JP4343190B2 - Mobile communication terminal - Google Patents

Description

The present invention relates to a mobile communication system, and more particularly to a soft handover control method in a mobile communication system and a mobile communication terminal used in the system.

In a mobile communication system such as a mobile phone, the entire service area is divided into zones called cells, and the service is performed. However, the mobile communication terminal switches the base station to be a communication partner in accordance with the movement, so that the terminal Even if it moves, it is possible to continue communication. This base station switching operation is called handover.

A CDMA (Code Division Multiple Access) communication system that has already been started in Japan is a system in which a plurality of receivers communicate at the same frequency using channels that are identified using different spreading codes. As a feature of this CDMA communication system, soft handover (
There is a channel switching method called Soft Hand Over (hereinafter referred to as SHO) or Soft Hand Off. This is to start communication with the SHO destination base station before the communication with the SHO source base station is completed, taking advantage of the feature of CDMA that performs channel identification based on the difference of spreading codes on the same frequency band. The channel switching method. As a result, it is possible to avoid the instantaneous interruption of communication that occurs at the time of conventional hard handover and to perform stable communication.

The mobile communication terminal adds a base station with good communication quality to the soft handover based on the propagation loss of the reception channel, the signal interference wave power ratio, and the like, and deletes the base station with poor communication quality from the soft handover. What is required here is that control is performed to maintain a communication state that satisfies the specifications with a small number of radio resources, and there is a method for effectively using the remaining radio resources by reducing unnecessary soft handover. (For example, refer to Patent Document 1).

In this specification, the remaining radio resources are the number of mobile communication terminals or traffic channels that the base station can newly communicate with, or the power value that the base station can newly transmit. That means. Furthermore, computing resources (CPU, memory, etc.) consumed in the soft handover process at the terminal, base station, etc. may be added.

In mobile communication, the communication path becomes a multi-wave propagation path due to the influence of buildings and landforms between the base station and the mobile communication terminal. In the CDMA system, the quality is improved by separating these multiple waves and combining them with a rake. It is improving. The process of separating each path from the multiple wave propagation path is a path search. In a mobile communication terminal, each path separated by path search is assigned to each rake finger and rake combined. Conventionally, each path is assigned to a rake finger regardless of which base station it is from. And synthesized the lake.
JP 2001-169323 A (page 1 to page 14, FIGS. 1 to 23)

In soft handover, it is desired to save the remaining radio resources as much as possible while maintaining a predetermined communication quality by simultaneously connecting with a plurality of base stations. However, it is generally difficult to appropriately select a base station that is a candidate for soft handover addition and a base station that is a candidate for soft handover deletion. Conventionally, it has been difficult to adaptively realize both the maintenance of communication quality in a trade-off and the saving of remaining radio resources according to the conditions of the base station and mobile communication terminal during communication.

In order to avoid disconnection of communication due to a sudden change in the communication environment, it is better to perform soft handover with as many base stations as possible, but finger assignment taking this into account has not been performed conventionally.

An object of the present invention is to save the remaining radio resources while maintaining communication quality. Another object of the present invention is to provide a handover method and a mobile communication terminal that perform soft handover with as many base stations as possible.

In order to achieve the above object, in one embodiment of the present invention , a rake combining means for rake combining by assigning a signal from each path received from a base station in communication with an antenna to each finger portion, and the rake combining A data determination unit that determines final data from a signal that has been rake combined by the combining unit, and a measurement value that is measured for a predetermined measurement item for each path received from the communicating and non-communication base station by an antenna Whether to add the path to the rake synthesis based on the comparison result by the comparison unit, the comparison unit that compares the magnitude relationship between the measured value obtained by the calculation unit and a predetermined threshold value And a rake synthesis control means for controlling which path the rake synthesis means causes signals to be rake synthesized. Means the case remaining radio resources of the non-communication base station is greater than a predetermined value, the determination unit adds the base station non-communication related to the path that has been determined to add to RAKE combining in the soft hand-over by communicating In addition, the predetermined threshold that is used to determine whether or not to add the path received from the added base station to the rake combination is not combined with the rake received from the base station communicating before the addition. The non-communication base station has a value that is easier to add to the rake composition than the predetermined threshold that determines whether or not to add the path to the rake composition. The number of mobile communication terminals that the station can newly communicate with, the number of traffic channels that the non-communication base station can newly communicate with, or the non-communication base Is a power value that can be newly transmitted, and if any of these values is larger than the predetermined threshold, the remaining radio resources of the non-communication base station are larger than a predetermined value. It is the providing mobile communication terminal, characterized in that.

