Image Processing Reference
In-Depth Information
The experiments are carried out with an input signal composed of three complex sine-
signals of different frequencies, mixed with white noise. Fig. 10 displays learning curves for
the coefficients  1 ,  2 and  3 . The ACFB shows the high efficacy of the parallel filtering
process. The main advantages of both the adaptive filter structure and the ACFB lie in their
low computational complexity and rapid convergence of adaptation.
Fig. 10. Learning curves of an ACFB consisting of three complex LS1-sections
2.2 Narrowband interference suppression for MIMO systems using adaptive complex
filtering
The sub-sections which follow examine the problem of narrowband interference in two
particular MIMO telecommunication systems. Different NBI suppression methods are
observed and experimentally compared to the complex DSP technique using adaptive
complex filtering in the frequency domain.
2.2.1 NBI Suppression in UWB MIMO systems
Ultrawideband (UWB) systems show excellent potential benefits when used in the design of
high-speed digital wireless home networks. Depending on how the available bandwidth of
the system is used, UWB can be divided into two groups: single-band and multi-band (MB).
Conventional UWB technology is based on single-band systems and employs carrier-free
communications. It is implemented by directly modulating information into a sequence of
impulse-like waveforms; support for multiple users is by means of time-hopping or direct
sequence spreading approaches.
The UWB frequency band of multi-band UWB systems is divided into several sub-bands. By
interleaving the symbols across sub-bands, multi-band UWB can maintain the power of the
transmission as though a wide bandwidth were being utilized. The advantage of the multi-
band approach is that it allows information to be processed over a much smaller bandwidth,
thereby reducing overall design complexity as well as improving spectral flexibility and
worldwide adherence to the relevant standards. The constantly-increasing demand for
higher data transmission rates can be satisfied by exploiting both multipath- and spatial-
diversity, using MIMO together with the appropriate modulation and coding techniques
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