ATSC-M/H

ATSC-M/H (Advanced Television Systems Committee - Mobile/Handheld) is a U.S. standard for mobile digital TV that allows TV broadcasts to be received by mobile devices.[1]

ATSC-M/H is a mobile TV extension to preexisting terrestrial TV broadcasting standard ATSC A/53. It corresponds to the European DVB-H and 1seg extensions of DVB-T and ISDB-T terrestrial digital TV standards respectively. ATSC is optimized for a fixed reception in the typical North American environment and uses 8VSB modulation. The ATSC transmission method is not robust enough against Doppler shift and multipath radio interference in mobile environments, and is designed for highly directional fixed antennas. To overcome these issues, additional channel coding mechanisms are introduced in ATSC-M/H to protect the signal.

Evolution of mobile TV standard

Requirements

Several requirements of the new standard were fixed right from the beginning:

  • Completely backward compatible with ATSC (A/53)
  • Broadcasters can use their available license without additional restrictions
  • Available legacy ATSC receivers can be used to receive the ATSC (A/53) standard without any modification.

Proposals

Ten systems from different companies were proposed, and two remaining systems were presented with transmitter and receiver prototypes:

To find the best solution, the Advanced Television Systems Committee assigned the Open Mobile Video Coalition (OMVC) to test both systems. The test report was presented on May 15, 2008. As a result of this detailed work by the OMVC, a final standard draft was designed by the Advanced Television Systems Committee, specialist group S-4. ATSC-M/H will be a hybrid. Basically the following components of the proposed systems are used:

  • RF-Layer from the MPH standard
  • Deterministic frame structure from A-VSB
  • Signaling of service designed on the base of the established mobile standards

Standard milestones

On December 1, 2008, the Advanced Television Systems Committee elevated its specification for Mobile Digital Television to Candidate Standard status. In the following six months, the industry tested the standard. Before it became an official standard, additional improvements were proposed.

  • ATSC members approved the ballot on October 15, 2009 to official standard A/153.
  • ATSC introduced in January 2010 at Consumer Electronics Show, the name and logo for "MDTV" for ATSC A/153.

Structure of mobile DTV standard

The ATSC Mobile DTV standard ATSC-M/H (A/153) is modular in concept, with the specifications for each of the modules contained separate Parts. The individual Parts of A/153 are as follows:

Principle

ATSC-M/H is a service for mobile TV receivers and partly uses the 19.39 Mbit/s ATSC 8VSB stream. The mobile data is carried in an unreferenced Packet ID, so legacy receivers ignore the mobile data.

ATSC Headend Block Diagram
Block Diagram Headend

Technology

ATSC-M/H bandwidth consumes fixed chunks of 917kbit/s out of the total ATSC Bandwidth. Each such chunk is called an M/H Group. A data pipe called a parade is a collection of one to eight M/H groups. A parade conveys one or two ensembles which are logical pipes of IP datagrams. Those datagrams in turn carry TV services, System Signaling tables, OMA DRM key streams and the Electronic Service Guide. ATSC-M/H has an improved design based on detailed analyses of experiences with other mobile DTV standards.

ATSC-MH Layer-Model
ATSC-M/H Layer Model

Protocol stack

ATSC-M/H protocol stack is mainly an umbrella protocol that uses OMA ESG, OMA DRM, MPEG-4 in addition to many IETF RFCs.

Transport stream data structure

The ATSC-M/H standard defines a fixed transport stream structure, based on M/H Frames, which establishes the location of M/H content within the VSB Frames and allows for easier processing by an M/H receiver. This is contrary to the legacy ATSC transport stream, defined in A/53, in which there is no fixed structure to establish the phase of the data relative to VSB Frames.

One M/H Frame is equivalent in size to 20 VSB Frames and has an offset of 37 transport stream (TS) packets relative to the beginning of the VSB Frame. Each M/H Frame, which has a fixed duration of 968 ms, is divided into five M/H sub-frames and each sub-frame is further subdivided into sixteen M/H Slots. Each slot is the equivalent amount of time needed to transmit 156 TS packets. A slot may either carry all main ATSC data (A/53) or 118 packets of M/H data and 38 packets of main data. The collection of 118 M/H packets transmitted within a slot is called an M/H Group. Each of the 118 M/H packets within an M/H Group are encapsulated inside a special TS packet, known as an MHE packet.

