JPH10178386A - Cdma system, its transmitter-receiver and random access method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce transmitting power by obtaining a correlated value with the spread code of a short cycle, obtaining a delay profile based on this related value and extracting a timing signal according to a delay profile so as to improve receiving characteristic. SOLUTION: A received signal obtained by demodulating a modulated signal by a receiving and demodulating part 1 is in the state of being spread- demodulated by the spread code, and is inputted to inverse spread processing parts 21 to 23 and a matched filter 3. A timing extracting part 6 obtains the delay profile based on an added around value and extracts the timing signal based on this delay profile to add to the parts 21 and 23 . In this case, prescribed number of signals are selected in order of decreasing the added around value to extract a timing signal according to each timing. In addition the part 21 to 23 generate the spread code synchronizing with the timing signal and gives inverse spread demodulation to a received signal, and a mixing part 8 mixes an inverse spread demodulation output signal to transfer to a data processing part, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a DS-CDMA.
(Direct Sequence Code Division Multiple Access
The present invention relates to a CDMA system for performing mobile communication or the like according to ss), a transmission / reception apparatus thereof, and a random access method. In a wireless communication system, an FDMA system, a TDMA system,
Various access methods such as the CDMA method are known.
The CDMA system can reduce the transmission power as compared with the FDMA system and the TDMA system, and can increase the number of terminals that can communicate in the same frequency band. This CDMA
In the system, there is a demand for facilitating random access and reducing transmission power.

[0002]

2. Description of the Related Art Various CDMA systems have already been proposed, some of which have been put into practical use. For example, there are a synchronous system and an asynchronous system. In the synchronous system, the timing of the leading position of the spreading code is synchronized with the spread time and the despread demodulation based on accurate time information by GPS or the like, so that the voice is transmitted. And data transmission and reception. However, there is a problem that the base station and the mobile station have an expensive configuration.

The asynchronous system does not require synchronization with respect to the timing of the leading position of the spreading code, but the receiving side detects the leading position of the spreading code included in the received signal and synchronizes with the leading position. It is necessary to perform despread demodulation using the spread code thus obtained. In addition, CDMA is applied to a pure ALOHA method and a slotted ALOHA method in packet communication.
It is also known to apply schemes.

In the packet communication to which the CDMA system is applied, for example, a packet is formed by adding a preamble part to the head of a data part of a predetermined length, and a reserved packet including the preamble part is a short-period spreading code. The transmission side spreads the transmission packet using a long-period spreading code and transmits it.The receiving side obtains a correlation value with the short-period spreading code, detects a timing at which the correlation value increases, and determines this timing. A configuration has also been proposed in which a transmission packet is despread and demodulated using a long-period spreading code. The preamble part in this case has a packet length of 5
It is also known that the length can be as short as about%.

[0005]

In the asynchronous CDMA system as described above, it is necessary to ensure the synchronization and at the same time to improve the reception characteristics and reduce the transmission power to facilitate random access. Requested. Therefore,
It is conceivable to apply a RAKE receiving method or a diversity method.

It has been proposed to apply the Aloha method as described above. In the Aloha method, it is said that the pure Aloha method is superior to the slotted Aloha method in the case of random access. However, when the pure Aloha method is applied, it is possible to distinguish whether a plurality of delay waves indicating a delay profile are due to multiple paths in the case of a single access, or to a plurality of accesses having a time difference. Can not. Therefore, it was difficult to perform RAKE reception based on the delay profile.

Further, it is necessary to switch between a short-period spreading code and a long-period spreading code for the above-mentioned reserved packet and transmission packet to perform despreading demodulation, which complicates the configuration and control on the receiving side. is there. SUMMARY OF THE INVENTION It is an object of the present invention to perform random access and improve the reception characteristics by enabling the application of a RAKE reception method, thereby reducing transmission power.

