TWI374621B - Decision-feedback channel estimator for mimo-ofdm system - Google Patents

Description

1374621 IX. Description of the Invention: [Technical Field] The present invention relates to a decision feedback type channel estimator for a multiple input multiple output orthogonal frequency division multiplexing system. [Prior Art] For the conventional multi-input multi-output orthogonal frequency division multiplexing system, when the receiving end wants to perform the decision feedback channel estimation, the interference caused by other antennas is estimated and deducted, refer to the prior art literature. [丨]·^]. In the decision-making town channel estimation, the received signals Λμ] and Λμ+1] can be expressed as: 哗+1]=-//. [Moxibustion +1]. Yang +1] + ugly χ μ χ μ] + "μ +1] The conventional decision-making feedback channel estimation method is expressed as follows: (1) (2) Free Sichuan = Department +1], 2 Department] : 2 o +1] Also shot correction and i]+^Wm part +11 2 *S[^ + l] -2 S' [/:] where mls.〇M is the improved least squares (M 〇dified Least Square, MLS) The initial channel obtained by the estimator, and the +1] is the signal demodulated by the initial channel, and ^ is the multipath number and the 5/person is the signal noise ratio. . Referring to Figures 1A and 1B, there is shown a schematic circuit diagram of a conventional channel estimator. The conventional channel estimator 1 includes: a fifth multiplier 一, a sixth 125058, a doc 21 multiplier m' - a second subtractor (1) _ n a music subtractor 114, a second music method [5, a fourth divider " 6 seventh multiplier (2), - eighth multiplier 122, a =="7, -_ ^., the fifth subtractor 123, ^ subtractor 124, a fifth divider 125, a (10)th 126, a seventh subtractor U7. Therefore, the calculation of the above equations (1) and (7) can be performed by using the circuit of the figure and (7). However, the circuit of the 'fognitive channel estimator is too complicated' to reduce the estimated performance of the conventional decision-making feedback channel estimator. ^ In addition, assuming that the data is fully demodulated correctly, the conventional decision-making feedback channel estimator The mean square error can be expressed as the following formula (3)

E 4 hnwi: j (3) g„[A:+l]-5[A: + l] + ^1 eH[k]S[k]-W\k + \\ 2·网^'[Ar + l] ~[moxime + 1].·^[moxibustion + 1] + ^Ί>] 2 marriage 2^5*[Λ + 1]

L

N SNR where £11[moxibustion]=//1[moxibustion or qing (>]; £^ + 1] = //|[moxibustion + 1]_ or _[moxibusia + 1]. Analysis, we can find that the conventional method will be affected by the initial channel estimation error, thus reducing the accuracy of the decision feedback channel estimation. Therefore, it is necessary to provide an innovative and progressive multi-input multi-output orthogonal frequency division. Decision-making feedback channel estimator for multiplexed systems to solve the above problems. Previous technical literature: [1] S.Bowei, Z. Wenjun, and G.Lin, "Iterative joint channel estimation and signal detection in ΜΙΜΟ OFDM systems , " 125〇58.doc 1374621 in Proc. Wireless comm. Con/., vol., Sep. 2005, pp. 23-23.

[2] C. Jiming and L. Shaoqian, "Iterative channel estimation for ΜΙΜΟ OFDM systems," in Proc. Circuit and System Conf., vol. 27-30, May 2005, pp. 180-184.

