- EI核心期刊
When thinking of information hidding technology, despite the fact that many positive results in the application field have been achieved, some basic problems in its basic theory are still remained. Starting with the feature of the information, a new theory of the generalized information hiding as well as the model buit was suggested when the research on the mechanism of the information hiding was done. And, many traditional steganography and modern information hiding methods was reasonably illustrated. An important conclusion shows that the existance of covered messages is not the necessary condition for information hidding.
Load balancing is proposed in the distributed processing network (DPN) layer of the distributed wireless communication system (DWCS) to manage the signal processing resources. The flat topology of the DPN is divided into hierarchically arranged load balancing domains (LBD). The rule that in one LBD the variance of the call loss probability is greater than a constant should be followed when dividing DPN into LBDs. The evaluation method of load, the granularity and the policy of load balancing are given. By the simulation of the distributed time-driven algorithm, the efficiency of load balancing and the division method are proved to be acceptable.
A modified link layer selective repeat automatic repeat qequest (ARQ) scheme is proposed to improve transport control protocol (TCP) performance over wireless networks——adaptive selective repeat ARQ(ASR-ARQ). According to the feature of every high layer packet being fragmented into several frames at link layer, ASR-ARQ limits the maximum retransmission number per packet and can adaptively allocate retransmission number to frames belonging to the same packet. The link layer packet error rate and transmission delay are derived to evaluate this scheme. The Padhye's TCP throughtput model is also used to evaluate the TCP performance of systems using ASR-ARQ. Numerical results demonstrate ASR-ARQ can achieve much lower packet error rate with slightly longer delay and higher TCP throughput than the conventional scheme.
Based on the characteristics of RTCP (real-time transport control protocol) extension, an extensible RTCP control framework designed for source specific multicast applications was proposed. In contrast to traditional control framework, the framework mentioned here could efficiently reduce the usage of network resources that the RTCP traffic would consume. In the meantime, it can feed back the QoS information to sender in time, so that the sender can raise the network congestion response time.
A new protocol to protect the intellectual property of digital multimedia using digital watermark was proposed. The proposition brings forward the protocols for copyright registering, watermarking embedding, watermarking detecting and dispute resolutions. The copyright owner could register his copyright information to a DRPC (digital copyright protection center), and DRPC will then decide to embed the watermark information into the media or not. Meanwhile the owner could also detect his watermark information in the watermarked media at any time. When the copyright is infracted, DRPC will be able to give an authoritative proof of the copyright for the owner in time. Analysis shows that the protocol is very secure and effective.
Based on the theorem of synchronization of digital-flow chaos in secure communications, a scheme of secure speech communication was presented and realized, a method using model references was given to solve the problem that noise will be increased with time going because of programming variance both communication sides. Reducing synchronic noise and promoting the ratio of signal power and noise power are made with the method. The experimental results show it will reduce noise efficiently.
Based on image scrambling and pattern recognition, a new watermarking scheme in huge index image is proposed. The scaling parameter according to HVS(human visual system) was adjusted by the system while embedding watermarks. The experimental results show that the proposed scheme has a good effect of anti-cutting, anti-modifying, anti-patching and invisibility.
The rerouting strategy in the low earth orbit (LEO) quality of service (QoS) satellite networks was proposed to accommodate as much QoS traffic as possible. The rerouting means to select an already accepted flow and replace its established path with some other path in order to accept a newly arriving transmission request which can not be accepted without doing so. The feasibility of the rerouting strategy in the LEO QoS satellite networks was verified by the computer simulation. The results illustrate that the rerouting strategy can raise the utilization of network resources effectively, on the other hand, it would cause a higher connection handover frequency. For solving this problem, a new approach to select the accepted flow for rerouting according to the characteristics of LEO constellation network topology was proposed. The simulation results show that the proposed approach improves the performance of the connection handover frequency.
