Abstract
Orthogonal Frequency Division Multiplexing
(OFDM) allow data to be transmitted efficiently and reliably by
using multiple orthogonal subcarriers. It provides robustness
against noise and corruption in the channel. The channel
can be either wired or wireless depending on the particular
application. Due to the close spacing of subcarriers, OFDM
is susceptible to corruption caused by various narrowband
signals such as Narrowband Interference (NBI). Spectral
shaping shapes the Power Spectral Density (PSD) in order
to have certain properties. Spectral shaping might improve
the effectiveness of OFDM and make it sustainable in the
long run for applications beyond the 4th generation of mobile
communications (4G) and Long Term Evolution (LTE). We
make use of spectral null codes and load them onto OFDM
subcarriers. Introducing narrowband signals in the channel
degrades the system’s performance and also eliminates the
designed spectral properties. From this observation we infer that
some narrowband noise is present in the channel. Previously,
carriers hit by NBI or other narrowband noise had to be
switched off manually. We found that combining OFDM with
spectral shaping allows the presence of Narrowband signals in
the channel to be detected and conclusions can be drawn over
the channel quality. This did not improve the system in terms
of bit error rate performance.