Redline Communications AN50 Access Node User Manual AN 50 v19

Redline Communications Inc. Access Node AN 50 v19

Contents

users manual 2

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Wireless Configuration:
Channel: specifies the operating channel of the system, within the 100
MHz available in the 5.8GHz UNII band. The table below specifies the
center frequencies of each permitted channel.
Channel Frequency
1 5735 MHz
1A 5745 MHz
2 5755 MHz
2A 5765 MHz
3 5775 MHz
3A 5785 MHz
4 5795 MHz
4A 5805 MHz
5 5815 MHz
To avoid interference, two PTP links operating in the same physical
location (co-located) or within close proximity (e.g. across the street) must
be separated by at least one channel, i.e. the gap between channels should
be 20 MHz or more (e.g. channels 1 and 3). Refer to Section 8.5 for
further information regarding deployment rules.
Tx Power: this parameter specifies the power level of the system, which is
preset at the factory and should not be altered. In the event that this
parameter needs to be changed, please contact the Redline support team at
support@redlinecommunications.com.
Adaptive rate: checking this box sets the system to operate in adaptive
modulation mode. It is recommended to keep the AN-50 in this mode so
that the system can automatically adjust the modulation level to the
highest possible data rate based on measured RF performance. The user
can define the minimum desired modulation level by setting the Main rate
parameter (see next item). If the system meets this data rate, then the
“Signal” LED on the front panel will light continuously green. If packet
errors exceed one out of a million, then the system will automatically
lower the modulation level to maintain the link. In this case, the LED will
flash green. If errors continue when the system reaches the lowest
modulation level, then the LED will flash red to indicate a failed RF link.
The user can also disable the dynamic modulation mode by unchecking
the Adaptive rate box. In this mode, the user is required to set the Main
rate and the Rate diff (see below). Refer to Table 1 to determine which
modulation level can be used based on the measured signal to noise ratio.
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It is recommended not to operate the system in manual mode, as this mode
is intended primarily for field support.
Note the “Signal” LED will light solid green when the packet error rate is
less than 1 out of a million. When the errors exceed this limit, the LED
will not illuminate, indicating the RF link has failed.
Main rate [Mb/s]: Defines the desired net data rate for the link.
Rate dif.: applies when the Adaptive rate is disabled. Rate dif specifies
how many levels the system must drop in modulation before beginning re-
transmission to address packet errors. The Rate diff value can be set from
1-7, with 2 being the typical value.
Master: Sets the AN-50 system to serve as the Master system, while the
other AN-50 assumes a slave role.
Version: Specifies the current version of the system software. Note,
software can be remotely downloaded into the AN-50. The system
comprises sufficient memory to hold two independent software loads – the
operator can specify which load to download into the system.
Peak Transmitted Power per channel and modulation
The maximum conducted power is limited by the software / firmware to limit the
maximum power for each channel. According to the rating showed in the
following table based on direct measurements the maximum power for each
channel isn’t user modifiable:
PEAK TRANSMIT POWER
(Measured a Peak Power Meter)
(dBm)
Transmitted
Channel Frequency
(MHz) 64QAM
(54 Mb/s) 16QAM
(36 Mb/s) QPSK
(18 Mb/s) BPSK
(9 Mb/s)
1 5.735 -7.4 -7.4 -7.4 -7.4
1A 5.745 16.6 16.6 16.6 16.6
2 5.755 17.3 17.3 17.3 17.3
2A 5.765 20.0 20.0 20.0 20.0
3 5.775 20.5 20.5 20.5 20.5
3A 5.785 20.0 20.0 20.0 20.0
4 5.795 17.3 17.3 17.3 17.3
4A 5.805 16.6 16.6 16.6 16.6
5 5.815 -7.4 -7.4 -7.4 -7.4
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6.4. Upgrade
The upgrade screen, shown in Figure 16, is used to upgrade the existing software
load of the AN-50 unit with new software stored in a binary file on the server or
host computer. The system uses the Trivial File Transfer Protocol (TFTP) to
execute the process. Two input fields have to be filled in by the operator: TFTP
Server IP Address and File name. The TFTP Server IP Address is the IP address
of the host computer or server that contains the upgraded software in binary
format, while File name is the name of the actual binary file.
Figure 16 Upgrade screen.
After typing the TFTP Server IP Address and File name, press Upload to begin
the file transfer. A status screen (see Figure 17) will immediately follow, which
displays, in real-time, the number of bytes being transferred from the host
computer/server to the AN-50 unit. The upgrade file size is approximately 1
Megabyte, and can take approximately 1-2 minutes to download from the server
to the AN-50 memory.
