A kind of precompensation method of the Doppler for up channel
Technical field
The present invention relates to the mobile communication technology field, relate in particular to a kind of precompensation method of the Doppler for up channel.
Background technology
Along with China Railway High-speed is constantly built and raises speed, carry out high-quality communication and become problem demanding prompt solution on high ferro.
The overlay network of high ferro comprises global system for mobile communications (GSM), Wideband Code Division Multiple Access (WCDMA) (WCDMA) system, code division multiple access (CDMA) system etc. at present.It is low that these networks exist transmission data rate, and cutting off rate is high, the problems such as poor user experience.Long Term Evolution project (LTE) system of rising has higher speed, higher spectrum efficiency, characteristics such as carrier bandwidths and better system compatibility more flexibly, fully meet the demand of broadband wireless access, really having realized the fusion of fixed network and mobile network, is therefore the inexorable trend of high ferro Communication Development to LTE evolution.
LTE can provide simply, the network of efficient, low time delay, low cost, can provide safe speech and data service simultaneously.In addition, the network architecture of LTE based on all-IP, allow the car-ground communication system that telecom operators and railway operator joint development are unified, and reuse website and the equipment of having disposed, the cost of reducing investment outlay.Because the LTE system has above advantage, therefore the high-speed railway wide-band communication system on the basis based on TD_LTE will be the high ferro communication system developing direction in future.
One of problem that needs solution in high ferro communication is that the closure of bullet train is fine, and the penetration loss of signal is larger.In order to solve the problem of car body penetration loss, can adopt the mode of train base station.The train base station comprises and is arranged on the first transceiver outside the high ferro compartment and is arranged on the second transceiver in compartment.The unified sending and receiving that carries out signal of the first transceiver and ground Remote Radio Unit (RRU), the UE on train with railway car in the second transceiver communicate.
Another problem existed in high ferro communication is the Doppler frequency shift that high-speed motion causes, the high ferro channel model is generally Rice channel, and the energy in direct projection footpath is very strong, so in high ferro communication, mainly consider by the caused Doppler frequency shift in direct projection footpath, and do not consider doppler spread.
The consequence of Doppler frequency shift is to make the reception signal frequency be offset, and causes the signal quality variation.In the LTE system, during the uplink business datum, each time slot only has a row pilot tone.And high ferro is in operation because speed is higher, can produces the Doppler frequency deviation expansion, thereby make channel variation very fast.In each time slot (5ms), only have a row pilot tone can't meet the requirement of channel estimating.So, under high-speed case, if do not take appropriate measures, up user data can't correctly receive.
Summary of the invention
The invention provides a kind of precompensation method of the Doppler for up channel, improve the signal transmission quality of up channel.
A kind of precompensation method of the Doppler for up channel that the embodiment of the present invention provides, comprise the steps:
A, user equipment (UE) receive the descending sub frame from base station, estimate the descending sub frame frequency deviation;
B, UE carry out frequency deviation pre-compensation according to described descending sub frame frequency deviation to the sub-frame of uplink that will send, then send sub-frame of uplink.
Preferably, before steps A, further comprise: the GPS equipment of holding by UE carries out the calibration of UE end crystal oscillator frequency, and the frequency of UE and the frequency of base station are consistent;
Described descending sub frame frequency deviation is the frequency deviation of descending sub frame frequency with respect to crystal oscillator frequency.
Preferably, described descending sub frame frequency deviation is F, and frequency deviation pre-compensation is-F.
Preferably, described UE is the train base station or carries out the equipment of radio communication with ground base station.
As can be seen from the above technical solutions, UE carries out sending sub-frame of uplink after frequency deviation pre-compensation to the sub-frame of uplink that will send again, and can avoid the problem of the quality of uplink signal variation that causes due to Doppler frequency shift that the UE high-speed mobile causes.This scheme is particularly useful for the radio communication on bullet train.
The accompanying drawing explanation
A kind of precompensation method of the Doppler for up channel schematic flow sheet that Fig. 1 provides for the embodiment of the present invention.
Embodiment
Because the data of all users on high ferro are received and dispatched (below the train base station referred to as UE) by the train base station, and then communicate with base station, so can think in each ascending-descending subframes and basically can have the business datum of UE to be sent or receive, the Doppler frequency deviation of up-downgoing is basic identical.Basic thought of the present invention is that the Doppler frequency deviation by descending estimation carries out the Doppler frequency deviation precompensation to the data of up transmission.
Clearer for the know-why, characteristics and the technique effect that make technical solution of the present invention, below in conjunction with specific embodiment, the present invention program is described in detail.
In embodiments of the present invention, at first need to GPS equipment be installed at the UE end, carry out the calibration of the crystal oscillator frequency of UE by GPS, the frequency of UE and the frequency of ground base station are consistent.
After UE receives the downlink data from ground base station, advanced line frequency is estimated partially, because the UE end has been installed GPS, crystal oscillator and the ground base station crystal oscillator of UE end are aimed at, so can estimate the Doppler frequency shift of introducing due to the UE motion in transmission by downlink data.Then up transmitted signal is carried out to the precompensation of frequency deviation according to the Doppler frequency shift obtained, eliminate the impact of Doppler frequency shift.
A kind of precompensation method of the Doppler for up channel flow process that the embodiment of the present invention provides as shown in Figure 1, comprises the steps:
Step 101: the GPS equipment of holding by UE carries out the calibration of the crystal oscillator frequency of UE end, and the frequency of UE end and the frequency of ground base station are consistent.
After step 102:UE receives the descending sub frame of ground base station transmission, according to the descending sub frame received, carry out the frequency deviation estimation, estimate the frequency deviation F with respect to the crystal oscillator standard frequency.This frequency deviation is the UE caused Doppler frequency shift F that moves.
Step 103:UE carries out precompensation frequency deviation-F to the sub-frame of uplink that will send, then sends sub-frame of uplink.
Owing in the signal transmission, can introducing the Doppler frequency shift of F, with precompensation, frequency deviation-F just in time offsets, so the frequency deviation of the signal that the base station termination is received will be very little.
Step 104: ground base station carries out the operations such as equilibrium, demodulation, decoding to the sub-frame of uplink received, and obtains last reception data.
The present invention program, except being applicable to communicating by letter of UE on high ferro and ground base station, also goes for the situation of UE and the base station communication of other high-speed motions.
The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of making, be equal to replacement, improvement etc., within all should being included in the scope of protection of the invention.