Detection of High Velocity Movement in a Telecommunication System

Abstract

Whether relative velocity between a transmitter and a receiver is higher than a predetermined amount is detected. This involves using a Doppler estimation technique to generate an estimate of Doppler spread, {circumflex over (f)}D(1), based on a received signal, and using an alternative velocity estimation technique to generate an estimate of velocity, {circumflex over (v)}, based on the received signal, wherein the alternative velocity estimation technique differs from the Doppler estimation technique. A plurality of estimates, including at least the estimate of Doppler spread and the estimate of velocity, are used to detect whether the relative velocity between the transmitter and the receiver is higher than the predetermined amount. The alternative velocity estimation technique may, for example, be a second Doppler estimation technique that differs from the other Doppler estimation technique.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will be understood by reading the following detailed description in conjunction with the drawings in which:

FIG. 1 depicts a mobile radio cellular telecommunication system 100, which may be, for example, a CDMA or a WCDMA communication system.

FIG. 2 is a block diagram of those parts of a UE involved in AFC operation.

FIGS. 3 a-c are graphs depicting the results of simulating the tracking ability of an AFC when it remains in a low speed mode of operation and the relative velocity between the simulated transmitter and receiver is relatively low (150 km/h).

FIGS. 4 a-c are graphs depicting the tracking ability of the AFC when it remains in a low speed mode of operation but the relative velocity increases to 350 km/h.

FIGS. 5 a-c are graphs depicting the tracking ability of the AFC when it operates at a high speed mode and the relative velocity is 350 km/h.

FIG. 6 a is a flowchart of steps/processes performed in an exemplary embodiment that excludes signals from a strongest RAKE finger.

FIG. 6 b is a flowchart of steps/processes performed in an alternative exemplary embodiment that excludes signals from a strongest RAKE finger to determine Doppler estimate for setting a speedmode parameter.

FIG. 7 is a block diagram of parts of a UE involved in AFC operation and LOS detection according to embodiments employing phase rotation as a LOS detector.

FIG. 8 is a flowchart depicting steps/processes performed by an exemplary LOS detector for determining whether to change operation of the AFC from low speed mode to high speed mode.

FIG. 9 is a flowchart depicting steps/processes performed by an exemplary LOS detector for determining whether to change operation of the AFC from high speed mode to low speed mode.

FIGS. 10 a-c are graphs depicting the tracking ability of an AFC when the speedmode parameter is controlled in accordance with herein-described LOS detection techniques and the relative velocity between transmitter and receiver is 350 km/h.

FIGS. 11 a-c are graphs depicting the tracking ability of an AFC when the speedmode parameter is controlled in accordance with herein-described LOS detection techniques and the relative velocity between transmitter and receiver is 450 km/h.

DETAILED DESCRIPTION

The various features of the invention will now be described with reference to the figures, in which like parts are identified with the same reference characters.

The various aspects of the invention will now be described in greater detail in connection with a number of exemplary embodiments. To facilitate an understanding of the invention, many aspects of the invention are described in terms of sequences of actions to be performed by elements of a computer system or other hardware capable of executing programmed instructions. It will be recognized that in each of the embodiments, the various actions could be performed by specialized circuits (e.g., discrete logic gates interconnected to perform a specialized function), by program instructions being executed by one or more processors, or by a combination of both. Moreover, the invention can additionally be considered to be embodied entirely within any form of computer readable carrier, such as solid-state memory, magnetic disk, optical disk or carrier wave (such as radio frequency, audio frequency or optical frequency carrier waves) containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein. Thus, the various aspects of the invention may be embodied in many different forms, and all such forms are contemplated to be within the scope of the invention. For each of the various aspects of the invention, any such form of embodiments may be referred to herein as “logic configured to” perform a described action, or alternatively as “logic that” performs a described action.

In one aspect, higher reliability of relative velocity estimates in LOS conditions is achieved by excluding the strongest path associated with the received signal from the Doppler estimation, since the other paths are more likely to be Rayleigh distributed at all times. The results of such a Doppler estimation can be used alone, but are advantageously combined (e.g., by means of a logical OR) with the results produced by standard Doppler estimation techniques.

