In heterogeneous cellular networks (HCN), which consists of macrocells and picocells, efficient interference management schemes between macrocells and picocells are crucial to the overall system performance. We propose a dynamic cooperative silencing (DCS) scheme for intercell interference control (ICIC). It is a low-complexity, low-feedback and distributed algorithm using only strongly interfered neighboring user information. A system simulation shows that the system performance and in particular the cell-edge throughput is significantly increased with the proposed silencing scheme.

The purpose of this paper is to present the static and dynamic characteristics and a smart design approach for the digital PID control forward type multiple-output dc-dc converter. The central problem of a smart design approach is how to decide the integral coefficient. Since the integral coefficient decision depends on the static characteristics, whatever integral coefficient is selected will not be yield superior dynamic characteristics. Accordingly, it is important to identify the integral coefficient that optimizes static as well as dynamic characteristics. In proposed design approach, it set the upper and lower of input voltage and output current of regulation range. The optimal integral coefficient is decided by the regulation range of the static characteristics and the dynamic characteristics and then the smart design approach is summarized. As a result, the convergence time is improved 50% compared with the conventional designed circuit.

Carrier aggregation (CA) is one of the most important techniques for LTE-Advanced because of its capability to support a wide transmission bandwidth of up to 100 MHz and heterogeneous networks effectively while achieving backward compatibility with the Release 8 LTE. In order to improve the performance of control information transmission in heterogeneous networks, cross-carrier scheduling is supported, i.e., control information on one component carrier (CC) can assign radio resources on another CC. To convey the control information efficiently, a search space is defined and used in Release 8 LTE. In cross-carrier scheduling, the optimum design for the search space for different CCs is a paramount issue. This paper presents two novel methods for search space design. In the first method using one hash function, a user equipment (UE)-specific offset is introduced among search spaces associated with different CCs. Due to the UE-specific offsets, search spaces of different UEs are staggered and the probability that the search space of one UE is totally overlapped by that of another UE can be greatly reduced. In the second method using multiple hash functions, a novel randomization scheme is proposed to generate independent hash functions for search spaces of different CCs. Because of the perfect randomization effect of the proposed method, search space overlapping of different UEs is reduced. Simulation results show that both the proposed methods effectively reduce the blocking probability of the control information compared to existing methods.

In this letter, we show that the code-trellis and the error-trellis for a convolutional code can be reduced simultaneously, if reduction is possible. Assume that the error-trellis can be reduced by shifting particular error-subsequences. In this case, if the identical shifts occur in the corresponding subsequences of each code-path, then the code-trellis can also be reduced. First, we obtain pairs of transformations which generate the identical shifts both in the subsequences of the code-path and in those of the error-path. Next, by applying these transformations to the generator matrix and the parity-check matrix, we show that reduction of these matrices is accomplished simultaneously, if it is possible. Moreover, it is shown that the two associated trellises are also reduced simultaneously.

A finite buffer shared by multiple packet queues is considered. Partitioning the buffer to maximize total throughput is formulated as a resource allocation problem, the solution is shown to be achieved by a greedy incremental algorithm in polynomial time. The optimal buffer allocation strategy is applied to different models for a wireless downlink. First, a set of parallel M/M/1/mi queues, corresponding to a downlink with orthogonal channels is considered. It is verified that at high load, optimal buffer partitioning can boost the throughput significantly with respect to complete sharing of the buffer. Next, the problem of optimal combined buffer allocation and channel assignment problems are shown to be separable in an outage scenario. Motivated by this observation, buffer allocation is considered in a system where users need to be multiplexed and scheduled based on channel state. It is observed that under finite buffers in the high load regime, scheduling simply with respect to channel state with a simply partitioned buffer achieves comparable throughput to combined channel and queue-aware scheduling.

