Base station and wireless communication method

Abstract

An aspect of the invention provides a base station including: a communication unit configured to communicate with a wireless terminal; a determination unit that determines whether or not the wireless terminal is in a cell edge which is a first communication area to be overlapped with other communication area based on a signal reception state of the wireless terminal; and a controller that controls the communication unit to communicate with the wireless terminal to alternately use one of first subcarriers when the wireless terminal is determined to be in the first communication area and that controls the communication unit to communicate with the wireless terminal to use a second subcarrier when the wireless terminal is determined to be outside of the cell edge which is a second communication area to be not overlapped with other communication area.

1 . A base station comprising:
 a communication unit configured to communicate with a wireless terminal;   a determination unit that determines whether or not the wireless terminal is in a cell edge which is a first communication area to be overlapped with other communication area based on a signal reception state of the wireless terminal; and   a controller that controls the communication unit to communicate with the wireless terminal to alternately use one of first subcarriers when the wireless terminal is determined to be in the first communication area and that controls the communication unit to communicate with the wireless terminal to use a second subcarrier when the wireless terminal is determined to be outside of the cell edge which is a second communication area to be not overlapped with other communication area.   
   
   
       2 . The base station according to  claim 1 ,
 wherein the communication unit receives a signal-to-interference and noise power ratio of a first receiving signal at the wireless terminal and a reception power of a second receiving signal at the wireless terminal,   wherein the determination unit determines that the wireless terminal is in the first communication area when the signal-to-interference and noise power ratio of the first receiving signal at the wireless terminal is less than a first predetermined value and the reception power of the second receiving signal at the wireless terminal is a second predetermined value or greater,   wherein the first receiving signal is transmitted from the base station with the second subcarrier, and   wherein the second receiving signal is transmitted from a second base station other than the base station with the first subcarriers.   
   
   
       3 . The base station according to  claim 1 ,
 wherein the communication unit receives a signal-to-interference and noise power ratio of a first receiving signal at the wireless terminal and a signal-to-interference and noise power ratio of a third receiving signal at the wireless terminal,   wherein the determination unit determines that the wireless terminal is in the first communication area when the signal-to-interference and noise power ratio of the first receiving signal at the wireless terminal is less than a first predetermined value, and the signal-to-interference and noise power ratio of the third receiving signal at the wireless terminal is a third predetermined value or greater,   wherein the first receiving signal is transmitted from the base station with the second subcarrier, and   wherein the third receiving signal is transmitted from a second base station with the first subcarriers.   
   
   
       4 . The base station according to  claim 1 ,
 wherein the first subcarriers and the second subcarrier used by the base station have the same frequencies respectively as the first subcarriers and the second subcarrier used by a second base station other than the base station.   
   
   
       5 . The base station according to  claim 1 ,
 wherein the controller includes a pattern storage that stores a plurality of transition patterns, and   wherein when the wireless terminal is determined to be in the first communication area, the controller controls the communication unit to communicate with the wireless terminal to alternately use one of the first subcarriers according to one of the transition patterns.   
   
   
       6 . The base station according to  claim 5 ,
 wherein the wireless terminal includes a plurality of wireless terminals, and   wherein the controller further includes a terminal information storage that stores types of the transition patterns in association with the wireless terminals.   
   
   
       7 . The base station according to  claim 5 ,
 wherein the controller controls the communication unit to use N (N≧1) of the first subcarriers every M (M≧1) symbols according to one of the transition patterns stored in the pattern storage.   
   
   
       8 . The base station according to  claim 1 ,
 wherein the second subcarrier includes a plurality of second subcarriers,   wherein the wireless terminal includes a plurality of wireless terminals,   wherein the first subcarriers and the second subcarriers have the same frequencies, and   wherein the controller controls the communication unit to use either of the first subcarriers and the second subcarriers to communicate with the wireless terminals.   
   
   
       9 . The base station according to  claim 1 ,
 wherein the wireless terminal includes a plurality of wireless terminals,   wherein a plurality of subcarriers are divided into first subcarriers and a second subcarrier, and   wherein the controller controls the communication unit to use both of the first subcarriers and the second subcarrier to communicate with the wireless terminals at the same time.   
   
   
       10 . The base station according to  claim 1 ,
 wherein the wireless terminal includes a plurality of wireless terminals,   wherein the controller controls the communication unit to communicate with the wireless terminals using either a first slot or a second slot,   wherein in the first slot, a plurality of subcarriers are used as the second subcarriers, and   wherein in the second slot, the subcarriers are divided to be used as the first subcarriers and the second subcarriers.   
   
   
       11 . A wireless communication method for a base station to communicate with a wireless terminal, the method comprising:
 detecting a signal reception state of a received signal at the wireless terminal;   determining whether or not the wireless terminal is in a cell edge which is a first communication area to be overlapped with other communication area based on the signal reception state;   making a wireless communication between the base station and the wireless terminal using a second subcarrier when the wireless terminal is determined to be outside of the cell edge which is a second communication area to be not overlapped with other communication area; and   making the wireless communication between the base station and the wireless terminal alternately using one of first subcarriers in a unit time when the wireless terminal is determined to be in the first communication area.   
   
   
       12 . The wireless communication method according to  claim 11 , further comprising:
 transmitting the signal reception state from the wireless terminal to the base station,   wherein the determining step is performed at the base station.   
   
   
       13 . The wireless communication method according to  claim 11 ,
 wherein the determining step is performed at the wireless terminal.   
   
   
       14 . A wireless communication method for a base station to communicate with a wireless terminal, the method comprising:
 determining whether or not the wireless terminal is in a cell edge which is a first communication area to be overlapped with other communication area based on a signal reception state of a received signal at the wireless terminal;   transmitting a request for using first subcarriers from the wireless terminal to the base station when the wireless terminal is determined to be in the first communication area;   making a wireless communication between the base station and the wireless terminal using a second subcarrier;   receiving the request for using the first subcarriers at the base station; and   making the wireless communication between the base station and the wireless terminal alternately using one of the first subcarriers in a unit time when the base station receives the request for using the first subcarriers.