KR100331866B1 - Adaptive Beamforming Method in ETSI system - Google Patents

Abstract

The present invention relates to an indirect method array antenna adaptive beam forming method based on a dedicated physical control channel (DPCCH) and a dedicated physical data channel (DPDCH) structure proposed in an ETSI system. . The beamforming scheme according to the present invention has a plurality of antennas to form a beam for a specific communication counterpart, and the CDMA mobile communication system in which a communication channel is divided into a data channel and a control channel is received through the control channel. Obtaining a first adaptive beam former coefficient by calculating a first adaptive beam former coefficient by inputting a signal received on the data channel and a first adaptive beam former coefficient by inputting the first adaptive beam former coefficient; Obtaining a second adaptive beam former coefficient by comparing the signal received through the data channel with the temporary decision value, and calculating the second adaptive beam former coefficient to the signal received through the data channel to output the received signal of the data channel Wideband CDMA other than the ETSI system because it is characterized in that it comprises a step Womb next generation mobile communication system, i.e., the pilot (Pilot) is an adaptive beam forming method for both systems can be applied using a channel and a traffic (Traffic) channel.

Description

Adaptive Beamforming Method of ETSI System. {Adaptive Beamforming Method in ETSI system}

The present invention relates to the formation of an indirect method of array antenna adaptive beam proposed by the European Telecommunications Standard Institute (ETSI) system, in particular in the form of an ETSI system and a wideband CDMA type. The present invention relates to an adaptive beamforming method of an ETSI system that is suitable for eliminating interference effects and maximizing antenna diversity effects by increasing system capacity in a reverse direction of a next generation mobile communication system.

In general, the adaptive beamforming method of the array antenna in the conventional direct spread CDMA system uses a method of using only pilot channel information or a blind algorithm using only traffic channel information without pilot channel information. This was used representatively.

Representative methods using only pilot channel information include a Least Mean Square (LMS) algorithm and a Recursive Least Square (RSL) algorithm. Blind methods that do not use a reference signal (training signal) known to all of the receivers include a constant modulus algorithm (hereinafter, abbreviated as CMA) and a second rake combiner method.

Here, the principle of forming the beam of the array antenna according to the LMS algorithm will be described.

The LMS algorithm is an adaptive algorithm using a data channel containing actual user information and a channel for transmitting a known reference signal (training signal) to both the transmitter and the receiver.

Since the LMS algorithm uses a reference signal, it is possible to stably update the coefficients of the filter. Since the evaluation function is convexed, the convergence to the global minimum is guaranteed.

In addition, in terms of hardware, the structure is simple and easy to design.

Because of these advantages, LMS algorithms are widely used in systems that can use reference signals.

The LMS algorithm described so far uses an array using a dedicated physical data channel (hereinafter referred to as DPDCH) and a dedicated physical control channel (hereinafter referred to as DPCCH) in a reverse dedicated channel. Form the adaptive beam of the antenna.

Hereinafter, a reverse channel slot structure in a CDMA mobile communication system proposed by a general ETSI will be described with reference to the accompanying drawings.

1 illustrates a slot structure of a reverse DPDCH and a DPCCH in a CDMA mobile communication system proposed by a general ETSI.

Referring to FIG. 1, a dedicated channel of a reverse channel of a CDMA mobile communication system proposed by ETSI is a channel used to transfer user information and control information from a mobile station (not shown) to a base station (not shown). to be.

In this reverse dedicated channel, there is a DPDCH (1) for transmitting actual user data, and a DPCCH (2) for transmitting pilot information, transmission power control information, and transmission format identification information.

The information transmitted through the DPCCH (2) of the reverse dedicated channel of the CDMA mobile communication system proposed by ETSI includes pilot information per slot, transmit power information (hereinafter, abbreviated as TPC) and The transport format identification information (hereinafter, abbreviated as TFI) is expected to have an approximately 6: 2: 2 ratio.

The pilot information can be used for channel estimation and adaptive beamforming. TPC is used for open loop power control and TFI is used to transmit a transmission format in units of 16 slots. .

