This document discusses quality of service (QoS) provisioning in wireless multimedia networks. It describes QoS challenges in wireless networks due to limited bandwidth, unreliable links, and varying channel conditions. It also discusses the characteristics of multimedia services and traffic modeling challenges. The document outlines IEEE 802.11 MAC layer enhancements including the distributed coordination function, point coordination function, and IEEE 802.11e standard for supporting QoS through enhanced distributed channel access and hybrid coordination function. It emphasizes the need for end-to-end QoS, adaptive frameworks, and call admission control for wireless multimedia networks.
Multimedia networking:
The term ‘multimedia’ refers to diverse classes of media employed to represent information.
The term ‘Networked Multimedia’ refers to the transmission and distribution of multimedia information on the network
This is the subject slides for the module MMS2401 - Multimedia System and Communication taught in Shepherd College of Media Technology, Affiliated with Purbanchal University.
Multimedia networking:
The term ‘multimedia’ refers to diverse classes of media employed to represent information.
The term ‘Networked Multimedia’ refers to the transmission and distribution of multimedia information on the network
This is the subject slides for the module MMS2401 - Multimedia System and Communication taught in Shepherd College of Media Technology, Affiliated with Purbanchal University.
RESOURCE ALLOCATION ALGORITHMS FOR QOS OPTIMIZATION IN MOBILE WIMAX NETWORKSijwmn
WiMAX is based on the standard IEEE 802.16e-2009 for wireless access in Metropolitan Area Networks. It
is one of the solutions for 4G IP based wireless technology. WiMAX utilizes Orthogonal Frequency
Division Multiple Access which also supports Multicast and Broadcast Service with appropriate
Modulation and Coding Scheme. Presently, Scheduling and Resource allocation algorithm in Opportunistic
Layered Multicasting provides multicasting of layered video over mobile WiMAX to ensure better QoS.
Initially, the knowledge based allocation of subcarriers is used for scheduling. In addition, to reduce the
burst overhead, delay and jitter, SWIM (Swapping Min-Max) algorithm is utilized. Another promising
technology that can greatly improve the system performance by exploring the broadcasting nature of
wireless channels and the cooperation among multiple users is the Cooperative Multicast Scheduling
(CMS) technique. The simulation results show, Swapping Min-Max performs better with lesser number of
bursts, Zero jitter and with optimal throughput. The results with Cooperative Multicast Scheduling show
the enhanced throughput for each member in the Multicasting Scenario.
Minimizing network delay or latency is a critical factor in delivering mobile broadband services; businesses and users expect network response will be close to instantaneous. Excess latency can have a profound effect on user experience—from excess delay during a simple phone conversation, reducing throughput at edge of cell coverage areas by reducing effectiveness of RAN optimization techniques, to slow- loading webpages and delays with streaming video. Response delays negatively impact revenue. In financial institutions, low latency networks have become a competitive advantage where even a few extra microseconds, can enable trades to execute ahead of the competition.
The direct correlation between delay and revenue in the web browsing experience is well documented. Amazon famously claimed that every 100 millisecond reduction in delay led to a one percent increase in sales. Google also stated that for every half second delay, it saw a 20 percent reduction in traffic.
For LTE network operators, control of latency is growing in importance as both an operational and business issue. Low latency is not only critical to maintaining the quality user experience (and therefore, the operator competitive advantage) of growing social, M2M, and real-time services, but latency reduction is fundamental to meeting the capacity expectations of LTE-A, where latency budgets will be cut in half and X2 will need to perform at microsecond speed.
Total network latency is the sum of delay from all the network components, including air interface, the processing, switching, and queuing of all network elements (core and RAN) along the path, and the propagation delay in the links. With ever tightening latency expectations, the relative contribution of any individual network element, such as a security gateway, must be minimized. For example, when latency budgets were targeting 150ms, a network node providing packet processing at 250μs was only adding 0.17% to the budget. However, in LTE-A, with latency targets slashed to 10ms, that same network node will consume almost 15x more of the budget. More important, when placed on the S1 with a target of only 1ms, 250 μs is 25% of the entire S1 latency allocation, and endangers meeting the microsecond latency needed at the X2. Clearly, operators need to apply stringent latency requirements for all network nodes, when designing LTE and LTE-A networks.
This is the subject slides for the module MMS2401 - Multimedia System and Communication taught in Shepherd College of Media Technology, Affiliated with Purbanchal University.
This slide-share contains details about the Multimedia networking and why it is important for us. Also this contains details regarding performance issues, applications, technical challenges and features of a multimedia system.
A multimedia networking system allows for the data exchange of discrete and continuous media among computers.
This communication requires proper service and protocols for data transmission.
LAYERS: Provide a set of operations to the requesting application. Logically related services are grouped into layers according to the OSI layes.
