Method, user equipment, base station and non-transitory computer-readable storage medium for utilizing special subframes for NB-IOT transmission in TDD mode

Abstract

A base station and a wireless device are configured for special subframe utilization for NB‑IoT transmission in TDD mode. In an exemplary embodiment, the base station or UE can utilize the available symbols in the DwPTS or UpPTS of the special subframe for NB‑IoT transmission, respectively. In one example, the base station can use the OFDM symbols in the DwPTS to repeat some of the symbols sent in the immediately preceding downlink subframe or in the subsequent downlink subframe in a predetermined manner. In other embodiments, the UE can use the symbols in the UpPTS to repeat some of the symbols sent in the immediately preceding uplink subframe or in the previous uplink subframe in a predetermined manner. The symbols repeated in the special subframe can be coherently combined at the receiver with the corresponding symbols sent in the downlink or uplink subframe to improve decoding performance, reduce errors, improve channel estimation, and increase system capacity.

Description

[0001] This application is a divisional application of the patent application with application number 201880051206.3 filed on August 6, 2018 and invention name “Special subframe utilization for NB-IOT transmission in TDD mode”. Technical Field

[0002] The present disclosure relates generally to wireless communication networks for narrowband Internet of Things (NB-IoT), and more particularly to time division duplex (TDD) communications for NB-IoT transmissions. Background Art

[0003] Long Term Evolution (LTE) supports both frequency division duplex (FDD) operation and TDD operation. In the case of FDD operation, different carrier frequencies are used for downlink transmission and uplink transmission. Type 1 frame structure is used for FDD operation. In the case of TDD operation, the same carrier frequency is used for both uplink and downlink transmission. Type 2 frame structure is used for TDD operation. In a type 2 frame, subframes within a radio frame are allocated for use as downlink subframes, uplink subframes, or special subframes. Downlink subframes are used for downlink transmissions, and uplink subframes are used for uplink transmissions. Switching between downlink and uplink occurs during special subframes.

[0004] The special subframe is divided into three parts: Downlink Pilot Time Slot (DwPTS), Guard Period (GP) and Uplink Pilot Time Slot (UpPTS). In LTE, although the length of DwPTS is smaller than that of normal subframes and the amount of data that can be sent is correspondingly smaller, DwPTS is sometimes treated like a normal downlink subframe and used for data transmission. UpPTS is not usually used for data transmission, but can be used for channel sounding or random access. UpPTS can also be left blank and used as an extended guard period.

[0005] The 3rd Generation Partnership Project (3GPP) is currently developing a standard called Narrowband Internet of Things (NB-IoT) that is specifically suited for the Internet of Things (IoT). This new radio access technology is designed to provide improved indoor coverage, support for a large number of low-throughput devices, low latency sensitivity, ultra-low device cost, low device power consumption, and an optimized network architecture. The NB-IoT radio access technology supports three operating modes: (1) standalone operation, where NB-IoT uses a standalone carrier in any available spectrum; (2) guard band operation, where NB-IoT uses spectrum within the LTE guard band; and (3) in-band operation, where NB-IoT uses spectrum within the normal LTE carrier.

[0006] 3GPP recently approved a work item on NB-IoT enhancements to support TDD operation. In LTE systems, the DwPTS field of special subframes can be used to send user data or control information on the downlink. By using an appropriate transport block size and taking advantage of the fact that the transmission time interval (TTI) length is always equal to one millisecond, special subframes can be used to carry autonomous data (e.g., new data, new scheduling information, etc.) and are therefore treated as any other available downlink subframe.

[0007] Compared to conventional LTE systems, NB-IoT transmissions use a large number of repetitions and variable resource unit (RU) lengths. Because NB-IoT uses repetitions and variable TTI lengths, the usage of DwPTS for downlink transmissions cannot be applied to NB-IoT in the same way. To further complicate matters, NB-IoT has three operating modes. It is desirable to use a common TDD design for all three operating modes. Summary of the invention

[0008] The present disclosure relates to a new TDD mode designed for NB-IoT transmission in an NB-IoT communication network. In an exemplary embodiment, a radio node such as a base station or a user equipment (UE) is configured for TDD operation and can use available symbols in a DwPTS or UpPTS for NB-IoT transmission, respectively. In one example, the base station can use the OFDM symbols in the DwPTS to repeat some of the OFDM symbols sent in the immediately preceding downlink subframe or in a subsequent downlink subframe in a predetermined manner. Similarly, the UE can use the symbols in the UpPTS to repeat some of the symbols sent in the immediately preceding uplink subframe or in a subsequent uplink subframe in a predetermined manner. The symbols repeated in the special subframe can be coherently combined at the receiver with the corresponding symbols sent in the downlink or uplink subframe to improve decoding performance and reduce the block error rate (BLER), which will increase system capacity. The radio nodes can also exploit redundant information in OFDM symbols carried on the DwPTS and UpPTS fields (e.g., for improved channel estimation to reduce the number of required repetitions), which can translate into lower power consumption and longer battery life.

