HK1183991A - Reverse channel estimation for rf transceiver with beamforming antenna - Google Patents

Abstract

The present invention is directed to a reverse channel estimation for RF transceiver with beamforming antenna. A radio frequency (RF) transceiver includes a plurality of RF transceiver sections that generate first transmissions to a non-beamforming first remote station based on a first plurality of steering weights for a plurality of antennas and to receive second transmissions from the first remote station, wherein the first transmissions and the second transmissions are via a first communication channel. A configuration controller generates the first plurality of steering weights based on a reverse channel estimation of the first communication channel.

Description

Reverse channel estimation for RF transceivers with beamforming antennas

Cross reference to related patent

This application claims priority from united states provisional application No. 61/552,835 filed on 28/10/2011 and from united states utility application No. 13/329,296 filed on 18/12/2011. The contents of which are hereby incorporated by reference.

Technical Field

The present invention relates generally to wireless communications, and more particularly to antennas for supporting wireless communications.

Background

Known communication systems support wireless and wired communication between wireless and/or wired communication devices. The communication system covers a range from national and/or international cellular telephone systems to the internet and to point-to-point home wireless networks to Radio Frequency Identification (RFID) systems. Each type of communication system is constructed and operates in accordance with one or more communication standards. For example, a wireless communication system may operate in accordance with one or more standards including, but not limited to, RFID, IEEE 802.11, Bluetooth, Advanced Mobile Phone Service (AMPS), digital AMPS, Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), Local Multipoint Distribution System (LMDS), Multi-channel multipoint distribution System (MMDS), and/or variations thereof.

Depending on the type of wireless communication system, wireless communication devices, such as cellular phones, two-way radios, Personal Digital Assistants (PDAs), Personal Computers (PCs), notebook computers, home entertainment equipment, RFID readers, RFID tags, etc., communicate directly or indirectly with other wireless communication devices. For direct communication (also referred to as point-to-point communication), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of a plurality of Radio Frequency (RF) carriers of the wireless communication system) and communicate via the channel. For indirect wireless communication, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for in-home or in-building wireless networks) via an assigned channel. To enable a communication connection between wireless communication devices, the associated base stations and/or associated access points communicate directly with each other via the system controller, via the public switched telephone network, via the internet, and/or via some other wide area network.

For each wireless communication device participating in wireless communication, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for a home and/or in-building wireless communication network, an RF modem, etc.). As is well known, the receiver is coupled to an antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives the inbound RF signal via the antenna and then amplifies it. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signals to baseband signals or Intermediate Frequency (IF) signals. The filtering stage filters the baseband signal or the IF signal to attenuate undesired out-of-band signals to produce a filtered signal. The data recovery stage recovers the original data from the filtered signal in accordance with a particular wireless communication standard.

It is also known for a transmitter to include a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts the raw data to a baseband signal according to a particular wireless communication standard. One or more intermediate frequency stages mix the baseband signal with one or more local oscillations to generate an RF signal. The power amplifier amplifies the RF signal before transmission via the antenna.

Currently, wireless communication occurs within licensed or unlicensed spectrum. For example, Wireless Local Area Network (WLAN) communications occur within the unlicensed industrial, scientific, and medical (ISM) spectrum at 900MHz, 2.4GHz, and 5 GHz. Although the ISM spectrum is not licensed, it has limitations on power, modulation techniques, and antenna gain. Another unlicensed spectrum is the V-band at 55-64 GHz.

Other drawbacks of conventional approaches will be apparent to those skilled in the art when given the ensuing disclosure.

Disclosure of Invention

The present invention is directed to apparatus and methods of operation further described in the following brief description of the drawings, detailed description of the invention, and the appended claims. Other features and advantages of the present invention will become apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings.

According to an aspect of the present invention, there is provided a Radio Frequency (RF) transceiver having a plurality of antennas, the RF transceiver including: a plurality of RF transceiver sections to generate a first transmission to a first remote station based on a first plurality of steering weights for the plurality of antennas and to receive a second transmission from the first remote station, wherein the first transmission and the second transmission are via a first communication channel; and a configuration controller, coupled to the RF transceiver section, for generating the first plurality of steering weights based on a reverse channel estimate of the first communication channel; wherein the first remote station is unable to beamform.

Preferably, said configuration controller is configured to generate said reverse channel estimate for said first communication channel based on said second transmission.

Preferably, the reverse channel estimate of the first communication channel comprises a reverse channel link estimate matrix.

Preferably, the reverse channel assessment of the first communication channel is based on a one-sided channel calibration that uses characteristics of a transmit path and a receive path of the RF transceiver as an assessment of characteristics of the first remote station.

Preferably, the configuration controller is configured to generate the first plurality of steering weights based on a forward link channel estimate of the first communication channel, the forward link channel estimate of the first communication channel being based on a reverse channel link estimate of the first communication channel.

Preferably, the configuration controller is configured to generate the forward link channel estimate for the first communication channel based on a matrix transpose of the reverse channel link estimate matrix.

Preferably, the configuration controller is further configured to update the reverse channel assessment of the first communication channel based on a current second transmission and to adjust the first steering weight based on the updated reverse channel assessment of the first communication channel.

Preferably, the first steering weight is adjusted based on time domain smoothing.

Preferably, the plurality of RF transceiver sections are further configured to generate a third transmission to a second remote station based on a second plurality of steering weights for the plurality of antennas, and to receive a fourth transmission from the second remote station, wherein the third transmission and the fourth transmission are via a second communication channel; and wherein the configuration controller is further configured to generate the second plurality of steering weights based on a reverse channel assessment of the second communication channel; and wherein the second remote station is not capable of beamforming.

