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Communications method, communications apparatus and communications system using same communications apparatusRelated Patent Categories: Error Detection/correction And Fault Detection/recovery, Pulse Or Data Error Handling, Digital Data Error Correction, Request For RetransmissionCommunications method, communications apparatus and communications system using same communications apparatus description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060085717, Communications method, communications apparatus and communications system using same communications apparatus. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a Divisional of co-pending application Ser. No. 09/974,799, filed on Oct. 12, 2001, for which priority is claimed under 35 U.S.C. .sctn. 120. Application Ser. No. 09/974,799 claims priority under 35 U.S.C. .sctn. 119 (a)-(d) from application Nos. 2000-312890 and 2001-142662 filed in Japan on Oct. 13, 2000 and May 14, 2001, respectively. The entire contents of the above applications are hereby incorporated by reference. FIELD OF THE INVENTION [0002] The present invention relates to a communications control method, especially to a communications method, a communications apparatus and a communications system using the same communications apparatus, which perform retransmission control so as to improve quality of communication. BACKGROUND OF THE INVENTION [0003] In general, there are two kinds of error recovery schemes, namely an ARQ (Automatic Retransmission Request) method and an FEC (Forward Error Correction) method. In the ARQ method, a receiving end carries out error detection in accordance with a redundant code that has been added by a transmitting end, so that, in case an error is detected, a retransmission request for a packet, which relating to the error, is transmitted to the transmitting end. Consequently, in the ARQ method, the transmission end retransmits the packet relating to the error. The FEC method carries out error correction at the receiving end referring to the redundant code added by the transmitting end. [0004] Moreover, for example, a hybrid ARQ method, in which the ARQ method and the FEC method are combined, is proposed in "A Two-Step Adaptive Error Recovery Scheme for Video Transmission over Wireless Networks": Daji Qiao and Kang G. Shin, IEEE INFOCOM 2000. In the hybrid ARQ method, the transmission end adds a block error correction code (RS code), while the receiving end carries out error correction in accordance with the information of the RS code. The receiving end transmits a positive ACK signal or a negative ACK signal to the transmitting end, depending on the result of the error correction. The transmitting end retransmits a packet relating to the error when the transmitting end receives the negative ACK signal or when none of the positive and negative ACK signal is received in a time-out interval. [0005] A high bit error rate makes it difficult to achieve an almost-error-free state without carrying out the retransmission, even if an error correction code having high correction ability is used. Therefore, it is necessary in general to have a joint code in which a convolutional code and a block code are combined, or a process such as inter-leave. This increases a size of a circuit and requires a large number of buffers in the transmitting and receiving ends. [0006] Furthermore, in the above literature, the retransmission request is transmitted in case the error cannot be corrected by the error-correction process of the receiving end, and the retransmission is carried out per packet. However, in this method, the length of packet is significantly long (800 to 900 bits) and requires many bands for carrying out the retransmission once. SUMMARY OF THE INVENTION [0007] The present invention has an object to provide a communications method, communications apparatus, and a communications system using the same communications apparatus which realize efficient communication that requires a smaller number of bands. [0008] To attain the foregoing objects, a communications method of the present invention, which uses a data packet composed of a plurality of blocks so as to communicate, includes steps of (1) transmitting an error correction state of each block from a receiving end to a transmitting end, and (2) retransmitting a block that is not error-corrected (corrected in terms of error) by the receiving end. [0009] With the above communications method, where the error correction status is transmitted per block from the receiving end to the transmitting end, it is possible to retransmit only a part of the data packet, which is uncorrectable as a result of the error correction, instead of the whole data packet, when there is a block that cannot be decoded by the receiving end. Note that, the transmitting end is a side where a station for transmission is located, and the receiving end is a side where a station for receiving is located, with respect to a transmission path. [0010] Moreover, a communications apparatus of the present invention, which uses a data packet composed of a plurality of blocks so as to communicate, and which transmits an error correction state of each block from a receiving end to a transmitting end so that retransmission is performed per block. [0011] Furthermore, a communications system of the present invention is provided with (1) the communications apparatus, in which only an undecodable block is selected out of the data packet that has been received, so that a retransmission request of the undecodable block is transmitted, and (2) the communications apparatus, in which transmits the data packet in such a manner that, in case the communications apparatus receives a retransmission request of a block that is undecodable for the receiving end, a data packet that is to be transmitted next includes the block requested by the retransmission request. [0012] With the above communications system using the communications apparatus, where one data packet is composed of a plurality of correction blocks of error correction codes of a block type, and the retransmission request is transmitted per correction block, it is possible to carries out the retransmission per correction block that is uncorrectable, instead of the retransmission of the whole data packet. [0013] For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0014] FIG. 1 is an explanatory view illustrating retransmitting control in accordance with a communications method of an embodiment of the present invention. [0015] FIG. 2 is a timing chart for operations of a communications system of the communications method shown in FIG. 1. [0016] FIG. 3 is a flow chart for operation of a root station of the communications system of the communications method shown in FIG. 1. [0017] FIG. 4 is a flow chart for operation of a leaf station of the communications system of the communications method shown in FIG. 1. [0018] FIG. 5 is an explanatory view showing an example of a packet format of a transmission data packet of the communications method shown in FIG. 1. [0019] FIG. 6 is an explanatory view showing an example of a packet format of a retransmission request packet of the communications method shown in FIG. 1. Continue reading about Communications method, communications apparatus and communications system using same communications apparatus... 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