Other embodiments are based on the behavior of the channel estimates in a LOS situation with little or no fading of the strongest path. In such a situation, the phase variations have a random superimposed component but, unless the AFC is completely aligned (or off by an amount k/Δt, where k is an integer), there is a deterministic phase rotation that is completely dominating. These other embodiments include detection of such rotation situations, and use this detection as an indicator of a high relative velocity LOS situation, in which there is an elevated risk of AFC wrap-around.

These and other aspects will now be described in even greater detail. FIG. 6a is a flowchart of steps/processes performed by logic in a UE in an exemplary embodiment that excludes signals from a strongest RAKE finger. The signals from the various fingers of the RAKE receiver in the UE are evaluated, and the finger generating the strongest signal is identified (step 601). Doppler estimation is then performed utilizing signals from one or more of the RAKE fingers excluding the RAKE finger identified as having the strongest signal (step 603). The Doppler estimation may be performed utilizing any of a number of techniques, such as but not limited to the level crossing algorithm and the argument crossing algorithm. In some embodiments, signals from only one RAKE finger are used, such as signals from the second strongest RAKE finger. In alternative embodiments, the number of crossings can be averaged over a number of RAKE fingers, with the signals from the strongest RAKE finger being excluded in the calculation.

It is noted that the secondary paths (i.e., the one or more signal paths remaining after the strongest path has been excluded) may be much weaker than the strongest path, and in some situations too weak to give a useful Doppler estimate, {circumflex over (f)}_D⁽²⁾. Such situations can cause unnecessary or ill-founded speedmode switching. Thus, in alternative embodiments, a plurality of Doppler estimates can be generated by different techniques, at least one of which excludes signals from the strongest RAKE finger as described above, and the results combined in a way that is useful to the particular application. For example, the speedmode parameter for controlling the AFC 205 in the UE of FIG. 2 can be determined by a Doppler estimator 209 performing steps such as the exemplary steps/processes illustrated in the flowchart of FIG. 6b. In one aspect, the signals from the various fingers of the RAKE receiver in the UE are evaluated, and the finger generating the strongest signal is identified (step 651). A first Doppler estimate, {circumflex over (f)}_D⁽¹⁾, is generated utilizing a Doppler estimation technique that includes signals from the RAKE finger identified as having the strongest signal (step 653). Additionally, a second Doppler estimate, {circumflex over (f)}_D⁽²⁾, is generated by means of a Doppler estimation technique that utilizes signals from one or more of the RAKE fingers excluding the RAKE finger identified as having the strongest signal (step 655). In each case, any Doppler estimation technique can be used, such as but not limited to the level crossing algorithm and the argument crossing algorithm.

If either of the first and second Doppler estimates ({circumflex over (f)}_D⁽¹⁾ and {circumflex over (f)}_D⁽²⁾) indicates relatively high speed between the receiver in the UE and the transmitter of the received signals (“YES” path out of decision block 657), then the speedmode parameter is set equal to “high speed” mode (step 659). Otherwise (“NO” path out of decision block 657), the speedmode parameter is set to a value indicating “low speed” mode (step 661).

Testing whether either of the first and second Doppler estimates ({circumflex over (f)}_D⁽¹⁾ and {circumflex over (f)}_D⁽²⁾) indicates relatively high speed between the receiver in the UE and the transmitter of the received signals can be performed in any of a number of ways. In one exemplary embodiment, the testing and consequent setting of the speedmode parameter is done in accordance with

$\begin{array}{cc}\mathrm{speedmode}\left(n\right)=\{\begin{array}{cc}\mathrm{high}& \begin{array}{c}\mathrm{if}\left({\hat{f}}_D^{\left(1\right)}\left(n\right)>{\tau }_{\mathrm{high}}\right)\mathrm{OR}(\left({\hat{f}}_D^{\left(2\right)}\left(n\right)>{\tau }_{\mathrm{high}}\right)\\ \mathrm{AND}\left(r\left({\hat{f}}_D^{\left(2\right)}\left(n\right)\right)>{\tau }_r\right)),\end{array}\\ \mathrm{low}& \begin{array}{c}\mathrm{if}\left({\hat{f}}_D^{\left(1\right)}\left(n\right)<{\tau }_{\mathrm{low}}\right)\mathrm{AND}(\left({\hat{f}}_D^{\left(2\right)}\left(n\right)<{\tau }_{\mathrm{low}}\right)\\ \mathrm{OR}\left(r\left({\hat{f}}_D^{\left(2\right)}\left(n\right)\right)<{\tau }_r\right)),\end{array}\\ \mathrm{speedmode}\left(n-1\right)& \mathrm{otherwise},\end{array}& \left(5\right)\end{array}$

