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SPS-100 - IBMSPSSSTATL1P - IBM SPSS Statistics Level 1 - Dump Information

Vendor	:	IBM
Exam Code	:	SPS-100
Exam Name	:	IBMSPSSSTATL1P - IBM SPSS Statistics Level 1
Questions and Answers	:	70 Q & A
Updated On	:	December 1, 2017
PDF Download Mirror	:	SPS-100 Brain Dump
Get Full Version	:	Pass4sure SPS-100 Full Version

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SPS-100 Questions and Answers

True
False

Answer: A

QUESTION: 65

The Date and Time Wizard can be used to do which operation? (Select all that apply)

Create a date/time variable from a string variable containing a date and time.
Construct a date/time variable by merging variables containing different parts of the date or time.
Add or subtract values from date/time variables, including add or subtracting two date/time variables.
Extract a part of a date or time variable.

Answer: A, B, C

QUESTION: 66

The output generated from the EXPLORE procedure includes various measures of variability. Which of the following is not included in this output?

Median
Mode
Mean
Interquartile Range

Answer: A

QUESTION: 67

After reading from an Excel 2007 file, the data in IBM SPSS Statistics are as shown in the figure below. Inspect the file and select the answer.

The Data import was successful
The Data import was successful because IBM SPSS Statistics cannot Excel 2007 files.
The Data import was unsuccessful because the option Read variable names from the first row of data was not selected.
The Data import was unsuccessful because the Excel file was open the import to IBM SPSS Statistics was initiated.

Answer: C

QUESTION: 68

In order to import data from database sources such as Access and Oracle into IBM SPSS Statistics; you must first export data from the database to a text file and then import this text file into IBM SPSS Statistics?

True
False

Answer: B

QUESTION: 69

Suppose you want to get help on the Cumulative Percent column in a FREQUENCIES table. Using the figure below how would you do it?

Go to Help Topics and search for Cumulative Percent
Go ID Help Command Syntax Reference and search for Cumulative Percent
Go to Help About
Double-Click the table, right click Cumulative Percent and select What's this? from the pop-up menu.

Answer: B

QUESTION: 70

There are two major types of errors one can make when attempting to draw conclusions about the larger population based on the information collected in the sample. For example, when performing an independent sample T-Test, one type of error that can occur is when there are significant differences between the groups based on a scale level dependent variable, but the test fails to detect them. Which of the following choice describes this sort of error? (Select all that apply)

Type I error
Type II error
False negative
False positive

Answer: A

IBM SPS-100 Exam (IBMSPSSSTATL1P - IBM SPSS Statistics Level 1) Detailed Information

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Managing wireless transmissions upon unintentional disconnection of service

Title: Managing wireless transmissions upon unintentional disconnection of service.Abstract: Disclosed are a method, system and computer program product for managing unintentional disconnection of a communication device. A system detects a first device to a transmission has been unintentionally disconnected from an ongoing communication with a second communication device. The connected second device is signaled regarding the disconnection. Recording of a disconnection voicemail message for the disconnected first communication device is enabled before disconnecting the second communication device. The second device may set an expiration time on the disconnection voicemail message. Upon resumption of service, the disconnected first device is informed of a new voicemail message left by the second device during the disconnection. A disconnection-specific voicemail greeting may be recorded by a user of the disconnected first device's system for use when a disconnection occurs. The disconnection-specific voicemail greeting is played to the connected second device when disconnection occurs. ...
The Patent Description & Claims data below is from USPTO Patent Application 20100035583, Managing wireless transmissions upon unintentional disconnection of service.
BACKGROUND

- Top of Page

1. Technical Field
The present invention generally relates to telecommunications between wireless communication devices, and in particular to managing unintentional disconnection of a communication device from a transmission by at least one party.
2. Description of the Art
It is common with telecommunications, regardless of type, (e.g., VOIP, landline, cordless telephone, cellular telephone) for a party to be disconnected from the communications provider prematurely, ending an ongoing communication. Upon disconnection, both parties may attempt to reinitiate communications, or one party may wait for the other party to reinitiate communications. Sometimes, one party may be without wireless communication access for extended periods of time before communications may be reinitiated between the parties who were disconnected. Disconnections are commonly abrupt without prior explicit warning or communications degradation.
Current art methods require the participants in a wireless communication that is disconnected to reinitiate communications upon disconnection. This requires one party to reinitiate communications with the disconnected party. With most conventional implementations, if one party is without service at the time of reinitiation, the calling party will be transferred to voicemail of the receiving party.
SUMMARY

- Top of Page

OF ILLUSTRATIVE EMBODIMENTS
Disclosed are a method, system and computer program product for managing unintentional disconnection of a communication device. A system detects a first device to a transmission has been unintentionally disconnected from an ongoing communication with a second communication device. The connected second device is signaled regarding the disconnection. Recording of a disconnection voicemail message for the disconnected first communication device is enabled before disconnecting the second communication device. The second device may set an expiration time on the disconnection voicemail message. Upon resumption of service, the disconnected first device is informed of a new voicemail message left by the second device during the disconnection. A disconnection-specific voicemail greeting may be recorded by a user of the disconnected first device's system for use when a disconnection occurs. The disconnection-specific voicemail greeting is played to the connected second device when disconnection occurs.
The above as well as additional features and advantages of the present invention will become apparent in the following detailed written description.
BRIEF DESCRIPTION OF THE DRAWINGS

- Top of Page

The invention itself will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:
FIG. 1 is a block diagram of a service provider system configured with hardware and software components for implementing one or more embodiments of the invention;
FIG. 2 illustrates a diagram of a call switching center that manages voicemail communication between a disconnected first device and remaining connected devices to a transmission, in accordance with one embodiment of the invention;
FIG. 3 is a flow chart of a general process by which the features of the invention are implemented, according to one embodiment of the invention; and
FIG. 4 is a flow chart showing a more detailed example of the process by which the features of the invention are implemented, according to one embodiment of the invention.
DETAILED DESCRIPTION

