HK1137577B - Method and system apply to multi-antenna system and self-adaptive among different closed loop, open loop and hybrid technology - Google Patents

Description

Method and system for adaptation between different closed-loop, open-loop and hybrid techniques for multi-antenna systems

Cross reference to related applications and incorporation by reference

This application references and claims priority from U.S. provisional patent application 61/946,181 filed on 26/6/2007.

This application also refers to:

U.S. patent application 11/759,203 filed 6/2007, and

U.S. patent application 11/846,611 filed on 9/28/2007.

The present application refers to the above-mentioned patent application in its entirety and is incorporated herein by reference.

Technical Field

Particular embodiments of the present invention relate to wireless communications, and more particularly, to a method and system for adapting between different closed-loop, open-loop, and hybrid techniques for use in a multiple antenna system.

Background

A multiple-input multiple-output (MIMO) communication system includes a transmitting station that transmits signals over a wireless communication medium using NTX > 1 transmit antennas and a receiving station that receives signals using NRX > 1 receive antennas. Such a system may be referred to as an NTX x NRXMIMO system. In contrast, a communication system including a transmitting station that transmits a signal using NTX ═ 1 and a receiving station that receives a signal using NRX ═ 1 may be referred to as a single-input single-output (SISO) communication system. A transmitting station in a MIMO communication system may use multiple NTX transmit antennas to synchronize (confluency) transmit signals that may include data received from different data streams or spatial data streams for NSS ≧ 1. For example, when the transmitting station uses space-time coding, NSS spatial coding may be used to generate space-time coding for NSTS ≧ 1, which will then be used to generate signals that can be simultaneously transmitted by NTX > 1.

In a MIMO communication system, multiple Radio Frequency (RF) channels may exist simultaneously between a transmitting station and a receiving station. For example, each simultaneous transmitting NTX transmit antenna may establish a channel to each NRX receive antenna. Each channel may be referred to as a spatial channel. Therefore, in the NTX × NRXMIMO system, a plurality of (NTX) × (NRX) spatial channels are supported. In a MIMO system using Orthogonal Frequency Division Multiplexing (OFDM), a plurality of different frequency carriers or tones (tones) fC may be used in the RF channel bandwidth. Each tone fC may be transmitted simultaneously over each RF spatial channel, e.g., 56 for a 20MHz bandwidth fC and 112 for a 40MHz bandwidth fC in an ieee802.11n WLAN system using OFDM. In a given RF spatial channel, each tone may be referred to as an RF subchannel. Thus, the NTX × NRXMIMO system supports a plurality of (fC) × (NTX) × (NRX) RF subchannels.

Compared to SISO communication systems, MIMO communication systems may be used to increase communication throughput (communication rate of data in Bits Per Second (BPS)) and/or increase communication reliability (in bit error rate). In the example of NTX NRX NSS, a MIMO system may maximize the aggregate data transmission rate between a transmitting station and a receiving station. In the case of NTX > NSS and NRX ≧ NSS, the MIMO system can increase the reliability of communication through diversity transmission. In a diversity transmission system, data from a given spatial data stream may be transmitted simultaneously through multiple transmit antennas. In the example of NSS ═ 1, the MIMO system can use diversity maximization (diversity maximization).

MIMO communication systems may also achieve diversity transmission by using STC techniques such as Space Time Block Code (STBC) or Space Frequency Block Code (SFBC). In a MIMO communication system using STC, NSS spatial data streams may include sequences of data symbols or code words (codewords), respectively, and may be converted into NSTS space-time data streams. The NSTS space-time data stream may cause the NTX transmit antenna to transmit a signal comprising a set of L codewords in a duration interval (time duration) of a TSTC time unit, where TSTC refers to the time interval of STC processing. In an STBC MIMO communication system, a given codeword or a transformed version thereof (e.g., complex conjugate version) may be transmitted multiple times within a TSTC time interval, with each transmission occurring on a different transmit antenna among the NTX transmit antennas.

To increase the throughput of data rate maximization or diversity transmission, the transmitting station will attempt to focus the transmitted energy in the direction of the receiving station. The focusing of the transmitted energy may increase the signal-to-noise ratio (SNR) of the signal received at the receiving station. By increasing the signal-to-noise ratio, the transmitting station may increase the data carrying capacity of the RF channel, thereby increasing the possible throughput. The transmitting station may focus the transmit energy by a technique such as that known as beamforming. The transmitting station may generate a beamformed signal by evaluating characteristics of a propagation path of an RF channel through a wireless communication medium between the transmitting station and the receiving station. The transmitting station may perform the evaluation by calculating a channel estimate.

In a closed-loop MIMO communication system, a transmitting station may calculate a channel estimate based on feedback information received from a receiving station. The receiving station may calculate a channel estimate based on the signal received from the transmitting station. The calculated channel estimates may be referred to as Channel State Information (CSI). The CSI may be represented as a channel estimation matrix H. The receiving station may send the channel estimation matrix to the transmitting station in feedback information. The transmitting station may use the feedback channel estimate matrix to generate beamformed signals that are transmitted to the receiving station.

One drawback of a closed-loop MIMO communication system is the amount of feedback signals that are transmitted from a receiving station to a transmitting station, which is manifested as overhead. A large amount of overhead will reduce the effective channel capacity for data communication. This overhead will then reduce the throughput of the RF channel. The channel estimation matrix H may include a plurality of (fC) × (NTX) × (NRX) elements, a matrix hij, components of respective RF spatial channels from the ith antenna of the transmitting station to the jth antenna of the receiving station. In addition, in a MIMO communication system using OFDM, for each hij element, it has fC elements, one for each OFDM tone. In the example where each element is represented by an nh-bit binary word, the amount of feedback information generated by the channel estimation matrix H is (nh) × (fC) × (NTX) × (NRX) bits.

