共查询到20条相似文献,搜索用时 15 毫秒
1.
Mukherjee B. Lantz A.C. Matloff N.S. Banerjee S. 《Communications, IEEE Transactions on》1991,39(6):887-898
The p i-persistent protocol is based on a probabilistic scheduling mechanism (see Mukherjee and Meditch, 1988). The authors further develop the protocol to make it easily implementable, by allowing it to be sensitive to changing load conditions. They study various properties of a simple algorithm which stations execute independently by using channel feedback information. This results in a fully distributed control mechanism that continuously adjusts the station probabilities p i at their proper levels as governed by the offered traffic. An extensive simulation model has been developed to study properties of this control mechanism such as p i settling time and accuracy, behavior under step changes in traffic load, effect of injection of additional packets, and effect of various parameters associated with the underlying algorithm. These experiments indicate that this algorithm is suitable for implementing the protocol 相似文献
2.
While a variety of medium access protocols have been proposed for metropolitan area networks (MANs), the problem of handling multipriority traffic effectively in these networks remains open. The authors present a simple and effective priority mechanism for an existing MAN protocol known as the p i-persistent protocol, a probabilistic scheduling scheme that has been shown to be suitable for applications requiring large bandwidth over long, repeater-free distances. The mechanism works by clipping the low-priority stations in a controlled manner, thereby increasing the bandwidth available to the high-priority stations. This mechanism operates entirely within the framework of the basic p i-persistent protocol and may be easily tailored to achieve specific performance goals by selection of a single operating parameter. A multipriority version of a distributed algorithm by which the stations can update their operating parameters and adapt to changing network conditions dynamically is also presented 相似文献
3.
The performance of a statistical multiplexer whose inputs consist of a superposition of voice packet streams is studied. The delay for such a system is analyzed by solving the ΣD i/ D /1 queue. The analytic method can be used to find the approximate mean delay for an arbitrarily large number of trunks and the approximate delay distribution when the number of trunks is less than 100. An efficient hybrid simulation of the packet voice multiplexer which can be used to find the delay distribution for a large number of trunks is presented. In addition, easily computable error bounds for the present approximation are provided, and the accuracy of the M / D /1 approximation is investigated 相似文献
4.
Expressions are obtained for specifying the optimal error probability (minimum P e) thresholds λ01 and λ02 for the traditional and modified sign detectors, respectively. These thresholds are shown to depend on the parameters p , P 1, and M where: M is the number of observations z i used in the test statistic; P 1=P (H 1 ) is the prior probability for hypothesis H 1 that signal s 1 is present and 1-P 1 =P (H 0) corresponds to the hypothesis H 0 that signal s 0 is present; and p =Pr{z i⩾0|H 1} with s 0=0 for the traditional sign detector and p =Pr{z i⩾λ|H 1 }=Pr{z i<λ|H 0} with λ =(s 0+s 1)/2 for the modified sign detector. The expressions for λ01 and λ02, are given explicitly, and shown to be independent of P 1 for sufficiently large M . Optimal P e versus M performance curves, corresponding to both versions of the sign detector, are obtained for a representative range of values for p and P 1 相似文献
5.
Sufficient conditions are derived for achieving the two most important fairness criteria in the design of access protocols for high-speed metropolitan area networks (MAN), the delay and throughput fairness criteria, a probabilistic scheduling scheme, known as the pi-persistent protocol is considered, which has been shown to be suitable for applications requiring large bandwidth over long repeater-free distances and also amenable to an approximate analytical performance evaluation. It is found that the throughput fairness criterion is easier to achieve than its delay counterpart. The delay fairness, when achieved, induces approximate throughput fairness. The current practice in the field of protocol design for unidirectional bus MANs appears to focus almost exclusively on the throughput fairness. For example, in the DQDB protocol, although a bandwidth balancing function exists, balancing delay performance has never been dealt with 相似文献
6.
7.
The probability of q i of successful packet reception when i users transmit simultaneously in a mobile packet radio system is shown to decrease monotonically with i for a number of commonly used capture and spatial distribution models, with no fading. Examples of both noiseless and noisy systems in which q i is not monotonically decreasing with i are also given 相似文献
8.
