Gao Xiqi

Channel estimation algorithms for broadband MIMO-OFDM sparse channel

In the broadband communication, channel impulse response usually exhibits sparse behavior (i.e.. many nearly zero taps). This paper considers the channel estimation of the sparse channel for broadband multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems. Three algorithms for MIMO-OFDM sparse channel estimation are presented and compared: least square channel estimation (LSCE), constraint least square channel estimation (CLSCE) with ideal delay estimation, matching pursuit based channel estimation (MPCE). Mean square error (MSE) performances an also analyzed. Simulation results show that MPCK has better performance than LSCE and is very close to CLSCE under the high SNR, and also MPCE does not require the a priori of channel. Using the MP-based channel estimator, the detection performance is nearly optimal.

Extracting rules from fuzzy neural network by particle swarm optimisation

A four layer fuzzy neural network is presented to realise knowledge acquisition from input-output samples. The network parameters including the necessary membership functions of the input variables and the consequent parameters are tuned and identified using a modified particle swarm algorithm which uses each particles best current performance of its neighbours to replace the best previous one and uses a non accumulative rate of change to replace the accumulative one for accelerating search procedure. The trained network is then pruned so that the general rules can be extracted and explained. The experimental results have shown that the similar classification rules can be obtained in comparison to that of other fuzzy neural approaches.

The 5G mobile communication：the development trends and its emerging key techniques

5G is a new generation mobile communication system that is to be commercialized in the year beyond 2020. Currently the development of 5G mobile communication system is on its earlier stage. In this article, the development requirements, technique features and possible approaches for the 5G are rstly addressed. The wireless transmission and networking techniques are introduced and remarked, which include massive multiple-input-multiple-output (MIMO),filter-bank based multi-carrier, full duplex, ultra dense network (UDN), self-organizing network (SON), software de ned networking (SDN), and content distribution network (CDN). Furthermore, the recent R&D and promotion activities for 5G mobile communication system in China are summarized.

Design of perfect reconstruction cosine-modulated QMF banks

The design problem of cosine-modulated QMF banks that satisfy the perfect-reconstruction (PR) property has been formulated as a quadratic constrained least-squares (QCLS) minimization problem in which all constrained matrices of the QCLS optimization problem are symmetrical and positive definite. In order to efficiently solve this QCLS optimization problem, we construct a cost function which is a convex function of our desired prototype filter coefficients. So, all its minimizers are global minimizers. Results of computer simulations are presented to support our derivatives and analyses.

Collision and Corruption Awareness Enhancement to IEEE 802.11 DCF: Scheme and Performance Analysis

The main motivation of the medium access control (MAC) protocol in 802.11 is to meet the need of high throughput and low access delay under distributed contention-based environment. Because the cause of transmission failures is unaware, a sender may misinterpret a transmission error as a collision. In this paper, a new strategy which aims at differentiating packet collisions and corruptions in MAC layer is proposed. Based on the approach, an modified backoff scheme is employed under saturated condition for the distributed coordination function (DCF) based wireless local area network (WLAN). Simulation results show that the new scheme achieves higher throughput for 802.11 DCF.