PDA

View Full Version : Question WiMAX vs. LTE frequency bands ?



fahmi
2011-11-21, 07:25 AM
Hi experts,
LTE deployments can be undertaken in any of the band range of 800 MHz to 2,62 GHz.

While WiMAX was first designed for line of sight (LOS) environments at high frequency bands of 10-66 GHz. Later versions support non line of sight (NLOS) in radio bands between 2-11 GHz.



Why LOS environments support higher Frequency bands compared to NLOS ?
Even for NLOS modes, WiMAX frequency bands remain higher than LTE (up to 11 GHz), Why ? and could we deploy LTE for higher frequencies ?

dekili
2011-11-21, 08:01 AM
Wimax was intended for the bands from 10GHz to 66GHz because these bands were not interesting for more important commercial systems and it was targeted to use these bands for alternative services. When Wimax was designed by IEEE, first intention was to replace wireless cable (as they used to call it) which was start of broadband wireless local loop. Later, band from 3.4-3.6GHz has een seen as better candidate because there were BWA systems like Canopy (********) or some Alvarion systems operating in this frequency band. Idea was to replace proprietary systems with standardized one.
Due to very high frequencies, propagation losses are very high and yo cold find strictly MW links in these bands. Any obstale (for 66GHz it is even leaf on on a tree) cause very high losses, allowing only small ranges. It was clear that only under 3GHz NLoS is an option.
LTE should serve as cellular technology and good propagation conditions, with PLL and processing units in the phone that should be cheap enough to be able to buy terminal (phone) are of critical importance. That is why lower frequencies are very interesting and since mobile operators are able to finance high prices for the licenses - LTE is in lower frequency bands.
Of course, from the technical point, LTE could be deployed in higher frequency bands. Simple example is Wi-Fi (11.a and ewer revisions) that operates on 5GHz. his is also OFDM technology deployed in higher frequency bands.
Cheers