PROTOCOL: A protocol consists of a set of rules which must be followed by peer layer instances during any communication between these two peers.
This is the subject slides for the module MMS2401 - Multimedia System and Communication taught in Shepherd College of Media Technology, Affiliated with Purbanchal University.
Performance Analysis of Wireless Networks With MDQOSIJERA Editor
In Wireless/Mobile networks various kinds of encoding schemes were used for transmission of data over a bandwidth. The desired quality and generated traffic varies with the requirement with this bandwidth. A generic video telephony may require more than 40 kbps whereas a low motion video telephony may require about 25 kbps for data transmission. From the designing point of view these requirements demands for an alternative resource planning, especially for bandwidth allocation in wireless networks. In wireless network where bandwidth is a scare resource, the system may need to block incoming user if all of the bandwidth has been used to provide highest quality of service to existing users. However this bandwidth resource planning may be unacceptable for larger application. A degradable approach to multiple users can be made on bandwidth allocation to reduce the blocking probability without degrading the quality of service to existing users.
This work aims towards a realization of a wireless/mobile network using W-CDMA multi access technique supporting multilevel quality of services. The bandwidth allocation to multiple users is adjusted dynamically according to the required network condition so as to increase bandwidth utilization. The work analyze the performance deriving the degradation period ratio, mean degradation time and degradation state for the implemented wireless network.The proposed work is aim to implement on Matlab tool for its functional verification considering various mobility patterns
A review over multimedia and how to share multimedia data between clients and servers.
Find me on:
AFCIT
http://www.afcit.xyz
YouTube
https://www.youtube.com/channel/UCuewOYbBXH5gwhfOrQOZOdw
Google Plus
https://plus.google.com/u/0/+AhmedGadIT
SlideShare
https://www.slideshare.net/AhmedGadFCIT
LinkedIn
https://www.linkedin.com/in/ahmedfgad/
ResearchGate
https://www.researchgate.net/profile/Ahmed_Gad13
Academia
https://www.academia.edu/
Google Scholar
https://scholar.google.com.eg/citations?user=r07tjocAAAAJ&hl=en
Mendelay
https://www.mendeley.com/profiles/ahmed-gad12/
ORCID
https://orcid.org/0000-0003-1978-8574
StackOverFlow
http://stackoverflow.com/users/5426539/ahmed-gad
Twitter
https://twitter.com/ahmedfgad
Facebook
https://www.facebook.com/ahmed.f.gadd
Pinterest
https://www.pinterest.com/ahmedfgad/
RESOURCE ALLOCATION ALGORITHMS FOR QOS OPTIMIZATION IN MOBILE WIMAX NETWORKSijwmn
WiMAX is based on the standard IEEE 802.16e-2009 for wireless access in Metropolitan Area Networks. It
is one of the solutions for 4G IP based wireless technology. WiMAX utilizes Orthogonal Frequency
Division Multiple Access which also supports Multicast and Broadcast Service with appropriate
Modulation and Coding Scheme. Presently, Scheduling and Resource allocation algorithm in Opportunistic
Layered Multicasting provides multicasting of layered video over mobile WiMAX to ensure better QoS.
Initially, the knowledge based allocation of subcarriers is used for scheduling. In addition, to reduce the
burst overhead, delay and jitter, SWIM (Swapping Min-Max) algorithm is utilized. Another promising
technology that can greatly improve the system performance by exploring the broadcasting nature of
wireless channels and the cooperation among multiple users is the Cooperative Multicast Scheduling
(CMS) technique. The simulation results show, Swapping Min-Max performs better with lesser number of
bursts, Zero jitter and with optimal throughput. The results with Cooperative Multicast Scheduling show
the enhanced throughput for each member in the Multicasting Scenario.
Minimizing network delay or latency is a critical factor in delivering mobile broadband services; businesses and users expect network response will be close to instantaneous. Excess latency can have a profound effect on user experience—from excess delay during a simple phone conversation, reducing throughput at edge of cell coverage areas by reducing effectiveness of RAN optimization techniques, to slow- loading webpages and delays with streaming video. Response delays negatively impact revenue. In financial institutions, low latency networks have become a competitive advantage where even a few extra microseconds, can enable trades to execute ahead of the competition.
The direct correlation between delay and revenue in the web browsing experience is well documented. Amazon famously claimed that every 100 millisecond reduction in delay led to a one percent increase in sales. Google also stated that for every half second delay, it saw a 20 percent reduction in traffic.
For LTE network operators, control of latency is growing in importance as both an operational and business issue. Low latency is not only critical to maintaining the quality user experience (and therefore, the operator competitive advantage) of growing social, M2M, and real-time services, but latency reduction is fundamental to meeting the capacity expectations of LTE-A, where latency budgets will be cut in half and X2 will need to perform at microsecond speed.