[3] E.Karami and M. Shiva, "A new joint channel estimation and detection algorithm for ΜΙΜΟ channels," in APCC Conf., vol.21-24, Sep. 2003, pp. 283-286. The present invention provides a decision feedback loop estimator for a multiple input multiple output orthogonal frequency division multiplexing system, comprising: a first multiplier, a second multiplier, a first subtractor, and a first A divider, a third multiplier, a fourth multiplier, a first adder, and a second divider. The first multiplier is configured to multiply a first received signal by a conjugate signal of a first initial channel demodulation signal to calculate a first multiplication result. The second multiplier is configured to multiply a second received signal by a second initial channel demodulation signal to calculate a second multiplication result. The first subtractor is configured to subtract the first multiplication result from the second multiplication result to calculate a first subtraction result. The first divider is configured to divide the first subtraction result by a first set value to calculate a first channel estimate. The third multiplier is configured to multiply the first received signal by a conjugate signal of a second initial channel demodulation signal to calculate a third multiplication result. The fourth multiplier is configured to multiply the second received signal by a first initial channel demodulation signal to calculate a fourth multiplication result. The first adder is configured to add the third multiplication result to the fourth multiplication result to calculate a first addition result. The second divider is configured to divide the first plus 1250S8.doc 1374621 method result by the first set value to calculate a second channel estimate. The invention is used for a decision-making back-channel channel estimator of a multi-wheeled multi-round orthogonal frequency division multiplexing system. Using the space-frequency block code or the space-time block code for the decision feedback channel estimation can reduce the complexity of the hardware circuit and improve the performance of the decision feedback channel estimation. [Embodiment] Referring to FIG. 2, the present embodiment is shown. A schematic diagram of a multi-input multiple-output orthogonal frequency division multiplexing system is invented. The multi-input multi-output orthogonal frequency division multiplexing system 2 of the present invention comprises: a modulator 21, a space-frequency block code encoder 22, a first inverse fast Fourier converter, and a cyclic prefix inserter 23, a first a two-inverse fast Fourier converter and a cyclic prefix inserter 24, a first transmitter 25'-the first transmitter 26, a receiver 31, a fast Fourier transformer and a cyclic prefix remover 32, a space frequency region The block code decoder 33, a decision feedback channel estimator 34 and a demodulation transformer 35. In the embodiment of the present invention, channel estimation is performed by using Space Frequency Block Codes (SFBC), so the space frequency block code encoder 22 and the space frequency block code decoder 33 are used for encoding and decoding. . However, the present invention is not limited to channel estimation using a space-frequency block code, and may also use a space-time block code (STBC) for channel estimation. In the embodiment of the present invention, the passage through which the two antennas pass is denoted as a channel butterfly and a ring, respectively, and a butterfly = / / is assumed. (d) with just $(four). The receiving signal is difficult] and difficult +1] can be expressed as: 125058.doc 1374621 R^k^l] = ~^〇[k^\]Xl[k + \] + H,[k\Xl[k) + W [k + \] As mentioned above, the conventional decision feedback channel estimation method is expressed as follows: μ], thin]-々_[外办+η, Μ“ι】-Α_μ+ιΜ·(9) 2 parts] -2· 5*μ + ΐ] 〇)

Exempt, Bubsha M_W marriage, *μ+ι]+々_μμ·Bu U ' 2-5^ + 1] -2-5* [Λ] * (2) The present invention is applied to multiple input multiple output orthogonal Frequency division multiplexing system decision

In the embodiment of the channel estimator, the channel estimation is performed by using the space-frequency block code, as expressed by the following equation: (4) (5) [lr]_m^]-R[k+i].s\k+i} ' |纲|2+|印+1]|2 仰+1]+哗^姻' 丨 2+[Mf

Referring to Figures 3A and 3B, there are shown circuit diagrams of a decision feedback loop estimator for a multiple input multiple output quadrature frequency division multiplexing system of the present invention. The decision feedback channel estimator 34 of the present invention for a multiple input multiple output orthogonal frequency division multiplexing system includes: a first multiplier 41, a second multiplier 42, a first subtractor 43, and a first The divider 44, a third multiplier 51, a fourth multiplier 52, a first adder 53 and a second divider 54 are provided. The first multiplier 41 is configured to multiply a first receiving signal Λ (4) and a conjugate signal of a first initial channel demodulation signal by (9) to calculate a first multiplication result Λ[Α:] xS|^] . The second multiplier 42 is configured to multiply a second received signal Λ[Α:+1] by a second initial channel demodulation signal ^+丨] to calculate a second multiplication result vulture+1]χί [* + ι]. The first subtractor 43 is configured to subtract the second multiplication result from the 125058.doc •10· 1374621 multiplication result to calculate a first subtraction result. The first divider 44 is configured to divide the first subtraction result by a first set value to calculate a first channel estimation score. The first set value is the first initial channel solution, the square of the size 2 of the signal 2 plus the square of the size of the second initial channel demodulation signal + know + 1]. Therefore, the calculation of equation (4) can be realized by using the circuit of Fig. 3.

The third multiplier 51 is configured to multiply the first received signal by a recording number &+ _ of a second initial channel dismissal to calculate a third multiplication result Χ^ + 1]. (4) The fourth multiplication method 52 is used to multiply the second connection: the signal difficulty +1] and the -first-initial channel demodulation signal heart] to calculate the fourth multiplication result, and the first adder 53 is used to The result of the first multiplication is added to the result of the fourth multiplication of the fourth multiplication, to calculate a first addition result. The second divider 54 is configured to divide the first addition result by the first set value to calculate a first -, Λ estimate 仏.1 [magic. Therefore, the calculation of equation (5) can be realized by using a circular 3 Β circuit.