Note the AN-50 contains two memory pages for storing the software/firmware
binary code images. One memory location holds the current software, while the
second memory area is used to store the new software load. Upon successful
transfer of the upgrade file, the AN-50 will verify the integrity of the new
software load before transitioning its system to the new binary image. If errors
were introduced during the transfer process, as a result of say link degradation,
then the AN-50 will reject the new software load, and provide a warning that the
upgrade was unsuccessful. In this case, the operator will need to repeat the
upgrade process. As mentioned previously, the upgrade process can be achieved
remotely, using HTTP over the Internet.
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Figure 17 Status of upgrade file transfer.
6.5. Change Password
The default password for the system, set from the factory, is ‘admin’. To change
the password, click on Change password from the main menu and apply a new
value in the Password field (see Figure 18) using any alphanumeric combination.
Note the field is case sensitive and should be up to 16 characters length.
A Long Reset – depressing the ‘reset’ button for more that five (5) seconds - will
restore the password to admin’.
Figure 18 Change Password Screen.
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6.6. Log File
The Log File screen, shown in Figure 19, provides a display of the last ten (10)
messages recorded by the AN-50 describing either system activity or errors that
have occurred.
Figure 19 Log File Screen.
The Log File will also indicate if the following transactions were successfully
completed:
• Save Configuration – Under the ‘Configuration’ screen.
• Upload – Under the ‘Upgrade’ screen.
• Change Password – Under the ‘Change Password’ screen.
The following provides a brief description of the key messages recorded onto the
Log File by the system:
Log File Message Description
100-Parameters loaded successfully! All system parameters have been successfully
downloaded.
101-Firmware configuration OK! The onboard firmware configuration have been
properly setup
102-Ethernet switch configured! The Ethernet port has been properly configured
and is operational.
103-Parameters saved successfully! The latest configuration parameters have been
successfully saved into the system memory.
104-Upgrade OK! The software upgrade process completed
successfully
105-Password change successful!
The new password entered in the system was
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successfully changed.
201-EEPROM corrupted. Def.
param. loaded! The memory area containing the system
configuration has been corrupted. Default
parameters loaded.
202-Error while saving parameters! The latest configuration parameters have not
been successfully saved. In this case, repeat the
save configuration process to try to resolve the
problem.
203-Another upgrade in progress! The system is already in the upgrade mode, in
the event the operator inadvertently invoked
multiple simultaneous upgrades.
204-Invalid upgrade parameters! The parameter entered is in error. If this
message appears, check for typing errors.
205-Upgrade failed! The software upgrade process completed
unsuccessfully.
206-Password change unsuccessful! The new password entered into the system was
not successful. In this case, repeat the process.
207-Timeout on reading data packet! The system has time-out looking for packets
from the host computer or server. Check for
obvious problems such as disconnected or faulty
cable.
209-TFTP error received! The Trivial File Transfer Protocol (TFTP)
routine used to download the software to the
AN-50 during the Upgrade process failed.
Likely cause is disconnected or faulty cable.
210-Error: TFTP unknown message! The TFTP client received an unknown message.
In this case, repeat the upgrade process.
211-Error: while writing flash!
While writing the parameters into AN-50 flash
memory an unexpected error occur. Try to
repeat the process and if the error persist contact
Red Line Communications support team.
212-Error firmware configuration! While writing the firmware into AN-50 system
memory an unexpected error occur. Try to
repeat the process and if the error persist contact
Red Line Communications support team.
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7. Diagnostics and Troubleshooting
This section provides basic diagnostic and troubleshooting steps to help you solve
problems that may have occurred with the AN-50. If, after reading this section,
you are unable to get the system operating properly, please contact the support
team at Redline at support@redlinecommunications.com. Include the model name
and serial number of the system (located at the bottom of the unit) in your
communication with Redline.
Troubleshooting can be performed using the front panel LEDs and the host
computer/server connected locally or remotely to the AN-50.
7.1. Diagnostics via the front panel
The front panel of the AN-50 comprises key status LEDs, grouped under the
headings System, Wireless and Ethernet, to help with first level diagnoses of
problems encountered with the unit.
Figure 20 Front panel status LEDs.
Throughout this section, reference is made to the ‘Reset’
button, which is a micro-switch recessed in the front panel
in the System block. Use a small narrow object, such as a
paper clip, to depress the button. Depressing the button for
less than five (5) seconds is known as a ‘quick reset’, and is
equivalent to turning on and off the unit. A quick reset essentially reloads the
current configuration software into the system’s processor from the flash memory
(long term memory) and restarts the unit.
