B3G／4G TDD试验平台框架及研究现状

1、引言 目前，世界各国在推动第三代移动通信系统（3G）商用化的同时，已将研究重点转入Beyond 3G或4G（下称B3G）移动通信的研究，在概念和技术上寻求创新和突破，以使无线通信系统容量和速率有十倍甚至百倍的大幅度提高。为适应未来发展的需要，B3G移动通信系统应当具备以下基本特征：无论何时何地，都能够为终端用户提供高分辨率业务；能够使用”空间分集”技术对抗更高频段上的电波传输特性，     

3G的传输需求和应对策略研究

3G代表了未来移动通信的发展走向,是移动业务发展的必然趋势,因此在目前建设传输网络时充分考虑3G系统的传输需求是十分必要的.本文针对目前业界在3G传输方面所存在的三大认识误区,分别从3G传输组网的特点、3G接入网络设备的功能和接口类型对传输组网的需求等方面的分析出发,并结合RNC和Node B接口的使用方法和新型城域传送技术的应用,剖析了3G的传输需求并研究了应对策略.     

清华宽带无线移动通信关键技术研究

文章针对清华大学无线与移动通信技术研究中心在B3G领域的研究情况,简要介绍了清华宽带无线城域网(BRadio)、分布式无线通信系统(DWCS)、DWCS容量分析和接收算法、DWCS无线资源管理算法、非正交传输多址技术、MIMO-OFDM技术以及HARQ技术等方面的研究成果。     

后三代移动通信系统的发展驱动与服务应用

众所周知，3G移动通信系统可以提供相对2G有所改善的Internet多媒体业务．如WCDMA系统的空中接口可以提供户外中速率(384kbit／s)和室内环境下的高速率(2Mbit/s)的信号传输，而且它还采用空中接口的统计复用技术，提高了分组模式传输的效率。但是，第二三代移动通信系统仍然有着很多不足和缺陷。由于     

AI使能的高能效无线通信技术

随着5G无线通信网络大规模部署的开展，网络所消耗的能量正在成倍提升。尽管传统基于站点、频带和时隙静态关断的技术能够显著地提升整个无线网络传输和运营的能效，但面对大通量、高动态的5G业务需求，缺少AI支持的静态关断已无法满足系统的能效指标。因此，从无线通信网络的业务与传输层、媒体接入层和物理层等层面，探讨AI技术引入对提升无线通信网络能效带来的积极影响。利用AI所提供的高度非线性拟合能力和泛化能力，针对无线网络业务的有效调度、传输任务的合理分配、收发机的通用架构以及基带和射频系统的联合优化等方面开展高能效的优化设计。通过搭建原型系统并分析部分案例，提出了相关建议，旨在促进5G和6G无线通信网络的能效提升。     

全球3G产业发展概况

1G是采用模拟技术的语音移动通信；2G是采用数字技术的语音移动通信，目前世界上多数国家的移动通信技术处于2G阶段；3G是将无线通信与互联网等多媒体通信结合的新一代移动通信系统。3G系统的目标是：世界范围内设计上的高度一致性；与固定网络各种业务的相互兼容；高服务质量；全球范围内使用的小终端；具有全球漫游能力；支持多媒体功能及广泛业务的终端。     

B3G无线试验系统中的软件关键技术研究

B3G无线蜂窝试验系统以窄中接口峰值速率达到100Mbps为目标.对于物理层能够提供这样高速率的通信系统,需要有相应的高速业务来验证.文章主要讨论B3G无线试验系统软件研究与实现,其中的关键技术包括:为了节约CPU资源的零拷贝操作设计,为了提高空中接口资源的利用率而采用的裸包设计,以及为了实现数据包可靠传输而采用的链路级差错控制机制设计.     

未来移动通信系统中的无线资源管理

文章结合当前正在研究的后3代（B3G），第4代（4G）移动通信系统的发展和处于运营及推广阶段的第3代移动通信系统，分析了未来移动通信系统中无线资源管理系统的关键技术，探讨了多体制标准下的无线通信网络和多种业务情况下的无线资源管理的研究方向。     

移动云计算发展历程研究

随着移动设备数量显著增加,当前的移动通信架构将很快达到极限,移动云计算应运而生。移动云计算可看作是移动通信和无线通信技术演进与融合的结果。文章首先从广域通信和短距离通信的角度,简要分析无线通信和移动通信的覆盖范围,归纳移动通信设备从1G到4G的发展历程,然后描述移动通信的空中接口发展情况,最后研究移动云计算高级架构的演进过程。     

论MIMO技术在LTE系统的应用与发展

LTE系统是由3G演进而来,其改进并增强了3G的空中接入技术,具有传输速度快、频谱效率高和服务质量好等特点.近年来,移动业务流量与日俱增,为更好地满足业务需求,在LTE系统中融入了新型的MIMO技术.MIMO技术在LTE系统中的应用,可有效提高LTE系统空间的资源,并增加无线系统的覆盖范围.本文在了解MIMO技术的基础上,对多用户MIMO技术在LTE系统中的应用及发展进行了探究.     

