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WO1999059273A1 - Estimation de la qualite d'un canal radioelectrique - Google Patents

Estimation de la qualite d'un canal radioelectrique Download PDF

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Publication number
WO1999059273A1
WO1999059273A1 PCT/GB1999/001530 GB9901530W WO9959273A1 WO 1999059273 A1 WO1999059273 A1 WO 1999059273A1 GB 9901530 W GB9901530 W GB 9901530W WO 9959273 A1 WO9959273 A1 WO 9959273A1
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Prior art keywords
quality
values
parameter
signal
distribution
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English (en)
Inventor
Andrew James Richardson
Adrian Paul Hillier
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Simoco International Ltd
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Simoco International Ltd
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Priority to AU39415/99A priority Critical patent/AU3941599A/en
Publication of WO1999059273A1 publication Critical patent/WO1999059273A1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector
    • H04L1/203—Details of error rate determination, e.g. BER, FER or WER

Definitions

  • the present invention relates to a method of and apparatus for estimating the quality of service provided by a radio channel.
  • Such quality estimates can be used, for example, to drive cell or base station reselection processes to maintain radio channel quality, or to help decide when and if to hand a portable radio over from its present base station or cell to an adjoining base station or cell as the radio moves around.
  • a cell reselection or handover decision would be based on, inter alia, which of the present and potential new radio channels have the better quality. There is therefore a need for a reliable method of estimating the quality of radio channels .
  • a number of different parameters can be used as an indication of the signal quality on a radio channel.
  • a high received signal strength implies a strong signal and thus could be equated to a "good" quality channel.
  • One way of estimating radio channel service quality therefore is to consider the instantaneous value of one or more of the parameters typically used as an indication of the channel quality.
  • a problem with such averaging is that for it to be practically useable, i.e. able to respond quickly to real quality changes, it must be performed over a relatively small number of samples, which means that the averaging process remains susceptible to errors caused by abnormal samples, such as unusually high error bursts arising, for instance, from some form of external interference.
  • a method of estimating the quality of service of a radio channel in a radio communications system comprising: determining the value of a parameter indicative of signal quality for each of a plurality of samples of a signal on the radio channel; and estimating the radio channel service quality on the basis of the distribution of the values in a set of two or more of the determined parameter values .
  • an apparatus for estimating the quality of service of a radio channel in a radio communication system comprising: means for determining the value of a parameter indicative of signal quality for each of a plurality of samples of a signal on the radio channel; and means for estimating the radio channel service - 3 - quality on the basis of the distribution of the values in a set of two or more of the determined parameter values .
  • a set of values of a parameter indicative of signal quality is determined for a signal on the radio channel, and the channel service quality is estimated in accordance with the distribution of the values in the set .
  • the Applicants have found that the way that the values in a set of sampled values of a parameter indicative of radio signal quality are distributed or spread differs for different signal qualities, such that the distribution of the parameter values can be used as an indicator of and thus to estimate radio channel service quality.
  • the quality estimate is less susceptible to errors introduced by abnormal sample values. It is believed therefore that the present invention provides a more reliable method of estimating radio channel service quality in a mobile radio system.
  • the frequency and spacing of the samples for which the parameter value is determined can be selected as desired, e.g. to achieve the required number of samples in the time period allowed to produce the quality estimate and/or the number necessary to achieve a reliable estimate.
  • the samples are taken at spaced, preferably regular and preferably predetermined, time intervals, e.g. every second.
  • the samples could be distributed in space across 100 to 200 radio carrier wavelengths. To achieve this at typical vehicle speeds at 400 MHz, it would therefore be convenient to take samples at 1 second intervals .
  • the sampling rate could, for example, be fixed at an interval corresponding to traversing about 20 wavelengths per sample at 3 mph. At 1800 MHz this would be 2.5 seconds. It would be possible to vary the sampling interval in direct proportion to the speed of the mobile radio unit, but this is not essential.
  • each sample preferably comprises a single packet, timeslot or burst, if appropriate (e.g. when using bit error rates as the parameter indicative of signal quality) .
  • samples are preferably taken every 18th frame, as that frame is idle and not necessarily used for traffic or useful information.
  • the number of sampled parameter values of the radio signal in the set of which the distribution is to be considered can also be selected as desired and would normally be predetermined.
  • a set of ten or more samples is preferred, to ensure adequate statistical reliability.
  • the upper limit on the number of samples in the set is determined by the time it takes to gather the samples. For a reasonable response, a collection time of 60 seconds or less is preferred.
  • the parameter indicative of signal quality can be - 5 - any such parameter known in the art, such as the received signal strength, the signal to noise ratio, or the carrier to interference ratio.
  • the signal quality parameter is a single variable, such as the bit error rate alone (rather than in combination with another variable) .
