CH4 Wireless Local Area Networks in wireless communication.pptx

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Wireless Local Area Networks
Chapter 4:
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Outlines
 WLAN overview
 IEEE 802.11 (WLAN) Standard
 HiperLAN
 WPAN Overview
 IEEE 802.15 (WPAN) Standards
 Wireless Sensor Networks and Zigbees

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WLANs Overview
WLANs:
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allow mobile devices in a small area (around 100 meters)
to communicate with each other
The WLAN devices communicate with each other by using
special cards that transmit and receive information over
wireless media.
They are cheap and flexible for users
The first generation of WLAN products, such as Lucent’s
WaveLAN, provided data rates of about 1-2 Mbps – a factor
of 10 slower than the traditional Ethernet
Most of the current generation of wireless LANs offer 10-11
Mbps (with some approaching 54 Mbps) – still a factor of 2
to 10 times slower than the 100 Mbps of wired Ethernet
Each mobile device in the wireless LAN has a wireless LAN
adapter (in fact a radio transmitter/receiver) that operates
in certain frequency ranges.

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WLANs Overview
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 Access point (local bridge): provide connectivity to wired
network.
 The access point (AP) can be connected to a wired LAN or
to any other type of network for access to corporate
databases and/or to the Internet
 The mobile devices connect to the AP when they are in the
range of the AP – a cell that may span 10 to 100 meters.
 Once connected to the AP, the mobile devices can
communicate with other devices in the cell or other
resources through the AP.

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WLANs Overview
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Fig. A simple wireless LAN configuration

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Benefits of WLANs are:
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Flexibility: allows the users to roam around a
building with their laptops. This is particularly useful
for wireless Internet access
Improvements in Productivity: provide LAN users
with access to real-time information anywhere in
their organization
Installation Speed and Simplicity: they eliminate
the need to pull cable through walls and ceilings.
Reduced Cost: lower overall installation cost
Scalability: Wireless LANs can be configured in a
variety of topologies to meet the needs of specific
applications and installations
WLANs Overview

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WLANs:
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 The wireless LAN industry has grown at a notable
rate of between 40 and 60% per year since the mid-
1990s
 It is expected to keep growing at this rate in the
future
 Reasons for this growth are:
 First, a widely accepted wireless LAN standard has
been approved by the Institute of Electrical and
Electronic Engineers (IEEE)
 Second, product prices have decreased dramatically
over the past several years
 Third, new wireless LAN applications are continually
being adopted.
 Fourth, the mobile computing paradigm is being
rapidly adopted by corporate users for office settings
WLANs Overview

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 Characteristics of WLANs
 Security: Security provisions such as encryption are
typically built into wireless LANs
 Interoperability: can be defined at two levels:
 Wireless to wired LANs/WANs. Industry-standard
interconnections exist between wireless LANs and
wired systems such as Ethernet (802.3) and Token
Ring (802.5).
 Wireless to wireless LANs IEEE 802.11 specifications
allow compliant products to interoperate without
explicit collaboration between vendors
 Interference: Radio-based wireless LANs operate in
unlicensed frequency ranges. Thus other products
such as microwave ovens and other wireless LANs
that transmit energy in the same frequency spectrum
can potentially cause interference
WLANs Overview

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WLANs:
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 Characteristics of WLANs
 Cost: adapter cost, interconnectivity cost, installation
cost
 Scalability: support large number of nodes and/or
large physical areas by adding access points to boost
or extend coverage.
 Battery: End-user wireless products are capable of
being completely untethered, and run off the battery
power from their host notebook or hand-held
computer
WLANs Overview

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WLANs:
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 Basic Information About WLANs
WLANs Overview
Factor Key points
Data rate and
Distance
covered
11 to 54 Mbps data rate over a range of about 100
meters.
Target
Applications
Mostly data applications in LAN settings,
Currently, voice over 802.11 is becoming popular
Frequency
Allocations
Mostly in unregulated bands (ISM band is
common)
Location
Management
Extensive location management is not needed
because the users do not move around very
much
Physical
Communication
s,
Signal Encoding,
Error
Mainly spread spectrum: FHSS or DSSS
Forward error correction, a combination of PSK
and .FSK.

