RF Networks

1
RF Networks
2
There are two aspects of networking which must be
considered when installing either an NCL or LMS
product
1. Ethernet Networking (IP)
2. Radio Networking (RF)
This presentation will focus on the RF side of
the NCL and LMS products.
3
RF Terminology
Wavelength is the distance between identical
points in the adjacent cycles of a waveform. In
wireless systems, this length is usually
specified in meters, centimeters, or millimeters
4
The size of the wavelength varies depending on
the frequency of the signal. Generally speaking,
the higher the frequency the smaller the
wavelength. The WaveRider family of products
operate in the 2.4000 - 2.4835 GHz range (NCL and
LMS2000) as well as the 905 - 925 MHz range
(LMS3000).
At 2.4 GHz the wavelength is 12.5cm
At 905 MHz the wavelength is 33cm
5
These values are calculated using the following
formula
Wavelength 3 x 102
f (frequency in MHz)
This calculation is important to remember,
especially when installing antennas. Ideally,
the antenna should be installed no closer than 10
wavelengths to the nearest reflective surface.
6
Frequency
Frequency is the number of complete cycles per
second in alternating current direction. The
standard unit of frequency is the hertz,
abbreviated Hz. If a current completes one cycle
per second, then the frequency is 1 Hz.
Kilohertz (kHz) Megahertz (MHz) Gigahertz
(GHz) Terahertz (THz)
7
Frequency Spectrum
8
Spectrum
9
Tx Power
Tx is short for Transmit All radios have a
certain level or Tx power that the radio
generates at the RF interface. This power is
calculated as the amount of energy given across a
defined bandwidth and is usually measured in one
of two units

1. dBm a relative power level referencing 1
   milliwatt

1. W a linear power level referencing Watts

10

dBm 10 x logPower in Watts / 0.001W
W 0.001 x 10Power in dBm / 10 dBm
The NCL and LMS radios have Tx power of 18dBm,
which translates into .064 W or 64 mW.
11
Rx Sensitivity
Rx is short for Receive All radios also have a
certain point of no return, where if they
receive a signal less than the stated Rx
Sensitivity, the radio will not be able to see
the data. This is also stated in dBm or W.
The NCL and LMS radios have a receive sensitivity
of 82 dBm. At this level, a Bit Error Rate
(BER) of 10-5 (99.999) is seen. The actual level
received at the radio will vary depending on many
factors.
12
Radiated Power
In a wireless system, antennas are used to
convert electrical waves into electromagnetic
waves. The amount of energy the antenna can
boost the sent and received signal by is
referred to as the antennas Gain. Antenna gain
is measured in

• dBi relative to an isotropic radiator
• dBd relative to a dipole radiator
• 0 dBd 2.15 dBi

13
There are certain guidelines set by the FCC that
must be met in terms of the amount of energy
radiated out of an antenna. This energy is
measured in one of two ways

• Effective Isotropic Radiated Power (EIRP)
• measured in dBm power at antenna input dBm
  relative antenna gain dBi

• Effective Radiated Power (ERP)
• measured in dBm power at antenna input dBm
  relative antenna gain dBd

