WO2010002366A1 - A method for scanning uplink frequencies in a wireless repeater - Google Patents

A method for scanning uplink frequencies in a wireless repeater Download PDF

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Publication number
WO2010002366A1
WO2010002366A1 PCT/US2008/008264 US2008008264W WO2010002366A1 WO 2010002366 A1 WO2010002366 A1 WO 2010002366A1 US 2008008264 W US2008008264 W US 2008008264W WO 2010002366 A1 WO2010002366 A1 WO 2010002366A1
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WO
WIPO (PCT)
Prior art keywords
uplink signal
uplink
rssi value
signal frequency
frequency
Prior art date
Application number
PCT/US2008/008264
Other languages
French (fr)
Inventor
Scott Terry
Original Assignee
Wireless Extenders, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Wireless Extenders, Inc. filed Critical Wireless Extenders, Inc.
Priority to PCT/US2008/008264 priority Critical patent/WO2010002366A1/en
Publication of WO2010002366A1 publication Critical patent/WO2010002366A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/15528—Control of operation parameters of a relay station to exploit the physical medium
    • H04B7/15542—Selecting at relay station its transmit and receive resources
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/02—Selection of wireless resources by user or terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
    • H04W72/542—Allocation or scheduling criteria for wireless resources based on quality criteria using measured or perceived quality
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/042—Public Land Mobile systems, e.g. cellular systems
    • H04W84/047—Public Land Mobile systems, e.g. cellular systems using dedicated repeater stations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/04—Terminal devices adapted for relaying to or from another terminal or user

Definitions

  • the present invention relates to wireless communication. More specifically, the present invention relates to repeaters used in wireless communications networks.
  • Cellular communication is one of the widely used types of wireless communication.
  • a geographical area is divided into a plurality of cells.
  • Each cell has a base station that communicates with one or more mobile devices in the cell.
  • Signals transmitted from the base station to a mobile device are known as downlink signals.
  • Signals transmitted from the mobile device to the base station are known as uplink signals.
  • a repeater amplifies downlink signals from a base station and re-transmits them to the mobile device.
  • the repeater amplifies uplink signals from a mobile device and re-transmits them to the base station.
  • An object of the present invention is to provide a method for selecting an uplink signal frequency by scanning a plurality of uplink frequencies in a bi-directional repeater.
  • Another object of the present invention is to provide a bi-directional repeater for selecting an uplink signal frequency by scanning a plurality of uplink frequencies.
  • various embodiments of the present invention provide a method of selecting an uplink signal frequency.
  • a plurality of uplink frequencies are scanned.
  • Signal strength indicator (RSSI) values associated with each of the plurality of uplink signal frequencies are determined.
  • a difference RSSI value between the maximum and the minimum RSSI value for each of the plurality of uplink signal frequencies is determined.
  • an average RSSI value for each of the plurality of uplink frequencies is determined.
  • the uplink signal frequency is selected based on at least one of the difference RSSI value and the average RSSI value.
  • a bi-directional repeater for selecting an uplink signal frequency from a plurality of uplink signal frequencies.
  • the bi-directional repeater comprises an uplink circuit for amplifying uplink signals from the mobile device to the base station and a downlink circuit for amplifying downlink signals from the base station to the mobile device.
  • a power detector within the bi-directional repeater measures a plurality of signal strength indicator (RSSI) values associated with each of the plurality of uplink signal frequencies.
  • RSSI signal strength indicator
  • a frequency synthesizer in the uplink circuit scans the plurality of uplink signal frequencies and a central processing unit (CPU) selects at least one of the plurality of uplink signal frequencies, wherein the at least one of the plurality of signal frequencies is the selected uplink signal frequency.
  • the bi-directional repeater scans the entire cellular sub-band. Further, the bi-directional repeater does not require any manual intervention for programming the operating sub-band. Moreover, since the entire uplink sub-band is scanned, a mobile device operating in the uplink sub-band is accurately detected.
  • FIG. 1 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater, in accordance with an embodiment of the present invention
  • FIG. 2 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on a difference RSSI value, in accordance with an embodiment of the present invention
  • FIG. 3 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on an average RSSI value, in accordance with an embodiment of the present invention
  • FIG. 4 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on a threshold RSSI value, in accordance with an embodiment of the present invention.
  • FIG. 5 is a block diagram of a bi-directional repeater for selecting an uplink signal frequency, in accordance with an embodiment of the present invention.
  • Various embodiments of the present invention provide a method for selecting an uplink signal frequency in a bi-directional repeater.
  • a plurality of uplink frequencies are scanned.
  • Signal strength indicator (RSSI) values associated with each of the plurality of uplink signal frequencies are determined.
  • a difference RSSI value between the maximum and the minimum RSSI value for each of the plurality of uplink signal frequencies is determined.
  • an average RSSI value for each of the plurality of uplink frequencies is determined.
  • the uplink signal frequency is selected based on at least one of the difference RSSI value and the average RSSI value.
  • FIG. 1 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater in accordance with an embodiment of the present invention.
