JP2011114716A - Random access channel receiving device and receiving method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a random access channel receiving device and a receiving method thereof, which can adapt a threshold value in a trade-off relation to the optimum point by an easy means according to conditions of a delay profile changing dependent on circumstances. <P>SOLUTION: A random access channel receiving device for receiving and controlling transmission of a message from a mobile station includes: a profile synthesizing section 7 for synthesizing power profiles from received data from each mobile station and forming a delay profile; a preamble detection section 9 for detecting, in the delay profile, existence or non-existence of a preamble transmitted from the mobile station to indicate a start of a frame; an error detection probability calculating section 11 for calculating probability of error detection of the preamble; and a detection threshold value calculating section 12 for calculating a threshold value corresponding to the error detection probability obtained by the error detection probability detection section. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a random access channel receiving apparatus and a receiving method thereof in a base station, and preferably to a random access receiving apparatus and a receiving method thereof in a base station constituting an LTE (Long Term Evolution) mobile communication system.

  In a mobile communication system, a plurality of mobile stations access a base station at an arbitrary timing using a common channel, and the base station receives a random access channel reception method for receiving and controlling message transmission from the mobile station. ing.

  At this time, prior to the transmission of the message, the mobile station transmits a preamble that notifies the base station that the message has occurred.

  FIG. 5 is a block diagram showing a conventional configuration of a random access channel receiving apparatus. Received data in the baseband frequency band is input to the random access channel receiver as uplink received data in a format converted from analog to digital. Uplink reception data is input in parallel for an arbitrary number of antennas, and the configuration of the random access channel reception apparatus is also parallel for the number of antennas before profile synthesis.

In FIG. 5, the pre-processing units 1 ₀ to 1 _n perform the following three processes on the reception data input to the random access channel reception device.

(1) Rotation removal This removes the rotation multiplied by the random access channel transmission signal generation, and removes the received data by complex multiplication of the rotator table.

(2) Frequency shift Since the random access channel is arranged at an arbitrary frequency position in the frequency band, the frequency is shifted, and the random access channel signal is shifted so as to be centered on the frequency axis. The frequency shift is performed by complex multiplication of the rotor table.

(3) Filtering Filtering processing performed to remove signals other than the random access channel on the frequency band, and passes through an FIR digital filter having a finite tap length.

DFT (Discrete Fourier Transform) 2 ₀ to 2 _n are discrete Fourier transformers that perform conversion from a time axis to a frequency axis.

Sequence removal units 3 _{0 to} 3 _n obtain correlation values by multiplying received data by a known replica sequence separately obtained from replica sequence generation unit 4. Since the LTE mobile communication system uses an Orthogonal Frequency Division Multiplexing (OFDM) communication system, this series removal processing is received data obtained by performing DFT (time axis → frequency axis) conversion on the data after the previous stage processing. To do.

_{IFFT (Inverse FFT) 5 0 ~5} n is the inverse discrete Fourier transformer after sequence removed inverse transform (frequency axis → time axis conversion) through the correlation values obtained by the power profile ₆ 0 to 6 _n Is added by the number of antennas by the profile synthesis unit 7 (profile synthesis) to obtain a delay profile. This delay profile is to collect data on how much the radio wave is delayed by giving various situations to investigate the radio wave delay.

  The preamble detection unit 9 adds a preamble detection threshold value, which is a fixed value, based on the interference power level of the profile obtained by the noise power calculation unit 8, and uses this as a preamble detection threshold value. If it is less than the threshold, a process for determining that no preamble has been detected is performed.

  The timing adjustment calculation unit 10 calculates a timing adjustment value from the peak position for the preamble determined to be preamble detection by the preamble detection unit 9.

  In this regard, conventionally, in a random access signal receiving apparatus, in order to determine whether or not a preamble signal has been received, a correlation value dispersion degree indicating a dispersion degree with respect to an average value of correlation values is calculated from a delay profile of the preamble reception signal. There is known a technique including correlation value dispersion degree calculating means for calculating a threshold value and calculating threshold values from the correlation value dispersion degree. (For example, refer to Patent Document 1).

JP 2004-356725 A

  However, in the prior art (Patent Document 1), the cause of variance of the correlation value is used as a means for obtaining the preamble detection threshold. However, since there are other causes of erroneous detection, the threshold cannot be optimized. .

  With reference to FIG. 6, the conventional problem will be specifically described.

