1,721,060 research outputs found
Goodput and delay analysis of a radio link control protocol operating over a multicarrier DS-CDMA architecture
No full textThis work proposes an analytical model to investigate the behavior of a Radio Link Control (RLC) protocol on the forward link of a mobile radio system and to relate its performance to transmission design. As a reference case, a multicarrier DS-CDMA architecture employing Walsh and Quasi-Orthogonal channelization codes, similar to the current cdma2000 system, is considered. Jointly modelling the features of the data link layer and of the underlying physical channels, it is possible to identify the interaction between transmission parameters and the RLC protocol behavior. The latter is assessed by analysis, determining the RLC protocol goodput and the average delivery time suffered by a data unit transferred over the radio channel, when two different coding approaches are. adopted: namely, rate compatible punctured convolutional codes and code combining
Effect of the Transmission Impairments on the Peformance of Packet Radio Network
No full textPacket radio has recently gained great interest in the wider context of mobile communications. In this scenario, the signal worsening due to real transmission conditions (linear and non linear distorsion, fading, interferences, noise) deeply affect the network performance. It is then necessary to verfy whether it is feasible, and if so, how to dimension the transmission system supporting the network itself, in order to respect a fixed quality condition.In this work we suggest the introduction of a quality criterion which seems particularly suitable to set up a relationship between transmission and network parameters, and therefore to solve the problem previously submitted. We determine this relationship with reference to a star topology network, where the slotted Aloha protocolo is employed in cojunction with a narrow band modulation scheme; independent, non-selective and slowly varying fading conditions on every link of the network are also assumed. The treatment developed is then applied to a significant example of packet radio network, and many numerical results are reported
Outage probability in packet radio networks due to cochannel interferences and Rayleigh fading
No full textThe behavior of a packet radio network which makes use of the slotted Aloha protocol is investigated, focusing on the effects of the transmission impairments on its performance. A narrowband modulation scheme has been considered. Independent Rayleigh fading conditions and cochannel interferences on every link of the network have been accounted for. The methodology highlights the simplifications that can be introduced in evaluating the interference effects. The numerical results reported show that a good single user performance is by far a more critical target than a good network performanc
Allocation policies of quasi-orthogonal codes on the forward link of a multicarrier DS-CDMA system
No full textAlternative code assignment policies for the forward link of a multicarrier DS-CDMA system employing the recently proposed quasi-orthogonal sequences are put forth in this letter. It is demonstrated how different allocation strategies of quasi-orthogonal codes alter the interference level suffered by active units; it is also shown how to shape the rate of interference growth as a function of the number of active users within the reference cell, implementing some specific code allocation patterns. The performance achieved by various schemes is assessed in a frequency selective fading environment, in terms of average bit error probability
PRIORITY TRAFFIC IN WIRELESS PCS SYSTEMS: TRANSMISSION AND TRAFFIC PARAMETERS TRADE-OFF,
No full textWe have investigated a possible technique for efficiently handling the reverse link (mobile-to-base) traffic inside a cell of a wireless PCS system, assigning different priority classes to new calls and hand-offs. For the corresponding queueing scheme we have determined those traffic quantities which more directly interact with the design of the transmission system. Further, we have targeted the issue of tying the engineering of both CDMA and TDMA systems to traffic constraints. To this regard we have quantitatively demonstrated how deeply and differently the traffic parameters of the examined queueing scheme influence the capacity determination for these two system
An analytical Model to Evaluate Throughput and TCP-Fairness of the SQRT Congestion Control Protocol over Wireless Lossy Links
No full textWe develop an accurate analytic model to predict the send rate of the SQRT binomial congestion control protocol, under the assumption that the protocol operates in an environment where the packet loss rate is relatively high. Based on this model, a study of its TCP-friendliness is performed, remarking on the non-negligible effects on fairness that different queue managements have
DCA Schemes For Differentiated Qos In Microcells
No full textThis paper investigates in a microcellularset-up the behavior of a new class of dynamic channelallocation policies, tailored to provide different QoS degreesto distinct user classes of a wireless system. Theperformance achieved by a network employing theseschemes is evaluated in terms of call blocking, taking intoaccount the requirements raised by multi-rate applications.Some design criteria effective to optimize the managementof the scarce radio resources are furnished andthe goal of providing radio users with both low and highspeed connections, suitable for a basic set of audio andvideo applications, is achieved
Supporting Multirate Services in a TDD-TD/CDMA Architecture
No full textIn this study we determine the Erlang capacityof a TDD-TD/CDMA architecture providing multirateservices to different classes of subscribers. The qualityof service perceived by speech and data users is assessedand some design criteria are evidenced, with referenceto both traffic and transmission parameters
Comparison between the performance of conventional and selective RAKE receiver schemes
No full textIn this paper, we determine the effects of different diversity schemes on the behavior of a direct-sequence spread-spectrum RAKE receiver that operates with random sequences in a multipath fading channel with an arbitrary power-delay profile. Two different receiver architectures, the former employing the L instantaneously strongest paths out of the N-r resolved ones and the latter simply the L strongest on average paths out of the received N-r, are confronted in terms of symbol-error probability, when an M-level phase-shift keying system is assumed. The analytical approach devised for assessing such a comparison gives the symbol-error probability in terms of simple elementary integrals and immediately evidences the influence on system behavior of the number of resolved paths, bandwidth occupancy of the signal- and power-delay profiles with a remarkably moderate computational effort
How Helpful Can Social Network Friends Be in Peer-to-Peer Video Distribution
No full textToday two keywords more and more frequently recur over the Internet: Peer-to-Peer (P2P)
and social networks. P2P, in all of its different declinations, represents a widely-adopted approach
for content distribution, particularly for video diffusion. In parallel, the proliferation of social
networks is an analogously stunning phenomenon, of unprecedented popularity and scope.
In the present work we examine a mesh-based P2P overlay, specifically designed for video
streaming, and put forth some modifications to the neighborhood creation and chunk scheduling
algorithm the platform adopts, with the goal of favoring peers belonging to a social network and
granting them better performance. The improvements that such modifications attain are measured in
terms of delivery ratio (throughput) and playback delay. We find that it is possible to guarantee a
clear service differentiation, so that social network peers experience an improved viewing
experience at the expense of ordinary overlay members, and that the scheduling mechanism
modifications warrant the more consistent gains; we also show the role that different percentages of
peers belonging to the social network have on the considered metrics. We finally suggest that the
attained differentiated service level can be leveraged as an incentive to convince peers of the video
overlay to join the social network
- …
