7.6.1 appendix 7.a: the okumura–hata model

26
7.6.1 Appendix 7.A: The Okumura–Hata Model Two forms of the Okumura-Hata model are available. In the first form, the pathloss (in dB) is written as PL = PL freespace + A exc + H cb + H cm (7.13) where PL freespace is the freespace pathloss, A exc is the excess pathloss (as a function of distance and frequency) for a BS height h b = 200 m, and a MS height h m = 3 m; it is shown in Fig. 7.12. The correction factors H cb and H cm are shown in Figs. 7.13 and 7.14, respectively. The more common form is a curve fitting of Okumura’s original results. 5 In that implementation, the pathloss is written as PL = A + B log(d) + C where A, B, and C are factors that depend on frequency and antenna height. A = 69.55 + 26.16 log(f c ) 13.82 log(h b ) a(h m ) (7.14) B = 44.9 6.55 log(h b ) (7.15) where f c is given in MHz and d in km. The function a(h m ) and the factor C depend on the environment: small and medium-size cities: a(h m ) = (1.1 log(f c ) 0.7)h m (1.56 log(f c ) 0.8) (7.16) C = 0. (7.17) metropolitan areas a(h m ) = 8.29(log(1.54h m ) 2 1.1 for f 200 MHz 3.2(log(11.75h m ) 2 4.97 for f 400 MHz (7.18) C = 0. (7.19) suburban environments C =−2[log(f c /28)] 2 5.4. (7.20) rural area C =−4.78[log(f c )] 2 + 18.33 log(f c ) 40.98 . (7.21) The function a(h m ) in suburban and rural areas is the same as for urban (small and medium-sized cities) areas. 5 Note that the results from the curve fitting can be slighltly different from the results of Eq. (7.13). Wireless Communications, Second Edition Andreas F. Molisch © 2011 John Wiley & Sons, Ltd

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Page 1: 7.6.1 Appendix 7.A: The Okumura–Hata Model

7.6.1 Appendix 7.A: The Okumura–Hata Model

Two forms of the Okumura-Hata model are available. In the first form, the pathloss (in dB) iswritten as

PL = PLfreespace + Aexc + Hcb + Hcm (7.13)

where PLfreespace is the freespace pathloss, Aexc is the excess pathloss (as a function of distanceand frequency) for a BS height hb = 200 m, and a MS height hm = 3 m; it is shown in Fig. 7.12.The correction factors Hcb and Hcm are shown in Figs. 7.13 and 7.14, respectively.

The more common form is a curve fitting of Okumura’s original results.5 In that implementation,the pathloss is written as

PL = A + B log(d) + C

where A,B, and C are factors that depend on frequency and antenna height.

A = 69.55 + 26.16 log(fc) − 13.82 log(hb) − a(hm) (7.14)

B = 44.9 − 6.55 log(hb) (7.15)

where fc is given in MHz and d in km.The function a(hm) and the factor C depend on the environment:

• small and medium-size cities:

a(hm) = (1.1 log(fc) − 0.7)hm − (1.56 log(fc) − 0.8) (7.16)

C = 0 . (7.17)

• metropolitan areas

a(hm) ={

8.29(log(1.54hm)2 − 1.1 for f ≤ 200 MHz

3.2(log(11.75hm)2 − 4.97 for f ≥ 400 MHz(7.18)

C = 0 . (7.19)

• suburban environments

C = −2[log(fc/28)]2 − 5.4 . (7.20)

• rural area

C = −4.78[log(fc)]2 + 18.33 log(fc) − 40.98 . (7.21)

The function a(hm) in suburban and rural areas is the same as for urban (small and medium-sizedcities) areas.

5 Note that the results from the curve fitting can be slighltly different from the results of Eq. (7.13).

Wireless Communications, Second Edition Andreas F. Molisch© 2011 John Wiley & Sons, Ltd

Page 2: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Figure 7.12 Pathloss according to the Okumura-Hata model. Excess loss is the difference between Okumura-Hatapathloss (at the reference points hb = 200m, hm = 3m), and free space loss.Reproduced from Okumura et al. [1968].

Figure 7.13 Correction factor for base station height.Reproduced from Okumura et al. [1968].

Page 3: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Figure 7.14 Correction factor for mobile station height.Reproduced from Okumura et al. [1968].

Table 7.1 Range of validity for the Okumura-Hata model.

carrier frequency fc 150...1500 MHzeffective BS-antenna height hb 30...200 meffective MS-antenna height hm 1...10 mdistance d 1...20 km

Table 7.1 gives the parameter range in which the model is valid. It is noteworthy that theparameter range does not encompass the 1800 MHz frequency range most commonly used forsecond-and third generation cellular systems. This problem was solved by the COST 231 - Hatamodel, which extends the validity region to the 1500 - 2000 MHz range by defining

A = 46.3 + 33.9 log(fc) − 13.82 log(hb) − a(hm)

B = 44.9 − 6.55 log(hb)(7.22)

where a(hm) is defined in Eq. (7.16). C is 0 in small and medium-sized cities, and 3 in metropolitanareas.

The Okumura-Hata model also assumes that there are no dominant obstacles between the BSand the MS, and that the terrain profile changes only slowly. [Badsberg et al. 1995] and [Isidoro etal. 1995] suggested correction factors that are intended to avoid these restrictions; however, theyhave not found the widespread acceptance of the COST 231 correction factors.

Page 4: 7.6.1 Appendix 7.A: The Okumura–Hata Model

7.6.2 Appendix 7.B: The COST 231–Walfish–Ikegami Model

Figure 7.15 Parameters in the COST 231-Walfish-Ikegami model.Reproduced with permission from Damosso and Correia [1999] © European Union.

The COST 231 model is a pathloss model for the case of small distances between MS and BS,and/or small height of the MS. The total pathloss for the LOS case is given by

PL = 42.6 + 26 log(d) + 20 log(fc) (7.23)

for d ≥ 20 m, where again d is in units of kilometers, and fc is in units of MHz.For the NLOS case, the pathloss consists of the free-space pathloss L0, the multiscreen loss Lmsd

along the propagation path, and the attenuation from the last roofedge to the MS, Lrts (roof-top-to-street diffraction and scatter loss):

PL ={

PL0 + Lrts + Lmsd for Lrts + Lmsd > 0

PL0 for Lrts + Lmsd ≤ 0. (7.24)

The free-space pathloss is

L0 = 32.4 + 20 log d + 20 log fc . (7.25)

Ikegami derived the diffraction loss Lrts as

Lrts = −16.9 − 10 log w + 10 log fc + 20 log �hm + Lori (7.26)

where w is the width of the street in meters, and

�hm = hRoof − hm (7.27)

is the difference between the building height hRoof and the height of the MS hm. The orientationof the street is taken into account by an empirical correction factor Lori

Lori =

⎧⎪⎨⎪⎩

−10 + 0.354ϕ for 0◦ ≤ ϕ ≤ 35◦

2.5 + 0.075(ϕ − 35) for 35◦ ≤ ϕ ≤ 55◦

4.0 − 0.114(ϕ − 55) for 55◦ ≤ ϕ ≤ 90◦(7.28)

where ϕ is the angle between the street orientation and the direction of incidence in degrees.For the computation of the multiscreen loss Lmsd, building edges are modeled as screens. The

multiscreen loss is then given as [Walfish and Bertoni 1988]:

Lmsd = Lbsh + ka + kd log d + kf log fc − 9 log b (7.29)

Wireless Communications, Second Edition Andreas F. Molisch© 2011 John Wiley & Sons, Ltd

Page 5: 7.6.1 Appendix 7.A: The Okumura–Hata Model

where b is the distance between two buildings (in meters). Furthermore,

Lbsh ={ −18 log(1 + �hb) for hb > hRoof

0 for hb ≤ hRoof(7.30)

ka =

⎧⎪⎪⎪⎨⎪⎪⎪⎩

54 for hb > hRoof

54 − 0.8�hb for d ≥ 0.5 km and hb ≤ hRoof

54 − 0.8�hbd

0.5for d < 0.5 km and hb ≤ hRoof

(7.31)

where

�hb = hb − hRoof (7.32)

and hb is the height of the BS. The dependence of the pathloss on the frequency and distance isgiven via the parameters kd and kf in Eq. (7.29):

kd =⎧⎨⎩

18 for hb > hRoof

18 − 15�hb

hRooffor hb ≤ hRoof

(7.33)

kf = −4 +

⎧⎪⎪⎨⎪⎪⎩

0.7

(fc

925− 1

)for medium-size citiessuburban areas with average vegetation density

1.5

(fc

925− 1

)for metropolitan areas

. (7.34)

Table 7.2 gives the validity range for this modelFurther assumptions include a Manhatten grid (streets intersecting at right angles), constant

building height, and flat terrain. Furthermore, the model does not include the effect of waveguidingthrough street canyons, which can lead to an underestimation of the received fieldstrength.

Table 7.2 Range of validity for the COST 231-Walfish-Ikegami model.

carrier frequency fc 800...2000 MHzheight of the BS antenna hb 4...50 mheight of the MS antenna hm 1...3 mdistance d 0.02...5 km

Page 6: 7.6.1 Appendix 7.A: The Okumura–Hata Model

7.6.3 Appendix 7.C: The COST 207 GSM Model

The COST 207 model [Failii 1989] gives normalized scattering functions, as well as amplitudestatistics, for four classes of environments: Rural Area, Typical Urban, Bad Urban, and HillyTerrain. The following PDPs are used:

• Rural Area (RA)

Ph(τ) =⎧⎨⎩ exp

(−9.2

τ

μs

)for 0 < τ < 0.7μs

0 elsewhere. (7.35)

• Typical Urban area (TU)

Ph(τ) =⎧⎨⎩ exp

(− τ

μs

)for 0 < τ < 7μs

0 elsewhere. (7.36)

• Bad Urban area (BU)

Ph(τ) =

⎧⎪⎪⎪⎪⎨⎪⎪⎪⎪⎩

exp

(− τ

μs

)for 0 < τ < 5μs

0.5 exp

(5 − τ

μs

)for 5 < τ < 10μs

0 elsewhere

. (7.37)

• Hilly Terrain (HT)

Ph(τ) =

⎧⎪⎪⎪⎪⎨⎪⎪⎪⎪⎩

exp

(−3.5

τ

μs

)for 0 < τ < 2μs

0.1 exp

(15 − τ

μs

)for 15 < τ < 20μs

0 elsewhere

. (7.38)

In a tapped delay-line realization, each channel has a Doppler spectrum Ps(ν, τi), where i is theindex of the tap. The following four types of Doppler spectra are defined in the COST 207 model,where νmax represents the maximum Doppler shift and G(A, ν1, ν2) is the Gaussian function

G(A, ν1, ν2) = A exp

(− (ν − ν1)

2

2ν22

)(7.39)

and A is a normalization constant chosen so that∫

Ps(ν, τi)dν = 1.

a) CLASS is the classical (Jakes) Doppler spectrum and is used for paths with delays not in excessof 500 ns (τi ≤ 0.5 μs):

Ps(ν, τi) = A√1 −

νmax

)2(7.40)

for ν ∈ [−νmax, νmax];

Wireless Communications, Second Edition Andreas F. Molisch© 2011 John Wiley & Sons, Ltd

Page 7: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Figure 7.16 Doppler spectra used in GSM channel models.

b) GAUS1 is the sum of two Gaussian functions and is used for excess delay times in the rangeof 500 ns to 2 μs (0.5 μs ≤ τi ≤ 2 μs):

Ps(ν, τi) = G(A, −0.8νmax, 0.05νmax) + G(A1, 0.4νmax, 0.1νmax) (7.41)

where A1 is 10 dB smaller than A;

c) GAUS2 is also the sum of two Gaussian functions and is used for paths with delays in excessof 2 μs (τi ≥ 2 μs):

Ps(ν, τi) = G(B, 0.7νmax, 0.1νmax) + G(B1, −0.4νmax, 0.15νmax) (7.42)

where B1 is 15 dB smaller than B;

d) RICE is the sum of a classical Doppler spectrum and one direct path, such that the totalmultipath contribution is equal to that of the direct path. This spectrum is used for theshortest path of the model for propagation in rural areas:

Ps(ν, τi) = 0.41

2πνmax

√1 −

νmax

)2+ 0.91δ(ν − 0.7νmax) (7.43)

for ν ∈ [−νmax, νmax];

Page 8: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Table 7.3 Parameters for rural (non-hilly) area (RA)

Tap# Delay [μs] Power [dB] Doppler category

1 0 0 RICE2 0.2 -2 CLASS3 0.4 -10 CLASS4 0.6 -20 CLASS

Table 7.4 Parameters for urban (non-hilly) area (TU)

Tap# Delay [μs] Power [dB] Doppler category

1 0 -3 CLASS2 0.2 0 CLASS3 0.6 -2 GAUS14 1.6 -6 GAUS15 2.4 -8 GAUS26 5.0 -10 GAUS2

Table 7.5 Parameters for hilly urban area (BU)

Tap# Delay [μs] Power [dB] Doppler category

1 0 -3 CLASS2 0.4 0 CLASS3 1.0 -3 GAUS14 1.6 -5 GAUS15 5.0 -2 GAUS26 6.6 -4 GAUS2

Table 7.6 Parameters for hilly terrain (HT)

Tap# Delay [μs] Power [dB] Doppler category

1 0 0 CLASS2 0.2 -2 CLASS3 0.4 -4 CLASS4 0.6 -7 CLASS5 15 -6 GAUS26 17.2 -12 GAUS2

Page 9: 7.6.1 Appendix 7.A: The Okumura–Hata Model

7.6.4 Appendix 7.D: The ITU-R Models

For the selection of the air interface of third-generation cellular systems, the International Telecom-munications Union (ITU) developed another set of models that is available only as a tapped-delay-line implementation [ITU 1997]. It specifies three environments: indoor, pedestrian (includingoutdoor to indoor), and vehicular (with high BS antennas). For each of those environments, twochannels are defined: channel A (low delay spread case) and channel B (high delay spread). Theoccurrence rate of these two models is also specified; all those parameters are given in Table 7.7.The amplitudes follow a Rayleigh distribution; the Doppler spectrum is uniform between -νmax

and νmax for the indoor case and is a classical Jakes spectrum for the pedestrian and vehicularenvironments.