Fukano H. Nakajima H. Ishibashi T. Takanashi Y. Fujimoto M. 《Electron Devices, IEEE Transactions on》1992,39(3):500-506
The effect of hot-electron injection energy (E i) into the base on the high-frequency characteristics of In0/52(Ga1-xAlx)0.48 As/InGaAs abrupt heterojunction bipolar transistors (HBTs) is investigated by changing the composition of the emitter. There exists an optimum E i at which a maximum current gain cutoff frequency (ft ) is obtained. Analysis of hot-electron transport in the base and collector by Monte Carlo simulation is carried out to understand the above phenomenon. The collector transit time (τc ) increases with E i, because electrons with higher energy transfer from the Γ valley into the upper L and X valleys. At first, the base transit time (τb ) decreases with E i at the low E i region. However, τb does not decrease monotically with E i, because of the nonparabolicity in the energy-band structure of InGaAs. Consequently, there exists a minimum in the sum of τb and τc , in other words a maximum f t, at an intermediate value of E i 相似文献
9.
The distribution of the lifetime (MTTF) of any consecutive k -within-m -out-of-n :F system, with independent exponentially distributed component lifetimes, is shown to be a convex combination of the distributions (MTTFs) of several convolutions of independent random variables, where each convolution represents a distinct path in the evolution of the system's history, and where in each convolution all but the last random variable is exponential. The last random variable in each convolution is either a zero lifetime or the lifetime of several disjoint consecutive k i within m i-out-of-n :F systems in series with each k i<k , each m i<m , and each n i<n . This enables the calculations to proceed recursively. Calculations are facilitated by the symmetric nature of the convex combination 相似文献
10.
Poki Chen Jin-Fu Chang 《Communications, IEEE Transactions on》1991,39(3):353-355
The protocol allows a 1.0 transmission probability for newly transmitted packets, while p for retransmitted packets. Compared to the protocol in which each packet is always transmitted with the same probability p , it shows better performance, especially when the channel traffic is light, as demonstrated by numerical results 相似文献
11.
The probability q i of successful reception in a nonfading mobile radio channel with i contending mobiles transmitting to a central base station is studied for a number of different capture and spatial distribution models. It is shown that a generalized capture model can be used to estimate q i's for a simplified example system which uses noncoherent frequency shift keying modulation. This model can be applied to other systems as well. An example of the use of the q i 's in the throughput evaluation of a finite population slotted ALOHA system is given. In most practical systems, the mobiles cannot get arbitrarily close to the base station. The effect of this constraint on q i is examined. Finally, the dependence of the capture probability for a test mobile on its distance from the base station is obtained 相似文献
12.
Zhang Z. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(4):976-982
The author evaluates the limiting efficiencies e (-S ) of burst-correcting array codes A (n 1,n 2, -s ) for all negative readouts -s as n 2 tends to infinity and n 1 is properly chosen to maximize the efficiency. Specializing the result to the products of the first i primes donated by s i (1⩽i <∞), which are optimal choices for readouts, gives the expression e (-s i)=(2pi+1 -2)/(2pi+1-1) where p i +1 is the next prime. Previously, it was known only that e (-2)⩾4/5 and e (-1)⩾2/3. This result reveals the existence of burst-correcting array codes with efficiencies arbitrarily close to 1 and with rates also arbitrarily close to 1 相似文献
13.
The performance of nonblocking packet switches such as the knockout switch and Batcher banyan switch for high-speed communication networks can be improved as the switching capacity L per output increases; the switching capacity per output refers to the maximum number of packets transferred to an output during a slot. The N ×N switch with L =N was shown to attain the best possible performance by M.J. Karol et al. (1987). Here a N ×N nonblocking packet switch with input and output buffers is analyzed for an arbitrary number of L such that 1⩽L ⩽N . The maximum throughput and packet loss probability at input are obtained when N =∞ 相似文献
14.
The contention-based lookahead reservation (CLAR) protocol can provide fast circuit-switching services that are particularly advantageous for networks supporting integrated services. The delay and throughput performance for message transmission are obtained, and they agree closely with that obtained by simulation. The delay performance of CLAR is similar to that of the M -CSMA protocol for an M -channel network, but only CLAR can give a stable maximum throughput of (M -1)/M independent of the cable length. Moreover, CLAR requires only two sets of transceivers, while M -CSMA requires M . The lookahead reservation technique can provide 9% throughput increase for fixed-size messages and 19% for geometrically distributed messages 相似文献
15.
