WO2010056166A1 - Procédé et agencement dans un système de communication - Google Patents

Procédé et agencement dans un système de communication Download PDF

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Publication number
WO2010056166A1
WO2010056166A1 PCT/SE2008/051309 SE2008051309W WO2010056166A1 WO 2010056166 A1 WO2010056166 A1 WO 2010056166A1 SE 2008051309 W SE2008051309 W SE 2008051309W WO 2010056166 A1 WO2010056166 A1 WO 2010056166A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
analogue
cancellation
relay node
digital
Prior art date
Application number
PCT/SE2008/051309
Other languages
English (en)
Inventor
Peter Larsson
Robert Baldemair
Original Assignee
Telefonaktiebolaget L M Ericsson (Publ)
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.)
Filing date
Publication date
Application filed by Telefonaktiebolaget L M Ericsson (Publ) filed Critical Telefonaktiebolaget L M Ericsson (Publ)
Priority to PCT/SE2008/051309 priority Critical patent/WO2010056166A1/fr
Publication of WO2010056166A1 publication Critical patent/WO2010056166A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/15564—Relay station antennae loop interference reduction
    • H04B7/15585—Relay station antennae loop interference reduction by interference cancellation

Definitions

  • the present invention relates to a method and an arrangement in a relay node comprised in a wireless communication network.
  • it relates to a mechanism for self interference cancellation within the relay node.
  • LTE Long Term Evolution
  • E-UTRAN evolved UTRAN
  • 3GPP 3rd Generation Partnership Project
  • Layer 1 relays also known as repeaters do not decode the signal but generally just perform an amplify-and-forward operation. These repeaters only have Layer 1 functionality.
  • Layer 2 relays demodulate the signal, and typically also perform forward error correction. Depending on the underlying physical layer this demodulation process introduces a non- negligible delay. In case of LTE-Advanced this delay is at least 1 ms and the repeated, delayed signal interferes with new transmissions. On the other hand, the demodulation process removes noise and forwards a "clean" signal.
  • Layer 2 relays have in addition to Layer 1 functionality, also Layer 2 functionality.
  • Layer 3 relays in the context of LTE, have the same functionality as an eNodeB but the connection of the base station with the network is done via a wireless link using the LTE air interface. Therefore Layer 3 relays are also denoted wireless backhauls. Layer 3 relays may encompass routing functionality.
  • the input and output antennas of a relay are not sufficiently isolated, then a certain part of the amplified output signals is received by the receive antennas and amplified even further. This effect is denoted self interference. In the worst case the system becomes instable and starts to oscillate. However, even in case the systems remains stable the requirement on the dynamic range of the Analogue to Digital Converter (ADC) is increased since the input signal, which probably is rather weak, is interfered by the amplified output signal, which possibly is rather strong. In order to resolve the input signal, a higher resolution of the ADC is generally required.
  • ADC Analogue to Digital Converter
  • the existing method also present weakness when it comes to dynamic range handling, i.e. when the desired input signal may be weaker than the feedback signal.
  • the input signal must be scaled down prior to the ADC based on the signal level given by the feedback signal, to avoid clipping rather than optimizing for the received low level signal of interest which may be preferable.
  • One possible solution to handle the requirement on a high dynamic range may be to use a high resolution ADC.
  • the ADC tends to become costly.
  • a second weakness relates to quantization noise from the feedback signal. This effect arise due to that the attenuation from the relay output to input is linear and continuous, but the ADC introduce a quantization error prior to the self interference cancelation is performed.
  • an analogue input signal is received.
  • the received analogue input signal is converted into a digital signal.
  • a cancellation signal is then extracted from the digitally processed digital signal.
  • the extracted cancellation signals are then filtered in a filter.
  • the filter is comprised within the relay node.
  • the filtered cancellation signal is then converted into an analogue cancellation signal by means of a digital to analogue converter.
  • the digital to analogue converter is comprised within the relay node.
  • the converted analogue cancellation signal is then subtracted from the analogue input signal.
  • the object is also achieved by an arrangement in a relay node for cancelling self-interference.
  • the arrangement comprises a first converter.
  • the first converter is configured to convert a received analogue input signal into a digital signal.
  • the arrangement further comprises a signal processing unit.
  • the signal processing unit is configured to digitally process the digital signal.
  • the arrangement also comprises an extraction unit.
  • the extraction unit is configured to extract a cancellation signal from the digitally processed digital signal.
  • the arrangement comprises a filter.
  • the filter is configured to filter the extracted cancellation signal.
  • the arrangement additionally comprises a second converter.
  • the second converter is configured to convert the cancellation signal into an analogue cancellation signal.
  • the arrangement furthermore comprises a subtracting unit.
  • the subtracting unit is configured to subtract the converted analogue cancellation signal from the analogue input signal.
  • the dynamic range of the relay input may be increased. Further, the feedback quantization noise may be reduced.
  • the quantization noise reduction may allow for increased relay gain. This is achieved by introducing a self interference cancellation mechanism that operates partly in the digital domain and partly in the analogue domain. Thus an improved performance of the wireless communication system is provided.
  • Figure 1 is a schematic block diagram illustrating embodiments of a wireless communication network.
  • Figure 2 is a block diagram illustrating embodiments of a relay node.
