An RL-based scheduling algorithm for video traffic in high-rate wireless personal area networks

The emerging high-rate wireless personal area network (WPAN) technology is capable of supporting high-speed and high-quality real-time multimedia applications. In particular, video streams are deemed to be a dominant traffic type, and require quality of service (QoS) support. However, in the current IEEE 802.15.3 standard for MAC (media access control) of high-rate WPANs, the implementation details of some key issues such as scheduling and QoS provisioning have not been addressed. In this paper, we first propose a Markov decision process (MDP) model for optimal scheduling for video flows in high-rate WPANs. Using this model, we also propose a scheduler that incorporates compact state space representation, function approximation, and reinforcement learning (RL). Simulation results show that our proposed RL scheduler achieves nearly optimal performance and performs better than F-SRPT, EDD + SRPT, and PAP scheduling algorithms in terms of a lower decoding failure rate.     

QoS management in heterogeneous home networks

An OSGi (Open Services Gateway Initiative) home gateway system manages the integration of heterogeneous home networks protocols and devices to develop ubiquitous applications. Wired and wireless heterogeneous home networks have different QoS concerns. For instance, jitter and latency are important concerns in web phones, while packet loss ratio is important in on-line video. This study adopts UPnP QoS specification version 1.0 to design an adaptive QoS management mechanism based on the RMD (Resource Management in DiffServ) architecture. This study monitors real-time network traffic, and adaptively controls the bandwidth, to satisfy the minimum but most important quality for each application in home network congestion. Simulation results indicate that the average jitter, latency and packet loss are reduced by 0.1391 ms, 0.0066 s, and 5.43%, respectively. The packet loss ratio is reduced by 4.53%, and the throughput is increased by 1.2% in high definition video stream; the packet loss ratio is reduced by 1.89% for standard definition video stream, and in VoIP (Voice over IP) the jitter and latency are reduced to 0.0407 ms and 0.0209 s, respectively.     

A scalable multimedia QoS architecture for ad hoc networks

Communication demands have grown from separate data and voice to integrated multimedia, paving the way to converging fixed, mobile and IP networks. Supporting Multimedia is a challenging task for wireless ad hoc network designers. Multimedia forms high data rate traffic with stringent Quality of Service (QoS) requirements. Wireless ad hoc networks are characterized by frequent topology changes, unreliable wireless channel, network congestion and resource contention. Providing scalable QoS is the most important challenge for multimedia delivery over ad hoc networks. We introduce here a provisioning and routing architecture for ad hoc networks which scales well while provisioning QoS. The proposed architecture is analysed using a mix of HTTP, voice and video streaming applications over 54 Mbps 802.11 g-based ad hoc networks. The architecture is simulated and compared to well-known routing protocols using the OPNET Modeller. The results show that our architecture scales well with increase in the network size, and outperforms well-known routing protocols.     

Short-term non-uniform access in IEEE 802.11-compliant WLANs: A study on its impact on the saturation performance

Along with the success of IEEE 802.11-compliant WLANs, the distributed coordinated function (DCF) specified as the contention-based medium access mechanism in IEEE 802.11 has been widely used to support applications in new regimes. A thorough understanding of the characteristics of IEEE 802.11 DCF is therefore a research focus. DCF assumes the binary exponential backoff algorithm (BEBA) [D. Bertsekas, R. Gallager, Data Networks, Prentice Hall, 1992]. Several existing models that characterize BEBA as a p-persistent scheme have ignored several subtle protocol details. This has practically constrained the models from being applied in a broader range of configurations, e.g., small contention window, and from being further extended, e.g., 802.11e EDCA.In this paper, we develop an analytical model that captures the subtlety, and faithfully describes the channel activities as governed by DCF. Based on the devised model, we perform a rigorous analysis on the saturation throughput performance in a single-hop WLAN. We show that the stochastic property of the backoff time, r, may substantially impact the system performance. For example, setting the range of r to [1, CW] instead of [0, CW − 1], can degrade the system throughput considerably. We also identify, by clearly defining and thus being able to differentiate the two terms, attempt probability and transmission probability, an erroneous extension made to Bianchi’s model [G. Bianchi, Performance analysis of the IEEE 802.11 distributed coordination function, IEEE JSAC, 18(3) (2000) 535–547]. All the findings are corroborated by ns-2 simulation.     

