JPH099331A - Hand-over control method for mobile communication and mobile radio equipment - Google Patents

Abstract

PURPOSE: To avoid alternate repetition of start of hand-over processing and switch back processing under the condition where communication quality is deteriorated in a radio communication service area end, hand-over processing is started, the processing is failed and the switch back processing is successful. CONSTITUTION: Detected communication quality is compared with a standard hand-over threshold level ths (S2 ), when the quality is wronger than the level ths, hand-over processing is started (S3 ), and when the communication is not continued by a new communication channel (S4 ), a threshold level thw wronger than the hand-over threshold level ths is set to a new hand-over threshold level (S7 ). When the hand-over processing is started by using the level thw and communication is continued through a new communication channel, the hand-over threshold level is restored to the level ths (S9 ).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system and a handover control method for shifting from a communicating radio zone to a communication through an adjacent radio zone.

[0002]

2. Description of the Related Art In a mobile communication system, a wireless communication service area is usually divided into a plurality of wireless zones. Handover refers to communication via the radio channel of the radio base station of the new radio zone through the radio channel with the radio base station of the old radio zone when the mobile radio moves from one radio zone to another radio zone during communication. Switching the channel and continuing communication. The mobile radio device has only one handover threshold value, measures the communication quality of the radio wave received during communication as shown in FIG. 3, and usually measures the frame error rate and the received power (S ₁ ), The communication quality is compared with the handover threshold, and the error rate is 1
It is checked whether the received power is 0% or less and the received power is, for example, 28 dBμV or more (S ₂ ), and if the communication quality is lower than the handover threshold, it is determined that the mobile wireless device is out of the wireless zone in communication and handover is performed. processing the start (S _3). If the mobile wireless device that initiated the handover processing is not located in any wireless zone, it is determined that there is no new wireless zone (S ₄ ), and the old wireless zone that was communicating before the handover processing was activated. Switch-back processing for resuming communication with the wireless base station is performed (S ₅ ). After this switching back process, the process returns to step S ₁ . This mobile wireless device is designed to detect the communication quality of the received radio wave and activate the handover process when the quality falls below the handover threshold again.

[0003]

In the prior art, a plurality of wireless zones are arranged to form a wireless communication service area so that the communication quality at the boundary with the adjacent wireless zones is all equal. The communication quality at the edge of the wireless zone was designed to be equal in the wireless communication service area. Therefore, the mobile radio is designed to operate according to whether it is better or worse than one standard handover threshold representing the wireless zone edge in order to activate the handover process at the optimum position within the wireless communication service area. It was Therefore, under the condition that there is no new wireless zone for switching communication by the handover process near the mobile wireless device such as at the end of the wireless communication service area, there is a problem that the handover process and the revertive process are alternately repeated. there were.

An object of the present invention is to solve such a problem, prevent the handover processing and the revertive processing from being alternately repeated at the end of the wireless communication service area, and perform the handover processing at an optimum place in the wireless communication service area. (EN) Provided are a mobile communication handover control method and a mobile wireless device, which activate a mobile communication system and enable stable communication.

[0005]

According to the method of the present invention, the threshold value is changed to a bad value when the communication can be continued through the new wireless zone by the handover processing, that is, when the handover fails. After the threshold value is changed, if the communication can be continued through the new wireless zone by the handover process, that is, if the handover is successful, the threshold value is returned to the initial value.

According to the invention of claim 2, in the invention of claim 1, if the handover process after changing the threshold value to a bad value fails, the threshold value is changed to an even worse value. This change may be made multiple times. According to the mobile radio device of the invention of claim 3, the second threshold value that is worse than the first threshold value is also stored in the storage means, and if the handover fails, the threshold value compared by the comparison means by the switching means. Is changed to the second threshold value, and if the handover succeeds after the change, the switching means returns the threshold value to be compared with the comparison means to the first threshold value.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 functionally shows the essential parts of an embodiment of a mobile radio device according to the invention of claim 3. The antenna 11 receives a radio wave during communication, and the communication quality of the received signal is measured by the communication quality detecting means 12. This measurement is usually the frame error rate and the received radio wave power (reception level). The communication quality signal 21 is compared with the threshold value th by the comparator 13. When the communication quality signal has a quality lower than the threshold value, the handover signal is notified to the handover means 14, and the handover means 14 starts the handover processing. When the communication cannot continue through the new wireless zone due to the handover, that is, when the handover fails, a switchback signal is notified to the switchback means 15, and the switchback means 1
5 starts the switching back processing. That is, the process of restarting the communication continuation via the old wireless zone which was in communication before the start of the handover process is performed.

