WO2019138561A1 - Radio base station and user equipment - Google Patents

Abstract

The radio base station transmits first and second radio signals, which include a common narrowband primary synchronization signal (NPSS) and narrowband secondary synchronization signal (NSSS), by using first and second carrier frequencies, respectively, and in a mutually synchronized manner. The user equipment detects the NPSS upon receipt of the first and/or the second radio signal, and detects the NSSS on the basis of a correlation between the first radio signal received from the first carrier frequency and the second radio signal received from the second carrier frequency.

Description

Radio base station and user terminal

The present invention relates to a radio base station and a user terminal.

In Internet-of-Things (IoT), various devices such as control devices, sensors, actuators or meters are connected to the Internet.

In the 3rd Generation Partnership Project (3GPP), in order to realize IoT, a wireless system of Machine-Type Communications (MTCs) capable of connecting a device to the Internet at low cost using a license band or an unlicensed band is considered. For example, in 3GPP, a Narrowband (NB) -IoT radio interface for efficiently multiplexing IoT traffic is defined based on the radio interface of Long Term Evolution (LTE).

In NB-IoT, the number of antennas mounted on the UE may be limited in order to realize low power consumption and low cost of the user equipment (UE). For example, when the number of antennas of the UE is one, the reception antenna diversity effect can not be expected. Therefore, for example, there is a possibility that the detection success rate in the UE of the synchronization signal transmitted by the radio base station may decrease.

One aspect of the present disclosure is to provide a radio base station and a user terminal that can improve the detection success rate of synchronization signals.

A wireless base station according to an aspect of the present disclosure includes: a transmitting unit that transmits a first wireless signal and a second wireless signal according to transmission timing synchronized at different frequencies; the first wireless signal; And a setting unit configured to set a synchronization signal common to the two radio signals to each of the first radio signal and the second radio signal.

According to one aspect of the present disclosure, it is possible to improve the detection success rate of the synchronization signal.

It is a figure which shows the radio | wireless interface of MTC prescribed | regulated by 3GPP. It is a figure which shows the example of the narrow band carrier assumed to use by NB-IoT. FIG. 6 illustrates an example of multiplexing of NPSS and NSSS into a radio frame. It is a figure which shows the example of the resource mapping of NPSS. It is a figure showing an example of resource mapping of NSSS. It is a figure which shows the example of the production | generation method of NPSS. It is a figure which shows the example of the production | generation method of NSSS. It is a figure which shows the transmission method of PVS transmission diversity by 2 transmitting antennas in LTE. It is a figure which shows the example which applies PVS transmission diversity to NPSS and NSSS. It is a figure which shows the example of the detection process of NPSS and NSSS which concern on this Embodiment. It is a figure which shows the example of the detection process of NPSS and NSSS which concerns on modification 1. FIG. FIG. 18 is a diagram showing an example of detection processing of the NPSS and the NSSS according to the second modification. FIG. 18 is a diagram showing an example of an NPSS and NSSS detection process according to a third modification. FIG. 18 is a diagram illustrating an example of an NPSS and NSSS detection process according to a fourth modification. It is a figure which shows the example of a detection process of cell ID in UE. FIG. 5 is a diagram illustrating autocorrelation of a received signal delayed by one FTT block interval. It is a figure which shows the example of the hardware constitutions of the wireless base station which concerns on this indication, and a user terminal.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the main radio interface of the MTC defined in 3GPP will be described with reference to FIG.

Category 1 is a wireless interface that supports system bandwidths from a minimum of 1.4 MHz to a maximum of 20 MHz.

Category M1 (eMTC) is a radio narrowed to 6 resource blocks (RB: Resource Block) (= 1.08 MHz), which have the same transmission bandwidth as LTE synchronization signals and physical broadcast channels (PBCH: Phjysical Broadcast Channel) It is an interface. By narrowing the bandwidth, the amount of computation and power consumption of a user terminal (UE: User Equipment) are reduced.

The category NB1 (NB-IoT) is a radio interface narrowed to 1 RB band (= 180 kHz) with the goal of further reducing the cost of the UE and expanding the coverage area.

Category M1 and category NB-IoT assume reception with one receive antenna without using receive antenna diversity in order to reduce the amount of computation and power consumption of the UE.

Next, the NB-IoT deployment scenario (introduction scenario) will be described with reference to FIG.

As shown in FIG. 2, NB-IoT defines three types of deployment scenarios: in-band, guard band and stand-alone.

The in-band scenario deploys NB-IoT using one or more RBs 2a in the LTE system band.

The guard band scenario develops NB-IoT using LTE guard band 2b. In LTE, 90% of the system bandwidth is a channel occupied bandwidth and 10% is a guard band. For example, when the system bandwidth is 10 MHz, guard bands of 500 kHz at both ends, for a total of 1 MHz, are provided. In the guard band scenario, this 10% guard band is used to deploy NB-IoT.

The standalone scenario deploys NB-IoT using frequency spectrum 2c outside the LTE system band.

In NB-IoT, as in LTE, a cell ID (PCID: Physical Cell ID) is detected using a synchronization signal. The synchronization signal according to NB-IoT includes narrowband primary synchronization signal (NPSS: Narrowband Primary Synchronization Signal) and narrowband secondary synchronization signal (NSSS: Narrowband Secondary Synchronization Signal).

The multiplexing method and sequence of NPSS and NSSS in NB-IoT are different from those in PSS and SSS in LTE. Then, with reference to FIG. 3, the multiplexing method of the NPSS and NSSS to the radio frame in the in-band scenario will be described.

The channel bandwidth of NB-IoT corresponds to 1 RB in LTE, and 1 RB is composed of 12 subcarriers (= 180 kHz). One radio frame length is 10 ms.

The NPSS is multiplexed into the fifth sub-frame b1 of each radio frame. The NSSS is multiplexed into the ninth subframe b2 of every other (for example, even-numbered) radio frame. Thus, the NPSS is periodically multiplexed at 10 ms intervals and the NSSS at 20 ms intervals.

Next, the resource mapping method of the NPSS and the NSSS will be described with reference to FIGS. 4A and 4B.

As shown in FIG. 4A and FIG. 4B, a physical downlink control channel (PDCCH: Physical Downlink Control Channael) is multiplexed in three OFDM symbol sections from the beginning of a subframe in LTE. Therefore, in any of the in-band, guard band and stand-alone scenarios, NPSS and NSSS are multiplexed between 4 OFDM symbols and 14 OFDM symbols in a subframe (11 OFDM symbol intervals) so as not to interfere with PDCCH .

In the in-band scenario, a cell-specific reference signal (CRS) may be multiplexed (may be referred to as "mapping" or "arrangement") into a resource element (RE: Resource Element), an NPSS, and If one or both of the NSSSs are to be mapped, one or both of the NPSS and the NSSS may be punctured. In guard band and stand-alone scenarios, the NPSS and NSSS may not necessarily be multiplexed to the RE on which the CRS is multiplexed.