When the transmitting and receiving stations are stationary, a closed-loop MIMO communication system may allow the transmitting station to more accurately characterize the propagation path from the transmitting station to the receiving station than an open-loop MIMO communication path. Yet another drawback of closed-loop MIMO communication systems is that the CSI feedback signal tends to become invalid when the transmitting and/or receiving stations are moving or when the surrounding environment is dynamic. In the example of motion, the motion may cause a change in a characteristic of a propagation path between the transmitting station and the receiving station. In such an example, the transmitting station may end up using the CSI previously received from the receiving station, and the receiving station may no longer be able to provide an accurate characterization of the RF channel. Such CSI is said to be invalid. The use of invalid CSI by the transmitting station to generate beamformed signals will result in a reduction in throughput. However, to compensate for the inefficient tendency of the CSI, this may be accomplished by increasing the frequency at which the receiving station sends updated CSI to the transmitting station, which, however, will also increase overhead and thereby reduce throughput.

In an open loop MIMO communication system, the transmitting station may transmit signals directly without using feedback signals received from the receiving station. A transmitting station in an open-loop MIMO communication system typically uses STC.

Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some features of the present invention as set forth in the remainder of the present application with reference to the drawings.

Disclosure of Invention

A method and system for adapting between different closed-loop, open-loop, and hybrid techniques for a multi-antenna system, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.

Various advantages, aspects and novel features of the invention, as well as details of an illustrated embodiment thereof, will be more fully described with reference to the following description and drawings.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is an exemplary block diagram of a wireless communication system that may be used in conjunction with embodiments of the present invention;

FIG. 2 is an exemplary block diagram of a transceiver that may be used in connection with embodiments of the present invention;

FIG. 3 is an exemplary block diagram that may be used in connection with embodiments of the present invention;

FIG. 4 is an exemplary diagram for performing Doppler shift based mechanism selection (region selection) in accordance with an embodiment of the invention;

FIG. 5 is an exemplary block diagram of an STBC with diversity transmission in accordance with an embodiment of the present invention;

fig. 6A is a flow chart of exemplary steps for transmitter station operation scheme adaptation in a MIMO communication system in accordance with an embodiment of the present invention;

fig. 6B is a flow chart of exemplary steps for transmitter station operation scheme adaptation in a MIMO communication system in accordance with an embodiment of the present invention;

FIG. 7 is a flowchart of exemplary steps for receiver station operation mechanism adaptation in a MIMO communication system, in accordance with an embodiment of the present invention

Detailed Description

Particular embodiments of the present invention relate to methods and systems for adapting between different closed loop, open loop and hybrid techniques for application to multi-antenna systems. Various embodiments of the present invention may include a method and system by which a receiving station and a transmitting station in a MIMO communication system may selectively determine an operating regime under which the transmitting station may generate signals based on measured doppler shifts. The selected operating regime may include a) open loop, b) closed loop, and c) mixed operation.

The receiving station may operate in open loopNo feedback CSI is sent to the transmitting station. The transmitting station may calculate a channel estimation matrix based on signals received from the receiving station, and generate a beamformed signal using the calculated channel estimation matrix and transmit the beamformed signal to the receiving station. In this way, the transmitting station may calculate a channel estimate that may be used to characterize the propagation path from the transmitting station to the receiving station based on the signal that follows the propagation path from the receiving station to the transmitting station. The transmitting station may generate beamforming weights based on the calculated channel estimation matrix. The beamforming weights may be used at a transmitting station for generating beamformed signals. In various embodiments of the present invention, the transmitting station and/or receiving station may determine a doppler shift of a signal transmitted over an RF channel between the transmitting station and the receiving station. For values greater than threshold D_openThe transmitting station and the receiving station may use open loop operation. Alternatively, in open-loop operation, the transmitting station may generate a space-time code (STC) signal based on, for example, STBC and/or SFBC, without using the calculated channel estimates.

In closed-loop operation, the receiving station may calculate a channel estimation matrix based on signals received from the transmitting station. The receiving station may generate CSI and/or beamforming weights based on the calculated channel estimation matrix. The amount of CSI and/or beamforming weight data may be referred to as full F1 and may be represented as D [ F1 ]_Full]. The receiving station may send the full F1 in feedback data to the transmitting station. The transmitting station may use the full or partial F1 to generate a beamformed signal that may be transmitted to the receiving station. In various embodiments of the present invention, for less than threshold D_closedThe transmitting station and the receiving station may operate using closed loop.

In the mixing operation, the receiving station may calculate a reduction amount of the feedback information (F1) based on the calculated channel estimation matrix. The reduced amount of feedback information may include a sum of D [ F1 ]_Full]The CSI and/or beamforming weight data is reduced by an amount compared to the amount of CSI and/or beamforming weight data contained therein. The reduction amount F1 can be represented by D [ F1 ]_Reduced]. In various embodiments of the present invention, D [ F1_Reduced]＜D[F1_Full]. The receiving station may send the reduction amount F1 in feedback data to the transmitting station. The transmitting station may use the reduction amount F1 to generate a signal that may be transmitted to the receiving station. The generated signal may be generated using beamforming, STC, or a combination thereof. The transmitting station may calculate one or more beamforming weights based on the received reduction amount F1. In various embodiments of the present invention, for values greater than lower threshold D_closedAnd is less than the upper threshold D_openThe transmitting station and the receiving station may use a mixed operation.

