216,371 research outputs found
Impact of Out-of-Sequence Processing on the Performance of Data Transmission
Application Level Framing (ALF) was proposed by Clark and Tennenhouse as an important concept for developing high performance applications. ALF relies in part on the ability of applications and protocols to process packets independently one from the other. Thus, performance gains one might expect from the use of ALF are clearly related to performance gains one might expect from applications that can handle and process packets received out-of-sequence, as compared to applicatiojn that require in-order delivery (FTP, TELNET, etc.). In this paper, we examine how the ability to process out-of-sequence packets impacts the efficiency of data transmission. We consider both the impact of application parameters such as the time to process a packet by the application, as well as transmission parameters such as transmission delay, loss rate and flow and congestion control characteristics. The performance measure of interest are total latency, buffer requirements, and jitter. We show, using experimental and simulation results, that out-of-sequence processing is beneficial only for very limited ranges of transmission delays and application processing time. We discuss the impact of this on the architecture of communication systems dedicated to distributed multimedia applications
Impact of Residual Transmit RF Impairments on Training-Based MIMO Systems
Radio-frequency (RF) impairments, that exist intimately in wireless
communications systems, can severely degrade the performance of traditional
multiple-input multiple-output (MIMO) systems. Although compensation schemes
can cancel out part of these RF impairments, there still remains a certain
amount of impairments. These residual impairments have fundamental impact on
the MIMO system performance. However, most of the previous works have neglected
this factor. In this paper, a training-based MIMO system with residual transmit
RF impairments (RTRI) is considered. In particular, we derive a new channel
estimator for the proposed model, and find that RTRI can create an irreducible
estimation error floor. Moreover, we show that, in the presence of RTRI, the
optimal training sequence length can be larger than the number of transmit
antennas, especially in the low and high signal-to-noise ratio (SNR) regimes.
An increase in the proposed approximated achievable rate is also observed by
adopting the optimal training sequence length. When the training and data
symbol powers are required to be equal, we demonstrate that, at high SNRs,
systems with RTRI demand more training, whereas at low SNRs, such demands are
nearly the same for all practical levels of RTRI.Comment: Accepted for publication at the IEEE International Conference on
Communications (ICC 2014), 6 pages, 5 figure
Transport of video over partial order connections
A Partial Order and partial reliable Connection (POC) is an end-to-end transport connection authorized to deliver objects in an order that can differ from the transmitted one. Such a connection is also authorized to lose some objects. The POC concept is motivated by the fact that heterogeneous best-effort networks such as Internet are plagued by unordered delivery of packets and losses, which tax the performances of current applications and protocols. It has been shown, in several research works, that out of order delivery is able to alleviate (with respect to CO service) the use of end systems’ communication resources. In this paper, the efficiency of out-of-sequence delivery on MPEG video streams processing is studied. Firstly, the transport constraints (in terms of order and reliability) that can be relaxed by MPEG video decoders, for improving video transport, are detailed. Then, we analyze the performance gain induced by this approach in terms of blocking times and recovered errors. We demonstrate that POC connections fill not only the conceptual gap between TCP and UDP but also provide real performance improvements for the transport of multimedia streams such MPEG video
A Software-Defined Channel Sounder for Industrial Environments with Fast Time Variance
Novel industrial wireless applications require wideband, real-time channel
characterization due to complex multipath propagation. Rapid machine motion
leads to fast time variance of the channel's reflective behavior, which must be
captured for radio channel characterization. Additionally, inhomogeneous radio
channels demand highly flexible measurements. Existing approaches for radio
channel measurements either lack flexibility or wide-band, real-time
performance with fast time variance. In this paper, we propose a correlative
channel sounding approach utilizing a software-defined architecture. The
approach enables real-time, wide-band measurements with fast time variance
immune to active interference. The desired performance is validated with a
demanding industrial application example.Comment: Submitted to the 15th International Symposium on Wireless
Communication Systems (ISWCS 2018
High-speed, in-band performance measurement instrumentation for next generation IP networks
Facilitating always-on instrumentation of Internet traffic for the purposes of performance measurement is crucial in order to enable accountability of resource usage and automated network control, management and optimisation. This has proven infeasible to date due to the lack of native measurement mechanisms that can form an integral part of the network‟s main forwarding operation. However, Internet Protocol version 6 (IPv6) specification enables the efficient encoding and processing of optional per-packet information as a native part of the network layer, and this constitutes a strong reason for IPv6 to be adopted as the ubiquitous next generation Internet transport.
In this paper we present a very high-speed hardware implementation of in-line measurement, a truly native traffic instrumentation mechanism for the next generation Internet, which facilitates performance measurement of the actual data-carrying traffic at small timescales between two points in the network. This system is designed to operate as part of the routers' fast path and to incur an absolutely minimal impact on the network operation even while instrumenting traffic between the edges of very high capacity links. Our results show that the implementation can be easily accommodated by current FPGA technology, and real Internet traffic traces verify that the overhead incurred by instrumenting every packet over a 10 Gb/s operational backbone link carrying a typical workload is indeed negligible
Stochastic Stability of Event-triggered Anytime Control
We investigate control of a non-linear process when communication and
processing capabilities are limited. The sensor communicates with a controller
node through an erasure channel which introduces i.i.d. packet dropouts.
Processor availability for control is random and, at times, insufficient to
calculate plant inputs. To make efficient use of communication and processing
resources, the sensor only transmits when the plant state lies outside a
bounded target set. Control calculations are triggered by the received data. If
a plant state measurement is successfully received and while the processor is
available for control, the algorithm recursively calculates a sequence of
tentative plant inputs, which are stored in a buffer for potential future use.
This safeguards for time-steps when the processor is unavailable for control.
We derive sufficient conditions on system parameters for stochastic stability
of the closed loop and illustrate performance gains through numerical studies.Comment: IEEE Transactions on Automatic Control, under revie
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