The channel using equations (4) and (5) is completely demodulated correctly. τ ^ is also a bamboo slippery, and the mean square error can be expressed as e| h "generation hi:丨=丄·丄h, N SNR (6) Compared with the mean squared m __ of the conventional formula (3), the error and the mean square error of the formula (6), it can be estimated that the B two-member block code is used for decision feedback channel estimation. The mean square error value is significantly smaller than the decision-making feedback channel for eliminating interference = the method of using interference cancellation. The conventional code feature is used for decision feedback. The mean square error of the first measurement is more than the use of the space-frequency block. The error amount is measured, so 125058.doc -11 · 1374621 will get poor performance. Referring to Figure 4, the simulation of the system is compared with the uninvented system milling. The verification using Matlab simulation can be found in the high Under the condition of signal-to-noise ratio, the theoretical and analog values are quite close. This is because the derivation of the theoretical value makes the assumption that the data demodulation is completely correct. Further, the decision feedback using the space-frequency block code can be found. Channel estimator, its performance is always better than the conventional direct interference cancellation The method of analyzing and comparing the complexity of the conventional circuit with the circuit of the present invention is known from equations (1) and (2) and FIGS. 1A and 1B. The conventional decision feedback channel estimation circuit requires four multipliers, four Divider, six adder-subtracters; from equations (4) and (5) and Figures 3A and 3B, the present invention utilizes a space-frequency block code for channel estimation requiring four multipliers, two dividers, two Addition and subtraction. Therefore, the present invention utilizes a decision-feedback channel estimator of a space-frequency block code, which requires only a low complexity. Although the above embodiment is orthogonal to a 2x1 space-frequency block code. The frequency division multiplexing system (SFBC-OFDM) can be extended, but the space frequency block code orthogonal frequency division multiplexing system (SFBC-OFDM) or the space time block code orthogonal frequency division multiplexing can be extended to the present invention. In the system (STBC-OFDM), the above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Therefore, those skilled in the art can make modifications and changes to the above embodiments without departing from the invention. The spirit of the present invention should be as described in the patent application scope described later. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a conventional channel estimator; 125058.doc -12- 1374621 FIG. 2 is a multi-input multi-output orthogonal frequency division multiplexing system according to the present invention. 3A and 3B are circuit diagrams showing a decision feedback type channel estimator for a multiple input multiple output orthogonal frequency division multiplexing system according to the present invention; and FIG. 4 is a diagram showing a conventional system and a system of the present invention. The simulation compares the circle. [Main component symbol description] 20 The multi-input multi-output orthogonal frequency division multiplexing system of the present invention

21 Modulator 22 23 24 25 26 31

32 33 34 35 41 42 43 44 51 52 Space-frequency block code encoder first inverse fast Fourier transformer and cyclic prefix inserter second inverse fast Fourier transformer and cyclic prefix inserter first transmitter second launch Receiver Fast Fourier Transformer and Cyclic Header Remover Space Frequency Block Code Decoder Decision Feedback Channel Estimator Demodulation Transformer First Multiplier Second Multiplier First Subtractor First Divider Third Multiplier fourth multiplier 125058.doc •13- i1374621

53 first adder S4 second divider 100 conventional channel estimator 111 fifth multiplier 112 sixth multiplier 113 second subtractor 114 third subtractor 115 third divider 116 fourth divider 117 fourth Subtractor 121 Seventh multiplier 122 Eighth multiplier 123 Fifth subtractor 124 Sixth subtractor 125 Fifth divider 126 Sixth divider 127 Seventh subtractor I25058.doc -14-

Claims (1)

~年' as amended daily replacement page ------- Patent application scope: Patent No. 097103118 Patent application Chinese patent application scope replacement (100 years December) - a kind of multi-input multi-output orthogonal frequency division The decision-making feedback channel estimator of the system includes: a first multiplier for multiplying a first received signal by a conjugate signal of a first initial channel demodulation signal to calculate a first multiplication a second multiplier for multiplying a second received signal by a second initial channel demodulation signal to calculate a second multiplication result; a first subtractor for the a multiplication result minus the second multiplication result 'to calculate a first subtraction result; a first-divider for dividing the first subtraction result by a first-set value to calculate a -first-channel estimation, The first setting value is the square of the initial channel demodulation signal size plus the square of the second initial channel demodulation signal size; the second multiplier is configured to use the first reception signal and a second initial Multiplying the conjugate signal of the channel demodulation signal, Calculating a third multiplication result; /". The fourth multiplier is configured to multiply the second received signal by a first-initial channel demodulation signal to calculate a fourth multiplication result; And the third multiplication result is added to the fourth multiplication result to calculate a first addition result; and a second divider is configured to divide the first addition result by the first set value' to calculate A second channel estimation. 2. If the decision-making feedback channel estimator of the D-luxury item is used, the channel is replaced by the space-frequency block 125058-1001226 1374621 _, / Estimation 3. If the decision-making feedback channel estimator of the request item is used, the space time block code is used for channel estimation. 125058-1001226