  • Figure 4 is a block diagram illustrating embodiments of an arrangement in a relay node.
  • Figure 1 depicts a wireless communication system 100 comprising a first node 110 communicating with a second node 120 in a cell 130.
  • the distance and/or the radio propagation conditions within the cell 130 may preclude direct radio communication between the first node 110 and the second node 120.
  • the communication between the first node 110 and the second node 120 may be made over a relay node 140 comprised in the wireless communication system 100.
  • the wireless communication system 100 may also comprise a control node, according to some optional embodiments, depending on the technology used.
  • the control node may be e.g. a Radio Network Controller.
  • the control node may carry out radio resource management and some of the mobility management functions.
  • the first node 110 may be represented by e.g. a user equipment, a wireless communication terminal, a mobile cellular telephone, a Personal Communications Systems terminal, a Personal Digital Assistant (PDA), a laptop, a computer or any other kind of device capable of managing radio resources.
  • a Personal Communication System terminal may combine a cellular radiotelephone with data processing, facsimile and data communications capabilities.
  • a PDA may include a radiotelephone, a pager, an Internet/intranet access device, a web browser, an organizer, calendars etc.
  • the second node 120 may in some embodiments be referred to as e.g. a base station, an access point, a Node B, an evolved Node B (eNode B) and/or a base transceiver station, Access Point Base Station, base station router, etc depending e.g. of the radio access technology and terminology used.
  • a base station an access point
  • Node B an evolved Node B
  • eNode B evolved Node B
  • base transceiver station e.g. of the radio access technology and terminology used.
  • the wireless communication system 100 may be based on technologies such as e.g. E- UTRAN, LTE, Code division multiple access (CDMA), Wideband Code Division Multiple Access (WCDMA), CDMA 2000, High Speed Downlink Packet Data Access (HSDPA), High Speed Uplink Packet Data Access (HSUPA), High Data Rate (HDR), TD-SCDMA, WLAN/ 802.11 , 802.16 etc.
  • technologies such as e.g. E- UTRAN, LTE, Code division multiple access (CDMA), Wideband Code Division Multiple Access (WCDMA), CDMA 2000, High Speed Downlink Packet Data Access (HSDPA), High Speed Uplink Packet Data Access (HSUPA), High Data Rate (HDR), TD-SCDMA, WLAN/ 802.11 , 802.16 etc.
  • the relay node 140 may sometimes be referred to e.g. as a cellular repeater, a cell phone repeater, or a wireless cellular signal booster.
  • the relay node 140 is adapted e.g. to boost the cell phone reception to the local area by the usage of inter alia a reception antenna, a signal amplifier and an internal rebroadcast antenna.
  • the relay node 140 may be adapted to amplify any received wireless signal and retransmit it.
  • Figure 2 illustrates the relay node 140, with an applied self interference cancelation mechanism.
  • the relay 140 may comprise, or be connected to, a reception unit 201 and a transmission unit 202.
  • the relay 140 comprises an Analogue to Digital Converter (ADC) 230 that converts a signal received at the reception unit 201 from an analogue signal to a digital signal.
  • ADC Analogue to Digital Converter
  • the relay 140 comprises a signal processing unit 240, adapted to digitally process the digital signal.
  • the relay 140 may comprise a constant delay 250, which delay 250 is adapted to cater for the processing delay in the filter 270 prior to the feedback channel, but the delay may also be an inherent part due to signal processing.
  • the relay 140 comprises a Digital to Analogue Converter (DAC) 260 that converts a signal from digital to analogue before transmission at the transmission unit 202. After having passed the filter 270, the cancellation signal is converted in a DAC 280, from digital to analogue, where after the cancellation signal is subtracted from the received signal received at the reception unit 201.
  • DAC Digital to Analogue Converter
  • the transmission unit 202 may comprise an antenna means for transmitting signals.
  • the transmission unit 202 may further comprise a number of components and/or units containing radio related functionality, such as e.g. converter, filter, local oscillators, mixer, gain control circuit and/or power amplifier.
  • the transmission unit 202 may be adapted for up-conversion to the transmitted frequency and/or adjusting the output power of the transmission unit 202 to a desired level.
  • the present solution comprises two parts.
  • the first part is to subtract the interference from the feedback channel 290 in the analogue domain 220 prior the analogue to digital conversion performed in the ADC 230. This is achieved by using a DAC 280, in the interference cancellation loop. This allows a strong feedback signal 290 to be attenuated and low level signal properties may be improved.
  • the second part of the present solution is as follows. Since the resolution of the radio output-to-input channel has for all practical purposes, i.e. omitting quantum theory, infinite resolution, it may be desired to mimic this by having a larger number of bits used in the filter 270 and the DAC 280, than that is used in the ADC 230. In this manner, the quantization noise of the feedback signal 290 may be reduced.
  • the filter 270 and the DAC 280 uses B bits, and the other circuitry outputs such as e.g. ADC 230 and the signal processing unit 240 uses b bits, where B > b. Reducing the feedback quantization noise may enable increased amplification gain of the relay 140.
  • a signal r(t) may be received at the reception unit 201.
  • s(t) is the desired low level signal
  • h(t) is the channel impulse response of the feedback channel 290
  • g1(t) is the impulse response of the filter 270 after the DAC 260 prior the feedback channel 290
  • ⁇ (t-mT) is the small constant delay ml introduced to cater for the processing delay in the filter prior the feedback channel
  • g2(t) is the impulse response of the filter 270 after the other DAC 280
  • F(nT) is a digital filter impulse response at discrete times nT with index n and time step T
  • u(nT) is a processed signal to be transmitted at the transmission unit 202.
  • the signal u(nT) is upsampled as much as needed, i.e. far above the Nyquist frequency.