  • a plurality of uplink frequencies are scanned.
  • scanning the plurality of uplink frequencies may comprise scanning the cellular sub-band for uplink.
  • Scanning a plurality of uplink frequencies may also comprise scanning a plurality of channels available in the cellular sub-band.
  • the scanning may be initiated by a user.
  • the user may initiate a call from his mobile phone and instruct the bi-directional repeater to start scanning.
  • the bi-directional repeater may continuously scan the plurality of uplink frequencies.
  • the bi-directional repeater may start scanning the plurality of uplink frequencies when it is powered on.
  • a plurality of RSSI values associated with each of the plurality of uplink frequencies are determined.
  • the plurality of the RSSI values may be determined over a single time interval or multiple time intervals.
  • a difference RSSI value between the maximum RSSI value and the minimum RSSI value associated with each of the plurality of uplink frequencies is determined.
  • the difference RSSI value may be determined over multiple time intervals.
  • an average RSSI value associated with each of the plurality of uplink frequencies is determined.
  • the average RSSI value corresponds to the average of the plurality of RSSI values associated with each of the plurality of uplink frequenices.
  • the average RSSI value may be determined over multiple time intervals.
  • the uplink signal frequency is selected from the plurality of uplink frequencies based on a first predefined criteria.
  • a detailed method for selecting the uplink signal frequency is explained in accordance with FIGs. 2, 3 and 4. Further, a bidirectional repeater capable of selecting the uplink signal frequency is explained in conjunction with FIG. 5.
  • FIG. 2 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on a difference RSSI value in accordance with an embodiment of the present invention.
  • a plurality of uplink frequencies are scanned.
  • a plurality of RSSI values associated with each of the plurality of uplink frequencies are determined.
  • Step 206 a difference RSSI value between the maximum RSSI value and the minimum RSSI value associated with each of the plurality of uplink frequencies is determined. Steps 202, 204 and 206 correspond to steps 102, 104 and 106 of FIG. 1 respectively.
  • a check is performed to determine whether the difference RSSI value switches between a first predetermined value and a second predetermined value over a first predetermined time interval. If it is determined at step 208 that the difference RSSI value switches between the first predetermined value and the second predetermined value over the first predetermined time interval, then it is determined that the uplink signal frequency is available and step 210 is performed. At step 210, the uplink signal frequency is selected. However, at step 208, if it is determined that the difference RSSI value does not switch between the first predetermined value and the second predetermined value over the first predetermined time interval, steps 202 till 208 are iteratively performed until the uplink signal frequency is selected.
  • the first predetermined value, the second predetermined value and the first predetermined time interval may be programmed appropriately.
  • the difference RSSI value may be in the range of -28 to -34 decibel units (dBm).
  • the first predetermined value may be approximately equal to -30 dBm and the second predetermined value may be approximately equal to -33 dBm.
  • the first predetermined time interval may be approximately equal to 100 milli-seconds (ms).
  • the maximum RSSI value and the minimum RSSI value may also be used to determine the cellular system in which the mobile phone is operating.
  • FIG. 3 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on an average RSSI value in accordance with an embodiment of the present invention.
  • a plurality of uplink frequencies are scanned.
  • a plurality of RSSI values associated with each of the plurality of uplink frequencies are determined.
  • the average RSSI value associated with each of the plurality of uplink frequencies is determined. Steps 302, 304 and 306 correspond to steps 102, 104 and 108 of FIG. 1, respectively.
  • a check is performed to determine whether the average RSSI value switches between a third predetermined value and a fourth predetermined value over a second predetermined time interval. If it is determined at step 308 that the average RSSI value switches between the third predetermined value and the fourth predetermined value over the second predetermined time interval, then it is determined that the uplink signal frequency is available and step 310 is performed. At step 310, the uplink signal frequency is selected. However, at step 308, if it is determined that the average RSSI value does not switch between the third predetermined value and the fourth predetermined value over the second predetermined time interval, steps 302 till 308 are iteratively performed until the uplink signal frequency is selected.
  • the third predetermined value, the fourth predetermined value and the second predetermined time interval may be programmed appropriately.
  • the average RSSI value may be in the range of -28 to -30 decibel units (dBm).
  • the third predetermined value may be approximately equal to -30 dBm and the fourth predetermined value may be approximately equal to -29 dBm.
  • the second predetermined time interval may be approximately equal to 100 milli-seconds (ms).
  • the calculation of the average RSSI value may differ based on the cellular system in which the mobile phone is operating. If the mobile phone is operating in a CDMA system, the average RSSI value may be determined using the plurality of RSSI values associated with the uplink signal frequency.
  • the average RSSI value may be determined using a peak value among the plurality of RSSI values.
  • a plurality of peak values may be determined by determining the plurality of RSSI values over multiple time intervals.
  • the average RSSI value may be determined based on the plurality of peak values.
  • FIG. 4 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on a threshold RSSI value in accordance with an embodiment of the present invention.
  • a plurality of uplink frequencies are scanned.