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 Wireless LAN Technologies
 Figure below shows the key wireless technologies:
LAN adapters, access points, and wireless
communication technologies
WLANs Overview
Fig. WLAN technologies

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 LAN adapter
 End users access WLANs through wireless LAN
adapters
 provide an interface between the client network
operating system (NOS) and the airwaves via an
omnidirectional antenna
 Access Point
 An access point is a transmitter/receiver (transceiver)
device that connects wireless LANs to other wired or
wireless
 It uses omnidirectional antenna
 It performs two functions:
1. it acts as a repeater between two wireless LANs
2. it acts as a connector (bridge) between wired and
wireless networks.
WLANs Overview

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 Microcells and Roaming
 Wireless communication is limited by how far signals
carry for a given power output
 Wireless LANs use cells, called microcells, similar to
the cellular telephone system to extend the range of
wireless connectivity
 Individual microcells overlap to allow continuous
communication within a wired network
 They handle low-power signals and “hand off” users as
they roam through a given geographic area.
WLANs Overview

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 Microcells and Roaming
WLANs Overview
Fig. Microcells and Roaming in a Wireless LAN Environment

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 Wireless Communication Technologies
 use electromagnetic airwaves (typically radio) to
communicate between LAN users
 The data being transmitted is modulated/demodulated
on the radio waves
 Currently available wireless LANs use one of three
signal types to transmit data
• spread spectrum (most commonly used)
 transmitted signal is deliberately varied
• narrowband microwave
 Must use line-of-sight dish to accept microwave
• Infrared
 Use infrared beam to send and receive
WLANs Overview

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IEEE 802.11 Standard
The IEEE 802 standards committee formed the 802.11
Wireless Local Area Networks Standards Working
Group in 1990
The standard has been issued in several stages
 The first part, issued in 1997, is simply called 802.11
and operates at 1 and 2 Mbps.
 The second part, issued in 1999, is called 802.11a and
operates at data rates up to 54 Mbps
 The third part, also issued in 1999, is known as 802.11b
and operates at data rates up to 11 Mbps
 The IEEE 802.11g was introduced in 2002 and operates
at 54 Mbps

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 802.11b, also known as Wi-Fi (abbreviated from
wireless fidelity), supports up to 11 Mbps data rates and
provides great vendor interoperability
 Security provisions in 802.11 are addressed in the
standard by a complex encryption such as:
 Wired Equivalent Privacy Algorithm (WEP)
• Protects transmitted data over the RF medium by
using
• use a 64-bit seed key
• And the RC4(Rivest cipher 4) encryption
algorithm
• WEP only protects the data packet information
• does not protect the physical layer header
RC4: 1 byte Stream Cipher

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 A closer look at IEEE 802.11
 General LAN Protocol Architecture
 It concentrates on the first 2 layers
 Subdivided into three layers
1. Logical link control (LLC)
 provides an interface to higher layers through service
access point
 performs flow and error control
2. Medium access control (MAC)
 governs access to the LAN transmission medium
 plays a central role in wireless transmissions
 This layer is responsible for dealing with ad hoc or
master-slave LANs
 Also responsible for handoffs between cells
 On transmission, assemble into frame and disassemble
the frame during reception

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 General LAN Protocol Architecture
3. Physical Layer
deals with the wireless transmission medium and
includes specification of the transmission medium
It is responsible:
• for encoding/decoding of signals (e.g.,
modulation)
• preamble generation/removal (for
synchronization)
• Bit transmission/reception over the wireless
medium

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 Key terms used in the 802.11 standard are:
 Station. Any device that contains an IEEE 802.11
conformant MAC and physical layer
 Access point (AP). A station that provides access to the
distribution system
 Basic service set (BSS) A collection of stations
 Distribution system (DS). A system that interconnects
several BSSs
 Extended service set (ESS). Two or more basic service
sets interconnected by DS

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Fig. IEEE 802.11 Stack

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 IEEE 802.11 Services
 IEEE 802.11 specifies several services that can be
categorized into association-related, distribution-related,
and privacy-related services.
1. Association-Related Services
 They are needed to identify what stations are associated
with an access point
 The standard defines different transition types based on
mobility:
• No transition – a station does not move or moves only
within the BSS
• BSS transition – a station moves from one BSS to another
BSS in the same ESS
• ESS transition – a station moves from a BSS in one ESS to
a BSS within another ESS.

