JP7194245B2 - Apparatus, method and integrated circuit - Google Patents

Description

The present invention relates to configuring subframes that include both uplink and downlink portions in wireless communication systems, and to transmitting and receiving data within such subframes.

Long Term Evolution (LTE)
Third generation mobile systems (3G) based on WCDMA(R) radio access technology are widely deployed around the world. The first step in enhancing or evolving this technology is the Enhanced Uplink, also known as High-Speed Downlink Packet Access (HSDPA) and High-Speed Uplink Packet Access (HSUPA). It is necessary to introduce and provide highly competitive radio access technology.

To prepare for further increases in user demand and to compete for new radio access technologies, 3GPP has introduced a new mobile communication system called Long Term Evolution (LTE). LTE is designed to meet carrier needs for high-speed data and media transfer and high-capacity voice support for the next decade. The ability to provide high bitrates is a key measure of LTE.

Long Term Evolution (LTE) work item (WI) specifications, called Evolved UTRA (UMTS Terrestrial Radio Access) and UTRAN (UMTS Terrestrial Radio Access Network), have been finalized as Release 8 (LTE Release 8). . The LTE system represents an efficient packet-based radio access and radio access network that offers full IP-based functionality with low latency and low cost. In LTE, scalable multiple frequencies such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz are used to achieve flexible system deployment using a given spectrum. transmission bandwidth is specified. In the downlink, the orthogonal Radio access based on Orthogonal Frequency Division Multiplexing (OFDM) has been adopted. Given the limited transmit power of User Equipment (UE), the provision of wide area coverage was prioritized over improvements in peak data rates, so Single-Carrier Frequency Division Multiple Access (SC-FDMA) Carrier Frequency Division Multiple Access) based radio access was adopted in the uplink. LTE Release 8/9 employs a number of key packet radio access techniques, including multiple-input multiple-output (MIMO) channel transmission techniques, to achieve a highly efficient control signaling structure.

LTE Architecture The overall architecture is shown in FIG. 1 and details of the E-UTRAN architecture are shown in FIG. The E-UTRAN consists of eNodeBs (eNodeBs) that provide protocol termination for the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) for user equipment (UE). The eNodeB (eNB) consists of a physical (PHY) layer, a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, and a It hosts the Packet Data Control Protocol (PDCP) layer. The eNodeB also provides Radio Resource Control (RRC) functionality for the control plane. The eNodeB provides radio resource management, admission control, scheduling, enhanced negotiated uplink Quality of Service (QoS), cell information broadcast, encryption/decryption of user plane and control plane data, and downlink/ It performs many functions, including compression/decompression of uplink user plane packet headers. The eNodeBs are interconnected with each other using the X2 interface.

Also, the eNodeB uses the S1 interface to the EPC (Evolved Packet Core), more specifically, the S1-MME to the Mobility Management Entity (MME), and the S1-U to the serving gateway. (SGW). The S1 interface supports many-to-many relationships between MME/Serving Gateways and eNodeBs. The SGW serves as a mobility anchor for the user plane during handovers between eNodeBs (terminating the S4 interface and relaying traffic between the 2G/3G system and the PDN GW) and with LTE and other 3GPP technologies. Routes and forwards user data packets while also acting as an anchor for mobility between For idle user equipment, the SGW terminates the downlink data path and triggers paging when downlink data reaches the user equipment. The SGW manages and stores user equipment context, eg IP bearer service parameters, network internal routing information. The SGW also performs duplication of user traffic in case of lawful interception.

The MME is the main control node for the LTE access network. The MME is responsible for idle mode user equipment tracking and paging procedures including retransmissions. The MME is involved in the bearer activation/deactivation process and is also responsible for selecting the SGW for the user equipment during initial connection and during intra-LTE handover including Core Network (CN) node relocation. . The MME is responsible for user authentication (by interacting with the HSS). Non-Access Stratum (NAS) signaling terminates at the MME, which is also responsible for generating and assigning temporary identities to user equipment. The MME checks the user equipment's authorization to camp on the service provider's Public Land Mobile Network (PLMN) and enforces user equipment roaming restrictions. The MME is the termination point in the network for ciphering/integrity protection for NAS signaling and handles security key management. Lawful interception of signaling is also supported by the MME. The MME also provides control plane functions for mobility between LTE and 2G/3G access networks with S3 interfaces terminating at the MME from the SGSN. The MME also terminates the S6a interface towards the home HSS for roaming user equipment.

Component Carrier Structure in LTE (Release 8) Downlink component carriers in 3GPP LTE (Release 8 onwards) are subdivided into the time-frequency domain within so-called subframes. In 3GPP LTE (Release 8 and later) each subframe is divided into two downlink slots, one of which is shown in FIG. The first downlink slot comprises the control channel region (PDCCH region) within the first OFDM symbol. Each subframe consists of a given number of OFDM symbols (12 or 14 OFDM symbols in 3GPP LTE, Release 8 and later) in the time domain, and each OFDM symbol spans the entire bandwidth of a component carrier. Thus, an OFDM symbol consists of a number of modulation symbols, each transmitted on N _RB ^DL ×N _SC ^RB subcarriers, respectively. For example, given a multi-carrier communication system employing OFDM, the smallest unit of resource that can be allocated by the scheduler, as used in 3GPP LTE, is one "resource block." A physical resource block (PRB) is N symb DL consecutive OFDM symbols (eg, 7 OFDM symbols) in the time domain and N _symb ^DL in the frequency domain, as illustrated in FIG. It is defined as _SC ^RB consecutive subcarriers (eg, 12 subcarriers for the component carriers). In 3GPP LTE (Release 8), a physical resource block therefore consists of N _symb ^DL ×N _SC ^RB resource elements corresponding to one slot in the time domain and 180 kHz in the frequency domain (downlink resource For further details on grids, see, for example, Non-Patent Document 1, available at http://www.3gpp.org and incorporated herein by reference).

One subframe consists of two slots. There are 14 OFDM symbols in a subframe when the so-called 'normal' CP (cyclic prefix) is used and 14 OFDM symbols in the subframe when the so-called 'extended' CP is used. There are 12 OFDM symbols. For the sake of terminology, time-frequency resources that are equal to the same N _SC ^RB contiguous subcarriers over a complete subframe are hereinafter referred to as "resource block pairs", "RB pairs" or "PRB pairs". .

The term "component carrier" refers to a combination of several resource blocks in the frequency domain. In future releases of LTE, the term "component carrier" will not be used, instead the term will be changed to "cell" to refer to the combination of downlink and optionally uplink resources. A concatenation between the carrier frequency of the downlink resource and the carrier frequency of the uplink resource is indicated in the system information transmitted on the downlink resource.

Similar assumptions about the component carrier structure apply to later releases.

Time Division Duplex Duplex - TDD
LTE supports Frequency Division Duplex (FDD) mode and Time Division Duplex (FDD) mode within a harmonized framework designed to support the evolution of TD-SCDMA It can operate in TDD (Time Division Duplex) mode. TDD separates uplink and downlink transmissions in the time domain, but may be on the same frequency.

The term "duplex" refers to two-way communication between two devices, as opposed to one-way communication. If bi-directional, transmissions on the link in each direction may occur simultaneously ("full duplex") or in mutually exclusive times ("half duplex") .

For TDD in the unpaired radio spectrum, the basic structure of RB and RE is shown in FIG. Only a subset of the subframes of the radio frame are available for downlink transmission, the remaining subframes are used for uplink transmission or special subframes. The special subframe is important to allow the uplink transmission timing to be advanced to ensure that the transmissions from the UE (ie uplink) arrive at the eNodeB at approximately the same time. Signal propagation delay is related to the distance between the transmitter and receiver (ignoring reflections and other similar effects). This means that signals transmitted by UEs closer to the eNodeB travel for a shorter time than signals transmitted by UEs farther away from the eNodeB. A distant UE must transmit its signal earlier than a near UE in order to arrive at the same time. It is solved by the so-called "timing advance" procedure in 3GPP systems. In TDD, transmission and reception occur on the same carrier frequency. That is, there are further situations where the downlink and uplink need to be duplicated in the time domain. UEs far from the eNodeB should start uplink transmission earlier than UEs closer to the eNodeB. On the other hand, downlink signals are received by UEs closer to the eNodeB earlier than UEs farther from the eNodeB. A guard time is defined in the special subframe to allow the circuit to switch from DL reception to UL transmission. To manage timing advance issues, guard times for far UEs should be longer than guard times for near UEs.

FIG. 4 specifically shows a switch point periodicity of 5 ms, ie frame structure type 2 for TDD configurations 0, 1, 2 and 6. FIG. Specifically, FIG. 4 shows a radio frame of length 10 ms and two corresponding half-frames of 5 ms each. A radio frame consists of 10 subframes of 1 ms each. Each subframe is defined by one of the uplink-downlink configurations according to the table of FIG. 5 and is assigned a type of uplink (U), downlink (D), or special (S).

This TDD structure is known as "Frame Structure Type 2" from 3GPP LTE Release 8 onwards, and seven different uplink-downlink configurations have been defined since 3GPP LTE Release 8, which are different Allows downlink-uplink ratio and switching periodicity. FIG. 5 shows a table with seven different TDD uplink-downlink configurations indexed from 0-6. 'D' indicates a downlink subframe, 'U' indicates an uplink subframe, and 'S' indicates a special subframe. These configurations differ from each other by the number and location of uplink (U) and downlink (D) subframes and a special subframe (S) for downlink-uplink switching in TDD operation. As can be seen, the seven available TDD uplink-downlink configurations are (for simplicity, some of the special subframes are available for downlink transmission, so the special subframes are the downlink subframes ) can provide between 40% and 90% of the downlink subframes.

As can be seen from Figure 5, subframe #1 ("#" means "number") is always a special subframe, and subframe #6 is a special subframe in some cases, i.e. TDD configuration 0. , 1, 2, and 6 are special subframes. On the other hand, for TDD configurations 3, 4, and 5, subframe #6 is for the downlink. The remaining subframes are either uplink subframes or downlink subframes.

The special subframe contains three fields: DwPTS (Downlink Pilot Time Slot), GP (Guard Period), and UpPTS (Uplinl Pilot Time Slot). They are used to separate uplink and downlink subframes. In special subframes, uplink and downlink signals may be transmitted within the subframe fields UpPTS and DwPTS, respectively. They are separated by guard periods, also called downlink-uplink switching points. The uplink and downlink capacities in this irregular subframe S are reduced compared to regular subframes, providing fewer bits of forward error correction redundancy for a given transport block size. can be used, or the transport block size itself should be reduced.

FIG. 6 shows a table for special subframe settings. Specifically, FIG. 6 lists the lengths of DwPTS and UpPTS in terms of the number of downlink symbols Nd and the number of uplink symbols Nu defined for 3GPP LTE Release-11. If 3GPP defined the lengths of DwPTS and UpPTS as multiples of the sampling frequency (Ts), they represent the number of OFDM or SC-FDMA symbols contained in DwPTS and UpPTS, respectively. For example, in special subframe configuration #1, the DwPTS length assuming a normal cyclic prefix is defined as 6592Ts. For the normal cyclic prefix, the first and seventh OFDM symbols are each 2208Ts long and the other symbols are 2192Ts long. Therefore, the DwPTS length of 6592Ts is equal to Nd=3 OFDM symbols: (2208+2192+2192)Ts=6592Ts. The GP (guard period) can be derived by subtracting the length of the associated DwPTS and UpPTS from the length (in number of symbols or multiples of Ts) of the special subframe (eg, 14). Since the special subframe configuration is independent of the uplink-downlink configuration shown in Figure 5, all combinations of these two configurations are possible.

The special subframe settings in the table of FIG. 6 can take values 0-9, each of which is associated with a particular configuration of the number of uplink and downlink symbols. The number of uplink and downlink symbols further depends on the length of the applied uplink and downlink cyclic prefixes. As can be seen from the table, the length of the uplink part (UpPTS) of the special subframe is very short and can only take one or two symbols. Therefore, UpPTS is only used to transmit uplink signals such as reference signals or random access requests in the form of access preambles.

The TDD configuration applied in the system includes mobile station and base station radio resource management (RRM) measurements, channel state information (CSI) measurements, channel estimation, PDCCH detection, and HARQ timing. Affects many operations performed at the station. In particular, the UE may select any subframe for TDD configuration in the current cell: measurements, CSI measurement and reporting, time domain filtering to obtain channel estimates, PDCCH detection, or UL/DL ACK/NACK feedback. Read system information to know about what to monitor.

Logical and Transport Channels The MAC layer provides data transfer services for the RLC layer through logical channels. A logical channel is either a control logical channel carrying control data such as RRC signaling, or a traffic logical channel carrying user plane data. Broadcast Control Channel (BCCH), Paging Control Channel (PCCH), Common Control Channel (CCCH), Multicast Control Channel (MCCH), and Dedicated Control Channel (DCCH) : Dedicated Control Channel) is a control logical channel. Dedicated Traffic Channel (DTCH) and Multicast Traffic Channel (MTCH) are traffic logical channels.

Data from the MAC layer is exchanged with the physical layer via transport channels. Data is multiplexed into transport channels according to how it is to be transmitted over the air. Transport channels are classified as downlink or uplink as follows: Broadcast Channel (BCH), Downlink Shared Channel (DL-SCH), Paging Channel (PCH). , and Multicast Channel (MCH) are downlink transport channels, and Uplink Shared Channel (UL-SCH) and Random Access Channel (RACH) are uplink transport channels. be.

Multiplexing is then performed between logical and transport channels in the downlink and uplink, respectively.

Layer 1/Layer 2 (L1/L2) Control Signaling Informs scheduled users of allocation status, transport format, and other data-related information (e.g., HARQ information, Transmit Power Control (TPC) commands). To notify, L1/L2 control signaling is sent on the downlink along with the data. Assuming that user allocation can vary from subframe to subframe, the L1/L2 control signaling is multiplexed with downlink data within subframes. User allocation may be performed on a Transmission Time Interval (TTI) basis, where the length of a TTI may be a multiple of subframes. The length of the TTI may be fixed within the coverage area for all users, may be different for different users, and may be dynamic for each user. In general, L1/2 control signaling only needs to be sent once per TTI. In LTE Release 8, the TTI is 1 ms, which corresponds to one subframe.

TTI is a parameter in UMTS and LTE (and other digital telecommunication networks) related to the encapsulation of data from higher layers for transmission over the radio link layer. The TTI also relates to the size of data blocks passed from higher network layers to the radio link layer. Specifically, the TTI determines the timing and granularity of mapping data to the physical layer. A TTI is the time interval during which given data is mapped to the physical layer.

L1/L2 control signaling is transmitted on a Physical Downlink Control Channel (PDCCH). The PDCCH mostly carries messages as Downlink Control Information (DCI), including resource allocations and other control information for a group of mobile terminals or UEs. In general, several PDCCHs can be transmitted within one subframe. In 3GPP LTE, assignments for uplink data transmission, also called uplink scheduling grants or uplink resource assignments, are also sent on the PDCCH.

In general, information sent on L1/L2 control signaling for allocating uplink or downlink radio resources (especially LTE(-A) Release 10) can be categorized into the following items.
- User identity, indicating the assigned user. This is usually included in the checksum by masking the CRC with user information.
• Resource allocation information, which indicates the resources (Resource Blocks, RBs) to which the user has been allocated. Note that the number of RBs assigned to a user can be dynamic.
• A carrier indicator, used when a control channel transmitted on a first carrier allocates resources for a second carrier, ie resources on or associated with a second carrier.
• Modulation and coding scheme, which determines the modulation scheme and coding rate employed.
• HARQ information, such as New Data Indicator (NDI) and/or Redundancy Version (RV), which are particularly useful in retransmissions of data packets or parts thereof.
• Power control commands, which adjust the transmission power of the assigned uplink data or control information transmissions.
• Reference signal information, such as applied cyclic shifts and/or orthogonal cover code indices, to be employed for transmission or reception of reference signals associated with the allocation.
• An uplink or downlink allocation index used to identify the order of allocation, particularly useful in TDD systems.
• Hopping information, eg, an indication of whether and how to apply resource hopping to increase frequency diversity.
- CSI request, which is used to trigger the transmission of channel state information within the allocated resources.
A flag used to indicate and control whether the transmission occurs in a single cluster (set of contiguous RBs) or in multiple clusters (at least two non-contiguous sets of contiguous RBs). , multi-cluster information. Multi-cluster allocation was introduced by 3GPP LTE-(A) Release 10.

Note that the above list is not exhaustive depending on the DCI format used and not all mentioned information items need to be present in each PDCCH transmission.

Downlink control information occurs in several formats that also differ in overall size and the information contained in its fields. The various DCI formats currently defined for LTE are: described in detail. For more information on DCI formats and specific information to be sent within DCI, see Chapter 9.3 of the Technical Standard or Non-Patent Document 3, which is incorporated herein by reference.

Error detection is provided by a 16-bit CRC (ie, DCI) appended to each PDCCH so that the UE can identify whether it received the PDCCH transmission correctly. Furthermore, it is necessary for the UE to be able to identify which PDCCH was intended for the UE. This could theoretically be achieved by adding an identifier to the PDCCH payload, but it would be more efficient to scramble the CRC with the 'UE identity', thereby saving additional overhead. be. CRC parity bits may be calculated using the entire payload. A parity bit is calculated and added. After addition, the CRC parity bits are scrambled with the corresponding RNTI if UE transmit antenna selection is not configured or not applicable.

Scrambling may further depend on UE transmit antenna selection. After addition, the CRC parity bits are scrambled with the antenna selection mask and the corresponding RNTI if UE transmit antenna selection is configured and applicable. In both cases the RNTI participates in the scrambling operation.

Correspondingly, the UE descrambles the CRC by applying the "UE identity" and if no CRC error is detected, the UE determines that the PDCCH carries its control information intended for itself. The terms "masking" and "demasking" are also used for the above-described process of scrambling the CRC with identification information.

The "UE identity" mentioned above, for which the DCI CRC may be scrambled, could also be the SI-RNTI (System Information Radio Network Temporary Identifier). The SI-RNTI is not such a "UE identity" but rather an identifier associated with the type of information indicated and transmitted, in this case system information. The SI-RNTI is typically fixed in the specification and known a priori to all UEs.

Generally, uplink control data in LTE is stored on the physical uplink shared channel (PUSCH) in the so-called uplink control information (UCI) or on the physical uplink control channel (PUCCH). Channel) with user data. The UCI is
– scheduling request;
- HARQ ACK/NACK in response to downlink data packets on PDSCH
- Channel State Information (CSI) including Channel Quality Indicator (CQI) and/or Rank Indicator (RI) related to MIMO transmission and/or Precoding Matrix Indicator (PMI)
at least one of

For more information on the UCI format and the specific information transmitted within the UCI, see Chapter 16.3 of the Technical Standard or Non-Patent Document 3, which is incorporated herein by reference.

Physical Downlink Control Channel (PDCCH) and Physical Downlink Shared Channel (PDSCH)
A physical downlink control channel (PDCCH) carries scheduling grants, eg, for allocating resources for downlink or uplink data transmission. Multiple PDCCHs can be transmitted within one subframe.

The PDCCH for user equipment shall be the first N _symb ^PDCCH OFDM symbols in a subframe (usually 1, 2 or 3 OFDM symbols as indicated by PCFICH, exception in the typical case, either 2, 3 or 4 OFDM symbols as indicated by the PCFICH). System bandwidth is typically equivalent to the span of a cell or component carrier. The region occupied by the first N _symb ^PDCCH OFDM symbols in the time domain and the N _RB ^DL ×N _SC ^RB subcarriers in the frequency domain is also called the PDCCH region or the control channel region. The remaining N _symb ^PDSCH =2·N _symb ^DL −N _symb ^PDCCH OFDM symbols in the time domain or N _RB ^DL ×N _SC ^RB subcarriers in the frequency domain are called the PDSCH region or the shared channel region ( See below).

For downlink grants (ie resource allocation) on the Physical Downlink Shared Channel (PDSCH), the PDCCH allocates PDSCH resources to (user) data in the same subframe. A PDCCH control channel region within a subframe consists of a set of CCEs, where the total number of CCEs within the control region of the subframe is distributed across time and frequency control resources. Multiple CCEs can be combined to effectively reduce the code rate of the control channel. CCEs are combined in a predetermined manner using a tree structure to achieve different code rates.

At the transport channel level, the information transmitted over the PDCCH is also called L1/L2 control signaling (see above for details of L1/L2 control signaling).

There is a certain pre-defined timing relationship between the uplink resource allocations received in the subframes and the corresponding uplink transmissions in the PUSCH. Details are given in Section 8.0 of Non-Patent Document 4, which is incorporated herein by reference. Specifically, Table 8-2 of TS 36.213 defines parameter k for TDD configurations 0-6. where k denotes the positive offset of the target of the uplink resource allocation received within the subframe, and for TDD configuration 0, uplink subframes 3 and 8, omitted here for simplicity. There is an additional definition of timing for For example, the parameter k is 6 for subframe 1 of TDD configuration 1, and the uplink resource allocation received in subframe 1 of TDD configuration 1 is actually an uplink subframe. It means that it is for subframe 1+6=7, and so on.

Hybrid ARQ Schemes A common technique for error detection and correction in packet transmission systems over unreliable channels is called Hybrid Automatic Repeat request (HARQ). Hybrid ARQ is a combination of Forward Error Correction (FEC) and ARQ.

If an FEC encoded packet is transmitted and the receiver cannot decode the packet correctly (errors are usually checked by CRC (Cyclic Redundancy Check)), the receiver requests retransmission of the packet. Generally (and throughout this document) the transmission of additional information is referred to as "retransmission (of a packet)". However, this retransmission does not necessarily imply transmission of the same encoded information, but may also imply transmission of any information belonging to the packet (eg additional redundancy information).

Depending on the information of which transmissions consist (generally code bits/symbols) and how the receiver processes the information, the following hybrid ARQ schemes are defined.

In Type I HARQ schemes, if the receiver cannot decode the packet correctly, the encoded packet information is discarded and a retransmission is requested. This means that every transmission is decoded separately. In general, retransmissions contain the same information (code bits/symbols) for the original transmission.

In Type II HARQ schemes, if the receiver fails to decode the packet correctly, a retransmission is requested and the receiver passes the information of the (erroneously received) encoded packet as soft information (soft bits/symbol). Store. This means that a soft buffer is required at the receiver. Retransmissions can consist of identical, partially identical, or non-identical information (code bits/symbols) according to the same packet as the previous transmission. Upon receiving a retransmission, the receiver combines the stored information from the soft buffer with the information just received and attempts to decode the packet based on the combined information. (The receiver could also attempt to decode the transmissions individually, but generally combining transmissions improves performance.) Combining transmissions refers to so-called soft combining, where multiple received code bits/symbols are The code bits/symbols that have been combined and received singly are code combined. Common methods for soft combining are Maximum Ratio Combining (MRC) of received modulation symbols, and Log Likelihood Ratio (LLR) combining (LLR combining is only for code bits). works).

Type II schemes are more sophisticated than Type I schemes because the probability of correct reception of a packet increases with each retransmission received. This increase comes at the expense of the hybrid ARQ soft buffer required at the receiver. This scheme can be used to perform dynamic link adaptation by controlling the amount of information to be resent. For example, if the receiver detects that the decoding was "almost" successful, it will send a small portion of the information for the next retransmission to be sent (a smaller number of code bits/symbol than the previous transmission). can only be requested. In this case, it is also theoretically possible that it is not possible to decode the packet correctly only by considering this retransmission by itself (non-self-decodable retransmission).

Type III HARQ schemes may be considered a subset of Type II schemes. In addition to the requirements of Type II schemes, each transmission in Type III schemes must be self-decodable.

Synchronous HARQ means that retransmissions of HARQ blocks occur at predefined periodic intervals. Therefore, no explicit signaling is required to indicate the retransmission schedule to the receiver.

Asynchronous HARQ provides flexibility to schedule retransmissions based on air interface conditions. In this case some identification of the HARQ processes needs to be signaled to allow correct combining and protocol operation. HARQ operation with eight processes is used in the 3GPP LTE system. The HARQ protocol operation for downlink data transmission is similar or even identical to HSDPA.

Uplink HARQ protocol operation has two different options for how to schedule retransmissions. Retransmissions are either “scheduled” by NACKs (also called synchronous non-adaptive retransmissions) or explicitly scheduled by the network by sending PDCCHs (also called synchronous adaptive retransmissions). For synchronous non-adaptive retransmissions, the retransmissions use the same parameters as the previous uplink transmission. That is, retransmissions are signaled on the same physical channel resources and each use the same modulation scheme/transport format.

Since synchronous adaptive retransmissions are explicitly scheduled via PDCCH, the eNodeB may change certain parameters for retransmissions. Retransmissions can be scheduled on different frequency resources, eg, to avoid fragmentation in the uplink. Alternatively, the eNodeB can change the modulation scheme or alternatively instruct the user equipment which redundancy version to use for retransmissions. It should be noted that HARQ feedback (ACK/NACK) and PDCCH signaling occur at the same timing. Therefore, the user equipment only checks once if a synchronous non-adaptive retransmission is triggered (i.e. only NACK received) or if the eNodeB requests a synchronous adaptive retransmission (i.e. PDCCH is signaled). OK.

HARQ and Control Signaling for TDD Operation As explained above, the transmission of downlink or uplink data by HARQ uses an acknowledgment (ACK or NACK (Negative ACK)) is required to be sent in the opposite direction.

For FDD operation, acknowledgment indicators associated with data transmissions in subframe n are transmitted in the opposite direction during subframe n+4. As a result, there is a one-to-one synchronization mapping between when the transport is sent and the corresponding acknowledgments. However, for TDD operation, subframes are designated on a cell-specific basis as uplink or downlink or special (see next section). This limits the amount of time resource grants, data transmissions, acknowledgments, and retransmissions can be sent in their respective directions. Therefore, the LTE design for TDD supports grouped ACK/NACK transmissions to carry multiple acknowledgments within one subframe.

For uplink HARQ, the transmission of multiple acknowledgments (within one downlink subframe) on the Physical Hybrid ARQ Indicator Channel (PHICH) is, from the eNodeB's point of view, a single This is not a problem as one acknowledgment is not significantly different from being sent to multiple UEs at the same time. However, for downlink HARQ, the FDD uplink control signaling (PUCCH) format is insufficient to carry the additional ACK/NACK information when the asymmetry is downlink biased. Each of the TDD subframe configurations in LTE (see below and FIG. 5) has its own predefined mapping between downlink and uplink subframes for HARQ purposes, the mapping being: It is designed to achieve a balance between minimizing acknowledgment delay and spreading ACK/NACK over the available uplink subframes. Further details are provided in Section 7.3 of Non-Patent Document 4, which is incorporated herein by reference.

Section 10.1.3 of Non-Patent Document 4, incorporated herein by reference, describes the TDD HARQ-ACK feedback procedure. Table 10.1.3-1 of TS36.213 gives the downlink association set index for ACK/NACK/DTX responses for subframes of a radio frame. Here, the number in the box for the TDD configuration indicates the negative offset of the subframe where the HARQ feedback is transported within said subframe. For example, subframe 9 for TDD configuration 0 transports HARQ feedback for subframes 9−4=5, and subframe 5 for TDD configuration 0 is actually a downlink subframe (see FIG. 5). .

In HARQ operation, the eNB can send different coded versions from the original TB in retransmissions. As a result, the UE can employ Incremental Redundancy (IR) combining to obtain additional coding gain relative to the combining gain. However, in a realistic system, it is possible for the eNB to send a TB to one specific UE on one resource segment, but the UE may not detect the data transmission due to the loss of DL control information. can't In this case, IR combining will have very poor performance for decoding retransmissions since no systematic data is available at the UE. To alleviate this problem, the UE feeds back a third state, namely discontinuous transmission (DTX) feedback, to provide TB on the associated resource segment (unlike NACK, which indicates decoding failure). is not detected.

As can be seen from Figure 5, some uplink/downlink configurations are asymmetric. For example, configuration 5 includes only 1 uplink subframe and 8 downlink subframes. Such configurations are sometimes denoted as heavy downlinks. They can lead to relatively high latency caused by limited resources for transmitting ACK/NACK feedback on the uplink corresponding to the transmitted downlink data. Latency is due to fewer opportunities for uplink data. In such cases, two or more ACK/NACK feedback responses are bundled by applying a logical AND. As a result, an ACK is sent only if all acknowledgments in the bundle are positive, otherwise the entire bundle is resent. This generally results in more retransmissions and thus potentially increased latency.

3GPP TS36.211, V8.9.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)", section 6.2 3GPP TS36.212, V12.7.0, "Multiplexing and channel coding", section 5.3.3.1 "LTE-The UMTS Long Term Evolution- From Theory to Practice", Edited by Stefanie Sesia, Issam Toufik, Matthew Baker, Wiley, 2011 3GPP TS36.213, V12.8.0, "Physical layer procedures (Release 11)"

One non-limiting exemplary embodiment provides an apparatus and method for efficient transmission and reception of data within special subframes including both downlink and uplink portions.

According to an embodiment, there is provided an apparatus for transmitting data in a frame having subframes of a wireless communication system, each subframe being an uplink subframe containing uplink signals and a downlink subframe containing downlink signals. either a subframe or a special subframe that includes a downlink signal portion and an uplink signal portion, and the device has a special subframe setting that specifies the length of the uplink portion and/or the downlink portion of the special subframe. a mapper for mapping control data including user data and/or feedback information within a transmission time interval (TTI) into one subframe; and transmitting the mapped data a transmitter, wherein i) the length of the second TTI for mapping to the uplink portion of the special subframe is shorter than the first TTI for mapping to the uplink subframe, or ii) The first number of TTIs mapped to the uplink subframe is greater than the second number of TTIs for mapping to the uplink portion of the special subframe.

According to an embodiment, there is provided an apparatus for receiving data in a frame having subframes of a wireless communication system, each subframe being an uplink subframe containing uplink signals and a downlink subframe containing downlink signals. either a subframe or a special subframe that includes a downlink signal portion and an uplink signal portion, and the device has a special subframe setting that specifies the length of the uplink portion and/or the downlink portion of the special subframe. a transmitting unit that transmits a control signal containing a subframe, a receiving unit that receives data mapped to the special subframe according to the special subframe setting, and user data within a transmission time interval (TTI) from one subframe and / or a mapper for demapping control data including feedback information, wherein i) the length of the second TTI for mapping to the uplink portion of the special subframe is the length of the first TTI for mapping to the uplink subframe; or ii) the first number of TTIs mapped to the uplink subframe is greater than the second number of TTIs for mapping to the uplink portion of the special subframe.

According to an embodiment, a method is provided for transmitting data in a frame having subframes in a wireless communication system, each subframe being an uplink subframe containing uplink signals and a downlink subframe containing downlink signals. either a subframe or a special subframe including a downlink signal portion and an uplink signal portion, the method is a special subframe setting that specifies the length of the uplink portion and/or the downlink portion of the special subframe; mapping the control data including user data and/or feedback information within a transmission time interval (TTI) into one subframe; transmitting the mapped data; i) the length of the second TTI for mapping to the uplink portion of the special subframe is shorter than the first TTI for mapping to the uplink subframe, or ii) the uplink subframe. is greater than the second number of TTIs for mapping to the uplink portion of the special subframe.

According to an embodiment, a method is provided for receiving data in a frame having subframes of a wireless communication system, each subframe being an uplink subframe containing uplink signals and a downlink subframe containing downlink signals. either a subframe or a special subframe including a downlink signal portion and an uplink signal portion, the method is a special subframe setting that specifies the length of the uplink portion and/or the downlink portion of the special subframe; receiving data mapped to the special subframe according to the special subframe configuration; and user data and/or feedback information within the transmission time interval TTI from one subframe and demapping the control data, wherein i) the length of the second TTI for mapping to the uplink portion of the special subframe is longer than the first TTI for mapping to the uplink subframe; short, or ii) the first number of TTIs mapped to the uplink subframe is greater than the second number of TTIs for mapping to the uplink portion of the special subframe.

The above and other objects and features of the present invention will become more apparent from the following description and preferred embodiments together with the accompanying drawings.

1 is a block diagram illustrating an example architecture of a 3GPP LTE system; FIG. 1 is a block diagram showing an exemplary overview of the overall E-UTRAN architecture for 3GPP LTE; FIG. 1 is a schematic diagram illustrating an exemplary downlink resource grid of downlink slots defined for 3GPP LTE (Release 8/9 and later); FIG. Fig. 3 is a schematic diagram showing the structure of a radio frame consisting of 10 subframes for a switch point periodicity of 5ms; Fig. 3 is a table showing the definition of each of the seven currently standardized (static) TDD UL/DL configurations 0-6, 10 subframes and their switching point periodicity; 4 is a table showing possible special subframe settings; 1 is a block diagram illustrating an apparatus for transmitting and receiving data using various configurations of special subframes; FIG. FIG. 4 is an exemplary table of special subframe settings; FIG. FIG. 4 is an exemplary table of special subframe settings; FIG. FIG. 4 is an exemplary table of special subframe settings; FIG. FIG. 4 is a schematic diagram showing the structure of a special subframe; FIG. 2 is a schematic diagram showing two examples of mapping transmission time intervals to special subframes; FIG. 4 is a schematic diagram showing four examples of mapping of transmission time intervals to uplink subframes and downlink subframes; FIG. 11 is a table showing uplink and downlink configurations including additional special subframes; FIG. FIG. 11 is a table showing uplink and downlink configurations including additional special subframes; FIG. FIG. 11 is a table showing uplink and downlink configurations including additional special subframes; FIG. FIG. 11 is a table showing uplink and downlink configurations including additional special subframes; FIG. FIG. 11 is a table showing uplink and downlink configurations including additional special subframes; FIG. FIG. 11 is a table showing uplink and downlink configurations including additional special subframes; FIG. FIG. 11 is a table showing uplink and downlink configurations including additional special subframes; FIG. FIG. 11 is a table showing uplink and downlink configurations including additional special subframes; FIG. Fig. 4 is a flow diagram showing a receiving method and a transmitting method;

As shown in FIG. 6, the uplink part (UpPTS) of the special subframe can have only one or two symbols. For LTE, these symbols are SC-FDMA symbols. One or two symbols may be used to transmit some reference signals (eg, sounding reference signals, SRS), but are insufficient to accommodate control or user data. For example, this short uplink portion is not sufficient to support PUSCH transmissions (user data) or control data transmissions containing feedback information such as positive and negative acknowledgments (ACK/NACK) or channel quality information. . In other words, even if puncturing is applied, the data and control signals provided for mapping to the physical layer within one uplink TTI may be too long to fit in a special subframe.

However, especially when the asymmetry between the downlink capacity and the uplink capacity is high, it is not possible to use the additional capacity of special subframes for transmission of control data or user data, especially to improve the uplink capacity. should be beneficial. For example, as can be seen from FIG. 5, in heavy downlink configurations such as configuration 5, uplink subframes are only transmitted once per frame. This can lead to long feedback latencies for parallel downlink traffic. Moreover, there may be insufficient resources for sending feedback. Consequently, acknowledgment bundling or multiplexing is applied. However, applying bundling or multiplexing can increase feedback loss. It contributes to increased latency on the other side. This loss can occur, for example, when only one joint feedback bit is required to convey the ACK/NACK status for two transport blocks. Since erroneously omitting a NACK is more harmful than an ACK, in that case a joint feedback bit should indicate an ACK, unless ACK is determined for both transport blocks such a joint feedback bit should indicate a NACK.

To maintain backward compatibility with existing systems and/or avoid interference problems, it is desirable to align the transmission structure with conventional TDD subframes. In particular, uplink/downlink subframe allocation, switching periodicity, and special subframe structure should be maintained.

According to this disclosure, special subframes may be used to reduce latency.

This may be achieved in conjunction with employing a short transmission time interval (sTTI), ie a TTI that is shorter than the length of a subframe. Specifically, in LTE, the TTI typically has a length of 1 ms, corresponding to the length of a subframe. Accordingly, a single TTI is typically mapped to a single subframe. In the short TTI, data may also be mapped separately to each uplink and downlink portion of the special subframe. A short TTI also reduces latency.

Better latency than previous generation 3GPP Radio Access Technology (RAT) was one performance metric that guided the design of LTE. Packet data latency is not only important for the perceived responsiveness of the system, it is also a parameter that indirectly affects throughput. HTTP/TCP is the dominant application-layer and transport-layer protocol suite used on the Internet today. Typical sizes of HTTP-based transactions on the Internet range from a few tens of kilobytes to one megabyte. In this size range, the TCP slow start period is most part of the total transport period of the packet stream. During TCP slow start, performance is latency limited. Therefore, improving latency can improve average throughput for these types of TCP-based data transactions. Additionally, to achieve very high bit rates (in the Gbps range with Release 13CA), the UE's L2 buffer needs to be dimensioned accordingly. The longer the round trip time, the larger the buffer needs to be. The only way to reduce buffering requirements on the UE and eNB side is to reduce latency.

Radio resource efficiency may also be positively impacted by reduced latency. Lowering packet data latency may increase the number of possible transmission attempts within a given delay range. Therefore, a higher BLER target can be used for data transmission, freeing radio resources but still maintaining the same level of robustness to users with poor radio conditions. Keeping the same BLER target, increasing the number of possible transmissions within a certain delay range can also translate into more robust transmissions of real-time data streams (eg, VoLTE). This should improve the capacity of VoLTE voice systems.

Latency can be reduced by shortening the TTI and reducing processing time. Specifically, TTI lengths between 0.5 ms and one OFDM/SC-FDMA symbol have implications for reference signals and physical layer control signaling, as well as backward compatibility, i.e., for previous releases on the same carrier. It may be beneficial to take into account allowing normal operation of the UE.

According to this disclosure, shorter TTIs are used to map user data or control data to the uplink or downlink portion of the special subframe. A short TTI is shorter than the duration of a subframe. Specifically, the short TTI may be equivalent to (or equal to) the duration of the downlink or uplink portion of the special subframe, or shorter.

The structure of the special subframe is modified with respect to the conventional special subframe (see Fig. 6) in order to further provide the possibility of mapping data to the uplink part (and/or downlink part) of the special subframe. be done.

FIG. 7 shows communication between a base station (eNB) and a terminal (user equipment, UE). A terminal may include a device 700B for transmitting data in frames having subframes of a wireless communication system. The wireless communication system may be an LTE system capable of operating as a cellular network and/or in device-to-device mode. The frame may then correspond to the radio frame currently defined to include the 10 subframes described above with reference to FIG. Each such subframe is either an uplink subframe containing uplink signals, a downlink subframe containing downlink signals, or a special subframe containing a downlink signal portion as well as an uplink signal portion. .

In the uplink direction, a terminal (UE) transmits data to a base station. In the downlink direction, a terminal receives data from a base station. The data may be user data (ie, data generated by a user application that may include higher layer control overhead) or control data such as Layer 1/Layer 2 signaling that includes feedback information. The feedback information may comprise HARQ positive or negative acknowledgments, channel quality indications, rank indicators, or PMI.

Note that the same device may also be implemented in relay nodes that communicate with base stations via backhaul links.

Device 700B comprises receiver 720 and transmitter 740 . The receiver and transmitter may, for example, embody the functions required for data reception and transmission, such as antennas, amplifiers, etc., implemented in dedicated or programmable circuits (hardware).

The receiving unit 720 receives a control signal including a special subframe setting that specifies the length of the uplink portion and/or the downlink portion of the special subframe. The control signal may be control signaling sent on any layer. For example, the control signal may be received via cell broadcast within the system information block. Control signaling may be provided via a dedicated RRC protocol or semi-statically via L1/L2 control signaling such as DCI in LTE. A control signal may be valid for a single UE or for a group of UEs including all UEs within a cell.

Sending control signals via cell broadcast, such as within the system information block of LTE, has the advantage of conveying information to multiple recipients with relatively low overhead. This is particularly advantageous for cells where all UEs are expected to behave similarly as far as the scope of the invention is concerned. For example, small cells, ie cells with small coverage areas and/or a low number of connected UEs, may operate beneficially in such a manner. Conveying control signals via dedicated RRC messages has the advantage that the receiver can verify that the control signals have been correctly received and processed. This is therefore advantageous if asynchronous operation due to errors is to be avoided, especially when the configuration conveyed by the control signal is not expected to change on a time scale of up to 320 subframes. Conveying control signals via L1/L2 control signals has the main advantage of being able to quickly adapt the configuration to ad-hoc needs such as highly fluctuating traffic changes due to data traffic models. have. Such L1/L2 control signaling is further advantageous for a group of UEs identified by a common Radio Network Temporary Identifier (RNTI), which is applied in a similar manner as dynamic TDD reconfiguration messages are supported in LTE. (see 3GPP TS36.213, v12.8.0, section 13.1). The use of dedicated RRC messages and L1/L2 control signaling has advantages for large cells, ie supporting wide areas or a large number of connected UEs. In such cases, especially in TDD, UEs near the center of the cell and UEs near the edge of the cell face large propagation delays, so that their timing advance offsets to compensate for the propagation delays need to be different. . As a result, UEs closer to the edge of the cell may require a longer GP than UEs closer to the center of the cell, so that UEs closer to the center of the cell are generally closer to the edge of the cell. It should be allowed to have a length of DwPTS+UpPTS (uplink part and/or downlink part of special subframe) longer than UE.

The special subframe setting is advantageously one of a set of predefined configurations. These configurations within a set may differ in the length of the uplink portion, downlink portion, and/or guard period between them. For example, in LTE, the special subframe has a length of 14 symbols and the subframe structure indicates which symbols are allocated for the uplink part, downlink part and GP. Note that for some scenarios, configurations with GPs with zero symbols (i.e., no GPs between the last symbol of the downlink part and the first symbol of the uplink part) may also be considered. . In particular, if the GP is shorter than one symbol, some or all of the cyclic prefix of the first symbol of the uplink portion may be used to accommodate the timing advance offset. That is, a UE may be allowed to omit transmission of some of the samples that make up its cyclic prefix.

The received special subframe configuration is then applied by the device. For example, controller 735 configures device 700B according to the special subframe configuration.

Device 700B further includes a mapper 730 that maps control data including user data and/or feedback information within a transmission time interval (TTI) to one subframe.

Specifically, the mapper receives data within a TTI and maps the received data to an uplink portion of a special subframe or uplink subframe for transmission. The mapping may include symbol forming, eg, in the case of SC-FDMA for LTE. Data is received by a mapper in device 700B. For example, user data may be received from a medium access control (MAC) layer. Control data may be generated in or between the MAC (layer 2) and physical layer (layer 1). For example, acknowledgments may be generated by the HARQ entity, while channel state feedback may be generated in response to physical layer measurements of the channel.

The length of the second TTI (short TTI) for mapping to the uplink part of the special subframe may be shorter than the first TTI (legacy TTI) for mapping to the uplink subframe. Alternatively, the first number of TTIs mapped to the uplink subframe is greater than the second number of TTIs for mapping to the uplink portion of the special subframe. Here, the TTI length may be equal for mapping to the special subframe and mapping to the uplink subframe. For example, a conventional TTI length or, in other words, a pre-configured length of the TTI that is less than the length of a single subframe may be used. Note, however, that in general the invention is not limited to the same TTI length. Simply, the length and/or number of TTIs should be chosen so that the special frame portion and the uplink or downlink frames match their duration.

Device 700B further comprises a transmitter 740 that transmits data mapped within the uplink portion of each uplink subframe and special subframe.

Correspondingly, the apparatus 700A for receiving data in frames having subframes of a wireless communication system may be part of a base station.

Apparatus 700A includes a transmitter 710 that transmits control signals including special subframe settings that specify the length of the uplink and/or downlink portions of the special subframe. Accordingly, the base station, which has information on cell resources and quality and also performs scheduling, can set the special subframe configuration to be used for communication with the UE.

Moreover, the device 700A further comprises a receiver 750 that receives data mapped to the special subframe according to the special subframe configuration. These are the uplink data transmitted by each UE in the cell.

Mapper 760 then demaps the data (user data and/or control data including feedback information) within the transmission time interval TTI from one subframe. The length of the second TTI for mapping to the uplink portion of the special subframe is shorter than the first TTI for mapping to the uplink subframe. Alternatively, the first number of TTIs mapped to the uplink subframe is greater than the second number of TTIs for mapping to the uplink portion of the special subframe.

Note that apparatus 700A may include a controller 765 that controls transmitter 710 to transmit appropriate settings and mapper 760 to demap received data accordingly.

The above description concentrates on the configuration and transmission of the uplink. However, the invention is not so limited. Specifically, the receiver of device 700B (which may be part of the UE) may also be configured to receive data in the downlink, including the downlink portion of the special subframe. For example, based on the special subframe configuration received from the base station, apparatus 700B receives downlink data within a specified TTI or multiple TTIs within the downlink portion of the special subframe. Downlink data includes user data (PDSCH) and/or control data such as L1/L2 control signals carrying scheduling information, e.g. downlink control information (DCI) carried by PDCCH/EPDCCH in LTE. It's okay.

As shown in FIG. 7, the transmitter 710 of the device 700A transmits not only the special frame and/or uplink/downlink frame configuration (dashed line), but also the data mapped according to the configuration (dashed line) to the device. 700B can be supplied to the receiver 720 of 700B. Meanwhile, the transmitter 740 of the device 700B supplies uplink data (user data or control data) to the receiver 750 of the device 700A.

Correspondingly, the apparatus 700A, which may be implemented in a base station, comprises a transmitter 710 for transmitting data to one or more UEs in the downlink portion of the special subframe set by the special subframe configuration. .

FIG. 8 (parts of FIGS. 8A, 8B, and 8C) shows an example of an expanded table of configurations for special subframes.

Accordingly, the special subframe setting takes a value out of a value set (0-65), and some settings within the set are for the length of the downlink part, the uplink part, and the length of the TTI. different.

Specifically, the first nine settings in FIG. 8 correspond to the settings described with reference to FIG. Configurations 10-65 allow accommodation of multiple short TTIs for the downlink and/or uplink. To achieve this, the length of the downlink portion and/or uplink portion of the special subframe is modified to provide more options. In some cases, the guard period between the downlink and uplink parts is shortened to provide more space (symbols) for the uplink and downlink short TTIs. Specifically, this can be seen from FIG. 8, a configuration with a longer uplink portion of the special subframe is provided for both the normal cyclic prefix and the extended cyclic prefix.

In this table, special subframe settings numbered from 0 to 65 are provided. Settings 21-65 provide longer uplink portions of the special subframe, ie between 3 and 11 SC-FDMA symbols in length. Different lengths of the downlink portion are possible, resulting in different lengths of the guard period (a special subframe is assumed to have 14 symbols plus at least one symbol for the guard period).

FIG. 8 is merely an example. A different number or order of possible settings may be provided. For example, to limit the number of bits required for signaling, the number of special subframe configurations is limited to 16 (4 bits), 32 (5 bits), 64 (6 bits), or 128 (7 bits). good too. Moreover, there may be settings that result in guard periods that are less than one symbol in length or even zero. FIG. 8 should not be understood as tying the special subframe configuration index to a particular configuration. For example, it is immaterial whether setting number 19 represents 7 symbols in DwPTS and 2 symbols in UpPTS or 6 symbols in DwPTS and 3 symbols in UpPTS. Similarly, FIG. 8 shows that certain combinations of symbols in the DwPTS/UpPTS for the normal cyclic prefix case and for the extended cyclic prefix the symbol combinations need to be as given in FIG. should not be understood to mean For example, FIG. 8 lists configuration number 19 as supporting 7 symbols in DwPTS and 2 symbols in UpPTS for normal cyclic prefix on both uplink and downlink. However, in contrast to FIG. 8, configuration number 19 is able to support 6 symbols for DwPTS and 2 symbols for UpPTS in both the uplink and downlink for the extended cyclic prefix (i.e. In that case the quantity notation indicated for setting number 18).

The table shown in FIG. 8 offers the advantage of supporting the first ten settings currently specified for LTE legacy systems (up to release 13). Additional settings are new and may be supported from release 14 onwards.

FIG. 8 shows many configurations for both normal and extended cyclic prefixes in the downlink as well as the uplink. However, the invention is not so limited. The number of settings may be reduced. For example, to support latency reduction, it may be beneficial not to support extended cyclic prefixes in the uplink or downlink or both.

Cyclic Prefix (CP) is the part that precedes each symbol in LTE (in downlink OFDM symbol, in uplink SC-FDMA symbol). In LTE, the cyclic prefix length is about 5 microseconds. The purpose of the cyclic prefix is to separate the symbols so that frequency shifts that occur eg due to high mobility can be compensated. Besides the normal CP, LTE also defines an extended CP with a duration of about 17 microseconds. This is to ensure that the delay spread should be contained within the CP even in large suburban and rural cells.

The number of configurations may be further reduced as not all configurations are attractive for a particular uplink and/or downlink TTI length and cell size. That is, not all possible configurations of uplink and downlink portion lengths should be listed in the table and thus not available for configuration. For example, a close inspection of FIG. 8 shows that configuration numbers 55, 59, 62, 64, 65 represent configurations that are available only if the cyclic prefix is "normal" in the downlink as well as the uplink, thus potentially indicates limited applicability. Therefore, if at least two of these settings are not available, there are up to 64 settings available that can be efficiently represented by 6 bits.

Additionally or alternatively, the special subframe setting value (index in the first column of the table of FIG. 8) may be unique only for a particular TTI length. For example, configuration #10 (with index 16) specifies 2 DwPTS symbols (OFDM symbols) and 2 UpPTS (SC-FDMA) symbols for a TTI length of 0.2 ms in the downlink and uplink parts. As can be shown, the number of DwPTS symbols is 5 and 5 for a TTI length of 0.5 ms. As such, configuration interpretation can take the TTI length as a parameter, and the TTI length is set by configuration signals that are not tied to special subframe configuration.

Alternatively, the special subframe configuration may imply a TTI length for at least the uplink part and/or the downlink part. For example, a special subframe configuration indicating the number of DwPTS symbols n1 means that the corresponding downlink TTI is at most n1 symbols long. Similarly, a special subframe configuration indicating the number of UpPTS symbols n2 means that the corresponding uplink TTI is at most n2 symbols long.

In general, the special subframe setting advantageously indicates at least the length of the uplink portion of the special subframe in which the first value is not sufficient to accommodate the data in the second TTI, and the second A value in the value set (e.g., shown in the first column of the table of FIG. 8) that indicates a sufficient length to accommodate the data in the second TTI but not the data in the first TTI. index).

In other words, the special subframe configuration includes at least one legacy configuration that includes an uplink portion length that is too short to accommodate even a short TTI, and (not enough to accommodate a TTI for a normal uplink subframe). and at least one new configuration with an uplink portion length sufficient to accommodate the short TTI (although no). This may be the case, for example, if the length of the short TTI is half the length of the legacy TTI. In such a case, configurations 0-9 of FIG. 8 cannot accommodate such short TTIs, as they provide an uplink portion length of only two symbols maximum. However, configurations 38-65 can accommodate such short TTIs.

The mapper 730 advantageously
- mapping physical layer signals including sounding reference signals to the uplink part if the special subframe configuration takes a first value;
- mapping control data and/or channel state information, including positive or negative acknowledgments to downlink data, to the uplink part if the special subframe setting takes a second value, or - if the special subframe setting takes a second value, If it takes the second value, map the user data to the uplink part.

In other words, if the uplink portion of the special subframe configuration is not long enough to accommodate a given (or configured) TTI, such uplink portion is used to provide pilot signals such as sounding reference signals. may be used for Alternatively or additionally, such uplink part is used for (initial) random access, i.e. for transmitting some other physical layer signal such as a preamble used for collision avoidance. may be On the other hand, if the uplink part of the special subframe configuration is long enough to accommodate the TTI, the uplink part may be used for transmitting user data and/or control signals.

As already mentioned above, each special subframe may consist of multiple symbols. The special subframe configuration indicates the number of symbols for the downlink and/or uplink portion, and the special subframe further comprises a guard period of one or more symbols separating the downlink and uplink portions. good too.

However, the special subframe configuration may generally be defined only by the length of the downlink part or only by the length of the uplink part if the guard period and special subframe length are fixed. Good thing to note. Any alternative is possible as long as the special subframe configuration can indicate the allocation of specific symbols for specific purposes (uplink, downlink, guard period).

FIG. 9 shows the detailed structure of the special subframe already shown in FIG. Specifically, the special subframe starts with Nd downlink symbols (DwPTS) and may include a guard period (GP) separating these downlink symbols from the following Nu uplink symbols (UpPTS). . In TDD LTE, a special subframe has a length of 30720 sample periods Ts equal to 1 ms.

FIG. 10 shows some exemplary mappings of TTIs to special subframes. For example, in the upper example of FIG. 10, the TTI length is different between the uplink portion of the special subframe and the downlink portion of the special subframe. At the same time, the number of TTIs is different between the uplink part of the special subframe and the downlink part of the special subframe. Specifically, in this example, two short downlink TTIs are mapped to the downlink portion of the special subframe. Besides, 3 short uplink TTIs are mapped to the uplink part of the special subframe. The length of uplink TTI is longer than the length of downlink TTI. At the same time, the number of downlink TTIs is less than the number of uplink TTIs.

The bottom example of FIG. 10 shows another configuration where the number of downlink TTIs is greater than the number of uplink TTIs. At the same time, the length of the downlink TTI is shorter than the length of the uplink TTI. The guard period in this example is also short relative to the guard period in the upper example of FIG. Shorter guard periods may be acceptable, especially for small cells, due to smaller timing advance requirements.

The length of a TTI determines the amount of data that can be conveyed within the TTI. The number of TTIs determines how often data can be collected for mapping to the resource grid. Therefore, both TTI length and number of TTIs affect latency. As mentioned above, the invention is not limited to these examples. For example, there may be a single TTI mapped to the downlink portion of the special subframe and a single TTI mapped to the uplink portion of the special subframe. Such uplink and downlink TTIs may be of the same length or of different lengths depending on the special subframe configuration, ie the number of symbols per part. Alternatively, preconfigured short TTIs of the same length may be applied to both uplink and downlink, with the number of such short TTIs being different for uplink and downlink parts.

Additionally, shorter TTIs may be applied to uplink subframes, downlink subframes, or both, as shown in FIG. Specifically, FIG. 11 shows that one 1 ms subframe accommodates 14, 7, 4 or 2 TTIs (assuming regular CPs for uplink symbols as well as downlink symbols, loss of generality). no) four examples are shown. Example (a) shows subframes to which data in 14 TTIs are mapped. Each TTI has a length of 1 symbol (OFDM symbol for downlink, SC-FDMA symbol for uplink). A TTI therefore corresponds to the duration of one symbol. A major advantage of a very short TTI, such as 1 symbol, is the ability to process data very quickly, eg the decoding procedure can be started immediately after receiving a symbol. In contrast, a TTI of 1 ms means that the entire subframe (=1 ms) needs to be received before the decoding procedure can start. Therefore, for short TTIs, the data as well as the corresponding ACK/NACK feedback are available much earlier at the receiver. ACK/NACK can be propagated back to what was sent much earlier than in the 1 ms TTI.

Example (b) shows one subframe in which 7 short TTIs each having a duration of 2 symbols are mapped. Example (c) shows one subframe in which four TTIs are mapped. The TTIs differ in their size. Specifically, two TTIs with a length of 3 symbols and two TTIs with a length of 4 symbols are alternately mapped (TTI(3 symbols), TTI(4 symbols), TTI(3 symbols), TTI (4 symbols)). Finally, example (d) shows two TTIs per subframe, each of the two TTIs having a length of 7 symbols. The length of these TTIs loses some of the gain mentioned for the 1-symbol TTI case, but has the advantage that these TTIs can support larger transport blocks. Coding gain increases with the length of the coded transport block, especially considering advanced forward error correction schemes such as turbo coding or low density parity check coding. Another advantage is that a TTI with multiple symbols can convey more energy because the transmit power per transmitted symbol is typically limited. Therefore, as far as the total energy per transport block or TTI is concerned, it is possible to obtain a higher SINR compared to a single symbol. This is particularly advantageous for uplink transmissions, where the transmit power is usually more limited than for the downlink due to hardware costs for power amplifiers employed at eNBs and UEs.

As mentioned above, in LTE currently the uplink part of the special subframe cannot be used to transmit control data or user data. Since it is very short (1-2 symbols), the uplink part is only used to transmit some uplink signals such as sound reference signals and/or preambles for random access (initial access) . Random access is used by UEs to obtain channel access. Random access is unscheduled access where collisions can occur. Pseudo-random sequences with good cross-correlation and auto-correlation properties are used to allow UEs to be distinguished in random access. Specifically, the UE randomly selects a sequence (preamble) and transmits it along with its identifier to the base station to obtain resources for transmission.

According to an example of this disclosure, the uplink portion of the special subframe includes a data portion in which user data and/or control data are mapped within one or more TTIs, and a sounding reference signal and/or random access channel preamble. consists of signal portions that carry For example, the uplink portion of the special subframe may be one or more TTIs, plus a predetermined number of symbols (e.g., 1 or 2) forming the signal portion for transmitting reference signals and/or initial access preambles. can be accommodated. Advantageously, the symbol of the signal part is the last symbol of the uplink part. Specifically, this configuration complies with the configuration of the current LTE system. Adherence to the LTE system allows the use of sounding reference signals by UEs of different standard versions, avoiding interference with PUSCH transmissions.

According to embodiments, new special subframes are introduced in radio frames apart from the legacy switching subframes 1 and 6 shown in FIG. Such new special subframes may be available to UEs from Release 13 of LTE where shorter TTIs are configurable.

Such new special subframes are advantageously set within subframes configurable as Multimedia Broadcast Single Frequency Network (MBSFN) subframes in LTE.

One of MBSFN's goals is the support of multimedia (eg TV) multicast or broadcast over LTE.

Specifically, according to Section 6.1 of TS 36.211, v12.8.0, "Physical channel and modulation", which is incorporated herein by reference, downlinks within a radio frame on carriers that support PDSCH transmission A subset of link subframes can be configured as MBSFN subframes by higher layers. Each MBSFN subframe is divided into a non-MBSFN region and an MBSFN region. The non-MBSFN region spans the first one or two OFDM symbols in the MBSFN subframe. The length of the non-MBSFN region is given by a table corresponding to Table 6.7-1 from TS 36.211 mentioned above. Transmissions in non-MBSFN regions should use the same cyclic prefix length as used for subframe 0. An MBSFN region within an MBSFN subframe is defined as OFDM symbols that are not used for non-MBSFN regions.

In MBSFN subframes, cell-specific reference signals are transmitted only in non-MBSFN regions of MBSFN subframes. Configuration of MBSFN subframes is performed via the RRC protocol. Specifically, the configuration is sent from the eNodeB (base station) to the terminal in System Information Block (SIB) number 2. Within RRC, the MBSFN configuration is embedded in the information element mbsfn-SubframeConfigList which also defines the subframes reserved for MBSFN in the downlink.

The MBSFN subframe configurability is a special subframe that offers interference reduction and backward compatibility benefits. Specifically, as mentioned above, MBSFN subframes transmit control and reference signals only in the first two OFDM symbols. Accordingly, the remainder of the MBSFN may be used to map uplink signals onto it without the risk of legacy UEs misinterpreting the uplink signals as reference signals or PDCCH signals. A special subframe with only 2-3 downlink OFDM symbols reserved for the downlink and a small guard period (suitable for small cells with a small time advance), as also shown in FIG. , up to 11 SC-FDMA symbols may be available for the uplink. Such configurations are also possible in MBSFN subframes. They may be used to convey HARQ feedback and/or PUSCH sTTIs, ie uplink user data, thus offering the advantage of reducing latency, especially for heavy downlinks.

In other words, in this embodiment, the control signal further includes an uplink/downlink configuration that specifies for each subframe of the frame whether it is a downlink, an uplink, or a special subframe. . The uplink/downlink configuration includes a first set of subframes configurable for multicast or broadcast and a second set of subframes not configurable for multicast or broadcast.

Figure 12 (parts 12a-12h thereof) shows an example of an uplink/downlink configuration including additional special subframes marked by "A" in the figure. Specifically, configurations with indices 0, 1, 2, 3, 4, 5, and 6 correspond to the respective configurations in the table of FIG. 5 and therefore do not include additional special subframes. Based on these seven conventional configurations, a new Configuration has been added.

Another advantage of using MBSFN subframes for those subframes is that some HARQ timing relationships between downlink and uplink are already defined. This is currently established in Table 10.1.3.1-1 of TS36.213, v12.8.0, subframes 3, 4, 7, 8, 9 (i.e. configurable for MBSFN). subframe), at least one UL/DL configuration is available that defines the HARQ timing relationship between downlink data and corresponding uplink ACK/NACK. Therefore, those established timing relationships can be reused without further effort. Moreover, subframe number 6 may be a useful candidate since it is already a special subframe in some configurations.

The additional special subframe (A) advantageously takes into account the length of the configurable (short) TTI for the uplink. This allows transmission of control and user data in the uplink portion of the special subframe, as described above. Specifically, sPUCCH and sPUSCH transmissions are possible. "sPUCCH" and "sPUSCH" denote respective short versions of the physical uplink control channel on the physical uplink shared channel. The short version of the physical uplink channel differs from the currently used PUCCH and PUSCH by supporting short TTI (sTTI) or multiple possible configurable sTTIs.

A special subframe configuration is advantageously configurable for the first and second set of subframes of the uplink/downlink configuration, i.e. for MBSFN and the remaining subframes 1, 6(S). It is different for subframes 3, 4, 7, 8, 9 (A). However, since subframe #6 may be used as both a legacy downlink subframe or a special subframe, both or either of the special subframe settings may be configurable for the subframe.

In other words, to facilitate coexistence with legacy UEs, it is advantageous to have two independent special subframe settings or configuration sets applicable to legacy special subframes (S) and additional special subframes (A). can be

Note that FIG. 12 shows many different uplink/downlink configurations. However, the invention is not limited to providing all of these combinations as configurable. Rather, the set of configurable uplink/downlink configurations may be limited to a subset of the table shown in FIG. The choice of set size depends on the flexibility of the settings (provided by a large selection, i.e. all possible configurations included in the set) and the amount of memory required to store and signal each selected setting. It is a trade-off between transmission capacity.

In summary, according to one embodiment, the wireless communication system is Long Term Evolution (LTE) and the first set of subframes are configurable as Multicast Broadcast Single Frequency Network (MBSFN) subframes. or the second set of subframes are subframes with numbers 1 and/or 6.

In the examples described above, various configurations of special subframes are shown and described. In wireless communication systems, there are typically several different channels that map to the available resources. These channels can carry different types of signals (control data or user data) with different reliability and latency requirements. Therefore, it may be advantageous to employ different special subframe configurations for different channels. Specifically, the shared channel (PDSCH) may employ a different TTI length or number of TTIs than the control channel (PUSCH). For example, the uplink shared channel may occupy more symbols than the uplink control channel. This is to set a larger TTI and/or more TTIs in the uplink part of the special subframe for the uplink shared channel (which can carry user data) than for the uplink control channel. may be realized by

It should be noted that the above description illustrates the invention based on the LTE system. However, the invention is not so limited. Any wireless communication system employing special subframes used to accommodate both uplink and downlink portions can embody the present invention. Moreover, the above examples primarily refer to communication between base stations and terminals. However, in general, the above approach may be used for communication between two nodes, such as two user equipments (inter-device communication). In such cases, the terms "uplink" and "downlink" shall simply refer to the first and second directions of transmission (ie, UE1 to UE2 and UE2 to UE1, respectively).

Currently, the uplink/downlink configuration and special subframe settings are sent from the base station to the UE via the RRC protocol in system information. However, it may be beneficial to dynamically allow reconfiguration of the sTTI length and/or the position and length of the short TTI special subframes.

According to an embodiment, therefore, the control signal carrying the special subframe configuration is sent within the downlink control information as Layer 1/Layer 2 signaling.

Such dynamic configuration is similar to eIMTA (enhanced Interference Mitigation and Traffic Adaption), which is a mechanism to reconfigure the TDD uplink/downlink configuration depending on intra- and inter-cell loading and interference. method may be implemented. Specifically, the eIMTA reconfiguration is performed using Layer 1 signaling, ie by employing Downlink Control Information (DCI) of format 1C. Format 1C is used in LTE for very compact transmission of PDSCH allocation, PDSCH transmission is constrained to QPSK for paging messages, broadcast information messages, etc. in which uplink/downlink configurations may be transmitted. be.

Therefore, DCI format 1C is advantageously used to reconfigure uplink/downlink configurations and special subframe settings for the low latency purposes described in the above embodiments and examples. may

A special RNTI may be used for low latency reconfiguration to ensure backward compatibility and preserve system design. This means that a DCI with a short latency reconfiguration will only be detected by a UE with a special RNTI. A special RNTI is different from the rest of the RNTIs employed for a UE or group of UEs.

Moreover, advantageously, the special subframe setting and uplink/downlink configuration include a first field specifying which subframes are special subframes, and which symbols are up in the case of special subframes. It belongs to the link and is carried in a second field that specifies which symbols belong to the downlink.

For example, the DCI carrying the short latency reconfiguration specifies for this purpose which subframes are used for special subframes of short TTIs (i.e. short TTIs, i.e. uplink subframes and downlink subframes). A special subframe supporting a TTI that is shorter than the TTI of the subframe) may be provided. The first field may have a length of 6 bits or less per radio frame, depending on the number of settings provided in the set of selectable configuration settings (such as the table of FIG. 5 or FIG. 12). . Assuming that the subframe pattern defined by the first field represents one subframe per bit and that the pattern repeats every 10 ms, the first field should not need to exceed 10 bits. An advantage of such a 10-bit field is that it can be used not only to indicate whether a special subframe is configured as a special subframe for short TTIs, but for normal downlink subframes or uplink subframes. It can even indicate whether or not is configured as a subframe of a short TTI. However, when the only configurable subframes for MBSFN plus subframes #1 and #6 are potential short TTI special subframes, only 7 subframes are such candidates. Therefore, a first field size of 7 bits for the 10 ms pattern is required. In practice, only subframes that can be set as MBSFN plus subframe #6 (that is, only subframes #3, #4, #6, #7, #8, and #9) of the radio frame are set as additional special subframes. When employing the possible embodiment, and if only additional special subframes are available for short TTI transmission, the first field containing 6 bits repeats every 10 ms matched with the MBSFN pattern that repeats every 10 ms. Should be enough to define a 10ms pattern. An alternative additional special subframe pattern may be similarly defined if the MBSFN configuration repeats every 40ms. In this case, a first field of length 24 bits should be sufficient to represent each additional special subframe candidate within a 40 ms period. The size of the first field is further increased to 5 bits in the 10ms pattern (or 20 bits in the 40ms pattern) when only the subframes that can be set as the MBSFN of the radio frame can be set as the special subframes of the short TTI. may be reduced.

The DCI carrying the low latency reconfiguration may further comprise a second field that specifies the special subframe configuration, ie number of symbols for the uplink portion and number of symbols for the downlink portion. The second field may have a length of 6 bits or less. Seven bits should be sufficient to provide sufficient flexibility (see tables in FIGS. 6 and 8).

FIG. 13 shows a flow diagram of a method according to an embodiment.

Method 1300B may be performed at a terminal (user equipment). Method 1300B is designed for transmitting data in frames having subframes in a wireless communication system. Each subframe is either an uplink subframe containing uplink signals, a downlink subframe containing downlink signals, or a special subframe containing a downlink signal portion and an uplink signal portion. The method includes receiving 1310 a control signal that includes a special subframe setting that specifies lengths of uplink and/or downlink portions of the special subframe. As noted above, receiving settings may be performed semi-statically and/or dynamically. For example, the configuration is first received via cell broadcast via RRC system information. The (re)configuration 1310 may then be performed dynamically by DCI, eg, on the PDCCH in LTE. However, the present disclosure is not limited to dynamic signaling. The (re)configuration may alternatively or additionally be conveyed (semi-statically) via the RRC protocol. The setting is separate from the special subframe setting. Upon receiving the settings, the UE, which may include an uplink/downlink configuration as illustrated above, applies the settings for its further transmissions and receptions.

In particular, the method 1300B further comprises mapping 1320 user data and/or control data including feedback information within a transmission time interval (TTI) to one subframe. Moreover, the length of the second TTI for mapping to the uplink part of the special subframe is shorter than the first TTI for mapping to the uplink subframe, or is mapped to the uplink subframe. The first number of TTIs to map to the uplink portion of the special subframe is greater than the second number of TTIs to map to. In other words, the received configuration determines the symbols that may be used for the uplink, and user data and/or control data to be transmitted in the uplink are mapped onto the resource grid according to the TTI length to be applied. The mapped data within the radio frame is then transmitted at step 1330 over the radio interface channel 1300 .

Note that the settings received in step 1310 may apply to data reception at the terminal. Specifically, the UE may perform step 1395 of receiving radio frames in which downlink data is conveyed, including downlink user data and downlink control data (eg, PDSCH and PDCCH in LTE). Data is demapped from the received frame in step 1390 according to the received settings of uplink/downlink subframes and/or special subframes and/or TTI length/number.

Another method 1300A is provided for receiving data in frames having subframes in a wireless communication system, each subframe being an uplink subframe containing uplink signals, a downlink subframe containing downlink signals, and a downlink subframe containing downlink signals. Either a subframe or a special subframe containing a downlink signal portion as well as an uplink signal portion. Method 1300A may be performed at a base station (eNB in LTE). Step 1370 includes transmitting a control signal including a special subframe setting that specifies the length of the uplink portion and/or downlink portion of the special subframe. The transmitted configuration may, for example, be based on the configuration received from another network entity, or based on the traffic within the cell, or based on the services to be carried within the cell, or based on the user profile, etc. , preselected at 1360 by the base station. Specifically, it is beneficial to consider the time advance offset required for uplink transmission by the UE, as well as the shortest possible guard period that can support the quality of service (QoS) requirements regarding the latency of the service.

Method 1300A further comprises step 1340 of receiving data mapped to the special subframe according to the special subframe configuration. In other words, the base station receives an uplink radio frame containing data from the terminal mapped and transmitted as described above with reference to method 1300B, steps 1310-1330.

After receiving frame 1340, step 1350 of demapping control data including user data and/or feedback information within a transmission time interval (TTI) from one subframe is performed. The length of the second TTI for mapping to the uplink part of the special subframe is shorter than the first TTI for mapping to the uplink subframe, or the length of the TTI to be mapped to the uplink subframe. The number of 1's is greater than the second number of TTIs for mapping to the uplink portion of the special subframe. Note that the demapping step 1350 applies the settings selected in step 1360 by the base station, sent to the UE in step 1370 and applied in step 1320 by the UE.

Moreover, the base station can apply the selected settings to the transmission of data as well. Specifically, the method may further include a step 1380 of mapping data to be sent to the UE based on the selected settings also sent to the UE in step 1370 . After the mapping step 1380, frames with mapped data are transmitted to the UE in step 1385. FIG.

According to another embodiment, a computer program product is provided comprising a computer readable medium having computer readable program code embodied therein, the program code adapted to carry out the present invention.

Other exemplary embodiments relate to implementation of the various embodiments described above using hardware and software. In this connection, a user terminal (mobile terminal) and an eNodeB (base station) are provided. User terminals and base stations are adapted to perform the methods described herein and include corresponding entities suitably participating in the methods such as receivers, transmitters, processors, and the like.

It is further recognized that various embodiments may be implemented or performed using a computing device (processor). A computing device or processor may be, for example, a general purpose processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other programmable logic device. Various embodiments may be performed or embodied by combinations of these devices.

Moreover, various embodiments may be implemented by a processor or by software modules executing directly in hardware. Also a combination of software modules and a hardware implementation may be possible. The software modules may be stored on any kind of computer readable storage media, for example RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc.

It should further be noted that individual features of the various embodiments, either individually or in any combination, are subject to further embodiments.

Those skilled in the art will appreciate that many variations and/or modifications may be made to the present disclosure as shown in specific embodiments. Accordingly, the present embodiments should be considered in all respects as illustrative and not restrictive.

In summary, the present disclosure relates to receiving and transmitting data in frames having subframes in a wireless communication system, each subframe being an uplink subframe containing uplink signals and a downlink subframe containing downlink signals. Either a link subframe or a special subframe containing a downlink signal portion as well as an uplink signal portion. The control signal includes a special subframe setting that specifies the length of the uplink portion and/or downlink portion of the special subframe. Mapping of user data and/or control data, including feedback information, within a transmission time interval (TTI) into one subframe and demapping from it is then performed and mapped into the uplink part of a special subframe. The length of the second TTI for mapping to the uplink subframe is shorter than the first TTI for mapping to the uplink subframe, or the first number of TTIs mapped to the uplink subframe is the length of the special subframe. Longer than the second number of TTIs for mapping to the uplink portion. Data is received or transmitted accordingly.

Claims (12)

A transmission unit that transmits a control signal indicating a special subframe setting including the length of the uplink portion in the special subframe including the downlink portion and the uplink portion;
a receiver that receives user data transmitted within a transmission time interval (TTI) based on the control signal;
and
The second TTI in the uplink portion of the special subframe is shorter than the first TTI in the uplink subframe,
The special subframe setting is
a first value indicating a length of the uplink portion that cannot accommodate the user data in the second TTI;
a second value indicating the length of the uplink portion that can accommodate the user data in the second TTI;
takes the value of one of
Device. receiving a sounding reference signal on the uplink portion if the special subframe configuration takes the first value;
receiving the user data on the uplink portion if the special subframe configuration takes the second value;
A device according to claim 1 . The special subframe consists of a plurality of symbols, the special subframe setting indicates the number of symbols in the downlink part and the uplink part,
The special subframe further comprises a guard period separating the downlink portion and the uplink portion.
3. Apparatus according to claim 1 or 2. The special subframe configuration takes one of a plurality of values, the plurality of values being at least the length of the downlink portion, the length of the uplink portion, and the second TTI. different about one,
4. Apparatus according to any of claims 1-3. The control signal further includes an uplink/downlink configuration indicating whether each subframe of one frame is a downlink subframe, an uplink subframe, or a special subframe;
The uplink/downlink configuration includes a first set of subframes configurable for multicast or broadcast and a second set of subframes not configurable for multicast or broadcast;
5. Apparatus according to any of claims 1-4. the special subframe configuration is different for the first set and the second set of subframes of the uplink/downlink configuration;
6. Apparatus according to claim 5. The first set of subframes are subframes among subframes configurable as Multicast Broadcast Single Frequency Network (MBSFN) subframes; or
the second set of subframes are subframes with number 1 and/or number 6;
7. Apparatus according to claim 5 or 6. the second TTI is different than the TTI in the downlink portion of the special subframe;
8. Apparatus according to any of claims 1-7. the control signal is transmitted as Layer 1/Layer 2 signaling;
9. Apparatus according to any of claims 1-8. The uplink part of the special subframe consists of a data part to which the user data is mapped and a signal part to which a sounding reference signal and/or a random access channel preamble is mapped.
10. Apparatus according to any of claims 1-9. transmitting a control signal indicating a special subframe setting including the length of the uplink portion in a special subframe including a downlink portion and an uplink portion;
receiving user data transmitted within a transmission time interval (TTI) based on the control signal;
and
The second TTI in the uplink portion of the special subframe is shorter than the first TTI in the uplink subframe,
The special subframe setting is
a first value indicating a length of the uplink portion that cannot accommodate the user data in the second TTI;
a second value indicating the length of the uplink portion that can accommodate the user data in the second TTI;
takes the value of one of
Method. A process of transmitting a control signal indicating a special subframe setting including the length of the uplink part in a special subframe including a downlink part and an uplink part;
a process of receiving user data transmitted within a transmission time interval (TTI) based on the control signal;
to control the
The second TTI in the uplink portion of the special subframe is shorter than the first TTI in the uplink subframe,
The special subframe setting is
a first value indicating a length of the uplink portion that cannot accommodate the user data in the second TTI;
a second value indicating the length of the uplink portion that can accommodate the user data in the second TTI;
takes the value of one of
integrated circuit.

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