CN101557255A - Time synchronization method, system thereof and time synchronous communication equipment - Google Patents
Time synchronization method, system thereof and time synchronous communication equipment Download PDFInfo
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- CN101557255A CN101557255A CNA2009101375600A CN200910137560A CN101557255A CN 101557255 A CN101557255 A CN 101557255A CN A2009101375600 A CNA2009101375600 A CN A2009101375600A CN 200910137560 A CN200910137560 A CN 200910137560A CN 101557255 A CN101557255 A CN 101557255A
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Abstract
The invention relates to a time synchronization method, a system thereof and time synchronous communication equipment. The embodiment of the time synchronization method comprises the following steps: a clock client end exchanges a time synchronization signal with a clock server to obtain a clock offset between the clock client end and the clock server; the time synchronization signal is transmitted by a special sub-carrier channel of a wire transmission medium; and a clock of the clock client end is adjusted according to the obtained clock offset. The embodiment of the invention lowers the networking cost of a time synchronization proposal applied to the existing base station transmission network adopting the wire transmission medium.
Description
Technical field
The present invention relates to the mobile communication technology field, relate in particular to a kind of method for synchronizing time, system and time synchronous communication equipment.
Background technology
Mobile communication system requires very outstanding to time synchronized, time synchronized is meant that the absolute time between the different system is identical.As in communication system, all there is internal time in each system, because the internal time independent operating of each system, so the internal time between each system is not necessarily identical.Time synchronization technique is exactly that the time deviation between each different system is controlled at technology within the particular range.
Different mobile communication system is also different to the requirement of time synchronized, as shown in table 1, for GSM (Global System for Mobile Communications), WIMAX (WorldwideInteroperability for Microwave Access), CDMA (Code Division MultipleAccess), WCDMA (Wideband CDMA), TD-SCDMA (TimeDivision-Synchronous Code Division Multiple Access) and LTE (Long TermEvolution) mobile communication system, all need to satisfy the demand of time synchronized, especially the WIMAX mobile communication system is the highest to the requirement of timing tracking accuracy, need reach+/-1us.
Table 1
| Mobile communication system | GSM | WIMAX | CDMA | TD-SCDMA | WCDMA | LTE |
| Timing tracking accuracy | / | +/-1us | +/-3us | +/-3us | / | +/-3us |
WIMAX mobile network based on IEEE802.16 adopts the IP network framework, and the major defect of IP network is that the base station has not just had reliably clock reference accurately if lose time synchronized, and the time synchronized distribution is suffered to destroy and finally may be caused call drop.So Time synchronization technique is very important concerning the WIMAX mobile communication system, the WIMAX mobile communication system is also very high to the requirement of timing tracking accuracy.
The time synchronized scheme that is applied in the existing network is the gps time synchronization scenario.
GPS is a high precision synchronous clock reference, and a pin-point accuracy and accurate one-level timing reference input are provided, and precision can reach 10
-11Ns provides time data and base station position data, is widely used in the synchronous of wireless base station.As shown in Figure 1, the gps time synchronization scenario is for each base station an outdoor GPS equipment to be installed all, each base station all obtains high-precision absolute time by the GPS equipment that is connected with self, and (10 are power line shown in the figure, 20 is Ethernet), the high-precision absolute time that each GPS equipment provides is the same, thereby has realized the time synchronized between each base station.Its major defect comprises: the networking cost height, and GPS equipment price costliness, an outdoor GPS equipment is all installed in each base station, makes the networking cost height.
As can be seen from the above, be applied to time synchronized scheme networking cost height in the existing network.
Summary of the invention
The purpose of the embodiment of the invention provides a kind of method for synchronizing time, system and time synchronous communication equipment, is applied to the networking cost of time synchronized scheme in the existing network with reduction.
For solving the problems of the technologies described above, the embodiment of the invention provides a kind of method for synchronizing time, system and time synchronous communication equipment to be achieved in that
A kind of method for synchronizing time comprises:
The mutual time synchronizing signal of clock client and clock server, obtain and described clock server between clock offset, described time synchronizing signal transmits by the dedicated subcarriers channel of wire transmission medium;
According to the described clock offset that obtains, adjust the clock of described clock client.
A kind of time synchronized communication equipment comprises:
First receiver module is used for the time synchronizing signal that the receive clock client sends to clock server;
Select module, be used for after first receiver module receives described time synchronizing signal, selecting the dedicated subcarriers channel of wire transmission medium;
First processing module is used for the dedicated subcarriers channel at described wire transmission medium, and the time synchronizing signal that described first receiver module is received carries out modulation treatment;
First sending module is used for the time synchronizing signal after described clock server sends the described first processing module modulation treatment.
A kind of clock synchronization system, comprise above-mentioned time synchronized communication equipment and clock server as time synchronized communication slave unit, described clock server, be used for receiving the time synchronizing signal of described time synchronized communication slave unit to the dedicated subcarriers Channel Transmission of passing through the wire transmission medium of clock server transmission to described time synchronized communication slave unit transmitting time synchronizing signal.
The technical scheme that is provided by the above embodiment of the invention as seen, the embodiment of the invention need not installed GPS equipment at the base station end, but realize time synchronized alternately by what realize time synchronizing signal between clock server and clock client at the dedicated subcarriers channel time synchronizing signal of wire transmission medium, reduced the networking cost that is applied to time synchronized scheme in the existing base station transmits network that adopts the wire transmission medium.
