Patent Application
20190268119
The present invention relates to a terminal, a base station, a communication system, and a communication method.
In a wireless communication system, such as Long Term Evolution (LTE) and LTE-Advanced (LTE-A) based on Third Generation Partnership (3GPP), or Wireless LAN and Worldwide Interoperability for Microwave Access (WiMAX) based on the Institute of Electrical and Electronics engineers (IEEE), a base station (a base station apparatus, a downlink transmitting apparatus, an uplink receiving apparatus, or an eNode B) and a terminal (terminal apparatus, a mobile station apparatus, a downlink receiving apparatus, an uplink transmitting apparatus, a user device, or UE) include multiple transmit/receive antennas and spatially multiplex data signals by using a Multi Input Multi Output (MIMO) technology, thereby realizing high-speed data communication. Furthermore, particularly, in LTE and LTE-A, high spectral efficiency is realized using an Orthogonal Frequency Division Multiplexing (OFDM) scheme for downlink, and peak power is suppressed using a Single Carrier-Frequency Division Multiple Access (SC-FDMA) scheme for uplink.
However, it is considered that an enhanced physical downlink control channel, as well as a physical downlink control channel, is used in order to increase the number of terminals that one base station can accommodate. The enhanced physical downlink control channel is not necessarily defined on an OFDM symbol at the front of a subframe. Accordingly, in a method in the related art, a position of a search space cannot be configured to be common to a base station and a terminal, which is a cause for reducing transmission efficiency.
The present invention is made in view of the problem described above, and an object of the present invention is to provide a base station, a terminal, a communication system, and a communication method, in each of which when the base station notifies the terminal of control information not only through a physical downlink control channel but also through an enhanced physical downlink control channel, a position of a search space can be efficiently configured in a wireless communication system in which a base station and a terminal communicate with each other.
(1) The present invention is made to solve the problem described above, and a terminal according to one embodiment performs communication with a base station; retains first information that specifies a first starting position which is a starting position of OFDM symbols in which an enhanced physical downlink control channel in a common search space is mapped, and second information, independent of the first information, which specifies a second starting position which is a starting position of OFDM symbols in which an enhanced physical downlink control channel in a terminal-specific search space is mapped; and detects the enhanced physical downlink control channel in the common search space and the terminal-specific search space, based on the first information and the second information, respectively.
(2) Furthermore, in the terminal according to one embodiment of the present invention, the first information may be obtained from a physical broadcast channel.
(3) Furthermore, in the terminal according to one embodiment of the present invention, the first starting position may be fixed, and the second starting position may be variable.
(4) Furthermore, in the terminal according to one embodiment of the present invention, the second information may be obtained using dedicated RRC signaling or a physical control format indicator channel.
(5) Furthermore, a base station according to one embodiment of the present invention performs communication with a terminal; retains first information that specifies a first starting position which is a starting position of OFDM symbols in which an enhanced physical downlink control channel in a common search space is mapped, and second information that specifies a second starting position which is a starting position of OFDM symbols that is configured independently of the first starting position of the OFDM symbol and which is the starting position of the OFDM symbols in which an enhanced physical downlink control channel in a terminal-specific search space is mapped; and maps the enhanced physical downlink control channel in the common search space and the terminal-specific search space, based on the first information and the second information, respectively.
(6) Furthermore, in the base station according to one embodiment of the present invention, the first information may be broadcast using a physical broadcast channel.
(7) Furthermore, in the base station according to one embodiment of the present invention, the first starting position may be fixed, and the second starting position may be controlled to be variable.
(8) Furthermore, in the base station according to one embodiment of the present invention, the terminal may be notified of the second information using dedicated RRC signaling or a physical control format indicator channel.
(9) Furthermore, a communication system according to one embodiment of the present invention is a communication system in which communication is performed between a base station and a terminal, in which the base station retains first information that specifies a first starting position which is a starting position of OFDM symbols in which an enhanced physical downlink control channel in a common search space is mapped, and second information that specifies a second starting position which is a starting position of OFDM symbols that is configured independently of the first starting position of the OFDM symbols and which is the starting position of the OFDM symbols in which an enhanced physical downlink control channel in a terminal-specific search space is mapped, and maps the enhanced physical downlink control channel in e the common search space and the terminal-specific search space, based on the first information and the second information, respectively, and in which the terminal retains the first information and the second information, and detects the enhanced physical downlink control channel in the common search space and the terminal-specific search space, based on the first information and the second information, respectively.
(10) Furthermore, a communication method according to one embodiment of the present invention is a communication method for a terminal that performs communication with a base station, the method including: a step of storing first information that specifies a first starting position which is a starting position of OFDM symbols in which an enhanced physical downlink control channel in a common search space is mapped, and second information, independent of the first information, which specifies a second starting position which is a starting position of OFDM symbols in which an enhanced physical downlink control channel in a terminal-specific search space is mapped; and a step of detecting the enhanced physical downlink control channel in the common search space and the terminal-specific search space, based on the first information and the second information, respectively.
