Limitation or disadvantages of WiMAX

One of the major problem with WiMax is Spectrum Allocation; there are two main types of spectrum Allocation. Licensed and unlicensed, the unlicensed bands such as 2.4 GHz and 5.8 GHz, which are used for some applications, may reduce the performance and QoS of WiMax, which may affect the commercial viability of the service. And for the licensed bands 2.5 GHz and 3.5 GHz bands, they are currently occupied by some other services such as fixed-satellite, broadcasting satellite, etc. in some countries. The scarcity of suitable spectrum for WiMax may not be a problem which can be satisfactorily resolved in the short term. 

 One problem with OFDM systems is the high peak-to-average power Ratio (PAPR), which significantly reduces the efficiency of the transmitter high power amplifier (HPA). Many solutions have been suggested to reduce the peak power of OFDM signals. Using typical HPA models and spectral masks, these PAPR reduction methods are evaluated in terms of the total system degradation.