JP2000013301A - Digital wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid interference in a digital radio communication system by detecting the moving direction and speed of the slot used by another station based on the variance of a carrier sense measured at of plural positions and moving its own slot based on the detected moving direction and speed. SOLUTION: When another station uses the same frequency for communication, a front slot 21 used by the station asynchronous and accordingly approaches a slot 22 from the front. Under such conditions, a carrier exists at a carrier sense point 24, the carrier exists between the carrier sense points 24 and 25, the carrier exists only at the carrier sense point 25 and then the carrier exists between the carrier sense points 25 and 26. If the carrier is varied at the points 24 to 26 as mentioned above, the backward movement and the moving speed can be detected by the slot 21. Thereby, the occurring time of interference can be estimated and the slot 22 is moved backward by this estimated time. Thus, the interference is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a TDMA such as a PHS.
More particularly, the present invention relates to a digital wireless communication system.

[0002]

2. Description of the Related Art Conventionally, in a TDMA radio communication system such as a PHS, a slot to be used is subjected to carrier sensing, and when there is no interfering carrier, transmission and reception are performed using the slot.

[0003]

However, at the time of carrier sensing, even if there is no interfering carrier, the slot used by another system using the same frequency moves due to the shift of the reference clock between the systems. Interference occurs.

As a means for avoiding this interference, there is a method of synchronizing base stations so that the used slots do not interfere with each other. However, interference occurs because there is no means for synchronizing base stations in a home base station. . The present invention solves the above-mentioned problems, and measures the level of a used slot of another system at a number of points, detects a moving direction and a moving speed based on a change in each measured value, and moves the used slot of the own system. Accordingly, an object of the present invention is to provide a wireless communication system that avoids interference without synchronization between base stations.

In the present invention, a carrier sense is performed at a plurality of points in the slots before and after the used slot, and the movement direction of the used slot of another system is determined by the fluctuation of the measured value at each measurement point.
The mobile station detects the moving speed and moves the slot used by the own station based on the detected moving speed to avoid interference.

[0006]

According to a first aspect of the present invention, there is provided a digital wireless communication system which performs carrier sensing at a plurality of positions, and changes a measured value of the carrier sense at each of the plurality of positions, thereby causing other than the own station. A digital radio communication system comprising a moving direction detecting means for detecting a moving direction of a slot used by a station system.

In the digital radio communication system according to the present invention, a carrier sense is performed at a plurality of positions, and a system of another station other than the own station is used by a change in a measured value of the carrier sense at each of the plurality of positions. And a moving speed detecting means for detecting a moving speed of the slot being operated.

According to a third aspect of the present invention, there is provided a digital radio communication system, comprising: a judging means for judging the presence or absence of interference based on the detected moving direction and moving speed of a slot used by the system of another station; 3. The digital radio communication according to claim 1, further comprising: interference avoiding means for avoiding the interference by changing the position of a slot used by the own station when it is determined that interference occurs. System.

In the digital radio communication system according to the present invention, carrier sensing is performed at a plurality of positions, and a system of another station other than the own station is used by the fluctuation of the measured value of the carrier sense at each of the plurality of positions. 3. The digital device according to claim 1, further comprising: a prediction unit that predicts whether or not a change in the slot position of the own station is necessary based on the moving direction and the moving speed of the slot. It is a wireless communication system.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of a system according to the present invention, FIG. 2 is a timing diagram, and FIG. 3 is a conceptual diagram when a slot used by another system approaches.

In FIG. 1, 11 is a base station, 12 is a mobile station, 13 and 15 are base stations of other systems, and 14 and 16
Is a mobile station of another system. Each base station and mobile station use the same frequency.

In FIG. 2, 24, 25, 26, 27, 2
Points 8 and 29 are points at which carrier sense is performed.
The times 4 to 26 and 27 to 29 are longer than the slot length.

