16 Kb/s high quality voice encoding for satellite communication networks

This paper describes applications of adaptive predictive coding (APC) with maximum likelihood quantization (MLQ) which can cover a wide range of coding rates from 4.8 to 16 kb/s for low C/N satellite communication systems, such as maritime, aeronautical mobile and thin-route satellite communication systems, and also for speech and data integration, including digital circuit multiplication equipment (DCME) in business communication systems, such as INTELSAT business services (IBS). A 16 kb/s APC–MLQ hardware codec has been implemented by NEC–7720 DSP chips and the performance has been confirmed in subjective quality of speech through conversational tests. The objective performance has also been evaluated for non-voice signals, such as single and multi-frequency tones, and 1200 and 2400 b/s voiceband data signals. The APC-MLQ codec can transmit the voice-band data at 1200 b/s over two asynchronous tandem links and at 2400 b/s over one link. It was noted that the APC-MLQ codec is superior in speech performance at 16 kb/s to a narrow-band companded FM and meets requirements for low C/N satellite communication systems. For voice and data integration into 16 kb/s for 64 kb/s links, we propose a multi-media multiplexing for low C/N digital satellite communication systems and also a small-scale circuit multiplication system for business use. In these systems, a variable rate coding of APC-MLQ from 4.8 to 16 kb/s can be effectively introduced for voice and data integration.     

The DTX-240D digital circuit multiplication system

This paper describes the DTX-240D digital circuit multiplication system (DCMS) offered by ECI Telecom. It will accept up to 240 × 64 kb/s trunks carrying either 64 kb/s voice, voice band analogue non-speech signals, or digital data for transmission over a 2·048 Mb/s digital link. Over 1000 are currently ‘on-line’ and carrying traffic. The system comprises a pair of terminals, one on each side of the interterminal digital link (bearer). It will normally operate in the network at a concentration ratio of 5:1, in which case 150 × 64 kb/s trunks, carrying voice, voice band data or digital data can be concentrated into one 2·048 Mb/s bearer. The users are able to increase the number of trunks up to 240 per 2·048 Mb/s bearer, when time zone differences cause a spread of busy-hour traffic carried on a single system. Each terminal will normally be located at an international switching centre (ISC) but may also be located at an earth-station. The system uses a DSI (digital speech interpolation) stage providing a 2·5:1 multiplication, followed by an additional 2:1 multiplication by means of ADPCM (adaptive differential pulse code modulation). In addition, the VBR (variable bit rate) technique is used to prevent clipping, due to overload congestion. The system can also be used with 1·544 Mb/s digital bit streams (trunk side or bearer).     

Telematic services via satellite in Europe

The word ‘telematics’ was used for the first time in France in 1978 by Simon Nora and Alain Minc; it is a contraction of the French words ‘tétécommunications’ and ‘informatique’, and defines a marriage between computers and data transmission networks. This paper describes the five systems which will be implemented to provide telematic services via satellite in Europe during the next few years: EUTELSAT, TELECOM 1, UNISAT, DFS and ITALSAT. The main characteristics of the ‘special service’ transponders are presented, showing that, in Europe, (a) 2 to 5 transponders per satellite will be devoted to the special (telematic) services; (b) 4 satellites out of the 5 use the 12.5–12.75 GHz down-link band for this purpose (only ITALSAT uses the 20 GHz down-link for the same purpose), and (c) e.i.r.p.s at 12 GHz are in the range 40–49 dBW. The ground and space segments corresponding to this new service are presented. The main peculiarity of the ground segment is the exclusive use of ‘small’ earth-stations equipped with fixed antennas and SCPC or 25–60 Mb/s TDMA multiple access equipment. Telematic services include videoconference at 2048 kb/s, voice services, computer-to-computer transfer of data, data distribution, remote printing, electronic mail, high-speed facsimile, offshore voice and data services, digital network overflow, transatlantic digital business etc… Customer bit rates start from 2.4, 4.8, 9.6 and 32 kb/s (for TELECOM 1) up to 2048 kb/s by 64 kb/s steps. Bit error rates are maintained below 10^?6 (standard) or 10^?10 (higher grade) during 99 per cent of the year using FEC. The five networks for telematics via satellite in Europe are independent. A large efficiency improvement of the different services should be obtained through a future interconnection of the various networks via intersatellite links.     

