Transcript ppt - UCI

Pervasive Computing and
Communication
 Proliferation of devices
System support for multitude of smart (mobile) devices
that
• attach and detach from a distribution infrastructure
• produce a large volume of information at a high rate
• limited by communication and power constraints
 Require a customizable global networking backbone.
That can handle heterogeneous needs of applications
• Quality of Service (QoS), security, reliability
That can make effective use of the underlying infrastructure
 Intelligent Middleware is key to supporting application needs
in a highly dynamic environment
Distributed Mobile
Applications
In the last 5 years…..
 New devices w/ new capabilities
Data capture, storage, presentation
 New apps
Social networking,….
Multimedia applications, gaming, data capturing,
download/upload/streaming
Information seek/notification
 New network infrastructures
DTN, WiMax, UWB,…
 New computational infrastructure
Cloud computing, grids…
New problems and challenges…
Introduction
Mobile Ecosystem
Users
Applications
Networks
Mobile
Devices
Access Point WLAN
Cell Phone
Internet
ad hoc
network
BS
GSM or
CDMA
PDA
Laptop
Technology Incentive
Growth in computational capacity
MM workstations with audio/video processing capability
Dramatic increase in CPU processing power
Dedicated compression engines for audio, video etc.
Rise in storage capacity
Large capacity disks (several gigabytes)
Increase in storage bandwidth,e.g. disk array technology
Surge in available network bandwidth
high speed fiber optic networks - gigabit networks
fast packet switching technology
CS234 – Mobile Computing
Tuesdays, Thursdays 3:30-4:50p.m.
ICS 243
Prof. Nalini Venkatasubramanian
[email protected]
Outline
 The Future: Mobile and Pervasive Computing
 An Applications View
 A Content View
 Multimedia Content
 QoS Basics and End-to-end support
 A Systems View
Device, Operating System
Networks, Middleware
Application, Content
A Cross-Layer Approach to Systems Support
 Supporting Cross Cutting Concerns (Security, Reliability,
Heterogeneous Interoperability)
Enabler: Mobile
Communication Networks
 Cellular - GSM (Europe+), TDMA & CDMA (US)
FM: 1.2-9.6 Kbps; Digital: 9.6-14.4 Kbps (ISDN-like services)
 Public Packet Radio - Proprietary
19.2 Kbps (raw), 9.6 Kbps (effective)
 Private and Share Mobile Radio
 Wireless LAN - wireless LAN bridge (IEEE 802.11)
Radio or Infrared frequencies: 1.2 Kbps-15 Mbps
 Paging Networks – typically one-way communication
low receiving power consumption
 Satellites – wide-area coverage (GEOS, MEOS, LEOS)
LEOS: 2.4 Kbps (uplink), 4.8Kbps (downlink)
Mobile Network
Architecture
Device Characteristics
Battery Power restrictions
Transmit/receive, disk spinning, display, CPUs,
memory consume power
Resource constraints
Mobile computers are resource poor
Reduce program size
Computation and communication load cannot be
distributed equally
Small screen sizes
Wireless network
characteristics
 Variant Connectivity
Low bandwidth and reliability
 Frequent disconnections
•
predictable or sudden
 Asymmetric Communication
Broadcast medium
 Monetarily expensive
Charges per connection or per message/packet
 Connectivity is weak, intermittent and expensive
Mobility Characteristics
 Location changes
• location management - cost to locate is added to communication
 Heterogeneity in services
bandwidth restrictions and variability
 Dynamic replication of data
• data and services follow users
 Querying data - location-based responses
 Security and authentication
 System configuration is no longer static
Challenges
Application Context
System support for multitude of components
Attach and detach from a distributed infrastructure  Increasing QoS., security, reliability demands
Deal with large vol. of information at a high rate Soft Real Time Constraints
Changing global system state
Support for traditional media (text, images) and
continuous media (audio/video)
Synchronization (e.g. lip sync., floor control)
Challenges
Need high degree of “network awareness”
and “customizability”
congestion rates, mobility patterns etc.
QoS driven resource provisioning
Heterogeneous networks
Heterogeneous devices
Limited battery lifetime
Size/weight limitations
Computation/Communication
constraints
Cellular Networks
Includes slides by Prof.
Lichun Bao and others
Principles of Cellular
Networks
Underlying technology for mobile phones,
personal communication systems, wireless
networking etc.
Developed for mobile radio telephone
Replace high power transmitter/receiver systems
Typical support for 25 channels over 80km
Use lower power, shorter range, more transmitters
Cellular Network
Organization
Multiple low power transmitters
100w or less
Area divided into cells
Each with own antenna
Each with own range of frequencies
Served by base station
Transmitter, receiver, control unit
Adjacent cells on different frequencies to avoid
crosstalk
Shape of Cells
 Square
Width d cell has four neighbors at distance d and four at distance 2 d
Better if all adjacent antennas equidistant
Simplifies choosing and switching to new antenna
 Hexagon
Provides equidistant antennas
Radius defined as radius of circum-circle
Distance from center to vertex equals length of side
Distance between centers of cells radius R is
Not always precise hexagons
Topographical limitations
Local signal propagation conditions
Location of antennas
3R
Cellular Geometries
Frequency Reuse
 Power of base transceiver controlled
Allow communications within cell on given frequency
Limit escaping power to adjacent cells
Allow re-use of frequencies in nearby cells
Use same frequency for multiple conversations
10 – 50 frequencies per cell
 E.g.
N cells all using same number of frequencies
K total number of frequencies used in systems
Each cell has K/N frequencies
Advanced Mobile Phone Service (AMPS) K=395, N=7 giving 57
frequencies per cell on average
Frequency
Reuse
Patterns
N = number of cells in repetitious pattern, i.e. Reuse factor
Each cell in pattern uses unique band of frequencies
Increasing Capacity (1)
 Add new channels
Not all channels used to start with
 Frequency borrowing
Taken from adjacent cells by congested cells
Or assign frequencies dynamically
 Cell splitting
Non-uniform distribution of topography and traffic
Smaller cells in high use areas
Original cells 6.5 – 13 km
1.5 km limit in general
More frequent handoff
More base stations
Cell Splitting
Increasing Capacity (2)
 Cell Sectoring
 Cell divided into wedge shaped sectors
 3 – 6 sectors per cell
 Each with own channel set
Subsets of cell’s channels
 Directional antennas
 Microcells
 Move antennas from tops of hills and large buildings to tops of small buildings
and sides of large buildings
Even lamp posts
 Form microcells
 Reduced power
 Good for city streets, along roads and inside large buildings
Frequency Reuse Example
Overview of Cellular
System
Operation of Cellular
Systems
 Base station (BS) at center of each cell
 Antenna, controller, transceivers
 Controller handles call process
 Number of mobile units may in use at a time
 BS connected to mobile telecommunications switching office (MTSO)
 One MTSO serves multiple BS
 MTSO to BS link by wire or wireless
 MTSO:
 Connects calls between mobile units and from mobile to fixed telecommunications
network
 Assigns voice channel
 Performs handoffs
 Monitors calls (billing)
 Fully automated
Channels
Control channels
Setting up and maintaining calls
Establish relationship between mobile unit and
nearest BS
Traffic channels
Carry voice and data
Typical Call in
Single MTSO Area (1)
 Mobile unit initialization
 Scan and select strongest set up control channel
 Automatically selected BS antenna of cell
 Usually but not always nearest (propagation anomalies)
 Handshake to identify user and register location
 Scan repeated to allow for movement
 Change of cell
 Mobile unit monitors for pages (see below)
 Mobile originated call
 Check set up channel is free
 Monitor forward channel (from BS) and wait for idle
 Send number on pre-selected channel
 Paging
 MTSO attempts to connect to mobile unit
 Paging message sent to BSs depending on called mobile number
 Paging signal transmitted on set up channel
Typical Call in
Single MTSO Area (2)
 Call accepted
Mobile unit recognizes number on set up channel
Responds to BS which sends response to MTSO
MTSO sets up circuit between calling and called BSs
MTSO selects available traffic channel within cells and notifies BSs
BSs notify mobile unit of channel
 Ongoing call
Voice/data exchanged through respective BSs and MTSO
 Handoff
Mobile unit moves out of range of cell into range of another cell
Traffic channel changes to one assigned to new BS
Without interruption of service to user
Call Stages
Other Functions
 Call blocking
 During mobile-initiated call stage, if all traffic channels busy, mobile tries
again
 After number of fails, busy tone returned
 Call termination
 User hangs up
 MTSO informed
 Traffic channels at two BSs released
 Call drop
 BS cannot maintain required signal strength
 Traffic channel dropped and MTSO informed
 Calls to/from fixed and remote mobile subscriber
 MTSO connects to PSTN
 MTSO can connect mobile user and fixed subscriber via PSTN
 MTSO can connect to remote MTSO via PSTN or via dedicated lines
 Can connect mobile user in its area and remote mobile user
Mobile Radio
Propagation Effects
 Signal strength
Strength of signal between BS and mobile unit strong enough to
maintain signal quality at the receiver
Not strong enough to create too much cochannel interference
Noise varies
Automobile ignition noise greater in city than in suburbs
Other signal sources vary
Signal strength varies as function of distance from BS
Signal strength varies dynamically as mobile unit moves
 Fading
Even if signal strength in effective range, signal propagation effects
may disrupt the signal
Networks for Mobile Computing
 Mobile Internet
 Mobile IP (MIP)
Introduction (goals, architecture,
protocol, examples)
MIP messages, encapsulations
MIP issues: triangular routing,
reverse tunneling, MobileIPv6
 Micro-mobility Protocols
Cellular IP
HMIP
MobileNAT
 Summary
 Mobile Ad Hoc Networks
 Introduction: difference from
Wireless Sensor Networks
(WSNs)
 Routing Protocols
WRP
AODV
DSR
Improvements:
• interference levels
• topology control/management
 Summary
Wireless Networking
35
Motivation for Mobile IP
 Internet routing
 based on IP destination address and network prefix
 change of physical subnet implies that the mobile node should
change its IP address to have a topologically correct address
 Challenges – 1) find the MS, 2) avoid disconnection
 DNS? Updates take to long time
 Per-host routing? Too many entries in the RT.
 Solution:
 Mobile IP is an open standard, defined by the Internet Engineering Task Force (IETF) RFC 2002, that
allows users to keep the same IP address, stay connected, and maintain ongoing applications while
roaming between IP networks
 Network supported Mobile IP (tunneling in IPv4)
 Host supported Mobile IPv6 (Routing extension header)
Wireless Networking
36
Requirements to Mobile IP (RFC
3344)
 Transparency
 Mobile keeps its IP address when changing subnets
 Communication continues after interruption of link possible
 Compatibility
 no changes to current end-systems and routers required - tunneling
 no changes to fixed systems – HA-FA tunneling
 Security
 authentication of all registration messages – MIP messages
 Efficiency and scalability
 only a few additional messages to the mobile system required (connection typically via a
low bandwidth radio link) – MIP messaging
 Global support of a large number of mobile systems in the whole Internet – HA for MN
Wireless Networking
37
Architectural Components
1.
End system elements


