High-capacity Links Research Articles

Pipelined Control-Path Effects on Area and Performance of a Wormhole-Switched Network-on-Chip

This paper presents design trade-off and performance impacts of the amount of pipeline phase of control path signals in a wormhole-switched network-on-chip (NoC). The numbers of the pipeline phase of the control path vary between twoand one-cycle pipeline phase. The control paths consist of the routing request paths for output selection and the arbitration paths for input selection. Data communications between on-chip routers are implemented synchronously and for quality of service, the inter-router data transports are controlled by using a link-level congestion control to avoid lose of data because of an overflow. The trade-off between the area (logic cell area) and the performance (bandwidth gain) of two proposed NoC router microarchitectures are presented in this paper. The performance evaluation is made by using a traffic scenario with different number of workloads under 2D mesh NoC topology using a static routing algorithm. By using a 130-nm CMOS standard-cell technology, our NoC routers can be clocked at 1 GHz, resulting in a high speed network link and high router bandwidth capacity of about 320 Gbit/s. Based on our experiments, the amount of control path pipeline stages gives more significant impact on the NoC performance than the impact on the logic area of the NoC router. Keywords—Network-on-Chip, Synchronous Parallel Pipeline, Router Architecture, Wormhole Switching

Analysis of trans-Pyrenean railway bottlenecks

This paper provides a full analysis of the bottlenecks in Irun and Portbou (located on the Spanish and French sides, bordering on the Atlantic and Mediterranean coast, respectively) to show the importance of the construction of a new trans-Pyrenean corridor to avoid congestion. The current freight traffic conditions in the Iberian Peninsula are analysed, focusing on incoming cargo flows and its subsequent transport to European destinations. One of the most favourable solutions is the construction of a new high-capacity railway link across Central Pyrenees. This corridor, together with more efficient short sea shipping transport, should complement the existing supply, thus allowing optimum development in south-west Europe. There are some environmental questions to study concerning the optimum location of the new corridor, as well as the political and institutional limitations.

Exploiting limited feedback in tomorrow's wireless communication networks

Recent research has demonstrated that by utilizing channel state information at the transmitter, the physical layer can be optimized to provide higher link capacity and throughput, more efficiently share the channel with multiple users, increase range by exploiting diversity due to spatial and frequency selectivity, and simplify multi-user receivers through known interference cancellation. Unfortunately, acquiring channel state information at the transmitter is difficult. In most systems, the only opportunity for the transmitter to learn about the channel is through a feedback control channel. Because feedback information is control overhead, the rate of the feedback channel is limited. This motivates the study of limited feedback techniques where only partial or quantized information from the receiver is conveyed back to the transmitter.

Satellite services for disaster management and security applications

Advantages of communications satellites are the inherent broadcast capability, high bandwidth, reliability and flexibility in network expansion. Small transportable terminals can be made operational very quickly. Recent developments in communications and computer technology allow to provide low-cost equipment, which is affordable even in developing countries. Communications satellites can also play an important role in case of emergencies or natural disasters. The combination of satellite communications and navigation can support new services for emergency teams. At the Institute of Applied Systems Technology and the Institute of Communication Networks and Satellite Communications highly transportable terminals have been developed, both for star and mesh network topologies. A fully meshed VSAT system is used for symmetrical links. For other applications, which do not require high return link capacity an asymmetrical system is an efficient solution. It uses low-cost DVB technology for the forward link and satellite phones with data capability on the return link. Novel multicast protocols allow to use these asymmetrical links in an efficient way. The paper describes the different systems and their applications in disaster management and security applications. Emphasis is put on transfer of remote sensing images and voice over IP (VoIP) as well as videoconference services.

Benders decomposition for the uncapacitated multiple allocation hub location problem

In telecommunication and transportation systems, the uncapacitated multiple allocation hub location problem (UMAHLP) arises when we must flow commodities or information between several origin–destination pairs. Instead of establishing a direct node to node connection from an origin to its destination, the flows are concentrated with others at facilities called hubs. These flows are transported on links established between hubs, being then splitted and delivered to its final destination. Systems with this sort of topology are named hub-and-spoke (HS) systems or hub-and-spoke networks. They are designed to exploit the scale economies attainable through the shared use of high capacity links between hubs. Therefore, the problem is to find the least expensive HS network, selecting hubs and assigning traffic to them, given the demands between each origin–destination pair and the respective transportation costs. In the present paper, we present efficient Benders decomposition algorithms based on a well known formulation to tackle the UMAHLP. We have been able to solve some large instances, considered ‘out of reach’ of other exact methods in reasonable time.