In various embodiments of the present invention, the use of a shuffle operation may avoid the transmitting station generating a beamformed signal based on a steady F1 by increasing the frequency at which the receiving station transmits the reduced amount F1.

Fig. 1 is a representative wireless communication system that may be used in conjunction with embodiments of the present invention. Referring to fig. 1, an Access Point (AP)102, a Wireless Local Area Network (WLAN) Station (STA)104, and a network 108 (e.g., the internet) are shown, with the AP102 and STA104 being capable of wireless communication over one or more Radio Frequency (RF) channels 106. The APs communicatively coupled to the network 108, the AP102, the STAs 104, and the network 108 may communicate based on one or more IEEE802 standards, such as IEEE 802.11.

The STA may use the RF channel 106 to communicate with the AP102 by transmitting signals via an uplink channel. The transmitted uplink channel signal may include one of a plurality of frequencies associated with a channel determined by an associated standard, such as IEEE 802.11. STA104 may receive signals from AP102 over a downlink channel using RF channel 106. Likewise, the received downlink signal may include one of a plurality of frequencies associated with a channel determined by an associated standard (e.g., IEEE 802.11).

In an exemplary embodiment of the invention using closed loop operation, AP102 may use N_TX4 transmit antennas to transmit beamformed signals to the STAs 104 over multiple downlink channels. The AP102 may generate the transmission signal using OFDM. Each RF signal may have a 20MHz channel bandwidth and may be used in the RF channel bandwidthTone f of_C56. STA104 may use N_RX1 receive antenna to receive the signal. A corresponding 4 x 1MIMO communication system may include 4RF spatial channels, where each channel may include 56 subchannels. The STA104 may calculate a channel estimation matrix H based on signals received from the AP102 over the downlink_down. The calculated channel estimate matrix may comprise 56 x 4 x 1 matrix elements. The channel estimation matrix H_downMay include data that may identify the signal propagation path of signals transmitted by the AP102 that are received at the STA 104. STA104 may generate CSI feedback data to map channel estimation matrix H with uplink RF signals_downTo AP 102. In the channel estimation matrix H_downIs represented by an 8-bit binary word, data D F1_Full]256 bytes. STA104 may generate beamforming weight data. In such an example, the channel estimation matrix H may be based on the channel estimation matrix H_downAnd/or the amount of data comprising beamforming weight data to determine data D F1_Full]The number of the cells. The AP102 may generate and transmit continuous beamforming signals to the STAs 104 using the received feedback data.

Various embodiments of the present invention may be implemented in conjunction with a plurality of wireless communication devices, such as a laptop computer having wireless communication means and/or a plurality of mobile handheld devices (e.g., smart phones).

Fig. 2 is an exemplary transceiver that may be used in connection with embodiments of the present invention. Referring to fig. 2, a transceiver system 200, a plurality of receive antennas 222a.. 222n, and a plurality of transmit antennas 232a.. 232n are shown (the same antenna may be used for the transmitter and receiver). In various embodiments of the present invention, the AP102 and/or the STA104 may each include a transceiver system 200 that enables the AP102 and the STA104 to communicate in a MIMO communication system. The transceiver system 200 may include at least one receiver 202, a transmitter 204, a processor 206, and a memory 208. However, a transceiver is shown in fig. 2, but the receiving and transmitting functions may be implemented separately. For example, the AP102 and/or the STAs 104 may include a receiver system and a transmitter system, which may include at least one receiver 202, a processor 206, and a memory 208; the transmitter system may include at least one transmitter 204, a processor 206, and a memory 208.

In an exemplary embodiment of the invention, the processor 206 may implement the functionality of a digital receiver and transmitter in accordance with an application communication standard. The processor may also perform various processing tasks on the received data. The processing tasks may include computing channel estimates that may distinguish the wireless communication medium, demarcate packet boundaries (packet boundaries) in the received data, and computing packet error rate statistics that may indicate whether erroneous bits were detected in the received data packets.

In a receiving station, such as STA104, processor 206 may calculate CSI feedback information, beamforming weights, and/or a reduced amount of feedback signals based on the received signals. The processor 206 may calculate a doppler shift in the received signal. The processor 206 may determine whether to generate feedback information including the full F1 or the reduced amount F1 based on the calculated doppler shift. In a transmitting station, such as AP102, the processor 206 may determine whether to generate a beamformed signal and/or an STC signal using the feedback information.

The receiver 202 may perform receiver functions that may include, but are not limited to, amplification of a received RF signal, generation of a frequency carrier signal corresponding to a selected RF channel (e.g., an uplink channel), down-conversion of the amplified RF signal by the generated frequency carrier signal, demodulation of data contained in data symbols based on application of a selected demodulation type, and detection of data contained in the demodulated signal. The RF signals may be received by one or more receive antennas 222a.. 222 n. Data detected by the receiver 202 may be communicated to the processor 206.

Transmitter 204 may perform transmit functions that may include, but are not limited to, modulating received data based on application of a selected modulation type to generate data symbols, generating a frequency carrier signal corresponding to a selected RF channel (e.g., a downlink channel), up-converting data symbols by the generated frequency carrier signal, generating and amplifying RF signals. Data processed by transmitter 204 may be received from processor 206. The RF signals generated by the transmitter 204 may be transmitted by one or more transmit antennas 232a.. 232 n.

