A method and apparatus for reducing distortion when determining the utilization rate of the signal

 

(57) Abstract:

A method of reducing distortion when determining the utilization rate of the signal receiver receiving a stream of information symbols, namely, that step by step: perform the stream of information symbols and receive a stream of characters, each information symbol stream of symbols includes a useful component of interfering component and a distortion component, define the characteristics of the distortion component and the receive characteristics of the distortion, determine the representation of a useful component and get a useful representation, determine the parasitic component on the basis of useful views and character stream, define the representation of the noise component on the basis of the parasitic component and distortion characteristics and determine the indication of the utilization of the flow of characters on the basis of useful views and views jamming component. The device includes a signal receiver, a detector useful component, the detector parasitic component, the detector characteristics distortion, detector noise component, filter, selector, device scaling. Tangala. 2 C. and 8 C.p. f-crystals, 7 Il.

The invention relates to communication systems and particularly to systems in which communications are reused when terrestrial communications.

Prior art

The prior art communication system with multiple means of communication for the implementation of terrestrial communications. Such systems involve the installation of group communication in the same geographical area and repeatedly use the same group communications in one or more geographic areas. This way multiple use means of communication increases the capacity of the connection by minimizing the number of communications needed to provide communication services to a large geographical area that includes several smaller sized geographic areas.

Two of the most common communication systems with multiple use of funds in the implementation of terrestrial communications are radio communication with the cellular service areas and long distance radio communication with mobile objects. In both systems communication establishing means of communication begins with the communication device requests a communication service. On the basis of the coefficient of getownerelement means of communication, for example, a frequency channel or time interval, a given communication device. Such forms of communication as negotiation or facsimile communication is carried out through the means of communication between the two communication devices or between the communication device and the subscriber's public telephone network. Communication continues until the session ends or until it is interrupted in the communication service. Upon completion of the communication session control device returns the means of communication in the initial state, thus making it suitable for another session.

An important parameter in determining the suitability of the means of communication is its utilization of the signal. In radio systems communications are typically RF channels /RF/, which occupy the specified frequency band. When information signals are transmitted on channels /communication/ parasitic phenomena in channels such as interference, noise and distortion introduced by the transmitter and the receiver, change the information signals during their transmission and reception. Therefore, the information signals received by the receiver in the communication device or a base station, are distorted because of the mutual influence of channels and distortion. Setting the level of interference and noise in existing cient use signal.

In communication systems with multiple geographically by using communication means utilization signal is usually limited to the value of co-channel interference present in the RF channel. Co-channel interference occurs when receivers receive spurious information signals from the neighboring communication devices or base stations that transmit on the same RF channel, which is transmitted useful signal. A detailed discussion of the method of determining the utilization rate of the signal based on the ratio of the useful signal (C) to the total value of co-channel interference (I) and noise (N) is known from U.S. patent 5440582 "Method and apparatus for determining the coefficient of use of the signal" by Motorola Inc. Despite the numerous advantages possessed by this method, it does not consider the aspect of limiting the dynamic range of the utilization of the signal due to distortion of the transmitter and receiver.

The distortions that arise for several reasons, lead to a common result, they tend to limit the maximum achievable value of the utilization rate of the signal (C/(I + N)). Distortions are added to the member, warehouse the new expression for the utilization of the signal, C/(I + N + D), where D represents the distortion caused by the receiver and the transmitter. Usually co-channel interference is significantly greater than the distortion, thus, the distortion can be neglected and the indication of the utilization of the signal can be obtained by evaluating the relationship of the carrier to the sum of interference and noise. When co-channel interference becomes small, the distortion is already impacting the value of the utilization rate of the signal and break the linearity in the correlation between the actual utilization of the signal and the ratio of the carrier to the sum of interference and noise. Therefore, without distortion values range accurate readings utilization of the signal is determined by assessing the relationship of the carrier to the sum of interference and noise, is limited due to the distortion to some maximum value. In the logarithmic representation of the maximum value of the ratio of the carrier to the sum of interference and noise, which can be measured is less than 25 dB typically because of the distortion inherent in this method. However, in some communication systems with multiple frequency channel for the optimal operation of the system requires the maximal value of the utilization rate of the signal, prevalitania signal and improve the functionality of the system is critical evaluation of distortion.

