WO2019030917A1 - User device and frequency offset estimation method - Google Patents

Abstract

This user device, which is used in a wireless communication system that supports D2D communication using transmission diversity, comprises: a receiving unit which receives a reference signal transmitted from one of a plurality of antenna ports of a transmission-side user device, in one or a plurality of first unit time sections within a predetermined time section; and a frequency offset estimation unit which estimates frequency offset on the basis of the reference signal received.

Description

User apparatus and frequency offset estimation method

The present invention relates to a user equipment in a wireless communication system.

In LTE (Long Term Evolution) and LTE's successor systems (for example, LTE-A (LTE-Advanced), NR (New Radio) (also referred to as 5G)), user apparatuses communicate directly with each other without passing through a radio base station. A D2D (Device to Device) technique to be performed is being studied.

D2D reduces traffic between a user apparatus and a base station, and enables communication between user apparatuses even when the base station becomes incapable of communication in a disaster or the like.

D2D is D2D discovery (also referred to as D2D discovery, also referred to as D2D discovery) for finding another user apparatus that can communicate, and D2D communication for direct communication between user apparatuses (D2D direct communication, D2D communication, direct communication between terminals) It is divided roughly into () and so on. In the following, D2D communication, D2D discovery and the like are simply referred to as D2D when not distinguished from each other. Further, a signal transmitted / received by D2D is called a D2D signal.

Although 3GPP (3rd Generation Partnership Project) refers to D2D as "sidelink", the more general term D2D is used in this specification. However, in the description of the embodiment described later, sidelink is also used as needed.

Further, in 3GPP, it is studied to realize V2X (Vehicle to Everything) by extending the above-mentioned D2D function, and specification is advanced. Here, V2X is a part of ITS (Intelligent Transport Systems), and as shown in FIG. 1, V2V (Vehicle to Vehicle), which means a form of communication performed between vehicles, is installed at the side of vehicles and roads. V2I (Vehicle to Infrastructure), which means the form of communication performed with the Road-Side Unit (RSU), V2N (Vehicle to Infrastructure, means the form of communication performed between the car and the mobile terminal of the driver. It is a generic name of V2P (Vehicle to Pedestrian) which means a form of communication performed between a Nomadic device and a mobile terminal between a car and a pedestrian.

In Rel-14 of LTE, specifications regarding some functions of V2X are made (eg, Non-Patent Document 1). In the specifications, Mode 3 and Mode 4 are defined for resource allocation for V2X communication to the user apparatus. In Mode 3, transmission resources are dynamically allocated by DCI (Downlink Control Information) sent from the base station to the user apparatus. In Mode 3, SPS (Semi Persistent Scheduling) is also possible. In Mode 4, the user apparatus autonomously selects transmission resources from the resource pool.

In V2X (especially V2V) where it is assumed that D2D communication between terminals moving at high speed is performed, the user equipment applies transmission diversity and performs transmission to improve the quality and reliability of communication. Is being considered. The transmit diversity scheme includes precoding vector switching (PVS) that switches a precoding vector in the time domain, cyclic delay diversity (CDD) that gives a cyclic shift amount to a transmission signal, and the like.

Further, in order to improve communication quality and reliability, it is also required to improve the accuracy of carrier frequency offset (CFO) estimation. Usually, the correlation between a plurality of demodulation reference signal (DMRS) symbols is used for CFO estimation. However, among terminals moving at high speed, the accuracy of CFO estimation using correlations between multiple DMRS symbols may be reduced.

Therefore, there has been proposed a CFO estimation method using DMRSs received in a single symbol (that is, a single DMRS symbol) without using the correlation between a plurality of DMRS symbols (for example, Non-Patent Document 2). However, when transmit diversity is applied, DMRS symbols may be transmitted from a plurality of antenna ports, for example, CFO using a single DMRS symbol when multiplexed by applying different cyclic shifts between ports. The estimation method can not be applied.

In view of the above, it is an object of the present invention to improve the accuracy of CFO estimation in a wireless communication system supporting D2D communication using transmit diversity.

According to the disclosed technology, a user equipment used in a wireless communication system supporting D2D communication using transmit diversity,
A receiver configured to receive a reference signal transmitted from one antenna port among a plurality of antenna ports of a transmitting user apparatus in one or more first unit time intervals within a predetermined time interval;
A frequency offset estimation unit that estimates a frequency offset based on the received reference signal;
A user device is provided.

According to the disclosed technology, it is possible to improve the accuracy of CFO estimation in a wireless communication system that supports D2D communication using transmit diversity.

It is a figure for demonstrating V2X. It is a figure for demonstrating D2D. It is a figure for demonstrating D2D. It is a figure which shows the structural example of the radio | wireless communications system which concerns on embodiment. FIG. 7 is a diagram showing a functional configuration relating to signal transmission in a specific example 1; FIG. 7 is a diagram showing a subframe configuration in a specific example 1. FIG. 7 is a diagram showing a functional configuration relating to signal reception in a first specific example. FIG. 18 is a diagram showing a functional configuration relating to signal transmission in a second specific example. It is a figure which shows the relationship between the moving speed of the user apparatus UE, and the transmission diversity system applied. It is a figure which shows an example of a function structure of the user apparatus UE which concerns on embodiment. It is a figure which shows an example of a function structure of base station 10 which concerns on embodiment. It is a figure which shows an example of the hardware constitutions of the base station 10 which concerns on embodiment, and the user apparatus UE.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the following embodiments. For example, although the radio communication system according to the present embodiment assumes a system based on LTE, the present invention is not limited to LTE, and is applicable to other systems. In the present specification and claims, “LTE” corresponds not only to a communication method corresponding to Release 8 or 9 of 3GPP, but also to Release 10, 11, 12, 13, or Release 14 or later of 3GPP. It is used in a broad sense including the 5th generation (5G, NR) communication method.

