RU2772302C2 - Terminal and transmission method - Google Patents

Abstract

FIELD: communication.

SUBSTANCE: invention relates to communication means. Information about resource allocation, related to a resource allocated for the transmission, and information about a demodulation reference signal (hereinafter – DMRS), related to a number of sequential symbols, to which DMRS must be displayed, are transmitted, wherein this resource consists of a set of symbols and a set of subcarriers. A signal including DMRS is received, which is displayed in part of the mentioned resource based on transmitted information about DMRS.

EFFECT: increase in the transmission quality for NB-IoT terminals.

38 cl, 13 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001] The present disclosure relates to a terminal and a transmission method.

PRIOR ART

[0002] In recent years, a promising mechanism to support the future of the information society is machine-to-machine (M2M) communication, which implements a service through autonomous communication between machines without the involvement of a user decision. "Smart network" (smart grid) is an example of a specific application case of the M2M communication system. A smart grid is an infrastructure system that efficiently delivers a life-saving resource such as electricity or gas. For example, in a smart grid, M2M communication is performed between smart meters installed in each house or each building and a central server, and the balance of resource demand is regulated autonomously and efficiently. Other application examples of the M2M communication system include monitoring systems for product management, environmental monitoring, telemedicine and the like, remote management of stocking and loading of vending machines, and the like.

[0003] In M2M communication systems, attention is paid to the use of cellular systems having a particularly wide communication area. 3GPP standardizes an M2M-centric evolution of cellular communications called Narrowband Internet of Things (NB-IoT) (eg see NPL 4) and considers specifications to meet the requirements of lower cost terminals, lower power consumption and better coverage. Specifically, unlike handset terminals, which are often used by users when moving, for terminals such as smart meters with little to no movement, guaranteeing coverage is an absolute prerequisite for providing a service. In view of this, in order to accommodate the case in which the terminal is located in a place that is unusable in the communication areas of existing cellular networks (for example, LTE and LTE-Advanced networks), such as the basement of a building, improving the coverage to further expand the communication area , is an important issue to consider.

[0004] While existing LTE resource blocks are composed of 12 subcarriers to expand the communication area while reducing the power consumption of the terminal (hereinafter also referred to as NB-IoT terminal), the NB-IoT uplink supports transmission on subcarrier numbers that are less than 12 (eg 1, 3 and 6 subcarriers). By forcing the terminal to transmit on fewer subcarriers (in other words, to transmit on a narrower frequency band), the power spectral density is increased, thereby increasing receiver sensitivity and expanding coverage.

[0005] In the case in which the terminal transmits on a number of subcarriers less than 12 subcarriers, if resources are allocated to the terminal every 1st subframe, which is the existing unit of time for LTE resource blocks, the number of resource elements (RE) that can be allocated to the terminal per once, decreases. For example, considering the PUSCH of the existing LTE as illustrated in FIG. 1, in the case where the terminal transmits on 12 subcarriers, 12 (SC-FDMA symbols)×12 (subcarriers)=144 REs can be allocated for data transmission. On the other hand, in the case in which the terminal transmits on 1 subcarrier, 12 (SC-FDMA symbols)×1 (subcarrier)=12 REs are allocated for data transmission. In the case in which data with the same transport block size is transmitted, the code rate is increased with fewer REs. Also, in order to maintain the same code rate, it is necessary to reduce the size of the transport block, but overhead information such as header information and cyclic redundancy check (CRC) become larger in size relative to data.

[0006] In NB-IoT, in order to keep the number of REs that can be allocated to a terminal at a time at the same level as existing LTE, the number of distributed subframes is increased according to the number of transmission subcarriers. For example, resource blocks to allocate at a time (hereinafter referred to as scheduling blocks or resource blocks) are taken to be 8 subframes in the case of a terminal transmitting on 1 subcarrier, 4 subframes in the case of a terminal transmitting on 3 subcarriers, and 2 subframes in the case of a terminal transmitting on 6 subcarriers.

[0007] In NB-IoT, coverage improvement of approximately 20 dB is required compared to the LTE area. In a transmission on less than 12 subcarriers as described above, for example, in the case of a terminal transmitting on M subcarriers, coverage improvement of 10 log ₁₀ (12/M) dB is theoretically expected compared to the case of transmission on 12 subcarriers. For example, in the case of 1 subcarrier transmission, coverage can be improved by up to about 11 dB compared to 12 subcarrier LTE transmission. However, in order to realize the 20 dB coverage improvement required by NB-IoT, in addition to 1-subcarrier transmission, it is essential to apply additional coverage improvement technology.

[0008] Accordingly, in order to improve coverage, the introduction of a repetition technique that repeatedly transmits the same signal at the transmitting side and combines the signals at the receiving side is considered to increase receiver sensitivity and improve coverage.

[0009] In addition, NB-IoT terminals requiring coverage improvement have little to no movement, and with a focus on the assumption of an environment without channel variability over time, the use of a technique to improve channel estimation accuracy is also being considered.

[0010] One example of a technique for improving channel estimation accuracy is "multiple subframe channel estimation and symbol-level combining" (eg, see NPL document 5). With channel estimation on a plurality of subframes and combining at a symbol level, as illustrated in FIG. 4, for a signal repeated over a plurality of subframes (R subframes), the base station performs coherent combining at the symbol level on the number of subframes equal to the number of repetitions, or a number of subframes less than the number of repeats (X subframes). Thereafter, the base station performs channel estimation using coherently combined DMRS and uses the obtained channel estimation result to perform demodulation/decoding of SC-FDMA data symbols.

[0011] In the case in which the blocks for performing channel estimation on a plurality of subframes and combining at the symbol level, namely, the number of subframes (X) is less than the number of repetitions (R), the base station combines (R/X) symbols after demodulation and decoding.

[0012] By using channel estimation on multiple subframes and combining at the symbol level, the quality of the PUSCH transmission can be improved compared to a simple repeat that performs channel estimation and demodulation/decoding of SC-FDMA data symbols at the subframe level (for example, see document NPL 5).

Link List

Non-Patent Literature

[0013] NPL 1: 3GPP TS 36.211 V13.0.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation (Release 13)", December 2015.

NPL 2: 3GPP TS 36.212 V13.0.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding (Release 13)", December 2015.

NPL 3: 3GPP TS 36.213 V13.0.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures (Release 13)", December 2015.

NPL 4: RP-151621, Qualcomm, "New Work Item: NarrowBand IOT (NB-IOT)"

NPL 5: R1-150312, Panasonic, "Discussion and performance evaluation on PUSCH coverage enhancement"

NPL 6: R1-151587, Samsung, "Considerations of legacy SRS impact on uplink transmission from low-cost UE", April 2015

NPL 7: R1-152703, LG Electronics, "Discussion on PUSCH transmission for MTC", May 2015

SUMMARY OF THE INVENTION

[0014] In a cell that supports NB-IoT terminals, it is necessary to accommodate the coexistence of NB-IoT terminals and existing LTE terminals, and it is desirable to improve transmission quality for NB-IoT terminals while minimizing the impact on the existing LTE system.

[0015] An aspect of the present disclosure provides a terminal and a transmission method capable of improving transmission quality for NB-IoT terminals while minimizing the impact on an existing LTE system.

[0016] A terminal according to an aspect of the present disclosure receives a configuration including: a repeat unit that repeats to display a data signal and a demodulation reference signal (DMRS) multiple times at a symbol level over a plurality of subframes; a signal allocator that, in a plurality of subframes, maps repeated DMRSs to symbols other than symbols corresponding to a potential candidate SRS resource, which is a potential candidate resource on which the sounding reference signal (SRS) used to measure the quality of the received uplink signal , must be displayed; and a transmission unit that transmits an uplink signal including a DMRS and a data signal in a plurality of subframes.

[0017] It should be noted that general or specific embodiments may be implemented as a system, method, integrated circuit, computer program, storage medium, or any selective combination thereof.

[0018] According to an aspect of the present disclosure, it is possible to improve transmission quality for NB-IoT terminals while minimizing the impact on the existing LTE system.

[0019] Additional benefits and advantages according to an aspect of the present disclosure will become apparent from the description of the invention and the drawings. Benefits and/or advantages may be separately obtained according to various embodiments and features from the description and drawings, which need not all be provided in order to obtain one or more such benefits and/or advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]

[Fig. 1] Fig. 1 is a diagram illustrating a configuration example of a PUSCH subframe.

[Figure 2] Figure 2 is a diagram illustrating an example of defining srs-SubframeConfig.

