陈丹 纪红 李曦
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60055-6
Cooperative relaying is emerging as an effective technology to fulfill requirements on high data rate coverage in next-generation cellular networks, like long term evolution-advanced (LTE-Advanced). In this paper, we propose a distributed joint relay node (RN) selection and power allocation scheme over multihop relaying cellular networks toward LTE-Advanced, taking both the wireless channel state and RNs’ residual energy into consideration. We formulate the multihop relaying cellular network as a restless bandit system. The first-order finite-state Markov chain is used to characterize the time-varying channel and residual energy state transitions. With this stochastic optimization formulation, the optimal policy has indexability property that dramatically reduces the computational complexity. Simulation results demonstrate that the proposed scheme can efficiently enhance the expected system reward, compared with other existing algorithms
李宏佳 胡丹 许晓东 TAO Xiao-feng ZHANG Ping
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60056-8
In the two-tier femtocell network, a central macrocell is underlaid with a large number of shorter range femtocell hotspots, which is preferably in the universal frequency reuse mode. This kind of new network architecture brings about urgent challenges to the schemes of interference management and the radio resource allocation. Motivated by these challenges, three contributions are made in this paper: 1) A novel joint subchannel and power allocation problem for orthogonal frequency division multiple access (OFDMA) downlink based femtocells is formulated on the premise of minimizing radiated interference of every Femto base station. 2) The pseudo-handover based scheduling information exchange method is proposed to exchange the co-tier and cross-tier information, and thus avoid the collision interference. 3) An iterative scheme of power control and subchannel is proposed to solve the formulated problem in contribution 1), which is an NP-complete problem. Through simulations and comparisons with four other schemes, better performance in reducing interference and improving the spectrum efficiency is achieved by the proposed scheme.
王成金 李曦 张琳 纪红
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60057-X
For cooperative relay multicast networks, the general cross-layer optimization approaches converge to the global optimal value slowly because of the large quantity of relay terminals. However, the mobility of relay terminals requires quick converging optimization strategies to refresh the relay links frequently. Based on the capacity analysis of multiple relay channels, an improved cross-layer optimization scheme is proposed to resolve this problem, in which the bound of the relay selecting region is determined as a pre-processing. Utilizing the primal-dual algorithm, a cross-layer framework with pre-processing optimizes both the relay terminal selection and power allocation with quick convergence. The simulation results prove the effectiveness of the proposed algorithm.
陈昌海 尹长川 乐光新
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60058-1
This article puts forward a new solution to the bound of the outage probability and transmission capacity of Ad-hoc networks. For the proofs of the upper and lower bounds are too complex, a much easier way is introduced to get the same results, and by using Taylor series, the asymptotic bound is derived. By comparing with the simulation results, we found that the asymptotic bound is sufficient accurate when the network parameters are selected properly, and is tighter than the upper and lower bounds.
王亚琛 马晓凤 李晔
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60059-3
This work has investigated coordinated multiple-input multiple-output (MIMO) transmission schemes in an interference-limited cellular downlink. It has proposed a novel block diagonalization (BD) coordinated transmission scheme, which combines with zero-forcing (ZF) criterion. In the scheme, the BD technique has advantages in suppressing multi-user interference while the ZF technique enables to mitigate interference among spatial data streams for a user. Based on the proposed coordinated scheme, an efficient power allocation is also put forward. The analyses show that the ergodic capacity of the proposed coordinated scheme is that of the MIMO channel with the maximum transmit power at each transmitter. Computer simulations demonstrate the effectiveness of the proposed coordinated scheme and its corresponding power allocation.
王莹 李根 弓风
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60060-X
This paper addresses the robust linear filter design issues for non-regenerative multiple input multiple output (MIMO) relay systems with imperfect channel state information (CSI) in both or partial hops. By considering statistical Kronecker channel model involving channel mean and antenna correlation, the robust linear processing schemes in imperfect CSI scenario for both hops are first derived based on mean squared error (MSE) criterion. In addition to this, the result is also extended to two practical scenarios, i.e. imperfect CSI for relay link with perfect CSI for access link and imperfect CSI for access link with perfect CSI for relay link. Simulation results show that the proposed scheme is capable of mitigating the performance degradation caused by the imperfect CSI.
王思野 许文俊 贺志强 牛凯 吴伟陵
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60061-1
In this work, we consider an amplify-and-forward two-way multi-relay system for wireless communication and investigate the effect of channel estimation error on the error rate performance. With the derivation of effective signal-to-noise ratio at the transceiver and its probability density function, we can get approximate expression for average bit error rate. Simulation results are performed to verify the analytical results.