Preferably, the plurality of RF transceiver sections operate in accordance with the 802.11 standard.

Preferably, the first steering weights are smoothed in the frequency domain via a smoothing filter.

Preferably, the first transmission comprises at least one packet comprising a first portion and a second portion, wherein the steering weights are applied to beamform the second portion, wherein the first portion is not beamformed.

Preferably, the at least one packet is a mixed mode packet, wherein the first portion is formatted according to a legacy (legacy) protocol, wherein the second portion is formatted according to a non-legacy protocol, wherein the first portion is placed before the second portion in the at least one packet.

According to another aspect of the present invention, there is provided a method of use in a Radio Frequency (RF) transceiver having a plurality of antennas, the method comprising: generating, via a plurality of RF transceiver sections, a first transmission to a first remote station via a first communication channel based on a first plurality of steering weights for the plurality of antennas; receiving, via the plurality of RF transceiver sections, a second transmission from the first remote station via the first communication channel; and generating the first plurality of steering weights based on a reverse channel assessment of the first communication channel; wherein the first remote station is not capable of beamforming.

Preferably, the reverse channel estimate for the first communication channel is generated based on the second transmission.

Preferably, the reverse channel estimate of the first communication channel comprises a reverse channel link estimate matrix.

Preferably, the reverse channel estimate of the first communication channel is generated based on a one-sided channel calibration that uses characteristics of a transmit path and a receive path of the RF transceiver as an estimate of characteristics of the first remote station.

Preferably, the first plurality of steering weights are generated based on a forward link channel estimate for the first communication channel, the forward link channel estimate being based on a reverse channel link estimate for the first communication channel.

Preferably, the forward link channel estimate for the first communication channel is generated based on a matrix transpose of the reverse channel link estimate matrix.

Preferably, the method further comprises: updating the reverse channel assessment of the first communication channel based on a current second transmission; and adjusting the first steering weight values based on the updated reverse channel assessment for the first communication channel.

Drawings

FIG. 1 is a schematic block diagram of one embodiment of a wireless communication system in accordance with the present invention;

fig. 2 is a schematic block diagram of another embodiment of a wireless communication system according to the present invention;

FIG. 3 is a schematic block diagram of an embodiment of a wireless transceiver 125 in accordance with the present invention;

FIG. 4 is a schematic block diagram of an embodiment of RF transceiver 112 in accordance with the present invention;

FIG. 5 is a schematic block diagram of various radiation patterns generated by the wireless transceiver 112 according to an embodiment of the present invention;

fig. 6 is a schematic block diagram of an embodiment of an RF transceiver section 111 according to the present invention;

FIG. 7 is a flow chart of an embodiment of a method according to the present invention;

fig. 8 is a flow chart of an embodiment of a method according to the present invention.

Detailed Description

Fig. 1 is a schematic block diagram of an embodiment of a communication system according to the present invention. In particular, a communication system is shown that includes a communication device 10 wirelessly communicating non-real time data 24 and/or real time data 26 with one or more other devices, such as a base station 18, a non-real time device 20, a real time device 22, and a non-real time and/or real time device 25. Further, communication device 10 may also optionally communicate with network 15, non-real time devices 12, real time devices 14, non-real time and/or real time devices 16 via a wired connection.

In embodiments of the present invention, the wired connection 28 may be a wired connection that operates according to one or more standard protocols, such as Universal Serial Bus (USB), Institute of Electrical and Electronics Engineers (IEEE) 488, IEEE 1394 (firewire), ethernet, Small Computer System Interface (SCSI), serial or parallel advanced technology attachment (SATA or PATA), or other standard or proprietary wired communication protocols. The wireless connection may communicate in accordance with a wireless network protocol (such as WiHD, NGMS, IEEE 802.11a, ac, b, g, n, or other 802.11 standard protocols, bluetooth, Ultra Wideband (UWB), WIMAX, or other wireless network protocols), a radiotelephone data/voice protocol (such as global system for mobile communications (GSM), General Packet Radio Service (GPRS), enhanced data rates for global evolution (EDGE), Long Term Evolution (LTE), Personal Communication Services (PCS), or other mobile wireless protocols), or other standard or proprietary wireless communication protocols. Further, the wireless communication path may include separate transmit and receive paths using separate carrier frequencies and/or separate frequency channels. Alternatively, a single frequency or frequency channel may be used to bi-directionally transfer data to and from the communication device 10.

The communication device 10 may be a mobile telephone such as a cellular telephone, a local area network device, a personal area network device or other wireless network device, a personal digital assistant, a game console, a personal computer, a notebook computer, or other device that performs one or more functions including communication of voice and/or data via a wired connection 28 and/or a wireless communication pathway. Further, the communication device 10 may be an access point, base station, or other network access device coupled to a public or private network 15, such as the internet or other wide area network, via a wired connection 28. In embodiments of the present invention, the real-time and non-real-time devices 12, 14, 16, 18, 20, 22, and 25 may be personal computers, notebooks, PDAs, mobile phones such as cellular phones, devices equipped with wireless local area networks or bluetooth transceivers, FM tuners, TV tuners, digital cameras, digital video cameras, or other devices that produce, process, or use audio, video signals, or other data or communications.

In operation, the communication device includes one or more applications including voice communications such as standard telephone applications, voice over internet protocol (VoIP) applications, local games, internet games, e-mail, instant messaging, multimedia messaging, web browsers, audio/video recording, audio/video playback, audio/video downloading, streaming audio/video playback, office applications such as databases, spreadsheets, word processing, image creation and processing, and other voice and data applications. In conjunction with these applications, real-time data 26 includes voice, audio, video, and multimedia applications including internet gaming and the like. Non-real-time data 24 includes text messages, e-mail, web browsing, file uploads and downloads, and the like.

