WO2011027347A2 - Dispositif et procédé de calcul d'instant d'arrivée d'une trame dans un réseau sans fil - Google Patents

Dispositif et procédé de calcul d'instant d'arrivée d'une trame dans un réseau sans fil Download PDF

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Publication number
WO2011027347A2
WO2011027347A2 PCT/IL2010/000725 IL2010000725W WO2011027347A2 WO 2011027347 A2 WO2011027347 A2 WO 2011027347A2 IL 2010000725 W IL2010000725 W IL 2010000725W WO 2011027347 A2 WO2011027347 A2 WO 2011027347A2
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Prior art keywords
waveform
network
frame
received
toa
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PCT/IL2010/000725
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English (en)
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WO2011027347A3 (fr
Inventor
Eliyahu Turetsky
Roman Kazarnovski
Haim Yashar
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Pin Nav Llc
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Publication of WO2011027347A2 publication Critical patent/WO2011027347A2/fr
Publication of WO2011027347A3 publication Critical patent/WO2011027347A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/04—Speed or phase control by synchronisation signals
    • H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
    • H04L7/042—Detectors therefor, e.g. correlators, state machines
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/14—Determining absolute distances from a plurality of spaced points of known location
    • 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
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0045—Arrangements at the receiver end

Definitions

  • the present invention relates to finding the start of a transmitted waveform in a wireless network, in general and, more particularly to methods, devices and a system for determining Time of Arrival (TOA) or Time of Arrival Differences (TOAD) of waveforms in a wireless signal stream.
  • TOA Time of Arrival
  • TOAD Time of Arrival Differences
  • Wireless networks are very popular and play an increasing role in network technology.
  • wireless network technologies may be implemented by the IEEE 802.11, 802.15 - 802.22 standards families.
  • spread spectrum is used for network communications.
  • the noise-shaped waveforms make itimpossible to determine "a priori" an arrival of not predefined signal. This gives rise to two important consequences: The TOA (time of arrival) for a not predefined signal cannot be determined in a straight- forward way; The waveform of a not predefined signal cannot be recognized in a straight-forward way.
  • a non-limited group of examples includes:
  • the determination of the location position of a wireless device has become very important for many reasons, including, for example:
  • the E91 1 demands for providing source location coordinates of a caller are obligatory for systems using a network for voice and/or video communications.
  • LBS Location Based Services
  • LBA Location Based Advertisement
  • the mobile device (MD) location, velocity and acceleration information can be used for mobile communications optimization with final purpose to provide seamless reconnection.
  • the position of an object in space is determined using distance or angle measurements from known points to the object to be located. If some signal propagates with a known velocity, the distance measurements can be replaced by thepropagation time measurements. To do this, one must identify as an event an arrival of a signal used for propagation time measurements and measure the TOA or/and TOAD of the signal used for propagation time measurements.
  • TOA measurements can be performed by triangulation-type algorithms to determine location position.
  • the radiobeam from a Mobile Device can arrive at an Access Point (AP) by several paths, due to refraction or can propagate not in a straight line. This can result in "several distances".
  • AP Access Point
  • about 20-30 years ago one of the inventors of the present invention developed and published an algorithm of source location in a non- homogeneous medium with multipath and not straight beam propagation. For this reason, the multipath problem is not considered to be critical for source location and is not relevant to the present invention.
  • the present invention relates to methods, devices and a system for determining TOA or TOAD of received network frames by comparing a selected portion of the transmitted frame with the received signals, using this to determine the 5TOA or TOAD and to determine the quality of the signal transmitted and/or for the location of a mobile device in the network.
  • an optimal portion of the waveform (which, in some cases, can be the whole frame) on which to perform the comparison between the reconstruction and the actual received frame.
  • one criterion for an optimal frame can be the frame lOhaving the highest Signal to Noise Ratio, calculated for this frame or portion of frame.
  • This optimal portion can be one or more waveform parts having characteristics that are easy to recognize, depending on the selected method of comparison, and having known time shifts from the start of the frame. These time shifts can be used for calculating TOA.
  • the invention provides, for completely received and decoded network frames, a method for locating the start of a received signal, including storing an original waveform stream or/and waveform representation in a time-indexed buffer, reconstructing an ideal waveform based on the received packet, analyzing and/or selecting an "optimal" segment or part of the reconstructed waveform/waveform 0representation, for use of the selected part or segment in comparison with the previously stored original waveform/waveform representation, (optionally) analyzing and/or choosing an optimal method of comparison or set of methods for comparing the waveform representation with the original waveform, comparing the received (stored) and original (ideal) waveform/waveform representation, and (optionally) 5analyzing the results from the previous step for use in TOA and/or TOAD calculation (location application), signal quality analysis, determining of changes occurring in the network, causes and wireless interfaces maintenance operation (e.g., signal quality control, improving of SNR, load balancing, etc.).