In this embodiment, the threshold value th used in the comparator 13 is stored in each of the registers 17 and 18, and the threshold value ths stored in the register 17 has the same value as that used conventionally, for example, 28 dBμV, which is called a standard handover threshold. Register 17
The threshold value thw stored in is a value that is worse than the standard handover threshold value, and in this example, it is set as a limit reception power value that can be received by this mobile radio, for example, 10 dBμV, and is set as a wide area handover threshold value. Call. Register 1
7, 18 are connected to the comparator 13 via the selector 16, and normally the register 17 is selected by the selector 16 and the standard handover threshold ths is continued to the comparator 13.

If the hand-over means 14 performs the hand-over process, but if it fails, the switch-back means 15 is activated as described above. In this embodiment, the selector 16 is controlled by the threshold value changing signal and the register 18 is selected. The wide area handover threshold thw is supplied to the comparator 13. Therefore, the threshold value thw is compared with the measured communication quality from the next time. When the handover means 14 is activated in this state and the handover is successful, that is, when communication is continued through the new zone, the handover means 14 controls the selector 16 with a clear signal to perform the standard handover of the register 17. The threshold value ths is supplied to the comparator 13.

The comparator 13 compares the received power with the threshold value ths or thw when the frame error rate becomes worse than a set value, for example, 10% (or about 5%). An embodiment of the handover control method in the mobile radio device shown in FIG. 1, that is, the embodiment of the invention method of claim 1 will be described with reference to FIG. 2A. In FIG. 2A, parts corresponding to those in FIG. 3 are designated by the same step symbols. The communication quality of the received radio wave is detected (S ₁ ), the communication quality is compared with a threshold th (S ₂ ), and if it is worse than the threshold th, handover processing is started (S ₃ ), and the handover is performed. It is the same as the conventional one in that it is determined whether it succeeds (S ₄ ), and if it fails, the switching back processing is performed (S ₅ ). In this embodiment, if communication cannot continue through the new wireless zone in step S ₄ , the selector 16 is notified of a threshold change signal (S ₆ ), and the threshold th used for comparison is handed over in a wide area in step S _2. The process returns to step S ₁ as the threshold value thw (S ₇ ).

Step S_FourThrough the new wireless zone
If communication can be continued, handover to it
Notify the selector 16 of the clear signal (S₈), Step
S ₂Threshold value th used for comparison in standard handover
Return to threshold ths (S₉). Thus this embodiment
Now compare with the standard handover threshold ths
If the original handover process fails, the threshold
Since it is changed to the wide area handover threshold thw,
Step S after return processing₂Communication quality detected in
It is less likely to be worse than the threshold value th, and handover processing
There is little possibility that the processing and the switching back processing are repeated. I
However, in the subsequent handover processing, the new wireless zone is passed.
When the continuous communication is started, the threshold th
Mobile communication to return to the standard handover threshold ths
Guaranteed communication when traveling within the service area
Quality is maintained.

