Emerging Wireless Technologies and Standards

MODULE 4
Emerging Wireless Technologies
and Standards

COURSE OUTCOME
Students shall be able to evaluate emerging wireless
technologies standards such as WLL, WLAN, WPAN, WMAN.

Wireless Local Loop
(WLL)
Module 4

NEED FOR WLL
A single broadband connection can provide all the necessary telecommunication
services like telephone, radio, fax and internet. For deploying a broadband connection
fixed wireless access systems are well suited.
Modern fixed wireless systems are generally designed at microwave or millimeter
frequencies in the 28 GHz band and higher. At these frequencies, the wavelengths are
very small.
In Fixed Wireless Access Systems (FWA), the Wireless Local Loops (WLL) are popular.
WLL is also called as fixed wireless loop.
The function of the WLL systems is to make primary access to the telephone networks.
It supports subscribers of fixed and known locations.
The WLL system enables connectivity with the Public Switched Telephone (PSTN). It uses
radio connectivity instead of wired cable
The microwave wireless links can be used to generate a Wireless Local Loop (WLL). It is
a milestone in telecommunication era and exists between the central office (CO) and
the individual residences near the CO.
In the developed countries, the copper or fiber optic cables are installed at homes,
offices and businesses in buildings. However, in the developing countries it is difficult
to install cables.
The wireless links can be deployed in a couple of hours.
In the WLL systems there are two concepts namely NWLL and BWLL.
NWLL (Narrowband WLL) is used to replace conventional telephone systems and BWLL

NEED FOR WLL
The WLL systems are based on the Personal Communication systems (PCS) like mobile
technologies like W-CDMA, GSM, PDC, etc.
The capacity requirement of WLL is different from that of the capacity need of fixed WLL
system. In a fixed system the capacity is provided to meet subscribers of known numbers
but it is no so in mobile wireless as it has to meet the traffic in worst cases.
WLL system must have features like:
They should provide better Quality of Service (QoS)
They should be compatible with other cellular technologies.
They should have complete scalability to meet the traffic requirements.
Advantages:
The cost of wireless equipment is less,once paid no additional costs are required whereas
the fibre
optic and copper cables need to be leased from the service provider on monthly basis.
Wireless equipment's can be installed in a couple of hours.
They have good scale of installation.

Wireless Local Loop
WLL stands for Wireless Local Loop. Microwave wireless links can be used to
create a wireless local loop such as shown in figure below.

Wireless Local Loop
Local Loop is a network that resides between the central office (CO) and the
individual homes and business in close proximity to the central office (CO).
In most developed countries, copper or optical fiber cable already has been
installed to residence and business.
One more advantage of WLL is that we have to pay only once for that
wireless equipment, after there is no additional costs involved. System WLL
is based on Cellular, satellite, microcellular.
The WLL can greatly improve the telecommunication facilities and services in
an inexpensive way. It provides
 High bandwidth is available
 Faster deployment
 Lower deployment costs
 Lower network maintenance, management and operating cost

Wireless Local Loop
Loop: . In telephone, loop is a circuit line from a subscriber’s phone to a line-
terminating equipment at a central office.
Wireless Local Loop (WLL):
Implementation of a local loop especially in rural areas used to remain a risk for
many operators due to less users and increased cost of materials. The loop lines
are copper wires which require more investments.
However today with Wireless local loop (WLL) has been introduced which solves
most of these problems.
As WLL is wireless, the labor-charges and time-consuming investments are no
longer relevant.
WLL systems can be based on one of the four below technologies:
 Satellite-based systems.
 Cellular-based systems.
 Microcellular-based Systems
 Fixed Wireless Access Systems

Wireless Local Loop
The WLL architecture is shown below:
• The given architecture consists of three major components i.e WANU,
WASU and SF

Wireless Local Loop
Wireless Access network unit (WANU): the WANU
consists of various components which include several
base stations transceivers or radio ports (RP), a Radio
port control unit, an Access manager (AM), an HLR.
• It provides various functionalities like:
Authentication
Air interface privacy
Over-the-air registration of subscriber units.
Operations and Maintenance
Routing
Billing
Switching functions
Transcoding of voice and data.

Wireless Local Loop
Wireless access subscriber unit (WASU): It provides an air interface
UWLL towards the network and a traditional interface TWLL towards
the subscriber.
• The power supply for it is provided locally.
• The interface includes
protocol conversion and transcoding
authentication functions
signaling functions
• The TWLL interface can be an RJ-11 or RJ-45 port.
• The UWLL interface can be AMPS, GSM, DECT and so one.

Wireless Local Loop
• Switching Function (SF): The switching function (SF) is associated with a switch that can be digital switch with
or without Advanced Intelligent Network (AIN) capability, an ISDN switch or a Mobile Switching Centre (MSC).
• The AWLL interface between the WANU and the SF can be ISDN-BRI or IS-634 or IS-653 or such variants.
Deployment Issues:
• To compete with other local loop technologies WLL needs tom [provide sufficient coverage and capacity, high
circuit quality and efficient data services.
• Moreover the WLL cost should be competitive with its wireline counterpart.
• Various issues are considered in WLL development which include:
Spectrum: The implementation of WLL should be flexible to accommodate different flexible bands as well as
non-continuous bands. More these bands are licensed by government.
Service quality: Customer expects that the quality of service should be better than the wireline counterpart.
The quality requirements include link quality, reliability and fraud immunity.
Network Planning: Unlike Mobile System, WLL assumes that user is stationary, not moving. Also the network
penetration should be greater than 90%. Therefore WLL should be installed based on parameters like
Population Density etc.
Economics: Major cost here is electronic equipment’s. In current scenario, the cost of such electronic
equipment is reducing periodically.
• In traditional telephone networks, your phone would be connected to the nearest exchange through a pair of
copper wires.
• Wireless local loop (WLL) technology simply means that the subscriber is connected to the nearest exchange
through a radio link instead of through these copper wires.