  FIG. 6 is a waveform diagram of the preamble detector 9 shown in FIG. As shown in the upper left diagram of FIG. 6, in the delay profile in which the preamble is not transmitted, the original peak value due to the preamble should not exist, but the correlation that occurs due to the characteristics of the sequence and the noise in the received data Alternatively, a pseudo peak point that occurs when a series is removed in a state where fading is on is in a state where the profile length exists at an arbitrary position.

  As shown in the lower left diagram of FIG. 6, with the preamble detection threshold, the false peak point is erroneously determined as preamble detection, resulting in erroneous preamble detection.

  The right diagram in FIG. 6 is also used for profile detection obtained by actually transmitting the preamble, so the preamble detection threshold (fixed value) is high enough not to cause false detection, and the real preamble is correctly detected. It is necessary to make it as low as possible, and the value is in a trade-off relationship.

  The present invention has been made in view of such a point, and according to the situation of a delay profile that varies depending on the environment, random access channel reception in which the threshold value in the above trade-off relationship can be adjusted to the best point by an easy means. An object is to provide an apparatus and a receiving method thereof.

  One aspect of an apparatus for solving the above problem is that a plurality of mobile stations access a base station at an arbitrary timing using a common channel, and the base station receives and controls message transmission from the mobile station. In a random access channel receiver, a profile combining unit that combines each power profile from received data from each mobile station to create a delay profile, and for signaling the start of the frame from the mobile station in the delay profile A preamble detection unit for detecting presence / absence of a preamble sent to the device, a false detection probability calculation unit for calculating a probability of erroneous detection of the preamble, and a threshold value corresponding to the false detection probability obtained by the false detection probability calculation unit And a detection threshold value calculation unit.

  According to one aspect of the apparatus, a preamble detection threshold value that provides a desired false detection probability is adjusted according to the interference power level of the received data input to the random access channel receiver, the propagation environment, the correlation caused by the sequence, and the like. Applicable. Furthermore, it is possible to provide a random access channel receiving apparatus that eliminates the need to manually change the preamble detection threshold value, which is a fixed value, according to each environment.

  A method is a random access channel reception method in which a plurality of mobile stations access a base station at an arbitrary timing using a common channel, and the base station receives and controls message transmission from the mobile station, Synthesizing each power profile from received data from the mobile station to create a delay profile, and detecting in the delay profile the presence or absence of a preamble sent to signal the start of a frame from the mobile station And calculating a probability of erroneous detection of the preamble and calculating a threshold corresponding to the obtained erroneous detection probability.

  According to this method, a preamble detection threshold value that provides a desired false detection probability is dynamically set according to the interference power level of the received data input to the random access channel receiver, the propagation environment, the correlation caused by the sequence, and the like. Applicable. Furthermore, it is possible to provide a random access channel receiving apparatus that eliminates the need to manually change the preamble detection threshold value, which is a fixed value, according to each environment.

  As described above, according to the disclosed technique, the preamble detection threshold value that provides a desired false detection probability is set according to the interference power level of the received data input to the random access channel receiver, the propagation environment, the correlation caused by the sequence, and the like. Can be applied dynamically. Furthermore, there is no need to manually change the preamble detection threshold value, which is a fixed value, according to each environment.

It is a block diagram of the random access channel delay profile which this invention makes object. 1 is a block diagram (Example 1) showing a configuration of a random access channel receiver according to the present invention. FIG. It is a block diagram (Example 2) which shows the structure of the random access channel receiver by this invention. 3 is a flowchart illustrating a random access channel reception method according to the present invention. It is a block diagram which shows the conventional structure of a random access channel receiver. FIG. 6 is a waveform diagram of the preamble detector shown in FIG. 5.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a random access channel delay profile targeted by the present invention, and in particular, an example of a delay profile obtained by a random access channel receiver in an apparatus constituting an LTE (Long Term Evolution) mobile communication system. Show. LTE is one of high-speed data communication specifications for mobile phones, and is a further evolution of the high-speed data communication standard of the third generation mobile phone system “W-CDMA”, and is being standardized.

  In a random access channel in LTE, a Zadoff-Chu (ZC) sequence is used as a preamble sequence. As an actually transmitted sequence, an arbitrary ZC sequence is cyclically shifted at a cyclic shift interval. FIG. 1 shows a case where the number of cyclic shifts = 4.

  Each delay profile range (A in FIG. 1) divided by the cyclic shift interval corresponds to 1 UE (User Equipment). Further, B in FIG. 1 is a profile range corresponding to the cell radius of the base station set in the receiving apparatus, and C in FIG. 1 is a profile range used for calculating a false detection probability.