  • the parameter is the bit error rate (BER) .
  • BER bit error rate
  • the bit error rate for each sample can be determined in any suitable way known in the art .
  • the sample could be taken from a portion of the signal comprising a known sequence of bits (e.g. a so- called 'training sequence') and the sampled sequence compared with the known sequence to determine the bit error rate.
  • the number of errors in a section of the signal could be assessed by examining the forward error correction (FEC) information which is inserted into the signal for protection of channel errors.
  • FEC forward error correction
  • the 'frequency correction burst ' and ' synchronisation channel ' may also be used to assess the bit error rate.
  • the parameter indicative of signal quality is the variation of a set of two or more determined values for a given parameter for a signal on the radio channel.
  • the present invention preferably further comprises steps of or means for determining the value of a particular parameter for each of a plurality of samples of a modulated signal on the radio channel; and determining the variation of a set of two or more of the determined parameter values.
  • the determined variation value or measurement would then be used as one sampled value of - 6 - the parameter indicative of signal "quality, such that plural such variation values would be used to form a set whose distribution could then be determined to " provide an estimate of service quality.
  • the variation of a set of determined values of a particular parameter for a radio signal gives an indication of the consistency of the signal over the set of samples, and can therefore be used as an indicator of signal quality.
  • the variation will depend upon both signal fading and any high-energy interference which is increasing the received signal energy, and thus is sensitive to the effects of interference (e.g. co-channel and adjacent channel interference and narrow band jamming), in addition to additive white Gaussian noise.
  • determining the variation does not involve the comparison of known signal sequences, and thus does not require any prior knowledge of what has been transmitted nor need any synchronisation between transmitter and receiver.
  • a method of estimating the quality of service of a radio channel in a radio communications system comprising: determining the instantaneous value of a particular parameter for each of a plurality of samples of a modulated signal on the radio channel; determining the variation of a set of two or more of the determined parameter values; determining the variation of at least one further set of two or more of the determined parameter values; and estimating the radio channel service quality on the basis of the distribution of the values in a set of two or more of the determined variation values.
  • an apparatus for estimating - 7 - the- quality of service of a radio channel in a radio communication system comprising: means for determining the instantaneous value of a particular parameter for each of a plurality of samples of a modulated signal on the radio channel; means for determining, for each of two or more sets of two or more of the determined parameter values, the variation of the determined parameter values in the set; and means for estimating the radio channel service quality on the basis of the distribution of the values in a set of two or more of the determined variation values .
  • the particular parameter, the instantaneous values and variation of which are to be determined, can be selected as desired and could comprise a parameter normally used to estimate signal quality such as signal strength. It is preferably predetermined.
  • the selected particular parameter is one that would, in an ideal signal, be substantially identical for each sample of the signal, as then any variation in the parameter value will be due substantially to signal degradation or distortion, i.e. quality loss.
  • the modulation technique used imparts to the carrier wave characteristics which at the instant of modulation are common to every sample or a particular set of samples of the signal on the radio channel.
  • the radio signal may be modulated to initially have one or more constant parameters. In FM (frequency modulation) the amplitude of each sample of the signal is set to be the same and in AM (amplitude modulation) the relative phase of the signal is set to be the same.
  • samples, and in particular symbols i.e. the discrete individual states to which - 8 - the modulated signal is constrained at periodic intervals, as is known in the art
  • samples, and in particular symbols are also initially modulated to have one or more identical, common characteristics or parameters.
  • each symbol may be modulated to have the same initial amplitude relative to the carrier wave.
  • each symbol may be initially modulated to have one of a set of predetermined values of a particular parameter or parameters, which value or values are then varied relative to each other for one or more symbols in a predetermined manner by the modulation, such that removal of the known modulation induced differences would leave each symbol with the same value for that particular parameter or parameters.
  • phase of each symbol relative to the carrier wave could be identical when the symbols are demodulated or mapped to a common phase quadrant so as to remove modulation-induced phase differences.
  • the particular parameter, the variation of which is to be considered could, for example, comprise the amplitude of each sample, or a phase measurement for each sample, relative to the carrier wave.
  • these common characteristics or parameters would remain unchanged (and thus identical) during transmission.
  • these common characteristics are distorted or changed by different amounts during transmission.
  • the samples of which the particular parameter values are to be determined can be selected (e.g. as regards their spacing in time) as desired, as can the - 9 - number of determined particular parameter values to be used in the set of which the variation is to be considered.
  • the set comprises a predetermined number of parameter values, and preferably at least sufficient values to average out variations caused by Gaussian noise, and, where appropriate, most preferably sufficient values to average out Rayleigh fading.
