Design of beam-forming networks using CORPS and evolutionary optimization

This paper deals with the design of beam-forming networks (BFNs) using coherently radiating periodic structures (CORPS) and evolutionary optimization. This design of feeding networks using the principles of CORPS considers the optimization of the complex inputs of the network by using genetic algorithms. Some results obtained by simulation for a CORPS network of several layers are presented. The results shown in this paper present certain improvement in the array factor response and the network simplification for the design of CORPS network over a conventional BFNs.     

Design and optimisation for cellular access network

The service quality of a cellular-radio network is dependent on the integrity of its access network. As a cellular-radio network evolves, the challenge to the operator is to provide near ubiquitous coverage (with adequate signal-to-noise ratio and a balanced uplink and downlink for handportables) and to accommodate a high traffic density yet at the same time to ensure that the carrier-to-interference ratio remains acceptable despite a finite amount of spectrum allocation. The large number of base sites deployed for coverage and capacity must be interconnected economically and efficiently back to the switch sites without compromising on resilience and transmission capacity. To meet these challenges, better efficiency for the radio links has to be achieved through the introduction of automated planning tools and adaptive system features; improvement of the transmission network performance can be attained by the flexible use of transmission media and network topologies     

A CDMA network architecture using optimized sectoring

We propose a network architecture for code-division multiple-access (CDMA) cellular systems based on adaptive sector coverage. We show that there is a capacity limit for a CDMA system, which for a soft limit is fairly hard. We also show that for nonhomogeneous traffic, changing the area of coverage for each sector in a sectored-cell can absorb the dynamics of the traffic. For a cell of a fixed radius, divided into n sectors, it is possible to select the angles of coverage of each sector in order to avoid excessive blocking due to temporary nonuniformity of traffic across the cell. This result is based on the fact that for a given set of system parameters (bandwidth, bit rates, E_b/N₀ etc.), a certain amount of area is covered. Hence, the exact shape of the cell/sector is not important. The idea presented is shown to be applicable to overlapping sectors     

Design and analysis of multiple-beam reflector antennas

Simplified design and analysis equations are presented for multiple-beam reflector antennas based on the Gaussian-beam analysis of the primary and secondary patterns. The derived equations are useful for the quick design and performance analysis in terms of the coverage-area directivity and the inter-beam isolation of multiple-beam antenna systems. Results of the analysis given in this paper agree well with rigorous computations based on physical-optics analysis of the reflector-antenna radiation patterns. Extension of the analysis to multiple-beam lens antennas, and to shaped/contoured-beam antennas, is also presented     

利用SRUDP的3G无线网络视频监控系统设计

为促进无线视频监控领域新技术的开发和应用,立足解决工程实际问题,提出了一种利用简单可靠用户数据报协议(SRUDP)的3G无线网络视频监控系统的新型设计方案.系统可以对H.264视频流进行分层模式的高效编码、压缩纠错和实时传输控制,并重新封装用户数据报协议(UDP)、SRUDP和IP报头.系统采用滑动窗口机制和重传机制来进行消息的收发同步和流量控制,可以实现任意用户终端对任意监控点的有效监控.系统视频QoS的控制方式运用迭代算法,发送端可以根据反馈信息通过编码器进行自适应调整速率,并参考SRUDP缓存进行参数修改,实现鲁棒控制.仿真实验表明,在3G网络环境下,基于SRUDP的视频应用在降低视频时延和包丢失率、减少网络拥塞、提高传输速率和改善视频质量等方面具有明显的优越性.     

基于Blumlein脉冲网络的直线型脉冲变压器设计

为了实现能产生重复频率矩形高压脉冲输出的紧凑型脉冲功率源,设计了基于脉冲形成网络的直线型脉冲变压器。以陶瓷电容和光导开关构建全固态Blumlein型脉冲形成网络,分析了磁芯参数对能量效率和平顶度的影响,计算了设计的脉冲功率源的分布参数,并基于分布参数建立了了全电路模型。研究结果表明足够的磁芯伏秒数是直线型脉冲变压器运行的必要条件,而分布参数是引成输出脉冲畸变的另一重要因素。     

Location service for wireless network using improved RSS-based cellular localisation

Value-added services, especially in mobile environments, have recently become the key component of making more profit and attracting more subscribers. One of the most commonly used such service is location-based advertiser services. The main issue which should be considered in providing such services is determining the position of the mobile terminals precisely. In this paper, one pattern recognition localisation method based on the signal strength appropriated for implementing a location-based service is presented. The main aim is to introduce some practical solutions to decrease error and computational load and also eliminate the necessity of updating the database. Practical results illustrate high accuracy of this technique and its suitability to apply in such services. The mean error declines to 9.7 m and mean error corresponding to CDF = 67% and CDF = 95% are less than 11 m and 23 m, respectively. We also present a location-based advertising service, in which the customer’s interests and local time are considered, in order to enhance the efficiency and individualism of this service.     