In addition, although the present embodiment mainly targets V2X, the technology according to the present embodiment is not limited to V2X, and can be widely applied to D2D in general. Also, "D2D" includes V2X as its meaning. Moreover, the term "D2D" is not limited to LTE, but refers to communication between terminals in general. In addition, although the present embodiment mainly targets “D2D communication”, the present invention is applicable not only to “D2D communication” but also to “D2D discovery”.

Also, unless otherwise specified, the "D2D signal" may be a data signal, an SCI, a discovery signal, or a combination of an SCI and a data signal. .

<Overview of D2D>
In the present embodiment, since D2D is a basic technology, first, an outline of D2D defined in LTE will be described. Also in V2X, it is possible to use the D2D technology described here, and the user apparatus in the present embodiment can transmit and receive D2D signals according to the technology.

As described above, D2D is broadly divided into "D2D discovery" and "D2D communication". For “D2D discovery”, as shown in FIG. 2A, a resource pool for a Discovery message is secured for each Discovery period, and the user apparatus transmits a Discovery message (discovery signal) in the resource pool. There are Type 1 and Type 2b in more detail. In Type 1, the user apparatus autonomously selects a transmission resource from the resource pool. In Type 2b, semi-static resources are allocated by higher layer signaling (for example, RRC signaling).

Also in “D2D communication”, as shown in FIG. 2B, resource pools for SCI (Sidelink Control Information) / data transmission are periodically secured. The user apparatus on the transmission side notifies the reception side of a data transmission resource (PSSCH resource pool) or the like by the SCI using a resource selected from the Control resource pool (PSCCH resource pool), and transmits data using the data transmission resource. There are Mode 1 and Mode 2 in more detail about "D2D communication". In Mode 1, resources are dynamically allocated by (E) PDCCH sent from the base station to the user apparatus. In Mode 2, the user apparatus autonomously selects transmission resources from the resource pool. The resource pool is notified by SIB or a predefined resource pool is used.

Also, as described above, Rel-14 has Mode 3 and Mode 4 in addition to Mode 1 and Mode 2. In Rel-14, it is possible to transmit SCI and data simultaneously (in one subframe) in resource blocks adjacent in the frequency direction. The SCI may be called SA (Scheduling Assignment).

In LTE, a channel used for "D2D discovery" is called PSDCH (Physical Sidelink Discovery Channel), and a channel for transmitting control information such as SCI in "D2D communication" is called PSCCH (Physical Sidelink Control Channel), and data The channel that transmits the channel is called PSSCH (Physical Sidelink Shared Channel). Also, PSCCH and PSSCH have a PUSCH-based structure, and are structured such that DMRS (Demodulation Reference Signal) is inserted.

<System configuration>
FIG. 3 is a diagram showing an example of configuration of a wireless communication system according to the present embodiment. As shown in FIG. 3, the wireless communication system according to the present embodiment includes a base station 10, a user apparatus UE1, and a user apparatus UE2. In FIG. 3, although the user apparatus UE1 intends the transmitting side and the user apparatus UE2 intends the receiving side, both the user apparatus UE1 and the user apparatus UE2 have both the transmitting function and the receiving function. Hereinafter, the user apparatus UE1 and the user apparatus UE2 will be simply described as "the user apparatus UE" when not particularly distinguished.

The user apparatus UE1 and the user apparatus UE2 illustrated in FIG. 3 respectively have the functions of cellular communication as the user apparatus UE in LTE (LTE in a meaning including 5G and NR in addition to existing LTE, and so on), and the above It has D2D functions including signal transmission and reception on the selected channel. Further, the user apparatus UE1 and the user apparatus UE2 have a function of executing the operation described in the present embodiment.

Also, the user apparatus UE may be any apparatus having the D2D function, but for example, the user apparatus UE may be a vehicle, a terminal held by a pedestrian, an RSU (UE type RSU having the UE function, etc.), etc. is there.

The signal waveform used by the user apparatus UE may be CP-OFDM (a waveform used in the existing LTE downlink) or DFT-S-OFDM (DFT-Spreading-OFDM) (a waveform used in the existing LTE uplink) Or other signal waveforms.

Moreover, the processing content of D2D transmission of the user apparatus UE is fundamentally the same as the processing content of uplink transmission in LTE (non-patent document 3). For example, when PVS (Precoding Vector Switching) is used as transmission diversity, the user apparatus UE scrambles and modulates a codeword of transmission data to generate complex-valued symbols, and the complex-valued symbols (transmission) are performed. Precoding is performed on the signal) while switching the precoding vector in the time domain. Then, precoded complex-valued symbols are mapped to resource elements, a transmission signal (eg, complex-valued time-domain SC-FDMA signal) is generated, and transmitted from each antenna port.

Note that precoding a signal with a precoding vector means multiplying the signal by the precoding vector, whereby a transmission beam can be formed. As in the time domain PVS, switching the precoding vector according to the passage of time corresponds to switching the direction of the transmission beam according to the passage of time. The PVS in the present embodiment is a PVS in the time domain. Also, the antenna port is a logical antenna port corresponding to one or more antenna elements. Also, "precoding vector" may be referred to as "precoding matrix". The "precoding vector" is a type of "precoding matrix".

Also, for example, when CDD (Cyclic Delay Diversity) is used as transmission diversity, the user apparatus UE scrambles and modulates the codeword of transmission data to generate complex-valued symbols, and the complex-valued symbols A different amount of cyclic shift is given to (transmission signal) for each antenna port. Then, the transmission signal given the cyclic shift amount is mapped to a resource element, a transmission signal (eg, complex-valued time-domain SC-FDMA signal) is generated, and transmitted from each antenna port. The “cyclic shift amount” may be referred to as “delay value”.

For base station 10, a function of cellular communication as base station 10 in LTE, and a function for enabling communication of user apparatus UE in the present embodiment (setting of DMRS mapping pattern, setting of transmission diversity scheme, etc. )have. Further, the base station 10 may be an RSU (eNB type RSUs having an eNB function).

In this embodiment, a method (specific example 1 to specific example 3) for improving the accuracy of CFO estimation when the user apparatus UE performs D2D communication using transmission diversity will be described.

