CN100531020C - Method for realizing pilot frequency in wireless communication system - Google Patents

Method for realizing pilot frequency in wireless communication system Download PDF

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CN100531020C
CN100531020C CNB2005101130130A CN200510113013A CN100531020C CN 100531020 C CN100531020 C CN 100531020C CN B2005101130130 A CNB2005101130130 A CN B2005101130130A CN 200510113013 A CN200510113013 A CN 200510113013A CN 100531020 C CN100531020 C CN 100531020C
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pilot
frequency
carrier frequency
ofdm symbol
pilot carrier
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CN1852069A (en
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曲秉玉
李洋
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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Abstract

This invention discloses a realization method for pilot frequency in the radio communication system including: selecting more than one OFDM symbols in each sub-frame to carry the pilot signals and setting an offset difference of the pilot frequency, generating a FH sequence set based on the designed interval of the pilot frequency and determining the offset of the pilot frequency of the first OFDM symbol of the carried pilot signals in each sub-frame by every FH sequence to determine the sub-carrier distribution on all OFDM symbols carrying pilot frequency signals in each sub-frame to get a pattern set, assigning a pattern to each area and emitting pilot signals in the area based on the pattern.

Description

The implementation method of pilot tone in a kind of wireless communication system
Technical field
The present invention relates to wireless communication technology, refer to the implementation method of pilot tone in a kind of wireless communication system especially.
Background technology
Owing to can overcome interference between the sub-district preferably, just the enhancement techniques as 3-G (Generation Three mobile communication system) is adopted by increasing normal structure based on the wireless communication system of orthogonal frequency division multiplexi (OFDM).In the OFDM technology, each OFDM symbol comprises one section Cyclic Prefix, to avoid the interference between the symbol.Simultaneously, whole frequency band is divided into a plurality of subcarriers, and user data is mapped on the corresponding subcarrier and sends.Because each subcarrier can be approximated to be Dan Jing under the situation of small scale decline,, the OFDM technology disturbs so can overcoming multipath.Just, adopt the communication system of OFDM technology, its data are to be carried on different OFDM symbols and the subcarrier to transmit, and promptly make up time-frequency plane with OFDM symbol and subcarrier as two-dimensional coordinate, so the OFDM technology has good interference free performance.
Identical with other wireless communication system, also need to launch pilot signal based on the wireless communication system of OFDM technology.The pilot signal of ofdm system is generally known signal, these known signals are distributed on the time-frequency plane according to certain pilot frequency design, receiver obtains the sampled value of channel on different time and frequency by pilot signal, and carry out time domain and frequency domain interpolation according to these sampled values, finally obtain the channel estimation value on the whole time-frequency plane.In order to guarantee the accuracy of channel estimating, the OFDM symbol of pilot frequency design and subcarrier distribute should satisfy the time-frequency two-dimensional sampling thheorem, and promptly pilot signal is separated with certain limitation between on time domain and the frequency domain.At present, the pilot frequency system that adopts in the OFDM technology has following several:
(1) time-division pilot tone
What Fig. 1 showed is the time-division pilot frequency system that provides among the 3GPP WG1 R1-050853, this method is specially: (TTI) is in the subframe at each Transmission Time Interval, first OFDM symbol place, subcarrier with fixed intervals are defined as the running time-frequency resource that pilot signal takies, and using determined running time-frequency resource emission pilot signal, the grey square among Fig. 1 is pilot channel.
Because communicating control information is generally understood in the beginning position of signal each TTI of when emission, thus the benefit of this method be, guarantee that as much as possible the channel of pilot signal and control information use is adjacent.Receiver is after utilizing pilot signal to finish channel estimating, can in time carry out demodulation to user's control information according to estimated result, and whether carry out subsequent operation by the control information after demodulation decision, if do not need then enter resting state, thereby reach purpose of power saving.But the pilot frequency design number that this method can provide is less, and different sub-districts can only be selected to use in limited pilot frequency design, so can't satisfy the requirement of the anti-Pilot Interference in minizone.