(11) Furthermore, a communication method according to one embodiment of the invention is a communication method for a base station that performs communication with a terminal, the method including: a step of storing first information that specifies a first starting position which is a starting position of OFDM symbols in which an enhanced physical downlink control channel in a common search space is mapped, and second information that specifies a second starting position which is a starting position that is configured independently of the first starting position of OFDM symbols and which is the starting position of the OFDM symbols in which an enhanced physical downlink control channel in a terminal-specific search space is mapped, and a step of arranging the enhanced physical downlink control channel in the common search space and the terminal-specific search space, based on the first information and the second information, respectively.
According to the present invention, even when the base station notifies the terminal of control information not only through a physical downlink control channel but also through an enhanced physical downlink control channel, a position of a search space can be efficiently configured in a wireless communication system in which a base station and a terminal communicate with each other.
A first embodiment of the present invention is described below. A communication system according to the first embodiment includes a base station (a base station apparatus, a downlink transmitting apparatus, an uplink receiving apparatus, or an eNode B) and a terminal (terminal apparatus, a mobile station apparatus, a downlink receiving apparatus, an uplink transmitting apparatus, a user equipment, or UE).
The PDCCH is allocated on a given number of the OFDM symbols which are positioned at a head portion within the subframe. The PDSCH is allocated on the OFDM symbol that is positioned behind the OFDM symbol on which the PDCCH is allocated. The PBCH is allocated to a second slot in 6 resource block pairs that are positioned in the center of a system band (CC band). Furthermore, the PBCH is arranged for every period of 10 subframes. The PCFICH is discretely allocated on the head OFDM symbol within the subframe. Any terminal can receive the PBCH and the PCFICH without terminal-dedicated (terminal-specific) signaling being performed.
First, a flow of transmission and reception of downlink data is described referring to
In the terminal 102, the OFDM signal is received through the receive antenna 501 in the OFDM signal receiving unit 502 and OFDM demodulation processing is performed. The downlink subframe processing unit 503 first detects the PDCCH (a first downlink control channel) or the E-PDCCH (a second downlink control channel) in the physical downlink control channel extraction unit 504. More specifically, a space (a first downlink control channel range) in which the PDCCH is arranged or a space (a second downlink control channel range, that is, the potential E-PDCCH) in which the E-PDCCH can be arranged is decoded and a CRC check bit that is attached in advance is checked (blind decoding). That is, the physical downlink control channel extraction unit 504 monitors the E-PDCCH that is arranged in the common search space and/or the terminal-specific search space. Furthermore, the physical downlink control channel extraction unit 504 has a function of extracting the PBCH or the PCFICH and obtains the CFI. In a case where the CRC check bit agrees with an ID (RNTI) that is allocated in advance from the base station, the downlink subframe processing unit 503 recognizes that the PDCCH or the E-PDCCH can be detected, and extracts the PDSCH using the control information that is included in the detected PDCCH or E-PDCCH. More specifically, RE demapping processing, demodulation processing or the like is performed which corresponds to RE mapping processing or the modulation processing, in the downlink subframe generation unit 402. The PDSCH extracted from the received downlink subframe is transmitted to the codeword extraction unit 505. In the codeword extraction unit 505, the rate matching processing, error correction decoding, or the like, which corresponds to the rate matching processing or the error correction coding in the codeword generation unit 401, is performed and the transport block is extracted and is delivered to the higher layer 506. That is, in a case where the physical downlink control channel extraction unit 504 detects the PDCCH or the E-PDCCH, the codeword extraction unit 505 extracts the transmission data in the PDSCH associated with the detected PDCCH or E-PDCCH and delivers the extracted transmission data to the higher layer 506.
Next, a flow of transmission and reception of uplink transmission data is described. In the terminal 102, in the uplink subframe generation unit 507, the uplink transmission data that is delivered from the higher layer 506 is mapped onto the RB within the uplink subframe. The SC-FDMA signal transmitting unit 508 performs SC-FDMA modulation on the uplink subframe and thus generates an SC-FDMA signal and transmits the generated SC-FDMA signal through the transmit antenna 509.
In the base station 101, the SC-FDMA signal is received in the SC-FDMA signal receiving unit 407 through the receive antenna 406, and SC-FDMA demodulation processing is performed. In the uplink subframe processing unit 408, the uplink transmission data is extracted from the RB onto which the uplink transmission data is mapped, and the extracted uplink transmission data is delivered to the higher layer 409.