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 Association-Related Services
 To deliver a message to a station, the distribution service
needs to know the AP identification
 Thus a station must maintain an association with an
access point (AP)
 The following three services support this requirement:
o Association – Establishes initial association between
station and AP
o Re-association – Enables transfer of association from one
AP to another, allowing station to move from one BSS to
another
o Disassociation – Association termination notice from
station or AP

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2. Distribution-Related Services
 They are needed to distribute messages within a DS
 Two types:
o Distribution service: is used to exchange MAC frames
from a station in one BSS to a station in another BSS
o Integration service: is used to transfer data between
stations on an IEEE 802.11 LAN and stations on an
integrated IEEE 802.x LAN (wired LAN).
 This supports exchange of information between wired
and wireless LANs.

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3. Access and Privacy Services
 have special requirements in the mobile environment
 The following three services are designed for adequate
security:
• Authentication is used to establish identity of stations to
each other
• De-authentication is invoked when existing
authentication is terminated
• Privacy prevents message contents from being read by
an unintended recipient

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1. IEEE 802.11 Physical Layer
 The physical layer of IEEE 802.11 has been issued in
several stages
 In 1997, IEEE 802.11 was issued, first part
 in 1999, IEEE 802.11a and IEEE 802.11b, were issued.
 The IEEE 802.11g was introduced in 2002
 the physical layer level, IEEE 802.11 supports data rates
that range from 1 Mbps to 54 Mbps.

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 Original IEEE 802.11 Physical Layer
 It is the oldest 802.11 physical layer specification
 It includes the following two RF (FHSS and DSSS)
transmission methods and one infrared
 All operating at data rates of 1 Mbps and 2 Mbps
 Frequency-Hopping Spread-Spectrum (FHSS) Physical
Layer
 data rate for an FHSS system is 1 Mbps
 It has 22 hop patterns to choose from
 Is required to hop across the 2.4GHz ISM (Industrial,
Scientific, Medical) band covering 79 channels
 Each channel occupies 1Mhz of bandwidth

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 Direct-Sequencing Spread-Spectrum (DSSS) Physical
Layer
 It makes the transmitted signal wider in bandwidth than
the information bandwidth.
 It supports both 1 Mbps and 2 Mbps data rates, operating
in the 2.4 GHz ISM band.
 It uses an 11-bit sequence to spread the data before it is
transmitted
 The receiver de-spreads the RF input to recover the
original data.
 This technique reduces the effect of interference

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 Infrared Physical Layer
 One infrared standard is supported which operates in the
850-to- 950 nM band.
 The standard uses omnidirectional infrared technology
 Operation of the WLAN in unlicensed RF bands

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 IEEE 802.11a and IEEE 802.11b Physical Layers
 IEEE 802.11a
 The specification makes use of 5 GHz band to provide
data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps
 It operates in the 5 GHz frequency band
 a much less congested frequency band than 2.4 GHz
 It supports twelve separate non-overlapping channels
• You can use up to twelve access points set to different
channels in the same physical location
 It uses orthogonal frequency division multiplexing
(OFDM).
 OFDM is similar to FDM but all subchannels are
dedicated to a single source

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 IEEE 802.11a and IEEE 802.11b Physical Layers
 IEEE 802.11b
 is commonly known as wireless Ethernet because,
 it competes with the old copper Ethernet LANs
 It uses an extension of the 802.11 DSSS scheme
 It provides data rates of 5.5 and 11 Mbps

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 IEEE 802.11g physical layer
 It’s an enhancement of 802.11b
 It offer data rate 54 Mbps within the 2.4 GHz band
 It uses OFDM technology
 It is compatible with 802.11b
 thus the 802.11b access points can be upgraded to be
802.11g compliant relatively easily
 An issue with 802.11g and also with 802.11b is that the
2.4 GHz band is very congested
 Many other devices such as Bluetooth and some cordless
phones operate in 2.4 GHz.