Total network latency is the sum of delay from all the network components, including air interface, the processing, switching, and queuing of all network elements (core and RAN) along the path, and the propagation delay in the links. With ever tightening latency expectations, the relative contribution of any individual network element, such as a security gateway, must be minimized. For example, when latency budgets were targeting 150ms, a network node providing packet processing at 250μs was only adding 0.17% to the budget. However, in LTE-A, with latency targets slashed to 10ms, that same network node will consume almost 15x more of the budget. More important, when placed on the S1 with a target of only 1ms, 250 μs is 25% of the entire S1 latency allocation, and endangers meeting the microsecond latency needed at the X2. Clearly, operators need to apply stringent latency requirements for all network nodes, when designing LTE and LTE-A networks.
This is the subject slides for the module MMS2401 - Multimedia System and Communication taught in Shepherd College of Media Technology, Affiliated with Purbanchal University.
This slide-share contains details about the Multimedia networking and why it is important for us. Also this contains details regarding performance issues, applications, technical challenges and features of a multimedia system.
A multimedia networking system allows for the data exchange of discrete and continuous media among computers.
This communication requires proper service and protocols for data transmission.
LAYERS: Provide a set of operations to the requesting application. Logically related services are grouped into layers according to the OSI layes.
PROTOCOL: A protocol consists of a set of rules which must be followed by peer layer instances during any communication between these two peers.
This is the subject slides for the module MMS2401 - Multimedia System and Communication taught in Shepherd College of Media Technology, Affiliated with Purbanchal University.
Performance Analysis of Wireless Networks With MDQOSIJERA Editor
In Wireless/Mobile networks various kinds of encoding schemes were used for transmission of data over a bandwidth. The desired quality and generated traffic varies with the requirement with this bandwidth. A generic video telephony may require more than 40 kbps whereas a low motion video telephony may require about 25 kbps for data transmission. From the designing point of view these requirements demands for an alternative resource planning, especially for bandwidth allocation in wireless networks. In wireless network where bandwidth is a scare resource, the system may need to block incoming user if all of the bandwidth has been used to provide highest quality of service to existing users. However this bandwidth resource planning may be unacceptable for larger application. A degradable approach to multiple users can be made on bandwidth allocation to reduce the blocking probability without degrading the quality of service to existing users.
This work aims towards a realization of a wireless/mobile network using W-CDMA multi access technique supporting multilevel quality of services. The bandwidth allocation to multiple users is adjusted dynamically according to the required network condition so as to increase bandwidth utilization. The work analyze the performance deriving the degradation period ratio, mean degradation time and degradation state for the implemented wireless network.The proposed work is aim to implement on Matlab tool for its functional verification considering various mobility patterns
A review over multimedia and how to share multimedia data between clients and servers.
Find me on:
AFCIT
http://www.afcit.xyz
YouTube
https://www.youtube.com/channel/UCuewOYbBXH5gwhfOrQOZOdw
Google Plus
https://plus.google.com/u/0/+AhmedGadIT
SlideShare
https://www.slideshare.net/AhmedGadFCIT
LinkedIn
https://www.linkedin.com/in/ahmedfgad/
ResearchGate
https://www.researchgate.net/profile/Ahmed_Gad13
Academia
https://www.academia.edu/
Google Scholar
https://scholar.google.com.eg/citations?user=r07tjocAAAAJ&hl=en
Mendelay
https://www.mendeley.com/profiles/ahmed-gad12/
ORCID
https://orcid.org/0000-0003-1978-8574
StackOverFlow
http://stackoverflow.com/users/5426539/ahmed-gad
Twitter
https://twitter.com/ahmedfgad
Facebook
https://www.facebook.com/ahmed.f.gadd
Pinterest
https://www.pinterest.com/ahmedfgad/
This template was created for DSCE, Aeronautical students. You have to replace the institution details.
Create a separate document for each chapter, so that under numbering, you can change the sequence of chapter main heading according to chapter wise. i.e., 2.1, 2.2 etc.
Same procedure is applicable to Figure caption and Table caption.
This template can be used to generate, BE seminar report, M.Tech and Ph.D thesis also.
This template is created to assist UG students in generating their thesis without much hassle.
Contents are taken from VTU website. I don’t hold any copyright for this document.
