MB-OFDM Based UWB Systems Research Articles

Low-Complexity Fine Frequency Synchronization for MB-OFDM Based UWB Systems

Low-Complexity Fine Frequency Synchronization for MB-OFDM Based UWB Systems

Channel Estimation Algorithms for MB-OFDM Based UWB System

To achieve an accurate channel impulse response (CIR) during channel equalization and coherent detection, the channel estimation plays an important role to the performance of system, especially the receiver. In this paper, we investigated two main kinds of channel estimation methods for MB-OFDM based UWB system. The performances are compared using MATLAB simulation. The simulation shows the NBIDCE algorithm has better performance for WBAN-based healthcare systems.

Carrier Frequency Offset and I/Q Imbalance Compensation for MB-OFDM Based UWB System

Two types of wireless communication system imperfections, namely carrier frequency offset (CFO) and in-phase/quadrature-phase (I/Q) imbalance, are addressed in this paper. We propose an efficient time domain CFO and I/Q imbalance estimation and compensation scheme for multi-band orthogonal frequency division multiplexing based ultra-wideband system. In this scheme, a data-aided CFO estimation algorithm, which is robust to a large I/Q imbalance, is presented. Also, a time domain I/Q imbalance estimation algorithm based on partially CFO compensated preambles is introduced. Finally a two-step joint CFO and I/Q imbalance compensation scheme is developed. Taking full advantage of the ECMA-368 preamble symbols, the proposed scheme is competent for large I/Q imbalance (2-dB gain error and 20-deg Phase error) and carrier frequency offset (50 ppm), and the results are confirmed by simulations.

Synchronization, Channel Estimation, and Equalization in MB-OFDM Systems

This paper addresses preamble-based low complexity synchronization, channel estimation and equalization for Zero-padded (ZP) MB-OFDM based UWB systems. The proposed synchronization method consists of sync detection, coarse timing estimation, fine timing estimation, and oscillator frequency offset estimation. The distinctive features of MB-OFDM systems and the interplay between the timing and carrier frequency hopping at the receiver are judiciously incorporated in the proposed synchronization method. In order to apply the low complexity one-tap frequency-domain equalizer, the required circular convolution property of the received signal is obtained by means of an overlap-add method after the frequency offset compensation. The proposed low complexity channel estimator for each band is developed by first averaging the over-lapadded received preamble symbols within the same band and then applying time-domain least-squares method followed by the discrete Fourier transform. We develop an MMSE equalizer and its approximate version with low complexity. We also derive the probability density functions of the UWB channel path delays, and using them we present several optimization criteria for our proposed synchronization, channel estimation, and equalization. The effectiveness of our proposed methods and optimization criteria are confirmed by computer simulation results.