transmission level (power). The number of accommodations can be increased. That is, it is very effective to apply the site diversity reception to the CDMA system.

As shown in FIG. 13B, a mobile communication system to which the CDMA system and the site diversity system are applied includes a terminal station 10, base stations 20-1 to 20-n (n is a natural number) and a base station upper layer. An apparatus 30 is provided. Here, the communication between the terminal station 10 and the base stations 20-1 to 20-n indicated by a broken line uses a radio line with poor line quality (many transmission errors occur), and the base station 20 indicated by a solid line. -1 to 20-
For communication between the n and the base station host device 30, a wired transmission line with good line quality (less transmission errors) is used.

Therefore, in such a system, transmission using an error correction code is performed in order to improve the quality of transmission over the radio channel between the terminal station 10 and the base stations 20-1 to 20-n. In the W-CDMA system, various multimedia data communication is performed, and a turbo code having a high coding gain is applied to realize high-quality multimedia data communication. The following first to third transmission schemes have been devised as transmission schemes for mobile communication systems using this turbo code.

First, as shown in FIG. 14A, the first transmission system provides an error correction encoder (ENC: Enc) to the terminal station 10.
coder) 11 and error correction decoders (DEC: Decoder) 21-1 to 21-2 in the base stations 20-1 to 20-n, respectively.
1-n, and further a selector 31 is provided in the base station host device 30 such as an exchange.
Select one of the signals transmitted from ~ 20-n.

Thus, in the mobile communication system of the system shown in FIG. 14A, the signal error-correction-coded by the error correction encoder (ENC) 11 of the terminal station 10 is transmitted to each base station 20- 1 to 20-n, and the error correction decoders 21-1 to 21-21 of the base stations 20-1 to 20-n.
After error correction decoding is performed in -n, each decoded signal is transmitted to the base station host apparatus 30 via a wired line.

The base station host apparatus 30 selects, from among the received decoded signals, a signal having good quality (less deterioration) as a received signal. Here, each error correction decoder (D
EC) The example of selecting the decoded signals from 21-1 to 21-n has been described.
, A combining unit may be provided, and the combining unit may combine decoded signals from the base stations 20-1 to 20-n to extract a high-quality received signal.

Next, as a second transmission method, as shown in FIG. 14B, an error correction encoder (E
NC) 11 and the base station host device 30 has a combining unit 32 and an error correction decoder (DEC) 3 without providing an error correction decoder (DEC) in each of the base stations 20-1 to 20-n.
3 is provided.

Therefore, in this mobile communication system, the signals that have been error-correction-coded by the error-correction coder (ENC) 11 of the terminal station 10 are transmitted to each of the base stations 20-1 to 20-1 through the radio channel.
The base station 20-1 transmits the error correction code signal to the base station host apparatus 30 via the wired line without performing error correction decoding.

In the base station host apparatus 30, each base station 20-
The error correction code signal received from the
2 and the error correction decoding device (DEC) 33 performs error correction decoding. Here, the base station host device 3
Although the configuration example in which the code signal from each of the base stations 20-1 to 20-n is combined by the combining unit 32 of 0 is shown, a code signal of good quality is selected, and error correction decoding is performed on the selected code signal. It is also possible to adopt a configuration for performing the modification.

Further, in the base stations 20-1 to 20-n in the mobile communication system shown in FIG.
When receiving a signal from the base station, soft decision information such as the reception level is acquired, and the soft decision information is transmitted to the base station host apparatus 30 together with the received signal. In this case, in the base station host device 30, each of the base stations 20-1 to 20-1
Since the signal from 20-n can be synthesized (or selected) using the soft decision information, a decoded signal with higher quality can be obtained.

However, in the first transmission scheme shown in FIG. 14A, the error correction encoder 1 of the terminal station 10
1 to the base stations 20-1 to 20-2.
After performing error correction decoding by 0-n, the base station host device 30 selects (or combines) the decoded signals. For example, when the decoded signal is a signal with many errors, the decoded signal is Select (or combine) decoded signal
However, there is a drawback in that a signal of good quality cannot be obtained, and the desired effects of site diversity reception and error correction code transmission cannot be obtained.

That is, the error-corrected decoded signal has an effect of improving the signal quality of a received signal having a small number of errors, but cannot improve the effect of the received signal having a large number of errors. For, since errors are further increased by the decoding process, if all the decoded signals are signals with many errors, the base station host apparatus 30 receives the signal with increased errors. .

When the decoded signals from the base stations 20-1 to 20-n are combined in the base station host apparatus 30, if there are many erroneous signals in each decoded signal, good quality decoding is performed. Even if a signal is included, a decoded signal having many errors will deteriorate to a high-quality decoded signal, so that there is a very high possibility that only a signal with many errors will be obtained as a composite signal. .

On the other hand, in the second transmission method shown in FIG. 14B, since the base station host device 30 performs the decoding process after synthesizing the error correction code signal, the base stations 20-1 to 20-1 There is a disadvantage that the flow rate of the code signal in the wired line between the base station 20-n and the base station host device 30 increases.

For example, since the coding rate of the turbo code used in the W-CDMA system is 1/3,
In the transmission method, the signal flow rate of the transmission line between the base stations 20-1 to 20-n and the base station host device 30 is tripled as compared with the first transmission method. Accordingly, in the second transmission method, the transmission capacity of the transmission line between the base stations 20-1 to 20-n and the base station host device 30 must be significantly increased at least as compared with the first transmission method. However, there is a problem that the cost is extremely high.

Further, in the second transmission system, the base station host apparatus 30 receives soft decision information such as a reception level together with an error correction code signal from the base stations 20-1 to 20-n, and receives the soft decision information. The error rate of the decoded signal can be improved by combining (or selecting) the error correction code signal using the information. In this case, however, the base station 20
In the transmission line between -1 to 20-n and the base station host device 30, the signal flow increases due to the transmission of soft decision information.

