Recent Trends in Wireless communication

Introduction
• Wireless Technology is an alternative to Wired Technology, which is commonly
used, for connecting devices in wireless mode.
• Wi-Fi (Wireless Fidelity) is a generic term that refers to the IEEE 802.11
communications standard for Wireless Local Area Networks (WLANs).
• Wi-Fi Network connect computers to each other, to the internet and to the wired
network.

IEEE 802.11 Architecture
 IEEE 802.11 standard, popularly known as WiFi, lays down the architecture and specifications of
wireless LANs (WLANs). WiFi or WLAN uses high-frequency radio waves instead of cables for
connecting the devices in LAN. Users connected by WLANs can move around within the area of
network coverage.

 Stations (STA) − Stations comprises of all devices and equipment that are connected to the
wireless LAN. A station can be of two types−
 Wireless Access Point (WAP) − WAPs or simply access points (AP) are generally wireless routers that form the
base stations or access.
 Client. Clients are workstations, computers, laptops, printers, smartphones, etc.
 Each station has a wireless network interface controller.

 Basic Service Set (BSS) − A basic service set is a group of stations communicating at the
physical layer level. BSS can be of two categories depending upon the mode of operation−
 Infrastructure BSS − Here, the devices communicate with other devices through access points.
 Independent BSS − Here, the devices communicate in a peer-to-peer basis in an ad hoc manner.
 Extended Service Set (ESS) − It is a set of all connected BSS.
 Distribution System (DS) − It connects access points in ESS.

Frame Format of IEEE 802.11
 The main fields of a frame of wireless LANs as laid down by IEEE 802.11 are −
 Frame Control − It is a 2 bytes starting field composed of 11 subfields. It contains control
information of the frame.
 Duration − It is a 2-byte field that specifies the time period for which the frame and its
acknowledgment occupy the channel.
 Address fields − There are three 6-byte address fields containing addresses of source, immediate
destination, and final endpoint respectively.
 Sequence − It a 2 bytes field that stores the frame numbers.
 Data − This is a variable-sized field that carries the data from the upper layers. The maximum
size of the data field is 2312 bytes.
 Check Sequence − It is a 4-byte field containing error detection information.

The Wi-Fi Technology
Wi-Fi Networks use Radio Technologies to transmit & receive data at high speed:
• IEEE 802.11b
• IEEE 802.11a
• IEEE 802.11g

IEEE 802.11b
• Appear in late 1999
• Operates at 2.4GHz radio spectrum
• 11 Mbps (theoretical speed) - within 30 m Range
• 4-6 Mbps (actual speed)
• 100 -150 feet range
• Most popular, Least Expensive
• Interference from mobile phones and Bluetooth devices which can reduce the
transmission speed.

IEEE 802.11a
• Introduced in 2001
• Operates at 5 GHz (less popular)
• 54 Mbps (theoretical speed)
• 15-20 Mbps (Actual speed)
• 50-75 feet range
• More expensive
• Not compatible with 802.11b

IEEE 802.11g
• Introduced in 2003
• Combine the feature of both standards (a,b)
• 100-150 feet range
• 54 Mbps Speed
• 2.4 GHz radio frequencies
• Compatible with ‘b’

802.11 Physical Layer
There are three sublayers in physical layer:
• Direct Sequence Spread Spectrum (DSSS)
• Frequency Hoping Spread Spectrum (FHSS)
• Diffused Infrared (DFIR) - Wide angle

DSSS
• Direct sequence signaling technique divides the 2.4 GHz band into 11 22-MHz channels. Adjacent channels overlap
one another partially, with three of the 11 being completely non-overlapping. Data is sent across one of these 22
MHz channels without hopping to other channels.

IEEE 802.11 Data Link Layer
The data link layer consists of two sublayers :
• Logical Link Control (LLC)
• Media Access Control (MAC).
802.11 uses the same 802.2 LLC and 48-bit addressing as other 802 LANs, allowing for very simple bridging
from wireless to IEEE wired networks, but the MAC is unique to WLANs.