In Long-Term Evolution (LTE)-Advanced, an important goal in addition to achieving high-speed, high-capacity communications is throughput enhancement for cell-edge users. One solution is to relay radio transmissions between an eNode B and user equipment (UE). Relays are expected to extend the coverage to the cell boundary and coverage hole areas, and are expected to reduce network costs. It was agreed that in Release 10 LTE, a Layer-3 (L3) relay, which achieves self-backhauling of radio signals between an eNode B and a UE in Layer 3 should be standardized. Meanwhile, a Layer-1 (L1) relay, which amplifies and forwards received radio frequency signals, has already found widespread use in second-generation and third-generation mobile communication systems. This paper investigates the downlink system level performance for L3 and L1 relays with orthogonal frequency division multiple access (OFDMA) in LTE-Advanced. Various practical factors are taken into account in the evaluations such as the processing delay and upper bound of the amplifier gain of the L1 relay, capacity limitation of the backhaul channels, and empty buffer status at the L3 relay. We also propose and investigate a downlink backhaul link (radio link between the eNode B and L3 relay node) scheduling method for the in-band half-duplex L3 relay. In the proposed scheduling method, radio resources from an eNode B to an L3 relay node and macro UE are multiplexed in the same backhaul subframe considering the number of relay UEs and macro UEs, and the channel quality of the backhaul link to the L3 relay and the access link to the macro UE. Based on system-level simulations, we clarify the system impact of several conditions for the relay such as the number of relay nodes and the number of backhaul (radio link between eNode B and L3 relay) subframes, the distance between the eNode B and relay, and show the throughput performance gain of the L3 relay compared to the L1 relay. We also clarify that the cell-edge UE throughput performance is increased by approximately 10% by applying the proposed scheduling method due to more efficient and fair resource allocation to the L3 relay and macro UEs.

In this paper, we propose an iterative minimum mean square error detection with interference cancellation (MMSED-IC) for frequency-domain filtered single carrier (SC)-frequency-division multiple-access (FDMA) uplink transmission. The use of a square-root Nyquist transmit filter reduces the peak-to-average power ratio (PAPR) while increases the frequency-diversity gain. However, if carrier-frequency separation among multiple-access users is kept the same as the one used for the case of roll-off factor α=0 (i.e., brick-wall filter), then the adjacent users' spectra will overlap and multi-user interference (MUI) occurs. The proposed MMSED-IC can sufficiently suppress the MUI from adjacent users while achieving the maximum frequency-diversity gain. We apply the proposed MMSED-IC to a packet access using filtered SC-FDMA, multi-input multi-output (MIMO) multiplexing, and hybrid automatic repeat request (HARQ). It is shown by computer simulation that filtered SC-FDMA with α=1 can achieve higher throughput than orthogonal frequency division multiple access (OFDMA).

Orthogonal frequency division multiple access (OFDMA) is adopted as a multiuser access scheme in recent cellular systems such as long term evolution (LTE) and WiMAX. In those systems, the performance improvement on cell-edge users is crucial to provide high-speed services. We propose a new resource allocation scheme based on multiple input multiple output – orthogonal frequency division multiple access – code division multiplexing (MIMO-OFDMA-CDM) to achieve performance improvements in terms of cell-edge user throughput, bit error rate, and fairness among users. The proposed scheme adopts code division multiplexing for MIMO-OFDMA and a modified proportional fairness algorithm for CDM, which enables the fairness among users and a higher throughput. The performance improvements are clarified by theoretical analysis and simulations.

The digital logic rewiring technique has been shown to be one of the most powerful logic transformation methods. It has been proven that rewiring is able to further improve some already excellent results on many EDA problems, ranging from logic minimization, partitioning, FPGA technology mappings to final routings. Previous studies have shown that ATPG-based rewiring is one of the most powerful tools for logic perturbation while a graph-based rewiring engine is able to cover nearly one fifth of the target wires with 50 times runtime speedup. For some problems that only require good-enough and very quick solutions, this new rewiring technique may serve as a useful and more practical alternative. In this work, essential elements in graph-based rewiring such as rewiring patterns, pattern size and locality, etc., have been studied to understand their relationship with rewiring performance. A structural analysis on the target-alternative wire pairs discovered by ATPG-based and graph-based engines has also been conducted to analyze the structural characteristics that favor the identification of alternative wires. We have also developed a hybrid rewiring approach that can take the advantages from both ATPG-based and graph-based rewiring. Experimental results suggest that our hybrid engine is able to achieve about 50% of alternative wire coverage when compared with the state-of-the-art ATPG-based rewiring engine with only 4% of the runtime. Through applying our hybrid rewiring approach to the FGPA technology mapping problem, we could achieve similar depth level and look-up table number reductions with much shorter runtime. This shows that the fast runtime of our hybrid approach does not sacrifice the quality of certain rewiring applications.

