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RF100 - 1November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Tonex RF BootcampTonex RF Bootcamp
RF100 - 2November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
History of RF AndEarly Telecommunications
History of RF AndEarly Telecommunications
RF100 - 3November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
How Did We Get Here?
Days before radio..... 1680 Newton first suggested
concept of spectrum, but for visible light only
1831 Faraday demonstrated that light, electricity, and magnetism are related
1864 Maxwells Equations: spectrum includes more than light
1890s First successful demos of radio transmission
UN S
LF HF VHF UHF MW IR UV XRAY
RF100 - 4November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Telegraphy Samuel F.B. Morse had the idea of the telegraph on a
sea cruise in the 1833. He studied physics for two years, and In 1835 demonstrated a working prototype, which he patented in 1837.
Derivatives of Morse binary code are still in use today The US Congress funded a demonstration line from
Washington to Baltimore, completed in 1844. 1844: the first commercial telegraph circuits were coming
into use. The railroads soon were using them for train dispatching, and the Western Union company resold idle time on railroad circuits for public telegrams, nationwide
1857: first trans-Atlantic submarine cable was installedSamuel F. B. Morse
at the peak of his career
Field Telegraphyduring the US Civil War, 1860s
Submarine Cable Installationnews sketch from the 1850s
RF100 - 5November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Telephony By the 1870s, the telegraph was in use all over the world and largely taken for
granted by the public, government, and business. In 1876, Alexander Graham Bell patented his telephone, a device for carrying
actual voices over wires. Initial telephone demonstrations sparked intense public interest and by the late
1890s, telephone service was available in most towns and cities across the USA
Telephone Line Installation Crew1880s
Alexander Graham Bell and his phonefrom 1876 demonstration
electricfield
magneticfield
Propagationdirection
Electromagnetic Radiation
Interrelated electric and magnetic fields traveling through space
Electromagnetic radiation travels at about c = 3108 m/s in a vacuum the cosmic speed limit!
299792458.0 m/s, more exactly in cables, 82-95% speed in a vacuum In glass, about 66% speed in a vacuum
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 6
RF100 - 7November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Radio Milestones 1888: Heinrich Hertz, German physicist, gives lab demo of
existance of electromagnetic waves at radio frequencies 1895: Guglielmo Marconi demonstrates a wireless radio
telegraph over a 3-km path near his home it Italy 1897: the British fund Marconis development of reliable
radio telegraphy over ranges of 100 kM 1902: Marconis successful trans-Atlantic demonstration 1902: Nathan Stubblefield demonstrates voice over radio 1906: Lee De Forest invents audion, triode vacuum tube
feasible now to make steady carriers, and to amplify signals
1914: Radio became valuable military tool in World War I 1920s: Radio used for commercial broadcasting 1940s: first application of RADAR - English detection of
incoming German planes during WW II 1950s: first public marriage of radio and telephony - MTS,
Mobile Telephone System 1961: transistor developed: portable radio now practical 1961: IMTS - Improved Mobile Telephone Service 1970s: Integrated circuit progress: MSI, LSI, VLSI, ASICs 1979, 1983: AMPS cellular demo, commercial deployment
Guglielmo Marconiradio pioneer, 1895
Lee De Forestvacuum tube inventor
MTS, IMTS
Prefixes for Large and Small Units
RF100 - 8November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Wavelength, Frequency, and Energy Relationships
Wavelength (m) Frequency (Hz) Energy (J)
Radio > 1 x 10-1 < 3 x 109 < 2 x 10-24
Microwave 1 x 10-3 - 1 x 10-1 3 x 109 - 3 x 1011 2 x 10-24- 2 x 10-22
Infrared 7 x 10-7 - 1 x 10-3 3 x 1011 - 4 x 1014 2 x 10-22 - 3 x 10-19
Optical 4 x 10-7 - 7 x 10-7 4 x 1014 - 7.5 x 1014 3 x 10-19 - 5 x 10-19
UV 1 x 10-8 - 4 x 10-7 7.5 x 1014 - 3 x 1016 5 x 10-19 - 2 x 10-17
X-ray 1 x 10-11 - 1 x 10-8 3 x 1016 - 3 x 1019 2 x 10-17 - 2 x 10-14
Gamma-ray < 1 x 10-11 > 3 x 1019 > 2 x 10-14
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 9
Frequency vs. Wavelength
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 10
Radio Spectrum Designations
Designation Abbreviation Frequencies Free-space Wavelengths
Very Low Frequency VLF 9 kHz - 30 kHz 33 km - 10 km
Low Frequency LF 30 kHz - 300 kHz 10 km - 1 km
Medium Frequency MF 300 kHz - 3 MHz 1 km - 100 m
High Frequency HF 3 MHz - 30 MHz 100 m - 10 m
Very High Frequency VHF 30 MHz - 300 MHz 10 m - 1 m
Ultra High Frequency UHF 300 MHz - 3 GHz 1 m - 100 mm
Super High Frequency SHF 3 GHz - 30 GHz 100 mm - 10 mm
Extremely High Frequency EHF 30 GHz - 300 GHz 10 mm - 1 mm
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 11
Common Terms for US Frequency Bands
Band Frequency range
UHF ISM 902-928 MHz
S-Band 2-4 GHz
S-Band ISM 2.4-2.5 GHz
C-Band 4-8 GHz
C-Band satellite downlink 3.7-4.2 GHz
C-Band Radar (weather) 5.25-5.925 GHz
C-Band ISM 5.725-5.875 GHz
C-Band satellite uplink 5.925-6.425 GHz
X-Band 8-12 GHz
X-Band Radar (police/weather) 8.5-10.55 GHz
Ku-Band 12-18 GHz
Ku-Band Radar (police) 13.4-14 GHz 15.7-17.7 GHz
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 12
L band 1 to 2 GHz
S band 2 to 4 GHz
C band 4 to 8 GHz
X band 8 to 12 GHz
Ku band 12 to 18 GHz
K band 18 to 26.5 GHz
Ka band 26.5 to 40 GHz
Q band 30 to 50 GHz
U band 40 to 60 GHz
V band 50 to 75 GHz
E band 60 to 90 GHz
W band 75 to 110 GHz
F band 90 to 140 GHz
D band 110 to 170 GHz
Microwave Bands (complete list)
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 13
November, 2014 RF100 - 14RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Frequencies Used by Wireless SystemsOverview of the Radio Spectrum
3 4 5 6 7 8 9 10 12 14 16 18 20 22 24 26 28 30 GHz30,000,000,000 i.e., 3x1010 Hz
Broadcasting Land-Mobile Aeronautical Mobile TelephonyTerrestrial Microwave Satellite
0.3 0.4 0.5 0/6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.4 3.0 GHz3,000,000,000 i.e., 3x109 Hz
UHF TV 14-59UHF GPSDCS, PCS, AWS700 + Cellular
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.4 3.0 MHz3,000,000 i.e., 3x106 Hz
AM LORAN Marine
3 4 5 6 7 8 9 10 12 14 16 18 20 22 24 26 28 30 MHz30,000,000 i.e., 3x107 Hz
Short Wave -- International Broadcast -- Amateur CB
30 40 50 60 70 80 90 100 120 140 160 180 200 240 300 MHz300,000,000 i.e., 3x108 Hz
FM VHF TV 7-13VHF LOW Band VHFVHF TV 2-6
November, 2014 RF100 - 15RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
The Broadband Wireless Spectrum
Five differently-regulated ranges of spectrum are available for broadband: ISM - the Industrial, Scientific, and Medical band. Unlicensed, already used for Wi-Fi networking,
cordless phones, toys, and microwave ovens. Spread-spectrum transmission is required. In some localities this spectrum may be too cluttered to be useful for broadband.
U-NII Unlicensed National Information Infrastructure band. Unlicensed, and spread-spectrum transmission is not required. This spectrum has far fewer users at present than ISM.
BRS - Broadband Radio Service. (Earlier called the Multipoint Distribution Service (MDS)/MMDS), it was used as wireless cable to bring video to end-users.) Links are licensed, so the potential for interference is small. Sprint and Nextel both control large blocks which are now combined.
EBS Educational Broadband Service (formerly ITFS/Instructional Television Fixed Service) instructional video and data for education. Licensed spectrum; can be used for wireless broadband. Clearwire/Craig McCaw control large blocks.
WCS Wireless Communications Service. Licensed spectrum available for broadband. Bellsouth owns large blocks.
5700 5800 5900 MHz.
ISM
900800 1000 MHz.
ISM
2400 2500 2600 MHz. 2690
EBSISM
2300
WCSWCSSATELLITE
BCST. BRS EBS BRS
Sirius& XM
5300 540052005100
U-NII
November, 2014 RF100 - 16RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Current Wireless/Cellular Spectrum in the US
Modern wireless began in the 800 MHz. range, when the US FCC reallocated UHF TV channels 70-83 for wireless use and AT&Ts Analog technology AMPS was chosen.
Nextel bought many existing 800 MHz. Enhanced Specialized Mobile Radio (ESMR) systems and converted to Motorolas IDEN technology
The FCC allocated 1900 MHz. spectrum for Personal Communications Services, PCS, auctioning the frequencies for over $20 billion dollars
With the end of Analog TV broadcasting in 2009, the FCC auctioned former TV channels 52-69 for wireless use, 700 MHz.
