CN102791009B - Multimode terminal and its time synchronizing method in cross form switching - Google Patents

Abstract

The present invention relates to a kind of multimode terminal and its time synchronizing method in cross form switching, above-mentioned terminal includes computing unit and switch unit；The above method is：Multimode terminal is calculated under work at present standard and safeguards the timing information of remaining inoperative standard；When needing to carry out service switching, the timing information of the target standard according to above-mentioned maintenance is by service switching to target standard.The present invention accelerates the process of switching, improves success rate, ability and the performance of service switching and measurement.

Description

Multi-mode terminal and its time synchronization method when switching between different standards

technical field

The invention relates to the field of mobile communication, in particular to a multi-mode terminal and a time synchronization method for switching between different standards.

Background technique

With the development of mobile communication standards and the promotion of commercialization, communication terminals have gradually developed from the initial GSM (globalsystem formobile communications, Global System for Mobile Communications) or narrowband CDMA (Code Division Multiple Access, called Code Division Multiple Access) single-mode to dual-mode or even multi-mode Die terminal form. At present, it is mainly GSM/WCDMA (Wideband Code Division Multiple Access, wideband code division multiple access) or GSM/TD-SCDMA (Time Division-Synchronous Code Division Multiple Access, time division synchronous code division multiple access) dual-mode, with the development of technology, now It has gradually evolved to GSM/TD-SCDMA/TD-LTE (TD-SCDMA Long Term Evolution, the long-term evolution of TD-SCDMA), GSM/WCDMA/FD-LTE and other multi-mode forms.

In a general single-mode terminal, there are usually two clock sources, one is a high-precision clock source for terminal work, generally using a 26MHz voltage-controlled crystal oscillator (TC-VCXO) with temperature compensation; the other is a low-precision clock source Low-frequency clock, the clock frequency is generally 32kHz. This clock is used to maintain the fast time recovery when the system wakes up in the standby state of the terminal in power-saving mode, especially in the sleep cycle, and to maintain the time when the system is turned off. , date clock, the above two clock sources, especially the high-precision 26MHz clock, the price is relatively high.

In order to reduce the cost of mobile terminals, in a dual-mode or multi-mode system, in addition to a low-frequency clock, usually only one high-precision clock is used. As shown in Figure 1, it is a schematic block diagram of a dual-mode receiver, and the communication systems are TD-SCDMA and TD-SCDMA respectively. GSM, the two systems share the same 26M crystal oscillator (clock source), the crystal oscillator is frequency multiplied/divided into TD-SCDMA receiver and GSM receiver through two sets of phase-locked loop circuits (Phase-Locked Loop, PLL) PLL1 and PLL2 The clocks required by each machine; as shown in Figure 2, it is a schematic diagram of the clock of the TD-SCDMA system in Figure 1. The crystal oscillator (clock source) outputs the clock signal to PLL1, and after frequency multiplication or/and frequency division, it obtains the needs of each link. For example, the 2GHz clock signal required by the RF module, the 51.2MHz clock signal required by the analog baseband module, and the 10.24MHz/5.12MHz clock required by the digital baseband module.

In addition, in order to reduce the power consumption of the terminal, during the working process of the dual-mode terminal, only one system standard is in the working state, while the other system standard will be closed or deep sleep. When switching is required, the target system will be quickly awakened from the working system. And perform fast switching of services. In this way, when a dual-mode or multi-mode terminal switches, how to achieve timing synchronization of two or more system standards.

A conventional method is to perform a cell search on the target system when switching or reselecting from the working system to the target system, so as to obtain time synchronization information. If the terminal is in the handover process at this time, since the cell search of the target system takes a lot of time, the probability of call drop will be increased; if the terminal is in the cross-system measurement measurement cell search at this time, it will consume precious The cross-system time segment makes it more difficult to schedule measurement tasks and also reduces measurement capabilities.

Contents of the invention

The purpose of the present invention is to provide a multi-mode terminal and its time synchronization method for cross-system switching, so as to solve the problems of high call drop probability and low measurement capability in the prior art.

The present invention provides a time synchronization method when a multi-mode terminal is switched across standards,

The above-mentioned multi-mode terminal calculates and maintains timing information of other non-working modes under the current working mode;

When service switching is required, the service is switched to the target system according to the above-maintained timing information of the target system.

