Integrated Wireless-pon access Network Architectures Milos Milosavljevic

6.3.4 WiMAX Receiver 
In order to include the realistic limitations, such as path loss, expected in the wireless receivers 
due to signal transmission over the air, the models needed to be modified to include typical 
noise figures encountered in practical devices. Therefore, for the downstream WiMAX receiver, 
the noise in considered 20 MHz bandwidth is given by [20]:
Noise
Power
=10log
6.1 
where kT is the thermal noise of the receiver, typically -174 dBm and B is the WiMAX 
bandwidth. 
The total noise in the given bandwidth is thus equal to -100.1 dBm which in association with 
the receiver noise figure of 4 dB, results to a noise floor of -96.1 dBm. According to the 
WiMAX standard for 64-QAM modulation the minimum received SNR should be 24.4 dB [13]. 
The downstream receiver sensitivity is then -71.7 dBm which with the effective isotropic power 
of +40 dBm, as specified in Table 6-1, allows for a maximum attenuation of 111.7 dB across 
the wireless channel.
Similar calculations have been performed for the upstream WiMAX receivers in the OLT 
giving a sensitivity figure of -81.8 dBm and a maximum allowable attenuation of 135 dB. The 
higher attenuation values allowed in upstream are due to the fact that 16-QAM modulation 
mapping has been utilized for the upstream transmitter.
Figure 6-8 demonstrates the VPI model at the wireless receiver utilized to set the constant noise 
floor. Essentially, the white noise source is initially band pass filtered, according to the 
transmission bandwidth, producing the required output noise power [20]. The transmission 

---

Chapter 6 Multi-Wavelength WiMAX-PONs with Overlapping Cells 
128 
bandwidth is considered as the WiMAX signal width applied in the model for transmission over 
the converged network. The resulting output noise is added to the input signal setting the noise 
floor.