In this paper we propose a method to use features of an individual object to locate and recognize this object concurrently in a static image with Multi-feature fusion based on multiple objects sample library. This method is proposed based on the observation that lots of previous works focuses on category recognition and takes advantage of common characters of special category to detect the existence of it. However, these algorithms cease to be effective if we search existence of individual objects instead of categories in complex background. To solve this problem, we abandon the concept of category and propose an effective way to use directly features of an individual object as clues to detection and recognition. In our system, we import multi-feature fusion method based on colour histogram and prominent SIFT (p-SIFT) feature to improve detection and recognition accuracy rate. p-SIFT feature is an improved SIFT feature acquired by further feature extraction of correlation information based on Feature Matrix aiming at low computation complexity with good matching rate that is proposed by ourselves. In process of detecting object, we abandon conventional methods and instead take full use of multi-feature to start with a simple but effective way-using colour feature to reduce amounts of patches of interest (POI). Our method is evaluated on several publicly available datasets including Pascal VOC 2005 dataset, Objects101 and datasets provided by Achanta et al.

I propose an acoustic model adaptation method using bases constructed through the sparse principal component analysis (SPCA) of acoustic models trained in a clean environment. I perform experiments on adaptation to a new speaker and noise. The SPCA-based method outperforms the PCA-based method in the presence of babble noise.

Periodic-finite-type shifts (PFT's) are sofic shifts which forbid the appearance of finitely many pre-specified words in a periodic manner. The class of PFT's strictly includes the class of shifts of finite type (SFT's). The zeta function of a PFT is a generating function for the number of periodic sequences in the shift. For a general sofic shift, there exists a formula, attributed to Manning and Bowen, which computes the zeta function of the shift from certain auxiliary graphs constructed from a presentation of the shift. In this paper, we derive an interesting alternative formula computable from certain “word-based graphs” constructed from the periodically-forbidden word description of the PFT. The advantages of our formula over the Manning-Bowen formula are discussed.

The interference rejection combining (IRC) receiver effectively improves the cell-edge user throughput by suppressing interference from the surrounding cells. The work item (WI) for the specification of the IRC receiver is now ongoing for Release 11 Long-Term Evolution (LTE)-Advanced. Furthermore, heterogeneous networks where low power nodes such as picocells are overlaid onto macrocells are important to further improve the system throughput per unit area. In heterogeneous networks, to achieve an offloading gain from macrocells to picocells, cell range expansion (CRE) is applied. Additionally, inter-cell interference coordination (ICIC) is applied to reduce the severe inter-cell interference imposed from the macrocells onto the sets of user equipment (UEs) connected to picocells. In such cases, the interference statistics are completely different from traditional well-planned macrocell deployments, which have been investigated for the IRC receiver. This paper clarifies the effect of the IRC receiver in a heterogeneous network employing CRE and ICIC. Simulation results show that when both CRE and ICIC are applied, the effect of the IRC receiver becomes small due to a reduction in the severe inter-cell interference from ICIC. However, we clarify that the user throughput gain at the cumulative distribution function of 5% from the IRC receiver exceeding 10% is achieved compared to the conventional minimum mean square error (MMSE) receiver in a heterogeneous network regardless of the usage of ICIC. Furthermore, in heterogeneous networks employing CRE and ICIC, we clarify that an average user throughput gain exceeding 5% is achieved from the IRC receiver and the improvement in the average user throughput is high especially for the UEs connected to picocells compared to UEs connected to macrocells.

This paper evaluates the downlink performance of an LTE-Advanced (LTE-A) heterogeneous network that uses carrier aggregation (CA) between macro and small cells. The concept of utilizing the CA functionalities in LTE-A is effective in increasing the network capacity in a congested area through raising of the base station density using small cells overlaid onto an existing macro cell network. This concept is also effective in maintaining the mobility performance of user equipment (UE) because handover operation is not applied when entering/leaving a small cell, but component carrier addition/removal is only performed through CA while maintaining the connection to a macro cell. In order to present comprehensive performance evaluations in an LTE-A heterogeneous network with CA, this paper evaluates various performance criteria, e.g., downlink cell throughput and downlink user throughput. According to the obtained simulation results, the total downlink cell throughput achieved in an LTE-A heterogeneous network deployment with CA (four small cells overlaid onto a macro cell sector) exhibits a 3.9-fold improvement compared to a conventional-macro-cell-only network deployment using two frequency bands.

