KEYWORDS: Orthogonal frequency division multiplexing, Niobium, Modulation, Receivers, Data conversion, Signal to noise ratio, Systems modeling, Demodulation, Forward error correction, Data modeling
Orthogonal Frequency Division Multiplexing (OFDM) is a popular technique used to combat frequency selective
fading in multipath channels. When spectral nulls are present in the channel, they can severely degrade or
cancel out several OFDM tones, resulting in an irreducible error rate. In Code-Spread OFDM (CS-OFDM), each
sinewave carries a weighted sum of all the information symbols being transmitted in an OFDM block interval.
In this paper, an MMSE estimator is derived for each symbol for a number of cases, including when the number
of carriers is greater than the number of symbols. The performance of CS-OFDM is evaluated using Hadamard,
Vandermonde, and Discrete Cosine spreading and compared to standard OFDM.
KEYWORDS: Antennas, Orthogonal frequency division multiplexing, Signal to noise ratio, Receivers, Telecommunications, Transmitters, Signal processing, Modulation, Interference (communication), Binary data
In this paper, a new method of space-time processing is proposed for Orthogonal Frequency Division Multiplexing
(OFDM) using complementary pairs of Golay sequences. Space-time processing with complementary Golay
sequences provides diversity at the transmitter which in turn helps improve performance in multipath fading
channels without the need for channel knowledge at the transmitter. The autocorrelative properties of complementary
Golay pairs allows multiple data signals at the transmitter to be perfectly separated at the receiver.
Further, these properties significantly boost the signal energy at the receiver, leading to a higher SNR and thus
better bit error performance. Building on work done in the field of orthogonal space-time block codes, the new
Golay method is proposed and derived for both a 2×1 and 2×2 MIMO-OFDM system with a channel exhibiting
Rayleigh fading; at the receiver, symbol estimation is effected via minimum mean-square estimation (MMSE).
Orthogonal Frequency Division Multiplexing (OFDM) is a popular technique used to combat frequency selective
fading in multipath channels. When spectral nulls are present in the channel, they can severely degrade or cancel
out several OFDM tones, resulting in an irreducible error rate. Code-Spreaded OFDM (CS-OFDM) combines
the characteristics of OFDM and Code Division Multiple Access (CDMA) to create a more robust modulation
scheme which provides substantial performance improvements relative to standard OFDM. In CS-OFDM, each
sinewave carries a weighted sum of all the information symbols being transmitted in an OFDM block interval. In
this paper, an MMSE estimator is derived for each symbol for a number of cases, including when the number of
carriers is greater than the number of symbols. The performance of CS-OFDM is analyzed and shown to provide
substantial improvements relative to standard OFDM, especially in the latter case.
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