A bandwidth sharing approach to improve licensed spectrum utilization

The spectrum of deployed wireless cellular communication systems is found to be underutilized, even though licensed spectrum is at a premium. To efficiently utilize the bandwidth left unused in a cellular system, the primary system (PRI), we propose an overlaid ad hoc secondary network (ASN) architecture, with the ASN operating over the resources left unutilized by the PRI. Our basic design principle is that the ASN operates in a nonintrusive manner and does not interact with the PRI. In this article we present the ad hoc secondary medium access control (AS-MAC) protocol to enable PRI-SEC interoperation, address a number of technical challenges pertinent to this networking environment, and evaluate the performance of the AS-MAC. In a single-hop ASN the AS-MAC transparently utilizes 75 percent of the bandwidth left unused by the PRI, while in multihop ASNs, due to spatial reuse, the AS-MAC can utilize up to 132 percent of the idle PRI resources in our experiments.     

Shunt bootstrapping technique to improve bandwidth oftransimpedance amplifiers

The input capacitance of transimpedance amplifiers can limit their response time. One novel technique based on a shunt bootstrap method is shown to be of advantage to op-amp based circuits with a high transimpedance gain     

提高高频雷达带宽的多载波技术研究

天波雷达工作在高频段,其工作带宽受电离层特性和人工信号干扰的限制,工程信号带宽一般只有十几千赫兹。利用多输入多输出(MIMO)原理,研究发射一组正交多载波调制的带宽为十几千赫兹的线性调频(LFM)信号照射目标,在接收端经匹配滤波和等效发射波束成形技术重建这一组回波信号成宽带信号,以增大雷达系统信号带宽。理论分析表明:在不考虑高频雷达多模多径情况下,发射N个频率间隔f_p=B的正交多载波调制LFM信号,在接收端采用匹配滤波和空时信号处理技术,将使接收信号带宽提高大约N倍。采用Watterson短波信道模型的仿真结果验证了理论分析的正确性。这表明在高频雷达多径环境不严重时,采用该方法可以提高雷达的距离分辨力。     

Microwave subcarrier multiplexing: new approach to widebandlightwave systems

Wideband communication systems for providing voice, data, and video services to the subscriber over optical fibers are discussed. The principles of microwave-multiplexed lightwave systems are introduced, and several transmission experiments that demonstrate the concepts are described     

Lightpath communications: an approach to high bandwidth opticalWAN's

An architectural approach that meets high bandwidth requirements by introducing a communication architecture based on lightpaths, optical transmission paths in the network, is introduced. Since lightpaths form the building block of the proposed architecture, its performance hinges on their efficient establishment and management. It is shown that although the problem of optimally establishing lightpaths is NP-complete, simple heuristics provide near optimal substitutes for several of the basic problems motivated by a lightpath-based architecture     

适用于软件无线电基带芯片验证的实时原型平台

随着半导体芯片器件规模急剧增长,对芯片的功能验证以及场景验证提出了更多的挑战。而对于基带SOC芯片,挑战则更加显著。基带SOC芯片的设计验证涉及到大量算法、信号处理专用电路、软硬件协同、实时复杂场景等功能评估与验证。一般通用的芯片验证方法(基于测试用例的服务器离线验证以及FPGA原型验证)无法覆盖对基带芯片评估、验证以及测试的要求。针对基带芯片设计验证需求,本文设计并实现了一个基于软件无线电的通用实时原型平台,可满足不同频段、不同协议的基带芯片的算法评估、功能及场景测试需求。本文基于该通用实时原型平台,成功的对一款GPS/BD导航基带芯片进行了实时原型验证,解决了原有离线仿真不能满足的实时场景验证需求,使得基带芯片的验证环境更加贴近真实环境,从而极大的提高了芯片的成功率。     

A framework for bandwidth management in ATM networks-aggregateequivalent bandwidth estimation approach

A unified framework for traffic control and bandwidth management in ATM networks is proposed. It bridges algorithms for real-time and data services. The central concept of this framework is adaptive connection admission. It employs an estimation of the aggregate equivalent bandwidth required by connections carried in each output port of the ATM switches. The estimation process takes into account both the traffic source declarations and the connection superposition process measurements in the switch output ports. This is done in an optimization framework based on a linear Kalman filter. To provide a required quality of service guarantee, bandwidth is reserved for possible estimation error. The algorithm is robust and copes very well with unpredicted changes in source parameters, thereby resulting in high bandwidth utilization while providing the required quality of service. The proposed approach can also take into account the influence of the source policing mechanism. The tradeoff between strict and relaxed source policing is discussed     

The use of a quantitative differential mode delay technique to improve fiber bandwidth

Three iterations of a simple quantitative differential mode delay (DMD) technique increased the bandwidth of multimode graded-index fibers at 1300 nm from an average of 530 MHz, km to an average of 1417 MHz . km. The bandwidth at other wavelengths showed a commensurate increase.     

