卫星气象业务在1670-1710MHz频段应用现状与发展

 卫星气象业务是一种用于气象目的的卫星地球探测业务,在人民的生产、生活中起到极为重要的作用。1670-1710MHz频段是国际电联《无线电规则》划分给卫星气象业务用于数据传输使用的重要频段之一,该频段还同时划分给气象辅助业务、固定业务、移动业务、卫星移动业务等共同使用。本文详细介绍了目前国际上卫星气象业务在这一频段的使用情况、干扰评估准则,并结合我国卫星气象业务的频率使用情况,介绍并研究该频段内卫星气象业务与卫星移动业务、气象辅助业务之间的共用现状与技术,以期给上述业务在该频段未来的发展和使用提供借鉴。     

A model for interference studies relating to multisatellite non-geostationary systems in the mobile satellite service

An option being considered by current and prospective mobile satellite service (MSS) operators is the use of constellations of non-geostationary orbit (NGSO) satellites to provide global personal communications. The scarcity of free spectrum, together with the bandwidth typically required, means that any new MSS system must consider sharing spectrum with other systems and services. Spectrum sharing must be based on defined interference criteria being satisfied. When multiple NGSO satellites are considered there is no accepted method for assessing interference. This paper describes a model used as the basis for a computer simulation of interference scenarios involving MSS, fixed service (FS) and fixed satellite service (FSS) systems. The simulation includes NGSO dynamics, constellations of MSS satellites with multi-spot antennas, multiple geostationary FSS satellites and multiple hop FS links. Interference events are based on C/I calculations, and statistics, such as the percentage of time that the C/I falls below a required protection ratio, are calculated. More generally C/I cumulative distribution functions are produced.     

Statistics of the Carrier-to-Interference Ratio in C/TDMA Cellular Mobile Radio Systems Applying Multi-User Detection

In cellular mobile radio systems, interference is a limiting factor with respect to both system performance and system capacity. Therefore, profound knowledge of the statistics of the carrier-to-interference ratio C/I, given by the received carrier power C and the sum I of received powers associated with various interferers, is essential. In this communication, a general approach allowing the calculation of C/I for both the up- and the downlink of any interference limited mobile radio system is presented. Power control algorithms are explicitly considered. The general approach is used to provide insight into the statistics of C/I of C/TDMA systems applying multi-user detection, which are promising candidates for third generation mobile radio systems. For these C/TDMA systems applying multi-user detection, a representative selection of results is collected from the general approach and presented in this communication. Furthermore, results concerning the composition of the intercell interference are given. These results are of particular interest when plumbing potential benefits of worthwhile future enhanced multi-user detection schemes which explicitly incorporate a given number of intercell interferers.     

25.25～27.5 GHz频段卫星间业务与IMT系统兼容性研究

基于现有技术参数,研究了25.25～27.5 GHz频段国际移动通信（IMT）系统与卫星间业务数据中继卫星（DRS）系统间的干扰共存情况。采用集总干扰评估方法,比较了数据中继卫星经度分别在59°、85°、113°时,IMT基站对其造成干扰的情况。此外,还通过固定干扰余量,推导了IMT基站总数及其与IMT发射功率之间的关系。研究结果可为未来25.25～27.5 GHz频段IMT系统设计与部署、5G频率规划提供借鉴。     

Joint interference coordination approach in femtocell networks for QoS performance optimization