Distortion commonly found in transmitters include transient errors in digital receivers, the penetration of high-frequency signals, the distortion of the leachate and the nonlinearity of the amplifiers. Temporary errors occur due to inaccurate sampling of the received signal and the mutual influence of symbols /intersymbol interference/. The penetration of high-frequency signal weakens useful signal due to the conversion of part of the power of the RF carrier modulated information signal. Distortion filter change amplitude and the phase of the useful signal due to the inherent frequency characteristics with different amplitude and group delay. The nonlinearity of the amplifiers, such as limousine distortion, making stray RF energy in the frequency band of the useful signal.

Thus, a need exists for a method and device that provide the expansion of the dynamic range for the utilization of the signal by reducing distortion.

Brief description of drawings

Fig. 1 depicts the configuration of the received information symbols in accordance with this invention.

Fig. 2 is a block diagram of a communication system which includes a receiver, made with amnic, made according to this invention.

Fig. 4 - frequency characteristics of the filter and channels of subcarriers of the received signal that contains a stream of information symbols according to this invention.

Fig. 5 - frequency characteristics of signal component representing distortion and noise component and filter, attenuation distortion, in accordance with this invention.

Fig. 6 in an enlarged scale the filtered configuration and atzelektronik parasitic components of the received information symbols in accordance with this invention.

Fig. 7 graphic functions of the scaling factor according to this invention.

The best option of carrying out the invention

In General, this invention is a method and apparatus for reducing distortion and increasing evidence of the utilization of the signal in the receiver. This is achieved by taking the discrete information signal comprising a stream of information symbols, and processing the received signal so as to obtain estimates of information symbols. Each character assessment is conducted with respect to three components: useful is Lena after you define a view useful component and characteristics of component distortion. Representation of the noise component can then be determined based on the parasitic component and characteristics of the distortion. Improved reading of the utilization rate of the signal to estimate each symbol is determined on the basis of representations of the useful component and noise component. Improved indication of the utilization of the signal is achieved by minimizing the influence of the distortion component when determining the noise component. Thus, an improved ratio of signal usage is approximately a function of only the useful component and a noise component, component distortion is essentially eliminated.

This invention can be described in more detail with reference to Fig. 1 - 7. Fig. 1 illustrates an image combination 100 16-quadrature-amplitude-modulated /Q AM/ information symbols. Each information symbol 102 in this configuration is a two-dimensional and has a value, which is determined by its coordinates relative to a pair of orthogonal axes.

As is known from the prior art, a signal consisting of a stream of discrete information symbols can be transmitted so the receiver, as well as interference, noise, and additional distortion in the transmitting channel, the received value of each information symbol 102 is usually changed. Except for the additional distortion in the transmitting channel this change will consist of approximately zero average value of the stochastic process, superimposed on each information symbol 102 of the transmitted stream. Thus, for each information symbol 102 accept the value is in the range of values 101, located in the circle, the center of which is the value corresponding to the magnitude of the transmitted information symbol.

Fig. 2 illustrates a transmitter 200 that transmits a stream of characters 201 through the means of communication to the receiver 202. The character stream 201 is changed on its way from the transmitter 200 and receiver 202 due to the insertion of the transmitter distortion 211, noise and interference in the RF channel and distortion 210 introduced by the receiver. Thus, the resulting modified stream of symbols at the input device 203, the receiving signal and input to the receiver 202, contains a useful component of interfering component, and component distortion, while a useful component represents the original unmodified stream symbol is 11 from the transmitter 200 and receiver 202, respectively.