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 802.11a Versus 802.11g
 both deliver the same data rates
Factor 802.11 a 802.11 g
Data rate 54Mbps 54Mbps
Frequency 5GHz 2.4GHz
Crowd Less crowded More crowded
Distance
coverage
Shorter
distance
coverage
More distance
coverage
Device cost Higher cost Less cost
Compatibility
with Wi-Fi
(802.11 b)
not compatible Compatible

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2. IEEE 802.11 Medium Access Control (MAC) Layer
 The MAC layer specification for 802.11 is similar to the
802.3 Ethernet wired line standard
 It uses the carrier-sense, multiple access, collision
avoidance (CSMA/CA) protocol
 The CSMA/CA protocol allows for options that can
minimize collisions by using different techniques
 It covers three functional areas:
o reliable data delivery,
o access control, and security

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 Reliable Data Delivery
 MAC must handle interference, noise, fading, etc.
 IEEE 802.11 includes a frame exchange protocol
o source station transmits data
o The destination responds with acknowledgment (ACK)
o If the source does not receive ACK, it retransmits the
frame
 The basic 802.11 data transfer mechanism only supports
two frame exchanges (a frame is sent and an ACK is
received).
 A four-frame exchange may be used to enhance reliability.
o the source issues a request to send (RTS), the
destination responds with “clear to send” (CTS), source
transmits data, and destination responds with ACK

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 Reliable Data Delivery
 It uses a clear channel assessment (CCA) algorithm to
determine if the channel is clear to avoid collision.
 This is accomplished by measuring the RF energy at the
antenna and determining the strength of the received
signal.
o If the received signal strength is below a specified
threshold
 the channel is declared clear and the MAC layer is
given the clear channel status for data transmission.
o If the RF energy is above the threshold
data transmissions are deferred in accordance with the
protocol rules

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 Access Control
 To support centralized as well as ad hoc LANs, the
following two approaches are accepted .
1. Distributed Coordination Function (required) that
uses Ethernet-type CSMA. DCF is useful in ad hoc
networks
 It is used to prevent collisions in IEEE 802.11-based
WLAN standard (Wi-Fi)
2. Point Coordination Function (optional), implemented
on top of DCF, uses polling, typically done by an access point.
PCF is suitable for a centralized LAN
 It is an optional technique used to prevent collisions in
IEEE 802.11-based WLAN standard including Wi-Fi
 It is used in centralized control system, and is present in
the access point (AP) of the wireless network
 MAC doesn't implement CSMA/CD

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 Access Control
 Instead a delay, known as Inter-frame Space (IFS), is used
to avoid conflicts and prioritize handling of requests
 Basically, MAC waits for a delay period of IFS before
transmitting
 In reality, DCF includes a set of delays (IFSs) with the
following values instead of one:
o Short IFS (SIFS). This is the shortest IFS and is used for
immediate response actions (high-priority) messages.
o Point coordination function IFS (PIFS). This is a mid-
length IFS that is used by the centralized controller in the
PCF scheme when using polls.
o Distributed coordination function IFS (DIFS). This is the
longest IFS, used as a minimum delay for ordinary
asynchronous frames contending for access

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 Security Services and the Wired Equivalent Privacy
Algorithm (WEP)
 Security provisions are addressed to address concerns
about eavesdropping
 Data security is achieved by complex encryption
technique such as:
• Wired equivalent privacy algorithm (WEP)
• It is designed to protect wireless communication from
eavesdropping
• is also intended to prevent unauthorized access to a
wireless network
• It is s intended to provide modest security (only
encryption and authentication) for 802.11 LANs.
• It uses 64-bit seed key and the RC4 encryption
algorithm

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3. IEEE 802.11 Logical Link Control (LLC)
 It is the highest layer in 802.11
 It should be noted that LLC is not specifically addressed
by 802.11 because of its emphasis on MAC and physical
layers.
 LLC services that are important to 802.11
 Basically, an LLC must support multi-access, shared-
medium nature of the link with the following services
 Unacknowledged connectionless service (datagram)
 This service provides no flow and error-control
mechanisms and data delivery is not guaranteed
 Thus higher-level applications are responsible for
reliable delivery
 This LLC service, also known as “fire and forget,” could
be used with TCP