14
Energy Losses
In all wireless communication systems there are
several factors that contribute to the loss of
signal strength. Cabling, connectors, lightning
arrestors can all impact the performance of your
system if not installed properly. In a low
power system (such as the NCL and LMS products)
every dB you can save is important!! Remember
the 3 dB Rule.
For every 3 dB gain/loss you will either double
your power (gain) or lose half your power (loss).
15
-3 dB 1/2 power -6 dB 1/4 power 3 dB 2x
power 6 dB 4x power
Sources of loss in a wireless system free space,
cables, connectors, jumpers, obstructions
16
FCC Guidelines
The ISM Bands are defined as follows 902 to 928
MHz 2400 to 2483.5 MHz 5725 to 5850 MHz FCC Part
15, Class B Unlicensed operation from 2400 to
2483.5 MHz P2P - EIRP 36 dBm (4 Watts)
31 i.e. 24 dBm into 24 dBi P2MP - EIRP 36
dBm (4 Watts) 31 at subscriber (considered
P2P)
17
FCC - Installer
System must be installed by a Professional
Installer as defined in FCC Document 15.247 Part
15 Complete understanding of FCC emissions
regulations for unlicensed operation in the 2.4
GHz ISM Band. Installer must have a full
understanding of the impact of various types of
antennae, amplifiers and other active and passive
components on the compliance of the equipment
under FCC regulations.
18
FCC - Installation
An external Power Amp cannot be used in
conjunction with WR radio components, in order to
comply with FCC regulatory emissions
requirements. Use of an external PA device with a
WaveRider system is deemed illegal and may result
in significant penalty to the manufacturer,
seller, and customer. Unique connectors provide
means of compliance. Standard connectors require
professional installation to ensure compliance.
19
WaveRider High Speed Wireless Systems
The NCL and LMS systems are designed to support
terrestrial fixed links in an outdoor
environment. Typical distances achieved while
staying within FCC guidelines are
Point to Multipoint up to 8km Point to Point
up to 15km
These distances may vary depending on the
installation, antennae chosen, cabling, etc.
20
NCL1155 Spec Sheet
21
Direct Sequence Spread Spectrum
Also known as Direct Sequence Code Division
Multiple Access (DS-CDMA), DSSS is one of two
approaches to spread spectrum modulation for
digital signal transmission over the air.
The stream of information to be transmitted is
divided into small pieces, each of which is
allocated to a frequency channel across the
spectrum.
When transmitted, the data is combined with a
higher data-rate bit sequence (also known as a
chipping code) that divides the data according to
a spreading ratio.
22
The transmitter and the receiver must be
synchronized with the same spreading code.
The chipping code helps the signal resist
interference and also enables the original data
to be recovered if data bits are damaged during
transmission.
22 MHz wide
23
(No Transcript)
24
Frequency Hopping Spread Spectrum
Also known as Frequency Hopping Code Division
Multiple Access (FH-CDMA), FHSS radios transmit
"hops" between available frequencies according to
a specified algorithm which can be either random
or preplanned. The transmitter operates in
synchronization with a receiver, which remains
tuned to the same center frequency as the
transmitter.
25
FHSS an example
f5
f4
f3
f2
f1
1
2
3
4
5
6
7
8
9
10
11
12
TIME
26
Signal Propagation
As the signal leaves the antenna it propagates,
or disperses, into space. The antenna selection
will determine how much propagation will
occur. At 2.4 GHz it is extremely important to
ensure a that a path (or tunnel) between the two
antennas is clear of any obstructions. Should
the propagating signal encounter any obstructions
in the path, signal degradation will occur.
Trees, buildings, hydro poles, and towers are
common examples of path obstructions.
27
The greatest amount of loss in your wireless
system will be from Free Space Propagation. The
Free Space Loss is predictable and given by the
formula
FSL(dB) 32.45 20Log10F(MHz) 20Log10D(km)
The Free Space Loss at 1km using a 2.4 GHz system
is
FSL(dB) 32.45 20Log10(2400) 20Log10(1)
32.45 67.6 0 100.05 dB
28
Line of Sight
Attaining good Line of Sight (LOS) between the
sending and receiving antenna is essential in
both Point to Point and Point to Multipoint
installations. Generally there are two types of
LOS that are used discussed during installations

1. Optical LOS - is related to the ability to see
   one site from the other
2. Radio LOS related to the ability of the
   receiver to see the transmitted signal

29
To quantify Radio Line of Sight, the Fresnel Zone
theory is applied. Think of the Fresnel Zone as
a football shaped tunnel between the two sites
which provides a path for the RF signals. At
WaveRider acceptable Radio Line of Sight means
that at least 60 of the first Fresnel Zone plus
3 meters is clear of any obstructions.
30
Fresnel Zones
Fresnel Zones
31
The First Fresnel Zone
Radius of n th Fresnel Zone given by
32
When obstructions intrude on the first Fresnel
Zone many issues can arise which will affect the
performance of the system. The main issues are

