CN107017975B - Time-frequency diversity copying method based on orthogonal frequency division multiplexing - Google Patents
Time-frequency diversity copying method based on orthogonal frequency division multiplexing Download PDFInfo
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Abstract
A time-frequency diversity copying method and system based on orthogonal frequency division multiplexing, the method includes: the physical layer receives the medium access control layer information and generates original data needing to be transmitted by the physical layer; determining the number of interleavers according to the number of copying times; calculating time-frequency diversity copy parameters according to the medium access control layer information and the determined number of the interleavers; calculating the length of data to be added according to the bit number of each part of data and the bit number of the last part of data during copying, and acquiring a new data sequence; or calculating the shift parameter of the time-frequency diversity copy according to the copy times and the bit number of the last orthogonal frequency division multiplexing symbol; calculating the interleaving offset step length according to the number of subcarriers corresponding to each interleaver and the number of interleavers during copying, determining the interleaving step length of each interleaver according to the interleaving offset step length, and finally calculating the interleaving address of each interleaver according to the interleaving step length; and performing time-frequency diversity copying.
Description
Technical Field
The invention relates to the technical field of power line carrier communication, in particular to a time-frequency diversity copying method based on orthogonal frequency division multiplexing.
Background
Power line carrier communication is a wired communication technology that uses power wiring to transmit and receive communication signals. Because the power line network is widely distributed, the power line is used as a communication medium, and the communication network is not required to be reconstructed by punching and wiring indoors, so that the power line network has the advantages of low cost, convenience in connection and the like, and is paid more and more attention to the aspects of smart power grids and broadband access.
Orthogonal Frequency Division Multiplexing (OFDM) is a spread spectrum technique that subdivides the available transmission channel bandwidth into a number of discrete channels or carriers that overlap and are Orthogonal to each other. Data is transmitted in the form of symbols having a particular duration and including a number of carrier frequencies. The data transmitted on these OFDM carriers may be encoded using conventional schemes such as Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK).
The communication channel is the basis of communication, and as with wireless communication, the performance of power line communication is mainly limited by the power line communication channel. The low voltage power network is not designed for transmitting high speed data, and its components constituting the power network are designed in order to minimize the loss of transmission power and ensure reliable transmission of low frequency current, so that when signal transmission is performed on the low voltage line, impulse noise of error burst and delay spread causing frequency selective fading may be generated on a channel, thereby causing a receiving end not to correctly demodulate a transmission signal, and it is necessary to adopt a diversity technique.
Disclosure of Invention
In order to solve the above problems in the background art, the present invention provides a time-frequency diversity copying method based on orthogonal frequency division multiplexing, which is characterized in that the method comprises:
and 8, sequentially copying the time frequency diversity according to the copying times, the shifting parameters, the interleaving address of the interleaver and the coding rate of the physical layer.
Further, diversity copying is performed in both time and frequency domains, where the frequency domain represents copying data to be transmitted on different subcarriers, and the time domain represents copying data to be transmitted on different orthogonal frequency division multiplexing symbols.
Further, the mac layer information received by the physical layer includes a carrier map index, which specifies the coding rate, copy number, and physical block size of the physical layer, and calculates the original data length that can be transmitted by the physical layer according to the physical block size.
Further, determining the number of interleavers based on the number of copies includes:
when the number of copying times is 2, the number of the interleavers is 8, and the number of the interleavers copied each time is 4;
when the number of copying times is 4, the number of the interleavers is 8, and the number of the interleavers copied each time is 2;
when the number of copying times is 5, the number of the interleavers is 10, and the number of the interleavers copied each time is 2;
when the number of copying times is 7, the number of interleavers is 14, and the number of interleavers copied each time is 2; and
when the number of times of copying is 11, the number of interleavers is 11, and the number of interleavers per copy is 1.
Further, the formula for calculating the time-frequency diversity copy parameter according to the medium access control layer information and the determined number of the interleavers comprises:
calculating the number N _ real _ carrier of subcarriers actually used during copying:
wherein, N _ real _ carrier represents the number of actually used sub-carriers during copying, InterNum represents the number of interleavers corresponding to the copying times, N _ carrier represents the number of usable sub-carriers,
the whole is taken down;
calculating the carrier number of each part in copying, namely Carrier PerPart:
wherein carrier Perpart represents the number of carriers of each part during copying, N _ real _ carrier represents the number of subcarriers actually used during copying, N _ copies represents the number of copying times,
the whole is taken down;
calculating the number of bits of each part during copying BitsPerpart:
BitsPerPart＝BPC*CarrierPerPart
wherein, BitsPerpart represents the bit number of each part during copying, BPC represents the physical layer coding rate, and Carrier Perpart represents the carrier number of each part during copying;
calculating the number N _ symbol of the needed orthogonal frequency division multiplexing (orthogonal frequency division multiplexing symbol) symbols during copying;
wherein, N _ symbol represents the number of orthogonal frequency division multiplexing symbols needed in copying, N _ data represents the original data length, BitsPerpart represents the number of bits of each part in copying,
the upper integer is taken;
calculating the bit number BitsPerSymbol of each orthogonal frequency division multiplexing symbol when copying:
BitsPerSymbol＝BPC*N_real_carrier
wherein, BitsPerSymbol represents the bit number of each orthogonal frequency division multiplexing symbol during copying, BPC represents the physical layer coding rate, and N _ real _ carrier represents the number of subcarriers actually used during copying;
calculating the bit number BitsInLastOFDM of the last orthogonal frequency division multiplexing symbol:
wherein BitsInLastOFDM represents the bit number of the last OFDM symbol, N _ data represents the original data length, BitsPerSymbol represents the bit number of each OFDM symbol at the time of copying,
the whole is taken down;
calculating the subcarrier number Carrier Per Interleaver corresponding to each interleaver during copying:
wherein, carrier per interleaver represents the number of subcarriers corresponding to each interleaver during copying, N _ real _ carrier represents the number of subcarriers actually used during copying, and lnnum represents the number of interleavers corresponding to the number of copying times;
calculating the bit number of the last part of the data during copying BitsInLastpart:
BitsInLastPart＝N_data-(N_symbol-1)*BitsPerPart
wherein, BitsInLastPart represents the bit number of the last part of data during copying, N _ data represents the original data length, N _ symbol represents the number of orthogonal frequency division multiplexing symbols required during copying, and BitsPerPart represents the bit number of each part during copying.
