The objective of this paper is to study the latest mobile technologies such as HSDPA (High Speed Downlink Packet Access) or 3.5G, and an approach to its successor LTE (Long Term Evolution) or 4G using network simulator called NS-2. First 2G technology came into existence which enabled mobile users with the technologies such as GSM, TDMA and CDMA. It also provided SMS services. After 2G many advanced versions were evolved like 2.5G with the enhancement such as high data transmission rate (56Kbps) and also enabled services like WAP, MMS, sending IPv4 services and GPRS technology. Then it leads to the evolution of 2.75G with the data transfer rate up to 236.8Kbps and it uses EDGE (Enhanced Data Rates for GSM Evolution) technology for data transmission. As the generations were evolving with new advancements the key factor which is mostly enhanced is data transmission rate, thus in the year 2002, 3G evolved which is based on technology named UMTS (Universal Mobile Telecommunication System) that provides 14 MB/s of data transmission rate. It enables internet, mobile TV and video calling services. Further improvement in communication between the user and network using HSDPA technology took 3.5G into existence. Based on simulation of HSDPA, the main objective is to simulate an improved downlink diversity increasing in frequency. © 2012 IEEE.