  • a method for locating the start of a received signal
  • step 2.b searching for the actually received frame waveform in the signals buffered during step 1 and utilizing at least one reconstruction from step 2.c.
  • step 4 Providing results of step 4 to information receivers including, but not limited by:
  • TOA waveforms - to client position location servers which will first determine TOAD and after that will determine client position location based on TOAD;
  • TOA waveforms of frames sent by APs - to servers responsible for APs time synchronization improvement
  • FIG. 1 is general system diagram of a wireless network system capable of lOreconstructing abstract/ideal waveforms of completely received and decoded network frames, search in input signal streams of a network device for the actually received waveforms of network frames, determining TOA of the waveforms of the identified network frames, using found actually received network frames waveforms and/or their abstract/ideal waveforms and/or the capability of determining client position 151ocation of wireless devices, according to embodiments of the present invention.
  • FIG. 2 is block diagram of a circuit responsible for reconstructing abstract/ideal waveforms of completely received and decoded network frames, searching in input signal streams of a network device for the actually received waveforms of network frames, determining TOA of the waveforms of the network 0frames, according to the embodiments of the present invention.
  • FIG. 3 is a logical operating diagram of a circuit shown on FIG.2.
  • FIG. 4 is a general structure of an 802.11 interface according to the prior art.
  • FIG. 5 is a general structure of an 802.11 interface modified according to the invention to be capable of reconstructing abstract/ideal waveforms of completely 5received and decoded network frames, searching in input signal streams of a network device the actually received waveforms of network frames, determining TOA of the waveforms of the network frames, according to the embodiments of the present invention.
  • FIG. 6 is a UML sequence-type operating diagram of a wireless network capable to use data supplied by device implementing embodiments of the invention.
  • FIG. 7 is a logical operating diagram of a wireless network, according to embodiments of the invention.
  • the present invention relates to a method for locating the start of a received signal, including storing an original waveform stream or/and waveform lOrepresentation in a time-indexed buffer, reconstructing an ideal waveform based on the received packet, analyzing and/or selecting an "optimal" segment or part of the reconstructed waveform/waveform representation, for use of the selected part or segment in comparison with the previously stored original waveform/waveform representation, and comparing the received (stored) and original (ideal)
  • the method may include analyzing and/or choosing an optimal method of comparison or set of methods for comparing the waveform representation with the original waveform.
  • the method may further include analyzing the results of the comparison for use in TO A and/or TOAD calculation (location application), signal quality analysis, determining of changes 0occurring in the network, causes and wireless interfaces maintenance operation (e.g., signal quality control, improving of SNR, load balancing, etc.).
  • the invention relates to methods, devices and a system for partial or/and complete reconstructing of abstract/ideal waveforms and/or waveform representations (Continuous or/and Discrete Transform, Wavelet Transform, etc) in 5Base Band Frequency (BF) or/and Intermediate Frequency (IF) or/and Radio Frequency (RF) for completely received and decoded network frames in a wireless communication network, and for searching in the input RF and/or IF and/or BF signal streams of a wireless network device for actual received waveforms or/and waveform parts or/and waveform representations or/and representations of waveform parts which correspond to those reconstructed waveforms or waveform representations.
  • BF Base Band Frequency
  • IF Intermediate Frequency
  • RF Radio Frequency
  • a wireless network system is capable of using this data, among other things, for determining client position location and/or for Access Point time synchronization improvement, as well as for quality of signal analyses, analysis and improvement of functionality of network Access Points (AP); lOanalysis and improvement of functionality of network clients; analysis and improvement of time synchronization of network components; analysis and improvement of functionality of the network system; analysis and improvement of functionality of a network system infrastructure.
  • TOA Time of Arrival
  • TOAD Time of Arrival Differences
  • a wireless network system is capable of using this data, among other things, for determining client position location and/or for Access Point time synchronization improvement, as well as for quality of signal analyses, analysis and improvement of functionality of network Access Points (AP); lOanalysis and improvement of functionality of network clients; analysis and improvement of time synchronization of network components; analysis and improvement of functionality of the network system; analysis and improvement of functionality of a network system infrastructure.