Further, calculating the length of data to be added according to the number of bits of each part of data and the number of bits of the last part of data when copying, and acquiring a new data sequence comprises:
N_add＝BitsPerPart-BitsInLastPart
wherein, N _ add represents the length of data to be added, BitsPerpart represents the bit number of each part during copying, and BitsInLastpart represents the bit number of the last part of the data during copying;
and step 3, updating the data length N _ data _ actual, wherein the calculation formula is as follows:
N_data_actual＝N_data+N_add
wherein, N _ data _ actual represents the updated data length, N _ data represents the original data length, and N _ add represents the data length required to be added.
Further, the rule for calculating the shift parameter of the time-frequency diversity copy according to the number of copies and the number of bits of the last ofdm symbol includes:
when the number of times of copying is 1, the shift parameter cyclicshift is 0;
when the number of copying times is 2, if the bit number of the last orthogonal frequency division multiplexing symbol BitsInLastOFDM is not more than the bit number of each part during copying BitsPerpart, the shifting parameter circshift is [0,0], otherwise, the shifting parameter circshift is [0,1 ];
when the number of copies is 4, BitsInLastOFDM ≦ bitsipart, shift parameter cyclicshift ═ 0,0,0], bitsipart < BitsInLastOFDM ≦ 2 × bitsipart, shift parameter cyclicshift ≦ 0,0,1,1], 2 × bitsipart < BitsInLastOFDM ≦ 3 × bitsipart, shift parameter cyclicshift ≦ 0,0,0,0], 3 × bitsipart < BitsInLastOFDM ≦ 4 × bitsipart, shift parameter cyclicshift ≦ 0,1,2,3 ];
when the number of copies is 5, BitsInLastOFDM is less than or equal to 4 multiplied by BitsPerpart, and the shifting parameter circhift is [0,0,0,0,0], otherwise, the shifting parameter circhift is [0,1,2,3,4 ];
when the number of copies is 7, BitsInLastOFDM is less than or equal to 6 xBitsPerpart, and the shifting parameter circhift is [0,0,0,0,0,0,0], or else, the shifting parameter circhift is [0,1,2,3,4,5,6 ];
when the number of copies is 11, BitsInLastOFDM is less than or equal to 10 × bitsiperpart, and the shift parameter circhift is [0,0,0,0,0,0,0, 0], otherwise, the shift parameter circhift is [0,1,2,3,4,5,6,7,8,9,10 ].
Further, calculating the interleaving offset step size according to the number of subcarriers corresponding to each interleaver and the number of interleavers during copying, determining the interleaving step size of each interleaver according to the interleaving offset step size, and finally calculating the interleaving address of each interleaver according to the interleaving step size includes:
wherein, Interstep represents interleaving offset step, Carrier PerInterleaver represents the number of sub-carriers corresponding to each interleaver during copying, InterNum represents the number of interleavers corresponding to the number of copying times,
the whole is taken down;
when Interstep < 1, InterShiftstep equals 0;
when 1 is not less than Interstep and is less than 2, InterShiftstep is equal to 1;
when 2 is more than or equal to Interstep and less than 4, InterShiftstep is equal to 2;
when 4 is less than or equal to Interstep and less than 8, InterShiftstep is equal to 4;
when 8 is less than or equal to Interstep < 16, InterShiftstep is equal to 8;
when each interleaver performs interleaving, a marching listing mode is adopted, an original address is firstly stored in a matrix with N rows and M columns according to the marching mode, elements in the matrix are read out according to the sequence of the columns, and after the elements are read out, each interleaver performs cyclic shift to obtain a final interleaving result, wherein a specific calculation formula is as follows:
when the ith interleaver performs interleaving, the matrix column number M (i) of the interleaver
M(i)＝i*InterShiftStep
Wherein M (i) represents the matrix column number when the ith interleaver interleaves, InterShiftStep represents the interleaving step size of the interleaver,
when the ith interleaver performs cyclic shift, its cyclic shift parameter cyc (i) is:
cyc(i)＝2*(i-1)*InterShiftStep
where cyc (i) represents the cyclic shift parameter of the ith interleaver, and InterShiftStep represents the interleaving step size of the interleaver.
Further, sequentially performing time-frequency diversity copying on the coding rate of the physical layer according to the shift parameter and the interleaving address of the interleaver comprises:
when the Nth copying is carried out, shifting the copied part according to the shifting parameter, wherein N is more than 1;
dividing each part of data into blocks with the same number of interleavers required by each copying;
at the time of copying, bits and subcarriers are mapped according to the coding rate of the physical layer.
According to another aspect of the present invention, the present invention provides a time-frequency diversity copying system based on orthogonal frequency division multiplexing, wherein the system comprises:
the data forming unit is used for receiving the medium access control layer information through the physical layer and generating original data needing to be transmitted by the physical layer;
an interleaver determining unit for determining the number of interleavers based on the number of copies;
a time-frequency diversity copy parameter determining unit, configured to calculate time-frequency diversity copy parameters according to the mac layer information and the determined number of interleavers, where the parameters include the number of subcarriers actually used in copying, the number of carriers of each part of data, the number of bits of each part of data, the number of required ofdm symbols, the number of bits of each ofdm symbol, the number of bits of a last ofdm symbol, the number of subcarriers corresponding to each interleaver, and the number of bits of a last part of data;
a data length judging unit for judging the number of bits of the last part of the transmitted data
Whether greater than 0;
a new data sequence determining unit, which is used for calculating the length of data to be added according to the bit number of each part of data and the bit number of the last part of data during copying and acquiring a new data sequence;
a time-frequency diversity copy shift parameter calculation unit for calculating the shift parameter of the time-frequency diversity copy according to the copy times and the bit number of the last OFDM symbol;
the interleaver interweaving address calculation unit is used for calculating interweaving offset step length according to the number of subcarriers corresponding to each interleaver and the number of the interleavers during copying, determining the interweaving step length of each interleaver according to the interweaving offset step length, and finally calculating the interweaving address of each interleaver according to the interweaving step length; and
and the time-frequency diversity copying unit is used for sequentially copying the time-frequency diversity according to the copying times, the shifting parameter, the interleaving address of the interleaver and the coding rate of the physical layer.