Future heterogeneous networks with dense cell deployment may cause high intercell interference. A number of interference coordination (IC) approaches have been proposed to reduce intercell interference. For dense small‐cell deployment with high intercell interference between cells, traditional forward link IC approaches intended to improve edge user throughput for best effort traffic (ie, file transfer protocol download), may not necessarily improve quality of service performance for delay‐sensitive traffic such as voice over long‐term evolution traffic. This study proposes a dynamic, centralized joint IC approach to improve forward link performance for delay‐sensitive traffic on densely deployed enterprise‐wide long‐term evolution femtocell networks. This approach uses a 2‐level scheme: central and femtocell. At the central level, the algorithm aims to maximize network utility (the utility‐based approach) and minimize network outage (the graphic‐based approach) by partitioning the network into clusters and conducting an exhaustive search for optimized resource allocation solutions among femtocells (femto access points) within each cluster. At the femtocell level, in contrast, the algorithm uses existing static approaches, such as conventional frequency reuse (ReUse3) or soft frequency reuse (SFR) to further improve user equipment quality of service performance. This combined approach uses utility‐ and graphic‐based SFR and ReUse3 (USFR/GSFR and UReUse3/GReUse3, respectively). The cell and edge user throughput of best effort traffic and the packet loss rate of voice over long‐term evolution traffic have been characterized and compared using both the proposed and traditional IC approaches.     

INTERFERENCE AND SHARING CONSIDERATIONS BETWEEN THE SPACE OPERATIONS/SPACE RESEARCH SERVICE AND NEW APPLICATIONS OF THE FIXED SERVICE NEAR 2 GHz

Many satellite projects use radio frequencies in the bands 2025–2110 MHz and 2200–2290 MHz for spacecraft operations and data transmission. Frequencies below a few GHz are of particular interest because of favourable propagation conditions and attractive antenna designs. The above bands have to be shared with the fixed service and the mobile service. The fixed service has announced plans for the introduction of vast quantities of a new type of application, referred to as the point-to-multipoint system to be used for data distribution or local access systems. At International Telecommunications Union (ITU) meetings, scenarios assuming the worldwide deployment of more than one million new fixed service installations have been presented. This paper assesses the interference potential from point-to-multipoint systems to conventional direct links between spacecraft and earth stations. The interference into the space as well as into the ground segment has been investigated. Typical earth stations with a 15 m dish size have been assumed. Interference received at low earth orbiters as well as geostationary satellites has been evaluated. It is shown that sharing will not be possible without technical or operational constraints on the fixed service systems. © 1997 by John Wiley & Sons, Ltd.     

卫星移动业务C频段的干扰研究

分析了卫星移动业务与地面固定业务共用C频段时,对该频段地面固定业务的干扰情况。以世界无线电通信大会议题提出的卫星移动业务候选频段为背景,从理论上分析了卫星移动系统上行链路与下行链路对固定业务的干扰情况。利用国际电联相关建议搭建了干扰分析模型,并进行了仿真分析。通过分析,在假设的场景下,卫星移动业务的上行链路会对地面固定业务产生干扰,而上行链路不会产生干扰。     

Ka‐band HTS channel uplink SNIR probability model

I present a novel analytical study of the signal‐to‐noise‐plus‐interference ratio (SNIR) for Ka‐band high throughput satellite uplink channels. The Ka‐band high throughput satellite systems employ frequency and polarization (color) reuse among the spot beams to achieve throughput increase many times the throughput of the system without reuse. However, color reuse also produces substantial co‐color interference and adding to it, tropospheric precipitation attenuation rises sharply in Ka‐band. The co‐color interference and precipitation induced fading vary randomly; they degrade the system performances. To assess the impact, I develop the uplink channel SNIR probability model in this study. Compared with the known studies of the same topic, this study takes the theoretic approach and is applicable to the urban users in particular. The model is feasible to implement and can provide accurate assessment of the channel SNIR performances statistically in theory for a wide array of system operational scenarios. The SNIR probability model is applied to a model spot beam system of 101 user beams to obtain and compare sample channel performances, which can be used for making system design choices at the early stage of a satellite project. Copyright © 2017 John Wiley & Sons, Ltd.     

Co‐channel interference cancelation at the user terminal in multibeam satellite systems

We study the applicability of soft interference cancelation in the forward link of multibeam satellite systems with focus on mobile terminals. We adopt a standard currently used in commercial satellite systems as a reference. The multibeam satellite antenna radiation diagram has been generated using a physical optics reflector model while a widely adopted channel model has been used for the land mobile satellite channel. The interference pattern has been derived using a system simulator developed by the European Space Agency. Starting from the analysis of the interference pattern, we study the application of a low‐complexity soft interference cancelation scheme for commercial applications. Our results show that, under realistic conditions, a two‐colors frequency reuse scheme can be employed while guaranteeing service availability across the coverage and keeping the complexity at the user terminals relatively low. Copyright © 2015 John Wiley & Sons, Ltd.     

