A Novel Adaptive Pilot Placement Algorithm for Channel Estimation in OFDM Based Systems

Abstract

The orthogonal frequency division multiplexing (OFDM) system, which is one of the multi-carrier communication systems, has been widely used due to its ability to provide high-speed data communication using bandwidth effectively and its resistance to echo delays. In OFDM system, the disturbing effects of the wireless communication channel can be reduced by estimating the channel in the receiver. In this study, a novel channel estimation method with a pilot placement algorithm which can adaptively change according to the structure of the channel is proposed for the OFDM system. The proposed algorithm is based on placing the pilot signals more frequently in the regions with deep fading of the channel. From the simulation results, it is seen that the proposed adaptive channel estimation algorithm gives better results than the classical channel estimation algorithms, and provides an improvement of up to 11.6 dB in bit error rate (BHO) performance. In addition, unlike the studies in the literature, a new mathematical expression is proposed in the last part of the study to determine the threshold level of the regions where the pilot frequency will be increased in the frequency domain of channel.

Keywords

• OFDM
• Channel estimation
• Irregular pilot placement
• Mobile radio channel

OFDM SİSTEMLERİNDE KANAL KESTİRİMİ İÇİN YENİ BİR UYARLAMALI PİLOT YERLEŞİM ALGORİTMASI

Abstract

Çok taşıyıcılı haberleşme sistemlerinden biri olan dikgen frekans bölmeli çoğullama (orthogonal frequency division multiplexing, OFDM) sistemi, bant genişliğini etkin kullanarak yüksek hızlı veri haberleşmesine olanak sağlaması ve yankı gecikmelerine karşı dayanıklılığı nedeniyle günümüzde yaygın olarak kullanılmaktadır. OFDM sisteminde gezgin iletim kanalının bozucu etkileri alıcıda kanal kestirimi yapılarak azaltılabilir. Bu çalışmada OFDM sistemi için kanalın yapısına göre uyarlamalı olarak değişebilen yeni bir pilot yerleşimli kanal kestirim algoritması önerilmiştir. Önerilen algoritma kanalın derin sönümlenmelerinin olduğu bölgelere daha sık pilot yerleştirilmesi temeline dayanmaktadır. Benzetim sonuçlarından, önerilen uyarlamalı kanal kestirim algoritmasının klasik kanal kestirim algoritmalarına göre daha iyi sonuç verdiği ve bit hata oranı (BHO) başarımında 11.6 dB’e varan bir iyileşme sağladığı görülmüştür. Ayrıca literatürdeki çalışmalardan farklı olarak bu çalışmada frekans düzleminde pilot sıklığının artırılacağı bölgelerin eşik seviyesini belirlemek için yeni bir matematiksel ifade önerilmiştir.

Keywords

• OFDM
• Kanal kestirimi
• Düzensiz pilot yerleşimi
• Gezgin iletim kanalı

References

1. Acar, Y., Aldırmaz, S. Ç., Basar, E., 2019, "Channel estimation for OFDM-IM systems", Turkish Journal of Electrical Engineering & Computer Sciences, Cilt 27, Sayı 3, ss.1908-1921.
2. Acar, Y., Dogan, H., Panayırcı E., 2017, "Pilot symbol aided channel estimation for spatial modulation-OFDM systems and its performance analysis with different types of interpolations", Wireless Personal Communications, Cilt 94, Sayı 3, ss.1387-1404.
3. Acar, Y, Dogan H., Başar E., Panayırcı, E., 2016, "Interpolation based pilot-aided channel estimation for STBC spatial modulation and performance analysis under imperfect CSI", IET Communications Cilt 10, Sayı 14, ss.1820-1828.
4. Ami Munshi, A., Unnikrishnan, S., 2021, “Performance Analysis of Compressive Sensing based LS and MMSE Channel Estimation Algorithm”, Journal of Communications Software and Systems, Cilt 17, Sayı 1, ss.13-19.
5. Ayvenli, F., 2019, ”Dikgen Frekans Bölmeli Çoğullama Sistemleri İçin Kanal Kestirim Yöntemlerinin Başarımının İncelenmesi”, Yüksek Lisans Tezi, Ondokuz Mayıs Üniversitesi, Fen Blimleri Enstitüsü.
6. Chen, J. C., Wen, C. K., Ting, P., 2013, “An efficient pilot design scheme for sparse channel estimation in OFDM systems”, IEEE Communications Letters, Cilt 17, Sayı 7, ss. 1352-1355.
7. Cho, Y. H., Ko, H. L., 2020, “Channel Estimation Based on Adaptive Denoising for Underwater Acoustic OFDM Systems”, IEEE Access, Cilt 8, ss. 157197-157210.
8. Coleri, S., Ergen, M., Puri, A. Bahai, A., 2002, “Channel estimation techniques based on pilot arrangement in OFDM systems”, IEEE Transactions on Broadcasting, Cilt 48, Sayı 3, ss. 223-229.