At this point, the CFI is described. The CFI that is indicated by the PCFICH normally indicates the number of the OFDM symbols to which the PDCCH is allocated. Furthermore, accordingly, the CFI that is indicated by the PCFICH specifies the OFDM symbol that is a starting position of the PDSCH. On the other hand, according to the present embodiment, the CFI is assumed which specifies the OFDM symbol that is a starting position of the E-PDCCH. The CFI may be a CFI that is indicated by the PCFICH, and may be a CFI that is indicated by another control information (for example, PBCH or RRC signaling, or the like). Alternatively, the CFI may be a predetermined CFI (that is, the OFDM symbol that is the starting position of the E-PDCCH is fixed). The CFI for the E-PDCCH is described in detail below. The physical downlink control channel extraction unit 504 and the physical downlink control channel generation unit 403 internally include a storage unit and have a function of retaining (storing) the CFI itself or the number of the OFDM symbols that are specified by the CFI.
Next, the PDCCH and the E-PDCCH are described.
The PDCCH is configured from multiple Control Channel Elements (CCE) within the PDCCH region. The CCE is configured from multiple downlink resource elements RE (each of which is a resource defined by one OFDM symbol and one subcarrier). A number nCCE for identifying the CCE is assigned to the CCE within the PDCCH region. The assignment to the CCE is performed based on a predetermined rule. The PDCCH is configured from an aggregation (CCE aggregation) that is made from the multiple CCE's. The number of the CCE's that make up the aggregation is referred to as a “CCE aggregation level”. The CCE aggregation level that makes up the PDCCH is determined in the base station 101, according to the coding rate that is set for the PDCCH and the number of bits of Downlink Control Information (DCI; downlink control information) (control information transmitted by the PDCCH or the E-PDCCH) that is included in the PDCCH. Moreover, a combination of the CCE aggregation levels that are potentially used for the terminal is predetermined. Furthermore, the aggregation that is made from the n CCE's is called “CCE aggregation level n”.
One REG (RE group) comprises 4 RE's that are adjacent in the frequency domain. Moreover, one CCE comprises 9 different REG's that are distributed in the frequency domain and the time domain within the PDCCH region. Specifically, interleaving is performed to all the REG's to which a number is assigned, in units of REG's, on the entire downlink CC by using a block interleaver, and one CCE comprises 9 REG's of which the numbers are consecutive after the interleaving.
A search space (SS) that is a space (a search space or a retrieval space) from which the PDCCH is retrieved is configured in the terminal. The SS comprises the multiple CCE's. Numbers are assigned to the CCE's, and the SS consists of the multiple CCE's of which the numbers are consecutive. The number of the CCE's that make up a certain SS is predetermined. The SS of each CCE aggregation level consists of a set of multiple candidates for the PDCCH. The SS is categorized into a cell-specific common search space CSS (cell-specific SS, common SS) in which the smallest CCE number, among the CCE's that make up the SS, is common in the cell, and a terminal-specific search space USS (UE-specific SS) in which the smallest CCE number is specific to the terminal. The PDCCH to (in) which the control information, such as the system information or the information relating to the paging, that the multiple terminals 102 read, is allocated (included), or the PDCCH to (in) which the downlink/uplink grant indicating an instruction for fallback to a low-level transmission scheme or random access is allocated (included) can be mapped in the CSS. On the other hand, these PDCCH's cannot be mapped in the USS.
The base station 101 transmits the PDCCH using one or more CCE's within the SS that are configured in the terminal 102. The terminal 102 performs processing for detecting the PDCCH that is intended for the terminal 102 itself, without performing decoding of a receive signal using one or more CCE's within the SS. As described above, such processing is referred to as blind decoding. The terminal 102 configures the SS that varies from one CCE aggregation level to another. Thereafter, the terminal 102 performs the blind decoding using a given combination of the CCE's within the SS that varies from one CCE aggregation level to another. In other words, the terminal 102 performs the blind decoding on the candidate for each PDCCH within the SS that varies from one CCE aggregation level to another. The sequence of processing is called monitoring of the PDCCH.
The base station arranges in the CSS the PDCCH that gives an instruction for the paging or system information, a random access response, or the like (the PDCCH that assigns common transmission data to the multiple terminals). Furthermore, in the CSS, the terminal performs the monitoring (the blind decoding and checking of the CRC check bit) of the PDCCH that uses a P-RNTI, an SI-RNTI, a RA-RNTI, or the like.
Next, the E-PDCCH is described. The E-PDCCH is basically mapped in the OFDM symbol other than the PDCCH (but, the E-PDCCH may be mapped in a partial overlapping manner). The E-PDCCH and the PDSCH are frequency-multiplexed. Furthermore, the resource block in which the E-PDCCH is potentially mapped is configured for each terminal.
Next,
In this manner, some of (or all of) the PRB pairs are configured as the E-PDCCH region (region in which the E-PDCCH can be potentially arranged). Moreover, with the mapping scheme that is specified explicitly or implicitly/suggestively, the E-PDCCH is arranged in some of (or all of) the PRB pairs in the PDSCH region.
