OFDM radio communications system

Abstract

A transmitter forms each subcarrier group of only frequency locations of subcarriers to which at least one pilot signal is allocated, and conducts transmission by allocating a macro-diversity signal into the subcarrier group and allocating a non-macro-diversity signal to other frequencies (outside the subcarrier group). As for the macro-diversity signal, a receiver conducts channel estimation on the basis of the pilot signal in the same subcarrier group as the macro-diversity signal. As for the non-macro-diversity signal outside the subcarrier group, the receiver conducts channel estimation on the basis of the pilot signal, and results of channel estimations of the macro-diversity signal and other non-macro-diversity signals.

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 a schematic illustration of an OFDM radio communications system according to an embodiment of the present invention;

FIG. 2 is a block diagram showing an example of an OFDM transmitter shown in FIG. 1;

FIG. 3 is an illustration describing subcarrier allocation and settings of subcarrier groups in the OFDM transmitter;

FIG. 4 is a block diagram showing an example of an OFDM receiver shown in FIG. 1;

FIG. 5 is a block diagram showing another example of an OFDM transmitter shown in FIG. 1;

FIG. 6 is a block diagram showing another example of an OFDM receiver shown in FIG. 1;

FIG. 7 is an illustration describing a first subcarrier group setting method;

FIG. 8 is an illustration describing the first subcarrier group setting method;

FIG. 9 is an illustration describing the first subcarrier group setting method;

FIG. 10 is an illustration describing the first subcarrier group setting method;

FIG. 11 is an illustration describing a second subcarrier group setting method;

FIG. 12 is an illustration describing the second subcarrier group setting method;

FIG. 13 is an illustration describing the second subcarrier group setting method;

FIG. 14 is an illustration describing a method of locating pilot subcarriers in a subcarrier group;

FIG. 15 is an illustration describing a method of locating pilot subcarriers in a subcarrier group;

FIG. 16 is an illustration describing a method of locating pilot subcarriers in a subcarrier group;

FIG. 17A and FIG. 17B are illustrations describing a complex number sequence defined in each subcarrier group;

FIG. 18 is a block diagram showing the other example of the OFDM receiver;

FIG. 19 is an illustration describing a method of setting a guard interval length;

FIG. 20 is an illustration describing a method of setting a guard interval length;

FIG. 21 is an illustration describing an example of setting a guard interval length in a case of decimating an OFDM symbol;

FIG. 22 is an illustration describing subcarrier allocation and settings of subcarrier groups in the OFDM transmitter;

FIG. 23 is a block diagram of an OFDM receiver receiving an OFDM signal in a subcarrier location shown in FIG. 22;

FIG. 24 is an illustration of a modified example of the subcarrier location shown in FIG. 22;

FIG. 25 is an illustration of a modified example of the subcarrier location shown in FIG. 22;

FIG. 26 is an illustration of a modified example of the subcarrier location shown in FIG. 22;

FIG. 27 is an illustration of a modified example of the subcarrier location shown in FIG. 22;

FIG. 28 is an illustration of a modified example of the subcarrier location shown in FIG. 22;

FIG. 29 is an illustration of a modified example of the subcarrier location shown in FIG. 22;

FIG. 30 is an illustration of a modified example of the subcarrier location shown in FIG. 22;

FIG. 31 is an illustration of a modified example of the subcarrier location shown in FIG. 22; and

FIG. 32 is an illustration of a modified example of the subcarrier location shown in FIG. 22.

