IoT Networking Technologies: Bluetooth Technology Overview

Sayed Chhattan Shah
Associate Professor
Department of Information Communications Engineering
Hankuk University of Foreign Studies Korea
www.mgclab.com
IoT Networking Technologies

Acknowledgements
 David B. Johnson, Rice University, Multihop Wireless Ad Hoc Networking:
Current Challenges and Future Opportunities
 Carlos Pomalaza-Ráez, University of Oulu, Finland, MAC protocols for Mobile Ad
hoc Network
 Jeroen Hoebeke, Ingrid Moerman, Bart Dhoedtand Piet Demeester, Ghent
University, An Overview of Mobile Ad Hoc Networks: Applications and Challenges
 Semtech, https://www.semtech.com/lora
 The Bluetooth SIG, https://www.bluetooth.com/bluetooth-resources

Wireless Networks
 Any type of computer network that utilizes some form of wireless network
connection
 Infrastructure-based wireless networks
Cellular Network Wireless LAN

Wireless Networks
 Infrastructure-based wireless networks
o Centralized base station or access point
o Communication via base station or access point
o Require planning, installation, and management

Wireless Networks
 Wireless ad hoc network
o A decentralized type of wireless networks
o Ad hoc because it does not rely on a pre existing network infrastructure such
as routers or access points
 Multi hop mobile ad hoc network
o Nearby users directly communicate not only to exchange their own data but
also to relay the traffic of other network nodes that cannot directly
communicate

Wireless Networks
 Mobile ad hoc network is used when
o Infrastructure is not available
 Remote areas
 Unplanned meetings
 Disaster relief
 Military operations
o User does not want to use available infrastructure
 Time or cost to access service
o There is a need to extend coverage of an infrastructure
 Allow users to be further away from infrastructure

 Mobile ad hoc networking paradigms
o Mesh network
o Sensor network
o Vehicular network
o Opportunistic network
Wireless Networks

 Mesh network is a network topology in which the infrastructure nodes
connect directly, dynamically and non-hierarchically to as many other
nodes as possible and cooperate with one another to efficiently route data
Wireless Networks
https://turbofuture.com/internet

 Sensor networks consist of spatially distributed devices communicating
through wireless radio and cooperatively sensing physical or environmental
conditions
Wireless Networks

 Vehicular ad hoc network is a multihop ad hoc network made up of
vehicles
 Opportunistic mobile social networks are a form of mobile ad hoc networks
that exploit the human social characteristics, such as similarities, daily
routines, mobility patterns, and interests to perform the message routing
and data sharing
Wireless Networks

https://blog-gn.dronacharya.info/index.php/iot-communication-protocols/

https://www.bluetooth.com/blog/wireless-connectivity-options-for-iot-applications/

Bluetooth Technology
 Bluetooth is a wireless LAN technology used for exchanging data between
fixed and mobile devices over short distances
 A Bluetooth LAN is an ad hoc network
 Low-cost and low-power
 IEEE 802.15.1
 This technology was invented by Ericson in 1994

https://www.bluetooth.com/wp-content/uploads/2018/04/2019-Bluetooth-Market-Update.pdf

100 percent of smart
phones, tablets, and
laptops include Bluetooth
https://www.bluetooth.com/wp-content/uploads/2018/04/2019-Bluetooth-Market-Update.pdf

 Bluetooth is meeting market demand for
o Audio Streaming
o Data Transfer
o Location Services
o Device Networks

 Bluetooth defines two types of networks
o Piconet
o Scatternet

 A Bluetooth network is called a Piconet
o A piconet can have up to eight stations
o Secondary stations synchronize their clocks and hopping sequence with primary
o The communication between primary and secondary can be
 one-to-one
 one-to-many

 Piconets can be combined to form what is called a Scatternet
o A secondary station in one piconet can be the primary in another piconet
o This station can receive messages from the primary in the first piconet and
deliver them to secondary stations in the second piconet

 Bluetooth Architecture
o The Bluetooth protocol stack
 The protocol stack defines how technology works
o The Bluetooth profiles
 The profiles define how to use Bluetooth technology to accomplish specific tasks

L2CAP: Logical Link Control and Adaptation Protocol

 Radio layer
o The radio layer is roughly equivalent to the physical layer of the Internet model
o The radio module in a Bluetooth device is responsible for modulation and
demodulation of data into RF signals
o Bluetooth devices operate at 2.4 GHz in the license-free, globally available
ISM radio band
 The advantage of operating in this band is worldwide availability and compatibility
 A potential disadvantage is that Bluetooth devices must share this band with many
other RF emitters such as ZigBee and WiFi
o Physical range of 10 m
 Bluetooth 5.0
• 40–400 m

