Non-real Time Research Articles

A low-complexity beamforming-based scheduling to downlink OFDMA/SDMA systems with multimedia traffic

In this paper, we propose a low-complexity beamforming-based scheduling scheme utilizing a semi-orthogonal user selection (SUS) algorithm in downlink orthogonal frequency division multiple access (OFDMA)/space division multiple access (SDMA) systems to support multimedia traffic. One of the challenges in the multi-dimensional (space, time, and frequency) radio resource allocation problem for OFDMA/SDMA systems is its high complexity, especially to simultaneously satisfy the quality of services (QoS) requirements for various traffic classes. In the literature, the SUS algorithm is usually applied to the single-class traffic environment, but extending the SUS algorithm to the multimedia environment is not straightforward because of the need to prioritize the real-time (RT) users and the non-real-time (NRT) users. To solve this problem, we propose the concept of urgency value to guarantee the fairness of the NRT as well as the best effort (BE) users while satisfying the delay requirement for the RT users. Simulation results show that, when traffic load is greater than 0.5, the proposed scheduling algorithm can improve the fairness performance by more than 100% over the most recently proposed algorithms.

Non-Real-time CT-Guided TBNA/TBB: A Novel Method of Increasing Diagnostic Yield in TBNA and TBB

PURPOSE: To enhance the yield of transbronchial needle aspiration (TBNA), advanced interventions like Endobronchial Ultrasound (EBUS) and CT fluoroscopic TBNA are utilized. However, these are not easily available in all countries and centers outside the USA. We conducted this analysis to evaluate the yield of NON-REAL TIME CT-guided TBNA transbronchial biopsy (TBB) sampling for mediastinal lymph nodes (LN) and peripheral lesions.

A Fair and Efficient Packet Scheduling Scheme for IEEE 802.16 Broadband Wireless Access Systems

This paper proposes a fair and efficient QoS scheduling scheme for IEEE 802.16 BWA systems that satisfies both throughput and delay guarantee to various real and non-real time applications. The proposed QoS scheduling scheme is compared with an existing QoS scheduling scheme proposed in literature in recent past. Simulation results show that the proposed scheduling scheme can provide a tight QoS guarantee in terms of delay, delay violation rate and throughput for all types of traffic as defined in the WiMAX standard, thereby maintaining the fairness and helps to eliminate starvation of lower priority class services. Bandwidth utilization of the system and fairness index of the resources are also encountered to validate the QoS provided by our proposed scheduling scheme.

SetExp: a method of transformation of timed automata into finite state automata

Real-time discrete event systems are discrete event systems with timing constraints, and can be modeled by timed automata. The latter are convenient for modeling real-time discrete event systems. However, due to their infinite state space, timed automata are not suitable for studying real-time discrete event systems. On the other hand, finite state automata, as the name suggests, are convenient for modeling and studying non-real time discrete event systems. To take into account the advantages of finite state automata, an approach for studying real-time discrete event systems is to transform, by abstraction, the timed automata modeling them into finite state automata which describe the same behaviors. Then, studies are performed on the finite state automata model by adapting methods designed for non real-time discrete event systems. In this paper, we present a method for transforming timed automata into special finite state automata called Set-Exp automata. The method, called SetExp, models the passing of time as real events in two types: Set events which correspond to resets with programming of clocks, and Exp events which correspond to the expiration of clocks. These events allow to express the timing constraints as events order constraints. SetExp limits the state space explosion problem in comparison to other transformation methods of timed automata, notably when the magnitude of the constants used to express the timing constraints are high. Moreover, SetExp is suitable, for example, in supervisory control and conformance testing of real-time discrete event systems.

Neuro-Fuzzy based Joint Relay-Selection and Resource-Allocation for Cooperative Networks

This paper focuses on a joint relay-selection and resource-allocation algorithm for an Amplify-and-Forward (AF) cooperative network. In a multiuser scenario, joint relay selection and power allocation is a combinational problem for heterogeneous, i.e., real time (RT) and non-real time (NRT), users. In single relay AF (S-AF) scheme, a source-destination pair selects best relay. Thus only two channels are needed (i.e., one for source-destination direct link and other one for the source-relay-destination indirect link) between a source-destination pair. We propose a Neuro Fuzzy (NF) based optimal relay selection algorithm for selecting best relay based on link's signal-to-noise ratio (SNR), link's delay and degree of mobility between a source-destination pair. The available radio resources are then allocated sub-optimally to the RT and NRT users on priority basis. The priority parameter depends on Quality-of-service (QoS) requirement of the RT and NRT users. We deduce a close form expression of the moment-generating-function (MGF) for independent and non identical Rayleigh fading channels. Performance evaluations reveal that the proposed joint scheme has lower complexity and better outage behavior as compared to the conventional schemes.

