Common Challenges With LMR Backhaul

LMR Backhaul

Land Mobile Radio (LMR) systems are critical communications networks used by public safety agencies that provide a dedicated means of connecting first responders in real-time where every second counts during emergency situations.

A reliable backhaul network is crucial for ensuring always-available communications between first responders, improving situational awareness, and ultimately saving lives. Maintaining these backhaul networks for LMR communications requires proactive monitoring of Quality of Service (QoS) as well as rapid fault detection allowing for quicker resolution of issues.

LMR systems have rigorous requirements for parameters such as latency, jitter, and packet loss. These systems also have extremely fast convergence requirements, which present unique challenges for monitoring and maintenance.

In my previous article, we discussed the purpose of the network backhaul in LMR communications and reviewed the transition of traditional Time-Division Multiplexing (TDM) backhaul to Internet Protocol (IP) backhaul methods. In this article, we’ll further explore the issues and challenges that radio operators commonly face while maintaining the backhaul supporting their LMR networks, and how monitoring is a critical yet difficult component of maintaining reliable communications.

In the context of network backhaul, site links refer to the connections between radio sites and a centralized radio core or master site. When a site link is degraded, it may result in reduced data rates, increased latency, and reduced voice quality.

A degraded site link can be caused by several factors, including weather conditions (such as heavy rainfall or snow), equipment malfunctions, or interference from other radio frequencies. Degraded site links can have a ripple effect on the rest of the network, causing congestion and reduced performance across the entire network.

One of the primary challenges associated with degraded site links is that they can be difficult to detect and diagnose. The exact cause of the degradation may not be immediately apparent, and it can be challenging to isolate the specific link or equipment that is causing the issue.

To address this issue, network administrators need to implement robust network monitoring and maintenance practices to detect and remediate these degradations quickly. This requires real-time monitoring and reporting on the network’s performance of both the LMR and the backhaul. They also must have backup systems in place to ensure continuity of communication in the event of link degradation.

Adaptive Modulation Inconsistency

Adaptive modulation is a technique commonly used on site links to adjust the modulation scheme and bandwidth of transmitted data based on the quality of the point-to-point wireless link. It allows for better spectral efficiency and increased data rates over wireless links, however adaptive modulation also brings additional challenges to LMR systems.

One of the primary challenges with adaptive modulation is maintaining a consistent QoS while changing the modulation scheme. When the wireless link experiences interference or variations in signal strength, the system may switch to a lower modulation scheme to maintain a reliable link. However, this can result in a decrease in data rate and voice quality. Conversely, switching to a higher modulation scheme when the link improves can increase the data rate but may result in more errors and reduced reliability.

Finally, adaptive modulation may also be affected by the environment, such as weather and atmospheric conditions, which can impact the quality of the wireless link. These environmental impacts can be transitory, and therefore may result in frequent modulation adjustments.

]Overall, the challenges associated with adaptive modulation require network administrators to carefully monitor the wireless link conditions, select the appropriate modulation scheme based on the signal strength, and optimize the network configuration to maintain a consistent quality of service. Building a backhaul network that prioritizes LMR traffic at the highest level will maximize uptime as adaptive modulation is employed.

Equipment Failure

Equipment failures are another common problem network administrators face, and they can significantly impact the functionality and performance of the network. Equipment failures can be caused by a variety of factors, including power outages, component failures, and physical damage.

Power outages can occur due to weather events, grid failures, or other reasons. They can cause equipment to shut down or fail, resulting in network downtime and disruption to communications. To mitigate the impact of power outages, network administrators can utilize backup power systems, such as generators or battery backups, however, these systems are often costly to implement.

Component failures can occur from wear and tear (aging equipment) or manufacturing defects. Components such as power supplies, transmitters, and receivers can fail, leading to reduced performance or complete failure of the network. Network administrators need to implement regular maintenance practices, including equipment inspections, to identify and replace faulty components before they cause disruptions to the network.

Finally, physical damage to equipment can be caused by environmental factors like weather, vandalism, or accidents. Physical damage can impact the functionality of the equipment, leading to reduced performance or complete failure. Network administrators need to ensure that equipment is located in secure locations and protected from potential physical damage.
No matter the cause of the equipment failure, it’s important that network administrators are able to quickly identify the network issue and the failed component. Regular testing and monitoring of the network’s performance can also help identify potential issues before they cause disruptions to communications. Having spare equipment on hand is a must for every component in the network.


Cybersecurity is a critical consideration for network backhaul. They are vulnerable to cyberattacks that can compromise the confidentiality, integrity, and availability of network communications. This is especially true in IP backhaul with remote access functionality, as they utilize standard communication protocols and are often connected to the wider internet. This makes them more vulnerable to cyber-attacks than a legacy backhaul that may have had the ability to utilize air gapping (i.e. physical isolation) from other networks.

The issue of cybersecurity in network backhaul is complex and continuously evolving. As such, we will further explore this topic in a subsequent post (stay tuned)!

Monitoring Network Backhauls

One common theme throughout these challenges is the importance of monitoring and identifying the sources of issues in a timely (and ideally proactive) manner. Monitoring network backhaul in LMR systems can be a difficult task due to several factors, including:

  1. Performance metrics: LMR networks must maintain rigorous performance requirements, such as latency, jitter, and packet loss, that must be met for reliable communication. LMR OEM monitoring tools may have difficulty accurately measuring and reporting on these performance metrics in real-time to identify potential issues before they affect communication quality.
  2. Unique network architecture/protocols: LMR network architecture can be unique and complex, with multiple interconnected network elements such as base stations, repeaters, and routers. Additionally, the LMR Network backhaul often uses specialized configurations and routing schemes. This can make it challenging for traditional network monitoring technologies to monitor packet loss and identify the root cause of network issues.
  3. Limited data points: Traditional network monitoring technologies typically rely on metrics such as network traffic, bandwidth utilization, and error rates to detect and diagnose network issues. In LMR systems, these metrics are not sufficient to identify root cause, which can occur at different points in the communication chain and may not be readily visible through standard network monitoring tools.

Addressing The Challenges In Network Backhaul

As we’ve discussed, Network backhaul plays a crucial role in ensuring that LMR systems function reliably and efficiently, and that there are a number of challenges that make monitoring them difficult.

To overcome these challenges, specialized monitoring tools and techniques may be required that are specifically designed for LMR systems. These tools may include software, hardware, and protocols that are tailored to the unique characteristics of LMR systems and can provide comprehensive monitoring and analysis of network backhaul performance.

We’ve built Cyberzcape NMS to help network administrators and radio operators of critical LMR infrastructure solve their biggest stability challenge: identifying and resolving issues that are tied to your backhaul.

About The Author

Dan Havens is the Chief Technology Officer of Municipal and Public Safety Networks. Dan oversees the identification and implementation of corporate technical direction for many of our products and services. Dan is also responsible for overall leadership of the San Diego, CA operations and the Municipal and Smart Grid services sectors. Dan’s technical background includes expertise in optical, satellite, VoIP, MPLS, SONET, metro, mesh, wireless, and LAN/WAN technologies with Cisco, Motorola, Tropos, Juniper, and many other leading networking/communications technology vendors. Dan holds a BS in Computer Science from the University of Washington.

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