This paper investigates the resource allocation problem for the cluster-based cooperative multicast in orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems. Aiming at maximizing the system sum rate, an efficient clustering scheme is proposed. It begins with the clustering phase where secondary users (SUs) with good channel conditions are selected as cluster heads, while others decide to which cluster they belong. When the clusters are organized, it turns to a two-stage data transmission phase: in stage 1, the secondary base station (BS) transmits data to the cluster heads; in stage 2, the cluster heads forward the received data to their cluster members. Based on this scheme, a joint subcarrier and power allocation algorithm is proposed. Simulation results show that the proposed scheme significantly outperforms the conventional multicast (CM) as well as the multiple description coding multicast (MDCM) in terms of the system sum rate.

The hybrid mobile satellite system operating in a single frequency network (SFN) mode is increasingly becoming attractive. The combination of satellite component (SC) and terrestrial component (TC) promises a better quality of service (QoS). Multimedia broadcast and multicast services (MBMS) are expected to be prevailed in this kind of system. Several space frequency (SF) or space time (ST) codes have been proposed to enhance the system performance due to the lack of reverse link and omni-directional transmission. However, they mostly consider the system with only one SC and one TC and fail to make full use of available diversities. This paper presents a novel way to realize the dual polarization multiple input multiple output (MIMO) transmission by using the space time frequency (STF) code. The theoretical analysis and simulations indicate that the application of STF code can improve the system performance dramatically. A higher diversity gain can be achieved due to the cooperative transmission of SC and TC, while the coding gain can be enhanced by the reusing of STF code between SCs or TCs. Even if some of the links are lost, it can still work properly and benefit from the STF code. The relative relay can result in a degradation up to 0.5 dB in the coding gain.

In this paper, the joint resource allocation (RA) problem with quality of service (QoS) provisioning in downlink heterogeneous cellular networks (HCN) is studied. To fully exploit the network capacity, the HCN is modeled as a K-tier cellular network where each tier's base stations (BSs) have different properties. However, deploying numbers of low power nodes (LPNs) which share the same frequency band with macrocell generates severe inter-cell interference. Enhancement of system capacity is restricted for inter-cell interference. Therefore, a feasible RA scheme has to be developed to fully exploit the resource efficiency. Under the constraint of inter-cell interference, we formulate the RA problem as a mixed integer programming problem. To solve the optimization problem we develop a two-stage solution. An integer subchannel assignment algorithm and Lagrangian-based power allocation algorithm are designed. In addition, the biasing factor is also considered and the caused influence on system capacity is evaluated. Simulation results show that the proposed algorithms achieve a good tradeoff between network capacity and interference. Moreover, the average network efficiency is highly improved and the outage probability is also decreased.

This paper discusses about the optimal mode allocation for the heterogeneous networks, in which the network can schedule users working in the device-to-device (D2D) mode or cellular mode. The D2D user is allowed to reuse the uplink resource of cellular system and the problem is formed as a sum-capacity optimization issue with outage constraints for both cellular and D2D links. The method for the optimal user proration is proved to be divided into three cases according to the total user density: when the total user density is small, the optimal proration trends to all users utilizing one mode; when the total user density is large, the optimal proration is all of users choosing D2D mode; and when the total user density situates in the between, there is a unique optimal transmission mode proportion for the hybrid networks to maximize its sum- capacity. The simulation results demonstrate the validity of the conclusions in the analysis part.

In co-channel deployment of macro cell and pico cells, cell range extension (RE), a simple and typical cell association scheme, is introduced to achieve better load balancing and improve cell edge performance. In this article, a novel dynamic and distributed bias setting scheme is proposed for RE technique in macro-pico heterogeneous networks. In this strategy, the worst user throughput of each cell during an adjusting time interval T is obtained to change the bias values according to certain procedures, where an introduced indicator is used to freeze the possibility of increasing bias value if needed. Furthermore, silent state and coarse control process are employed to achieve low overheads and computational complexity. Simulation results show that the proposed scheme can greatly improve the cell-edge performance compared with the static bias setting strategies, while maintaining the overall cell performance at the same time.

