EP3304764A1 - Sondage de canal radio - Google Patents

Sondage de canal radio

Info

Publication number
EP3304764A1
EP3304764A1 EP16727172.5A EP16727172A EP3304764A1 EP 3304764 A1 EP3304764 A1 EP 3304764A1 EP 16727172 A EP16727172 A EP 16727172A EP 3304764 A1 EP3304764 A1 EP 3304764A1
Authority
EP
European Patent Office
Prior art keywords
packet
preamble
downstream
sounding
channel state
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP16727172.5A
Other languages
German (de)
English (en)
Inventor
Avi MANSOUR
Ziv AVITAL
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Intel Germany Holding GmbH
Original Assignee
Lantiq Beteiligungs GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lantiq Beteiligungs GmbH and Co KG filed Critical Lantiq Beteiligungs GmbH and Co KG
Publication of EP3304764A1 publication Critical patent/EP3304764A1/fr
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0417—Feedback systems
    • H04B7/0421—Feedback systems utilizing implicit feedback, e.g. steered pilot signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0621—Feedback content
    • H04B7/0626—Channel coefficients, e.g. channel state information [CSI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0621—Feedback content
    • H04B7/0634—Antenna weights or vector/matrix coefficients
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636—Feedback format
    • H04B7/0639—Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636—Feedback format
    • H04B7/0643—Feedback on request
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0686—Hybrid systems, i.e. switching and simultaneous transmission
    • H04B7/0695—Hybrid systems, i.e. switching and simultaneous transmission using beam selection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0026—Transmission of channel quality indication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0027—Scheduling of signalling, e.g. occurrence thereof
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H04L1/0618—Space-time coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0204—Channel estimation of multiple channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver

Definitions

  • a device configured to transmit a downstream sounding packet and to determine a downstream channel state of a radio channel based on a receive property of the preamble of the downstream sounding packet.
  • the device is further configured to receive an upstream packet and to reevaluate the determined downstream channel state based on a receive property of the preamble of the upstream packet. Further examples relate to a corresponding method.
  • BACKGROUND Channel sounding helps to tailor transmission properties of data communication on a radio channel. E.g., based on channel sounding, the transmission properties can be tailored depending on the particular transmission environment. Thereby, transmission reliability can be increased. While, generally, channel sounding may be desirable for all kinds of radio channels, one particular field of application is the sounding of a channel comprising a plurality of time-space streams. Such a scenario is often applicable where an antenna array is used to implement multiple input multiple output (MIMO) techniques. MIMO techniques may be combined with multi-user (MU) or single-user (SU) beamforming.
  • MIMO techniques may be combined with multi-user (MU) or single-user (SU) beamforming.
  • MU multi-user
  • SU single-user
  • sounding packets sometimes also referred to as pilot packets or reference packets
  • pilot packets or reference packets are employed which comprise a preamble of well-defined form. Based on one or more receive properties of the preamble, it is then possible to evaluate the channel state. Such techniques are sometimes referred to as acquiring a channel.
  • a device comprises an interface and at least one processor.
  • the interface is configured to transceive on a bi-directional radio channel.
  • the at least one processor is configured to transmit a downstream sounding packet via the interface.
  • the at least one processor is further configured to determine a downstream channel state of the radio channel based on at least one receive property of a preamble of the downstream sounding packet.
  • the at least one processor is further configured to receive an upstream packet via the interface.
  • the at least one processor is further configured to reevaluate the downstream channel state based on at least one receive property of a preamble of the upstream packet.
  • a method is executed by a device and comprises transmitting a downstream packet on a bi-directional radio channel.
  • the method further comprises determining a downstream channel state of the radio channel based on at least one receive property of a preamble of the downstream sounding packet.
  • the method further comprises receiving an upstream packet on the radio channel.
  • the method further comprises reevaluating the determined downstream channel state based on at least one receive property of a preamble of the upstream packet.
  • a computer program product comprises program code to be executed by at least one processor. Executing the program code causes the at least one processor to perform a method comprising transmitting a downstream packet on a bidirectional radio channel.
