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N. Farvardin - IEEE Xplore Author Profile

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In this paper, a protocol is designed to manage source rate/channel coding rate adaptation, code allocation, and power control to transmit real-time MPEG-4 FGS video over downlink multicode CDMA networks. We develop a fast adaptive scheme of distortion management to reduce the overall distortion received by all users subject, to the limited number of codes and maximal transmitted power. Compared w...Show More
In CDMA, resource allocation is a task critical to the performance of this inherently interference limited multiple access technique. This paper also presents the solution to the problem of optimal resource allocation to resolve interference-generated congestion for an arbitrary set of real-time source encoders and shows that this problem could be viewed as the one of statistical multiplexing in s...Show More
We present a joint source-channel coding scheme based on incremental redundancy and feedback for transmission of real-time sources over wireless channels under strict delay constraints. The proposed scheme operates at constant bit rate and delay so as to capture the benefits of a feedback channel, while keeping the synchronous nature of pure forward error correction systems. We formulate the under...Show More
In CDMA, resource allocation is a task critical to the performance of this inherently interference limited multiple access technique. In this paper we introduce a new technique aimed at increasing the number of real-time calls supported in a CDMA network at the cost of a smooth controllable degradation of reconstructed source quality while channel-induced distortion remains bounded by fixing a max...Show More
In multiple access wireless networks with co-channel interference, allocating resources such as transmitted powers and source rates is a task critical to improve performance. In this paper, we introduce a new technique aimed at minimizing the overall transmitted power subject to constraints on the incurred source distortion. The technique is based on the use of real-time source codecs with externa...Show More
Consider a memoryless, loss-tolerant and delay-sensitive source, the output of which is transmitted through a packet-switched communication network. Network parameters such as congestion, route quality, link capacity etc., have a great impact on the achievable distortion at the receiver. In our previous publication (see IEEE Trans. on Inform. Theory, vol.47, no.3, p.891-903, March 2000)., we inves...Show More
Suppose that the description of a stochastic process needs to be sent to a destination through a communication network. Also assume there is a risk that the description may be lost. A technique to reduce the risk of losing such descriptions is by sending two (or more) descriptions and hoping that in this way at least one of the descriptions will get through. This problem is referred to as multiple...Show More
Consider a communication system and a memoryless, loss-tolerant and delay-sensitive source the output of which is transmitted through an arbitrary network. In multiple routing the encoder output is distributed among several independent paths. The percentage of packets that follows the route "i" is denoted by q/sub i/ where /spl Sigma//sub i=1//sup K/ q/sub i/=1. The total delay experienced by a pa...Show More
We study the design of channel-optimized vector quantizers in the presence of channel mismatch. We show that when the statistics of the channel bit-error rate (BER) are not known, a minimax solution is the one obtained by designing for the worst possible channel. Then, we consider the case when the probability density function of channel BER is known and propose an algorithm that provides a minimu...Show More
In this correspondence, we propose a channel-matched hierarchical table-lookup vector quantizer for a discrete memoryless channel. We show that this scheme simultaneously provides low encoding complexity and robustness against transmission noise. Additionally, we propose the use of lookup tables for transcoding in heterogeneous networks. We show, through an example motivated by an application in m...Show More
A diffusion approximation is proposed for the data section of the source encoding assisted multiple access (SEAMA) protocol, a voice and data communication wireless network. In SEAMA, a reservation mechanism handles the slot assignment for the voice traffic which operates as an M/M/N/sub max//N/sub max/ loss system. The data traffic is a Markovian queueing system with a random number of channels a...Show More
We consider the problem of joint source-channel coding for progressive packetized transmission of an image over a packet-loss network whose packet-loss rate is a random variable. We obtain an algorithm for unequal erasure protection which, by design, maintains progressivity i.e., good performance at intermediate transmission budgets.Show More