Depressing the ‘reset’ button for more than five (5) seconds executes what is
known as a ‘long reset’. A long reset reloads the previously saved operating
software load (which may be the manufacturer’s original software load) and
restarts the system. Note, the software version that existed in the system before
the long reset will have to be reloaded, either locally or remotely. An example of
where a reset will help, is in the event that your password or IP address if
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forgotten. The reset function will simply restore the system back to its original
settings.
The remainder of this section lists possible problems that may occur and the
corresponding remedies.
7.1.1. System Power
Check to see if the Pwr LED is solid and green. If no, then
power is not getting to the unit. The most probable causes
are:
Table 1 System Power Diagnostics.
Symptom Possible Problem Solution
On/Off switch in Off position Turn on switch.
Fuse blown Replace fuse.
No power
(Pwr LED does
not illuminate) Power cord disconnected Securely connect cord to terminal
and outlet.
7.1.2. System Fault
If the Fault LED illuminates solid red, then it is an
indication that there is a serious problem with the system
software or hardware. A long reset may remedy the
problem. If not, then contact the Redline support team.
7.1.3. Wireless Link
The Wireless Link LED illuminates solid green when the system is
properly communicating with the remote terminal. The LED will
flash green when the system is operating below the desired
modulation level, but at low packet errors (i.e. less than 1 packet
lossed out of 1 million packets). When the LED does not
illuminate, it is an indication that there is a problem either in the terminal, radio,
host computers/servers, or with the actual propagation path itself. The table below
lists some of the potential problems:
Table 2 Wireless Link Diagnostics.
Symptom Possible Problem Solution
Remote terminal is not on or is
mal-functioning. Verify operation of remote
terminal.
No wireless link
(Link LED does
not illuminate) The propagation path is
blocked. Clear path or re-locate antennas
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Symptom Possible Problem Solution
The transceiver is mal-
functioning. Repair or replace transceiver.
Antenna has moved and is no
longer boresight with remote
terminal.
Re-align antenna
Cable between transceiver and
antenna or between transceiver
and terminal not properly
connected.
Properly secure cables.
Power not getting to the
transceiver from the terminal. Repair or replace terminal.
7.1.4. Wireless Signal
The Wireless Signal will flash in amber when RF signals (frames)
are not being properly received by the transceiver. This may not be
a serious problem if the LED only flashes intermittently, however,
if it flashes constantly, then the table below summarizes some of
the problems that may be occurring.
Table 3 Wireless Signal Diagnostics.
Symptom Possible Problem Solution
Obstructions in the propagation
path causing signal
degradation.
Try to remove obstacles or re-
locate antenna.
Antenna moved, due to high
winds. Re-align antenna.
Poor RF Link
(Signal LED
flashes)
Poor cable connection between
transceiver and antenna Repair or replace cable.
7.1.5. Ethernet Link
The Ethernet Link LED will illuminate green and solid
when the LAN connection to the host computer/server or
switch/router is properly functioning. If this LED is not
on, then the following possible problems may exist:
Table 4 Ethernet Link Diagnostics.
Symptom Possible Problem Solution
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Symptom Possible Problem Solution
Poor cable connection between
terminal and computer/server
or between terminal and
switch/router.
Carefully check all cable
connections.
Wrong type of Ethernet cable
between terminal LAN port
and host computer/server or
switch/router.
If the terminal LAN port is
connected to a host computer or
server directly, then ensure a
straight-through cable is used.
Otherwise, to connect the terminal
to a switch or router, ensure a
crossover cable is used.
The auxiliary Network
equipment including
switch/router, host
computer/server, may be
malfunctioning.
Repair or replace faulty units.
Poor Ehternet
Link
(Link LED off)
System processor hang-up Try quick reset or long reset.
7.1.6. Ethernet Collision
The Ethernet Col LED flashes amber when packet
collisions occur over the LAN. Note, in any shared IP
network, it is typical for packet collisions to occur
intermittently. However, if the LED flashes constantly,
then there is a serious problem somewhere in the LAN
connection. Some possible causes are:
Table 5 Ethernet Collision Diagnostics.
Symptom Possible Problem Solution
Poor Collision
Link connection.
(Col LED
flashes)
Poor cable connection between
terminal and computer/server
or between terminal and
switch/router.
Carefully check all cable
connections.
7.2. Troubleshooting via the screen menu
The section assumes that the LEDs on the front panel of the AN-50 are indicating
normal functionality, i.e. Ethernet - Link is illuminated green and solid.