Preferably, before all the above steps, the following steps are also included:

The above-mentioned multi-mode terminal performs cell search during initialization, and obtains and stores offsets between the frame header positions of the first subframe of each standard and the frame header positions of the first subframe of other standards.

Preferably, after the terminal successfully switches to the target system, the timing information of other non-working systems is brought into the current working system, and the calculation and maintenance are continued.

Preferably, the above timing information includes the subframe number N _T and its working time τ _T .

Preferably, when the above-mentioned terminal does not consider the frequency offset of the carrier frequency, the timing information of the corresponding non-working system is calculated by the following formula:

τ _T ＝T _C ×N _C +τ _C -τ ₀ -T _T ×N _T

Among them, T _C represents the subframe duration of the current working system, N _C represents the current subframe number of the current working system, and τ _C represents the number of subframes in the _NC +1th subframe of the current working system after _NC +1 subframes At the τ _Cth moment, τ ₀ represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and T _T represents the above-mentioned corresponding non-working Standard subframe duration.

Preferably, when considering the frequency offset of the carrier frequency, before the above-mentioned terminal calculates the timing information of the remaining non-working systems, it also performs the following operations:

Calculate the sampling time T _s ′ with frequency offset under the current working system;

Calculate the total time t _C from the first subframe of the current working system to the τ _Cth moment of the N _C +1th subframe sampled according to the above sampling time T _s ′ with frequency offset.

Preferably, the sampling time T _s ′ with frequency offset is calculated by the following formula:

T _s ′＝T _s ×(1/(1+f _offset /f _c ))≈T _s ×(1-f _offset /f _c )

Among them, T _s =1/f _s is the baseband sampling time of the current working system, f _s is the baseband sampling frequency of the current working system, f _c is the working carrier frequency of the current working system, and f _offset is the carrier frequency of the current working system Partial.

Preferably, if the carrier frequency offset of the current working system remains unchanged, then the above-mentioned time τ _C from the first subframe to the N _C +1th subframe of the current working system sampled according to the sampling time T _s ' with frequency offset The total time t _C is calculated by the following formula:

t _C ＝(T _C ×N _C +τ _C -τ ₀ )×(1+f _offset /f _c )

Among them, T _C represents the subframe duration of the current working system, N _C represents the current subframe number of the current working system, and τ _C represents the number of subframes in the _NC +1th subframe of the current working system after _NC +1 subframes At the _τCth moment, _τ0 represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and f _c is the offset of the frame header position of the first subframe of the current working system Working carrier frequency, f _offset is the carrier frequency offset of the current working system.

Preferably, if the carrier frequency offset of the current working system changes according to subframes, the τ _C of the first subframe to the N _C +1th subframe of the current working system sampled according to the sampling time T _s ' with frequency offset The total time t _C of the moment is calculated by the following formula:

Among them, T _C represents the subframe duration of the current working system, N _C represents the current subframe number of the current working system, and τ _C represents the number of subframes in the _NC +1th subframe of the current working system after _NC +1 subframes At the _τCth moment, _τ0 represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and f _c is the offset of the frame header position of the first subframe of the current working system Working carrier frequency, f _{offset, i} represents the carrier frequency offset corresponding to the i-th subframe of the current working system, Indicates the carrier frequency offset corresponding to the N _C +1th subframe of the current working mode.

Preferably, when the above-mentioned terminal considers the frequency offset of the carrier frequency, it calculates the timing information of the corresponding non-working system through the following formula:

τ _T =t _C -T _T ×N _T

Among them, t _C represents the total time from the first subframe of the current working system to the τ _Cth moment of the N _C + 1th subframe sampled according to the sampling time T _s ′ with frequency offset, and T _T represents the above-mentioned corresponding non-working system subframe duration.

The present invention also provides a multi-mode terminal, including a switching unit and a computing unit,

The calculation unit is used to calculate and maintain the timing information of other non-working systems under the working system, and the above-mentioned timing information includes the subframe number N _T and its working time τ _T ;

The switching unit is configured to switch the service to the target standard according to the timing information of the target standard calculated by the calculation unit.