Low-complexity FFT/IFFT IP hardware macrocells for OFDM and MIMO–OFDM CMOS transceivers

The paper presents an automated environment for fast design space exploration and automatic generation of FFT/IFFT macrocells with minimum circuit and memory complexity within the numerical accuracy budget of the target application. The effectiveness of the tool is demonstrated through FPGA and CMOS implementations (90 nm, 65 nm and 45 nm technologies) of the baseband processing in embedded OFDM transceivers. Compared with state-of-art FFT/IFFT IP cores, the proposed work provides macrocells with lower circuit complexity while keeping the same system performance (throughput, transform size and accuracy) and is the first addressing the requirements of all OFDM standards including MIMO systems: 802.11 WLAN, 802.16 WMAN, Digital Audio and Video Broadcasting in terrestrial, handheld and hybrid satellite-scenarios, Ultra Wide Band, Broadband on Power Lines, xDSL.     

QoS provisioning in IEEE 802.11-compliant networks: Past,present, and future

Proliferation of portable, wireless-enabled laptop computers and PDAs, cost-effective deployment of access points, and availability of the license-exempt bands and appropriate networking standards contribute to the conspicuous success of IEEE 802.11 WLANs. In the article, we provide a comprehensive overview of techniques for capacity improvement and QoS provisioning in the IEEE 802.11 protocol family. These techniques represent the R&D efforts both in the research community and the IEEE 802.11 Working Groups. Specifically, we summarize the operations of IEEE 802.11 legacy as well as its extension, introduce several protocol modeling techniques, and categorize the various approaches to improve protocol capacity, to provide QoS (by either devising new MAC protocol components or fine-tuning protocol parameters in IEEE 802.11), and to judiciously arbitrate radio resources (e.g., transmission rate and power). To demonstrate how to adapt QoS provisioning in newly emerging areas, we use the wireless mesh network as an example, discuss the role IEEE 802.11 plays in such a network, and outline research issues that arise.     

Differentiation, QoS guarantee, and optimization for real-time traffic over one-hop ad hoc networks

Nodes having a self-centrically broadcasting nature of communication form a wireless ad hoc network. Many issues are involved to provide quality of service (QoS) for ad hoc networks, including routing, medium access, resource reservation, mobility management, etc. Previous work mostly focuses on QoS routing with an assumption that the medium access control (MAC) layer can support QoS very well. However, contention-based MAC protocols are adopted in most ad hoc networks since there is no centralized control. QoS support in contention-based MAC layer is a very challenging issue. Carefully designed distributed medium access techniques must be used as foundations for most ad hoc networks. In this paper, we study and enhance distributed medium access techniques for real-time transmissions in the IEEE 802.11 single-hop ad hoc wireless networks. In the IEEE 802.11 MAC, error control adopts positive acknowledgement and retransmission to improve transmission reliability in the wireless medium (WM). However, for real-time multimedia traffic with sensitive delay requirements, retransmitted frames may be too late to be useful due to the fact that the delay of competing the WM is unpredictable. In this paper, we address several MAC issues and QoS issues for delay-sensitive real-time traffic. First, a priority scheme is proposed to differentiate the delay sensitive real-time traffic from the best-effort traffic. In the proposed priority scheme, retransmission is not used for the real-time traffic, and a smaller backoff window size is adopted. Second, we propose several schemes to guarantee QoS requirements. The first scheme is to guarantee frame-dropping probability for the real-time traffic. The second scheme is to guarantee throughput and delay. The last scheme is to guarantee throughput, delay, and frame-dropping probability simultaneously. Finally, we propose adaptive window backoff schemes to optimize throughput with and without QoS constraints.     

An analytic study of tuning systems parameters in IEEE 802.11e enhanced distributed channel access

In this paper, we derive, based on the analytical model developed by Cali et al., a multi-class model to study how to adaptively tune parameters in IEEE 802.11e EDCA and support service differentiation in WLANs. Through analytical modeling, we demonstrate that by assigning appropriate different attempt probabilities (or contention window sizes) to stations of different classes, it is feasible to provide (proportional) service differentiation and achieve pre-specified targeted throughput ratios among different classes, while at the same time, maximizing the total system capacity. We also extend the derived theoretical model to analyze the role of AIFS and TXOP values on service differentiation perceived by different traffic classes. We show that, to achieve QoS guarantees (i.e., throughput differentiation) and high channel utilization, it may not be desirable to allow tuning of multiple parameters (e.g., both the contention window sizes and the AIFS values). Instead, the design dimension should be kept small by turning only one set of parameters, while keeping the other two sets of parameters for all the access categories fixed (i.e., setting the AIFS values of all access categories to 2, which is equivalent to AIFS = DIFS).We also elaborate on how to incorporate our derived theoretical results into IEEE 802.11e. These include (i) how to reduce the computational complexity and practically calculate results on-line, (ii) how to convert the optimal parameters derived in the model that characterizes the p-persistent version of IEEE 802.11e to those in IEEE 802.11e (which is based on the notion of the contention window to determine whether or not to transmit in a slot), and (iii) how to on-line measure parameters needed for calculating the best value of the contention window size. Both the analytical models and the proposed approaches for practically incorporating theoretical findings into IEEE 802.11e EDCA are validated through detailed ns-2 simulations and empirical experimentation on a Linux-based MADWifi driver for wireless LAN devices with the Atheros chipset.     

