JPH05145470A - Multiple access mobile communication system - Google Patents

Abstract

PURPOSE:To increase number of correlation codes in use by reducing control processing in the large capacity CDMA mobile communication system and simplifying a base station controller and a mobile station control system. CONSTITUTION:In the cellular mobile communication system employing the code division multiple access (CDMA), a base station of each cell applies sector cell processing (T1, T2, T3) to an area of a cell to divide the cell into plural areas and to cover its own area, applies time division multiplex corresponding to the number of sector cells to allocate each time slot to each sector cell, gives numbering sequentially to each sector cell, and sector cells of the same number (T1, T2, T3) are in existence in the same direction with respect to each base station, the sequence (T1, T2, T3) of the time slots of each sector cell is the same in all the base stations, the transmission reception between the mobile station and the base station are subjected to time division multiplex in the allocated time slot for each sector cell and the communication is made with the mobile station in each sector cell for each sector cell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large capacity cellular mobile communication system having a simple device configuration.

[0002]

2. Description of the Related Art In a cellular mobile communication system using a CDMA technique, the same is applied to all communication of all cells, and also of respective radio lines from a base station to a mobile station (downlink) and from a mobile station to a base station (uplink). A different spreading code is assigned to each communication using a radio frequency, and the other party of communication demodulates the signal by performing correlation detection of the assigned spreading code. Since each communication uses the same radio frequency, if the strength of the radio wave at the time of reception is different, the strongest radio wave will mask other communications. Therefore, in mobile communication in which the distance between the base station and each mobile station is different, transmission power control is essential to control the output on the transmission side so that the radio waves from each station are received with approximately the same strength. Further, since communication is identified by a spread code, it is necessary to prepare a huge number of codes corresponding to the number of mobile stations.

FIG. 3 is a diagram for explaining a conventional system. 1 to 7 are cells, 8 to 14 are base stations, 15 to 18 are mobile stations, and 19 to 22 are communication partners and communication partners. It is a line showing the relationship of the base stations. Here, the mobile stations 15 and 17 are located far from the base stations 8 and 14, respectively.
8 is located close to the base stations 8 and 14, respectively. The base station 8 receives the transmission outputs of the mobile stations 15 and 16 communicating in the cell 1 with the same radio frequency but different spread codes at substantially the same level in the base station 8. Control the transmission output of. Even in the adjacent cell 7, the base station 14 uses the same radio frequency as that of the cell 1 but a different spreading code and the mobile station 17
The base station 14 controls the transmission output of each mobile station so that the radio waves from each mobile station can be received at substantially the same level. When the mobile station 15 to communicate with the base station 8 is near the cell 1 and near the cell 7, and the strength of the radio wave from the base station 14 is stronger than the transmission wave from the base station 8. The mobile station 15 cannot demodulate the transmission wave from the base station 8. Therefore, in the vicinity of the cell, each base station needs to control its transmission power so that the radio waves from its own station and the adjacent base station have almost the same level.

On the other hand, when the mobile station 15 and the mobile station 17 are in the vicinity of the cell 1 and the cell 7 and close to each other, the strength of the radio wave from the mobile station 17 is higher than that of the transmission wave from the mobile station 15. When it is strong, the base station 8 cannot demodulate the transmission wave from the mobile station 15. Therefore, each base station needs to control the transmission power of the mobile station around the cell to be at a level almost equal to that of the mobile station around the adjacent cell. Further, for example, when the base station 14 lowers the transmission power for the nearby mobile station 18 lower than the transmission power for the distant mobile station 17, the radio wave 22 for the nearby mobile stations 22.
Is masked by the radio waves 21 for distant mobile stations, so it is necessary to control the transmission power for each mobile station so that the transmission power becomes substantially equal at the same distance from the base station.

Further, in the conventional system, different frequencies are used for the uplink and downlink radio lines, and the radio wave propagation characteristics differ depending on the frequency. Therefore, the base station controls the transmission power by causing the mobile station to report the reception level. In addition, the base station instructs the mobile station to perform transmission power control based on the received level. That is, the control is performed individually for the upstream and the downstream.

[0006]

As described above,
In the conventional method, each base station needs to perform transmission power control for all mobile stations in its own cell, and its control device is extremely large. Furthermore, each base station communicates with all adjacent cells and controls the transmission power so that the level of radio waves from each base station around the cell and the transmission power of each mobile station around the cell are equal. The transmission and reception of control signals between the base stations for this purpose is enormous, and an extremely complicated control device is required.
Furthermore, it is necessary to perform control on each of the uplink and downlink radio lines, and for mobile stations that are required to be small and lightweight,
A complicated control system was a burden. Further, since the communication is identified by the spread code, it is necessary to prepare a huge number of codes corresponding to the number of mobile stations.

The present invention has been made in view of the above, and an object thereof is to reduce the amount of control processing, simplify the base station control device and the mobile station control system, and increase the number of usable correlation codes. The purpose is to provide a large-capacity mobile communication system.

[0008]

A feature of the present invention for achieving the above object is that in a cellular mobile communication system using code division multiple access, a base station of each cell is provided with a plurality of cells by converting a cell area into a sector cell. To cover its own area, perform time division multiplexing corresponding to the number of sector cells, assign each time slot to each sector cell, number each sector cell in order, and see from each base station the sector cell of the same number. Are in the same direction, the order of time slots in each sector cell is the same in all base stations, and transmission / reception with a mobile station is time-division multiplexed in the time slot assigned to each sector cell, In the multiple access mobile communication system, communication is performed with each mobile station for each sector cell.

