M. Suneetha Rani et al. / IJAIR
ISSN: 2278-7844 2278-7844
Comparison of Standard Propagation Model (SPM) and Stanford University Interim (SUI) Radio Propagation Models for Long Term Evolution (LTE) M.Suneetha Rani
#1
, Subrahmanyam VVRK Behara
*2
, K.Suresh
#3
#
Department of ECE, Chaitanya Engineering College Visakhapatnam, A.P. INDIA 1
[email protected]
3
[email protected]
*
Department of ECE, BITS, Visakhapatnam, A.P. INDIA 2
[email protected]
Abstract This paper deals with comparison of SPM (Standard propagation models) used in many planning tools such as Atoll, Asset and Planet for several wireless telecommunication telecommunication standards and SUI (Stanford University Interim) Radio Propagation Model compared with many conventional models like COST 231 model, HATA, Okumura model and Ericsson 9999 th model for the upcoming 4 Generation mobile network known as LTE. Radio Propagation model is intended for knowing cell radius which is a very important factor during planning phase of of network deployment. Cell radius directly depends on Path loss generated by different propagation scenarios which are modeled using different Propagation models. Present work makes a comparative analysis through design of mathematical modeling of all the above mentioned propagation models using Matlab. Frequency bands considered are for Asia taken as 1800MHZ and 2100MHz. SPM has given the least Path loss for different areas such as URBAN,SUBURBAN,RURAL compared with all other propagation Models.
Keywords: Long Term Evolution, Standard Propagation Model, Stanford University Interim Radio Propagation Model
I INTRODUCTION Long Term Evolution, LTE is a standard for wireless for wireless communication of high-speed data for mobile phones and data terminals. It is based on the GSM/EDGE GSM/EDGE and UMTS/HSPA UMTS/HSPA network technologies, increasing the capacity and speed using a different radio interface together with core network improvements. LTE technology is a third option worth considering considering two technology options 3G and WiMAX to support mobile broadband., as it may provide operators with better performance a t a lower
cost than either 3G or WiMAX. LTE is a superior technology that offers much higher data throughput and lower latency than 3G. Moreover, the promise of a well-developed 3G/LTE ecosystem in the US and Europe may result in more new devices that support both, opening opportunities for Indian operators to explore new business models and potentially new sources. LTE is based on OFDMA (Orthogonal Frequency Division Multiple Access) to be able to reach even higher data rates and data volumes. LTE offers many advantages over competing technologies. However, in the Indian context there are several questions that need to be answered before LTE can become a credible alternative to 3G and WiMAX [ 3]. 1.1 Spectrum availability The LTE spectrum in India stills lack clarity. Operators may consider deployment in BWA (20 MHz of unpaired spectrum in 2.3 GHz) and 3G (paired spectrum of 2x5 MHz in 2.1 GHz) spectrum bands. In addition, approximately 120 MHz of spectrum in the 700 MHz band — an an effective and cost efficient frequency band for LTE deployment — deployment — could be used for LTE in the future.
LTE is developed for a number of frequency bands, ranging from 800 MHz up to 3.5 GHz. The available bandwidths are also flexible starting with 1.4 MHz up to 20 MHz. LTE is developed to support both the time division duplex technology (TDD) as well as frequency division duplex (FDD).
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M. Suneetha Rani et al. / IJAIR
1.2 Current voice congestion Though LTE has a lot of advantages as a mobile broadband technology, any voice solution for it will take a few years or more to materialize. LTE will not serve the purpose of operators looking at 3G spectrum options to ease congestion on their current voice networks. These operators would have to incur incremental capital expenditures in 2G base stations to use 3G spectrum for LTE deployment. 1.3 Technical maturity Many operators worldwide have already committed to LTE and are actively preparing for deployments in the near future. There is an expectation that most Western operators on 3G will eventually move to LTE. However, there has been only limited commercial deployment of LTE to date. Hence, Indian operators need to be careful when considering their LTE deployment time line, given that LTE is still a relatively new technology. 1.4 The motivation for LTE The need to ensure the continuity of competitiveness of the 3G system for the future, user demand for higher data rates and quality of service are the main motivation for LTE. The frequency bands used in various global regions are presented in the Table 1.1 Table 1.1
Region North America Europe Asia Australia
Frequency Bands 700/800 and 1700/1900 MHz 800, 900, 1800, 2600 MHz 1800 and 2600 MHz in Asia 1800 MHz
The LTE standard can be used with many different frequency bands. As a result, phones from one country may not work in other countries. Users will need a multi-band capable phone for roaming internationally. The selection of a suitable radio propagation model for LTE is of great importance. A radio propagation model describes the behavior of the signal while it is transmitted from the transmitter towards the receiver. It gives a relation between the distance of transmitter and receiver and the path loss. Path loss depends on the condition of environment (urban, suburban, rural, dense urban, open, etc.) operating frequency, atmospheric conditions, indoor/outdoor and the distance between the transmitter and receiver. In this paper a comparison is made between SUI and SPM models in different terrains to find out the model having least path loss in a particular terrain in coverage point of view.
