Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W76/00—Connection management
  • H04W76/10—Connection setup
  • H04W76/14—Direct-mode setup
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W8/00—Network data management
  • H04W8/005—Discovery of network devices, e.g. terminals

Definitions

• the present invention relates to the technical field of wireless communications, and particularly, to device-to-device communication.
• a cellular wireless communication network such as Long Term Evolution LTE or LTE-A Long Term Evolution-Advance of 3GPP
• two user equipments communicate with each other via a base station (eNB).
• eNB base station
• D2D communication Through D2D communication, a load of the base station may be shared, and coverage of the base station may be increased by way of mobile relay. Therefore, in LTE-A, D2D communication has already been accepted as an important enhancement for cellular mobile communication.
• LTE TDD time division duplex
• the D2D communication is particularly applicable because uplink and downlink use the same frequency band.
• the current LTE-TDD system cannot implement the D2D communication mainly because a transceiver of the current LTE-TDD UE uses different wireless access modes at a transmitter and a receiver. What is used by the transmitter is a single carrier- frequency division multiple access SC-FDMA, whereas what is used at the receiver is orthogonal frequency division multiple access OFDMA. Hence, direct communication cannot be achieved between the UEs, thereby neither can the D2D communication be achieved between the UEs.
• introducing D2D communication into the LTE-TDD system may cause mutual interference between the cellular communication link and the D2D communication link, so how to achieve frequency multiplexing to avoid the interference is a problem that must be solved upon introducing D2D communication.
• some related work has already been conducted to solve the problem mentioned above, for example, FlashLinQ technology proposed by Qualcomm. Key points of the technical solution include the following:
• Drawbacks of the solution lie in the following: as an out-band solution, it needs to additionally occupy precious frequency resource, so the frequency resource for use by the cellular communication system reduces correspondingly; furthermore, this portion of resource cannot be dynamically retrieved so that such resource cannot be used even when there is no demand for D2D communication, which causes a waste of the frequency resource; in addition, a set of stand-alone transceiver needs to be added in the UE, which substantially increases costs and complexity of the UE.
• LTE-TDD cellular communication system needs a new in-band D2D communication solution which shall require no extra spectrum and must solve problems about frequency multiplexing and dynamic frequency allocation.
• a transceiver of the UE needs to be improved to support the solution, and such improvement to the UE must be simple and cost-efficient.
• the present invention provides a novel solution for implementing D2D communication in the LTE-TDD cellular wireless communication system, performing D2D communication by using frequency resource in the same format as that in the cellular wireless communication system and improving the transceiver of the UE to enable a transmitter and a receiver to use the same wireless access mode.
• a method for performing device-to-device communication in an LTE-TDD cellular wireless communication system comprising: allocating frequency resource for UEs in need of the device-to-device communication, wherein a format of the frequency resource is identical with a format used by a cellular link in the cellular wireless communication system; and the UE performs the device-to-device communication on the frequency resource, wherein the UE uses the same wireless access mode at a transmitter and a receiver.
• the frequency resource allocated to the UE in need of the device-to-device communication and the frequency resource occupied by a cellular uplink and a cellular downlink in the cellular wireless communication system are multiplexed on a frequency domain.
• the frequency resource is allocated by the base station in the cellular wireless communication system.
• the method further comprises: the base station sends to the UE a first signaling message to indicate the frequency resource to the UE; the UE receives the first signaling message sent by the base station.
• the base station sends to the UE a second signaling message to indicate a change of the frequency resource to the UE; the UE receives the second signaling message sent by the base station and performs the device-to-device communication on the changed frequency resource.
• the frequency resource is allocated by the UE in need of the device-to-device communication.
• the same wireless access mode is orthogonal frequency division multiple access OFDMA or single carrier- frequency division multiple access SC-FDMA.
