As the demand for wireless service increases, the number of channels assigned to a cell eventually becomes insufficient to support the required number of users. This has been a major concern for both the users and network operators. Every Communication network is required to offer a very high capacity within limited spectrum allocation. The allocated spectrum gradually becomes congested and eventually becomes used up. Congestion in the spectrum leads to increase in call blocking probability which is not desired in the system. There are many techniques available that can be used to enhance the capacity of code division Multiple Access Systems. Some of the techniques include cell splitting, acquiring additional spectrum, using directional antennas. These directional antennas seem not to be as smart as required, sincethey do not carry dedicated digital signal processors like adaptive antennas do. Omni-directional antenna which is believed to radiate signal in all directions consumes more energy because it radiates signal even where it is not required unlike adaptive antenna that radiate signal to where it is desired and as such consumes less energy. Adaptive antennawill be more efficient, since it is actually a combination of an array of individual antenna elements and dedicated signal processing algorithm. Such system can distinguish signal combinations arriving from different directions and subsequently increase the received power from the desired users. This work tends to improve the signal quality of Code Division Multiple Access by the use of Multiple Element Antenna consisting of sixteen (16) elements on 0.5λ wavelength separation distance. Based on this antennavariable and Least Mean Square (LMS) algorithm simulation of the performance of the system is carried out. Result shows that as offered traffic increases, the Cumulative Density Function (CDF) is constant initially from 5-6 users, and drops to 0-2 users. When the number of arrays is kept constant and the distance of separation varied for the following 0.1, 0.5, 2 and 5 times the wavelength, it was found that antenna elements of half the wavelength (i.e. 0.5λ) was, however, the best performed of all the distance of separation. Element spacing of less or more than 0.5λ wavelength increases sidelobe which can interfere with mainlobe, its evident that it is possible to direct the Radiations maximum pattern for user position into desired direction, also direct a null for undesired interference and sources. This work shows that adaptive antenna has powerful capabilities to reduce interference and sending data towards the wanted direction only, and it can be recommended in Base Station to ameliorate power problem, also in radio and astronomy.
CDMA, Antenna, Beamforming, Communication
Idiode Kingsley , Mbachu C. B , Iloh J. P "Enhancing CDMA Network Capacity Using Adaptive Beam Forming Technique" Iconic Research And Engineering Journals Volume 3 Issue 3 2019 Page 23-30
Idiode Kingsley , Mbachu C. B , Iloh J. P "Enhancing CDMA Network Capacity Using Adaptive Beam Forming Technique" Iconic Research And Engineering Journals, 3(3)