[0008]

SUMMARY OF THE INVENTION A CDMA system according to the present invention is provided.
The packet consists of (1) a packet consisting of a preamble part and a data part.
Random access by spreading modulation of the packet with a spreading code
And a receiving unit for transmitting the spread modulated signal.
And a receiving unit that performs despread demodulation by the spreading code.
In a CDMA system, the receiver is spread-modulated.
At least the preamble part of the packet and the spreading code
Matched filter 3 for calculating correlation value and calculation based on correlation value
The timing signal according to the delay profile
The timing extraction unit 6
Timing signal extracted according to the delay profile
A plurality of despreading processing units 2 for despreading respectively₁, 2_Two,
2 _ThreeAnd these despreading processing units 2₁, 2_Two, 2_Threefrom
A synthesizing unit 8 for synthesizing the despread demodulated signal. This
These despreading processing units 2₁, 2_Two, 2_ThreeAnd the combining unit 8
RAKE reception will be performed.

(2) The CDMA system described above has an addition processing unit 4 including a correlation value table 7 for storing a correlation value from the matched filter 3 according to a time series and a cyclic addition value obtained by cyclically adding the correlation value. And a timing extraction unit 6 for extracting a timing signal based on a delay profile according to the cyclic addition value of the correlation value table 7.

(3) The receiving unit in the CDMA system has a branch configuration corresponding to a plurality of antennas.
In addition, a combining unit for combining the output signals of the respective branch configurations is provided. That is, the reception characteristics can be improved by applying the space diversity system.

The transmitting and receiving apparatus in the CDMA system according to the present invention comprises: (4) a transmitting section for spreading and modulating a packet comprising a preamble section and a data section with a spreading code and transmitting the modulated packet to the opposite apparatus by random access; And a receiving unit for receiving the spread-modulated signal from the receiver and performing despread demodulation with the spreading code, the receiving unit includes at least the preamble unit of the spread-modulated packet and A matched filter 3 for obtaining a correlation value with a spreading code; a timing extraction unit 6 for extracting a timing signal according to a delay profile obtained based on the correlation value; and a timing extracted by the timing extraction unit 6 according to the delay profile. A plurality of despreading processing units 2 ₁ , 2 each performing despreading with a signal
₂ , 2 ₃ and the plurality of despreading processing units 2 ₁ , 2 ₂ , 2 ₃
And a synthesizing unit 8 for synthesizing the despread demodulated signal from the.

Further, the random access method of the present invention
(5) A random number in a CDMA system in which a packet composed of a preamble part and a data part is spread-modulated by a spread code and transmitted by random access, and the spread-modulated signal is received and despread and demodulated by the spread code. In the access method, a correlation value between at least a preamble part of a packet and a short-cycle spreading code is repeatedly obtained and cyclically added, a delay profile is obtained based on the cyclic addition result, and a plurality of timings based on the delay profile are obtained. Using a synchronized spreading code, despreading demodulation of the spread-modulated received signal is performed, and the process includes combining and outputting the despread demodulated output signal. Since the data is spread and modulated with the same spreading code, including the data part, the receiving side uses the same spreading code Can be spread demodulation, and by obtaining the even including the delay profile preamble portion or the data portion, it is possible to RAKE reception.

Further, the random access method of the present invention
(6) A random number in a CDMA system in which a packet composed of a preamble part and a data part is spread-modulated by a spread code and transmitted by random access, and the spread-modulated signal is received and despread and demodulated by the spread code. In the access method, a transmitting side of a packet transmits a packet at a timing according to a slotted Aloha scheme, and a receiving side periodically correlates at least a preamble portion of the packet with a spreading code according to a slotted Aloha scheme. Start the value calculation, obtain a delay profile based on the correlation value, using a spreading code respectively synchronized with a plurality of timings based on the delay profile, perform despread demodulation of the spread modulated received signal, It includes the step of combining and outputting the despread demodulated output signal. In this case, even if a long-cycle spreading code is used, synchronization on the receiving side can be easily achieved, and RAKE reception can be performed. Therefore, by using a spreading code with a longer period, a long delay profile can be obtained, and the reception characteristics in random access can be improved.

In the above random access method,
(7) The transmission side sets the packet transmission timing interval as follows:
Set to be equal to the length of the preamble part of the packet. In this case, the configuration for obtaining the delay profile using the preamble part can be used repeatedly.

