Cellular wireless technologies have made significant popular impact and have been incorporated into university curriculums. However wireless local area networks (WLANs) based on IEEE 802.11 standards and popularly known as WiFi have captured the mindshare of all. The IEEE 802.11 standards have successfully leveraged key concepts in wireless like MIMO, OFDM/OFDMA/MU-MIMO amongst among many others to give users high-speed connectivity at home and other indoor areas. In this course, we shall look at the use of such key technologies in the latest generation of WiFi systems. Hands on exercises will be on real-life captures which will enable linking of the concepts with real-life happenings.
Module 1: Wi-Fi Overview(3 – 4 hours)
Objective: To understand basics of WLAN systems including standardizing bodies, unlicensed spectrum ranges, network types.To know the various specialized terminology used in the WLAN area and get an idea of the various components of a WiFi product. Appreciate the differences between cellular and WiFi and their evolutions.
- Wi-FI Overview
- IEEE 802.11 standards and its role
- WFA and its role; interoperability and certification
- Relationship between 802.11 and Wi-Fi
- Wi-Fi networks; BSS/IBSS/P2P/mesh
- BSS, IBSS, ESS, DS, BSSID, SSID, MBSS
- Typical evolution of the Wi-Fi AP along with the ecosystem
- Important chipset players
- ODMs
- Breakup of solution; software, hardware, and firmware
- Role of open-source solutions like openWRT
- Wi-Fi direct vs. ad-hoc networks ; differences
- Mesh and WDS; what is the need?
- IEEE 802.11 set of standards and their evolution
- Speeds and bandwidths
- Key technologies; OFDM, MIMO, and their impacts
- Upcoming standards; new technologies like OFDMA
- Spectrum of operation
- Security, QoS, and other features evolution
- WLAN deployment scenarios; home vs. hotspot vs. service provider vs. enterprise
- Wi-Fi product space; a survey of some interesting features
- Wi-Fi and IOT; link with BLE and ZigBee/Thread
- 802.11ba; Wi-Fi Wakeup radio and its impacts
- Wi-Fi and voice ; Wi-Fi calling
- Wi-Fi and LTE unlicensed
- 802.11ad/ay; 60 GHz Wi-Fi status
- Future of Wi-Fi; multiband optimization, optimized connectivity and other initiatives
Module 2: Wi-Fi PHY. Layer Basics (9 hours)
Objective: Appreciate physical layer challenges and solutions in 802.11 standards and be able to simulate channel conditions. Understand the evolution of the physical layer in different generations of 802.11 standards and be able to calculate PHY. Rates in different scenarios.
- Challenges; the channel environment
- Problems with high data rate communication
- Role of PHY. Layer in 802.11
- 2.4 and 5 GHz channels ; 20/40/80/160 MHz bandwidth operations
- Power of Wi-Fi; use of dBs, dBms, dBi
- DFS; Why and some rules
- Modulation and error control coding; MCS
- PHY. layer technology evolution; 802.11/11b/11a/11g/11n/11ac/11ax
- OFDM fundamentals
- Subcarrier spacing, OFDM symbol period, cyclic prefix
- Calculation of PHY. Data rate and its implication
- OFDM in 802.11..evolution and calculations
- MIMO basics
- Differences between diversity, spatial multiplexing, and STBC
- Costs of MIMO
- Spatial streams ; product and link configurations and their impacts
- Data rate calculations; different rates of operation in a Wi-Fi network
- Receive sensitivity
- Beamforming
- Differences with STBC
- Feedback steps
- MU-MIMO
- How is it different to normal MIMO
- Advantages
- Links with beamforming
- Future of the PHY in 802.11
- OFDMA
- MU-MIMO enhancements
Module 3: WiFI Medium Access Control – Fundamentals (9 hours)
Objective: Be able to explain MAC layer steps in WLAN. Understand the application fo CSMA/CA along with the impacts on throughput and coexistence. Appreciate the evolution of the MAC layer using ideas like frame aggregation.
- Role of MAC, interactions with other layers
- Terminology ; MSDU/MPDU, header, FCS
- DCF Protocol in WLAN
- CSMA/CA – Role of PHY in CCA
- DCF parameters; DIFS/SIFS, slot time
- Basic DCF frame exchange
- Hidden node problems
- RTS/CTS/CTS-Self; virtual carrier sensing, NAV concepts
- MAC frame formats; types of frames, frame headers
- Basic DCF throughput analysis
- QoS in WLANs ; EDCF
- MAC layer aspects of 802.11n
- Frame aggregation and its impact
- A-MSDU and A-MPDU
- TCP/IP and UDP/IP throughput impact with aggregation
- MAC frame impacts with frame aggregation
- Block Acknowledgement and TXoP
- MAC layer enhancements in 802.11ac
- Impact of MAC and PHY on performance
Module4: Wi-Fi PHY/MAC operations basics (6 hours)
Objective: To understand how a client discovers and connects to an AP. Understand key steps of scanning, association, rate adaptation principles amongst other things.
- Beacons
- Quick recap of Wi-Fi protocol and capabilities understanding
- Network Entry Process – Active and Passive Scanning
- Scanning behavior of STAs
- Active and passive scanning
- Challenges and practical aspects of probing in different scenarios
- Typical WiFi state machine steps
- Authentication, association, and security basics
- WiFi data transfer basics
- Rate adaptation
- Virtual APs
- Evolution of power save techniques (Legacy, WMM , and SM power save)
Module 5: WiFi Security (6 hours)
Objective: Clearly understand the challenges and the various evolutions of WiFi security including the latest. Appreciate the differences between home and enterprise security along with an understanding of vulnerabilities at each step.