2.
Mobile Node (MN)
Correspondent Node (CN): communication partner
Network elements

Home Agent (HA): System in the home network of the MN, typically a router
 Registers the location of the MN, tunnels IP datagrams to the COA
 Foreign Agent (FA): the default router for MN


Forwards the tunneled datagrams to the MN
Can be collocated with MN
 Care-of Address (COA): address of the current tunnel end-point for the
MN

Can be associated with the MN or FA.
Wireless Networking
38
Mobile IP Protocol
 Agent Advertisement using ICMP
 HA and FA periodically send advertisement messages into
their physical subnets in ICMP messages
 MN listens to these messages and detects, if it is in the
home or a foreign network (standard case for home
network)
 MN reads a COA from the FA advertisement messages
 MN may send out router (agent) solicitation.
 Registering the COA using UDP
 binding for the mobile node – tuple (home address, COA,
registration lifetime, authentication)
 binding update sent by MN to HA for remote redirect.
 Traffic forwarding using Tunneling
 HA advertises the IP address of the MN (as for fixed
systems) via proxy ARP
 routers adjust their entries, these are stable for a longer time
(HA responsible for a MN over a longer period of time)
 packets to the MN are sent to the HA, which tunnels to the
COA.
 independent of changes in COA/FA
Wireless Networking
39
Example network
HA
MN
router
home network
mobile end-system
Internet
(physical home network
for the MN)
FA
foreign
network
router
(current physical network
for the MN)
CN
end-system
router
Wireless Networking
40
Data transfer to the mobile
system
HA
2
MN
home network
Internet
receiver
3
FA
1
CN
sender
foreign
network
1. Sender sends to the IP address of MN,
HA intercepts packet (via proxy ARP)
2. HA tunnels packet to COA, here FA,
by encapsulation
3. FA forwards the packet to the MN
Wireless Networking
41
Data transfer from the
mobile
system
HA
1
home network
MN
sender
Internet
FA
foreign
network
1. Sender sends to the IP address
of the receiver as usual,
FA works as default router
CN
receiver
Wireless Networking
42
Design Factors
 Propagation effects
 Dynamic
 Hard to predict







Maximum transmit power level at BS and mobile units
Typical height of mobile unit antenna
Available height of the BS antenna
These factors determine size of individual cell
Model based on empirical data
Apply model to given environment to develop guidelines for cell size
E.g. model by Okumura et al refined by Hata
 Detailed analysis of Tokyo area
 Produced path loss information for an urban environment
 Hata's model is an empirical formulation
 Takes into account variety of environments and conditions
WLAN technologies
Adapted from slides by
Prof. Lichun Bao and others
Characteristics of selected
wireless standards
54 Mbps
802.11{a,g}
5-11 Mbps802.11b
.11 p-to-p link
1 Mbps
802.15
384 Kbps
3G
UMTS/WCDMA, CDMA2000
2G
IS-95 CDMA, GSM
56 Kbps
Indoor
Outdoor
Mid range
outdoor
Long range
outdoor
10 – 30m
50 – 200m
200m – 4Km
5Km – 20Km
Wireless Networking
45
Elements of a wireless network

