Fuzzy logic power Control for Zigbee Cognitive Radio
Sai Keerthi Varikuti · 2014
Spectrum sharing without interfering to the primary users is one of the challenging issue in cognitive networks, at the same time power control is one of the feasible solution for spectrum sharing without disturbing the primary user to achieve required performance at cognitive radio. In this paper one Zigbee is configured as primary user and another Zigbee as secondary user which together forms a cognitive network. Here the implementation of the designed setup is carried out by analyzing signal strength , transmit power level assignment and routing algorithm on specific transceiver model of IEEE 802.15.4/Zigbee on Arduino board which leads to better performance of cognitive radio to access spectrum. Keywords—CR (Cognitive Radio), PU (Primary User), SU (Secondary User), TPC(Transmit power control), (RSSI)Received signal strength indicator. INTRODUCTION Today wireless systems take up more and more of the frequencies that are available. Most of them are licensed to high speed wireless internet, telephone and mobile operators internet[1]. There is a need to develop the new system due to high demands on frequencies as there seems to be lack of free frequencies while new wireless systems are developed One such technology is called Cognitive Radio, which allow the re-use of spectrum.[2] The idea for cognitive radio has come out of the need to utilize the radio spectrum more efficiently, it is possible to develop a radio that is able to look at the spectrum, detect which frequencies are clear, and then implement the best form of communication for the required conditions thus one can say Cognitive Radio (CR) is a form of wireless communication in which a transreciever can intelligently detect which communication channels are in use and which are not, and instantly move into vacant channels while avoiding occupied ones. This optimizes the use of available radio-frequency (RF) spectrum while minimizing interference to other users. [2]. In an underlay CR system the secondary users (SUs) protect the primary user (PU) by regulating their transmit power to maintain the PU receiver interference below a well defined threshold level. The limits on this received interference level at the PU receiver can be imposed by an average/peak constraint [3]. Power control in CR systems presents its own unique challenges. In spectrum sharing applications, SU power must be allocated in a manner that achieves the goals of the CR system while not adversely affecting the operation of the PU. In [4], a distributed approach was used for power allocation to maximise SU sum capacity under a peak interference constraint. Fuzzy logic decision has been to choose the most suitable access opportunity for various transmit power levels using Zigbee to dynamically adjust to various power levels to analyze the interference scenario effectively[5] In this paper hardware system is proposed with Zigbee modules in the ISM band and microcontroller ATMEL ATMEGA328P based Arduino board to control the transmit power levels and spectrum sensing in order to provide a reliable communication by reducing the interference w.r.t to the power levels to the primary user unit of the cognitive radio thus to design a system to limit the interference w.r.t to transmit power levels The outline of the paper is as follows. Section II describes system model of primary user system and cognitive secondary user system with respect to receiver and transmitter and their working model. Section III shows the experimental setup. Experimental measurements and results are shown and described in section IV. Section V tells about the future work. International Journal of Engineering Research and General Science Volume 2, Issue 3, April-May 2014 ISSN 2091-2730 123 www.ijergs.org SYSTEM MODEL In this paper we consider scenario in which a primary system is licensed service and cognitive secondary system present in the same area along with primary system using opportunistic radio spectrum access which should not increase level of interference observed by primary system. Here the cognitive system consists of two units namely Surveilling Unit and Regulating/Supervising Unit. Fig 1 : Surveilling Unit Surveilling Unit consists two Zigbee module one for each primary user and secondary user which are connected to PC and monitored through the X-CTU software. Fig 2 : Regulating/Supervising Unit PC PU Zigbee Module SU Zigbee Module PC