Design of location areas with QoS considerations in a cellular network

In this paper, we present a location area (LA) planning model which explicitly has more QoS-conscious constraints than any other models. In order to specify an acceptable level of QoS, paging delay time (PDT) and paging blocking rate (PBR) are introduced. The paging process is described by the M/M/c/K queuing system and queuing analysis is carried out to obtain PDT and PBR. Also, in the proposed model, the time-varying call arrival rates are used to define the paging load on each cell, which helps to reflect the pattern of incoming calls more precisely and subsequently to improve the QoS level. To evaluate the proposed model, some examples are solved along with the average rate model and the peak rate model. The results show that the proposed model has the capability to maintain the acceptable level of QoS with the reasonable location management cost, compared to other models. Also, the sensitivity analysis is performed to see the effect of PDT and PBR in the formulation and it turns out that both PBR and PDT are important elements of the QoS measure and influential to the location management cost.     

蜂窝网络信道分配均衡化控制器的设计与实现

当前的蜂窝网络中,移动具有随机特征,使得蜂窝网络信道到达率、业务应用类型等都具有随机性,导致部分蜂窝网络信道负载过大,资源均衡性较差的缺陷。因此,依据分层架构和模块化思想,设计并实现蜂窝网络信道分配均衡化控制器,其包括应用层、控制层以及基础设施层。控制器的基础模块和应用模块协同运行,实现网络信道资源的均衡分配,控制器通过Open Flow协议控制下的南向接口,同底层网络设备交流信息。蜂窝网络信道业务通过REST接口将资源申请命令反馈给控制器,促使控制器管理底层设备完成资源数据的转发,确保信道资源分配的均衡化。实验结果表明,所设计控制器下的网络信道吞吐量、平均系统公平性指数、用户平均中断概率以及信道负载率四个指标都较优秀,取得了令人满意的结果。     

Development of a 45 GHz multiple-beam antenna for militarysatellite communications

Design and experimental results of a wide-angle coverage 45 GHz multiple-beam antenna for military satellite communications are presented in this paper. The high-gain spot beams with low sidelobe levels and efficient adjacent beam overlap are generated by employing an offset parabolic reflector with overlapping feed clusters. The beam shape can be adapted to cancel either single- or multiple-jammers by varying excitations within the feed cluster corresponding to the beam. Development of antenna components including Potter horn, polarizer, phase-amplitude controller, and beamforming network is discussed. Measured results of the demonstration antenna have shown that sidelobe and crosspolar levels of better than -25 dB are achieved for beams scanned over an eight-degree diameter circular coverage region. The adapted patterns of the antenna agree well with the computations, and null depths of better than 30 dB have been realized over a 4.5% bandwidth     

Analysis of a multiple-beam waveguide for free-space transmissionof microwaves

The transmission of several quasi-optical beams via one system of oversized focusing mirrors is discussed. The analysis of this multiple-beam waveguide shows that such a system can substantially reduce the total mirror surface compared to the corresponding number of individual lines. With the help of analytic coupling coefficients for Gaussian beam modes deduced from the coupling integrals, configurations of four mirrors are found, which give low losses due to the reconversion of spurious modes generated at the different mirrors. Optimization of the mirror surfaces as a function of system parameters is performed and expressions for the loss as a function of the number of transmission channels are deduced. The results are confirmed by diffraction calculations and laboratory scale experiments. The application to a high-power system promises a very efficient transmission with high mode purity     

