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Boosting long-haul microwave capacity with 1024 QAM

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EricOleary
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re: Boosting long-haul microwave capacity with 1024 QAM
EricOleary   3/29/2012 4:27:32 PM
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1024 QAM presents a huge challenge to both tx and rx. On the ttx side, 1024 QAM has a much higher peak to average power ratio which means a big issue to the non-linear power amp. Would that be a compromise between the linearisation technique and the power backoff? On the RX side, it is susceptible to multiopath fading, which can imply a very expensive adaptive equaliser to compensate it. Given the maturity of technologies such as OFDM or SC FDE, should the system be considered with one of these advanced technologies?

Eirik
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re: Boosting long-haul microwave capacity with 1024 QAM
Eirik   4/10/2012 8:48:25 AM
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Hi, indeed 1024QAM pose huge challenges in several areas. The peak to average ratio depend strongly on how the 1024QAM constellation is implemented. In the radio described in this case the peak to average for 1024QAM is really not much different to 256QAM. It does require Tx linearization and sufficient power backoff, but compared to 256QAM it’s really not very different. Long Haul microwave radios operate typically with 28-30, 40 or 56 MHz carrier bandwidth (varying with different frequency bands). With such bandwidth, it is indeed susceptible to multipath fading. The debate of OFDM vs single carrier, is not clear cut. OFDM offers both pros and cons in this area. OFDM is potentially offering better robustness to selective (multipath) fading but requires more signal processing and secondly the OFDM signal could offer better spectrum utilisation (due to the more “square” spectrum) but spectrum masks issued by the regulatory bodies (FCC, ETSI) are optimised to single carrier modulation.

ersujan
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re: Boosting long-haul microwave capacity with 1024 QAM
ersujan   7/13/2012 11:00:47 AM
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5000iP SerHello Erik Good to hear that you have used 1024 QAM over a 65 km path in Western Norway, using the 6.7 GHz frequency band. We are also looking to deploy Higher capacity Microwave Link for long distance above 65 Km using higher order modulation like 1024 QAM. Could you please share me some technical parametrs ( like TX power, antenna type, antenna dimension, antenna gain, Channel Bandwidth, Modulation,Rx level,Rx sensitivity, Fade margin,Channels) with the link budget calculation used. Which Company Microwave radio you are using for such link. Hope you information would be very helpful to me and my companyies

van13
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re: Boosting long-haul microwave capacity with 1024 QAM
van13   1/10/2013 6:02:10 AM
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Hi Eirik, Can you share technical parameters on your trial link. We also want to try a microwave system using 1024 QAM modulation. Thanks!

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