Next, the NPSS sequence and the NSSS sequence will be described.

In the case of LTE, using 168 SSS sequences corresponding to identification information (identifier, ID) of a wireless base station (eNodeB) and three PSS sequences representing the numbers of three cells belonging to the same wireless base station , Identifies 504 cell IDs. In the case of NB-IoT, unlike in the case of LTE, the NSSS sequence represents 504 cell IDs.

The NPSS sequence is represented by a sequence obtained by modulating a ZC (Zadoff-Chu) sequence with a binary sequence in 11 OFDM symbol intervals in a subframe. The modulation by the sequence of binary values, ie, {+1, -1}, is called a code cover (Code cover). A ZC sequence of OFDM symbols (FFT block length) is used for 11 OFDM symbols in a subframe.

The synchronization timing of an OFDM symbol can be detected by calculating the correlation between consecutive OFDM symbols using a ZC sequence. However, since the correlation peak of the ZC sequence appears at 11 places in the sub-frame, 11 OFDM symbols are multiplied by the code cover. The sequence of the code cover is S (l) = {1 1 1 1 −1 −1 1 1 1 1 −1 1}, and l = 3, 4,.

Next, a method of generating an NPSS sequence (symbol) in the radio base station 10 will be described with reference to FIG.

First, the radio base station 10 generates a ZC sequence of sequence length 11 in the frequency domain (S11). An NPSS sequence of OFDM symbol index l in the frequency domain is represented by Equation 1 below.

In Equation 1, n = 0, 1, ..., 10, and u = 5 is the root index.

Next, the radio base station 10 maps the ZC sequence generated in S11 to a subcarrier (S12), and generates a ZC sequence (FFT block) in the time domain by IFFT (S13). Next, the radio base station 10 inserts a CP (Cyclic Prefix) into each FFT block (S14). Next, the radio base station 10 multiplies the FFT block including 11 CPs by the binary modulation sequence (code cover) (S15), and generates an NPSS symbol (sequence) (S16).

The UE can detect the start position of 11 OFDM symbol sections by calculating the correlation between a plurality of OFDM symbols as described later.

The NSSS sequence represents one of the 504 cell IDs and is used to detect an 80 ms superframe. The NSSS sequence is generated by combining the 131 sequence length ZC sequence and the binary scrambling sequence in the frequency domain. The 504 cell IDs are identified by the 126 root indexes of the ZC sequence and the scrambling codes of the 4 Hadamard sequences.

The NSSS sequence is represented by Equation 2 below.

In Equation 2, n = 0, 1, ..., 131, and n ^{^} = n mod 131. Further, exp [−j (((πun ^{^} ) × (n ^{^} +1)) / 131)] is a ZC sequence.

U in Equation 2 is the 126 root indexes represented by Equation 3 below.

In Equation 3, N ^Ncell _ID is the cell ID of NB-IoT.

In Equation 2, b _q (m) represents four types of Hadamard sequences of 128 sequence lengths, and m = n mod 128. q is expressed by the following equation 3-2.

In Expression 3-2, exp [−j 2πθ _f n] is a term indicating a cyclic shift of a sequence according to the radio frame number n _f , and is used to detect synchronization timing in an 80 ms period.

The amount of cyclic shift θ _f is expressed by the following equation 4.

Next, a method of generating an NSSS symbol (sequence) in the radio base station 10 will be described with reference to FIG.

First, the radio base station 10 generates a ZC sequence of sequence length 11 in the frequency domain (S21). Next, the radio base station 10 maps the ZC sequence generated in S21 to a subcarrier (S22), and generates a ZC sequence (FFT block) in the time domain by IFFT (S23). Next, the radio base station 10 inserts a CP into each FFT block (S24). Next, the radio base station 10 multiplies the FFT block including the CP by the binary scrambling sequence (S25), and generates an NSSS symbol (sequence) (S26).

Transmission diversity using Precoding Vector Switching (PVS) is applied to PSS and SSS in LTE. Therefore, next, a transmission method of PVS transmission diversity by two transmission antennas in LTE will be described with reference to FIG.

In LTE, two sets of PSS and SSS are multiplexed in one radio frame (10 ms). Then, one set is multiplied by the precoding vector {1, 1}, and the other set is multiplied by the precoding vector {1, −1}.

The PSS and SSS are channels that the UE first supplements in downlink. In order to simplify the detection process of PSS and SSS in the UE, LTE adopts selective transmission diversity, which does not require any change in the UE for the signal waveform transmitted by the radio base station from one transmit antenna. Furthermore, LTE adopts PVS transmission diversity which can efficiently utilize transmission power from two transmitters among selective transmission diversity.

The UE calculates an estimate of the channel response of each subcarrier position from the PSS sequence detected first. Then, the UE performs in-phase synthesis of the correlation of the SSS sequence in the frequency domain, using the estimated value of the channel response of each subcarrier position. As described above, the method of in-phase combining the correlation of each subcarrier position across a plurality of subcarriers can reduce the noise component as compared to the method by power combining, so that false detection of the SSS sequence can be reduced.

As described above, in the case of LTE, since the same set of PSS and SSS are multiplied by the same precoding vector, the UE does not need to be aware of (detect) the precoding vector, and each subs estimated by PSS The channel response of the carrier position can be used to perform in-phase combination (addition) of the SSS correlation value.

Next, a transmission method in the case of applying PVS transmission diversity in time domain to NPSS and NSSS will be described with reference to FIG. The details of the contents are disclosed in Non-Patent Document 3.

The PVS transmission diversity method disclosed in Non-Patent Document 3 alternately switches two types of precoding vectors in each of NPSS and NSSS.

In the case of NB-IoT, the multiple interval (period) of NPSS is 10 ms, which is longer than in the case of LTE. Therefore, in order to obtain the PVS transmission diversity effect in the detection of the NPSS, it is necessary to receive a reception signal of at least a 20 ms period in one detection loop process.

Furthermore, the multiplexing interval (period) of the NSSS is 20 ms. Therefore, in order to obtain the PVS transmission diversity effect in the detection of the NSSS, a single detection loop process may require a maximum of 40 ms.

The longer the time required for one detection loop process, the longer the time required for cell ID detection. Also, if detection loop processing is performed a plurality of times in order to increase the detection success rate of the cell ID, the number of processing for calculating the correlation also increases accordingly. All of these are factors that increase the power consumption of the UE. Reduction in power consumption is required of NB-IoT UEs. Therefore, in the present embodiment, an NB-IoT system will be described, in which the time required to detect a cell ID in the UE is shortened, and the time for standby is increased accordingly, and thus the power consumption in the UE is reduced.