802.11 Media Access Control
• Carrier Sense Medium Access with collision avoidance protocol (CSMA/CA)
• Listen before talking
• Avoid collision by explicit Acknowledgement (ACK)
• Problem: additional overhead of ACK packets, so slow performance
• Request to Send/Clear to Send (RTS/CTS) protocol
• Solution for “hidden node” problem
• Problem: Adds additional overhead by temporarily reserving the medium, so used for large
size packets only retransmission would be expensive

802.11 Media Access Control(cont.)
• Power Management
• MAC supports power conservation to extend the battery life of portable devices
• Power utilization modes
• Continuous Aware Mode
• Radio is always on and drawing power
• Power Save Polling Mode
• Radio is “dozing” with access point queuing any data for it
• The client radio will wake up periodically in time to receive regular beacon signals from the access point.
• The beacon includes information regarding which stations have traffic waiting for them
• The client awake on beacon notification and receive its data

802.11 Media Access Control(cont.)
• Fragmentation
• CRC checksum
• Each pkt has a CRC checksum calculated and attached to ensure that the data was not corrupted in transit
• Association & Roaming

Elements of a WI-FI Network
• Access Point (AP) - The AP is a wireless LAN transceiver or “base station” that can connect
one or many wireless devices simultaneously to the Internet.
• Wi-Fi cards - They accept the wireless signal and relay information.They can be internal and
external.(e.g PCMCIA Card for Laptop and PCI Card for Desktop PC)
• Safeguards - Firewalls and anti-virus software protect networks from uninvited users and keep
information secure.

How a Wi-Fi Network Works
• Basic concept is same as Walkie talkies.
• A Wi-Fi hotspot is created by installing an access point to an internet connection.
• An access point acts as a base station.
• When Wi-Fi enabled device encounters a hotspot the device can then connect to that network
wirelessly.
• A single access point can support up to 30 users and can function within a range of 100 – 150
feet indoors and up to 300 feet outdoors.
• Many access points can be connected to each other via Ethernet cables to create a single large
network.

Wi-Fi Network Topologies
• AP-based topology (Infrastructure Mode)
• Peer-to-peer topology (Ad-hoc Mode)
• Point-to-multipoint bridge topology

AP-based topology
• The client communicate through Access Point.
• BSA-RF coverage provided by an AP.
• ESA-It consists of 2 or more BSA.
• ESA cell includes 10-15% overlap to allow roaming.

Peer-to-peer topology
• AP is not required.
• Client devices within a cell can communicate directly with each other.
• It is useful for setting up of a wireless network quickly and easily.

Point-to-multipoint bridge topology
This is used to connect a LAN in one building to a LANs in other buildings even if the buildings
are miles apart.These conditions receive a clear line of sight between buildings. The line-of-sight
range varies based on the type of wireless bridge and antenna used as well as the environmental
conditions.

Wi-Fi Applications
• Home
• Small Businesses or SOHO
• Large Corporations & Campuses
• Health Care
• Wireless ISP (WISP)
• Travellers

Wi-Fi Security Threats
• Wireless technology doesn’t remove any old security issues, but introduces new ones
• Eavesdropping
• Man-in-the-middle attacks
• Denial of Service

Eavesdropping
• Easy to perform, almost impossible to detect
• By default, everything is transmitted in clear text
• Usernames, passwords, content ...
• No security offered by the transmission medium
• Different tools available on the internet
• Network sniffers, protocol analysers . . .
• Password collectors
• With the right equipment, it’s possible to eavesdrop traffic from few kilometers
away

MITM Attack
1. Attacker spoofes a disassociate message from the victim
2. The victim starts to look for a new access point, and the attacker advertises his own AP on a
different channel, using the real AP’s MAC address
3. The attacker connects to the real AP using victim’s MAC address

Denial of Service
• Attack on transmission frequecy used
• Frequency jamming
• Not very technical, but works
• Attack on MAC layer
• Spoofed deauthentication / disassociation messages
• can target one specific user
• Attacks on higher layer protocol (TCP/IP protocol)
• SYN Flooding

Wi-Fi Security
The requirements for Wi-Fi network security can be broken down into two primary components:
• Authentication
 User Authentication
 Server Authentication
• Privacy

Authentication
• Keeping unauthorized users off the network
• User Authentication
• Authentication Server is used
• Username and password
• Risk:
• Data (username & password) send before secure channel established
• Prone to passive eavesdropping by attacker
• Solution
• Establishing a encrypted channel before sending username and password

Authentication (cont..)
• Server Authentication
• Digital Certificate is used
• Validation of digital certificate occurs automatically within client software

Wi-Fi Security Techniques
• Service Set Identifier (SSID)
• Wired Equivalent Privacy (WEP)
• 802.1X Access Control
• Wireless Protected Access (WPA)
• IEEE 802.11i

Service Set Identifier (SSID)
• SSID is used to identify an 802.11 network
• It can be pre-configured or advertised in beacon broadcast
• It is transmitted in clear text
• Provide very little security

