Xin-Wei Yao

A fast CU depth decision mechanism for HEVC

HEVC requires a high computational complexity.The RD cost calculations outside the adaptive CU depth range are skipped.The RD cost calculations at the current CU depth are further skipped.The computational complexity of HEVC is reduced by about 16% on average.The proposed mechanism still maintains high video quality. In order to reduce the computational complexity of High Efficiency Video Coding (HEVC), a fast Coding Unit (CU) depth decision mechanism is proposed by utilizing the spacial correlations in the sequence frame. The proposed mechanism includes an adaptive CU depth range determination and a CU depth comparison algorithm. CU depth range is determined according to the distribution of CU depths in the same sequence. Thus, the Rate Distortion (RD) cost calculations at the CU depths outside of the range can be skipped. Furthermore, by comparing the depths of neighbor CUs with the current CU depth, the RD cost calculations at the current CU depth may be further skipped. Experimental results show that the proposed mechanism achieves a significant reduction of the computational complexity by comparing with the original HEVC, while still maintaining high video quality.

Ipb-frame adaptive mapping mechanism for video transmission over IEEE 802.11e WLANs

This paper proposed an IPB-frame Adaptive Mapping Mechanism (AMM) to improve the video transmission quality over IEEE 802.11e Wireless Local Area Networks (WLANs). Based on the frame structure of hierarchical coding technology, the probability of each frame allocated to the most appropriate Access Category (AC) was dynamically updated according to its importance and traffic load of each AC. Simulation results showed the superior performance of the proposed AMM by comparing with three other existing mechanisms in terms of three objective metrics.

Bio-inspired self-adaptive rate control for multi-priority data transmission over WLANs

In Wireless Local Area Networks (WLANs), the unpredictable injection of traffic load and the limitations of DCF based bandwidth allocation may result in network congestion. Also the Quality of Service (QoS) of data flows with different priorities may not be strictly guaranteed. In order to support service differentiation and guarantee QoS of data transmission over WLANs, based on the extended Lotka-Volterra (LV) biological competitive model, a bio-inspired self-adaptive rate control approach for multi-priority data transmission is proposed in this paper. This approach guides data flows to compete for network bandwidth in the way of a native ecosystem. As a result, both service differentiation and QoS can be guaranteed, simultaneously. In particular, it also achieves higher bandwidth utilization. Then the proposed approach is applied to four categories of data flows defined in the EDCA protocol, the allocated bandwidth of each category is optimized through model parameters (i.e. competition coefficients among categories) optimization. Extensive simulation studies have been conducted to show the superior performance of the proposed approach. Under the recommended model parameter values, the total bandwidth utilization is maximized up to 93% compared with 60-70% achieved by the EDCA protocol, whilst maintaining the service differentiation of multi-priority flows.

Video streaming transmission: performance modelling over wireless local area networks under saturation condition

Transmitting delay-sensitive video streaming over IEEE 802.11e wireless local area networks (WLANs) is becoming increasingly popular. However, the transmission of real-time video streaming is very challenging because of the time-varying wireless channels and video content characteristics. The authors propose an accurate model to assess the perceived quality of video streaming over WLANs with enhanced distributed coordination function (EDCF) mechanism. The analytical model considers not only the packet loss caused by wireless interference and channel fading, but also the effects of loss from channel access competition. Based on the Markov chain, the authors then present the discrete probability distribution of medium access control (MAC) layer packet service time by using the signal transfer function of the generalised state transition diagram. Moreover, the coding relation of lost video frames is also explored in the performance analysis of the proposed model. Simulations based on Network Simulator 2 (NS-2) are conducted to verify the performance of the analytical model. The results show that the proposed model provides superior accuracy for the perceived quality of MPEG-4 video streaming over IEEE 802.11e EDCF-based WLANs.

Joint Parameter Optimization for Perpetual Nanonetworks and Maximum Network Capacity

One of the major bottlenecks in nanonetworks is the very limited energy that can be accessed by nanodevices. To achieve perpetual data transmission, it is required to investigate in-depth the relationship between energy harvesting and consumption, and the underlying constraints in nanonetworks. In this paper, the tradeoff between energy harvesting and consumption is analyzed by considering the peculiarities of THz communication. First, based on the TS-OOK scheme and constrained energy in nanodevices, the upper bound of the transmitted pulse amplitude is presented. Second, given the proposed mathematical expression of the signal-to-interference-noise ratio (SINR) in multi-user nanonetworks, the lower bound of pulse amplitude is presented to satisfy the required SINR threshold. Third, the minimum spreading factor is derived to guarantee the perpetual nanonetworks by considering the energy harvesting-consumption tradeoff. Finally, the maximization of network capacity is investigated by jointly optimizing the parameters of spreading factor, transmission distance, amplitude of the transmitted pulse, pulse probability, and node density for perpetual nanonetworks. The simulation results demonstrate short transmission distance and small spreading factor are recommended to improve the network capacity. Moreover, pulse probability, pulse amplitude, spreading factor, and node density are required to be comprehensively manipulated to achieve the maximum network capacity and perpetual communication.