The FCC also auctioned spectrum near 1700 and 2100 MHz. for Advanced Wireless Services, AWS.
Technically speaking, any technology can operate in any band. The choice of technology is largely a business decision.
700 MHz 800 900 1700 1800 1900 2000 2100 2200
700 MHz.I
D
E
N
I
D
E
N
C
E
L
L
D
N
L
N
K
C
E
L
L
U
P
L
I
N
K
AWSUplink
AWSDown-Link
PCSUplink
PCSDown-Link
Proposed AWS-2
A
W
S
?
S
A
T
S
A
T
Frequency, MegaHertz
November, 2014 Page 17RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
North American Cellular Spectrum
In each MSA and RSA, eligibility for ownership was restricted A licenses awarded to non-telephone-company applicants only B licenses awarded to existing telephone companies only subsequent sales are unrestricted after system in actual operation
Downlink Frequencies(Forward Path)
Uplink Frequencies(Reverse Path)
Frequency, MHz824 835 845 870 880 894
869
849
846.5825
890
891.5
Paging, ESMR, etc. A B
Ownership andLicensing
Frequencies used by A Cellular OperatorInitial ownership by Non-Wireline companies
Frequencies used by B Cellular OperatorInitial ownership by Wireline companies
November, 2014 Page 18RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
By 1994, US cellular systems were seriously overloaded and looking for capacity relief
The FCC allocated 120 MHz. of spectrum around 1900 MHz. for new wireless telephony known as PCS (Personal Communications Systems), and 20 MHz. for unlicensed services
allocation was divided into 6 blocks; 10-year licenses were auctioned to highest bidders
Development of North America PCS
51 MTAs493 BTAs
PCS Licensing and Auction Details A & B spectrum blocks licensed in 51 MTAs (Major Trading Areas )
Revenue from auction: $7.2 billion (1995) C, D, E, F blocks were licensed in 493 BTAs (Basic Trading Areas)
C-block auction revenue: $10.2 B, D-E-F block auction: $2+ B (1996) Auction winners are free to choose any desired technology
A D B E F C data unlic.voice A D B E F C
1850 MHz.
1910 MHz.
1990 MHz.
1930 MHz.
15 15 155 5 5 15 15 155 5 5
PCS SPECTRUM ALLOCATIONS IN NORTH AMERICA
G G
November, 2014Page 19 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Advanced Wireless Services: The AWS Spectrum
To further satisfy growing demand for wireless data services as well as traditional voice, the FCC has also allocated more spectrum for wireless in the 1700 and 2100 MHz. ranges
The US AWS spectrum lines up with International wireless spectrum allocations, making world wireless handsets more practical than in the past
Many AWS licensees will simply use their AWS spectrum to add more capacity to their existing networks; some will use it to introduce their service to new areas
November, 2014Page 20 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
AWS Spectrum Blocks
The AWS spectrum is divided into blocks Different wireless operator companies are licensed to use specific
blocks in specific areas This is the same arrangement used in original 800 MHz. cellular,
1900 MHz. PCS, and the new 700 MHz. allocations
November, 2014Page 21 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
The US 700 MHz. Spectrum and Its Blocks
To satisfy growing demand for wireless data services as well as traditional voice, the FCC has also taken the spectrum formerly used as TV channels 52-69 and allocated them for wireless
The TV broadcasters will completely vacate these frequencies when analog television broadcasting ends in February, 2009
At that time, the winning wireless bidders may begin building and operating their networks
In many cases, 700 MHz. spectrum will be used as an extension of existing operators networks. In other cases, entirely new service will be provided.
November, 2014RF100 - 22 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
RF100 - 23November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Wireless Systems:Modulation and Signal Bandwidth
Wireless Systems:Modulation and Signal Bandwidth
fc
fc
Upper Sideband
Lower Sideband
fc
fc
I axis
Q axis
a
b
c
QPSK
I axis
Q axis
c
a
b
p
r
v/4 shifted DQPSK
1 0 1 0
1 0 1 0
1 0 1 0
RF100 - 24November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Characteristics of a Radio Signal
The purpose of telecommunications is to send information from one place to another
Our civilization exploits the transmissible nature of radio signals, using them in a sense as our carrier pigeons
To convey information, some characteristic of the radio signal must be altered (I.e., modulated) to represent the information
The sender and receiver must have a consistent understanding of what the variations mean to each other
RF signal characteristics which can be varied for information transmission:
Amplitude Frequency Phase
SIGNAL CHARACTERISTICS
S (t) = A cos [ c t + ]The complete, time-varying radio signal
Amplitude (strength) of the signal
Natural Frequencyof the signal
Phase of the signal
Compare these Signals:
Different Amplitudes
Different Frequencies
Different Phases
RF100 - 25November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Modulation and Occupied Bandwidth
The bandwidth occupied by a signal depends on:
input information bandwidth modulation method
Information to be transmitted, called input or baseband
bandwidth usually is small, much lower than frequency of carrier
Unmodulated carrier the carrier itself has Zero bandwidth!!
AM-modulated carrier Notice the upper & lower sidebands total bandwidth = 2 x baseband
FM-modulated carrier Many sidebands! bandwidth is a
complex mathematical function PM-modulated carrier
Many sidebands! bandwidth is a complex mathematical function
Voltage
Time
Time-Domain(as viewed on an
Oscilloscope)
Frequency-Domain(as viewed on a
Spectrum Analyzer)Voltage
Frequency0
fc
fc
Upper Sideband
Lower Sideband
fc
fc
RF100 - 26November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
The Emergence of AM: A bit of History
The early radio pioneers first used binary transmission, turning their crude transmitters on and off to form the dots and dashes of Morse code. The first successful demonstrations of radio occurred during the mid-1890s by experimenters in Italy, England, Kentucky, and elsewhere.
Amplitude modulation was the first method used to transmit voice over radio. The early experimenters couldnt foresee other methods (FM, etc.), or todays advanced digital devices and techniques.
Commercial AM broadcasting to the public began in the early 1920s.
Despite its disadvantages and antiquity, AM is still alive: AM broadcasting continues today in 540-1600 KHz. AM modulation remains the international civil aviation standard,
used by all commercial aircraft (108-132 MHz. band). AM modulation is used for the visual portion of commercial
television signals (sound portion carried by FM modulation) Citizens Band (CB) radios use AM modulation Special variations of AM featuring single or independent
sidebands, with carrier suppressed or attenuated, are used for marine, commercial, military, and amateur communicationsSSB
LSB USB
RF100 - 27November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Frequency Modulation (FM) Frequency Modulation (FM) is a type of
angle modulation in FM, the instantaneous frequency
of the signal is varied by the modulating waveform
Advantages of FM the amplitude is constant
simple saturated amplifiers can be used
the signal is relatively immune to external noise
the signal is relatively robust; required C/I values are typically 17-18 dB. in wireless applications
Disadvantages of FM relatively complex detectors are
required a large number of sidebands are
produced, requiring even larger bandwidth than AM
TIME-DOMAIN VIEW
sFM(t) =A cos [c t + mm(x)dx+ ]t
t0
where:A = signal amplitude (constant)c = radian carrier frequency
mfrequency deviation indexm(x) = modulating signal
= initial phase
FREQUENCY-DOMAIN VIEW
V
o
l
t
a
g
e
Frequency0 fc
SFM(t)UPPERSIDEBANDS
LOWERSIDEBANDS
RF100 - 28November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
The Digital Advantage
The modulating signals shown in previous slides were all analog. It is also possible to quantize modulating signals, restricting them to discrete values, and use such signals to perform digital modulation. Digital modulation has several advantages over analog modulation:
Digital signals can be more easily regenerated than analog
in analog systems, the effects of noise and distortion are cumulative: each demodulation and remodulation introduces new noise and distortion, added to the noise and distortion from previous demodulations/remodulations.
in digital systems, each demodulation and remodulation produces a cleanoutput signal free of past noise and distortion
Digital bit streams are ideally suited to many flexible multiplexing schemes
transmission
demodulation-remodulation
transmission
demodulation-remodulation
transmission
demodulation-remodulation
RF100 - 29November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Theory of Digital Modulation: Sampling
Voice and other analog signals first must be sampled (converted to digital form) for digital modulation and transmission
The sampling theorem gives the criteria necessary for successful sampling, digital modulation, and demodulation
The analog signal must be band-limited (low-pass filtered) to contain no frequencies higher than fM
Sampling must occur at least twice as fast as fM in the analog signal. This is called the Nyquist Rate
Required Bandwidth for p(t) If each sample p(t) is expressed as
an n-bit binary number, the bandwidth required to convey p(t) as a digital signal is at least N*2* fM
this follows Shannons Theorem: at least one Hertz of bandwidth is required to convey one bit per second of data
The Sampling Theorem: Two PartsIf the signal contains no frequency higher than fM Hz., it is comletely described by specifying its samples taken at instants of time spaced 1/2 fM s.The signal can be completely recovered from its samples taken at the rate of 2 fMsamples per second or higher.
m(t)
Sampling
Recoverym(t)
p(t)
RF100 - 30November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Sampling Example: the 64 kb/s DS-0 Telephony has adopted a world-wide PCM
standard digital signal employing a 64 kb/s stream derived from sampled voice data
Voice waveforms are band-limited upper cutoff between 3500-4000 Hz. to
avoid aliasing rolloff below 300 Hz. to minimize
vulnerability to hum from AC power mains Voice waveforms sampled at 8000/second rate
8000 samples x 1 byte = 64,000 bits/second A>D conversion is non-linear, one byte per
sample, thus 256 quantized levels are possible
Levels are defined logarithmically rather than linearly to accommodate a wider range of audio levels with minimum distortion
-law companding (popular in North America & Japan)
A-law companding (used in most other countries)
A>D and D>A functions are performed in a CODEC (coder-decoder) (see following figure)
-10dB
-20dB
-30dB
-40dB
0 dB
100 300 1000 3000 10000Frequency, Hz
C-Message Weighting
t
0123456879101112131415
16
4
16
13
15
8
3 48
A-LAWy sgn(x) A|x|
ln(1A) for 0 x1A
(where A 87.6)y sgn(x) ln(1A|x)|
ln(1A) for1A x 1
-Lawy sgn(x) ln(1 |x|)
ln(1 )(where 255)
Companding
Band-Limiting
x = analog audio voltagey = quantized level (digital)
RF100 - 31November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Digital ModulationDigital Modulation
RF100 - 32November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Modulation by Digital Inputs
For example, modulate a signal with this digital waveform. No more continuous analog variations, now were shifting between discrete levels. We call this shift keying.
