JPH08242482A - Communication system - Google Patents

Abstract

PURPOSE: To provide a communication system where a base station can be effectively scanned by a mobile station in the mobile communication. CONSTITUTION: The base stations 100, 200 and 300 perform the communication in a multi-carrier system where plural carriers of different levels of frequency are simultaneously transmitted through a single transmission channel. Then a mobile station 400 performs the communication with optional one of stations 100, 200 and 300. In such a communication system, the stations 100 to 300 transmit the known signals through a specific common transmission channel synchronously with each other and with every assigned timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system suitable for use when communicating with a mobile unit such as a radio telephone system.

[0002]

2. Description of the Related Art Conventionally, various mobile communication systems have been put into practical use for communicating with mobile devices such as car phones and mobile phones. The conventional mobile communication is basically the same communication method as that used for communication between fixed stations.

However, a received signal received by a mobile communication terminal such as a car telephone or a portable telephone is apt to be distorted due to the influence of multipath fading. That is, multipath fading occurs, the propagation delay between the paths increases, intersymbol interference occurs, and the codes before and after overlap, which deteriorates the transmission characteristics.

In order to ensure good reception even when the transmission characteristics deteriorate, it is necessary to apply a synchronous detection circuit or the like using an adaptive equalizer or a PLL circuit, which makes the structure of the receiver complicated and expensive. turn into.

In order to solve this problem, the present applicant has previously proposed a communication system in which a plurality of carriers having different frequencies are simultaneously transmitted in one transmission channel and data is transmitted with a phase difference between the carriers. (Japanese Patent Application No. 6-241691, etc.).

According to the communication system for simultaneously transmitting a plurality of carriers, even if the condition of the transmission path is bad, the reception processing can be satisfactorily performed by the circuit having a relatively simple structure, which is suitable for mobile communication. is there.

[0007]

By the way, in the case of mobile communication such as a radio telephone system, each mobile station needs to scan a base station with which communication is possible. That is, for example, in the case of a wireless telephone system, a plurality of base stations are arranged at intervals of several kilometers, and each base station transmits control signals and synchronization data through a specific channel determined in advance. . Then, each mobile station receives this specific channel, determines from the reception level and the like whether communication with the base station is possible, and performs communication at the timing synchronized with the synchronization data transmitted on this channel. I am doing it.

In this case, in a conventional system, adjacent base stations are arranged to change a specific channel (here, referred to as a synchronization channel) for transmitting the synchronization data or the like, and each mobile station is prepared. Each synchronization channel is periodically received intermittently to determine which base station it is preferable to communicate with.

In the so-called multi-carrier communication system in which a plurality of carriers having different frequencies are simultaneously transmitted on one transmission channel as described above, if the communication method of the synchronization channel is applied, there is a disadvantage that the frequency use efficiency is poor. It was That is, in the case of a so-called multi-carrier method in which a plurality of carriers are simultaneously transmitted, the frequency band that constitutes one transmission channel is wide, and if a plurality of scanning channels are prepared, the frequency band that can be used for the communication channel for data transmission is as much as that. Will be less, and the efficiency of frequency usage will deteriorate.

When the frequency of the sync channel prepared for each base station is different as described above, it is necessary for the mobile station side to scan all the prepared sync channels in order, until the base station with which communication is possible is determined. There was an inconvenience that it took time.

In the case of the conventional mobile communication as described above, the base station with which communication is to be performed is selected as the station having the best reception state. When a large number of mobile stations are concentrated,
The base station installed in this area needs to process communication with a large number of mobile stations at the same time, which may exceed the communication processing capability.

A first object of the present invention is to provide a communication system in which a mobile station can efficiently scan a base station.

A second object of the present invention is to provide a communication system capable of relaxing the concentration of communication to a specific base station.

[0014]

SUMMARY OF THE INVENTION The present invention provides a plurality of base stations that perform communication in a multi-carrier communication system in which a plurality of carriers having different frequencies are simultaneously transmitted in one transmission channel. In a communication system having a mobile station that communicates with any base station among the base stations, a known signal is transmitted from a plurality of base stations in synchronization with a common specific transmission channel at a timing assigned to each station. It is the one.

Further, according to the present invention, in a communication system having a mobile station which arranges a plurality of base stations in a predetermined state and communicates with an arbitrary base station among the plurality of base stations, the plurality of base stations are divided into a plurality of groups. As a mobile station, a group to which each mobile station belongs is determined, communication with the base station of this group is preferentially performed, and when communication with the base station of the group to which it belongs cannot be performed, It is adapted to communicate with a base station.

[0016]

According to the present invention, in synchronization with a plurality of base stations,
By transmitting a known signal at the timing assigned to each station through a common specific transmission channel, each mobile station can receive the known signal from multiple base stations only by receiving this specific transmission channel. become.

Further, according to the present invention, a plurality of base stations are divided into a plurality of groups, a group to which each mobile station belongs is determined as a mobile station, and communication with the base station of this belonging group is preferentially performed. By doing so, the communication between each mobile station and the base station is dispersed for each group.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

This example is applied to a communication system in which digital data is wirelessly communicated, and the configuration of the entire system is shown in FIG. In FIG. 1, 100, 20
Reference numerals 0 and 300 denote base stations, and the base stations 100, 200, and 300 are arranged at predetermined intervals and have the same configuration. Here, three sets of base stations 1
Only 00, 200, and 300 are shown, but in reality, more base stations are arranged.

