Combining A Cellular and Public Safety DAS

Combining Emergency responder radio coverage systems (ERRCS) and cellular distributed antenna systems (Cell DAS) can offer several benefits to a building owner, provided good engineering practices were used for design and implementation of the system. ERRCS and Cell DAS are both used for enhancing radio communication – ERRCS for LMR technology, Cell DAS for cellular service. The combined system can be very attractive to a building owner. ERRCS is a code required system, and cellular is a huge benefit to tenants. Being able to utilize the required infrastructure for ERRCS to provide the tenant with cellular service can be a cost effective way to implement cellular coverage.

Here is a list highlighting the advantages and disadvantages of combining ERRCS and Cell DAS:

1.       Cost Efficiency: Integrating cellular and public safety DAS allows for shared infrastructure, reducing costs associated with installation and reducing the total amount of passive infrastructure that is required. The more expensive parts will come through the requirement for additional filters, more cost spent on engineering and commissioning, and maintenance will cost more time due to the necessity of coordination between cell users in the building as well as the need to ensure the fire alarm system is put into test mode and it is known to first responders that the ERRCS is offline during maintenance.

2.       Interference Mitigation: With a combined system, the designing engineer can put filtering in place to ensure there is no interference between the two systems. With separate systems (especially with separate design and installation teams), it is likely that interference between the two systems will not be considered and interference is much more likely. The common mistake here for combined systems is to not use proper filtering when combining, leading to interference being introduced by poor engineering.

3.       Enhanced Coverage: By integrating both systems, you can ensure your system reaches the “critical areas” as used for ERRCS (stairwells, basements, elevators) as well as the “common areas” that are more critical for cellular users. This ensures that first responders can communicate on their portable everywhere as well as ensuring that the public can use their phones everywhere. This can help with coverage for priority services for cellular as well, including AT&T FirstNET, Verizon FrontLine, and T-Mobile Connecting Heroes.

4.       Maintenance: With a combined system, there is only one system to maintain. However, the maintenance is mainly a disadvantage. With any work that must be done to the system, a full check of both public safety and cellular services must be performed at the end to ensure no interference was introduced, all portable devices (radios and cell phones) work, and all parties are notified. The maintenance to a combined system will cost more per “service call”, but with only a single system, it may be less costly overall.

5.       Scalability: With wideband components readily available (350-6000 MHz), it is possible to design a system that can support UHF up to all “sub-6GHz” cellular services. The cost will remain to upgrade to future bands, but the infrastructure can be design to support these from day 1.

6.       Regulatory Compliance: In some jurisdictions, combining ERRCS and Cell DAS is expressly prohibited. In these cases, a combined system cannot be installed. However, a building owner that wants both systems should coordinate designs to mitigate interference.

 It’s worth noting that designing and implementing a combined cellular and public safety DAS requires careful planning, coordination with relevant stakeholders, and compliance with applicable regulations. Working with experienced professionals in the field can help ensure a successful integration and maximize the benefits of the combined system.