Different Channel Coding Techniques In 4G Wireless Communications
4G Communications
One method of optimizing throughput for a wireless system while maintaining a certain level of performance is to design the error control system so that it offers two or more different rate codes. The system uses channel state information to determine which of the various codes should be used at any given moment. In order to minimize system complexity, the same encoder and decoder are used for the different rate codes. This part presents a method of comparing the performance of the system for different coding rates. Results will show the optimal code rate for various channel conditions and the gain in throughput by using adaptive rate codes in wireless systems.
First we will talk about the basic different channel coding techniques and
its performance to know how we can adapt the coding rate according to channel conditions.
I- The Basics Different Channel Coding Techniques:
The channel coding refers to the class of signal transformations designed to improve communications performance by enabling the transmitted signals to better with-stand the effects of various channel impairments, such as noise, interference and fading.
The channel coding is considered as an important signal processing
operation which provides a reliable transmission of information over channel.
It is used mainly to minimize the effect of NOISE by two basic operations, Error detection and Error correction.
Coding Principle:
Coding is achieved by adding redundant bits to each message,or make
an operation on the message to get it encoded with some methods. These redundant bits are used for detecting and/or correcting transmission errors, in other words for protecting data against channel impairments (e.g., noise, fading, interference).
Block Codes vs. Convolutional codes :
Historically, the error correcting codes have been classified into block codes and convolutional codes. The distinguishing feature for this particular classification is the presence or absence of memory in the encoder.
In linear block codes, which are described by two integers n and k and
generator mat-rix or polynomial.The integer k is the number of input data bits to a block encoder. The integer n is the total number of bits in the codeword out of the encoder.Each codeword n-bits is uniquely determined by the input message k-bits (Memoryless).
In a convolutional code, the encoding operation may be viewed as the discrete time convolution of the input sequence with the impulse response of the encoder. The duration of the impulse response equals the memory of the encoder
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Different Channel Coding Techniques In 4G wireless Communication channel,wireless Communications channel,
4G Communications,Different Channel Coding Techniques In 4G wireless Communications channel
Different Channel Coding Techniques In 4G wireless Communication channel,wireless Communication channel,
Different Channel Coding Techniques In 4G wireless Communications channel,wireless Communications channel,
Different Channel Coding Techniques In 4G wireless Communication channel in 4G communication,wireless Communication channel in 4G communication ,
Different Channel Coding Techniques In 4G wireless Communications channel in 4G communications,wireless Communications channel in 4G communications,
Different Channel Coding Techniques In 4G 4G wireless Communication channel,4G wireless Communication channel,
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