  • the method further comprises determining a downstream channel state of the radio channel based on at least one receive property of a preamble of the downstream sounding packet.
  • the method further comprises receiving an upstream packet on the radio channel.
  • the method further comprises reevaluating the determined downstream channel state based on at least one receive property of a preamble
  • FIG. 1A schematically illustrates a first device and the second device configured to communicate on a bi-directional radio channel according to various embodiments.
  • FIG. 1 B illustrates a plurality of time-space streams on the radio channel of FIG. 1 A.
  • FIG. 2 schematically illustrates a transmission protocol stack of a radio access technology (RAT) for communicating on the radio channel.
  • RAT radio access technology
  • FIG. 3A illustrates a time evolution of a downstream channel state of the radio channel, wherein the channel state is reevaluated based on a receive property of preambles of upstream packets in a first operational mode.
  • FIG. 3B illustrates a time evolution of a downstream channel state of the radio channel, wherein the channel state is not reevaluated based on receive properties of preambles of upstream packets in a second operational mode different from the first operational mode of FIG. 3A.
  • FIG. 4 schematically illustrates a sounding packet implemented by a null data packet comprising a preamble and no payload section.
  • FIG. 5 schematically illustrates a data packet comprising a preamble and a payload section.
  • FIG. 6 is a signaling diagram of signaling between two devices on a bi-directional radio channel according to various embodiments.
  • FIG. 7 is a signaling diagram of signaling between two devices on a bi-directional radio channel according to various embodiments.
  • FIG. 8 illustrates antenna weights of an antenna array determined based on a channel state of the radio channel according to various embodiments.
  • FIG. 9 is a flowchart of a method according to various embodiments.
  • FIG. 10 is a flowchart of a method according to various embodiments.
  • FIG. 1 1 is a flowchart of a method according to various embodiments.
  • DS downstream
  • US upstream
  • the techniques described herein can be applied for any one of the two directions of the bi-directional radio channel; for sake of simplicity, hereinafter, reference is made to the DS direction which, however, may be arbitrarily defined.
  • DS downstream
  • US upstream
  • the techniques described herein can be applied for any one of the two directions of the bi-directional radio channel; for sake of simplicity, hereinafter, reference is made to the DS direction which, however, may be arbitrarily defined.
  • to sound the DS channel first, at least one receive property of a preamble of a DS sounding packet is evaluated. For this, the DS sounding packet is transmitted by a first device and received by a second device.
  • the second device may provide an US report message back to the first device, the US report message being indicative of the at least one receive property of the preamble of the DS sounding packet. Then, the first device can determine a DS channel state based on the at least one receive property.
  • the DS sounding packet may be implemented by null data packet (NDP) not comprising a payload section.
  • NDP null data packet
  • the DS sounding packet in some examples, may only comprise a preamble, but not include any application-layer user data or control data of higher layers. This may reduce the overhead imposed by the DS sounding packet.
  • the DS channel state may be indicative of elements selected from the group comprising: path loss; multipath fading; phase shift; residual phase error of modulated symbols; interference from external noise sources; bit error rate; packet error rate; signal-to-noise ratio; decoding errors; decoding reliability; etc..
  • the first device is configured to receive an US packet communicated on an US channel.
  • the US packet can be used to reevaluate the DS channel state.
  • the DS channel state may be reevaluated based on a receive property of a preamble of the US packet.
  • Such techniques of reevaluating the DS channel state based on the US packet may be referred to as implicit channel sounding.
  • said reevaluating comprises updating or refining the DS channel state.
  • said reevaluating comprises checking a validity of the DS channel state.
  • the US packet may be a packet communicated anyway on the radio channel, e.g., to deliver application-layer user data or control data of the radio channel; as such, the US packet may be a US data packet such as a US payload data packet or an US control data packet.
  • the control data may, e.g., include one or more of the following: an acknowledgement message of an Automatic Repeat Request (ARQ) protocol, e.g., a block acknowledgement; a Request of Send (RTS) / Clear to Send (CTS) collision avoidance control message; etc.