[FIG. 3] FIG. 3 is a diagram illustrating an exemplary subframe setup of a potentially suitable SRS transmission and SRS resources.

[FIG. 4] FIG. 4 is a diagram illustrating exemplary operations of channel estimation on a plurality of subframes and combining at a symbol level.

[FIG. 5] FIG. 5 is a diagram illustrating exemplary retry operations at the resource block level.

[Fig. 6] Fig. 6 is a diagram illustrating exemplary repeat operations at the subframe level.

[FIG. 7] FIG. 7 is a diagram illustrating exemplary symbol-level repeat operations.

[Fig. 8] Fig. 8 is a block diagram illustrating the main configuration of a terminal according to Embodiment 1.

[Fig. 9] Fig. 9 is a block diagram illustrating the configuration of a base station according to Embodiment 1.

[Fig. 10] Fig. 10 is a block diagram illustrating a configuration of a terminal according to Embodiment 1.

[Fig. 11] Fig. 11 is a diagram illustrating exemplary PUSCH repeat transmission operations according to Embodiment 1.

[FIG. 12] FIG. 12 is a diagram illustrating exemplary PUSCH repeat transmission operations according to Embodiment 2.

[Fig. 13] Fig. 13 is a diagram illustrating exemplary PUSCH repeat transmission operations according to Embodiment 3.

Description of Embodiments

[0021] [Potentially Suitable SRS Resources in LTE]

First, potentially suitable resources in LTE will be described.

[0022] In the 3rd Generation Communications Systems Partnership Project (LTE 3GPP) Long Term Network Evolution standard, orthogonal frequency division multiple access (OFDMA) is adopted as a downlink communication method from a base station (also referred to as an eNB) to a terminal ( user equipment (UE)), while Single Carrier Frequency Division Multiple Access (SC-FDMA) has been adopted as a terminal to base station uplink communication method (eg, see NPL documents 1-3).

[0023] In LTE, communication is performed by causing a base station to allocate resource blocks (RBs) within a system bandwidth to terminals per unit of time, referred to as a subframe. 1 illustrates an exemplary subframe configuration in a Physical Uplink Shared Channel (PUSCH) in LTE. As illustrated in Figure 1, one subframe contains two time intervals (slots). In each slot, a plurality of SC-FDMA data symbols and a demodulation reference signal (DMRS) are time-multiplexed. The base station receives the PUSCH and uses the DMRS to perform channel estimation. Thereafter, the base station uses the channel estimation result to perform demodulation/decoding of the SC-FDMA data symbols.

[0024] Also, on the LTE uplink, a sounding reference signal (SRS) is used to measure the received signal quality between a base station and a terminal (eg, see NPL documents 1, 3). The SRS is mapped to the SRS resources and transmitted from the terminal to the base station. Here, by cell-specific higher-layer indication, the base station defines a group of candidate SRS resources, which includes candidate SRS resources shared among all terminals present in the target cell. Thereafter, according to the higher layer terminal-specific indication, the SRS resources in a subset of the potentially eligible SRS resource group are allocated to each terminal to be allocated with the SRS resources. The terminal maps the SRS to the allocated SRS resources and transmits to the base station. It should be noted that each candidate SRS resource is the last symbol in a subframe acting as a candidate SRS transmission (subframe of a candidate SRS transmission). Also, regarding symbols that act as candidate SRS resources, none of the terminals in the cell in which the candidate SRS resource group is defined perform data transmission, thereby preventing collisions between the SRS and the data signal (PUSCH signal).

[0025] In LTE, srs-SubframeConfig and the like are defined as a higher layer cell-specific indication that specifies a group of potentially eligible SRS resources (eg, see NPL document 1). 2 illustrates an example of srs-SubframeConfig definitions. One of the srs-SubframeConfig numbers (0 to 15) illustrated in FIG. 2 is transmitted from the base station to the terminal. With this scheme, a transmission interval (T _SFC ) at which to transmit the SRS and an offset (Δ _SFC ) for indicating a subframe at which to start transmitting the SRS are indicated from the base station to the terminal. For example, in FIG. 2, in the case where the srs-SubframeConfig number is 4 (binary=0100), the transmission interval T _SFC =5 and the offset Δ _SFC =1. In this case, subframes 2nd (=1+ _ΔSFC ), 7th (=1+ _ΔSFC +(T _SFC ×1)), 12th (=1+ _ΔSFC +(T _SFC ×2)) and so on until the nth (1+Δ _SFC +(T _SFC ×n)) become subframes of a potentially suitable SRS transmission (eg, see FIG. 3).

[0026] [Background leading to this disclosure]

The background leading to the present disclosure will then be described.

[0027] As described above, in NB-IoT, a terminal transmits on a number of subcarriers less than 12 subcarriers and a number of subframes greater than 1 subframe as one resource allocation unit (resource block). In addition, to improve coverage, repetition is applied to repeatedly transmit the same signal several times. In other words, in the time domain, assuming that X is the number of subframes per resource block and R is the number of repetitions, (X×R) subframes are used for transmission.

[0028] With regard to the method of repeating resource blocks several times, the three methods below can be assumed.

[0029] The first is repetition at the resource block level. 5 illustrates an example of repetition at the resource block level (case X=8 and R=4).

[0030] The second is to repeat at the subframe level. When repeating at the subframe level, the terminal transmits a subframe signal including the same signal within a resource block in successive subframes. 6 illustrates an example of repetition at the subframe level (case X=8 and R=4). With repetition at the subframe level, since a subframe signal including the same signal is transmitted in successive subframes, compared with repetition at the resource block level, the signals are less susceptible to frequency error, and the symbol level combining described above is easy to applications.

[0031] The third is to repeat at the character level. In symbol-level repetition, the terminal transmits Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols including the same signal within a resource block in consecutive symbols. 7 illustrates an example of symbol-level repetition (case X=1 and R=4). It should be noted that in Fig. 7 and the following description, for the sake of simplicity, the case in which the number of subframes per resource block is X=1 is illustrated as an example. With symbol level repetition, since symbols including the same signal are transmitted sequentially compared to subframe level repetition, the signals are even less susceptible to frequency error, and the coverage improvement effect due to symbol level combining is greater.

[0032] Meanwhile, in the NB-IoT, three operating modes are prescribed, namely, "Standalone mode", which uses the frequency band of the Global System for Mobile Communications (GSM®), "Guardband Operation Mode" ( Guard-band mode), which uses an unused frequency band provided to prevent interference from a single system using an adjacent frequency band in LTE, and "In-band mode", which uses a portion of the existing LTE frequency band.

[0033] In "Band Mode", in a cell that supports NB-IoT terminals, it is necessary to accommodate the coexistence of existing LTE terminals and NB-IoT terminals, and it is desirable to support NB-IoT terminals in order to minimize the impact on the existing LTE system. For this reason, in the uplink transmission of NB-IoT terminals, it is necessary to prevent collisions with the SRS, which is likely to be transmitted over the entire system bandwidth by existing LTE terminals.

[0034] In a PUSCH transmission in an LTE system, the following two methods exist as a format in which an LTE terminal transmits data in a subframe of a potentially suitable SRS transmission. The first method is a method that eliminates the last symbol after mapping data to 12 SC-FDMA symbols without affecting DMRS like other subframes, as illustrated in FIG. 1 (eg, see NPL document 6). The second method is a method (rate matching) of mapping data to 11 SC-FDMA symbols, minus the last symbol, while changing the code rate for data from other subframes, as a data transmission format in a subframe of a potentially suitable SRS transmission (for example, see document NPL 7).

[0035] Both of the two methods described above assume the existing LTE PUSCH subframe configuration as illustrated in FIG. 1, or in other words, that the last symbol of a single 14-symbol subframe is always a data symbol.

[0036] Among the repetition methods described above, repetition at the resource block level (see FIG. 5) and repetition at the subframe level (see FIG. 6) can maintain the PUSCH subframe configuration of the existing LTE, thereby enabling avoidance of collisions SRS of existing LTE due to puncturing the last symbol of a single subframe or layer rate matching. However, with repetition at the resource block level and repetition at the subframe level, symbol-level combining effects may not be sufficiently obtained.

[0037] On the other hand, in symbol-level repetition (see FIG. 7), in which symbol-level combining effects are sufficiently obtained, the last symbol of a single 14-symbol subframe is not necessarily a data symbol. For example, in the example illustrated in FIG. 7, the last symbol of the first and third subframes is DMRS. Thus, in the case in which these subframes are subframes of a potentially suitable SRS transmission, the NB-IoT terminal must exclude the DMRS mapped to the last symbol, like existing LTE. It should be noted that since DMRS is not encoded like data, rate matching cannot be applied to DMRS.