The time-frequency diversity copying method and the time-frequency diversity copying system based on the orthogonal frequency division multiplexing carry out time-frequency diversity copying according to different data lengths, different modulation modes and different copying times, thereby improving the diversity gain of the system.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
fig. 1 is a flowchart of a time-frequency diversity copying method based on orthogonal frequency division multiplexing according to an embodiment of the present invention;
FIG. 2 is a graphical illustration of calculated parameter magnitudes according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an interleaver interleaving manner according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating an embodiment of time-frequency diversity copying according to the present invention;
FIG. 5 is a partial diagram illustrating a mapping relationship between bits and carriers when performing time-frequency diversity copying according to an embodiment of the present invention;
fig. 6 is a schematic diagram of an experimental result of a time-frequency diversity copying method based on orthogonal frequency division multiplexing according to an embodiment of the present invention;
fig. 7 is a schematic diagram of another experimental result of a time-frequency diversity copying method based on orthogonal frequency division multiplexing according to an embodiment of the present invention; and
fig. 8 is a structural diagram of a time-frequency diversity copy system based on orthogonal frequency division multiplexing according to an embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 is a flowchart of a time-frequency diversity copying method based on orthogonal frequency division multiplexing according to an embodiment of the present invention. As shown in fig. 1, the time-frequency diversity copying method based on orthogonal frequency division multiplexing starts with step S101.
In step S101, the physical layer receives the medium access control layer information and generates original data that the physical layer needs to transmit. The medium access control layer information received by the physical layer comprises a carrier mapping table index, the carrier mapping table index specifies the coding rate, the copying times and the size of a physical block of the physical layer, and the length of original data which can be transmitted by the physical layer is calculated according to the size of the physical block. In this embodiment, a frequency band 0 is adopted, a carrier mapping table index is 2, a coding rate is 2, QPSK is adopted, the number of copying times is 5, the number of usable subcarriers is 411, a physical block is 136, and a data length N _ data which can be transmitted by a physical layer is 1088.
In step S102, the number of interleavers is determined based on the number of copies. Determining the number of interleavers based on the number of copies includes: when the number of copying times is 2, the number of the interleavers is 8, and the number of the interleavers copied each time is 4; when the number of copying times is 4, the number of the interleavers is 8, and the number of the interleavers copied each time is 2; when the number of copying times is 5, the number of the interleavers is 10, and the number of the interleavers copied each time is 2; when the number of copying times is 7, the number of interleavers is 14, and the number of interleavers copied each time is 2; and when the number of copying times is 11, the number of interleavers is 11, and the number of interleavers per copying is 1. In this embodiment, since the number of copies is 5, the number of interleavers should be 10, and the number of interleavers per copy is 2.
In step S103, time-frequency diversity copying parameters are calculated according to the mac layer information and the determined number of interleavers, where the parameters include the number of subcarriers actually used in copying, the number of carriers of each part of data, the number of bits of each part of data, the number of required ofdm symbols, the number of bits of each ofdm symbol, the number of bits of the last ofdm symbol, the number of subcarriers corresponding to each interleaver, and the number of bits of the last part of data. The calculation process for each parameter is as follows.
a) Calculating the number N _ real _ carrier of subcarriers actually used during copying:
wherein, N _ real _ carrier represents the number of actually used sub-carriers during copying, InterNum represents the number of interleavers corresponding to the copying times, N _ carrier represents the number of usable sub-carriers,
the number of actually used sub-carriers is shown as
b) Calculating the carrier number of each part in copying, namely Carrier PerPart:
wherein carrier Perpart represents the number of carriers of each part during copying, N _ real _ carrier represents the number of subcarriers actually used during copying, N _ copies represents the number of copying times,
in the embodiment, the original data is divided into 7 parts, and the number of carriers of each part is
c) Calculating the number of bits of each part during copying BitsPerpart:
BitsPerPart＝BPC*CarrierPerPart
wherein, BitsPerPart indicates the number of bits per part during copying, BPC indicates the physical layer coding rate, and CarriersPerPart indicates the number of carriers per part during copying, in the embodiment, the physical layer coding rate is 2, and the number of bits per part is 2 × 82 ═ 164.
d) Calculating the number N _ symbol of the needed orthogonal frequency division multiplexing (orthogonal frequency division multiplexing symbol) symbols during copying;
wherein, N _ symbol represents the number of orthogonal frequency division multiplexing symbols needed in copying, N _ data represents the original data length, BitsPerpart represents the number of bits of each part in copying,
in the embodiment, the original data length is 1088, the number of bits of each portion is 164, and the number of OFDM symbols required for obtaining the copy is 7.
e) Calculating the bit number BitsPerSymbol of each orthogonal frequency division multiplexing symbol when copying:
BitsPerSymbol＝BPC*N_real_carrier
wherein, bitspsymbol represents the number of bits of each OFDM symbol during copying, BPC represents the physical layer coding rate, and N _ real _ carrier represents the number of subcarriers actually used during copying, and in the embodiment, the number of bits of each OFDM symbol is 2 × 410 — 820.
