AU2232992A - Method and apparatus for estimating the doppler frequency of a mobile station - Google Patents

Method and apparatus for estimating the doppler frequency of a mobile station

Info

Publication number
AU2232992A
AU2232992A AU22329/92A AU2232992A AU2232992A AU 2232992 A AU2232992 A AU 2232992A AU 22329/92 A AU22329/92 A AU 22329/92A AU 2232992 A AU2232992 A AU 2232992A AU 2232992 A AU2232992 A AU 2232992A
Authority
AU
Australia
Prior art keywords
signal
mobile
mobile station
doppler frequency
estimating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
AU22329/92A
Inventor
Olof Tomas Backstrom
Bengt Erik Lennart Dahlman
Bengt Anders Sandell
Lars Peter Wahlstrom
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Publication of AU2232992A publication Critical patent/AU2232992A/en
Abandoned legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
    • G01S11/02—Systems for determining distance or velocity not using reflection or reradiation using radio waves
    • G01S11/10—Systems for determining distance or velocity not using reflection or reradiation using radio waves using Doppler effect
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/32—Reselection being triggered by specific parameters by location or mobility data, e.g. speed data
    • H04W36/324—Reselection being triggered by specific parameters by location or mobility data, e.g. speed data by mobility data, e.g. speed data
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
    • H04W64/006—Locating users or terminals or network equipment for network management purposes, e.g. mobility management with additional information processing, e.g. for direction or speed determination

