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Understand Passive Intermodulation (PIM) For Successful Wireless Network Modernization

Wireless
Posted by James Donovan on 23 August 2017 Connect with James on LinkedIn Estimated reading time: 3 minutes

Preventing Negative Network Performance Issues

Pervasive network performance issues are a consistent presence in wireless communications. Yet in today’s competitive and rapidly growing wireless communications industry, no provider can afford to ignore them. As networks expand and increase in complexity, disruptive issues such as passive intermodulation (PIM) will only worsen – negatively impacting the entire network, with potentially disastrous consequences.

So what is PIM? What causes it and how can it be addressed and prevented swiftly, to avoid negative impact?

When Does Passive Intermodulation (PIM) Occur, and Why is it an Obstacle to Network Efficiency?

PIM results when two or more wireless signals mix together and create disruptive frequencies that cause interference or degrade signal transmission in wireless networks. This common phenomenon is well known in the industry and recognized by RF engineers as a real obstacle to network efficiency. And, since data usage is on the rise and network antennas and radios are more sensitive than ever to smaller levels of distortion, PIM incidents and their negative impact will become more prevalent.

For example, even a 1dB drop in uplink sensitivity due to PIM can reduce coverage by 11 percent. Adding to the problem is network complexity, with each component in the RF path representing a potential source of PIM.

Passive intermodulation (PIM) is a huge challenge for network operators, with the potential to impact efficiency, capacity and the bottom line.

So, since PIM is such a concern, what can you do about it?

  • What are the technical considerations and the specific areas, components and conditions that can cause PIM?
  • Can tower design or even installation factors cause PIM?
  • Most importantly, what can you do to minimize PIM in today’s congested, multi-signal environment?

All these questions give you a lot to think about.

As you look to modernize your network, it’s important to look at the “big picture.” Upgrading your network is like solving a big puzzle with several key pieces. PIM is one of the pieces of the network modernization puzzle.

How Can Passive Intermodulation (PIM) Impact LTE?

PIM is generated in a circuit carrying more than one frequency whenever nonlinearity occurs. The greater the degree of nonlinearity (the greater the curvature of the voltage/current or output power/input power characteristic) then the greater the level of the PIM signal generated.

In long-term evolution (LTE) systems, PIM affects many 180 kHz resource blocks which reduces cell and neighbor capacity. PIM also increases LTE intercell interference on the affected band and overall in the system. Furthermore, PIM can cause the system to operate at maximum power instead of under power control, causing undesirable increased power dissipation in the components.

Clearly, understanding PIM is a first step toward gaining control, and improving the efficiency of your network.

To learn more about passive intermodulation and start improving your network, why not check out our PIM/VSWR Certification [SP6160] Course?

Or, take a look at our latest eBook: Understand the Passive Infrastructure that Underpins Your Network, to gain a better understanding of all aspects of passive infrastructure (from fiber optics, to the RF path, to radio transmission and more), and gain the knowledge you need to build more modern, more effective networks.