HK1180512A - Beamforming training within a wireless communication system utilizing a directional antenna - Google Patents

Abstract

The invention relates to a beamforming training within a wireless communication system utilizing a directional antenna. A technique to identify that a station is capable of transmitting a PHY-BRP packet for use in training a directional antenna. The PHY-BRP packet is transmitted, when requested to do so, by appending the PHY-BRP packet to a BRP-Response in order to associate source and destination information to the PHY-BRP packet.

Description

Calibration of beamforming in wireless communication systems using directional antennas

Cross Reference to Related Applications

Priority of U.S. provisional patent application No. 61/545,941 filed on 11/10/2011 and U.S. patent application No. 13/630,613 filed on 28/9/2012, which are incorporated herein by reference in their entirety, are claimed.

Technical Field

Embodiments of the present invention relate to wireless communications, and more particularly, to linking of two devices in the millimeter wave band.

Background

It is well known that many wireless communication systems today provide communication links between devices either directly or through a network. Such communication systems include national and/or international cellular telephone systems, the internet, point-to-point in-home systems, and other systems. Communication systems typically operate in accordance with one or more communication standards or protocols. For example, a wireless communication system may operate using protocols such as IEEE802.11, Bluetooth (trademark), 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 others.

Each wireless communication device participating in wireless communications typically includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station, modem, etc. for an in-home and/or in-building wireless communication network). Generally, a transceiver includes a baseband processing stage and a Radio Frequency (RF) stage. The baseband processing provides conversion of data to baseband signals for transmission and baseband signals to data for reception in accordance with a particular wireless communication protocol. The baseband processing stage is coupled to RF stages (transmitter and receiver sections) that provide conversion between baseband and RF signals. The RF stage may be a direct conversion transceiver that converts directly between baseband and RF or may include one or more intermediate frequency stages.

Further, wireless devices typically operate within a certain radio frequency range or band established by regulatory agencies and used by one or more communication standards or protocols. The 2.4GHz band, which includes the established WiFi and bluetooth (trademark) protocols, has limited capacity and therefore limited data throughput. Recently, higher frequencies in the millimeter wave range are being used by newer 60GHz standards in pursuit of higher throughput demands. High data rate transmissions, such as real-time uncompressed/compressed High Definition (HD) video and audio streams, may be transmitted wirelessly between two devices using 60GHz band technology. Due to the inherent real-time requirements for target applications, the emerging 60GHz standard explicitly defines quality of service (QoS) requirements for traffic flows to meet high throughput between devices.

One of the protocols/standards developed to use the 60GHz band is the IEEE802.11ad standard. Devices operating in the 60GHz band, also referred to as the D-band (or DBand) by the IEEE802.11ad standard, use directional communication, rather than omni-directional propagation of signals (such as at the 2.4 and 5GHz bands) to overcome severe path loss at these higher frequencies. The 60GHz extended D-band TSPEC describes the timing and traffic requirements for Traffic Streams (TS) that exist within the network, such as the Personal Basic Service Set (PBSS) and Infrastructure Basic Service Set (IBSS) operating in the 60GHz D-band. The 60GHz D-band specification DBand device, specified by the wireless gigabit alliance (WGA or WiGig), uses directional antennas to direct the transmitted spectral energy. The 60GHz standard in these developments sets forth certain requirements for protocol/standard compliant devices. One implemented technique for directional signal propagation is beamforming, where D-band (and other millimeter wave) devices radiate propagating energy from a directional antenna or antenna array.

To establish a directional communication link, a typical approach is for an initiating D-band device to initiate a series of transmissions through a sweep of multiple transmit sectors (beam propagation sectors) to cover an omni (or quasi-omni) area, after which another D-band device replies with a series of transmissions through a sweep of its transmit sectors, and informs the initiating device which initiator transmit sector is the best sector for communicating with the responder. After the responder completes its sector scan, the initiator sends back a feedback signal to indicate which of the responder sectors is best suited to communicate with the initiator.

Beamforming allows a pair of Stations (STAs) or Access Points (APs) and STAs to calibrate (train) and position their directional antennas for optimal wireless connectivity to communicate with each other. After both devices follow a successful calibration sequence as mentioned above, beamforming is established. One feature of beamforming is beam refinement. Beam refinement is a process in which a STA may refine its antenna configuration (or antenna weight and vector) for transmission and/or reception. In the beam improvement protocol process, a beam improvement protocol (BRP) packet is used to calibrate the receiver.

