JP2000165955A - Digital radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the information transfer ability of an up line from becoming excessive even if a system is designed by means of adjusting it to a down line whose information quantity is large. SOLUTION: In a digital radio communication method for executing radio communication between a base station and plural mobile stations, a down line from the base station to the mobile stations executes continuous transmission by a CDMA system and an up line from the mobile stations to the base station executes burst transmission by a CDMA-TDMA system obtained by compounding time divisional multiplex and code division multiplex. The information quantity of the down line can sufficiently be secured and that of the up line can be secured just enough.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital radio communication method, and in particular, the amount of information (bit / s) in a downlink from a base station to a mobile station is larger than the amount of information in the reverse direction (uplink). The present invention relates to a digital wireless communication method applied to a related wireless communication system.

[0002]

2. Description of the Related Art A communication line configuration method in which a common repeater or relay base is efficiently and commonly used by many users is called a "multiple access system". Satellite communication and land mobile communication are typical examples. In satellite communication, communication between ground stations is performed via a repeater mounted on a satellite, and in land mobile communication, communication between mobiles is performed via a base station.

As a multiple access system, frequency division multiple access (Frequency Division Multiple Access) was first used.
ccess: FDMA). In the FDMA system, a specific frequency channel is assigned to each user. The frequency allocation may be fixed or may be variably performed as required. Next, in order to increase the number of users, Time Division Multip
le Access: TDMA). In the TDMA system, a specific time slot in a time frame is allocated to each user, and communication is performed by digital modulation.

[0004] In the FDMA system, channels are separated by frequency, and in the TDMA system, channels are separated by time. However, when both frequency channels or all time slots are occupied, both channels are separated. Access is denied. That is, n
In a system designed with channels, communication over n + 1 channels is impossible.

[0005] In contrast, codes specific to each user,
That is, a specific PN (pseudo-noise) sequence or a specific frequency hopping pattern is assigned and collated with its own code to separate channels by code division multiple access (CDM).
A) In the method, even if the number of simultaneous call users exceeds the design value, only the S / N ratio deteriorates and the call quality deteriorates.
It has an excellent feature that access is not denied unlike MA and TDMA, and can flexibly cope with an increase in the number of users. It is. Note that CDMA
Since the method uses multiple access by SS communication (Spread Spectrum Communication), the spread spectrum multiple access (Spread Spectrum Multiple Access)
Access: SSMA) method.

FIG. 14 is a block diagram of a conventional CDMA radio communication apparatus. 1 transmits data to PSK (Phase Shif
t Keying) or a primary modulator that modulates with FSK (Frequency Shift Keying), 2 is a PN code generator, 3 is a multiplier that multiplies a PN code and transmission data to generate a wideband spread spectrum signal (transmission signal), Reference numeral 4 denotes an antenna for transmitting a transmission signal, and these components constitute a transmission system. Also,
Reference numeral 5 denotes an antenna, 6 denotes a phase synchronization signal of a PN code included in a broadband spread spectrum signal (received signal) received by the antenna 5, for example, a synchronization circuit including a sliding correlator and a matched filter, and 7 denotes a synchronization circuit. A PN code generator for generating a PN code having the same phase as the PN code in the received signal in accordance with the signal; 8 a de-spread of the received signal using the PN code; 9 is a PSK or FS
This is a primary demodulator that demodulates received data with K, and these units constitute a receiving system. It is needless to say that the base station and the plurality of mobile stations are constituted by both the transmission system and the reception system.

As described above, according to the CDMA digital radio communication apparatus, multiple access between a base station and each mobile station can be performed through a plurality of communication channels separated by a PN code, and satellite communication can be performed. And the frequency utilization efficiency of the mobile communication system can be improved.

[0008]

In the CDMA system, the amount of downlink information from the base station to each mobile station (hereinafter, "Ddown") and the amount of uplink information in the reverse direction (hereinafter, "Dup"). ) Is the same, for example, e-mail or W
Data distribution services such as WW (World Wide Web) contents, three-party call service for intercommunication between multiple mobile stations via a base station, or the task of transmitting information from a base station to multiple mobile stations simultaneously In wireless services (such as taxis and security services), the amount of downlink information is overwhelmingly large, and the relationship of Ddown> Dup is almost constant. When the system is designed, there is a problem that the information transfer capability of the uplink becomes excessively large.

Further, since the base station receives signals from a plurality of mobile stations in the same frequency band and the same time range, strong signals from short-range mobile stations may cause channel interference, which is avoided. Therefore, there is a problem that accurate transmission power control must be performed on the mobile station side.