Description of drawings
In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, accompanying drawing in describing below only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.
Fig. 1 is the gps time synchronization scenario network diagram that prior art provides;
Fig. 2 is the network diagram of the method for synchronizing time embodiment that provides of the embodiment of the invention;
Fig. 3 is the information interaction flow chart of the method for synchronizing time embodiment that provides of the embodiment of the invention;
Fig. 4 is a method embodiment flow chart of the method for synchronizing time that provides of the embodiment of the invention;
Fig. 5 a is an embodiment network diagram of the method for synchronizing time that is applied to the WIMAX mobile communication system that provides of the embodiment of the invention;
Fig. 5 b is an embodiment flow chart of the method for synchronizing time that is applied to the WIMAX mobile communication system that provides of the embodiment of the invention;
Fig. 6 is an embodiment schematic diagram of the time synchronized communication equipment that provides of the embodiment of the invention;
Fig. 7 is the structural representation of clock skew module among Fig. 6;
Fig. 8 is a system embodiment schematic diagram of the clock synchronization system that provides of the embodiment of the invention;
Fig. 9 is an embodiment schematic diagram of the clock server that provides of the embodiment of the invention.
Embodiment
The embodiment of the invention provides a kind of method for synchronizing time, system and time synchronous communication equipment.
In order to make those skilled in the art person understand the present invention program better, below in conjunction with the accompanying drawing in the embodiment of the invention, technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills should belong to the scope of protection of the invention not making the every other embodiment that is obtained under the creative work prerequisite.
The embodiment of the invention provides a kind of method for synchronizing time, comprising:
The mutual time synchronizing signal of clock client and clock server, obtain and described clock server between clock offset, described time synchronizing signal transmits by the dedicated subcarriers channel of wire transmission medium;
According to the described clock offset that obtains, adjust the clock of described clock client.
Wherein, described clock client and the mutual time synchronizing signal of clock server, obtain and described clock server between the clock skew measuring comprise:
The clock client receives and is sent by clock server, via the very first time synchronizing signal of communication main equipment, the transmission of communication slave unit, obtains the t time of advent of very first time synchronizing signal
2
The clock client receives and is sent by clock server, via second time synchronizing signal of communication main equipment, the transmission of communication slave unit, obtains the transmitting time t of very first time synchronizing signal from second time synchronizing signal
1
The clock client sends the 3rd time synchronizing signal, obtains the transmitting time t of the 3rd time synchronizing signal
3, the 3rd time synchronizing signal via communication slave unit, communication master transmissions to clock server;
The clock client receives and is sent by clock server, via the 4th time synchronizing signal of communication main equipment, the transmission of communication slave unit, obtains the time of reception t of the 3rd time synchronizing signal from the 4th time synchronizing signal
4
The clock client is according to t
1, t
2, t
3And t
4Calculate clock offset.
Described very first time synchronizing signal, second time synchronizing signal, the 3rd time synchronizing signal and the 4th time synchronizing signal transmit by the dedicated subcarriers channel of wire transmission medium;
When the dedicated subcarriers channel of described wire transmission medium was power line dedicated subcarriers channel, described communication main equipment was the power line communication main equipment, and described communication slave unit is the power line communication slave unit.When the dedicated subcarriers channel of described wire transmission medium was coaxial cable dedicated subcarriers channel, described communication main equipment was the coaxial cable communication main equipment, and described communication slave unit is the coaxial cable communication slave unit.
Described communication main equipment is the time synchronized communication equipment with the slave unit of communicating by letter, and also can be called the time synchronized communication main equipment slave unit of communicating by letter with time synchronized.
Expense is low, scope extensively, is easily installed and use advantages such as flexible because have for power line communication in the prior art (PLC, Power Line Communication), more and more receives publicity.Described PLC is meant and utilizes power line transmission data, voice and video signal.Described PLC technology is that the high-frequency signal of carrying information is loaded on the existing power line communication equipment, utilizes power line to transmit information, and the modulator-demodulator that receives information is separated high-frequency signal again, and is sent to equipment, transmits with realization information.The PLC technology does not need rewiring, only needs to utilize existing power line can realize data, multiple services carrying such as voice and video, advantage such as have that expense is low, scope extensively, is easily installed and use flexibly.One embodiment of the invention adopts power line communication technology exactly.
The network diagram of the method for synchronizing time embodiment that Fig. 2 provides for the embodiment of the invention, as shown in Figure 2, clock server is connected with the power line communication main equipment; The power line communication main equipment is connected by power line 30 with a plurality of power line communication slave units; Each power line communication slave unit is connected with a base station.Wherein clock server is as master clock, and the clock client is the base station, and the base station conduct is from clock.
Wherein said base station can be the little base station of family.
The information interaction flow chart of the method for synchronizing time embodiment that Fig. 3 provides for the embodiment of the invention, clock server be as master clock, and the clock client is as from clock, and described clock client is the base station, as shown in Figure 3, comprising:
S301: master clock sends very first time synchronizing signal to the power line communication main equipment.
S302: described power line communication main equipment receives very first time synchronizing signal, select power line dedicated subcarriers channel, very first time synchronizing signal is modulated on the described power line dedicated subcarriers channel, and the very first time synchronizing signal after the described modulation of power line transmission is to the power line communication slave unit.
