OFDM radio communications system, transmitter and receiver

• US 20070223364A1
• Filed: 09/01/2006
• Published: 09/27/2007
• Est. Priority Date: 03/27/2006
• Status: Active Grant

• Current Assignee: Fujitsu Mobile Communications Limited (Fujitsu Limited)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kurose, Kengo, Asanuma, Yutaka, Terabe, Shigeo
• Granted Patent: US 7,693,038 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/0232 by interpolation between sounding signals
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

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.

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 that

each of the plurality of receivers comprises:

quality detecting means for detecting receiving quality of the OFDM signals received from the transmitters; and

transmission 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; and

rate 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; and

transmission 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; and

second 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, and

each of the plurality of receivers further comprises;

first reception means for receiving the control information; and

second 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; and

second 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.

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; and

second 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.

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; and

second 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; and

second 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.