[0010] Therefore, the present invention prevents the information transfer capability of the uplink from becoming unnecessarily large even when the system is designed for the downlink having a large amount of information, and also realizes accurate transmission power at the mobile station side. An object of the present invention is to provide a digital wireless communication method that does not require control.

[0011]

According to the first aspect of the present invention,
In a digital wireless communication method for performing wireless communication between a base station and a plurality of mobile stations, a downlink from the base station to each mobile station is continuously transmitted by CDMA, and an uplink from each mobile station to the base station is transmitted at a certain time. CD that combines division multiplexing and code division multiplexing
The burst transmission is performed by the MA-TDMA method. The invention according to claim 2 is a digital wireless communication method for performing wireless communication between a base station and a plurality of mobile stations,
The structure of the transmission and reception frames is time division multiplexed duplex (TDD), the downlink from the base station to each mobile station sends the same information to each mobile station by CDMA, and the uplink from each mobile station to the base station is Burst transmission is performed by a CDMA / TDMA-TDD scheme in which time division multiplexing and code division multiplexing are combined. According to a third aspect of the present invention, in the digital wireless communication method for performing wireless communication between a base station and a plurality of mobile stations, a configuration of transmission and reception frames is time division multiplexed duplex (TDD), and both uplink and downlink are used. CDM combining time division multiplexing and code division multiplexing
The burst transmission is performed by the A / TDMA-TDD method. According to a fourth aspect of the present invention, there is provided a digital radio communication method for performing a three-way call by radio communication between a plurality of mobile stations via one base station, wherein time-division multiplexing and code division multiplexing are performed for both the uplink and the downlink. Complex CDMA-
Using a TDMA method, a common spreading code for three-way communication is assigned to each mobile station and base station, each mobile station receives a downlink frame from the base station as a common frame, and The transmission slot allocated to the mobile station is used. According to a fifth aspect of the present invention, the downlink from the base station to a plurality of mobile stations transmits the same information simultaneously through a common slot, and the uplink from each mobile station to the base station is allocated to each mobile station. In a digital radio communication method for individually transmitting via a channel, a CDMA-TDMA system combining time division multiplexing and code division multiplexing is used for both the uplink and the downlink, and the downlink is information spread with a common spreading code. Is always transmitted in the base station slot, and the uplink is transmitted by allocating an empty slot to a mobile station requiring transmission and performing spectrum spreading with a common spreading code.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1. FIG. 1 is a configuration example of a land mobile communication system.
Denotes base stations (hereinafter “BS”), and 21 to 23 denote mobile stations (hereinafter “MS1 to MS3”). BS and MS1-MS3
Is equipped with the following transmission system and reception system,
The downlink to S3 performs continuous spread spectrum transmission on different frequency channels, and the uplink from MS1 to MS3 to the BS performs spread spectrum burst transmission.

FIG. 2 is a block diagram of a transmission system.
Is a speed converter for compressing transmission data of one frame time to one slot time, 31 is a primary modulator for modulating the compressed data with a carrier, and 32 is a secondary modulator of the primary modulated signal with a spreading code (PN code). A multiplier for generating a spread spectrum signal (transmission signal) by performing modulation (spread modulation), a burst transmission unit 33 for performing burst transmission of a transmission signal of one slot time for each frame, an antenna 34, and a P
The N code generator 36 controls the spread code so as to be synchronized with the PN code of the base station based on the control signal from the base station, and controls the timing of burst transmission in the transmission slot allocated by the base station. It is a control unit.

FIG. 3 is a block diagram of a receiving system.
Is an antenna, 41 is a multiplier for performing despreading by multiplying a broadband spread spectrum signal (received signal) received by the antenna with a synchronized PN code, and 42 is a demodulator 1 for demodulating the despread narrowband modulated wave. A next demodulator 43 is a decoding unit that decodes the demodulated signal and reproduces n-channel data corresponding to the multiplicity n of TDMA, 44 is a PN code generator, 45 is a synchronization circuit, and 46 is a timing control unit. is there.

FIG. 4 is a diagram showing a frame configuration of an uplink in the first embodiment. The multiplicity n of TDMA is 3 for convenience. In FIG. 4, each mobile station MS1
MS3 uses one of the three slots that make up one frame. For example, MS1 uses the first slot, MS2 uses the second slot, and MS3 uses the third slot. However, each mobile station (MS1 to M
In S3), it is assumed that synchronization has been established with the base station (BS).