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WIRELESS LOCAL AREA NETWORKS - WLAN
 Wireless LAN (WLAN/ WiFi) is a data transmission system designed
to provide location-independent network access between computing
devices by using radio waves
 Provides a basis for implementation of high performance, short range
wireless networks with a wide range of data throughput
 A trend today… Consumers of high speed internet access share their
connection with other users using WLAN

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 IEEE 802.11 : Standard for Wireless LAN
 Defines over the air protocols necessary to
support networking in a LAN environment
 Focuses on bottom two levels the ISO model,
Physical layer & Data link layer
 PCMIA cards/ WiFi chips used in devices

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IEEE 802.11 STANDARD
 Initial Standard
 Frequency - 2.4 GHz – ISM band
 Data rate - 1 Mbps and 2 Mbps
 Uses FHSS/DSSS
 IEEE 802.11b
 IEEE 802.11a
 IEEE 802.11g

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DEVELOPMENTS OF IEEE 802.11 STANDARDS

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How are WLANs different…………
1. They use specialized physical and data link layer protocol
2. They integrate into existing networks through access points which
provide a bridge type function
3. They let you stay connected as you roam from one network area to
another
4. They have unique security considerations
5. They have different hardware
6. They offer performance that differs from wired LANs

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COMPETING TECHNOLOGIES TO IEEE 802.11
 HiperLAN2
 5.4 to 5.7 GHz band
 Development by the European
Telecommunications Standardization Institute
(ETSI)
 Based on connection-oriented links
 Best suited to wireless multimedia because of
its integrated Quality of Service (QoS) support
 HomeRF
 Home networking technology developed in
2000
 Uses radio frequencies to transmit data over
ranges of 75 to 125 feet
 Can connect up to 127 network devices and

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DIFFERENCE BETWEEN
WIRED AND WIRELESS LAN
 WIRED:
 IP address is equivalent to a physical location or
hardwired connection
 Uses a CAT-n LAN cable to connect NIC to LAN
 WIRELESS:
 Addressable unit is a Station (STA) - Does not
indicate a fixed location

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 WIRED:
 Highly predictable and reliable transmission
 Challenges to be addressed by WLAN
 Highly unreliable
 Dynamic topology
 Prone to outside EM interference
 Experiences time-varying multipath effects
and hence usable range of system varies
 Must handle portable and mobile stations
 Deal with battery powered equipment

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IEEE 802.11 ARCHITECTURE
 Each computer, mobile -
portable or fixed, is
referred to as a station
 When two or more
stations come together to
communicate with each
other without any base,
they form an Independent
Basic Service Set (IBSS)
 Such a network is called
Ad-Hoc network/Peer to
peer network

When two or more stations come together to
communicate with each other with a base (AP), they
form a Basic Service Set (BSS)
25

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BSS's are interconnected
using a Distribution System:
forms Infrastructure Network
Data moves between the BSS
and the DS with the help of
APs
DS increases network
coverage
Creating large networks
using BSS's and DS's leads to
Extended Service Set (ESS)

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If a node/station can move within its BSS, then it is called No Transition
Node.
If a node/station can move within its ESS, then it is called BSS transition
node.
If a node station can more from one ESS to another it is called ESS
transition node

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TYPES OF STATIONS IN ESS
 Three types of stations defined by IEEE 802.11
depending on their mobility in WLAN
 No transition Mobility: Defined as a station
which is non-moving or moving only inside a
BSS
 BSS Transition Mobility: Defined as a station
which can move from BSS to another but does
not move outside one ESS
 ESS transition Mobility: Defined as a station
which can move from one ESS to another

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WLAN EQUIPMENTS
 Three main links that form basis of a wireless
network
 LAN adapter
 Same as wired adapters: PCMCIA, Card bus,
PCI and USB
 Enable users to access network
 Access point (AP)
 Wireless equivalent of a LAN hub
 Receives, buffers and transmits data
between WLAN and wired network
 Outdoor LAN bridges
 Used to connect LANs in different buildings

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802.11 Services
This station is within the range of
various APs.
To which AP should it get
associated?
Now that we are connected…..

34
The process by which each station associates itself to its AP is called
Scanning….
1. The station will send a Probe frame and will be received by each AP
2. The APs will send Probe Response frame to all stations
3. The Association Request is send by the station
4. The Association Response frame is send by AP
5. Connection is build

35
Physical layer – 802.11a 802.11b 802.11g
Distributed Co-ordination Function (DCF)
Point Co-ordination Function (PCF)
IEEE 802.1
Contention Free (Optional) Contention Based
(Compulsory)
{Based on coding, multiplexing, encryption/decryption, modulation}

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Distributed Co-ordination Function
1. Provides contention based services ( ie multiple stations content among
themselves to get access of channels.)
2. Uses CSMA/CA (and not CSMA/CD)
3. Operates on half duplex
Note: Actually CSMA/CD is a better technique….. Since we can do
retransmission
But we cannot use CSMA/CD in wireless because of the following reason-
In order to detect collision the
station has to be full duplex
Sending Listening
PC1

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Sender Receiver
DIFS
SIFS
SIFS
SIFS
RTS (Request to send)
CTS (Clear to send)
(data)
ACK
1. Distributed Inter Frame
Space time (DIFS)
2. Short Inter Frame Space
(SIFS)
?? How do the
other stations
know that they do
not have to send
data in between
these??
Control Frame

38
RTS has a field of time (Duration field). Other channels know that the
channel is going to be busy for that much amount of time
When they sense the RTS frame, they start their NAV (Network Allocation
Vector)

39
 Basic CSMA-CA Operation
Had Sensed the NAV

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duration depends
on MAC load type