For example, without changing the above coding rate (1/1 /
3) When soft decision information is added, the soft decision information is 1
Assuming that 4 bits are added per bit, the signal flow between the base stations 20-1 to 20-n and the base station host device 30 in this case is 12 times (=
3 × 4). Therefore, in any case, the second transmission method is not feasible in terms of cost.

As a transmission method for solving these problems,
Japanese Patent Application Laid-Open No. Hei 10-247873 by the applicant of the present application "Site diversity receiving method in mobile communication system,
A third transmission scheme disclosed in "Base station host apparatus in mobile communication system employing site diversity reception scheme" is known.

The third transmission system satisfies the conflicting demands not to increase the signal flow between the base station and the higher-level equipment of the base station while maximizing the effects of the site diversity reception and the error correction code transmission. The base station host apparatus performs error correction coding, combining, and decoding processing again, thereby increasing the signal flow between the base station and the base station host apparatus without increasing the signal flow rate. This is to improve the signal error rate.

FIG. 14C shows a mobile communication system of the third transmission method. In this mobile communication system, an error correction encoder (ENC) 11
Is coded by a plurality of base stations 2 via a radio line.
0-1 to 20-n and a plurality of base stations 20-1 to 20-2
0-n are error correction decoders (DEC) 21-1 respectively.
To 21-n, and the decoded signals are respectively transmitted to the base station host device 30 via a wired transmission line.
Send to

The base station higher-level equipment 30 includes a plurality of base stations 20.
For the decoded signals received from -1 to 20-n, an error correction encoder (ENC) 34 equivalent to the terminal station 10 is provided.
After performing error correction coding according to -1 to 34-n, the error correction code signal is combined by the combining unit 35, and then error correction decoding is performed by the error correction decoder (DEC) 36.

The third transmission method is effective when any code such as a block code or a convolutional code is applied as an error correction code, and is used in a W-CDMA system. This is effective for any of the turbo codes. As an error correction code, for example, W-
When the element code applied to the CDMA system uses two parallel turbo codes, the error correction encoder (ENC) 11 of the terminal station 10 is a turbo encoder having a configuration as shown in FIG. be able to.

As shown in FIG. 15A, the turbo encoder is a first elementary encoder (hereinafter referred to as "elementary encoder B").
111, a second element encoder (hereinafter referred to as “element encoder C”) 112, an interleaver 113, and a parallel-serial converter 114.

Element encoder B (111) and element encoder C
(112) performs error correction encoding on the input information bits and outputs an error correction code signal. The error correction code may be a convolutional code or a block code. Even if the same encoding process is performed by the encoder B (111) and the elementary encoder C (112),
A different encoding process may be performed.

The information bits to be transmitted are directly input to the element coder B (111), and the information bits are rearranged and input by the interleaver to the element coder C (112). The information bit signal xa to be transmitted and the elementary encoder B (11
The error correction code signal xb output from 1) and the error correction code signal xc output from the elementary encoder C (112) are input, converted into serial signals, and output.

The error correction code by the turbo encoder is
The decoding is performed by the turbo decoder as shown in FIG. The turbo decoder comprises two element decoders, a first element decoder (hereinafter, referred to as “element decoder B”) 211 and a second element decoder (hereinafter, referred to as “element decoder C”) 212, An interleaver 213, a deinterleaver 214, and a serial-parallel converter 215 are provided.

The element decoder B (211) decodes the coded signal by the element encoder B (111), and the element decoder C (212) outputs the element encoder C (1).
The decoding of the encoded signal according to 12) is performed. The interleaver 213 performs the same rearrangement of the information bit array as the interleaver 113 in the above-described turbo encoder, and the deinterleaver 214 performs the process of returning the rearrangement by the interleaver 113 to the original array.

The information bit signal xa, the error correction code signal xb, and the error correction code signal xc from the terminal station are received via the radio line and received by the base station. xa is output in parallel as a received signal ya, error correction code signal xb is received signal yb, and error correction code signal xc is received signal yc.

The element decoder B (211) receives the information bit received signal ya and the error correction code signal xb received signal yb.
b and the output signal of the deinterleaver 214 are input,
The element decoder B (211) performs error correction decoding based on these, and outputs the decoded signal.

The element decoder C (212) interleaves the signal obtained by rearranging the arrangement of the decoded signals output from the element decoder B (211) by the interleaver 213 and the arrangement of the information bit received signal ya. 213 and the received signal yc of the error correction code signal xc are input, the element decoder C (212) performs an error correction decoding process based on them, and converts the decoded signal into a deinterleaver 214.
Output to

The deinterleaver 214 rearranges the data array of the decoded signal into the original array, and feeds back the output signal to the aforementioned element decoder B (211). The element decoder B (211) performs similar decoding processing again based on the output signal from the deinterleaver 214, supplies the output signal to the element decoder C (212), and decodes the element decoder C similarly. Perform the conversion process. After repeating the above process multiple times,
The output of the deinterleaver 214 or the element decoder B (21
The output of 1) is output as a decoded signal of the turbo decoder. As described above, transmission using the turbo code can perform error-resistant transmission by using a plurality of element encoders and performing error correction encoding on signals having different data arrangements and transmitting the signals.

FIG. 16 shows the configuration of turbo coding, combining, and decoding in the base station host apparatus. As shown in the figure, the base station host apparatus includes turbo encoding units 34-1 to 34-n corresponding to a plurality of base stations, and the turbo encoding units 3 to 34-n.
A plurality of error correction code signals output from 4-1 to 34-n are combined by the combining unit 35, and the signal combined by the combining unit 35 is decoded by the turbo decoding unit 36.

Each of the turbo encoding units 34-1 to 34-n
It has substantially the same configuration as the turbo encoder of the terminal station shown in FIG. However, without performing parallel-serial conversion, information bits za1 to zan, element encoder B
, And the code signals zc1 to zcn of the element encoder C are output in parallel as they are.

