[0001]
　The present invention relates to a base station, a terminal, a wireless communication system, a wireless communication method.
Background technique
[0002]
　In recent years, smart phones and tablet, etc., along with the explosive growth of high-function terminal, to the mobile network, a significant expansion of the network capacity is required. Therefore, LTE (Long Term Evolution) and LTE-advanced (LTE is, 3GPP (3rd Generation Partnership Project) of Release8 and it refers to a subsequent Release) in a communication standard called, the standard to meet the demand for network capacity expansion It has been determined. Specifically, as a communication system for enhancing the frequency utilization efficiency, the downstream communication is adopted OFDM (Orthogonal Frequency Division Multiplexing), also capable of transmitting and operate together multiple carriers in bulk standard of carrier aggregation, etc. have been established. However, only combining them, not been able to meet the requirements of today's network capacity expansion. Therefore, 5G is the next generation communication standard: In (Fifth Generation 5th generation), discussions for further expansion of the network capacity is about to be made. 5G is aimed at commercialization of 2020, from around 2016, in the 3GPP standards body, is scheduled to debate is started.
[0003]
　In order to realize rapid expansion of network capacity in a mobile network, and several hundred MHz band currently used, in addition to the frequency band of several gigahertz band, necessary to use a frequency band of higher several tens giga hertz band there is. Becomes the age 5G is operated, using a large number of antennas, transmitting a signal down the transmission beam to the user direction, Massive MIMO (Multiple Input Multiple Output) or the like is employed, the number of antennas is dramatically increased that There is assumed. Meanwhile, in the LTE specification the current, as described above, OFDM is adopted as a downlink communication scheme. However, in general, OFDM is a PAPR (Peak to Average Power Ratio) is greater communication scheme representing the ratio between the average power and peak power of the transmission signal. Therefore, when using a large number of antennas and employing the PAPR is larger communication system such as OFDM, there is a problem that the power consumption of the entire transmission system becomes very large. In general, in the OFDM, the frequency domain packet scheduling by using the variation of each user channel are applied in the frequency domain. Frequency range packet scheduling for each user, the channel state of the user is good (= optimal for the user) allocates a frequency band for data transmission, a method of multiplexing a plurality of users simultaneously. The methods generally have multi-user diversity effect, i.e., are believed to contribute to the improvement of the throughput of the entire system. But on the other hand, the method for multiplexing a plurality of users at the same time resource, causing a further increase in PAPR. Thus, for example, a large amount of system or such as using an antenna, in a system such as to provide a relatively small number of users to the service in small cells, than multi-diversity effect obtained by multiplexing a plurality of users, the PAPR Write obtain the effect of reducing is considered desirable. Therefore, in this type of system, more and scheduling method that the PAPR can be reduced (= few concurrent number of multiplexed users), the less PAPR (= low power consumption), may be suitable single-carrier transmission scheme. Therefore, in the 5G, a smaller communication method of PAPR, the single-carrier transmission scheme is likely to become prosperous as a candidate for the downlink communication scheme. More specifically, and zero padding the cyclic prefix single carrier transmission scheme, a null cyclic prefix single carrier transmission scheme (zero padding the cyclic prefix single carrier transmission scheme and null cyclic prefix single-carrier transmission system, for example, is described in non-Patent Document 1). By using these single-carrier transmission scheme, while suppressing the power consumption, it is possible to expand the network capacity. And later, a cyclic prefix, there is a case to be described as CP (Cyclic Prefix) for short.
[0004]
　Figure 1 shows an exemplary configuration of a subframe (subframe) zero padding the cyclic prefix single carrier transmission scheme. Also, FIG. 2 shows a configuration example of a sub-frame of the null cyclic prefix single carrier transmission scheme. Here, the sub-frame, and represents the smallest unit of time resources allocated to the user. The sampling period is a 3072M sample / s, which corresponds to 100 times the bandwidth of the LTE 20MHz system. The sub-frame length, and 100μs is one tenth of the LTE radio frame length. In addition, FFT (Fast Fourier Transform) size, and 2048.
[0005]
　Referring to FIG. 1, in the zero-padding the cyclic prefix single-carrier transmission scheme of the present embodiment, each block constituting a subframe, the FFT unit (in this example, FFT unit length 0.667 (= 2/3) and .mu.s) of data section having a length (data part), the CP interval (CP part. this example is inserted behind it, CP length and 0.0625μs), made of. Then, this block is a total of 137 pieces articulated constitute one subframe. The data section is a section for transmitting data (Data), control information (Control Information), or the reference signal (Reference Signal). Further, CP interval, in this example, by inserting 0 on the assumption that the non-transmission. Further, the interval of the last about 0.1μs is left as a non-transmission interval.
[0006]
　Referring also to FIG. 2, in the null cyclic prefix single-carrier transmission scheme of the present embodiment, each block itself constituting a subframe has a length of FFT units, data section in the FFT unit and comprising a structure containing both CP section. Then, this block is a total of 150 articulated constitute one subframe.
