A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Khara, Sibaram
- Basis Expansion Models Analysis for MIMO/OFDM Systems
Authors
1 School of Electronics Engineering, VIT University, Vellore, Tamil Nadu, IN
2 School of Electronics Engineering, VIT University, Vellore, Tamil Nadu, IN
Source
Wireless Communication, Vol 3, No 6 (2011), Pagination: 398-402Abstract
We consider Channel estimation for multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/ OFDM) systems in time-varying wireless channels using superimposed training (ST). By using a discrete prolate spheroidal basis expansion model (DPSS) and truncated discrete fourier bases expansion models (Fourier-BEM) for representing the time varying channel. Based on these models, a weighted average approach is adopted for estimating linear time varying (LTV) channels for OFDM symbols. The performance analysis between two BEM models based on Mean square error (MSE) is present in this paper. Simulation results show that the DPSS-BEM model outperforms the Fourier Bases expansion model.Keywords
Basis Expansion Models (BEMS), MIMO/OFDM, Slepian Sequences, Superimposed Training.
- Review of UMTS/WLAN Integration Techniques for Next Generation Networks
Authors
1 VIT University, Vellore, Tamil Nadu, 632014, IN
Source
Wireless Communication, Vol 2, No 9 (2010), Pagination: 281-291Abstract
Recent trends indicate that many current generation wireless technologies will converge to form next generation heterogeneous wireless networks (such as fourth generation (4G) network) to provide multimedia services through multi-mode mobile devices. Third generation (3G) cellular data networks (such as Universal Mobile Telecommunication System (UMTS)) and wireless local area network (WLAN) are two potential constituents to form 4G wireless heterogeneous networks. However, UMTS and WLAN systems are technologically different and are not designed to work together. UMTS/WLAN integration needs seamless interworking strategies between the two technologies not only at access level but also at both core and service levels. The design complexity and implementation implications, cost effectiveness and efficiency of the integrated network need to be considered for optimal solutions. In this article, we present the feasible UMTS/WLAN integration techniques. We compare among various solution techniques and observe that at lower protocol layer of UMTS, WLAN can be managed with UMTS-like access network but it increases implementation complexity. On the other hand, at IP and upper layer convergence help simple integration but it provides larger handoff delay. Our ns-2 based simulation results show that vertical handoff delay in loose coupling, is 19% more than that in tight coupling architecture. But end-to-end packet delay in loose coupling is 6% less.