In NB-IoT, to reduce the amount of computation and power consumption, the UE adopts a wireless interface of narrow band transmission of 180 kHz. In this case, when the reception level drops due to frequency flat fading, the entire signal band drops, and the UE may not be able to obtain a frequency diversity effect. Moreover, since UE receives a signal by one receiving antenna, there is a possibility that a reception diversity effect may not be obtained. As a result, burst errors may occur and the cell ID detection success rate may be reduced.

Also, in NB-IoT, adoption of PVS transmit diversity for transmitting signals with two transmit antennas as a wireless base station is being considered. However, as described above, the PVS transmit diversity method discussed herein is designed to multiplex the NPSS and NSSS into predetermined multiplexes while alternately switching between two precoding vectors in each of the NPSS and NSSS regardless of the reception quality. It is a method of transmitting at intervals (period). Therefore, the precoding gain is small as compared with the method of selecting the optimal precoding vector according to channel state information (CSI) of reception.

In addition, when a configuration is employed in which a downlink signal is transmitted from one transmission antenna to a wireless base station (access point) in order to miniaturize the wireless base station and reduce power consumption, the UE is required to have a transmit antenna diversity gain. I can not get As a result, the cell ID detection success rate decreases.

In the present embodiment, a synchronization signal multiplexing method and a cell search method will be described which enhance the cell ID detection success rate. As a result, even when a sufficient antenna diversity effect can not be obtained, the cell ID detection success rate can be increased.

<Method of Detecting Synchronization Signal Using Two Channels>
Next, the transmission method and detection method of the NPSS and the NSSS according to the present embodiment will be described with reference to FIG. FIG. 9 is an example of detecting both NPSS and NSSS using frequency hopping. Although the case where two channels (carrier frequencies) are used is described in this embodiment, this embodiment can also be applied to the case where three or more carrier frequencies are used.

The radio base station 10 synchronizes and transmits the transmission timings of radio frames in two different channels according to NB-IoT. Here, the two channels used to transmit the radio frame are a combination of two RBs 2a in the LTE channel occupied band, a combination of the RB 2a in the LTE channel occupied band and an RB 2b in the guard band shown in FIG. Alternatively, any combination may be used, such as a combination of RB 2 a in the LTE channel occupancy band and RB 2 c in a frequency band outside the LTE system band. In other words, the two channels may be any combination of in-band scenario, guard-band scenario and stand-alone scenario.

In the in-band scenario, it is desirable to allocate two RBs separated by frequency intervals so that the frequency correlation between the two NB-IoT channels is sufficiently small.

In general, the UE searches for carrier frequencies in a system-predefined frequency raster upon detection of a cell ID. In this case, when searching for a carrier frequency, the UE can perform blind search for a carrier frequency on which frequency hopping should be performed.

However, frequency intervals of two channels (corresponding to frequency hopping intervals) and frequency interval candidates may be predetermined between the radio base station 10 and the UE (that is, in the NB-IoT system). Thereby, the search time of cell ID in UE can be shortened.

Next, the detection process of the NPSS in the UE will be described.

At the timing when the UE starts the process of detecting the cell ID for the first time (for example, when power is turned on), the multiplexing position of the NPSS in one radio frame is unknown. Therefore, the UE estimates the multiplexing position of the NPSS in one radio frame as follows.

First, UE, of the two channels, the carrier frequency f _1, and calculates a correlation value ρ ^NPSS _f1 [k] of the complex quantity in each sample timing of the search period 101 of "T ^NPSS _Ave = 10ms + 11OFDM symbol". Here, 10 ms is the multiplexing interval of NPSS, 1 ≦ k ≦ (N _rf + 11 × N _OFDM ), N _rf is the number of samples in one radio frame length, and N _OFDM is the number of samples in one OFDM symbol length is there.

The reason why the search period is extended by 11 OFDM symbols is to be able to detect the NPSS even when the timing at which the UE starts the NPSS detection process is in the middle of the NPSS multiplexed subframe. . Further, details of a method of calculating the correlation value ^{N NPSS} _f1 [k] at each sample timing for detecting the NPSS will be described later.

Next, the UE calculates the correlation value ^{N NPSS} _f2 [k] at each sample timing of the search period 102 of T ^NPSS _{Ave at} the carrier frequency f ₂ .

Then, UE adds the correlation value ρ ^NPSS _f1 [k] according to the carrier frequency f ₁ definitive search period 101, and a correlation value [rho ^NPSS _f2 according to the carrier frequency f ₂ definitive search period 102 [k], adding The correlation value ^{~ ~ NPSS} [k] is calculated. In the addition, the in-phase component and the quadrature component are independently added.

Next, the UE calculates k at which the power | ρ ^̃NPSS [k] | ^{2 of} the added correlation value ^{~ ̃NPSS} [k] is maximum. The k corresponds to the reception timing of the NPSS. That is, the process in which the UE calculates the k corresponds to the process of detecting (estimating) the reception timing of the NPSS.

Note that, since the NPSS is multiplexed at an interval of one radio frame length (10 ms), a period of at least two radio frame lengths (20 ms) is required to detect the correlation of the NPSS.

According to the above-described method, since the correlation values of 2 RBs with relatively low frequency correlation are averaged, the frequency diversity effect is obtained, and the detection success rate of the NPSS reception timing is increased.

Next, detection processing of NSSS in the UE will be described.

The UE estimates the NSSS reception timing from the NPSS reception timing estimate. The NSSS is multiplexed into one subframe of any of two consecutive radio frames. Therefore, although it is possible to detect the multiplex position of the NPSS, it is not immediately known as to which of the two radio frames the NSSS is multiplexed. Therefore, the UE detects, for each of the two radio frames, the NSSS sequence that is the maximum correlation power, and estimates that the NSSS is multiplexed in the radio frame that is the higher correlation power. Then, the UE detects (estimates) the cell ID using the NSSS sequence that is the maximum correlation power. The details will be described below.

First, UE, in a carrier frequency f _1, and calculates the received signal at multiple timings NSSS the frequency domain, the correlation value between NSSS sequence replica. Specifically, the UE sets the NSSS correlation value P ⁽¹⁾ _f ¹ [ ^1] _f ¹ [at each sample timing of the first half 10 ms period (hereinafter referred to as “first half period”) 121 in the search period 120 of “T ^NSSS _Ave = 20 ms”. m] to calculate. That is, the correlation value P ⁽¹⁾ _f1 [m] is the carrier frequency f _1, a correlation value NSSS in one radio frame length in the first half of the second radio frame length.

