Download Wireless Technology and convergence

Wireless Technology and
Network Convergence
A Brief History
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Wireless communications originated with
the demonstration by Tesla in 1893,
followed by the invention of wireless
telegraph by Marconi in 1896
Advances in wireless communications
have led to radio, television, mobile
telephones, and communication satellites
Development of wireless networks: LAN,
MAN, and WAN
Trend continues: Voice – Data –
Broadband
Need to support mobility
Trends
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Revenue for wireless communication
industry has surpassed that of wired
telephony industry
Wireless applications span both local area
and wide area for:
• voice-oriented services, and
• data-oriented services
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Global cellular networks are providing very
convenient communication infrastructure
Broadband wireless networks are
evolving: Wireless LANs are very popular
Licensed and Unlicensed Bands
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Licensed:
• Cellular/PCS
• Expensive (PCS bands in US were sold for around $20B)
• Time consuming to deploy new applications rapidly at
low costs
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Unlicensed:
• Industrial, Medical, and Scientific (ISM) Bands
• Free, component costs are also low
• New applications such as WLAN, Bluetooth are easily
developed
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With the increase in frequency and data rate, the
hardware cost increases, and the ability to
penetrate walls also decreases
Duplexing
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Duplexing facilitates communications in
both directions simultaneously: base
station to mobile and mobile to base
station
Duplexing is done either using frequency
or time domain techniques:
• Frequency division duplexing (FDD)
• Time division duplexing (TDD)
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FDD is suitable for radio communication
systems, whereas TDD is more suitable for
fixed wireless systems
Multiple Access Techniques
Frequency Division Multiple Access
 Time Division Multiple Access
 Spread Spectrum Multiple Access
 Space Division Multiple Access
 Packet Radio
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Frequency Division Multiple Access
(FDMA)
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The frequency spectrum is divided into
unique frequency bands or channels
These channels are assigned to users on
demand
Multiple users cannot share a channel
Users are assigned a channel as a pair of
frequencies (forward and reverse
channels)
FDMA requires tight RF filtering to reduce
adjacent channel interference
FREQUENCY
Channel-9
Channel-8
Channel-7
Channel-6
Channel-5
Channel-4
Channel-3
Channel-2
Channel-1
TIME
FDMA
Time Division Multiple Access-TDMA
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TDMA systems divides the radio spectrum
into time slots, and in each time slot only
one use is allowed to either transmit or
receive
Transmission for any user is noncontinuous
In each TDMA frame, the preamble
contains the address and synchronization
information
TDMA shares a single carrier frequency
with several users
TDMA could allocate varied number of
time slots per frame to different users
TIME
Channel-10
Channel-9
Channel-8
Channel-7
Channel-6
Channel-5
Channel-4
Channel-3
Channel-2
Channel-1
FREQUENCY
TDMA
Spread Spectrum Multiple Access
(SSMA)
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SSMA uses signals that have a
transmission bandwidth several orders of
magnitude greater than the minimum
required RF bandwidth
SSMA provides immunity to multipath
interference and robust multiple access
capability
SSMA is bandwidth efficient in multi-user
environment
SSMA techniques:
• Frequency hopped (FH) multiple access
• Direct sequence (DS) multiple access
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Also known as code division multiple access (CDMA)
FHMA
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Carrier frequencies of individual users are varied
in a pseudorandom fashion within a wideband
channel
Data of each user is broken into uniform size
bursts that are transmitted on different channels
at different time instants based on their pseudonoise (PN) code sequence
In the FH receiver, a locally generated PN code is
used to synchronize the receiver’s instantaneous
frequency with that of the transmitter
FHMA provides inherent security, and guard
against erasures through error control coding and
interleaving
Use: Bluetooth and HomeRF
CDMA
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The narrowband message signal is multiplied by a very
large bandwidth signal called spreading signal
The spreading signal has a pseudo-noise code sequence
that has a chip rate which is orders of magnitudes greater
than the data rates of the message
All users use the same carrier frequency and can transmit
simultaneously
Each use has its own pseudorandom codeword that is
orthogonal to the others
The receivers need to know the codeword of the
corresponding sender
Power control is used to combat the near-far problem
Near-far problem:
• When many mobile users share the same channel, the
strongest received mobile signal will capture the
demodulator at a base station. Thus a nearby subscriber
could overpower the base-station receiver by drowning
out the signals of far away subscribers.