where r({circumflex over (f)}_D⁽²⁾(n)) is a parameter indicating the reliability of {circumflex over (f)}_D⁽²⁾(n), τ_high is a threshold representing the minimum Doppler value associated with high speed mode, τ_low is a threshold representing the maximum Doppler value associated with low speed mode, and τ_r is a threshold representing a minimum required value of reliability. The parameter r({circumflex over (f)}_D⁽²⁾(n)) can be defined in any of a number of ways, including but limited to: a filtered SIR value of the second strongest finger, a power level of the second strongest finger, and an average SIR or power level value for all but the strongest fingers. The reliability threshold, τ_r, can be an absolute (i.e., constant) threshold value, or may alternatively be determined dynamically, such as having it be a function of a filtered SIR value of the strongest finger.

The embodiments described above should be able to detect high relative velocity in all situations except LOS situations with no or very weak secondary paths. The situation in which the strongest path is not a LOS path, but is Rayleigh distributed should not have any negative impact on the method. The robustness to, for example, imperfect channel estimates should be the same as for standard Doppler estimators. The extra implementation cost is basically duplication of the Doppler estimator, and a slightly more complicated comparison (e.g., as in Equation (5)).

The discussion will now focus on other embodiments that include detection of phase rotation, and the use of such detection as an indicator of high relative velocity LOS situations. In a LOS situation, the envelope of the channel estimates for the strongest path will be fairly constant. Studying the phase variations, there is a phase rotation that is alternatively constant, increasing or decreasing, and this rotation is typically dominating over the random phase variations caused by fading. The rotation is constant, for example, when the UE is moving straight towards or away from a base station, and it is increasing or decreasing when the UE is, for example, passing a base station, accelerating, or warming up.

Hence, one criterion for detecting a LOS situation is to evaluate whether the angle between the channel estimates of the strongest path (with UE frequency reference updates taken into account) has the same sign over time, which means that the channel estimates are rotating.

Detecting uninterrupted rotation of the channel estimates indicates a LOS situation, but alone does not necessarily mean that the relative speed between the transmitter and receiver is high. Thus, an additional criterion is helpful to prevent low relative velocity LOS situations from triggering high speed mode AFC operation. For example, embodiments can be configured to permit high speed mode operation only if the rotation angle is greater than some threshold.

FIG. 7 is a block diagram of parts of a UE involved in AFC operation and LOS detection according to embodiments employing phase rotation as a LOS detector. The local oscillator (VCXO) 201 generates the frequencies necessary for operating the Front End Receiver (RX Fe) 203 and Front End Transmitter (not shown) sections. An AFC 205 generates a digital control signal (f_err) that, after conversion to analog by a Digital-to-Analog Converter (DAC) 207 adjusts the output frequency of the local oscillator 201.

The UE further includes an LOS detector 701 that receives channel estimates, ĥ_f, from the channel estimator 211; and the frequency error signal, f_err, from the AFC 205. The LOS detector 701 generates the speedmode parameter for controlling the AFC 205. Exemplary operation of the LOS detector 701 is illustrated by the steps/processes depicted in the flowcharts of FIGS. 8 and 9. FIG. 8 is a flowchart depicting steps/processes for determining whether the UE's speedmode parameter should be changed from indicating a low speed mode to indicating a high speed mode of operation for the AFC 205. The strategy is to determine whether the channel estimates are experiencing a phase rotation for a predetermined period of time. In this exemplary embodiment, a counter is initialized to zero (step 801). Then logic in the UE determines whether a phase rotation has been detected between a most recent channel estimate and the previous channel estimate, and whether the rotation is of the same sign as previously detected rotation (decision block 803). If no phase rotation is detected (“NO” path out of decision block 803), the counter is reset to zero (step 801).

If a phase rotation is detected (“YES” path out of decision block 803), then the counter value is adjusted (e.g., by incrementing by “1”) (step 805), and the resulting counter value is compared to a threshold value, τ_{min—for—HS}, that corresponds to the predetermined minimum period of time that the phase rotation should be continuously detected before AFC operation should be changed from “low” to “high” speed mode (decision block 807). If the counter is greater than or equal to τ_{min—for—HS} (“YES” path out of decision block 807), then the speedmode parameter is set to indicate a “high” mode of operation (step 809). Otherwise (“NO” path out of decision block 807), the phase rotation has not been detected for a sufficient period of time, and testing continues back at decision block 803.