An M/H Parade is a collection of M/H Groups and can carry one or two M/H Ensembles. These Ensembles are logical pipes for IP datagrams. Those datagrams in turn carry TV services and the signaling of mobile content. The M/H Groups from a single Parade are placed within M/H Slots according to an algorithm defined in A/153 Part 2. The Number of Groups per M/H Sub-Frame (NoG) for an M/H Parade ranges from 1 to 8 and therefore the number of Groups per an M/H Frame for a Parade ranges from 5 to 40 with a step of 5. The data of a Parade are channel coded and distributed by an interleaver during an M/H Frame.

Mobile Data are protected by an additional FEC, as Interleaving and Convolutional codes. To improve the reception in the receiver, training sequences are introduced into the ATSC-M/H signal to allow channel estimation on the receiver side.

Time slicing is a technique used by ATSC-M/H to provide power savings on receivers. It is based on the time-multiplexed transmission of different services.

Error protection

ATSC-M/H combines multiple error protection mechanisms for added robustness. One is an outer Reed–Solomon error correction code which corrects defective bytes after decoding the outer convolutional code in the receiver. The correction is improved by an additional CRC checksum since bytes can be marked as defective before they are decoded (erasure decoding).

The number of RS parity symbols can represent 24, 36 or 48. The symbols and the additional checksum form the outer elements of a data matrix which is allocated by the payload of the M/H Ensemble. The number of lines is fixed and the number of columns is variable according to how many slots per Subframe are occupied.

The RS Frame is then partitioned into several segments of different sizes and assigned to specified regions. The M/H data in these regions are protected by an SCCC (Series Concatenated Convolutional Code), incorporating a code rate of 1/2 or 1/4, and is specific to each region in a group. A 1/4 rate PCCC (Parallel Concatenated Convolutional Code) is also employed as an inner code for the M/H signaling channel, which includes FIC (Fast Information Channel) and TPC (Transmission Parameter Channel). The TPC carries various FEC modes and M/H Frame information. Once the TPC is extracted, the receiver then knows the code rates being employed and can decode each region at its specified rate.

A modified trellis encoder is also employed for backwards compatibility with legacy A/53 receivers.

The time interleaving of ATSC-M/H is 1 second.

Signaling

ATSC M/H Signaling and Announcement defines three different layers of signalling. The layers are organized hierarchically and optimized to characteristics of the transmission layer.

  • Transmission Signaling System is the lowest layer and uses the Transmission Parameter Channel (TPC). It provides information for the receiver needed to decode the signal
  • Transport Signaling System is the second layer, which uses the Fast Information Channel (FIC) in combination with the Service Signaling Channel (SSC). The main purpose of the FIC is to deliver essential information to allow rapid service acquisition by the receiver. The Service Signaling Channel (SSC), consists of several different signaling tables. The information carried within these tables can be compared to the PSIP information of ATSC. The SSC provides mainly the basic information, the logical structure of the transmitted services and the decoding parameters for video and audio.
  • Announcement / Electronic Service Guide (ESG) is the highest layer of signaling. It uses the Open Mobile Alliance (OMA) Broadcast Service Enabler Suite (OMA BCAST) Electronic Service Guide (ESG). An ESG is delivered as a file data session File Delivery over Unidirectional Transport (FLUTE), and is used as the delivery protocol. The ESG consists of several XML sections. With this structure, a program guide and enabled interactive services can be realized.

Signaling of video- and audio coding

Each video- or audio decoder needs information about the used coding parameters, for instance resolution, frame rate and IDR (Random Access Point) repetition rate. In MPEG-4/AVC, mobile TV systems the receiver uses information from the Session Description Protocol File (SDP-File). The SDP-file is a format which describes streaming media initialization parameters. In ATSC-M/H, the SDP-File is transmitted within the SMT-Table. Most of the information is coded in binary, but some is coded in the original ASCII text format. The SMT-Table combines information that is typically in different tables and reduces the complexity for the network and the receivers. In case of signaling with ESG, the complete SDP-File is transmitted.

