Clock skews of devices on the Internet are viewed as one way delay noise, but their distribution is unknown. We explore the distribution of clock skews to see the conflict probability. In this paper, we introduce an accurate clock skew estimation algorithm to filter inaccurate clock skew estimation by comparing the results between linear programming method and least square fitting. Delay jitter and other noises affect the estimation result. When the difference of two methods is large, the estimation result is unstable and inaccurate, so the estimation result should be dropped. Based on this algorithm, we use traces of real Internet measurements to collect 1825 accurate clock skews of different devices to establish a fingerprint database. Furthermore, we show the distribution of clock skews and comparing conflict probability with different number of devices. The distribution shows that clock skews are diverse, and most of clock skews are in the region of [-100, 100] PPM. The results indicate that when the number of devices is small (<5), clock skews won’t be conflict with each other, so clock skews are good tools to detect faked devices or NAT; When the number of devices increases, the conflict probability increases linearly, so clock skews of different devices can not distinguish each devices effectively.

The impact of Doppler frequency hopping on code tracking performance is simulated. A design on pseudo-noise (PN) Code Tracking Loop aided by the carrier tracking loop according to the carrier frequency hoping pattern is proposed in this paper. This scheme can be applied in the Telemetry, Tracking, and Commanding system which uses Direct Sequence/Frequency Hopping Spread Spectrum (DS/FH) hybrid spread spectrum technology. Simulations of the code tracking loop under different carrier to noise ratios are compared based on this scheme. The results show this method on PN code tracking of DS/FH signals is valid.

Aiming at the shortcomings of the traditional ranging algorithm, this paper proposes a new ranging technique for 802.16e uplink in the frequency domain. The ranging technique eliminates the effect of the timing offset by computing the frequency difference of adjacent sub-carriers in the ranging channel, which reduces the search space from two dimensions to one dimension. When there is slot, the ranging code can be detected by adopting a threshold. The ranging technique is implemented through one-dimension search in the frequency domain, and consequently the complexity can be reduced and without losing the performance of timing estimation. The simulation results show the good ranging performance of this technique.

Data similarity measurement is an important direction for data mining research. This paper is concentrated on the issue of protecting the underlying attribute values when sharing data for the similarity of objects measurement and proposes a simple data transformation method: Isometric-Based Transformation (IBT). IBT selects the attribute pairs and then distorts them with Isometric Transformation. In the process of transformation, the goal is to find the proper angle ranges to satisfy the least privacy preserving requirement and then randomly choose one angle in this interval. The experiment demonstrates that the method can distort attribute values, preserve privacy information and guarantee valid similarity measurement.

This article examines the relationship between timely project completion and the management’s integrative capability. Measures of the integrative capability are used to predict on-time project completion, where completion is a function of the duration of IT-related project delays. In a longitudinal study of 74 enterprise application integration projects in the medical sector, integrative capability was measured from the point of view of the CIO and a facility IT manager. Accounting for several project controls, our Cox regression results indicate both integrative dimensions significantly mitigate the duration of IT-related project delays, thus promoting timely project completion. The analysis also reveals the importance of taking management structure into consideration when studying IT phenomena in networked organizations.

The original R*Q-tree is an important class of query index in the spatial database, but when carry on frequent insertion and deletion, the efficiency is very low, because its construction cost is much more than that of the other query methods. So the new R*Q-tree using the delaying and Clustering splitting technology has been proposed for improving the shortcomings of the original R*Q-tree. When the data objects are inserted into the new R*Q-tree, the nodes may overflow. During the process of insertion, rather than split the node immediately, it attempts to insert the nodes into the adjacent neighboring nodes by using of the delaying selection splitting technology until they are full. If the adjacent neighboring nodes are full, it will use the clustering technology to split the nodes, data items will be reorganized between the neighboring nodes and the splitted nodes. The new R*Q-tree can ensure the premise of the query performance and the cost of structure greatly reduced, at the same time, significantly the space utilization of the index structure is improved. Finally, the experimental analysis and appraisals show that the operation efficiency of the new R*Q-tree is enhanced. And in the new R*Q-tree and the promoter region, there are no duplicated elements, so the structure of the new R*Q-tree can be simplified.

After analyzing the current networks of Guizhou University，we brought forward a scheme of next generation campus networks based on softswitch technology by choosing SoftX3000 switching system of HuaWei and provided the specific solution of accessing campus networks in this paper. It is proved that this scheme is feasible by using OPNET, which not only accomplished the integration of the PSTN and IP networks but also achieved the combining of voice services and data services.

Antenna Selection in MIMO systems can increase the system capacity, reduce the MIMO system complexity and cost of radio links effectively. In this paper, a new joint antenna selection algorithm was presented which can adaptively change the number of the selected transmitting and receiving antenna number according to the channel station. It can obtain the similar system capacity with the optimal joint antenna selection algorithm in any correlation coefficient, but the calculated amount is far less than the optimal joint algorithm.

The goal of key exchange protocol is to establish a common and secure session key using the interactive communications. The existing schemes are usually in the pattern of ‘user-server-user’, so are weak in reality. In this paper, a new three-party key exchange protocol based on Diffie-Hellman was proposed which contains the following characteristics: without server; providing key secrecy and forward secrecy; ensuring no key control; ensuring known-key secrecy.

Delay Tolerant Mobile Sensor Network (DTMSN) is the network for pervasive information gathering. Traditional static routing approaches may not fit for DTMSN due to its intermittent connectivity. This paper proposes an relative distance based routing (RDBR) strategy for DTMSN, in which nodes delivery probabilities are calculated and updated according to the latest relative distance from themselves to the sink node, and data are delivered according to nodes’ delivery probabilities. RDBR also introduces a redundant copies controlling technique based on the message priority. Simulation results show that RDBR achieves a well tradeoff between the data delivery ratio/delay and the delivery overhead.