In Long-Term Evolution (LTE)-Advanced, heterogeneous networks are important to further improve the system throughput per unit area. In heterogeneous network deployment, low power nodes such as picocells are overlaid onto macrocells. In the downlink, the combined usage of inter-cell interference coordination (ICIC), which is a technique that reduces the severe interference from macrocells by reducing the transmission power or stopping the transmission from the macrocells, and cell range expansion (CRE), which is a technique that expands the cell radius of picocells by biasing the received signal power, is very effective in improving the system and cell-edge user throughput. In this paper, we consider two types of ICIC. The first one reduces the transmission power from the macrocells (referred to as reduced power ICIC) and the second one stops the transmission from the macrocells (referred to as zero power ICIC). This paper investigates the impact of the reduction in the transmission power when using reduced power ICIC and the restriction on the modulation scheme caused by the reduction in the transmission power when using reduced power ICIC on the user throughput performance with the CRE offset value as a parameter. In addition, the throughput performance when applying reduced power ICIC is compared to that when applying zero power ICIC. Simulation results show that the user throughput with reduced power ICIC is not sensitive to the protected subframe ratio compared to that with zero power ICIC even if the modulation scheme is restricted to only QPSK in the protected subframes. This indicates that reduced power ICIC is more robust than zero power ICIC for non-optimum protected subframe ratios.

In this article, we propose a method to reduce the impact of primary traffic on spectrum sensing performance. In practice, the sensing performance is degraded by noise-only sample in the spectrum sensing time. Therefore, we employ a time of primary user (PU) signal arrival detector in order to remove the noise-only portion. Then, we employ equal-weight-based energy detection (EWED) to provide the detection decision. The analysis and simulation results show that there exists an optimal early time of arrival (ToA) false alarm which provides better performance compared to the use of a single EWED scheme.

In this paper, we consider a multi-cell cognitive radio network (CRN), which overlays a multi-cell primary network. To manage the coexistence, a primary-willingness based coexistent architecture and a novel intra-cell spectrum overlay and inter-cell spectrum underlay sharing method are proposed. In the system, primary base stations will broadcast pilot signals and interference margins to assist the CRN for interference channel evaluation and power control. Subject to the interference margins imposed by the primary network, we define a utility (payoff) function that can represent the secondary system performance while taking into account the co-channel interference among secondary cells. A distributed resource allocation scheme is devised to guarantee the primary performance, and at the same time, maximize the secondary utility without any cooperation among cognitive base stations (CBS). Quality of Service among users is also considered by the scheme such that the instantaneous data rate for each secondary user is larger than a given minimum rate. The resource allocation problem can be decomposed into two subproblems: subchannel allocation and distributed power allocation game (DPAG). We prove that there exists a Nash equilibrium in the DPAG and the equilibrium is unique. Moreover, the DPAG is also Pareto optimal in some constrained environments, that is, no CBS can further improve its performance without impairing others. The proposed algorithm turns out to converge to an equilibrium within a small number of iterations.

One major challenge to implement orthogonal frequency division multiplexing (OFDM) systems over doubly selective channels is the non-negligible intercarrier interference (ICI), which significantly degrades the system performance. Existing solutions to cope with ICI include zero-forcing (ZF), minimum mean square error (MMSE) and other linear or nonlinear equalization methods. However, these schemes fail to achieve a satisfactory tradeoff between performance and computational complexity. To address this problem, in this paper we propose two novel nonlinear ICI cancellation techniques, which are referred to as parallel interference cancelation (PIC) and hybrid interference cancelation (HIC). Taking advantage of the special structure of basis expansion model (BEM) based channel matrices, our proposed schemes enjoy low computational complexity and are capable of cancelling ICI effectively. Moreover, since the proposed schemes can flexibly select different basis functions and be independent of the channel statistics, they are applicable to practical OFDM based systems such as DVB-T2 over doubly selective channels. Theoretical analysis and simulation results both confirm their performance-complexity advantages in comparison with some existing methods.