  • the 802.11 0family will be used for exemplary embodiments, which do not limit the generality of the invention or its usability under other wireless standards.
  • MAC Mobile Broadband identifier
  • MD identifier is used for purposes of the present invention. This is 5done to eliminate excessive dependence on a particular standard. The latter makes it possible to use the abbreviation MAC, as it is used in 802.11 and other standards families as standing for "Media Access Control" layer.
  • a network operates according to a certain protocol (802.11 or whatever group of standards).
  • Some network member transmit a frame which is received by other network members (sometimes referred to herein as clients or APs .
  • a good, non-limiting example from the 802.11 standard group is a "Probe Request" frame, which is broadcast by WiFi clients to all visible APs. This frame hosts client identification information, can be accepted by all visible APs of all networks deployed in this location, and the AP is not obligated to answer it.
  • the frame is received and decoded by some plurality of network members.
  • network frame abstract/ideal waveform; part of an abstract/ideal waveform of the network frame; the representation of an abstract/ideal waveform of the network frame; the representation of a part of an abstract/ideal waveform of the network frame; the actually received network frame waveform on any or all frequencies (RF,IF,BF); part of the actually received waveform of the network frame; a representation of the actually received waveform of the network frame; a representation of a part of the actually received waveform of the network frame.
  • ⁇ AP and other network elements time synchronization improvements.
  • step iii) Reconstruction of the selected type of the Ideal/Abstract frame waveforms or/and their representations or/and Simplified Reconstruction of the waveforms; iii) Using the method selected in step ii.b, searching for the actually received frame waveform in the signals buffered during step i and utilizing at least one reconstruction from step ii.c.
  • step 4 Providing results of step 4 to information receivers including, but not limited by:
  • the present invention incorporates, where possible, conventional "known signal pattern” methods.
  • "known signal pattern” methods will be limited mainly by some synchronization fields of theframes. For example, for the 802.1 1 group of standards, it will probably be a part of the preamble of PLCP and a part of some MAC frames. In the latter case, several “signal patterns” are needed. For this group, "reconstruction of a part of an ideal/abstract waveform" is just an extraction the signal pattern from a constant memory. Much more interesting is the situation with a real reconstruction of parts of a waveform:
  • the usage of a part of a wave frame can decrease the demands to the method implementation equipment.
  • the part can be selected in a way which makes the search in a stored input signals buffers much easier.
  • the frame identification (discussed in detail below) must be updated by the time difference from the selected part of the waveform (network frame) to the real beginning of the frame. This is not hard. 4.
  • Mutual usage of several different, possibly intersecting parts, can improve TOA accuracy and accuracy of estimation of TOA.
  • waveform representation is a Continuous or Discrete Transform, for which the correspondence between waveform and representation has been proved, although, generally speaking, the correspondence is not obligatory.
  • Fourier Transform is a common example, i.e., the spectrum is the waveform representation.
  • transforms such as Wavelet Transform, Fractal and Multifractal methods are very useful during frame reconstruction, search and comparison
  • Input RF signals and/or signals down-banded to IF and/or BF of a network device are buffered. Signal samples are stored with timestamps. 2.
  • the arrived network frame signal is recognized and decoded by appropriate network standard signal processing algorithms, sometimes very comprehensive. (The group of 802.11 standards can be taken as a non- limiting example.)
  • the informational contents and knowledge of the applicable network standard are used to reconstruct an abstract/ideal network frame waveform on IF and/or RF and/or BF frequencies, a representation of the waveform, or preferably part of the waveform, or a representation of a part of the waveform.
  • the actual received waveform of the received and completely decoded network frame is found in RF and/or IF and/or BF data previously stored in a buffer.
  • the search for the received frame waveform is implemented using:
  • the TOA of the waveform of the completely received and decoded network frame is now determined using the time stamps and, if necessary, the known time from the start of the frame to the reconstructed part of the waveform or part of the representation of the waveform of the frame is determined.
  • representations e.g., spectrum
  • any conventional method can be employed.
  • the waveform can be stored in the best form for the particularly treatment.
  • the system according to the invention includes: a plurality of mobile devices (MD);
  • devices capable of implementing the proposed method for the location 0 calculation application, at least three devices, preferably more;
  • the devices capable of implementing this method may be independent devices 5or may update conventional APs that lack the capability to implement this method.
  • the devices capable of implementing this method of calculating TOA must be synchronized in time and have known antenna coordinates.
  • the present invention utilizes monitoring and can search for the arrival of any received frame, even from a device that is not part of the network.