S303: the power line communication slave unit demodulates very first time synchronizing signal from described power line dedicated subcarriers channel, revert to original very first time synchronizing signal, the very first time synchronizing signal after described original very first time synchronizing signal is encapsulated after the described encapsulation of transmission is extremely from clock.
S304: receive very first time synchronizing signal from clock, the t time of advent of record very first time synchronizing signal
2Thereby, obtain the t time of advent of very first time synchronizing signal from clock
2
S305: master clock sends second time synchronizing signal to the power line communication main equipment.
Wherein, the transmitting time t that comprises very first time synchronizing signal in second time synchronizing signal
1
S306: the power line communication main equipment receives second time synchronizing signal, select power line dedicated subcarriers channel, second time synchronizing signal is modulated on the described power line dedicated subcarriers channel, and second time synchronizing signal after the described modulation of power line transmission is to the power line communication slave unit.
S307: the power line communication slave unit demodulates second time synchronizing signal from power line dedicated subcarriers channel, revert to the second original time synchronizing signal, second time synchronizing signal after the described second original time synchronizing signal is encapsulated after the described encapsulation of transmission is extremely from clock.
S308: receive second time synchronizing signal from clock, from second time synchronizing signal, obtain the transmitting time t of very first time synchronizing signal
1
S309: send the 3rd time synchronizing signal to the power line communication slave unit from clock, from the transmitting time t of clock log the 3rd time synchronizing signal
3Thereby, obtain the transmitting time t of the 3rd time synchronizing signal
3
S310: the power line communication slave unit receives the 3rd time synchronizing signal, select power line dedicated subcarriers channel, the 3rd time synchronizing signal is modulated on the described power line dedicated subcarriers channel, and the 3rd time synchronizing signal after the described modulation of power line transmission is to the power line communication main equipment.
S311: the power line communication main equipment demodulates the 3rd time synchronizing signal from power line dedicated subcarriers channel, revert to the 3rd original time synchronizing signal, the 3rd time synchronizing signal after described original the 3rd time synchronizing signal is encapsulated after the described encapsulation of transmission is to master clock.
S312: master clock receives the 3rd time synchronizing signal, and master clock writes down the t time of advent of the 3rd time synchronizing signal
4Thereby master clock obtains the t time of advent of the 3rd time synchronizing signal
4
S313: master clock sends the 4th time synchronizing signal to the power line communication main equipment.
Wherein, the t time of advent that comprises the 3rd time synchronizing signal in the 4th time synchronizing signal
4
S314: the power line communication main equipment receives the 4th time synchronizing signal, select power line dedicated subcarriers channel, the 4th time synchronizing signal is modulated on the described power line dedicated subcarriers channel, and the 4th time synchronizing signal after the described modulation of power line transmission is to the power line communication slave unit.
S315: the power line communication slave unit demodulates the 4th time synchronizing signal from power line dedicated subcarriers channel, revert to the 4th original time synchronizing signal, the 4th time synchronizing signal after described the 4th original time synchronizing signal is encapsulated after the described encapsulation of transmission is extremely from clock.
S316: receive the 4th time synchronizing signal from clock, from the 4th time synchronizing signal, obtain the t time of advent of the 3rd time synchronizing signal
4
Below introduce a method embodiment of a kind of method for synchronizing time that the embodiment of the invention provides, wherein, master clock can be integrated in the clock server, can be integrated in the base station from clock, need GPS equipment be installed at each base station end, be that example describes with master clock and one from the time synchronized between clock only below.Fig. 4 shows the flow chart of this embodiment, comprising:
S401: receive the very first time synchronizing signal of the dedicated subcarriers channel of wire transmission medium from clock, obtain the t time of advent of very first time synchronizing signal
2
The dedicated subcarriers channel is meant the sub-carrier channels that is used for transmitting specially certain information in certain concrete technology.Employing can realize the embodiment of the invention as the dedicated subcarriers channel of the wire transmission medium of multi-transceiver technologies such as OFDM.Usually, the dedicated subcarriers channel of described wire transmission medium can have multiple, such as power line dedicated subcarriers channel or coaxial cable dedicated subcarriers channel, is that example describes with power line dedicated subcarriers channel below.
The transmission course of very first time synchronizing signal is as described below:
Master clock sends very first time synchronizing signal to the power line communication main equipment, and wherein the power line communication main equipment can be modulator-demodulator; The power line communication main equipment receives very first time synchronizing signal, select power line dedicated subcarriers channel, very first time synchronizing signal is modulated on the described power line dedicated subcarriers channel, to the power line communication slave unit, wherein the power line communication slave unit also can be modulator-demodulator through power line transmission; The power line communication slave unit demodulates very first time synchronizing signal from described power line dedicated subcarriers channel, reverts to original very first time synchronizing signal, is sent to from clock after described original very first time synchronizing signal is encapsulated; Receive very first time synchronizing signal from clock, the t time of advent of record very first time synchronizing signal
2Thereby, obtain the t time of advent of very first time synchronizing signal from clock
2
Very first time synchronizing signal is by the master clock cycle transmission, and it is every through sending very first time synchronizing signal two seconds one time to be defined as master clock.