In this case, the respective base stations 100, 20
A synchronization signal is supplied to 0, 300 from a separately installed communication control unit (not shown) side via a terminal 91 so that the communication operation in each base station is performed at the timing synchronized with the synchronization signal. I am doing it.

Then, each base station 100, 200, 300
The configuration of each base station 100, 200,
300 includes sync generation circuits 101, 201 and 301, and multi-carrier modulators 102 and 20 synchronize the synchronization data output from the sync generation circuits 101, 201 and 301.
2,302. This sync generation circuit 101,2
Reference numerals 01 and 301 denote circuits for generating and outputting 8-bit synchronization data prepared in advance for several types for each base station. Also, the multi-carrier modulators 102, 20
Reference numerals 2 and 302 denote modulators that perform so-called multi-carrier modulation that modulates synchronous data by using a plurality of carriers having different frequencies, the details of which will be described later. Then, the modulated outputs of the modulators 102, 202 and 302 are supplied to the framers 103, 203 and 303.

The framers 103, 203, 303 are
A processing circuit for forming a transmission signal having a frame structure applied to a communication system in which the base stations 100, 200, and 300 communicate with each other. A predetermined slot period within one frame for each base station (this slot period is the base station). The transmission signals (outputs of the modulators 102, 202, 302) are arranged in each of them (changed for each). The frame-structured signals output by the framers 103, 203, 303 are converted into high-frequency circuit units (hereinafter referred to as RF units) 104, 2
04, 304, and the RF unit 104, 204, 3
In 04, frequency conversion to a transmission channel is performed, and a high-frequency signal is wirelessly transmitted from the antennas 105, 205, and 305. In this case, the sync generation circuits 101 and 20
The synchronization data output from the output terminals 1, 301
The transmission channel (transmission frequency) in the case where the transmission processing is performed by the circuits up to 204 and 304 for wireless transmission is the same frequency in all base stations. In the following description,
This transmission channel is called a synchronization channel.

Further, in the base stations 100, 200 and 300, reference numerals 106, 206 and 306 denote transmission data input terminals, and 8 are obtained at these input terminals 106, 206 and 306.
The transmission data with the bit as one unit is supplied to the multicarrier modulators 107, 207, 307. The multi-carrier modulators 107, 207, 307 are modulators that perform so-called multi-carrier modulation that modulates transmission data by using a plurality of carriers having different frequencies, and the modulator 102 that modulates the above-mentioned synchronization data, 202, 302
It is a modulator with the same configuration as.

Then, this multi-carrier modulator 10
The modulated outputs of 7, 207 and 307 are converted to framers 108 and 20.
Supply to 8,308. These framers 108, 208,
Reference numeral 308 denotes a processing circuit for forming a transmission signal having a frame structure, which is applied to a communication system in which the base stations 100, 200 and 300 communicate, and a transmission signal (modulators 107 and 207) in a predetermined slot period within one frame. , 307) are arranged. The frame structure signals output by the framers 108, 208, 308 are converted into high frequency circuit sections (hereinafter referred to as RF sections) 104, 20.
The RF unit 104, 204, 30
The frequency conversion to the transmission channel is performed at 4 and wireless transmission is performed from the antennas 105, 205 and 305 as a high frequency signal. In this case, the channel (transmission frequency) transmitted by the processing in the RF units 104, 204, 304 is a channel different from the above-mentioned synchronization channel (hereinafter referred to as a communication channel). Also, this transmission data input terminal 10
As for the communication channels for transmitting the data obtained in 6, 206, 306, the channel arrangement to be used is decided so that the adjacent base stations use different channels.

The base stations 100 and 20 shown in FIG.
0 and 300 show only the configuration of the transmission system, and the configuration of the reception system is omitted.

Here, each base station 100, 200, 300
2, a plurality of prepared base stations are divided into three groups A, B, C, and 13 types of bases are provided for each group A, B, C. Bureau is prepared.
That is, 13 base stations of A group, 13 base stations of B group,
A total of 39 base stations together with 13 base stations in the C group make up one large base station group, and the 39 base stations are evenly arranged as shown in FIG. In FIG. 2, A1,
A13, A3, ... A13 are areas formed by 13 base stations of the A group (the base station is located at the center of each area, the same for other groups), B1, B2, B
3 ... B13 is an area centered on 13 base stations of the B group, and C1, C2, C3 ... C13 is an area centered on 13 base stations of the C group. . In this case, the base stations of the same number in each of the groups A, B, and C (for example, the base station A1 of the group A, the base station B1 of the group B, and the base station C1 of the group C) are arranged adjacent to each other. The base stations are evenly distributed.

When the number of base stations is 39 or more, the arrangement of 39 base stations is repeated.

Next, the structure of the mobile station 400 used in the communication system shown in FIG. 1 will be described.
A reception process 0 includes an antenna 401, supplies a signal received by the antenna 401 to a high frequency circuit unit (RF unit) 402, and demodulates a signal transmitted on a predetermined channel into a baseband signal (or an intermediate frequency signal). And supplies the processed reception signal to the correlator 403 and the deframer 408.

In this case, the RF section 402 receives the signal of the synchronization channel transmitted from the base station and supplies the received signal to the correlator 403. And this correlator 4
In 03, the signal pattern that the correlator has in advance (known signal)
And the received signal pattern are compared with each other, and the comparison result data (that is, the correlation value data) is supplied to the frame sync detector 404, the slot sync detector 405, and the reception level detector 406.