2 is a block diagram illustrating a device configuration for beamforming of a general array antenna.

2 is a block diagram illustrating a general device configuration for beamforming of an array antenna.

Referring to FIG. 2, when a signal is received through each array antenna array, the received signal is despread through demodulation and down sampling. Then, one symbol is inputted by the weight of the beam forming unit 30. It is made up of a structure that updates every moment.

First, assume a system in which there are K transmission signals and L array antennas, and consider adaptive beam formation after despreading. Here, the adaptive beamforming before despreading can also be easily applied by substituting a spreading code in the following equation.

The weight vector of the beam forming unit 30 for the first transmission signal of the K transmission signals, Evaluation function in the LMS algorithm Can be defined as:

here, Is the signal size of the pilot channel for the first transmission signal, Is the nth signal known to the receiver in advance, Is a pilot signal vector despread through the channel and defined as follows.

The LMS algorithm according to Equations 1 and 2 is defined in Equation 3 below using a pilot signal known to the receiver. We can repeatedly find the optimal coefficient. Known here means that the receiver knows the symbol of the transmitted pilot signal in advance.

Where the superscript * means a complex conjugate, Is

Is defined as

Since only the traffic signal, that is, the data signal, exists in the DPDCH and there is no reference signal known in advance at the receiving end, a temporary decision value is obtained using the DD algorithm. It is called LMS-DD to obtain a temporary decision value and to use LMS algorithm. In this case, the absence of a known reference signal means that the receiver does not know the symbol of the data signal in advance. In addition, the temporary decision value refers to a symbol value temporarily substituted in place of a signal which is not known in advance.

At this time, the evaluation function of the LMS-DD is shown in Equation 5 below.

here Means the size of the traffic signal, Is a tentative decision to use the LMS algorithm. Formula may be expressed as Equation 6 below.

At this time, dec {} represents a detection function.

Here, in order to ensure the reliability of the temporary decision value, fading is severe and coefficient updating may not be performed when the signal is below the threshold (bypass mode).

Thus, received at the receiver The despread signal vector whose value is unknown is defined as in the following equation.

In addition, the coefficient of the filter in the DD-LMS algorithm is updated by the following equation.

Here, ε_DD is defined by the following equation.

Since the DPCCH (2) of the reverse dedicated channel of the CDMA mobile communication system proposed by the general ETSI is not configured for pure pilot channel support, TPC and TFI intervals that cannot use pilot information are not used to form an adaptive beam. I'm not doing it.

In particular, in the CDMA mobile communication system proposed by ETSI, there is no specific technique for an adaptive beamforming method.

The present invention has been made to solve such a problem, and the LMS-DD algorithm using a temporary decision value of traffic data and the LMS algorithm using a pilot symbol are used for adaptively forming a despread signal. The purpose of the present invention is to provide an adaptive beamforming technique using a double least square average (LMS) of a CDMA mobile communication system proposed by ITS, which is suitable for forming an adaptive beam of an array antenna using a combining method.

