University of Kufa Channel Coding and Decoding PRESENTED BY Haider Hasan Department of Electronics and Communications Contents • What’s Channel Coding & Decoding? • Categories of FEC (Forward Error Correction) Codes • Categories of Channel Decoders • Applications • Limitations What’s Channel Coding & Decoding? Definition It’s a process used in modern communication systems to ensure that the data received is the same as the data sent. Channel Coding can be achieved by adding additional information to the data before transmission (redundancy). This redundant information helps to overcome errors at the receiver end caused during transmission of information. The channel decoder uses sophisticated algorithms to interpret the additional information to recover the original data. ππ Channel Coder Channel Noise Channel Decoder π ΰ· π What’s Channel Coding & Decoding? Definition Input Signal Output Signal What’s Channel Coding & Decoding? Why is it an Important process It’s a crucial process in communication systems for several reasons: • Error Detection and Correction • Enhanced Reliability of Data Transmission • Improved Data Integrity • Robustness in Noisy Environments • Reduced BER (Bit Error Rate) Categories of FEC The key idea of Forward Error Correction is to transmit enough redundant data to allow the receiver to recover the original data from errors by itself, with no reverse channel to request retransmission needed. Main categories of FEC: FEC Codes Block Codes Cyclic Codes Convolutional Codes Turbo Codes Categories of FEC Block Codes The channel encoder that implements this methodology receives the data in k-bit blocks and divide it into blocks to create an (n, k) block code, and it adds (n-k) redundant bits, resulting in an encoded block of n-bits. Channel Encoder n-bits k-bits Information Codewords Categories of FEC Cyclic Codes They are a subclass of block codes. Cyclic coders shift the bits of the codeword to result in another valid codeword. It has 2 important properties: • Linearity: πΆπ + πΆπ = πΆπ , where πΆπ , πΆπ , πππ πΆπ are codewords • Cyclic Shifting: Categories of FEC Convolutional Codes Encoding in this type is of information stream rather than information blocks with considering some information of the previous stream. Thus, this type of codes need memory. Categories of FEC Turbo Codes This type is a high performance class of FEC. Turbo codes were the first practical codes to closely approach the maximum channel capacity (Shannon Limit), which is the channel capacity of a continuous channel with bandwidth π΅ π»πππ‘π§. Categories of Channel Decoders The channel decoder takes the transmitted encoded data and convert it back into its original form, it allows the receiver to detect and correct errors. The categories of channel decoders are: Channel Decoders Hard Decision Decoders Soft Decision Decoders Iterative Decoders Maximum Likelihood Decoders Applications Due to the importance of channel coding & decoding, it takes an important role in many applications, some of them are: • Wireless Communication Systems • Cellular Mobile Systems • IoT • Deep-Space Communication • Autoencoders (specific tool in ML & DL) Limitations Even though channel coding & decoding is an important process and has many applications, it still faces limitations such as: • Complexity of encoding & decoding: channel coding and decoding can have high complexity which will lead to increased computational requirements and power consumption • Latency: Latency is a challenge for real-time applications, especially the ones that require high speeds. • Error Floor: means that at a certain point, increasing the SNR wouldn’t lead to decreasing the BER, which limits the performance of the communication system Conclusion Channel Coding and Decoding play a crucial role in digital communication system, they enhance the reliability of data transmission by adding redundancy to the transmitted data allowing the receiver to detect and correct errors caused by the noise introduced during transmission. However, they face some limitations as covered previously which limits the benefits of the process. As technology continues to advance, we expect new developments in the field and improvements to eliminate the limitations and implement in more applications References • Modern Digital and Analog Communication Systems 5th Edition. B. P. Lathi, Zhi Ding • What is Channel Coding? | AccelerComm • Source Coding and Channel Coding (electronicsandcommunications.com) • Information Theory. Mohamed Hamada. The University of Aizu • An Introduction to Channel Coding and Decoding over BSC • Channel Coding. Nada Nasih • Source–Channel Coding for Wireless Networks. Niklas Wenerson. KTH Electrical Engineering • The Basics of Channel Coding | AccelerComm Thanks For Listening ο Any Questions?