[0038] However, improvements in channel estimation accuracy are very important, especially in environments where coverage improvement is desired and avoiding DMRS exclusion is desirable. On the other hand, it is also valid to set the SRS subframe at the base station side such that the NB-IoT terminal avoids the subframes that transmit DMRS in the last symbol, but this setting limits the operation of the existing LTE.

[0039] Accordingly, one aspect of the present disclosure minimizes the effect of collision (DMRS eliminated in a subframe of a potentially eligible SRS transmission) between uplink transmission of an NB-IoT terminal that transmits symbol-level repetitions and SRS transmission by an existing LTE terminal in an environment which ensures the coexistence of LTE terminals and NB-IoT terminals. With this scheme, by performing channel estimation and symbol-level combining using a sufficient number of DMRS symbols in signal demodulation from the NB-IoT terminal, the base station is able to improve the channel estimation accuracy and received signal quality.

[0040] Below in the document, exemplary embodiments of the present disclosure will be described in detail and with reference to the drawings.

[0041] [Communication System Overview]

The communication system according to each embodiment of the present disclosure is provided by base station 100 and terminal 200. Terminal 200 is an NB-IoT terminal, for example. Also, the communication system relies on an environment in which NB-IoT terminals (terminal 200) and existing LTE terminals coexist.

[0042] FIG. 8 is a block diagram illustrating a basic configuration of a terminal 200 according to each embodiment of the present disclosure. In terminal 200 illustrated in FIG. 8, repeater 212 repeats the data signal and the demodulation reference signal (DMRS) at the symbol level over a plurality of subframes. The signal allocator 213 maps, in a plurality of subframes, repeated DMRS per symbol other than the symbol corresponding to the potential candidate SRS resource, which is the potential candidate resource on which the sounding reference signal (SRS) used to measure the quality of the received uplink signal, should be displayed. The transmission unit 216 transmits an uplink signal (PUSCH) including DMRS and a data signal in a plurality of subframes.

[0043] (Embodiment 1)

[Base Station Configuration]

9 is a block diagram illustrating the configuration of a base station 100 according to Embodiment 1 of the present disclosure. 9, the base station 100 includes a control block 101, a control signal generating block 102, an encoding block 103, a modulation block 104, a signal distribution block 105, an inverse fast Fourier transform (IFFT) block 106, a cyclic prefix (CP) addition block 107 ), transmitting block 108, antenna 109, receiving block 110, CP removal block 111, fast Fourier transform (FFT) block 112, combining block 113, inverse mapping block 114, channel estimation block 115, equalization block 116, demodulation block 117, block 118 decoding and block 119 determine.

[0044] The control unit 101 makes a selection of a group of potentially suitable SRS resources in the cell, while taking into account the amounts of SRS resources required by each terminal of the plurality of terminals (existing LTE terminals) present in the cell served by the base station 100, and outputs information indicating the selected a group of potentially suitable SRS resources, to a control signal generation unit 102 and a combiner 113 . A group of potentially eligible SRS resources is selected from the table illustrated in FIG. 2, for example.

[0045] Also, the control unit 101 outputs to the combiner 113 and the demapper 114 information related to mapping DMRS and data to SC-FDMA symbols when the NB-IoT terminal (terminal 200) transmits in repetition.

[0046] In addition, the control unit 101 decides to allocate the PUSCH with respect to the NB-IoT terminal. At this point, the control section 101 makes a selection of frequency allocation resources, a modulation/coding scheme, and the like to point to the NB-IoT terminal, and outputs information related to the selected parameters to the control signal generating section 102.

[0047] Also, the control unit 101 makes a coding level selection for the control signal, and outputs the selected coding level to the coding unit 103. Also, the control unit 101 makes selection of the radio resources (downlink resources) to which the control signal is to be mapped, and outputs information related to the selected radio resources to the signal distribution unit 105.

[0048] In addition, the control unit 101 makes selection of the coverage enhancement level for the NB-IoT terminal, and outputs information related to the selected coverage enhancement level or a count of retries required for PUSCH transmission at the selected coverage enhancement level to the control signal generation unit 102 . Also, the control section 101 generates information related to the number of subcarriers to be used for PUSCH transmission by the NB-IoT terminal, and outputs the generated information to the control signal generation section 102.

[0049] The control signal generation unit 102 generates a control signal directed to the NB-IoT terminal. The control signal includes a cell-specific higher layer signal, a terminal specific higher layer signal, or an uplink grant indicating PUSCH allocation.

[0050] The uplink grant comprises a plurality of bits and includes information indicative of frequency allocation resources, a modulation/coding scheme, and the like. In addition, the uplink grant may also include information related to the level of coverage improvement or the number of repetitions required for PUSCH transmission, and information related to the number of subcarriers to be used for PUSCH transmission by the NB-IoT terminal.

[0051] The control signal generating unit 102 uses the control information input from the control unit 101 to generate a control information bit sequence, and outputs the generated control information bit sequence (control signal) to the encoding unit 103 . It should be noted that since the control information can also be transmitted to a plurality of NB-IoT terminals, the control signal generator 102 generates bit sequences that include the identification information (ID) of each NB-IoT terminal in the control information directed to each NB-IoT terminal. For example, cyclic redundancy check (CRC) bits masked by the terminal ID corresponding to the destination terminal are added to the control information.

[0052] In addition, information about a group of potentially suitable SRS resources is notified to the NB-IoT terminal (control block 206, described later) through higher-layer cell-specific signaling. Information indicating frequency allocation resources and modulation/coding scheme, information related to coverage enhancement level or number of repetitions required for PUSCH transmission, and information related to the number of subcarriers to be used for PUSCH transmission by the NB-IoT terminal may also be notified on NB-IoT terminal via terminal-specific higher layer signaling or by using an uplink grant indicating PUSCH allocation as described above.

[0053] The coding unit 103, following the coding level specified from the control unit 101, encodes the control signal (control information bit sequence) received from the control signal generation unit 102, and outputs the encoded control signal to the modulation unit 104.

[0054] The modulation section 104 modulates the control signal received from the encoding section 103 and outputs the modulated control signal (symbol sequence) to the signal distribution section 105 .

[0055] The signal distribution block 105 maps the control signal (symbol sequence) received from the modulation block 104 to the radio resources specified by the control block 101 . It should be noted that the control channel to which the control signal is to be mapped is the downlink control channel for NB-IoT. The signal distribution section 105 outputs to the IFFT section 106 the downlink subframe signal including the NB-IoT downlink control channel to which the control signal is mapped.

[0056] The IFFT block 106 performs an IFFT process on the signal received from the signal distribution block 105, thereby converting the frequency domain signal to a time domain signal. The IFFT block 106 outputs the time domain signal to the CP adding block 107 .

[0057] The CP adding section 107 adds CP to the signal received from the IFFT section 106 and outputs the CP added signal (OFDM signal) to the transmission section 108 .

[0058] The transmission unit 108 performs radio frequency (RF) processing such as digital-to-analog (D/A) conversion and upconversion on the OFDM signal received from the CP adding unit 107, and transmits the radio signal to the NB-IoT terminal (terminal 200) through antenna 109.

[0059] The receiving unit 110 performs RF processing such as downconversion and analog-to-digital conversion (A/D) on the uplink signal (PUSCH) from the terminal 200 received via the antenna 109, and outputs the received received signal to a CP removal unit 111 . The uplink signal (PUSCH) transmitted from the terminal 200 includes a signal that is repeated over a plurality of subframes.

[0060] The CP removing unit 111 removes the CP added to the received signal received from the receiving unit 110, and outputs the CP removed signal to the FFT unit 112.

[0061] The FFT unit 112 applies the FFT process to the signal received from the CP remover 111, decomposes the signal into a sequence of signals in the frequency domain, extracts the signals corresponding to the PUSCH subframes, and outputs the extracted PUSCH signals to the combining unit 113.

[0062] The combining unit 113 uses information related to the group of potentially eligible SRS resources and information related to the PUSCH repeat transmitted by the NB-IoT terminal (information related to the number of repetitions and the mapping of DMRS and data to SC-FDMA symbols when the NB -IoT repeat transmission) input from the control unit 101 to perform symbol-level combining of the PUSCH repeated over a plurality of subframes and coherently combines the signals in a chunk corresponding to the data signal and the DMRS.

The combiner 113 outputs the combined signal to the demapper 114 .

