30/20-GHz domestic satellite communication system in the public communication network of Japan: Design and operation

Nippon Telegraph and Telephone Public Corporation (NTT) initiated the world's first 30/20-GHz domestic satellite communication system for commercial use, using CS-2s launched from Japan in 1983. This system utilizes TDMA digital communication in the trunk transmission route of the public communication network, which includes interregional-center routes and main-island-to-remoteisland routes. Small transportable earth stations enable easy access to the public communication network from any place in Japan. The adoption of the 30/20-GHz band enables use of a compact on-board antenna that has a shaped beam that effectively covers the main islands of Japan. It also enables the use of high-performance, compact antennas at the earth stations. These antennas can easily be installed on the roof of telephone offices or set on motor vehicles. One apparent disadvantage of using the 30/20-GHz band is rain attenuation. However, NTT has realized a commercial system that is affected very little by rain attenuation. This was accomplished by utilizing high-performance radio equipment and by concentrating on appropriate system design. Adoption of the 30/20-GHz band is quite significant because the wide bandwidth available enables construction of high-capacity economical transmission systems. It also enables use of small antennas, which allow construction of high-speed digital direct-to-user transmission systems using small earth stations. These expand the application of the domestic satellite communication system to even small service areas. Therefore, NTT considers satellite communication to be of primary importance for its proposed digital communication network, and has begun research on a high-capacity, economical, multibeam communication satellite system using the 30/20-GHz band. This paper describes the 30/20-GHz band radio technology, digital communication technology utilizing high-speed TDMA, and operational technology in the public communication network.     

Combating sun outage in satellite television distribution systems

Two methods of sun outage avoidance in satellite television transmission are discussed. Each method requires two satellites and dual-beam antennas. The two C-band satellites transmit identical programs at the time when the sun outage period occurs. The separation of the spacecraft is dependent on the dual-feed earth station antenna size. For large television receive-only antennas, the separation must be small; for small antennas, or antennas with large beamwidths, the satellite separation can be large. If the separation is larger than 8° on the geosynchronous arc, only one transmit station is required to transmit program information. Scaling this system for Ku-band use is then considered. It is concluded that in a Ku-band direct-broadcasting system with earth station antenna diameters of 1-m and below, the rise in noise temperature due to sun outage is not significant and can be overcome by a modest amount of system margin, equivalent to that normally provided against rain fades     

大都市网络的解决方案——ROF技术

ROF技术充分结合光纤和高频无线电波传输的特点，能实现大容量、低成本的射频信号有线传输和超过1Gbit／s的超宽带无线接入，并具有覆盖面广、易于动态管理和维护等特点，在未来泛在超宽带蜂窝网络、室内无线局域网络、卫星通信、视频分布式系统、智能交通通信和控制等领域具有巨大的应用前景。     

A technique for assessing the severity of terrain shadowing in mobile satellite service

A graphical analysis technique is presented that produces an estimate of the severity of terrain shadowing of a particular geosynchronous satellite. The technique can be used to analyze the coverage provided by a new group of satellites capable of direct communication with mobile and transportable units. Application of the technique to a number of highways in Alaska is described.     

Ka频段卫星通信系统降雨衰减分析

Ka频段卫星通信因其具有可提供的带宽大(3.5GHz)、通信容量大、波束窄、终端尺寸小,轨道平面内可容纳的卫星多和抗干扰能力强等优势成为未来卫星通信的必然趋势。Ka频段卫星通信面临的一个巨大挑战在于它受气象因素的影响大,这一度使研究人员认为Ka频段卫星通信是不可能实现的。降雨、闪烁、大气吸收等因素都会导致Ka频段地空链路信道质量的恶化。根据Ka频段卫星通信的特点,分析了降雨衰减的特性,提出了几种抗雨衰的办法。     

The Use of Resource Sharing and Coding to Increase the Capacity of Digital Satellites

Resource sharing is a technique which can improve the circuit availability of digital satellites operating at frequencies above 10 GHz, without requiring large fade margins. In this paper, the resource sharing concept is generalized by fully exploiting the available clear-air carrier-to-noise ratio of the satellite link to achieve very high transmission capacity while maintaining low rain outage. During clear-air conditions, convolutional codes with a large channel signaling alphabet are employed to permit a high rate of information transfer. When the fade depth exceeds the built-in fade margin, the signaling alphabet is reduced and enough time slots are borrowed from a resource sharing reserved pool to maintain the data rate at the fade site. It is shown that this approach greatly diminishes the impact of rain attenuation on satellite communications. Effective utilized capacities exceeding 85 percent of that possible if it never rains are feasible, and the increase in capacity compared to a system not using resourcesharing protection is typically a factor of 3-10.     