 Bluetooth uses the frequency-hopping spread spectrum (FHSS) method in
the physical layer to avoid interference from other devices or networks
o After a Bluetooth device sends or receives a packet, it and the device(s) it is
communicating with hop to another frequency before next packet is sent
o Bluetooth hops 1600 times per second, which means that each device changes
its modulation frequency 1600 times per second
o This scheme has two main advantages
 It ensures that any interference will be short-lived
• Any packet that doesn't arrive safely at its destination can be resent at the next frequency
 It provides a base level of security because it's very difficult for an eavesdropping
device to predict which frequency the Bluetooth devices will use next

 There are three classes of BT devices
o Class 1
 Laptops and desktops
 Range 100 meters
 Power 100mW (20dBm)
o Class 2
 Phones and headsets
 Range 20~50 meters
 Power 2.5mW (4 dBm)
o Class 3
 Extremely low power devices
 Range 1~10 meters
 Power 1mW (0 dBm)

 Baseband layer
o The baseband layer is roughly equivalent to the MAC sublayer in LANs
o Bluetooth uses a form of TDMA
 Time division duplex TDMA
o The primary and secondary communicate using time slots
o Single-Secondary Communication
 The time is divided into slots of 625 μs
 The primary uses even numbered slots and secondary uses odd-numbered slots

 Baseband layer
o Multiple-Secondary Communication
 The primary uses the even-numbered slots
 All secondary units listen on even-numbered slots, but only one secondary sends in
any odd-numbered slot
In slot 0, primary sends a frame to secondary 1
In slot 1, only secondary 1 sends a frame to primary
because previous frame was addressed to secondary 1
In slot 2, primary sends a frame to secondary 2
In slot 3, only secondary 2 sends a frame to primary
If secondary has no frame to send, channel is silent.

 The Bluetooth specification defines two types of links between BT devices
o Synchronous connection-oriented (SCO)
 A synchronous connection-oriented link is used when avoiding latency is more
important
 A physical link is created between the primary and a secondary by reserving specific
slots at regular intervals
 No retransmission if packet is damaged
 Voice information
o Asynchronous connectionless link (ACL) is used when error-free delivery is
more important than avoiding latency
 Retransmission if packet is damaged

 Frame Format
o Access code 72-bit field normally contains synchronization bits and the identifier of
the primary to distinguish the frame of one piconet from another
o Header is 54-bit field
 The 3-bit address subfield can define up to seven secondary units
 The 4-bit type subfield defines the type of data coming from the upper layers
 F 1-bit subfield is for flow control
 A 1-bit subfield is for acknowledgment.
• Bluetooth uses Stop-and-Wait ARQ
 S 1-bit subfield holds a sequence number
 HEC 8-bit header error correction subfield
is a checksum to detect errors in each
18-bit header section
o Data or Payload can be 0 to 2744 bits long

 The Logical Link Control and Adaptation Protocol (L2CAP)
o It is used for data exchange on an ACL link
o SCO channels do not use L2CAP
o Services
 Multiplexing
 Segmentation and reassembly
 Quality of service
 Group management

o Multiplexing
 At the sender site, it accepts data from one of the upper-layer protocols, frames
them, and delivers them to the baseband layer
 At the receiver site, it accepts a frame from the baseband layer, extracts the data,
and delivers them to the appropriate protocol layer
o Segmentation and Reassembly
 The maximum size of payload field in baseband layer is 2774 bits or 343 bytes
 Application layers sometimes need to send a data packet that can be up to 65,535
bytes
 The L2CAP divides these large packets into segments and adds extra information to
define the location of the segments in the original packet
 The L2CAP segments the packet at the source and reassembles them at the
destination

o Quality of service
 Bluetooth allows the stations to define a quality-of-service level
 If no quality-of-service level is defined, Bluetooth defaults to what is called best-
effort service
o Group Management
 Another functionality of L2CAP is to allow devices to create a type of logical
addressing between themselves
 For example, two or three secondary devices can be part of a multicast group to
receive data from the primary

 Bluetooth defines several protocols for the upper layers that use the
services of L2CAP
o Service discovery protocol (SDP) is used to discover services
 An SDP client communicates with an SDP server using a reserved channel on an
L2CAP link to find out what services are available
 When the client finds the desired service, it requests a separate connection to use the
service. The reserved channel is dedicated to SDP communication so that a device
always knows how to connect to the SDP service on any other device
 An SDP server maintains its own SDP database, which is a set of service records
that describe the services the server offers.

