Friday, August 13, 2010

Some drawbacks and Suggested Solutions of WiMax

There are some drawbacks of this Technology; we must consider those when going to the phase of implementation of this technology. Some important objections to WiMAX are:
Interference: The interference from other broadcasters may degrade the quality of the WiMAX service.
1. Quality of Service (QoS): Wireless is inherently unstable so this can affect voice and video services.
2. Security: As it is believed that Wireless medium is less secure so Security of WiMax can be big question.
3. Reliability: Also reliability of any wireless technology isn’t that much as compare to cable network, so reliability of Wimax can be a question too.

The solutions to these drawbacks are best understood through the Physical (PHY) and Medium Access Control (MAC) Layers. The WiMax Working Group no doubt were aware of these objections based on experiences with earlier wireless technologies (Wi-Fi, LMDS, MMDS,CDMA, GSM) and they made Wimax to fix failures of past wireless technologies.
Spectrum Allocation Problem
A 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.
Peak to average power Ratio
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.

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