CN107682289B - Mark symbol design method for mark auxiliary clustering receiver - Google Patents
Mark symbol design method for mark auxiliary clustering receiver Download PDFInfo
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- CN107682289B CN107682289B CN201710944515.0A CN201710944515A CN107682289B CN 107682289 B CN107682289 B CN 107682289B CN 201710944515 A CN201710944515 A CN 201710944515A CN 107682289 B CN107682289 B CN 107682289B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H—ELECTRICITY
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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
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Abstract
The invention belongs to the technical field of communication, in particular to a mark symbol design method for a mark auxiliary clustering receiver, which mainly comprises the steps of inserting mark symbols before a transmitter sends data information at a transmitting end, wherein a matrix formed by the mark symbols is phi, the content of the mark symbols is known at a receiving end, marking a mark signal corresponding to the received mark symbols as Y at the receiving end, forming a plurality of categories by marking the mark signal as Y R obtained through mark reconstruction, and recovering the sent symbols according to a clustering result and the mark symbols.
Description
Technical Field
The invention belongs to the technical field of communication, and particularly relates to a mark symbol design method for a mark auxiliary clustering receiver.
Background
the symbol detection performed by conventional receivers is performed in steps. Channel estimation is first performed based on the pilot signal at the transmitting end and then the transmitted symbols are recovered by a maximum likelihood detector or other simpler detector. The mark auxiliary clustering receiver directly clusters the signals received by the receiving end and judges corresponding transmitting symbols by using the mark symbols transmitted by the transmitting end. It is therefore necessary to design a marker symbol that improves the accuracy and clustering performance of the reconstructed tag, and thus improves the detection performance of the receiver.
Disclosure of Invention
The invention aims to provide a mark symbol design method for a mark auxiliary clustering receiver, which mainly aims at the mark auxiliary clustering receiver, wherein the receiver firstly conducts mark reconstruction after receiving signals, then classifies the received signals by using a clustering method, and finally indicates a sending symbol corresponding to each category through the reconstructed marks, thereby realizing symbol detection.
The technical scheme of the invention is as follows:
A method of tag symbol design for a tag assisted clustered receiver, comprising:
At the transmitting end: before a transmitter sends data information, inserting a marker symbol, wherein a matrix formed by the marker symbol is phi, and the content of the marker symbol is known by a receiving end;
At the receiving end: marking the mark signal corresponding to the received mark symbol as Y, and marking the mark signal obtained by mark reconstruction as YRForming a plurality of categories of the received signals through a clustering algorithm; recovering the sending symbol according to the clustering result and the mark symbol;
wherein the design method of the mark symbol is that the mark Y reconstructed by Y is usedRThe error is minimal.
The general technical scheme of the invention is that for a mark auxiliary clustering receiver, after the receiver receives signals, the receiver firstly carries out mark reconstruction, the invention specifies that a matrix formed by sent mark symbols is phi, a mark signal corresponding to the mark symbols received at a receiving end is Y, and a mark reconstructed at the receiving end is YR. Since the clustered receiver requires the initial center point to be closer to the true center point to achieve better convergence performance, the present invention aims to design the optimal phi to minimize the labeling error reconstructed by using Y.
The invention has the beneficial effects that the invention provides an optimal mark symbol design method, which can improve the accuracy and clustering performance of the reconstructed label, thereby improving the detection performance of a receiver.
Drawings
Fig. 1 shows a schematic diagram of a clustered receiver according to the present invention;
FIG. 2 illustrates a method for designing a marker symbol in OFDM according to the present invention;
FIG. 3 illustrates a method for designing a marker symbol in MIMO according to the present invention;
FIG. 4 shows a comparison of the performance of the best and worst case design methods of the OFDM system of the present invention;
Fig. 5 shows the performance comparison between the optimal marking and the suboptimal marking scheme of the MIMO system of the present invention.
Detailed Description
The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.