• a transmitter for supporting device-to-device communication in a user equipment UE of an LTE-TDD cellular wireless communication system comprising: a discrete Fourier transform module configured to conduct discrete Fourier transform to an input signal to obtain a transformed signal; a modulation module configured to map each symbol of the transformed signal to a plurality of carriers and modulate it to obtain a modulated signal; a cyclic prefix insertion module configured to insert a cyclic prefix to the modulated signal to obtain a inserted signal; a digital-analog conversion module configured to conduct digital-analog conversion to the inserted signal to obtain a to-be-transmitted signal; a transmission module configured to transmit the to-be-transmitter signal; wherein the transmitter further comprises a mode selection module configured to select whether to bypass the discrete Fourier transform module and directly input the input signal to the modulation module.
• the transmitter further comprises a power control module between the cyclic prefix insertion module and the digital-analog conversion module to conduct power control for the inserted signal outputted by the cyclic prefix insertion module when the mode selection mode selects to bypass the discrete Fourier transform module.
• a power control module between the cyclic prefix insertion module and the digital-analog conversion module to conduct power control for the inserted signal outputted by the cyclic prefix insertion module when the mode selection mode selects to bypass the discrete Fourier transform module.
• the mode selection module receives indication information sent by the base station, and performs the selection according to the indication information.
• a method for transmitting a signal in a user equipment UE of an LTE-TDD cellular wireless communication system comprising the following steps of: b. conducting discrete Fourier transform to an input signal to obtain a transformed signal; c. mapping each symbol of the transformed signal to a plurality of sub-carriers and performing OFDM modulation to obtain a modulated signal; d. inserting a cyclic prefix to the modulated signal to obtain a inserted signal; e. conducting digital-analog conversion to the inserted signal to obtain a to-be-transmitted signal; f. transmitting the to-be-transmitter signal, wherein the method further comprises the following step before the step b: a. selecting whether to skip the step b and directly perform the step c.
• the method further comprises a step g of conducting power control to the inserted signal between the step d and the step e.
• the step a further comprises receiving indication information sent by the base station; conducting the selection according to received indication information.
• a receiver for supporting device-to-device communication in a user equipment UE of an LTE-TDD cellular wireless communication system comprising: a reception module configured to receive a wireless signal to obtain a received signal; an analog-digital conversion module configured to conduct analog-digital conversion to the received signal to obtain a analog-digital-converted signal; a cyclic prefix removal module configured to remove the cyclic prefix from the analog-digital-converted signal to obtain a removed signal; a demodulation module configured to perform OFDM demodulation to the removed signal to obtain a demodulated signal; a equalization module configured to conduct frequency domain equalization for the demodulated signal to obtain a equalized signal; an inverse discrete Fourier transform module configured to conduct inverse discrete Fourier transform to the equalized signal to obtain an output signal; wherein the receiver further comprises an output selection module configured to select whether to bypass the equalization module and the inverse discrete Fourier transform module to directly output the demodulated signal
• the output selection module receives indication information sent by the base station, and performs the selection according to the indication information.
• a method for receiving a signal in a user equipment UE of an LTE-TDD cellular wireless communication system comprising the following steps of: m. receiving a wireless signal to obtain a received signal; n. conducting analog-digital conversion to the received signal to obtain a analog-digital-converted signal; o. removing the cyclic prefix from the analog-digital-converted signal to obtain a removed signal; p. performing OFDM demodulation to the removed signal to obtain a demodulated signal; q. conducting frequency domain equalization for the demodulated signal to obtain a equalized signal; r. conducting inverse discrete Fourier transform to the equalized signal to obtain an output signal, wherein the method further comprises the following step before the step q: s. selecting whether to bypass the step q and the step r and directly output the demodulated signal.
• the current frequency resource may be used without additionally increasing the frequency resource, and meanwhile effective frequency multiplexing may be achieved and interference may be avoided; dynamic frequency allocation can be achieved in a way that the base station controls the frequency resource; by adding a bypass and simply improving the power control module, the transmitter can be enabled to transmit SC-FDMA signal as well as OFDMA signals so as to implement direct communication between UEs; by adding a frequency equalizer and simply improving an inverse Fourier transform module, the receiver can be enabled to receive SC-FDMA signals as well as OFDMA signals so as to realize direct communication between UEs. Therefore, by adopting the solution of the present invention, D2D communication function may be simply and conveniently implemented in the LTE-TDD cellular communication system and existing problems in the prior art are solved.
