Multiple Antennas Based Collaborative Spectrum Sensing Techniques
Mobile radio network with cellular structure demand high spectral efficiency for minimizing number of connections in a given bandwidth. Cognitive Radio is the effective utility of spectrum based on the criteria such as the time, transmitted wave and frequency. Increased users in the wireless world paved the way for the deployment of spectral efficiency which is easily achieved by the concept of cognitive. CR provides better bandwidth efficiency in spectrum utility.
The objective of this chapter is to provide the readers the advancements in antenna techniques. It also helps them to understand the concept of antenna, algorithm involved in design and the structure implementation. The thrust of next generation mobile, afford the development in the technologies. This chapter delivers an impression of the state of research and investigations into smart antennas and their potential utility in commercial mobile radio networks. Antennas embodying these techniques are generally referred to as smart antennas because their characteristics are adapted to the signal regime in which they are situated. Although some authors distinguish between smart, intelligent and adaptive antennas, the terms are effectively synonymous.
A smart antenna is actually combination of an array of individual antenna elements and dedicated signal processing algorithm. Smart antenna is used to efficiently utilize the limited radio frequency. Adaptive beamforming algorithms are used to receive signal from desired direction. The performance of adaptive LMS, RLS, SMI, CMA and Vector RLS algorithm for smart antenna are analyzed. The vector RLS beamforming algorithm is an effective algorithm for weight vector adjustment in many smart antenna applications because of its linear computational complexity and high convergence ratio that provide optimal solution.