CDMA Features
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Many users of CDMA share the same frequency –
either TDD or FDD may be used
CDMA has soft capacity limit – system
performance is inversely proportional to the
number of users
Multipath fading is reduced because of the signal
spread
Channel data rates are very high
Prone to self-jamming and near-far problem
• Self-jamming: when the spreading sequences of
different users are not exactly orthogonal
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Near-far problem occurs at a CDMA receiver if an
undesired user has a high detected power
compared to the desired user
Space Division Multiple Access
(SDMA)
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SDMA controls the radiated energy for
each user and serves different users by
using spot beam antennas
Different areas covered by antenna beam
may be served by same or different
frequencies
Reverse links present difficulty:
• Transmitted power from each subscriber must
be controlled to prevent any single user from
driving up the interference level
• Transmit power is limited by battery
consumption at the subscriber unit
Packet Radio
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In Packet Radio (PR) access techniques,
many subscribers attempt to access a
single channel in an uncoordinated
manner
Collisions from simultaneous transmissions
from multiple transmitters are detected at
the base station receiver, in which case an
ACK or NACK signal is broadcasted by the
base station to alert the user
PR subscribers use a contention technique
to transmit on a common channel
Carrier Sense Multiple Access
Protocols (CSMA)
In CSMA protocols, each terminal on
the network is able to monitor the
status of the channel before
transmitting information
 Variations:
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1-persistent CSMA
non-persistent CSMA
p-persistent CSMA
CSMA/CD
Convergence of Public Network
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Carriers now use converged technology
primarily in core, backbone portion of their
networks to carry customer traffic more
efficiently
Although carriers increasingly add IP
equipment when they replace their voice
switches, the majority of voice traffic is
still carried in circuit switched networks
A circuit is a physical path for the
transmission of voice, image or data.
ITU defines circuit switching as :
“The switching of circuits for the exclusive
use of the connection for the duration of a
call”
 When a person or modem dials a call, the
network sets up a path between the caller
and the dialed party
 Circuit switching is an example of a
connection-oriented system
 The path is maintained exclusively for the
duration of the call and not shared
 This causes wasteful utilization of network
capacity
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Circuit-Switching
Other Switching TechniqueMessage Switching
Message switching transfers arbitrary
sized messages from a source to a
destination using one or more
message switches
 Each switch stores the complete
message before forwarding it
 Normally messages are stored for
only a short time, but they may be
stored for days in some cases
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A message being sent using one
intermediate message switch.
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The telex network is an example of a
message switched network
Since the messages are stored in each
message switch, message switching is
suitable for the transfer of electronic mail
and is used to send email to isolated parts
of the world using connections provided by
modems over the telephone network
Since there is no direct connection
between the sender and the recipient, it is
not possible to use message switching to
login to a remote computer
Rationale for Convergence
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The Internet Protocol (IP) does not have this
limitation
The Internet is a connection-less packet-switched
network.