Adaptive modulation in ad hoc DS/CDMA packet radio networks

This paper investigates the benefit of adaptive modulation based on channel state information (CSI) in direct-sequence/ code-division multiple-access (DS/CDMA) multihop packet radio networks. By exploiting varying channel conditions, adaptive modulation can be used in ad hoc networks to provide upper layers with higher capacity links over which to relay traffic. Using the /spl alpha/-stable interference model, the distribution of the signal-to-interference ratio (SIR) is obtained for a slotted system of randomly, uniformly distributed nodes using multilevel coherent modulation schemes. Performance is evaluated in terms of the information efficiency, which is a new progress-related measure for multihop networks. Three types of adaptivity are analyzed, differing in the level of CSI available: 1) full knowledge of the SIR at the receiver; 2) knowledge of only the signal attenuation due to fading; and 3) knowledge of only the slow fading component of the signal attenuation. The effect of imperfect channel information is also investigated. Sample results are given for interference-limited networks experiencing fourth-power path loss with distance, Ricean fading, and lognormal shadowing.

MIMO channel capacity and modeling issues on a measured indoor radio channel at 5.8 GHz

Multiple transmitters and receivers can be used to provide high link capacity in future wireless systems. Herein, an analysis of indoor environment multiple-input-multiple-output (MIMO) measurements in the industrial, scientific, and medical (ISM) band at 5.8 GHz is performed and the possible increase in capacity, utilizing multiple transmitters and receivers is examined. The investigation shows that in the measured indoor environment, the scattering is sufficiently rich to provide substantial link capacity increases. Furthermore, the effect of intra-element spacing on the channel capacity is studied. Our investigation also shows that the envelope of the channel coefficients for this obstructed-line-of-sight (OLOS) indoor scenario is approximately Rayleigh distributed and the MIMO channel covariance matrix can be well approximated by a Kronecker product of the covariance matrices describing the correlation at the transmitter side and the receiver side, respectively. A statistical narrowband model for the OLOS indoor MIMO channel based on this covariance structure is presented.

Capacity of ad hoc wireless networks with infrastructure support

We determine the asymptotic scaling for the per user throughput in a large hybrid ad hoc network, i.e., a network with both ad hoc nodes, which communicate with each other via shared wireless links of capacity W bits/s, and infrastructure nodes which in addition are interconnected with each other via high capacity links. Specifically, we consider a network model where ad hoc nodes are randomly spatially distributed and choose to communicate with a random destination. We identify three scaling regimes, depending on the growth of the number of infrastructure nodes, m relative to the number of ad hoc nodes n, and show the asymptotic scaling for the per user throughput as n becomes large. We show that when m /spl lsim/ /spl radic/n/logn the per user throughput is of order W//spl radic/n log n and could be realized by allowing only ad hoc communications, i.e., not deploying the infrastructure nodes at all. Whenever /spl radic/n/log n /spl lsim/ m /spl lsim/ n/log n, the order for the per user throughput is Wm/n and, thus, the total additional bandwidth provided by m infrastructure nodes is effectively shared among ad hoc nodes. Finally, whenever m /spl gsim/ n/log n, the order of the per user throughput is only W/log n, suggesting that further investments in infrastructure nodes will not lead to improvement in throughput. The results are shown through an upper bound which is independent of the routing strategy, and by constructing scenarios showing that the upper bound is asymptotically tight.

Joint predistortion and nonlinear equalisation for high-capacity wireless links

A nonlinearity compensation scheme for a high-capacity wireless link employing multilevel QAM as the signalling format is discussed in the paper. The distinctive feature of this scheme is that the linearisation task is split over a predistorter and a nonlinear equaliser, to be implemented at the transmit and receive sections, respectively. It is shown that this scheme considerably relieves the overall computational requirement for nonlinear channel compensation, as compared to the approach in which the task of linearisation is entirely allocated to a nonlinear equaliser without any signal predistortion.