Furthermore, the UE is the correlation value of the NSSS at each sample timing of the second half 10 ms (122) period (hereinafter referred to as "second half period") 122 in the search period 120 of "T ^NSSS _Ave = 20 ms" for the carrier frequency f ₁ P ⁽²⁾ Calculate _f1 [m]. That is, the correlation value P ⁽²⁾ _f1 [m] is the correlation value of the NSSS at one radio frame length in the second half of the two radio frame lengths at the carrier frequency f ₁ . Here, 20 ms is a multiplexing interval of NSSS, 1 ≦ m ≦ N _NSSS , and N _NSSS is the number of NSSS sequences.

Next, the UE switches the carrier frequency to f ₂ by frequency hopping, and similarly to the above, the correlation value P ⁽¹⁾ _{f 2} [m] of the NSSS in the first half period 131 in the search period 130 for the carrier frequency f ₂ and the second half The correlation value P ⁽²⁾ _f2 [m] of the NSSS in the period 132 is calculated.

Next, from the correlation values of the NSSS in the first half periods 121 and 131 of the carrier frequencies f ₁ and f ₂ , the UE calculates the combined correlation power of the first half periods 121 and 131 (| P ⁽¹⁾ _f ¹ [m] | ² + | P ⁽¹⁾ Calculate _f2 [m] | ² ). In addition, the UE detects the combined correlation power (| P ⁽¹⁾ _f2 [m] | ² + | P ^{( )} from the correlation values of the NSSS in the second half periods 122 and 132 of the carrier frequencies f ₁ and f ₂ ^{). 2)} Calculate _f2 [m] | ² ).

Next, the UE compares the combined correlation power in the first half period with the combined correlation power in the second half period, and estimates that the NSSS is multiplexed in the larger one of the first half period or the second half period. Then, the UE calculates an NSSS sequence m ^{^ in} which the larger combined correlation power is maximum. The NSSS sequence m ^{^} corresponds to a cell ID. That is, the process in which the UE calculates the NSSS sequence m ^{^} corresponds to the process of detecting (estimating) the cell ID. As detected.

Note that the radio base station 10 may transmit information regarding the frequency hopping interval (hereinafter referred to as “frequency hopping interval information”) in the NPSS sequence. Alternatively, the radio base station 10 may transmit frequency hopping interval information in symbol information. By this means, the UE can omit the blind search process for frequency hopping information.

Also, the configuration of the radio frame, ie, the multiplexing position of the NPSS in the radio frame may be known at the UE. Also, since the sample rate in one radio frame is known, the number of samples in one radio frame may also be known.

According to the above process, it is possible to increase the detection success rate of the NPSS and the NSSS by the frequency diversity effect.

<Modification 1>
As shown in the example of FIG. 10, the UE does not use frequency hopping for NPSS, but detects using the received signal (140) transmitted on one carrier (1 RB) (carrier frequency f _{1 in} FIG. 10) The frequency hopping may be used for the NSSS, as in FIG.

As shown in FIG. 10, NB-IoT can increase the cell ID detection success rate even if frequency hopping is used only for NSSS detection as shown in FIG.

<Modification 2>
Next, with reference to FIG. 11, an example in which the radio base station 10 multiplexes the NPSS and the NSSS onto two carriers (2 RBs) and transmits will be described.

As shown in FIG. 11, the radio base station 10 synchronizes the transmission timing of the NPSS in the radio frame of the same transmission timing on two carriers, and multiplies the synchronized NPSS by the same precoding vector. Similarly, the radio base station 10 synchronizes the transmission timing of the NSSS in the radio frame of the same transmission timing on two carriers, and multiplies the synchronized NSSS by the same precoding vector.

For example, assuming that the transmit weights of transmit antenna # 1 and transmit antenna # 2 are {w ₁ , w ₂ }, the radio base station 10 sets {w ₁ , w ₂ } = {1, 1} and The precoding vectors of {w ₁ , w ₂ } = {1, −1} are alternately multiplied. For example, odd and _{{w 1, w 2} =} {1,1} (third transmission timing) NPSS of the even-numbered {w _1, w _2} to NPSS the (fourth transmission timing) = { Multiply by 1, -1}. The radio base station 10, even for nsss, similarly, a precoding vector of _{{w 1, w 2} =} {1,1} and _{{w 1, w 2} =} {1, -1}, alternating Multiply by

Next, the detection process of the NPSS in the UE will be described.

As shown in the example of FIG. 11, the UE ^transmits correlation values ^{相関 NPSS (1)} _f1 [k] and ρ ^NPSS for search periods 211 and 212 of “T ^NPSS _Ave = 10 ms + 11 OFDM symbol” at carrier frequency f ₁ , respectively. ⁽²⁾ Calculate _f1 [k]. Similarly, the UE ^detects correlation values ^{N NPSS (3)} _f1 [k] and ^{N NPSS (4)} _f1 [k 1 for search periods 221 and 222 of “T ^NPSS _Ave = 10 ms + 11 OFDM symbol” at carrier frequency f ₂ . Calculate].

Next, the UE calculates the correlation values ^{N NPSS (1)} _f ¹ [k], ^{N NPSS (2)} _{f 1} [k], ^{N NPSS (3)} _{f 1} [k], ^{N NPSS (4)} relating to the calculated four radio frames. ⁴⁾ Calculate the added correlation value by adding _f1 [k]. Next, the UE calculates k that maximizes the power of the added correlation value among the sample timing candidates of 1 ≦ k ≦ (N _rf + 11 × N _OFDM ). That is, the UE detects the reception timing of the NPSS.

Next, detection processing of NSSS in the UE will be described.

First, the UE determines the correlation value P ^(1a) _f1 [m] of the NSSS of the first half period 311 and the NSSS of the second half period 312 in the first search period 310 (T ^NSSS _Ave = 20 ms) at the carrier frequency f ₁ The correlation value P ^(2a) _f1 [m] is calculated.

Next, the UE calculates the correlation value P ^(1b) _f1 [m] of the NSSS in the first half period 321 and the correlation value P ^(2b) _f1 [m] of the second half period 322 in the second search period 320. calculate. Then, the UE adds the correlation values P ^(1a) _f1 [m] and P ^(1b) _f1 [m] in the first half periods 311 and 321, respectively, for the carrier frequency f ₁ and adds the correlation value P ^{̄ (1 )} Calculate _f1 [m].

Next, the UE switches the carrier frequency to f ₂ by frequency hopping, and similarly, the correlation value P ^(1a) _{f 2} [m] of the NSSS in the first half period 331 and the second half period 332 in the third search period 330. Calculate the correlation value P ^(2a) _f1 [m] of NSSS.

Next, the UE generates the correlation value P ^(1b) _f2 [m] of the NSSS in the first half period 341 and the correlation value P ^(2b) _f2 [m] of the second half period 342 in the fourth search period 340. calculate. Then, the UE adds the correlation values P ^(1a) _f2 [m] and P ^(1b) _f2 [m] in the first half periods 331 and 341, respectively, for the carrier frequency f ₂ and adds the correlation values P ^{̄ (1)} Calculate _f2 [m]. Also, the UE adds the correlation values P ^(2a) _f2 [m] and P ^{(1 b)} _f2 [m] in the second half periods 332 and 342, respectively, and adds the correlation values P ⁽²⁾ _f2 [m]. calculate.