The spreading code uses the same code for each of the mobile stations (MS1 to MS3), but does not interfere with each other because the burst operation is performed so that they do not overlap each other on the time axis during transmission. Note that it is desirable to provide a guard time between each slot in order to prevent burst signal collisions due to multipath delays and synchronization deviations during reception at the base station (BS).

As described above, in the first embodiment,
The CDMA system is adopted for the downlink from the base station (BS) to each mobile station (MS1 to MS3), and the CD is used for the uplink.
Since the MA-TDMA hybrid (composite) system is adopted, it is possible to obtain an effect that a sufficient amount of downlink information can be ensured, and an amount of uplink information can be secured without excess or shortage.

Further, if time division multiplexing duplex (TDD) is adopted for the uplink, the effect of reducing channel interference such as multipath fading to the base station (BS) can be obtained. In the above description, the multiplexing number n of the TDMA is set to 3, but may be set to an arbitrary number L. Further, although TDMA is used for compressing continuous data and allocating a frame for data transmission, data packets from a plurality of mobile stations may be randomly allocated to vacant slots and transmitted as in packet data transmission. .

In the first embodiment, an example has been described in which different information is allocated to different channels of the downlink and transmitted. However, the present invention is not limited to this. For example, an information distribution service or a three-way call service may be used. The present invention can also be applied to an example in which the same information is transmitted to a plurality of users on a common channel.

Further, the structure of the transmission and reception frames may be time division multiplexed duplex (TDD). By doing so, the transmission and reception frames can be configured as one frame. FIG. 5 is a frame configuration diagram in the case of a time division multiplex duplex. It is assumed that the base station (BS) and the mobile stations (MS1 to MS3) are synchronized. One frame for transmission / reception is divided into an uplink and a downlink, and the uplink from each mobile station (MS1 to MS3) to the base station (BS) is divided by the number of mobile stations (in this example, divided into three). The reception slots of the mobile stations (MS1 to MS3) are allocated in advance to all mobile stations in advance, but the transmission slots from the mobile stations are individually allocated to each mobile station.

FIG. 6 is a modification of FIG. 5, in which the downlink is also time-division multiplexed so that separate data can be transmitted for each mobile station. This example is similar to a normal time division multiplexing frame configuration, but differs in that time division multiplexing is further performed within one code division multiplexing channel.

According to the example of FIG. 5 or FIG. 6, the reception frame configuration (the transmission frame configuration in the example of FIG. 6) is also a time division multiplexed duplex (TDD), so that the frequency channel can be further effectively used. In addition, the same information from the base station (BS) can be received by a plurality of mobile stations (MS1 to MS3) at the same time, and there is an advantage that a synchronization deviation of uplink time division multiplexing can be suppressed. In the example of FIG. 5 or FIG. 6, the multiplicity n of TDMA is set to 3, but may be set to an arbitrary number L. Further, continuous transmission is performed for both the downlink and the uplink. Uplink may be used for packet transmission. The packet transmission has an advantage that the number of users is not limited, particularly when applied to a chat service of personal computer communication.

2. Example of application to a three-way call service system A three-way call service is a service for performing mutual communication (transfer of data and voice) between a plurality of mobile stations via a base station. If so, MS via BS
The transmission and reception are simultaneously performed between 1 and MS3.

The block configurations of the transmission system and the reception system in the three-way call service are the same as those shown in FIGS. However,
A difference is that a code for three-way communication is assigned as a spreading code, and a mobile station that performs three-way communication uses this common spreading code. The frame configuration of the three-way call service is the same as in FIG. That is, the transmission / reception frame configuration is time division multiplexed duplex (TDD), the reception slot of the mobile station is common to MS1 to MS3, the transmission slot is assigned to a position determined by MS1 to MS3, respectively, and the downlink The length of the slot for the uplink is made longer than that of the slot for the uplink so that the difference between the information amounts of the uplink and the downlink can be accommodated.

FIG. 7 is a control flowchart of a three-party call in the base station. There is a connection request from the mobile station (S
1) When the three-way call mode is selected (S
2) In addition to allocating a spreading code for three-way communication and a mobile station transmission frame, a common spreading code and transmission slot are allocated to other mobile stations of the other party (S4). When there is no connection request, a predetermined system control process is executed, when the normal call mode is selected, a normal call process is executed, and when other than the three-party call or the normal call mode, another call mode process is executed. (S3). In order to prevent interference with other calls, it is desirable to perform transmission power control on a mobile station that is closer to the base station among mobile stations that perform a three-way call.

