Mei Shun-liang

TD-LTE network indoor offloading study in a realistic metropolitan scenario

In the wireless broadband network, most traffic are generated from indoor users. Meanwhile the indoor coverage is identified as the major bottleneck especially in dense urban environment with high-rising buildings. In this paper, the TD-LTE network downlink performance of indoor is studied with various network deployment options, including outdoor Macro cell, outdoor Micro cell, indoor distributed antenna system (DAS), indoor Femto cell, and their combinations in a realistic large-scale dense urban scenario. Since a DAS cell consists of several or even tens of access points (AP), the computation load is too high to be accepted when calculating the received signal power and the interference power by traditional widely-used methodology. Thus a new DAS model is proposed to decrease the computation complexity to a reasonable level in the simulation. To have more accurate channel modeling, the real three-dimensional (3D) city map of the investigated area is employed. A 3D ray-tracing tool is used to estimate the large scale propagation occurring between outdoor sites and buildings. The traffic offloading features of Micro, DAS, and Femto cell are evaluated through system simulations.

Optimal multicast opportunistic routing based on Markov chain

Improving the network capacity is one of the most important topics in the area of wireless networks. The broadcasting and fading feature of the wireless communications has not been sufficiently exploited in traditional routings. However, in opportunistic routing, they are able to be used to provide diversity. In this paper, the multicast opportunistic routing problem is studied in a Markov chain method, and the optimal algorithm called Least ETX Multicast Opportunistic Routing (LEMOR) is designed and proved to have the least end-to-end ETX. Simulation results show that LEMOR is able to significantly improve the network throughput by exploiting both opportunistic routing and multicast compared to the algorithms using either of them.

Sparse constraint multidelay frequency adaptive filtering algorithm for echo cancellation

Sparse constraint Least Mean Square (LMS) is a recently proposed efficient adaptive algorithm for sparse system identification. However, its computational complexity is quite high especially when the filter length is long and convergence is slow for colored input signal. This paper extends the idea of sparse constraint into multidelay frequency adaptive filter (MDF) algorithm and proposes the sparse MDF algorithm for echo cancellation. The proposed algorithm perserves both the advantage of sparse LMS which has fast convergence performance for sparse system and MDF algorithm which has temporal decorrelation effect with lower implementation complexity. Two typical sparse constraints, l1-norm and an approximate l0-norm, are employed. And their performances of various aspects are simulated. Experiments show they have better performance than existing algorithms.

A new method of flow control for ABR based on chaos

Traffic management is important in ATM networks. Recently, self-similarity has been revealed in traffic and influenced the performance of networks greatly. We present a new flow control method for the ABR service category based on chaotic control and prediction as well as the ATM feedback control mechanism so as to eliminate the negative effect of self-similarity in ATM traffic. From the simulation results, our method is more efficient in improving system performance, such as cell loss rate (CLR) and fairness, than EFCI.

Multiple antennas system for multiaccess capacity enhancement with flexible antenna locations

The scheme proposed here is an alternative of smart antenna systems, with flexible antenna locations and easy capacity expansion. Here, unlike cell splitting, the only purpose of building a base station is for radio coverage, and capacity enlargement is done by multiple antennas. In this paper, after analyzing its capacity, we put forward a transceiver method (group transmission) for multiple antenna system to approach the great capacity enhancement, without any multi-user coding/decoding technique and excessive bandwidth. Performance evaluation shows that this scheme approaches the capacity well and is quite suitable for PCS.