마르코프 연쇄 모델링과 동적 계획 기법을 이용한 지상파 DTV 채널에서의 Push-VOD의 콘텐츠 스케줄링 방법

DTV 방송이 개시된 이후로 방송망의 비디오, 오디오 및 채널 정보들을 제외한 나머지 대역폭에 부가 정보를 전송하여 데이터 방송 등과 같은 서비스를 제공하고자 하는 노력이 있었다. 최근에는 이러한 대역폭에 장시간 동안 VOD 콘텐츠를 전송하여 수신기에 저장시키는 방법으로 콘텐츠를 제공하는 Push-VOD 서비스가 주목을 받고 있으며, ATSC에서도 NRT(Non-Real-Time)[1]라는 이름으로 해당 전송 방법을 규격화하는 작업을 진행하고 있다. 그러나 이러한 방식으로 콘텐츠를 전송할 때 DTV 수신환경이나 수신기의 문제 등으로 인해 한 번의 전송만으로는 콘텐츠가 에러없이 전송되지 않을 확률이 높다. 따라서 이를 극복하기 위해서는 방송망의 단방향적 특성상 콘텐츠를 여러 번 반복 전송하여 전송 신뢰도를 높여야 한다. 본 논문에서는 단방향 전송환경인 방송망으로 제한된 시간 내에 여러 콘텐츠를 수신기로 전송하고자 할 때, 마르코프 연쇄 모델링과 동적 계획 기법을 이용하여 전송된 콘텐츠들의 에러를 최소화하는 콘텐츠들의 최적 반복 전송 횟수를 구하는 방법을 제안한다. After starting digital terrestrial broadcasting, there have been a number oftrials to provide new services like data broadcasting on a spare bandwidth of a DTV channel. Recently, the Push-VOD service, which provides A/V contents on that bandwidth, gets more attention and is being standardized as NRT(Non-Real-Time) by ATSC. However, it is highly probable that the contents transmitted in this way contain many errors due to the DTV receiving environment. Thus, in order to improve the reliability of transmission, the contents should be transmitted repeatedly several times, considering the unidirectional property of DTV terrestrial network. In this paper, we propose a method to calculate the optimal number of repetitions to transmit each contents in a way that minimizes the number of errors occured, when trying to transmit several contents to the receiver in a restricted time, using Markov-chain modeling and dynamic programming approach.

A novel scheduling scheme for multiple traffic classes

In this paper, a novel scheduling scheme is proposed for multiple traffic classes to exploit multiuser diversity of the non-real-time (NRT) traffic. The proposed scheduling algorithm consists of two stages, i.e. at the first scheduling stage, the inter-traffic scheduler dynamically allocates the bandwidth resources to each traffic class by a periodic and triggered way with the objective of maximizing a room for NRT traffic while guaranteeing the quality of service (QoS) requirements of real-time (RT) traffics; at the second scheduling stage, the intra-traffic scheduler is used to schedule different users' packets within each traffic class simultaneously. The proposed algorithm not only enhances the system throughput but also satisfies the QoS requirements of RT traffic. Simulation results validate the effectiveness and good performance of the proposed scheme.

Traffic differentiation support in vehicular delay-tolerant networks

Vehicular Delay-Tolerant Networking (VDTN) is a Delay-Tolerant Network (DTN) based architecture concept for transit networks, where vehicles movement and their bundle relaying service is opportunistically exploited to enable non-real time applications, under environments prone to connectivity disruptions, network partitions and potentially long delays. In VDTNs, network resources may be limited, for instance due to physical constraints of the network nodes. In order to be able to prioritize applications traffic according to its requirements in such constrained scenarios, traffic differentiation mechanisms must be introduced at the VDTN architecture. This work considers a priority classes of service (CoS) model and investigates how different buffer management strategies can be combined with drop and scheduling policies, to provide strict priority based services, or to provide custom allocation of network resources. The efficiency and tradeoffs of these proposals is evaluated through extensive simulation.