One particular type of BRP packet is known as a physical layer (PHY) BRP packet, or PHY-BRP packet. The PHY-BRP packet is an optional BRP packet that may or may not be used in some devices. Some devices may be optional as they may not have the capability of PHY-BRP packets. The PHY-BRP packet is introduced to simplify weight and vector alignment of the receiver antennas. The PHY-BRP packet duration is short to shorten the overall time for calibration. As currently indicated by the specifications in at least one standard, PHY-BRP packets have at least two drawbacks that affect the performance of 60GHz and other millimeter wave devices. First, not every device uses PHY-BRP packets, so there needs to be a way to discern whether a particular device has PHY-BRP packet capabilities; second, PHY-BRP packets do not have a PHY or MAC (media access control) header, and thus there may be ambiguity as to the source and intended destination of the transmitted PHY-BRP packet.

Therefore, there is a need to find a solution to these two drawbacks of PHY-BRP packets.

Disclosure of Invention

(1) A method, comprising: transmitting an identification indicating that a device is capable of transmitting a calibration packet to calibrate a directional antenna for positioning toward the device, wherein the calibration packet does not include an address associated with the device transmitting the calibration packet; receiving a request from a requester to send the calibration packet to the requester to calibrate the requester's directional antenna; responding to the request by sending a response from the device, wherein the response includes an identification indicating that the calibration packet locating the directional antenna is appended to the response, the response including an address associated with the device; and appending the calibration packet to the reply and transmitting the appended calibration packet with the reply.

(2) The method of (1), wherein the calibration packet is an optional packet to locate the directional antenna.

(3) The method of (1), wherein the calibration packet is an optional beam improvement protocol (BRP) packet.

(4) The method of (1), wherein a value of a selected bit in the reply is used as an identifier indicating that a calibration packet to locate the directional antenna is appended to the reply.

(5) The method of (4), wherein a delay period is introduced between the reply and the additional calibration packet.

(6) The method of (4), wherein the calibration packet is to be used to calibrate and position the directional antenna for millimeter wave transmission.

(7) The method of (4), wherein the calibration packet is to be used to calibrate and position the directional antenna for 60GHz band transmission.

(8) A method, comprising: transmitting an identification that a device is capable of transmitting a physical beam improvement protocol (PHY-BRP) packet to calibrate a directional antenna for positioning toward the device, wherein the physical beam improvement protocol packet does not include an address associated with the device transmitting the physical beam improvement protocol packet, and wherein a structure of the physical beam improvement protocol packet is specified by a communication protocol; receiving a beam improvement protocol request from a requester to send the physical beam improvement protocol packet to the requester to calibrate the directional antenna of the requester; acknowledging the request by transmitting a beam improvement protocol acknowledgement from the apparatus, wherein the beam improvement protocol acknowledgement includes an identification indicating that the physical beam improvement protocol packet locating the directional antenna is appended to the beam improvement protocol acknowledgement, the beam improvement protocol acknowledgement including an address related to the apparatus; and, appending the physical beam improvement protocol packet to the beam improvement protocol reply and transmitting the appended physical beam improvement protocol packet with the beam improvement protocol reply.

(9) The method of (8), wherein the physical beam improvement protocol packet is an optional beam improvement protocol packet for positioning the directional antenna.

(10) The method of (9), wherein a value of a selected bit in the beam improvement protocol reply is used as an indication that a physical beam improvement protocol packet that locates the directional antenna is appended to the beam improvement protocol reply.

(11) The method of (10), wherein an identification indicating that the apparatus can transmit the physical beam improvement protocol packet to calibrate the directional antenna is included in a capability information field transmitted by the apparatus to identify a capability of the apparatus.

(12) The method of (11), wherein a value of a selected bit in the capability information field is used as an identification indicating that the apparatus is capable of transmitting the physical beam improvement protocol packet to calibrate the directional antenna.

(13) The method of (9), wherein a delay period is introduced between the beam improvement protocol reply and the additional physical beam improvement protocol packet.

(14) The method of (9), wherein the physical beam improvement protocol package is to be used to calibrate and position the directional antenna for millimeter wave transmission.

(15) The method of (9), wherein the physical beam improvement protocol package is to be used to calibrate and position the directional antenna for 60GHz band transmission.

(16) The method of (9), wherein the communication protocol is based on the IEEE802.11ad specification.

