The Local Image Fitting (LIF) model is sensitive to the size, shape and position of initial contour. In order to solve the problem, a local image intensity fitting model combined with global information was proposed. Firstly, a global term based on global image information was constructed. Secondly, the global term was linearly combined with the local term of LIF model. Finally, an image segmentation model in the form of partial differential equation was obtained. Finite difference method was used in numerical implementation, simultaneously, a level set function was regularized by a Gaussian filter to ensure the smoothness of the level set function. In the segmentation experiments, when different initial contours are selected, the proposed model can get the correct segmentation results, and its segmentation time is only 20% to 50% of LIF model. The experimental results show that, the proposed model is not sensitive to the size, shape and position of the initial contour of evolutionary curve, it can effectively segment images with intensity inhomogeneity, and its segmentation speed is faster. In addition, the proposed model can segment some real and synthetic images quickly without initial contours.

In view of the problem of a sharp fall on network performance due to network interference caused by channel overlapping aroused by ISM (Industrial Scientific Medical) band shared between WiFi and ZigBee, and severe spectrum underutilization induced by the current CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism, a subcarrier-nulling 2×2 noncoherent antenna MIMO (Multi-Input Multi-Output) PHY (Physical Layer) model was proposed in this paper. In this model, to avoid co-channel interference, a WiFi transmitter needs to detect ZigBee signals appearing in its adopted channel before data transmission, and if any, this transmitter will null the subcarriers within the spectrum occupied by ZigBees, and take advantage of the rest subcarriers to transmit its packets. The receiver needs to identify the subcarriers used by the transmitter, and finish the follow-up work. By this means, interference will be eliminated by signal spectrum separation, thus achieving the goal of heterogeneous network coexistence and making parallel data transmission available. The experiments were run on the test bed composed of GNURadio/USRP platform and ZigBee nodes, and the experiment results show that subcarrier-nulling enabled 2×2 noncoherent antenna MIMO to gain 50%-70% throughput of that in the full bandwidth scenario, and during parallel data transmission ZigBee’s valid received packets ratio is at least 90%.