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 Connection-mode service
 This provides the logical connection that is set up between
two users with support for flow and error control.
 It builds tables to keep track of session activities.
 Because this service takes care of many connection-
oriented details, it could be used in situations where thin
application software is needed.
 Acknowledged connectionless service
 This is a cross between the previous two. It is basically a
datagram service but the datagrams are acknowledged.
 This service is useful in situations where no prior logical
setup between the communicating parties is needed but
some acknowledge is desirable.
 It can be used when many users are involved in a session,
but the connection-mode tables could be too many. By
using this service, no connection tables are needed.

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HiperLAN
 It stands for High Performance Local Area Network
 It is wireless LAN standard developed by the European
Telecommunications Standards Institute (ETSI) in 1996
 HIPERLAN 1 was originally one out of four HIPERLANs
envisaged, as ETSI decided to have different types of networks for
different purposes
 The key feature of all four networks is their integration of time-
sensitive data transfer services.
 HiperLAN 1, 2,3 and 4 are now called HiperLAN 1, HiperLAN 2,
HIPERACCESS, and HIPERLINK.
 The current focus is on HiperLAN2, a standard that comprises
many elements from ETSI’s BRAN (broadband radio access
networks) and wireless ATM activities
 Neither wireless ATM nor HIPERLAN 1 were a commercial
success

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HiperLAN
 HiperLAN 1
 data transfer at 23.5 Mbit/s
 It support priorities , packet life time, topology
discovery, user data encryption, network identification
and power conservation mechanisms
 should operate at 5.1–5.3 GHz with a range of 50 m at 1
W transmit power
 Addressing is based on standard 48 bit MAC addresses.
 The service is compatible with the standard MAC
service known from IEEE 802.x LANs
 The identification scheme allows the concurrent
operation of two or more physically overlapping
HIPERLANs without mingling their communication

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HiperLAN
 HiperLAN 1
 Confidentiality is ensured by encryption/decryption
algorithm
 An Innovative feature is its ability to forward data packets
using several relays
 Relays can extend the communication on the MAC layer
beyond the radio range
 For power conservation, a node may set up a specific wake-
up pattern.
 This pattern determines at what time the node is ready to
receive, so that at other times, the node can turn off its
receiver and save energy
 These nodes are called p-savers and need so-called p-
supporters

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HiperLAN
 HiperLAN 1
 A p-supporter only forwards data to a p-saver at the
moment the p-saver is awake
 It provides QoS and a powerful prioritization scheme
 IEEE 802.11 in its standard versions does not offer
priorities, the optional PCF is typically not
implemented in products – yet 802.11 is very popular
 Elimination-yield non-preemptive priority multiple
access (EY-NPMA) is the heart of the channel access
providing priorities and different access schemes
 EY-NPMA divides the medium access of different
competing nodes into three phases

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HiperLAN
 HiperLAN 1
 Prioritization: Determine the highest priority of a data
packet ready to be sent by competing nodes.
 Contention: Eliminate all but one of the contenders, if more
than one sender has the highest current priority.
 Transmission: Finally, transmit the packet of the remaining
node.
 MAC layer offer QoS by HMQoS parameters
 User can set priority for the data; 0 high P and 1 low P
 The user can determine the lifetime of an MSDU to
specify time bounded delivery; ranges b/n 0 – 16,000 ms
 MAC also offer encryption/decryption using simple XOR-
scheme together with random numbers

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HiperLAN
 HiperLAN 2
 Next generation of HiperLAN family: Proposed by ETSI
BRAN (Broadband Radio Access Networks) in 1999, and
is still under development.
 It is a broadband radio networking technology and
provide interconnection to any type of network
 Benefits
 5 GHz technology, up to 54 Mbit/s
 A high level of security
 QoS capabilities to support virtually any type of
service or application
 High and scalable capacity
 Managed bandwidth with predictable performance
for each user and application
 Robust protocols that also optimize the overall
throughput of the available radio resource
 Ease of use through a set of auto-configuration tools