The user gets to decide what levels mean 0 and 1 -- there are no inherent values
Steady Carrier without modulation Amplitude Shift Keying
ASK applications: digital microwave Frequency Shift Keying
FSK applications: control messages in AMPS cellular; TDMA cellular
Phase Shift KeyingPSK applications: TDMA cellular,
GSM & PCS-1900
Our previous modulation examples used continuously-variable analog inputs. If we quantize the inputs, restricting them to digital values, we will produce digital modulation.
Voltage
Time1 0 1 0
1 0 1 0
1 0 1 0
1 0 1 0
RF100 - 33November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Claude Shannon: The Einstein of Information Theory and Signal Science
The core idea that makes CDMA possible was first explained by Claude Shannon, a Bell Labs research mathematician
Shannon's work relates amount of information carried, channel bandwidth, signal-to-noise-ratio, and detection error probability
It shows the theoretical upper limit attainable
In 1948 Claude Shannon published his landmark paper on information theory, A Mathematical Theory of Communication. He observed that "the fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point." His paper so clearly established the foundations of information theory that his framework and terminology are standard today.Shannon died Feb. 24, 2001, at age 84.
RF100 - 34November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Modulation Techniques of 1xEV Technologies
1xEV, 1x Evolution, is a family of alternative fast-data schemes that can be implemented on a 1x CDMA carrier.
1xEV DO means 1x Evolution, Data Only, originally proposed by Qualcomm as High Data Rates (HDR).
Up to 2.4576 Mbps forward, 153.6 kbps reverse
A 1xEV DO carrier holds only packet data, and does not support circuit-switched voice
Commercially available in 2003 1xEV DV means 1x Evolution, Data and Voice.
Max throughput of 5 Mbps forward, 307.2k reverse
Backward compatible with IS-95/1xRTT voice calls on the same carrier as the data
Not yet commercially available; work continues
All versions of 1xEV use advanced modulation techniques to achieve high throughputs.
QPSKCDMA IS-95,
IS-2000 1xRTT,and lower ratesof 1xEV-DO, DV
16QAM1xEV-DOat highest
rates
64QAM1xEV-DV
at highestrates
RF100 - 35November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Digital Modulation Systems
Each symbol of a digitally modulated RF signal conveys a number of bits of information
determined by the number of degrees of modulation freedom
More complex modulation schemes can carry more bits per symbol in a given bandwidth, but require better signal-to-noise ratios
The actual number of bits per second which can be conveyed in a given bandwidth under given signal-to-noise conditions is described by Shannons equations
ModulationScheme
Shannon Limit,BitsHz
BPSK 1 b/s/hzQPSK 2 b/s/hz8PSK 3 b/s/hz
16 QAM 4 b/s/hz32 QAM 5 b/s/hz64 QAM 6 b/s/hz256 QAM 8 b/s/hz
SHANNONS CAPACITY EQUATION
C = B log2 [ 1 + ]S N B = bandwidth in HertzC = channel capacity in bits/secondS = signal powerN = noise power
RF100 - 36November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Digital Modulation Schemes There are many different schemes for digital modulation, each a
compromise between complexity, immunity to errors in transmission, required channel bandwidth, and possible requirement for linear amplifiers
Linear Modulation Techniques BPSK Binary Phase Shift Keying DPSK Differential Phase Shift Keying QPSK Quadrature Phase Shift Keying IS-95 CDMA forward link
Offset QPSK IS-95 CDMA reverse link Pi/4 DQPSK IS-54, IS-136 control and traffic channels
Constant Envelope Modulation Schemes BFSK Binary Frequency Shift Keying AMPS control channels MSK Minimum Shift Keying GMSK Gaussian Minimum Shift Keying GSM systems, CDPD
Hybrid Combinations of Linear and Constant Envelope Modulation MPSK M-ary Phase Shift Keying QAM M-ary Quadrature Amplitude Modulation MFSK M-ary Frequency Shift Keying FLEX paging protocol
Spread Spectrum Multiple Access Techniques DSSS Direct-Sequence Spread Spectrum IS-95 CDMA FHSS Frequency-Hopping Spread Spectrum
RF100 - 37November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Error Vulnerabilities ofHigher-Order Modulation Schemes
Higher-Order Modulation Schemes (16PSK, 32QAM, 64QAM...) are more vulnerable to transmission errors than the simpler, more rugged schemes (BPSK, QPSK)
Closely-packed constellations leave little room for vector error
Non-linearities (gain compression, clipping, reflections within antenna system) warp the constellation
Noise and long-delayed echoes cause scatter around constellation points
Interference blurs constellation points into rings of error
Q
I
Normal 64QAMQ
I
Distortion(Gain Compression)
Q
I
Noise Q
I
Interference
RF100 - 38November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Error Vector Magnitude and (Rho)
A common measurement of overall error is Error Vector Magnitude EVM
usually a small fraction of total vector amplitude, ~0.1
EVM is usually averaged over a large number of symbols
Root-mean-square (RMS) Commercial test equipment
for BTS maintenance measures EVM
Signal quality is often expressed as 1-EVM
normally called (Rho) typically 0.89-0.96
November, 2014RF100 - 39 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
RF Fundamentals: Noise
RF Fundamentals: Noise
Receiving Weak Signals:Noise, Unwelcome Guest Who Wont Go Home!
To hear a very weak signal, why cant we just add amplifier after amplifier until we get enough gain to hear it?
Unfortunately, theres always noise in the background free! The signal must be strong enough to hear despite the noise Signal-to-Noise Ratio SNR Different kinds of signals have different resistance to noise
The most common, ever-present kind of noise is thermal noise Electrons in metal are always randomly moving around,
propelled by free ambient heat Electron flow is the same thing as current noise current Thermal noise power is distributed evenly through the radio
spectrum a certain amount per hertz of bandwidth
November, 2014RF100 - 40 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
How Strong is the Thermal Noise?
The strength of the noise we receive is determined by three things: Its proportional to absolute temperature (degrees Kelvin) Its proportional to the bandwidth were looking at (thermal noise
is uniformly distributed in watts per hertz) The exact amount of noise per degree kelvin per hertz is
determined by Boltzmanns constant In the world of radio, we usually express noise power in decibels
above a milliwatt (dbm). Heres the everyday formula for the amount of thermal noise in dbm:
Where P is the power in dbm Delta F is the bandwidth were watching, in hertz
November, 2014RF100 - 41 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
the Noise Floor
Thermal Noise Strength in the Bandwidths of Common Signals
November, 2014RF100 - 42 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
RF100 - 43November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Physical Principles of Propagation
Physical Principles of Propagation
Working in Decibels
Amplifiers increase the power of electrical signals (an increase is called gain)
Cables, attenuators, or simple radiation through space decrease signal power (called loss)
Decibels are logarithmic units, so db values are never very big or very small db, even if the gains or losses are extremely big or small
Db are always small enough to allow doing the arithmetic in your head without needing a calculator
RF100 - 44November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
db = 10 * Log10 (Pout/Pin)
Ratio to Decibels
(Pout/Pin) = 10 (db/10)Decibels to Ratio
1 x
10 x
100 x
1,000 x
10,000 x
100,000 x
1,000,000 x
.1 x
.01 x
.001 x
.0001 x
.00001 x
.000001 x
+10 db
+20 db
+40 db
+50 db
+60 db
0 db
-10 db
-20 db
-30 db
-40 db
-50 db
-60 db
+30 db
2 x4 x +6 db
+3 db
GAIN and LOSSRatio vs. dB
Decibels can Express Relative Gains/Losses, or Absolute Amounts of Power,or Gains of Specific Antennas
dB - relative gain or loss When you see just a simple value 30 dB, this tells what happens to a
signal when it passes through a certain device or system If a device increases the signal power 1000x, that is 30 db gain. If signal power decreases 1000x, that is -30 db gain (thats loss).