The synthesizing unit 35 includes the turbo encoding units 34
Information bits za1 to za output from −1 to 34-n
n and a combiner 35 for combining code signals zb1 to zbn by a plurality of component encoders B as well.
2 and code signals zc1 to zc by a plurality of element encoders C
and a synthesizer 353 for synthesizing n, and inputs the synthesized signals to the element decoder B and the element decoder C of the turbo decoding unit 36. The turbo decoder 36 in the base station host apparatus has the same configuration as that of the turbo decoder of the base station shown in FIG. 15 (b) (however, serial-parallel conversion and the like are not performed), so description thereof will be omitted. I do.

[0044]

In the above third transmission method, it is best for the base station host apparatus to perform coding processing corresponding to the decoding processing in each base station. This is important so that errors are not propagated. Performing the encoding process corresponding to the decoding process at the base station is equivalent to returning the decoding process at the base station, and no error is propagated.

Conversely, when different encoding processes are performed, especially in the case of convolutional codes, errors are also convoluted, so that errors are propagated and errors increase. Turbo codes are no exception. By the way, since a turbo code is composed of a combination of element codes, it is possible to further improve the error rate characteristic by considering the combination of the element codes. Hereinafter, it will be described that there is room for improvement in error rate characteristics when a turbo code is applied to the third transmission method shown in FIG. 14B.

When the decoder of the base station is the decoder shown in FIG. 15 (b), the decoded signal transmitted from the base station is the element decoded signal from the element decoder C which has performed decoding last. is there. Therefore, when encoding is performed by the base station host device in FIG. 15, the encoding result (zc1 to zcn) in the element encoder C is used.
Does not increase the error, but the error increases in the encoding result (zb1 to zbn) of the elementary encoder B.

According to the present invention, in a mobile communication system in which a turbo code is applied to a site diversity reception and an error correction code, an error rate is improved without increasing a signal flow rate in a transmission line between a base station and a base station host device. Furthermore, the base station host apparatus pays attention to the last element decoder performed in the base station and performs the encoding and decoding processing corresponding to the element decoder, thereby further improving the error of the decoded signal. The aim is to improve the rate.

[0048]

In order to solve the above-mentioned problems, the present invention provides a method in which an element decoder used in the last decoding is different for each base station, and an element decoder C is used last. For the decoded signal from the base station, the base station host device performs encoding only with the element encoder C, and for the decoded signal from the base station where the element decoder B was used last, the base station The station higher-level apparatus performs coding only with the element code B, combines signals coded by the same type of element coder, and performs turbo decoding processing.

Therefore, since the base station host apparatus performs encoding using the same error correction scheme as that of the last element decoder decoded in each base station, the base station host apparatus involves error propagation due to coding. The error rate characteristic can be improved by reproducing the turbo code signal and combining or selecting the turbo code signal by site diversity reception.

[0050]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of the present invention, it is assumed that a terminal station transmits a turbo code signal encoded by a turbo encoder having a configuration example shown in FIG. FIG. 2 shows a configuration example of a turbo decoder of each base station that decodes this turbo code signal. Each base station prepares a type in which the last decoding is performed by the element decoder C and a type in which the last decoding is performed by the element decoder B, as shown in FIG.

The turbo decoder shown in FIG.
The configuration is the same as that of the turbo decoder shown in (b), and the last decoding is performed by the element decoder C. FIG.
The turbo decoder shown in (b) is a type in which the last decoding is performed by the element decoder B. The turbo decoder shown in FIG. 2C is of a type in which the last decoding is performed by the element decoder B.

FIG. 1 shows an embodiment of a turbo encoding / combining / turbo decoding apparatus in a base station host apparatus according to the present invention. The turbo encoding / synthesizing / turbo decoding apparatus includes a classification unit 37. The classification unit 37 converts each decoded signal received from each base station into a decoded signal finally decoded by the element decoder B, And the decoded signal decoded by the element decoder C.

First turbo encoding sections 34B-1 to 34B
For -k, a decoded signal decoded by the element decoder B at the base station is input, and the decoded signal is encoded only by the element encoder B. Also, the second turbo encoding units 34C-1 to 34C-1 to 34C-1-3
In 4C-m, a decoded signal that is finally decoded by the element decoder C in the base station is input, and the decoded signal is encoded only by the element encoder C.

First turbo encoders 34B-1 to 34B
The signal for each base station encoded with -k is supplied to the first combining unit 3
5B, and the second turbo encoding unit 34C
The signals for each base station encoded by −1 to 34 C-m are combined by the second combining unit 35 </ b> C.

The first synthesizing unit 35B outputs the information bit signal z
a1 to zak (not shown except for za1) and a signal zb1 encoded by the element encoder B
To 3 zak (not shown except for zb1)
5B2. The second combining unit 35C includes a combiner 35C1 that combines information bit signals za1 to zam (not shown except for za1) and signals zc1 to zcm encoded by the element encoder C (not shown except for zc1). ) For synthesizing the same. Here, it is assumed that k base stations use the element decoder B last and m base stations use the element decoder C last.

The composite output signal za,
zb is the element decoder B (361) of the turbo decoding unit 36
, Is decoded, and the combined output signal of the second combining unit 35C is rearranged by the interleaver 363, and then input to the element decoder C (362) to be decoded. The decoding process in the turbo decoding unit 36 is substantially the same as that described with reference to FIG.

That is, in the turbo coding / combining / turbo decoding apparatus of the present invention, only the decoded signal decoded by the element decoder B at the base station is encoded and combined by the element encoder B, and Only the decoded signal decoded by the element decoder C at the station is encoded by the element encoder C and synthesized. Then, the former is input to the element decoder B and the latter is input to the element decoder C for decoding by the turbo decoder 36.

