- EI核心期刊
A novel approach for solving complicated nonreciprocal transmission line(NTL) problems using standard Smith Chart was proposed. Based on a nonlinear mapping, it transforms the parameters of NTL model into the parameters of traditional reciprocal transmission line(RTL) model and, as a result, the design and calculation in NTL can be easily done by using a standard Smith chart(SSC). The feasibility and convenience of the approach was tested through the complete design process of NTL single-stub series-matching and NTL double-stub parallel matching network.
In this paper, a reinforcement learning based joint session admission control algorithm is proposed to realize the autonomic and distributed joint resource optimization between the heterogeneous radio access technologies (RAT) in a reconfigurable system. By introducing Q-learning into the admission control algorithm and adjusting the strength of the reinforcement signals for different types of sessions considering the inherent characteristics of different RATs, RATs are driven to absorb the suitable traffic for a proper service distribution, which improves the efficiency of resource utilization. The simulation results show that, through the “trial-and-error” on-line learning process, overlapping RATs can converge to the optimized admission control policies that reduce the overall blocking probability while achieve lower handover dropping probability as well as higher revenue.
The characteristics of the multigranularity optical cross connect (MG-OXC) node with the tunable wavelength converters is analyzed. A new dynamic routing and wavelength assignment algorithm which is applied in multi-granularity optical switching network is also proposed. The performance of the MG OXC with tunable optical converters, compared with traditional OXC and MG-OXC, is evaluated with help of numerical calculations under NSFNET topology. The results show that the performance of the network with MG-OXC with tunable wavelength converters is superior to that of the network composed with only traditional OXC and MG-OXC.
Through theoretical spreading principle analysis, it is proved that the benefit of pseudo-orthogonal carrier interferometry (PO-CI) spreading code is not able to be supported when complex signal modulation(for example,quadrature phase-shift keying(QPSK) and quadrature amplitude modu-lation (QAM)) types are employed. On this basis, a feasible structure for its solution is brought forward. Within the structure mentioned, instead of complex modulation patterns, pulse amplitude modulation (PAM) combined with PO-CI spreading code is utilized, it manages to maintain the doubled throughput increase of multicarrier code division multiple access （MC-CDMA） system with minimal loss in performance and no bandwidth expansion.
A kind of GCL(Generalized chirp-like) sequences are adopted as the preambles of the random access channel(RACH), and a cyclic postfix is added. This structure can utilize the perfect periodic correlation properties of GCL sequences effectively to improve the detection performance. Furthermore, a kind of detection algorithm is proposed, which is based on the peak-average ratio detection within a window. Threshold is designed based on the proposed algorithm, and both false alarming probability and missing detection probability are analyzed. The possibility to adapt the proposed algorithm to be used as collision detection algorithm and channel estimation algorithm is also analyzed. Analysis and simulation results show that the proposed preamble structure and the corresponding detection algorithms have good performance.
LI Yi, JI Hong, MA Shuhui
An improved cooperative retransmission scheme based on node cooperative stop and wait automatic repeat request （ARQ） protocol is proposed. In order to avoid ambiguous acknowledgement or negative acknowledgement (ACK/NAK) and diffusion of cooperation process, cooperative and noncooperative frames are distinguished. Traffic categories within each node are introduced so that cooperative frames can be sent in advance. According to instantaneous channel conditions, the “best” partner is selected to help the source retransmit data. Analytical and simulation results indicate that improved scheme can alleviate collision problem caused by cooperation, increase probability of successful retransmissions and enhance system throughput.
For the purpose of implementing integrative and accurate SLA-based service management, the SLA parameter representation and parameter mapping have been studied. Firstly, SLA representation parameters have been defined from different perspectives, the analytical method of bidirectional data flow is proposed to extract representation parameters, and then parameter mapping mechanism has been adopted to study correlation among data, in this way the hierarchical SLA-based service management data model viewed from multi-perspectives is established. Secondly, Analytic Hierarchy Process (AHP) combined with other different judging arithmetic is introduced to perform correlative computing, which realizes the mapping of representation parameters among sub-layers. Finally, service management data model of FTP service over UMTS network is built and parameter mapping arithmetic is validated. The simulation results demonstrate that the proposed approach is rational and valid.