In the first specific example, an example in which the transmitting user apparatus UE1 transmits a DMRS for CFO estimation from one antenna port among a plurality of antenna ports, and the receiving user apparatus UE2 estimates a CFO based on the DMRS for CFO estimation will be described. Do.

In the second embodiment, when CDD is used as transmission diversity, the transmitting user apparatus UE1 applies CDDs with small delay values to transmit DMRS from a plurality of antenna ports, and the receiving user apparatus UE2 transmits small DMDSs. An example of estimating CFO based on DMRS to which CDD is applied will be described.

In Example 3, an example will be described in which a CFO estimated based on DMRS transmitted together with SA is used as a CFO for a data signal.

Hereinafter, each specific example will be described in more detail.

<Specific example 1>
FIG. 4 is a diagram showing a functional unit (a functional unit included in the signal transmission unit 101 described later) regarding signal transmission of the transmission side user apparatus UE1 in the specific example 1. The user apparatus UE1 in the specific example 1 applies transmission diversity and transmits data signals (PSSCH) from a plurality of antenna ports. The technique applied to the data signal in the first embodiment may be applied to the control signal or the discovery signal.

As shown in FIG. 4, the functional unit includes a transmission diversity unit 11 and antenna ports 12 and 13. As an example of the transmission diversity unit 11, a precoder that precodes a transmission signal (multiplies a precoding vector) may be used. Although it is assumed that each antenna port corresponds to one antenna element (physical antenna element) in specific example 1 (the same applies to specific examples 2 to 3), each antenna port corresponds to a plurality of antenna elements. It may be done. Also, the number of antenna ports is not limited to two, and any number of antenna ports may be used.

The horizontal length of the horizontal rectangle for which the signal mapping is shown in FIG. 4 is one subframe (this may be called a slot or may be called a TTI), and the vertical length is one sub-frame. It is a career. Note that the length in the vertical direction may be a plurality of subcarriers or may be a transmission bandwidth. In FIG. 4, one subframe has 14 symbols, and the data signal and the DMRS are mapped as shown. One subframe is an example of “predetermined time interval”, and one symbol is an example of “unit time interval”. In the present embodiment, one subframe is used as the “predetermined time period”, and one symbol is used as the “unit time period”, but these are examples. For example, in the present embodiment, a time interval longer (or shorter) than one subframe is used as the "predetermined time interval", and a time interval longer than (or shorter than one symbol) is used as the "unit time interval". You may

In order to enable the receiving user equipment UE2 to estimate the CFO using the DMRS received in a single symbol, the transmitting user equipment UE1 transmits part of the DMRS from one antenna port 12; The other DMRS is transmitted from the two antenna ports 12, 13. The receiving user apparatus UE2 can estimate CFO using the DMRS transmitted from one antenna port. Thus, although DMRS transmitted from one antenna port is called "DMRS for CFO estimation" in order to make DMRS special from other antennas, DMRS for CFO estimation is transmitted except from one antenna port, The same signal as other DMRS may be used. One CFO estimation DMRS may be included in one subframe, and a plurality of CFO estimation DMRSs may be included. The symbol position of the CFO estimation DMRS may be determined in advance according to specifications or the like, may be set from the base station 10, or may be previously set.

The transmission diversity unit 11 receives a data signal and a DMRS as a transmission signal, and these signals are precoded and transmitted as radio signals from each antenna port. As an example, DMRS is a Zadoff-Chu sequence like LTE, and cyclic shift can generate a plurality of orthogonal DMRSs. The same applies to a non-precoded RS (reference signal) described later.

The transmission diversity unit 11 in specific example 1 multiplies the CFO estimation DMRS by a precoding vector determined in advance. The precoding vector to be multiplied by the CFO estimation DMRS may be predetermined according to the specification or the like, may be set from the base station 10, or may be preset. For example, precoding vector [1, 0] may be multiplied to transmit DMRS for CFO estimation from antenna port 12, and precoding vector [0] may be transmitted to transmit DMRS for CFO estimation from antenna port 13. , 1] may be multiplied. Alternatively, DMRS may be transmitted from the antenna port 12 with the number of antenna ports set to one. For other DMRSs, multiply the precoding vector (eg, [1, -1] / √ (2), [−1, 1] / √ (2), etc.) to transmit from multiple antenna ports Do. Also, the same precoding vector as PSCCH or PSSCH may be applied.

The CFO estimation DMRS may be transmitted when transmission diversity is applied and may not be transmitted when transmission diversity is not applied. Also, the CFO estimation DMRS may be transmitted when transmission diversity is applied and when a predetermined condition is satisfied.

For example, the CFO estimation DMRS may be transmitted when transmission diversity is applied and when the transmitting user apparatus UE1 explicitly instructs the receiving user apparatus UE2 by the SA.

For example, the CFO estimation DMRS may be transmitted according to the moving speed of the transmitting user apparatus UE1 or the receiving user apparatus UE2 when transmission diversity is applied. For example, when the moving speed is equal to or less than the threshold, the CFO estimation DMRS may not be transmitted, and the receiving user apparatus UE2 may estimate the CFO using the correlation among a plurality of DMRS symbols. On the other hand, when the moving speed is higher than the threshold, the CFO estimation DMRS may be transmitted, and the receiving user apparatus UE2 may estimate the CFO based on the CFO estimation DMRS.

For example, when transmit diversity is applied, CFO estimation DMRS may be transmitted according to a modulation and coding scheme (MCS) of a data signal. For example, when the MCS is equal to or less than a predetermined MCS, the CFO estimation DMRS may not be transmitted, and the receiving user apparatus UE2 may estimate the CFO using the correlation among a plurality of DMRS symbols. On the other hand, when the MCS is higher than the predetermined MCS, the CFO estimation DMRS may be transmitted, and the receiving user apparatus UE2 may estimate the CFO based on the CFO estimation DMRS.