FIG. 3 shows a configuration example of a terminal station, a base station, and a base station host device of a mobile communication system according to the present invention using turbo codes. FIG. 3A shows a configuration of a terminal station. The terminal station turbo-encodes transmission data transmitted from the data generation device 3-1 by a turbo encoding device 3-2, and converts the turbo code signal into a frame generation device. It is framed by 3-3 and transmitted as a radio signal by the transmitting device 3-4. As the turbo encoding device 3-2, the same one as the turbo encoder shown in FIG. 15A can be used.

FIG. 3B shows the configuration of a base station. The base station receives a radio signal transmitted from a terminal station by a receiving device 3-5, and receives the received signal by a frame decomposing device 3-6. The frame is decoded by a turbo decoding device 3-7, the decoded signal is framed by a frame generation device 3-8, and transmitted to a base station host device such as an exchange by a transmission device 3-9. This turbo decoding device 3-7 can use the turbo decoder shown in FIG.

FIG. 3C shows a base station host apparatus, which receives a decoded signal transmitted from each base station by a receiving apparatus 3-10 corresponding to the base station and outputs a frame of the received signal. The number (No) is extracted by the data etc. extracting unit 3-11, and is delayed by the delay unit 3-12 so that the received signals of the same frame number are aligned, and the signal is turbo-coded
Output to the synthesizing / turbo decoding device 3-13. As the turbo encoding / synthesis / turbo decoding device 3-13, the one shown in FIG. 1 can be used.

FIG. 4 shows an embodiment of the present invention when a turbo code including a systematic code is used. Most turbo coding outputs systematic bits, and turbo codes used in W-CDMA systems also output systematic bits. This embodiment is effective when a turbo code that outputs systematic bits at the time of turbo coding is used.

The systematic bits are output bits that are exactly the same as the input bits and are output when encoding is performed. On the other hand, an output bit different from an input bit is called an encoded bit. In the encoder of FIG.
a is called a systematic bit, and xb and xc are called coded bits.
A code having a systematic bit is called a systematic code.

When the systematic code is used as the turbo code,
Each device in the mobile communication system uses the terminal station, the base station, and the base station host device shown in (a), (b), and (c) of FIG. 3, and the turbo encoding device of the terminal station is shown in FIG.
5 (a), the turbo decoding device of the base station can use the configuration shown in FIG. However, the turbo coding / combining / turbo decoding device in the base station host device is configured as shown in FIG.

In the turbo coding / combining / turbo decoding apparatus shown in FIG. 4, the first and second turbo coding units 34B-34
Regarding the organization bits za1 to zak and za1 to zam output from the base stations 1 to 34B-k and 34C-1 to 34C-m, as in the conventional example shown in FIG. The combining is performed by the two combining units 351.
The systematic bits can be combined together because the error does not increase without depending on the elementary decoder last decoded in the base station, and can be combined as compared with the embodiment shown in FIG. The part can be simplified.

The coded bits zb1 to zbk obtained by encoding the signal decoded by the elementary decoder B at the base station last by the elementary encoder B are the same as in the embodiment shown in FIG. The coded bits zb1 to zbk are combined with each other by the combining unit 3
52. In addition, as for the encoded bits zc1 to zcm obtained by encoding the signal decoded by the element decoder C last at the base station by the element encoder C, similarly to the embodiment shown in FIG. Encoding bits zc1 to zcm
These are combined by the combining unit 353. Turbo decoding unit 3
The configuration of No. 6 is the same as that shown in FIG.

FIG. 5 shows an embodiment of the present invention for performing error detection coding and turbo coding. This embodiment is an embodiment in which error detection coding is further applied to the embodiment shown in FIG. Usually, error detection coding is often used together with error correction coding such as turbo coding, and this embodiment is an embodiment in such a case. 5A shows a configuration of a terminal station, FIG. 5B shows a configuration of a base station, and FIG.

In this embodiment, the turbo coding device of the terminal station is shown in FIG. 15A, the turbo decoding device of the base station is shown in FIG. 2, and the turbo coding / synthesis / turbo decoding device of the base station host device is shown in FIG. 1 or the configuration shown in FIG. 4 can be used. As shown in FIG. 5A, the terminal station performs error detection coding by the error detection coding device 5-1 before performing turbo coding by the turbo coding device 3-2.

As shown in FIG. 5B, the base station performs turbo decoding by the turbo decoding device 3-7, and then performs error detection of the received data by the error detection device 5-2.
The frame generation unit 3-8 stores, in a header or the like, a detection result of the presence or absence of an error by the error detection device 5-2 together with the decoded data by the turbo decoding device 3-7 in a header or the like, and forms a frame via the transmission device 3-9. Transmit to the base station host device.

As shown in FIG. 5 (c), the base station host apparatus includes an error determination apparatus 5-3 for inputting the detection result of the presence or absence of an error transmitted from each base station, and turbo coding / synthesis / turbo decoding. A selection device 5-4 is provided for inputting the decoded data by the device 3-13 and the decoded data transmitted from each base station, and selecting and outputting one of them.

The error determination device 5-3 determines whether all the detection results of the presence or absence of an error transmitted from each base station indicate that there is an error, and determines from which base station the detection result of no error is from. The determination result is notified to the selection device 5-4. The selection device 5-4 selects and outputs the decoded data from the turbo encoding / synthesis / turbo decoding device 3-13 when all the detection results of the presence or absence of the error transmitted from each base station indicate an error, If there is an error-free detection result, the base station selects and outputs decoded data from the base station.

The embodiment for performing the error detection coding shown in FIG. 5 can be combined with the above-described embodiment using the turbo code including the systematic bits. This is the form applied in the W-CDMA system. In this embodiment, the terminal station has the configuration shown in FIG. 5A, the base station has the configuration shown in FIG. 5B, and the base station host device has the configuration shown in FIG. 5C. The decoding device can have the configuration shown in FIG.