Preferably, the above-mentioned terminal further includes a search unit, which is used to perform cell search during initialization, so as to obtain the initial offset between the frame header position of the first subframe of each standard and the frame header position of the first subframe of other standards Measure and store.

Preferably, the calculation unit includes a time calculation module and a timing calculation module,

The above-mentioned time calculation module is used to calculate the sampling time T _s ′ with frequency offset, and calculate the first subframe to the _NC +1th subframe of the current system sampled according to the above-mentioned sampling time T _s ′ with frequency offset The total time t _{C at the moment τ C ;}

The above-mentioned timing calculation module is used to calculate and maintain the timing information of the non-working system.

Preferably, when considering the frequency offset of the carrier frequency,

The above time calculation module calculates the sampling time T _s ′ with frequency offset by the following formula:

T _s ′＝T _s ×(1/(1+f _offset /f _c ))≈T _s ×(1-f _offset /f _c )

The above time calculation module calculates the τ _C from the first subframe to the N _C +1th subframe of the current working system sampled according to the sampling time T _s ′ with frequency offset by the following formula when the carrier frequency offset remains unchanged The total time t _C of the moment:

t _C ＝(T _C ×N _C +τ _C -τ ₀ )×(1+f _offset /f _c )

The above time calculation module calculates the τ from the first subframe to the N _C +1th subframe of the current working system sampled according to the sampling time T _s ′ with frequency offset by the following formula when the frequency offset of the carrier frequency changes according to the subframe Total time t _C at time _C :

Among them, T _s =1/f _s is the baseband sampling time of the current working system, f _s is the baseband sampling frequency of the current working system, f _c is the working carrier frequency of the current working system, and f _offset is the carrier frequency of the current working system T _C represents the duration of the subframe of the current working system, τ _C represents the τ _C time when the current working system falls in the _NC +1 subframe after N _C +1 subframes, and τ ₀ represents the above corresponding non-working The offset of the frame header position of the first subframe of the standard relative to the frame header position of the first subframe of the current working standard, f _{offset, i} represents the carrier frequency offset corresponding to the i-th subframe of the current working standard, Indicates the carrier frequency offset corresponding to the N _C +1th subframe of the current working mode.

Preferably, the above-mentioned timing calculation module calculates the timing information of the corresponding non-working system by the following formula when the carrier frequency deviation is not considered:

τ _T ＝T _C ×N _C +τ _C -τ ₀ -T _T ×N _T

And when considering the frequency offset of the carrier frequency, the timing information of the corresponding non-working system is calculated by the following formula:

τ _T =t _C -T _T ×N _T

Among them, T _C represents the subframe duration of the current working system, N _C represents the current subframe number of the current working system, and τ _C represents the number of subframes in the _NC +1th subframe of the current working system after _NC +1 subframes At the τ _Cth moment, τ ₀ represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and T _T represents the above-mentioned corresponding non-working The subframe duration of the standard, t _C represents the total time from the 1st subframe to the _NC +1th subframe of the current standard at the τ _Cth moment sampled according to the sampling time T _s ′ with frequency offset.

In the working system, the present invention calculates and maintains the timing information of the other non-working systems, calculates the timing positions of the other non-working systems in real time, and uses the maintained timing information to switch when it is necessary to switch to the target system, ensuring business synchronization, and after the switching is successful, the timing information of other non-working systems is directly brought to the current working system to continue calculation and maintenance. The present invention speeds up the switching process and improves the success rate, capability and performance of business switching and measurement .

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention, and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute improper limitations to the present invention. In the attached picture:

Fig. 1 is a schematic block diagram of a dual-mode receiver;

Fig. 2 is the clock schematic diagram of TD-SCDMA system in Fig. 1;

FIG. 3 is a flowchart of a first embodiment of a time synchronization method when a multi-mode terminal is switched across standards according to the present invention;

FIG. 4 is a flowchart of a second embodiment of the time synchronization method when a multi-mode terminal is switched across standards according to the present invention;

Fig. 5 is a schematic diagram of a synchronous calculation relationship in a TD-SCDMA/GSM dual-mode terminal;

Fig. 6 is a relationship diagram between frequency offset and timing information;

Fig. 7 is a functional block diagram of a multi-mode terminal according to the present invention.

