CN101938306B - Inhibition method of uplink base noise of GSM (Global System for Mobile Communication) digital optical fiber repeater station - Google Patents
Inhibition method of uplink base noise of GSM (Global System for Mobile Communication) digital optical fiber repeater station Download PDFInfo
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Abstract
The invention discloses an inhibition method of an uplink base noise of a GSM (Global System for Mobile Communication) digital optical fiber repeater station. In the method, the GSM digital optical fiber repeater station used as a remote machine converts wireless multi-carrier signals to zero intermediate frequency signals, a base noise inhibition module calculates an energy spectrum of each frequency point in the zero intermediate frequency signals by arranging a power calculation and discrimination unit behind a last level decimation filter of each frequency point of a digital down conversion module, and the energy spectrum is compared with a noise opening and closing threshold; when the energy of input signals is smaller than the noise closing threshold, signal output is zero, and if the energy of the input signals is gradually increased and is bigger than a noise opening threshold, the input signals are output without distortion; when the energy of the input signals is reduced and is higher than a noise closing threshold, the input signals are continuously output without distortion until the energy of input signals is smaller than the noise closing threshold, and the signal output is zero. The invention inhibits the base noise in the input signals and can better control the interference of the base noise to a whole system without base noise accumulation when multiple remote machines are cascaded.
Description
Technical field
The invention belongs to the multi-carrier wireless communication field, especially for the GSM cell mobile communication systems, proposed a kind of inhibition method of back noise, especially be applicable to the inhibition method of GSM digital optical fiber direct station uplink back noise.
Background technology
Along with the develop rapidly of mobile communication cause, people improve constantly the area coverage of cellular mobile communication networks and the requirement of covering quality.Due to the transmission feature of wireless signal, inevitably in the urban district or the suburb have coverage hole.And these blind areas are often little due to scope, and customer volume is also few, adopt the way of newly-built base station to seem that cost is higher in these blind areas.The repeater is with less, simple in structure, the easy for installation advantage such as flexibly of its investment, becomes to make up the blind area, the important means of optimizing network coverage.
Up to now, the two-way treatment technology of the signal of analog system is all adopted in the GSM repeater, because it directly receives, amplifies and retransmit the radiofrequency signal of base station, place and user mobile phone, therefore the quality of its performance and index also directly affects the quality of mobile communications network.A high-quality repeater can be improved these regional communication qualities effectively, solve the problems such as call drop, otherwise unnecessary interference and noise can be brought to mobile communications network in a performance inferior repeater, cause that call drop or base station are inaccessible, have a strong impact on network quality.
In wireless communication system, the factors such as communicating pair can change due to communication distance, barrier obstruction, the signal that makes communicating pair receive is less, when the signal strength signal intensity that receives when threshold level fluctuates up and down, when communication will occur and connect, the time and the phenomenon that disconnects has so just been brought unnecessary interference and noise to cordless communication network, have a strong impact on communication quality.
Digital optical fiber direct station can be realized multicarrier, flexile quickly networking mode, supports multiband and open architecture, and this system is comprised of the remote termination of a near-end machine and Duo Tai cascade usually.Present applied digital optical fiber direct station remote termination structure as shown in Figure 1a, generally include analog module and digital signal processing module, wherein the analog module comprises that mainly digital to analog converter (DAC), analog to digital converter (ADC), low noise amplifier, multi-carrier power amplifier and analog radio frequency receive, transmitter; This digital signal processing module mainly comprises Digital Down Converter Module, Digital Up Convert module and optical fiber communication (CPRI) interface; Be used for realizing Digital up and down convert, and the function such as optical fiber communication (CPRI).Fig. 1 b description habit has the structure chart of one of the main modular of digital optical fiber direct station Digital Down Converter Module.When a GSM residential quarter that is assigned n carrier frequency frequency, it should have n frequency-selecting passage, and namely the number of its frequency-selecting passage must be identical with the carrier frequency number that cell allocation arrives.Wherein can configure by the frequency word that configures each frequency-selecting passage the angular frequency w of mixing, this can artificially be configured by engineering staff's means such as man-machine interactive system by equipment when equipment is installed.
There is no the back noise inhibit feature in the GSM digital optical fiber repeater system that has due to habit, like this when many remote termination cascades, in same time slot, each remote termination upstream noise also can superpose at near-end machine, thereby higher back noise appears, be coupled to the base station by near-end machine, affect the performance of base station system.
Summary of the invention
The object of the invention is to propose a kind of inhibition method of GSM digital optical fiber direct station uplink back noise, can be effectively according to the feature of each carrier signal in multi-carrier communications systems, realize noise suppressed by increase back noise inhibition module in remote termination, avoid the stack of upstream noise; Open and close simultaneously the thresholding of two noises by setting, avoid frequently switching at the switch that carries out occurring when back noise suppresses.
