Fiber optic microcellular radio

A distributed antenna system consisting of optical fiber connected canisters is proposed to replace or supplement the base station antennas required for cell splitting of growing cellular mobile radio systems. The end-to-end linear transmission of RF signal voltage can be maintained over the wide dynamic range of mobile radio. The technical feasibility of multiplexed subcarrier transmission using available lightwave components has been verified by signal-to-noise ratio and intermodulation distortion measurements. Measurements of a two-way audio link over both simulated and real radio paths have demonstrated the compatibility of a prototype lightwave transceiver, designed for the canister, with the existing base station and mobile equipment     

A low-cost cellular mobile communication system: a hierarchicaloptimization network resource planning approach

This paper deals with the optimization of the design and radio network resource planning for cellular mobile communication systems. The key element to be considered for mobile network planning is cost. A hierarchical optimization planning method (HOP) is utilized since there are so many factors like system performance, terrain features, base station parameters, and cost factors which are involved in the large-scale system design. We present a three-level optimization approach for designing a cellular mobile system. It determines the cell number, cell site allocation, and the specific base station parameters in order to minimize the total system cost and to comply with the required system performance. The problem is formulated as a large combinatorial optimization model which can determine the optimal number of cells and select the best base stations' locations. The simulated annealing approach is developed to solve the hard combinatorial problem. Simulation results demonstrate the feasibility and effectiveness of the HOP approach for radio network planning     

Linearized transmitters: an enabling technology for softwaredefined radio

Power amplifier and transmitter linearization techniques are now a mature technology, with feedforward systems installed in many US base station sites for both TDMA and CDMA systems. Similarly, transmitter linearization techniques, such as Cartesian loop and predistortion, have been employed in mobile and portable equipment, and these have enabled a number of systems (e.g., iDEN in the United States and TETRA in Europe) to be realizable from a power consumption, cost, and size perspective. Such techniques are essential in the realization of an efficient and cost-effective software-defined radio system, whether deployed in a base station or a handset, and are thus a key enabling technology, without which SDR will not succeed. This article examines the current status of power amplifier and transmitter linearization technologies for mobile and base station equipment, and highlights some of the novel base station and network topologies now emerging based on these techniques. In many cases, these new topologies will revolutionize the way a cellular network is constructed and lead to very substantial cost reductions for a network operator     

Theoretical studies of a simulcast digital radio paging system using a carrier frequency offset strategy

In a multistation simulcast digital radio paging system, each base station transmits the same RF signal simultaneously with the resulting efficient frequency utilization and simplified receiver design. In this system a paging receiver in the overlapping area receives several RF signals transmitted from different base stations. When frequency-shift keying (FSK) is used as a modulation method, experimental test results have already shown that the timing of each RF signal should be synchronized as closely as possible, but that the carrier frequency of each transmitter should be set following a certain offset assignment. The signal transmission performance in a multipath fading environment can then be markedly improved. The cause of this improvement effect is theoretically analyzed. It is clarified that the improvement effect is caused by transforming the probability distribution of time-averaged signal power.     

OPM产生四倍频光载毫米波的双向ROF系统

提出一种采用单个光相位调制器(OPM)和光纤布拉格光栅(FBG)滤波器产生四倍频光载毫米波的双向光纤无线通信(ROF)系统。在中心站(CS),系统采用基带信号与射频(RF)信号混频后去驱动OPM,以产生抑制一阶边带的多边带光信号。在基站(BS),利用FBG滤波器将信号的重复频率增至4倍。实验结果显示,经过40km光纤传输后,下行链路信号的眼图清晰可见,功率代价小于1.6dB。本文方案中,由于没有额外增加激光源使得基站结构进一步简化,同时四倍频技术降低了RF信号的频率,系统成本大大降低。     

A slotted ALOHA packet radio system with multiple antennas andreceivers

The problem of data transmission in a mobile packet radio system with one central base station and a number of mobile terminals is addressed. A method using multiple directional antennas and receivers at the base station to improve the efficiency of transmission on the inbound channel (from the terminals to the base station) is proposed. A number of channel models are considered, including flat terrestrial propagation loss, Rayleigh fading, and noise. A finite population Markov model is used to obtain the throughput of a multiantenna and multireceiver slotted ALOHA system. Numerical results indicate that substantial gains are possible with the use of several antennas and receivers. The dynamic behavior of the system is also improved     

Antenna selection in a multisector packet radio system

To improve performance on the inbound (mobile-to-base-station) channel of a packet radio system consisting of a base station and a number of mobile users, the area around the base station is divided into M sectors. Signals originating from users in different sectors are received by different directional antennas at the base station. It is shown that, if the number of receivers at the base station is less than M, the selection of the antennas to be connected to the receivers becomes an issue. A number of antenna selection schemes are compared for three different channel models, assuming an ideal antenna pattern. It is found that the scheme that selects the antennas with the largest received signal powers is nearly optimum. The effects of a more practical nonideal antenna pattern are discussed     

Outage probability calculations for a mobile radio system having two log-normal interferers

Outage probability calculations are presented for the case when the transmission from a wanted base station is received by a mobile in the presence of two cochannel-interfering signals for the case where the transmissions suffer log-normal shadowing only. The calculations consider the need to achieve simultaneously both a sufficient SNR and SIR to obtain satisfactory radio reception.     

