This paper presents an alternative traffic model for an ATM multiplexer providing video, voice, image, and data services. The traffic model classifies the input traffic into two types: real-time and non-real-time. The input process for realtime traffic is periodic and correlated, while that for non-realtime traffic is batch Poisson and independent. This multiplexer is assumed to be a priority queueing system with synchronous servers operating on time-frame basis and with separate finite buffers for each type of traffic. State probabilities and performance measures are successfully obtained using a Markov analysis technique and an application of the residue theorem in complex variable. The results can be applied in the design of an ATM multiplexer.

Recently, Hwang and Yeh demonstrated that Peyravian-Zunic's password authentication scheme is vulnerable to several attacks, and then proposed a modified version. In this letter, we show that Hwang-Yeh's scheme still has several weaknesses and drawbacks.

In this paper, a novel continuous complementary sliding control was proposed to improve the tracking performance given the available control bandwidth and the extend of parameter uncertainty. With this control law, the ultimate bound of tracking error was shown to be reduced at least by half, as compared with the conventional continuous sliding control. More strikingly, the proposed control can effectively improve the error transient response during the reaching phase. We presented a composite complementary sliding control scheme for a class of uncertain nonlinear systems including the nonlinear electrohydraulic position servo control system, which will be used as an illustrated example. Simulation results indicated exceptional good tracking performance to step and sine wave reference inputs can be obtained. In addition, the disturbance rejection property of the controller to single-frequency sinusoidal disturbances is also outstanding.

A Wavelength Division Multiaccess (WDMA) network with buffer sharing among stations is studied. All stations in the network are connected to a passive optical star coupler and each station has a different fixed wavelength laser for transmitting packets. Each station in the network reports its packet backlog to a scheduler which computes and then broadcasts a transmission schedule to all the stations through a control channel in each time slot. A transmission schedule includes two types of assignments: 1) assign a maximum number of stations for conflict-free transmissions, and 2) assign the relocation of packets from congested stations to uncongested relaying stations through idling transceivers for distributed buffer sharing. The first assignment aims at maximizing throughput and the second assignment aims at minimizing packet loss. Simulation results show that as much as 75% of the buffers can be saved with the use of buffer sharing when 50% of the packets are of the non-sequenced type.

Wireless sensor networks usually deploy sensor nodes with limited energy resources in unattended environments so that people have difficulty in replacing or recharging the depleted devices. In order to balance the energy dissipation and prolong the network lifetime, this paper proposes a routing spanning tree-based clustering algorithm (RSTCA) which uses routing spanning tree to analyze clustering. In this study, the proposed scheme consists of three phases: setup phase, cluster head (CH) selection phase and steady phase. In the setup phase, several clusters are formed by adopting the K-means algorithm to balance network load on the basis of geographic location, which solves the randomness problem in traditional distributed clustering algorithm. Meanwhile, a conditional inter-cluster data traffic routing strategy is created to simplify the networks into subsystems. For the CH selection phase, a novel CH selection method, where CH is selected by a probability based on the residual energy of each node and its estimated next-time energy consumption as a function of distance, is formulated for optimizing the energy dissipation among the nodes in the same cluster. In the steady phase, an effective modification that counters the boundary node problem by adjusting the data traffic routing is designed. Additionally, by the simulation, the construction procedure of routing spanning tree (RST) and the effect of the three phases are presented. Finally, a comparison is made between the RSTCA and the current distributed clustering protocols such as LEACH and LEACH-DT. The results show that RSTCA outperforms other protocols in terms of network lifetime, energy dissipation and coverage ratio.

The paper studies a high-ranking node in a broadband integrated services digital network(B-ISDN). The input traffic is classified into two types: real-time and non-real-time. For each type of input traffic, we assume that the message arrival process is a batch Poisson process and that the message size is arbitrarily distributed so as to describe services from narrowband to wideband. We model the high-ranking node by a queueing system with multiple synchronous servers and two separate finite buffers, one for each type of traffic. We derive performance measures exactly by using a two-dimensional imbedded discrete-time Markov chain analysis, within which the transition probabilities are obtained via an application of the residue theorem in complex variables. The performance measures include the blocking probability, delay, and throughput.