  The cell radius of the base station set in the receiving apparatus is set narrower than the delay profile range (A in FIG. 1) corresponding to 1 UE in consideration of the margin. For delay profiles greater than the cell radius setting, search for preamble detection is performed. Not targeted.

  Therefore, there is a delay profile range that is a surplus of the difference (= C) between A and B in FIG.

  This surplus delay profile portion is a range in which a mobile device (UE: User Equipment) cannot exist. Therefore, a real correlation peak does not appear, and all peak points exceeding the threshold in this range are false detections. Can be considered.

  In this patent, the delay profile in the range of C in FIG. 1 is used for calculating the false detection probability.

  FIG. 2 is a block diagram (Example 1) which shows the structure of the random access channel receiver by this invention. Hereinafter, differences from the conventional method described in FIG. 4 will be mainly described.

  The preamble detector (within the cell radius) 9a is for “within the cell radius” for searching the delay profile portion of FIG. 1B, and the preamble detector (outside of the cell radius) 9b is the delay profile portion of FIG. 1C. For “outside cell radius”.

  The delay profile obtained from the profile synthesizing unit 7 is input to each of the preamble detection unit (within the cell radius) 9a and the preamble detection unit (outside the cell radius) 9b.

  A preamble detection threshold (initial value) is input to the preamble detection unit (outside the cell radius) 9b. The initial value may be an arbitrary value, but for example, an interference power level obtained by the noise power calculator 8 can be used.

  Further, a value obtained by adding the threshold value obtained from the detection threshold value calculation unit 12 and the interference level obtained from the noise power calculation unit 8 is input to the preamble detection unit (outside the cell radius) 9b.

  This is feedback information used when repeating a series of processing of preamble detection unit (outside cell radius) 9b → false detection probability calculation unit 11 → detection threshold calculation unit 12 until a desired false detection probability is obtained while changing the threshold value. It becomes.

  Further, the false detection probability calculation unit 11 calculates information (= false detection probability) necessary to raise and lower the preamble detection threshold.

  The calculation formula is as follows.

False detection probability = number of preamble false detections / number of physical random access channel receptions Here, the number of preamble false detections corresponding to the numerator in the above formula is the number of preamble detections detected per arbitrary time used in the false detection probability calculation unit 11 The number of times detected by the “outside cell radius” preamble detection unit 9b. This is because the surplus portion of the profile is used, and can be regarded as “preamble detection outside cell radius = false detection”.

  Further, the “number of physical random access channel receptions” corresponding to the denominator in the above equation is obtained by “the number of physical random access channel receptions included per arbitrary time × the number of cyclic shifts” used in the false detection probability calculation unit 11. .

  The number of physical random access channel receptions included per arbitrary time is determined by the arrangement of the physical random access channel structure. For example, when the arrangement of the physical random access channel structure = 3, the random access channel exists for 10 ms in 10 ms, When the arbitrary time of the erroneous detection probability calculation unit 11 is 10 ms, the number of physical random access channel receptions included per arbitrary time = 1.

  The number of cyclic shifts can be easily calculated by a known mathematical formula, although the calculation formula differs depending on conditions such as low mobility or high mobility.

  The detection threshold value calculation unit 12 is a functional unit that determines whether the preamble detection threshold value should be moved up or down from the false detection probability obtained by the false detection probability calculation unit 11 and determines the threshold value.

  An example of threshold determination is shown below.

When the false detection probability of the target is set to 99.0% (1) When the false detection probability obtained by the false detection probability calculation unit is 98.0% Raise in 1d steps.
(2) When the false detection probability obtained by the false detection probability calculation unit is 99.9% It is assumed that the false detection is less than the target, and the detection threshold is lowered by 0.1 dΒ steps.

  As described above, each time the detection threshold value is changed up and down, the error detection probability is obtained, and a series of processes for feeding back to the preamble detection (outside the cell radius) unit 9b is repeated, so that a threshold value that provides a desired error detection probability is obtained. I can decide.

  In addition, the step width for updating the detection threshold is related to the number of process repetitions. If the number of process repetitions is small, the step width is set to a large value. If the number of process repetitions is large, the step width is set to a small value. Set. This makes it possible to obtain (converge) a detection threshold value that provides a desired false detection probability with a smaller number of process repetitions (time).

  In the configuration in which the preamble detection threshold is applied from the dynamic calculation of the preamble detection threshold according to the present invention, a training period is provided in a part of the apparatus start-up period before entering the actual operation, and the method for determining an appropriate threshold is not used. Therefore, it can be applied in actual operation.