A particular implementation of the principles discussed above with respect to FIG. 8 can be in accordance with the following pseudocode:

if (sign (ferr,momtot (present)) == sign (ferr,momtot (previous)))
AND (|ferr,mom (present)| > τ1)
Counter = Counter + 1;
else
Counter = 0;
end
if Counter ≧ τmin_for_HS
speedmode = high
end

where f_err,mom represents the momentary (i.e., non-filtered) frequency error of the strongest finger, f_err,mom^(tot) represents the momentary (i.e., non-filtered) frequency error of the strongest finger with accumulated UE frequency reference updates, Δf_UE^(tot), taken into account; that is, f_err,mom^(tot)=f_err,mom−Δf_UE^(tot). Here, f_err,mom depends on the rotation angle

${\varphi }_{\mathrm{mom}}=\arg \left({\hat{h}\left({\hat{h}}^{\left(\mathrm{previous}\right)}\right)}^{*}\right)$

as f_err,mom=φ_mom/2πΔt, ĥ and ĥ^(previous) are the channel estimates for the strongest path for the current and previous slot respectively, and Δt is the low-speed mode time interval between two consecutive updates of the AFC 205, for example

$\Delta t=\frac{1}{1500}s.$

It is noted that the purpose of the test for |f_err,mom(present)|>τ₁ in the first “if” statement in the above pseudocode is to permit entry into high speed mode only if the rotation angle is greater than a predetermined threshold.

In alternative embodiments, an extra condition can be added to the LOS detection, namely a comparison of the envelope of h to an upper and lower threshold to determine that there is little or no fading.

In another aspect, once it is operating in high speed mode, the UE may make a determination of when to return to low speed mode. FIG. 9 is a flowchart depicting steps/processes for determining whether the UE's speedmode parameter should be changed from indicating a high speed mode to indicating a low speed mode of operation for the AFC 205. The strategy is to determine when the magnitude of the frequency error generated by the AFC 205 has continuously remained below a threshold value, herein denoted τ_{max—FE—for—LS}, for a predetermined amount of time. This is to avoid changing operation of the AFC 205 back to low speed mode too quickly, which can cause aliasing problems to be encountered right away. Instead, operation of the AFC 205 is permitted to remain in high speed mode until it can be confirmed that the frequency error is no longer increasing. This indicates that the local oscillator (VCXO) 201 has assumed a correct value and that the Doppler shift is static.

Accordingly, in the exemplary embodiment of FIG. 9, a counter is initialized to zero (step 901). Next, the frequency error (generated by the AFC 205) is compared with a threshold value, τ_{max—FE—for—LS} (decision block 903). If the frequency error is not less than the threshold value τ_{max—FE—for—LS} (“NO” path out of decision block 903), the counter is reset to zero (step 901) and testing continues.

If the frequency error is less than the threshold value τ_{max—FE—for—LS} (“YES” path out of decision block 903), then the counter value is adjusted (e.g., by incrementing by “1”) (step 905). The adjusted counter value is then compared with a threshold value, τ_{min—for—LS}, that corresponds to a predetermined period of time that the frequency error should continuously be found to be less than the threshold value τ_{max—FE—for—LS} in order to go back to low speed mode (decision block 907). If the adjusted counter value is not greater than the threshold value τ_{min—for—LS} (“NO” path out of decision block 907), testing is repeated, starting back at decision block 903.

However, if the adjusted counter value is greater than the threshold value τ_{min—for—LS} (“YES” path out of decision block 907), then the speedmode parameter is set to indicate low speed mode (step 909).

A particular implementation of the principles discussed above with respect to FIG. 9 can be in accordance with the following pseudocode:

if (|ferr| < τmax—FE—for—LS )
Counter = Counter + 1;
else
Counter = 0;
end
if Counter ≧ τmin—for—LS
speedmode = low;
end

In another aspect, embodiments are able to have proper speed mode operation when the strongest path is fading by combining the algorithm described with reference to FIGS. 8 and 9 with results generated by, for example, Doppler estimation techniques, such as those described earlier. Combination can be achieved in a logical OR fashion (i.e., if at least one of the LOS detection and the Doppler estimation results indicates high speed mode, then the AFC 205 should be operated in high speed mode, and the AFC 205 should be operated in low speed mode if and only if both of the LOS detection and the Doppler estimation results indicate low speed mode). This arrangement is illustrated in FIG. 7 by the inclusion of a Doppler estimator 703 (depicted in dashed lines to indicate that it is an optional element), which provides its results to the LOS detector 701. The Doppler estimator 703 can, for example, operate as discussed above with respect to FIG. 6a or 6b, or in accordance any other Doppler estimation techniques, including conventional techniques.

