CN100459791C - Handover control method and related device - Google Patents

Abstract

A method and related apparatus for handover control. The method includes first measuring, with a user equipment, a strength of a first pilot signal transmitted by a first base station in an active set, wherein the first base station has a maximum pilot signal strength. Then, a handover parameter for the ue to perform a handover is dynamically set according to the strength of the first pilot signal, and a handover threshold is determined according to the handover parameter. In addition, when the sum of the strengths of the pilot signals transmitted by other base stations except the first base station in the active set is less than a predetermined value, the handover parameter is further adjusted. The method may be embodied in a tangible medium by way of program code, the program code being loaded into and executed by a machine, the machine thereby becoming an apparatus for practicing the invention. The invention solves the problem of handover control, so that the UE can ensure the utility of the handover and enhance the connection quality of the UE when performing soft handover.

Description

Handover control method and related device

technical field

The present invention relates to communication management, and in particular to a handoff (Handoff) control method and related devices.

Background technique

In the third-generation communication system, such as the Universal Mobile Telecommunications System (UMTS), the user equipment (User Equipment, UE), such as a mobile phone, will measure the common pilot channel ( Common PilotChannel, CPICH) in a pilot signal (Pilot Signal) strength (Strength), to determine the signal strength of the base station. After determining the signal strength of the base station, the user equipment, such as a mobile phone, will decide whether to add the base station to the active set (Active Set), and determine whether to perform soft handoff (Soft Handoff) to Communication services are provided by new base stations.

Since the diversity gain (Diversity Gain) can be obtained during soft handover, and the diversity gain will reduce the transmission energy (Power) of the user equipment in the uplink (Up Link), so that the total interference in the uplink will be reduced will decrease. Therefore, through the soft handover, the UE can obtain better connection quality. On the other hand, since the UE can communicate with more than one base station during soft handover, the UE can obtain a better aggregated steering strength (aggregated steering strength (Ec)/total received energy (Io) , (Ec/Io)), which also means better connection quality.

FIG. 1 is a schematic diagram showing a known GSM handover threshold. Wherein, the handover threshold includes an adding threshold (Tr_add) and a removing threshold (Tr_drop). When the strength of the pilot signal of a base station out of the active set is greater than the join threshold for a predetermined time, the base station will be added to the active set. When the strength of the pilot signal of a base station in the active set is less than the removal threshold for a predetermined time, the base station will be removed from the active set. In addition, the handover threshold may also include a swap threshold (Tr_swap) (not shown in FIG. 1 ). When the capacity of the active set is full, if the strength of the pilot signal sent by a base station outside the active set is greater than the exchange threshold value after a predetermined time, then this base station will be added to the active set, and from the active set, the The strength of the emitted pilot signal is removed for the weakest base station.

However, when soft handover is performed, the user equipment will use more system resources, and since multiple base stations transmit energy to the user equipment at the same time, the total interference (total reception) in the downlink (Down Link) energy) will increase. Due to the increase of the total interference in the downlink, other UEs in the system will be interfered and the connection quality will be degraded (aggregated steering strength will be reduced). Since the handover threshold in the known GSM is fixed, as the connection quality decreases (the optimal guidance strength decreases), the handover threshold will also decrease, as shown in Figure 1 As shown, thus causing many unnecessary soft handoffs to occur. Therefore, when a UE is performing soft handover, a mechanism must be provided to ensure that the handover is useful without disrupting the connection quality to other UEs.

Contents of the invention

In view of this, the present invention is used to solve the aforementioned problems of handover control.

Therefore, the purpose of the present invention is to provide a handover control method and a related device that can dynamically adjust the handover threshold according to the connection quality.

In order to achieve the above object of the present invention, the present invention provides a handover control method. Firstly, a UE measures the strength of a first pilot signal sent by a first base station in an active set, wherein the first base station has the largest pilot signal strength. Afterwards, according to the strength of the first pilot signal, dynamically set a handover parameter for the user equipment to perform a handover, and determine a handover threshold according to the handover parameter.