In order to achieve the above object, the adaptive beamforming technique using the double least square mean (LMS) of the ITS system according to the present invention forms a beam for a specific communication counterpart with a plurality of antennas, In a CDMA mobile communication system divided into a data channel and a control channel, calculating a signal received through the control channel to obtain a first adaptive beam former coefficient, and a signal received through the data channel and the first adaptive beam former. Obtaining a temporal decision value of a received signal of a data channel by inputting a coefficient; obtaining a second adaptive beam former coefficient by comparing the temporal decision value with a signal received through the data channel; receiving the data channel Calculating the second adaptive beam former coefficients to the received signal and outputting the second adaptive beamformer coefficients as received signals of a data channel. Preferably, the signal received through the control channel is a pilot signal. The step of obtaining the first adaptive beamformer coefficient may be performed by comparing a known pilot symbol with a symbol of the received pilot signal. And calculating the second adaptive beamformer coefficient by comparing a symbol of a received data signal with a symbol obtained as the temporary decision value. The method of obtaining the first and second adaptive beamformer coefficients may be performed by a minimum. According to another aspect of the present invention for achieving the above object, it has a plurality of antennas to form a beam for a specific communication counterpart, the communication channel is a data channel and a control channel In the CDMA mobile communication system divided by, the signal received through the control channel and the conventional second adaptive beam former Computing coefficients to update a first adaptive beamformer coefficient; obtaining a temporary decision value of a received signal of a data channel by inputting the signal received on the data channel and the updated first adaptive beamformer coefficient; Comparing the signal received through the data channel with the temporary decision value to update a second adaptive beam former coefficient, and calculating the updated second adaptive beam former coefficient to the signal received through the data channel. Preferably, the two updates are made during the same symbol time period. According to another aspect of the present invention for achieving the above object, a plurality of antennas are provided. Form a beam for a specific communication counterpart, and the communication channel is divided into a data channel and a control channel. Obtaining a temporary decision value of a received signal of a data channel by inputting a signal received on the data channel and a previous adaptive beam former coefficient in a CDMA mobile communication system Comparing the signal received through the control channel with a value to update the adaptive beam former coefficients, and calculating and outputting the updated adaptive beam former coefficients to the signal received through the data channel. Preferably, the step of updating the adaptive beam former coefficients is achieved by comparing the signals received in the control channel with a known signal. According to another aspect of the present invention for achieving the above object Has a plurality of antennas to form a beam for a specific communication counterpart, In a CDMA mobile communication system in which a new channel is divided into a data channel and a control channel, calculating a signal received through the control channel and a previous first adaptive beam former coefficient to update the first adaptive beam former coefficient; Obtaining a temporal decision value of a received signal of a data channel by inputting a signal received through a data channel and the updated first adaptive beam former coefficients, and comparing the temporal decision value with a signal received through the data channel; Updating the adaptive beamformer coefficients and outputting the updated second adaptive beamformer coefficients to a signal received on the data channel and outputting the updated adaptive beamformer coefficients as a received signal of the data channel. Two updates are made during the same symbol time.

1 is a view illustrating a slot structure of a reverse DPDCH and a DPCCH in a conventional ETSI system.

Figure 2 is a block diagram showing a general device structure for forming a beam of a conventional array antenna.

Figure 3 is a block diagram showing the structure of an adaptive beamformer using dual LMS according to the first embodiment of the present invention.

4 is a block diagram showing a configuration of an adaptive beamformer using a crystal-oriented LMS according to a second embodiment of the present invention.

5 is a block diagram showing a configuration of an adaptive beamformer using a crystal-oriented LMS according to a third embodiment of the present invention.

Description of the main parts of the drawing

30: beam forming unit 31, 42, 52, 54: LMS (Least Mean Square)

32: LMS-DD 33: Detection function

34, 40, 50: first beam forming portion 35, 44, 56: second beam forming portion

41, 51: decision part

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings. According to the present invention, a dedicated channel (DCH) of an ETSI reverse channel transmits user information and control information from a mobile station. Transfer to Base Station.

The DPDCH is a channel for transmitting the actual user data, and the DPCCH is a channel for transmitting a pilot signal, a TPC signal, and a TFI signal.

Of these, TPC and TFI account for a small percentage. In this part, it is not unreasonable to assume that a dedicated physical control channel (DPCCH) that obtains accurate data in a Decision Dedicated (DD) method is a pilot channel.

In the adaptive beamforming method according to the present invention, a DD-LMS (Least Mean Square) method is basically used to use traffic information, and pilot information is used as an LMS algorithm method. And it is divided into three techniques according to the application method using two kinds of information.

First of all, it is divided into two categories: Cascade Structure and Parallel Structure. Parallel structure is divided into DD-LMS (1) and DD-LMS (2) according to the method of making tentative decision.

3 is a block diagram showing the structure of an adaptive beamformer using dual LMS according to a first embodiment of the present invention.