The receiver 202, which includes a receiver 203 of the signal detector 204 characteristics of the distortion detector 205 useful component detector 206 parasitic component, the filter 207, the device 208 scaling of the amplitude and the detector 209 jamming component is used to process the modified stream of characters and provides the definition of utilization of the flow of the characters. The receiver signal 203 receives, amplifies, filters and converts the modified stream of characters in a modulated stream of characters that can be processed using the detectors 205 and 206 are useful and spurious and detector 204 characteristics of the distortion. The receiver 203 of the signal typically includes an RF unit, filters, converters, step-down frequency, analog-to-digital converters and digital signal processing required to generate estimates of the received stream of symbols. A modulated stream of characters includes modulated presentation of useful, ECM components, and component distortion. The detector 204 characteristics of the distortion accepts a modulated stream of characters and determines the distortion characteristics of its component distortion is usually based on pre useful component also receives a modulated stream of characters and determines the representation of its useful component. A detailed description of how the definition of a view useful component is contained in U.S. patent 5519730 Signal communication with the pilot component with a time interval of the firm Motorola Inc., and U.S. patent 5519730 "Method and apparatus for determining the coefficient of use of the signal" firm Motorola.

The detector 206 parasitic component receives a modulated stream of characters and the output signal from the detector 205 useful component and determines the parasitic component of the modulated stream of characters usually by subtracting the presentation of useful component of the modulated stream of characters. Parasitic component, which includes the noise from the RF channel and distortion 210 and 211 of the transmitter and receiver, is fed to the filter 207. The filter 207 reduces the frequency characteristic of the distortion component by attenuating frequency components outside the bandwidth of the filter 207. Frequency response of the filter 207 is based on the characteristics of the distortion obtained by the detector 204 characteristics of distortion.

Device scaling amplitude 208 receives the filtered parasitic component from the filter 207 and scales it with the specified coefficientd. The reference amplitude values may be preset or dynamically determined /in the process/ device with device scaling amplitude 208 on the basis of the characteristics of distortion obtained in the detector 204 characteristics of the distortion. For example, device scaling amplitude 208 can scale the amplitude of the filtered parasitic component with one factor, if the amplitude of the filtered parasitic component is less than the selected reference value of the amplitude and scale the amplitude of the other factor, if this amplitude is greater than the selected reference value. In addition, the device scaling amplitude 208 may perform scaling filtered parasitic component functional /variable rate/ in contrast scale with discrete coefficient values. Typically, the device scaling 208 includes a processor that contains the algorithm that performs the scaling filtered parasitic component. The output signal from device scaling amplitude 208 is input to detector noise component 209, where the interfering component modelirovaniya mainly contains interference and noise on the channel, with a minor component of the distortion. The output signal from detector noise component 209 is processed with a useful component to determine an indication of utilization of the flow of the characters. The method for determining the utilization of the flow of the characters described in the aforementioned application, SEE 01662H "Method and apparatus for determining the utilization rate of the signal, firm Motorola Inc. and having a filing date the same as this application. So there is no need to provide more explanation except that simplify understanding of the present invention. Determination of the coefficient of use of the stream of characters is critical for communication systems, since it allows to evaluate the conditions of the connection on the RF channel.

Detector characteristics distortion 204 can operate either as an adaptive system in online mode, continuously working with modulated stream of characters, or as a standalone system, which in its memory contains predefined characteristics of the distortion. In both cases, the characteristics used to attenuate distortion component, include the frequency spectrum, the amplitude as a function of transmitted symbols, such as the locations 211 and 210 of the transmitter and the receivers. In this embodiment of the invention the detector characteristics distortion 204 is a stand-alone type. Known computer simulation model distortion 211 and 210 in the transmitter and the receiver 202. With the help of each individual program schemes in the simulation is measured one of the characteristics of distortion ; as a result, this modeling provides the accumulation characteristics of the distortion in the storage portion of the detector characteristics distortion 204.

Because of the frequency power spectra of the component of the distortion and noise component differ in spectral composition, frequency response of the filter 207 can be selected so that it, in essence, have an impact on the energy spectrum of the distortion component. Energy spectrum distortion component in the main is not smooth, that is, in a certain frequency band energy spectrum has a nonuniform power spectral density /PSD/. Power spectral density /PSD/ part distortion in some frequency regions more than in other areas within the frequency band of interest. Conversely, the energy spectrum of the noise component is shining distortion with respect to the power of the noise component, the filter 207 is performed with attenuation of frequency components of the parasitic component that are in the area of PSD with large distortions, and left at this frequency domain PSD with less distortion relatively unaffected. This method of filtering reduces the power component of the distortion to a greater extent than the power of the noise component. Thus, filter 207 is achieved goal - weakening component of the distortion relative to the clutter component. Due to the fact that as a rule, the power component of the more distortion around the edges of the frequency band of interest, usually for a filter 207 selects the frequency response, which topology is the amplitude-frequency response at low frequencies.

