1,721,001 research outputs found
Effective Scheduling of Real-time Traffic in HSUPA
No full textScheduling of real-time uplink flows in HSUPA is hampered by the fact that the NodeB does not know the size and dead-lines of the uplink packets, as the User Equipment (UE) only reports coarse-grained Scheduling Information (SI) advertising the overall backlog. In this paper, we describe how the NodeB can use the sequence of SI to reconstruct a UE queue, using affordable computations. This makes it possible to use scheduling algorithms employing packet sizes and deadlines in HSUPA, with obvious performance benefits. We present a general Virtual Queueing framework, that can be employed with any kind of traffic, and a specialized version of it for periodic (e.g., voice) traffic
Throughput-optimal Resource Allocation in LTE-Advanced with Distributed Antennas
No full textDistributed antennas are envisaged for LTEAdvanced
deployments in order to improve
the coverage and increase the cell throughput.
The latter in turn depends on how resources
are allocated to the User Equipments (UEs) at
the MAC layer. In this paper we discuss how
to allocate resources to UEs so as to maximize
the cell throughput, given that UEs may receive
from several antennas simultaneously.
We first show that the problem is both NPhard
and APX-hard, i.e. no polynomial-time
algorithm exists that approximates the optimum
within a constant factor. Hence, we propose
and evaluate two polynomial-time heuristics
whose complexity is feasible for practical
purposes. Our simulative analysis shows that,
in practical scenarios, the two heuristics are
highly accurate
Throughput-optimal Resource Allocation in LTE-Advanced with Distributed Antennas
Full text linkDistributed antennas are envisaged for LTE-Advanced deployments in order to improve the coverage and increase the cell throughput. The latter in turn depends on how resources are allocated to the User Equipments (UEs) at the MAC layer. In this paper we discuss how to allocate resources to UEs so as to maximize the cell throughput, given that UEs may re-ceive from several antennas simultaneously. We first show that the problem is both NP-hard and APX-hard, i.e. no polynomial-time algorithm exists that approximates the opti-mum within a constant factor. Hence, we pro-pose and evaluate two polynomial-time heuristics whose complexity is feasible for practical purposes. Our simulative analysis shows that, in practical scenarios, the two heuristics are highly accurate
A method of scheduling transmission in a communication network, corresponding communication node and computer program product
No full textData streams are transmitted from a node (BS) towards a receiver in a communication network in the form of data packets for play out via a reproduction buffer at the receiver. The data packets are arranged in a scheduling queue (SQ) and dropped from the scheduling queue (SQ) if their sojourn time (t) in the queue (SQ) exceeds a given drop deadline (d). The reproduction buffer (B) is emulated at the node (BS) in order to determine respective playout values (po) for the data packets which are indicative of expected playout instants (p) for the data packets by the reproduction buffer at the receiver. The drop deadlines (d) are assigned to the data packets as a function of the respective play out values (po) determined via the reproduction buffer as emulated at the node (BS)
OptiMOS: Optimal MOS-based scheduling of downlink voice flows in point-to-multipoint access networks
No full textWe introduce OptiMOS, a method for selecting deadlines for the scheduling of downlink voice flows in a centralized-scheduling point-to-multipoint network. These include cellular networks such as LTE, UMTS HSDPA, or WiMAX, and WLANs with centralized control. OptiMOS selects the deadline of each packet so as to maximize the expected Mean Opinion Score (MOS) for the talkspurt it belongs to. It requires that absolute time is both included in RTP timestamps at the source and checked for scheduling decisions, in a cross-layer approach. OptiMOS can be employed in conjunction with any deadline-based scheduling algorithm, and does not require a specific playout buffering scheme at the receiver. Simulations of an LTE system show a performance improvement in terms of MOS for the VoIP flows, good tolerance to relatively large synchronization errors and qualitatively similar results with different playout buffers
Flexible Scheduling for Real-Time Services in High-Speed Packet Access Cellular Networks
No full textThis paper presents the hybrid channel-aware and real-time scheduler (HY-CART) for UMTS high-speed packet access networks. The latter works for both downlink and uplink scheduling, with slightly different embodiments due to the different technology constraints. Its basic principle is to select users based on their channel conditions when the deadlines are far ahead: as the deadlines approach, they become progressively more important. Furthermore, resources for scheduled users are allocated sparingly, i.e. enough to serve packets whose deadline is actually near, so as to make room for a possibly larger number of simultaneous users, and keeping into account the user channel state. Simulative evaluation shows that HY-CART performs better than the previous work, allowing more users to be served with the same resources
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
Peri-prosthetic humeral non-union: Where biology meets bio-mechanic. A case report
No full textIntroduction The worldwide incidence of traumatic fractures has been growing over the last years due to the progressive aging of the population. Today, the increase of arthroplasty procedures in orthopaedic surgery is related to a high rate of peri-prosthetic fractures. Healing of the fracture is a multifactorial metabolic process; if these factors are impaired, healing process could be interrupted resulting in non-union. Presentation of case We report our experience about a case of a humeral diaphysis non-union secondary to peri-prosthetic fracture (reverse shoulder arthroplasty) treated by conservative approach. Discussion We treated this patient using a multilevel approach, consisting of revision surgery and drug therapy. Conclusion We assume that an aggressive revision surgery done with bone autograft implant and a bone healing therapy administering teriparatide off-label can reduce the convalescence in non-unions and can improve prognosis
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