Next, the UE calculates the combined correlation power of the first half periods 311, 321, 331, 341 of the carrier frequencies f ₁ and f ₂ (| P ⁽⁽¹⁾ _f ¹ [m] | ² + | P ^{1 (1)} _{f 2} [m ² ) and the _second half period 312, 322, 332, 342 of the carrier frequencies f ₁ and f ₂ (│P ^{1 (1)} _f ² [m] │ ² + | P ⁽⁽²⁾ _f ² [m ² ] | ² ) and. That is, the combined correlation power of the first half period and the combined correlation power of the second half period are respectively calculated by the correlation value of the number of precoding vector sets “2” × the number of carriers of frequency hopping “2” = 4 cycles. Become.

Next, the UE compares the combined correlation power in the first half period with the combined correlation power in the second half period, and estimates that the NSSS is multiplexed in the larger one of the first half period and the second half period. Then, the UE calculates an NSSS sequence m ^{^ in} which the larger combined correlation power is the largest correlation power. That is, the UE detects (estimates) the cell ID.

According to the process according to the above-described modification 2, compared to the case where only PVS transmission diversity is used, the frequency diversity effect is obtained, so that the detection success rate of the NPSS and NSSS sequences is improved.

<Modification 3>
Next, referring to FIG. 12, the radio base station 10, the radio frame in the carrier frequency f ₁ (radio frame number), and a radio frame (radio frame number) in the carrier frequency f _2, 1 radio frame length fraction An example of time-shifted transmission will be described. That is, the radio base station 10 transmits the radio frame transmitted using the carrier frequency f ₁ at the first transmission timing and the carrier frequency at the second transmission timing that is one radio frame length later than the first transmission timing. transmitted using the f _2. Thus, nsss is straddling carrier frequencies f ₁ and the carrier frequency f _2, will have been transmitted at intervals of 1 radio frame length.

In FIG. 12, the method for the UE to detect the reception timing of the NPSS is the same as that in the case of FIG. Next, the detection method of NSSS in UE will be described.

As shown in FIG. 12, when frequency hopping is used, the NSSS multiplexing interval is equivalent to one radio frame length. However, it is not immediately known whether the NSSS is multiplexed in the next radio frame of the radio frame in which the NPSS is detected. Thus, the UE detects which of two consecutive radio frames an NSSS is multiplexed for a signal transmitted using the same carrier frequency.

For example, UE, as shown in FIG. 12, the carrier frequency f _1, a first radio frame length periods of 401 consecutive after NPSS detected for the second radio frame length periods 402, respectively, nsss The correlation values P ⁽¹⁾ _f1 [m] and P ⁽²⁾ _f1 [m] are calculated.

Next, the UE compares max | P ⁽¹⁾ _f1 [m] | ² with max | P ⁽²⁾ _f1 [m] | ² and, during the larger radio frame length period, NSSS Estimated to be multiplexed.

Next, when the UE estimates that the NSSS is multiplexed in the first radio frame length period 401, the correlation power of the NSSS for the third radio frame length period 403A in the same carrier frequency f _{1 ^{| P (3) f1 [m}} ] | 2 is calculated. Next, the UE switches to the carrier frequency f ₂ and calculates the correlation power | P ⁽⁴⁾ _f ² [m] | ² of the NSSS for the period 404 of the fourth radio frame length. Next, the UE obtains an NSSS sequence m for which (| P ⁽¹⁾ _f1 [m] | ² + | P ⁽³⁾ _f1 [m] | ² + | P ⁽⁴⁾ _f2 [m] | ² ) is maximum. Calculate ^{^} . That is, the UE detects (estimates) the cell ID.

Meanwhile, UE has two if eye NSSS the radio frame length periods of 402 was estimated to be multiplexed by switching the carrier frequency f _2, the correlation of the NSSS for the third period of the radio frame length 403B power _{^{| P (3) f2 [m}} ] | 2 is calculated. Then, the UE calculates an NSSS sequence m ^{^} that maximizes (| P ⁽²⁾ _f ² [m] | ² + | P ⁽³⁾ _f ² [m] | ² ). That is, the UE detects (estimates) the cell ID.

As described above, in the NB-IoT wireless interface, the NSSS sequence cyclically shifts the sequence every 20 ms, and synchronizes for 80 ms with four types of cyclic shift amounts. Thus, when the radio frame (radio frame number) is shifted by one radio frame and transmitted from two carriers (2 RBs), the UE calculates the correlation value of the NSSS sequence for the following two ways: . That is, the correlation value is calculated for the case where the cyclic shift amount of the NSSS of the carrier frequency f ₂ is the same as the cyclic shift amount of the carrier frequency f ₂ with respect to the cyclic shift amount of the NSSS sequence of the carrier frequency f ₁ . Then, the UE calculates the correlation power for each of the two correlation values, and estimates that the NSSS sequence is multiplexed in the radio frame with the larger correlation power.

In addition, as shown in FIG. 9, the radio base station 10 does not perform the time shift for one radio frame length, and shifts the search period related to the NPSS by the one radio frame length at the UE side. The process according to the third modification may be realized.

According to the process according to the third modification, it is possible to increase the detection success rate of NSSS by the frequency diversity effect.

<Modification 4>
Next, referring to FIG. 13, the radio base station 10 multiplexes the NPSS and the NSSS onto two carriers (two RBs), and a radio frame (radio frame number) at the carrier frequency f ₁ and a carrier frequency a radio frame (radio frame number) in f _2, 1 radio frame, for example in the case of transmitting by shifting will be described. That is, FIG. 13 corresponds to the combination of FIG. 11 and FIG.

In this case, as in the case of FIG. 11, the base station transmits {w ₁ , w ₂ } = {1, 1} and {w ₁ , w ₂ } = {1, −1} to the NPSS. The coding vectors are alternately multiplied, and for NSSS also alternating precoding vectors of {w ₁ , w ₂ } = {1, 1} and {w ₁ , w ₂ } = {1, −1} Multiply by

The detection process of the NPSS of the UE in the case of FIG. 13 is the same as that of the case of FIG. Next, detection processing of NSSS in the UE will be described.

The UE adds the correlation values P ⁽¹⁾ _f1 [m] of the NSSS in the first half periods 501 and 503 for the carrier frequency f ₁ to calculate P P ⁽¹⁾ _f1 [m]. Further, UE calculates the _{^{P ¯ (2) f1 [m}} ] from the second half of the correlation value P ⁽²⁾ of the NSSS of the period 502 _f1 [m].

