WO2008000187A1 - Procédé, dispositif et système pour la détection d'une interférence dans un système mrof - Google Patents

Procédé, dispositif et système pour la détection d'une interférence dans un système mrof Download PDF

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Publication number
WO2008000187A1
WO2008000187A1 PCT/CN2007/070156 CN2007070156W WO2008000187A1 WO 2008000187 A1 WO2008000187 A1 WO 2008000187A1 CN 2007070156 W CN2007070156 W CN 2007070156W WO 2008000187 A1 WO2008000187 A1 WO 2008000187A1
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WIPO (PCT)
Prior art keywords
interference
signal
threshold
signals
detection
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PCT/CN2007/070156
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English (en)
Chinese (zh)
Inventor
Linjun Lv
Jun Rong
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Huawei Technologies Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Publication of WO2008000187A1 publication Critical patent/WO2008000187A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
    • H04J11/0023—Interference mitigation or co-ordination

Definitions

  • the present application claims to be submitted to the Chinese Patent Office on June 22, 2006, the application number is 200610061272.8, and the invention name is "orthogonal frequency division multiplexing system interference detection method" The priority of the Chinese Patent Application, the entire disclosure of which is incorporated herein by reference.
  • the present invention relates to the field of communications, and in particular, to an interference detection method, apparatus, and system for an orthogonal frequency division multiplexing system.
  • license-exempt systems such as WRA (Wireless Regional Area Network), WLAN (Wireless Local Area Network), and the like. These systems are characterized by the fact that their operating frequency bands do not require authorization. In the operating band, these license-exempt systems need to coexist with the authorization system. For example, the WRAN system needs to coexist with the authorization system DTV (Digital Television). The license-exempt system cannot interfere with the licensed system. When a licensed or authorized system is used to use a certain frequency band, the license-exempt system must exit the frequency band without conditions and jump to other frequency bands to continue working.
  • WRA Wireless Regional Area Network
  • WLAN Wireless Local Area Network
  • DTV Digital Television
  • This mode of operation also known as the SP (Pradition Pooling) system
  • LU Liense User
  • RU license-free user or leased user
  • SP Radition Pooling
  • the LU user does not have the obligation to detect the RU user signal, that is, when the RU user does not exist.
  • RU users assume all obligations not to interfere with LU users.
  • the WRAN network is an emerging network technology that provides high-bandwidth and large-scale coverage for remote areas and low-density population areas.
  • WRAN system is a license-free operation (license-exempt In the system of operation, the WRAN network uses cognitive radio technology to find the free frequency band of the LU for communication. For example, in a licensed band such as VHF/UHF of DTV, a frequency band that is not occupied is searched for as a bearer band of the WRAN network.
  • the physical technology of the current WRAN system uses OFDMA (Orthogonal Frequency Division Multiplexing Access) technology based on TDD (Time Division Duplex) for communication.
  • OFDMA Orthogonal Frequency Division Multiplexing Access
  • TDD Time Division Duplex
  • Each frame structure is divided into two sub-frames, one downlink sub-frame, after a guard time (can be inserted into TRG or SSS sliding self-coexisting time slot) followed by an uplink sub-frame.
  • the downlink subframe includes a Preamble, and the CPE (Customer Premises Equipment) can be used for synchronization and signal estimation.
  • the FCH Fre Control Head
  • US-MAP messages DS-MAP messages
  • UCD messages User Deformation Protocol
  • DCD messages wherein US-MAP and DS-MAP are used to allocate downlink and uplink channel assignments for each CPE, respectively.
  • a TTG guard slot is inserted between the downlink subframe and the uplink subframe.
  • the main function of the guard slot is that the RF (Radio Frequency) of the BS (Base Station) can be sufficient.
  • the time is changed from sending to receiving.
  • WRAN uses QP (Quiet Time) to specifically detect it.
  • QP Quality of Service
  • energy detection performs fast detection, so the scheduling time is very short.
  • a longer QP is scheduled in a subsequent frame to further detect the characteristics of the LU user signal, thereby facilitating determination of the type of the LU user.
  • the insertion of QP requires the entire system to remain silent during QP, thus having the following disadvantages:
  • the QP time is very short. Although the QP remains silent, if there is multipath, the QP cannot be too short. For example, some QPs are scheduled from tens of microseconds to hundreds of microseconds. For large coverage WRAN, the multipath delay may reach this time, or the QP time may be swallowed, resulting in inaccurate interference detection results.
  • the timeliness of detection is related to the scheduling period of QP.
  • QP scheduling is frequent, so as to ensure the timeliness of LU signal detection; however, QP scheduling is frequent, which causes waste of resources of the system, thereby reducing system usage efficiency.
  • interference detection techniques use squared coordinate errors on constellation maps. The expected value calculates the power of the interference and noise:
  • the signal transmitted by the transmitter at subcarrier k at time i is Xk
  • ⁇ is the channel at subcarrier k at time i
  • I t is the interference signal of other system transmitters on subcarrier k at time i.
  • Embodiments of the present invention provide an interference detection method, apparatus, and system for an orthogonal frequency division multiplexing system, which can achieve high accuracy detection without performing channel estimation.
  • an interference detection method for an orthogonal frequency division multiplexing system may be provided, including: receiving an OFDM signal sent by a transmitter of the system, an orthogonal signal thereof, and an interference signal sent by another system transmitter; Performing an inner product on the OFDM signal and its orthogonal signal to obtain a residual signal; performing energy detection on the residual signal to obtain a metric of other system interference signals.
