EP-3562112-B1 - COMMUNICATION SYSTEM

Inventors

• SUZUKI KUNIYUKI
• NAKAZAWA MASAYUKI

Dates

Publication Date

20260506

Application Date

20171221

Claims (6)

1. A communication system comprising: - a base station device (203); and - a user equipment (202) configured to perform radio communication with the base station device (203), wherein a rotation amount of the IFFT is stored in advance as a system parameter in a non-volatile memory of the base station (203) or the rotation amount is specified by a higher-layer device of the base station (203), wherein the base station device (203) notifies the user equipment (202) of the rotation amount corresponding to the circular permutated IFFT output as broadcast information, wherein the base station device (203) operating as a transmitting device is configured to, based on the rotation amount, circular permutate inverse fast Fourier transform, IFFT, output, and copy a last portion of the circular permutated IFFT output to a head of the circular permutated IFFT output as a cyclic prefix, CP, to thereby generate a transmission signal and perform a reception operation so that there is no phase rotation at a head of the demodulation reception window set in the user equipment (202), and - the user equipment (202) adjusts a position of a demodulation reception window by an amount corresponding to the circular permutated IFFT output from the base station (203), and then performs demodulation.
2. The communication system according to claim 1, wherein the amount corresponding to the circular permutated IFFT output is in coordination with at least one of a CP length that is a length of the CP, a head position of the demodulation reception window with respect to the CP, and a variable margin of the head position of the demodulation reception window.
3. The communication system according to claim 1, wherein when the base station device (203) performs radio communication with a plurality of user equipments (202), the base station device (203) is configured to determine at least one of the amount corresponding to the circular permutated IFFT output and a CP length that is a length of the CP so that a head of the demodulation reception window for each of the plurality of user equipments (202) aligns in a defined unit of data concerning transmission data.
4. The communication system according to claim 3, wherein the base station device (203) is configured to sort the plurality of user equipments (202) into groups in accordance with a predetermined reference, and to determine at least one of the amount corresponding to the circular permutated IFFT output and the CP length for each of the groups.
5. The communication system according to claim 1, wherein the amount corresponding to the circular permutated IFFT output is 1/2 of a CP length that is a length of the CP.
6. The communication system according to claim 1, wherein the base station detects the deviation of arrival time from a known sequence transmitted by the user equipment (202), wherein the base station device (203) notifies the user equipment (202) of correct information of the amount corresponding to the circular permutated IFFT output.

Description

Technical Field The present invention relates to a communication system in which radio communication is performed between a communication terminal device such as a user equipment device and a base station device. Background Art The 3rd generation partnership project (3GPP), the standard organization regarding the mobile communication system, is studying communication systems referred to as long term evolution (LTE) regarding radio sections and system architecture evolution (SAE) regarding the overall system configuration including a core network and a radio access network, which will be hereinafter collectively referred to as a network as well (for example, see Non-Patent Documents 1 to 4). This communication system is also referred to as 3.9 generation (3.9 G) system. As the access scheme of the LTE, orthogonal frequency division multiplexing (OFDM) is used in a downlink direction and single carrier frequency division multiple access (SC-FDMA) is used in an uplink direction. Further, differently from the wideband code division multiple access (W-CDMA), circuit switching is not provided but a packet communication system is only provided in the LTE. The decisions by 3GPP regarding the frame configuration in the LTE system described in Non-Patent Document 1 (Chapter 5) will be described with reference to FIG. 1. FIG. 1 is a diagram illustrating the configuration of a radio frame used in the LTE communication system. With reference to FIG. 1, one radio frame is 10 ms. The radio frame is divided into ten equally sized subframes. The subframe is divided into two equally sized slots. The first and sixth subframes contain a downlink synchronization signal per radio frame. The synchronization signals are classified into a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS). Non-Patent Document 1 (Chapter 5) describes the decisions by 3GPP regarding the channel configuration in the LTE system. It is assumed that the same channel configuration is used in a closed subscriber group (CSG) cell as that of a non-CSG cell. A physical broadcast channel (PBCH) is a channel for downlink transmission from a base station device (hereinafter may be simply referred to as a "base station") to a communication terminal device (hereinafter may be simply referred to as a "communication terminal") such as a user equipment device (hereinafter may be simply referred to as a "user equipment"). A BCH transport block is mapped to four subframes within a 40 ms interval. There is no explicit signaling indicating 40 ms timing. A physical control format indicator channel (PCFICH) is a channel for downlink transmission from a base station to a communication terminal. The PCFICH notifies the number of orthogonal frequency division multiplexing (OFDM) symbols used for PDCCHs from the base station to the communication terminal. The PCFICH is transmitted per subframe. A physical downlink control channel (PDCCH) is a channel for downlink transmission from a base station to a communication terminal. The PDCCH notifies of the resource allocation information for downlink shared channel (DL-SCH) being one of the transport channels described below, resource allocation information for a paging channel (PCH) being one of the transport channels described below, and hybrid automatic repeat request (HARQ) information related to DL-SCH. The PDCCH carries an uplink scheduling grant. The PDCCH carries acknowledgement (Ack) / negative acknowledgement (Nack) that is a response signal to uplink transmission. The PDCCH is referred to as an L1/L2 control signal as well. A physical downlink shared channel (PDSCH) is a channel for downlink transmission from a base station to a communication terminal. A downlink shared channel (DL-SCH) that is a transport channel and a PCH that is a transport channel are mapped to the PDSCH. A physical multicast channel (PMCH) is a channel for downlink transmission from a base station to a communication terminal. A multicast channel (MCH) that is a transport channel is mapped to the PMCH. A physical uplink control channel (PUCCH) is a channel for uplink transmission from a communication terminal to a base station. The PUCCH carries Ack/Nack that is a response signal to downlink transmission. The PUCCH carries a channel quality indicator (CQI) report. The CQI is quality information indicating the quality of received data or channel quality. In addition, the PUCCH carries a scheduling request (SR). A physical uplink shared channel (PUSCH) is a channel for uplink transmission from a communication terminal to a base station. An uplink shared channel (UL-SCH) that is one of the transport channels is mapped to the PUSCH. A physical hybrid ARQ indicator channel (PHICH) is a channel for downlink transmission from a base station to a communication terminal. The PHICH carries Ack/Nack that is a response signal to uplink transmission. A physical random access channel (PRACH) is a channel for uplink transmission from