  • the spacing and timing of the samples, and the number in a set should be such as to provide a practically useful and statistically reliable result (e.g. to avoid sampling over too long a period for a given set which might lead to errors induced by users deliberately changing the power of their signals) , as will be appreciated by those skilled in the art.
  • the samples, the particular parameter values of which are to be determined are selected to ensure that the parameter value being considered would be substantially identical for each sample in an ideal signal.
  • the samples preferably comprise symbols, and most preferably immediately successive symbols, of the digitally modulated signal.
  • the particular parameter value for each sample can be determined in any suitable manner known in the art .
  • the sampled symbols of a digitally modulated phase-shift keyed signal can be demodulated (or differentially demodulated, if differential phase- shift keying is used, such as would be the case in the TETRA system) or mapped to give notionally common characteristics (e.g. phase values) i.e. to remove any modulation induced parameter, e.g. phase, differences, and the variation of one or more of the parameters, such as amplitude or phase of the so mapped or demodulated signals then analysed.
  • This mapping could be done by, e.g. taking the modulus of the real and imaging parts of each symbol, and/or by changing the determined - 10 - instantaneous parameter- value in a predetermined manner based on the determined instantaneous value .
  • the variation of the set of determined particular parameter values can be determined in any suitable manner. For example, the extent of deviation of the values from a mean, modal or middle value, the range of the values, the difference between two selected values (e.g. the highest and lowest), or the standard deviation of the set of values could be used to indicate and represent the variation.
  • the variation is determined by calculating the variance of the set of the determined particular parameter values. This is a particularly suitable way of determining the variation of a set of parameter values .
  • the apparatus of the present invention preferably comprises means for calculating the variance of the set of the determined particular parameter values.
  • the variance of the set of determined parameter values can be calculated using known statistical techniques.
  • the variation of the set of sampled values is determined by considering the error of each value from its expected value and then considering the errors of a set of sampled values. For example, by statistical analysis, such as taking the mean or modal error value, or considering the variation (e.g. variance or standard deviation) of the error values, a measure of the variation of the parameter values can be obtained.
  • the error value for each sample can be derived as desired. It is preferably the difference between the expected instantaneous parameter value (e.g. amplitude or phase) (which value would normally be predetermined by the modulation technique being used) and the observed determined value of that parameter for that sample.
  • the samples should be symbols of the signal, and thus the error value is - 11 - preferably the difference between the expected instantaneous amplitude or phase of a symbol of that type and the observed amplitude or phase value " , respectively, for the symbol.
  • the present invention preferably comprises steps of or means for measuring the amplitude and/or phase of each of a plurality of symbols in a digitally modulated signal on the radio channel; and determining the variation of a set of two or more of the measured amplitude and/or phase values.
  • This embodiment of the present invention preferably further comprises steps of or means for removing any modulation induced phase and/or amplitude differences between the symbols in the set to provide a modified set of symbols having nominally identical amplitudes and phases, and then measuring the amplitude and/or phase of each symbol in the modified set of symbols and using these measurements for the variation determination.
  • the determined variation measurements can be used directly, to form a set the distribution of which is then considered to estimate service quality, or they can first be converted into a corresponding bit error rate measurement, if desired.
  • the latter can be achieved, for example, by relating the variation results to equivalent bit error rates (e.g. experimentally or by using a simulation) , and determining therefrom a relationship, curve-fit or look-up table from which the corresponding bit error rates can in future be derived.
  • the distribution of parameter values indicative of signal quality in the sampled set can be assessed as desired. For example, the way that the values in the set are spread or dispersed across a range of the parameter values can be considered.
  • the distribution is assessed by determining the number of determined values in the set - 12 - falling within each of a plurality of particular ranges of the parameter value.
  • This sorting of the determined values in the set into plural ranges is a particularly convenient way of representing the distribution for subsequent analysis and use in the estimation process. It effectively estimates the probability density function of the parameter values in the set (i.e. the probability of the parameter having a particular value) , since the number of values in a range, divided by the total number of values in the set, is the probability of the parameter value falling within that range.
  • the number and size of the ranges of parameter values to be used can be selected as desired.
  • the ranges would normally be predetermined.
  • Each range could, for example, be defined by the value of the parameter being greater than or less than a particular value, or being between two particular values. More ranges are more accurate, but increase any calculation complexity. Three has been found to be a suitable number to give a useful estimate of the service quality. These ranges could, for example, be as follows: Range 1: ⁇ 0.7% BER; Range 2: 0.7% to ⁇ 5.7% BER; and Range 3: > 5.7% BER. In this example, range 2 spans the bit error rates thought to be marginal for communication purposes, range 1 represents a good signal, and range 3 an unusable signal.