[0063] The demapper 114 extracts the signal in the PUSCH subframe portion from the signal received from the combiner 113 . Then, the demapper 114 uses the information related to the NB-IoT PUSCH repeat transmission by the terminal input from the control unit 101, decomposes the allocated PUSCH subframe portion signal into SC-FDMA and DMRS data symbols, and outputs the DMRS to the channel estimation unit 115, performing while outputting SC-FDMA data symbols to an equalizer 116 .

[0064] The channel estimator 115 performs channel estimation using the DMRS input from the demapper 114 . The channel estimator 115 outputs the obtained channel estimate values to the equalizer 116 .

[0065] The equalizer 116 uses the channel estimate values input from the channel estimator 115 to perform symbol alignment of the SC-FDMA data input from the demapper 114 . An equalizer 116 outputs the aligned SC-FDMA data symbols to a demodulator 117 .

[0066] The demodulation section 117 applies an Inverse Discrete Fourier Transform (IDFT) to the frequency domain SC-FDMA data symbols input from the equalizer 116, and after conversion to the time domain signal, demodulates the data. Specifically, the demodulation section 117 converts the symbol sequence into a bit sequence based on the modulation scheme specified on the NB-IoT terminal, and outputs the obtained bit sequence to the decoding section 118 .

[0067] The decoding unit 118 performs error correction decoding on the bit sequence input from the demodulation unit 117 and outputs the decoded bit sequence to the determination unit 119 .

[0068] The determination block 119 performs error detection on the bit sequence input from the decoding block 118 . The determination unit 119 performs error detection using the CRC bits added to the bit sequence. If the result of determining the CRC bits is error-free, the determining unit 119 extracts the received data and reports an ACK to the control unit 101 . On the other hand, if the result of determining the CRC bits returns an error, the determining unit 119 reports NACK to the control unit 101 .

[0069] [Terminal Configuration]

10 is a block diagram illustrating the configuration of a terminal 200 according to Embodiment 1 of the present disclosure. 10, the terminal 200 includes an antenna 201, a receiving section 202, a CP removal section 203, an FFT section 204, a control signal extraction section 205, a control section 206, an encoding section 207, a modulation section 208, a DMRS generation section 209, a block 210 multiplexing block 211 DFT block 212 repetition block 213 signal distribution block 214 IFFT block 215 add CP and block 216 transmission.

[0070] The receiving unit 202 receives the control signal (downlink control channel for NB-IoT) transmitted from the base station 100 via the antenna 201, performs RF processing such as down-conversion and analog-to-digital conversion on the received radio signal, and receives the baseband OFDM signal. The receiving section 202 outputs the OFDM signal to the CP removal section 203 .

[0071] The CP removing unit 203 removes the CP added to the OFDM signal received from the receiving unit 202 and outputs the CP removed signal to the FFT unit 204 .

[0072] The FFT block 204 performs an FFT process on the signal received from the CP remover 203, thereby converting the time domain signal to a frequency domain signal. The FFT block 204 outputs the frequency domain signal to the control signal extractor 205 .

[0073] The control signal extractor 205 performs blind decoding on the frequency domain signal (downlink control channel for NB-IoT) received from the FFT 204 and attempts to decode the control signal addressed to itself. The control signal addressed to the terminal 200 includes an added CRC masked by the terminal ID corresponding to the NB-IoT terminal. Therefore, if the CRC determination is successful as a result of blind decoding, the control signal extractor 205 extracts control information and outputs it to the control block 206 .

[0074] The control unit 206 controls the transmission of the PUSCH based on the control signal input from the control signal extractor 205 .

[0075] Specifically, the control unit 206 indicates the resource allocation for PUSCH transmission to the signal allocation unit 213 based on the PUSCH resource allocation information included in the control signal.

[0076] Also, based on information about the coding scheme and the modulation scheme included in the control signal, the control unit 206 indicates the coding scheme and the modulation scheme for PUSCH transmission to the coding unit 207 and the modulation unit 208, respectively. Also, in a case in which information related to the coverage improvement level or information related to the number of repetitions required for transmitting the PUSCH is included in the control signal, based on the information, the control section 206 makes selection of the number of repetitions for transmitting the PUSCH repetition, and indicates to the repetition block 212, information expressing the selected number of repetitions. In addition, in the case where information related to the number of subcarriers to be used for PUSCH transmission by the NB-IoT terminal is included in the control signal, based on the information, the control section 206 indicates to the signal allocation section 213 the number of subcarriers and the number X of subframes per one resource block for PUSCH transmission.

[0077] Also, in the case in which information related to the coverage enhancement level, information related to the number of repetitions required for PUSCH transmission, or information related to the coding scheme and modulation scheme is notified from the base station 100 at a higher level , based on the notified information, the control section 206 makes a selection of the number of repetitions for the PUSCH repeat transmission, or a coding scheme and a modulation scheme, and indicates the selected information to the repeat section 212 or to the coding section 207 and the modulation section 208 . Similarly, in the case where information related to the number of subcarriers to be used for PUSCH transmission by the NB-IoT terminal is notified from the base station 100 at a higher level, based on the notified information, the control section 206 indicates to the signal allocation section 213 the number subcarriers and the number X of subframes per resource block for PUSCH transmission.

[0078] Also, the control unit 206 outputs information related to the group of potentially suitable SRS resources notified from the base station 100 at a cell-specific higher layer to the signal distribution unit 213 .

[0079] Also, the control section 206 outputs information related to the mapping of DMRS and data to SC-FDMA symbols when the NB-IoT terminal transmits in repetition to the multiplexing section 210, the repeating section 212, and the signal distribution section 213.

[0080] The encoder 207 adds CRC bits masked by the terminal ID to the input transmission data, performs error correction coding according to the coding scheme specified from the control unit 206, and outputs the coded bit sequence to the modulation unit 208.

[0081] The modulation unit 208 modulates the bit sequence received from the coding unit 207 based on the modulation scheme specified from the control unit 206 and outputs the modulated data symbol sequence to the multiplexing unit 210 .

[0082] The DMRS generating unit 209 generates DMRS information and outputs the generated DMRS to the multiplexing unit 210 .

[0083] Based on information related to the mapping of DMRS and data to SC-FDMA symbols input from the control unit 206, the multiplexing unit 210 multiplexes the data symbol sequence received from the modulation unit 208 and the DMRS received from the DMRS generation unit 209, and outputs the multiplexed signal to block 211 DFT.

[0084] The DFT block 211 applies DFT to the signal input from the multiplex block 210 to generate and output a frequency domain signal to the repeat block 212 .

[0085] In the case where the local terminal is in the coverage enhancement mode, based on the number of repeats indicated from the control unit 206, the repeat unit 212 repeats the signal input from the DFT unit 211 over a plurality of subframes and generates a repeat signal. The repeat block 212 outputs the repeat signal to the signal distribution block 213 .

[0086] Block 213 distribution of the signal maps the signal received from the block 212 repetition, frequency/time PUSCH resources allocated in accordance with the instructions from block 206 control. Also, based on the information associated with the group of potentially suitable SRS resources received from the control unit 206, the signal allocator 213 excludes the signal mapped to symbols corresponding to the potentially suitable SRS resources from the subframes of the potentially suitable SRS transmission. The signal distribution block 213 outputs to the IFFT block 214 the PUSCH signal mapped to the signal.

[0087] The IFFT block 214 performs an IFFT process on the time-frequency domain PUSCH signal input from the signal distributor 213, and thereby generates a time domain signal. The IFFT block 214 outputs the generated signal to the CP adding block 215 .

[0088] The CP adding block 215 adds a CP to the time domain signal received from the IFFT block 214 and outputs the CP added signal to the transmission block 216 .

[0089] The transmission unit 216 performs RF processing such as D/A conversion and upconversion on the signal received from the CP adding unit 215, and transmits the radio signal to the base station 100 via the antenna 201.

[0090] [Operations of base station 100 and terminal 200]

Operations in the base station 100 and the terminal 200 having the above configurations will be described in detail.

[0091] The base station 100 notifies the srs-SubframeConfig to the terminal 200 in the form of a higher layer cell-specific indication that specifies a group of potentially eligible SRS resources. Also, communication is performed by causing the base station 100 to allocate NB-IoT resource blocks in the NB-IoT frequency band to the terminal, namely, the terminal 200.

[0092] In addition, the base station 100 makes a PUSCH allocation decision with respect to the NB-IoT terminal. The PUSCH allocation information includes frequency allocation resource information to point to the NB-IoT terminal, information related to a coding scheme and a modulation scheme, and the like. The PUSCH allocation information may be notified from the base station 100 to the terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NB-IoT.

