CN104519004B - The forming method of the preserved sub-carrier position pattern of NGB W systems - Google Patents
The forming method of the preserved sub-carrier position pattern of NGB W systems Download PDFInfo
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Abstract
The present invention provides a kind of forming method of the preserved sub-carrier position pattern of NGB W systems, and each physical frame includes signaling symbols, data symbol and postamble symbol in NGB W systems, and every kind of symbol has respective different pilot tones；Signaling symbols include signaling pilot tone；Data symbol includes scattered pilot, edge pilot and CP continuous pilot；Postamble symbol, which includes edge pilot and postamble pilot tone, methods described, to be included：The position of preserved sub-carrier is selected in the non-pilot position of signaling symbols, data symbol and postamble symbol；Wherein, scattered pilot, CP continuous pilot, CP continuous pilot are removed in data symbol again move to right the position, CP continuous pilot that 3 subcarriers obtain and move to right the position, CP continuous pilot that 6 subcarriers obtain and move to right the position behind the position, the position of edge pilot, each 12 sub-carrier positions of two subband left hand edges of NGB W systems that 9 subcarriers obtain.The present invention only only takes up 1% subcarrier reduces PAPR effect with regard to that can reach well.
Description
Technical Field
The invention relates to the technical field of mobile communication, in particular to the technical field of communication methods of digital multimedia radio broadcasting, and specifically relates to a method for forming a reserved subcarrier position pattern of an NGB-W system by using a method for reducing the peak-to-average power ratio of OFDM symbols by using reserved subcarriers.
Background
With the rapid development of the world economic culture, the demand of mobile users for information services is rapidly increasing. The optimized transmission of mobile information services cannot be realized by relying on a traditional broadcast network or a traditional two-way communication network alone. The next generation radio broadcast network wireless (NGB-W) communication system can realize the fusion and coexistence of radio broadcast and two-way communication, and is an effective way to solve the contradiction between the rapid increase of the mobile information service data volume and the limited transmission capacity of the wireless network. The NGB-W system is a multi-carrier communication system based on OFDM technology.
In a multi-carrier system, especially an OFDM system, since an OFDM symbol is formed by superimposing a plurality of independently modulated subcarrier signals, when phases of the respective subcarriers are the same or close to each other, the superimposed signal is modulated by the same initial phase signal, so as to generate a larger instantaneous Power Peak, thereby further bringing a higher Peak-to-Average Power Ratio (PAPR), which is referred to as a Peak-to-Average Power Ratio (PAPR). Because the dynamic range of a general power amplifier is limited, an OFDM signal with a large peak-to-average ratio easily enters a nonlinear region of the power amplifier, so that nonlinear distortion is generated on the signal, obvious spectrum spreading interference and in-band signal distortion are caused, the performance of the whole system is seriously reduced, and the high peak-to-average ratio becomes a main technical obstacle of OFDM.
At present, there are two main technical solutions for solving the problem of high PAPR of a signal: amplifier linearization techniques and PAPR reduction techniques. The linearization technique is to perform predistortion compensation on the nonlinearity caused by the amplifier at the baseband, and the realization has higher cost and complexity. Commonly used PAPR reduction techniques include 3: signal distortion techniques, coding techniques, and scrambling techniques. Signal distortion technology realizes PAPR reduction through signal peak value amplitude limiting processing, but introduces nonlinear distortion of signals; the coding technology enables the coded signal to have lower PAPR by designing a special forward error correction code group, but the cost of the technology is to reduce the transmission rate of the system; the scrambling technique is to scramble the signal separately by using several special sequences and then select the sequence with the smallest PAPR for transmission. It can be seen that each of these techniques has advantages and disadvantages: the complexity of the hard clipping and filtering type techniques is low, but the BER performance is poor compared with the scrambling and coding type techniques; the system complexity of the selective mapping and partial transmission sequence technology is high; while the bandwidth efficiency of the encoding-class technique is low.
Disclosure of Invention
In view of the above drawbacks of the prior art, an object of the present invention is to provide a method for forming a reserved subcarrier position pattern of an NGB-W system, so as to solve the problem of an excessively high peak-to-average power ratio of a time domain signal of the existing NGB-W system and improve the power amplification efficiency of a transmitting end.