  • the above preferred minimum of 10 samples in the set is particularly suitable for sorting into three ranges. If additional ranges over three are to be used, the number of samples in each set is preferably increased above the preferred minimum of 10 (in proportion to the number of ranges) to make better use of the additional ranges.
  • the channel service quality is preferably estimated by comparing the distribution of values in the sampled set with one or more predetermined reference - 13 - distributions of values of the parameter, and making the estimation on the basis of that comparison.
  • the comparison is with plural, preferably three or more, predetermined distributions of parameter values, each corresponding to a particular, different channel service quality.
  • the channel service quality of the sampled radio channel can then be determined to be that of the reference distribution which its sampled set distribution most closely matches.
  • the predetermined reference comparison distributions can conveniently be stored in memory means in the radio channel quality estimation apparatus.
  • the number of predetermined distributions for comparison can be selected as desired. More comparison distributions increase the usefulness of the quality estimation, but are more susceptible to erroneous estimation, whereas fewer comparison distributions make the process less useful. Three comparison distributions, corresponding to "good”, “neither” and “bad” channel service quality, have been found to provide a useful estimation function.
  • the reference distributions are preferably represented in a manner corresponding to the way in which the distribution of parameter values in the sampled set of values is to be assessed, as this makes the comparison process more straightforward.
  • the comparison reference distributions each comprise a set of numbers representing the probability of the parameter value falling within the same particular value ranges for a signal of the quality that the reference distribution represents.
  • the comparison distributions comprise the number of the values in a set of that predetermined number of values that should fall within each of the particular ranges for a signal of the quality that the reference distribution represents.
  • the closest comparison distribution can be found by comparing directly the numbers in the comparison distribution with the number of values in each range determined for the set of sampled values.
  • the closest comparison distribution can be found, for example, by determining which comparison distribution has the minimum estimated mean square error with the sampled set value distribution.
  • a method of estimating the quality of service of a radio channel in a radio communications system comprising: determining the value of a parameter indicative of signal quality for each of a plurality of samples of a signal on the radio channel; determining the number of values, of a predetermined number of the determined parameter values, falling within each of a plurality of predetermined ranges of the parameter value ; comparing the set of determined numbers of values falling within each range with two or more predetermined sets of numbers of parameter values falling within each range, each predetermined set corresponding to a particular signal quality; and estimating the quality of service to be the quality of service represented by the predetermined set that the set of determined numbers of values falling within each range most closely matches.
  • an apparatus for estimating the quality of service of a radio channel in a " radio communications system comprising: means for determining the value of a parameter indicative of signal quality for each of a plurality of samples of a signal on the radio channel; means for determining the number of values, of a predetermined number of the determined parameter values, falling within each of a plurality of predetermined ranges of the parameter value; means for storing two or more predetermined sets of numbers of parameter values falling within each range, each predetermined set corresponding to a particular signal quality; means for comparing the set of determined numbers of values falling within each range with the predetermined sets of numbers of parameter values falling within each range; and means for estimating the quality of service on the basis of the comparison.
  • the predetermined reference distributions can be determined as desired, e.g. by analysing the parameter value distribution in samples of actual radio signals.
  • the radio signals could be simulated in known radio system simulation packages and the distributions determined from the simulation.
  • these reference distributions are determined using a large number of samples, to make them statistically reliable.
  • the distribution of values from the simulation or actual measurement may be used directly for the reference distributions, or the comparison distributions can be modified, e.g. in the light of practical experience, to, for example, take account of quantisation effects if a limited number of value ranges is to be used in the estimation process.
  • the - 16 - estimation is further dependent on the speed of the mobile radio and thus the present invention further comprises a step of or means for determining the speed of a mobile radio.
  • the velocity of a mobile radio can affect the results of a radio channel quality estimation process. This is because, inter alia , radio signal fades are determined by nodes in the signal, and thus the more rapidly a mobile radio is travelling the closer together any fades will be in time. Also, the faster a mobile is travelling, the more quickly it is likely to leave its present cell. Thus by modifying the estimation process to take account of the mobile's speed, it can be further optimised.
  • the reference distributions used in the estimation process could be selected depending upon the mobile's speed, with there being different such distributions associated with different speeds of the mobile.
  • three sets of reference distributions could be stored in the mobile radio unit, corresponding to low, medium and high speed (e.g. ⁇ 3 km/h (no mobility, no handover expected) , 3 to 30 km/h, 30 to 100 km/h, and 100 to 500 km/h) .
