Terminal device, base station device, and frequency resource allocation method
It is possible to realize reduction of inter-cell interference by an adaptive FFR with a low delay. A terminal ( 200 ) includes: an interference condition detection unit ( 209 ) which detects an interference condition of other cell to the local cell; a cell identification unit ( 210 ) which acquires signals for cell identification of each base station; and a sub-band selection unit ( 211 ) which selects a sub-band used for the downstream line transmission to the local station according to the interference condition detected by the interference condition detection unit ( 209 ) and the signals for cell identification of each base station obtained by the cell identification unit ( 210 ). Thus, the terminal ( 200 ) can autonomously select a small sub-band of inter-cell interference and to realize reduction of the inter-cell interference by the adaptive FFR with a low delay.
1. A terminal apparatus comprising:
an interference state detecting section configured to detect a state of interference from other cells to a cell to which the terminal apparatus belongs, based on signals transmitted from a plurality of base stations;
a subband selecting section configured to select a subband used in downlink transmission for the terminal apparatus, based on the interference state detected in the interference state detecting section; and
a transmitting section configured to transmit information on the subband selected in the subband selecting section, to a base station of the cell to which the terminal apparatus belongs,
wherein the subband selecting section selects all subbands when interference from other cells to the cell to which the terminal apparatus belongs is equal to or less than a predetermined threshold.
2. A terminal apparatus comprising:
an interference state detecting section configured to detect a state of interference from other cells to a cell to which the terminal apparatus belongs, based on signals transmitted from a plurality of base stations;
a subband selecting section configured to select a subband used in uplink transmission for a base station of a cell to which the terminal apparatus belongs, based on the interference state detected in the interference state detecting section; and
a transmitting section configured to perform uplink transmission using the subband selected in the subband selecting section,
wherein the subband selecting section selects all subbands when interference from other cells to the cell to which the terminal apparatus belongs is equal to or less than a predetermined threshold.
3. The terminal apparatus according to one of claim 1 and claim 2 , wherein the subband selecting section selects a subband that is distant apart from a center frequency toward one of a lower frequency side and a higher frequency side when interference from other cells to the cell to which the terminal apparatus belongs is significant.
4. The terminal apparatus according to one of claim 1 and claim 2 , wherein the subband selecting section expands subbands to select, toward both sides of a center frequency when interference from other cells to the cell to which the terminal apparatus belongs becomes more significant.
5. The terminal apparatus according to one of claim 1 and claim 2 , wherein the interference state detecting section detects the interference state based on a signal for synchronization used in an initial cell search.
6. The terminal apparatus according to one of claim 1 and claim 2 , wherein:
the subband selected in the subband selecting section is determined by a subband index; and
the transmitting section transmits a subband index matching the subband selected in the subband selecting section.
7. The terminal apparatus according to claim 6 , wherein subbands determined by subband indices partially overlap between subband indices.
8. The terminal apparatus according to one of claim 1 and claim 2 , further comprising a cell identifying section configured to acquire signals for cell identification of the plurality of base stations,
wherein the subband selecting section selects the subband based on the interference state detected in the interference state detecting section and the signals for cell identification of the base stations acquired in the cell identifying section.
9. The terminal apparatus according to claim 8 , wherein the subband selecting section selects a subband that is distant apart from a center frequency toward one of a lower frequency side and a higher frequency side when interference from other cells to the cell to which the terminal apparatus belongs is significant, and decides whether to select one of a subband of the lower frequency side and a subband of the higher frequency side of the center frequency, based on an identification signal of the cell to which the terminal apparatus belongs and identification signals of the other cells.
10. The terminal apparatus according to claim 8 , wherein:
the signals for cell identification of each base station is a cell identification; and
the subband selecting section decides whether to select one of a subband of a lower frequency side and a subband of a higher frequency side of the center frequency, based on whether a cell identification of the cell to which the terminal apparatus belongs is greater than cell identifications of the other cells.
11. The terminal apparatus according to claim 8 , wherein:
the subband selected in the subband selecting section is determined by a subband index; and
the transmitting section transmits a subband index matching the subband selected in the subband selecting section.
12. The terminal apparatus according to claim 11 , wherein subbands determined by subband indices partially overlap between subband indices.
13. A base station apparatus comprising:
a subband selection information acquiring section that acquires information about a subband selected by a terminal;
a transmitting/receiving section that performs transmission to and reception from the terminal using the subband selected by the terminal; and
a transmission power controlling section that controls transmission power of the transmitting/receiving section, based on the information about the subband selected by the terminal,
wherein a channel quality measurement signal is transmitted in a bandwidth wider than the subband selected by the terminal.
14. The base station apparatus according to claim 13 , wherein, when the terminal selects a subband including a center frequency, the transmission power controlling section decreases transmission power for a subband that is more distant apart from the center frequency.
15. The base station apparatus according to claim 13 , further comprising an adaptive fractional frequency reuse transmission timing controlling section configured to synchronize, between neighboring base station apparatuses, adaptive fractional frequency reuse transmission fields to which data addressed to the terminal is assigned according to the information about the subband selected by the terminal.
16. The base station apparatus according to claim 15 , wherein the adaptive fractional frequency reuse transmission timing controlling section controls a range of the adaptive fractional frequency reuse transmission field, based on the information about the subband selected by the terminal.
17. The base station apparatus according to claim 15 , wherein an operating carrier is changed based on the information about the subband selected by the terminal.
18. The base station apparatus according to claim 13 , wherein:
the terminal detects a state of interference from other cells to the cell to which the terminal belongs, based on signals transmitted from a plurality of base station apparatuses, and selects a subband based on the detected interference state; and
the base station apparatus further comprises a reporting section configured to report to the terminal a timing to detect the interference state.
19. A frequency resource allocation method performed by a terminal apparatus, comprising:
detecting a state of interference from other cells to a cell to which the terminal apparatus belongs, based on signals transmitted from a plurality of base stations;
selecting a subband based on the detected interference state; and
performing communication using the selected subband,
wherein all subbands are selected when interference from other cells to the cell to which the terminal apparatus belongs is equal to or less than a predetermined threshold.
20. The frequency resource allocation method according to claim 19 , further comprising:
acquiring signals for cell identification of the plurality of base stations,
wherein the subband is selected based on the interference state and the signals for cell identification.
21. A frequency resource allocation method performed by a terminal apparatus, comprising:
detecting a state of interference from other cells to a cell to which the terminal apparatus belongs, based on signals transmitted from a plurality of base stations;
selecting a subband based on the detected interference state; and
transmitting information on the selected subband to a base station of the cell which the terminal apparatus belongs,
wherein all subbands are selected when interference from other cells to the cell to which the terminal apparatus belongs is equal to or less than a predetermined threshold.
22. A transmission method performed by a base station apparatus, comprising:
acquiring information about a subband selected by a terminal;
performing transmission to and reception from the terminal using the subband selected by the terminal; and
controlling transmission power based on the information about the subband selected by the terminal,
wherein a channel quality measurement signal is transmitted in a bandwidth wider than the subband selected by the terminal.