Referring to FIG. 3, the coefficient update equation in FIG. 3 is expressed as in Equation 10 below.

Here, p [n] and r [n] are respectively defined as n-th pilot signal vectors and traffic signal vectors passed through the channel and despread as shown in Equation 11 below.

For convenience, the subscript indicating user 1 is omitted.

In this method, the nth signal vector p [n] despread in series is first counted by the LMS 31. After updating the value to LMS-DD (32) And the final determined value via the second beam forming unit 35 This is induced.

In addition, the despread n th traffic signal vector is temporarily determined through a detection function 33 via the first beam forming unit 34. This is determined.

Equation 12 of the temporary decision value is as follows.

Therefore, combine the above two expressions and determine the error rate Considering this, the update equation 13 is as follows.

Therefore, if the power of the signals coming from each channel is the same and the temporary decision is relatively accurate, then it is likely that the step size μ is doubled while ensuring convergence. When an error occurs in the temporary decision value, the sign of the reference signal is reversed, and the beamforming coefficients do not find the optimal value.

A miscalculated decision When a probability occurs, the misadjustment value increases accordingly.

The advantage of this structure is the decision error rate Is close to 0, it is advantageous to double the convergence in steady state compared to LMS by updating the coefficient twice in one symbol.

4 is a block diagram illustrating a configuration of an adaptive beamformer using a crystal-oriented LMS according to a second embodiment of the present invention.

According to the second embodiment of the present invention, an adaptive beamformer using a decision-directed LMS is configured to receive a despread nth traffic signal vector r [n] and form a beam. The first beamformer 40 performing beamforming and the signal output from the first beamformer 40 receive a temporary decision value. Decision section 41 for outputting the LMS 42 to a temporary decision value; And the despread n th pilot signal vector p [n] and the known signal vector And an LMS 42 that receives a despreaded traffic signal vector r [n], obtains a least mean square value, and outputs a coefficient update equation value w [n], and a coefficient update equation value w [n ] And despread traffic signal vector r [n], and the final coefficient update decision value The second beam forming unit 44 for outputting the.

In the adaptive beamforming method using the DD-LMS according to the second embodiment of the present invention, first, the coefficient update equation may be expressed by the following equation.

here,

gamma is 0 <gamma <1, and the equation of the temporary decision value is as follows.

The characteristics of the DD-LMS according to the second embodiment of the present invention are a parallel structure and a temporary decision value. Is the final value It is used to determine.

This method doubles the strength of the signal used in the LMS when the temporary decision value is correctly determined.

At this time, the temporary decision value Conversely, if restored, the reference signal may be reversed and the coefficient estimation may proceed in a different direction. However, the degree should be adjusted according to the gamma and the probability of the temporary decision value error.

5 is a block diagram illustrating a configuration of an adaptive beamformer using a crystal-oriented LMS according to a third embodiment of the present invention.

The adaptive beamformer using DD-LMS according to the third embodiment of the present invention includes a first beamformer 50 for beamforming by receiving the despread n th traffic signal vector [n] and a first beamformer Temporary decision value based on the signal output from (50) A decision unit 51 for outputting the signal to the second LMS 54 and a known signal vector. And a first mean update equation value obtained by receiving the despread n th pilot signal vector p [n] and obtaining a least mean-square value. The first LMS 52 outputting the demultiplexed signal, the despread traffic signal vector r [n], and the temporary decision value And the despread n th pilot signal vector p [n] and the known signal vector An input receiving the second LMS (54) for outputting a second coefficient updating expression value w ₍₁₎ [n] to the second beam forming unit 56 to save the minimum square average value and the second coefficient updating expression value w _{(1 )} [n] and a traffic signal vector [n] are inputted, and a final coefficient update determination value (adaptive beamforming) It consists of a second beam forming unit 54 for outputting.

The coefficient update equation in the adaptive beamforming method using the DD-LMS according to the third embodiment of the present invention is as follows.

As in the second embodiment of the present invention, the overall structure is the same as the parallel structure.

here,

to be.

