DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] In the following detailed description, only the preferred embodiment of the invention has been shown and described, simply by way of illustration of the best mode contemplated by the inventor(s) of carrying out the invention. As will be realized, the invention is capable of modification in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive.

[0043] An adaptive antenna transmit and receive device for a wireless communication system with multiple antennas according to a preferred embodiment of the present invention will be described referring to figures.

[0044] FIG. 1 shows a block diagram of an adaptive antenna transmit and receive device for a wireless communication system with multiple antennas according to a preferred embodiment of the present invention.

[0045] As shown in FIG. 1 , the adaptive antenna transmit and receive device transmits and receives data through M transmit antennas and N receive antennas, and comprises a transmitter 110 for coding and modulating the data and transmitting processed data through an MIMO channel 120 , and a receiver 130 for demodulating and decoding the data received through the MIMO channel 120 to restore the original data.

[0046] The transmitter 110 comprises an adaptive transmit controller 111 , a channel encoder 112 , a symbol mapper 113 , an antenna mapper 114 , and a transmit end 115 .

[0047] First, the adaptive transmit controller 111 selects an encoding method of the channel encoder 112 , a modulation method of the symbol mapper 113 , and an antenna mapping method of the antenna mapper 114 according to a transmit mode selected by a signal fed back by the receiver 130 .

[0048] The channel encoder 112 receives data b _i to be transmitted, and encodes the same according to an encoding method selected by the adaptive transmit controller 111 .

[0049] The symbol mapper 113 modulates the data encoded by the channel encoder 112 using a modulation method (e.g., QAM and PSK) selected by the adaptive transmit controller 111 , maps them to modulation symbols s _j , and outputs result data.

[0050] The antenna mapper 114 receives outputs s _j of the symbol mapper 113 , maps the outputs s _j to a symbol vector x _j =(x _j,l . . . , x _j,M ) ^T to be transmitted through each transmit antenna according to an antenna mapping method selected by the adaptive transmit controller 111 , and outputs result data.

[0051] The transmit end 115 receives outputs x _j =(x _j,l . . . , x _j,M ) ^T of the antenna mapper 114 , configures signals according to a multi-carrier transmission method such as OFDM, or a single carrier transmission method and a multiple access method, and transmits the signals to the MIMO channel 120 that is an MIMO channel through the M transmit antennas.

[0052] Multiple-antenna transmit outputs at the transmit end 115 are provided to the receiver 130 with N receive antennas through the MIMO channel 120 .

[0053] The receiver 130 comprises a receive end 131 , an antenna/symbol demodulator 132 , a channel decoder 133 , a channel estimator 134 , and an adaptive transmit parameter extractor 135 .

[0054] First, the receive end 131 performs an inverse operation of the process of the transmitter 110 to extract signals r _j =(r _j,l . . . , r _j,N ) ^T received through each receive antenna, and outputs them.

[0055] The antenna/symbol demodulator 132 acquires symbol information for each transmit antenna from the signals r _j =(r _j,l . . . , r _j,N ) ^T output by the receive end 131 according to transmit mode information determined by the adaptive transmit controller 111 .

[0056] The channel decoder 133 performs channel decoding according to the symbol information for each transmit antenna acquired by the antenna/symbol demodulator 132 to outputs result data {circumflex over (b)} _i that are estimates of the transmitted data information b _i .

[0057] The channel estimator 134 receives the signals r _j =(r _j,1 . . . , r _j,N ) ^T output by the receive end 131 , and estimates an MIMO channel response by using pilot symbols.

[0058] The antenna/symbol demodulator 132 performs orthogonal diversity combination by using the MIMO channel response estimated by the channel estimator 134 to detect transmit symbols when the antenna mapping method from among the transmit mode information determined by the adaptive transmit controller 111 of the transmitter 110 is a space encoding method, and to detect the transmit symbols by using one of the ML detection method, the OSIC detection method, the MMSE linear equalization method, and the ZF linear equalization method when the antenna mapping method is an SM method.

