Performance comparison of LS, LMMSE and Adaptive Averaging Channel Estimation (AACE) for DVB-T2

© 2015 IEEE. In this paper the performance of the Adaptive Averaging Channel Estimator (AACE-LS) which is a modified Least Square (LS) estimator and the AACE-LMMSE which is a modified Linear Minimum Mean Error (LMMSE) estimator, are compared with respect to the conventional LS and the LMMSE estimators. The AACE is an estimator which is based on the averaging of the last N Scattered Pilots (SP) from the DVB-T2 model carried in the received OFDM symbols. The proposed method could in general be applied to any pilot based estimator. The noise introduced by the channel is considered as Additive White Gaussian Noise (AWGN) with zero mean and thus an averaging process is used to eliminate it. The estimator adaptively follows the fluctuations of the amplitude envelope in the time domain and adapts the size of the buffer N, with respect to the coherence time (Tc). Finally, based on the averaged estimated channel, the LS or the LMMSE equalizer is applied to the received signal in the frequency domain. Simulations clearly show that the performance of the AACE-LS is superior to the conventional LS estimator and is near to the performance of the LMMSE with no need of a prior knowledge of the statistics and the noise of the channel and thus if the channel is unknown to the receiver, the AACE is a good choice

Ipsilateral hip and femoral shaft fractures treated with intramedullary nails

This study retrospectively analysed 34 patients with ipsilateral hip and femoral shaft fractures treated over a period of 10 years between January 1995 and January 2005. They had an average age of 35 years. Twenty-six (76.47%) of these cases suffered high-velocity trauma (RTA); six others had fallen from a height (17.65%), and two had suffered only minimal trauma (5.88%). Twenty were extracapsular (58.82%) and 14 were intracapsular. They were evaluated with an average follow-up of 28 months, both clinically and radiologically; 26 patients (76.47%) had a good result (Friedman and Wyman score). When the intracapsular fracture was detected postperatively, there was one delayed union and one non-union. When the fracture is diagnosed preoperatively, we recommend reconstruction nail fixation. If the hip fracture is diagnosed intra- or postoperatively following nailing of the shaft, we propose the miss-a-nail technique as an option