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VIRTUAL CARRIER SENSING
 Each transmitted data frame contains duration field, which indicates
time for which channel is reserved for transmission of that data frame
 This information used by stations that can hear transmitter to update
their Network Allocation Vectors (NAVs)
 NAV is a timer that is always decreasing if its value is nonzero
 Station is not allowed to initiate a transmission if its NAV is nonzero
 Use of NAV to determine busy/idle status of channel is referred as
virtual carrier sense mechanism

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Lets consider the case when A wants to send some data to B and C wants to
send some data to B
But A and C are hidden from each other. They can both send the data at the
same time and will lead to collision
Suppose A and C sense the channel at the same time and they will find it idle
A B C
RTS RTS
CTS

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Station is not able to send data even when channel is idle

46
USE OF RTS/CTS
 To handle Hidden-station and Exposed-station problem

50
PHYSICAL LAYER OF IEEE 802.11
 Handles transmission of data between stations
 Defines a single MAC which interacts with any of the
three PHYs
 Physical layer comprises of the two sub layers for each
station:
 Physical Layer Convergence Procedure (PLCP)
 Physical Medium Dependent (PMD)

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 Physical Layer Convergence Procedure (PLCP)
 Provides a convergence function that maps MAC
PDU into a format suitable for transmission and
reception over given medium
 Delivers the incoming frames from the wireless
medium to the MAC layer
 Physical Medium Dependent (PMD)
 Concerned with the characteristics and methods for
transmitting over wireless medium, like modulation
techniques, data rate etc.

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 Stations deliver MAC Service Data Units (MSDUs) (up to
2312 bytes) to MAC layer
 In MAC layer, MSDUs are fragmented into smaller frames
called MAC protocol data units (MPDUs)
 MPDUs sent as independent transmissions, each of which
is separately acknowledged
 The fragments of a single MSDU are sent as a burst during
the CP or as individual frames during a CFP.

53
PHYSICAL LAYER
 Preamble: Provide sync & start of frame info
 Header: Provides transmission bit rate, other initialization info, frame
length info & CRC

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 Specific structure of PLCP depends on the particular
physical layer definition
 FHSS PLCP frame format
 80 bits of 0101 pattern : used by Rx to detect presence of
signal & to acquire symbol timing
 Pattern : 0000 1100 1011 1101
 Specifies PLCP length
 1 bit for 1/2 Mbps; 3 bits reserved
 For ECC

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 DSSS PLCP frame format
 Used by Rx to detect presence of signals
 For bit sync; F3A0
 Indicates the modulation technique used; 0A:1 Mbps DBPSK;
14:2 Mbps DQPSK
 For future use
 Number of bytes in payload
 For ECC

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 IR PLCP frame format
Transmission is using slots of 250 ns and not bits
For 1 Mbps: 16 PPM slots; only one slot can contain a pulse;
modulation using 4 bits at a time
 57-73 PPM slots of alternating presence and absence of
pulses
 For bit and symbol sync and to indicate start of frame; 1001
 000: 1 Mbps; 001: 2 Mbps
 DC level adjust of pulses
 Length of payload
 For ECC

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DATA LINK LAYER
 Consists of two sublayers
 Logical Link Control (LLC)
 Media Access Control (MAC)
 Uses 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... CSMA/CD

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802.11 FRAME STRUCTURE
 Support three types of frames-
 Management frames: Used for
 Station association and disassociation with AP
 Timing & synchronization
 Authentication & Deauthentication
 Control frames: Used for
 Handshaking
 Positive acknowledgement during data exchange
 Data frames: Used for
 Transmission of data

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 Version: 0 for now
 Type: Mgmt:00; Control:01; Data: 10
 Subtype: eg. Association request, authentication etc.
 More Frag: if 1; there is another fragment of current MSDU to follow
 Retry: if 1; data/mgmt frames are retransmitted ; to identify duplicate frames
 Pwr mgt: if 1; set
 More data: if 1 indicates to station in power save mode that there are more MSDUs
buffered for it in AP
 WEP: if 1; frame body field is encrypted

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 Duration /ID: Contains NAV or if control info is sent, contains ID of STA that
transmitted the frame
 Sequence control: Indicates the number of fragment of MSDU
 Frame body: Payload
 CRC: For ECC; calculated over header and frame body

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 WHY FRAGMENTATION
 To deal with noisy wireless channels, frames are
fragmented into smaller pieces, each with its own
checksum
 Fragments are numbered and acknowledged
 Fragmentation increases the throughput by restricting
retransmissions to the bad fragment rather than the
entire frame

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MAC SUBLAYER FUNCTIONS
 Channel access procedures
 PDU addressing
 Frame formatting
 Error checking
 Fragmentation and reassembly of MSDUs
 Support security services through authentication
and privacy mechanisms
 Supports roaming within ESS
 Power management

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IEEE 802.11 MAC PROTOCOL
 Specified in terms of coordination function
 Determines when a station in BSS is allowed to
transmit and when it may be able to receive PDUs
over the wireless medium
 Two types of
coordination
function
 Distributed
coordination
function (DCF)
 Point
coordination
function (PCF)

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 Distributed coordination function (DCF)
 Implemented in all STA
 Provides support for async data transfer of MAC
SDUs on best effort basis
 Transmission medium operates in contention mode
exclusively
 Point coordination function (PCF)
 It is optional
 Implemented by AP to support connection oriented
time bounded transfer of MAC SDUs
 Under PCF, medium can alternate between
contention mode and contention-free period (CFP)
 During CFP, medium usage is controlled by AP
eliminating need for STAs to contend for channel
access

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DISTRIBUTED COORDINATION FUNCTION
 Uses contention services based on CSMA-CA
 Three different IFS defined
 SIFS – Short interframe space
 PIFS – PCF interframe space
 DIFS - DCF interframe space
 Length of IFS depends on type of frame to be transmitted
 Provide priority levels for access to wireless media