Packets from other sources fill pauses in one
conversation
Eg. when a call is on hold, network capacity is
used for other traffic
Moreover, technical advances have improved the
quality of voice and video carried on packet
networks
In addition, costs for routers, hard drives and
fiber optics have decreased
The capability to deploy and maintain a single
network for voice, data and video
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As VoIP protocols become
increasingly standardised, custom
interfaces between switches and
applications will increasingly become
unnecessary
VoIP Networks
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Cable TV, wireless mobile and traditional
local exchange carriers use common IP
core and edge IP network components
when they upgrade their networks to IP
Components include:
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Softswitches
Media gateways
Media servers
Application servers
Softswitches
Process calls (issue commands on
setting up and ending calls)
 Communicate with billing systems
 Acts as an overall network control
point
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Media Gateways
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Switch calls and translate protocols
between different networks and
between public network trunks such
as T-1 and T-3 trunks and IP
networks
Media Servers
Generate touch-tone
 Play announcements
 Generate voice over IP packets from
voice mail application
 Convert voice mail messages to
digital IP packet and vice versa
 Record voice mail messages
 Generate ring tones, busy signals,
dial tone
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Application Servers
Contain complex applications
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• unified messaging (capability to receive
voice mail, e-mail, and fax messages on
personal computers)
• Large audio conferencing systems
Peer-to-Peer Services
P2P services operate in a
decentralised mode without
softswitches to control signaling and
communication
 Napster, Gnutella, KaZaA – enable
sharing of free music over the
Internet
 Skype introduced P2P architecture
for VoIP without central servers
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Calling 911VoIP vs Circuit switched
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The Wireless Communication and Public Safety
Act (1999) establishes 911 as the emergency
number throughout the US.
The first emergency number was 999 used in
London
The act mandated all carriers to connect 911 call
to appropriate local emergency dispatch centre
It also mandated FCC to develop a plan for
wireless providers to transition to enhanced 911
(E911)
Under E911, the agent who answer 911 calls is
able to receive the callers’ phone number and
location
Mobile Services
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Competition between mobile network
operators, and the desire for more
robust networks have led to the
implementation of third generation
digital networks by major mobile
operators
Evolution from 1G, 2G, 2.5G to 3G
The 1st G of cellular service used
analog equipment in the early 1980s
st service in US is AMPS
 The 1
 The 2nd G started in 1990s when
carriers upgrade their analog to
digital networks to gain more
capacity
 These include GSM, CDMA, TDMA
and iDEN (Motorola)
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2.5 G
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Provides transition to WCDMA
Most GSM operators implemented GPRS
and EDGE before WCDMA for the following
reasons:
• WCDMA equipment was not stable until 2004
• Small, lightweight 3G handset were not widely
available prior to 2004
• Installing GPRS and EDGE delayed the large
expenses to upgrade to WCDMA
• Handset for GPRS and EDGE were readily
available
• GPRS and EDGE operate on the same
frequencies as GSM
3G
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Transition from 2G CDMA TO 3G
CDMA2000 is less costly and complex than
transition from GSM networks to WCDMA
The major incentive for upgarding is the
increased voice capacity as well as the
desire for a network capable of handling
advanced application
Because it is easier to implement,
CDMA2000 has more subscribers
compared to WCDMA
CDMA2000 1X (voice and data)
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Provides “always on” data rates
Doubles the voice capacity
SK Telecom, the largest carrier in South
Korea implements the 1st release of
CDMA2000 in October 2000
Only requires new cards in the base
transceiver system and software in the
mobile switching centre
Routers, billing, authentication and
authorisation systems, and connection to
IP networks are necessary for data
services
CDMA2000 1xEV-DO (data
optimised- high data rate)
Network providers already have the
1st stage CDMA2000 can upgrade to
higher data speeds by adding
software and channel cards to their
base stations for high data rate
 HDR service is a data-only
enhancement with higher downlink
speeds
 No capacity is gained for voice traffic
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WCDMA
Release
Features
WCDMA
Enables operators to prioritise
(Release 4) data services per customer
subscription
WCDMA
HSDPA (high speed downlink
(Release 5) packet access)
IP voice and data
WCDMA
HASUPA (high speed uplink
(Release 6) packet access)
Doubles the uplink speed
MobileFi
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802.20: IP Mobile Broadband Wireless Access
In 2002, the IEEE stated its intention to provide
mobility in vehicles such as trains traveling up to
150mph or 250kmph, and to support higher data
rates and more users than currently available
Flarion uses a form of orthogonal FDM (OFDM) in
equipment called FLASH-OFDM.