Then, the frame sync detector 404 detects the frame synchronization data contained in the received signal from the data of the correlation value. In addition, the slot sync detector 4
In 05, the slot synchronization data included in the received signal is
It is detected from the correlation value data. Further, the reception level detector 406 detects the reception level (reception field strength) from the correlation value data.

Then, each detector 404, 405, 406
The data detected by is supplied to the frame synchronization circuit and the optimum base station selector 407, and the deframer 408 controls the frame to be synchronized with the received signal based on the obtained synchronization data. A process of selecting a base station to receive is performed.

The received signal received by the RF unit 402 and supplied to the deframer 408 is the received signal of the channel transmitted from the base station selected by the frame synchronization circuit and the optimum base station selector 407. The deframer 408 extracts the signal of the predetermined slot in the received signal of the selected channel, and supplies the extracted signal to the multicarrier demodulator 409.

The multi-carrier demodulator 409 is a demodulator that performs so-called multi-carrier demodulation for demodulating transmission data modulated using a plurality of carriers having different frequencies, and the data demodulated by the demodulator 409 is used. To
It is supplied to the demodulation data input terminal 410.

In this mobile station 400, only the configuration of the receiving system is shown, and the configuration of the transmitting system is omitted.

Further, for each mobile station used in the communication system of this example, a group of base stations that preferentially communicate with each mobile station is predetermined. That is, as described above, the base stations are divided into three groups, that is, the A group, the B group, and the C group, and it is determined that each mobile station prepared in this communication system belongs to one of the groups. is there. When selecting the group to which the mobile station belongs, for example, the group is randomly selected without considering the usage status of the mobile station.

Next, a configuration for modulating a transmission signal when communication is performed between each base station and a mobile station will be described.
The multi-carrier modulators 102, 107, 202, 207, 3 shown in the base stations 100, 200, 300 shown in FIG.
In 02 and 307, the modulation processing is performed with the configuration shown in FIG. That is, in FIG. 3, reference numeral 1 denotes a transmission data input terminal, and 8-bit data is sequentially supplied to the input terminal 1, and the circuit of this example processes the 8-bit data as one modulation unit. Then, the 8-bit data is divided into 2 bits each, and the divided 2-bit data is divided into different transmission data / phase data conversion circuits 2, 3, 4, respectively.
5 This transmission data / phase data conversion circuit 2
At ~ 5, the phase data is generated according to the state of the supplied 2-bit data [X, Y]. That is, as the states of the 2-bit data [X, Y], the four states shown in Table 1 below can be considered, and the respective conversion circuits 2 to 5 generate different phase data Δφ for each of the four states.

[0037]

[Table 1]

Here, the phase data output from the four transmission data / phase data conversion circuits 2, 3, 4, and 5 are Δ
Let φ ₀ , Δφ ₁ , Δφ ₂ , and Δφ ₃ .

Further, in FIG. 3, 6 is a reference phase data source.
A raw circuit is shown, and this reference phase data generation circuit 6 is
Initial phase data φ₀To generate this initial phase data
Φ ₀Is supplied to the phase multiplier 7 and the carrier multiplier 11.
It Then, the transmission data / phase data conversion circuit 2 outputs
Phase data Δφ₀Is supplied to the phase multiplier 7,
Phase data φ₀And phase data Δφ₀Multiply with
Data φ₁Get. Then, the phase data obtained by this multiplication
Φ₁Is supplied to the phase multiplier 8 and the carrier multiplier 12.
It

Further, the transmission data / phase data conversion circuit 3
The phase data Δφ ₁ output by the
The phase data φ ₁ and the phase data Δφ ₁ are multiplied to obtain the phase data φ ₂ . Then, the phase data φ ₂ obtained by this multiplication is supplied to the phase multiplier 9 and the carrier multiplier 13.

Further, the transmission data / phase data conversion circuit 4
The phase data Δφ ₂ output by the
The phase data φ ₂ and the phase data Δφ ₂ are multiplied to obtain the phase data φ ₃ . Then, the phase data φ ₃ obtained by this multiplication is supplied to the phase multiplier 10 and the carrier multiplier 14.

Further, the phase data Δφ ₃ output from the transmission data / phase data conversion circuit 5 is supplied to the phase multiplier 10, and the phase data φ ₃ and the phase data Δφ ₃ are multiplied,
Obtain the phase data φ ₄ . Then, the phase data φ ₄ obtained by this multiplication is supplied to the carrier multiplier 15.

Therefore, the initial phase data φ₀To each multiplier
Phase data Δφ at 7, 8, 9, and 10 ₀~ Δφ₃Are ranked in order
Phase data φ₁~ Φ_FourIs formed
It

Further, in FIG. 3, 16, 17, 18, 1
Reference numerals 9 and 20 denote first, second, third, fourth and fifth carrier input terminals, respectively, to which carrier signals having different frequencies are supplied. In this case, input terminals 16 and 1
The frequencies of the carrier signals supplied to 7, 18, 19, and 20 are frequencies separated by a constant angular frequency ωs. That is, the first, second, third, fourth and fifth carrier signals are changed, for example, as shown in A, B, C, D and E of FIG. However, in reality, each carrier signal is a complex signal.

