Forward Error Correction Overhead Research Articles

Integrating packet‐level FEC with data carousels for reliable content delivery in satellite broadcast/multicast systems

AbstractOne key aspect of digital multimedia broadcasting is the reliable point‐to‐multipoint distribution of content. Since the capacity and energy constraints in wireless environments do not favour the provision of a return channel for user feedback, the use of partial reliability techniques is often the only realistic option for the reliable transport layer design. In this paper, we focus on the two main reliable transport mechanisms in unidirectional, point‐to‐multipoint systems, namely packet‐level forward error correction (FEC) and data carousels. We approach them as building components of an integrated scheme and investigate its performance via analytical means. Our analysis demonstrates that the network responsiveness, expressed by the average content access time, is optimized for certain packet‐level FEC redundancy values. This is clearly different from setting FEC without considering the data carousel dimension, where the FEC redundancy is determined from the probability of recovering the whole file versus FEC overhead trade‐off curves. We describe design alternatives for both scheme components, such as different FEC code types, rules for assigning FEC redundancy per carousel item, and ways to retrieve items from the data carousel, and evaluate their impact on the performance of the scheme. Our results suggest that the superposition of FEC on data carousels mitigates the otherwise significant impact of the data item retrieval technique on performance, at least for close‐to‐optimal FEC settings. On the contrary, the careful selection of FEC code and FEC redundancy assignment rule for data carousel items results in performance gains of up to 11 and 18% for the average content access time and FEC overhead, respectively, depending on the item demand and length distributions. Copyright © 2006 John Wiley & Sons, Ltd.

Performance analysis of a file delivery system based on the FLUTE protocol

AbstractThis paper presents the results of performance tests carried out for a file delivery system based on the file delivery over unidirectional transport (FLUTE) protocol. FLUTE is a file transport protocol used to deliver files over IP networks, including the Internet and unidirectional systems, from a sender to one or more receivers. FLUTE uses UDP, an unreliable transport protocol, and so reliable delivery must be guaranteed by other means. This paper shows how FLUTE manages to recover from packet losses using forward path redundancy (forward error correction (FEC) and repeat transmissions in a data carousel), and a simple HTTP‐based point‐to‐point file repair scheme which is specified in 3GPP and DVB standards. The results presented in this paper show that careful optimization of FEC overhead, and the number of repeat transmissions, gives the best system performance in most cases. Based on the simplified error reception and distribution model depicted in this study, it is illustrated that the simple client‐server point‐to‐point file repair is optimal only for small groups. Several options to improve the configuration of FLUTE senders are provided, to deliver reception guarantees with optimal data expense from the system point of view. Copyright © 2006 John Wiley & Sons, Ltd.

A Standalone Receiver With Multiple Access Interference Rejection, Clock and Data Recovery, and FEC for 2-D$lambda -t$OCDMA

We demonstrate a standalone (no global clock) receiver for two-dimensional wavelength-time optical code-division multiple-access. The receiver provides the following functions: quantization (to eliminate multiple access interference), clock and data recovery, return-to-zero to nonreturn-to-zero conversion (for optical code-division multiple-access compatibility with digital logic), framing (for byte synchronization), and forward-error correction (FEC) using a (255, 239) Reed-Solomon decoder. The receiver more than doubles the number of supported users at a bit-error rate <10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> . The receiver supports an information rate of 156.25 Mb/s. We performed the measurements at a bit rate of 167.4 Mb/s and a chip rate of 1.339 Gb/s (eight chips per bit) to account for FEC overhead

Optimization of WDM (Ν × 40 Gbit/s) Transmission in Strong Symmetric Dispersion Maps

We have performed numerical and experimental optimization of dispersion-managed Wavelength Division Multiplexed (WDM) Return-to-Zero (RZ) transmission without in-line control at 40 Gbit/s per channel in symmetric dispersion maps using effective area enlarged positive dispersion fiber and reverse dispersion fiber. Our results show the feasibility of transmission over 2800 km without Forward Error Correction (FEC) and over 4500 km with 8 % FEC overhead. The results of numerical modeling are in good agreement with experimental data.

Design of multicode CDMA systems for 3-D stereoscopic video over wireless ATM networks

This paper investigates the application of multicode spread-spectrum code-division multiple-access (SS-CDMA) techniques to three-dimensional (3-D) stereoscopic video transmission over wireless asynchronous transfer mode (ATM) networks. Three-dimensional visual communications, made through the use of stereoscopic images, are able to achieve total display realism. Such services allow users to share the virtual reality (VR) world without any geographical restrictions. In order to create a 3-D system with two images (left and right) that should be transmitted over a bandlimited mobile channel simultaneously, a cost-effective motion picture experts group (MPEG)-based wavelet multiresolution coding with a joint motion and disparity compensation is developed to reduce a large amount of information contained in the images to meet the low-transmission rate limitation of mobile channels. However, the rapidly variable bit rate (VBR) characteristics of the MPEG-based 3-D videos seems a weakness to the transmission of such videos via a constant bit-rate (CBR) mobile channel. The ATM technique is especially well suited for VBR MPEG-based 3-D video because of its ability to allocate bandwidth on demand to these services. However, since the mobile radio has a limited channel capacity, the overall capacity of the traditional ATM-based SS-CDMA system may not be sufficient to accommodate the MPEG-based 3-D video services requested by the multiple mobile users simultaneously. To tackle this difficulty, a multicode CDMA technique is proposed to provide VBR MPEG-based 3-D video services by varying the number of spreading codes assigned to the 3-D video to meet its dynamic throughput requirement. Powerful forward error correction (FEC) codes are necessary to protect the video data so that it can be successfully transmitted at an acceptable signal power level. Two separate FEC code schemes are applied to the header and payload of an ATM cell containing 3-D video data, respectively. The ATM cell header is protected by a relatively powerful FEC code to ensure correct delivery and low cell loss rate (CLR). On the other hand, the ATM cell payload is encoded for varying degrees of error protection according to the priority of the payload data in 3-D videos. An adaptive FEC code combining scheme is proposed to provide the good protection for payload data with the maximization of its code rate to minimize the extra bandwidth for FEC overhead.