CN107528807B - Spatial modulation MQAM signal detection method based on phase decision - Google Patents
Spatial modulation MQAM signal detection method based on phase decision Download PDFInfo
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Abstract
The invention discloses a phase decision-based spatial modulation MQAM signal detection method, belongs to the technical field of mobile communication signal detection, and provides a simplification method of maximum likelihood estimation from the perspective of maximum likelihood estimation (ML) demodulation of two-dimensional vector quantization. According to the characteristics of the MQAM constellation diagram, the phase of a modulation symbol is used for judgment, and a spatial modulation MQAM signal detection method (PDM) based on phase judgment is provided. The invention avoids the search of the modulation symbol space in the ML joint detection method, thereby greatly reducing the price and the complexity. The method not only approaches the ML performance, but also has lower complexity and has excellent theoretical and practical significance. The invention has better practical application significance in the antenna technology and the green communication technology.
Description
Technical Field
The invention relates to the field of mobile communication, in particular to a spatial modulation MQAM signal detection method based on phase decision.
Background
SM (spatial modulation) is one of the hot spots studied as a new technology in MIMO (multiple input multiple output) systems, which can transfer channel bits using transmission antenna numbers while avoiding inter-channel interference. In the spatial modulation system, information bits are divided into two parts, one part is mapped to the selected antenna serial number, and the other part is mapped to the traditional modulation constellation diagram, so that the information bits can be transmitted by effectively utilizing the spatial dimension formed by the transmitting antenna serial numbers. In addition, the spatial modulation system only allows one antenna to be activated in the same transmission time slot, and other antennas keep a silent state, so that the inter-channel interference is effectively avoided.
In the spatial modulation system, the spectral efficiency is calculated by η ═ log2Nt+log2And M. I.e. the input information bit stream is in terms of log2Nt+log2The length of M is divided into frames, where NtThe number of transmitting antennas is expressed, M represents the number of modulating signal points, and the number of transmitting antennas of the spatial modulation system must be a power of 2. In each frame information bit, the first log2Ntbit is used to decide on NtOne sending antenna is selected from the sending antennas for data transmission, and the log is recorded2The M bits are used to select which symbol is transmitted in the modulation symbol set.
The spatial modulation technology is an emerging research of the large-scale MIMO technology in recent years, most of signal detection, modulation technology and even channel estimation technology use the correlation criterion of MIMO, although the system model and principle are approximately the same, the spatial modulation technology is improved, so that the correlation method in the MIMO technology lacks the characteristics and attributes of spatial modulation, and more advantages and characteristics of the spatial modulation technology are still to be researched. The research trend of the detection method shows how to reduce the calculation complexity of the method and improve the detection performance by improving the research. Therefore, in the spatial modulation MIMO system, the detection method is researched, the detection accuracy of the signal detection method is guaranteed to a certain extent through research and improvement, and meanwhile, the method flow and the calculation process are not complex, so that the method is significant. The principle of maximum likelihood estimation (ML) is to search all the transmitted symbols for the most suitable combination of antenna sequence numbers and modulation symbols, thus obtaining the closest error rate performance, which is called the best performance detection method. However, the method has too many searching targets, and the implementation steps are very complicated, so that the method is difficult to be practically applied to a large-scale antenna system. The invention reduces the complexity of symbol search by researching the characteristics of the MQAM constellation diagram, and has the difficulty of estimating possible constellation points with different amplitudes. Therefore, the invention provides a spatial modulation MQAM signal detection method based on phase decision, which can effectively reduce the number of connected channelsThe computational complexity of the receiving end and the better the performance as the number of modulation points increases. The computational complexity of the ML method is 6NrNtM, the complexity of the method provided by the invention is (6N)r+2+5R)Nt。
Disclosure of Invention
The present invention is directed to solving the above problems of the prior art. A spatial modulation MQAM signal detection method based on phase decision with low receiving end calculation complexity is provided. The technical scheme of the invention is as follows:
a spatial modulation MQAM signal detection method based on phase decision comprises the following steps:
firstly, in a spatial modulation system, converting the detection problem of symbols sent by the spatial modulation system into a quantization demodulation problem; secondly, quantizing the converted received signals according to the distribution characteristics of the constellation points in the constellation diagram, then estimating the transmitted symbols according to the phase size of the quantized signals, and then performing maximum likelihood optimal estimation on the activated antenna indexes; and finally, obtaining a signal detection result of the spatial modulation system.
Further, the converting the detection problem of the symbols sent by the spatial modulation system into the quantization demodulation problem specifically includes: in a spatial modulation system, the ML maximum likelihood estimation can be expressed as 2 nested search problems, i.e. first searching for the transmitted symbol s and then the antenna index l, can be expressed as
Wherein,
indicates the index of the transmit antenna and,
denotes a transmitted symbol, y denotes a received signal vector, hlRepresenting the ith column of the channel matrix. For internal optimization problems
I.e. given an active antenna index lUnder the condition, solving the transmission symbol s, and for the MQAM modulation signal, the internal optimization problem is still equivalent to
Wherein,
the detection problem of the SM system transmission symbol can be converted into a quantization demodulation problem.