[0093] Also, before transmitting and receiving a PUSCH, the base station 100 pre-indicates the number of repetitions (R) to the NB-IoT terminal. The number of retries (R) may be indicated from base station 100 to terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NBIoT.

[0094] In addition, before transmitting and receiving a PUSCH, the base station 100 pre-specifies the number of transmission subcarriers (eg, 1, 3, 6, or 12 subcarriers) to be used for NB-IoT terminal PUSCH transmission to the NB-IoT terminal. The number of transmission subcarriers may be indicated from base station 100 to terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NB-IoT.

[0095] The terminal 200 makes a selection of the number X of subframes per resource block based on the specified number of subcarriers. For example, in the case where the number of transmission subcarriers is 1, 3, 6, or 12, the terminal 200 decides that the number of subframes per resource block is X=8, 4, 2, or 1, respectively.

[0096] Also, the terminal 200 transmits the PUSCH repeatedly, for the number of repetitions (R) notified from the base station 100. Therefore, the terminal 200 transmits the PUSCH on (XxR) subframes. For example, if the number of SC-FDMA symbols per frame is the same 14 symbols as existing LTE systems, (14×X×R) SC-FDMA symbols are included in (X×R) subframes.

[0097] Also, terminal 200 transmits PUSCH using symbol-level repetition. At this point, the terminal 200 displays the entire DMRS included in the repeat signal (PUSCH signal) sequentially from the start symbol of the plurality of subframes in which PUSCH repeat can be performed. Specifically, the terminal 200 displays the DMRS sequentially 2R symbols from the beginning of the subframes in which to perform the PUSCH repetition.

[0098] FIG. 11 illustrates how the PUSCH repetition is performed in the case of X=1 subframe and R=4 subframes.

[0099] As illustrated in FIG. 11, one subframe includes two DMRSs, and 8 (=2R) DMRSs are included in 4 (=X×R) subframes in which terminal 200 repeats. Accordingly, in FIG. 11, the terminal 200 maps the DMRS sequentially (also referred to as DMRS repeat in the document below) 8 SC-FDMA symbols (=2R) from the start of subframes in which PUSCH repeat (4-symbol repeat) is performed.

[0100] It should be noted that in the case where X>1 (not illustrated), it is sufficient for the terminal 200 to perform DMRS repetition of 2R symbols in the R subframe cycle.

[0101] Here, in the case of 2R<14 (the number of SC-FDMA symbols per frame), or in other words, in the case in which the number of repetitions R is less than (14/2)=7, in the terminal 200, DMRS is not displayed to the last symbol (14th symbol from the beginning) of one subframe. In other words, terminal 200 maps DMRS to SC-FDMA symbols other than the last symbol of a subframe (a subframe of a potentially eligible SRS transmission) in which an existing LTE terminal may potentially transmit SRS.

[0102] Also, terminal 200 indicates subframes of a potential SRS transmission based on the srs-SubframeConfig specified from base station 100. In addition, in subframes of a potential SRS transmission, terminal 200 excludes the last symbol of 14 SC-FDMA symbols. As described above, the DMRS is not mapped to the last symbol of the subframe. In other words, the data symbol is always mapped to the last symbol of a subframe of a potentially eligible SRS transmission. Thus, at terminal 200, in the last symbol of a subframe of a potentially eligible SRS transmission, the data symbol rather than the DMRS is omitted.

[0103] Thus, in the case in which the NB-IoT terminal, namely the terminal 200, performs symbol-level PUSCH repetition, DMRS is mapped to SC-FDMA symbols other than the SC-FDMA symbol (the last symbol of a subframe of a potentially suitable transmission SRS) corresponding to the potentially eligible SRS resource in which the LTE terminal can potentially transmit the SRS.

[0104] On the other hand, the base station 100 demodulates the data signal using the DMRS included in the PUSCH transmitted from the terminal 200. As described above, even in the case in which subframes of a potentially suitable SRS transmission are included among the subframes in which the PUSCH repetition is performed NB-IoT terminal, DMRS is not excluded in NB-IoT terminal. Thus, base station 100 is able to perform channel estimation and symbol-level combining using a sufficient number of DMRS symbols for the received PUSCH.

[0105] In addition, in Fig. 11, since all DMRS symbols are mapped sequentially from the start symbol of the plurality of subframes in which PUSCH repetition is performed, compared with the case of simply expanding the data signal and DMRS mapping of the existing LTE system (Fig. 7), the basic station 100 is able to perform symbol-level combining using twice the DMRS. Thus, according to the present embodiment, the base station 100 is able to improve the channel estimation accuracy.

[0106] Also, since a known signal, namely DMRS, is displayed sequentially at the beginning of subframes in which PUSCH repetition is performed, the base station 100 is able to accurately perform frequency error estimation and timing detection.

[0107] Also, as described above, by controlling the DMRS display in the NB-IoT terminal, the DMRS exception is avoided. In other words, according to the present embodiment, in the base station 100, it is not necessary to change the settings of the SRS subframe with respect to the existing LTE system.

[0108] According to the above, in the present embodiment, it is possible to improve the transmission quality for NB-IoT terminals while minimizing the impact on the existing LTE system.

[0109] (Embodiment 2)

Embodiment 1 describes a method for avoiding collisions between the SRS transmission of the existing LTE terminal and the DMRS transmission of the NB-IoT terminal in the case where the number of repetitions R<7. On the contrary, the present embodiment describes a method for avoiding collisions between the SRS transmission of the existing LTE terminal and the DMRS transmission of the NB-IoT terminal even in the case where the number of repetitions R≥7. In other words, the present embodiment describes a method in which DMRS is not mapped to the last symbol of a subframe, regardless of the value of the number of repetitions R.

[0110] It should be noted that the base station and the terminal according to the present embodiment share the basic configurations of the base station 100 and the terminal 200 according to Embodiment 1, and thus will be described by referring to FIG. 9 and 10.

[0111] The base station 100 points the srs-SubframeConfig to the terminal 200 as a cell-specific upper layer indication that specifies a group of potentially eligible SRS resources. Also, communication is performed by causing the base station 100 to allocate resource blocks within the NB-IoT frequency band to the NB-IoT terminal, namely the terminal 200.

[0112] In addition, the base station 100 makes a PUSCH allocation decision with respect to the NB-IoT terminal. The PUSCH allocation information includes frequency allocation resource information to indicate the NB-IoT terminal, information related to a coding scheme and a modulation scheme, and the like. The PUSCH allocation information may be indicated from base station 100 to terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NB-IoT.

[0113] Also, before transmitting and receiving a PUSCH, the base station 100 pre-indicates the number of repetitions (R) to the NB-IoT terminal. The number of retries (R) may be indicated from base station 100 to terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NB-IoT.

[0114] Also, before transmitting and receiving a PUSCH, the base station 100 previously indicates to the NB-IoT terminal the number of transmission subcarriers (eg, 1, 3, 6, or 12 subcarriers) to be used for PUSCH transmission by the NB-IoT terminal. The number of transmission subcarriers may be indicated from base station 100 to terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NB-IoT.

[0115] Also, the base station 100 makes a selection of the number of DMRS segments (N) or the number of symbol repetitions (R'), which expresses the number of DMRS symbols to transmit sequentially, with respect to the NB-IoT terminal. The number of DMRS segments (N) or the number of symbol repetitions (R') may be indicated from base station 100 to terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NB-IoT. Also, the number of DMRS segments (N) or the number of symbol repetitions (R') may be predefined parameters provided by the standard.

[0116] The terminal 200 makes a selection of the number X of subframes per resource block based on the specified number of subcarriers. For example, in the case where the number of transmission subcarriers is 1, 3, 6, or 12, the terminal 200 decides that the number of subframes per resource block is X=8, 4, 2, or 1, respectively.

[0117] Also, the terminal 200 transmits the PUSCH with repetition, for the number of repetitions (R) indicated from the base station 100. Therefore, the terminal 200 transmits the PUSCH on (XxR) subframes. For example, if the number of SC-FDMA symbols per frame is the same 14 symbols as existing LTE systems, (14×X×R) SC-FDMA symbols are included in (X×R) subframes.

[0118] Also, terminal 200 transmits PUSCH using symbol-level repetition. At this point, the terminal 200 displays a plurality of DMRSs included in the repeat signal (PUSCH signal) scattered over each certain number (R') of consecutive symbols (divided into N groups). Specifically, the terminal 200 performs DMRS sequential mapping, (DMRS repeat) (2R/N) symbols on a period of R/N subframes from the beginning of the plurality of subframes in which PUSCH repeat is to be performed.

