Ming L. Liou

M-PSK and M-QAM BER computation using signal-space concepts

In this paper, we introduce a simple geometric approach that is based on signal-space concepts to efficiently evaluate the performance of M-ary phase-shift keying (M-PSK) and M-ary quadrature amplitude modulation (M-QAM) schemes over an additive white Gaussian noise channel. In particular, new bit error rate approximations are derived and shown to be in excellent agreement with Monte Carlo simulation results.

Genetic motion search algorithm for video compression

A new approach to block-based motion estimation for video compression, called the genetic motion search (GMS) algorithm, is introduced. It makes use of a natural processing concept called genetic algorithm (GA). In contrast to existing fast algorithms, which rely on the assumption that the matching error decreases monotonically as the search point moves closer to the global optimum, the GMS algorithm is not fundamentally limited by this restriction. Experimental results demonstrate that GMS is more robust than other algorithms in locating the global optimum and is computationally simpler than the full search algorithm. GMS is also suitable for VLSI implementation because of its regularity and high architectural parallelism. >

Robust video transmission over correlated mobile fading channels

We develop a unique set of techniques to support reliable and efficient video transmission over bandwidth-limited mobile networks. The video coder is based on the H.263 coding standard, while its transmission system design is based on a joint study of combined source and channel coding, diversity reception, and pre/postprocessing techniques. In particular, a finite-state Markov model for representing a correlated fading channel with diversity is developed. Based on this model, a recursive algorithm is further devised for an efficient estimation of block-code performance. By doing so, an important means for finding proper diversity and channel coding schemes for correlated video data in correlated fading channels is obtained. In addition, robust decoding together with a combined spatial-temporal concealment is employed to mitigate the effects of decoding mismatch caused by residual errors. Simulation results confirm that the proposed system can significantly reduce the bursty error effects on the H.263 coded video data while maintaining high transmission efficiency.

Mobile image transmission using combined source and channel coding with low complexity concealment

Abstract In this paper, we propose an efficient image transmission system for reliable transmission of vulnerable compressed images over mobile radio channels. The image coder is fully compatible with the JPEG baseline coding standard. Its transmission system is designed based on lossy transmission with combined source and channel coding (CSCC) and low complexity error concealment. Specifically, the proposed CSCC uses block codes which are designed to match both the coded image characteristics and wireless channel statistics, thereby accomplishing efficient transmission along with good visual quality. Together with a block-shuffling scheme, a simple error-concealment technique is introduced to effectively reconstruct the damaged image blocks caused by the residual errors. It is shown that the proposed techniques are applicable to mobile image transmission with different compression ratios under various mobile channel conditions. Performance results based on images `LENA and `AIRPLANE, which are coded at 0.85 and 0.90xa0bit/pixel, respectively, under the simulated GSM channel (Pan-European Cellular Standard) with an average SNR (signal-to-noise ratio) of 18xa0dB and various vehicle speeds (2–50xa0miles/h) indicate that the proposed system achieves a throughput as high as 70% with good visual quality at PSNRs (peak signal-to-noise ratio) around 30xa0dB for the reconstructed images.

Joint source and channel coding for mobile multimedia communications

We present a strategy of joint source and channel coding (JSCC) for mobile multimedia communications. An integrated multimedia system, which comprises speech, data, image and video, is considered. The JSCC scheme is based on the use of efficient block codes coupled with pre/post-processing techniques, which best fit the individual characteristics of different media as well as the statistics of the wireless channels. Simulations under different channel conditions show that the proposed JSCC strategy offers high transmission efficiencies and low implementation complexity while maintaining high transmission reliability for multimedia communications. Furthermore, it is shown that the developed techniques can achieve an efficient system design which substantially outperforms the error protection scheme used in GSM (pan-European cellular standard).

Error resilient transmission of H.263 coded video over mobile networks

In this paper, we propose an error resilient transmission system for reliable transmission of H.263 coded video sequence over mobile networks. Both the coded video characteristics and mobile channel statistics are investigated. The error protection schemes are designed based on the best matched block codes coupled with diversity reception. A low complexity error concealment based on prediction of inter-block correlation is also introduced to effectively reconstruct the damaged image blocks caused by the residual errors. Simulations with different test video sequences under various mobile channel conditions confirm that good visual quality can be achieved by the proposed system.

Efficient image transmission over wireless channels

An efficient image transmission system based on simple block shuffling, intelligent data-block partition of the encoded bit stream with FEC (Forward Error Correction) coding and error concealment is proposed over wireless channels. It is shown that the proposed system has the features of simplicity in implementation, compatibility with the JPEG coding standard and high transmission efficiency because of the low bit-expansion required for error protection. Simulations over a non-transparent GSM (a cellular mobile standard) channel demonstrate that good visual quality can be achieved by the proposed system.

Modeling correlated fading with diversity and its application to block codes performance estimation

The error structure in wireless channels is very crucial to various system designs, but it is also very difficult to describe. In this paper, we first develop a finite state channel model for representing a correlated fading channel with diversity. Specifically, general expressions for determining the steady state probability of each state, transition probabilities between states and error probability in each state are derived for a correlated fading channel with N-branch selection diversity. Based on this model, we then study the error structure in wireless environments with/without diversity reception through estimating the performance of block codes, which is very important for finding the best error detection/correction coding design in correlated fading. In particular, a recursive algorithm is devised for an efficient computation of the error rates of block codes. Finally, Rayleigh fading channels are simulated to verify the accuracy of the estimated error rate performance of block codes, and thus the usefulness of the developed model.

Mobile video transmission with efficient fading countermeasures and robust decoding

We develop a unique set of techniques to support reliable and efficient video transmission over bandwidth limited mobile networks. The video coder is based on H.263 coding standard while its transmission system design is based on efficient and effective fading countermeasures and robust decoding. In particular, combined source and channel coding coupled with diversity reception substantially improves the error resilience capability of H.263 coded video as well as the efficiency of the proposed transmission system. Moreover, robust decoding is accomplished by the use of a look-ahead strategy and a combined spatial-temporal concealment. Simulation results confirm that the proposed system can yield very good visual quality and high transmission efficiency.

On the use of modulation and diversity for enhancing cellular spectrum efficiency of wireless multimedia communication networks

The third generation wireless personal communication systems are likely to support multimedia traffic, for which high spectrum efficiency is extremely important. We investigate M-PSK and M-QAM with diversity in the presence of fading and co-channel interference. Simple closed-form and general BER (bit-error-rate) expressions, in terms of M (M-ary PSK or M-ary QAM), N (N-branch diversity), E/sub b//N/sub 0/(signal-to-noise ratio per bit) and SIR (signal-to-interference ratio), are derived and shown to be in excellent agreement with Monte-Carlo simulations. Based on these expressions, tradeoffs among spectrum efficiency, power efficiency and implementation complexity are studied. Important issues in determining parameters for modulation and diversity in wireless multimedia communication networks are discussed.