9. Edfors, O., Sandell, M., van de Beek, J.J., Wilson, S.K., Brjesson, P.O. 1998, “OFDM channel estimation by singular value decomposition”, IEEE Transactions on Communications, Cilt 46, Sayı 7, ss. 931-939.
10. Engiz, B.K., Kurnaz, Ç., Sezgin, H., “Determining the Optimum Pilot Density in OFDM Systems over Propagation Measurement Based Channels”, 55th International Symposium ELMAR-2013, Zadar, Croatia, 25-27 September 2013.
11. Engiz, B. K., Kurnaz, Ç., Sezgin, H., 2015, “Approach for determining the optimum pilot placement in orthogonal frequency division multiplexing systems”, IET Communications, Cilt 9, Sayı 15, ss. 1915-1923.
12. Fertl, P., Matz, G., 2010, “Channel estimation in wireless OFDM systems with irregular pilot distribution”, IEEE Transactions on Signal Processing, Cilt 58, Sayı 6, ss. 3180-3194.
13. Gu, F., Fan, Y., Wang L., Tan, X., Wei, J., 2019, “A Universal Channel Estimation Algorithm Based on DFT Smoothing Filtering”, IEEE Access, Cilt 7, ss. 129883-129891.
14. Han, P., Wang J., Xu, P., “Adaptive pilot design based on Doppler frequency shift estimation for OFDM system”, International Conference on Computer Design and Applications, Qinhuangdao, Çin, 25-27 Temmuz 2010.
15. Hsieh, M. H., Wei, C. H., 1998, “Channel estimation for OFDM systems based on comb-type pilot arrangement in frequency selective fading channels”, IEEE Transactions on Consumer Electronics, Cilt 44, Sayı 1, ss. 217-225.
16. Jain, R., 2007, “Channel models: A tutorial”, WiMAX forum AATG (Vol. 10), Washington Univ. St. Louis, Dept. CSE. Jency, G. B., Gladwin, S. J., “Channel estimation using optimized pilot placement in OFDM system”, International Conference on Communication and Signal Processing, Bangkok, Tayland, 10-12 Ekim 2014.
17. Kurnaz, C., Gökalp H., “Investigating MC-CDMA System Performance Using Measurement-Based Channel Models” 14th European Wireless Conference, Prague, Czech Republic, 22-25 June 2008.
18. Kurnaz, C., Engiz, B. K., Gökalp, H., Sezgin, H., 2012, “Dikgen Frekans Bölmeli Çoğullama Sisteminde En Uygun Pilot Aralığının Kanal Değişkenleri ile İlişkilendirilmesi”, Uludağ Üniversitesi, Mühendislik-Mimarlık Fakültesi Dergisi, Cilt 17, Sayı 1, ss. 79-92.
19. Kurnaz, Ç., Engiz, B.K., Ayvenli, F., “Performance Comparison of Regular and Irregular Pilot Placements in OFDM Systems”, 5th International Conference on Advanced Technologies (ICAT), İstanbul, Türkiye, 9-12 Mayıs 2017.
20. Lee, S., Ju, H., Shim, B., “Pilot Assignment and Channel Estimation via Deep Neural Network”, 24th Asia-Pacific Conference on Communications (APCC), Ningbo, Çin, 12-14 Kasım 2018.,
21. Leus, G. Van der Veen, A., 2005, Channel estimation. Smart Antennas-State of the Art, Hindawi Publishing Corporation, 293-319.
22. Li, Q., Wen, M., Zhang, Y., Li, J., Chen, F., Ji, F., 2018, “Information-guided pilot insertion for OFDM-based vehicular communications systems”, IEEE Internet of Things Journal, Cilt 6, Sayı 1, ss. 26-37.
23. Nan, Y., Sun, X., Zhang, L., “Near-optimal pilot allocation in sparse channel estimation for massive MIMO OFDM systems”, International Symposium on Wireless Communication Systems (ISWCS), Brüksel, Belçika, 25-28 Ağustos 2015.
24. Nee, R.V., Prasad, R., 2000, OFDM for Wireless Multimedia Communications, Artech House, Inc. 280.