  • the AP operates normally, receives network frames, decodes them and provides the data to all the requiredlayers of network protocols.
  • the determination of TOA of a frame waveform is made by implementing the method described above.
  • each frame includes an identifier of the device which sent it.
  • the algorithm implemented in the wireless interface for receiving and decoding of network frames can be represented by a simplified sequence of known steps. This simplifiedsequence of steps can be modified to use timestamps stored with the received signals (which are not required for the standard algorithm) and to adopt higher/other sampling rate of the data and can be easily implemented using the data with time stamps stored in the buffer. In the present invention, this is called "the reconstruction of the receiving network frames algorithm”.
  • a location server communicates with the wireless network and receives the calculated TOAs of a frame from several devices or APs. It then implements a location algorithm, which calculates the MD coordinates.
  • the location algorithm can be implemented on the mobile device, if it is a client of the network. From the network and functional point of view, the mobile device client does notdiffer from a dedicated location server.
  • the MD with the location algorithm can detect its own location.
  • the TOAs of received frames which are stored in buffers can be sent to the server for determining the TOADs, rather than TOA.
  • the usage of a TOAD for location calculations can reach better accuracy than the calculations on the basis of TOA.
  • the estimation of a TOAD by comparing waveform samples from a pair of transmitters can also provide better accuracy in some cases.
  • a waveform sample or its representation can be sent to theserver from a set of devices and/or APs. Those samples can be used by the server.
  • the system operates as follows:
  • Input RF signals and/or signals down-banded to IF and/or BF of a network device are buffered. Signal samples are stored with timestamps.
  • An arrived network frame signal is recognized and decoded by appropriate network standard signal processing algorithms.
  • the informational contents and knowledge of the applicable network standard are used to determine the time interval which hosts the actually received waveform of a frame in the IF and/or RF and/or BF buffers.
  • the simplified algorithm is used to search for the waveform in a buffer.
  • Data for this time interval are moved from input IF and/or RF and/or BF buffers to some intermediate storage.
  • the system checks whether the number of devices which received the particular frame is enough to solve the task defined for the system. For example, the number of APs which received a frame must be at least 3, for the MD position location task.
  • time interval data stored in intermediate storage for the waveform fragment or/and its representations are sent to the servers, which implement the task defined for the system. For example, TOAD and position location calculations.
  • the base method described above can be modified and adapted to a particular task. It is a particular feature that the present system dramatically decreases resource demands, as compared to known in the art methods of continuous or semi- continuous signal correlation processing, based on Nanosecond Pulse Location.
  • waveforms of the received frames by themselves and/or the results of comparison with reconstructed abstract/ideal waveforms can be sent to the application server responsible for utilization of this information for the particular applications required.
  • the network system of the present invention can combine, in an unlimited manner, a plurality of applications, for example, network devices location, monitoring of Quality of Signal, wireless controller maintenance and fine tuning, Quality of Service applications, and others. This is because waveforms are an excellent source of information for functionality control.
  • the server is located on the MD, it will be an additional application for the MD.
  • the task of network member position location is considered particularlybecause of its great importance in all network applications.
  • the method of the present invention has much wider applicability.
  • this method advantageously provides an opportunity to replace or update the "Location Server" by some other server which will implement most or all network opportunities mentioned in the method description.
  • the position location of mobile clients (MD) will be described. This does not limit the generality of the applicability of the method for location position of any wireless network object located under the radio coverage of a network.
  • the wireless network object whose position will be determined need not be a member of the network which will determine its location position.
  • the device which implements the present method may be implemented as part of an AP or as a separate device.
  • the separate device can be installed near an AP and, in such a way, can upgrade a conventional AP.
  • the separate device equipped with an antenna having known coordinates, can be installed separately, specifically for method implementation.
  • the method can be implemented on any independent wireless network member, whether it is mobile or not mobile client or just any other wireless network device.
  • FIG. 1 is a general system diagram of a wireless network system capable of locating wireless mobile devices.
  • the system includes a plurality of access points (AP) 1 and/or a plurality of independent devices 13 capable of implementing the present invention, a plurality of mobile devices 2 - 9 and a server 10. All these lOAccess Points 1 and independent devices 13 are referred to herein as APs (as defined above) and are coupled to server 10.
  • APs as defined above
  • Facilities 1 1 supplying wireless connectivity with APs 1 are coupled to the APs 1 and to server 10, as by a cable network infrastructure 12.