Description

Method and apparatus for estimating the Doppler frequency of a mobile station.
Field of the Invention
The present invention relates generally to cellular mobile radio systems having channels for transmitting information between base stations and mobile stations. More precisely, the invention relates to a method and apparatus for estimating the doppler frequency of a mobile station.
Background of the Invention
In cellular mobile radio systems, it is fundamental that a mobile station with an established connection on a radio channel shall be able to maintain the established connection when moving from one cell to another cell wherein the cells are serviced by different or the same base station. It is also highly desirable that the mobile station with an established connection on a radio channel shall be able to maintain the established connection on the radio channel shall be able to maintain the established connection when moving within the same cell and when the radio channel which is used is subject to increased interference. A process by which a mobile station can maintain an established connection when moving in a cellular radio system is generally called a handoff.
As the capacity demands on a cellular mobile radio system increase, it becomes increasingly important to be able to determine the speed of a mobile station when processing data received from the mobile station or when handling request for handoff. In a mobile cellular system which sets up a queue for mobile stations waiting to make a handoff to a free channel, problems arise when the speed of the mobile station is not taken into account in determining which mobile station receives the first available free channel. For instance, two mobile stations may be waiting in a handoff queue for a free channel to become available. The first mobile station may be traveling very fast and the second mobile station may be moving very slow. If the second mobile station has requested a handoff before the first mobile station has requested a handoff, the second mobile station will be given the first available free channel even though the signal strength between the base station and the first mobile station is rapidly decreasing. As a result, the first mobile station may lose its signal entirely breaking the call before it ever receives an available channel. This problem will only increase as the size of the individual cells decrease and the capacity of the system increases.
In a mobile telephone system, the variations in a received signals phase and strength is due to the movement of the mobile station. Short term variations depend upon ultipath propagation and is called short term fading, multipath fading or just fading. The maximum frequency of the fading is called doppler frequency and is proportional to the velocity of the mobile station. Another variation in a received signals phase and strength is long term variations due to the change in the propagation lose between the mobile station and the base station. The rate of the variation also depends upon the speed of the mobile station, e.g., the doppler frequency.
In cellular mobile radio systems, detecting algorithms are used to detect data in a signal received from a mobile station. However, some detecting algorithms work better for slow moving mobiles while other detecting algorithms work better for fast moving mobile stations. In most prior art systems, the systems uses detecting algorithms that usually optimize a received signal from a fast moving mobile station. As a result, a non-optimum solution results for slow moving mobile stations.
Summary of the Invention
The present invention overcomes the shortcomings of the prior art by taking into account the speed of a mobile station during a call handoff and when detecting data in a received signal. In the present invention, the speed of a mobile station is deter¬ mined when the mobile station requests a handoff. As a result. a handoff queue can be prioritized according to the speed of the mobile station. For example, a fast moving mobile station will be given a higher priority than a slow moving mobile station. As a result, the faster moving mobile stations, which are losing their signals faster than the slower moving mobile stations, receive the first available free channels. As a result, fewer mobile stations will lose their calls.
In addition, the speed of a mobile station can be used when deciding which detecting algorithm should be used for detecting data in a received signal. As a result, the cellular mobile radio system can select detecting algorithms which give the best results for each individual mobile station.
In one embodiment of the present invention, an estimate of the doppler frequency is determined by first determining an estimate of the channel between the transmitter and the receiver. The channel is considered to be a linear transfer function with an impulse response which creates all the variations in phase and signal strength between the transmitter and the receiver. Several channel estimates are made at different times and the difference between the channel estimates is used to determine the approximate doppler frequency of the mobile station.
Brief Description of the Drawing
For a detailed description of the preferred embodiments of the present invention reference will now be made to the accompanying drawings wherein;
Figure 1 illustrates a portion of a cellular mobile radio system having cells, a mobile switching center, base stations and mobile stations.
Figure 2 is a block diagram of the relationship between the transmitter and the receiver.
Figure 3 is a block diagram of the circuit arrangement used in the method according to the present invention.
Figure 4 is a flow chart illustrating the calculation of the doppler frequency.
Detailed Description
Figure 1 illustrates 10 cells C1-C10, in a cellular mobile radio system. Normally, a cellular mobile radio system according to the present invention would be implemented with more than 10 cells. However, for the purposes of simplicity, the present invention can be explained using the simplified representation illustrated in Figure 1.
For each cell C1-C10 there is a base station B1-B10 with the same reference number as the corresponding cell. Figure 1 illustrates the base stations as situated in the vicinity of the cell center and having omni directional antennas. The cells C1-C10 are, therefore, schematically represented as hexagons. The base stations of adjacent cells may, however, be co-located in the vicinity of the cell borders and have directional antennas as is well known to those skilled in the art. Figure 1 also illustrates 9 mobile stations M1-M9 movable within a cell and from one cell to another. In a typical cellular radio system there would normally be 9 cellular mobile stations. In fact, there are typically many times the number of mobile stations as there are base stations. However, for the purposes of explaining the invention, the reduced number of mobile stations is suf- ficient.
Also illustrated in Figure 1 is a mobile switching center MSC. The mobile switching center MSC illustrated in Figure 1 is connected to all 10 base stations B1-B10 by cables. The mobile switching center MSC is also connected by cables to a fixed public switching telephone network. All cables from the mobile switching center MSC to the base stations B1-B10 and cables to the fixed network are not illustrated. In addition, to the mobile switching center MSC illustrated, there may be another mobile switching center connected by cables to base stations other than those illustrated in Figure 1. Instead of cables, other means, for example, fixed radio links may be used for connecting base stations B1-B10 to the mobile switching center MSC. The mobile switching center MSC, the base station B1-B10 and the mobile stations M1-M9 are all computer controlled. Figure 2 illustrates an overview picture of the link between a transmitter 10 and a receiver 14. In one embodiment of the present invention, the transmitter 10 is in the mobile station and the receiver 14 is located at the base station. Transmitter 10 sends a signal to the receiver 14 through a channel 12. The channel is considered to be a linear transfer function with an impulse response h(t) which creates all the variations and phase and signal strength between the transmitter and the receiver. The transmitted signal s(t) is affected by the channel impulse response h(t) to form the received signal r(t) which is fed into a channel estimator 16 which calculates a discrete approximation to h(t) called h(n) . The discrete approximation h(n) is then fed into the fading frequency estimator 18 which produces an estimate of the doppler frequency for the mobile station.
Figure 3 provides a detailed description of the components contained in the fading frequency estimator 18. The fading frequency estimator circuit contains a delay circuit D for delaying a channel estimate for D samples. An arrangement 24 is used for forming the difference between two channel estimates wherein one estimate has been delayed for D samples. The result of the arrangement 24 is a signal Vj(n) which is equal to the difference between two channel estimates. The circuit also contains low pass filters 26, 30 and 34 which reduce the amount of noise and modulation rests in a signal. The circuit also contains squaring circuits 28 and 32 which square the Vj(n) signal and the hj(n) signal. In the alternative, magnitude calculators can be substituted for the squaring circuits 28 and 32 to calculate the amplitude of the signals. Finally, the circuit contains a comparing component for dividing two signals. The operation of the fading frequency estimator shown in Figur 3 will be described in more detail with reference to Figure 4 When the receiver 14 receives a signal from the transmitter 10 the channel estimator 16 calculates a channel estimate of th impulse response h(t) for a time tl. The channel estimator the calculates a second channel estimate component at a time t2 whic occurs D samples later in Step 52. The arrangement 24 the calculates the difference between the two channel estimat components hj(n) and hj(n-D) in Step 52. The result of th difference between the two signals is the signal Vj(n) . Th signal V (n) is then filtered by a low pass filter 26 to reduce the amount of noise and modulation in the signal. This is essential to getting a useful doppler frequency estimate in a noise environment. The Vj(n) signal is then squared in Step 58. The square value of the signal Vj(n) is then passed through a low pass filter 30 in Step 60. In the meantime, the hj(n) signal is squared in Step 62 and passed through a low pass filter 34 in Step 64. Finally, the square value of the signal Vj(n) is divided by the square value of the hj(n) signal to normalize the signal in Step 56. The result is proportional to the squared value of the doppler frequency for the mobile station. As a result, the speed of the mobile station can be estimated by determining the approximate doppler frequency for the mobile station.
The present invention, as described above, determines an approximation of the doppler frequency of a mobile station. As a result, the cellular mobile radio system can use the doppler frequency or the speed of the mobile station to prioritize a handoff queue or to select an appropriate detecting algorithm. While the invention has been described in its preferred embodi¬ ments, it is to be understood that the words that have been used to words of description rather than of limitation and the changes within purview of the appended claims may be made without the party from the true scope and spirit of the invention in its broader aspects.

