`Nearly instantaneous? digital compandor for transmitting six sound-programme signals in a 2.048 Mbit/s multiplex

A `near-instantaneous? digital compandor for the transmission of high-quality sound signals is described that reduces the bit rate from 416 kbit/s to about 322 kbit/s per channel without noticeable impairment of the sound quality. Hence six audio channels can be multiplexed to form a 2.048 Mbit/s stream including frame synchronisation and transmission error-protection facilities.     

PCM Subckannels for Video Microwave

A PCM subcarrier system has been developed which will permit video microwave to carry 24 6-kHz channels along with the normal video signal. The channels may be used directly or split into 48 3-kHz voice channels. The subcarrier system uses a differentially coherent quadraphase approach and has a data rate of 3 Mbit.     

1.544 Mbit/s Data Above FDM Voice and Data Under FDM Voice Microwave Transmission

Methods are presented for the transmission of wideband digital signals above and below the frequency division multiplexing (FDM) baseband spectrum of analog microwave systems. In particular, it is shown that a Data Above Voice (DAV) system employing a 1.544 Mbit/s data channel above FDM channels and a Data Under Voice (DUV) system employing 1.544 Mbit/s channel below 720 FDM channels, are practical hybrid systems. Theoretical models of hybrid transmission are disucssed and the DAV/DUV methods are compared. A conceptual hybrid system design procedure is introduced and field measurement results on an 8 hop 6 GHz system are presented, comparing favorably with theoretical predictions.     

OFDM for broadcasting in presence of analogue co-channelinterference

This paper treats the problems of digital TV terrestrial broadcasting in presence of co-channel interference from analogue TV services. The channel capacity is calculated for the optimum distribution of the transmitted power. An OFDM scheme is presented which is designed to be robust to the analogue TV interference. Power and number of bits per symbol are assigned to each OFDM channel to give the maximum data rate for a given signal to interference ratio. Simulations of the proposed scheme, for 8 MHz bandwidth and interference from a system G PAL signal, show that acceptable error rate can be achieved for e.g. 27 Mbit/s and 39 Mbit/s at signal to interference ratios of -6 dB and 0 dB, respectively. The proposed scheme is suitable for the next generation terrestrial TV networks which are going to coexist with the current analogue systems     

220GHz短程无线通信系统的设计与搭建

设计与搭建了工作在220GHz的短程无线模拟通信系统与数字通信系统,通信距离为0．6m。在模拟通信系统中,实现了音频信号（WAV格式）的实时传输与接收,达到了理想的播放效果。在数字通信系统中,实现了对文件（图片、音频、视频等）的加密、格雷编码、格雷解码与解密,由于受制于采集卡采样速率的硬件限制,实现的最大数据传输速率为1Mbit／s。     

Analysis of simultaneous digital and analogue signal transmission in a coherent optical subcarrier multiplexed system

The performance of the coherent subcarrier multiplexed system with mixed digital and analogue signals is analysed. The result shows that the performance of the digital channels in this system may be better than the pure digital system if the modulation index of the analogue channel is less than half of the modulation index of the digital channel. It is predicted that the system will have a 14 dB improvement over the corresponding intensity modulation/direct detection system.<>     

Analogue and digital transmission using polymer optical fibre

The performance of a hybrid AM/BPSK (amplitude modulated/binary phase shift keying) polymer optical fibre transmission system has been investigated. A BPSK modulated 2 Mbit/s pseudorandom digital channel is substituted for one of the AM channels in a 60-channel cable TV system. For the digital channel, a bit error rate of <10^-9 is obtained after transmission through 200 m of fibre. The results show that distortion caused by laser nonlinearity did not degrade the system at low modulation depth     

Digital visions: where the superhighway will lead

The author looks forward to the world of interactivity made possible entirely by digital communications, storage and compression. Digital technology has also expanded the capacity of communications networks, supporting an enormous rate of growth in traffic. Compression has immediate transmission cost benefits for satellite broadcasters, since an analogue PAL transponder covering Europe, say, may cost £4 million per year. A compressed 8 Mbit/s digital service (Filmnet), with four digital channels per transponder, quarters the cost per programme service. For a 2 Mbit/s digital service, costs could fall to around £250 000 per year. As the cost of compression equipment falls, many more services can be delivered direct to homes by satellite or cable systems     

800 Mbit/s Digital Transmission System Over Coaxial Cable

800 Mbit/s digital transmission systems, using nonredundant three-level and four-level codes, have been studied as a means of providing an economically attractive digital transmission system. These systems have been designed to be compatible with a 60 MHz analog system in repeater spacing and repeater size, so as to be easily introduced into the existing network. These systems with 11 520 telephone channels, exceed the 60 MHz analog system in both capacity and economy. Due to repeater construction factors, it became clear that the three-level code is more suitable. This paper describes the design and performance of 800 Mbit/s digital transmission systems and repeaters.     