The heterogeneous network (HetNet), which deploys small cells such as picocells, femotcells, and relay nodes within macrocell, is regarded as a cost-efficient and energy-efficient approach to resolve increasing demand for data bandwidth and thus has received a lot of attention from research and industry. Since small cells share the same licensed spectrum with macrocells, concurrent transmission induces severe interference, which causes performance degradation, particularly when coordination among small cell base stations (BSs) is infeasible. Given the dense, massive, and unplanned deployment of small cells, mitigating interference in a distributed manner is a challenge and has been explored in recent papers. An efficient and innovative approach is to apply cognitive radio (CR) into HetNet, which enables small cells to sense and to adapt to their surrounding environments. Consequently, stations in each small cell are able to acquire additional information from surrounding environments and opportunistically operate in the spectrum hole, constrained by minimal inducing interference. This paper summarizes and highlights the CR-based interference mitigation approaches in orthogonal frequency division multiple access (OFDMA)-based HetNet networks. With special discussing the role of sensed information at small cells for the interference mitigation, this paper presents the potential cross-layer facilitation of the CR-enable HetNet.

Smart TVs are expected to play a leading role in the future networked intelligent screen market. Currently, many operators are planning to deploy it in large scale in a few years. Therefore, it is necessary for smart TVs to provide high quality services for users. Packet loss is one critical reason that decreases the QoS in smart TVs. Even a very small amount of packet loss (1-2%) can decrease the QoS and affect users' experience seriously. This paper applies stochastic differential equations to analyzing the queue in the buffer of access points in smart TV multicast systems, demonstrates the reason for packet loss, and then proposes an end-to-end error recovery scheme (short as OPRSFEC) whose core algorithm is based on Reed-Solomon theory, and optimizes four aspects in finite fields: 1) Using Cauchy matrix instead of Vandermonde matrix to code and decode; 2) generating inverse matrix by table look-up; 3) changing the matrix multiplication into the table look-up; 4) originally dividing the matrix multiplication. This paper implements the scheme on the application layer, which screens the heterogeneity of terminals and servers, corrects 100% packet loss (loss rate is 1%-2%) in multicast systems, and brings very little effect on real-time users experience. Simulations demonstrate that the proposed scheme has good performances, successfully runs on Sigma and Mstar Moca TV terminals, and increases the QoS of smart TVs. Recently, OPRSFEC middleware has become a part of IPTV2.0 standard in Shanghai Telecom and has been running on the Mstar boards of Haier Moca TVs properly.

This paper presents a high-throughput VLSI architecture for LZFG data compression and decompression. To reduce the hardware cost and maintain both of the interior node and the leaf node numbering systems, we modify the original LZFG data structure. Compared to the original LZFG tree, the number of characters in our modified LZFG data structure must be greater than one to establish one new interior node down the root node into the new node. Meanwhile, this architecture employs a series of encoding cells with content addressable memory (CAM) to search the longest match and maintain the LZFG data tree during the encoding and decoding processes. By using the parallel design, the compressor and decompressor can keep a constant high bit rate to encode and decode one character per clock cycle, that is, it is directly proportional to the operating clock rate, but independent of the sizes of the word dictionary and the input file. By using 0.25 µm CMOS silicon technology, the operating clock rate can be as high as 85 MHz. Some untargeted encoding cells will be disabled to reduce the power consumption during the comparison operation. Therefore, this architecture can be easily applied in the high-speed real-time communication and data storage systems.

Cooperative communication can reduce energy consumption effectively due to its superior diversity gain. To further prolong network lifetime and improve the energy efficiency, this paper studies energy-efficient packet transmission in wireless ad-hoc networks and proposes a novel cluster-based cooperative packet transmission (CCPT) protocol to mitigate the packet loss and balance the energy consumption of networks. The proposed CCPT protocol first constructs a highly energy-efficient initial routing path based on the required energy cost of non-cooperative transmission. Then an iterative cluster recruitment algorithm is proposed that selects cooperative nodes and organizing them into clusters, which can create transmit diversity in each hop of communication. Finally, a novel two-step cluster-to-cluster cooperative transmission scheme is designed, where all cluster members cooperatively forward the packet to the next-hop cluster. Simulation results show that the CCPT protocol effectively reduces the energy cost and prolongs the network lifetime compared with the previous CwR and noC schemes. The results also have shown that the proposed CCPT protocol outperforms the traditional CwR protocol in terms of transmit efficiency per energy, which indicates that CCPT protocol has achieved a better trade-off between energy and packet arrival ratio.