一种适用于W-CDMA系统的多业务无线资源调度算法

3G系统将以分组交换方式提供语音、数据、视频等具有不同QoS要求的多种业务，资源调度对保证系统服务质量和提高资源利用效率起关键作用．本文提出了一种基于业务类型、当前待发送负荷以及剩余延时限的时间调度策略和基于资源优化的资源调度策略，并使无线链路的传输质量与业务的优先级水平一致．通过系统仿真评价了算法的性能．     

A survey of overlay and underlay paradigms in cognitive radio networks

In the recent years, wireless applications and services have grown tremendously, resulting to a shortage of radio spectrum. On one hand, most of the available radio spectrum has already been allocated to different users and service providers. On another hand, research and statistics have revealed that the spectrum utilization usability is very limited. To address this dilemma, the concept of cognitive radio has emerged, which promotes the use of overlay and underlay transmission techniques to boost the utilization of radio spectrum resources. This paper provides a comprehensive survey of these 2 techniques and compares them qualitatively based on several network parameters. Next, this paper simulates overlay and underlay transmission techniques in OMNeT++ simulator on different network parameters, namely, Primary user arrival rate, throughput, sensing duration, and energy consumption. Our findings reveal that neither the overlay nor the underlay technique is sufficient itself to fulfill the demands for future wireless systems, and adopting a hybrid access technique consisting of a joint utilization of overlay and underlay approaches is desirable. Furthermore, the key challenges and open research issues in radio spectrum resources utilization are discussed.     

The Complementary Use of 3G WCDMA and GSM/GPRS Cellular Radio Networks

The traffic performance of integrated 3G wide-band code division multiple access (WCDMA) and GSM/GPRS network is evaluated. This type of network links two cellular radio systems which have different set of frequency bands and the same coverage size. The base station of 3G WCDMA is installed on an existing GSM/GPRS site. Dual-mode mobile terminals use handoff to establish calls on the better system. The soft handoff or inter-frequency hard handoff occurs when mobile terminals of 3G WCDMA or GSM/GPRS move between two adjacent cells, respectively. The inter-system hard handoffs are used between 3G WCDMA and GSM/GPRS systems. The data rate conversions between different systems, soft handoff region size, multiple data rate multimedia services, and the effect of the mobile terminal mobility on the user mean dwell time in each system are considered in the study. The simulation results demonstrate that a great traffic performance improvement on the complementary use of 3G WCDMA and GSM/GPRS cellular radio networks compared with the use of GSM/GPRS cellular radio networks. When high-data rate transmission is chosen for low-mobility subscribers, both the handoff failure probability, and carried traffic rates increase with the new call generation rate. However, both rates decrease conversely with the increasing new call generation rate as soon as the new call generation rate exceeds a critical value. This causes the integrated networks saturation. The higher mean speed for the mobile terminals produces lower new call blocking probabilities and total carried traffic. The new call blocking probabilities and total carried traffic increase with the size of the soft handoff region.     

QoS-Based Admission and Load Control Algorithm for Integrated Voice/Data Services over Wideband CDMA

In order to maximize the system capacity in third generation wireless system, efficient call admission and load control algorithms are required to handle the different services having diverse traffic patterns and Quality of Service (QoS) requirements. We propose an admission and load control algorithm that considers the network loading information, propagation conditions, and the interference level. The algorithm takes advantage of the new features of third-generation (3G) wireless system such as the reported pilot measurements, auxiliary pilot for smart antennas, and variable spreading gain. Dynamic resource allocation is employed to scale the amount of the assigned radio resources taking the network loading conditions and channel characteristics into consideration. The results show that integrating the voice service and the data service with high transmission rate (>144 Kbps) can be realized using efficient resource management.     

Provisioning multimedia wireless networks for better QoS: RRM strategies for 3G W-CDMA

Third-generation mobile communication systems will bring a wide range of new services with different quality of service requirements and will open the ability to exploit radio resource management functions to guarantee a certain target QoS, to maintain the planned coverage area and to offer a high-capacity while using the radio resources in an efficient way. RRM functions impact the overall system efficiency and the operator infrastructure cost, so they will definitively play an important role in a mature 3G scenario. In order to provide some insight into radio resource management (RRM) strategies implementation, a range of representative case-studies with several innovative algorithms are presented and supported by simulation results in a realistic UMTS Terrestrial Radio Access Network scenario as devised in the 3GGP standardization forum. In particular, a decentralized uplink transmission rate selection algorithm in the short term, a congestion control mechanism to cope with overload situations, and downlink scheduling for layered streaming video packets are proposed.     