Hareesha N G
Assistant Professor
DSCE, Bengaluru
Wimax technology has reshaped the framework of broadband wireless internet
service. It provides the internet service to unconnected or detached areas such as east South
Africa, rural areas of America and Asia region. Full duplex helpers employed with one of
the relay stations selection and indexing method that is Randomized Distributed Space Time
are used to expand the coverage area of primary Wimax station. The basic problem was
identified at cell edge due to weather conditions (rain, fog), insertion of destruction because
of multiple paths in the same communication channel and due to interference created by
other users in that communication. It is impractical task for the receiver station to decode
the transmitted signal successfully at the cell edges, which increases the high packet loss and
retransmissions. But Wimax is a outstanding technology which is used for improving the
quality of internet service and also it offers various services like Voice over Internet
Protocol, Video conferencing and Multimedia broadcast etc where a little delay in packet
transmission can cause a big loss in the communication. Even setup and initialization of
another Wimax station nearer to each other is not a good alternate, where any mobile
station can easily handover to another base station if it gets a strong signal from other one.
But in rural areas, for few numbers of customers, installation of base station nearer to each
other is costlier task. In this review article, we present a scheme using R-DSTC technique to
choose and select helpers (relay nodes) randomly to expand the coverage area and help to
mobile station as a helper to provide secure communication with base station. In this work,
we use full duplex helpers for better utilization of bandwidth.
High performance browser networking ch5,6Seung-Bum Lee
Presentation material including summary of "High Performance Browser Networking" by Ilya Grigorik. This book includes very good summary of computer network not only for internet browsing but also multimedia streaming.
History, Basic concepts of wireless communication, challenges in wireless communication, cellular communication, performance criteria, wireless communication standars, how call is made?
MODULE III Parallel Processors and Memory Organization 15 Hours
Parallel Processors: Introduction to parallel processors, Concurrent access to memory and cache
coherency. Introduction to multicore architecture. Memory system design: semiconductor memory
technologies, memory organization. Memory interleaving, concept of hierarchical memory
organization, cache memory, cache size vs. block size, mapping functions, replacement
algorithms, write policies.
Case Study: Instruction sets of some common CPUs - Design of a simple hypothetical CPU- A
sequential Y86-64 design-Sun Ultra SPARC II pipeline structure
MODULE II Control unit, I/O systems and Pipelining 15 Hours
CPU control unit design: Hardwired and micro-programmed design approaches, Peripheral
devices and their characteristics: Input-output subsystems, I/O device interface, I/O transfersprogram controlled, interrupt driven and DMA, privileged and non-privileged instructions, software
interrupts and exceptions. Programs and processes-role of interrupts in process state transitions,
I/O device interfaces - SCII, USB. Basic concepts of pipelining, throughput and speedup, pipeline
hazards.
Functional Blocks of a Computer: Functional blocks and its operations. Instruction set architecture of a CPU - registers, instruction execution cycle, Data path, RTL interpretation of
instructions, instruction set. Performance metrics. Addressing modes. Data Representation:
Signed number representation, fixed and floating point representations, character representation.
Computer arithmetic - integer addition and subtraction, ripple carry adder, carry look-ahead
adder, etc. multiplication - shift-and add, Booth multiplier, carry save multiplier, etc. Division
restoring and non-restoring techniques, floating point arithmetic.
Module II - Distributed objects and file systems:
Introduction - Communication between distributed objects - Remote procedure call - Events and notifications - case study - Operating system support - introduction - operating system layer - protection - process and threads - communication and invocation - architecture - Introduction to DFS - File service architecture - Sun network file system - Andrew file system - Enhancements and future developments.
Module 2 - Distributed Objects and File Systems
Introduction - Communication between distributed objects - Remote procedure call - Events and notifications - case study - Operating system support - introduction - operating system layer - protection - process and threads - communication and invocation - architecture - Introduction to DFS - File service architecture - Sun network file system - Andrew file system - Enhancements and future developments.
Module I
Introduction to Distributed systems - Examples of distributed systems, resource sharing and the web, challenges - System model - introduction - architectural models - fundamental models - Introduction to inter-process communications - API for Internet protocol - external data.
Module I
Introduction to Distributed systems - Examples of distributed systems, resource sharing and the web, challenges - System model - introduction - architectural models - fundamental models - Introduction to inter-process communications - API for Internet protocol - external data.
Module 6: IP and System Security
IP security overview-IP security policy-Encapsulating Security payload-intruders-intrusion detectionvirus/worms-countermeasure-need for firewalls-firewall characteristics-types of fire
Module 4: Key Management and User Authentication
X.509 certificates- Public Key infrastructure-remote user authentication principles-remote user
authentication using symmetric and asymmetric encryption-Kerberos V5
Module 1: Introduction to Cryptography and Symmetric Key Ciphers
Computer Security Concepts - OSI Security Architecture -Security Attacks - Services, Mechanisms -
Symmetric Cipher Model - Traditional Block Cipher Structure - The Data Encryption Standard -The Strength of DES - Advanced Encryption Standard.
Module 6
Advanced Networking
Security problems with internet architecture, Introduction to Software defined networking, Working of SDN, SDN in data centre, SDN applications, Data centre networking, IoT.