  • the mobile unit would then choose the appropriate set of reference distributions for comparison with the observed samples' distribution on the basis of its current speed.
  • a method of estimating the quality of service of a radio channel for a mobile radio in a radio communications system comprising: determining the current speed of the mobile radio; selecting in accordance with the determined speed - 17 - of the mobile radio one radio channel quality estimation algorithm from a group of predetermined radio channel quality estimation algorithms; and estimating the radio channel quality using the selected algorithm.
  • an apparatus for estimating the quality of service of a radio channel for a mobile radio in a radio communications system comprising: means for determining the current speed of the mobile radio; means for storing a number of predetermined radio channel quality estimation algorithms, each algorithm being associated with a particular mobile radio speed or speeds; means for selecting one of the stored predetermined algorithms on the basis of the determined speed; and means for estimating the radio channel quality using the selected algorithm.
  • the quality of service estimation method and apparatus of the present invention can be used whenever quality of service estimates would normally be used, for example in handover and cell or base station reselection processes. It could be operated repeatedly at selected, e.g.
  • the channel quality can be estimated each time without duplication of the parameter values in the sets of which the distribution is being considered, e.g. when ten values are used, every ten new samples.
  • it can be estimated using values used in a previous estimation together with new values, e.g. after each new sample (using the necessary number of immediately preceding values as the remaining values) or every two or three new samples, etc. - 18 -
  • the methods in accordance with the present invention may be implemented at least partially using software e.g. computer programs. It will thus "be seen that when viewed from a further aspect the present invention provides computer software specifically adapted to carry out the methods hereinabove described when installed on data processing means.
  • the invention also extends to a computer software carrier comprising such software which when used to operate a radio system comprising a digital computer causes in conjunction with said computer said system to carry out the steps of the method of the present invention.
  • a computer software carrier could be a physical storage medium such as a ROM chip, CD ROM or disk, or could be a signal such as an electronic signal over wires, an optical signal or a radio signal such as to a satellite or the like.
  • Figure 1 shows a probability density function of burst errors for a TETRA signal having a 0.7% bit error rate
  • Figure 2 shows a probability density function of burst errors for a TETRA signal having a 2% bit error rate
  • Figure 3 shows a probability density function of burst errors for a TETRA signal having a 6% bit error rate
  • Figure 4 shows an apparatus for determining the - 19 - variation of a set of sampled parameter values
  • Figure 5 shows a modulated ⁇ /4 differential quaternary phase-shift keying modulated TETRA signal
  • Figure 6 shows the demodulated form of the signal shown in Figure 5 ;
  • Figure 7 shows the demodulated constellation points of Figure 6 mapped to the first quadrant of the graph.
  • Figure 8 shows the probability density function of the points on the graph in Figure 7.
  • Figure 9 is a graph of signal power against time for an exemplary radio signal subjected to a Rayleigh fading envelope.
  • the following embodiment of the present invention illustrates its use in a TETRA system using the bit error rate alone as the parameter indicative of signal quality (although as noted above, other parameters can be used instead) , and compares it to channel service quality estimation using the average bit error rate.
  • bit error rate probability density functions for known signal strengths and qualities were determined to act as reference parameter value distributions.
  • COSSAP is a digital simulation software package licensed by Synopsis Inc., 700 East Middlefield Road, Mountain View, CA 94043, U.S.A.
  • the simulation was configured to provide the bit error rates (BERs) of the bursts (i.e. packets) in the signals.
  • the measured BERs from the simulation were grouped into three ranges or bins as shown in Table 1 below.
  • Table 2 shows the estimated value distributions:
  • the numbers of values differ slightly from the values that would be derived directly from the determined PDFs, because it was found that by varying slightly the number of values obtained from the PDF estimate for the channel quality a better overall result could be obtained.
  • the amount to vary the number of values by can be determined experimentally by seeing which distributions of values work best in practice. (It is believed that the best set of numbers of values may not correspond directly to PDFs estimated from the simulations because of the effects of quantisation noise when using only three ranges with ten samples per quality estimate. These factors are presumed to add a slight weighting to the numbers of values in each range - 22 - that may be difficult to assess- from a theoretical analysis . )
  • the value distributions or channel quality "fingerprints" in Table 2 may be used to estimate which of the 3 quality states a given radio channel is in, by comparing them with the distribution of a set of parameter values sampled from a radio signal on the radio channel .
  • bit error rate of the packets (or bursts) in every 18th frame of a TETRA signal on a radio channel was determined and the distribution of a set of ten bit error rate values sampled from that single channel compared with the reference bit error rate value distributions of Table 2.
  • the distribution of the bit error rate values of the ten samples was determined by sorting them into the three ranges described in Table 1, and this distribution was then compared with the three predetermined distributions described above by estimating the mean square error between it and each comparison reference distribution.