detailed description

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in Figure 3, it is a flow chart of the first embodiment of the time synchronization method when the multi-mode terminal is switched across the standard of the present invention. This embodiment does not consider the influence of frequency offset, and specifically includes the following steps:

Step S001: During initialization, the multi-mode terminal performs a cell search, obtains and stores the offset between the frame header position of the first subframe of each standard and the frame header position of the first subframe of other standards;

Assuming that the multi-mode terminal has three communication systems, namely A, B, and E, the offset obtained at this time is: the frame header position of the first subframe of A and the frame header of the first subframe of B The offset τ _AB of the position, the offset τ _AE between the frame header position of the first subframe of A and the frame header position of the first subframe of E, and the frame header position of the first subframe of B and The offset τ _BE of the frame header position of the first subframe of E is obtained and stored after obtaining the corresponding offset. No matter which system is working, when calculating the timing information of other non-working systems, it can be directly used .

Step S002: Under the current working mode, calculate and maintain the timing information of other non-working modes;

Assuming that the current working system is A, this step calculates and maintains the timing information of B and E.

In the present invention, the timing information includes the subframe number _{NT and its working time τ T .}

Assuming the total time from the first subframe of the current working system to the τ _Cth moment of N _C +1 subframe is t _C , then:

t _C ＝T _C ×N _C +τ _C -τ ₀

In this step, the timing information of the non-working mode is calculated by the following formula:

τ _T ＝T _C ×N _C +τ _C -τ ₀ -T _T ×N _T ＝t _C -T _T ×N _T

Among them, in the formula, Indicates rounding down, T _C indicates the subframe duration of the current working system, N _C indicates the current subframe number of the current working system, τ _C indicates that the current working system starts from the first subframe and passes through N _C +1 subframes The frame falls at the τ _Cth moment in the N _C + 1th subframe, and τ ₀ represents the frame header position of the first subframe of the above-mentioned corresponding non-working system relative to the frame header position of the first subframe of the current working system The offset of T _T represents the subframe duration of the above-mentioned corresponding non-working mode.

The timing information _NT is the subframe number of the non-working system after N _C subframes of the working system have passed, and τ _T represents the relative position of the timing information in the N _T + 1th subframe in the non-working system.

Step S003: When service switching is required, switch according to the timing information of the target standard maintained above;

Assuming that the target system is B, the formula for calculating the timing information of B is:

τ _B ＝T _A ×N _A +τ _A -τ _AB -T _B ×N _B

Among them, T _A represents the subframe duration of A, N _A represents the current subframe number of A, τ _A represents the moment when A passes through N _C + 1 subframes, and τ _AB represents the frame header position of the first subframe of B Relative to the offset of the header position of the first subframe of A, T _B represents the subframe duration of B.

In this step, because the timing information of the target system is known, the switching between systems can be completed quickly and accurately, for example, switching to the τ _B -th time point of the NB-th subframe of _B.

Step S004: After the switching is successful, the timing information of other non-working systems is brought into the current working system, and the calculation and maintenance are continued.

When the multi-mode terminal successfully switches to B, B becomes the current working system. The multi-mode terminal brings the timing information of E originally maintained in A and its own timing information into B, and works in B at the same time. , continue to calculate and maintain the timing information of A and E, so as to switch from B to A or C again. By analogy, when the multimode terminal works in any standard, it dynamically calculates and maintains the timing information of other standards.

During the actual working process of the terminal, due to temperature changes, movement and system stability, etc., the terminal must have a frequency tracking loop to ensure frequency synchronization. The essence of the frequency tracking loop is that the terminal receiver estimates the frequency deviation between the terminal and the current working standard according to the signal detection theory, and adjusts the local carrier frequency of the terminal by adjusting the local crystal oscillator of the terminal, thereby eliminating the frequency deviation. However, the adjustment of the crystal oscillator will cause the reference frequency of the clock signal to change, thereby affecting the time synchronization information. The influence of the frequency tracking loop on the synchronization of the current working standard is relatively small, and the terminal can easily eliminate the influence of the frequency offset on the timing information of the current working standard, but due to the time accumulation effect, the calculation of the timing information of the cross-standard Influence, this needs to be adjusted through the timing information of the other non-working modes of the terminal to calibrate the positioning information of the non-working mode.