[0119] For example, the terminal 200 displays DMRS sequentially on (2R/N) symbols from the start symbol of a plurality of subframes in which to perform PUSCH repetition, and thereafter displays DMRS on (2R/N) symbols on a period of (R/N) subframes . In other words, the terminal 200 displays the DMRS sequentially on R' symbols at the beginning of the PUSCH repeat subframes, and thereafter displays the DMRS on R' symbols over a period of (R'/2) subframes.

[0120] FIG. 12 illustrates how the PUSCH repetition is performed in the case of X=1 subframe, R=4 subframes, and N=2 (or R'=4).

[0121] As illustrated in FIG. 12, one subframe includes two DMRSs, and 8 (=2R) DMRSs are included in 4 (=X×R)) subframes in which terminal 200 repeats.

[0122] In Fig. 12, the terminal 200 displays the DMRS sequentially 4 symbols (=2R/N or =R') from the beginning of the subframes in which to perform the PUSCH repeat (4 symbol repeats). In addition, the terminal 200 displays the DMRS sequentially 4 symbols from the beginning of the 3rd subframe after 2 subframes (=R/N or R'/2) from the start subframe in which to perform PUSCH repetition.

[0123] Here, in the case where N>R/7 or R'<14, in the terminal 200, DMRS is not mapped to the last symbol of the subframe. In other words, terminal 200 maps DMRS to SC-FDMA symbols other than the last symbol of a subframe (subframe of a potentially eligible SRS transmission) in which an existing LTE terminal may potentially transmit SRS.

[0124] Also, terminal 200 designates subframes of a potential SRS transmission based on the srs-SubframeConfig specified from base station 100. In addition, in subframes of a potential SRS transmission, terminal 200 excludes the last symbol of 14 SC-FDMA symbols. As described above, DMRS is not mapped to the last symbol of the subframe. In other words, the data symbol is always mapped to the last symbol of a subframe of a potentially eligible SRS transmission. Thus, at terminal 200, in the last symbol of a subframe of a potentially eligible SRS transmission, the data symbol rather than the DMRS is discarded.

[0125] Thus, in the case in which the NB-IoT terminal, namely the terminal 200, performs symbol-level PUSCH repetition like Embodiment 1, DMRS is mapped to SC-FDMA symbols other than the SC-FDMA symbol (last subframe symbol of a potentially eligible SRS transmission) corresponding to a potentially eligible SRS resource in which an LTE terminal can potentially transmit an SRS.

[0126] On the other hand, the base station 100 demodulates the data signal using the DMRS included in the PUSCH transmitted from the terminal 200. As described above, even in the case in which subframes of a potentially suitable SRS transmission are included among the subframes in which the PUSCH repetition is performed NB-IoT terminal, DMRS is not excluded in NB-IoT terminal. Thus, base station 100 is able to perform channel estimation and symbol-level combining using a sufficient number of DMRS symbols for the received PUSCH.

[0127] Also, in FIG. 12, since a number (R') of DMRS symbols are displayed sequentially, by appropriately setting the number of segments N or the number of repetitions R', the received DMRS signal power gain is obtained by combining at the symbol level.

[0128] Also, in the present embodiment, as illustrated in FIG. 12, since DMRS is dispersed in the time domain, it becomes possible to monitor channel jitter and compensate for a frequency error. Thus, according to the present embodiment, the channel estimation accuracy can be improved.

[0129] Also, in FIG. 12, since a known signal, namely DMRS, is sequentially displayed at the beginning of the signal in which the PUSCH is repeated, the base station 100 is able to accurately perform frequency error estimation and timing detection.

[0130] Also, as described above, by controlling the DMRS display in the NB-IoT terminal, the DMRS exception is avoided. In other words, according to the present embodiment, in the base station 100, it is not necessary to change the setting parameters of the SRS subframe with respect to the existing LTE system.

[0131] According to the above, in the present embodiment, it is possible to improve the transmission quality for NB-IoT terminals while minimizing the impact on the existing LTE system.

[0132] It should be noted that although the present embodiment describes the case of starting the DMRS repeat from the start of the PUSCH repeat as one example, the starting position of the DMRS repeat is not limited to the start of the PUSCH repeat. For example, terminal 200 may also add an offset in subframe units or slot units to the DMRS repeat start position.

[0133] Even if an offset in units of a subframe is added to the DMRS repeat start position, if N<R/7 or R'<14, like FIG. 12, DMRS is not mapped to the last symbol of the subframe.

[0134] Also, in the case of adding an offset in time interval units (let Δ be the offset value) to the DMRS repeat start position, if N>2R/(14-Δ) or R'<14-Δ, DMRS is not mapped to the last symbol subframe.

[0135] (Embodiment 3)

Embodiments 1 and 2 assume a case in which the NB-IoT terminal excludes the last symbol of 14 SC-FDMA symbols in subframes of a potentially eligible SRS transmission. In this case, assuming that X is the number of subframes per resource block and R is the number of repetitions, the NB-IoT terminal transmits a PUSCH over (X×R) subframes regardless of whether or not the subframe is a subframe of a potentially eligible SRS transmission, or the number of subframes of a potentially suitable SRS transmission in a PUSCH transmission segment.

[0136] In other words, the transmission time required to repeat the PUSCH is fixed. However, in Embodiments 1 and 2, although DMRS symbols are avoided, data symbols are excluded. Thus, there is a possibility that signal degradation may occur due to the loss of data symbols, especially in the case of a low number of repetitions.

[0137] Accordingly, the present embodiment describes a method for preventing deletion of DMRS symbols and data symbols in a subframe of a potential candidate SRS transmission by assuming that the transmission time required for PUSCH repeat will be different depending on whether or not the subframe is a subframe of a potential candidate transmission. SRS, or the number of subframes of a potentially suitable SRS transmission in a PUSCH transmission segment.

[0138] The base station and the terminal according to the present embodiment share the basic configurations of the base station 100 and the terminal 200 according to Embodiment 1, and thus will be described by referring to FIG. 9 and 10.

[0139] The base station 100 points the srs-SubframeConfig to the terminal 200 as a cell-specific upper layer indication that specifies a group of potentially eligible SRS resources. Also, communication is performed by causing the base station 100 to allocate resource blocks within the NB-IoT band of the NB-IoT terminal, namely, the terminal 200.

[0140] Also, the base station 100 makes a PUSCH allocation decision with respect to the NB-IoT terminal. The PUSCH allocation information includes frequency allocation resource information for pointing to the NB-IoT terminal, information related to a coding scheme and a modulation scheme, and the like. The PUSCH allocation information may be indicated from the base station 100 to the terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NB-IoT.

[0141] Also, before transmitting and receiving a PUSCH, the base station 100 pre-indicates the number of repetitions (R) to the NB-IoT terminal. The number of retries (R) may be indicated from base station 100 to terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NBIoT.

[0142] Also, prior to transmitting and receiving a PUSCH, the base station 100 pre-indicates the number of transmission subcarriers (eg, 1, 3, 6, or 12 subcarriers) to be used for PUSCH transmission by the NB-IoT terminal to the NB-IoT terminal. The number of transmission subcarriers may be indicated from base station 100 to terminal 200 via a terminal-specific higher layer or by using a downlink control channel for NB-IoT.

[0143] The terminal 200 makes a selection of the number X of subframes per resource block based on the specified number of subcarriers. For example, in the case where the number of transmission subcarriers is 1, 3, 6, or 12, the terminal 200 selects that the number of subframes per resource block is X=8, 4, 2, or 1, respectively.

[0144] Also, terminal 200 designates subframes of a potentially suitable SRS transmission based on the srs-SubframeConfig specified from base station 100.

[0145] Also, the terminal 200 transmits the PUSCH with repetition, for the number of repetitions (R) indicated from the base station 100. At this point, the terminal 200 transmits the PUSCH using the repetition at the symbol level. During transmission of the PUSCH retry, the terminal 200 does not map DMRS and data symbols to the last symbol corresponding to a potential candidate SRS resource out of 14 SC-FDMA symbols in subframes of a candidate SRS transmission. In other words, terminal 200 maps the DMRS and data symbols to symbols other than the last symbol of the 14 SC-FDMA symbols in subframes of a potentially eligible SRS transmission.

[0146] In other words, the terminal 200 delays transmission of the PUSCH signal after the last symbol of a subframe of a potentially suitable SRS transmission by a delay amount that is equal to the last symbol (an amount in which the PUSCH signal is not displayed).