  • the channel state represented by the comparison distribution that produced the minimum mean square error - 23 - was selected as the current channel quality state of the channel carrying the sampled signal.
  • x x is the number of sampled BER values in the i tn bin or range
  • this process can be repeatedly performed (e.g. in the present embodiment every 10s (which corresponds to 10 lots of the 18th frame) , or by using a sliding process where the most recent 10 measurements are used) .
  • the numerical processing only involves the squaring of nine numbers, and can easily be performed in the control processor of a mobile radio, or base station, as desired.
  • These thresholds are nominally the same as the ranges used for estimating the BER value distribution in the method of the present embodiment.
  • Table 4 shows the number of occasions for which the channel was classified as either good, bad or neither for each method. It can be seen that the present invention provides the most accurate reporting of channel states with no inaccurate estimates and a small number of "neithers” . The mean estimation does not 25 perform quite so well reporting a larger number of " neithers " but no incorrect estimates .
  • the COSSAP simulation was then repeated with an average BER of 12% and a typical urban channel model at 3 kph.
  • the present invention predicts the bad channel marginally better, but also reports more good channels.
  • the distribution of the bit error rates is different at low speeds. If the vehicle speed can be estimated, then the set of comparison distributions can be optimised for different speeds.
  • the first simulation propagation channel used a typical urban propagation model at 50kph.
  • the two methods were also compared for situations where a burst with a high average error rate (50%) is present . These high bursts of errors may occur due to external interference effects, or from the decoding of the wrong channel type.
  • bit error rate as the parameter indicative of signal quality
  • other parameters could be used, and one preferred such measure is the variation of a set of determined instantaneous values of a particular parameter for a signal on the radio channel .
  • Figure 4 shows an apparatus 1 suitable for assessing the variation in parameter values of a physical TETRA channel, and in particular of a ⁇ /4 differential quaternary phase-shift keying ( ⁇ /4 DQPSK) modulated signal, such as might be present on that channel .
  • ⁇ /4 DQPSK differential quaternary phase-shift keying
  • a signal 2 such as this is input to a differential demodulator 3 of the apparatus 1, in which a sequence of such constellation points, x, which may be described by:
  • n 1, , N
  • the points in Figure 6 are the symbols of the signal (i.e. the parts of the signal which represent the data in the signal) and form the samples whose instantaneous parameter values (and their variation) are to be determined.
  • the radius of the circle on which the constellation points lie is proportional to the mean symbol energy
  • Each demodulated constellation point comprises two orthogonal ' sof decisions ' whose magnitude represents the instantaneous energy in the in-phase and quadrature- phase components of the signal samples.
  • the variance ⁇ 2 of a set of the values in the scalar amplitude sequence can then be determined using standard statistical analysis:
  • a parameter indication of signal quality is given - 30 - by the variance :
  • a low value of o indicates a good signal quality.
  • the signal quality indication therefore responds to co-channel interference, adjacent channel interference, and narrow band jamming in addition to additive white Gaussian noise .
  • Figure 8 shows an exemplary probability density function for a symbol scalar amplitude sequence derived as described above. Although in the above example the variance of the energy sequence was determined, as can be seen from Figure 7, there are four common characteristics or parameters of the mapped symbols . These are :
  • the above example uses the variance of the set of parameter values as an indicator of signal quality.
  • Other metrics indicative of the sampled values' variation can be used.
  • One preferred such metric is to divide the mean of the set of values, e.g. symbol energy ⁇ p , by the standard deviation of the set, ⁇ . This gives a metric which is proportional to the mean symbol energy (Es) and inversely proportional to both the background noise (N 0 )and the interference (C ⁇ ) levels, which will each serve to increase the standard deviation - 31 - of the energy distribution:
  • Q IND is preferably used as the quality of service indicator:
  • the value Q IND may be readily calculated and gets smaller as the quality of service improves .
  • the mean symbol energy, ⁇ p is preferably substantially constant throughout the set of symbols, as then any variation will be due to signal distortion. This has important implications when considering a practical radio communications system which may be subjected to a Rayleigh fading envelope, as shown for example, in Figure 9.
  • the number of successive symbols N, over which ⁇ 2 is evaluated should be less than T Q /T S (where T Q is the period over which the mean signal amplitude ⁇ p is substantially constant and T s is the symbol period) , since over this set of symbols the mean symbol amplitude remains substantially constant.
  • ⁇ 2 is evaluated over an over an extended period T v , by taking one long symbol sequence of length (T v /T s ) - 32 - then the value ⁇ p is no longer constant, and its variation would contribute to the signal quality metric ⁇ 2 and make it less reliable.
  • the time T ⁇ over which to evaluate the metric ⁇ ⁇ can be selected as desired with these factors in mind.
  • variation values for successive sets of parameters would be determined as above, and then the distribution of a set of plural variation values used to estimate the radio channel service quality.
  • the present invention can be implemented in a mobile radio system as desired. It could, for example, be used by the mobile radio unit itself or a base- station of the system. It can be implemented in hardware or software, as will be appreciated by those skilled in the art.
  • the quality of service estimate provided by the present invention can be used wherever such estimates are normally used, such as to aid handover and cell- reselection decisions.

