Perspectives on future communications

The communication industry is changing rapidly. The future changes in telecommunications will be more complex and pervasive than the changes of the past. Communication, like transportation, is essential to the health and vitality of the U.S. economy and to the effective maintenance of its national security. Because of the increasing significance of communication in the United States, consideration should be given to establishing a Federal Department of Communication.     

Optical communications: past, present and future

A quiet revolution is taking place in communications technology, where light is replacing its low-frequency counterparts, the radio wave and signals by wire. The author traces the development of optical communication technology from simple beginnings using fire and beacons, through early valve and solid-state devices to integrated optics and advanced fibre systems. Because of the very rapid growth in the area recently, only a sample of current developments can be presented. Leading-edge developments are considered in the light of current and advancing technologies     

宽带无线通信的现状和展望

目前第二代移动通信系统的主要制式有ＧＳＭ、ＴＤＭＡ（Ｄ－ＡＭＰＳ）、ＰＤＣ、ｃｄｍａＯｎｅ等,它们提供的主要是语音业务。日本１９９８年引入了ｉ－Ｍｏｄｅ移动数据业务后,欧洲和中国也部署了２．５Ｇ的基于ＧＰＲＳ的数据业务,北美和韩国则是采用基于ｃｄｍａＯｎｅ的无线数据业务。 全球移动通信发展的速度非常迅速,１９９９年已经超过４亿用户。按照最新的估计,全球达到１０亿用户的记录将会在２００２年上半年载入史册。全球上网手机的数量超过ＰＣ机上网数量的时间将提前到２００２年。据预测,在２０００年,具有上网功…     

移动通信产业的现状与未来

"冬天"的根源与出路 从金融和投资的角度来看,全球的电信业无疑正经历一场前所未有的冬天.在更为动荡的股市上,纳斯达克电信指数也在某种程度上反映了这一点.     

MIMO MC-CDMA communications for future cellular systems

We propose an efficient multiple-input multiple-output concept based on space-time turbo coded modulation and layered spatial multiplexing architectures for cellular multicarrier code-division multiple access systems. We design appropriate receiver algorithms, and compare their performance to competing schemes in a single-cell system. We then evaluate the performance of the scheme in a seven-cell system with universal frequency reuse. The proposed MIMO scheme improves throughput significantly compared to the corresponding single-antenna communications even in the presence of spatial correlation     

Tropospheric scatter communications Past, present, and future

In the 11 years since the first practicable operational tropo systems were developed, there has been a tremendous growth in their number and complexity. This article describes the principles and applications of tropospheric scatter communications and discusses current development trends. Included is a table listing practically all of the tropo systems installed around the world, with pertinent technical data, together with maps showing the geographic location of most systems. The maps are keyed to the table for easy reference.     

40-Gb/s ICs for future lightwave communications systems

This paper describes the device, circuit design, and packaging technologies applicable to 40-Gb/s-class future lightwave communications systems. A 0.1-μm gate InAlAs-InGaAs high electron mobility transistors (HEMTs) with InP recess etch stopper was adopted mainly for IC fabrication. Fabricated ICs demonstrate excellent data-multiplexing, demultiplexing, and amplifying operation at 10 Gb/s     

On-board digital signal processing technologies for present and future SCPC systems

Devices and architectures for on-board SCPC (single channel per carrier) multi-carrier demodulators suitable for use in satellites to be launched between the present and the year 2000 are discussed in the light of trends in the development of device technology towards lower on-board weight and power consumption. It is shown that at the present time (equivalent to about 1990 for on-board use). The choice of demodulation scheme depends on the number of channels available for regeneration on board the satellite. The total weight and power consumption for several suitable on-board multicarrier demodulation schemes are predicted for 1990, 1995 and 2000, as functions of the number of channels to be regenerated.     

Integration of satellite and terrestrial systems in future multimedia communications

In this article we examine the role of satellite communications in future telecommunication networks and service provision. Lessons from the past indicate that satellites are successful as a result of their wide area coverage or speed to market for new services. Niche areas such as coverage of air and sea will persist, but for land masses convergence of fixed, mobile, and broadcasting will dictate that the only way forward for satellites is in an integrated format with terrestrial systems. We outline future ways forward for satellites, and discuss the research challenges and technology advances needed to facilitate this integrated approach.     