ISSN: 2278-7844
II RADIO PROPAGATION MODELS Radio planning tools have interfaces for external propagation prediction models, and a large number of different propagation models are commercially available. Radio planning tools also have internal propagation models. The internal models that are used in cellular network planning are typically based on the Okumura-Hata (O-H) formulas. For a given frequency band, the Okumura-Hata formulas are simple functions of distance, but the effect of the digital map is included by adding antenna height, diffraction and clutter corrections into the basic Okumura-Hata loss. The exact implementation of the antenna height, diffraction and clutter corrections as well as other possible adjustments varies from one planning tool to another.
To find an accurate model for propagation losses is a leading issue when planning a mobile radio network. Two strategies for predicting propagation losses are in use these days: one is to derive an empirical propagation model from measurement data and the other is to use a deterministic propagation model. 2.1 Standard Propagation Model Propagation models in Asset and Atoll are based on Okumura-Hata models which support frequencies higher than 1500 MHz. These models in Asset and Atoll are termed as standard propagation models. Standard Propagation Model (SPM) is based on empirical formulas and a set of parameters are set to their default values[1]. However, they can be adjusted to tune the propagation model according to actual propagation conditions. SPM is based on the following formula[1] + 3 = 1 + 2 ) + 4 + 5 ( + 6 + -------------(1)
∗
∗
For hilly terrain, the correction path loss when transmitter and receiver are in LOS is given by = 1 + 2 + 3 +
+ + + -------------(2) 5
6
When transmitter and receiver are not in line of sight NLOS, the path loss formula is
= + + + ∗ + + ∗ + ∗ -------------(3) 1
3 5
2
4
6
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M. Suneetha Rani et al. / IJAIR
ISSN: 2278-7844
Where, . 1 = frequency constant 2 = Distance attenuation constant . d =distance between the receiver and transmitter (m). 3 , 4 = Correction coefficient of height of mobile station antenna Diffractiion loss: loss due to diffraction over an obstructed path (dB). = Correction coefficient of height of base 5 , 6 station antenna. = correction coefficient of clutter attenuation, the signal strength of a given point is modified according to the clutter class at this point and is irrelevant to the clutter class in the transmission path. All losses in the transmission path are included in the median loss. hm , hb = effective height of antenna in mobile station and base station respectively, unit: m In radio transmissions, the value of K varies according to terrains, features and environment of cities. ( ). = f(clutter)= average of weighted losses due to clutter.
Table 2.1 K-Parameters for a Metropolitan City in India(Asia)
K Values
Dense Urban
K1
16.375
K2
The path loss in SUI model can be described as
+ + ---------(4) PL= A+ 10 γ log ( / ) + where PL represents Path Loss in dBs, d is the distance between the transmitte and receiver, is the reference distance (Here its value is 100), is the frequency correction factor, is the Correction factor for Base station height, S is shadowing and γ is the path loss component and it is described as c γ = a bhb + -------------(5)
−
A = 20 log
4πd o
Where A is the free space path loss while do is the distance between Tx and Rx and λ is the wavelength, The correction factor for frequency and base station height are as follows:
∆X =6log f
f
Rural
17.675
5.275
26.625
∆X
48
45.9
44.9
48
40.1
S = 0.65(log f)
K3
5.83
5.83
5.83
5.83
5.83
K4
0.8
0.8
0.8
0.8
0.8
K5
-6.55
-6.55
-6.55
-6.55
-6.55
K6
0
0
0
0
0
Kclutter
1
1
1
1
1
Terrain B 4 0.0065 17.1
Terrain C 3.6 0.005 20
∆X
h=
10.8 log
hr 2000
--(7) & (8)
Where f is the frequency in MHz, and hr is the height of the receiver antenna. This expression is used for terrain type A and B. For terrain C, the below expression is used.