[0007]
　In the example of FIGS. 1 and 2, CP interval is assumed to be the non-transmission may be transmitted repeatedly a part of the immediately preceding data interval. Further, the insertion position of the CP interval, but is behind the data section, it is possible to the previous data interval.
[0008]
　Here, in general, the delay wave length of the radio signals, using a frequency band and, and the distance from the base station to the user terminal is determined by various other factors. For the sake of explanation, it is assumed the maximum value of the length of the delay wave of the radio signal (worst value) and 0.06Myuesu. In that case, with respect to the worst value, CP length necessary for not causing interference between blocks is at least 0.06μs is required. As LTE, employed in the system assumes that multiplexing multiple users for the same time resource to set the CP length to match this worst value, it is necessary to system operation. Based on the idea, in the example of FIGS. 1 and 2, by adding a margin of 0.0025μs the worst value (0.06μs), it is set to 0.0625μs the CP length. CP is is necessary to suppress the interference between blocks, on the other hand, becomes the overhead, which causes reduction in throughput. In the example of FIGS. 1 and 2, the percentage of overhead CP occupied in one block, thereby respectively increased as follows.
[0009]
Zero padding the cyclic prefix single carrier transmission scheme
　0.0625 / (0.667 + 0.0625) = 8.6%
nulls cyclic prefix single carrier transmission scheme
　0.0625 / 0.667 = 9.4%
[0010]
　Incidentally, the related art for setting the CP length of CP interval, for example, described in Patent Documents 1-4.
CITATION
Patent Literature
[0011]
Patent Document 1: JP 2010-081446 Patent Publication
Patent Document 2: JP 2010-110022 Patent Publication
Patent Document 3: JP-T 2010-516066 Patent Publication
Patent Document 4: WO 2009/072171
Non-Patent Document
[0012]
非特許文献1 : Shuichi Ohno, “Performance of Single-Carrier Block Transmissions Over Multipath Fading Channels With Linear Equalization”, IEEE TRANSACTIONS ON SIGNAL PROCESSING, VOL. 54, NO. 10, OCTOBER 2006
Summary of the Invention
Problems that the Invention is to Solve
[0013]
　As described above, in the example of FIGS. 1 and 2, a CP length, since the fixed value corresponding to the worst value of the length of the delay wave of the radio signal, the percentage of overhead becomes very large put away. Therefore, since the data length of the data segment that can be used for transmission of data and the like is shortened, the overall system throughput is lowered.
　Accordingly one object of the present invention is to solve the problems described above, by reducing the overhead of the subframe, the base station capable of improving throughput of the entire system, a terminal, a wireless communication system, a wireless communication method It is to provide.
Means for Solving the Problems
[0014]
　In one embodiment, the base station communicates with the terminal. The base station for each subframe, cyclic prefix length control unit that variably sets a cyclic prefix length set in the sub-frame by the control unit of the cyclic prefix interval to be inserted into the sub-frame identification information for identifying, and a communication unit that transmits to the terminals assigned to the sub-frame.
[0015]
　In one embodiment, the terminal communicates with the base station. Here, the base station for each subframe, in which a cyclic prefix length of the cyclic prefix interval to be inserted into the sub-frame set variably. The terminal identification information for identifying a cyclic prefix length set in the subframe allocated to the terminal, a communication unit for receiving from the base station.
[0016]
　In one embodiment, the wireless communication system includes a terminal, and a base station communicating with the terminal. The base station for each subframe, cyclic prefix length control unit that variably sets a cyclic prefix length set in the sub-frame by the control unit of the cyclic prefix interval to be inserted into the sub-frame identification information for identifying, and a communication unit that transmits to the terminals assigned to the sub-frame.
[0017]
　In one embodiment, the wireless communication method is a wireless communication method by a base station communicating with the terminal. In the wireless communication method, for each subframe, the cyclic prefix length of the cyclic prefix interval to be inserted into the sub-frame is set variably, the identification information identifying the cyclic prefix length set to the sub-frame to the terminal allocated the sub-frame.
[0018]
　In one embodiment, the wireless communication method is a wireless communication method by a terminal that communicates with a base station. Here, the base station for each subframe, in which a cyclic prefix length of the cyclic prefix interval to be inserted into the sub-frame set variably. Wherein the wireless communication method, the identification information identifying the cyclic prefix length set in the subframe allocated to the terminal, receiving from the base station.
Effect of the invention
[0019]
　According to the embodiments described above, by reducing the overhead of the subframe, the effect is obtained that it is possible to improve the throughput of the entire system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
FIG. 1 is a diagram illustrating a configuration example of a subframe zero padding the cyclic prefix single carrier transmission scheme of the related art.
