The communication system transmits information from one place to another using electrical energy. This article describes the analysis and design of electronic circuits used in radio frequency communication systems covering the frequency range up to several hundred megahertz. The actual frequency switched depends on whether the circuit is made with decree components or as an integrated circuit. The electromagnetic waves that leave the transmitting antenna arrive at the receiving antenna in one of many waves. These include ground waves, sky waves, space waves and satellite waves. Earth waves travel along the ground and follow the terrain. Radio wave propagation involves how the radio signal generated by a transmitter travels to the receiver located some distance away. Since the portion of the electromagnetic frequency spectrum used for broadband wireless communication extends from 300 MHz to 300 GHz. The frequency range covers the wavelength from 1 m to 1 mm. In these frequency bands, radio waves are transmitted as space waves. That is, neither ground nor sky waves are used at these frequencies. The simplest radio propagation environment is free space with no atmosphere and no solid objects along the path between the transmitter and receiver. Such an environment allows radio signals to travel within line of sight and be received as direct waves. Unfortunately, this model is an oversimplification of practical propagation environments where the radiated wave comes into contact with solid objects that produce changes in its amplitude, phase, and direction of propagation. Even in the absence of solid objects, the strength of radio signals decreases as the test distance increases. The medium over which radio waves pass......middle of paper......ts. This means that the network management system must be such that it periodically monitors the RSSI for each mote. When the RSSI is below a predefined threshold, it should be possible to remotely reconfigure the affected mote so that it can access the network via the second access point it can see. The task of managing the network is complicated by many factors, including different network technologies, heterogeneous systems from myriad vendors; and a number of distributed applications, some of which have vendor-specific requirements. Added to this is the fact that many new network applications place high demands on the network in terms of QoS and security. The task of configuring the network to meet each application's end-to-end QoS and security requirements is tedious and cannot be handled by traditional network management systems.