  • the mobile devices may include one or more of: a mobile phone client 2 with wireless capabilities, a tag 3 (usually some small device used in asset
  • an IP phone 4 15assistance to mark some asset
  • an IP phone 4 15assistance to mark some asset
  • a pager 5 15assistance to mark some asset
  • a PDA 6 15assistance to mark some asset
  • a PDA 6 15assistance to mark some asset
  • a notebook 7 or similar computer client 15assistance to mark some asset
  • a wireless camera 8 15assistance to mark some asset
  • any wireless client within system radio coverage, can be located.
  • Reliable location needs at least 3, preferably 4 or more, measurements of TOA, which differs from the ideal deployment for networking radio coverage.
  • 0devices 13 may be utilized to fulfill the topology of the network to suit the demands of location calculation.
  • the terms "AP” and “wireless client (MD)” will be used to refer to all above-mentioned cases, but without any preference or limitation to any of them.
  • FIG. 2 is a block diagram of a circuit responsible for implementation of the 5proposed invention method, according to major embodiments of the invention.
  • This is a non-limiting example of a device that can implement all measurements described in the invention of abstract/ideal and actually received waveforms of the network frames.
  • the illustrated circuit in can be built into the circuit which implements a WiFi network interface, for example. This illustration in no way limits the general applicability of the block diagram shown in FIG. 2.
  • the circuit operation scenario inside an Access Point is as follows:
  • a Time Synchronization Signal (218), used to synchronize Analog to Digital Converters (ADC 204 - 206) and digitized signals timestamps.
  • Wireless network frame informational contents including MD identification and protocol dependent information 219 are received, typically from the Medium Access Controller or from an external network interface.
  • the circuit behavior can be modified by "Follow MD” and "Waveform Needed” input signals (220) stored in a buffer 211.
  • the RF signal of a network frame is received by the antenna and processed by the RF input circuits 201. After that, the signal is processed by an RF Analog to Digital Converter (ADC) 206. The digitized RF signal is stored by an RF Buffer 210, possibly a ring buffer. After input processing 201the RF signal is also processed byan RF/IF (Radio Frequency to Intermediate Frequency) converter 202. The IF signal is processed by an IF ADC 205 and stored by an IF buffer 209. In practice, several intermediate frequencies can be used. All of them can be digitized and stored, each in its own IF Buffer 209, several of which are shown. The IF signal is also processed by a demodulator 203 (Intermediate Frequency to Baseband Frequency converter). The resulting BF signal is digitized by a BF ADC 204 and stored by BF Buffer 208.
  • ADC Analog to Digital Converter
  • RF ADC 206, IF ADC 205 and BR ADC 204 are all synchronized by a synchronization time signal 218, which is received from an external source.
  • This 5 synchronization time signal can be a modern GPS signal or other signal from sources of time synchronization known in the art.
  • the location accuracy of a system according to the invention is defined by the accuracy of time synchronization of the APs.
  • the usage of accessible GPS with 15 nsec accuracy makes it possible to implement a system with accuracy of about 5 m, which is better lOthan an ordinary GPS working in non differential mode. In fact, better accuracy can be reached by the present invention using the ability of the proposed system to measure time differences between APs.
  • the device is controlled by a "Follow MD” and/or “Waveform Needed” Identifiers buffer 211.
  • "Follow MD” and/or “Waveform Needed” are configuration
  • Buffer 211 stores information concerning additional services demanded by/to clients, described by their identifiers, received from a source 220.
  • a particular MD 10 position locations/network frames analyses per second may be not enough.
  • the identifier of this client can be inserted into a 0"Follow MD" list.
  • all network frames will be evaluated.
  • waveforms may need to be sent elsewhere, for example, to the Position Location Server for TOAD determination and/or time for time synchronization improvement.
  • the AP receives wireless network frames, MD identifiers and protocol dependent information from an external source 219.
  • This source can be an AP, a Medium Access Controller of a wireless interface (see, for example, FIG. 5) or a wireless analysis facility (usually a wireless interface in a Monitoring Mode with 5package analysis software).
  • the received frames are stored and processed by a RF/IF/BF wireless network frames waveforms reconstructor and/or a network frames receiving algorithm reconstructor 207, which operates according to the information received from 211.
  • Reconstructed abstract/ideal wireless network frame waveforms and/or reconstructed receiving network frame algorithm and MD identifiers are sent lOto a signal comparator 212 through connections 216 and 217.
