Department of Engineering Science
ES465/CES 440, Intro. to Networking & Network Management
Wireless Networking Technologies
http://www.sonoma.edu/users/k/kujoory
References
• “Computer Networks & Internet,” Douglas Comer, 6th ed, Pearson, 2014, Ch 16,
Textbook, 5th ed, slides by Lami Kaya (LKaya@ieee.org) with some changes.
• “Computer Networks,” A. Tanenbaum, 5th ed., Prentice Hall, 2011, ISBN:
13:978013212695-3.
• “Computer & Communication Networks,” Nader F. Mir, 2nd ed, Prentice Hall, 2015, ISBN:
13: 9780133814743.
• “Data Communications Networking,” Behrouz A. Forouzan, 4th ed, Mc-Graw Hill, 2007
• “Data & Computer Communications,” W. Stallings, 7th ed., Prentice Hall, 2004.
• “Computer Networks: A Systems Approach," L. Peterson, B. Davie, 4th Ed., Morgan
Kaufmann 2007.
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Topics Covered
• 16.1 Introduction
• 16.2 A Taxonomy of Wireless
Networks
• 16.3 Personal Area Networks
(PANs)
• 16.4 ISM Wireless Bands Used by
LANs & PANs
• 16.5 Wireless LAN Technologies &
Wi-Fi
• 16.6 Spread Spectrum Techniques
• 16.7 Other Wireless LAN
Standards
• 16.8 Wireless LAN Architecture
• 16.9 Overlap, Association, &
802.11 Frame Format
• 16.10 Coordination Among Access
Points
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• 16.11 Contention & ContentionFree Access
• 16.12 Wireless MAN Technology
& WiMax
• 16.13 PAN Technologies &
Standards
• 16.14 Other Short-Distance
Communication Technologies
• 16.15 Wireless WAN Technologies
• 16.16 Cell Clusters & Frequency
Reuse
• 16.17 Generations of Cellular
Technologies
• 16.18 VSAT Satellite Technology
• 16.19 GPS Satellites
• 16.20 Software Radio & the Future
of Wireless
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16.1 Introduction
• This chapter
– describes wireless technologies
– explains that a myriad of wireless technologies have been
proposed
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16.2 A Taxonomy of Wireless Networks
• Wireless communication applies across a wide range of
network types & sizes
• Government regulations make specific ranges of the
EM spectrum available for communication
• A license is required to operate transmission
equipment in some parts of the spectrum, &
– other parts of the spectrum are unlicensed
• Many wireless technologies have been created &
– new variants appear continually
• Wireless technologies can be classified broadly
according to network type
• The taxonomy in Fig. 16.1 illustrates the fact
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16.2 A Taxonomy of Wireless Networks
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16.3 Personal Area Networks (PANs)
• A PAN technology provides communication over a short
distance
• It is intended for use with devices that are owned &
operated by a single user, e.g., between
– a wireless headset & a cell phone
– a computer & a nearby wireless mouse or keyboard
• PAN technologies can be grouped into three categories
• Fig. 16.2 lists the categories, & gives a brief description
of each
• Later sections explain PAN communication in more detail
– & list PAN standards
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16.3 Personal Area Networks (PANs)
Figure 16.2 Four types of wireless Personal Area technologies
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16.4 ISM Wireless Bands Used by LANs & PANs
• A region of electromagnetic spectrum is reserved for use
by Industrial, Scientific, & Medical (ISM) groups
– ISM wireless & WLAN (WiFI) are based on IEEE 802.11
• The frequencies are not licensed to specific carriers are
– broadly available for products, & are used for LANs & PANs
• Fig. 16.3 illustrates the ISM frequency ranges
Figure 16.3 A taxonomy of wireless networking technologies.
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16.5 Wireless LAN Technologies & Wi-Fi
• A variety of wireless LAN
technologies exist that use
– various frequencies
– modulation techniques, &
– data rates
• IEEE provides most of the
standards
– categorized as IEEE 802.11
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• A group of vendors who
build wireless equipment
formed the Wi-Fi Alliance
– a non-profit organization
– tests & certifies wireless
equipment using the 802.11
standards
• Alliance has received
extensive marketing, most
consumers associate
wireless LANs with the
term Wi-Fi
• Fig. 16.4 lists the key
IEEE standards that fall
under the Wi-Fi Alliance
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16.5 Wireless LAN Technologies & Wi-Fi
Figure 16.4 Key wireless standards certified by Wi-Fi Alliance.
