EP2636158A1 - A radio base station and a method therein for estimating a doppler spread - Google Patents
A radio base station and a method therein for estimating a doppler spreadInfo
- Publication number
- EP2636158A1 EP2636158A1 EP10859336.9A EP10859336A EP2636158A1 EP 2636158 A1 EP2636158 A1 EP 2636158A1 EP 10859336 A EP10859336 A EP 10859336A EP 2636158 A1 EP2636158 A1 EP 2636158A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- signal
- base station
- radio base
- channel
- doppler spread
- 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- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0222—Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0667—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/10—Polarisation diversity; Directional diversity
Definitions
- Embodiments herein relate to a radio base station and a method therein. In particular, embodiments herein relate to estimation of Doppler spread in a radio communications network.
- a user equipment communicates information over a radio link to a radio base station, in a so called uplink (UL)
- a Doppler shift is a frequency shift experienced by a receiver of a radio signal when a transmitter and the receiver are moving relative to one another.
- a Doppler spread is a spread of Doppler shifts for a number of incoming signaling rays to the receiver from the transmitter. The Doppler spread causes variations in a propagation channel between the transmitter and the receiver. Knowledge of the Doppler spread has numerous applications in mobile communications systems. Such applications include receiver algorithms like smoothing filters for channel estimation and radio resource management algorithms such as link adaptation, scheduling, and selection of closed-loop or open-loop spatial multiplexing.
- the Doppler spread of a radio link is inversely proportional to a channel coherence time.
- the channel coherence time is the time duration over which a channel impulse response is considered to be correlated, that is, the channel impulse response is correlated to another channel impulse response made during the channel coherence time.
- a long channel coherence time allows the receiver, for example the radio base station, to follow effects of small scale fading for scheduling and link adaptation, e.g. for using closed-loop spatial multiplexing in downlink and time-dependent scheduling in mobile communications systems such as Evolved Universal Terrestrial Radio Access (E-UTRA) systems.
- E-UTRA Evolved Universal Terrestrial Radio Access
- a period for transmitting channel quality information reports from the user equipment to the radio base station should be shorter than the channel coherence time to provide downlink channel state information that is accurate during the report period.
- a periodicity of transmitted channel sounding reference signals in the uplink should be shorter than the channel coherence time to enable valid uplink channel quality estimation between the sounding reference signal transmissions.
- the Doppler spread may be estimated in a number of ways using Doppler spread estimators.
- One class of Doppler spread estimators is based on the temporal properties of channel estimates of received signals. In time domain, a propagation channel may be modeled as a tapped delay line with time-dependent channel taps. Assuming that a channel tap C is a Rayleigh fading channel tap, the Doppler spread may be estimated from a measured level-crossing rate of the channel tap C .
- Several estimators rely on an autocorrelation function R c of the channel tap C :
- ⁇ is the delay
- J 0 is the zero-order Bessel function of the first kind
- f D denotes the Doppler spread estimate
- the Doppler spread estimate f D may also be obtained from the auto cova ance functions of functions of the channel taps.
- An example of such a function of the channel tap is the squared amplitude of the channel tap.
- Channel estimates for a certain time instance are typically obtained from a transmission of a pilot or reference signal.
- Channel estimators are simplified and more efficient if there are continuous or periodic transmissions on fixed frequencies. The shorter the periodicity of the transmissions, the higher Doppler spreads, or shorter channel coherence times, may be estimated leading to a better resolution of the estimates.
- the mobile may change the transmit power between subsequent transmissions. Such a change alters the amplitude and possibly also the phase of the transmitted signal.
- the radio base station estimates a composite channel that is composed of the transmitter gain, i.e. amplitude and phase, and a propagation channel.
- the composite channel is relevant for a compensation in the receiver but not relevant for estimating propagation of the transmission.
- the autocorrelation function as well as other temporal properties of the composite channel may be very different from those of the propagation channel and therefore Doppler spread estimates based on channel estimates may be erroneous.