In contrast to the COST207 model, the ITU model also specifies the pathloss (in dB) dependingon the distance d:

• indoor :

PL = 37 + 30 log10 d + 18.3 · N(

Nfloor+2Nfloor+1 −0.46)

floor . (7.44)

• pedestrian:

PL = 40 log10 d + 30 log10 fc + 49 (7.45)

where again d is in km and fc is in MHz. For the outdoor-to-indoor case, the additional buildingpenetration loss (in dB) is modeled as a normal variable with 12 dB mean and 8 dB standarddeviation

Table 7.7 Tapped-delay-line implementation of ITU-R models.

Tap No. delay/ns power/dB delay/ns power/dBINDOOR CHANNEL A (50%) CHANNEL B (45%)

1 0 0 0 02 50 -3 100 -3.63 110 -10 200 -7.24 170 -18 300 -10.85 290 -26 500 -18.06 310 -32 700 -25.2

PEDESTRIAN CHANNEL A (40%) CHANNEL B (55%)1 0 0 0 02 110 -9.7 200 -0.93 190 -19.2 800 -4.94 410 -22.8 1200 -8.05 2300 -7.86 3700 -23.9

VEHICULAR CHANNEL A (40%) CHANNEL B (55%)1 0 0 0 -2.52 310 -1 300 03 710 -9 8900 -12.84 1090 -10 12900 -10.05 1730 -15 17100 -25.26 2510 -20 20000 -16.0

Wireless Communications, Second Edition Andreas F. Molisch© 2011 John Wiley & Sons, Ltd

Page 10: 7.6.1 Appendix 7.A: The Okumura–Hata Model

• vehicular :

PL = 40(1 − 4 · 10−3�hb) log10 d − 18 log10 �hb + 21 log10 fc + 80 (7.46)

where �hb is the BS height measured from the rooftop level; the model is valid for 0< �hb <

50 m.

In all three cases, lognormal shadowing is imposed. The standard deviation is 12 dB for theindoor case, and 10 dB in the vehicular and outdoor pedestrian case. The autocorrelation functionof the shadowing is assumed to be exponential, ACF(�x) = exp(− ln(2)|�x|/dcorr) where thecorrelation length dcorr is 20 m in vehicular environments, but not specified for other environments.

The ITU models have been widely used, because they were accepted by international standardsorganizations. However, they are not very satisfactory from a scientific point of view. It is difficultto motivate differences in the power delay profile of pedestrian and vehicular channels, whileneglecting the differences between suburban and metropolitan areas. Also, some of the channelshave regularly spaced taps, which leads to a periodicity in frequency of the transfer function; thiscan lead to problems when evaluting the correlation between duplex frequencies (see Chapter 17).Finally, the number of taps is too low for realistic modeling of 5 MHz wide systems.

Page 11: 7.6.1 Appendix 7.A: The Okumura–Hata Model

7.6.5 Appendix 7.E: The 3GPP Spatial Channel Model

The 3GPP and 3GPP2 industry alliances jointly developed channel models that are to be used for theevaluation of cellular systems with multiple antenna elements. The bandwidth of the tested systemsshould not exceed 5 MHz. The models are defined for three environments, namely urban microcells,urban macrocells, and suburban macrocells. The model is a mixed geometrical–stochastic modelthat can simulate a cellular layout including interference. The description closely follows [Calcevet al. 2007].

Pathloss

In a first step, the environment and the locations of NBS BSs are chosen, and locations of theMSs are generated at random. One also needs to specify other user-specific quantities, such astheir velocity vector v, with its direction θv drawn from a uniform [0, 360◦) distribution, as well asthe specifics of the MS antenna or antenna array such as array orientation, �MS , etc. Figure 7.17illustrates the various angle definitions.

For the suburban and urban macrocells, the pathloss is determined as:

PL[dB] = (44.9 − 6.55 log10(hBS)) log10

(d

1000

)+ 45.5 + (35.46 − 1.1hMS) log10(fc) (7.47)

− 13.82 log10(hMS) + 0.7hMS + C

where hBS is the BS antenna height in meters, hMS the MS antenna height in meters, fc the carrierfrequency in MHz, d is the distance between the BS and MS in meters (has to be at least 35 m),and C is a constant factor (C = 0 dB for suburban macro and C = 3 dB for urban macro). Themicrocell non-line-of-sight (NLOS) pathloss is:

PL[dB] = −55.9 + 38 log10(d) + (24.5 + fc

616.67) log10(fc) (7.48)

Narrowband Parameters

The delay-spread σDS,n, BS angle-spread σAS,n and shadow fading σSF,n parameters of the signalfrom BS n, where n = 1, . . . , NBS , to a given user can be written as:

10 log10(σDS,n) = μDS+ ∈DSX1n (7.49)

10 log10(σAS,n) = μAS+ ∈ASX2n (7.50)

10 log10(σSF,n) = ∈SFX3n (7.51)

In the above equations X1n, X2n, X3n are zero-mean, unit-variance Gaussian random variables.μDS and μAS represent the median of the delay-spread and angle-spreads in dB. Similarly, the∈-coefficients are the log-normal variances of each parameter. The values of μ and ε are given in

Wireless Communications, Second Edition Andreas F. Molisch© 2011 John Wiley & Sons, Ltd

Page 12: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Cluster n

ΩMS

ΩBS

N

N

BS array broadside

MS array broadside

BS array

MS array

Δn,m,AoD

Δn,m,AoA

dn,AoD

dn,AoA

qn,m,AoA

qn,m,AoDqBS

qMS

qV

Subpath m

MS direction

of travel

Figure 7.17 Angular variables definitions. From [Calcev et al. 2007] © IEEE.

Table 7.8. Once σDS,n and σAS,n have been determined, they are used to generate the relative delaysand mean angles of departure of the intra-cluster paths.

Correlations between shadowing, delay spread, and angular spread are expressed in terms of acovariance matrix A, as seen in Eq. (7.52), whose Aij component represents the correlations betweenXin and Xjn, with i, j = 1, 2, 3. Correlations between spreads from different BSs are expressedby a matrix B with Bij representing the correlations between Xin and Xjm, for i, j = 1, 2, 3 andn �= m.