[0147] Thus, terminal 200 does not transmit a signal (DMRS or data) in the last symbol of a subframe of a potentially eligible SRS transmission. In other words, terminal 200 does not exclude any of the DMRS signals or data symbols.

[0148] FIG. 13 illustrates how the PUSCH repetition is performed in case of subframe X=1 and R=4 subframes. Also, in FIG. 13, srs-SubframeConfig=0, or in other words, subframes of a potentially suitable SRS transmission exist in a period of 1 millisecond (see FIG. 2).

[0149] As illustrated in FIG. 13, terminal 200 performs symbol-level repetition of each SC-FDMA symbol included in one resource block (X=1). In other words, similar to FIG. 7, terminal 200 sequentially displays SC-FDMA symbols including the same signals (DMRS symbols and data symbols).

[0150] However, terminal 200 does not signal the last symbol (the symbol corresponding to the potentially eligible SRS resource) in the subframes of the potential SRS transmission, and instead delays by one symbol the SC-FDMA symbols to be transmitted after the SC-FDMA symbol.

[0151] With this scheme, as illustrated in FIG. 13, in terminal 200, DMRS and data symbols are not mapped to the last symbol of a subframe. In other words, the terminal 200 does not transmit DMRS and data symbols in the last symbol of a subframe (subframe of a potentially eligible SRS transmission) in which an existing LTE terminal can potentially transmit SRS. In other words, terminal 200 does not exclude DMRS and data symbols in subframes of a potentially eligible SRS transmission.

[0152] It should be noted that, assuming that N _SRS is the number of subframes of a potentially eligible SRS transmission in the PUSCH repeat, terminal 200 performs PUSCH repeat transmission using (14×X×R+N _SRS ) SC-FDMA symbols. In other words, terminal 200 performs PUSCH retransmission using ceiling((14×X×R+N _SRS )/14) subframes. Here, the ceiling(X) function expresses a ceiling function that returns the smallest integer equal to or greater than x. For example, in FIG. 13, since X=1, R=4, and N _SRS =4, there is a delay of 4 SC-FDMA symbols in the PUSCH repeat transmission, and 5 subframes are used.

[0153] Thus, in the case in which the NB-IoT terminal, namely the terminal 200, performs symbol-level PUSCH repetition like Embodiment 1, the DMRS and the data signal are mapped to SC-FDMA symbols other than the SC- FDMA (last symbol of a potentially eligible SRS transmission subframe) corresponding to a potentially eligible SRS resource in which an LTE terminal can potentially transmit an SRS.

[0154] On the other hand, the base station 100 demodulates the data signal using the DMRS included in the PUSCH transmitted from the terminal 200. As described above, in the case in which subframes of a potentially suitable SRS transmission are included among the subframes in which the PUSCH repetition is performed by NB -IoT terminal, the base station 100 considers that the signal from the NB-IoT terminal is not mapped to the last symbol of a subframe of a potentially suitable SRS transmission and is transmitted with a delay of 1 symbol.

[0155] With this scheme, loss due to an exception in terminal 200 can be avoided not only for DMRS, but also for data symbols. Thus, in the present embodiment, the base station 100 is able to improve the channel estimate and received signal quality for the received PUSCH. Thus, in the present embodiment, it is possible to improve the transmission quality for NB-IoT terminals while minimizing the impact on the existing LTE system.

[0156] It should be noted that in the present embodiment, the method of mapping data and DMRS to SC-FDMA symbols is arbitrary. Also, in the present embodiment, unlike Embodiment 1 or 2, since data symbols are also not excluded, the received signal quality at the base station 100 does not depend on the number of subframes of a potentially suitable SRS transmission.

[0157] Thus, the above describes exemplary embodiments of the present disclosure.

[0158] It should be noted that the values of the number of repetitions, the value of the X parameter, the number of segments (N), the number of repetitions (R') of the symbol, and the values of the parameters set in srs-SubframeConfig are only examples and are not limited to the above.

[0159] Also, although the previous embodiments are described by taking the case of configuring an aspect of the present disclosure in hardware as an example, it is also possible to implement the present disclosure in software in conjunction with hardware.

[0160] In addition, each functional block used in the description of the previous embodiments is usually implemented in the form of an integrated circuit, that is, a large scale integrated circuit (LSI) chip. The integrated circuit controls each functional block used in the description of the previous embodiments and may be equipped with inputs and outputs. The functional blocks may be implemented individually as individual chips, or as a single chip that includes some or all of the functional blocks. Although LSIs are discussed here, circuit integration technology may also be referred to as IC, system LSI, super-LSI, or ultra-LSI, depending on the degree of integration.

[0161] In addition, the circuit integration technology is not limited to LSI, and can also be implemented with dedicated circuits or general purpose processors. A basic matrix die (FPGA) capable of being programmed after the manufacture of the LSI die, or a reconfigurable processor whose circuit interconnects and settings within the LSI die can be reconfigured can also be used.

[0162] In addition, if a circuit integration technology that can replace LSI emerges as a result of the development of semiconductor technology or other derivative technology, obviously the new technology can be used to integrate functional blocks. Biotechnology applications and the like are also a possibility.

[0163] The terminal of the present disclosure receives a configuration including: a repeat unit that performs repeat for displaying a data signal and a demodulation reference signal (DMRS) repeatedly at a symbol level over a plurality of subframes; a signal allocator that maps, in a plurality of subframes, repeated DMRSs to symbols other than symbols corresponding to a potential candidate SRS resource, which is a potential candidate resource on which the sounding reference signal (SRS) used to measure the quality of the received uplink signal , must be displayed; and a transmission unit that transmits an uplink signal including a DMRS and a data signal in a plurality of subframes.

[0164] In the terminal of the present disclosure, the signal distributor maps all DMRSs included in the uplink signal sequentially from the start symbol of the plurality of subframes, and discards the data signal mapped to symbols corresponding to a potentially eligible SRS resource.

[0165] In the terminal of the present disclosure, the signal allocator maps the plurality of DMRSs included in the uplink signal dispersed over each certain number of consecutive symbols, and discards the data signal mapped to symbols corresponding to a potentially eligible SRS resource.

[0166] In the terminal of the present disclosure, from the number of multiple subframes, the signal allocator maps the DMRS and the data signal to symbols other than the symbols corresponding to the potentially suitable SRS resource, and does not map the uplink signal to the symbols corresponding to the potentially suitable SRS resource .

[0167] The transmission method of the present disclosure includes: repeating to display a data signal and a demodulation reference signal (DMRS) repeatedly at a symbol level over a plurality of subframes; mapping, in a plurality of subframes repeated by the DMRS, to symbols other than symbols corresponding to a potential candidate SRS resource, which is a potential candidate resource on which a sounding reference signal (SRS) used to measure the quality of a received uplink signal is to be mapped; and transmitting an uplink signal including the DMRS and the data signal in the plurality of subframes.

[0168] An aspect of the present disclosure is useful in a mobile communication system.

List of reference marks

[0169]

100 base station

200 terminal

101, 206 control unit

102 control signal generation unit

103, 207 coding block

104, 208 modulation block

105, 213 signal distribution unit

106, 214 IFFT block

107, 215 CP add block

108, 216 transmission unit

109, 201 antenna

110, 202 receive block

111, 203 CP removal unit

112, 204 FFT block

113 unity block

114 reverse display unit

115 channel estimator

116 alignment block

117 demodulation block

118 decoding block

119 definition block

205 control signal extraction unit

209 DMRS generation unit

210 multiplexing unit

211 DFT block

212 repeat block

Statement 1. Terminal containing:

a repeat unit that repeats for displaying the data signal and the demodulation reference signal (DMRS) repeatedly at a symbol level over a plurality of subframes;

a signal allocator that maps, in a plurality of subframes, repeated DMRSs to symbols other than symbols corresponding to a potential candidate SRS resource, which is a potential candidate resource on which the sounding reference signal (SRS) to be used to measure the quality of the received uplink signal links, must be displayed; and

a transmission unit that transmits an uplink signal including a DMRS and a data signal over a plurality of subframes.

Statement 2: The terminal according to Statement 1, in which the signal distributor maps all DMRSs included in the uplink signal sequentially from the start symbol of a plurality of subframes, and excludes the data signal mapped to symbols corresponding to a potentially suitable SRS resource.

Statement 3: The terminal according to Statement 1, in which the signal spreader maps the plurality of DMRSs included in the uplink signal distributed to every certain number of consecutive symbols, and excludes the data signal mapped to symbols corresponding to a potentially suitable SRS resource.

