Non-orthogonality among adjacent OFDM channels creates OFDM adjacent channel interference and it heavily affects the entire system’s performance. Conventional methods to avoid OFDM adjacent channel interference are not only insufficient but also are wasting a lot of frequency resources. In this research, a method using combinations of modulation
schemes is proposed to avoid effects of OFDM adjacent channel interference. It can be obtained by modulating the sub-carriers at the outer sides of an OFDM channel with lower order modulation schemes (such as BPSK or QPSK), while modulating the sub-carriers at the inner side of the OFDM channel with higher order modulation schemes (such as 16QAM or 64QAM). Intensive simulations have been carried out to evaluate the performance of the
proposed method. The simulation results have shown an increase in the OFDM system’s resistance against adjacent channel interference while still maintain the bandwidth efficiency.
Table of Contents
- Abstract
- Introduction
- OFDM adjacent channel interference
- Conventional Methods
- Windowing
- Filtering
- Guard-band and virtual sub-carrier
- Forward Error Correction coding
- Adaptive modulation
- Combinations of modulation schemes
- Performance of OFDM modulation schemes
- Proposal
- Simulation model and results
- Simulations of the proposed method
- Optimization
- Conclusion
- Acknowledgments
- References
Objectives and Key Themes
This work aims to investigate and propose a method to mitigate the effects of adjacent channel interference (ACI) in Orthogonal Frequency-Division Multiplexing (OFDM) systems. The study explores various conventional ACI mitigation techniques and introduces a novel approach using combinations of modulation schemes.
- Adjacent Channel Interference (ACI) in OFDM systems
- Performance analysis of different OFDM modulation schemes (BPSK, QPSK, 16QAM, 64QAM)
- Development and evaluation of a novel ACI mitigation method using modulation scheme combinations
- Simulation and optimization of the proposed method
- Comparison of the proposed method with conventional ACI mitigation techniques
Chapter Summaries
The introduction sets the context for the research on adjacent channel interference in OFDM systems. Chapter 2 details the nature of OFDM adjacent channel interference. Chapter 3 reviews conventional methods for mitigating this interference, including windowing, filtering, guard bands, error correction, and adaptive modulation. Chapter 4 presents the core of the research, introducing a novel approach utilizing combinations of modulation schemes to combat ACI. This chapter includes performance evaluations and simulations of the proposed method, along with optimization strategies. Note that the conclusion and results are not included in this preview.
Keywords
OFDM, adjacent channel interference, modulation schemes (BPSK, QPSK, 16QAM, 64QAM), error correction, adaptive modulation, simulation, mitigation techniques.
- Quote paper
- Master of Science in Engineering Le Tien Anh (Author), 2008, Avoiding Effects of OFDM Adjacent Channel Interference by Using Combinations of Modulation Schemes, Munich, GRIN Verlag, https://www.grin.com/document/120771