This paper presents an overview of radio interface technologies for cooperative transmission in 3GPP LTE-Advanced, i.e., coordinated multi-point (CoMP) transmission, enhanced inter-cell interference coordination (eICIC) for heterogeneous deployments, and relay transmission techniques. This paper covers not only the technical components in the 3GPP specifications that have already been released, but also those that were discussed in the Study Item phase of LTE-Advanced, and those that are currently being discussed in 3GPP for potential specification in future LTE releases.

This paper proposes a novel approach to traffic state estimation using mobile phones. In this work, a real-time traffic data collection policy based on the so-called “3R” philosophy, a unique vehicle classification method, and a reasonable traffic state quantification model are proposed. The “3R” philosophy, in which the Right data are collected by the Right mobile devices at the Right time, helps to improve not only the effectiveness but also the scalability of the traffic state estimation model. The vehicle classification method using the simple data collected by mobile phones makes the traffic state estimation more accurate. The traffic state quantification model integrates both the mean speed capacity and the density of a traffic flow to improve the comprehensibility of the traffic condition. The experimental results reveal the effectiveness as well as the robustness of the proposed solutions.

With the progress of process technology in recent years, low voltage power supplies have become quite predominant. With this, the voltage margin has decreased and therefore the on-chip decoupling capacitance optimization that satisfies the voltage drop constraint becomes more important. In addition, the reduction of the on-chip decoupling capacitance area will reduce the chip area and, therefore, manufacturing costs. Hence, we propose an algorithm that satisfies the voltage drop constraint and at the same time, minimizes the total on-chip decoupling capacitance area. The proposed algorithm uses the idea of the network algorithm where the path which has the most influence on voltage drop is found. Voltage drop is improved by adding the on-chip capacitance to the node on the path. The proposed algorithm is efficient and effectively adds the on-chip capacitance to the greatest influence on the voltage drop. Experimental results demonstrate that, with the proposed algorithm, real size power/ground network could be optimized in just a few minutes which are quite practical. Compared with the conventional algorithm, we confirmed that the total on-chip decoupling capacitance area of the power/ground network was reducible by about 4050%.

We propose a novel saliency detection model based on Bayes' theorem. The model integrates the two parts of Bayes' equation to measure saliency, each part of which was considered separately in the previous models. The proposed model measures saliency by computing local kernel density estimation of features in the center-surround region and global kernel density estimation of features at each pixel across the whole image. Under the proposed model, a saliency detection method is presented that extracts DCT (Discrete Cosine Transform) magnitude of local region around each pixel as the feature. Experiments show that the proposed model not only performs competitively on psychological patterns and better than the current state-of-the-art models on human visual fixation data, but also is robust against signal uncertainty.

A signal model and weighted-average based estimation techniques are proposed to estimate the angle-of-arrival (AOA) parameters of multiple clusters for a low data rate ultrawide band (LR-UWB) based wireless positioning system. The optimal AOA estimation techniques for the LR-UWB wireless positioning system according to the cluster condition are introduced and it is shown that the proposed techniques are superior to the conventional technique from the standpoint of performance.