(2) utilize frequency hop sequences to produce pilot frequency design, this method is specially:
1) on single TTI, equally spaced selects the OFDM symbol that is used to be provided with pilot signal, and be respectively each OFDM symbol of selecting according to frequency hop sequences and determine pilot carrier frequency biasing, on the OFDM symbol that each is selected, select the subcarrier of pilot signal use at interval, thereby generate required pilot frequency design set according to determined pilot carrier frequency biasing and fixing pilot carrier frequency.
Shown in Figure 2 is that { 0,1,3,2} generates, pilot carrier frequency is spaced apart a pilot frequency design of 4 to the employing frequency hop sequences, and the grey square is pilot channel.Wherein, the pilot carrier frequency of first OFDM symbol is biased to 0, the pilot carrier frequency of second OFDM symbol is biased to 1, and the pilot carrier frequency biasing of these two OFDM symbols is uncorrelated, and promptly single TTI is provided with the pilot carrier frequency of the OFDM symbol of pilot signal and setovers uncorrelated mutually.
2) a plurality of pilot frequency designs that will generate are distributed to the different districts use, thereby the pilot channel that reduces between the neighbor cell disturbs.
Though it is many as far as possible that this pilot frequency system can guarantee the pilot frequency design number, thereby satisfy the anti-Pilot Interference requirement of minizone, but because the pilot signal in each pilot frequency design is evenly distributed on the OFDM symbol of a TTI, after receiver must receive whole pilot signals, just can carry out the control channel demodulation, so can't satisfy the demand of terminal power saving.
Summary of the invention
In view of this, main purpose of the present invention is to provide the implementation method of pilot tone in a kind of wireless communication system, under the situation that guarantees receiving terminal power saving and good channel estimating performance as far as possible, can provide a plurality of pilot frequency designs to distribute to different districts, thereby reduce the Pilot Interference of minizone.
For achieving the above object, technical scheme of the present invention specifically is achieved in that
The implementation method of pilot tone in a kind of wireless communication system, this method comprises:
An initial above OFDM symbols carry pilot signal in a, selected each subframe, and set the pilot carrier frequency bias difference of selecting between the OFDM symbol;
B, generate the frequency hop sequences set at interval according to the pilot carrier frequency that is provided with, and determine the pilot carrier frequency biasing of first OFDM symbol of the carrying pilot signal of each subframe in the system by the frequency hop sequences in the described set, according to the pilot carrier frequency biasing of fixing pilot carrier frequency interval, first OFDM symbol and the pilot carrier frequency bias difference between the OFDM symbol, determine in each subframe that the subcarrier on all OFDM symbols of carrying pilot signal distributes, and obtains the pilot frequency design set;
C, the pilot frequency design that obtains for step b of each cell allocation are launched pilot signal according to the pilot frequency design that is distributed in the sub-district.
The method of the OFDM symbol of the described selected carrying pilot signal of step a is: select in each subframe from least two of initial OFDM sign-on continuous OFDM symbols.
Described frequency hop sequences is a Coase tower sequence, and then the described method that generates frequency hop sequences set at interval according to pilot carrier frequency of step b is:
B1, generate the Coase tower sequence that comprises an above element, the element of this Coase tower sequence is carried out the time cyclic shift, generate an above time shift sequence according to pilot carrier frequency primitive root at interval;
B2, all time shift sequences that step b1 is generated are carried out frequency shift one by one, and with sequential element with pilot carrier frequency delivery at interval, be that each time shift sequence generates an above frequency shift sequence.
The time shift sequence number that generates among the step b1 equals Coase tower sequential element number.
The method of the pilot carrier frequency of the first OFDM symbol of the carrying pilot signal of each subframe biasing is in the described definite system of step b:
According to the frame number of all subframes in the system, the order of elements in the Coase tower sequence is set to the pilot carrier frequency biasing of first OFDM symbol of the carrying pilot signal of corresponding frame.