FIG. 6 shows an embodiment in which the base station notifies the base station host device of the last element decoding performed by the base station. FIG. 3A shows the configuration of a base station, and FIG. 3B shows the configuration of a base station host device. In this embodiment, the configuration of the terminal station may be the configuration shown in FIG.

As shown in FIG. 6 (a), the base station asks the turbo decoder 3-7 whether the decoding should be performed last by the element decoder B or by the element decoder C. And a control device 6-1 that outputs a signal indicating whether the last decoder is the element decoder B or the element decoder C to the frame generation apparatus 3-8. And the frame generation device 3-8 forms the frame indicating the information indicating the last element decoder together with the decoded data and notifies the information to the base station host device. Other configurations are the same as those shown in FIG.

The base station host apparatus receives the information of the last element decoder notified from each base station, and separates and combines the decoded data based on the information. The concrete means is shown in FIG.
As shown in (b), the data extraction unit 3-11 extracts the information of the last element decoder together with the extraction of the frame number and the error detection.

The information of the last element decoder is output to the classifier 37.
, And the classifier 37 classifies the decoded data from the base station into those decoded by the element decoder B and those decoded by the element decoder C based on the information of the last element decoder. , Turbo encoding / synthesizing the separated decoded data,
Output to the turbo decoding device 3-13.

Turbo encoding / combining / turbo decoding device 3
For -13, the one shown in FIG. 1 or FIG. 4 is used.
The turbo coding device of the terminal station uses the one shown in FIG. 15 (a), and the turbo decoding device of the base station uses the element decoder B for the last decoding as shown in FIG. Two types of devices using the device C are prepared.

In the embodiment shown in FIG.
Finally, each base station independently determines the element decoder to be decoded. However, by randomly changing the determination, the error rate of the decoded data in the base station host device can be further improved.

That is, by randomly changing the last element decoder independently for each base station, a plurality of base stations are statistically changed without exchanging signals between the base station and the base station host apparatus in advance. There is no bias in the last element decoder between stations. For example, as shown in the example of the table shown in FIG.
When the base stations # 1 to # 4 to receive the site diversity fixedly determine and output the last element decoder to be used, respectively, the base stations # 3 and # 2 with respect to the base stations # 1 and # 2.
In the situation where the line quality of No. 4 is poor, the element decoder B
, And the last decoded data by the element decoder C have a quality imbalance, so that one (the last decoded data by the element decoder C) always has poor quality.

Also, as shown in the example of the table shown in FIG. 7B, even when the base stations # 1 to # 4 to be subjected to site diversity alternately output the last element decoders to be used, respectively, and output. Similarly, when the channel quality of the base stations # 3 and # 4 is poor with respect to the base stations # 1 and # 2, the last decoded data by the element decoder B and the last decoded data by the element decoder C At the same time, in order to cause an imbalance in quality, one of them is always alternated and the quality becomes poor.

On the other hand, when the last element decoder is randomly switched and output for each base station as shown in the example of the table in FIG. Since the combination of the base station of the decoder B and the combination of the base station of the element decoder C to be used last change arbitrarily and randomly, one of them does not always become a poor-quality combination. , And the last decoded data by the element decoder C can obtain a statistically balanced quality, so that the error rate of the decoded data in the base station host apparatus can be improved.

In the above-described embodiment, each base station independently determines the last element decoder to be decoded. However, the last element decoder to be decoded in each base station is well-balanced in advance. The assignment is fixedly set, the base station host apparatus is notified of the assignment in advance, and the base station host apparatus separates the decoded data by the element decoder B and the decoded data by the element decoder C according to the set assignment. It can be configured.

However, when arranging the base station of the element decoder B as the last decoder and the base station of the element decoder C as the last decoder, the last operation is performed between the base stations targeted for site diversity. In order that the element decoders are not locally and numerically biased, it is necessary to arrange the element decoders to be performed last differently in adjacent base stations as shown in FIG. 8A, for example.

In this case, the base station host device needs to recognize in advance the element decoder which each base station performs element decoding last. Therefore, the base station host device includes, for example, as shown in FIG. 8B, a table storing an element decoder for performing element decoding at the end corresponding to each base station. In accordance with, the decoded data from each base station is separated.

In this embodiment also, there is no need to exchange signals between the base station and the base station host device. In this embodiment, the terminal station uses the one shown in FIG. 3 (a) or FIG. 5 (a), and the base station host device uses the one shown in FIG. 3 (c) or FIG. 5 (c). The turbo coding / synthesizing / turbo decoding device used may be the one shown in FIG. 1 or FIG. However, the base station needs to prepare only one of the turbo decoders shown in FIG. 2, whether the last decoding is performed by the element decoder B or the element decoder C.

Further, as shown in FIG. 8, when the last element decoder B and the last element decoder C are allocated and arranged in advance to each base station, the base station host apparatus performs A means for selecting a base station to receive site diversity can be added so that the element decoding to be performed is not biased, and the decoding accuracy can be improved.

For example, in the arrangement example shown in FIG. 8A, when performing site diversity reception for a terminal station connected only to the base station # 1, the base station host apparatus transmits the base station # 1 and the last element decoding B are the same base station #
Instead of connecting the base station # 5, the base station # 2 or the base station # 4 having a different last element decoding is preferentially connected.

Next, base stations cannot be arranged without deviation as shown in FIG. 8 due to terrain or traffic conditions. For example, only base stations with deviation can be arranged as shown in FIG. 9A. , The base station host device instructs the base station to decode the last element to be used each time the connection is established.

For example, in FIG. 9A, base station # 1
When the terminal station connected to the base station moves toward the base station # 5, the base station # 1 and the base station # 5 use the last element decoding when adding the base station # 5 to the diversity reception. Need to be different. In such a case, assuming that base station # 1 has finally used element decoder B,
The base station host apparatus finally sends a command to the base station # 5 to use the element decoder C.