SRA-MSDU: Enhanced A-MSDU frame aggregation with selective retransmission in 802.11n wireless networks

The main goal of the IEEE 802.11n standard is to achieve more than 100 Mbps of throughput at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. One of the MAC enhancements is the frame aggregation in which multiple frames are concatenated into a single large frame before being transmitted. The 802.11n MAC layer defines two types of aggregation, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). The A-MPDU outperforms A-MSDU due to its large aggregation size and the subframes retransmission in erroneous channels. However, in error free channels and under the same aggregation size the A-MSDU performs better than the A-MPDU due to its smaller headers. Thus, adding a selective retransmission capability to the A-MSDU would improve the system performance. In this paper, we have proposed an MSDU frame aggregation scheme that enables selective retransmission at the MSDU level without altering the original MAC header. In this proposed scheme an implicit sequence control mechanism has been introduced in order to keep the frames in sequence and preserve their correct order at the receiver side. The results show that the proposed scheme improves the system performance in terms of throughput and delay even under highly erroneous channels.     

Extending multimedia research: How do prerequisite knowledge and reading comprehension affect learning from text and pictures

The present study aimed at extending research on multimedia design principles by investigating their validity as a function of learners’ reading comprehension and scientific literacy. Students (N = 125; age: M = 15.11 years) learned about cell reproduction during their regular Biology lessons in one of six conditions resulting from cross-varying multimedia (text only vs. text plus animations) and text modality (spoken vs. written vs. spoken and written). Recall and transfer were assessed immediately after learning and again 1 week later. Overall, adding animations to text as well as using spoken rather than written text improved only immediate recall; in addition, a multimedia effect for delayed recall was observed for learners with higher levels of scientific literacy. A redundant presentation of text proved harmful especially for delayed performance measures. Reading comprehension did not moderate multimedia design effects. Students with more suitable cognitive prerequisites were better able to maintain performance from the immediate to the delayed tests. Future multimedia research should further investigate the boundary conditions that moderate multimedia effectiveness.     

Extended EDCA for delay guarantees in wireless local area networks

Despite their very broad diffusion, IEEE 802.11 Wireless Local Area Networks (WLANs) are not able to provide service differentiation and to support real-time multimedia applications, due to their channel access methods. To overcome these limitations, the 802.11e working group has proposed the Enhanced Distributed Coordination Access (EDCA) scheme, which achieves service differentiation on a statistical basis by properly mapping user Quality of Service (QoS) requirements to channel contention parameters. Such a scheme will be included in the emerging 802.11n standard and in the revision of the 802.11 standard. However, it has been widely demonstrated that, especially at high network loads, EDCA does not provide an effective usage of the channel capacity. In particular, it is unable to provide a bounded delay service to all kinds of multimedia flow because flows with lower channel access priorities are starved to advantage only those with the highest priority. To fix this undesired behavior and improve wireless LAN performance, this paper proposes a new Extended EDCA (E²DCA) scheme, that is compliant with 802.11e specifications. By exploiting a closed-loop control algorithm, E²DCA performs a distributed dynamic bandwidth allocation, providing guarantees on average/absolute delays to real-time media flows, regardless of their priorities. Moreover, an innovative Call Admission Control (CAC) procedure has been developed. Using the ns-2 simulator, the effectiveness of the algorithm has been investigated in realistic network scenarios, involving a mix of audio, video, and FTP flows, at several network loads and with random losses. Results have shown that the proposed scheme is able to provide a bounded delay service to multimedia flows in a wide range of network loads and frame loss ratios.     