Next, the UE adds the correlation value P ⁽¹⁾ _f2 [m] of the NSSS in the first half period 504 and 506 with respect to the carrier frequency f ₂ to calculate P ⁽⁽¹⁾ _f2 [m]. Calculates the correlation value P ⁽²⁾ _f2 [m] of the NSSS in the second half period 505 to P ⁽²⁾ _f2 [m].

Next, the UE determines the combined correlation power of the first half periods 501, 503, 504, and 506 of the carrier frequencies f ₁ and f ₂ (| P ⁽⁽¹⁾ _f ¹ [m] | ² + | P ^{1 (1)} _{f 2} [m ² ) and the _second half period 502, 505 of the carrier frequency f ₁ and f ₂ combined correlation power (| P ⁽⁽²⁾ _{f 1} [m] | ² + | P ⁽⁽²⁾ _f ² [m] | ² ) And calculate.

Next, the UE compares the combined correlation power in the first half period with the combined correlation power in the second half period, and estimates that the NSSS is multiplexed in the larger one of the first half period and the second half period. Then, the UE calculates an NSSS sequence m ^{^ in} which the larger combined correlation power is the largest correlation power. That is, the UE detects the cell ID.

In addition, as shown in FIG. 11, the radio base station 10 does not perform time shift by one radio frame length, and shifts the search period related to the NPSS by one radio frame length at the UE side. The process according to the fourth modification may be realized.

According to the process according to the fourth modification, the frequency diversity effect is obtained as compared with the case where only PVS transmission diversity is used, so that the detection success rate of the NPSS and NSSS sequences is improved.

<Specific Example of Cell ID Detection Process>
Next, with reference to FIG. 14, a specific example of the cell ID detection process in the UE 20 will be described. Although not shown in FIG. 14, the UE 20 may have a functional block that performs processing reverse to the processing in the radio base station 10 shown in FIGS. 5 and 6. That is, after the UE performs the process shown in FIG. 14 to detect the NPSS (cell ID), the UE may perform processes such as CP removal, FFT, demapping, ZC sequence extraction and the like.

In the correlation detection of PSS in LTE, the cross correlation between the received signal including PSS and the PSS sequence replica in the time domain is calculated.

However, in NB-IoT, it is assumed that UE 20 has a relatively large reference error of frequency error. If the frequency error of the reference oscillator is large, the frequency offset will be large. For example, under NB-IoT simulation conditions, a frequency offset of 20 ppm is assumed.

The multiplexing interval of NPSS and NSSS is 10 ms or more. Therefore, there is a possibility that the NSSS reception timing estimated from the NPSS reception timing may deviate from the original correct reception timing due to the frequency offset, that is, the frequency difference of the reference oscillator between the radio base station 10 and the UE 20. is there. As a result, the correlation value of the correct NSSS sequence may be reduced, and the detection success rate of the NSSS sequence may be greatly reduced.

Therefore, NB-IoT uses a method of detecting autocorrelation between sequences of NPSSs multiplexed into 11 OFDM symbols in a subframe.

In the following, in order to make the description easy to understand, the case where the UE 20 does not perform oversampling in the reception process and the sampling frequency in the UE 20 is set equal to the chip rate of the ZC sequence will be described. However, the present embodiment is not limited to this configuration, and can be applied to other configurations.

<Detection of NPSS Reception Timing and Radio Frame Timing>
Next, the detection method of the NPSS reception timing and the radio frame timing will be described.

The UE 20 can detect the FFT block timing, the reception timing of the NPSS, the subframe timing, and the radio frame timing from the timing at which the autocorrelation of the NPSS is maximum.

The NPSS is multiplexed into 11 FFT blocks. Therefore, the UE 20 sets the vector γ (τ) as a sample value signal of the received signal of 11 FFT blocks with the sampling time τ as the start timing as shown in the following Equation 5.

In Equation 5, R ₁ (1 = 1, 2,..., 11) represents a received signal of the FFT block length of NPSS spread with the same ZC sequence.

The UE 20 calculates the autocorrelation of the received signal delayed by k FFT block intervals (1 ≦ k ≦ 11) as shown in the following Equation 6.

In Equation 6, s (l) represents the modulation component in the l-th FFT block of NPSS, and the superscript "H" represents Hermitian transposition.

For example, when k = 1, as shown in FIG. 15, the autocorrelation of the received signal delayed by 1FTT block interval is shown. Assuming that the correct reception timing of the NPSS is τ ₀ , the phase rotation amount in one FFT block section due to the frequency offset is represented by θ, and E [A _k (τ ₀ )] ∝e ^jkθ .

In order to reduce the influence of the frequency offset, the UE 20 uses a cost function represented by the following Equation 7.

As the value of A _k (τ) becomes larger, the frequency offset becomes larger, so the error of the correlation peak position becomes larger. Therefore, in Equation 7, in order to reduce the influence of the frequency offset, each correlation value is multiplied by a weighting factor and synthesized.

The weighting factor may be set to maximize the detection success rate of the NPSS. For example, in Non-Patent Document 3, the weighting factors are set to w ₁ = 0.76, w ₂ = 0.54 and w ₃ = 0.34.

When the moving speed of the UE 20 is low or stationary, the maximum Doppler frequency is low, and channel fluctuation in the time domain is very small. Therefore, as shown in the following equation 8, the influence of noise can be reduced by adjusting the cost functions of a plurality of NPSSs multiplexed at intervals of 10 ms to the same phase and adding them.

<Frequency offset estimation>
Next, a method of estimating the frequency offset will be described.

The cost function _{m m} (τ) represents the amount of phase rotation due to the frequency offset of one FFT block interval including CP. Therefore, the frequency offset Δf ^{^} is expressed by the following equation 9.

In Expression 9, −π <arg [ρ (τ ^{^} )] <π. Further, f _s represents a sampling frequency, f _SC represents a subcarrier interval, N _FFT represents the number of samples in an effective symbol section (FFT block section), and N _CP represents a sample number in a CP section. In the case of f _s = 7.67 MHz, f _SC = 15 kHz, N _FFT = 512, and N _CP = 36, the frequency offset Δf ^{^} is calculated by the following equation 10.

Equations 9 and 10 are capable of phase detection in the range of −π <arg [τ (τ ^{^} )] <π. However, when the frequency offset becomes high, arg [ρ (τ ^{^} )] exceeds the range of 2π. Therefore, as shown in the following equation, the detection range of the frequency offset is expanded.

In Equation 11, the values of arg [ρ (τ ^{^} )] and G are detected most likely. The value of G is, for example, a value of G∈ {0, ± 1, ± 2} according to the magnitude of the frequency offset value.

<NSSS Sequence Estimation>
Next, a method of estimating an NSSS sequence, that is, a method of estimating a cell ID will be described.