Next, the operation of the above embodiment will be described. As shown in FIG. 1, a case is described in which other systems 13, 14, 15, 16 other than the own systems 11, 12 are communicating, and the used slots approach each other because of the asynchronous between the systems. When the used slots of the other systems 13 and 14 approach from the front, first, the measurement point 2
4 has a carrier level, there are carrier sense points 311 and 312 carriers as shown in FIG. 3A, and then there is a carrier only at carrier sense point 322 as shown in FIG. As shown in c), carriers are present at the carrier sense points 332 and 333.

When the carrier sense level fluctuates in this way, it is possible to detect that the used slot of another system is moving backward (in a direction approaching the used slot).

The time from the state where there is a carrier to the carrier sense points 24 and 25 in FIG. 2 to the state where only the carrier sense point 25 has a carrier and the state where only the carrier sense point 25 has a carrier and the carrier sense points 25 and 26 are shown. The movement speed can be detected by the time until the carrier is present, and the time at which interference will occur can be predicted. By moving the used slot backward by this time, interference is avoided.

Conversely, even if there is a carrier only at the carrier sense point 25 in FIG.
When there is a carrier at 4, 25, the movement direction of the other system is a direction that does not interfere (forward), so that the slot is not moved.

Even when a slot used by another station exists behind a slot used by the own station, the carrier sense point 2
The movement direction and the movement speed can be similarly detected from the fluctuations of the measured values at 7, 28 and 29.

In this case, similar interference avoidance can be performed only by reversing the above control.

Next, control when there is a slot used by another system before and after is described.

As shown in FIG. 4 (a), when the used slots 411 and 413 of another system move in the direction of the used slot 412, no matter which slot is moved, interference will eventually occur. Therefore, the position 414 in front of the use slot 415 of another system in front of the use slot,
Alternatively, the use slot of the own station is shifted to a position 417 behind the use slot 416 of another system at the rear.

As shown in FIG. 4B, slot 4 of another station
21 and 423, the front slot 421 moves forward, the rear slot 423 moves forward, and when the slot 423 moves faster than the slot 421, interference also eventually occurs. Therefore, the process moves to the position 426 behind the slot 425 used by another station behind.

As shown in FIG. 4C, when the used slots 431 and 433 of the other station move forward and the slot 431 is earlier, the interference is avoided by moving the used slot 435 of the own station forward. I do.

As shown in FIG. 4D, when the used slots 441 and 443 of the other station move to the opposite side of the used slot 442, no interference occurs and no movement occurs.

As shown in FIG. 4E, the used slots 451 and 453 of the other station move backward, and when the slot 453 is earlier, the used slot 455 is moved backward to avoid interference.

As shown in FIG. 4 (f), when the used slots 461 and 463 of the other station move backward and the slot 461 is earlier, interference eventually occurs, so that the front used slot 465 is used. To a position 464 in front of to avoid interference.

As described above, according to the above-described embodiment, the moving direction of the slot used by the other station can be
By detecting the moving speed and thereby moving the used slot, it is possible to avoid interference between unnecessary slots and the movement of the used slot without taking the synchronization between the base stations, thereby enabling efficient interference avoidance.

Although the interference avoidance operation has been described above, consider a system in which another system performs the interference avoidance operation in the same manner. At this time, under the situation where the own station observes the carrier sense level and determines that interference avoidance should be performed as described above, it is highly likely that other stations have also determined to avoid interference.

Therefore, it is conceivable that the self-station and the other system simultaneously perform the above-mentioned avoidance measures, and the above-mentioned avoidance measures may not be effective at all.

In order to avoid this, even when interference prediction is performed by the own station, an operation of monitoring another system is performed without performing the interference avoiding operation. As a result, if another station changes the slot position and no interference occurs as a result, the interference avoiding operation is stopped thereafter.

More specifically, “own station” in FIG. 4 is replaced with “other station” to avoid interference.
Looking at (a), (b), and (f), the slot used by the station that avoids interference changes irregularly. This is observed because the carrier sense output level at a certain position (and its surroundings) suddenly disappears and the carrier sense output level at another position (and its surroundings) suddenly appears.