- Top of Page

OF AN ILLUSTRATIVE EMBODIMENT
The illustrative embodiments provide a method, system and computer program product for managing unintentional disconnection of a communication device. A system detects a first device to a transmission has been unintentionally disconnected from an ongoing communication with a second communication device. The connected second device is signaled regarding the disconnection. Recording of a disconnection voicemail message for the disconnected first communication device is enabled before disconnecting the second communication device. The second device may set an expiration time on the disconnection voicemail message. Upon resumption of service, the disconnected first device is informed of a new voicemail message left by the second device during the disconnection. A disconnection-specific voicemail greeting may be recorded by a user of the disconnected first device\'s system for use when a disconnection occurs. The disconnection-specific voicemail greeting is played to the connected second device when disconnection occurs.
In the following detailed description of exemplary embodiments of the invention, specific exemplary embodiments in which the invention may be practiced are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, architectural, programmatic, mechanical, electrical and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
Within the descriptions of the figures, similar elements are provided similar names and reference numerals as those of the previous figure(s). Where a later figure utilizes the element in a different context or with different functionality, the element is provided a different leading numeral representative of the figure number (e.g, 145 for FIG. 1 and 245 for FIG. 2). The specific numerals assigned to the elements are provided solely to aid in the description and not meant to imply any limitations (structural or functional) on the invention.
It is understood that the use of specific component, device andor parameter names are for example only and not meant to imply any limitations on the invention. The invention may thus be implemented with different nomenclatureterminology utilized to describe the componentsdevicesparameters herein, without limitation. Each term utilized herein is to be given its broadest interpretation given the context in which that term is utilized.
While the embodiment to be subsequently described relates to cellular telephones, the principles of the invention would be applicable to any wireless personal communication device that could be used to communicate in a cellular or similar telecommunications system. These would include the wide variety of currently available communicating personal palm devices or Personal Digital Assistants (PDAs), which include, for example, devices using Microsoft\'s WinCE, Palm, .\'s Palm OS, and ACCESS\'s Garnet OS, or other such wireless communication device. Also, while the embodiment to be subsequently described relates primarily to voice transmissions, the embodiment may also apply to video transmissions, multimedia transmissions, and text transmissions. One embodiment of the invention may apply to wired communications.
With reference now to the figures, FIG. 1 depicts a block diagram representation of a service provider system (SPS). SPS 100 comprises at least one processor 110 connected to memory 106 via system interconnectbus 105. Memory 106 is defined as a lowest level of volatile memory (not shown), which may include, but is not limited to, cache memory, registers, and buffers. Also connected to system bus 105 is a storage database 152, comprising a voicemail mailbox 153 and a voicemail disconnect-specific greeting component 154 for a user\'s wireless communication device (not shown).
SPS 100 is also illustrated with a wireless transceiver 150 coupled to system bus 105. Wireless transceiver 150 enables SPS 100 to connect to and exchange communication with one or more wireless communication devices.
Those of ordinary skill in the art will appreciate that the hardware depicted in FIG. 1 is a basic illustration of a service provider system, and thus the hardware utilized in actual implementation may vary. Thus, the depicted example is not meant to imply architectural limitations with respect to the present invention. Also, components of the SPS 100 may be distributed components, not present in a single device or single casing. Also, while the illustrative embodiments are described from the perspective of functions occurring at the SPS 100, it is appreciated that various functions of the described embodiments may also be performed by the wireless communication device. This implementation is also covered by the scope of the invention.
Notably, in addition to the above described hardware components of SPS 100, various features of the invention are completed via software (or firmware) code or logic stored within memory 106 or other storage (e.g., storage database 152) and executed by a processor 110. In one embodiment, datainstructionscode from storage database 152 populates the memory 106. Thus, illustrated within memory 106 are a number of softwarefirmware components, including operating system (OS) 130, and Voicemail Transfer upon Disconnect (VTD) utility 145.
In actual implementation, VTD utility 145 may be a single, clustered, or distributed application providing the various functions of multiple individual software components when the corresponding code is executed by the processor 110. For simplicity, VTD utility 145 is illustrated and described as a stand alone or separate softwarefirmware component, which is stored in memory 106 to providesupport the specific novel functions described herein. A user connection monitoring and voicemail transfer (UCMVT) component 245 as depicted in FIG. 2 operates as a VTD utility 145 within the mobile communication infrastructure 222 as depicted in FIG. 2.
Processor 110 executes VTD utility 145 as well as OS 130, which supports the user interface features of VTD utility 145. In the illustrative embodiment, VTD utility 145 generatesprovides several graphical user interfaces (GUI) to enable user interaction with, or manipulation of, the functional features of the VTD utility 145. Among the software codeinstructions provided by VTD utility 145, and which enables features specific to the invention, are: (a) code for detecting a first communication device to a transmission has been unintentionally disconnected from an ongoing communication with a second communication device; (b) code for signaling the second communication device of the unintentional disconnection by the first communication device; code for enabling recording of a voicemail message to be left for the disconnected first communication device by the second communication device before disconnecting the second communication device; and (d) code for enabling pre-recording of a disconnection-specific voicemail greeting by the disconnected first communication device for use when a disconnection occurs during a later communication. For simplicity of the description, the collective body of code that enables these various features is referred to herein as VTD utility 145. According to the illustrative embodiment, when processor 110 executes VTD utility 145, SPS 100 initiates a series of functional processes that enable the above functional features as well as additional featuresfunctionality, which are described below within the description of FIGS. 2-4.
With reference now to FIG. 2, a diagram of a communication system is shown 200 in which a call switching component manages voicemail communication between a disconnected party and remaining connected parties to a wireless transmission. In FIG. 2, three users 204, 210, 216 are shown in communication with each other via their wireless or mobile communication devices 202, 208, 214, respectively. The communication device 202 of user A 204 is connected via a signal 206 to a mobile communication infrastructure 222. The communication device 208 of user B 210 is connected via a signal 212 to the same mobile communication infrastructure 222. However, the signal 218 between the communication device 214 of user C 216 and the mobile communication infrastructure 222 has been disconnected 220. User C 216 has unintentionally become disconnected from the communication between user A 204 and user B 210. In addition to detecting the communication device 220 has become disconnected due to signal loss, other means of determining an unintentional disconnection include: communication device 220 not transmitting an end call signal prior to disconnect, user not pressing an established key or key sequence to signify to a service provider purposeful disconnection, and the like.
A user connection monitoring and voicemail transfer (UCMVT) component 245 operates as a voicemail transfer upon disconnect (VTD) utility within the mobile communication infrastructure 222. The UCMVT manages wireless transmissions upon the unintentional disconnection 220 of the communication device 214 of user C 216. The communication device 214 of user C 216 is detected by the UCMVT 245 as being unintentionally disconnected from the telecommunications provider. The UCMVT 245 informs the remaining connected parties, e.g. user A 204 and user B 210, of the disconnection of user C 216. Users A 204 and B 210 are prompted, individually or as a group, regarding whether they would like to disconnect immediately, remain on the line, or leave a voicemail message for the disconnected party, i.e. user C 216, by being transferred to the 216 voicemail mailbox of user C 216.
In some embodiments, when a disconnection occurs, a user\'s voicemail system may play back an unintentional disconnection-specific voicemail greeting other than the standard voicemail greeting. User C 216 configures a disconnection-specific voicemail greeting to be played to remaining connected parties, e.g. user A 204 and user B 210 for use when a disconnection occurs during a later communication. The disconnection-specific voicemail greeting can be pre-recorded by user C 216, or automated at the UCMVT 245 component. In other embodiments, the standard voicemail greeting would be played. At the completion of the voicemail greeting play back, the disconnected user\'s (e.g., user C 216) voicemail mailbox records a voicemail message from a remaining connected party (e.g., either user A 204 or user B 210, or both). When the disconnected party (user C 216) is capable of resuming telecommunications service, the disconnected party (user C 216) can be notified of new voicemail left by the previously remaining connected parties (user A 204 and user B 210) using methods known in the art.
FIG. 3 is a flow chart illustrating one method by which the above process of the illustrative embodiments is completed. Although the method illustrated in FIG. 3 may be described with reference to components shown in FIGS. 1 and 2, it should be understood that this is merely for convenience and alternative components andor configurations thereof can be employed when implementing the method. Key portions of the method may be completed by VTD utility 145 executing within SPS 100 (FIG. 1) and controlling specific operations ofon SPS 100, and the method is thus described from the perspective of eitherboth VTD utility 145 and SPS 100.
The process of FIG. 3 begins at initiator block 302 and proceeds to block 304, at which a telecommunications or wireless telephone call is initiated between two or more parties. A determination is made at block 306 regarding whether a party to the telecommunication has become unintentionally disconnected from the transmission. If none of the parties have been unintentionally disconnected, the process repeats the determination step in block 306, until one of the parties is unintentionally disconnected. If one of the parties has been unintentionally disconnected, the remaining connected parties are informed of the unintentional disconnection of one of the parties, block 308. The remaining connected parties are given the option of leaving a voicemail for the disconnected party. A determination is made regarding whether one or more of the remaining connected parties elects to leave a voicemail message for the disconnected party, block 310. If none of the remaining connected parties want to leave a message for the disconnected party, the connected party\'s device is disconnected from the wireless transmission, block 314, and the process ends, block 316. If the remaining connected party elects to leave a voicemail message for the disconnected party, the disconnected party\'s voicemail system is invoked, and the connected party records a voicemail message for the disconnected party, block 312. Once the voicemail message has been recorded, the connected party is then disconnected, block 314, and the process ends, block 316. If the call is terminated at any point in the process, the process immediately ends, block 316.
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1

2 NEXT Generation in Data Acquisition Finally, a portable instrument that is truly compact and self-contained. Regardless of the application, you will appreciate how little equipment you will actually need to carry to the field. No laptop, PDA or breakout box, just a seismometer, cable, Taurus and battery. A complete seismograph you can hold in your hand The Taurus Digital Seismograph is a revolution in performance, capability and packaging in field portable seismographs. This small and lightweight hand-held instrument can directly interface with almost any sensor, record continuous data for over 800 days, and operate using a mere 750 mw. Taurus combines all the attributes of a stand-alone recorder with the benefits of Internet and wireless communication capabilities, and includes a high resolution 24-bit ADC, a precision GPS clock, and internal removable storage options with 1 to 40 Gbyte capacities. An integrated colour graphics display and a five-button keypad provide instant access to real-time or recorded data. Applications Broadband seismic studies Emergency networks Aftershock studies Strong motion studies Seismic networking over the Internet Controlled source recording Vibration monitoring Infrasound data acquisition Local site data storage in Libra networks Benefits Excellent quality data with 24-bit resolution and precise GPS timing Hand-held,all-in-one seismograph Long term deployments with over 800 day recording capacity Quick and convenient data retrieval using internal hot-swap media Real-time data streaming for network applications Real-time,historic and calibration data review at-a-glance Data output directly in industry-standard formats

3 TAURUS: Class-leading dyna A high dynamic range is essential in modern broadband data acquisition. Taurus is well-equipped with a Nanometrics proprietary sigma-delta digitiser providing 24-bits of resolution and a dynamic range of 138 db. Sampling is simultaneous on all channels and timing accuracy is sub millisecond with the GPS locked. (ACTUAL SIZE) Quick and convenient data retrieval using internal hot swap storage media Compact Flash and 1.8 ATA hard disk drive slots are standard on every unit. A watertight access door affords quick and easy access for fast media exchange in the field without interruption to data acquisition. Memory options can be selected as appropriate for environmental conditions and Compact Flash media can be purchased directly from local suppliers. Minimal power,maximum data availability Taurus has an impressively low power consumption of just 750 mw in a typical portable system configuration acquiring 3-channels at 100 sps. This significantly reduces the size of the solar panels and batteries required at any site. Users will appreciate the importance of low power consumption and increased reliability it is not uncommon for the Taurus to operate continuously from a 10 Ah battery and 18 W solar panel. Integrated display provides clear concise feedback Every Taurus includes a large colour graphics LCD display and a five-button keypad which provides direct access to various acquisition, monitoring, configuration and instrument status web pages. There is no guesswork or interpretation of LED sequences just concise instrument status messages and graphics. Familiar web browser interface for local or remote operation No special software is required to configure the Taurus or to display real-time waveform or state-of-health information. A familiar web browser provides onboard and remote access to the many interactive web pages which make up the Taurus interface. Real-time and historic data, GPS status, instrument configuration and field procedures are all richly presented on the large colour graphics display. Many of the html pages can be translated into other languages or edited to include customer workflow requirements for configuration, monitoring and data retrieval. Connects directly to all modern seismometers with single cable Taurus can interface directly with any modern broadband or short period sensor without the need for external breakout boxes or power supplies. Hardware and software gain are user-configurable via the browser interface, as are the sensor control lines for mass centering, cal enable, and lockunlock. Taurus will monitor the sensor mass position and center the masses as required, facilitating single visit deployments of broadband sensors. This is most important immediately after installation while the sensor is acclimatizing.