17.575
Terrain A 4.6 0.0075 12.6
,
2000
Urban
Table 2.2: Different Terrains and their parameters
-------------(6)
λ
High ways
Parameters a b (1/m) c (m)
hb
Where hb is the height of the base station and a, b and c represent the terrain for which the values are selected from the above table.
Suburban
2.2 Stanford University Interim (SUI) Model Stanford University Interim (SUI) model is developed for IEEE 802.16 by Stanford University[2]. It is used for frequencies above 1900MHz. In this propagation model, three different types of terrains or areas are considered(Table 2.2). These are called as terrain A,B and C. Terrain A represents an area with highest path loss; it can be a very dense populated region while terrain B represents an area with moderate path loss, a suburban environment. Terrain C has the least path loss which describes a rural or flat area.
h=
- 20 log (
hr 2000 2
),
− 1.3 logf + α --------(9) & (10)
Here α dB for rural and suburban environments(Terrain A & B) and 6.6 dB for urban environment (Terrain C). 2.3 Free Space Loss Model In telecommunication, free-space path loss (FSPL) is the loss in signal strength of an electromagnetic wave that would result from a lineof-sight path through free space (usually air ), with no obstacles nearby to cause reflection or diffraction. It does not include factors such as the gain of the antennas used at the transmitter and receiver, nor any loss associated with hardware imperfections. A discussion of these losses may be found in the article on link budget. Free-space path loss formula Free-space path loss is proportional to the square of the distance between the transmitter and receiver, and also proportional to the square of the frequency of the radio signal.
)=4 / 2 The basic equation is ( -----(11) FSPL(dB)= 32.44+ 20 log 10(d) + 20 log10(f) --(12)
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Where ‗f‘ is the signal frequency (in megahertz), ‗d‘ is the distance from the transmitter (in km). This equation is only accurate in the far field where spherical spreading can be assumed. It does not hold good when receiver is close to the transmitter. 2.4 Cost – 231 Hata Model
The COST-Hata-Model is the most often cited of the COST 231 models[5]. Also called the Hata Model PCS Extension, it is a radio propagation model that extends the Hata Model (which in turn is based on the Okumura Model) to cover a more elaborated range of frequencies. COST is a European Union Forum for cooperative scientific research which has developed this model accordingly to various experiments and researches. Coverage Frequency: 150 MHz to 2000 MHz Mobile Station Antenna Height: 1 up to 10m Base station Antenna Height: 30m to 200m Link Distance: 1 up to 30 km Mathematical Formulation: The COST-Hata-Model is formulated as, Path Loss(L)= 46.3 + 33.9 log10(f) – 13.82 log10(h b) – a(hm) + (44.9 - 6.55 log(h b))log10(d) + C [dB]--(13) For suburban or rural environments: Where, L = Median path loss. Unit: Decibel (dB) f = Frequency of Transmission. (MHz) h b = Base Station Antenna effective height.Meter (m) d = Link distance. (km) hm = Mobile Station Antenna effective height (m) a(hm) = Mobile station Antenna height correction factor as described in the Hata model for Urban Areas.
ISSN: 2278-7844
2.5 COST-231 Walfisch-Ikegami Model
COST-231 Walfisch-Ikegami model is an extension of COST Hata model. It can be used for frequencies above 2000 MHz. Line of Site(LOS) path loss is given by following formula PL=42.64+26log(d)+20 log (f) -------------(14) For NLOS condition, the path loss is given by PL=Lo+Lrts+Lmsd -------------(15) where Lo is the attenuation in free space and is described as: Lo=32.45+20 log(d)+20log(f) ---------------(16) Lrts represents diffraction from rooftop to street and is defined as: Lrts= 16.9 10 log w + 10 log f + 20 log hb hm + Lori --------(17)
−
− −
Here Lori is a function of the orientation of the antenna relative to the street a (in degrees) and is defined as: Lori= -10+0.354 a for 0h t
b
K d=18 for ht