  • a plurality of RSSI values associated with each of the plurality of uplink frequencies are determined.
  • the average RSSI value associated with each of the plurality of uplink frequencies is determined. Steps 402, 404 and 406 correspond to steps 102, 104 and 108 of FIG. 1 , respectively.
  • a check is performed to determine whether the average RSSI value is greater than a first predetermined threshold. If it is determined at step 408 that the average RSSI value is greater than the first predetermined threshold, then it is determined that the uplink signal frequency is available and step 410 is performed. At step 410, the uplink signal frequency is selected. However, at step 408, if it is determined that the average RSSI value is not greater than the first predetermined threshold, steps 402 till 408 are iteratively performed, until the uplink signal frequency is selected.
  • the first predetermined threshold may be programmed appropriately. In an exemplary embodiment of the present invention, the first predetermined threshold may be approximately equal to -30 dBm. Further, the calculation of the average RSSI value may differ based on the cellular system in which the mobile phone is operating. If the mobile phone is operating in a CDMA system, the average RSSI value may be determined using the plurality of RSSI values associated with the uplink signal frequency. However, if the mobile phone is operating in a GSM system, the average RSSI value may be determined using a peak value among the plurality of RSSI values. A plurality of peak values may be determined by determining the plurality of RSSI values over multiple time intervals. The average RSSI value may be determined based on the plurality of peak values.
  • different combinations of the methods explained in conjunction with FIGs. 1 , 2 and 3 may be used for selecting an uplink frequency.
  • the uplink frequency may be selected based on one or more criterions as explained in conjunction with FIGs. 1 , 2 and 3.
  • the downlink frequency is offset from the uplink frequency by a fixed value.
  • the downlink frequency may be selected based on the uplink frequency.
  • FIG. 5 is a block diagram of a bi-directional repeater 500 for selecting an uplink signal frequency in accordance with an embodiment of the present invention.
  • Bidirectional repeater 500 comprises a downlink circuit 502, an uplink circuit 504, a tower side antenna 506, a mobile side antenna 508, a plurality of duplexers, such as duplexer 510a and duplexer 510b, a central processing unit (CPU) 512, a memory device 514 and a display unit 516.
  • CPU central processing unit
  • Downlink circuit 502 comprises a downlink local oscillator 518a, a downlink frequency synthesizer 520a, a plurality of downlink filters, such as downlink filters 522a and 522b, a plurality of downlink mixers, such as downlink mixers 524a and 524b, a downlink intermediate frequency (IF) filter 526a, a downlink power detector 528a and a downlink power amplifier 530a.
  • IF intermediate frequency
  • Uplink circuit 504 comprises an uplink local oscillator 518b, an uplink frequency synthesizer 520b, a plurality of uplink filters, such as uplink filters 532a and 532b, a plurality of uplink mixers, such as uplink mixers 524c and 524d, an uplink IF filter 526b, an uplink power detector 528b and an uplink power amplifier 530b.
  • Tower side antenna 506 receives downlink signals from a base station and carries them to downlink circuit 502 for further processing, through duplexer 510a. Likewise, tower side antenna 506 receives uplink signals from uplink circuit 504, through duplexer 510a and radiates them to the base station. Mobile side antenna 508 receives uplink signals from a mobile device and carries them to uplink circuit 504 for further processing, through duplexer 510b. Likewise, mobile side antenna 508 receives downlink signals from downlink circuit 502, through duplexer 510b and radiates them to the mobile device.
  • Downlink filter 522a filters the downlink signal frequencies to pass the entire downlink signal band in which a mobile device is operating.
  • Downlink local oscillator 518a and downlink frequency synthesizer 520a generate a downlink local oscillator signal.
  • the downlink signal and the downlink local oscillator signal are mixed by downlink mixer 524a and filtered by downlink IF filter 526a to generate a downlink IF signal that represents the desired RF sub band.
  • Downlink power detector 528a measures the RSSI value of the downlink IF signal.
  • the downlink IF signal is then mixed with the local oscillator signal by downlink mixer 524b and filtered by downlink filter 522b to re-generate the downlink signal. Subsequently, the downlink signal is amplified by downlink power amplifier 530a.
  • Mobile side antenna 508 receives the amplified downlink signal through duplexer 510b and radiates the amplified downlink signal to the mobile device.
  • Uplink filter 532a filters the uplink signal frequencies to pass the entire uplink signal band in which the mobile device is operating.
  • Uplink local oscillator 518b and uplink frequency synthesizer 520b generate an uplink local oscillator signal.
  • the uplink signal and the uplink local oscillator signal are mixed by uplink mixer 524c and filtered by uplink IF filter 526b to generate an uplink IF signal that represents the desired RF sub band.
  • Uplink power detector 528b measures the RSSI value of the uplink IF signal.
  • the uplink IF signal is then mixed with the local oscillator signal by uplink mixer 524d and filtered by uplink filter 532b to re-generate the uplink signal.
  • the uplink signal is amplified by uplink power amplifier 530b.
