See also: Trick Play

CIMM DEFINITION: Returns viewer to the previous screen.  As distinguished from “Last” – primarily a Remote Control function – which returns the viewer to the last channel viewed.  Usage of the term “Last” and its function varies across operators and platforms.

Back Channel

See also Back Haul and Back Path

CIMM DEFINITION: A return path connection that can be used by a Set-Top Box to communicate with the cable headend; Can be used to communicate to cable headend or the service provider. It applies to asymmetric data connections and is the slower of the two data paths in the connection.

2: “A communication channel that can be used by a Set-Top Box to communicate with the cable headend or other devices. Also known as Back Haul. A term used to describe the technology which provides the infrastructure for electronic traffic traveling from the subscriber to the platform company.” (Source: Nielsen)

3: “Term commonly used to describe the action of sending data back to a host server over a phone wire or cable pipe.” (Source:

NOTE – Many other types of homes (with the exception of digital Set-Top Box homes) do not have backchannels. Satellite homes receive back signals from landline phone lines which vary from home to home.

NOTE – Available bandwidth on the return path is severely limited within the existing digital cable environment, and exceeding bandwidth limits can be catastrophic —i.e., STB reboots, network downtime. Motorola systems are limited to a raw bitrate of 256 Kbps per node (i.e., 500 to 1500 STBs), much of which is consumed by the system itself, VOD session management, IPG interaction, interactive application processing, etc.,  Also, communication on this return path is limited to UDP, which does not guarantee delivery of information from STB to the back-end, and generates additional bandwidth usage by applications to confirm delivery and resend lost data. Cisco systems provide slightly more return path bandwidth and support TCP (i.e., guaranteed delivery of data), but typically reserve more return path bandwidth for system and resident application (e.g., SARA) use. Collecting STB measurement data with low Latency is a complex task, especially for census data. Load on the back channel is an issue in downloading STB data. (Source: FourthWall Media)

NOTE – From Mediapost TV Board article by Weisler, Feb09- A way to get data back to the operator. Cable systems have a back channel but satellite operators can only send data back via the phone lines. Since not all satellite Set-Top Boxes  connect to phone lines, this must be taken into account when receiving Set-Top Box data from satellite homes. Kantar Media Audiences says there is no significant difference in the satellite homes with and without the back channel. Rentrak says boxes are connected in different ways – some need to back channel to get scheduling data, others connect via broadband. It all varies by operator. More examination may be in order.


Back Haul

See also: Back Channel, Back Path

CIMM DEFINITION: Another term for Back Channel.

Back Path

See also: Back Haul, Back Path

CIMM DEFINITION: Another term for Back Channel.


CIMM DEFINITION: High-volume, central, generally ―long-haul‖ portion of a data network. (Source: IAB)


CIMM DEFINITION: In computer networks, bandwidth is often used as a synonym for data transfer rate – the amount of data that can be carried from one point to another in a given time period (usually a second). Usually expressed in bits (of data) per second (bps). A link with a high bandwidth is one that may be able to carry enough information to sustain the succession of images in a video presentation. In electronic communication, bandwidth is the width of the range (or band) of frequencies that an electronic signal uses on a given transmission medium. Here bandwidth is expressed in terms of the difference between the highest-frequency signal component and the lowest-frequency signal component. Since the frequency of a signal is measured in hertz (the number of cycles of change per second), a given bandwidth is the difference in hertz between the highest frequency the signal uses and the lowest frequency it uses. (Source:

2: The transmission rate of a communications line or system, expressed as kilobits per second (kbps) or megabits per second (Mbps) for digital systems; the amount of data that can be transmitted over communications lines in a given time. (Source: IAB)

NOTE – Bandwidth impacts Latency and therefore Dwell Time measurement. Restricting or price tiering of bandwidth size impacts measurement too.

NOTE – It should be remembered that a real communications path usually consists of a succession of links, each with its own bandwidth. If one of these is much slower than the rest, it is said to be a bandwidth bottleneck.

NOTE – Key constraint determining the amount and type of addressable, interactive applications, which can be run at any one time. (Source: Visible World)

NOTE – In the digital cable environment there are multiple data paths, each with distinct characteristics. Most obvious is the downstream video path, carrying large volumes of MPEG-2 video data from cable headends to STBs. Non-video data (e.g., EBIF applications) may be embedded within the MPEG-2 data stream at any point in the delivery of video from programmer to headend, and retrieved on the STB. This path provides the most downstream bandwidth, but requires the STB to tune to a specific channel to access it. A second downstream data path is the Out-of-band network, which provides less downstream IP network bandwidth than the video path, but does not require channel tuning, and is thus always available. The out-of-band network also provides a small amount of upstream IP bandwidth (see Back Channel, Return Path). (Source: FourthWall Media)

Bandwidth Allocation

See also: Bandwidth Cap, Spectrum

CIMM DEFINITION: How frequencies are allocated by bands or within a spectrum and assigned to different applications, content providers, data and information flows.

Bandwidth Caps aka Bit Cap

CIMM DEFINITION: Limits the transfer of a specified amount of data over a period of time. A cap is sometimes applied by a content delivery channel such as an internet service provider to moderate the content flow so it does not become over-loaded by a few heavier users.

NOTE – Implementation of a bandwidth cap is sometimes termed a Fair Access Policy or Usage-Based Billing. (Source:

Bandwidth Contention

CIMM DEFINITION: A bottleneck that occurs when two or more files are simultaneously transmitted over a single data line. Unless the system is able to prioritize among the files, the effect is to slow delivery of each. (Source: IAB)


Bandwidth Optimization

See also: QAM, Switched Digital Video

CIMM DEFINITION: Managing the trade-off between the cost and the efficiency of delivering video.

NOTE – Bandwidth is one of the primary cost concerns cable and telecommunications operators deal with when considering new consumer or advertising applications. Bandwidth optimization solutions have been developed to accommodate the growth in consumer applications including HD video and higher broadband speeds and advertiser applications such as household addressable TV advertising. (Source: Visible World)