2 is a diagram showing a configuration example of a sub-frame of the null cyclic prefix single carrier transmission scheme of the related art.
3 is a diagram showing a configuration example of a wireless communication system of Embodiment 1-5.
4 is a diagram showing an example of the configuration of the base station of the first embodiment.
5 is a diagram showing an exemplary configuration of the terminal according to the first embodiment.
6 is a sequence diagram showing an operation example of the wireless communication system according to the first embodiment.
7 is a diagram showing an example of the configuration of the base station embodiment 2-5.
8 is a diagram showing a configuration example of a terminal of Embodiment 2-5.
9 is a diagram showing an example of a CP length correspondence table represents an embodiment 2-5 can be set CP length subframes and the CP length identifier corresponding to the CP length.
FIG. 10 is a conceptual diagram showing a schematic configuration example of a subframe zero padding the cyclic prefix single carrier transmission method embodiments 2-5.
11 is an image diagram showing a specific configuration example of a subframe zero padding the cyclic prefix single carrier transmission method embodiments 2-5.
DESCRIPTION OF THE INVENTION
[0021]
　Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described.
(1) Embodiment 1
　Figure 3 shows an example of the configuration of a wireless communication system of this embodiment. Referring to FIG. 3, the radio communication system of the present embodiment includes a base station 10, the user # 0 to # 3 of the terminals 20-0 to 20-3, the. The base station 10 and terminals 20-0 to 20-3 performs uplink communication and downlink communication. In FIG 3, the cell 10A to the base station 10, the four terminals 20-0 to 20-3 (four users # 0 to # 3) it is assumed that there exists a terminal ( the number of users) is not limited to four. In the following, if not specified terminals 20-0 to 20-3 may be described as the terminal 20.
[0022]
　4 shows an example of the configuration of the base station 10 of the present embodiment. Referring to FIG. 4, the base station 10 of the present embodiment includes a communication unit 11, a control unit 12, a. Control unit 12, for each subframe, sets the CP length of CP section to be inserted into the sub-frame variable. Incidentally, CP interval is assumed to be periodically inserted into the sub-frame, it may be inserted into non-periodic. The sub-frame to set the CP length variable can be in either the sub-frame for a and downlink communication uplink communication. If the subframe for uplink communication, a CP length set on the sub-frame, it is necessary to notify the terminal 20 assigned the sub-frame. Also, when a sub-frame for the downlink communication, a CP length set on the sub-frame, and notify the terminal 20 assigned the sub-frame, the terminal 20 is the data or the like is transmitted in which section It can not determine which of the either the, can not determine when to perform the FFT. Therefore, the communication unit 11, the identification information for identifying a CP length set to the sub-frame by the control unit 12 to the terminal 20 assigned the sub-frame. The communication unit 11 performs reception of such data in the data section is inserted into a subframe for uplink communication, also the transmission of data and the like in the data section is inserted into a subframe for downlink communication. Further, the insertion position of the CP section may be either the data interval before or behind.
[0023]
　5 shows an example of the configuration of the terminal 20-0 to 20-3 of the present embodiment. Referring to FIG. 5, the terminal 20-0 to 20-3 of the present embodiment includes a communication unit 21. Communication unit 21, the identification information for identifying a CP length set in the sub-frames assigned to its own terminal 20, receives from the base station 10. The communication unit 21 performs transmission or the like data in the data section is inserted into a subframe for uplink communication, also receives data and the like in the data section is inserted into a subframe for downlink communication.
[0024]
　Hereinafter, an operation example of the wireless communication system of the present embodiment will be described with reference to FIG. Here, given the operation performed between the base station 10 and the terminal 20-0 as an example. Referring to FIG. 6, the control unit 12 of the base station 10, the CP length of CP section to be inserted into the sub-frame assigned to the terminal 20-0 variably sets (step A1). The communication unit 11 of the base station 10, the identification information for identifying a CP length set to the sub-frame by the control unit 12, to the terminal 20-0 (step A2). This identification information is received by the communication unit 21 of the terminal 20-0. Incidentally, if you set the CP length for the subframe for downlink communication in variable since the base station 10, according to CP length set on the sub-frame, and transmits the data and the like. On the other hand, if you set the CP length for the subframe for uplink communication variable, since the terminal 20-0 is in accordance with CP length set on the sub-frame, and transmits the data and the like.
[0025]
　In this embodiment as described above, the base station 10, for each subframe, sets the CP length of CP section to be inserted into the sub-frame variable. Further, the base station 10, the identification information for identifying a CP length set in the subframe to the terminal 20 assigned the sub-frame. Therefore, for example, it is possible to measure such a shorter CP length of a subframe allocated to a specific terminal 20. Therefore, it is possible to reduce the overhead of the subframe, since it is possible to increase the data length of the data segment that can be used for transmission of data and the like, it is possible to improve the effective throughput in the entire system.