Design trade-offs in cellular/PCS systems

With the increasing demand for all kinds of wireless access services, including cellular/PCS, wireless local loop, and broadband access, the system architects will have opportunities to design new communication systems, not necessarily based on existing wireless standards. In the design of wireless communication systems, there are usually multiple objectives such as low cost, small size, high reliability, and large capacity. The system architect would need to study the trade-offs among different combinations of modulation, coding, multiple access, and antenna techniques to determine the best design. In this tutorial we focus on the trade-offs between user bandwidth and multi-user interference in order to maximize the system capacity. The design trade-offs are depicted on a B-γ₀ plane. Where B is the user bandwidth and γ₀ is the carrier-to-interference ratio (C/I). For F/TDMA and CDMA systems, the author first shows that the contours of equal system capacity are straight lines with different slope's depending on the propagation environment, and the capacity decreases for increasing B and γ₀. Then as feasible solutions, the author plots the different combinations of modulation and coding with diversity to satisfy a certain quality of service in a multipath environment. The best design is obtained by moving a line with a certain slope from the lower left corner in the B-γ₀ plane until it touches the first feasible solution. From these plots we can see that, for example, while 1/2-rate channel coding is the best choice for F/TDMA systems, 1/3-rate is better for CDMA systems     

A channel allocation for cellular mobile radio systems using simulated annealing

We consider the channel allocation problem, which is one of the most interesting problems in mobile radio systems. This problem is known to be NP‐complete and a couple of heuristic algorithms have been developed. In this paper, we convert the problem into a simpler form through the concept of pattern, a set of cochannel cells. We suggest another algorithm based on simulated annealing for this simplified problem. The algorithm is applied into different benchmark problems that have appeared in the literature. The presented examples illustrate that our method works very well. Computational results using our formulation and simulated annealing algorithm are reported. This revised version was published online in August 2006 with corrections to the Cover Date.     

Downlink scheduling in a cellular network for quality-of-service assurance

We consider the problem of scheduling data in the downlink of a cellular network over parallel time-varying channels, while providing quality-of-service (QoS) guarantees to multiple users in the network. We design simple and efficient admission control, resource allocation, and scheduling algorithms for guaranteeing requested QoS. In our design, a joint Knopp and Humblet (K&H)/round robin (RR) scheduler, composed of K&H scheduling and RR scheduling, utilizes both multiuser and frequency diversity to achieve capacity gain when delay constraints are loose or moderate. However, for tight delay constraints, an additional reference channel scheduler is required to obtain additional frequency diversity gain. The key advantage of our formulation is that the desired QoS constraints can be explicitly enforced by utilizing the concept of effective capacity.     

级联Blumlein型脉冲网络充电电源设计

各级Blumlein型脉冲形成网络充电电压的不一致是影响级联脉冲形成网络电压传输效率的因素之一,为了使级联网络的充电电压一致,设计了一种多路充电电源.每路电源由脉冲变压器,IGBT,初级储能电容组成,IGBT的同步触发使得每路电源同时对负载充电.实验结果表明各级网络的充电电压不一致性＜0.1％.     

A cellular neural network and utility-based radio resource scheduler for multimedia CDMA communication systems

The paper proposes a cellular neural network and utility (CNNU)-based radio resource scheduler for multimedia CDMA communication systems supporting differentiated quality-of-service (QoS). Here, we define a relevant utility function for each connection, which is its radio resource function weighted by a QoS requirement deviation function and a fairness compensation function. We also propose cellular neural networks (CNN) to design the utility-based radio resource scheduler according to the Lyapunov method to solve the constrained optimization problem. The CNN is powerful for complicated optimization problems and has been proved that it can rapidly converge to a desired equilibrium; the utility-based scheduling algorithm can efficiently utilize the radio resource for system, keep the QoS requirements of connections guaranteed, and provide the weighted fairness for connections. Therefore, the CNNUbased scheduler, which determines a radio resource assignment vector for all connections by maximizing an overall system utility, can achieve high system throughput and keep the performance measures of all connections to meet their QoS requirements. Simulation results show that the CNNU-based scheduler attains the average system throughput greater than the EXP [9] and the HOLPRO [5] scheduling schemes by an amount of 23% and 33%, respectively, in the QoS guaranteed region.     

Design of a matching network for an HF antenna using the realfrequency method

The real frequency method (RFM) is used to design a matching network for an electrically short loaded dipole. The RFM is demonstrated to be superior to other analytical and numerical techniques in the sense that it yields the maximum flat transducer power gain possible, and that it does not require any analytical modeling of the load impedance to be matched. For this reason, the RFM is found to be well suited for matching distributed systems such as antennas     

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.