# US 2008/0188192 A1 · Apparatus and method for selecting transmission mode in multi-antenna system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0188192 A1 - Document ID: US20080188192A1 - Status: Published application - Kind: A1 - Application number: 12/012,673 - Filed: 2008-02-05 - Published: 2008-08-07 - Earliest claimed: 2007-02-05 - Assignees: Samsung Electronics Co., Ltd. - Inventors: Heon-Ki Chae; Keun-Chul Hwang; Sung-Woo Park - Web page: https://patentgrep.com/patent/US20080188192A1 ## CPC - H04B 7/063: {Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection} - H04B 7/0689: {using different transmission schemes, at least one of them being a diversity transmission scheme} - H04B 7/0697: {using spatial multiplexing} - H04B 17/336: Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] - H04B: TRANSMISSION ## Abstract An apparatus and a method for selecting a transmission mode in a multi-antenna system are provided. The method includes checking a channel characteristic of a transmitting end using a signal received over at least two antennas; and determining a multi-antenna transmission mode according to the channel characteristic. Accordingly, the loss of the system capacity gain can be reduced and the capacity gain of the system can be increased. ## Claims ### Claim 1 A method for selecting a transmission mode in a multi-antenna system, the method comprising: checking a channel characteristic, from a transmitter, using a signal received over at least two antennas; and determining a multi-antenna transmission mode according to the channel characteristic. ### Claim 2 (depends on 1) The method of claim 1, wherein the multi-antenna transmission mode comprises at least one of a diversity mode and a spatial multiplexing mode. ### Claim 3 (depends on 1) The method of claim 1, wherein the channel characteristic comprises at least one of carrier to interference and noise ratios of transmit streams of the transmitter, an average carrier to interference and noise ratio of the transmit streams, a carrier to interference and noise ratio in the multi-antenna transmission mode used at the transmitter to send the signal, and a correlation value between channels of the received signal. ### Claim 4 (depends on 1) The method of claim 1, further comprising: checking whether a multi-antenna transmission mode selection request signal is received from the transmitter, wherein the channel characteristic is checked when the multi-antenna transmission mode selection request signal is received. ### Claim 5 (depends on 4) The method of claim 4, wherein the multi-antenna transmission mode selection request signal is one of a fast feedback subheader and a Channel Quality Indicator (CQI) Channel_Allocation_Information Element. ### Claim 6 (depends on 1) The method of claim 1, wherein the step of checking the channel characteristic comprises: checking carrier to interference and noise ratios of transmit streams of the transmitter. ### Claim 7 (depends on 6) The method of claim 6, wherein the step of determining the multi-antenna transmission mode comprises: comparing the carrier to interference and noise ratios of the transmit streams; and determining a spatial multiplexing mode as the multi-antenna transmission mode when a difference of the carrier to interference and noise ratios of the transmit streams is smaller than a first threshold. ### Claim 8 (depends on 7) The method of claim 7, further comprising: determining a diversity mode as the multi-antenna transmission mode when the difference of the carrier to interference and noise ratios of the transmit streams is greater than the first threshold. ### Claim 9 (depends on 1) The method of claim 1, further comprising: checking carrier to interference and noise ratios of transmit streams of the transmitter; and checking an average of the carrier to interference and noise ratios of the transmit streams. ### Claim 10 (depends on 9) The method of claim 9, wherein the step of determining the multi-antenna transmission mode comprises: comparing the carrier to interference and noise ratios of the transmit streams; comparing the average of the carrier to interference and noise ratios of the transmit streams with a second threshold when a difference of the carrier to interference and noise ratios of the transmit streams is smaller than a first threshold; and determining a spatial multiplexing mode as the multi-antenna transmission mode of the transmitter when the average of the carrier to interference and noise ratios of the transmit streams is greater than the second threshold. ### Claim 11 (depends on 10) The method of claim 10, further comprising: determining a diversity mode of the transmitter as the multi-antenna transmission mode when the difference of the carrier to interference and noise ratios of the transmit streams is greater than the first threshold or when the average of the carrier to interference and noise ratios of the transmit streams is smaller than the second threshold. ### Claim 12 (depends on 1) The method of claim 1, wherein the step of checking the channel characteristic comprises: checking a carrier to interference and noise ratio in relation with a multi-antenna transmission mode used by the transmitter to send the signal; and checking a correlation value between channels of the received signal. ### Claim 13 (depends on 12) The method of claim 12, wherein the step of determining the multi-antenna transmission mode comprises: comparing a carrier to interference and noise ratio of the multi-antenna transmission mode with a third threshold; comparing a correlation value of the channels with a fourth threshold when the carrier to interference and noise ratio of the multi-antenna transmission mode is greater than the third threshold; and determining a spatial multiplexing scheme as the multi-antenna transmission mode when the inter-channel correlation value is smaller than the fourth threshold. ### Claim 14 (depends on 13) The method of claim 13, further comprising: determining a diversity scheme as the multi-antenna transmission mode of the transmitter when the carrier to interference and noise ratio of the multi-antenna transmission mode is smaller than the third threshold or when the inter-channel correlation value is greater than the fourth threshold. ### Claim 15 (depends on 12) The method of claim 12, wherein the step of checking the inter-channel correlation value comprises: estimating channels using the received signal; and checking the inter-channel correlation value by estimating an eigenvalue spread of the estimated channels. ### Claim 16 (depends on 1) The method of claim 1, further comprising: sending the