焦传海 王可人 门硕
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60062-3
To improve the spectrum sensing performance in cognitive radios, a scheme of cooperative blind spectrum sensing based on autocorrelation matrix is proposed. The test statistic is extracted from the autocorrelation matrix of the received signal samples and a bi-threshold hybrid decision scheme is designed for local spectrum sensing. The cognitive radio base station makes a credibility fusion based on the local soft decisions and then takes global fusion combining with the local hard decisions. The proposed method is blind in the sense since it requires no apriori knowledge of the signal and the noise power. Theoretical analysis and computer simulation results show that the proposed method can enhance the spectrum sensing capability.
杨鼎成 徐继生 胡树凯
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60063-5
This paper studies the resource allocation for a multi-user two-way amplify-and-forward (AF) relay network over orthogonal frequency-division multiplexing (OFDM) technology, where all users communicate with their pre-assigned partners. Using convex optimization techniques, an optimal solution to minimize the total transmit power while satisfy each user-pair’s data rate requirements is proposed. We divide the resource allocation problem into two subproblems: (1) power optimization within user-pair and relay in each subcarrier. (2) optimal subcarrier allocation and sum power assignment among N parallel OFDM subcarriers. Closed-form expressions of the power among user-pair and relay can be obtained in subproblem (1), and so the proposed algorithm decreases the variable dimensionality of the objective function to reduce the complexity of this optimization problem. To solve it, a three-step suboptimal approach is proposed to assign the resources to user-pairs: Firstly, decompose each user-pair into two sub user-pairs which have one-way and two-way relaying transmission modes. Secondly, allocate the subcarriers to the new mode user-pairs and assign the transmit power to each carrier. Thirdly, distribute the assigned power to three nodes allocated in the subcarrier. Simulation results demonstrate the significant power is saved with the proposed solutions, as compared to a fixed subcarrier allocation.
王坦 王莹 张平
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60064-7
Distributed multipoint systems (DMS) are important and timely for the move to future broadband wireless communication systems. Traditional studies on DMS have mainly focused on the issues with the spatial division multiple access such as precoding techniques, which only consider a narrowband case. This paper addresses the downlink radio resource management of the orthogonal frequency division multiple access DMS (OFDMA-DMS), including power allocation between users or subcarriers, and distributed antenna selection. Signal models with incoherent and coherent transmitters are built. To maximize the system throughput, for the incoherent transmitter case, a strategy based on the iterative water-filling power allocation is proposed to approach the optimality. As for the coherent case, where coherent additions of the signal could occur at the users, the problem is transformed into an integer programming which is solvable. Numerical results show that the gain from the coherent transmitter is promising. And to achieve a near-optimal solution, only part of the DA ports will be used, which have better channel conditions.
漆渊 钱荣荣 PENG Tao 王文博
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60065-9
Although multiple-input-multiple-output (MIMO) detection has received much research attention in the past years, to the author’s knowledge, few detection methods demonstrate optimal/near-optimal performance with low complexity. This paper proposes to incorporate automatic retransmission request (ARQ) with sub-optimal MIMO detectors so as to achieve both favorable performance and low complexity. In the study, retransmission delay induced by ARQ is exploited as a source of improving the detection performance of low complexity algorithms. In particular, the detection performance of sub-optimal algorithms improved by introducing ARQ is analyzed theoretically. A sufficient condition for such scheme to achieve full-diversity performance is also derived which relates detection performance with number of transmission times. Moreover, throughput cost by retransmission is deduced as well as its lower bound. The zero-forcing (ZF) equalizer cooperating with ARQ, as a case study, is shown to have evident performance improvement through theoretical analysis. And numerical results are presented to verify the effectiveness of the proposed scheme which boosts the performance of sub-optimal detector and possesses lower implementation complexity for practical reality simultaneously.
王亚峰 魏国兴 XIANG Wei
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60066-0
In this paper, we develop and analyze several inter-cell interference modeling methods for cellular network. The models can analyze multiple interfering signals under different fading scenarios. Incoherent addition of summing multiple interfering signals is assumed. We propose an approximate method that uses the generalized Gram-Charlier series to analyze the error of the reference model. The approximate method is not only simple but also with neglectable errors. The methods proposed could be very useful in practical system design and analysis.
赵成林 刘德强 孙学斌 蒋挺
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60067-2
In orthogonal frequency division multiplexing (OFDM) systems, spectrum notch can be generated to mitigate interference to other narrow-band services by turning off corresponding subcarriers. However, the inter-carrier interference may limit considerably the produced notch depth. Another problem in OFDM is the high peak-to-average power ratio (PAPR). In this paper, a technique combining subcarriers precoding with tone reservation is proposed to deepen spectrum notch and simultaneously reduce peak-to-average power ratio. Simulation results show that this presented joint algorithm can produce satisfied results to solve these problems at the expense of a moderate loss in bit error rate (BER) performance.