Then, the carrier multiplier 11 multiplies the carrier obtained at the first carrier input terminal 16 by (initial) phase data φ ₀ , and the carrier multiplier 12 obtains the carrier obtained at the second carrier input terminal 17. The phase data φ ₁ is multiplied, the carrier multiplier 13 multiplies the carrier obtained at the third carrier input terminal 18 by the phase data φ ₂ , and the carrier multiplier 14 obtains the carrier obtained at the fourth carrier input terminal 19. The phase data φ ₃ is multiplied, the carrier multiplier 15 multiplies the carrier obtained at the fifth carrier input terminal 20 by the phase data φ _4, and the phase of the carrier signal at each multiplier is the phase indicated by the phase data. Proceed.

Then, the multiplication outputs of the carrier multipliers 11 to 15 are supplied to the mixer 21, mixed by this mixer 21 and supplied to the transmission signal output terminal 22.

The signal obtained at the transmission signal output terminal 22 is frequency-converted into a predetermined transmission channel (transmission frequency) by each RF section in each base station shown in FIG. Is done.

In the case of this example, each slot period in one frame is 2 when the frame structure is transmitted.
Assuming T, this 1 slot period is 2 in the communication channel.
In the period T in the central portion of the T, A of FIG. 5, B, C, D, by using the carrier signal ω ₁ ~ω ₅ of the first to fifth shown in E modulated.

Then, in the synchronization channel, the first to fifth carrier signals ω _{1 to} ω ₅ are used in the entire period of one slot period 2T, as shown in F, G, H, I, and J of FIG. And modulate. Note that the period T here is T = 2π / ω ₁
Is a period defined by (i.e., a period corresponding to one cycle of the first carrier signal ω ₁ ).

Next, a configuration for receiving the signal thus transmitted will be described with reference to FIG. In FIG. 4, reference numeral 51 denotes an antenna for reception. The signal received by the antenna 51 is amplified by an amplifier 52, then supplied to a frequency conversion circuit 53, and frequency-converted by a reception carrier obtained at a reception carrier input terminal 54. Demodulate to baseband signal. Up to this point, the processing is performed by the RF unit.

Then, the baseband signal whose frequency is converted by the frequency conversion circuit 53 is supplied to the five carrier multipliers 55, 56, 57, 58 and 59. Each carrier multiplier 55, 56, 57, 58, 59 has a first, a second, a third, a fourth and a fifth carrier input terminals 61, 62,
The carrier signals of different frequencies obtained by 63, 64, and 65 are supplied to the respective carrier multipliers 55 to 55.
At 59, the corresponding carrier signal is multiplied and demodulated.

In this case, the first, second, third, fourth and fifth
The frequency of each carrier signal obtained at the carrier input terminals 61, 62, 63, 64, 65 of the same as the frequency of the carrier signal obtained at terminals 16, 17, 18, 19, 20 of the transmission circuit shown in FIG. Frequency.

Then, the demodulated signals obtained by multiplication by the carrier multipliers 55 to 59 are respectively switched 66, 67,
Integration circuits 72, 73, 74 via 68, 69, 70,
Supply to 75 and 76. In this case, each switch 66-7
For 0, opening / closing is controlled based on a switch control signal obtained at the control signal input terminal 71, and opening / closing of each of the switches 66 to 70 is simultaneously controlled.

Each of the switches 66 to 70 is controlled to open / close for each modulation unit of the transmitted signal. That is, the switches 66 to 70 are closed for a predetermined period at the center of one modulation unit.

Therefore, when the switches 66 to 70 are closed in the central section of each modulation unit, the carrier multipliers 55 to 55 are provided.
The demodulated signals supplied from the 59 side are the integration circuits 72 to 76.
Is integrated with. Here, in the case of this example, this integrated signal becomes phase data indicating the amount of change in phase during the integration period (that is, one modulation unit period). Here, each integration circuit 7
The phase data detected at 2, 73, 74, 75 and 76 are converted into φ ₀ ′, φ ₁ ′, φ ₂ ′, φ ₃ ′ and φ ₄ ′, respectively.
And

Then, the phase data detected by the integrating circuit 72 is detected.
Φ₀′ And the phase data φ detected by the integration circuit 73₁′
To the phase multiplier 77 to perform complex multiplication and
Phase data Δφ due to data phase difference₀'Is detected.
In addition, the phase data φ detected by the integration circuit 73₁′ And product
Phase data φ detected by the branch circuit 74₂′ Is the phase multiplier
It supplies to 78, the complex multiplication is performed, and the phase difference of both phase data
Phase data Δφ ₁'Is detected. Also, the integration circuit
Phase data φ detected by 74₂'And the integration circuit 75 detects
Output phase data φ₃′ Is supplied to the phase multiplier 79,
The complex multiplication is performed to obtain the phase data based on the phase difference between the two phase data.
Δφ₂'Is detected. Furthermore, the integration circuit 75 detects
Phase data φ₃'And the phase deceleration detected by the integration circuit 76.
Data φ_Four′ Is supplied to the phase multiplier 80 to perform complex multiplication.
Therefore, the phase data Δφ due to the phase difference between both phase data₃′
To detect.

