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Nandakumar, S.
- Improving Mobile-TCP Performance over Wireless Networks
Authors
1 School of Electronics Engineering, VIT University, IN
2 VIT University, IN
3 School of Electronics Engineering, VIT University, and Tamilnadu, IN
Source
Networking and Communication Engineering, Vol 2, No 8 (2010), Pagination: 268-272Abstract
TCP is designed to perform in traditional wired networks where packet losses occur mainly due to network congestion. Wireless link losses result in poor TCP throughput since losses are perceived as congestion and TCP responds to all such losses by invoking congestion control and avoidance algorithms. Wireless link loss also incurs source throttling and hence degraded end-to-end performance. Wireless link designers have augmented mobile TCP a modified version of TCP to suit wireless conditions. But this mechanism has reduced the impact of losses on TCP throughput for smaller file transfer. In this paper, we propose an enhanced mobile TCP scheme for performance improvement for both smaller and larger file transfer over wireless link. OPNET based simulation results shows that proposed scheme improves TCP throughput by 60% over existing solutions.Keywords
HTTP, M-TCP, SMSS INTRODUCTION.
- Frequency Domain Equalization for Single Carrier Wireless Systems
Authors
1 School of Electrical Sciences of VIT University, Vellore–632014, TamilNadu, IN
Source
Networking and Communication Engineering, Vol 1, No 4 (2009), Pagination: 177-183Abstract
Computational complexity and error propagation phenomenon are important drawbacks of existing Decision Feedback Equalizers (DFE) for dispersive channels. A new Iterative Block DFE (IBDFE) is considered where the equalization is performed iteratively on blocks of received signal in the frequency domain i.e. both signal processing and filter design are in frequency domain. Thus computational complexity is reduced and error propagation is limited to one block. The feed forward and feedback filters of DFE are designed with the minimization of Mean Square Error (MSE) at detector input as the parameter for effective detection. Two design methods have been solved and simulated for a Rayleigh fading channel. Channel is assumed to be time in-variant during one block of data (128 symbols) transmission. In the first method, the hard detected data are used as the input to the feedback, and filters are designed according to the correlation between detected and transmitted data. In the second method, the feedback signal is directly designed from soft detection of the equalized signal at the previous iteration. Estimates of the parameters involved in the FF and FB filters are also solved and used to evaluate the filter coefficients. From simulation, it was found that the IBDFE as claimed in the research literature performs better than the time domain DFE.