- Doppler spread estimators encompass the temporal properties relating to time of the received signal on a receive antenna resulting in erroneous Doppler spread estimates leading to a transmission scheme of poor efficiency.
- the object is achieved by a method in a radio base station for estimating Doppler spread of a signal transmitted by a user equipment over a channel in a radio communications network.
- the radio base station and user equipment are comprised in the radio communications network.
- the radio base station receives a first signal and a second signal from the user equipment, which first signal and second signal are based on the signal transmitted by the user equipment. Also, the first and second signals are separated in space, time and/or polarisation.
- the radio base station estimates a first channel estimate of the received first signal by comparing the received first signal to a known signal, and a second channel estimate of the received second signal by comparing the received second signal to the known signal.
- the radio base station furthermore determines a ratio of the first channel estimate to the second channel estimate, and estimates an autocorrelation function of a function of the determined ratio.
- the radio base station then estimates the Doppler spread based on the estimated autocorrelation function.
- a radio base station is provided for estimating
- the radio base station is arranged to be comprised in the radio communications network. Furthermore, the radio base station comprises a receiving circuit configured to receive a first signal and a second signal from the user equipment. The first signal and the second signal are based on the signal transmitted by the user equipment, which first signal and second signal are separated in space, time and/or polarisation. In addition, the radio base station comprises a first estimating circuit configured to estimate a first channel estimate of the received first signal by comparing the received first signal to a known signal. Also, the radio base station comprises a second estimating circuit configured to estimate a second channel estimate of the received second signal by comparing the received second signal to the known signal.
- the radio base station further comprises a determining circuit configured to determine a ratio of the first channel estimate to the second channel estimate.
- the radio base station comprises an estimating autocorrelation circuit configured to estimate an autocorrelation function of a function of the determined ratio.
- the radio base station also comprises an estimating Doppler spread circuit configured to estimate the Doppler spread based on the estimated autocorrelation function.
- the estimate of the Doppler spread is based on the ratio of channel estimates of two separated received signals, which signals are based on the same transmitted reference signal. This is performed by using, for example, two receive antennas. Thereby, the changes of the amplitude and phase of the transmitted reference signal do not impact when estimating the Doppler spread.
- the Doppler spread estimate is more accurate leading to more efficient transmission schemes, link adaptations, scheduling etc., which result in an improved performance of the radio communications network. Also, higher throughput and data rate may be achieved in the radio communications network with a more accurate Doppler spread estimate.
- Fig. 1 is a block diagram depicting a radio communications network
- Fig. 2 is a schematic overview depicting a combined flow chart and signalling scheme in a radio communications network
- Fig. 3 is a block diagram depicting a radio base station
- Fig. 4 is a schematic overview of a graph depicting a curve of an autocorrelation function
- Fig. 5 is a block diagram of a method in a radio base station
- Fig. 6 is a block diagram of a radio base station. DETAILED DESCRIPTION
- Fig. 1 shows a schematic overview of a radio communications network, such as e.g. the Long Term Evolution (LTE), LTE-Advanced, 3rd Generation Partnership Project (3GPP) Wideband Code Division Multiple Access (WCDMA) system, Global System for Mobile communications/Enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention some possible options for implementing embodiments disclosed herein.
- LTE Long Term Evolution
- 3GPP 3rd Generation Partnership Project
- WCDMA Wideband Code Division Multiple Access
- GSM/EDGE Global System for Mobile communications/Enhanced Data rate for GSM Evolution
- WiMax Worldwide Interoperability for Microwave Access
- UMB Ultra Mobile Broadband
- a User Equipment (UE) 10, served by a radio base station 12, is
- a Doppler shift is the frequency shift experienced by the radio base station 12 of a radio signal when the user equipment 10 and the radio base station 12 are moving relative to one another with a velocity v. That is, the radio base station 12 may be stationary or moving, and the user equipment 10 may be still or moving, and the difference in velocity between them is v in a direction.
- the user equipment 10 transmits an original signal to the radio base station 12 in the UL.
