Transcript MULTIMEDIA ENTERTAINMENT

MULTIMEDIA
ENTERTAINMENT
Abhilash
Contents
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Introduction
Music delivery over cellular networks
Issues and Solutions
Conclusion
References
Introduction
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Multimedia is the use of several different media
(e.g. text, audio, graphics, animation, video, and
interactivity) to convey information.
Multimedia also refers to the use of computer
technology to create, store, and experience
multimedia content.
As the information is presented in various formats,
multimedia enhances user experience and makes it
easier and faster to grasp information.
Require high bandwidth, low end-to-end delay, and
synchronization.
Background
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The evolution of multimedia can be traced
through three major stages
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Stand alone applications and CD-ROM
based applications.
Creation of large scale video servers.
Creation of content that can be delivered by
means of low cost and bandwidth
Music delivery over cellular
networks
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With multimedia entertainment music can be
delivered over cellular networks.
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The users are given an option of downloading
music on the move.
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Mobile phones equipped with wireless technology
can provide a platform for downloading music.
Contd..
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Downloadable music is one of the more
important features of multimedia.
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The consumer will need seamless distribution
of music that supports mobile and nomadic
services.
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The system is designed as an ABS (always
best served) model.
What is an ABS?
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ABS is an emerging model supporting mobile
and ubiquitous computing, and its key service is
to allow nomadic users to switch terminal and
network technology so as to obtain the best
connection available.
System Architecture
Contd..
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The architecture is comprised of three components
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Mobile clients
Intermediate system
Set of web server replicas
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Mobile clients – music handheld devices connected
through wireless network access points
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Intermediate system – manages all the
communications between the handheld device and
the wired internet infrastructure. It has three
subsystems
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Application gateway – guarantees reliable
communication between the IS and the mobile client
Discovery – discovers the music resources on the web
Download Manager – downloads the songs that have
been identified by the Discovery system
Web server replicas – distributed over the internet
which function as replicated music repositories
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A number of problems arise while using the IP stack
in a wireless context.
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The IP stack is not designed to handle mobility and
effectively manage the wireless connections.
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The service replication built into IP leads to
unwanted feature interactions with similar services
provided by wireless networks.
Issues with music distribution
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Connection continuity
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Packet loss
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Resource management
Issue 1 – Connection
Continuity
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If the wireless link is interrupted for a prolonged
time, the download may just be aborted.
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The application should have the following
requirements
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Automatically switch connection in case of network
failure or handoffs
Automatically freeze a download in case of absence of
networks
Automatically resume a download frozen by absence
of networks
Freeze a download if required by the user
Resume a download interrupted by the user
Transfer the download to a different terminal if required
by the user
Solution
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The ABS system needs to modify at least a layer of
the IP stack.
A promising solution is to build an application in the
session layer.
This layer is called the Session Management Layer
(SML).
Such a layer could effectively support all the issues
by using an ID based mechanism to provide
services for the nomadic applications.
Also the session layer is responsible for initiating
and terminating user sessions.
Protocol stack
Contd..
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SML supports
 End-to-end IP continuity of a download activity in
the face of failures, link outages or handovers.
 A price/performance sensitive vertical roaming
scheme for switching across alternative wireless
technologies (eg., WiFi, cellular).
Contd..
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The goal is achieved by freezing the download state
activity at the session layer when handoffs are
detected, thus permitting resumption of the music
data stream as soon as the problems have cleared.
Experimental Assessments
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Performance of the system when the user is moving
along a path covered by different radio technologies
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Performance of the system when the user
nomadically changes his download device
Network coverage and
download processes
Download time comparison
Result
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The ABS system provides the best download
performance across different network technologies.
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The ABS system completes downloads whenever
and wherever possible, regardless of
noncontinuous network coverage.
Issue 2 – Packet loss
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A fundamental issue in transport of fragmented
audio data is the priority distinction.
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It is essential to have the critical data to decode any
of the remaining data.
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This is why appropriate techniques have to be
utilized to transport the critical data more reliably
than the lower priority data.
Solution
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There are two solutions to increase the reliability of
data transport.
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Retransmission based transport – the data
packets are replicated only if the original packet
is lost.
Redundancy based transport – the sender
replicates the data elements. Probability of data
loss is decreased but bandwidth usage
increases
Contd..
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Data are arranged in different packets, depending
on priority.
Higher priority packets are transmitted before lower
priority packets.
This allocates more time to retransmission attempts
for the critical packets.
However, in streaming applications there is a
definite deadline for data delivery, which limits the
number of retransmission attempts.