Then, each phase multiplier 77, 78, 79,
Phase data Δφ ₀ ′, Δφ ₁ ′, Δ detected by 80
φ ₂ ′ and Δφ ₃ ′ are supplied to different phase data / reception data conversion circuits 81, 82, 83 and 84, respectively. In the phase data / reception data conversion circuits 81 to 84, conversion processing reverse to the conversion processing in the transmission data / phase data conversion circuits 2, 3, 4, 5 at the time of transmission is performed. That is, the conversion circuit 8
The phase data supplied to 1 to 84 are the four phases (π / 4, 3π / 4, −3π / 4, −π / 4) shown in Table 1 above.
Which of the two is the closest, and the determined phase value is converted into 2-bit [X, Y] data shown in Table 1.

Then, the 2-bit data obtained by the conversion in each of the conversion circuits 81 to 84 is combined into 8-bit data, and this 8-bit data is output from the reception data output terminal 85.

By performing the transmission processing and the reception processing described above, the bit data obtained at the terminal 1 on the transmission side is wirelessly transmitted and obtained at the terminal 85 on the reception side. The transmission process in this case is a so-called multi-carrier system in which a plurality of carriers are used for transmission, but it is a process for transmitting data with a phase difference between the carriers. Therefore, the receiving side can detect the transmitted data by simply detecting the phase of each carrier and detecting the phase difference, as in the case where the data is modulated on the carrier itself as in the conventional case. In addition, it is not necessary to regenerate the transmitted clock and the like, and transmission processing and reception processing can be performed with a simple configuration that does not require a complicated synchronizing circuit such as a PLL circuit.

Here, although each carrier is individually generated to modulate into a multi-carrier signal and demodulate from the multi-carrier signal, a similar multi-carrier signal can be converted into a similar multi-carrier signal by calculation processing such as fast Fourier transform. It is also possible to perform modulation and demodulation from multicarrier signals.

Next, the communication control between the base station and the mobile station which perform communication by such a communication method will be described. Here, a process required to select a base station with which each mobile station communicates and to synchronize with the selected base station will be described.

First, as shown in the entire communication system of FIG. 1, in the case of this example, each of the base stations 100, 200, 300 ...
In the case of the base station 100, for example, the signal transmitted from the multi-channel signal is a signal of a sync channel that modulates the output of the sync generator 101 or the like in multi-channel and transmits, and the transmission data obtained at the transmission data input terminal 106. There is a signal of at least two channels, which is the signal of the communication channel that is modulated by the channel and transmitted, but here the transmission configuration of the synchronization channel will be described.

FIGS. 6 and 7 are diagrams showing the structure of the synchronization channel. A of FIG. 6 (the same as A of FIG. 7) shows a frame structure. In this example, one frame is 28T.
A period (T here is the same as the carrier modulation period T shown in FIG. 5), and A is set for each frame of this 28T period.
The group, B group, or C group is assigned. That is,
As shown in A of FIG. 6, in a certain three frame period X, A
Group, B group, and C group are arranged in this order, in the next three frame periods Y, B group, C group, and A group are arranged in that order, and in the next three frame periods Z, C group, A group, They are arranged in the order of group B. Then, the three frame periods X, Y and Z are repeated.

Each frame of the 28T period is shown in FIG.
B and FIG. 7B, each of the 14 subframes is composed of 1T.
It is composed of a transmission part for a period and a non-transmission part for a 1T period following it. That is, for example, in the case of the frames assigned as the group A, the 14 subframes forming one frame are A0, A1, A2, A3 in order from the beginning of each frame.
... A13 and 2T periods are divided into 14, and a signal is transmitted in the central T period of each subframe of the 2T period.

Of the 14 sub-frames, the first sub-frame A0 is transmitted by all 13 base stations A1 to A13 constituting the A group. And the remaining one
In subframes A1 to A13 of No. 3, transmission is performed from the base stations A1 to A13 of the same number in the A group, respectively. For example, as shown in D of FIG. 7, the base station A1 of the group A performs transmission in the first subframe A0 and the next subframe A1.
Further, in the base station A2 of the A group, as shown in E of FIG.
After transmission in the first subframe A0, transmission is performed in subframe A2, which is one subframe apart. Further, in the base station A13 of the A group, as shown in F of FIG. 7, after transmitting in the first subframe A0, transmission is performed in the last subframe A13 of this frame.

Also in the case of the frames assigned as the B group, as shown in B of FIG. 7, in the first subframe B0, the 13 base stations B1 to B13 forming the B group are formed.
, And the remaining 13 subframes B1 to B13 transmit only one subframe according to the numbers assigned to the base stations B1 to B13.

Further, also in the case of the frames assigned as the C group, as shown in B of FIG. 7, one base frame C0 at the head makes the 13 base stations C1 to C13 constituting the C group.
, And the remaining 13 subframes C1 to C13 transmit only one subframe according to the numbers assigned to the base stations C1 to C13.

As data to be transmitted in each subframe period on the synchronization channel, for example, the subframes A0, B0, and C0 at the head of each frame are added with data indicating which group of frames they are to be transmitted. . Then, the remaining subframes of each frame are assigned the same data in each group and transmitted. For example, B in FIG. 6 or B in FIG.
As shown in, in the frame period assigned to the group A,
In the first subframe A0 of one frame, a synchronization signal S1 with data indicating that it is a frame of group A is transmitted, and in the remaining subframes A1 to A13, a synchronization signal S2 different from this signal S1 is transmitted. Send. Then, in the frame period assigned to the B group, the synchronization signal S3 to which the data indicating the frame of the B group is added is transmitted in the first subframe B0 of one frame, and the remaining subframes B1 to B13 are transmitted. Then, a synchronization signal S4 different from the signal S3 is transmitted. Further, in the frame period assigned to the C group, the subframe C0 at the head of one frame is
Then, the synchronization signal S5 to which data indicating that the frame is the group C is added is transmitted, and the remaining subframes C1 to C are transmitted.
At 13, a synchronization signal S6 different from this signal S5 is transmitted.

