A theoretical analysis of the overall mean squared error (MSE) in hybrid video coding is presented for the case of error prone transmission. Our model covers the complete transmission system including the rate-distortion performance of the video encoder, forward error correction, interleaving, and the effect of error concealment and interframe error propagation at the video decoder. The channel model used is a 2-state Markov model describing burst errors on the symbol level. Reed-Solomon codes are used for forward error correction. Extensive simulation results using an H.263 video codec are provided for verification. Using the model, the optimal tradeoff between INTRA and INTER coding as well as the optimal channel code rate can be determined for given channel parameters by minimizing the expected MSE at the decoder. The main focus of this paper is to show the accuracy of the derived analytical model and its applicability to the analysis and optimization of an entire video transmission system.

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Analysis of video transmission over lossy channels

In a communication system capable of variable rate transmission, scheduling of high speed data transmission improves utilization of the forward link and decreases the transmission delay in data communication. Each remote station is assigned one primary code channel for the duration of the communication with a cell. Secondary code channels of various types and transmission capabilities can be assigned by a channel scheduler for scheduled transmission of data traffic at high rates. Secondary code channels are assigned in accordance with a set of system goals, a list of parameters, and collected information on the status of the communication network. Secondary code channels can be grouped into sets of secondary code channels. Data is partitioned in data frames and transmitted over the primary and secondary code channels which have been assigned to the scheduled user.

Method and apparatus for forward link rate scheduling

A Viterbi decoder (20) for recovering the original bit data stream that was convolutionally encoded as a code symbol stream in a Code Division Multiple Access (CDMA) mobile communication system (22). The decoder (20) simultaneously decodes at the several data rates associated with certain multirate vocoders. The decoder (20) can decode at an unknown data rate in either continuous or framed packed modes. It accomplishes this by simultaneously decoding at multiple rates and by creating one or more data quality metrics for each decoded data packet. Special input and output buffering is provided to isolate the decoder (50) from system timing constraints. The input buffer (48) includes selection and accumulation logic to organize code symbol data into the packet order for repeat mode or random burst mode at lower frame data rates. Decoded data packets for each of several predetermined data transfer rates are held in an output buffer (54) for about half of the decoding cycle, thereby permitting the system microprocessor to examine and select the appropriate decoded data packet. The decoder (50) also can be reconfigured to operate at any one of several predetermined convolutional encoding algorithms. The Viterbi decoder (20), implemented as a single monolithic integrated circuit, can be used in any and all of many different multiuser telecommunications channels.

Multirate serial viterbi decoder for code division multiple access system applications

In this paper, we investigate the issue of error control in wireless communication networks. We review the alternative error control schemes available for providing reliable end-to-end communication in wireless environments. Through case studies, the performance and tradeoffs of these schemes are shown. Based on the application environments and QoS requirements, the design issues of error control are discussed to achieve the best solution.

/pdf/error-control-schemes-for-networks-an-overview-5dnt6nqqj9.pdf

Error control schemes for networks: an overview

This paper considers truncated type-II hybrid automatic repeat-request (ARQ) schemes with noisy feedback over block fading channels. With these ARQ techniques, the number of retransmissions is limited, and, similar to forward error correction (FEC), error-free delivery of data packets cannot be guaranteed. Bounds on the average number of transmissions, the average coding rate as well as the reliability of the schemes are derived using random coding techniques, and the performance is compared with FEC. The random coding bounds reveal the achievable performance with block codes and maximum-likelihood soft-decision decoding. Union upper bounds and simulation results show that over block fading channels, these bounds can be closely approached with simple terminated convolutional codes and soft-decision Viterbi decoding. Truncated type-II hybrid ARQ and the corresponding FEC schemes have the same probability of packet erasure; however, the truncated ARQ schemes offer a trade-off between the average coding rate and the probability of undetected error. Truncated ARQ schemes have significantly higher average coding rates than FEC at high and medium signal-to-noise ratio even with noisy feedback. Truncated ARQ can be viewed as adaptive FEC that adapts to the instantaneous channel conditions.

