Abstract
Whenever a communication system operates in a time-frequency dispersive radio channel, the link adaptation provides a benefit in terms of any system performance metric by employing time, frequency, and, in case of multiple users, multiuser diversities. With respect to an orthogonal frequency division multiplexing (OFDM) system, link adaptation includes bit, power, and subcarrier allocations. While the well-known water-filling principle provides the optimal solution for both margin-maximization and rate-maximization problems, implementation complexity often makes difficult its application in practical systems. This paper presents a few suboptimal (low-complexity) adaptive loading algorithms for both single- and multiuser OFDM systems. We show that the single-user system performance can be improved by suitable power loading and an algorithm based on the incomplete channel state information is derived. At the same time, the power loading in a multiuser system only slightly affects performance while the initial subcarrier allocation has a rather big impact. A number of subcarrier allocation algorithms are discussed and the best one is derived on the basis of the order statistics theory.
Highlights
For a few last decades, the orthogonal frequency division multiplexing (OFDM) has gained a lot of practical and research interest because of the number of advantages that this technique exhibits compared with the single carrier modulation formats
We consider practical approaches to the problem of optimal resource allocation in OFDM-based systems. We study both single- and multiuser systems and show that the single-user system performance can be improved by a suitable power loading and an algorithm based on the incomplete channel state information is derived
We show that in a multiuser system the power loading only slightly affects performance while the initial subcarrier allocation has a rather big impact
Summary
For a few last decades, the orthogonal frequency division multiplexing (OFDM) has gained a lot of practical and research interest because of the number of advantages that this technique exhibits compared with the single carrier modulation formats. The ordered subcarrier selection algorithm (OSSA) [15] results in a good BER performance close to optimal in a Rayleigh environment and its implementation complexity is very low because it is noniterative and employs a constant constellation size. This method requires the CSI only in terms of “used-not used” subcarriers. One adaptive initial subcarrier allocation algorithm was presented and analyzed in [24] and it was shown that the application of the OSSA provides a significant power gain while the procedure of implementation is noniterative.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: EURASIP Journal on Wireless Communications and Networking
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
