CN109617849B - Mixed activated carrier index modulation method - Google Patents

Mixed activated carrier index modulation method Download PDF

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CN109617849B
CN109617849B CN201811590864.8A CN201811590864A CN109617849B CN 109617849 B CN109617849 B CN 109617849B CN 201811590864 A CN201811590864 A CN 201811590864A CN 109617849 B CN109617849 B CN 109617849B
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subcarrier
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但黎琳
尤花征
李洋
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators

Abstract

The invention belongs to the technical field of wireless communication, and particularly relates to a design scheme of a multi-carrier waveform of an index modulation OFDM system by adopting a mixed subcarrier activation scheme. Compared with the index modulation of a single mode of activating k subcarriers by n subcarriers of the existing subblocks, one subblock can be used for selecting multiple subcarrier activation modes, and index information is increased; meanwhile, the activation modes of overlapping a plurality of single modes are included in the activation modes of the plurality of subcarriers, the information quantity of subblock transmission is greatly increased by the overlapping mode, and the spectrum efficiency of the system is further remarkably improved.

Description

Mixed activated carrier index modulation method
Technical Field
The invention belongs to the technical field of wireless communication, relates to a mixed activated carrier index modulation method, and particularly relates to a multi-carrier waveform design method of an index modulation OFDM system adopting a mixed subcarrier activation scheme.
Background
Orthogonal Frequency Division Multiplexing (OFDM) has become one of the core technologies of 4G mobile communication systems. The method modulates bit stream to orthogonal sub-carriers for transmission to enable fading experienced by each sub-channel to be relatively flat, and then reduces inter-symbol interference by introducing cyclic prefix.
The OFDM (OFDM-Index Modulation, OFDM-IM) is a new type of multicarrier transmission scheme proposed in recent years. The basic principle of index modulation OFDM is to expand the dimensionality to a subcarrier index domain and a digital modulation domain on the basis of the traditional OFDM one-dimensional multi-carrier technology. It has the same characteristics as the traditional multi-carrier technology, such as high spectrum efficiency, strong multipath effect resistance and the like. Compared with the traditional OFDM, the OFDM-IM system has lower peak-to-average ratio due to frequency domain sparsity, is less sensitive to frequency offset, can provide a new compromise between the system spectrum efficiency and the transmission performance, and has lower uncoded Bit Error probability (BER) than that of the OFDM system under the same spectrum efficiency. However, silencing a part of subcarriers can cause the spectrum efficiency of the OFDM-IM system to be lower than that of the OFDM system adopting the same modulation order, and although the position of the active carrier can carry a part of extra information, when the modulation order is higher, the defect cannot be compensated.
As the demand for communication services increases, the wireless communication system in the future needs more efficient data transmission rate, higher spectrum utilization rate and higher system capacity, and we know that frequency band resources are very rare and important, and when the traffic volume of various types of data increases, how to improve the spectrum utilization rate or search for a new available frequency band is also an important direction for the wireless communication system in the future to be researched.
Disclosure of Invention
The invention provides a mixed subcarrier activation scheme based on an index modulation OFDM system based on the purpose of improving the spectral efficiency of the system. The user selects one of the activation modes of the multiple subcarriers according to the index bit by taking the subblock as a unit for index modulation. The invention increases index bits by selecting multiple subcarrier activation modes, and further improves the spectral efficiency of the system by utilizing a part of subcarrier activation modes with high spectral efficiency.
The technical scheme of the invention is as follows:
the method is used for SIM-OFDM system, which carries out bit mapping by taking subblock as unit, each subblock is independent, so any subblock is taken as an example for explanation. The system is provided with N sub-carriers, and is divided into N/N sub-blocks, and each sub-block is provided with N sub-carriers; the method is characterized by comprising the following steps:
a. setting the mixed subcarrier activation mode of the system: setting m-m for sub-blocks1+m2The sub-carrier activation mode, namely the settable mode, has two types, wherein the type is that k is activated on n sub-carriers of a sub-block according to index bitsjThe sub-carriers are used for transmission of constellation point symbols, wherein
Figure BDA0001920223110000021
Type two has m2The method comprises the following steps that a subcarrier activation mode is selected, each activation mode is a certain number of activation modes of type one, index modulation is simultaneously and independently carried out on a subblock according to the activation modes, and modulated signals are transmitted in a superposition mode;