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 SIFS – Short Interframe Space : eg. ACK, CTS,
frames from STA responding to a poll from AP in
PCF, any frame from AP during CFP
 PIFS – PCF Interframe Space: Used by PCF to gain
priority access to medium at start of CFP
 DIFS - DCF Interframe Space : Used by DCF to
transmit data and manage MPDUs

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PHYSICAL SENSING
 Each station with a packet to transmit first senses channel to find
out whether it is in use
 If channel is sensed to be idle for an interval greater than
distributed interframe space (DIFS), station proceeds with its
transmission
 If channel is sensed as busy, station defers transmission till end
of ongoing transmission
 Station then initializes its backoff timer with a randomly selected
backoff interval and decrements this timer every time it senses
channel to be idle
 Station starts its transmission when backoff timer reaches zero

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POINT COORDINATION FUNCTION
 Optional capability
 Provides connection-oriented,
contention-free services by
enabling polled stations to
transmit without contending for
the channel
 Performed by point coordinator
(PC) in AP within BSS
 Coexists with DCF and logically
operates over DCF

 Stations capable to operating in CFP called CF-aware stations
 CFP repetition interval determines the frequency with which PCF
occurs
 Within repetition interval, a portion of time is allocated to
contention-free traffic, remaining to contention-based traffic
 Maximum size of CFP is determined by a parameter
CFP_Max_Duration (set by AP) and used by STAs to set their
NAV
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 CFP initiated at TBBT (Target beacon transmission time) by transmitting a
beacon frame by PC in AP
 STAs can transmit only to respond to poll or to transmit ack one SIFS interval
after receipt of MPDU
 RTS/CTS not used by PC or CF-aware stations.
 CF-ware stations transmit frames and piggyback ack
 If frame sent to non-CF aware station, ack sent using DCF rules
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WPAN- 802.15.1/3/4
(BLUETOOTH,
ZIGBEE)
Module 4

WPAN
A wireless personal area network (WPAN) is a short-distance (typically 10 m but as far
as 20 m) wireless network specially designed to support portable and mobile
computing devices such as PCs, PDAs, printers, storage devices, cellphones, pagers,
set-up boxes, and a variety of consumer electronic equipment.
Many cell phones already have two radio interfaces, one for the cellular network and
the other for PAN connections.
WPANs such as Bluetooth provide enough bandwidth and convenience to make data
exchange practical for certain mobile devices requiring data exchanges at rates up to
1 Mbps.
At the other end of the scale, UWB will provide the capability of streaming video
signals at data rates up to 1 Gbps.
However, many control and command applications require much lower data rates and
also the lowest possible cost, thus ZigBee.

EXAMPLE TECHNOLOGIES FOR
WPAN
Bluetooth (IEEE 802.15.1)
UWB (IEEE 802.15.3a)
ZigBee (IEEE 802.15.4)
are examples of WPANs that allow devices within close proximity to
join together in wireless networks in order to exchange
information.

- WLAN WPAN
Standard IEEE 802.11.x = b, g, a, n, ac IEEE 802.15.1, 802.15.3,
802.15.4
Definition A wireless local area network
(WLAN) is a wireless
computer network that links
two or more devices using a
wireless distribution method
within a limited area such as
a home, school, computer
laboratory, or office
building.
A (WPAN) wireless personal
area network is a low range
wireless network which
covers an area of only a few
dozens of meters
Layers PHY and MAC used with
TCP/IP
PHY and MAC used with
Zigbee
Frequency Band 2.4 GHz ISM (802.11b/g/n)
5 GHz (802.11a/n/ac)
2.4 GHz ISM (also 868/900
MHz)
Power consumption (low power mode Low power
Peak current 100-200 mA 18 mA
Max. Tx-Power 100-200 mA typ. 0 dBm
Range 30m/300m in/outdoor 20 m indoor
Modulation OFDM DSSS (802.11b) DSSS, O-QPSK

BLUETOOTH ARCHITECTURE
(802.15.1)
Bluetooth defines two types of networks: piconet and scatternet.
Piconets:
 A Bluetooth network is called a piconet, or a small net. A piconet can have up
to eight stations, one of which is called the primary; the rest are called
secondaries. All the secondary stations synchronize their clocks and hopping
sequence with the primary. Note that a piconet can have only one primary
station. The communication between the primary and secondary stations can
be one-to-one or one-to-many. Fig.1 shows a piconet.

PICONET
Although a piconet can have a maximum of seven secondaries, additional
secondaries can be in the parked state. A secondary in a parked state is
synchronized with the primary, but cannot take part in communication until it is
moved from the parked state to the active state. Because only eight stations can
be active in a piconet, activating a station from the parked state means that an
active station must go to the parked state.

SCATTERNET
Piconets can be combined to form what is called a scatternet. A secondary
station in one piconet can be the primary in another piconet. This station can
receive messages from the primary in the first piconet (as a secondary) and,
acting as a primary, deliver them to secondaries in the second piconet. A
station can be a member of two piconets.
Fig.2 shows a scatternet.

ZIGBEE
zigbee is an IEEE 802.15.4-based specification for a suite of high-level
communication protocols used to create personal area networks with small, low-
power digital radios, such as for home automation, medical device data
collection, and other low-power low-bandwidth needs, designed for small scale
projects which need wireless connection. Hence, Zigbee is a low-power, low data
rate, and close proximity (i.e., personal area) wireless ad hoc network.
The technology defined by the Zigbee specification is intended to be simpler and
less expensive than other wireless personal area networks (WPANs), such as
Bluetooth or more general wireless networking such as Wi-Fi. Applications
include wireless light switches, home energy monitors, traffic management
systems, and other consumer and industrial equipment that requires short-range
low-rate wireless data transfer.

