CN107770780B

CN107770780B - GAP measuring method and equipment based on idle state

Info

Publication number: CN107770780B
Application number: CN201610712367.5A
Authority: CN
Inventors: 鲜柯
Original assignee: Chengdu TD Tech Ltd
Current assignee: Chengdu TD Tech Ltd
Priority date: 2016-08-23
Filing date: 2016-08-23
Publication date: 2020-08-04
Anticipated expiration: 2036-08-23
Also published as: CN107770780A

Abstract

The invention provides a GAP measuring method and equipment based on an idle state. The GAP measuring method based on the idle state is applied to the UE and comprises the following steps: acquiring an RSRP value of a serving cell in which the UE is located; when the UE is in an idle state, judging whether the difference value between the RSRP value and a preset residence threshold associated with the serving cell is smaller than or equal to a preset difference value or not; if yes, configuring GAP measurement parameters, and performing GAP measurement according to the GAP measurement parameters. According to the GAP measurement method based on the idle state, the UE in the idle state starts GAP measurement without configuring GAP measurement parameters through the eNodeB, the GAP measurement of the UE without RRC connection in the idle state is realized, and the influence on the continuity of the monitoring cluster service of the UE and abnormal off-line of the UE are avoided.

Description

GAP measuring method and equipment based on idle state

Technical Field

The invention relates to a mobile communication technology, in particular to an idle-state-based GAP measurement method and equipment.

Background

In order To better promote the development and standardization of the trunking network, a single cell point To multiple system (SC-PTM) protocol is introduced into the third generation mobile communication partner organization (3 GPP), and the protocol is based on a Physical Downlink Shared Channel (PDSCH), and two logical channels, namely a single cell broadcast Control Channel (SC-MCCH) and a single cell broadcast traffic Channel (SC-MTCH), are introduced for transmitting the Control code and user plane data of the trunking user. In a pilot frequency networking scenario in the SC-PTM solution, a situation that a User Equipment (User Equipment, abbreviated as UE) needs to perform pilot frequency handover or cell reselection when moving between adjacent cells covered by two different frequency points may exist.

Because the UE usually has only one receiver, the UE can only receive signals on one frequency point at the same time, and cannot receive signals on two frequency points at the same time, in the SC-PTM solution, if the current UE is in an idle state and is receiving the monitoring cluster service, when the UE reselects from one frequency point to another frequency point, the UE needs to measure the signal condition of the target frequency point before reselection to determine whether the target cell signal meets the reselection condition, and in order to ensure that the UE does not miss receiving the downlink monitoring cluster service data of the current cell when performing signal quality measurement on the target frequency point, GAP measurement needs to be started. The GAP measurement is a time period from the UE leaving the current frequency point to another frequency point and not receiving downlink monitoring cluster service data, and is used for inter-frequency measurement or inter-system measurement. Whether the UE needs to perform the pilot frequency measurement or not is determined by the eNodeB, and when the eNodeB determines that the GAP measurement needs to be performed, the eNodeB issues the GAP measurement configuration to the corresponding UE and informs the UE of performing the GAP measurement; the GAP measurement is to measure the signal quality of the target cell during the GAP measurement period.

Therefore, in the pilot frequency networking scenario of the current SC-PTM solution, when the UE in an idle state is monitoring the trunking service and needs to reselect a cell, the eNodeB needs to configure the UE to perform GAP measurement, but since the UE is in the idle state and has no Radio Resource Control (RRC) connection, the eNodeB cannot configure GAP measurement parameters to the UE through the RRC to perform GAP measurement, so that the UE cannot perform cell reselection, and finally affects continuity of monitoring the trunking service and abnormal offline.

Disclosure of Invention

The invention provides an idle-state-based GAP (GAP measurement) method and idle-state-based GAP measurement equipment, which are used for overcoming the technical problem that UE (user equipment) without RRC (radio resource control) connection cannot start GAP measurement in a pilot frequency networking scene of an SC-PTM (support carrier-packet transfer) solution in the prior art.