As described above, according to the present invention, in the CDMA mobile communication system, depending on the situation of the base station and the mobile communication terminal at the time of communication, it is possible to maintain communication quality that is in a trade-off at the time of soft handover and to maintain the remaining radio resources. Can be realized adaptively according to the situation of the base station and the mobile communication terminal during communication.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram for explaining a situation of a base station and a mobile communication terminal at the time of non-soft handover.

In FIG. 1, reference numeral 200 denotes a control device for controlling the entire mobile communication system, 10, 20, 3
0 is a base station of the mobile communication system, and 100 is a mobile communication terminal such as a mobile phone used in the mobile communication system.

The mobile communication terminal 100 improves the quality by separating and multiplexing the multiplex wave (direct wave + multipath wave) input from the base station 10. In FIG. 1, a broken line indicated by a straight line is a direct wave, and a broken line bent in the middle of a route indicates a multipath wave.

The number of mobile communication terminals, the number of traffic channels, and the total power that can be transmitted by the base station are limited.

The control device 200 on the telecommunications carrier side operates, for example, by executing a program stored in an arithmetic device, and the number of mobile communication terminals or traffic channels that can be newly communicated, or A power value that can be newly transmitted is supplied,
By storing this in a built-in memory or the like, it is always grasped.

In a CDMA mobile communication system, for example, a mobile communication terminal 100 is connected to a base station 10.
Mobile communication terminal 1 when communicating only with the other base station and not performing a soft handover with another base station.
00 receives the pilot channel transmitted by other base stations (base stations 20, 30,...) At any time. The mobile communication terminal 100 uses the received pilot channel power propagation loss, signal interference wave power ratio (hereinafter referred to as SIR), error rate within a predetermined time using error detection information (hereinafter referred to as CRC), etc. It is a general soft handover method to measure at least one of the above and add a base station whose values satisfy a predetermined criterion to the soft handover.

The mobile communication terminal 100 measures the error rate within a predetermined time using the propagation loss of power of the pilot channel, SIR, and CRC, and transmits this measurement result to the base station in communication periodically (for example, every several seconds). To report. The base station that has received this measurement result transmits it to the control device 200. The control device 200 stores the measurement result transmitted from the base station in a built-in memory or the like.

In this way, the control device 200 on the telecommunications carrier side is, for each base station, (1) the number of mobile communication terminals with which the base station can physically communicate, (2) the number of traffic channels, and (3) the total number that can be transmitted In addition to power, for each terminal, (4) propagation loss of pilot channel power, (5) SIR, (
6) The error rate within a predetermined time using the CRC is grasped.

  FIG. 2 is a diagram for explaining the configuration of the control device 200 in more detail.

In FIG. 2, the control device 200 includes an arithmetic device 201, ROM 202, RAM 203, I
/ F204 and is connected via a common bus 205.

The control device 200 controls the entire mobile communication system by executing a program stored in the ROM 202. The base station and the control device 200 are connected to be communicable wirelessly or by wire.

(1) Number of mobile communication terminals that can be physically communicated with each base station, (2) Number of traffic channels related to each base station, (3) Each base station (4) Propagation loss of pilot channel power for each terminal, (5
R) The error rate within a predetermined time using the SIR for each terminal and (6) the CRC for each terminal.
Store in AM 203. The RAM 203 is also used as a work area for programs.

FIG. 3 is a diagram showing a time change of propagation loss of a pilot channel of a base station in a mobile communication terminal.

For example, it is assumed that what is measured is the propagation loss of pilot channel power. The measured propagation loss is supplied to the control device periodically (every few seconds) via the base station, and the propagation loss of the pilot channel from the base station is smaller than the predetermined threshold Th _loss shown in FIG. Is held for the holding time T _add or more, the base station is added to the soft handover because the criterion is satisfied. Actually, a request to soft handover the base station
When the control device 200 receives the signal via the communicating base station, the control device 200 permits the mobile communication terminal 100 to perform a soft handover with the base station.

In the above example, the propagation loss of the pilot channel power has been described. However, an error rate within a predetermined time using SIR and CRC may be used instead.

FIG. 4 is a diagram for explaining the situation of the base station and the mobile communication terminal at the time of soft handover.

FIG. 4 is different from FIG. 1 in that the mobile communication terminal 100 is communicating with the base station 10 and the mobile communication terminal 100 is in soft handover with the base station 20.