f) Calculating the bit number BitsInLastOFDM of the last orthogonal frequency division multiplexing symbol:
wherein BitsInLastOFDM represents the bit number of the last OFDM symbol, N _ data represents the original data length, BitsPerSymbol represents the bit number of each OFDM symbol at the time of copying,
indicating the whole, in the embodiment, the number of bits 1088 and 820 of the last OFDM symbol is 268.
g) Calculating the subcarrier number Carrier Per Interleaver corresponding to each interleaver during copying:
in the embodiment, carrier per interleaver indicates the number of subcarriers corresponding to each interleaver during copying, N _ real _ carrier indicates the number of subcarriers actually used during copying, and lnnum indicates the number of interleavers corresponding to the number of copying times, where in the embodiment, the number of subcarriers corresponding to each interleaver is 410 ÷ 10 ÷ 41.
h) Calculating the bit number of the last part of the data during copying BitsInLastpart:
BitsInLastPart＝N_data-(N_symbol-1)*BitsPerPart
wherein, BitsInLastPart represents the bit number of the last part of the data during copying, N _ data represents the original data length, N _ symbol represents the number of orthogonal frequency division multiplexing symbols required during copying, and BitsPerPart represents the bit number of each part during copying, in the embodiment, the bit number of the last part is 1088-6 × 164 — 104.
In step S104, it is determined whether the bit number of the last portion of data is greater than 0, if so, step S105 is performed, otherwise, step S106 is performed. In this embodiment, the number of bits of the last portion of data is 104, so step S105 is performed.
In step S105, the data length to be added is calculated from the number of bits of each part of data and the number of bits of the last part of data at the time of copying, and a new data sequence is acquired. In the present embodiment, the process of acquiring a new data sequence is as follows.
N_add＝BitsPerPart-BitsInLastPart
wherein, N _ add represents the length of data to be added, BitsPerPart represents the number of bits of each part during copying, and BitsInLastPart represents the number of bits of the last part of data during copying. In this embodiment, the length of the added data is 164-.
and step 3, updating the data length N _ data _ actual, wherein the calculation formula is as follows:
N_data_actual＝N_data+N_add
wherein, N _ data _ actual represents the updated data length, N _ data represents the original data length, and N _ add represents the data length required to be added. In the present embodiment, the updated data length is 1088+ 60-1148.
Fig. 2 is a schematic diagram of the calculated parameter size according to the embodiment of the present invention. As shown in fig. 2, through the calculation in step S103 and step S105, the sizes of the parameters for performing time-frequency diversity copying in the embodiment of the present invention are respectively: the number of actually used subcarriers in copying is 410, the number of carriers of each part of data is 82, the number of bits of each part of data is 164, the number of required orthogonal frequency division multiplexing symbols is 7, the number of bits of each orthogonal frequency division multiplexing symbol is 820, the number of bits of the last orthogonal frequency division multiplexing symbol is 268, the number of corresponding subcarriers of each interleaver is 41, the number of bits of the last part of data is 104, and the new data length is 1148.
In step S106, a shift parameter of the time-frequency diversity copy is calculated according to the number of copies and the number of bits of the last ofdm symbol. The specific rules include:
when the number of times of copying is 1, the shift parameter cyclicshift is 0;
when the number of copying times is 2, if the bit number of the last orthogonal frequency division multiplexing symbol BitsInLastOFDM is not more than the bit number of each part during copying BitsPerpart, the shifting parameter circshift is [0,0], otherwise, the shifting parameter circshift is [0,1 ];
when the number of copies is 4, BitsInLastOFDM ≦ bitsipart, shift parameter cyclicshift ═ 0,0,0], bitsipart < BitsInLastOFDM ≦ 2 × bitsipart, shift parameter cyclicshift ≦ 0,0,1,1], 2 × bitsipart < BitsInLastOFDM ≦ 3 × bitsipart, shift parameter cyclicshift ≦ 0,0,0,0], 3 × bitsipart < BitsInLastOFDM ≦ 4 × bitsipart, shift parameter cyclicshift ≦ 0,1,2,3 ];
when the number of copies is 5, BitsInLastOFDM is less than or equal to 4 multiplied by BitsPerpart, and the shifting parameter circhift is [0,0,0,0,0], otherwise, the shifting parameter circhift is [0,1,2,3,4 ];
when the number of copies is 7, BitsInLastOFDM is less than or equal to 6 xBitsPerpart, and the shifting parameter circhift is [0,0,0,0,0,0,0], or else, the shifting parameter circhift is [0,1,2,3,4,5,6 ];
when the number of copies is 11, BitsInLastOFDM is less than or equal to 10 × bitsiperpart, and the shift parameter circhift is [0,0,0,0,0,0,0, 0], otherwise, the shift parameter circhift is [0,1,2,3,4,5,6,7,8,9,10 ].
In this embodiment, the number of copies is 5, BitsInLastOFDM is 268, BitsPerPart is 164, and BitsInLastOFDM ≦ 4 × BitsPerPart, so that the shift parameter is circhift [0,0,0,0,0]
In step S107, an interleaving offset step is calculated according to the number of subcarriers corresponding to each interleaver during copying and the number of interleavers, an interleaving step of each interleaver is determined according to the interleaving offset step, and finally an interleaving address of each interleaver is calculated according to the interleaving step. The specific calculation method is as follows.
wherein, Interstep represents interleaving offset step, Carrier PerInterleaver represents the number of sub-carriers corresponding to each interleaver during copying, InterNum represents the number of interleavers corresponding to the number of copying times,
in this embodiment, the number of subcarriers corresponding to each interleaver during copying is 41, the number of interleavers corresponding to the number of copies is 10, and the interleaving offset step is 2 as can be seen from calculation.
when Interstep < 1, InterShiftstep equals 0;
when 1 is not less than Interstep and is less than 2, InterShiftstep is equal to 1;
when 2 is more than or equal to Interstep and less than 4, InterShiftstep is equal to 2;
when 4 is less than or equal to Interstep and less than 8, InterShiftstep is equal to 4;
when 8 is less than or equal to Interstep < 16, InterShiftstep is equal to 8;
in this embodiment, the interleaving offset step size is 2, and the interleaving step size is also 2.