Wired Equivalent Privacy (WEP)
• Provide same level of security as by wired network
• Original security solution offered by the IEEE 802.11 standard
• Uses RC4 encryption with pre-shared keys and 24 bit initialization vectors (IV)
• key schedule is generated by concatenating the shared secret key with a random generated 24-
bit IV
• 32 bit ICV (Integrity check value)
• No. of bits in keyschedule is equal to sum of length of the plaintext and ICV

Wired Equivalent Privacy (WEP) (cont.)
• 64 bit preshared key-WEP
• 128 bit preshared key-WEP2
• Encrypt data only between 802.11 stations.once it enters the wired side of the network (between
access point) WEP is no longer valid
• Security Issue with WEP
• Short IV
• Static key
• Offers very little security at all

802.1x Access Control
• Designed as a general purpose network access control mechanism
• Not Wi-Fi specific
• Authenticate each client connected to AP (for WLAN) or switch port (for Ethernet)
• Authentication is done with the RADIUS server, which ”tells” the access point whether access to controlled ports
should be allowed or not
• AP forces the user into an unauthorized state
• user send an EAP start message
• AP return an EAP message requesting the user’s identity
• Identity send by user is then forwared to the authentication server by AP
• Authentication server authenticate user and return an accept or reject message back to the AP
• If accept message is return, the AP changes the client’s state to authorized and normal traffic flows

Wireless Protected Access (WPA)
• WPA is a specification of standard based, interoperable security enhancements that strongly increase the level of
data protection and access control for existing and future wireless LAN system.
• User Authentication
• 802.1x
• EAP
• TKIP (Temporal Key Integrity Protocol) encryption
• RC4, dynamic encryption keys (session based)
• 48 bit IV
• per packet key mixing function
• Fixes all issues found from WEP
• Uses Message Integrity Code (MIC) Michael
• Ensures data integrity
• Old hardware should be upgradeable to WPA

Wireless Protected Access (WPA)(cont.)
• WPA comes in two flavors
• WPA-PSK
• use pre-shared key
• For SOHO environments
• Single master key used for all users
• WPA Enterprise
• For large organisation
• Most secure method
• Unique keys for each user
• Separate username & password for each user

WPA and Security Threats
• Data is encrypted
• Protection against eavesdropping and man-in-the-middle attacks
• Denial of Service
• Attack based on fake massages can not be used.
• As a security precaution, if WPA equipment sees two packets with invalid MICs within a second, it disassociates all its
clients, and stops all activity for a minute
• Only two packets a minute enough to completely stop a wireless network

802.11i
• Provides standard for WLAN security
• Authentication
• 802.1x
• Data encryption
• AES protocol is used
• Secure fast handoff-This allow roaming between APs without requiring client to fully
reauthenticate to every AP.
• Will require new hardware

Advantages
• Mobility
• Ease of Installation
• Flexibility
• Cost
• Reliability
• Security
• Use unlicensed part of the radio spectrum
• Roaming
• Speed

Limitations
• Interference
• Degradation in performance
• High power consumption
• Limited range

What is WiMax?
 WiMax (Worldwide Interoperability for Microwave Access) is a standards-based
technology enabling the delivery of last mile wireless broadband access as an
alternative to cable and DSL.
 The technology is specified by the Institute of Electrical and Electronics Engineers
Inc., as the IEEE 802.16 standard.

WiMax Forum
 It is a non-profit industry body dedicated to promoting the adoption of this technology
and ensuring that different vendors’ products will interoperate.
 It is doing this through developing conformance and interoperability test plans and
certification program.
 WiMAX Forum Certified™ means a service provider can buy equipment from more than
one company and be confident that everything works together.

WiMax Technology
 WiMAX is expected to provide fixed , nomadic, portable and, eventually, mobile wireless
broadband connectivity without the need for direct line-of-sight (LOS) with a base station.
 In a typical cell radius deployment of three to ten kilometers, WiMAX Forum Certified™
systems can be expected to deliver capacity of up to 40 Mbps per channel, for fixed and
portable access applications.
 Mobile network deployments are expected to provide up to 15 Mbps of capacity within a
typical cell radius deployment of up to three kilometers.