[0059] The adaptive transmit parameter extractor 135 finds parameters for the adaptive transmit by using channel estimation results output by the channel estimator 134 , and transmits the parameters to the transmitter 110 .

[0060] As a first example, outputs by the antenna mapper 114 following the STBC (or SFBC if it is applied in the frequency domain) method are given in Equation 1, and outputs by the antenna mapper 114 following the SM method are given in Equation 2 when the number M of the transmit antenna is 2.

x _j =( s _j −s* _j+1 ) ^T , for even j

( s _j s* _j−1 ) ^T , for odd j Equation 1

x _j =( s _2j s _2j+1 ) ^T Equation 2

[0061] FIG. 2 shows a detailed block diagram of a transmitter of the adaptive antenna transmit and receive device for a wireless communication system with multiple antennas according to a preferred embodiment of the present invention.

[0062] The transmit mode of the transmitter according to the preferred embodiment includes at least one main transmit mode for supporting other data rates, and the main transmit mode includes two maximum sub-transmit modes sharing the same channel encoding method.

[0063] As shown in FIG. 2 , the transmitter of the adaptive antenna transmit and receive device comprises an adaptive transmit controller 2200 for determining information on the main transmit mode and the sub-transmit mode, and a transmit mode block 2100 for transmitting input data according to the data rate determined by the transmit mode (main transmit mode and sub-transmit mode) information output by the adaptive transmit controller 2200 .

[0064] The transmit mode block 2100 comprises a channel encoder 2110 for encoding input data according to the channel code rate r _I determined by the transmit mode information I output by the adaptive transmit controller 2200 ; a sub-transmit mode 0 block 2130 for performing symbol mapping and antenna mapping on the sub-transmit mode 0; a sub-transmit mode 1 block 2140 for performing symbol mapping and antenna mapping on the sub-transmit mode 1; a demultiplexer 2120 for connecting the channel encoder 2110 to one of the two sub-transmit mode blocks 2130 and 2140 according to sub-transmit mode information output by the adaptive transmit controller 2200 ; and a multiplexer 2150 for selecting one of the outputs of the two sub-transmit mode blocks 2130 and 2140 according to the sub-transmit mode information output by the adaptive transmit controller 2200 .

[0065] In this instance, the sub-transmit mode 0 block 2130 comprises a symbol mapper 2131 having a modulation constellation Q _I ^M , and an antenna mapper 2132 for space block coding, and sub-transmit mode 1 block 2140 comprises a symbol mapper 2141 having a modulation constellation Q _I , and an antenna mapper 2142 for SM.

[0066] The sub-transmit modes 0 and 1 at the above-configured transmitter support the same data rate r _l M log2(Q _l ), and one of the two sub-transmit modes is selected according to a characteristic of the MIMO channel.

[0067] The conventional adaptive transmit method supports a single transmit mode configured by a specific transmit antenna method for a single data rate, and the preferred embodiment uses a sub-transmit mode of using a different transmit antenna method to a main transmit mode of supporting the same data rates so as to maximize the data rates by applying an MIMO channel characteristic.

[0068] In the preferred embodiment, all of the main transmit modes have two sub-transmit modes, and for ease of realization, the case of supporting a single sub-transmit mode from among the two sub-transmit modes is also allowed.

[0069] FIG. 3 shows an exemplified transmit mode supported by the transmitter of the adaptive antenna transmit and receive device for a wireless communication system with multiple antennas according to a preferred embodiment of the present invention.

[0070] As shown in FIG. 3 , the transmit mode has six main transmit modes that support different data rates when two transmit antennas are provided.

[0071] The main transmit modes 310 for supporting different data rates are numbered from 0 to 5, and there is at least one sub-transmit mode 320 that supports the respective main transmit modes 310 , and it is assumed that a maximum of two sub-transmit modes are provided below.

