Machine-to-Machine (M2M) networks are an emerging technology with applications in numerous areas including smart grids, smart cities, vehicular telematics, and healthcare. In this paper, we design two estimation protocols for rapidly obtaining separate estimates of the number of active nodes of each traffic type in a heterogeneous M2M network with T types of M2M nodes (e.g., those that send emergency, periodic, normal type data etc), where T ≥ 2 is an arbitrary integer. One of these protocols, Method I, is a simple scheme, and the other, Method II, is more sophisticated and performs better than Method I. Also, we design a medium access control (MAC) protocol that supports multi-channel operation for a heterogeneous M2M network with an arbitrary number of types of M2M nodes, operating as a secondary network using Cognitive Radio technology. Our Cognitive MAC protocol uses the proposed node cardinality estimation protocols to rapidly estimate the number of active nodes of each type in every time frame; these estimates are used to find the optimal contention probabilities to be used in the MAC protocol. We compute a closed form expression for the expected number of time slots required by Method I to execute as well as a simple upper bound on it. Also, we mathematically analyze the performance of the Cognitive MAC protocol and obtain expressions for the expected number of successful contentions per frame and the expected amount of energy consumed. Finally, we evaluate the performances of our proposed estimation protocols and Cognitive MAC protocol using simulations.
Polysulfone (Psf) hollow fiber membranes (HFMs) have been widely used in blood purification but their biocompatibility remains a concern. To enhance their biocompatibility, Psf/TPGS (d-α-tocopheryl polyethylene glycol 1000 succinate) composite HFMs and 2-methacryloyloxyethyl phosphorylcholine (MPC) coated Psf HFMs have been prepared. They have been evaluated for in vivo biocompatibility and graft acceptance and compared with sham and commercial membranes by intra-peritoneal implantation in rats at day 7 and 21. Normal body weights, tissue formation and angiogenesis indicate acceptance of implants by the animals. Hematological observations show presence of post-surgical stress which subsides over time. Serum biochemistry results reveal normal organ function and elevated liver ALP levels at day 21. Histological studies exhibit fibroblast recruitment cells, angiogenesis and collagen deposition at the implant surface indicating new tissue formation. Immuno-histochemistry studies show non-activation of MHC molecules signifying biocompatibilty. Additionally, Psf/TPGS exhibit most favorable tissue response as compared with other HFMs making them the material of choice for HFM preparation for hemodialysis applications.
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