Mobile OFDM refers to OFDM systems with fast moving transceivers, in contrast to traditional OFDM systems whose transceivers are stationary or have a low velocity. In this paper, we use the basis expansion model (BEM) to model time-varying OFDM channels. Using different BEM’s, we investigate various architectures to implement the least-squares (LS) channel estimation and its corresponding zero-...

Orthogonal frequency division multiplexing (OFDM) is a promising technique for high-data-rate wireless communications because it can combat inter-symbol interference (ISI) caused by the dispersive fading of wireless channels. The proposed research focuses on techniques that improve the performance of OFDM based wireless communications and its commercial and military applications. In particular,...

For wireless transmission, the channel estimation is necessary to improve the performance of receiver. In the ultra-wideband (UWB) wireless systems, there are two practicable modulation schemes: orthogonal frequency-division multiplexing (OFDM) and single-carrier direct-sequence UWB (DS-UWB). The OFDM based scheme is an attractive mode because it can capture the multipath energy more efficientl...

Time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) has advantages in spectral efficiency and synchronization. However, its iterative interference cancellation algorithm will suffer from performance loss especially under severely fading channels with long delays and has difficulty supporting high-order modulations like 256 QAM, which may not accommodate the emerging ul...

In this paper a novel detection scheme for guard interval free OFDM is presented, that uses the Frequency Domain Channel Length Indicator (FCLI) algorithm for improved channel estimation and joint channel impulse response length estimation. In contrast to traditional OFDM, omitting the guard interval (GI) can achieve a significant enhancement of throughput and spectral efficiency. Conversely, t...

The combination of multiple-antenna and orthogonal frequency division multiplexing (OFDM) provides reliable communications over frequency selective fading channels. We investigate this approach and focus on the application of space-time block codes (STBC) and space-frequency block codes (SFBC) in OFDM systems. We compare the performance of maximum likelihood (ML), zero forcing (ZF) and conventi...

In the present scenario, there is a rising demand of high capacity, high performance and low Bit Error Rate (BER) in Wireless Communication systems. The Orthogonal Frequency Division Multiplexing (OFDM) is an attractive multi carrier modulation technique for wireless transmission systems. In this paper, we discuss the effect of Doppler frequency in Fast Fourier Transform (FFT) based OFDM system...

IEEE 802.11ad is an enhancement to the IEEE 802.11 family standard, that enables multi-gigabyte wireless communication in 60 GHz. In this paper, we propose a unique pilot design and corresponding channel estimation method for a frequency selective fading 60 GHz channel. It is shown that in our proposed channel estimation the number of pilot subcarrier are fixed in one OFDM symbol, but the pilot...

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technique, which divides the available spectrum into many subcarriers, each one being modulated by a low data rate stream[1]. Compare with the traditional ways, the OFDM system has the features of resisting frequency selective fading and high frequency-band utility ratio and so on. OFDM has been successfully appli...

This thesis consists of a prologue and six parts that address two aspects of orthogonal frequency-division multiplexing (OFDM) communication systems: synchronization and channel estimation. For the synchronization aspect, focus is on estimators of time and frequency offsets that exploit the cyclic prefix. For the channel estimation aspect, a concept is presented and analyzed that exploits the f...