Layered bandwidth allocation algorithm for multi-service in orthogonal frequency division multiplexing passive optical network

Due to the superiority in large bandwidth capacity and flexible resource allocation,orthogonal frequency division multiplexing passive optical network (OFDM-PON) has been recognized as one of the promising candidates for the next generation PON.There are many research works on the system architecture design of OFDM-PON.However,most of these works focused on the techniques of physical structure and signal transmission and less addressed the bandwidth allocation algorithms supporting the new types of system architecture.The bandwidth allocation in OFDM-PON,which is one of the key techniques to enable the access of multi-service,refers to the joint optimization of multi-dimensional resources in time domain,frequency domain and bits.A layered bandwidth allocation algorithm was proposed for multi-service in the enhanced system architecture of OFDM-PON,aiming at the efficient bandwidth resource utilization.Simulation results prove that the proposed bandwidth allocation algorithm outperforms the conventional algorithms without layered transmission significantly in terms of resource utilization and packet delay.     

Signal bandwidth of general n×n multimode interferencecouplers

Analytical expression of signal bandwidth of general straight and tapered N×N multimode interference (MMI) couplers is presented. The signal bandwidth is characterized as a function of mode relative energy, mode propagation delay time, and mode pulse broadening in the multimode section of MMI coupler. The model is used to evaluate the signal bandwidth of specific couplers. Results indicate that the signal bandwidth decreases seriously with the increase of channel number and channel guide space. Compared with the straight MMI coupler, the tapered MMI coupler has an improved signal bandwidth     

Three-dimensional switchbox multiplexing in emerging 3D-FPGAs to reduce chip footprint and improve TSV usage

Three-dimensional integration technology is proposed to break down long wires and increase integration level of emerging complex designs. However, efficiency of this technology heavily depends on the usage of Through-Silicon Vias. TSVs are key solutions for cooling the 3D-chips but they occupy considerable silicon area. Therefore, reducing the number of required TSVs in routing step is very critical in 3D-chips. In this paper, a TSV multiplexing approach is proposed to reduce the number of required routing TSV. We proposed two multiplexed 3D-switchbox architectures. In the first architecture, the TSVs inside the switchboxes are multiplexed while in the second architecture, TSVs are multiplexed between the switchboxes. Moreover, a routing algorithm is suggested to route the FPGA using the multiplexed switchboxes to evaluate the proposed architectures. Experimental results show that the presented architectures and algorithms reduce the number of used TSVs by 64.58% and 71.27% on average for the first and second architectures respectively, in cost of a negligible overheads in total wire length and auxiliary switches.     

A low-cost platform for the prototyping and characterization of digital circuit IPs

A novel low-cost platform for prototyping and characterizing the performance of digital circuit intellectual properties (IPs) has been developed. Compromised of several HW/SW components, it allows developers of circuit IPs to verify the functionality of any number of IPs on the same prototype chip and characterize their speeds without the need for any expensive test equipment special/custom IP-wrappers, or high-speed test board design. A complete prototype of the proposed platform has been realized and successfully used to test a prototype IC fabricated in a 150 nm technology with frequencies up to 2.1 GHz. Design conditions/constraints for portability to any fabrication process have been developed and verified using measurements from the fabricated IC.     

A multilevel optimal control approach to dynamic bandwidth allocation in broadband ISDN

In this paper a novel scheme for the dynamic allocation of bandwidth at the virtual path level in B-ISDNs is presented. A fluid flow model is developed to describe the time varying mean behaviour of a virtual path and serves as a state variable model. A multilevel optimal control theoretic approach is used in conjunction with the state model to derive a coordinated decentralised algorithm for virtual path bandwidth allocation. The integration of the virtual path bandwidth controller into a hierarchically organised network control scheme is incorporated in the problem formulation. The performance of the proposed scheme is evaluated using simulation.A version of this paper appears in the proceedings of INFOCOM'95.     

Signal bandwidth consideration of mutual coupling effects on adaptive array performance

The effect of mutual coupling on the performance of a least mean square (LMS) adaptive array using dipole elements is analyzed in consideration of the signal bandwidth. The purpose here is to illustrate quantitatively the significance of the effect of mutual coupling. The results show that the effect in the broad-band signal cases is much greater than that in the narrow-band cases, particularly when few antenna elements are used.     

A disciplined approach to the development of platform architectures

Silicon capability has enabled the embedding of an entire system on a single silicon die. These devices are known as systems-on-a-chip. Currently, the design of these devices is undisciplined, expensive, and risky. One way of amortizing the cost and ameliorating this design risk is to make a single integrated circuit serve multiple applications, and the natural way of enabling this is through end-user programmability. The aim of the MESCAL project, which is the subject of this paper, is to introduce a disciplined approach to producing reusable architectural platforms that can be easily programmed to meet a variety of applications. (MESCAL stands for Modern Embedded Systems, Compilers, Architectures, and Languages.)     

Effective bandwidth approach to connection admission control formultimedia traffic in ATM networks

The authors propose an effective bandwidth approach to connection admission control in ATM networks. The aggregate arrival traffic is accurately modelled by a two-state Markov modulated Poisson process (MMPP) via the matching of four important statistics. If the buffer is large, admission control can be achieved by computing the effective bandwidth of the two-state MMPP. Simulation tests show that approach is simple and results in higher utilisation compared with conventional methods