ZIGBEE
Its low power consumption limits transmission distances to 10–100 meters line-of-
sight, depending on power output and environmental characteristics. Zigbee
devices can transmit data over long distances by passing data through a mesh
network of intermediate devices to reach more distant ones. Zigbee is typically used
in low data rate applications that require long battery life and secure networking
(Zigbee networks are secured by 128 bit symmetric encryption keys.) Zigbee has a
defined rate of 250 kbit/s, best suited for intermittent data transmissions from a
sensor or input device.
Zigbee was conceived in 1998, standardized in 2003, and revised in 2006. The
name refers to the waggle dance of honey bees after their return to the beehive.

STAR TOPOLOGY
In the star topology, communication is established between devices and a single
central controller, called the PAN coordinator.
After an FFD is activated for first time, it may establish its own network and
become PAN coordinator.
Each star network chooses a PAN identifier, which is not currently used by any
other network within the radio sphere of influence. This allows each star network
to operate independently.
The PAN coordinator may be powered by mains while the devices will most likely
be battery powered.
Applications that benefit from this topology are home automation, personal
computer (PC) peripherals, toys and games.

PEER-TO-PEER TOPOLOGY
In peer-to-peer topology too, there is one PAN coordinator.
Any device can communicate with any other device as long as they
are in range of one another.
Thus a peer-to-peer network can be ad hoc (unfixed), self-
organizing, and self-healing.
Peer-to-peer topology allows multiple hops to route messages from
any device to any other device in the network. It can provide
reliability by multipath routing.
Applications such as industrial control and monitoring, wireless
sensor networks and assets and inventory tracking would benefit
from such a topology.

CLUSTER-TREE TOPOLOGY
The cluster-tree topology is a special case of a peer-to-peer network in which most devices
are FFDs.
Any of the FFDs can act as a coordinator and provide synchronization services to other
devices and coordinators. However, only one of these coordinators is PAN coordinator.
The PAN coordinator forms the first cluster by establishing itself as cluster head (CLH) with
a cluster identifier of zero (CID), choosing an unused PAN identifier.
The CLH broadcasts beacon frames to neighboring devices.
A candidate device receiving a beacon frame may request to join the network at cluster
head.
If the PAN coordinator permits the device to join, it will add this new device to its neighbor
list.
The newly joined device will add the cluster head as its parent in its neighbor list and begin
transmitting periodic beacons such that other candidate devices may then join the network
at that device.
Once application or network requirements are met, the PAN coordinator may instruct a
device to become the cluster head of a new cluster adjacent to the first one.
In this way, an RFD may connect to a cluster tree network as a leaf node at the end of a
branch.

NEED OF ZIGBEE IN WIRELESS
SENSOR NETWORK
A wireless sensor network (WSN) consists of sensors which are densely
distributed to monitor physical or environmental conditions, such as
temperature, sound, pressure, etc.
The sensor data is transmitted to network coordinator which is heart of the
wireless personal area network.
In the modern scenario wireless networks contains sensors as well as
actuators. ZigBee is newly developed technology that works on IEEE standard
802.15.4, which can be used in the wireless sensor network (WSN).
The low data rates, low power consumption, low cost are main features of
ZigBee. WSN is composed of ZigBee coordinator (network coordinator),
ZigBee router and ZigBee end device.
The sensor nodes information in the network will be sent to the coordinator,
the coordinator collects sensor data, stores the data in memory, process the
data, and route the data to appropriate node.

NEED OF ZIGBEE IN WIRELESS
SENSOR NETWORK

Zigbee is low power, low cost, wireless network communication based on the standard
IEEE 802.15.4.
Zigbee is suitable for low power, low data rate and secure application for wireless
personal area networking (WPAN).
Zigbee supports mesh, start, tree and other networking topologies.
Zigbee works on the unlicensed spectrum ranging from 2.4-2.48GHz, 902 to 928 MHz
and 86 to 868.6MHz.
It works on an operating distance upto 100m at a data rate of 20 to 250kbps. As shown
in the diagram above, zigbee devices can be classified into 3 categories.
a. Zigbee coordinator: This device is responsible for the creation of the network and for
initiation of communication
b. ZigBee Router: It is responsible for routing the data to de=different end-devices
across the network.
c. ZigBee End Device: It can only communicate with the ZR or ZC but doesn’t have
capability to act as the mediator for transferring data from one device to another.
Zigbee is used for applications involving wireless sensor networks, industrial
automation, home automation, Automatic meter reading, smoke detectors, etc.

ZIGBEE PROTOCOL
The IEEE 802.15.4 committee and ZigBee Alliance worked together and developed the
technology commercially known as ZigBee. The IEEE 802.15.4 committee focuses on
the specifications of the lower two layers of the protocol (the physical and data link
layers). On the other hand, ZigBee Alliance aims to provide the upper layers of the
protocol stack (from the network to the application layer)
1. Physical Layer Protocol
i. The PHY provides two services: the PHY data service and PHY management service
interfacing to the physical layer management entity (PLME).
ii. To maintain a common simple interface with MAC, both PHY share a single packet
structure.

ZIGBEE PROTOCOL
Each PHY protocol data unit (PPDU) contains a synchronization header
(preamble plus start of packet delimiter), a PHY header to indicate the packet
length, and the payload, or PHY service data unit (PSDU).
The 32-bit preamble is designed for the acquisition of symbol and chip timing,
and in some cases may be used for coarse frequency adjustment.
Within the PHY header, 7 bits are used to specify the length of the payload (in
bytes). This supports packets of length 0–127 bytes, although, due to MAC
layer overhead, zero-length packets will not occur in practice.
Typical packet sizes for home applications such as lighting, air conditioning,
etc. are expected to be of the order of 30–60 bytes, while more demanding
applications such as interactive games and computer peripherals, or multihop
applications with more address overhead, may require larger packet sizes.
The maximum packet durations are 4.25 ms for the 2.4 GHz band, 26.6 ms for
the 915 MHz band, and 53.2 ms for the 868 MHz band.