In the first embodiment, in the situation shown in FIG. 1 and in the situation where the base station 20 has already soft handover with the mobile communication terminal 100 as shown in FIG. A case where it is determined whether to perform soft handover will be described.

When the number of mobile communication terminals or traffic channels to which the base station 30 can newly communicate or the power value that can be newly transmitted is less than a predetermined value, the control device 200, that is, When the remaining radio resources are less than the predetermined value,
The pilot channel propagation loss threshold Th _{loss in} the situation of FIG.
In comparison with FIG. 4, Th _{loss in} the situation of FIG. 4 which has already been handed over is set to a smaller value. In addition, the control device 200 is configured such that the number of mobile communication terminals or traffic channels that the base station 30 can newly communicate with or the power value that can be newly transmitted is less than a predetermined value. That is, when the remaining radio resources are less than a predetermined value, the threshold Th _loss of the pilot channel propagation loss in the situation of FIG.

As a result, when the remaining radio resources are less than the predetermined value, soft handover with the base station 30 becomes difficult compared to when the remaining radio resources are not less than the predetermined value.

FIG. 5 is a diagram for explaining the situation of the base station and the mobile communication terminal at the time of soft handover.

FIG. 5 is different from FIG. 4 in that the mobile communication terminal 100 is also in soft handover with the base station 40.

When the number of mobile communication terminals or traffic channels to which the base station 30 can newly communicate or the power value that can be newly transmitted is less than a predetermined value, the control device 200, that is, When the remaining radio resources are less than the predetermined value,
Compared to the threshold Th _loss in FIG. 4, the Th _loss in FIG. 5, it is set to a smaller value. Thus, the threshold Th _loss is reduced as the number of base stations performing soft handover increases.

Summarizing the above, the smaller the Th _loss size in each figure, the better the communication quality.
The Th _loss in Th _loss> 5 in Th _loss> 4 in FIG.

The more the number of base stations performing soft handover, the more severe the conditions for adding soft handover.

As a result, when the remaining radio resources of the base station 30 are low, it is possible for a mobile communication terminal that has already undergone soft handover and is considered to have relatively stable communication quality. It is possible to reduce unnecessary soft handovers, adaptively according to the situation of the base station and mobile communication terminal at the time of communication, maintaining the communication quality in a trade-off and saving the remaining radio resources. It can be realized.

In the above description, the measurement item performed on the pilot channel by the mobile communication terminal is the propagation loss. However, an error rate within a predetermined time using SIR or CRC may be used instead of the propagation loss. In this case, assuming that the threshold of _SIR is Th _SIR and the error rate threshold within a predetermined time using CRC is Th _error , the higher the SIR, the better the communication quality, and the smaller the error rate within the predetermined time using CRC, the communication Because the quality is good
Th _SIR <Th _SIR at Th _SIR <5 in FIG. 4, Th _error in Th _error> 4 in FIG. 1> in FIG. 1 and Th _error in FIG.

(Change T _add )
Further, the holding time T _{the add} of 3 independent of the measurement items for these pilot channels, as T _{the add} at T _{the add} <5 at T _{the add} <4 in FIG. 1, to achieve the purpose of the present invention May be. When changing this T _add , it is not necessary to change the above Th _loss , Th _SIR , and Th _error .

(Furthermore, Th _loss is changed _depending on the size of the remaining radio resources)
Furthermore, when the control device 200 determines whether or not to soft handover the base station 30 with the mobile communication terminal 100, the number of mobile communication terminals or traffic channels that the base station 30 can newly communicate with, Alternatively, when the measured value of the power value that can be newly transmitted is larger than the predetermined value, it is determined that the remaining radio resources have a margin. When the mobile communication terminal 100 is larger than the predetermined value for the purpose of avoiding a momentary disconnection due to a sudden change in communication state when the remaining radio resources have a margin, the control device 200 The predetermined value is changed so as to facilitate soft handover as compared with the following cases.

Specifically, when the measured value is a propagation loss of the pilot channel, Th _loss when the remaining radio resource is larger than a predetermined value> Th _lo when the remaining radio resource is smaller than the predetermined value
_{Let ss} .

If the measured value is SIR of the pilot channel, the Th _SIR <remaining radio resources when the remaining wireless resources greater than a predetermined value and Th _SIR when less than the predetermined value.

If the measured value is an error rate within a predetermined time using the CRC of the pilot channel, the Th _error> remaining radio resources when the remaining wireless resources greater than a predetermined value and Th _error when less than the predetermined value.