(17) An apparatus, comprising: a transmitter transmitting a Radio Frequency (RF) signal; a receiver that receives a radio frequency signal; and a baseband processor module including a processor and coupled to the transmitter and the receiver to provide processing of packets specified by a communication protocol to: transmitting an identification indicating that a device is capable of transmitting a calibration packet to calibrate a directional antenna for positioning toward the device, wherein the calibration packet does not include an address associated with the device transmitting the calibration packet; receiving a request from a requester to send the calibration packet to the requester to calibrate the requester's directional antenna; responding to the request by transmitting a response from the device, wherein the response includes an identification indicating that the calibration packet locating the directional antenna is appended to the response, the response including an address associated with the device; and appending the calibration packet to the reply and transmitting the appended calibration packet with the reply.

(18) The device of (17), wherein the calibration packet is an optional beam improvement protocol (BRP) packet.

(19) The device of (18), wherein the calibration packet is a physical beam improvement protocol packet.

(20) The device of (19), wherein the communication protocol is based on the IEEE802.11ad specification.

Drawings

Fig. 1 is a network diagram in which a plurality of Stations (STAs) are present in a network, wherein a particular station communicates with other stations and/or network control or access points in accordance with one embodiment for implementing the present invention.

Fig. 2 is a diagram illustrating directional signal propagation between the various devices shown in fig. 1 using directional antennas in accordance with one embodiment for implementing the present invention.

Fig. 3 is a hardware schematic block diagram illustrating an embodiment of a wireless communication device according to one embodiment for implementing the present invention.

Fig. 4 shows a BRP packet structure for the D-band as specified in the WGA specification imposed on a protocol or standard used in accordance with one embodiment for implementing the present invention.

Fig. 5 shows an alternative PHY-BRP packet structure for the D-band as specified in the WGA specification imposed on a protocol or standard used in accordance with one embodiment for implementing the invention.

Fig. 6 illustrates an existing D-band STA capability information field frame structure applicable according to an embodiment for implementing the present invention.

Fig. 7 illustrates a modified D-band STA capability information field frame structure in which PHY-BRP capability bits are used to indicate that a particular STA has PHY-BRP capability, according to one embodiment for implementing the present invention.

Fig. 8 illustrates a modified D-band BRP response frame structure in which PHY-BRP compliant bits are used to indicate PHY-BRP compliant BRP responses, according to one embodiment for implementing the invention.

Fig. 9 illustrates the addition of a PHY-BRP packet to a BRP response in accordance with one embodiment for implementing the present invention.

Detailed Description

Embodiments of the present invention may be implemented in a variety of wireless communication devices operating in a wireless environment or network. The examples described herein are suitable for devices operating approximately within the 60GHz Band (also known as D-Band). Note that 60GHz, the frequency wavelength is in the millimeter order, and therefore, is determined as a millimeter wave band. However, the present invention need not be limited to the 60GHz band. Other millimeter wave bands of directional signal propagation may also be used to implement the present invention. Further, the examples described herein refer to specific standards, protocols, specifications, etc., such as applications of the present invention based on the WGA specification and/or the IEEE802.11ad specification. Accordingly, specific frame formats and structures are described with reference to these specifications. However, the invention is not limited to the specific designations set forth herein. The present invention is readily applicable to other applications in which directional beamformed signals are used and calibration is required to determine antenna direction to establish a communication link between two wireless devices.

Further, embodiments are described for establishing a communication link between two wireless Stations (STAs). However, the wireless link may be between a control point (or access point) and a station, or between other wireless devices. The term STA is used herein to describe two devices that communicate wirelessly and use a calibration domain therein to provide calibration of a directional antenna or antenna array for the two STAs to establish a communication link. Thus, a STA as used herein pertains to any wireless device, whether it plays the role of a station device, the role of an access point, the role of a control point, or any other wireless communication role.

As mentioned above, devices operating in the 60GHz band (e.g., D-band or DBand) according to the WGA (or WiGig) specification or according to the IEEE802.11ad specification use directional communication to overcome the severe path loss experienced at millimeter wave frequencies. Operation of the 60GHz D-band provides for D-band devices to use directional antennas to direct the transmitted spectral energy as defined by WGA (or WiGig). One of the protocols/standards being developed that use the 60GHz band is the ieee802.11ad standard. These developed standards set out certain requirements for devices that comply with the protocol/standard. One implemented technique for directional signal propagation is beamforming, where D-band (and other millimeter wave) devices direct or localize the propagating energy from a directional antenna or antenna array. Thus, beamforming allows a pair of STAs to calibrate their Transmit (TX) and Receive (RX) antennas to obtain an optimal wireless link to communicate with each other. After both STAs follow a successful calibration sequence, beamforming is established.