The memory 208 may comprise suitable logic, circuitry, and/or code that may enable storage and retrieval of data and/or code. The memory 208 may use any of a number of storage media technologies such as volatile memory (e.g., Random Access Memory (RAM)) and/or non-volatile memory (electrically erasable read-only memory (EEPROM)). In the context of the present invention, the memory 208 may be used for storing code for calculations, storing F1 feedback information and calculations and/or for storing channel estimates.

In various embodiments of the present invention, transceiver system 200 may use a set of antennas that may be shared by transmitter 204 and receiver 202. In a typical transceiver system 200 for Time Division Duplex (TDD) communications, the transceiver system 200 may include a transmit/receive switch that may couple the set of antennas to a transmitter 204 to cause the transceiver system 200 to transmit signals. The transmit/receive switch may also couple the set of antennas to the receiver 202 so that the transceiver system 200 receives signals. In a typical transceiver system 200 applied to Time Division Duplex (TDD) communications, the transmit/receive switch may also couple the set of antennas to both the transmitter 204 and the receiver 202, thereby enabling the transceiver system 200 to transmit and receive signals simultaneously.

Fig. 3 is an exemplary block diagram of channel feedback that may be used in connection with embodiments of the present invention. Referring to fig. 3, there is shown a transmitting station 402, a receiving station 422, and a communication medium 444. The communication medium may represent a wireless communication medium. For example, transmitting station 402 may represent AP102 and receiving station may represent STA 104. The transmitting station 402 may transmit a signal vector (vector) S to the receiving station 422 via the communication medium 444. The direction of communication from transmitting station 402 to receiving station 422 may be referred to as the downlink. The signal vector S may include a corresponding plurality N_TXMultiple N transmitted simultaneously by transmitting antenna_TXA signal.

Vector of signalQuantity S may be communicated over communication medium 444. The signal vector S may change when transmitted over the communication medium 444. Transfer functions may be used to represent transmission characteristics associated with the communication medium 444. The transfer function may be characterized by a channel estimation matrix H. The signal vector S may be modified based on a transfer function, which may be represented by a channel estimation matrix H. In the downlink direction, the channel estimation matrix may be referred to as H_down. The altered signal vector S can be represented as signal Y. Receiving station 422 may receive signal Y. Receiving station 422 may calculate and channel estimate matrix H based on signals Y received via communication medium 444_downAssociated one or more transfer coefficient values h_ij。

The receiving station 422 may calculate a channel estimate matrix H_down. The receiving station 422 may send feedback information to the transmitting station 402. In various embodiments of the invention, the feedback information may include the full F1, F1_FullOr reduction amounts F1, F1_Reduced. Receiving station 422 may transmit signal vector S by_fTransmitting feedback information (F1)_FullOr F1_Reduced). Transmitting signal vector S_fMay be communicated to transmitting station 402 via communication medium 444. When transmitted over the communication medium 444, a signal vector S is transmitted_fChanges may occur. The direction of communication from receiving station 422 to transmitting station 402 may be referred to as the uplink direction. The signal vector S can be varied on the basis of the transfer function_f. In the uplink direction, the transfer function may be estimated from the channel estimation matrix H_upAnd (5) characterizing. Modified signal vector S_fCan be represented as a signal Y_f。

In one of the various embodiments of the invention, the receiving station 422 may determine the doppler shift based on a level crossing rate (level crossing rate) of the received signal. The doppler shift results from a non-zero relative velocity difference between transmitting station 402 and receiving station 422. In a typical environment, this non-zero relative rate difference is a result of one station moving while the other station is stationary.

In various embodiments of the present invention, the doppler shift calculated by receiving station 422 may be used to determine the operating regimeThis is done by applying the calculated Doppler frequency shift value D_RXAnd a threshold value D_openAnd D_closedA comparison is made to determine. At D_RX≤D_closedIn the example of (a), the receiving station 422 may operate in a closed-loop operating mechanism. When operating in a closed-loop operating regime, the receiving station 422 may communicate feedback information F1_FullTo the transmitting station 402. At D_closed≤D_RX≤D_openIn the example of (2), the receiving station 422 may operate in a mixed-use operating regime. When operating in a mixed-use operating regime, the receiving station 422 may send feedback information F1_ReducedTo the transmitting station 402. At D_RX≥D_openIn the example of (a), the receiving station 422 may operate in an open loop operating regime. When operating in the open-loop operating regime, the receiving station 422 will not transmit feedback information to the transmitting station 402.

In various embodiments of the present invention, the transmitting station 402 may be based on a transmit signal vector S_fThe doppler shift is calculated. The calculated Doppler frequency shift value D_TXMay be used by transmitting station 402 to determine the open-loop mechanism by applying the calculated doppler shift value D_TXAnd a threshold value D_openAnd D_closedA comparison is made to determine.

At D_TX≤D_closedIn an example, the transmitting station 402 may operate in a closed-loop operating regime. When operating in a closed-loop operating mechanism, the transmitting station 402 may generate a beamforming vector S based on feedback information received from the receiving station 422. The feedback information may include full F1, F1_Full. At D_closed≤D_TX≤D_openIn an example, the transmitting station 402 may operate in a hybrid operation regime. When operating in a mixed-use operating regime, the transmitting station 402 may generate a beamforming vector S based on feedback information received from the receiving station 422. The feedback information may include reduction amounts F1, F1_Reduced. At D_TX≥D_openIn the example of (a), the transmitting station 402 may operate in an open loop operating regime. When operating in an open-loop operating regime, the transmitting station 402 will base its channel estimation matrix H calculated at the transmitting station 402 on_upGenerating beamforming signal vectorsAnd S. The channel estimation matrix H_upMay be based on a received signal vector Y_fTo calculate.