 Bluetooth defines several protocols for the upper layers that use the
services of L2CAP
o Radio frequency communication (RFCOMM) is a simple set of transport
protocols providing emulated RS-232 serial ports
o Telephony control protocol (TCS) is used to set up and control speech and data
calls between Bluetooth devices

 Address
o Bluetooth device address (BD_ADDR)
 48 bit IEEE MAC address
o Active Member address (AM_ADDR)
 3 bits active slave address
 all zero broadcast address
o Parked Member address (PM_ADDR)
 8 bit parked slave address

Bluetooth Connection
 A connection between two devices occur in the following fashion
o Nothing is known about a remote device
 The inquiry and page procedure
o Some details are known about a remote device
 The paging procedure
• Two nodes cannot exchange messages until they agree to a common channel hop sequence
INQUIRY to discover
nodes in proximity
PAGING to establish
connections

 Inquiry procedure enables a device to discover which devices are in range,
and determine the addresses and clocks for the devices
o A device send inquiry packets and then receive inquiry reply
o Device sends inquiry packets on 16 different frequencies
(16 channel train)

 Inquiry Scan
o A device periodically listens for inquiry packets at a single frequency – chosen
out of 6 frequencies
o Device stays in the state long enough for a inquiring device to cover 16
frequencies
o It will re-enter inquiry scan state even after responding to an inquire

 Inquiry Response
o When a device receives inquire, it will wait between 0 and 0.32 seconds before
sending an FHS packet as a response
 This is done to avoid collision with another device that also wants to send an FHS packet
o FHS Packet contains
 Device ID
 Clock
o After inquiring procedure, inquiring device knows all discoverable devices
within range

 Paging procedure
o A unit that establishes a connection will carry out a page procedure and will
automatically be the master of the connection
o Connection process involves a 6 steps of communication between the master
and the slave

 Step 1
o A source device broadcasts a PAGE message to destination device
o Once page response is received, source device stops paging

 Step 2
o The destination node sends response to master or source device
 The response includes destination or slave ID
 Step 3
o Master sends an FHS packet to destination or slave node

 Step 4
o The destination sends a final response to the master
o Using the data from the FHS packet, the slave or destination node adopts the
master’s frequency hopping pattern and synchronizes to its clock

 Step 5
o When the master receives the packet, it jumps back to its frequency hopping
pattern and assigns the slave an Active Member Address (AMA) for the piconet
o Master sends out a poll packet to ensure that the slave is on its frequency
hopping pattern

 Step 6
o Once the slave receives the poll packet, the slave replies with any kind of
packet to ensure that it is on the right channel
o A new synchronized connection is established between the master and the slave
at the end of step 6

 A device in connection state can be in following modes
o Active mode is a regular connected mode, where device is actively transmitting
or receiving data
o Sniff mode is a power-saving mode, where device is less active. It sleeps and
only listen for transmissions at a set interval
o Hold mode is a temporary, power-saving mode where a device sleeps for a
defined period and then returns back to active mode when that interval has
passed. The master can command a slave device to hold.
o Park mode is a deepest of sleep modes. A master can command a slave to park,
and that slave will become inactive until master tells it to wake back up

 Bonding and pairing
o Bonded devices automatically establish connection whenever they are in range
o Bonds are created through one-time a process called pairing
o Pairing usually requires an authentication process where a user must validate
the connection between devices

 The Bluetooth Profiles
o The profiles define how to use Bluetooth technology to accomplish specific tasks
o A wide range of profiles
o Each profile specification contains following information
 Dependencies on other profiles
• Every profile depends on the base profile, called the generic access profile, and some also
depend on intermediate profiles
 Suggested user interface formats
• Each profile describes how a user should view the profile so that a consistent user
experience is maintained
 Specific parts of the Bluetooth protocol stack used by the profile
• To perform its task, each profile uses particular options and parameters at each layer of
the stack

 Service discovery application profile describes how an application should
use the SDP to discover services on a remote device.
 Headset profile describes how a Bluetooth enabled headset should
communicate with a computer or other Bluetooth device such as a mobile
phone
 File transfer profile provides guidelines for applications that need to
exchange objects such as files and folders

https://medium.com/jaycon-systems
Version Year Major Improvements
1.2 2003 Faster connection and discovery, adaptive frequency hopping, introduced flow control
and retransmission modes
2.0 2004 2.1 Mbps peak data rates
2.1 2007 3.0 Mbps peak data rates
3.0 2009 24 Mbps peak data rates using Wi-Fi PHY + Bluetooth PHY for lower rates
4.0 2010 Lower energy consumption, broadcasting, lower connection latency
4.2 2014 Improved security, low energy packet length extension, link layer privacy
5.0 2016 48 Mbps peak data rates, energy efficiency, higher broadcasting message capacity,
larger range and strong point-to-point connection and reliability