In embodiments of the present invention, the communication device 10 includes a wireless transceiver that includes one or more features or functions of the present invention. Such a wireless transceiver will be described in more detail in connection with subsequent fig. 3-8.

Fig. 2 is a schematic block diagram of an embodiment of another communication system according to the present invention. In particular, fig. 2 shows a communication system comprising a plurality of identical elements of fig. 1, which are denoted by identical reference numerals. The communication device 30 is similar to the communication device 10 and is provided with any of the applications, functions and features attributed to the communication device 10 as discussed in connection with fig. 1. However, the communication device 30 includes more than two separate wireless transceivers for communicating with the data device 32 and/or the data base station 34 via the RF data 40 and the voice base station 36 and/or the voice device 38 via the RF voice signals 42 simultaneously over two or more wireless communication protocols.

Fig. 3 is a schematic block diagram of one embodiment of a wireless transceiver 125 in accordance with the present invention. RF transceiver 125 represents a wireless transceiver used in conjunction with communication devices 10 or 30, base station 18, non-real time devices 20, real time devices 22 and non-real time and/or real time devices 25, data devices 32 and/or data base stations 34, and voice base stations 36 and/or voice devices 38. The RF transceiver 125 includes an RF transmitter 129 and an RF receiver 127. The RF receiver 127 includes an RF front end 140, a down conversion module 142, and a receiver processing module 144. The RF transmitter 129 includes a transmitter processing module 146, an up-conversion module 148, and a radio transmitter front end 150.

As shown, the receiver and transmitter are coupled to an antenna through an antenna interface 171 and a duplexer (diplexer) 177 that couples the transmit signal 155 to the antenna to generate the outbound RF signal 170 and the inbound signal 152 to generate the receive signal 153, respectively. Alternatively, a transmit/receive switch may be used in place of the duplexer 177. Although a single antenna is shown, the receiver and transmitter may share a multi-antenna structure including more than two antennas. In another embodiment, the receiver and transmitter may share a multiple-input multiple-output (MIMO) antenna structure, a diversity antenna structure, a phased array or other controllable antenna structure including multiple antennas, and other RF transceivers similar to RF transceiver 125. Each of these antennas may be fixed, programmable, and an antenna array or other antenna configuration. In addition, the antenna structure of the wireless transceiver may depend on the particular standard to which the wireless transceiver is following and its application.

In operation, the RF transmitter 129 receives outbound data 162. The transmitter processing module 146 packetizes the outbound data 162 in accordance with a standard or proprietary millimeter-wave protocol or a wireless telephony protocol to produce a baseband or low Intermediate Frequency (IF) Transmit (TX) signal 164, the signal 164 comprising an outbound symbol stream that includes the outbound data 162. The baseband or low IF TX signal 164 may be a digital baseband signal (e.g., with zero IF) or a digital low IF signal, where the low IF will typically be in the frequency range of one hundred kilohertz to several megahertz. Note that the processing performed by transmitter processing module 146 may include, but is not limited to, scrambling, encoding, adding and deleting, mapping, modulating, and/or digital baseband to IF conversion.

The up-conversion module 148 includes a digital-to-analog conversion (DAC) module, a filtering and/or gain module, and a mixing section. The DAC module converts the baseband or low IF TX signal 164 from the digital domain to the analog domain. The filtering and/or gain module filters and/or adjusts the gain of the analog signal before providing it to the mixing section. The mixing section converts the analog baseband or low IF signal to an up-converted signal 166 based on the transmitter local oscillation.

The radio transmitter front end 150 includes a power amplifier and may also include a transmit filtering module. The power amplifier amplifies the upconverted signal 166 to generate an outbound RF signal 170, and if included, the signal 170 may be filtered by a transmit filter module. The antenna structure transmits the outbound RF signal 170 via an antenna interface 171 coupled to an antenna that provides impedance matching and optional bandpass filtering.

The RF receiver 127 receives the inbound RF signals 152 via an antenna and an antenna interface 171 that operates to process the inbound RF signals 152 into received signals 153 for the receiver front end 140. In general, the antenna interface 171 provides impedance matching of the antenna to the RF front end 140, optional bandpass filtering of the inbound RF signal 152.

The down conversion module 142 includes a mixing section, an analog-to-digital conversion (ADC) module, and may also include a filtering and/or gain module. The mixing section converts the desired RF signal 154 to a down-converted signal 156, such as an analog baseband or low IF signal, based on a receiver local oscillation 158. The ADC module converts the analog baseband or low IF signal to a digital baseband or low IF signal. The filtering and/or gain module high pass and/or low pass filters the digital baseband or low IF signal to produce a baseband or low IF signal 156 that includes the inbound symbol stream. Note that the order of the ADC module and the filtering and/or gain module may be interchanged, making the filtering and/or gain module an analog module.

The receiver processing module 144 processes the baseband or low IF signal 156 according to a standard or proprietary millimeter wave protocol to generate inbound data 160, such as probe data received from the probe device 105 or the devices 100 or 101. The processing performed by the receiver processing module 144 may include, but is not limited to, digital intermediate frequency to baseband conversion, demodulation, demapping, de-scrambling, decoding, and/or descrambling.

In embodiments of the present invention, the receiver processing module 144 and the transmitter processing module 146 may be implemented via any means using microprocessors, microcontrollers, digital signal processors, microcomputers, central processing units, field programmable gate arrays, programmable logic devices, state machines, logic circuits, analog circuits, digital circuits, and/or directing signals (analog and/or digital) based on operational instructions. The associated memory may be a single memory device or a plurality of memory devices, on-chip or off-chip. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that stores digital information. Note that when the processing device implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the associated memory storing the corresponding operational instructions for that circuitry is embedded within the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. As shown, a feedback path exists between the receiver processing module 144 and the transmitter processing module 146 for purposes of beamforming calibration, which will be described in more detail in conjunction with fig. 4-8.

