Implementation of intelsat IDR operation

Over the next few years INTELSAT IDR carriers are expected to replace analogue FDM/FM carriers carrying trunk public switched telephony traffic. This paper describes the activities necessary to implement INTELSAT IDR operation into an existing or new earth-station. The operational planning aspects discussed include the initial traffic and marketing forecasts to determine the IDR carrier requirements, use of DCME, the type of signalling system to be used and the interfaces with the terrestrial network, including synchronization. Typical earth-station equipment configurations for IDR operation are described, and the design options that should be considered for the DCME, IDR modem, frequency converters, HPA and control and monitor systems are discussed.     

The role of intermediate data rate (IDR) carriers in the intelsat system and their impact upon operational planning

IDR carriers will provide a significant proportion of the services in the INTELSAT system within the next few years. A number of factors have been identified which must be considered when developing satellite operational plans, in order to ensure satisfactory operation of an integrated environment consisting of a number of different access techniques and modulation methods.     

New trends in digital circuit multiplication technology

This paper discusses the achievements and the unsolved problems of the first generation of Digital Circuit Multiplication Systems (DCMS)

1 DCMS is an abbreviation for Digital Circuit Multiplication Systems. DCME is an abbreviation for Digital Channel Multiplication Equipment. Both refer to the same technique of combining digital speech interpolation and low rate encoding.

. The following summarizes proposed improvements in DCMS technology. A major improvement in DCMS gain may be achieved by implementation of facsimile demodulation. The design considerations of this technique are discussed. The CCITT activities on standardization of a 16 kb/s speech coding algorithm are reviewed. In order to adapt this algorithm to implementation in a DCMS, the operation of the algorithm has been modified to enable variable bit rate operation at rates between 12·8 and 24 kb/s. The implementation of such an algorithm in DCMS will further increase the overall compression gain. The first generation of DCMS has been implemented mainly on heavy traffic routes. A DCMS terminal which is optimized for operation on ‘thin’, or smaller, routes, using an IDR link operating at 512 kb/s, is described. Tandem operation of DCMS is becoming an increasingly important consideration on both international and national routes. The accumulation of qdu's (quantization distortion units) when two pairs of DCME/S terminals are operated in tandem can be avoided by an arrangement without ADPCM decoding/encoding in the transit terminals so that the ADPCM decoding is carried out only at the final destination DCMS terminal.     

Advanced techniques for circuit multiplication: Celtic 3G

The Celtic 3G is Alcatel CIT's new digital circuit multiplication system designed to enhance the cost-effectiveness of long-haul links by increasing their capacity by a factor of between 5 and 8. The Celtic 3G offers an effective, versatile solution to congestion problems on 2048 and 1544 kb/s digital transmission links. The paper describes the compression modes used by Celtic 3G family to transmit the various types of signals (speech, voice band data, 64 kb/s digital data), the applications and the operating principles of the equipment. A number of telecommunication administrations and agencies have adopted and will this year deploy the Celtic 3G because of its benefits, technical qualities and the savings which it will achieve on digital links.     

The use of digital circuit multiplication equipment in satellite communications

The use, within satellite communications, of low rate encoding (LRE) techniques, based on 24, 32 and 40 kb/s ADPCM coding, coupled with digital speech interpolation (DSI) to form a digital circuit multiplication equipment (DCME), is addressed in this paper. The need for a system simulation tool, in order to plan for and correctly use the DCME concept is identified. Results obtained with this simulation tool are presented. The simulation model makes it possible to predict the behaviour of the system from a quality point of view, with external conditions simulated to be very close to actual operating conditions.     

Transmission quality of Group III facsimile on IDR satellite links with circuit multiplication equipment

The focus of this paper is on ways to improve the quality of Group III facsimile on intermediate data rate (IDR) satellite links. First, we present the results of an evaluation of the quality of Group III (G3) facsimile images transmitted on satellite links through circuit multiplication equipment (CME). Based on the results of this study, we propose a model to relate the facsimile image quality requirements to the bit error ratio (BER) on the link. A procedure is introduced to associate the long-term percentage of error-free pages in G3 facsimile transmission with various bit error probability (BEP) masks used for satellite link design. The intent of this procedure is to provide comparable end-to-end transmission quality for international telephone circuits, irrespective of whether the transmission medium is a satellite link or a fibre-optic cable. It is concluded that, unless the performance objectives of satellite systems significantly exceed those derived from CCITT/ITU-T Recommendation G.826, fibre-optic cables will become the preferred choice for international transmission.     

Novel route to carboxylic acids via the DCME reaction

Brown's DCME reaction was successfully performed employing B-alkyl-9-oxa-10-borabicyclo[3.3.2]decanes (1) to provide carboxylic acids (2) in good to excellent yields with complete retention of configuration.     

应急卫星通信系统中一种节省带宽的方法

利用DCME设备对中继线路话音进行20:1压缩,再利用承载侧分群技术,进一步提高卫星信道带宽利用率。使应急卫星通信系统中有限的频率资源得到充分利用。     

通用DCME信号识别系统设计

本文提出了一种适用于各种类型DCME信号的识别系统的概念,并初步论述了系统的识别算法原理与实现方法及优缺点。     

Circuit multiplication equipment

This paper discusses the main issues relating to the configuration and equipment which are to be provided in earth-stations for implementing satellite links with digital circuit multiplication (DCM). Such an implementation is possible using either FDMA/TDM/PSK (continuous) or TDMA/PSK (burst mode) carriers. The main accent will be put in the paper on earth-stations operating with FMDA/TDM/PSK carriers (called IDR carriers by INTELSAT). As regards the RF/IF subsystem, it is shown that IDR and TDMA are very effective in terms of earth-station equipment as compared with conventional FDM/FM operation. As regards the communication subsystem—independently of the DCM equipment proper—a compact terminal, integrating all the signal processing and baseband functions is described.