As shown in FIG. 4, it is a flow chart of the second embodiment of the time synchronization method when the multi-mode terminal is switched across the standard of the present invention. In this embodiment, it is assumed that the frequency offset of the carrier frequency changes according to the subframe, and specifically includes the following steps:

Step S101: During initialization, the multi-mode terminal performs cell search, obtains and stores the offsets between the frame header positions of the first subframe of each standard and the frame header positions of the first subframes of other standards;

It is also assumed that the multi-mode terminal has three communication systems, which are A, B, and E respectively.

Step S102: Under the current working mode, calculate the sampling time T _s ′ with frequency offset;

In this step, the sampling time T _s ′ with frequency offset is calculated by the following formula:

T _s ′＝T _s ×(1/(1+f _offset /f _c ))≈T _s ×(1-f _offset /f _c )

Among them, T _s =1/f _s is the baseband sampling time of the current working system, f _s is the baseband sampling frequency of the current working system, f _c is the working carrier frequency of the current working system, and f _offset is the carrier frequency of the current working system On the other hand, generally, f _offset is relatively small compared to f _c , and the above formula is approximately true.

Step S103: Calculate the total time t _{C at the τ C time} from the first subframe to the _NC +1 subframe of the current working system sampled according to the above sampling time T _s ′ with frequency offset;

Because in this embodiment, the carrier frequency offset f _offset of the current working system changes according to the subframe, so this step uses the following formula to calculate the current working system sampled from the first subframe to the first subframe according to the above-mentioned sampling time T _s ′ with frequency offset The total time t _C at the τ Cth moment of _{N C} +1 subframe:

Among them, T _C represents the subframe duration of the current working standard, f _c is the working carrier frequency of the current working standard, and τ _C represents the first subframe in the _NC +1th subframe of the current working standard after _NC +1 subframes. At time τ _C , τ ₀ represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and f _{offset, i} represents the current working system The carrier frequency offset corresponding to the ith subframe of , Indicates the carrier frequency offset corresponding to the N _C +1th subframe of the current working mode.

In other embodiments, if the carrier frequency offset f _offset of the current working system remains unchanged, the current working system sampled according to the sampling time T _s ′ with frequency offset is calculated from the first subframe to the N _C +1th subframe The _{formula for the total time t C at} the τ Cth moment of the frame is:

t _C ＝(T _C ×N _C +τ _C -τ ₀ )×(1+f _offset /f _c ) (2)

Step S104: According to the calculation result of step S103, calculate and maintain the timing information of the corresponding non-working system;

In this step, the timing information is calculated by the following formula:

τ _T =t _C -T _T ×N _T

Wherein, T _T represents the subframe duration of the corresponding non-working mode.

Assuming that the current working system is A, if the corresponding non-working system is B, then the above formula is:

τ _B ＝t _A -T _B ×N _B

Wherein, T _B represents the subframe duration of the B standard.

If the corresponding working system is E, then the above formula is:

τ _E ＝t _A -T _E ×N _E

Wherein, T _E represents the subframe duration of the E standard.

Step S105: When service switching is required, switching is performed according to the timing information of the above-mentioned maintained target standard;

Step S106: the switching is successful, and the timing information of other non-working systems is brought into the current working system, and the calculation and maintenance are continued.

Taking the dual-mode terminal as an example, assuming that the communication systems are TD-SCDMA and GSM respectively, the subframe time of TD-SCDMA is 5ms, the subframe time of GSM is 4.615ms, and the current working system is TD-SCDMA, then GSM The offset of the frame head position of the subframe relative to the frame head position of the TD-SCDMA subframe is τ ₀ , and τ ₀ is obtained by searching cells when the terminal is initialized, after N _TD-SCDMA + 1 TD-SCDMA subframes After the τ _TD-SCDMA ms time in the working system, if the carrier frequency offset is not considered in the working system, then according to the formula in step S002, the positioning information of the GSM system, that is, the τ _GSM time of the N _GSM +1 subframe points, calculated as follows:

τ _GSM ＝T _TD-SCDMA ×N _TD-SCDMA +τ _TD-SCDMA -τ ₀ -T _GSM ×N _GSM

As shown in FIG. 5 , it is a schematic diagram of a synchronous calculation relationship in a TD-SCDMA/GSM dual-mode terminal. Refer to FIG. 5 for the relationship of the above parameters.

