RF Engineering & Network Planning

RF Engineering and Network Planning

The world we live in today benefits by a lot of advanced technologies that we often take for granted owing to its simplicity in manifestation. For example, mobile radio communications is a very complex working system that is simplified in output to receiving and making calls on a mobile device. But have you ever taken the time to pause and wonder about the effort, technology and meticulous planning that goes into making mobile communications a reality in a our daily lives ?

The governing process of defining parameters and working premises for a wireless system in mobile communication is known as RF Engineering. In simpler terms the wireframe for mapping mobile towers and their reception points within a given geographical area is known as Network Planning and the force that provides stimulus to this is known as RF engineering or radio frequency engineering. The RF plan for any communication wireframe determines two very important elements that complete the equation for any wireless network planning and design, capacity & coverage. While capacity indicates the number of users any particular RF plan can sustain, coverage indicates the geographical area under which the users can be mapped. It might be clear by now, capacity & coverage go hand in hand.

If capacity has to be increased, coverage area has to be limited and for coverage area to be increased, capacity takes a hit, or in other words, somethings gotta give.

1. Initial Radio Link Budgeting

The start of any system has to be with budgeting or approximating the extent of the work that is about to be enabled. The RF Link budgeting is a measure of approximately the extent of the coverage area and the number of sites required to fulfill the same to completion. The budgetary planning is accomplished with the help of the RF link projected by the statistical propagation model to assess and determine the coverage area. The statistical propagation model is marked by a slope and intercept value for specific environment types (rural, urban, suburban, etc.) and does not include the effect of terrains.

This information is documented in the form of two inputs, simple radio transceiver characteristics and ‘flat’ map of the area.

This fairly simplistic method of budgetary calculation is quick to implement and easily analyses the number of sites required to fulfill the mapping of the desired coverage area. At the end of this stage, the RF engineer has a clear estimate of the number of sites required to move ahead with the remaining stages.

2. Detailed RF Propagation Model

The second level of the RF Planning process is a slightly more detailed propagation model. It employs the use of automatic tools such as robots to cover large areas and predict detail and accurate results. The inputs in this stage for the statistic propagation model to consider are multiple such as the terrain, and the land use and land clutter in and around each site. Unlike the budgetary phase, this stage has a three dimensional mapping of the terrain.Thus needless to mention, the result is a detailed and more accurate representation of the sites required across coverage area. Combined with the results from the previous stage, the RF link budget, this function produces an accurate determination of the number of sites required and their precise co-ordinates respectively. A typical list of outputs derived from this stage are :

Number of sites, site locations, height of each site
Antenna directions and downtilts
Neighbour cell lists for each site
Mobility parameters for each site : handover and cell re-selection
Frequency plan
Detailed coverage predictions : (RSRP), signal quality (RSRQ) best CINR, best server areas, uplink and downlink throughput

3. Detailed RF Propagation Model

The third phase of the RF planning process furthers the progress of RF planning with attention to minute detail with an intention to accurately fulfill expectations. This stage involves collection and assimilation of drive data for fine tuning and calibration of the statistical propagation prediction model. By repeated iterations and elimination of unforced errors through this stage, the data extracted throughout each site is used for fine tuning of parameter settings of input variables such as antenna orientation, downtilting, frequency plan. This process precedes the deployment of the system and is critical for finalizing the service contract based on coverage area.

A list of outputs typically extracted at this stage are:

A complete list of sites mapped with locations and their respective altitude.
Optimized antenna directions and downtilts.
Optimized neighbour cell lists for each site.
Mobility parameters for each site.
An optimized frequency plan
Detailed coverage predictions across varied metrics of measurement such as signal strength (RSRP), signal quality (RSRQ) best CINR, best server areas, uplink and downlink throughput.

4. Continuous Optimization

The final phase of the RF planning boils down to continuous optimization of the RF plan to accommodate for the changing environment thereby affecting additional service requirements such as additional coverage or capacity.

This phase begins with the network deployment initially and involves collection of data for measurement & analysis on the move on a regular basis.

The continuous process of data collection is then used to improve and optimize the parameter settings of existing sites.