In various embodiments of the present invention, the transmitting station 402 may generate the STC signal vector S when operating in an open loop operating mechanism. In various embodiments of the invention, the transmitting station may use beamforming and STC to base on the channel estimation matrix H when operating in an open loop operating mechanism_upA signal vector S is generated.

Fig. 4 is an exemplary diagram for performing doppler shift based mechanism selection (region selection) in accordance with an embodiment of the present invention. Referring to fig. 4, a set of curves illustrating throughput performance results for a simulated MIMO communication system is shown. The chart shown in fig. 4 is used to describe various aspects of an exemplary embodiment of the present invention. Accordingly, the features of the simulation shown in FIG. 4 may be altered to implement various embodiments of the present invention.

The horizontal axis in fig. 4 represents the measured doppler shift values in Hz. The vertical axis in fig. 4 represents the measured throughput performance in BPS/Hz. The emulated MIMO communication system is typically a 4 × 1MIMO system, where f_center2 GHz. The simulation boundaries shown in fig. 4 provide simulation of RF channel communications between a node B (a typical transmitting station) and a single User Equipment (UE) (a typical receiving station) in a 3gpp lte mimo communication system. The signals transmitted over the emulated RF channel use OFDM. The codeword for the signal transmission may be generated using 4-QAM. The data used to generate the code words may be generated using a Binary Convolutional Code (BCC) with a code rate of 2/3. The SNR measured at the receiving station is 10 dB. The delay in transmitting feedback data from the receiving station to the transmitting station is 0.75 milliseconds (ms).

In fig. 4, curve 502 represents typical throughput results for a simulated MIMO system when operating in a closed-loop operating regime. In the closed-loop operation mechanism, the signals of the simulation MIMO system are transmitted by adopting the beam forming technology. In the closed-loop operation scheme, each channel estimation coefficient in the channel estimation matrix H may be expressed as a floating-point number. Curve 504 represents typical throughput results for a simulated MIMO system when operating in a mixed-use operating regime. In the mixed operation mechanism, STC is adopted to transmit the simulation MIMO system signal. The feedback information is represented as a 1-bit binary value. Curve 506 represents typical throughput results for a simulated MIMO system when operating in an open loop operating regime. In the open-loop operation mechanism, an STC is adopted to transmit the simulation MIMO system signal.

In the simulated MIMO system shown in FIG. 4, the Doppler frequency shift value is located at D ≦ D_closedWhen operating in a closed-loop operating regime, the throughput performance of the simulated MIMO system is optimal. At the salient point 503 in fig. 4, D ═ D_closed. At point 503, the throughput performance of the simulated MIMO system is approximately equal to 2.59BPS/Hz for both the closed-loop and the mixed-use operating mechanisms.

For Doppler frequency shift value D_closed＜D＜D_openWhen the simulation system operates in a mixed operation mechanism, the throughput performance of the simulation MIMO system is optimal. At the salient point 505 in fig. 4, D ═ D_open. At point 505, the throughput performance of the simulated MIMO system is approximately equal to 2.59BPS/Hz for both the mixed-use and open-loop operating mechanisms. For Doppler frequency shift value D_closed＞D＞D_openWhen the simulation system operates in a mixed operation mechanism, the throughput performance of the simulation MIMO system is optimal. For a Doppler frequency shift value D ≧ D_openWhen the system operates in an open-loop operation mechanism, the throughput performance of the simulation MIMO system is optimal.

In various embodiments of the present invention, the transmitting station 402, when used in a shuffle operation regime, may generate a transmit signal based on the reduced amount feedback information (F1) using the STC. In this example, the transmitting station 402 may generate a transmit signal based on an angle rotation value θ in the feedback data received from the receiving station 422. In an exemplary embodiment of the present invention, the receiving station 422 may send feedback information that may specify the angle of rotation value θ using a single bit value. The transmitting station may use the received single bit value with a quasi-orthogonal STBC or SFBC.

Exemplary methods for quasi-orthogonal STBC or SFBC are disclosed in U.S. patent application No. 11/759,203, 6/2007, which is incorporated herein by reference.

Fig. 5 is an exemplary block diagram of STBC with diversity transmission according to an embodiment of the present invention. Referring to fig. 5, a transmitting station 402 and a receiving station 422 are shown. The transmitting station 402 may include an STBC encoder 602. The transmitting station 402 may transmit diversity by simultaneously transmitting multiple RF output signals using at least a portion of the transmit antennas 512a, 512b, 512c, and 512 d. The receiving station 422 may include an STBC decoder 604. The receiving station 422 may receive signals via a receive antenna 522.