Retransmission
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Reserve fixed size slots for each frame and
a reservoir area for codewords that do not fit
in the base slot.
Packetization scheme for
retransmission
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The loss rate for the critical packets is assumed to
be low due to retransmissions.
If one of the critical packets is lost, error
propagation to the other frames is restricted to the
reservoir section only.
Critical data sections are interleaved among the
critical packets to avoid loss of adjacent packets.
This allows us to employ traditional frame-based
error concealment techniques to recover the
missing frames.
Redundancy based
transmission
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Transport and packetization techniques based on
added redundancy can be relatively cost efficient,
especially if the proportional amount of critical data
is low. This is because only the critical portion of the
data has to be replicated.
Redundancy
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If multiple packets are lost, the number of lost
critical sections can be limited by designing rules for
shuffling and adding redundancy carefully.
Most importantly, no critical sections of two different
frames should be written in the same set of
redundant packets.
It is also beneficial to use pseudorandom shuffling
sequences instead of direct interleaving for the noncritical data elements.
Issue 3 – Resource
management
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Multimedia traffic puts heavy bandwidth demand on
the cellular network.
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Bandwidth is the most critical resource in cellular
networks and thus requires mechanisms to
efficiently use the available bandwidth.
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In cellular networks carrying multimedia traffic,
resource allocation and management is an
important issue.
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Resource management performed in the mobile
networks is commonly referred to as Channel
Allocation.
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A number of channel allocation algorithms have
been developed to efficiently utilize the available
spectrum.
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Fixed Channel Allocation (FCA)
Dynamic Channel Allocation (DCA)
Hybrid Channel Allocation (HCA)
Resource Allocation
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The support for multimedia services in mobile
cellular networks increases network congestion and
requires the use of microcellular architecture.
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This architecture introduces the problem of frequent
handoffs and makes resource allocation difficult.
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In these networks, the resource allocation schemes
have to be designed such that a call can be
assured a certain QoS once it is accepted into the
network.
Resource Allocation Schemes
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Admission Threshold (AT) based scheme –
resource management is done by periodically
calculating the admission threshold and by blocking
all new call connection requests once the threshold
is reached.
If a call connection request arrives at time t0, then
the following conditions must be satisfied
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At time t0 + T, the handoff probability in the current cell as
well as the adjacent cells must not exceed PHD.
At time t0 + T, the overload probability must not exceed POL.
At time t0 + T, the overload probability in the adjacent cells
due to traffic handoffs must be smaller than POL.
Contd..
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Resource Sharing (RS) based scheme – This scheme
employs a resource sharing mechanism that reacts to rapidly
changing traffic conditions in a cell.
It differentiates the new call on basis of its traffic class and a
particular decision is taken.
For real time call connections, a new call is blocked if no
bandwidth is available to service the request.
Some of the resource sharing schemes are
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Complete Partition (CP)
Complete Access (CA)
Restricted Access (RA)
Contd..
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Resource Reservation (RR) based scheme – In this
scheme, the decision to accept a call depends on
the bandwidth available in the cell in which the call
arrives and in the adjacent cells.
For real time call connections, bandwidth
reservation is performed in all cells adjacent to the
cell in which the call arrives.
A connection is refused if either the bandwidth is
not available in the cell or sufficient bandwidth
cannot be reserved in the adjacent cells.
Issues in Resource
Reservation
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The resource reservation scheme can provide the
best service but there is a tradeoff between service
quality and processing overhead.
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One issue is to determine in which cells the
reservation needs to be performed.
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The next issue is to determine how much bandwidth
needs to be reserved in surrounding cells.
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Another issue is to determine when to release and
reserve bandwidth in the surrounding cells.
Resource Reservation with
Renegotiation
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RRN uses resource reservation in surrounding cells for real
time traffic and bandwidth readjustment for non real time calls.
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Resource Reservation – Bandwidth is reserved in all cells
adjacent to the cell in which the call arrives.
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When a call hands off to another cell ,if enough bandwidth is
not available, it uses the bandwidth reserved in the target cell.
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When a call is successfully handed off to another cell, we
release the bandwidth reserved for the call earlier and reserve
bandwidth in the cell cluster of the new cell.
Bandwidth Reservation
New call setup
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When a call connection is requested, the base
station determines the bandwidth B available to
service the calls.
If B is more than the requested bandwidth Br, the
base station then calculates the bandwidth Bres it
needs to reserve in the adjacent cells.
The information from other cells in the cell cluster is
gathered and if Bres can be reserved, the call is
accepted.
If Bres is not available in all cells of the cell cluster,
the call is blocked.
New call setup
Conclusion
References