High-Speed Digital Switching Technology Using Space-Division-Switch LSI's

NTT is planning a high-speed broad-band switching network that offers high-speed digital and 4 MHz video services. This paper discusses the hardware design of the high-speed space-division digital switching network and requirements for a switch LSI. In addition, the design and measured performance of a 32 × 32 CMOS space-division-switch LSI are described. In this network, video signals are converted into 32 Mbit/s digital signals by band-compression technology. In order to switch such digital signals, space-division switches are more advantageous than time-division switches. This is because time-division switches cannot multiplex many channels at that bit rate. Furthermore, the use of the space-division-switch LSI is the most effective way to miniaturize the switching system.     

Digital television terrestrial broadcasting

Digital transmission will change the way television channels are allocated and will force broadcasters to master a new set of parameters for optimizing service coverage. This article discusses modulation and channel coding issues related to digital television terrestrial broadcasting (DTTB), such as data throughput, spectrum efficiency, single- and multicarrier modulations, interferences under simulcasting conditions, multilayer services, and DTTB coverage. Current advanced television (ATV) research for terrestrial broadcasting in the VHF/UHF bands is converging toward a fully digital implementation. In a digital ATV system, the digitized high definition video sources, with raw bit rate of up to l-Gb/s, are compressed using source coding techniques based on the discrete cosine transform (DCT) coding. The output data rate of the video source encoder, with present technology, is typically 15 to 20 Mb/s. This data rate is sufficient to provide a satisfactory distribution quality video service     

Bidirectional multichannel 1.44 Gbit/s lightwave distributionsystem using subcarrier multiplexing

Demonstrates a bidirectional lightwave distribution system that uses subcarrier multiplexing to transmit data to eight nodes from a single head-end laser. Data for each node (180 Mbit/s) and return date (45 Mbit/s digital video) are transmitted as FSK subcarrier, between 2.5 and 5.0 GHz. Penalties from laser nonlinearities, interchannel interference or bidirectional transmission are negligible     

Design of integrated services digital broadcasting systems usingmultirate optical fiber code-division multiplexing

This paper presents the design of a new type of integrated services digital broadcasting (ISDB) systems which use a multirate optical fiber code-division multiplexing (OF-CDM) technique. The proposed system can efficiently multiplex various kinds of digital signals with multiple bit rates. This is feasibly achieved by using strict optical orthogonal codes of both auto- and cross-correlation constraints being “1” in multirate OF-CDM systems. Moreover, the low-cost design of OF-CDM transmitters is presented, and experimental demonstrations are also carried out. The measured results show that a transmission distance up to 13 km can be feasibly accomplished by using the proposed transmitter design and the external optical injection-locking scheme. It is expected that the proposed ISDB systems can be employed to cost-effectively transmit fast ethernet (125 Mbit/s), FDDI (125 Mbit/s), ATM (155 Mbit/s), and ESCON (200 Mbit/s) protocol data. Their potential applications include Internet services and multimedia broadcasting, such as videoconferencing, video on demand, HDTV, distance learning, and World Wide Web     

Orthogonal Cochannel Operation for High Spectrum Efficiency Based on the Example of 16 QAM-140 Mbit/s Systems Using Rolloff 0.19

In view of the rapidly increasing demands for transmission capacity of public networks and the limited number of radio frequencies available, the band efficiency of existing systems in general will become insufficient for future high-capacity requirements. This fact is becoming increasingly evident for 16 QAM-140 Mbit/s radio systerns at 3.9, 6.7, and 11.2 GHz which are in widespread use in todays long-haul transmission networks. Conceptual and technological measures for making cochannel operation feasible and practical are presented using the example of a system family. By these means, even the capacity of existing 16 QAM-140 Mbit/s radio routes with 40 MHz interleaved channel arrangements can be doubled with the particular advantage of reutilizing the existing antennas and radio equipment with only minor modifications. A progressive filter concept makes orthogonal cochannel transmission possible with negligible adjacent channel spectrum interference. Surface acoustic wave IF filters are used to convert existing systems from 0.5 rolloff to 0.19 rolloff. Special RF channel/antenna arrangements were developed for the transmission of all RF channels in both directions, including space diversity and using only two antennas. A field experiment verified the feasibility of the concept and indicated that a crosspolar interference canceller is generally not necessary for 16 QAM140 Mbit/s cochannel operation.     