  • Reconstruction is based on information in an already received and completely decoded network frame and knowledge about the wireless standard implemented by the network. According to some embodiments of the invention, the entire network frame, or/and its representation, will be reconstructed, although only a portion may
  • the signal comparator 212 uses the information received from the reconstructor 207 to perform one or several of the following actions:
  • waveforms of the wireless network frame reconstructed by reconstructor 207 calculates TOA and prepares the TOA with the MD identifier for sending out through line 222 to the location server.
  • reconstructor 207 calculate TOA and prepare the TOA with the MD identifier for sending out through line 222 to the location server.
  • TOA is calculated based on reconstruction of the received network frame algorithm, then it is implemented for searching the content of the buffers to find the network frame; TOA and accuracy are calculated and, with the MD, are prepared for sending out through line 222 to the location server.
  • the radio channel of a standard wireless interface has delays, which create problems with accuracy of TOA determination using BF and IF. For this reason, and in some cases, the radio channel must be calibrated.
  • the radio channel can be specially designed according to a criterion "to keep signal waveform recognition" without frame decoding.
  • frame decoding is a stage that follows demodulation. In some systems, it is combined with demodulation. Correct decoding is a main purpose of all signal processing; but for waveform comparison, good reliability can be achieved without reliable decoding.
  • the radio channel can be simplified to avoid uncontrolled delays. In this case, a completely decoded network frame can be received from an external interface through the line 219.
  • the signal delay of the first IF will be less than that of the next IF.
  • FIG. 3 is a UML (Unified Modeling Language) sequence-like operatingdiagram of the operation of a portion of the circuit of FIG. 2. It illustrates the main parallel processes for the bottommost flow of the circuit of FIG. 2. As a non- limiting embodiment, only the case of operating with waveforms reconstruction is presented. This diagram can be implemented in hardware and/or in software.
  • the contents of the received frame with the MD identifier is sent to the wireless network frames RF/IF waveforms reconstructor (block 302).
  • the system determines (block 306) whether the frame is a Probe Request, and/or the MD is on the "Follow MD” list and/or is stored in the "TOAD demanded” 5buffer. Since it is, then a frame waveform or partial frame waveform reconstruction is prepared (block 308) and performed (310). Data regarding the MD is stored in the "Follow MD” and/or "TOAD demanded" identifiers buffer (block 304), and this information is used in (block 306).
  • the frame waveform is reconstructed for RF and/or IF and/or BF (block 310) lOand the system starts a TOA search by comparing waveforms (block 312). This is accomplished for BF, IF and RF frequencies by finding the best compared waveform in the appropriate buffer (block 314), as by means of wavelets or fractals. This waveform will be searched for in the RF, IF and/or BF buffers, where the corresponding digitized input data streams are stored, as described above.
  • the actually received waveform is found, and its TOA, MD identification and other parameters are prepared for sending out of the device. If the MD identification is also found in the "TOAD demanded" buffer (block 318), then the found actually received 0waveform is added to the output parameters (block 319).
  • FIG. 4 illustrates a general structure of a conventional 802.11 WiFi interface, according to the prior art. Most conventional WiFi interfaces and chipsets fit this diagram, which will be well understood by those skilled in the art.
  • FIG. 5 illustrates the general structure of a standard wireless 802.11 interface, modified in accordance with the present invention, to permit it to perform TOA and TOAD calculations and use them to perform location calculations and quality of signal calculations.
  • This interface is a combination of the prior art interface (FIG. 4) with the circuit of FIG. 2, and includes the following modifications.
  • a BF decimator 304 is provided, receiving data from the IF/BF converter (modem) via the BF ADC, and returning processed data to the baseband processor.
  • the ADC rate of a "standard" BF ADC may not be enough for TOA calculation purposes. For this reason, two ADCs, working in parallel (not shown), can be used - one with a rate needed for Baseband Processing and another with a rate needed for TOA calculation.
  • a single ADC 301 can be utilized with a decimator 304 coupled after it. The latter case is shown on FIG. 5.
  • the ADC rate is usually about 40 MSPS. This limits the location accuracy to 8-9 m. This may not be enough for Asset Assistance Tasks.
  • Line 311 is equivalent to line 219 on FIG.2 - the incoming wireless frames contents is received from a Medium Access Controller.
  • Line 312 is equivalent to line 220 of FIG.2.
  • Line 313 is equivalent to line 222 of FIG.2.
  • the bidirectional arrangement of lines 312 and 313 is typical for communications with a Bus Interface. Operation is substantially as described with regard to Fig. 3.
  • the frames contents from the MAC are introduced tothe wireless network frame RF/IF/BF waveforms reconstructor.
