A new approach for fec decoding based on the bp algorithm in lte and wi m ax system


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A new approach for fec decoding based on the bp algorithm in lte and wi m ax system

  1. 1. A New Approach for FEC Decoding Based on theBP Algorithm in LTE and WiMAX SystemsABSTRACT:Many wireless communication systems such as IS- 54, enhanced data rates for the GSMevolution (EDGE), worldwide interoperability for microwave access (WiMAX) and longterm evolution (LTE) have adopted low-density parity-check (LDPC), tail-bitingconvolutional, and turbo codes as the forward error correcting codes (FEC) scheme fordata and overhead channels. Therefore, many efficient algorithms have been proposed fordecoding these codes. However, the different decoding approaches for these two familiesof codes usually lead to different hardware architectures. Since these codes work side byside in these new wireless systems, it is a good idea to introduce a universal decoder tohandle these two families of codes. The present work exploits the parity-check matrix (H)representation of tailbiting convolutional and turbo codes, thus enabling decoding via aunified belief propagation (BP) algorithm. Indeed, the BP algorithm provides a highlyeffective general methodology for devising low-complexity iterative decoding algorithmsfor all convolutional code classes as well as turbo codes. While a small performance lossis observed when decoding turbo codes with BP instead of MAP, this is offset by thelower complexity of the BP algorithm and the inherent advantage of a unified decodingarchitecture.Existing System:• For analysis purposes the packet-loss process resulting from the single-multiplexer model was assumed to be independent and, consequently, thesimulation results provided show that this simplified analysis considerablyoverestimates the performance of FEC.• Evaluation of FEC performance in multiple session was more complex in existingapplications.www.nanocdac.com www.nsrcnano.com branches: hyderabad nagpur
  2. 2. • Surprisingly, all numerical results given indicates that the resulting residualpacket-loss rates with coding are always greater than without coding, i.e., FEC isineffective in this application.• The increase in the redundant packets added to the data will increase theperformance, but it will also make the data large and it will also lead to increasein data loss.Proposed System:• In this work we have evaluated the performance of FEC coding more accuratelythan previous works.• We have reduced the complexity in multiple session and introduced a simple wayfor its implementation.• We show that the unified approach provides an integrated framework forexploring the tradeoffs between the key coding parameters: specifically,Interleaving depths, channel coding rates and block lengths.• Thus by choosing the coding parameter appropriately we have achieved highperformance of FEC, reduced the time delay for Encoding and Decoding withInterleaving.System RequirementsHardware:PROCESSOR : PENTIUM IV 2.6 GHzRAM : 512 MBMONITOR : 15”HARD DISK : 20 GBCDDRIVE : 52Xwww.nanocdac.com www.nsrcnano.com branches: hyderabad nagpur
  3. 3. Software:FRONT END : JAVA, SWINGTOOLS USED : JFRAME BUILDEROPERATING SYSTEM: WINDOWS XPModules of the Project• FEC Encoder• Interleaver• Implementation of the Queue• De-Interleaver• FEC Decoder• Performance EvaluationModule Description1. FEC Encoder:FEC is a system of error control for data transmission, where the sender addsredundant data to its messages. This allows the receiver to detect and correct errors(within some bounds) without the need to ask the sender for additional data. In thismodule we add redundant data to the given input data, known as FEC Encoding.The text available in the input text file is converted into binary. The binaryconversion is done for each and every character in the input file. Then we add theredundant data for each bit of the binary. After adding we have a block of packets foreach character.The User Interface design is also done in this module. We use the Swing packageavailable in Java to design the User Interface. Swing is a widget toolkit for Java. It is partwww.nanocdac.com www.nsrcnano.com branches: hyderabad nagpur
  4. 4. of Sun Microsystems Java Foundation Classes (JFC) — an API for providing a graphicaluser interface (GUI) for Java programs.2. Interleaver:Interleaving is a way of arranging data in a non-contiguous way in order toincrease performance. It is used in data transmission to protest against burst errors. In thismodule we arrange the data (shuffling) to avoid burst errors which is useful to increasethe performance of FEC Encoding.This module gets the input as blocks of bits from the FEC Encoder. In this modulewe shuffle the bits inside a single block in order to convert burst errors into randomerrors. This shuffling process is done for each and every block comes from the FECEncoder. Then we create a Socket connection to transfer the blocks from Source to theQueue. This connection is created by using the Server Socket and Socket class Availablein Java.3. Implementation of the Queue:In this module we receive the data from the Source system. This data is the blocksafter FEC Encoding and Interleaving processes are done. These blocks come from theSource system through Server Socket and Socket. Server socket and Socket are classesavailable inside Java. These two classes are used to create a connection between twosystems inside a network for data transmission. After we receive the packets fromSource, we create packet loss. Packet loss is a process of deleting the packets randomly.After creating loss we send the remaining blocks to the Destination through the socketconnection.4. De-Interleaver:www.nanocdac.com www.nsrcnano.com branches: hyderabad nagpur
  5. 5. This module receives the blocks of data from the Queue through the socketconnection. These blocks are the remaining packets after the loss in the Queue. In thismodule we re arrange the data packets inside a block in the order in which it is beforeInterleaving. This process of Interleaving and De-Interleaving is done to convert bursterrors into random errors. After De-Interleaving the blocks are arranged in the originalorder. Then the data blocks are sent to the FEC Decoder.5. FEC Decoder:This module gets the input from the De-Interleaver. The received packets areprocessed to remove the original bits from it. Thus we recover the original bits of acharacter in this module. After retrieving the original bits, we convert it to characters andwrite it inside a text file.6. Performance Evaluation:In this module we calculate the overall performance of FEC Coding in recoveringthe packet losses. After retrieving the original bits, we convert it to characters and write itinside a text file. This performance is calculated by using the coding parameters likeCoding rate, Interleaving depth, Block length and several other parameters. First wecalculate the amount of packet loss and with it we use various formulas to calculate theoverall performance of Forward Error Correction in recovering the network packet losses.In module given input and expected outputModule-1Given Input:Text file.Expected Output:Packets coded with redundant data.www.nanocdac.com www.nsrcnano.com branches: hyderabad nagpur
  6. 6. Module-2Given Input:Packets coded with redundant data.Expected Output:Packets shuffled inside every block of data.Module-3Given Input:Shuffled packetsExpected Output:Packets passed successfully (other than lost packets)Module-4Given Input:Packets from the queueExpected Output:Packets re-ordered like it was before InterleavingModule-5Given Input:Packets from De-InterleaverExpected Output:Original packetsModule-6Given Input:www.nanocdac.com www.nsrcnano.com branches: hyderabad nagpur
  7. 7. All the parameters used in FEC CodingExpected Output:Output file and the calculations resultREFERENCE:Ahmed Refaey, Sebastien Roy and Paul Fortier, “A New approach for FEC Decodingbased on the BP algorithm in LTE and WiMAX Systems”, IEEE Conference 2011.www.nanocdac.com www.nsrcnano.com branches: hyderabad nagpur