Single-frequency network (SFN)

In an SFN, two or more transmitters with an overlapping coverage send the same program content simultaneously on the same frequency. The 8VSB modulation used by ATSC allows SFN transmissions. To allow regular channel approximation, ATSC-M/H provides additional training sequences. ATSC A/110 defines a method to synchronize the ATSC modulator as part of the transmitter. The A/110 standard sets up the Trellis coder in a pre-calculated way to all transmitters of the SFN. In such an SFN, the ATSC-M/H multiplexer and the ATSC-M/H transmitter are synchronized by a GPS reference. The ATSC-M/H multiplexer operates as a network adapter and inserts time stamps in the MPEG transport stream. The transmitter analyzes the time stamp, delays the transport stream before it is modulated and transmitted. Eventually, all SFN transmitters generate a synchronized signal.

Other mobile standards

Until its shutdown, MediaFLO had been available in parts of the United States. It was a premium service that required subscription. ATSC-M/H would be free to air, as are regular broadcast signals.

References

  1. ^ A/153: ATSC Mobile DTV Standard, Parts 1 - 9 Archived April 3, 2012, at the Wayback Machine
CBMT-DT

CBMT-DT, virtual channel 6 (UHF digital channel 21), is a CBC Television owned-and-operated television station in Montreal, Quebec, Canada. The station is owned by the Canadian Broadcasting Corporation, as part of a twinstick with Ici Radio-Canada Télé outlet CBFT-DT (channel 2). The two stations share studios based at Maison Radio-Canada on René Lévesque Boulevard East in Downtown Montreal, CBMT's transmitter is located atop Mount Royal.

This station can also be seen on Vidéotron cable channel 6 in the Montreal area (channel 13 in standard definition) and in high definition on digital channel 606. On Shaw Direct, the channel is available on 301 (Classic) or 56 (Advanced), and in high definition on channel 44 (Classic) or 544 (Advanced). It is also available on Bell TV on channel 206 and in high definition on channel 1030; and on Bell Fibe TV on channel 205 and in high definition on channel 1205.

Datacasting

Datacasting (data broadcasting) is the broadcasting of data over a wide area via radio waves. It most often refers to supplemental information sent by television stations along with digital terrestrial television, but may also be applied to digital signals on analog TV or radio. It generally does not apply to data which is inherent to the medium, such as PSIP data which defines virtual channels for DTT or direct broadcast satellite systems; or to things like cable modem or satellite modem, which use a completely separate channel for data.

E-VSB

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Additionally, the standard can use either the MPEG-4 AVC or VC-1 video codecs. As these codecs have higher video compression than the original MPEG-2, they require less bandwidth.

As 8VSB lacks both link adaptation and hierarchical modulation of DVB, which would allow the SDTV part of an HDTV signal (or the LDTV part of SDTV) to be received even in fringe reception areas where signal strength is low, E-VSB yields a similar benefit. However, E-VSB places a significant processing overhead on the receiver, as well as a significant transmission overhead on the broadcaster's total bitrate. These are not a problem with DVB-H.

A-VSB is a different and, as of July 2008, unapproved addition to ATSC, which is also designed to send programming to mobile devices, and to allow for single-frequency networks. It is one of several proposals for ATSC-M/H, the as-yet undecided standard for mobile broadcasting via ATSC.

KKPX-TV

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KMEX-DT

KMEX-DT, virtual and UHF digital channel 34, is a Univision owned-and-operated television station licensed to Los Angeles, California, United States, serving as the West Coast flagship station of the Spanish-language network. The station is owned by the Univision Local Media subsidiary of Univision Communications, as part of a duopoly with Ontario-licensed UniMás West Coast flagship KFTR-DT (channel 46). The two stations share studios on Center Drive (near I-405) in West Los Angeles; KMEX's transmitter is located atop Mount Wilson. Since its debut in 1962, the station has been a pioneering Spanish-language station, paving the way for other such stations and networks in the United States.

KONG (TV)

KONG, virtual channel 16 (UHF digital channel 31), is an independent television station serving Seattle and Tacoma, Washington, United States that is licensed to Everett. The station is owned by Tegna Inc., as part of a duopoly with Seattle-licensed NBC affiliate KING-TV (channel 5). The two stations share studios at the Home Plate Center in the SoDo district of Seattle; KONG's transmitter is located in the Queen Anne neighborhood of Seattle.

The station is usually carried on most cable television providers in Western Washington on cable channel 6, next to KING-TV's position on channel 5. KONG's high definition feed is carried by Comcast Xfinity and Wave Broadband on digital channel 106.