麻海圆 孟相如 马志强 李金良
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60068-4
To enhance multicast throughput in heterogeneous environment, a new layered multicast congestion control scheme is proposed. With the goal of maximizing global satisfaction of the whole group, allocating sending rate in each layer is formulated to an optimization problem. Since the problem is noncovexity, the sender uses particle swarm optimization to search a set of optimal layers rates. The new scheme also eliminates ‘lowest-first’ phenomenon by proposing a feedbacks suppression algorithm named equal-probability sampling (EPS). Upon EPS all the receivers send feedbacks at equal probability without bias. Simulation results prove that the new scheme can enhance global satisfaction and multicast throughput efficiently, compared with the traditional layered multicast congestion control scheme based on representatives.
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60069-6
Aiming at the hysteretic characteristics of classification problem existed in current internet traffic identification field, this paper investigates the traffic characteristic suitable for the on-line traffic classification, such as quality of service (QoS). By the theoretical analysis and the experimental observation, two characteristics (the ACK-Len ab and ACK-Len ba) were obtained. They are the data volume which first be sent by the communication parties continuously. For these two characteristics only depend on data’s total length of the first few packets on the flow, network traffic can be classified in the early time when the flow arrived. The experiment based on decision tree C4.5 algorithm, with above 97% accuracy. The result indicated that the characteristics proposed can commendably reflect behavior patterns of the network application, although they are simple.
LIU Wen 张洪欣 WANG Hong 吕英华 CHEN Nan 门硕
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60070-2
Two kinds of controllable doped left-handed materials (DLHMs) were designed by inserting inductors and capacitors into the traditional left-handed material (LHM) as heterogeneous elements respectively, which are DLHM with inductors (LDLHM) and DLHM with capacitors (CDLHM). The characteristics of transmission spectrum were studied by using finite-difference time-domain method (FDTD). Compared with the traditional LHM, the resonance strength of the LDLHM is weakened and the pass-band is narrowed, but with the increase of the value of the inserted inductors, the bandwidth is expanded. As capacitors inserted into the LHM, the pass-band of the CDLHM is expanded, but the pass-band is shifted to low frequency and the bandwidth is narrowed with the increase of the value of the capacitors, meanwhile, a new generated pass-band is also shifted to low frequency. Therefore, a quantized controllable doped left-handed material can be achieved.
史雪飞 Wang Zhi-liang PING An ZHANG Li-kun
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60071-4
A hierarchical-processed frame construction of artificial emotion model for intelligent system is proposed in the paper according to the basic conclusion of emotional psychology. The general method of emotion processing, which considers only one single layer, has been changed in the presented construction. An artificial emotional development model is put forward based on reinforcement learning mechanism of neural network. The new model takes the emotion itself as reinforcement signal and describes its different influences on action learning efficiency corresponding to different individualities. In the end, simulation result based on child playmate robot is discussed and the effectiveness of the model is verified.
任柯燕 孙汉旭 贾庆轩 WU Yao-hong Zhang Wei-yu GAO Xin YE Ping SONG Jing-zhou
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60072-6
This paper proposes a simple and discriminative framework, using graphical model and 3D geometry to understand the diversity of urban scenes with varying viewpoints. Our algorithm constructs a conditional random field (CRF) network using over-segmented superpixels and learns the appearance model from different set of features for specific classes of our interest. Also, we introduce a training algorithm to learn a model for edge potential among these superpixel areas based on their feature difference. The proposed algorithm gives competitive and visually pleasing results for urban scene segmentation. We show the inference from our trained network improves the class labeling performance compared to the result when using the appearance model solely.
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60073-8
This paper presents an integrated complementary metal oxide semiconductor (CMOS) low power low noise amplifier (LNA) for global positioning system (GPS) receivers. To achieve low power dissipation, the MOS transistors in the proposed LNA are biased in moderate inversion region. It is implemented by SMIC 180 nm 1P6M CMOS process. The experiment results show that a gain of 12.14 dB@1.57 GHz is achieved with low noise figure (NF) of 1.62 dB. The power consumption of the circuit is 1.5 mW at supply voltage of 1.8 V. The ratio of gain to dc power consumption is 8 dB/mW. The size of the LNA is only 980 μm× 720 μm including the pads.
费宁 庄毅 陈春玲 杨亮
中国邮电高校学报(英文版), 2011, 18 (3). doi： 10.1016/S1005-8885(10)60074-X
The compressed ready-only-memory (ROM) file system (CramFS) has been widely used in Linux-based devices. However, it is a read-only filesystem which can not meet the requirement of today’s smart mobile devices because most of them require updating the software on the air (OTA). This paper presents a design and implementation of write-enabled CramFS which only introduces minor architecture changes and very limited space cost. The performance benchmark with other popular write-enabled filesystems also proves the feasibility of this solution.