  • an interference detection system for an Orthogonal Frequency Division Multiplexing system including: a transmitter of the system, configured to transmit an OFDM signal and an orthogonal signal thereof; a system transmitter, configured to send an interference signal; a receiver of the system, configured to receive an OFDM signal sent by the transmitter of the system, an orthogonal signal, and an interference signal sent by another system transmitter; and the received OFDM signal
  • the quadrature signal is subjected to an inner product operation to obtain a residual signal, and the remaining signal is subjected to energy detection to obtain a measure of interference signals of other systems.
  • an interference detecting apparatus for an orthogonal frequency division multiplexing system including: An OFDM demodulation module, configured to perform FFT transform and OFDM demodulation on the received OFDM signal sent by the transmitter of the system and the orthogonal signal thereof, and the interference signal sent by another system transmitter;
  • the interference detection module is configured to perform an inner product operation on the signal provided by the OFDM demodulation module to obtain a residual signal, perform energy detection on the remaining signal, and obtain a metric of other system interference signals.
  • the detection of interference signals of other systems can be realized without interrupting the communication of the system. Since the channel estimation is not required in the process of implementing interference detection in the embodiment of the present invention, the error of the channel estimation does not affect the detection effect.
  • FIG. 1 is a schematic diagram of an interference detection system of an OFDM system according to an embodiment of the present invention
  • FIGS. 3a-c are schematic diagrams showing simulations of transmitting five pilot signals on one subcarrier according to an embodiment of the present invention
  • FIG. 5 is a graph showing the probability of detection on an OFDM simulation platform at a drying ratio of 30 dB according to an embodiment of the present invention
  • FIG. 6 is a graph showing the probability of detection on an OFDM simulation platform at a drying ratio of 25 dB according to an embodiment of the present invention
  • the RU system is a system using OFDM technology, and is called this system.
  • the LU system is called another system.
  • the technology used by the LU system is not limited.
  • the LU system may be a single carrier or a multi-carrier, and may be a digital signal or an analog signal.
  • FIG. 1 it is a schematic diagram of an interference detection system of an OFDM system according to an embodiment of the present invention. These include: the system transmitter 101, other system transmitters 102, and the system receiver 103.
  • OFDM OFDM Mobile Communication Technology
  • the signal transmitted by the transmitter 101 of the system at subcarrier k at time i is X k ; : 3 ⁇ 4, 1 is the channel of subcarrier k at time 1; the receiver 103 of the present system receives the signal at subcarrier k at time i, I is the interference signal of the other system transmitter 102 on subcarrier k at time i.
  • Y k X kj xH k +n k ( 2 )
  • Hk is constant.
  • the channel is not frequency selective or that the coherence bandwidth of the channel is large, that is, Hk is constant within the coherent bandwidth for a period of time.
  • the signal selected by the detection algorithm is a signal for orthogonal operation in the coherent time and the coherent bandwidth. So the channel here can be simplified as H.
  • the interference signal detecting method of the embodiment of the present invention includes the following steps:
  • the transmitter sends the OFDM signal to the receiver;
  • the transmitter passes the data through binary phase shift keying, rotary binary phase shift keying, repeated binary phase shift keying, quadrature phase shift keying, rotary quadrature phase shift keying and/or repeated quadrature phase shift keying.
  • the modulation obtains the modulation symbol Xk on the subcarrier k at the time i, passes the IFFT (Inverse Fast Fourier Transform) and adds the CP to obtain the transmitted OFDM signal.
  • IFFT Inverse Fast Fourier Transform
  • the receiver receives the signal, performs OFDM demodulation on the received signal, and performs FFT (fast Fourier transform);
  • the receiver wants to obtain the data transmitted by the transmitter, it needs to perform channel estimation as in the existing OFDM receiver, and further demodulate the data transmitted by the transmitter.
  • step B the signal demodulated in step B is expressed as follows:
  • step ⁇ When there is no interference, the signal demodulated in step ⁇ is expressed as follows: 7, ⁇ X ⁇ xH+n ⁇ (4)
  • two received signals will be used for detection. For example, you can select two consecutive time signals on the same subcarrier: and +1 ; you can also select the signals of two adjacent subcarriers at the same time: and 1 +1 ; you can also select two different times and different children.
  • Signal on the carrier H +u+1 . As long as the selected signal is within the coherence time and the coherence bandwidth.
  • signals at different times on the same subcarrier will be used to illustrate the algorithm of an embodiment of the present invention.
  • the signal ( Q t ,, Q,, +1 ) is a signal orthogonal to the signal ( X t ,, X t , +1 ), that is, satisfy: for any ( X,, , X l+l ) signal vector , there is always its orthogonal signal ( Q kl , Q,, +1 ), for example, take
  • the received signal is orthogonally calculated:
  • the energy of (5) will be significantly greater than (6). Based on this assumption, it can pass The energy of Y kJ xQ,, +Y,, +1 Q,, +1 is detected to determine whether interference occurs.
  • an embodiment of the present invention provides a method of determining a threshold.
  • a given signal ⁇ , ⁇ office. +1
  • the complex The linear combination of Gaussian signals is a complex Gaussian signal whose modulus square satisfies the distribution and has a degree of freedom of 2. Therefore, for (Q t ,, Q t , +1 ) given cases, that is, ( X , X t , + 1 ) Given a situation, a threshold T (X,,, x,, +1 ) can be given to detect interference.
  • the detection algorithm of the embodiment of the present invention may use multiple sets of data. Because the different sets of signals (Q kJ , Q k +l ) may be different.
  • these different time signals are not necessarily within the coherence time. But as long as the two signals of the same group are within the coherence time. All signals need to be within the time and timeliness of the detection signal.
  • the detection algorithm is as follows: When ⁇ 1 ( 8.b ) is established, it can be judged that there is interference, NO N _ ⁇
  • the number of interference detection signal groups used can be as long as the interference detection sensitivity is satisfied. For example, five sets of signals can be used to detect.