In order to achieve the above and other related objects, the present invention provides a method for forming a reserved sub-carrier position pattern of an NGB-W system, which is applied to the NGB-W system, wherein each physical frame in the NGB-W system includes a signaling symbol, a data symbol and a frame tail symbol, and each symbol has a different pilot frequency; the signaling symbol contains a signaling pilot; the data symbols comprise scattered pilots, edge pilots and continuous pilots; the frame tail symbol comprises an edge pilot frequency and a frame tail pilot frequency; the transmission band of NGB-W system is divided into left and right sub-bands, and all the pilot frequency is distributed on the left and right sub-bands completely same, the method includes: selecting the positions of reserved subcarriers at non-pilot positions of a signaling symbol, a data symbol and a frame tail symbol; wherein, the data symbol is removed with scattered pilot, continuous pilot, position obtained by shifting continuous pilot by 3 sub-carriers to the right, position obtained by shifting continuous pilot by 6 sub-carriers to the right, position obtained by shifting continuous pilot by 9 sub-carriers to the right, position of edge pilot, and position after 12 sub-carrier positions at the left edge of two sub-bands of NGB-W system.
Preferably, the manner of selecting the position of the reserved sub-carrier in the signaling symbol is as follows: and removing the effective subcarrier positions after the signaling pilot frequency positions to form a selection space of the reserved subcarriers, searching the reserved subcarrier positions with the number of 1% of the total number of the effective subcarriers in the selection space, and taking a reserved subcarrier index set corresponding to the time domain pulse signal with the minimum secondary peak value.
Preferably, the scattered pilot positions vary cyclically with increasing data symbol index; the positions of the edge pilot frequency and the continuous pilot frequency are not changed along with the increase of the index of the data symbol; the scattered pilot comprises scattered pilots PP 1-PP 8; the pilot density of the scattered pilot PP1 is the largest, the search space in the scattered pilot PP1 mode is a subset of the search space in other scattered pilot types, and the reserved subcarrier set searched out in the scattered pilot PP1 also belongs to the search space in other scattered pilot types; under the scattered pilot PP1, the way to select the position of the reserved sub-carriers in the data symbols is:
and after removing the scattered pilot frequency, the continuous pilot frequency index, the index obtained by shifting the continuous pilot frequency to the right by 3 subcarriers, the index obtained by shifting the continuous pilot frequency to the right by 6 subcarriers, the index obtained by shifting the continuous pilot frequency to the right by 9 subcarriers, the edge pilot frequency index and the index of 12 subcarriers respectively at the left edges of two subbands of the NGB-W system, forming a reserved subcarrier index space, searching reserved subcarrier positions with the number of 1 percent of the total number of effective reserved subcarriers in the reserved subcarrier index space, and taking a reserved subcarrier index set corresponding to the time domain type pulse signal with the minimum secondary peak value.
Preferably, the manner of selecting the position of the reserved sub-carrier in the end-of-frame symbol is as follows: the reserved subcarrier search space in the signaling symbol is a subset of the reserved subcarrier search space of the end-of-frame symbol, and the reserved subcarrier index set of the signaling symbol is also used as the reserved subcarrier index set of the end-of-frame symbol.
Preferably, specific index values of the reserved subcarrier index set in SISO mode or MIXO mode are shown in table 1 for signaling symbols and end-of-frame symbols:
TABLE 1
Preferably, for data symbols, specific index values of the reserved subcarrier index set in SISO mode or MIXO mode are shown in table 2:
TABLE 2
As described above, the method for forming the reserved subcarrier position pattern of the NGB-W system provided by the present invention has the following beneficial effects:
1. the invention selects the position of the reserved sub-carrier and provides the selected result aiming at the NGB-W system, and the result of the selection of the position of the reserved sub-carrier can construct a time domain pulse signal close to a time domain impulse signal, so that the signal can carry out peak clipping processing on a transmitted signal, thereby achieving the purpose of reducing the peak-to-average power ratio of OFDM symbols.
2. In the invention, the signal is not distorted based on the method of reserving the subcarrier, so the BER performance of the system is not influenced, and the effect of reducing the PAPR can be achieved by only occupying 1 percent of the subcarrier.