Due to the influence of frequency offset, when the above-mentioned dual-mode terminal needs to switch to the GSM system after working in the TD-SCDMA system for a period of time, according to the timing information maintained by the TD-SCDMA system, the timing information _NGSM and τ _GSM of the GSM system need calibration.

Let f _DBB be the baseband frequency offset of the TD-SCDMA system, f _s be the baseband sampling frequency of the TD-SCDMA system, f _c be the working carrier frequency of the TD-SCDMA system, f _offset be the carrier frequency offset of the TD-SCDMA system, T _s = 1/f _s , which is the baseband sampling time of TD-SCDAM system, then the frequency offset from the carrier frequency to the baseband frequency offset is:

f _DBB ＝(f _s /f _c )×f _offset

At this time, the sampling time T _s ′ with frequency offset:

T _s ′＝1/(f _s +f _DBB )＝T _s ×(1/(1+f _offset /f _c ))≈T _s ×(1-f _offset /f _c )

Because in general, the carrier frequency offset f _offset is much smaller than the working carrier frequency f _c (for example, in 3G, the working carrier frequency f _c is about 2GHz or 1GHz, and the carrier frequency offset f _offset generally does not exceed 10kHz at most, typically in the hundreds Hz or dozens of Hz), so the above approximation is made.

Difference between baseband sampling time and sampling time with frequency offset:

ΔT _s =T _s -T _s '=T _s ×f _offset /f _c

Table 1 shows the relationship between frequency deviation and time sampling deviation of the TD-SCDMA system.

Table 1

According to Table 1, if the frequency offset of the terminal receiver is 5kHz, every 62.5 subframes, it is necessary to adjust one chip time to achieve sampling synchronization. The actual synchronization adjustment is adjusted according to 1/8 chip, that is, It is said that every 7.8125 sub-subframes need to be adjusted by 1/8 chip.

If the carrier frequency offset f _offset remains unchanged from the first TD-SCDMA subframe to the τ _TD-SCDMA ms moment in the N _TD-SCDMA +1 TD-SCDMA subframe, then according to the sampling with frequency offset The total time t _TD-SCDMA sampled at time T _s ′ from the 1st TD-SCDMA subframe to the τ _TD-SCDMA ms moment in the N _TD-SCDMA + 1th TD-SCDMA subframe is no longer:

T _TD-SCDMA ×N _TD-SCDMA +τ _TD-SCDMA -τ ₀

Instead:

t _TD-SCDMA ＝(T _TD-SCDMA ×N _TD-SCDMA +τ _TD-SCDMA -τ ₀ )×(1+f _offset /f _c )

If the carrier frequency offset f _offset changes according to the subframe from the beginning, then the samples from the first TD-SCDMA subframe to the Nth _TD-SCDMA +1 TD-SCDMA subframe are sampled according to the sampling time T _s ′ with frequency offset The total time t _TD-SCDMA at the time τ _TD-SCDMAms in the time should be:

At this point, the calculated GSM timing information is:

τ _GSM ＝t _TD -S _CDMA -T _GSM ×N _GSM

As shown in FIG. 6 , it is a relationship diagram between frequency offset and timing information. In the figure, the TX axis represents a strict clock, and the RX axis represents a clock with frequency offset calibration.

As shown in FIG. 7, it is a functional block diagram of the multimode terminal of the present invention, including a search unit 01, a calculation unit 02, and a switching unit 03, wherein,

The search unit 01 is configured to perform a cell search when the terminal is initialized to obtain and store initial offsets between the frame header positions of the first subframes of each standard and the frame header positions of the first subframes of other standards;

Calculation unit 02, used to calculate and maintain the timing information of other non-working systems under the working system;

The computing unit 02 includes a timing computing module 21 and a time computing module 22, the timing computing module 21 is used to calculate and adjust the timing information of the non-working system according to the formula in step S002; the time computing module 22 is used to calculate and adjust the timing information according to the formula in step S102 Calculate the sampling time T _s ′ with frequency offset, and when considering the frequency offset of the carrier frequency and the frequency offset of the carrier frequency changes according to the subframe, _calculate the current The total time t _C from the 1st subframe of the working system to the _τC time of the _NC +1th subframe, or when the carrier frequency deviation is considered but the carrier frequency deviation remains unchanged, according to the formula (2) in step S103 Calculate the total time t _C from the 1st subframe of the current working system to the _τCth moment of the _NC +1th subframe sampled according to the sampling time T _s ′ with frequency offset;

The switching unit 03 is configured to switch the service to the target standard according to the timing information of the target standard calculated by the calculation unit 02 .