[0015]

FIG. 1 shows a first embodiment of the present invention.
FIG. 1 illustrates a reception demodulation unit, 2₁~ 2 _ThreeIs despread
Processing unit, 3 is matched filter (MF), 4 is addition processing
, 5 is a control unit, 6 is a timing extraction unit, and 7 is a correlation value text.
Table 8, reference numeral 8 denotes a combining unit, and reference numeral 9 denotes an antenna. In addition,
The configuration of the processing unit and transmission unit of the communication data is already known
The configuration can be applied, and illustration is omitted.

A transmission signal in a CDMA system is modulated by a high-frequency signal of several hundred MHz to several GHz. The reception signal received by the antenna 9 and demodulated by the reception demodulation unit 1 is spread by a spreading code. a state in which modulated, is inputted to the inverse diffusion processing section 2 ₁ to 2 ₃ and matched filter 3. The matched filter 3 outputs a correlation value between the received signal and the spreading code, and the addition processing unit 4 sequentially stores the time-series correlation values in the correlation value table 7 and performs cyclic addition. The cyclic addition value is stored.

[0017] The timing extraction unit 6 obtains the cyclic addition value delay based on the profile, is added to the inverse diffusion processing section 2 ₁ to 2 ₃ to extract a timing signal based on the delay profile. In this case, a predetermined number is selected in descending order of the cyclic addition value, and a timing signal according to each timing is extracted. The despread processing unit 2 ₁ -
2 _3, generates a spreading code synchronized with the timing signal, and despreading the demodulated received signal, and transfers the despread demodulated output signal to the combined data processing unit not shown in such a combining unit 8. Thus, a plurality of despreading process unit 2 ₁ to 2 ₃ is R
This corresponds to each finger of the AKE method. That is, RAKE
Reception can improve reception characteristics.

[0018] The combining unit 8, the despread processing unit 2 ₁ to 2 ₃
Control to match the phase of the despread demodulation output signal of
For the levels, a configuration in which the levels are simply added or a method in which weights are added according to the magnitude of the correlation value and the levels are added can be applied. The control unit 5 controls the addition processing unit 4 and the timing extraction unit 6 that perform processes such as cyclic addition of correlation values.

FIG. 2 is an explanatory diagram of a matched filter.
A shift register 11 having, for example, a 64-bit configuration for receiving and shifting a received signal, a register 12 having regions indicated by 0 to 63 for setting a spreading code sequence having the same bit configuration as the shift register 11, and a shift register 11 Multiplier 13 for multiplying bit corresponding to register 12
And an adder 14 for adding the output signal of the multiplier 13. The received signal is a packet-type configuration including a preamble part PA and a data part.
It is sampled at the chip cycle of the spread code, and becomes a digital value between -1.0 and +1.0 by AD conversion.

In this case, the shift register 11 shifts the received signal every one chip cycle according to the sampling cycle of the received signal. Note that the received signal is over-sampled, that is, sampled at a cycle shorter than one chip cycle of the spread code and subjected to A / D conversion, and the shift register 11 shifts the received signal according to the sampling cycle. Although the configuration is generally raised, for convenience of explanation, a case where the reception signal is sampled and shifted for each one-chip cycle as described above is shown.

The output signal of each stage of the shift register 11 is multiplied by each bit of the spread code sequence set in the register 12 by a multiplier 13 for each shift, and the multiplication result is added to an adder 14. Are added to obtain a correlation value. When the correlation values are arranged on the time axis, as shown below, for example, a delay profile in which the correlation value increases at τ0, τ1, τ2 is obtained. This delay profile changes according to fading, movement of a mobile terminal, and the like.

FIG. 3 is an explanatory diagram of the correlation value table, and shows an example of the contents of the correlation value table 7 of the addition processing section 3. This correlation value is obtained by multiplying each bit of the spreading code of the combination of “1” and “−1” by the received signal composed of a digital value of −1.0 to +1.0. The value indicates a case where the value is 1 or less.
Then, correlation values at 64 timings from time 0 to 63
(1) to (10) are sequentially stored, and a value obtained by cyclic addition of the correlation values (1) to (10) is stored. By such a cyclic addition, a correlation value with reduced influence of noise can be obtained. 7.8 indicated by an arrow indicates that the cyclic addition value is the maximum value.