[0026]
(2) Embodiment 2
　This embodiment is an example which is a more specific version of the configuration and operation in the first embodiment. Wireless communication system of the present embodiment, although the entire configuration is the same as in the first embodiment of FIG. 3, the different configurations of the base station 10 and terminals 20-0 to 20-3.
[0027]
　7 shows an example of the configuration of the base station 10 of the present embodiment. Referring to FIG. 7, the base station 10 of the present embodiment differs from the first embodiment in FIG. 4, are added to the storage unit 13. In the present embodiment, as described below, the identification information identifying the CP length set to the sub-frame by the control unit 12, the CP associated with the CP length length identifier (CP length Identifier). Storage unit 13 stores the CP length correspondence table (see FIG. 9 described later) or the like indicating the CP length corresponding to the CP length identifier and CP length identifier.
[0028]
　8 shows an example of the configuration of the terminal 20-0 to 20-3 of the present embodiment. Referring to FIG. 8, terminals 20-0 to 20-3 of the present embodiment differs from the first embodiment in FIG. 5, are added to the control unit 22 and the storage unit 23. Storage unit 23 stores the above-mentioned CP length correspondence table (refer to FIG. 9 below) and the like. Control unit 22, when receiving the CP length identifier from the base station 10, with reference to the CP length correspondence table stored in the storage unit 23, determines CP length corresponding to the CP length identifier received from the base station 10 .
[0029]
　Hereinafter, the operation of the wireless communication system of this embodiment. In the present embodiment, assuming a downlink communication from the base station 10 to the terminals 20-0 to 20-3, and sets the CP length for the subframe for downlink communication variable. Further, as the communication method, and use of zero padding the cyclic prefix single carrier transmission scheme described above. The sampling period, sub-frame length, FFT size and the like, the same as the example of FIGS.
[0030]
　9 shows an example of a CP length corresponding table indicating the CP length identifier corresponding to the settable CP length in the sub-frame in the present embodiment and its CP length. Further, in FIG. 10 shows a schematic configuration example of a sub-frame of this embodiment, FIG. 11 shows a specific configuration example of a sub-frame of this embodiment. Referring to FIG. 9, in the present embodiment, the four stages to switch the CP length, the steps of the switching, and 4 equal portions CP length 0.0625μs set fixed in the example of FIGS. 1 and 2, and 0.0625 / 4 = 0.015625μs. That is, the control unit 12 of base station 10, as a CP length of CP interval, 0.0625μs, 0.046875μs, 0.03125μs, and can be set to four different 0.015625Myuesu. Also, the CP length 0.0625μs, 0.046875μs, 0.03125μs, the 0.015625Myuesu, respectively, 0, 1, 2, and 3 and is assigned as the CP length identifier. Referring to FIG. 10, for each subframe, the CP interval of each block in the sub-frame, one of the CP length of the four types are set. However, when the CP length is changed, the block length of each block also varies, thereby also changes the number of blocks constituting the subframe. Therefore, CP length 0.0625μs, 0.046875μs, 0.03125μs, if it is 0.015625μs is the number of blocks constituting the sub-frame, respectively, the 137, 140 or 143 amino, and 146 amino. In FIG. 10, CP interval, but by inserting 0 on the assumption that the non-transmission may be transmitted repeatedly a part of the immediately preceding data interval. Further, the insertion position of the CP interval, but is behind the data section may be previous data segment. Referring also to FIG. 11, specific image view of each subframe is shown when the CP length of four types were respectively set.
[0031]
　In the present embodiment, the cell 10A to the base station 10, the four terminals 20-0 to 20-3 (four users # 0 to # 3) assumes that there is, four terminals 20 -0 to 20-3, respectively, and the sub-frame # 0 to # 3 are allocated. In other words, data, etc. to the terminal 20-0 is transmitted in subframe # 0, the data for the terminal 20-1 is transmitted in subframe # 1, data, etc. to the terminal 20-2 is transmitted in subframe # 2, sub and data and the like to the terminal 20-3 in the frame # 3 is transmitted. The length of the delay wave of the downlink radio signals between the four terminals 20-0 to 20-3, respectively 0.015μs, 0.015μs, 0.03μs, to be 0.06Myuesu. The length of the delay wave of the downlink radio signal can be determined in any manner. For example, the control unit 12 of the base station 10, every time it receives an uplink radio signal, performs the channel estimation (propagation path estimation) process, the length of the delay wave of the uplink radio signal is found by this process. The length of the delay wave of the uplink radio signal and a downlink radio signal is normally considered to be substantially the same length. Therefore, the control unit 12 of the base station 10, the length of the delay wave of the uplink radio signal obtained by the channel estimation process described above, may be delayed wave of the downlink radio signal.