DSSS= Direct Sequence Spread Spectrum
FHSS= Frequency Hopping Spread Spectrum
PPM= Pulse-Position Modulation
OFDM= Orthogonal Frequency Division Multiplexing
802,11a, 5 GHz, 6-54 Mbps, OFDM,
https://en.wikipedia.org/wiki/IEEE_802.11
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16.6 Spread Spectrum Techniques
• The term spread spectrum transmission uses multiple
frequencies to send data
– the sender spreads data across multiple frequencies
– the receiver combines the information obtained from multiple
frequencies to reproduce the original data
• Spread spectrum can be used to achieve one of the
following two goals:
– Increase overall performance
– Make transmission more immune to noise
• The table in Fig. 16.5 summarizes the three key
multiplexing techniques used in Wi-Fi wireless networks
– Each technique has advantages
– Thus, when a wireless technology is defined, the designers choose
an appropriate multiplexing technique
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16.6 Spread Spectrum Techniques
code
http://www.rfwireless-world.com/Articles/difference-between-FDM-and-OFDM.html
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16.7 Other Wireless LAN Standards
• IEEE has created many wireless networking standards
– that handle various types of communication
• Each standard specifies the
–
–
–
–
Frequency range
Modulation
Multiplexing to be used
Data rate
• Fig. 16.6 lists the major standards that have been
created or proposed, & gives a brief description of each
• In 2007, IEEE “rolled up” many of the existing 802.11
standards into a single document known as 802.11-2007
– The document describes basics
– It has an appendix for each variant
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16.7 Other Wireless LAN Standards
Fig.16.6 Major 802.11 standards & the purpose of each.
https://en.wikipedia.org/wiki/IEEE_802.11
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16.8 Wireless LAN Architecture
• The three building blocks of a
wireless LAN are:
– access points (AP)
– Ad hoc
• which are informally called base
stations
– an interconnection mechanism
• such as a switch or router used to
connect access points
– a set of wireless hosts
• also called wireless nodes or
wireless stations
• In principle, two types of
wireless LANs are possible:
• wireless hosts communicate
amongst themselves without a
base station
– Infrastructure based
• a wireless host only communicates
with an access point, &
• the access point relays all packets
• An organization might deploy
AP throughout its buildings
• Fig. 16.7 illustrates a sample
architecture
To Switch to
Internet
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16.8 Wireless LAN Architecture
Internet
Note: The set of computers within range of a given access point is known
as a Basic Service Set (BSS)
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16.9 Overlap, Association, & 802.11 Frame Format
• Many details can complicate an infrastructure
architecture
– On one hand, if a pair of APs are too far apart
• a dead zone will exist between them
• a physical location with no wireless connectivity
– On the other hand, if a pair of access points is too close together
• an overlap will exist in which a wireless host can reach both access
points
• Most wireless LANs connect to the Internet
– Thus, the interconnect mechanism usually has an additional wired
connection to an Internet router
• Fig. 16.8 illustrates the architecture
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16.9 Overlap, Association, & 802.11 Frame Format
BSS= Basic Service Set
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16.9 Overlap, Association, & 802.11 Frame Format
• To handle overlap, 802.11 networks require a wireless
host to associate with a single AP
– That is, a wireless host sends frames to a particular AP
– Then AP forwards the frames across the network
• Fig. 16.9 (below) illustrates the 802.11 frame format
– The figure shows that when used with an infrastructure architecture
– the frame carries the MAC address of an AP & the address of an
Internet router
https://technet.microsoft.com/en-us/library/cc757419(v=ws.10).aspx
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16.10 Coordination Among Access Points
• To what extent do APs need to coordinate?