For example, the CFO estimation DMRS may be transmitted according to the applied transmission diversity when the transmission diversity is applied. For example, when a small delay CDD is applied, the CFO estimation DMRS may not be transmitted. The receiving user apparatus UE2 regards DMRSs transmitted at the same timing from a plurality of antenna ports as a single DMRS and receives the DMRS in a single symbol, as described in the second embodiment described later. The CFO estimation method using can be applied.

In addition, as shown in FIG. 5, the transmission diversity unit 11 includes a predetermined number of data symbols before and after the CFO estimation DMRS (referred to as “peripheral data symbol”) and a predetermined number of data symbols before and after another DMRS. Different transmission diversity schemes may be applied to the peripheral data symbols and the non-peripheral data symbols (hereinafter referred to as “non-peripheral data symbols”). In addition, the transmission diversity unit 11 may apply different parameters of the same transmission diversity scheme to the peripheral data symbol and the non-peripheral data symbol. Which data symbol is used as the peripheral data symbol and which data symbol is used as the non-peripheral data symbol may be determined in advance according to the specification, etc., may be set from the base station 10, or may be previously set. The user apparatus may optionally select and notify the receiving user apparatus using PSCCH or the like. Also, parameters of the transmit diversity scheme or the transmit diversity scheme applied to the peripheral data symbol and the non-peripheral data symbol may be determined in advance according to the specification, etc., or may be set from the base station 10 or are preset. It is also good.

For example, the transmission diversity unit 11 may multiply the peripheral data symbols by the precoding vector to be applied to the CFO estimation DMRS, and may multiply the non-peripheral data symbols by the precoding vector to be applied to other DMRSs. .

For example, the transmission diversity unit 11 may change the delay value of CDD applied to peripheral data symbols and the delay value of CDD applied to non-peripheral data symbols.

For example, the transmission diversity unit 11 may apply SFBC to non-peripheral data symbols without applying SFBC (Space Frequency Block Coding) to neighboring data symbols.

FIG. 6 is a diagram illustrating a functional unit (functional unit included in the signal receiving unit 102 described later) regarding signal reception and CFO estimation of the reception-side user apparatus UE2 in the specific example 1. The user apparatus UE2 in the present embodiment receives the CFO estimation DMRS transmitted by the transmitting user apparatus UE1 as described above, and estimates the CFO based on the CFO estimation DMRS.

The received signal is converted from the time domain to the frequency domain by DFT (Discrete Fourier Transform) 21, and the signal separation unit 22 extracts a signal addressed to the own user apparatus UE 2. When the frequency offset estimation unit 23 receives the CFO estimation DMRS, the frequency offset estimation unit 23 estimates the CFO based on the CFO estimation DMRS. As described above, when transmission diversity is not applied or when a predetermined condition is not satisfied, the CFO estimation DMRS may not be transmitted. In this case, the frequency offset estimation unit 23 can estimate CFO using the correlation between a plurality of DMRS symbols in one subframe. The frequency offset compensation unit 24 compensates for the CFO estimated in the frequency offset estimation unit 23, and the demodulation and decoding unit 25 performs channel estimation based on the DMRS to demodulate and decode the original data signal.

When different transmission diversity schemes or different parameters of the same transmission diversity scheme are used for the peripheral data symbol and the non-peripheral data symbol, the demodulation and decoding unit 25 also uses the CFO estimation DMRS as data according to the applicable transmission diversity scheme. It can be used for demodulation.

For example, when different precoding vectors are multiplied to the peripheral data symbol and the non-peripheral data symbol, and the RS that is not precoded to the DMRS except for the DMRS for CFO estimation is used, the demodulation and decoding unit 25 calculates the peripheral data symbol. At the time of demodulation, DMRSs (four DMRSs in FIG. 5) including DMRSs for CFO estimation can be used. In addition, at the time of demodulation of non-peripheral data symbols, the demodulation and decoding unit 25 can use DMRSs (three DMRSs in FIG. 5) excluding the CFO estimation DMRSs.

For example, when the delay value of CDD applied to peripheral data symbols and the delay value of CDD applied to non-peripheral data symbols are changed, the demodulation and decoding unit 25 performs DMRS for CFO estimation at the time of demodulation of peripheral data symbols. Can be used. In addition, at the time of demodulation of non-peripheral data symbols, the demodulation and decoding unit 25 can use DMRSs (three DMRSs in FIG. 5) excluding the CFO estimation DMRSs.

For example, when SFBC is not applied to neighboring data symbols, SFBC is applied to non-neighboring data symbols, and RSs not precoded in DMRS other than DMRS for CFO estimation are used for demodulation and decoding. The unit 25 can use DMRSs (four DMRSs in FIG. 5) including DMRSs for CFO estimation when demodulating peripheral data symbols. In addition, at the time of demodulation of non-peripheral data symbols, the demodulation and decoding unit 25 can use DMRSs (three DMRSs in FIG. 5) excluding the CFO estimation DMRSs.

<Specific example 2>
FIG. 7 is a diagram showing a functional unit (a functional unit included in the signal transmission unit 101 described later) related to signal transmission of the transmission side user apparatus UE1 in the specific example 2. The user apparatus UE1 in the specific example 2 transmits a data signal (PSSCH) from a plurality of antenna ports using CDD as a transmission diversity scheme. The technique applied to the data signal in the second embodiment may be applied to the control signal or the discovery signal.

In order to enable the receiving user equipment UE2 to estimate the CFO using the DMRS received in a single symbol, the transmitting user equipment UE1 applies a CDD with small delay value to the DMRS with two antennas Transmit from ports 12 and 13. The small delay value is set within the range [0, x] (y> x) smaller than the range [0, y] of the delay value of CDD used for normal data communication including communication with a base station. Mean the delayed value. Alternatively, it may be a specific delay value x. The upper limits x and y of the delay value may be determined in advance according to specifications, etc., may be set from the base station 10, or may be set in advance. The receiving side user apparatus UE2 may apply a CFO estimation method using DMRSs received in a single symbol, regarding multiple DMRSs transmitted from the multiple antenna ports at the same timing as a single DMRS. it can.

