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In order to calibrate the sensitivity of fiber grating hydrophone,a calibration technique of fiber grating hydrophone was studied.In this paper,the working principle of fiber grating hydrophone was introduced firstly.Secondly,using tunable laser and intensity modulation method with work-point controlling,the signal demodulation and stably measurement of fiber grating hydrophone was realized.Based on these methods,a calibration system of fiber grating hydrophone was established using comparison methods,and its calibration frequency range was 20 Hz to 10 kHz.Finally,using this calibration system,the sensitivity of a fiber grating hydrophone made of equivalent phase shift fiber Bragg grating was calibrated in the frequency range 20 Hz to 10 kHz,and measurement uncertainty of the system was estimated.The results proved that this system can correctly calibrate the sensitivity of fiber grating hydrophone,with its expand uncertainty(at k=2) of 0.9 dB.

In this paper, the authors propose a new optimization method of path bandwidth allocation for large-scale telecommunication networks. By using the decomposition-coordination method to get an optimal solution of path bandwidth allocation for large-scale communication networks, a big network is divided into small and inter-connected sub-networks. The path bandwidth allocation procedure is composed of three phases. Firstly, the large-scale network is divided into small sub-networks; then, a decomposition-coordination procedure is imposed to allocate path bandwidths between nodes within each sub-network and to find the bottleneck subnet of the whole network and to evaluate the worst call blocking probability of it; finally, path bandwidths of source-destination pairs between different sub-networks are computed out by successive use of an ordinary optimization algorithm. Comparing with existing algorithms, our results show that the Decomposition-Coordination Large-scale Path Bandwidth Management (DCLPBM) algorithm can get results with high accuracy and both spatial and time complexities are reduced. As the coordination procedure in our model is quite simple, the DCLPBM can be converted to a distributed computing version easily. This is fascinating from a point of view of managing the network in a real network environment.

A queueing model for performance analysis of goback- N (GBN) automatic repeat request (ARQ) protocols in wireless networks using dynamic radio link adaptation with fixed feedback was proposed. Firstly, the paper analyzes the major factors affecting residence time of the packets, aiming at the problem that packets in a batch arrival at relay. Secondly, the paper establishes Markov model of packet transmission and deduces the system state is a G/M/1 type Markov chains, and the delay statistics at relay node are figured out by using matrix geometric methods. At last, the paper analyzes the influence of the arrival rate, channel bit error rate and the doppler frequency shift on the system.

It is difficult to implement a mature cryptography mechanism in the low-cost RFID system because of the limitation of available resources. Following the analysis of several kinds of typical authentication protocols, an enhanced authentication protocol is proposed to confront security defects in low-cost RFID systems. This scheme adopts a bi-directional authentication mechanism, and has resolved the data synchronization problem caused by IDspsila dynamic refreshment. Furthermore, the possibility of denial-of-service attacks can be reduced. This scheme is applicable to a system with a large number of tags and can meet the requirements of the users.