The invention provides an idle state-based GAP (GAP measurement) method, which is applied to UE (user equipment), and comprises the following steps:

acquiring an RSRP value of a serving cell in which the UE is located;

when the UE is in an idle state, judging whether the difference value between the RSRP value and a preset residence threshold associated with the serving cell is smaller than or equal to a preset difference value or not;

if yes, configuring GAP measurement parameters, and performing GAP measurement according to the GAP measurement parameters.

The invention also provides GAP measuring equipment based on an idle state, which comprises:

the acquisition module is used for acquiring the RSRP value of the serving cell where the UE is located;

a determining module, configured to determine whether a difference between the RSRP value and a preset camping threshold associated with the serving cell is less than or equal to a preset difference when the UE is in an idle state;

a configuration module, configured to configure a GAP measurement parameter if a difference between the RSRP value and a preset camping threshold associated with the serving cell is less than or equal to the preset difference;

and the measurement module is used for carrying out GAP measurement according to the GAP measurement parameters.

According to the idle-state-based GAP measuring method, the UE judges whether GAP measurement needs to be started or not according to the difference value between the RSRP value of the serving cell where the UE is located and the preset residence threshold, if the GAP measurement needs to be started, the UE configures GAP measurement parameters to the physical layer of the UE, the physical layer carries out the GAP measurement according to the configured GAP measurement parameters, the GAP measurement parameters do not need to be configured through an eNodeB, the GAP measurement of the idle-state UE without RRC connection is achieved, and the influence on the continuity of monitoring cluster services by the UE and abnormal off-line of the UE are avoided.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a flowchart of a first embodiment of a GAP measurement method based on an idle state according to the present invention;

fig. 2 is a flowchart of a second embodiment of the GAP measurement method based on an idle state according to the present invention;

FIG. 3 is a diagram illustrating a first user interface of the auxiliary device when configuring a GAP period;

FIG. 4 is a schematic diagram of a second user interface of the auxiliary device when configuring the GAP period;

FIG. 5 is a diagram illustrating a first user interface of the UE when configuring the GAP period;

FIG. 6 is a diagram illustrating a second user interface of the UE when configuring the GAP period;

fig. 7 is a flowchart of a third embodiment of the GAP measurement method based on an idle state according to the present invention;

fig. 8 is a schematic structural diagram of a first embodiment of an idle-state-based GAP measurement device provided in the present invention;

fig. 9 is a schematic structural diagram of a second embodiment of the GAP measurement device based on an idle state according to the present invention;

fig. 10 is a schematic structural diagram of a third embodiment of the GAP measurement device based on an idle state provided in the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the pilot frequency networking scenario of the current SC-PTM solution, when the UE located at the cell edge detects that the signal strength of the serving cell is weak, GAP measurement needs to be performed to select an adjacent cell with good signal strength for cell handover or cell reselection, and at this time, the eNodeB configures GAP measurement parameters for the terminal through the RRC, so that the terminal starts GAP measurement. However, the UE in an idle state and receiving the monitored trunking service has no RRC connection with the eNodeB, and the eNodeB cannot configure GAP measurement parameters to the UE through RRC to perform GAP measurement, so that the UE cannot perform cell reselection. Therefore, the invention provides a GAP measuring method in a pilot frequency networking scene of an SC-PTM solution, when UE which is not in RRC connection with an eNodeB detects weak signal intensity of a service cell, the UE starts GAP measurement, the UE configures GAP measurement parameters to a physical layer, and then the GAP measurement is carried out according to the GAP measurement parameters, thereby ensuring that the GAP measurement does not influence the receiving of the UE on service data on PCCH and SC-MCCH and the UE can normally receive paging. The method of the present invention will be described in detail below.

Fig. 1 is a flowchart of a first embodiment of a GAP measurement method based on an idle state provided in the present invention, where the method may be implemented based on a UE, and as shown in fig. 1, the method of this embodiment may include:

s101, acquiring an RSRP value of a serving cell where the UE is located;

s102, when the UE is in an idle state, judging whether a difference value between the RSRP value and a preset residence threshold associated with a serving cell is smaller than or equal to a preset difference value or not; if yes, executing S103, otherwise, not starting GAP measurement;

s103, configuring GAP measurement parameters, and performing GAP measurement according to the GAP measurement parameters.