When the interference prediction is performed again after the occurrence of this event, the situation changes to a state where no interference occurs (other stations avoid interference). If this is detected and the setting is made so that the interference avoidance at the own station is not performed, only the other station performs the interference avoidance, and it is possible to lead to a situation where no interference occurs in the whole including the own station and the other station.

This operation is more preferably performed by 1) waiting for the execution of the avoidance operation for a random time from the interference prediction time (or from the interference time), and observing the operation of the other system as described above. 2) Even when the own station is performing the interference avoidance operation, the interference avoidance operation is temporarily suspended at random, and it is detected whether or not another station performs the interference avoidance operation.

[0033]

According to the first and second aspects of the present invention, the moving direction and moving speed of a used slot of another station are detected by carrier sensing at multiple points, and the used slot is moved accordingly. Thus, efficient interference avoidance can be achieved without synchronizing between base stations without moving unnecessary slots or moving use slots.

According to the third aspect of the present invention, the interference is avoided by estimating the time of the interference. Therefore, the interference can be avoided before the occurrence of the interference, so that the influence of the interference on the call can be avoided.

According to the fourth aspect of the invention, for example, when another system performing the same interference avoidance operation as the own station uses the same frequency, the other system performs the interference avoidance. Even if the interference avoidance operation is not performed, no interference occurs, so that extra control need not be performed.

Also, by waiting for a random avoidance operation, it is possible to avoid starting the interference avoidance operation at the same timing as another station, so that interference after avoidance can be avoided.

Furthermore, by temporarily suspending interference avoidance during the execution of the interference avoidance operation and investigating it, it is possible to execute a decision not to avoid interference at any time.

[Brief description of the drawings]

FIG. 1 is a system schematic diagram of a digital wireless communication system according to an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of one embodiment of the present invention.

FIG. 3A is a diagram (part 1) for describing the effect of the present invention; (B) is a figure (the 2) for explaining an effect of the present invention. (C) It is a figure (the 3) for explaining the effect of the present invention.

FIG. 4A is a diagram (part 1) for describing the effect of the present invention; (B) is a figure (the 2) for explaining an effect of the present invention. (C) It is a figure (the 3) for explaining the effect of the present invention. FIG. 4D is a diagram (part 4) for describing the effect of the present invention. (E) It is a figure (the 5) for explaining the effect of the present invention. (F) It is a figure (the 6) for explaining the effect of the present invention.

[Explanation of symbols]

11 base station of own system 12 mobile station of own system 13, 15 base station of other system 14, 16 mobile station of other system 21 slot one slot before used slot 22 used slot of own system 23 one slot after used slot Slots 25, 26, 27, 28, 29, 311, 312, 31
3,321,322,323,331,332,333
Carrier sense points 411, 421, 431, 441, 451, 461 Slots used by other stations located in front 412, 423, 433, 443, 453, 463 Slots used by other stations located behind 413, 422, 432, 442 , 452, 462 Slots used by own station 414, 417, 426, 435, 446, 455, 4
64 Slot used by own station after avoiding interference

Claims (4)

[Claims] 1. Carrier sense is performed at a plurality of positions,
Digital wireless communication comprising moving direction detecting means for detecting a moving direction of a slot used by a system of another station other than the own station based on a change in a measured value of carrier sense at each of the plurality of positions. system. 2. Carrier sense is performed at a plurality of positions,
Digital wireless communication characterized by comprising moving speed detecting means for detecting a moving speed of a slot used by a system of a station other than the own station based on a change in a measured value of carrier sense at each of the plurality of positions. system. 3. A determining means for determining the presence or absence of interference based on the detected moving direction and moving speed of a slot used by the system of another station, and 3. The digital wireless communication system according to claim 1, further comprising: interference avoiding means for avoiding interference by changing the position of a slot used by the own station. 4. Carrier sense is performed at a plurality of positions,
Due to the fluctuation of the measured value of the carrier sense at each of the plurality of positions, based on the moving direction and moving speed of the slot used by the system of another station other than the own station, is it necessary to change the slot position of the own station? The digital wireless communication system according to claim 1, further comprising a prediction unit that predicts whether or not the digital radio communication system is to be used.