As component of the distortion and noise component may not be fully separated by filtration to further reduce distortion component is used scaling method. Complete separation of the components of the distortion and jamming prevents that their PSD overlap in frequency: therefore a non-zero component of the distortion remains in the structure of the parasitic component after filtering. Closebuy component distortion. In order to account for this deviation device scaling amplitude 208 scales any output component of the filter, the amplitude of which is less than some specified value, with a lower ratio than the component whose amplitude is greater than a given value. This scaling method provides a reduction in the weight of those components that can be attributed to distortions in contrast to those components that can be considered noise ; thus there is a weakening of the overall component distortion compared to the full jamming component.

Fig. 3 illustrates a transmitter 200 that transmits a stream of characters 201 to RF channel tunable receiver 303. The receiver 303 includes device 301, which contains a signal receiver 203, the detector characteristics distortion 204, the detector is a useful component 205, the detector parasitic component 206, the filter 207, the device scaling amplitude 208, the detector noise component 209 and the selector 302. As previously noted with reference to Fig. 2, a stream of characters 201 is changed with the passage way from the transmitter 200 to the receiver 303 due to interference and noise in the RF channel and distortion 211 and 210, inherent to the transmitter and the receiver.

Owing to the changing distortion 210 and 211 in the transmitter 200 and the receiver 303, each character of the character stream 201 may have a different level of distortion. For example, in a system with multiple channels of subcarriers for U.S. patent 5519730 Signal communication with the pilot component in the time interval" company Motorola Inc. information symbols carried by one of the four channels of subcarriers may be lower distortion than those tolerated by the three other channels of subcarriers. In addition, distortion 210 and 211 some values of information symbols may distort more than others depending on the coordinates of the characters on the drawing representing the dispersion of information the device scaling amplitude 208 when determining the jamming component selector 302 selects only those information symbols, which is the least sensitive to distortions. The degree of sensitivity to distortion is determined based on the characteristics of distortion obtained in the detector characteristics distortion 204.

Fig. 4 illustrates the amplitude-frequency characteristics of the channels of the internal waveforms 402 and external channels of subcarriers 403 information symbols relative to the amplitude of the 400 and group delay 401 filter. This configuration of the channels of the subcarriers is typical for systems with multiple channels of subcarriers that were previously described with reference to U.S. patent 5519730 Signal communication with the pilot component in the time interval", the firm Motorola Inc. The amplitude of 400 and group delay 401 filter can represent the amplitude and group delay obtained with bandpass crystal filter used in the receiver Autonomous type.

As shown in Fig. 4, the distortion in the amplitude and group delay are external channels of subcarriers 403 is larger than the inner channels of subcarriers 402. A large amount of distortion filter on the external channels of subcarriers 403 causes greater distortion component in the corresponding information symbols compared to sostavlyajushie is Ino, in such a situation further processing of the information symbols in the internal channels of subcarriers 402 is more preferable, since they are exposed to lower distortion. On the other hand, due to other distorting processes of internal channels of carrier 402 can be more distorted than the outer channels of subcarriers 403. In this case, it is more preferable to perform further processing of the information symbols on the outer channels of the subcarriers 403. In any case, for further processing, you should take the information symbols with the lowest distortion.

In Fig. 5 shows the amplitude-frequency response of the filter 501, attenuation distortion; this characteristic is shown in relation to the energy spectral density /PSD/ jamming component 500 parasitic component and a distortion component 502. As noted earlier with reference to Fig. 2, the PSD component of the distortion 502 heterogeneous in the considered frequency band. Conversely, PSD jamming component 500 on the same frequency band uniform. Therefore, by using a filter having a frequency response characteristic 501, it is possible to obtain a significant decrease in PSD 502 component of the distortion on the base allows you to get a more accurate similarity of the amplitude-frequency characteristics of the parasitic component of the PSD noise component 500 after filtering. Thus, this filtering technique provides a more accurate determination of the coefficient of use of the signal, because the utilization rate of the signal is directly dependent on the noise component of the parasitic component.