This paper first introduces the performance analysis of two classical channel quality indicator (CQI) feedback schemes which are best-n feedback and the threshold based feedback and derives the mathematical expressions of average capacity which is described by Theorem 1 and 2. Then, a reduced feedback scheme is designed for multiple traffics and multi-channel. The novel scheme combines the best-n feedback and the threshold based feedback together to reduce the feedback overhead. The proposed scheme can not only guarantee the quality of service (QoS) requirement of real time (RT) traffic but also reduce feedback overhead at the cost of a marginal increased downlink overhead. Simulation results demonstrated the good performance of the proposed feedback scheme.

In this paper, we have proposed a multi-relay selection and power allocation scheme for two-way relay network which aims to maximize the sum-rate of two-way relay system. First, to prolong network lifetime, a multi-relay selection strategy is proposed in which both channel state information (CSI) and remaining energy (RE) are considered. Next, a multi-relay power allocation algorithm based on convex optimization (MRPA-CO) is presented. To reduce the computational complexity, it can be divided into two steps: terminal nodes power allocation (TNPA) and relay nodes power allocation (RNPA). Simulation results indicate that the proposed relay selection strategy can significantly prolong network lifetime compared to other relay selection strategies which consider CSI only, and the MRPA-CO algorithm has great advantage over equal power allocation (EPA) on sum-rate in two-way relay network.

By exploiting favorable characteristics of a uniform cross-array, a passive localization algorithm of narrowband sources in the spherical coordinates (azimuth, elevation and range) is proposed. Based on the properly chosen sensor outputs, we compute the third-order cyclic moment matrices, and exploit a pre-calibration technique to eliminate multiplicative noise. Then, we construct a parallel factor (PARAFAC) model, and adopt trilinear alternating least squares regression (TALS) to estimate three-dimensional (3-D) near-field parameters. The investigated algorithm is efficient in the sense that it can eliminate multiplicative noise and additive noise, provide the improved estimation accuracy, as well as avoid the parameter-pairing procedure. Simulation results are carried out to demonstrate the performance of the proposed algorithm.

Multi-cell processing (MCP) is capable of providing significant performance gain, but this improvement is accompanied by dramatic signaling overhead between cooperative base stations. Therefore, balancing the performance gain and overhead growth is crucial for a practical multi-base cooperation scheme. In this paper, we propose a decentralized algorithm to jointly optimize the power allocation and beamforming vector with the goal of maximizing the system performance under the constraint of limited overhead signal and backhaul link capacity. In particular, combined with calculating the transmission beamforming vector according to the local channel state information, an adaptive power allocation is presented based on the result of sum capacity estimation. Furthermore, by utilizing the concept of cell clustering, the proposed framework can be implemented in a practical cellular system without major modification of network architecture. Simulation results demonstrate that the proposed scheme improves the system performance in terms of the sum capacity and cell-edge capacity.

Echo state network (ESN) has become one of the most popular recurrent neural networks (RNN) for its good prediction performance of non-linear time series and simple training process. But several problems still prevent ESN from becoming a widely used tool. The most prominent problem is its high complexity with lots of random parameters. Aiming at this problem, a minimum complexity ESN model (MCESN) was proposed. In this paper, we proposed a new wavelet minimum complexity ESN model (WMCESN) to improve the prediction accuracy and increase the practical applicability. Our new model inherits the characters of minimum complexity ESN model using the fixed parameters and simple circle topology. We injected wavelet neurons to replace the original neurons in internal reservoir and designed a wavelet parameter matrix to reduce the computing time. By using different datasets, our new model performed better than the minimum complexity ESN model with normal neurons, but only utilized tiny time cost. We also used our own packets of transmission control protocol (TCP) and user datagram protocol (UDP) dataset to prove that our model can deal with the data packet bit prediction problem well.