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  • Computer Networks & Wireless Communication (AREA)
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  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé et un appareil permettant d'estimer la qualité de service d'un canal radioélectrique dans un système de radiocommunications. Le procédé de cette invention consiste tout d'abord à estimer le taux d'erreur sur les bits pour chacun des ensembles constitués de plusieurs échantillons d'un signal sur un canal radioélectrique, puis à définir le nombre de valeurs de taux d'erreur sur les bits de l'ensemble correspondant à chaque plage de taux d'erreur sur les bits. On compare ensuite la distribution de ces valeurs de taux d'erreur sur les bits dans l'ensemble échantillonné avec les distributions des taux d'erreur sur les bits de référence, qui représentent chacune une différence qualité de service. On définit enfin la qualité du signal échantillonné comme la qualité de la distribution de référence dont s'approche le plus la distribution des valeurs de taux d'erreur sur les bits dudit signal échantillonné.
PCT/GB1999/001530 1998-05-14 1999-05-14 Estimation de la qualite d'un canal radioelectrique Ceased WO1999059273A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU39415/99A AU3941599A (en) 1998-05-14 1999-05-14 Radio channel quality estimation

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9810396.3 1998-05-14
GB9810396A GB9810396D0 (en) 1998-05-14 1998-05-14 Radio channel quality estimation