Fig. 1 illustrates a wireless network 100 that may be any type of wireless network. In one embodiment, the network 100 may be a Basic Service Set (BSS). In one embodiment, network 100 may be and/or include a Personal Basic Service Set (PBSS) forming a personal network. In another embodiment, the network 100 may be a set of infrastructure services that form a larger infrastructure network. In still other embodiments, the network may operate in other wireless environments.

In the illustrated embodiment, the example network 100 of fig. 1 is comprised of a control point 104 and a plurality of Stations (STAs) 101, 102, 103 (also noted as STA _ A, STA _ B and STA _ C, respectively), where one or more of the STAs may be under the control of the control point 104. It should be noted that only three STAs are shown, but the network 100 may consist of fewer STAs or more STAs than shown. The control point may be a Base Station (BS), an Access Point (AP), a personal BSs control point (PCP), or some other device. Hereinafter in the description, the control point is referred to as a PCP 104. STAs 101-103 may be fixed or mobile devices. Further, in other embodiments, PCP104 may also be a station device, in which case multiple STAs communicate in peer-to-peer communication.

In the example shown, STAs 101 and 103 communicate with PCP104, but STA 102 communicates directly with STA 101. Although the STAs 101 through 103 may represent a variety of wireless devices, in a particular example, the STA 101 is a personal computing device, the STA 103 is a handheld mobile device (such as a mobile handset or handheld multimedia player), and the STA 102 is a wireless headset operating with the STA 101. As an example, in one embodiment, the wireless headset may be a bluetooth (trademark) device coupled to the STA 101. In another example embodiment, the STA 102 may be a wireless display device operating with the STA 101. Again, the STA 102 may be some other device. One intent of fig. 1 is to show that the device can communicate wirelessly with other devices, whether the other devices are control point or station devices. The following description describes wireless communication between two STAs for simplicity of explanation. It should be noted, however, that one or both devices may have other roles, such as control points, as mentioned above.

To communicate between two STAs, the STAs employ a particular communication protocol or standard to provide a wireless link. A particular protocol may be applied to devices in the network or may be applied between only a pair of devices. In one embodiment, the network operates within the D-band of 60GHz as in the WGA specification. In other embodiments, the network may operate in other frequency bands or ranges. When operating in the D-band of 60GHz or other higher frequency band, the device uses a directional antenna to direct the transmit beam.

In a typical 60GHz communication process, beamforming techniques are used to radiate energy with a certain beamwidth in a certain direction to communicate between two devices. The directional propagation concentrates the transmit energy towards the target device to compensate for the significant energy loss in the channel between the two communication devices. Thus, as shown in fig. 2, for a directional communication link between PCP104 and STA 101, PCP104 propagates a directional beam 111 towards STA 101 and STA 101 propagates a directional beam 114 towards PCP 104. Likewise, when PCP104 and STA 103 need to communicate with each other, PCP104 propagates a directional beam 112 to STA 103 and STA 103 propagates a directional beam 113 to PCP104 for a directional communication link between the two devices. Directional transmission extends the range of millimeter wave communications relative to the same transmit energy used in omni-directional propagation.

Likewise, when the STA 101 and the STA 102 communicate, the directional beams 115, 116 are each directed toward each other. The example of fig. 2 shows a plurality of directional energy lobes radiating from the device, with one lobe being larger than the other to indicate directional energy at a particular azimuth. Note that for a general beamforming process, a particular device operates by having multiple propagation sectors. When the optimal sector is oriented or determined, the device positions the antenna (or antenna array) to operate in the optimal sector. Generally, a calibration sequence is used to determine the optimal direction for positioning the antenna. Thus, in fig. 2, the larger lobe represents the orientation of the directional antenna for the two wireless devices to optimally communicate with each other.

Fig. 3 is a schematic block diagram illustrating a portion of a wireless communication device 200, the wireless communication device 200 including a Transmitter (TX) 201, a Receiver (RX) 202, a Local Oscillator (LO) 207, and a baseband module 205. The baseband module 205 includes a processor to provide baseband processing operations. In some embodiments, the baseband module 205 is or includes a Digital Signal Processor (DSP). The baseband module 205 is generally coupled to a host unit, application processor, or other unit that provides operational processing for the device and/or interface with a user.