To reach necessary end-to-end connectivity between the Internet and wireless sensor networks (WSNs), the Internet Engineering Task Force (IETF) IPv6 over low power wireless personal area network (6LowPAN) working group has been established and introduced an adaptation layer for integration of IEEE 802.15.4 physical layer/media access control (PHY/MAC) layers and the upper layers of any Internet protocol (IP)-based networks, such as the Internet. The energy efficiency is one of the most important performance measures in WSNs because most sensor nodes are only battery powered so we should reduce the energy consumption to the lowest to extend the life of nodes. Therefore the determination of MAC frame length should be carefully considered since that the radio frequency (RF) module consumes most the energy of a sensor node meanwhile the MAC protocol is the direct controller of RF module. In this paper, we provide a star-shaped 6LowPAN non-beacon mode with unslotted carrier sense multiple access with collision avoidance (CSMA/CA) mechanism to access to the channel and model the stochastic behavior of a target end node as the M/G/1 queuing system. Analytical expressions for some parameters such as channel busy probability, packet loss probability and energy efficiency are obtained in this paper and our analytical results can clearly show the impact of MAC frame length on the energy efficiency of a target node in both ideal and lossy channel.

How to efficiently build routes among nodes is increasing important for mobile ad hoc networks (MANETs). This paper puts forward an interference aware routing protocol called Interference aware cross layer routing protocol (IA-CLR) for MANETs based on the IEEE 802.11 medium access layer (MAC). By defining the node’s sending and receiving capabilities, IA-CLR can indicate the interference strength of the link in a real and comprehensive way. Further more, in order to choose the route with minimum bottleneck link interference, a new routing metric is proposed by combining the MAC layer and the network layer for cross layer design. Simulation results show that IA-CLR can significantly improve the performances of network such as the average end-to-end delay, the packets loss ratio and the throughput.

Identity-based cryptography (IBC) has drawn a lot of attentions in delay tolerant environment. However, the high computational cost of IBC becomes the most critical issue in delay tolerant mobile sensor network (DTMSN) because of the limited processing power. In this paper, an efficient identify-based signature scheme with batch authentication (ISBA) is proposed for DTMSN. ISBA designs an online/offline signature with batch authentication to reduce the computational cost, and improves data delivery mechanism to increase the number of messages for each batch authentication. Simulation results show that ISBA not only realizes a lower computational cost than existed schemes, but also does not induce negative impact on the delivery performance.

Anonymous proxy signature scheme can provide the privacy protection for the proxy signer. Recently, Yu et al. proposed an anonymous proxy signature, which can be viewed as the organic combination of proxy signature and ring signature. However, the efficiency is low. In this paper, we propose an efficient and secure proxy signature with the properties of anonymity and traceability, and it is provably secure in the random oracle model. Compared with Yu et al.’s scheme, the scheme has higher efficiency.

The display image of the video display unit (VDU) can be reconstructed by receiving and analyzing the unexpected electromagnetic noise emanated from a personal computer system. This fact is one of the information leakage threats in information security. Therefore, in order to choose the best frequency range for receiving the electromagnetic compromising emanations form a PC display effectively and quickly, a method based on the correlation power analysis (CPA) and the common equipments is proposed. Firstly, the frequency spectrum of 10 MHz to 1 GHz is measured about 10 times respectively when the PC is displaying the white-black vertical strips image and black image. The frequency range which contains the display information can be obtained through the CPA. And then, the special image signal is searched around the dot frequency and harmonics. If the special signal disappears when displaying the total black image, it can be judged to be the real special signal. Finally, the best receiving frequency range can be chosen by comprehensive considering the results of CPA and the signal to noise ratio (SNR) of the special image signal. In order to check the validity of the chosen frequency range, eavesdropping experiments are carried out. The results demonstrate that the selected frequency range can retrieve the higher quality image than other frequency bands.

