BASE STATION APPARATUS AND TERMINAL DEVICE

• US 20170127444A1
• Filed: 06/18/2015
• Published: 05/04/2017
• Est. Priority Date: 07/03/2014
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: GOTO, Jungo, NAKAMURA, Osamu, TOMEBA, Hiromichi, WAKAHARA, Shiro, HAMAGUCHI, Yasuhiro
• Granted Patent: US 10,034,306 B2
• Time in Patent Office: Days
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]

Abstract

In an LTE-A system, there is a problem that it is difficult to perform stable communication in a case where there is a time when another system occupies an unlicensed band being used. There is provided a base station apparatus that communicates with a terminal device in a second frequency band different from a first frequency band capable of being used as a dedicated frequency band. The base station apparatus includes: a CS determination unit that performs carrier sense in a subframe of carrier sense configured in the second frequency band; a synchronization signal generation unit that generates a synchronization signal; and a wireless transmission unit that transmits the synchronization signal. In a case where the CS determination unit determines that another system does not perform communication in the second frequency band, the wireless transmission unit transmits the synchronization signal generated by the synchronization signal generation unit.

Claims

1. A base station apparatus that communicates with a terminal device in a second frequency band different from a first frequency band capable of being used as a dedicated frequency band, the base station apparatus comprising:

a CS determination unit that performs carrier sense in a subframe of carrier sense configured in the second frequency band;

a synchronization signal generation unit that generates a synchronization signal; and

a wireless transmission unit that transmits the synchronization signal,

wherein, in a case where the CS determination unit determines that another system does not perform communication in the second frequency band, the wireless transmission unit transmits the synchronization signal generated by the synchronization signal generation unit.

2. The base station apparatus according to claim 1,

wherein a timing when the wireless transmission unit transmits the synchronization signal is a first OFDM symbol of a downlink subframe configured after at least the subframe of the carrier sense.

3. The base station apparatus according to claim 1,

wherein a timing when the wireless transmission unit transmits the synchronization signal is a last OFDM symbol of at least the subframe of the carrier sense.

4. The base station apparatus according to claim 3, further comprising:

a transmit-power control unit,

wherein, in a case where the synchronization signal is transmitted in the last OFDM symbol of the subframe of the carrier sense, the transmit-power control unit further lowers a transmit power than that in a case where the synchronization signal is transmitted in a subframe of a downlink.

5. The base station apparatus according to claim 3, further comprising:

a wireless reception unit,

wherein the wireless reception unit starts a process of receiving a signal transmitted from the terminal device at a timing shorter than a previously configured guard period by at least one OFDM symbol time.

6. The base station apparatus according to claim 5,

wherein the wireless transmission unit transmits the synchronization signal in a part of the guard period.

7. The base station apparatus according to claim 1, further comprising:

a data amount management unit,

wherein, in a case where a data amount of a downlink buffered from the data amount management unit is less than a previously configured threshold, the synchronization signal generation unit generates a synchronization signal of a sequence different from that in a case where the buffered data amount of the downlink exceeds the threshold.

8. A terminal device that communicates with a base station apparatus in a second frequency band different from a first frequency band capable of being used as a dedicated frequency band, the terminal device comprising:

an available subframe determination unit that detects a synchronization signal transmitted from the base station apparatus;

a reception signal detection unit that performs a process of receiving a data signal transmitted from the base station apparatus; and

a wireless transmission unit that transmits a signal to the base station apparatus,

wherein, only in a case where the synchronization signal is detected in a downlink subframe after a subframe of carrier sense by the available subframe determination unit, at least one of data reception by the reception signal detection unit and transmission of a signal through the wireless transmission unit is performed.

9. The terminal device according to claim 8,

wherein the available subframe determination unit performs a process of detecting a timing when the synchronization signal is received, as a first OFDM symbol of a downlink subframe configured after the subframe of the carrier sense.

10. The terminal device according to claim 8, further comprising:

a control signal detection unit that detects control information transmitted from the base station apparatus,

wherein, in a case where the available subframe determination unit is not able to detect the synchronization signal in a downlink subframe after the subframe of the carrier sense, the control signal detection unit determines that the control information is not transmitted from the base station apparatus.

11. The terminal device according to claim 10,

wherein the available subframe determination unit performs a process of detecting a timing when the synchronization signal is received, as a last OFDM symbol of the subframe of the carrier sense, and

the control signal detection unit determines that the control information is not transmitted from the base station apparatus in a case where the available subframe determination unit is not able to detect the synchronization signal.

12. The terminal device according to claim 8,

wherein the wireless transmission unit transmits a signal at a timing shorter than a previously configured guard period by at least one OFDM symbol time.

13. The terminal device according to claim 8, further comprising:

a wireless reception unit that performs carrier sense for determining whether or not another system performs communication in the second frequency band,

wherein the available subframe determination unit detects the synchronization signal transmitted from the base station apparatus, recognizes a sequence used for the synchronization signal, and determines whether or not to perform carrier sense in a subframe switched to an uplink from a downlink before a subframe in which ACK/NACK of downlink data or data transmitted to the base station apparatus is transmitted, based on the recognized sequence.