An Experiment in Integrated Digital Satellite Communications

The experiment we conducted for integrated digital satellite communications is aimed at realizing integrated services digital networks by satellite communication. The experiment was carried out in 1980 using the Japanese experimental communication satellite "CS." This experiment uses 30/20 GHz small earth stations and demand-assignment time-division multiple-access (TDMA) systems. Communications between customer terminals, which contain video conferencing, high-speed facsimile communication, high-speed computer communication, and packet-switching signal transmission, were carried out through the experimental digital satellite link. This paper describes the configuration of the experimental integrated digital satellite communications system and the experimental results of communications between customer terminals.     

快速发展的蜂窝网通信和卫星通信

主要说明无线通信将应用于移动通信、个人通信和全球通信。数字蜂窝网将增设微蜂窝区 ,频率从 90 0MHz升至 1 .8～ 2GHz ,向宽带和多媒体方向发展 ,数据速率从 1 44kb /s升至 2Mb /s。手机将是TDMA /CDMA双模。蜂窝网不仅用于移动通信 ,而且用于固定用户的市内接入网。卫星通信将加快发展低轨道 /中轨道卫星通信网 ,而同步卫星仍需利用。移动卫星网可通电话 ,可进行多媒体通信 ,速率为 2Mb /s,并通过地面信关站 ,与陆地固定通信网结合一起 ,实现全球个人通信。     

The transmission capacity of multibeam communication satellites

The transmission capacity which can be provided by a geosynchronous multiple-beam satellite employing frequency reuse is studied. Like all communication channels, satellite capacity is limited by available power, transmission bandwidth, and noise. In addition, factors peculiar to satellite links include cochannel interference among neighboring beams, channel nonlinearity, nonuniformly distributed traffic, and for satellites operating at frequencies above 10-GHz, rain attenuation. The effects of these factors upon the capacity of a satellite system are examined in detail. Results for a 12/14-GHz system with assumed satellite parameters compatible with a space shuttle launch and small 5 m earth station antennas show that a capacity of about 30 Gbit/s can be provided if the unavailability due to rain outage is no greater than 0.1 percent, and that about 10 Gbit/s can be provided for an unavailability no greater than 0.01 percent. Efficient utilization of the geosynchronous arc is also explored, and current trends in communication satellites are discussed.     

Japanese commercial tdma system

This paper reviews two TDMA systems which have been developed at NTT (Nippon Telegraph and Telephone Public Corporation) for domestic use in Japan. The first system uses K-Bands (30/20 GHz) and is called the TDMA-65M system. This system constructs a variable channel capacity network between 8 major cities (regional centres). The second system uses C-Bands (6/4 GHz) and is called the TDMA-100M system. This system provides remote island communication links for simultaneous transmission of voice and colour television signals. These two TDMA systems were put into commercial operation in summer 1983 by using, respectively, the Communication Satellite-2s, CS-2a which was launched in February 1983 and CS-2b which was launched in August 1983.     

自适应TDMA抗雨衰对策在Ka波段卫星通信中的应用

自适应TDMA是一种非常有效的Ka波段卫星通信抗雨衰对策。本文研究了自适应TDMA的解决方案，包括地球站结构、帧结构安排、系统体系结构和链路质量估计及其传输。本文可以为Ka波段卫星通信设计人员提供TDMA系统设计的参考。     

卫星固定站天线控制系统改造的探讨

卫星固定站是指在特定站点的卫星通信地球站,通常是通过同步轨道通信卫星进行卫星业务的通信。卫星固定站大多使用的是2.4 m-7.3 m静中通天线,早期的工程施工中大部分天线未安装自动控制系统,靠手动控制驱动电机进行对星。文章对Ku频段卫星固定站天线控制系统改造进行探讨,提出更好的改造方案。     

Cost-effective networking via digital satellite communications

This paper presents the major issues in forming a cost-effective and efficient network from a set of earth stations sharing the satellite resource. The discussion is in the context of satisfying the performance requirements for transmission of data, voice, and image presented to earth stations in digital form. Multiple access techniques have significant impacts on the network economy. Although wide-band single-carrier time-division multiple access (TDMA) uses the satellite capacity efficiently and is cost-effective for networks with large traffic volumes per node, it requires expensive earth stations and is not cost-effective for networks with small traffic volumes per node. The concept of multicarrier-TDMA (MC-TDMA) is described and its economic advantage over TDMA is demonstrated for networks with dispersed points of traffic origination. Application of demand assignment to MC-TDMA is also presented. Some implementation issues are also discussed.     

20, 30 GHz Band Cassegrain Earth Station Antenna for the Japanese Domestic Satellite Communication System

An 11.5 m 30/20 GHz band Cassegrain antenna has been developed for a Japanese domestic satellite communication system earth station. In order to form an economical satellite communication network, the earth station antenna is required to be installed on the top of a telephone office building in a large city. Therefore, interference with terrestrial radio relay systems and antenna load on a building become the most important problems to be investigated. Considering the satellite position in geostationary orbit, a limited steerable system combined with a two-jackscrew drive mechanism is employed to lighten and simplify the antenna structure. Measured antenna aperture efficiencies are 72% in 20 GHz band and 68% in 30 GHz band. Measured wide angle radiation patterns satisfy the CCIR recommendation level. TheG/Tof the antenna at the feed horn port is measured to be 53.9 dB/K atEl = 45degat 18.75 GHz. Interference with the 20 GHz band terrestrial radio relay system in extremely near field was experimentally studied. Results show that the terrestrial system's antennas can be installed closely up to about 20 m without serious interference.     