[0072] Sub-transmit modes that support a single main transmit mode use the same channel code rates 330 , but use a different modulation method 340 and transmit method 350 . Part of the channel code rates 330 , the modulation methods 340 , and the antenna transmit methods 350 configuring different main transmit modes 310 may be the same, but corresponding data rates and performance are different.

[0073] FIG. 4 shows a flowchart of a transmit mode selection method at the transmitter of the adaptive antenna transmit and receive device for a wireless communication system with multiple antennas according to a preferred embodiment of the present invention.

[0074] As shown in FIG. 4 , the transmitter selects a main transmit mode that provides the highest data rates and reduces a transmit power from among the main transmit modes that satisfy the required performance according to the characteristic of the MIMO channel, and a sub-transmit mode, when the number of the transmit antennas is M and the number of the main transmit modes having indexes in the ascending order of the data rates is L.

[0075] First, a main transmit mode I _B with the minimum difference Δ _B,l =S _B −T _B,l (Δ _B,l >0) between STBC performance parameters S _B greater than a threshold value T _B,l of the STBC mode and the threshold value T _B,l is found in the main transmit modes having the sub-transmit mode 0 in step S 10 .

[0076] Next, a main transmit mode I _M with the minimum difference Δ _M,l =S _M −T _M,l (Δ _M,l >0) between SM performance parameters S _M greater than a threshold value T _M,l of the SM mode and the threshold value T _M,l is found in the main transmit modes having the sub-transmit mode 1 in step S 20 . In this instance, the order of the steps S 10 and S 20 can be exchanged or the steps S 10 and S 20 can be executed in parallel.

[0077] The steps S 10 and S 20 represent a process for finding the main transmit modes I _B and I _M that support the maximum data rates for satisfying the required performance for the respective two sub-transmit modes in the main transmit modes supported by the respective sub-transmit modes.

[0078] Next, it is determined whether the transmit modes I _B and I _M found through the steps S 10 and S 20 satisfy that I _B >I _M or satisfy that I=I _B =I _M and Δ _B,l >Δ _M,l in step S 30 .

[0079] If I _B >I _M or if I=I _B =I _M and Δ _B,l >Δ _M,l the sub-transmit mode 0 of the main transmit mode I _B is selected in step S 40 , or else the sub-transmit mode 1 of the main transmit mode I _M is selected in step S 50 .

[0080] In the step S 30 , a main transmit mode for supporting high data rates from among the data rates supported according to sub-transmit modes, that is, a value having a large main transmit mode index is initially selected, and when the data rates respectively supported by the sub-transmit modes are the same, a mode for requiring less transmit power, that is, a sub-transmit mode for further decreasing the transmit power, is selected.

[0081] When the number of the transmit antennas is M according to the preferred embodiment, the STBC performance parameter S _B is given as Equation 3. 1 $\begin{array}{cc}{S}_B=10{\log }_{10}\left({\mathrm{SNR}}_{\mathrm{SBC}}\right)=10{\log }_{10}\left(\frac{{H}^2}{M}\frac{E_S}{N_0}\right)& \mathrm{Equation}3\end{array}$

[0082] where 2 ${H}^2=\sum _{p=1}^N\sum _{q=1}^M{h_{p,q}}^2,H=\left[\begin{array}{cccc}{h}_{1,1}& h_{1,2}& \cdots & h_{1,M}\\ h_{2,1}& h_{2,2}& \cdots & h_{2,M}\\ ⋮& ⋮& ⋰& ⋮\\ h_{N,1}& h_{N,2}& \cdots & h_{N,M}\end{array}\right]$

[0083] is an MIMO channel response,

[0084] E _S is a transmit symbol energy, and N ₀ is the variance of complex additive white noise.