As described above, a great difference between the PDCCH and the E-PDCCH is that while on the OFDM symbol at the head portion of the subframe, the PDCCH is arranged in a distributed manner along the frequency axis over the entire system band, the E-PDCCH is used up to the OFDM symbol at the rear of the subframe along the time axis, but is mapped onto some bands (PRB) along the frequency axis.
Moreover, here, the E-CSS is described on the assumption that the E-CSS is the CSS, but is not limited to this. Also in a case where the E-CCS is the USS that is configured with the terminal-specific signaling, in a case where the base station 101 configures the common SS as the E-CSS for the multiple terminals, the E-CSS can be used as substantially the CSS. In this case, because both are one portion of the USS, instead of being called the E-CSS and the E-USS, both may be called a primary SS and a secondary SS, respectively. Furthermore, in this case, it is preferable that the terminal 102 further monitor the PDCCH with the normal CSS for the purpose of the fallback. In a case where a state of a channel between the base station 101 and the terminal 102 is not understood, or during a period of time when the RRC configuration is reconfigured, the base station 101 uses the PDCCH in the normal CSS.
A number nE-PDCCHCCE is assigned to the E-PDCCH constituent element. For example, nE-PDCCHCCE is 0, 1, 2, and so forth up to NE-PDCCHCCE−1, in ascending order of frequency. That is, in the frequency domain, a set of PRB's of which the number is NE-PDCCHPRB is configured by high-level layer signaling (for example, the signaling by each terminal or the common signaling within the cell) for the potential E-PDCCH transmission, and the E-PDCCH constituent elements of which the number is NE-PDCCHCCE are available. In this manner, when nE-PDCCHCCE is configured independently of nCCE, one portion of a value of nE-PDCCHCCE overlaps a value that can be used as nCCE. Alternatively, an initial (minimum) value of nE-PDCCHCCE is configured to NCCE or a value greater than NCCE. Accordingly, one portion of the value of nE-PDCCHCCE cannot overlap the value that can be used as nCCE.
In the same manner as with the PDCCH, the E-PDCCH is configured from a set that is made from a given number (an aggregation level) of the E-PDCCH logical resource elements. For example, there are 4 types of aggregation levels ranging from aggregation level 1 to aggregation level 8, and one E-PDCCH is configured from 1 to 8 E-PDCCH logical resource elements.
At this point, when attention is paid to the length along a time axis, of the E-PDCCH region on a physical frame, in the E-PDCCH region corresponding to the CSS and the E-PDCCH region corresponding to the USS, the length (the number of the OFDM symbols) along the time axis is configured independently (can be configured to different values). More specifically, a starting position (for example, the third OFDM symbol) of the OFDM symbol, in which the E-PDCCH channel corresponding to the CSS is defined, and a starting position (for example, the second OFDM symbol) of the OFDM symbol, in which the E-PDCCH region corresponding to the USS is defined are configured independently. These can be configured using the CFI. A CFI1 that is a first CFI indicates the number of the OFDM symbols onto which the E-CSS is mapped, and a CFI2 that is a second CFI indicates the number of the OFDM symbols onto which the E-CSS is mapped.
Alternatively, a mapping rule is that the mapping always begins with the leading OFDM symbol, and in the E-CSS and the E-USS, the number of the OFDM symbols that is overwritten can be configured independently. For example, for the E-PDCCH region corresponding to the CSS, the leading symbol to the second OFDM symbol are overwritten, and for the E-PDCCH channel corresponding to the USS, the leading symbol is overwritten. The CFI also can be used in configuring these. Moreover, as a channel or a signal with which to overwrite the E-PDCCH, a control channel channel, such as the PDCCH, the PCFICH, a Physical Hyblid Automatic Repeat Request (HARQ) Indicator Channel (PHICH), or the like may be possible, and a reference signal, such as a Common Reference Signal (CRS), may be possible. Alternatively, a null signal (signal of which amplitude is zero) may be possible. The overwriting of the E-PDCCH with the channels or the signals by the base station 101 is referred to as puncturing of the E-PDCCH (of the RE). In a case where the puncturing is performed, the terminal 102 may perform the demodulation processing after performing processing that replaces (de-puncturing) a receive symbol of the corresponding RE with the null signal, and may perform the demodulation on the assumption that the receive signal of the overwritten RE is the E-PDCCH.
