---

---

Operated on one block at a time and no interleaving occurs between blocks.the following steps can define a more general block-interleaving algorithm

---

Posted by waqqas1

In AWGN channels error occurs at random.The conventional way of correcting errors is using error correcting codes.These codes add some extra bits called parity bits.At the receiver by using these extra bits the position where the error has occurred can be found and corrected.The random error correcting codes are designed to correct single or few bit errors (depending on the code) only.Since for AWGN channels long bursts of error occurring is highly improbable event there will be no problem in using these codes.

Wireless channels are channels with memory.It means if at any time instant the channels is in bad condition then next few instants also the channel will be in bad condition.At these instants the channel will cause severe attenuation and bursts of error occurs.The bursts can not be corrected by random error correcting codes.

The easiest way to use the random error correcting codes for correcting burst errors is called interleaving.

At the transmitter let K information bits produce code word bits of length n.Let the encoder fill the code word in column-wise.Subsequent code words are filled in different coulns.The codewords are read row-wise and transmitted through the modulator.This process is called interleaving.Let the number of columns be l.

At the receiver the demodulated bits are filled row-wise.Subsequently the bits are read column-wise and given to the decoder for error correction.This process is called de-interleaving.

If there is an error burst of length l during transmission any one row of the received nl matrix will have the burst error.But since the codewords are read column-wise before sending to the decoeder utmost 1 bit will be in error at the decoder input.This 1 bit error can easily be corrected by the decoder which is capable of correcting random errors only.

---

Posted by Mannai_Murali

Interleaving is an operation often carried out as part of channel coding in a radio system.the purpose of interleaving is to distribute transmitted bits in time/frequency or both.consecutive bits on the input stream should not be transmitted consecutively in time(or on the same frequency in an OFDM system).Interleaving reduces the effect of burst errors caused by fast fading.the requirements of nterleaving depend both on the modulation and error corection schemes used and on channel characterstics.

One common method for interleaving is to use block interleaver.a block interleaver operated on one block at a time and no interleaving occurs between blocks.the following steps can define a more general block-interleaving algorithm

1.Write bits to matrix row by row.
2.perform intra-row permutations.
3.perform intra-column permutations.
4.Read bits columns by column.

---

Posted by gsmxprt

It is basically a method in which in block interleaver operates on discreate blocks with no overlapping between blocks..

So we can say that it is useful because it reduces the effect of fast fading..and slowly decrease the power level.

---

Posted by sagitraz