- the radio base station 12 receives the first signal and the second signal from the user equipment 10.
- the first and second signals are based on the original signal but are separated in, for example, space, time and/or polarisation.
- transmission power of the user equipment 0 influences the amplitude and phase, varying transmission power of the user equipment 10 will change channel autocorrelation properties as obtained from a single received signal.
- the radio base station 12 estimates a first channel estimate of the first signal by comparing the received first signal to an initial signal also referred to as a known signal. Furthermore, the radio base station 12 estimates a second channel estimate of the second signal by comparing the received second signal to the initial signal. For example, a reference signal comprised in the received first signal and second signal may be compared to a known reference signal stored in the radio base station 12. The radio base station 12 then determines a ratio of the channel estimates by dividing the first channel estimate with the second channel estimate. The ratio is a dimensionless parameter cancelling out the transmit amplitude and phase dependency of the Doppler spread estimation. The ratio of the channel estimates is then used in a function to estimate an autocorrelation function. This estimated autocorrelation function is then used to estimate the Doppler spread.
- the thus more accurate estimated Doppler spread may be used for frequency selective scheduling, link adaptation, modulation and coding for DL transmissions, Multiple Input Multiple Output (MIMO) mode etc.
- MIMO Multiple Input Multiple Output
- Fig. 2 shows a schematic combined signaling and flow chart in a radio
- the radio communications network comprises the radio base station 12 and the user equipment 10 moving relative to one another.
- the user equipment 10 transmits a signal s to the radio base station 12.
- the signal may comprise reference or pilot symbols known at the radio base station 12.
- the signal is separated along the way to the radio base station into a first signal s1 and a second signal s2.
- the first and second signals s1 ,s2 are thus originating from the same transmitted signal, the originating signal, and separated in space, polarisation and/or in time.
- Signals separated in space are distinguished by receive antennas with some distance between them.
- Signals separated in polarisation are distinguished by cross-polarised receive antennas.
- Signals separated in time are distinguished in a channel estimator. Also combinations thereof may be used to distinguish the first and second signal.
- the radio base station 12 receives, in the illustrated example, the first signal s1 at a first antenna and the second signal s2 at a second antenna. Step 202.
- the radio base station 12 estimates the Doppler spread by first estimating a first channel estimate of the first signal and a second channel estimate of the second signal. Then, the radio base station 12 determines a ratio of the first channel estimate to the second channel estimate and estimates an autocorrelation function of a function of the determined ratio. The radio base station 12 then estimates the Doppler spread based on the estimated autocorrelation function.
- the radio base station 12 has by basing the estimation of the Doppler spread on a ratio of channel estimates of the first and second signals eliminated the transmitter influence. That is, the influence of the amplitude and phase of the transmitted signal on the estimated Doppler spread has been cancelled out.
- FIG. 3 a block diagram depicting a radio base station 12 in a radio
- the radio base station 12 comprises a first antenna do and a second antenna aj.
- a baseband equivalent signal, Y a is a complex representation of a signal received over an antenna a.
- A is the number of receive antennas
- ft is noise and interference.
- ⁇ (*) is the baseband equivalent signal received over antenna a;. , i.e. in this case a e ⁇ ao , aj ⁇
- the transmitted signal is a product of the reference signal S and a complex gain factor 3 ⁇ 4 > with amplitude ⁇ and phase ⁇ which is constant during the transmission of the reference signal, used for one channel estimate of the channel, but possibly different between subsequent transmissions.
- the channel estimates are estimates of the composite channel because ⁇ ⁇ ⁇ is unknown in the receiver.
- both composite channel coefficients are proportional to the complex gain factor ⁇ 1 ⁇ of the transmission.
- An autocorrelation of a ratio of the two separate composite channel coefficients ⁇ r will reflect coherence properties of the channel excluding the gain factor variations so that the estimate of the Doppler spread may be unaffected by changes of amplitude and phase of the transmitted reference signal.
- the radio base station 12 comprises at least two receive antennas, achieving separation in space and/or polarisation, thereby always providing at least two channel coefficients, one for each receive antenna.