射频功率放大器告警功能模拟检测方案

射频功放模块是基站系统中的核心部件,出厂前对射频功放模块的功能进行检测意义重大.设计了一块告警功能测试板,通过观察与射频功放模块相连的测试板上的LED灯,判断射频功率放大器功能是否正常.实践证明,该方法能模仿射频功率放大器在实际基站系统中的工作行为,不仅有效地提高了射频功率放大器的良品率,而且适用于商业化大规模批量生产...     

Digital mobile telephone system using TD/FDMA scheme

Multiple access is an indispensable technique for efficient radio spectrum utilization in mobile radio systems, because a large number of subscribers can be connected only when they require radio channels. Frequency division multiple access (FDMA) scheme using single channel per carrier (SCPC) has been widely used. However, the SCPC-FDMA scheme has some problems, such as difficulty in setting up a large number of base station transceivers and in realizing a low-cost highly stabilized local oscillator. A time and frequency division multiple access (TD/FDMA) scheme, which is a combination scheme of TDMA and FDMA, is proposed as one of the possible solutions for these problems. After explaining the background of the proposal, some of the restrictions of the TD/FDMA scheme resulting from the land mobile radio channel characteristics are described. Basic concept of the digital mobile radio telephone system using TD/ FDMA scheme is then presented. An example of the possible system design is finally shown.     

A radio access system with distributed antennas

This paper analyzes a radio access system that has multiple antennas spatially distributed throughout each cell, instead of a single antenna at each cell. The same signal is simulcast by each antenna in the cell. The signals at a given cell could be multiplexed and modulated for radio transmission at a single node, then transmitted on a coaxial cable distribution system to and from the distributed antennas in a cell. Frequency translation and radio frequency (RF) amplification may need to be performed at each antenna, except for indoor applications with short coaxial cables. This paper presents calculations of signal-to-interference ratios (SIR) and handoff performance for cells with distributed antennas. It is shown that the use of distributed antennas can substantially increase the SIR above a system with a single antenna per cell, and this increase is quantified. It is also shown that increasing the number of antennas results in better overall handoff performance, with a lower number of handoffs and higher received signal power. Minimizing the number of handoffs will reduce the impact of wireless services on network elements     

L波段高效率射频功率放大器的设计与仿真

射频功率放大器是无线通信系统中的重要组成部分,其工作效率直接影响着整个系统的耗能、稳定度和对电源散热装置的要求,提高射频功率放大器的效率,能够节约能源,降低功耗,因此实现射频功率放大器的高效率工作是目前射频功率放大器领域的热点问题之一。本文选用Freescale晶体管MW6S004N,借助ADS2013软件,采用负载牵引技术和源牵引技术得到最佳负载阻抗和最佳源阻抗,并用Smith圆图进行电路的匹配设计,对射频功率放大器进行了仿真和优化。仿真结果表明,在频率为1960MHz的L波段,输入功率为21d Bm时,射频功率放大器的输出功率大于36d Bm,功率附加效率大于50%。这种高效率射频功率放大器适用于WCDMA基站,对基站中高效率功率放大器的设计有着重要的参考价值。     

Smart Antennas with Two-Dimensional Array Configurations for Performance Enhancement of a Joint Detection CDMA Mobile Radio System

Smart antennas for base stations of cellular mobile radio systems offer the potential of system performance enhancement by taking advantage of the directionally inhomogeneous signal reception at the receiver. In this paper, two-dimensional array configurations employed at the uplink receiver of a joint detection CDMA (JD-CDMA) mobile radio system are investigated. This smart antenna concept can be split up into a novel channel estimator and data detector which incorporate explicitely the information of the direction-of-arrival (DOA) of signals emerging from users assigned to the considered base station. Proceeding from channel models that model the directional inhomogeneity of the mobile radio channel with single DOAs, the link level performance of a JD-CDMA mobile radio system using this smart antenna concept is evaluated for the rural propagation environment. The performance evaluation is based on Monte Carlo simulations of data transmission and average bit error rates versus the average signal to noise ratio per net information bit are presented for different array configurations. Although these results should be considered as upper bounds for the link level performance, they reveal the advantages of implementing two-dimensional array configurations at the uplink receiver of a JD-CDMA mobile radio system.     