• 1. Reflection
• incident wave propagates away from smooth
  scattering plane
• multipath fading is when secondary waves arrive
  out-of-phase with the incident wave causing
  signal degradation

33

• 2. Refraction
• incident wave propagates through scattering
  plane but at an angle
• frequencies less than 10 GHz are not affected
  by heavy rains, snow, pea-soup fog
• at 2.4 GHz, attenuation is 0.01 dB/Km for
  150mm/hr of rain

• 3. Diffraction
• incident wave passes around obstruction into
  shadow regions

34
The Path Profile
Path Profile characteristics may change over
time, due to vegetation, building construction,
etc.
Path Profile characteristics may change over
time, due to vegetation, building construction,
etc.
35
FiveNines V1.2
36
Antenna - How it Works
The antenna converts radio frequency electrical
energy fed to it (via the transmission line) to
an electromagnetic wave propagated into space.
The physical size of the radiating element is
proportional to the wavelength. The higher the
frequency, the smaller the antenna size. Assuming
that the operating frequency in both cases is the
same, the antenna will perform identically in
Transmit or Receive mode
37
The type of system you are installing will help
determine the type of antenna used. Generally
speaking, there are two types of antennae

• Directional
• - this type of antenna has a narrow beamwidth
  with the power being more directional, greater
  distances are usually achieved but area coverage
  is sacrificed
• - Yagi, Panel, Sector and Parabolic antennae
• - an EUM, NCL Station/Master will use this type
  of antenna in both Point to Point and Point to
  Multipoint

38

• Omni-Directional
• - this type of antenna has a wide beamwidth and
  radiates 3600 with the power being more spread
  out, shorter distances are achieved but greater
  coverage attained
• - Omni antenna
• - a CCU or an NCL Master will use this type of
  antenna

39
Yagi

• better suited for shorter links
• lower dBi gain usually between 7 and 15 dBi

40
Typical Radiation Pattern for a Yagi
41
Parabolic

• used in medium to long links
• gains of 18 to 28 dBi
• most common

42
Typical Radiation Pattern for a Parabolic
43
Sectoral

• directional in nature, but can be adjusted
  anywhere from 450 to 1800
• typical gains vary from 10 to 19 dBi

44
Typical Radiation Pattern for a Sector
45
Omni

• used at the CCU or Master NCL for wide coverage
• typical gains of 3 to 10 dBi

46
Typical Radiation Pattern for an Omni
47
Antenna Radiation Patterns

• Common parameters
• main lobe (boresight)
• half-power beamwidth (HPBW)
• front-back ratio (F/B)
• pattern nulls

Typically measured in two planes

• Vector electric field referred to E-field
• Vector magnetic field referred to H-field

48
Polarization

• An antennas polarization is relative to the
  E-field of antenna.
• If the E-field is horizontal, than the antenna
  is Horizontally Polarized.
• If the E-field is vertical, than the antenna is
  Vertically Polarized.

No matter what polarity you choose, all antennas
in the same RF network must be polarized
identically regardless of the antenna type.
49

• Polarization may deliberately be used to
• Increase isolation from unwanted signal sources
  (Cross Polarization Discrimination (x-pol)
  typically 25 dB)
• Reduce interference
• Help define a specific coverage area

