EP1232589A1 - Estimation de vitesse relative a l'aide de commandes de puissance d'emission de signaux - Google Patents

Estimation de vitesse relative a l'aide de commandes de puissance d'emission de signaux

Info

Publication number
EP1232589A1
EP1232589A1 EP00974524A EP00974524A EP1232589A1 EP 1232589 A1 EP1232589 A1 EP 1232589A1 EP 00974524 A EP00974524 A EP 00974524A EP 00974524 A EP00974524 A EP 00974524A EP 1232589 A1 EP1232589 A1 EP 1232589A1
Authority
EP
European Patent Office
Prior art keywords
transmitter
receiver
fading
radio channel
transmission power
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.)
Withdrawn
Application number
EP00974524A
Other languages
German (de)
English (en)
Inventor
Roozbeh Atarius
Johan Nilsson
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 EP1232589A1 publication Critical patent/EP1232589A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/28—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission
    • H04W52/282—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission taking into account the speed of the mobile
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/309—Measuring or estimating channel quality parameters
    • H04B17/336—Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC

Definitions

  • the invention relates to wireless telecommunications, and in particular to estimating the velocity of a mobile station relative to a transmitter in a mobile communications system.
  • FIG. 1 illustrates an exemplary radio channel that is known in the art.
  • a transmitter 102 transmits signals via a radio channel 104, which is affected by AWGN (Additive White Gaussian Noise) as represented by element 106.
  • the signal is then received at a receiver 108.
  • AWGN Additional White Gaussian Noise
  • Radio channels are often subject to multipath propogation, which arises when a path between a transmitter and a receiver includes reflections from large objects, so that rays of the transmission signal from the transmitter travel along different paths having different lengths, before meeting at the receiver.
  • rays of the signal meet there are phase differences between them because of the different path lengths.
  • This can give rise to Rayleigh fading, where the rays or echoes of the transmission signal constructively or destructively combine, depending on their phases.
  • the combined signal received at the receiver appears to vary randomly in amplitude and phase, due to being composed of the many smaller rays or echoes of the transmission signal that traveled along different paths on their way to the receiver.
  • the amplitude or power of the transmission signal at the receiver can vary due to Rayleigh fading.
  • the Rayleigh Distribution describes a distribution of signal components in a Rayleigh Fading Channel within an envelope about an RMS value of a signal transmitted from a transmitter to a receiver, when the line-of-sight path between the receiver and the transmitter is obstructed so that the signal transmitted by the transmitter reaches the receiver in a multipath fashion, with different rays or components of the signal reflecting along different paths to the receiver.
  • the Rayleigh Distribution describes the envelope because, due to the arrival of numerous out-of-phase multipath components or rays, the in-phase and quadrature components of the signal are Gaussian in nature.
  • the signal envelope which is the square root of the sum of the squares of the in-phase and quadrature components, follows a Rayleigh Distribution.
  • the receiver changes position relative to the transmitter and the environment, it can move through positions where the rays combine differently.
  • the rays will combine at the receiver constructively and then destructively in an alternating fashion, so that the receiver experiences a series of "fading dips" where the amplitude of the received signal periodically dips down and then returns to its former level.
  • the frequency of these fading dips, or in other words the number of fading dips per unit time, is commonly referred to as the "fading rate" of the radio channel.
  • the fading rate corresponds to the velocity of the receiver relative to the transmitter, so that as the velocity of the receiver increases, so does the fading rate.
  • the fading rate is equivalent to the "Doppler spread" of the Rayleigh fading radio channel, which is defined as:
  • V velocity of the receiver relative to the transmitter
  • F c frequency of the transmission signal from the transmitter
  • c the speed of light (3 x 10 8 meters/second).
  • the Doppler spread will be about 185 hertz.
  • the fading rate will be 185 hertz, which means that the amplitude of the transmission signal at the receiver will dip, or cyclically fade in amplitude and then recover, 185 times per second.
  • this equation can be used to determine the relative velocity of the receiver.
  • the relative velocity between the receiver and the transmitter is proportional to a bandwidth of the Rayleigh distribution, which in turn is related to the properties of the radio channel, such as the radio channel's second moment statistical properties. If the properties of the radio channel are known, commutation or communication between the transmitter and the receiver can be significantly improved. In other words, the relative velocity between the receiver and the transmitter determines or reflects properties of the radio channel that are useful to enhance communication between the transmitter and the receiver. Consequently, it is important to accurately determine the relative velocity between the receiver and the transmitter, e.g. , between a Mobile Station (MS) and a Base Station (BS) in a mobile communications network.