Although receiver processing module 144 and transmitter processing module 146 are shown separately, it should be understood that these elements may be implemented separately, together through operation of one or more shared processing devices, or in conjunction with separate and shared processing.

Additional details including optional functions and features of the RF transceiver are discussed in connection with subsequent fig. 4-8.

Fig. 4 is a schematic block diagram of an embodiment of RF transceiver 112 in accordance with the present invention. In particular, wireless transceiver 112 is shown as being usable in place of RF transceiver 125. The wireless transceiver 112 includes an RF transceiver section 111, the RF transceiver section 111 including one or more RF transmitters, such as RF transmitter 129, and one or more RF receivers, such as RF receiver 127, and the array antenna 100. The RF transceiver 112 transmits an outbound RF signal 170 including the outbound data 162 via the array antenna 100 to one or more remote transceivers, such as the wireless transceiver 110. In addition, the array antenna 100 receives inbound RF signals 152 including inbound data 160 from the wireless transceiver 110. The array antenna 100 may be configured to a plurality of different radiation patterns based on a control signal 106 from the configuration controller 104.

The array antenna 100 includes a plurality of individual antenna elements. Examples of such individual antenna elements include monopole or dipole antennas, three-dimensional aerial helical antennas, aperture antennas of rectangular, horn shape, etc.; dipole antennas having conical, cylindrical, elliptical, etc.; and a reflector antenna with a planar, corner or parabolic reflector, a meandering pattern or a microstrip line configuration. Furthermore, the RF transceiver section 111 comprises a control matrix that controls the phase and amplitude of the signals to and from each individual antenna element in order to adjust the transmit and/or receive radiation pattern of the array based on steering (steering) weights wi. The steering weights wi control the gain and phase of the transmit signal before it reaches the antenna array 100. Each set of steering weights may include frequencies that depend on gain and phase in order to shape the beamformed transmissions over the signal bandwidth. One example is the unique gain and phase for each OFDM frequency bin in the case of 802.11n/802.11ac transmission. The steering weights may be selected to characterize a particular radiation pattern, or may be generated by a set of mathematical equations that do not characterize a physical radiation pattern. Antenna array 100 may be tuned for operation in the V-band of 55-64GHz or other millimeter wave frequency band or other portion of the RF spectrum, such as the 900MHz band, the 2.4GHz band, or the 5GHz band.

The configuration controller 104 may be implemented with a shared processing device, an individual processing device, or multiple processing devices and may further include memory. Such a processing device may be a microprocessor, microcontroller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that processes (analog and/or digital) signals based on operational instructions. The memory may be a single memory device or a plurality of memory devices. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that stores digital information. Note that when the configuration controller 104 implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory storing the corresponding operational instructions is embedded with the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry.

In an embodiment of the present invention, the configuration controller 104 includes a table of control signals 106 corresponding to a plurality of steering weight values. In operation, a specific set of steering weights is generated for the array antenna 100 by configuring the controller 104 to generate a corresponding control signal 106 and the RF transceiver section to adjust the gain and phase of the signal to and from each antenna in the array in response thereto. In an embodiment of the invention, the control signal 106 comprises steering weights w corresponding to the desired radiation pattern_iSpecific values of (a). Alternatively, the control signal 106 may include other signals indicative of a desired radiation pattern. Configuration controller 104 may adjust the radiation pattern based on feedback signal 108 from RF transceiver section 111. In this system, the RF transceiver 112 is defined as a beamformer (transform), while the RF transceiver 110 is defined as a beamformee (transform) because it receives transmitted beamformed frames.

In an embodiment of the present invention, RF transceiver 112 implements transparent TX beamforming, essentially TX beamforming without any involvement by the beam receiver (in this case transceiver 110). In operation, RF transceiver 112 obtains Channel State Information (CSI) from reverse link channel estimates (i.e., ACK frames and/or receive frames) and performs self-reciprocity calibration on the measured reverse link channels generated by configuration controller 104. This allows the RF transceiver 112 to beamform for devices that are not TXBF capable, such as legacy 802.11a/c devices, or 802.11n/11ac devices that do not support TX beamforming. It improves the quality of the CSI information because it can be applied directly after the reception of the previous information frame. Without instant-around, the CSI becomes less correlated due to delays as it is measured and applied to beamformer transmissions. It also improves CSI quality by reducing latency (beneficial for SU-MIMO and MU-MIMO configurations) and enables transparent DL-MU-MIMO TX beamforming without implementation of STAs. This configuration also saves feedback overhead and does not involve over-the-air communication of steering weights when communicating with explicit TXBF devices.

In operation, the RF transceiver 112 exploits channel reciprocity in order to improve Channel State Information (CSI) quality at the transmitter. Specifically, RF transceiver 112 performs ambiguous feedback beamforming (explicit beamforming) by obtaining CSI via reverse link channel estimation. To the extent that RF transceiver 112 is station "a" and transceiver 110 is station "B," controller 104 is configured to operate based on feedback signal 108 to obtain channel state information on the "a" side via reverse link channel assessment H _ BA. Based on channel reciprocity, the forward link channel response can be determined by H AB = (H BA)^TAnd (4) obtaining. Differences exist between the forward and reverse link paths based on the transfer functions of the beamformer (beamformer) and the beamformee (beamformer) radio transceivers. The forward path includes station a transmit transfer function (G _ TA), channel (H), and station B receive transfer function (G _ RB). The reverse path includes the station B transmit transfer function (G _ TB), the reverse channel (H)^T) And station a receives the transfer function (G _ RA). The goal is to measure the baseband-to-baseband reverse link path, H _ BA = (G _ TB) (H)^T) (G _ RA), and then evaluates the forward link channel, H _ AB = (G _ TA) (H) (G _ RB). Solving the measured reverse path link using H _ AB = (G _ TA/G _ RA) (H _ BA)^T) (G _ RB/G _ TB) forward link estimates are calculated. The beamformer can compensate for its own transmit-receive mismatch (G _ TA/G _ RA) and, if known, for the mismatch on the beamformee side. In general, the forward linkIs less sensitive to beam-receiver mismatch (G _ TA/G _ RA) and can be ignored in practice, i.e. H _ AB = (G _ TA/G _ RA) (H _ BA)^T）。