[0032]
　Under the above assumptions, the control unit 12 of the base station 10 performs scheduling to sub-frame # 0 ~ # every 3. For example, a subframe # 0 is assigned to the terminal 20-0, the length of the delay wave of the downlink radio signals to and from the terminal 20-0 is 0.015Myuesu. Further, according to the CP length correspondence table of FIG. 9, in the larger CP length than 0.015Myuesu, the minimum CP length is 0.015625Myuesu. Therefore, the control unit 12 of base station 10, in the scheduling subframe # 0 in accordance with CP length correspondence table in FIG. 9 to determine the CP length of CP section of the subframe # 0 in 0.015625Myuesu. Thus, the data length of the data section of the subframe # 0 is also determined. Controller 12 of the base station 10 in the same manner, the sub-frame # 1, # 2, the CP length of CP interval # 3, respectively, to determine 0.015625μs, 0.03125μs, the 0.0625Myuesu. Therefore, a subframe # 0, # 1 becomes the configuration of the bottom of the subframe of FIG. 11, subframe # 2 is made to the configuration of the second sub-frame top from the bottom in FIG. 11, the sub-frame # 3 will configure the top of the subframe of FIG. 11.
[0033]
　As a result, the proportion of the overhead of the cyclic prefix occupied in one block, on average the subframe # 0 to # 3 is as follows.
　(0.015625 + 0.015625 + 0.03125 + 0.0625) /4/0.667=4.6875Pasento
[0034]
　Therefore, in this embodiment, CP length be a 0.0625μs fixed in FIGS. 1 and 2 (the ratio of above 8.6%) when compared with, it is possible to reduce the overhead to about half. Further, CP length, 0.0625μs, 0.046875μs, 0.03125μs, the number of blocks in one subframe in the case of 0.015625μs, respectively, becomes 137,140,143,146. Thus, the number of blocks is increased, accordingly, the data length of the data segment that can be used for transmission of data and the like is prolonged. Thus, in terms of the effective data throughput, as compared with the case CP length is 0.0625μs fixed, CP length 0.046875μs, 0.03125μs, if it is 0.015625μs, respectively, 2.2 %, so that the 4.4%, 6.6% throughput improvement is obtained.
[0035]
　Here, (in this example, in the same sense, "the terminal (user) for each") for each subframe in the case of setting the CP length variable, the CP length control unit 12 is set by the base station 10, the and notify the terminal 20 assigned subframe, the terminal 20 can not determine whether the data or the like is transmitted in any interval can not determine when to perform the FFT. Therefore, the communication unit 11 of the base station 10 transmits shown in Figure 9, the CP length identifier 2bit corresponding to CP length control unit 12 is set to the terminal 20. As a method of transmitting the CP length identifier, it can be considered a variety of ways. For example, in the LTE specification of current, any number from the head of the sub-frame (e.g., 1-4) minutes blocks (block referred to here, in the case of OFDM, correctly, that OFDM symbol) in the data section, called DCI (Downlink control information), control information on coding rate or the like of the modulation level, error correction used for data transmission is transmitted is placed. If this is based, for example, in the DCI, to add a field called "CP length identifier field". Then, the control unit 12 of the base station 10, including a CP length identifier "CP length identifier field" of DCI, the DCI communication unit 11 transmits. Thus, the base station 10, for each subframe, the CP length that configure the CP length variable and set based on the length of the delay wave of the downlink radio signals between the terminal 20 assigned the sub-frame the makes it possible to notify the terminal 20.
[0036]
　Terminal 20 (in the above example, DCI containing CP length identifier) ​​control information from the base station 10 receives the, first, demodulates the control information, from the CP length identifier contained therein, own terminal 20 determining CP length set in the sub-frame addressed.
[0037]
　Hereinafter, specific description of an operation of the terminal 20. Control unit 22 of the terminal 20 receives the control information from the base station 10 (DCI containing CP length identifier) ​​at the communication unit 21, demodulates the control information, retrieve the respective information elements included in the control information . Next, the control unit 22 of the terminal 20, the CP length identifier of the information element extracted from the control information, a storage unit 23 in the stored CP length correspondence table (see FIG. 9), based on, of the self determining CP length set in the sub-frame of the terminal 20 destined. Thereafter, the control unit 22 of the terminal 20, according to the CP length, performs receiving processing of data and reference signal transmitted later.
[0038]
　In this embodiment as described above, the base station 10, for each subframe, depending on the length of the delay wave of the downlink radio signals between the terminal 20 assigned the sub-frame, the sub-frame the CP length of CP interval is set to be variable. Further, the base station 10, a CP length identifier for identifying a CP length set in the subframe to the terminal 20 assigned the sub-frame. Therefore, for example, it is possible to shorten the CP length of the subframe length of the delay wave is assigned to short the terminal 20. Therefore, it is possible to reduce the overhead of the subframe, since it is possible to increase the data length of the data segment that can be used for transmission of data and the like, it is possible to improve the effective throughput in the entire system.