Simulations of the LOS detection techniques described above with respect to FIGS. 8 and 9 were performed, and the results depicted in FIGS. 10-11. Doppler estimates are not used in the speedmode setting in any of the simulations. The thresholds were set as follows:

τ₁=60 Hz;

τ_{min—for—HS}=16 counts (=16 slots in low speed mode);

τ_{max—FE—for—LS}=50 Hz; and

τ_{min—for—LS}=64 counts (=64/5 slots in high speed mode).

FIGS. 10 a-c are graphs depicting the tracking ability of the AFC 205 when the speedmode parameter is controlled in accordance with the above-described LOS detection techniques and the relative velocity between transmitter and receiver is 350 km/h under the scenario conditions described earlier. FIG. 10a allows a comparison to be made between the true Doppler shift (graph 1001) and the shift in the UE frequency (graph 1003). FIG. 10b allows a comparison to be made between the true frequency error (graph 1005) and the reported frequency error (graph 1007) generated by the AFC 205. A large frequency change occurs over the interval spanning approximately slot 925 through slot 1075. As can be seen from FIG. 10c, the above-described LOS detection techniques cause the AFC 205 to switch to high speed operation during the interval spanning approximately slot 975 through slot 1140. As a result, the AFC 205 is able to successfully track the frequency change (compare with FIG. 4).

FIGS. 11 a-c are graphs depicting the tracking ability of the AFC 205 when the speedmode parameter is controlled in accordance with the above-described LOS detection techniques and the relative velocity between transmitter and receiver is 450 km/h under scenario 1 conditions. FIG. 11a allows a comparison to be made between the true Doppler shift (graph 1101) and the shift in the UE frequency (graph 1103). FIG. 11b allows a comparison to be made between the true frequency error (graph 1105) and the reported frequency error (graph 1107) generated by the AFC 205. A large frequency change occurs over the interval spanning approximately slot 925 through slot 1075. As can be seen from FIG. 11c, the above-described LOS detection techniques cause the AFC 205 to switch to high speed operation during the interval spanning approximately slot 960 through slot 1130. As a result, the AFC 205 is able to successfully track the frequency change.

Alternative embodiments could involve trying to detect LOS situations only when the Doppler shift is gradually changing. This can be accomplished by evaluating whether the angle between the channel estimates of the strongest path (with UE frequency reference updates taken into account) is increasing or decreasing gradually.

In another aspect, when the received signal comprises several multipath components and/or signals from multiple cells (e.g., as occurs in soft handover), several RAKE fingers are then involved in AFC operation, and in such cases a typical AFC reports a frequency error, f_err, that is a weighted combination of the frequency errors of the respective fingers of the RAKE receiver. Other combinations of the fingers' frequency errors are possible. For example, one might use a non-weighted combination, the median value, or simply the frequency error of the strongest finger. The reported frequency error could even be equal to that of one of the cells in soft handover, for example, the HSDPA serving cell when applicable. In any case, the AFC will report a single frequency error, which is used to set the frequency of the local oscillator 201. This frequency is herein denoted the AFC frequency, and the remaining frequency error per finger (i.e., the difference between the frequency of the respective finger and the AFC frequency) is herein referred to as the residual frequency offset per finger, f_err,f^(res), where f denotes a particular one of the fingers in the RAKE receiver.

Knowledge about the residual frequency offsets of the respective fingers can be used to improve UE receiver performance in high relative velocity scenarios. That is, a function of f_err,f^(res), fεF (where F represents the set of fingers involved in AFC operation) may be used as a switch to turn on and off receiver algorithms, or it may be used to set parameters in receiver algorithms such as the speedmode for AFC. The function may be, for example,

$\begin{array}{cc}\zeta \left(f_{\mathrm{err},f}^{\left(\mathrm{res}\right)}\right)=\underset{f\in F}{\max }f_{\mathrm{err},f}^{\left(\mathrm{res}\right)}.& \left(6\right)\end{array}$

Alternatively, the function could be

$\begin{array}{cc}\zeta \left(f_{\mathrm{err},f}^{\left(\mathrm{res}\right)}\right)=\frac{1}{F}\sum _{f\in F}f_{\mathrm{err},f}^{\left(\mathrm{res}\right)},& \left(7\right)\end{array}$

among others.