  • the reconstructed waveforms or/and partial waveforms or/and representations are sent to the signals comparator 308.
  • Frame sender identifier and the frame TOA and other results of block 308 are sent to the bus interface.
  • an AP capable of MD location can be implementedbased on a computer with some hardware superfluity.
  • a computer 400 To implement the invention on a computer, one needs: a computer 400, a GPS unit 402, an SDR set, which consists of a Radio Transceiver 404 and an ADC 406.
  • the invention is implemented on a base of a standard desktop/laptop/embedded computer.
  • the hardware superfluity is used to decrease the amount of new development by using a prior existing AP and Network Sniffer software.
  • TOA determination accuracy depends on signal lOfrequencies, sampling frequencies and details of the wireless standard.
  • the method of the invention can be implemented in real time. It can be implemented without a buffer or with a very small one, used to adapt the decimation and some time delays.
  • the implementation without a buffer in "a strange form" makes this patent very, very general.
  • AP ' receives the frame at time moment r * .
  • At - Atj t(- tibsoiute c ⁇ l) 5 where: absoiutemoand absoiutemu- "absolute exact time" of arrival of frame * at APs ' and J ;
  • the wireless network system described above is a non-limiting example having the capability to find actually received network frames waveforms and/or their abstract/ideal waveforms and/or capable of determining client position locationandVor time synchronization improvement. It is capable of locating the position of a MD in communication with a wireless network and to improve time synchronization of AP, as well as utilization of all or any other features of received network frames determined by the network device of the AP.
  • the system includes:
  • ⁇ a server (LS) which communicates with the APs throughout the network.
  • the antenna coordinates of the APs are known. All APs are synchronized in time.
  • the APs and MDs communicate using wireless communication signals, typically spread spectrum.
  • the server receives from the APs the measured TOA and MD identifiers and calculates the coordinates of the MD location.
  • waveforms of received frames are sent to the location server for determining the Time of Arrival Differences (TOAD).
  • TOAD Time of Arrival Differences
  • the TOAD of a frames sent by APs can be used to improve time synchronization of APs, as described above.
  • Each AP operates normally, i.e., receives network frames, decodes them and presents the received data (including contents) to all the required layers of the network protocols (see, for example, Fig. 4).
  • the system can be used to calculate TOAD. While location based on TOAD 0can be more accurate, the traffic to the location server will be larger. For TOAD, waveforms or/and their representations must be transferred.
  • TOA For TOA based location, only numbers (TOA, MD identifiers and some limited additional information) are required.
  • This limited “additional information” preferably includes the information that identifies a particular frame and, in case 5when parts of a frame are used, identification of those parts. The list of such information is easy to build and it is outside of this patent. However, it is important to mention that it is taken into account.
  • a MD rapidly sends frames one after another. To determine location of the MD, the TOA of the same frame must be measured by several APs. Sequential frames sent by the MD differ in some way, even if they are of the same type. This can be, for example, the time of sending of a frame by MD. Depending on the type of frame, there can be a list of such frame fields which can be used to identify the particular frame. It is important to underline that "time of sending 5and/or receiving" of the frame are not usable for location purposes, because they are not accurate.
  • FIGS 6a and 6b summarize the proposed invention method.
  • the method is implemented to actually received and completely decoded frames (1).
  • a wireless interface receives the frame as a radio signal (RF) which can be down banded to lOlower frequencies IF and BF.
  • RF radio signal
  • Those data streams are digitized and buffered (block 2).
  • ADCs providing sampling are synchronized by external precise synchronization signals. Synchronization signals are often, but not necessarily, presented by PPS (Pulse per Second) and ADC timing pulses series. This makes it possible to store digitized data streams indexed by time. As usual, the sampling rate must be not less
  • the buffer size can vary from relatively small for actually received waveform search algorithm like "Reconstructed Simplified Algorithm" to the length capable to store a maximum frame length plus frame processing delay plus time needed for frame information contents based reconstructions.
  • Block (4) implements the reconstructions selected by block (3).
  • the retrieved data can be used (block (10).
  • Mutual processing of Ideal/ Abstract reconstructions and Actual Received Data can be implemented.
  • FIG. 7 is a UML sequence-type operating diagram of a wireless network capable of using data supplied by device implementing the method of the present invention, in general, and of MD location, in particular. Several working in parallel objects are shown:
  • a mobile device with a Location Server installed on it (21). Such device must be connected to the network.
  • Access Points (30). For ease of description, only one is shown. In fact, there are a plurality of APs.