The described method of determining that each subframe sub-carriers distributes of step b is:
According to the pilot carrier frequency biasing of pilot carrier frequency interval and described first OFDM symbol, determine the subcarrier that pilot signal takies on described first OFDM symbol;
According to the pilot carrier frequency biasing on other OFDM symbol of the pilot carrier frequency biasing of described first OFDM symbol and the definite carrying of the pilot carrier frequency bias difference pilot signal between the OFDM symbol, by the pilot carrier frequency biasing on pilot carrier frequency interval and the OFDM symbol, determine the subcarrier that pilot signal takies on corresponding OFDM symbol.
Step c is described for the method for cell allocation pilot frequency design to be: in the pilot frequency design set, adopting at random, scrambler is that respective cell is selected pilot frequency design.
As seen from the above technical solution, the implementation method of pilot tone in this wireless communication system of the present invention, an above OFDM symbol initial at each TTI is provided with pilot signal, so receiver can utilize pilot signal to demodulate control information as early as possible, and whether enter resting state according to control information decision, thereby save the unnecessary reception stand-by period, reach purpose of power saving.
In addition, this method determines to be provided with among each TTI the pilot carrier frequency bias difference between the OFDM symbol of pilot signal according to the actual channel environment, determine the pilot carrier frequency biasing according to frequency hop sequences for the first OFDM symbol that is provided with pilot signal among each TTI, and in each TTI, be provided with on the OFDM symbol of pilot signal, according to fixing pilot carrier frequency interval and pilot carrier frequency biasing and the pilot carrier frequency bias difference of determining, the subcarrier that selected pilot signal is used, thereby obtain required pilot frequency design set, include more pilot frequency design in this set.
In addition, this method can also be specified or the different pilot frequency design of Random assignment for neighbor cell, thereby guarantees that the Pilot Interference between the sub-district is less.
Description of drawings
Fig. 1 is the schematic diagram of time-division pilot tone in the prior art;
The pilot frequency design schematic diagram of Fig. 2 for utilizing frequency hop sequences to generate in the prior art;
Fig. 3 is the realization flow of pilot frequency system among the present invention;
Fig. 4 is the pilot frequency design schematic diagram in a preferred embodiment of the present invention.
Embodiment
For making purpose of the present invention, technical scheme and advantage clearer, below with reference to the accompanying drawing embodiment that develops simultaneously, the present invention is described in more detail.
The realization flow of pilot frequency system specifically may further comprise the steps as shown in Figure 3 among the present invention:
Step 301, a selected initial above OFDM symbol of each TTI are provided with pilot signal on selected OFDM symbol, and determine to be provided with among each TTI the pilot carrier frequency bias difference between the OFDM symbol of pilot signal according to the actual channel environment.
In this step, the method for selected OFDM symbol is comparatively various, and preferable mode is to select in each subframe from two of initial OFDM sign-on continuous OFDM symbols carry pilot signals, thereby can reach purpose of power saving preferably.In addition, if required pilot frequency design number is more, and for more excellent channel estimating performance is provided, can select three or three above OFDM symbols to carry pilot signal.
Step 302, determine the pilot carrier frequency biasing for the first OFDM symbol that is provided with pilot signal among each TTI according to frequency hop sequences set, and on the OFDM of each TTI symbol, setover and the pilot carrier frequency bias difference according to fixing pilot carrier frequency interval and the pilot carrier frequency of determining, the sub-carrier positions at selected pilot signal place generates the required set that comprises a plurality of pilot frequency designs on time-frequency plane.
The pilot frequency design schematic diagram that shown in Figure 4 is in a preferred embodiment of the present invention, the grey square among Fig. 4 is pilot channel.The pilot carrier frequency of this pattern is spaced apart 4, and the pilot carrier frequency bias difference of two OFDM symbols is 2.