Claims (12)

WE C AIM;
1. A method for estimating the doppler frequency of the mobile station in a cellular mobile radio system having a plurality of base stations and a plurality of mobile stations comprising the steps of: determining channel estimate components at a plurality of different times for a signal between a transmitter and a receiver to produce a first and second signal; calculating the difference between said first and second signals to produce a third signal; and calculating the amplitude of said third signal and said first signal.
2. A method for estimating the doppler frequency of a mobile station in a cellular mobile radio system having a plurality of base stations and a plurality of mobile stations according to claim 1, wherein said second signal is delayed for a predeter¬ mined period of time.
3. A method for estimating the doppler frequency of a mobile station in a cellular mobile radio system having a plurality of base stations and a plurality of mobile stations according to claim 1, further comprising the step of filtering said third signal to reduce noise and modulation rests.
4. A method for estimating the doppler frequency of a mobile station in a cellular mobile radio system having a plurality of base stations and a plurality of mobile stations according to claim 3, wherein said third signal is filtered by a low pass filter.
5. A method for estimating the doppler frequency of the mobile station in a cellular mobile radio system having a plurality of base stations and a plurality of mobile stations according to claim 1, wherein said third signal and said first signal are squared to calculate the amplitude of said signals.
6. A method for estimating the doppler frequency of a mobile station in a cellular mobile radio system having a plurality of base stations in a plurality of mobile stations according to claim 5, wherein said squared first signal and said squared third signal are filtered by a low pass filter.
7. A method for estimating the doppler frequency of a mobile station in a cellular mobile radio system having a plurality of base stations and a plurality of mobile stations according to claim 1, wherein the amplitude of said third signal and said first signal are calculated by a magnitude calculator.
8. A method for estimating the doppler frequency of a mobile station in a cellular mobile radio system having a plurality of base stations and a plurality of mobile stations according to claim 1, wherein said third signal is normalized by dividing said third signal by said first signal.
9. A circuit for estimating the doppler frequency of a signal between a mobile station and a base station in a cellular mobile radio system having a plurality of base stations and a plurality of mobile stations comprising: calculating means for calculating channel estimate com¬ ponents for said signal between the mobile station and the base station to produce a first and second signal; differential means for calculating the difference between said first and second signals to produce a third signal; filtering means for filtering said third signal; multiplying means for squaring the first signal and the third signal; means for dividing said squared third signal by said squared first signal.
10. A circuit according to claim 9, wherein said filtering means is a low pass filter.
11. A circuit according to claim 9, further comprising a second filtering means for filtering said squared first signal and said squared third signal.
12. A circuit according to claim 11, wherein said second filtering means is a low pass filter.
AU22329/92A 1991-06-27 1992-06-16 Method and apparatus for estimating the doppler frequency of a mobile station Abandoned AU2232992A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US72187891A 1991-06-27 1991-06-27
US721878 1996-09-27