25. Panah, A. Y., Nosrat-Makouei, B., Vaughan, R. G., 2008, “Non-uniform pilot-symbol allocation for closed-loop OFDM”, IEEE Transactions on Wireless Communications, Cilt 7, Sayı 7, ss. 2723-2731.
26. Patil, S., Jadhav A.N., 2014, “Channel Estimation Using LS and MMSE Estimators”, KIET International Journal of Communications &Electronics, Cilt 2, Sayı 1, ss. 51-55.
27. Petropulu, A., Zhang, R. Lin, R., 2004, “Blind OFDM channel estimation through simple linear precoding”, IEEE Transactions on Wireless Communications, Cilt 3, Sayı 2, ss. 647-655.
28. Raghavendra, M. R., Lior, E., Bhashyam, S. Giridhar, K., 2007, “Parametric channel estimation for pseudo-random tile-allocation in uplink OFDMA”, IEEE Transactions on Signal Processing, Cilt 55, Sayı 11, ss. 5370-5381.
29. Shin, C., Heath, R. W. Powers, E. J., 2007, “Blind channel estimation for MIMO-OFDM systems”, IEEE Transactions on Vehicular Technology, Cilt 56, Sayı 2, ss. 670-685.
30. Singh, H., Bansal, S., 2016, “Comparison of Channel Estimators for OFDM Channel Estimation”, International Journal of Computer Applications, Cilt ICAET 2016, Sayı 7, ss.41-44.
31. Simeone, O., Bar-Ness Y., Spagnolini, U., 2004, “Pilot-based channel estimation for OFDM systems by tracking the delay-subspace”, IEEE Transactions on Wireless Communications, Cilt 3, Sayı 1, ss. 315-325.
32. Song, W.G., Lim, J. T., 2003, “Pilot-symbol aided channel estimation for OFDM with fast fading channels”, IEEE Transactions on Broadcasting, Cilt 49, Sayı 4, ss. 398-402.
33. Souleymane, B., Mondol, S.R., Wei, Z., 2016, “Comparative Performance Study of LS and MMSE Channel Estimation over Time Varying Channel in OFDM System”, International Journal of Engineering Research & Technology (IJERT), Cilt 5, Sayı 3, ss.847-850.
34. Steendam, H., “How to select the pilot carrier positions in CP-OFDM?”, IEEE International Conference on Communications (ICC), Budapeşte, Macaristan, 9-13 Haziran 2013.
35. Sung, K. Y., Hong, Y. W. P., Chao, C. C., “Feedback-aided pilot placement for amplify-and-forward OFDM relay links”, IEEE 11th International Symposium on Spread Spectrum Techniques and Applications, Taichung, Tayvan, 17-20 Ekim 2010.
36. Sung, K. Y., Hong, Y. W. P., Chao, C. C., “Feedback-aided pilot placement for OFDM relay links with subcarrier pairing”, IEEE International Conference on Communications (ICC), Kyoto, Japonya, 5-9 Haziran 2011.
37. Sung, K. Y., Hong, Y. W. P., Chao, C. C., 2012, “Feedback-aided pilot placement and subcarrier pairing for AF OFDM relay channels”, IEEE Transactions on Vehicular Technology, Cilt 62, Sayı 2, ss. 704-720.
38. Tang, Z., Cannizzaro, R.C., Leus, G., Banelli, P., 2007, “Pilot-Assisted Time-Varying Channel Estimation for OFDM Systems”, IEEE Transactions on Signal Processing, Cilt 55, Sayı 5, ss. 2226-2238.
39. Vithanage, C., Cepeda, R., Coon, J, McGeehan, J., 2010, “MIMO-OFDM pilot placement algorithms for wideband indoor communications”, IEEE Transactions on Communications, Cilt 59 Sayı 2, ss. 466-476.
40. Wu, W., Jia, X., Cai, Y., Hu, H., “Feedback-aided pilot placement for two-way cooperative-OFDM”, International Conference on Wireless Communications and Signal Processing (WCSP), Nanjing, Çin, 9-11 Kasım 2011.
41. Zhao, X., Peng, T. Wang, W., “Parametric channel estimation by exploiting hopping pilots in uplink OFDMA”, IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications, Cannes, Fransa, 15-18 Eylül 2008.