FIG. 9B shows an example of a flow in which the base station host determines the decoder to be used last by the base station. The base station host apparatus determines whether there is a base station to be added to the diversity reception (9-1). If there is a base station to be added, the last element decoder in the base station already performing the diversity reception is determined. Is determined whether there are many element decoders B or many element decoders C (9-
2).

In the above decision (9-2), when there are many element decoders B, a command to set the last element decoder of the base station to be added to the element decoder C is transmitted (9-9).
3) If there are many element decoders C, a command to set the last element decoder of the base station to be added to the element decoder B is transmitted (9-4).

Next, an embodiment in which the base station host device sets the last element decoder based on the frame error rate (FER) will be described. In the above embodiment using the error detection code, the base station host device can measure the frame error rate for each base station from the error detection result notified from the base station.

Then, based on the measurement result of the frame error rate for each base station, the base station host apparatus determines whether the last element decoder has the frame error rate from the base station of the element decoder B and the last element decoder. Requests the base station to set the last element decoder such that the frame error rate from the base station of the element decoder C becomes equal.

For example, the base station host device has four base stations #
The site diversity reception is performed from # 1 to # 4, and the frame error rates of the base stations # 1 to # 4 are the same for the base stations # 1 and # 2 as in the numerical example shown in FIG. When the base station # 3 and # 4 have the same frame error rate at the frame error rate of, the base station host apparatus requests the last element decoder C from the base stations # 1 and # 3, and Request the last element decoder B for # 2 and # 4.

By doing so, the last element decoder C
Of the signal obtained by combining the signals from the base stations (base stations # 1 and # 3) and the signal obtained by combining the signals from the base stations of the last element decoder B (base stations # 2 and # 4) And the bias with the quality can be reduced.

Further, as shown in the numerical example of FIG. 10B, the frame error rates of the base stations # 1 to # 4 are low and only the base station # 1 has a low frame error rate.
When the frame error rate of # 4 is high, the base station host device requests the last element decoder C only for the base station # 1 and the last element decoder B for the base stations # 2 to # 4. Request.

As described above, even if the signal has a high frame error rate, the quality is improved by collecting and combining a large number of them, and the quality of the combined signal from the base stations # 2 to # 4 of the last element decoder B is improved. Base station # 1 of last element decoder C
Bias from the signal quality of the received signal.

Further, as in the numerical example shown in FIG. 10 (c), a decoded signal from base station # 5 having an extremely poor frame error rate is subjected to turbo encoding / combining / decoding in the base station host apparatus. Avoid using it. Signals with too many frame error rates are just noise,
The characteristics can be improved by not using this as a synthesis target.

Also, the maximum number of signals from the base station to be combined in the base station host apparatus is determined in advance, and the signals are extracted and processed in order from the one with the lowest frame error rate to obtain the base station. The station higher-order apparatus does not need to prepare an extra turbo encoding unit more than necessary, and can achieve small size and low power consumption.

For example, if the maximum number of signals from the base station to be combined by the base station host device is limited to four stations, FIG.
In the case of a frame error rate such as 0 (c), signals from the base stations # 1 to # 4 are extracted and processed in ascending order of the frame error rate. Further, in the case of the frame error rate as shown in FIG. 10D, the signal of the base station # 1 having the lowest frame error rate and the base stations # 2 to # 5 having the same frame error rate correspond to three stations (for example, , Base stations # 2 to # 4).

FIG. 11 shows the configuration of the base station host apparatus for setting the last element decoder based on the frame error rate as described above. The base station host device shown in the figure includes an error rate measurement device 11-1 that measures a frame error rate for each base station from an error detection result notified from the base station, and based on the frame error rate measurement result, The base station is requested to make the last setting of the element decoder, and the signal from the combining target base station is selected and selected by the selection / separation unit 11-2.
Separate. The other configuration is the same as the configuration described with reference to FIG.

Further, as shown in FIG. 12, according to the frame error rate measured by the error rate measuring device 11-1,
The weighting device 12-1 multiplies a signal having a low frame error rate by a large weighting factor, and multiplies a signal having a high frame error rate by a small weighting factor, and then performs turbo encoding / synthesis / turbo decoding. Device 3-1
3, the reliability can be increased.