A =⎡⎣ 1 ρDA ρDF

ρDA 1 ρAF

ρDF ρAF 1

⎤⎦ B =

⎡⎢⎢⎣

0 0 00 0 00 0 ζ

⎤⎥⎥⎦ (7.52)

where

ρDA = E [X1nX2n] = +0.5

ρDF = E [X2nX3n] = −0.6

ρAF = E [X3nX1n] = −0.6

ζ = E [X3nX3m] = +0.5 n �= m

Wideband Parameters–Macrocellular Case

The wideband parameters are determined the following way:

1. Path Delays: The (random) delays of the paths are written as

τ ′n = −rDSσDS ln zn n = 1, . . . , N (7.53)

Page 13: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Table 7.8 Environment Parameters

Channel Scenario Suburban Macro Urban Macro Urban Micro

Number of paths 6 6 6Number of sub-paths (M) per-path 20 20 20Mean rms AS at BS E(σAS) = 5◦ E(σAS) = 8◦, 15◦ NLOS: E(σAS) = 19◦AS at BS as a lognormal RV μAS = 0.69 8◦ μAS = 0.810 N/AσAS = 10(εAS ·x+μAS) εAS = 0.13 εAS = 0.34x ∼ N(0, 1) 15◦ μAS = 1.18σAS in degrees εAS = 0.210rAS = σAoD/σAS 1.2 1.3 N/APer-path AS at BS (Fixed) 2◦ 2◦ 5◦ (LOS and NLOS)BS per-path AoD Distribution N(0, σ 2

AoD) where N(0, σ 2AoD) where U(−40◦, 40◦)

standard deviation σAoD = rAS · σAS σAoD = rAS · σAS

Mean rms AS at MS E(σAS,MS) = 68◦ E(σAS,MS) = 68◦ E(σAS,MS) = 68◦Per-path AS at MS (Fixed) 35◦ 35◦ 35◦MS Per-path AoA Distribution N(0, σ 2

AoA(P r)) N(0, σ 2AoA(P r)) N(0, σ 2

AoA(P r))

Delay spread as a lognormal RV μDS = −6.80 μDS = −6.18 N/AσDS = 10(εDS ·x+μDS) εDS = 0.288 εDS = 0.18x ∼ N(0, 1)

σDS in μsecMean total rms Delay Spread E(σDS) = 0.17μs E(σDS) = 0.65μs E(σDS) = 0.251μs (output)rDS = σdelays/σDS 1.4 1.7 N/ADistribution for path delays U(0, 1.2μs)

Lognormal shadowing 8 dB 8 dB NLOS: 10 dBstandard deviation σSF LOS: 4 dBPathloss model (dB) 31.5 + 35 log10(d) 34.5 + 35 log10(d) NLOS: 34.53 + 38 log10(d)

d is in meters LOS: 30.18 + 26 log10(d)

where zn (n = 1, . . . , N) are i.i.d. random variables with uniform distribution U(0, 1). The τ ′n

variables are then ordered so that τ ′(N) > τ ′

(N−1) > · · · > τ ′(1). Then their minimum is subtracted

from all, i.e., τn =(τ ′(n) − τ ′

(1)

), with n = 1, . . . , N , so that τN > · · · > τ1 = 0.

2. Path Powers: the average powers of the N paths are expressed as

P ′n = e

(1−rDS )τnrDS ·σDS · 10−0.1ξn n = 1, . . . , N. (7.54)

ξn for n = 1, . . . , N are i.i.d. Gaussian random variables with standard deviation σRND

= 3dB,signifying the fluctuations of the powers away from the average exponential behavior. Averagepowers are then normalized, so that the total average power for all N paths is equal to unity.

3. Angles of Departure (AoD): the distribution of angles of departure at the BS has a Gaussiandistribution with variance σAoD = rASσAS . The values of the AoD are thus initially given by

δ′n ∼ N(0, σ 2

AoD), (7.55)

where n = 1, . . . , N . These variables are given in degrees and they are ordered in increasingabsolute value so that

∣∣∣δ′(1)

∣∣∣ <

∣∣∣δ′(2)

∣∣∣ < · · · <

∣∣∣δ′(N)

∣∣∣. The AoDs δn,AoD , n = 1, . . . , N are assigned

to the ordered variables so that δn,AoD = δ′(n), n = 1, . . . , N .

4. Angles of Arrival (AoA): The AoA at the MS has a truncated normal distribution with meanzero with respect to the LOS direction, i.e.

δn,AoA ∼ N(0, σ 2n,AoA), (7.56)

Page 14: 7.6.1 Appendix 7.A: The Okumura–Hata Model

with n = 1, . . . , N . The variance of each path σn,AoA depends on the relative power of that path:

σn,AoA = 104.12◦ · (1 − exp(0.2175 · Pn,dBr)). (7.57)

The σn,AoA represents the standard deviation of the non-circular angle spread and Pn,dBr < 0 isthe relative power of the n-th path, in dBr , with respect to total received power.

Wideband Parameters–Microcellular Case

1. Path Delays: The delays τn, n = 1, . . . , N are i.i.d. random variables drawn from a uniformdistribution U(0, 1.2μsec). The minimum of these delays is subtracted from all so that the firstdelay is zero.

2. Path Powers: The power of each of the N paths depends on the delay as

P ′n = 10−(τn+0.1zn) (7.58)

where τn are the delays of each path in units of microseconds, and zn (n = 1, . . . , N) are i.i.d.zero mean Gaussian random variables with a standard deviation of 3dB. Average powers arenormalized so that total average power for all N paths is equal to unity.

3. Angles of Departure (AoD): In the microcell case the AoD of each of the N paths at the basecan be modelled as i.i.d. uniformly distributed random variables between −40 and +40 degrees:

δn,AoD ∼ U(−40◦, +40◦), (7.59)

where n = 1, . . . , N . One can now associate a power to each of the path delays determinedabove. Note that, unlike the macrocell environment, the AoDs do not need to be sorted beforebeing assigned to a path power.

4. Angles of Arrival (AoA): The mean AoA of each path can be determined similar to the waydiscussed in the macrocell case, i.e., i.i.d Gaussian random variables

δn,AoA ∼ N(0, σ 2n,AoA), where n = 1, . . . , N (7.60)

σn,AoA = 104.12◦ [1 − exp (0.265 · PdBr)

](7.61)

where PdBr is the relative power of the n-th path in dBr. When the LOS model is used, theAoA for the direct component is set equal to the LOS path direction.

Generation of Fast-Fading Coefficients

We now describe how to generate fast fading coefficients for wideband time-varying MIMO chan-nels with Nt transmit antennas and Nr receive antennas. The fast-fading coefficients for each ofthe N paths are constructed by the superposition of M individual sub-paths. The m-th component(m = 1, . . . , M) is characterized by a relative angular offset to the mean AoD of the path at theBS, a relative angular offset to the mean AoA at the MS, a power and an overall phase. M is fixedto M = 20, and all sub-paths have the same power Pn/M . The sub-path delays are identical andequal to their corresponding path’s delay. The overall phase of each subpath �n,m is i.i.d., with auniform distribution between 0 and 2π . The relative offset of the m-th subpath n,m,AoD at theBS, and n,m,AoA at the MS are given in Table 7.9. These offsets are chosen to result to the desiredfixed per-path angle spreads (2◦ for the macrocell environments, 5◦ for the microcell environmentfor n,m,AoD at the BS and 35◦ at the MS for n,m,AoA). These per-path angle spreads are differentfrom the narrowband angle spread σAS of the composite signal with N paths.

