OFDMA Pros and Cons

In OFDMA multiple access is two dimensional (time and frequency)

Multiple users use separate subchannels for multiple access

- Improved capacity

- Improved scheduling and QoS support

- Reduced interference (no intra-cell interference)

- Improved link margin (subchannelization gain)

- High spectral efficiency

Flexible subchannelization

- Pseudo-random permutation (PUSC) for frequency diversity, or

- Contiguous assignment (AMC) to enable beamforming

- Scalable structure to support variable bandwidths

- Allocation of subcarriers to multiple SS's (Subscriber Stations) in an OFDM symbol time- Group of M subcarriers as a unit of allocation - Subchannel

- Narrow subcarrer spacing is sensitive to carreer frequency error

- high PAR ratio (Peak to Average Power Ratio), which reduces the eficiency and hence increases the cost of the power amplifier, which is one of the most expesive component in Radio