A retransmission scheme for circuit-mode data on wireless links

The cellular radio link is characterized by deep fades leading to long error bursts (lasting hundreds of milliseconds). Data transmission over such links results in large packet error rates (in the range 10^-3 to 10^-1). We have designed a radio link protocol (RLP) to achieve high throughput on such links. The RLP is based on frequent, complete or partial feedback of the receiver state. Performance results for the US digital cellular TDMA standard show that the scheme can provide the equivalent of 9.6 kb/s service per full-rate TDMA channel above a carrier to interference ratio of 18 dB     

语音数字信号压缩技术在TES系统中的应用

介绍ADPCM标准、RLPC编码原理,编、解码器方框图及工作过程。民航卫星通信网TES系统为节省卫星转发器频率资源对传输的语音信号进行压缩处理,其信道单元基带信号处理器对语音信号进行CCITT推荐的G.721-ADPCM编码和修斯公司专利技术开发的RLPC编码处理,将64 kb/s语音数字信号压缩至32 kb/s,16 kb/s,9.6 kb/s传输,实现语音质量满足一般通信要求的低速率语音信号传输。     

Two approaches for waveform coding of 9.6 kbit/s voiceband datasignals through 32 kbit/s ADPCM

Two approaches are presented for accommodating 9.6 kb/s modem signals (e.g. V.29) through 32 kb/s ADPCM (adaptive digital pulse-code modulation) links. These are small changes in the existing algorithm and coding with ADPCM incorporating a 5-bit, rather than 4-bit quantizer. For each approach, tradeoffs between performance and implementation complexity are described     

Overview of wideband packet protocols

Wideband packet networks operate at rates equal to, or higher than, 64 kb/s, but lower than the basic broadband rate of 150 Mb/s, on cables or satellite links. Wideband packet protocols are the transmission protocols for these networks. They define open interfaces that can be used for public and private ISDNs. The protocols are defined in CCITT Recommendations G.764 and G.765. This paper describes the objectives of the wideband protocols, and how the objectives were achieved.     

ITU-T G.729 Annex A: reduced complexity 8 kb/s CS-ACELP codec fordigital simultaneous voice and data

This article describes the ITU-T Recommendation G.729 Annex A (G.729A) for encoding speech signals at 8 kb/s with low complexity. G.729A is the standard speech coding algorithm for multimedia digital simultaneous voice and data (DSVD). G.729A is bitstream interoperable with G.729; that is, speech coded with G.729A can be decoded with G.729, and vice versa. Like G.729, it uses the conjugate-structure algebraic code excited linear prediction (CS-ACELP) algorithm with 10 ms frames. However, several algorithmic changes have been introduced which result in a 50 percent reduction in complexity. This article describes the algorithm introduced to achieve the low complexity goal while meeting the terms of reference. Subjective tests showed that the performance of G.729A is equivalent to both G.729 and G.726 at 32 kb/s in most operating conditions; however, it is slightly worse in the case of three tandems and in the presence of background noise. A breakdown of the complexities of both G.729 and G.729A is also given     

A multimode 0.3-200-kb/s transceiver for the 433/868/915-MHz bands in 0.25-/spl mu/m CMOS