Radio Resource Allocation for Heterogeneous Services in Relay Enhanced OFDMA Systems

We propose a priority based resource allocation algorithm for heterogeneous services in the relay enhanced OFDMA downlink systems. The aim is to maximize the system throughput while satisfying the quality of service (QoS) requirements of heterogeneous services, comprising real time (RT) and non real time (NRT) services. The base station (BS) allocates resources dynamically to the users in a prioritized manner. The priority parameter depends on the channel condition, QoS requirement and data buffer information. We propose a suboptimal algorithm to reduce the computational complexity. The simulation results are compared with the fixed as well as dynamic resource allocation algorithms proposed in different researches. Our proposed scheme reduces the outage probability of the system and increases the system throughput.

Novel Radio Link Buffer Management Schemes for End-User Multi-class Traffic in High Speed Packet Access Networks

The requirement to provide multimedia services with QoS support in mobile networks has led to standardization and deployment of high speed data access technologies such as the High Speed Downlink Packet Access (HSDPA) system. HSDPA improves downlink packet data and multimedia services support in WCDMA-based cellular networks. As is the trend in emerging wireless access technologies, HSDPA supports end-user multi-class sessions comprising parallel flows with diverse Quality of Service (QoS) requirements, such as real-time (RT) voice or video streaming concurrent with non real-time (NRT) data service being transmitted to the same user, with differentiated queuing at the radio link interface. Hence, in this paper we present and evaluate novel radio link buffer management schemes for QoS control of multimedia traffic comprising concurrent RT and NRT flows in the same HSDPA end-user session. The new buffer management schemes—Enhanced Time Space Priority (E-TSP) and Dynamic Time Space Priority (D-TSP)—are designed to improve radio link and network resource utilization as well as optimize end-to-end QoS performance of both RT and NRT flows in the end-user session. Both schemes are based on a Time-Space Priority (TSP) queuing system, which provides joint delay and loss differentiation between the flows by queuing (partially) loss tolerant RT flow packets for higher transmission priority but with restricted access to the buffer space, whilst allowing unlimited access to the buffer space for delay-tolerant NRT flow but with queuing for lower transmission priority. Experiments by means of extensive system-level HSDPA simulations demonstrates that with the proposed TSP-based radio link buffer management schemes, significant end-to-end QoS performance gains accrue to end-user traffic with simultaneous RT and NRT flows, in addition to improved resource utilization in the radio access network.

Adaptive channel and superframe allocation (ACSA) for 60 GHz wireless networks

Millimeter-wave (MMW) systems are high frequency wireless systems with a center frequency of around 60 GHz. In this article we propose an adaptive channel–superframe allocation (ACSA) scheme for such a system and evaluate its throughput and delay performance. The ACSA algorithm is designed to serve real-time (RT) and non-real-time (NRT) flows separately in different channels instead of serving them in different times. We also propose to change the sliced superframe of IEEE 802.15.3 to an adaptive unsliced superframe in order to decrease the TCP round-trip time. We compared IEEE 802.15.3 MAC with ACSA MAC, which shows that the throughput and delay could be improved in ACSA MAC. We observed significant improvement in the throughput of NRT flows via the better distribution of bandwidth in ACSA MAC. The channel access delay is also improved by providing an unsliced superframe. In brief, the simulation results also support the analysis of the proposed adaptive channel–superframe allocation algorithm, which could generally improve the quality of service (QoS) in MMW systems.

Optimal Resource Allocation Based on Resource Factor for Power-Line Communication Systems

The optimal multilayer, multiobjective resource allocation model for multiuser and multitraffic orthogonal frequency-division multiplexing (OFDM)-based power-line communication (PLC) systems is analyzed with the restrictions of maximal total power, constant rates for every real time (RT) user, minimal rates for every non-real time (NRT) user, maximal upper limit of power and number of bits for every subcarrier in each OFDM symbol. A bit-loading lookup table resource allocation algorithm with rate- and margin-adaptation is proposed based on resource factor, which first assigns fairly Pareto non-dominated resources for all RT users according to resource factor so as to attain their constant rates, second computes the relevant remaining power and non-used subcarriers for every Pareto solution and assigns fairly them for all NRT users so as to attain their minimal rates, third also computes the relevant remaining resources and assigns them so as to achieve the maximal sum of the allocated rates for all NRT users, lastly selects out the globally optimal solution according to the order of partial information. Based on the typical power-line channel, the simulation results illustrate that the proposed algorithm outperforms the existed multiuser bit-loading greedy algorithm and it realizes better the multiple aims of resource allocation in OFDM-based PLC systems.

