Symbol timing recovery for generalized minimum shift keying modulations in software radio receiver

A new symbol timing estimator for generalized MSK signals is proposed. It is based on the squaring algorithm and has a feedforward structure. The proposed timing estimator is fully-digital and is suitable for implementation in software radios. The performance in AWGN channel is compared with the Modified Cramer-Rao bound and that of the ML algorithm. The proposed timing estimator is found to have a performance close to that of the ML algorithm, but with a lower implementation complexity.published_or_final_versio

FPGA implementation of digital timing recovery in software radio receiver

This paper describes an implementation of an all-digital timing recovery scheme. Squaring nonlinearity is employed to generate the timing estimate and an IIR is used to extract the spectral component at symbol rate. Hardware design is performed using VHDL and realized in FPGA. The whole design can be fitted into an Altera EPF1OK70 FPGA chip, with 95.5% utilization of logic elements and 22% utilization of memory bits. The implementation exploits features of FPGA, which enable easy implementation of look up table and variable data precision at different nodes.published_or_final_versio

New implementation of a GMSK demodulator in linear software radio receiver

This paper proposes a practical linear software-radio architecture (dealing with linear modulations) that is suitable for multi-mode operation. In particular, it is shown how to integrate GMSK into the proposed architecture. Coherent and noncoherent detections of GMSK signals are detailed for the implementation of the proposed software radio.published_or_final_versio

Symbol timing recovery for GMSK modulation based on squaring algorithm

A new all-digital symbol timing estimator for GMSK signals is proposed. It is based on the squaring algorithm and has a feedforward structure. Performance in AWGN channel is assessed by computer simulation, and is compared with the modified Cramer-Rao bound and other existing algorithms. The performance of the proposed estimator is shown to be close to that of ML algorithm.published_or_final_versio

Impacts of multipath fading on the timing synchronization of IEEE 802.11a wireless LANs

The timing-synchronization performance of IEEE 802.11a wireless LANs on multipath Rician fading channels is investigated. Simulation results yield the following observations. A higher Rician factor gives a better performance. At low signal-to-noise conditions, the multipath-diversity gain enables an improvement in the synchronization performance but at high signal-to-noise conditions, irreducible probabilities of synchronization failure, which cannot be reduced even if the signal power is increased, occur. A more dispersive channel gives a poorer synchronization performance, and the performance is poor for Rayleigh fading environments.published_or_final_versio

Design of multiplierless correlators for timing synchronization in IEEE 802.11a wireless LANs

Timing synchronization for IEEE 802.11a WLANs requires using a correlator to correlate the received signal with a known waveform. Straightforward implementation of this correlator results in the need to perform 320 million complex multiplications per second. This significant requirement can be eliminated by using multiplierless correlators. In this paper, multiplierless correlators are designed based on constraining the real and imaginary parts of correlator coefficients to be sums of powers of two. Sets of coefficients that yield good synchronization performance for simple A WGN channels are first identified; then their goodness for indoor communication environments is verified by simulation for multipath fading channels. Several multiplierless correlators are found. Comparison among these correlators identifies a good one that requires to perform only 26 addition/subtraction operations per correlator output while a similar synchronization performance can be maintained.published_or_final_versio

Timing-Synchronization Analysis for IEEE 802.11a Wireless LANs in Frequency-Nonselective Rician Fading Environments

This paper derives and computes the probability of synchronization failure Pfail for IEEE 802.11a wireless LANs on frequency-flat Rician fading channels. For a frequency offset within ±232 kHz, it is shown that its effect on the synchronization performance is minor. The Eds/N 0 ratios required to achieve Pfail = 10-3 and 10-4 are computed, where Eds is the data-symbol energy. We find that Eds/N0 ratios over 20 dB are generally required for channels with Rician factors K ≤ 6 dB. In particular, E ds/N0 ratios that yield Pfail = 10-4 exceed 30 dB for K ≤ 4 dB.published_or_final_versio

Semi-blind CFO, channel estimation and data detection for ofdm systems over doubly selective channels

Proceedings of the IEEE International Symposium on Circuits and Systems, 2010, p. 1887-1890Semi-blind joint CFO, channel estimation and data detection for OFDM systems over doubly selective channels (DSCs) is investigated in this work. A joint iterative algorithm is developed based on the maximum a posteriori expectation-maximization (MAP-EM) algorithm. In addition, a novel algorithm is also proposed to obtain the initial estimates of CFO and channels. Simulation results show that the performance of the proposed CFO and channel estimators approaches to that of the estimators with full training at high SNRs. Moreover, after convergence, the performance of data detection is close to the ideal case with perfect CFO and channel state information. ©2010 IEEE.published_or_final_versionThe IEEE International Symposium on Circuits and Systems (ISCAS), Paris, France, 30 May-2 June 2010. In Proceedings of ISCAS, 2010, p. 1887-189

IQ imbalance compensation: A semi-blind method for OFDM systems in fast fading channels

Proceedings of the IEEE Asia-Pacific Conference on Circuits and Systems, 2010, p. 362-365In this paper, an orthogonal frequency division multiplexing (OFDM) system operating in a fast fading environment modeled by a doubly selective channel (DSC) is considered. The paper first reformulates a commonly adopted system model using the generalized complex exponential basis expansion technique. The resulting model enables the IQ imbalance and DSC to be estimated in the time domain with a small number of scattered pilots within an OFDM symbol. A joint estimation and compensation scheme is then proposed which compensates all the inter-carrier interference terms. Simulation results show that the proposed compensation method achieves better symbol error rate performance than previous proposed methods. © 2010 IEEE.published_or_final_versionThe IEEE Asia Pacific Conference on Circuits and Systems (APCCAS'2010), Kuala Lumpur, Malaysia, 6-9 December 2010. in Proceedings of APCCAS'2010, 2010, p. 362-36

ML symbol synchronization for OFDM-based WLANs in unknown frequency-selective fading channels

Based on the maximum-likelihood principle and the preamble structure of IEEE 802.11a WLAN standard, this paper proposes a new symbol synchronization algorithm for IEEE 802.11a WLANs over frequency-selective fading channels. In addition to the physical channel, the effects of filtering and unknown sampling phase offset are also considered. Loss in system performance due to synchronization error is used as a performance criterion. Computer simulations show that the proposed algorithm has comparable performances to the algorithm based on the generalized Akaike information criterion (GAIC), but the proposed algorithm exhibits reduced complexity. © 2004 IEEE.published_or_final_versio