Phase and amplitude dispersion for Earth-satellite propagation in the 20- to 30-GHz frequency range

Amplitude and phase dispersion have been measured for over a year on a 19- and 28-GHz earth-space propagation path. In the experiment amplitude and phase differences were compared for a 28-GHz carrier withpm264-MHz sidebands and a 19-GHz carrier, all transmitted from a COMSTAR satellite. No dispersion (frequency selective fading) was found of the type caused by multipath propagation with a large spread in time delay or by resonances in the propagation medium. The only frequency dependences evident were due to the bulk properties of water in rain. The conclusion from this investigation is that amplitude and phase dispersion should not pose a problem for wideband (on the order of 1 GHz) satellite communication systems operating at frequencies greater than 10 GHz with elevation angles from the earth terminals of greater than15deg.     

Copolar and cochannel interference from adjacent satellites duringrain at 12 GHz

The authors report experimental results on copolar and cochannel interference from adjacent satellites during rain obtained by measuring simultaneous rain attenuations in the 12 GHz band in two convergent slant paths to receivers located in the Fucino plain (Italy) from the geostationary satellites SIRIO (15°W) and OTS (10°E) in 1978-1980. The results presented here are directly applicable to the design of actual TV satellite broadcasting systems and they can be extrapolated to higher frequencies to design future satellite communication systems     

Mobile P-service satellite system comparison

Several future operators of the mobile handheld telephone (P-service) satellite communications systems are gearing up for system implementation to compete for the mobile handheld telephone market of the future. While these companies are proceeding with system realization, they are also looking for partners to finance these huge satellite projects. Potential partners or bulk users are administrations of national communication systems and operators of national communication satellites. These future partners ask themselves which P-service satellite communication system they should choose. There is not an easy answer because P-service satellite systems come in many varieties. There are the low altitude earth orbiting satellites (LEOs), the medium altitude earth orbiting satellites (MEOs), and the geosynchronous altitude earth orbiting satellites (GEOs). Each system has a different type of satellite repeater: digital regenerative, transparent digital, and the bent-pipe. And each satellite system uses its own modulation/multiple access system. The fact that satellites circle the earth at different altitudes has an impact on speech quality, and, because systems vary in satellite as well as constellation complexity, there are different price tags attached. All systems display ingenious features and will eventually work. Mobile users will decide which system will best serve their purposes. This article attempts to compare six P-service satellite systems and find a method for system selection. By use of self-established system criteria, it is possible to arrive at a P-service system selection. By weighing the system criteria, the sensitivity of system selection can be tested. The results or the selection of a particular system should not be considered a recommendation; rather, the process of selection should be used as a possible guideline.     

Simple and spectrally-efficient design of high capacity hybrid WDM/TDM-PON with improved receiver sensitivity

A simple design of hybrid wavelength division multiplexed/time division multiplexed passive optical network （WDM/ TDM-PON） is demonstrated for the high capacity next generation access （NGA） network, having advantages of both WDM and TDM based PON techniques. A 10 Gbit/s differential quadrature phase shift keying （DQPSK） data signal is used at optical line terminal （OLT） for downstream, whereas a 2.5 Gbit/s inverse return-to-zero （IRZ） data signal with high extinction ratio is used for upstream signal by intensity re-modulation of downstream signal, no additional laser is used at optical network unit （ONU）. Simulation results verify that aggregated 100 Gbit/s downstream transmissions of 10 DQPSK channels and aggregated 25 Gbit/s upstream transmission of 10 IRZ channels, using spectrally-efficient 50 GHz channel spacing, can be successfully achieved over a distance of 20 km with less than 1 dB transmission power penalties and improved receiver sensitivity.     