This letter proposes a practical scheme that can estimate ADSL link rates. The proposed scheme allows us to estimate ADSL link rates from measurements made at the NOC using existing communications protocols and network node facilities; it imposes no heavy traffic overhead. The proposed scheme consists of two major steps. The first step is to collect measured data of round trip times (RTT) for both long and short packets to find their minimum values of RTTs by sending Internet Control Message Protocol (ICMP) echo request messages. The second step is to estimate the ADSL down- and up-link rates by using the difference in RTT between long and short packets and the experimentally-obtained correlated relationships between ADSL down- and up-link rates. RTTs are experimentally measured for an IP network, and it is shown that the down- and up-link rates can be obtained in a simple manner.

In this study, we investigate reference signal (RS) transmission schemes that aim to efficiently support coordinated multi-point (CoMP) transmission by providing improved channel estimation accuracy so that transmission parameters can be appropriately chosen on a cellular network. First, we investigate typical scenarios for transmission parameter selection with the widely used CoMP transmission and precoding schemes aligned with those considered for Long Term Evolution (LTE)-Advanced systems. Second, we investigate an RS transmission scheme that can provide accurate channel estimation even with severe inter-cell interference. Finally, we verify the performance benefit of the investigated scheme by a multi-cell link level evaluation. The results obtained indicate: 1) the investigated scheme improves block error rate performance compared to conventional schemes for fixed modulation and coding schemes (MCSs) allocation with a better precoding control accuracy on the LTE-Advanced system downlink and 2) the investigated scheme provides a throughput performance gain compared to conventional schemes for adaptive MCS allocation and coordinated beamforming.

This paper presents a 65-nm CMOS 8-antenna array transmitter operating in 117–130-GHz range for short range and portable millimeter-wave (mm-wave) active imaging applications. Each antenna element is a new on-chip antenna located on the top metal. By using on-chip transformer, pulse output of each resistor-less mm-wave pulse generators (PG) are sent to each integrated antenna. To adjust pulse delays for the purpose of pulse beam-forming, a 7-bit digitally programmable delay circuit (DPDC) is added to each of PGs. Moreover, in order to dynamically adjust pulse delays among eight SW's outputs, we implemented on-chip jitter and relative skew measuring circuit with 20-bit digital output to achieve cumulative distribution (CDF) and probability density (PDF) functions from which DPDC's input codes are decided to align eight antenna's output pulses. Two measured radiation peaks after relative skew alignment are obtained at (θ; φ) angles of (-56; 0) and (+57; 0). Measurement results shows that beam-forming angles of the fully integrated antenna array can be adjusted by digital input codes and by the on-chip skew adjustment circuit for active imaging applications.

Device-parameter estimation sensors inside a chip are gaining its importance as the post-fabrication tuning is becoming of a practical use. In estimation of variational parameters using on-chip sensors, it is often assumed that the outputs of variation sensors are not affected by random variations. However, random variations can deteriorate the accuracy of the estimation result. In this paper, we propose a device-parameter estimation method with on-chip variation sensors explicitly considering random variability. The proposed method derives the global variation parameters and the standard deviation of the random variability using the maximum likelihood estimation. We experimentally verified that the proposed method improves the accuracy of device-parameter estimation by 11.1 to 73.4% compared to the conventional method that neglects random variations.

In this paper, a distributed cooperative multicell beamforming algorithm is proposed, and a detail analysis and solving method for instantaneous and statistical channel state information (CSI) are presented. Firstly, an improved distributed iterative beamforming algorithm is proposed for the multiple-input single-output interference channel (MISO IC) scenario which chooses virtual signal-to-interference-and-noise (SINR) as decision criterion to initialize and then iteratively solves the constrained optimization problem of maximizing the virtual SINR for a given level of generated interference to other users. Then, the algorithm is generalized to the multicell date sharing scenario with a heuristics power allocation scheme based on a viewpoint of the layered channel. Finally, the performance is illustrated through numerical simulations.

In the framework of supervisory control of timed discrete event systems (TDESs), a supervisor decides the set of events to be enabled to occur and the set of events to be forced to occur in order for a given specification to be satisfied. In this paper, we consider decentralized supervisory control of TDESs where enforcement decisions of local supervisors are fused by the AND rule or the OR rule. We derive existence conditions of a decentralized supervisor under these decision fusion rules.