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The Effect of A Priori Fade Level Information on Bandwidth Control in a Satellite Channel: Comparisons in a Real Case Study
No full text
Long-lived TCP connections via satellite: cross-layer bandwidth allocation, pricing and adaptive control
No full textThe paper focuses on the assignment of a common
bandwidth resource to TCP connections over a satellite channel.
The connections are grouped according to their source–destination
pairs, which correspond to the up- and down-link channels traversed,
and each group may experience different fading conditions.
By exploiting the tradeoff between bandwidth and channel redundancy
(as determined by bit and coding rates) in the maximization
of TCP goodput, an overall optimization problem is constructed,
which can be solved by numerical techniques. Different relations
between goodput maximization and fairness of the allocations are
investigated, and a possible pricing scheme is proposed. The allocation
strategies are tested and compared in a fading environment,
first under static conditions, and then in a real dynamic scenario.
The goodput-fairness optimization allows significant gains
over bandwidth allocations only aimed at keeping the channel bit
error rate below a given threshold in all fading conditions
Employing contention resolution random access schemes for elastic traffic on satellite channels
No full textA Control Architecture for Short- and Medium-Term Bandwidth Allocation in Satellite Channels with Fading
No full textAdaptive cross-layer bandwidth allocation in a rain-faded satellite environment
No full textTwo control schemes, based on cross-layer adaptation and a hierarchical parametric optimization of the
bandwidth allocation, are described and investigated in a satellite network environment, in the presence of
both real-time and best-effort traffic flows. A number of earth stations (traffic stations) operate in different
weather conditions, with different levels of fade, which affect the transmitted signals. The call admission
control policy for real-time connections is administered locally at the traffic stations. A master station is
charged to manage the time division multiple access bandwidth allocation policy, by defining bandwidth
partitions to the traffic stations. Upon detecting significant fade changes, the signalling from the traffic
stations triggers new bandwidth redistributions. The control schemes are compared, and the effect of fade
countermeasures, applied at the physical layer, on the bandwidth occupation is explicitly accounted for.
For each policy, figures of merit such as loss, blocking and dropping probabilities are computed for a
specific real environment, based on the Italsat satellite national coverage payload characteristics
Video Streaming Transfer in a Smart Satellite Mobile Environment
Full text linkTransportation media are becoming “smart spaces”, where sophisticated services are offered to the passengers. We concentrate on video streaming provided on buses that move in urban, suburban, or highway environments. A content provider utilizes a DVB-S2
satellite link for transmitting video streams to a bus, where they are relayed to passengers' devices. We say that a bus works in smart mode if it takes advantage of the knowledge of the exact points where fixed obstacles will prevent receiving the satellite signal for a certain time period. This information is sent to the hub via a return channel. The hub, in its turn, suspends the transmissions to that specific bus for the given time interval, thus avoiding information losses and unnecessary bandwidth occupation. Buffering video packets, without any quality of service (QoS) degradation, seamlessly compensates channel blockages up to a given duration. We determine the most appropriate transmission parameters for video streaming with good video QoS in a mobile satellite environment; moreover, we evaluate how “smart” the system can be in terms of bandwidth saving, by comparing it with the situation where the bus does not exploit the description of its route, still maintaining the same QoS requirements
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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