Wireless stations



APs, laptops, PDAs, IP phones - run
applications
may be stationary (non-mobile) or
mobile
Wireless links

network
infrastructure


typically used to connect mobile to
base station, also used as backbone
link
multiple access protocol coordinates
link access
various data rates, transmission
distance
Wireless Networking
46
Operational modes of a wireless
network – Infrastructure mode

network
infrastructure

base station
 typically connected to
wired network
 responsible for sending
packets between wired
network and wireless
host(s) in its “area”. e.g.,
cell towers 802.11 access
points
Handoff: mobile changes base
station providing connection
into wired network
Wireless Networking
47
Operational modes of a wireless
network – Infrastructure mode
Ad hoc mode
 no base stations
 nodes can only
transmit to other nodes
within link coverage
 nodes organize
themselves into a
network: route among
themselves
Wireless Networking
48
Evaluations of Wireless
LANs
 Advantages
Flexible deployments (infrastructure and ad hoc modes)
Robust against disasters like, e.g., earthquakes, fire
 Disadvantages
typically lower bandwidth compared to wired networks (110 Mbit/s)
many proprietary solutions, products have to follow many
national restrictions, it takes a vary long time to establish
global solutions, e.g., IMT-2000
Wireless Networking
49
Design Goals for Wireless
LANs
 Design
 Data plane:
 Channel efficiency: robust transmission technology
 Power efficiency: low power for battery use
 Management plane:
 easy to use for everyone, easy to program
 security (authentication, authorization, accounting and privacy), safety (low radiation)
 Operation
 global, seamless operation – protection of investments in wired networks
 no special permissions or licenses needed to use the LAN
 Infrastructure-mode and ad-hoc-mode support
 transparency concerning applications and higher layer protocols, but also
location awareness if necessary
Wireless Networking
50
IEEE 802 Protocol Layers
Organization of 802.11 w.r.t.
Other Modules
OSI Layer 3
LLC
OSI Layer 2
(data link)
MAC
OSI Layer 1
(physical)
Wireless Networking
802.11 – Layers, Planes
and Functions
 Management Plane
 Data Plane
 MAC: synchronization,
roaming, MIB, power
management
 PHY: channel selection,
MIB
 Station: coordination of all
management functions
MAC
PLCP
MAC Management
PHY Management
PMD
Station Management
DATA Plane
LLC
Management Plane
PHY
DLL
 MAC: access mechanisms, fragmentation,
encryption
 PLCP (Physical Layer Convergence
Protocol): clear channel assessment
signal (carrier sense)
 PMD (Physical Medium Dependent):
modulation, coding
Example implementation
Correspondent
Node (fixed terminal)
Infrastructure
Network (Internet)
access point
Mobile terminal
application
application
TCP
TCP
IP
IP
IP
LLC
LLC
LLC
802.11 MAC
802.11 MAC
802.3 MAC
802.3 MAC
802.11 PHY
802.11 PHY
802.3 PHY
802.3 PHY
Wireless Networking
54
Protocol Architecture
 Functions of physical layer:
 Encoding/decoding of signals
 Preamble generation/removal (for synchronization)
 Bit transmission/reception
 Includes specification of the transmission medium
 Functions of medium access control (MAC) layer:
 On transmission, assemble data into a frame with address and error detection
fields
 On reception, disassemble frame and perform address recognition and error
detection
 Govern access to the LAN transmission medium
 Functions of logical link control (LLC) Layer:
 Provide an interface to higher layers and perform flow and error control
Separation of LLC and MAC
The logic required to manage access to a
shared-access medium not found in traditional
layer 2 data link control
For the same LLC, several MAC options may
be provided
IEEE 802.11 Infrastructure-mode
Network
802.11 LAN
802.x LAN
STA1
BSS1
Portal
Access
Point
Distribution System
Access
Point
ESS
BSS2
STA2
802.11 LAN
STA3
 Station (STA): terminal with
access mechanisms to the wireless
medium and radio contact to the
access point
 Basic Service Set (BSS): group of
stations using the same radio
frequency
 Access Point (AP): station
integrated into the wireless LAN
and the distribution system
 Portal: bridge to other (wired)
networks
 Distribution System:
interconnection network to form
one logical network (EES:
Extended Service Set) based on
several BSS
Wireless Networking
57
Elements in an IEEE 802.11 ad-hoc
network
 Direct communication
within a limited range
802.11 LAN
Station (STA):
terminal with access
mechanisms to the wireless
medium
Independent Basic Service
Set (IBSS):
group of stations using the
same radio frequency
STA1
STA3
IBSS1
STA2
IBSS2
STA5
STA4
802.11 LAN
Wireless Networking
58
IEEE 802.11 Physical Medium
802.11a
802.11b
802.11g
802.11
Standard
approved
Sep. 1999
Sep. 1999
June 2003
July 1997
Available
bandwidth
300 MHZ
83.5 MHZ
83.5 MHZ
83.5 MHZ
freq. of operation
5.15-5.35G
5.725-5.825G
2.4-2.4835G
2.4-2.4835G
2.4-2.4835G
No. of nonoverlapping Ch.
4
3
3
3
Rate per channel
(Mbps)
6,12,24,36,48,54
1, 2, 5.5, 11
1, 2, 5.5, 11, 6, 9, 1, 2
12, 18, 24, 36,
48, 54
Range
~150 feet
(indoor) 225
(outdoor)
~225 feet
~225 feet
~ 300 feet
Modulation
OFDM
DSSS/CCK
DSSS/CCK;
DSSS/OFDM
DSSS, FHSS
FHSS: frequency hopping spread spectrum
DSSS: direct sequence spread spectrum
OFDM: orthogonal frequency division multiplexing
Wireless Networking
59
802.11 - MAC layer
 Distributed Foundation Wireless MAC (DFWMAC): includes both DCF & PCF
 Traffic services
 Asynchronous Data Service (mandatory) – DCF
 “best-effort”
 Time-Bounded Service (optional) – PCF
 Access methods
 DCF CSMA/CA (mandatory)
 collision avoidance via randomized "back-off" mechanism
 minimum distance between consecutive packets
 ACK packet for acknowledgements (not for broadcasts)
 DCF w/ RTS/CTS (optional)
 Distributed Foundation Wireless MAC
 avoids hidden terminal problem
 PCF (optional)
 access point polls terminals according to a list
Wireless Networking
60
802.11 - MAC layer
 Priorities based on interframe spacing (IFS)
 defined through different inter frame spaces
 no guaranteed, hard priorities
 SIFS (Short Inter Frame Spacing) ~ DSSS 10us.
highest priority, for ACK, CTS, polling response
Time slot ~ 20 us
 PIFS (PCF IFS) ~ DSSS 30us = 1 SIFS + 1 time slot.
medium priority, for time-bounded service using PCF
 DIFS (DCF, Distributed Coordination Function IFS) ~ DSSS 50us.
lowest priority, for asynchronous data service
DIFS
DIFS
PIFS
SIFS
medium busy
contention
next frame
t
direct access if
medium is free  DIFS
CSMA/CA Access Method
DIFS
data
sender
SIFS
ACK
receiver
DIFS
data
other
stations
waiting time
t
contention
 When the sender ready, starts Carrier Sensing based on CCA (Clear Channel
Assessment)
1.
2.
If the medium is free for a DIFS, the sender can start sending
If the medium is busy, the sender keeps sensing every time slot (DSSS~20us).
 If the medium is idle again, the sender must additionally wait a random back-off time
(collision avoidance, multiple of slot-time)
 If another station occupies the medium during the back-off time of the station, the sender’s
back-off timer stops (to ensure fairness), and go back to step 2.
3.
After the station sends the packet,
 If the receiver gets the packet correctly, the receiver sends ACK after SIFS
 If not, the station goes back to step 1 after EIFS, and retransmits packets.
Wireless Networking
62
CSMA/CA Competing Stations
DIFS
DIFS
DIFS
boe
bor
boe
busy
DIFS
boe bor
boe
boe
boe
busy
station1
station2
busy
station3
busy
bor
station4
boe
bor
boe
busy
boe
bor
station5
t
busy
medium not idle (frame, ack etc.)
packet arrival at MAC
boe
elapsed backoff time
bor
residual backoff time
Wireless Networking
63
NAV – Virtual Carrier
Sensing for Unicast
 The sender can reserve the channel in RTS using NAV (network allocation
vector)
 Receiver can again reserve the channel in CTS using NAV.
 Other stations backoff for the longest NAV in RTS and CTS
DIFS
sender
RTS
data
SIFS
receiver
other
stations
CTS SIFS
SIFS
NAV (RTS)
NAV (CTS)
defer access
ACK
DIFS
data
t
contention
Wireless Networking
64
Summary: DCF Collision
Avoidance Methods
1.
2.
3.
4.
5.
Interframe spacing (IFS) used as a priority mechanism
 SIFS (Short InterFrame Spacing): Used to give nodes in an ongoing
dialogue the chance to transmit. Example is RTS-CTS handshake,
ACK to data, or consecutive data packets.
 DIFS (DCF InterFrame Spacing ): Any station may attempt to
transmit after DIFS elapses.
 PIFS (PCF InterFrame Spacing): Base station can send poll or beacon
if no station accesses channel after PIFS interval.
 EIFS (Extended InterFrame Spacing): Longer than DIFS and used by
station to recover from a bad exchange
Carrier sensing
RTS/CTS handshake
Virtual carrier sensing
 NAV – network allocation vector
BEB (binary exponential backoff)
65
Wireless Networking
802.11 – Generic Frame
format
 Types: control, management or data.
 Sequence numbers
 important against duplicated frames due to lost ACKs
 Addresses
 receiver, transmitter (physical), BSS identifier, sender (logical)
 Miscellaneous