Next, description will be made regarding the case where the mobile station receives the signal of the synchronization channel transmitted from the base station as described above. As shown in C of FIG. 6 and G of FIG. Correlator 40 only in the middle period T of the subframe
In 3, the window for processing is set so as to detect the correlation with the received signal. Therefore, in the frame period received by the mobile station, as shown in D of FIG. 6, receptions r1, r2, r3, ...
Wait for each reception. Further, the correlator 403 performs the correlation detection processing of the above-mentioned synchronization signals S1 to S6. However, the correlation detection processing of the synchronization signal transmitted from the base station of the group set in each mobile station is preferentially performed, and is transmitted from the base stations of other groups only when the correlation detection result is not good. The correlation detection processing of the synchronization signal is performed.

As shown in E of FIG. 6, the frame structure used in the transmission / reception processing in each mobile station is 1
Receiving R during a frame period, idle period I during one frame period (a period during which neither transmission nor reception is performed, but may be received to search for another channel, etc.) and transmission T during one frame period are repeated. To do. In this case, the frame structure on the transmitting side has a cycle of 9 frames as shown in A of FIG. 6, and if reception R every 3 frames is performed, no matter which frame is synchronized with reception, bases of group A A frame transmitted from the station, a frame transmitted from the group B base station, and a frame transmitted from the group C base station are sequentially received (the first frame received is not always the group A), It enables reception of synchronization channels transmitted from all groups of base stations.

In this example, the mobile station performs reception at such a timing, and based on the received signal at this timing, the frame sync detector 40 shown in FIG.
4. By performing the detection processing by the slot sync detector 405 and the reception level detector 406, it is possible to synchronize with the transmission signal from the base station, and it is possible to select the base station that can perform the best communication.

That is, for example, the mobile station 400 shown in FIG.
When the group is set to be preferentially received, the correlator 403 first performs the correlation detection process of the synchronization signal S1 transmitted from the base station of the group A. At this time,
The frame sync detector 404 performs continuous reception instead of reception in every T cycle in the frame structure described above, and the frame sync detector 404 has a correlation value of a predetermined level or more and the phase of the correlation value is almost zero.
To detect the timing. Setting the timing at which this phase becomes 0 means, for example, that the carrier ω ₁ shown in A of FIG. 5 can be accurately captured by the signal phase of the central period T of the waveform shown in F of FIG. Is to set the window of the vessel. That is, if the window of the correlator is out of phase, the waveform of the carrier ω ₁ is out of phase, and the phase is not zero. Then, when the phase of the window of the correlator matches the phase of the transmission signal, the phase of the correlation value becomes 0, which means that the synchronization signal S1 has been correctly captured.

Then, at the detected timing, that is, at the timing when the correlation is almost completely obtained, the subframe A at the head of the frame in which the synchronization signal is transmitted from the base stations of the group A
It is judged that 0 has been received, and with this timing as a reference,
The window of the correlator 403 shown in G of FIG. 7 is set so that the window of the correlator 403 is at the center of each subframe.

Then, with the window thus set, the first subframe A0 to the subsequent subframe A0
At the timing of receiving 1 to A13, the correlator 403
Then, the processing for detecting the correlation of the synchronization signal S2 is performed, the slot sync detector 405 determines whether the phase of the correlation value at this time is substantially 0, and when the subframes A1 to A13 are received, the correlation is determined. The window of the correlator 403 is set at the timing when the phase of the value becomes almost 0, and the correct window of the correlator is set even at the time of reception in the subframes A1 to A13.

Then, with the setting of this window maintained, the reception levels of the subframes A1 to A13 are determined by the reception level detector 406 to determine which subframe has the highest reception level. And
The position of the subframe determined to have the highest reception level is determined, the number of the base station transmitting the synchronization signal S2 to this subframe is determined by the optimum base station selector 407, and the signal from this base station is determined. The RF unit 402 is controlled to set the communication channel to be received, and the deframer 408 is controlled to receive the corresponding subframe in the set communication channel.

For example, when the reception level of the subframe A1 is the highest among the reception levels of the subframes A1 to A13, it is determined that the base station A1 that transmits the synchronization signal S2 in this subframe A1 is the optimum base station. Then, control is performed to communicate with the base station A1.

When the optimum base station is selected and communication is performed with the base station on the communication channel,
The deframer 409 causes the deframer 409 to perform a reception process in synchronization with the window of the correlator 403 set at the reception timing of the synchronization signal S2 transmitted from the optimum base station. That is, at the timing synchronized with the window of the correlator 403 set at the reception timing of the synchronization signal S2, the deframer 409 performs reception processing so as to extract the reception data of a predetermined subframe.

When communication is performed on this communication channel, reception R for one frame period, idle period I for one frame period, and transmission T for one frame period are repeated as shown in E of FIG. Setting is repeated, and reception in the frame of reception R and transmission in the frame of transmission T are repeated to perform bidirectional communication, and at the same time, the synchronization channel is received in the idle period I of 3 frame cycles, which is better. It is determined whether or not there is a base station that can be received.