At successive time instances (time instant), the transmitting station 402 may transmit the groups of data symbols 632, 634, 636, and 638 simultaneously using STBC. In an exemplary embodiment of the invention, each data symbol x (t)_k) May comprise an OFDM symbol, which may be at time t_kAppear in the spatial data stream. Thus, in the 4 × 1STBC diversity transmission system, at time t_k、t_k+1、t_k+2、t_k+3Multiple data symbols x (t) that appear in a single data stream_k)、x(t_k+1)、x(t_k+2)、x(t_k+3) May be transmitted simultaneously via multiple transmit antennas 512a, 512b, 512c, and 512 d. When transmitting a data symbol set 632, transmitting station 402 may transmit a codeword, s (0, k) ═ x (t), through transmit antenna 512a_k) And transmits the codeword s (1, k +1) ═ x through the transmitting antenna 512b^*(t_k+1) Where x is^*Refers to the complex conjugate of x. Transmitting station 402 may transmit codeword s (2, k +2) ═ x (t) through transmit antenna 512c_k+2) And transmits the codeword s (3, k +3) ═ x through the transmitting antenna 512d^*(t_k+3)。

When transmitting the set of data symbols 634, transmitting station 402 may transmit a codeword s (0, k +1) ═ x (t) through transmit antenna 512a_k+1) And transmits the codeword s (1, k) ═ x through the transmitting antenna 512b^*(t_k). Transmitting station 402 may transmit codeword s (2, k +3) ═ x (t) through transmit antenna 512c_k+3) And transmits the codeword s (3, k +2) ═ x through the transmitting antenna 512d^*(t_k+2)。

When transmitting a data symbol set 636, transmitting station 402 may transmit a codeword s (0, k +2) x (t) via transmit antenna 512a_k+2) And transmits the codeword s (1, k +3) ═ c · x through the transmitting antenna 512b^*(t_k+3). The transmitting station 402 may transmit a codeword s (2, k) — c · x (t) over a transmit antenna 512c_k) And transmits the codeword s (3, k +1) ═ x through the transmitting antenna 512d^*(t_k+1). The variable c refers to the angle value as shown in the following equation:

c＝e^jθ[3]

here, θ means a rotation angle value. In various embodiments of the present invention, receiving station 422 may calculate the value c in equation [3 ].

May be based on a transfer coefficient factor h₀The signal transmitted by the transmitting antenna 512a and communicated over the communication medium to the receiving station 422 is modified. May be based on a transfer coefficient factor h₁The signal transmitted by the transmitting antenna 512b and communicated over the communication medium is modified. May be based on a transfer coefficient factor h₂The signal transmitted by the transmit antenna 512c and communicated over the communication medium is modified and may be based on a transfer coefficient factor h₃The signal transmitted by the transmitting antenna 512d and communicated over the communication medium is modified.

Quasi-orthogonal space-time block codes (STBC) are methods used in some diversity transmission systems in the field of wireless communications. The purpose of quasi-orthogonal STBC is that it can enable a wireless communication system to use the advantages of diversity transmission at a transmitting station while using simplified decoding techniques at a receiving station.

As shown below, in an exemplary embodiment of the present invention, the channel estimation matrix H_newMay be based on a matrix H_effAnd the Hadamard product of the rotation matrix C:

here, equation [4 ]]The first matrix on the left represents the effective channel estimate for quasi-orthogonal STBC transmission, equation [4 ]]The second matrix on the left is the rotation matrix C and equation [4 ]]The matrix on the right is the matrix Hnew. Matrix H is a rotation matrix C that is used to rotate the signals simultaneously transmitted by transmitting station 402_newThe effective channel estimation matrix of the representation. In the rotation matrix C, the matrix coefficient value C represents equation [3]]The corner factor shown in (a). The crosstalk term (crosstalk term) δ related to quasi-orthogonal space-time coding can be expressed as shown in the following equation:

in various embodiments of the present invention, the value of c may be determined such that the crosstalk term δ ≈ 0. The calculated c value may correspond to the situation shown by the following equation:

the rotation angle value θ indicated in equation [3] can be expressed as shown in the following equation:

in this case, the amount of the solvent to be used,

in an exemplary embodiment of the invention, the rotation angle factor c may be expressed as a single bit value, for example:

if it is not

c＝1； /^＊θ＝0，angle(a)＝0^＊/

Otherwise

c＝-1； /^＊θ＝π，angle(a)＝¹/₂π^＊/

In the exemplary embodiment of the present invention shown in equation [9], a single bit representation of the rotation angle factor c is such that the value of c indicates two different rotation angle values: θ ═ 0 and θ ═ pi. In another exemplary embodiment of the present invention, the rotation angle factor may be expressed as a two-bit value. The two-bit value representation of c is such that the value of c may indicate 4 different rotation angle values. In various embodiments of the present invention, the rotation angle factor c may be represented by m-bits, where m represents a selected number of bits.

In various embodiments of the present invention, the receiving station 422 may send the single-bit value in feedback data to the transmitting station 402 when the receiving station 422 is operating in a hybrid mechanism. The single bit value may represent the value of the rotation angle factor c. When the transmitting station 402 operates in a mixed operation regime and receives a single bit value in the feedback data, the transmitting station may transmit a signal using STC based on the received rotation angle factor c.

Various embodiments of the present invention may be implemented when the principles disclosed herein are applied to cause the receiving station 422 to generate the reduction amount F1 based on the detected doppler shift and/or based on the measured rate. The reduction amount F1 may be transmitted in the feedback data. In this regard, the receiving station 422 may transmit feedback data, which may be used to generate beamformed signals and/or space-time coded signals, for example. Based on the reduction amount F1 in the received feedback data, the transmitting station 402 may generate, for example, a beamformed and/or space-time encoded signal.