[0039]
　In the present embodiment, the CP length correspondence table of FIG. 9, and 0.015625μs the step width of the CP length, but the number of steps 4, the step width and number of steps CP length is not limited thereto , it can be set arbitrarily. Further, the step width of the CP length is set to equal intervals, but this is not restrictive. For example, if concentrated around a certain value the length of the delayed wave may be finer interval step width in the vicinity thereof.
[0040]
　In the present embodiment, the base station 10, for each subframe, processing for setting the CP length, but performs a process of transmitting including the CP length identifier to the control information, measures the length of the delay wave the frequency of treatment is not limited for each subframe. Base station 10, when determining the CP length may be determined CP length using the most recent measurement results of the measurement results the length of the delay wave.
[0041]
(3) Embodiment 3
　In the embodiment 2 described above, the communication unit 11 of the base station 10, in the data section from the beginning of any number of blocks of the sub-frame, and transmits the CP length identifier 2bit to the terminal 20. Therefore, the communication unit 11 of the base station 10, must be sent in every subframe CP length identifier 2bit, reception characteristics of the control information may degrade. On the other hand, the control unit 12 of the base station 10 is the length of the delay wave is a factor for determining the CP length, in the real environment, is considered in many cases does not vary significantly in a short time.
[0042]
　Therefore, in this embodiment, to suppress the increase in the control information, make changes to the method of transmitting the CP length identifier in the second embodiment. Note that the structure itself of the present embodiment is similar to that of Embodiment 2.
[0043]
　More specifically, the control unit 12 of base station 10, when the terminal 20 is connected to the base station 10 measures the length of the delay wave of the downlink radio signals between the terminal 20, the measurement result the CP length variably set based on the CP length identifier corresponding to the CP length set, adding the base station 10 to the connection setting information is transmitted to the terminal 20. For example, in the LTE specification, the RRC (Radio Resource Control) Connection Setup Request message as the connection setting information, add a field called "CP length identifier field". Then, the control unit 12 of the base station 10, including a CP length identifier "CP length identifier field" of the RRC Connection Setup Request message, the communication unit 11 transmits the RRC Connection Setup Request message. Thus, at the time of actual data communication, the base station 10 transmits data in accordance with CP length set in advance when connecting to the terminal 20, the terminal 20 also line the reception processing of data according to the preset CP length it example.
[0044]
　In this embodiment as described above, the base station 10, when connected with the terminal 20, sets the CP length for the subframe allocated to the terminal 20, the CP length in RRC Connection Setup Request message is a connection setting information to send, including the identifier. Thus, were performed for each subframe in the second embodiment, the process and the base station 10 sets a CP length, it is possible to eliminate the processing for transmitting including CP length identifier to the control information. Other effects are the same as in Embodiment 2.
[0045]
(4) Embodiment 4
　In the embodiments 2 and 3, the control unit 12 of the base station 10 had limited number of users to be multiplexed in one subframe (number of terminals) to 1.
　In contrast, in this embodiment, the control unit 12 of the base station 10, the terminal 20 grouped according to the length of the delay wave, assigns the same subframe to the terminal 20 belonging to the same group. Thus, although the user multiplexing PAPR increases, it is possible to ensure flexibility of scheduling by allowing the user multiplexing. Other effects are the same as in Embodiment 2.
[0046]
　The terminal 20 in the present embodiment, as a method for grouping having, for example, the length of the delay wave is set to one or more thresholds to the length of the delayed wave, separated by the threshold region so that each other are the same group, it is conceivable to perform the grouping. Further, if a plurality of terminals 20 assigns the same sub-frame, the communication unit 11 of the base station 10, for all of the plurality of terminals 20, and transmits the CP length identifier of the sub-frame.
[0047]
(5) Embodiment 5
　In the Embodiment 2-4, all data to be inserted into the sub-frame is the data of the particular terminal 20 (a specific user) for, to have been assumed. However, in the actual cellular system, the base station 10, in particular sub-frame, in the cell 10A sends system information unspecified terminal 20 (user) for all the system information in the cell 10A there is a possibility that the terminal 20 is received. For example, in the LTE radio communications system, 10 subframes (hereinafter referred to as sub-frames # 0 to # 9) radio frame is composed of. Among them, in subframe # 0 and # 5, downlink synchronization synchronization signal for the purpose of: or (PSS / SSS Primary Synchronization Signal / Secondary Synchronization Signal) is inserted, also, a notification of system information unique to the cell 10A information of PBCH aimed (Physical Broadcast CHannel) is or are inserted. In such a wireless communication system, even for a sub-frame in which information to be transmitted to unspecified terminals 20 in cell 10A is inserted, applying the technique to the CP length described in Embodiment 2-4 is variable If you, in accordance with the longest terminal 20 delayed waves will set the CP length. However, this overhead can not be reduced, the effect of the embodiment 2-4 can not be obtained. Therefore, in such a wireless communication system, the CP length described in Embodiment 2-4 to apply the technique to be variable, and the sub-frame in which information for unspecified terminals 20 in cell 10A is inserted , it is necessary to change the other sub-frame which, in the behavior.