• Many early AP designs were complex
• The access points coordinated to provide seamless
mobility similar to the cellular phone system
– That is, the APs communicated amongst themselves to insure
smooth handoff as a wireless computer moved from the region to
another
– Some designs measured signal strength & attempted to move a
wireless node to a new AP
• when the signal received at the new AP exceeded the signal strength at
the existing AP
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16.10 Coordination Among Access Points
• Some vendors began to offer lower cost, less complex
APs that do not coordinate
• The vendors argue that signal strength does not provide
a valid measure of mobility
– a mobile computer can handle changing from one AP to another &
– that the wired infrastructure connecting APs has sufficient capacity
to allow more centralized coordination
• A less complex AP design is appropriate in situations
where an installation consists of a single AP
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16.11 Contention & Contention-Free Access
• The original 802.11 standard defined two general approaches for
channel access
– Point Coordinated Function (PCF) for contention-free service
• an AP controls stations in the Basic Service Set (BSS) to insure that
transmissions do not interfere with one another
• E.g., an AP can assign each station a separate frequency
• In practice, PCF is never used
– Distributed Coordinated Function (DCF) for contention-based service
• arranges for each station in a BSS to run a random access protocol
• Wireless networks can experience a hidden station problem
– where two stations can communicate but a third station can only receive
the signal from one of them
• 802.11 networks use CSMA/CA
– which requires a pair to exchange Ready To Send (RTS) & Clear To
Send (CTS) messages before transmitting a packet
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16.11 Contention & Contention-Free Access
• The 802.11 standard defines
three timing parameters as
follows:
• Short Inter-Frame Space
(SIFC) of 10 micro-sec
– defines how long a receiving
station waits before sending an
ACK or other response
• Distributed Inter-Frame Space
(DIFC) of 50 micro-sec
– defines how long a channel must
be idle before a station can
attempt transmission, which is
equal to SIFS + two Slot Times
• Slot Time of 20 micro-sec
• Fig. 16.10 illustrates how the
parameters are used in a
packet transmission
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16.11 Contention & Contention-Free Access
• Physical separation among stations & electrical noise makes it
difficult to distinguish between
– weak signals, interference, & collisions
• Wi-Fi networks do not employ collision detection
– That is, the hardware does not attempt to sense interference during a
transmission
– Instead, a sender waits for an acknowledgement (ACK) message
– If no ACK arrives, the sender assumes the transmission was lost, &
• employs a backoff strategy similar to the strategy in wired Ethernet
• In practice, 802.11 networks that have few users & do not
experience electrical interference seldom need
retransmission
– However, other 802.11 networks experience frequent packet loss &
depend on retransmission
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16.12 Wireless MAN Technology & WiMax
• Standardized by IEEE
under the category 802.16
• A group of companies
coined the term (WiMax)
– which is interpreted to mean
World-wide Interoperability for
Microwave Access
– & they formed WiMAX Forum
to promote use of the
technology
• Two main versions of
WiMAX are being
developed that differ in
their overall approach:
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• Fixed WiMAX
– refers to systems built using
IEEE 802.16-2004, which is
informally called 802.16d
– the technology does not provide
for handoff among access points
– designed to provide connections
between a service provider & a
fixed location
• such as a residence or office building,
rather than between a provider & a cell
phone
• Mobile WiMAX
– Next slide
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16.12 Wireless MAN Technology & WiMax
• Mobile WiMAX
– built according to standard 802.16e-2005, known also as 802.16e
– the technology offers handoff among APs
• which means a mobile WiMAX system can be used with portable
devices such as laptop computers or cell phones
• WiMAX offers broadband communication that can be
used in a variety of ways:
– WiMAX can be used as an Internet access technology
– WiMAX can provide a general-purpose interconnection among
physical sites
• especially in a city
– To be used as backhaul connection between a service provider's
central network facility & remote locations
• such as cell towers
• Fig. 16.11 lists a few of the proposed uses
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16.12 Wireless MAN Technology & WiMax
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16.12 Wireless MAN Technology & WiMax
• Deployments of WiMAX used for backhaul will have the
highest data rates
• It will use frequencies that require a clear Line-Of-Sight
(LOS) between two entities
– LOS stations are typically mounted on towers or on tops of
buildings
• Deployments used for Internet access may use fixed or
mobile WiMAX
– such deployments usually use frequencies that do not require LOS
– thus, they are classified as Non-Line-Of-Sight (NLOS)
• Fig. 16.12 illustrates the two deployments
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16.12 Wireless MAN Technology & WiMax
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16.12 Wireless MAN Technology & WiMax
• The key features of WiMAX can be summarized as
follows:
–
–
–
–
–
–
Uses licensed spectrum (i.e., offered by carriers)
Each cell can cover a radius of 3 to 10 Km
Uses scalable Orthogonal FDM
Guarantees quality of services (for voice or video)
Can transport 70 Mbps in each direction at short distances
Provides 10 Mbps over a long distance (10 Km)
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16.13 PAN Technologies & Standards
• IEEE has assigned the number 802.15 to PAN standards
• Several task groups & industry consortia have been
formed for each of the key PAN technologies
• Fig. 16.13 lists the major IEEE PAN standards
Fig.16.13 IEEE PAN standards.