b. selecting a subcarrier activation pattern type: for any one sub-block, according to b1The bit index bits select whether the sub-carrier activation pattern to be used by the sub-block is type one or type two,
Figure BDA0001920223110000022
c. selecting a subcarrier activation pattern:
if the type-one sub-carrier activation mode is selected in step b, according to b2Bit index bits select a sub-carrier activation pattern in type one, when
Figure BDA0001920223110000023
Figure BDA0001920223110000024
Represents rounding down;
if the type two sub-carrier activation mode is selected in the step b, according to the step b2Selecting a sub-carrier activation mode from type two by using bit index bit
Figure BDA0001920223110000025
d. Calculating the power configuration of the sub-blocks: one sub-block has n sub-carriers, and the normalized power of the sub-block is n;
if the sub-carrier activation mode selected in step c is activation k in type onejSub-carriers, each constellation point symbol by power αs＝n/kjCarrying out power configuration;
if the subcarrier activation pattern selected in step c is a pattern of type two, which includes s activated subcarrier patterns of type one, activating the activated subcarrier patterns respectively
Figure BDA0001920223110000026
Sub-carriers of which
Figure BDA0001920223110000027
Each constellation point symbol is in terms of power
Figure BDA0001920223110000028
Carrying out power configuration;
e. index modulation is carried out: index modulation is carried out by taking the subblocks as a unit; when M-order constellation point modulation is carried out, constellation point sets adopted in different types-I activated subcarrier modes are the same, or the M-order constellation points are obtained by rotating by different angles;
e1. if the sub-carrier activation mode selected in step c is activation k in type onejSub-carriers according to b3Bit index bit selects out kjThe sub-carriers are used as active sub-carriers,
Figure BDA0001920223110000031
then b is tocPerforming M-order constellation point modulation on the bit modulation bits to obtain kjIndividual constellation point symbol, bc＝kj·log2M, mixing kjSymbol per constellation point by power αsIs placed at k after power configurationjF, activating sub-carriers to obtain the final sending symbol vector X of the sub-block, and entering the step f;
e2. if the subcarrier activation mode selected in step c is a certain mode of type two, including s types of activation subcarrier modes of type one, then index modulation under the s types of activation subcarrier modes is independently performed to obtain a transmission symbol vector X under each modeiI is 1,2, …, s, and then X is addediThe final sending symbol vector X of the sub-block is obtained by superposition,
Figure BDA0001920223110000032
the index bits of the s type-active subcarrier patterns are respectively
Figure BDA0001920223110000033
The modulation bits for M-order constellation point modulation are respectively
Figure BDA0001920223110000034
When one sub-block transmits the index bit length
Figure BDA0001920223110000035
Modulating bit length
Figure BDA0001920223110000036
f. Frequency domain-time domain transformation: and sequentially carrying out serial-parallel conversion, IFFT, parallel-serial conversion and cyclic prefix adding operation on the obtained transmitting symbol vector X, and then transmitting the transmitting symbol vector X through an antenna.
The invention has the beneficial effects that: compared with the index modulation of a single mode of activating k subcarriers by n subcarriers of the existing subblocks, one subblock can be used for selecting multiple subcarrier activation modes, and index bits are increased; meanwhile, the activation modes of overlapping a plurality of single modes are included in the activation modes of the plurality of subcarriers, the information quantity of subblock transmission is greatly increased by the overlapping mode, and the spectrum efficiency of the system is further improved.
Drawings
FIG. 1 is a schematic diagram of the modulation scheme of any sub-block when the type-one sub-carrier activation mode is selected in the embodiment, where X is1Represents constellation point symbols, X, obtained by modulating constellation points of order M in a type-1 subcarrier activation mode2,iRepresenting the ith constellation point symbol obtained by modulating the constellation point of M order under the mode of activating 2 sub-carriers.
Fig. 2 is a modulation schematic diagram of any one sub-block when the type two sub-carrier activation mode is selected in the embodiment.
Detailed Description
The technical scheme of the invention is described in detail in the following with reference to the accompanying drawings and embodiments:
example (b):
it is assumed that the SIM-OFDM system has N1024 subcarriers, and is divided into 256 sub-blocks, where each sub-block has N4 subcarriers. The system takes the sub-blocks as a unit to carry out bit mapping in sequence, each sub-block is independent, and any sub-block is taken as an example for explanation. The method comprises the following steps:
a transmitting end:
a. setting various subcarrier activation modes of the system: the sub-block is set with 3 sub-carrier activation patterns, which are divided into two types. Type one includes 2 subcarrier activation modes, i.e. 1 subcarrier is activated or 2 subcarriers are activated for constellation point symbol transmission according to index bits in 4 subcarriers of a subblock, namely k1＝1,k 22; the second type includes a 1-subcarrier activation mode, which is to independently perform index modulation for activating 1 subcarrier and 2 subcarriers on a subblock, and perform superposition transmission on the obtained 2 modulation signals on the subblock.
b. Selecting a subcarrier activation pattern type: for any one sub-block, according to b1The sub-carrier activation mode to be used by the sub-block is selected to be type one or type two by 1-bit index bit, the type one is selected if the index bit is 0, and the type two is selected if the index bit is 1.
c. Selecting a sub-carrier activation mode, if the type-one sub-carrier activation mode is selected in b, according to b2Selecting a subcarrier activation mode in type one by 1-bit index bit, if the index bit is 0, selecting to activate 1 subcarrier in 4 subcarriers, and if the index bit is 1, selecting to activate 2 subcarriers; if the type two sub-carrier activation mode is selected in b, directly selecting the only sub-carrier activation mode in the type two, at this time
Figure BDA0001920223110000041
d. Calculating the power configuration of the sub-blocks: a sub-block has n-4 sub-carriers and the normalized power of the sub-block is 4. If the sub-carrier activation mode selected in c is 1 (2) sub-carriers activated in type one, each constellation point symbol is according to power αs＝n/kj＝4(αs＝n/kj2) performing power configuration; if the selected sub-carrier activation pattern in c is of type twoUnique subcarrier activation pattern, which comprises 2 active subcarrier patterns in type one, and respectively activates
Figure BDA0001920223110000042
Sub-carriers, then each constellation point symbol by power
Figure BDA0001920223110000043
And carrying out power configuration.
e. Index modulation is carried out: index modulation is performed in units of sub-blocks. Performing M-2-order constellation point modulation, wherein constellation point set psi adopted by activating 1 subcarrier mode in type one1Set of constellation points Ψ for activating 2 subcarrier patterns in type one for normalizing the set of BPSK constellation points2By Ψ1Clockwise rotation by pi/2.
1. If the subcarrier activation pattern selected in c is 1 subcarrier in type one, then according to b3Selecting 1 subcarrier as active subcarrier from 2-bit index bit, and modulating 1-bit according to psi1Mapping the constellation points to obtain 1 constellation point symbol according to the power alphasAfter power configuration, placing the sub-block on an activated sub-carrier to obtain a final sending symbol vector X of the sub-block; if the sub-carrier activation mode selected in c is to activate 2 sub-carriers in type one, then according to b 32 sub-carriers are selected as active sub-carriers by 2-bit index bit, and then 2-bit modulation bit is used according to psi2Mapping the constellation points to obtain 2 constellation point symbols according to the power alphasAfter power configuration, the sub-block is placed on an active sub-carrier to obtain a final sending symbol vector X of the sub-block
2. If the only subcarrier activation mode in the type two is selected in the step c, index modulation under the modes of activating 1 subcarrier and activating 2 subcarriers is independently carried out according to the type one to obtain a transmitting symbol vector X under the 2 modes1,X2Then, X is added1,X2The final transmission symbol vector X of the sub-block is obtained by superposition, and X is equal to X1+X2. When the index modulation in the 1 subcarrier mode is activated independently,index bit length
Figure BDA0001920223110000051
Length is bc,1Modulation bit of 1 according to Ψ1Carrying out constellation point mapping; index bit length when index modulation in the mode of activating 2 subcarriers is independently performed
Figure BDA0001920223110000052
Length is b c,12 modulation bits according to Ψ2And carrying out constellation point mapping. So that one sub-block transmission index bit length at this time
Figure BDA0001920223110000053
Modulating bit length
Figure BDA0001920223110000054
f. Frequency domain-time domain transformation: and e, sequentially carrying out operations of serial-parallel conversion, IFFT, parallel-serial conversion, Cyclic Prefix (CP) addition and the like on the transmission symbol vector X obtained by e, and then transmitting the transmission symbol vector X through an antenna.
For the embodiment, the user defines two types of subcarrier activation manners, and assuming that the index bits are uniformly distributed, the average length of the index bits transmitted by one sub-block is 4.5 bits, and the average length of the modulation bits transmitted by one sub-block is 2.25 bits in BPSK modulation, so that about 1.7 bits are transmitted per carrier on average. When the traditional index modulation OFDM system adopts BPSK modulation, a 1-out-of-4 mode transmits 0.75 bit per carrier, and a 2-out-of-4 mode transmits 1 bit per carrier. Therefore, the method can be seen intuitively that index bits are added by selecting the activation modes of a plurality of subcarriers; meanwhile, the activation modes of overlapping a plurality of single modes are included in the activation modes of the plurality of subcarriers, the information quantity of subblock transmission is greatly increased by the overlapping mode, and the spectrum efficiency of the system is obviously improved.