dBm - absolute power A value 30 dBm expresses an actual amount of power. m stands for
milliwatts. Example: 1000 milliwatts is +30 dBm
dBi or dBd gain of test antenna compared to a reference antenna 12.1 dbi gain means the test antenna makes signals seem 12.1 db
stronger than if an isotropic antenna had been used 10 dbd gain means the test antenna makes signals seem 10 db
stronger than if a dipole antenna had been used
RF100 - 45November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
RF100 - 46November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Introduction to Propagation
Propagation is a key process within every radio link. During propagation, many processes act on the radio signal.
attenuation the signal amplitude is reduced by various natural mechanisms; if there is
too much attenuation, the signal will fall below the reliable detection threshold at the receiver. Attenuation is the most important single factor in propagation.
multipath and group delay distortions the signal diffracts and reflects off irregularly shaped objects, producing a
host of components which arrive in random timings and random RF phases at the receiver. This blurs pulses and also produces intermittent signal cancellation and reinforcement. These effects are combatted through a variety of special techniques
time variability - signal strength and quality varies with time, often dramatically space variability - signal strength and quality varies with location and distance frequency variability - signal strength and quality differs on different
frequencies Effective mastery of propagation relies on
Physics: understand the basic propagation processes Measurement: obtain data on propagation behavior in area of interest Statistics: characterize what is known, extrapolate to predict the unknown Modelmaking: formalize all the above into useful models
November, 2014RF100 - 47 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Some Physics: Wavelength of the Signaland Its Influence on Propagation
Radio signals in the atmosphere travel at the speed of light
= wavelengthC = distance traveled in 1 secondF = frequency, Hertz
The wavelength of a radio signal determines many of its propagation characteristics
Internal antenna elements size are typically in the order of 1/4 to 1/2 wavelength
Objects bigger than a wavelength can reflect or obstruct RF energy
RF energy can penetrate into a building or vehicle if it has openings the size of a wavelength, or larger
C / FFrequency,
GHz.Wavelengthcm. in.
0.92 32.6 12.82.4 12.5 4.95.8 5.2 2.0
/2
Propagation Effects of Earths Atmosphere
Earths unique atmosphere supports life (ours included) and also introduces many propagation effects -- some useful, some troublesome
Skywave Propagation: reflection from Ionized Layers LF and HF frequencies (below roughly 50 MHz.) are
routinely reflected off layers of the upper atmosphere which become ionized by the sun
this phenomena produces intermittent world-wide propagation and occasional total outages
this phenomena is strongly correlated with frequency, day/night cycles, variations in earths magnetic field, 11-year sunspot cycle
these effects are negligible for wireless systems at their much-higher frequencies
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 48
More Atmospheric Propagation Effects
Attenuation at Microwave Frequencies rain droplets can substantially attenuate RF signals
whose wavelengths are comparable to, or smaller than, droplet size
rain attenuations of 20 dB. or more per km. are possible troublesome mainly above 10 GHz., and in tropical
areas must be considered in reliability calculations during path
design not major factor in wireless systems propagation
Diffraction, Wave Bending, Ducting signals 50-2000 MHz. can be bent or reflected at
boundaries of different air density or humidity phenomena: very sporadic unexpected long-distance
propagation beyond the horizon. May last minutes or hours
can occur in wireless systems
Refraction by air layers
Ducting by air layers
>100 mi.
Rain Fades onMIcrowave Links
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 49
RF100 - 50November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Dominant Mechanisms of Mobile PropagationMost propagation in the mobile
environment is dominated by these three mechanisms:
Free space No reflections, no obstructions
first Fresnel Zone clear Signal spreading is only mechanism Signal decays 20 dB/decade
Reflection Reflected wave 180out of phase Reflected wave not attenuated much Signal decays 30-40 dB/decade
Knife-edge diffraction Direct path is blocked by obstruction Additional loss is introduced Formulae available for simple cases
Well explore each of these further...
Knife-edge Diffraction
Reflection with partial cancellation
B
A
d
D
Free Space
November, 2014RF100 - 51 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Propagation: Getting the Signal to the Customer
Propagation is the name for the general process of getting a radio signal from one place to another
During propagation, the signal gets weaker because of several natural processes. This weakening is called attenuation.
Point-to-point radio links work best when there is line-of-sight between the two antennas. This is the condition of least attenuation
nothing along the way to block the signal In mobile systems, line-of-sight only happens near base stations or from
high spots (hilltops, top floors of buildings and parking garages, etc.)
AP SM
November, 2014RF100 - 52 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
The First Fresnel Zone and Free-Space Propagation
Most of the signal power sent from one antenna to another travels in an elliptical, football shape called the First Fresnel zone. the thickness of the zone depends on the signal frequency
If the First Fresnel zone is free of penetration or obstruction by any objects, we say free-space conditions apply this is the desirable condition providing highest received signal strength
Sometimes obstructions are unavoidable, and penetrate the first fresnel zone this attenuates the signal and reduces the signal strength received at the
other end of the link the amount of attenuation depends on the degree of penetration by the
obstruction, and its absorbing characteristics
Frequency,GHz.
Path,Miles
Mid-PtFresnel
R, ft0.92 10 1192.4 10 745.8 10 47
AP SM
LoS, nLoS, and NLoS Definitions
Line of Site(LoS)
Near Line of Site
(nLoS)
Non Line of Site
(NLoS)
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 53
November, 2014RF100 - 54 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Free-Space Propagation Technical Details
The simplest propagation mode Antenna radiates energy which spreads in space Path Loss, db (between two isotropic antennas)
= 36.58 +20*Log10(FMHZ)+20Log10(DistMILES ) Path Loss, db (between two dipole antennas)
= 32.26 +20*Log10(FMHZ)+20Log10(DistMILES ) Notice the rate of signal decay: 6 db per octave of distance change, which is
20 db per decade of distance change Free-Space propagation is applicable if:
there is only one signal path (no reflections) the path is unobstructed (i.e., first Fresnel zone
is not penetrated by obstacles)
First Fresnel Zone ={Points P where AP + PB - AB < }Fresnel Zone radius d = 1/2 (D)^(1/2)
1st Fresnel Zone
B
A
d
D
Free Space Spreading Lossenergy intercepted by receiving antenna is proportional to 1/r2
r
November, 2014RF100 - 55 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Path Profiles from Propagation Prediction Tools
Propagation models can also prepare automated path profiles From a path profile, you can quickly determine whether the path is
line-of-sight or obstructed
RF100 - 56November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Reflection With Partial Cancellation
Mobile environment characteristics: Small angles of incidence and reflection Reflection is unattenuated (reflection coefficient =1) Reflection causes phase shift of 180 degrees
Analysis Physics of the reflection cancellation predicts signal
decay of 40 dB per decade of distance
Heights Exaggerated for Clarity
HTFTHTFT
DMILES
Comparison of Free-Space and Reflection Propagation ModesAssumptions: Flat earth, TX ERP = 50 dBm, @ 1950 MHz. Base Ht = 200 ft, Mobile Ht = 5 ft.
Received Signal in Free Space, DBMReceived Signal inReflection Mode
DistanceMILES-52.4-69.0
1-58.4-79.2
2-64.4-89.5
4-67.9-95.4
6-70.4-99.7
8-72.4-103.0
10-75.9-109.0
15-78.4-113.2
20
Path Loss [dB ]= 172 + 34 x Log (DMiles )- 20 x Log (Base Ant. HtFeet)
- 10 x Log (Mobile Ant. HtFeet)
SCALE PERSPECTIVE
RF100 - 57November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Signal Decay Rates in Various Environments
Weve seen how the signal decays with distance in two basic modes of propagation:
Free-Space 20 dB per decade of distance 6 db per octave of distance
Reflection Cancellation 40 dB per decade of distance 12 db per octave of distance
Real-life wireless propagation decay rates are typically somewhere between 30 and 40 dB per decade of distance
Signal Level vs. Distance
-40
-30
-20
-10
0
Distance, Miles1 3.16 102 5 7 86
One Octaveof distance (2x)
One Decadeof distance (10x)
November, 2014RF100 - 58 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Obstructions and their Effects
When an obstruction penetrates the first fresnel zone, the signal is attenuated. The degree of attenuation depends on
how much of the first fresnel zone is obstructed the absorptive characteristics of the obstructing object(s) whether the signal is also reflecting off of other nearby objects,
possibly providing a degree of fill-in Depending on the length of the path, the transmitter power, and
the receiver sensitivity, the link may still work despite the obstruction
AP SM
November, 2014RF100 - 59 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Severe Obstructions
When the path is blocked by a major obstruction (large hill, downtown building, etc.) there will be substantial signal attenuation
Even under this undesirable condition, if the distance is small there may be enough signal to make the link usable
A very small amount of the signal will actually diffract (bend) over the obstruction
the extra attenuation caused by the obstruction can be calculated by the knife edge diffraction model
this diffraction loss can be considered in the link budget to see if the link is likely to be usable anyway
AP SM
RF100 - 60November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Knife-Edge Diffraction Sometimes a single well-defined
obstruction blocks the path, introducing additional loss. This calculation is fairly easy and can be used as a manual tool to estimate the effects of individual obstructions.
First calculate the diffraction parameter from the geometry of the path
Next consult the table to obtain the obstruction loss in db
Add this loss to the otherwise-determined path loss to obtain the total path loss.