Comprise master clock in the very first time synchronizing signal and choose the required clock attribute of algorithm.
Described selection power line dedicated subcarriers channel can adopt the method for default definition to select in the power line communication frequency spectrum resource of 2-28MHz, selects a sub-carrier channels in the power line communication frequency spectrum resource of described 2-28MHz as the dedicated subcarriers channel of transmission very first time synchronizing signal;
Described selection power line dedicated subcarriers channel also can according to quality of channel selective channel quality preferably the power line sub-carrier channels as power line dedicated subcarriers channel.The power line sub-carrier channels that described channel quality is good comprises the low-frequency range subcarrier in the 2-28MHz power line communication frequency spectrum resource, because the frequency of carrier wave is high more, it is big more to decay, and noise power can be big more, so the decay of low-frequency range subcarrier and noise power can be less, channel quality can be better; The channel quality of the sub-carrier channels in measuring low-frequency range subcarrier 2.0-3.5MHz or 4.0-7.0MHz is relatively good, is fit to the carrying time synchronizing signal.
S402: receive second time synchronizing signal of the dedicated subcarriers channel of wire transmission medium from clock, from second time synchronizing signal, obtain the transmitting time t of very first time synchronizing signal
1
Master clock sends second time synchronizing signal to the power line communication main equipment, and wherein the power line communication main equipment can be modulator-demodulator; The power line communication main equipment receives second time synchronizing signal, select power line dedicated subcarriers channel, second time synchronizing signal is modulated on the described power line dedicated subcarriers channel, to the power line communication slave unit, wherein the power line communication slave unit can be modulator-demodulator through power line transmission; The power line communication slave unit demodulates second time synchronizing signal from described power line dedicated subcarriers channel, reverts to the second original time synchronizing signal, is sent to from clock after the described second original time synchronizing signal is encapsulated; Receive second time synchronizing signal from clock, from second time synchronizing signal, obtain the transmitting time t of very first time synchronizing signal
1
Second time synchronizing signal is the signal of following of very first time synchronizing signal, and second time synchronizing signal is sent by master clock after the very first time, synchronizing signal was sent, and wherein comprises the transmitting time t of very first time synchronizing signal in second time synchronizing signal
1
Used power line dedicated subcarriers channel can be same power line sub-carrier channels when the very first time, synchronizing signal was modulated described in used power line dedicated subcarriers channel and the S401 when second time synchronizing signal was modulated, also can be different power line sub-carrier channels.If different power line sub-carrier channels selects the method for power line dedicated subcarriers channel to see the method for selecting power line dedicated subcarriers channel described in the S401 so described in the S402.
Not time-delay on the transmission path under the perfect condition just can be according to the transmitting time t of the very first time synchronizing signal of obtaining among described S401 and the S402
1With the t time of advent
2, calculate from the clock offset between clock and the master clock, thereby, reach principal and subordinate's clock synchronization according to the clock of clock offset adjustment from clock.But there is time-delay under the virtual condition on the transmission path, according to t
1And t
2The described clock offset that calculates is actual to have comprised master clock to the network delay from clock, so can not be according to directly by t under the virtual condition
1And t
2Resulting clock offset realize master clock with from clock synchronously, also should come the computing network time-delay in conjunction with the 3rd following time synchronizing signal and the 4th time synchronizing signal, thus obtain clock offset correct under the virtual condition realize master clock with from clock synchronously.
S403: from clock send the 3rd time synchronizing signal through the dedicated subcarriers Channel Transmission of wire transmission medium to master clock, and obtain the transmitting time t of the 3rd time synchronizing signal from clock
3
When the dedicated subcarriers channel of described wire transmission medium was power line dedicated subcarriers channel, the transmission course of the 3rd time synchronizing signal was as described below:
Send the 3rd time synchronizing signal to the power line communication slave unit from clock, wherein the power line communication slave unit can be modulator-demodulator, from the transmitting time t of clock log the 3rd time synchronizing signal
3Thereby, obtain the transmitting time t of the 3rd time synchronizing signal from clock
3The power line communication slave unit receives the 3rd time synchronizing signal, selects power line dedicated subcarriers channel, the 3rd time synchronizing signal is modulated on the described power line dedicated subcarriers channel, through power line transmission to the power line communication main equipment; The power line communication main equipment demodulates the 3rd time synchronizing signal from described power line dedicated subcarriers channel, reverts to the 3rd original time synchronizing signal, is sent to master clock after described original the 3rd time synchronizing signal is encapsulated; Master clock receives the 3rd time synchronizing signal, writes down the t time of advent of the 3rd time synchronizing signal
4
The 3rd time synchronizing signal after receiving very first time synchronizing signal from clock by being issued to master clock from clock.
The 3rd time synchronizing signal is used for the network delay request; The transmission of described the 3rd time synchronizing signal is independent the setting at interval, and the interval of general more described very first time synchronizing signal is long.
Used power line dedicated subcarriers channel can be same power line sub-carrier channels when the very first time, synchronizing signal was modulated described in used power line dedicated subcarriers channel and the S401 when the 3rd time synchronizing signal was modulated, also can be different power line sub-carrier channels.If different power line sub-carrier channels selects the method for power line dedicated subcarriers channel to see the method for selecting power line dedicated subcarriers channel described in the S401 so described in the S403.