when each interleaver performs interleaving, a marching listing mode is adopted, an original address is firstly stored in a matrix with N rows and M columns according to the marching mode, elements in the matrix are read out according to the sequence of the columns, and after the elements are read out, each interleaver performs cyclic shift to obtain a final interleaving result, wherein a specific calculation formula is as follows:
when the ith interleaver performs interleaving, the matrix column number M (i) of the interleaver
M(i)＝i*InterShiftStep
Wherein M (i) represents the matrix column number when the ith interleaver interleaves, InterShiftStep represents the interleaving step size of the interleaver,
when the ith interleaver performs cyclic shift, its cyclic shift parameter cyc (i) is:
cyc(i)＝2*(i-1)*InterShiftStep
where cyc (i) represents the cyclic shift parameter of the ith interleaver, and InterShiftStep represents the interleaving step size of the interleaver.
In this embodiment, there are 10 interleavers, where the number M of matrix columns for the first interleaver is 2, the number M of matrix columns for the second interleaver is 4, and the number M of matrix columns for the tenth interleaver is 20, and 10 interleaving output results can be obtained by interleaving with 10 interleavers. Fig. 3 is a schematic diagram of an interleaver interleaving manner according to an embodiment of the present invention. As shown in fig. 3, in the third interleaver, the number M of columns of the matrix during interleaving is 6, the number N of rows of the matrix is 7, the cyclic shift parameter is 8, the result of the interleaving output in fig. 3 is [1,7,13,19,25,31,37, … …, 17,23,29,35,41,6,12,18,24,30,36], and then the interleaving result is cyclically shifted, and since the cyclic shift parameter is 8, the interleaving address of the final interleaver 3 is [35,41,6,12,18,24,30,36,1,7,13,19,25,31,37, … …, 17,23,29 ].
In step S108, time-frequency diversity copying is performed in sequence according to the copying times, the shifting parameter, the interleaving address of the interleaver, and the coding rate of the physical layer.
Preferably, sequentially performing time-frequency diversity copying on the coding rate of the physical layer according to the shift parameter and the interleaving address of the interleaver comprises:
when the Nth copying is carried out, shifting the copied part according to the shifting parameter, wherein N is more than 1;
dividing each part of data into blocks with the same number of interleavers required by each copying;
at the time of copying, bits and subcarriers are mapped according to the coding rate of the physical layer.
Fig. 4 is a schematic diagram of an embodiment of time-frequency diversity copying according to the embodiment of the present invention. In the embodiment shown in fig. 4, copy 5 times, when copying for the first time, each Part uses the interleaved addresses of interleavers 1,2, for the first Part1, the copy result is P1_1(I1), P1_2(I2), P1_1 represents the first block bits of Part1, in the embodiment, 82 bits, P1_2 represents the second block bits of Part1, in the embodiment, also 82 bits, I1 represents the final interleaved address of interleaver 1, I2 represents the final interleaved address of interleaver 2, for the second Part, the copy result is P2_1(I1), P2_2(I2), P2_1 represents the first block bits of Part2, P2_2 represents the second block bits of Part2, for the I Part I copied for the first time, the copy result is Part I _1(I1), P2_2 represents the first block bits of Part 493P 2(I _ 1), pi _2 represents the second block of bits of Part i; during the second copying, shifting the Part to be copied according to the shift parameter, and then interleaving each Part by using the interleaving addresses of the interleavers 3,4, where the second element of the shift parameter is 0 in the embodiment, so that no shift is needed, and when each Part is interleaved, similar to the case of the first copying, except that the interleaving addresses use the output results of the interleavers 3,4, as shown in fig. 5, for the first Part1, the copy results are P1_1(I3), P1_2(I4), for the second Part, the copy results are P2_1(I3), P2_2(I4), and for the I-th Part I of the second copying, the copy results are Pi _1(I3), Pi _2 (I4); for the jth copy, firstly, shifting 7 parts needing to be copied according to the jth element in the shifting parameter, and then interleaving each part according to the output of the interleaver 2j-1, 2j until the copying is finished.
Fig. 5 is a partial schematic diagram of a mapping relationship between bits and carriers when performing time-frequency diversity copying according to an embodiment of the present invention. During copying, bits and subcarriers are mapped according to the BPC parameters, if the BPC is 1,1 bit may be mapped to each subcarrier, and if the BPC is 2, 2 bits may be mapped to each subcarrier. In this embodiment, the BPC is 2, as shown in fig. 5, in the first block bit P3_1 of the third part of the first OFDM symbol, the mapping relationship between bits and subcarriers is adopted, and in mapping, the interleaver output I (1) of the interleaver 1 is used, in fig. 6, the bit number corresponding to P3_1 is 329-410, and the subcarrier number corresponding to mapping is 164+ I (1,1) corresponding to 329, 330 bits, where I (1,1) represents the first interleaving result output by the first interleaver, and for (328+2m-1), (328+2m) bits, the subcarrier number corresponding to mapping is 164+ I (1, m), where 1 ≦ m ≦ 41, and I (1, m) represents the mth interleaving result output by the first interleaver. The mapping relationship between bits and subcarriers in other parts is similar to that in fig. 5, except that the corresponding interleaver is different during mapping.
Preferably, the diversity copying is performed in both time and frequency domains, the frequency domain representing that the data to be transmitted is copied on different subcarriers, and the time domain representing that the data to be transmitted is copied on different orthogonal frequency division multiplexing symbols.
In order to verify the effect of the present invention, the following description is further made in conjunction with simulation experiments.