Flash is short for Fast, Low-latency Access with
Seamless Handoff
FLASH-OFDM spreads signals over a wider
frequencies and at faster rate than OFDM
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Flarion service includes handoffs between
Wi-Fi and FLASH-OFDM networks so that
users use Wi-Fi when it is availabale and
Flarion when it is not
Flarion supports VoIP and able to prioritise
traffic
It is not expected to be available until
2008
T-Mobile, Vodafone and TIME dotCOM (in
Malaysia) are conducting trials of Flarion
equipment
Wi-Fi, Wireless broadband, Sensor
Networks and PANs
Wi-Fi IEEE 802.11
 Wireless broadband - WiMax
 Zigbee and IEEE 802.15
 PANs
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Evolution of Wireless LAN
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Early experiences (1970-72): IBM, HP, Motorola
• Abandoned due to limited performance and
unavailability of frequency bands
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Early challenges:
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Complexity and cost
Bandwidth
Coverage
Interference
Frequency administration
Emergence of unlicensed bands
• Release of Industrial, Scientific and Medical (ISM) bands
in 1985
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Applications: military, home and enterprise
networks, mobile networks, teetherless access
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Wi-Fi is based on 802.11 technology
It is originally intended tio provide wireless
computing for staffs within businesses and
commercial organisations
However, residential customers adopted Wi-Fi
faster than enterprises because of its simplicity,
fewer concerns about security and the benefit of
avoiding the expenses for cabling
Its advantage is low equipment cost and easier
installation
Benefits were also immediately noticed for
healthcare, education, retailing and warehousing
IEEE 802.11
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Standardization group formed in 1990,
first standards completed in 1997
IEEE 802.11 is the first WLAN standard;
only one to secure a market
802.11a: PHY layer supports 11Mbps
using CKK (complementary code keying)
technology
802.11b: PHY layer supports 54 Mbps
using OFDM
Uses CSMA/CA for contention data
Supports both infrastructure as well as ad
hoc modes
IEEE 802.11 Protocol Architecture
Logical link control
Contentionfree service
MAC
layer
Contention
service
Point coordination function
(PCF)
Distributed coordination function (DCF)
2.4-Ghz
frequencyhopping
spread
spectrum
1Mbps
2Mbps
2.4-Ghz
direct
sequence
spread
spectrum
1Mbps
2Mbps
IEEE 802.11
Infrared
1Mbps
2Mbps
5-Ghz
orthogonal
FDM 6, 9.
12. 18, 24,
36, 48, 54
Mbps
IEEE 802.11a
2.4-Ghz
direct
sequence
spread
spectrum
5.5 Mbps
11 Mbps
IEEE 802.11b
802.11a – higher speeds, smaller
coverage, more channels
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Wi-Fi is also sold to hotspot operators particularly
hotel, convention centres, cafes, airports
Hotspots offer higher-speed Internet access than
most cellular network’s data offering and cost
less to build than cellular base station
802.11 wireless standards are based on Ethernet
protocols
802.11a is the only 802.11 standard that
operates at 5 GHz
The use of 5 GHz band avoids interference from
microwave ovens, Bluetooth equipments and
cordless phones that operate at 2.4 GHz
Disadvantage is the signal fade faster
802.11b
When they were first available,
802.11 equipments were equipped
with only 802.11b chips
 Now most use b and g which are
designed to interoperate
 Because home broadband
connections are slower than 802.11
networks, no advantage is gained
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802.11g
Support higher data rates than
802.11b
 Use 2.4 gHz bands
 The higher speeds and capacity of g
and a are required to support voice
over IP on WLANs
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802.11n
Backward compatibility with a, b and
g
 Improve coverage by overcoming a
certain amount of interference
 Increase speeds and supports more
users per access point
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Broadband wireless access
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Wimax and universal mobile telecommunication
system time division duplex (UMTS TDD) may in
the future provide mobile wireless broadband
service for pedestrian, people in moving vehicles
and within buildings
However, most current implementations are for
less complex wireless service between fixed
locations or for wireless service with Internet