Module 6: Standards for Information Security Management
Information Security Management Systems (ISMS) - ISO 27001 - Framing Security Policy of
Organization- Committees- Security Forum, Core Committee, Custodian and Users, Business
Continuity Process Team & Procedure- Information Security Auditing Process. IT Security Incidents
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
2. Unit - V
End to End QoS provisioning in Wireless
Multimedia Networks – Adaptive Framework
– MAC layer QoS enhancements in Wireless
Networks – A Hybrid MAC protocol for 10
Multimedia Traffic – Call Admission Control
in Wireless Multimedia Networks – A Global
QoS Management for Wireless Networks
3. The Two Successful Domains
• Wireless networks (Cellular)
–
–
–
–
Supports voice
Total coverage in many countries
Decreasing cost
The boon – user mobility
• Wireless extension to the Internet (Wi-Fi)
–
–
–
–
Information content
Supports multimedia services
Global penetration – millions of nodes
Decreasing cost
• IEEE 802.16 based WiMax
• LTE (Long Term Evolution)
4. General Problems in Wireless
Networks
• Resource scarcity
– Limited bandwidth
• Unreliable wireless link
– Error prone channels (BER 10-4 to 10-3)
• Varying channel conditions
– Channel models fluctuates
In spite of all these problems, voice services are well supported.
Can it support multimedia services?
5. Characteristics of Multimedia Services
A picture is worth thousand words
Combination of various medium – text, audio/video, graphics
– Audio/video conferencing, shared whiteboard, surfing, email, etc.
• Varied requirements
– Low bit error rate
– High bandwidth
– Low delay
• Synchronization of multiple data types
– Proper scheduling
• Different coding schemes for different types
– Source coding
6. Data on Wireless Networks!
What are the Problems?
• True characterization of data traffic is yet unknown
– Traffic modeling needs to be done
• Data services cannot tolerate bit errors
– Corrupt packets need to be recovered
• Unpredictable nature of wireless medium
– QoS provisioning becomes difficult
• Bottleneck due to the bandwidth limitation
– Proper buffering / filtering required
• No differentiated service plans for customers
– Class based services required
7. What is QoS?
Specified by <bandwidth, delay, reliability>
Ability of a network element (e.g. an application, host or router) to
have some level of assurance that its traffic and service requirements
can be satisfied
Predictable service for the traffic from the network
e.g., CPU time, bandwidth, buffer space
Acceptable end-to-end delay and minimum delay jitter
What is QoE (Quality of Experience)?
Human subjectivity associated with quality
How happy is a user with respect to the service he gets
8. End-to-End QoS
Requires cooperation of all network layers from top-to-bottom, as well as
every network element
Knowledge of application at end points decides QoS functions
implemented at every layer of the network protocol stack
Type of Services
- Best-effort: the Internet (lack of QoS)
- Differentiated service (soft QoS) : partial to some traffic but most
effective
- Guaranteed service (hard QoS) : absolute reservation of
resources (RSVP), more expensive
9. Wireless QoS Challenges
A limited spectral bandwidth to be shared, causes interference
Communication links are time varying, frequency selective channels
User mobility in wireless networks makes QoS provisioning complex
because routes from source to destination cells are different, thus causing
varying packet delays and delay jitters
Error rate of wireless channel is higher due to mobility, interference from
other media, multi-path fading. So mobile hosts may experience different
channel rates in the same or different cells
Different applications have different requirements for bandwidth, delay,
jitter (e.g., 9.6Kbps for voice and 76.8Kbps for packetized video)
10. Wireless QoS: Desirable Features
Adapt to dynamically changing network and traffic
conditions
Good performance for large networks and large number
of connections (like the Internet)
Higher data rate
Modest buffer requirement
Higher capacity utilization
Low overhead in header bits/packet
Low processing overhead/packet within network and end
system
11. Bandwidth Requirement for
Multimedia Traffic
Application bandwidth requirements on log-scale axis in bits per second
(bps)
Vertical dashed lines show the bandwidth capability of a few network
technologies
12. Multi-rate Traffic Scenario
Base Station
C channels
Mobile Users
Real-time traffic (voice, video)
Non real-time traffic (TCP/IP
packets)
13. Evolution of Wireless Data Networks
2G wireless systems ( voice-centric, data loss unimportant)
- IS-95 CDMA, TDMA, GSM
2.5G systems (voice and low data rate)
- CDPD, GPRS, HSCSD, IS-99 CDMA, IS-136+
- Date rates: CDPD (19.2Kbps), HSCSD (76.8Kbps), GPRS (114Kbps)
3G proposed standards (data-centric, high data rate)
- UMTS, EDGE, W-CDMA, cdma2000, UWC 136, IMT-2000
- Data rates: EDGE (384Kbps), cdma2000 (2Mbps), W-CDMA (10Mbps)
15. Cellular Framework
HLR
BSC MSC/VLR
MSC/VLRBSC
BTS
Cellular Network
Mobile
Terminal
Air Link
Local Switch
Terms to remember
MSC: Mobile Switching Center
VLR: Visiting Location Register
HLR: Home Location Register
BSC: Base Station Controller
BTS: Base Transmitter Station
Mobile Terminal
Air Link
BTS
PSTN Network
16. Cell: geometric representation of areas. Geographic area is divided into
cells, each serviced by an antenna called base station (BS)
Mobile Switching Center (MSC) controls several BSs and serves as
gateway to the backbone network (PSTN, ISDN, Internet)
WHY CHANNEL REUSE?