Other losses such as free space and reflection cancellation still apply, but computed independently for the path as if the obstruction did not exist
H
R1 R2
attendB
0-5
-10-15-20-25
-4 -3 -2 -1 0 1 2 3-5
= -H R1 R22 ( R1 + R2)
November, 2014RF100 - 61 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Foliage and Building Penetration Considerations
At broadband wireless frequencies, the penetration loss entering a building often exceeds 35 db.
this restricts range so greatly that antennas are almost never located inside a building
At broadband wireless frequencies, trees and other vegetation effectively block and absorb the signal
typical attenuation for just one mature tree can be 20 db or more
Unfortunately, neither building nor vegetation loss can be predicted accurately. Measurement is the only way to know accurately what is happening.
Building
SM
AP
BuildingSM
AP
RF100 - 62November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Combating Rayleigh Fading: Space Diversity
Fortunately, Rayleigh fades are very short and last a small percentage of the time
Two antennas separated by several wavelengths will not generally experience fades at the same time
Space Diversity can be obtained by using two receiving antennas and switching instant-by-instant to whichever is best
Required separation D for good decorrelation is 10-20
12-24 ft. @ 800 MHz. 5-10 ft. @ 1900 MHz.
Signal received by Antenna 1
Signal received by Antenna 2
Combined Signal
D
RF100 - 63November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Types Of Propagation Models And Their Uses
Simple Analytical models Used for understanding and
predicting individual paths and specific obstruction cases
General Area models Primary drivers: statistical Used for early system
dimensioning (cell counts, etc.) Point-to-Point models
Primary drivers: analytical Used for detailed coverage
analysis and cell planning Local Variability models
Primary drivers: statistical Characterizes microscopic level
fluctuations in a given locale, confidence-of-service probability
Simple Analytical Free space (Friis formula) Reflection cancellation Knife-edge diffraction
Area Okumura-Hata Euro/Cost-231 Walfisch-Betroni/Ikegami
Point-to-Point Ray Tracing
- Lees Method, others Tech-Note 101 Longley-Rice, Biby-C
Local Variability Rayleigh Distribution Normal Distribution Joint Probability Techniques
Examples of various model types
RF100 - 64November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
General Principles Of Area Models
Area models mimic an averagepath in a defined area
Theyre based on measured data alone, with no consideration of individual path features or physical mechanisms
Typical inputs used by model: Frequency Distance from transmitter to
receiver Actual or effective base
station & mobile heights Average terrain elevation Morphology correction loss
(Urban, Suburban, Rural, etc.) Results may be quite different
than observed on individual paths in the area
RSSI, dBm
-120
-110
-100
-90
-80
-70
-60
-50
0 3 6 9 12 15 18 21 24 27 30 33
Distance from Cell Site, km
FieldStrength,dBV/m
+90
+80
+70
+60
+50
+40
+30
+20
Green Trace shows actual measured signal strengths on a drive test radial, as determined by real-world physics.
Red Trace shows the Okumura-Hata prediction for the same radial. The smooth curve is a good fit for real data. However, the signal strength at a specific location on the radial may be much higher or much lower than the simple prediction.
RF100 - 65November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
The Okumura Model: General Concept
The Okumura model is based on detailed analysis of exhaustive drive-test measurements made in Tokyo and its suburbs during the late 1960s and early 1970s. The collected date included measurements on numerous VHF, UHF, and microwave signal sources, both horizontally and vertically polarized, at a wide range of heights.
The measurements were statistically processed and analyzed with respect to almost every imaginable variable. This analysis was distilled into the curves above, showing a median attenuation relative to free space loss Amu (f,d) and correlation factor Garea (f,area), for BS antenna height ht = 200 m and MS antenna height hr = 3 m.
Okumura has served as the basis for high-level design of many existing wireless systems, and has spawned a number of newer models adapted from its basic concepts and numerical parameters.
M
e
d
i
a
n
A
t
t
e
n
u
a
t
i
o
n
A
(
f
,
d
)
,
d
B
1
2
5
40
70
80
100
100 3000500Frequency f, MHz
10
50
70 Urban Area
d
,
k
m
30
850
26
35
100 200 300 500 700 1000 2000 3000Frequency f, (MHz)
5
10
15
20
25
30
C
o
r
r
e
c
t
i
o
n
f
a
c
t
o
r
,
G
a
r
e
a
(
d
B
)
9 dB
850 MHz
RF100 - 66November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Structure of the Okumura Model
The Okumura Model uses a combination of terms from basic physical mechanisms and arbitrary factors to fit 1960-1970 Tokyo drive test data
Later researchers (HATA, COST231, others) have expressed Okumuras curves as formulas and automated the computation
Path Loss [dB] = LFS + Amu(f,d) - G(Hb) - G(Hm) - Garea
Free-Space Path Loss
Base StationHeight Gain
= 20 x Log (Hb/200)
Mobile StationHeight Gain
= 10 x Log (Hm/3)
Amu(f,d) Additional Median Loss
from Okumuras Curves
M
e
d
i
a
n
A
t
t
e
n
u
a
t
i
o
n
A
(
f
,
d
)
,
d
B
1
2
5
40
70
80
100
100 3000500
Frequency f, MHz10
50
70Urban Area
d
,
k
m
30
850
26
Morphology Gain0 dense urban5 urban10 suburban17 rural
35
100 200 300 500 700 1000 2000 3000Frequency f, (MHz)
5
10
15
20
25
30
C
o
r
r
e
c
t
i
o
n
f
a
c
t
o
r
,
G
a
r
e
a
(
d
B
)
850 MHz
November, 2014RF100 - 67 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Examples of Morphological Zones Suburban: Mix of
residential and business communities. Structures include 1-2 story houses 50 feet apart and 2-5 story shops and offices.
Urban: Urban residential and office areas (Typical structures are 5-10 story buildings, hotels, hospitals, etc.)
Dense Urban: Dense business districts with skyscrapers (10-20 stories and above) and high-rise apartments
Suburban Suburban
UrbanUrban
Dense Urban Dense Urban
Although zone definitions are arbitrary, the examples and definitions illustrated above are typical of practice in North American PCS designs.
November, 2014RF100 - 68 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Example Morphological Zones
Rural - Highway: Highways near open farm land, large open spaces, and sparsely populated residential areas. Typical structures are 1-2 story houses, barns, etc.
Rural - In-town: Open farm land, large open spaces, and sparsely populated residential areas. Typical structures are 1-2 story houses, barns, etc.Suburban
Rural
Suburban
Rural
Rural - HighwayRural - Highway
Notice how different zones may abruptly adjoin one another. In the case immediately above, farm land (rural) adjoins built-up subdivisions (suburban) -- same terrain, but different land use, penetration requirements, and anticipated traffic densities.
Radio Network Planning Tools -Basics
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 69
November, 2014RF100 - 70 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Rough Planning with Propagation Prediction Tools
Access Point locations can be compared using commercial propagation prediction tools
Tools include terrain databases and land-use or land-cover data to predict the signal levels between the AP and neighborhoods needing service
the AP antenna patterns can also be included in the model
Actual field test measurements should be used to tune the model parameters for best agreement with the field data
Such models are especially valuable for analyzing effects of terrain obstructions
RF100 - 71November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Typical Model Results Including Environmental Correction
TowerHeight,
mEIRP
(watts)C,dB
Range,kmf = 870 MHz.
Dense UrbanUrban
SuburbanRural
30303050
200200200200
-2-5-10-26
4.04.96.726.8
Okumura/Hata
TowerHeight,
mEIRP
(watts)C,dB
Range,kmf =1900 MHz.
Dense UrbanUrban
SuburbanRural
30303050
200200200200
0-5-10-17
2.523.504.810.3
COST-231/Hata
November, 2014RF100 - 72 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Propagation at 1900 MHz. vs. 800 MHz.
Propagation at 1900 MHz. is similar to 800 MHz., but all effects are more pronounced.
Reflections are more effective Shadows from obstructions are deeper Foliage absorption is more attenuative Penetration into buildings through openings is more effective,
but absorbing materials within buildings and their walls attenuate the signal more severely than at 800 MHz.
The net result of all these effects is to increase the contrast of hot and cold signal areas throughout a 1900 MHz. system, compared to what would have been obtained at 800 MHz.
Overall, coverage radius of a 1900 MHz. BTS is approximately two-thirds the distance which would be obtained with the same ERP, same antenna height, at 800 MHz.