[0009] According to one aspect of the present disclosure, in the case of NB-IoT transmissions without repetition (i.e., where the number of repetitions is equal to 1), special subframes may be used for rate matching. In the case where the number of repetitions of a downlink or uplink transmission is equal to 1 (meaning that no resource units are repeated) and the number of symbols used by the DwPTS or UpPTS of the special subframe is sufficiently large (e.g., greater than the threshold) according to a threshold, the special subframe may be counted as part of the resource unit and the available symbols in the DwPTS or UpPTS of the special subframe may be used for rate matching. If the number of symbols in the DwPTS or UpPTS of the special subframe is small (e.g., less than the threshold) according to a threshold, the special subframe may be counted as part of the resource unit, but the symbols in the DwPTS or UpPTS of the special subframe are not used for rate matching.

[0010] One aspect of the present disclosure includes a method implemented by a transmitting radio node for time division duplex (TDD) communication. In one embodiment, the method includes: transmitting a first subframe including a plurality of symbols, the first subframe including one of a downlink subframe and an uplink subframe in a radio frame for TDD communication; and repeating resource elements in one or more symbols in the first subframe in a special subframe in the radio frame, the special subframe including a protection period for switching the radio node between a downlink transmission mode and an uplink transmission mode.

[0011] Another aspect of the present disclosure includes a transmitting radio node in a wireless communication network configured for TDD communication. In one embodiment, the transmitting radio node includes: an interface circuit for sending a signal to a second radio node in the wireless communication network; and a processing circuit. The processing circuit is configured to: send data in a first subframe including a plurality of symbols, the first subframe including one of a downlink subframe and an uplink subframe in a radio frame for TDD communication; and repeat resource elements in one or more symbols of the first subframe in a special subframe, the special subframe including a protection period for switching the radio node between a downlink transmission mode and an uplink transmission mode.

[0012] One aspect of the present disclosure includes a method implemented by a receiving radio node for time division duplex (TDD) communication. In one embodiment, the method includes: receiving a first subframe including a plurality of symbols, the first subframe including one of a downlink subframe and an uplink subframe in a radio frame for TDD communication; and receiving a special subframe in the radio frame, the special subframe including a protection period for switching the radio node between a downlink transmission mode and an uplink transmission mode, the special subframe including a repetition of resource elements in one or more symbols of the first subframe.

[0013] Another aspect of the present disclosure includes a receiving radio node in a wireless communication network configured for TDD communication. In one embodiment, the receiving radio node includes: an interface circuit for sending a signal to a second radio node in the wireless communication network; and a processing circuit. The processing circuit is configured to: receive a first subframe including a plurality of symbols, the first subframe including one of a downlink subframe and an uplink subframe in a radio frame for TDD communication; and receive a special subframe in the radio frame, the special subframe including a protection period for switching the radio node between a downlink transmission mode and an uplink transmission mode, the special subframe including a repetition of resource elements in one or more symbols of the first subframe. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 shows a NB-IoT communication network using TDD;

[0015] Figure 2A shows the radio resources used in the NB-IoT communication network;

[0016] Figure 2B shows the structure of an exemplary radio frame used in TDD communications;

[0017] Figure 3 shows resource mapping in an exemplary downlink subframe for TDD communication;

[0018] Figure 4 shows the mapping of OFDM symbols from downlink subframes to special subframes;

[0019] Figure 5A The mapping of OFDM symbols containing only data in a downlink subframe to OFDM symbols containing reference signals in a special subframe is shown;

[0020] Figure 5B The mapping of OFDM symbols containing reference signals in a downlink subframe to OFDM symbols containing reference signals at the same position in a special subframe is shown;

[0021] Figure 5C The mapping of OFDM symbols containing reference signals in a downlink subframe to OFDM symbols without reference signals in a special subframe is shown;

[0022] Figure 5D shows the mapping of OFDM symbols containing reference signals in a downlink subframe to OFDM symbols containing reference signals of different types in a special subframe;

[0023] Figure 6shows resource mapping in an exemplary uplink subframe for TDD communication;

[0024] Figure 7 shows the mapping of symbols from uplink subframes to special subframes;

[0025] Fig. 8A and 8B shows rate matching using symbols in special subframes;

[0026] Fig. 9 An exemplary data transmission method implemented by a radio node in a TDD communication network is shown;

[0027] Fig.10 An exemplary data reception method implemented by a radio node in a TDD communication network is shown;

[0028] Fig.11 An exemplary data reception method implemented by a radio node in a TDD communication network is shown;

[0029] Fig.12 The main functional elements of a radio node configured for TDD communications as described herein are shown. DETAILED DESCRIPTION