Limited number of frequency spectrum allocated by FCC and
remarkable growth of mobile (wireless) communication users
Frequency band allocated by FCC to the mobile telephone system is
824-849 MHz for transmission from mobiles (uplink) and 869-894
MHz for transmission from base stations (downlink)
With a channel spacing of 30 KHz, this frequency band can
accommodate 832 duplex channels
Frequency Reuse: use same carrier frequency or channel at different
areas (cells) avoiding co-channel interference
Number of simultaneous calls (capacity) greatly exceeds the total
number of frequencies (channels) allocated
17. Hand-off Problem
Hand-off is the process of switching from one frequency channel to
another by the user in midst of a communication
Normally induced by the quality of the ongoing communication
channel parameters: Received Signal Strength (RSS), Signal-to-Noise
Ratio (SNR) and Bit Error Rate (BER)
RSS attenuates due to the distance from BS, slow fading (shadow or
lognormal fading), and fast fading (Rayleigh fading)
Hand-offs are triggered either by the BS or the mobile station itself
BS-1
BS-2
19. Hand-off: Who Triggers?
The quality of the RSS from the mobile station is monitored by the BS.
When the RSS is below a certain threshold. BS instructs the mobile
station to collect signal strength measurements from neighboring BSs
Case 1: mobile station sends the collected information to the BS.
BS conveys the signal information to its parent MSC (mobile
switching center) which selects the most suitable next BS for the
mobile station
Both the selected BS and the mobile station are informed when new
BS assigns an unoccupied channel to the mobile station
Case 2: mobile station itself selects the most suitable BS.
The mobile station informs the current BS, who conveys information
about the next BS to its MSC
The selected BS is informed by the MSC which assigns a new channel
20. Hand-off Policies
BS handles hand-off requests in the same manner as originating calls
- Disadvantage: Ignores the fact an ongoing call has higher priority for a new
channel than originating calls
- Solution: Prioritize hand-off channel assignment at the expense of tolerable
increase in call blocking probability
Guard channel concepts (Prioritizing Handoffs)
- Reserve some channels exclusively for hand-offs. Remaining channels shared
equally between hand-offs and originating calls
- For fixed assignment. Each cell has a set of guard channels. While for dynamic
assignment, channels are assigned during hand-off from a central pool
- Disadvantages:
-- Penalty in reduction of total carried traffic. Since fewer channels are available for
originating calls. Can be partially solved by queuing up blocked originating calls
-- Insufficient spectrum utilization – need to evaluate an optimum number of guard
channels.
21. Capacity Improvement and Interference Reduction
There is a close correspondence between the network capacity
(expressed by N) and the interference conditions (expressed by C/I)
Cell sectoring reduces the interference by reducing the number of co-
channel interferers that each cell is exposed to. For example, for 60
degrees sectorization, only one interferer is present, compared to 6 in
omnidirectional antennas. But, cell sectorization also splits the channel
sets into smaller groups
Cell splitting allows to create more smaller cells. Thus, the same
number of channels is used for smaller area. For the same probability
of blocking, more users could be allocated
24. View point
• IEEE 802.11 experiences serious challenges in
meeting the demands of multimedia services and
applications.
• IEEE 802.11e standard support quality of service at
MAC layer.
• The viewpoint
– 802.11 QoS schemes
– 802.11e
25. Introduction(1/2)
• WLANs are becoming ubiquitous and increasingly
relied on 802.11
• Wireless users can access real-time and Internet
services virtually anytime, anywhere.
• In wireless home and office networks, QoS and
multimedia support are critical.
• QoS and multimedia support are essential ingredients
to offer VOD audio on demand and high-speed
Internet access.
26. Introduction(2/2)
• The lack of a built-in mechanism for support of real
time services makes it difficult to provide QoS
guaranteed for throughput-sensitive and delaysensitive multimedia applications.
• IEEE 802.11e is being proposed as the upcoming
standard for the enhancement of the vice
differentiation.