Further, the quantizing the converted received signal according to the distribution characteristics of the constellation points in the MQAM constellation diagram, and determining the optimal estimation value of the transmitted signal specifically includes:
calculating corresponding M constellation points with R constellation points with different amplitudes according to MQAM signals with different points, wherein each amplitude is A from small to large1，A2…，Ar，…，ARI.e. the M constellation points are distributed in R with radius A1，A2，…，Ar，…，AROn the concentric circles of (1), the number of constellation points on each circle is m1，m2，…，mr，…，mRFor the MQAM constellation diagram, assuming that the initial phase is 0, the ith constellation point on the r-th circle can be represented as
Wherein ir is 1,2, …, mr，
For a given antenna/is calculated
Indicating the estimated phase of the transmitted symbol. The internal optimization problem in an SM system can be equated with
Wherein 0 is not less than thetal≤2π，θlWhich represents the phase of the received symbol,
further, the estimation of the phase of the transmitted symbol is performed according to the phase size of the received symbol: using formulas
Where A is the signal amplitude, the corresponding transmitted symbol is calculated
Further, the maximum likelihood optimal estimation of the active antenna index includes the steps of: corresponding transmission symbols are calculated
Substituting into ML optimal detection formula, ML search of active antenna index is carried out, namely
Wherein
The invention has the following advantages and beneficial effects:
the invention judges by utilizing the phase of the modulation symbol according to the characteristics of the QAM constellation diagram, avoids the search of the modulation symbol space in the ML joint detection method, and has extremely low price and complexity. The method not only approaches the ML performance, but also has lower complexity and has excellent theoretical and practical significance. The method can be applied to a Space Modulation (SM) system, and great economic and social benefits are generated.
Drawings
Fig. 1 is a schematic diagram of constellation points on a first circle of a 16QAM according to a preferred embodiment of the present invention;
fig. 2 is a preferred embodiment 8QAM constellation of the present invention;
fig. 3 is a diagram of a 16QAM constellation according to a preferred embodiment of the present invention;
FIG. 4 is a flow chart of a spatial modulation MQAM signal detection method based on phase decision according to a preferred embodiment of the present invention;
fig. 5 is a schematic diagram of a simulation curve of the preferred embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described in detail and clearly with reference to the accompanying drawings. The described embodiments are only some of the embodiments of the present invention.
The technical scheme for solving the technical problems is as follows:
the invention provides a spatial modulation MQAM signal detection method based on phase decision. First, in the spatial modulation system, the ML maximum likelihood estimation can be expressed as 2 nested search problems, i.e. first searching for the transmitted symbol s and then searching for the antenna index l, which can be expressed as
From this equation, it can be seen that the optimization problem is internal
I.e. the transmitted symbol s is solved given the active antenna index i. For MQAM modulated signals, the internal optimization problem remains equivalent
Wherein,
the detection problem of the SM system transmission symbol can be converted into a quantization demodulation problem. And then quantizing the converted received signals according to the distribution characteristics of the constellation points in the MQAM constellation diagram, further judging the optimal estimation value of the transmitted signals, and then performing ML optimal estimation on the activated antenna indexes. The method comprises the following specific steps:
the method comprises the following steps: calculating R constellation points with different amplitudes corresponding to the M constellation points according to MQAM signals with different orders, wherein each amplitude is A from small to large1，A2，…，Ar，…，ARI.e. the M constellation points are distributed in R with radius A1，A2，…，Ar，…，AROn the concentric circles of (1), the number of constellation points on each circle is m1，m2，…，mr，…，mR. For the MQAM constellation diagram, assuming that the initial phase is 0, the ith constellation point on the r-th circle can be represented as
Wherein ir is 1,2, …, mr，
The constellation points on the first circle are shown in fig. 1 as being 16 QAM. In fig. 2 and 3, M is 8, R is 2, and M is1＝4，m24 and M16, R3, M1＝4，m2＝8，m34 constellation.
Step two: for a given antenna/is calculated
The internal optimization problem in an SM system can be equated with
Wherein 0 is not less than thetal≤2π，
. Receiving a vector
The smaller the angle β between transmitted symbol s,
the larger the value of (a).
Step three: to obtain
Using the formula
Where A is the signal amplitude, the corresponding transmitted symbol is calculated
Step four: corresponding transmission symbols are calculated
Substituting into ML optimal detection formula, ML search of active antenna index is carried out, namely
Wherein
Step five: output l and corresponding s.
As described below with reference to fig. 4 and by way of example, the method may be generalized to an MQAM signal with a larger modulation point number M:
for example: number of antennas N when transmittingtNumber of receive antennas N4rWhen the symbol is 16QAM and the spectral efficiency η is 6bit/s/Hz, the method reduces the computational complexity by about 85% compared to ML.
