© 2018 ФГБОУ ВО МГППУ «Московский государственный психолого-педагогический университет» © 2018 Moscow State University of Psychology & Education E-journal «Journal of Modern Foreign Psychology» 2018, vol. 7, no. 2, pp. 90—99. doi: 10.17759/jmfp.2018070209 ISSN: 2304-4977 (online) Электронный журнал «Современная зарубежная психология» 2018. Том 7. No 2. С. 90—99. doi: 10.17759/jmfp.2018070209 ISSN: 2304-4977 (online)

Анализ конструктивно-технологических ограничений при проектировании лавинных фотодиодов, работающих в режиме счета фотонов

In this paper, a generalized proportional fair (GPF) scheduling algorithm is presented, which allows tweaking the trade-off between fairness and throughput performance for best effort traffic in a cellular downlink scenario. The GPF is extended to frequency scheduling in an OFDMA system by performing dynamic channel allocation on a subband basis including link adaptation by adaptive modulation and coding. In this way, multiuser diversity can be utilized in time domain - as for CDMA - and in frequency domain. Compared to a system without frequency scheduling, this increases the system throughput and yields an improved fairness with respect to the allocated resources and with respect to the achieved data-rate per user. OFDMA system level simulations are carried out in order to analyze short/long-term fairness, multiuser diversity gain and system throughput of various GPF configurations with and without applying frequency scheduling.

Fairness and throughput analysis for generalized proportional fair frequency scheduling in OFDMA

The paper describes integration of HSDPA (high-speed downlink packet access) link-level simulation results into network-level simulations for enhanced UMTS. The link-level simulations model all physical layer features depicted in the 3GPP standards. These include: generation of transport blocks; turbo coding; rate matching; spreading; scrambling; modulation. At the receiver side, all complementary blocks are designed, with soft-decision demodulation, and a turbo decoder using the MAP (maximum a posteriori) algorithm with 8 iterations. An analytical formula is defined that fits the CQI (channel quality indicator) dependent BLER (block error rate) versus E/sub b//N/sub 0/ results in an AWGN channel. This formula models the physical layer in the network-level simulator. A further extension for frequency selective fading channels has been defined. The network-level simulator includes propagation models that provide SNR values. Based on these SNR values and the simplified physical layer model, an algorithm selects the CQI, and determines the actual BLER at time of reception. The rounding down and delaying of the CQI reporting, which corresponds to the W-CDMA standard, has a significant impact on throughput and transfer delay of the HS-DSCH. Some compensation can be found in a modified transmission. The integration of the link-level and network-level simulators gives accurate and realistic results that can be used in more studies that focus on network layer aspects of packet based services over HSDPA.

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Usage of link-level performance indicators for HSDPA network-level simulations in E-UMTS

This research studies Dynamic Adaptive Streaming over HTTP (DASH) in cellular broadband access networks (e.g. HSDPA, HSPA+, LTE). We propose a wireless DASH (WiDASH) proxy to enhance the Quality-of-Experience (QoE) of wireless DASH. WiDASH proxy locates at the edge between Internet and wireless core networks. Different from conventional DASH, whose rate adaptation logics are either implemented locally in the user equipment or in the DASH server, WiDASH proxy is in charge of video adaptation, which makes it feasible to perform global optimization over multiple concurrent DASH flows. WiDASH proxy improves DASH QoE by three novel technologies. The first one is architecture level innovation. WiDASH simultaneously explores the potential of both split TCP and parallel TCP. It splits the original TCP connection from DASH server to a wireless user into one wired TCP and multiple wireless TCPs. This approach is able to increase video streams' average throughput without sacrificing inter user fairness. Second, WiDASH proxy employs video quality aware dynamic prioritization. Low bit rate video streams are entitled with high priority to guarantee minimum QoE for users with bad wireless channel quality. A video stream's priority is gradually dropped to normal state with the growth of its bit rate so that inter flow fairness between video streams and background best effort flows are still maintained. Third, we design a multiple-input multiple-output adaptive optimal controller, based on adaptive control theory. This rate controller minimizes a quadratic cost function which is defined as the weighted sum of multiple concurrent DASH videos' distortion, bit rate variation, and playback jitter. The solution of the optimization problem implicitly coordinates multiple DASH streams to improve overall streaming QoE. Simulation results verify that WiDASH proxy is able to improve QoE by providing smoother video streams with higher average visual quality for wireless HTTP video streaming.

Video adaptation proxy for wireless Dynamic Adaptive Streaming over HTTP

Forecasts for emerging mobile device markets anticipate that bandwidth will be squeezed by demanding applications like multimedia on demand. This will spur the need for data rates beyond what the upcoming 3G wireless cellular systems such as UMTS can offer. To boost the support for such high data rates, HSDPA, labeled as a 3.5G wireless system, has been introduced in Release 5 of UMTS technical specifications. HSDPA is a definite step toward meeting the "anywhere, anytime, and in any form" 4G communication concept. HSDPA promises a peak data rate of up to 10 Mb/s, five times larger than the data rate offered by 3G systems. In order to support such high data rates, HSDPA relies on many new technologies, among which is packet scheduling. In this article we provide breadth and depth related issues of packet scheduling in HSDPA, discuss state-of-the-art HSDPA scheduling algorithms in terms of their objectives, advantages, and limitations, and suggest further research issues that need to be addressed. In addition, we propose a packet scheduling algorithm for data traffic in HSDPA. Simulation results demonstrate the effectiveness of the proposed algorithm

Packet scheduling in 3.5G high-speed downlink packet access networks: breadth and depth

End-to-end network model for Enhanced UMTS

In this study a scheduling algorithm for CDMA systems is presented which is a trade-off between two extreme ways of scheduling: C/I based and Round-Robin scheduling. The simulation results indeed display that the advantages of both these extremes have been combined in the new algorithm: a good fairness, comparable to that of the Round-Robin scheduling, together with almost the same power gain as reached in the C/I based scheduling.

/pdf/fair-channel-dependent-scheduling-in-cdma-systems-451ygy1dzb.pdf

Fair channel-dependent scheduling in CDMA systems

This paper investigates the performance of multimedia services over HSDPA. A network level simulator has been used to analyse the end-to-end quality of service results for VoIP and best effort traffic. Three different scheduler algorithms have been considered, with a focus on a time-to-live scheduler that is expected to satisfy the delay constraints imposed by VoIP. On the other hand, the periodic character in the generation of VoIP packets in first hand fits best to the round-robin way of selecting the queues to be scheduled. This paper investigates this tradeoff, together with a scheduler that selects the user with the best channel condition. Moreover, several modifications in the use of discard timers are explored. All users are moving at vehicular speeds.

I. de Bruin

Papers

Usage of link-level performance indicators for HSDPA network-level simulations in E-UMTS

End-to-end network model for Enhanced UMTS

Fair channel-dependent scheduling in CDMA systems

Scheduling performance of multimedia services over HSDPA