determined multi-antenna transmission mode to the transmitter. ### Claim 17 A method for sending a signal in a multi-antenna system, the method comprising: checking a multi-antenna transmitting mode determined by a receiver, from a feedback signal received from the receiver; and sending a signal to the receiver in the multi-antenna transmission mode, to the receiver. ### Claim 18 (depends on 17) The method of claim 17, wherein the multi-antenna transmission mode comprises at least one of a diversity mode and a spatial multiplexing mode. ### Claim 19 (depends on 17) The method of claim 17, further comprising: sending a signal which requests to select a multi-antenna transmission mode to the receiver, wherein the multi-antenna transmission mode determined by the receiver is confirmed from the feedback signal as requested to select the multi-antenna transmission mode. ### Claim 20 (depends on 17) The method of claim 17, wherein the signal which requests to select the multi-antenna transmission mode is one of a fast feedback subheader and a Channel Quality Indicator (CQI) Channel_Allocation_Information Element. ### Claim 21 An apparatus for selecting a transmission mode in a multi-antenna system, the apparatus comprising: a receiver for receiving a signal over at least two antennas; a channel estimator for checking a channel characteristic from a transmitter using the received signal; and a transmission mode determiner for determining a multi-antenna transmission mode according to the channel characteristic. ### Claim 22 (depends on 21) The apparatus of claim 21, wherein the channel estimator estimates at least one of carrier to interference and noise ratios (CINRs) of transmit streams of the transmitter, an average carrier to interference and noise ratio of the transmit streams, a carrier to interference and noise ratio in the multi-antenna transmission mode used at the transmitter to send the signal, and a correlation value between channels of the received signal. ### Claim 23 (depends on 21) The apparatus of claim 21, wherein the transmission mode determiner selects either a diversity mode or a spatial multiplexing mode as the multi-antenna transmission mode according to the channel characteristic checked by the channel estimator. ### Claim 24 (depends on 21) The apparatus of claim 21, wherein the channel estimator checks the channel characteristic when a multi-antenna transmission mode selection request signal is received from the transmitter through the receiver. ### Claim 25 (depends on 24) The apparatus of claim 24, wherein the receiver receives the multi-antenna transmission mode selection request signal which includes one of a fast feedback subheader and a Channel Quality Indicator (CQI) Channel_Allocation_Information Element. ### Claim 26 (depends on 21) The apparatus of claim 21, wherein the channel estimator checks carrier to interference and noise ratios of transmit streams. ### Claim 27 (depends on 26) The apparatus of claim 26, wherein the transmission mode determiner determines a spatial multiplexing mode as the multi-antenna transmission mode when a difference of the carrier to interference and noise ratios of the transmit streams, which is checked at the channel estimator, is smaller than a first threshold, and the transmission mode determiner determines a diversity mode as the multi-antenna transmission mode when the difference of the carrier to interference and noise ratios of the transmit streams is greater than the first threshold. ### Claim 28 (depends on 21) The apparatus of claim 21, wherein the channel estimator checks carrier to interference and noise ratios of the transmit streams and an average of the carrier to interference and noise ratios of the transmit streams. ### Claim 29 (depends on 28) The apparatus of claim 28, wherein the transmission mode determiner determines a spatial multiplexing mode as the multi-antenna transmission mode when a difference of the carrier to interference and noise ratios of the transmit streams, which is checked at the channel estimator, is smaller than a first threshold and the average of the carrier to interference and noise ratios of the transmit streams is greater than a second threshold, and the transmission mode determiner determines a diversity mode as the multi-antenna transmission mode when the difference of the carrier to interference and noise ratios of the transmit streams is greater than the first threshold or the average of the carrier to interference and noise ratios of the transmit streams is smaller than the second threshold. ### Claim 30 (depends on 21) The apparatus of claim 21, wherein the channel estimator comprises: an estimation part for checking a carrier to interference and noise ratio of the multi-antenna transmission mode used by the transmitter to send a signal; and a correlation part for checking a correlation value between channels of the signal. ### Claim 31 (depends on 30) The apparatus of claim 30, wherein the transmission mode determiner determines a spatial multiplexing mode as the multi-antenna transmission mode when the carrier to interference and noise ratio of the multi-antenna transmission mode used by the transmitter to send the signal, which is checked at the channel estimator, is greater than a third threshold and the inter-channel correlation value is smaller than a fourth threshold, and the transmission mode determiner determines a diversity mode as the multi-antenna transmission mode when the carrier to interference and noise ratio of the multi-antenna transmission mode is smaller than the third threshold or the inter-channel correlation value is greater than the fourth threshold. ### Claim 32 (depends on 30) The apparatus of claim 30, wherein the correlation part estimates channels using the received signal, and the correlation part checks the inter-channel correlation value by estimating an eigenvalue spread of the estimated channels. ### Claim 33 (depends on 21) The apparatus of claim 21, further comprising: a sender for sending the determined multi-antenna transmission mode to the transmitter over at least two antennas. ### Claim 34 An apparatus for sending a signal in a multi-antenna system, comprising: a feedback receiver for checking a multi-antenna transmission mode determined by a receiver, from a feedback signal received from the receiver; and a sender for sending a signal to the receiver in the multi-antenna transmission mode over at least two antennas. ### Claim 35 (depends on 34) The apparatus of claim 34, wherein the feedback receiver confirms either a diversity mode or a spatial multiplexing mode, which is determined by the receiver, from the feedback signal.