Adaptive modulation scheme and coding rate control method

• US 7,555,269 B2
• Filed: 01/18/2006
• Issued: 06/30/2009
• Est. Priority Date: 01/21/2005
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi Communication Technologies, Ltd. (Hitachi, Ltd.)
• Inventors: Saito, Toshiyuki, Yano, Takashi, Tamaki, Satoshi, Hanaoka, Seishi
• Primary Examiner(s): Vuong; Quochien B
• Application Number:
  US11/333,199
• Publication Number:
  US 20060165189A1
• Time in Patent Office: 1,259 Days
• Field of Search: 455/23, 455/42, 455/102, 455/108, 455/205, 455/296, 375/259, 375/260, 375/261, 375/268, 375/271, 375/295, 375/298, 375/300, 375/302, 375/316, 375/322, 375/324, 375/353, 370/335, 370/342, 370/441
• US Class Current: 455/102
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]

Abstract

A radio communication system for enabling control of a modulation scheme following variation in the propagation channel and control of a coding rate in a small amount of delay and arithmetic operation. In order to attain the object explained above, a transmitter station and a receiver station use in common the information of the maximum number of bits used for communication of each symbol. The transmitter station generates codeword by previously encoding the communication signal with the code having sufficient error correcting capability, assigns, to each symbol, the codeword to result in the maximum number of bits per symbol, and modulates and transmits the bits using the modulation scheme in which the number of bits per symbol is equal to or less than the maximum number of bits per symbol. Meanwhile, the receiver station demodulates, for each symbol, the bits with the modulation scheme, in which the number of bits per symbol is larger as the propagation channel quality is higher, among the modulation schemes in which the number of bits per symbol is less than the maximum number of bits per symbol and summarizes the demodulation results and executes the decoding process by adding the signal of zero likelihood to restore the shortage when the total sum of the number of bits per symbol in the modulation scheme used for the demodulation becomes equal to or larger than the predetermined value.

Claims

1. A radio communication system comprising:

a first radio station for dividing a codeword generated through a channel encoding by the channel code to transmit the codeword; and

a second radio station for combining and decoding the received signals, wherein

said first radio station and said second radio station use in common information of a first number of bits as a maximum number of propagation bits per symbol,

said first radio station generates a codeword by encoding the transmitting information, assigns and divides said codeword to result in said first number of bits per symbol, and transmits the bits through modulation thereof with a modulation scheme which can transmit, for each symbol, a second number of bits which is a value equal to or less than said first number of bits using at least a part of said assigned bits, and

said second radio station determines a propagation channel quality from said first radio station, receives the signals from said first radio station, demodulates said received signal with a modulation scheme which can transmit, for each symbol, a third number of bits which is the value equal to or less than said first number of bits and the value having positive correlation with said propagation channel quality, and combining and decoding said received signal when an accumulation result of said third number of bits for said codeword has exceeded a predetermined value.

2. The radio communication system according to claim 1,

wherein said second radio station transmits a notifying signal for notifying end of reception when the accumulation result of said third number of bits for said codeword has exceeded said predetermined value, and

said first radio station suspends transmission of said codeword, upon reception of said notifying signal.

3. The radio communication system according to claim 1,

wherein said second radio station sends said third number of bits to said first radio station, and

said first radio station accumulates said third number of bits sent and suspends transmission of said codeword when the accumulation result of said third number of bits for said codeword has exceeded said predetermined value.

4. The radio communication system according to claims 1, wherein said first radio station determines the propagation channel quality for said second radio station and sets said second number of bits as the value having positive correlation with said determined propagation channel quality.

5. The radio communication system according to claim 4, wherein said second radio station sends said third number of bits to said first radio station, and

said first radio station determines said propagation channel quality on the basis of said sent third number of bits.

6. A communication method of signal transmitter station in the radio communication system in which a channel decoding is conducted when an accumulation result of the number of bits demodulated for each codeword has exceeded a predetermined value in a signal receiver station, wherein

information of a first number of bits as a maximum number of propagation bits per symbol in a modulation scheme is used in common with said signal receiver station,

each codeword is generated by encoding transmitting information,

said codeword is assigned and divided to result in said first number of bits per symbol,

a second number of bits as the value equal to or less than said first number of bits is modulated with a modulation scheme which can transmit the bits for each symbol using at least a part of said assigned bits,

said modulated signal is transmitted,

the information of number of bits demodulated in said signal receiver station is received from said signal receiver station, and

termination or continuation of the transmission processes of the codeword is determined on the basis of said information of number of bits demodulated.

7. The communication method according to claim 6, wherein the information of number of demodulated bits received from said signal receiver station indicates whether the result of accumulation of number of bits per symbol in the modulation scheme selected for the demodulation process in said signal receiver station has exceeded the predetermined value or not.

8. The communication method according to claim 6, wherein the information of number of demodulated bits received from said signal receiver station indicates the number of bits per symbol in the modulation scheme selected for the demodulation process in said signal receiver station, and said signal transmitter station accumulates said information of number of demodulated bits for each codeword and terminates transmission of said codeword when said accumulation result has exceeded the predetermined value.

9. The communication method according to claims 8, wherein said modulation scheme of the transmitting information is selected on the basis of said information of number of bits demodulated in said signal transmitter station.