Hamid, Hamood Shehab
(2010)
Development And Implementation Of Improved Coded OFDM System Using SDR Platform.
PhD thesis, Universiti Sains Malaysia.
Abstract
he increasing demand for high speed wireless connectivity at low cost poses new
challenges for communication system designers, to implement solutions that increase
the data rate by utilizing the limited radio resources more efficiently at a low
additional complexity. Adaptive Coding and Modulation (ACM) exploits the
flexibility of channel coding and constellation in Orthogonal Frequency Division
Multiplexing (OFDM) to obtain higher data rates. This technique employs multiple
modulation and coding schemes to instantaneously adapt to the variations in the
channel Signal to Noise Ratio (SNR), thus maximizing the system throughput and
improving Bit Error Rate (BER) performance. On the other hand, OFDM system
suffers from inter-symbol interference (ISI), especially in mobile communication
environments. This problem may be tackled by increasing the individual symbol
duration for each subcarrier together with the use of guard time. Nevertheless, this
does not solve the problem completely in multipath fading channel, because all
subcarriers will arrive at the receiver with different amplitudes. Unfortunately, some
subcarriers may be completely lost because of deep fades. Hence even though most
subcarriers may be detected without errors, the overall BER will be largely
dominated by a few subcarriers with bad SNR. To eliminate this problem, OFDM
based systems usually employ a special technique like error correction coding
(ECC). Various coding methods are adopted by many standards to mitigate the
effects of frequency selective channel which causes bit errors to occur in burs
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