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16.13 PAN Technologies & Standards
• Bluetooth
– The IEEE 802.15.1a standard evolved after vendors created
Bluetooth technology as a short-distance wireless connection
technology
• The characteristics of Bluetooth technology are:
– Wireless replacement for cables (e.g., headphones or mouse)
– Uses 2.4 GHz frequency band
– Short distance (up to 5 meters, with variations that extend the
range to 10 or 50 meters)
– Device is Controller or Controlee
– Controller grants permission to Controlee
– Data rate is up to 721 Kbps
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16.13 PAN Technologies & Standards
• Ultra Wideband (UWB)
– The idea behind UWB communication is that spreading data
across many frequencies
• requires less power to reach the same distance
• The key characteristics of UWB are:
–
–
–
–
–
Uses wide spectrum of frequencies
Consumes very low power
Short distance (2 to 10 meters)
Signal permeates obstacles such as walls
Data rate of 110 Mbps at 10 meters, & up to 500 Mbps at 2
meters
– IEEE unable to resolve disputes & form a single standard
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16.13 PAN Technologies & Standards
• Zigbee
– The Zigbee standard
(802.15.4) arose from a
desire to standardize wireless
remote control technology
• especially for industrial
equipment
– Because remote control units
only send short command
• high data rates are not
required
– Target is industry as well as
home automation
– Three frequency bands used
(868 MHz, 915 MHz, & 2.4
GHz)
– Data rate of 20, 40, or 250
Kbps, depending on
frequency band
– Low power consumption
– Three levels of security being
defined
• The chief characteristics
of Zigbee are:
– Wireless standard for remote
control, not data
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16.14 Other Short-Distance Communication Technol.
• Two other wireless technologies provide communication
over short distances, but they are not listed under PANs
– InfraRED technologies provide control & low-speed data
communications
– RFID technologies are used with sensors
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16.14 Other Short-Distance Communication Technol.
• InfraRED
– InfraRED technology is often used in remote controls, &
• may be used as a cable replacement (e.g., for a wireless mouse)
– The Infrared Data Association (IrDA) has produced a set of standards
that are widely accepted
• The chief characteristics of the IrDA technology are:
– Family of standards for various speeds & purposes
– Practical systems have range of one to several meters
– Directional transmission with a cone covering 30
– Data rates between 2.4 Kbps (control) & 16 Mbps (data)
– Generally low power consumption with very-low power versions
– Signal may reflect from surfaces
• but cannot penetrate solid objects
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16.14 Other Short-Distance Communication Technol.
• Radio Frequency Identification (RFID)
– RFID technology uses an interesting form of wireless
communication to create a mechanism
– A small tag contains identification information
• that a receiver can “pull” from the tag
• Some features of RFID:
– Over 140 RFID standards exist for a variety of applications
– Passive RFIDs draw power from the signal sent by the reader
– Active RFIDs contain a battery
• which may last up to 10 years
– Limited distance
• although active RFIDs extend farther than passive
– Can use frequencies from less than 100 MHz to 868-954 MHz
– Used for
• inventory control, sensors, passports, & other applications
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16.15 Wireless WAN Technologies
• Wireless WAN technologies can be divided into two
categories:
– Cellular communication systems
– Satellite communication systems
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16.15 Wireless WAN Technologies
• Cellular systems were originally designed to provide
voice services to mobile customers
– System was designed to interconnect cells to the public telephone
• Currently, cellular systems are being used to provide
data services & Internet connectivity
• In terms of architecture
– each cell contains a tower
– a group of (usually adjacent) cells is connected to a Mobile
Switching Center (MSC)
• The center tracks a mobile user &
– manages handoff as the user passes from one cell to another
• Fig. 16.14 illustrates how cells might be arranged along a
highway
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16.15 Wireless WAN Technologies
T1 Trunk
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16.15 Wireless WAN Technologies
• When moving between two cells belonging to the same MSC
– the switching center handles the change
• When a user passes from one geographic region to another
– two MSCs are involved in the handoff
• Perfect cellular coverage occurs if each cell is a hexagon
– because the cells can be arranged in a honeycomb
– In practice, cellular coverage is imperfect
• Most cell towers use omnidirectional antennas