It is noted that ζ(f_err,f^(res)) may be interpreted as a form of relative velocity estimate, since large residual frequency offset values only occur in high relative velocity situations. It is further noted, however, that high values of ζ(f_err,f^(res)) may not be seen in all high relative velocity situations, such as in a single cell LOS situation.

Thus, in alternative embodiments, the function ζ(f_err,f^(res)) may be used as a supplementary relative velocity estimate, with high speed being indicated when ζ(f_err,f^(res)) is greater than a predefined threshold value. The results of this test can then be combined (e.g., in an OR fashion) with a Doppler estimate, and/or possibly with one or two of the various supplementary methods described earlier. When at least one of the Doppler estimator, the detection algorithms described earlier, and ζ(f_err,f^(res)) indicates high speed, the UE should engage into high speed mode operation, and low speed mode should only be applied if all algorithms indicate low speed.

The invention has been described with reference to particular embodiments. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the embodiment described above.

For example, the exemplary embodiments focus on downlink reception at the UE. However, the various aspects described herein are equally applicable to uplink reception by a base station.

Additionally, the various embodiments have been described in the context of cellular telecommunications. However, the invention is not limited to such embodiments, but rather can be applied in other types of communications systems, such as but not limited to Wireless Local Area Network (WLAN) and Personal Are Network (PAN) systems using, for example, Bluetooth® technology. In such embodiments, it will be recognized that the relative velocity detected represents the combined affect of movement between the several communicating devices.

Furthermore, the various embodiments illustrate situations in which relative velocities are assumed to be characterized by one of two states, for example, “high” and “low.” However, the invention is useful for detecting whether a relative velocity between a transmitter and a receiver is higher than a predetermined threshold. Thus, in some embodiments, several threshold values can be defined, which in turn define more than two states of relative velocity. For example, defining two thresholds can enable relative velocity to be characterized as “low”, “medium”, and “high.” Those of ordinary skill in the art will readily be able to adapt the teachings above to embodiments that test against several possible threshold values, so that the relative velocity can be characterized with higher resolution.

Thus, the described embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is given by the appended claims, rather than the preceding description, and all variations and equivalents which fall within the range of the claims are intended to be embraced therein.

Claims

1. A method of detecting that a relative velocity between a transmitter and a receiver in a telecommunications system is higher than a predetermined amount, the method comprising: using a Doppler estimation technique to generate an estimate of Doppler spread, {circumflex over (f)}D(1), based on a received signal;using an alternative velocity estimation technique to generate an estimate of velocity, {circumflex over (v)}, based on the received signal, wherein the alternative velocity estimation technique differs from the Doppler estimation technique; andusing a plurality of estimates to detect whether the relative velocity between the transmitter and the receiver is higher than the predetermined amount, wherein the plurality of estimates includes at least the estimate of Doppler spread and the estimate of velocity.

2. The method of claim 1, wherein: the Doppler estimation technique is a first Doppler estimation technique;the estimate of Doppler spread, {circumflex over (f)}D(1), is a first estimate of Doppler spread;the alternative velocity estimation technique is a second Doppler estimation technique that differs from the first Doppler estimation technique; andthe estimate of velocity is a second estimate of Doppler spread, {circumflex over (f)}D(2).

3. The method of claim 2, wherein: the first Doppler estimation technique comprises utilizing information about a part of the received signal associated with a strongest path between the transmitter and the receiver; andthe second Doppler estimation technique comprises: excluding information about a part of the received signal associated with the strongest path between the transmitter and the receiver; andutilizing information about a part of the received signal associated with a secondary path between the transmitter and the receiver.