[0085] Meanwhile, the SM performance parameter S _M can be given as Equation 4 for having the minimum value of the post-processing SNR as a reference or Equation 5 for having the geometric mean of the post-processing SNR as a reference. S _M =min _q 10 log ₁₀ ( SNR _SM,q ) Equation 4

[0086] 3 $\begin{array}{cc}{S}_M=\frac{1}{M}\sum _{q=1}^M10{\log }_{10}\left({\mathrm{SNR}}_{\mathrm{SM},q}\right)& \mathrm{Equation}5\end{array}$

[0087] From Equations 4 and 5, SNR _SM,q is a post-processing SNR of the symbol transmitted to the q-th transmit antenna, Equation 4 is found based on the fact that the performance before a channel decoding depends on the minimum SNR, and Equation 5 is for introducing a performance improvement caused by a well-performed symbol after the channel decoding, and hence, usage of Equation 5 generates improved performance after channel decoding.

[0088] Equation 6 shows an SM post-processing SNR calculated based on a linear reception is processed, when the number of the transmit antennas is M. 4 $\begin{array}{cc}{\mathrm{SNR}}_{\mathrm{SM},q}=\frac{E_Sg_q^Hh_q}{{\mathrm{MN}}_0+E_S\sum _{j\ne q}^{}g_q^Hh_j}& \mathrm{Equation}6\end{array}$

[0089] where h _q is the q-th column vector of H, and g _q is the q-th column vector of the linear equalization matrix G.

[0090] The linear equalization matrix G is differentiated according to the linear equalization criterion, and it uses Equation 7 when using the ZF criterion, and it uses Equation 8 when using the MMSE criterion.

G =( H ^H H ) ⁻¹ H ^H Equation 7

[0091] 5 $\begin{array}{cc}G={\left(H^HH+\frac{N_0}{{\mathrm{ME}}_S}I_M\right)}^{-1}H^H& \mathrm{Equation}8\end{array}$

[0092] After this process, the SNR can be used in any case when the receiver uses any method for the antenna/symbol demodulator on the SM. The threshold value T _M,l and T _l for determining the transmit mode are modified according to the antenna/symbol demodulation method and the SM post-processing SNR calculation method.

[0093] Equation 9 shows the SNR after processing the SM method calculated based on the ZF criterion when the number of the transmit antennas is 2, and the number N of the receive antennas is greater than 2. From Equation 9, Equation 4 can be given as Equation 10, and Equation 5 can be given as Equation 11. 6 $\begin{array}{cc}{\mathrm{SNR}}_{\mathrm{SM},q}=\frac{1}{2{\left(H^HH\right)}_{\mathrm{qq}}^{-1}}\frac{E_S}{N_0}={\alpha }_q\left(1-{\rho }^2\right){\mathrm{SNR}}_{\mathrm{SBC}}& \mathrm{Equation}9\end{array}$

[0094] where A _qq ⁻¹ is the (q,q)-th element of A ⁻¹ , 7 ${\alpha }_q=\frac{{h_q}^2}{{H}^2}$

[0095] is a channel power ratio of the q-th transmit antenna, 8 $\rho =\frac{h_1^Hh_2}{h_1h_2}$

[0096] is a channel correlation between two transmit antennas, and ∥v∥ is a norm of v.

S _M =10 log ₁₀ (α _min (1−ρ ² ))+ S _B Equation 10

[0097] where α _min =min _q α _q .

S _M =10 log ₁₀ ({square root over (α ₁ α ₂ )}(1−ρ ² ))+ S _B Equation 11

[0098] where α ₁ and α ₂ are channel power ratio for each transmit antenna, and ρ is a channel correlation of the transmit antenna.

[0099] Therefore, the channel power ratio for each channel transmit antenna can be calculated from the MIMO channel, and (S _B −S _M ) can be calculated from the channel correlation of the transmit antenna instead of directly calculating the SM performance parameter S _M .

[0100] FIG. 5 shows a detailed block diagram of an adaptive transmit parameter extractor at the receiver of the adaptive antenna transmit and receive device for a wireless communication system with multiple antennas according to a preferred embodiment of the present invention.