7.2.1. Home page does not appear
If, after trying to log onto the AN-50 terminal(using HTTP commands) the Home
Page does not appear on the screen, then several possibilities exist. The first test
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is to ping the terminal from the host computer by typing in the following text
from the command line:
>Ping 192.168.25.2
Note the IP address used in this example is the default address supplied by the
factory. If the IP address has been changed since then, it is important to use the
current address.
If the ping test was successful (i.e. the computer was able to send and receive
packets with the terminal) then the problem may be with the text that was entered
into the HTTP navigator or with the HTTP program itself. Retype the text or re-
boot the host computer to try to resolve the problem.
If the ping was unsuccessful, then there may be problems with the IP address that
you are using. Try retyping the address. If this fails, and it appears you have
forgotten the IP address of the terminal, then perform a Long Reset to restore the
terminal to the default value.
Table 6 Home Page Diagnostics.
Symptom Possible Problem Solution
Incorrect IP address Perform a ping test from the host
computer command line.
If the ping test is unsuccessful, then
problem is with the IP address.
Perform long reset to apply default
address.
Home Page does
not appear
Problems with HTTP or host
computer. If Ping is successful, then the
problem is most likely with the
HTTP program or host computer.
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8. Fixed Wireless Access Primer
8.1. Introduction
This section provides an overview of the design and benefits of a Fixed Wireless
Access (FWA) network architecture based on the Redline AN-50 system. There
are several advantages of an FWA system over traditional wireline alternatives
such as PSTN, ISDN, T1, DSL, cable and Fiber, including:
• Greater availability
• Lower cost of ownership per link
• Higher throughput (with the exception of fiber)
• Greater distances
• Quicker time to market
• Greater portability
The Redline AN-50 can be configured as a point-to-point (PTP) or switched PTP
(S-PTP) system (Rev 0.7) to provide both backhaul and access distribution
services under one infrastructure and management system. The Revision 0.7
product will be a software upgrade to the current version, which can be
accomplished remotely.
The system functions logically as a transparent bridge, hence, providing all the
benefits of a converged IP network, i.e. ‘IP everywhere’. A converged network
allows operators to reduce network buildout costs significantly by employing
standard IP appliances everywhere, from backbone to end-user.
8.2. Who can benefit from the AN-50?
The AN-50 is an ideal solution for:
• Carriers
• Internet Service Providers (ISPs)
• Enterprises
• Education and Campuses
A) Carriers
The AN-50 will provide benefit to both Incumbent and Competitive Local
Exchange Carriers (ILECs and CLECs, respectively). Although ILECs own and
provide services over wireline infrastructures within a specific geographical area,
they are faced with challenges of reaching outlining regions suffering from poor
to no services. The ILEC is usually compelled to provide an expensive solution
using a series of PTP radio links, with low throughput (e.g. T1) and costly license
fees and network interfaces including T1 multiplexers. The AN-50 provides a cost
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effective alternative, by connecting a remote site from the local CO, as shown in
see Figure 21.
Fiber Ring
Remote
C.O./POP
Local
C.O.
10/100 BT
Extension
Figure 21 Wireless Extension for Carriers.
The same challenges are faced by the CLECs, who will use the AN-50 to quickly;
• Extend their existing fiber network, and
• Establish a remote Point of Presence (POP).
B) Internet Service Providers
The AN-50 is perfect for ISPs looking to provide cost effective broadband
solutions to demanding business customers including Small Office Home Office
(SOHO) and Small to Medium sized Enterprises (SME) located just outside of the
downtown core, where there is a lack of infrastructure. High speed leased lines
are expensive and hard to obtain, especially from local telephone companies.
Wireless access provides a reliable quality of service, over longer distances while
avoiding giving away access dollars to the Telco.
Internet ISP
SME
SOHO
SME
Figure 22 Wireless Solution for ISPs
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C) Enterprise
Enterprises are particularly frustrated by the lack of broadband connectivity to
their branch offices, factories, or warehouses located just outside of the urban
core. Establishing a LAN solution over several remote locations presents a
significant inter-network challenge using conventional wireline solutions. The
AN-50 is well suited for addressing the LAN extension requirement, offering
superior data rates quickly and efficiently, and in a secure format using Data
Encryption Standard (DES) to protect sensitive information.
Internet Head
Office
Branch
Office
Factory
10/100 BT
Figure 23. Wireless Solution for Enterprise.
