The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60101-6
Abstract ( 1577 ) PDF (0 KB)( 147 )
Due to its opportunistic spectrum sharing capability, cognitive radio (CR) has been proposed as a fundamental solution to alleviate the contradiction between spectrum scarcity and inefficient utilization of licensed spectrum. In CR system (CRS), to efficiently utilize the spectrum resource, one important issue is to allocate the sensing and transmission duration reasonably. In this paper, the evaluation metric of energy efficiency, which represented the total number of bits that were delivered with per joule of energy consumed, is adopted to evaluate the proposed scheme. We study a joint design of energy efficient sensing and transmission durations to maximize energy efficiency capacity (EEC) of CRS. The tradeoff between EEC and sensing and transmission durations are formulized as an optimization problem under constraints on target detection probability of secondary users (SUs) and toleration interference threshold of primary users (PUs). To obtain the optimal solution, optimizing sensing duration and transmission duration will be first performed separately. Then, a joint optimization iterative algorithm is proposed to search the optimal pair of sensing and transmission durations. Analytical and simulation results show that there exists a unique duration pair where the EEC is maximized, and that the EEC of the proposed joint optimization algorithm outperforms that of existed algorithms. Furthermore, the simulation results also reveal that the performance of the proposed low complexity iterative algorithm is comparable with that of the exhaustive search scheme.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60102-8
Abstract ( 1568 ) PDF (0 KB)( 135 )
This paper investigates the power allocation issues for joint transmission in heterogeneous network (HetNet), which is characterized by severe cross-tier interference. The optimization problem of maximizing the HetNet throughput is formulated. The original problem turns out to be a non-convex problem, the global optima of which cannot be obtained by conventional optimization methods. This paper develops a novel method to achieve the global optima by turning the original problem into quasi-convex problem. In addition, this paper considers a constant power allocation scheme, as a tradeoff between the system throughput and computational complexity. Based on duality gap theory, the bound of constant power allocation scheme is mathematically derived. Numerical results under different system parameters indicate that both the proposed schemes outperform conventional interference coordination schemes.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60103-X
Abstract ( 1488 ) PDF (0 KB)( 194 )
Cooperative communication systems can effectively increase channel capacity and combat fading. Effective cooperation requires synchronization impairments such as multiple timing offsets and multiple carrier frequency offsets to be accurately estimated and mitigated. This paper seeks to address the joint estimation of synchronization impairments in multi-relay decode-and-forward (DF) cooperative networks. Firstly, a simple yet effective estimation method based on the devised training signals is presented for achieving synchronization. Then, an iterative algorithm is further derived in order to improve the performance associated with the estimation of synchronization impairments. Our proposed algorithm converts the difficult multiple parameter estimation problem into more tractable sub-problems of estimating many individual impairments pairs for the independent relays. Simulations indicate that, the proposed estimator can asymptotically achieve the mean square error (MSE) for the perfectly timing or frequency synchronized case.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60104-1
Abstract ( 1448 ) PDF (0 KB)( 140 )
A parabolic equation method (PEM)-based discrete algorithm is proposed and is used to obtain the field distribution in the evaporation duct space. This method not only improves the computing speed, but also provides the flexibility to adjust the simulation accuracy. Numerical simulation of the wave propagation in the oceanic waveguide structure is done. In addition, the initial field distribution and progressive steps are determined. The loss model in the waveguide is solved through the numerical solution. By comparing the characteristics of the radio wave propagation in the duct and in the normal atmospheric structure, we analyses the radio transmission over the horizon detection in the oceanic waveguide.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60105-3
Abstract ( 1439 ) PDF (0 KB)( 126 )
Due to the constraint of single carrier frequency division multiple access (SC-FDMA) adopted in long term evolution (LTE) uplink, subcarriers allocated to single user equipment (UE) must be contiguous. This contiguous allocation constraint limits resource allocation flexibility and makes the resource scheduling problem more complex. Most of the existing work cannot well meet UE’s quality of service (QoS) requirement, because they just try to improve system performance mainly based on channel condition or buffer size. This paper proposes a novel resource scheduling scheme considering channel condition, buffer size and packet delay when allocating frequency resource. Firstly, optimization function is formulated, which aims to minimize sum of weight for bits still left in UE buffer after each scheduling slot. QoS is the main concern factor here. Then, to get packet delay information, this paper proposes a delay estimation algorithm. Relay node (RN) is introduced to improve overall channel condition. Specific RN selection strategy is also depicted in the scheme. Most important of all, a creative negotiation mechanism is included in the subcarrier allocation process. It can improve the overall system throughput performance in guarantee of user’s QoS requirement. Simulation results demonstrate that the scheme can greatly enhance system performance like delay, throughput and jitter.