The RF transceiver 111 generates a transmit precoding matrix to generate the desired steering weights w based on H _ AB_i. Beamformed (steered) packets from station a may be formed without reference or involvement of a beamformee (station B). However, the link budget between stations a and B may be increased in terms of range and rate.

As discussed above, the use of this transparent beamforming method enables MIMO TX beamforming for legacy devices (802.11 a/g) or TXBF-incapable devices and avoids the use of an over-the-air two-station channel calibration procedure. In practice, only self-calibration on the beamformer side panel is required for good performance. This further serves to reduce channel mismatch due to doppler and/or feedback delay, reducing feedback overhead. Furthermore, it benefits the MU-MIMO TXBF algorithm due to its increased sensitivity to CSI quality compared to SU-MIMO.

The operation of the embodiments of the present invention can be described with reference to the following examples. RF transceiver 112 generates a first transmission to non-beamforming station 110 based on the first plurality of steering weights for array antenna 100 and receives a second transmission from station 110. These first and second transmissions are via a first communication channel. Station 110 may be a non-beamforming cable station such as a legacy device or other device that is not capable of beamforming transmissions.

Other mechanisms may be employed to enhance compatibility with legacy devices. For example, the RF transceiver may transmit a mixed-mode packet that includes a legacy portion transmitted according to a legacy protocol and a non-legacy portion transmitted according to a non-legacy protocol. For example, in an 802.11n/ac system, a mixed-mode packet may be sent that includes a first portion that follows 802.11a and a second portion that follows 802.11 n. In embodiments of the present invention, the legacy portion of such a mixed mode packet may also be transmitted without beamforming, while the non-legacy portion of the packet may be transmitted with beamforming via steering weights calculated as described previously. It should be noted that some portions of the packet may be beamformed and other portions may not be beamformed in any order or arrangement.

Configuration controller 104 generates a first plurality of steering weights based on a reverse channel estimate of the first communication channel as discussed above. When a new transmission is received from the secondary station 110, the configuration controller 104 operates to update the reverse channel estimate for the first communication channel based on the current second transmission and to adjust the first steering weights based on the updated reverse channel estimate for the first communication channel. In embodiments of the invention, the steering weight adjustments are smoothed over time, such as via a low pass filter, exponentially weighted moving average, or other smoothing process. In this manner, adjustments are smoothed in the time domain to avoid rapid adjustments to the estimates that may or may not reflect actual changes in channel conditions. Additionally, or alternatively, the steering weights themselves may be smoothed in the frequency domain via a smoothing filter to provide better frequency response characteristics.

Although a single remote station 110 is shown, it should be noted that RF transceiver 112 may operate in a similar manner to simultaneously transmit beam transmissions to multiple stations via channel estimates specific to each station.

Fig. 5 is a schematic block diagram of various radiation patterns generated by the wireless transceiver 112 according to an embodiment of the present invention. In particular, in addition to or alternatively to transparent beamforming described in connection with fig. 4, RF transceiver 112 may be capable of beamforming beacon transmissions to locate and associate with remote transceivers such as transceiver 110 that are outside of the omni-directional transmitted beacon signal range.

In the 802.11 protocol, an Access Point (AP) periodically transmits beacon frames in order to broadcast all information about the network. It includes a critical portion of information including timestamps, beacon intervals, capability information, and Service Set Identifiers (SSIDs). This is a key frame that gives a Station (STA) the ability to learn about the network, start the process of connecting to the AP, and establish a data connection.

One of the key issues with the transmit beamforming (TxBF) protocol in the 802.11 standard is that it only benefits when an initial connection is established. Once the connection between the AP and the STA is established, the TxBF may improve the effective signal-to-noise ratio (SNR), thereby improving system performance. Unfortunately, since reception of beacons is the limiting factor, it does not increase the effective range of the AP. This means that STAs outside the initial range of the AP (without beamforming) cannot connect to the network even if they are reachable through TxBF.

The RF transceiver 112 is implemented at the access point by utilizing TxBF on beacon frames to increase its effective range, thereby enabling the STA to receive the beacon and begin a connection with the AP (typically through authentication and related steps thereafter). The AP broadcasts beacons with a set of known TxBF steering weights and then periodically transmits beacons with a set of different TxBF weights to cover the entire area of interest. It may be TxBF weights that are spatially optimized for space, and may be optimized in the frequency domain (antenna geometry without specific implicit steering weights). In addition, the AP may also include non-directional beacon frames so as not to affect the AP's general coverage. A particular AP may decide between the number of TxBF beacons and the transmission frequency in order to balance the ability of out-of-range STAs to enter the network and allow in-range STAs to connect. Due to the directional nature of the wireless signals, the beamformed beacon may not be received by all available STAs that are very close to the AP.