After the frequency offset value estimated by Equation 11 is compensated for the received signal, the received signal including NSSS is converted to a frequency domain signal by FFT using FFT block timing and subframe timing estimated using NPSS.

There are the following two methods for estimating an NSSS sequence, for example. (A1) Method of in-phase addition of correlation value of each subcarrier position in the frequency domain of NSSS using frequency response estimated using NPSS (A2) Assuming flat fading in transmission band of NSSS, In-phase addition of correlation values

First, the method (A1) will be described.

The UE 20 represents a subcarrier index by n (n = 1, 2,..., 11), and obtains a channel response of each subcarrier position from a received signal in the frequency domain of the NPSS. In addition, UE20 may use only NPSS multiplexed to the same radio | wireless frame as NSSS for estimation of the channel response of NSSS. The estimated value of the channel response in subcarrier #n of the radio frame v can be calculated as the following equation 12.

It is unknown whether the UE 20 multiplexes the NSSS in the radio frame that starts the correlation detection of the NSSS sequence. Therefore, the UE 20 performs the correlation detection process of the NSSS sequence at the NSSS multiplex timing of the continuous radio frame, and estimates that the NSSS is multiplexed in the radio frame with the large correlation value.

Further, an index μ is defined as an index indicating a radio frame of 20 ms period (μ = v mod 2). Also, the index of the 504 cell IDs represented by the root index of 126 ZC sequences and 4 scrambled sequences is denoted by κ (0 ≦ κ <504). Also, the index of the cyclic shift pattern of the scrambled sequence is represented by c (0 ≦ c <4). Then, κ, c and μ are detected according to the following equation 13.

In Equation 13, d _l ^{NSSS (κ, (c + λ / 2) mod 4} (n) represents an NSSS sequence replica.

Next, the method (A2) will be described. The method (A2) is a method in which the correlation value of the NSSS sequence of each subcarrier in the frequency domain is in-phase added assuming flat fading since the transmission band of NB-IoT is a narrow band.

As shown in the following Equation 14, assuming that the channel response in the frequency domain is constant, the in-phase component and the quadrature component of the correlation value are averaged independently.

<Effect of the embodiment>
In the present embodiment, the radio base station 10 transmits the first and second radio signals including the common NPSS and NSSS in frame synchronization on the first carrier frequency and the second carrier frequency. The UE 20 detects the NPSS from the first and / or second radio signals, switches between the first carrier frequency and the second carrier frequency, and receives the first radio signal and the second radio signal received from each of them. Detect NSSS based on correlation with

According to the said structure, the detection success rate of NSSS in UE20 can be raised by the frequency diversity effect.

Note that the expressions "first", "second", "third" and "fourth" in the above description are used to make the explanation easy to understand, and do not necessarily mean that they are related .

(Hardware configuration)
Note that the block diagram used in the description of the above embodiment shows blocks in units of functions. 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 physically and / or logically coupled device, or directly and / or indirectly two or more physically and / or logically separated devices. It may be connected by (for example, wired and / or wireless) and realized by the plurality of devices.

For example, the wireless base station 10, the user terminal 20, and the like in one embodiment of the present invention may function as a computer that performs the processing of the wireless communication method of the present invention. FIG. 16 is a diagram showing an example of a hardware configuration of a radio base station and a user terminal according to an embodiment of the present invention. The above-described wireless base station 10 and user terminal 20 may be physically configured as a computer device including a processor 1001, a memory 1002, a storage 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007 and the like. Good.

In the following description, the term "device" can be read as a circuit, a device, a unit, or the like. The hardware configuration of the radio base station 10 and the user terminal 20 may be configured to include one or more of the devices illustrated in the figure, or may be configured without including some devices.

For example, although only one processor 1001 is illustrated, there may be a plurality of processors. Also, the processing may be performed by one processor, or the processing may be performed by one or more processors simultaneously, sequentially, or in other manners. The processor 1001 may be implemented by one or more chips.

Each function in the radio base station 10 and the user terminal 20 performs a calculation by causing the processor 1001 to read predetermined software (program) on hardware such as the processor 1001 and the memory 1002, and performs communication by the communication device 1004 or This is realized by controlling reading and / or writing of data in the memory 1002 and 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. For example, the above-mentioned generation of ZC sequence (S11, S21), subcarrier mapping (S12, S22), IFFT (S13, S23), CP insertion (S14, S24), multiplication of binary modulation sequence (code cover) (code cover) S15), multiplication of a binary scrambling sequence (S25), generation of an NPSS symbol (sequence) (S16), generation of an NSSS symbol (sequence) (S26), etc. may be realized by the processor 1001.

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 control unit of the radio base station 10 may be realized by a control program stored in the memory 1002 and operated by the processor 1001, or may be realized similarly for other functional blocks. 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 implement the wireless communication method according to an 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 transmission unit, the antenna, the reception unit, and the like included in the above-described wireless base station 10 and user terminal 20 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, the radio base station 10 and the user terminal 20 may be microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), 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.

(Information notification, signaling)
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 referred to as an RRC message, and may be, for example, an RRC connection setup (RRC Connection Setup) message, an RRC connection reconfiguration (RRC Connection Reconfiguration) message, or the like.

(Adaptive system)
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.

(Processing procedure etc.)
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.

(Operation of base station)
The specific operation supposed to be performed by the base station (radio base station) in this specification may be performed by the upper node in some cases. In a network of one or more network nodes with a base station, the various operations performed for communication with the terminals may be the base station and / or other network nodes other than the base station (eg, It is obvious that this may be performed by, but not limited to, MME (Mobility Management Entity) or S-GW (Serving Gateway). Although the case where one other network node other than a base station was illustrated above was illustrated, it may be a combination of a plurality of other network nodes (for example, MME and S-GW).

(Direction of input / output)
Information, signals, etc. may be output from the upper layer (or lower layer) to the lower layer (or upper layer). Input and output may be performed via a plurality of network nodes.

(Handling of input / output information etc.)
The input / output information or the like may be stored in a specific place (for example, a memory) or may be managed by a management table. Information to be input or output may be overwritten, updated or added. The output information etc. may be deleted. The input information or the like may be transmitted to another device.

(Judgment method)
The determination may be performed by a value (0 or 1) represented by one bit, may be performed by a boolean value (Boolean: true or false), or may be compared with a numerical value (for example, a predetermined value). Comparison with the value).

(software)
Software may be called software, firmware, middleware, microcode, hardware description language, or any other name, and may be instructions, instruction sets, codes, code segments, program codes, programs, subprograms, software modules. Should be interpreted broadly to mean applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc.

Also, software, instructions, etc. may be sent and received via a transmission medium. For example, software may use a wireline technology such as coaxial cable, fiber optic cable, twisted pair and digital subscriber line (DSL) and / or a website, server or other using wireless technology such as infrared, radio and microwave When transmitted from a remote source, these wired and / or wireless technologies are included within the definition of transmission medium.