S404: receive the 4th time synchronizing signal of the dedicated subcarriers channel of wire transmission medium from clock, from the 4th time synchronizing signal, obtain the t time of advent of the 3rd time synchronizing signal
4
After master clock received the 3rd time synchronizing signal, master clock sent the 4th time synchronizing signal to the power line communication main equipment, and wherein the power line communication main equipment can be modulator-demodulator; The power line communication main equipment receives the 4th time synchronizing signal, select power line dedicated subcarriers channel, the 4th time synchronizing signal is modulated on the described power line dedicated subcarriers channel, to the power line communication slave unit, wherein the power line communication slave unit also can be modulator-demodulator through power line transmission; The power line communication slave unit demodulates the 4th time synchronizing signal from described power line dedicated subcarriers channel, reverts to the 4th original time synchronizing signal, is sent to from clock after described the 4th original time synchronizing signal is encapsulated; Receive the 4th time synchronizing signal from clock, from the 4th time synchronizing signal, obtain the t time of advent of the 3rd time synchronizing signal
4
Wherein, the t time of advent that comprises the 3rd time synchronizing signal in the 4th time synchronizing signal
4
Used power line dedicated subcarriers channel can be same power line sub-carrier channels when the very first time, synchronizing signal was modulated among used power line dedicated subcarriers channel and the S201 when the 4th time synchronizing signal was modulated, also can be different power line sub-carrier channels.If different power line sub-carrier channels selects the method for power line dedicated subcarriers channel to see the method for selecting power line dedicated subcarriers channel described in the S401 so described in the S404.
S405: from clock according to t
1, t
2, t
3And t
4Calculate clock offset, adjust the clock of self according to described clock offset.
All have network delay under the virtual condition on the transmission path, promptly master clock is to from all existing network delay between the clock and between from the clock to the master clock.Master clock is to representing with Master_Slave_Delay that from the network delay between the clock network delay from the clock to the master clock is represented with Slave_Master_Delay.
Can utilize the clock offset offset of following formula calculating from clock:
offset＝[(t2-t1)-(t4-t3)]/2-(MasterSlave_Delay-Slave_MasterDelay)/2 (1)
Master_Slave_Delay in the formula (1) and Slave_Master_Delay are two-way time-delays.In the embodiment of the invention, the two-way delay inequality in the above-mentioned formula, i.e. the assembly average of (Master_Slave_Delay-Slave_Master_Delay) meets average and is 0 normal distribution.Therefore, under this situation, t
1, t
2, t
3And t
4Can average by repeatedly measuring, formula (1) can become like this:
offset＝[(t
2-t
1)-(t
4-t
3)]/2 (2)
From clock according to t
1, t
2, t
3And t
4Calculate clock offset offset, from the clock of clock according to described offset value adjustment self, thus synchronous with master clock.
Described t
1, t
2, t
3And t
4For (time, divide, second) absolute time.
Very first time synchronizing signal, second time synchronizing signal, the 3rd time synchronizing signal and the 4th time synchronizing signal are the absolute time signal.
Above-mentioned power line communication main equipment can be integrated in the described master clock, thereby master clock self also can have the function of above-mentioned power line communication main equipment.
Above-mentioned power line communication slave unit can be integrated in described from clock, thereby also can have the function of above-mentioned power line communication slave unit from clock self.
The method for synchronizing time that in the existing network each provides by the embodiment of the invention respectively from clock realize with master clock synchronously, and then realize between the clock synchronously.
In the prior art, unique time synchronized scheme that has been applied in the existing network is exactly the gps time synchronization scenario at present.The gps time synchronization scenario is realized time synchronized between the base station by an outdoor GPS equipment all is installed on each base station, but GPS equipment price costliness, so the networking cost of gps time synchronization scenario is very high.People thirst for solving high this problem of time synchronized scheme networking cost in the existing network that is applied to always, the IEEE1588V2 agreement has been proposed subsequently, but most equipment do not support the IEEE1588V2 agreement to realize time synchronized in backhaul transport in the existing network, though the IEEE1588V2 agreement is suggested, but also be in theory stage now, can not be applied in the existing network, still can not solve the high problem of time synchronized scheme networking cost in the existing network that is applied to that people thirst for solving always.
When it is found that the time synchronized scheme networking cost that is applied in the existing network is high, the technical staff tends to expect whether can share the number of saving GPS equipment by GPS equipment between the base station, thereby reduction networking cost, departed from understanding to time synchronized scheme in the existing network, and do not consider and adopt cheaply power line communication to realize low networking cost, thereby hindered the research and development of people in this technical field.
The embodiment of the invention the base station end realize without GPS equipment between the base station synchronously, but adopt power line communication to realize the low time synchronized scheme of networking cost.The embodiment of the invention adopts dedicated subcarriers Channel Modulation time synchronizing signal to transmit through power line on power line communications apparatus, makes processed that time synchronizing signal can be all timely, preferential; Time synchronizing signal adopts the dedicated subcarriers channel to transmit, can not take place congested, thereby reduced master clock and from the network delay between the clock, make time synchronizing signal arrive the destination faster, satisfy the requirement of timing tracking accuracy, realize quickly master clock and between clock synchronously.
Embodiment of the invention base station end is no longer installed GPS equipment, not only has the low advantage of networking cost, and for the gps time synchronization scenario, have indoor deployment simple relatively, maintain easily and advantage such as dependence reduction.