The present invention also provides a device, including: an active set including at least a first base station, wherein the first pilot signal sent by the first base station has the largest pilot signal strength; and a processing unit for Measuring the strength of the first pilot signal, dynamically setting at least one handover parameter for the device to perform a handover according to the strength of the first pilot signal, and determining at least one handover threshold according to the handover parameter .

In addition, when the sum of the strengths of the pilot signals sent by other base stations in the active set except the first base station is less than a predetermined value, the handover parameter is further adjusted.

The above-mentioned method of the present invention can be recorded in a physical medium through program code. When the program code is loaded and executed by the machine, the machine becomes an apparatus for implementing the present invention.

Through the implementation of the present invention, the problem of handover control is solved, so that when the user equipment performs soft handover, it not only ensures that the handover is useful, but also enhances the connection quality of the user equipment.

In order to make the above-mentioned objects, features and advantages of the present invention more comprehensible, the following specific examples are given together with the accompanying diagrams, and are described in detail as follows.

Description of drawings

FIG. 1 is a schematic diagram showing a known GSM handover threshold;

FIG. 2 is a schematic diagram showing a user equipment according to an embodiment of the present invention;

FIG. 3 is a flowchart showing a handover parameter setting method according to an embodiment of the present invention;

FIG. 4 is a flowchart showing a handover method according to an embodiment of the present invention;

FIG. 5 is a schematic diagram showing handover thresholds of the GSM system according to an embodiment of the present invention;

FIG. 6 is a flowchart showing a handover parameter adjustment method according to an embodiment of the present invention;

FIG. 7 is a schematic diagram showing simulation results according to an embodiment of the present invention;

FIG. 8 is a flowchart showing an example of handover parameter setting and adjustment according to an embodiment of the present invention.

Symbol Description:

Tr_add Add threshold value;

Tr_drop removes the threshold;

210 User Equipment;

211 processing unit;

212 list;

221, 222 base stations;

S310, S320, S330 Operation steps;

S410, S420, ..., S480 Operation steps;

S610, S620 Operation steps;

S810, S820, ..., S880 Operation steps.

Detailed ways

The present invention provides novel methods and apparatus to overcome the aforementioned handover control problems.

FIG. 2 is a schematic diagram showing a user equipment according to an embodiment of the present invention. As shown in the figure, a user equipment 210, such as a mobile phone, includes at least a processing unit 211 for performing handover control and other related operations in the embodiment of the present invention. The UE 210 has to measure the strength of pilot signals sent by multiple base stations to obtain an active base station list 212 . The UE 210 may determine whether to perform handover between different base stations (eg, 221 and 222 ) according to the communication quality, so that the base station with a stronger pilot signal provides the communication service.

FIG. 3 is a flowchart showing a handover parameter setting method according to an embodiment of the present invention. First, in step S310, the UE 210 measures the strength of a first pilot signal sent by a first base station in the active set, wherein the first base station has the largest pilot signal strength. Next, in step S320, dynamically set handover parameters for the UE 210 to perform a handover according to the strength of the first pilot signal, and in step S330, determine a handover threshold according to the handover parameters. Wherein, the delivery parameters may include Reporting Range, Hysteresis parameter, Replacement Hysteresis parameter, and Time to Trigger (TtT)). In addition, the handover threshold may include an add threshold (Tr_add), a remove threshold (Tr_drop), and a swap threshold (Tr_swap). The formula for its decision is:

Tr_add=Best_Ss-AS_Th+AS_Th_Hyst,

Tr_drop=Best_Ss-AS_Th-AS_Th_Hyst,

Tr_swap=Worst_Old_Ss+AS_Rep_Hyst.