Specifically, Reference Signal Received Power (RSRP) refers to an average value of Signal powers Received on all resource elements carrying cell-specific signals over a measurement bandwidth, and can be used to determine the strength of a serving cell Signal of a UE; the UE may periodically measure the RSRP value of the serving cell.

In practical application scenarios, there are different sets of projects, such as subway projects, city projects, mountain projects. In different project groups, the UE density and the geographic features are different, and therefore, different residence thresholds need to be set for the UE for different project groups, that is, the preset residence threshold in the above embodiment. The principle of setting the residence threshold in this embodiment is as follows: when the density of the UE is small and/or the terrain is flat, the value of the camping threshold is relatively small, and when the density of the UE is large and/or the terrain is complex, the value of the camping threshold is relatively large. For example, when the density of the UE is less than the preset density and/or the terrain flatness is greater than the preset flatness, the value of the camping threshold is a first camping threshold value, and when the density of the UE is greater than the preset density and/or the terrain flatness is less than the preset flatness, the value of the camping threshold is a second camping threshold value, and the first camping threshold value is less than the second camping threshold value. Optionally, the value range of the residence threshold is-143 to-108 db.

And the UE compares the RSRP value obtained by measurement with a preset residing threshold and judges the size relation between the difference value of the RSRP value and the preset residing threshold and a preset difference value. Similarly, the preset difference is determined by different item groups. The preset difference is set as follows in this embodiment: when the density of the UE is small and/or the terrain is flat, the preset difference is relatively large, and when the density of the UE is large and/or the terrain is complex, the preset difference is relatively small. In this embodiment, the value range of the preset difference is 0-62 db.

If the difference between the RSRP value and the preset residing threshold is judged to be less than or equal to the preset difference by the UE, which indicates that the signal quality of the current service cell received by the UE is poor, the UE in an idle state without RRC connection starts GAP measurement to measure the signal quality of the adjacent cell.

When the UE is in an idle state and has no RRC connection, after the UE starts GAP measurement, the GAP measurement parameters are firstly configured into a physical layer of the UE, and the physical layer of the UE carries out the GAP measurement according to the configured GAP measurement parameters. Optionally, the GAP measurement parameters include a GAP period and a GAP offset, and after the UE starts the GAP measurement, the GAP period and the GAP offset need to be configured first before the UE can perform the GAP measurement.

Through GAP measurement, the UE can know the signal quality of the adjacent cells, and the UE selects the adjacent cell with the best signal quality to reselect the cell according to the signal quality result of the adjacent cell.

In the idle-state-based GAP measurement method of this embodiment, the UE determines whether GAP measurement needs to be started according to a difference between an RSRP value of a serving cell in which the UE is located and a preset residence threshold, and if GAP measurement needs to be started, the UE configures GAP measurement parameters to a physical layer of the UE, and the physical layer performs GAP measurement according to the configured GAP measurement parameters, without configuring GAP measurement parameters through an eNodeB, thereby implementing GAP measurement of the idle-state UE without RRC connection, and avoiding that the continuity of monitoring trunking services by the UE is affected and abnormal off-line of the UE.

The configuration of the GAP period and GAP offset of the embodiment of fig. 1 is described in detail below.

First, the configuration of the GAP period will be described in detail.

Fig. 2 is a flowchart of a second embodiment of the GAP measurement method based on an idle state provided in the present invention, where the method of this embodiment includes:

step S201, acquiring a GAP period setting instruction;

step S202, according to the GAP period setting instruction, obtaining the GAP period.

Specifically, there are two modes of GAP measurement, one is that GAP measurement duration Tgap is 6ms, and measurement period Tperiod is 40ms, that is, GAP measurement is performed every 40ms, and each measurement duration is 6 ms; another measurement mode is that the GAP measurement time Tgap is 6ms, and the measurement period Tperiod is 80ms, that is, GAP measurement is performed every 80ms, and the measurement time is 6ms each time. Therefore, the GAP period may be set to 40ms or 80 ms.