Lift the method for instantiation description of step 301~302 described generation pilot frequency designs below, the frequency hop sequences that adopts in this example is Coase tower (Costas) sequence.Initial two continuous OFDM symbols carry pilot signals among selected each TTI, the pilot carrier frequency on the single OFDM symbol is spaced apart 7, and the pilot carrier frequency bias difference between two OFDM symbols is 3, and the generative process of pilot frequency design is as follows:
A, determine pilot carrier frequency primitive root at interval, described primitive root is a basic conception of number theory.Because pilot carrier frequency is spaced apart 7,3 is primitive roots of 7 on mathematics, thus by the Costas sequences of 3 generations be 3,2,6,4,5,1}.Here, how generating the Costas sequence according to primitive root is prior art.
B, the Costas sequence that step a is generated are carried out the time cyclic shift, and described time cyclic shift refers to all elements in the sequence is moved forward or backward, generate 2,6,4,5,1,3}, 6,4,5,1,3,6 sequences such as 2}.
C, with all 6 sequences by frequency shift mould 7, described frequency shift refers to each element value in the sequence is added 1, finally obtain 3,0,5,6,2,42 different sequences such as 4}.
D, obtain corresponding pilot frequency design according to the sequence among the step c.
Such as, { 3,2,6,4,5,1} can determine, the pilot carrier frequency of first OFDM symbol is biased to 3 among the 1st TTI according to sequence.Because the pilot carrier frequency bias difference of two OFDM symbols is 3, then the pilot carrier frequency of second OFDM symbol is biased to 6, and promptly the pilot frequency design of the 1st TTI is (3,6).
Similarly, the pilot frequency design of the 2nd TTI is (2,5), and the pilot frequency design of the 3rd TTI is (6,2), the pilot frequency design of the 4th TTI is (4,0), and the pilot frequency design of the 5th TTI is (5,1), the pilot frequency design of the 6th TTI is (1,4), and the pilot frequency design of the follow-up TTI in this sub-district repeats to be provided with according to above-mentioned rule.
Find out that from said process be used to carry between the OFDM symbol of pilot signal independent among each TTI, in case the pilot carrier frequency offset control of first OFDM symbol is good, the biasing of the pilot carrier frequency of all the other OFDM symbols is also fixing among this TTI.
Step 303, be the adjacent different pilot frequency design of each cell allocation, and on the running time-frequency resource of this pilot frequency design correspondence, launch pilot signal.
Sequence set self characteristics according to step 302 generation, intersection point in the group between the sequence has one at most, so pilot frequency design at most per 6 TTI has an intersection point, promptly the maximum Pilot Interference between the neighbor cell is 1/6, so can guarantee that interfering with each other of pilot tone between the sub-district is less.
In addition, when being the cell allocation pilot frequency design, can specify in advance, also can utilize the scrambler that produces at random to distribute according to systems organization.Such as, when optional pilot frequency design had four, get 2 yuan of scrambler sequence last two, then this scrambler can produce one of them of 0,1,2,3 these four values arbitrarily, thereby determined certain sub-district to adopt which in four kinds of pilot frequency designs.Different sub-districts can adopt different scramblers to select pilot frequency design, thereby this sub-district is reduced greatly to the Pilot Interference of its neighbor cell.
By the above embodiments as seen, the implementation method of pilot tone in this wireless communication system of the present invention, an above OFDM symbol initial at each TTI is provided with pilot signal, so receiver can utilize pilot signal to demodulate control information as early as possible, thereby save the unnecessary reception stand-by period, reach purpose of power saving, performance for estimating channel is guaranteed.In addition, this method can provide a plurality of pilot frequency designs to distribute to different districts and use, thereby reduces the Pilot Interference of minizone.

Claims (7)

1, the implementation method of pilot tone in a kind of wireless communication system is characterized in that this method comprises:
An initial above OFDM symbols carry pilot signal in a, selected each subframe, and set the pilot carrier frequency bias difference of selecting between the OFDM symbol;
B, generate the frequency hop sequences set at interval according to the pilot carrier frequency that is provided with, and determine the pilot carrier frequency biasing of first OFDM symbol of the carrying pilot signal of each subframe in the system by the frequency hop sequences in the described set, according to the pilot carrier frequency biasing of fixing pilot carrier frequency interval, first OFDM symbol and the pilot carrier frequency bias difference between the OFDM symbol, determine in each subframe that the subcarrier on all OFDM symbols of carrying pilot signal distributes, and obtains the pilot frequency design set;
C, the pilot frequency design that obtains for step b of each cell allocation are launched pilot signal according to the pilot frequency design that is distributed in the sub-district.
