Base station apparatus and terminal device
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.
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 a transmit signal including 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 transmit signal during a prescribed time,
the wireless transmission unit transmits the transmit signal at all subframes in a radio frame on the first frequency band and transmits the transmit signal at a portion of a subframe in a radio frame on the second frequency band after the carrier sense, and
a timing when the wireless transmission unit transmits the synchronization signal on the second frequency band is a same OFDM symbol number as the first frequency band after the carrier sense.
2. The base station apparatus according to claim 1 , further comprising:
a transmit-power control unit,
wherein, in a case where the synchronization signal is transmitted in a last OFDM symbol of a subframe of the carrier sense, the transmit-power control unit reduces a transmit power lower than that in a case where the synchronization signal is transmitted in a subframe of a downlink.
3. The base station apparatus according to claim 1 , 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.
4. The base station apparatus according to claim 3 ,
wherein the wireless transmission unit transmits the synchronization signal in a part of the guard period.
5. 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.