The embodiment of the invention can be applied to realize time synchronized in WIMAX, TD-SCDMA, CDMA, the LTE mobile communication system.
The WIMAX mobile communication system not only needs to satisfy time synchronized, and also very high to the requirement of timing tracking accuracy.
Below introduce the embodiment that the embodiment of the invention is applied to the WIMAX mobile communication system, Fig. 5 a shows the Time Synchronization Network schematic diagram that is applied to the WIMAX mobile communication system, and Fig. 5 b shows the flow chart of the method for synchronizing time that is applied to the WIMAX mobile communication system.Shown in Fig. 5 a, clock server is connected with LAN switch; Described LAN switch is connected by Ethernet 40 with the power line communication main equipment; Described power line communication main equipment is connected by power line 30 with a plurality of power line communication slave units; Each power line communication slave unit all is connected with a WIMAX base station.Wherein clock server is as master clock, and the conduct of WIMAX base station is from clock, and described WIMAX base station is the little base station of family.
Fig. 5 b shows the flow chart of described embodiment, and wherein, time synchronizing signal comprises very first time synchronizing signal, second time synchronizing signal, the 3rd time synchronizing signal and the 4th time synchronizing signal.Described embodiment comprises:
S501: clock server send very first time synchronizing signal through LAN switch to the power line communication main equipment;
Before clock server sent very first time synchronizing signal, clock server at first obtained high-precision absolute time;
Described very first time synchronizing signal is periodically sent by clock server.
Wherein, the power line communication main equipment can be modulator-demodulator.
S502: the power line communication main equipment receives very first time synchronizing signal, select power line dedicated subcarriers channel, very first time synchronizing signal is modulated on the described power line dedicated subcarriers channel, send very first time synchronizing signal after the described modulation by power line transmission to the power line communication slave unit that is connected with specific base;
Described selection power line dedicated subcarriers channel can adopt the method for default definition, also can select the low-frequency range carrier wave 2.0-3.5MHz of 2-28MHz power line communication frequency spectrum resource or the sub-carrier channels among the 4.0-7.0MHz dedicated subcarriers channel as transmission very first time synchronizing signal.
Wherein, the power line communication slave unit can be modulator-demodulator.
S503: the described power line communication slave unit that is connected with specific base receives the very first time synchronizing signal after the described modulation, demodulates very first time synchronizing signal from power line dedicated subcarriers channel, sends very first time synchronizing signal to the WIMAX base station;
The time of reception t of S504:WIMAX base station record very first time synchronizing signal
2
S505: clock server sends second time synchronizing signal to described WIMAX base station, and described WIMAX base station obtains the transmitting time t of very first time synchronizing signal from second time synchronizing signal
1Absolute time stab information;
Second time synchronizing signal is also finished from clock server to the transmission between described WIMAX base station through the flow process of S501 to S503.Wherein, second time synchronizing signal is the signal of following of very first time synchronizing signal, and second time synchronizing signal is sent by clock server after the very first time, synchronizing signal was sent, and comprises the transmitting time t of described synchronizing signal in second time synchronizing signal
1Absolute time stab information.
S506: described WIMAX base station sends the 3rd time synchronizing signal to clock server, and described WIMAX writes down the base station transmitting time t of the 3rd time synchronizing signal
3, clock server writes down the t time of advent of the 3rd time synchronizing signal
4
The transmission flow of the 3rd time synchronizing signal is opposite with very first time synchronizing signal, be to send by described WIMAX base station, modulate through the described power line communication slave unit that is connected with specific base, the 3rd time synchronizing signal is modulated on the power line dedicated subcarriers channel, the 3rd time synchronizing signal after the modulation by power line transmission to described power line communication main equipment; Described power line communication main equipment demodulates the 3rd time synchronizing signal from power line dedicated subcarriers channel, sends the 3rd time synchronizing signal to clock server through LAN switch.
S507: clock server receives the 3rd time synchronizing signal, sends the 4th time synchronizing signal to described WIMAX base station, and described WIMAX base station obtains the t time of advent of the 3rd time synchronizing signal from the 4th time synchronizing signal
4Absolute time stab information;
The 4th time synchronizing signal is also finished from clock server to the transmission between described WIMAX base station through the flow process of S501 to S503.The t time of advent that comprises the 3rd time synchronizing signal in the 4th time synchronizing signal
4Absolute time stab information.
S508: the t of described WIMAX base station by obtaining
1, t
2, t
3And t
4Calculate the clock offset offset of WIMAX base station;
Described clock offset can be through repeatedly measurements and calculations, progressively to converge near actual value.
Clock is adjusted according to described clock offset offset in the S509:WIMAX base station, and realization is synchronous with clock server.
Repeat the time synchronized that above-mentioned S501-S509 realizes clock server and all WIMAX base stations, thereby realize synchronous between the WIMAX base station.
The definition of the message field of described synchronizing signal and time-delay request signal is as shown in table 2:
Table 2
The definition of the message header in the table 2 is as shown in table 3:
Table 3
The preferred embodiment of the present invention adopts power line communication to realize the time synchronized scheme of low networking cost.The preferred embodiment of the present invention is by adopting dedicated subcarriers Channel Modulation time synchronizing signal on power line communications apparatus, be modulated at time synchronizing signal on the dedicated subcarriers channel by power line transmission again, make that time synchronizing signal can be timely, preferential employing dedicated channel is transmitted, time synchronizing signal can not take place congested, thereby reduced the network delay between clock server and WIMAX base station, make time synchronizing signal arrive the destination faster, satisfy the requirement of timing tracking accuracy, realize quickly between clock server and WIMAX base station synchronously.