  • ARQ Automatic Repeat Request
  • RTS Request of Send
  • CTS Clear to Send
  • the US packet may not correspond to a dedicated sounding packet; in other examples, the US packet may correspond to an US sounding packet implemented, e.g., implemented by a null data packet (NDP) not comprising a payload section.
  • NDP null data packet
  • the techniques described herein rely on the finding that even for scenarios where reciprocity between the US channel and the DS channel is not given - i.e., where the radio channel is non-reciprocal -, implicit / relative adjustments to the determined DS channel state can still be reliably performed by said reevaluating of the DS channel state based on the US packet.
  • the receive properties of the preamble of the DS sounding packet can provide a reference baseline based on which the reevaluating of the determined DS channel state can be performed taking into consideration the receive property of the preamble of the US packet.
  • the techniques described herein enable to reduce the overhead on the radio channel. Thereby, it is also possible to reduce energy consumption. As such, techniques described herein may facilitate Internet of Things (loT) applications.
  • LoT Internet of Things
  • FIG. 1A illustrates a radio channel 120 implemented between a device 101 and a device 1 1 1.
  • the device 101 implements an IEEE 802.1 1 x Wi-Fi station (STA); also the device 1 1 1 implements a Wi-Fi STA.
  • STA Wi-Fi station
  • Wi-Fi RAT While, hereinafter, various techniques will be described with respect to the Wi-Fi RAT, respective techniques may be readily employed for other kinds and types of RATs. Examples include the Third Generation Partnership Project (3GPP) 2G, 3G, 4G, and upcoming 5G RATs, Bluetooth, and Satellite communication.
  • 3GPP Third Generation Partnership Project
  • the DS channel 121 is arbitrarily defined from the STA 101 to the STA 1 1 1 ; and the US channel 122 is arbitrarily defined from the STA 1 1 1 to the STA 101 .
  • the STA 101 comprises a processor 105 and an interface 106.
  • the interface 106 may comprise a radio transceiver having an analog stage and/or a digital stage.
  • the interface 106 is configured to transmit and/or receive (communicate) data on the radio channel 120.
  • the processor 105 is configured to perform techniques as described herein with respect to channel sounding.
  • the processor 105 is configured to transmit a DS sounding packet, determine a DS channel state of the radio channel 120 based on a receive property of the preamble of the DS sounding packet, receive an US packet, and to reevaluate the determined DS channel state based on at least one receive property of a preamble of the US packet.
  • the STA 1 1 1 comprises a processor 1 15 and an interface 1 16.
  • the interface 1 16 may comprise a radio transceiver having an analog stage and/or a digital stage.
  • the interface 1 16 is configured to communicate data on the radio channel 120.
  • the processor 1 15 is configured to perform techniques as described herein with respect to channel sounding. In detail, the processor 1 15 is configured to receive a DS sounding packet, report at least one receive property of the DS sounding packet to the STA 101 , transmit in US packet, etc.
  • FIG. 1 B illustrates aspects with respect to a plurality of time-space streams 125, 126 implemented on the radio channel 120.
  • the interface 106 comprises an antenna array 160 comprising two antennas.
  • the interface 1 16 does not comprise an antenna array, but comprises a single antenna.
  • two time-space streams 125, 126 are defined between the STA 101 and the STA 1 1 1 .
  • both devices 101 , 1 1 1 comprise antenna arrays. It is also possible that the each antenna array comprises a larger number of antennas, e.g. more than two antennas, more than ten antennas or even more than 50 antennas.
  • the number of time-space streams 125, 126 generally depends on the number of antennas implemented by the interfaces 106, 1 16.