[0009]

According to the multiple access mobile communication system of the present invention, in the cellular mobile communication system using the CDMA technology, each base station performs time division communication for each sector cell, and communication is performed at a time within the cell. By reducing the area being used to a fraction of the time division compared to the conventional method, the influence from mobile stations and base stations of adjacent cells is reduced, and the control amount for transmission power control per communication is reduced. To reduce. Furthermore, by performing communication in each sector cell according to time division multiplexing, the spreading code used in one sector cell can also be used in another sector cell, so the same spreading code is used in multiple times in time division. Also, by time-multiplexing transmission and reception, the same frequency can be used for uplink and downlink, so the radio wave propagation characteristics can be grasped by either the base station or the mobile station, and therefore the base station alone can control the transmission power. By performing such control, the control system of the mobile station is simplified.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a system configuration according to an embodiment of the present invention, showing a case of a 3-sector cell configuration.

In the figure, 23 and 27 are base stations, and
Reference numerals 26, 28 to 30 denote the respective sector cells T1 to T3. T
If T1, T2, and T3 are time-division-multiplexed time slot lengths, T1 + T2 + T3 is a repetition period (frame period), and 24 and 28 sector cells have 2 times at the time of T1.
At 5 and 29 sector cells, at time T2, and at 26 and 30 sector cells, at time T3, transmission and reception are time-multiplexed and communicated between each mobile station and base station in each sector cell.

By setting the relationship between the sector cells and the time slots in each cell in this way, each base station communicates only with sector cells in the same direction at a certain time. Thus, for example, the spreading code used in 24 sector cells is also used in 25 and 26 sector cells. Since transmission and reception are time-multiplexed within the time slot lengths of T1, T2, and T3, the number of time-division multiplexes is 3 × 2 6-channel multiplexing.

FIG. 1 is a diagram showing the relationship between the operation of the base station and time with respect to each sector cell of the embodiment described in FIG. 2, in which 31 is a time division multiplexing frame period and 32 to 34 are assigned to each sector cell. Time slot, 35 is a transmission slot, 36 is a reception slot, 37 is a transmission slot length,
38 is the receiving slot length, 39 to 41 are the respective sector cells T1
The operation at ~ T3 is shown.

In the sector cell T1, as indicated by 39, 3
Within time slot T1 of 2, the base station communicates with each mobile station in each of the 37 and 38 transmit / receive slots. The same operation is performed in the sector cells T2 and T3, and each sector cell repeats the operation at the frame period F = T1 + T2 + T3 indicated by 31.

The base station, for example, 23 base stations in communication with mobile stations within 24 of the sector cell T1, has information from the peripheral base station regarding the transmission power which the peripheral base station is transmitting to its own sector cell T1, The synchronization and the transmission power of the transmission slot to be transmitted by the mobile station are corrected and determined based on the synchronization state and the reception level in the reception slot, and the mobile station is instructed to perform the synchronization correction and the transmission power. The mobile station in each sector cell communicates with the base station by performing reception in the base station transmission slot in the time slot of the sector cell to which the sector cell belongs and transmitting in the base station reception slot. The mobile station transmits based on the synchronization correction and transmission power instructions from the base station.

[0016]

As described above, according to the present invention,
By making each base station perform time division communication for each sector cell, the area in which communication is performed at a certain time in the cell is reduced to a fraction of the time division as compared with the conventional method. It is possible to reduce the influence from the mobile station and the base station of the adjacent cells, and reduce the control amount required for the transmission power control per communication to a fraction of the time division. Furthermore, by performing communication in each sector cell according to time division multiplexing, the spreading code used in one sector cell can also be used in another sector cell, so that the same spreading code can be used several times in time division. Also, by time-multiplexing transmission and reception, the same frequency can be used for uplink and downlink, so the radio wave propagation characteristics can be grasped by either the base station or the mobile station, and therefore the base station alone can control the transmission power. By performing such control, the control system of the mobile station can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between operation of a base station and time regarding each sector cell according to the present invention.

FIG. 2 is a diagram showing a system configuration of the present invention.

FIG. 3 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1 to 7 cells 8 to 14 base stations 15 to 18 mobile stations 19 to 22 lines showing the relationship between mobile stations and the base stations of the other party of communication 23, 27 base stations 24 to 26, 28 to 30 each sector cell T1 to T3 31 o'clock Division multiplexing frame period 32 to 34 Time slot assigned to each sector cell 35 Transmission slot 36 Reception slot 37 Transmission slot length 38 Reception slot length 39 to 41 Operation in each sector cell T1 to T3

Claims (1)

[Claims] 1. In a cellular mobile communication system using code division multiple access, when a base station of each cell divides the area of the cell into sector cells to cover its own area and corresponds to the number of sector cells. By performing division multiplexing, each time slot is assigned to each sector cell, and each sector cell is numbered in order.When seen from each base station, the sector cells with the same number are in the same direction, and the time slot order of each sector cell is all bases. It is the same for all stations, and multiple access is characterized in that transmission / reception with a mobile station is time-division multiplexed within a time slot assigned to each sector cell and communication is performed with the mobile station within each sector cell. Mobile communication system.