Radio communication system, radio communication method, and radio communication device

Abstract

In the environment of a communication area including a SDM-compatible mobile station for space division multiplex transmission and a SDM-uncompatible mobile station not compatible with space division multiplex transmission, a base station having a plurality of antennas and capable of adaptively changing directivity performs allocation of a mobile station which simultaneously performs space division multiplex transmission (SDM) and space division multiplex access (SDMA) by using a predetermined space division multiplex transmission evaluation criterion and a space division multi access evaluation criterion. By using this radio communication method, it is possible to use the spatial degree of freedom at its maximum and provide a radio communication system having an improved communication capacity.

1 . A base station apparatus comprising:
 a beam forming section for forming a first transmission beam by use of a single maximum ratio synthetic directional transmission beam in a single space division multiplex channel in order to send a first transmission data sequence to a SDM uncompatible mobile station, and forming a plurality of other directional transmission beams in a plurality of other space division multiplex channels in order to send a second transmission data sequence to an SDM compatible mobile station such that the directional beams are orthogonal to each other, the SDM compatible mobile station being a terminal allocated for SDM communication in a communication area of the base station, and   an antenna for simultaneously transmitting the directional transmission beams to the SDM uncompatible and SDM compatible mobile stations at the same frequency.   
     
     
         2 . The base station according to  claim 1 , wherein the second transmission data sequence includes a plurality of third transmission data sequence by performing a weighting process and the plurality of third transmission data sequence have orthogonality. 
     
     
         3 . A method, for a downlink multi-user multiple input multiple output (MIMO) scheme for enabling a base station to allocate resources to communicate data to a plurality of mobile users, wherein a mobile user of the plurality of mobile users existing within a communication area has N receiving antennas, the method comprising:
 obtaining, by the base station, a feedback information from the plurality of mobile users, the feedback information including:
 an information about a channel state information between the base station and each of the plurality of mobile users, and 
 a received quality information, 
   determining multiple mobile users to simultaneously transmit data to according to certain criteria;   deciding, adaptively, a number of space-division multiplex channels for transmitting to each of the mobile users according to the feedback information;   generating a number of space streams by using serial to parallel mapping according to the decisions, for allocating resources in space dimension to the plurality of users,   wherein a maximum number of the allocated resources are limited by a number of transmitting antennas of the base station;   determining weight vectors according to the feedback information; and   applying the weight vectors to the space streams and communicating data to each of the plurality of mobile users simultaneously with the N transmitting antennas.   
     
     
         4 . The method according to  claim 3 , wherein the generating step applies a sum of a unitary matrix. 
     
     
         5 . The method according to  claim 3 , wherein the number of antennas is 1 for a space-division-multiplex uncompatible mobile user, and the number of antennas is greater than 1 for a space-division-multiplex compatible mobile user. 
     
     
         6 . The method according to  claim 3 , wherein the base station forms a closed feedback loop with each of the plurality of mobile users. 
     
     
         7 . The method according to  claim 3 , wherein when time division duplex is used in the obtaining step, and the information about the channel state is derived from corresponding reciprocal uplink channels from each of the mobile users to the base station. 
     
     
         8 . The method of  claim 3 , wherein in the determining step, weight vectors for the mobile users are determined based on the channel information, and the weight vectors of the mobile users are determined based on weight vectors of other mobile users. 
     
     
         9 . A radio communication system comprising:
 a space-division-multiplex compatible mobile station compatible with space division multiplex transmission;   a space-division-multiplex uncompatible mobile station uncompatible with space division multiplex transmission; and   a base station apparatus including:
 a partial-space orthogonalizing means for making a weighting process, for enhancing orthogonality over a propagation path for the space division multiplex transmission, on a transmission data sequence to be sent by space division multiplex to the space-division-multiplex compatible mobile station allocated for space division multiplex transmission within a communication area, and 
 a beam forming section for forming a transmission beam to the space-division-multiplex compatible mobile station and the space-division-multiple-access mobile station, responsive to a transmission data sequence to the space-division-multiple-access mobile station allocated for space division multiple access within a communication area and to an output of the partial-space orthogonalizing means, the transmission beam being to reduce an interference with another mobile station to access simultaneously, and a plurality of antennas for transmitting the transmission beam. 
   
     
     
         10 . The radio communication system according to  claim 9 , wherein forming the transmission beam for reducing an interference by the beam forming section of the base station apparatus is to form the transmission beam from the transmission data sequence to the allocated space-division-multiple-access mobile station and an output of the partial-space orthogonalizing means in a manner being orthogonal to a channel estimation matrix on another mobile station for providing simultaneous access.