RF100 - 73November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Walfisch-Betroni/Walfisch-Ikegami Models
Ordinary Okumura-type models do work in this environment, but the Walfisch models attempt to improve accuracy by exploiting the actual propagation mechanisms involved
Path Loss = LFS + LRT + LMS
LFS = free space path loss (Friis formula)LRT = rooftop diffraction lossLMS = multiscreen reflection loss Propagation in built-up portions of cities is
dominated by ray diffraction over the tops of buildings and by ray channeling through multiple reflections down the street canyons
-20 dBm-30 dBm-40 dBm-50 dBm-60 dBm-70 dBm-80 dBm-90 dBm-100 dBm-110 dBm-120 dBm
Signal Level
Legend
Area View
November, 2014RF100 - 74 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Elements of Propagation Measurement Systems
WirelessReceiver
PC or Collector
GPSReceiver
DeadReckoning
Main Features Field strength measurement
Accurate collection in real-time Multi-channel, averaging
capability Location Data Collection Methods:
Global Positioning System (GPS) Dead reckoning on digitized map
database using on-board compass and wheel revolutions sensor
A combination of both methods is recommended for the best results
Ideally, a system should be calibrated in absolute units, not just raw received power level indications
Record normalized antenna gain, measured line loss
November, 2014RF100 - 75 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Typical Test Transmitter Operations
Typical Characteristics portable, low power needs weatherproof or weather resistant regulated power output frequency-agile: synthesized
Operational Concerns spectrum coordination and proper
authorization to radiate test signal antenna unobstructed stable AC power SAFETY:
people/equipment falling due to wind, or tripping on obstacles
electric shock damage to rooftop
Statistical TechniquesDistribution Statistics Concept
An area model predicts signal strength Vs. distance over an area
This is the median or most probable signal strength at every distance from the cell
The actual signal strength at any real location is determined by local physical effects, and will be higher or lower
It is feasible to measure the observed median signal strength M and standard deviation
M and can be applied to find probability of receiving an arbitrary signal level at a given distance
Median Signal Strength
,dB
Occurrences
RSSI
Normal Distribution
RSSI,dBm
Distance
Signal Strength predictedby area model
Signal Strength Predicted Vs. Observed
Observed Signal Strength
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 76
Statistical TechniquesPractical Application Of Distribution Statistics
General Approach: Use a model to predict RSSI Compare measurements with model
obtain median signal strength M obtain standard deviation now apply correction factor to obtain field
strength required for desired probability of service
Applications: Given A desired outdoor signal level (dbm) The observed standard deviation from signal
strength measurements A desired percentage of locations which must
receive that signal level Compute a cushion in dB which will give us
that % coverage confidence
RSSI,dBm
Distance
10% of locations exceed this RSSI
50%
90%
Percentage of locations where observed RSSI exceeds predicted
RSSI
Median Signal Strength ,
dB
Occurrences
RSSI
Normal Distribution
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 77
Cell Edge Area Availability And Probability Of Service
Overall probability of service is best close to the BTS, and decreases with increasing distance away from BTS
For overall 90% location probability within cell coverage area, probability will be 75% at cell edge
Result derived theoretically, confirmed in modeling with propagation tools, and observed from measurements
True if path loss variations are log-normally distributed around predicted median values, as in mobile environment
90%/75% is a commonly-used wireless numerical coverage objective
Recent publications by Nortels Dr. Pete Bernardin describe the relationship between area and edge reliability, and the field measurement techniques necessary to demonstrate an arbitrary degree of coverage reliability
Statistical View ofCell Coverage
Area Availability:90% overall within area
75%at edge of area
90%
75%
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 78
Application Of Distribution Statistics: Example
Lets design a cell to deliver at least -95 dBm to at least 75% of the locations at the cell edge (This will provide coverage to 90% of total locations within the cell)
Assume that measurements you have made show a 10 dB standard deviation
On the chart: To serve 75% of locations at the cell edge , we
must deliver a median signal strength which is.675 times stronger than -95 dBm
Calculate:- 95 dBm + ( .675 x 10 dB ) = - 88 dBm
So, design for a median signal strength of -88 dBm!
Standard Deviations from Median (Average) Signal Strength
Cumulative Normal Distribution
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
75%
0.675
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 79
Statistical Techniques:Normal Distribution Graph & Table For Convenient
ReferenceCumulative Normal Distribution
Standard Deviation from Mean Signal Strength
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
CumulativeProbability
0.1%
1%
5%
10%
StandardDeviation
-3.09
-2.32
-1.65
-1.28
-0.84 20%
-0.52 30%
0.675 75%
0 50%
0.52 70%
0.84 80%
1.28 90%
1.65 95%
2.35 99%
3.09 99.9%
3.72 99.99%
4.27 99.999%
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 80
Composite Probability Of ServiceAdding Multiple Attenuating Mechanisms
For an in-building user, the actual signal level includes regular outdoor path attenuation plus building penetration loss
Both outdoor and penetration losses have their own variabilities with their own standard deviations
The users overall composite probability of service must include composite median and standard deviation factors
COMPOSITE = ((OUTDOOR)2+(PENETRATION)2)1/2LOSSCOMPOSITE = LOSSOUTDOOR+LOSSPENETRATION
Building
Outdoor Loss + Penetration Loss
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 81
Composite Probability of ServiceCalculating Fade Margin For Link Budget
Example Case: Outdoor attenuation is 8 dB., and penetration loss is 8 dB. Desired probability of service is 75% at the cell edge
What is the composite ? How much fade margin is required?
Composite Probability of ServiceCalculating Required Fade Margin
EnvironmentType
(morphology)MedianLoss,
dB
Std.Dev., dB
Urban Bldg. 15 8
Suburban Bldg. 10 8
Rural Bldg. 10 8
8 4Typical Vehicle
Dense Urban Bldg. 20 8
BuildingPenetration
Out-Door
Std.Dev., dB
8
8
8
8
8
CompositeTotal
AreaAvailabilityTarget, %
90%/75% @edge
90%/75% @edge
90%/75% @edge
90%/75% @edge
90%/75% @edge
FadeMargin
dB
7.6
7.6
7.6
6.0
7.6
COMPOSITE = ((OUTDOOR)2+(PENETRATION)2)1/2= ((8)2+(8)2)1/2 =(64+64)1/2 =(128)1/2 = 11.31 dB
On cumulative normal distribution curve, 75%
probability is 0.675 above median. Fade Margin required =
(11.31) (0.675) = 7.63 dB.Cumulative Normal Distribution
Standard Deviations from Median (Average) Signal Strength
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
75%
.675
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 82
RF propagationPropagation loss in non free space
For outdoor usage models have been created that include
path loss coefficient up to a measured breakpoint (
path loss coefficient beyond measured breakpoint (
breakpoint depend on antenna height (dbr)
L(2.4GHz) = 40 +10 * * log(dbr) + 10 * * log(d/dbr)November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 83
Link Budget Analysis
Since each bit rate requires a specific receive sensitivity for a given radio, any wireless network (simply referred to as link for the purpose of this discussion) design must estimate the available link budget in dB to make sure that that the link budget is at least 0 dB for the highest bit rate desired.
It is also a good practice to leave some reasonable margin (e.g., 10 dB) in the link budget to accommodate any variations in signal strength caused by interferers or reflectors and to increase the reliability of the link.
The link budget analysis can be used to estimate the range or capacity or to select an antenna.
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 84
Link Budget Calculation
The first step in the calculation of the link budget is to calculate the received power at the receiver.
The Received Power is given as: Received Power = Radiated Power/EIRP Path Loss + Receiver Gain
The radiated power (EIRP or Effective Isotropic Radiated Power is the correct technical term) in dBm is given as:
EIRP (dBm) = Radio Transmit Power (dBm) Cable/Connector/Switch Loss (dB) at Transmitter + Transmit Antenna Gain (dBi)
The Path Loss can be calculated using the appropriate path loss exponent, as discussed earlier, and may include attenuations caused by other objects in the path, if known. The Receiver Gain is given as:
Receiver Gain = Receive Antenna Gain (dBi) - Cable/Connector/Switch Loss (dB) at Receiver
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 85
Link Budget
One important point to note here is that the antenna gain is reciprocal, i.e., the antenna gain can be added to the wireless device at either end to increase the overall link budget. For example, a wireless system with a 10 dBi antenna on the transmitter and a 2 dBi antenna on the receiver will have the same range as a system with a 4 dBi antenna the transmitter and an 8 dBi antenna on the receiver, everything else being equal. Therefore, adding a high gain antenna allows a device not only to transmit signals farther, but also to receive weaker signals.
Once the received power (or signal strength) is known, the link budget can be calculated by subtracting the receive sensitivity of the receiver from the received power, i.e.,
Link Budget = Received Power Receive Sensitivity
The Noise Floor at the receiver can be subtracted from the received power to calculate the SNR. If the noise is lower than the Rx sensitivity, the link will be limited by the Rx sensitivity. Otherwise, the link will be limited by the Noise Floor.
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 86
An Example
For example, with 30 dB EIRP (e.g., 23 dBm Transmit Power, 10 dBi antenna gain and 3 dB cable/connector loss) in 2.4 GHz, the signal attenuates to -50 dBm at 100 meters in free space. For a receiver with Receive Gain of 0 dB (e.g., 2 dBi Receiver antenna and 2 dB cable/connector loss), the received power is -50 dBm.
If the receive sensitivity is -91 dBm for 1 Mbps, then the link margin is 41 dB. However, if the Noise Floor is -85 dBm, then the SNR is 35 dB. In either case, the signal is more than enough to decode 1 Mbps. However, as the distance increases the Noise Floor will be the limiting factor in this specific example.
