RBB network: Entertainment at Your Doorsteps

Today’s

homes are connected to a variety of networks delivering various

services. That includes voice and data services over telephone

networks and TV services through cable TV or even direct from

the skies. However, convergence among computers, communications,

and entertainment has brought about the need for development of

Residential Broadband (RBB) networks to deliver these as well as

new multimedia and broadband services to the homes. Such

networks are expensive to deploy and, therefore, they need to

bring greater benefits in terms of services because fast access

alone may not justify the cost.

Demand for New

Services

Among

such premium services are likely to be Digital TV,

Video-on-Demand (VoD), near VoD, the World Wide Web (WWW), and

virtual channels. Digital TV offers  better pictures and

with better frequency utilization, a wider programme selection

than what over-the-air broadcasters or cable operators can offer

over analog networks. In addition, the Internet offers a

tremendous variety of information and entertainment for the

home. In fact, Digital TV and the Internet, offered separately

or in combination, are creating new forms of entertainment and

information

services to the home that are expected to be among the key

market drivers for RBB

networking.

High-Definition

TV

The

key facilitator in the shift to Digital TV was the development

of digital compression techniques. PAL and SECAM would need more

than 400 Mbps of bandwidth to deliver pictures with existing

pixel density and colour. Now we have High-Definition TV (HDTV)

which would require more than a Gbps (109 bps). These bit

rates could not fit in a 6 MHz channel without compression.

The solution has been

found in Motion Picture Experts Group (MPEG) compression

technique. MPEG compression enables HDTV to fit into 19.3 Mbps,

a reduction in bit rate of more than 50 to 1, which could fit

into a 6 MHz channel.

The general agreement

among broadcasters, consumer electronics/computer industry, and

the film industry seems to be for video compression using MPEG-2

and audio compression using Dolby AC-3 techniques.

For most content, picture

quality improves with digital transmission compared with analog

transmission, even with standard-definition digital. This is

because fewer problems occur with ghosting, vertical hold, and

noise. Broadcasters, both over-the-air and cable, can encode

with MPEG-2 at speeds from 3 Mbps to 9 Mbps for Standard

Definition Television (SDTV). With this amount of control,

broadcasters have a means by which to improve picture quality

incrementally as picture and audio content dictate. Video-on-Demand

Video

on Demand (VoD) enables consumers to order movies over a network

rather than going to a video rental store. VoD is a convenient

and highly customized way to view stored content such as movies,

documentaries, and other educational fare. Not only does VoD

give the viewer access to larger libraries than are available at

a single retailer, but it also is a convenient means of access

because it provides search mechanisms to locate specific topics.

Furthermore, VoD is highly customized because it enables the

viewer to choose what and when to watch instead of having the

service provider decide. Storage prices are dropping and access

is improving.

VoD service is a

"pull mode" service where the subscriber demands and

receives data from the provider. The consumer decides what to

watch and when to watch it from a range of alternatives and then

retrieves the selection, much like pulling information from a

database.

VoD includes VCR controls,

such as rewind, pause, and fast forward. It also has options for

jumping to selected scenes, choosing language and subtitles, and

activating captioning.

VoD’s pull mode delivery

stands in contrast to "Pay-Per-View" (PPV), which

operates in "push mode". In push mode the service

provider transmits data to the subscriber on a fixed,

predetermined schedule, or in response to some event such as the

updating of data in the provider’s database. The consumer

simply decides whether or not to partake.

No VCR type controls are

available. Given the service characteristics of push mode, it is

especially appropriate for live one-time events such as boxing

and wrestling matches–the two most popular forms of PPV in the

US.

In a pull mode

environment, no two subscribers are likely to be watching the

same movie. Therefore, separate data flows are established, one

for each viewer. Each data flow consumes bandwidth dedicated to

a single consumer.

• The traditional market

• Real-time metering
• Minimal bandwidth
  
  requirement
• Leverages widespread
  
  presence of utilities

VoD was made feasible by

the development of digital compression. Without compression, a

single-colour movie would consume perhaps as much as 100 GB of

storage and could not be transmitted, even over an E3 link to

the home. With MPEG, a movie can be stored in 3 GB (providing

broadcast TV quality) and played out at 3 Mbps. These are still

large numbers, but achievable by proposed networks.

The financial viability of

a VoD offering depends on the "take rate". The take

rate is the number of movies rented per month divided by the

subscriber base. If a service provider has 1,000 consumers and

2,000 movies were rented in a month, the take rate is 200

percent. Take rates of 200 percent or more are likely to be

essential to make VoD financially viable.

Near

Video-on-Demand

An

alternative to VoD is "Near Video-on-Demand" (nVoD),

also known as advanced or enhanced PPV or "staggercast".

With nVoD, the service provider elects to offer a particular

movie beginning at certain intervals, say every 15 minutes, on a

small number of channels, say four. The interval is called the

stagger time, hence the term "staggercast". nVoD

provides widespread availability of movies without the need for

a dedicated point-to-point connection between the viewer and the

video server. This reduces server and network resources when

compared with VoD but at a loss of consumer flexibility. Given

the experience with PPV, consumers appear to be willing to

accept these limitations. With nVoD, the viewer is offered the

same content continuously, whereas for PPV, the content is offered once. nVoD

is still an experimental service undergoing research.

Multipoint-to-Multipoint

Services

One

example of such services is Karaoke-on-Demand (KoD) which is the

networked version of Karaoke. When you pick a song, the music,

lyrics, and possibly visuals are streamed to your local Karaoke

unit. With KoD, it would be possible to select music from a

large centralized library. Moreover, it would be possible to

have participants in other locations join in to create a virtual

chorus! Lyrics could be available in a number of languages, and,

in the case of a single participant, it would be possible to

select tempo, reverberation, octave, background music, and

background scenes. ISDN-based KoD in Japan is a good example of

an actual deployment. Although not the strongest

market driver for RBB as yet, KoD raises some interesting

issues. Firstly, it signifies that entertainment is something

which people will pay for. In many parts of Asia, Karaoke

machines sell well, not only to entertainment establishments but

also to high-end residential users. Secondly, KoD represents

challenging technical problems, especially with regard to

synchronization and conferencing, which also require attention

for business conferences and VoD. Most importantly, the virtual

chorus represents an application that requires a

multipoint-to-multipoint topology. Other such applications are

interactive gaming and videoconferencing, both of which have

consumer applications. A popular interactive game is Doom, in

which players at multiple sites stalk and shoot each other in a

virtual combat zone. Videoconferencing also is a way for

families to celebrate special occasions together, when family

members are geographically distant. 

Multipoint-to-multipoint

applications raise a particularly difficult Quality of Service (QoS)

problem. A single receiver might receive input from multiple

sites simultaneously, producing congestion at the receiving

site. Techniques are being explored to arbitrate the congestion

and yet provide some bandwidth to each sender.

Bandwidth Is

the Key

As the new

networks are being designed, needs for such applications, which

are becoming reality in other parts of the world, need to be

addressed. Undoubtedly, these applications are bandwidth hungry.

But so will be the information driven

society.