SBS TDMA-DA system with VAC and DAC

This paper describes many of the design considerations involved in developlng the demand assignment (DA) subsystem of the TDMA satellite communication system for Satellite Business Systems. Each earth station has a satellite communications controller (SCC) which requests capacity to meet current voice and data traffic demands. A central reference station frequently reallocates capacity based on the requests of all the earth stations in a network. To minimize the amount of satellite capacity required, the SCC has a circuit-switching capability for voice calls as well as for digital data calls. Furthermore, the SCC employs voice activity, compression (VAC) and data activity cornpression (DAC), In which the amount of capacity requested is based on measured average speech activity as well as the number of off-hook voice ports and the number of off-hook data ports. Data calls are queued on a first-come, first-served basis when capacity is not immediateiy available. The reference station distributes excess capacity according to a nonlinear table lookup procedure so that the voice call blocking probability is equalized across the network. The DA system makes much more efficient use of satellite transmission capacity than a design with fixed-capacity trunk routes.     

30/20 GHz Band SCPC Satellite Communication Using Small Earth Stations

This paper presents a domestic satellite communication system accommodating numerous 30/20 GHz band small earth stations emphasizing the system outline, the use of multiple-access (MA) techniques. It also describes associated earth station configurations, equipment performance, and experimental results using the Japanese CS (medium capacity communications satellite for experimental purposes). Two kinds of earth stations are employed in this system, a small earth terminal (SET) and a master earth station (MES). The SET, which has an antenna about 2 m in diameter, is placed near a subscriber. The MES, which has an 11.5 m diameter antenna, is connected to the terrestrial telephone network through a satellite telephone switching center (STC). There are about 50 two-way channels with bit rates of 32 kbits/s which are achieved through the use of a 30/20 GHz band transponder whose EIRP is about 71.5 dBm, aG/Tof about 2.7 dB/K and an SET's antenna diameter of 1.8 m. This results in a system availability of 99.5 percent under typical Japanese statistical rain attenuation data. To enable a demand-assigned MA technique to be employed in this system, a single channel per carrier (SCPC) is selected, taking into consideration power efficiency of the SET, flexibility of system configurations, and the adaptability of the adaptive power control during rainy periods.     

Novel satellite digital video TDMA system for business videocommunications

The authors propose a satellite video signal transmission system that uses a time division multiple access (TDMA) scheme for digital video signal transmission and a code division multiple access (CDMA) scheme for voice signal transmission from a video signal reception-only earth station (backward voice signal transmission). The adoption of a TDMA scheme makes it possible to transmit video signals from various places and to communicate in multipoint-to-(multi)point mode. For backward voice channel transmission from video signal reception-only earth stations, a superposed CDMA voice signal transmission over TDMA video signals by using the same transponder is proposed. The employment of high coding gain forward error correction and development of a cochannel interference cancellation technique have made it possible for the proposed system to transmit a practical number of voice channels. The performance of the proposed system has been experimentally evaluated and the results show the proposed scheme can transmit about 20 CDMA voice channels simultaneously     

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.     

Microwave and Millimeter-Wave Communications in Japan

This paper reviews the status of research and development in both microwave radio-relay systems and millimeter-wave transmission systems as well as the technical features in these fields, mainly developed under the auspices of Nippon Telegraph and Telephone Public Corporation (NTT). Recent activities have been the development of new solid-state devices and high-capacity systems. The application of solid-state techniques is being extended to systems of both analog and digital transmission, such as the 2700 multichannel telephone transmission system in frequency division multiplexing (FDM)-FM radio-relay system, an experimental 20-GHz PCM radio-relay system capable of 400 Mbits/s pulse transmission, and a guided millimeter-wave system of 800-Mbit/s transmission at 40-80 GHz. The microwave integrated circuit (MIC) is also becoming very important in utilizing these high-frequency regions, which should be a valuable resource in the future when a vast information transmission capability will be required.     