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HiperLAN
MAC
CAC
PHY
HiperLAN Type 1 Reference Model
PHY
MAC
EC
ACF DCC
RLC
DLC
CL
HiperLAN Type 2 Reference Model
Control
Plane
User Plane
MAC: Medium Access Sub layer EC: Error Control
CAC: Channel Access Control Sub layer RLC: Radio Link Control
PHY: Physical Layer RRC: Radio Resource Control
DLC: Data Link Control Layer ACF: Association Control Function
CL: Convergence Layer DCC: DLC Connection Control
Architecture
RRC

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HiperLAN
1. Physical Layer
Operates in the 5.2 Ghz frequency band
Transmission rate of up to 54 Mbps
Use of Orthogonal Frequency Digital
Multiplexing (OFDM)
It is very similar to 802.11a

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HiperLAN
2. Data Link Control Layer

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HiperLAN
Three main control functions for Radio link Control
 Association control function (ACF): authentication, key
management, association, disassociation, encryption
 Radio resource control function (RRC): handover, dynamic
frequency selection, mobile terminal alive/absent, power saving,
power control
 DLC user connection control function (DCC): setup and release of
user connections, multicast and broadcast
Connection-oriented
 After completing association, a mobile terminal may request one
or several DLC connections, with one unique DLC address
corresponding to each DLC connection, thus providing different

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HiperLAN
DLC: Error Control
 Acknowledged mode: selective-repeat ARQ
 Repetition mode: typically used for broadcast
 Unacknowledged mode: unreliable, low latency
DLC: other features
 Radio network functions: Dynamic frequency selection;
handover; link adaptation; Multibeam antennas; power control
 QoS support: Appropriate error control mode selected;
Scheduling performed at MAC level; link adaptation; internal
functions (admission, congestion control, and dropping
mechanisms) for avoiding overload

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HiperLAN
3. Convergence Layer
This layer has two main functions:
I. adapting service requests from higher layers to the service
offered by the DLC
II. converting the higher-layer packets with variable or possibly
fixed size into a fixed size that is used within the DLC

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HiperLAN
Hiperlan1 Hiperlan2 HiperAccess HiperLink
Description Wireless
Ethernet
Wireless ATM Wireless Local
Loop
Wireless Point-
to-Point
Freq. Range 5GHz 5GHz 5GHz 17GHz
PHY Bit Rate 23.5Mbps 6~54Mbps ~25Mbps
(data rate)
~155Mbps
(data rate)

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Wireless Personal Area Networks(WPANs)
WPANs
• Short range networks (< 10 meters)
• Used in homes, cars, small offices
• Can be interconnected to form large networks
• IEEE 802.15 is the main standards environment
• Many active areas of work: Bluetooth, UWB,
Wireless sensor networks, Zigbees

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The IEEE 802.15 Working Group (WG) has been formed
to develop standards for WPANs
As a starting point, the group accepted significant
parts of the Bluetooth specification without
modification and enriched it with various other
features and considerations
The work of 802.15 WG is currently divided into the
following task groups:
 802.15.1 (Bluetooth): This Task Group has reviewed
and provided a standard adaptation of the Bluetooth
Specifications
 802.15.2 (Coexistence). This Task Group is developing
Recommended Practices to facilitate coexistence of
Wireless Personal Area Networks (802.15) and
Wireless Local Area Networks (802.11).
 802.15.3 (WPAN High Rate). This Task Group is
working on a standard for high-rate (20 Mbps or

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 802.15.3a (WPAN Higher Rate). This Task Group is
chartered to develop a new standard for a higher
speed (110 Mbps or greater) needed by streaming
video and other multimedia applications. A new
physical layer (PHY) is being developed by this Task
Group for such high data rates
 the 802.15.3a TG is working actively on UWB (Ultra
Wideband Communication).
 802.15.4 (WPAN Low Rate). This Task Group is
investigating a low data rate solution with multi-
month to multi-year battery life and very low
complexity. This standard specifies 250 Kbps in the 2.4
GHz band and 20 Kbps-40 Kbps in the 868 MHz bands.
The target applications for this standard are sensors,
interactive toys, smart badges, remote controls, and
home automation
 ZigBee Alliance