The above-described timing extracting section 6 obtains a delay profile based on the cyclic addition value of the correlation value table 7.
The delay profile has a plurality of maximum values, and the maximum value is represented by a curve that tends to decrease as the delay time increases, and the timing at which the maximum value of the delay profile is extracted is extracted. is there. In addition,
For simplicity, if the correlation value is represented as shown in Figure 2, by choosing a large correlation value, extracts the respective timing, different timings despread processing unit 2 ₁ to 2 ₃ Signal.

FIG. 4 is a diagram for explaining the operation of the embodiment of the present invention. FIG. 4A shows a preamble PA constituting a packet.
And a case where the period of the spreading code is shorter than the length of the data portion.
In the case of a chip configuration, the shift register 1
By shifting 1 (see FIG. 2), correlation values (1) to (10) as shown in FIG. 3 are obtained.

Also, at the time of random access, since the head timing of the preamble portion PA of each packet is shifted, the delay profile can also be separated for each packet, and the timing is extracted based on the correlation value for each packet. Despread reception demodulation can be performed.

The correlation value table 7 can be configured to store the correlation value for the preamble portion PA of the packet, or can be configured to store the correlation value for the data portion. That is, by obtaining a correlation value based on a short-period spreading code including not only the preamble part PA but also the data part, and extracting a timing according to a delay profile based on the correlation value, a propagation path that fluctuates at a relatively high speed is obtained. RAKE reception that follows the state change of. Also, a configuration is shown in which cyclic addition is performed after a correlation value is once stored. However, it is also possible to perform a cyclic addition every time a correlation value is obtained and store the cyclic addition value. In this case, the storage capacity of the correlation value table 7 can be reduced.

FIG. 4B shows a case where the slotted Aloha (ALOHA) system is applied. Since the transmission of the preamble PA of each packet is started according to the access timing, each preamble PA is transmitted.
Can be determined separately with respect to the delay profile based on the correlation value for. Therefore, it is possible to extract the timing of each packet, and it is possible to perform reception despread demodulation. Thereby, random access according to the access timing can be performed. The spreading code can be applied to either a short cycle or a long cycle because the reference timing of the long cycle is known.

FIG. 4C shows an example in which the period of the spreading code is long. The register 12 in the matched filter 3 is set so that the long-period spreading code is divided into a plurality of parts. This case shows a case where the circuit size of the matched filter 3 is reduced. In this case, the ALOHA method with a slot in which access timing is set is applied,
At the head position (1) of the code part obtained by dividing the spread code into a plurality, the code part is set in the register 12 of the matched filter 3 so as to be indicated as the MF setting code.

Then, a correlation value is determined for the received signal in the form of a packet including the preamble part PA and the data part, and for example, a correlation value table shown in FIG. 3 is formed. FIG. 3 shows the case of 0 to 63, but in the case of a long period, for example, 0 to 255. Then, at the head position (2) of the code part next to the spread code, the code part is stored in the register 12 of the matched filter 3.
To obtain a further subsequent correlation value for the received signal. By repeating such processing, a correlation value is obtained, and timing extraction can be performed according to a delay profile based on the correlation value.

FIG. 5 is an explanatory view of a second embodiment of the present invention, 20 ₁ to 20 ₃ is an antenna, 21 ₁ to 21 ₃ received despreading demodulator having the configuration shown in FIG. 1, 22 ₁ ~ 2
2 ₃ the delay adjusting unit, 23 is a synthetic unit. This embodiment, a plurality of received spread demodulation unit 21 ₁ to 21 ₃ corresponds to each branch of the space diversity scheme, and each received spread demodulation unit 21 ₁ to 21 _3, RAK shown in FIG. 1 described above
It has a configuration to which the E method is applied.