移动卫星系统与LTE网络间干扰共存性能的研究

The interference coexistence performance between the systems of a Long Term Evolution (LTE) network and Mobile Satellite Service (MSS) system, both of which work around the frequency of approximately 2 GHz according to the bandwidth allocation in China, is proposed in this article. The related background of an MSS system and the common terminologies are introduced. Further, the coexistence scenarios of different coverage situations shared by the two systems are discussed. The interference impact of an MSS transmission on an LTE system is evaluated using a specific Monte Carlo method. Finally, simulation results show that although no crucial issues for the coexistence of an LTE downlink and the MSS are observed, the LTE uplink suffers a considerable amount of interference from the MSS transmission. Given the insufficient isolation between LTE and MSS existing networks, and the rapid advance in the field of LTE, problems may emerge in the near future. Further, this article can be of sig-nificance in providing reference for frequency spectrum planning in the existing LTE net-works.     

On the interference from space research service uplink transmissions into the inter‐satellite links of a non‐GSO system operating in the 22‐GHz band

This paper presents a compatibility analysis involving space research service lunar mission uplink transmissions and the inter‐satellite links of non‐geostationary orbit systems operating in the 22‐GHz band. Three points differentiate this analysis from the currently available studies: (1) the mathematical model used here allows for the consideration of the time varying nature of the inclination of the Moon orbital plane; (2) besides the usual unconditional interference cumulative distribution functions, this analysis also considers the conditional cumulative distribution functions given that the victim satellite is receiving interference, important to characterize the interference affecting users that, because of their location, are most of the time using satellites, which are under interference; and (3) instead of dynamic time simulation, the analytical method in Recommendation ITU‐R S.1529 is used to determine the various cumulative distribution functions involved. Four scenarios are examined in the paper. Their main differences concern the number and location of the space research service transmitting Earth stations and the strategy under which they are active (transmitting). In all scenarios, cumulative distribution functions of the ratio I/N were determined for both the in‐band and the out‐of‐band interference cases. Copyright © 2012 John Wiley & Sons, Ltd.     

面向移动互联网的业务创新生态环境研究

面对移动互联网业务的发展,核心业务、业务能力、生态圈成为行业竞争的焦点。本文从移动互联网环境下的业务特征入手,论述了移动互联网业务提供的3种模式,详细阐述了业务生态链模型,并提出了移动互联网业务创新生态环境的总体架构。对总体架构中的各个子系统,包括业务能力开放中间件、业务开发生成环境、业务部署运行环境、内容发布环境、业务运营和管理环境、业务能力系统、应用和内容商店、自助服务等进行了研究分析。     

Frequency shift filter‐based multi‐carrier transceiver

It is well known that orthogonal frequency division multiplexing (OFDM) is sensitive to carrier frequency offset (CFO) and suffers from a high peak‐to‐average ratio. In addition, the performance of OFDM is severely affected by strong co‐channel interference and strong narrowband interference. To mitigate the limitations of OFDM, we propose a new multi‐carrier transceiver based on frequency‐shift filter. A frequency‐shift filter can separate spectrally overlapping sub‐carrier signals by exploiting the spectral correlation inherent in the cyclostationary modulated signals. To increase spectral efficiency, we increase the percentage of spectral overlap between two adjacent sub‐channels. We derive an upper bound and a lower bound on the bit error rate performance of the proposed multi‐carrier transceiver in additive white Gaussian noise channel and frequency‐nonselective Rayleigh fading channel, respectively. Compared with OFDM, our simulation results show that the proposed multi‐carrier transceiver is much less sensitive to CFO and has a lower peak‐to‐average ratio; moreover, without any additional interference suppression technique, the proposed transceiver has the advantage of being able to mitigate strong co‐channel interference with CFO from the intended multi‐carrier signal and mitigate strong narrowband interference in additive white Gaussian noise channel and in Rayleigh fading channel in which a large CFO between the transmitted signal and the received signal often occurs. Copyright © 2011 John Wiley & Sons, Ltd.     