bytes
bits
MoreFrag – DLL fragmentation,
MoreData – for PS STAs,
Retry – retransmission
PowerMgmt – STA PS state change.
2
2
6
6
6
2
6
0-2312
4
Frame
Control
Duration/
ID
Address
1
Address
2
Address
3
Sequence
Control
Address
4
Data
CRC
2
2
4
1
1
1
1
1
1
1
Protocol
version
Type
Subtype
To
DS
From
DS
More
Frag
Retry
Power
Mgmt
More
Data
WEP
1
Order

























802.11a - 54 Mbps standard, 5 GHz signaling (ratified 1999)
802.11b - 11 Mbps standard, 2.4 GHz signaling (1999)
802.11c - operation of bridge connections (moved to 802.1D)
802.11d - worldwide compliance with regulations for use of wireless signal spectrum (2001)
802.11e - Quality of Service (QoS) support (not yet ratified)
802.11F - Inter-Access Point Protocol recommendation for communication between access points to support
roaming clients (2003)
802.11g - 54 Mbps standard, 2.4 GHz signaling (2003)
802.11h - enhanced version of 802.11a to support European regulatory requirements (2003)
802.11i - security improvements for the 802.11 family (2004)
802.11j - enhancements to 5 GHz signaling to support Japan regulatory requirements (2004)
802.11k - WLAN system management (in progress)
802.11l - skipped to avoid confusion with 802.11i
802.11m - maintenance of 802.11 family documentation
802.11n - 100+ Mbps standard improvements over 802.11g (in progress)
802.11o - skipped
802.11p - Wireless Access for the Vehicular Environment
802.11q - skipped
802.11r - fast roaming support via Basic Service Set transitions
802.11s - ESS mesh networking for access points
802.11T - Wireless Performance Prediction - recommendation for testing standards and metrics
802.11u - internetworking with 3G / cellular and other forms of external networks
802.11v - wireless network management / device configuration
802.11w - Protected Management Frames security enhancement
802.11x - skipped (generic name for the 802.11 family)
67
Wireless
Networking
802.11y - Contention Based Protocol for interference avoidance
Product Certification
WiFi
Originally created to ensure compatibility among
802.11b products
Can run under any 802.11 standard
Indicates interoperability certification by Wi-Fi
Alliance
Wireless Networking
68
MOBILE ADHOC
NETWORKS (MANETS)
Mobile Ad-hoc Networks (MANET)
 Ad-hoc network:
A collection of wireless mobile hosts forming a
temporary network without the aid of any established
infrastructure or centralized administration.
 Significant differences to existing wired networks:
Wireless
Self-starting
No administrator
Cannot assume, that every computer is within
communication range of every other computer
Possibly quite dynamic topology of interconnections
 Traffic types: unicast/multicast/anycast/geocast
Wireless Networking
70
Routing in MANET
 Routing assumptions for unicast traffic
Flat topology assumption
Proactive: DSDV, TORA, WRP
Reactive: AODV, DSR, STAR
Hierarchical topology assumption
Clustering: CBRP, PATM
Geographic assumption
Location aided routing: LAR, GeoCast
Wireless Networking
71
Classification of Routing Protocols
for MANETS
Unicast-Routing Protocol for
MANET (Topology-based)
Table-Driven/
Proactive
Distance
Vector
LinkState
DSDV
OLSR
TBRPF
FSR
STAR
Hybrid
On-Demand
/Reactive
Clusterbased/
Hierarchical
ZRP
DSR
AODV
TORA
LANMAR
CEDAR
MANET: Mobile Ad hoc Network
(IETF working group)
Wireless Networking
72
Desired Properties of Ad Hoc Routing Protocols
 Distributed
 Bandwidth efficient
Reduce control traffic/overhead
 Battery efficient
 Fast route convergence
 Correct: loop free
Reduce overhead
 Unidirectional Link Support
Wireless Networking
73
Performance Metrics of Ad Hoc Routing Protocols
 Maximize
end-to-end throughput
delivery ratio
load balancing (congestion)
 Minimize
end-to-end delay
packet loss
shortest path/minimum hop (route length)
overhead (bandwidth)
energy consumption
Wireless Networking
74
Mobile Ad hoc Networks (MANET) vs.
Sensor Networks
MANET
SensorNet
applications
meeting, grp collaboration
smart building, habitat monitoring
comm.
address-centric comm.
data centric comm.
topology
peer-to-peer
sensors  base & peer-to-peer
traffic
random
periodic, synchronous
platform
laptops, PDAs
motes: more resource constrained
scale
10’s
>1000: larger scale and more
redundancy
mobility
slow (meeting) ~ fast (cars):
focus on mobility
slow (habitat) ~ fast: less focus on
mobility so far
similarity
No infrastructure, multi-hop, wireless networks
Wireless Networking
75
Address Centric Routing
(AC)
Temperature Reading
(source 2)
Temperature Reading
(source 1)
source 2
source 1
source 2
Z
B
source 1
source 2
Give Me The Average Temperature?
( sink )
Wireless Networking
76
Data Centric Routing (DC)
Temperature Reading
(source 2)
Temperature Reading
(source 1)
source 2
source 1
source 2
Z
B
source 1 & 2
Give Me The Average Temperature?
( sink )
Wireless Networking
77
Distance-Vector routing
 Each node maintains a routing table containing
list of all available destinations
number distance to each each destination
next hop to reach a destination
 The succession of next hops leads to a destination
 Each node periodically broadcasts its current estimate
of the shortest distance to each available destination to
all of its neighbors
 Typical representative: Distributed Bellman-Ford
(DBF)
Wireless Networking
78
AODV (Ad Hoc On-Demand Distance
Vector)
 AODV is based on the DSDV (Destination-Sequenced
Distance Vector) algorithm
Distance vector
Sequence numbers controlled by the destination.
 Creation of routes on a demand basis – traffic reactive
 Nodes that are not on a selected path do not maintain
routing information or participate in routing table
exchanges!
 Goal: Minimize broadcast overhead and transmission
latency
Wireless Networking
79
Route Requests from S to
D in AODV
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Represents a node that has received RREQ for D from S
Wireless Networking
80
Route Requests from S to
D in AODV
Y
Broadcast transmission
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Represents transmission of RREQ
Wireless Networking
81
Route Requests from S to
D in AODV
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
D
I
N
Represents links on Reverse Path
Wireless Networking
82
Reverse Path Setup from S
to D in AODV
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
• Node C receives RREQ from G and H, but does not forward
it again, because node C has already forwarded RREQ once
Wireless Networking
83
Reverse Path Setup from S
to D in AODV
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Wireless Networking
84
Reverse Path Setup in
AODV
• Node D does not forward RREQ, because node D
is the intended target of the RREQ
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Wireless Networking
85
Route Reply from D to S in
AODV
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
D
I
N
Represents links on path taken by RREP
Wireless Networking
86
Route Reply in AODV
 Intermediate node may also send a Route Reply
(RREP) provided that it knows a more recent path
than the one previously known to sender S
To determine whether the path known to an intermediate
node is more recent, destination sequence numbers are
used
 The likelihood that an intermediate node will send a
RREP not as high as DSR
An intermediate node which knows a route, but with a
smaller sequence number, cannot send Route Reply
Wireless Networking
87
Forward Path Setup in
AODV
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Forward links are setup when RREP travels along
the reverse path
Represents a link on the forward path
Wireless Networking
88
Data Delivery in AODV
Routing table entries used to forward data packet.
Route is not included in packet header.
DATA
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Wireless Networking
89
AODV Key Advantages
 “Partial” routing tables are constructed reactively
Entries are updated only when a node sends to another unreachable
node