Concatenated Reed-Solomon/convolutional coding for datatransmission in CDMA-based cellular systems

A robust error control scheme for data transmission in CDMA-based cellular systems is proposed which employs outer Reed-Solomon codes concatenated with inner convolutional codes. The performance of this scheme is analyzed assuming nonperiodic random spreading sequences and a Rake receiver with perfect knowledge of the channel. In particular, a simple model for the memoryless inner coding channel that encompasses the effects of multiple access interference, self-noise and thermal noise is first derived. Using new tight upper bounds on bit- and symbol-error probabilities of convolutional codes over Nakagami, Rayleigh, and Rician fading multipath channels, the performance of the concatenated coding scheme is then evaluated. The Reed-Solomon/convolutional coding scheme has been adopted by the European RACE Project Code Division Testbed (CODIT) and implemented in an experimental testbed. The code design methodology, which has been used to specify the 9.6-, 64-, and 128-kbit/s data traffic channels of the CODIT testbed, is presented and the single-cell CDMA capacity is computed     

CDMA-based anti-collision algorithm for EPC global C1 Gen2 systems

Frame slotted ALOHA protocol as a key technology to improve system throughput has been widely applied to modern radio frequency identification systems. In this paper, a novel frame slotted ALOHA collision arbitration protocol based on code division multiple access has been proposed. The main aim of the proposed algorithm is to avoid collisions between multiple tags. In the scheme, an orthogonal sequence is used as the means to distinguish the transmitted data from different tags within the same time slot and frequency band. The theoretical analysis and simulation results proved that the performance of our proposed algorithm outperforms the existing ALOHA-based protocols.     

Satellite systems for personal communications

A number of industrial groups are planning to construct satellite systems to provide personal communications services (typically voice, data, and fax) to users who will employ small, hand-held, cellular-type telephones. Some of these systems (e.g., Iridium and Globalstar) will be constructed using satellites in low Earth orbit. Two (Odyssey and ICO) will employ medium Earth orbit (six-hour period), and still others (ACeS and Agrani) will operate from geostationary altitude. The origin and evolution of mobile satellite communications is discussed first, including the INMARSAT system and several land-based mobile satellite systems in operation. The rival approaches to the personal communications services (PCS) market are then described, and some of the technical challenges inherent in each are indicated. The paper concludes with speculation on the factors influencing the likelihood of business success for the various PCS systems     

Enhanced RAMA protocol for future wireless communications

The original RAMA protocol was designed for fixed rate services, but it wastes radio resources since it uses a dedicated carrier for fast resource allocations. The authors propose an enhanced RAMA protocol without using the dedicated carrier. The proposed protocol can support multiple quality of services for future wireless multi-media communications     

Satellite systems for personal communications

A number of industry groups are planning to construct satellite systems that will provide a personal communications service (PCS) (typically voice, data, and fax) to users over small, hand-held, cellular-type telephones. Some of these systems (e.g., Iridium and Globalstar) will be constructed using satellites in low Earth orbit. Two (Ellipso and ICO) will employ medium Earth orbit (3-8-h period), and still others (ACeS and Agrani) will operate from geostationary altitude. The origin and evolution of mobile satellite communications is discussed first, including the Inmarsat system and several land-based mobile satellite systems in operation. The rival approaches to the PCS market are then described, and some of the technical challenges inherent in each are indicated. This paper concludes with speculation on the factors influencing the likelihood of business success for the various PCS systems     

A new CDMA-based bandwidth request method for IEEE 802.16 OFDMA/TDD systems

This paper proposes an efficient bandwidth request method for a non-real-time polling service and best effort service in the IEEE 802.16 system. The proposed method produces a bandwidth request code to indicate the channel quality and the necessary number of slots. The base station allocates uplink bandwidth depending on the bandwidth request code. Thus, the proposed method can omit the transmission procedure of the bandwidth request message. The performance analysis results show that the proposed method can reduce the delay for the uplink data transmission.     

MIMO systems for broadband wireless communications

The emergence of broadband wireless access (BWA) and mobility poses significant challenges to the future telecommunications landscape. Multiple input multiple output (MIMO) is a potential technology that can be used to improve system performances such as coverage, capacity and data rates for broadband wireless networks. Although this technology has proved to be beneficial for both current and future services by many research results, it is not clear how these benefits can be practically achieved with a MIMO system. Fundamental issues on capacity enhancement and performance limits need to be addressed before operators will be willing to deploy MIMO systems in their networks. This paper addresses some of the key issues that remain open regarding MIMO technology for BWA. The paper focuses on MIMO channel modelling and capacity analysis.     

Mobility management for personal communications systems

Using a combination of empirical data and theoretical models, this paper develops a model of user behavior for a personal communications system environment. This model is used to analyze a mobility management strategy that combines automatic updates by the users-either when they make significant moves or when they go extended periods without network interaction; multiple hysteresis in the form of dynamic registration areas and delayed updates; and a focused paging strategy that minimizes the number of pages given a constraint on the time allowed to a page. Over a range of system and user parameters, the total paging and update traffic can be kept below 1 per 2000 user seconds. The impact on the user's handset is less than ten brief updates per day. The total traffic is only a factor of three more than the minimum, immobile users case     

Electronic tracking systems for space communications

Since the first television pictures were received from Telstar by aerial 1 at Goonhilly Down in Cornwall, commercial operation of satellite systems has dictated that the earth-space link must be maintained as consistently as possible. Any break in transmission or lowering of quality results in huge losses for the operator and as a result the performance of the antenna tracking system has received a great deal of attention. Recently a new technique, termed `electronic beam-squinting', has been developed to solve this problem both elegantly and economically. It is capable of a performance approaching that of the most expensive systems currently available for fixed earth stations and is also applicable to mobile terminals