In fig. 3, a host unit 210 is shown. For example, in a tablet or laptop computer, the host 210 may represent the computing portion of the computer, while the device 200 is used to provide WiFi and/or bluetooth components for wireless communication between the computer and an access point and/or between the computer and a bluetooth device. Similarly, for handheld audio or video devices, the host 210 may represent an application portion of the handheld device, while the device 200 is used to provide WiFi and/or bluetooth components for wireless communications between the handheld device and an access point and/or between the handheld device and a bluetooth device. Alternatively, for a mobile phone such as a cellular handset, the device 200 may represent the Radio Frequency (RF) and baseband portions of the handset and the host 210 may provide the user application/interface portion of the handset. Further, the device 200, as well as the host 210, may be incorporated into one or more of the wireless communication devices of fig. 1.

Memory 206 is shown coupled to baseband module 205, where memory 206 is used to store data and program instructions operating on baseband module 205. Various types of memory devices may be used as the memory 206. It should be noted that the memory 206 may be placed anywhere in the apparatus 200, and in one example, may also be part of the baseband module 205.

The transmitter 201 and receiver 202 are coupled to an antenna assembly 204 via a transmit/receive (T/R) switching module 203. The T/R switching module 203 switches the antenna between the transmitter and the receiver according to the operation mode. In other embodiments, separate antennas may be used for the transmitter 201 and receiver 202, respectively. Further, in other embodiments, multiple antennas or antenna arrays may be used with the apparatus 200 to provide antenna diversity or multiple input and/or multiple output capabilities such as MIMO. Antenna 204 may be a directional antenna or a directional antenna array to position antenna 204 in a particular direction for transmitting and/or receiving radio frequency signals, as appropriate for the above beamforming.

At frequencies in the lower gigahertz range, omni-directional antennas provide adequate coverage for communications between wireless devices. Thus, at frequencies of 2.4 to 5GHz, one or more omni-directional antennas may be generally used for both transmission and reception. At higher frequencies, however, directional antennas with beamforming capability are used to direct the beam to concentrate the transmitted energy due to the limited range of the signal. In these examples, directional antennas and antenna arrays allow for beams to be directed in specific directions. The 60GHz D-band provides for D-band devices to use directional antennas to direct the transmitted spectral energy, as defined by the wireless gigabit alliance (WGA or WiGig). The device 200 in this example is capable of transmitting and receiving in the millimeter wave range including the D-band of 60 GHz. Thus, the antenna assembly 204 is a directional antenna or antenna array.

Outbound data for transmission from the host unit 210 is coupled to the baseband module 205 and converted to baseband signals and then coupled to the transmitter 201. The transmitter 201 converts the baseband signals to outbound Radio Frequency (RF) signals for transmission from the device 200 via an antenna assembly 204. The transmitter 201 may convert the outbound baseband signals to outbound RF signals using one of a variety of upconversion or modulation techniques. In general, the conversion process depends on the particular communication standard or protocol being used.

In a similar manner, inbound RF signals are received by the antenna assembly 204 and coupled to the receiver 202. The receiver 202 then converts the inbound RF signals to inbound baseband signals, which are then coupled to the baseband module 205. The receiver 202 may convert the inbound RF signals to inbound baseband signals using one of a variety of downconversion or demodulation techniques. The inbound baseband signals are processed by the baseband module 205 and inbound data is output from the baseband module 205 to the host unit 210.

The baseband module 205 generally operates using one or more communication protocols and provides the necessary packetization (or operates in conjunction with other components that provide packetization) and other data processing operations on the received signals and signals to be transmitted. Thus, the baseband module 205 also provides data (e.g., packet) processing as described with reference to the invention described herein. In other embodiments, other components may provide for the described data manipulation and formatting of packets based on a particular communication protocol.

LO207 provides a local oscillator signal that is used by transmitter 201 for frequency upconversion and by receiver 202 for frequency downconversion. In some embodiments, separate LOs may be used for the transmitter 201 and the receiver 202. Although a variety of LO circuitry may be used, in some embodiments, a PLL may be used to lock the LO to output a frequency-stable LO signal based on the selected channel frequency.

It should be noted that in one embodiment, baseband module 205, LO207, transmitter 201, and receiver 202 are integrated on the same Integrated Circuit (IC) chip. The transmitter 201 and receiver 202 are generally referred to as RF front ends. In other embodiments, one or more of these components may be on separate IC chips. Similarly, the other components shown in fig. 3 may be incorporated on the same IC chip with baseband module 205, LO207, transmitter 201, and receiver 202. In some embodiments, antenna 204 may also be incorporated onto the same IC chip. Further, with the advent of System On Chip (SOC) integration, a host device such as host unit 210, an application processor, and/or a user interface may be integrated on the same IC chip with baseband module 205, transmitter 201, and receiver 202.