Fig. 6 illustrates an enlarged graphic image area 101, including filtered and selected parasitic components 601 received information symbols that are normally present in the output signal of the detector parasitic component 206. Several filtered and selected spurious 601 are randomly located around the initial count due to interference and distortion superimposed on the useful components of information symbols. In the absence of jamming in the RF channel such scatter filtered and selected spurious 601 occurs due to distortion. A large part of the values of the components is the initial radius that corresponds to the given value of the amplitude 600. Setting a lower weighting factor or scaling factor for values filtered and selected parasitic components that are within a certain radius of the I is primarily a function from the set amplitude value 600 or another specified amplitude value. As shown in Fig. 6, the filtered and selected parasitic components 601, lying within a radius corresponding to a given value of the amplitude 600, have the same scaling factor, and those characters that lie outside this radius, have another, larger magnitude, the scaling factor; this allows you to separate more distorted characters from less distorted characters. In another case, multiple radii, each corresponding to a specific amplitude, can be concentrically located relative to the initial radius. Thus, the selected filtered parasitic components 601, lying between the two radii, set one specified scaling factor depending on which radii are these components 601. Moreover, this mnogorazemny method can be extended, if you enter the scaling function, all selected filtered parasitic components 601 are scaled with a factor equal to the value of this function at a certain radius.

In Fig. 7 shows two possible functions with the given scale factor 700 and 701, depending on the selected amplitude and otvetnuyu component, amplitude which is less than the setpoint amplitude 600, by multiplying this component to zero. Those selected filtered parasitic components, the amplitude of which is greater than the set value of the amplitude 600, multiplied by a certain value other than zero. The second function 701 is different from the first function 700 the fact that it is continuous over the entire range of variation of the amplitude of the selected filtered parasitic component 703. The second function 701 has a smaller scaling factor for those components, the amplitude of which is less than the preset amplitude value of 600, and a larger scaling factor for those components, the amplitude of which is greater than the preset amplitude value of 600. Any function can be used to obtain a scaling factor selected filtered spurious, but these functions usually contain polynomials of second or third order or are linear. The zoom feature is selected depends on how much you want to reduce distortion to obtain a reliable value of the utilization rate of the signal.

The present invention proposed a method and apparatus for reducing distortion and took the tion increases the dynamic range when determining the utilization rate of the signal, which is limited due to distortions in the parasitic component of the received stream of symbols. As a result, the maximum value of the utilization rate of the signal can exceed 30 dB, in contrast to the testimony of 25 dB, which is achieved by our competitors. Initial attempts to measure the utilization rate of the signal directly by measuring the relationship of the carrier (C) to the interference level (I) gave limited value, because the measurement noise was present significant component of the distortion. Despite the fact that it was supposed to measure the ratio of the high-frequency signal-to-interference (C/I, in fact, was measured against the high-frequency signal to the total noise and distortion C/(I + D), where D is the power component of the distortion. Therefore, if the interference power is largely reduced, the measurement will tend to a constant value, defined as the ratio of the value of a high frequency signal to the magnitude of the distortion, S/D. This leads to the limitation of the dynamic range when measuring the ratio of the high-frequency signal to the magnitude of the interference From/(I + D), due to the limitations of its maximum value, equal to the ratio of the execution of the high-frequency signal SC to use the signal due to the significant reduction of the power member, expressing distortion, compared to the capacity of the member in the above expression, characterizing interference; thus can be achieved a higher maximum value when the measurement of the ratio of a high frequency signal to noise.

1. A method of reducing distortion when determining the utilization rate of the signal receiver receiving a stream of information symbols, wherein stages (a) carry out the stream of information symbols and receive a stream of characters, each information symbol stream of symbols includes a useful component of interfering component, and component distortion, (b) identify the characteristics of component distortion and gain characteristics of the distortion, (C) determine the representation of a useful component and get a useful representation, d) determine the parasitic component on the basis of useful views and character stream, e) define the representation of the noise component on the basis of the parasitic component and characteristics of distortion and f) determine the indication of the utilization of the flow of characters on the basis of useful views and views jamming component.