ZIGBEE PROTOCOL
2. Data Link layer Protocol
i. The data link layer is divided into two sublayers, the MAC and LLC sublayers.
The logical link control is standardized in IEEE 802.2 and is common among all
IEEE 802 standards.
ii. The MAC frame structure is very flexible to accommodate the needs of
different applications and network topologies while maintaining a simple
protocol.

ZIGBEE PROTOCOL
The MAC protocol data unit (MPDU) consists of the MAC header (MHR), MAC
service data unit (MSDU), and MAC footer (MFR).
The first field of the MAC header is the frame control field, which indicates the
type of MAC frame being transmitted, specifies the format of the address field,
and controls the acknowledgment.
The frame control field specifies how the rest of the frame looks and what it
contains.
The size of the address field may vary between 0 and 20 bytes.
The payload field is variable in length; however, the complete MAC frame may not
exceed 127 bytes in length. The data contained in the payload is dependent on
the frame type.
The MAC has four different frame types. These are the beacon frame, data frame,
acknowledgment frame and MAC command frame. Only the data and beacon
frames actually contain information sent by higher layers; the acknowledgment
and MAC command frames originate in the MAC and are used for MAC peer-to-
peer communication.
Other fields in the MAC frame are the sequence number and frame check
sequence (FCS). The sequence number in the MAC header matches the
acknowledgment frame with the previous transmission. The FCS (16 bit CRC) helps

ZIGBEE PROTOCOL
3. Super frame
Some applications may require a dedicated bandwidth to achieve low
latencies. To accomplish these low latencies, the IEEE 802.15.4 LR-WPAN can
operate in an optional superframe mode.
In a super frame, a dedicated PAN coordinator transmits super frame beacons
in predetermined intervals.
These intervals can be as short as 15 ms or as long as 245 seconds.

ZIGBEE PROTOCOL
The time between two beacons is divided into 16 equal time slots independent of the
duration of the superframe.
The beacon frame is sent in the first slot of each superframe. The beacons are used to
synchronize the attached devices, to identify PAN, and describe the structure of
superframes.
A device can transmit at any time during the slot, but must complete its transaction
before the next superframe beacon.
The channel access in time slots is contention based; however, the PAN coordinator
may assign time slots to a single device that requires a dedicated bandwidth or low
latency transmissions.
These assigned time slots are called guaranteed time slots (GTSs) and together form a
contention-free period (CFP) located immediately before the next beacon.
The size of the CFP may vary depending on the demand by the associated network
devices; when guaranteed time slots are used, all devices must complete their
contention-based transactions before the CFP begins. The beginning of the CFP and
duration of the superframe are communicated to the attached network devices by the
PAN coordinator.
The PAN coordinator may allocate up to seven of the GTSs and a GTS can occupy more
than one slot period.

4. Network Layer Protocols
The network layer of Zigbee (IEEE 802.15.4) is responsible for topology
construction and maintenance as well as naming and binding services, which
include the tasks of addressing, routing, and security.
The network layer should be self-organizing and self-maintaining to minimize
energy consumption and total cost.
IEEE 802.15.4 supports multiple network topologies, including star, peer-to-peer,
and cluster tree. The topology is an application design choice.
The topology of the network is formed on the basis of algorithms (e.g. cluster tree
algorithm). The devices communicate with each other only on the basis of
algorithm to form the network.
Routing protocols for ad hoc networks can be divided into two groups: table
driven (proactive) (e.g. ‘Destination Sequenced Distance Vector (DSDV)’) and
source-initiated on-demand-driven(reactive) (e.g. ‘Ad-hoc on demand Distance
Vector (AODV)’).
The table-driven approach has low latency and high overhead, and is more
suitable when time constraints are significant.
On the other hand, the source-initiated on-demand-driven approach has high
latency and low overhead. It is more suitable for a mobile environment with a
limited bandwidth capacity.
The Zigbee routing algorithm is based on a hierarchical routing strategy with
table-driven optimizations applied where possible.

Sr No Parameter Zigbee Bluetooth
1 Frequency Band 2.4 GHz(Globally) 2.4GHz
2 Nodes Per Network 65000 7
3 IEEE Standard 802.15.4 802.15.1
4 Topology Tree, Star, Mesh, Cluster Tree
5 Bandwidth 20-250 KBPS 1 MBPS
6 Range(Meter) 1 to75 & more 1 ...

WIMAX
The ‘World Interoperability for MicroAcess, Inc. (WiMAX)’ forum, an industry
group, focuses on creating advanced technology solution for high speed
wide area internet access.
The WiMAX product certification program ensures interoperability between
WiMAX equipment from vendors worldwide.
WiMAX can serve as a backbone for 802.11 hotspots for connecting to the
internet. Alternatively, users can connect mobile devices such as laptops and
handsets directly to WiMAX base stations. Mobile devices connected directly
can achieve a range of 4 to 6 miles.
There are 2 types of WiMAX, fixed WiMAX(IEEE 802.16d-2004) and mobile
WiMAX(IEEE802.16e-2005). Fixed WiMAX is a point-to-multipoint
technology, whereas mobile WiMAX is a multipoint-to-multipoint
technology, similar to that of a cellular infrastructure.