Further, although one transmitter 201 and one receiver 202 are shown, it should be noted that other embodiments may use multiple transmitter units and receiver units, as well as multiple LOs. For example, diversity communications and/or multiple-input and/or multiple-output communications, such as multiple-input multiple-output (MIMO) communications, may use multiple transmitters 201 and/or receivers 202 as part of the RF front end. Further, it should be noted that fig. 3 shows basic components for transmitting and receiving and that a practical arrangement may incorporate other components than those shown.

As mentioned above, beamforming with directional antennas and/or arrays is a technique that provides for the directional transmission and/or reception of RF signals in the millimeter wave frequency band. One feature of beamforming is beam refinement. Beam refinement is a process by which a STA may improve its antenna configuration (or antenna weight and vector) for transmission and/or reception. In the Beam improvement Protocol process, a Beam improvement Protocol (BRP) packet is used to calibrate the receiver.

BRP is a process in which a STA calibrates its receive and transmit antennas (or arrays) to improve its antenna configuration with an iterative process. BRP may be used regardless of the antenna configuration supported by the STA. The BRP packet is sent in response to a BRP request, where the request is sent by a device desiring BRP communication to calibrate the directional antenna. When receiving the BRP request, the receiving device sends back a BRP response, which includes a BRP packet. Fig. 4 shows the structure of a general BRP packet 300, including a short calibration field (STF), a channel estimation field (CE), a header, data, an AGC subfield, and a TRN-R/T (calibration receiver/transmitter) subfield. The BRP packet 300 includes a header 301 (e.g., a PHY or MAC header) that provides identification of the source and intended destination of the BRP packet.

One particular type of BRP packet is referred to as a physical layer (PHY) BRP packet or PHY-BRP packet (the singular is used herein, but it should be noted that for the use of all "packets," the plural "packets" may also be used). The PHY-BRP packet is an optional BRP packet that may or may not be used in some devices. Some devices may be optional as they may not have PHY-BRP packet capability. The PHY-BRP packet is introduced to simplify receiver antenna weight and vector calibration for directivity over the structure of the BRP packet 300. Fig. 5 shows a general PHY-BRP packet 310 structure including an STF field 311 and a plurality of CE fields 312. STF 311 is the control PHY short calibration sequence and CE 312 is the channel estimation sequence. CE repeats 8 (L-RX +1) times, where L-RX is the value of the L-RX field. The L-RX field indicates the number of compressions of a receive calibration (TRN-R) subfield requested by the transmitting STA as part of a beam improvement procedure. Note that the STA may respond to the BRP request with either the BRP packet 300 or the PHY-BRP packet 310. Of course, if the STA does not have the capability of the optional PHY-BRP310, the STA will respond to the BRP request with the BRP 300. Note that the D-band specification for IEEE802.11ad may employ both BRP packet 300 and PHY-BRP310 structures.

As mentioned above, there are potentially at least two drawbacks to the current format of the PHY-BRP packet structure 310. First, not every STA uses an optional PHY-BRP packet, so a method of discrimination is needed when a STA has PHY-BRP packet capability. Second, PHY-BRP packets do not have PHY or MAC (media access control) headers, such as header 301 in BRP packet 300 in fig. 4, so there may be ambiguity as to the source and intended destination of the transmitted PHY-BRP packet. For example, if the responder to a BRP request signal sends out a PHY-BRP packet as part of the BRP response signal, there is a possibility that the requester receives other PHY-BRP packets from different STAs between them. If this occurs, the requester may calibrate the antenna to the wrong STA, not the intended STA, simply because there is no way to identify the source and/or intended destination of the PHY-BRP packet. The embodiments of the present invention described below address these concerns or disadvantages.

Fig. 6 shows a packet structure 320 for the existing D-band capability information field as specified by the specifications of the IEEE802.11ad standard. The D-band STA capability information field represents the capability of the transmitting STA regardless of the role of the STA. The diagram of FIG. 6 identifies the name of each field and the bit arrangement of each field is shown on each corresponding box. The numbers below the boxes indicate the number of bits in each corresponding field. A total of 64 bits are used for the D-band STA capability information field 320. The number of bits (e.g., B58-B63) is currently reserved and therefore not used. Note that packet 320 does not indicate that the device has (or does not have) optional PHY-BRP capabilities. Thus, the device transmit D-band capability information field 320 does not identify whether a PHY-BRP packet can be transmitted and the recipient of the D-band capability information receive field will not know whether the sender is PHY-BRP capable.