4 Taurus Data Management mic range and 24-bit resolution To excel in modern broadband data acquisition, a higher dynamic range is essential. Taurus is well-equipped with Nanometrics' proprietary Data output in industry-standard formats In addition to waveform data,taurus records the entire configuration history, all log file entries and status information data in a single project file or Store. Data is organized to facilitate the rapid review and retrieval of waveform, configuration and log file information. The Store contents can be reviewed using a web browser and data can be directly accessed in a number of international formats including miniseed, sorted miniseed, ASCII, SEISAN and SEG-Y. Real-time data streaming for network applications Taurus includes a wide range of physical interfaces and software protocols to support continuous real-time data streaming. Where network connections exist, real-time data streaming is available via UDPIP multicast and http over 10100Base-T Ethernet or the serial data port (SLIP). Optionally,Taurus data can be accessed through dial-up or wireless internet connections. New capabilities readily incorporated into Linux & Java based architecture Today s portable seismograph must operate unattended for long periods in remote areas, and seamlessly integrate with communications technologies such as VSAT, wireless and the Internet. To meet these challenges the Taurus architecture combines the versatility of the Linux operating system with modern Java applications while interconnecting with standard IP protocols over either Ethernet or serial interfaces. A winning combination designed to keep Taurus on the cutting edge for years to come.

5 TRIDENT Digitiser TheTrident 305 is a low-power, standalone, 3-channel, 24-bit analog-digital converter (digitiser) whose performance specifications are identical to the internaltaurus digitiser. Add-on expansion digitisers The Taurus supports 3-channel add-on Trident 305 digitisers expanding the total number of channels supported by a single Taurus from 3 to 6 or 9 channels. The Trident 305 settings (ex. gain, input impedance ) can be configured independently of the Taurus internal digitiser while making use of the Taurus for communications, GPS timing, data storage and power. Trident 305 connects to the Taurus via a simple twisted pair NMXbus cable which can be up to hundreds of meters in length. A TaurusTrident 305 combination makes an excellent 6 or 9 channel system. APOLLO Project Data management,simplified Apollo PROJECT is a server application which manages the time consuming and repetitive task of downloading large data sets from multiple Taurus recorders. The user defines the type of project: archive, one-time data request, trigger or controlled source. Apollo PROJECT locates the data, downloads the requested time series, combines the data into network files and outputs the data in the format of choice. There is no more convenient way to simultaneously manage large data sets from multiple Taurus instruments.

6 TAURUS Technical Specifications Specifications subject to change without notice. S E N S O R I N P U T S Channels 3 standard, field upgradeable to 6 or 9 with external Trident digitisers Simultaneous Selectable 2V, 4V, 8V, 16V, 40V peak-to-peak differential 1 countµv (gain=1) Sampling Input voltage range Nominal sensitivity Hardware gain selectable 0.4, 1, 2, 4, 8 Input impedance selectable 43k or high-z (> 9MΩ) D I G I T I S E R P E R F O R M A N C E Type Proprietary high order sigma-delta Digital filter 140dB attenuation at output Nyquist Filter type Linear phase (consult factory for other options) Dynamic range 100sps (max sine wave above shorted input) Shorted input noise 0.7µV RMS typical at 100sps, unity gain Sample rates 10, 20, 40, 50, 80, 100, 120, 200, 250, 500sps Software gain User configurable to 100 High pass filter User configurable to 1Hz S E N S O R S U P P O RT Sensor types Broadband active and short period passive Control lines 6; typically used for Cal enable, mass center, mass lockunlock, and XYZUVW select Logic level assert 0V, 512V, High-Z de-assert configurable Sensor power Supply power pass-through to sensor (9-36VDC, 1A). Over-current protected. Sensor power can be switched onoff from user interface. Auto mass centering Configurable delayed and immediate auto-centering mass position thresholds with configurable repeat interval and maximum retry limit. Serial interface Supports digital management of Nanometrics Trillium 120240 seismometers C A L I B R AT I O N O U T P U T Calibration signal Fully-configurable ramped sine wave, pseudo-random binary and pulse Calibration initiation User interface (local or remote) Calibration modes Voltage or current T I M I N G Timing system Timing accuracy GPS receiver GPS antenna Duty cycle selectable Internal DCXO clock disciplined to GPS <100µsec Internal 12 channel receiver External active antenna supplied with 5 m cable Auto-adaptive, always-on, 10 min, 30 min DATA R E T R I E VA L Media exchange Compact Flash and ATA drives are field swappable Download interfaces 10100Base-T Ethernet Data Download Direct connection or media exchange. Multiple Taurus with optional Apollo Project Data Management Software R E A L - T I M E DATA C O M M U N I C AT I O N S Interfaces 10100Base-T Ethernet, RS-232 serial Protocols UDPIP unicastmulticast HTTP (POST and GET) RS-232 serial with IP drivers I N T E G R AT E D U S E R I N T E R FA C E LCD display 240*320 colour graphics display with backlight Interface Integrated browser with five button navigation LED indicators System status tri-colour LED, Ethernet communications LED, Media status LED C O N F I G U R AT I O N Taurus is configurable locally via the colour LCD display and integrated browser or remotely using any web browser. Multiple unit configuration is achieved using optional group configuration software. Consult factory for further information. S O F T WA R E Operating system Applications software C O N N E C TO R S Sensor connector SerialUSB GPS Ethernet User SOH NMXBus Power USB Linux Nanometrics Apollo acquisition server with web interface 26-pin mil circular. Primary input and sensor SOH channels, sensor control lines, calibration signal outputs, protectedswitchable sensor power, digital serial sensor management interface 19-pin mil circular Serial port 1; Rx,Tx, RTS, CTS, DTR, DSR, CD, RI Serial port 2; Rx,Tx, RTS, CTS (data collection from serial devices) Serial peripheral power (pass-through supply voltage) USB master; Data, Pwr (5V, 100mA) TNC, active antenna connection (3.3V) 4-pin mil circular, 10100Base-T 7-pin mil circular, 4 analog SOH inputs and common reference, 10mA peripheral power 4-pin mil circular, NMXbus data and power 3-pin mil circular, 9-36VDC input USB masterslave accessible behind media door S TAT E - O F - H E A LT H R E C O R D I N G Taurus records extensive continuous state-of-health: Instrument and Power supply voltage Environment: Digitiser and controller current consumption NMX and serial port peripheral current consumption Temperature GPS timing and channel parameters 4 general-purpose SOH voltage inputs (12-bit) Configuration audit trail Software message and event log Sensor Port: Seismometer mass positions Current consumption I N T E R N A L DATA S TO R A G E Standard Removable Type III Compact Flash slot Removable 1.8 ATA disk drive slot Easily accessible via weatherproof media door P O W E R Power system Ultra-low power mode Low power Communications mode Configuration Protected electronic resettable fuse design with configurable low voltage disconnect and restart, reverse battery and short circuit protection V, 3-channel continuous 100 sps, <100 µsec timing precision, Compact Flash recording V; 3-channel continuous 100 sps, continuous serial data acquisition (external geodetic GPS or equivalent), <100 µsec timing precision, internal disk or Compact Flash recording. 2.3 W typical; 3-channel continuous 100 sps, <100 µsec timing precision, real-time Ethernet or serial communications 3.3 W typical. All systems operational including colour graphics display T H E F O L LO W I N G M E D I A O P T I O N S A R E AVA I L A B L E : Compact Flash 2 to 16 Gbyte; 1.8 ATA disk drive 40 Gbyte Duration >800 days continuous recording, 100 sps on 40 Gbyte ATA drive (>320 days on 16 Gbyte Compact Flash) Recording modes Continuous; write once or ringbuffer (overwrites oldest data). Continuous with STALTA trigger flags File system Journaling Linux system ext3, readable in Windows Storage format Nanometrics Store Direct data output MiniSEED, sorted MiniSEED,ASCII, Seisan, SEGY and Nanometrics NP formats E N V I R O N M E N TA L Operating temp. -20º C to +60º C using Compact Flash storage +5º C to +55º C using 1.8 ATA disk storage Storage temp. Altitude -40º C to +70º C No altitude limit with Compact Flash, -60 m to 3000 m with IDE disk drive Humidity 100% Weather resistance Full IP67 when closed and with optional connector caps Length 264 mm Width 147 mm Depth 60 mm Weight 1.8 Kg 250 Herzberg Road, Kanata, Ontario, Canada K2K 2A Fax:

Accuracy and performance of a hybrid positioning system

CROSS-REFERENCE TO APPLICATIONS This application is related to the following references:
U.S. patent application Ser. No. 12479,721, filed Jun. 5, 2009 and entitled “Systems and methods for Using Environmental Information in a Hybrid Positioning System;”
U.S. patent application Ser. No. 12479,722, filed Jun. 5, 2009 and entitled “Systems and Methods for Maintaining Clock Bias Accuracy in a Hybrid Positioning System;”
U.S. patent application Ser. No. 12479,723, filed Jun. 5, 2009 and entitled “System and Method for Refining a WLAN-PS Estimated Location Using Satellite Measurements in a Hybrid Positioning System;”
U.S. patent application Ser. No. 12479,724, filed Jun. 5, 2009 and entitled “Systems and Methods for Determining Position Using a WLAN-PS Estimated Position as an Initial Position in a Hybrid Positioning System;”
U.S. patent application Ser. No. 12479,727, filed Jun. 5, 2009 and entitled “Methods and Systems for Improving the Accuracy of Expected Error Estimation in a Hybrid Positioning System;”
U.S. patent application Ser. No. 12479,729, filed Jun. 5, 2009 and entitled “Methods and Systems for Stationary User Detection in a Hybrid Positioning System;”
U.S. patent application Ser. No. 12479,734, filed Jun. 5, 2009 and entitled “System and Method for Using a Satellite Positioning System to Filter WLAN Access Points in a Hybrid Positioning System;”
U.S. patent application Ser. No. 12479,718, filed Jun. 5, 2009 and entitled “Method and System for Determining Location Using a Hybrid Satellite and WLAN Positioning System by Selecting the Best WLAN-PS Solution;”
U.S. patent application Ser. No. 12485,588, filed Jun. 16, 2009 and entitled “Methods and Systems for Determining Location Using a Cellular and WLAN Positioning System by Selecting the Best WLAN PS Solution;”
U.S. patent application Ser. No. 12485,591, filed Jun. 16, 2009 and entitled “Methods and Systems for Determining Location Using a Cellular and WLAN Positioning System by Selecting the Best Cellular Positioning System Solution;”
U.S. patent application Ser. No. 12485,595, filed Jun. 16, 2009 and entitled “Methods and Systems for Improving the Accuracy of Expected Error Estimation in Location Determinations Using a Hybrid Cellular and WLAN Positioning System;”
U.S. patent application Ser. No. 12504,373, filed Jul. 16, 2009 and entitled “Systems and Methods for Using a Satellite Positioning System to Detect Moved WLAN Access Points;” and
U.S. patent application Ser. No. 12504,379, filed Jul. 16, 2009 and entitled “Methods and Systems for Determining Location Using a Hybrid Satellite and WLAN Positioning System by Selecting the Best SPS Measurements.”
BACKGROUND
1. Field
The present disclosure generally relates to hybrid positioning and more specifically, describes a new method to assess the quality of a set of satellite positioning system (SPS) measurements to be used for hybrid positioning. In order to do so, the disclosure proposes to use variations of clock bias at the receiver side to assess the quality of current set of satellites and their respective range measurements.
2. Description of the Art
Positioning using radio signals has attracted increasing attention in the field of location and tracking. The initial research studies on SPS resulted in a Global Positioning System (GPS) which was initially used for military applications and later broadly used for commercial and personal applications as well. The availability of SPS-based positioning has been a major factor in the introduction of Location Based Services (LBS) in advanced mobile communication devices such as smartphones. By determining the position of the receiver, the system is able to provide more effective and more appropriate services to the user.
The Navstar Global Positioning System (GPS) operated by the US Government leverages about two-dozen orbiting satellites in medium-earth orbits as reference points. A user equipped with a GPS receiver can estimate his three-dimensional position (latitude, longitude, and altitude) anywhere at any time within several meters of the true location as long as the receiver can see enough of the sky to have four or more satellites “in view.” Cellular carriers can use signals originating from and received at cell towers to determine a user's or a mobile device's location. Assisted GPS (AGPS) is another model that combines both GPS and cellular tower techniques to estimate the locations of mobile users who may be indoors and must cope with attenuation of GPS signals on account of sky blockage. In this model, the cellular network attempts to help a GPS receiver improve its signal reception by transmitting information about the satellite positions, their clock offsets, a precise estimate of the current time, and a rough location of the user based on the location of cell towers. No distinction is made in what follows between GPS and AGPS.
All positioning systems using satellites as reference points are referred to herein as Satellite-based Positioning System (SPS). While GPS is the only operational SPS at this writing, other systems are under development or in planning A Russian system called GLONASS and a European system called Galileo may become operational in the next few years. All such systems are referred to herein as SPS. GPS, GLONASS and Galileo are all based on the same basic idea of trilateration, i.e., estimating a position on the basis of measurements of ranges to the satellites whose positions are known. In each case, the satellites transmit the values of certain parameters which allow the receiver to compute the satellite position at a specific instant. The ranges to satellites from a receiver are measured in terms of the transit times of the signals. These range measurements can contain a common bias due to the lack of synchronization between the satellite and receiver (user device) clocks, and are referred to as pseudoranges. The lack of synchronization between the satellite clock and the receiver (user device) clock can result in a difference between the receiver clock and the satellite clock, which is referred to as internal SPS receiver clock bias or receiver clock bias. In order to estimate a three dimensional position there is a need for four satellites to estimate receiver clock bias along with three dimensional measurements. Additional measurements from each satellite correspond to pseudorange rates in the form of Doppler frequency. References below to raw SPS measurements are intended generally to mean pseudoranges and Doppler frequency measurements. References to SPS data are intended generally to mean data broadcast by the satellites. References to an SPS equation are intended to mean a mathematical equation relating the measurements and data from a satellite to the position and velocity of an SPS receiver.
WLAN-based positioning is a technology which uses WLAN access points to determine the location of mobile users. Metro-wide WLAN-based positioning systems have been explored by several research labs. The most important research efforts in this area have been conducted by the PlaceLab (.placelabm, a project sponsored by Microsoft and Intel); the University of California, San Diego ActiveCampus project (ActiveCampus—Sustaining Educational Communities through Mobile Technology, technical report #CS2002-0714); and the MIT campus-wide location system. There is only one commercial metropolitan WLAN-based positioning system in the market at the time of this writing, and it is referred to herein as the WPS (WiFi positioning system) product of Skyhook Wireless, (.skyhookwirelessm).
SPS is based on triangulation (trilateration) using multiple distance measurements from multiple satellites. The receiver measures its distance from at least four satellites. Based on the distance measurements, the receiver solves a set of quadratic equations including, coordinates of the receiver, and, receiver clock bias. In order to quantify the accuracy of the location estimate (quality of estimate of the reported location,) SPS systems use several metrics such as Dilution of Precision (DOP0). (Indices, like index 0, are used to differentiate different DOP definitions here). Widely used in literature, the geometry of the set of visible satellites, indicated by DOP0 metric, is assumed to have correlation with estimated location error. In other words, DOP0 relates the geometry of the satellites to the quality of the location estimate.
In hybrid positioning, the IEL of the receiver is estimated by using a method other than SPS (such as Wireless Local Area Network-based Positioning System or WLAN-PS). The results are then refined once SPS signals are acquired. In current hybrid positioning systems, a 3-D region is constructed centered on the IEL. The size of this 3-D region is related to the accuracy of the estimated location (IEL). Then the positioning system searches through all the possible locations inside the region and selects the location with minimum SPS receiver clock bias variations (Hybrid positioning systems are disclosed in the following commonly used application, the entire contents of which are hereby incorporated by reference: U.S. patent application Ser. No. 12479,718, filed Jun. 5, 2009 and entitled “Method and System for Determining Location using a Hybrid Satellite and WLAN Positioning System by Selecting the Best WLAN-PS Solution;” U.S. patent application Ser. No. 12485,588, filed Jun. 16, 2009 and entitled “Method and Systems for Determining Location Using a Cellular and WLAN Positioning System by Selecting the Best WLAN PS Solution;” U.S. patent application Ser. No. 12485,591, filed Jun. 16, 2009 and entitled “Methods and Systems for Determining Location Using a Cellular and WLAN Positioning System by Selecting the Best Cellular Positioning System Solution;” and U.S. patent application Ser. No. 12485,595, filed Jun. 16, 2009 and entitled “Methods and Systems for Improving the Accuracy of Expected Error Estimation in Location Determinations Using a Hybrid Cellular and WLAN Positioning System.”). The concept is summarized in FIG. 1, as described below. In current hybrid positioning systems, all visible satellites are used to refine IEL. However, some satellites experience multipath and their range estimates are too inaccurate for use in hybrid positioning. Therefore, there is a need for methods to assess the quality of set of current measurements and detect satellites with erroneous range estimates so the system can remove them from location estimation.
It is also possible for the hybrid positioning system to receive a set of SPS signals which are pointing the system very far from the location obtained in the initial estimate. In such cases, SPS measurements might be consistently close to one another, but the overall SPS result might be very different from initial location. In such cases, there is a need to detect the discrepancies between the IEL and the SPS-refined location estimate.
The current hybrid positioning systems use the location with absolute minimum SPS receiver clock bias variation and neglects all the other locations in the region with similar SPS receiver clock bias characteristics. An optimal result can be achieved if one combines results of all the locations with similar SPS receiver clock biases. In such cases, there is a need for an algorithm to combine such locations and obtain a final location.
The conventional methods perform the task of searching through all three dimensions of the region's grid-locations one by one (referred to as 3D-search) and computing the SPS receiver clock bias for each location and then selecting the point with minimum SPS receiver clock bias variation, as illustrated in FIG. 1. In such cases, there is a need for an algorithm to perform a faster search and obtain the final location faster.
SUMMARY