Fig. 6 is a schematic diagram of an experimental result of a time-frequency diversity copying method based on orthogonal frequency division multiplexing according to an embodiment of the present invention. Fig. 7 is a schematic diagram of another experimental result of the time-frequency diversity copying method based on orthogonal frequency division multiplexing according to the embodiment of the present invention. The simulation conditions of fig. 6 are: the bandwidth is 1.953-11.96 MHz, the number of available subcarriers is 411, the adopted physical block is 136, the data length is 1088, the modulation mode is QPSK, and the copying is performed for 5 times; the simulation conditions of fig. 7 are: the bandwidth is 2.441-5.615 MHz, the number of available subcarriers is 131, the physical block is 136, the data length is 1088, the modulation mode is QPSK, and 5 times of copying are carried out. The channel adopted in simulation is a power line channel, and the channel model is a 4-path fading channel. The horizontal axis in fig. 6 and 7 represents the signal-to-noise ratio in dB, and the vertical axis represents the bit error rate. In fig. 6 and 7, the curves marked with circles represent the error rate curves for non-diversity copies, and the curves marked with squares represent the error rate curves of the present invention. As can be seen from the simulation experiment results of fig. 6 and fig. 7, compared with the case without diversity, the present invention can provide higher diversity gain, well combat the frequency selectivity of the channel, and greatly improve the reliability of the system.
Fig. 8 is a structural diagram of a time-frequency diversity copy system based on orthogonal frequency division multiplexing according to an embodiment of the present invention. As shown in fig. 8, the ofdm-based time-frequency diversity copy system includes a data forming unit 801, an interleaver determining unit 802, a time-frequency diversity copy parameter determining unit 803, a data length determining unit 804, a new data sequence determining unit 805, a time-frequency diversity copy shift parameter calculating unit 806, an interleaver interleaving address calculating unit 807, and a time-frequency diversity copy unit 808.
A data forming unit 801, configured to receive the medium access control layer information through the physical layer, and generate original data that needs to be transmitted by the physical layer;
an interleaver determining unit 802 for determining the number of interleavers according to the number of copies;
a time-frequency diversity copy parameter determining unit 803, configured to calculate time-frequency diversity copy parameters according to the medium access control layer information and the determined number of interleavers, where the parameters include the number of subcarriers actually used in copying, the number of carriers of each part of data, the number of bits of each part of data, the number of required orthogonal frequency division multiplexing symbols, the number of bits of each orthogonal frequency division multiplexing symbol, the number of bits of a last orthogonal frequency division multiplexing symbol, the number of subcarriers corresponding to each interleaver, and the number of bits of a last part of data;
a data length judging unit 804 for judging whether the number of bits of the last part of the transmitted data is greater than 0;
a new data sequence determination unit 805 configured to calculate a data length to be added according to the number of bits of each part of data and the number of bits of the last part of data at the time of copying, and acquire a new data sequence;
a time-frequency diversity copy shift parameter calculation unit 806, configured to calculate a shift parameter of the time-frequency diversity copy according to the number of copies and the number of bits of the last ofdm symbol;
an interleaver interleaving address calculation unit 807, configured to calculate an interleaving offset step size according to the number of subcarriers corresponding to each interleaver during copying and the number of interleavers, determine an interleaving step size of each interleaver according to the interleaving offset step size, and finally calculate an interleaving address of each interleaver according to the interleaving step size; and
and the time-frequency diversity copying unit 808 is used for sequentially copying the time-frequency diversity according to the copying times, the shifting parameter, the interleaving address of the interleaver and the coding rate of the physical layer.
And the time-frequency diversity copying unit 808 is used for sequentially copying the time-frequency diversity according to the copying times, the shifting parameter, the interleaving address of the interleaver and the coding rate of the physical layer.
The present invention has been described through the above embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ means, component, etc. ] are to be interpreted openly as referring to at least one instance of said means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
Claims (9)
1. A time-frequency diversity copying method based on orthogonal frequency division multiplexing is characterized by comprising the following steps:
step 1, a physical layer receives medium access control layer information and generates original data needing to be transmitted by the physical layer;
step 2, determining the number of interleavers according to the number of copying times;
step 3, calculating time-frequency diversity copying parameters according to the medium access control layer information and the determined number of the interleavers, wherein the parameters comprise the number of subcarriers actually used in copying, the number of carriers of each part of data, the number of bits of each part of data, the number of required orthogonal frequency division multiplexing symbols, the number of bits of each orthogonal frequency division multiplexing symbol, the number of bits of the last orthogonal frequency division multiplexing symbol, the number of subcarriers corresponding to each interleaver and the number of bits of the last part of data;
step 4, judging whether the bit number of the last part of data is greater than 0, if so, executing step 5, otherwise, executing step 6;
step 5, calculating the length of data to be added according to the bit number of each part of data and the bit number of the last part of data during copying, and acquiring a new data sequence;
step 6, calculating the shift parameter of the time-frequency diversity copy according to the copy times and the bit number of the last orthogonal frequency division multiplexing symbol;
step 7, calculating the interleaving offset step size according to the number of the subcarriers corresponding to each interleaver and the number of the interleavers during copying, determining the interleaving step size of each interleaver according to the interleaving offset step size, and finally calculating the interleaving address of each interleaver according to the interleaving step size, wherein:
calculating an interleaving offset step length Interstep, wherein the calculation formula is as follows:
wherein, Carrier PerInterleaver represents the number of sub-carriers corresponding to each interleaver during copying, InterNum represents the number of interleavers corresponding to the number of copying times,
the whole is taken down;
determining an interleaving step size InterShiftstep of each interleaver according to the interleaving offset step size Interstep, wherein the corresponding relation is as follows:
when Interstep < 1, InterShiftstep equals 0;
when 1 is not less than Interstep and is less than 2, InterShiftstep is equal to 1;
when 2 is more than or equal to Interstep and less than 4, InterShiftstep is equal to 2;
when 4 is less than or equal to Interstep and less than 8, InterShiftstep is equal to 4;
when 8 is less than or equal to Interstep < 16, InterShiftstep is equal to 8;
calculating the interleaving address of each interleaver of the InterShiftStep according to the interleaving step size comprises the following steps:
when each interleaver performs interleaving, a marching listing mode is adopted, an original address is firstly stored in a matrix with N rows and M columns according to the marching mode, elements in the matrix are read out according to the sequence of the columns, and after the elements are read out, each interleaver performs cyclic shift to obtain a final interleaving result, wherein a specific calculation formula is as follows:
when the ith interleaver performs interleaving, the matrix column number m (i) of the interleaver is:
M(i)＝i*InterShiftStep
when the ith interleaver performs cyclic shift, its cyclic shift parameter cyc (i) is:
cyc(i)＝2*(i-1)*InterShiftStep；
and 8, sequentially copying the time-frequency diversity according to the copying times, the shifting parameters of the time-frequency diversity copy, the interleaving address of the interleaver and the coding rate of the physical layer.