Ling WU Li-Ya HUANG
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60106-5
Abstract ( 1507 ) PDF (0 KB)( 130 )
The most common location algorithms based on received signal strength (RSS) are location identification based on dynamic active radio frequency identification (LANDMARC) and virtual reference elimination (VIRE). However, both the original algorithms suffer from some drawbacks. In this paper, several aspects of the two original algorithms have been modified to reduce the positioning errors. Firstly, Lagrange interpolation has been used instead of linear interpolation. Secondly, adaptive threshold has been introduced in the new algorithm. Thirdly, insert virtual reference tags to improve the location accuracy of the boundary of the sensing area. Finally, combine LANDMARC with VIRE to absorb both advantages. Compared with the original algorithms, on average, simulated results show that the modified algorithms can improve the location performance efficiently and achieve the goal of accurate positioning in indoor environment.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60107-7
Abstract ( 1426 ) PDF (0 KB)( 137 )
In wireless sensor network (MSN), reliability is the main issue to design any routing technique. To design a comprehensive reliable wireless sensor network, it is essential to consider node failure and energy constrain as inevitable phenomena. In this paper we present energy efficient node fault diagnosis and recovery for wireless sensor networks referred as energy efficient fault tolerant multipath routing scheme for wireless sensor network. The scheme is based on multipath data routing. One shortest path is used for main data routing in our scheme and other two backup paths are used as alternative path for faulty network and to handle the overloaded traffic on main channel. Shortest pat data routing ensures energy efficient data routing. Extensive simulation results have revealed that the performance of the proposed scheme is energy efficient and can tolerates more than 60% of fault.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60108-9
Abstract ( 1489 ) PDF (0 KB)( 143 )
Orthogonal frequency division multiplexing (OFDM) is one of the key techniques for long term evolution (LTE) system. Frequency offset estimation of OFDM is an essential issue. Especially in the high-speed environment, the frequency offset will become large. Based on the features of LTE uplink physical random access channel (PRACH), this paper proposes a new frequency offset algorithm by using peak power ratio to enlarge the range of frequency offset estimation. According to the relation between frequency offset and the power delay profile (PDP), the ratio of the peak power of the PDP at the main window to that at the negative window or positive window is utilized to estimate frequency offset. Simulation results show that the new proposed algorithm extends the estimation range of frequency offset from 1 000 Hz to 1 250 Hz. Meanwhile the accuracy of frequency offset estimation is almost not lost. Particularly in low signal noise ratio (SNR), the new algorithm has lower mean square error (MSE) compared with traditional phase differential algorithm.
Yijun Guo Jian-Jun HAO
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60109-0
Abstract ( 1445 ) PDF (0 KB)( 129 )
The throughput gain obtained by linear network coding (LNC) grows as the generation size increases, while the decoding complexity also grows exponentially. High decoding complexity makes the decoder to be the bottleneck for high speed and large data transmissions. In order to reduce the decoding complexity of network coding, a segment linear network coding (SLNC) scheme is proposed. SLNC provides a general coding structure for the generation-based network coding. By dividing a generation into several segments and restraining the coding coefficients of the symbols within the same segment, SLNC splits a high-rank matrix inversion into several low-rank matrix inversions, therefore reduces the decoding complexity dramatically. In addition, two coefficient selection strategies are proposed for both centrally controlled networks and distributed networks respectively. The theoretical analysis and simulation results prove that SLNC achieves a fairly low decoding complexity at a cost of rarely few extra transmissions.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60110-7
Abstract ( 1454 ) PDF (0 KB)( 218 )
Path computation elements (PCEs) are employed to compute end-to-end paths across multi-domain optical networks due to the advantages of powerful computation capability. However, PCEs’ location selection is still an open problem which is closely related to the communication overhead. This paper mainly focuses on the problem of PCEs’ location selection to minimize the overall communication overhead in the control plane. The problem is formulated as a quadratic integer programming (QIP) model, and an optimal decision rule is gained from the solution of the QIP model. Then based on the decision rule, a distributed heuristic algorithm is proposed for dynamic network scenario. Simulation results demonstrate the benefit and the effectiveness of our proposed approach by comparing it with random selection policy.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60111-9
Abstract ( 1478 ) PDF (0 KB)( 135 )
Due to having a large bandwidth to support Gbps-level data rate, terahertz communication attracts more and more attention in recent years. However, there are few medium access control (MAC) protocols for terahertz ultra-high data-rate wireless networks, which affects the research and application of terahertz communications. To address this problem and to achieve ultra-high data-rate wireless access with terahertz communication, a novel MAC protocol, called medium access control for terahertz communication (MAC-TC), is proposed. Through designing a new channel access scheme, a new superframe structure, and related key parameters, MAC-TC can support a maximum data rate up to 10 Gbit/s even higher. Theoretical analysis and simulation results show that our proposed MAC protocol realizes the function of medium access control and attains a maximum data rate of 18.3 Gbit/s, which is 2 times higher than 5.78 Gbit/s, the theoretical maximum data rate of IEEE 802.15.3c standard.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60112-0