Among them, Tr_add is the threshold value for adding, Tr_drop is the threshold value for removal, Tr_swap is the threshold value for exchange, Best_Ss is the strongest pilot signal strength in the effective set, Worst_Old_Ss is the weakest pilot signal strength in the effective set, AS_Th is the return range, AS_Th_Hyst is the hysteresis parameter, and AS_Rep_Hyst is the replacement hysteresis parameter.

FIG. 4 is a flowchart showing a handover method according to an embodiment of the present invention. First, in step S410, the UE 210 measures the strength of the pilot signal. Afterwards, in step S420, it is determined whether the pilot signal is in the active set, and whether the time when the strength of the pilot signal is less than the removal threshold exceeds the trigger time. If not ("No" in step S420), proceed to step S440. If yes ("Yes" in step S420), in step S430, the pilot signal is removed from the active set. Next, in step S440, it is determined whether the pilot signal is not in the active set, and whether the time for which the strength of the pilot signal is greater than the adding threshold exceeds the trigger time. If not ("No" in step S440), return to step S410. If so ("Yes" in step S440), as in step S450, it is judged whether the active set has reached a predetermined capacity (full). If not ("No" in step S450), in step S460, directly add the pilot signal into the active set, and return to step S410. If the capacity of the active set is full ("Yes" in step S450), as in step S470, it is judged whether the time when the strength of the pilot signal is greater than the switching threshold exceeds the trigger time. If not ("No" in step S470), return to step S410. If yes ("Yes" in step S470), in step S480, the pilot signal is exchanged with the weakest pilot signal in the active set.

In the above embodiments, when the strength of the strongest pilot signal in the active set is weak, the reporting range and trigger time can be set to smaller values. For example, when the strength of the strongest pilot signal in the active set is greater than -6dB, the reporting range is set to 5dB, and the trigger time is set to 0.8sec. When the intensity is not less than -10dB and not greater than -6dB, set the return range to 4dB and the trigger time to 0.8sec. When the intensity is less than -10dB, set the return range to 3dB and the trigger time to 0.4sec. In addition, in an embodiment, the hysteresis parameter and the replacement hysteresis parameter corresponding to the strongest pilot signals of different strengths may be set to 1 dB.

Due to the increase of the total interference in the downlink, the individual aggregated steering strength of the user equipment 210 will be reduced, thereby degrading the connection quality. Therefore, according to the strength of the strongest pilot signal, the embodiment of the present invention dynamically sets the handover threshold for the UE 210 to determine whether to perform handover, so as to prevent the UE 210 from performing unnecessary handover. FIG. 5 is a schematic diagram showing handover thresholds of the GSM system according to an embodiment of the present invention. As shown in the figure, when the strength of the strongest pilot signal decreases, the handover threshold will be raised. In addition, when the strength of the strongest pilot signal weakens, resulting in poor connection quality, the user equipment 210 can reduce the time condition for the pilot signal to meet the handover threshold, so as to use the available The pilot signal is added to the active set to avoid disconnection.

In addition to reducing the time condition that the pilot signal must meet the handover threshold, in order to enhance the connection quality of the user equipment 210 when the strength of the strongest pilot signal is weakened, the embodiment of the present invention can further improve the handover threshold. Pass parameters to adjust. FIG. 6 is a flowchart showing a handover parameter adjustment method according to an embodiment of the present invention. First, in step S610, it is determined whether the strengths (Δ) of other pilot signals except the strongest pilot signal in the active set of the UE 210 are smaller than a predetermined value, such as 2dB. If not ("No" in step S610), continue the operation in step S610. If so ("Yes" in step S610), in step S620, the handover parameters are adjusted. Afterwards, return to step S610. Wherein, the adjustment method is to increase the return range and the hysteresis parameter by a predetermined value, such as 0.5dB, and set the replacement hysteresis parameter to an updated value, such as 0.5dB. Among them, since the return range and the hysteresis parameter increase by a predetermined value at the same time, the adding threshold will not change, while the removing threshold and the exchanging threshold will decrease, so that the weaker pilots in the effective set Signals are not shifted or swapped out of the active set.