Page 15: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Table 7.9 Sub-path AoD and AoA offsets

Sub- Offset at BS, Offset at BS Offset at MSpath AS = 2◦, AS = 5◦ AS = 35◦number Macrocell Microcell(m) n,m,AoD n,m,AoD n,m,AoA

(degrees) (degrees) (degrees)

1, 2 ±0.0894 ±0.2236 ±1.56493, 4 ±0.2826 ±0.7064 ±4.94475, 6 ±0.4984 ±1.2461 ±8.72247, 8 ±0.7431 ±1.8578 ±13.00459, 10 ±1.0257 ±2.5642 ±17.949211, 12 ±1.3594 ±3.3986 ±23.789913, 14 ±1.7688 ±4.4220 ±30.953815, 16 ±2.2961 ±5.7403 ±40.182417, 18 ±3.0389 ±7.5974 ±53.181619, 20 ±4.3101 ±10.7753 ±75.4274

The BS and MS sub-paths are associated by connecting their respective parameters. The n-th BSpath (defined by its delay τn, power Pn, and AoD δn,AoD) is uniquely associated with the n-th MSpath (defined by its AoA δn,AoA) because of the ordering. For the n-th path, each of the M BS sub-paths (defined by its offset n,m,AoD) is randomly paired with a MS sub-path (defined by its offset n,m,AoA) and the phases defined by �n,m are applied. To simplify the notation, a renumbering ofthe M MS sub-path offsets with their newly associated BS sub-path is done. Summarizing, for then-th path, the AoD of the m-th sub-path (from the BS broadside) is

θn,m,AoD = θBS + δn,AoD + n,m,AoD, (7.62)

Similarly, the AoA of the m-th sub-path for the n-th path (from the MS array broadside) is

θn,m,AoA = θMS + δn,AoA + n,m,AoA (7.63)

The antenna gains are dependent on these sub-path AoDs and AoAs. For the BS and MS, theseare given respectively as |GBS(θn,m,AoD)|2 and |GMS(θn,m,AoA)|2, where G(θ) is the correspondingcomplex antenna response to and from radiation with angle θ .

Lastly, the path loss, based on the BS to MS distance and the log normal shadow fading, isapplied to each of the sub-path powers of the channel model.

The channel transfer function between receiver u and transmitter s at path n and time t is

hu,s,n(t) =√

PnσSF

M

M∑m=1

(ejk‖v‖ cos(θn,m,AoA−θv)t

GBS(θn,m,AoD) · ej (kds sin(θn,m,AoD)+�n,m)

GMS(θn,m,AoA) · ejkdu sin(θn,m,AoA))

(7.64)

Page 16: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Further Options

In addition, the model also specifies several options including line-of-sight situations in urbanmicrocells, waveguiding in street canyons, far scatterer clusters, and polarization diversity. Detailscan be found in Calcev et al. [2007].

Page 17: 7.6.1 Appendix 7.A: The Okumura–Hata Model

7.6.6 Appendix 7.F: The ITU-Advanced Channel Model

The ITU has defined a set of channel models for the evaluation of IMT-Advanced systemsproposals. The modeling method is almost identical to the 3GPP model; but for the convenienceof the reader, we repeat here the step-by-step instructions for implementation (closely followingthe offical report [ITU 2008]). Also, the ITU models are based on more extensive measurementcampaigns (mostly done within the framework of the EU projects WINNER and WINNER 2), andcover a larger range of scenarios.

The double-directional impulse response consists of a number of (delay) taps, where each tapconsists of multiple rays that have different DOAs and DODs. The delays and angles all dependon large-scale parameters that can change from drop to drop.

The following steps have to be performed in order to get the channel in a particular environment:

1. The ITU models are based on the “drop” concept. Thus, in a first step, locations of the basestations are selected. For the mobile stations, we select locations, orientation, and velocityvectors, according to probability density functions.6

2. Assign whether an MS has LOS or NLOS, according to the pdf given in Table 7.10

Table 7.10 Probability for line-of-sight. For meaning of scenario abbreviations, see Table 7.11.

Scenario LoS probability as a function of distance, d(m)

InH PLOS =⎧⎨⎩

1, d ≤ 18exp(−(d − 18)/27), 18 < d < 370.5, d ≥ 37

UMi PLOS = min(18/d, 1) · (1 − exp(−d/36)) + exp(−d/36) (for outdoor users only)

UMa PLOS = min(18/d, 1) · (1 − exp(−d/63)) + exp(−d/63)

SMa PLOS = 1, d ≤ 10exp(−(d − 10)/200), d > 10

RMa PLOS =1, d ≤ 10

exp

(−d − 10

1000

), d > 10

3. Calculate the pathloss according to the equations in Table 7.114. Generate the large-scale parameters: angular spread at BS, angular spread at MS, delay spread,

shadowing, and Rice factor. All of those variables are modeled as lognormal, so that theirlogarithms are Gaussian variables, with correlation coefficients prescribed in Table 7.12. Fur-thermore, the correlation of parameters of different MSs connected to one BS (or equivalently,parameters for a single MS moving to different locations) are correlated. The correlation ismodeled as exponentially decaying, with the 1/e decorrelation distance prescribed in Table7.12. Correlations of links from one MS to different BSs are neglected.

6 For system evaluations that are accepted by the ITU, the BS and MS parameters and distributions are prescribedin ITU [2008].

Wireless Communications, Second Edition Andreas F. Molisch© 2011 John Wiley & Sons, Ltd

Page 18: 7.6.1 Appendix 7.A: The Okumura–Hata Model

5. Generate delays of the taps, either according to a uniform distribution, or - when the delaydistribution is exponential - according to

τ ′n = −rDSσDS ln zn n = 1, . . . , N (7.65)

where zn (n = 1, . . . , N) are i.i.d. random variables with uniform distribution U(0, 1) The τ ′n

variables are then ordered so that τ ′(N) > τ ′

(N−1) > · · · > τ ′(1). Then their minimum is subtracted

from all, i.e. τn =(τ ′(n) − τ ′

(1)

), with n = 1, . . . , N , so that τN > · · · > τ1 = 0. In the case of

LOS, each of the τn is to be divided by a factor

D = 0.7705 − 0.0433K + 0.0002K2 + 0.000017K3 (7.66)

where K is the Rice factor in dB, as given in Table 7.12. Note, however, that for the generationof the tap powers (see next step) the unscaled τn are to be used.

Table 7.11 Parameters for the path loss models

Scenario Path loss (dB) Shadow Applicability range, antennaNote: f c is given in GHz fading std height default valuesand distance in m! (dB)

Indo

orH

otsp

ot(I

nH)

PL = 16.9 log10(d) + 32.8 + 20 log10(fc) σ = 3 3 m < d < 100 mLoS hns = 3 − 6 m

hUT = 1 − 2.5 mPL = 43.3 log10(d) + 11.5 + 20 log10(fc) σ = 4 10 m < d < 150 m

NLoS hns = 3 − 6 mhUT = 1 − 2.5 m

PL = 22.0 log10(d) + 28.0 + 20 log10(fc) σ = 3 10 m < d1 < d ′BP

(1)

LoSPL = 40 log10(d1) + 7.8 − 18 log10(h

′BS) −

18 log10(h′UT) + 2 log10(fc)

σ = 3 d ′BP < d1 < 5000 m(1)

hBS = 10 m(1), hUT = 1.5 m(1)

Urb

anM

icro

(UM

i)

Manhattan grid layout:PL = min(PL(d1, d2), PL(d2, d1)) σ = 4 10 m < d1 + d2 < 5000 m,

w/2 < min(d1, d2)(2)

where:PL(dk, dt ) = PLLOS(dk) + 17.9 −12.5 nj + 10 nj log10(dl) + 3 log10(fc)

w = 20 m (street width)

h′BS = 10 m, hUT = 1.5 m.