D) Education and Campuses
The World Wide Web (WWW) represents a key element of the education system
today, with FWA systems serving as an important enabler in bringing Internet
content to the student body. Fixed wireless systems such as the AN-50 provide a
cost effective means of creating a backbone for connecting existing and new
campus buildings to the educational infrastructure to support distant learning, and
two way interactive training.
8.3. The UNII band advantage
Wireless systems provide an effective means of achieving broadband connectivity
quickly and over large distances. The AN-50 currently operates in the Unlicensed
National Information Infrastructure (UNII) band, which is the license exempt
(LE) portion of the spectrum. LE bands allow any operator to freely set up a
wireless network without requiring formal consent from the regulatory agent.
While this provides great advantages in terms of cost effectiveness (e.g. no license
fees) and time to market (no regulatory process to follow), the ease of access to
the spectrum opens the door for potential interference arising from other operators
attempting to exploit the ‘free’ band. The Redline product includes several key
features to mitigate the effects of interference arising from other systems
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operating co-channel in the vicinity, as well as to cope with propagation
anomalies such as multipath. These features include:
Adaptive Modulation
The AN-50 automatically selects modulation level, in both the up and
downstream direction (an Industry first), to maximize spectral efficiency based on
the measured signal to noise (S/N) level. The modulation levels supported are:
• Binary Phase Shift Keying (BPSK)
• Quadrature Phase Shift Keying (QPSK)
• 16 Qaudrature-Carrier Amplitude Modulation (QAM)
• 64 QAM
Refer to Table 7 for a summary of data rates for each modulation level.
Advanced Error Correction
In addition to conventional forward error correction techniques, the AN-50 uses
an Acknowledge/Request (ARQ) scheme to dramatically reduce errors from
interference and multipath
Orthogonal Frequency Division Multiplex (OFDM) processing
The Redline OFDM technique offers tremendous robustness in the presence of
harsh multipath interference.
Narrow Beamwidth
Narrow antenna beams reduce considerably the probability of interference
entering the system.
Adaptive Frequency Tuning
In the event the interference is too great, the system will switch over to an
alternate ‘clean’ channel.
In addition to the anti-interference features described above, the AN-50 also holds
several advantages other competitive advantages:
• High Data Rates (54)
• High Bandwidth Efficiency
• Long Reach and Wide Coverage
• Higher Power Efficiency
• ‘Over the air’ Security
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8.4. Wireless Facts
Wireless technology has been around for many years, proving to be a reliable
communication medium, primarily for long haul point to point applications,
supporting critical links across the country for telephony and broadcast services.
With the recent surge of two-way Internet use and the corresponding need for
tremendous broadband to end users, fixed wireless systems are playing an even
more important role in supporting network infrastructures.
The AN-50 has been designed to operate in the UNII band, which occupies the
license exempt portion of the spectrum. License exempt allows any operator to
freely set up a wireless network without requiring formal consent from the
regulatory agent. While this provides great advantages in terms of cost and time to
market, the ease of access to the spectrum can produce undesirable effects, such
as potential interference arising from other users exploiting the ‘free’ band. By
following some simple deployment guidelines, issues of this nature can be
avoided. Note there exist professional engineering firms that specialize in
deploying fixed wireless access systems, if you do not wish to do it alone.
The following provides a checklist of steps to be taken in deploying your AN-50
link:
• Conduct Site Survey
• Install the antenna
• Run the IF cable
• Install the terminal.
Refer to section 5, page 12, for a description of each deployment step listed
above. This section provides additional background material to Section 5, to
include a description of the Link Budget tool, Fresnel zone considerations, height
calculations and radar horizon issues, interference issues with other systems, etc.
8.4.1. Link Budget
Redline has developed a link budget to help characterize the range performance of
the AN-50 for both LOS and NLOS conditions using different system parameters.
This link budget can be obtained by contacting us at
sales@redlinecommunications.com. Note the tool provides a first order
approximation, and does not consider the details of any specific terrain profile,
which may impact performance. Rather, a generalized terrain is used in the
calculations, based on empirical formulas approved by governing bodies such as
the IEEE and ITU. The tool also assumes the terminal heights are 100 ft and 15 ft
above the mean terrain level. Higher installs will improve the link performance,
while lower heights on either end will reduce range performance.
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The link budget tool estimates the distance over which the system can operate for
a desired error rate to achieve robust communication. A link is considered robust
if the average error rate is less than 1 bit out of every 1000 million bits, expressed
as 10-9, for an availability of 99.99%. Availability is described in more detail
below.
The table below describes the net data rate (after coding overhead) that can be
obtained for each modulation type in an ideal propagation situation.
Table 7 Modulation and Data Rate Table.
