An accurate and numerically efficient model for the rectangular microstrip antenna is presented. It concerns a transmission-line model which features the following three major improvements with respect to earlier such models: the mutual radiative coupling (both real and imaginary parts) between the equivalent slots is fully taken into account; the influence of the side slots on the radiation conductance is taken into account implicitly; simple analytic expressions are introduced for all relevant model parameters. By way of illustration, the new model is applied to antennas with a single microstrip feed line. Excellent agreement is shown with available experimental and theoretical results for the input impedance of a rectangular antenna. The improvements with respect to previous transmission-line models are illustrated for a square antenna.

In this paper a novel analytical model for the saturation throughput of unslotted Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA) in wireless networks is proposed. A fixed point procedure is developed based on the interaction of the Physical layer (PHY) and the Medium Access Control sub-layer (MAC). The output of the Clear Channel Assessment (CCA), i.e. idle or busy medium in the neighborhood of a node, serves as a feedback mechanism for the dynamical scheduling rate controlled by the back-off procedure. The PHY is described by a renewal process between successful transmissions with failed attempts and collided packets in between. A semi-Markov process of the internal states of a node is used as a model for the MAC. An event-driven simulator for the non-beacon enabled IEEE Std 802.15.4™MAC is developed to verify the numerical results of the analytical method. A detailed analysis of the idle period after a transmission is carried out based on the proposed analytical approach. The probability that the CCA senses the channel idle depends clearly on the actual back-off stage and the first back-off expiration after a transmission cannot be modeled by a exponential distribution when a finite number of nodes are in contention. The output of the event-driven simulations confirms both statements in great detail and the saturated throughput evaluated B. Lauwens ( ) · B. Scheers CISS, Royal Military Academy, 30 Renaissancelaan,

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