No periodic updates
Node not on active paths maintain no routing entries
 Reduce packet overhead
 Routing table
No source routing needed  reduce bit overhead
“Route caching”  reduce establishment latency
Sequence number  loop freedom
 Push link failure to relevant nodes
 Reduce establishment latency
Wireless Networking
90
Dynamic Source Routing (DSR)
[Johnson96]
When node S wants to send a packet to node D,
but does not know a route to D, node S initiates
a route discovery using Route Request (RREQ)
Each node appends own identifier when
forwarding RREQ
Wireless Networking
91
Route Discovery in DSR
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Represents a node that has received RREQ for D from S
Wireless Networking
92
Route Discovery in DSR
Y
Broadcast transmission
[S]
S
Z
E
F
B
C
M
J
A
L
G
H
K
D
I
N
Represents transmission of RREQ
[X,Y]
Represents list of identifiers appended to RREQ
Wireless Networking
93
Route Discovery in DSR
Y
Z
S
E
[S,E]
F
B
C
A
M
J
[S,C]
H
L
G
K
D
I
N
• Node H receives packet RREQ from two neighbors:
potential for collision
Wireless Networking
94
Route Discovery in DSR
Y
Z
S
E
F
B
[S,E,F]
C
M
J
A
L
G
H
I
[S,C,G]
K
D
N
• Node C receives RREQ from G and H, but does not forward
it again, because node C has already forwarded RREQ once
Wireless Networking
95
Route Discovery in DSR
Y
Z
S
E
[S,E,F,J]
F
B
C
M
J
A
L
G
H
K
I
D
[S,C,G,K]
N
• Nodes J and K both broadcast RREQ to node D
• Caveat: Since nodes J and K are hidden from each other, their
transmissions may collide
Wireless Networking
96
Route Discovery in DSR
Destination D on receiving the first RREQ,
sends a Route Reply (RREP)
RREP is sent on a route obtained by reversing the
route appended to received RREQ
RREP includes the route from S to D on which
RREQ was received by node D
Wireless Networking
97
Route Reply in DSR
Y
Z
S
E
RREP [S,E,F,J,D]
F
B
C
M
J
A
L
G
H
K
I
D
N
Represents RREP control message
Wireless Networking
98
Dynamic Source Routing
(DSR)
 Node S on receiving RREP, caches the route included in
the RREP
 When node S sends a data packet to D, the entire route is
included in the packet header
hence the name source routing
 Intermediate nodes use the source route included in a
packet to determine to whom a packet should be
forwarded
Wireless Networking
99
Data Delivery in DSR
Y
DATA [S,E,F,J,D]
S
Z
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Packet header size grows with route length
Wireless Networking
100
DSR Optimization: Route
Caching
 Each node caches a new route it learns by any means
 Through Route Request (RREQ)
When node K receives RREQ [S,C,G] destined for node D, node K learns route
[K,G,C,S] to node S
 Through Route Reply (RREP)
When node S finds RREP [S,E,F,J,D] to node D, node S also learns route [S,E,F] to
node F
When node F forwards RREP [S,E,F,J,D], node F learns route [F,J,D] to node D
 Through DATA packet’s source routes
When node E forwards Data [S,E,F,J,D] it learns route [E,F,J,D] to node D
A node may also learn a route when it overhears Data
 Problem: Stale caches may increase overheads
Wireless Networking
101
Dynamic Source Routing:
Advantages
Routes maintained only between nodes who
need to communicate
reduces overhead of route table maintenance
Routing cache can further reduce route
discovery overhead
A single route discovery may yield many routes
to the destination, due to intermediate nodes
replying from local caches
Wireless Networking
102
Dynamic Source Routing: Disadvantages
 Packet header size grows with route length due to source
routing
 Flooding of route requests may potentially reach all nodes
in the network
 Stale caches will lead to increased overhead
 Common problems for both AODV and DSR
Potential collisions between route requests propagated by
neighboring nodes - insertion of random delays before forwarding
RREQ
Increased contention if too many route replies come back due to
nodes replying using their local cache - Route Reply Storm
problem
Wireless Networking
103
MOBILE MULTIMEDIA
Mobile Multimedia – Rich Media
applications on mobile devices
OBJECTIVE : Stream rich multimedia content at highest possible quality (user experience) over
wired and wireless networks
Low-power
mobile device
Video stream
Wide Area
Network
MEDIA SERVER
Wireless
Network
Access point
Video request
Challenges
• Soft Real time Requirements
• High demands on CPU / Network
• Loss in performance directly affects user perception
Opportunities
• Predictable regular behavior allows for interesting optimizations and
adaptations
Multimedia Information
Systems: Challenges
Sheer volume of data
Need to manage huge volumes of data
Timing requirements
among components of data computation and communication.
Must work internally with given timing constraints - real-time
performance is required.
Integration requirements
need to process traditional media (text, images) as well as
continuous media (audio/video).
Media are not always independent of each other - synchronization
among the media may be required.
High Data Volume of
Multimedia Information
Speech
8000 samples/s
8Kbytes/s
CD Audio
44,100 samples/s, 2
bytes/sample
176Kbytes/s
Satellite
Imagery
180X180 km^2
30m^2 resolution
NTSC Video
30fps, 640X480
pixels, 3bytes/pixel
600MB/image
(60MB
compressed)
30Mbytes/s
(2-8 Mbits/s
compressed)
Quality of Service in MM
Applications
QoS: A Design
Parameter for MM
Minor violations of
performance
requirements
Generally used to
express constraints on
Timing, availability,
reliability,security,
resource utilization
User
(Perceptual QoS)
Application
(Application QoS)
System
(Operating and Communication System)
(System QoS)
(Device QoS)
MM devices
(Network QoS)
Network
QoS Classes
 QoS Service Classes determine
reliability of offered QoS
utilization of resources
Guaranteed Service Class
QoS guarantees are provided based on deterministic and statistical QoS
parameter values.
Predictive Service Class
QoS parameter values are estimated and based on the past behavior of the
service
Best-effort Service Class
No guarantees or only partial guarantees provided
No QoS parameters are specified or some minimal bounds are given.
Supporting continuous
media: Approaches
Admission control
Provide different service classes
Fast storage and retrieval of Multimedia content
Optimized organization (placement) of multimedia
files on disk
Special disk scheduling algorithms
Efficient Memory Management
Sufficient buffers to avoid jitter
 Intelligent Caching
End-to-end QoS for Wired Applications
Usually achieved through QoS Brokers
Coordinates interactions between multiple sessions
with QoS needs
Typical Functions of a QoS broker
Resource Provisioning
Deal adaptively with incoming requests
Allocate server, network and client resources
Predictive and Adaptive Data Placement
Re(configure) data to service requests more efficiently
Must maintain resource allocation invariants
Supporting QoS in Mobile
Applications
 New challenges
Constantly changing system conditions
Network connectivity, user mobility
Device constraints
Energy, CPU, display, bandwidth
 This needs
 Provisioning, re-provisioning based on local conditions of wireless network
 Data Placement based on current and projected data access patterns
 Cross-layer awareness required
 Resource provisioning algorithms utilize current system resource availability
information to ensure that applications meet their QoS requirements
QoS-based resource
provisioning
 Provisioning Network and Server Resources Effectively
State information enables decision making for resource provisioning - e.g.
Routing, Scheduling and Placement
Maintaining accurate and current system information is important
 Existing Approaches
 In network : QoS Based Routing
 At Server : Server Load Balancing
 Future: Techniques to support CPSS (Combined Path and Server Scheduling )
l
l : UF (l , r , n), DL 
s1
l
l : BWavail
, DLl 
s1
O
s2
s3
s2
O
CD
s3
s : UF ( s1, r , n ), RSP
s