(Change T _add )
Also, independently of the measured values for these pilot channels, the holding time T _add in FIG.
The gist of the present invention may be achieved as T _add when the remaining radio resources are larger than a predetermined value <T _add when the remaining radio resources are smaller than the predetermined value.

FIG. 6 is a control flowchart of control apparatus 200 showing the soft handover algorithm in the present embodiment including this case when the measured value is a propagation loss of the pilot channel.

In FIG. 6, the propagation loss of the traffic channel of the base station 30 is measured (measurement result L) (step 601).

Next, it is determined whether or not the remaining radio resources of the base station 30 are equal to or less than a predetermined value (step 60).
2).

In step 602, if the remaining radio resources are not less than or equal to the predetermined value, Th _loss = a
It is set to 0 (step 603), and it jumps to the process of step 607 mentioned later. On the other hand, when the remaining radio resources are equal to or smaller than the predetermined value in step 602, the mobile communication terminal 100 performs S
It is determined whether or not HO is performed (step 604).

In step 604, if the mobile communication terminal 100 is not performing SHO, Th _loss = a
1 (step 605), the process jumps to the process of step 607 described later.

On the other hand, when the mobile communication terminal 100 is in SHO at step 604,
When the number of SHO base stations = 2, Th _loss = a2
When the number of SHO base stations is 3, Th _loss = a3
When the number of SHO base stations ≧ 4, Th _loss = a4
(Step 606).

Next, Th _loss is compared with the measurement result L obtained in step 601, and Th _loss > measurement result L
It is determined whether or not (step 607).

If Th _loss > measurement result L is not satisfied in step 607, the base station 30 is not added to the SHO of the mobile communication terminal 100 (step 608). Conversely, at step 607, Th
_{If loss} > measurement result L 1, the base station 30 is added to the SHO of the mobile communication terminal 100 (
Step 609).

  The magnitude relationship between a0 and a4 is a0> a1> a2> a3> a4.

Accordingly, when the remaining radio resources are small according to the remaining radio resources of the base station 30, there is a base station that has already performed a soft handover, and a mobile communication terminal that is considered to be relatively stable in communication. As a result, it is possible to reduce unnecessary soft handovers as much as possible, and when the remaining radio resources are free, active soft handovers can stabilize and improve communication quality, and communication is in a trade-off. It is possible to adaptively realize both the maintenance of quality and the saving of remaining radio resources according to the conditions of the base station and mobile communication terminal during communication.

Further, the remaining radio resources described above and the measurement items that the mobile communication terminal performs on the pilot channel are not limited to the present embodiment, and there are various options within the scope of the present invention. obtain.

The fewer the remaining radio resources of the base station to be soft handover,
The conditions for further soft handover addition may be made stricter.

Further, if the remaining radio resources of the base station are greater than or equal to a predetermined value, the handover may be easier than when no handover is performed.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to the drawings.

The second embodiment is different from the first embodiment in that the threshold Th _loss is changed according to the moving speed of the mobile communication terminal, and is the same for FIGS. 1 to 5.

In the second embodiment, in the situation shown in FIG. 1 and in the situation where the base station 20 has already soft handover with the mobile communication terminal 100 as shown in FIG. A case where it is determined whether to perform soft handover will be described.

When the mobile communication terminal 100 is moving at a speed lower than a predetermined speed, the control device 200 has a pilot channel propagation loss threshold value Th _{lo in} the situation of FIG.
Compared to _ss , the threshold Th _loss in the situation of FIG. 4 that has already been handed over is set to a smaller value.

Here, as a method for detecting the moving speed of the mobile communication terminal 100, a method using an automobile speedometer, a method using GPS, a method for detecting a fading pitch of a received signal, and the like can be considered. The selection may not affect the effect of the present invention.

Also, as further shown in FIG. 5, when the number of base stations that are soft handover from at 4 is large, compared to the threshold Th _loss in FIG. 4, the threshold value Th _loss in FIG. 5, more Set to a small value.

The size of the Th _loss in the figures summarized above, it indicates that the communication quality smaller the better, and Th _loss in Th _loss> 5 in Th _loss> 4 in FIG.

The more the number of base stations performing soft handover, the more severe the conditions for adding soft handover.

As a result, the mobile communication terminal 100 is moving as slowly as possible, and there is a base station that has already performed a soft handover, and it is as wasteful as possible for a mobile communication terminal that is considered to have a relatively stable communication state. Soft handover can be reduced, and maintaining the trade-off of communication quality and saving the remaining radio resources are realized adaptively according to the situation of the base station and mobile communication terminal at the time of communication It becomes possible.