The following description describes a method in hybrid positioning systems to remove satellites with erroneous range estimates from the process of estimation of receiver location. The remaining satellites can then be used to estimate the location of the receiver by the hybrid positioning system which results in more accurate results. Once hybrid positioning system decides on using SPS measurements to refine the IEL, the disclosure describes a method to obtain a more accurate final location estimate using an aggregate of locations with sufficiently small SPS receiver clock bias variation. The following description also describes a method in hybrid positioning to assess the quality of current set of satellites and remove a set of satellites with erroneous range estimate from the process of location estimation. The outcome of the process will determine if the IEL should be used for positioning the receiver location or SPS reported location. The following disclosure also describes a method in hybrid positioning to obtain a faster and relatively more accurate final estimate of the receiver location using two-dimensional searches (referred to as 2D-searches) in each XY, XZ, and YZ planes and combining the results of each of 2D-searches to find the final estimate of the receiver location. The present disclosure also relates to hybrid positioning and more specifically, describes a new method to refine the initial estimated location (IEL) and obtain an improved estimate of the receiver location. In order to so, the method includes a proposal for the removal of satellites with erroneous range estimates from the current set of visible satellites.
In one aspect, the present disclosure relates to a method of determining the position of a WLAN positioning system (WPS) and satellite positioning system (SPS) enabled device including determining an initial WPS position of the device using WPS, calculating an error region around the initial WPS position of the device, dividing the error region into a plurality of points, obtaining satellite measurements from at least two satellites in view of the device, determining a variation in a receiver clock bias for each point within the error region based on the satellite measurements from at least two satellites, selecting the point with the lowest variation in the receiver clock bias, and determining whether or not to use the point with the lowest variation in receiver clock bias to refine the initial WPS position of the device.
In one embodiment, determining whether or not to use the point with the lowest variation in receiver clock bias to refine the initial WPS position of the device includes rejecting the point with the lowest receiver clock bias variation if the point is located on an edge of the error region. In some embodiments, determining whether or not to use the point with the lowest variation in receiver clock bias to refine the initial WPS position of the device includes rejecting the satellite measurements if the region displays monotonicity. In some embodiments, determining whether or not to use the point with the lowest variation in receiver clock bias to refine the initial WPS position of the device includes rejecting a point having a large variation in receiver clock bias. In some embodiments, a large variation in receiver clock bias can include 20 and greater.
In one embodiment, the method includes evaluating the accuracy of individual satellite measurements in order to lower the variation in the receiver clock bias for a set of satellites, and wherein the number of satellites is greater than two. In one embodiment, evaluating the accuracy of individual satellite measurements includes: grouping the satellites into sub-groups of two or more satellites, determining a variation in receiver clock bias for each of the sub-groups, comparing the variation of receiver clock bias in the sub-groups to select a sub-group with a minimum SPS receiver clock bias variation, and determining an individual satellite measurement with an inaccurate receiver clock bias estimate as the satellite which was excluded from the sub-group selected in the previous step. In one embodiment, the method includes determining a minimum value of the receiver clock bias, determining a maximum value of the receiver clock bias, determining a median value of the receiver clock bias, comparing the difference between the minimum value and median and maximum value and median and selecting the larger of these two differences, and determining an individual satellite measurement with an inaccurate receiver clock bias estimate as the satellite which corresponded to the larger selected value in the previous step.
In one embodiment, the method includes discarding satellite measurements from satellites that have inaccurate receiver clock bias estimates. In one embodiment, determining whether or not to use the point with the lowest variation in receiver clock bias as a refined estimate of the initial WPS position of the device includes accepting a point having a small receiver clock bias. In one embodiment, a small variation comprises a value between 0 and 5. In one embodiment, the method includes determining that the WPS position is a final location of the device if no minimum of receiver clock bias variation exists in the error region. In one embodiment, the method includes determining that the WPS position is a final location of the device if value of SPS receiver clock bias was large. In one embodiment, the satellite measurements are obtained from at least three satellites. In one embodiment, the satellite measurements are obtained from more than three satellites.
In another aspect, the present disclosure also relates to a method for determining the position of a WLAN positioning system (WPS) and satellite positioning system (SPS) enabled device including determining an initial WPS position of the device using WPS, calculating an error region around the initial WPS position of the device, dividing the error region into a plurality of points, obtaining satellite measurements from at least two satellites in view of the device, determining a variation of a SPS receiver clock bias for each point within the error region based on the satellite measurements from at least two satellites, selecting a group of points with the lowest variation in the receiver clock bias, and determining a new refined position based on the group of points, wherein the refined location is computed as an average of all the group of points wherein the refined location is computed as a weighted average of all the aggregate points.
In one aspect, the present disclosure also relates a method for to determining the position of a WLAN positioning system (WPS) and satellite positioning system (SPS) enabled device including determining an initial WPS position of the device using WPS, calculating an error region around the initial WPS position of the device, dividing the error region into three planes including an x-y plane, a x-z plane, and a y-z plane, determining a point in each plane with the lowest value of receiver clock bias, and determining a final location of the device by averaging the points in each plane with the lowest value of receiver clock bias.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of various embodiments of the present invention, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:
FIG. 1 is a flow chart describing the basic operation of a hybrid positioning system, according to one embodiment of the present disclosure;
FIG. 2 represents a simple scenario where hybrid positioning system can use SPS signals to improve the accuracy of the IEL. IEL is provided by WLAN-based positioning system and satellite signals from two satellites are used to refine IEL;
FIG. 3 is a graphical representation of a single surface demonstrating a single z-plane for cases of bad satellite information, according to one embodiment of the present disclosure;
FIG. 4 is a graphical representation of multiple surfaces demonstrating the entire region and their respective SPS receiver clock bias for cases of bad satellite geometry, according to one embodiment of the present disclosure;
FIG. 5 is a color-coded graphical representation of a region to indicate the location of the location with minimum SPS receiver clock bias for cases with bad satellite geometry, according to one embodiment of the present disclosure;
FIG. 6 is a graphical representation of a single surface demonstrating a single z-plane for cases of good satellite information, according to one embodiment of the present disclosure;
FIG. 7 is a graphical representation of multiple surfaces demonstrating the entire region and their respective SPS receiver clock bias for cases of good satellite geometry, according to one embodiment of the present disclosure;
FIG. 8 is color-coded region to indicate the position of the location with minimum SPS receiver clock bias for cases with good satellite geometry, according to one embodiment of the present disclosure;
FIG. 9 depicts a two dimensional averaging method, according to one embodiment of the present disclosure.
DETAILED DESCRIPTION
The following disclosure relates to systems and methods for evaluating the quality of either a set of satellites or individual satellites in a hybrid positioning system. The quality of the set satellites is evaluated using receiver clock bias. In that capacity, a high quality set of satellites is the one that satellites show consistency in predicting receiver clock bias. For that matter, all the estimations of receiver clock bias from different satellites should be close to one another. On the other hand, a bad quality set of satellites is the one that shows large variations when receiver clock bias is estimated for all satellites. In order to determine receiver clock bias for each satellite, the WLAN positioning system, in the hybrid system, provides an IEL and a region of error around that IEL. The shape and size of the region of error is based on IEL and its accuracy and hence this region relates to the quality of the IEL measurement (QoS). The IEL and the region of error create what will be referred to as the region. The region provides a set of locations where the receiver can be located, i.e., the receiver could be located at any point within the region. In the following paragraphs, the word variation is used to illustrate any measure of disparity between the taken measurements or elements of a vector. As an example of this disparity we have used variance in some of our calculations. Other means of variation such as range between the values can also be used in this approach.
By using each point in the region as an initial location, the receiver clock bias for each satellite at each location can be determined. This results in an array of values for estimates of receiver clock bias for each location inside the region. From these determinations, the variance of the receiver clock bias for each location inside the region can be calculated. This variation in the receiver clock bias can be used to eliminate low quality satellite measurements. For a high quality set of satellites this variation is small and for a low quality set of satellite this variation is large. In principle, if a satellite or several satellites are providing erroneous information, the estimate of the receiver clock bias for those satellites is very different from the other satellites and hence we see large variations when we examine the array of receiver clock bias estimates.
In another embodiment, the variation in the receiver clock bias among all visible satellites for each location can be calculated. The locations with the smallest variation in receiver clock bias can be selected. Those selected locations are then averaged to determine a final location of the receiver.
In another embodiment, the searching of the region for the points with the lowest variation in receiver clock bias is simplified by using a two dimensional method instead of a three dimensional method.
Generally, in such hybrid positioning systems, the final reported location can be one of the following;