Intelnet Services—A global data distribution and collection scheme

Responding to the recent availability of very small earth-stations (commonly called micro terminals) for data/voice communications, INTELSAT has introduced a new service called INTELNET. INTELNET services are designed to operate with two different modulation and coding techniques, i.e. spread spectrum and binary phase-shift keying (BPSK) with rate 1/2 forward error correction (FEC). The INTELNET I service is a data distribution service, whereas the INTELNET II service is a data collection service. These services are facilitated by the use of micro terminals at remote locations (i.e. outposts) which will be linked through the INTELSAT space segment to relatively large INTELSAT earth-stations (e.g. Standard A, B, C and E-3). INTELNET services are leased transponder services offered on a range of INTELSAT satellites in C- or Ku-bands on a pre-emptible or non-pre-emptible basis. These services are offered on a full-time or occasional-use basis, by assigning predetermined satellite resources of bandwidth and power with a smallest allotment of 1 MHz. In this paper, the system design and network architecture for the INTELNET I and II services are addressed. Representative transmission parameters have also been developed for the INTELNET I and II services. System cost considerations as a result of the use of micro terminals are analysed.     

Layered Video and Differentiated Coding for Adaptive QoS in Mixed Wired-Satellite Networks

Mobile networks are becoming nothing but a way to allow ubiquitous access to multimedia services. To allow efficient use of resources, new systems provide flexible bandwidth and different error protection techniques to match channel behavior. As the backbone network is increasingly becoming based on packet techniques and in particular on IP and related transport protocols, end to end service quality must be analyzed considering both the fixed and the mobile part. Source scalability may help in coping with a mixed and heterogeneous environment. In this work we present some results of a transmission chain comprising a scalable MPEG-2 coder, an IP network and a radio access exploiting the availability of satellites. It is shown that for a given target rate, differentiated coding can be exploited to achieve decodability and good quality at a channel SNR much lower that single layer streams. This revised version was published online in July 2006 with corrections to the Cover Date.     

太赫兹频段星地通信信道建模与仿真

太赫兹频段作为至今尚未被完全开发的超高通信频段,具有超大带宽等优点,将其应用于第五代（the 5th Generation,5G）、后五代（Beyond 5G,B5G）移动通信系统,除实现更高速率传输外,还可实现地面移动网络与卫星网络频谱资源的共享,有利于推动新一代空天地一体化通信网络建设.文章提出了一种适用于星地通信系统的太赫兹信道建模与仿真方法,分析了自由空间损耗、分子吸收损耗、云雾衰减、雨衰减及多普勒频移等太赫兹信道的影响因素,构建了星地太赫兹通信信道建模流程,并给出了分步骤信道参数的生成方法.通过数值仿真,对不同天气状况下传输距离和频率对传输信号的影响进行了分析,并基于所生成的信道响应对误码率进行评估,从而验证了所提出模型和方法的可用性.所提建模方法能够提供不同传输条件下的动态太赫兹信道响应数据,从而为今后太赫兹频段无线通信系统的设计与开发提供评估与测试依据.     

Microcell design principles

The ways in which microcell systems can help cellular operators face a number of challenges to achieve continued growth, including the need for increased system capacity, enhanced coverage, lower network cost per subscriber, improved performance, delivery of innovative value-added services, and well-planned equipment and service migration strategies, are discussed. It is argued that microcells must work with conventional cellular systems with lower equipment costs per subscriber, and should require only minimal preinstallation RF design and engineering. Keys to cost-effective microcell deployment are high-performance RF component and digital signal processing technology, efficient radio resource management, optimized distributed network design, and effective switch and network integration     

Challenges in low-cost wireless data transmission

Second- and third-generation (2G and 3G) wireless systems have been designed primarily for voice, a connection-oriented, delay-sensitive service requiring a specified bit rate. In contrast, data services are often connectionless, delay insensitive, and have no specific bit-rate requirements. These differences suggest that ubiquitous (anytime/anywhere) coverage may not be a strict requirement for wireless data networks and in fact may needlessly complicate the design. This line of thought leads to systems that provide isolated high bit-rate “pockets” of coverage close to base station antennas through multilevel modulation and increased spectrum reuse allowed by pocket isolation. Specific issues that are relevant for such tier architectures range from the physical layer extending to radio resource management and even application layers. We describe some issues for wireless data targeting the following: transceiver techniques and radio resource management