27. An Overview of IEEE 802.11
Task Group
Responsibility
802.11a—OFDM 5GHz
54Mbs
802.11b—HR/DSSS 2.4GHz
22Mbs
802.11c—Bridge Operation Procedures
Bridge
802.11d—Global Harmonization
Additional regulatory domains
802.11e—MAC Enhancements for QoS
EDCF
802.11f—Inter Access Point Protocol
Interoperability
802.11g—OFDM 2.4GHz
36/54Mbs
802.11h—DFS
Dynamic channel selection
802.11i—security
WEP
HCF
29. 802.11MAC (2/4)
• Distributed Coordination Function (DCF)
– Defines a basic access mechanism and optional RTS/CTS
mechanism.
– Shall be implemented in all stations and APs.
– Used within both ad hoc and infrastructure configurations.
• Point Coordination Function (PCF)
– An alternative access method
– Shall be implemented on top of the DCF
– A point coordinator (polling master) is used to determine which
station currently has the right to transmit.
– Shall be built up from the DCF through the use of an access
priority mechanism
30. 802.11MAC (3/4)
• Different accesses to medium can be defined through the use of
different values of IFS (inter-frame space).
– PCF IFS (PIFS) < DCF IFS (DIFS)
– PCF traffic should have higher priority to access the medium, to
provide a contention-free access.
– This PIFS allows the PC (point coordinator) to seize control of the
medium away from the other stations.
• Coexistence of DCF and PCF
– DCF and PCF can coexist through superframe.
– superframe: a contention-free period followed by a contention
period.
超級訊框
免競爭訊框
需競爭訊框
32. Distributed Coordination Function (1/3)
• Allows sharing of medium between PHYs through
– CSMA/CA
– random backoff following a busy medium.
• All packets should be acknowledged (through ACK
frame) immediately and positively.
– Retransmission should be scheduled immediately
if no ACK is received.
33. Distributed Coordination Function (2/3)
• Carrier Sense shall be performed through 2 ways:
– physical carrier sensing: provided by the PHY
– virtual carrier sensing: provided by MAC
• by sending medium reservation through RTS and CTS frames
– duration field in these frames
• The use of RTS/CTS is under control of RTS_Threshold.
• An NAV (Net Allocation Vector) is calculated to estimate the
amount of medium busy time in the future.
• Requirements on STAs:
– can receive any frame transmitted on a given set of rates
– can transmit in at least one of these rates
– This assures that the Virtual Carrier Sense mechanism work on
multiple-rate environments
34. Distributed Coordination Function (3/3)
• MAC-Level ACKs
– Frames that should be ACKed:
• Data
• Poll
• Request
• Response
– An ACK shall be returned immediately following a successfully
received frame.
– After receiving a frame, an ACK shall be sent after SIFS (Short
IFS).
• SIFS < PIFS < DIFS
• So ACK has the highest priority
35. DCF: the Random Backoff Time (1/2)
• Before transmitting asynchronous MPDUs, a STA shall use the
CS function to determine the medium state.
• If idle, the STA
– defer a DIFS gap
– transmit MPDU
• If busy, the STA
– defer a DIFS gap
– then generate a random backoff period (within the
contention window CW) for an additional deferral time to
resolve contention.
36. DCF: the Random Backoff Time (2/2)
Backoff time = CW* Random() * Slot time
where CW = starts at CWmin, and doubles after each failure
until reaching CWmax and remains there in
all remaining retries
CWmax
(e.g., CWmin = 7, CWmax = 255)
Random() = (0,1)
Slot Time = Transmitter turn-on delay +
medium propagation delay +
medium busy detect response time
255 255
8
127
63
31
15
CWmin
7
第三次重送
初始值
第二次重送
第一次重送
37. Duration Reservation Strategy (1/2)
• Each Fragment and ACK acts as a “virtual” RTS and
CTS for the next fragment.
• The duration field in the data and ACK specifies the
total duration of the next fragment and ACK.
• The last fragment and ACK will have the duration set
to zero.
38. Duration Reservation Strategy (2/2)
• Goal of fragmentation:
– shorter frames are less suspectable to transmission
errors, especially under bad channel conditions
39. Point Coordination Function (1/6)
• The PCF provides contention-free services.
• One STA will serve as the Point Coordinator (PC), which
is responsible of generating the Superframe (SF).
– The SF starts with a beacon and consists of a
Contention Free period and a Contention Period.
– The length of a SF is a manageable parameter and that
of the CF period may be variable on a per SF basis.
• There is one PC per BSS.
– This is an option; it is not necessary that all stations are
capable of transmitting PCF data frames
40. Point Coordination Function (2/6)
• The PC first waits for a PIFS period.
– PC sends a data frame (CF-Down) with the CF-Poll
Subtype bit = 1, to the next station on the polling list.
