Scaling of analog LDPC decoders in sub-100 nm CMOS processes

Analog implementations of digital error control decoders, generally referred to as analog decoding, have recently been proposed as an energy and area competitive methodology. Despite several successful implementations of small analog error control decoders, little is currently known about how this methodology scales to smaller process technologies and copes with the non-idealities of nano-scale transistor sizing. A comprehensive analysis of the potential of sub-threshold analog decoding is examined in this paper. It is shown that mismatch effects dominated by threshold mismatch impose firm lower limits on the sizes of transistors. The effect of various forms of leakage currents is also investigated and minimal leakage current to normalizing currents are found using density evolution and control simulations. Finally, the convergence speed of analog decoders is examined via a density evolution approach. The results are compiled and predictions are given which show that process scaling below 90 nm processes brings no advantages, and, in some cases, may even degrade performance or increase required resources.     

长途高速骨干网光传输系统的优化设计

为了改善长途高速骨干网光传输系统的传输性能,对其系统器件进行了优化配置,主要包括提出一种新的光放大器的配置方案,在光传送单元（OTU）中引入FEC技术。以便实现在确保低成本的条件下实现高效、高质量传输要求的目的。     

Efficient implementation of complementary Golay sequences for PAR reduction and forward error correction in OFDM-based WLAN systems

In this paper the use of complementary Golay sequences (CGS) for peak-to-average power ratio (PAR) reduction and forward error correction (FEC) in an orthogonal frequency division multiplexing (OFDM)-based wireless local area network (WLAN) system is explored; performance is examined and complexity issues are analyzed. We study their PAR reduction performance depending on sequence lengths and we have found that, for the case that the number of sub-carriers differs from the sequence length, some interesting relationships can still be stated. Regarding their error correction capabilities, these sequences are investigated considering M-PSK constellations applied to the OFDM signal specified in IEEE 802.11a standard. Computational load for both Golay encoding and decoding processes is addressed and we provide an exhaustive analysis of their complexity. In order to overcome memory restrictions and speed up algorithmic operations, a novel algorithm for real-time generation of the Golay Base Sequences is proposed and evaluated giving as a conclusion that these sequences can be real-time generated with actual Digital Signal Processors (DSP). Our proposal lies on an efficient permutation algorithm that obtains the current permutation without the need for generating previous ones. Its complexity is calculated and turns out to be significantly low; the advantages are specially appreciated at the decoding stage. We also introduce a hybrid solution to get a trade-off between complexity and memory requirements. Moreover, the whole system is also implemented in a DSP to validate the proposal in a prototype, where its feasibility has been confirmed.     

Error repair for broadcast transmissions in DVB‐H systems

People travelling in public transportation vehicles are foreseen to be a relevant use case of future Digital Video Broadcast—Handhelds (DVB‐H) systems. However, it is also one of the critical user cases, since, besides the vehicle penetration loss, the received signal quality is strongly affected by the high mobility of the users, which is accompanied by temporary shadowing and fast fading. On the other hand, mobility can be also beneficial thanks to the bursty character of DVB‐H transmissions, as additional repair data can be sent in the time intervals between original service bursts in order to hide the coverage discontinuities from the users' perception. In this way, users which miss the original transmission have more chances to receive the information correctly. By managing the amount of repair data the network operator can trade system capacity and network latency for improved vehicular user satisfaction in a DVB‐H network with imperfect coverage of the service area (as perceived by the vehicular users). To illustrate the potential of this approach, we evaluate the mentioned trade‐off in a DVB‐H system dimensioned for pedestrian outdoor users, for both streaming and filecasting services. To enable an easy and efficient implementation of the repair mechanisms, we adopt application layer forward error correction (FEC), as it can provide a multi‐burst protection of the transmission. Copyright © 2008 John Wiley & Sons, Ltd.     

使用主动前向纠错技术的可扩展的可靠组播协议

在分析研究了一些现有可靠组播协议的基础上,提出了一种主动前向纠错的可扩展可靠组播协议AFR,该协议能够使传送丢失数据的恢复包本地化,且只能到达需要它的组播接收者,从而节省了网络资源,降低了对接收者处理能力的要求,而所需要的开销也非常小。     

一种无线实时流媒体增强型自适应FEC控制机制

无线网络动态的信道特性和带宽有限等特点,使得在无线环境下为流媒体应用提供QoS保证面临更大的挑战。提出一种用于无线实时流媒体传输的增强型自适应前向纠错控制策略,以提高接收方的播放质量。该策略采用跨层设计的方法,根据当前的网络状态,自适应地调整MPEG视频帧的发送速率,在视频源数据和冗余数据之间动态分配网络带宽。仿真结果表明,该策略能使接收方获得最大的可播放帧率,有效提高流媒体传输的可靠性和实时性。     

数字视频广播（DVB）

文章主要介绍数字视频广播(DVB)标准;数字视、音频特点;数据组成格式;MPEG-2码流复用方式;以及各种传输方式(包括:DVB-S、DVB-C、DVB-T)和传输电路的组成。     

CableModem下行流物理层编码

对IEEE802.14物理层草案A型下行流编码方案和FEC帧同步方案进行了详细分析给出了可执行的方案并从理论上分析和计算了在64QAM调制下该编码方案传输数据所占用的带宽和误码率     

Efficiency of mechano-catalytic water-splitting system

Input energy to mechano-catalytic water-splitting system is transferred partly to organize the frictional electric condenser (FEC) system, which motivates the water-splitting, and partly to rotate the slurry. A part of the rotational energy is regained as a feedback, while the remainder is wasted to the dispersion loss through the viscous motion. The mechanism of the cyclic transfer of charge between the stirrer (Teflon), the vessel wall (Pyrex glass) and the semiconductor particles (NiO, etc.) is discussed. System efficiency, dynamic efficiency, energy conversions and the dispersion processes are analyzed. System design of the cell and the stability of FEC system are discussed as well.     

EPON系统物理层参数优化

EPON是一种新出现的接入网技术,针对EPON系统的特点,对原来IEEE802.3z链路模型进行了改进,并以其为参考对EPON系统进行了分析。目的是结合目前光器件水平,对EPON系统物理层参数进行优化,如传输距离与分光比等。