Due to its high-performance broadcast capability, -ary phase-shift-keying (MPSK) direct sequence code division multiple access (DS/CDMA) technique is widely used in terrestrial and satellite communications to provide wired/wireless services such as audio broadcasting, video broadcasting and high-speed data transmission. However, both coherent and noncoherent MPSK modulation schemes are sensitiv...

Due to the constraint of cost and size for mobile wireless communication terminals, many orthogonal frequency division multiplexing (OFDM)-based systems required the same crystal driving the sampling and the channel frequencies, which leads to the challenge of a more comprehensive sampling clock synchronization scheme needed. In this article, the effect of sampling clock error on the system per...

The two most important parameters to be considered while designing an OFDM based communication system are phase noise and carrier frequency offset (CFO). It has been observed that the OFDM systems are very sensitive to phase noise and CFO, and an accurate prediction of the tolerable values of these parameters can help the system to relax the specifications. This paper analyses the performance o...

In this paper, challenges regarding the provision of channel state information (CSI) and carrier frequency synchronization for multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) systems with null subcarriers are addressed. We propose a novel maximum likelihood (ML) based scheme that estimates the aggregate effects of the channel and carrier frequency offset (C...

The frequency hopping (FH) based ultra-wideband (UWB) communication system divides its available frequency spectrum into several sub-bands, which leads to inherent disparities between carrier frequencies of each sub-band. Since the propagation loss is proportional to the square of the transmission frequency, the propagation loss on the sub-band having the highest carrier frequency is much large...

Orthogonal Frequency Division Multiplexing (OFDM) has recently been used widely in wireless communication systems. OFDM is very effective in combating inter-symbol interference and can achieve high data rate in frequency selective channel. For OFDM communication systems, the frequency offsets in mobile radio channels distort the orthogonality between subcarriers resulting in Inter Carrier Inter...

In Orthogonal Frequency Division Multiplexing (OFDM) carriers are orthogonally related and hence no guard band is necessary like in Frequency Division Multiplexing (FDM). So spectrums of users can overlap which enhances the spectrum efficiency of the network. In this thesis one of the main concern of OFDM, inter carrier interference (ICI) is considered using different window functions in freque...

In this paper we present an analytical approach to evaluate the M-QAM symbol error rate (SER) of Alamouti space time coded OFDM direct conversion receivers subject to carrier frequency offset (CFO), channel estimation errors, outdated channel state information, limited ADC resolution and flat receiver I/Q imbalance in Rayleigh time and frequency selective fading channels. The SER is numerically...

Orthogonal frequency division multiplexing (OFDM) systems are known to be sensitive to carrier frequency offset (CFO). This paper is concerned with the CFO estimation for multiple input multiple output (MIMO)systemsemployingOFDMwaveforms. We present two approaches to derive maximum likelihood (ML) pilot-assisted frequency estimators that use either two or multiple identical training symbols. It...

In this study, we use hierarchical modulation technology to estimate the carrier frequency offset (CFO) caused by the Doppler effect; and hierarchical modulation has been implemented in the orthogonal frequency-division multiplexing (OFDM) system. Different threshold levels have been used to demodulate various bits of the hierarchical modulated symbols and it has the characteristic that the bit...