Claims (1)

1. A mixed activated carrier index modulation method is used for an index modulation OFDM system, the system is provided with N sub-carriers and is divided into N/G sub-blocks, and each sub-block is provided with N sub-carriers; the method is characterized by comprising the following steps:
a. setting the mixed subcarrier activation mode of the system: setting m-m for sub-blocks1+m2The sub-carrier activation mode, namely the settable mode, has two types, wherein the type is that k is activated on n sub-carriers of a sub-block according to index bitsjSub-carriers are used for the transmission of constellation point symbols, where j is 1,2, …, m1，
Figure FDA0002928648600000011
Type two has m2The method comprises the following steps that a subcarrier activation mode is selected, each activation mode is a certain number of activation modes of type one, index modulation is simultaneously and independently carried out on a subblock according to the activation modes, and modulated signals are transmitted in a superposition mode;
b. selecting a subcarrier activation pattern type: for any one sub-block, according to b1The bit index bits select whether the sub-carrier activation pattern to be used by the sub-block is type one or type two,
Figure FDA0002928648600000012
if the index bit is 0, selecting type one, and if the index bit is 1, selecting type two;
c. selecting a subcarrier activation pattern:
if the type-one sub-carrier activation mode is selected in step b, according to b2Bit index bits select a sub-carrier activation pattern in type one, when
Figure FDA0002928648600000013
Figure FDA0002928648600000014
Represents rounding down;
if the type two sub-carrier activation mode is selected in the step b, according to the step b2Selecting a sub-carrier activation mode from type two by using bit index bit
Figure FDA0002928648600000015
d. Calculating the power configuration of the sub-blocks: one sub-block has n sub-carriers, and the normalized power of the sub-block is n;
if the sub-carrier activation mode selected in step c is activation k in type onejSub-carriers, each constellation point symbol by power αs＝n/kjCarrying out power configuration;
if the subcarrier activation pattern selected in step c is a pattern of type two, which includes s activated subcarrier patterns of type one, activating the activated subcarrier patterns respectively
Figure FDA0002928648600000016
Sub-carriers of which
Figure FDA0002928648600000017
Each constellation point symbol is in terms of power
Figure FDA0002928648600000018
Carrying out power configuration;
e. index modulation is carried out: index modulation is carried out by taking the subblocks as a unit; when M-order constellation point modulation is carried out, constellation point sets adopted in different types-I activated subcarrier modes are the same, or the M-order constellation points are obtained by rotating by different angles;
e1. if the sub-carrier activation mode selected in step c is activation k in type onejSub-carriers according to b3Bit index bit selects out kjThe sub-carriers are used as active sub-carriers,
Figure FDA0002928648600000021
then b is tocPerforming M-order constellation point modulation on the bit modulation bits to obtain kjIndividual constellation point symbol, bc＝kj·log2M, mixing kjSymbol per constellation point by power αsIs placed at k after power configurationjOn each active sub-carrier, obtaining the final transmission of the sub-blockSymbol vector X, enter step f;
e2. if the subcarrier activation mode selected in step c is a certain mode of type two, including s types of activation subcarrier modes of type one, then index modulation under the s types of activation subcarrier modes is independently performed to obtain a transmission symbol vector X under each modeiI is 1,2, …, s, and then X is addediThe final sending symbol vector X of the sub-block is obtained by superposition,
Figure FDA0002928648600000022
the index bits of the s type-active subcarrier patterns are respectively
Figure FDA0002928648600000023
The modulation bits for M-order constellation point modulation are respectively
Figure FDA0002928648600000024
When one sub-block transmits the index bit length
Figure FDA0002928648600000025
Modulating bit length
Figure FDA0002928648600000026
f. Frequency domain-time domain transformation: and sequentially carrying out serial-parallel conversion, IFFT, parallel-serial conversion and cyclic prefix adding operation on the obtained transmitting symbol vector X, and then transmitting the transmitting symbol vector X through an antenna.
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CN111478871B (en) * 2020-04-20 2021-11-19 西安电子科技大学 High-spectrum-efficiency carrier index modulation method based on replenishment index
CN111884983B (en) * 2020-07-22 2022-07-15 中国人民解放军海军航空大学 Multi-carrier signal index modulation and demodulation method based on constellation diagram optimization
US11689409B2 (en) * 2021-01-28 2023-06-27 Qualcomm Incorporated Index modulation for low-power analog-to-digital converters
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