Integrated Wireless-pon access Network Architectures Milos Milosavljevic

Chapter 8 Project Achievements and Future Work 
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rates were calculated in view of guard and pilot subcarriers used for synchronisation and 
estimation purposes. A worst case scenario 25% cyclic prefix was also included. The 
downstream WiMAX channel transmitter relative constellation error (RCE) was -50 dB, a 
figure higher than the minimum required for 64-QAM modulation. 
Four WiMAX channels, forming an FDM window, at the standard 3.5 GHz with 30 MHz 
subcarrier spacing were generated at the OLT. The number of generated WiMAX channels was 
defined by the limitation of the Aeoflex device. Ideally the number of generated WiMAX 
channels should match the passive optical network split and as a result for a targeted 1:16 split 
to comply with current deployments of legacy PONs, a minimum of 16 channels should be 
generated. This assumes that one or more ONU/BSs would require more than one WiMAX 
channels. The 30 MHz subcarrier spacing was chosen to match the Aeroflex receiver filter 
specifications. 
To address individual ONU/BSs each WiMAX channel should be shifted in frequency from 3.5 
GHz to any higher value that avoids adjacent channel interference. This was being achieved by 
using a predetermined local oscillator (LO) and BPFs in the OLT. In succession the WiMAX 
channels are combined and modulated onto an optical carrier. At ONU/BS, a LO is required, 
operating at the exact same frequency for a specific ONU/BS to downshift the appropriate 
WiMAX channels. Multiple BPFs are also needed to select each channel prior to transmission 
over the air. Also significant to mention is that an additional un-modulated wavelength at 
λ
d2
=1557.3 nm was connected at one of the unused AWG inputs to investigate interference at 
ONU/BSs. 
Complying with downstream, a single IEEE 802.16-2005, 3.5 GHz channel was generated in 
upstream to directly modulate a VCSEL at 
λ
u1
=1548.5 nm. An 8.3 mA bias was used producing 
-0.94 dBm output power prior to being transmitted over the SSMF. Since the experimental 

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