The wireless mesh networks based on the IEEE 802.16 standard and controlled in a centralizedway were studied. And an interference set based tree routing algorithm and a maximal clique based fair downlink scheduling algorithm were proposed. The proposed routing algorithm will make the nodes on the routing tree be of less interference degree in order to get an interference-aware tree, while the proposed downlink scheduling on the basis of this tree will take full advantage of maximal cliques, as well as ensures fairness among request satisfaction ratios. Simulation shows that a great network throughput enhancement which is benefited from the decrease of node’s interference degree along with the increase of concurrent transmissions, and a satisfaction with the fairness.
The leakage of channel impulse response (CIR) in channel estimation for the orthogonal frequency division multiplexing (OFDM) systems is analyzed. A channel estimation algorithm in time domain is newly proposed. To overcome the leakage of CIR, the frequency guard bands are reduced by using the polynomial cancellation coding (PCC) training symbols .The symbols have fast spectral rolloff. Comparison has been done between the proposed algorithm and the existing channel estimation algorithms. Simulation results show the decreasing of channel estimation mean square (MSE) and the improvement of bit error rate (BER) performance by the proposed algorithm.
The concept of connections batched is proposed to support multiple connections in a call session in automatically switched optical network (ASON). To support a call request having multiple similar connections, the function of component and procedure of signaling perform are extended. A testbed of 15 nodes is built, the control plane of ASON by running resource reservation protocoltraffic engineering (RSVPTE), open shortest path firsttraffic engineering (OSPFTE) and link management protocol (LMP) is implemented. The experimental results shows that multiple connections per a call have less connection setup time and network traffic than one connection per a call have.
Traditional search algorithm has defections such as the convergence direction is hard to decide and the convergence speed is very slow when using a stochastic probability search algorithm. Also the global optimal solution is hard to approach when using a heuristic structured algorithm, though it could converge in time. A new concept of location area element (LAE) and its corresponding LAE correlated aggregation algorithms were proposed. The experimental results indicate that the new algorithm could compress the solution space of location area planning or optimizing efficiently, thus ensuring the convergence direction to the global optimum and speeding up the convergence process when searching the optimal solution in the compressed solution space.
In response to the request of seamless handoff for streaming video service in heterogeneous IP network, a stepbystep linklayer trigger mechanism is proposed to guarantee the veracity of handoff under fast mobile IPv6 （FMIPv6） protocol structure. Analysis and simulation results show that handoff latency could be reduced by making use of dejitter buffer window of streaming video traffic to satisfy the near realtime service.
The suitable modeclass is adaptively selected for the current macroblock (MB) based on the context of encoded MBmodes in the spatiotemporal neighborhoods of the previous and current H264 video frames. Two matrixes which are composed of sum of absolute values of the integer transform coefficients in 4×4residualblock contained in luminance 16×16block and 8×8block are defined respectively, the novel MB and subMB mode selection criteria which use the derived gradients of the two matrixes are then proposed. Experiments show that the proposed algorithm can averagely save about 11% and 7% encoding time compared to joint video team (JVT)J033 and JVTK021 respectively with almost no rate distortion efficiency degradation.
Heuristic packet classification algorithms based on decision tree aim to classify packets with minimal time and space requirements. In this paper ,an adjustable algorithm based on parameter evaluation is presented. It follows the idea of popular packet classification algorithms,introduces the conception of performance parameters, and adjusts weights of these parameters to aquire data structure with the best performance . Simulations show that , compared with other algorithms of the same kind ,a good improvement can be obtained when using our new algorithm.
Lifting scheme wavelet design based on multi-population genetic algorithm (GA) and ant system (AS) for effective image compression is proposed. Firstly, a multi-population genetic algorithm and lifting are used to evolve wavelets. The global fitness and the local fitness are introduced in GA for the first time and they are homologous to the global elicitation information and the local one utilized by ants in AS. So the AS algorithm is then used to find the exact wavelet that is adapted best to the given application of the wavelet transform, and the resulting stochastic optimization method with elicitation is good both in time efficiency and with accurate solution. The wavelets designed are applied to wavelet-based image coders for compression of fingerprint and medical image, and the experiment results validate the effectiveness of the design method and the advantage of the resulting image compression.
