Channel Model Introduction Lin, Wen-bin

Proprietary of NTHU Communication SOC Lab, 2006 Propagation Reflection –When electronic wave are incident something with dimensions large compared to the wavelengh Diffraction –Occurs when there is an obstruction in the transmission path, and secondary waves are generated behind the obstruction body Scattering –Arise when the incident wave length is in the order or lager than the blocking object with non- regular shape, the transmitting energy will be redirected in many directions A: free space B: reflection C: diffraction D: scattering

Proprietary of NTHU Communication SOC Lab, 2006

Doppler Effect A relative motion between BS and MS –Random frequency modulation –Independent on each multipath component –May be positive or negative Assumptions –Velocity: v –Incident angle: Θ –Distance difference: Δl

Proprietary of NTHU Communication SOC Lab, 2006 Doppler Effect

Proprietary of NTHU Communication SOC Lab, 2006 Channel Impulse Response Consider a bandpass signal to be transmitted If the channel is comprised of N propagation paths, ignore channel noise, the received band-pass signal waveform is The baseband equivalent signal is then Thus, we can extract the channel impulse response as

Proprietary of NTHU Communication SOC Lab, 2006 Channel Impulse Response

Proprietary of NTHU Communication SOC Lab, 2006 Important Parameters Excess delay –The relative delay of the i-th multipath component as compared to the first arriving component Mean excess delay –The first moment of the power delay profile RMS delay spread –The square root of the second central moment of the power delay profile

Proprietary of NTHU Communication SOC Lab, 2006 Important Parameters Coherence bandwidth –A statistical measurement of frequency range over which the channel can be considered “flat” Coherence time –A statistical measurement of the time duration over which the channel impulse response is essentially invariant, and quantifies the similarity of the channel response at different times Doppler spread –A measure of the range of frequencies over which the received Doppler spectrum is essentially non-zero

Proprietary of NTHU Communication SOC Lab, 2006 Fading Types 小規模衰減通道 ( 多路徑時間延遲 ) ( 時間散佈 ) 平坦衰減通道 1. 訊號頻寛 < 相關頻寛 2. 延遲擴展 < 符號週期 頻率選擇衰減通道 1. 訊號頻寛 > 相關頻寛 2. 延遲擴展 > 符號週期 小規模衰減通道 ( 都卜勒擴展 ) ( 頻率散佈 ) 快速衰減通道 ( 時間選擇衰減 ) 1. 高都卜勒擴展 2. 相關時間 < 符號週期 3. 通道變動 > 基頻訊號變動 慢速衰減通道 1. 低都卜勒擴展 2. 相關時間 > 符號週期 3. 通道變動 < 基頻訊號變動

Proprietary of NTHU Communication SOC Lab, 2006 Fading Example

Proprietary of NTHU Communication SOC Lab, 2006 Correlation and Spectrum

Proprietary of NTHU Communication SOC Lab, 2006 Correlation and Spectrum

Proprietary of NTHU Communication SOC Lab, 2006 Correlation and Spectrum

Proprietary of NTHU Communication SOC Lab, 2006 Correlation and Spectrum

Proprietary of NTHU Communication SOC Lab, 2006 Correlation and Spectrum

Proprietary of NTHU Communication SOC Lab, 2006 Doppler Spectrum

Proprietary of NTHU Communication SOC Lab, 2006 Rayleigh Fading

Proprietary of NTHU Communication SOC Lab, 2006 Tap Delay Model

Proprietary of NTHU Communication SOC Lab, 2006 Indoor Office Model Channel AChannel B Doppler spectrum Tap Relative delay (ns) Average power (dB) Relative delay (ns) Average power (dB) 10000Flat 250 – – 3.6 Flat 3110 – – 7.2 Flat 4170 – – 10.8 Flat 5290 – – 18.0 Flat 6310 – – 25.2 Flat

Proprietary of NTHU Communication SOC Lab, 2006 Outdoor to Indoor and Pedestrian Model Channel AChannel B Doppler spectrum Tap Relative delay (ns) Average power (dB) Relative delay (ns) Average power (dB) 10000Classic 2110 – – 0.9 Classic 3190 – – 4.9 Classic 4410 – – 8.0 Classic 5 –– – 7.8 Classic 6 –– – 23.9 Classic

Proprietary of NTHU Communication SOC Lab, 2006 Vehicular Model Channel AChannel B Doppler spectrum Tap Relative delay (ns) Average power (dB) Relative delay (ns) Average power (dB) – 2.5 Classic 2310 – Classic 3710 – – 12.8 Classic – – 10.0 Classic – – 25.2 Classic – – 16.0 Classic