Integrated Wireless-pon access Network Architectures Milos Milosavljevic

Chapter 8 Project Achievements and Future Work 
157 
power sensitivity. The path loss of the channel was calculated based on empirical models taking 
into consideration parameters such as base station antenna height, gain and loss, to mention a 
few.
Multiple IEEE802.16d channels, with 70 Mbit/s downstream and 40 Mbit/s upstream data rates, 
were frequency shifted around the same RF carrier and transmitted on two different 
wavelengths. The obtained results have demonstrated standard EVMs of -31 dB at ONU/BS 
remote antenna inputs and minimum 1E-4 BERs bidirectionally over combined 20km optical 
and 330m faded overlapping micro-cells circumference without any error coding or relay 
techniques. The application of a low-cost, long-wavelength VCSEL array in upstream for 
colorless transmission demonstrated a 0.7 dB power penalty on the received WiMAX channels 
in the OLT. 
Furthermore, in order to validate the new integrated access network core features, an 
experimental test-bed was implemented to demonstrate bidirectional WiMAX routing over 
xPON. Readily-available Aeroflex PXI WiMAX transceivers, terminating either side of the 
multi-wavelength, splitter-PON links were employed. Also, an add/drop multiplexer was used 
inside each ONU/BS instead of tuneable optical filters. Before being assigned to a subcarrier, 
the OFDMA symbols are coded and modulated using convolutional coding and 64QAM 
downstream, 16QAM upstream modulators respectively. The formulated OFDMA symbols are 
then applied to an inverse FFT producing their time domain equivalent. The number of 
OFDMA subcarriers (corresponding to the FFT size) was selected according to standard 
deployments and was set to 1024. Consequently, for a 10MHz bandwidth, due to the limit of the 
Aeroflex RF output channels spacing, and 64-QAM modulation, the resulting aggregate data 
rate per sector for the downstream WiMAX link was specified at 25.2 Mbps. In view of 16-
QAM modulation in upstream, the corresponding figure was defined at 18.9 Mbps. These data 

---