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Performance enhancement of MC-CDMA system through novel sensitive bit algorithm aided turbo multi user detection.

Kumaravel R, Narayanaswamy K - PLoS ONE (2015)

Bottom Line: The OFDM parts reduce multipath fading and inter symbol interference (ISI) and the CDMA part increases spectrum utilization.The multiuser detection (MUD) and turbo coding are the two dominant techniques for enhancing the performance of the MC-CDMA systems in terms of BER as a solution of overcome to MAI effects.Simulation results show that the proposed method provides better BER performance with low complexity decoding, by mitigating the detrimental effects of MAI.

View Article: PubMed Central - PubMed

Affiliation: Department of Information Technology, Sri Venkateswara College of Engineering, Pennalur-602117, Sriperumbudur, India.

ABSTRACT
Multi carrier code division multiple access (MC-CDMA) system is a promising multi carrier modulation (MCM) technique for high data rate wireless communication over frequency selective fading channels. MC-CDMA system is a combination of code division multiple access (CDMA) and orthogonal frequency division multiplexing (OFDM). The OFDM parts reduce multipath fading and inter symbol interference (ISI) and the CDMA part increases spectrum utilization. Advantages of this technique are its robustness in case of multipath propagation and improve security with the minimize ISI. Nevertheless, due to the loss of orthogonality at the receiver in a mobile environment, the multiple access interference (MAI) appears. The MAI is one of the factors that degrade the bit error rate (BER) performance of MC-CDMA system. The multiuser detection (MUD) and turbo coding are the two dominant techniques for enhancing the performance of the MC-CDMA systems in terms of BER as a solution of overcome to MAI effects. In this paper a low complexity iterative soft sensitive bits algorithm (SBA) aided logarithmic-Maximum a-Posteriori algorithm (Log MAP) based turbo MUD is proposed. Simulation results show that the proposed method provides better BER performance with low complexity decoding, by mitigating the detrimental effects of MAI.

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Proposed SBA aided Log MAP based turbo MUD.
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pone.0115710.g002: Proposed SBA aided Log MAP based turbo MUD.

Mentions: Fig. 2 shows the proposed SBA aided Log MAP based turbo MUD. From the received user symbol vector, initial bits are found and then f sensitive bits are identified and updated by flipping and reversing the polarity of the error bits. These defined estimates are fed as an initial input to the Log MAP based turbo MUD [12, 13] as the first iteration intrinsic information. By turbo processing the estimates, sensitive bits are updated and better priori is achieved. The kth user channel decoder in a previous iteration from the received bits delivers the required extrinsic information. The estimated priori information goes through iterative decoding process. The priori information is decoded by the MAP decoder and interleaved using a random interleaver, the estimated posteriori information is fed back to the SBA aided Log MAP section for further processing. The turbo MUD process is repeated for all K users. At the end of Ith iterations the required extrinsic information LLR for K users will be found using SBA and Log MAP algorithms. The proposed sensitive bits algorithm [1, 14] greatly improves the performance of the MC-CDMA systems, by obtaining initial estimates of all the user coded bits, to identify some specific bits, which refer as “sensitive bits.” These bits correspond to error bits, assuming that all the other bits are correctly detected. In the next step the Log MAP algorithm is applied to correct these sensitive bits.


Performance enhancement of MC-CDMA system through novel sensitive bit algorithm aided turbo multi user detection.

Kumaravel R, Narayanaswamy K - PLoS ONE (2015)

Proposed SBA aided Log MAP based turbo MUD.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4340792&req=5

pone.0115710.g002: Proposed SBA aided Log MAP based turbo MUD.
Mentions: Fig. 2 shows the proposed SBA aided Log MAP based turbo MUD. From the received user symbol vector, initial bits are found and then f sensitive bits are identified and updated by flipping and reversing the polarity of the error bits. These defined estimates are fed as an initial input to the Log MAP based turbo MUD [12, 13] as the first iteration intrinsic information. By turbo processing the estimates, sensitive bits are updated and better priori is achieved. The kth user channel decoder in a previous iteration from the received bits delivers the required extrinsic information. The estimated priori information goes through iterative decoding process. The priori information is decoded by the MAP decoder and interleaved using a random interleaver, the estimated posteriori information is fed back to the SBA aided Log MAP section for further processing. The turbo MUD process is repeated for all K users. At the end of Ith iterations the required extrinsic information LLR for K users will be found using SBA and Log MAP algorithms. The proposed sensitive bits algorithm [1, 14] greatly improves the performance of the MC-CDMA systems, by obtaining initial estimates of all the user coded bits, to identify some specific bits, which refer as “sensitive bits.” These bits correspond to error bits, assuming that all the other bits are correctly detected. In the next step the Log MAP algorithm is applied to correct these sensitive bits.

Bottom Line: The OFDM parts reduce multipath fading and inter symbol interference (ISI) and the CDMA part increases spectrum utilization.The multiuser detection (MUD) and turbo coding are the two dominant techniques for enhancing the performance of the MC-CDMA systems in terms of BER as a solution of overcome to MAI effects.Simulation results show that the proposed method provides better BER performance with low complexity decoding, by mitigating the detrimental effects of MAI.

View Article: PubMed Central - PubMed

Affiliation: Department of Information Technology, Sri Venkateswara College of Engineering, Pennalur-602117, Sriperumbudur, India.

ABSTRACT
Multi carrier code division multiple access (MC-CDMA) system is a promising multi carrier modulation (MCM) technique for high data rate wireless communication over frequency selective fading channels. MC-CDMA system is a combination of code division multiple access (CDMA) and orthogonal frequency division multiplexing (OFDM). The OFDM parts reduce multipath fading and inter symbol interference (ISI) and the CDMA part increases spectrum utilization. Advantages of this technique are its robustness in case of multipath propagation and improve security with the minimize ISI. Nevertheless, due to the loss of orthogonality at the receiver in a mobile environment, the multiple access interference (MAI) appears. The MAI is one of the factors that degrade the bit error rate (BER) performance of MC-CDMA system. The multiuser detection (MUD) and turbo coding are the two dominant techniques for enhancing the performance of the MC-CDMA systems in terms of BER as a solution of overcome to MAI effects. In this paper a low complexity iterative soft sensitive bits algorithm (SBA) aided logarithmic-Maximum a-Posteriori algorithm (Log MAP) based turbo MUD is proposed. Simulation results show that the proposed method provides better BER performance with low complexity decoding, by mitigating the detrimental effects of MAI.

Show MeSH