• Fig. l illustrates frequency multiplexing of an uplink in a current LTE-TDD system
• Fig.2 illustrates frequency multiplexing of a downlink in a current LTE-TDD system
• Fig.3 illustrates frequency multiplexing of an uplink of a D2D communication and cellular communication system according to the present invention
• Fig.4 illustrates frequency multiplexing of a downlink of a D2D communication and cellular communication system according to the present invention
• Fig.5 illustrates frequency multiplexing of an uplink of another D2D communication and cellular communication system according to the present invention
• Fig.6 illustrates frequency multiplexing of a downlink of another D2D communication and cellular communication system according to the present invention
• Fig.7 illustrates a D2D communication frequency allocation approach according to the present invention
• Fig.8 illustrates a transmitter which is in a user equipment UE of a LTE-TDD cellular wireless communication system and supports D2D communication according to the present invention
• Fig.9 illustrates a receiver which is in a user equipment UE of a LTE-TDD cellular wireless communication system and supports D2D communication according to the present invention.
• the uplink employs SC-FDMA access
• the downlink employs OFDMA access.
• Either the uplink or the downlink may support flexible frequency resource allocation by way of frequency domain multiplexing.
• the so-called frequency domain multiplexing means that different user terminals use different frequency resources for communication.
• the base station may, based on specific service situations, allocate frequency resources with different bandwidths to different UEs, and these frequency resources are multiplexed in the frequency domain so that overlapping will not be formed.
• SC-FDMA employed by the uplink adopts a very similar parameter setting as the OFDMA access employed by the downlink, which includes the same subcarrier space, the same number of occupied subcarriers in a unit bandwidth, and the same cyclic prefix lengths. That is to say, the frequency resource allocated for the uplink and downlink is the same in format.
• the present invention proposes to use the same frequency resource format as that in the cellular communication system to allocate frequency resource for D2D communication.
• a corresponding frequency resource is allocated for D2D communication, and this portion of frequency resource is in the same format as that used by the cellular communication link of the current LTE-TDD system.
• upon allocating the frequency resource reference may be made to the method of the cellular communication system so that this portion of frequency resource is concurrently multiplexed in frequency domain with the frequency resource occupied by the SC-FDMA uplink and the frequency resource occupied by OFDMA uplink.
• the corresponding UE performs reception and transmission of D2D communication data in the same wireless access manner at the transmitter and receiver on the frequency resource.
• the OFDMA or SC-FDMA mode is employed so that one of the receiver and the transmitter may conform to the original design without modification.
• the present invention also applies to other wireless access mode, for example, CDMA.
• Fig.3 and Fig.4 illustrate that D2D communication uses the OFDMA mode, and the frequency resource used by the D2D communication is concurrently multiplexed with the SC-FDMA uplink and OFDMA downlink, that is, the frequency resource used by the D2D communication is different from both of the frequency resource used by the SC-FDMA uplink and the frequency resource used by OFDMA downlink;
• Fig.5 and Fig.6 illustrate that D2D communication uses the SC-FDMA mode, and the frequency resource used by D2D communication is concurrently multiplexed with the SC-FDMA uplink and OFDMA downlink, that is, the frequency resource used by the D2D communication is different from both of the frequency resource used by the SC-FDMA uplink and the frequency resource used by OFDMA downlink.
• allocation of the above frequency resource may be decided by the base station. After determining the frequency resource allocated to the D2D communication according to the network conditions, the base station sends a first signaling message to notify a corresponding UE, and the corresponding UE obtains a corresponding frequency resource according to the received first signaling message to perform D2D communication. In this case, it may also be enabled that the base station performs dynamic adjustment of the frequency resource of D2D communication.