Next, the base station 101 signals the CFI2 to the terminal 102 (Step S1204). Preferably, individual signaling, such as dedicated RRC signaling, for the destination to each terminal 102 should be used. Moreover, here, a case is illustrated where when the terminal 102 monitors the E-CSS, the CFI2 is signaled, but the signaling of the CFI2 is not limited to this case. For example, instead of the E-PDCCH, even though only the PDCCH is monitored, the CFI2 can be signaled. The terminal 102 configures the E-USS based on the number of the OFDM symbols that are specified by the CFI2 that is signaled (Step S1205). When the U-CSS is configured, in the U-CSS that is configured, the terminal 102 monitors the E-PDCCH (the normal DL grant) that indicates the normal transmission data that is intended for the terminal 102, the E-PDCCH (the UL grant) that gives an instruction for the data transmission from the terminal 102, and the like. In the case where there is a need for transmitting the normal transmission data that is intended for the terminal 102 or the data from the terminal 102, or the like, in the E-CSS or the E-USS, the base station 101 transmits the E-PDCCH (Step S1206). Furthermore, in the case where the E-PDCCH is the downlink grant, the transmission data for downlink is transmitted with the same subframe. Moreover, here, a case is described where the E-CSS and the E-USS are monitored at the same time, but there is no limitation to this. For example, the base station 101 may signal to the terminal 102 to configure and cancel the monitoring of the E-CSS and/or the monitoring of the U-CSS, and in response to the signaling, the terminal 102 may start to monitor the E-CSS and/or the E-USS or stop monitoring the E-CSS and/or the E-USS. In this case, the E-CSS and the E-USS can be configured not to be monitored at the same time.
Alternatively, the puncturing may be changed in the E-CSS and the E-USS.
In this manner, in the E-CSS and the E-USS, the base station 101 individually configures the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped). Furthermore, the base station 101 broadcasts the information that specifies the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-CSS, and notifies the terminal 102 of the information that specifies the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-USS, with the dedicated RRC signaling. The terminal 102 configures the E-CSS, based on the information that specifies the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-CSS, and monitors the E-PDCCH in the E-CSS. Furthermore, the terminal 102 configures the E-USS, based on the information that specifies the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-USS, and monitors the E-PDCCH in the E-USS.
Accordingly, a position of the search space can be configured to be common to the base station 101 and the terminal 102. Furthermore, because the E-CSS and the E-USS can be individually configured, it is possible to perform the efficient transmission and reception of the E-PDCCH. Particularly, in a case where the base station 101 performs communication with the terminal 102 and the terminal 106 using the PDCCH at the same time, because the PDCCH region does not overlap the E-CSS and the E-USS, the E-PDCCH and the PDCCH do not interfere with each other. Furthermore, in the terminal 102, even though the PCFICH's that are widely distributed within the system band are not obtained, because the E-CSS that does not overlap the PDCCH region can be used, a reception band can be narrowly configured compared to the terminal that obtains the PCFICH. Moreover, even though dedicated signaling to the base station 101 is not performed, because the terminal 102 can use the E-CSS that does not overlap the PDCCH region, the transmission and reception of the E-PDCCH is possible in a case where a connection is not established like in a case of initial access. Furthermore, by broadcasting the information specifying the number of the OFDM symbols for the E-CSS in which the DL grant as to the paging or system information is arranged, common, efficient configuration can be performed on the multiple terminals. At the same time, the terminal 102 can configure the E-CSS to be static on the safe OFDM symbol in such a manner that the E-CSS does not overlap the PDCCH region, and the configuration of the E-USS can be adaptively changed according to the PDCCH region. Accordingly, efficient use of the control channel can be performed.
The configuration is described above in which according to the first embodiment, the CFI1 is broadcast from the base station to the terminal and the CFI2 is transmitted. In contrast, a configuration is described in which according to a second embodiment, the CFI1 is fixed, and the terminal is notified of the CFI2 from the base station. The second embodiment of the present invention is described below. Moreover, the base station apparatus and the terminal apparatus according to the present embodiment can be realized with the same configuration as the configuration example of the base station 101 and the terminal 102 that are illustrated in
Next, the base station 101 signals the CFI2 to the terminal 102 (Step S1503). Preferably, individual signaling, such as dedicated RRC signaling, for the destination to each terminal 102 should be used. Moreover, here, a case is illustrated where when the terminal 102 monitors the E-CSS, the CFI2 is signaled, but the signaling of the CFI2 is not limited to this case. For example, instead of the E-PDCCH, even though only the PDCCH is monitored, the CFI2 can be signaled. The terminal 102 configures the E-USS based on the number of the symbols that are specified by the CFI2 that is signaled (Step S1504). When the U-CSS is configured, in the U-CSS that is configured, the terminal 102 monitors the E-PDCCH (the normal DL grant) that indicates the normal transmission data that is intended for the terminal 102, the E-PDCCH (the UL grant) that gives an instruction for the data transmission from the terminal 102, and the like. In the case where there is a need for transmitting the normal transmission data that is intended for the terminal 102 or the data from the terminal 102, or the like, in the E-CSS or the E-USS, the base station 101 transmits the E-PDCCH (Step S1505). Furthermore, in the case where the E-PDCCH is the downlink grant, the transmission data for downlink is transmitted with the same subframe.