A small delay value in the range [0, x] may be used when a predetermined condition is satisfied, and a delay value in the range [0, y] is used when the predetermined condition is not satisfied. It is also good.

For example, small delay values in the range [0, x] may be used according to the moving speed of the transmitting user apparatus UE1 or the receiving user apparatus UE2. For example, when the moving speed is equal to or less than the threshold, a delay value in the range [0, y] may be used, and the receiving user apparatus UE2 estimates CFO using correlation among a plurality of DMRS symbols. It is also good. For example, when the moving speed is higher than the threshold, a small delay value in the range [0, x] may be used, and the receiving user apparatus UE2 estimates the CFO using DMRS received in a single symbol. The CFO may be estimated according to

For example, small delay values in the range [0, x] may be used depending on the MCS of the data signal. For example, when the MCS is equal to or less than a predetermined MCS, delay values in the range [0, y] may be used, and the receiving user apparatus UE2 estimates CFO using correlations between multiple DMRS symbols. May be For example, when the MCS is higher than a predetermined MCS, a small delay value in the range [0, x] may be used, and the receiving user apparatus UE2 estimates CFO using DMRS received in a single symbol. The CFO may be estimated according to the method.

In addition, it is determined by the receiving user apparatus UE2 whether the receiving user apparatus UE2 estimates the CFO using the correlation between a plurality of DMRS symbols or the CRS using the DMRS received in a single symbol. And may be instructed by the SA from the transmitting user equipment UE1.

The functional unit of the reception-side user apparatus UE2 is configured as in FIG. The received signal is converted from the time domain to the frequency domain by the DFT 21, and the signal separation unit 22 extracts a signal addressed to the own user apparatus UE 2. When a small delay value in the range [0, x] is used, the frequency offset estimation unit 23 regards a plurality of DMRSs transmitted at the same timing from a plurality of antenna ports as a single DMRS, The CFO is estimated according to the CFO estimation method using DMRS received in a single symbol. For example, if the moving speed is equal to or less than a threshold or if the MCS is equal to or less than a predetermined MCS, the frequency offset estimation unit 23 may estimate CFO using the correlation between a plurality of DMRS symbols in one subframe. . The frequency offset compensation unit 24 compensates for the CFO estimated in the frequency offset estimation unit 23, and the demodulation and decoding unit 25 performs channel estimation based on the DMRS to demodulate and decode the original data signal.

Example 3
The transmission side user apparatus UE1 in the specific example 3 applies transmission diversity to transmit SAs from a plurality of antenna ports. The application of transmission diversity in the transmitting user apparatus UE1 and the SFO estimation in the receiving user apparatus UE2 can be performed in the same manner as in the first example or the second example. The receiving user apparatus UE2 also uses the SFO estimated at SA as a CFO for the data signal. The SFO estimated in SA may be applied to the data signal associated with the SA as shown in FIG. 2B, and may be applied to the data signal in a predetermined period after receiving the SA. .

For example, as in Example 2, small delay values in the range [0, x] may be used for SFO estimation in SA. Further, when the predetermined condition as shown in the specific example 2 is satisfied (for example, when the moving speed is equal to or less than the threshold, the MCS is equal to or less than the predetermined MCS), the range [0,0 Delay values within y] may be used. Furthermore, for example, if the PSD (Power Spectral Density) of the data signal is equal to the PSD of SA and the MCS of the data signal is less than or equal to the MCS of SA, then for SFO estimation in SA, within the range [0, y]. A delay value of may be used. The predetermined condition of whether a small delay value in the range [0, x] is used or a delay value in the range [0, y] is used may be determined in advance by a specification or the like, and is set from the base station 10 It may be done or it may be preset.

Also, for example, when transmission diversity is applied, and when the transmitting user apparatus UE1 instructs in SA, SFO estimation in SA may be applied to data signals. The indication in SA may be an explicit indication or an implicit indication. For example, if a small delay value in the range [0, x] is used in SA, SFO estimation in SA may be treated as applying to the data signal as well. For example, if the PSD of the data signal is equal to the PSD of the SA and the MCS of the data signal is less than or equal to the MCS of the SA, then the SFO estimation in the SA may be treated as applying to the data signal. However, when the moving speed is equal to or less than the threshold, the receiving user apparatus UE2 may estimate CFO using the correlation among a plurality of DMRS symbols, for example, when the MCS of the data signal is equal to or less than a predetermined MCS. It is not necessary to apply the SFO estimate at SA to the data signal as it can.

<Others>
In each of the specific examples 1 to 3, whether or not to apply transmission diversity and the type of transmission diversity in the case of application may be determined according to the moving speed of the user apparatus UE.

FIG. 8 is a diagram showing the relationship between the moving speed of the user apparatus UE and the transmission diversity scheme to be applied. For example, as shown in Example # 1, when the moving speed of the user apparatus UE is higher than the threshold, transmission diversity may not be applied. When the moving speed of the user apparatus UE is equal to or less than the threshold value, transmission diversity scheme # 1 or transmission diversity scheme # 2 may be applied, and transmission diversity may not be applied. Also, for example, as shown in Example # 2, when the moving speed of the user apparatus UE is higher than the threshold, transmission diversity scheme # 1 may be applied, and transmission diversity may not be applied. When the moving speed of the user apparatus UE is equal to or less than the threshold value, transmission diversity scheme # 1 or transmission diversity scheme # 2 may be applied, and transmission diversity may not be applied.

The moving speed threshold, whether or not to apply transmission diversity, and the type of transmission diversity when applied may be determined by the specification, etc., may be set by the base station 10, or may be preset. Good. Also, a plurality of patterns such as example # 1 and example # 2 shown in FIG. 8 may be determined by the specification or the like, may be set by the base station 10, or may be preset.

Furthermore, in each of the specific examples 1 to 3, the user apparatus UE1 may notify the user apparatus UE2 of the presence / absence of application of transmission diversity to the data signal (PSSCH) using SCI (PSCCH).

