Thesis
A joint bit-loading and symbol rotation scheme for multi carrier systems
Master of Science (M.S.), Drexel University
Dec 2011
DOI:
https://doi.org/10.17918/00010313
Abstract
Multi-carrier systems have become the core of many communication systems. For the last 50 years, researchers have constantly been refining such solutions to convey large amounts of information. In this thesis, two problems are addressed; i) high peak to average power ratio (PAPR) in multi-carrier systems and ii) throughput improvement in multi-carrier systems by PAPR-aware rate adaptive bit loading. The first issue is one of the biggest drawbacks of Orthogonal Frequency Division Multiplexing (OFDM) systems and the second aims to improve the system data rate in scenarios where the communication system adapts to environmental channel conditions. Towards this goal, two symbol rotation-inversion algorithms that reduce the peak to average power ratio in multi carrier OFDM systems are implemented on a software defined radio platform. One is evaluated in a single input single output (SISO) OFDM system and the second in a multiple input multiple output (MIMO) OFDM communication system. Results from both algorithms show the benefit of PAPR reduction and motivate the proposed novel solution. A new scheme that combines the benefits of bit allocation and symbol rotation to reduce the PAPR is presented, simulated and evaluated. It is demonstrated in simulations by means of post processing signal to noise ratio (PPSNR), throughput and bit error rates, how this new framework succeeds in achieving higher data rates in a more robust way. PAPR remediation in OFDM communication systems can dramatically improve PPSNR and thus improve system range and robustness to noise. When coupled with adaptive bit loading techniques, these PAPR remediation strategies can substantially increase link throughput. For a fixed number of permutations, measurements showed PPSNR improvements of 2dB in SISO OFDM and almost 1dB in MIMO OFDM. Simulations showed that symbol rotation results in more than one order of magnitude BER reduction for SISO OFDM and one order of magnitude reduction in MIMO OFDM. These techniques thus have the potential to significantly improve future multi-carrier communication systems.
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Details
- Title
- A joint bit-loading and symbol rotation scheme for multi carrier systems
- Creators
- Guillermo Andres Sosa Barreto
- Contributors
- Kapil R. Dandekar (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xii, 76 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Electrical (and Computer) Engineering (1970-2026); Drexel University
- Other Identifier
- 991021889072604721