  • the relative velocity between the receiver and the transmitter is usually estimated by studying the fading properties of the radio channel as seen by the receiver, for example in accordance with the Doppler spread equation described above. Due to the high chip rate in mobile communications systems that use CDMA (Code
  • receivers in such systems are usually equipped with a power control to reduce or combat the effects of fading dips in the radio channel.
  • Control of the power of the signal broadcast by the transmitter is typically based on the receiver's estimation of the SIR (Signal to Interference Ratio).
  • the SIR is typically estimated using pilot techniques such as pilot signals or channels, data, or a combination of pilot techniques and data.
  • the receiver uses the estimate of the SIR to inform or instruct the transmitter to reduce or increase the power with which it broadcasts signals to the receiver. In essence, the transmitter varies the signal broadcast power to compensate for Rayleigh fading.
  • FIG. 2 shows an exemplary procedure known in the art, wherein as shown in step 202, the SIR is estimated using data and/or pilot techniques. From step 202 control flows to step 204, where the SIR is compared against a reference. From step 204 control flows to step 206, where TPC-commands are formed based on the comparison in step 204, and then sent to the transmitter to inform the transmitter how it should change the power or amplitude of the signal it is transmitting to the receiver.
  • Communications between the receiver and the transmitter e.g. , the mobile station and the base station relating to controlling signal power transmitted from the transmitter are usually performed using TPC commands.
  • FIG. 3 illustrates an exemplary structure of data transmitted in downlink from a network to a mobile station in a W-CDMA (Wideband - Code Division Multiple Access) system.
  • a super frame 302 contains 72 frames such as the frame 304.
  • Each of the frames contains 15 slots such as the slot 306.
  • Each slot contains symbols, including pilot symbols and TPC symbols. The number of symbols of each kind, and the total number of all symbols in the slot, depends on the spreading factor used for the CDMA spreading. For example, each slot can contain a total of 20 symbols including 4 pilot symbols 308 and a single TPC symbol 310 as shown in slot 306.
  • the transmission power control rate applied to the transmitter limits the maximum fading rate which the transmitter can effectively compensate for. For example, in W-CDMA (Wideband - Code Division Multiple Access) where the power control rate is 1,500 hertz, fading dips can be effectively combated using TPC commands when the mobile station is moving with a velocity of less than 30 kilometers per hour.
  • the power control typically operates most effectively to combat fade when the relative velocity is low with respect to the power control rate. This is because the power control rate determines how quickly the transmitter can react and alter its broadcast power output to combat fading dips at the receiver, and the relative velocity between the receiver and the transmitter determines how quickly fading dips can occur at the receiver. As the relative velocity increases and therefore also the fade rate, the power control rate necessary to effectively combat the fade must also increase.
  • a higher fading rate due to a greater relative velocity of the receiver can in theory be effectively combated using TPC commands if the power control rate is increased appropriately.
  • the relative velocity between the receiver and the transmitter is usually estimated by studying the fading properties of the radio channel as seen by the receiver.
  • this technique for estimating the relative velocity is inaccurate when the TPC commands are effectively used to combat the Rayleigh fading seen by the receiver, because the compensation removes the fade seen by the receiver.
  • inaccuracy of the velocity estimation increases with the effectiveness of the power control.
  • the velocity estimation will be inaccurate.
  • the Rayleigh fading rate or Doppler spread of the radio channel and thus the relative velocity between the transmitter and the receiver are estimated by effectively observing fluctuations in signal power or amplitude that occur at the transmitter, instead of fluctuations in power or quality of a signal received at the receiver. This is done by observing the TPC commands, or the signal broadcast power changes represented by the TPC commands, sent by the receiver to the transmitter to cause the transmitter to adjust its signal transmission power so that the signal will have an effectively constant power level or signal quality when it is received by the receiver.
  • the TPC commands can be observed over a period of time to determine how many fading dips occurred in the channel during that time. Consequently, the TPC commands, or the signal broadcast power changes indicated by the TPC commands, can be used to accurately estimate the fading rate, and also a relative velocity between the receiver and the transmitter using the Doppler spread technique described above with respect to the fading rate. Such estimations are appropriate when fading dips can be combated using TPC commands.
  • FIG. 1 shows radio communications in accordance with the prior art.
  • FIG. 2 shows an exemplary transmission power control procedure in accordance with the prior art.
  • FIG. 3 shows an exemplary structure of transmitted data in a downlink from a network to a mobile station in a W-CDMA (Wireless - Code Division Multiple Access) system.
  • W-CDMA Wireless - Code Division Multiple Access