In order to support the increasing amount of mobile data traffic, Third Generation Partnership Project (3GPP) is actively discusses cell range expansion (CRE) and time domain multiplexing – inter-cell interference coordination (TDM-ICIC). They have shown to be attractive techniques for heterogeneous network (HetNet) deployment where pico base stations (BSs) overlay macro BSs. There are two control schemes of the TDM-ICIC. One, named ZP-scheme, stops radio resource assignments for data traffic in predetermined radio resources in the time domain (subframes). The other, named RP-scheme, maintains the resource assignment whereas it reduces the transmission power at macro BSs at predetermined subframes. In this paper, we clarify the effective ranges of both ZP-scheme and RP-scheme by conducting the system level simulations. Moreover, the appropriate power reduction value at predetermined subframes is also clarified from the difference in the effective range of various power reduction values. The comprehensive evaluation results show that both ZP-scheme and RP-scheme are not effective when the CRE bias value is 0 dB or less. If the CRE bias value is larger than 0 dB, they are effective when the ratio of predetermined subframes in all subframes is set to appropriate values. These values depend on the CRE bias value and power reduction in the predetermined subframes. The effective range is expanded when the power reduction in the predetermined subframes changes with the CRE bias value. Therefore, the effective range of RP-scheme is larger than that of ZP-scheme by setting an appropriate power reduction in the predetermined subframes.

Scheduling restriction is attracting much attention in LTE-Advanced as a technique to reduce the power consumption and network overheads in interference coordinated heterogeneous networks (HetNets). Such a network with inter-cell interference coordination (ICIC) provides two radio resources with different channel quality statistics. One of the resources is protected (unprotected) from inter-cell interference (hence, called protected (non-protected) resource) and has higher (lower) average channel quality. Without scheduling restriction, the channel quality feedback would be doubled to reflect the quality difference of the two resources. We present a simple scheduling restriction scheme that addresses the problem without significant performance degradation. Users with relatively larger (smaller) average channel quality difference between the two resources are scheduled in the protected (non-protected) resource only, and a boundary user, determined by a proportional fair resource allocation (PFRA) under simplified static channels, is scheduled on one of the two resources or both depending on PFRA. Having most users scheduled in only one of the resources, the power consumption and network overheads that would otherwise be required for the channel quality feedback on the other resource can be avoided. System level simulation of LTE-Advanced downlink shows that the performance degradation due to our scheduling restriction scheme is less than 2%, with the average feedback reduction of 40%.

This paper proposes a novel approach for implementing an ultra-low-power voltage reference using the structure of self-cascode MOSFET, operating in the subthreshold region with a self-biased body effect. The difference between the two gate-source voltages in the structure enables the voltage reference circuit to produce a low output voltage below the threshold voltage. The circuit is designed with only MOSFETs and fabricated in standard 0.18-µm CMOS technology. Measurements show that the reference voltage is about 107.5 mV, and the temperature coefficient is about 40 ppm/, at a range from -20 to 80. The voltage line sensitivity is 0.017%/V. The minimum supply voltage is 0.85 V, and the supply current is approximately 24 nA at 80. The occupied chip area is around 0.028 mm2.

A wireless emergency communication network with a fixed allocation of spectrum resources cannot meet the tremendous demand for spectrum access when a crisis occurs. It is necessary to develop an effective spectrum access scheme to improve the performance of emergency communication systems. In this paper, we study a new emergency communication system combines cognitive radio technology and an emergency communication network. Emergency users can utility resources in a general network when traffic becomes congested in an emergency network. Non-reciprocal spectrum access scheme (NRA) and reciprocal spectrum access scheme (RA) for two heterogeneous cognitive networks, namely emergency network and general network are proposed to compare with traditional spectrum access scheme (TA). User behavior with each scheme is modeled by continuous-time Markov chains. Moreover, the blocking and dropping probabilities of users in two heterogeneous cognitive networks are derived as the performance metrics. In addition, the throughput and the spectrum utilization rate of the system are evaluated. Finally, we compare the performance of three dynamic spectrum access schemes. The simulation results show that the RA scheme is an effective scheme to enhance the performance of emergency systems.

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.

