Motorola Inc’s Information Systems Group has announced Voice Relay, its offering for integrating speech and facsimile traffic with local network and serial SNA traffic over private or public Frame Relay networks. The company has also revealed the 6560 MPRouter Pro network access and concentrator system. According to the group, Voice Relay enables the simultaneous transmission of speech and data over a wide area Frame Relay link at speeds from 19.2Kbps to 2.048Mbps. To overcome the problems of sending time-sensitive data over frame-based networks, the company said it has employed both prioritisation and compression techniques. On the prioritisation side, the company claims that that Voice Relay recognises the presence or absence of speech packets in a queue, and segments all traffic into a fixed, small packet size when speech is present, giving the speech packets priority. Specifically, it limits frames from serial and local area network stations to a size requiring 5mS to 10mS to transmit when speech is present, and limits the number of these frames queued up in front of any speech frame to two. This, in effect, turns the frame network into a cell-based one for the duration of a speech call. When no more speech calls are active, variable data packets are allowed again. The speech compression uses Motorola-patented algorithms based on the CELP technique which, it says, gives significant savings on line capacity as a result of its low speed 16Kbps and 8Kbps encoding rates.
Idle periods
Statistical multiplexing, Digital Speech Interpolation, is also used, removing idle periods in speech and giving an additional two-to-one saving, while echo cancellation filters out ‘reflected’ speech returning to its point of origin. Finally, Motorola adds that facsimile detection and demodulation enable speech and facsimile traffic to share a circuit from the PABX with no loss in efficiency. Voice Relay will be available on both its 6520 Multimedia Periphery Router and its new 6560 offerings. Speech traffic can be added to existing 6520 networks without increasing line speeds by using the company’s Framed Data Compressor option to free capacity on existing lines, said the group. Pricing for the system is configuration-dependent and ranges from ú400 per connection for a multi-connection 2.048Mbps PABX offering, to ú690 per connection for two analogue offerings. It is available immediately for analogue and within 30 days for 2.048Mbps digital. The 6560 extends the 6520 family to address large branch offices with higher throughput needs and regional concentration sites, said the firm. The base unit includes an Ethernet AUI port; three serial data ports, supporting synchronous data rates up to 2Mbps; and a low-speed (up to 115Kbps) asynchronous serial Control Terminal Point. It is also said to support Token Ring, Ethernet or Dual Ethernet local area network connection through option boards. Other options are serial port expansion for 16 additional serial ports; an integral Simple Network Management Protocol-compliant 10Base-T Ethernet hub, providing up to 24 ports; up to eight ISDN Basic Rate Interface ports; integral 56Kbps DSU; and dual port T1 or E1 boards. Speech options include up to 12 analogue ports, as well as up to 28 digital speech channels within a single T1/E1 stream, said the company. The base price for the 6560, which will be out in 30 days, is ú4,375.
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