The foregoing description shows and describes preferred embodiments of the present invention, but as previously stated, it should be understood that the present invention is not limited to the form disclosed herein, and should not be viewed as excluding other embodiments, but can be used in various Other combinations, modifications and circumstances, and can be modified within the scope of the inventive concept described herein, by the above teachings or by skill or knowledge in the relevant field. However, changes and changes made by those skilled in the art do not depart from the spirit and scope of the present invention, and should all be within the protection scope of the appended claims of the present invention.

Claims (10)

1. A time synchronization method when a multi-mode terminal is switched across systems, characterized in that, The multi-mode terminal calculates and maintains timing information of other non-working modes under the current working mode; When service switching is required, switch the service to the target system according to the timing information of the target system in the remaining non-working systems maintained; When the multi-mode terminal does not consider the frequency offset of the carrier frequency, the timing information of the corresponding non-working system is calculated by the following formula: τ _T ＝T _C ×N _C +τ _C -τ ₀ -T _T ×N _T ; Among them, T _C represents the subframe duration of the current working system, N _C represents the current subframe number of the current working system, and τ _C represents the number of subframes in the _NC +1th subframe of the current working system after _NC +1 subframes At the _τCth moment, _τ0 represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and T _T represents the corresponding The subframe duration of the non-working system, _{NT represents the subframe number, and τ T represents} the working time; When considering the frequency offset of the carrier frequency, before the multi-mode terminal calculates the timing information of other non-working systems, it also performs the following operations: Calculate the sampling time T _s 'with frequency offset under the current working system; Calculating the total time t _C of the τ _Cth moment from the first subframe to the _NC +1th subframe of the current working system sampled according to the sampling time T _s 'with frequency offset; When the multi-mode terminal considers the frequency deviation of the carrier frequency, the timing information of the corresponding non-working system is calculated by the following formula: τ _T = t _C - T _T × N _T ; Among them, t _C represents the total time from the first subframe of the current working system to the τ _C time of the N _C +1th subframe sampled according to the sampling time T _s 'with frequency offset, and T _T represents the corresponding non-working Standard subframe duration. 2. time synchronization method according to claim 1, is characterized in that, before described all steps, also comprises the following steps: The multi-mode terminal performs cell search during initialization, and obtains and stores offsets between the frame header positions of the first subframe of each standard and the frame header positions of the first subframes of other standards. 3. The time synchronization method according to claim 1, wherein after the multi-mode terminal successfully switches to the target system, it brings the timing information of other non-working systems into the current working system, and continues to calculate and maintain. 4. The synchronization method according to claim 1, wherein the timing information includes a subframe number _{NT and its working time τ T .} 5. The time synchronization method according to claim 1, characterized in that, the sampling time T _s ' of band frequency offset is calculated by the following formula: T _s '=T _s ×(1/(1+f _offset /f _c ))≈T _s ×(1-f _offset /f _c ); Among them, T _s =1/f _s is the baseband sampling time of the current working system, f _s is the baseband sampling frequency of the current working system, f _c is the working carrier frequency of the current working system, and f _offset is the carrier frequency of the current working system Partial. 6. The time synchronization method according to claim 1, wherein if the carrier frequency deviation of the current working system remains unchanged, the first frequency of the current working system sampled according to the sampling time T _s 'with frequency deviation The total time t _C from the first subframe to the τ _Cth moment of the N _C +1th subframe is calculated by the following formula: t _C ＝(T _C ×N _C +τ _C -τ ₀ )×(1+f _offset /f _c ); Among them, T _C represents the subframe duration of the current working system, N _C represents the current subframe number of the current working system, and τ _C represents the number of subframes in the _NC +1th subframe of the current working system after _NC +1 subframes At the τ _Cth moment, τ ₀ represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and f _c is the working value of the current working system Carrier frequency, f _offset is the carrier frequency offset of the current working system. 