National Telephony

 

 

Satellite-based network for National telephony and IP

UTS's VSAT (Very Small Aperture Terminals) is a low-cost telephony product that provides on-demand voice, fax and data services to and from mul;tiple locations via satellite. VSAT delivers toll-quality voice and IP transmission and represents the most cost-effective solution for communities in areas where PSTN telephone and fax service is unavailable, unreliable or too expensive. The system is ideal for providing public call office, payphone and emergency telephone services in any location.

 

 

VSAT features:

 

Toll-quality full duplex voice

 

·          Payphone support (prepaid)

·          Group 3 fax relay

·          Voice band data

·          High speed Internet-access

·          Full mesh or star topology

·          Multiple PSTN gateways

·          Conventional numbering plan

·          Remote control and monitoring

·          Ultra-low power consumption

·          Superior reliability

·          Low-cost installation and operation

·          Rapid deployment

 

 

Architecture

 A VSAT networks consists of a central hub, multiple PSTN gateways, satellite channels and remote terminals. A remote terminal consists of a small outdoor antenna (typically 0.55 to 1.2 meters), an Outdoor Unit and an Indoor Unit. The hub consists of RFT and baseband equipment. The baseband includes a Hub for Satellite Communication, and a Network Management System. Each system can be connected directly to the PSTN or to a PABX. The option is to interface with the ISP. The hub design permits easy scalability and incorporation of new features.

 

The PSTN gateways are provided with digital E1 connectivity with central office using the same unites as a remote terminal. Two solutions are available. Satellite gateways, which utilize satellite channels and terrestrial gateways, which carry compressed voice data over leased lines.

 

 

 

 

Operation

Operation of VSAT is simple. In order to place an outgoing call, the handset is raised on the telephone (or fax) and a local dial tone is heard. The caller may then dial a PSTN or another VSAT subscriber number. The VSAT sends a request to the hub demanding the bandwidth and voice resources needed for the call. The moment the hub allocates the resources, the VSAT enters DAMA mode and the call is executed. The call is routed to the hub or gateway according to the destination and resource availability.

 

In order to place an incoming call to a VSAT telephone, the PSTN caller dials the remote VSAT number, which is routed by the PSTN to the hub or gateway location. When the necessary bandwidth is assigned, a point-to-point satellite link is established between the calling telephone and the remote site. The caller receives a ring back tone as indication of a successful call setup. A conversation is terminated when either party hangs up.

 

 

Voice/Fax Transmission

With VSAT, the analog voice input is digitized and compressed to 4.8 or 6.4 kbps. The compressed voice is packetized and transmitted to the hub or to another remote VSAT via the satellite. At the destination, a voice/fax/data card decodes the incoming voice packets into digitized voice, which is then reconverted into analog form. The voice/fax/ data channel is configured for voice mode by default. When a Group 3 fax transmission is detected, the channel automatically switches to fax mode. Upon completion of the fax message, the channel automatically returns to voice mode.

 

 

Internet Access

Asymmetric IP routing is available, The Hub transmits a high-speed outbound carrier up to 2 Mbps containing IP data. The remotes transmit an inbound carrier of up to 153.6 kbps. The IP is time multiplexed with the telephony data. An Ethernet LAN port (RJ-45) at the VSAT is used for PC connections.