In the example shown in fig. 5, the transceiver 110 is outside the nominal range of the standard omni-directional beacon frame transmission 82. In the example, if the APs use the appropriate steering weights w_iThen the wireless signal is enhanced in the direction of STA-2 and then successfully receives the beacon and begins authentication and related frame exchange. In operation, the RF transceiver 112 generates a signal with a corresponding steering weight w_iA plurality of candidate radiation patterns 80. For example, the candidate radiation patterns may be sequentially scanned, randomly generated, and the like.

Once a candidate beacon is transmitted with a candidate radiation pattern, the AP must then track all new STAs that enter the network using the beacon. Tracking is very important because consecutive packets sent specifically to the STA should use the same TxBF weight to reach the STA. Once a full connection is established, the AP may further improve the TxBF weight to the STA by measuring the reverse link channel, as described in connection with fig. 4. The AP may associate the STA with the TxBF beacon in a number of ways, preferably by time-based elements. For any STA that responds immediately after the beacon, the AP may continue communication with the STA using the TxBF weight. There are alternative methods in which the AP may use a unique SSID for each TxBF steering beacon, thereby identifying the appropriate TxBF steering weights based on the SSID in the next packet from the STA.

In the embodiment of the invention, the AP has the weight value w through sending_iThe beacon of the group starts. If the AP receives a response from a STA, it records the weight w of the particular STA_iAnd initiates further packet switching using these weights. After the beacon interval is reached, the AP updates the TxBF weight of the beacon to the new candidate radiation pattern 80 and re-looks for STA responses.

Fig. 6 is a schematic block diagram of an embodiment of an RF transceiver section 111 according to the present invention. Specifically, the RF transceiver section includes, for example, a plurality of RF sections 137 corresponding to each antenna in the antenna array 100. For example, each RF section may include an RF front end 140, a down conversion module 142, an up conversion module 148, and a radio transmitter front end 150. For each RF section 137, the functions of the receiver processing module 144 and the transmitter processing module 146 may be implemented by the baseband section 139.

As discussed in connection with FIG. 4, the configuration controller 104 may include a plurality of different steering weights w_iA table of corresponding control signals 106. In operation, a particular set of steering weights is generated for the array antenna 100 by configuring the controller 104 to generate a corresponding control signal 106 and the RF transceiver section to adjust the gain and phase of the signal to and from each antenna in the array in response thereto. In embodiments of the present invention, feedback signal 108 may include reverse link channel estimate H BA, forward channel link estimate H AB, CSI, or other feedback used to generate control signal 106. Control signalNumber 106 may include steering weights w corresponding to desired radiation patterns generated based on feedback signal 108 or based on updated candidate radiation patterns or based on other inputs_iThe specific value. Alternatively, the control signal 106 may comprise any other signal indicative of a desired radiation pattern. Configuration controller 104 may adjust the radiation pattern based on feedback signal 108 from RF transceiver section 111.

The operation of the RF transceiver 111 may be described in connection with the following example. The controller 104 is configured to generate a control signal 106 to select a first candidate radiation pattern for the beamforming antenna array 100 based on the first plurality of steering weights. RF transceiver section 111 broadcasts a first beacon transmission with a first candidate radiation pattern to generate feedback signal 108 to indicate whether the remote station has responded to the first beacon transmission during several predetermined intervals. The configuration controller 104 is also operative to store a first plurality of steering weights used in association with the first beacon transmission when a remote station, such as the transceiver 110, has responded to the first beacon transmission. In a packet transmission addressed to a remote station, the controller 104 is configured to generate a control signal 106 to the RF transceiver 111 to use the first candidate radiation pattern when communicating with the remote station.

Whether or not the station transmits in response to the first beacon during the predetermined interval, the controller 104 is further configured to generate a control signal 106 to select a second candidate radiation pattern for the beamforming antenna 100 based on the second plurality of steering weights. RF transceiver section 111 is also operative to broadcast a second beacon transmission with a second candidate radiation pattern and generate feedback signal 108 to indicate whether any remote stations have responded to the second beacon transmission.

In this method, the controller 104 is configured to generate a control signal 106 to select a plurality of candidate radiation patterns 90 via which the RF transceiver section 111 periodically broadcasts beacon transmissions. The plurality of candidate radiation patterns may include an omnidirectional radiation pattern and a plurality of different narrow beam radiation patterns. In particular, the configuration controller 104 may generate the control signal 106 to alternate between the omnidirectional radiation pattern and the selected one of the plurality of different narrow beam radiation patterns.

As discussed above, when a remote station responds to a beacon transmission, the configuration controller 104 is further operable to determine a reverse channel estimate for the remote station based on communications with the remote station using the corresponding candidate radiation pattern, and to adjust the steering weights and radiation pattern based on the reverse channel estimate. It should be noted that while the above description focuses on communication with a single remote station, association with multiple remote stations may be accomplished in a similar manner, with each remote station having the same or different steering weights depending on the response of the stations to beacon transmissions.

It should be noted that while the candidate steering weights discussed above are shown as generating narrow beam radiation patterns, the control of amplitude, phase and frequency used to adjust the candidate steering weights may or may not generate such narrow band or directional radiation patterns.

Fig. 7 is a flow chart of an embodiment of a method according to the present invention. In particular, the method is provided for use in conjunction with one or more of the functions and features described in conjunction with fig. 1-6. In step 400, a control signal is generated to select a candidate radiation pattern for a beamforming antenna based on a plurality of steering weights. In step 402, a beacon transmission is broadcast with a candidate radiation pattern via an RF transceiver. In step 404, the feedback signal from the RF transceiver is evaluated to determine whether one or more remote stations have responded to the first beacon transmission. If the remote station has not responded to a beacon transmission during the response interval, the method returns to step 400 to select a new candidate radiation pattern. If the remote station has responded during the evaluation interval, the method proceeds to step 406 to store a plurality of steering weights used in association with the beacon transmission and proceeds to step 408 to communicate with the first remote station using the first candidate radiation pattern. At a predetermined time, the RF transceiver returns to 400 and resumes a new beacon transmission.

