Radio frame structure

Abstract

To provide a first radio frame configuration that defines a frame construction of a radio frame containing at least one sub-frame dedicated for downlink transmission, and a second radio frame configuration that defines a radio frame construction containing at least one flexible special sub-frame that can be constructed as one of a flexible downlink sub-frame and a flexible uplink sub-frame.SOLUTION: In a processing for selecting a frame construction of a mobile communication system, a flexible downlink sub-frame and a flexible uplink sub-frame contain both of an uplink part and a downlink part, respectively. Both of the uplink part and the downlink part transmit at least one of control information and a reference signal, select a radio frame configuration from a radio frame configuration group containing at least first and second radio frame configurations, and transmit a radio signal that transmits an information element indicating the selected radio frame configuration.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to wireless communication in a mobile communication system, and more particularly to a frame structure in a cell. [Background technology]

[0002] Explosive mobile data demand and the emergence of the Internet of Things (IoT) with billions of connected devices will require further developments in telecommunications. Technologies such as remote health care and advanced logistics will require increasingly shorter network response times for faster responses. Summary of the Invention [Means for solving the problem]

[0003] In certain aspects, the subject matter of the independent claims is provided. Some embodiments are defined in the dependent claims.

[0004] One or more embodiments are described in more detail in the drawings and the description that follows. Other features will be apparent from the description and drawings, and from the claims. [Brief explanation of the drawings]

[0005] Hereinafter, embodiments will be described in detail with reference to the drawings. [Figure 1] FIG. 1 is a diagram showing a wireless communication system to which an embodiment of the present invention can be applied. [Figure 2] FIG. 2 illustrates a process for selecting a frame structure according to some embodiments of the present invention. [Figure 3] FIG. 3 illustrates a process for selecting a frame structure according to some embodiments of the present invention. [Figure 4] FIG. 4 is a diagram illustrating a frame structure of a flexible special subframe according to an embodiment of the present invention. [Figure 5]FIG. 5 is a signaling diagram describing signaling of subframe configuration for flexible special subframes according to an embodiment of the present invention. [Figure 6] FIG. 6 illustrates a process for configuring and transmitting discovery reference signals in a cell according to an embodiment of the present invention. [Figure 7] FIG. 7 illustrates a process for configuring and transmitting discovery reference signals in a cell according to an embodiment of the present invention. [Figure 8] FIG. 8 is a diagram illustrating a procedure for performing a cell search in a terminal device according to an embodiment of the present invention. [Figure 9] FIG. 9 is a block diagram illustrating the structure of an apparatus according to some embodiments of the present invention. [Figure 10] FIG. 10 is a block diagram illustrating the structure of an apparatus according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0006] The following embodiments are for illustrative purposes. Although multiple references in this specification may be made to "an embodiment," "one embodiment," or "some embodiments," this does not necessarily mean that each reference is to the same embodiment or that a particular feature applies only to a single embodiment. Single features of different embodiments may be combined to form other embodiments.

[0007] The embodiments described herein may be implemented in wireless systems such as, but not limited to, Universal Mobile Telecommunication System (UMTS, 3G) based on Wideband-Code Division Multiple Access (W-CDMA), High-Speed ​​Packet Access (HSPA), Long Term Evolution (LTE), LTE-Advanced, and / or 5G systems.

[0008] The embodiments are not limited to the illustrated system, and a person skilled in the art would be able to apply the solution to another communication system having the required characteristics. The 5G system listed above is an example of an applicable communication system. The 5G network architecture is expected to be quite similar to LTE-Advanced. 5G will likely use multiple input-multiple output (MIMO) antennas and a significantly larger number of base stations and nodes than the current LTE network configuration (the so-called small cell concept). This means that macro cell sites will likely cooperate with smaller local area access nodes, and various radio technologies will be used to improve coverage and data rates. 5G is expected to use multiple radio access technologies (RATs), each specialized for a specific application and / or spectrum.

[0009] Future networks are expected to utilize network function virtualization (NFV). NFV is a network architecture concept that proposes virtualizing network node functions into "blocks" or entities that are operatively connected or linked to provide services. A virtualized network function (VNF) may include one or more virtualized machines running computer program code using standard or general-purpose servers rather than dedicated hardware. Cloud computing and cloud data storage may also be utilized. In wireless communications, this means that node operations may be performed, at least in part, on a server, host, or node operatively connected to a remote radio head (RRH). Furthermore, node operations may be shared among multiple servers, nodes, or hosts. It should be understood that the division of labor between core network operations and base station operations may differ from that in LTE, or may even be nonexistent. Additional emerging technologies, such as software-defined networking (SDN), big data, and all-IP, that could disrupt current network configuration and management practices may also be utilized.

[0010] FIG. 1 illustrates an example of a mobile communication system to which embodiments of the present invention may be applied. Wireless mobile communication networks, such as Long Term Evolution (LTE), Third Generation Partnership Project (3GPP) LTE-Advanced (LTE-A), and upcoming 5G technologies, typically include at least one network element, such as network element 110, that implements a cell 100. Each cell may be, for example, a macrocell, a microcell, a femtocell, or a picocell. Network element 110 may be an Evolved Node B (eNB), as in LTE and LTE-A, or another device capable of controlling radio communication and managing radio resources within a cell. 5G technology may be implemented in a similar manner to LTE-A, as described above. Network element 110 may also be referred to as a base station or an access node. The mobile communication system may comprise a radio access network of network elements 110, 112, and 114, such as eNBs, that control each cell or multiple cells 100, 102, and 104. Each of the network elements 110-114 may control a macrocell 100-104, which provides a large coverage area for the terminal device 120. The network elements 110-114 may be referred to as an access node because they enable the terminal device 120 to have wireless access to other networks, such as the Internet. In addition, one or more local area access nodes 116 may be located within the control area of ​​the network element 110, 112, 114 controlling the macrocell 100-104. The local area access node 116 may enable wireless access within a subcell 106, which may be located within the macrocell 100. Examples of such subcells include microcells, picocells, and / or femtocells. Typically, the subcells form hotspots within the macrocell. The operation of the local area access node 116 may be controlled by the network element 110 whose control area includes the subcell.The network element 110 and the other network elements 112-116 may support Dual Connectivity (DC), in which case the terminal device 120 establishes multiple Radio Resource Control (RRC) connections to the radio access network of the network elements 110-116. The terminal device 120 may establish one RRC connection with the network element 110 and another RRC connection with the local area access node 116, thereby improving communication performance.

[0011] The network element 110, alone or in conjunction with other network elements 116, may utilize carrier aggregation, in which case the terminal device 112 is allocated resources from multiple component carriers, which may be on contiguous or non-contiguous frequency bands. One network element 110 may provide one component carrier, e.g., a primary component carrier, and another network element 116 may provide another component carrier, e.g., a secondary component carrier. The network element 110 corresponding to the primary component carrier may perform scheduling of resources on all component carriers. Alternatively, the network elements 110 and 116 may each control the scheduling of their corresponding component carriers. Alternatively, the network element 110 may provide one component carrier, e.g., a primary component carrier, and another component carrier, e.g., a secondary component carrier.

[0012] If the communication network includes multiple eNBs, the eNBs may be connected via an X2 interface as defined in LTE. Other communication methods may also be used between the network elements. The network elements 110-116 may be connected to an Evolved Packet Core (EPC) 130, more specifically, a Mobility Management Entity (MME) 132 and a System Architecture Evolution Gateway (SAE-GW) 134, via an S1 interface.

[0013] The wireless system of FIG. 1 may support Machine Type Communication (MTC). MTC may be capable of serving a large number of MTC-enabled devices, such as at least one terminal device 120. The at least one terminal device 120 may include a mobile phone, a smartphone, a tablet computer, a laptop computer, and other devices for performing user communication over a wireless communication network, such as an MTC network. These devices may provide more advanced functionality than the MTC scheme, such as communication links for voice, video, and / or data transmission. However, in MTC, the at least one terminal device 120 may be understood as an MTC device. It should be understood that the at least one terminal device 120 may also include other MTC-enabled devices, such as sensor devices that provide information such as location, acceleration, and / or temperature.

[0014] In MTC, wireless communication networks may need to handle a large number of irregular accesses by MTC devices. Because MTC devices may be deployed in large numbers, network access may become a limiting factor, unlike previous network limitations where interference and / or limited coverage may be an issue. Many MTC devices may transmit small amounts of data sporadically. In this case, the MTC devices are essentially in a sleep mode, disconnected from the network elements 110-116 and / or the mobile communication network. Therefore, the power consumption of the MTC devices is kept very low.

[0015] Figures 2 and 3 illustrate processes for configuring frame transmissions in a cell of a mobile communication system, such as cell 100 served by network element 110. Figure 2 illustrates processes performed in network element 110 controlling cell 100, and Figure 3 illustrates processes in a terminal device 120 in cell 100 for communicating with network element 110 within cell 100.

[0016] Referring to FIG. 2, the network element 110 provides a first radio frame configuration (block 200) that defines a frame structure of a radio frame including at least one subframe used only for downlink transmission. The network element further provides a second radio frame configuration (block 202) that defines a frame structure of a radio frame including at least one flexible special subframe. This special subframe can be configured as a flexible downlink subframe or a flexible uplink subframe. The flexible downlink subframe and the flexible uplink subframe each include both an uplink portion and a downlink portion. Both the uplink portion and the downlink portion carry control information and / or reference signals. In block 204, the network element selects a radio frame configuration from a group of radio frame configurations that includes at least the first and second radio frame configurations. In block 206, the network element transmits a radio signal carrying an information element indicating the selected radio frame configuration.

[0017] Referring to FIG. 3 , in block 300, the terminal device 120 stores a first radio frame configuration definition defining a frame structure of a radio frame including at least one subframe dedicated to downlink transmission. Furthermore, in block 302, the terminal device stores a second radio frame configuration definition defining a frame structure of a radio frame including at least one flexible special subframe configurable as one of a flexible downlink subframe and a flexible uplink subframe. The flexible downlink subframe and the flexible uplink subframe each include both an uplink portion and a downlink portion. Both the uplink portion and the downlink portion carry at least one of control information and reference signals. In block 304, the terminal device 120 receives a radio signal from the network element 110 carrying an information element indicating a radio frame configuration to be applied to a cell of the mobile communication system. In block 306, based on the received information element, the terminal device selects a radio frame configuration from a group of radio frame configurations including at least the first radio frame configuration and the second radio frame configuration and uses the selected frame configuration for communication with the network element in the cell.

[0018] In one embodiment, the first radio frame configuration further includes at least one subframe dedicated to uplink transmission and at least one special subframe including an uplink portion and a downlink portion. The first radio frame configuration may correspond to an LTE radio frame configuration. Table 1 below shows a conventional radio frame configuration in a Time Division (TD)-LTE system. Table 1 shows the structure of a radio frame including 10 subframes. The radio frame may be a 10 millisecond (ms) frame, in which case a subframe in TD-LTE is a 1 ms subframe. JPEG0007778840000001.jpg82168

[0019] In Table 1, "D" denotes a downlink subframe dedicated to downlink transmission, e.g., from an access node to a terminal device; "U" denotes an uplink subframe dedicated to uplink transmission, e.g., from a terminal device to an access node; and "S" denotes a special subframe including an uplink portion and a downlink portion. In an LTE system, the special subframe configuration is represented by network elements 110-116 in System Information Block 1 (SIB1), and is therefore a semi-static parameter. That is, all special subframes in a radio frame configuration are homogeneous. Special subframes can be considered as guard subframes during the transition from downlink subframes to uplink subframes.

[0020] In one embodiment, the set of radio frame configurations includes one or more, or even all, of the radio frame configurations in Table 1. One of the radio frame configurations in Table 1 is the first radio frame configuration.

[0021] The second radio frame configuration includes at least one flexible special subframe, which may be configured as a downlink special subframe or an uplink special subframe. In either configuration, the flexible special subframe includes bidirectional control / reference signals, allowing bidirectional communication of non-data information in all flexible special subframes. Depending on the configuration of the flexible special subframe, downlink or uplink transmission may be emphasized such that downlink special subframes have longer downlink transmission times than uplink transmission times, and uplink special subframes have longer uplink transmission times than downlink transmission times.

[0022] In one embodiment, one configuration of the flexible special subframe allocates equal transmission time to both the uplink and downlink.

[0023] In one embodiment, each configuration of a flexible special subframe defines the length of the guard period between the downlink and uplink portions. Different configurations may define guard periods of different lengths. Thus, a network element can configure the structure of a flexible special subframe with respect to the length, uplink and downlink portions, and the order of the guard periods.

[0024] Table 2 below shows some embodiments of radio frame configurations that may be loaded into the second radio frame configuration. One or more, or even all, of the radio frame configurations in Table 2 may be included in the set of radio frame configurations from which the network element 110 selects the radio frame configuration to be used in the cell. While the selection may be cell-specific, in some embodiments the network element 110 may select the radio frame configuration for each user or group of users. Thus, the network element may utilize multiple radio frame configurations in parallel, with different radio frame configurations being used by different users or groups of users. JPEG0007778840000002.jpg76167

[0025] In Table 2, "SF" denotes a flexible special subframe that can be dynamically configured as a flexible special downlink subframe or a flexible special uplink subframe; "SD" denotes a flexible special subframe configured statistically (or quasi-statistically) as a flexible special downlink subframe; and "SU" denotes a flexible special subframe configured statistically (or quasi-statistically) as a flexible special uplink subframe. SD may also be considered an SF configured statistically (or quasi-statistically) as a flexible special downlink subframe. SU may also be considered an SF configured statistically (or quasi-statistically) as a flexible special uplink subframe. As noted above, SD and SU may each include a downlink portion and an uplink portion, which distinguishes them from D and U in Table 1. The use of statistically or quasi-statistically configured flexible special subframes improves inter-cell interference coordination. Furthermore, more advanced channel estimation and power control can be performed for subframes SD and SU than for subframe SF. SD and SU may be used for special purposes, such as transmitting important or critical signaling messages.

[0026] In the embodiment shown in Table 2, some of the radio frame configurations consist of flexible special subframes that are dynamically configurable as flexible special uplink or downlink subframes, such as radio frame configurations 7, 9, and 11. Within some of the radio frame configurations in Table 2, the flexible special subframes that are dynamically configurable as flexible special uplink or downlink subframes form a subset, such as radio frame configurations 8 and 10. However, even within radio frame configurations 8 and 10, the majority of the subframes are made up of flexible special subframes that are dynamically configurable as flexible special uplink or downlink subframes.

[0027] As a variation of the set of radio frame configurations in Table 2, at least some of the radio frame configurations may include downlink subframes D and / or uplink subframes U in Table 1, such that each radio frame configuration in Table 2 still includes at least one flexible special subframe SF, SD, or SU. However, even in some of the radio frame configurations, the flexible special subframes occupy a majority of the subframes. This allows for flexible switching between the uplink and downlink. In one embodiment, all subframes in at least one radio frame configuration are flexible special subframes.

[0028] By designating most or all of the subframes as flexible special subframes with bidirectional control (using both the uplink and downlink parts of each subframe), lower latency can be achieved than with the radio frame configurations in Table 1. In the radio frame configurations in Table 1, there can be as many as nine consecutive downlink frames between two uplink subframes (Configuration 5). This can significantly delay uplink communications, such as the transmission of ACK / NAK acknowledgment messages, which are only possible in uplink subframes. Therefore, designating at least most of the subframes as bidirectional control-enabled subframes can achieve low latency, parallel Hybrid Automatic Repeat Request (HARQ) processing, and reduced HARQ buffering. If all subframes are flexible special subframes, acknowledgment messages can be transmitted in both the downlink and uplink directions in each subframe, enabling HARQ processing, including HARQ-aware scheduling, similar to frequency division duplexing (FDD) systems such as FDD LTE.

[0029] Several embodiments of flexible special subframes are described below with reference to FIG. 4. FIG. 4 illustrates an embodiment of a flexible special downlink subframe 408 and an embodiment of a flexible special uplink subframe 418. The flexible special downlink subframe 408 includes a downlink portion 400, an uplink portion 406, and a guard period 404 between the downlink and uplink portions. In accordance with LTE terminology, the downlink portion 400 is denoted as a Downlink Pilot Time Slot (DwPTS), and the uplink portion 406 is denoted as an Uplink Pilot Time Slot (UpPTS). The downlink portion 400 may carry one or more downlink control channels and / or downlink reference signals, such as downlink sounding reference signals (DWSRS). The reference signals may be used for channel estimation, cell discovery, synchronization, etc. The downlink control channels carried by the downlink portion may include a Physical Downlink Control Channel (PDCCH) and / or other physical layer control channels. The downlink unit 400 may carry user data, for example, over a Physical Downlink Shared Channel (PDSCH).

[0030] The flexible special downlink subframe 408 may include a further downlink portion 402. This downlink portion may include or consist of downlink data, which may include payload data to the terminal device 120.

[0031] The uplink unit 406 may include an uplink control signal and / or an uplink reference signal, which may include at least one of an acknowledgement message ACK / NAK for a HARQ process, a scheduling request (SR) for requesting scheduling of uplink transmission resources, and a channel information indicator (CSI) indicating the quality of a radio environment between the network element 110 and the terminal device 120.

[0032] The flexible special uplink subframe 418 may include a downlink portion 410, an uplink portion 416, and a guard period 412 between the downlink and uplink portions. Similar to the flexible special downlink subframe 408, the downlink portion 410 is denoted as a downlink pilot time slot (DwPTS), and the uplink portion 416 is denoted as an uplink pilot time slot (UpPTS). The downlink portion 410 may carry one or more downlink control channels and / or downlink reference signals, such as, for example, downlink sounding reference signals.

[0033] The flexible special downlink subframe 408 may include an additional uplink portion 414. This uplink portion 414 may include or consist of uplink data, which may include payload data from the terminal device 120.

[0034] The uplink unit 416 may include uplink control signals and / or uplink reference signals, which may include at least one of an acknowledgement message ACK / NAK for HARQ processing, a scheduling request (SR) for requesting scheduling of uplink transmission resources, and a channel information indicator (CSI) indicating the quality of the radio environment between the network element 110 and the terminal device 120.

[0035] As shown in FIG. 4, the flexible special downlink subframe 408 includes an additional downlink portion 402 for transmitting downlink data, and the flexible special uplink subframe 408 includes an additional uplink portion 414 for transmitting uplink data.

[0036] In some embodiments, a flexible special subframe may include an additional downlink portion 402 and an additional uplink portion 414. A flexible special subframe may be defined as a flexible special uplink subframe or a flexible special downlink subframe depending on the allocation of transmission resources for the link direction in the subframe. A subframe may be defined as a flexible special downlink subframe if more transmission resources are allocated in the downlink direction than in the uplink direction. A subframe may be defined as a flexible special uplink subframe if more transmission resources are allocated in the uplink direction than in the downlink direction. Transmission resources for the link directions may be dynamically allocated.

[0037] The subframe length may be defined separately for each radio frame configuration, as shown in Table 2. Therefore, different subframe lengths may be applied to different radio frame configurations.

[0038] In one embodiment, some or all of the subframe lengths in the radio frame structure of Table 2 may be 1 ms, as in Table 1.

[0039] In some embodiments, when configuring a radio frame configuration with multiple subframe lengths, the subcarrier spacing of multicarrier signals transmitted with shorter subframe lengths may be wider, while the subcarrier spacing of multicarrier signals transmitted with longer subframe lengths may be narrower. For example, for a 20 megahertz (MHz) carrier, a subcarrier spacing of 15 kilohertz (kHz) may be configured for a 1 ms subframe, and a subcarrier spacing of 60 kHz may be configured for a 0.25 ms subframe. In this example, a fixed fast Fourier transform size may be assumed. Increasing the subcarrier spacing increases the bandwidth of the multicarrier signal. For example, a 20 MHz carrier with 60 kHz spacing may result in an 80 MHz carrier bandwidth. Similar time-frequency scaling can be used to achieve variable subframe lengths. In a typical application, the same number of subcarriers and multicarrier symbols are transmitted, but time-frequency scaling can be used to increase the subcarrier spacing to shorten the subframe length, or decrease the subcarrier spacing to lengthen the subframe length.

[0040] In other embodiments, different subframe lengths may be used by allocating different numbers of symbols, e.g., multi-carrier symbols. For example, a radio frame structure with a 1 ms subframe length may include more carrier symbols than a radio frame structure with a 0.25 ms subframe length. In other words, a radio frame structure with a 1 ms subframe length may include more subcarriers than a radio frame structure with a 0.25 ms subframe length, thereby achieving a constant carrier bandwidth.

[0041] Furthermore, a variable bandwidth may be used so that radio frame configurations with different subframe lengths are applied to multiple carriers with different bandwidths. For example, 1 ms subframes may be used for carriers or cells with a bandwidth of 20 MHz or less, and subframes shorter than 1 ms may be used for carriers or cells with a bandwidth of more than 20 MHz.

[0042] Further embodiments may combine the above embodiments. For example, different subcarrier spacings and / or bandwidths may be used in different parts of a subframe. For example, a first subcarrier spacing may be applied to the further downlink portion 402 and the further uplink portion 414, and a different second subcarrier spacing may be applied to the downlink portions 400, 410 and the uplink portions 406, 416. However, the same cyclic prefix may be applied to all symbols of a subframe. The total length of the downlink portion 400 / 410, the uplink portion 406 / 416, and the guard period 404 / 412 of a subframe may be equal to the length of one or more multicarrier symbols of the further downlink portion 402 / uplink portion 414 of the subframe. The length of the radio frame, in terms of the number of subframes, may be the same for all radio frame configurations. For example, 10 subframes as in the embodiment shown in Table 2. Additionally, the time length of the radio frame may be scaled for different radio frame configurations, corresponding to the scaled subframe length.

[0043] In some embodiments, time domain scaling of the subframe may be used to indicate arbitrary timing within the subframe, for example to indicate periodic radio resources.

[0044] In some embodiments, in all radio frame configurations and / or all subframe configurations, the flexible special subframe begins with a downlink portion, and the uplink portion or further uplink portion ends the flexible special subframe. The subframe may include a further downlink portion or a guard period after the downlink portion.

[0045] In some embodiments, further downlink portions may be consecutive with downlink portions within a subframe. Similarly, further uplink portions may be consecutive with uplink portions within a subframe.

[0046] In one embodiment, network element 110 supports the radio frame configurations of Table 1 and the radio frame configurations of Table 2. In another embodiment, network element supports only the radio frame configurations of Table 2, e.g., only the radio frame configurations that include flexible special subframes.

[0047] Next, several embodiments are described that define portions of the downlink portions 400, 402, 410 and uplink portions 406, 414, 416 of a flexible special subframe. Table 3 below shows several subframe configurations for a flexible special subframe. In the embodiments of Table 3, the subframe length is fixed at 14 symbols. JPEG0007778840000003.jpg156158

[0048] As mentioned above, the length of the flexible special subframe may be variable, for example, depending on time-frequency scaling. Therefore, the lengths in Table 3 are to be taken as exemplary and may also be defined as "variable."

[0049] Table 4 below shows some alternative subframe configurations for the flexible special subframe: In this embodiment, the length of the subframe is variable. JPEG0007778840000004.jpg150158

[0050] For example, in embodiments in which a network element supports the radio frame configurations in Tables 1 and 2, the network element may utilize at least part of the same subframe configurations in Tables 3 or 4 for special subframes and flexible special subframes. For example, subframe configurations 0-9 may be applied to special subframes and flexible special subframes. However, some of the subframe configurations may be applicable only to flexible special subframes, such as subframe configurations 10-15 in Table 3 and subframe configurations 10-14 in Table 4.

[0051] Several embodiments for the ratio of downlink portions to further downlink portions in a flexible special downlink subframe and the ratio of uplink portions to further uplink portions in a flexible special uplink subframe are described herein. In one example, the lengths of downlink portions 400, 410 and uplink portions 406, 416 may be fixed, e.g., one multicarrier symbol. The lengths of guard periods 404, 412 are defined in Tables 3 and 4. Other portions are used for further downlink / uplink portions. In other embodiments, the lengths of downlink portions 400, 410, uplink portions 406, 416, further downlink portions 402, and further uplink portions 414 are explicitly signaled or defined in the subframe configuration.

[0052] For example, subframe configuration 2 may define a flexible special downlink subframe 408 with 1 symbol allocated to the downlink portion 400, 9 symbols allocated to the further downlink portion 402, 3 symbols allocated to the guard period 404, and 1 symbol allocated to the uplink portion 406.

[0053] For example, subframe configuration 4 may define a flexible special downlink subframe 408 with 1 symbol allocated to the downlink portion 400, 11 symbols allocated to the further downlink portion 402, and 1 symbol each allocated to the guard period 404 and uplink portion 406.

[0054] For example, subframe configuration 12 in Table 3 may define a flexible special uplink subframe 418 with 1 symbol in the downlink portion 410, 1 symbol in the guard period 412, 11 symbols in the further uplink portion 414, and 1 symbol in the uplink portion 416.

[0055] For example, subframe configuration 12 of Table 4 may define a flexible special uplink subframe 418 with two symbols in the downlink portion 410, one symbol in the guard period 412, three symbols in the further uplink portion 414, and one symbol in the uplink portion 416.

[0056] In one embodiment, the flexible special subframe begins with the downlink portion 400, 410 in all subframe configurations. This allows the link direction of the flexible special subframe to be dynamically indicated within the subframe itself. The link direction may also be indicated for the control channel carried in the downlink portion 400, 410. Dynamic scheduling allows the subframe configuration to be quickly adapted to current traffic demands, thus improving performance. Figure 5 illustrates one embodiment of dynamic link direction selection for flexible special subframes.

[0057] Referring to FIG. 5, network element 110 selects a radio frame configuration for the cell in block 204 and transmits a signal indicating the selected radio frame configuration for the cell in step 500. Step 500 also includes terminal device 120 receiving the radio frame configuration and applying the radio frame configuration in block 306. Functions 204, 500, and 306 can be performed as described above. In block 502, the network element selects a link direction for the next subframe. This selection may be based on the amount of downlink data stored in the network element for transmission (downlink resource need), the number of pending uplink scheduling requests (uplink resource need), or other criteria(s). Upon selecting the link direction for the next subframe, the network element may insert an information element for the downlink portion of the next subframe indicating the link direction of the subframe and begin transmitting the downlink portion of the subframe (step 504). When a subframe begins, the terminal device scans the control channel of the downlink portion to determine the link direction of the subframe, and in some embodiments, for another information element indicating whether the terminal device has resources in the subframe. If the terminal device has resources in the subframe, the terminal device may perform signal processing in response to the information element indicating the link direction of the subframe (block 506). For example, if the terminal device is assigned uplink transmission resources in a subframe designated by the information element as a flexible special uplink subframe, the terminal device may transmit uplink data in the further uplink portion of the subframe.

[0058] In one embodiment, the information element carried in the downlink portion of the subframe in step 504 may indicate a subframe configuration index from Table 3 or Table 4.

[0059] Providing different radio frame configurations (and in some embodiments, subcarrier spacing) can complicate cell discovery at terminal devices 120. Cell discovery may be based on network elements 110 broadcasting discovery reference signals that are scanned by terminal devices 120 when performing cell search. Figures 6 and 7 illustrate some embodiments for facilitating cell search when utilizing radio frame configurations according to some embodiments.

[0060] 6 illustrates an embodiment in which the same discovery reference signal is broadcast in all radio frame configurations. Referring to FIG. 6, the network element selects a radio frame configuration in block 204 and indicates the radio frame configuration in block 206. In block 600, the network element 110 performs periodic discovery signal transmission. Thereafter, the network element may select a new, different radio frame configuration in block 602 and indicate the new radio frame configuration in block 604. After block 604, the network element may transmit a discovery reference signal of the same configuration as that transmitted in block 600 in block 606. In this embodiment, regardless of the radio frame configuration selected in blocks 204 and 602 and indicated in blocks 206 and 604, the network element may transmit the periodic discovery signal using a predetermined, fixed radio frame configuration.

[0061] The discovery reference signals may have the same subcarrier spacing and periodicity in all radio frame configurations. If the discovery reference signals are transmitted in the uplink or further uplink portions, the transmission of the discovery reference signals may disrupt uplink transmissions. For example, the network element 110 may refrain from scheduling uplink resources that overlap with periodic transmissions of the discovery reference signals. A terminal device that signals that it has been assigned periodic uplink transmission resources that specify transmission resources that overlap with periodic discovery reference signals may refrain from transmitting on those transmission resources. Typically, the periodicity of the assigned periodic uplink transmission resources is different from the periodicity of the discovery reference signals, thereby limiting overlap.

[0062] In the present embodiment shown in FIG. 6, terminal device 120 may need to scan for discovery signals using only a single scanning configuration applied to the discovery signals.

[0063] In Figure 7, the network element utilizes multiple discovery reference signal configurations. For example, the periodicity of the discovery reference signals and / or the subcarrier spacing of the discovery reference signals may be adapted to a radio frame configuration. The discovery reference signals may follow a periodicity that maps the discovery reference signals to the downlink portion, and the discovery reference signals may use the same subcarrier spacing as other signals in the radio frame configuration.

[0064] Upon selecting the radio frame configuration in block 204 , network element 110 may select a discovery signal associated with the radio frame configuration and transmit the selected discovery signal in block 700 .

[0065] In this embodiment shown in Figure 7, the terminal device 120 may scan for discovery signals using only multiple scan configurations. Figure 8 illustrates an embodiment of a scanning procedure performed by the terminal device 120. Referring to Figure 8, the terminal device may store multiple configurations for discovery reference signal (DRS) searching in block 800. Different configurations may define different periods and / or different magnitudes of fast Fourier transform. Different subcarrier spacings of the DRS may require different lengths of the fast Fourier transform.

[0066] In block 802, the terminal device selects a DRS configuration and starts scanning the radio channels of the DRS mapped to the DRS configuration. The terminal device may scan at least one period of the DRS based on the periodicity of the DRS configuration. In block 804, the terminal device determines whether a DRS of the DRS configuration is found. If not, the process returns to block 802, where the terminal device selects a new DRS configuration and performs a new scan. If a DRS is found, the terminal device may synchronize to the cell transmitting the DRS and extract system information of the cell from a broadcast signal transmitted in the cell. The system information may define, for example, the radio frame configuration used in the cell.

[0067] In an embodiment in which the network element 110 supports the radio frame configurations of Table 1 (legacy devices) and also supports the radio frame configurations shown in Table 2, there may be terminal devices that support only the radio frame configuration of Table 1 and terminal devices that support the radio frame configurations shown in Table 1 and Table 2. In such a case, it is desirable that at least some terminal devices be able to use the radio frame configuration shown in Table 2. Several embodiments that enable the network element to solve this problem of applying both types of terminal devices to the same carrier signal are described below.

[0068] In one embodiment, a subset of subframes, or a portion of subframes in a radio frame configuration, accommodates legacy devices. In this embodiment, the subframes may be 1 ms long. Table 5 shows an example of such a radio frame configuration. TIFF0007778840000005.tif39160

[0069] As shown in Table 5, this radio frame configuration is a variation of radio frame configuration 0 in Table 1, and a given subframe is modified to become a flexible special subframe. A network element may configure the use of a radio frame configuration such that legacy devices are assigned to subframes corresponding to subframe types (D, S, U) in Table 1, and devices corresponding to flexible special subframe types are assigned to corresponding subframes. In addition, devices corresponding to flexible special subframe types may be assigned to subframes corresponding to subframe types (D, S, U) in Table 1. If the physical uplink shared channel (PUSCH) is not transmitted by legacy devices, uplink subframes of the physical uplink control channel (PUCCH) that do not contain HARQ ACK / NAK may be converted to flexible special subframes SF. Uplink subframes U that contain HARQ on the PUCCH may be converted to flexible special subframes SF if they are not occupied by legacy devices.

[0070] All devices that support flexible special subframes may use the uplink portion of the special subframe S, provided that the network element does not schedule reference signals or a short random access channel (S-RACH) in the uplink portion.

[0071] The remaining subframes or portions of subframes may be designated as flexible special subframes SF. However, the network element may determine the subframe configuration depending on whether legacy devices are present in each subframe. For example, the special subframe S may have a specific configuration for the downlink portion DwPTS1 to provide sufficient resources for legacy devices (including synchronization signals). The length of the downlink portion may be more than three symbols.

[0072] As another example, the subframe for transmitting the downlink HARQ acknowledgement in subframe 0 may be statistically designated as a flexible special uplink subframe SU. A subframe containing uplink control information from one or more legacy devices may be fixed to the uplink frame, i.e., the downlink portion may be omitted from that subframe.

[0073] As another example, any downlink signals transmitted in downlink subframe D or special subframe S may leave legacy signals unchanged. Such legacy signals may include primary synchronization signals, secondary synchronization signals, and cell-specific reference signals.

[0074] When signaling the special subframe S configuration, the network element may signal the radio frame configuration through a device-specific higher layer (e.g., Layer 3). A cell that does not contain legacy devices may signal the special subframe configuration in system information broadcast within the cell. The flexible special subframe configuration may be signaled as described above with reference to FIG. 5.

[0075] For example, the embodiments of Tables 1 to 5 are described based on time division duplexing (TDD). For example, both the first radio frame structure and the second radio frame structure utilize the principles of TDD. The embodiments of Figures 2 and 3 can also be applied to frequency-division duplexing (FDD) or auxiliary downlink / uplink (SDL / SDU) schemes. The auxiliary downlink / uplink may be defined as an auxiliary carrier for capturing the primary carrier. In this case, the auxiliary carrier is used only for downlink / uplink transmission. Therefore, the auxiliary carrier is an auxiliary downlink / uplink resource.

[0076] In the embodiments of Figures 2 and 3, the first radio frame structure may be applied according to FDD, SDL, and / or SDU. Table 6 below shows an embodiment of the first radio frame structure in such a case. TIFF0007778840000006.tif64149

[0077] Referring to Table 6, radio frame configuration A may be used for a frequency band or carrier dedicated to downlink transmission according to the FDD or SDL scheme. Radio frame configuration B may be used for a frequency band or carrier dedicated to uplink transmission according to the FDD or SDU scheme. In the case of an FDD scheme, frame configurations A and B may be used simultaneously as the first frame configuration. Similarly, radio frame configurations C and D may be used for the downlink band, and radio frame configuration E may be used for the uplink band. These radio frame configurations C, D, and E may use special subframes, which may be the above-mentioned special subframe S, including uplink and downlink portions such as UpPTS and DwPTS. In some embodiments, if the configuration is SDL / SDU, the uplink and downlink portions of the special subframe may be configured to be unused. The special subframe may be used to provide additional uplink / downlink resources for the downlink / uplink scheme. For example, in an unlicensed frequency band, transmission time is limited to a maximum extent, and the special subframe may be used to interrupt transmission.

[0078] In one embodiment, network element 110 may utilize a set of radio frame configurations that includes, for example, a first radio frame configuration selected from Table 6 and a second radio frame configuration selected from Table 2. The first radio frame configuration may be utilized for a first frequency band, and the second radio frame configuration may be utilized for a second frequency band operated by network element 110. The two radio frame configurations may be utilized simultaneously.

[0079] In another embodiment, the network element may switch from the first radio frame configuration (Table 6) to the second radio frame configuration (Table 2) such that the first radio frame configuration is used at a first time and the second radio frame configuration is used at a second time that is later than the first time. The first radio frame configuration and the second radio frame configuration may operate in the same frequency band or different frequency bands.

[0080] 9 and 10 illustrate apparatus according to some embodiments of the present invention. Figure 9 illustrates an apparatus configured to perform the functions described above in relation to a network element 110. Figure 10 illustrates an apparatus configured to perform the functions described above in relation to a terminal device 120. Each apparatus has communication control circuitry 10, 30, such as at least one processor and at least one memory 20, 40 containing computer program code (software) 22, 42. The at least one memory and computer program code (software) are configured by the at least one processor to cause the corresponding apparatus to implement any one of the embodiments of each apparatus described above.

[0081] The memories 20, 40 may be implemented using any suitable data storage technology, including semiconductor memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The memories may include a configuration database 24, 44 for storing configuration data for communication within a cell over the wireless interface. For example, the configuration database 24, 44 may store the wireless frame configurations supported by each device, such as the wireless frame configurations shown in Table 1 and / or Table 2.

[0082] The device may further include a communication interface (TX / RX) 26, 46 including hardware and / or software for providing communication connectivity in accordance with one or more communication protocols. This communication interface enables the device to communicate in a mobile communication system, for example, to enable communication between a communication network element 110 and a terminal device 120. The communication interface 26, 46 may include commonly known elements such as amplifiers, filters, frequency converters, (de)modulators, encoder / decoder circuitry, and one or more antennas. The communication interface 26, 46 may include radio interface elements that enable the network element 110 and the terminal device 120 to communicate wirelessly within a cell.

[0083] In the embodiment shown in FIG. 9 , at least some of the functionality of the network element 110 may be shared between two physically independent devices to form one operating entity. Thus, the apparatus may be considered to represent an operating entity including one or more physically independent devices for performing at least some of the above-described processing. Thus, the apparatus of FIG. 9 using a shared architecture may include a Remote Control Unit (RCU), such as a host computer or a server computer, operatively connected (e.g., via a wireless or wired network) to a remote radio head (RRH) in a base station facility. In some embodiments, at least some of the above-described processing of the network element 110 may be performed by the RCU. In some embodiments, at least some of the above-described processing may be shared between the RRH and the RCU. To this end, the RCU may have the elements shown in FIG. 9 , and a communication interface 26 may enable the RCU to be connected to the RRH. Meanwhile, the RRH may include, for example, radio frequency signal processing circuitry and an antenna.

[0084] In an embodiment, the RCU may create a virtual network for communicating with the RRH. Typically, virtual networking includes integrating hardware, software network resources, and network functions into a virtual network as a single software-based management entity. Network virtualization may include platform virtualization, which is often combined with resource virtualization. Network virtualization can be categorized as external virtual networking, that is, integrating many networks or parts of networks into a server computer or a host computer (i.e., the RCU). The purpose of external network virtualization is to optimize network sharing. It can also be categorized as internal virtual networking, that is, locating network-like functions in a software component on a single system. Virtual networking can also be used to test terminal devices.

[0085] In an embodiment, a virtual network flexibly distributes operations between the RRH and the RCU. In fact, any digital signal processing task may be performed in either the RRH or the RCU, and the distribution boundary between the RRH and the RCU may be drawn depending on the implementation.

[0086] 9, the apparatus may have control circuitry 12 that performs control plane signaling with a terminal device, another access node of a radio access network, and a network element of core network 130. The control circuitry 12 may perform steps 206, 500, 504, 600, 604, 606, and 700 at network element 110.

[0087] The device may further include radio frame configuration selection circuitry 18 configured to select a radio frame configuration from radio frame configurations stored in configuration database 24. Upon selecting a radio frame configuration, the radio frame configuration selection circuitry instructs control circuitry 12 to broadcast the radio frame configuration as system information in a cell controlled by the first network element. The device may further include subframe configuration selection circuitry 14 that dynamically selects a subframe configuration for each flexible special subframe. After selection, subframe configuration selection circuitry 14 instructs a controller to include in each flexible special subframe an information element indicating the subframe configuration of the subframe. The subframe configuration may define whether the flexible special subframe is a flexible special downlink subframe or a flexible special uplink subframe.

[0088] The apparatus may further include data communications circuitry 16 configured to transmit and receive payload data. For each flexible special subframe, data communications circuitry 16 may receive information from subframe configuration selection circuitry 14 indicating whether the flexible special subframe includes an additional downlink portion or an additional uplink portion. If the flexible special subframe includes an additional downlink portion, data communications circuitry 16 may control data transmission in the additional downlink portion. If the flexible special subframe includes an additional uplink portion, data communications circuitry 16 may extract data from the additional uplink portion.

[0089] 10 , the apparatus may include control circuitry 32 that performs control plane signaling with one or more network elements of a mobile communication system, such as, for example, access node 110. The control circuitry 32 may also perform a cell search procedure. The control circuitry 32 may perform steps 304, 500, 504, and 802 in the terminal device 120.

[0090] The apparatus may further include a radio frame configuration controller 38 configured to determine a radio frame configuration to be used in the cell based on system information received from the network element, and to configure the control circuitry 32 to implement the radio frame configuration for uplink and downlink communications in the cell.

[0091] The device may further include data communications circuitry 16 configured to transmit and receive payload data. For each flexible special subframe, data communications circuitry 36 receives information from control circuitry 32 indicating whether the flexible special subframe includes an additional downlink portion or an additional uplink portion. If the flexible special subframe includes an additional uplink portion, data communications circuitry 36 may control data transmission in the additional uplink portion. If the flexible special subframe includes an additional downlink portion, data communications circuitry 36 may extract data from the additional downlink portion.

[0092] As used herein, the term "circuitry" refers to any circuitry, including (a) a purely hardware implementation of a circuit, such as an implementation solely in analog and / or digital circuitry; (b) a combination of circuitry and software (and / or firmware), such as (in each case, a combination of software, software, and memory(s) including (i) processor(s) or (ii) portions of processor(s) / digital signal processor(s) that cooperate to cause a device to perform various functions; and (c) a microprocessor(s) or portions of microprocessors that require software or firmware for operation, even if such software or firmware is not physically present. This definition of "circuitry" applies to all "circuitry" described herein. Furthermore, as used herein, the term "circuitry" also encompasses implementations of simply a processor(s) or portions of a processor and associated software and / or firmware. The term "circuitry" also encompasses, for example, baseband integrated circuits, application processor integrated circuits (for mobile phones), or similar integrated circuits used in servers, mobile network devices, or other network devices, where applicable to the particular element.

[0093] In some examples, at least some of the processes described with reference to Figures 2-8 may be performed by an apparatus including corresponding means for performing at least some of the processes described above. Examples of means for performing the processes described above include at least one of a detector, a processor (e.g., a dual-core processor, a multi-core processor, etc.), a digital signal processor, a controller, a receiver, a transmitter, an encoder, a decoder, memory, RAM, ROM, software, firmware, a display, a user interface, display circuitry, user interface circuitry, user interface software, display software, circuitry, an antenna, antenna circuitry, and circuitry. In some examples, the at least one processor, memory, and computer program code form processing means or comprise one or more computer program code portions for performing one or more operations according to any of the embodiments shown in Figures 2-8.

[0094] The techniques and methods described herein may be implemented by various means. For example, these techniques may be implemented by hardware (one or more devices), firmware (one or more devices), software (one or more modules), or a combination thereof. In a hardware implementation, the apparatus(es) of an embodiment may be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or other electronic units designed to perform the functions described herein, or a combination thereof. In a firmware or software implementation, the implementation may be via modules (e.g., procedures, functions, etc.) of at least one chipset that perform the functions described herein. Software code may be stored in a memory unit and executed by a processor. This memory unit may be implemented either internally or externally to the processor. When implemented external to the processor, the memory unit may be communicatively connected to the processor via various means known in the art. In addition, it will be apparent to those skilled in the art that the components of the systems described herein may be rearranged or supplemented with additional components to facilitate implementation of the various aspects described in connection therewith, and that these components are not limited to the precise configuration shown.

[0095] The above-described embodiments may be implemented in the form of computer processes defined by a computer program or a portion thereof. The method embodiments described with reference to FIGS. 2-8 may be implemented by at least a portion of a computer program including corresponding instructions. The computer program may be in the form of source code, object code, or any intermediate form, and may be stored on some kind of carrier, which may be any entity or device capable of carrying the program. For example, the computer program may be stored on a computer program distribution medium readable by a computer or processor. Examples of the computer program medium include, but are not limited to, a recording medium, computer memory, read-only memory, an electrical carrier signal, a telecommunications signal, and a software distribution package. The computer program medium may also be a non-transitory medium. Coding software to implement the illustrated and described embodiments is within the common general knowledge of one of ordinary skill in the art.

[0096] Although the present invention has been described with reference to the drawings, it is clear that the present invention is not limited to the above description and can be modified in various ways within the scope of the claims. Therefore, all terms should be interpreted broadly and should be interpreted as illustrating the embodiments rather than limiting them. It will be obvious to those skilled in the art that with the advancement of technology, the concept of the present invention can be implemented in various ways. Furthermore, it will be obvious to those skilled in the art that the above-described embodiments can be combined in various ways with other embodiments, although this is not required.

[0097] The embodiments of the present invention, which were described in the scope of the claims of the original application of this application (Patent Application No. 2018-509621) at the time of filing, are as follows. ● Embodiment (1) providing, by a network element of a mobile communication system, a first radio frame configuration defining a frame structure of a radio frame including at least one subframe dedicated to downlink transmission; providing, by the network element, a second radio frame configuration defining a frame structure of a radio frame including at least one flexible special subframe configurable as one of a flexible downlink subframe and a flexible uplink subframe; selecting, by the network element, a radio frame configuration from a group of radio frame configurations including at least the first and second radio frame configurations, and transmitting a radio signal carrying an information element indicating the selected radio frame configuration; A method comprising: the flexible downlink subframe and the flexible uplink subframe each include both an uplink portion and a downlink portion; both the uplink and downlink parts carry control information and / or reference signals; method. ● Embodiment (2) The method according to embodiment (1), wherein the first radio frame configuration further includes at least one subframe dedicated to uplink transmission and at least one special subframe including an uplink portion and a downlink portion. ● Embodiment (3) The method of embodiment (1) or (2), wherein the flexible special subframe includes an additional uplink portion or an additional downlink portion depending on whether the flexible subframe is configured as the flexible uplink subframe or the flexible downlink subframe. ● Embodiment (4) The method of embodiment (3), wherein the further uplink unit carries uplink data and the further downlink unit carries downlink data. ● Embodiment (5) The method of any one of embodiments (1) to (4), wherein the uplink portion of the flexible special subframe carries a confirmation message indicating whether the terminal device correctly transmitted the downlink message. ● Embodiment (6) The method of any one of embodiments (1) to (5), wherein the network element provides a plurality of different radio frame configurations each defining the at least one flexible special subframe, and at least two of the plurality of different radio frame configurations have different subframe lengths. ● Embodiment (7) The method according to embodiment (6), wherein the longer the subframe length of the radio frame configuration, the larger the subcarrier spacing in the subframe. ● Embodiment (8) The method of any one of embodiments (1) to (7), wherein the network element provides the plurality of different radio frame configurations, each defining the at least one flexible special subframe, and at least one of the plurality of different radio frame configurations defines at least one subframe that is statistically designated as a flexible special downlink frame or a flexible special uplink frame. ● Embodiment (9) The method of any one of embodiments (1) to (8), wherein a majority of the subframes of the second radio frame configuration are flexible special subframes. ● Embodiment (10) 10. The method of any one of embodiments (1) to (9), wherein the flexible special subframe of the second radio frame configuration has a maximum length of an uplink portion that is greater than a maximum length of an uplink portion of the special subframe of the first radio frame configuration. ● Embodiment (11) 11. The method of any one of embodiments 1 to 10, further comprising: indicating, at the network element, for each flexible special subframe, whether the flexible special subframe is a flexible special downlink frame or a flexible special uplink frame. ● Embodiment (12) storing, in a terminal device of a mobile communication system, a first radio frame configuration definition defining a frame structure of a radio frame including at least one subframe dedicated to downlink transmission; storing, in the terminal device, a second radio frame configuration definition that defines a frame structure of a radio frame including at least one flexible special subframe configurable as one of a flexible downlink subframe and a flexible uplink subframe; receiving, from a network element of a mobile communication system, a radio signal carrying an information element indicating a radio frame structure applied in a cell of said mobile communication system; selecting a radio frame configuration from a group of radio frame configurations including at least the first and second radio frame configurations based on the received information element, and using the selected frame configuration for communication with the network element in the cell; A method comprising: the flexible downlink subframe and the flexible uplink subframe each include both an uplink portion and a downlink portion; both the uplink and downlink parts carry control information and / or reference signals; method. ● Embodiment (13) The method of embodiment (12), wherein the first radio frame configuration further includes at least one subframe dedicated to uplink transmission and at least one special subframe including an uplink portion and a downlink portion. ● Embodiment (14) 14. The method of claim 12, wherein the flexible special subframe includes an additional uplink portion or an additional downlink portion depending on whether the flexible subframe is configured as the flexible uplink subframe or the flexible downlink subframe. ● Embodiment (15) 15. The method of embodiment 14, wherein the further uplink portion carries uplink data and the further downlink portion carries downlink data. ● Embodiment (16) The method of any one of embodiments (12) to (15), wherein the uplink portion of the flexible special subframe carries a confirmation message indicating whether the terminal device correctly transmitted the downlink message. ● Embodiment (17) The method of any one of embodiments (12) to (16), wherein the terminal device stores definitions of a plurality of different radio frame configurations, each of which defines the at least one flexible special subframe, and at least two of the plurality of different radio frame configurations have different subframe lengths. ● Embodiment (18) The method according to embodiment (17), wherein the longer the subframe length of the radio frame configuration, the larger the subcarrier spacing in the subframe. ● Embodiment (19) The method of any one of embodiments (12) to (18), wherein the terminal device stores definitions of the plurality of different radio frame configurations, each of which defines the at least one flexible special subframe, and at least one of the plurality of different radio frame configurations defines at least one subframe that is statistically designated as a flexible special downlink frame or a flexible special uplink frame. ● Embodiment (20) The method of any one of embodiments (12) to (19), wherein a majority of the subframes of the second radio frame configuration are flexible special subframes. ● Embodiment (21) 21. The method of any one of embodiments 12 to 20, wherein the flexible special subframe of the second radio frame configuration has a maximum length of an uplink portion that is greater than a maximum length of an uplink portion of the special subframe of the first radio frame configuration. ● Embodiment (22) In the terminal device, receiving a flexible special subframe and receiving, together with the flexible special subframe, information indicating whether the flexible special subframe is a flexible special downlink frame or a flexible special uplink frame; applying a subframe structure mapped to the received information to the received flexible special subframe; and The method of any one of embodiments (12) to (21), further comprising: ● Embodiment (23) The method according to any one of embodiments (1) to (22), wherein the first radio frame structure corresponds to a specification of the Long Term Evolution standard. ● Embodiment (24) at least one processor; at least one memory containing computer program code, The processor, the memory, and the computer program code cause the device to: providing a first radio frame configuration defining a frame structure of a radio frame including at least one subframe dedicated to downlink transmission; providing, by the network element, a second radio frame configuration defining a frame structure of a radio frame including at least one flexible special subframe configurable as one of a flexible downlink subframe and a flexible uplink subframe; selecting a radio frame configuration from a group of radio frame configurations including at least the first and second radio frame configurations, and transmitting a radio signal carrying an information element indicating the selected radio frame configuration; Execute the flexible downlink subframe and the flexible uplink subframe each include both an uplink portion and a downlink portion; both the uplink and downlink parts carry control information and / or reference signals; Device. ● Embodiment (25) The apparatus of embodiment (24), wherein the first radio frame configuration further includes at least one subframe dedicated to uplink transmission and at least one special subframe including an uplink portion and a downlink portion. ● Embodiment (26) The apparatus of embodiment (24) or (25), wherein the flexible special subframe includes an additional uplink portion or an additional downlink portion depending on whether the flexible subframe is configured as the flexible uplink subframe or the flexible downlink subframe. ● Embodiment (27) The apparatus of embodiment (26), wherein the further uplink unit carries uplink data and the further downlink unit carries downlink data. ● Embodiment (28) The apparatus of any one of embodiments (24) to (27), wherein the uplink portion of the flexible special subframe carries a confirmation message indicating whether the terminal device correctly transmitted the downlink message. ● Embodiment (29) The apparatus of any one of embodiments (24) to (28), wherein the processor, the memory, and the computer program code cause the apparatus to provide a plurality of different radio frame configurations that each define the at least one flexible special subframe, and at least two of the plurality of different radio frame configurations have different subframe lengths. ● Embodiment (30) An apparatus as described in embodiment (29), wherein the longer the subframe length of the radio frame configuration, the larger the subcarrier spacing in the subframe. ● Embodiment (31) 31. The apparatus of any one of embodiments 24 to 30, wherein the processor, the memory, and the computer program code cause the apparatus to provide the plurality of different radio frame configurations, each defining the at least one flexible special subframe, and wherein at least one of the plurality of different radio frame configurations defines at least one subframe that is statistically designated to be a flexible special downlink frame or a flexible special uplink frame. ● Embodiment (32) The apparatus of any one of embodiments (24) to (31), wherein a majority of the subframes of the second radio frame configuration are flexible special subframes. ● Embodiment (33) The apparatus of any one of embodiments (24) to (32), wherein the flexible special subframe of the second radio frame configuration has a maximum length of an uplink portion that is greater than a maximum length of an uplink portion of the special subframe of the first radio frame configuration. ● Embodiment (34) The apparatus of any one of embodiments (24) to (33), wherein the processor, the memory, and the computer program code further cause the apparatus to indicate, for each flexible special subframe, whether the flexible special subframe is a flexible special downlink frame or a flexible special uplink frame. ● Embodiment (35) at least one processor; at least one memory containing computer program code, The processor, the memory, and the computer program code cause the device to: storing in the at least one memory a first radio frame configuration definition defining a frame structure of a radio frame including at least one subframe dedicated to downlink transmission; storing, in the at least one memory, a second radio frame configuration definition defining a frame structure of a radio frame including at least one flexible special subframe configurable as one of a flexible downlink subframe and a flexible uplink subframe; receiving a message from a network element of a mobile communication system, the message carrying an information element indicating a radio frame structure to be applied in a cell of said mobile communication system; selecting a radio frame configuration from a group of radio frame configurations including at least the first and second radio frame configurations based on the received information element, and using the selected radio frame configuration for communication with the network element in the cell; Execute the flexible downlink subframe and the flexible uplink subframe each include both an uplink portion and a downlink portion; both the uplink and downlink parts carry control information and / or reference signals; Device. ● Embodiment (36) The apparatus of embodiment (35), wherein the first radio frame configuration further includes at least one subframe dedicated to uplink transmission and at least one special subframe including an uplink portion and a downlink portion. ● Embodiment (37) The apparatus of embodiment (35) or (36), wherein the flexible special subframe includes an additional uplink portion or an additional downlink portion depending on whether the flexible subframe is configured as the flexible uplink subframe or the flexible downlink subframe. ● Embodiment (38) The apparatus of embodiment (37), wherein the further uplink unit carries uplink data and the further downlink unit carries downlink data. ● Embodiment (39) The apparatus of any one of embodiments (35) to (38), wherein the uplink portion of the flexible special subframe carries a confirmation message indicating whether the terminal device correctly transmitted the downlink message. ● Embodiment (40) The apparatus of any one of embodiments (35) to (39), wherein the processor, the memory, and the computer program code cause the apparatus to store definitions of a plurality of different radio frame configurations, each defining the at least one flexible special subframe, and at least two of the plurality of different radio frame configurations have different subframe lengths. ● Embodiment (41) An apparatus as described in embodiment (40), wherein the longer the subframe length of the radio frame structure, the larger the subcarrier spacing in the subframe. ● Embodiment (42) 42. The apparatus of any one of embodiments 35 to 41, wherein the processor, the memory, and the computer program code cause the apparatus to store definitions of the plurality of different radio frame configurations, each defining the at least one flexible special subframe, and at least one of the plurality of different radio frame configurations defines at least one subframe that is statistically designated to be a flexible special downlink frame or a flexible special uplink frame. ● Embodiment (43) The apparatus of any one of embodiments (35) to (42), wherein a majority of the subframes of the second radio frame configuration are flexible special subframes. ● Embodiment (44) The apparatus of any one of embodiments (35) to (43), wherein the flexible special subframe of the second radio frame configuration has a maximum length of an uplink portion that is greater than a maximum length of an uplink portion of the special subframe of the first radio frame configuration. ● Embodiment (45) The processor, the memory, and the computer program code cause the device to: receiving a flexible special subframe and receiving, together with the flexible special subframe, information indicating whether the flexible special subframe is a flexible special downlink frame or a flexible special uplink frame; applying a subframe structure mapped to the received information to the received flexible special subframe; and The apparatus of any one of embodiments (35) to (44), further comprising: ● Embodiment (46) The device according to any one of embodiments (24) to (45), comprising a wireless interface element configured to provide wireless communication capabilities to the device. ● Embodiment (47) A system comprising the device according to any one of embodiments (24) to (34) and the device according to any one of embodiments (35) to (45). ● Embodiment (48) An apparatus comprising means for performing all the steps of the method according to any one of embodiments (1) to (23). ● Embodiment (49) A computer program product embodied in a computer-readable distribution medium, the computer program product including program instructions that, when deployed in an apparatus, implements the method according to any one of embodiments (1) to (23).

Claims

1. Storing, in a terminal device of a mobile communication system, a definition of a first radio frame configuration defining a frame structure of a radio frame including at least one subframe dedicated to downlink transmission, wherein the terminal device stores definitions for a plurality of different radio frame configurations, each defining at least one flexible special subframe, at least two of the plurality of different radio frame configurations having different subframe lengths; storing, in the terminal device, a second radio frame configuration definition defining a frame structure of a radio frame including the at least one flexible special subframe configurable as one of a flexible special downlink subframe or a flexible special uplink subframe, wherein both the flexible special downlink subframe and the flexible special uplink subframe include an uplink portion and a downlink portion, and both the uplink portion and the downlink portion carry at least one of control information and reference signals; receiving, from a network element of the mobile communication system, a radio signal carrying an information element indicating a radio frame structure to be applied in a cell of the mobile communication system; selecting a radio frame configuration from a group of radio frame configurations including at least the first radio frame configuration and the second radio frame configuration based on the received information element, and using the selected radio frame configuration for communication with the network element in the cell; Including, Among the at least two of the plurality of radio frame structures having different lengths, either the radio frame structure having a larger subframe length has a smaller subcarrier spacing within the subframe, or the radio frame structure having a smaller subframe length has a larger subcarrier spacing within the subframe. method.

2. 2. The method of claim 1, wherein the first radio frame configuration further includes at least one subframe dedicated to uplink transmission, and the at least one flexible special subframe including an uplink portion and a downlink portion.

3. 10. The method of claim 1, wherein the at least one flexible special subframe includes an additional uplink portion or an additional downlink portion depending on whether the at least one flexible special subframe is configured as the flexible special uplink subframe or the flexible special downlink subframe.

4. In the terminal device, receiving a flexible special subframe and, together with the flexible special subframe, receiving information indicating whether the flexible special subframe is a flexible special downlink subframe or a flexible special uplink subframe; applying a subframe structure mapped to the received information to the received flexible special subframe; and The method of claim 1 further comprising:

5. at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the method of any one of claims 1 to 4.

6. storing definitions for a plurality of different radio frame configurations, each defining at least one flexible special subframe, at least two of the plurality of different radio frame configurations having different subframe lengths; wherein the definitions include a first radio frame configuration definition defining a frame structure of a radio frame including at least one subframe dedicated to downlink transmission, and a second radio frame configuration definition defining a frame structure of a radio frame including the at least one flexible special subframe configurable as one of a flexible special downlink subframe or a flexible special uplink subframe, wherein both the flexible special downlink subframe and the flexible special uplink subframe include an uplink portion and a downlink portion, and both the uplink portion and the downlink portion carry at least one of control information and reference signals; receiving a message from a network element of a mobile communication system, the message carrying an information element indicating a radio frame structure to be applied in a cell of said mobile communication system; selecting a radio frame configuration from a group of radio frame configurations including at least the first radio frame configuration and the second radio frame configuration based on the received information element, and using the selected radio frame configuration for communication with the network element in the cell; Including, Among the at least two of the plurality of radio frame structures having different lengths, either the radio frame structure having a larger subframe length has a smaller subcarrier spacing within the subframe, or the radio frame structure having a smaller subframe length has a larger subcarrier spacing within the subframe. method.

7. 7. The method of claim 6, wherein the first radio frame configuration further includes at least one subframe dedicated to uplink transmission, and the at least one flexible special subframe includes an uplink portion and a downlink portion.

8. 7. The method of claim 6, wherein the at least one flexible special subframe includes an additional uplink portion or an additional downlink portion depending on whether the at least one flexible special subframe is configured as the flexible special uplink subframe or the flexible special downlink subframe.

9. 9. The method of claim 8, wherein the further uplink part carries uplink data and the further downlink part carries downlink data.

10. 8. The method of claim 7, wherein the at least one flexible special subframe of the second radio frame configuration has a maximum length of an uplink portion that is greater than a maximum length of an uplink portion of the at least one flexible special subframe of the first radio frame configuration.

11. receiving a flexible special subframe and, together with the flexible special subframe, receiving information indicating whether the flexible special subframe is a flexible special downlink subframe or a flexible special uplink subframe; applying a subframe structure mapped to the received information to the received flexible special subframe; and The method of claim 7 further comprising:

12. at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the method of any one of claims 6 to 11.

13. Storing a definition of a radio frame configuration that defines a frame structure of a radio frame including an uplink portion configured to carry at least control information on a physical uplink control channel, a downlink portion, and at least one flexible special subframe including a flexible portion configurable for use for downlink transmission or uplink transmission; receiving a message from a network element of a mobile communication system, the message carrying an information element indicating a radio frame structure to be applied within said mobile communication system; selecting a radio frame configuration from a group of radio frame configurations including at least the radio frame configuration corresponding to the stored definition based on the received information element; using the selected radio frame structure for communication with the network element; Including, The radio frame structures correspond to different subcarrier spacings.

14. 14. The method of claim 13, wherein the uplink part is configured to carry at least a first reference signal multiplexed with the physical uplink control channel, and the downlink part is configured to carry at least control information and at least a second reference signal.

15. at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the method of any one of claims 13 to 14.

16. In a terminal device used in a mobile communication system, storing a radio frame structure definition defining a frame structure of a radio frame including at least an uplink portion configured to carry control information on a physical uplink control channel, a downlink portion, and at least one flexible special subframe including a flexible portion configurable for use for downlink transmission or uplink transmission; receiving a message from a network element of the mobile communication system, the message carrying an information element indicating a radio frame structure to be applied within the mobile communication system; selecting a radio frame configuration from a group of radio frame configurations including at least the radio frame configuration corresponding to the stored definition based on the received information element; using the selected radio frame structure for communication with the network element within a cell; Including, The radio frame structures correspond to different subcarrier spacings.

17. 17. The method of claim 16, wherein the uplink part is configured to carry at least a first reference signal multiplexed with the physical uplink control channel, and the downlink part is configured to carry at least control information and at least a second reference signal.

18. 17. The method of claim 16, wherein the set of radio frame configurations further includes a second radio frame configuration including at least one subframe dedicated to downlink transmission, at least one subframe dedicated to uplink transmission, and at least one flexible special subframe including an uplink portion and a downlink portion.

19. 17. The method of claim 16, wherein two or more sets of radio frame configurations each define the at least one flexible special subframe, and at least two of the two or more radio frame configurations have different subframe lengths.

20. The method of claim 19, wherein a radio frame configuration having a larger subframe length has a smaller subcarrier spacing in the subframe.

21. 20. The method of claim 18, wherein the at least one flexible special subframe has a maximum length of an uplink portion that is greater than a maximum length of an uplink portion of the flexible special subframe of the second radio frame configuration.

22. 17. The method of claim 16, wherein the at least one flexible special subframe includes an additional uplink portion or an additional downlink portion depending on whether the flexible portion is configured for downlink or uplink transmission.

23. 23. The method of claim 22, wherein the further uplink part carries uplink data and the further downlink part carries downlink data.

24. at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the method of any one of claims 16 to 23.

25. receiving a message from a network element of the mobile communication system, the message carrying an information element indicating a radio frame structure to be applied within the mobile communication system; selecting, based on the received information element, a radio frame configuration from a group of radio frame configurations, the radio frame configuration corresponding to a subcarrier spacing different from other subcarrier spacings corresponding to other radio frame configurations of the group of radio frame configurations, the group of radio frame configurations including radio frame configurations defining a frame structure of a radio frame including an uplink portion configured to carry at least control information, a downlink portion, and at least one flexible special subframe including a flexible portion configurable for use for downlink transmission or uplink transmission; using the selected radio frame structure for communication with the network element; A method comprising:

26. 26. The method of claim 25, wherein the set of radio frame configurations further includes a second radio frame configuration including at least one subframe dedicated to downlink transmission, at least one subframe dedicated to uplink transmission, and the at least one flexible special subframe including an uplink portion and a downlink portion.

27. 26. The method of claim 25, wherein two or more sets of radio frame configurations each define the at least one flexible special subframe, and at least two of the two or more radio frame configurations have different subframe lengths.

28. The method of claim 27, wherein a radio frame configuration having a larger subframe length has a smaller subcarrier spacing in the subframe.

29. 27. The method of claim 26, wherein the at least one flexible special subframe has a maximum length of an uplink portion that is greater than a maximum length of an uplink portion of the flexible special subframe of the second radio frame configuration.

30. 26. The method of claim 25, wherein the at least one flexible special subframe includes an additional uplink portion or an additional downlink portion depending on whether the flexible portion is configured for downlink or uplink transmission.

31. 31. The method of claim 30, wherein the further uplink part carries uplink data and the further downlink part carries downlink data.

32. at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the method of any one of claims 25 to 31.

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