This paper presents SEAMA, a source encoding assisted multiple access (MAC) protocol, to integrate voice and data traffic in a wireless network. SEAMA exploits the time variations of the speech coding rate, through statistical multiplexing, to efficiently use the available bandwidth and to increase the link utilization. In each frame, SEAMA allocates bandwidth among calls as needed. Ongoing calls ...Show More
An embedded source code allows the decoder to reconstruct the source progressively from the prefixes of a single bit stream. It is desirable to design joint source-channel coding schemes which retain the capability of progressive reconstruction in the presence of channel noise or packet loss. Here, we address the problem of joint source-channel coding of images for progressive transmission over me...Show More
When a feedback channel is available from the receiver to the transmitter, adaptive schemes for source-channel coding can be used for image transmission. In this paper we see that the use of embedded source codes and embedded channel codes, when combined in a hybrid ARQ protocol, can provide the desired flexibility at high efficiency, low complexity and low feedback channel usage. We propose optim...Show More
We propose an admission control policy subject to a quality of service constraint for real-time traffic in a packet-switched network. Taking advantage of the statistical multiplexing of voice packets, the calls employ a multi-state source encoder whose state is determined by the level of source activity. Further, in each state, the source encoder outputs an embedded bit stream in the sense that an...Show More
Summary form only given. The combination of jointly optimized rate compatible punctured convolutional (RCPC) codes and channel-matched tree-structured vector quantizers (CM-TSVQ) is shown to provide improved performance, in some cases, compared to the use of CM-TSVQ. The embedded nature of the RCPC codes and CM-TSVQ is inherited by the jointly optimized combination so that the resulting coder is i...Show More
We propose a fast reconstruction method for a subband-decomposed, progressive signal coding system. We show that unlike the conventional approach which requires a fixed computational complexity, the computational complexity of the proposed approach is proportional to the number of refined coefficients at each level of progression. Therefore, unrefined coefficients do not add to the computational c...Show More
We present a scheme for joint source-channel coding for transmission of sources compressed by embedded source coders over a memoryless noisy channel. We find an exact solution to the problem of optimal channel code allocation. Then we investigate the properties of the solution which allow us to transmit the source progressively while retaining the optimality at intermediate and final transmission ...Show More
A new variable-rate embedded quantization technique, called embedded entropy-constrained trellis coded quantization (E-ECTCQ) is developed. Its performance is compared to that of variable-rate embedded scalar quantizers. Simulations indicate that performance depends both upon the number of embedded quantization stages and the number of trellis states.Show More
We address the problem of design of a hybrid ARQ system from a family of channel codes, so as to maximize the throughput for a given channel, subject to constraints on the feedback channel usage. We show that the problem can be modeled in a controlled Markov chain framework.Show More
We have incorporated a region-of-interest (RoI) coding functionality into Said and Pearlman's (see IEEE. Trans. CSVT, vol.6, p.243-50, 1996) SPIHT coding with integer transforms. By placing a higher emphasis on the transform coefficients pertaining to the RoI, the RoI is coded with higher fidelity than the rest of the image in earlier stages of progressive reconstruction thus the "important" part ...Show More
We propose algorithms to design channel-optimized vector quantizers in the presence of channel mismatch. We consider two cases: (i) no information about the statistics of the channel bit error rate is available and (ii) the probability density function of the channel bit error rate is known. We also consider the use of an estimate of the channel signal-to-noise ratio to improve the performance. Si...Show More
Embedded trellis coded quantization (E-TCQ) is introduced as an embedded quantization technique which achieves good rate-distortion performance for reasonable computational complexity. The performance of E-TCQ is investigated for memoryless Gaussian, Laplacian, and uniform sources. E-TCQ is shown to outperform multi-stage TCQ. For Gaussian and Laplacian sources the performance of ETCQ shows large ...Show More
Summary form only given. We propose a joint source-channel coding scheme for the transmission of images over noisy channels. In this scheme, the interaction between source coding and channel coding is through a small number of parameters. A robust source coder based on the classification of the discrete wavelet transform (DWT) coefficients of the image is coupled with a flexible error control sche...Show More