• the base station When the base station decides to perform dynamic adjustment of the frequency resource of D2D communication according to current network conditions, the base station sends a second signaling message to notify a corresponding UE, and the corresponding UE obtains a corresponding adjusted frequency resource according to the received second signaling message and performs D2D communication by using the adjusted frequency resource.
• D2D communication and cellular wireless communication may achieve flexible allocation of resources to adapt for diverse network conditions. For example, when the cellular wireless communication in the network has a higher load, the resource allocated to D2D communication may be reduced appropriately, whereas when the cellular wireless communication has a lower load, the resource allocated to the D2D communication may be increased.
• allocation of the above frequency resource may be voluntarily decided by a respective UE in need of D2D communication.
• the UE voluntarily allocates a certain segment of frequency resource for communication. The decision may be made by a party originating the communication or the other party of the communication, or may be made by both parties of the communication through negotiation. As such, under the circumstance of out of the reach of the base station coverage, it can be ensured the user still achieves some applications by means of the UE having D2D communication function.
• D2D communication requires the UE to have a capability of using the same wireless access mode to receive and transmit D2D communication data.
• the UE transmitter used by the current LTE-TDD system employs SC-FDMA and the receiver employs OFDMA, so the UE does not have the above-mentioned capability and must be improved to enable D2D communication method advanced by the present invention.
• General application scenarios of D2D communication have the following features: a distance between UEs performing communications is very short (generally less than 30m), channel quality between UEs is relatively good, and applications require D2D communication to support high-rate transmission, and so on. Therefore, the present invention proposes that the same wireless access mode employed by the D2D communication is preferably OFDMA or SC-FDMA.
• Such preferred solution takes full considerations into both of the features of D2D communication and its compatibility with the current apparatus, so that the current UE receiver or transmitter can continue to be used without being improved and it is economical in terms of costs.
• the present invention provides a solution without modifying the radio-frequency circuit but only modifying a digital circuit.
• Fig.8 illustrates a block diagram of a transmitter according to the present invention.
• This transmitter can not only, like the current LTE-TDD UE, transmit SC-FDMA signals used by the uplink of cellular communication, but also transmit OFDMA signals used by D2D communication according to the present invention.
• the receiver of the UE needn't to be modified at all because the received D2D communication signal is the same OFDMA signal used by the downlink of cellular communication.
• the transmitter comprises a discrete Fourier transform module 81 configured to conduct discrete Fourier transform to an input signal to obtain a transformed signal;
• a modulation module 82 configured to map each symbol of the transformed signal to a plurality of sub-carriers and perform OFDM modulation to obtain a modulated signal
• a cyclic prefix insertion module 83 configured to insert a cyclic prefix to the modulated signal to obtain an inserted signal
• a digital- analog conversion module 84 configured to conduct digital-analog conversion to the inserted signal to obtain a to-be-transmitted signal;
• a transmission module 85 configured to transmit the to-be-transmitter signal; and
• a mode selection module 80 configured to select whether to bypass the discrete
• the mode selection module 80 chooses not to bypass the discrete Fourier transform module 81, whereupon the transmitter processes the input signal (a 0 , a 1; aM-i) in the same way as the current UE does, and the finally-transmitted signal is the SC-FDMA signal for uplink transmission of cellular communication.
• the model selection module 80 chooses to bypass the discrete Fourier transform module 81, whereupon the input signal is not subjected to the discrete Fourier transformation but directly mapped to carriers for OFDM modulation, and therefore the finally-transmitted signal is OFDMA signal.
• a power control module 86 may be preferably added between the cyclic prefix insertion module 83 and the digital-analog conversion module 84 to improve a peak-to-average ratio.
• the power control module 86 may conduct power control for a signal outputted by the cyclic prefix insertion module 83 so as to achieve an effect of reducing the peak-to-average ratio.
• the mode selection module 80 may conveniently conduct mode conversion according to the received instructions of the base station and switch the wireless access mode of the transmitted signal.
