Introduction to 802.16 – WiMAX

 

I attended a session on “Introduction to 802.16 – WiMAX” at Lucent’s Whippany office on 15th June, 2006. It was organized by IEEE Vehicular Technology Society The speaker Steve Crain was from Agilent Technologies. Please find viewgraphs

 

It was an informative talk. The speaker had an excellent presentation skill and in-depth knowledge of the subject. He compared WiFi 802.11a, WiMAX 802.16d Fixed and WiMAX 802.16e Mobile. Audience asked many good questions that help to clarify the subject matters further. Some times, audience asked some questions, whose answers were present in just next slides. He handled all the questions very well. He simplified that time domain signal; we can view with Oscilloscope and frequency domain with spectrum analyzer. He shared his own experience. He switched ON wireless router, cordless phone and microwave oven; all operate in same frequency band. Then he analyzed the RF signal with help of spectrum analyzer and how all the device reacts to the unwanted signals from other devices. He explained that here orthogonal does not mean at right angle (90 degree) Orthogonal means many carriers who do not interact with each other and who tightly placed in a band with help of DSP.

 

WiMax standard gives so many alternatives to operator. So operator has to carefully choose between different setup options and WiMax equipment vendor can help them. He addressed mainly the physical layer aspects. He explained relations of all physical layer parameters like symbol rate, bandwidth, carrier spacing, modulation, symbol interval, slots, Data Burst etc. The view graphs depict signals for time domain and frequency domain both. The data bits can be detects only in frequency domain. So there is no meaning for instantaneous signal in OFDM!! The receiver and transmitter implement FFT and inverse FFT to switch the domain. All such complex signal processing is possible only because of advancement in DSP. He explained how receiver SS tuned to signal with coarse tuning and fine tuning. How SS knows, which carriers carries data intended for it.  We all surprised that such a complex standard works! :) WiMax 802.16e OFDMA is already implemented at Korea. WiMax will be launched at US possibly in April 2007. WiMax may become threat to EvDo technology.

 

I asked few questions from my project ‘AirPro’ perspective. WiMax is different from cdma and other cellular technology. Here we do not have power management. We do not have flexibility to reduce and increase coverage area by changing pilot power percentage. Off Course no soft handoff for high data rate channel. The major drawback is higher peak to average power ratio. At Hotel we met one student working at Lucent Germany, on reducing this ratio.

 

I interact with audience before and after session. One person talked with me about cdma at India. He told there are two brothers involved in cdma business in India. (Mukesh Ambani and Anil Ambani) and one of them has married with a famous heroine. (Tina Munim/Tian Ambani). It was a different kind of feeling, that some foreigners have all this information about cdma business at India !

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