Data Placement in Mobile
Environments
Initial placement
 Design replication and intelligent
S1
data placement mechanisms that
 Ensure effective resource
management
 Ensure QoS for admitted clients
S2
S3
v1
v2
v5
v6
v1
v2
v3
v4
v1
v2
v3
v4
 Design caching mechanisms
 Partition data/processing between
mobile clients and infrastructure
S1
S2
S3
 Allows disconnected operation
v1
v2
v5
v6
v6
v5
 Efficient power management
v3
v4
v1
v2
v3
v4
After replication degree enforcement
Need for a Cross Layer
Approach
 Information exchange needed
To provide information good enough for resource provisioning tasks
such as admission control, load balancing etc.
Need an information collection mechanism that is :
• is aware of multiple levels of imprecision in data
• is aware of quality requirements of applications
• makes optimum use of the system (network and server)
resources
 Sample Parameters
Network link status, Data server capacity (Remote disk bandwidth,
Processor capacity), device constraints (battery power, memory
limitations)
Case Study: Power
Management
 Power Optimization in battery operated mobile
devices is a crucial research challenge
 Devices operate in dynamic distributed environments
 Power Management strategies need to be aware of
global system state and exploit it.
Misc.
NETWORK
CARD
CPU
DISPLAY
CPU
NIC
Display
Existing Work in Power
Optimization
• Flinn (ICDSP 2001), Yau (ICME 2002)
• Krintz, Wolski (ISLPED 2004)
• Noble (SOSP 97, MCSA 1999)
• Li (CASES 2002), Othman (1998)
• Ellis,
Vahdat
(IEEE
• Abeni
(RTSS
98)pervasive 05, Usenix 03, ASPLOS 02)
• Hao,
Nahrstedt
(ICMCS
99, Globecom
•Rudenko
( ACM
SAC 99,
99),HPDC
Satyanarayan
(2001) 01)
• Yuan (MMCN 03,04, SOSP 03, ACM MM 04),
• Rajkumar (03), Anand (Mobicom 03, Mobisys 04)
• DVS (Shin, Gupta, Weiser, Srivastava, Govil et. al.)
• DPM (Douglis, Hembold, Delaluz, Kumpf et. al.)
• Chandra (MMCN 04,02, USENIX 2002, ICPP 04)
• Shenoy (ACM MM 2002)
• Feeney, Nilson ( Infocom 2001)
Katz (IEICE
97) Multimedia 97)
• Soderquist
(ACM
• Azevedo (AWIA 2001)
• Hughes, Adve (MICRO 01, ICSA 01)
• Brooks (ISCA 2000), Choi (ISLPED 02)
• Leback (ASPLOS 2000), Microsoft’s ACPI
Quality of Service
Application/user feedback
DVS, DPM, Driver
Interfaces, system calls
User/Application
Network
Interface Card
Operating System
Architecture
(cpu, memory)
Network
Architecture
Power Optimization has been extensively researched
Limitations of Current
Approaches