For facilitating the efficient routing planning, node management for upper computers or sink nodes, longdistance node service and prolonging the lifetime of wireless sensor network （WSN）, a new method for node fault diagnosis in WSN is proposed. The attribute reduction for decisionmaking of fault diagnosis is found based on the discriminate matrix in rough set theory. The algorithms of node fault classification are proposed based on attribute matching. The fault can be located and diagnosed individually for each node and module in WSN. Simulations show that the proposed method yields high diagnosis accuracy with low communication cost and energy consumption. It is suitable for wireless sensor networks with stringing energy limits.
To improve the performance of block matching algorithm in motion estimation and motion complement (ME+MC)，a motion pattern recognition (MPR) algorithm based on selforganizing feature maps (SOM) is proposed and tested in object－based conference video coding. A frequency sensitive self－organizing feature maps (FSSOM) algorithm is proposed to improve the SOM algorithm’s performance. Experimental results show that FSSOM－MPR algorithm has better coding performances than ME+MC algorithm. When the compression ratio is 180∶1, the peak signal to noise ratio（PSNR） improvement of reconstructed video images is about 3.3 dB.
To study the terminal energy consumption in wireless heterogeneous networks, a semiMarkov chain to reflect the communication states and deduct an analytical energy consumption evaluation model is adopted through the investigation of a terminal’s operation modes. Comparing with the previous works, the proposed model will incorporate all the communication states of a terminal; the probability of successful wireless local area network （WLAN） discovery; and service type. Analysis results show that the energy consumption will increase as the call arrival rate and call holding time increase. Moreover, it is found that the energy consumption is approximately linear with respect to the voice call ratio and the probability of successful WLAN discovery. It is also found that making WLAN module in low energy consumption waiting state does not save terminal energy.
A new ordering method and detection algorithm based on the Schmidt decomposition for the multiple－input multiple－output (MIMO) system are proposed. The algorithm can achieve the same bit error rate （BER） performance as the traditional zero forcing serial interference cancellation (ZF－SIC ) algorithm while the computational complexity of the proposed algorithm is 1/3 to 2/3 to the traditional ZF－SIC algorithm. Analysis and computer simulation are also presented to verify the algorithm.
An approach for calculating the multiservices access capacities of uplink time division duplexing－coding division multiple access (TDD－CDMA) system is proposed. The relationship between service access capacities and TDD－CDMA interference is analyzed. And the specialty of TDD－CDMA interference distribution is also considered. By using Delbrouck’s algorithm, the call congestion, traffic congestion, time congestion and carried traffic of different services in a multi－dimensional loss TDD－CDMA system can be resolved. Both analysis and simulation results are given to support the method mentioned above.
In order to accelerate power control (PC) simulation, a low computational complexity simulation algorithm is proposed. It replaces multiplication, division, and nonlinear operations with decibel (dB) addition and subtraction to perform wideband code division multiple access (WCDMA) PC. Furthermore, the error of the proposed algorithm is analytically derived. Numerical results show that the proposed algorithm can save lots of simulation time whereas introducing a small amount of error. The proposed algorithm saves 60％～65% central processing unit (CPU) time over the conventional algorithm, and 20％～30% CPU time over the modified conventional algorithm. Equivalently, simulation system aimed at the proposed algorithm reduces 50% CPU time compared to one with the conventional algorithm, and 15% CPU time compared to one with the modified conventional algorithm. To a certain extent, the proposed algorithm has solved the problem that makes dynamic simulator run slowly.
A new multicarrier modulation system M band lifting wavelet multicarrier modulation (LWMT) system was proposed based on M band wavelet theory and its lifting scheme. Through analyzing bit error rate（BER） and simulated the system under additive white Gaussian noise（AWGN） channel and fading channel, the result shows that: in fading channel the performance of LWMT system is better than orthogonal frequency division multiplexing （OFDM） system. In AWGN channel the performance of LWMT system is same as OFDM system but LWMT system performance is superior to OFDM system in the antinarrow interference.
An upper bound of overlapped time division multiplexing (OVTDM) system in additive white Gaussian noise（AWGN） channel with binary phase－shift keying (BPSK） modulation named modified union bound is given using the maximum likelihood (ML) rule. The bound approaches the real performance by no more than 3?dB at a symbol error rate(SER) of 10-6 in the simulation.