Moreover, an example in
In this manner, in the E-CSS and the E-USS, the base station 101 individually configures the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped). Furthermore, the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-CSS is configured to be fixed, and the base station 101 notifies the terminal 102 of the information that specifies the number (variable) of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-USS, with the dedicated RRC signaling. Based on the fixed number of the OFDM symbols to which the E-PDCCH is substantially mapped (is not substantially mapped) in the E-CSS, the terminal 102 configures the E-CSS, and monitors the E-PDCCH in the E-CSS. Furthermore, the terminal 102 configures the E-USS, based on the information that specifies the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-USS, and monitors the E-PDCCH in the E-USS.
Accordingly, a position of the search space can be configured to be common to the base station 101 and the terminal 102. Furthermore, because the E-CSS and the E-USS can be individually configured, it is possible to perform the efficient transmission and reception of the E-PDCCH. Particularly, in a case where the base station 101 performs at the same time the communication with the terminal 102 and the terminal 106 that uses the PDCCH, the overlapping of the PDCCH region by the E-CSS and E-USS can be controlled. Even though the PCFICH's that are widely distributed within the system band are not obtained, because the E-CSS that does not overlap the PDCCH region can be used, the terminal 102 can configure a reception band to be narrow, compared to the terminal that obtains the PCFICH. Moreover, even though dedicated signaling with the base station 101 is not performed, because the terminal 102 can use the E-CSS that does not overlap the PDCCH region, the transmission and reception of the E-PDCCH is possible in a case where a connection is not established like in a case of initial access. Furthermore, by broadcasting the information specifying the number of the OFDM symbols for the E-CSS in which the DL grant as to the paging or system information is arranged, common, efficient configuration can be performed on the multiple terminals. At the same time, the terminal 102 can configure the E-CSS to be static on the safe OFDM symbol in such a manner that the E-CSS does not overlap the PDCCH region, and the configuration of the E-USS can be adaptively changed according to the PDCCH region. Accordingly, the efficient use of the control channel can be performed.
In a case where the E-CSS space is fixed in such a manner that the E-CSS space does not overlap the PDCCH, the E-CSS and the PDCCH can interfere with each other. Furthermore, in a case where the E-CSS space is fixed in such a manner that the overlapping of the PDCCH is allowed (for example, the mapping begins with the leading symbol and the puncturing is not performed), the common mapping can be performed in the terminal in which the PDCCH region may be known and the terminal in which the PDCCH region may not be known. Accordingly, the E-PDCCH can be shared in the E-CSS in the terminal in which the PDCCH region may be known and the terminal in which the PDCCH region may not be known. On the other hand, regardless of whether or not the PDCCH region may be known in the terminal, for the E-USS to which only the terminal-specific E-PDCCH is allocated, the number of the OFDM symbols can be configured in a manner that is specific to the terminal, interference with the PDCCH does not occur and even in a case where the PDCCH region is small, the efficient use of a resource can be performed by enlarging the E-PDCCH region.
The configuration is described above in which according to the first embodiment, the CFI1 is broadcast from the base station to the terminal and the CFI2 is transmitted. In contrast, a configuration is described in which according to a third embodiment, the CFI1 is transmitted from the base station to the terminal (or the CFI1 is fixed), and the CFI2 is broadcast from the base station to the terminal over a different channel than the CFI1. The third embodiment of the present invention is described below. Moreover, the base station apparatus and the terminal apparatus according to the present embodiment can be realized with the same configuration as the configuration example of the base station 101 and the terminal 102 that are illustrated in
The terminal 102 configures the E-USS based on the number of the OFDM symbols that are specified by the CFI2 that is signaled (Step S1504). When the U-CSS is configured, in the U-CSS that is configured, the terminal 102 monitors the E-PDCCH (the normal DL grant) that indicates the normal transmission data that is intended for the terminal 102, the E-PDCCH (the UL grant) that gives an instruction for the data transmission from the terminal 102, and the like. In the case where there is a need for transmitting the normal transmission data that is intended for the terminal 102 or the data from the terminal 102, or the like, in the E-CSS or the E-USS, the base station 101 transmits the E-PDCCH (Step S1505). Furthermore, in the case where the E-PDCCH is the downlink grant, the transmission data for downlink is transmitted with the same subframe.
Moreover, an example in
In this manner, in the E-CSS and the E-USS, the base station 101 individually configures the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped). Furthermore, the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-CSS is fixed (the parameter that is broadcast over the PBCH can also be regarded as almost fixed (static)), and the base station 101 notifies the terminal 102 of the information specifying the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or is not substantially mapped) in the E-USS, with a broadcast channel, over a broadcast channel that can dynamically change broadcast content, such as the PCFICH or the ePCFICH. Based on the fixed number of the OFDM symbols to which the E-PDCCH is substantially mapped (or, is not substantially mapped) in the E-CSS, the terminal 102 configures the E-CSS, and monitors the E-PDCCH in the E-CSS. Furthermore, the terminal 102 configures the E-USS, based on the information that specifies the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or, is not substantially mapped) in the E-USS, and monitors the E-PDCCH in the E-USS.