In a specific GAP period configuration process, the UE first needs to obtain a setting instruction of a GAP period, and then configures the GAP period according to the GAP period included in the setting instruction of the GAP period.

The UE may obtain the setting instruction of the GAP period in the following two ways.

One way to implement this is to receive a GAP period setting instruction sent by the auxiliary device after the user inputs the GAP period setting instruction through the auxiliary device.

Specifically, the auxiliary device outside the UE is wirelessly or wiredly connected to the UE, the GAP period is manually input or voice input or selectively input on a user interface of the auxiliary device, and then the UE receives a GAP period setting instruction with the GAP period sent by the auxiliary device. Alternatively, the auxiliary device may be a computer.

Another way to implement this method is to display a GAP period command input interface in the UE and receive a GAP period triggered by the user through the command input interface.

Specifically, when the UE detects that the difference value between the RSRP value and the preset resident threshold associated with the service cell is smaller than or equal to the preset difference value, the UE pops up a GAP period instruction input interface, a user manually inputs or inputs voice or selects to input a GAP period on the GAP period instruction input interface, and the UE receives the GAP period triggered by the user through the instruction input interface.

The embodiment shown in fig. 2 will be further described with reference to fig. 3 to 6.

Fig. 3 is a schematic diagram of a user interface of the auxiliary device when configuring a GAP period, and fig. 4 is a schematic diagram of a user interface of the auxiliary device when configuring a GAP period; fig. 5 is a schematic diagram of a user interface of the UE when configuring the GAP period, and fig. 6 is a schematic diagram of a user interface of the UE when configuring the GAP period.

Referring to fig. 3, the auxiliary device is a computer, a GAP period input box is provided on a user interface of the computer, and a user may manually input a GAP period of 40ms or 80ms, and then a GAP period setting instruction is sent to the UE; the user interface can also be provided with a voice input identifier, the voice input identifier is clicked, the user inputs GAP period of 40ms or 80ms by voice, and then a GAP period setting instruction is sent to the UE. Referring to fig. 4, the user interface may also be provided with a GAP period selection list, click 40ms or 80ms in the GAP period selection list, and then send a GAP period setting instruction to the UE.

Referring to fig. 5, a GAP period input box is displayed on a GAP period instruction input interface of the UE, a user manually inputs a GAP period of 40ms or 80ms in the GAP period input box, and then a physical layer of the UE receives the set GAP period; the user interface can also display a voice input identifier, click the voice input identifier, input the GAP period by the user voice for 40ms or 80ms, and then the physical layer of the UE receives the set GAP period. Referring to fig. 6, the user interface may also display a GAP period selection list, click on 40ms or 80ms within the GAP period selection list, and then the physical layer of the UE receives the set GAP period.

In this embodiment, by receiving a GAP period setting instruction, the user equipment configures a GAP period into its physical layer, so that the user equipment itself performs GAP period configuration, and thus, the UE without RRC can perform GAP measurement.

Next, the arrangement of the GAP offset will be described in detail.

Fig. 7 is a flowchart of a third embodiment of the GAP measurement method based on an idle state provided in the present invention, where the method of this embodiment includes:

step S701, calculating SC-MCCH offset and PCCH offset;

step S702, obtaining GAP offset according to SC-MCCH offset and PCCH offset.

Specifically, GAP offset refers to the starting position of the GAP measurement within the GAP period; in the SC-PTM protocol system, in order to prevent the PCCH and SC-MCCH signaling from being received during GAP measurement, the UE needs to stagger the GAP measurement time from the signaling transmission time of the PCCH and SC-MCCH according to the channel positions of the PCCH and SC-MCCH transmitted in the received system message, so that the terminal can perform paging normally, that is, the SC-MCCH offset and the PCCH offset need to be calculated, thereby obtaining the GAP offset.

Optionally, the SC-MCCH offset is calculated as follows:

acquiring the repeat period bias of an SC-MCCH channel;

acquiring fixed offset of a UE side;

and obtaining the SC-MCCH offset according to the repeated period offset of the SC-MCCH channel and the fixed offset of the UE side. Specifically, the SC-MCCH offset may be acquired by the following formula one.

