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Making the Good Better – Maximizing Available P25 Spectrum

New advancement to P25 Phase 2 technology improves interoperability in a cost-efficient manner.

Image from Hendon Pub

The APCO Project 25 (P25) Phase 2 standard is now ready for critical communications users. This further advancement of P25 was intended to improve upon the digital public safety radio communications standards used by first-responders, homeland security, emergency response professionals, and other agencies.

A natural progression from Phase 1 standards, P25 Phase 2 creates improved spectrum efficiency through two-slot Time Division Multiple Access (TDMA) technology. It enables multiple transmissions over the same channel for better use of limited spectrum resources. In many large systems with a high number of subscribers, P25 Phase 2 can boost spectral efficiency of the system without any compromise of coverage or functionality.

As new and advanced as it is, many communications companies are taking basic elements of the Phase 2 standard and improving upon them. For instance, Harris engineers have expanded the capability of the standard Dynamic Dual Mode (DDM) technology that it uses in its P25 products. (Standard Dynamic Dual Mode (DDM) allows Phase 1 and Phase 2 users to interoperate in a mixed mode by “downgrading” the Phase 2 user to a phase 1 capability.)

Calling it Enhanced Dynamic Dual Mode (EDDM), the upgraded technology ensures efficient use of available channel resources. It provides users with improved interoperability and increased voice capacity on P25 systems using a mix of Phase 1 and Phase 2 radios.

Additionally, EDDM offers a cost-efficient, manageable, seamless, flexible migration path to P25 Phase 2 operation that supports an agency’s own pace, budget, and frequency availability. It does this while still taking advantage of the latest technology to deliver an optimal grade of service to meet the most demanding situations. In today’s economic climate, that is good news for any financially strapped department.

In improving DDM, EDDM provides several key advantages by actively determining the most effective path to process calls to maximize capacity. Rather than defaulting to the lowest common mode of operation across the entire system, EDDM actively analyzes the most effective mode of operation and allows for Phase 1 calls on one site to interoperate with Phase 2 calls on a different site, while utilizing the most capable P25 technology at each specific site.

The following example of a wide-area call placed by a Phase 2 unit on a Phase 2-only site shows how each participating site can use a different mode of operation, based on the capability of that site and the subscribing units.

With EDDM technology, transmissions made on a P25 Phase 1 site – using Phase 1 radios – will be Phase 1 calls. If the call includes another site that is Phase 2 and Phase 2 radios are participating, the system provides a Phase 2 call to that site. However, if a mixed-mode site that supports both Phase 1 and Phase 2 modes has only Phase 2 radios participating in the call, the system provides a Phase 2 call on that site, thereby maximizing channel efficiency and increasing overall system capacity. EDDM ensures automatic interoperability between P25 Phase 1 and Phase 2 technologies to deliver increased capacity for emergency, group, individual, encrypted, or ISSI calls.

I am heartened by the advances continually made in interoperable communications that not only make the jobs of first responders, emergency crews, law enforcement agencies and the like easier, but also afford them increased protection and information. I look forward to even more changes in the months ahead.

 

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