Modulation
Level S/Nmin
(dB) Coding
Rate Symbol
Rate
(Mbps)
Raw Data
Rate
(Mbps)
Net Data
Rate
(Mbps)
BPSK 7 ½ 3 8 6
BPSK 8 ¾ 4.5 12 9
QPSK 11 ½ 6 16 12
QPSK 13 ¾ 9 24 18
16 QAM 16 ½ 12 32 24
16 QAM 20 ¾ 18 48 36
64 QAM 23 ? 24 64 48
64 QAM 25 ¾ 27 72 54
As given in the table, higher order modulation levels require greater S/N to
maintain the same BER performance. The noise in this case is defined as the noise
floor of the receiver, i.e. it assumes no interference from other sources
(interference from other sources are addressed below). The main path calculation
for determining range performance is given as:
RSL = Ptx + Gtx – FSL + Grx
Where:
Ptx is the transmit power level in dBm
Gtx is the transmit antenna gain in dB
FSL is the free space loss attenuation in dB, and
Grx is the receive antenna gain in dB
The FSL value is dependent on the range between the two terminals, the type of
terrain over which the link is deployed, and whether or not the link is operating
line of sight (LOS) or non-LOS (NLOS). The LOS FSL calculation is well
understood and easy to calculate, and relies on the fact that there is absolutely no
obstacle near the direct path. The precise method for determining the amount of
clearance required in claiming LOS is to make use of a factor called the Fresnel
zone. A Fresnel zone is defined as the path difference of ?/2 away from the direct
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path, as shown in Figure 24. A ‘cleared LOS’ link assumes there are no obstacles
within 60% of the first Fresnel zone of the direct path.
First
Fresnel
Zone
Obstruction within
first Fresnel Zone
Figure 24 Fresnel Zone obstruction.
The formula for calculating the radius of the first Fresnel zone, as depicted in
Figure 25, is given as:
)21(*
2*1
1.72 DDf
DD
R+
= (ft)
where,
- D1 and D2 are the distances from the terminals to the point of interest (in
miles), and
- F is the frequency (in GHz)
D1
D2
Fresnel Zone Radius
R
Figure 25 Fresnel zone radius calculation.
Specific FSL formulas are required to deal with this NLOS phenomenon. There
are many NLOS calculations available from established institutions including the
Institute of Electrical and Electronics Engineers (IEEE) and International
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Telecommunications Union (ITU), who are chartered with developing
standardized calculations. The Redline link budget tool is built upon these
formulas, however, it is important to bear in mind that the calculations are an
estimate only, with relatively large standard deviations (5-15 dB) depending on
the exact deployment scenario and obstacle characteristics.
The last element to consider in the path calculation is the signal to noise (S/N)
ratio, which is defined as:
S/N = RSL – Smin
where,
Smin is the receiver sensitivity expressed in dBm.
The Smin is determined by the thermal noise generated by the amplifier as well as
the bandwidth of the filter used in the receiver front-end. It defines the power
level at which the receiver is sensitive enough to properly detect the signal. For
the AN-50 operating in a channel spacing of 20 MHz, the Smin is approximately
–96 dBm. Therefore, to operate the link at the specified BER, the received signal
must exceed Smin by the S/Nmin specified for each modulation level in Table 7.
To ensure the link is sufficiently robust to deal with unexpected attenuation
effects and seasonal fades, the S/N must be set higher than the S/Nmin specified in
Table 7. The difference between these two levels is called the Fade Margin
(FM). FM is similar to a ‘power reserve’ in which extra power is designed into
the link budget to deal with additional fades arising from such factors as climatic
conditions (seasonal), multipath dispersions, and shadowing effects from natural
(foliage) and man-made obstacles (buildings). The FM is determined by the
availability one desires. Availability is defined as the amount of time (expressed
in % per year) that a link properly detects the signal. “Properly” in this case is a
BER that is less than 10-9. The table below describes the outage period per year
that corresponds to the different availability values.
Table 8 Availability versus outage time.
Availability (%) Outage Period per year
99.9 8.8 hours
99.99 53 minutes
99.999 5.3 minutes
99.9999 32 seconds
The link should be designed for an availability greater than 99.99%. Based on this
value, the FM for different ranges is given below:
Table 9 Fade margin versus distance for 99.99% availability
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Distance (km) Fade Margin (dB)
10 5
20 14
30 18
40 23
50 25
The table assumes an average terrain with some roughness and normal inland
temperature climate (i.e. non-coastal and non-artic).