[0030] Figure 1 1 shows communication between a base station 20 and a UE 30 in a wireless communication network 10. The base station 20 is sometimes referred to as an evolved Node B (eNB) or a 5G Node B (gNB) in applicable standards. The UE 30, which is sometimes referred to as a wireless device, may include a cellular phone, a smart phone, a laptop, a notebook computer, a tablet computer, a machine-to-machine (M2M) communication device (also known as a machine-type communication (MTC) device), or other device with wireless communication capabilities. The term "radio node" is used herein to broadly refer to a base station 20, a UE 30, or other device that uses radio frequency signals for communication. As Figure 1 As shown, the base station 20 transmits data in the downlink on the narrowband physical downlink shared channel (NPDSCH), the narrowband physical downlink control channel (NPDCCH) and the narrowband physical broadcast channel (NPBCH) to the UE 30. The UE 30 transmits data to the base station 20 in the uplink on the narrowband physical uplink shared channel (NPUSCH).

[0031] The NB-IoT communication network 10 uses orthogonal frequency division multiplexing (OFDM) in the downlink and single carrier frequency division multiple access (SC-FDMA) in the uplink. The available radio resources in the NB-IoT communication network 10 can be considered as follows: Figure 2AThe time-frequency grid 50 shown. In the time domain, the physical resources are divided into subframes. Each subframe includes multiple symbols (e.g., OFDM symbols for downlink and SC-FDMA symbols for uplink). For a normal cyclic prefix (CP) length (suitable for use when multipath diffusion is not expected to be very severe), the subframe includes 14 symbols. If an extended cyclic prefix is ​​used, the subframe includes 12 symbols. In the frequency domain, the physical resources are divided into adjacent subcarriers spaced 15kHz apart. The number of subcarriers varies depending on the allocated system bandwidth. The smallest element in the time-frequency grid 50 is a resource element (RE) 52.

[0032] In an exemplary embodiment, the base station 20 and the UE 30 are configured to support TDD operation. In the case of TDD operation, uplink and downlink transmissions use the same carrier frequency. A type 2 frame structure is used for TDD operation. Figure 2B An exemplary frame structure for TDD communication is shown. Figure 2B In the type 2 frame structure shown, subframes within a radio frame are allocated for use as downlink (DL) subframes, uplink (UL) subframes, or special (S) subframes. Downlink subframes are used for downlink transmissions on NPDSCH, NPDCCH, or NPBCH, and uplink subframes are used for uplink transmissions on NPUSCH. Switching between downlink and uplink occurs during special subframes.

[0033] Different numbers of resources (e.g., subframes) may be allocated to uplink and downlink transmissions. Table 1 below shows an existing LTE TDD configuration described in 3GPP TS 36.211, "Physical Channels and Modulation", V14.2.0. As shown in Table 1, subframes 0 and 5 are always allocated to downlink transmissions, while subframe 2 is always allocated to uplink transmissions. The remaining subframes (except for special subframes) may then be flexibly allocated to downlink or uplink transmissions depending on the TDD configuration.

[0034] Table 1: Uplink-Downlink TDD configuration

[0035]

[0036]

[0037] As shown in Table 1, for TDD configurations 3, 4, and 5, the switch from downlink to uplink transmission occurs every 10 milliseconds, resulting in only one special subframe for each radio frame. For TDD configurations 0, 1, 2, and 6, the downlink to uplink switching period is 5 milliseconds, resulting in two special subframes used for switching in each radio frame.

[0038] The TDD configuration is usually provided as part of the System Information (SI) and usually changes infrequently. According to Release 14 of the LTE specification, the TDD configuration information is contained in a System Information Block Type 1 message shown below.

[0039] System Information Block Type 1 Message

[0040]

[0041] More specifically, the TDD Configuration Information Element (IE) is used to specify the TDD-specific physical channel configuration. The TDD Configuration IE is shown below.

[0042] TDD Configuration Information Elements

[0043]

[0044] Table 2 below contains the relevant portion of 3GPP TS 36.331 describing the content in the TDD Configuration IE.

[0045] Table 2 - TDD configuration field description

[0046]

[0047]

[0048] Reference again Figure 2B The special subframe in the radio frame is divided into three parts: DwPTS (also called the downlink part), GP, and UpPTS (also called the uplink part). The total length of the special subframe is 30,720xT S =1ms, while the various parts of the subframe have variable lengths. S It is the basic time unit defined in the LTE specification. LTE specifies 11 different configurations for special subframes, which are shown in Table 3 below.