In an embodiment of the present invention, steps 400 and 402 are part of a process of periodically broadcasting a beacon transmission via a plurality of candidate radiation patterns. The plurality of candidate radiation patterns may include an omnidirectional radiation pattern and a plurality of different narrow beam radiation patterns. In particular, the plurality of candidate radiation patterns may alternate between the omnidirectional radiation pattern and a selected one of a plurality of different narrow beam radiation patterns. However, as discussed above, control of the amplitude, phase and frequency used to adjust the candidate steering weights may or may not generate such narrowband or directional radiation patterns.

In one example, when a station has not responded to a beacon transmission during a predetermined interval, a control signal is generated to select a new candidate radiation pattern for the beamforming antenna based on another plurality of steering weights. A new beacon transmission may be broadcast with a new candidate radiation pattern via the RF transceiver. The feedback signal from the RF transceiver may be evaluated to determine whether the remote station has responded to a new beacon transmission.

In another example, when the first station has responded to a beacon transmission during a predetermined interval, a control signal is generated to select a new candidate radiation pattern for the beamforming antenna based on another plurality of steering weights. A new beacon transmission may be broadcast with a new candidate radiation pattern via the RF transceiver. It should be noted that although the above description focuses on communication with a single remote station, association with multiple remote stations, each having the same or different steering weights, may be accomplished in a similar manner, depending on the station's response to beacon transmissions. The feedback signals from the RF transceiver may be evaluated to determine whether one or more other remote stations have responded to any particular beacon transmission and used to assign steering weights for communication with those stations.

Step 408 may include addressing the packet transmission to the remote according to the 802.11n/ac standard.

Fig. 8 is a flow chart of an embodiment of a method according to the present invention. In particular, the method is proposed for use in combination with one or more of the functions and features described in connection with fig. 1 to 7. In step 410, the RF transceiver performs a reverse channel assessment of the remote station based on the received packet transmissions and then determines a set of steering weights to optimize the connection back to the remote station. In step 412, the steering weights determined by the reverse link are used to communicate with the remote station, and the steering weights are calculated to optimize the communication link back to the remote station.

The method can comprise the following steps: generating, via a plurality of RF transceiver sections, a first transmission via a first communication channel to a first (non-beamforming capable) remote station based on a first plurality of steering weights for a plurality of antennas; and receiving, via the plurality of RF transceiver sections, a second transmission from the first remote station via the first communication channel. A first plurality of steering weights is generated based on a reverse channel estimate of a first communication channel.

For example, a reverse channel estimate for the first communication channel is generated based on the second transmission and may include a reverse channel link estimate matrix. The reverse channel estimate of the first communication channel may be generated based on a one-sided channel calibration that uses characteristics of the RF transceiver transmit path and receive path as an estimate of characteristics of the first remote station. The first plurality of steering weights may be generated based on a forward link channel estimate for the first communication channel based on a reverse channel link estimate for the first communication channel. A forward link channel estimate for the first communication channel may be generated based on a matrix transpose of a reverse channel link estimate matrix.

Although transmission to a single remote station is described above, it should be noted that the method may operate in a similar manner to transmit beamformed transmissions to multiple stations simultaneously via channel estimates specific to each station. For example, a third transmission to the second remote station via the second communication channel may be generated based on a second plurality of steering weights for the plurality of antennas, and a fourth transmission may be received from the second remote station via the second communication channel. The second plurality of steering weights may be generated based on a reverse channel estimate of the second communication channel.

As used herein, the terms "substantially" and "about" provide an industry-accepted tolerance for their respective items and/or relatedness between items. Such industry-accepted tolerances range from less than one percent to fifty percent and correspond to, but are not limited to, component values, integrated circuit process variables, temperature variations, rise and fall times, and/or thermal noise. Such correlations between items range from a few percent difference to large differences. Also as used herein, the terms "operatively coupled to," "coupled to," and/or "coupled to" include direct couplings between items and/or indirect couplings between items via intervening items (e.g., items include, but are not limited to, components, elements, circuits, and/or modules), where for indirect couplings, intervening items do not modify signal information, but may adjust their current levels, voltage levels, and/or power levels. Also as used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as "coupled to". Further as used herein, the term "operable" or "operably coupled to" indicates that the item includes one or more of a power connection, input, output, etc. to perform one or more of its respective functions when activated, and may also include an inferred coupling to one or more other items. As also used herein, the term "associated with …" includes direct and/or indirect coupling of separate items and/or embedding of one item within another item. As used herein, the term "favorable comparison" indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater amplitude than signal 2, a favorable comparison may be obtained when the amplitude of signal 1 is greater than the amplitude of signal 2 or when the amplitude of signal 2 is less than the amplitude of signal 1.

Also as used herein, the terms "processing module," "processing circuit," and/or "processing unit" may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, microcontroller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that directs signals (analog and/or digital) based on hard-coded and/or operational instructions for the circuitry. The processing module, processing circuit, and/or processing unit may be or further include memory and/or may be an integrated memory element of a single memory device, multiple memory devices, and/or embedded circuitry of other processing modules, processing circuits, and/or processing units. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, any device that caches and/or stores digital information. Note that if the processing module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributed (e.g., employing cloud computing via indirect coupling via a local area network and/or a wide area network). It is further noted that if the processing module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or storage elements storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. It is further noted that the memory elements may store, and the processing modules, processing circuits and/or processing units may be capable of executing, hard-coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the figures. Such a memory device or memory element may be included in an article of manufacture.