IEEE 802.11 Architecture and Services

 IEEE 802 is a family of Institute of Electrical and Electronics Engineers
(IEEE) standards for local area networks (LAN), personal area network
(PAN), and metropolitan area networks (MAN)

 In 1990, IEEE 802 Committee formed a new working group, IEEE 802.11,
specifically devoted to wireless LANs, with a charter to develop a MAC
protocol and physical medium specification

Key IEEE 802.11 Standards
Standard Scope
IEEE
802.11a
Physical layer: 5-GHz OFDM at rates from 6 to 54 Mbps
IEEE
802.11b
Physical layer: 2.4-GHz DSSS at 5.5 and 11 Mbps
IEEE
802.11c
Bridge operation at 802.11 MAC layer
IEEE
802.11d
Physical layer: Extend operation of 802.11 WLANs to new
regulatory domains (countries)
IEEE
802.11e
MAC: Enhance to improve quality of service and enhance
security mechanisms
IEEE
802.11g
Physical layer: Extend 802.11b to data rates >20 Mbps
IEEE
802.11i
MAC: Enhance security and authentication mechanisms
IEEE
802.11n
Physical/MAC: Enhancements to enable higher throughput
IEEE
802.11T
Recommended practice for the evaluation of 802.11
wireless performance
IEEE
802.11ac
Physical/MAC: Enhancements to support 0.5–1 Gbps in 5-GHz
band
IEEE
802.11ad
Physical/MAC: Enhancements to support ≥ 1 Gbps in the 60-
GHz band

Wi-Fi
 Wi-Fi is a family of wireless network protocols, based on the IEEE 802.11
family of standards
 Wi-Fi is a brand name created by a marketing firm
2003 2009 2013 2019

Wi-Fi Alliance
 There is always a concern whether products from different vendors will
successfully interoperate
 Wireless Ethernet Compatibility Alliance (WECA)
 Industry consortium formed in 1999
 Renamed the Wi-Fi Alliance
 Created a test suite to certify interoperability for 802.11 products

Basic service
set (BSS)
STA2
STA3
STA = station
STA4
Basic
Service Set
Extended
service set (ESS)
Figure 13.4 IEEE 802.11 Architecture
STA6
STA7
IEEE 802.x LAN
STA1
Access
point
(AP)
STA5
Access
point
(AP)
portal
Distribution System (DS)
IEEE 802.11 Architecture
The smallest building block is a basic service set (BSS)

 Basic service set (BSS) consists of some number of stations executing same
MAC protocol and competing for access to same shared wireless medium
 A BSS may be isolated or it may connect to a backbone distribution system
(DS) through an access point (AP)
o The DS can be a switch, a wired network, or a wireless network
 In a BSS, client stations do not communicate directly with one another

 In an IBSS, stations communicate directly
 No AP is involved
 An IBSS is typically an ad hoc network
 An extended service set (ESS) consists of two or more basic service sets
interconnected by a distribution system
 To integrate the IEEE 802.11 architecture with a traditional wired LAN, a
portal is used

 802.11 Infrastructure Mode
o at least one wireless AP and one wireless client
 802.11 Ad Hoc Mode
o wireless clients communicate directly with each other without the use of a
wireless AP
IEEE 802.11 Operating Modes

IEEE 802.11 Terminology
 Each layer has Service Data Unit (SDU) as input
 Each layer makes Protocol Data Unit (PDU) as output to communicate with
the corresponding layer at the other end
 SDUs may be fragmented or aggregated to form a PDU
 PDUs have a header specific to the layer

IEEE 802.11 Services
Service Provider Used to support
Association Distribution
system
MSDU delivery
Authentication Station LAN access and
security
Deauthentication Station LAN access and
security
Dissassociation Distribution
system
MSDU delivery
Distribution Distribution
system
MSDU delivery
Integration Distribution
system
MSDU delivery
MSDU delivery Station MSDU delivery
Privacy Station LAN access and
security
Reassocation Distribution
system
MSDU delivery
IEEE 802.11 defines nine services that need to be provided by WLAN

Distribution of Messages Within a DS
Distribution service
Primary service used by
stations to exchange MAC
frames when frame must
traverse the DS to get from a
station in one BSS to a station
in another BSS
If stations are in the same BSS,
distribution service logically
goes through the single AP of
that BSS
Integration service
Enables transfer of data
between a station on an IEEE
802.11 LAN and a station on an
integrated IEEE 802.x LAN
Takes care of any address
translation and media
conversion logic required for the
exchange of data
Services involved with the distribution of messages within a DS