Drawings
Fig. 1 is a schematic diagram illustrating the PAPR reduction method based on the reserved sub-carrier position pattern in the present invention.
Fig. 2 is a graph showing PAPR reduction performance comparison of data symbols in SISO mode in PAPR reduction method based on reserved sub-carrier position pattern in the present invention.
Fig. 3 is a graph showing PAPR reduction performance comparison of data symbols in an MIXO mode in a PAPR reduction method based on a reserved subcarrier position pattern in the present invention.
Fig. 4 is a graph showing PAPR reduction performance comparison of signaling symbols in SISO mode in PAPR reduction method based on reserved sub-carrier position pattern in the present invention.
Fig. 5 is a graph showing PAPR reduction performance comparison of signaling symbols in an MIXO mode in a PAPR reduction method based on a reserved subcarrier position pattern in the present invention.
Fig. 6 is a flow chart illustrating PAPR reduction through peak clipping in the PAPR reduction method based on the reserved subcarrier location pattern in the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
The invention aims to provide a method for forming a reserved subcarrier position pattern of an NGB-W system, which is used for solving the problem that the time domain signal peak-to-average power ratio of the existing NGB-W system is too high and improving the power amplification efficiency of a transmitting end. The principle and the embodiment of the method for forming the reserved sub-carrier location pattern of the NGB-W system according to the present invention will be described in detail below, so that those skilled in the art can understand the method for forming the reserved sub-carrier location pattern of the NGB-W system according to the present invention without creative work.
The invention provides a method for forming a reserved subcarrier position pattern of an NGB-W system, which is applied to the NGB-W system, wherein each physical frame in the NGB-W system comprises a signaling symbol, a data symbol and a frame tail symbol, and each symbol has different pilot frequencies; the signaling symbol contains a signaling pilot; the data symbols comprise scattered pilots, edge pilots and continuous pilots; the frame tail symbol comprises an edge pilot frequency and a frame tail pilot frequency; the transmission band of NGB-W system is divided into left and right sub-bands, and all the pilot frequency is distributed on the left and right sub-bands completely same, the method includes: selecting the positions of reserved subcarriers at non-pilot positions of a signaling symbol, a data symbol and a frame tail symbol; wherein, the data symbol is removed with scattered pilot, continuous pilot, position obtained by shifting continuous pilot by 3 sub-carriers to the right, position obtained by shifting continuous pilot by 6 sub-carriers to the right, position obtained by shifting continuous pilot by 9 sub-carriers to the right, position of edge pilot, and position after 12 sub-carrier positions at the left edge of two sub-bands of NGB-W system. The above-mentioned method of the present invention is explained in detail below.
The invention introduces the PAPR reduction method based on the reserved sub-carrier (TR) into the NGB-W system, and the signal is not distorted by the method based on the reserved sub-carrier, so the BER performance of the system is not influenced, and the effect of reducing the PAPR can be achieved by only occupying 1 percent of the sub-carriers. And specific reserved subcarrier positions are selected for the NGB-W system, so that the aim of reducing the PAPR of the time domain signal of the NGB-W system is fulfilled.
Each physical frame in the NGB-W system includes signaling symbols, data symbols, and end-of-frame symbols. Each symbol has a different respective pilot: the signaling symbol contains a signaling pilot; the data symbols comprise scattered pilots, continuous pilots and edge pilots; the end-of-frame symbols contain end-of-frame pilots and edge pilots. The different pilots are located at different positions. In addition, there are 8 scattered pilots of the data symbol: in modes 1 (PP 1) to 8 (PP 8), the positions of the subcarriers in which different scattered pilot patterns are located are also different. The PAPR reduction method based on the reserved sub-carriers places random information at some positions except the pilot frequency positions, and achieves the effect of reducing the PAPR of the OFDM symbols.
The main technical point of the invention is to find several reserved sub-carrier positions so as to meet the requirement of PAPR reduction based on the reserved sub-carriers. The criteria for finding the reserved sub-carrier positions are: and carrying 1 on the reserved sub-carrier positions and carrying 0 on other sub-carriers to construct a basic time domain pulse signal. The transmitted time domain signal is subjected to peak clipping by utilizing the pulse signal and an iterative peak clipping algorithm, so that the aim of reducing the PAPR can be fulfilled.