FIG. 8 is a flowchart showing an example of handover parameter setting and adjustment according to an embodiment of the present invention. First, as in step S810, it is determined whether the strength of the strongest pilot signal (Best_Ss) in the active set is greater than -6dB. If the strength of the strongest pilot signal (Best_Ss) is greater than -6dB ("Yes" in step S810), as in step S820, the setting return range (AS_Th) is 5dB, and the hysteresis parameter (AS_Th_Hyst) is 1dB to replace the hysteresis The parameter (AS_Rep_Hyst) is 1 dB, and the trigger time (TtT) is 0.8 sec. If the strength of the strongest pilot signal (Best_Ss) is not greater than -6dB ("No" in step S810), as in step S830, it is determined whether the strength of the strongest pilot signal (Best_Ss) in the active set is less than -10dB. If the strength of the strongest pilot signal (Best_Ss) is not less than -10dB ("No" in step S830), as in step S840, the setting return range (AS_Th) is 4dB, and the hysteresis parameter (AS_Th_Hyst) is 1dB, replacing The hysteresis parameter (AS_Rep_Hyst) is 1dB, and the trigger time (TtT) is 0.8sec. If the strength of the strongest pilot signal (Best_Ss) is less than -10dB ("Yes" in step S830), as in step S850, the setting return range (AS_Th) is 3dB, and the hysteresis parameter (AS_Th_Hyst) is 1dB to replace the hysteresis The parameter (AS_Rep_Hyst) is 1 dB, and the trigger time (TtT) is 0.4 sec.

After the handover parameter is dynamically set according to the strength of the strongest pilot signal, the handover parameter can be adjusted. In step S860, it is determined whether the number of pilot signals (CS) in the active set is greater than 1 and whether the strengths (Δ) of other pilot signals in the active set except the strongest pilot signal are less than 2 dB. If not ("No" in step S860), proceed to step S880 directly. If so ("Yes" in step S860), as in step S870, readjust the handover parameters to set the return range as the return range plus 0.5dB (AS_Th=AS_Th+0.5dB), and the hysteresis parameter is the hysteresis parameter plus 0.5dB (AS_Th_Hyst=AS_Th_Hyst+0.5dB), and the replacement hysteresis parameter (AS_Rep_Hyst) is 0.5dB. Next, in step S880, a handover threshold is determined according to the handover parameter. Wherein, Tr_add=Best_Ss-AS_Th+AS_Th_Hyst, Tr_drop=Best_Ss-AS_Th-AS_Th_Hyst, and Tr_swap=Worst_Old_Ss+AS_Rep_Hyst. Afterwards, the flow returns to step S810 to make a new judgment.

FIG. 7 is a schematic diagram showing simulation results according to an embodiment of the present invention. In this simulation, it is assumed that there are 6 UEs in 19 communication cells (Cells), and each communication cell has 3 sections (Sections). Among them, the communication unit in the middle is used for performance statistics learning. The Propagation Model is Cellular Band, Hata model. LognormalFading is a correction distance of 400 meters and a variation of 8dB. In addition, it is known that the handover parameters of GSM are: the return range is 5dB, the hysteresis parameter is 1dB, the replacement hysteresis parameter is 3dB, the trigger time is 0.8sec, and the effective set capacity is 3. The overall sampling time is 200ms. As shown in the figure, the average aggregated pilot signal strength difference between the embodiment of the present invention and the known technology is positive most of the time. In other words, the embodiment of the present invention can obtain better pilot signal strength and continuous thread quality.

Therefore, the present invention provides a handover control method and a related device that can dynamically adjust the handover threshold according to the connection quality.