Association-Related Services
 Distribution service requires information about stations within the ESS that
is provided by the association-related services
 Station must be associated before DS can deliver data to or accept data
from it

 Association Station must establish an association with an AP within a
particular BSS
 The AP can then communicate this information to other APs within the ESS to
facilitate routing and delivery of addressed frames
 Reassociation Enables an established association to be transferred from one
AP to another, allowing a mobile station to move from one BSS to another
 Disassociation A notification from either a station or an AP that an existing
association is terminated
Association-Related Services

IEEE 802.11 Medium Access Control
MAC layer covers
three functional
areas
Reliable data
delivery
Access control
Security

Reliable Data Delivery
 802.11 physical and MAC layers are unreliable
o Noise, interference, and other propagation effects result in the loss of a
significant number of frames
o The issue can be addressed at a higher layer such as TCP
 Timers used for retransmission at higher layers are typically on the order of seconds
 More efficient to deal with errors at MAC level
 802.11 includes frame exchange protocol
o Station receiving frame returns acknowledgment (ACK) frame
o Exchange treated as atomic unit
o If no ACK within short period of time, retransmit

 To further enhance reliability, a four
frame exchange may be used
o RTS alerts all stations within range of
source that exchange is under way
o CTS alerts all stations within range of
destination
o Other stations don’t transmit to avoid
collision
o RTS and CTS exchange is a required
function of MAC but may be disabled
Source issues a Request
to Send (RTS) frame
Destination responds
with Clear to Send (CTS)
After receiving CTS,
source transmits data
Destination responds
with ACK
Reliable Data Delivery

 Two types of proposals for a MAC algorithm
o Distributed access protocol which distribute the decision to transmit over
all the nodes using a carrier sense mechanism
o Centralized access protocol which involve regulation of transmission by
a centralized decision maker
 The end result is a MAC algorithm called DFWMAC (distributed
foundation wireless MAC) that provides a distributed access control
mechanism with an optional centralized control built on top of that
Access Control

Point
Coordination
Function (PCF)
Contention-free
service
Contention
service
Figure 13.5 IEEE 802.11 Protocol Architecture
MAC
layer
Distributed Coordination Function (DCF)
LOGICAL LINK CONTROL (LLC)
PHYSICAL LAYER
(802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, 802.11ad)
IEEE 802.11 Protocol Architecture
DCF uses CSMA
algorithm to provide
access to all traffic
PCF is a centralized MAC algorithm

Distributed Coordination Function (DCF)
 DCF sublayer uses CSMA
algorithm
 Does not include a collision
detection function because it
is not practical on a wireless
network
 Includes a set of delays that
amounts as a priority scheme
If station has frame to
send it listens to
medium
If medium is idle, station
may transmit
Else waits until current
transmission is complete

Wait for frame
to transmit
Wait IFS
Figure 13.6 IEEE 802.11 Medium Access Control Logic
No
Yes
Yes
Yes
No
No
Wait IFS
Medium
idle?
Still
idle?
Wait until current
transmission ends
Exponential backoff
while medium idle
Transmit frame
Transmit frame
Still
idle?
IEEE 802.11 Medium Access Control Logic

Priority IFS Values
SIFS
short IFS
For all
immediate
response
actions
PIFS
point coordination
function IFS
Used by the
centralized
controller in PCF
scheme when
issuing polls
DIFS
distributed coordination
function IFS
Used as
minimum delay
for
asynchronous
frames
contending for
access

Defer access
DIFS
Immediate access
when medium is free
longer than DIFS
SIFS
PIFS
DIFS
Busy Medium Next frame
Backoff window
Contention window
Slot time
Select slot using binary exponential backoff
(a) Basic Access Method
time
Superframe (fixed nominal length)
Superframe (fixed nominal length)
Foreshortened actual
IEEE 802.11 MAC Timing
Any station using SIFS to determine transmission opportunity has the highest
priority, because it will always gain access in preference to a station waiting an
amount of time equal to PIFS or DIFS

SIFS
 Any station using SIFS to determine transmission opportunity has the
highest priority
 SIFS is used in the following circumstances:
o Acknowledgment (ACK)
 Station responds with an ACK frame after waiting only for a SIFS gap
 Provides for efficient collision recovery
o Clear to Send (CTS)
 Station ensures data frame gets through by issuing RTS

