18,712 research outputs found
Cross-Layer Optimization in OFDM Wireless Communication Network
The wide use of OFDM systems in multiuser environments to overcome problem of communication
over the wireless channel has gained prominence in recent years. Cross-layer Optimization technique
is aimed to further improve the efficiency of this network. This chapter demonstrates that significant
improvements in data traffic parameters can be achieved by applying cross-layer optimization tech-
niques to packet switched wireless networks. This work compares the system capacity, delay time and
data throughput of QoS traffic in a multiuser OFDM system using two algorithms. The first algorithm,
Maximum Weighted Capacity, uses a cross-layer design to share resources and schedule traffic to users
on the network, while the other algorithm (Maximum Capacity) simply allocates resources based only
on the users channel quality. The results of the research shows that the delay time and data throughput
of the Maximum Weighted Capacity algorithm in cross layer OFDM system is much better than that of
the Maximum Capacity in simply based users channel quality system. The cost incurred for this gain is
the increased complexity of the Maximum Weighted Capacity scheme
A Cross-layer Monitoring Solution based on Quality Models
In order to implement cross-organizational workflows and to realize collaborations between small and medium
enterprises (SMEs), the use ofWeb service technology, Service-Oriented Architecture and Infrastructure-as-a-
Service (IaaS) has become a necessity. Based on these technologies, the need for monitoring the quality of (a)
the acquired resources, (b) the services offered to the final users and (c) the workflow-based procedures used
by SMEs in order to use services, has come to the fore. To tackle this need, we propose four metric Quality
Models that cover quality terms for the Workflow, Service and Infrastructure layers and an additional one for
expressing the equality and inter-dependency relations between the previous ones. To support these models
we have implemented a cross-layer monitoring system, whose main advantages are the layer-specific metric
aggregators and an event pattern discoverer for processing the monitoring log. Our evaluation is based on the
performance and accuracy aspects of the proposed cross-layer monitoring system
Cross-layer optimization in TCP/IP networks
TCP-AQM can be interpreted as distributed primal-dual algorithms to maximize aggregate utility over source rates. We show that an equilibrium of TCP/IP, if exists, maximizes aggregate utility over both source rates and routes, provided congestion prices are used as link costs. An equilibrium exists if and only if this utility maximization problem and its Lagrangian dual have no duality gap. In this case, TCP/IP incurs no penalty in not splitting traffic across multiple paths. Such an equilibrium, however, can be unstable. It can be stabilized by adding a static component to link cost, but at the expense of a reduced utility in equilibrium. If link capacities are optimally provisioned, however, pure static routing, which is necessarily stable, is sufficient to maximize utility. Moreover single-path routing again achieves the same utility as multipath routing at optimality
Cross-Layer Design for Green Power Control
In this work, we propose a new energy efficiency metric which allows one to
optimize the performance of a wireless system through a novel power control
mechanism. The proposed metric possesses two important features. First, it
considers the whole power of the terminal and not just the radiated power.
Second, it can account for the limited buffer memory of transmitters which
store arriving packets as a queue and transmit them with a success rate that is
determined by the transmit power and channel conditions. Remarkably, this
metric is shown to have attractive properties such as quasi-concavity with
respect to the transmit power and a unique maximum, allowing to derive an
optimal power control scheme. Based on analytical and numerical results, the
influence of the packet arrival rate, the size of the queue, and the
constraints in terms of quality of service are studied. Simulations show that
the proposed cross-layer approach of power control may lead to significant
gains in terms of transmit power compared to a physical layer approach of green
communications.Comment: Presented in ICC 201
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