The method comprises the following steps: for 16QAM, the constellation diagram is shown in fig. 3, where M is 16, R is 3, and M is1＝4，m2＝8， m3＝4。
Step two: for a given antenna/is calculated
At a radius of
When the constellation point number on the first circle is 4; when r is 2, i.e. at radius A2When the second circle is 1, the number of constellation points on the circle is 8; when r is 3, i.e. at a radius of
The number of constellation points on this circle is 4. When r is 1, r is 3,
when the r is 2, the reaction time is as short as possible,
wherein n is 1,2, …, 8.
Step three: obtained in the last step
Value bringing in
To obtain
Using formulas
Obtaining the minimum PlValue is corresponded to
Step four: corresponding transmission symbols are calculated
Performing ML searches of active antenna indices by substituting into ML maximum likelihood estimation formula, i.e. by
Wherein
Step five: output l and corresponding s.
Now the signal proposed by the present inventionThe detection method flow is summarized in FIG. 5, and for the active antenna index l, first, it is calculated
Then, the phase of the estimated constellation point and the corresponding symbol are calculated, and finally ML search of the activated antenna index is carried out.
The above examples are to be construed as merely illustrative and not limitative of the remainder of the disclosure. After reading the description of the invention, the skilled person can make various changes or modifications to the invention, and these equivalent changes and modifications also fall into the scope of the invention defined by the claims.
Claims (1)
1. A spatial modulation MQAM signal detection method based on phase decision is characterized by comprising the following steps:
firstly, in a spatial modulation system, converting the detection problem of symbols sent by the spatial modulation system into a quantization demodulation problem; secondly, quantizing the converted received signals according to the distribution characteristics of the constellation points in the MQAM constellation diagram, estimating the transmitted symbols according to the phase of the quantized signals, and performing maximum likelihood optimal estimation on the activated antenna indexes; finally, obtaining a signal detection result of the spatial modulation system;
the conversion of the detection problem of symbols sent by the spatial modulation system into the quantization demodulation problem specifically includes: in a spatial modulation system, the ML maximum likelihood estimation can be expressed as 2 nested search problems, i.e. first searching for the transmitted symbol s and then the antenna index l, can be expressed as
Wherein,
indicates the index of the transmit antenna and,
denotes a transmission symbol, y denotesReceiving the signal vector, hlColumn l representing the channel matrix, for the internal optimization problem
That is, under the condition of giving the activated antenna index l, the transmitted symbol s is solved, and for the MQAM modulated signal, the internal optimization problem is still equivalent to that of the MQAM modulated signal
Wherein,
the detection problem of symbols sent by an SM system can be converted into a quantization demodulation problem;
the quantizing the converted received signals according to the distribution characteristics of the constellation points in the MQAM constellation diagram, and the judging of the optimal estimation value of the transmitted signals specifically comprises the following steps:
calculating corresponding M constellation points with R constellation points with different amplitudes according to MQAM signals with different points, wherein each amplitude is A from small to large1,A2,…,Ar,…,ARI.e. the M constellation points are distributed in R with radius A1,A2,…,Ar,…,AROn the concentric circles of (1), the number of constellation points on each circle is m1,m2,…,mr,…,mRFor the MQAM constellation diagram, assuming that the initial phase is 0, the ith constellation point on the r-th circle can be represented as
Wherein ir is 1,2, …, mr，
For a given antenna/is calculated
Representing the estimated phase of the transmitted symbol, the internal optimization problem in SM systems can be equated with
Wherein 0 is not less than thetal≤2π，θlWhich represents the phase of the received symbol,
estimating a transmission symbol according to the phase of the received symbol, wherein the maximum likelihood estimation adopted for the estimation of the transmission antenna comprises: using formulas
Where A is the signal amplitude, the corresponding transmitted symbol is calculated
The maximum likelihood optimal estimation of the active antenna index comprises the following steps: corresponding transmission symbols are calculated
Substituting into ML optimal detection formula, ML search of active antenna index is carried out, namely
Wherein
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| CN101442390A (en) * | 2007-11-19 | 2009-05-27 | 电子科技大学 | Equilibrium acceptance method and apparatus for Turbo of spatial correlation MIMO |
| CN103023622A (en) * | 2012-12-31 | 2013-04-03 | 电信科学技术研究院 | Signal detection method and signal detection equipment |
| CN104994047A (en) * | 2015-07-31 | 2015-10-21 | 电子科技大学 | Antenna selection method for spatial phase modulation |
| CN105681236A (en) * | 2016-01-13 | 2016-06-15 | 中国人民解放军国防科学技术大学 | Initial value selection method of sphere decoding algorithm |
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| CN101442390A (en) * | 2007-11-19 | 2009-05-27 | 电子科技大学 | Equilibrium acceptance method and apparatus for Turbo of spatial correlation MIMO |
| CN103023622A (en) * | 2012-12-31 | 2013-04-03 | 电信科学技术研究院 | Signal detection method and signal detection equipment |
| CN104994047A (en) * | 2015-07-31 | 2015-10-21 | 电子科技大学 | Antenna selection method for spatial phase modulation |
| CN105681236A (en) * | 2016-01-13 | 2016-06-15 | 中国人民解放军国防科学技术大学 | Initial value selection method of sphere decoding algorithm |
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