How SIP is unifying radio communications

SIP (session initiated protocol) technology, developed for IP communications, has moved radio communications from being an isolated system to being truly unified with the broader communications infrastructure allowing for communications between digital and analog radio, PBX, mobile phones, computers and more.

Two-way radio has always been used to provide communications across a broad spectrum of industries ranging from emergency services and security, to utilities, resources and transport. So far, radio has proved to be the most effective, reliable and cost-efficient method of communications for day-to-day operations.

Historically, two-way radio was considered an adjunct to the corporate communications system and was treated as an independent system, isolated from the broader corporate communications infrastructure. To provide interoperability between users of the radio network and other communications systems (including other radio systems), the installation of special bridging and patching equipment was required.

While this works to a certain extent, it doesn’t make it easy for an organisation to streamline the flow of communications throughout its workforce. To enable an organisation to achieve maximum levels of collaboration and productivity, it needs to unify its communications mediums, regardless of whether they are digital or analog radio, PBX, mobile phones or PCs.

It has been difficult to achieve this in the past. However, with the proliferation of SIP technology, the goal of providing unified communications is now feasible and two-way radio no longer needs to be isolated.

The first requirement for unified communications is that the radio signal is converted into IP. In most cases, analog (and even digital) radio transceivers can be connected to the digital domain through VoIP gateways or adapters.

A standard VoIP gateway/adapter will convert the analog signal from a transceiver into a digital form and then into voice over IP packets. The method of conversion is important when considering unified communications and, normally, G.711 is the lowest common denominator.

The buzzword now is radio over IP. However, this can be confusing in that it suggests that the technology is different from the standard VoIP that is used in telephony. There is some truth in this, in that some early implementations of radio over IP gateways were proprietary and some manufacturers sought to handle radio-specific issues through proprietary technology. Nevertheless, adapters such as the IPR100 are standards based and the radio-specific functionality is handled through standard protocol extensions.

This means that once a two-way radio transceiver is married with a VoIP (or RoIP) adapter, the radio signal can be integrated into an IP network and will traverse a corporate LAN or WAN as usual. This has enabled organisations to interconnect repeater sites over IP and to bridge the communications paths between the repeater sites and the communications centre operators through private or public IP infrastructures.

The benefits are enormous and have been well publicised.

However, having ‘IP connected’ radios doesn’t mean that an organisation can achieve unified communications. That’s why SIP was introduced into the VoIP gateways and adapters.

SIP is an IETF-driven protocol that has revolutionised telecommunications. It is a signalling protocol that controls multimedia communications sessions over IP. Its sole purpose is to negotiate, set up and tear down the sessions.

Other protocols such as VoIP actually do the bulk of the work. However, its simplicity makes it a powerful technology. In fact, SIP is used in the backbone of most telecommunications networks around the world.

One of its key design goals was to improve interoperability and this is where two-way radio technology benefits.

Radio over IP gateways/adapters that are SIP compliant enable the connected radio system to integrate with a broader range of corporate communications mediums, without worrying about proprietary technology.

In such an organisation, subscribers on handheld portables or vehicle-mounted radios can communicate with people who are not normally connected to the radio network. As an example, calls can be made between radio users and office staff with SIP-compliant telephones.

More recently, there has been a proliferation of soft-phones that are also SIP compliant. Omnitronics is starting to see applications where this level of unified communications eliminates the need for office staff to be desk bound and dramatically increases productivity.

Here is a simple example of how this works:

Besides unification with telephony, two-way radio systems that are SIP enabled also improve interoperability with radio systems from different manufacturers and in different frequency bands.

In the US, the Department of Homeland Security was instrumental in establishing a working group to address the issue of interoperability within and among radio-dependent agencies. One of the outcomes has been the introduction of a possible standard for interconnecting radio systems in the public safety community.

This is known as the Bridging Systems Interface (BSI). The interesting thing here is that the implementation is heavily based on SIP and, because it is based on SIP, it was developed in quick time.

Clearly, there are significant advantages in having two-way radio networks connected to the digital domain through IP. Most organisations that rely on radio for communications have seen this and have taken the first steps of using radio over IP through gateways and adapters.

Now that SIP can also be supported in the two-way radio system, the ability to achieve real unified communications throughout the organisation is a reality and will lead to improved communications.