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In this paper, QR-RLS based IIR adaptive channel TEQ(Time Domain Equalizer) to make the OFDM systems robust for delay spreads exceeding the CP(cyclic prefix) is presented. IIR based TEQ results in much shorter length equalizer compared to FIR based TEQ, at the same time guarantee for global convergence within the training period. The length of zeros of the proposed QR-IIR TEQ is restricted to CP. Givens rotation based QRD updation of TEQ coefficients results in computational advantage. The performance of the proposed method is then compared with conventional LMS and QR-FIR TEQ in terms of convergence, computational complexity and BER. The simulation results show that proposed QR-IIR method gives better results as compared to the aforementioned methods.

World University root node

Electrical Engineering

(SoE) School of Engineering

2007 3rd International Conference on Wireless Communication and Sensor Networks, WCSN

QR-RLS based adaptive channel shortening IIR-TEQ for OFDM wireless LAN

A new computationally efficient channel shortening technique, to make the OFDM systems robust for delay spreads exceeding the cyclic prefix is presented. The proposed technique gives same BER performance with shorter equalizer. The method is based on pole-zero modeling of the channel impulse response. This gives low computational complexity, both during initialization and data transmission. Moreover no delay search is required as compared with other methods. IEEE 802.11a is considered as underlying OFDM system. ©2007 IEEE.

IEEE Region 10 Annual International Conference, Proceedings/TENCON

A model based channel shortening technique for IEEE 802.11a OFDM system

In this paper, increase in data rate is achieved by removing the cyclic prefix between the OFDM symbols. The intersymbol interference and intercarrier interference caused by the removal of cyclic prefix are removed by equalization. We propose two methods of equalization. In the first method, the zero frequency domain equalization (ZF-FEQ) is done by making use of spill over in the unused carriers. The pre-FFT time domain Equalizer minimizes the noise amplification caused by ZF-FEQ. In the second method, the Inter Symbol Interference and Inter Carrier Interference are removed at the transmitter itself by transmitting data in the unused carriers, which is the combination of data in the used carriers. The requirement of power in the unused carriers increases as the length of the channel increases. Using the TEQ, the effective length of the channel is reduced to minimum. The simulation results are presented in support of these two methods.

Enhancing data efficiency in IEEE- 802.11a using frequency and time domain equalization

Tracking of multiple targets by using only the bearing information is an important problem in passive sensing scenarios such as passive sonar or infrared seeker applications. In this paper, a new algorithm is presented to adaptively estimate the DOA's of multiple moving targets when Linear Equispace Array (LES) is used for making the measurements. These algorithms are based on Differential MUSIC method. The results obtained by these algorithms are then applied as input to a Non-Linear state linear Measurement unscented filter. The unscented filter based tracker is compared with the EKF based tracker. Simulation results show that the former is superior to the latter.