Wireless Communications Principles and Practice 2nd Edition T. S Wireless Communications Principles and Practice 2nd Edition T.S. Rappaport Chapter 5: Mobile Radio Propagation: Small-Scale Fading and Multipath as it applies to Modulation Techniques

Doppler Shift Geomerty

Channel issues Fig. 3.2

Example 5.1 Consider a transmitter which radiates a sinusoidal carrier frequency of 1850 MHz. For a vehicle moving 60 mph, compute the received carrier frequency if the mobile is moving directly towards the transmitter directly away from the transmitter in a direction which is perpendicular to the direction of arrival of the transmitted signal.

Solution 5.1

Solution 5.1

Complex Baseband model for RF systems

Time-varying impulse response Fig. 2.3

Measured impulse responses

Channel Sounder: Pulse type

Channel Sounder: PN Type Fig. 2.4

Channel Sounder: Swept Freq. type Fig. 2.5

Measured power delay profiles Fig. 2.6

Indoor Power Delay Profile Fig. 2.7

Typical RMS delay spreads Fig. 2.16

Time Dispersion Parameters  

Time Dispersion Parameters The mean excess delay is the first moment of the power delay profile and is defined to be (5.35) The rms delay spread is the square root of the second central moment of the power delay profile and is defined to be (5.36) (5.37)

Time Dispersion Parameters  

Example 5.2 Assume a discrete channel impulse response is used to model urban radio channels with excess delays as large as 100 s and microcellular channels with excess delays no larger than 4 s. If the number of multipath bins is fixed at 64, find a) , and b) the maximum bandwidth which the two models can accurately represent. Repeat the exercise for an indoor channel model with excess delays as large as 500 ns. As described in section 4.7.6, SIRCIM and SMRCIM are statistical channel models based on equation (5.12) that use parameters in this example.

Solution 5.2  

Example 5.3  

Solution 5.3

Solution 5.3

Solution 5.3

Solution 5.3

Example 5.4 Calculate the mean excess delay, rms delay spread, and the maximum excess delay (10 dB) for the multipath profile given in the figure below. Estimate the 50% coherence bandwidth of the channel. Would this channel be suitable for AMPS or GSM service without the use of an equalizer?

Solution 5.4 The rms delay spread for the given multipath profile can be obtained using equations (5.35)-(5.37). The delays of each profile are measured relative to the first detectable signal. The mean excess delay for the given profile   The second moment for the given power delay profile can be calculated as  

Solution 5.4  

Example 5.5  

Solution 5.5  

Solution 5.5  

Solution 5.5  

Solution 5.5  

Solution 5.5  

Solution 5.5  

Two independent fading issues Fig. 2.8

Flat-fading (non-freq. Selective) Fig. 2.9

Frequency selective fading Fig. 2.10

Two independent fading issues Fig. 2.11

Rayleigh fading Fig. 2.12

Small-scale envelope distributions Fig. 2.13

Ricean and Rayleigh fading distributions Fig. 2.14

Small-scale fading mechanism Fig. 2.15

Doppler Effect and Frequency Variations Doppler spectrum Fig. 2.16

Spectrum of Envelope of doppler faded signal Fig. 2.16

Simulating Doppler/Small-scale fading Fig. 2.16

Simulating Doppler fading Fig. 2.16

Simulating Doppler fading Fig. 2.16

Simulating multipath with Doppler-induced Rayleigh fading Fig. 2.16

Simulating 2-ray multipath Fig. 2.16

SIRCIM Simulation of all indoor propagation Characteristics Fig. 2.16

SMRCIM Simulation of all outdoor propagation Characteristics Fig. 2.16

SIRCIM and SMRCIM Available from Wireless Valley Communications, Inc. Source code in C is available www. Wirelessvalley.com

Angular Spread model Fig. 2.16

Spatial distribution of Multipath Fig. 2.16

Angular Spread key to fading Fig. 2.16

Spatial orientation of multipath impacts the depths of fading Fig. 2.16

Angular Distribution of power Fig. 2.16

Angular Spread predicts correlation distances Fig. 2.16

Angular Spread predicts correlation distances Fig. 2.16

Example 5.6  

Solution 5.6