access and portability within a service provider’s
coverage area
Currently no portability is provided within
buildings (therefore, Wi-Fi is still needed)
Wimax is based on 802.16
WCDMA Modified for Wireless
Local Loop
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SOMA Networks provide a packetized wireless
local loop service to replace broadband cable and
DSL service
The service is designed for circuit-switched voice,
fax and high-speed data
The equipments operate in the 1.9, 2.3 and 2.6
GHz licensed frequency bands
SOMA is used in developing countries where
cabling to residential or rural areas is rare
SOMA modified 3G WCDMA to provide end-to-end
QOS and multimegabit data speed
SOMA is not portable or mobile
However, it is rolling out integrated Wi-Fi handset
for portable voice within home
Jaring uses SOMA equipments
Sensor Networks
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An emerging technology to monitor condition in
buildings, control manufacturing systems, etc
Until recently, large-scale sensor networks are
expensive because sensors require wired
connection to each other and the LAN
The new sensor network is able to send info
wirelessly
2 topology can be deployed
Full-mesh: each sensor is connected to every
other device
Partial-mesh: some nodes are connected to each
other, others only to the nodes they exchange
the info most
Based on 802.15.4 which is slow speed (20250kbps), non line-of-sight (LOS)
IEEE 802.15.4 and ZigBee
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Home Applications
• Internet connectivity, multi-PC connectivity,
audio/video networking
[broadband, always-on, relatively expensive]
• Home automation, security, device
management
[low-throughput, power-constraint, low-cost]
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IEEE 802.11 and Bluetooth do not satisfy
the requirements of the second set
Evolution of IEEE 802.15.4 and ZigBee in
2000
ZigBee
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Based on 802.15.4 standard, developed by
ZigBee Alliance
Defined higher-level protocols that will operate
over network using 802.15.4
ZigBee 1.0 was announced in Dec 2004
It is a lightweight routing protocol for mesh
network that adds security and additional mesh
networking function to 802.15.4
It has potential to control alarms, monitor
electricity, provide status from smoke detectors,
thermostat, and hot water tanks in commercial or
residential buildings
Protocol Stack
APPLICATIONS
User Defined
APPLICATION FRAMEWORK
ZigBee Alliance
NETWORK/SECURITY LAYERS
MAC LAYER
IEEE 802.15.4
PHY LAYER
It can monitor windows to determine
if they are closed or not
 Its target application include remote
controls (now using infrared that
requires LOS)
 However, it receives competition
from companies providing alarm
services like ADT
 Has potential for future use
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PANs
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Bluetooth- widely used (not discussed here)
Ultra-Wideband (802.15.3a)
Is high-speed, short range wireless tech that
works by transmitting low-power signals over a
wide range of frequencies
Does not require spectrum license
It is designed not to interfere with conventional
radio
It can penetrate walls and do not drain batteries
quickly
It is faster than Bluetooth and Wi-Fi
Can be used to link electronics for home
entertainment network and asset tracking
However, lack of uniform standard is holding its
sales
RFID
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A non-LOS wireless tech used to control,
detect and tract objects
RFID system is made up of
• Interrogator – readers
• Transponder with integrated antenna on chips
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Active transponder has battery, larger in
size, more costly than passive one.
However can be read at further distance
from reader
Passive one has no battery, size of a 5
cent coin, are woken up by magnetic
induction from reader, also known as tag
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A middleware is required to reformat
information gathered by readers to make
it compatible with database
RFID tags have electronic product codes
(EPC)
Super RFID can be used for sensor
network –requires intelligent tags and
readers that record conditions being
monitored and set off alarms if the
thresholds are exceeded
Operates in
• low frequency (30-500KHz)- shorter range
• High frequency (850-950KHz/2.4-2.5GHz)
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– range up to 90 feet
- may interfere with Bluetooth and Wi-Fi gear