Bluetooth Vs 802.11b: stateoftheart and research challenges

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Bluetooth Vs 802.11b state-of-the-art and
research challenges

• Pravin Bhagwat
• ReefEdge, Inc.
• pravin_at_reefedge.com
• http//www.winlab.rutgers.edu/pravin

Workshop on Ad hoc networking IISc Bangalore Jan
22, 2002
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Emerging Landscape
Who will be the winner ?
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Two options 802.11 and Bluetooth
Bluetooth
802.11
Cordless headset
Access Point
Designed for wired Ethernet replacement
Designed for cable replacement
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Bluetooth Specifications
Applications
SDP
RFCOMM
Audio
L2CAP
Link Manager
Baseband
RF

• A hardware/software/protocol description
• An application framework

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802.11 Specifications
Applications
LLC
MAC Mgmt
WEP
MAC
MIB
PHY
DSSS
FH
IR
OFDM

• Specification of layers below LLC
• Associated management/control interfaces

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Bluetooth Vs. 802.11
Applications
IP
SDP
RFCOMM
WEP
MAC Mgmt
MAC
MIB
L2CAP
Audio
Link Manager
PHY
Baseband
DSSS
FH
IR
OFDM
RF

• Bluetooth is a (top down) market driven
  consortium
• Business interests take precedence over other
  considerations
• Designed primarily for voice data an
  afterthought
• 802.11 is a (bottom up) open standard effort
• Designed primarily for data voice an
  afterthought
• Good piece of engineering except for WEP

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Comparison Axes
Application
Network
Link
Radio
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Unlicensed Radio Spectrum
?
12cm
5cm
33cm
26 Mhz
83.5 Mhz
200 Mhz
902 Mhz
2.4 Ghz
5.15 Ghz
2.4835 Ghz
5.35 Ghz
928 Mhz
802.11b Bluetooth Microwave oven
802.11a
cordless phones baby monitors Wireless LANs
Spectrum is free, but the right of way is not free
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CMUs spectrum sharing policy

• Computing Services will approach the shared
  use of the 2.4 GHz radio frequency in the same
  way that it manages the shared use of the wired
  network. While we will not actively monitor use
  of the airspace for potential interfering
  devices, we will seek out the user of a specific
  device if we find that it is actually causing
  interference and disrupting the campus network.
  In these cases, Computing Services reserves the
  right to restrict the use of all 2.4 GHz radio
  devices in university-owned buildings and all
  outdoor spaces on the Carnegie Mellon Campus.
• http//www.cmu.edu/computing/wireless/airspace
  .html

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Spectrum War Status today
Enterprise 802.11 Network
Public 802.11
Wireless Carrier
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Spectrum War Next phase of evolution
Enterprise 802.11 Network
Public 802.11
Wireless Carrier

• Market consolidation
• Entry of Wireless Carriers
• Entry of new players
• Footprint growth

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Spectrum War Eventual Steady State
Enterprise 802.11 Network
Public 802.11
Wireless Carrier
Virtual Carrier

• Emergence of virtual carriers
• Roaming agreements

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Comparison Axes
Application
Network
Link
Radio
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Design considerations
Noise, interference
power
spectrum
Recovered data signal
Data signal x(t)
cost
Goal

• high bandwidth
• conserve battery power
• cost lt 10

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Bluetooth Radio

• Low Cost
• Single chip radio (minimize external components)
• Todays technology
• Time division duplex

• Low Power
• Standby modes Sniff, Hold, Park
• Low voltage RF

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Radio architecture 802.11b
SiGe or GaAs
CMOS
Analog
Digital
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Radio architecture Bluetooth
CMOS
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Receiver sensitivity range of comm.
100 mW
30 mW
1 mW
802.11
BT
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Radio cost, power, range tradeoff
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Comparison Axes
Application
Network
Link
Radio
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Bluetooth Physical link

• Point to point link
• master - slave relationship
• radios can function as masters or slaves

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802.11 Architecture
Basic Service Set (BSS) a set of stations which
communicate with one another
Independent Basic Service Set (IBSS)

• only direct communication possible
• no relay function

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Extended Service Set
ESS a set of BSSs interconnected by a
distribution system (DS)

• ESS and all of its stations appear to be a single
  MAC layer
• AP communicate among themselves to forward
  traffic
• Station mobility within an ESS is invisible to
  the higher layers

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Bluetooth MAC Layer
m
s1
s2
625 ?sec
1600 hops/sec
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802.11 - MAC layer

• Priorities
• defined through different inter frame spaces
• no guaranteed, hard priorities
• SIFS (Short Inter Frame Spacing)
• highest priority, for ACK, CTS, polling response
• PIFS (PCF IFS)
• medium priority, for time-bounded service using
  PCF
• DIFS (DCF, Distributed Coordination Function IFS)
• lowest priority, for asynchronous data service

DIFS
DIFS
PIFS
SIFS
medium busy
next frame
contention
t
direct access if medium is free ? DIFS
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Physical Link Types

• Synchronous Connection Oriented (SCO) Link
• slot reservation at fixed intervals

• Asynchronous Connection-less (ACL) Link
• Polling access method

m
s1
s2
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Bluetooth Vs. 802.11 MAC issues
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Comparison Axes
Application
Network
Link
Radio
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The Connectivity Problem
Internet
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Basic network access issues
Accounting
Access Control
Authentication
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802.11 security design goals
Accounting
Access Control
Authentication
Unfortunately, WEP fails on all three counts
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Comparison Axes
Application
Network
Link
Radio
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Market drivers Mobile Business Users
Traveling
Inside office
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Indian Market ?

• Benefits
• Low cost method of expanding telephony services
• PCOs can offer in-bound call service
• Portability
• Additional revenue stream via offering Internet
  access
• Unlimited potential for offering value-added
  services

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Internet Access in Rural India
Internet
Metro
10 Km
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Mobile Telephony on IITK Campus
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Biggest challenges facing Bluetooth

• Interoperability
• Always a challenge for any new technology
• Hyped up expectations
• Out of the box ease of use
• Cost target 5
• Critical mass
• RF in silicon

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802.11 current status
LLC
MAC Mgmt
WEP
MAC
MIB
PHY
FH
IR
DSSS
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Bluetooth Vs. 802.11 Market issues
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Concluding remarks

• Will Bluetooth survive?
• Bluetooth is ideal for cable replacement
• Initial applications of Bluetooth will exploit
  its point-to-point or point-to-multipoint
  connectivity feature
• Attempts to turn it into a LAN technology will
  fail
• Multi-hop over Bluetooth is a challenging
  research problem
• Higher chance of success in Europe and Asia
• 802.11
• Will continue to grow in
• Public spaces, home, industry vertical, and
  enterprise market
• 802.11 will provide a viable alternative to 3G in
  public places
• Offers a great promise for bringing low cost
  networking services to the Indian mass market