The peak clipping principle is described first, and then the design scheme of the reserved sub-carrier positions required to meet the principle in the NGB-W system is given.
The principle of the PAPR reduction method based on the reserved subcarriers is adopted:
1) the reserved sub-carriers in the OFDM symbols carry 1 (the reserved sub-carrier position design scheme of the NGB-W system is described later), and the other sub-carriers carry 0, which constitutes a Kernel function for reducing PAPR, as shown in fig. 1;
2) finding a time domain position I of a transmitted signal Data signal exceeding Vclip;
3) moving the impulse of the Kernel function to a position I to obtain a Shifted Kernel function;
4) the Shifted Kernel function is scaled (multiplied by a certain complex number) and then superimposed on the signal Datasignal to achieve the purpose of reducing the PAPR.
Reserved sub-carrier positions are used for constructing a time domain pulse-like signal, therefore, in an NGB-W system, the reserved sub-carrier positions are not used for data and signaling transmission, namely for an OFDM symbol of the NGB-W, the corresponding unit values of the reserved sub-carriers are initialized to ym,l,kAnd 0+0j, wherein m is a frame index, j is an OFDM symbol index in the NGB-W frame, and k is a subcarrier index.
The OFDM symbols of the NGB-W system are divided into signaling symbols, data symbols, and end-of-frame symbols. In each symbol, a pilot or data is carried on a subcarrier. The pilot positions are designed to meet the normal operation of the system, so the positions of the reserved sub-carriers should be found in non-pilot positions. The pilot frequency distribution of the signaling symbol and the data symbol is different; under different FFT points, the pilot frequency distribution of the data symbols is different; the pilots are different in the MIXO and SISO modes. The location of the reserved sub-carriers therefore requires the selection of several groups for different symbol types and multi-antenna patterns. The number of groups is as small as possible while satisfying the PAPR reduction performance, so as to avoid excessive system complexity.
From these points of view, the method for selecting the reserved sub-carriers for the signaling symbol, the data symbol and the end-of-frame symbol of the NGB-W system is as follows:
1. selection of reserved sub-carriers in NGB-W system signaling symbols
The signaling symbol comprises signaling pilot frequency, the effective subcarrier position after removing the signaling pilot frequency position forms a selection space of the reserved subcarrier, the reserved subcarrier position with the number of 1% of the total number of the effective subcarrier is searched in the selection space, and a reserved subcarrier index set corresponding to the time domain type pulse signal with the minimum secondary peak value can be constructed.
That is, the signaling symbol contains a signaling pilot, and the selection space of the reserved sub-carriers is the effective sub-carrier position after the signaling pilot position is removed. In the space, the positions of subcarriers with the number of 1% of the total number of effective subcarriers are searched, and a subcarrier index set corresponding to the constructed time domain pulse signal with the minimum secondary peak value is taken.
For example, in the signaling symbol, when a 4K FFT, 8K FFT or 16K FFT mode is adopted and the effective subcarrier K satisfies the following relationship, the signaling pilot is placed at the position of the subcarrier K.
And the reserved subcarriers form an index space in the subcarriers k which do not satisfy the relation, and the search is carried out on the index space. For example, in the 16K FFT mode, the number of NGB-W effective subcarriers is 12626, and 1% of the subcarriers, that is, 133, are selected. The computer searches 133 subcarrier indexes in the search space, and carries 1 on the 133 subcarriers, and carries 0 in other 16384-133=16251 positions, resulting in a time-domain function whose secondary peak is small enough to approach the theoretical impulse function.
2. Selection of reserved sub-carriers in NGB-W system data symbols
The data symbols comprise scattered pilots, edge pilots and continuous pilots, the positions of the scattered pilots change circularly along with the increase of the indexes of the data symbols, and the positions of the edge pilots and the continuous pilots of all the data symbols are the same.
The scattered pilots include 8 scattered pilots PP1 to PP 8. The pilot density of the scattered pilot PP1 is the largest, and the search space in the scattered pilot PP1 mode is a subset of the search spaces in other scattered pilot types, so the reserved subcarrier set searched out in the scattered pilot PP1 necessarily also belongs to the search spaces in other scattered pilot types. Therefore, the design is based on the scattered pilot PP1 type.