(Supplementary Note 1) A mobile terminal station, a plurality of base stations connected to the mobile terminal station via radio lines, and a base station host device connected to these base stations via transmission lines, respectively. In the mobile communication system comprising: the mobile terminal station transmits a signal subjected to turbo encoding processing by a plurality of element encoders, the plurality of base stations, the mobile terminal station via the radio line , And the base station host apparatus receives the signals decoded by the plurality of base stations via the transmission line, and performs site decoding on the received signals. In the method, the plurality of base stations are configured such that, in turbo decoding processing using a plurality of types of element decoders corresponding to the plurality of element encoders, the type of an element decoder used last is determined by the base station. Set differently, the base station host device, for the received signal from each of the base stations, coded with the same type of element encoder corresponding to the last element decoder used in each base station respectively A mobile communication system comprising: synthesizing signals; inputting a synthesized signal for each type of the element encoder to an element decoder corresponding to each element encoder type; and performing turbo decoding processing. Site diversity reception method in. (Supplementary note 2) In the site diversity receiving method according to Supplementary note 1, wherein the mobile terminal station transmits a signal subjected to turbo coding processing including systematic bits in a mobile communication system, Each systematic bit signal output from each element encoder corresponding to the last used element decoder for each station,
Combined by a common combining unit, and the combined tissue bit signal is
A method for receiving site diversity in a mobile communication system, comprising inputting to each element decoder corresponding to the type of each element encoder and performing turbo decoding processing. (Supplementary note 3) The site diversity receiving method according to supplementary note 1 or 2, wherein an error detection code is transmitted from the mobile terminal station, and error detection is performed in each of the plurality of base stations based on the error detection code. In the site diversity receiving method for a mobile communication system in which the error detection result is notified to a base station host device, the base station host device performs all base station operations based on the error detection results notified from the plurality of base stations. It is determined whether or not an error detection result has been notified from the station. If all error detection results have been notified from the base station, a signal subjected to the turbo decoding processing is output, and at least one base station is output. And outputting a received signal from the base station when a detection result indicating no error is notified from the base station. (Supplementary note 4) In the site diversity reception method according to any one of Supplementary notes 1 to 3, information of an element decoder used last by each base station is notified to the base station host device together with a decoded signal, and the base station host device is notified. A site diversity receiving method in a mobile communication system, wherein the apparatus selects a base station to be subjected to site diversity reception based on information of a last used element decoder from each base station. (Supplementary note 5) The site diversity receiving method according to the supplementary note 4, wherein each base station randomly changes an element decoder used last. (Supplementary Note 6) In the site diversity receiving method according to any one of Supplementary Notes 1 to 3, a component decoder used last by each base station is fixedly assigned in advance to each base station. A site diversity receiving method in a mobile communication system. (Supplementary Note 7) In the site diversity receiving method according to Supplementary Note 6, the base station host apparatus may be the site diversity receiving target base station so that the last used element decoder is not biased between the site diversity receiving target base stations. And selecting a site diversity reception method in the mobile communication system. (Supplementary note 8) In the site diversity receiving method according to any one of Supplementary notes 1 to 3, the base station host apparatus sends a command for designating an element decoder to be used last to each base station. Site diversity reception method in the system. (Supplementary note 9) In the site diversity receiving method according to supplementary note 3, the base station host apparatus measures a frame error rate of a decoded signal for each base station based on an error detection result, and determines whether a type of an element decoder used last is used. Site diversity in a mobile communication system characterized by sending a command for designating an element decoder to be used last to each base station so that frame signals are equalized between synthesized signals obtained by synthesizing the same signals. Receiving method. (Supplementary note 10) In the site diversity receiving method according to supplementary note 9, a decoded signal from a base station having a frame error rate higher than a predetermined value is not used for the turbo decoding process in the base station host device. Site diversity reception method in the system. (Supplementary Note 11) In the site diversity receiving method according to Supplementary Note 9, a decoded signal from a base station with a low frame error rate is multiplied by a large weighting factor according to the frame error rate, and a base station with a high frame error rate is used. And performing the combining by multiplying the decoded signal by a small weight coefficient. (Supplementary Note 12) In the mobile terminal station, a signal transmitted by performing turbo coding processing by a plurality of elementary encoders is received by a plurality of base stations via a radio line, and the plurality of base stations transmit the signals to the plurality of base stations. Using a plurality of types of elemental decoders corresponding to the elementary encoders, and receiving, through a transmission line, a site-diversity-received signal subjected to turbo decoding processing in which the type of the elementary decoder to be used is different depending on the base station. In the base station host device of the mobile communication system, the base station host device receives the signal from each of the base stations, and uses the same type of element encoder corresponding to the last element decoder used in each base station. Encoding means for encoding, and synthesizing means for synthesizing signals encoded by the element encoders of the same type, and a synthesized signal for each type of the element encoder, Decoding means for inputting to an elementary decoder corresponding to (1) and performing turbo decoding processing, the base station host device of the mobile communication system. (Supplementary Note 13) The base station host device according to Supplementary Note 12, wherein the mobile terminal station transmits a signal that has been subjected to turbo encoding processing including systematic bits, in the mobile communication system. The respective systematic bit signals output from the respective encoding means for encoding by the elementary encoder corresponding to the last used elementary decoder for each station are combined by common combining means, and the combined systematic bit signals are combined. A base station higher-level apparatus of a mobile communication system, characterized in that the configuration is applied to each element decoder corresponding to the type of each element encoder to perform turbo decoding processing. (Supplementary note 14) The base station host apparatus according to supplementary note 12 or 13, wherein an error detection code is transmitted from the mobile terminal station, and error detection is performed in each of the plurality of base stations based on the error detection code. The base station host device of the mobile communication system in which the error detection result is notified to the base station host device, wherein the base station host device performs all base station operations based on the error detection results notified from the plurality of base stations. An error determining means for determining whether or not an error detection result is notified from the station; and when the base station has notified the error detection result, the encoding means, the combining means, and the decoding means A mobile station, comprising: outputting a signal subjected to turbo decoding processing; and outputting a received signal from the base station when at least one base station notifies the base station of a detection result indicating no error. Base station host device of the communication system. (Supplementary note 15) The base station host apparatus according to supplementary note 14, further comprising: an error rate measuring unit that measures an error rate of a received signal in each base station in response to a notification of an error detection result from each of the base stations. According to the error rate of the received signal in the above, the type of the last element decoder to be used in each of the base stations is determined and notified, and the selection or weighting of the received signal to be subjected to the turbo decoding process in the base station host device. A base station host device of a mobile communication system, comprising: (Supplementary note 16) The base station host apparatus according to supplementary note 15, wherein a configuration is provided in which a decoded signal from a base station whose error rate of the received signal is equal to or more than a predetermined value is excluded from the target of the turbo decoding processing and combined. A base station host device of a mobile communication system, characterized by: (Supplementary Note 17) In a base station that performs turbo decoding on a transmission signal that has been subjected to turbo encoding processing from a mobile terminal station, a plurality of turbo decoders that use different element decoders at the end or finally A base station apparatus for a mobile communication system, comprising: a turbo decoder for changing an element decoder to be used. Note that, in the above supplementary notes, only typical combinations of the above-described embodiments have been described. It is also possible to combine with the technique disclosed in "Base station host device in mobile communication system adopting reception method".

[0103]

As described above, according to the present invention,
A signal obtained by decoding a turbo code from a terminal station at a plurality of base stations is transmitted to a base station host device, and the base station host device encodes the signal using an element encoder corresponding to the last element decoder for each base station. By performing turbo decoding after synthesizing the combined signals, it is possible to obtain a more reliable decoded signal without increasing the signal flow rate with the base station host apparatus.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a turbo encoding / combining / turbo decoding device in a base station host device of the present invention.