  • the DS channel state of the DS channel 121 and the US channel state of the US channel 122 are non-reciprocal. I.e., it is possible that the channel state 121 of the DS channel is at least partly different from the channel state of the US channel 122. I.e., it is possible that the channel state 121 of the DS channel is different from the channel state of the US channel 122 with respect to one or more figures of merit. Because of this lack of reciprocity, in reference implementations, separate and frequent sounding of the DS channel 121 and the US channel 122 based on DS sounding packets and US sounding packets, respectively, is implemented. This increases overhead. Some reference implementations also rely on channel calibration in order to achieve reciprocity. However, it has been found that such calibration of the radio channel 120 is prone to failures and may show significant time-dependencies such that re- calibration is required comparably often. This, in turn, again increases overhead.
  • FIG. 2 illustrates aspects with respect to the transmission protocol stack 130 of the respective RAT employed for communicating on the radio channel 120 - 122.
  • Layer 1 is the Physical layer (PHY) 131 .
  • Layer 2 is the Data Link Layer (DLL) 132.
  • Layer 3 is the Network layer 133.
  • Higher layers can include, e.g.: the transport layer; and the application layer (both not shown in FIG. 2).
  • the DLL 132 is subdivided into the Medium Access Control layer (MAC) 132-1 and the Logical Link Control layer (LLC) 132-2.
  • the MAC 132-1 is responsible for implementing the ARQ protocol. Control data may originate from the MAC 132-1 .
  • the packets discussed herein may be defined with respect to the PHY 131.
  • the packets, e.g., the DS sounding packet and/or the US packet, discussed herein may be defined with respect to the DLL 132.
  • FIG. 3A illustrates aspects of reevaluating the DS channel state based on a receive property of a preamble of an US packet 21 1 - 214.
  • FIG. 3A illustrates DS channel state 499 which is initially determined based on a receive property of a preamble of a DS sounding packet 201 and which is further reevaluated based on at least one receive property of a preamble of US packets 21 1 - 214 over the course of time.
  • the DS sounding packet 201 is initially communicated from the STA 101 to the STA 1 1 1 on the DS channel 121 .
  • the STA 1 1 1 then sends a US report message to the STA 101 , the US report message being indicative of the at least one receive property of a preamble of the DS sounding packet 201 (in FIG. 3A, the report message is not illustrated).
  • the STA 101 may explicitly and accurately sound the DS channel 121 including all time-space streams 125, 126.
  • the STA 101 may accurately determine the DS channel state 499 at the time of communication of the DS sounding packet 201 .
  • the time evolution of the DS channel state 499 can be tracked by means of the US packets 21 1 - 214.
  • the STA 101 receives the US packets 21 1 - 214 communicated from the STA 1 1 1 to the STA 101 on the US channel 122. Based on at least one receive property of the preamble of each one of the US packets 21 1 - 214, the STA 101 can then reevaluate the determined DS channel state.
  • the radio channel 120 is non-reciprocal. Hence, it is not possible to ab initio conclude back on the DS channel state 499 based on information derived solely from each one of the US packets 21 1 - 214 alone. Therefore, the DS channel state 499 - as determined based on the at least one receive property of the preamble of the DS sounding packet 201 - is used as a reference baseline 251 (indicated in FIG. 3A by the dashed line). Then, based on the at least one receive property of the preamble of the US packet 21 1 - 214, a relative deviation 252 from the reference baseline 251 can be determined.
  • said reevaluating of the determined DS channel state 499 may be based on, both, the at least one receive property of the preamble of the DS sounding packet and the at least one receive property of the preamble of the US packet.
  • a relative deviation 252 of the DS channel state 499 may have a limited accuracy - in particular, the accuracy may be lower if compared to the scenario where the DS channel state 499 is explicitly sounded each time based on a dedicated DS sounding packet - it is possible to reduce the overhead by limiting the number of DS sounding packets. Still, a more or less rough estimate of the temporal evolution of the DS channel state 499 can be obtained based on the US packets 21 1 - 214. As illustrated in FIG. 3A, a temporal resolution of the reevaluating of the determined DS channel state 499 corresponds to a temporal offset 241 between adjacent US packets 21 1 - 214. E.g., the temporal offset 241 may be smaller than 500 milliseconds, preferably smaller than 100 milliseconds, more preferably smaller than 20 milliseconds.
