Digital Home 101
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With the world moving at a breakneck pace,
no industry is left untouched by the digitization process.
Beginning with the advent and proliferation of the computer
to the ubiquity of the mobile phone and portable MP3 players,
the race is on as competing companies and their competing
proprietary standards do battle over the trillion-dollar consumer
electronics (CE) industry. What began with a formats war in
the PC industry is now spilling over to the CE industry, where
an inevitable coalescing with the PC industry is the ultimate
destiny of the digital home. At the center of this evolution,
and in the minds of consumers worldwide, is the trillion-dollar
question of interoperability. Is it possible
for billion-dollar companies to work together and devise ways
for their products to work seamlessly with one another? |
The Digital Living Network Alliance
(DLNA), a vast network of companies (200+) consisting of
industry leaders in the CE, mobile, and PC industries, is the forerunner
in the digital home movement. They have specified existing standards
that ensure interoperability among all digital
home devices. Refer to the image below that illustrates the
basic components or layers of a digital home network (from DLNA
1.0 Guidelines). Click here
to visit the official Web site.
All 6 layers address the basic
tenets of the digital home—sharing and interoperability.
Let's begin looking at each layer individually, or click on
the image for direct access to any layer.
Network Connectivity - Wired/Wireless
The most rudimentary layer, network connectivity,
is governed by protocols that define basic point-to-point
communication; for example, communication between two devices
within a local area network (LAN). Typically, point-to-point
communication is conducted within a confined area such as
a private residence or office building.
The DLNA has provided two choices for network
connectivity: Ethernet (802.3i,
802.3u) and Wi-Fi (i.e. WLAN).
The latter (IEEE 802.11a/b/g) is
one of the possible WLAN (wireless local area network) solutions,
but thanks to Intelâs Centrino campaign, it is becoming synonymous
with mobile technology and WLAN. |
Network
Stack - IPv4 Protocol Suite
The second layer is concerned with end-to-end communication
(e.g. requesting information from ISPs—Internet service providers—such
as downloading streaming content or video/audio clips from a Web
site) as opposed to point-to-point communication in LANs. IPv4
protocol stacks, widely used, cost-effective, and chosen
by DLNA, provides a foundation for applications to run over different
networks and enable Internet connection to devices of all kinds.
Waiting in the wings is IPv6, which is able to alleviate the current
IP address depletion concern of IPv5 addresses.
Media
Transport - HTTP 1.0/1.1
HTTP (Hypertext Transfer Protocol)
is one of the most common media transport protocols in the world
today, presiding over Web traffic with an iron rule. It acts as
the baseline transport for data traffic or media streaming traffic,
with the latter possessing inherent characteristics that make media
transport complicated. However, HTTP is a proven technology that
optimally addresses both types of traffic. All digital home devices
send or receive media content on the Web need to support HTTP 1.0.
RTP (realtime transport protocol) and other similar protocols might
be adopted by DLNA in the future in order to alleviate the Internet
bottleneck.
Device
Discovery and Control - UPnP Device Architecture 1.0
The device discovery and control DLNA standard is UPnP
(Universal Plug and Play) DCP (Device Control Protocol). It enables
networked devices to automatically self-configure networking properties
(e.g. obtaining an IP address automatically) and discover the presence
and capabilities of other devices on the network, such as dynamically
receiving an IP address, declaring its name, conveying its capabilities
upon request, and learning about the presence and capabilities of
other devices.
In sum, UPnP requires no configuration—all devices collaborate
in a uniform and consistent manner. Other UPnP DCP functions include
addressing, discovery,
description, control
& evening, and presentation.
Media
Management - UPnP AV 1.0
Specified as the DLNA standard media management protocol, UPnP
AV enables media content to be identified, managed and distributed
across all media devices by seeking a universally understood language
between media applications. The UPnP architecture defines a set
of standardized rules for media content properties and the interaction
model between UPnP A/V and control point applications. It performs
the following functions: content directory service,
connection manager service, AV
transport service, and rendering control
service.
Media
Formats - JPEG, LPCM, MPEG-2
Media formats have their own coding schemes that dictate how video,
audio or other signals are coded/decoded, compressed/decompressed,
and presented in a display device. Currently, the mandatory
media formats are JPEG (image), LPCM (audio), and MPEG-2 (digital
video). Mandatory and optional formats—currently a
few set for each type of media—all need to establish an interoperability
baseline for transporting and rendering. It is either the hardware
or software that will be responsible for rendering the format resulting
in the proper display.
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