A key advantage of the Redline product is that it features a transmission
correction scheme called Acknowledge/ReQuest (ARQ). The ARQ algorithm
essentially detects when a packet(s) has been lost, due to fading, and makes a
request to the remote system to re-transmit the lost packet(s). This feature
provides an equivalent link budget gain of over 5 dB, which translates directly to
an improved margin.
Another key advantage of the Redline product is that it features dynamic adaptive
modulation, i.e., the system adjusts the modulation level automatically, on a burst-
by-burst basis, based on the measured S/N response. In this manner, the network
is constantly balanced for the optimum spectral efficiency, no matter what
propagation conditions prevail. Higher modulation levels (e.g. 64 QAM) are
typically deployed at reduced ranges while lower modulation levels (e.g. BPSK)
are implemented at far ranges.
A sample link budget is shown in Figure 26 for the AN-50 operating in 16 QAM,
3/4 code rating, providing a net data rate of 36 Megabits per second (Mbps). The
tool calculation is performed for LOS, however the graphs below cover the NLOS
conditions as well.
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Redline Link Budget
Transmitter Down Up
Frequency 5.8 5.8 GHz
Average Power Into Antenna 19 19 dBm
Tx Ant Gain (Dn/Up) 27 27 dBi
EIRP 46 46 dBm
Range 25.0 25.0 km
Path loss 135.63 135.63 dB
Signal Profile
Channel BW 20.00 20.00 MHz
Modulation/Coding Rate 3ee
Alpha Factor 0.75 0.75
Guard Interval 0.80 0.80
Net Data Throughput 36.00 36.00 Mb/s
Total Spectral Efficiency 1.80 1.80 bits/s/Hz
Receiver
Receiver Antenna Gain 27.00 27.00 dB
Rx Signal Level -62.63 -62.63 dBm
RX Noise Figure 5.00 5.00 dB
Rx Implementation Loss 0.50 0.50 dB
RX Noise level -96.74 -96.74 dBm
Req'd min SNR 20.00 20.00 dB
Fade Margin at 25 Km 14.11 14.11 dB
28 Note: Graphs are based on upstream link.
Line of Sight (LOS)
16 QAM 3/4
Rls 1
5.8
4.5 deg pencil beam
4.5 deg pencil beam
20
Point to Point
Max Power
Propagation
Figure 26 Link Budget for 16 QAM ¾ code rate, 36 Mbps
The fade margin graph for this link budget is given in Figure 27 for three
conditions, LOS (top blue line), NLOS with outdoor antenna (middle red line),
and NLOS for indoor antenna (bottom green line). The middle scenario, NLOS
outdoor install, assumes the Fresnel zone is completely obstructed, with near
optical LOS or partially obstructed LOS resulting from limited tree blockages.
290.977
290.977
Range
Scale
35 Km
Fade Margin vs Distance for 16 QAM Rate 3/4, 36.0 Mb/s
-30
-20
-10
0
10
20
30
40
50
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
Range (km)
Fade Margin (dB)
Show Fade
Figure 27 Fade margin graphs for LOS and NLOS.
The LOS profile in the graph shows that a range of ~25 Km can be obtained with
a fade margin of 15 dB. With ARQ, the range can be extended to ~35 km for the
same BER performance and availability.
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The graph assumes a fade margin of 15 dB, as discussed earlier. The effects of
rain at UNII bands are negligible, hence are not included in the link budget.
It is important to note the link calculation assumes that the Earth’s curvature is not
blocking the propagation path. The equation for determining the distance at which
the Earth will cause blockage is called the Radar Horizon, and is given as follows:
Rh=)(1.421 hh + (Km)
where, h1 is the height of terminal 1 (m)
h2 is the height of terminal 2 (m)
The table below specifies the horizon distance (Km) that can be achieved for
different terminal heights ranging from 10 to 70 m above mean terrain level.
Table 10 Radar horizon ranges for different terminal heights (H1 and H2).
H2
10 20 30 40 50 60 70
10
25.9 31.3 35.4 38.9 42.0 44.7 47.3
20
31.3 36.7 40.8 44.3 47.3 50.1 52.6
30
35.4 40.8 44.9 48.4 51.4 54.2 56.8
40
38.9 44.3 48.4 51.9 54.9 57.7 60.2
50
42.0 47.3 51.4 54.9 58.0 60.7 63.3
60
44.7 50.1 54.2 57.7 60.7 63.5 66.1
H1
70
47.3 52.6 56.8 60.2 63.3 66.1 68.6
8.5. Deployment Scenarios
This section examines two types of deployment scenarios: co-located (same roof
top) and adjacent area.