– When a STA is polled, if there is a data frame (CF-Up) in
its queue, the frame is sent after SIFS with CF-Poll bit = 1.
– Then after another SIFS, the CF polls the next STA.
– This results in a burst of CF traffic.
– To end the CF period, a CF-End frame is sent.
41. Point Coordination Function (3/6)
• If a polled STA has nothing to send, after PIFS the PC will poll
the next STA.
• NAV setup:
– Each STA should preset it’s NAV to the maximum CFPeriod Length at the beginning of every SF.
– On receiving the PC’s CF-End frame, the NAV can be reset
(thus may terminate the CF period earlier).
42. Point Coordination Function (4/6)
超級訊框
免競爭週期
PIFS
媒介忙碌中
CF-D1
CF-D2
CF-U1
SIFS
競爭週期
PIFS
SIFS
SIFS
CF-D3
SIFS
CF-D4
CF-U2
SIFS
Dx = Down Traffic
Ux = Up Traffic
CF-U4
SIFS
NAV
CF-End
重設 NAV
CF-邊界
43. Point Coordination Function (5/6)
• When the PC is neither a transmitter nor a recipient:
– When the polled STA hears the CF-Down:
• It may send a Data frame to any STA in the BSS after an
SIFS period.
• The recipient (.neq. PC) of the Data frame returns an
ACK after SIFS.
– Then PC transmits the next CF-Down after an SIFS period
after the ACK frame.
• If no ACK is heard, the next poll will start after a PIFS
period
44. Point Coordination Function (6/6)
超級訊框
免競爭週期
競爭週期
PIFS
媒介忙碌中
SIFS
SIFS
CF-D1
CF-D2
S-To-S
SIFS
CF-End
ACK
CF-U2
SIFS
SIFS
NAV
Dx = Down Traffic
Ux = Up Traffic
重設 NAV
CF-邊界
45. QoS Mechanisms
• QoS mechanisms for 802.11 can be classified into three
categories:
– Service differentiation
– Admission control and bandwidth reservation
– Link adaptation
46. BETTER THAN BEST EFFORT SCHEMES:
SERVICE DIFFERENTIATION (1/3)
• Enhanced DCF (EDCF)
– prioritizes traffic categories by different contention parameters,
including
• arbitrary interframe space (AIFS),
• maximum and minimum backoff window size
• (CWmax/min), and a multiplication factor for expanding the
backoff window.
• Persistent Factor DCF (P-DCF)
– each traffic class is associated with a persistent factor P
– a uniformly distributed random number r is generated in every slot
time
– Each flow stops the backoff and starts transmission only if (r > P)
47. BETTER THAN BEST EFFORT SCHEMES:
SERVICE DIFFERENTIATION (2/3)
• Distributed Weighted Fair Queue (DWFQ)
– the backoff window size CW of any traffic flow is adjusted based
on the difference between the actual and expected throughputs.
– a ratio (Li′ = Ri/Wi) is calculated, where Ri is the actual throughput
and Wi the corresponding weight of the ith station.
• Distributed Fair Scheduling (DFS)
– differentiate thebackoff interval (BI) based on the packet length
and traffic class
– For the ith flow, BIi = ρi × scaling × factor × Li/ϕi,
• Distributed Deficit Round Robin (DDRR)
– the ith throughput class at the jth station is assigned with a service
quantum rate (Qi,j) equal to the throughput it requires
51. QOS MECHANISM FOR LINK
ADAPTATION (1/2)
•
•
•
•
•
Received signal strength (RSS)
PER-prediction
MPDU-based link adaptation
Link adaptation with success/fail (S/F) thresholds
Code Adapts To Enhance Reliability (CATER)
56. DISTRIBUTED ADMISSION CONTROL
FOR EDCF
• TXOPBudget[i]
=Max(ATL[i] – TxTime[i]*SurplusFactor[i],0)
• If TXOPBudget[i] = 0
–TxMemory[i] shall be set to zero
all other QSTAs TxMemory[i] remains unchanged
• If the TXOPBudget[i] >0
–TxMemory[i] = f*TxMemory[i] + (1 – f)*
(TxCounter[i]*SurplusFactor[i] + TXOPBudget[i])
–TxCounter[i] = 0
–TxLimit[i] = TxMemory[i] + TxRemainder[i]
57. THE CONTROLLED HCF
• Controlled channel access function
• allows reservation of transmission opportunities
(TXOPs) with a hybrid coordinator (HC)
• a type of PC handling rules defined by the HCF
58. ADMISSION CONTROL AND
SCHEDULING FOR THE CONTROLLED HCF
• The behavior of the scheduler is as follows:
– The scheduler shall be implemented
– if a traffic stream is admitted by the HC, the scheduler shall
send polls anywhere between the minimum service interval
and the maximum service interval within the specification
interval.