- a first channel estimator 303 performs a channel estimation on the baseband equivalent signal Y a ( received over antenna ⁇ 3 ⁇ 4 .
- the first channel estimator 303 compares the baseband equivalent signal ⁇ a o( ⁇ ) comprising a reference signal with a known reference signal stored in the radio base station 12. This results in a first channel estimate h a0 (t) .
- a second channel estimator 305 performs a channel estimation on the baseband equivalent signal ⁇ (*) received over antenna aj.
- the second channel estimator 305 compares the baseband equivalent signal r a ⁇ $) comprising the reference signal with the known reference signal stored in the radio base station 12. This results in a second channel estimate h al (t)
- a normalized ratio g(t) of the composite channel coefficients is considered.
- the normalized ratio t) may be expressed as
- a ratio estimate g(t) is calculated in a channel tap ratio calculator 307, also referred to as a determining circuit.
- the ratio estimate g(t) is the estimate of g(t) and is obtained from channel estimates h a0 (t) and h al (t) according to
- An autocorrelation function of g ⁇ t) is denoted i ⁇ (r) and is given by a normalized autocorrelation function p(x) and the Doppler spread f D :
- ⁇ is the delay, i.e. the time difference between two time instances to and t] in the argument of g(t) and hence the dimension of ⁇ is time.
- R g ty an estimate of the autocorrelation function of g(t) , denoted as R g ( ) , is first obtained from channel estimates of the signal.
- K is the number of sampled delays
- L is the number of estimated channel samples
- g is the ratio estimate of the normalized ratio g and is obtained from channel estimates according to (Eq. 3),
- AT is a delay sampling interval
- / is a delay index related to a reception time of the first and second signal
- g denotes the complex conjugate of the ratio estimate g .
- the Doppier spread can be estimated in an analyzer 311.
- the Doppier spread may be the maximum-likelihood estimate, i.e. the maximum-likelihood estimate is the Doppier spread that gives the largest probability of the estimate of the autocorrelation function.
- the Doppler spread is estimated as the value of that minimizes the discrepancy function i ⁇ g D ⁇
- Embodiments herein allow for robust Doppler spread estimation in systems where the amplitude and phase of the transmitted signal changes between transmissions due to variations in transmission power. By using a ratio of the channel estimates the complex gain factor ⁇ ] ⁇ from the different channel estimates may be eliminated.
- the normalized autocorrelation function p(x) mentioned above may be calculated numerically for uncorrelated Rayleigh fading channel coefficients and is plotted in Fig. 4.
- the values of the normalized autocorrelation function p(x) are defined along the y-axis and x is defined along the x-axis.
- Autocorrelation functions for different Doppler spread, scaled versions of p(x) may be compared to the estimated autocorrelation function and from the autocorrelation function that most resembles the estimated autocorrelation function the Doppler spread is estimated. That is, the Doppler spread with the
- autocorrelation function that most resembles the estimated autocorrelation function is the estimated Doppler spread.
- the method steps in the radio base station 12 for estimating Doppler spread of a signal transmitted by a user equipment 10 over a channel in a radio communications network will now be described with reference to a flowchart depicted in Fig. 5. The steps do not have to be taken in the order stated below, but may be taken in any suitable order.
- the radio base station 12 and user equipment 10 are comprised in the radio communications network.
- Step 501 The radio base station 12 receives a first signal and a second signal from the user equipment 10.
- the first signal and second signal are based on the signal transmitted by the user equipment 0 and the first and second signals are separated in space, time and/or polarisation.
- the first signal may be received at a first antenna and the second signal may be received at a second antenna.
- the first signal may be separated from the second signal by being received at a different point in space compared to the second signal, by being differently polarised than the second signal and/or by being delayed in time compared to the second signal.
- Step 502. The radio base station 12 estimates a first channel estimate of the received first signal by comparing the received first signal to a known signal. Step 503. The radio base station 12 estimates a second channel estimate of the received second signal by comparing the received second signal to the known signal.