7. The time synchronization method according to claim 1, characterized in that, if the carrier frequency offset of the current working system changes according to subframes, the first frequency of the current working system sampled according to the sampling time T _s 'with frequency offset The total time t _C from 1 subframe to the τ _Cth moment of the N _C + 1th subframe is calculated by the following formula: ${\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$ Among them, T _C represents the subframe duration of the current working system, N _C represents the current subframe number of the current working system, and τ _C represents the time of the current working system falling into the _NC +1 subframe after _NC +1 subframes At the τ _Cth moment, τ ₀ represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and f _c is the working value of the current working system Carrier frequency, f _{offset, i} represents the carrier frequency offset corresponding to the i-th subframe of the current working system, Indicates the carrier frequency offset corresponding to the N _C +1th subframe of the current working mode. 8. A multi-mode terminal, including a switching unit, characterized in that it also includes a computing unit, The calculation unit is used to calculate and maintain the timing information of the remaining non-working systems under the current working system, and the timing information includes the subframe number N _T and its working time τ _T ; The switching unit is configured to switch the service to the target standard according to the timing information of the target standard calculated by the calculation unit; The calculation unit includes a time calculation module and a timing calculation module, The time calculation module is used to calculate the sampling time T _s 'with frequency offset, and calculate the first subframe to the N _C +1th subframe of the current working system sampled according to the sampling time T _s 'with frequency offset The total time t _C of the τ _C moment of the frame; The timing calculation module is used to calculate and maintain the timing information of the non-working system; The timing calculation module calculates the timing information of the corresponding non-working system by the following formula when the carrier frequency deviation is not considered: τ _T ＝T _C ×N _C +τ _C -τ ₀ -T _T ×N _T ; And when considering the frequency offset of the carrier frequency, the timing information of the corresponding non-working system is calculated by the following formula: τ _T = t _C - T _T × N _T ; Among them, T _C represents the subframe duration of the current working system, N _C represents the current subframe number of the current working system, and τ _C represents the number of subframes in the _NC +1th subframe of the current working system after _NC +1 subframes At the _τCth moment, _τ0 represents the offset of the frame header position of the first subframe of the corresponding non-working system relative to the frame header position of the first subframe of the current working system, and T _T represents the corresponding The subframe duration of the non-working system, t _C represents the total time from the 1st subframe of the current working system to the _τCth moment of the _NC +1th subframe sampled according to the sampling time T _s 'with frequency offset. 9. The multi-mode terminal according to claim 8, characterized in that the multi-mode terminal further comprises a search unit for performing cell search during initialization to obtain the frame header position of the first subframe of each standard The initial offset from the frame header position of the first subframe in other formats and stored. 10. The multimode terminal according to claim 8, characterized in that, when considering carrier frequency offset, The time calculation module calculates the sampling time T _s 'with frequency offset by the following formula: T _s '=T _s ×(1/(1+f _offset /f _c ))≈T _s ×(1-f _offset /f _c ); When the frequency offset of the carrier frequency remains unchanged, the time calculation module calculates the first subframe to the N _C +1th subframe of the current working system sampled according to the sampling time T _s 'with frequency offset by the following formula Total time t _{C at time τ C :} t _C ＝(T _C ×N _C +τ _C -τ ₀ )×(1+f _offset /f _c ); When the frequency offset of the carrier frequency changes according to the subframe, the time calculation module calculates the time from the first subframe to the N _C +1th subframe of the current working system sampled according to the sampling time T _s 'with frequency offset by the following formula The total time t _C at the τ _Cth moment: ${\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$ Among them, T _s =1/f _s is the baseband sampling time of the current working system, f _s is the baseband sampling frequency of the current working system, f _c is the working carrier frequency of the current working system, and f _offset is the carrier frequency of the current working system T _C represents the subframe duration of the current working system, τ _C represents the τ _C moment when the current working system falls in the _NC +1th subframe after N _C +1 subframes, and τ ₀ represents the corresponding non-working system The offset of the frame header position of the first subframe of the current working system relative to the frame header position of the first subframe of the current working system, f _{offset, i} represents the carrier frequency offset corresponding to the i-th subframe of the current working system, Indicates the carrier frequency offset corresponding to the N _C +1th subframe of the current working mode.