Capocelli R.M. De Santis A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(1):174-179
An upper bound on the redundancy of D -ary Huffman codes in terms of the probability p 1 of the most likely source letter is provided. For large values of p 1, the bound improves the one given by R.G. Gallager (1978). Additionally, some results known for the binary case (D =2) are extended to arbitrary D -ary Huffman codes. As a consequence, a tight lower bound that corrects a bound recently proposed by J.D. Golic and M.M. Obradovic (1987) is derived 相似文献
16.
Of the automatic-repeat-request (ARQ) techniques commonly used in communication systems, selective protocols, while the most efficient, have the notable drawback of requiring large buffers at the receiver side. A selective ARQ protocol with a finite-length buffer is described. If N is the number of codewords transmittable in the round-trip delay, the protocol requires a buffer length N +N a , N a⩾2 being an integer. A lower bound on the throughput of the protocol is derived. It achieves higher throughputs than similar schemes giving results comparable to those for selective protocols with infinite-length buffer for high error rates in the communication channel 相似文献
17.
Hajek B. Cruz R.L. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1993,39(1):84-91
Consider a packet walking along a directed graph with each node having two edges directed out. The packet is headed towards one of N destinations, chosen according to a probability distribution p . At each step, the packet is forced to use a nonpreferred edge with some probability q , independently of past events. Using information theory and sequential analysis, it is shown that the mean number of steps required by the packet to reach the destination is roughly, at least H (p )/(1-h (q ), where h is the binary entropy function and H (p ) is the entropy (base two) of p . This lower bound is shown to be asymptotically achievable in the case where the packet always begins at a fixed node. Also considered is the maximum, over all pairs of nodes in a graph, of the mean transit time from one node to the other. The work is motivated by the search for graphs that work well in conjunction with deflection routing in communication networks 相似文献
18.
Nomination sampling is a sampling process in which every observation is the maximum of a random sample from some distribution. If all samples are taken from a single underlying CDF, F , data can be viewed as consisting of pairs (X i,K i) where K i is the size of sample i and, given K i=k i, X i is distributed according to CDF F ki. R.A. Boyles and F.J. Samaniego (1986) developed a nonparametric maximum-likelihood estimator of F . In the present work, their approach is extended to obtain estimates of the quantiles of F and to study the limit theory and consistency properties of these estimates. These results generalize the results of T.R. Willemain (1980), who discussed the estimation of the median of F based on nomination samples 相似文献
19.
Nomination sampling is a sampling process in which every observation is the maximum of a random sample from some distribution. If the data are {(Y i, K i), i =1, . . ., n } where K i is the size of sample i , and Y i is the maximum of a random sample of size K i from an unknown Cdf, F ; the Bayes estimator of F is derived by discretizing F over a fixed finite partition of the support of F and taking a Dirichlet distribution as the prior for the probabilities of the partitioning intervals. For the flood data of the Nidd River considered by R.A. Boyles and F.J. Samaniego (J. Am. Stat. Assoc., vol.81, p.1039-45, 1986), the plots of the Bayes estimator of F are obtained for several sets of values of the parameters of the Dirichlet distribution 相似文献
20.
Previous work on analyzing three switching schemes for isotropic networks, namely single hop and two cut-through communication schemes (with and without error checking by intermediate nodes), is extended. Each scheme is modeled by a discrete Markov chain. It is shown how the performance of the communication schemes depends on path length (n ), load on the network (λ), and the error rate (p ). As expected, the cut-through schemes perform much better than the single hop when the communication load is light, but as the load increases, the cut-through schemes deteriorate more rapidly, until they are comparable. In fact, when the load approaches saturation (λ is close to 1-p ), the cut-through schemes are actually worse than the single-hop schemes. The schemes with checking always outperform those without, but each node must perform more work in checking the correctness of the packets passing through. The time delay becomes infinite when the throughput approaches 1-p . The solutions are expressed as simple formulas and/or algorithms for each scheme 相似文献