Limited co-ordination between the different system layers
• Address concerns at one or two system levels
• Make assumptions about adaptations at other system levels (lack awareness)

Device Centric
• Cannot exploit global system knowledge (e.g. congestion, mobility, location)
• Reactive Adaptations

Lack of generalized framework
What if new applications are started or
residual battery energy changes?
Illustration
Client
Client
congestion
Server
Wired
Network
Proxy
Wireless
Network
Client
Power-aware middleware
A power-cognizant distributed middleware framework can
o dynamically adapt to global changes
o co-ordinate techniques at different system levels
o maximize the utility (application QoS, power savings) of a low-power device.
o study and evaluate cross layer adaptation techniques for performance vs. quality vs. power
tradeoffs for mobile handheld devices.
Caching
Compression
Traffic Shaping
State Monitor
Compositing
Transcoding
Use proxy to dynamically
adapt to global changes
Execute Remote Tasks
Low-power
mobile device
Wide Area
Network
server
Wireless
Network
proxy
Use a Proxy-Based Architecture
Coordinate techniques
on device
Power-Aware Adaptive
Middleware
Quality of Service
Application/user feedback
Distributed Adaptation
Cross-Layer Adaptation
Power-Aware API
Distributed Adaptation
Cross-Layer Adaptation
Appl. specific Adaptation
User/Application
Middleware
• DYNAMO SYSTEM
Mohapatra et. al (ICN 05, ITCC 05, ACM
Middleware 04, DATE 04, ICDCS 03, MWCN 03,
ACM MM 03, RTAS/RTSS Workshops 03,
Estimedia 03, CIPC 03, ICDCS 01)
Operating System
Architecture
(cpu, memory)
Network
Architecture
Cross-Layer Approach
User/Application
network
Distributed Middleware
Middleware
Operating System
Architecture
Proxy
LOCAL
CROSS LAYER ADAPTATION
GLOBAL (End-to-End)
PROXY BASED ADAPTATION
1. Design end-to-end adaptations that
can exploit global state (network noise,
mobility patterns, device state etc.)
2. Use control information to notify
mobile device of adaptations
3. Adapt strategies on device
1.
Expose “state” information to
other layers
2. Design strategies at each layer to
dynamically adapt to changes at
other layers
device
Energy-Sensitive Video Transcoding for
Mobile devices
► We conducted a survey to subjectively assess human
perception of video quality on handhelds.
► Hard to programmatically identify video quality parameters
► We identified 8 perceptible video quality levels that produced noticeable
difference in power consumption (Compaq iPaq 3600)
VIDEO TRANSCODING PARAMETERS
QUALITY
Q1 (Like original)
Video transformation
parameters
SIF, 30fps, 650Kbps
Avg. Power
(Windows CE)
4.42 W
Avg. Power
(Linux)
6.07 W
Q2 (Excellent)
SIF, 25fps, 450Kbps
4.37 W
5.99 W
Q3 (Very Good)
SIF, 25fps, 350Kbps
4.31 W
5.86 W
Q4 (Good)
HSIF, 24fps, 350Kbps
4.24 W
5.81 W
Q5 (Fair)
HSIF, 24fps, 200Kbps
4.15 W
5.73 W
Q6(Poor)
HSIF, 24fps, 150Kbps
4.06 W
5.63 W
Q7 (Bad)
QSIF, 20fps, 150Kbps
3.95 W
5.5 W
Q8 (Terrible)
QSIF, 20fps,100kbps
3.88 W
5.38 W
Quality/Power Matrix for COMPAQ IPAQ 3600 ( Grand Theft Auto Action Video Sequence)
Energy-Sensitive Video Transcoding:
Visual Comparison
Quality 1
(like original)
Avg. Power : 6.24 W
Quality 4
(good)
Avg. Power : 5.81 W
Quality 7
(bad)
Avg. Power : 5.41 W
Parameters varying: frame size, bit-rate, frame rate
• Profile power for each quality
• Optimize system for each quality
Energy-Aware Video
Transcoding
Video Stream (QSTREAM)
Mobile
Device
Proxy
Residual Energy (ERES)
User defined Quality (Qthreshold)
12
QSTREAM
=
Max(Qi) such that
PSTREAM * T < ERES
QSTREAM > QTHRESHOLD
QSTREAM
= Video streamed by proxy
Qthreshold = Threshold quality level acceptable to the user
PSTREAM
= Avg. Power consumption for video playback
ERES
= Residual Energy of device
T
= Time of playback
Normalized Energy saved (%)
10
8
6
4
2
0
Q1
Q2
Q3
Q4
Q5
Q6
Energy-Aware Application
Adaptation
User
Profile
Negotiation
Application
QoS
Monitor
E-Q
profile Transcoder
Communication
Dynamo Middleware
Dynamo Middleware
CPU
NIC
Linux OS
NIC
Wireless
Network
Proxy
Wireless Network
DISPLAY
CPU
Mobile Device
Network Card Optimization
 Wireless NIC cards can operate in various power modes
 Avg. power consumption in sleep mode (0.184 W) whereas idle/receive modes
consume (1.34/1.435 W) respectively.
 NIC can be transitioned to sleep mode (high energy savings)
 Packets can get lost (quality drop)
 Adaptation
Proxy buffers video and sends it in bursts to the device
Control info added - when device should wake up
 Allows for long sleep intervals of the network card on device
Limitations
 Large bursts can result in high packet loss rates
 Access point and mobile device buffering limitations
Adaptation at Proxy
QSTREAM
=
Max(Qi) such that
PSTREAM * T < ERES
QSTREAM > QTHRESHOLD
Video Stream (QSTREAM)
# of frames, buffer size, quality
Proxy
Residual Energy, Quality threshold
+ Noise (SL), Buffer capacity (Bf),
Decode rate (Fd)
Set local buffer size based on noise level (empirical)
Fix quality level (Qi) to be streamed (QSTREAM ... QTHRESHOLD)
Let
N = number of transcoded frames in local buffer
Burst Size (I) = N / Fd
Send next burst after I seconds.
Mobile
Device
Adaptation at Mobile
Burst Size (I) = N / F
Device
Video Stream (QSTREAM)
# of frames (N), buffer size, quality, σ
Proxy
d
Mobile
Device
total number of packets at the
Access Point
Worst case transmission delay of burst (D) = σ x TAP
Therefore total sleep time (δ) for NIC at the device
δ = I – D + γ. DEtoE
Psaved ≥ δ x (PIDLE - PSLEEP)
Switch network card to
“sleep” mode for δ seconds
after receiving video
Network Card Adaptation
in Dynamo
User
Profile
Negotiation
Application
QoS
E-Q
Monitor
profile
Network
Transmission Transcoder
NIC
adaptation
Communication
Dynamo Middleware
Dynamo Middleware
CPU
NIC
Linux OS
NIC
Wireless
Network
Proxy
Wireless Network
DISPLAY
CPU
Mobile Device
Network Energy Savings
NIC
Backlight
1738 Frames
Energy Savings – 35% - 57% (over no optimization)
Frames Lost – < 12%
399 Frames
Energy Savings – 50% - 75% (over no optimization)
Frames Lost – < 5%
2924 Frames
Energy Savings – 25% - 45% (over no optimization)
Frames Lost – < 10%
CPU
Backlight Compensation

