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Dive into the research topics where V.K. Dubey is active.

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Featured researches published by V.K. Dubey.


global communications conference | 1995

Performance of pitch synchronous multi-band (PSMB) speech coder with error-correction coding

Haiyun Yang; Soo Ngee Koh; V.K. Dubey

A novel speech coding algorithm, named pitch synchronous multiband-excitation (PSMB), is presented in this paper. It uses the multiband excitation (MBE) model to generate a representative pitch-cycle waveform (PCW) for each frame. The representative PCW of a frame is encoded using two out of three codebooks depending upon whether the frame is related or unrelated to the previous frame. The PSMB coder operating at 4 kbps outperforms the Inmarsat 4.15 kbps IMBE coder by a clear margin. The sensitivity of the source bits to channel errors is extensively investigated, All the source bits can be classified into several groups according to their perceptual significance. The BCH codes and punctured convolutional (PC) codes are used to protect the perceptually significant source bits in order to minimize the effect of channel errors on the performance of the proposed coder.


international conference on information and communication security | 1997

Performance of DS-CDMA system with M-ary orthogonal modulation and successive interference cancellation

Guoqiang Xue; Erry Gunawan; V.K. Dubey; C. B. Soh

The performance of a DS-CDMA system with M-ary orthogonal modulation is investigated; through computer experiments and mathematical analysis we find the variance of multiple access interference (MAI) in synchronous AWGN channels should be twice as much as adopted in previous references. The system performance of successive interference cancellation in multipath Rayleigh fading channels is also investigated by means of simulation. Our results show that successive interference cancellation is a simple yet effective way to mitigate MAI when the user density is low.


international conference on information and communication security | 1997

MTCM versus TCM codes in a fading environment

T.P. Choo; Kwok Hung Li; V.K. Dubey

It is well known that conventional trellis-coded modulation (TCM) codes are optimally designed in an additive white Gaussian noise (AWGN) environment. Multiple TCM (MTCM) codes were proposed as a solution to the poor performance of conventional TCM codes over fading channels. However, it is observed that the performance of MTCM codes may be inferior to that of conventional TCM codes under certain situations. In this article, we attempt to provide a clear and quantitative description of these conditions. In particular, a method is presented to easily determine if a particular MTCM code will perform better than its equivalent conventional TCM code by simply examining the number of code states, the code rate and the code design (connectivity).


Electronics Letters | 2000

Bit error probability of OFDM system over frequency nonselective fast Rayleigh fading channels

Lei Wan; V.K. Dubey


Electronics Letters | 1999

Multidimensional TCM schemes for ADSL

M. Cao; K.R. Subramanian; V.K. Dubey


Electronics Letters | 2005

Effect of angle-of-arrival on transmit diversity and beamforming systems under correlated fading

A.W. Umrani; V.K. Dubey


Electronics Letters | 1999

Optimal interleaver design for concatenated coding in DSL systems

M. Cao; K.R. Subramanian; V.K. Dubey


Electronics Letters | 1999

Adaptive bit loading scheme using COFDM at low elevation over LEO satellite communication channel

Lei Wan; I.G. Gosling; V.K. Dubey


Archive | 2002

Portable ground terminal for LEO satellite communication

Choi Look Law; K. Arichandra; S. Seumahu; V.K. Dubey; Ian Gilbert Gosling; Yilong Lu; Ching Kwang Lee


Archive | 2001

Communication techniques and systems.

Soo Ngee. Koh; V.K. Dubey; Erry. Gunawan; Xiang. Gui

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Choi Look Law

Nanyang Technological University

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E. Gunawan

Nanyang Technological University

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K.R. Subramanian

Nanyang Technological University

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Kwok Hung Li

Nanyang Technological University

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M. Cao

Nanyang Technological University

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Q.X. Zhang

Nanyang Technological University

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A.W. Umrani

Nanyang Technological University

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C. B. Soh

Nanyang Technological University

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Erry Gunawan

Nanyang Technological University

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Haiyun Yang

Nanyang Technological University

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