Results from the 19- and 28-GHz COMSTAR satellite propagation experiments at Crawford Hill

Strong interactions of radio waves with rain and ice particles in the lower atmosphere significantly affect the performance of earth-space radio links operating at frequencies above 10 GHz. Because of the uncertainties and variabilities in the microstructures of weather phenomena, direct measurements of the effects of rain and ice on radio propagation are needed for the economic design of reliable satellite communications systems. Unique and comprehensive space-earth propagation measurements have been made at Crawford Hill, New Jersey, using the 19- and 28-GHz beacons on the COMSTAR satellites. This paper summarizes these measurements of rain attenuation, rain and ice depolarization, phase and amplitude dispersion, off-path rain-scatter coupling, angle-of-arrival variations, and cloud scintillation. These results provide empirical design data and will serve as checks on theoretical models needed for predicting communication system performance in geographical regions where measurements are not available.     

Rain Rate Statistics and Fade Distribution of Millimeter Waves in Indian Continents

For any communication service operating in the Microwave/ Millimeter wave region, statistical information characterising the attenuation due to rain along satellite slant path would be required for the design of satellite communication links and for the broadcasting network above 20 Ghz. It is necessary to have a prior knowledge of the probability of exceeding different levels of rain attenuation in order to design appropriate fade margins into systems and establishing estimates of the year to year variability of rain fade margin for particular geographic regions of India so that the communication system reflects the extremes of these variabilities. Direct measurement of beacon signals from geostationary satellites have been a mean to determine the above information and experiments can be pursued with satellite such as INSAT. [1] Attenuatiuon of Millimeter Waves by rainfall restricts the path length of a communication system. A knowledge of the rain attenuation at such frequencies is therefore desirable in designing a reliable communication system. Signal level fading over line-of-sight links strongly depends on the hop length, frequency and climate. For short hops, the probability of occurance of deep fades becomes diminishingly small. However, since an extended hop length is possible for regions with little rain activity, clear weather fading can affect the link reliability in a similar way ti a rain.[2]     

Technology of InP-based 1.55-μm ultrafast OEMMICs: 40-Gbit/sbroad-band and 38/60-GHz narrow-band photoreceivers

For future long-haul communication systems operating at bitrates of 40 Gbit/s and for broad-band mobile access systems using 38- or 60-GHz carrier frequencies, ultrafast photoreceivers have to be provided. Therefore, an integration concept for InP-based optoelectronic microwave monolithic integrated circuits for the 1.55-μm wavelength regime is demonstrated, which allows independent optimization of the constituting devices. Two different types of photodetectors (PDs), a waveguide-integrated PIN photodiode (PD) and a top-illuminated metal-semiconductor-metal PD, both having bandwidths of up to 70 GHz, have been developed. These are fabricated together with different amplifier designs employing high electron mobility transistors which exhibit transit frequencies of up to 90 GHz. The application to a 40-Gbit/s broadband photoreceiver for high-bit-rate time-division multiplexing systems is reported, as well as the application to 38- and 60-GHz narrow-band photoreceivers for use as optic/millimeterwave converters in mobile communication systems     

基于Nand Flash的星载综合数据固态记录系统

在星载平台资源受限条件下,采用以FPGA+CPU为控制核心、Nand Flash为固态存储阵列的系统架构,实现了高速、大容量、高可靠的数据记录.针对传统双Plane操作与并行扩展对存储速度提升有限、芯片使用较多的问题,采用4级流水线方式控制Flash阵列.为解决标准传输协议传输效率低的问题,设计了一种自定义高速串行传输协议.为减缓空间辐射环境对存储数据的影响,采用了三模冗余、配置回读与部分重构等容错机制.对所提出系统进行的实验验证结果表明,该星载记录系统存储容量达36 Tbit,记录与回放速度分别达到16 Gbit/s与8 Gbit/s,传输误码率为10-12,传输包效率为96.7％,可作为通用存储系统以满足航天应用需求.     

Multiyear slant-path rain fade statistics at 28.56 GHz for Wallops Island, VA

Multiyear rain fade statistics at 28.56 GHz have been compiled for the region of Wallops Island, VA, covering the time periods April 1, 1977-March 31, 1978, and September 1, 1978-August 31, 1979. The 28.56-GHz attenuations were derived by monitoring the beacon signals from the Comstar geosynchronous satellite,D_{2}, during the first year, and satellite,D_{3}, during the second year. Comparisons are made of yearly, monthly, and time of day fade statistics for the first, second, and combined years. Although considerable year to year variations in exceedance times exist for the monthly and time of day fade statistics, the overall fade distributions for the individual years showed relatively small differences. For example, comparing the second year fades relative to those of the first year at equal percentages of time, less than 20 percent rms deviation was found. The year to year variations of rain rate distributions are also examined and show consistently small differences. The resultant fade distribution at 28.56 GHz for Wallops Island, VA, are compared with that arrived at using a prediction method which is a recent refinement of the International Radio Consultative Committee (CCIR) global model, and an rms decibel deviation of less than 14 percent was noted.     