SOAP response caching strategy for non-real time services and its application

Concerning the repetitive requests to non-real time services in the Service Oriented Architecture(SOA),the authors proposed a response caching strategy based on the extension of Simple Object Access Protocol(SOAP)and XML-binary Optimized Packaging(XOP)and implemented it in Enterprise Service Bus(ESB),which cached the service responses for replying the same requests within a certain period of time in order to accelerate the response to these requests.This strategy can be applied to the general SOAP responses and that with attachments,and it also sets a mechanism to prevent the duplicate caching of the same attachments.For the two services been tested,the response time to the same request is shortened by 38% and 22% with the use of the response caching strategy.

QoS Based Capacity Enhancement for WCDMA Network with Coding Scheme

The wide-band code division multiple access (WCDMA) based 3G and beyond cellular mobile wireless networks are expected to provide a diverse range of multimedia services to mobile users with guaranteed quality of service (QoS). To serve diverse quality of service requirements of these networks it necessitates new radio resource management strategies for effective utilization of network resources with coding schemes. Call admission control (CAC) is a significant component in wireless networks to guarantee quality of service requirements and also to enhance the network resilience. In this paper capacity enhancement for WCDMA network with convolutional coding scheme is discussed and compared with block code and without coding scheme to achieve a better balance between resource utilization and quality of service provisioning. The model of this network is valid for the real-time (RT) and non-real-time (NRT) services having different data rate. Simulation results demonstrate the effectiveness of the network using convolutional code in terms of capacity enhancement and QoS of the voice and video services.

An optimal warning-zone-length assignment algorithm for real-time and multiple-QoS on-chip bus arbitration

In an advanced System-on-Chip (SoC) for real-time applications, the arbiter of its on-chip communication subsystem needs to support multiple QoS criteria while providing a hard real-time guarantee. To fulfill both objectives, the arbitration algorithm must dynamically switch between NonReal-Time (NRT) and Real-Time (RT) modes such that use of the RT mode is minimized to best accommodate the overall QoS criteria. In this article, we define a model for this problem, and propose optimal solutions to its associated problems with static and dynamic warning-zone-length assignment. Compared with previous works, the proposed approach enables a bus arbiter to use much less RT mode in providing a Real-Time (RT) guarantee and, therefore, gives the arbiter more opportunity to employ non-RT modes to achieve better overall QoS. Experimental results show that the proposed approach reduces RT mode usage by as much as 37.1%. Moreover, that reduction in RT mode usage helps cut the execution time by 27.0% when applying our approach to an industrial DRAM controller. Another case study on an AMBA-compliant ultra-high-resolution H.264 decoder IP shows that the proposed approach reduces RT mode usage by 26.4%, which leads to an average reduction of 10.4% in decoding time. Finally, when implementing a 16 master arbiter, it costs only 6.9K and 9.5K gates of overhead using the proposed static and dynamic approach, respectively. Therefore, the proposed approach is suitable for real-time SoC applications.

A game-theoretic approach to joint rate and power control for uplink CDMA communications

Next generation wireless systems will be required to support heterogeneous services with different transmission rates that include real time multimedia transmissions, as well as non-real time data transmissions. In order to provide such flexible transmission rates, efficient use of system resources in next generation systems will require control of both data transmission rate and power for mobile terminals. In this paper we formulate the problem of joint transmission rate and power control for the uplink of a single cell CDMA system as a non-cooperative game. We assume that the utility function depends on both transmission rates and powers and show the existence of Nash equilibrium in the non-cooperative joint transmission rate and power control game (NRPG). We include numerical results obtained from simulations that compare the proposed algorithm with a similar one which is also based on game theory and it also updates the transmission rates and powers simultaneously in a single step.