/pdf/performance-of-truncated-type-ii-hybrid-arq-schemes-with-44xq0hv8ap.pdf

Performance of truncated type-II hybrid ARQ schemes with noisy feedback over block fading channels

In a multi-level QAM communication system, Reed-Solomon encoders and Reed-Solomon decoders are employed for error correction purposes. The phase ambiguity of the received signal is eliminated with differential coding. The multi-level QAM communication system utilizing n bits ("n" being an integer) QAM signal having 2 n signal points, comprises: a quadrature differential encoder/decoder unit for differentially encoding/decoding n pieces of input digital signal series to produce n pieces of differentially coded signal series; an error correction unit including a Reed-Solomon encoder and a Reed-Solomon decoder, provided inside the quadrature differential encoder/decoder unit along a signal processing path of the input digital signal series, for error-correcting the n pieces of differentially-coded signal series by utilizing at least one of the digital signal series with employment of a Reed-Solomon code; and, a QAM modulator/demodulator unit for QAM-modulating/demodulating n pieces of error-corrected signal series so as to produce 2 n QAM signals.

Quadrature amplitude modulation communication system with transparent error correction

PURPOSE: To perform error correction which allows information transmission requiring real-time processing by providing each of the transmission side and the reception side with a means which adds information for retransmission to each time slot and a retransmission time limiting means which handles information retransmitted within a certain time out of erroneous information as an information signal. CONSTITUTION: In a transmitter 20, packets of plural information signals are collected to constitute each block by a control information adding circuit 2. A block identification number and a check bit for error detection are added to this block by the control information adding circuit 2. Signals led from the adding circuit 2 are temporarily stored in a buffer 3, and a signal having the requested block identification number is outputted to a signal synthesizer 4 when a retransmission request signal is received by a confirmation signal discriminating circuit 7. These signals are erased in the buffer 3 when a certain time elapses after input of signals from the adding circuit 2, and only signals retransmitted within the certain time are handled as information signals. In a receiver 20, it is discriminated by an error detecting circuit 10 whether signals received by a terminal 9 include error or not, and a confirmation signal generator 13 transmits the retransmission request signal to the transmitter 20 through a terminal 14 in accordance with the discrimination result. COPYRIGHT: (C)1989,JPO&Japio

Error control system

A reduction of the redundancy due to the use of the convolutional codes as the error correction codes is achieved by a convolutional encoding at an identical encoding rate and a puncture process using different puncture rates for different classes of the input signals classified by the error sensitivity of each bit. A reduction of the decoding delay time without deteriorating the decoding error rate is achieved by updating the survivor path by remaining bits of the selected survivor path for each state other than the oldest bit and an additional bit indicative of the each state to which a transition is made at the present stage of decoding. A reduction of a circuit size of a Viterbi decoder is achieved by using a single RAM for memorizing a path metric and a survivor path for each state at an immediately previous stage of decoding together in each word of the memory capacity. A reduction of the decoding error rate for the data block encoded by the convolutional encoding is achieved by using the (i+N+j) bits of decoder input signals containing entire N bits of the received signals, preceded by last i bits of the received signals and followed by first j bits of the received signals.

Method and apparatus for encoding and decoding convolutional codes

Performance Evaluation for ARQ Schemes in Power and/or Bandwidth Limited Systems

PURPOSE:To decrease the circuit scale by calculating a remainder from an inputted digital signal and converting the calculated remainder into a syndrome. CONSTITUTION:A remainder conversion means 21 converting a remainder calculated by a remainder calculation means 19 into a syndrome is provided and the remainder is calculated at first from an inputted digital signal and the remainder is converted into a syndrome. Moreover, a burst error is estimated from the remainder calculated by a burst error estimate circuit 7 and a random error is estimated from the syndrome by the random error estimate circuit 3. Then the error is corrected from the estimated random error pattern and the inputted digital signal and the estimated burst error pattern and a signal in which any of errors is corrected is selectively outputted. Thus, the circuit scale of the remainder calculation circuit 19 and the remainder conversion circuit 21 is decreased and the circuit scale of the entire error correction device is decreased.

Nakamura Makoto

Papers

Quadrature amplitude modulation communication system with transparent error correction

Error control system

Method and apparatus for encoding and decoding convolutional codes

Performance Evaluation for ARQ Schemes in Power and/or Bandwidth Limited Systems

Error correction device