WI-MAX AND LTE /3GPP
COMPARISON, MI-FI, LY-FI
MODULE 4

WIMAX
WiMAX is one of the hottest broadband wireless technologies around today. WiMAX systems
are expected to deliver broadband access services to residential and enterprise customers in
an economical way.
Loosely, WiMax is a standardized wireless version of Ethernet intended primarily as an
alternative to wire technologies (such as Cable Modems, DSL and T1/E1 links) to provide
broadband access to customer premises.
More strictly, WiMAX is an industry trade organization formed by leading communications,
component, and equipment companies to promote and certify compatibility and
interoperability of broadband wireless access equipment that conforms to the IEEE 802.16 and
ETSI HIPERMAN standards.
WiMAX would operate similar to Wi-Fi, but at higher speeds over greater distances and for a
greater number of users.
WiMAX has the ability to provide service even in areas that are difficult for wired infrastructure
to reach and the ability to overcome the physical limitations of traditional wired infrastructure.
WiMAX was formed in April 2001, in anticipation of the publication of the original 10-66 GHz
IEEE 802.16 specifications.
WiMAX is to 802.16 as the Wi-Fi Alliance is to 802.11.
WiMAX is Acronym for Worldwide Interoperability for Microwave Access.
Based on Wireless MAN technology it is a wireless technology optimized for the delivery of IP
centric services over a wide area.
It is a scalable wireless platform for constructing alternative and complementary broadband

WIMAX
The IEEE 802.16, the Air Interface for Fixed Broadband Wireless
Access Systems, also known as the IEEE Wireless MAN air interface, is
an emerging suite of standards for fixed, portable and mobile BWA in
MAN.
These standards are issued by IEEE 802.16 work group that originally
covered the wireless local loop (WLL) technologies in the 10.66 GHz
radio spectrum, which were later extended through amendment
projects to include both licensed and unlicensed spectra from 2 to 11
GHz.
The WiMAX umbrella currently includes 802.16-2004 and 802.16e.
802.16-2004 utilizes OFDM to serve multiple users in a time division
fashion in a sort of a round-robin technique, but done extremely
quickly so that users have the perception that they are always
transmitting/receiving. 802.16e utilizes OFDMA and can serve
multiple users simultaneously by allocating sets of tones to each

FEATURES OF WI-MAX
1) Frequency Band = 10-66 GHz
2) Modulation used = QPSK-16
3) Channel bandwidth =1.25 MHz--- 25 MHz
4) IEEE Standard =802.16 ,802.16,802.16 e
5) Data rate = max of 75 Mbps
6) Coverage area = 10 Km

SALIENT FEATURES SUPPORTED BY
WIMAX
High data rates:
 WiMAX can typically support data rates from 500 Kbps to 2 Mbps. - The inclusion of multi-
input multi-output(MIMO) antenna techniques along with flexible sub-channelization schemes,
advanced coding and modulation all enable mobile to support peak downlink data rates of 63
Mbps per sector and peak uplink data rates of up to 28 Mbps per sector in a 10 MHz channel.
Quality of service (QoS):
 WiMAX has clearly defined QoS classes for applications with different requirements such as
VoIP, real time video streaming, file transfer and web traffic.
Scalability:
 Mobile WiMAX is designed to able to work in different channelization from 1.25 to 20 MHz to
comply with varied world-wide requirements.
Security:
 There is support for diverse set of user credentials like SIM/USIM cards, smart cards, digital
certificates, username/password schemes.
 All this is based on relevant ‘extensible authentication protocol (EAP)’ methods for credential
type.
Mobility:
 Mobile WiMAX supports optimized handoff schemes with latencies less than 50ms to ensure
that real time applications such as VoIP can be performed without service degradation.
 Flexible key management schemes assume that security is maintained during handoff.

WIMAX PHYSICAL LAYER (PHY):
For bands in 10-66GHz range, 802.16 defines one interface called Wireless
MAN-SC
For 2-11GHz (both licensed and unlicensed):
Wireless MAN-SC (single carrier modulation)
Wireless MAN-OFDM (256 carrier OFDM with access to different stations using
TDMA)
Wireless MAN-OFDM (2048 carrier OFDM by assigning subset of carriers to
individual station)
WiMAX PHY features include ‘Adaptive Modulation and Coding (AMC)’, ‘Hybrid
Automatic Repeat Request (HARQ)’, ‘Channel Quality Indicator Channel (CQICH)’
which is a feedback channel.
All these features provide robust link adoption in mobile environment at
vehicular speeds in excess of 120Km/h.

WIMAX MEDIUM ACCESS CONTROL
(MAC):
Each subscriber station need to compete for media only one (for
entry).Then, WiMAX base station provides time slot to each subscriber
station which may increase or decrease depending on need.
There is a scheduling algorithm for service to each station. This
algorithm is robust and not affected by over loading and over
subscription.
WiMAX supports different transport technologies such as IPv4, IPv6 and
Ethernet.
WiMAX mesh networking allows subscriber stations to communicate
with each other i.e. “Subscriber” mode and with base station i.e. “base
station” mode simultaneously.

SPECTRUM ALLOCATION FOR
WIMAX:
The biggest spectrum segment for WiMAX is around 2.5GHz.
The other bands are around 3.5HZ, 2.3/2.5GHz, or 5GHz, with
2.3/2.5GHz.

OTHER FEATURES
The mesh mode of WiMAX enables subscriber stations to relay traffic to one
another. Thus, a station that does not have line-of-sight with the base station
can get its traffic from another station.
WiMAX technology can provide fast and cheap broadband access to markets that
lack infrastructure (fiber optics, copper wire), such as rural areas and unwired
countries. WiMAX can also be used in backup during disasters, which may lead
the wired networks to get broken down.
As mobile WiMAX is scalable in both radio access and network architecture, it
provides flexibility in network deployment options and service offerings.
Mobile WiMAX based on 802.16e uses OFDMA in which carriers are divided
among users to form sub channels. The coding and modulation are adapted
separately for each sub channel.
SOFDMA is an enhancement of OFDMA that scale the number of subcarriers in a
channel with possible values of 128, 512, 1024, and 2048.
802.16e includes power-saving and sleep modes to extend battery life if mobile
devices.
802.16e also supports hard and soft handoff to provide users with seamless
connections as they move across coverage areas of adjacent cells.