[0101] As shown in FIG. 5 , the adaptive transmit parameter extractor 500 comprises an S _B calculator 510 and an S _M calculator 520 , and respectively calculates the STBC performance parameter S _B and the SM performance parameter S _M by using a channel response matrix estimate H and a receive SNR estimate E _s /N ₀ input by the channel estimator.

[0102] The S _B calculator 510 comprises a channel power sum calculator 511 and a combiner 512 , and the channel power sum calculator 511 calculates the channel power sum ∥H∥ ² by using a channel response matrix estimate input by the channel estimator.

[0103] The combiner 512 calculates the STBC performance parameter S _B following Equation 3 by combining the channel power sum calculated by the channel power sum calculator 511 and the receive SNR estimate E _S /N ₀ input by the channel estimator.

[0104] The S _M calculator 520 comprises a linear equalizer 521 , an SM post-processing SNR calculator 522 , and a representative calculator 523 . The linear equalizer 521 calculates the equalization matrix G shown as Equation 7 or 8 on the basis of the ZF or MMSE criterion.

[0105] The SM post-processing SNR calculator 522 calculates a transmit antenna post-processing SNR based on Equation 6 by using the equalization matrix G calculated by the linear equalizer 521 .

[0106] The representative calculator 523 calculates a representative of the SM performance parameters S _M according to Equation 4 or 5 by using the transmit antenna post-processing SNR calculated by the SM post-processing SNR calculator 522 .

[0107] The S _B calculated by the S _B calculator 510 and the S _M calculated by the S _M calculator 520 are quantized, or they are converted to S _B and (S _B −S _M ) and quantized, and fed back ( 501 ) to the transmitter so that the adaptive transmit controller of the transmitter may use them to select a transmit mode.

[0108] FIG. 6 shows a detailed block diagram of an adaptive transmit controller 600 of the adaptive antenna transmit and receive device for a wireless communication system with multiple antennas according to a preferred embodiment of the present invention.

[0109] As shown in FIG. 6 , the adaptive transmit controller 600 comprises a STBC transmit mode selector 610 , a T _B,I lookup table 620 , an SM transmit mode selector 630 , a T _M,I lookup table 640 , and a comparator 650 .

[0110] The STBC transmit mode selector 610 compares the STBC performance parameter S _B fed back ( 601 ) from the receiver with T _B,I values of the T _B,I lookup table 620 to calculate Δ _B,l =S _B −T _B,l as shown in the step S 10 of FIG. 4 , and outputs a main transmit mode value I _B which is a positive number and has the minimum value, and a corresponding Δ _B,l .

[0111] The SM transmit mode selector 630 compares the SM performance parameter S _M fed back ( 601 ) from the receiver with T _M,I values of the T _M,I lookup table 640 to calculate Δ _M,l =S _M −T _M,l as shown in the step S 20 of FIG. 4 , and outputs a main transmit mode value I _M which is a positive number and has the minimum value, and a corresponding Δ _M,l .

[0112] The comparator 650 selects the sub-transmit mode 0 of the main transmit mode I _B when l _B >l _M , and selects the sub-transmit mode 1 of the main transmit mode I _M when l _B <l _M , as shown in the step S 30 of FIG. 4 .

[0113] In addition, in the case that l=l _B =l _M , the comparator 650 selects the sub-transmit mode 0 of the main transmit mode I when Δ _B,l >Δ _M,l and selects the sub-transmit mode 1 if not, thereby outputting finally selected transmit mode and sub-transmit mode information.

[0114] According to the present invention, the main transmit mode for transmitting specific data rates using the adaptive transmit method is configured with the transmit and receive method based on the SM antenna transmit method and the transmit and receive method based on the STBC antenna transmit method so as to adaptively select a desired method depending on the MIMO channel environment in the wireless communication system with multiple antennas, thereby more effectively handling the MIMO channel environment to further increase the data rates in the given transmit power, and reduce transmit power consumption in the given data rates.

[0115] While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.