Fig. 1 shows the working flow of the clustered receiver proposed by the present invention. The transmitted symbols include a mark symbol and a data symbol, and correspond to a mark signal and a data signal of a receiving end. The marking signal is firstly marked and reconstructed, and the reconstructed mark marks each category and is used as an initial central point of a clustering algorithm. After the algorithm converges, the estimated class center point and variance are obtained, and the corresponding class also keeps the mark. The data signals clustered to the same category are detected and judged as the corresponding transmitting symbols of the category.
Example 1
As shown in fig. 2, this example is a method for designing a marker symbol, which takes an OFDM system as an example.
for an OFDM system, φ is a vector, defined as sLAccordingly, Y is also a vector, defined as YL，YRIs also a vector yR. Assuming a total of M subcarriers, there are L paths to the receiving end, and these time domain channels are denoted as h0,h1,…,hL-1After the receiving end performs the processes of cyclic prefix removal and fast discrete fourier transform (FFT), the frequency domain signal at the nth time can be represented as
yn＝Λsn+un,
Wherein s isnRefers to an OFDM symbol, s ═ sn,0,sn,1,…,sn,M-1]T，sn,mA symbol representing the nth time on the mth subcarrier and selected from a symbol set S, where S is a set of symbols that the transmitting end can transmit, for example, if the transmitting end adopts a QPSK modulation scheme, thenΛ＝diag(H0,H1,…,HM-1) The frequency domain response of the channel, is represented,And is
the optimal mark design scheme is explained in three aspects of (i) the minimum number of sent marks, (ii) mark reconstruction, and (iii) mark position and mark symbol selection.
the minimum number of transmitted markers: in order to reduce the number of transmission symbols, the present example performs the flag reconstruction using the relationship between subcarriers and the relationship between transmission symbols. The relationship between the frequency domain channel responses of the subcarriers can be expressed as
Designating the marked sub-carriers as p1,p2,…pTwhere T is the number of marked subcarriers. These marked subcarriers may be denoted as
wherein
whereinl＝0,…L-1,pt＝p1,…pT. It can be shown that when T ═ L, B is an invertible matrix, so the frequency domain channel response on subcarrier m can be written as
Hm＝wmB-1d (3)
WhereinAnd is
As can be seen from equation (3), when T is equal to L, the frequency domain channel response of the marked subcarriers can indicate the frequency domain channel responses of all subcarriers, so the transmitting end should mark at least L subcarriers.
secondly, label reconstruction: at the receiving end, the receiver obtains K — MQ class by clustering, where Q represents a modulation order, for example, when the OFDM system adopts a QPSK modulation scheme, Q is 4. The true mean value of the received signal at the receiving end is muk＝HmSqwhere k is M + Mq, M is 0, …, M-1, Q is 0, …, Q-1, Sqrepresents an element in the set S, and is known from formula (3)k＝HmSq＝wmB-1dS0fq＝akdS0wherein a isk＝wmB-1fq，In order to identify the groups obtained by clustering of the receivers, the invention obtains K marks by using a mark reconstruction mode. The mark symbol sent by the sending end isThe marker received at the receiving end may be represented aswhere operator deg. represents the multiplication of corresponding elements of a matrix or vector,The received mark is pre-processed and,Whereinthe reconstructed mark isWherein
③ selecting the marking position and the marking symbol: in order to determine the position of the transmitted symbols and what marker symbols are transmitted, the invention requires that the reconstruction error is minimized, i.e.
WhereinWherein the optimal solution isl is a constant, where l ∈ {0, … M-1 }. Wherein the operatorIndicating rounding down, mod (·, M) denotes a modulo M addition operation. As can be seen from the optimal solution, the symbol to be transmitted is selected to be optimal with the largest energy, and the subcarriers for transmitting the marks are optimally located at the farthest positions from each other.
Therefore, in this example, 1 marker symbol is inserted into each of L subcarriers spaced farthest from each other before transmitting a data symbol, and in the case of M ═ 64, 32 subcarriers not transmitting markers are spaced between subcarriers transmitting markers, and there is no requirement on the specific positions of subcarriers transmitting markers, and for example, the marker symbols may be transmitted on the 1 st and 33 th subcarriers, or the marker symbols may be transmitted on the 25 th and 57 th subcarriers, but the subcarriers transmitting markers are spaced farthest from each other. For the symbol to be transmitted, it needs to satisfy the maximum amplitude in the transmittable symbol set S, and for example, the OFDM system adopts the 16QAM method, the transmitted symbol can be in the setIf QPSK system is used, the transmitted marker symbol can be arbitrarily selected in the symbol set S.
