4,916 research outputs found
Optimal Pricing Effect on Equilibrium Behaviors of Delay-Sensitive Users in Cognitive Radio Networks
This paper studies price-based spectrum access control in cognitive radio
networks, which characterizes network operators' service provisions to
delay-sensitive secondary users (SUs) via pricing strategies. Based on the two
paradigms of shared-use and exclusive-use dynamic spectrum access (DSA), we
examine three network scenarios corresponding to three types of secondary
markets. In the first monopoly market with one operator using opportunistic
shared-use DSA, we study the operator's pricing effect on the equilibrium
behaviors of self-optimizing SUs in a queueing system. %This queue represents
the congestion of the multiple SUs sharing the operator's single \ON-\OFF
channel that models the primary users (PUs) traffic. We provide a queueing
delay analysis with the general distributions of the SU service time and PU
traffic using the renewal theory. In terms of SUs, we show that there exists a
unique Nash equilibrium in a non-cooperative game where SUs are players
employing individual optimal strategies. We also provide a sufficient condition
and iterative algorithms for equilibrium convergence. In terms of operators,
two pricing mechanisms are proposed with different goals: revenue maximization
and social welfare maximization. In the second monopoly market, an operator
exploiting exclusive-use DSA has many channels that will be allocated
separately to each entering SU. We also analyze the pricing effect on the
equilibrium behaviors of the SUs and the revenue-optimal and socially-optimal
pricing strategies of the operator in this market. In the third duopoly market,
we study a price competition between two operators employing shared-use and
exclusive-use DSA, respectively, as a two-stage Stackelberg game. Using a
backward induction method, we show that there exists a unique equilibrium for
this game and investigate the equilibrium convergence.Comment: 30 pages, one column, double spac
A critical look at power law modelling of the Internet
This paper takes a critical look at the usefulness of power law models of the
Internet. The twin focuses of the paper are Internet traffic and topology
generation. The aim of the paper is twofold. Firstly it summarises the state of
the art in power law modelling particularly giving attention to existing open
research questions. Secondly it provides insight into the failings of such
models and where progress needs to be made for power law research to feed
through to actual improvements in network performance.Comment: To appear Computer Communication
Modeling and Control of Server-based Systems
When deploying networked computing-based applications, proper resource management of the server-side resources is essential for maintaining quality of service and cost efficiency. The work presented in this thesis is based on six papers, all investigating problems that relate to resource management of server-based systems. Using a queueing system approach we model the performance of a database system being subjected to write-heavy traffic. We then evaluate the model using simulations and validate that it accurately mimics the behavior of a real test bed. In collaboration with Ericsson we model and design a per-request admission control scheme for a Mobile Service Support System (MSS). The model is then validated and the control scheme is evaluated in a test bed. Also, we investigate the feasibility to estimate the state of a server in an MSS using an event-based Extended Kalman Filter. In the brownout paradigm of server resource management, the amount of work required to serve a client is adjusted to compensate for temporary resource shortages. In this thesis we investigate how to perform load balancing over self-adaptive server instances. The load balancing schemes are evaluated in both simulations and test bed experiments. Further, we investigate how to employ delay-compensated feedback control to automatically adjust the amount of resources to deploy to a cloud application in the presence of a large, stochastic delay. The delay-compensated control scheme is evaluated in simulations and the conclusion is that it can be made fast and responsive compared to an industry-standard solution
Holistic assessment of call centre performance
In modern call centres 60–70% of the operational costs come in the form of the human agents who take the calls. Ensuring that the call centre operates at lowest cost and maximum efficiency involves a trade‐off of the cost of agents against lost revenue and increased customer dissatisfaction due to lost calls. Modelling the performance characteristics of a call centre in terms of the agent queue alone misses key performance influencers, specifically the interaction between channel availability at the media gateway and the time a call is queued. A blocking probability at the media gateway, as low as 0.45%, has a significant impact on the degree of queuing observed and therefore the cost and performance of the call centre. Our analysis also shows how abandonment impacts queuing delay. However, the call centre manager has less control over this than the level of contention at the media gateway. Our commercial assessment provides an evaluation of the balance between abandonment and contention, and shows that the difference in cost between the best and worst strategy is £130K per annum, however this must be balanced against a possible additional £2.98 m exposure in lost calls if abandonment alone is used
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