共查询到20条相似文献,搜索用时 109 毫秒
1.
Herger P. Niestegge G. Wallmeier E. 《Selected Areas in Communications, IEEE Journal on》1987,5(8):1309-1314
A broadband ISDN switching network model is presented, switching the channel types H2, H3, and H4 envisaged by the CCITT. The synchronous time division multiplex technique is applied. The switching network operates at the basic bit rate of the H2-channel; H3and H4-connections are established via multichannel connections of up to four basic channels. H2-connections which are part of one H3- or H4-connection always have to use common interconnection links. This is a favorable solution to keep digit sequence integrity for multichannel connections, but influences blocking characteristics of the switching network. The implementation of an optimal path selection method plays a fundamental role. In such a multichannel switching network, blocking probabilities for H2-, H3-, and H4-connections must be distinguished. They do not only depend on the total offered load, but also on the proportions of H2-, H3-, and H4-connections (traffic mix). The simulation results presented in this paper prove that multirate switching via multichannel connections is feasible for the broadband channel types H2, H3, and H4, and that the proposed switching network has a sufficiently high traffic capacity whatever the traffic mix may be. 相似文献
2.
Message, packet and line switching in computer communication networks are analyzed by a queueing model. Message transmission delay time and network throughput between a source-destination node pair are obtained as a function of various parameters including message length, traffic arriving at the network, and the number of switching nodes existing between the nodes. A criterion to determine the most suitable switching method under the given conditions is offered. Also, the maximum length of a packet in packet switching is discussed. 相似文献
3.
We present a performance evaluation model of cell reassembly mechanism in an ATM switching system. An ATM switching system may be designed so that communications between processors of its control part can be performed via its switching network rather than a separate inter-processor communications network. In such a system, there should be interface to convert inter-processor communication traffic from message format to cell format and vice versa, that is, mechanisms to perform the segmentation and reassembly sublayer. In this paper, we employ a continuous-time Markov chain for the performance evaluation model of cell reassembly mechanism with individual buffering, judicially defining the states of the mechanism. Performance measures such as message loss probability and average reassembly delay are obtained in closed forms. Some numerical illustrations are given for the performance analysis and dimensioning of the cell reassembly mechanism. 相似文献
4.
5.
A probabilistic switching circuit is a switching circuit where each input, each component, and each output are all probabilistic. It is shown that each component of such a circuit can be treated as a random variable with value set {0, 1} so that probabilities of the output of the component can be represented by a Boolean function and the calculation of the probabilities of the outputs of the whole circuit can be performed with Boolean algebra techniques. Therefore, the estimation of the reliability of a probabilistic switching circuit can be done more simply and in a way familiar to the circuit designer. 相似文献
6.
7.
A closed cyclic queueing system with multiple classes is analyzed numerically. The queueing system was originally motivated by a need to model circuit switching traffic in a data multiplexing scheme which provides both circuit and switching capabilities. The queueing system consists of two nodes, a primary and a secondary node. Customers in the primary node may require a random number of servers simultaneously. The secondary node simply provides the means of modeling the arrival process to the primary node. An efficient numerical procedure is used to obtain performance measures such as throughput, queue-length distribution, and utilization. 相似文献
8.
《Lightwave Technology, Journal of》2009,27(14):2621-2633
9.
An approximate model of a multistage switching network carrying a mixture of different multichannel traffic streams is proposed. In the model the multistage switching network is reduced to a single-channel system, that is, to an Erlang ideal grading to which a mixture of different multichannel traffic is offered. An approximate method for recurrence determination of the distribution of being busy in such grading is presented. The determined distribution enables calculation of blocking probabilities for traffic streams of various classes. The derived formula is a generalization of Kaufman (1981) and Robert's (1981) recurrence formula covering a full-availability trunk group with various multichannel traffic streams, and it can be useful for the analysis of ISDN systems 相似文献
10.
11.
This paper focuses on network delays as they apply to voice traffic. First the nature of the delay problem is discussed and this is followed by a review of enhanced circuit, packet, and hybrid switching techniques: these include fast circuit switching (FCS), virtual circuit switching (VCS), buffered speech interpolation (SI), packetized virtual circuit (PVC), cut-through switching (CTS), composite packets, and various frame management strategies for hybrid switching. In particular, the concept of introducing delay to resolve contention in SI is emphasized, and when applied to both voice talkspurts and data messages, forms a basis for a relatively new approach to network design called transparent message switching (TMS). This approach and its potential performance advantages are reviewed in terms of packet structure, multiplexing scheme, network topology, and network protocols. The paper then deals more specifically with the impact of variable delays on voice traffic. In this regard the importance of generating and preserving appropriate length speech talkspurts in order to mitigate the effects of variable network delay is emphasized. The results indicate that a desirable length of talkspurt "hangover" of about 200 ms will accomplish this without unduly affecting speech activity, and that, under these circumstances, the perceptable threshold of variable talkspurt delay can be as high as about 200 ms average. As such, the results provide a useful guideline for integrated services system designers. Finally, suggestions are made for further studies on performance analysis and subjective evaluation of advanced integrated services systems. 相似文献
12.