The delay adjusters 22 _{1 to} 22 ₃ adjust the phases of the output signals of the respective reception despreading demodulators 21 _{1 to} 21 ₃ and combine them in the combiner 23. In this case, Various means already known can be applied as the means for synthesizing. At for example, so that the output signal level of the composite portion 23 is maximum, the means and each receiving the despreading demodulation unit 21 ₁ to 21 ₃ for controlling the delay amount of each delay adjusting unit 22 ₁ to 22 ₃ (phase) For example, means for performing weighting in accordance with the reception level to be combined and combining them can be applied.

FIG. 6 is an explanatory diagram of the third embodiment of the present invention, in which 30 is a mobile terminal, 31 is an antenna, 32 is a duplexer (DUP), 33 is a receiving unit, 34 is a transmitting unit, and 35 is
Is a transmission timing extractor, 40 is a base station, 41 is an antenna, 42 is a duplexer (DUP), 43 is a despread demodulator, 44 is a transmission processor, 45 is a downlink signal generator, 46 is a downlink signal generator.
Is a timing generation unit, 47 is a delay profile measurement unit,
48 _{1-48 3} is a despread processing unit.

This embodiment shows a case where the Aloha system with slots is applied, and the receiving section 33 of the mobile terminal 30
Has a configuration for receiving a spread-modulated signal and performing despread demodulation with a spreading code, and a transmitting unit that spreads and modulates transmission data in synchronization with downlink slot timing using a spreading code and transmits the spread data. It has.

The reception despreading demodulation unit 43 of the base station 40
It has a configuration similar to the configuration shown in FIG.
_{1-48. 3} is equivalent to in the inverse diffusion processing section 2 ₁ to 2 ₃ 1, the combining unit 8 for combining the despread demodulated output signal is omitted. Also, a configuration corresponding to the reception demodulation unit 1 is not shown. The delay profile measurement unit 47 corresponds to a configuration including the matched filter 3, the addition processing unit 4, the control unit 5, and the timing extraction unit 6 in FIG. Is calculated based on the delay profile. Transmission processing unit 44
Includes a spread modulation unit, a transmission modulation unit, and the like.

The base station 40 receives the downlink signal from the downlink signal generator 4 according to the slot timing signal from the timing generator 46.
5, the packet composed of the preamble part and the data part generated in step 5 is spread-modulated in the transmission processing unit 44,
The signal is transmitted from the antenna 41 via the duplexer 42. That is, a downlink reference signal is transmitted. In this case, the downlink reference signal can be transmitted at time intervals that match the length of the preamble PA, as shown in FIG. 4B.

The mobile terminal 30 receives the downlink reference signal via the antenna 31 and the duplexer 32 by the receiving unit 33, detects the downlink reference signal at the transmission timing extracting unit 35, and transmits the downlink reference signal. As a timing signal, the transmitting unit 34 performs random access according to the transmission timing signal.

The delay profile measuring section 47 of the base station 40
Calculates the correlation value of the preamble part of the random access signal from the mobile terminal 30 with the spreading code as described above, obtains the delay profile based on the cyclic addition value obtained by reducing the influence of noise by the cyclic addition, Part 48 ₁ ~
Each 48 ₃ Add timing signal. Despreading processing unit 48 ₁ to 48 ₃ despreads demodulating the received signal by the spreading code synchronized with the timing signal. Therefore, R
The reception characteristics can be improved by performing reception processing by the AKE method.

[0038]

As described above, according to the present invention, when a packet consisting of a preamble part and a data part is spread-modulated with a short-cycle spreading code, at least the preamble part or the data part is included. A correlation value with a short-period spreading code is obtained, a delay profile is obtained based on the correlation value, and a timing signal according to the delay profile is extracted, thereby enabling reception processing by the RAKE method and improving reception characteristics. Thus, transmission power can be reduced.

When the slotted Aloha system is applied, the transmission / reception delay time can be estimated, so that it becomes easy to synchronize on the receiving side even if spread modulation is performed using a long-cycle spreading code. Also, as described above, the reception processing by the RAKE method can be performed, the reception characteristics can be improved, the transmission power can be reduced, and the delay profile longer than the short cycle can be separated.
There is an advantage that random access becomes easy.