Thus, in one embodiment of the invention, as shown in fig. 7, for the packet structure 340, one of the reserved bits is used as the PHY-BRP capability bit 341 (bit B58 in the example). When the bit 341 is set (such as a bit value of "1"), the STA transmitting the D-band STA capability information field can transmit an optional PHY-BRP packet to the receiver identifying the transmitter of the D-band STA capability information field 320. The receiver of the D-band STA capability information field 320 then knows that the sender is PHY-BRP capable and may then send a BPR request requesting a PHY-BRP packet as part of the BRP response. The use of the BHY-BRP capability bit 341 eliminates the guesswork of trying to determine whether a device is PHY-BRP capable. A particular STA that identifies itself as a PHY-BPR capable device may do so when receiving a BRP request signal that is requested to transmit a PHY-BRP packet.

The use of the PHY-BRP capability bit addresses the first disadvantage mentioned above, and thus there is now a way to identify which STA has the capability to transmit PHY-BRP packets. Note that in the example, bit B58 is used. It should be understood that any other reserved bit or bits may be used in other embodiments.

To address the second disadvantage mentioned above, where there is no PHY and/or MAC header in the PHY-BRP packet, fig. 8 and 9 illustrate how this problem is solved in one embodiment. When a PHY-BRP capable STA receives a BRP request from another STA, the PHY-BRP capable STA has the capability to send a BRP response with or without an optional PHY-BRP packet. If the STA is not or cannot transmit the PHY-BRP packet, the STA may use the usual acknowledgement for the STA that is not transmitting the PHY-BRP packet, such as the format shown in FIG. 4. However, if the BRP request requests a PHY-BRP packet, the STA may respond by transmitting the PHY-BRP packet. Note that since the STA transmits the D-band STA capability information field with the bit 341 set, the originator of the BRP request knows that the STA has PHY-BRP packet capability.

Fig. 8 shows a packet structure 400 for a BRP response. As shown in fig. 8, if the STA sends any kind of receiver calibration acknowledgement for the BRP request, an RX calibration acknowledgement bit 401 (bit B18 in the example) is set (such as to a bit value of "1") to identify that there is a calibration acknowledgement from the STA with an accompanying BRP acknowledgement. However, if the STA decides to transmit a PHY-BRP packet in response to a BRP request, then the other bit 402, designated as the PHY-BRP following bit, is set (such as a bit value of "1") to inform the receiver that the PHY-BRP packet follows the BRP response. In a specific example, one of the reserved bit values (bit B53) is used for PHY-BRP following bit 402. It should be understood that in other embodiments, any other reserved bit or bits may be used. Setting of bit 402 in BRP response 400 indicates to the sender of the BRP request that the PHY-BRP packet will follow the BRP response.

The sequence of the originator sending a BRP request with a PHY-BRP packet request and the responder responding with a BRP response with an appended PHY-BRP packet is shown in fig. 9. The use of bit 402 for "PHY-BRP follow" is an indication that the originator PHY-BRP packet 310 of the advertised BRP request 420 is appended to the BRP request 400, as shown in fig. 9. Bits 401 and 402 in BRP acknowledgement 400 will be set. Since the PHY-BRP packet 310 is appended to the BPR response 400, the originator may use the PHY and/or MAC flags present in the BRP response 400 to obtain source and destination information for the BRP response and for the appended PHY-BRP packet. Thus, the transmitted PHY-BRP packet is now related to the source and destination, in this example the information in the BRP reply.

To protect the PHY-BRP packet from interference by other stations, the Network Allocation Vector (NAV) of the network is set with the duration field in the BRP response 400 to include the time period associated with the attached PHY-BRP packet. As shown in fig. 9, there is a delay 431 (shown as SIFS) between the BRP response 400 and the PHY-BRP packet 310. The NAV is set to advertise to the network that the STA is about to transmit for a duration of at least (SIFS) + (PHY-BRP). In one embodiment, the duration is set to (SIFS) + (PHY-BRP) to ensure sufficient time to transmit without interference. It should be noted that other durations may be used for other embodiments. In fig. 9, the time period BRPIFS indicates a delay period 430 permitted by the originator of the BRP request to allow a BRP response from the responder. In one embodiment, the BRPIFS is approximately 3 to 40 microseconds. Also, in one embodiment, the SIFS is approximately 3 microseconds.