A kind of inhibition method of GSM digital optical fiber direct station uplink back noise mainly comprises following step:
Step 1: the back noise that first goes out whole system by apparatus measures, setting is closed thresholding than the bigger 3dB of back noise of the whole system of measuring gained as the noise that back noise in the GSM digital high-frequency amplification station of remote termination suppresses module, and sets noise unlatching thresholding and close the high 2dB to 8dB of thresholding than noise;
Step 3: this back noise suppresses module by after each frequency afterbody decimation filter of Digital Down Converter Module, power calculation and judgement unit being set, calculate the energy spectrum of each frequency afterbody decimation filter in this zero intermediate frequency signals, and current energy spectrum and noise open and close thresholding are compared, when the input signal energy spectrum is closed thresholding less than noise, signal is output as 0, if the input signal energy increases gradually and greater than the noise door capable of being opened in limited time, ability is with the undistorted output of input signal; And when the input signal energy reduces and also closes thresholding higher than noise, continue to allow input signal export undistortedly, until the input signal energy is when closing thresholding lower than noise, signal is output as 0.
The inhibition method of a kind of GSM digital optical fiber direct station of the present invention uplink back noise, back noise is set in the GSM digital optical fiber direct station as remote termination suppresses module, by input signal and noise are closed and the comparison of opening thresholding, the back noise in input signal is suppressed; Like this when many remote termination cascades, in same time slot, thereby back noise stack can not appear in each remote termination upstream noise in near-end machine produces higher back noise, and be coupled to the base station, and then have influence on the performance of base station system, therefore, the present invention can control back noise preferably to the interference of whole base station system.
Description of drawings
Fig. 1 a is the operation principle block diagram of existing GSM digital optical fiber repeater system;
Fig. 1 b is the operation principle block diagram of the Digital Down Convert of existing GSM digital optical fiber repeater system;
Fig. 2 a is the operation principle block diagram that has increased the GSM digital optical fiber repeater system of back noise inhibition module;
Fig. 2 b is the detailed operation theory diagram after Digital Down Convert has increased back noise inhibition module;
Fig. 3 is the processing procedure schematic diagram of noise elimination thresholding in the present invention.
The invention will be further described below in conjunction with the drawings and specific embodiments.
Embodiment
As shown in Fig. 2 a, the present invention proposes a kind of inhibition method of GSM digital optical fiber direct station uplink back noise, with the as close as possible radio frequency of analog to digital converter (ADC) in broadband, realize to the full extent the various functions of communication system by software.
This GSM digital optical fiber direct station can be realized multicarrier, flexile quickly networking mode, supports multiband and open architecture, and this system is comprised of the remote termination of a near-end machine and Duo Tai cascade usually.The present invention is directed to the inhibition that this remote termination carries out back noise.GSM digital optical fiber direct station as remote termination mainly comprises analog module 1 and digital signal processing module 2, and wherein analog module 1 comprises antenna 11, radio frequency processing module 14, analog to digital converter (ADC) 15, digital to analog converter (DAC) 16; This digital signal processing module 2 comprises that Digital Down Convert (DDC) module 21, Digital Up Convert (DUC) module 22, back noise suppress module 23, optical fiber communication module (CPRI) 24 and optical-electrical converter 25.
At first, GSM digital optical fiber direct station as remote termination is coupled into by antenna 11 the wireless multi-carrier signal with radiofrequency signal, radio frequency processing module 14 is completed the conversion between radiofrequency signal and analog if signal, then convert digital signal to by analog to digital converter (ADC) 15, the processing procedures such as the digital mixing by Digital Down Convert (DDC) module 21 and filtering extraction become the digital signal of input into zero intermediate frequency signals at last.
If the baseband signal of wireless communication system is through pseudo-random process, the power spectral density of this signal size is directly proportional to the energy spectrum of signal, and the energy spectrum of signal is directly proportional to signal energy in a period of time.Therefore the present invention can obtain the energy of input signal in a period of time, namely can be equivalent to the power spectral density of input signal.On Project Realization, the Out-of-band rejection of General Requirements filter reaches 60dBc.Therefore the power spectrum of this input signal mainly concentrates in a certain frequency band range.
As shown in Figure 3, the present invention proposes a kind of method that two noise gates suppress noise that arranges, one of them opens thresholding for noise, and another closes thresholding for noise.
Close thresholding when the input signal energy less than noise, output signal is set to 0, if the input signal energy increases gradually and, just output signal is equaled undistorted output greater than the noise door capable of being opened in limited time; And when the input signal energy reduces and also closes thresholding higher than noise, continue to allow input signal export, until the input signal energy when closing thresholding lower than noise, is set to 0 with signal output undistortedly.