In the above description, the measurement item performed on the pilot channel by the mobile communication terminal is the propagation loss. However, an error rate within a predetermined time using SIR or CRC may be used instead of the propagation loss. In this case, assuming that the threshold of _SIR is Th _SIR and the error rate threshold within a predetermined time using CRC is Th _error , the higher the SIR, the better the communication quality, and the smaller the error rate within the predetermined time using CRC, the communication Because the quality is good
Th _SIR <Th _SIR at 4 in FIG. 1 <Th _SIR in FIG
Th _error in Th _error> 5 in Th _error> 4 in FIG. 1
And

(Change T _add )
In addition, the holding time T _add in FIG. 3 is set independently from the measurement items for these pilot channels.
T _{the add} in FIG 1 <T _{the add} at T _{the add} <5 in FIG. 4
As the number of base stations performing soft handover increases, the condition for further soft handover addition may be made stricter and the gist of the present invention may be achieved. When changing this T _add , it is not necessary to change the above Th _loss , Th _SIR , and Th _error .

(Furthermore, Th _loss is changed _depending on the moving speed of mobile communication terminal 100)
Furthermore, when the control device 200 determines whether or not to soft handover the base station 30 with the mobile communication terminal 100, if the measured value of the speed of the mobile communication terminal 100 is moving faster than a predetermined speed, the communication state Is unstable, and there is a concern about a momentary interruption due to a sudden change in the communication state. Therefore, it is determined that soft handover should be performed with as many base stations as possible. When the mobile communication terminal 100 is moving at a higher speed than the predetermined speed, the control device 200 changes the predetermined speed so that soft handover is easier than when the mobile communication terminal 100 is moving at a lower speed than the predetermined speed.

Specifically, if the measurement is a pilot channel propagation loss,
Th _loss> Th _loss during movement speed is slower than the predetermined speed when the moving speed is faster than a predetermined speed
And

If the measured value is the SIR of the pilot channel,
Th _SIR during movement speed is faster than the predetermined speed <Th _SIR during movement speed is slower than the predetermined speed
And

If the measured value is the error rate in the predetermined time in using the CRC of the pilot channel, the moving speed is at a higher speed than the predetermined speed Th _error> moving speed is at low speed than a predetermined speed Th _error
And

(Change T _add )
Also, independently of these measured values for the pilot channel, the holding time T _add in FIG.
T _{the add} of T _{the add} <moving speed during movement speed is faster than the predetermined speed is at low speed than a predetermined speed
As such, the gist of the present invention may be achieved.

FIG. 7 is a control flowchart of control apparatus 200 showing the soft handover algorithm in the present embodiment including this case when the measured value is a propagation loss of a pilot channel.

In FIG. 7, the propagation loss of the traffic channel of the base station 30 is measured (measurement result L) (step 701).

Next, it is determined whether or not the moving speed of the mobile communication terminal 100 is lower than a predetermined speed (step 702).

In step 702, if the mobile communication terminal is not slower than the predetermined speed, Th _loss =
It is set as a0 (step 703), and it jumps to the process of step 707 mentioned later. On the other hand, if the mobile communication terminal is slower than the predetermined value in step 702, the mobile communication terminal 100
It is determined whether or not HO is performed (step 704).

In step 704, if the mobile communication terminal 100 is not performing SHO, Th _loss = a
1 (step 705), the process jumps to the processing of step 707 described later.

On the other hand, if the mobile communication terminal 100 is in SHO at step 704,
When the number of SHO base stations = 2, Th _loss = a2
When the number of SHO base stations is 3, Th _loss = a3
When the number of SHO base stations ≧ 4, Th _loss = a4
(Step 706).

Next, Th _loss is compared with the measurement result L obtained in step 701, and Th _loss > measurement result L
Whether or not (step 707).

If Th _loss > measurement result L is not satisfied in step 707, the base station 30 is not added to the SHO of the mobile communication terminal 100 (step 708). Conversely, at step 707, Th
_{If loss} > measurement result L 1, the base station 30 is added to the SHO of the mobile communication terminal 100 (
Step 709).

  The magnitude relationship between a0 and a4 is a0> a1> a2> a3> a4.

As a result, depending on the moving speed of the mobile communication terminal 100, when moving at a speed lower than the predetermined speed, there is a base station that has already performed soft handover, and the mobile communication terminal that is considered to be relatively stable in communication. Can reduce unnecessary soft handover as much as possible,
During high-speed movement, active soft handover can improve and stabilize the communication quality, maintaining the trade-off communication quality and saving the remaining radio resources. It can be realized adaptively according to the situation of the mobile communication terminal.