Example 2
As shown in fig. 3, in this example, the MIMO system is taken as an example, and the method for designing the marker symbol is as follows:
For general has MtRoot transmitting antenna and MrMIMO model of root receiving antenna, where the number of mark symbols T is Mt，Is a matrix of, correspondingly,is also a matrix, YR＝Y·V。Representing the signal received at time n, the transmitted symbols s (n) being from a finite codebook of common K elementsIs the transmit power, H is the transmitter-to-receiver channel matrix, whose elements are independent of each other and Is MtSymbols transmitted together from transmit antennas, w (n) being noise subject to a Circularly Symmetric Complex Gaussian (CSCG) distribution, i.e.w (n) and s (n) are independent of each other, then the receiving antenna receivesthe resulting signal is represented as:
Since the noise follows the CSCG distribution, at a given timesubject to the condition that the signal received at the receiving antenna is subject to an average value ofVariance is sigmakOf CSCG distribution, i.e.And the distribution of the signals received by all the antennas of the receiver in the time period satisfies
The minimum number of transmitted markers: to pairThe maximum rank decomposition is carried out byWhere U is a full rank matrix. After passing through the channel, havewhereinIf and only if U is a full rank matrix, then That is at this timeCan be recovered solely from phi, so MtIs the minimum number of tokens.
Secondly, label reconstruction: at the receiving end, the received signals corresponding to the mark symbols are formed into a matrixWhereinIs the noise on the received signal. All other center points can be obtained by right-multiplying the recovery matrix, i.e.
Third, the mark symbol selection sent: the sum of the distances between the center point obtained by the recovery and the real center point is taken as the recovery error, and the optimal mark selection aims at minimizing the recovery error, namely
The optimal marker design criterion to solve for is to minimize the marker matrix UOtherwise if the number of transmitting antennas MtIs a power of 2 m, m being a natural number, the optimal mark design criterion is fromMiddle selection of MtThe orthogonal energy-maximum vectors form a matrix U.
thus, this example inserts M before transmitting the data symbolstEach marker symbol vector is one possible transmitted symbol vector. Take 4 × 4 antenna array, 16QAM modulation as an example, with a total of 44A possible transmitted symbol vector. Due to Mt4 is a power of 2, so the optimal mark is designed to pick 4 orthogonal energy maximumsThe vector of (2). Here, a Hadamard matrix-based selection strategy is provided, namely:
Fig. 4 shows a performance comparison diagram of the optimal and worst design methods of the marker symbol according to the example of the OFDM system of the present invention, in this diagram, the transmitting end uses the QPSK modulation scheme, and sets M64, N5, and L2, where the worst design means that subcarriers for transmitting the marker symbol are adjacent, in this simulation, the 1 st and 2 nd subcarriers transmit the marker symbol, the optimal design means that the subcarriers for transmitting the marker symbol are separated by 32 subcarriers, and in this simulation, the 1 st and 33 th subcarriers transmit the marker symbol, it can be seen that the performance difference between the two design schemes is large because when the subcarriers for transmitting the marker symbol are adjacent, all reconstructed marker symbols have a large error compared with the real marker symbol.
FIG. 5 shows a graph of the performance comparison of the optimal and worst-case design methods for the marker symbols of the MIMO system of the present invention, where Mt＝MrThe transmitting end adopts a QPSK modulation mode, the optimal design is orthogonal vector with maximum energy, and the sub-optimal design is a matrix U consisting of 2 non-orthogonal vectors with the same energy. Specifically, let the optimal mark be designed asthe suboptimal mark is designed asis provided with
it can be seen that the performance of the clustered receiver with the optimal tag design is significantly higher than that of the clustered receiver using sub-optimal tags.