In this paper, the problem of target detection and tracking utilizing the single frequency network (SFN) is addressed. Specifically, by exploiting the characteristics of the signal in SFN, a novel likelihood model which avoids the measurement origin uncertain problem in the point measurement model is proposed. The particle filter based track-before-detect (PF-TBD) algorithm is adopted for the proposed SFN likelihood to detect and track the possibly existed target. The advantage of using TBD algorithm is that it is suitable for the condition of low SNR, and specially, in SFN, it can avoid the data association between the measurement and the transmitters. The performance of the adopted algorithm is examined via simulations.

This brief presents a slope analog-digital converter (ADC)-based supply voltage monitor (SVM) for biofuel-cell-powered supply-sensing systems operating in a supply voltage range of 0.18-0.35V. The proposed SVM is designed to utilize the output of energy harvester extracting power from biological reactions, realizing energy-autonomous sensor interfaces. A burst pulse generator uses a dynamic leakage suppression logic oscillator to generate a stable clock signal under the sub-threshold region for pulse counting. A slope-based voltage-to-time converter is employed to generate a pulse width proportional to the supply voltage with high linearity. The test chip of the proposed SVM is implemented in 180-nm CMOS technology with an active area of 0.018mm2. It consumes 2.1nW at 0.3V and achieves a conversion time of 117-673ms at 0.18-0.35V with a nonlinearity error of -5.5/+8.3mV, achieving an energy-efficient biosensing frontend.

In this letter, we propose an energy beamforming empowered relaying scheme for a batteryless IoT network, where wireless-powered relays are deployed between the hybrid access point (HAP) and batteryless IoT devices to assist the uplink information transmission from the devices to the HAP. In particular, the HAP first exploits energy beamforming to efficiently transmit radio frequency (RF) signals to transfer energy to the relays and as the incident signals to enable the information backscattering of batteryless IoT devices. Then, each relay uses the harvested energy to forward the decoded signals from its corresponding batteryless IoT device to the HAP, where the maximum-ratio combing is used for further performance improvement. To maximize the network sum-rate, the joint optimization of energy beamforming vectors at the HAP, network time scheduling, power allocation at the relays, and relection coefficient at the users is investigated. As the formulated problem is non-convex, we propose an alternating optimization algorithm with the variable substitution and semi-definite relaxation (SDR) techniques to solve it efficiently. Specifically, we prove that the obtained energy beamforming matrices are always rank-one. Numerical results show that compared to the benchmark schemes, the proposed scheme can achieve a significant sum-rate gain.

This paper studies a dual-hop amplify-and-forward (AF) relaying systems over shadowed Nakagami-m fading channels and derives an approximate analytical expression for the outage probability. The numerical results show that the derived analytical expression can provide very well approximations to the simulation results.

High-frequency characteristics of SiGe heterojunction bipolar transistors with different emitter sizes are studied based on pulsed measurements. Because the self-heating effect in transistors will enhance the Kirk effect, as the devices operate in high current region, the measured cutoff frequency and maximum oscillation frequency decrease with measurement time in the pulsed duration. By analyzing the equivalent small-signal device parameters, we know the reduction of cutoff frequency and maximum oscillation frequency is attributed to the reduction of transconductance and the increase of junction capacitances for fixed base-emitter voltage, while it is only attributed to the degradation of transconductance for fixed collector current. Besides, the degradation of high-frequency performance due to self-heating effect would be improved with the layout design combining narrow emitter finger and parallel-interconnected subcells structure.