4. The method of claim 3, wherein using the plurality of estimates to detect whether a relative velocity between the transmitter and the receiver is higher than the predetermined amount comprises: concluding that the relative velocity between the transmitter and the receiver is higher than the predetermined amount if ({circumflex over (f)}D(1)>τhigh)OR(({circumflex over (f)}D(2)>τhigh)AND(r({circumflex over (f)}D(2))>τr)); andconcluding that the relative velocity between the transmitter and the receiver is lower than the predetermined amount if ({circumflex over (f)}D(1)<τlow)AND(({circumflex over (f)}D(2)<τlow)OR(r({circumflex over (f)}D(2))<τr)),

5. The method of claim 2, comprising: detecting whether there exists uninterrupted rotation of a channel estimate over a predetermined period of time; andin response to detecting the existence of uninterrupted rotation of the channel estimate over the predetermined period of time, concluding that the relative velocity between the transmitter and the receiver is higher than the predetermined amount.

6. The method of claim 5, comprising: in response to detecting that the relative velocity between the transmitter and the receiver is higher than the predetermined amount, operating an automatic frequency controller at a high update rate; andchanging operation of the automatic frequency controller to a low update rate in response to determining that a magnitude of a frequency error generated by the automatic frequency controller has continuously remained below a predetermined threshold value for a predetermined period of time.

7. The method of claim 2, comprising: determining a residual frequency offset value, ferr,f(res), fεF, wherein F represents a set of RAKE receiver fingers involved in automatic frequency control operation;determining a function of the residual frequency offset value, ζ(ferr,f(res)); andconcluding that the relative velocity between the transmitter and the receiver is higher than the predetermined amount in response to determining that the function of the residual frequency offset value, ζ(ferr,f(res)), is greater than a predetermined threshold value.

8. The method of claim 1, wherein using the plurality of estimates comprises concluding that the relative velocity between the transmitter and the receiver is not higher than the predetermined amount only if none of the plurality of estimates indicates that the relative velocity between the transmitter and the receiver is higher than the predetermined amount.

9. The method of claim 1, wherein the alternative velocity estimation technique comprises: detecting whether there exists uninterrupted rotation of a channel estimate over a predetermined period of time; andin response to detecting the existence of uninterrupted rotation of the channel estimate over the predetermined period of time, concluding that the relative velocity between the transmitter and the receiver is higher than the predetermined amount.

10. The method of claim 1, wherein the alternative velocity estimation technique comprises: determining a residual frequency offset value, ferr,f(res), fεF, wherein F represents a set of RAKE receiver fingers involved in automatic frequency control operation;determining a function of the residual frequency offset value, ζ(ferr,f(res)); andconcluding that the relative velocity between the transmitter and the receiver is higher than the predetermined amount in response to determining that the function of the residual frequency offset value, ζ(ferr,f(res)), is greater than a predetermined threshold value.

11. The method of claim 10, wherein:

12. The method of claim 10, wherein:

13. The method of claim 1, comprising: setting receiver parameters based on whether the relative velocity between the transmitter and the receiver is detected to be higher than the predetermined amount.

14. The method of claim 1, comprising: setting automatic frequency control parameters based on whether the relative velocity between the transmitter and the receiver is detected to be higher than the predetermined amount.

15. The method of claim 1, wherein the method is performed in a user equipment.

16. The method of claim 1, wherein the method is performed in a base station of the telecommunication system.

17. The method of claim 1, wherein: the telecommunication system is a Wideband Code Division Multiple Access (WCDMA) telecommunications system; andthe method is performed in a device associated with the WCDMA telecommunications system.

18. An apparatus for detecting that a relative velocity between a transmitter and a receiver in a telecommunications system is higher than a predetermined amount, the apparatus comprising: a Doppler estimator that generates an estimate of Doppler spread, {circumflex over (f)}D(1), based on a received signal;an alternative velocity estimator that generates an estimate of velocity, {circumflex over (v)}, based on the received signal; andlogic that uses a plurality of estimates to detect whether the relative velocity between the transmitter and the receiver is higher than the predetermined amount,wherein: the plurality of estimates includes at least the estimate of Doppler spread and the estimate of velocity;the Doppler estimator uses a Doppler estimation technique;the alternative velocity estimator uses an alternative velocity estimation technique; andthe Doppler estimation technique differs from the alternative velocity estimation technique.

19. The apparatus of claim 18, wherein: the Doppler estimation technique is a first Doppler estimation technique;the estimate of Doppler spread, {circumflex over (f)}D(1), is a first estimate of Doppler spread;the alternative velocity estimation technique is a second Doppler estimation technique that differs from the first Doppler estimation technique; andthe estimate of velocity is a second estimate of Doppler spread, {circumflex over (f)}D(2).

