Category Archives: Network Planning

Network planning using ray-tracing and other techniques.

Open Signal Coverage Maps for Pakistan

Fundamentals, LTE, Network Planning, , , ,

Open Signal is a mobile application that collects the data about your wireless network (2G/3G/4G) and generates coverage maps and host of other reports. The data is collected in the background while the user is busy in his daily routines. But data can also be collected on the request of the user. This is much better than drive testing since the data is collected in real life scenarios and on thousands of different devices that are in use.

The app works while the user is indoor or outdoor, at rest or in motion, on land or on water, at sea level or on a mountain, in dry weather or in rain. Basically anywhere and anytime there are wireless signals available. There are currently 20 million users of the app (both Android and iOS combined) and this number is increasing. In Pakistan all major networks are supported including Jazz, Telenor, Zong and Ufone (both 2G/3G and 4G networks are supported).

JAZZ Islamabad Coverage Map

Telenor Islamabad Coverage Map

Zong Islamabad Coverage Map

Ufone Islamabad Coverage Map

Eclipse

Channel Modeling, LTE, Network Planning, Simulation, , , , , , ,

Eclipse 1.0 – A Paradigm Shift in RF Planning

NEW: Simulation of a Moving Transmitter (such as a car)

NEW: Simulation of a Moving Transmitter (such as a pedestrian)

Radio frequency planning is an essential component of network planning, roll-out, up-gradation, expansion etc. Several methods can be adopted for this from something as simple as free space models, empirical path loss models to the significantly more complicated, time consuming and expensive drive testing. Drive testing gives very accurate results but these results can be rendered useless by changing the position of an antenna or the tilt or transmit power of an antenna requiring another run in the field. One solution to this problem is ray-tracing which is very accurate but is usually considered to be very computationally expensive and of little practical value. But recent advances in computational power of machines coupled with efficient techniques have given a new lease of life to this method.

Eclipse is a near real-time simulation software for prediction of signal strength in urban areas. The software uses shooting and bouncing ray (SBR) method of ray tracing with 1 degree ray separation, 1 m step size and 9 interactions per ray path. The simulation parameters can be varied according to the resolution required. The code is highly optimized to give results in shortest possible time. It is especially useful for network planning of ultra-dense wireless networks where a dense network of antennas is placed on lamp posts instead of telecom towers. Various frequency bands can be simulated, along with different antenna radiation patterns and MIMO configurations.

Helsinki 3D Building Data

Received Signal Strength Over Area of Interest

Note: If you would like to run a test simulation send us a request at info@raymaps.com

Android Apps

Network Planning, ,

1. Rx Signal Meter

Received signal strength calculation is required by RF engineers working in the field. This application provides an easy to use interface to calculate the received signal strength. Input parameters include the transmit power, transmit antenna gain, receive antenna gain, transmit receive separation and frequency of operation. Output is the received signal strength in dBm.

https://play.google.com/store/apps/details?id=com.raymaps.path.loss

2. Rx Signal Pro

A simple application that can be used to calculate the Received Signal Strength using one of the following six models.
1. Free Space Path Loss
2. Hata Model
3. COST-231 Model
4. ECC-33 Model
5. Ericsson Model
6. SUI Model
Input parameters include the transmit power, frequency, transmit-receive separation, base station antenna height and mobile station antenna height. Output parameter is the Received Signal Strength in dBm. The application is also available in Desktop version.

https://play.google.com/store/apps/details?id=com.raymaps.signal.me…

3. Path Loss Calculator

A simple application that can be used to calculate the Path Loss using one of the following six models.

1. Free Space Path Loss
2. Hata Model
3. COST-231 Model
4. ECC-33 Model
5. Ericsson Model
6. SUI Model

Input parameters include the frequency, transmit-receive separation, base station antenna height and mobile station antenna height. Output parameter is the Path Loss in dB. The application is also available in Desktop version.

https://play.google.com/store/apps/details?id=com.raymaps.path.loss…

4. RF Planner

This is a simple application which can be used to do RF planning of a GSM, WCDMA, LTE or WiMAX site. The input parameters are the Tx Power, Rx Sensitivity, Tx Height, Rx Height and Frequency of operation. The output parameter is the Cell Radius which is used to plot the coverage area of the cell site on Google Maps. The coverage scenario can be selected from the following three options:
1. Urban
2. Suburban
3. Rural
The underlying model is applicable to Frequencies of up to 3500 MHz, Distances of 100-8000 m, BS Antenna Heights of 10-80 m and MS Antenna Height of 2-10 m.

https://play.google.com/store/apps/details?id=com.raymaps.rf.planner1

Antenna Radiation Pattern and Antenna Tilt

Antennas, LTE, Network Planning, WiMAX, , , ,

An introductory text in Communication Theory would tell you that antennas radiate uniformly in all directions and the power received at a given distance ‘d’ is proportional to 1/(d)^2. Such an antenna is called an isotropic radiator. However, real world antennas are not isotropic radiators. They transmit energy in only those directions where it is needed. The Gain of a antenna is defined as the ratio of the power transmitted (or received) in a given direction to the power transmitted in that direction by an isotropic source and is expressed in dBi.

Although antenna Gain is a three dimensional quantity, the Gain is usually given along horizontal and vertical planes passing through the center of the antenna. The Horizontal and Vertical Gain patterns for a popular base station antenna Kathrein 742215 are shown in the figure below.

