In this paper, the channel estimation techniques for multiband (MB) OFDM ultra-wideband (UWB) wireless communications are investigated. By combining orthogonal frequency-division multiplexing (OFDM) with multi-band, the MB-OFDM systems can capture multipath energy more efficiently than single-band directsequence UWB (DS-UWB). However, most researches for UWB channel estimation are focused on th...

In this paper, the high spectral efficiency of a transmission scheme called Time frequency training (TFT) Orthogonal frequency division multiplexing (OFDM) using MIMO system is proposed. The time frequency joint channel estimation for TFT-OFDM utilizes the time-domain training sequence without interference cancellation to merely acquire the time delay profile of the channel, while the path coef...

Orthogonal Frequency Division Multiplexing (OFDM) is multiplexing technology of orthogonal multicarrier, and the channel estimation model based on pilot in OFDM systems is analyzed; Now that, the channel estimation based on pilot needs interpolation, in order to reduce the complexity of the interpolation algorithm, the FFT channel estimation algorithm based on pilot is studied. Because of the d...

OFDM may be combined with multiple antennas at both the access point and mobile terminal to increase diversity gain and/or enhance system capacity on a time-varying multipath fading channel, resulting in a multiple-input multiple-output (MIMO) OFDM system. This paper discusses the basic introduction to a general MIMO-OFDM system including the block diagram, governing equation, relevant designin...

A channel estimation method for multiple input multiple output (MIMO)-OFDM with fast fading channels is proposed to increase estimation quality and reduce the computational complexity. Specifically, we use a space-time correlation between channel coefficients, and compensate the ICI term. Since ICI compensation can be obtained without any pilot symbols for target OFDM block, our proposal is pra...

OFDM has been proven to be a viable technique to overcome multipath fading in wireless channels. While OFDM systems convert a multipath fading channel into a series of equivalent flat fading channels they lack the inherent diversity available in multipath channels. Theoretically an uncoded OFDM system needs a simple receiver due to ISI free channel, but their performance deteriorates in the pre...

OFDM has been proven to be a viable technique to overcome multipath fading in wireless channels. While OFDM systems convert a multipath fading channel into a series of equivalent flat fading channels they lack the inherent diversity available in multipath channels. Theoretically an uncoded OFDM system needs a simple receiver due to ISI free channel, but their performance deteriorates in the pre...

Using a priori knowledge of maximum channel impulse response (CIR) length, time domain OFDM channel estimation systems outperforms frequency domain channel estimation. Because CIR length is an unknown quantity at the receiver side, a suitable estimation method is necessary. In this paper, we propose a novel algorithm named FCLI-Frequency Domain Channel Length Indicator, which estimates CIR leng...

In this paper, challenges regarding the provision of channel state information (CSI) and carrier frequency synchronization for orthogonal frequency division multiplexing (OFDM) systems with null subcarriers are addressed. We propose novel maximum likelihood (ML) based schemes that estimate the aggregate effects of the CFO and channel by using two successive OFDM preambles. In the presented sche...

Packet services are dominant in future broadband wireless communications, where hybrid automatic repeat request (HARQ) is used for error control [1]. HARQ schemes combine error detection and forward error correction to make more efficient use of the channel. In type I HARQ, all the necessary parity bits are sent with each transmission. However, type II HARQ sends only the error detection parity...