Why is it Interesting?
 Simultaneously support hundreds of businesses with T-1 speed connectivity and thousands of
homes with DSL speed connectivity.
 Promise of potential low cost and flexibility in building broadband networks.
 Scalability, as extra channels and base stations can be added incrementally as bandwidth
demand grows.
 Support for both voice and video as well as Internet data.
 Semiconductor vendors envisage WiMax-enabled chips appearing in PCs in 2006 and in
notebook computers and PDAs by 2007

Wi-Fi: The Predecessor of WiMax
 Wi-Fi (Wireless Fidelity) is a set of technologies that are based on the IEEE 802.11a,b, and
g standards.
 Wi-Fi is considered to be one of the first widely deployed fixed broadband wireless
networks.
 The Wi-Fi architecture consists of a base station that wireless hosts connect to in order
to access network resources.
 As long as the users remain within 300 feet of the fixed wireless access point, they can
maintain broadband wireless connectivity.

Wi-Fi Standards
Standard Throughput Range Frequency
802.11a Up to 54 Mbps Up to 300 ft Between 5 and 6
Ghz
802.11b Up to 11 Mbps Up to 300 ft 2.4 Ghz
802.11g Up to 54 Mbps Up to 300 ft 2.4 Ghz

Strengths of Wi-Fi
 Simplicity and ease of deployment given that it uses unlicensed radio spectrum which does not
require regulatory approval.
 Cost of rolling out this wireless solution is low.
 Users are able to be mobile for up to 300 feet from the access point.
 There are many Wi-Fi compatible products that are available at a low cost and can interoperate
with other network technologies. Wi-Fi clients can work seamlessly in other countries with
minimal configuration.

Weaknesses of Wi-Fi
 Limited level of mobility.
 Susceptible to interference.
 Designed technically for short-range operations and basically an indoors technology.
 Security is a concern.

Relation of Wi-Fi and WiMax
 WiMax eliminates the constraints of Wi-Fi.
 Unlike Wi-Fi, WiMax is intended to work outdoors over long distances.
 WiMax is a more complex technology and has to handle issues of importance such
as QoS guarantees, carrier-class reliability, NLOS.
 WiMax is not intended to replace Wi-Fi. Instead, the two technologies complement
each other.

WiMax Standards
802.16 802.16a 802.16-2004 802.16e-2005
Date
Completed
December 2001 January 2003 June 2004 December 2005
Spectrum 10-66 GHz < 11 GHz < 11 GHz < 6 GHz
Operation LOS Non-LOS Non-LOS Non-LOS and
Mobile
Bit Rate 32-134 Mbps Up to 75 Mbps Up to 75
Mbps
Up to 15 Mbps
Cell Radius 1-3 miles 3-5 miles 3-5 miles 1-3 miles

WiMax is well suited to offer both fixed and mobile
access

How WiMax Works
 WiMax can provide 2 forms of wireless service:
- Non-LOS, Wi-Fi sort of service, where a small antenna on a computer connects to the tower.
Uses lower frequency range (2 to 11 GHz).
- LOS, where a fixed antenna points straight at the WiMax tower from a rooftop or pole. The LOS
connection is stronger and more stable, so it is able to send a lot of data with fewer errors. Uses
higher frequencies, with ranges reaching a possible 66 GHz.
 Through stronger LOS antennas, WiMax transmitting stations would send data to WiMax enabled
computers or routers set up within 30 (3,600 square miles of coverage) mile radius.

WiMax Rollout
 WiMax Forum anticipates rollout of its technology in 3 phases:
- Phase 1: Fixed Location, Private Line Services, Hot Spot Backhaul.
- Phase 2: Broadband Wireless Access/Wireless DSL
- Phase 3: Mobile/Nomadic Users.

WiMax Spectrum
 Broad Operating Range
 WiMax Forum is focusing on 3 spectrum bands for global deployment:
 Unlicensed 5 GHz: Includes bands between 5.25 and 5.85 GHz. In the upper 5 GHz band (5.725 –
5.850 GHz) many countries allow higher power output (4 Watts) that makes it attractive for
WiMax applications.
 Licensed 3.5 GHz: Bands between 3.4 and 3.6 GHz have been allocated for BWA in majority of
countries.
 Licensed 2.5 GHz: The bands between 2.5 and 2.6 GHz have been allocated in the US, Mexico,
Brazil and in some SEA countries. In US this spectrum is licensed for MDS and ITFS.