The method and system of the present invention, or specific forms or parts thereof, may be contained in a physical medium in the form of program code, such as a floppy disk, an optical disk, a hard disk, or any other machine-readable (such as computer-readable) A storage medium in which, when the program code is loaded and executed by a machine, such as a computer, the machine becomes an apparatus for participating in the present invention. The method and device of the present invention can also be transmitted in the form of program code through some transmission media, such as wires or cables, optical fibers, or any transmission mode, wherein when the program code is received, loaded and executed by a machine, such as a computer , this machine becomes a device for participating in the present invention. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique device that operates similarly to application-specific logic circuits.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore The scope of protection of the present invention should be as defined by the scope of the patent application.

Claims (20)

1. a handover control method is characterized in that comprising the following steps:

The intensity of first pilot signal of being sent with one first base station in user's device measuring one efficient set, wherein this first base station has maximum pilot signal strength;

According to the intensity of this first pilot signal, dynamically set at least one handover parameter that this user's equipment carries out a handover; And

Determine at least one handover threshold value according to this handover parameter.

2. handover control method as claimed in claim 1, it is characterized in that, wherein this handover parameter comprises a repayment scope at least, and when the intensity of this first pilot signal is worth greater than one first, should the repayment scope be made as one second value, when the intensity of this first pilot signal is not less than one the 3rd value and is not more than this first value, should the repayment scope be made as one the 4th value, and when the intensity of this first pilot signal is worth less than the 3rd, should the repayment scope be made as one the 5th value, wherein this first value is not less than the 3rd value, and this second value is not less than the 4th value, and the 4th value is not less than the 5th value.

3. handover control method as claimed in claim 1, it is characterized in that, wherein this handover parameter comprises a triggered time at least, and the time that the intensity of one second pilot signal of being sent when one second base station of this user's device measuring meets this handover threshold value is when reaching this triggered time, for this second pilot signal carry out mutually should the handover threshold value a set operation.

4. handover control method as claimed in claim 3, it is characterized in that more comprising that working as this handover threshold value is an adding threshold value, and this second pilot signal is not in this efficient set the time, if the intensity of this second pilot signal is higher than the time of this adding threshold value when reaching this triggered time, this second pilot signal is added this efficient set.

5. handover control method as claimed in claim 3, it is characterized in that more comprising when this handover threshold value be one to remove threshold value, and this second pilot signal is in this efficient set the time, if the intensity of this second pilot signal is lower than this time that removes threshold value when reaching this triggered time, this second pilot signal is shifted out this efficient set.

6. handover control method as claimed in claim 3, it is characterized in that more comprising that working as this handover threshold value is an exchange threshold value, this efficient set has reached a both constant volume, and this second pilot signal is not in this efficient set the time, if the intensity of this second pilot signal is higher than the time of this exchange threshold value when reaching this triggered time, with this second pilot signal and in this efficient set the most weak one the 3rd pilot signal of intensity exchange.

7. handover control method as claimed in claim 3, when it is characterized in that more comprising that intensity when this first pilot signal is greater than one the 6th value, this triggered time is made as one the 7th value, when the intensity of this first pilot signal is not less than one the 8th value and is not more than the 6th value, this triggered time is made as one the 9th value, and when the intensity of this first pilot signal is worth less than the 8th, this triggered time is made as 1 the tenth value, wherein the 6th value is not less than the 8th value, the 7th value is not less than the 9th value, and the 9th value is not less than the tenth value.

8. handover control method as claimed in claim 1 when it is characterized in that more comprising that intensity when other pilot signal outside this first pilot signal in this efficient set is less than a set value, is then adjusted described handover parameter.

9. handover control method as claimed in claim 8, it is characterized in that, wherein said handover parameter comprises a repayment scope and a magnetic hysteresis parameter at least, and when the intensity of one the 4th pilot signal in other pilot signal outside this first pilot signal in this efficient set during less than this set value, should the repayment scope and this magnetic hysteresis parameter increase by a set value simultaneously.

10. handover control method as claimed in claim 8, it is characterized in that, wherein said handover parameter comprises that also having one of an original value replaces the magnetic hysteresis parameter, and when the intensity of one the 4th pilot signal in other pilot signal outside this first pilot signal in this efficient set during less than this set value, should replace the magnetic hysteresis parameter and be made as a updating value, wherein this updating value is less than this original value.