It is easy to further improve the reception characteristics by applying the space diversity system together with the RAKE system, and by reducing the transmission power, the usable time of the mobile terminal can be extended and the same area can be used. It is also possible to increase the number of accommodated mobile terminals.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a matched filter.

FIG. 3 is an explanatory diagram of a correlation value table.

FIG. 4 is an operation explanatory diagram of the embodiment of the present invention.

FIG. 5 is an explanatory diagram of a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a third embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 reception demodulation unit 2 _{1 to} 2 ₃ despreading processing unit 3 matched filter (MF) 4 addition processing unit 5 control unit 6 timing extraction unit 7 correlation value table 8 synthesis unit 9 antenna

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Obuchi 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Hiroaki Iwamoto 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Limited (72) Inventor Yoshiharu Tajima 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture 1-1 (Fujitsu Limited) (72) Kenji Suda 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Limited (72) Inventor Tetsuya Yano 4-1-1 Kamikodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited

Claims (7)

[Claims] 1. A transmitting unit for spreading and modulating a packet consisting of a preamble part and a data part with a spreading code and transmitting the spread modulated signal by random access, and receiving the spread modulated signal and despreading and demodulating it with the spreading code. A CDMA system including: a matched filter for calculating a correlation value between at least the preamble portion of the spread-modulated packet and a spreading code; and a delay calculated based on the correlation value. A timing extraction unit for extracting a timing signal according to the profile; a plurality of despread processing units each performing despreading with the timing signal extracted according to the delay profile by the timing extraction unit; A CDMA system, comprising: a combining unit that combines a despread demodulated signal. 2. An addition processing unit including a correlation value table for storing a correlation value according to a time series from the matched filter and a cyclic addition value obtained by cyclically adding the correlation value, and a cyclic addition value of the correlation value table. 2. The CDMA system according to claim 1, further comprising a timing extracting unit for extracting a timing signal based on the delay profile according to the following. 3. The reception unit according to claim 1, wherein the reception unit has a branch configuration corresponding to a plurality of antennas, and further includes a combining unit that combines output signals of the respective branch configurations.
A CDMA system as described. 4. A transmitting unit for spreading and modulating a packet comprising a preamble part and a data part by a spreading code and transmitting the packet to an opposite device by random access, and receiving a spread modulated signal from the opposite device and receiving the spread code. And a receiving unit for despreading and demodulating the packet by using a matched filter for obtaining a correlation value between at least the preamble portion of the spread-modulated packet and a spreading code. A timing extraction unit for extracting a timing signal according to a delay profile obtained based on the correlation value; and a plurality of despreading processing units for respectively performing despreading with the timing signal extracted according to the delay profile by the timing extraction unit. And a combining unit for combining the despread demodulated signals from the plurality of despreading processing units. In transceiver in a CDMA system, characterized in that the. 5. A CDMA system in which a packet composed of a preamble part and a data part is spread-modulated by a spreading code and transmitted by random access, and the spread-modulated signal is received and despread and demodulated by the spreading code. In the random access method in which, at least the correlation value between the preamble portion of the packet and the short-cycle spreading code is repeatedly obtained and cyclically added,
A delay profile is obtained based on the cyclic addition result, and a spread code synchronized with each of a plurality of timings based on the delay profile is used to perform despread demodulation of the spread modulated received signal. A random access method, comprising a step of synthesizing and outputting the same. 6. A CDMA system in which a packet composed of a preamble part and a data part is spread-modulated by a spreading code and transmitted by random access, and the spread-modulated signal is received and despread and demodulated by the spreading code. In the random access method, the transmitting side of the packet transmits the packet at a timing according to the slotted Aloha scheme, and the receiving side periodically spreads at least a preamble portion of the packet according to the slotted Aloha scheme. Starts a correlation value calculation with a code, obtains a delay profile based on the correlation value, and despread demodulates the spread-modulated received signal using spreading codes respectively synchronized with a plurality of timings based on the delay profile. And combining and outputting the despread demodulated output signal. Random access method. 7. The random access method according to claim 5, wherein the transmitting side sets a transmission timing interval of the packet to be equal to a length of a preamble portion of the packet.