Cell Range Expansion (CRE) is a promising technique for the enhancement of traffic offload to pico cells. CRE is realized by adjusting the trigger timing of handover (HO) toward/from pico cells. However, inappropriate setting of trigger timing results in HO failures or Ping-Pong HOs. Both the HO failures and the Ping-Pong HOs degrade the continuity of user data services. Therefore, when CRE is applied, both the HO failures and the Ping-Pong HOs should be kept suppressed in order to guarantee the continuity of services for users. However, in the conventional studies, the application of CRE is discussed without consideration of HO performance. This paper clarifies the application range of CRE from the perspective of HO performance by taking the HO failure rates and the Ping-Pong HO rates as HO performance measures. As an example, we reveal that there is an appropriate CRE bias values which keep both the HO failure rate and Ping-Pong HO rate less than 1%. Such an appropriate CRE bias value range is smaller than the one without consideration of HO performance, which is reported in the conventional studies. The authors also observed that Ping-Pong HO occurs due to the short staying time of users at pico cells in high velocity environment. The rate of such Ping-Pong HOs becomes more than about 1% when the user velocity is more than 60 km/h. Therefore, it is more difficult in high velocity environment than that in low velocity environment to find appropriate CRE bias values.

In this paper we aim to group visual correspondences in order to detect objects or parts of objects commonly appearing in a pair of images. We first extract visual keypoints from images and establish initial point correspondences between two images by comparing their descriptors. Our method is based on two types of graphs, named relational graphs and correspondence graphs. A relational graph of a point is constructed by thresholding geometric and topological distances between the point and its neighboring points. A threshold value of a geometric distance is determined according to the scale of each keypoint, and a topological distance is defined as the shortest path on a Delaunay triangulation built from keypoints. We also construct a correspondence graph whose nodes represent two pairs of matched points or correspondences and edges connect consistent correspondences. Two correspondences are consistent with each other if they meet the local consistency induced by their relational graphs. The consistent neighborhoods should represent an object or a part of an object contained in a pair of images. The enumeration of maximal cliques of a correspondence graph results in groups of keypoint pairs which therefore involve common objects or parts of objects. We apply our method to common visual pattern detection, object detection, and object recognition. Quantitative experimental results demonstrate that our method is comparable to or better than other methods.

Cognitive beamforming exploiting spatial opportunity is an attractive technique for secondary users to coexist with primary users in cognitive radio environments. If perfect channel state information of the interfering link is available, interference from a secondary transmitter to a primary receiver can be perfectly pre-nulled by choosing the ideal transmit beam. In practice, however, there is channel estimation error due to noise and the time-varying channels. To minimize the residual interference due to those channel estimation errors, channel prediction based on auto regressive (AR) model is introduced in this paper. Further, to cope with extremely rapidly-varying channels, a cognitive transmit power control technique is proposed as well. By combining channel prediction and transmit power control in cognitive beamforming, the cognitive users can share the spectrum with the primary users with a limited interference level in time-varying channels.

Heterogeneous networks (HetNets) can provide higher capacity and user throughput than homogeneous networks in Long Term Evolution (LTE)-Advanced systems. However, because of increased interference from neighboring cells and the characteristics of the embedded small cells, handover performance is impacted adversely, especially when the user equipment (UE) moves at medium or high speeds. In this paper, to improve mobility performance, we propose two schemes, i.e., 1) using wideband signal-to-interference noise ratio (SINR) as the handover metric and 2) emergency attaching. The schemes can enhance mobility performance since handovers are performed based on the quality of the radio link. Importantly, the two schemes compliment rather than contradict each other. System-level simulations show that both the individual proposed schemes and the joint schemes can improve mobility performance significantly.

There has been an explosion in wireless devices and mobile data traffic, and cellular network alone is unable to support such fast growing demand on data transmission. Therefore, it is reasonable to add another network to the cellular network to augment the capacity. In fact, the dilemma of cellular network is mainly caused by that the same content is repeatedly transmitted in the network, since many people are interested in the same content. A broadcast network, however, could mitigate this problem and save wireless bandwidth by delivering popular content to multiple clients simultaneously. This paper presents a content dissemination system that combines broadcast and cellular networks. Using the model of Markov Decision Process (MDP), we propose an online optimal scheme to maximize the expected number of clients receiving their interested content, which takes clients' interests and queuing length at broadcast and cellular base stations into full consideration. Simulations demonstrate that the proposed scheme effectively decreases item drop rate at base stations and enhances the average number of clients who receive their interested content.

In 2004, Menezes and Smart left an open problem that is whether there exists a realistic scenario where message and key substitution (MKS) attacks can have damaging consequences. In this letter, we show that MKS attacks can have damaging consequences in practice, by pointing out that a verifiably encrypted signature (VES) scheme is not opaque if MKS attacks are possible.