2. The method according to claim what th least one of the amplitude based on the characteristics of the distortion scale parasitic component with the first predetermined ratio, if the amplitude of the spurious component is less than the value of at least one of the amplitude and scale of the parasitic component with a second predetermined ratio, if the amplitude of the spurious component is greater than the value of at least one of amplitude, and the second predetermined coefficient greater than the first specified factor.

3. The method according to p. 1 or 2, characterized in that when determining the characteristics of the distortion component optional component is identified misstatements on the basis of pre-existing data about the distortion of a receiver and a transmitter, transmitting a stream of characters, in this case, when determining the parasitic component perform the subtraction useful component from a stream of characters, and if the view definition jamming component additionally carry out filtering of the spurious component with a filter for attenuating a component of distortion.

4. The method according to p. 1, characterized in that when determining the characteristics of the distortion component is determined using receiver features IP the characters, when determining the parasitic component determine the parasitic component-based representations of characters and character stream, and further determined by the selected receiver spurious components from among the obtained characteristics of the distortion, perform filtering in the receiver components of the distortion of the selected parasitic components using a filter to obtain selected and filtered spurious, and when the view definition jamming component perform the operation of determining, using the receiver's view of disturbances of the components based on the selected and filtered spurious and useful components with education taking into account the views of disturbances components and useful components of the basis for determining the indication of the utilization of the flow of characters.

5. The method according to p. 4, characterized in that when determining the view of disturbances of components perform the determination of the value of at least one of the amplitude on the basis of the characteristics of distortion, scaling selected and filtered parasitic component with the first predetermined ratio, if the amplitude is less than the value of at least one of amplitude, and scaling the filtered selected parasitic component with a second predetermined ratio, if the amplitude of the filtered selected parasitic component from the filtered selected parasitic components is greater than the value of at least one of amplitude, and the second predetermined coefficient greater than the first specified factor.

6. Device for reducing distortion when determining the utilization rate of the signal in the receiver, characterized in that it comprises a signal receiver that receives the stream of information symbols to obtain a stream of symbols, the detector characteristics distortions that defines the characteristics of the distortion for distortion component of each information symbol stream of symbols, the detector is a useful component connected to the receiver and defining a useful component for each information stream of characters, the detector parasitic component, coupled with the detector useful component and the signal receiver and determining the parasitic component for each information symbol stream of characters on the basis of the useful component and flow simalarity distortion and defines the interfering component for each information stream of characters on the basis of the useful component, characteristics of distortion and spurious component.

7. The device under item 6 or 7, characterized in that it contains a device scaling amplitude, coupled with the detector noise component detector characteristics and distortion detector parasitic component, and device scaling amplitude made with the possibility of scaling the amplitude of the spurious component with the first predetermined ratio, if the amplitude of the spurious component is less than the value of at least one of amplitude, and scaling the amplitude of the spurious component with a second predetermined ratio, if the amplitude of the spurious component exceeds at least one of the amplitude.

8. The device according to p. 6, characterized in that it comprises a filter connected to the detector characteristics and distortion detector parasitic component, and the filter is made with the possibility of attenuation distortion component in the parasitic component.

9. Device according to any one of paragraphs.6 to 8, characterized in that it contains a selector, coupled to the detector parasitic component and the detector characteristics of the distortion, and the selector is configured to from the tor jamming component is connected to the selector and detector characteristics distortion, moreover, the detector noise component of the spurious component is configured to determine the noise component for each information symbol stream of characters on the basis of the useful component, the characteristics of the distortion and selected parasitic component.

10. Device according to any one of paragraphs.7 and 9, characterized in that the device scaling amplitude is connected to the selector and detector noise component, and device scaling amplitude made with the possibility of scaling the amplitude of selected parasitic components with the first predetermined ratio, if the amplitude of the noise component is less than the value of at least one of amplitude, and amplitude scaling of selected parasitic components with a second predetermined ratio, if the amplitude of the noise component exceeds the amount of at least one of the amplitude.

 

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