THE UNIFICATION OF DIFFERENTIAL ENCODING AND DECODING ALGORITHM FOR VARIOUS SIGNALS

Many monographs point out that differential encoding and decoding is necessary for ef- fectual information transmission against phase ambiguity while seldom discuss the reason why phase ambiguity will emerge inevitably.Available algorithms are specially designed for certain modulation scheme;these algorithms cannot satisfy the requirement of soft-defined radio,which perhaps demands a uniform algorithm for different modulations.This paper proposes a new opinion on phase ambiguity from the view of probability.This opinion believes that modulating symbol sequence can affect,at optimum sampling epoch,the modulated waveform as oscillating carrier has done,and so the stochastic sequence leads to phase ambiguity.Based on a general signal model,this paper also puts forward a novel universal algorithm,which is suitable for different signals,even some new ones,by configuring several parameters.

Stability and Robust Stability of Switched Positive Linear Systems With All Modes Unstable

This paper is concerned with the stability and robust stability of switched positive linear systems(SPLSs) whose subsystems are all unstable. By means of the mode-dependent dwell time approach and a class of discretized co-positive Lyapunov functions, some stability conditions of switched positive linear systems with all modes unstable are derived in both the continuous-time and the discrete-time cases, respectively. The copositive Lyapunov functions constructed in this paper are timevarying during the dwell time and time-invariant afterwards. In addition, the above approach is extended to the switched interval positive systems. A numerical example is proposed to illustrate our approach.

LESO-based Position Synchronization Control for Networked Multi-Axis Servo Systems With Time-Varying Delay

The position synchronization control(PSC) problem is studied for networked multi-axis servo systems(NMASSs) with time-varying delay that is smaller than one sampling period. To improve the control performance of the system, time-varying delays, modeling uncertainties, and external disturbances are first modeled as a lumped disturbance. Then, a linear extended state observer(LESO) is devised to estimate the system state and the lumped disturbance, and a linear feedback controller with disturbance compensation is designed to perform individual-axis tracking control. After that, a cross-coupled control approach is used to further improve synchronization performance. The bounded-input-bounded-output(BIBO) stability of the closedloop control system is analyzed. Finally, both simulation and experiment are carried out to demonstrate the effectiveness of the proposed method.

Smart Caching for QoS-Guaranteed Device-to-Device Content Delivery

Caching at user equipment(UE) provides a feasible way for device-to-device(D2D) content delivery among proximal users without deploying additional infrastructures. To support D2D content delivery for mobile traffics with quality-of-service(QoS) requirements, smart caching problem is essential to be solved especially when there is no prior knowledge on demands of proximal users. In this paper, impacts of Qo S requirements and limited caching capacity on UE caching are analyzed, respectively, based on which a caching scheme is proposed. With the proposed caching scheme, UE can determine whether caching a content or not intelligently to guarantee a content request via D2D communications in the network. Simulation results are presented which verify the analyzed influencing factors on D2D caching and the proposed QoS-provisioning caching scheme.

LPR-Trie: A Fast IPv6 Routing Lookup Algorithm with Virtual Nodes

The number of IPv6 routes in todays backbone routers has grown rapidly,which has put tremendous pressure on route lookup and storage.Based on the analysis of IPv6 address prefix length and distribution characteristics,this paper proposes an IPv6 route lookup architecture called LPR-Trie.The core idea of the algorithm is to utilize more spaces and accelerate routing lookup.Moreover,we put forward the concept of virtual nodes,and leverage the link between virtual nodes and ordinary nodes to accelerate routing lookup.We provide the longest prefix routing entry(LPR)calculation algorithm to achieve the longest prefix match.The experimental results show that the virtual node mechanism increases the search speed up to 244%,and the virtual nodes have better stability by setting an appropriate keep-alive time according to the characteristics of actual traffic.This paper shows that our design improves the routing lookup speed and have better memory utilization.

5G ENTERING INTO A NEW ERA

The ever increasing wireless data services, such asimaging, video, audio, multimedia, etc., have de-mands for the very high speed wireless communicationsand network, which are unfortunately a bottleneck whencombining with the wireline core network. Users＇ arenow expecting high quality of experience with low-costdevices, ubiquitous connectivity, energy efficiency, highreliability, or even ultra-low latency if a vehicle terminalis applied.