Horizontal Vertical
50
Antenna Impedance
A proper Impedance Match is essential for maximum
power transfer. The antenna must also function
as a matching load for the Transmitter ( 50
ohms). Voltage Standing Wave Ratio (VSWR), is an
indicator of how well an antenna matches the
transmission line that feeds it. It is the
ratio of the forward voltage to the reflected
voltage. The better the match, the Lower the
VSWR. A value of 1.51 over the frequency band
of interest is a practical maximum limit.
51
Return Loss is related to VSWR, and is a measure
of the signal power reflected by the antenna
relative to the forward power delivered to the
antenna. The higher the value (usually
expressed in dB), the better. A figure of 13.9dB
is equivalent to a VSWR of 1.51. A Return Loss
of 20dB is considered quite good, and is
equivalent to a VSWR of 1.21.
52
(No Transcript)
53
(No Transcript)
54
Environmental Effects
Ice and wind loading, Salt spray Radomes used to
improve performance in icy, windy conditions
(more common with larger solid parabolic dishes).
Wind loading can be reduced substantially by
using a radome. Wind loading can produce
vibration, which in turn can produce azimuth
errors. For longer paths, this can be
critical. Installation - pay close attention to
proper sealing of all connector junctions.
55
(No Transcript)
56
(No Transcript)
57
(No Transcript)
58
(No Transcript)
59
(No Transcript)
60
(No Transcript)
61
(No Transcript)
62
The Transmission Line
The type of cable selected depends mostly on the
length of that cable required. Generally, the
longer the cable run the better the cable must be
in terms of attenuation. Attenuation refers to
the degradation of the signal as it travels
through the cable. This is usually stated as a
loss in dB per 100 feet.
63
Attenuation Table
64
Transmission Line Selection
Physical Characteristics Bend radius Diameter -
transition considerations (interface jumper
cable use) Environmental considerations Plenum
installation (fire retardant) Special
weather-resistant types UV resistance very
important in tropics
65
Line Loss or Attenuation paramount refer to
your Link Budget Calculations to determine how
much loss is acceptable and still have a viable
link. Foam dielectric, Air Dielectric,
Pressurized types of Coaxial Cable. Waveguide
use also possible but typically not cost-effective
66
Connectors
Your connector selection will be determined based
on the following

• connector gender at antenna
• type of cable being used
• use of lightning protection
• gender of jumpers being used

67
For the most part the cabling manufacturers also
manufacture the connectors that go on the cables.
Knock off connectors are available, but dont
always fit the cable the way the manufacturers
connectors do. Generally the only decision that
needs to be made is what gender of connector to
installMale or Female
Antennas usually Female Lightning Arrestors
usually Female
68
Connectors
N-male
RP-SMA- male
N-female
RP-SMA-female
69
The Lightning Arrestor

• To avoid the potential for damage during a
  lightning strike, the use of lightning is highly
  recommended.
• For maximum protection, ground must be connected
  close to point of entry into building - within
  2ft.
• Typically structural steel OK for ground
  connection

Do not use Gas Lines or Water pipes. Check
Electrical Code for grounding restrictions.
70
Network Feasibility Assessment
Through WaveRiders Professional Services Group
(PSG), a Network Feasibility Assessment can be
done to establish the viability of a proposed
wireless network with either the NCL or LMS
products.

• System and Program Planning
• Implementation Management
• Application engineering
• Network engineering
• Backhaul Design

71

• - Electrical Inspection
• Certified electrician, equipment grounding
• Primary Power Sources
• Site Lease / Costs
• Antenna
• Floor space

72
Link Budget Calculations
To establish the viability of a link prior to
installing any equipment, a Link Budget
Calculation needs to be made. Performing this
calculation will give you an idea as to how much
room for path loss you have, and give you an idea
as to link quality. Using the WaveRider Link Path
Analysis Tool (LPA Tool), the Fade Margin and
other link criteria can be mathematically
calculated to determine link quality.
73

• Fade Margin
• Defined as the difference between the Receive
  Signal Level RSL, and the Rx Threshold or other
  chosen reference Level.
• For path lengths of 16km or less, a minimum 10dB
  Fade Margin is recommended

Ie. If you have an RSL of 60dB and a Rx
Threshold of 72dB, than your fade Margin would
be 12dB
74
(No Transcript)
75
(No Transcript)
76
(No Transcript)
77
Interference Countermeasures

• 1. Short Paths
• 2. Narrow Beam Antennas (high gain)
• 3. Frequency Selection
• 4. Antenna Polarization
• 5. Antenna Azimuth
• 6. Equipment/Antenna Location