How do you optimize radio frequency propagation in urban environments with complex terrain and buildings?

It is a big challenge to optimize RF propagation in urban environments, where there is a complex terrain with high buildings density. In such scenario more accurate high resolution geographical maps play a huge role for RF planning and optimization. Using these high resolution maps (terrain, clutter and buildings), cell-wise best antenna pattern, height, azimuth and tilts need to be planned, while considering neighbor cells configuration, clutter type, clutter height, building density, spacing between buildings etc. These will help to maximize the RF coverage with minimum overlap. Path loss calculation and prediction done at 2*2m resolution using digital maps of 2*2m resolution with proper planning gives more accurate results in urban.

In my experience, point to point wireless links have couple main requirements: clear Line Of Sight, Distance of the link, Link Elevation, Terrain, Fresnel Zone clearance, Sturdy mounts etc..

Implement channel quality feedback and update the multipath coefficients to match the channel characteristics of the urban environment.

Every system is unique whether optical, microwave point-to-point, low power RFID, etc. The key is to use the minimum power and bandwidth needed for communications. Of course, you will want some overhead to "future" proof the deployment. The beauty of an urban environment is there tend to be available height. The Achilles heel is multi-path due to density of structures and the dynamic nature over a day, a month, and year.

Use longer wavelength carrier signals with frequency modulation (FM). Deploy high-altitude broadcasting stations like balloons. Implement a cellular network architecture with broadband antennas. Strategically place signal amplifiers and repeaters. Conduct propagation analysis to optimize network design.

Using dynamic digital predistortion is one way to mitigate interference sources. This can be along with programmable RF front end filters to minimize the interference signal.

Hemish is correct in that predistortion can be helpful and it can be done both in digital and analog if needed. The problem there isn't a lot of usage of it from what I've seen. Interference comes in many forms as noted in the item. Understanding and recognizing them is crucial. Some can be mitigated easily while others cannot but one cannot take a shotgun approach to the solution.

RF propagation models used by Modeling tools are not very accurate, because they determine the signal strength based on the obstacles and interferences input given by the user. In reality, these obstacles and interferences source (For example, buildings, trees, hills, and other objects) may be differ in actual as compare to the inputs used by Modeling tools. The RF signals can vary rapidly due to change in these buildings, trees, hills, and other object’s information. Actual obstacles and interferences can block, reflect, or scatter the RF waves differently as compare to predicted one, causing them to lose more or less power than expected one. Propagation Model Tuning is done to improve the accuracy of a propagation model.

Urban environment conditions vary with time. So the device needs to implement adaptive algorithms to optimize for a given channel conditions. Think of using modeling tools to model adaptive rake receiver or model hypothesis based optimization problem.

Covered much of this under item #4. Models are models. They are imperfect. They can give you a good starting point but experience and understanding of the effect of the terrain on signal propagation is more important. I was involved in terminal deployment on a land mobile system where the designer used cellular methods. It had many problems including very smart people involved not understanding basic RF theory. We are teaching analytics without the practical.

RF Frequency Ranges HF: 2 - 30 MHZ. : Long Range Communications VHF: 30 - 300 MHZ Line of Sight - Beach Communication UHF : 300- 3 GHZ Line of Sight and SATCOM SHF: 3 GHZ - 30 GHZ SATCOM EHF: 30 - 300 GHZ SATCOM

Field testing is most important experience that once can have in the telecommunication industry. It is the one of the few tasks that provide insights to digital, analog, RF, sync, multipath and other relevent issues and most importantly, processing the data and identifying any patters in the data. So understanding testing is one of the most essential qualities.

Field testing is the most important step while deploying any radio communication network, Anyone can verify the RF propagation in a real environment and measure the actual performance and quality of wireless networks by performing the field testing. Field testing results ( drive measurements and survey data ) can be used to enhance the RF propagation models used by Modeling tools (Propagation Model Tuning). Field testing should be done very precisely so that outputs of field testing can be used as a feedback for Model Tuning which will enhance the performance and quality of wireless networks.

Based on my experience in RF optimization for 2G & 4G .. best coverage/quality will be made by choosing best position of coverage stations (so called Base Stations) with paying special attention for Antenna height and tilting in parallel with population / buildings density and how many sites per area .. having enough number of sites with suitable height and antenna tilting, all other optimization techniques will pay off and would be really fruitful

I have to agree with Hemish. You have to test in the live environment and with the actual equipment going to be deployed. In addition, it must be done over a period of time to understand dynamic changes in the environment such as a truck yard. Propagation will change during different periods due to the number of trucks in the yard. No different that the sound mix in a venue changes from an empty venue to a full one. We tend neglect both paths, RX and TX. A device may hear the base station, gateway, etc. but is unable to get a signal back to it. This drives system balance and coverage overlap. I have had several occasions where device could not determine the best routing path due to equal signal strengths and BER.