[0048]
　Specifically, first, to define the following two subframes.
· CP variably settable subframe length (hereinafter, referred to as a first sub-frame): PSS / SSS, subframe information of unspecified terminal 20 for is not inserted, such as PBCH
· CP length variably setting disabled a sub-frame (hereinafter, referred to as a second sub-frame): PSS / SSS, subframe information unspecified terminal 20 for such PBCH is inserted
[0049]
　Then, the control unit 12 of the base station 10, in the first sub-frame of the former, as in Embodiment 2-4, the length of the delay wave of the downlink radio signals between the terminal 20 assigned the sub-frame depending on, it sets the CP length variable. On the other hand, the control unit 12 of the base station 10, in the second sub-frame of the latter, the CP length without variable always set defined maximum value of the CP length in a wireless communication system (worst value) at a fixed I decided to. Therefore, CP length to be set in the second sub-frame is unnecessary notification to the terminal 20.
[0050]
　In this embodiment as described above, the base station 10, as a sub-frame constituting the radio frame, defines two sub-frames of the first and second sub-frames, unspecified terminal 20 for only the first subframe information is not inserted, sets the CP length variable. Thus, even in an environment such as information unspecified terminal 20 for is inserted into the sub-frame, it is possible to apply the technique to a CP length described in Embodiment 2-4 is variable.
[0051]
　In the present embodiment, among the 10 sub-frames # 0 to # 9, the sub-frame # 0 and # 5, a second sub-frame (CP length is fixed), the remaining sub-frame, the When one sub-frame (CP length variable) is, subframe pattern of the sub-frame # 0 to # 9 had assumed case is predetermined. Therefore, the base station 10 to the terminal 20, it was not necessary to notify the sub-frame pattern.
[0052]
　However, the sub-frame pattern need not be predetermined, for example, may be changed periodically. The communication unit 11 of this case, the base station 10 periodically transmits to the terminal 20 of the current sub-frame pattern as a downlink system information, the communication unit 21 of the terminal 20 receives the downlink system information, the downlink according system information, it is conceivable to perform the reception processing of the data and the like in the control unit 22. In that case, as the transmission method of subframes pattern bitmap having a bit width of the period it can be considered. For example, if notified by 10ms period, providing a bit map having a 10-bit bit width, whether each of the sub-frame of 10 pieces of each bit is either the first subframe or second subframe show. For example, among the subframes # 0 to # 9, the subframe # 0, # 1, # 5, in the second subframe (CP length is fixed), the other subframe, the first sub-frame (CP length If There is a variable), the communication unit 11 of the base station 10 notifies the bit map of 10 bits (1,1,0,0,0,1,0,0,0,0) to the terminal 20 . Incidentally, in this bitmap, i-th (i = 0,1, ..., 9) if the bit is "0", the sub-frame #i may be the first subframe (CP length is variable) means, if "1" is a sub-frame #i means that the second sub-frame (CP length is fixed).
[0053]
　Further, the communication unit 11 of the base station 10 does not transmit the sub-frame patterns, subframes # 0 to be the first sub-frame # 1 may send information specifying # 5 (e.g., subframe # 0, # 1, etc. for transmitting the identification information of # 5 in any way).
[0054]
　Although the present invention has been described with reference to the embodiments, the present invention is not limited by the foregoing. Configuration and details of the present invention, it is possible to make various modifications that those skilled in the art can understand within the scope of the invention.
　For example, in the above embodiment, as a communication system has been described with reference to the zero padding the cyclic prefix single-carrier transmission scheme, the present invention is not limited thereto, and the null cyclic prefix single-carrier transmission scheme, otherwise Single-carrier transmission method is also applicable. For example, the present invention is applied to a null cyclic prefix single-carrier transmission scheme, although does not change the length of the blocks included in the subframe, it can be shortened CP length of CP section occupying the block. Therefore, it is possible to reduce the overhead of the subframe, thereby improving throughput.
[0055]
　In the above-described embodiment, the communication unit 11 of the base station 10, as identification information for identifying the CP length that is variably set on the sub-frame by the control unit 12, CP length identifier corresponding to the CP length, i.e., CP the absolute value of the length has been transmitted to the terminal 20. However, the communication unit 11, a CP length is variably determined as the subframe by the control unit 12 may transmit a CP length set at the moment the terminal 20, a relative value that represents the difference. In this case, the initial value of the CP length is set to the terminal 20 can be predetermined to the maximum value of the CP length defined in the radio communication system (worst value) and the like. Or, the initial value of the CP length is set to the terminal 20, when connecting to the base station 10 and the terminal 20 may notify by RRC Connection Setup Request message from the base station 10. In this case, the relative value of the subsequent CP length can be notified in DCI.