Statement 4: The terminal according to Statement 1, in which, in a plurality of subframes, the signal distributor maps the DMRS and the data signal to symbols other than symbols corresponding to the potentially suitable SRS resource and does not map the uplink signal to symbols corresponding to the potentially suitable SRS resource .

Statement 5. A transmission method, comprising the steps of:

repeating to display the data signal and the demodulation reference signal (DMRS) multiple times at the symbol level over a plurality of subframes;

map, in a plurality of subframes, repeated DMRS to symbols other than the symbols corresponding to the potential candidate SRS resource, which is the potential candidate resource on which the sounding reference signal (SRS) to be used to measure the quality of the received uplink signal is to be mapped ; and

transmitting an uplink signal including a DMRS and a data signal over a plurality of subframes.

Claims (50)

1. Communication device, comprising: a receiver that, in operation, receives resource allocation information relating to a resource allocated for transmission and demodulation reference signal (DMRS) information subcarriers; and a transmitter that, in operation, transmits a signal including a DMRS that is mapped to a portion of said resource based on the received DMRS information. 2. The communication device of claim 1, wherein the DMRS is periodically allocated in multiple time periods within said resource, and the DMRS is mapped to one or more symbols for each of these multiple time periods based on the received DMRS information. 3. The communications device of claim 1, wherein the DMRS is mapped to symbols other than potentially suitable symbols to which the sounding reference signal (SRS) is to be mapped. 4. The communication device of claim 1, wherein the DMRS is mapped to one or more symbols corresponding to the received DMRS information from at least the first symbol of the resource. 5. The communication device according to claim 1, wherein the DMRS is mapped to one or more symbols corresponding to the received DMRS information from the first symbol in a time unit, wherein said resource consists of a plurality of time units and each of the time units contains a plurality of symbols. 6. The communication device according to claim 1, wherein the DMRS information is transmitted via upper layer signaling. 7. The communication device according to claim 1, wherein the resource allocation information indicates a number of subcarriers allocated for said transmission among a set of potentially suitable subcarriers for a given number of subcarriers, and each of this set of potentially suitable subcarriers for a number of subcarriers corresponds to a different number of symbols. 8. The communication device according to claim 1, wherein said plurality of subcarriers is 12 subcarriers or less than 12 subcarriers. 9. The communication device according to claim 1, wherein data is allocated in said resource, which data is generated without assumption regarding potentially suitable symbols to which a sounding reference signal (SRS) should be mapped, and some of the data related to potentially suitable symbols is excluded before transmission. 10. Method of communication, containing the steps in which: receiving resource allocation information related to a resource allocated for transmission and demodulation reference signal (DMRS) information related to a number of consecutive symbols to which the DMRS is to be mapped, the resource being composed of a plurality of symbols and a plurality of subcarriers; and transmitting a signal including a DMRS that is mapped to a portion of said resource based on the received DMRS information. 11. The communication method of claim 10, wherein the DMRS is periodically allocated in multiple time periods within said resource, and the DMRS is mapped to one or more symbols for each of those multiple time periods based on the received DMRS information. 12. The communication method of claim 10, wherein the DMRS is mapped to symbols other than potentially suitable symbols to which the sounding reference signal (SRS) is to be mapped. 13. The communication method of claim 10, wherein the DMRS is mapped to one or more symbols corresponding to the received DMRS information from at least the first symbol of the resource. 14. The communication method according to claim 10, wherein the DMRS is mapped to one or more symbols corresponding to the received DMRS information from the first symbol in a time unit, wherein said resource consists of a plurality of time units and each of the time units comprises a plurality of symbols. 15. The communication method of claim 10, wherein the DMRS information is transmitted via upper layer signaling. 16. The communication method according to claim 10, wherein the resource allocation information indicates a number of subcarriers allocated for said transmission among a set of potential candidates for a given number of subcarriers, each of the set of potential candidates for a number of subcarriers corresponding to a different number of symbols. 17. The communication method according to claim 10, wherein said plurality of subcarriers is 12 subcarriers or less than 12 subcarriers. 18. The communication method according to claim 10, wherein data is allocated in said resource, which data is generated without the assumption regarding potentially suitable symbols to which a sounding reference signal (SRS) should be mapped, and some of the data related to potentially suitable symbols is excluded before transmission. 19. Communication device, comprising: a transmitter that, in operation, transmits resource allocation information relating to a resource allocated for transmission and demodulation reference signal (DMRS) information subcarriers; and a receiver that, in operation, receives a signal including a DMRS that is mapped to a portion of said resource based on the transmitted DMRS information. 20. The communications device of claim 19, wherein the DMRS is periodically allocated in multiple time periods within said resource, and the DMRS is mapped to one or more symbols for each of these multiple time periods based on the transmitted DMRS information. 21. The communications device of claim 19, wherein the DMRS is mapped to symbols other than potentially suitable symbols to which the sounding reference signal (SRS) is to be mapped. 22. The communication device of claim 19, wherein the DMRS is mapped to one or more symbols corresponding to the transmitted DMRS information from at least the first symbol of the resource. 23. The communication device according to claim 19, wherein the DMRS is mapped to one or more symbols corresponding to the transmitted DMRS information from the first symbol in a time unit, wherein said resource consists of a plurality of time units and each of the time units contains a plurality of symbols. 24. The communication device according to claim 19, wherein the DMRS information is transmitted via upper layer signaling. 25. The communication device according to claim 19, wherein the resource allocation information indicates a number of subcarriers allocated for said transmission among a set of potentially suitable subcarriers for a given number of subcarriers, and each of this set of potentially suitable subcarriers for a number of subcarriers corresponds to a different number of symbols. 26. The communication device according to claim 19, wherein said plurality of subcarriers is 12 subcarriers or less than 12 subcarriers. 27. The communication device according to claim 19, wherein data is allocated in said resource, which data is generated without assumption regarding potentially suitable symbols to which a sounding reference signal (SRS) should be mapped, and some of the data related to potentially suitable symbols is excluded before transmission. 28. Method of communication, containing the steps in which: transmitting resource allocation information relating to a resource allocated for transmission and demodulation reference signal (DMRS) information relating to a number of consecutive symbols to which the DMRS is to be mapped, the resource being composed of a plurality of symbols and a plurality of subcarriers; and receiving a signal including a DMRS that is mapped to a part of said resource based on the transmitted DMRS information. 29. The communication method of claim 28, wherein the DMRS is periodically allocated in multiple time periods within said resource, and the DMRS is mapped to one or more symbols for each of those multiple time periods based on the transmitted DMRS information. 30. The communication method of claim 28, wherein the DMRS is mapped to symbols other than potentially suitable symbols to which the sounding reference signal (SRS) is to be mapped. 31. The communication method of claim 28, wherein the DMRS is mapped to one or more symbols corresponding to the transmitted DMRS information from at least the first symbol of the resource. 32. The communication method of claim 28, wherein the DMRS is mapped to one or more symbols corresponding to the transmitted DMRS information from the first symbol in a time unit, wherein said resource consists of a plurality of time units and each of the time units comprises a plurality of symbols. 33. The communication method of claim 28, wherein the DMRS information is transmitted via upper layer signaling. 34. The communication method of claim 28, wherein the resource allocation information indicates a number of subcarriers allocated for said transmission among a plurality of potential candidates for the number of subcarriers, each of the plurality of potential candidates for the number of subcarriers corresponding to a different number of symbols. 35. The communication method of claim 28, wherein said plurality of subcarriers is 12 subcarriers or less than 12 subcarriers. 36. The communication method according to claim 28, wherein data is allocated in said resource, which data is generated without the assumption regarding potentially suitable symbols to which a sounding reference signal (SRS) should be mapped, and some of the data related to potentially suitable symbols is excluded before transmission. 37. An integrated circuit for controlling the communication process, containing circuits that, during their operation, perform control for: receiving resource allocation information relating to a resource allocated for transmission and demodulation reference signal (DMRS) information relating to a number of consecutive symbols to which the DMRS is to be mapped, the resource being composed of a plurality of symbols and a plurality of subcarriers; and transmitting a signal including the DMRS that is mapped to the part of said resource based on the received DMRS information. 38. An integrated circuit for controlling the communication process, containing circuits that, during their operation, perform control for: transmitting resource allocation information relating to a resource allocated for transmission and demodulation reference signal (DMRS) information relating to a number of consecutive symbols to which the DMRS is to be mapped, the resource being composed of a plurality of symbols and a plurality of subcarriers; and receiving a signal including a DMRS that is mapped to a portion of said resource based on the transmitted DMRS information.

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