- Basics of Network Security
- Confidentiality, Integrity and Authentication
- WiFi Security Evolution – big picture
- Introduction to WLAN Security
- WEP – Encapsulation & Decapsulation
- WEP failure
- 802.11i – WPA and WPA2
- Home and enterprise security differences
- Security keys in WLAN – PMK/PTK
- Basic steps in encryption and integrity protection, role of PNs
- Replay attacks and Krack attack fundamentals
- Understanding WPA/WPA2 PSK through traces
- Security capabilities from beacons and probe responses
- 4-way handshakes – concepts and traces
- Enterprise case with roaming
- Home case roaming
- WPA3 SAE
- Problems with WPA2 PSK
- How does WPA3 SAE solve it?
- Capabilities in Beacons
- Steps and traces
- OWE
- Why is OWE needed
- Steps
- DPP basics
Module 6: WiFi Mobility (3 hours)
Objective: We shall focus on the various mobility and roaming aspects of WiFi. We shall start with the challenges and context of WiFi mobility and outline the various approaches followed. We shall then outline 802.11r and the detailed steps with an example using real-life traces. We shall also discuss passpoint and the recent open roaming initiative.
- WiFi mobility; the context and the backdrop
- Wi-Fi roaming without 11r; various initiatives like PMK caching, OKC, etc.
- 802.11r basics
- How does it reduce roaming delays
- Capability and initial network entry steps
- Steps during roaming
- Trace analysis with and without 11r
- 11r related capabilities exchange
- Concepts of mobility domain and FT authentication
- Impact of 11r on roaming performance
- Use of 11k and its impacts
- 11k related capabilities
- Neighbour request messages
- 11v BSS Transition management and its impacts
- 11v capabilities
- 802.11u concepts ; relation HS 2.0 and passpoint and its evolutions
- Where does passpoint help
- What is openroaming?
Module 7: WiFi6/802.11ax Technology (6 hours)
Objective: This course shall address all aspects of WiFi6 technology. Various new techniques like OFDMA and enhancements to MU-MIMO introduced in the IEEE 802.11ax standard will be discussed thoroughly.
- Key technologies in Wi-Fi 6; what problems do they solve?
- Inside OFDMA in Wi-Fi 6
- All about OFDMA RUs; what is allowed?
- How is it handled on DL and UL?
- Unique challenges of UL OFDMA; how are timing, power, and other issues sorted out amongst multiple transmitters
- How is multiuser allocation communicated on the DL and UL?
- MU-MIMO differences between Wi-Fi 6 and earlier generation
- DL MU-MIMO and UL MU-MIMO differences
- DL MU-MIMO in 11ac and 11ax
- Common aspects in MU-MIMO and OFDMA
- Differences between OFDMA and MU-MIMO; when to use what?
- Supporting aspects for multiuser communications
- Triger frames for UL multiuser communications scheduling
- ACK handling mechanisms for DL and UL
- MU-RTS , buffer status handling steps
- Data rate improvements ; 1024 QAM and OFDM efficiencies; comparisons with 11ac
- Enhancements for the IOT world
- 20 MHz only operation; how can it potentially coexist with other STAs
- TWT; how does it help in power save?
- Spatial reuse
- How does it help in solving high density problems
- BSS colour, SRGs, what are they?
- Some results from simulations
- What is happening today in the 11ax product world
- What features are we seeing being used?
- Where are the challenges?
- What are next features likely to come to market
- Sniffing WiFi 6; why is it difficult? Some sample traces
Srikanth obtained his B.E., degree from College of Engineering, Anna University, Chennai, and M. A.Sc, and Ph. D. degrees from University of Victoria, British Columbia, Canada. He is currently the Chief Knowledge Officer for Nanocell Networks Pvt. Ltd.. Srikanth began his career as a research associate at the University of Victoria, British Columbia, Canada working in the area of DSL and CDMA Systems. After his Ph. D., he joined Harris Corporation and worked on baseband algorithms for various wireless standards including IS-136 and 1S-95 systems. He then joined the KBC Research Foundation/AU-KBC Research Centre and he has focused on OFDM systems for powerline and wireless applications. From 2004-2007 he was awarded a Young Scientist Fellowship by the Government of India to work on technologies related to upgrades on 802.11 and 802.16 standards. He has been following 802.11 and cellular standards and delivers several courses to corporate clients in this area. He consults on various areas and has also been involved in the setting up of a test lab for 802.11. He is also involved with the organization of WiFi and 5G knowledge summits to help develop a community for exchange of technical information in these areas.
Text Books
- Eldad Perahia and Robert Stacey, Next Generation wireless LANS 802.11n and 802.11ac, 2nd edition, Cambridge University Press, 2013
- Mathew Gast, 802.11 Wireless Networks: The Definitive Guide, 2nd Edition, OReily, 2009
Reference Books
- Mathew Gast, 802.11n: A Survival Guide: Wi-Fi Above 100 Mbps, OReilly, 2012
- Mathew Gast, 802.11ac: A Survival Guide: Wi-Fi at Gigabit and Beyond, OReilly, 2012