  • the US packet 21 1 is communicated shortly after communication of the DS sounding packet 201 . Then, for a certain duration 242, said reevaluating of the DS channel state 499 continues.
  • the STA 101 may be configured to receive US packets 21 1 - 214 and reevaluate the DS channel state 499 at least for 5 milliseconds after transmitting the DS sounding packet 201 , preferably for at least 15 milliseconds, more preferably for at least 50 milliseconds.
  • a validity of the determined DS channel state 499 based on the at least one receive property of the preamble of the US packets 21 1 - 214. In other words, it could be possible to monitor the magnitude of the deviation 252. If the magnitude of the deviation 252 exceeds a certain threshold, it could be possible to conclude that the initially determined DS channel state 499 is not valid anymore. Then, appropriate action may be taken, such as explicitly sounding the DS channel 121 anew: E.g., it is possible that a further DS sounding packet 202 is selectively transmitted from the STA 101 to the STA 1 1 1 depending on said checking of the validity.
  • a further DS channel state 499 of the DS channel 121 can be determined based on at least one receive property of the preamble of the further DS sounding packet 202.
  • it is not required to communicate DS data packets on the DS channel 121 according to a value of the DS channel state 499 which is refined based on the at least one receive property of the preamble of the US packets 21 1— 214 if compared to the baseline 251.
  • communication on the DS channel 120 is performed based on a value of the DS channel state 499 corresponding to the baseline 251 .
  • said reevaluating may be restricted to checking whether this value is still up-to-date.
  • the scenario of FIG. 3A corresponds to a first operational mode 391.
  • the DS channel state 499 is reevaluated based on the US packets 21 1 - 214. Because such a reevaluation is available, a time sequence 220 of the DS sounding packets 201 , 202 has a comparably low temporal density of DS sounding packets 201 , 202. I.e., the number of DS sounding packets 201 , 202 per time unit is comparably low in the first operational mode 391 .
  • a time-offset 245 between subsequent DS sounding packets 201 , 202 is long.
  • FIG. 3B corresponds to a second operational mode 392.
  • reevaluating of the DS channel state 499 is not implemented based on US packets.
  • channel sounding of the DS channel 121 is implemented explicitly and relies solely on DS sounding packets 201 - 204.
  • the time sequence 220 of DS sounding packets 201 - 202 in the first operational mode 391 has a larger number of DS sounding packets 201 , 202 per time than the time sequence 220 in the second operational mode 392.
  • the second operational mode 392 a shorter time offset 245 between subsequent US sounding packets 245 is obtained.
  • the accuracy may be reduced if compared to the channel sounding in the second operational mode 392.
  • the STA 101 dynamically switches between the modes of operation 391 , 392.
  • Various decision criteria may be taken into account for said switching, e.g., an absolute value of the DS channel state 499.
  • the DS channel state 499 is comparably degraded, it is possible that accurate channel sounding is desirable such that the STA 101 operates in the second operational mode 392.
  • the first operational mode 391 may be activated.
  • the DS sounding packets 201 - 204 are implemented by NDPs.
  • a NDP does not comprise a payload section.
  • the DS sounding packets 201 - 204 may also comprise a payload section.
  • FIG. 4 illustrates schematically a NDP that may be used as a DS sounding packet 201 - 204.
  • the NDP 201 - 204 comprises a preamble 421 .
  • the NDP 201 - 204 does not comprise a payload section.
  • the preamble 421 comprises training symbols 422.
  • the preamble 421 comprises a long training field (LTF) comprising a comparably large number of training symbols.
  • the number of training symbols 422 comprised in the preamble 421 is not smaller than a number of the time-space streams 125, 126 implemented on the radio channel 120. This allows accurate sounding of the DS channel 121 .
  • the training symbols may or may not be modulated.
  • the training symbols may not be coded or scrambled.
  • the training symbols may be Orthogonal Frequency Duplex Modulated (OFDM) symbols. They may serve for synchronization purposes, e.g., in addition to the channel sounding: here, the beginning of the respective packet may be indicated by the training symbols.