20. The apparatus of claim 19, wherein: the first Doppler estimator comprises logic that utilizes information about a part of the received signal associated with a strongest path between the transmitter and the receiver; andthe second Doppler estimation technique comprises: excluding information about a part of the received signal associated with the strongest path between the transmitter and the receiver; andutilizing information about a part of the received signal associated with a secondary path between the transmitter and the receiver.

21. The apparatus of claim 20, wherein the logic that uses the plurality of estimates to detect whether a relative velocity between the transmitter and the receiver is higher than the predetermined amount comprises: logic that concludes that the relative velocity between the transmitter and the receiver is higher than the predetermined amount if ({circumflex over (f)}D(1)>τhigh)OR(({circumflex over (f)}D(2)>τhigh)AND(r({circumflex over (f)}D(2))>τr)); andlogic that concludes that the relative velocity between the transmitter and the receiver is not higher than the predetermined amount if ({circumflex over (f)}D(1)<τlow)AND(({circumflex over (f)}D(2)<τlow)OR(r({circumflex over (f)}D(2))<τr)),

22. The apparatus of claim 19, comprising: logic that detects whether there exists uninterrupted rotation of a channel estimate over a predetermined period of time; andlogic that, in response to detecting the existence of uninterrupted rotation of the channel estimate over the predetermined period of time, concludes that the relative velocity between the transmitter and the receiver is higher than the predetermined amount.

23. The apparatus of claim 22, comprising: logic that, in response to detecting that the relative velocity between the transmitter and the receiver is higher than the predetermined amount, operates an automatic frequency controller at a high update rate; andlogic that changes operation of the automatic frequency controller to a low update rate in response to determining that a magnitude of a frequency error generated by the automatic frequency controller has continuously remained below a predetermined threshold value for a predetermined period of time.

24. The apparatus of claim 19, comprising: logic that determines a residual frequency offset value, ferr,f(res), fεF, wherein F represents a set of RAKE receiver fingers involved in automatic frequency control operation;logic that determines a function of the residual frequency offset value, ζ(ferr,f(res)); andlogic that concludes that the relative velocity between the transmitter and the receiver is higher than the predetermined amount in response to determining that the function of the residual frequency offset value, ζ(ferr,f(res)), is greater than a predetermined threshold value.

25. The apparatus of claim 18, wherein the logic that uses the plurality of estimates comprises logic that concludes that the relative velocity between the transmitter and the receiver is not higher than the predetermined amount only if none of the plurality of estimates indicates that the relative velocity between the transmitter and the receiver is higher than the predetermined amount.

26. The apparatus of claim 18, wherein the alternative velocity estimator comprises: logic that detects whether there exists uninterrupted rotation of a channel estimate over a predetermined period of time; andlogic that, in response to detecting the existence of uninterrupted rotation of the channel estimate over the predetermined period of time, concludes that the relative velocity between the transmitter and the receiver is higher than the predetermined amount.

27. The apparatus of claim 18, wherein the alternative velocity estimator comprises: logic that determines a residual frequency offset value, ferr,f(res), fεF, wherein F represents a set of RAKE receiver fingers involved in automatic frequency control operation;logic that determines a function of the residual frequency offset value, ζ(ferr,f(res)); andlogic that concludes that the relative velocity between the transmitter and the receiver is higher than the predetermined amount in response to determining that the function of the residual frequency offset value, ζ(ferr,f(res)), is greater than a predetermined threshold value.

28. The apparatus of claim 27, wherein:

29. The apparatus of claim 27, wherein:

30. The apparatus of claim 18, comprising: logic that sets receiver parameters based on whether the relative velocity between the transmitter and the receiver is detected to be higher than the predetermined amount.

31. The apparatus of claim 18, comprising: logic that sets automatic frequency control parameters based on whether the relative velocity between the transmitter and the receiver is detected to be higher than the predetermined amount.

32. The apparatus of claim 18, wherein the apparatus is part of a user equipment.

33. The apparatus of claim 18, wherein the apparatus is part of a base station of the telecommunication system.

34. The apparatus of claim 18, wherein: the telecommunication system is a Wideband Code Division Multiple Access (WCDMA) telecommunications system; andthe apparatus is part of a device associated with the WCDMA telecommunications system.