In addition, the measurement items that the mobile communication terminal described above performs on the pilot channel are not limited to the present embodiment, and there may be various options within the scope of the present invention.

The fewer the remaining radio resources of the base station to be soft handover,
The conditions for further soft handover addition may be made stricter.

Further, if the remaining radio resources of the base station are greater than or equal to a predetermined value, the handover may be easier than when no handover is performed.

(Third embodiment)
Next, a third embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 8 is a diagram illustrating the internal configuration of the mobile communication terminal 100 up to the rake combination in the third embodiment.

In FIG. 8, the signal received by the antenna 801 is down-converted by the analog front end 802 to become a baseband signal, and becomes a digital signal by the A / D converter 803.

Using the information such as the path timing obtained from the pilot channel from each base station divided into a plurality of waves in a multipath fading environment, the control unit 804 uses each finger 805-1.
A path is assigned to ˜805-n, and signal processing such as despreading and phase correction is performed.

Thereafter, the signal of each finger is rake synthesized by the rake synthesizer 806, and the data judgment unit 80
7, signal processing such as decoding processing is performed to obtain a desired information sequence.

In the mobile communication terminal of the present embodiment, any path of the pilot channel transmitted by the base station is received, and the power propagation loss, SIR, error rate within a predetermined time using CRC, etc. When the state where these measured values satisfy a predetermined standard is held for the holding time T _add or longer, an operation of adding the path to the rake synthesis is performed.

In FIG. 1, the path between the mobile communication terminal 100 and the base station 30 that has not been softly handed over is softly handed over with the mobile communication terminal 100 and assigned to any of the fingers 5-1 to 5-n in FIG. When determining whether or not, the number of mobile communication terminals or the number of traffic channels to which the base station 30 can newly communicate or the power value that can be newly transmitted is greater than a predetermined value. When the remaining radio resources are considered to have room, and the purpose is to avoid a momentary interruption due to a sudden change in the communication state, the rake The predetermined reference Th _loss of the measurement value is changed so as to facilitate the synthesis.

Specifically, if the measurement is a pilot channel propagation loss,
Th _loss for path of base station 30 in FIG. 1> Th _loss for unraked combined path of base station 10 in FIG.
And

If the measured value is the SIR of the pilot channel,
Th _SIR for the path of the base station 30 of FIG. 1 <Th _SIR for the unraked combined path of the base station 10 of FIG.
And

If the measured value is the error rate within a predetermined time using the CRC of the pilot channel,
Th _error for path of base station 30 in FIG. 1> Th _error for unraked combined path of base station 10 in FIG.
And

(Change T _add )
In addition, the holding time T _add in FIG. 3 is set independently from the measurement items for these pilot channels.
T _add for the path of the base station 30 of FIG. 1 <T _add for the _unraked combined path of the base station 10 of FIG.
By relaxing the condition for soft handover with the base station 30 and adding the path to the rake composition from the condition for adding the non-rake composite path of the already communicating base station 10 to the rake composition, You may achieve the meaning of invention.

FIG. 9 is a control flowchart of control apparatus 200 showing the soft handover algorithm in the present embodiment including this case in the case where the measured value is the SIR of the pilot channel.

In FIG. 9, the SIR of a specific path of the traffic channel of the base station X is measured (measurement result S) (step 901).

Next, it is determined whether or not the base station X is communicating with the mobile communication terminal Y (step 902).
.

In step 902, if the base station X is communicating with the mobile communication terminal Y, Th _SIR =
Set to a2 (step 903), the process jumps to the process of step 907 described later. On the other hand, if the base station X is not communicating with the mobile communication terminal Y in step 902, it is determined whether or not the remaining radio resources of the base station X are greater than or equal to a predetermined value (step 904).

In step 904, if the remaining radio resources of the base station X are not equal to or greater than the predetermined value, T
h _SIR = a0 is set (step 905), and the process jumps to step 907 described later.
On the other hand, if the remaining radio resources of the base station X are greater than or equal to a predetermined value in step 904, T
h _SIR = a1 (step 906).

Next, Th _SIR and the measurement result S obtained in step 901 are compared, and Th _SIR <measurement result S
It is determined whether or not (step 907).

If it is not Th _SIR <measurement result S in step 907, the specific path of the base station X is not added to the rake combination of the mobile communication terminal Y (step 908). On the other hand, in step 907, if Th _SIR <measurement result S 1, base station X is added to the soft handover (step 909), and a specific path of base station X is added to the rake combination of mobile communication terminal Y ( Step 910).

