r greater amount So there are two questions that we need to try and answer in this chapter. Can OFDM combined with enhanced functionality at the MAC layer and higher layers of the protocol stack deliver a significant improvement in system efficiency and power efficiency and can this in turn be translated into additional single-user value? To do this we need to take a view of how transformative the transforms that we use are really going to be in terms of realisable single-user added value and how effectively contention and scheduling algorithms arbitrate between the single- and multiuser experience. Can OFDM combined with enhanced functionality at the MAC layer and higher layers of the protocol stack be translated into multiple-user value? One argument made here is that OFDM systems are more resilient to user to user interference but this has yet to be proven in practice within fully loaded real-life networks. The real answer to this question as above is more likely to be found in contention and scheduling algorithms, both of which we explore. 3.2 OFDM and the Transformative Power of Transforms In Chapter 2 we reviewed the Fourier transform and its role in processing OFDM signal wave- forms. Essentially, the difference at the physical layer between 3G mobile broadband systems and LTE '4G' systems is that Fourier transforms have replaced Hadamard-Rademacher-Walsh transforms. So the first thing we need to try and do is quantify the difference between Hadamard- Rademacher-Walsh transforms and Fourier transforms. 2 2 We should also be covering Hilbert transforms and their role in IQ modulation but for reasons of space and brevity we recommend that you download this excellent tutorial http://www.complextoreal.com/tcomplex.htm A less comprehensive but broader treatment can be found in the August 2011 RTT Technology Topic Transforms that can be downloaded here http://www.rttonline.com/techtopics.html Interrelationship of the Physical Layer with Other Layers of the OSI Model Fast Fourier transforms are already used in 3G