Benefits of Licensed and License-Exempt Solutions
Licensed Solution License-Exempt Solution
Better QoS Fast Rollout
Better NLOS reception at lower
frequencies
Lower Costs
Higher barriers for entrance More worldwide options

Technical Similarities and Differences Between Licensed and License-Exempt Bands
 Both solutions are based on IEEE 802.16-2004 standard, which uses OFDM in the
physical (PHY) layer.
 OFDM provides benefits such as increased SNR of subscriber stations and
improved resiliency to multi-path interference.
 For creating bi-directional channels for uplink and downlink, licensed solutions use
FDD while license exempt solutions use TDD.

WiMax Mobility Issues
 Device availability is a major issue
- Market introduction may be delayed
- High initial costs will limit adoption growth
 In some markets spectrum availability is limited
- Bands < 3 GHz is better suited for mobile access
- Licenses for fixed WiMAX may not allow service provider to offer mobile services
 Current demand for WiMax is mostly for fixed services.
- Underserved Regions, Developing Markets

WiMax Mobility Issues (Continued)
 Demand for wireless data is growing, but still it is limited
- Mobile operators may see need for a data-only technology when demand is
higher
- Demand may drive additional spectrum allocations for wireless mobile data
service
 WiMax is not going to supplant other wireless technologies
- It will not replace Wi-Fi in the LAN
- Cellular technologies may still be needed for voice and data in the WAN

WiMax Mobility Issues (Continued)
 Competing technologies have a time-to-market advantage
- Many mobile operators have invested heavily in 3G systems.
 Multiple technologies will co-exist as they meet different needs
 Mobility may become a powerful differentiating factor when competing with DSL or
Cable

WiMax Applications
 According to WiMax Forum it supports 5 classes of applications:
 Multi-player Interactive Gaming.
 VOIP and Video Conference
 Streaming Media
 Web Browsing and Instant Messaging
 Media Content Downloads

WiMax Success Factors
 It is crucial that WiMax becomes an important building block to enable
fixed/mobile convergence and to ensure its success.
 Ability to offer ease of use is crucial to the success of WiMAX service
providers
 Success of WiMAX may depend on the ability to combine fixed and
mobile access over the same infrastructure

What is Zigbee?
• ZigBee is a new wireless technology
• Technological Standard Created for Control and
Sensor Networks
• Based on the IEEE 802.15.4 Standard
• Created by the ZigBee Alliance
• Philips,Motorola,Intel,HP are all members of the
allience.

Zigbee
• Designed for low power consumption allowing
batteries to essentially last for ever
• ZigBee makes possible completely networked homes
where all devices are able to communicate and be
controlled by a single unit
• It provides network,security and application support
services operating on the top of IEEE

IEEE 802.15.4 & ZigBee
– “the software”
– Network, Security &
Application layers
– Brand management
IEEE 802.15.4
– “the hardware”
– Physical & Media Access
Control layers
PHY
868MHz / 915MHz / 2.4GHz
MAC
Network
Star / Mesh / Cluster-Tree
Security
32- / 64- / 128-bitencryption
Application
API
ZigBee
Alliance
IEEE
802.15.4
Customer
Silicon Stack App

Architecture
• Layered architecture
• These layers facilitate the features that make
ZigBee very attractive:
low cost
 easy implementation
 reliable data transfer
 short-range operations
 very low power consumption
adequate security features

Architecture
Layers
1.Network and Application Support layer 2.Physical
(PHY) layer
3.Media access control (MAC) layer

Zigbee Device Types
• There are three different ZigBee device types that
operate on the layers in any self-organizing
application network
1. Zigbee Coordinator node
2. Full Function Device (FFD)
3. Reduced Function Device(RFD)

1.Zigbee Coordinator Node
 It is the root of network tree and a bridge to other network
 Able to store information about the network
 Only one ZCN for a network
 It act as a repositary for other security keys

2.The full Function Device
• An intermediatory router transmitting data from other
devices
• Needs lesser memory than Zigbee coordinator
node
• Lesser manufacturing cost
• Can operate on all topologies
• Also act as a coordinator

3.The Reduced Function Device
• Device capable of talking in the network
• It cannot relay data from other devices
• Less memory
• Cheaper than FFD
• It talks only to the n/w coordinator

1.Star Topology
Network Topologies

2. Peer-to-Peer Topology
Network Topologies(cont…)

Network Topologies(cont...)
3.Cluster Network

Characteristics
• Low power consumption with battery life ranging from
months to years
• High density of nodes per network
• Low cost
• Simple implementation
• Low data rate
• Small packet devices

Applications
• The ZigBee Alliance targets applications Across
consumer, commercial, industrial and government
markets worldwide
• Home networking
• Industrial control and management

Recent Trends in Wireless communication

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