  • Tower side antenna 506 receives the amplified uplink signal through duplexer 510a and radiates the amplified uplink signal to the base station.
  • downlink filters 522a and 522b and uplink filters 532a and 532b may be RF filters.
  • uplink frequency synthesizer 520b scans a plurality of uplink signal frequencies by varying the local oscillator signal frequency generated by uplink local oscillator 518b.
  • Uplink power detector 528b measures a plurality of RSSI values associated with each of the plurality of uplink signal frequencies.
  • the plurality of RSSI values are stored in memory device 514.
  • CPU 512 determines a difference RSSI value between a maximum RSSI value and a minimum RSSI value associated with each of the plurality of uplink signal frequencies over at least one time interval.
  • CPU 512 further determines an average RSSI value of the plurality of RSSI values associated with each of the plurality of uplink signal frequencies over the at least one time interval.
  • CPU 512 selects the uplink signal frequency by instructing uplink frequency synthesizer 520b to lock to the uplink local oscillator signal frequency, based on the first predetermined criteria.
  • the method of selecting the uplink signal frequency has been explained in detail in conjunction with FIGS. 2, 3 and 4.
  • Display unit 516 displays an indicator when the uplink signal frequency is selected.
  • the indicator may be a light emitting display (LED), a liquid crystal display (LCD) or any other alphanumeric display.
  • Display unit 516 may also display an indicator if the uplink signal frequency is not selected.
  • memory device 514 records the uplink signal frequency.
  • CPU 512 may instruct uplink frequency synthesizer 520b to initiate re-scanning based on the RSSI value associated with the uplink signal frequency dropping below a second predetermined threshold.
  • the second predetermined threshold may be programmed appropriately.
  • bi-directional repeater 500 may operate according to at least one of the Universal Mobile Telecommunications System (UMTS), Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), High Speed Downlink Packet Access (HSDPA), Evolution-Data Optimized (EVDO), Long term evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX) standards.
  • UMTS Universal Mobile Telecommunications System
  • GSM Global System for Mobile communications
  • CDMA Code Division Multiple Access
  • HSDPA High Speed Downlink Packet Access
  • EVDO Evolution-Data Optimized
  • LTE Long term evolution
  • WiMAX Worldwide Interoperability for Microwave Access
  • the bi-directional repeater scans the entire cellular sub-band. Further, the bi-directional repeater does not require any manual intervention for programming the operating sub- band. Since the entire uplink sub-band is scanned, a mobile device operating in the uplink sub-band is accurately detected.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Quality & Reliability (AREA)
  • Radio Relay Systems (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The invention relates to a method for selecting an uplink signal frequency in a bi-directional repeater. A plurality of uplink signal frequencies are scanned. A plurality of RSSI values associated with each of the plurality of uplink signal frequencies is determined. A difference RSSI value or an average RSSI value for each of the plurality of signal frequencies is determined. The uplink signal frequency is selected based on at least one of the difference RSSI value and the average RSSI value.

Description

A METHOD FOR SCANNING UPLINK FREQUENICES IN A WIRELESS REPEATER
BACKGROUND OF THE INVENTION
The present invention relates to wireless communication. More specifically, the present invention relates to repeaters used in wireless communications networks.
Cellular communication is one of the widely used types of wireless communication. In cellular communication systems, a geographical area is divided into a plurality of cells. Each cell has a base station that communicates with one or more mobile devices in the cell. Signals transmitted from the base station to a mobile device are known as downlink signals. Signals transmitted from the mobile device to the base station are known as uplink signals.
In cellular communication networks, there exist areas within a cell where the reception of downlink signals from the base station to a mobile device may be poor. Such areas may include, but are not limited to, tall buildings, car parking basements and residential areas with poor signal coverage. Mobile devices operating in such areas often face connectivity problems that result in frequent call interruptions. Hence, wireless devices such as repeaters are used to improve the signal coverage in such areas. A repeater amplifies downlink signals from a base station and re-transmits them to the mobile device. Likewise, the repeater amplifies uplink signals from a mobile device and re-transmits them to the base station.
Existing repeaters usually operate in the entire cellular spectrum to detect mobile activity. However, in such cases, the sub band in which the mobile device is operating needs to be pre-determined and the repeater needs to be manually programmed to that sub band.
In light of the foregoing discussion, there is a need for a repeater that can scan uplink frequencies. Further, there is a need for a repeater that can scan uplink frequencies in a particular cellular sub-band. Moreover, there is a need for a repeater that does not require manual intervention for programming the sub-band. SUMMARY
An object of the present invention is to provide a method for selecting an uplink signal frequency by scanning a plurality of uplink frequencies in a bi-directional repeater.
Another object of the present invention is to provide a bi-directional repeater for selecting an uplink signal frequency by scanning a plurality of uplink frequencies.