  • the Nyquist frequency is half the sampling frequency of a discrete signal processing system. It is sometimes also referred to as the folding frequency, or the cut-off frequency of a sampling system.
  • the filter 270 may benefit from having infinite resolution in time and in amplitude. This may not be achieved in practice but asymptotically well with approximations.
  • the time aspect may be decently handled e.g. by over sampling the signal sufficiently, whereas as an approximation suffice to use a higher quantization resolution of B bits than the input ADC 230 using b bits, i.e. B > b,
  • the filter parameters may be optimized to minimize a selected performance measure, such as Mean Square Error (MSE), of the feedback signal 290.
  • MSE Mean Square Error
  • the filter weights W n of the filter 270 may for instance be computed through:
  • the dynamic range of the relay input may be increased.
  • the term dynamic range is here used to describe the ratio between the smallest and largest possible values of the relayed signal, received and transmitted at the relay.
  • the feedback quantization noise may be reduced. The quantization noise reduction may allow for increased relay gain.
  • FIG. 3 is a flow chart illustrating embodiments of a method performed in a relay node or repeater node 140.
  • the node 140 will, continuously be referred to as a "relay node".
  • the method aims at cancelling, or at least somewhat reducing, self-interference.
  • the relay node 140 may optionally comprise, be associated with or be connected to a reception unit 201, configured to receive analogue input signals, and a transmission unit 202, configured to transmit analogue signals.
  • the method may comprise a number of method steps 301-309. It is however to be noted that some of the described method steps are optional and only comprised within some embodiments.
  • the method steps 301-309 may be performed in any arbitrary chronological order and that some of them, e.g. step 304 and step 308, or even all steps may be performed simultaneously or in an altered, arbitrarily rearranged, decomposed or even completely reversed chronological order.
  • the method may comprise the following steps:
  • Step 301 An analogue input signal is received from the reception unit 201.
  • the received analogue input signal is converted into a digital signal.
  • the digital signal is digitally processed, e.g. in the signal processing unit 240.
  • the digital processing may comprise amplification of the digital signal.
  • Step 304 A cancellation signal is extracted from the digitally processed digital signal.
  • the filtered cancellation signal is converted into an analogue cancellation signal by means of a digital to analogue converter 230, comprised within the relay node.
  • the converted analogue cancellation signal is subtracted from the analogue input signal.
  • the digitally processed digital signal to be transmitted may be converted into an analogue signal by means of a digital to analogue converter 260, according to some embodiments.
  • Step 309 This step is optional and may only be comprised within some embodiments of the present method.
  • the analogue signal may be transmitted at the transmission unit 202, according to some embodiments.
  • the analogue signal may be transmitted over a continuous and attenuating radio channel that at least partially interferes with the analogue input signals.
  • the interference may be represented by a feedback channel 290.
  • FIG. 4 is a block diagram illustrating embodiments of an arrangement 400 situated in the relay node or a repeater node, here referred to as "relay node" 140.
  • the arrangement 400 is configured to perform the method steps 301-309 for cancelling or at least somewhat reducing, self-interference.
  • the relay node 140 may optionally comprise, be associated with or be connected to a reception unit 201 , configured to receive analogue input signals, and a transmission unit 202, configured to transmit analogue signals.
  • the arrangement 400 comprises a first converter 230.
  • the first converter 230 is configured to convert a received analogue input signal into a digital signal.
  • the arrangement 400 comprises an extraction unit 404.
  • the extraction unit 404 is configured to extract a cancellation signal from the digital signal.
  • the arrangement 400 comprises a filter 270.
  • the filter 270 is configured to filter the extracted cancellation signal.
  • the filter 270 may further be configured to decrease unnecessary frequency components of the extracted cancellation signals, according to some embodiments.
  • the arrangement 400 comprises a second converter 280.
  • the second converter 280 is configured to convert the filtered cancellation signal into an analogue cancellation signal.
  • the arrangement 400 comprises a subtracting unit 407.
  • the subtracting unit 407 is configured to subtract the converted analogue cancellation signal from the analogue input signal.
  • the described units 201-407 comprised within the arrangement 400 are to be regarded as separate logical entities but not with necessity separate physical entities. Any, some or all of the units 201-407 may be comprised or co-arranged within the same physical unit. However, in order to facilitate the understanding of the functionality of the arrangement 400, the comprised units 201-407 are illustrated as separate physical units in Figure 4.
  • the method in the relay node 140 for cancelling self-interference may be implemented through one or more processors in the relay node 140, together with computer program code for performing the functions of the method.
  • the program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the method according to the present invention when being loaded into the processing unit.
  • the data carrier may be a CD ROM disc, a memory stick, or any other appropriate medium such as a disk or tape that can hold machine readable data.
  • the computer program code can furthermore be provided as pure program code on a server and downloaded to the relay node 140 remotely.
  • a computer program comprising instruction sets for performing the method according to at least some of the method steps 301-309 may be used for implementing the previously described method.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Radio Relay Systems (AREA)