1) IEL along with its quality estimate (“QoS”);

2) SPS reported location when four or more satellites are visible along with its quality estimate; or

3) A combination of IEL and SPS reported locations.

In the process of location determination using SPS only, the receiver receives raw SPS range measurements and satellite information from satellites in the view of the receiver. Using the range measurements and satellite information of four or more satellites, the receiver solves a set of quadratic equations for the location and the SPS receiver clock bias. Because the same receiver receives all of the satellite information, the SPS receiver clock bias for all the satellites should be the same.
If the SPS location could not be determined or its expected error exceeded its threshold, i.e. poor QoS, the positioning system will look into IEL (reported by a method other than SPS, for example, WPS). If the IEL had sufficiently small expected error, i.e. acceptable QoS, the hybrid positioning system reports IEL as the final location. Otherwise, the system uses the SPS signals to refine the IEL. In the refinement process, the positioning system constructs a 3D region around IEL and searches all the locations in that region for a location with minimum SPS receiver clock bias variation. This location with minimum SPS receiver clock bias variation is the best estimate of the true location inside the region. This process is illustrated in FIG. 1. In FIG. 1, satellite positioning system (SPS) 100 provides satellite information to hybrid positioning system 102. Wireless LAN positioning system (WLAN-PS) 101 provides an IEL. The hybrid positioning system 102 collects the inputs from SPS and WLAN-PS and attempts to improve the precision of the IEL by providing a better estimated location with better accuracy. In 103, the hybrid positioning system checks if SPS has provided an estimated location. If a location was provided by SPS and its accuracy fulfills the requirements set in hybrid positioning system (in 104), the hybrid positioning system reports the SPS location in 105. If a location was not provided by SPS or if its accuracy was not met by the standards set by the hybrid positioning system, hybrid positioning system checks if there is an IEL 106. If no location was provided through IEL as well, the hybrid positioning system reports no location 107. If the IEL was provided, the hybrid positioning system checks to see if the accuracy of the IEL is acceptable 108. If it was acceptable, system reports the IEL as its reported location 109. If the IEL accuracy is unacceptable, the system constructs a region around the IEL 110. For each location inside the constructed region, the hybrid positioning system then finds all the estimates of receiver clock bias and calculates the variance of this set 111. The system then selects the location with minimum variance as its best estimated location within the region 112 and reports it to the interface 113. In perfect scenarios, all the estimates of SPS clock bias are equal so their variance is zero. However, in realistic scenarios this variation is not zero, but it is preferred for the hybrid positioning system to have very small variations for the estimate of SPS receiver clock bias.
The embodiments of this disclosure propose to relate the variations of the SPS receiver clock bias to the quality of the current set of satellites. In order to do so, the disclosure proposes to analyze the SPS receiver clock bias variations for all the locations inside the region specified by IEL and its QoS. The definition of such region can simply start from a sphere with its center on IEL and radius equal (or directly proportional) to QoS and extend to a complex shape around IEL. For all the locations inside this specified region, the hybrid positioning system calculates the variation of the SPS receiver clock bias and selects the location with minimum variation of the SPS receiver clock bias. Based on the value of the location and its position relative to the region, the hybrid positioning system can assess the quality of the current set of satellites to be used in hybrid positioning.
The process of calculating the variation of SPS receiver clock bias starts with estimating the receiver clock bias corresponding to each satellite in the set. Ideally, all the receiver clock biases should be equal. However, in practice, the estimates of receiver clock bias can be different. Then the variation of the estimates can be used to illustrate how far the receiver clock bias estimates are apart. In the case of a large variation of the SPS receiver clock bias, the hybrid positioning system detects discrepancies between the IEL and SPS signals and can reject the use of SPS signals in the hybrid positioning. Alternatively, the relative position of the grid-location with minimum variation inside the region can be used to assess the quality of the SPS signals. If the location with the minimum variation is on the boundary of the defined region, the positioning system can reject the use of SPS signals in hybrid positioning.
As an example, in a hybrid positioning system consisting of an SPS and a WLAN-PS, the WLAN-PS reports an IEL with its expected error, QoS. The hybrid positioning system then has to check if an SPS location is reported. If the SPS location is provided and the SPS expected error is sufficiently small, i.e. an acceptable QoS—for example values of error less than 50 meters, the hybrid positioning system reports the SPS location. If the SPS location is not provided or its expected error exceeds the threshold, i.e. poor QoS, the hybrid positioning system checks the IEL reported by WLAN-PS and its expected error. If the IEL's expected error is sufficiently small, i.e. acceptable QoS—for example values less than 100 meters, the hybrid positioning system reports IEL as the final location. Otherwise, the positioning system uses SPS satellite information and range measurements to refine the IEL and improve the accuracy of the location estimation (in terms of QoS).
In order to assess the quality of current set of satellites in such hybrid positioning systems, the hybrid positioning system constructs a region centered on IEL. The region spans over x, y, and z axes. FIG. 2 represents such scenario. Satellites 200 provide satellite information which can be used in hybrid positioning system to refine the IEL 201. The IEL is provided by WLAN-PS and it is used to construct region 203 around it by hybrid positioning system. The refined location 202 is calculated after the hybrid positioning system uses the satellite information to improve the accuracy of the IEL. The hybrid positioning system then evaluates the variations of SPS receiver clock bias for all the locations inside the region. For each location inside the region, the hybrid positioning system finds all the estimates of the SPS receiver clock bias from all the satellites and catalogs them in an array. The system then finds the variation of the set by comparing the estimates to check how close or how far the SPS receiver clock bias estimates are. The system then selects the location with the minimum SPS receiver clock bias variation. Based on the value and location of the minimum SPS receiver clock bias variation, the hybrid positioning system decides if it should use the SPS information and range measurements to refine the IEL and report the location with minimum SPS receiver clock bias variation. Values between 0 and 5 can be considered as good, while values more than 20 should be rejected. In the case of a large variance of SPS receiver clock bias andor large distance between the location with minimum variation and the IEL, the hybrid positioning system detects discrepancies between the IEL and the SPS signals and hence rejects the use of SPS signals in hybrid positioning.
For the example of the hybrid positioning system including a WLAN-PS and a SPS, the hybrid positioning system can construct a region centered on IEL (reported by WLAN-PS) using grid locations on different axes. Then for each location inside the region (which are referred to as grid locations), the hybrid positioning system can evaluate the variation of SPS receiver clock bias using
τ _ rms = 1 N ⁢ ∑ i = 1 N ⁢ ⁢ ( τ i - τ _ ) 2 ⁢ ⁢ where ⁢ ⁢ τ _ = 1 N ⁢ ∑ i = 1 N ⁢ ⁢ τ 1is the unbiased sample mean of SPS receiver clock bias and τi is the estimate of SPS receiver clock bias from the i th satellite. For example, if for a specific location with four satellites in view the system found SPS receiver clock biases from different satellites to be [10000 10010 10500 9500], the system first finds the average of the set which is 10002.5. Then each element is subtracted from the average and squared which results in [6.25 56.25 247506.25 252506.25]. Then the system sums all the resulted values to get 500075 and the final value for variation is the square root of 500075 divided by number of satellites which gives us. 176.78. This value is high. Therefore, these satellites would not be used for positioning.
FIG. 3 illustrates such variations for an assessment of the quality of SPS measurements. The Figure represents the values of SPS receiver clock bias for different values of x-axis and y-axis coordinates for a fixed z-value (different from figure's z-axis which shows the value of SPS receiver clock bias).
The large values of the z-axis (which show variations of SPS receiver clock bias) and its monotonic shape for the entire plane prove that for this case the SPS receiver clock bias variation was large and SPS measurements were not in agreement with the IEL.
For the purpose of illustration, we divided the region into different z-planes and sketched the various values of SPS receiver clock bias versus x and y axes. For all the z-planes, and consequently the entire region, we can sketch all the surfaces on top of each other, which will look like FIG. 4. Again, it can be seen that for all z-planes, the shape of the SPS receiver clock bias variation is monotonic as it does not have any minimums on its local surface and values of SPS receiver clock bias variation are large. Therefore, it can be concluded that a local minimum for SPS receiver clock bias variation could not be obtained and hence, the current set of SPS measurements are not in agreement with the IEL.