The invention provides a kind of inhibition method of GSM digital optical fiber direct station uplink back noise, comprise following step:
Step 1: back noise suppresses the setting of the noise open and close thresholding of module 23
Situation about generally using according to engineering determines, the gain of general and front radio-frequency module is relevant with the SNR of analog to digital converter 15, and the prime radio-frequency module gains larger, and the back noise of its radio-frequency module is also larger accordingly.It is higher than the maximum back noise of radio-frequency module that general noise is closed thresholding; Noise is opened thresholding to close thresholding than noise high, concrete relevant with the back noise of system hardware circuit in addition.The present invention sets the noise of back noise inhibition module 23 and closes thresholding than more than the bigger 3dB of the back noise of the measured whole system that obtains by the back noise of apparatus measures whole system, can guarantee that like this circuit noise of system can not disturb the digital processing process; And set noise unlatching thresholding and close the high 2dB to 8dB of thresholding than noise, can avoid so the frequent switching due to signal, after the signal that causes is truncated, the frequency spectrum diffusion that signal non-linear distortion causes;
step 3: as shown in Fig. 2 b, this back noise suppresses power calculation and the judgement unit of module 23 by arranging after Digital Down Converter Module 21 each frequency afterbody decimation filters, calculate the energy spectrum of each frequency afterbody decimation filter in this zero intermediate frequency signals, and current energy spectrum and noise opening and closing thresholding are compared, when the input signal energy spectrum is closed thresholding less than noise, this input signal is considered as back noise, signal is output as 0, if the input signal energy increases gradually and greater than the noise door capable of being opened in limited time, with the undistorted output of input signal, and when the input signal energy reduces and closes thresholding higher than noise, continue to allow input signal export undistortedly, until the input signal energy when closing thresholding lower than noise, is considered as this signal back noise, signal is output as 0.
The energy spectrum Ex (n) of described input zero intermediate frequency signals Xn (n)=Ix (n)
2+ Qx (n)
2, the energy spectrum of Ex (n) expression input signal Xn (n) wherein, Ix (n) expression I road signal, Qx (n) expression Q road signal, j is used for representing complex signal; In the FPGA implementation procedure, generally can adopt the process computation of multiply accumulating to go out above-mentioned energy spectrum.
As shown in Figure 3, described Ex represents the energy spectrum of input signal X (n), and Eoff and Eon represent that respectively noise is closed thresholding and noise is opened thresholding, Disable is that noise suppressing function is not enabled in 1 expression, namely output signal X (n) out is equaled input signal X (n), input signal is exported undistortedly; And Disable be 0 the expression enable noise suppressing function, namely input signal X (n) is considered as back noise not export, output signal X (n) out equals 0, also can see the inhibition flow process of back noise from Fig. 2 b.
Claims (1)
1. the inhibition method of a GSM digital optical fiber direct station uplink back noise is characterized in that comprising following step:
Step 1: the back noise that first goes out whole system by apparatus measures, setting is closed thresholding than the bigger 3dB of back noise of the whole system of measuring gained as the noise that back noise in the GSM digital high-frequency amplification station of remote termination suppresses module, and sets noise unlatching thresholding and close the high 2dB to 8dB of thresholding than noise;
Step 2, the wireless multi-carrier signal coupling is come in by antenna as the GSM digital optical fiber direct station of remote termination, amplification, mixing, filtering processing via the radio frequency processing module are transformed into the analog intermediate frequency multi-carrier signal, then by analog to digital converter, it are become digital signal; Convert through mixing, filtering extraction the digital signal of inputting to zero intermediate frequency signals respectively by Digital Down Converter Module at last, and deliver to back noise and suppress module;
Step 3: this back noise suppresses power calculation and the judgement unit of module by arranging after each frequency afterbody decimation filter of Digital Down Converter Module, calculate the energy spectrum of each frequency afterbody decimation filter in this zero intermediate frequency signals, and current energy spectrum and noise opening and closing thresholding are compared, when the input signal energy is closed thresholding less than noise, signal is output as 0, if the input signal energy increases gradually and greater than the noise door capable of being opened in limited time, with the undistorted output of input signal; And when the input signal energy reduces and closes thresholding higher than noise, continue to allow input signal export undistortedly, until the input signal energy is when closing thresholding lower than noise, signal is output as 0.
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| CN101977426B (en) * | 2010-10-26 | 2013-07-10 | 三维通信股份有限公司 | Method for reducing uplink noise of GSM (Global System for Mobile Communications) digital repeater |
| CN102170690B (en) * | 2011-04-20 | 2014-08-20 | 京信通信系统（中国）有限公司 | A gain control method of a WCDMA radio remote unit |
| CN103634250B (en) * | 2013-12-16 | 2017-04-12 | 深圳国人通信股份有限公司 | Method and device for restraining ground noise signal from upraising |
| CN103957020B (en) * | 2014-05-06 | 2016-08-10 | 重庆邮电大学 | A kind of signal intermediate frequency supporting multi-mode mobile communication system receives device |
| CN106685867B (en) * | 2017-01-22 | 2020-01-17 | 东南大学 | Uplink noise suppression method with adaptive noise threshold in LTE distributed relay system |
| CN106850033B (en) * | 2017-02-06 | 2020-05-05 | 东南大学 | Uplink noise suppression method in LTE (Long term evolution) distributed relay system |
| CN107197471A (en) * | 2017-05-25 | 2017-09-22 | 京信通信系统（中国）有限公司 | A kind of repeater business statistical method and device |
| CN112615802B (en) * | 2020-12-18 | 2023-04-14 | 深圳市佳贤通信设备有限公司 | Uplink background noise and interference suppression system and method for 5G communication base station |
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| CN101409579A (en) * | 2008-10-15 | 2009-04-15 | 京信通信系统（中国）有限公司 | Traffic stream system and method for GSM discharging-directly station |
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