  • the training symbols may be pre-negotiated, i.e., the respective receiver may expect a certain sequence of training symbols to be received.
  • FIG. 5 schematically illustrates a data packet that may be used as a US packet 21 1 - 214 based on which the determined DS channel state 499 is reevaluated.
  • the data packet - different to the NDP - comprises a payload section 433.
  • the payload section 433 comprises application-layer user data or control data of the radio channel 120.
  • the control data may correspond to MAC 132-1 control data, e.g., an ARQ or CTS message.
  • the data packet 21 1 - 214 also comprises a preamble 431 .
  • the preamble 431 comprises training symbols 432.
  • the preamble 431 comprises a training field (TF) comprising a comparably small number of training symbols if compared to the LTF.
  • the number of training symbols 432 comprised in the preamble 431 is smaller than a number of time-space streams 125, 126 implemented on the radio channel 120. This allows to limit overhead introduced by the preamble 431. While, in the example of FIG.
  • the number of training symbols 432 included in the preamble 431 of the US packet 21 1 - 214 may be smaller, equal to, or larger than the number of training symbols 422 included in the preamble 421 of the DS sounding packet 21 1 - 204. It is generally not required that the US packet 21 1 - 214 used for reevaluating the determined DS channel state 499 is a data packet. In further examples, it is possible that a NDP is employed as the US packet for reevaluating the DS channel state 499. Here, a particularly large number of training symbols 432 may be included in the preamble 431 which facilitates accurate reevaulating.
  • FIG. 6 is a signaling diagram illustrating aspects of reevaluating the DS channel state 499 based on at least one receive property of the preamble 431 of an US packet 21 1 , 212.
  • a NDP implementing a DS sounding packet 201 is communicated from the STA 101 to the STA 1 1 1 .
  • the STA 1 1 1 determines the feedback matrix 1002 and reports the feedback matrix as a US report message 209 back to the STA 101 , see 1002 and 1003.
  • the feedback matrix corresponds to the at least one receive property of the preamble 421 of the NDP 201 .
  • the STA 101 determines the steering matrix.
  • the steering matrix defines antenna weights of different antennas of an antenna array of the interface 106.
  • the steering matrix is used in order to implement beamforming at the STA 101. Beamforming employs MIMO capabilities of the STA 101 to bundle energy into the direction at which the STA 1 1 1 is positioned. This increases a transmission reliability.
  • US communication of data is ongoing: in detail, at 1005, and US data packet 21 1 is communicated from the STA 1 1 1 to the STA 101 . Based on the at least one receive property of the preamble 431 of the US data packet 21 1 , the steering matrix is refined, 1006. At 1007, a further US data packet 21 1 is communicated from the STA 1 1 1 to the STA 101 . Based on the at least one receive property of the preamble 431 of the US data packet 212, the steering matrix is further refined, 1008.
  • a further DS sounding packet 202 is transmitted by the STA 101 and received by the STA 1 1 1 . 1010 - 1012 correspond to 1002 - 1004, respectively.
  • the further DS sounding packet 202 may be triggered by timeout of a timer initialized at 1001 .
  • the further DS sounding packet 202 may be triggered by a timing pattern of communicating DS sounding packets.
  • refining of the steering matrix at 1008 may be based on the deviation 252 which is larger than a threshold (cf. FIG. 3A).
  • the US data packets 21 1 , 212 are communicated in response to the need of delivering US data to the STA 101. Transmission occurrences of the US data packets 21 1 , 212 may be controlled by the MAC 132-1 according to reference techniques. If no US data is available, zero padding may be employed.
  • the US packets 21 1 - 214 used for reevaluating the DS channel state 499 are scheduled.
  • the persistently scheduled timing of repetitive transmission occurrences or a dedicated scheduled transmission occurrence defined for each individual US packet 21 1 - 214 can be employed.
  • FIG. 7 is a signaling diagram illustrating aspects of reevaluating the DS channel state 499 based on at least one receive property of the preamble 431 of an US packet 21 1 , 212.
  • FIG. 7 generally corresponds to FIG. 6.