It is worth mentioning that monotonicity of the clock variation cannot be observed by simply looking at the minimum value of SPS receiver clock bias. Hence, the above-mentioned analysis allows the hybrid positioning system to determine if monotonicity of clock variation exists and hence rejects the current set of satellites.
In order to automate the process for mobile computing devices, we propose the following approach to detect the monotonicity by analyzing the variations of SPS receiver clock bias. Similar to the above methods, we form a region around the IEL and for each location we find the SPS receiver clock bias variance as described above. Then we find the minimum of all the locations' variations and choose the one with the absolute minimum value. If the minimum falls on the edges of the region, as indicated by FIG. 5, this will lead us to the fact that SPS receiver clock bias variation was a monotonic function and could not converge to a point inside the region. It should be noted that figures such as FIG. 5 are color coded to show the value of SPS receiver clock bias. Darker colors illustrate smaller variances for SPS receiver clock bias and consequently better estimates of the receiver location. In this case, the darkest location fell on the edge of the region and hence was rejected.
Through this method, low quality SPS measurements can be rejected. By detecting if the minimum point is on the edge, we can then declare that the received set of SPS measurements are of poor quality and their range measurements are erroneous; hence they cannot be used for hybrid positioning. For minimums that are located on the edge of the region, their value as a true minimum are untrustworthy. This is because only the interior of the region is searched. If the true minimum location was located two kilometers away from the region the location on the edge will be reported to be the minimum. For this reason we have to exclude all the locations that are on the edge.
On the other hand, if the hybrid positioning system is able to find a location inside the region, the result will look similar to FIGS. 6-8. FIG. 6 illustrates variations of GPS receiver clock bias for an example of location with minimum variation. The Figure represents the values of SPS receiver clock bias for different values of x-axis and y-axis coordinates for a fixed z-value (different from figure's z-axis which shows the value of SPS receiver clock bias). The dark parts of the graph (which corresponds to the trough part of the graph) illustrate all the receiver location with close to minimum GPS receiver clock bias variation. It demonstrates that when the surface is not monotonic and has minimum values inside the box, those locations can be used for hybrid positioning. The same concept can be observed in FIG. 7 where several surfaces are illustrated together. The existence of the minimum 700 assures the system that system using SPS can find a better estimate of the location than just using the IEL alone. Hence it can provide a good estimate of the refined position of the end-user. In FIG. 8, it is possible to see that the darkest location 800 is inside the region. This darkest location is a minimum for the surface and the system from this minimum one can conclude that there exists at least one grid-location inside the region that can satisfy the variance requirement of the system.
Other embodiments of this disclosure describe a new technique in an integrated hybrid positioning environment, including an initial estimated location (IEL) along with its expected error, i.e. QoS, and SPS satellite information and range measurements, to remove a satellite from the current set of visible satellites to improve the accuracy of the location estimation. In order to do so, the invention relates the variations of SPS receiver clock bias estimate of the current set of satellites to the quality of estimated location.
As described above, in order to assess the quality of SPS measurements, the hybrid positioning system constructs a region centered on the IEL, calculates the variations of SPS receiver clock bias for all the locations inside the region, and selects the location with minimum variation.
The hybrid positioning system then compares this minimum variation of SPS receiver clock bias to its threshold. If sufficiently small, the current set of satellites can be used for positioning. The threshold value is a function of the QoS, i.e. expected error, of the SPS and IEL and level of desired accuracy. For more accurate applications, the system can set the threshold to smaller values. One example of the threshold values is 5 when the values are described in meters. Values between 0 and 5 are acceptable, while more than 20 should be rejected.
In the case of a large variance, we propose that the positioning system can check the subsets of the current visible satellites for the same defined region and remove the satellite which causes the large variation, i.e. the satellite with most inaccurate SPS receiver clock bias estimation. In order to do so, the positioning system forms different subset combinations. Similar to the general case, for each subset combination the positioning system finds the value of the minimum SPS receiver clock bias within the specified region.
The combination with smallest SPS receiver clock bias variation then can be chosen as our preferred set of satellites and the satellite which was excluded from that set can now be safely removed from the positioning algorithm. The resulting set of satellites then can be examined for further improvement using the same method. The process is repeated several times until the resulting set of satellites shows a consistent SPS receiver clock bias, i.e. very small variations, or only two satellites remain in the set. If the faulty satellite is removed, the resulting set of satellites will exhibit a smaller SPS receiver clock bias variation. The process is explained below.
For example, assume we have a set of N satellites, (S1, . . . , SN), we denote the estimated SPS receiver clock bias variation of this set as
τ _ rms = 1 N ⁢ ∑ i = 1 N ⁢ ( τ i - τ _ ) 2 ⁢ ⁢ where ⁢ ⁢ τ _ = 1 N ⁢ ∑ i = 1 N ⁢ τ iis the unbiased sample mean of SPS receiver clock bias and r is the estimate of SPS receiver clock bias of the i th satellite by the receiver.
We start with combination (S1, . . . , SN-1) and find its SPS receiver clock bias,
τ _ rms i ∈ { 1 , N } - { i = N } .we repeat the process for different combinations of N−1 satellites out of N satellites and acquire a set of
τ _ rms i ∈ { 1 , N } - { i = I } ⁢ s .We can then select the set with minimum
τ _ rms i ∈ { 1 , N } - { i = I }as the best possible set of satellites.
We then conclude that the I th satellite, SI, is satellite with the most inaccurate estimate of SPS receiver clock bias and can be removed from the set of visible satellites in order to improve the accuracy of the estimate of SPS receiver clock bias and ultimately to improve the accuracy of the estimation of the end-user location.
By removing the most inaccurate satellite from each set, we can improve the estimate of the SPS receiver clock bias. The process can be repeated until the SPS receiver clock bias variation is sufficiently small to ensure the needed consistency for location determination or there are only two satellites remaining Values of receiver clock bias variance between 0 and 5 can be acceptable.
Another embodiment of the disclosure describes a different method to assess the quality of the current set of satellites and to remove a satellite with the most inaccurate SPS receiver clock bias estimate from the current set. The embodiments use statistical parameters obtained from a set of receiver clock bias estimates to find and remove a satellite with an erroneous receiver clock bias estimate. In order to do so, the embodiments propose to analyze the set of receiver clock bias estimates and pick one which is an outlier to the current set and remove the corresponding satellite from the current set of satellites. This statistical analysis can be performed on any location within the defined region around IEL. This method reduces the computational cost of searching through all possible subsets of a set of SPS measurements.
Assume we have N satellites with estimates of SPS receiver clock bias estimates of (τ1, . . . , τN). The estimate of the SPS receiver clock bias is then calculated with a sample mean as follows;
τ ^ = 1 N ⁢ ∑ i = 1 N ⁢ τ i
In order to detect the satellite with the most inaccurate range estimate, we find the minimum, maximum, and median of the (τ1, . . . , τN), denoted asτmax=max(τ1, . . . , τN)τmin=min(τ1, . . . , τN)τmed=med(τ1, . . . , τN)
We then compare the two values of |τmax−τmed| to |τmin−τmed|. If |τmax−τmed|>|τmin−τmed|, we pick the satellite with maximum SPS receiver clock bias and remove that satellite from our set. Otherwise, we remove the satellite with minimum SPS receiver clock bias from our set of satellites.
It is also possible to identify the worst satellite (in terms of SPS receiver clock bias error) from a set without repeating the process for all the subsets. For this purpose, suppose we have N estimates of the SPS receiver clock bias,
τ i i ∈ { 1 ⁢ ⁢ … ⁢ ⁢ N } .We first calculate the median of the set, τmed.
Then we find the maximum and minimum estimates, denoted by τmax and τmin. We then find the two variables defined as:p 1=|τmax−τmed|p 2=|τmin−τmed|
If any of the pointers is more than certain threshold, i.e. p1>η or p2>η, We take the maximum variable and remove the satellite corresponding to that estimate of SPS receiver clock bias. If p1>p2 we select the satellite with maximum SPS receiver clock bias estimate and remove it from the current set of satellites. Otherwise, we select the satellite with minimum SPS receiver clock bias estimate and remove it from the current set of satellites.