- Step 504. The radio base station 12 determines a ratio of the first channel estimate to the second channel estimate.
- the ratio may be a normalised ratio.
- the radio base station 12 estimates an autocorrelation function of a function of the determined ratio.
- the radio base station 12 estimates the Doppler spread of the transmitted signal based on the estimated autocorrelation function.
- the Doppler spread may be estimated by comparing the estimated autocorrelation function to at least one pre- calculated autocorrelation function.
- the Doppler spread may be estimated by minimizing a discrepancy function, which discrepancy function may be calculated as a mean square error between the estimated autocorrelation function and the at least one pre-calculated autocorrelation function.
- a radio base station is provided.
- Fig. 6 is a block diagram depicting the radio base station 12 for estimating Doppler spread of a signal transmitted by the user equipment 10 over the channel in the radio communications network.
- the radio base station 12 is arranged to be comprised in the radio
- the radio base station 12 comprises a receiving circuit 601 configured to receive a first signal and a second signal from the user equipment 10.
- the first signal and second signal are based on the signal transmitted by the user equipment 10 and the first and second signals are separated in space, time and/or polarisation.
- the receiving circuit 601 may comprise a first antenna ⁇ 3 ⁇ 4 arranged to receive the first signal and a second antenna a arranged to receive the second signal.
- the first signal may be separated from the second signal by being received at a different point in space compared to the second signal and may be distinguished by antennas, ⁇ 3 ⁇ 4, and ⁇ 2y, with a distance between them.
- the first signal may alternatively or additionally be separated from the second signal by being received differently polarised compared to the second signal and may be distinguished by cross-polarised antennas.
- the first antenna ⁇ 3 ⁇ 4, and the second antenna aj may be cross polarised.
- the first signal may alternatively or additionally be separated in time by being delayed in time compared to the second signal and these signals are then distinguished in a channel estimator. It should be understood that also any combination of separation is possible.
- the radio base station 12 further comprises a first estimating circuit 602, corresponding to the first channel estimator 303 in Fig. 3, configured to estimate a first channel estimate of the received first signal by comparing the received first signal to a known signal.
- the radio base station 12 comprises a second estimating circuit 603, corresponding to the second channel estimator 305 in Fig. 3, configured to estimate a second channel estimate of the received second signal by comparing the received second signal to the known signal.
- the radio base station 12 comprises a determining circuit 604, corresponding to the channel tap ratio calculator 307 in Fig. 3, configured to determine a ratio of the first channel estimate to the second channel estimate. In some embodiments, the ratio may be a normalised ratio.
- the radio base station 12 further comprises an estimating autocorrelation circuit 605, corresponding to the autocorrelation estimator 309 in Fig. 3, configured to estimate an autocorrelation function of a function of the determined ratio. Also, the radio base station 12 comprises an estimating Doppler spread circuit 606, corresponding to the analyser 31 1 in Fig. 3, configured to estimate the Doppler spread based on the estimated autocorrelation function.
- the estimating Doppler spread circuit 606 may in some embodiments be configured to estimate Doppler spread by comparing the estimated autocorrelation function to at least one pre-calculated autocorrelation function.
- the estimating Doppler spread circuit 606 may be configured to estimate Doppler spread by minimizing a discrepancy function, which discrepancy function is calculated as a mean square error between the estimated autocorrelation function and the at least one pre-calculated autocorrelation function.
- the present mechanism for estimating Doppler spread of a signal transmitted by a user equipment may be implemented through one or more processors, such as a processing circuit 607 in the radio base station 12 depicted in Fig. 6, together with computer program code for performing the functions of the embodiments herein.
- the program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the present solution when being loaded into the radio base station 12.
- One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick.
- the computer program code may furthermore be provided as pure program code on a server and downloaded to the radio base station 12.
- the radio base station 12 may comprise a memory circuit 608 arranged to be used to store estimates, data, applications to perform embodiments herein, or the like.
