Real-time variable bit rate（VBR） video is expected to take a significant portion of multimedia applications.However,plentiful challenges to VBR video service provision have been raised for its characteristic of high traffic abruptness.To support multi-user real-time VBR video transmission with high bandwidth utilization and satisfied quality of service（QoS）,this article proposes a practical dynamic bandwidth management scheme.This scheme forecasts future media rate of VBR video by employing time-domain adaptive linear predictor and using media delivery index（MDI） as both QoS measurement and complementary management reference.In addition,to support multi-user application,an adjustment priorities classified strategy is also put forward.Finally,a test-bed based on this management scheme is established.The experimental results demonstrate that the scheme proposed in this article is efficient with bandwidth utilization increased by 20%-60% compared to a fixed service rate and QoS guaranteed.
In this article,the problem of load balance in hierarchical routing network is studied.Since conventional shortest path first（SPF） algorithm over aggregated topology in hierarchical routing network may result in worse routing performance,a traffic sharing path selection algorithm and a variable weight scheme are put forward for hierarchical routing network,which can equilibrate the utilities of link resources and reduce the blocking probability of connections with the improvement on survivability.Simulations are conducted to evaluate proposed variable weight and traffics balance（VWTB） algorithm,which combines traffic sharing and variable weight.From the simulation results,it can be found that the proposed VWTB algorithm can balance the traffics and equilibrate the utilities of link resources significantly.
A contention resolution scheme.P-cycle auto-switching（PCAS）.is proposed in wavelength-switched optical networks（WSONs） based on generalized multi-protocol label switching（GMPLS） to solve backward blocking.This system permits the preferable request and switches the other to a backup path generated by the P-cycle.Simulation results show that the PCAS scheme is effective in mitigating backward blocking, especially under concentrated load.
An optical burst switching （OBS） network platform is established with a ring topology of three nodes. A congestion Mleviated scheme using advanced token protocol and wavelength tunable receivers is demon- strated to optimize the network platform. Experimental results testify that this scheme can resist collision at the level of 0.1% congestion rate.
Current generalized multi-protocol label switching （GMPLS） standards do not include adequate models for wavelength-switched optical networks （WSON） in recovery mechanisms. In this letter, GMPLS/path computation element （PCE） extensions are applied for the restoration of the lightpaths disrupted by collision or optical impairment. A reserved deflection routing scheme is proposed to achieve fast restoration. It uses the expanded PCE component to compute and assign the backup paths for lightpath recovery. Numerical results demonstrate that this scheme is effective and low cost.
We obtain the photonic bands and intrinsic losses for the triangular lattice three-component two- dimensional （2D） photonic crystal （PhC） slabs by expanding the electromagnetic field on the basis of waveguide modes of an effective homogeneous waveguide. The introduction of the third component into the 2D PhC slabs influences the photonic band structure and the intrinsic losses of the system. We examine the dependences of the band gap width and gap edge position on the interlayer dielectric constant and interlayer thickness. It is found that the gap edges shift to lower frequencies and the intrinsic losses of each band decrease with the increasing interlayer thickness or dielectric constant. During the design of the real PhC system, the effect of unintentional native oxide surface layer on the optical properties of 2D PhC slabs has to be taken into consideration. At the same time, intentional oxidization of macroporous PhC structure can be utilized to optimize the design.
The newly developed multi-protocol label switching transport profile （MPLS-TP） fails to actively alarm the fault in advance when conducting restoration in network, or to avoid the false-alarm when equipped with the active-fault-alarm （AFA） to support carrier-grade reliability. In order to solve this problem, a new AFA based pre-restoration mechanism （AFABPRM） is proposed for MPLS-TP controlled optical network, along with the three levels quality-of-service （QoS） based shortest path first rerouting algorithm （TQ-SPF） in this article. The AFABPRM takes full advantage of the AFA technologies, and can solve the false-alarm problem. Analytical and experimental results suggest the better performances of the new mechanism when compared restoration mechanism with or without AFA function, and show that the AFABPRM can solve the false-alarm problem efficiently.
BAI Hui-feng, LU Yue-ming, JI Yue-feng Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, China