A multiaccess model for packet switching with a satellite having the capability of interrogating the uplink header and creating the downlink header is proposed. The satellite broadcasts slot assignments, based on the users' reported queue status, to the users for transmission in the next frame. With the protocols being done at both the earth stations and at the satellite, the proposed multiaccess model avoids collisions that are prevalent in schemes of the ALOHA type. The actual model is too complex to handle analytically. We derive analytical equations for a two-group model. Calculated and simulated buffer overflow probabilities as a function of traffic intensity and buffer size are compared. We also evaluate the performance of the actual model in terms of average system delay as a function of traffic intensity by means of computer simulation. 相似文献
13.
Self‐Limited Switching in Ta2O5/TaOx Memristors Exhibiting Uniform Multilevel Changes in Resistance 下载免费PDF全文
Kyung Min Kim Seung Ryul Lee Sungho Kim Man Chang Cheol Seong Hwang 《Advanced functional materials》2015,25(10):1527-1534
To facilitate the development of memristive devices, it is essential to resolve the problem of non‐uniformity in switching, which is caused by the random nature of the filamentary switching mechanism in many resistance switching memories based on transition metal oxide. In addition, device parameters such as low‐ and high‐state resistance should be regulated as desired. These issues can be overcome if memristive devices have switching limits for both the low‐ and high‐resistance states and if their resistance values are highly controllable. In this study, a method termed self‐limited switching for uniformly regulating the values of both the low‐ and high‐resistance states is suggested, and the circuit configuration required for the self‐limited switching is established in a Ta2O5/TaOx memristive structure. A method of improving the uniformity of multi‐level resistance states in this memristive system is also proposed. 相似文献
14.
Bhanja S. Ranganathan N. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2003,11(4):558-567
Switching activity estimation is an important aspect of power estimation at circuit level. Switching activity in a node is temporally correlated with its previous value and is spatially correlated with other nodes in the circuit. It is important to capture the effects of such correlations while estimating the switching activity of a circuit. In this paper, we propose a new switching probability model for combinational circuits that uses a logic-induced directed-acyclic graph (LIDAG) and prove that such a graph corresponds to a Bayesian network (BN), which is guaranteed to map all the dependencies inherent in the circuit. BNs can be used to effectively model complex conditional dependencies over a set of random variables. The BN inference schemes serve as a computational mechanism that transforms the LIDAG into a junction tree of cliques to allow for probability propagation by local message passing. The proposed approach is accurate and fast. Switching activity estimation of ISCAS and MCNC circuits with random and biased input streams yield high accuracy (average mean error=0.002) and low computational time (average elapsed time including CPU, memory access and I/O time for the benchmark circuits=3.93 s). 相似文献
15.
In a time-multiplex switching system, the incoming traffic must be scheduled to avoid conflict at the switch output (two or more users converging simultaneously upon a single output). Two scheduling algorithms, random scheduling and optimal scheduling, are explored in this paper. Random scheduling is computationally simple, whereas optimal scheduling is currently very difficult. We have found, using a traffic model appropriate for circuit switched traffic that increases of typically 10 to 15 percent in offered load can be obtained through optimal scheduling (as compared to the much simpler random scheduling algorithm). The improvement is a function of the number of time slots (or circuits) per time-multiplexed frame, and falls to zero for both very small and very large frame sizes. Thus, in many circuit switching applications, providing a computationally expensive optimal schedule may not be warranted. This conclusion has important ramifications for both electronic and emerging photonic switching systems since it reduces the importance of the costly design feature of optimal scheduling. 相似文献
16.
Ralf Burda Manfred Folgmann Stefan Michaelis Jrn Seger Matthias Seifert 《AEUE-International Journal of Electronics and Communications》2004,58(3):183-191
Traffic Theory has accompanied the evolution from early switching systems to an omnipresent communication infrastructure through the last century. Targeting at the mathematical modelling of call attempts at first the main goal was the dimensioning of telephone infrastructure. Emerging new services, mobile communication environments and the integration of packet style communication links into by then well known switched circuit equipment has put new challenges to traffic theory. Still new interpretations and facets of the basic models are found and elaborated to make traffic theory useful for modern systems as the internet. 相似文献
17.
18.
Roy K. Prasad S.C. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1993,1(4):503-513
A system developed to synthesize both finite state machines and combinational logic for low-power applications, called SYCLOP, is described. SYCLOP tries to minimize the transition density at the internal nodes of a circuit to minimize power dissipation during normal operation. As input signal probabilities and transition densities are considered during the synthesis process, a particular circuit can be synthesized in different ways for different applications that require different types of inputs. For the present state inputs to the combinational circuit of a state machine, simulation was used to determine the signal probabilities and transition densities. The algorithm is not limited by the number of bits used for state assignment. The multilevel optimization process extracts kernels so that there is a balance between area and power optimization. Results have been obtained for a wide range of MCNC benchmark examples 相似文献
19.
20.
When a relief toll switching system is used to alleviate the exhaust problem of an existing toll switching system of the same generic, type, a rehoming program (specifying amounts and timings of trunk rearrangements) is dictated primarily by the ratio of the monetary discount rate to the traffic growth rate. If this ratio is greater than unity, the rehoming strategy calls for a conservative program of restraint whereas if this ratio is smaller than unity, the rehoming strategy adopts an aggressive program of activity. When the relief and the existing switching systems are not of the same type, the lower trunk maintenance expenses on the relief switching system provide an impetus to rehome more existing trunks onto the relief switching system. It is found that this stimulation of early deloading affects the rehoming strategies significantly. Depending on the amount of stimulation involved, a conservative rehoming program could be changed to a moderate and even an aggressive one. 相似文献