Publications (1)

Publication Number Publication Date
WO1999059273A1 true WO1999059273A1 (fr) 1999-11-18

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PCT/GB1999/001530 Ceased WO1999059273A1 (fr) 1998-05-14 1999-05-14 Estimation de la qualite d'un canal radioelectrique

Country Status (3)

Country Link
AU (1) AU3941599A (fr)
GB (2) GB9810396D0 (fr)
WO (1) WO1999059273A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001043333A1 (fr) * 1999-12-09 2001-06-14 Nokia Corporation Filtrage fonction de l'equipement mobile pour service radio a commutation par paquet
EP1359697A1 (fr) * 2002-04-30 2003-11-05 Psytechnics Ltd Procédé et dispositif pour la caractérisation des erreurs de transmission
EP1359698A1 (fr) * 2002-04-30 2003-11-05 Psytechnics Ltd Procédé et dispositif pour la caractérisation des erreurs de transmission
WO2014068363A1 (fr) * 2012-10-30 2014-05-08 Freescale Semiconductor, Inc. Système radio à évasion de fréquence

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0008117D0 (en) * 2000-04-03 2000-05-24 Nokia Networks Oy Estimating communication quality
DE602004022438D1 (de) 2004-12-20 2009-09-17 Mitsubishi Electric Corp Verfahren zum Bestimmen einer Metrik zur Beurteilung der Übertragungsqualität eines Datenrahmens
US8265209B2 (en) * 2005-10-28 2012-09-11 Qualcomm Incorporated Method and apparatus for channel and noise estimation
DE102011087745A1 (de) * 2011-12-05 2013-06-06 Sennheiser Electronic Gmbh & Co. Kg Verfahren zum Bestimmen einer Übertragungsqualität beim Empfangen von Audiosignalen
US11075721B2 (en) 2019-04-29 2021-07-27 Itron, Inc. Channel plan management in a radio network
US11102050B2 (en) 2019-04-29 2021-08-24 Itron, Inc. Broadband digitizer used for channel assessment
WO2020223253A2 (fr) * 2019-04-29 2020-11-05 Itron, Inc. Estimateur de taux d'erreur de paquet destiné à une radio

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991009482A1 (fr) * 1989-12-07 1991-06-27 The Commonwealth Of Australia Moniteur de taux d'erreurs
US5214687A (en) * 1991-06-05 1993-05-25 Nokia Mobile Phones Ltd. Method to determine transmission quality
US5239667A (en) * 1990-01-31 1993-08-24 Nec Corporation Method of controlling handoff in cellular mobile radio communications system
US5490204A (en) * 1994-03-01 1996-02-06 Safco Corporation Automated quality assessment system for cellular networks
GB2307375A (en) * 1995-11-20 1997-05-21 British Broadcasting Corp Mobile Radio Communication System with Diversity Reception

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03104329A (ja) * 1989-09-19 1991-05-01 Nippon Telegr & Teleph Corp <Ntt> 移動通信チャネル割当て制御方式
SE469580B (sv) * 1992-08-18 1993-07-26 Televerket Foerfarande foer uppskattning av c/i-densitet och interferenssannolikhet i upplaenk
GB2285724B (en) * 1994-01-18 1997-10-15 Motorola Ltd Communications system
US5603093A (en) * 1994-12-28 1997-02-11 Ntt Mobile Communications Network, Inc. Method for monitoring the state of interference by a base station of a mobile radio communication system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991009482A1 (fr) * 1989-12-07 1991-06-27 The Commonwealth Of Australia Moniteur de taux d'erreurs
US5239667A (en) * 1990-01-31 1993-08-24 Nec Corporation Method of controlling handoff in cellular mobile radio communications system
US5214687A (en) * 1991-06-05 1993-05-25 Nokia Mobile Phones Ltd. Method to determine transmission quality
US5490204A (en) * 1994-03-01 1996-02-06 Safco Corporation Automated quality assessment system for cellular networks
GB2307375A (en) * 1995-11-20 1997-05-21 British Broadcasting Corp Mobile Radio Communication System with Diversity Reception

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001043333A1 (fr) * 1999-12-09 2001-06-14 Nokia Corporation Filtrage fonction de l'equipement mobile pour service radio a commutation par paquet
EP1548973A1 (fr) * 1999-12-09 2005-06-29 Nokia Corporation Filtrage basé sur un équipement mobile pour applications de service radio à commutation par paquets
KR100749029B1 (ko) * 1999-12-09 2007-08-13 노키아 코포레이션 패킷 무선 서비스 애플리케이션들을 위한 이동 장비 기반필터링
US7383022B2 (en) 1999-12-09 2008-06-03 Nokia Corporation Mobile equipment based filtering for packet radio service
US7599664B2 (en) 1999-12-09 2009-10-06 Nokia Corporation Mobile equipment based filtering for packet radio service (PRS)
EP1359697A1 (fr) * 2002-04-30 2003-11-05 Psytechnics Ltd Procédé et dispositif pour la caractérisation des erreurs de transmission
EP1359698A1 (fr) * 2002-04-30 2003-11-05 Psytechnics Ltd Procédé et dispositif pour la caractérisation des erreurs de transmission
US7124349B2 (en) 2002-04-30 2006-10-17 Psytechnics Limited Method and apparatus for transmission error characterization
WO2014068363A1 (fr) * 2012-10-30 2014-05-08 Freescale Semiconductor, Inc. Système radio à évasion de fréquence
US9356652B2 (en) 2012-10-30 2016-05-31 Freescale Semiconductor, Inc. Frequency hopping radio system

Also Published As

Publication number Publication date
AU3941599A (en) 1999-11-29
GB9810396D0 (en) 1998-07-15
GB2337425B (en) 2000-12-13
GB2337425A (en) 1999-11-17
GB9911285D0 (en) 1999-07-14

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