<Device configuration>
Next, a functional configuration example of the user apparatus UE and the base station 10 that execute the processing operations described above will be described. The user apparatus UE and the base station 10 may have all the functions of Example 1, Example 2, Example 3, and others, or may have the function of any one or more of the examples. Good.

<User device>
FIG. 9 is a diagram illustrating an example of a functional configuration of the user apparatus UE. As shown in FIG. 9, the user apparatus UE includes a signal transmission unit 101, a signal reception unit 102, and a setting information storage unit 103. The functional configuration shown in FIG. 9 is merely an example. As long as the operation according to the present embodiment can be performed, the names of the function classifications and the function parts may be any names.

The signal transmission unit 101 creates a transmission from transmission data, and wirelessly transmits the transmission signal. The signal reception unit 102 wirelessly receives various signals, and acquires higher layer signals from the received physical layer signals. The signal transmission unit 101 and the signal reception unit 102 both include a D2D function and a cellular communication function. The signal transmission unit 101 includes the function of executing the signal transmission operation described in the specific examples 1 to 3 and the others, and the signal reception unit 102 performs the signal reception operation described in the specific examples 1 to 3 and the others. Including features.

The setting information storage unit 103 stores various setting information received from the base station 10 by the signal receiving unit 102 and setting information set in advance. For example, the setting information storage unit 103 is configured to store the setting of the DMRS mapping pattern, the setting of the transmission diversity scheme, and the like.

The signal transmission unit 101 is configured to apply transmission diversity to the D2D signal and transmit the D2D signal. For example, the signal transmission unit 101 may transmit the DMRS for CFO estimation from one antenna port, and may transmit the DMRS from a plurality of antenna ports by applying CDD with a small delay value. The signal transmission unit 101 may transmit control information including information used for transmission diversity of the D2D signal.

The signal receiving unit 102 is configured to receive the D2D signal and estimate and compensate for the CFO. For example, when receiving the CFO estimation DMRS, the signal receiving unit 102 may estimate the CFO using the CFO estimation DMRS received in a single symbol. For example, when receiving a DMRS to which a CDD with a small delay value is applied, the signal reception unit 102 may estimate the CFO using the DMRS received in a single symbol. Also, the signal receiving unit 102 can estimate CFO using correlations between multiple DMRS symbols.

<Base station 10>
FIG. 10 is a diagram showing an example of a functional configuration of the base station 10. As shown in FIG. As shown in FIG. 10, the base station 10 includes a signal transmission unit 201, a signal reception unit 202, a setting information storage unit 203, and an NW communication unit 204. The functional configuration shown in FIG. 10 is merely an example. As long as the operation according to the present embodiment can be performed, the names of the function classifications and the function parts may be any names.

The signal transmission unit 201 includes a function of generating a signal to be transmitted to the user apparatus UE side and wirelessly transmitting the signal. The signal receiving unit 202 includes a function of receiving various signals transmitted from the user apparatus UE and acquiring, for example, higher layer information from the received signals.

The signal transmission unit 201 includes the function of executing the operation of transmitting a signal (eg, setting information) to the user apparatus UE described in the specific examples 1 to 3 and others.

The setting information storage unit 203 stores various setting information to be transmitted to the user apparatus UE, various setting information received from the user apparatus UE, and setting information set in advance. The NW communication unit 204 executes, for example, information communication between base stations.

<Hardware configuration>
The block diagrams (FIGS. 9 to 10) used in the description of the above embodiment show blocks in functional units. These functional blocks (components) are realized by any combination of hardware and / or software. Moreover, the implementation means of each functional block is not particularly limited. That is, each functional block may be realized by one device physically and / or logically connected to a plurality of elements, or directly and two or more physically and / or logically separated devices. And / or indirectly (for example, wired and / or wirelessly) connected, and may be realized by the plurality of devices.

Also, for example, both the user apparatus UE and the base station 10 in an embodiment of the present invention may function as a computer that performs the process according to the present embodiment. FIG. 11 is a diagram showing an example of the hardware configuration of the user apparatus UE and the base station 10 according to the present embodiment. Even if the above-mentioned user apparatus UE and base station 10 are physically configured as a computer apparatus including processor 1001, memory 1002, storage 1003, communication apparatus 1004, input apparatus 1005, output apparatus 1006, bus 1007, etc. Good.

In the following description, the term "device" can be read as a circuit, a device, a unit, or the like. The hardware configurations of the user apparatus UE and the base station 10 may be configured to include one or more devices indicated by 1001 to 1006 shown in the figure, or may be configured without including some devices. May be

Each function in the user apparatus UE and the base station 10 causes the processor 1001 to perform an operation by reading predetermined software (program) on hardware such as the processor 1001, the memory 1002, and the like, and communication by the communication apparatus 1004; And by controlling the reading and / or writing of data in the storage 1003.

The processor 1001 operates, for example, an operating system to control the entire computer. The processor 1001 may be configured by a central processing unit (CPU: Central Processing Unit) including an interface with a peripheral device, a control device, an arithmetic device, a register, and the like.

Also, the processor 1001 reads a program (program code), a software module or data from the storage 1003 and / or the communication device 1004 to the memory 1002, and executes various processing according to these. As a program, a program that causes a computer to execute at least a part of the operations described in the above embodiments is used. For example, the signal transmission unit 101, the signal reception unit 102, and the setting information storage unit 103 of the user apparatus UE illustrated in FIG. 9 may be realized by a control program stored in the memory 1002 and operated by the processor 1001. Further, for example, the signal transmission unit 201, the signal reception unit 202, the setting information storage unit 203, and the NW communication unit 204 of the base station 10 shown in FIG. 10 are stored in the memory 1002 and controlled by the processor 1001. It may be realized by a program. The various processes described above have been described to be executed by one processor 1001, but may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The program may be transmitted from the network via a telecommunication line.