In the above, two thresholds are provided,
This was switched and used, but the standard handover threshold t
If the handover process fails based on the comparison in hs, the threshold th is changed to a bad value by a predetermined value, and if the subsequent handover process fails, the threshold th is changed to a worse one. You can also This is claim 2
Invention. In this case, step S ₆ in FIG. 2A,
Instead of S ₇ , as shown in FIG. 2B, the threshold th used in the comparison in step S ₂ is the longest threshold thm, and the limit reception power that can be received by the mobile radio device is, for example, 1
It is checked whether it is equal to or worse than 0 dBμV (S ₁₀ ), and if it is not equal or bad, the threshold th used in the comparison in step S ₂ is deteriorated by a, for example, lowered by 3 dB, and this th-a Is the threshold value th used in the comparison in step S ₂ (S ₁₁ ). This increases the possibility that communication will continue through the old wireless zone in the switchback processing. Then, it becomes less communication quality threshold th again in step S _2, and the handover process, when this fails, the threshold value th is decreased by a at step S ₁₁ through step S _10. Such it is repeated, the threshold th is worse than matches to or the worst value thm used for comparison in step S _2, not change the threshold value th to be used for comparison in step S _2. During the above processing, that is, the threshold value th used in step S ₂
If any of the values is, the threshold value used for the comparison in step S ₂ is returned to the initial value, which is the standard handover threshold value ths in this example, when the handover is successful in step S ₄ .

In the threshold value change shown in FIG. 2B, the standard handover threshold value ths as an initial threshold value is stored in the register 17 in FIG. 1 and the threshold value change is made in another register. The amount a is stored, and the threshold value t used in the comparator 13 is stored by using both of them.
It is only necessary to change h. As shown in FIG. 2A, as the threshold value used for the comparison in step S ₂ , in either case of ths and thw, ths and the difference (ths−thw) = Δth between ths and thw are To change the threshold value used for comparison to thw in advance, ths-Δth
May be calculated and supplied to the comparator 13. This is the case where ths-a becomes thm in FIG. 2B.

The actual processing in FIG. 1 is the so-called CP.
In many cases, the comparator 13, the handover means 14, the switchback means 15, the selector 16, etc., which are provided with U, are performed by the CPU decoding and executing the program.

[0015]

As described above, according to the present invention, when the handover process is started using the standard handover threshold and the call cannot be continued on the new communication channel, that is, when the handover fails, the standard handover is performed. Even if the communication quality of the radio wave received by the mobile radio after the switchback process is successful is the same as the condition that initiated the handover process, the handover process is performed to change to a threshold value that indicates a communication quality that is worse than the threshold value. It is unlikely that the handover process and the switching back process are repeatedly performed without activating the above. Furthermore, when the handover process is started with the threshold value worsened, communication can continue through the new wireless zone, that is, when the handover succeeds,
Since the handover threshold is returned to the standard handover threshold, the handover process can be activated at an optimum location within the wireless communication service area.

[Brief description of drawings]

FIG. 1 is a block diagram functionally showing only a main part of an embodiment of a mobile radio device according to the invention of claim 3;

FIG. 2A is a flow chart showing an embodiment of a handover control method according to the invention of claim 1, and B is a flow chart showing a part of the embodiment of the invention method of claim 2;

FIG. 3 is a flowchart showing a conventional handover control method.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Koichi Adachi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. The communication quality of a radio wave during communication is measured, the measured value is compared with a threshold value, and if the measured quality is worse than the threshold value, handover processing is started, and communication through a new wireless zone is performed. If you cannot continue,
In the handover control method for mobile communication that switches back to the communication through the old wireless zone that was performing communication before the handover processing is activated, if the communication through the new wireless zone cannot be continued, the threshold value is set to a bad value. A handover control method for mobile communication, comprising changing the threshold value and returning the threshold value to the initial value when communication can be continued through a new wireless zone by the handover process after the threshold value is changed. 2. The control method according to claim 1, wherein when the handover processing after changing the threshold value does not allow communication to continue through a new wireless zone, the threshold value is changed to a worse value. A mobile communication handover control method. 3. The communication quality of the radio wave during communication is measured by the communication quality detection means, and the measured value is compared with the threshold value from the first threshold value storage means by the comparison means, and the measured value is the above-mentioned value. If it is worse than the first threshold value, the handover processing means is activated, and if the handover by the handover processing means fails, the switchback means communicates through the old wireless zone in which the communication was performed before the activation of the handover processing means. In the mobile wireless device for switching back to the above, the storage means for storing the second threshold value that is worse than the first threshold value and the threshold value for comparison with the comparison means when the handover by the handover processing means fails. In the comparison between the means for switching to the second threshold value and the second threshold value, if the handover by the handover processing means is successful, the comparison And a means for switching the threshold value to be compared with the first threshold value to the first threshold value.