To achieve the above-mentioned objectives, various embodiments of the present invention provide a method of selecting an uplink signal frequency. A plurality of uplink frequencies are scanned. Signal strength indicator (RSSI) values associated with each of the plurality of uplink signal frequencies are determined. A difference RSSI value between the maximum and the minimum RSSI value for each of the plurality of uplink signal frequencies is determined. Further, an average RSSI value for each of the plurality of uplink frequencies is determined. The uplink signal frequency is selected based on at least one of the difference RSSI value and the average RSSI value.
In an embodiment of the present invention, a bi-directional repeater is provided for selecting an uplink signal frequency from a plurality of uplink signal frequencies. The bi-directional repeater comprises an uplink circuit for amplifying uplink signals from the mobile device to the base station and a downlink circuit for amplifying downlink signals from the base station to the mobile device. A power detector within the bi-directional repeater measures a plurality of signal strength indicator (RSSI) values associated with each of the plurality of uplink signal frequencies. A frequency synthesizer in the uplink circuit scans the plurality of uplink signal frequencies and a central processing unit (CPU) selects at least one of the plurality of uplink signal frequencies, wherein the at least one of the plurality of signal frequencies is the selected uplink signal frequency.
The bi-directional repeater scans the entire cellular sub-band. Further, the bi- directional repeater does not require any manual intervention for programming the operating sub-band. Moreover, since the entire uplink sub-band is scanned, a mobile device operating in the uplink sub-band is accurately detected.
BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, wherein like designations denote like elements, and in which:
FIG. 1 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater, in accordance with an embodiment of the present invention;
FIG. 2 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on a difference RSSI value, in accordance with an embodiment of the present invention;
FIG. 3 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on an average RSSI value, in accordance with an embodiment of the present invention;
FIG. 4 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on a threshold RSSI value, in accordance with an embodiment of the present invention; and
FIG. 5 is a block diagram of a bi-directional repeater for selecting an uplink signal frequency, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the present invention provide a method for selecting an uplink signal frequency in a bi-directional repeater. A plurality of uplink frequencies are scanned. Signal strength indicator (RSSI) values associated with each of the plurality of uplink signal frequencies are determined. A difference RSSI value between the maximum and the minimum RSSI value for each of the plurality of uplink signal frequencies is determined. Further, an average RSSI value for each of the plurality of uplink frequencies is determined. The uplink signal frequency is selected based on at least one of the difference RSSI value and the average RSSI value.
FIG. 1 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater in accordance with an embodiment of the present invention. At step 102, a plurality of uplink frequencies are scanned. In various embodiments of the present invention, scanning the plurality of uplink frequencies may comprise scanning the cellular sub-band for uplink. Scanning a plurality of uplink frequencies may also comprise scanning a plurality of channels available in the cellular sub-band.
In various embodiments of the present invention, the scanning may be initiated by a user. The user may initiate a call from his mobile phone and instruct the bi-directional repeater to start scanning. In one embodiment of the present invention, the bi-directional repeater may continuously scan the plurality of uplink frequencies. In another embodiment of the present invention, the bi-directional repeater may start scanning the plurality of uplink frequencies when it is powered on.
At step 104, a plurality of RSSI values associated with each of the plurality of uplink frequencies are determined. In various embodiments of the present invention, the plurality of the RSSI values may be determined over a single time interval or multiple time intervals. At step 106, a difference RSSI value between the maximum RSSI value and the minimum RSSI value associated with each of the plurality of uplink frequencies is determined. In various embodiments of the present invention, the difference RSSI value may be determined over multiple time intervals.
At step 108, an average RSSI value associated with each of the plurality of uplink frequencies is determined. The average RSSI value corresponds to the average of the plurality of RSSI values associated with each of the plurality of uplink frequenices. In various embodiments of the present invention, the average RSSI value may be determined over multiple time intervals.
At step 110, the uplink signal frequency is selected from the plurality of uplink frequencies based on a first predefined criteria. A detailed method for selecting the uplink signal frequency is explained in accordance with FIGs. 2, 3 and 4. Further, a bidirectional repeater capable of selecting the uplink signal frequency is explained in conjunction with FIG. 5. FIG. 2 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on a difference RSSI value in accordance with an embodiment of the present invention. At step 202, a plurality of uplink frequencies are scanned. At step 204, a plurality of RSSI values associated with each of the plurality of uplink frequencies are determined. At step 206, a difference RSSI value between the maximum RSSI value and the minimum RSSI value associated with each of the plurality of uplink frequencies is determined. Steps 202, 204 and 206 correspond to steps 102, 104 and 106 of FIG. 1 respectively.
At step 208, a check is performed to determine whether the difference RSSI value switches between a first predetermined value and a second predetermined value over a first predetermined time interval. If it is determined at step 208 that the difference RSSI value switches between the first predetermined value and the second predetermined value over the first predetermined time interval, then it is determined that the uplink signal frequency is available and step 210 is performed. At step 210, the uplink signal frequency is selected. However, at step 208, if it is determined that the difference RSSI value does not switch between the first predetermined value and the second predetermined value over the first predetermined time interval, steps 202 till 208 are iteratively performed until the uplink signal frequency is selected.