非同步轨道卫星移动业务馈送链路的干扰研究

本文讨论了卫星移动通信中由于ＮＧＳＯ／ＭＳＳ馈送链路与ＧＳＯ／ＦＳＳ共享频率而引起的干扰问题，作为解决手段引入了反向频率工作模式。通过对具体数据的分析表明，这一模式可以有效地减轻两个系统之间的干扰，是协调ＮＧＳＯ与ＧＳＯ间干扰的一种最具吸引力的方案。     

A Linear Prediction Based Estimation of Signal‐to‐Noise Ratio in AWGN Channel

Most signal‐to‐noise ratio (SNR) estimation techniques in digital communication channels derive the SNR estimates solely from samples of the received signal after the matched filter. They are based on symbol SNR and assume perfect synchronization and intersymbol interference (ISI)‐free symbols. In severe channel distortion where ISI is significant, the performance of these estimators badly deteriorates. We propose an SNR estimator which can operate on data samples collected at the front‐end of a receiver or at the input to the decision device. This will relax the restrictions over channel distortions and help extend the application of SNR estimators beyond system monitoring. The proposed estimator uses the characteristics of the second order moments of the additive white Gaussian noise digital communication channel and a linear predictor based on the modified‐covariance algorithm in estimating the SNR value. The performance of the proposed technique is investigated and compared with other in‐service SNR estimators in digital communication channels. The simulated performance is also compared to the Cramér‐Rao bound as derived at the input of the decision circuit.     

On feasibility examination of DS‐CDMA systems with imperfect successive interference cancellation

In DS‐CDMA systems with the successive interference cancellation (SIC) technique, there are K! possible decoding orders for K active users and the decoding order has considerable impact on system performance. Once the constraints on the received powers of mobile stations and the bit‐energy‐to‐interference‐power‐spectral‐density ratio requirements are satisfied under some decoding order of SIC, the system is feasible. Otherwise, if the constraints are violated under all possible decoding orders, the system is infeasible. It is highly time‐consuming to examine the system feasibility directly by using the usual exhaustive search method (ESM) for a system with even moderate number of users. In this paper, we propose an efficient approach for examining the feasibility of DS‐CDMA systems with imperfect SIC. The proposed approach has significantly lower computational complexity than that of ESM and thus benefits the quick decisions of admission control and/or scheduling, which are essential for Quality of Service provisioning in DS‐CDMA systems. Furthermore, we theoretically prove that the system under the resultant decoding order obtained by the proposed approach is able to achieve the lowest outage probability among all possible decoding orders. We conduct extensive simulation experiments, and the numerical results validate our analysis and demonstrate the effectiveness of our approach. Copyright © 2010 John Wiley & Sons, Ltd.     

Performance Analysis of Location-Aware Mobile Service Proxies for Reducing Network Cost in Personal Communication Systems