  • An AP can be an AP implementing the proposed method or a regular AP updated by a device implementing the proposed method, as described above.
  • each AP permanently runs means implementing proposed method. This not shown explicitly, as continuous process is considered to be an internal feature of AP (30). It is also preferred that the AP be able to process at least some frames from other APs.
  • servers (10) can be servers that were updated or replaced to have the capability to utilize the data supplied by the APs implementing the proposed method.
  • the Location Server (10, 20) must initiate the APs (30) with "Follow MD” and "TOAD demanded” parameters needed by theserver, messages (11, 21). It will be appreciated that the server can follow the movements of any mobile client. For a server located on a mobile client, the same is true. After initiation, the APs can operate with the servers.
  • Mobile devices (20) work in a normal way. When they need to, they transmit to the APs or broadcast frames (messages 41, 42).
  • Processing according to the proposed method will be carried out when the AP receives a frame suggested for signal on this AP according to the above described initialization. In the illustrated example, it's a "Probe Request” frame or any frame from a client whose identifier is in "Follow MD” configuration for this AP.
  • the AP send messages (31, 32, 33) to the Location Server (10) which, in this case, is a general network server (and not a server on a single mobile device).
  • Block (18) will gather a sufficient amount of TOADs for solving equations for Time Corrections and will solve them. The exact procedure of gathering sufficient amount of TOADs is not significant in the current example, as it depends on many factors and can be supported by some additional software. Block (18) will produce Time Corrections for the APs and accuracy estimations. Server (10)will prepare these results for sending (19). This can be placing the results in a Time Synchronization History Data Base and/or sending a message (110) to the appropriate APs with Time Corrections for those APs.
  • Messages (31, 32, 33) can be updated by those hosting any or all accessible results of the proposed method (ideal/abstract and actually received waveforms of frames or/and portions thereof or/and their representations or/and representations of their portions). Each such message will initiate a thread providing information for any/all additional system tasks like:
  • This use may include: determining Time of Arrival (TO A) of the waveforms of a network frame; determining Time of Arrival Differences (TOAD) of the waveforms of a network frame at different points of reception; mutual analyses of abstract/ideal waveforms and actually received waveforms or/and their representations for: analysis and improvement of functionality of network Access Points (AP); analysis and improvement of functionality of network clients; analysis and improvement of time synchronization of network components; analysis and improvement of functionality of the network system; analysis and improvement of functionality of a network system infrastructure; a wireless network system capable of using all the above, generally, and, in particular, for determining client position location and/or Access Points time synchronization improvement.
  • Another use of the present invention is to improve quality of signal.
  • the actual received signal is compared with the abstract/ideal signal and one can determine the way in which the environment influenced the packet.
  • This information can be sent to the controller managing the receiver to permit the receiver to decode later packets in 5 such a way as to counteract the effects of the environment, or to the server, which can move the client to a different access point.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Pour des trames de réseau reçues et décodées de façon complète, l'invention porte sur un procédé de localisation du début d'un signal reçu, consistant à stocker un flux de forme d'onde originale dans un tampon indexé temporellement, reconstruire une forme d'onde idéale sur la base du paquet reçu, sélectionner et/ou analyser une partie optimale de la forme d'onde reconstruite, en vue d'une utilisation de la partie sélectionnée dans une comparaison à la forme d'onde originale préalablement stockée, comparer les formes d'onde, ou des représentations de forme d'onde, reçue (stockée) et originale (idéale), et analyser de façon optimale les résultats en vue d'une utilisation dans un calcul d'instant d'arrivée (TOA) et/ou de différence d'instant d'arrivée (TOAD), une analyse de qualité de signal, une synchronisation temporelle AP.
PCT/IL2010/000725 2009-09-02 2010-09-02 Dispositif et procédé de calcul d'instant d'arrivée d'une trame dans un réseau sans fil WO2011027347A2 (fr)

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WO2014145073A1 (fr) * 2013-03-15 2014-09-18 Ruckus Wireless, Inc. Amélioration de la distribution de clients au sein d'un réseau
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US10171959B2 (en) 2004-11-05 2019-01-01 Arris Enterprises Llc Distributed access point for IP based communications
WO2014145073A1 (fr) * 2013-03-15 2014-09-18 Ruckus Wireless, Inc. Amélioration de la distribution de clients au sein d'un réseau
TWI642322B (zh) * 2013-03-15 2018-11-21 美商洛克斯無線股份有限公司 改良客戶在整個網路上之分佈的技術
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