MESH MODE IN IEEE 802.16
(WIMAX)

WIMAX STANDARDS
A certification that denotes interoperability of equipment built to the
IEEE 802.16 or compatible standard. The IEEE 802.16 Working Group
develops standards that address three types of usage models –
IEEE 802.16a (2003)
A fixed usage model (IEEE 802.16).(2004)
A portable usage model (IEEE 802.16e).(2005)

IEEE 802.16A
WiMAX is such an easy term that people tend to use it for the 802.16
standards and technology themselves, although strictly it applies only
to systems that meet specific conformance criteria laid down by the
WiMAX Forum.
The 802.16a standard for 2-11 GHz is a wireless metropolitan area
network (MAN) technology that will provide broadband wireless
connectivity to Fixed, Portable and Nomadic devices.
It can be used to connect 802.11 hot spots to the Internet, provide
campus connectivity, and provide a wireless alternative to cable and
DSL for last mile broadband access.

WI-MAX 802.16 BASED PROTOCOL
ARCHITECTURE
WiMAX is an advanced technology designed for very high speed wide
area Internet access(Point to Multipoint), in a low-cost, flexible way.
• IEEE 802.16 Standard is used for Wi Max.
• Fig 1 Shows Wi- Max Protocol Architecture.

WI- MAX PROTOCOL
ARCHITECTURE
• There are Four protocol layers as shown in fig 1.
• Physical Layer :- It is responsible for the frequency band & medium
of transmission, bit rate ,generating frames etc
• Transmission layer : It deals with encoding or decoding of signals ,
Transmission or reception of data bits.
• Medium Access Cotrol (MAC)Layer : It is responsible for
transmitting data frames & controlling wireless access.
• Convergence layer : Provides Functions that are required for
providing required service

WI- MAX PROTOCOL
ARCHITECTURE
There are four protocol layers:-
Physical Layer: - It is responsible for performing functions like
encoding/decoding of signals, generating preamble,
transmitting/receiving a data bit. It comprises of the frequency band
and medium of transmission.
Transmission Layer: It deals with encoding/decoding signals,
generating preamble, transmitting/receiving data bits.
Medium Access Control Layer (MAC) Layer: It is responsible for
transmitting the data frames and controlling wireless access. This
layer is simple. It indicates when a subscriber or base station can
begin transmission.
Convergence Layer: It provides functions that are required for
providing a particular service.

SPEED AND RANGE:
WiMAX is expected to offer initially up to about 40 Mbps capacity per wireless
channel for both fixed and portable applications, depending on the particular
technical configuration chosen, enough to support hundreds of businesses with
T-1 speed connectivity and thousands of residences with DSL speed
connectivity. WiMAX can support voice and video as well as Internet data.
WiMax developed to provide wireless broadband access to buildings, either in
competition to existing wired networks or alone in currently unserved rural or
thinly populated areas. It can also be used to connect WLAN hotspots to the
Internet.
WiMAX is also intended to provide broadband connectivity to mobile devices. It
would not be as fast as in these fixed applications, but expectations are for
about 15 Mbps capacity in a 3 km cell coverage area.
With WiMAX, users could really cut free from today's Internet access
arrangements and be able to go online at broadband speeds, almost wherever
they like from within a Metro Zone.
WiMAX could potentially be deployed in a variety of spectrum bands: 2.3GHz,
2.5GHz, 3.5GHz, and 5.8GHz

ADVANTAGES OF WIMAX
WiMAX can satisfy a variety of access needs. Potential applications include
extending broadband capabilities to bring them closer to subscribers, filling
gaps in cable, DSL and T1 services, Wi-Fi, and cellular backhaul, providing
last-100 meter access from fiber to the curb and giving service providers
another cost-effective option for supporting broadband services.
WiMAX can support very high bandwidth solutions where large spectrum
deployments (i.e. >10 MHz) are desired using existing infrastructure keeping
costs down while delivering the bandwidth needed to support a full range of
high-value multimedia services.
WiMAX can help service providers meet many of the challenges they face due
to increasing customer demands without discarding their existing
infrastructure investments because it has the ability to seamlessly
interoperate across various network types.
WiMAX can provide wide area coverage and quality of service capabilities for
applications ranging from real-time delay-sensitive voice-over-IP (VoIP) to
real-time streaming video and non-real-time downloads, ensuring that
subscribers obtain the performance they expect for all types of
communications.
WiMAX, which is an IP-based wireless broadband technology, can be
integrated into both wide-area third-generation (3G) mobile and wireless and
wireline networks allowing it to become part of a seamless anytime, anywhere
broadband access solution.

ADVANTAGES & DISADVANTAGES
OF WIMAX
Advantages:
1. Single station can serve hundreds of users.
2. Speed of 10 Mbps at 10 kilometers with line-of-sight.
Disadvantages :
1. Line of sight is needed for longer connection.
2. Weather conditions like rain can interrupt the signal.
3 Other wireless equipment’s can interrupt the signal.
4 multiplied frequencies are used.

DIFFERENCE BETWEEN WI-FI AND
WIMAX:
Sr.No Wi-Fi WiMAX
1. Wi-Fi technology is based on IEEE
802.11 standards.
WiMAX technology is based on IEEE
802.16 standards.
2. 802.11a-OFDM,maximum
rate=54Mbps.,802.11b-
DSSS,maximum
rate=11Mbps.,802.11g-
OFDM,maximum rate=54Mbps.
802.16-OFDM, maximum
rate=50Mbps.,802.16e-OFDM,
maximum rate~30Mbps.
3. The stations gain access to media
based on CSMA/CA and back off
algorithm schemes.
There is time slot for each station and
there is scheduling algorithm used by
base station.
4. Range is less than 100 meters. A kilometer non-line-of-sight, more
with line-of-sight.
5. Indoor Environment. Outdoor Environment.
6. No Quality of Service. Five Quality of service enforced by
base station.

Emerging Wireless Technologies and Standards

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