[0049] Table 3: Configuration of special subframes (length of DwPTS / GP / UpPTS)

[0050]

[0051] In an exemplary embodiment, the base station 20 or the UE 30 may utilize the available symbols in the DwPTS or UpPTS for downlink and / or uplink NB-IoT transmissions, respectively. In one example, the base station 20 may use the OFDM symbols in the DwPTS to repeat in a predetermined manner some of the OFDM symbols sent in the valid downlink subframe immediately before the special subframe or in the valid downlink subframe after the special subframe. Similarly, the UE 30 may use the SC-FDMA symbols in the UpPTS to repeat in a predetermined manner some of the SC-FDMA symbols sent in the valid uplink subframe immediately after the special subframe or in the valid uplink subframe before the special subframe. The symbols repeated in the special subframe can be coherently combined at the receiver with the corresponding symbols transmitted in the downlink or uplink subframe to improve decoding performance and reduce the block error rate (BLER), which will increase system capacity. The radio nodes may also exploit redundant information in OFDM symbols carried on the DwPTS and UpPTS fields (eg, for improved channel estimation to reduce the number of required repetitions), which may translate into lower power consumption and longer battery life.

[0052] In some embodiments, a special subframe is used for downlink or uplink transmission only when the number of OFDM or SC-FDMA symbols in DwPTS or UpPTS meets the threshold requirements, respectively. In the current version of NB-IoT, valid and invalid subframes are represented by a bitmap with a predetermined maximum number of bits (e.g., 40 bits for in-band and 10 bits for standalone). Because the length of the bitmap is limited, special subframes can be omitted from the bitmap to save bits, and threshold requirements can be used to determine whether the special subframe is valid. If the special subframe is valid (e.g., the number of symbols in DwPTS or UpPTS meets the threshold requirements), the subframe is used for downlink or uplink transmission. If the special subframe is invalid (e.g., the number of symbols in DwPTS or UpPTS does not meet the threshold requirements), the subframe is not used for downlink or uplink transmission.

[0053] In the case of downlink transmission from the base station 20 to the UE 30, the OFDM symbols in the DwPTS are used to repeat the OFDM symbols sent on the NPDSCH, NPDCCH or NPBCH in the immediately preceding subframe or in the subsequent downlink frame. In one embodiment, the OFDM symbols in the DwPTS are used to repeat the OFDM symbols carrying SI in the downlink subframe. In another embodiment, the OFDM symbols in the DwPTS are used to repeat the OFDM symbols carrying synchronization signals (such as the primary synchronization signal (PSS) and the secondary synchronization signal (SSS)) in the downlink subframe.

[0054] NPDCCH is used, for example, to send downlink scheduling information (indicating which UE 30 is scheduled to receive downlink transmission), uplink grant information (indicating uplink resources to be used by UE 30 for uplink transmission), paging notifications, and indications of SI changes. For NB-IoT, the number of NPDCCH repetitions can be 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, and 2048. The NPDCCH subframe is divided into narrowband control channel elements (NCCE) 0 and 1, such as Figure 3 NCCE 0 uses the lowest 6 subcarriers, while NCCE 1 uses the highest 6 subcarriers. The number of resource elements (REs) used by NCCE depends on the deployment mode (standalone, in-band or guard band) and the number of logical antenna ports.

[0055] Figure 3 An exemplary resource mapping for NPDCCH for in-band deployment and two logical antenna ports is shown. Resource elements (REs) carrying narrowband reference signals (NRS) and cell-specific reference signals (CRS) (i.e., REs represented in black and gray) can be moved up or down depending on the cell identity. UE 30 uses NRS for channel estimation and performs downlink measurements. In subframes used to send NPBCH, NPDCCH, and NPDSCH, 8 resource elements are used per antenna port per subframe to map NRS. In some special subframe configurations, the number of OFDM symbols in the DwPTS is not sufficient to carry one NCCE. For these special subframe configurations, special subframes are not used for downlink transmission of NPDCCH. In this case, there is no need to include special subframes in the configuration of the NPDCCH search space. Therefore, in some embodiments, special subframes are used for downlink transmission on NPDCCH and are included in the NPDCCH search space for some special subframe configurations but not for other special subframe configurations.

[0056] Figure 4 An example is shown how the OFDM symbols carrying NPDCCH in a downlink subframe are mapped and repeated in the DwPTS part of a special subframe. Figure 4 The example shown assumes a special subframe configuration 0 (Table 2) in which the DwPTS includes 3 OFDM symbols. OFDM symbols 5, 6 and 12 in the downlink subframe are mapped to OFDM symbols 0, 1 and 2 in the DwPTS. It can be observed in this example that only OFDM symbols containing NRS are repeated in the downlink subframe. OFDM symbols containing NRS are mapped to special subframes in ascending order until the last available OFDM in the DwPTS is filled. It can also be observed that the OFDM symbols in the downlink subframe are mapped to different index positions in the DwPTS.

[0057] There are other situations where the DwPTS contains a larger number of OFDM symbols. In the case where a large number of OFDM symbols are available in the DwPTS, the OFDM symbols containing the NRS may be prioritized and mapped first to the special subframe in ascending order, descending order, or according to other schemes. Once all OFDM symbols containing the NRS are mapped, the remaining OFDM symbols may be mapped in ascending order, descending order, or according to some other specified order until the available OFDM symbols in the DwPTS are filled.

[0058] In some cases, the OFDM symbols in the special subframe may include NRSs specific to the special subframe. These NRSs may occupy different positions from the NRSs in the downlink subframe. In addition, for in-band deployment, the OFDM symbols in the special subframe may include legacy cell-specific reference signals (CRS). Therefore, when mapping OFDM symbols from a downlink subframe to the DwPTS of a special subframe, it may be necessary to omit specific REs. That is, when mapping OFDM symbols from a downlink subframe to a special subframe, the REs at positions corresponding to the NRS or legacy CRS in the special subframe may be omitted (i.e., these REs are not mapped) and replaced with the NRS or CRS in the special subframe.

[0059] Figures 5A to 5D A non-exclusive example of how OFDM symbols are mapped from a downlink subframe to a DwPTS of a special subframe is shown. For simplicity, Figures 5A to 5D The example in shows the mapping of a single OFDM symbol. However, in most use cases, two or more OFDM symbols will be repeated. The same principle applies when several symbols are repeated in the DwPTS of a special subframe.

[0060] Likewise, it can be noted that FIG. 5A to FIG. 5D The NRS in the DwPTS of the special subframe is shown to be located at the same position as the regular downlink subframe, which may not be the case for some special subframe configurations. That is, the NRS in the special subframe can be placed in a different OFDM symbol and the NRS in the special subframe is generated accordingly, for example, based on the OFDM symbol index in the special subframe.

[0061] Figure 5AA case is shown in which an OFDM symbol from a downlink subframe that does not contain a reference signal (e.g., OFDM symbol 3) is mapped to an OFDM symbol containing an NRS in a special subframe (e.g., OFDM symbol 5) and is repeated in the OFDM symbol. In this case, the REs in the OFDM symbol where the NRS is located cannot be repeated. These REs are omitted and replaced by NRSs specific to the special subframe. The same method is used in the case in which an OFDM symbol from a downlink subframe that does not contain a reference signal (e.g., OFDM symbol 3) is mapped to an OFDM symbol carrying a legacy CRS in a special subframe (e.g., OFDM symbol 4) and is repeated in the OFDM symbol. In this case, the REs in the OFDM symbol where the CRS is located are omitted and replaced by the legacy CRS.

[0062] Figure 5B Such a situation is shown, where an OFDM symbol containing an NRS from a downlink subframe (e.g., OFDM symbol 5) is mapped to an OFDM symbol containing an NRS at the same position in a special subframe (e.g., OFDM symbol 5) and is repeated in the OFDM symbol. In this case, only REs containing user data are repeated in the special subframe.

[0063] Figure 5C A situation is shown where an OFDM symbol from a downlink subframe containing an NRS (e.g., OFDM symbol 5) is mapped to an OFDM symbol in a special subframe that does not contain an NRS at the same position (e.g., OFDM symbol 3) and is repeated in that OFDM symbol. In this case, several mapping methods are possible. In the first method, only the REs carrying user data are repeated, and the reference signal positions are left empty. In the second method, the entire OFDM symbol is repeated, i.e., user data plus reference signals. In the third method, only the REs carrying user data are repeated in the special subframe, and a new NRS specific to the special subframe is generated to fill the empty REs. That is, the data REs are repeated, but the reference signals are newly generated.

[0064] Figure 5D A case is shown where an OFDM symbol (e.g., OFDM symbol 5) containing an NRS from a downlink subframe is mapped to an OFDM symbol (e.g., OFDM symbol 5) containing a legacy CRS at the same position in a special subframe and repeated in that OFDM symbol. In this case, only REs containing user data are repeated in the special subframe, and the NRS in the OFDM symbol is replaced by the CRS in the special subframe.

[0065] In the case of uplink transmission from UE 30 to base station 20, the SC-FDMA symbol in UpPTS can be used to repeat the SC-FDMA symbol sent on NPUSCH in the immediately following uplink subframe or in the previous uplink subframe. NPUSCH carries uplink user data and control information from higher layers (format 1). In addition, NPUSCH can carry a hybrid automatic repeat request (HARQ) acknowledgment for NPDSCH (format 2). The maximum transmit block size (TBS) is 1000 bits, and the subcarrier spacing can be 15KHz or 3.75KHz. Multi-tone and single-tone transmission are supported. Orthogonal phase shift keying (QPSK) is used for multi-tone transmission, while single-tone uses π / 2-BPSK or π / 4-QPSK to reduce the peak-to-average power ratio. The smallest unit for mapping a transport block (TB) is a resource unit (RU), which depends on the user's bandwidth allocation and NPUSCH format. The repetition numbers of NPUSCH are 1, 2, 4, 8, 16, 32, 64, 128 and 256.

[0066] Figure 6 An example of resource mapping for NPUSCH is shown.For 15kHz subcarrier spacing, the SC-FDMA symbol at the center of each slot carries a demodulation reference symbol (DMRS), which allows the base station 20 to estimate the uplink channel conditions.

[0067] Figure 7 An example is shown of how the SC-FDMA symbols carrying NPUSCH in subsequent uplink subframes are mapped to the UpPTS portion of a special subframe and repeated in the UpPTS portion. The example is based on NPUSCH format 1, which has one DMRS per time slot. In the case of NPUSCH format 2, there are 3 DMRS per time slot. The example takes special subframe configuration 0 (Table 2), in which the UpPTS includes 1 SC-FDMA symbol. SC-FDMA symbol 3 in the uplink subframe after the special subframe is mapped to SC-FDMA symbol 6 in the second time slot of the UpPTS. It can be observed in this example that only one SC-FDMA symbol containing DMRS in the uplink subframe is mapped. If more SC-FDMA symbols are available in the UpPTS, the SC-FDMA symbols containing DMRS in the uplink subframe will be mapped to the UpPTS in the special subframe unit in ascending, descending, or other specified order until all available SC-FDMA symbols in the UpPTS are filled.

[0068] In the case where a large number of SC-FDMA symbols in the UpPTS are available, the SC-FDMA symbols containing DMRS can be prioritized and mapped to the special subframe first in ascending order, descending order, or according to other schemes. Once all SC-FDMA symbols containing DMRS are mapped, the remaining SC-FDMA symbols can be mapped to the UpPTS in special subframe units in ascending order, descending order, or some other specified order until the available SC-FDMA symbols in the UpPTS are filled.

[0069] In addition to using special subframes to repeat SC-FDMA symbols in a downlink subframe or uplink subframe, DwPTS and / or UpPTS can also be used to send other data. In one example, UE 30 sends an uplink reference signal in one or more SC-FDMA symbols in a special subframe. In another example, UE 30 sends an uplink scheduling request or a sounding reference signal (SRS) in one or more SC-FDMA symbols in the UpPTS of a special subframe. Similarly, the base station 20 can send an NRS in one or more OFDM symbols in the DwPTS of a special subframe (not necessarily in the same position as a normal subframe).

[0070] Special subframes can also be used to adjust the timing advance. For example, if a UE 30 far away from the base station 20 is scheduled to use UpPTS, the UE 30 may need a large timing advance. The timing advance may be greater than the GP duration in the special subframe. In this case, one or more OFDM symbols used in the DwPTS may be left blank and thus used to accommodate the timing advance of the UE 30 scheduled to transmit in the UpPTS.

[0071] In the case of NB-IoT transmissions without repetition (i.e., where the number of repetitions is equal to 1), special subframes can be used in different ways. As mentioned above, there are several different special subframe configurations, some of which have a very large number of OFDM symbols available for DwPTS. In the case where the number of repetitions for NPDSCH or NPDCCH is equal to 1 (meaning that no resource units are repeated) and the number of OFDM symbols used by DwPTS is large enough (e.g., greater than the threshold) according to the threshold, the special subframe is counted as part of the resource unit and rate matching is performed using the available OFDM symbols in DwPTS. It should be noted for the in-band case that some OFDM symbols in DwPTS can be reserved for legacy LTE control channels. The reserved OFDM symbols are not used for rate matching. On the other hand, if the number of OFDM symbols used by DwPTS is small (e.g., less than the threshold) according to the threshold, the special subframe can be counted as part of the resource unit containing multiple subframes, but the OFDM symbols in the special subframe are not used for rate matching.

[0072] To perform rate matching, the base station 20 may 1) use the same code rate as the resource unit without special subframes and adjust the TBS in the resource unit containing special subframes to fill the available OFDM symbols, or 2) use the same size TBS as the resource unit without special subframes and adjust the code rate in the resource unit containing special subframes to fill the available OFDM symbols. The OFDM symbols allocated to GP and UpPTS may be left blank.

[0073] Fig. 8A An example in which each resource unit includes two subframes is shown. Fig. 8A The case where the number of OFDM symbols in the DwPTS meets the threshold requirement is shown. The shading indicates the subframes used for rate matching. In this example, RU1 includes a special subframe and the available OFDM symbols in the DwPTS are used for rate matching. Figure 8B The case where the number of OFDM symbols in the DwPTS does not meet the threshold requirement is shown. In this example, RU1 includes a special subframe (i.e., the special subframe is counted as part of RU1), but the available OFDM symbols in the DwPTS are not used for rate matching. In this case, the code rate and / or TBS are adjusted to fit the data in the downlink subframe.

[0074] The rate matching technique using special subframes may also be applied to the NPUSCH when the number of repetitions for the NPUSCH is equal to 1. In this case, when the number of SC-FDMA symbols in the UpPTS is large enough (e.g., greater than the threshold) according to the threshold, the UE 30 may use the available SC-FDMA symbols in the UpPTS of the special subframe for rate matching.

[0075] Fig. 9 An exemplary data transmission method 100 implemented by a radio node (e.g., a base station 20 or a UE 30) is shown. The radio node 20, 30 sends data in a first subframe including a plurality of symbols (block 110). The first subframe includes one of a downlink subframe and an uplink subframe in a radio frame for TDD communication. In other words, the first subframe may be a conventional downlink subframe or a conventional uplink subframe. The radio node 20, 30 repeats resource elements in one or more symbols of the first subframe in a special subframe (block 120). In some embodiments, the repetition of resource elements in symbols in a special subframe may include fewer resource elements than all resource elements of corresponding symbols in the first subframe. Resource elements that are not repeated may be replaced by reference signals in the special subframe.

[0076] Fig.10 An exemplary method 150 for receiving data implemented by a radio node (e.g., a base station 20 or a UE 30) is shown. The radio node 20, 30 receives data in a first subframe including a plurality of symbols (block 160). The first subframe includes one of a downlink subframe and an uplink subframe in a radio frame for TDD communication. The radio node receives a special subframe before or after the first subframe (block 170). The special subframe includes a repetition of resource elements in one or more symbols of the first subframe. The radio node may then optionally combine the symbols received in the special subframe with the corresponding symbols received in the first subframe (block 180). In some embodiments, the repetition of the symbols in the special subframe may include fewer resource elements than all resource elements of the corresponding symbols in the first subframe. The resource elements that are not repeated may be replaced by reference signals in the special subframe.

[0077] Fig.11An exemplary method 200 implemented by a radio node (e.g., a base station 20 or a UE 30) configured to use a special subframe for rate matching is shown. The radio node 20 or 30 determines the number of repetitions of the transmission (block 210). If the number of repetitions is equal to a predetermined number (e.g., number of repetitions = 1), the radio node 20 or 30 determines the number of symbols in the special subframe (block 220). In the case of the base station 20, the base station 20 determines the number of OFDM symbols in the DwPTS of the special subframe. In the case of the UE 30, the UE 30 determines the number of SC-FDMA symbols in the UpPTS of the special subframe. The determined number may include or exclude reserved symbols in the DwPTS or UpPTS. If the number of OFDM or SC-FDMA symbols in the DwPTS or UpPTS of the special subframe, respectively, meets the threshold requirement, the radio node 20, 30 uses the available symbols in the special subframe to perform rate matching (block 230). If the number of symbols in the DwPTS or UpPTS of the special subframe, respectively, does not meet the threshold requirement, the radio node 20, 30 does not use the symbols of the special subframe for rate matching (block 240). In some embodiments, the special subframe may be counted as part of a resource unit comprising two or more subframes. Even if the number of available symbols is less than the threshold, the special subframe may be counted as part of a resource unit and these symbols are not used for rate matching.

[0078] Fig.12 The main functional components of a radio node 300 (eg, base station 20 or UE 30 ) configured for TDD communications as described herein are shown. The radio node 300 comprises a processing circuit 310 , a memory 340 , and an interface circuit 350 .

[0079] The interface circuit 350 includes RF circuitry 355 coupled to one or more antennas 360. The RF circuitry 355 includes RF components required to communicate with one or more UEs over a wireless communication channel. Typically, the RF components include a transmitter and a receiver suitable for communicating according to the LTE standard or other RAT.

[0080] The processing circuit 310 processes signals transmitted to or received by the network node 300. Such processing includes encoding and modulation of transmitted signals and demodulation and decoding of received signals. The processing circuit 310 may include one or more microprocessors, hardware, firmware, or a combination thereof. The processing circuit 310 is configured to perform the methods and processes described herein, including Fig. 9 and 10 method.

[0081] exist Fig.12In the exemplary embodiment shown, the processing circuit 310 includes a sending unit 315, a receiving unit 320, a rate matching unit 325, and a timing advance unit 330. The sending unit 315 and the receiving unit 320 are configured to Fig. 9 and 10 The methods 100 and 200 shown perform TDD transmission and reception. The rate matching unit 325 is configured to perform rate matching as described above, including Fig.11 The timing advance unit is configured to adjust the transmission and reception timing as described above.