SC-MCCH _ Offset + GapShift formula one

Wherein, SC-MCCH _ Offset is SC-MCCH Offset, ScMcch Offset is the repeated period Offset of the SC-MCCH channel, and Gap Shift is the fixed Offset of the UE side.

The UE obtains the repetition period offset of the SC-MCCH channel through the system message, and the method for setting the fixed offset on the UE side is the same as the method for setting the GAP period, which is not described herein again. Optionally, the fixed offset on the UE side has a value range of 0 to 79ms, preferably 20 ms.

Optionally, the PCCH offset calculation method includes:

calculating a UE paging occasion radio frame and a UE paging occasion subframe;

acquiring a repetition period of an SC-MCCH channel;

and obtaining PCCH offset according to the UE paging occasion radio frame, the UE paging occasion radio frame and the repetition period of the SC-MCCH. Specifically, the PCCH offset can be obtained by the following formula two;

PCCH _ Offset ═ (PF × 10+ PO) MOD ScMcchPeriod equation two

Wherein, PCCH _ Offset is PCCH Offset, ScMcchPeriod is the repetition period of the SC-MCCH channel, PF is a UE paging occasion radio frame, and PO is a UE paging occasion subframe.

The PCCH channel parameters received by the UE and sent by a system are calculated for a subframe PO of the paging occasion of the UE and a radio frame PF of the paging occasion of the UE by the conventional calculation method; and the UE of the SC-MCCH channel in the repetition period is acquired through the system message.

After the SC-MCCH offset and the PCCH offset are obtained, the GAP offset may be obtained. The method can be specifically realized by the following steps:

if the PCCH offset is greater than or equal to the SC-MCCH offset and the PCCH offset is less than the sum of the SC-MCCH offset and the GAP measurement time T, determining the GAP offset as the sum of the SC-MCCH offset and the GAP measurement time T; or

And if the PCCH offset is smaller than the SC-MCCH offset and/or the PCCH offset is larger than the sum of the SC-MCCH offset and the GAP measurement time T, determining that the GAP offset is equal to the SC-MCCH offset.

Namely: if SC-MCCH _ Offset is less than or equal to PCCH _ Offset and less than SC-MCCH _ Offset + T,

then the GAP Offset is SC-MCCH Offset + T

If PCCH _ Offset < SC-MCCH _ Offset or

PCCH_Offset≥SC-MCCH_Offset+T，

Then the GAP Offset is SC-MCCH _ Offset.

Wherein T is 6 ms.

In this embodiment, the GAP offset is calculated by the UE, so that the UE itself performs GAP offset configuration, and the UE without RRC connection can perform GAP measurement.

Fig. 8 is a schematic structural diagram of a first embodiment of an idle-state-based GAP measurement device provided in the present invention; as shown in fig. 8, the apparatus of the present embodiment may include: an obtaining module 811, configured to obtain an RSRP value of a serving cell in which the UE is located; a determining module 812, configured to determine whether a difference between the RSRP value and a preset camping threshold associated with the serving cell is less than or equal to a preset difference when the UE is in an idle state; a configuration module 813, configured to configure a GAP measurement parameter if a difference between the RSRP value and a preset camping threshold associated with the serving cell is less than or equal to a preset difference; and a measurement module 814, configured to perform GAP measurement according to the GAP measurement parameters.

The device of this embodiment may be configured to execute the technical solution of the method embodiment shown in fig. 1, and the implementation principle and the technical effect are similar, which are not described herein again.

Fig. 9 is a schematic structural diagram of a second embodiment of the GAP measurement device based on an idle state according to the present invention; as shown in fig. 9, the apparatus of this embodiment is based on the apparatus structure shown in fig. 8, and further, the configuration module 813 may include: a first obtaining unit 8131, configured to obtain a GAP period setting instruction; and a second obtaining unit 8132, configured to obtain a GAP period according to the GAP period setting instruction.

The device of this embodiment may be configured to execute the technical solution of the method embodiment shown in fig. 2, and the implementation principle and the technical effect are similar, which are not described herein again.