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Bluetooth Overview
• Founders: Ericsson, IBM, Intel, Nokia, Toshiba;
May 98
• Currently: Over 1000 companies
• Low-cost, short range radio link between mobile
PCs, phones and other portable devices
• 2.4 GHz ISM band (unlicensed): Short packets and
fast-hopping
• Software for service and device discovery
• Typical application: cellular phone to PDA or
earphone
• Supports open-ended list of applications
– Data, audio, graphics, video
• Many products from Nokia, Motorala, Apple, etc.
• Bluetooth.com and palowireless.com/bluetooth

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Bluetooth Application Areas
• Cable replacement
– Eliminates need for numerous cable
attachments for connection (e.g., RS232)
• Data and voice access points
– Real-time voice and data transmissions
• Ad hoc networking
– Device with Bluetooth radio can establish
connection with another when in range

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Piconets and Scatternets
• Piconet
– Basic unit of Bluetooth networking
– Master and one to seven slave devices
– Master determines channel and phase
• Scatternet
– Device in one piconet may exist as master or
slave in another piconet
– Allows many devices to share same area
– Makes efficient use of bandwidth

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Piconets Vs. Scatternets
Piconet Scatternet
Piconet is the type of
connection formed between 2
or more Bluetooth enabled
devices
between 2 or more Bluetooth
enabled devices. It is a type of
ad-hoc computer network
consisting of 2 or more
piconets
It supports maximum 8 nodes
i.e,1 master & 7 slaves
It supports more than 8 nodes.
It Allows less efficient use of
Bluetooth channel bandwidth.
It is usually applied to
Bluetooth devices.
It is a smaller coverage area
It Allows more efficient use of
Bluetooth channel bandwidth.
It is applied to Bluetooth
devices too.
It is a larger coverage area.

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Bluetooth Piconets
Master
Slave Slave
Slave
/Master
Slave Slave
Piconet1
(Cubicle 1)
Piconet3
(Cubicle3)
PC
Cellular
Phone
Ear
Phone
PC
PC
printer
Master
Slave
Slave
Piconet2
(Cubicle2)
PC
PC
printer

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UWB -- Overview
 Ultra Wideband (UWB) is emerging as a new
wireless personal area network technology.
 Originally developed in the 1960s for the military.
 FCC approved the commercial implementation of
UWB in February 2002, within limits.
 UWB provides high data rates (around 50 Mbps) in
very short distances (10 meters).
 UWB is a radio system that uses narrow pulses
(millions of pules per second) for communication
and sensing by using short-range radar.
 UWB radio sends data in millions of pulses across a
wide frequency band
 Legal in the US as long as it uses less power than
normal radio frequency leakage.

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Wireless Sensor Networks
(Overview)
 WSNs) typically consist of small, low-powered
devices (sensors)
 Sensors can be developed to measure
temperature, humidity, motion, color changes in
a painting, or any other measurable thing.
 Most WSNs consist of millions of tiny processors
communicating over slow wireless networks,
 WSNs may consist of devices with a wide range of
computation, communication, and sensing
capabilities.
 The WSNs may use Bluetooth or IEEE 802.11
networks

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Factor Bluetooth Wi fi UWB WSN
Data Rate 1Mbps 11Mbps 50Mbps <1Mbps
Distance
Covered
(range)
10 Meters 100 Meters 10 Meters 10-30 Meters
b/n motes
Applicatio
n focus
Cable replacement Connection to
corporate
networks
Military
applications
so far, home
entertainmen
t in
future
Numerous
military
and civilian
applications
Frequenc
y Band
2.4 GHz 2.4 GHz 3.1 – 10.6 GHz Unregulated
Ease of
use
Piconets very easy
to use for small
networks
Complex even
for 2
devices
Complex and
intricate
Easy to use,
once
installed
Security Multiple levels (link
level, application
level)
WEP and its
improvement
s
Very high
security
Many security
exposures

01/02/2025 WC & MC 76
The End!
Wireless Local Area Networks
Chapter 4

CH4 Wireless Local Area Networks in wireless communication.pptx

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