Under PP1, the reserved sub-carriers are selected by selecting a set of reserved sub-carrier indices ZTR,D,0And shifting the subcarriers based on the set to the left by 3,6 and 9 subcarriers respectively to obtain other three subcarrier index sets ZTR,D,1、ZTR,D,2、ZTR,D,3. These four subcarrier sets are cyclically used for different data symbols.
Set of subcarrier indices ZTR,D,0The search space is the effective sub-carrier index after removing the scattered pilot index, the continuous pilot index, the index obtained by shifting the continuous pilot right by 3 sub-carriers, the index obtained by shifting the continuous pilot right by 6 sub-carriers, the index obtained by shifting the continuous pilot right by 9 sub-carriers, the index of the edge pilot and the index of each 12 sub-carriers at the left edge of two sub-bands of the NGB-W system in the first data symbol in the NGB-W frame, so as to form a reserved sub-carrier index space. Searching out subcarrier position indexes with 1% of total number of effective subcarriers in the formed reserved subcarrier index space, and taking the reserved subcarrier position corresponding to the constructed time domain pulse signal with the minimum secondary peak value as a reserved subcarrier index set, namely ZTR,D,0。
For example, in the 16K FFT mode, the search space for the data symbols is as follows.
The effective subcarrier indexes are from 0 to 12625, and 12626 in total, which is marked as a set IAllThe indexes that need to be excluded are of the following three types:
(a) scattered pilot index
In the data symbol, when the effective subcarrier k satisfies the following relationship, the scattered pilot is placed at the position of the subcarrier k.
Wherein l is an OFDM symbol index in an NGB-W frame; dXIs the frequency domain minimum spacing of scattered pilots, DYIs the time domain minimum interval of the scattered pilot; n is a radical ofS_SymThe number of the signaling symbols in the NGB-W frame; n is a radical ofaIs the number of active subcarriers. N in 16K FFT modea＝12626，NS_Sym1, PP1 lower DX＝3,DYThe second OFDM symbol in the NGB-W frame is the data symbol, so the index l =1,the index of the scattered pilot sub-carrier can be obtained from the formula and is marked as a set ISP。
(b) The index of the edge pilot is 0, 12626/2-1, 12626/2, 12626-1, which is marked as set IEP。
(c) Location of continual pilots
In the data symbol, when the effective subcarrier k satisfies the following relationship, the continuous pilot is placed at the position of the subcarrier k.
Wherein N isCPThe number of continuous pilot frequencies in the data symbols; when 4K FFT or 8K FFT is employed, NCP50; when using 16K FFT, NCP90; when using 32K FFT, NCP＝180；WhereinFor D under various scattered pilot frequency typesXIs measured. N in 16K FFT modea＝12626，NCP＝90，The index set I of continuous pilot frequency sub-carrier can be obtained from the formulaCP,0. Index of subcarrier ICP,0Index set I composed of 3,6 and 9 pieces of right shiftCP,1、ICP,2、ICP,3And is also excluded from the search space.
(d) In addition, consider a set of reserved subcarriers ZTR,D,0Will shift left 3,6,9 sub-carriers to form a reserved sub-carrier set ZTR,D,1、ZTR,D,2、ZTR,D,3To prevent the subcarriers from shifting beyond space IAllOf the two sub-bands, leftmostThe subcarriers with indexes of 0-11 and 12626/2-126/2 +11 also need to be excluded from the search space, and the 24 subcarriers are marked as a set I24。
This results in a search space of 133 reserved sub-carriers:
ISearch_space＝IAll-ISP-IEP-ICP,0-ICP,1-ICP,2-ICP,3-I24
the computer searches 133 subcarrier indexes in the search space, and carries 1 on the 133 subcarriers, and carries 0 in other 16384-133=16251 positions, resulting in a time-domain function whose secondary peak is small enough to approach the theoretical impulse function. This set of 133 subcarrier indices is ZTR,D,0。
3. Selection of reserved sub-carriers in NGB-W system frame tail symbols
The frame tail symbol comprises an edge pilot and a frame tail pilot, the reserved subcarrier search space of the signaling symbol is a subset of the reserved subcarrier search space of the frame tail symbol, and therefore, the reserved subcarrier index set of the frame tail symbol adopts the reserved subcarrier index set of the signaling symbol.