Impact of Fiber Non-linearity in High Capacity WDM Systems and in Cross-Connected Backbone Networks

The rapidly increasing data traffic volumes will demand for very high transmission capacity and network nodes’ throughput. Wavelength division multiplexing (WDM) technology will be asked to support many channels on the same fiber, both in point-to-point links and in WDM optical networks. The transmission of a high number of wavelength channels in all these systems is a key issue. This paper analyzes this topic, in both high capacity links and optical networks, highlighting the impact of fiber non-linearity, and addressing the main source of impairments. This is done through the use of a semi-analytical model recently upgraded to account for all the contributions deriving from Kerr effects, particularly four-wave mixing and cross-phase modulation. The analysis reveals that more than one hundred of channels at 2.5 Gbit/s can be transmitted in point-to-point links whose length can span until the order of 1000 km, and 32 channels per fiber, at the previous bit rate, can be handled in WDM networks, without dispersion compensation. For a higher number of channels (e.g., 64) dispersion compensation is needed.

Applications of Chaotic Digital Code-Division Multiple Access (CDMA) to Cable Communication Systems

In this paper the technical details of chaotic digital code-division multiple access ((CD)2MA) communication systems used in cable communication systems are presented. The cable communication system may be a pure coaxial RF cable network, a hybrid fiber-coax network, or a pure optical fibre network for high-capacity data link. As an example of its many potential applications in cable communication systems, (CD)2MA is used to support the upstream digital data communications in cable TV systems occupying the very noisy 5–40 MHz portion of spectrum. Although the (CD)2MA proposed in this paper is only used to support current Internet services via cable TV networks, it can also be used to support the high-speed data-link provided in the 550–750 MHz band in hybrid fiber-coax networks. (CD)2MA is a new communication framework which uses band-limited chaotic carriers insted of linear ones. For the purpose of generality, in this paper the band-limited chaotic carriers are approximated by groups of linear sub-carriers, which distribute within the same bandwidth with a fixed amplitude, random phases and uniformly distributed frequencies. The theoretical result of the performance of (CD)2MA is given. We also provide the simulation results of the bit-error-rate (BER) performances of a synchronous (CD)2MA used in cable communication systems. The results show that the (CD)2MA system has a better performance than the synchronous CDMA system proposed for the same cable communication system. Technical details of (CD)2MA are also presented for the future design of prototype systems. We present the framework of the whole (CD)2MA system including carrier syncronization, timing recovery and the details of nonlinear carrier generators.

Toward wide-scale all-optical transparent networking: the ACTS optical pan-European network (OPEN) project

The European ACTS project optical pan-European network (OPEN) aims at assessing the feasibility of an optical pan-European overlay network, interconnecting major European cities by means of a mesh of high-capacity optical fiber links, cross-connected through transparent photonic nodes. Both the transmission links and the routing network elements rely on wavelength division multiplexing (WDM) all-optical technologies, such as wavelength translation. This paper presents results obtained in the following domains covered within the project: network topology considerations (optimization and dimensioning); network physical layer simulation; fabrications of packaged functional modules based on advanced optoelectronic devices; laboratory demonstrations of N/spl times/10 Gb/s transmission and routing; feasibility of an optical time division multiplexing/WDM (OTDM/WDM) interface; and the field implementation of a 4/spl times/4 multiwavelength crossconnect prototype, featuring all-optical space and wavelength routing. This implementation was realized in two cross-border field trials, one conducted between Norway and Denmark and the other between France and Belgium. The final results of the Norway to Denmark field trials are presented, featuring the successful cascade of three wavelength-translating optical crossconnects (OXCs), along with the transmission over 1000 km of a mix of standard/submarine cable links for four channels at 2.5 Gb/s.

Network architecture and traffic transport for integrated wireless communications over enterprise networks

A novel network architecture based on the IEEE 802.6 metropolitan area networks (MAN) is proposed to integrate the wireless and wired segments of a regional enterprise network (REN) within a city. This architecture functions like a distributed switch for all types of services, reducing traffic congestion by sharing the high capacity link dynamically and facilitating signaling, mobility management, call processing and network management through its distributed functions, transport facilities and broadcasting capability. It also serves as a peripheral gathering network of REN traffic for transport over a wide area ATM/BISDN, enabling integration of an enterprise's regional networks into a global EN. Two major wireless applications, i.e., wireless PABX (WPABX) and wireless LAN (WLAN) are discussed to illustrate the advantages of this MAN-based architecture. Although a REN is likely to support a wide range of different services, voice and data will continue to be the predominant traffic generated by WPABXs and WLANs, respectively, and are also representative of isochronous and asynchronous multimedia traffic carried by future wireless networks. We compare the traffic capacity of several voice transport alternatives under integrated (voice/data) network traffic with various data traffic loads, and study voice and data integration under three different integration schemes by simulations. Results indicate that the MAN-based architecture is most effective employing queue arbitrated (QA) access for asynchronous traffic, pre-arbitrated access for constant bit-rate isochronous traffic, and the new reservation arbitrated (RA) access for variable bit-rate isochronous traffic, under a scheme that permits full sharing between QA and RA traffic.