2. The method of claim 1, wherein the diversity copying is performed in both time and frequency domains, the frequency domain representing data to be transmitted being copied on different subcarriers, and the time domain representing data to be transmitted being copied on different orthogonal frequency division multiplexing symbols.
3. The method of claim 1, wherein the mac layer information received by the phy layer comprises a carragemap index, wherein the carragemap index specifies a coding rate, a copy number, and a phy block size of the phy layer, and wherein the length of original data transmittable by the phy layer is calculated according to the phy block size.
4. The method of claim 1, wherein determining the number of interleavers based on the number of copies comprises:
when the number of copying times is 2, the number of the interleavers is 8, and the number of the interleavers copied each time is 4;
when the number of copying times is 4, the number of the interleavers is 8, and the number of the interleavers copied each time is 2;
when the number of copying times is 5, the number of the interleavers is 10, and the number of the interleavers copied each time is 2;
when the number of copying times is 7, the number of interleavers is 14, and the number of interleavers copied each time is 2; and
when the number of times of copying is 11, the number of interleavers is 11, and the number of interleavers per copy is 1.
5. The method of claim 1, wherein the formula for calculating the parameters of the time-frequency diversity copies according to the MAC layer information and the determined number of interleavers comprises:
calculating the number N _ real _ carrier of subcarriers actually used during copying:
wherein, N _ real _ carrier represents the number of actually used sub-carriers during copying, InterNum represents the number of interleavers corresponding to the copying times, N _ carrier represents the number of usable sub-carriers,
the whole is taken down;
calculating the carrier number of each part in copying, namely Carrier PerPart:
wherein carrier Perpart represents the number of carriers of each part during copying, N _ real _ carrier represents the number of subcarriers actually used during copying, N _ copies represents the number of copying times,
the whole is taken down;
calculating the number of bits of each part during copying BitsPerpart:
BitsPerPart＝BPC*CarrierPerPart
wherein, BitsPerpart represents the bit number of each part during copying, BPC represents the physical layer coding rate, and Carrier Perpart represents the carrier number of each part during copying;
calculating the number of orthogonal frequency division multiplexing symbols N _ symbol required in copying:
wherein, N _ symbol represents the number of orthogonal frequency division multiplexing symbols needed in copying, N _ data represents the original data length, BitsPerpart represents the number of bits of each part in copying,
the upper integer is taken;
calculating the bit number BitsPerSymbol of each orthogonal frequency division multiplexing symbol when copying:
BitsPerSymbol＝BPC*N_real_carrier
wherein, BitsPerSymbol represents the bit number of each orthogonal frequency division multiplexing symbol during copying, BPC represents the physical layer coding rate, and N _ real _ carrier represents the number of subcarriers actually used during copying;
calculating the bit number BitsInLastOFDM of the last orthogonal frequency division multiplexing symbol:
wherein BitsInLastOFDM represents the bit number of the last OFDM symbol, N _ data represents the original data length, BitsPerSymbol represents the bit number of each OFDM symbol at the time of copying,
the whole is taken down;
calculating the subcarrier number Carrier Per Interleaver corresponding to each interleaver during copying:
wherein, carrier per interleaver represents the number of subcarriers corresponding to each interleaver during copying, N _ real _ carrier represents the number of subcarriers actually used during copying, and lnnum represents the number of interleavers corresponding to the number of copying times;
calculating the bit number of the last part of the data during copying BitsInLastpart:
BitsInLastPart＝N_data-(N_symbol-1)*BitsPerPart
wherein, BitsInLastPart represents the bit number of the last part of data during copying, N _ data represents the original data length, N _ symbol represents the number of orthogonal frequency division multiplexing symbols required during copying, and BitsPerPart represents the bit number of each part during copying.
6. The method of claim 1, wherein calculating the length of data to be added according to the number of bits of each portion of data and the number of bits of the last portion of data at the time of copying, and obtaining a new data sequence comprises:
step 1, calculating the data length N _ add required to be added:
N_add＝BitsPerPart-BitsInLastPart
wherein, N _ add represents the length of data to be added, BitsPerpart represents the bit number of each part during copying, and BitsInLastpart represents the bit number of the last part of the data during copying;
step 2, adding the data of the N _ add length in each copying, wherein the adding principle is as follows: the first copied N _ add length data comes from 1 to N _ add bits of the original data, the second copied N _ add length data comes from (N _ add +1) to 2N _ add bits of the original data, and so on until the Nth copied N _ add length data comes from [ (N-1) × N _ add +1] to N _ add bits of the original data; and
and step 3, updating the data length N _ data _ actual, wherein the calculation formula is as follows:
N_data_actual＝N_data+N_add
wherein, N _ data _ actual represents the updated data length, N _ data represents the original data length, and N _ add represents the data length required to be added.