• a signal transmitting method provided by the present invention corresponding to the above transmitter is introduced hereunder. Since step features in the method correspond to structural features of the above transmitter, the method will be described briefly.
• the signal transmitting method comprises the following steps: b. conducting discrete Fourier transform to an input signal to obtain a transformed signal; c. mapping each symbol of the transformed signal to a plurality of sub-carriers and performing OFDM modulation to obtain a modulated signal; d. inserting a cyclic prefix to the modulated signal to obtain a inserted signal; e. conducting digital-analog conversion to the inserted signal to obtain a to-be-transmitted signal; f. transmitting the to-be-transmitter signal, wherein the method further comprises the following step before the step b: a. selecting whether to skip the step b and directly perform the step c.
• the method further comprises a step g of conducting power control of the inserted signal between the step d and the step e.
• the step a further comprises conducting selection according to received indication information sent by the base station.
• Fig.9 illustrates a block diagram of the receiver according to the present invention.
• This receiver can not only, like the current LTE-TDD UE, receive the OFDMA signal used by the downlink of the cellular communication, but also receive the SC-FDMA signal used by D2D communication according to the present invention.
• the transmitter of the UE needn't to be modified at all because the transmitted D2D communication signal is the same SC-FDMA signal used by the uplink of the cellular communication.
• the receiver comprises a reception module 91 configured to receive a wireless signal to obtain a received signal;
• An analog-digital conversion module 92 configured to conduct analog-digital conversion to the received signal to obtain an analog-digital-converted signal
• a cyclic prefix removal module 98 configured to remove the cyclic prefix from the analog-digital-converted signal to obtain a removed signal
• a demodulation module 94 configured to OFDM demodulate the removed signal to obtain a demodulated signal
• An equalization module 95 configured to conduct frequency domain equalization for the demodulated signal to obtain an equalized signal
• An inverse discrete Fourier transform module 96 configured to conduct inverse discrete Fourier transformation of the equalized signal to obtain an output signal
• An output selection module 97 configured to select whether to bypass the equalization module 95 and the inverse discrete Fourier transform module 96 to directly output the demodulated signal.
• the mode selection module 97 selects to bypass the equalization module 95 and the inverse discrete Fourier transform module 96 and directly outputs the demodulated signal, whereupon the receiver processes the input signal in the same way as the current UE does, and the finally- outputted signal (a 0 , a 1; aM-i) is the OFDMA signal for downlink transmission of cellular communication.
• the mode selection module 97 selects not to bypass the equalization module 95 and the inverse discrete Fourier transform module 96, whereupon the received signal, after being OFDM demodulated, conducts wireless channel frequency-selective compensation via the equalization module 95, and then is subjected to the inverse discrete Fourier transform, and therefore the finally- outputted signal (a 0 , a 1; a M -i) is the SC-FDMA signal.
• the mode selection module 97 may conveniently conduct mode conversion according to the received instructions of the base station and switch a processing mode of the received signal.
• a signal receiving method provided by the present invention corresponding to the above receiver is introduced hereunder. Since step features in the method correspond to structural features of the above receiver, the method will be described briefly.
• the signal receiving method comprises the following steps: m. receiving a wireless signal to obtain a received signal; n. conducting analog-digital conversion to the received signal to obtain a analog-digital-converted signal; o. removing the cyclic prefix from the analog-digital-converted signal to obtain a removed signal; p. performing OFDM demodulation to the removed signal to obtain a demodulated signal; q. conducting frequency domain equalization for the demodulated signal to obtain a equalized signal; r. conducting inverse discrete Fourier transformation to the equalized signal to obtain an output signal, wherein the method further comprises the following step before the step q: s. selecting whether to bypass the step q and the step r and directly outputting the demodulated signal.
• the step s performs selection according to the received indication information sent from the base station.

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• 2012
  • 2012-06-27 CN CN201210215565.2A patent/CN103517275B/zh active Active
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