As described above, according to the second embodiment, the CDMA-TDMA hybrid system is adopted for three-way communication, and the downlink to each mobile station is a common frame. Is the number of channels used in a three-party call). Only one required communication channel is required, and effective use of the communication line can be achieved.

Further, since a dedicated three-way spreading code is provided, the control of generation and allocation of the spreading code can be simplified. Further, since the downlink frame is made longer than the uplink frame, it is possible to optimize the communication capacity in asymmetric communication having a difference in information amount between the downlink and the uplink. The number of simultaneous three-way calls is three, but is not limited to this. For example, if the number of frames is 1
The number of frames may be increased to 4, and the number of frames may be increased to 3 + f. Further, the present invention may be applied not only to voice communication but also to packet data transmission, or may have a two-channel configuration using different frequencies for transmission and reception.

In the second embodiment, an example in which the present invention is applied to a three-way call is shown. However, the present invention can also be applied to a business radio service such as a taxi and security service. In the case of the commercial radio service, the downlink from the base station is always transmitted, and the uplink from each mobile station is often transmitted in an arbitrary short time. Therefore, time-division multiplexing is applied to the uplink, and an empty slot is allocated only when transmission is necessary, and transmission is performed.

FIG. 8 is a block diagram of a business radio service, wherein BS is a base station, and MS1 to MS6 are mobile stations (for example,
Wireless taxis, etc.). The wireless system uses spread spectrum communication, and the downlink from the BS transmits the same information to all mobile stations in the area.

FIG. 9 shows a C applied to a business radio service.
FIG. 2 is a diagram illustrating a configuration of a DMA-TDMA frame. A transmission frame from the BS is received by all mobile stations.
When the MS 3 newly transmits while the MS 1 and the MS 2 are transmitting, the transmission slot of the BS 3 is allocated to an empty slot of the transmission frame.

In general, in a business radio service, since there are few simultaneous transmissions from many mobile stations, there are many empty slots,
Even if the slot is occupied, the transmission is completed in a short time, so that an empty slot is easily created, and the empty slot can be allocated to the next mobile station to transmit. Therefore, by allocating a transmission slot from a mobile station to a vacant slot for uplink transmission only for a required time, it is possible to efficiently perform wireless communication with an arbitrary number of mobile stations with a predetermined number of slots, and use the same channel. In addition to this, it is possible to obtain the effect that a large number of mobile stations can be communicated with a fixed frame length.

In order to transmit and receive different information contents, different spread codes may be assigned in the same system. Also in this embodiment, it is desirable to perform transmission power control on the mobile station side closer to the base station so as not to interfere with other stations. Further, in this embodiment, the uplink and downlink are transmitted and received in the same frame. However, wireless communication may be performed using different frequencies for uplink and downlink, and furthermore, each slot length in the frame may be changed. May have any length.

3. Example of application to shared service system by different operators Conventionally, when operating a CDMA wireless service, it was necessary to allocate radio waves to each operator, but this occupies limited radio wave resources on a first-come, first-served basis. Because it is a factor that hinders healthy economic activity by refusing the participation of late-stage businesses,
Must be resolved.

In the present embodiment, a plurality of carriers (hereinafter referred to as three carriers for convenience) share one radio resource, and the effective use of the limited radio resource to join the later carriers. It seeks to encourage and eliminate factors that hinder sound economic activity.

FIG. 10 is a diagram showing the system configuration.
S1 to BS3 are base stations of each operator, and M is BS1 to BS3.
, A1, A2, B1, B2,
C1, C2, D1, D2, D3 are mobile stations. Each base station is assigned a code to be used in CDMA (at the same frequency), and the number varies depending on the number of subscribers of each operator. In the illustrated example, a code A is allocated to BS1, a code B is allocated to BS2, and a code C and a code D are allocated to BS3. Note that the number of base stations may be one in the case of joint use.

Each mobile station communicates using a spreading code (A, B, C or D) of a business operator to which the user who owns (or uses) the mobile station is subscribed. Each mobile station must perform transmission power control so as not to interfere with other users.

The point of the system shown in FIG. 10 is that each base station BS1 to BS3 (operator) does not independently perform frame timing control, but allocates (synchronized) slots by the base station controller M. It is to perform division control.