The invention has been described above with method steps illustrating the performance of specified functions and relationships thereof. Boundaries and the order of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences may be defined so long as the specified functions and relationships are appropriately performed. Accordingly, any such alternate boundaries or sequences are within the scope and spirit of the claimed invention. Further, for convenience of description, boundaries of these functional building blocks have been arbitrarily defined. Alternate boundaries may be defined so long as certain important functions are properly performed. Similarly, flow diagram blocks may be arbitrarily defined herein to illustrate certain significant functions. To the extent used, the boundaries and sequence of flowchart blocks may be otherwise defined and still perform the specified important functions. Accordingly, alternative definitions and sequences of such functional building blocks and flow diagram blocks are within the scope and spirit of the claimed invention. Those of ordinary skill in the art will also appreciate that the functional building blocks, as well as other exemplary blocks, modules, and components herein, may be implemented as shown or by discrete components, application specific integrated circuits, processors executing appropriate software, etc., or any combination thereof.

The present invention may also be described, at least in part, in terms of one or more embodiments. Embodiments of the present invention are used herein to describe the present invention, aspects thereof, features thereof, concepts thereof and/or examples thereof. The physical embodiments of the device, article of manufacture, machine, and/or process implementing the invention may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more embodiments discussed herein. Further, from figure to figure, these embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers, and thus, these functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different functions, steps, modules, etc.

Although the transistors in the above figures are shown as Field Effect Transistors (FETs), as one of ordinary skill in the art will recognize, the transistors may be implemented using any type of transistor structure including, but not limited to, bipolar transistors, Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), N-well transistors, P-well transistors, enhancement mode transistors, depletion mode transistors, and zero Voltage Threshold (VT) transistors.

Unless specifically stated to the contrary, in any of the figures shown herein, signals to, from, and/or between elements may be analog or digital, continuous-time or discrete-time, and single-ended or differential. For example, if the signal path is shown as a single ended path, it also represents a differential signal path. Similarly, if the signal path is shown as a differential path, it also represents a single-ended signal path. Although one or more specific architectures are described herein, other architectures may similarly be implemented using one or more data buses that are not explicitly shown, direct connections between elements, and/or indirect couplings between other elements, as will be appreciated by those of ordinary skill in the art.

The term "module" is used in the description of the various embodiments of the present invention. The modules include processing modules, functional blocks, hardware, and/or software stored on memory for performing one or more functions as described herein. Note that if the modules are implemented via hardware, the hardware may work alone and/or in combination with software and/or firmware. As used herein, a module may include one or more sub-modules, each of which may be one or more modules.

Although specific combinations of features and functions are described herein, other combinations of features and functions are also possible. The invention is not limited by the specific examples disclosed herein, and these other combinations are expressly incorporated.

Claims (10)

1. A Radio Frequency (RF) transceiver having a plurality of antennas, the RF transceiver comprising:

a plurality of radio frequency transceiver sections to generate a first transmission to a first remote station based on a first plurality of steering weights for the plurality of antennas and to receive a second transmission from the first remote station, wherein the first transmission and the second transmission are via a first communication channel;

and

a configuration controller, coupled to the RF transceiver portion, for generating the first plurality of pilot weights based on a reverse channel estimation of the first communication channel;

wherein the first remote station is unable to beamform.

2. The radio frequency transceiver of claim 1, wherein the configuration controller is to generate the reverse channel assessment of the first communication channel based on the second transmission.

3. The radio frequency transceiver of claim 2, wherein the reverse channel estimate of the first communication channel comprises a reverse channel link estimate matrix.

4. The radio frequency transceiver of claim 3, wherein the reverse channel assessment of the first communication channel is based on a one-sided channel calibration that uses characteristics of a transmit path and a receive path of the radio frequency transceiver as an assessment of characteristics of the first remote station.

5. The radio frequency transceiver of claim 3, wherein the configuration controller is to generate the first plurality of steering weights based on a forward link channel estimate of the first communication channel, the forward link channel estimate of the first communication channel being based on a reverse channel link estimate of the first communication channel.

6. The radio frequency transceiver of claim 1, wherein the configuration controller is further to update the reverse channel estimate for the first communication channel based on a current second transmission and to adjust the first steering weights based on the updated reverse channel estimate for the first communication channel.

7. The radio frequency transceiver of claim 1, wherein the plurality of radio frequency transceiver sections are further to generate a third transmission to a second remote station based on a second plurality of steering weights for the plurality of antennas, and to receive a fourth transmission from the second remote station, wherein the third transmission and the fourth transmission are via a second communication channel; and

wherein the configuration controller is further configured to generate the second plurality of steering weights based on a reverse channel assessment of the second communication channel; and

wherein the second remote station is not capable of beamforming.

8. The radio frequency transceiver of claim 1, wherein the first transmission includes at least one packet, the packet including a first portion and a second portion, wherein the steering weights are applied to beamform the second portion, wherein the first portion is not beamformed.

9. A method for use in a Radio Frequency (RF) transceiver having a plurality of antennas, the method comprising:

generating, via a plurality of radio-frequency transceiver sections, a first transmission to a first remote station via a first communication channel based on a first plurality of steering weights for the plurality of antennas;

receiving, via the plurality of radio-frequency transceiver sections, a second transmission from the first remote station via the first communication channel; and

generating the first plurality of steering weights based on a reverse channel assessment of the first communication channel;

wherein the first remote station is not capable of beamforming.

10. The method of claim 9, further comprising:

updating the reverse channel assessment of the first communication channel based on a current second transmission; and

adjusting the first steering weight value based on the updated reverse channel assessment of the first communication channel.