Wednesday, October 31, 2012

2048 QAM

Martin Sauter on 2048QAM Over The Air. Wow!

Quadrature Amplitude Modulation, or QAM for short, is a modulation technique used by systems such as UMTS, LTE and also by microwave backhaul systems. UMTS and LTE use QAM, 16QAM and 64QAM to encode 2, 4 or 6 bits per transmission step. And 64QAM already pushes the limits quite hard and is only used when a user is very close to the base station.

The highest modulation technique I have heard about for microwave Ethernet backhaul systems to transfer data back and forth from and to the cellular base stations so far is 256QAM, i.e. 5 bits per transmission step. This is possible due to the very directional focus of the radio beam versus sectorized transmission in cellular systems.

Now Dragonwave is saying that their latest system is capable of 2048QAM, i.e. 11 bits per transmission step. Further numbers cited in the article match that claim. A peak throughput of 550 Mbit/s over the channel mentioned in the article would mean that a 50 MHz channel is used for data transmission. Quite a fat pipe but not unheard of for microwave backhaul (see also link above).

An incredible number from today's perspective despite the directional nature of the transmission and pushes the state of the art quite a bit.

P.S. The latest version of Wi-Fi, 802.11ac uses 256QAM for very good signal conditions.

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