Optimum utilization of the channel capacity of a satellite link inthe presence of amplitude scintillations and rain attenuation

By considering the global fading process on the link caused by rain attenuation and amplitude scintillations, particularly at K_a band, it is possible to derive a long-term statistical model of the satellite channel capacity. The four-parameter distribution, which combines amplitude scintillations and rain fade within an up/down link system, is presented. Also presented are the degradation (and improvement) of bit error rate (BER) in the presence of amplitude scintillations, thus complementing the flat fade effect due to rain only. By implementation of adaptive communication systems, a more efficient channel capacity utilization is possible. The concepts and the use of novel analytical expressions combining a log-normal model of rain fade with a Moulsley-Vilar distribution for scintillations are illustrated. These are then applied to a very-small-aperture terminal (VSAT) example of a 29/19-GHz digital communications link through the Olympus satellite using M-ary phase shift keying (PSK) modulation schemes     

降雨对于CAPS微小卫星终端通信的影响

中国区域卫星定位系统（CAPS）是卫星导航通信一体化的系统。当利用CAPS微小卫星终端系统进行卫星通信时,所用的天线口径极小,增益低,终端的有效全向辐射功率EIRP。较小,整个通信链路的余量较小。虽然C波段的降雨衰减远没有Ku波段大,但是相对于微小卫星终端的整个卫星通信链路来说,降雨带来的信号衰减、地球站接收天线G／T值的变化以及对卫星通信上、下行链路载噪比的影响也是不可忽视的。文章对这些影响进行了分析,并利用ITU—R给出的降雨衰减预报模式,给出了C波段的降雨衰减的计算方法及结果,并且分析了降雨对CAPS微小卫星通信系统的整个链路余量的影响。     

21.4 Gbit/s transmission over 200 km multimode fibre using coherent optical OFDM

Multimode fibre (MMF) has been deployed for local area networks and for optical interconnects. MMF has long been perceived as the medium for short reach systems, although it can achieve very high capacity [1]. In fact, the longest transmission distance for a channel rate of 10 Gbit/s and beyond is 11 km, requiring feedback from the receiver to the transmitter [2], and 5 km without receiver feedback [3]. Nevertheless it is instructive to note three important advantages that MMF possesses over single-mode fibre (SMF). First, MMF has proven ease of installation, maintenance and handling, which in turn leads to cost reduction. Secondly, MMF has much larger core area than SMF, which translates into much greater nonlinearity tolerance over SMF. Thirdly, from the information theoretical point of view, because of the existence of many modes in MMF, it can provide much higher information capacity than SMF via multiple-input multiple- out (MIMO) signal processing [4, 5]. Therefore a natural and fundamental question should be asked: is the multimode fibre fit for highspeed (.10 Gbit/s) and high-capacity communication system beyond short reach (.100 km)? The aforementioned third point becomes more relevant as recent research has shown rapid progress in the channel speed, whereas the improvement of overall capacity seems to be stalled. A sense of spectral efficiency bottleneck is looming large in the optical communication community.     

亚洲蜂窝网卫星通信系统新计划

本文先全面说明同步卫星和低 /中轨道移动卫星通信系统的最新动态。其后着重介绍发展中国家利用同步卫星组成区域移动通信系统。文中特别讲到亚洲蜂窝网卫星通信系统和中东的Thuraya卫星移动通信系统。最后指出 ,这种利用同步卫星的区域通信系统与全球低 /中轨道卫星系统相比 ,投资节省 ,管理简便 ,手持机价格和每分钟通话资费都较低廉 ,在发展中国家地区值得提倡。     

Rogue Commercial Geosynchronous Communications Satellites

The growth in numbers of commercial communications satellites in geosynchronous orbit raises the possibilities for radio frequency interference into space-earth transmission systems due to a malfunctioning satellite and of physical damage to an operating satellite due to collision with co-orbiting objects. These possibilities are addressed and recommendations are presented to minimize such occurrences.