[0056]
　This application claims priority based on Japanese Patent Application No. 2015-071617 filed on March 31, 2015, the entire disclosure of which is incorporated herein.
DESCRIPTION OF SYMBOLS
[0057]
　10 base station
　10A cell
　11 communication section
　12 control section
　13 storage section
　20-0 to 20-3 terminal
　21 communication section
　22 control section
　23 memory unit

[Claim 1]
　A base station that communicates with the terminals and
　for each sub-frame, and a control unit for setting the cyclic prefix length of the cyclic prefix interval to be inserted into the sub-frame variable and
　set to the sub-frame by the control unit identification information for identifying a cyclic prefix length that is, the base station comprising: a communication unit, the to be transmitted to the terminal allocated the sub-frame.
[Claim 2]
　Wherein the control unit,
　the identification information, among the cyclic data segment to be inserted before or after the prefix section included from the beginning of the sub-frame in the control information in the data section of an arbitrary number of,
　the communication unit ,
　and transmits the control information including the identification information to the terminal, the base station according to claim 1.
[Claim 3]
　Wherein,
　when connecting with the terminal, including the identification information to the RRC (Radio Resource Control) Connection Setup Request message,
　the communication unit,
　when connecting with the terminal, the RRC Connection Setup including the identification information sends a Request message to the terminal, the base station according to claim 1.
[Claim 4]
　The identification information is
　information for identifying the absolute value of the cyclic prefix length set in the sub-frame by the control unit, the base station according to any one of claims 1 to 3.
[Claim 5]
　The identification information is
　information for identifying a cyclic prefix length set in the sub-frame by the control unit, and the cyclic prefix length that is set at present in the terminal, the relative value representing the difference, the base station according to any one of claims 1 to 3.
[Claim 6]
　Wherein the control unit,
　based on the length of the delay wave of the radio signal between the terminals, setting the cyclic prefix length of the sub-frame assigned to the terminal variable, one of claims 1 to 5 1 the base station according to claim.
[Claim 7]
　Wherein the control unit,
　based on the length of the delay wave of the radio signal between the terminal, the terminal grouping, allocating a same sub-frame to a terminal belonging to the same group, according to claim 6 base station.
[8.]
　The subframe is
　a subframe to be used from the base station in the downlink communication to the terminal,
　the first subframe information transmitted to unspecified of the terminal in the cell of the base station is not inserted,
　the includes a second subframe information transmitted to unspecified of the terminal in the cell of the base station is inserted, the two sub-frames,
　the control unit,
　for each of the first sub-frame, said the cyclic prefix length of the cyclic prefix interval to be inserted into one subframe variably set,
　the communication unit,
　the identification information for identifying the cyclic prefix length set in the first sub-frame by the control unit to the terminal that has been assigned the first subframe, the base station according to any one of claims 1 to 7.
[Claim 9]
　The control unit,
　the for the second sub-frame, to set the cyclic prefix length of the cyclic prefix interval is inserted into the second sub-frame is fixed, the base station according to claim 8.
[Claim 10]
　The communication unit
　for each of the sub-frame, the bitmap comprising a bit indicating whether the sub-frame is either of the first subframe or the second sub-frame, and transmits to the terminal, according to claim 8 or the base station according to 9.
[Claim 11]
　The communication unit
　information for specifying the first subframe among the plurality of sub-frames constituting a radio frame, and transmits to the terminal, the base station according to claim 8 or 9.
[Claim 12]
　A terminal for communicating with a base station,
　the base station for each subframe, which cyclic prefix length of the cyclic prefix interval to be inserted into the sub-frame set variably,
　assigned to the terminal identification information for identifying a cyclic prefix length set in the subframe that is, the terminal comprising a communication unit for receiving from the base station.
[Claim 13]
　A terminal, a wireless communication system and a base station communicating with the terminal,
　the base station,
　a variable for each sub-frame, the cyclic prefix length of the cyclic prefix interval to be inserted into the sub-frame and a control unit that sets, in
　a wireless communication system comprising an identification information identifying a cyclic prefix length set in the sub-frame by the control unit, a communication unit for transmitting to the terminals assigned to the sub-frame.
[Claim 14]
　A wireless communication method by a base station that communicates with the terminals and
　for each sub-frame, the cyclic prefix length of the cyclic prefix interval to be inserted into the sub-frame is set variably,
　set in the sub-frame Sai identification information for identifying the prefix length to the terminal allocated the sub-frame, the radio communication method.
[Claim 15]
　A wireless communication method by a terminal that communicates with a base station,
　the base station for each subframe, which cyclic prefix length of the cyclic prefix interval to be inserted into the sub-frame set variably,
　identification information for identifying a cyclic prefix length set in the subframe allocated to the terminal, receiving from the base station, a wireless communication method.