A new approach for network survivability problem in Internet protocol (IP) over wavelength division multiplexing (WDM) optical network is proposed to enhance the IP layer restorability under physical link failure through logical topology reconfiguration. More specifically, after traffic arrival and departure, reconfiguring the logical topology correspondingly is helpful to minimize the traffic disruption after physical link failure. So, in this paper, this problem is proposed for first time and formulated as an integer linear programming (ILP) problem. And then, two heuristic algorithms are proposed. The performance of proposed algorithms have been evaluated through simulations, and the results show that reconfiguring the logical topology dynamically could achieve more than 20% improvement of the restorability of traffic in IP layer, but with acceptable resource cost.

In this paper, we present a wavelength depended ray-tracing algorithm to model the indoor multisource channel impulse response for visible light communication (VLC). We compare the multipath loss difference between multisource and unisource channel. We also analyze the root mean square (RMS) delay spread and average time delay of three typical wavelengths as VLC holds a wide spectrum from 380 nm to 780 nm, the spectral reflectance of walls is wavelength-dependent. And the result shows that the blue light emitting diode (LED) owns a larger communication bandwidth than other wavelengths in the room with plastic walls. Also, the path loss of three different wavelengths is compared.

A kind of dual-band-stop filter with an unsymmetrical T-shape defected ground structure (DGS) is proposed. The filter has two band gap centers at 4.9 GHz and 7.35 GHz, respectively, where the two centre frequencies are just the second and third harmonics 2.45 GHz. The filters with high band-stop performance and wideband spurious suppression can be achieved by cascading miniaturized unsymmetrical T-shape DGS. The attenuation of three-cascaded T-shape DGS filter is 30.77 dB at 4.9 GHz and 17.96 dB at 7.35 GHz respectively. The above experimental results are in good agreement with the simulation results, especially for the third harmonic.

In a radio frequency identification (RFID) system, the backscattered signal is small and prone to interference. The performance of RFID tag identi?cation in interference scenarios is degraded compared to that in error-free scenarios. In this paper, a novel Mahalanobis distance estimate (MDE) method is proposed to jointly estimate the number of tags and packet error rate (PER). The MDE method is error resilient owing to its ability to achieve a stable estimation when interference is impairing the observed information. The proposed method achieves significantly enhanced accuracy over existing methods by taking all the information and correlations among the observed results into account. The MDE method improves the estimate performance based on efficient decorrelation and classification of the observed information. Moreover, the performance of the PER estimate is analyzed both in theory and through simulations. It can be concluded from the analysis that the estimated PER is unbiased and variance-bounded. Simulations show that the proposed estimate outperforms the previous proposals in terms of accuracy and stability, which makes it suitable for application in interference scenarios.

According to the decline of recognition rate of speech recognition system in the noise environments, an improved perceptually non-uniform spectral compression feature extraction algorithm is put forward in this paper. This method can realize an effective compression of the speech signals and make the training and recognition environments more matching, so the recognition rate can be improved in the noise environments. By experimenting on the intelligent wheelchair platform, the result shows that the algorithm can effectively enhance the robustness of speech recognition, and ensure the recognition rate in the noise environments.

This article presents a data management solution based on the data distribution service (DDS) communication model. The basic DDS communication model consists of a unidirectional data exchange where applications that publish data ‘push’ the relevant data, which is updated to the local caches of co-located subscribers to the data [1]. DDS has no specified center node to forward data packets and maintain the communication data. This type of publish-subscribe (P/S) model presents integrity and consistency challenges in data management. Unlike peer-to-peer (P2P) distributed storage, DDS applications have a hard real-time environment and fewer data features, and the core problem is ensuring the integrity and consistency of data in distributed systems under this hard real-time environment. This article begins with a brief introduction of the communication model used by DDS, then analyzes persistent data management problems caused by such model, and provides an appropriate solution to these problems. This solution has been implemented in a prototype system of the real-time service bus (RTSB) of Tsinghua University.