– that transmit in a circular pattern
– obstructions & electrical interference can attenuate a signal or cause an
irregular pattern
• in some cases, cells overlap & in others, gaps exist with no coverage
• Fig. 16.15 illustrates ideal & realistic coverage
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16.15 Wireless WAN Technologies
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16.15 Wireless WAN Technologies
• The variability of cell density is possible
• In rural areas (expected density of cell phones is low)
– cell size is large, a single tower is adequate for a large area
• In an urban setting (many cell phones in a given area)
– E.g., consider a city block in a large metropolitan area
– In addition to pedestrians & people riding in vehicles, such an area
can contain office or apartment buildings with many occupants
• Designers break a region into many cells to handle more
calls
– a practical deployment uses various size cells, with smaller cells
used to cover metropolitan areas
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16.16 Micro Cells
• Micro cells are used in are was where the population is high &
– where high-rise buildings obstruct receptions &
– where a single cell may not suffice
– providers add extra micro cell devices to provide better reception
• In a special case a provider may offer micro cell devices to
companies or individual customers, or
– Customers may purchase or lease micro cell devices
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16.17 Cell Clusters & Frequency Reuse
• Cellular communication follows a key principle:
– Interference can be minimized if an adjacent pair of cells do not
use the same frequency
• To implement the principle
– cellular planners employ a cluster approach
• in which a small pattern of cells is replicated
• Fig. 16.16 illustrates clusters of size 3, 4, 7, & 12 that are
commonly used
Each cell assigned a
unique frequency
Fig.16.16 Illustration of typical cell clusters.
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16.17 Cell Clusters & Frequency Reuse
• In geometric terms, each
of the shapes in the figure
can be used to tile a
plane, i.e.,
– by replicating the same
shape
– it is possible to cover an
entire area without leaving
any gaps
• Fig. 16.17 illustrates a
replication of the 7-cell
cluster
– Each cell with a letter
corresponding to a particular
assigned frequency to that
cell, &
– the cluster pattern is
replicated
• no adjacent cells share a
common frequency
• If each cell in a given
shape is assigned a
unique frequency
– the repeated pattern will not
assign the same frequency to
any pair of adjacent cells
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16.17 Cell Clusters & Frequency Reuse
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16.18 Generations of Cellular Technologies
• Telecommunications
industry divides cellular
technologies into four
generations
• 2G & 2.5G
– that are labeled 1G, 2G, 3G,
& 4G
– with intermediate versions
labeled 2.5G & 3.5G
• 1G
– Began in the late 1970s, &
extended through the 1980s
– Originally called cellular
mobile radio telephones
– Began in the early 1990s &
continues to be used
– The main distinction between
1G & 2G arises
• because 2G uses digital
signals to carry voice
– The label 2.5G is used for
systems that extend a 2G
system
• to include some 3G features
• used analog signals to carry
voice
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16.18 Generations of Cellular Technologies
• 3G & 3.5G
• 4G
– Began in the 2000s
– Began around 2008
– Focuses on the addition of
higher-speed data services
– Focuses on support for realtime multimedia
– A 3G system offers download
rates of 400 Kbps to 2 Mbps,
& is intended to support
applications such as web
browsing & photo sharing
• such as a television program
or high-speed video
– Communicates easily with an
arbitrary website on the
Internet with packet switching
– 3G allows a single telephone
to roam across the world
– They include multiple
connection technologies
• such as Wi-Fi & satellite
• at any time, the phone
automatically chooses the
best connection technology
available
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16.18 Generations of Cellular Technologies
• A variety of standards have evolved
(many attempted to choose an approach & create a standard)
– The European Conference of Postal & Telecommunications
Administrators chose a TDMA technology known as Global
System for Mobile Communications (GSM)
– In the United States, each carrier created a network with its own
technology
– Motorola invented a TDMA system known as iDEN
– Most US & Asian carriers adopted a CDMA approach that was
standardized as IS-95A
– Japan created a TDMA technology known as PDC
• Fig. 16.18 summarizes major 2G standards, &
– some of the 2.5G standards that evolved
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16.18 Generations of Cellular Technologies
Fig.16.18 Major second & third generation cellular technologies.