Fig. 6A is a flow chart of exemplary steps for transmitter station operation mechanism adaptation in a MIMO communication system in accordance with an embodiment of the present invention. In the exemplary embodiment of the present invention illustrated in fig. 6, the transmitting station transmits a beamformed signal when operating in an open loop operating regime. Referring to fig. 6A, in step 601, a doppler shift threshold may be established: d_closedRepresents a closed loop operating regime threshold, and D_openRepresenting an open loop operating regime threshold. In step 603, the transmitting station may receive a signal vector Y over the uplink RF channel. In step 606, the transmitting station may determine a doppler shift D based on the received signal vector Y_TX. In step 608, the transmitting station may determine whether D_TXIs less than D_closedAnd (4) a threshold value. At D_TX＜D_closedIn step 610, the transmitting station may receive the complete F1. In step 612, the transmitting station may generate a beamformed signal vector based on the full F1. The signal vector S represents a set of signals that may be simultaneously transmitted by a transmitting station.

Returning to step 608, at D_TX≥D_closedIn step 614, the transmitting station may calculate a channel estimation matrix H based on the received signal vector Y. In step 616, the transmitting station may determine D_TXWhether or not it is greater than D_openAnd (4) a threshold value. At D_TX≥D_closedIn step 618, the transmitting station may generate a signal vector S based on the calculated channel estimation matrix.

Returning to step 616, at D_closed≥D_TX≥D_openIn step 620, the transmitting station may decrement F1. In step 622, the transmitting station may baseThe signal vector S is generated at the reduction amount F1.

Fig. 6B is a flow chart of exemplary steps for transmitter station operation mechanism adaptation in a MIMO communication system in accordance with an embodiment of the present invention. In the exemplary embodiment of the invention shown in fig. 6B, the transmitting station transmits the STC when operating in an open loop operating mechanism. Comparing fig. 6A and 6B, in fig. 6B, the step of calculating the channel estimate based on the received signal vector Y (fig. 6A, step 614) is not shown. Alternatively, step 616 follows step 608. At D_TX≥D_closedIn step 619, the transmitting station may generate a signal vector S based on the STC.

Fig. 7 is a flow chart of exemplary steps for receiver station operation mechanism adaptation in a MIMO communication system in accordance with an embodiment of the present invention. Referring to fig. 7, in step 702, a doppler shift threshold may be established: d_closedRepresents a closed loop operating regime threshold, and D_openRepresenting an open loop operating regime threshold. In step 704, the receiving station may receive a signal vector Y over a downlink RF channel. In step 706, the receiving station may calculate a signal estimate matrix based on the received signal vector Y. In step 708, the receiving station may determine a doppler shift D based on the received signal vector_RX. In step 710, the receiving station may determine D_RXWhether or not less than D_closedAnd (4) a threshold value. At D_RX＜D_closedIn step 710, the receiving station may generate a complete F1 based on the channel estimation matrix H. In step 714, the receiving station may send the full F1 in the feedback information over the uplink RF channel.

Returning to step 710, at D_RX≥D_closedIn step 716, the receiving station may determine D_RXWhether or not it is greater than D_openAnd (4) a threshold value. At D_RX≥D_openIn step 718, no feedback information is generated and/or transmitted.

Returning to step 716, at D_closed≥D_RX≥D_openIn step 720, the receiving station may generate a reductionAmount F1. At step 722, the receiving station may transmit the reduction amount F1 over the uplink RF channel.

Various aspects of a method and system for adapting between different closed-loop, open-loop, and hybrid techniques for use in a multiple antenna system include a transmitting station 402 that can generate multiple signals for simultaneous transmission over a communication medium, the multiple signals being generated based on a selected one of: full F1, reduced amount F1, or no feedback information. The selection may be determined at the transmitting station based on the determined doppler shift. The doppler shift may be determined based on signals received at transmitting station 402 over a communication medium.

The transmitting station 402 may operate in a closed-loop operating regime when the determined doppler shift frequency is less than or equal to a closed-loop operating regime threshold. When the transmitting station 402 is operating in a closed-loop operating regime, the transmitting station 402 may generate multiple simultaneously transmitted signals based on the full F1 in the feedback information. A plurality of beamforming weights may be generated based on the full F1. The transmitting station 402 may generate a beamformed plurality of simultaneously transmitted signals based on the plurality of beamforming weights.

The transmitting station 402 may operate in a hybrid operating regime when the determined doppler shift is greater than or equal to the closed-loop operating regime threshold but less than or equal to the open-loop operating regime threshold. When the transmitting station 402 is operating in the mixed-use operating regime, the transmitting station 402 may generate multiple simultaneously transmitted signals based on the reduction amount F1. The reduction amount F1 may be represented as an m-bit binary value. In an exemplary embodiment of the present invention, the reduction amount F1 may be expressed as a single-bit value. The binary value may be given to determine a rotation angle value θ. The angle value may be used to generate a plurality of transmit signals based on Space Time Coding (STC) such as STBC or SFBC.

The transmitting station 402 may operate in an open-loop operating regime when the determined doppler shift is greater than the open-loop operating regime threshold. When transmitting station 402 operates in an open-loop operating regime, transmitting station 402 may generate multiple simultaneously transmitted signals without using feedback information. The transmitting station 402 may calculate a channel estimation matrix based on signals received over the communication medium. The transmitting station 402 may generate multiple simultaneously transmitted signals based on the calculated channel estimation matrix and/or based on the STC.

In an exemplary embodiment of the invention, the number D [ F1 ] of complete F1_Full]A floating point representation of CSI data (represented by the channel estimation matrix H) and/or beam weight data (represented by the beamforming matrix V) may be included.