2, method according to claim 1 is characterized in that, the method for the OFDM symbol of the described selected carrying pilot signal of step a is: select in each subframe from least two of initial OFDM sign-on continuous OFDM symbols.
3, method according to claim 1 is characterized in that, described frequency hop sequences is a Coase tower sequence, and then the described method that generates frequency hop sequences set at interval according to pilot carrier frequency of step b is:
B1, generate the Coase tower sequence that comprises an above element, the element of this Coase tower sequence is carried out the time cyclic shift, generate an above time shift sequence according to pilot carrier frequency primitive root at interval;
B2, all time shift sequences that step b1 is generated are carried out frequency shift one by one, and with sequential element with pilot carrier frequency delivery at interval, be that each time shift sequence generates an above frequency shift sequence.
4, method according to claim 3 is characterized in that, the time shift sequence number that generates among the step b1 equals Coase tower sequential element number.
5, method according to claim 3 is characterized in that, the method for the pilot carrier frequency of the first OFDM symbol of the carrying pilot signal of each subframe biasing is in the described definite system of step b:
According to the frame number of all subframes in the system, the order of elements in the Coase tower sequence is set to the pilot carrier frequency biasing of first OFDM symbol of the carrying pilot signal of corresponding frame.
6, method according to claim 3 is characterized in that, the described method of determining that each subframe sub-carriers distributes of step b is:
According to the pilot carrier frequency biasing of pilot carrier frequency interval and described first OFDM symbol, determine the subcarrier that pilot signal takies on described first OFDM symbol;
According to the pilot carrier frequency biasing on other OFDM symbol of the pilot carrier frequency biasing of described first OFDM symbol and the definite carrying of the pilot carrier frequency bias difference pilot signal between the OFDM symbol, by the pilot carrier frequency biasing on pilot carrier frequency interval and the OFDM symbol, determine the subcarrier that pilot signal takies on corresponding OFDM symbol.
7, method according to claim 1 is characterized in that, step c is described for the method for cell allocation pilot frequency design to be: in the pilot frequency design set, adopting at random, scrambler is that respective cell is selected pilot frequency design.
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EP2161941B1 (en) * 2007-06-18 2013-05-08 Alcatel Lucent A method and device for pilot mapping in multiplexing mode of unicast and broadcast/multicast services
WO2009069638A1 (en) * 2007-11-27 2009-06-04 Nec Corporation Radio signal transmission device, radio signal transmission method, radio signal reception device, radio signal reception method, and radio signal reception program
CN101610101B (en) * 2008-06-16 2013-02-27 中兴通讯股份有限公司 Frequency hopping method for downlink special pilot frequencies
CN101610231B (en) * 2008-06-18 2013-06-05 中兴通讯股份有限公司 Method and device for realizing frequency hopping
KR101230780B1 (en) * 2008-10-10 2013-02-06 엘지전자 주식회사 Method for transmitting control signal in wireless communication system
CN101540751B (en) * 2009-04-30 2013-01-02 北京邮电大学 Demodulating method for multi-stream data and system thereof
CN101965058B (en) * 2009-07-23 2013-10-02 华为技术有限公司 Method and device for carrier level cell selection
CN102739382A (en) * 2011-03-25 2012-10-17 北京新岸线无线技术有限公司 Adjustment method and system for demodulating pilot frequency in wireless communication system
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EP2959628B1 (en) * 2013-03-11 2018-05-30 Huawei Technologies Co., Ltd. Upstream pilot structure in point to multipoint orthogonal frequency division multiplexing communication system
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