  • FIG. 4 shows an example of a series of TPC commands corresponding to a fading dip.
  • FIG. 5 shows a process in accordance with exemplary embodiments of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • the Rayleigh fading rate of the radio channel in accordance with exemplary embodiments of the invention, are estimated by effectively observing the adjustments or fluctuations in signal transmission power or amplitude of the transmitter.
  • the receiver controls and adjusts the transmission power of the transmitter to compensate for Rayleigh fading, i.e.
  • the receiver can send TPC (Transmission Power Control) commands to the transmitter to cause the transmitter to adjust its signal transmission power to combat the fading dips. Since the transmission power fluctuations correspond to and indicate the fading dips in the channel, the fading rate (fading dips per unit time) or Doppler spread can be determined by observing the TPC commands. In turn, the fading rate or Doppler spread can be used to accurately estimate the relative velocity between the receiver and the transmitter using the Doppler spread technique described above with respect to the fading rate.
  • TPC Transmission Power Control
  • FIG. 4 shows an example of a series of TPC commands and a corresponding signal transmission power, indicating a fading dip.
  • the signal transmission power is indicated on the Y-axis.
  • a slot structure such as that shown in FIG. 3 is used, wherein each slot that the receiver sends to the transmitter includes a TPC command.
  • the frequency of TPC commands can be, for example, 1 ,500 hertz in a WCDMA system. Exemplary signal transmission power increments and other exemplary TPC command frequencies are well known in the art, and are therefore not described in further detail here.
  • the TPC commands instruct the transmitter to effectively maintain a steady state signal transmission power.
  • the overall effect is an increase in signal transmission power
  • the TPC commands issued by the receiver to the transmitter cause the transmitter to decrease the signal transmission power to the steady state level.
  • the TPC commands instruct the transmitter to effectively maintain a steady state signal transmission power.
  • FIG. 4 shows a single fading dip that occurred in the channel during a time period spanning the time segments B and C.
  • a bit of noise or variation in rate of signal power change during the dip can also be seen midway through time segment B, where one of the TPC commands causes the signal transmission power to decrease momentarily before the next TPC command causes the signal transmission power to continue increasing.
  • it can be necessary to represent different rates of change in signal power using mixtures of "up” and "down” binary TPC commands. For example, a TPC sequence up-up-up-down-up-up-down represents a higher rate of change than a TPC series up-up-down-up-up-down.
  • FIG. 5 illustrates a method of using TPC commands to estimate a relative velocity between a receiver and a transmitter in accordance with exemplary embodiments of the present invention.
  • TPC commands are first observed.
  • control flows to step 504, where a number of signal transmission power level fluctuations that correspond to fading dips in the radio channel between the transmitter and the receiver are identified based on the observed TPC commands.
  • a time frame in which the identified fluctuations occur is also identified, to determine the rate or frequency of the identified fluctuations. This rate is an estimated fading rate or Doppler spread.
  • control proceeds to step 506, where a velocity of the receiver relative to the transmitter is estimated based on the estimated fading rate or Doppler spread.
  • the velocity can be estimated by plugging the estimated fading rate and the known carrier frequency of the signal transmitted by the transmitter into the Doppler spread equation set forth further above.
  • control proceeds to step 508, where the estimated velocity of the receiver relative to the transmitter is used to estimate or characterize properties of the radio channel.
  • control proceeds to step 510, where the properties of the radio channel are then used to maintain or enhance the quality of communications between the receiver and the transmitter across the radio channel.
  • control proceeds to step 502 where the cycle repeats.
  • observation and analysis of TPC commands to determine fading rate and relative velocity between a mobile station and a base station can take place within the mobile station.
  • observation and analysis of TPC commands to determine fading rate and relative velocity between a receiver and a transmitter can take place within the receiver.
  • the analysis and determination can take place at any appropriate location or locations within, or connected to, the communication system.
  • a mobile station can act both as a transmitter and as a receiver, and a base station can also act both as a transmitter and as a receiver, because communication between the mobile station and the base station is typically two-way. Accordingly, the principles described herein can apply variously and reciprocally to both mobile stations and base stations, as well as other transceivers. Those skilled in the art will also appreciate that the present invention can be applied in systems having different or broader sets of available TPC commands, including for example TPC commands having a variety of available power increment magnitudes including zero.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Quality & Reliability (AREA)
  • Electromagnetism (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Monitoring And Testing Of Transmission In General (AREA)