  FIG. 3 is a block diagram (Example 2) which shows the structure of the random access channel receiver by this invention. The difference from the block diagram (Embodiment 1) showing the configuration of the random access channel receiving apparatus according to the present invention described in FIG. 2 will be described below.

  In FIG. 3, two types of preamble detection units 9a and 9b are integrated into one type of preamble detection unit (inside / outside cell radius) 9.

  The integrated preamble detector (inside / outside the cell radius) 9 performs time division multiplexing on the preamble detection of both B (inside the cell radius of the base station) in FIG. 1 and C (outside the cell radius of the base station) in FIG. To do.

  FIG. 4 is a flowchart illustrating a random access channel reception method according to the present invention. Hereinafter, a random access channel reception method for uplink reception data transmitted from the mobile station to the base station will be described with reference to FIG. 2 and FIG.

S1. In each of the upstream processing units 1 ₀ to 1 _n , upstream processing as described above is performed on uplink reception data input in parallel for an arbitrary number of antennas.

S2. A discrete Fourier transformer (DFT) 2 ₀ to 2 _n performs conversion from the time axis to the frequency axis.

S3. Correlation values are obtained by multiplying the replica sequences in the sequence removal units 3 _{0 to} 3 _n .

S4. Inverse discrete Fourier transform (IFFT) 5 _{0 to} 5 _n performs conversion from the frequency axis to the time axis.

S5. At power profile ₆ 0 to 6 _n, to obtain a correlation value.

  S6. The profile synthesizing unit 7 obtains a delay profile by adding the correlation values for the number of antennas.

  S7. The noise power calculation unit 8 obtains the interference power level of the profile.

  S8. The preamble detection unit (outside the cell radius) 9b receives the delay profile obtained from the profile synthesis unit 7, determines the preamble detection threshold using only the surplus profile section (C in FIG. 1), and moves according to the profile state. Will be updated and applied.

  S9. The random access channel reception count is a value of physical random access channel reception count x cyclic shift number included per arbitrary time, and it is determined whether or not a predetermined value has been reached.

  S10. The false detection probability calculation unit 11 calculates the false detection probability from the number of preamble false detections / the number of physical random access channel receptions. As described above, it can be considered that preamble detection outside the cell radius = false detection.

  S11. The detection threshold value calculation unit 12 determines a threshold value from the erroneous detection probability obtained in S10. The initial value is set for the first time, and the threshold value is increased or decreased at any step other than the first time.

  S12. The preamble detection threshold is converged by associating the step width for updating the preamble detection threshold with the number of process repetitions.

  S13. In the preamble detection unit (within the cell radius) 9a, the delay profile obtained from the profile synthesis unit 7 is input, and the converged preamble detection threshold is input. In this case, it is determined that the preamble has not been detected.

  S14. The timing adjustment calculation unit 10 calculates a timing adjustment value from the peak position of the preamble detected and detected in the preamble, and outputs it as preamble detection information.

  INDUSTRIAL APPLICABILITY The present invention can be used in a random access channel receiving apparatus that can dynamically apply a preamble detection threshold that provides a desired erroneous detection probability of received data.