When 0 < min(d1, d2) < w/2,and the LoS PL is applied.

NLoSnj = max(2.8 − 0.0024dk, 1.84)

PLLOS path loss of scenario UMi LoSand

k, l ∈ {1, 2}.Hexagonal cell layout: σ = 4 10 m < d < 2000 mPL = 36.7 log10(d) + 22.7 + 26 log10(fc) hBS = 10 m

hUT = 1 − 2.5 mPL = PLb + PLtw + PLin

Manhattan grid layout (θ known): σ = 7 10 m < dout + din < 1000 m,0 m < din < 25 m,

O-to-I

⎧⎨⎩

PLb = PLB1(dout + div)

PLtw = 14 + 15(1 − cos(θ))2

PLin = 0.5din

hBS = 10 m, hUT = 3(nF l − 1)

+ 1.5 m,

nF l = 1Explanations : see(3)

For hexagonal layout(θ unknown):PLtw = 20, other values remain the same.

Page 19: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Scenario Path loss (dB) Shadow Applicability range, antennaNote: f c is given in GHz fading std height default valuesand distance in m! (dB)PL = 22.0 log10(d) + 28.0 +20 log10(fc)

σ = 4 10 m < d < d ′BP

(1)

LoS

Urb

anM

acro

(UM

a) PL = 40.0 log10(d1) + 7.8 −18.0 log10(h

′BS) − 18.0 log10(h

′UT ) +

2.0 log10(fc)

σ = 4 d ′BP < d < 5000 m(1)

hBS = 25 m(1), hUT = 1.5 m(1)

PL = 161.04 − 7.1 log10(W) +7.5 log10(h) − (24.37 −3.7(h/hBS)

2) log10(hBS) + (43.42 −3.1 log10(hBS))(log10(d) − 3) +20 log10(fc) −(3.2(log10(11.75hUT ))2 − 4.97)

σ = 6 10 m < d < 5 000 mh = avg. building heightW = street widthhBS = 25 m, hUT = 1.5 m,W = 20 m, h = 20 mThe applicability ranges:NLoS5 m < h < 50 m5 m < W < 50 m10 m < hBS < 150 m1 m < hUT < 10 m

Subu

rban

Mac

ro(S

Ma,

optio

nal) PL1 = 20 log10(40πdfc/3) +

min(0.03h1.72, 10) log10(d)

σ = 4 10 m < d < dBP(4)

− min(0.044h1.72, 14.77) +0.002 log10(h)d

PL2 = PL1(dBP ) + 40 log10(d/dBP ) σ = 6 dBP < d < 5000 mLoS hBS = 35 m, hUT = 1.5 m,

W = 20 m, h = 10 m(The applicability ranges ofh,W, hBS, hUT are same as inUMa NLoS)

NLoS

PL = 161.04 − 7.1 log10(W) +7.5 log10(h) − (24.37 −3.7(h/hBS)

2) log10(hBS) + (43.42 −3.1 log10(hBS))(log10(d) − 3) +20 log10(fc) −(3.2(log10(11.75hUT ))2 − 4.97)

σ = 8 10 m < d < 5000 mhBS = 35 m, hUT = 1.5 m,W = 20 m, h = 10 m(Applicability ranges ofh,W, hBS, hUT are same as inUMa NLoS)

PLl = 20 log10(40πdfc/3) +min(0.03h1.72, 10) log10(d)

σ = 4 10 m < d < dBP(4)

− min(0.044h1.72, 14.77) +0.002 log10(h)d

Rur

alM

acro

(RM

a) PL2 = PL1(dBP ) + 40 log10(d/dBP ) σ = 6 dBP < d < 10000 m,LoS hBS = 35 m, hUT = 1.5 m,

W = 20 m, h = 5 m(Applicability ranges ofh,W, hBS, hUT are same asUMa NLoS)

NLoS

PL = 161.04 − 7.1 log10(W) +7.5 log10(h) − (24.37 −3.7(h/hBS)

2) log10(hBS) + (43.42 −3.1 log10(hBS))(log10(d) − 3) +20 log10(fc) −(3.2(log10(11.75hUT ))2 − 4.97)

σ = 8 10 m < d < 5000 m

hBS = 35 m, hUT = 1.5 m,W = 20 m, h = 5 m(Applicability ranges ofh,W, hBS, hUT are same asUMa NLoS)

Page 20: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Tab

le7.

12Pa

ram

eter

sfo

rch

anne

lm

odel

inva

riou

sen

viro

nmen

ts

Scen

ario

sIa

HU

Mi

SMa

UM

aR

Ma

LoS

NL

oSL

oSN

LoS

O-i

n-I

LoS

NL

oSL

oSN

LoS

LoS

NL

oSD

elay

spre

ad(D

S)lo

g 10(s

−7.7

0−7

.41

−7.1

9−6

.89

−6.6

2−7

.23

−7.1

2−7

.03

−6.4

4−7

.49

−7.4

0.18

0.14

0.40

0.54

0.32

0.38

0.33

0.66

0.39

0.55

0.48

AoD

spre

ad(A

SD)

log n

s10

(deg

rees

1.60

1.62

1.20

1.41

1.25

0.78

0.90

1.15

1.41

0.90

0.95

σ0.

180.

250.

430.

170.

420.

120.

360.

280.

280.

380.

45A

oAsp

read

(ASA

)lo

g 10

(deg

rees

1.62

1.77

1.75

1.84

1.76

1.48

1.65

1.81

1.87

1.52

1.52

σ0.

220.

160.

190.

150.

160.

200.

250.

200.

110.

240.

13Sh

adow

fadi

ng(S

F)(d

B)

σ3

43

47

48

46

48

μ7

N/A

9N

/AN

/A9

N/A

9N

/A7

N/A

K-f

acto

r(K

)(d

B)

σ4

N/A

5N

/AN

/A7

N/A

3.5

N/A

4N

/AA

SDvs

DS

0.6

0.4

0.5

00.

40

00.

40.

40

−0.4

Cro

ss-c

orre

latio

ns∗

ASA

vsD

S0.

80

0.8

0.4

0.4

0.8

0.7

0.8

0.6

00

ASA

vsSF

−0.5

−0.4

−0.4

−0.4

0−0

.50

−0.5

00

0A

SDvs

SF−0

.40

−0.5

00.

2−0

.5−0

.4−0

.5−0

.60

0.6

DS

vsSF

−0.8

−0.5

−0.4

−0.7

−0.5

−0.6

−0.4

−0.4

−0.4

−0.5

−0.5

ASD

vsA

SA0.

40

0.4

00

00

00.