Building the US superhighway

Countless news stories in the US and elsewhere have marvelled at the growth of the Internet, the global network of networks that is thought to connect around 20 million computer users. The headlines are to some extent the result of pressure applied by the Clinton administration to move forward with what has come to be called the information superhighway, more officially known as the National Information Infrastructure. It is planned to be a technologically It is planned to be a technologically advanced web of high-speed and high-capacity links designed to serve everyone, not just researchers seated at sophisticated workstations.

Toward an optimum use of the optical channel capacity

Abstract In recent decades, in addition to long-haul, high-capacity links, research activity in optical fiber communication systems has addressed possible advantageous applications in distribution networks, local and metropolitan area networks, CATV backbones and distribution, and high-speed computer networks. As a consequence, new possibilities in optical transmission systems have been explored to face the new requirements in terms of capacity, spectral efficiency, and receiver sensitivity. Among the possible solutions capable to exploit effectively the potentials offered by the optical channel, novel multilevel modulation formats have been proposed for future communication environment. This paper reviews multilevel modulation techniques for optical transmission: a comparative analysis is performed between conventional modulations, such as N-PSK and N-QAM, and new modulation/demodulation techniques, such as N-4QSK, N-SPSK, and PM-DD, taking into account both system performance and technological constraints.

Two-channel fibre Raman amplification for wavelength division multiplexed systems

The simultaneous amplification of two wavelength-division, multiplexed channels is of interest for long-haul high data capacity links. The use of fibre Raman amplification in this application is discussed, and the trade-off between on/off ratio and gain is evaluated as a function of channel spacing. The analysis is performed in the pump nondepletion region, and the effect of optical bandpass filtering on this trade-off is presented.

Decision-Directed Diversity Combiners--Principles and Simulation Results

Diversity combining methods for medium- and high-capacity digital microwave radio links employing QAM signaling are studied theoretically and by computer simulations. The selective fading diversity channels are represented by a two-path model with complex envelopes. Emphasis is put to find simple receiver structures where combining is controlled by detected symbols to minimize a given error criterion. Two criteria are discussed-minimum mean-square error (MMSE) and minimum projection (MP). The latter criterion is believed to be new and its behavior is analyzed in two extreme cases. It turns out that the MP combiners obey the maximal ratio rule in the absence of dispersion and the minimum distortion rule in the absence of noise. This versatility is achieved with minor circuit complexity. The results have been verified by computer simulations for a 4 PSK 70 Mbit/s system. The resulting diversity signatures are very narrow on the frequency axis, indicating good performance. Moreover, the MP combining tolerates extremely well nonminimum phase fading in one diversity branch, situations where most cophasing schemes have difficulties.

Microcomputer-aided measurement equipment for performance monitoring of a digital radio-relay system in the presence of multipath propagation

A microcomputer-controlled radio-communication controller (μCC) was designed and constructed to analyze and measure a `true' error rate in a high-capacity digital radio link and to record fast-level variations of received radio frequency power (IF amplifier-AGC voltage) for a better characterization of propagation anomalies. The μCC represents a high-performance measuring device for ascertaining bit, block, and burst errors on out-of-service digital radios, to provide information on the performance degradation owing to the presence of propagation anomalies. The error measurement criteria were chosen specifically to evaluate parameters relating to the CCIR criterion of accuracy. Performance results and a burst statistic are reported.

Electricity and gas supply in south-eastern Australia, 1980–2020

A linear programming computer model, MENSA, was used to examine the energy systems of the south-eastern states of Australia. A regime of stable extraction costs for primary fuels was assumed and capital and operating costs for energy technologies were assumed to remain constant in real terms over the 40 year period 1980–2020. Particular attention was focused on the final demand sectors which consume electricity and natural gas. The costs and benefits attributeble to various proposed linkages of the gas supply networks and the electricity grids were examined, using minimum overall system cost as the criterion for deciding optimal configurations. The only gas pipeline which proved viable within the assumptions and data presented to the model was a low-capacity link between the existing systems of New South Wales and Victoria. A number of options for supplying South Australian electricity needs after the year 2000 were studied. Nuclear power was found to give the greatest system savings but at considerable capital cost. An alternative scheme involving a high-capacity link with the Victorian grid was also investigated. Within the model, this link proved viable if nuclear power continued to be proscribed.

High-capacity link

High-capacity link