The general package radio service (GPRS) intelligent network based on customized applications for mobile network enhanced logic (CAMEL) specification is analyzed in detail. And some disadvantages that are caused by serving GPRS support node (SGSN) triggering are presented. Thereby, a whole GPRS intelligent network solution based on gateway GPRS support node (GGSN) triggering is proposed. The new solution contains the functional architecture, the state models and the information flows. The fundamental signaling flows of GPRS intelligent services in the new solution are illustrated finally.
Issue of automatic channel routing in transport network under multi-vendor environment was analyzed for introduction of concise and effective design of adapter based on application framework pattern. The framework provides skeleton of the routing algorithm, whereas individual adapters focus on implementing key operations that are specific to different equipment types and associated management interfaces. A correlative channel routing algorithm within sub-network was discussed which could choose appropriate routes effectively according to the resources available in the network and rules defined by the management interfaces. Automatic channel routing functionality in network management system was implemented by leveraging the above-mentioned design and algorithm.
First in first out (FIFO) queue is currently used in media access control (MAC) protocols for mobile ad hoc networks. As a result, the head-of-line blocking might be happened. Based on power controlled multiple access protocol (PCMA), a MAC protocol without head-of-line blocking (PCMA+) was proposed. Simulation shows that, compared with PCMA in which FIFO queue is adopted, a good improvement will be obtained when in use of PCMA+.
A proxy signature scheme was presented with the properties of anonymity and traceability. After the proxy signature has been verified, only the signature from delegation of the original signer could be confirmed by the verifier. On the other hand, the identity of the proxy signer could not be known at the same time. In appearing of disputation, the verifier can reveal the real identity of the proxy signer with the help of the original signer. A trusted party isn't involved in the scheme.
Based on the good relation of degree of polarization (DOP) of feed-back signals and differential group delay (DGD), DOP was extracted as monitor signal to find out the maximum DOP of fiber link with the aid of controlling algorithm to control compensators to obtain optimal compensation. Chirped fiber grating made of photosensitive polarization maintaining fiber was fabricated through the equivalent chirp technology, which was used as time delay line of PMD compensator. The experimental study of adaptive polarization mode dispersion (PMD) compensation in the 10 Gbit/s nonreturn-to-zero(NRZ) transmission system was reported. Meanwhile, a particle swarm optimization (PSO) technique into automatic PMD compensation was used. PSO has the characteristics of converging for global optimum rapidly and avoiding for being trapped into local sub-optima and robust to noise. The experiments show that the adaptive PMD compensation system on which chirped fiber gratings are used as compensators woks very well.
An ultra-wideband (UWB) pulse design approach for multiple narrowband interference suppression was presented. The generated UWB pulse not only has a very short time duration, but can entirely meet federal communications commission (FCC) spectral mask and effectively suppress the interferences between UWB systems and multiple narrowband communication systems. The coexistence problem between UWB systems and the existing narrowband systems was successfully solved after that. In this approach, the power spectral density of UWB pulse does not need to be reduced over the whole frequency band. Therefore, it is possible to enlarge the communication range of UWB systems by increasing the transmitted power of UWB pulses.
The design and performance of a multi-path routing based on adaptive modulation and coding algorithm for mobile ad-hoc networks were presented. For achieving the minimum total delay, single-path or multi-paths would be selected to route packets, according to both channel condition and traffic load. Considering the costs and overheads of searching and spending of routing tables, the maximum two paths (minimum cost and secondary cost path) were taken into account. The simulation results show that the channel adaptive routing of maximum two-path can obtain better delay performance.
With the aid of modeling a long optical fiber with 1 000 cascaded small fiber segments, the statistical dependence existed between the first-and the second-order polarization mode dispersion (PMD) vector was numerically simulated. The simulated result shows that: the higher the PMD value of an optical fiber is, the larger range the covering of the polarization-dependent chromatic dispersion (PCD), the principal state of polarization (PSP) rotation rate, and the depolarization become. For a specified PMD value, with the increasing of differential group delay, the averaged PCD keeps constant; the averaged depolarization and second-order PMD will be increased linearly; but the averaged PSP rotation rate will be decreased rapidly. It is also shown that the depolarization will play a role of domination in the second-order PMD, and PCD will only have a little contribution.