Accordingly, a position of the search space can be configured to be common to the base station 101 and the terminal 102. Furthermore, because the E-CSS and the E-USS can be individually configured, it is possible to perform the efficient transmission and reception of the E-PDCCH. Particularly, in a case where the base station 101 performs at the same time the communication with the terminal 102 and the terminal 106 that uses the PDCCH, the overlapping of the PDCCH region by the E-CSS and E-USS can be controlled. Even though the PCFICH's that are widely distributed within the system band are not obtained, because the E-CSS that does not overlap the PDCCH region can be used, the terminal 102 can configure a reception band to be narrow, compared to the terminal that obtains the PCFICH. Moreover, even though dedicated signaling to the base station 101 is not performed, because the terminal 102 can use the E-CSS that does not overlap the PDCCH region, the transmission and reception of the E-PDCCH is possible in a case where a connection is not established like in a case of initial access. Furthermore, by broadcasting the information specifying the number of the OFDM symbols for the E-CSS in which the DL grant as to the paging or system information is arranged, common, efficient configuration can be performed on the multiple terminals. At the same time, the terminal 102 can configure the E-CSS to be static on the safe OFDM symbol in such a manner that the E-CSS does not overlap the PDCCH region, and the configuration of the E-USS can be adaptively changed according to the PDCCH region. Accordingly, the efficient use of the control channel can be performed.
In a case where the E-CSS space is fixed in such a manner that the E-CSS space does not overlap the PDCCH, the E-CSS and the PDCCH can be made not to interfere with each other. Furthermore, in a case where the E-CSS space is fixed in such a manner that the overlapping of the PDCCH is allowed (for example, the mapping begins with the leading symbol and the puncturing is not performed), the common mapping can be performed for the terminal in which the PDCCH region may be known and the terminal in which the PDCCH region may not be known. Accordingly, the E-PDCCH can be shared in the E-CSS in the terminal that can know the PDCCH region and the terminal that cannot know the PDCCH region. On the other hand, because the number of the OFDM symbols that are common to the terminals can be configured, according to the PDCCH region, in the E-USS to which only the E-PDCCH specific to the terminal is allocated, the inference with the PDCCH does not occur, and even though the PDCCH region is small, the efficient use of the resource can be performed by enlarging the E-PDCCH region.
According to the first to third embodiments, the configuration of the CFI1 and the CFI2 between one base station and the terminal is described above. In contrast, according to a fourth embodiment, the configuration of the CFI1 and the CFI2 at the time of a handover (HO) between the base stations is described. The fourth embodiment of the present invention is described below. Moreover, the base station apparatus (source base station and a target base station) and the terminal apparatus according to the present embodiment can be realized with the same configuration as the configuration example of the base station 101 and the terminal 102 that are illustrated in
Based on the number of the OFDM symbols that are specified by the CFI2 that is signaled, the terminal 102 configures the E-USS (Step S1907). When the U-CSS is configured, in the U-CSS that is configured, the terminal 102 monitors the E-PDCCH (the normal DL grant) that indicates the normal transmission data that is intended for the terminal 102, the E-PDCCH (the UL grant) that gives an instruction for the data transmission from the terminal 102, and the like. In the case where there is a need for transmitting the normal transmission data that is intended for the terminal 102 or the data from the terminal 102, or the like, in the E-CSS or the E-USS, the base station 101 transmits the E-PDCCH (Step S1908). Furthermore, in the case where the E-PDCCH is the downlink grant, the transmission data for downlink is transmitted with the same subframe.
Moreover, an example in
In this manner, the source base station individually configures the number of the OFDM symbols to which the target base station substantially maps (or does not substantially map) the E-PDCCH in the E-CSS and the E-USS. Furthermore, the terminal 102 configures the E-CSS and the E-USS, based on the information that specifies the number of the OFDM symbols to which the E-PDCCH is substantially mapped (or, is not substantially mapped) in each of the E-CSS and the E-USS, and monitors the E-PDCCH in the E-CSS and the E-USS.
Accordingly, the position of the search space can be configured to be common to the target base station and the terminal 102. Furthermore, because the E-CSS and the E-USS can be individually configured, it is possible to perform the efficient transmission and reception of the E-PDCCH.
Moreover, according to each of the embodiments described above, the terminal detects the PDCCH or the E-PDCCH in the CSS, but the number of the OFDM symbols to which the E-PDCCH is substantially mapped is changed according to whether the PDCCH or the E-PDCCH is detected in the USS. However, instead of the SS, even though the change is made according to a DCI format, an effect similar to that according to each of the embodiments described above can be obtained. More specifically, the terminal detects the DCI format that is available for the transmission in the CSS, as the PDCCH or the E-PDCCH, the number of the OFDM symbols to which the E-PDCCH is substantially mapped being changed according to whether he DCI format is detected that is available for the transmission in only the USS. Furthermore, the base station transmits the DCI format that is available for the transmission in the CSS, as the PDCCH or the E-PDCCH, but the number of the OFDM symbols to which the E-PDCCH is substantially mapped is changed according to whether the DCI format is detected that is available for the transmission in only the USS.