Vulnerability Assessment of Distributed Load Shedding Algorithm for Active Distribution Power System Under Denial of Service Attack

In order to deal with frequency deviation andsupply-demand imbalance in active distribution power system, inthis paper a distributed under frequency load shedding (UFLS)strategy is proposed. Different from conventional centralizedUFLS schemes, no centralized master station gathering all thebuses’ information is required. Instead, each bus decides itsown load shedding amount by only relying on limited peer-topeer communication. However, such UFLS strategy may sufferfrom some unexpected cyber-attacks such as integrity attacksand denial of service (DoS) attack. The latter DoS attack aimsto degrade the system performance by jamming or breakingthe communication, which is of high probability to happen inpractical power system. To assess the vulnerability of proposeddistributed UFLS algorithm, the effect of DoS attack on distributed average consensus algorithm is theoretically derived,which indicates that the final consensus value can be estimatedby a given attack probability. It is also investigated that such DoSattack does harm to the load shedding amount and finally affectsthe system frequency performance in the active distributionpower system. Several case studies implemented on an IEEE33-bus active distribution power system are conducted to verifythe effectiveness of the theoretical findings and investigate thevulnerability of the considered power system.

MIMO-OFDM system based on fractional Fourier transform and selecting algorithm for optimal order

In the rapidly time-varying channel environment,the performance of traditional MIMO-OFDM system is deteriorated due to the intercarrier interference. In this paper,a novel MIMO-OFDM system is proposed,in which the modulation and demodulation of the symbols are implemented by the fractional Fourier transform instead of traditional Fourier transform. Through selecting the optimal order of the fractional Fourier transform,the modulated signals can match the time-varying channel characteristics,which results in a mitigation of the intercarrier interference. Furthermore,an algorithm is presented for selecting the optimal order of fractional Fourier transform,and the impact of system parameters on the optimal order is analyzed. Simulation results show that the proposed system can concentrate the power of desired signal effectively and improve the performance over rapidly time-varying channels with respect to the traditional MIMO-OFDM system.

Performance Evaluation and Dynamic Optimization of Speed Scaling on Web Servers in Cloud Computing

The energy consumption in large-scale data centers is attracting more and more attention today with the increasing data center energy costs making the enhanced performance very expensive. This is becoming a bottleneck to further developments in terms of both scale and performance of cloud computing. Thus, the reduction of the energy consumption by data centers is becoming a key research topic in green IT and green computing. The web servers providing cloud service computing run at various speeds for different scenarios. By shifting among these states using speed scaling, the energy consumption is proportional to the workload, which is termed energy-proportionality. This study uses stochastic service decision nets to investigate energy-efficient speed scaling on web servers. This model combines stochastic Petri nets with Markov decision process models. This enables the model to dynamically optimize the speed scaling strategy and make performance evaluations. The model is graphical and intuitive enough to characterize complicated system behavior and decisions. The model is service-oriented using the typical service patterns to reduce the complex model to a simple model with a smaller state space. Performance and reward equivalent analyse substantially reduces the system behavior sub-net. The model gives the optimal strategy and evaluates performance and energy metrics more concisely.

Unified Residue Method for Design of Compact Wide-area Damping Controller Based on Power System Stabilizer

A wide-area damping controller(WADC)is effective in damping inter-area low-frequency oscillation(LFO),if the time delay in a wide-area control loop can be properly handled.In order to simplify the WADC design and enlarge the delay adaptation range,the classic power system stabilizer(PSS)is adopted,and a new unified residue(UR)method is proposed for compact WADC design.The strategy of control loop selection is also improved by modifying the relative residue index based on a few dominant oscillation modes.The designed PSSbased compact WADC is as simple as classic PSS with no more than two lead-lag phase compensation units.Case studies are carried out on an IEEE 16-machine 68-bus power system.Simulation results demonstrate that the control loop selection before the WADC design is necessary and that the proposed selection strategy can easily pick out the suitable candidate control loops.In addition,it is feasible for the UR method to design WADCs with different time delays in the selected control loops.All the designed WADCs are effective in damping inter-area LFO and robust to time delay variations under operation conditions.Comparisons among five design methods for PSS-based WADC show that the proposed UR method is superior in delay adaptation,the conciseness of WADC structure and computation speed of parameters.