Claims

1. An OFDM radio communications system comprising a plurality of transmitters transmitting OFDM signals and a receiver conducting macro-diversity reception based on the OFDM signals, the OFDM radio communications system being wherein each of the transmitters comprises:first allocation means for allocating pilot signals to a first pilot subcarrier and a second pilot subcarrier different in frequency, respectively;second allocation means for allocating a macro-diversity signal subjected to macro-diversity to a first data subcarrier whose frequency is same as the first pilot subcarrier and whose transmission timing is successive to the first pilot subcarrier, and for allocating a macro-diversity signal subjected to macro-diversity to a second data subcarrier whose frequency is same as the second pilot subcarrier and whose transmission timing is successive to the second pilot subcarrier;third allocation means for allocating a non-macro-diversity signal not subjected to the macro-diversity to a third data subcarrier whose frequency is between the frequency of the first pilot subcarrier and the frequency of the second pilot subcarrier and whose transmission timing is between the transmission timing of the first pilot subcarrier and the transmission timing of the second pilot subcarrier; andtransmission means for OFDM-modulating and transmitting the pilot signals, the macro-diversity signals and the non-macro-diversity signal, through the subcarriers to which the signals are allocated by the first allocation means, the second allocation means and the third allocation means, andthe receiver comprises:reception means for receiving the pilot signals, the macro-diversity signals and the non-macro-diversity signal, through the subcarriers transmitted by the transmission means;first estimation means for conducting channel estimation of the first data subcarrier in accordance with the pilot signal of the first pilot subcarrier received by the reception means, and for conducting channel estimation of the second data subcarrier in accordance with the pilot signal of the second pilot subcarrier received by the reception means; andsecond estimation means for conducting channel estimation of the third data subcarrier in accordance with the pilot signal of the first pilot subcarrier received by the reception means and the pilot signal of the second pilot subcarrier received by the reception means.

2. The OFDM radio communications system according to claim 1, wherein the receiver further comprises third estimation means for conducting channel estimation of the non-macro-diversity signal transmitted with a frequency which is same as a frequency of the third data subcarrier, in accordance with a result of the channel estimation conducted by the second estimation means.

3. The OFDM radio communications system according to claim 1, wherein the receiver further comprises third estimation means for conducting channel estimation of the non-macro-diversity signal transmitted at a timing which is same as the first data subcarrier and the second data subcarrier, with a frequency which is same as a frequency of the third data subcarrier, in accordance with results of the channel estimations of the first data subcarrier and the second data subcarrier conducted by the first estimation means.

4. The OFDM radio communications system according to claim 1, wherein the second allocation means allocates the macro-diversity signals to a plurality of first data subcarriers whose frequency is same as the first pilot subcarrier and whose transmission timing is successive to the first pilot subcarrier, respectively, and allocates the macro-diversity signals to a plurality of second data subcarriers whose frequency is same as the second pilot subcarrier and whose transmission timing is successive to the second pilot subcarrier, respectively;the first allocation means allocates the pilot signals, respectively, to the first pilot subcarrier and a third pilot subcarrier temporally sandwiching the transmission timing of the plurality of first data subcarriers to which the second allocation means allocates the macro-diversity signals, and allocates the pilot signals, respectively, to the second pilot subcarrier and a fourth pilot subcarrier temporally sandwiching the transmission timing of the plurality of second data subcarriers to which the second allocation means allocates the macro-diversity signals; andthe first estimation means conducts the channel estimation of the plurality of first data subcarriers received at the reception timing between the reception timing of the pilot signal of the first pilot subcarrier and the reception timing of the pilot signal of the third pilot subcarrier received by the reception means, in accordance with the pilot signal of the first pilot subcarrier and the pilot signal of the third pilot subcarrier, and conducts the channel estimation of the plurality of second data subcarriers received at the reception timing between the reception timing of the pilot signal of the second pilot subcarrier and the reception timing of the pilot signal of the fourth pilot subcarrier received by the reception means, in accordance with the pilot signal of the second pilot subcarrier and the pilot signal of the fourth pilot subcarrier.

5. The OFDM radio communications system according to claim 1, wherein the first allocation means allocates the pilot signals, respectively, to a plurality of pilot subcarriers whose frequencies are different from one another and whose transmission timings are same as one another;the third allocation means allocates the non-macro-diversity signal to a data subcarrier whose frequency is among frequencies of the plurality of pilot subcarriers and whose transmission timing is same as the transmission timings of the plurality of pilot subcarriers; andthe second estimation means conducts channel estimation of the data subcarrier, in accordance with a moving average based on the plurality of pilot subcarriers received by the reception means.