Thus, beamforming calibration in a wireless communication system using directional antennas is described. Although the invention has been described with a specific example adapted to the IEEE802.11ad specification, the invention is not limited to such use, and as such the invention is discussed in a manner adapted to the 60GHz and D frequency bands, but the invention can be readily adapted to other frequencies and frequency bands using directional antennas or antenna arrays.

Embodiments of the invention have been described above with the aid of functional building blocks illustrating specific functional representations. Boundaries of these functional building blocks have been arbitrarily defined for the convenience of the description. Alternative boundaries may be defined so long as the specified functionality is appropriately expressed. Those skilled in the art will also recognize that the functional building blocks and other exemplary blocks, modules, and components herein can be implemented as shown or by discrete components, application specific integrated circuits, processors executing appropriate software, etc., or any combination thereof.

As also 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 manipulates signals (analog and/or digital) based on hard code and/or operational instructions within the circuitry. The processing module, processing circuit, and/or processing unit may be or further include memory and/or integrated memory elements that may be single memory devices, multiple memory devices, and/or embedded circuitry within other processing modules, processing circuits, and/or processing units. Such a storage device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache, and/or any device that stores digital information.

Claims (10)

1. A method, comprising:

transmitting an identification indicating that a device is capable of transmitting a calibration packet to calibrate a directional antenna for positioning toward the device, wherein the calibration packet does not include an address associated with the device transmitting the calibration packet;

receiving a request from a requester to send the calibration packet to the requester to calibrate the requester's directional antenna;

responding to the request by sending a response from the device, wherein the response includes an identification indicating that the calibration packet locating the directional antenna is appended to the response, the response including an address associated with the device; and

appending the calibration packet to the reply and transmitting the appended calibration packet with the reply.

2. The method of claim 1, wherein the calibration packet is an optional packet to locate the directional antenna.

3. The method of claim 1, wherein the calibration packet is an optional beam improvement protocol (BRP) packet.

4. The method of claim 1, wherein a value of a selected bit in the reply is used as an identification indicating that a calibration packet to locate the directional antenna is appended to the reply.

5. The method of claim 4, wherein the calibration packet is to be used to calibrate and position the directional antenna for millimeter wave transmission.

6. A method, comprising:

transmitting an identification that a device is capable of transmitting a physical beam improvement protocol (PHY-BRP) packet to calibrate a directional antenna for positioning toward the device, wherein the physical beam improvement protocol packet does not include an address associated with the device transmitting the physical beam improvement protocol packet, and wherein a structure of the physical beam improvement protocol packet is specified by a communication protocol;

receiving a beam improvement protocol request from a requester to send the physical beam improvement protocol packet to the requester to calibrate the directional antenna of the requester;

acknowledging the request by transmitting a beam improvement protocol acknowledgement from the apparatus, wherein the beam improvement protocol acknowledgement includes an identification indicating that the physical beam improvement protocol packet locating the directional antenna is appended to the beam improvement protocol acknowledgement, the beam improvement protocol acknowledgement including an address related to the apparatus; and

appending the physical beam improvement protocol packet to the beam improvement protocol reply and transmitting the appended physical beam improvement protocol packet with the beam improvement protocol reply.

7. The method of claim 6, wherein the physical beam improvement protocol packet is a pair

An optional beam improvement protocol packet for positioning by the directional antenna.

8. The method of claim 7, wherein a value of a selected bit in the beam improvement protocol reply is used as an indication that a physical beam improvement protocol packet that locates the directional antenna is appended to the beam improvement protocol reply.

9. The method of claim 8, wherein an identification indicating that the apparatus can transmit the physical beam improvement protocol packet to calibrate the directional antenna is included in a capability information field transmitted by the apparatus to identify a capability of the apparatus.

10. An apparatus, comprising:

a transmitter transmitting a Radio Frequency (RF) signal;

a receiver that receives a radio frequency signal; and

a baseband processor module comprising a processor and coupled to the transmitter and the receiver to provide processing of packets specified by a communication protocol to:

transmitting an identification indicating that a device is capable of transmitting a calibration packet to calibrate a directional antenna for positioning toward the device, wherein the calibration packet does not include an address associated with the device transmitting the calibration packet;

receiving a request from a requester to send the calibration packet to the requester to calibrate the requester's directional antenna;

responding to the request by transmitting a response from the device, wherein the response includes an identification indicating that the calibration packet locating the directional antenna is appended to the response, the response including an address associated with the device; and

appending the calibration packet to the reply and transmitting the appended calibration packet with the reply.