Here, in the case of this example, as the frame structure of the synchronization channel, as shown in A of FIG.
Since the frame arrangements of the B group and the C group are sequentially changed as indicated by X, Y, and Z, it is only necessary to receive the synchronization channel in the idle period I of three frame periods, and the base stations of all the groups are received. The synchronization signals from the can be received in order.

If there is a base station that can receive better than the base station currently in communication (however, the base station of the group to which the mobile station belongs has priority), the base station that switches to communication with that base station. Switch processing is executed.

Even when the synchronization signals of the base stations of the same group can be favorably received, the base station may be connected to the base stations of another group if the communication channel of the base station is not available.

According to the system of this example in which communication is performed in this manner, the mobile station can select the optimum base station only by receiving the common synchronization channel in each base station.
That is, since each base station has a common synchronization channel, and the subframes in it are used in order in each base station, the signal from which base station is received at the reception timing of the synchronization signal that can be received well. You can judge whether you can receive well. Therefore, when selecting a base station for each mobile station,
It is only necessary to receive this synchronization channel, and there is no need to switch and scan multiple channels to select a connectable base station as in the case where the synchronization channel differs for each base station. The scanning of can be executed easily and at high speed without changing the channel.

In particular, in this example, two processes, that is, the selection process of the base station and the detection of the synchronization timing can be simultaneously performed by receiving the signal transmitted by one synchronization channel.
The use efficiency of the channel is high, and the communication control in the mobile station can be easily performed by receiving this one channel. In the case of this example, the window is set in the correlator 403 so that the synchronization signal transmitted from the selected base station can be correctly received, but the adjustment amount of this window (that is, the reference window position). Depending on how much the
It is also possible to detect a rough distance from the selected base station to the mobile station.

Further, in the case of performing communication in the multi-channel system as in this example, if the frequency bandwidth of one channel is wide and each base station has a different synchronization channel, that much is used in the communication channel. Although the frequency band that can be formed becomes narrow, which is not preferable in terms of frequency usage efficiency, in this example, each base station only needs to have one common channel as a synchronization channel, and thus the frequency band that can be used for communication channels is widened accordingly. It is possible,
It is possible to set a larger number of communication channels as compared with the conventional multi-channel system.

In the case of this example, D, E, F in FIG.
As shown in, in the sub-frame at the beginning of each frame,
Since the same signal (synchronization signal S1 and the like) is simultaneously transmitted from all base stations of the group to which the frame belongs, each mobile station simultaneously receives the signals transmitted from each base station. In such a case, in the case of a general communication method using a conventionally known carrier as a direct carrier wave, the carrier itself is likely to be disturbed and received, and the transmitted data is accurately demodulated. Is very difficult, but in the case of the communication system of this example, since data is transmitted by the phase difference between a plurality of carriers that are transmitted at the same time, each mobile station detects the phase difference between carriers. Since the data can be demodulated only by itself, even if the signals transmitted from each base station at the same time are received, a slight phase difference may occur, but it can be obtained by demodulating the transmitted data almost accurately. .

Further, in the case of this example, each base station is divided into groups by a predetermined number (13 stations in the above-mentioned embodiment), and the base stations of each group are arranged so as to be evenly distributed and moved. The station side is also divided into groups, and the base station that preferentially communicates with the base station of the group to which the station belongs is prevented from being concentrated on a specific base station. it can.

Since the order in which the synchronization signals of each group are transmitted is changed sequentially, the base stations of each group can be efficiently scanned in the case of such grouping. That is, as the frame structure of the synchronization channel, as shown in A of FIG. 6, the frame arrangement of groups A, B, and C is X,
Since it is designed to change sequentially as indicated by Y and Z,
By only receiving the synchronization channel in the idle period I (refer to E in FIG. 6) of three frame periods, the synchronization signals from the base stations of all the groups can be received in order, and efficient scanning can be performed.

Here, it will be described using mathematical expressions that the synchronization timing can be detected and the reception level can be measured based on the correlation value detected by the correlator as described in the above embodiments. First, the phase data φ _{n (n} = 1~ multiplying each carrier of the transmission signal obtained by the transmission circuit of the configuration of FIG. 3
5), the transmission signal obtained at the output terminal 22 is
[Equation 1] It is shown by a formula.

[0089]

[Equation 1]

Further, ω _n is expressed by the equation (2).

[0091]

[Equation 2]

This value is multiplied by A due to the attenuation in the propagation path when it is received. On the other hand, the comparison value of the correlator is expressed by the formula [3].

[0093]

(Equation 3)

Then, the correlation value when the received signal is delayed by δ from the desired time is expressed by the equation (4).

[0095]

[Equation 4]

Here, the following equation [Equation 5] makes the movement shown in FIG. 8 in the plane shown by the two axes I and Q which are orthogonal to each other.

[0097]

(Equation 5)

In FIG. 8, δ is determined to be one from Arg (E) within the range shown by the following equation [Equation 6].

[0099]

(Equation 6)

From this, the deviation of the synchronization timing can be known. Then, when δ is determined within the range of the formula 6,
Since the size of F (δ) is determined to be one, the value A due to the attenuation in the propagation path can be obtained by the following equation (Equation 7).

[0101]

(Equation 7)

This value A becomes the received electric field strength. Also δ =
If 0, the following expression [Equation 8] is obtained.

[0103]

(Equation 8)

Therefore, if δ is within a certain range, the position of the synchronization timing and the received electric field strength can be specified from the correlation value.

[0105]

According to the present invention, by transmitting a known signal in synchronization with a plurality of base stations through a common specific transmission channel at a timing assigned to each station, each mobile station can perform this specific transmission. Only by receiving a channel, it becomes possible to receive known signals from a plurality of base stations.

Further, in this case, by performing communication between the base station and the mobile station on a transmission channel different from the specific transmission channel, it is necessary for the base station to control a synchronization signal or the like on this specific transmission channel. You only have to send the signal,
Transmission of control data such as various synchronization signals using a specific transmission channel can be favorably performed without being disturbed by communication between the base station and the mobile station.

Also, the process of selecting a base station with which the mobile station can communicate by detecting the reception level of a known signal transmitted by the mobile station through a specific transmission channel and determining the base station with which the mobile station can communicate is It becomes possible to do it easily and accurately without switching.

When the mobile station starts the communication with the base station by detecting the reception timing of the known signal transmitted by the mobile station on the specific transmission channel and judging the communication timing with the base station. Timing control becomes easy.

Further, as the multi-carrier communication method, data is transmitted according to the phase difference between the respective carriers, so that the transmission on the specific transmission channel from each base station can be performed simultaneously at the same timing. It becomes possible and can use channels efficiently.

Further, a plurality of base stations are divided into a plurality of groups, and the timing allocation for transmission on a specific transmission channel is
The periodical change for each group enables the mobile station to efficiently scan the base station using the specific transmission channel for each group.

Further, according to the present invention, a plurality of base stations are divided into a plurality of groups, a group to which each mobile station belongs is determined as a mobile station, and communication with the base station of the group to which it belongs is preferentially performed. By doing so, the communication between each mobile station and the base station is dispersed for each group, and it is possible to prevent the communication from being concentrated on a specific base station.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a communication system configuration of an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a cell arrangement according to an embodiment.

FIG. 3 is a configuration diagram illustrating a transmission process according to an embodiment.

FIG. 4 is a configuration diagram showing a reception process of an embodiment.

FIG. 5 is a waveform diagram showing carriers in a communication slot and a synchronization slot according to an embodiment.

FIG. 6 is a configuration diagram showing a frame configuration of a synchronization channel according to an embodiment.

FIG. 7 is a configuration diagram showing a transmission state of a synchronization channel according to an embodiment.

FIG. 8 is an explanatory diagram showing an IQ plane for explaining one embodiment.

[Explanation of symbols]

1 Transmission Data Input Terminal 2, 3, 4, 5 Transmission Data / Phase Data Conversion Circuit 6 Reference Phase Data Generation Circuit 7, 8, 9, 10 Phase Multiplier 11, 12, 13, 14, 15 Carrier Multiplier 16 1st Carrier input terminal 17 second carrier input terminal 18 third carrier input terminal 19 fourth carrier input terminal 20 fifth carrier input terminal 21 mixer 22 transmission signal output terminal 53 frequency conversion circuit 54 reception carrier input terminal 55 , 56, 57, 58, 59 carrier multiplier 61 first carrier input terminal 62 second carrier input terminal 63 third carrier input terminal 64 fourth carrier input terminal 65 fifth carrier input terminal 66, 67, 68, 69, 70 switch 71 control signal input terminal 72, 73, 74, 75, 76 integrating circuit 77, 78, 7 9,80 Phase multiplier 81,82,83,84 Phase data / reception data conversion circuit 85 Reception data output terminal 100,200,300 Base station 101,201,301 Sync generator 102,107,202,207,302, 307 multi-carrier modulator 103, 108, 203, 208, 303, 308 framer 400 mobile station 403 correlator 404 frame sync detector 405 slot sync detector 406 reception level detector 407 frame synchronization circuit and optimum base station selector 408 deframer 409 Multi-carrier demodulator 410 Received data output terminal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H04Q 7/22 H04Q 7/04 A 7/24 7/26 7/30

Claims (7)

[Claims] 1. A plurality of base stations that perform communication by a multi-carrier communication method in which a plurality of carriers each having a different frequency are simultaneously transmitted in one transmission channel, and an arbitrary base station among the plurality of base stations is provided. A communication system having a mobile station that performs communication, wherein a known signal is transmitted at a timing assigned to each station through a common specific transmission channel in synchronization with the plurality of base stations. 2. The communication system according to claim 1, wherein communication is performed between the base station and the mobile station on a transmission channel different from the specific transmission channel. 3. The communication system according to claim 1, wherein the mobile station detects a reception level of a known signal to determine a base station with which communication is possible. 4. The communication system according to claim 1, wherein the mobile station detects the reception timing of a known signal and determines the communication timing with the base station. 5. The communication system according to any one of claims 1 to 4, wherein, as the multi-carrier communication method, data is transmitted by a phase difference between the respective carriers. 6. The plurality of base stations are divided into a plurality of groups, and allocation of timing for transmitting on the specific transmission channel is periodically changed in units of each group.
5. The communication system according to any one of 5 to 5. 7. A communication system having a mobile station in which a plurality of base stations are arranged in a predetermined state and which communicates with an arbitrary base station among the plurality of base stations, wherein the plurality of base stations are divided into a plurality of groups. , As the above-mentioned mobile station, decide the group to which each mobile station belongs, preferentially communicate with the base station of this group, and when communication with the base station of the group to which it belongs is not possible, A communication system adapted to communicate with a base station.