MPSoC based on Transport Triggered Architecture for baseband processing of an LTE receiver

Wireless communication over LTE (long term evolution) brings several design challenges to industry and academia, due to its high throughput demand. Specially in the case of hand held mobile devices where the power budget is very limited and high throughput requires more computation power. On the other hand, the industry is struggling for flexible hardware solution, a Software Defined Radio (SDR), to amortize huge costs of hardware changes to suit the continued evolution in wireless standards. In this article, an MPSoC design has been presented for the baseband processing of a 20 MHz LTE system. Transport Triggered Architecture (TTA) has been preferred over conventional DSPs/VLIW architectures as processing element (PE) of MPSoC. Processing tasks are statically scheduled. Synchronization among the PEs is based on polling of a shared memory space. In addition an approach is presented to organize I/O buffer in such a way that the stalling probability of a PE should be reduced to exploit efficiently data and task level parallelism. The total power consumption by all the PEs synthesized on 130 nm technology at 200 MHz and 1.5 V is 105.04 mW. The total energy consumption to process one subframe including carrier recovery is 0.0767 mJ. Our study shows that TTA architecture brings several improvements in conventional SIMD/VLIW architectures. TTA as contrary to other run time designs has a guaranteed performance and lower energy consumption due to the fact that all the data dependency/independency issues are resolved at compile time. Further, it is also true due to the fact that TTA has a reduced register file (RF) traffic, number of RF ports and lower overall cycle count for a given task. To the best of author’s knowledge this article is among the first few published articles on LTE receiver implementation with published figures like time, frequency, power and perhaps the first article explaining further in detail about data access pattern to process an LTE subframe, memory organization, subsystem interconnection, and synchronization.     

Upper-level scheduling supporting multimedia traffic in cellular data networks

Wireless data networks such as cdma2000 1x EV-DO and UMTS HSDPA use downlink scheduling that exploits channel fading to increase the system throughput. As future wireless networks will eventually support multimedia and data traffic together, we need a proper criterion for scheduling that can count various service requirements such as delay and packet loss. Although some previous approaches proposed opportunistic schedulers at the lower layer, it has not been investigated well whether they are able to meet explicit QoS defined at the upper layer. Hence, in this paper, we develop a hierarchical scheduling model that considers QoS provisioning and the time-varying channel feature separately. We focus on the upper-level QoS scheduling that supports various traffic classes in a unified manner. Supposing that a user gets some satisfaction or utility when served, we introduce a novel concept of opportunity cost, which is defined as the maximum utility loss among users incurred by serving a particular user at the current turn. We obtain each user’s net profit by subtracting the opportunity cost from its expected utility, and then select a user with the maximum profit for service. Simulation results reveal that our scheme supports various QoS classes well that are represented by delay and packet loss under various traffic loadings.     

A survey on wireless sensor network infrastructure for agriculture

The hybrid wireless sensor network is a promising application of wireless sensor networking techniques. The main difference between a hybrid WSN and a terrestrial wireless sensor network is the wireless underground sensor network, which communicates in the soil. In this paper, a hybrid wireless sensor network architecture is introduced. The framework to deploy and operate a hybrid WSN is developed. Experiments were conducted using a soil that was 50% sand, 35% silt, and 15% clay; it had a bulk density of 1.5 g/cm³ and a specific density of 2.6 cm^? 3. The experiment was conducted for several soil moistures (5, 10, 15, 20 and 25%) and three signal frequencies (433, 868 and 915 MHz). The results show that the radio signal path loss is smallest for low frequency signals and low moisture soils. Furthermore, the node deployment depth affected signal attenuation for the 433 MHz signal. The best node deployment depth for effective transmission in a wireless underground sensor network was determined.     

Channel time allocation scheme based on feedback information in IEEE 802.11e wireless LANs

The IEEE 802.11e standard defines a set of quality of service (QoS) enhancements for wireless local area network (WLAN) applications such as voice and streaming multimedia traffic. In the standard, a new medium access control (MAC) protocol is called the hybrid coordinator function (HCF), and also a channel access scheme to transmit multimedia traffic is called the HCF controlled channel access (HCCA). In the IEEE 802.11e WLANs, to satisfy the stringent real-time constraints of multimedia services it is very important to provide an efficient method of allocating network resources. In this regard, we propose a feedback-assisted dynamic channel time allocation scheme considering the application layer information in order to achieve better performance of multimedia traffic over IEEE 802.11e HCCA under the constrained QoS requirements. Performance of the proposed scheme is investigated by simulation. Our results show that under typical channel error conditions, the proposed scheme is very effective regardless of the variation of station numbers and service intervals. Also, it yields high performances while guaranteeing the delay bound.     