  • NDPs 21 1 and 212 are used at 1 105, 1007 for reevaluating the determined DS channel state 499.
  • the timing 245 of the transmission occurrences of the US NDPs 21 1 , 212 is persistently scheduled, e.g., as part of transmission setup 201 between the STAs 101 , 1 1 1 at 1 100.
  • the respective timing 241 is thus predefined.
  • the STA 101 may transmit respective dedicated request messages to the STA 1 1 1 , the request message is prompting transmission of a US NDP. This corresponds to a dedicated scheduled transmission occurrence.
  • 1 101 - 1 104 corresponds to 1001 - 1004.
  • 1 106 corresponds to 1006.
  • 1 108 corresponds to 1008.
  • 1 109 - 1 1 12 corresponds to 1009 - 1012, respectively.
  • FIG. 8 illustrates aspects with respect to the interfaces 106, 1 16.
  • the interfaces 106, 1 16 comprise an antenna array 160.
  • Each antenna 160 is associated with a certain antenna weight 161 defining amplitude and phase of the respective signal handled by that antenna.
  • the antenna weights correspond to the steering matrix.
  • the antenna weights 161 may be determined based on the DS channel state.
  • the antenna array 160 may facilitate MIMO techniques.
  • a plurality of time-space streams may be implemented based on the antenna array 160. Thereby, SU or MU beamforming can be implemented.
  • FIG. 9 is a flowchart of a method according to various examples.
  • a DS sounding packet is transmitted, e.g., from the STA 101 to the STA 1 1 1 or vice versa.
  • the DS sounding packet may be transmitted according to a predefined timing.
  • the DS packet may be a NDP.
  • the DS channel state is determined based on the at least one receive property of a preamble of the DS sounding packet communicated at 2001.
  • a US report message indicative of the at least one receive property may be received.
  • an US packet is received, e.g., a NDP or a data packet.
  • the DS channel state is reevaluated at 2004.
  • FIG. 10 is a flowchart of a method according to various examples.
  • the flowchart of FIG. 10 illustrates a possible implementation of reevaluating the DS channel state determined at 2004.
  • 201 1 it is checked whether the deviation 252 from a reference baseline 251 associated with the at least one receive property of the preamble of the DS sounding packet is smaller than a threshold (cf. FIG. 3A). If this is the case, 2003 is re-executed, i.e., a further US packet is received and evaluated. If this is not the case, transmission of a further DS sounding packet is triggered by re-executing 2001.
  • a threshold cf. FIG. 3A
  • FIG. 1 1 is a flowchart of a method according to various examples.
  • the flowchart of FIG. 1 1 illustrates a possible implementation of reevaluating the DS channel state determined at 2002.
  • the value of the DS channel state 499 is refined / updated. I.e., the value of the DS channel state 499 can be changed.
  • subsequent communication on the DS channel 121 uses new parameters, e.g., as defined by the steering matrix.
  • the further US packet is received at 2003 and 2021 , 2022 are executed anew.
  • a dedicated request message may be communicated to trigger the further US packet in some examples.

Abstract

Un paquet de sondage aval (201) est transmis, et un état de canal aval (499) d'un canal radio est déterminé sur la base d'au moins une propriété de réception du préambule du paquet de sondage aval (209). Un paquet amont (211–214) est reçu. L'état de canal aval déterminé (499) est réévalué sur la base d'une propriété de réception d'un préambule du paquet amont (211–214). FIG. 3A:
EP16727172.5A 2015-06-02 2016-06-02 Sondage de canal radio Pending EP3304764A1 (fr)

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PCT/EP2016/062448 WO2016193342A1 (fr) 2015-06-02 2016-06-02 Sondage de canal radio

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US20070189412A1 (en) * 2006-02-15 2007-08-16 Samsung Electronics Co., Ltd. Method and system for sounding packet exchange in wireless communication systems
US8787841B2 (en) * 2006-06-27 2014-07-22 Qualcomm Incorporated Method and system for providing beamforming feedback in wireless communication systems

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