无源中继系统在网络覆盖中的应用

移动通信蜂窝组网,以基站覆盖"面",直放站补充覆盖"点".直放站的引入抬高了蜂窝系统底噪声,加大系统干扰,影响网络质量.在适当场景下,引入无源中继系统可以达到解决弱信号的目的,同时不影响网络质量.本文对无源中继系统可行性进行理论论证与实验论证,提出无源中继实用化的思路.通过对应用案例多角度重点分析,提出无源中继系统的技术要求、应用场景.     

X/Ka频段遥感卫星地面接收信道便携式测试系统设计

为解决X/Ka信道在建设和运行维护过程中测试设备笨重、功能单一、设备操作复杂、工作状态无法获取等弊端,通过优化中频与射频链路方案、小型化与多功能集成设计、集中监控与射频线缆供电等方式,设计了一种便携式X/Ka频段遥感卫星接收信道测试系统,实现了1 GHz宽带X/Ka卫星数据地面接收系统射频(7.9~8.9 GHz、18~20 GHz、25~27.5 GHz 3个频段,有线或无线)、中频环路的调试和测试(1.2 GHz、1.5 GHz 2个频段)及信道的测试系统的集中监控、高阶调制、多种编码、多普勒仿真、噪声源添加等功能,极大地方便了现场或野外测试应用。     

软件无线电技术在GSM基站中的实现

针对移动通信GSM基站软件化的问题,依据软件无线电的基本理论,采用宽带中频带通采样软件无线电的方法来实现GSM基站的信号接收,建立了移动通信GSM基站接收机的系统模型,并给出了具体方案。     

宽带数字预失真硬件平台设计与实现

针对第3代移动网络基站射频功率放大器的线性化需求的不断提高和立足于未来第4代移动通信系统基站,设计并实现了一款以FPGA为核心的宽带数字预失真硬件平台。首先,对整体硬件框架进行了阐述并着重分析了LTM9003的带通采样定理和AD9788的数字单边带调制;其次,根据2-D(ADC)和ADC多次采样技术,提出了超宽带矢量信号测试的系统结构和原理实现;最后,对整机进行了ADC和DAC链路的测试,测试结果表明其性能基本达到了数字预失真的需求。     

Radio resources allocation for decentrally controlled relay stations

To enhance throughput and to extend coverage of wireless networks based on IEEE 802.16 standards, relay stations can be implemented. The crucial point influencing the overall system performance is allocation of appropriate amount of resources to individual relay stations depending on their current needs. If resources are not allocated properly, relay stations can experience congestion situations resulting in system throughput decrease and packet delays increase. If the base station is enhanced purely by centrally controlled relay stations, the base station itself is able to dynamically schedule data transmissions of its relays. Nevertheless, decentrally controlled relays schedule data for its users on its own and the base station is no longer capable to allocate the right amount of radio resources for them. The decentrally controlled relays have to ask for radio resources by means of existing scheduling services defined in IEEE 802.16 standard. While utilization of the conventional unsolicited grant service decreases the system capacity, the use of real-time polling or extended real-time polling services results in higher signaling overhead and longer packet delays. In order to maximize system throughput and to minimize packet delays and signaling overhead, we suggest a mechanism that pre-allocates to decentrally controlled relay stations a certain amount of default radio resources while the remaining resources are dynamically shared. The obtained results show that for low traffic load, overhead and packet delays are significantly smaller as relays do not have to ask base stations for resources. On the other hand, at heavy traffic load the system throughput slightly decreases whereas packet delays and signaling overhead are still significantly smaller.     

Design of optimal relay location in two-hop cellular systems

Relay stations are usually used to enhance the signal strength for the users near cell boundary, thereby extending the cell coverage. However, transmission through a relay station needs two transmission phases. The first phase is from base station to relay station, and the second one is from relay station to mobile station. Thus, using relay station may decrease system capacity due to two-phase transmission time. As a result, whether or not data are transmitted by one-hop or two-hop phases should be determined according to both signal strength and throughput. In this paper, we investigate the optimal relay location aiming to maximize system capacity. We consider two relay selection rules for determining whether two-hop transmission will be used: signal strength-oriented and throughput-oriented selection rules. We find that the signal strength-oriented two-hop transmission may yield even lower system capacity than the one-hop transmission. In the throughput-oriented scheme, the two-hop transmission can achieve higher system capacity than the one-hop transmission. By simulations, we determine the optimal relay location and show the coverage enhancement by the relaying network. Extensive simulations are performed to investigate the impacts of relay transmission power and the number of relay stations on system capacity and optimal relay location. The simulation results reveal important insights into designing a relaying network with high system capacity.