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RF Wireless Site Survey Explained

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An RF (Radio Frequency) site survey is a vital process in planning and deploying cellular wireless networks. It involves a detailed evaluation and analysis of the radio frequency characteristics of a location. The goal? To determine the optimal placement and configuration of wireless infrastructure like cell towers, antennas, and access points.

RF Survey is the systematic collection of data from a site or in the field, necessary for installing a new site. This data is crucial for:

  • Cell site analysis
  • Determining the coverage area of a proposed new cell site
  • Deciding the type of connectivity (link) with another cell site.

This task often leads to physical changes in the existing network, either through modification or addition of new sites/equipment. Usually, the customer provides specific details as a starting point, often called a “nominal point” or “reference point,” including:

  • Latitude and longitude values
  • X-Y coordinates
  • North/East coordinate details
  • Location Area name

RF Surveys are also invaluable in diagnosing issues within existing GSM/CDMA/LTE or VSAT networks, such as interference, multi-path distortion, or the impact of new construction near cell towers. By identifying and addressing these problems through RF Surveys, we ensure the installed RF network operates effectively.

Just like any project, a well-planned RF site survey is key to an efficient execution and successful network rollout. Prior to physically surveying the area, it’s essential to analyze the region using available resources like aerial photos, Google Maps, and Google Earth.

There are different types of tower for which RF survey need to be done:

  • Ground Base Tower(GBT)-Avg. Tower height-30-60 meter
  • Roof Top Tower(RTT)-Avg. Tower Height-18-27 meter
  • Roof Top Pole(RTP)-Standard Height of Roof Top Pole is 3M, 6M & 9M from ARL (Above Roof Level).

RF site survey

RF Wireless Site Survey Checklist

When conducting an RF Wireless site survey for cellular wireless networks, use the following checklist:

  • Identify Potential Obstacles: Utilize facility diagrams to pinpoint probable RF obstacles.
  • Visual Inspection: Visually inspect the location for physical barriers to RF signal propagation, and identify any metallic structures.
  • Identify Congestion Areas: Locate both highly congested and less congested mobile user areas.
  • Determine Power and Network Access: Identify locations with available power and wired network access.
  • Cell Coverage and Overlap Maps: Determine existing cell coverage and overlap maps.
  • Finalize Frequency Channel: Select the appropriate frequency channel for the site.
  • Mounting Structures: Finalize mounting structure specifications based on antenna size and other equipment requirements.
  • Verify Base Station Location: Perform the actual surveying to confirm and finalize the Base Station/Node-B/eNB/eNodeB location. Use the same Base Station model as the production environment.
  • Optimize Signal Strength: Relocate the Base Stations as needed during the survey and re-test to achieve maximum signal strength.
  • Document Analysis: Finalize and thoroughly document the analysis performed during the survey. Record signal readings, data rates, and network logs (if any) at various locations within the facility and at outer boundary regions.

Objective of RF Site Survey

RF site surveys are conducted before installing cellular or other wireless networks, including satellite ground stations, VSATs, and microwave relay stations, for several key reasons:

  • Coverage Analysis: Identifies areas with poor or no signal coverage, enabling planned signal transmission with appropriate strength.
  • Signal Strength Evaluation: Measures signal strength at different locations, allowing engineers to optimize antenna and Wi-Fi access point placement for optimal signal propagation.
  • Interference Detection: Identifies potential sources of RF interference.
  • Capacity Planning: Determines the necessary capacity of the network to handle the expected traffic.
  • Channel Allocation: Assists in selecting appropriate channels to minimize interference and maximize network performance. Multiple channels are typically used to support many simultaneous connections.
  • Antenna Orientation and Tilt: Helps determine the best orientation and tilt angles for antennas to focus the signal in the desired areas and avoid undesired regions.
  • Signal-to-Noise Ratio (SNR) Analysis: Ensures sufficient signal quality for reliable communication and data transfer.
  • Handover Analysis: Identifies areas where handovers are likely to occur, ensuring smooth transitions for mobile users.

Types of RF Survey

There are primarily two types of RF Surveys:

  1. Radio Network Design (RND) Survey: Used to determine the coverage zone of a cell site and its overall feasibility. This includes deciding on:

    • Cell Site Location Point
    • Orientation/Azimuth of GSM Antenna
    • Height of GSM Antenna
    • Tilt of the GSM Antenna

    RND surveys are further divided into Coverage Site Surveys and Capacity Site Surveys.

  2. Transmission Network Design (TND) Survey: Focuses on the path study between a new site and an existing site, to decide on the height of the microwave antenna for Fresnel zone clearance. Various methods can connect cell sites, including microwave links, satellite links using VSAT, and optical fiber cables. Microwave antennas are used to establish radio frequency links with nearby cellular sites, referred to as microwave links due to their use of microwave frequencies.

    Microwave link frequencies are categorized based on the distance between the cell sites:

    • 23 GHz: 0 to 3 Km
    • 15 GHz: 0 to 10 Km
    • 7 GHz: 10 Km and above

RF Survey Tools for Cellular Wireless Networks

Engineers use a variety of tools for RF site surveys when installing GSM, CDMA, UMTS, and LTE networks globally:

  • GPS (Global Positioning System): Provides location and time information, independent of weather conditions, as long as there’s an unobstructed line of sight to at least 4 GPS satellites. Provides information such as Lat-Long, Acceleration, Highway Map, Direction and Distance between to Lat-Long. Two types: 12-channel GPS and 72-channel GPS.

  • Distance Laser Meter: Measures distances using a laser beam, primarily used for determining the height or dimensions of buildings or the site.

  • Magnetic Compass: Used for checking antenna direction and capturing a 360-degree view by taking pictures every 30 degrees.

  • Binocular with high visual range

  • Digital Camera: Used for capturing photographs required for the RF survey report.

    • Take photos of buildings within a 20-meter radius of the candidate site.
    • Buildings with a height of G+5 or greater within this radius are considered obstructions.
    • Obstruction photos are included in the report.

  • Altimeter: Used for measuring AMSL (Above Mean Sea Level) value.

In addition to the physical tools, the following software tools are also essential:

  • MapInfo Professional (Various Versions)
  • Path Loss (Various Versions)
  • RL Tool (Demo Version)
  • Global Mapper (Various Versions)
  • Mint Tool (For MapInfo Tools)
  • Cell Tool/ Make Sector/Sitesee (For MapInfo Tools)
  • Google Earth
  • Microsoft Office

Conclusion

Overall, RF site surveys are crucial in designing and optimizing cellular and wireless networks. They ensure that telecom service providers can offer reliable and consistent connectivity to their customers within the desired coverage area. The survey is applicable to any wireless networks such as GSM, CDMA, 4G LTE, 5G NR, WiFi, VSAT, etc.