FIG. 11 is a diagram showing the TD-CDMA frame structure. Even in the case of shared use by a plurality of operators, from the viewpoint of statistical time, each slot is hardly filled up, and an empty slot is often generated. Such an empty slot is stored in the base station controller M
, The subscriber capacity can be statistically increased. This utilizes the fact that the number of empty slots increases as the connection time per user is shorter. For example, even if only three people can talk at the same time per one (frequency) channel, as shown in FIG. If one empty slot always occurs, it means that code division multiple access for 3 + 1 people is possible.

The system shown in FIG. 10 can also be applied to satellite communication. In particular, in satellite communication, the area covered by one satellite is much larger (compared to terrestrial radio communication). The control for increasing the capacity is particularly effective.

FIG. 12 is a configuration diagram applied to satellite communication. In this figure, ST is a communication satellite, FT is a gateway station,
A1, A2, B1, B2, and B3 are mobile stations. The spreading codes of the mobile stations A1, A2 are A codes, and the mobile stations B1, B2, B
The spreading codes of 2 are B codes, and these mobile stations exist in the area of ST. The downlink from the ST receives the same information at A1 and A2 (or B1, B2 and B3), and uses the radio slot assigned to each mobile station in the uplink. Uplink slot (A1 or A2)
On the other hand, the downlink slot (RX) is long, so that the amount of downlink information can be sufficiently covered.

The A system (a system including A1 and A2) and the B system (a system including B1, B2, and B3) have different spreading codes, and thus are services of different operators. Synchronized, and the slot assignment is also totally controlled by the gateway station FT. Practical examples of such services include:
For example, a three-way call, an interactive information service, a taxi radio or a security radio may be considered.

FIG. 13 is a connection flowchart in the system of FIG. In the case of terrestrial radio, the operation is basically the same as that of a satellite (just because no relay is provided). FIG.
In step 3, first, when the mobile station is turned on, the gateway station reads the information of the mobile station via the satellite and authenticates the registered device of each connection operator as to whether or not the subscriber is an authorized subscriber. . If the mobile station is a regular subscriber, the subscriber information and location information of the terminal are registered, and then the gateway station indicates a radio channel for the mobile station to communicate. The mobile station receives the downlink (waits for a three-party call) and, when making a call, transmits using the designated transmission slot.

According to such a system, it is possible to perform frame control including a plurality of carriers simply by assigning a spreading code to each carrier, and to further increase the subscriber capacity. It is possible to improve the system, and it is possible to obtain a special effect that a new company can be added without changing the system configuration. In addition, by assigning a plurality of spreading codes to a business having a large number of users, it is possible to absorb subscriber variations among the businesses and to reduce bias and waste of the system configuration.

[0044]

According to the first aspect of the present invention, in a digital radio communication method for performing radio communication between a base station and a plurality of mobile stations, a downlink from the base station to each mobile station is a CD.
Continuous transmission is performed by the MA system, and the uplink from each mobile station to the base station is CDMA-T combining time division multiplexing and code division multiplexing.
Since the burst transmission is performed by the DMA method, it is possible to obtain an effect that a sufficient amount of downlink information can be ensured, and an enough amount of uplink information can be ensured. According to the second aspect of the present invention, in a digital wireless communication method for performing wireless communication between a base station and a plurality of mobile stations, the configuration of transmission and reception frames is time division multiplexed duplex (TDD), On the downlink to the mobile station, the same information is sent to each mobile station by the CDMA system, and on the uplink from each mobile station to the base station, burst transmission is performed by the CDMA / TDMA-TDD system that combines time division multiplexing and code division multiplexing. Since this is performed, an effect is obtained that channel interference such as multipath fading to the base station can be reduced. According to the third aspect of the present invention, in a digital wireless communication method for performing wireless communication between a base station and a plurality of mobile stations, the configuration of transmission and reception frames is time division multiplexed duplex (TDD), and uplink and downlink are configured. CDMA / T that combines time division multiplexing and code division multiplexing on both lines
Since the burst transmission is performed by the DMA-TDD method, the frequency channel can be more effectively used, and the same information from the base station can be received by a plurality of mobile stations at the same time. An effect is obtained that the synchronization shift of the division multiplex can be suppressed. According to a fourth aspect of the present invention, there is provided a digital radio communication method for performing a three-party call by radio communication between a plurality of mobile stations via one base station, wherein time-division multiplexing and code division are used for both the uplink and the downlink. Using a multiplexed CDMA-TDMA scheme, a common spreading code for three-way communication is allocated to each mobile station and base station, and each mobile station receives a downlink frame from the base station as a common frame, Further, since the uplink uses the transmission slot allocated to each mobile station, the conventional channel is m (where m is the number of channels used for three-way communication).
Only one required communication channel is required, and effective use of the communication line can be achieved. According to the invention described in claim 5, the downlink from the base station to a plurality of mobile stations transmits the same information simultaneously through a common slot, and the uplink from each mobile station to the base station is transmitted to each mobile station. In a digital radio communication method for individually transmitting via an assigned channel, a CDMA-TDMA system combining time division multiplexing and code division multiplexing is used for both uplink and downlink, and the downlink is spread with a common spreading code. The transmitted information is always transmitted in the base station slot, and the uplink is allocated an empty slot to the mobile station requiring transmission, and the spectrum is spread and transmitted with a common spreading code. By allocating a transmission slot from a mobile station to a slot for a required time, wireless communication with an arbitrary number of mobile stations can be efficiently performed with a predetermined number of slots. It can, after the effect is obtained that allows a large number of radio communication on the same channel, is an effect that it is possible to increase the number of mobile stations that can communicate in a fixed frame length is obtained.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a first embodiment.