- the radio base station 12 also may be referred to as e.g. a NodeB, an evolved Node B (eNB, eNode B), a base transceiver station, Access Point Base Station, base station router, or any other network unit capable to communicate with a user equipment within a cell served by the radio base station 12, depending e.g. of the radio access technology and terminology used.
- the user equipment 10 may e.g. be represented by a wireless communication terminal, a mobile cellular phone, a Personal Digital Assistant (PDA), a wireless platform, a laptop, a computer or any other kind of device capable to communicate wirelessly with the radio base station 12.
- PDA Personal Digital Assistant
Abstract
Description
Claims
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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PCT/SE2010/051203 WO2012060751A1 (en) | 2010-11-04 | 2010-11-04 | A radio base station and a method therein for estimating a doppler spread |
Publications (2)
Publication Number | Publication Date |
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EP2636158A1 true EP2636158A1 (en) | 2013-09-11 |
EP2636158A4 EP2636158A4 (en) | 2016-02-17 |
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ID=46024691
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP10859336.9A Withdrawn EP2636158A4 (en) | 2010-11-04 | 2010-11-04 | A radio base station and a method therein for estimating a doppler spread |
Country Status (3)
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EP (1) | EP2636158A4 (en) |
CN (1) | CN103181094B (en) |
WO (1) | WO2012060751A1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9112737B2 (en) * | 2013-03-06 | 2015-08-18 | Qualcomm Incorporated | Systems and methods for determining a channel variation metric |
CN107852211A (en) * | 2015-08-07 | 2018-03-27 | 华为技术有限公司 | Analog beam former |
CN106100692A (en) * | 2016-08-29 | 2016-11-09 | 东南大学 | MIMO OFDM underwater sound communication system doppler spread method of estimation |
US11038719B2 (en) | 2019-04-30 | 2021-06-15 | Qualcomm Incorporated | Channel estimation for systems with PLL phase discontinuities |
CN114244655B (en) * | 2021-12-16 | 2023-09-12 | 哲库科技(北京)有限公司 | Signal processing method and related device |
WO2024033810A1 (en) * | 2022-08-08 | 2024-02-15 | Telefonaktiebolaget Lm Ericsson (Publ) | Autocorrelation function characteristics estimation and reporting |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6680969B1 (en) * | 1999-03-22 | 2004-01-20 | Ericsson, Inc. | Methods for estimating doppler spreads including autocorrelation function hypotheses and related systems and receivers |
US6563861B1 (en) * | 1999-03-22 | 2003-05-13 | Ericsson, Inc. | Doppler spread estimation system |
MY125793A (en) * | 1999-08-12 | 2006-08-30 | Ericsson Inc | Methods for estimating doppler spreads including autocorrelation function hypotheses and related systems and receivers |
US6922452B2 (en) * | 2001-03-27 | 2005-07-26 | Telefonaktiebolaget L M Ericsson (Publ) | Method and apparatus for estimating Doppler spread |
US6636574B2 (en) * | 2001-05-31 | 2003-10-21 | Motorola, Inc. | Doppler spread/velocity estimation in mobile wireless communication devices and methods therefor |
KR101488028B1 (en) * | 2008-07-17 | 2015-01-30 | 엘지전자 주식회사 | Method for transmitting reference signal in multiple antenna system |
US8897385B2 (en) * | 2009-10-20 | 2014-11-25 | Maxlinear, Inc. | Doppler estimator for OFDM systems |
-
2010
- 2010-11-04 CN CN201080069929.XA patent/CN103181094B/en not_active Expired - Fee Related
- 2010-11-04 EP EP10859336.9A patent/EP2636158A4/en not_active Withdrawn
- 2010-11-04 WO PCT/SE2010/051203 patent/WO2012060751A1/en active Application Filing
Also Published As
Publication number | Publication date |
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CN103181094A (en) | 2013-06-26 |
WO2012060751A1 (en) | 2012-05-10 |
EP2636158A4 (en) | 2016-02-17 |
CN103181094B (en) | 2016-05-04 |
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