The current version of the AN-50 is a high-speed point-to-point (PTP) system,
supporting a single link (two terminals communicating with each other only). A
subsequent software release of the AN-50 will upgrade the system to a Switched-
PTP (S-PTP) system. This upgrade will be achieved remotely (i.e. through the
internet using the HTTP command set). Hence, it is prudent to design your access
network with the knowledge that the system will be upgradeable to a S-PTP unit,
to support multiple links from a single node, as shown in Figure 29.
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T1
T
2
T
3
Figure 29 Switched PTP configuration.
8.5.1. Co-located deployments.
It is possible to deploy more than one AN-50 from the same roof-top to support
multiple links, however, it is important to consider issues that may arise from co-
channel and adjacent channel interference.
Co-channel interference results when two systems operate simultaneously in the
same channel. This must be avoided by programming different channels from the
AN-50 Configuration screen. Adjacent channels are acceptable, however, it is
important that the adjacent channel does not exceed the acceptable channel to
interference (C/I) ratio for the system, as shown in Figure 30 (C is the desired
channel, while I is the interferer).
Frequency (Mhz)
P
o
w
e
r
(
d
B
)
Figure 30 Adjacent channel interference.
8.5.2. Adjacent area deployments.
It is important during the installation process to ensure there is no potential for
interference from other systems deployed in adjacent areas. Figure 31 presents a
simple deployment configuration to illustrate the potential interference that may
arise from adjacent area sources (Users 1-4 in the figure). The desired
communication link is between Terminals 1 and 2. The link between Users 1 and
2 must operate in an adjacent channel to avoid interference with the desired link.
Users 3 and 4, on the other hand, can operate co-channel, since they are outside
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the narrow beamwidth of both terminals. Narrow beamwidths are one feature of
the AN-50 to help address potential interference.
Terminal
1
Terminal
2
User 4
User 3
User 1
User 2
Adjacent
Channel
Co-Channel
Figure 31 Deployment Scenarios.
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GLOSSARY OF TERMS
A/D Analog to Digital
AC Alternating Current
AN-50 Access Node 50
ARQ Acknowledge Request
BER Bit Error Rate
Bin Binary
BPSK Binary Phase Shift Keying
Col Collision
DB Decibels
DBm Decibels above a milliwatt
DHCP Dynamic Host Configuration Protocol
FD Dull Duplex
FWA Fixed Wireless Access
GHz GigaHertz
GHz Gigahertz
GUI Graphical User Interface
HTTP Hyper Text Transfer Protocol
IF Intermediate Frequency
IP Internet Protocol
KB Kilobyte
LAN Local Area Network
LED Light Emitting Diode
LOS Line of Sight
MAC Medium Access Control
MB Megabyte
MHz MegaHertz
MHz Megahertz
NLOS Non LOS
OFDM Orthogonal Frequency Division Multiplex
PHY Physical
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PTP Point to Point
QAM Quadrature-Carrier Amplitude Modulation
QPSK Quadrature Phase Shift Keying
RF Radio Frequency
Rx Receiver
S/N Signal to Noise ratio
S-PTP Switched Point to Point
TFTP Trivial File Transfer Protocol
Tx Transmitter
UNII Unlicensed National Information Infrastructure
VAC Voltage AC
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9. AN-50 Specifications
AN-5 System Characteristics
System Capability Non Line of Sight operations
PTP and Switched PTP configurations (Rls 0.7)
Services Supported High speed IP data
RF Band 5.8 GHz (UNII)
Channel Size 20 MHz
RF dynamic range > 50 dB
Data Rate (Mbps) in 20 MHz channel Up to 54 Mbps
Network Attributes • DHCP client/server/passthrough
• VLAN
Modulation Adaptive modulation automatically selects:
• BPSK • QPSK • 16 QAM • 64 QAM
Coding rates ½, ¾, and ?
QoS • Peak information rate (PIR) (Rls 2)
• Committed information rate (CIR) (Rls 2)
MAC • Point to multipoint
• Dynamic bandwidth allocation (Best Effort), and QoS
• Polling based scheduler
• Acknowledge/Request (ARQ) error correction
• Concatenation
• Fragmentation
Range Up to 50 Km, dependent on deployment conditions.
Total number of remote terminals node >32 active users
Network Services Supported High speed data, IP Layer 3 services
Duplex Technique Time division duplex
OFDM carrier profile 64 point FFT
Backhaul Connection 100 BT Ethernet
Physical Configuration • Terminal, radio, and antenna
• 3rd party hub/switch
Configuration & Management • DHCP client/server/passthrough
• SNMP relay agent

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