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16.18 Generations of Cellular Technologies
• The standards listed in the figure each provide a basic
communication mechanism over which many services
can operate
–
–
–
–
General Packet Radio Service (GPRS) for Internet access
Short Message Service (SMS) is used for texting
Wireless Application Service (WAP) is used to access Internet
Multimedia Messaging service (MMS) is used for multi-media
• GPRS technologies have been further developed that
use more sophisticated modulation & multiplexing
techniques (to increase data rates)
– Enhanced Data rate for GSM Evolution (EDGE)
• known as Enchanced GPRS (EGPRS), offers higher transfer rates
– EDGE Evolution provides higher rates
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16.18 Generations of Cellular Technologies
• Service providers pushed to make technologies
interoperable
– the industry consolidated many of the approaches from 2G into a
few key standards
– IS-136, PDC, IS-95A, & EDGE all influenced the design of UMTS,
a technology that uses Wideband CDMA (WCDMA)
– IS-95B was extended to produce CDMA 2000, as in Fig. 16.19
• Several standards evolved for 3G data services
– EVDO (Evolution Data Optimized or Evolution Data Only) & EVDV
emerged at approximately the same time
• They combine CDMA & FDM to increase the overall performance
– High-Speed Downlink Packet Access (HSDPA) offers download
speeds of 14 Mbps
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16.18 Generations of Cellular Technologies
Fig.16.19 Fourth generation cellular wireless standards.
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16.19 VSAT (Very Small Aperture Transmission) Satellite Technology
• Earlier chapters provided
some information on
satellites
– The parabolic shape means
that EM energy arriving from
a distant satellite
– Ch 7 describes the three
types of communication
satellites
– Ch 14 discusses channel
access mechanisms
– By aiming the dish at a
satellite & placing a detector
at the focus point
• Here we describe some
specific satellite
technologies
• The key to satellite
communication is a
parabolic antenna
– It is known as a dish
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• is reflected to a single focus
point
• a designer can guarantee that
a strong signal is received
• Fig. 16.20 illustrates
reflection parabolic dish
antenna, &
– shows how incoming energy
is reflected from the surface
of the dish toward the
receiver
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16.19 VSAT Satellite Technology
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16.19 VSAT Satellite Technology
• VSAT satellites use three frequency ranges that differ in
– the strength of the signal delivered
– the sensitivity to rain & other atmospheric conditions
– the area of the earth's surface covered (satellite's footprint)
• Fig. 16.21 describes the characteristics of each frequency band
Ali Kujoory
6/30/2016
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57
16.20 GPS Satellites
• Global Positioning System
(GPS) provide accurate
time & location
information
– Location info is increasingly
used in mobile networking,
location-based services
• Key features are:
• military ones have higher
accuracy
– 24 total satellites orbit the
earth
6/30/2016
• that can be used in some
communications
• Obtaining position info is
straightforward:
– All GPS satellites orbit in
well-known positions
– Accuracy between 2-20
meters
Ali Kujoory
– Satellites arranged in six (6)
orbital planes
– Provides time
synchronization
• a receiver can determine a
unique location on the earth's
surface by finding the distance
to three satellites
See text for more info
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58
16.21 Software Defined Radio & the Future of Wireless
• Wireless technologies use special-purpose radio
hardware
– The antenna, transmitter, & receiver in a given device are
designed to operate on predetermined frequencies
• using specific forms of modulation & multiplexing
• A cell phone that can use GSM, Wi-Fi, & CDMA networks
– But it must have three completely separate radio systems, & must
choose among them
• Traditional radios are being replaced by radios that follow
a programmable paradigm
– in which features are controlled by software running on a
processor
• Fig. 16.22 lists major radio features that can be controlled
in a software programmable radio
Ali Kujoory
6/30/2016
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59
16.21 Software Defined Radio & the Future of Wireless
Ali Kujoory
6/30/2016
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60
16.21 Software Defined Radio & the Future of Wireless
• The key technologies that enable software radios are:
– Tunable analog filters & multiple antenna management
• Analog chips are currently available that provide tunable analog filters
– Digital Signal Processors (DSPs) are available to handle signal
coding & modulation
– Multiple-Input Multiple-Output (MIMO) denotes a system that
employs multiple antennas for both transmission & reception
– Universal Software Radio Peripheral (USRP) & GNU Radio are
currently available for experimentation
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6/30/2016
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61