In various embodiments of the present invention, the first predetermined value, the second predetermined value and the first predetermined time interval may be programmed appropriately. In an exemplary embodiment of the present invention, the difference RSSI value may be in the range of -28 to -34 decibel units (dBm). The first predetermined value may be approximately equal to -30 dBm and the second predetermined value may be approximately equal to -33 dBm. Further, the first predetermined time interval may be approximately equal to 100 milli-seconds (ms). In an embodiment of the present invention, the maximum RSSI value and the minimum RSSI value may also be used to determine the cellular system in which the mobile phone is operating. If the minimum RSSI value is close to zero and the maximum RSSI value remains almost constant it may be determined that the cellular system is a GSM system, otherwise it is a CDMA system. FIG. 3 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on an average RSSI value in accordance with an embodiment of the present invention. At step 302, a plurality of uplink frequencies are scanned. At step 304, a plurality of RSSI values associated with each of the plurality of uplink frequencies are determined. At step 306, the average RSSI value associated with each of the plurality of uplink frequencies is determined. Steps 302, 304 and 306 correspond to steps 102, 104 and 108 of FIG. 1, respectively.
At step 308, a check is performed to determine whether the average RSSI value switches between a third predetermined value and a fourth predetermined value over a second predetermined time interval. If it is determined at step 308 that the average RSSI value switches between the third predetermined value and the fourth predetermined value over the second predetermined time interval, then it is determined that the uplink signal frequency is available and step 310 is performed. At step 310, the uplink signal frequency is selected. However, at step 308, if it is determined that the average RSSI value does not switch between the third predetermined value and the fourth predetermined value over the second predetermined time interval, steps 302 till 308 are iteratively performed until the uplink signal frequency is selected.
In various embodiments of the present invention, the third predetermined value, the fourth predetermined value and the second predetermined time interval may be programmed appropriately. In an exemplary embodiment of the present invention, the average RSSI value may be in the range of -28 to -30 decibel units (dBm). The third predetermined value may be approximately equal to -30 dBm and the fourth predetermined value may be approximately equal to -29 dBm. Further, the second predetermined time interval may be approximately equal to 100 milli-seconds (ms). Further, the calculation of the average RSSI value may differ based on the cellular system in which the mobile phone is operating. If the mobile phone is operating in a CDMA system, the average RSSI value may be determined using the plurality of RSSI values associated with the uplink signal frequency. However, if the mobile phone is operating in a GSM system, the average RSSI value may be determined using a peak value among the plurality of RSSI values. A plurality of peak values may be determined by determining the plurality of RSSI values over multiple time intervals. The average RSSI value may be determined based on the plurality of peak values.
FIG. 4 is a flowchart illustrating a method for selecting an uplink signal frequency in a bi-directional repeater based on a threshold RSSI value in accordance with an embodiment of the present invention. At step 402, a plurality of uplink frequencies are scanned. At step 404, a plurality of RSSI values associated with each of the plurality of uplink frequencies are determined. At step 406, the average RSSI value associated with each of the plurality of uplink frequencies is determined. Steps 402, 404 and 406 correspond to steps 102, 104 and 108 of FIG. 1 , respectively.
At step 408, a check is performed to determine whether the average RSSI value is greater than a first predetermined threshold. If it is determined at step 408 that the average RSSI value is greater than the first predetermined threshold, then it is determined that the uplink signal frequency is available and step 410 is performed. At step 410, the uplink signal frequency is selected. However, at step 408, if it is determined that the average RSSI value is not greater than the first predetermined threshold, steps 402 till 408 are iteratively performed, until the uplink signal frequency is selected.
In various embodiments of the present invention, the first predetermined threshold may be programmed appropriately. In an exemplary embodiment of the present invention, the first predetermined threshold may be approximately equal to -30 dBm. Further, the calculation of the average RSSI value may differ based on the cellular system in which the mobile phone is operating. If the mobile phone is operating in a CDMA system, the average RSSI value may be determined using the plurality of RSSI values associated with the uplink signal frequency. However, if the mobile phone is operating in a GSM system, the average RSSI value may be determined using a peak value among the plurality of RSSI values. A plurality of peak values may be determined by determining the plurality of RSSI values over multiple time intervals. The average RSSI value may be determined based on the plurality of peak values. In various embodiments of the present invention, different combinations of the methods explained in conjunction with FIGs. 1 , 2 and 3 may be used for selecting an uplink frequency. The uplink frequency may be selected based on one or more criterions as explained in conjunction with FIGs. 1 , 2 and 3. Moreover, the downlink frequency is offset from the uplink frequency by a fixed value. Hence, the downlink frequency may be selected based on the uplink frequency.