A new satellite communication system integrated into publicswitched networks-DYANET

A system concept of a common alternative routing system is proposed for reducing total network costs by integrating satellite communications into public-switched networks, where satellite systems carry overflow traffic from terrestrial systems through common satellite channels. This concept has been realized by a satellite communication system called DYANET (dynamic channel assigning and routing satellite aided digital networks), which provides trunk circuits in combination with terrestrial systems. The key technologies developed for DYANET are a centralized network control system and a transponder hopping demand assignment TDMA (time-division multiple-access) system, to assure single-hop connection and to use satellite channel efficiently. The authors describe the system concept and configuration, the network control system, and the results of its commercial use     

Dual-Space Diversity over Land Mobile Satellite Channels Operating in the L and K Frequency Bands

Land mobile satellite communication systems at Ka/K band (30/20 GHz) are attracting more and more attention to researchers because of its frequency band availability and the possibility of using small earth stations and satellite antennas for the systems. However, the Ka/K-band communications also give significant challenges in the system design due to severe channel impairments expected from the satellite links. In this paper, K-band channel characteristics are studied and compared with those at L band. The channel is modeled as Rayleigh multipath fading with the line-of-sight (LOS) component following a lognormal distribution. The first and second-order statistics of the fading channel are studied. Dual-space diversity reception is investigated to combat the flat channel fading. The bit error rate performance of coherent binary phase shift keying (BPSK) with ideal bit and carrier phase synchronization over the fading channel at K band is evaluated theoretically and verified by computer simulations in the case with and without diversity reception.     

Network Control for Multibeam TDMA and SS/TDMA

This paper concentrates on the control of individual burst transmissions of traffic and reference stations in TDMA and SS/ TDMA networks. In a TDMA system, the principal task of a TDMA terminal is to transmit each burst at the proper time to assure that, at the satellite, the burst resides in its assigned location in the TDMA frame. The composite of assigned positions for all bursts in the TDMA frame, or frames if more than one transponder is involved, is called the burst time plan. The paper discusses a specific concept of control used by a station to acquire and synchronize its burst transmission to assigned time slot(s) in the TDMA frame. The concept is applied to single-beam (global or regional) and muitibeam systems. The method used controls the instant of traffic burst transmission by introducing a time delay at each station which causes the round-trip propagation time between the satellite and all earth stations to be equal for burst position control purposes. This time delay is simple to implement in the TDMA terminal's timing circuitry and does not require the storage of traffic to accomplish it. It is also shown that the control method leads to a simple means for accomplishing synchronous burst time plan changes throughout the network. The functions of the reference stations needed to accomplish the burst time plan control are defined and explained. The discussion extends to SS/TDMA, and explains how the satellite switch state time plan change can be synchronized to the overall network burst time plan change.     

Advanced on-board processing for user oriented communication systems

The continuing improvement of RF components, particularly in the field of spot-beam antennas, combined with the steady progress in digital technology, leads us to consider the advantages of a satellite system able to provide full connectivity to ground stations operating at different data rates. For low data rates, two different access methods: continuous TDM and Multi-carrier TDMA, are compared for earth-stations operating at 2Mb/s. The two methods are compared from the point of view of efficiency and adaptability in a non-uniform load environment. Some control criteria are proposed for the Multi-carrier system. Both methods are particularly suited for small users.     

The key technologies of millimeter wave MIMO communication system in space information network

With the rapid development of space information network and the increasing expansion of mankind activity,the requirements of communication quality become higher between mobile satellites and earth stations.In order to meet the demands of high data rate,large capacity and broadband real-time communication,applying millimeter wave frequency band to mobile satellite communication system has attracted great attention.Beamforming,tracking and channel estimation were introduced in millimeter wave MIMO system to fully understand the challenges of space information network which will face in the future.     

Performance of uplink random-access and downlink TDMA techniques for packet satellite networks

In this paper the integration of ALOHA random-access schemes and TDMA techniques in a multibeam packet satellite network are analyzed. The uplink channels operate according to a slotted-ALOHA protocol, while the downlink channels use a TDMA strategy. Two different models are described. In the first model, each transponder on-board the satellite is permanently connected to a preassigned spot beam. The second model uses a number of transponders lower than the number of spot beams. Some different strategies of transmission are proposed in the latter model, able to provide full interconnection among earth stations by channel-hopping capability of the transponders. The performance of the models is evaluated through queueing theory analysis and extensive computer simulations. The obtained results suggest the second model as an efficient candidate for the implementation of a multibeam packet satellite network. In that case, the system parameters must be carefully chosen in order to avoid possible instability conditions.     

Integration of Voice and Data in the Wideband Packet Satellite Network

The Wideband (packet satellite) network is an experimental 3 Mbit/s communications system developed under sponsorship of the Defense Advanced Research Projects Agency and the Defense Communications Agency. This system is being used to evaluate the use of packet transmission for efficient voice communication, voice conferencing, and integration of voice and data over a satellite channel. Each station in the Wideband network consists of an earth terminal (dedicated 5 m antenna plus associated IF/RF equipment), a burst-modem and codec unit, and a station controller. Station controllers provide interfaces to host computers (including packet speech sources) and manage the allocation of the satellite channel on a TDMA demand-assigned basis. TDMA demand-assignment is implemented using a reservation-based packet-oriented protocol capableof handling traffic at multiple priority levels. The channel protocol provides a reservation-per-message mode of service (datagrams) to support transmission from bursty traffic sources and a reservation-per-call mode of service (streams) to support traffic with more regular arrival statisticS (e.g., vioce). A distributed scheduler running in every station controller eliminates the need for a central control station and minimizes network transit delay for datagram transmission as well as stream creation, modification, and deletion. In this paper we describe the protocols and mechanisms upon which the Wideband packet satellite network is based.