tailieunhanh - Radio Propagation

S/N ratio should be above a certain threshold (a function of modulation scheme). Signal power should be above the sensitivity threshold. Predict received signal strength when the transmitter and receiver have a clear line-of-sight path between them. | Chapter 2: RADIO PROPAGATION Đặng Lê Khoa Email: dlkhoa@ Facuty of Electronics & Telecommunications, HCMUS Understanding RF Propagation Goals Estimate radio coverage area Estimate link performance Estimate network design parameters Transmitters and their location Transmit power Antenna type How many APs will be needed to cover IITK campus? Conditions for correct reception S/N ratio should be above a certain threshold (a function of modulation scheme) Signal power should be above the sensitivity threshold What will happen if noise level increases? What will happen in presence of another transmitter? Pt B C A sensitivity threshold Noise power Interesting Scenarios At which locations will correct reception take place? Antenna Basics Isotropic Dipole High gain directional 0 dBi dBi 14 dBi Free Space Propagation Model PT PR d Isotropic power density Power density along the direction of maximum radiation Power received by Antenna Predict received signal strength when the transmitter and receiver have a clear line-of-sight path between them Also known as Friis free space formula Near Field and Far Field Pt PR near field Good predictor when receiver is in far field (the region beyond df) df Largest physical dimension of antenna Example Find the near field distance for an antenna with max dimension of 1m And operating frequency of 900 Mhz Answer at 900 Mhz = 33 cm Path Loss (relative measure) Pt PR f is in MHz d is in Km Path Loss represents signal attenuation (measured on dB) between the effective transmitted power and the receive power (excluding antenna gains) Path Loss (Example) Pt PR 50 W = 47 dBm Assume that antennas are isotropic. Calculate receive power (in dBm) at free space distance of 100m from the antenna. What is PR at 10Km? -20 (for d = ) 59 20 (for d = 10) Path Loss (another example) Path Loss (another example) Quiz questions Path loss between point A & point B ? Path loss between point A & point C ? Path loss between . | Chapter 2: RADIO PROPAGATION Đặng Lê Khoa Email: dlkhoa@ Facuty of Electronics & Telecommunications, HCMUS Understanding RF Propagation Goals Estimate radio coverage area Estimate link performance Estimate network design parameters Transmitters and their location Transmit power Antenna type How many APs will be needed to cover IITK campus? Conditions for correct reception S/N ratio should be above a certain threshold (a function of modulation scheme) Signal power should be above the sensitivity threshold What will happen if noise level increases? What will happen in presence of another transmitter? Pt B C A sensitivity threshold Noise power Interesting Scenarios At which locations will correct reception take place? Antenna Basics Isotropic Dipole High gain directional 0 dBi dBi 14 dBi Free Space Propagation Model PT PR d Isotropic power density Power density along the direction of maximum radiation Power received by Antenna Predict received signal .