Tag: Network Planning

Channel Modeling, LTE

WINNER-II Path Loss Model

In simple terms the path loss is the difference between the transmitted power and the received power of a wireless communication system. This may range from tens of dB to more than a 100 dB e.g. if the transmitted power of a wireless communication system is 30 dBm and the received power is -90 dBm then the path loss is calculated as 30-(-90)=120 dB. Path loss is sometimes categorized as a large scale effect (in contrast to fading which is a small scale effect). According to the WINNER-II model the path loss can be calculated  as: Here d is the […]

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Capacity, LTE

Soft Frequency Reuse in LTE

Frequency Reuse is a well known concept that has been applied to wireless systems over the past two decades e.g. in GSM systems. As the name suggests Frequency Reuse implies using the same frequencies over different geographical areas. If we have a 25MHz band then we can have 125 GSM channels and 125*8=1000 time multiplexed users in a given geographical area. Now if we want to increase the number of users we would have to reuse the same frequency band in a geographically separated area. The technique usually adopted is to use a fraction of the total frequency band in […]

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Network Planning, WiMAX

WiMAX Path Loss and Antenna Height

As discussed previously the SUI (Stanford University Interim) model can be used to calculate the path loss of a WiMAX link. The SUI model is given as: SUI Path Loss Equation It has five components: 1. The free space path loss (A) up to the reference distance of ‘do’. 2. Additional path loss for distance ‘d’ with path loss exponent ‘n’. 3. Additional path loss (Xf) for frequencies above 2000 MHz. 4. Path gain (Xh) for receive antenna heights greater than 2 m. 5. Shadowing factor (s). The most important factor in this equation is the distance dependent path loss. […]

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Channel Modeling, WiMAX

WiMAX Path Loss Calculation

Calculation of the path loss is fundamental to Wireless System Design. There are many models available for calculating the path loss such as Okumura Model, Hata Model, COST-231 Model and more recently the SUI (Stanford University Interim) Model. The SUI Model has been specifically proposed for Broadband Wireless Access Systems such as WiMAX. It defines three types of environments namely A, B and C which are equivalent to the urban, suburban and rural environments defined in the earlier models. According to this model the path loss can be calculated as: PL=A+10*n*log10(d/do)+Xf+Xh+s where n=a-(b*hb)+(c/hb) A=20*log10(4*pi*do/lambda) Xf=6.0*log10(f/2000) Xh=-10.8*log10(hr/2) for A&B Xh=-20.0*log10(hr/2) for […]

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LTE, Network Planning

LTE Path Loss at 700 MHz

In the previous post we had compared the path loss of LTE at 728 MHz and 1805 MHz in a free space line of sight channel. This is a very simplistic channel model which tells us that ratio of the received signal strengths at these frequencies can be simply found as: (f1/f2)^2=(1805/728)^2=6.15 That is the received signal strength at 728 MHz is 6.15 times higher than the received signal strength at 1805 MHz. Now let us consider a more realistic channel model known as the COST-231 model. According to this model the path loss (difference between the transmit power and […]

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Network Planning

Ray-Tracing for Network Planning-II

It’s very easy to get lost in the jargon when selecting a simulation tool for planning your wireless network. You will be faced with complex terminology which would not make much sense. At one end of the spectrum are solutions based on simple empirical models while at the other end are solutions based on ray-tracing techniques. Empirical models are based on measurement data and are your best bet if you want a quick and cheap solution whereas ray-tracing techniques are based on laws of physics and promise more accurate results. In principle ray-tracing techniques are quite simple: just transmit a […]

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Network Planning

Ray-Tracing for Network Planning-I

It’s very easy to get lost in the jargon when selecting a simulation tool for planning your wireless network. You will be faced with complex terminology which would not make much sense. You will be told that ray-tracing is the solution to all problems and outperforms all other techniques. However ray-tracing is only accurate when the following factors have been considered. Granularity of the terrain database Granularity in field calculations Accuracy in representation of building materials Accuracy in modeling the various propagation phenomenon Upper limit on the number of interactions

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