Enhancement: Enhancements In WiMAX

Sub Channelization

Another option within WiMAX in the uplink is Sub Channelization. Without sub channelization, narrow restrictions and requirement for cost effective Customer Premise Equipments (CPEs), usually cause the link budget to be unbalanced, for that reason the system range to be up link is restricted. Sub channeling allows the link budget to be objective such that the system gains are parallel for both the up and down links. Sub channeling focuses the broadcasting power into fewer OFDM carriers; this is what boosts the system gain that can either be applied to widen the reach of the system, overcome the infrastructure penetration losses, and or lessen the power consumption of the CPE. The use of sub channeling is promoted expansion in Orthogonal Frequency Division Multiple Access (OFDMA) to permit a more flexible use of resources that can maintain roaming or mobile operation. (Deepak Boppana, 2005)

Transmission Diversity

Diversity formats are used for improvement of multi-path and reflections signals that arise in Non-Line-of-Sight (NLOS) environment. Diversity is an optional element in WiMAX. The diversity algorithms presented by WiMAX in both the transmitter and receiver significantly enhances the system accessibility. The WiMAX transmit diversity option uses space time coding to offer transmit source freedom; this decreases the weaken margin requirement and resist the interference with other devices. For receive diversity, a variety of joining techniques are present to increase the accessibility of the system. For example, Maximum Ratio Combining (MRC) takes benefit of two separate receive chains to prevent fading and decrease path loss. Diversity has verified to be a helpful tool for coping with the challenges of NLOS transmission. (Srikanth Mettukuru, 2007)

See Also:

OFDM (Orthogonal Frequency Division Multiplexing)

WiMAX & IMT-Advanced

Power Control & Error Detection

Antennas & Adaptive Modulation