Ε_LMS is different from the second embodiment of the present invention and is a temporary decision value Is obtained by the following equation.

Temporary decision value as shown in FIG. The coefficients used for the recovery of the temporary decision value to increase the reliability of are determined only by pilot information with high reliability.

Thus, the temporary decision error Becomes To do this in a separate LMS The strength of the signal used to find is reduced than the scheme shown in FIG.

In this case This may cause the reliability of the temporary decision value to deteriorate. However, if the reliability of the final decision value is sufficiently ensured, this is not a problem.

As described above, the present invention is a technique for beamforming an adaptive antenna using multiple antennas in the reverse direction of a CDMA mobile communication system proposed by ETSI. It has the effect of reducing the power burden. In addition, there is an effect that can increase the capacity of the system and increase the transmission rate as a result.

Claims (11)

In a CDMA mobile communication system having a plurality of antennas to form a beam for a specific communication counterpart, and the communication channel is divided into a data channel and a control channel, Calculating a signal received in the control channel to obtain a first adaptive beam former coefficient; Obtaining a temporary determination value of a received signal of a data channel by inputting the signal received on the data channel and the first adaptive beam former coefficients; Obtaining a second adaptive beam former coefficient by comparing the temporal decision value with a signal received on the data channel; And calculating the second adaptive beam former coefficients on the signal received through the data channel and outputting the second adaptive beam former coefficient as a received signal of the data channel. The method of claim 1, wherein the signal received through the control channel is a pilot signal. 3. The method of claim 2, wherein the obtaining of the first adaptive beamformer coefficient is performed by comparing a symbol of a received pilot signal with a known pilot symbol. The method of claim 1, wherein the obtaining of the second adaptive beamformer coefficient is performed by comparing a symbol of a received data signal with a symbol obtained by the temporary decision value. 5. The method of claim 1, wherein the method for obtaining the first and second adaptive beamformer coefficients uses a least squares mean (LMS) method. In a CDMA mobile communication system having a plurality of antennas to form a beam for a specific communication counterpart, and the communication channel is divided into a data channel and a control channel, Updating a first adaptive beam former coefficient by calculating a signal received on the control channel and a previous second adaptive beam former coefficient; Obtaining a temporary determination value of a received signal of a data channel by inputting the signal received on the data channel and the updated first adaptive beam former coefficients; Updating a second adaptive beam former coefficient by comparing the temporary decision value with a signal received on the data channel; And calculating the updated second adaptive beamformer coefficients on the signal received through the data channel and outputting the updated second adaptive beamformer coefficient as a received signal of the data channel. 7. The method of claim 6, wherein said two updates are made during the same symbol time. In a CDMA mobile communication system having a plurality of antennas to form a beam for a specific communication counterpart, and the communication channel is divided into a data channel and a control channel, Obtaining a temporary determination value of a received signal of a data channel by inputting a signal received through the data channel and a previous adaptive beam former coefficient; Updating the adaptive beam former coefficients by comparing the signal received in the data channel with the temporary decision value and the signal received in the control channel; And calculating the updated adaptive beamformer coefficients on the signal received through the data channel and outputting the updated adaptive beamformer coefficients as a received signal of the data channel. 10. The method of claim 8, wherein updating the adaptive beamformer coefficients is accomplished by comparing a known signal to a signal received on a control channel. In a CDMA mobile communication system having a plurality of antennas to form a beam for a specific communication counterpart, and the communication channel is divided into a data channel and a control channel, Updating a first adaptive beam former coefficient by calculating a signal received on the control channel and a previous first adaptive beam former coefficient; Obtaining a temporary determination value of a received signal of a data channel by inputting the signal received on the data channel and the updated first adaptive beam former coefficients; Updating a second adaptive beam former coefficient by comparing the temporary decision value with a signal received on the data channel; And calculating the updated second adaptive beamformer coefficients on the signal received through the data channel and outputting the updated second adaptive beamformer coefficient as a received signal of the data channel. 11. The method of claim 10, wherein said two updates are made during the same symbol time.