Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1997-03-26
2001-02-13
De Cady, Albert (Department: 2784)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S752000
Reexamination Certificate
active
06189123
ABSTRACT:
The present invention relates generally to the communication of a block of digital information in encoded form between a sending station and a receiving station in a digital communication system. More particularly, the present invention relates to apparatus, and an associated method, by which to communicate a transmission set formed of at least portions of at least one selected parallel-concatenated coded version of the block of digital information between the sending and receiving station.
If the receiving station is unable to accurately recover the informational content of the digital information from the transmission set transmitted thereto, successive, redundant transmission of additional transmission sets, formed of additional portions of selected encoded versions to the receiving station is initiated.
When channel conditions of a channel extending between the sending and receiving stations are of good quality, information throughput between the sending and receiving stations can be increased by sending only a small number of the transmission sets to the receiving station. And, when the channel conditions are poor, successive redundant transmission to the receiving station of the additional transmission sets better ensures that the informational content of the digital information can be accurately recreated. Feedback signals returned from the receiving to the sending station prompt the sending station to implement the successive, redundant transmission of the additional transmission sets to the receiving station.
BACKGROUND OF THE INVENTION
A communication system is formed, at a minimum, by a transmitter and a receiver interconnected by a communication channel. The transmitter forms at least a portion of a sending station, and the receiver forms at least a portion of a receiving station. Communication signals transmitted by the sending station are transmitted upon the communication channel to be received by the receiving station. Information contained in the communication signals transmitted by the sending station is recovered once received at the receiving station. In a digital communication system, information to be communicated to the receiving station is digitized. The digitized information is then used to form the communication signal.
In some conventional, digital communication systems, the communication signals are transmitted in bursts. Blocks of digital information are communicated by a sending station to a receiving station during transmission of the bursts upon the communication channel.
In a non-ideal communication system, the communication signal is distorted during its transmission upon the communication channel. Because of such distortion, when the communication signal is received at the receiving station, the received signal differs somewhat from the communication signal transmitted from the sending station. If the communication channel is of poor quality, and the amount of distortion is significant, the informational content of the communication signal cannot be properly recovered at the receiving station.
In a digital, radio communication system, for instance, multi-path and Rayleigh distortion is sometimes introduced upon the communication signal as it is transmitted on the communication channel from the sending station to the receiving station.
Various schemes have been developed to better ensure that the informational content of the communication signal transmitted upon a non-ideal channel can be recovered at a receiving station. Several of such schemes utilize a feedback arrangement in which the receiving station reports back to the sending station whether the informational content of the received signal can be adequately recovered.
Several of such schemes have been implemented in a digital communication system in which blocks of information are communicated in bursts. The receiving station determines whether a burst of the block of information received at the receiving station is of an acceptable quality level. Indications of the determinations, forming feedback information, are returned to the sending station by way of a feedback channel. The indication may also be communicated back to the sending station implicitly. That is to say, lack of transmission of feedback information from the receiving to the sending station may be indicative of successful recovery of the informational content of the block of digital information. Or, the feedback information may be provided to the sending station in a manner other than by way of a direct feedback channel extending directly to the sending station. The indication may alternately be communicated back to the sending station indirectly. For example, the sending station might measure the channel conditions and decide that the probability of the receiving station successfully decoding the block of digital information to be so low that retransmission of the block of digital information would be justifiable.
Most simply, the receiving station simply detects whether the received signal burst is of an acceptable quality level. If the signal quality level of the received signal burst is not good enough to permit recovery of the informational content thereof, the receiving station merely requests the sending station to retransmit the block of digital information in a subsequent burst. Such a scheme is sometimes referred to as an ARQ (automatic request) scheme.
Retransmission of the block of digital information can be repeated in successive bursts until the block of digital information is received at the receiving station with at least a minimum quality level. The receiving station makes the determination of the quality of the received block of digital information responsive, for example, to detection of an error detecting code, knowledge of the communication channel upon which the block of information is transmitted, or some other suitable scheme.
The block of digital information can also be transmitted using an error protecting code, such as type I hybrid ARQ (Automatic Repeat Request) scheme, a general channel decoding technique. When the receiving station receives the block of digital information, the received block is decoded by a decoder to extract the informational content from the received signal. A determination is made if the informational content of the block of digital information can be recovered with at least an acceptable quality level. Because of the error protection, the block of digital information is better able to be recovered even if transmitted upon a communication channel of lowered quality.
Furthermore, if the decoder has the ability to exploit, not only the values of the received symbols, but also reliability information on the symbols, so-called soft information, the performance will increase substantially. Decoder circuitry at the receiving station capable of utilizing soft information is referred to as a soft input decoder.
In some other schemes, such as a type II and type III, hybrid ARQ (Automatic Repeat Request) scheme, blocks of digital information determined by the receiving station to be corrupt, i.e., to be of poor quality, are not merely discarded. Instead, the corrupt blocks are combined with subsequently-transmitted blocks of digital information. Information contained in previously-transmitted blocks is accumulated and forms accumulated knowledge. Such accumulated knowledge can be used to facilitate recovery of subsequently-transmitted blocks. Thereby, “accumulated knowledge” results, the number of times in which the blocks of digital information must otherwise be retransmitted decreases. The advantages of utilization of accumulated knowledge permitted by the combining of successive retransmissions of the blocks of digital information occur with increased amounts of information contained in the blocks of digital information.
This is advantageous as the probability of correct decoding generally increases if the accumulated knowledge is used during the decoding rather than if only the latest retransmitted block is utilized. Decoder circuitry at the receiving station capable of utili
Anders Nyström Per Johan
Larsson Carl Johan Henrik
Cady Albert De
Jenkens & Gilchrist
Telefonaktiebolaget LM Ericsson
Ton David
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