The memory 1002 is a computer readable recording medium, and includes, for example, at least one of a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electrically Erasable Programmable ROM), and a RAM (Random Access Memory). It may be done. The memory 1002 may be called a register, a cache, a main memory (main storage device) or the like. The memory 1002 can store a program (program code), a software module, and the like that can be executed to execute the process according to the embodiment of the present invention.

The storage 1003 is a computer readable recording medium, and for example, an optical disc such as a CD-ROM (Compact Disc ROM), a hard disc drive, a flexible disc, a magneto-optical disc (eg, a compact disc, a digital versatile disc, a Blu-ray A (registered trademark) disk, a smart card, a flash memory (for example, a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, and the like may be used. The storage 1003 may be called an auxiliary storage device. The above-mentioned storage medium may be, for example, a database including the memory 1002 and / or the storage 1003, a server or any other suitable medium.

The communication device 1004 is hardware (transmission / reception device) for performing communication between computers via a wired and / or wireless network, and is also called, for example, a network device, a network controller, a network card, a communication module, or the like. For example, the signal transmission unit 101 and the signal reception unit 102 of the user apparatus UE may be realized by the communication apparatus 1004. Also, the signal transmission unit 201, the signal reception unit 202, and the NW communication unit 204 of the base station 10 may be realized by the communication device 1004.

The input device 1005 is an input device (for example, a keyboard, a mouse, a microphone, a switch, a button, a sensor, and the like) that receives an input from the outside. The output device 1006 is an output device (for example, a display, a speaker, an LED lamp, etc.) that performs output to the outside. The input device 1005 and the output device 1006 may be integrated (for example, a touch panel).

Also, each device such as the processor 1001 and the memory 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured by a single bus or may be configured by different buses among the devices.

Also, each of the user apparatus UE and the base station 10 includes a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), etc. It may be configured to include hardware, and part or all of each functional block may be realized by the hardware. For example, processor 1001 may be implemented in at least one of these hardware.

<Summary of Embodiment>
As described above, according to the present embodiment, a user apparatus used in a wireless communication system supporting D2D communication using transmit diversity, which is one or more than a plurality of A receiver configured to receive a reference signal transmitted from one of a plurality of antenna ports of a transmitting user apparatus in one unit time interval, and a frequency offset to estimate a frequency offset based on the received reference signal A user device is provided having an estimation unit.

Since the above user equipment can receive DMRS for CFO estimation from one antenna port even when transmission diversity is used, the accuracy of CFO estimation can be improved between terminals moving at high speed. it can. In addition, in other DMRSs other than the CFO estimation DMRS, diversity gain can be obtained, and communication quality and reliability can be improved.

Also, the CFO estimation DMRS may be transmitted when transmission diversity is applied and / or when a predetermined condition is satisfied. In other words, when transmission diversity is not applied and / or when predetermined conditions are not satisfied, DMRSs are transmitted from the multiple antenna ports at the same timing. Thus, the diversity gain can be increased.

Further, the receiving unit may further receive reference signals transmitted from a plurality of antenna ports of the transmitting user apparatus in one or more second unit time intervals within the predetermined time interval. Transmission diversity different between predetermined number of unit time intervals before and after the one or more first unit time intervals and predetermined number of unit time intervals before and after the one or more second unit time intervals Schemes, or different parameters of the same transmit diversity scheme may be used.

According to the above configuration, data symbols can be received in the same manner as in the CFO estimation DMRS in time intervals before and after the CFO estimation DMRS, and diversity gain can be obtained in time intervals before and after another DMRS. Can.

Further, according to the present embodiment, the user equipment used in a wireless communication system supporting D2D communication using cyclic delay diversity, in one or more unit time intervals within a predetermined time interval, A receiver for receiving reference signals transmitted from a plurality of antenna ports of a transmitting user apparatus, and a frequency offset estimation unit for estimating a frequency offset based on the reference signals, and a cyclic circuit used for the reference signals A user apparatus is provided, characterized in that the upper limit of the delay value for delay diversity is smaller than the delay value for cyclic delay diversity used for communication with the base station or the upper limit thereof.

The above user equipment can regard multiple DMRSs transmitted at the same timing from multiple antenna ports as a single DMRS, in order to receive the DMRS to which the CDD with small delay value is applied. Therefore, the CFO estimation method using DMRS received in a single symbol can be applied to improve the accuracy of CFO estimation between terminals moving at high speed. There is a possibility that diversity gain may be reduced by reducing the delay value of CDD, but the same DMRS can be used in one subframe even if transmission diversity is used or transmission diversity is not used. An arrangement can be used.

The frequency offset estimation unit may use a frequency offset estimated based on a reference signal transmitted together with control information as a frequency offset for the data signal.

The above user equipment can simplify CFO estimation by applying the CFO estimated in the control information also to the data signal. Further, even when transmission diversity is used or transmission diversity is not used, the same DMRS arrangement can be used in one subframe in which a data signal is transmitted.

<Supplement of embodiment>
Although the embodiments of the present invention have been described above, the disclosed invention is not limited to such embodiments, and those skilled in the art should understand various modifications, modifications, alternatives, replacements, and the like. I will. Although specific numerical examples are used to facilitate understanding of the invention, unless otherwise noted, those numerical values are merely examples and any appropriate values may be used. The division of items in the above description is not essential to the present invention, and the items described in two or more items may be used in combination as necessary, and the items described in one item may be used in another item. It may be applied to the matters described in (unless contradictory). The boundaries of the functional units or processing units in the functional block diagram do not necessarily correspond to the boundaries of physical parts. The operations of multiple functional units may be physically performed by one component, or the operations of one functional unit may be physically performed by multiple components. With regard to the processing procedures described in the embodiment, the order of processing may be changed as long as there is no contradiction. Although the user apparatus UE and the base station 10 have been described using functional block diagrams for the convenience of the processing description, such an apparatus may be realized in hardware, software or a combination thereof. The software operated by the processor of the user apparatus UE according to the embodiment of the present invention and the software operated by the processor of the base station 10 according to the embodiment of the present invention are random access memory (RAM), flash memory, read only It may be stored in memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server or any other suitable storage medium.