11. a device is characterized in that comprising at least:

One efficient set comprises one first base station at least, and wherein first pilot signal sent of this first base station has maximum pilot signal strength; And

One processing unit in order to measure the intensity of this first pilot signal, according to the intensity of this first pilot signal, is dynamically set at least one handover parameter that this device carries out a handover, and is determined at least one handover threshold value according to this handover parameter.

12. device as claimed in claim 11, it is characterized in that, wherein this handover parameter comprises a repayment scope at least, and when this processing unit is worth greater than one first when the intensity of this first pilot signal, should the repayment scope be made as one second value, when the intensity of this first pilot signal is not less than one the 3rd value and is not more than this first value, should the repayment scope be made as one the 4th value, and when the intensity of this first pilot signal is worth less than the 3rd, should the repayment scope be made as one the 5th value, wherein this first value is not less than the 3rd value, and this second value is not less than the 4th value, and the 4th value is not less than the 5th value.

13. device as claimed in claim 11, it is characterized in that, wherein said handover parameter comprises a triggered time at least, and the time that the intensity of one second pilot signal that this processing unit is sent when one second base station of this measurement device meets this handover threshold value is when reaching this triggered time, for this second pilot signal carry out mutually should the handover threshold value a set operation.

14. device as claimed in claim 13, it is characterized in that more comprising that working as this handover threshold value is an adding threshold value, and this second pilot signal is not in this efficient set the time, if the intensity of this second pilot signal is higher than the time of this adding threshold value when reaching this triggered time, this processing unit adds this efficient set with this second pilot signal.

15. device as claimed in claim 13, it is characterized in that more comprising when this handover threshold value be one to remove threshold value, and this second pilot signal is in this efficient set the time, if the intensity of this second pilot signal is lower than this time that removes threshold value when reaching this triggered time, this processing unit shifts out this efficient set with this second pilot signal.

16. device as claimed in claim 13, it is characterized in that more comprising that working as this handover threshold value is an exchange threshold value, this efficient set has reached a both constant volume, and this second pilot signal is not in this efficient set the time, if the intensity of this second pilot signal is higher than the time of this exchange threshold value when reaching this triggered time, this processing unit with this second pilot signal and in this efficient set the most weak one the 3rd pilot signal of intensity exchange.

17. device as claimed in claim 13, it is characterized in that, when wherein this processing unit comprises that more intensity when this first pilot signal is greater than one the 6th value, this triggered time is made as one the 7th value, when the intensity of this first pilot signal is not less than one the 8th value and is not more than the 6th value, this triggered time is made as one the 9th value, and when the intensity of this first pilot signal is worth less than the 8th, this triggered time is made as 1 the tenth value, wherein the 6th value is not less than the 8th value, the 7th value is not less than the 9th value, and the 9th value is not less than the tenth value.

18. device as claimed in claim 11, when it is characterized in that more comprising that intensity when other pilot signal outside this first pilot signal in this efficient set is less than a set value, this processing unit is adjusted described handover parameter.

19. device as claimed in claim 18, it is characterized in that, wherein this handover parameter comprises a repayment scope and a magnetic hysteresis parameter at least, and when the intensity of one the 4th pilot signal in other pilot signal outside this first pilot signal in this efficient set during less than this set value, this processing unit should the repayment scope and this magnetic hysteresis parameter increase by a set value simultaneously.

20. device as claimed in claim 18, it is characterized in that, wherein this handover parameter comprises that also having one of an original value replaces the magnetic hysteresis parameter, and when the intensity of one the 4th pilot signal in other pilot signal outside this first pilot signal in this efficient set during less than this set value, this processing unit should replace the magnetic hysteresis parameter and be made as a updating value, and wherein this updating value is less than this original value.

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