  Note that the magnitude relationship of a0 to a2 is a2 ≧ a0> a1.

As a result, when the remaining radio resources have room, communication quality can be stabilized and improved by actively performing soft handover. In this way, the softer handover may be facilitated by _reducing the Th _SIR as the remaining radio resource has a margin.

Further, the remaining radio resources described above and the measurement items that the mobile communication terminal performs on the pilot channel are not limited to the present embodiment, and there are various options within the scope of the present invention. obtain.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings.

The internal configuration of the mobile communication terminal 100 up to the rake combination in the fourth embodiment is as follows:
FIG. 8 is the same as in the third embodiment. Here, the description of FIG. 8 is omitted.

In the mobile communication terminal of the present embodiment, any path of the pilot channel transmitted by the base station is received, and the power propagation loss, SIR, error rate within a predetermined time using CRC, etc. If the state where these measured values satisfy a predetermined standard is held for the holding time T _add or more, an operation of adding the path to the rake composition is performed.

In FIG. 1, the path between the mobile communication terminal 100 and the base station 30 that has not been softly handed over is softly handed over with the mobile communication terminal 100 and assigned to any of the fingers 5-1 to 5-n in FIG. When determining whether or not the mobile communication terminal 100 is moving at a speed higher than a predetermined speed, the communication state is unstable, and there is a concern about an instantaneous interruption due to a sudden change in the communication state. Therefore, the predetermined reference Th _loss of the measurement value is changed so that rake combining is easier than a path that has not yet been added to the rake combining of the base station 10 that is already communicating.

Specifically, if the measurement is a pilot channel propagation loss,
Th _loss for path of base station 30 in FIG. 1> Th _loss for unraked combined path of base station 10 in FIG.
And

If the measured value is the SIR of the pilot channel,
Th _SIR for the path of the base station 30 of FIG. 1 <Th _SIR for the unraked combined path of the base station 10 of FIG.
And

If the measured value is the error rate within a predetermined time using the CRC of the pilot channel,
Th _error for path of base station 30 in FIG. 1> Th _error for unraked combined path of base station 10 in FIG.
And

(Change T _add )
In addition, the holding time T _add in FIG. 3 is set independently from the measurement items for these pilot channels.
T _add for the path of the base station 30 of FIG. 1 <T _add for the _unraked combined path of the base station 10 of FIG.
By relaxing the condition for soft handover with the base station 30 and adding the path to the rake composition from the condition for adding the non-rake composite path of the already communicating base station 10 to the rake composition, You may achieve the meaning of invention.

FIG. 10 is a control flowchart of the control apparatus 200 showing the soft handover algorithm in the present embodiment including this case in the case where the measurement value is an error rate within a predetermined time using the CRC of the pilot channel.

In FIG. 10, an error rate within a predetermined time using the CRC of a specific path of the traffic channel of the base station X is measured (measurement result E) (step 1001).

Next, it is determined whether or not the base station X is communicating with the mobile communication terminal Y (step 1002).
).

In step 1002, if the base station X is communicating with the mobile communication terminal Y, Th _erro
r = a2 is set (step 1003), and the process jumps to step 1007 described later.
On the other hand, if the base station X is not communicating with the mobile communication terminal Y in step 1002, it is determined whether or not the remaining radio resources of the base station X are equal to or greater than a predetermined value (step 1004).

In step 1004, if the remaining radio resources of the base station X are not equal to or greater than a predetermined value,
Set Th _error = a0 (step 1005), and jump to the processing of step 1007 described later. On the other hand, if the remaining radio resources of the base station X are greater than or equal to a predetermined value in step 1004, Th _error = a1 is set (step 1006).

Next, Th _error is compared with the measurement result E obtained at step 1001, and it is determined whether Th _error > measurement result E (step 1007).

In step 1007, if Th _error <measurement result E 1, the specific path of the base station X is not added to the rake combination of the mobile communication terminal Y (step 1008).

On the other hand, in step 1007, if Th _error <measurement result E 1, base station X is added to the soft handover (step 1009), and a specific path of base station X is added to the rake composition of mobile communication terminal Y ( Step 1010).

  The magnitude relationship between a0 and a2 is a2 ≦ a0 <a1.

As a result, when the mobile communication terminal is moving at high speed, it is possible to stabilize and improve communication quality by actively performing soft handover. In this way, the higher the speed of movement, the larger the Th _SIR may be set to facilitate soft handover.