Adaptation
1) Enhance luminance of video frames at proxy
2) Dim backlight on the device to compensate luminance enhancement

Problems


Technique to achieve the suitable (optimal) backlight dimming factor
Reduce flicker induced by frequent backlight switching
Backlight Adaptation
Fair
Good
Excellent
Fair
Good
Excellent
Fair
Good
Excellent
Backlight
Level
Quality
(PSNR)
Power
Savings
149
162
205
30.17
34.28
42.31
41.8%
36.7%
27.3%
Backlight
Level
Power
Savings
80
125
186
44.8%
39.7%
30.3%
Backlight
Level
Power
Savings
172
162
205
34.8%
27.7%
21.4%
Backlight Adaptation in
Dynamo
Video Stream (QSTREAM)
# of frames, buffer size, quality
+ Backlight Setting
Proxy
Mobile
Device
Residual Energy, Quality threshold
+ Noise (SL), Buffer capacity (Bf),
Decode rate (Fd)
Stream luminance
compensated video
Use backlight quantization
table to set backlight
Backlight Adaptation using
Dynamo
NIC
Backlight
CPU
User
Profile
Negotiation
Application
QoS
E-Q
profile
B/L Scaling
NIC
adaptor
Backlight
Monitor adaptor
Network
Transmission
Transcoder
Communication
Dynamo Middleware
Dynamo Middleware
CPU
NIC
Linux OS
NIC
Wireless
Network
Proxy
Wireless Network
DISPLAY
CPU
Mobile Device
Architecture/CPU
Adaptation
 DVS idea: trade off processor speed for power
 MPEG frame decoding – good candidate
Frame decoding takes less than the frame delay
Decoding time – depends on frame type: I, P, B
Voltage
I
B
B
P
B
B
P
no DVS
with DVS
MPEG Stream
0
D
Fd
time
CPU Adaptation using
Dynamo
Video Stream (QSTREAM)
# of frames, buffer size, quality
Backlight Setting + Profiled WCET,
BCET, Avg. Execution time
Proxy
Mobile
Device
Residual Energy, Quality threshold
+ Noise (SL), Buffer capacity (Bf),
Decode rate (Fd)
• Determine video quality
• Use a rule base of profiled data to
send execution parameters to the mobile
device
• Middleware communicates execution
characteristics to scheduler
• Scheduler can now dynamically recompute slowdown parameters for the
new video quality
CPU Adaptation
User
Profile
Negotiation
Application
QoS
Rule Base
E-Q
profile
B/L Scaling
Network
Transmission
Transcoder
NIC
adaptor
Backlight
CPU
adaptation
Monitor adaptation
Communication
Dynamo Middleware
Dynamo Middleware
scheduler
Linux OS
NIC
Wireless
Network
Proxy
Wireless Network
DISPLAY
CPU
Mobile Device
Overall Energy Savings
Other
(8.2%)
CPU
(27.2%)
Network
(37.7%)
Display
(26.9%)
Energy Distribution
(Before Optimization)
After Cross-Layer
Optimizations
Other Network
CPU (8.2%) (15.09%)
Savings
(13.6%)
NIC Savings
CPU
(22.64%)
(13.6%)
Display Display
Savings (14.8%)
(12.1%)
Energy Distribution
(After Optimization)
Note: These are avg. energy savings
Total energy savings ~ 48% (for a medium action video clip called Foreman)
Implications for a commercial PDA
Avg. Battery lifetime of the mobile device increases by approximately 2 times its
original lifetime under similar load (i.e. battery power consumption).
•
Secure Mobile Multimedia – Energy Implications
Problem and Motivation
Measured Energy (Joules)
 Mobile multimedia applications
are vulnerable to security attacks
in wireless networks
 Significant computation for
video encryption is expected
on battery-operated mobiles
▶ Evaluate symmetric video
encryption schemes w.r.t. energy
Battery
-Operated
Devices
Attacks
Video
Encoder
Symmetric
Encryption
Technique
Secure Video Encoder
Insecure
network
80
Encoding without Encryption
60
50
Encoding with Encryption
(Selective)
40
30
Encoding with Encryption
(Naïve)
20
10
0
FOREMAN.qcif
NEWS.qcif
Video Clips
Symmetric
Decryption
Technique
Secure Video Decoder
Experimental Study
90 Negligible Energy Overhead
70
Video
Decoder
Reliable Mobile Multimedia – Energy
Implications
Problem and Motivation
Idea: ME (Motion Estimation) is..
Most energy consuming operation
Avoiding ME can improve energy profile
at the cost of encoding efficiency
High impact on image quality
Making ME algorithm robust against packet loss
can improve error resiliency
Video streams over a wireless network
Data loss  Error control
•Channel coding : FEC, Retransmission
•Source coding: Error-resilient coding
Video Encoder
Raw
Video
ME
DCT
Q
Multiplexing,
Packetizing
& Channel
Encoding
VLC
Lossy
Network
Probability Based Partial intra-coding
 trade-offs among error resiliency, encoding efficiency, energy consumption
Experimental Study
36
25
25
30
20
15
10
5
Encoding
Energy(J)
20
NO
PBPAIR
PGOP-3
GOP-3
AIR-24
PSNR (dB)
24
18
12
15
10
5
0
0
49
47
45
43
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
9
11
7
5
3
0
akiyo
garden
Energy efficiency
PBPAIR
PGOP-1
GOP-8
Fast recovery
AIR-10
0.2
0.4
PLR
Frame Number
0
foreman
0.9
0.6
0.3
6
1
Encoding Energy (J)
Encoding Energy Consumption (iPAQ)
PNSR Variation
Encoding Energy Consumption (iPAQ)
0-5
5-10
0.6
10-15
0.8
1
15-20
0
20-25
Flexibility
Intra_Th