We propose and analyze mobile service management schemes based on location-aware proxies with the objective to reduce the network signaling and communication cost in future personal communication systems (PCS). Under these schemes, a mobile user uses personal proxies as intelligent client-side agents to communication with services engaged by the mobile user. A personal proxy cooperates with the underlying location management system so that it is location-aware and can optimally decide when and how often it should move with the roaming user. We show that, when given a set of model parameters characterizing the network and workload conditions, there exists an optimal proxy service area size for service handoffs such that the overall network signaling and communication cost for servicing location and service operations is minimized. We demonstrate via Petri net models that our proposed proxy-based mobile service management schemes outperform non-proxy-based schemes over a wide range of identified conditions. Further, when the mobile user is concurrently engaged in multiple services, the per-service proxy scheme that uses a separate proxy for each service outperforms the aggregate proxy scheme that uses a single proxy to interface with multiple services taking their aggregate service characteristics into consideration. Baoshan Gu received the BS degree from University of Science and Technology of China, Hefei, China, in 1992 and the MS degree in computer science from Institute of Computing Technology, Chinese Academia of Science, Beijing, China, in 1995. From 1995 to 2000, he was a research and development engineer in Institute of Computing Technology, Chinese Academia of Science. He is currently pursuing his PhD degree in the Department of Computer Science, Virginia Tech, where he is a research assistant in the Systems and Software Engineering Laboratory. His research interests include next-generation wireless system architectures, design and evaluation of location and service management schemes in mobile computing environments, and mobile database systems. Ing-Ray Chen received the BS degree from the National Taiwan University, Taipei, Taiwan, and the MS and PhD degrees in computer science from the University of Houston, Texas. He is currently an associate professor in the Department of Computer Science at Virginia Tech. His research interests include mobile computing, pervasive computing, multimedia, distributed systems, real-time intelligent systems, and reliability and performance analysis. Dr. Chen has served on the program committee of numerous conferences, including being as program chair of 14th IEEE International Conference on Tools with Artificial Intelligence in 2002, and 3rd IEEE Symposium on Application-Specific Systems and Software Engineering Technology in 2000. Dr. Chen currently serves as an Associate Editor for IEEE Transactions on Knowledge and Data Engineering, The Computer Journal, and International Journal on Artificial Intelligence Tools. He is a member of the IEEE/CS and ACM.This revised version was published online in August 2005 with a corrected cover date.     

BER of OFDM in Rayleigh fading environments with selective diversity

This paper derives the analytical bit error rate (BER) of orthogonal frequency division multiplexing (OFDM) systems employing selective diversity in Rayleigh fading environments. First, the probability density function (pdf) of inter‐carrier interference (ICI) power in Rayleigh fading environments is derived. Second, the pdf of the signal‐to‐interference ratio (SIR) is then derived. The cumulative distribution function (cdf) and hence pdf of the SIR with selective diversity are then given in the third and fourth steps. Using the BER expressions of binary phase shift keying (BPSK) and differential BPSK (DBPSK) modulation in an added white Gaussian noise (AWGN), the corresponding BER expressions of OFDM systems can then be derived. Detailed discussions are given. Possible future work is also outlined. Copyright © 2009 John Wiley & Sons, Ltd.     

Maximized achievable rate of SINR‐measurement‐based spectrum sharing with binary feedback

Motivated by the difficulty in measuring channel state information between heterogeneous primary and secondary systems, we propose a signal‐to‐interference‐noise ratio (SINR)‐based spectrum sharing policy. In the proposed spectrum sharing policy, a secondary user who does not cause SINR outage at the primary receiver is admitted to share the primary user's spectrum. In this article, we analyze the achievable rate of a secondary user and for whom the achievable rate is maximized in the SINR‐constrained spectrum sharing. The maximized achievable rate is determined by the ratio of the distance between the secondary transmitter and the primary receiver to the distance between the secondary transmitter and receiver, and it is proportional to the distance ratio. In conclusion, secondary links with large distance ratio can support high data rate applications so long as SINR constraint of the primary user is guaranteed. Copyright © 2011 John Wiley & Sons, Ltd.     

Closed‐Form Expressions for Selection Combining System Statistics over Correlated Generalized‐K Fading Channels in the Presence of Interference

This paper considers the effects of simultaneous correlated multipath fading and shadowing on the performances of a signal‐to‐interference ratio (SIR)‐based dual‐branch selection combining (SC) diversity receiver. This analysis includes the presence of cochannel interference. A generalized fading/shadowing channel model in an interference‐limited correlated fading environment is modeled by generalized‐K distribution. Closed‐form expressions are obtained for probability density function and cumulative distribution function of the SC output SIR, as well as for the outage probability. Based on this, the influence of various fading and shadowing parameter values and the correlation level on the outage probability is examined.