The following appendices are further disclosed with respect to the embodiments including Examples 1 and 2 above.
(Appendix 1)
A plurality of mobile stations access a base station at an arbitrary timing using a common channel, and the base station receives a message transmission from the mobile station and controls it in a random access channel receiver,
A profile synthesis unit that creates a delay profile by synthesizing each power profile from the received data from each mobile station;
A preamble detector for detecting presence / absence of a preamble sent to signal the start of a frame from the mobile station in the delay profile;
A false detection probability calculating unit for calculating a probability of erroneous detection of the preamble;
A detection threshold value calculation unit that calculates a threshold value corresponding to the false detection probability obtained by the false detection probability calculation unit;
A random access channel receiving apparatus comprising:
(Appendix 2)
In the random access channel receiver according to appendix 1,
The random access channel receiving apparatus according to claim 1, wherein the preamble detecting unit includes means for switching between two types of ranges within and outside the cell radius of the base station.
(Appendix 3)
In the random access channel receiver according to appendix 1,
The random access channel reception device, wherein the preamble error detection probability calculation unit obtains the number of preamble error detections from a surplus profile section outside the cell radius of the base station.
(Appendix 4)
In the random access channel receiver according to appendix 3,
The random access channel reception device, wherein the preamble error detection probability calculation unit calculates a preamble error detection probability from the number of preamble error detections and the number of random access channel receptions.
(Appendix 5)
In the random access channel receiver according to appendix 4,
The random access channel reception apparatus, wherein the preamble error detection probability calculation unit calculates a preamble error detection probability using a time average.
(Appendix 6)
In the random access channel receiver according to appendix 1,
The random access channel reception device, wherein the detection threshold calculation unit determines the number of threshold determination process repetitions corresponding to a step width for updating the detection threshold.
(Appendix 7)
A plurality of mobile stations access a base station at an arbitrary timing using a common channel, the base station is a random access channel reception method for receiving and controlling message transmission from the mobile station,
Synthesizing each power profile from the received data from each mobile station to create a delay profile;
Performing presence / absence detection of a preamble sent to signal the start of a frame from the mobile station in the delay profile;
Calculating a probability of erroneous detection of the preamble;
Calculating a threshold corresponding to the obtained false detection probability;
A random access channel receiving method comprising:
(Appendix 8)
A random access channel reception method according to appendix 7,
The method for receiving a random access channel according to claim 1, wherein the step of detecting the presence or absence of the preamble includes a step of switching between two types of ranges inside and outside the cell radius of the base station.
(Appendix 9)
A random access channel reception method according to appendix 7,
The method of calculating a probability of erroneous detection of a preamble includes obtaining a number of times of erroneous preamble detection from a surplus profile section outside the cell radius of the base station.
(Appendix 10)
A random access channel reception method according to attachment 9, wherein
The method of calculating a probability of erroneous detection of a preamble includes calculating a probability of erroneous detection of a preamble based on the number of erroneous preamble detections and the number of receptions of the random access channel.
(Appendix 11)
A random access channel reception method according to appendix 10,
The method of receiving a random access channel according to claim 1, wherein the step of calculating a probability of erroneous detection of a preamble calculates a probability of erroneous preamble detection using a time average.
(Appendix 12)
A random access channel reception method according to appendix 7,
The method of receiving a random access channel according to claim 1, wherein the step of calculating the threshold value determines the number of threshold determination process repetitions corresponding to a step width for updating the detection threshold value.

1 ₀ to 1 _n pre-processing unit 2 ₀ to 2 _n Discrete Fourier Transform (DFT)
3 _{0 to} 3 _n sequence removal unit 4 replica sequence generation unit 5 _{0 to} 5 _n inverse discrete Fourier transform (IFFT: Inverse FET)
6 _{0 to} 6 _n power profile 7 profile synthesis unit 8 noise power calculation unit 9 preamble detection unit (power determination)
9 'Preamble detector (inside / outside of cell radius)
9a Preamble detector (within cell radius)
9b Preamble detector (outside cell radius)
10 Timing adjustment calculator 11 False detection probability calculator (time average)
12 Detection threshold value calculation part

Claims (5)

A plurality of mobile stations access a base station at an arbitrary timing using a common channel, and the base station receives a message transmission from the mobile station and controls it in a random access channel receiver,
A profile synthesis unit that creates a delay profile by synthesizing each power profile from the received data from each mobile station;
A preamble detector for detecting presence / absence of a preamble sent to signal the start of a frame from the mobile station in the delay profile;
A false detection probability calculating unit for calculating a probability of erroneous detection of the preamble;
A detection threshold value calculation unit that calculates a threshold value corresponding to the false detection probability obtained by the false detection probability calculation unit;
A random access channel receiving apparatus comprising: The random access channel receiver according to claim 1, wherein
The random access channel reception device, wherein the preamble error detection probability calculation unit obtains the number of preamble error detections from a surplus profile section outside the cell radius of the base station. The random access channel receiver according to claim 1, wherein
The random access channel reception device, wherein the detection threshold calculation unit determines the number of threshold determination process repetitions corresponding to a step width for updating the detection threshold. A plurality of mobile stations access a base station at an arbitrary timing using a common channel, the base station is a random access channel reception method for receiving and controlling message transmission from the mobile station,
Synthesizing each power profile from the received data from each mobile station to create a delay profile;
Performing presence / absence detection of a preamble sent to signal the start of a frame from the mobile station in the delay profile;
Calculating a probability of erroneous detection of the preamble;
Calculating a threshold corresponding to the obtained false detection probability;
A random access channel receiving method comprising: A method for receiving a random access channel according to claim 4,
The method of calculating a probability of erroneous detection of a preamble includes obtaining a number of times of erroneous preamble detection from a surplus profile section outside the cell radius of the base station.

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