OFDM radio communications system, transmitter and receiver

Abstract

Each of a general chunk to which pilot signals are allocated at a general density, and a high-density chunk to which pilot signals are allocated at a higher density than the density of the general chunk, is transmitted in a frequency band common to OFDM transmitters. Each of the OFDM transmitters allocates the high-density chunk to any one of OFDM receivers, which notifies poor receiving quality.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.

FIG. 1 is an illustration schematically showing a configuration of an OFDM radio communications system according to an embodiment of the present invention;

FIG. 2 is a block diagram showing an OFDM transmitter in the OFDM radio communications system shown in FIG. 1;

FIG. 3A is an illustration showing an arrangement of subcarriers employed in the OFDM radio communications system shown in FIG. 1;

FIG. 3B is an illustration showing an arrangement of subcarriers employed in the OFDM radio communications system shown in FIG. 1;

FIG. 4 is a block diagram showing a configuration of an OFDM receiver in the OFDM radio communications system shown in FIG. 1;

FIG. 5 is a block diagram showing a configuration of a modified example of the OFDM transmitter shown in FIG. 1;

FIG. 6 is a block diagram showing a configuration of an OFDM receiver corresponding to the OFDM transmitter shown in FIG. 5; and

FIG. 7 is an illustration showing operations of a modified example of the OFDM radio communications system shown in FIG. 1.

Claims

1. An OFDM radio communications system, comprising a plurality of transmitters that are housed in a controller and that transmit OFDM signals including as a chunk a plurality of subcarriers to which pilot signals and data signals are allocated, and a plurality of receivers receiving the OFDM signals in frequency bands designated by the transmitters, the system being characterized in thateach of the plurality of receivers comprises:quality detecting means for detecting receiving quality of the OFDM signals received from the transmitters; andtransmission means for transmitting channel quality information indicating the receiving quality detected by the quality detecting means,each of the plurality of transmitters comprises:first reception means for receiving the channel quality information from each of the plurality of receivers;determination means for determining which of a general chunk to which the pilot signals are allocated at a general rate and a high-density chunk to which the pilot signals are allocated at a higher rate than the rate of the general chunk, should be allocated to each of the plurality of receivers, in accordance with the channel quality information received by the first reception means;rate detecting means for obtaining a rate of allocation of the general chunk and the high-density chunk, in accordance with the chunk allocation determined by the determination means; andrate information transmitting means for transmitting the rate obtained by the rate detecting means to the controller as rate information,the controller comprises:reception means for receiving the rate information;band determining means for determining a general frequency band to which the general chunk is allocated and a high-density frequency band to which the high-density chunk is allocated, in accordance with the rate information received by the reception means; andtransmission means for transmitting band information indicating the frequency bands determined by the band determining means to the plurality of transmitters,each of the plurality of transmitters further comprises:second reception means for receiving the band information;allocation means for allocating the general chunk to the general frequency band and the high-density chunk to the high-density frequency band, in accordance with the band information received by the second reception means;first transmission means for transmitting control information indicating the frequency bands with which the OFDM signals are transmitted to the respective receivers, to the plurality of receivers, in accordance with the frequency bands allocated by the allocation means; andsecond transmission means for allocating the pilot signals and the data signals to the general chunk and the high-density chunk allocated by the allocation means, and transmitting the general chunk and the high-density chunk to the receivers, andeach of the plurality of receivers further comprises:first reception means for receiving the control information; andsecond reception means for receiving the chunk transmitted to the own receiver, in the frequency band based on the control information received by the first reception means.

2. A transmitter, transmitting OFDM signals including as a chunk a plurality of subcarriers to which pilot signals and data signals are allocated, to a plurality of receivers, respectively, the transmitter being characterized by comprising:reception means for receiving channel quality information from each of the plurality of receivers;determination means for determining which of a general chunk to which the pilot signals are allocated at a general rate and a high-density chunk to which the pilot signals are allocated at a higher rate than the rate of the general chunk, should be allocated to each of the plurality of receivers, in accordance with the channel quality information received by the reception means;allocation means for allocating the general chunk to a general frequency band common to other transmitters and the high-density chunk to the high-density frequency band, in accordance with the chunk allocation determined by the determination means;first transmission means for transmitting control information indicating the frequency bands with which the OFDM signals are transmitted to the respective receivers, to the plurality of receivers, in accordance with the frequency bands allocated by the allocation means; andsecond transmission means for allocating the pilot signals and the data signals to the general chunk and the high-density chunk allocated by the allocation means, and transmitting the general chunk and the high-density chunk to the receivers.

3. A transmitter, housed in a controller and transmitting OFDM signals including as a chunk a plurality of subcarriers to which pilot signals and data signals are allocated, to a plurality of receivers, respectively, the transmitter being characterized by comprising:first reception means for receiving the channel quality information from each of the plurality of receivers;determination means for determining which of a general chunk to which the pilot signals are allocated at a general rate and a high-density chunk to which the pilot signals are allocated at a higher rate than the rate of the general chunk, should be allocated to each of the plurality of receivers, in accordance with the channel quality information received by the first reception means;rate detecting means for obtaining a rate of allocation of the general chunk and the high-density chunk, in accordance with the chunk allocation determined by the determination means;rate information transmitting means for transmitting the rate obtained by the rate detecting means to the controller as rate information;second reception means for receiving band information indicating a general frequency band to which the general chunk is allocated and a high-density frequency band to which the high-density chunk is allocated, as determined based on the rate information by the controller;allocation means for allocating the general chunk to the general frequency band and the high-density chunk to the high-density frequency band, in accordance with the band information received by the second reception means;first transmission means for transmitting control information indicating kind of the chunks and the frequency bands with which the OFDM signals are transmitted to the respective receivers, to the plurality of receivers, in accordance with the frequency bands allocated by the allocation means; andsecond transmission means for allocating the pilot signals and the data signals to the general chunk and the high-density chunk allocated by the allocation means, and transmitting the general chunk and the high-density chunk to the receivers.

4. The transmitter according to claim 2, further comprising spreading means for spreading the data signal at a scrambling code preliminarily allocated inherently to the transmitter, the transmitter being characterized in that the second transmission means allocates the data signal spread by the spreading means and the pilot signal to the general chunk and the high-density chunk allocated by the allocation means, and transmits the chunks to the receivers.

5. A receiver, receiving OFDM signals including as a chunk a plurality of subcarriers to which pilot signals and data signals are allocated, in a frequency band designated by a transmitter, the receiver being characterized by comprising:quality detecting means for detecting receiving quality of the OFDM signals received from the transmitters;transmission means for transmitting channel quality information indicating the receiving quality detected by the quality detecting means;first reception means for receiving the control information indicating the frequency band of transmitting the OFDM signals from the transmitter; andsecond reception means for receiving the chunk transmitted to the own receiver, in the frequency band based on the control information received by the first reception means.

6. A receiver, receiving OFDM signals including as a chunk a plurality of subcarriers to which pilot signals and data signals are allocated, in a frequency band designated by a transmitter, the receiver being characterized by comprising:quality detecting means for detecting receiving quality of the OFDM signals received from the transmitters;transmission means for transmitting channel quality information indicating the receiving quality detected by the quality detecting means;first reception means for receiving the control information indicating kind of the chunks and the frequency band of transmitting the OFDM signals from the transmitter; andsecond reception means for receiving the chunk of the kind indicated by the control information for the receiver, in the frequency band based on the control information received by the first reception means.