Kathrein 742215 Gain Pattern
Kathrein 742215 Gain Pattern

The actual Gain is given with respect to the maximum Gain which is a function of the frequency e.g. in the 1710-1880 MHz band the maximum Gain has a value of 17.7dBi. Another important parameter is the Half Power Beam Width (HPBW) which has values of 68 degree and 7.1 degree in the horizontal and vertical planes respectively. HPBW is defined as the angle in degrees within which the power level is equal to or above the -3 dB level of the maximum.

Also shown in the above figure are approximate Horizontal Gain patterns for two antennas that have been rotated at 120 degrees and 240 degrees. Together these three antennas cover the region defined as a cell. There would obviously be lesser coverage in areas around the intersection of two beams.

A somewhat more interesting pattern is in the vertical direction where the HPBW is only 7.1 degrees. Thus it is very important to direct this beam in the right direction. A perfectly horizontal beam would result in a large cell radius but may also result in weak signal areas around the base station. A solution to this problem is to give a small tilt to the antenna in the downward direction, usually 5-10 degrees. This would reduce the cell radius but allow for a more uniform distribution of energy within the cell. In reality the signal from the main beam and side lobes (one significant side lobe around -15 dB) would bounce off the ground and buildings around the cell site and spread the signal around the cell.

Antenna Tilt of 10 Degrees
Antenna Tilt of 10 Degrees

The above figure gives a 2D view of signal propagation from an elevated antenna with a downward tilt of 10 degrees in an urban environment.

Base Station Antenna Tilt and Path Loss

Antennas, LTE, Network Planning, WiMAX, , , ,

Path loss is basically the difference in transmit and receive powers of a wireless communication link. In a Free Space Line of Sight (LOS) channel the path loss is defined as:

L=20*log10(4*pi*d/lambda)

where ‘d’ is the transmit receive separation and ‘lambda’ is the wavelength. It is also possible to include the antenna gains in the link budget calculation to find the end to end path loss (cable and connector losses may also be factored in). Antenna gains are usually defined along a horizontal plane and vertical plane passing through the center of the antenna. The antenna gain can then be calculated at any angle in 3D using the gains in these two planes.

Although 3D antenna gains are quite complex quantities simplified models are usually used in simulations e.g. a popular antenna Kathrein 742215 has the following antenna gain models [1] along the horizontal and vertical planes:

Gh(phi)=-min(12*(phi/HPBWh)^2, FBRh)+Gm

Gv(theta)=max(-12*((theta-theta_tilt)/HPBWv)^2, SLLv)

where

Gm=18 dBi
HPBWh=65 degrees
HPBWv=6.2 degrees
SLLv=-18 dB

We are particularly interested in the gain in the vertical plane and the effect of base station antenna tilt on the path loss. We assume that the mobile antenna station has uniform gain in all directions. The path loss can be then calculated as:

L=20*log10(4*pi*d/lambda)+Gv(theta)+Gh(phi)

where we have assumed that Gh(phi)=0 for all phi (this is a reasonable simplification since changing the distance along the line of sight would not change Gh(phi) ). Using the above expression the path loss in free space is calculated for a frequency of 1805 MHz, base station antenna height of 30 m and an antenna tilt of 5 degrees.

Effect of Antenna Tilt on Path Loss
Effect of Antenna Tilt on Path Loss

It is observed that there is a sudden decrease in path loss at distances where the antenna main beam is directed. If the antenna tilt is increased this behavior would be observed at smaller distances. Since we have used a side lobe level that is fixed at -18 dB we see a rapid change in behavior at around 100 m. If a more realistic antenna model is used we would see a gradual decrease in path loss at this critical distance.

[1] Fredrik Gunnarsson, Martin N Johansson, Anders Furuskär, Magnus Lundevall, Arne Simonsson, Claes Tidestav, Mats Blomgren, “Downtilted Base Station Antennas – A Simulation Model Proposal and Impact on HSPA and LTE Performance”,
Ericsson Research, Ericsson AB, Sweden. Presented at VTC 2008.

Qualcomm In Muddy Waters In India

Network Planning, Random Thoughts, , , ,

Remember Qualcomm CEO Paul Jacobs proudly claiming that his company had prevented WiMAX from getting a hold in India by acquiring BWA licenses in four regions of India. Well now Qualcomm is in a bit of bother as the Department of Telecommunication (DoT) in India has raised objections to the license application filed by Qualcomm. According to news circulating on the internet the DoT has objected to Qualcomm filing four separate applications through its nominee companies in the four regions (Delhi, Mumbai, Kerala and Haryana) it had won the licenses on June 12, 2010. Secondly the DoT has also objected to the delay in the filing of application outside the three month period required by the laws.

Qualcomm has rejected these objections saying that it has followed all rules in letter and spirit. According to Qualcomm the license application was filed in August 2010 within the three month period as required by the laws. However this is disputable as Qualcomm also submitted a revised application in December 2010. Qualcomm has also countered the second objection by saying that it plans to merge the four nominee companies so that there is no breach of law. As per the rules “if at any stage the spectrum allocation is revoked, withdrawn, varied or surrendered, no refund will be made”. So if an understanding is not reached between Qualcomm and DoT, Qualcomm is set to lose more than $1 billion that it had paid for the BWA spectrum.

Qualcomm Inc. is a leading wireless chip manufacturing company of the world. It is the pioneer of CDMA technology and its chipsets have been embedded in more than a billion cell phones. Qualcomm has greatly invested in UMTS technology and is a strong proponent of WCMDA, HSPA and LTE standards. It had a paid about a billion dollars for the right to use a 20 MHz chunk of spectrum in the 2.3 GHz band. It plans to bring TDD LTE to India, which is a considered to be a comparatively economical 4G technology.