In addition, notification of information is not limited to the aspect / embodiment described herein, and may be performed by other methods. For example, notification of information may be physical layer signaling (for example, Downlink Control Information (DCI), Uplink Control Information (UCI)), upper layer signaling (for example, Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling, It may be implemented by broadcast information (MIB (Master Information Block), SIB (System Information Block), other signals, or a combination thereof. Also, RRC signaling may be called an RRC message, for example, RRC Connection setup (RRC Con ection Setup) message, RRC connection reconfiguration (it may be a RRC Connection Reconfiguration) message.

Each aspect / embodiment described in the present specification is LTE (Long Term Evolution), LTE-A (LTE-Advanced), SUPER 3G, IMT-Advanced, 4G, 5G, FRA (Future Radio Access), W-CDMA (Registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, UWB (Ultra-Wide Band), The present invention may be applied to a system utilizing Bluetooth (registered trademark), other appropriate systems, and / or an advanced next-generation system based on these.

As long as there is no contradiction, the processing procedure, sequence, flow chart, etc. of each aspect / embodiment described in this specification may be reversed. For example, for the methods described herein, elements of the various steps are presented in an exemplary order and are not limited to the particular order presented.

The specific operation supposed to be performed by the base station 10 in this specification may be performed by the upper node in some cases. In a network configured of one or more network nodes having a base station 10, various operations performed for communication with the user apparatus UE may be performed by the base station 10 and / or the base station 10 other than the base station 10. It will be clear that it may be performed by other network nodes, such as but not limited to MME or S-GW etc. Although the case where one network node other than the base station 10 has been described above is illustrated, it may be a combination of a plurality of other network nodes (for example, MME and S-GW).

Each aspect / embodiment described in this specification may be used alone, may be used in combination, and may be switched and used along with execution.

The user equipment UE may be a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communication device, a remote communication device, a mobile subscriber station, an access terminal, a mobile terminal, by a person skilled in the art. It may also be called a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable term.

Base station 10 may also be referred to by those skilled in the art with NB (Node B), eNB (enhanced Node B), Base Station, gNB, or some other suitable terminology.

The terms "determining", "determining" as used herein may encompass a wide variety of operations. "Judgment", "decision" are, for example, judging, calculating, calculating, processing, processing, deriving, investigating, looking up (for example, a table) (Searching in a database or another data structure), ascertaining may be regarded as “decision”, “decision”, etc. Also, "determination" and "determination" are receiving (e.g. receiving information), transmitting (e.g. transmitting information), input (input), output (output), access (Accessing) (for example, accessing data in a memory) may be regarded as “judged” or “decided”. Also, "judgement" and "decision" are to be considered as "judgement" and "decision" that they have resolved (resolving), selecting (selecting), choosing (choosing), establishing (establishing), etc. May be included. That is, "judgment" "decision" may include considering that some action is "judged" "decision".

As used herein, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

As long as "include", "including", and variations thereof are used in the present specification or claims, these terms are as used in the term "comprising". It is intended to be comprehensive. Further, it is intended that the term "or" as used herein or in the claims is not an exclusive OR.

Throughout the present disclosure, when articles are added by translation, such as, for example, a, an, and the in English, these articles are not clearly indicated by the context: May contain more than one.

Although the present invention has been described above in detail, it is obvious for those skilled in the art that the present invention is not limited to the embodiments described herein. The present invention can be implemented as modifications and changes without departing from the spirit and scope of the present invention defined by the description of the claims. Therefore, the description in the present specification is for the purpose of illustration and does not have any limiting meaning on the present invention.

UE User Equipment 101 Signal Transmission Unit 102 Signal Reception Unit 103 Configuration Information Storage Unit 10 Base Station 201 Signal Transmission Unit 202 Signal Reception Unit 203 Configuration Information Storage Unit 204 NW Communication Unit 1001 Processor 1002 Memory 1003 Storage 1003 Storage Device 1005 Communication Device 1005 Input Device 1006 Output apparatus

Claims (5)

1. A user equipment for use in a wireless communication system supporting D2D communication using transmit diversity, comprising:
   A receiver configured to receive a reference signal transmitted from one antenna port among a plurality of antenna ports of a transmitting user apparatus in one or more first unit time intervals within a predetermined time interval;
   A frequency offset estimation unit that estimates a frequency offset based on the received reference signal;
   User equipment having
2. The receiving unit further receives reference signals transmitted from a plurality of antenna ports of the transmitting user apparatus in one or more second unit time intervals within the predetermined time interval,
   Different transmission diversity schemes in a predetermined number of unit time intervals before and after the one or more first unit time intervals and a predetermined number of unit time intervals before and after the one or more second unit time intervals The user equipment according to claim 1, characterized in that different parameters of the same or a same transmit diversity scheme are used.
3. A user equipment for use in a wireless communication system supporting D2D communication using cyclic delay diversity, comprising:
   A receiver configured to receive reference signals transmitted from a plurality of antenna ports of a transmitting user apparatus in one or more unit time intervals within a predetermined time interval;
   A frequency offset estimation unit that estimates a frequency offset based on the reference signal;
   Have
   A user apparatus characterized in that an upper limit of a delay value for cyclic delay diversity used for the reference signal is smaller than an upper limit of a delay value for cyclic delay diversity used for communication with a base station.
4. The said frequency offset estimation part uses the frequency offset estimated based on the reference signal transmitted with control information as a frequency offset with respect to a data signal, It is characterized by the above-mentioned. User equipment as described.
5. A method for frequency offset estimation in a user equipment used in a wireless communication system supporting D2D communication using transmit diversity, comprising:
   Receiving a reference signal transmitted from one antenna port among a plurality of antenna ports of the transmitting user apparatus in one or more first unit time intervals within a predetermined time interval;
   Estimating a frequency offset based on the received reference signal;
   Method of estimating frequency offset with

Images