If they are both below a threshold, i.e. p1≦η and p2≦η, we proceed as following; if p1>>p2, i.e. p1 is twice as large as p2, we select the satellite with maximum SPS receiver clock bias estimate and remove it. Otherwise, if p2>>p1, we select the satellite with minimum SPS receiver clock bias estimate and remove it. If they are approximately on the same level, p1≈p2, the estimate of SPS receiver clock bias is good enough and there is no need to remove any satellite.
Other embodiments of this disclosure describe a new technique in an integrated hybrid positioning environment, including an initial estimated location (IEL) along with its expected error, i.e. QoS, and SPS satellite information and range measurements, to obtain a more accurate estimate of the receiver location. In order to do so, the method combines an aggregate or group of locations with small variations of SPS receiver clock bias to obtain a more accurate location. Specifically, all possible locations are examined and only those locations with a small receiver clock bias variation are selected. Then those selected locations are combined to determine a final location.
As described above, in order to refine the IEL with SPS measurements, the hybrid positioning system constructs a region centered on the IEL, calculates the variations of SPS receiver clock bias for all the locations inside the region, and selects the location with the minimum variation. Then, a second search is initiated through the locations inside the region and those locations whose SPS receiver clock biases are sufficiently small (i.e. locations with small clock variations) are selected. The current hybrid positioning uses the location with the absolute minimum of clock variation as its final reported location. The threshold to detect if a location has small SPS receiver clock bias is dependent on the QoS of SPS, QoS of IEL, statistics of the current set of receiver clock bias estimates, and desired level of accuracy.
In this disclosure we propose that the final estimate of the user location can then be computed from all these selected locations, because they are representing all the possible solutions for a receiver location. A simple combination method to obtain the final location is to average the locations with small SPS receiver clock bias variations. Other sophisticated methods such as weighted averaging are also possible.
In order to proceed to finding the final estimated hybrid location, note that each location inside the constructed region is associated with an SPS receiver clock bias. We can classify each location based on the value of its SPS receiver clock bias as depicted in FIG. 8. FIG. 8 represents the values for SPS receiver clock bias variation for a sample point for the specified region. The center of the region is provided by the IEL and the region is constructed by hybrid positioning system around the IEL. For each grid-location inside the region, the hybrid positioning system calculates the SPS receiver clock bias variation and represents its value with a color. The darker colors are used for small variations while lighter colors are for large variations. Since the system is interested in grid-locations with small variation, it has to select all the grid-locations which are marked by darker colors.
As shown in FIG. 8, we are interested in the set of locations with small SPS receiver clock bias variation, illustrated by darker colors in the figure. The set of such locations can be denoted by R to show that there is an area in the region which includes such locations. The final estimate of receiver location is then calculated as
X t = 1 N ⁢ ∑ i = 1 N ⁢ X i Y t = 1 N ⁢ ∑ i = 1 N ⁢ Y i Z t = 1 N ⁢ ∑ i = 1 N ⁢ Z i ( X i , Y i , Z i ) ∈ R
For the best result in the implementation of the disclosed methods, when the three dimensional search through all locations is performed we start with an empty array and each new location which fits into this description, i.e. exhibits small variation in SPS receiver clock bias, can be appended to the array.
Other embodiments of this disclosure describe a new technique in an integrated hybrid positioning environment, including an initial estimated location (IEL) along with its expected error and SPS satellite information and range measurements, to speed up the process of location estimation. In order to do so, the method proposes to modify the three dimensional search and perform three two dimensional searches which consequently reduces the number of searches.
Exhaustive searching through all the locations for the location with minimum SPS receiver clock bias variation is a power consuming function which puts a considerable burden on the device's CPU and can slow down the process of positioning. For a region having a size of 200 meters with a step size of 10 meters, the processor has to search through 8000 locations and calculate the SPS receiver clock bias for each location and find the location with minimum SPS receiver clock bias variations which can take up to several seconds with current processors used in small mobile devices.
The present embodiment describes a method to reduce the size of a search for a given region size with specific number of locations. The 3D-search has to perform a search in all three local dimensions, namely X, Y, and Z.
In order to obtain SPS receiver clock bias, for each location we have to find the individual clock biases from the location to each satellite. If we name the location by Gijk notation (i.e. location i from X axis, j from Y axis, and k from Z axis), we can formulate the problem as following;
τ _ ijk = ∑ m = 1 n ⁢ τ m ijk nwhere τ ijk presents the unbiased estimate of SPS receiver clock bias at Gijk, τmijk represents GPS receiver clock bias of Gijk from m th satellite, and n is the number of visible satellites.
Similar to the above methods, we define SPS receiver clock bias variation as;
τ _ ijk rms = ∑ m = 1 n ⁢ ( τ m ijk - τ _ ijk ) 2 nwhich provides information about the deviation of the individual SPS receiver clock biases from the best estimate of SPS receiver clock bias, τ ijk.
In traditional hybrid positioning system, the location with minimum τ ijkrms is the solution to hybrid positioning problem. Mathematically,
( x ^ , y ^ , z ^ ) = arg ⁢ ⁢ min G ijk ⁢ ( τ _ ijk rms ) = { G IJK ❘ τ _ IJK rms = arg ⁢ ⁢ min ijk ⁢ ( τ _ ijk rms ) }where ({circumflex over (x)}, ŷ, {circumflex over (z)}) represents the x, y, and z coordinates of the refined estimate.
We propose to find the aggregate of locations with sufficiently small τ ijkrms and use this aggregate set to refine the initial position using following;
X t = 1 N ⁢ ∑ i = 1 N ⁢ X i Y t = 1 N ⁢ ∑ i = 1 N ⁢ Y i Z t = 1 N ⁢ ∑ i = 1 N ⁢ Z i ( X i , Y i , Z i ) ∈ Rthis method is referred to as 3D search.
The 3D search requires to search over all possible i, j, and k.
Instead of performing a complete three dimensional search, this invention proposes to perform 2D-searches in all three dimensions. The 2D-searches are performed in XY dimension (XY plane), XZ dimension (XZ plane), and YZ dimension (YZ plane).
The number of searches in each 2D-search is smaller than the total number of searches in 3D-search, by order of the number of grid-locations in one direction. For a region size of 200 with step size of 10, we can perform a 20×20=400 search in each dimension. The total number of searches then reduces to 400×3=1200 instead of original 8000 searches. The resulting locations from each 2D-search which has the minimum SPS receiver clock bias can then be used to find the final estimate of the location of the receiver using the following;
X t = X 1 + X 2 + X 3 3 Y t = Y 1 + Y 2 + Y 3 3 Z t = Z 1 + Z 2 + Z 3 3where (X1,Y1,Z1) is the location with minimum SPS receiver clock bias in XY 2D-search, (X2,Y2,Z2) is the location with minimum SPS receiver clock bias in XZ 2D-search, and (X3, Y3, Z3) is the location with minimum SPS receiver clock bias in YZ 2D-search.
Mathematically;
( X 1 , Y 1 , Z 1 ) = arg ⁢ ⁢ min G ij , k = 0 ⁢ ( τ _ ij , k = 0 rms ) = { G IJ , K = 0 ❘ τ _ IJ , K = 0 rms = arg ⁢ ⁢ min ij , k = 0 ⁢ ( τ _ ij , k = 0 rms ) } ( X 2 , Y 2 , Z 2 ) = arg ⁢ ⁢ min G ik , j = 0 ⁢ ( τ _ ik , j = 0 rms ) = { G IK , J = 0 ❘ τ _ IK , J = 0 rms = arg ⁢ ⁢ min ik , j = 0 ⁢ ( τ _ ik , j = 0 rms ) } ( X 3 , Y 3 , Z 3 ) = arg ⁢ ⁢ min G jk , i = 0 ⁢ ( τ _ jk , i = 0 rms ) = { G JK , I = 0 ❘ τ _ JK , I = 0 rms = arg ⁢ ⁢ min jk , i = 0 ⁢ ( τ _ jk , i = 0 rms ) }
FIG. 9 depicts this 2D search method. The IEL 201 is provided by WLAN-PS and hybrid positioning system constructs the region 203. The hybrid positioning system then calculates the variation for all grid-locations on the XY-plane and finds the grid location with minimum variation 901. The process is repeated for XZ-plane and YZ-plane to find the best estimates on those planes 902 and 903. The system then average the three estimates 901,902, and 903 to obtain the final estimate 904. It can be observed that each 2D search consumes less time, by an order of number of locations in one dimension. The total number of searches is then three times the number of searches in a 2D search. Therefore, the receiver clock bias variation within the region can be calculated in less time and consuming less computational power by using the 2D method as opposed to the 3D method. The 2D search is less time consuming and more computationally efficient. However, the accuracy of 3D search is better than 2D search.
The many features and advantages of the embodiments of the present invention are apparent from the detail specification, and thus, it is intended to cover all such features and advantages of the invention that fall within the true spirit and scope of the invention. All suitable modifications and equivalents maybe resorted to, falling within the scope of the invention.

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