FIG. 2 is a block diagram of a transmission system.

FIG. 3 is a block diagram of a receiving system.

FIG. 4 is a diagram illustrating an uplink frame configuration according to the first embodiment;

FIG. 5 is a diagram illustrating a frame configuration when a time division multiplex duplex is used.

FIG. 6 is a frame configuration diagram in a case where the downlink is also time-division multiplexed so that different data can be transmitted for each mobile station.

FIG. 7 is a control flowchart of a three-party call in a base station.

FIG. 8 is a configuration diagram of a business wireless service.

FIG. 9 shows a CDMA-TD applied to a commercial radio service.
FIG. 4 is a diagram illustrating a configuration of an MA frame.

FIG. 10 is a system configuration diagram applied to a shared service of a plurality of businesses.

FIG. 11 is a TD applied to a shared service of a plurality of operators.
FIG. 3 is a diagram illustrating a frame configuration of CDMA.

FIG. 12 is a configuration diagram applied to satellite communication.

FIG. 13 is a connection flowchart in a satellite communication system.

FIG. 14 is a block diagram of a conventional CDMA wireless communication device.

[Explanation of symbols]

 BS Base station MS1-MS3 Mobile station

Claims (5)

[Claims] 1. A digital radio communication method for performing radio communication between a base station and a plurality of mobile stations, wherein a downlink from the base station to each mobile station is continuously transmitted by a CDMA system, and each mobile station is transmitted from the mobile station to the base station. A burst transmission by a CDMA-TDMA system in which time division multiplexing and code division multiplexing are combined on the uplink. 2. A digital radio communication method for performing radio communication between a base station and a plurality of mobile stations, wherein a configuration of transmission and reception frames is time division multiplexed duplex (TDD), and downlink from the base station to each mobile station is performed. The line transmits the same information to each mobile station by the CDMA system, and the uplink from each mobile station to the base station performs burst transmission by the CDMA / TDMA-TDD system that combines time division multiplexing and code division multiplexing. Digital radio communication method. 3. A digital radio communication method for performing radio communication between a base station and a plurality of mobile stations, wherein a configuration of transmission and reception frames is time division multiplexed duplex (TDD), and both uplink and downlink are time division multiplexed. A digital radio communication method comprising: performing burst transmission by a CDMA / TDMA-TDD scheme which is a combination of code division multiplexing and code division multiplexing. 4. A digital radio communication method for performing a three-party call by radio communication between a plurality of mobile stations via one base station, wherein CDMA combining time division multiplexing and code division multiplexing for both uplink and downlink. -Using a TDMA scheme, assigning a common spreading code for three-way communication to each mobile station and base station, each mobile station receives a downlink frame from the base station as a common frame, and A digital radio communication method using a transmission slot assigned to each mobile station. 5. A downlink from a base station to a plurality of mobile stations transmits the same information simultaneously through a common slot, and an uplink from each mobile station to a base station uses a channel assigned to each mobile station. A digital radio communication method for individually transmitting data via a CDMA-TDMA system combining time division multiplexing and code division multiplexing for both the uplink and the downlink, wherein the downlink uses base station to transmit information spread by a common spreading code. A digital wireless communication method, wherein the mobile station always transmits in a dedicated slot, and the uplink is allocated an empty slot to a mobile station requiring transmission, and spreads the spectrum with a common spreading code for transmission.