40

0A

SDvs

K0

N/A

−0.2

N/A

N/A

0N

/A0

N/A

0N

/AA

SAvs

K0

N/A

−0.3

N/A

N/A

0N

/A−0

.2N

/A0

N/A

DS

vsK

−0.5

N/A

−0.7

N/A

N/A

0N

/A−0

.4N

/A0

N/A

SFvs

K0.

5N

/A0.

5N

/AN

/A0

N/A

0N

/A0

N/A

Del

aydi

stri

butio

nE

xpE

xpE

xpE

xpE

xpE

xpE

xpE

xpE

xpE

xpE

xpA

oDan

dA

oAdi

stri

butio

nL

apla

cian

Wra

pped

Gau

ssia

nW

rapp

edG

auss

ian

Wra

pped

Gau

ssia

nW

rapp

edG

auss

ian

Del

aysc

alin

gpa

ram

eter

r τ3.

63

3.2

32.

22.

41.

52.

52.

33.

81.

7X

PR(d

B)

μ11

109

8.0

98

48

712

7N

umbe

rof

clus

ters

1519

1219

1215

1412

2011

10N

umbe

rof

rays

per

clus

ter

2020

2020

2020

2020

2020

20C

lust

erA

SD5

53

105

52

52

22

Clu

ster

ASA

811

1722

85

1011

153

3Pe

rcl

uste

rsh

adow

ing

std

ζ(d

B)

63

33

43

33

33

3D

S8

57

1010

640

3040

5036

ASD

73

810

1115

3018

5025

30C

orre

latio

ndi

stan

ce(m

)A

SA5

38

917

2030

1550

3540

SF10

610

137

4050

3750

3712

0K

4N

/A15

N/A

N/A

10N

/A12

N/A

40N

/A

Page 21: 7.6.1 Appendix 7.A: The Okumura–Hata Model

6. Generate the average powers of the N taps as

P ′n = e

(1−rDS )τnrDS ·σDS · 10−0.1ξn n = 1, . . . , N. (7.67)

ξn for n = 1, . . . , N are the cluster shadowing terms. Average powers are then normalized, sothat the total average power for all N paths is equal to unity. Each ray in a tap is assigned1/M = 1/20 of the tap power.

7. Generate the angles of arrival. The angular spectra are modeled as wrapped Gaussians, exceptfor the indoor hotspot scenario, where it is Laplacian. The angles are computed in the Gaussiancase as

θ ′n = 2σAOA

√− ln(Pn/ max(Pn))

C(7.68)

and for the Laplacian case

θ ′n = −σq ln(Pn/ max(Pn))

C(7.69)

where σAOA = σq/1.4 is the standard deviation. The scaling constant C is a scaling factorrelated to the number of clusters, and is given in Table 7.13. In the case of LOS, the scalingconstant has to be replaced by

CLOS = C(1.1035 − 0.028K − 0.002K2 + 0.0001K3) (7.70)

CLOS = C(0.9275 + 0.0439K − 0.0071K2 + 0.0002K3) (7.71)

for Gaussian and Laplacian spectrum, respectively.The mean angles θn are then computed as

θn = Xnθn + Yn + θLOS (7.72)

where Xn is a random variable that equiprobably takes on the values +1 and −1, Yn is anormally distributed random variable with standard deviation σq/7, and θLOS is the arrivalangle of the LOS component (which is known from gometrical considerations).

For the LOS case, θn is normalized by subtracting X1θ1 + Y1 from every θn; this enforcesthat the first cluster is seen in the direction θLOS. The angles of the rays are computed byadding the offset angles (where the angles given in Table 7.14 have to be multiplied by thecluster angular spread) to the mean angles θn of each cluster.

The same procedure applies for the angles of departure8. Perform a random coupling of the ray AOAs and AODs within each tap (or subcluster, see

below).9. For each ray, and each polarization (vv, vh, hv, hh) draw an initial random phase � from a

uniform distribution in [−π, π]. In the LOS case, also draw a random initial phase for the LOScomponent for the vv and hh polarization.

10. For the two strongest taps, split the taps into “subclusters”, according to Table 7.15, so thatsome of the taps have a delay offset compared to the nominal computed delays. For the weakerclusters, no such splitting is done. Compute the polarized impulse responses at the antennaelements as

hNLOSu,s,n (t) =

√Pn

M∑m=1

(ejk‖v‖ cos(θn,m,AoA−θv)t

GT X(θn,m,AoD) ·[

exp(j�vv

n,m

)κ−1/2 exp

(j�vh

n,m

)κ−1/2 exp

(j�hv

n,m

)exp

(j�hh

n,m

) ]

GRX(θn,m,AoA) · ejkdu,n,mej (kds,n,m) (7.73)

Page 22: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Table 7.13

No. 4 5 8 10 11 12 14 15 15 16 19 19 20clusters (InH) (InH)

C 0.779 0.860 1.018 1.090 1.123 1.146 1.190 1.211 1.434 1.226 1.273 1.501 1.289

Table 7.14 Ray offset angles within a cluster, givenfor 1 degree rms angle spread

Ray number, m Basis vector of offset angles, αms

1,2 ±0.04473,4 ±0.14135,6 ±0.24927,8 ±0.3715

9,10 ±0.512911,12 ±0.679713,14 ±0.884415,16 ±1.148117,18 ±1.519519,20 ±2.1551

Table 7.15 Sub-cluster information for intra clusterdelay spread clusters

Sub-cluster No. Mapping to rays Power Delay offset1 1, 2, 3, 4, 5, 6, 7, 8, 19, 20 10/20 0 ns2 9, 10, 11, 12, 17, 18 6/20 5 ns3 13, 14, 15, 16 4/20 10 ns

where GT X(θn,m,AoD) is a 2 × 1 vector containing the transmit antenna pattern for vertical andhoriztonal polarization, and ds,n,m is the projection of the distance vector from the referenceantenna element to antenna element s onto a line in the direction θn,m,AoD:√

x2s + y2

s cos(arctan (ys/xs) − θn,m,AoA

)sin(θn,m,AoA)

(7.74)

in the case of a uniform linear array, this becomes ds sin(θn,m,AoD).

In the case of LOS, add a component, so that the overall impulse response in the LOSsituation is

hLOSu,s,n(t) =

√1

1 + KhNLOS

u,s,n (t) + δ(n − 1)

√K

1 + K

(ejk‖v‖ cos(θLOS−θv)t

GT X(θn,m,LOS) ·[

exp(j�vv

LOS

)0

0 exp(j�hh

LOS

) ]

GRX(θn,m,LOS) · ejkdu,LOS ej (kds,LOS) (7.75)

11. Apply the pathloss and (bulk) shadowing to the overall impulse response.

Page 23: 7.6.1 Appendix 7.A: The Okumura–Hata Model

7.6.7 Appendix 7.G: The 802.15.4a UWB Channel Model

The IEEE 802.15.4a group defined ultrawideband channel models: one model for office envi-ronments below 1 GHz, one model for body-area networks, and one group of models for indoorresidential, indoor office, outdoor, and industrial environments. In this appendix, we only describethe last group of models, since it is the most frequently used. The other models are discussed inMolisch et al. [2006].

