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==Basics== Channel coding is referred to the processes done in both transmitter and receiver of a digital communications system. The mentioned processes require allocating extra bits, a.k.a. parity bits, and consuming extra bandwidth. Using this amount of communications resources results in more reliable connection between transmitter and its receiver. There are two policies to deal with channel coding: #Forward error correction (FEC) #Automatic repeat request (ARQ) FEC tries to discover the errors and correct them if it can. However, ARQ just discovers the error and sends a resend request to the transmitter. FEC-based methods are more complex in comparison with ARQ ones. Obviously, to use the benefits of two methods the combination of the above said policies is possible. Back to channel coding theory. There are two types of channel codes: #Block codes #Convolutional codes Block codes submit k bits in their inputs and forwards n bits in their output. These codes are frequently known as (n,k) codes. Apparently, whatever coding scheme is, it has added n-k bits to the coded block. Contrary to block codes which are memoryless, convolutional codes are coding algorithms with memory. Since their coding rate (R) is higher than the counterpart in block codes, convolutional codes are more used in practice. Every convolutional code uses m units of memory, therefore a convolutional code is represented with (n,k,m). In digital communications, a channel code is a broadly used term mostly referring to the forward error correction code and interleaving in communication and storage where the communication media or storage media is viewed as a channel. The channel code is used to protect data sent over it for storage or retrieval even in the presence of noise (errors). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「channel code」の詳細全文を読む スポンサード リンク
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