Transcript WirelessComm

WIRELESS
COMMUNICATION
RF Design

Considerations when starting an RF design:
 How
many members/nodes will participate the
wireless network?
 What
 Is
is the required range between the devices
there a special need for low power consumption?
 Are
there common standards that have to be met?
Point to Point or Star topology
Range and Data Rate


How far nodes would be?
How much Data need to be transferred per unit
time?
Range and Data Rate
Power Consumption

Is power consumption a factor?
 Source
of Power
 Battery
 Ease

powered
of replenishing power source?
Environment
 Obstruction,
multipath, Line of sight
Power Consumption- Duty Cycle
Power Consumption- Duty Cycle

Use the lowest possible duty cycle
 Send
data only when needed, do not send more data
than necessary
 Use
the highest data rate if you can (trade-off vs.
range)
 Watch

out for protocol-related overhead
Use the lowest possible voltage
 RF
chips have reduced current draw at lower voltages
 Low
voltage degrades RF performance
Selecting Wireless Solution

How to choose the perfect wireless solution:
 Does
the application need to associate with an
existing system?
 What
kind of software protocols fit the application
best?
 Are
there regulations to be considered?
 How
much time/resources are available to get the
product to market?
Regulation: ISM Bands
Regulation: 2.4 GHz ISM Bands


2.4 GHz Pros

Same solution for all markets without SW/HW alterations

Large bandwidth available, allows many separate channels
and high datarates

More compact antenna solution than below 1 GHz
• 2.4 GHz Cons

Shorter range than a sub 1 GHz solution (with the same
current consumption)

Many possible interferers are present in the band
Regulation: sub 1 GHz ISM Bands



The ISM bands under 1 GHz are not world-wide. Limitations vary a lot
from region to region and getting a full overview is not an easy task
Sub 1GHz Pros

Better range than 2.4 GHz with the same output power and current
consumption

Lower frequencies have better penetration through concrete and steel
(buildings and office environments) compared to 2.4 GHz
Sub 1GHz Cons

No worldwide solution possible. Since different bands are used in
different regions a custom solution has to be designed for each area

Duty cycle restrictions in some regions
Antenna Design
Wireless Networks

Wireless networks are standardized by IEEE.

Under 802 LAN MAN standards committee.
ISO
OSI
7-layer
model
Application
Presentation
Session
IEEE 802
standards
Transport
Network
Logical Link Control
Data Link
Medium Access (MAC)
Physical
Physical (PHY)
Short range Wireless Communication

Bluetooth – 802.15.1

Zigbee - 802.15.4

Wi-Fi

- 802.11
WPAN (wireless personal area network) Vs
WLAN(wireless local area network)
Bluetooth

Designed for short range networks also called piconets

Provide device connectivity to computer peripherals


Printers, Smartphone's , PDA’s

Keyboard, mouse
versions

Bluetooth 1.x

Bluetooth 2.x – Extended data rate

Bluetooth 3.0 – High Speed

Bluetooth 4.0 – Bluetooth Low Energy
Bluetooth

2.4 GHz frequency range

Use FHSS with 79 channels and 1 MHz bandwidth

Low Power Consumption

Typical range is about 10 meters extendable up to 100 meters

Data Rates

Bluetooth 1.2 - 1Mbps (721 Kbps)

Bluetooth 2.0 – Extended data rate - 3 Mbps (2.1Mbps)

Bluetooth 3.0 – High Speed - (24Mbps with 802.11)

Bluetooth 4.0 – Bluetooth Low Energy (200
Kbps)
Bluetooth




Master slave configuration
Slaves communicate only with their master in a
point-to-point fashion
Master’s transmissions may be either point-to-point
or point-to-multipoint
besides in an active mode, a slave device can be in
the parked or standby modes so as to reduce
power consumptions
Bluetooth Topology
a) Piconet with one slave b) Piconet with multiple slaves c) a Scatternet
Bluetooth programming

Similar to network programming

Steps in programming
– Choosing a communication partner
• Each device has a 48 bit address given by
manufacturer similar to mac addresses
• Each device has a symbolic name but actually 48
bit address is used for communication
• Master broadcast a search message and slave
respond. Searching take considerable time.
Bluetooth programming

Steps in programming
– Choosing a Transport protocol
• Choose among many available
– RFCOMM - Establishes point to point communication
over which reliably streams of data can be
exchanged
– L2CAP - Connection oriented protocol that sends
individual datagram's of fixed maximum length
– Selecting port number – 1-30 for RFCOMM, Odd
numbers in range 1 to 32767 for L2CAP
Bluetooth programming

Steps in programming
– Making a outgoing connection
– Accepting an incoming connection
– Sending and receiving data
• Uses sockets programming framework similar to
network programming
• Functions like create, bind, listen, connect, accept,
receive and send
BLE-Bluetooth Low Energy

For small form factor devices in healthcare, fitness,
security and home entertainment industries

Simplified protocol

40, 2MHz channels

Range up to 50 meters

Not Compatible with Classic Bluetooth
Wi-Fi – 802.11


Provide wireless connectivity for fixed, portable
and moving stations within a local area
Internet access
 Public

Wi-Fi Direct
 For

– Wi-Fi hotspots
file sharing and media sharing
Range 30-100m
Overview, 802.11 Architecture
ESS
Existing
Wired LAN
AP
STA
BSS
AP
STA
STA
BSS
STA
Infrastructure
Network
STA
Ad Hoc
Network
STA
BSS
BSS
STA
STA
Ad Hoc
Network
Zigbee – 802.15.4

Applications- WSN, Industrial Control Network

Frequencies and data rates
 868
MHz - 20Kbps
 915
MHz – 40 Kbps
 2.4
GHz – 250 kbps
• Self organized, Multi Hop and reliable mesh
networking

Zigbee RF4CE - Radio frequency based remote control
Zigbee – 802.15.4
Zigbee Layer Structure
Zigbee
Comparison between Bluetooth, Zigbee and Wi-Fi
Radio interference

Adaptive Frequency hopping(Bluetooth)

CSMA CA