Publications (1)

Publication Number Publication Date
AU2232992A true AU2232992A (en) 1993-01-25

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Family Applications (1)

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AU22329/92A Abandoned AU2232992A (en) 1991-06-27 1992-06-16 Method and apparatus for estimating the doppler frequency of a mobile station

Country Status (6)

Country Link
JP (1) JPH06502291A (en)
AU (1) AU2232992A (en)
CA (1) CA2089090A1 (en)
GB (1) GB2262688A (en)
MX (1) MX9203067A (en)
WO (1) WO1993000777A1 (en)

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JP2972445B2 (en) * 1992-07-17 1999-11-08 日本電気通信システム株式会社 Electric field level measurement method
JP2878052B2 (en) * 1993-01-12 1999-04-05 日本電気通信システム株式会社 Electric field level measurement area control method
GB2285198B (en) * 1993-12-22 1998-03-04 Nokia Mobile Phones Ltd Multi-mode radio telephone
US5465389A (en) * 1994-02-25 1995-11-07 At&T Corp. Method of prioritizing handoff procedures in a cellular system
US5551058A (en) * 1994-10-31 1996-08-27 Motorola, Inc. Method and system for intelligent cell selection using location data in cellular systems
US5551059A (en) * 1994-10-31 1996-08-27 Motorola, Inc. Method and system for intelligent cell selection using doppler data in cellular systems
FI105370B (en) * 1995-06-16 2000-07-31 Nokia Networks Oy Procedure for identifying a fast mobile terminal as well as a base station
FR2789492A1 (en) * 1999-02-08 2000-08-11 Mitsubishi Electric Inf Tech METHOD OF ESTIMATING THE RELATIVE MOTION SPEED OF A TRANSMITTER AND A COMMUNICATION RECEIVER WITH EACH OTHER OF A TELECOMMUNICATIONS SYSTEM
US6850505B1 (en) * 1999-09-01 2005-02-01 Telefonaktiebolaget L M Ericsson (Publ) Method and apparatus for Doppler frequency estimation
WO2002037136A1 (en) * 2000-10-23 2002-05-10 Linkair Communications, Inc. Method of measuring the doppler frequency-shift and the relevant device
GB2370449A (en) * 2000-12-15 2002-06-26 Motorola Inc Cell selection using kinetic characteristics
US8199696B2 (en) 2001-03-29 2012-06-12 Qualcomm Incorporated Method and apparatus for power control in a wireless communication system
US10536243B2 (en) 2014-08-20 2020-01-14 Telefonaktiebolaget Lm Ericsson (Publ) Method and apparatus for coordinating resources
WO2017211388A1 (en) 2016-06-07 2017-12-14 Telefonaktiebolaget Lm Ericsson (Publ) Doppler shift or doppler spread as input for beam-switching or node-switching in wireless networks

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI83999C (en) * 1989-10-26 1991-09-25 Vaisala Oy FOERFARANDE OCH ANORDNING FOER MAETNING AV HASTIGHETEN AV ETT OBJEKT GENOM ATT UTNYTTJA DOPPLER -FOERSKJUTNINGEN AV ELEKTROMAGNETISK STRAOLNING.
US5239667A (en) * 1990-01-31 1993-08-24 Nec Corporation Method of controlling handoff in cellular mobile radio communications system
GB9016341D0 (en) * 1990-07-25 1990-09-12 British Telecomm Speed estimation

Also Published As

Publication number Publication date
JPH06502291A (en) 1994-03-10
MX9203067A (en) 1992-12-01
CA2089090A1 (en) 1992-12-28
GB2262688A (en) 1993-06-23
GB9303107D0 (en) 1993-04-21
WO1993000777A1 (en) 1993-01-07

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