  • Embodiments of the present invention do not require channel estimation.
  • Embodiments of the present invention can adapt to different precisions by performing interference detection in different distributions in the time domain and the frequency domain. For example, only one signal in the subcarrier wave is taken, so that the interference signal can be detected by using the subcarrier as the granularity; the signal in the same time can also be taken, so that the instantaneous interference generated in one OFDM symbol can be detected.
  • the embodiment of the present invention takes multiple sets of signals, which can increase the correctness of the detection. This can be clearly seen from the simulations that follow.
  • the embodiment of the present invention does not need to interrupt the current communication. Data communication and interference detection can be performed simultaneously.
  • the transmitted signals are roughly classified into two types: one is a data signal, and the other is a pilot signal.
  • the purpose of the pilot signal is for channel estimation and is located at a previously known location (time, subcarrier). Therefore, the pilot can be used for interference detection, as follows:
  • pilots are symbols that use BPSK fixed modulation 1. However, it may also be for other The purpose is to design the pilot to a 1,7-phase BPSK modulation symbol.
  • the detecting step of the embodiment of the present invention includes:
  • the transmitter constructs a pilot signal
  • the transmitter sends the constructed pilot signal to the receiver
  • the receiver performs interference detection by using the received pilot signal.
  • Palarm is the false alarm probability
  • HO is the condition without interference
  • Threshold is the judgment threshold to be sought.
  • the H0 indicates that: the power of the pilot signal and the power is only the noise component, and there is no interference component.
  • the formula is expressed as follows:
  • P( ⁇ i > threshold I HI) Pdetection
  • Pdetection the detection probability
  • HI the condition with interference
  • Threshold the threshold to be sought.
  • the HI indicates that: the pilot signal and the power have both a noise component and an interference component, and the formula is expressed as follows:
  • test formula is as follows:
  • the channel sum is not required to be estimated when calculating the signal sum.
  • the symmetric pilot signal is then transmitted on the pilot subcarriers. In the transmission process, if there is interference, it is assumed that the interference is not a symmetric signal at the pilot position, and the power of the received pilot signal sum increases.
  • Embodiments of the present invention determine whether interference exists based on the magnitude of power received by the signal. In order to verify the result of the embodiment of the present invention, the interference detection method of the embodiment of the present invention is simulated. It can be seen from the simulation result that the embodiment of the present invention can effectively perform interference detection, and the detection success rate is high.
  • FIG. 2 shows a simulation diagram of transmitting two pilot signals on one subcarrier, as shown in FIG.
  • the axis represents the subcarrier subscript and the ordinate axis represents the detection probability.
  • Figure 3 shows a simulation of the transmission of five pilot signals on one subcarrier, as shown in Figure 3, where the abscissa axis represents the subcarrier subscript and the ordinate axis represents the detection probability.
  • FIG. 4 it is a schematic diagram of an interference detecting apparatus jointly decoded by an embodiment of the present invention. For the sake of convenience, only the relevant module for receiver interference detection is shown here. For other descriptions, reference may be made to the aforementioned portion for detecting interference using pilots.
  • the specific implementation is as follows:
  • the receiver receives the signal for FFT conversion and performs the OFDM demodulation module 411.
  • the interference detection module 412 is provided to perform interference detection.
  • the receiver performs FFT conversion on the received signal and performs OFDM demodulation through the OFDM demodulation module 411.
  • the subsequent decoding module 421 is then decoded (including deinterleaving, descrambling, etc.). If the decoding is correct, the decoded data is encoded into the subsequent encoding module 422 (including interleaving, scrambling, etc.), and then modulated by the modulation module 423 to obtain the modulated signal X t transmitted by the transmitter. Then, in combination with the aforementioned interference detection algorithm, the interference signal can be detected. If the decoding is not correct, then the FER (Frame Error Rate) is calculated. If the FER exceeds a certain threshold, the current FER is reported. The system calculates that the FER exceeds a certain threshold and considers that there may be interference currently. At this time, the QP is scheduled to perform interference detection for the CPE.
  • FER Fre Error Rate
  • the frequency of interference detection is reduced, the resources of the system are saved, and the working efficiency of the system is improved; on the other hand, the requirement of detection probability can be met. Therefore, the detection algorithm has strong practicability, and the subsequent simulation tests have also confirmed and supported this.
  • the receiver 103 of the present system as shown in FIG. 1 includes:
  • the OFDM demodulation module 1031 performs FFT conversion and OFDM demodulation on the received OFDM signal sent by the transmitter of the system and its orthogonal signal, and the interference signal sent by other system transmitters;
  • the interference detecting module 1032 performs interference detection on the signal provided by the OFDM demodulation module 1031.
  • FIG. 5 it is the detection probability measured on the OFDM simulation platform when the INR is 30 dB.
  • the above figure shows the effect of single point calculation using equation (7)
  • the figure below shows the effect detection diagram of 8 points average calculation using (8.a).
  • the abscissa is the subcarrier number and the ordinate is the detection probability.
  • the figure above shows the effect of a single point calculation using equation (7).
  • the figure below shows the average of 8 points using (8.a). Calculated effect detection map.
  • the abscissa is the subcarrier number and the ordinate is the detection probability.
  • the storage medium is, for example, a ROM/RAM, a magnetic disk, an optical disk, or the like.