In addition, the measurement items that the mobile communication terminal described above performs on the pilot channel are not limited to the present embodiment, and there may be various options within the scope of the present invention.

The figure for demonstrating the condition of the base station at the time of the non-soft handover of this invention, and a mobile communication terminal. The figure for demonstrating the structure of the control apparatus of this invention. The figure which shows the time change of the propagation loss of the pilot channel of the base station in the mobile communication terminal of this invention. The figure for demonstrating the condition of the base station at the time of the soft handover of this invention, and a mobile communication terminal. The figure for demonstrating the condition of the base station at the time of the soft handover of this invention, and a mobile communication terminal. The figure which showed the algorithm of the soft handover in the 1st Embodiment of this invention about the case where a measured value is a propagation loss of a pilot channel. The figure which showed the algorithm of the soft handover in the 2nd Embodiment of this invention about the case where a measured value is a propagation loss of a pilot channel. The figure which showed the structure inside the terminal until the rake | combination of the mobile communication terminal 100 in the 3rd and 4th embodiment of this invention. The figure which showed the algorithm of the soft handover in the 3rd Embodiment of this invention about the case where a measured value is SIR of a pilot channel. The figure which showed the algorithm of the soft handover in the 4th Embodiment of this invention about the case where the measured value is the error rate within the predetermined time using CRC of the pilot channel.

Explanation of symbols

10, 20, 30, 40 ... base station, 100 ... mobile communication terminal, 200 ... control device, 201
... arithmetic unit, 202 ... ROM, 203 ... RAM, 204 ... I / F, 205 ... common bus,
801 ... Antenna, 802 ... Analog front end, 803 ... A / D converter, 804 ...
Control unit, 805-1 to 805-n finger, 806 ... Rake synthesis unit, 807 ... data determination unit.

Claims (2)

Rake combining means for assigning a signal from each path received from the base station in communication with the antenna to each finger unit and rake combining;
A data determination unit for determining final data from a signal subjected to rake synthesis by the rake synthesis means;
An arithmetic unit for calculating a measurement value measured for a predetermined measurement item for each path received from the communicating and non-communication base station by an antenna;
Comparison means for comparing the magnitude relationship between the measured value obtained by the calculation unit and a predetermined threshold value;
A determination unit for determining whether to add the path to the rake composition based on a comparison result by the comparison unit;
Rake synthesis control means for controlling which path the signal from which the rake synthesis means is rake synthesized, and
The rake composition control means includes:
When the remaining radio resources of the non-communication base station are larger than a predetermined value,
The non-communication base station related to the path determined to be added to the rake combination by the determination unit is added to the soft handover and is in communication, and whether the path received from the added base station is added to the rake combination is determined. The above-mentioned predetermined threshold value is added to the rake combination from the above-mentioned predetermined threshold value which is the basis for determining whether or not to add the non-rake-combined path received from the base station communicating before the addition to the rake combination. Easy to use,
The remaining radio resources of the non-communication base station are the number of mobile communication terminals that the non-communication base station can newly communicate with, or the non-communication base station can newly communicate with Or the power value that the non-communication base station can newly transmit,
A mobile communication terminal characterized in that, when any of these values is larger than the predetermined threshold, the remaining radio resources of the non-communication base station are larger than a predetermined value . Rake combining means for assigning a signal from each path received from the base station in communication with the antenna to each finger unit and rake combining;
A data determination unit for determining final data from a signal subjected to rake synthesis by the rake synthesis means;
An arithmetic unit for calculating a measurement value measured for a predetermined measurement item for each path received from the communicating and non-communication base station by an antenna;
Comparison means for comparing the magnitude relationship between the measured value obtained by the calculation unit and a predetermined threshold value;
A determination unit for determining whether to add the path to the rake composition based on a comparison result by the comparison unit;
Rake synthesis control means for controlling from which path the signal is to be rake synthesized by the rake synthesis means;
Detecting means for detecting the speed at which the communication terminal is moving,
The rake composition control means includes:
When the self-communication terminal is moving faster than a predetermined speed,
The non-communication base station related to the path determined to be added to the rake combination by the determination unit is added to the soft handover and is in communication, and whether the path received from the added base station is added to the rake combination is determined. The above-mentioned predetermined threshold value is added to the rake combination from the above-mentioned predetermined threshold value which is the basis for determining whether or not to add the non-rake-combined path received from the base station communicating before the addition to the rake combination. A mobile communication terminal characterized by an easy value.

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