Telecommunication

What is UEM (unwanted emissions mask)

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Unwanted Emissions Mask (UEM) Explained Technically

UEM, or Unwanted Emissions Mask, refers to a regulatory limit placed on the amount of radio frequency (RF) energy a base station (BS) can emit outside its designated operating band. In simpler terms, it dictates how much "electronic noise" a cell tower can produce beyond the specific frequencies it's supposed to use for communication.

Here's a deeper dive into the technical aspects of UEM:

  • Scope: UEM primarily applies to cellular networks and is defined by organizations like the 3GPP (3rd Generation Partnership Project).
  • Regulation: The specific UEM limits are outlined in technical specifications like 3GPP TS 37.105 and 3GPP TS 37.145-2. These documents detail the maximum permissible emission levels at different frequency offsets from the carrier frequency.
  • Parameters: UEM is defined by two key parameters:
    • Frequency Offset (f): This represents the difference between the edge of the base station's operating band and the measured frequency.
    • Offset Limit (f_offsetmax): This defines the maximum allowable frequency offset where emissions must be within the specified limits.
  • Limits: The UEM defines the maximum allowed emission power at various frequency offsets. These limits are typically expressed in decibel-milliwatts (dBm) or decibel microvolts (dBμV).
  • Compliance: Manufacturers demonstrate compliance with UEM by measuring the emissions at the antenna connection points (TAB connectors) of the base station.

Here are some additional points to consider:

  • UEM Classes: UEM limits may vary depending on the base station class (e.g., Wide Area, Medium Range, Local Area) and the specific band it operates in (BC1, BC2, BC3).
  • AAS BS (Active Antenna System Base Station): For these types of base stations, the UEM requirement is met by ensuring the sum of emissions from all antenna elements stays within the specified limits.

Understanding UEM is crucial for ensuring efficient spectrum utilization and minimizing interference between different radio systems. It helps maintain signal quality and network performance while adhering to regulatory requirements.

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