The model of correlated multiinput multioutput (MIMO) frequencyselective channels in frequency domain is introduced. And the pairwise error probability (PEP) of spacefrequency systems is analyzed based on this model. Then, the performance of spacefrequency equalizer (SFE) is derived and simulated based on minimum mean square error (MMSE). Analysis and simulation results show that the performance of spacefrequency systems degrades with the increasing of correlation.
An economical fault detection method, employing cycle cover theory, is proposed in terms of costly sing-hop test module in meshed optical burst switching (OBS) networks. Three kinds of cycle cover finding algorithms, heuristic depth first searching (HDFS), shortest path Eulerian matching (SPEM) and Heuristic spanning-tree (HST) based cycle finding, are used to find cycle cover for meshed OBS networks. Then a probe module is assigned for each cycle, and a fault detection mechanism based on probe cycle cover is formed. The computation and statistic results show that the proposed mechanism can reduce the cost of fault detection deeply compared to single-hop test scheme in meshed OBS networks.
A new channel estimation algorithm for MIMO-OFDM is proposed. The channel impulse response is estimated by the conventional DFT algorithm. Adaptive channel parameters estimation is proposed to estimate the noise variance and multi-path delay profile. The estimation results are used to derive the channel impulse response on the multi-path taps and eliminate the noise on the other taps. Simulation results show that the proposed channel estimation gives better performance than conventional LS channel estimation algorithm.
A routing algorithm utilizing the multirate and multi－range characteristic in wireless fidelity (WiFi) mesh networks is proposed. A cross－layer design scheme is newly introduced. The mechanism of adaptive data－rate transition in physical layer is considered in this algorithm. The maximum data－rate is used as the performance metric when establishing the route, and the minimum hop－count is regarded as a criterion under the same data－rate. The method to discover the path under different datarate is presented. It will adjust the transmitted power level and expand the transmission range step by step when failed to establish the route within the given area. When the proposed algorithm is adopted, the Ad hoc on－demand distance vector (AODV) routing can be improved as WiFi－AODV. Simulation results show that WiFiAODV is capable of establishing a route which has high data－rate, short linkdelay and greate network throughput.
A sub-carrier and power allocation algorithm is proposed for OFDMA distributed antenna system, which can maximize the effective sum-capacity, and fulfill the proportional rate requirement and per antenna power constraint. Through decomposition, the multi antenna resource allocation problem is divided into several sub-problems on each independent antenna, thus the complexity is reduced greatly. Simulation result shows that the proposed algorithm can fulfill the proportional rate requirement well, and remarkable capacity gain is observed compared with the centralized antenna system and a fixed FDMA allocation algorithm.
In order to solve the problems that 3D display methods of virtual soldiers vivid model is heavily dependent on expensive hardware and difficult to realize and popularize, the 3D display methods based on textureswitch are presented according to the actual need of 3D display of virtual soldiers in the case of “unit commanding simulated confrontation training system”. The basic ideas, algorithms ideological, technical routes to achieve, and the realization of algorithms are described in details. Moreover, the two key issues, that how to keep texture framework always against the screen and the logic orientation of virtual soldiers when the viewpoint is changing, have been demonstrated.
Quality of service (QoS) extensions to open shortest path first (QOSPF) algorithm prunes the highdelay network links before routing with only the bandwidth metric. A QOSPF-improved routing algorithm with bandwidth and delay metrics (BD-QOSPF) is proposed to seek feasible paths so as to meet the QoS requests (bandwidth constraint, delay optimization or delay constraint) for application flows. It keeps the same complexity as the original QOSPF and supports hop-by-hop and explicit routing. It compares available bandwidth and delay metrics to pre-compute routing table, deals with the equal-resource and equal-cost paths and reroutes the blocked flows. Simulation results show that BD-QOSPF can increase the routing-success-ratio of QoS flows, and decrease the path delay and save the path bandwidth as well. The effectiveness of rerouting strategy in BD-QOSPF is also verified to improve the flow-block performance, however more rerouting costs directly associated with more flow loads should be paid.
A shunt three phase power factor correcting scheme was presented. An optimized active power filtering algorithm and high speed space vector pulse width modulation (SVPWM) theory were used to achieve unity power factor without destroying the structure of electronic facility. The scheme improves both synchronous detection frequency and dynamic response of the PWM inverter, and reduces switching losses. Current voltage synchronization and complete compensation of harmonic currents are realized under distorted voltage conditions. Theoretical analysis and experiment results have verified its feasibilities of this scheme.