Fig. 10 is a schematic structural diagram of a third embodiment of the GAP measurement device based on an idle state according to the present invention; as shown in fig. 10, the apparatus of this embodiment is based on the apparatus structure shown in fig. 8, and further, the configuration module 813 may further include: a first calculation unit 8133, configured to calculate an SC-MCCH offset and a PCCH offset; and a second calculating unit 8134, configured to obtain the GAP offset according to the SC-MCCH offset and the PCCH offset.

The device of this embodiment may be configured to execute the technical solution of the method embodiment shown in fig. 7, and the implementation principle and the technical effect are similar, which are not described herein again.

Optionally, the calculating, by the first calculating unit 8133, the SC-MCCH offset includes:

acquiring the repeat period bias of an SC-MCCH channel;

acquiring fixed offset of a UE side;

and obtaining the SC-MCCH offset according to the repeated period offset of the SC-MCCH channel and the fixed offset of the UE side.

Optionally, the first calculation unit 8133 calculating the PCCH offset includes:

calculating a UE paging occasion radio frame and a UE paging occasion subframe;

acquiring a repetition period of an SC-MCCH channel;

and obtaining PCCH offset according to the UE paging occasion radio frame, the UE paging occasion radio frame and the repetition period of the SC-MCCH.

Optionally, the second calculating unit 8134 obtains the GAP offset according to the SC-MCCH offset and the PCCH offset, including:

Those of ordinary skill in the art will understand that: all or a portion of the steps of implementing the above-described method embodiments may be performed by hardware associated with program instructions. The program may be stored in a computer-readable storage medium. When executed, the program performs steps comprising the method embodiments described above; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A GAP measurement method based on idle state is applied to UE, and the method comprises the following steps:

acquiring an RSRP value of a serving cell in which the UE is located;

if yes, configuring GAP measurement parameters, and performing GAP measurement according to the GAP measurement parameters;

the GAP measurement parameters comprise a GAP period, and the configuring the GAP measurement parameters comprises:

acquiring a GAP period setting instruction;

obtaining the GAP period according to the GAP period setting instruction;

the GAP measurement parameters further include: a GAP offset, the method further comprising:

calculating SC-MCCH offset and PCCH offset;

obtaining the GAP offset according to the SC-MCCH offset and the PCCH offset;

the obtaining the GAP offset according to the SC-MCCH offset and the PCCH offset includes:

Determining that the GAP offset is equal to the SC-MCCH offset if the PCCH offset is less than the SC-MCCH offset and/or the PCCH offset is greater than the sum of the SC-MCCH offset and the GAP measurement time T.

2. The method of claim 1, wherein the obtaining the GAP period setting instruction comprises:

after a user inputs a GAP period setting instruction through auxiliary equipment, receiving the GAP period setting instruction sent by the auxiliary equipment; alternatively, the first and second electrodes may be,

displaying an instruction input interface in the UE, and receiving a GAP period triggered by the user through the instruction input interface.

3. The method of claim 1, wherein the calculating the SC-MCCH offset comprises:

acquiring the repeat period bias of an SC-MCCH channel;

acquiring fixed offset of a UE side;

4. The method of claim 1, wherein the calculating the PCCH offset comprises:

calculating a UE paging occasion radio frame and a UE paging occasion subframe;

acquiring a repetition period of an SC-MCCH channel;

and obtaining the PCCH offset according to the UE paging occasion radio frame, the UE paging occasion radio frame and the repetition period of the SC-MCCH channel.

5. An idle-state-based GAP measurement device, comprising:

a measurement module for performing GAP measurement according to the GAP measurement parameters

The configuration module includes:

the first acquisition unit is used for acquiring a GAP period setting instruction;

the second acquisition unit is used for setting an instruction according to the GAP period to obtain the GAP period;

a first calculating unit, configured to calculate an SC-MCCH offset and a PCCH offset;

a second calculating unit, configured to obtain the GAP offset according to the SC-MCCH offset and the PCCH offset;

the second calculating unit is specifically configured to obtain the GAP offset, and includes: