FIG. 1 shows a wireless communication system. The wireless communication system can be widely deployed to provide a variety of communication services, such as voices, packet data, etc.

Referring to FIG. 1, the wireless communication system includes a base station (BS) 20 and at least one user equipment (UE) 10. The UE 10 may be fixed or mobile, and may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, etc. The BS 20 is generally a fixed station that communicates with the UE 10 and may be referred to as another terminology, such as a node-B, a base transceiver system (BTS), an access point, etc. There are one or more cells within the coverage of the BS 20.

Hereinafter, a downlink denotes a communication link from the BS 20 to the UE 10, and an uplink denotes a communication link from the UE 10 to the BS 20. In downlink, a transmitter may be a part of the BS 20, and a receiver may be a part of the UE 10. In uplink, the transmitter may be a part of the UE 10, and the receiver may be a part of the BS 20.

The wireless communication system may be a system based on orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA). The OFDM uses a plurality of orthogonal subcarriers. The OFDM uses orthogonality between an inverse fast Fourier transform (IFFT) and a fast Fourier transform (FFT). The transmitter transmits data by performing the IFFT. The receiver restores original data by performing the FFT on a received signal. The transmitter uses the IFFT to combine the plurality of subcarriers. The receiver uses the FFT to separate the plurality of subcarriers.

FIG. 2 shows an example of a frame structure. A frame is a data sequence used according to a physical specification in a fixed time duration. This may be found in section 8.4.4.2 of "Part 16: Air Interface for Fixed Broadband Wireless Access Systems" in the institute of electrical and electronics engineers (IEEE) standard 802.16-2004, the entire contents of which is incorporated herein by reference.

Referring to FIG. 2, the frame includes a downlink (DL) frame and an uplink (UL) frame. In a time division duplexing (TDD) scheme, UL and DL transmissions are achieved at different time points but share the same frequency band. The DL frame temporally precedes the UL frame. The DL frame sequentially includes a preamble, a frame control header (FCH), a DL-MAP, a UL-MAP, and a burst region. Guard times are provided to identify the UL frame and the DL frame and are inserted to a middle portion (between the DL frame and the UL frame) and a last portion (next to the UL frame) of the frame. A transmit/receive transition gap (TTG) is a gap between a downlink burst and a subsequent uplink burst. A receive/transmit transition gap (RTG) is a gap between an uplink burst and a subsequent downlink burst.

The preamble is used between a BS and a UE for initial synchronization, cell search, and frequency-offset and channel estimation. The FCH includes information on a length of a DL-MAP message and a coding scheme of the DL-MAP.

The DL-MAP is a region for transmitting the DL-MAP message. The DL-MAP message defines access to a DL channel. The DL-MAP message includes a configuration change count of a downlink channel descriptor (DCD) and a BS identifier (ID). The DCD describes a downlink burst profile applied to a current MAP. The downlink burst profile indicates characteristics of a DL physical channel. The DCD is periodically transmitted by the BS by using a DCD message.

The UL-MAP is a region for transmitting a UL-MAP message. The UL-MAP message defines access to a UL channel. The UL-MAP message includes a configuration change count of an uplink channel descriptor (UCD) and also includes an effective start time of uplink allocation defined by the UL-MAP. The UCD describes an uplink burst profile. The uplink burst profile indicates characteristics of a UL physical channel and is periodically transmitted by the BS by using a UCD message.

FIG. 3 shows an example of a frame hierarchy.

Referring to FIG. 3, a superframe is divided into four radio frames (hereinafter, frames) each having the same size. The superframe may include a superframe header. The superframe header may be assigned to a first frame among a plurality of frames constituting the superframe. A common control channel may be allocated to the superframe header. The common control channel is used to transmit information regarding the frames constituting the superframe or control information (e.g., system information) that can be commonly used by all UEs. The system information is necessary information which must be known to perform communication between a UE and a BS. The BS periodically transmits the system information. The system information may be periodically transmitted in every 20 to 40 milliseconds (ms). A size of the superframe can be determined by considering a transmission period of the system information. Although a size of each superframe is 20 ms and a size of each frame is 5 ms in FIG. 3, this is for exemplary purposes only, and thus the present invention is not limited thereto.

One frame consists of 8 subframes. One subframe can be allocated for uplink or downlink transmission. Each subframe for downlink transmission may include a signal for resource allocation. For example, the subframe may include 6 OFDM symbols. This is for exemplary purposes only, and thus the present invention is not limited thereto.

Now, a TDD frame structure and an FDD frame structure satisfying backward compatibility with a legacy system will be described. A TDD frame is a frame in which the entire frequency band is used for uplink or downlink transmission. Uplink and downlink regions are separated in a time domain. An FDD frame is a frame in which the uplink transmission and the downlink transmission occupy different frequency bands and are simultaneously achieved. A dual frame is a frame that satisfies backward compatibility with the legacy system. The dual frame includes a resource region that supports the legacy system and a resource region that supports a new/evolved system. The legacy system may be the institute of electrical and electronics engineers (IEEE) 802.16e system. The new system may be the IEEE 802.16m system. The terms used in the IEEE 802.16e frame structure described in FIG. 2 may be equally defined in the IEEE 802.16m frame structure without modification or with minor modifications.

Table 1 below shows frame parameters.

Table 1

To satisfy backward compatibility with the frame of the legacy system (i.e., IEEE 802.16e system), parameters (e.g., a transmission bandwidth, a sampling frequency, an FFT size, a subcarrier spacing, etc.) of the new system may conform to IEEE 802.16e frame parameters. In a conventional legacy system mode supporting IEEE 802.16e, a cyclic prefix (CP) length can be set to 1/8 useful symbol time (Tu) and one frame can include 48 OFDM symbols. In a conventional legacy support disabled mode not supporting the legacy system, new CP lengths can be set to 1/4 Tu, 1/16 Tu, and 1/32 Tu and one frame can include 43, 51, and 53 OFDM symbols respectively for the new CP lengths. For example, when one subframe consists of 6 OFDM symbols, a frame with a CP length of 1/4 Tu may consist of 7 subframes and one residual OFDM symbol, a frame with a CP length of 1/16 Tu may consist of 8 subframes and three residual OFDM symbols, and a frame with a CP length of 1/32 Tu may consist of 8 subframes and 5 residual OFDM symbols.

A CP is a copy of a final useful symbol period Tg, and can be expressed by a ratio with respect to a useful symbol time (Tu).

Table 2 below shows lengths of a TTG and an RTG in a TDD structure according to the IEEE 802.16e standard. The TTG can be expressed hereinafter in other terms such as a switching point, an idle frame, etc. This is for exemplary purposes only, and thus the present invention is not limited thereto. The switching points of the new system may be a longer or shorter than those in the IEEE 802.16e standard.

Table 2

FIG. 4 to FIG. 7 show examples of a TDD frame structure having a CP length of 1/8 Tu when a downlink-to-uplink ratio (DL/UL ratio) is 4:4 (FIG. 4), 5:3 (FIG. 5), 6:2 (FIG. 6), or 7:1 (FIG. 7).

Referring to FIG. 4 to FIG. 7, a new TDD frame satisfying backward compatibility is based on the conventional TDD frame structure and based on the aforementioned parameters and values of Table 1 and Table 2 above. That is, the new TDD frame has a length of 5 ms, a CP length of 1/8 Tu, and a bandwidth of 10 megahertz (MHz). Further, the new TDD frame includes 48 OFDM symbols. In addition, basic control information (e.g., preamble, FCH, and MAP) can be defined according to the IEEE 802.16e standard. The TTG length and the RTG length are the same as shown in Table 2 above.

In FIG. 4 to FIG. 7, one TDD frame consists of 8 subframes. A subframe is a basic unit of data allocation and scheduling, and generally consists of 6 OFDM symbols. Herein, the number 6 is determined by considering a bandwidth in a time axis and a pilot allocation pattern. In this case, a radio channel property is considered together with a size of data which is allocated through coding and modulation of media access control (MAC) and physical (PHY) entities. When one subframe is constructed of 6 OFDM symbols, a DL/UL ratio can be effectively configured, the number of OFDM symbols in a UL duration can be set to a multiple of 3 in a dual frame, and data delay capability can be improved. However, the number of OFDM symbols constituting one subframe is not limited thereto.

A TTG is located between a DL region and a UL region. An RTG is located between the UL region and a subsequent frame. An idle time may be included in the TTG or the RTG according to a CP length.

Specifically, referring to FIG. 4, a DL duration is a time period between a start point of a frame and a time point of 2364.86 microseconds (μs), and includes 23 OFDM symbols with a CP length of 1/8 Tu. A TTG duration is a time period between the time point of 2364.86 μs and a time point of 2472.32 μs, and thus includes a time period of 107.46 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 2472.32 μs and a time point of 4940 μs, and includes 24 OFDM symbols with a CP length of 1/8 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2.

Referring to FIG. 5, a DL duration is a time period between a start point of a frame and a time point of 2981.78 μs, and includes 29 OFDM symbols with a CP length of 1/8 Tu. A TTG duration is a time period between the time point of 2981.78 μs and a time point of 3089.24 μs, and thus includes a time period of 107.46 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3089.24 μs and a time point of 4940 μs, and includes 18 OFDM symbols with a CP length of 1/8 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2.

Referring to FIG. 6, a DL duration is a time period between a start point of a frame and a time point of 3598.7 μs, and includes 35 OFDM symbols with a CP length of 1/8 Tu. A TTG duration is a time period between the time point of 3598.7 μs and a time point of 3706.16 μs, and thus includes a time period of 107.46 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3706.16 μs and a time point of 4940 μs, and includes 12 OFDM symbols with a CP length of 1/8 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2.

Referring to FIG. 7, a DL duration is a time period between a start point of a frame and a time point of 4215.62 μs, and includes 41 OFDM symbols with a CP length of 1/8 Tu. A TTG duration is a time period between the time point of 4215.62 μs and a time point of 4323.08 μs, and thus includes a time period of 107.46 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 4323.08 μs and a time point of 4940 μs, and includes 6 OFDM symbols with a CP length of 1/8 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2.

In FIG. 4 to FIG. 7, the RTG is set to 60.0 μs, and the TTG is set to 107.46 μs by allowing most of idle time to belong to the TTG. However, as shown in Table 2 above, it is also possible to set the TTG to 105.71 μs and the RTG to 61.77 μs by allowing most of idle time to belong to the RTG.

FIG. 8 shows an example of an FDD frame structure having a CP length of 1/8 Tu.

Referring to FIG. 8, 48 OFDM symbols are included in one frame when a total frame length is 5 ms. One frame consists of 8 subframes. One subframe consists of 6 OFDM symbols. The idle time at the end of the frame is 64.64 μs as shown in Table 1 above.

The TDD and FDD frame structures shown in FIG. 4 to FIG. 8 have a CP length of 1/8 Tu. However, when a TDD frame structure having a different CP length coexists in an adjacent cell, mutual interference from mis-alignment between DL and UL transmissions may occur in data transmission. The present invention provides a TDD frame structure, in which TDD frames have various CP lengths to prevent mutual interference with a TDD frame having a CP length of 1/8 Tu, and also provides an FDD frame structure having a common feature with the TDD frame structure.

<Frame Structure In Which Switching Points Overlap Between Frames Having Different CP Lengths>

FIG. 9 shows a TDD frame structure having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu when a DL/UL ratio is 4:4 according to an embodiment of the present invention.

Referring to FIG. 9, a reference frame has the same conventional structure of FIG. 4. That is, the frame has a total length of 5 ms and a CP length of 1/8 Tu, and includes 8 subframes.

In a first TDD frame structure of this embodiment, a CP length is 1/4 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 2399.25 μs, and includes 21 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 2399.25 μs and a time point of 2540.75 μs, and thus includes a time period of 141.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 2540.75 μs and a time point of 4940 μs, and includes 21 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 5 OFDM symbols, one residual OFDM symbol is further allocated to the DL duration, one residual OFDM symbol is further allocated to the UL duration, and the remaining one residual OFDM symbol is allocated between the TTG and RTG durations. In other words, the last DL subframe is constructed of 6 OFDM symbols in FDD, and the last symbol in this subframe is punctured and is converted to a subframe of 5 OFDM symbols in TDD due to the TTG duration. In the first TDD frame structure of FIG. 9, a first subframe of the DL duration and a last subframe of the UL duration are constructed of 6 OFDM symbols. However, any one subframe belonging to the DL duration can be constructed of 6 OFDM symbols instead of the first subframe, and any one subframe belonging to the UL duration can be constructed of 6 OFDM symbols instead of the last subframe. In addition, the DL duration can be constructed of a plurality of subframes consisting of 5 OFDM symbols and the remaining one independent OFDM symbol, and the UL duration can be constructed of a plurality of subframes consisting of 5 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

In a second TDD frame structure of this embodiment, a CP length is 1/16 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 2427.8 μs, and includes 25 OFDM symbols with a CP length of 1/16 Tu. A TTG duration is a time period between the time point of 2427.8 μs and a time point of 2511.6 μs, and thus includes a time period of 84.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 2511.6 μs and a time point of 4940 μs, and includes 25 OFDM symbols with a CP length of 1/16 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, three residual OFDM symbols remain. Among the three residual OFDM symbols, one OFDM symbol is further allocated to the DL duration, one OFDM symbol is further allocated to the UL duration, and the remaining one OFDM symbol is allocated between the TTG and RTG durations. In other words, the last DL subframe is constructed of 7 OFDM symbols in FDD, and the last symbol in this subframe is punctured and is converted to a subframe of 6 OFDM symbols in TDD due to the TTG duration. In the second TDD frame structure of FIG. 9, a first subframe of the DL duration is constructed of 7 OFDM symbols and a last subframe of the UL duration is constructed of 7 OFDM symbols. However, any one subframe belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first subframe, and any one subframe belonging to the UL duration can be constructed of 7 OFDM symbols instead of the last subframe. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol, and the UL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

In a third TDD frame structure of this embodiment, a CP length is 1/32 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 2450.76 μs, and includes 26 OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a time period between the time point of 2450.76 μs and a time point of 2583.5 μs, and thus includes a time period of 132.42 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 2583.5 μs and a time point of 4940 μs, and includes 25 OFDM symbols with a CP length of 1/32 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, 5 residual OFDM symbols remain. Among the 5 residual OFDM symbol, two OFDM symbols are further allocated to the DL duration, one OFDM symbol is further allocated to the UL duration, and the remaining two OFDM symbols are allocated between the TTG and RTG durations. In the third TDD frame structure of FIG. 9, a first subframe and a last subframe of the DL duration are constructed of 7 OFDM symbols and a last subframe of the UL duration is constructed of 7 OFDM symbols. However, any two subframes belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first and last DL subframes, and any one subframe belonging to the UL duration can be constructed of 7 OFDM symbols instead of the last UL subframe. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining two independent OFDM symbols, and the UL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

When the TDD frame is configured as shown in FIG. 9, mutual interference does not occur even if the frame structures having different CP lengths exist in adjacent cells. That is, mutual interference does not occur because a DL duration of a frame having a CP length of 1/8 Tu does not overlap with a UL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a frame having a CP length of 1/8 Tu does not overlap with a DL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu.

FIG. 10 shows TDD frame structures having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu when a DL/UL ratio is 5:3 with a CP length of 1/8 Tu according to an embodiment of the present invention.

Referring to FIG. 10, a reference frame has the same conventional structure of FIG. 5. That is, the frame has a total length of 5 ms and a CP length of 1/8 Tu, and includes 8 subframes.

In a first TDD frame structure of this embodiment, a CP length is 1/4 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 2856.25 μs, and includes 25 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 2856.25 μs and a time point of 2997.75 μs, and thus includes a time period of 141.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 2997.75 μs and a time point of 4940 μs, and includes 17 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, one residual OFDM symbol is further allocated to the DL duration, a first subframe of the UL duration is constructed of 5 OFDM symbols, and one OFDM symbol preceding the first subframe of the UL duration is punctured. In the first TDD frame structure of FIG. 10, a first subframe of the DL duration is constructed of 7 OFDM symbols. However, any one subframe belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first subframe. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

Alternatively, in the TDD frame structure having a CP length of 1/4 Tu, if one subframe is constructed of 5 OFDM symbols, one residual OFDM symbol can be further allocated to the DL duration, one residual OFDM symbol can be further allocated to the UL duration, and the remaining one residual OFDM symbol can be allocated to the TTG duration. This alternative method is the same as the case of 1/4 Tu, which was explained with a DL to UL ratio of 4:4 in FIG. 9.

In a second TDD frame structure of this embodiment, a CP length is 1/16 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 3010.41 μs, and includes 31 OFDM symbols with a CP length of 1/16 Tu. A TTG duration is a time period between the time point of 3010.41 μs and a time point of 3094.91 μs, and thus includes a time period of 84.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3094.91 μs and a time point of 4940 μs, and includes 19 OFDM symbols with a CP length of 1/16 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, three residual OFDM symbols remain. Among the three residual OFDM symbols, one OFDM symbol is further allocated to the DL duration, one OFDM symbol is further allocated to the UL duration, and the remaining one OFDM symbol is allocated between the TTG and RTG durations. In other words, the last DL subframe is constructed of 7 OFDM symbols in FDD, and the last symbol in this subframe is punctured and is converted to a subframe of 6 OFDM symbols in TDD due to the TTG duration. This may be considered an idle symbol. In the second TDD frame structure of FIG. 10, a first subframe of the DL duration is constructed of 7 OFDM symbols and a last subframe of the UL duration is constructed of 7 OFDM symbols. However, any one subframe belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first subframe, and any one subframe belonging to the UL duration can be constructed of 7 OFDM symbols instead of the last subframe. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol, and the UL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. The remaining one independent OFDM may follow a subframe consisting of 6 OFDM symbols, or may be a symbol of a subframe consisting of 7 OFDM symbols (e.g., a seventh, or last, symbol). Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

In a third TDD frame structure of this embodiment, a CP length is 1/32 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 3016.32 μs, and includes 32 OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a time period between the time point of 3016.32 μs and a time point of 3054.80 μs, and thus includes a time period of 38.48 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3054.80 μs and a time point of 4940 μs, and includes 20 OFDM symbols with a CP length of 1/32 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, 5 residual OFDM symbols remain. Among the 5 residual OFDM symbols, two OFDM symbols are further allocated to the DL duration, two OFDM symbols are further allocated to the UL duration, and the remaining one OFDM symbol is allocated between the TTG and RTG durations. In the third TDD frame structure of FIG. 10, a first subframe and a last subframe of the DL duration are constructed of 7 OFDM symbols and a first subframe and a last subframe of the UL duration are constructed of 7 OFDM symbols. However, any two subframes belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first and last DL subframes, and any two subframes belonging to the UL duration can be constructed of 7 OFDM symbols instead of the first and the last UL subframes. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining two independent OFDM symbols, and the UL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining two independent OFDM symbols. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

If the TTG duration requires a longer duration than 38.48 μs, one of OFDM symbols additionally allocated to the DL duration or the UL duration can be further allocated for the TTG duration. For example, one of OFDM symbols additionally allocated to the UL duration can be further allocated for the TTG duration, and thus the TTG duration may be 132.74 μs.

When the TDD frame is configured as shown in FIG. 10, mutual interference does not occur even if the frame structures having different CP lengths exist in adjacent cells. That is, mutual interference does not occur since a DL duration of a frame having a CP length of 1/8 Tu does not overlap with a UL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a frame having a CP length of 1/8 Tu does not overlap with a DL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu.

FIG. 11 shows TDD frame structures having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu with a CP length of 1/8 Tu and when a DL/UL ratio is 6:2 according to an embodiment of the present invention.

Referring to FIG. 11, a reference frame has the same conventional structure of FIG. 6. That is, the frame has a total length of 5 ms and a CP length of 1/8 Tu, and includes 8 subframes.

In a first TDD frame structure of this embodiment, a CP length is 1/4 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 3541.8 μs, and includes 31 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 3541.8 μs and a time point of 3683.25 μs, and thus includes a time period of 141.45 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3683.25 μs and a time point of 4940 μs, and includes 11 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, one residual OFDM symbol is further allocated to the DL duration, a first subframe of the UL duration is constructed of 5 OFDM symbols, and one OFDM symbol preceding the first subframe of the UL duration is punctured. In the first TDD frame structure of FIG. 11, a first subframe of the DL duration is constructed of 7 OFDM symbols. However, any one subframe belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first subframe. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

Alternatively, in the TDD frame structure having a CP length of 1/4 Tu, if one subframe is constructed of 5 OFDM symbols, one residual OFDM symbol can be further allocated to the DL duration, one residual OFDM symbol can be further allocated to the UL duration, and the remaining one OFDM symbol can be allocated to the TTG duration. This alternative method is the same as the case of 1/4 Tu, which was explained with a DL to UL ratio of 4:4 in FIG. 9.

In a second TDD frame structure of this embodiment, a CP length is 1/16 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 3593.07 μs, and includes 37 OFDM symbols with a CP length of 1/16 Tu. A TTG duration is a time period between the time point of 3593.07 μs and a time point of 3677.57 μs, and thus includes a time period of 84.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3677.57 μs and a time point of 4940 μs, and includes 13 OFDM symbols with a CP length of 1/16 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, three residual OFDM symbols remain. Among the three residual OFDM symbols, one OFDM symbol is further allocated to the DL duration, one OFDM symbol is further allocated to the UL duration, and the remaining one OFDM symbol is allocated between the TTG and RTG durations. In other words, the last DL subframe is constructed of 7 OFDM symbols in FDD, and the last symbol in this subframe is punctured and is converted to a subframe of 6 OFDM symbols in TDD due to the TTG duration. In the second TDD frame structure of FIG. 11, a first subframe of the DL duration is constructed of 7 OFDM symbols and a last subframe of the UL duration is constructed of 7 OFDM symbols. However, any one subframe belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first subframe, and any one subframe belonging to the UL duration can be constructed of 7 OFDM symbols instead of the last subframe. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol, and the UL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

In a third TDD frame structure of this embodiment, a CP length is 1/32 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 3581.88 μs, and includes 38 OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a time period between the time point of 3581.88 μs and a time point of 3620.36 μs, and thus includes a time period of 38.48 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3620.36 μs and a time point of 4940 μs, and includes 14 OFDM symbols with a CP length of 1/32 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, 5 residual OFDM symbols remain. Among the 5 residual OFDM symbols, two OFDM symbols are further allocated to the DL duration, two OFDM symbols are further allocated to the UL duration, and the remaining one OFDM symbol is allocated between the TTG and RTG durations. In the third TDD frame structure of FIG. 11, a first subframe and a last subframe of the DL duration are constructed of 7 OFDM symbols. However, any two subframes belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first and last DL subframes. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining two independent OFDM symbols, and the UL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining two independent OFDM symbols. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

If the TTG duration requires a longer duration than 38.48 μs, one of OFDM symbols additionally allocated to the DL duration or the UL duration can be further allocated for the TTG duration. For example, one of OFDM symbols additionally allocated to the UL duration can be further allocated for the TTG duration, and thus the TTG duration may be 132.74 μs.

When the TDD frame is configured as shown in FIG. 11, mutual interference does not occur even if the frame structures having different CP lengths exist in adjacent cells. That is, mutual interference does not occur since a DL duration of a frame having a CP length of 1/8 Tu does not overlap with a UL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a frame having a CP length of 1/8 Tu does not overlap with a DL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu.

FIG. 12 shows TDD frame structures having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu with a CP length of 1/8 Tu and when a DL/UL ratio is 7:1 according to an embodiment of the present invention.

Referring to FIG. 12, a reference frame has the same conventional structure of FIG. 7. That is, the frame has a total length of 5 ms and a CP length of 1/8 Tu, and includes 8 subframes.

In a first TDD frame structure of this embodiment, a CP length is 1/4 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 4227.25 μs, and includes 37 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 4227.25 μs and a time point of 4368.75 μs, and thus includes a time period of 141.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 4368.75 μs and a time point of 4940 μs, and includes 5 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, one residual OFDM symbol is further allocated to the DL duration, a first subframe of the UL duration is constructed of 5 OFDM symbols, and one OFDM symbol preceding the first subframe of the UL duration is punctured. In the first TDD frame structure of FIG. 12, a first subframe of the DL duration is constructed of 7 OFDM symbols. However, any one subframe belonging to the DL duration can be constructed of 7 OFDM symbols. instead of the first subframe In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

Alternatively, in the TDD frame structure having a CP length of 1/4 Tu, if one subframe is constructed of 5 OFDM symbols, one residual OFDM symbol can be further allocated to the DL duration, one residual OFDM symbol can be further allocated to the UL duration, and the remaining one residual OFDM symbol can be allocated to the TTG duration. This alternative method is the same as the case of 1/4 Tu, which was explained with a DL to UL ratio of 4:4 in FIG. 9.

In a second TDD frame structure of this embodiment, a CP length is 1/16 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 4175.73 μs, and includes 43 OFDM symbols with a CP length of 1/16 Tu. A TTG duration is a time period between the time point of 4175.73 μs and a time point of 4260.23 μs, and thus includes a time period of 84.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 4260.23 μs and a time point of 4940 μs, and includes 7 OFDM symbols with a CP length of 1/16 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of a plurality of OFDM symbols, three residual OFDM symbols remain. Among the three residual OFDM symbols, one OFDM symbol is further allocated to the DL duration, one OFDM symbol is further allocated to the UL duration, and the remaining one OFDM symbol is allocated between the TTG and RTG durations. In other words, the last DL subframe is constructed of 7 OFDM symbols in FDD, and the last symbol in this subframe is punctured and is converted to a subframe of 6 OFDM symbols in TDD due to the TTG duration. In the second TDD frame structure of FIG. 12, a first subframe of the DL duration is constructed of 7 OFDM symbols. However, any one subframe belonging to the DL duration can be constructed of 7 OFDM symbols instead of the first subframe. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

In a third TDD frame structure of this embodiment, a CP length is 1/32 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 4241.7 μs and includes 45 OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a time period between the time point of 4241.7 μs and a time point of 4280.18 μs, and thus includes a time period of 38.48 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 4280.18 μs and a time point of 4940 μs, and includes 7 OFDM symbols with a CP length of 1/32 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations. Accordingly, if one subframe is constructed of 6 OFDM symbols, 5 residual OFDM symbols remain. Among the 5 residual OFDM symbols, 3 OFDM symbols are further allocated to the DL duration, one OFDM symbol is further allocated to the UL duration, and the remaining one OFDM symbol is allocated between the TTG and RTG durations. In the third TDD frame structure of FIG. 12, 1st, 6th, and 7th subframes of the DL duration are constructed of 7 OFDM symbols. However, any three subframes belonging to the DL duration can be constructed of 7 OFDM symbols instead of these three subframes. In addition, the DL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining three independent OFDM symbols, and the UL duration can be constructed of a plurality of subframes consisting of 6 OFDM symbols and the remaining one independent OFDM symbol. Such a subframe structure is for exemplary purposes only. That is, the subframes belonging to the DL duration can be constructed of any number of OFDM symbols, and the subframes belonging to the UL duration can be constructed of any number of OFDM symbols, wherein the subframes can have different sizes.

If the TTG duration requires a longer duration than 38.48 μs, one of OFDM symbols additionally allocated to the DL duration or the UL duration can be further allocated for the TTG duration. For example, one of OFDM symbols additionally allocated to the UL duration can be further allocated for the TTG duration, and thus the TTG duration may be 132.74 μs.

When the TDD frame is configured as shown in FIG. 12, mutual interference does not occur even if the frame structures having different CP lengths exist in adjacent cells. That is, mutual interference does not occur since a DL duration of a frame having a CP length of 1/8 Tu does not overlap with a UL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a frame having a CP length of 1/8 Tu does not overlap with a DL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu.

Table 3 below summarizes some of the features shown in FIGs. 9-12 and shows a frame structure having a different CP length according to the above-described embodiments of the invention and coexisting with a conventional reference frame structure.

Table 3

In the TDD frame structure having a DL/UL ratio of 4:4 and having a CP length of 1/4 Tu shown in Table 3, it is assumed that one subframe consists of 5 OFDM symbols, and one OFDM symbol is further allocated to the TTG duration in the TDD frame structure having a CP length of 1/32 Tu. In the TDD frame structure having a DL/UL ratio of 7:1 and having a CP length of 1/32 Tu, a residual OFDM symbol is further allocated to the UL duration since only one subframe is allocated for the DL duration. In Table 3, the last two rows indicated by a mark (*) vary according to the number of OFDM symbols constituting one subframe. When the configuration of Table 3 above is applied in systems, one symbol can be optionally further punctured in a UL or DL duration.

<Type Of Subframe Depending On The Number Of OFDM Symbols Included In Subframe>

FIG. 13 to FIG. 16 each show 1) TDD frame structures from FIG. 9 to 12, respectively, which has a different CP length and coexists with the aforementioned TDD frame structure having a CP length of 1/8 Tu in an adjacent cell, and 2) FDD frame structures having a common feature with the TDD frame structures. A TDD frame and an FDD frame, each of which has a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu, are configured using three types of subframes.

Hereinafter, a type of the subframe consisting of 6 OFDM symbols is referred to as a subframe type-1 (SFT-1), a type of the subframe consisting of 5 OFDM symbols is referred to as an SFT-2, and a type of the subframe consisting of 7 OFDM symbols is referred to as an SFT-3. An SFT-3 type subframe has a format in which one OFDM symbol is added to an SFT-1 type subframe. The added OFDM symbol may precede or follow the SFT-1 type subframe, or may be located in the middle of the SFT-1 type subframe. The added OFDM symbol may be used for control information (e.g., preambles, sounding, etc.) or for data.

FIG. 13 shows TDD frame structures having a CP length of 1/4 Tu and FDD frame structures having a common feature with the TDD frame structures according to an embodiment of the present invention. In FIG. 13, subframes other than the SFT-2 type and SFT-3 type subframes are SFT-1 type subframes.

Referring to FIG. 13, in a first TDD frame structure of this embodiment, a DL/UL ratio is 4:3 and a CP length is 1/4 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 2856.25 μs, and includes 25 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 2856.25 μs and a time point of 2997.75 μs, and thus includes a time period of 141.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 2997.75 μs and a time point of 4940 μs, and includes 17 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations.

Accordingly, the DL duration consists of three SFT-1 subframes and one SFT-3 subframe, and the UL duration consists of two SFT-1 subframes and one SFT-2 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a second TDD frame structure of this embodiment, a DL/UL ratio is 5:2 and a CP length is 1/4 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 3541.8 μs, and includes 31 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 3541.8 μs and a time point of 3683.25 μs, and thus includes a time period of 141.45 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3683.25 μs and a time point of 4940 μs, and includes 11 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations.

Accordingly, the DL duration consists of four SFT-1 subframes and one SFT-3 subframe, and the UL duration consists of one SFT-1 subframe and one SFT-2 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a third TDD frame structure of this embodiment, a DL/UL ratio is 6:1 and a CP length is 1/4 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 4227.25 μs, and includes 37 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 4227.25 μs and a time point of 4368.75 μs, and thus includes a time period of 141.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 4368.75 μs and a time point of 4940 μs, and includes 5 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations.

Accordingly, the DL duration consists of five SFT-1 subframes and one SFT-3 subframe, and the UL duration consists of one SFT-2 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

By configuring the TDD frame as described above, a DL/UL switch duration can conform to a frame structure having a CP length of 1/8 Tu. Thus, even if a system having a CP length of 1/8 Tu exists in an adjacent cell, interference between uplink and downlink transmissions can be minimized.

Irrespective of a DL/UL ratio, the DL duration includes one SFT-3 type subframe. In FIG. 13, a first subframe #1 of the DL duration is constructed of one SFT-3 type subframe, but this is for exemplary purposes only. That is, if the DL/UL ratio is 4:3, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, and #4. If the DL/UL ratio is 5:2, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, #4, and #5. If the DL/UL ratio is 6:1, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, #4, #5, and #6.

In addition, irrespective of a DL/UL ratio, the UL duration includes one SFT-2 type subframe. In FIG. 13, a first subframe #1 of the UL duration is constructed of the SFT-2 type subframe, but this is for exemplary purposes only. That is, if the DL/UL ratio is 4:3, the SFT-2 type subframe can be located at one position selected from positions #5, #6, and #7, if the DL/UL ratio is 5:2, the SFT-2 type subframe can be located at one position selected from positions #6 and #7, and if the DL/UL ratio is 6:1, the SFT-2 type subframe can be located at a position #7.

Next, in the FDD frame structure, the FDD frame includes one pivot subframe. The pivot subframe is a subframe located at a position corresponding to a TTG duration of the TDD frame so as to maintain a common feature with the TDD frame. When the CP length is 1/4 Tu, the pivot subframe is an SFT-1 type subframe. If the DL/UL ratio is 4:3, the TTG duration in the TDD frame is located between positions #4 and #5, and thus the pivot subframe in the FDD frame can be located at a position #5. If the DL/UL ratio is 5:2, the TTG duration in the TDD frame is located between positions #5 and #6, and thus the pivot subframe in the FDD frame can be located at a position #6. If the DL/UL ratio is 6:1, the TTG duration in the TDD frame is located between positions #6 and #7, and thus the pivot subframe in the FDD frame can be located at a position #7. To maintain the common feature with the TDD frame, one SFT-3 type subframe is located ahead of the pivot subframe. That is, if the DL/UL ratio is 4:3, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, and #4, if the DL/UL ratio is 5:2, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, #4, and #5, and if the DL/UL ratio is 6:1, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, #4, #5, and #6.

In FIG. 13, the pivot subframe is only located in #5, #6, and #7. But this is for exemplary purposes only. The other FDD frame with different locations of the pivot subframe may be considered in the same way.

In FIG. 13, a base subframe is constructed of an SFT-1 type subframe in the TDD frame structure having a CP length of 1/4 Tu. The base subframe may be constructed of an SFT-2 type subframe.

FIG. 14 shows a TDD frame having a CP length of 1/4 Tu and including a base subframe constructed of an SFT-2 type subframe and an FDD frame having a common feature with the TDD frame. In FIG. 14, subframes other than the SFT-1 type subframes are SFT-2 type subframes.

Referring to FIG. 14, in a first TDD frame structure of this embodiment, a DL/UL ratio is 4:4, a CP length is 1/4 Tu, and a base subframe is constructed of an SFT-2 type subframe. This structure is the same as the TDD frame structure having a CP length of 1/4 Tu as shown in FIG. 9. Accordingly, a DL duration consists of one SFT-1 subframe and three SFT-3 subframes, and a UL duration consists of one SFT-1 subframe and three SFT-2 subframes. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a second TDD frame of this embodiment, a DL/UL ratio is 5:3, a CP length is 1/4 Tu, and a base subframe is constructed of an SFT-2 type subframe. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 2970.5 μs and includes 26 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 2970.5 μs and a time point of 3112 μs, and thus includes a time period of 141.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 3112 μs and a time point of 4940 μs, and includes 16 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations.

Accordingly, a DL duration consists of one SFT-1 subframe and four SFT-2 subframes, and a UL duration consists of one SFT-1 subframe and two SFT-2 subframes. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a third TDD frame structure of this embodiment, a DL/UL ratio is 6:2, a CP length is 1/4 Tu, and a base subframe is constructed of an SFT-2 type subframe. This structure is the same as the TDD frame structure having a CP length of 1/4 Tu as shown in FIG. 11. Accordingly, a DL duration consists of one SFT-1 subframe and five SFT-2 subframes, and a UL duration consists of one SFT-1 subframe and one SFT-2 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a fourth TDD frame structure of this embodiment, a DL/UL ratio is 7:1, a CP length is 1/4 Tu, and a base subframe is constructed of an SFT-2 type subframe. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 4113 μs, and includes 36 OFDM symbols with a CP length of 1/4 Tu. A TTG duration is a time period between the time point of 4113 μs and a time point of 4254.5 μs, and thus includes a time period of 141.5 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 4254.5 μs and a time point of 4940 μs, and includes 6 OFDM symbols with a CP length of 1/4 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2. The time points may be varied according to the TTG and RTG durations.

Accordingly, a DL duration consists of one SFT-1 subframe and six SFT-2 subframes, and a UL duration consists of one SFT-1 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

By configuring the TDD frame as described above, a DL/UL switch duration can conform to a frame structure having a CP length of 1/8 Tu. Thus, even if a system having a CP length of 1/8 Tu exists in an adjacent cell, interference between uplink and downlink transmissions can be minimized.

If the base subframe is constructed of the SFT-2 type subframe, the DL duration includes one SFT-1 type subframe irrespective of a DL/UL ratio. If the DL/UL ratio is 4:4, the SFT-1 type subframe can be located at one position selected from positions #1, #2, #3, and #4. If the DL/UL ratio is 5:3, the SFT-1 type subframe can be located at one position selected from positions #1, #2, #3, #4, and #5. If the DL/UL ratio is 6:2, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, #4, #5, and #6. If the DL/UL ratio is 7:1, the SFT-1 type subframe can be located at one position selected from positions #1, #2, #3, #4, #5, #6, and #7.

If the base subframe is constructed of the SFT-2 type subframe, the UL duration includes one SFT-1 type subframe irrespective of a DL/UL ratio. If the DL/UL ratio is 4:4, the SFT-1 type subframe can be located at one position selected from positions #5, #6, #7, and #8. If the DL/UL ratio is 5:3, the SFT-1 type subframe can be located at one position selected from positions #6, #7, and #8. If the DL/UL ratio is 6:2, the SFT-3 type subframe can be located at one position selected from positions #7 and #8. If the DL/UL ratio is 7:1, the SFT-1 type subframe can be located at a position #8.

Next, in the FDD frame structure in which a CP length is 1/4 Tu and a base subframe is constructed of an SFT-2 subframe, the pivot subframe can be located at a position corresponding to a TTG duration of the TDD frame. Herein, the pivot subframe is an SFT-1 type subframe. If the DL/UL ratio is 4:4, the TTG duration in the TDD frame is located between positions #4 and #5, and thus the pivot subframe in the FDD frame can be located at a position #4 or #5. If the DL/UL ratio is 5:3, the TTG duration in the TDD frame is located between positions #5 and #6, and thus the pivot subframe in the FDD frame can be located at a position #5 or #6. If the DL/UL ratio is 6:2, the TTG duration in the TDD frame is located between positions #6 and #7, and thus the pivot subframe in the FDD frame can be located at a position #6 or #7. If the DL/UL ratio is 7:1, the TTG duration in the TDD frame is located between positions #7 and #8, and thus the pivot subframe in the FDD frame can be located at a position #7 or #8. However, since the UL duration includes one SFT-1 type subframe, if the DL/UL ratio is 7:1, the pivot subframe is preferably located at the position #7.

To maintain the common feature with the TDD frame, one SFT-1 type subframe is located ahead of the pivot subframe, and one SFT-1 type subframe is located behind of the pivot subframe. That is, if the DL/UL ratio is 4:4, when the pivot subframe is located at a position #4, the SFT-1 type subframes other than the pivot subframe can be located at one position selected from positions #1, #2, and #3 and at one position selected from positions #5, #6, #7, and #8, or when the pivot subframe is located at the position #5, the SFT-1 type subframes can be located at one position selected from positions #1, #2, #3, and #4 and at one position selected from positions #6, #7, and #8. If the DL/UL ratio is 5:3, when the pivot subframe is located at a position #5, the SFT-1 type subframes other than the pivot subframe can be located at one position selected from positions #1, #2, #3, and #4 and at one position selected from positions #6, #7, and #8, or when the pivot subframe is located at the position #6, the SFT-1 type subframes can be located at one position selected from positions #1, #2, #3, #4, and #5 and at one position selected from positions #7 and #8. If the DL/UL ratio is 6:2, when the pivot subframe is located at a position #6, the SFT-1 type subframes other than the pivot subframe can be located at one position selected from positions #1, #2, #3, #4, and #5 and at one position selected from positions #7 and #8, or when the pivot subframe is located at the position #7, the SFT-1 type subframes can be located at one position selected from positions #1, #2, #3, #4, #5, and #6 and at a position #8. If the DL/UL ratio is 7:1, when the pivot subframe is located at a position #7, the SFT-1 type subframes other than the pivot subframe can be located at one position selected from positions #1, #2, #3, #4, #5, and #6 and at a position #8, or when the pivot subframe is located at the position #8, the SFT-1 type subframes can be located at two positions selected from positions #1, #2, #3, #4, #5, #6, and #7.

In FIG. 14, the pivot subframe is only located in #5, #6, #7, and #8. But this is for exemplary purposes only. The other FDD frame with different locations of the pivot subframe may be considered in the same way.

FIG. 15 shows TDD frame structures having a CP length of 1/16 Tu and FDD frame structures having a common feature with the TDD frame structures according to an embodiment of the present invention. In FIG. 15, subframes other than the SFT-3 type subframes are SFT-1 type subframes.

Referring to FIG. 15, in a first TDD frame structure of this embodiment, a DL/UL ratio is 4:4 and a CP length is 1/16 Tu. This structure is the same as the TDD frame structure having a CP length of 1/16 Tu as shown in FIG. 9. Accordingly, a DL duration consists of one SFT-3 subframe and three SFT-1 subframes, and a UL duration consists of one SFT-3 subframe and three SFT-1 subframes. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a second TDD frame structure of this embodiment, a DL/UL ratio is 5:3 and a CP length is 1/16 Tu. This structure is the same as the TDD frame structure having a CP length of 1/16 Tu as shown in FIG. 10. Accordingly, a DL duration consists of one SFT-3 subframe and four SFT-1 subframes, and a UL duration consists of one SFT-3 subframe and two SFT-1 subframes. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a third TDD frame structure of this embodiment, a DL/UL ratio is 6:2 and a CP length is 1/16 Tu. This structure is the same as the TDD frame structure having a CP length of 1/16 Tu as shown in FIG. 11. Accordingly, a DL duration consists of one SFT-3 subframe and five SFT-1 subframes, and a UL duration consists of one SFT-3 subframe and one SFT-1 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a fourth TDD frame structure of this embodiment, a DL/UL ratio is 7:1 and a CP length is 1/16 Tu. This structure is the same as the TDD frame structure having a CP length of 1/16 Tu as shown in FIG. 12.

Accordingly, a DL duration consists of one SFT-3 subframe and six SFT-1 subframes, and a UL duration consists of one SFT-3 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

By configuring the TDD frame as described above, a DL/UL switch duration can conform to a frame structure having a CP length of 1/8 Tu. Thus, even if a system having a CP length of 1/8 Tu exists in an adjacent cell, interference between uplink and downlink transmissions can be minimized.

Irrespective of a DL/UL ratio, the DL duration includes one SFT-3 type subframe. In FIG. 15, a first subframe #1 of the DL duration is constructed of the SFT-3 type subframe, but this is for exemplary purposes only. That is, if the DL/UL ratio is 4:4, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, and #4. If the DL/UL ratio is 5:3, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, #4, and #5. If the DL/UL ratio is 6:2, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, #4, #5, and #6. If the DL/UL ratio is 7:1, the SFT-3 type subframe can be located at one position selected from positions #1, #2, #3, #4, #5, #6, and #7.

In addition, irrespective of a DL/UL ratio, the DL duration includes one SFT-3 type subframe. In FIG. 15, a last subframe #8 of the UL duration is constructed of the SFT-3 type subframe, but this is for exemplary purposes only.

That is, if the DL/UL ratio is 4:4, the SFT-3 type subframe can be located at one position selected from positions #5, #6, #7, and #8. If the DL/UL ratio is 5:3, the SFT-3 type subframe can be located at one position selected from positions #6, #7, and #8. If the DL/UL ratio is 6:2, the SFT-3 type subframe can be located at one position selected from positions #7 and #8. If the DL/UL ratio is 7:1, the SFT-3 type subframe can be located at a position #8.

Next, in the FDD frame structure, the FDD frame includes one pivot subframe. As shown in FIG. 15, the pivot subframe may be an SFT-3 type subframe. The pivot subframe may be located at a position corresponding to a TTG duration of the TDD frame. That is, if the DL/UL ratio is 4:4, the TTG duration in the TDD frame is located between positions #4 and #5, and thus the pivot subframe in the FDD frame can be located at a position #4 or #5. If the DL/UL ratio is 5:3, the TTG duration in the TDD frame is located between positions #5 and #6, and thus the pivot subframe in the FDD frame can be located at a position #5 (preferably) or position #6. If the DL/UL ratio is 6:2, the TTG duration in the TDD frame is located between positions #6 and #7, and thus the pivot subframe in the FDD frame can be located at a position #6 or #7. If the DL/UL ratio is 7:1, the TTG duration in the TDD frame is located between positions #7 and #8, and thus the pivot subframe in the FDD frame can be located at a position #7 or #8. However, since the UL duration includes one SFT-3 type subframe, if the DL/UL ratio is 7:1, the pivot subframe is preferably located at the position #7.

To maintain the common feature with the TDD frame, one SFT-3 type subframe is located ahead of the pivot subframe, and one SFT-3 type subframe is located behind of the pivot subframe. That is, if the DL/UL ratio is 4:4, when the pivot subframe is located at a position #4, the SFT-3 type subframes other than the pivot subframe can be located at one position selected from positions #1, #2, and #3 and at one position selected from positions #5, #6, #7, and #8, or when the pivot subframe is located at the position #5, the SFT-3 type subframes can be located at one position selected from positions #1, #2, #3, and #4 and at one position selected from positions #6, #7, and #8. If the DL/UL ratio is 5:3, when the pivot subframe is located at a position #5, the SFT-3 type subframes other than the pivot subframe can be located at one position selected from positions #1, #2, #3, and #4 (preferably position #1) and at one position selected from positions #6, #7, and #8 (preferably position #8), or when the pivot subframe is located at the position #6, the SFT-3 type subframes can be located at one position selected from positions #1, #2, #3, #4, and #5 and at one position selected from positions #7 and #8. If the DL/UL ratio is 6:2, when the pivot subframe is located at a position #6, the SFT-3 type subframes other than the pivot subframe can be located at one position selected from positions #1, #2, #3, #4, and #5 and at one position selected from positions #7 and #8, or when the pivot subframe is located at the position #7, the SFT-3 type subframes can be located at one position selected from positions #1, #2, #3, #4, #5, and #6 and at a position #8. If the DL/UL ratio is 7:1, when the pivot subframe is located at a position #7, the SFT-3 type subframes other than the pivot subframe can be located at one position selected from positions #1, #2, #3, #4, #5, and #6 and at a position #8.

In FIG. 15, the pivot subframe is only located in #4, #5, #6, and #7. But this is for exemplary purposes only. The other FDD frame with different locations of the pivot subframe may be considered in the same way.

FIG. 16 shows a TDD frame structure having a CP length of 1/32 Tu and an FDD frame structure having a common feature with the TDD frame structure according to an embodiment of the present invention. In FIG. 16, subframes other than the SFT-3 type subframes are SFT-1 type subframes.

Referring to FIG. 16, in a first TDD frame structure of this embodiment, a DL/UL ratio is 4:4 and a CP length is 1/32 Tu. A total frame length is 5 ms. A DL duration is a time period between a start point of a frame and a time point of 2450.76 μs, and includes 26 OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a time period between the time point of 2450.76 μs and a time point of 2489.24 μs, and thus includes a time period of 38.48 μs corresponding to a portion of the idle time and the TTG duration of Table. 2. A UL duration is a time period between the time point of 2489.24 μs and a time point of 4940 μs, and includes 26 OFDM symbols with a CP length of 1/32 Tu. An RTG duration is a time period between the time point of 4940 μs and an end point of the frame, and thus includes a time period of 60 μs corresponding to the RTG duration of Table 2.

Accordingly, the DL duration consists of two SFT-3 subframes and two SFT-1 subframes, and the UL duration consists of two SFT-3 subframes and two SFT-1 subframes. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a second TDD frame structure of this embodiment, a DL/UL ratio is 5:3 and a CP length is 1/32 Tu. This structure is the same as the frame structure having a CP length of 1/32 Tu as shown in FIG. 10. Accordingly, a DL duration consists of two SFT-3 subframes and three SFT-1 subframes, and a UL duration consists of two SFT-3 subframes and one SFT-1 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a third TDD frame structure of this embodiment, a DL/UL ratio is 6:2 and a CP length is 1/32 Tu. This structure is the same as the frame structure having a CP length of 1/32 Tu as shown in FIG. 11. Accordingly, a DL duration consists of two SFT-3 subframes and four SFT-1 subframes, and a UL duration consists of two SFT-3 subframes. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

In a fourth TDD frame structure of this embodiment, a DL/UL ratio is 7:1 and a CP length is 1/32 Tu. This structure is the same as the frame structure having a CP length of 1/32 Tu as shown in FIG. 12. Accordingly, a DL duration consists of three SFT-3 subframes and four SFT-1 subframes, and a UL duration consists of one SFT-3 subframe. In this case, there is no restriction on a subframe type arrangement within the UL duration and the DL duration.

By configuring the TDD frame as described above, a DL/UL switch duration can conform to a frame structure having a CP length of 1/8 Tu. Thus, even if a system having a CP length of 1/8 Tu exists in an adjacent cell, interference between uplink and downlink transmissions can be minimized.

The DL duration includes a plurality of SFT-3 type subframes. If the DL/UL ratio is 4:4, the SFT-3 type subframes can be located at two positions selected from positions #1, #2, #3, and #4. If the DL/UL ratio is 5:3, the SFT-3 type subframes can be located at two positions selected from positions #1, #2, #3, #4, and #5. If the DL/UL ratio is 6:2, the SFT-3 type subframes can be located at two positions selected from positions #1, #2, #3, #4, #5, and #6. If the DL/UL ratio is 7:1, the SFT-3 type subframes can be located at three positions selected from positions #1, #2, #3, #4, #5, #6, and #7.

In addition, the UL duration includes a plurality of SFT-3 type subframes. If the DL/UL ratio is 4:4, the SFT-3 type subframes can be located at two positions selected from positions #5, #6, #7, and #8. If the DL/UL ratio is 5:3, the SFT-3 type subframes can be located at two positions selected from positions #6, #7, and #8. If the DL/UL ratio is 6:2, the SFT-3 type subframes can be located at positions #7 and #8. If the DL/UL ratio is 7:1, the SFT-3 type subframe can be located at a position #8.

If the TTG duration requires a longer duration than 38.48 μs, two OFDM symbols can be allocated to the TTG duration. For example, one of OFDM symbols of the UL duration can be further allocated for the TTG duration, and thus the TTG duration may be 132.74 μs. In this case, if the DL/UL ratio is 4:4, the SFT-3 type subframes can be located at two positions selected from #1, #2, #3, and #4 and at one position selected from positions #5, #6, #7, and #8. If the DL/UL ratio is 5:3, the SFT-3 type subframes can be located at two positions selected from positions #1, #2, #3, #4, and #5 and at one position selected from positions #6, #7, and #8. If the DL/UL ratio is 6:2, the SFT-3 type subframes can be located at two positions selected from #1, #2, #3, #4, #5, and #6 and at one position selected from positions #7 and #8. If the DL/UL ratio is 7:1, the SFT-3 type subframes can be located at two positions selected from positions #1, #2, #3, #4, #5, #6, and #7 and at a position #8.

Next, in the FDD frame structure, the FDD frame includes one pivot subframe. As shown in FIG. 16, the pivot subframe may be an SFT-3 type subframe. The pivot subframe may be located at a position corresponding to a TTG duration of the TDD frame. That is, if the DL/UL ratio is 4:4, the TTG duration in the TDD frame is located between positions #4 and #5, and thus the pivot subframe in the FDD frame can be located at a position #4 or #5. If the DL/UL ratio is 5:3, the TTG duration in the TDD frame is located between positions #5 and #6, and thus the pivot subframe in the FDD frame can be located at a position #5 or #6. If the DL/UL ratio is 6:2, the TTG duration in the TDD frame is located between positions #6 and #7, and thus the pivot subframe in the FDD frame can be located at a position #6 or #7. However, since the UL duration includes two SFT-3 type subframes, the pivot subframe is preferably located at the position #6. If the DL/UL ratio is 7:1, the TTG duration in the TDD frame is located between positions #7 and #8, and thus the pivot subframe in the FDD frame can be located at a position #7 or #8. However, since the UL duration includes one SFT-3 type subframe, the pivot subframe is preferably located at the position #7.

To maintain the common feature with the TDD frame, two SFT-3 type subframes are located ahead of the pivot subframe, and two SFT-3 type subframes are located behind of the pivot subframe. That is, if the DL/UL ratio is 4:4, when the pivot subframe is located at a position #4, the SFT-3 type subframes other than the pivot subframe can be located at two positions selected from positions #1, #2, and #3 and at two positions selected from positions #5, #6, #7, and #8, or when the pivot subframe is located at the position #5, the SFT-3 type subframes can be located at two positions selected from positions #1, #2, #3, and #4 and at two positions selected from positions #6, #7, and #8. If the DL/UL ratio is 5:3, when the pivot subframe is located at a position #5, the SFT-3 type subframes other than the pivot subframe can be located at two positions selected from positions #1, #2, #3, and #4 and at two positions selected from positions #6, #7, and #8, or when the pivot subframe is located at the position #6, the SFT-3 type subframes can be located at two positions selected from positions #1, #2, #3, #4, and #5 and at positions #7 and #8. If the DL/UL ratio is 6:2, when the pivot subframe is located at a position #6, the SFT-3 type subframes other than the pivot subframe can be located at two positions selected from positions #1, #2, #3, #4, and #5 and at positions #7 and #8, or when the pivot subframe is located at the position #7, the SFT-3 type subframes can be located at three positions selected from positions #1, #2, #3, #4, #5, and #6 and at a position #8. If the DL/UL ratio is 6:2, when the pivot subframe is located at a position #7, the SFT-3 type subframes other than the pivot subframe can be located at three positions selected from positions #1, #2, #3, #4, #5, and #6 and at a position #8, or when the pivot subframe is located at the position #8, the SFT-3 type subframes can be located at four positions selected from positions #1, #2, #3, #4, #5, #6, and #7.

In FIG. 16, the pivot subframe is only located in #4, #5, #6, and #7. But this is for exemplary purposes only. The other FDD frame with different locations of the pivot subframe may be considered in the same way.

When the TDD frame is configured as shown in FIG. 13 to FIG. 16, mutual interference does not occur even if the frame structures having different CP lengths exist in adjacent cells. That is, mutual interference does not occur since a DL duration of a frame having a CP length of 1/8 Tu does not overlap with a UL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a frame having a CP length of 1/8 Tu does not overlap with a DL duration of a frame having a CP length of 1/4 Tu, 1/16 Tu, or 1/32 Tu.

Since the FDD frame configured as shown in FIG. 13 to FIG. 16 has a common feature with the corresponding TDD frame, an algorithm used in a TDD system or a related communication algorithm (i.e., resource allocation) can be reused in an FDD system.

Table 4 below summarizes some of the features of FIGs. 13-16 and shows a characteristic of a TDD frame structure according to an embodiment of the present invention.

Table 4

Table 5 below summarizes features of FIGs. 13-16 and shows a characteristic of a TDD frame having a structure in which a CP length is 1/4 Tu and a base subframe is constructed of an SFT-2 type subframe according to an embodiment of the present invention.

Table 5

Table 6 below summarizes features of FIGs. 13-16 and shows a characteristic of a TDD frame having a structure in which a CP length is 1/32 Tu and two OFDM symbols are allocated to a TTG duration according to an embodiment of the present invention.

Table 6

Table 7 below summarizes additional features of FIGs. 13-16 and shows a characteristic of an FDD frame structure according to an embodiment of the present invention.

Table 7

Table 8 below summarizes additional features of FIGs. 13-16 and shows a characteristic of an FDD frame having a structure in which a CP length is 1/4 Tu and a base subframe is constructed of an SFT-2 type subframe according to an embodiment of the present invention.

Table 8

Table 9 below summarizes additional features of FIGs. 13-15 and shows a characteristic of an FDD frame having a structure in which a CP length is 1/32 Tu and two OFDM symbols are allocated to a TTG duration according to an embodiment of the present invention.

Table 9

FIG. 17 is a block diagram showing an apparatus of wireless communication that may be used with the previously described embodiments. An apparatus 50 may be a part of UE. The apparatus 50 includes a processor 51, a memory 52, a transceiver 53, a display 54, and a user interface unit 55. The processor 51 may be configured to configure at least one subframe in a frame. The frame may be constructed by the proposed schemes. The memory 52 is coupled with the processor 51 and stores a variety of information to configure the at least one subframe in the frame. The display 54 displays a variety of information of the UE 50 and may use a well-known element such as a liquid crystal display (LCD), an organic light emitting diode (OLED), etc. The user interface unit 55 can be configured with a combination of well-known user interfaces such as a keypad, a touch screen, etc. The transceiver 53 is coupled with the processor 51 and transmits and/or receives a subframe in the frame.

According to the present invention, when frame structures having various cyclic prefix (CP) lengths and supporting an Institute of Electrical and Electronics Engineers (IEEE) 802.16m format coexist in adjacent cells, mutual interference can be mitigated in data transmission. The entire contents of IEEE 802.16m is incorporated herein by reference.

In addition, by providing a frequency division duplexing (FDD) frame structure having a common feature with a time division duplexing (TDD) frame structure, an algorithm used in a TDD system or a related communication algorithm (i.e., resource allocation) can be reused in an FDD system.

The present invention can be implemented with hardware, software, or combination thereof. In hardware implementation, the present invention can be implemented with one of an application specific integrated circuit (ASIC), a digital signal processor (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microprocessor, other electronic units, and combination thereof, which are designed to perform the aforementioned functions. In software implementation, the present invention can be implemented with a module for performing the aforementioned functions. Software is storable in a memory unit and executed by the processor. Various means widely known to those skilled in the art can be used as the memory unit or the processor.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.