A fully integrated transceiver suitable for low-data-rate wireless telemetry and sensor networks operating in the license-free ISM frequency bands at 433, 868, or 915 MHz implemented in 0.25-/spl mu/m CMOS is presented. G/FSK, ASK, and OOK modulation formats are supported at data rates from 0.3 to 200 kb/s. The transceiver's analog building blocks include a low-noise amplifier, mixer, channel filter, received signal-strength indication, frequency synthesizer, voltage-controlled oscillator, and power amplifier. FSK demodulation is implemented using a novel digital complex-frequency correlator that operates over a wide modulation-index range and approximates matched filter detection performance. Automatic gain control, automatic frequency control, and symbol timing recovery loops are included on chip. Operating in the 915-MHz band in FSK mode at 9.6 kb/s, the receiver consumes 19.7 mA from a 3-V supply and achieves a sensitivity of -112.8dBm at 0.1% BER. The transmitter consumes 28.5 mA for an output power of 10 dBm and delivers up to 14 dBm.     

PDH通信二次群复接器在CPLD中的实现

简要介绍了准同步二灰群复接的基本原理，分析了正码速调整的基本原理及所涉及的一般问题，在此基础上，用VHDL语言对准同步复接电路进行全数字化描述，并在Max＋Plus Ⅱ环境中进行编译和仿真，得到了理想的结果，实现了基群速率2048kb／s的数字信号准同步通信二次群的复接器，其主要功能是在复接端将4个支路的2048kb／s数据通过正码速调整技术，合路成1路8448kb／s的高速数据流，由仿真结果可以看出系统的设计与理论值相符。     

Burst error characterization of FEC coded digital channels

This paper reports on laboratory measurements to determine the characteristics of error bursts encountered on INTELSAT IDR and IBS links for data rates between 64 and 44,736 kb/s. In addition to burst length distributions, several other burst statistics are presented: number of errors per burst, average BER within bursts, and the distribution of error-free block lengths. These results are intended for use in system design and evaluation of video/speech/data codec performance which are employed on such links.     

International Connection of Plesiochronous Networks via TDMA Satellite Link

Digital transmission techniques are expected to spread throughout the fixed-satellite service in the near future. The introduction of digital satellite systems will lead to a new requirement regarding how to connect the satellite link with terrestrial digital networks. This paper presents a satellite/terrestrial digital interface that has been developed to interconnect 2.048 Mbit/s PCM terrestrial and INTELSAT TDMA links which are in the plesiochronous relationship. Major functions of the interface include frame slip control, compensation for path length variation, and rate and format conversions. This paper also describes the design and implementation of the developed equipment, and experimental results for signal impairment due to the frame slips and PCM multiplex standard conversion. The experimental results demonstrate that a large humber of bit errors are induced by frame slips for voiceband data transmission above 4800 bits/s.     

A 256-element CMOS imaging receiver for free-space optical communication

This paper describes a CMOS imaging receiver for free-space optical (FSO) communication. The die contains 256 optical receive channels with -47 dBm optical sensitivity and 30 dB optical dynamic range at 500 kb/s/channel while consuming 67 mW. Received signals are amplified by digitally self-calibrated open-loop amplifiers and digitized before clock and data recovery. The sampled data also provide inputs for digital automatic gain and offset control loops closed around the analog amplifier chain to compensate for signal variations due to atmospheric turbulence and daylight interference. Gain control logic can adapt to incident signals over the 30 dB dynamic range within 28 bit periods. Low-power logic design and analog circuit techniques are used to minimize digital crosstalk to single-ended photodetectors referenced to a bulk substrate. Local arbitration circuitry at each channel forms an intrachip data passing network to multiplex received data words from the 16 /spl times/ 16 array onto a common off-chip bus. The 1.6 M transistor mixed-signal die fabricated in a 0.25 /spl mu/m CMOS process measures 6.5/spl times/6.5 mm/sup 2/. Reception at 500 kb/s through a 1.5 km atmospheric channel is demonstrated with 3 mW optical transmit power during nighttime and daylight hours.     

