HFCL Unlicensed Band Radio Instructions
- May 15, 2024
- HFCL
Table of Contents
White Paper
Best Practices for UBR Installation in
Urban Areas to Mitigate RF Interference
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Optimal Strategies for UBR Installation
The Unlicensed Band Radio (UBR) operates in the 2.5GHz and 5/6GHz frequency
bands, which are license-free in most countries and commonly used in Wi-Fi
networks. Currently, the 5GHz UBR is employed for providing wireless leased
lines with dedicated capacity to enterprise customers in a point-to-multipoint
(P2MP) configuration. Additionally, it is utilized for backhauling small cell
Base Transceiver Stations (BTS) in point-to-point (P2P) mode within mobile
networks.
The license-free status of the 5GHz frequency band makes it the preferred
choice for telecom operators, particularly for small cell BTS backhauling.
UBRs are priced significantly lower than traditional licensed-band microwave
radios, resulting in substantial cost savings for telecom operators,
encompassing equipment costs, operation and maintenance (O&M) expenses, and
recurring licensing fees.
Due to the increased deployment of UBRs in Telco networks, interference issues
are on the rise. Careful planning and installation of UBRs in the field are
essential to mitigate interference impact and enhance overall network
performance. As collated based on field experience, below points should be
considered while planning and installing UBRs in the field so that optimum
performance is achieved and interference impact is reduced.
Link Budget & Planning
Plan the Transmit Power carefully to achieve a Received Signal Level (RSL)
around -46dBm for MCS-9 and -40dBm for MCS-11 UBR. This ensures a link fade
margin of at least 15dB.
Avoid using maximum transmit power to prevent interference with other links
and to maintain network performance.
In urban areas, limit UBR deployment plans to a hop distance of a maximum of 5
km. Optimal UBR performance, in terms of throughput and stability, is observed
for links with a hop distance equal to or less than 3 km.
In Rural, the hop distance can be extended to 12 km to 15 km because the
deployment of UBRs are very less compared with urban. Therefore, the RF
environment in rural areas is much cleaner than in urban areas.
Plan two or more links from the same site only if the azimuth difference
between two adjacent links is more than 60º.
Restrict maximum four links from a single site.
Antenna Installation
Install the antenna at the lowest height necessary to maintain a clear Line of
Sight (LOS). Avoid placing the UBR antenna at the tower’s top, as this
location is more susceptible to interference.
Position the UBR antenna at least 2 m away, both horizontally and vertically,
from the BTS/RRU. This separation helps eliminate the impact of high-power
radiation from the RRU on the UBR. UBRs are equipped with wide-band filters and
amplifiers, which may not sufficiently suppress high-power RF signals radiated
from nearby BTS/RRU installations, potentially causing interference and impact
on UBR performance.
UBR Antenna Installation on the Rooftop of a Building
Scenario 1
Edge Installation
Installation on the edge of the building using a 2 ft pole, as depicted in
the diagram below. This type of setup is not recommended as it exposes the
antenna to receive undesired and interfering signals.
When installing
the UBR antenna on the rooftop of a building, consider the following scenarios
to optimize performance by mitigating interference from surrounding signals.
Scenario 2
Near-Edge Roof Installation
Install the antenna on the roof approximately 3 ft away from the building’s edge, as illustrated in the diagram. The building’s edge/wall serves as a barrier, blocking interfering signals and improving performance in highly interfered environments. This is the preferred and recommended installation.
Scenario 3
Backside Roof Installation
Install the UBR antenna on the back side of the roof with the roof area in front of the antenna left exposed. The exposed roof in front acts as an effective obstruction against interfering signals from various directions. Refer to the diagram below for this scenario. Maintain a height of approximately 2 m or 7 ft from the roof to ensure that any human activity on the roof does not obstruct the Line of Sight (LOS) for the link. This installation is highly recommended when feasible.
Antenna Alignment Procedure for Optimal RSL Achievement
Performing antenna alignment is crucial to achieving the Received Signal Level (RSL) specified in the link budget. Acceptable RSL variation falls within the range of +/- 2dB. If the planned RSL is not attained, it has been observed that the antenna may be locked in the side lobe. To come out from such a situation, it is advised to do antenna alignment following below steps:
Horizontal Alignment (Azimuth)
a| Vertical Alignment (Tilt)
b| Horizontal Realignment
c| Vertical Realignment
d| Iterative Alignment
e
---|---|---|---|---
Slowly align the antenna from left to right and then from right to left.
Tighten the alignment at the point where the maximum RSL is achieved.| Align
the antenna from top to bottom and then from bottom to top, adjusting it
slowly.
Lock the alignment at the point where the maximum RSL is reached.| Repeat the
alignment process slowly in the horizontal direction, moving left and right
from the previously achieved
point in step (a).
Lock the alignment at hemaximum RSL point.| Move the antenna in the vertical
direction, both up
and down, from the last
achieved point in step (b).
Lock the alignment at the
point where the maximum
RSL is obtained.| Repeat steps (c) and (d) until the planned RSL is
consistently achieved.
Adhering to these alignment steps systematically ensures that the antenna is precisely positioned to meet the desired RSL, contributing to optimal performance in the link configuration.
Optimal Channel Selection
Following antenna alignment, conduct a spectrum scan and choose the channel
with the least interference at the specific site. Configure the UBR to operate
on the selected optimal frequency channel.
Dynamic Channel Selection (DCS) for Interference-Prone Sites
For sites with high interference susceptibility, consider enabling the
Dynamic Channel Selection (DCS) feature in the UBR to enhance channel
adaptability and mitigate interference.
Routine Radio Health Check
Perform regular day-to-day health checks on the radio, monitoring critical
Key Performance Indicators (KPIs) such as Received Signal Level (RSL),
throughput, and latency to ensure ongoing operational integrity.
Summary
The strategic deployment of Unlicensed Band Radios (UBRs) in urban areas
offers a compelling solution for wireless communication, balancing cost-
efficiency and operational excellence. The detailed considerations provided,
encompassing frequency planning, antenna installation, alignment procedures,
and interference mitigation, establish a robust framework for telecom
operators aiming to enhance UBR performance while navigating the challenges of
urban environments. By diligently implementing these practices, operators can
optimize wireless networks, ensuring resilience against RF interference and
fostering a reliable communication infrastructure for the evolving demands of
urban connectivity.
Author: Rakesh Kumar (Senior Vice President)
Disclaimer
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may be reproduced in any form or by any means or used to make any derivative
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permission from HFCL Limited (“HFCL”). HFCL reserves the right to revise or
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to provide notification of such revision or change.
Not all offerings are available in every country in which HFCL operates. The
data used in this report may be derived from third-party sources and HFCL does
not independently verify, validate, or audit such data. The information in
this document is provided “as is” without any warranty, express or implied,
including without any warranties of merchantability, fitness for a particular
purpose and any warranty or condition of noninfringement’s This report is
intended for general guidance only. It is not intended to be a substitute for
detailed research or the exercise of professional judgment. HFCL shall not be
responsible for any loss whatsoever sustained by any organization or person
who relies on this publication.
For further information about this document,
contact our sales teamiosales@hfcl.com
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References
- HFCL | Leading Digital Network Solutions | Manufacturers of Optical Fiber Cables
- IO by HFCL: Transforming Telecom and Technology Solutions
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