7. The method of claim 1, wherein the rule for calculating the shift parameter of the time-frequency diversity copy according to the number of copies and the number of bits of the last OFDM symbol comprises:
when the copying times are 1, the shifting parameter cyclicshift of the time-frequency diversity copy is 0;
when the number of times of copying is 2, if the bit number of the last orthogonal frequency division multiplexing symbol BitsInLastOFDM is not more than the bit number of each part during copying BitsPerpart, the shifting parameter of time-frequency diversity copying is [0,0], otherwise, the shifting parameter is [0,1 ];
when the number of times of copying is 4, BitsInLastOFDM is not more than BitsPerpart, the shifting parameter cyclichhift of time-frequency diversity copy is [0,0,0,0], BitsPerpart < BitsInLastOFDM is not more than 2 xBitsPerpart, the shifting parameter cyclichhift of time-frequency diversity copy is [0,0,1,1], 2 xBitsPerpart < BitsInLastOFDM is not more than 3 xBitsPerpart, the shifting parameter cyclichhift of time-frequency diversity copy is [0,0,0,0], 3 xBitsPerpart < BitsInLastOFDM is not more than 4 xBitsPerpart, the shifting parameter cyclichhift of time-frequency diversity copy is [0,1,2,3 ];
when the copying times is 5, BitsInLastOFDM is not more than 4 multiplied by BitsPerpart, the shifting parameter cyclicshift of the time-frequency diversity copy is [0,0,0,0,0], otherwise, the shifting parameter cyclicshift of the time-frequency diversity copy is [0,1,2,3,4 ];
when the copying times are 7, BitsInLastOFDM is not more than 6 multiplied by BitsPerpart, the shifting parameter cyclicshift of the time-frequency diversity copy is [0,0,0,0,0,0,0, 0], otherwise, the shifting parameter cyclicshift of the time-frequency diversity copy is [0,1,2,3,4,5,6 ];
when the number of times of copying is 11, BitsInLastOFDM is less than or equal to 10 × bitsiperpart, the shift parameter cyclicshift of the time-frequency diversity copy is [0,0,0,0,0,0,0,0,0, 0], otherwise, the shift parameter cyclicshift of the time-frequency diversity copy is [0,1,2,3,4,5,6,7,8,9,10 ].
8. The method of claim 1, wherein the time-frequency diversity copying sequentially according to the copying times, the shifting parameters of the time-frequency diversity copying, the interleaving address of the interleaver, and the coding rate of the physical layer comprises:
when the Nth copying is carried out, shifting the copied part according to the shifting parameters of the time-frequency diversity copying, wherein N is more than 1;
dividing each part of data into blocks with the same number of interleavers required by each copying;
at the time of copying, bits and subcarriers are mapped according to the coding rate of the physical layer.
9. A time-frequency diversity copy system based on orthogonal frequency division multiplexing, the system comprising:
the data forming unit is used for receiving the medium access control layer information through the physical layer and generating original data needing to be transmitted by the physical layer;
an interleaver determining unit for determining the number of interleavers based on the number of copies;
a time-frequency diversity copy parameter determining unit, configured to calculate time-frequency diversity copy parameters according to the mac layer information and the determined number of interleavers, where the parameters include the number of subcarriers actually used in copying, the number of carriers of each part of data, the number of bits of each part of data, the number of required ofdm symbols, the number of bits of each ofdm symbol, the number of bits of a last ofdm symbol, the number of subcarriers corresponding to each interleaver, and the number of bits of a last part of data;
a data length judging unit for judging whether the number of bits of the last part of the transmitted data is greater than 0;
a new data sequence determining unit, which is used for calculating the length of data to be added according to the bit number of each part of data and the bit number of the last part of data during copying and acquiring a new data sequence;
a time-frequency diversity copy shift parameter calculation unit for calculating the shift parameter of the time-frequency diversity copy according to the copy times and the bit number of the last OFDM symbol;
an interleaver interleaving address calculation unit, configured to calculate an interleaving offset step size according to the number of subcarriers corresponding to each interleaver during copying and the number of interleavers, determine an interleaving step size of each interleaver according to the interleaving offset step size, and finally calculate an interleaving address of each interleaver according to the interleaving step size, where:
calculating an interleaving offset step length Interstep, wherein the calculation formula is as follows:
wherein, Carrier PerInterleaver represents the number of sub-carriers corresponding to each interleaver during copying, InterNum represents the number of interleavers corresponding to the number of copying times,
the whole is taken down;
determining an interleaving step size InterShiftstep of each interleaver according to the interleaving offset step size Interstep, wherein the corresponding relation is as follows:
when Interstep < 1, InterShiftstep equals 0;
when 1 is not less than Interstep and is less than 2, InterShiftstep is equal to 1;
when 2 is more than or equal to Interstep and less than 4, InterShiftstep is equal to 2;
when 4 is less than or equal to Interstep and less than 8, InterShiftstep is equal to 4;
when 8 is less than or equal to Interstep < 16, InterShiftstep is equal to 8;
calculating the interleaving address of each interleaver of the InterShiftStep according to the interleaving step size comprises the following steps:
when each interleaver performs interleaving, a marching listing mode is adopted, an original address is firstly stored in a matrix with N rows and M columns according to the marching mode, elements in the matrix are read out according to the sequence of the columns, and after the elements are read out, each interleaver performs cyclic shift to obtain a final interleaving result, wherein a specific calculation formula is as follows:
when the ith interleaver performs interleaving, the matrix column number m (i) of the interleaver is:
M(i)＝i*InterShiftStep
when the ith interleaver performs cyclic shift, its cyclic shift parameter cyc (i) is:
cyc(i)＝2*(i-1)*InterShiftStep；
and the time-frequency diversity copying unit is used for sequentially copying the time-frequency diversity according to the copying times, the shifting parameter of the time-frequency diversity copying, the interleaving address of the interleaver and the coding rate of the physical layer.
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| CN107395546B (en) * | 2017-08-30 | 2020-04-24 | 重庆物奇科技有限公司 | Method for carrying out frequency domain information expansion on data symbols in power line carrier communication |
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| CN112543088A (en) * | 2020-12-04 | 2021-03-23 | 青岛鼎信通讯股份有限公司 | Data diversity copying method suitable for medium-voltage power line broadband communication |
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| CN107017975A (en) | 2017-08-04 |
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