Abstract ( 1517 ) PDF (0 KB)( 123 )
We present an approach to optimize the MapReduce architecture, which could make heterogeneous cloud environment more stable and efficient. Fundamentally different from previous methods, our approach introduces the machine learning technique into MapReduce framework, and dynamically improve MapReduce algorithm according to the statistics result of machine learning. There are three main aspects: learning machine performance, reduce task assignment algorithm based on learning result, and speculative execution optimization mechanism. Furthermore, there are two important features in our approach. First, the MapReduce framework can obtain nodes’ performance values in the cluster through machine learning module. And machine learning module will daily calibrate nodes’ performance values to make an accurate assessment of cluster performance. Second, with the optimization of tasks assignment algorithm, we can maximize the performance of heterogeneous clusters. According to our evaluation result, the cluster performance could have 19% improvement in current heterogeneous cloud environment, and the stability of cluster has greatly enhanced.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60113-2
Abstract ( 1497 ) PDF (0 KB)( 118 )
Cloud computing provides a convenient way of content trading and sharing. In this paper, we propose a secure and privacy-preserving digital rights management (DRM) scheme using homomorphic encryption in cloud computing. We present an efficient digital rights management framework in cloud computing, which allows content provider to outsource encrypted contents to centralized content server and allows user to consume contents with the license issued by license server. Further, we provide a secure content key distribution scheme based on additive homomorphic probabilistic public key encryption and proxy re-encryption. The provided scheme prevents malicious employees of license server from issuing the license to unauthorized user. In addition, we achieve privacy preserving by allowing users to stay anonymous towards the key server and service provider. The analysis and comparison results indicate that the proposed scheme has high efficiency and security.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60114-4
Abstract ( 1468 ) PDF (0 KB)( 122 )
Complexity measures for multisequences over finite fields, such as the joint linear complexity and the k-error joint linear complexity, play an important role in cryptology. In this paper we study a fast algorithm, presented by Venkateswarlu A, to computer the k-error joint linear complexity of a binary periodic multisequence. In this paper, the aim is mainly to complement the theoretical derivation and proof of the existing algorithm. Moreover, our algorithm reduces computation.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60115-6
Abstract ( 1473 ) PDF (0 KB)( 138 )
In this paper, a novel simple detector is designed to remove the intra-signal interference in high efficiency differential chaos shift keying (HE-DCSK) modulation scheme. With the help of data bit estimated before correlation detection, this new detector could remove the modulated chaotic segment that would form intra-signal interference component in the correlator output from every received information-bearing signal in HE-DCSK, leading to greatly and effectively improved system bit error rate (BER) performance. The effectiveness of this proposed detector is studied analytically based on the numerical integration method and evaluated by computer simulation in additive-white-Gaussian- noise (AWGN) channel. Simulation results reveal that the proposed detector can dramatically improve the overall BER performance of HE-DCSK even at relatively low signal noise ratio (SNR) levels.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60116-8
Abstract ( 1438 ) PDF (0 KB)( 120 )
Remote state preparation is increasingly becoming attractive in recent years, people have already started theoretical and experimental research, and have made valuable research results. Recently, a scheme for probabilistic remote preparation of a general two-qubit state was proposed (Wang Z Y in Quantum Inf Process. 11:1585, 2012)). In this paper, we present a modified scheme for probabilistic remote preparation of a general two-qubit state. To complete the scheme, the new and feasible complete orthogonal basis vectors have been introduced. Compared with the previous schemes, the advantage of our schemes is that the total success probability of remote state preparation will be greatly improved. The probability of success regarding this scheme is calculated in both general and particular cases. The results show that the success probability of remote state preparation can be improved a little. However, in certain special cases, the success probability of preparation can be greatly improved. In special cases, the success probability of preparation can be improved to 1. The security analysis of the scheme is provided in details.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60117-X
Abstract ( 1583 ) PDF (0 KB)( 120 )
In this paper, the characteristics of soliton in a passively mode-locked Er-doped fiber laser modeled by a non-distributed model are numerically investigated with the split-step Fourier method. Based on the analysis and model, sech2-shaped soliton is obtained by controlling the group velocity dispersion (GVD) and small-signal gain of the gain fiber. The law that the dispersion influences the characteristics of soliton in the mode-locked fiber laser is researched in net-cavity averaged anomalous dispersion regime.
The Journal of China Universities of Posts and Telecommunications, 2013, 20 (6). doi： 10.1016/S1005-8885(13)60118-1
Abstract ( 1434 ) PDF (0 KB)( 122 )
With a typical and simple 2-bit problem, a dynamic model of multi-agent social evolutionary algorithm (MASEA) is constructed by dynamic method. Then, the global dynamic shape of MASEA is comprehensively analyzed and the common evolution operators are also formally described. Furthermore, the effect that every evolutionary operator has on the dynamic shape is discovered by attraction analysis of the fixed points in the models. The global convergence of MASEA is also proved.