A Novel Hybrid Slot Allocation Mechanism for 802.11e EDCA Protocol

This letter proposes a novel Hybrid Slot Allocation Mechanism (HSAM) to solve the high collision problem among four Access Categories (ACs) introduced by IEEE 802.11e EDCA protocol. In the HSAM, three time slots are assembled into a super-slot, each slot in the super slot is allocated to a particular AC according to its priority. The main idea of HSAM is to stagger the transmission slots of different ACs to reduce collisions, while maintaining the service differentiation. Extensive results from simulations have demonstrated good performance of HSAM comparing with EDCA protocol in terms of throughput, packet loss and MAC delay.

PABM-EDCF: parameter adaptive bi-directional mapping mechanism for video transmission over WSNs

To support and keep high quality of video transmission over wireless sensor networks, this paper proposes a parameter adaptive bi-directional cross-layer mapping algorithm on the basis of the operation mechanism of IEEE 802.11e Enhanced Distributed Coordination Function (EDCF) supporting video service differentiation, named PABM-EDCF. Instead of classifying video data to a specific access category in 802.11e network, our proposed adaptive cross-layer scheme makes use of the hierarchy characteristic of video stream, dynamically maps video data to the appropriate access categories according to both the significance of the different video frames and the network traffic load. The significance passes from the application layer to the media access layer through a cross-layer architecture. In order to prevent the network congestion and keep the high transmission quality, the proposed algorithm adopts bi-directional floating mapping algorithm and congestion awareness mechanism based on the queue length and frame types. The mapping parameters are updated according to the network condition in time. Our simulation results indicate: the proposed method (a) improves the video transmission quality; (b) optimizes the management and utilization of queue resources; and (c) yields superior performance (under different loads) over 802.11e, static mapping and adaptive mapping schemes.

MA-ADM: A memory-assisted angular-division-multiplexing MAC protocol in Terahertz communication networks

Abstract Terahertz band communication is envisioned as a key technology to satisfy the increasing demand for ultra-high-speed wireless links and enable interconnections in a nanonetwork. In this paper, a memory-assisted medium access control (MAC) protocol with angular-division-multiplexing (ADM) is proposed for THz communication networks. The service region of an access point (AP) is divided into multiple angular slots by exploiting the 3D quantized angular space, For efficient service discovery and communications, a node equips with (i) the omni-directional antennas at the service discovery phase, and (ii) directional antennas for message transmissions. Moreover, the memory is leveraged in the ADM scheme to assist the AP to skip the unregistered angular slots to improve the network performance. Based on the proposed MAC protocol, the analytical models of the interference, SINR, outage probability, throughput and the delay in the THz network are derived respectively. According to the simulation and numerical analysis, the results show that our proposed MAC protocol can effectively improve the throughput by over 15% and substantially reduce the delay, in comparison with the ADM scheme without the memory guidance.

Pulse Position Coding for Information Capacity Promotion in Electromagnetic Nanonetworks

With the development of nanotechnology, Wireless Nano Sensor Networks (WNSN) have been envisioned for many unique applications. In order to optimize the data transmission in nanonetworks, the information rate of individual nanonode should be manipulated to maximize the network capacity. In this paper, information capacity is formulated as a function of the parameters of transmission distance and spreading factor in data transmission. The information interference is also presented and regulated by proposing a novel Pulse Position Coding (PPC) for nanonetworks. According to the experimental results, the achievable information capacity is improved significantly with the proposed coding mechanism, and the most appropriate values of spreading factor and transmission distance for nanonetworks are recommended. Moreover, low interference power is also achieved with PPC mechanism.

Bio-inspired rate control scheme for IEEE 802.11e WLANs

The uncontrolled use of limited resources in conjunction with unpredictable nature of traffic load injection in Wireless Local Area Networks (WLANs) may lead to congestion, and cannot guarantee strict Quality of Service (QoS) required by real-time service. Rate control is an important mechanism for the provisioning of QoS in the IEEE 802.11e WLANs. In this paper, a bio-inspired rate control scheme is proposed based on the extended Lotka-Volterra model, which considers the effects of arrival traffic on the system stability according to the limited network resources and competitions with others traffic flows, and ensures that the network works in unsaturated case and rapidly converge to a global stable equilibrium point (EP). Moreover, all traffic flows are of peaceful coexistence and QoS differentiation. Extensive simulations are conducted to illustrate the performance of the proposed rate control scheme.