Based on the selection method, the invention sets four groups of basic reserved subcarrier index sets under each FFT point number aiming at the NGB-W system, and the method comprises the following steps:
aiming at the signaling symbol and the frame tail symbol, a corresponding group of reserved subcarrier index sets Z in SISO mode and MIXO modeTR,SISO,SThe specific index values are shown in Table 1.
TABLE 1
For data symbols, corresponding to a set of reserved subcarrier index sets Z in SISO mode and MIXO modeTR,SISO,D,0The specific index values are shown in attached table 2.
TABLE 2
In addition, since the scattered pilots are shifted in frequency domain as the index of the data symbol increases, the frequency at Z is shiftedTR,D,0（ZTR,SISO,D,0And ZTR,SISO,D,0General name of (c) to derive three other sets of reserved subcarriers ZTR,D,1ZTR,D,2ZTR,D,3. In the data symbols, the index set of the reserved subcarriers is cyclically used, and the cyclic mode is shown in table 3.
For example, in PP1 mode, the reserved sub-carriers cyclically use Z as the data symbol index is incremented from 0TR,D, 0ZTR,D,1ZTR,D,2ZTR,D,3(ii) a In PP2 mode, the reserved sub-carriers cyclically use Z as the data symbol index is incremented from 0TR,D,0ZTR,D,2(ii) a In PP4 mode, the reserved sub-carriers cyclically use Z as the data symbol index is incremented from 0TR,D,0......。
Table 3 relation of reserved subcarrier index set and data symbol index
Wherein Z isTR,D,1Is ZTR,D,0A set of subcarrier indexes formed by shifting 3 subcarriers to the left; zTR,D,2Is ZTR,D,0A set of subcarrier indexes formed by shifting 6 subcarriers to the left; zTR,D,3Is ZTR,D,0The set of subcarrier indexes, which is left shifted by 9 subcarriers, can be expressed as:
ZTR,D,1＝ZTR,D,0-3,ZTR,D,2＝ZTR,D,0-6,ZTR,D,3＝ZTR,D,0-9。
reserved subcarrier set Z established by the inventionTRAnd constructing a time domain pulse signal, and utilizing the pulse signal to carry out PAPR reduction processing on the transmitted signal.
The number of FFT points: 2K/4K/8K/16K/32K; multi-antenna mode: SISO/MIXO mode; OFDM symbol type: signaling symbols, data symbols. The obtained effect graphs are shown in fig. 2 to fig. 5, which are convenient for quantitative analysis of PAPR reduction performance, and also show PAPR reduction performance of reserved subcarriers in DVB-T2 system.
Fig. 2 to fig. 5 include the original peak-to-average ratio curve without PAPR processing and the curve after PAPR reduction under different peak clipping parameters and peak clipping iteration times, and by comparison, it can be seen that: the PAPR reduction effect is slightly different due to different peak clipping parameter selections; the performance of reducing PAPR of the NGB-W system is basically equivalent to that of the DVB-T2 system, and the PAPR can be reduced by about 3dB under different FFT points and multi-antenna modes.
The reserved sub-carrier PAPR reduction algorithm established based on the invention is implemented as follows.
The transmission signal is iteratively peak-clipped by a series of pulse-like time domain signals, which are carried by the reserved sub-carriers. The basic pulse-like time domain signal is defined as follows:
wherein,NFFTand NTRRespectively representing the number of FFT points and the number of reserved sub-carriers. Vector ITRIn which is NTREach element is 1, and the corresponding position is the position of the reserved subcarrier established by the invention; with NFFT-NTREach element is 0, and the corresponding position is the position of other subcarriers.
The implementation process of iterative peak clipping and PAPR reduction based on the reserved sub-carriers of the present invention can be described by using the flow chart shown in fig. 6, and the flow description of the PAPR reduction method based on the reserved sub-carrier algorithm is shown in table 4.