Claims (1)
1. a method of tag symbol design for a tag assisted clustered receiver, comprising:
at the transmitting end: before a transmitter sends data information, inserting a marker symbol, wherein a matrix formed by the marker symbol is phi, and the content of the marker symbol is known by a receiving end;
at the receiving end: marking the mark signal corresponding to the received mark symbol as Y, and marking the mark signal obtained by mark reconstruction as YRForming a plurality of categories of the received signals through a clustering algorithm; recovering the sending symbol according to the clustering result and the mark symbol;
Wherein the design method of the mark symbol is that the mark Y reconstructed by Y is usedRthe method comprises the following specific steps:
For an OFDM system, φ is a vector, defined as sLAccordingly, Y is also a vector, defined as YL，YRIs also a vector, defined as yRLet a total of M subcarriers, with L paths to the receiving end, these time-domain channels are denoted as h0,h1,…,hL-1After the receiving end performs the processes of cyclic prefix removal and fast discrete fourier transform, the frequency domain signal at the nth time is represented as:
yn＝Λsn+un
Wherein s isnRefers to an OFDM symbol, s ═ sn,0,sn,1,…,sn,M-1]T，sn,mRepresents the symbol at the nth time instant on the mth subcarrier and is selected from a set of symbols, S, which is a set of symbols that the transmitting end can transmit, Λ ═ diag (H)0,H1,…,HM-1) Which represents the frequency-domain response of the channel,And is
The design method of the mark symbol comprises the following steps:
The minimum number of transmitted markers: in order to reduce the number of transmitted symbols, the mark reconstruction is carried out by utilizing the relation between subcarriers and the relation between transmitted symbols, and the relation between frequency domain channel responses of the subcarriers is expressed as:
Designating the marked sub-carriers as p1,p2,…pTWhere T is the number of marked subcarriers; these marked subcarriers are denoted as:
Wherein
WhereinWhen T ═ L, B is an invertible matrix, and the frequency domain channel response on subcarrier m is:
Hm＝wmB-1d (3)
WhereinAnd is
As shown in equation (3), when T is equal to L, the marked subcarrier frequency domain channel response may indicate frequency domain channel responses on all subcarriers, that is, the transmitting end should mark at least L subcarriers;
Secondly, label reconstruction: at a receiving end, a receiver obtains a class K as an MQ through clustering, wherein Q represents a modulation order; the true mean value of the received signal at the receiving end is muk＝HmSqWhere k is M + Mq, M is 0, …, M-1, Q is 0, …, Q-1, SqRepresents an element of the set S, and is represented by formula (3):
μk＝HmSq＝wmB-1dS0fq＝akdS0
Wherein a isk＝wmB-1fq，In order to identify the groups obtained by clustering of the receiver, K marks are obtained by using a mark reconstruction mode; the mark symbols sent by the sending end are as follows:
The mark received at the receiving end is denoted as
Wherein the operatorRepresenting the multiplication of corresponding elements of a matrix or vector,Preprocessing the received mark:
WhereinThe reconstructed mark isWherein
③ selecting the marking position and the marking symbol: minimizing reconstruction errors, i.e.
WhereinThe optimal solution is Operatorrepresents rounding down, mod (·, M) represents a modulo-M addition operation; it can be obtained from the optimal solution that the symbol to be transmitted is selected to be optimal with the largest energy, and the subcarriers for transmitting the marks are optimally located at the farthest positions from each other.
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| CN107135180A (en) * | 2017-04-28 | 2017-09-05 | 电子科技大学 | Ofdm system signal method of sending and receiving |
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| CN102571113A (en) * | 2010-12-30 | 2012-07-11 | 创杰科技股份有限公司 | Receiver and symbol decoder thereof |
| CN103413157A (en) * | 2013-08-01 | 2013-11-27 | 复旦大学 | RFID reader-writer capable of detecting number of labels within time slot and detection method of RFID reader-writer |
| CN106549692A (en) * | 2016-12-12 | 2017-03-29 | 电子科技大学 | A kind of signal acceptance method for backscatter communication system |
| CN107017929A (en) * | 2017-04-28 | 2017-08-04 | 电子科技大学 | Mimo system signal method of sending and receiving |
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