Point Coordination Function (PCF)
 Point coordination function (PCF) resides in a point coordinator also
known as Access Point , to coordinate the communication within the
network
 The AP waits for PIFS duration rather than DIFS duration to grasp the
channel
 Channel access in PCF mode is centralized
o Access to the medium is restricted by the point coordinator
o Associated stations can transmit data only when they are allowed to do so by
the point coordinator

PCF Operation
 The polling list
o Stations get on the polling list when they associate with the AP
o Polls any associated stations on a polling list for data transmissions
o Each CF-Poll is a license to transmit one frame
o Multiple frames can be transmitted only if the access point sends multiple
poll requests

Frame Control
Figure 13.8 IEEE 802.11 MAC Frame Format
2
Duration/ID
2
Address 1
6
Sequence Control
2
QoS Control
2
High Throughput Control
4
Frame Check Sequence (FCS)
4
Always present
0—7951
Address 4
6
Address 2
6
Address 3
MAC
header
6
octets
Present only in
certain frame
types and subtypes
IEEE 802.11 MAC Frame Format

Control Frames
• The purpose is to request that the AP transmit a frame that has been
buffered for this station while the station was in power saving mode
Power Save-Poll (PS-Poll)
• First frame in four-way frame exchange
Request to Send (RTS)
• Second frame in four-way exchange
Clear to Send (CTS)
• Acknowledges correct receipt
Acknowledgment (ACK)
• Announces end of contention-free period that is part of PCF
Contention-Free (CF)-end
• Acknowledges CF-end to end contention-free period and release stations
from associated restrictions
CF-End + CF-Ack
Control frames assist in the reliable delivery of data frames

Control Frames
All control frames use the same Frame Control field

Control Frames
Duration field in RTS frame

Control Frames
The receiver of a CTS frame is the transmitter of the previous RTS frame, so the MAC
copies the transmitter address of the RTS frame into the receiver address of the CTS frame
CTS duration

Data Frames
 Data frames carry higher-level protocol data in the frame body
o Data
 Simplest data frame
o Data + CF-Ack
 Carries data and acknowledges previously received data
o Data + CF-Poll
 It is used by point coordinator to deliver data and also to request that the mobile station
send a data frame that it may have buffered
o Data + CF-Ack + CF-Poll
 Combines Data + CF-Ack and Data + CF-Poll

Management Frames
 Management frames are used to manage communications between
stations and Aps
 Functions covered include management of associations
o Request, response, reassociation, dissociation, and authentication

Management Frames
 Beacon
o announce the existence of a network
o transmitted at regular intervals to allow mobile stations to find and identify a network,
as well as match parameters for joining the network
 Probe Request
o Mobile stations use Probe Request frames to scan an area for existing 802.11
networks
o Include SSID and the rates supported by the mobile station
o Stations that receive Probe Requests use the information to determine whether the
mobile station can join the network
 Probe Response

Management Frames
 Disassociation and Deauthentication
 Association Request
 Authentication

Frame Control
2
Duration/ID
2
Address 1
6
Sequence Control
2
QoS Control
2
4
4
Always present
0—7951
Address 4
6
Address 2
6
Address 3
MAC
header
6
octets
Present only in
certain frame
types and subtypes
It contains the value indicating
the time period for which the
medium is occupied

Frame Control
2
Duration/ID
2
Address 1
6
Sequence Control
2
QoS Control
2
4
4
Always present
0—7951
Address 4
6
Address 2
6
Address 3
MAC
header
6
octets
Present only in
certain frame
types and subtypes
The number and function
of the address fields
depends on context

Use of the address fields in data frames
In the case of an IBSS, no access points are used, and no distribution system is present

Figure shows a simple network in which a wireless client is connected to a server
through an 802.11 network

When the server replies to the client, frames are transmitted to the client through the
access point

Two wired networks are joined by access points acting as wireless bridges

IEEE 802.11 Physical Layer Standards
Standard 802.11a 802.11b 802.11g 802.11n 802.11ac 802.11ad
Year
introduced
1999 1999 2003 2000 2012 2014
Maximum data
transfer
speed
54 Mbps 11 Mbps 54 Mbps
65 to
600 Mbps
78 Mbps
to 3.2
Gbps
6.76 Gbps
Frequency
band
5 GHz 2.4 GHz 2.4 GHz
2.4 or 5
GHz
5 GHz 60 GHz
Channel
bandwidth
20 MHz 20 MHz 20 MHz
20, 40
MHz
40, 80,
160 MHz
2160 MHz
Highest order
modulation
64 QAM 11 CCK 64 QAM 64 QAM 256 QAM 64 QAM
Spectrum
usage
DSSS OFDM
DSSS,
OFDM
OFDM SC-OFDM SC, OFDM
Antenna
configuration
1´1 SISO 1´1 SISO 1´1 SISO
Up to 4´4
MIMO
Up to 8´8
MIMO, MU-
MIMO
1´1 SISO

