Forward error correction

Regarding the transmission of audio and video data over networks with limited capacity, a framework was developed to adapt the amount of data transmitted to the currently free capacity. One possible way of reaction to a bottleneck causing packet loss is to use Forward Error Correction [903]. To avoid jitter unacceptable for a continuous playoiit, ]666] and ]802] cover the optimization of transmission and playout of multimedia data streams. Flirthermore, [1017] gives an overview of several other adaptive techniques in multimedia data transmission. The approach realized in IMPROVE partly uses these technologies but additionally covers the applicability in wireless networks for supporting mobile project partners. 

In order to improve the chaimel capacity, forward error correction techniques are used. These teclmiques add redundant information to the data bits and make a... 

Introduction Source Coding Forward Error Correction... 

The ATSC VSB system offers two basic operational modes a terrestrial broadcast mode (8-VSB) and a high data rate mode (16-VSB) intended for cable applications. Both modes provide a pilot, segment syncs, and a training sequence (as part of data field sync) for acquisition and operation. The two system modes can use the same carrier recovery, demodulation, sync recovery, and clock recovery circuits. Adaptive equalization for the two modes can use the same equalizer structure with some differences in the decision feedback and adaptation of the filter coefficients. Furthermore, both modes use the same Reed-Solomon (RS) code and circuitry for forward error correction (FEC). The terrestrial broadcast mode is optimized for maximum service area and provides a data payload of approximately 19.4 Mbps in a 6 MHz channel. The high data rate mode, which provides twice the data rate at the cost of reduced robustness for channel degradations such as noise and multipath, provides a data payload of 38.8 Mbps in a single 6 MHz channel. 

From Dorf, R.C. and Wan, Z., Error control coding, in The Electrical Engineering Handbook, 2nd ed., Dorf, R.C., Ed., CRC Press, Boca Raton, FL, 1998, p. 1554. Originally from V.K. Bhargava, Forward error correction schemes for digital communications, IEEE Communication Magazine, 21, 11-19, 1983 IEEE. With permission. 

In this section I will outline the idea of memory error correction as put forward by Peter Shor and Andrew Steane (Shor 1995, Steane 1996). In classical bits the only kind of error which can happen is a hit flip which changes the logical value from 0 to 1 and vice versa. In qubits a second type of error can happen which we shall call phase errors. A bit flip error in a qubit will give rise to the following... 

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The only real error source for the output voltage are the forward drop characteristics of this diode. Each of the three SPICE simulators has a model for the 1N4002 diode, with all of the simulators within about 100 mV of each other. The question is, which model is correct The answer is they are probably all correct. The forward drop tolerance of a diode varies from lot to lot, from manufacturer to manufacturer, and from device to device. Table 10.1 shows the results of each of the three simulators along with the breadboard results. 

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