An Insight into the Use of Smart Antennas in Mobile Cellular Networks

Abstract

3G and 4G cellular networks are designed to provide mobile broadband access offering high quality of service as well as high spectral efficiency1. The main two candidates for 4G systems are WiMAX and LTE. While in details WiMAX and LTE are different, there are many concepts, features, and capabilities commonly used in both systems to meet the requirements and expectations for 4G cellular networks. For instance, at the physical layer both technologies use Orthogonal Frequency Division Multiple Access (OFDMA) as the multiple access scheme together with space time processing (STP) and link adaptation techniques (LA) In particular, Space Time Processing has become one of the most studied technologies because it provides solutions to ever increasing interference or limited bandwidth (Van Rooyen, 2002), (Paulraj & Papadias, 1997). STP implies the signal processing performed on a system consisting of several antenna elements in order to exploit both the spatial (space) and temporal (time) dimensions of the radio channel. STP techniques can be applied at the transmitter, the receiver or both. When STP is applied at only one end of the link, Smart Antenna (SA) techniques are used. If STP is applied at both the transmitter and the receiver, multiple-input, multiple-output (MIMO) techniques are used. Both technologies have emerged as a wide area of research and development in wireless communications, promising to solve the traffic capacity bottlenecks in 4G broadband wireless access networks (Paulraj & Papadias, 1997). MIMO techniques and their application in wireless communication systems have been extensively studied (Ball et. Al, 2009), (Kusume et. Al, 2010), (Phasouliotis & So, 2009), (Nishimori et. al, 2006), (Chiani et. al, 2010), (Seki & Tsutsui, 2007), (Hemrungrote et. al, 2010), (Gowrishankar et. al, 2005), (Jingming-Wang & Daneshrad, 2010); however, critical aspects of using SA techniques in cellular networks remain fragmental (Alexiou et. al, 2007). In particular those aspects related with the influence of users’ mobility and radio environment at system level in SA systems which use Spatial Division Multiple Access (SDMA) as a medium access technique.