Abstract

L'invention concerne un procédé et un agencement dans un noeud relais, permettant d'annuler des auto-interférences. Le noeud relais reçoit des signaux d'entrée sans fil. Le procédé consiste à recevoir un signal d'entrée analogique, à convertir chaque signal d'entrée analogique reçu en un signal numérique, à traiter ce signal numérique, à extraire un signal d'annulation de chaque signal numérique traité numériquement respectif, à filtrer les signaux d'annulation extraits, à convertir chaque signal d'annulation en un signal d'annulation analogique et, à soustraire chaque signal d'annulation analogique du signal d'entrée analogique.
PCT/SE2008/051309 2008-11-14 2008-11-14 Procédé et agencement dans un système de communication WO2010056166A1 (fr)

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Application Number Priority Date Filing Date Title
PCT/SE2008/051309 WO2010056166A1 (fr) 2008-11-14 2008-11-14 Procédé et agencement dans un système de communication

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE2008/051309 WO2010056166A1 (fr) 2008-11-14 2008-11-14 Procédé et agencement dans un système de communication

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3101813A4 (fr) * 2014-02-27 2017-02-22 Huawei Technologies Co., Ltd. Procédé et dispositif relais pour réduire des interférences de fréquences adjacentes
CN107707291A (zh) * 2017-10-30 2018-02-16 珠海格力电器股份有限公司 中继装置以及控制系统

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1261148A1 (fr) * 2000-02-18 2002-11-27 Mier Communicaciones S.A. Procede de reemission de signaux en isofrequence et reemetteur de signaux en isofrequence
US20070191071A1 (en) * 2005-07-13 2007-08-16 Teamcast Method for isofrequency transmission of a digital signal with echo suppression and corresponding retransmission device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1261148A1 (fr) * 2000-02-18 2002-11-27 Mier Communicaciones S.A. Procede de reemission de signaux en isofrequence et reemetteur de signaux en isofrequence
US20070191071A1 (en) * 2005-07-13 2007-08-16 Teamcast Method for isofrequency transmission of a digital signal with echo suppression and corresponding retransmission device

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3101813A4 (fr) * 2014-02-27 2017-02-22 Huawei Technologies Co., Ltd. Procédé et dispositif relais pour réduire des interférences de fréquences adjacentes
US10056962B2 (en) 2014-02-27 2018-08-21 Huawei Technologies Co., Ltd. Method for reducing adjacent-channel interference and relay device
CN107707291A (zh) * 2017-10-30 2018-02-16 珠海格力电器股份有限公司 中继装置以及控制系统
CN107707291B (zh) * 2017-10-30 2023-06-30 珠海格力电器股份有限公司 中继装置以及控制系统

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