The preferred embodiment of the present invention need not installed GPS equipment at each WIMAX base station end, not only have the low advantage of networking cost, and for the gps time synchronization scenario, have indoor deployment simple relatively, maintain easily and advantage such as dependence reduction.
The embodiment of the invention is that the modulation time synchronizing signal is realized time synchronized on power line dedicated subcarriers channel, and described time synchronizing signal is the absolute time signal.
The embodiment of the invention has just realized Frequency Synchronization on the basis of realizing time synchronized.
Below introduce the embodiment of a kind of time synchronized communication equipment that the embodiment of the invention provides, Fig. 6 shows the schematic diagram of this embodiment, comprising:
Select module 602, be used for after first receiver module 601 receives described time synchronizing signal, selecting the dedicated subcarriers channel of wire transmission medium.
First sending module 604 is used for the time synchronizing signal after described clock server sends described first processing module, 603 modulation treatment.
Described time synchronized communication equipment further comprises:
Second receiver module 605 is used for the time synchronizing signal that the receive clock server sends to the clock client, and the time synchronizing signal that described clock server sends to the clock client transmits by the dedicated subcarriers channel of wire transmission medium.
Second processing module 606 is used for the time synchronizing signal that described second receiver module 605 receives is carried out demodulation process.
Clock skew module 608, be used for by with the mutual time synchronizing signal of described clock server, obtain and described clock server between clock offset, wherein, described time synchronizing signal comprises the time synchronizing signal that sends to clock server by described first sending module 604, and the time synchronizing signal that sends to the clock client by the clock server that described second receiver module 607 receives.
Adjusting module 609 is used for the described clock offset that obtains according to described clock skew module 608, adjusts the clock of described clock client.
Wherein, described clock skew module 608 and described adjusting module 609 are the functional module of clock client.
Described time synchronized communication equipment can be modulator-demodulator, also can be integrated in the base station, and described base station can comprise clock client and modulator-demodulator.
The described time synchronizing signal that sends to clock server by described first sending module 603 comprises: the 3rd time synchronizing signal, the time synchronizing signal that the described clock server that receives by described second receiver module 606 sends to the clock client comprises very first time synchronizing signal, second time synchronizing signal and the 4th time synchronizing signal.
Fig. 7 is the structural representation of clock skew module among Fig. 6, and as shown in Figure 7, described clock skew module 608 comprises:
The 3rd subelement 6083 is used to obtain the transmitting time t of the 3rd time synchronizing signal
3
The 4th subelement 6084 is used for obtaining from the 4th time synchronizing signal the time of reception t of the 3rd time synchronizing signal
4
Obtain subelement 6085, be used for according to described t
1, t
2, t
3And t
4Obtain clock offset.
Below introduce a system embodiment of a kind of clock synchronization system that the embodiment of the invention provides, comprise time synchronized communication slave unit 804, and clock server 801.Wherein, time synchronized communication slave unit 804 can be the time synchronized communication equipment of describing among the embodiment of front, repeats no more herein.In addition, clock server 801 is used for to time synchronized communication slave unit 804 transmitting time synchronizing signals, and time of reception synchronous communication slave unit 804 is to the time synchronizing signal of the dedicated subcarriers Channel Transmission of passing through the wire transmission medium of clock server transmission.
Further, this system can also comprise: wire transmission medium 803 (such as power line) is used to transmit the time synchronizing signal on the dedicated subcarriers channel that is modulated to the wire transmission medium.This time synchronizing signal comprises: very first time synchronizing signal, second time synchronizing signal, the 3rd time synchronizing signal and the 4th time synchronizing signal.
In addition, this system can also comprise time synchronized communication main equipment 802, is used for the time synchronizing signal that the receive clock server sends to time synchronized communication slave unit 804; After receiving time synchronizing signal, select the dedicated subcarriers channel of wire transmission medium; On the dedicated subcarriers channel of the wire transmission medium of selecting, the time synchronizing signal that receives is carried out modulation treatment; Time synchronizing signal after time synchronized communication slave unit 804 sends modulation treatment.Wherein, clock server comprises very first time synchronizing signal, second time synchronizing signal and the 4th time synchronizing signal to the time synchronizing signal that time synchronized communication slave unit 804 sends.
Time synchronized communication main equipment 802 can also be used for the time synchronizing signal of time of reception synchronous communication slave unit 804 to the dedicated subcarriers Channel Transmission of passing through the wire transmission medium of clock server 801 transmissions; The time synchronizing signal that receives is carried out demodulation process, the time synchronizing signal after clock server 801 sends demodulation process.Wherein, the time synchronizing signal after clock server 801 sends demodulation process is the 3rd time synchronizing signal.
The embodiment of the invention does not adopt GPS equipment at the base station end, makes networking cost reduce; Can also make indoor deployment simple relatively, maintain easily.