FIG. 5 is a block diagram of a bi-directional repeater 500 for selecting an uplink signal frequency in accordance with an embodiment of the present invention. Bidirectional repeater 500 comprises a downlink circuit 502, an uplink circuit 504, a tower side antenna 506, a mobile side antenna 508, a plurality of duplexers, such as duplexer 510a and duplexer 510b, a central processing unit (CPU) 512, a memory device 514 and a display unit 516. Downlink circuit 502 comprises a downlink local oscillator 518a, a downlink frequency synthesizer 520a, a plurality of downlink filters, such as downlink filters 522a and 522b, a plurality of downlink mixers, such as downlink mixers 524a and 524b, a downlink intermediate frequency (IF) filter 526a, a downlink power detector 528a and a downlink power amplifier 530a. Uplink circuit 504 comprises an uplink local oscillator 518b, an uplink frequency synthesizer 520b, a plurality of uplink filters, such as uplink filters 532a and 532b, a plurality of uplink mixers, such as uplink mixers 524c and 524d, an uplink IF filter 526b, an uplink power detector 528b and an uplink power amplifier 530b.
Tower side antenna 506 receives downlink signals from a base station and carries them to downlink circuit 502 for further processing, through duplexer 510a. Likewise, tower side antenna 506 receives uplink signals from uplink circuit 504, through duplexer 510a and radiates them to the base station. Mobile side antenna 508 receives uplink signals from a mobile device and carries them to uplink circuit 504 for further processing, through duplexer 510b. Likewise, mobile side antenna 508 receives downlink signals from downlink circuit 502, through duplexer 510b and radiates them to the mobile device.
Downlink filter 522a filters the downlink signal frequencies to pass the entire downlink signal band in which a mobile device is operating. Downlink local oscillator 518a and downlink frequency synthesizer 520a generate a downlink local oscillator signal. The downlink signal and the downlink local oscillator signal are mixed by downlink mixer 524a and filtered by downlink IF filter 526a to generate a downlink IF signal that represents the desired RF sub band. Downlink power detector 528a measures the RSSI value of the downlink IF signal. The downlink IF signal is then mixed with the local oscillator signal by downlink mixer 524b and filtered by downlink filter 522b to re-generate the downlink signal. Subsequently, the downlink signal is amplified by downlink power amplifier 530a. Mobile side antenna 508 receives the amplified downlink signal through duplexer 510b and radiates the amplified downlink signal to the mobile device.
Uplink filter 532a filters the uplink signal frequencies to pass the entire uplink signal band in which the mobile device is operating. Uplink local oscillator 518b and uplink frequency synthesizer 520b generate an uplink local oscillator signal. The uplink signal and the uplink local oscillator signal are mixed by uplink mixer 524c and filtered by uplink IF filter 526b to generate an uplink IF signal that represents the desired RF sub band. Uplink power detector 528b measures the RSSI value of the uplink IF signal. The uplink IF signal is then mixed with the local oscillator signal by uplink mixer 524d and filtered by uplink filter 532b to re-generate the uplink signal. Subsequently, the uplink signal is amplified by uplink power amplifier 530b. Tower side antenna 506 receives the amplified uplink signal through duplexer 510a and radiates the amplified uplink signal to the base station. In various embodiments of the present invention, downlink filters 522a and 522b and uplink filters 532a and 532b may be RF filters.
When CPU 512 initiates scanning, uplink frequency synthesizer 520b scans a plurality of uplink signal frequencies by varying the local oscillator signal frequency generated by uplink local oscillator 518b. Uplink power detector 528b measures a plurality of RSSI values associated with each of the plurality of uplink signal frequencies. The plurality of RSSI values are stored in memory device 514. CPU 512 determines a difference RSSI value between a maximum RSSI value and a minimum RSSI value associated with each of the plurality of uplink signal frequencies over at least one time interval. CPU 512 further determines an average RSSI value of the plurality of RSSI values associated with each of the plurality of uplink signal frequencies over the at least one time interval. CPU 512 selects the uplink signal frequency by instructing uplink frequency synthesizer 520b to lock to the uplink local oscillator signal frequency, based on the first predetermined criteria. The method of selecting the uplink signal frequency has been explained in detail in conjunction with FIGS. 2, 3 and 4.
Display unit 516 displays an indicator when the uplink signal frequency is selected. The indicator may be a light emitting display (LED), a liquid crystal display (LCD) or any other alphanumeric display. Display unit 516 may also display an indicator if the uplink signal frequency is not selected.
In various embodiments of the present invention, memory device 514 records the uplink signal frequency. CPU 512 may instruct uplink frequency synthesizer 520b to initiate re-scanning based on the RSSI value associated with the uplink signal frequency dropping below a second predetermined threshold. The second predetermined threshold may be programmed appropriately.
In various embodiments of the present invention, bi-directional repeater 500 may operate according to at least one of the Universal Mobile Telecommunications System (UMTS), Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), High Speed Downlink Packet Access (HSDPA), Evolution-Data Optimized (EVDO), Long term evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX) standards.
Various embodiments of the present invention have numerous advantages. The bi-directional repeater scans the entire cellular sub-band. Further, the bi-directional repeater does not require any manual intervention for programming the operating sub- band. Since the entire uplink sub-band is scanned, a mobile device operating in the uplink sub-band is accurately detected.