Table 4: PAPR reduction method based on reserved subcarrier algorithm
In summary, the method for forming the reserved subcarrier position pattern of the NGB-W system provided by the present invention achieves the following beneficial effects:
the invention selects the reserved subcarrier position of the NGB-W system and provides a selection result, and the result of the reserved subcarrier position selection can construct a time domain pulse signal close to a time domain impulse signal, so that the signal performs peak clipping processing on a transmitted signal, and the aim of reducing the peak-to-average power ratio of OFDM symbols is fulfilled. The reserved sub-carrier based method can not distort the signal, thereby not affecting the BER performance of the system, and the reserved sub-carrier pattern in the invention only occupies 1 percent of sub-carriers to achieve the effect of reducing the PAPR well. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (3)
1. A method for forming reserved subcarrier position patterns of an NGB-W system is applied to the NGB-W system, each physical frame in the NGB-W system comprises a signaling symbol, a data symbol and a frame tail symbol, and each symbol has different pilot frequencies; the signaling symbol contains a signaling pilot; the data symbols comprise scattered pilots, edge pilots and continuous pilots; the frame tail symbol comprises an edge pilot frequency and a frame tail pilot frequency; the NGB-W system transmission band is divided into left and right sub-bands, and all pilots are distributed on the left and right sub-bands completely and identically, characterized in that the method comprises:
selecting the positions of reserved subcarriers at non-pilot positions of a signaling symbol, a data symbol and a frame tail symbol; wherein, the data symbol is removed with scattered pilot frequency, continuous pilot frequency, position obtained by shifting continuous pilot frequency to right by 3 sub-carriers, position obtained by shifting continuous pilot frequency to right by 6 sub-carriers, position obtained by shifting continuous pilot frequency to right by 9 sub-carriers, position of edge pilot frequency, and position after 12 sub-carrier positions of left edges of two sub-bands of NGB-W system;
the way of selecting the position of the reserved sub-carrier in the signaling symbol is as follows: the effective subcarrier positions after removing the signaling pilot frequency position form a selection space of reserved subcarriers, the reserved subcarrier positions with the number of 1% of the total number of the effective subcarriers are searched in the selection space, and a reserved subcarrier index set corresponding to a time domain type pulse signal with the minimum secondary peak value can be constructed;
the position of the scattered pilot frequency changes along with the increase of the index of the data symbol; the positions of the edge pilot frequency and the continuous pilot frequency are not changed along with the increase of the index of the data symbol; the scattered pilot comprises scattered pilots PP 1-PP 8; the pilot density of the scattered pilot PP1 is the largest, the search space in the scattered pilot PP1 mode is a subset of the search space in other scattered pilot types, and the reserved subcarrier set searched out in the scattered pilot PP1 also belongs to the search space in other scattered pilot types; under the scattered pilot PP1, the way to select the position of the reserved sub-carriers in the data symbols is:
removing a scattered pilot frequency, a continuous pilot frequency index, an index obtained by shifting a continuous pilot frequency to the right by 3 subcarriers, an index obtained by shifting a continuous pilot frequency to the right by 6 subcarriers, an index obtained by shifting a continuous pilot frequency to the right by 9 subcarriers, an edge pilot frequency index and 12 subcarrier indexes of the left edges of two subbands of an NGB-W system to form a reserved subcarrier index space, searching reserved subcarrier positions with the number of 1% of the total number of effective reserved subcarriers in the reserved subcarrier index space, and taking a reserved subcarrier index set corresponding to a time domain type pulse signal with the minimum secondary peak value;
the way of selecting the position of the reserved sub-carrier in the frame end symbol is as follows: the reserved subcarrier search space in the signaling symbol is a subset of the reserved subcarrier search space of the end-of-frame symbol, and the reserved subcarrier index set of the signaling symbol is also used as the reserved subcarrier index set of the end-of-frame symbol.
2. The method of claim 1, wherein specific index values of the index set of the reserved sub-carriers in SISO mode or MIXO mode for the signaling symbols and the end-of-frame symbols are shown in table 1:
TABLE 1
3. The method of claim 1, wherein specific index values of index sets of reserved sub-carriers in SISO mode or MIXO mode are shown in table 2 for data symbols:
TABLE 2
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