Below introduce an embodiment of a kind of clock server that the embodiment of the invention provides, Fig. 9 shows the schematic diagram of this embodiment, and described clock server 90 comprises:
First sending module 902 is used to send very first time synchronizing signal, second time synchronizing signal and the 4th time synchronizing signal to processing module 903;
Above-described embodiment of the present invention does not constitute the qualification to protection range of the present invention.Any modification of being done within the spirit and principles in the present invention, be equal to and replace and improvement etc., all should be included within the claim protection range of the present invention.
Claims (10)
1, a kind of method for synchronizing time is characterized in that, comprising:
The mutual time synchronizing signal of clock client and clock server, obtain and described clock server between clock offset, described time synchronizing signal transmits by the dedicated subcarriers channel of wire transmission medium;
According to the described clock offset that obtains, adjust the clock of described clock client.
2, method for synchronizing time according to claim 1 is characterized in that, described clock client and the mutual time synchronizing signal of clock server, obtain and described clock server between clock offset comprise:
The clock client receives to be sent by clock server, in the very first time synchronizing signal of the dedicated subcarriers channel of wire transmission medium, obtains the t time of advent of very first time synchronizing signal
2
The clock client receives to be sent by clock server, at second time synchronizing signal of the dedicated subcarriers channel of wire transmission medium, obtains the transmitting time t of very first time synchronizing signal from second time synchronizing signal
1
The clock client sends the 3rd time synchronizing signal to clock server, and the clock client is obtained the transmitting time t of the 3rd time synchronizing signal
3
The clock client receives to be sent by clock server, at the 4th time synchronizing signal of the dedicated subcarriers channel of wire transmission medium, obtains the time of reception t of the 3rd time synchronizing signal from the 4th time synchronizing signal
4
The clock client is according to described t
1, t
2, t
3And t
4Calculate clock offset.
3, method for synchronizing time according to claim 1 and 2 is characterized in that, the dedicated subcarriers channel of described wire transmission medium comprises power line dedicated subcarriers channel or coaxial cable dedicated subcarriers channel.
4, method for synchronizing time according to claim 3 is characterized in that, described clock client is integrated in the base station.
5, a kind of time synchronized communication equipment is characterized in that, comprising:
First receiver module is used for the time synchronizing signal that the receive clock client sends to clock server;
Select module, be used for after first receiver module receives described time synchronizing signal, selecting the dedicated subcarriers channel of wire transmission medium;
First processing module is used for the dedicated subcarriers channel at described wire transmission medium, and the time synchronizing signal that described first receiver module is received carries out modulation treatment;
First sending module is used for the time synchronizing signal after described clock server sends the described first processing module modulation treatment.
6, time synchronized communication equipment according to claim 5 is characterized in that, also comprises:
Second receiver module is used for the time synchronizing signal that the receive clock server sends to the clock client, and the time synchronizing signal that described clock server sends to the clock client transmits by the dedicated subcarriers channel of wire transmission medium;
Second processing module is used for the time synchronizing signal that described second receiver module receives is carried out demodulation process;
Second sending module is used for the time synchronizing signal after described clock client sends the described second processing module demodulation process.
7, time synchronized communication equipment according to claim 6 is characterized in that, also comprises the clock client, and described clock client comprises:
The clock skew module, be used for by with the mutual time synchronizing signal of described clock server, obtain and described clock server between clock offset, wherein, described time synchronizing signal comprises the time synchronizing signal that sends to clock server by described first sending module, and the time synchronizing signal that sends to the clock client by the clock server that described second receiver module receives;
Adjusting module is used for the described clock offset that obtains according to described clock skew module, adjusts the clock of described clock client.
8, time synchronized communication equipment according to claim 7, it is characterized in that, the described time synchronizing signal that sends to clock server by described first sending module comprises: the 3rd time synchronizing signal, and the time synchronizing signal that the described clock server that receives by described second receiver module sends to the clock client comprises very first time synchronizing signal, second time synchronizing signal and the 4th time synchronizing signal;
Described clock skew module comprises:
First subelement is used to obtain the t time of advent of very first time synchronizing signal
2
Second subelement is used for obtaining from second time synchronizing signal transmitting time t of very first time synchronizing signal
1
The 3rd subelement is used to obtain the transmitting time t of the 3rd time synchronizing signal
3
The 4th subelement is used for obtaining from the 4th time synchronizing signal the time of reception t of the 3rd time synchronizing signal
4
Obtain subelement, be used for according to described t
1, t
2, t
3And t
4Obtain clock offset.
9, a kind of clock synchronization system, it is characterized in that, comprise as time synchronized communication slave unit as each described time synchronized communication equipment of claim 5-8, and clock server, wherein, described clock server is used for receiving the time synchronizing signal of described time synchronized communication slave unit to the dedicated subcarriers Channel Transmission of passing through the wire transmission medium of clock server transmission to described time synchronized communication slave unit transmitting time synchronizing signal.
10, clock synchronization system according to claim 9 is characterized in that, also comprises: time synchronized communication main equipment is used to receive the time synchronizing signal that described clock server sends to described time synchronized communication slave unit; After receiving described time synchronizing signal, select the dedicated subcarriers channel of wire transmission medium; On the dedicated subcarriers channel of described wire transmission medium, the described time synchronizing signal that receives is carried out modulation treatment; Time synchronizing signal after described time synchronized communication slave unit sends described modulation treatment.
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