Wireless communication has been one of the fastest-growing areas of electrical engineering in the last decades. More and more advanced methods were developed while the number of wireless devices increased with a growing pace. Simultaneously operating wireless data transmission systems might interfere with one another, and in certain cases this interference might degrade data transmission characteristics.
In conventional spectrum management the frequencies the authority allocates to radio communication services to prevent collision. Some radio communication services however do not use their spectrum continually. As the frequency spectrum readily available for wireless data transmission (e.g. 2.4~GHz band) gets saturated, the need to re-use the frequencies temporarily not used by their selected user emerges. This is what the cognitive radio aims at.
The cognitive radio scheme enables primary and secondary radio communication systems to operate quasi-simultaneously using the same frequency band. This scheme imposes special requirements on the wireless communication devices, this is why OFDM (Orthogonal Frequency Division Multiplexing), the method often used in high-speed data communication systems, might be substituted by alternative, better-suited modulation methods.
In my diploma thesis first I introduce the cognitive radio scheme, then OFDM and 3 other modulation methods. I examine the operation and characteristics of these methods in the cognitive context, and I select the method which might provide the best performance in a cognitive radio system.