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 87
RF100 - 88November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Link BudgetsLink Budgets
RF100 - 89November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Link Budget Example: Usage Model and Service Assumptions
This section outlines the number of subscribers and amount of traffic by year
This section shows the variability of outdoor and indoor signals, and the building penetration loss
Interactive Initial System Design Example v1.2fill in GREEN fieldsYELLOW fields calculate automatically
Step 1. Basic Business Plan Details
Year Launch 1 2 3 4 5Population 3,886,000 3,949,350 4,012,700 4,076,050 4,139,400 4,202,750Penetration, % 0.05% 1.85% 3.72% 5.64% 7.60% 9.57%#Customers 1,781 72,933 149,453 229,941 314,451 402,360BH Erl/Cust 0.1 0.05 0.045 0.05 0.05 0.05Total BH erl 178.1 3,646.7 6,725.4 11,497.0 15,722.6 20,118.0
2. Enter building penetration loss and standard deviations from measurements.
Composite Probability Of Service & Required Fade MarginEnvironment
Type ("morphology")
Building Median
Loss, dB
Building Std. Dev,
dB
Outdoor Std. Dev,
dB.
Composite Standard Deviation
Desired Reliability at Cell Edge, %
Fade Margin,
dB.Dense Urban 20 8 8 11.31 75.0% 7.63Urban 15 8 8 11.31 75.0% 7.63Suburban 15 8 8 11.31 75.0% 7.63Rural 10 8 8 11.31 75.0% 7.63Highway 8 6 8 10.00 75.0% 6.74
RF100 - 90November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Reverse Link Budget Example
The Reverse Link Budget describes how the energy from the phone is distributed to the base station, including the major components of loss and gain within the system
3. Construct Link Budgets
Reverse Link Budget
Term or Factor GivenDense Urb. Urban Suburban Rural Highway Formula
MS TX Power (dbm) (+) 23MS antenna gain and body loss (+/-) 0MS EIRP (dBm) (+) 23.00 23.00 23.00 23.00 23.00 AFade Margin, (dB) (-) -7.63 -7.63 -7.63 -7.63 -6.74 BSoft Handoff Gain (dB) (+) 4 4 4 4 4 CReceiver Interf. Margin (dB) (-) -3 -3 -3 -3 -3 DBuilding Penetration Loss (dB) (-) -20.00 -15.00 -15.00 -10.00 -8.00 EBTS RX antenna gain (dBi) (+) 17 17 17 17 17 FBTS cable loss (dB) (-) -3 -3 -3 -3 -3 G
kTB (dBm/14.4 KHz.) -132.4 HBTS noise figure (dB) 6.5 I
Eb/Nt (dB) 5.9 JBTS RX sensitivity (dBm) (-) -120.0 -120.0 -120.0 -120.0 -120.0 H+I+J
Survivable Uplink Path Loss (dB) (+) 130.4 135.4 135.4 140.4 143.3
A+B+C+D+E+F+G-(H+I+J)
RF100 - 91November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Forward Link Budget Example
This section shows the forward link power distribution, and compares the relative balance of the forward and reverse links
Forward Link Budget
Term or Factor GivenDense Urb. Urban Suburban Rural Highway Formula
BTS TX power (dBm) (+) 45 45 45 45 45BTS TX power (watts) 31.62 31.62 31.62 31.62 31.62% Power for traffic channels 74.0% 74.0% 74.0% 74.0% 74.0%Number of Traffic Channels in use 19 19 19 19 19BTS cable loss (dB) (-) -3 -3 -3 -3 -3BTS TX antenna gain (dBi) (+) 17 17 17 17 17BTS EIRP/traffic channel (dBm) (+,-) 44.9 44.9 44.9 44.9 44.9 AFade margin (dB) (-) -7.63 -7.63 -7.63 -7.63 -6.74 BReceiver interference margin (db) (-) -3 -3 -3 -3 -3 CBuilding Penetration Loss (dB) (-) -20.0 -15.0 -15.0 -10.0 -8.0 DMS antenna gain & body loss (dB) (+,-) 0 0 0 0 0 E
kTB (dBm/14.4 KHz.) -132.4Subscriber RX noise figure (dB) 10.5
Eb/Nt (dB) 6Subscriber RX sensitivity (dBm) (-) -115.9 -115.9 -115.9 -115.9 -115.9 F
Survivable Downlink Path Loss, dB (+) 130.2 135.2 135.2 140.2 143.1A+B+C+D
+E-F
Forward/Reverse Link Balance DenseUrban Urban Suburban Rural Highway
Which link is dominant? Reverse Reverse Reverse Reverse ReverseWhat advantage, dB? 0.2 0.2 0.2 0.2 0.2
RF100 - 92November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Link Budgets: What is the Radius of a Cell?
This section uses the Okumura-Hata/Cost-231 model to describe the frequency, antenna heights, and environmental factors, and their relationship on the cells coverage distance
4. Explore propagation model to figure coverage radius of cell.
Frequency, MHz. 870Subscriber Antenna Height, M 1.5
DenseUrban Urban Suburban Rural Highway
Base Station Antenna Height, M 20 20 30 50 50
DenseUrban Urban Suburban Rural Highway
Environmental Correction, dB -2 -5 -10 -17 -17
Coverage Radius, kM 1.30 2.17 6.87 20.86 25.40Coverage Radius, Miles 0.81 1.35 4.27 12.96 15.78
RF100 - 93November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Link Budgets: Putting It All Together
Step 4 estimates the number of cells required to serve each distinct environment within the system
Steps 5, 6, and 7 estimate the RF coverage from each cell, and the number of cells required
5. Calculate number of cells required for coverage, ignoring traffic considerations.
Dense TotalUrban Urban Suburban Rural Highway # Cells
Covered Area of this type, kM^2 55 450 1700 3400 1400 RequiredOne cell's coverage in this zone, kM^2 5.35 14.73 148.46 1367.34 2026.72 for System
# Cells required to cover zone 10.3 30.6 11.5 2.5 0.7 55.5
6. What is the traffic capacity (in erlangs) of your chosen BTS configuration, year-by-year?
Year Launch 1 2 3 4 5Erlangs which one BTS can carry 18.3 18.3 90 90 450 450
7, 8. What is the total busy-hour erlang traffic on your system? How many BTS are required?
Year Launch 1 2 3 4 5Total System Busy-Hour Erlangs 178.1 3,646.7 6,725.4 11,497.0 15,722.6 20,118.0
Capacity of One BTS, erlangs 18.3 18.3 90 90 450 450# BTS required to handle all the traffic 9.7 199.3 74.7 127.7 34.9 44.7
9. Examine your market, #BTS required for coverage and capacity; estimate totalnumber of BTS required.
Year Launch 1 2 3 4 5#BTS req'd just to achieve coverage 55.5 55.5 55.5 55.5 55.5 55.5
#BTS required just to carry traffic 9.7 199.3 74.7 127.7 34.9 44.7Estimated total #BTS required 56.3 206.8 206.8 206.8 206.8 206.8
Radio Link - Simplified Model
Tx Rx
Attenuator
Lt LrPt Pr
Gt Gr
Lp
free space path obstruction atmospheric gases multipath beam spreading variation of angle of arrival and launch Precipitation (rainfall) sand and dust storms
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 94
Link Budget Calculations
TxTx RxRxd = 12 km
f = 18 GHz
Pt = 23 dBm
Lt = 1.5 dB
Gt = 38 dBiGr = 38 dBi
Lr = 1.5 dB
Pr = ? dBm
Pr = Pt - Lt + Gt - Lp + Gr - Lr dBm
Lp = 92.45 + 20 log(18) + 20 log(12) = 119.11 dBm
Pr = 23 - 1.5 + 38 119.11 + 38 - 1.5 = -23dBm
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 95
Path Loss Calculations
The simplest propagation mode Antenna radiates energy which spreads in space
Lp or Path Loss, db (between two isotropic antennas) = 36.56 +20*Log10(F MHZ)+20Log10(Dist MILES )
Lp or Path Loss, db (between two dipole antennas) = 32.26 +20*Log10(F MHZ)+20Log10(Dist MILES )
Lp = Path Loss, db (between two isotropic antennas) = 92.45 (30+62.45) + 20 log(FGHz) + 20 log( Distance km)
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 96
Passive Repeater Configuration
TxTx
RxRx
d = 0.8 km
f = 18 GHzPt = 23 dBm
Lt = 1.5 dB
Gt = 38 dBi
Gr = 38 dBi
Lr = 1.5 dB
Pr = ? dBm
d = 12 km
Gt = 42 dBi
Gt = 42 dBi
1 dB
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 97
RF propagation Simple Path Analysis Concept (alternative)
WP II
PC Card
pigtail cable
Lightning Protector
RF Cable Antenna
WP II
PC Card
pigtail cable
Lightning Protector
RF CableAntenna
+ Transmit Power
- LOSS Cable/connectors
+ Antenna Gain + Antenna Gain
- LOSS Cable/connectors
RSL (receive signal level) or P r> sensitivity + Fade Margin
- Path Loss over link distance
Calculate signal in one direction if Antennas and active components are equal
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 98
RF propagation FADE MARGIN
WP II
Tx =15 dBm
1.3 dB
.7 dB
50 ft.LMR 400
3.4 dB 24 dBi
WP II
Rx = -82 dBm
1.3 dB
.7 dB
50 ft.LMR 400
3.4 dB24 dBi parabolic
For a Reliable link - the signal arriving at the receiver - should be greater than the Sensitivity of the Radio (-82dBm for 11 Mbit)
This EXTRA signal strength is FADE MARGIN
FADE MARGIN can be equated to UPTIME
Minimum Fade Margin = 10 dB
Links subject to interference (city) = 15dB
Links with Adverse Weather = 20dB
Calculate RSL > -82 + 10 = -72dBm
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 99
RF propagation Sample Calculation
WP II
Tx =15 dBm
1.3 dB
.7 dB
50 ft.LMR 400
3.4 dB 24 dBi
WP II
Rx = -82 dBm
1.3 dB
.7 dB
50 ft.LMR 400
3.4 dB24 dBi parabolic
RSL > PTx - Cable Loss + Antenna Gain - Path loss + Antenna Gain - Cable Loss
16 Km = - 124 dB
+ 15 dBm
- 2 dB
- 3.4 dB
+ 24 dBi
- 124 dB
+ 24 dBi
- 3.4 dB
- 2 dB
- 71.8 dB > -72
This lets us know that if the Fresnel zone is clear, the Link should work. If RSL < than -72 then MORE GAIN is needed, using Higher Gain Antennas or Lower loss Cables or Amplifiers (not a Agere Systems provided option)
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 100
Earth Curvature
Obstacle Clearance
Fresnel Zone Clearance Antenna
HeightAntenna Height