Abstract

Dans un système comprenant un émetteur et un récepteur qui communiquent sur un canal radio, et dans lequel la puissance d'émission de signaux de l'émetteur est régulée de façon à compenser des baisses d'évanouissement dans ledit canal, le taux d'évanouissements de Raleigh du canal radio, et donc la vitesse relative entre l'émetteur et le récepteur, sont estimés par une observation efficace des régulations et fluctuations dans la puissance d'émission de signaux ou dans l'amplitude de l'émetteur. Conformément au mode de réalisation exemplaire de cette invention, on obtient ce résultat, par observation des commandes de puissance d'émission (TCP) qui amènent l'émetteur à réguler sa puissance d'émission de signaux pour combattre un évanouissement de Rayleigh, c'est-à-dire des baisses d'évanouissement dans le canal radio. Du fait que les commandes TPC amènent l'émetteur à faire varier sa puissance d'émission de signaux pour compenser les baisses d'évanouissement, lesdites baisses d'évanouissement et donc le taux d'évanouissements et la vitesse relative entre l'émetteur et le récepteur peuvent être déterminés par observation des fluctuations de la puissance d'émission de signaux représentées par les commandes TPC.
EP00974524A 1999-11-22 2000-11-13 Estimation de vitesse relative a l'aide de commandes de puissance d'emission de signaux Withdrawn EP1232589A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US44735499A 1999-11-22 1999-11-22
US447354 1999-11-22
PCT/EP2000/011188 WO2001041335A1 (fr) 1999-11-22 2000-11-13 Estimation de vitesse relative a l'aide de commandes de puissance d'emission de signaux

Publications (1)

Publication Number Publication Date
EP1232589A1 true EP1232589A1 (fr) 2002-08-21

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP00974524A Withdrawn EP1232589A1 (fr) 1999-11-22 2000-11-13 Estimation de vitesse relative a l'aide de commandes de puissance d'emission de signaux

Country Status (5)

Country Link
EP (1) EP1232589A1 (fr)
JP (1) JP2003516091A (fr)
CN (1) CN1391742A (fr)
AU (1) AU1279501A (fr)
WO (1) WO2001041335A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4138668B2 (ja) 2002-03-08 2008-08-27 テレフオンアクチーボラゲット エル エム エリクソン（パブル） 送信電力制御コマンドを通じて速度情報を行なうシステム及び方法

Family Cites Families (4)

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Publication number Priority date Publication date Assignee Title
SE517660C2 (sv) * 1997-06-23 2002-07-02 Telia Ab Förbättringar av, eller med avseende på, mobilradiotelefoni
WO1999012275A1 (fr) * 1997-09-02 1999-03-11 Motorola Inc. Commande adaptative de la puissance d'un sous-canal pilote
JP3393365B2 (ja) * 1997-10-08 2003-04-07 沖電気工業株式会社 送信電力制御方法
JP3913879B2 (ja) * 1998-02-03 2007-05-09 富士通株式会社 移動速度に基づく通信制御装置および方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0141335A1 *

Also Published As

Publication number Publication date
WO2001041335A1 (fr) 2001-06-07
CN1391742A (zh) 2003-01-15
AU1279501A (en) 2001-06-12
JP2003516091A (ja) 2003-05-07

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