We assume that the path gain as a function of the distance and frequency can be written as aproduct of the terms

G(f, d) = G(f ) · G(d). (7.76)

where the frequency dependence of the channel path gain is√G(f ) ∝ f −κ (7.77)

where κ is the frequency dependency decaying factor. The distance dependence is given by thestandard power-decay law Eq. (3.8) with a breakpoint distance of 1 m, combined with lognormalshadowing (Sec. 5.8).

The power delay profile is given by a modified Saleh-Valenzuela model (Sec. 7.3.3)

hdiscr(t) =L∑

l=0

K∑k=0

ak,l exp(jφk,l)δ(t − Tl − τk,l), (7.78)

where the phases φk,l are uniformly distributed in [0,2π) with a number of clusters that is Poissondistributed.

pdfL(L) = (L)L exp(−L)

L!(7.79)

so that the mean L completely characterizes the distribution.By definition, we have τ0,l = 0. The distributions of the cluster arrival times are given by a

Poisson process

p(Tl|Tl−1) = �l exp[−�l(Tl − Tl−1)

], l > 0 (7.80)

where �l is the cluster arrival rate (assumed to be independent of l). The classical SV model alsouses a Poisson process for the ray arrival times. Due to the discrepancy in the fitting for the indoorresidential, indoor office, and outdoor environments, we model ray arrival times with a mixture oftwo Poisson processes as

p(τk,l|τ(k−1),l

) = βλ1 exp[−λ1

(τk,l − τ(k−1),l

)]+ (1−β) λ2 exp

[−λ2(τk,l − τ(k−1),l

)], k > 0

(7.81)

where β is the mixture probability, while λ1 and λ2 are the ray arrival rates.For some environments, most notably the industrial environment, a “dense” arrival of MPCs was

observed, i.e., each resolvable delay bin contains significant energy. In that case, the concept of rayarrival rates loses its meaning, and a realization of the impulse response based on a tapped delayline model with regular tap spacings is to be used.

Wireless Communications, Second Edition Andreas F. Molisch© 2011 John Wiley & Sons, Ltd

Page 24: 7.6.1 Appendix 7.A: The Okumura–Hata Model

The next step is the determination of the cluster powers and cluster shapes. The PDP (meanpower of the different paths) is exponential within each cluster

E{∣∣ak,l

∣∣2} ∝ �l exp(−τk,l/γ l) (7.82)

where �l is the integrated energy of the lth cluster, and γl is the intra-cluster decay time constant.Another important deviation from the classical SV model is that we find the cluster decay time

to depend on the arrival time of the cluster. In other words, the larger the delay, the larger thedecay time of the cluster. A linear dependence

γl ∝ kγ Tl + γ0 (7.83)

where kγ describes the increase of the decay constant with delay, gives good agreement withmeasurement values.

The energy of the lth cluster, normalized to γl , and averaged over the cluster shadowing and thesmall-scale fading, follows in general an exponential decay

10 log(�l) = 10 log(exp(−Tl/�)) + Mcluster (7.84)

where Mcluster is a normally distributed variable with standard deviation σcluster.For the non-LOS (NLOS) case of some environments (office and industrial), the above description

is not a good model for the PDP. Rather, we observe only a single cluster, whose power firstincreases (with increasing delay), goes through a maximum, and then decreases again. Such ashape of the PDP can significantly influence the ranging and geolocation performance of UWBsystems, as ranging algorithms require the identification of the first (not the strongest) MPC.

Table 7.16 Parameters for channel models CM 1 and CM 2(residential)

Residential LOS NLOSvalid range of d 7 − 20 m 7 − 20 m

Path gainG0 [dB] −43.9 −48.7n 1.79 4.58S[dB] 2.22 3.51κ 1.12 1.53Power delay profileL 3 3.5� [1/ns] 0.047 0.12λ1, λ2 [1/ns], β 1.54, 0.15, 0.095 1.77, 0.15, 0.045� [ns] 22.61 26.27kγ 0 0γ0 [ns] 12.53 17.50σcluster [dB] 2.75 2.93Small-scale fadingm0 [dB] 0.67 0.69m̂0 [dB] 0.28 0.32m̃0 NA NA

Page 25: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Table 7.17 Parameters for channel models CM 3 and CM 4 (office)

Office LOS NLOSvalid range of d 3 − 28 m 3 − 28 m

Path gainn 1.63 3.07σS 1.9 3.9G0 [dB] −35.4 −59.9κ 0.03 0.71Power delay profileL 5.4 1� [1/ns] 0.016 NAλ1, λ2 [1/ns], β 0.19, 2.97, 0.0184 NA� [ns] 14.6 NAkγ 0 NAγ0 [ns] 6.4 NAσcluster [dB] 3 NASmall-scale fadingm0 0.42 dB 0.50 dBm̂0 0.31 0.25m̃0 NA NAχ NA 0.86γrise NA 15.21γ1 NA 11.84

Table 7.18 Parameters for channel models CM 5, CM 6, and CM 9(outdoor LOS, outdoor NLOS, and farm environments)

Outdoor LOS NLOS Farmvalid range of d 5 − 17 m 5 − 17 m

Path gainn 1.76 2.5 1.58σS 0.83 2 3.96G0 −45.6 −73.0 −48.96κ 0.12 0.13 0Power delay profileL 13.6 10.5 3.31� [1/ns] 0.0048 0.0243 0.0305λ1

[1/ns

]0.27 0.15 0.0225, 0, 0

λ2[1/ns

]2.41 1.13

β 0.0078 0.062� [ns] 31.7 104.7 56kγ 0 0 0γ0 [ns] 3.7 9.3 0.92σcluster [dB] 3 3 3Small-scale fadingm0 0.77 dB 0.56 dB 4.1 dBm̂0 0.78 0.25 2.5 dBm̃0 NA NA 0

Page 26: 7.6.1 Appendix 7.A: The Okumura–Hata Model

Table 7.19 Parameters for channel models CM 7 and CM 8 (industrial)

Industrial LOS NLOSvalid range of d 2 − 8 m 2 − 8 m

Path gainn 1.2 2.15σS [dB] 6 6G0 [dB] −56.7 −56.7κ −1.103 −1.427Power delay profileL 4.75 1�

[1/ns

]0.0709 NA

λ[1/ns

]NA NA

� 13.47 NAkγ 0.926 NAγ0 0.651 NAσcluster [dB] 4.32 NASmall-scale fadingm0 0.36 dB 0.30 dBm̂0 1.13 1.15m̃0 dB 12.99χ NA 1γrise [ns] NA 17.35γ1 [ns] NA 85.36

We found in the course of our investigation that the following functional fit gives a gooddescription:

E{∣∣ak,1∣∣2} ∝ (1 − χ · exp(−τk,l/γrise)) · exp(−τk,l/γ1). (7.85)

Here, the parameter χ describes the attenuation of the first component, the parameter γrise deter-mines how fast the PDP increases to its local maximum, and γ1 determines the decay at latertimes. The numerical values of the parameters used in Eq. (7.76)–(7.85) are specified, for differentenvironments, in Tables 7.16–7.19.