Midpoint clearance = 0.6F + Earth curvature + 10' when K=1First Fresnel Distance (meters) F1= 17.3 [(d1*d2)/(f*D)]1/2 where D=path length Km, f=frequency (GHz) , d1= distance from Antenna1(Km) , d2 = distance from Antenna 2 (Km)Earth Curvature h = (d1*d2) /2 where h = change in vertical distance from Horizontal line (meters), d1&d2 distance from antennas 1&2 respectively
Clearance for Earths Curvature 13 feet for 10 Km path200 feet for 40 Km path
Fresnel Zone Clearance = 0.6 first Fresnel distance (Clear Path for Signal at mid point) 30 feet for 10 Km path
57 feet for 40 Km path
RF PropagationAntenna Height requirements
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 101
RF Propagation Reflections
Signals arrive 180 out of phase ( 1/2 ) from reflective surface Cancel at antenna - Try moving Antenna to change geometry of link - 6cm is the
difference in-phase to out of phase
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 102
RF100 - 103November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Elements of Typical Measurement Systems
WirelessReceiver
PC or Collector
GPSReceiver
DeadReckoning
Main Features Field strength measurement
Accurate collection in real-time Multi-channel, averaging
capability Location Data Collection Methods:
Global Positioning System (GPS) Dead reckoning on digitized map
database using on-board compass and wheel revolutions sensor
A combination of both methods is recommended for the best results
Ideally, a system should be calibrated in absolute units, not just raw received power level indications
Record normalized antenna gain, measured line loss
RF100 - 104November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Typical Test Transmitter Operations
Typical Characteristics portable, low power needs weatherproof or weather resistant regulated power output frequency-agile: synthesized
Operational Concerns spectrum coordination and proper
authorization to radiate test signal antenna unobstructed stable AC power SAFETY:
people/equipment falling due to wind, or tripping on obstacles
electric shock damage to rooftop
RF100 - 105November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Antennas for Wireless Systems
Antennas for Wireless Systems
Dipole
Typical WirelessOmni Antenna
Isotropic
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Understanding Antenna RadiationThe Principle Of Current Moments
An antenna is just a passive conductor carrying RF current
RF power causes the current flow
Current flowing radiates electromagnetic fields
Electromagnetic fields cause current in receiving antennas
The effect of the total antenna is the sum of what every tiny slice of the antenna is doing
Radiation of a tiny slice is proportional to its length times the magnitude of the current in it, at the phase of the current
TX RX
Width of banddenotes current
magnitude
Zero currentat each end
Maximum currentat the middle
Current induced inreceiving antennais vector sum of
contribution of everytiny slice of
radiating antenna
each tiny imaginary sliceof the antennadoes its share
of radiating
Polarization of an Antenna and its Effects
To intercept significant energy, a receiving antenna must be oriented parallel to the transmitting antenna
A receiving antenna oriented at right angles to the transmitting antenna is cross-polarized; will have very little current induced
Vertical polarization is the default convention in wireless telephony In the cluttered urban environment, energy becomes scattered and de-
polarized during propagation, so polarization is not as critical Handset users hold the antennas at seemingly random angles..
TX
ElectromagneticField
currentalmost
nocurrent
Antenna 1VerticallyPolarized
Antenna 2Horizontally
Polarized
RX
RF current in a conductor causes electromagnetic fields that seek to induce current flowing in the same directionin other conductors.
The orientation of the antenna is called its polarization.
November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex RF100 - 107
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Antenna Gain
Antennas are passive devices: they do not produce power
Can only receive power in one form and pass it on in another, minus incidental losses
Cannot generate power or amplify However, an antenna can appear to have gain
compared against another antenna or condition. This gain can be expressed in dB or as a power ratio. It applies both to radiating and receiving
A directional antenna, in its direction of maximum radiation, appears to have gain compared against a non-directional antenna
Gain in one direction comes at the expense of less radiation in other directions
Antenna Gain is RELATIVE, not ABSOLUTE When describing antenna gain, the
comparison condition must be stated or implied
Omni-directionalAntenna
DirectionalAntenna
RF100 - 109November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Reference AntennasDefining Gain And Effective Radiated Power
Isotropic Radiator Truly non-directional -- in 3 dimensions Difficult to build or approximate physically,
but mathematically very simple to describe A popular reference: 1000 MHz and above
PCS, microwave, etc. Dipole Antenna
Non-directional in 2-dimensional plane only Can be easily constructed, physically
practical A popular reference: below 1000 MHz
800 MHz. cellular, land mobile, TV & FM
IsotropicAntenna
(watts or dBm) ERP Effective Radiated Power Vs. DipoleEffective Radiated Power Vs. Isotropic
Gain above Dipole referenceGain above Isotropic radiator
(watts or dBm) EIRP dBddBi
Quantity Units Dipole Antenna
Notice that a dipolehas 2.15 dB gaincompared to an isotropic antenna.
RF100 - 110November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Radiation PatternsKey Features And Terminology
An antennas directivity is expressed as a series of patterns
The Horizontal Plane Pattern graphs the radiation as a function of azimuth (i.e..,direction N-E-S-W)
The Vertical Plane Pattern graphs the radiation as a function of elevation (i.e.., up, down, horizontal)
Antennas are often compared by noting specific landmark points on their patterns:
-3 dB (HPBW), -6 dB, -10 dB points
Front-to-back ratio Angles of nulls, minor lobes, etc.
Typical ExampleHorizontal Plane Pattern
0 (N)
90(E)
180 (S)
270(W)
0
-10
-20
-30 dB
Notice -3 dB points
Front-to-back Ratio
10 dBpoints
MainLobe
a MinorLobe
nulls orminima
RF100 - 111November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
In phase
Out of phase
How Antennas Achieve Their Gain
Quasi-Optical Techniques (reflection, focusing) Reflectors can be used to concentrate
radiation technique works best at microwave frequencies,
where reflectors are small Examples:
corner reflector used at cellular or higher frequencies
parabolic reflector used at microwave frequencies
grid or single pipe reflector for cellular
Array techniques (discrete elements) Power is fed or coupled to multiple
antenna elements; each element radiates Elements radiation in phase in some
directions In other directions, a phase delay for each
element creates pattern lobes and nulls
RF100 - 112November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Types Of Arrays
Collinear vertical arrays Essentially omnidirectional in
horizontal plane Power gain approximately
equal to the number of elements
Nulls exist in vertical pattern, unless deliberately filled
Arrays in horizontal plane Directional in horizontal
plane: useful for sectorization Yagi
one driven element, parasitic coupling to others
Log-periodic all elements driven wide bandwidth
All of these types of antennas are used in wireless
RF power
RF power
RF100 - 113November, 2014 RF Bootcamp - Course RF100 v10.0 - (c) 2014 Tonex
Omni AntennasCollinear Vertical Arrays
The family of omni-directional wireless antennas:
Number of elements determines Physical size Gain Beamwidth, first null angle
Models with many elements have very narrow beamwidths
Require stable mounting and careful alignment
Watch out: be sure nulls do not fall in important coverage areas
Rod and grid reflectors are sometimes added for mild directivity
Examples: 800 MHz.: dB803, PD10017, BCR-10O, Kathrein 740-198
1900 MHz.: dB-910, ASPP2933
beamwidth
Angleof
firstnull
-3
dB
Vertical Plane Pattern
Number ofElements
PowerGain
Gain,dB
Angle
0.00 n/a3.01 26.574.77 18.436.02 14.046.99 11.317.78 9.468.45 8.139.03 7.139.54 6.3410.00 5.7110.41 5.1910.79 4.7611.14 4.40
1234567891011121314
1234567891011121314 11.46 4.09
Typical Collinear Arrays
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Sector AntennasReflectors And Vertical Arrays
Typical commercial sector antennas are vertical combinations of dipoles, yagis, or log-periodic elements with reflector (panel or grid) backing
Vertical plane pattern is determined by number of vertically-separated elements
varies from 1 to 8, affecting mainly gain and vertical plane beamwidth
Horizontal plane pattern is determined by:
number of horizontally-spaced elements
shape of reflectors (is reflector folded?)
Vertical Plane PatternUp
Down
Horizontal Plane PatternN
E
S
W
Cassegrain a
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