FIG. 2 is an explanatory diagram of a turbo decoder of a base station used in the present invention.

FIG. 3 is a diagram illustrating a configuration example of a terminal station, a base station, and a base station host device of a mobile communication system according to the present invention using turbo codes.

FIG. 4 is an explanatory diagram of an embodiment of the present invention when a turbo code including a systematic code is used.

FIG. 5 is a diagram illustrating a configuration example of an embodiment of the present invention that performs error detection coding and turbo coding.

FIG. 6 is an explanatory diagram of an embodiment of the present invention for notifying the base station host device of the last element decoding performed by the base station.

FIG. 7 is a diagram illustrating an example of an element decoder used last in each base station.

FIG. 8 is a diagram showing an arrangement example in which the last element decoder B and the last element decoder C are assigned to each base station in advance.

FIG. 9 is a diagram illustrating an example of an arrangement in which the assignment of the last element decoder B and the last element decoder C to each base station is biased.

FIG. 10 is a diagram illustrating an example of a frame error rate of each base station.

FIG. 11 is an explanatory diagram of a base station host device that sets a last element decoder based on a frame error rate.

FIG. 12 is an explanatory diagram of a base station host device that performs weighting according to a frame error rate.

FIG. 13 is an explanatory diagram of a mobile communication system to which site diversity reception is applied.

FIG. 14 is an explanatory diagram of a conventional site diversity reception system.

FIG. 15 is an explanatory diagram of a conventional turbo encoder and turbo decoder.

FIG. 16 is an explanatory diagram of turbo encoding, combining, and decoding in a conventional base station host device.

[Explanation of symbols]

 34B-1 to 34B-k First turbo encoding unit 34C-1 to 34C-m Second turbo encoding unit 35B First combining unit 35C Second combining unit 35B1, 35B2, 35C1, 35C2 Combiner 36 Turbo decoding unit 361 Element decoder B 362 Element decoder C 363 Interleaver 364 Deinterleaver 37 Classification unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 1/02 H04J 13/00 A F term (Reference) 5K014 AA03 BA10 EA08 GA06 HA10 5K022 EE01 EE31 5K059 CC03 DD05 DD31 5K067 AA23 CC10 CC24 EE02 EE10 EE16 EE22 GG11 HH01 HH21 HH26

Claims (5)

[Claims] 1. A mobile terminal station, a plurality of base stations connected to the mobile terminal station via a wireless line, and a base station host device connected to the base stations via a transmission line. In the mobile communication system provided, the mobile terminal station transmits a signal that has been subjected to turbo encoding processing by a plurality of elementary encoders, and the plurality of base stations are transmitted from the mobile terminal station via the radio line. A transmission signal is received, the received signal is subjected to turbo decoding processing, and the base station host apparatus receives a signal decoded by the plurality of base stations via the transmission line by a site diversity reception method. In the plurality of base stations, in the turbo decoding process using a plurality of types of element decoders corresponding to the plurality of element encoders, the type of the last element decoder used differs depending on the base station. The base station higher-level device is configured to receive signals from each of the base stations, and to encode signals with the same type of element encoder corresponding to the last element decoder used in each base station. Are combined, and the combined signal for each type of the element encoder is input to an element decoder corresponding to each element encoder type,
A site diversity receiving method in a mobile communication system, characterized by performing turbo decoding processing. 2. A signal transmitted by performing turbo encoding processing by a plurality of component encoders in a mobile terminal station is received by a plurality of base stations via a radio channel, and the plurality of base stations transmit the signals by the plurality of base stations. Using a plurality of types of element decoders corresponding to the respective element encoders, and receiving a signal obtained by performing turbo decoding processing in which the type of the last element decoder used differs depending on the base station via a transmission line, site diversity reception In the base station host device of the mobile communication system, the base station host device receives the signal from each of the base stations, and receives the same type of element code corresponding to the last element decoder used in each base station. Encoding means for encoding by the encoder, synthesizing means for synthesizing signals encoded by the same type of element encoder, and a synthesized signal for each type of the element encoder,
Decoding means for inputting to each element decoder corresponding to the type of each element encoder and performing a turbo decoding process, the base station host apparatus of the mobile communication system. 3. The base station host device according to claim 2, wherein the mobile terminal station transmits a signal subjected to turbo encoding processing including systematic bits, in the mobile communication system. The respective systematic bit signals output from the respective encoding units for encoding by the elementary encoder corresponding to the last used elementary decoder for each base station are combined by a common combining unit, and the combined tissue A base station host apparatus of a mobile communication system, comprising: a configuration in which a bit signal is input to each element decoder corresponding to the type of each element encoder to perform turbo decoding processing. 4. The base station host device according to claim 2, wherein an error detection code is transmitted from the mobile terminal station, and error detection is performed at each of the plurality of base stations based on the error detection code. Performed, in the base station host device of the mobile communication system in which the error detection result is notified to the base station host device, the base station host device, based on the error detection result notified from each of the plurality of base stations, Error detecting means for determining whether or not an error detection result is notified from all the base stations; and when the error detection results are all notified from the base station, the coding means, the combining means, and the decoding means And outputs a signal that has been subjected to turbo decoding processing by at least
A base station host device of a mobile communication system, characterized in that when a detection result indicating no error is notified from one base station, a reception signal from the base station is output. 5. The base station host apparatus according to claim 4, further comprising: an error rate measuring unit that measures an error rate of a received signal in each base station based on a notification of an error detection result from each of the base stations. According to the error rate of the received signal in the base station, the type of the last element decoder used in each base station is determined and notified, and the base station host device selects the received signal to be subjected to the turbo decoding process. Alternatively, a base station host device of a mobile communication system, comprising a configuration for performing weighting.