(Information, signal)
The information, signals, etc. described herein may be represented using any of a variety of different techniques. For example, data, instructions, commands, information, signals, bits, symbols, chips etc that may be mentioned throughout the above description may be voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or photons, or any of these May be represented by a combination of

The terms described in the present specification and / or the terms necessary for the understanding of the present specification may be replaced with terms having the same or similar meanings. For example, the channels and / or symbols may be signals. Also, the signal may be a message. Also, the component carrier (CC) may be called a carrier frequency, a cell or the like.

("System", "Network")
The terms "system" and "network" as used herein are used interchangeably.

(Name of parameter, channel)
In addition, the information, parameters, and the like described in the present specification may be represented by absolute values, may be represented by relative values from predetermined values, or may be represented by corresponding other information. . For example, radio resources may be indexed.

The names used for the parameters described above are in no way limiting. In addition, the formulas etc. that use these parameters may differ from those explicitly disclosed herein. Since various channels (eg PUCCH, PDCCH etc.) and information elements (eg TPC etc.) can be identified by any suitable names, the various names assigned to these various channels and information elements can be Is not limited.

(base station)
A base station (radio base station) can accommodate one or more (e.g., three) cells (also called sectors). If the base station accommodates multiple cells, the entire coverage area of the base station can be divided into multiple smaller areas, each smaller area being a base station subsystem (eg, a small base station RRH for indoor use: Remote Communication service can also be provided by Radio Head. The terms "cell" or "sector" refer to a part or all of the coverage area of a base station and / or a base station subsystem serving communication services in this coverage. Moreover, the terms "base station", "eNB", "cell" and "sector" may be used interchangeably herein. A base station may be called in terms of a fixed station (Node station), NodeB, eNodeB (eNB), access point (access point), femtocell, small cell, and the like.

(Terminal)
The user terminal may be a mobile station, 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 terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, a UE (User Equipment), or some other suitable term.

(Meaning and interpretation of terms)
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".

The terms "connected", "coupled" or any variants thereof mean any direct or indirect connection or coupling between two or more elements, It can include the presence of one or more intermediate elements between two elements that are “connected” or “coupled”. The coupling or connection between elements may be physical, logical or a combination thereof. As used herein, the two elements are by using one or more wires, cables and / or printed electrical connections, and radio frequency as some non-limiting and non-exclusive examples. It can be considered "connected" or "coupled" to one another by using electromagnetic energy such as electromagnetic energy having wavelengths in the region, microwave region and light (both visible and invisible) regions.

The reference signal may be abbreviated as RS (Reference Signal), and may be called a pilot (Pilot) according to the applied standard. Further, the correction RS may be called TRS (Tracking RS), PC-RS (Phase Compensation RS), PTRS (Phase Tracking RS), or Additional RS. Also, the demodulation RS and the correction RS may be different names corresponding to each other. Also, the demodulation RS and the correction RS may be defined by the same name (for example, the demodulation RS).

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."

The “parts” in the configuration of each of the above-described devices may be replaced with “means”, “circuit”, “device” or the like.

As long as “including”, “comprising”, and variations thereof are used in the present specification or claims, these terms as well as the term “comprising” are inclusive. Intended to be Further, it is intended that the term "or" as used in the present specification or in the claims is not an exclusive OR.

A radio frame may be comprised of one or more frames in the time domain. One or more frames in the time domain may be referred to as subframes, time units, and so on. A subframe may be further comprised of one or more slots in the time domain. The slot may be further configured with one or more symbols (such as orthogonal frequency division multiplexing (OFDM) symbols, single carrier-frequency division multiple access (SC-FDMA) symbols, etc.) in the time domain.

A radio frame, a subframe, a slot, and a symbol all represent time units in transmitting a signal. A radio frame, a subframe, a slot, and a symbol may be another name corresponding to each.

For example, in the LTE system, the base station performs scheduling to assign radio resources (frequency bandwidth usable in each mobile station, transmission power, etc.) to each mobile station. The minimum time unit of scheduling may be called a TTI (Transmission Time Interval).

For example, one subframe may be called a TTI, a plurality of consecutive subframes may be called a TTI, and one slot may be called a TTI.

A resource unit is a resource allocation unit in time domain and frequency domain, and may include one or more consecutive subcarriers in frequency domain. Also, the time domain of a resource unit may include one or more symbols, and may be one slot, one subframe, or one TTI long. One TTI and one subframe may be configured of one or more resource units, respectively. Also, resource units may be referred to as resource blocks (RBs), physical resource blocks (PRBs: physical RBs), PRB pairs, RB pairs, scheduling units, frequency units, and subbands. Also, a resource unit may be configured of one or more REs. For example, 1 RE may be a resource of a unit smaller than the resource unit serving as a resource allocation unit (for example, the smallest resource unit), and is not limited to the name of RE.

The above-described radio frame structure is merely an example, and the number of subframes included in the radio frame, the number of slots included in the subframe, the number of symbols and resource blocks included in the slots, and the sub The number of carriers can vary.

Throughout the 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: It shall contain several things.

(Variation of aspect etc.)
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. In addition, notification of predetermined information (for example, notification of "it is X") is not limited to what is explicitly performed, but is performed by implicit (for example, not notifying of the predetermined information) It is also good.

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

One aspect of the present disclosure is useful for a wireless communication system.

10 radio base station 20 user terminal

Claims (6)

1. A transmitter configured to transmit the first wireless signal and the second wireless signal according to transmission timing synchronized at different frequencies;
   A setting unit configured to set a synchronization signal common to the first wireless signal and the second wireless signal to each of the first wireless signal and the second wireless signal;
   A wireless base station comprising
2. The transmission unit transmits the first radio signal transmitted at a first frequency at a first transmission timing at a second frequency at a second transmission timing.
   The radio base station according to claim 1.
3. Each of the synchronization signals is for detecting a primary synchronization signal used to detect a transmission timing of at least one of the first and second radio signals and identification information of a wireless area provided by the wireless base station. And a secondary synchronization signal used for
   The radio base station according to claim 1 or 2.
4. The primary synchronization signal includes information for identifying the first frequency and the second frequency,
   The radio base station according to claim 3.
5. The setting unit sets different precodings for the synchronization signal transmitted at a third transmission timing and the synchronization signal transmitted at a fourth transmission timing.
   The radio base station according to any one of claims 1 to 4.
6. A receiver configured to receive a first wireless signal and a second wireless signal transmitted according to transmission timings synchronized with each other at different frequencies;
   A detection unit that switches the frequency and detects a synchronization signal commonly set to each of the first wireless signal and the second wireless signal;
   A user terminal comprising

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