A Digital Satellite Communications System for Corporate Telecommunications

A satellite communications system has been implemented by Citicorp to meet its present and future internal domestic telecommunications requirements. This system is currently being used for voice and data transmission and video teleconferencing between corporate facilities in New York, Los Angeles, San Francisco, and Sioux Falls, SD. Six additional cities will be served by the end of 1984. This system utilizes an 11-m earth station in each city to transmit and receive 60 Mbit/s TDMA signals from a satellite transponder on the Western Union WESTAR V satellite. Various terrestrial microwave, fiber optic, and copper cable facilities interconnect the earth stations to the users of the system. The basic trunk is digital at a T1, or 1.544 Mbit/s rate or multiple thereof, except some local distribution. A network control center provides centralized monitoring and control for all facilities in the system.     

Indicating Service Outages of High Capacity Digital Systems at the Affected Channel Banks

In a digital transmission network including 1.5 Mbit/s and higher speed systems, it is desirable to signal service outages of the higher speed systems to the multitude of affected channel banks terminating the 1.5 Mbit/s systems in order to avoid unnecessary maintenance activity. To do this, it is proposed that a special signal be transmitted to the channel banks from the multiplex terminating the higher capacity systems. This special signal causes the channel bank alarm lights to flash, and thus can be recognized without special test equipment or modification of the channel banks. While the special signal may be quite complex to operate properly with several generations of channel banks, the circuitry required to generate it fits comfortably on a single circuit board and can be shared by all 1.5 Mbit/s outputs of the multiplex.     

A high-capacity broadband packet switch architecture based on a multilink approach

Broadband packet networks based on asynchronous transfer mode (ATM) are expected to provide a wide range of services, including motion video, voice, data and image. When these networks become prevalent, some applications such as motion video and high-speed LAN interconnections will place a very large bit rate requirement on the channels. Currently, the physical layer supported by the synchronous optical network (SONET) allows the transmission of up to 2.4 Gbit/s with the OC-48 optical interface. However, it is not feasible for the electronic packet switch to route packets at this rate on a single link. In this paper we present a design of a broadband packet switch that uses multiple links in parallel to realize a high-speed channel. This implementation permits the switch to operate at the lower link rate, which can be at 150 Mbit/s, while having the ability to support a virtual circuit at a higher rate (up to 2.4 Gbit/s). The main contribution of the design is that packet sequence on a channel is still maintained even though packets are allowed to use any of the links belonging to the same channel. Besides allowing the switch to function at a slower rate than the transmission channel rate, the implementation of the multilinks benefits from statistical multiplexing gain. Analytical results show the performance advantages of multilink design with respect to delay, throughput and packet loss probability.     

Investigations on bit error performance for video over DAB

The digital audio broadcasting (DAB) system which was originally designed for high quality audio transmission to mobile receivers is investigated for transmission of compressed digital video and multimedia signals. The bit error performance is considered using various levels of error protection provided by the DAB system. As a result, a net bit rate of about 1.5 Mbit/s can be achieved. With additional error correction coding, a bit error ratio (BER) of less than 10^-10 can be realized. This is the requirement for compressed video signals. The SNR per bit is below 16 dB. The results are demonstrated and compared using computer simulations of the complete system     

The impact of CSO/CTB distortion on BER characteristics by hybridmultichannel analog/QAM transmission systems

The FEC limit (uncorrectable errors) with CSO/CTB (composite second order/composite triple beats) distortion presence in a channel is not for modulated lasers only, but for coaxial networks with amplifiers too. The system quality reserve depends not only on CNR, but is more limited on CSO/CTB. It is important, for the definition of the system quality reserve, to calculate the CSO/CTB spectrum caused by analogue channels within analogue and digital QAM channels and also to calculate the changing of CNR from the intermodulation interaction between analog and digital channels in a CATV network     

RF microelectronics for W-CDMA mobile communication systems

Third generation (3G) mobile communication systems are now just starting to be introduced. With a maximum data rate of 2 Mbit/s they will make wireless access to broadband data services like the Internet or video applications feasible. Most of the different physical layer technologies summarised under the acronym 3G are based on wideband-CDMA (W-CDMA), in contrast to existing second generation systems, which mostly use TDMA and FDMA. This has severe consequences for the design of the transceiver front-ends. During standardisation these were assumed to have an adequate RF performance yet they still present a performance bottleneck for the system. Starting with a short introduction to UMTS (Universal Mobile Telecommunications System)-the 3G standard to be deployed in Europe and already operating in Japan-this paper describes by way of example some of the test cases specified for UMTS and their impact on the analogue front-end. It is shown that accurate simulation of all the analogue and digital signal processing is necessary in order to predict the RF performance needed of today's commercial RFICs. The paper then presents and reviews some actual design examples. Finally, possible technologies and techniques for application in future mobile terminals are discussed