KPXD-TV

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KSTS

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WCPX-TV

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WFDC-DT

WFDC-DT, virtual channel 14 (UHF digital channel 15), is a Univision-owned television station serving the American capital city of Washington, District of Columbia that is licensed to Arlington, Virginia. Owned by the Univision Local Media subsidiary of Univision Communications, the station is operated by Entravision Communications under a local marketing agreement (LMA), making it a sister station to Silver Spring, Maryland-licensed Sonlife Broadcasting Network affiliate WJAL (channel 68) and Washington-licensed low-power, Class A UniMás affiliate WMDO-CD (channel 47). WFDC and WMDO-CD share studios on Constitution Avenue near the Capitol Building, and WFDC shares transmitter facilities with CW affiliate WDCW (channel 50) in the Tenleytown section of Washington's northwest quadrant. WFDC also serves as the de facto Univision outlet for the Baltimore market.

On cable, the station is carried on channel 14 on most systems in the Washington area and on channel 11 in Baltimore (the latter market's NBC affiliate, WBAL-TV, broadcasts over-the-air on channel 11, but is carried on channel 21 due to signal issues that existed during the analog era).

WHUT-TV

WHUT-TV, virtual channel 32 (UHF digital channel 33), is a Public Broadcasting Service (PBS) member television station licensed to the American capital city of Washington, District of Columbia. The station is owned by Howard University, a historically black college, and is sister to commercial urban contemporary radio station WHUR (96.3 FM). WHUT's studios are located on the Howard University campus, and its transmitter is located in the Tenleytown neighborhood in the northwest quadrant of Washington.

WMBC-TV

WMBC-TV, virtual channel 63 (UHF digital channel 18), is an independent television station licensed to Newton, New Jersey and serving the New York metropolitan area. Founded and owned by the Mountain Broadcasting Corporation (whose initials serve as the station's call letters), the station maintains studios and offices in West Caldwell, New Jersey. Its primary transmitter is located on the campus of Montclair State University, with a secondary transmitter located at the Empire State Building in midtown Manhattan.

The station's lineup consists of brokered ethnic and religious programs, a one-hour weekday newscast, infomercials and children's programs to satisfy the Federal Communications Commission's "educational/informational" requirements.

WNJU

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WNYX-LD

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WPPX-TV

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WPXA-TV

WPXA-TV, virtual channel 14 (UHF digital channel 31), is an Ion Television owned-and-operated television station serving Atlanta, Georgia, United States that is licensed to Rome. The station is owned by Ion Media Networks. WPXA-TV's offices are located on North Cobb Parkway (US 41) in Marietta, and its transmitter is located on Bear Mountain, near the Cherokee–Bartow county line.

The station's broadcast range extends into parts of Alabama and Chattanooga, Tennessee and even the southwest corner of North Carolina. However, terrain shielding not accounted for in radio propagation models prevents this from regularly occurring, due to the north Georgia mountains.

On cable, WPXA-TV is available in standard definition on channel 12 on Comcast Xfinity and channel 11 on Charter Spectrum, and in high definition on Xfinity channel 812 and Spectrum channel 711.

WPXW-TV

WPXW-TV, virtual channel 66 (UHF digital channel 34), is an Ion Television owned-and-operated television station serving the American capital city of Washington, District of Columbia that is licensed to nearby Manassas, Virginia. The station is owned by Ion Media Networks (the former Paxson Communications). WPXW's studios are located in Fairfax Station, Virginia, and its transmitter is located in the tower complex near the intersection of Wisconsin Avenue and 41st Street NW in the Tenleytown neighborhood of Washington.

On cable, the station is available on Comcast Xfinity channel 33 in Washington, D.C., Cox Communications channel 15 in Fairfax County, Virginia, and channel 16 or 17 on most other systems in the market.

WWPX-TV (channel 60) in Martinsburg, West Virginia, serves as a full-time satellite of WPXW.

WTVE

WTVE, virtual channel 51 (UHF digital channel 50), is a Sonlife-affiliated television station serving Philadelphia, Pennsylvania, United States that is licensed to Willow Grove. Owned by NRJ TV LLC, it is a sister station to Trenton, New Jersey-licensed Class A station WPHY-CD (channel 25). WTVE's studios are located on North 11th Street in Reading, and its transmitter is located in the Chestnut Hill section of Philadelphia.

WXNY-LD

WXNY-LD is a low-power television station in New York, New York, broadcasting locally on channel 32.

Digital television in North America
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