IEEE 802.11b
 Extension of 802.11 DSSS scheme
o Data rates of 5.5 and 11 Mbps
o Complementary Code Keying (CCK) modulation gives higher data rate with
same bandwidth and chipping rate

IEEE 802.11a
 Makes use of the frequency
band called Universal
Networking Information
Infrastructure (UNNI)
o UNNI-1 band (5.15 to 5.25 GHz)
for indoor use
o UNNI-2 band (5.25 to 5.35GHz)
for indoor or outdoor
o UNNI-3 band (5.725 to 5.825
GHz) for outdoor
 Advantages over IEEE
802.11b and g
 IEEE 802.11a
 Utilizes more available
bandwidth
 Provides much higher data
rates
 Uses a relatively uncluttered
frequency spectrum (5 GHz)

IEEE 802.11g
 Higher-speed extension to 802.11b
 Operates in 2.4GHz band
 Compatible with 802.11b devices
 Combines physical layer encoding techniques used in 802.11 and 802.11b
to provide service at a variety of data rates
o ERP-OFDM for 6, 9, 12, 18, 24, 36, 48, 54Mbps rates
o ERP-PBCC for 22 and 33Mbps rates

IEEE 802.11n
 Enhancements in three general areas:
o Multiple-input-multiple-output (MIMO) antenna architecture
 with MIMO – multiple antennas on sending and receiving devices to reduce error
and boost speed – this standard supports higher data rates
o Radio transmission scheme to increase capacity
 combines two 20-MHz channels to create a 40-MHz channel
o MAC enhancements
 Most significant change is to aggregate multiple MAC frames into a single block for
transmission

MSDU1
MAC
header
PHY
header
MSDU1
MAC
header
PHY
header
MSDU2
MAC
header
PHY
header
ACK
PHY
header
SIFS
or
backoff
MSDU2
SIFS
ACK
PHY
header
SIFS
MSDU3
MAC
header
PHY
header MSDU4
MAC
header
PHY
header
ACK
PHY
header
SIFS
or
backoff
SIFS
ACK
PHY
header
SIFS
Block
ACK
PHY
header
SIFS
Block
ACK
PHY
header
SIFS
ACK
PHY
header
SIFS
x
x
Retransmitted due to single bit error
x
x
x
MPDU subframe MPDU subframe
MPDU subframe
(a) No aggregation
(c) A-MPDU aggregation
(b) A-MSDU aggregation
(d) A-MPDU of A-MSDU aggregation
MPDU subframe
MPDU delimiter
MPDU subframe MPDU subframe
MAC
header
PHY
header MSDU1
A-MSDU
subframe
MSDU2
A-MSDU
subframe
MAC
header
PHY
header MSDU1
A-MSDU
subframe
MSDU2
A-MSDU
subframe
MAC
header MSDU3
A-MSDU
subframe
MSDU4
A-MSDU
subframe
MSDU3
A-MSDU
subframe
MSDU4
A-MSDU
subframe
MSDU2
MAC
header MSDU3
MAC
header MSDU4
MAC
header x
x
x
A-tMSDU delimiter
Figure 13.11 Forms of Aggregation
Forms of Aggregation

IEEE 802.11ac
 This standard aims to provide a throughput close to 1 Gbps
 Supports larger channel widths up to 160MHz
 Introduced a new modulation scheme
o 256-QAM modulation

IEEE 802.11ac
 Support of MU-MIMO transmissions in the downlink
o Multiple simultaneous transmissions from the AP to different stations
o Each antenna of a MU-MIMO AP can simultaneously communicate with a
different single-antenna device, such as a smart phone or tablet
o AP can be equipped with a maximum of eight antennas
 Allows the transmission of several MPDUs aggregated in a single A-
MPDU
o To acknowledge each MPDU individually a Block ACK packet is used, which
contains a bitmap to indicate the correct reception of all included MPDUs.