高速无线数传技术在集群通信系统中的应用

根据目前模拟集群移动通信系统的发展和现状,给出了一种在用户现有的系统和链路资源下实现高速无线数据传输的解决方案,即利用移动用户终端,通过现有的无线集群系统或常规无线通信系统的无线信道对用户系统的数据库进行实时访问,以获取所需的数据信息,采用高速无线数传调制解调器芯片MX909,使系统数据传输速率达到9.6kb s。     

畜产品可追溯系统的设计与研究

针对动物养殖、屠宰加工和销售整个畜产品生产流程,设计了基于RED技术的畜产品可追溯系统来对畜产品进行全程标识,保证可以追溯到每个动物食品生产环节.通过自行设计读写器和电子标签的实际测试,实现了数据的自动采集,并得出下列结果:随着数据传输率呈倍数的减小,通讯距离和信号强度都逐渐增加;采用60 kb/s或者10 kb/s数...     

G.718: A New Embedded Speech and Audio Coding Standard with High Resilience to Error-Prone Transmission Channels

This article is an overview of the standardization, architecture, and performance of the new ITU-T Recommendation G.718. G.718 is an embedded variable bit rate codec providing a scalable solution for compression of 8 and 16 kHz sampled speech and audio signals at rates between 8 kb/s and 32 kb/s. It comprises five layers where higher-layer bitstreams can be discarded without affecting the lower layersiquest decoding. The codec also has an optional core layer interoperable with ITU-T G.722.2 (3GPP AMR-WB) at 12.65 kb/s. G.718 was designed to provide high speech quality at low bit rates and to be robust to significant rates of frame erasures or packet losses. It is also targeting good quality for generic audio at higher rates.     

一种基于纠缠交换的远程量子链路建立策略

提出一种以纠缠交换作为核心技术的远程量子链路建立策略,建立了基于链路状态矩阵的量子链路模型并分析了纠缠交换的实现和矩阵表示。提出了链路协议栈以及端到端的建立策略,分析了矩阵控制下的纠缠交换和纠缠纯化流程,计算得出了在基于自动重传请求( ARQ )协议经典信息辅助下的链路时延和吞吐量与节点数、误帧率、平均距离、操作成功率之间的定量关系。仿真结果表明：处于同一状态区间内的链路性能随节点数呈现出较为一致和平缓的变化;不同区间内的链路性能差异较为显著,在节点平均距离为1 km、经典信息误帧率为0、纠缠保真度为0.98的情况下,当节点数分别为32、33和34时,链路时延分别为1.0770 ms、1.0903 ms和1.6690 ms,链路吞吐量分别为0.9285 kb/s、0.9172 kb/s和0.5992 kb/s。     

Phase jitter≡timing jitter?

In digital communication systems, the periodicity of timing signals is often disturbed. While timing jitter has been adopted by the International Telecommunication Union (ITU) as the standardized measurement for such disturbances, phase jitter is often used instead in much of the current relevant literature. The fundamental concepts of timing jitter and phase jitter are examined and definitions are presented. A nonlinear relationship between timing jitter and phase jitter is developed, and a general rendition under which one can be approximated by the other is obtained. This condition is tested against the timing jitter and wander tolerance for digital equipment operating at 2048 kb/s, as specified in ITU-T Recommendation G.823     

谈谈烟草板块数据资源的管与用

伴随5G的应用,物联互通必将在各行业各板块得以实现.每次科技变革的时间周期相对于上一次而言都更短,此次5G的从应用到成熟必然也是如此.在未来各行业数字化程度将更高,数据资源的采集会更快、更广、更深、更准,由此而产生的大数据(Big Data)资源,必将是企业求存与发展过程中不可或缺的资源.数据资源的管与用,将决定企业发展好与坏.大数据如何在烟草行业中得以有效利用,为消费者提供更适合的产品和更优质的服务?这需要通过做好产、运、销各环节大数据的采集、挖掘分析,确保数据的安全和完整性,做到合理配置和有效利用.