A-VSB

A-VSB or Advanced VSB is a modification of the 8VSB modulation system used for transmission of digital television using the ATSC system. One of the constraints of conventional ATSC transmission is that reliable reception is difficult or impossible when the receiver is moving at speeds associated with normal vehicular traffic. The technology was jointly developed by Samsung and Rohde & Schwarz.

A-VSB builds on the existing ATSC transmission standard to enhance DTV receivers’ ability to receive the main MPEG transport stream in dynamic environments. The system enables broadcasters to include multiple streams with additional error correction and time diversity encoding for enhanced reception. In addition, A-VSB facilitates synchronization of multiple transmission towers, which should improve coverage with higher uniform signal strength throughout a service area, even in locations that normally would be shielded by obstacles such as hills or buildings.

A-VSB incorporates three new elements: a Supplementary Reference Signal (SRS), a Scalable Turbo Stream (STS), and support for Single Frequency Networks (SFN).

16VSB

16VSB is an abbreviation for 16-level vestigial sideband modulation, capable of transmitting four bits (2⁴=16) at a time.

How it works

Other slower but more rugged forms of VSB include 2VSB, 4VSB, and 8VSB. 16VSB is capable of twice the data capacity of 8VSB; while 8VSB delivers 19.39 Mbit/s (Megabits per second) in a 6-MHz television channel, 16VSB could deliver 38.78 Mbit/s, while making the sacrifice of being more prone to transmission error.

History

While 8VSB is the ATSC digital broadcast modulation format, 16VSB was planned for cable distribution. 16VSB is about twice as susceptible to noise, therefore less suitable than 8VSB for broadcast, but well suited to the signal-to-noise ratio of hybrid fiber-coax distribution, allowing twice as much programming in a 6-MHz channel.

Technological obsolescence

However, as of 2007, a majority of cable companies have chosen to extend their existing quadrature amplitude modulation-based systems to carry digital television rather than adopting any form of VSB. It is probable that 16VSB has been replaced by ANSI/SCTE 07 2006: Digital Transmission Standard For Cable Television, a cable standard that defines 64QAM and 256QAM transmission for digital cable.

2VSB

In telecommunications, 2VSB is an abbreviation for 2-level vestigial sideband modulation, a transmission method capable of transmitting one bit (2¹=2) at a time.

Other faster but less rugged forms include 4VSB, 8VSB, and 16VSB.

References

4VSB

4VSB is an abbreviation for 4-level vestigial sideband modulation, a type of radio transmission capable of transmitting two bits of information (2²=4) at a time. Other faster but less rugged forms include 8VSB and 16VSB. While 2VSB is more rugged, it is also slower.