In another exemplary embodiment of the invention, the reduction amount F1D [ F1 ]_Reduced]May comprise a quantized version of the beamforming weight data in the beamforming matrix V. Quantized version V of beamforming matrix^QMay be a reduced-size version of the beamforming matrix such that dv^Q]＜D[V]。

In yet another exemplary embodiment of the present invention, the amount of F1 is reduced by an amount D [ F1 ]_Reduced]A data compressed version of the beamforming weight data in the beamforming matrix V may be included. Data compressed version V of beamforming matrix^CmpMay be a reduced-size version of the beamforming matrix such that dv^Cmp]＜D[V]。

In yet another exemplary embodiment of the present invention, the amount of F1 is reduced by an amount D [ F1 ]_Reduced]Beamforming weight data may be included, which may be selected from a codebook (codebook). The codebook may be a licensed value (transmitted value) specifically designated for each beamforming weight. The value of each beam weight may be selected from a set of privileged values specifically specified in the codebook. Version V of the codebook generated beamforming matrix^CbkMay be a reduced-size version of the beamforming matrix such that dv^Cbk]＜D[V]。

In yet another exemplary embodiment of the present invention, the amount of F1 is reduced by an amount D [ F1 ]_Reduced]A reduced amount version of the channel estimation data H may be included. Reduced amount version H of the beamforming matrix^εMay be a reduced-size version of the channel estimation matrix, such that DH^ε]＜D[H]。

Various embodiments of the present invention may be implemented in a MIMO communication system when the characteristics of the communication medium change dynamically. The transmitting station and/or receiving station may determine the degree of dynamic change in the communication medium by observing changes in the calculated channel estimate values and/or based on changes in the values of the data contained in the received feedback information observed at particular time intervals. For example, when the communication medium includes a slow fading channel environment (slow fading channel environment), the transmitting station and the receiving station may operate in a closed-loop operation mechanism. When the communication medium comprises a fast fading channel environment, the transmitting station and the receiving station may operate in an open loop operating regime. When the communication medium includes neither a slow fading channel environment nor a fast fading channel environment, the transmitting station and the receiving station may operate in a mixed operation regime.

In one embodiment of the invention, a machine readable storage may be provided. A computer program stored therein comprises at least one code segment for execution by a machine to cause the machine to perform the above-described steps for processing a signal in a wireless communication system to perform adaptive noise filtering in HSDPA CQI selection.

Accordingly, the present invention may be realized in hardware, software, or a combination of hardware and software. The present invention can be realized in a centralized fashion in at least one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software could be a general purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the methods described herein. The method is implemented in a computer system using a processor and a memory unit.

The present invention can also be implemented by a computer program product, which comprises all the features enabling the implementation of the methods of the invention and which, when loaded in a computer system, is able to carry out these methods. The computer program in the present document refers to: any expression, in any programming language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following a) conversion to another language, code or notation; b) reproduced in different formats to implement specific functions.

While the invention has been described with reference to several embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (5)

1. A method of signal processing in a communication system, the method comprising:

generating a plurality of signals for simultaneous transmission over a communications medium using a selected one of the following conditions:

a basic amount of feedback information is provided,

a reduced version of the base quantity of feedback information,

or the feedback information is not used and,

wherein the selecting is based on a determined Doppler shift, the step of selecting one of the conditions based on the determined Doppler shift comprising:

establishing a closed-loop operating mechanism threshold and an open-loop operating mechanism threshold;

determining a doppler shift based on a signal vector received through a communication medium;

judging whether the determined Doppler frequency shift is smaller than the threshold value of the closed-loop operation mechanism, if so, receiving the feedback information of the basic quantity, and generating a beam forming signal vector based on the feedback information of the basic quantity; otherwise, calculating a channel estimation matrix based on the received signal vector;

judging whether the determined Doppler frequency shift is larger than the threshold value of the open-loop operation mechanism, if so, generating a beam forming signal vector based on the calculated channel estimation matrix; otherwise, receiving feedback information of the reduced versions of the basic quantity;

generating a beamforming signal vector based on the received feedback information for the reduced version of the base number;

wherein the generated beamformed signal vector represents a plurality of signals simultaneously transmitted over the communication medium.

2. The method of claim 1, comprising generating a plurality of beamforming weights based on the base number of feedback information.

3. The method of claim 2, comprising generating the plurality of simultaneously transmitted signals based on the plurality of beamforming weights.

4. A system for signal processing in a communication system, the system comprising:

one or more circuits configured to generate a plurality of signals for simultaneous transmission over a communication medium using a selected one of the following conditions:

a basic amount of feedback information is provided,

a reduced version of the base quantity of feedback information,

or the feedback information is not used and,

wherein the selecting is based on a determined Doppler shift:

the one or more circuits establish a closed-loop operating regime threshold and an open-loop operating regime threshold;

the one or more circuits determine a doppler shift based on a signal vector received through a communication medium;

the one or more circuits determine whether the determined doppler shift is less than the closed-loop operating regime threshold, receive the base quantity of feedback information, and generate a beamformed signal vector based on the base quantity of feedback information; otherwise, calculating a channel estimation matrix based on the received signal vector;

the one or more circuits determine whether the determined doppler shift is greater than the open loop operating mechanism threshold, and if so, generate a beamforming signal vector based on the calculated channel estimation matrix; otherwise, receiving feedback information of the reduced versions of the basic quantity;

the one or more circuits generate a beamformed signal vector based on the received feedback information for the reduced version of the base number;

wherein the generated beamformed signal vector represents a plurality of signals simultaneously transmitted over the communication medium.

5. The system according to claim 4, wherein said one or more circuits enable generation of a plurality of beamforming weights based on said base number of feedback information.