This paper proposes a weighted large margin nearest center (WLMNC) distance-based human depth recovery method for tele-immersive video interaction systems with limited bandwidth consumption. In the remote stage, the proposed method highly compresses the depth data of the remote human into skeletal block structures by learning the WLMNC distance, which is equivalent to downsampling the human depth map at $64{\times}$ the sampling rate. In the local stage, the method first recovers a rough human depth map based on a WLMNC distance augmented clustering approach and then obtains a fine depth map based on a rough depth-guided autoregressive model to preserve the depth discontinuities and suppress texture copy artifacts. The proposed WLMNC distance is learned by the large margin clustering problem with a weighted hinge loss to balance the clustering accuracy and depth recovery accuracy and is verified to be able to preserve depth discontinuities between skeletal block structures with occlusion. A theoretical analysis is conducted to verify the effectiveness of using the weighted hinge loss. Furthermore, a novel data set containing various types of human postures with self-occlusion is built to benchmark the human depth recovery methods. The quantitative comparison with the state-of-the-art depth recovery methods on the introduced benchmark data set demonstrates the effectiveness of the proposed method for human depth recovery with such a high upsampling rate.

Abstract Ranging is one of the most important processes in the mobile worldwide interoperability for microwave access (WiMAX) standard, for resolving the uplink synchronization and near/far problems. In this paper, we focus on the multi‐user carrier frequency offset (CFO) estimation in both initial ranging and periodic ranging. After the analysis of some existing ranging methods, we propose two algorithms based on the correlation properties of pseudo noise (PN) sequences in time domain and frequency domain respectively. The root mean square error (RMSE) performance is evaluated in both additive white Gaussian noise (AWGN) channel and multi‐path fading channel. Simulation results show that the proposed frequency‐domain cross‐correlation method performs better than the proposed time‐domain cross‐correlation method, and is more robust to multi‐user interference and residual timing offset. Copyright © 2009 John Wiley & Sons, Ltd.

Wordwide interoperability for microwave access (WiMAX), or the IEEE 802.16d/e standard, is a technology for broadband wireless access (BWA) with significant market potential. In this paper, we propose a base station (BS) physical layer (PHY) transceiver solution for WiMAX orthogonal- frequency division-multiplexing access (OFDMA) mode. Our aim is to provide a single chip solution for baseband processing of WiMAX PHY. The data throughput should achieve 20 Mbps both for uplink and downlink. The solution is implemented on cell broadband engine, which is a multicore processor jointly developed by IBM, SONY and Toshiba for high performance computing(HPC). Algorithms for symbol timing offset, carrier frequency offset, channel estimation and space-frequency block code (SFBC) are embedded in this transceiver. Simulation and real test on Cell show that the proposed solution can fulfill the bit-error-rate (BER) requirements under most situations.