[0082] Memory 340 includes volatile and non-volatile memory for storing computer program code and data required for processing circuit 310 to operate. Memory 340 may include any tangible, non-transitory computer-readable storage medium for storing data, including electronic, magnetic, optical, electromagnetic or semiconductor data storage devices. Memory 340 stores a computer program 345, which includes executable instructions that configure processing circuit 310 to implement the methods and processes described herein, including the methods shown in Figures 8 and 9. Typically, computer program instructions and configuration information are stored in non-volatile memory such as ROM, EPROM or flash memory. Temporary data generated during operation can be stored in volatile memory such as RAM. In some embodiments, computer program 345 for configuring processing circuit 310 can be stored in a removable memory such as a portable optical disk, a portable digital video disk or other removable medium. Computer program 345 can also be embodied in a carrier such as an electronic signal, an optical signal, a radio signal or a computer-readable storage medium.

Claims

1. A method for transmitting data in a radio frame configured for time division duplex (TDD) communication in a user equipment (30), wherein: The radio frame comprises a special subframe, wherein the special subframe comprises at least one uplink part, the method comprising: determining a number of symbols in the uplink portion of the special subframe without repeated data transmission; It is characterized in that if the number of symbols in the uplink part of the special subframe is greater than a threshold, the uplink part of the special subframe is counted as a part of a resource unit containing at least one normal uplink subframe, and rate matching is performed for the resource unit.

2. The method according to claim 1, further comprising: Rate matching is performed using the same code rate as that used for resource units without the special subframe, and a transmission block size TBS in the resource unit including the special subframe is adjusted to fill the symbol.

3. The method according to claim 2, further comprising: Rate matching is performed by using a transport block size TBS that is the same as a transport block size TBS for a resource unit without the special subframe, and the code rate in the resource unit including the special subframe is adjusted to fill the symbol.

4. A method for transmitting data in a radio frame configured for time division duplex (TDD) communication in a base station (20), wherein: The radio frame comprises a special subframe, wherein the special subframe comprises at least one downlink part, the method comprising: determining a number of symbols in the downlink portion of the special subframe without repeated data transmission; It is characterized in that if the number of symbols in the downlink part of the special subframe is greater than a threshold, the downlink part of the special subframe is counted as a part of a resource unit containing at least one normal downlink subframe, and rate matching is performed for the resource unit.

5. The method according to claim 4, further comprising: Rate matching is performed using the same code rate as that used for resource units without the special subframe, and a transmission block size TBS in the resource unit including the special subframe is adjusted to fill the symbol.

6. The method according to claim 5, further comprising: Rate matching is performed by using a transport block size TBS that is the same as a transport block size TBS for a resource unit without the special subframe, and the code rate in the resource unit including the special subframe is adjusted to fill the symbol.

7. A user equipment (30) for transmitting data in a radio frame configured for time division duplex (TDD) communication, wherein: The radio frame comprises a special subframe, wherein the special subframe comprises at least one uplink part, the user equipment (30) being adapted to perform the following steps: determining a number of symbols in the uplink portion of the special subframe without repeated data transmission; It is characterized in that if the number of symbols in the uplink part of the special subframe is greater than a threshold, the uplink part of the special subframe is counted as a part of a resource unit containing at least one normal uplink subframe, and rate matching is performed for the resource unit.

8. The user equipment according to claim 7, further adapted to perform the steps of any one of claims 2 to 3.

9. A base station (20) configured to transmit data in a radio frame for time division duplex (TDD) communication, wherein: The radio frame comprises a special subframe, wherein the special subframe comprises at least one downlink part, the base station (20) being adapted to: determining a number of symbols in the downlink portion of the special subframe without repeated data transmission; It is characterized in that if the number of symbols in the downlink part of the special subframe is greater than a threshold, the downlink part of the special subframe is counted as a part of a resource unit containing at least one normal downlink subframe, and rate matching is performed for the resource unit.

10. The base station (20) according to claim 9, further adapted to perform the steps of any one of claims 5 to 6.

11. A non-transitory computer-readable storage medium containing a computer program, the computer program comprising executable instructions, which when executed by a user equipment (30) in a wireless communication network transmitting data in a radio frame for time division duplex (TDD) communication, wherein the radio frame comprises a special subframe, and wherein the special subframe comprises at least one uplink part, causes the user equipment (30) to: determining a number of symbols in the uplink portion of the special subframe without repeated data transmission; It is characterized in that If the number of symbols in the uplink portion of the special subframe is greater than a threshold, the uplink portion of the special subframe is counted as a portion of a resource unit containing at least one normal uplink subframe, and rate matching is performed for the resource unit.

12. A non-transitory computer-readable storage medium containing a computer program, the computer program comprising executable instructions, which when executed by a base station (20) in a wireless communication network transmitting data in a radio frame for time division duplex (TDD) communication, wherein the radio frame comprises a special subframe, and wherein the special subframe comprises at least one downlink part, causes the base station (20) to: determining a number of symbols in the downlink portion of the special subframe without repeated data transmission; If the number of symbols in the downlink portion of the special subframe is greater than a threshold, the downlink portion of the special subframe is counted as a part of a resource unit containing at least one normal downlink subframe, and rate matching is performed for the resource unit.

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