Abstract

L'invention concerne un procédé pour la détection d'interférence dans un système MROF. Ledit procédé consiste à recevoir un signal MROF et son signal orthogonal transmis par l'émetteur et le signal d'interférence transmis par un autre système, à acquérir un signal restant par corrélation du signal MROF et de son signal orthogonal, à détecter la puissance du signal restant et à atteindre le signal d'interférence à partir d'un autre système. En outre, cette invention concerne un dispositif et un système correspondant le procédé susmentionné. Le procédé présente les avantages suivants. Dans un premier temps, il ne requiert pas d'estimation de voie, l'erreur de ladite estimation n'a pas d'impact sur l'effet de la détection, dans un deuxième temps, la détection d'interférence de différents points d'échantillonnage distribués dans le domaine temporel ou le domaine de fréquence peut s'adapter aux différentes demandes de précision, dans un troisième temps, la précision de la détection peut être améliorée par des données multi-groupes, dans un quatrième temps, la communication de données et la détection d'interférence peuvent être réalisées simultanément et la communication ne doit pas être interrompue. En dernier lieu, la possibilité de mise en oeuvre dudit procédé peut être améliorée par combinaison de l'autre module de traitement de signal.
PCT/CN2007/070156 2006-06-22 2007-06-21 Procédé, dispositif et système pour la détection d'une interférence dans un système mrof WO2008000187A1 (fr)

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CN200610061272.8 2006-06-22
CN2006100612728A CN101060511B (zh) 2006-06-22 2006-06-22 正交频分复用系统的干扰检测方法及系统

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CN107544549B (zh) * 2016-06-24 2021-03-12 北京末元科技有限公司 一种适用于vr设备的定位和数据传输方法及系统
CN110100420B (zh) * 2016-12-21 2022-07-22 三菱电机株式会社 通信系统
CN112001460B (zh) * 2020-07-16 2022-04-01 中国科学院微电子研究所 信号处理方法以及装置、rfid系统

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CN103560864B (zh) * 2013-11-06 2017-02-08 上海贝岭股份有限公司 一种盲信道自适应方法及其装置

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