Chair of Information and Coding Theory

Adaptive Modulation and Channel Coding


Mobile radio channels are time-varying (due to Doppler spread) as well as dispersive (due to multipath propagation) [1,2]. For these reasons, adaptive modulation and coding schemes should be exploited in order to improve the throughput and to reduce outage. In most situations, quality of service can be improved significantly by applying multiple antennas at the transmitter and receiver side, known as multiple-input multiple-output (MIMO) processing [3,4,5].

If high-order modulation schemes are used, reliable channel estimation is necessary. In [6], pilot-aided channel estimation has been invented for multi-carrier modulation schemes. In pilot-aided channel estimation, known training symbols are inserted into the data symbols [7]. Nowadays, almost all state-of-the-art communication systems are based on orthogonal frequency-division multiplexing (OFDM) and employ this technique. A low-complexity graph-based channel estimator suitable for time/frequency/spatial/polarization domains has been proposed and studied in [8,9].

Channel adaptation is particularly simple yet efficient, if binary sequences are simply superimposed. The better the channel quality, the more sequences are resolvable at the receiver side. In order to avoid ambiguities in the detection process, it is necessary to perform channel coding. A low-complexity version is the employ a single channel encoder for all binary sequences ("layers"), but to permute the ordering of the encoded symbols by layer-wise interleaving, before superposition takes place. This concept is called interleave-division multiplexing (IDM), if the superposition is treated as a high-order modulation scheme, or interleave-division multiple access (IDMA), if the layers are generated by different users [10,11]. Recently, IDMA has been proposed as a potential candidate for the fifth wireless radio generation (5G).

IDM and IDMA are incidents of superposition modulation (SM), intensively investigated in [12,13,14,15]. In [16], SM has been exported to optical wireless communications (OWC).


Selected References:

[1] P. Hoeher, "A statistical discrete-time model for the WSSUS multipath channel," IEEE Trans. Veh. Technol., vol. 41, no. 4, pp. 461-468, Nov. 1992.

[2] J. Mietzner and P. A. Hoeher, "A rigorous analysis of the statistical properties of the discrete-time triply-selective MIMO Rayleigh fading channel model," IEEE Transactions on Wireless Communications, vol. 6, no. 12, pp. 4199-4203, Dec. 2007.

[3] J. Mietzner, R. Schober, L. Lampe, W. H. Gerstacker, and P. A. Hoeher, "Multiple-antenna techniques for wireless communications - a comprehensive literature survey," IEEE Communications Surveys and Tutorials, vol. 11, no. 2, pp. 87-105, Second Quarter 2009.

[4] J. Mietzner, Spatial Diversity in MIMO Communication Systems with Distributed or Co-located Antennas. Dissertation, Faculty of Engineering, University of Kiel, 2007.

[5] J. Mietzner and P. A. Hoeher, "Boosting the performance of wireless communication systems - Theory and practice of multiple antenna techniques," IEEE Commun. Mag., vol. 42, no. 10, pp. 40-47, Oct. 2004.

[6] P. Hoeher, "TCM on frequency-selective land-mobile fading channels," in Proc. 5th Tirrenia Intern. Workshop on Digital Commun. , Tirrenia, Italy, Sept. 1991, pp. 317-328; E. Biglieri and M. Luise (Eds.), Coded Modulation and Bandwidth-Efficient Transmission. Amsterdam: Elsevier Science Publishers, 1992.

[7] P. Hoeher, S. Kaiser, and P. Robertson, "Two-dimensional pilot-symbol-aided channel estimation by Wiener filtering," in Proc. IEEE ICASSP '97, Munich, Germany, Apr. 1997, pp. 1845-1848.

[8] C. Knievel, P. A. Hoeher, and G. Auer, "On the combining of correlated random measures with application to graph-based receivers", IEEE Communications Letters, vol. 16, no. 12, pp. 1996-1999, Dec. 2012.

[9] C. Knievel, Multi-Dimensional Channel Estimation for MIMO-OFDM. Dissertation, Faculty of Engineering, University of Kiel, 2014.

[10] P. A. Hoeher, H. Schoeneich, and J. Ch. Fricke, "Multi-layer interleave-division multiple access: Theory and practice," European Transactions on Telecommunications (ETT), vol. 19, no. 5, pp. 523-536, Aug. 2008.

[11] H. Schoeneich, Adaptiver Interleave-Divison Mehrfachzugriff (IDMA) mit Anwendung in der Mobilfunkkommunikation. Dissertation, Faculty of Engineering, University of Kiel, 2008.

[12] P. A. Hoeher and T. Wo, "Superposition modulation: Myths and facts," IEEE Communications Magazine, vol. 49, no. 12, Dec. 2011.

[13] T. Wo, Superposition Mapping & Related Coding Techniques. Dissertation, Faculty of Engineering, University of Kiel, 2011.

[14] T. Wo, P. A. Hoeher, and Z. Shi, "Graph-based soft channel estimation for fast fading channels," IEEE Transactions on Wireless Communications, vol. 11, no. 12, pp. 4243-4251, Dec. 2012.

[15] Z. Shi, Low-Density Hybrid-Check Coded Superposition Mapping and its Application in OFDM and MIMO. Dissertation, Faculty of Engineering, University of Kiel, 2014.

[16] G.J.M. Forkel and P.A. Hoeher, "Constrained intensity superposition: A hardware-friendly modulation method," IEEE/OSA Journal of Lightwave Technology, vol. 36, no. 3, pp. 658-665, Feb. 2018.


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