Encore has developed the V.150.1 based Modem Relay or MoIP (Modem Over IP) solution. The modem relay facilitates reliable and efficient modem connectivity over a hybrid of PSTN and the IP network, as in a VoIP connection.

The implementation supports modem over IP operation in both the classes, which are defined by the ITU-T V.150.1 recommendations, namely, the Voice Band Data (VDB) and the Modem Relay.

For Voice Band Data (VBD) mode of operation, the path between the two MoIP entities (MoIP gateways) remains in voice configuration. The modem signals are encoded using speech codec and the RTP packets are transported across the packet network. VBD operation in G.711 A-Law, G.711 Mu-Law and G.726 (32Kbps and 40Kbps) are supported. (The speech codecs are not part of the modem relay module, but are externally implemented).

In modem relay mode of operation, the physical layer and error-correction functions are terminated at the MoIP entity (gateway). That is, the modem relay does the demodulation and re-modulation and performs error-correction over the modem data. This error corrected data is transferred between the relays through the SPRT protocol (Simple Packet Relay Transfer protocol).

The State Signaling Events (SSE) protocol is implemented, a mechanism by which the media states are synchronized between the media gateways. Based on detection of the modem tones/signals, it is via the state signaling events that the modem over IP functionality transitions from one operational mode to the other.

The modem relay solution is designed around a flexible, programmable architecture, and the protocols are written as highly modular libraries, which can be easily incorporated in various DSP and embedded applications such as media gateways.

The modem relay solution has been implemented on DSP and embedded platforms such as PowerQUICC and TI DSPs. However, Encore is also willing to take up customization / optimization of these technologies to clients target platforms.

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