Improvement of Handoff-state and QOS in Wireless Environment

In this paper, we propose for improving QoS in wireless micro cellular network using Cellular-IP/PRC(Paging Route Cache) with Paging Cache and Route Cache in Cellular-IP and propose for performance of realtime and non-real time handoff service using Handoff state machine Paging Route Cache. Although the Cellular-IP/PRC technology is devised for mobile internet communication, it bas its vulnerability in frequent handoff environment. On the other hand, Cellular IP combines the capability of cellular networks to provide high performance handoff and efficient location management of active and idle mobile users with the inherent flexibility, robustness and scalability found in IP networks. Also Cellular-IP/PRC use semi-soft handoff. During semi-soft hand off a mobile host may be in contact with either of the old and new base stations and receive packets from them. Packets intended to the mobile node are sent to both base stations and buffered, so when the mobile host eventually moves to the new location it can continue to receive packets without interruption. It should be suitable for realtime service such as multimedia traffic. But, much waste of resource will occur in this method, especially for non-real time services such as FTP and E-mail. Therefore, a new algorithm that performs different handoff according to characteristic of each traffic by use of reserved field in IP packet is proposed in this thesis. This hand off state machine using differentiated handoff improves quality of services in Cellular-IP/PRC. Suggested algorithm shows better performance than existing technology in wireless mobile internet communication environment. Matlab simulation results are improving QoS, show call drop and call blocking provided to Paging Router Cache during handoff state machine in Cellular-IP/PRC.

Monthly pass-through ratios

This paper estimates monthly pass-through ratios from import prices to consumer prices in real time. Conventional time series methods impose restrictions to generate exogenous shocks on exchange rates or import prices when estimating pass-through coefficients. Instead, our estimation strategy follows an event-study approach based on monthly releases in import prices. Projections from a dynamic common factor model with daily panels before and after monthly releases of import prices define the innovation for import prices. We apply our identification procedure to Swiss prices and find strong evidence that the median of the monthly pass-through ratio is around 0.3. Tests show that standard assumptions of non-real time data and limited information breath are critical for the pass-through estimates.

A Comparative Study of Kernel and Robust Canonical Correlation Analysis

Broadband satellite constellation networks will be required to carry all types of IP traffic, real time interactive traffic as well as non-real time one, warranting the need for appropriate QoS for these different traffic flows. In this paper we investigate the need for MPLS traffic engineering in GEO/MEO/LEO satellite networks to address QoS issues. We compare the service received by TCP and UDP flows when they share a link and when they are routed on explicit MPLS traffic trunks. Since MPLS traffic trunks allow non-shortest path links also to be used, the total network throughput goes up with proper traffic engineering. If UDP and TCP flows are mixed in a trunk, TCP flows receive reduced service as the UDP flows increase their rates. Also, we found that with MPLS traffic engineering we can protect real time traffic and VoIP traffic from packet loss and excessive jitter by separating them from other congestion unresponsive flows.

A silicon strip detector dose magnifying glass for IMRT dosimetry

Intensity modulated radiation therapy (IMRT) allows the delivery of escalated radiation dose to tumor while sparing adjacent critical organs. In doing so, IMRT plans tend to incorporate steep dose gradients at interfaces between the target and the organs at risk. Current quality assurance (QA) verification tools such as 2D diode arrays, are limited by their spatial resolution and conventional films are nonreal time. In this article, the authors describe a novel silicon strip detector (CMRP DMG) of high spatial resolution (200 microm) suitable for measuring the high dose gradients in an IMRT delivery. A full characterization of the detector was performed, including dose per pulse effect, percent depth dose comparison with Farmer ion chamber measurements, stem effect, dose linearity, uniformity, energy response, angular response, and penumbra measurements. They also present the application of the CMRP DMG in the dosimetric verification of a clinical IMRT plan. The detector response changed by 23% for a 390-fold change in the dose per pulse. A correction function is derived to correct for this effect. The strip detector depth dose curve agrees with the Farmer ion chamber within 0.8%. The stem effect was negligible (0.2%). The dose linearity was excellent for the dose range of 3-300 cGy. A uniformity correction method is described to correct for variations in the individual detector pixel responses. The detector showed an over-response relative to tissue dose at lower photon energies with the maximum dose response at 75 kVp nominal photon energy. Penumbra studies using a Varian Clinac 21EX at 1.5 and 10.0 cm depths were measured to be 2.77 and 3.94 mm for the secondary collimators, 3.52 and 5.60 mm for the multileaf collimator rounded leaf ends, respectively. Point doses measured with the strip detector were compared to doses measured with EBT film and doses predicted by the Philips Pinnacle treatment planning system. The differences were 1.1% +/- 1.8% and 1.0% +/- 1.6%, respectively. They demonstrated the high temporal resolution capability of the detector readout system, which will allow one to investigate the temporal dose pattern of IMRT and volumetric modulated are therapy (VMAT) deliveries. The CMRP silicon strip detector dose magnifying glass interfaced to a TERA ASIC DAQ system has high spatial and temporal resolution. It is a novel and valuable tool for QA in IMRT dose delivery and for VMAT dose delivery.