In the actual wireless communication systems, the transmission delay is one of dominant factors which determine the system performances. A new incremental redundancy hybrid automatic repeat request (HARQ) scheme based on the characters of rate compatible punctured turbo codes is proposed. With the method, the initial state of incremental redundancy system and the initial sending parity bits according to the channel condition will be set. As to the new scheme, simulation results are provided that transmission delay for the data frame received correctly is distinctly reduced and it is applied easily.
As media-shared network, gigabit-capable passive optical networks (GPON) needs some form of media access control(MAC) protocol to arbitrate the upstream channel among terminations, and avoid collisions. But there is no media access control protocol suitable for GPON system up to now. A MAC protocol for GPON system according to the ITU-T G.GPON.gtc was brought forward and analyzed based on computer simulations. And it is approved effective in practice.
A dynamic fuzzy clustering method is presented based on the genetic algorithm. By calculating the fuzzy similarity between samples the essential associations among samples are modeled factually. The fuzzy similarity between two samples is mapped into their Euclidean distance, that is, the high dimensional samples are mapped into the two dimensional plane. The mapping is optimized globally by the genetic algorithm, which adjusts the coordinates of each sample, and thus the Euclidean distance, to approximate to the fuzzy similarity between samples gradually. A key advantage of the proposed method is that the clustering is independent of the space distribution of input samples, which improves the flexibility and visualization. This method possesses characteristics of faster convergence rate and more exact clustering results than some typical clustering algorithms. Simulated experiments show the feasibility and availability of the proposed method.
For good adaptation of Internet protocol traffic to optical network, more efficient and flexibility optical transmission and switching technology are required. In order to reduce the port numbers of switch components and to reduce the switch grains, a new switch mode based on the integration of time-slot and waveband switch was proposed. The basic idea of this switch mode and the integer linear programming formulation were also given. The corresponding curve of optimization rate was computed and analysed.
Based on the real-time constrain of the multimedia stream and the disk data stream model, the relationship between the performances and the online storage subsystem in video on demand was presented quantitatively with the analysis of memory and interface bus. The experiment shows that the system performance, the maximal throughput and concurrent stream number, are influenced by the combination of disk performance, the redundant arrays of inexpensive disk scheduler, the memory capacity and the bandwidth of interface bus.
The attack of multi-time interceptions must be considered in the protocols of quantum identity verification, though it makes no sense in its classical counterpart. By this means, an active attacker could precisely obtain the state of the particle carrying the identity verification information, when he measured enough copies of the particle. So the two protocols released lately by Daniel Ljunggren et al and Zeng Guihua et al respectively could be broken. Based on the pseudorandom bit generator with time parameters and the verification keys, the identity verification protocol in quantum key distribution proposed can avoid the attack because the attacker has to intercept exponential times in the length of time parameters to obtain just one copy of a particle.
A new method for constructing perfect binary array pairs taking advantage of the characters of dyadic theory was presented. More perfect binary array pairs could be constructed through the known perfect binary array pairs, however, the new binary array pairs have the same property as the original ones. As a result, it indicates that the method is handy and flexible. With this method more perfect signals could be obtained in engineering.
A new frame synchronization scheme in orthogonal frequency-division multiplexing (OFDM) system was proposed. Based on a central-symmetric training sequence, the miss detection probability of a training sequence in the proposed algorithm could be as small as 10-3 when signal noise rate is 10 dB and the false alarm probability is assumed to be 10-3. Carrier frequency offset could also be partially corrected within sub-carrier spacing of 0.5 as soon as frame synchronization is performed.