IEEE 802.11ax
 IEEE 802.11ax aims to provide at least a four-fold capacity increase
compared to IEEE 802.11ac
 Support multi-user transmission strategies by further developing MU-
MIMO and Orthogonal Frequency Division Multiple Access (OFDMA)
capabilities in both downlink and uplink
 A fast handoff between APs in the same administration domain
 Device-to-device communication

IEEE 802.11ax
 Open challenges are related to EDCA extensions
o To support a large number of STAs
o Improve traffic differentiation capabilities
o Improve the energy consumption
o Provide mechanisms to fairly co-exist with neighboring wireless networks

IEEE 802.11aa
 Developed to include new features and additional mechanisms to improve the
performance of real-time multimedia content delivery
 Groupcast communication mechanisms
o In most audio-video streaming applications a group of clients must receive the
same stream simultaneously
o A multicast protocol is necessary to avoid that the same content is replicated
throughout the network
 Traditional approach is to use Direct Multicast Service that converts
multicast streams into unicast streams

IEEE 802.11aa
 The IEEE 802.11e amendment only allows traffic differentiation between
four different access categories: voice, video, best-effort, and background.
 Variety of streaming services, ranging from simple videoconferencing to
HD streaming over IPTV systems, have different QoS requirements

IEEE 802.11ah
 IEEE 802.11ah aims to provide WLANs with the ability to both manage a
large number of heterogeneous STAs within a single BSS, and minimize
the energy consumption of the sensor-type battery-powered STAs
o support of up to 8192 STAs associated with a single AP
o minimum data rate of 100 kbps
o a coverage up to 1 km in outdoor areas
o Channel widths of 1 MHz and 2 MHz

IEEE 802.11ad
 A version of 802.11 operating in the 60-GHz frequency band
o Offers the potential for much wider channel bandwidth than the 5-GHz band
o Few devices operate in the 60-GHz which means communications would
experience less interference than in the other bands used by 802.11
o Designed for single-antenna operation
o Huge channel bandwidth of 2160 MHz

IEEE 802.11ad
 802.11ad is operating in the millimeter range, which has some undesirable
propagation characteristics:
o Losses are much higher in this range than in the ranges used for traditional
microwave systems
o Multipath losses can be quite high
o Millimeter-wave signals generally don’t penetrate solid objects

Low Power Wide Area Networks
 LoRaWAN, https://www.lora-alliance.org
 SIGFOX, http://www.sigfox.com/

 LoRa
o Long Range radio
o Developed by a
company called
Semtech
o Uses ISM band
o Covers physical layer
o Enables long range
transmissions with low
power consumption
o Low bandwidth up to
27 kbs
https://lora-developers.semtech.com/library/tech-papers-and-guides/lora-and-lorawan/

https://lora-developers.semtech.com/library/tech-papers-and-guides/lora-and-lorawan/

 LoRaWAN
o LoRa only defines the lower-level layers of the network stack, and LoRaWAN
defines the upper layers of the stack
o The LoRaWAN protocols are defined by the LoRa Alliance
o LoRaWAN operates in unlicensed radio spectrum

 End device is a sensor or an actuator which is wirelessly connected to a
LoRaWAN network through radio gateways
o LoRa-based devices are assigned several unique identifiers
 Gateway receives messages from any end device in range and forwards these
messages to network server, which is connected through an IP backbone
o There is no fixed association between an end device and a specific gateway. Same
sensor can be served by multiple gateways in the area
o IP traffic from a gateway to the network server can be backhauled via Wi-Fi or
Cellular connection
o Gateways operate entirely at physical layer
 They are just LoRa radio message forwarders
 They only check the data integrity of each incoming LoRa RF message. If error, message
will be dropped otherwise will be forwarded to network server

 Network server manages entire network
o Route messages from end devices to right applications and back
o Device address checking
o Frame authentication
o Acknowledgements of received messages
o Adapting data rates
o Queuing of downlink payloads coming from any Application Server to any de
 Application servers are responsible for securely handling, managing and
interpreting sensor application data and generate all the application-layer
downlink payloads to connected end devices

 Device Classes
o The device classes trade off network downlink communication latency versus
battery lifetime

 Class A
o Class A devices support bi-directional communication between a device and a gateway
o Uplink messages can be sent at any time.
 When there is a change in the environment related to whatever the device is programmed to
monitor, it wakes up and initiates an uplink, transmitting the data about the changed state
back to the network.
 The device then opens two receive windows at specified times after an uplink transmission.
 If the server does not respond in either of these receive windows, the next opportunity will be
after the next uplink transmission from the device.
 The server can respond either in the first receive window, or in the second receive window,
but should not use both windows.

 Class B
o Class B devices extend Class A by adding scheduled receive windows for
downlink messages from the server.
o Using time-synchronized beacons transmitted by the gateway, the devices
periodically open receive windows.
 Class C
o Class C devices extend Class A by keeping the receive windows open unless
they are transmitting
 This allows for low-latency communication but is many times more energy
consuming than Class A devices

https://www.mdpi.com/1424-8220/17/10/2364

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