A wireless multi-step attack pattern recognition method for WLAN

Intrusion detection and prevention technology has been broadly applied to wired networks as an important means to protect network security. However, few work in this area has been extended to the WLAN. In this paper, we propose a wireless multi-step attack pattern recognition method (WMAPRM) based on correlation analysis with the main attributes of the IEEE 802.11 frame. The method consists of six steps: clustering wireless intrusion alerts, constructing a global attack database, building candidate attack chains, filtering candidate attack chains, correlating multi-step attack behaviors and recognizing multi-step attack patterns. Experimental results in real world environment show that WMAPRM is capable of identifying highly correlated multi-step attack patterns such as WEP crack with ARP + Deauthentication Flood, WEP crack with wesside-ng, config file stealing attack and authentication session hijack attack etc. The method is expected to improve both wireless intrusion detection and prevention performance in practical WLAN security scenarios.     

Performance analysis of a threshold-based dynamic TXOP scheme for intra-AC QoS in wireless LANs

The IEEE 802.11e Enhanced Distributed Channel Access (EDCA) protocol has been proposed for provisioning of differentiated Quality-of-Service (QoS) between various Access Categories (ACs), i.e., inter-AC QoS, in Wireless Local Area Networks (WLANs). However, the EDCA lacks the support of the intra-AC QoS provisioning, which is indispensable in practical WLANs since the network loads are always asymmetric between traffic flows of ACs with the same priority. To address the intra-AC QoS issue, this paper proposes a Threshold-Based Dynamic Transmission Opportunity (TBD-TXOP) scheme which sets the TXOP limits adaptive to the current status of the transmission queue based on the pre-setting threshold. An analytical model is further developed to evaluate the QoS performance of this scheme in terms of throughput, end-to-end delay, and frame loss probability. NS-2 simulation experiments validate the accuracy of the proposed analytical model. The performance results demonstrate the efficacy of TBD-TXOP for the intra-AC QoS differentiation.     

无线网络中实时业务的信道预留

随着无线数据服务的流行和多媒体应用需求的增长,需要无线网络能够为不同种类的业务提供有区别的服务质量(QoS),因此如何在无线网络中提供有区分和有保证的服务质量,成为一个非常重要的问题。论文提出了一种在IEEE802.11无线网络中为实时业务提供服务质量保证的有效方法,即通过修改介质访问控制(MAC)层的分布式协调功能(DCF),为实时数据预留信道。当一个节点竞争到信道后,可以连续向同一个目标节点发送多个实时数据帧,称作传送突发(TB,TransmissionBurst),即在一个TB中第一个数据帧将为实时业务预留信道,直到这个TB结束,这样实时业务将比其他业务占有更多的信道资源。仿真结果表明,该方法能够明显改进实时业务的吞吐率和延迟性能,提高无线网络的信道利用率,而且,对DCF的修改没有增加任何控制开销。     

On design and performance evaluation of an integrated SIP and HCoP-B architecture for nested network mobility

This paper proposes a fully-integrated SIP + HCoP-B architecture to provide efficient mobility management of the nested mobile network. It achieves the following merits, which are rare in the literature. First, it reduces network deployment costs by only equipping an integrated SIP mobile server. Second, it supports both SIP-based and non-SIP-based applications. Third, by adopting the analytical model proposed in Mohanty and Akyildiz (2007) [19], mathematical analyses are provided to investigate six performance metrics of SIP + HCoP-B and the other four well-known SIP's over NEMO schemes over the error-prone wireless link. Finally, it is shown that SIP + HCoP-B outperforms these four traditional schemes through intensive simulations.     

Quality-of-service-aware adaptation scheme for multi-core protocol processing architecture

Employing adaptable protocol processing architectures has shown a high potential in provisioning Quality-of-Service (QoS) while retaining efficient use of available energy budget. Nevertheless, successful QoS provisioning using adaptable protocol processing architectures requires adaption to be agile and to have low latency. That is, a long adaptation latency might lead to violating desired packet processing latency, desired throughput or loss of packets if the memory fails to accommodate packet accumulation. This paper presents an elastic management scheme to permit agile and QoS-aware adaptation of processing elements (PEs) within the protocol processing architecture, such that desired QoS is maintained. Moreover, our proposed scheme has the potential to reduce energy consumption since it employs the PEs upon demand. We quantify the latency required for PEs adaptation, the reduction in energy and the reduction in area that can be achieved using our scheme. We also consider two different real-life use cases to demonstrate the effectiveness of our proposed management scheme in maintaining QoS while conserving available energy.