Codan Radio Communications has developed a Digital Link Controller (DLC) to connect Codan repeaters together via IP into an all digital network. In the past, repeaters could only be linked together in an analog format using E&M circuits connected together via leased lines or microwave. More recently, products have been developed to convert E&M to IP enabling linking over an IP network but the connection was still analog with the resulting loss of: audio quality in the analog to digital (A/D) conversion, limited control signalling and no encryption.
Codan now offers an all digital IP solution called the DLC (Digital Link Controller) that overcomes the above problems by enabling Codan Repeaters and Base Stations to be linked together in an all digital network via IP as shown in the diagram below.
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The Codan solution is based on the P25 digital standard and uses the standard digital IP connection from a repeater/base station — the P25 Digital Fixed Station Interface (FSI) protocol. This is available on any Codan base station with the addition of a Universal Interface Card (UIC). The Codan Digital Link Controller (DLC) receives the digital audio and control signals from the radio via the FSI and then routes the call based on the P25 Network Access Code (NAC), Talk Group ID (TGID) or Unit ID. Encrypted calls are routed transparently. P25 supports mixed mode operation so the subscribers can be analog, digital or encrypted digital and all three modes are supported by the DLC.
From a standards perspective the system (shown below) forms a RFSS (RF Subsystem). A future release will enable linking RFSS’s together via the Inter Subsystem Interface (ISSI).
