Introduction of IEEE P802.11
Prepared by Vic Hayes, Chair, AT&T
Utrecht, the Netherlands

Representation
•	For the Frequency Hopping medium
–	Peter Chadwick, G3RZP
•	GEC Plessey Semiconductors, Inc
•	Wiltshire, United Kingdom
–	Naftali Chayat
•	BreezeCom
•	Tel Aviv, Israel
•	For the Direct Sequence medium
–	Don Sloan
•	Aironet Wireless Communications Inc.
•	Akron, Ohio
Outline
•	Organization
–	IEEE P802
–	IEEE P802.11
•	Functional requirements
•	Physical layers
•	Medium AccessControl
IEEE PROJECT 802
•	Local and Metropolitan Standards Committee (LMSC)
•	Formed in 1980
•	Sponsored by the Computer Society
–	Largest of 35 Societies
•	Local Area Networks (LANs)
–	The only LAN standards development organization
•	8 Standards adopted as International Standard by ISO/IEC
–	International Standards Organization and International Electrical Committee
•	Metropolitan Area Networks
•	Over 450 Voting Members, over 600 Observers
•	11 Working Groups, 2 Technical Advisory Groups
802.1 through 802.14
IEEE PROJECT 802 
•	Local Area Network - Definition
–	Moderate to high signalling rate
•	> 1 Mbit/s
–	Moderately sized geographic area
•	Room  to campus size
–	Generally owned, used and operated by single user
•	In contrast to wide area networks
–	Common shared medium
IEEE Project 802.11
•	Wireless Local Area Networks Standards Working Group
•	Established July 1990
•	Membership
–	79 voting members, 28 aspirant voting members 
–	Membership is by individual, not by company
–	Complete mailing list with over 180 addresses
•	USA, Canada, Europe, Israel, Japan, Korea, Taiwan
–	Manufacturers
•	Computers
•	Micro-electronics
•	Infra-red
•	Radio equipment
–	Users
•	Government
•	Manufacturers
802.11 Functional requirements
•	Requirements study showed two types of networking needs:
–	asynchronous, that is bursty traffic, but when something to send: need for very fast delivery
–	isochronous, that is regular traffic, in small amounts at a time, but at a constant pace
•	Therefore 802.11 adopted the following requirements:
–	Asynchronous MSDU delivery on all stations
•	MSDU is the MAC Service Data Unit
–	Optionally "time-bound MSDU delivery service"
•	Pedestrian speed and vehicular speed	
–	premises environment
•	Security: first review 802.10 provisions
•	Common MAC to support various PHYs
–	regulation dependency
Computer Architecture
Multiple PHYs
802.11, MAC: Basics
•	“Distributed Medium Access Control Protocol” using an Ethernet like CSMA/CA + Ack scheme.
–	Collision “Avoidance” rather then a “Detection” scheme.
•	Effectiveness demonstrated in Wavelan product.
–	Allows MAC level recovery of “Lost Packet” using a retransmission algorithm.
–	Includes provisions to deal with “Hidden Nodes”.
802.11, MAC: Performance 
•	Efficient and stable throughput.
–	Example: Based on 2 Mbps Wavelan speed.
802.11, MAC: Other Functions
•	Roaming through the Wireless Infrastructure
–	Maintain Continuous connectivity 
–	Station will “Re-Associate” with Access Points based on “Signal / Link Quality”.
–	Support multi channel roaming.
–	“Distribution System” will adapt to logical location changes of the station.
•	Provisions to use minimum Battery Power
–	Strategy: Switch nodes off as much as possible, while maintaining network configuration.
–	Traffic buffering functions are included in the Access Point to support this.
•	“Wired Equivalent Privacy” encryption algorithm is included.
802.11, PHY, Radio
•	Concentrate radio work on the 2.4 GHz band (ISM)
–	Most promising globally	Spread Spectrum required
•	Also allowed to start work in 1.9, 5.2 and 5.8 GHz bands
–	no activity yet
Direct Sequence Spread Spectrum
•	Direct Sequence uses an 11 chip Barker Sequence to multiply the transmitted data
•	Receiver divides received signal by same Sequence to recover the data
–	narrow band interference deminished
–	implementations can resolve multipath in the correlation
•	modulation of 2 Mbit/s in DQPSK (Differential Quaternary Phase Shift Keying)
•	fall back modulation of 1 Mbit/s in DBPSK (Differential Binary PSK)
•	3 channel pairs for USA
•	3 channel pairs for Europe (1 pair with single channel)
•	1 channel for Japan
Frequency Hopping Spread Spectrum
•	Frequency Hopping uses one of out 79 channels at a time
•	hops from one frequency channel to the next at a 2.5 hops/s
–	3 sets of 22 hop sequences defined
•	modulation for 1 Mbit/s in 2 level GFSK (Gaussian Frequency Shift Keying)
•	modulation for 2 Mbit/s in 4 level GFSK, channel permitting
802.11, PHY, Infra-Red
•	Modulation for 1 Mbit/s (basic rate) in 16-PPM (Pulse Position Modulation)
•	Modulation for 2 Mbit/s (enhanced rate) in 4 -PPM
•	Transmitter illuminates the ceiling with a diffuse 
Status
•	Second draft ballot conducted
•	47.5 % approval (75 % required, unanimous preferred)
–	31 (17) approving
–	33 (66) 	disapproving
–	  5 (11) 	abstaining
•	Resolving negative votes at November/January meeting 
•	Second draft sent to ISO annexed to a Proposed New Work Item
IEEE P802.11 schedule
•	 	WG Confirmation ballot Jan/Feb 1995
•	 	Resolve issues at March 1996 meeting
•	 Sponsor Ballot Mar/Apr1996
•	 	Resolve issues at May 1996 meeting
•	 	Sponsor Confirmation ballot Jun 1996
•	 Resolve issues at July 1996 meeting
•	 	Standards Board meeting September 17-18, 1996