This study proposes the application and implementation of a new power factor correction (PFC) with a variable slope ramp for a small wind power system without any input voltage sensing circuits or external control components in the current shaping loop. The hardware description of the variable slope ramp simplifies the complexity of integrated circuit realization with low resolution analog-to-digital converters, and achieves a high power factor for multi and three-phase AC/DC converters such as wind power systems. Up to 1 kW small wind power system is tested to verify the performance of the proposed PFC control. The highest achieved power factor reaches 99.5%.

LT codes are the first practical rateless codes whose reception overhead totally depends on the degree distribution adopted. The capability of LT codes with a particular degree distribution named robust soliton has been theoretically analyzed; it asymptotically approaches the optimum when the message length approaches infinity. However, real applications making use of LT codes have finite number of input symbols. It is quite important to refine degree distributions because there are distributions whose performance can exceed that of the robust soliton distribution for short message length. In this work, a practical framework that employs evolutionary algorithms is proposed to search for better degree distributions. Our experiments empirically prove that the proposed framework is robust and can customize degree distributions for LT codes with different message length. The decoding error probabilities of the distributions found in the experiments compare well with those of robust soliton distributions. The significant improvement of LT codes with the optimized degree distributions is demonstrated in the paper.

In the Coordinated Multi-Point (CoMP) system under the condition of limited feedback, a reasonable coordinated set relies heavily on the splitting factor that is used to divide the total feedback bits into channel direction information (CDI) feedback bits and channel quality information (CQI) feedback bits. The relation of splitting factor and coordinated set is examined in this paper. After defining a penalty factor, we derive the net ergodic capacity optimization problem, whose variables to be optimized are the number of coordinated BSs, the divided area's radius and the splitting factor. According to an existing codebook and the quantized channel error model, the downlink received signal model is updated after adding the splitting factor. Through random matrix knowledge, the stochastic property of this model is obtained. A close approximate expression including the splitting factor to be optimized related to coordinated set is given. In addition, a revised adaptive feedback scheme is proposed to split the feedback bits. Simulation results show that the proposed scheme provides a significant performance gain, especially as the user velocity is high.

With the advancement of VLSI manufacturing technology, entire electronic systems can be implemented in a single integrated circuit. Due to the complexity in SoC design, circuit testability becomes one of the most challenging works. Without careful planning in Design For Testability (DFT) design, circuits consume more power in test mode operation than that in normal functional mode. This elevated testing power may cause problems including overall yield lost and instant circuit damage. In this paper, we present two approaches to minimize scan based DFT power dissipation. First methodology includes routing cost consideration in scan chain reordering after cell placement, while second methodology provides test pattern compression for lower power. We formulate the first problem as a Traveling Salesman Problem (TSP), with different cost evaluation from, and apply an efficient heuristic to solve it. In the second problem, we provide a selective scan chain architecture and perform a simple yet effective encoding scheme for lower scan testing power dissipation. The experimental results of ISCAS'89 benchmarks show that the first methodology obtains up to 10% average power saving under the same low routing cost compared with a recent result in . The second methodology reduces over 17% of test power compared with filling all don't care (X) bit with 0 in one of ISCAS'89 benchmarks. We also provide the integration flow of these two approaches in this paper.

Voice over Internet protocol (VoIP) is to transfer voice packets over IP networks, while voice signal is processed by using digital signal processing technology before being transmitted. VoIP quality cannot be expected, because it is hard to predict the influence of delay, packet loss rate, packet error, etc. It is difficult to rebuild the voice wave form, if a large amount of voice packets are lost. This paper mainly studies on how to maintain a better voice quality over hybrid fiber/coaxial (HFC) networks, if it is inevitable to drop packets. We particularly consider the data over cable service interface specification (DOCSIS) version 1.1 with the unsolicited grant service with activity detection (UGS/AD) for VoIP services. We propose a smallest successive times first (SSTF) scheduling algorithm to schedule VoIP packets for cable modem termination system (CMTS), which can support fair transmission and long-term transmission continuity for VoIP connections. We analyze voice quality about continuity of the transmitted VoIP packets, consecutive clipping times, and VoIP packet drop rate for all connections. Performance measurement shows excellent results for the proposed algorithm by simulation experiments and objective evaluation.