Moreover, according to each of the embodiments, the resource element or the resource block is described as being used as a unit for mapping the data channel, the control channel, the PDSCH, the PDCCH, and the reference signal, and the subframe or the radio frame is described as being used as a unit of transmission in a time direction, but the present invention is not limited to this. Even though, instead of these, the space and the time unit that are configured from an arbitrary frequency and time, are used, the same effect can be obtained.
Furthermore, according to each of the embodiments described above, the enhanced physical downlink control channel that is arranged in the PDSCH region is called the E-PDCCH and the description is provided in such a manner that the enhanced physical downlink control channel is clearly distinguished from a physical downlink control channel (PDCCH) in the related art, but the present invention is not limited to this. Even though the E-PDCCH and the PDCCH are called the PDCCH, if different operations are performed in the enhanced physical downlink control channel that is typically arranged in the PDSCH region and in the physical downlink control channel in the related art that is arranged in the PDCCH region, substantially the same effect as in the embodiments described above in each of which the E-PDCCH and the PDCCH are distinguished from each other is obtained.
Moreover, in a case where the terminal starts to communicate with the base station, the terminal notifies the base station of information (information on the ability of the terminal, or functional block information) indicating whether or not the function that is mentioned according to each of the embodiments described above is usable with respect to the base station. Thus, the base station can determine whether or not the function that is mentioned according to each of the embodiments described above is usable. More specifically, in a case where the function that is mentioned according to each of the embodiments described above is usable, information to that effect may be included in the information on the ability of the terminal, and in a case where the function that is mentioned according to each of the embodiments described above is not usable, information relating to that function may not be included in the information on the ability of the terminal. Alternatively, in a case where the function that is mentioned according to each of the embodiments described above is usable, a value of 1 may be entered into a predetermined bit field of the functional group information, and in a case where the function that is mentioned according to each of the embodiments described above is not usable, a value of 0 may be entered into the predetermined bit field of the functional group information.
A program running on the base station and the terminal according to the present invention is a program (a program for causing a computer to operate) that controls a CPU and the like in such a manner as to realize the function according to the embodiment of the present invention. Then, the information that is handled in these apparatuses is temporarily stored in a RAM while being processed. Thereafter, the information is stored in various ROM's or HDD's, and whenever necessary, is read by the CPU to be modified or written. As a recording medium on which the program is stored, among a semiconductor (for example, a ROM, a nonvolatile memory card, and the like), an optical storage medium (for example, a DVD, a MO, a MD, a CD, a BD, and the like), a magnetic storage medium (for example, a magnetic tape, a flexible disk, and the like), and the like, any one may be possible. Furthermore, in some cases, the function according to the embodiment described above is realized by running the loaded program, and in addition, the function according to the present invention is realized in conjunction with an operating system or other application programs, based on an instruction from the program.
Furthermore, in a case where the programs are available on the market, the program stored on a portable recording medium can be distributed or the program can be transmitted to a server computer that connects through a network such as the Internet. In this case, a storage device in the server computer also is included in the present invention. Furthermore, some or all of the base station and the terminal according to the embodiment described above may be realized as an LSI that is a typical integrated circuit. Each functional block of the base station and the terminal may be individually built into a chip, and some or all functional blocks may be integrated into a chip. Furthermore, a technique of the integrated circuit is not limited to the LSI, and an integrated circuit for the functional block may be realized with a dedicated circuit or a general-purpose processor. Furthermore, if with advances in a semiconductor technology, a technology of an integrated circuit that substitutes for the LSI appears, it is also possible to use an integrated circuit to which the technology applies.
The embodiments of the invention are described in detail above referring to the drawings, but the specific configuration is not limited to the embodiments and includes an amendment to a design that falls within a scope not deviating from the gist of the present invention. Furthermore, various modifications are possible within the scope of the present invention defined by claims, and embodiments that are made by suitably combining technical means disclosed according to the different embodiments are also included in the technical scope of the present invention. Furthermore, a configuration in which a constituent element that achieves the same effect is substituted for the one that is mentioned according to each of the embodiments is also included in the technical scope of the present invention.
The present invention is suitable for use in a wireless base station apparatus, a wireless terminal apparatus, a wireless communication system, or a wireless communication method.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-114488 | May 2012 | JP | national |
This application is a Continuation of copending application Ser. No. 14/400,766, filed on Nov. 12, 2014, which was filed as PCT International Application No. PCT/JP2013/063510 on May 15, 2013, which claims the benefit under 35 U.S.C. § 119(a) to Patent Application No. 2012-114488, filed in Japan on May 18, 2012, all of which are hereby expressly incorporated by reference into the present application.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14400766 | Nov 2014 | US |
| Child | 16409166 | US |
