Frequency offset estimation for MB-OFDM-based UWB systems

Circuits Syst Signal Process

2009

This paper presents a highly accurate frequency offset estimation algorithm for multi-band orthogonal frequency division multiplexing (MB-OFDM) systems effective for realistic ultra-wideband (UWB) environment. The proposed algorithm derives its estimates based on phase differences in the received subcarrier signals of several successive OFDM symbols in the preamble. We consider different carrier frequency offsets and different channel responses in different bands to keep the analysis and simulation compatible for practical multi-band UWB scenario. Performance of the proposed algorithm is studied by means of bit error rate (BER) performance of MB-OFDM system. In order to compare the variance of the synchronizer to that of the theoretical optimum, we derive the Cramer-Rao lower bound (CRLB) of the estimation error variance and compare it with the simulated error variance both in additive white Gaussian noise and UWB channel model (CM) environments, CM1-CM4. Next, we modify the estimation algorithm by proposing a multi-band averaging frequency offset synchronization (MBAFS) scheme. We establish superior BER performance with MBAFS compared to our first scheme. We calculate modified CRLB for MBAFS and compare it with simulation results for CM1-CM4. Both analysis and simulation show that MBAFS algorithm can estimate the carrier frequency offset effectively and precisely in UWB fading channels for MB-OFDM applications. We also analyze the computational complexity of both the proposed algorithms in order to verify their feasibility of implementation in practical UWB receiver design.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Technique for Frequency Synchronization in Multi-Band OFDM in Realistic UWB Channel

Circuits Syst Signal Process

2009

“…The model of the impulse response of a RF UWB channel is given in [9]. Its equivalent complex base band impulse response component (CIR) applicable for band 'b' can be shown as [11],…”

Section: Introductionmentioning

confidence: 99%

An Adaptive Timing Synchronization Scheme for Multi-Band Orthogonal Frequency Division Multiplexing Based Ultra-Wideband Communication Systems

2009

Wireless Pers Commun

This article deals with a new energy based adaptive timing synchronization scheme (ATS) which estimates the symbol timing information within two (2) OFDM symbols and updates the information with different frequency bands (adaptive in sense) in a multi-band orthogonal frequency division multiplexing (MB-OFDM) based system. The new approach provides significant improvement in system performance for high delay spread ultra-wideband (UWB) channel model (CM) environments where fast and low-complexity timing synchronization is a critical issue. This paper also addresses a crucial aspect of UWB channel which is frequency dependent delay characteristics. This effect contributes to different dispersion and timing shift of an UWB signal for different frequency bands. In this work, the wideband channel delay characteristics are studied and delay parameters are found considerably different over frequency bands 3.1-4.6 GHz. Based on this observation, the ATS which estimates and maintains the timing delays of each band separately is presented. The performance of ATS algorithm is measured by mean-squared error (MSE), synchronization probability, signal to interference ratio (SIR) reduction due to synchronization errors and bit error rate (BER) through the computer simulation for several UWB CM environments CM2-CM4. Each of these UWB CMs is simulated for 100,000 noisy channel realizations for both coded and uncoded MB-OFDM system. It is shown that ATS gives signal-to-noise ratio (SNR) improvement of 1.1 dB at BER of 1 × 10 −3 , 1.2 dB at BER of 2 × 10 −4 , and 0.7 dB at BER of 2×10 −4 for CM4, CM3, and CM2 respectively for coded MB-OFDM system over a non-adaptive synchronization scheme [Yak et al.

“…The frequency offset estimation algorithms for MB-OFDM system is reported in [2][3][4], and [5]. Yak et al [2] derived the maximum likelihood (ML) estimator for frequency offset following [6] using the last two successive OFDM symbols of the packet synchronization (PS) sequence of the preamble after timing synchronization.…”

mentioning

confidence: 99%

Frequency Offset Estimation by Multi-Band Averaging Method: A New Approach for MB-OFDM Based Ultra-Wideband Communication System

2009

Wireless Pers Commun

In this literature, we present a new method for estimating the coarse frequency offset in multi-band orthogonal frequency division multiplexing (MB-OFDM) based ultrawideband (UWB) communication systems. The proposed training based coarse frequency offset (CFO) estimator performs an averaging of initial estimate over the multiple bands of transmission during estimation process. The proposed multi-band averaging provides an improved estimation of approximately three times for band group 1 (BG1) compared to our earlier proposed scheme. To prove the efficiency of the proposed scheme, the Cramer Rao lower bound (CRLB) of the estimation error is calculated and compared with the simulation results. We illustrate the performance of MB-OFDM system in terms of bit-error rate (BER) with multi-band averaged frequency synchronization (MBAFS) and compare with earlier reported results for 100,000 noisy realizations in UWB channel model 2 (CM2).