While various embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the invention as described in the claims.

Claims

What is claimed is:
1. A method of selecting an uplink signal frequency to be amplified by a bi-directional repeater, the uplink signal frequency being selected from a plurality of uplink signal frequencies, the method comprising: scanning the plurality of uplink signal frequencies; determining a plurality of signal strength indicator (RSSI) values associated with each of the plurality of uplink signal frequencies over at least one time interval; determining a difference RSSI value between a maximum RSSI value and a minimum RSSI value associated with each of the plurality of uplink signal frequencies over the at least one time interval; and selecting the uplink signal frequency based on a first predefined criteria.
2. The method according to claim 1 further comprising determining an average RSSI value of the plurality of RSSI values associated with each of the plurality of uplink signal frequencies over the at least one time interval.
3. The method according to claim 1 , wherein the first predefined criteria comprises the difference RSSI value for the uplink signal frequency switching between a first predetermined value and a second predetermined value over a first predetermined time interval.
4. The method according to claim 2, wherein the first predefined criteria further comprises the average RSSI value for the uplink signal frequency switching between a third predetermined value and a fourth predetermined value over a second predetermined time interval.
5. The method according to claim 2, wherein the first predefined criteria further comprises the average RSSI value for the uplink signal frequency being greater than a first predetermined threshold.
6. The method according to claim 1 further comprising determining downlink frequency based on the uplink frequency.
7. The method according to claim 1 further comprising displaying an indicator when the uplink signal frequency is selected.
8. The method according to claim 1 further comprising re-scanning the plurality of uplink signal frequencies based on a second predefined criterion.
9. The method according to claim 8, wherein the second predefined criterion comprises the RSSI value associated with the uplink signal frequency being less than a second predetermined threshold.
10. A method of selecting an uplink signal frequency to be amplified by a bidirectional repeater, the uplink signal frequency being selected from a plurality of uplink signal frequencies, the method comprising: scanning the plurality of uplink signal frequencies; determining a plurality of signal strength indicator (RSSI) values associated with each of the plurality of uplink signal frequencies over at least one time interval; determining an average RSSI value of the plurality of RSSI values associated with each of the plurality of uplink signal frequencies over the at least one time interval and selecting the uplink signal frequency based on a first predefined criteria.
11. The method according to claim 10 further comprising determining a difference RSSI value between a maximum RSSI value and a minimum RSSI value associated with each of the plurality of uplink signal frequencies over the at least one time interval.
12. The method according to claim 10, wherein the first predefined criteria further comprises the average RSSI value for the uplink signal frequency switching between a third predetermined value and a fourth predetermined value over a second predetermined time interval.
13. The method according to claim 11 , wherein the first predefined criteria comprises the difference RSSI value for the uplink signal frequency switching between a first predetermined value and a second predetermined value over a first predetermined time interval.
14. The method according to claim 10, wherein the first predefined criteria comprises the average RSSI value for the uplink signal frequency being greater than a first predetermined threshold.
15. The method according to claim 10 further comprising determining downlink frequency based on the uplink frequency
16. The method according to claim 10 further comprising displaying an indicator when the uplink signal frequency is selected.
17. The method according to claim 10 further comprising re-scanning the plurality of uplink signal frequencies based on a second predefined criterion.
18. The method according to claim 17, wherein the second predefined criterion comprises the RSSI value associated with the uplink signal frequency being less than a second predetermined threshold.
19. The method according to claim 10 further comprising continuously scanning the plurality of uplink signal frequencies.
20. A bi-directional repeater for selecting an uplink signal frequency from a plurality of uplink signal frequencies, the bi-directional repeater amplifying signals between a mobile device and a base station, the bi-directional repeater comprising: an uplink circuit, the uplink circuit amplifying uplink signals from the mobile device to the base station; a downlink circuit, the downlink circuit amplifying downlink signals from the base station to the mobile device; a power detector, the power detector measuring a plurality of signal strength indicator
(RSSI) values associated with each of the plurality of uplink signal frequencies; a frequency synthesizer, the frequency synthesizer scanning the plurality of uplink signal frequencies; and a central processing unit (CPU), the CPU selecting at least one of the plurality of uplink signal frequencies, wherein the at least one of the plurality of signal frequencies is the selected uplink signal frequency.
21. The bi-directional repeater according to claim 20 further comprising a memory, the memory storing the plurality of RSSI values.
22. The bi-directional repeater according to claim 21 , wherein the memory further records the uplink signal frequency.
23. The bi-directional repeater according to claim 20 further comprising a display unit, the display unit displaying an indicator when the uplink signal is selected.
24. The bi-directional repeater according to claim 20, wherein the bi-directional repeater operates according to at least one of the Universal Mobile Telecommunications System (UMTS), Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), High Speed Downlink Packet Access (HSDPA), Evolution-Data Optimized (EVDO), Long term evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX) standards.
PCT/US2008/008264 2008-07-03 2008-07-03 A method for scanning uplink frequencies in a wireless repeater WO2010002366A1 (en)

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