P3CI_InterferenceHunting2013

7/29/2019 P3CI_InterferenceHunting2013

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Interference Hunting

Fast Reaction Time

Exceptional Quality

2G

3G

LTE

Interference

Shutdown

PIM

Nationwide

Service

SPECTRUM

REFARMINGMEASUREMENTS

External

Interference

Hunting

Outdoor &

In-building

Installations

700 MHz850 MHzAWSPCS

Pre- and

Post-launchInvestigation


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Spectrum Scanning

The rst step in the radio spectrum clear-

ance process is to get an overview of thestatus quo. When scanning frequency

bands that are supposedly unused, inter-

ferers can easily be seen in the spectrum.

An experienced equipment operator can

often determine the type of the interfer-

ing signal from its shape and duration.

With their long experience in measure-

ments of all kinds of communication

systems, P3 communications experts are

one step ahead in recognizing different

transmission systems from their spec-

tral pattern. During scanning activities,

P3 communications has also observedand analyzed complicated patterns, like

inter-modulation products of digital and

analogue transmissions.

For the analysis of interfering sources,P3 communications is using equipment

that is also able to demodulate the inter-

fering signal. In case of analogue trans-

missions this often gives clues to nding

the interfering source. A striking example

of this was when P3 communications ex-

perts listened to an FM radio station over

an inter modulation signal found in the

frequency band reserved for cellular sys-

tems. In order to meet every customers

needs, the P3 communications measure-

ment system can be congured to au-

tomatically measure several frequencybands sequentially.

Thus P3 communications is offering to

evaluate, e.g., designated LTE spectrum

plus UMTS uplink, UMTS downlink, andGSM bands simultaneously by driving a

certain route only once.

Typical spectral ranges scanned in the

U.S. are:

There are many causes of interference.

They all add up to an increased noise

oor, resulting in either decreased QoS or

the need to invest more CAPEX into the

network deployment. Long story short:

interference costs money. P3 communi-

cations offers spectrum clearance and

audit services that measure and identify

the interference in a given band, before

service launch, or after. We help carriers

to defend their licensed spectrum and to

protect their investments. This improves

network quality, capacity and coverage

and frees valuable resources at the car-

riers organization.

Interference hunting and spectrum clear-

ance services are very CAPEX intensive

services, that require expert knowledge

and professional equipment. Our long

collaboration with Rohde & Schwarz

gives our experts access to professional

equipment in use by many government

agencies around the globe. The service is

launched across the US.

P3 communications investigated more

than 500 interference problems in the

US covering states as Maine, New Hamp-

shire, Vermont, Massachusetts, Rhode

Island, Connecticut, New York, New Jer-

sey, Pennsylvania, Maryland, Delaware,

Washington D.C., West Virginia, Virginia,

Michigan, Missouri, Illinois, Mississippi

and Alabama. Since 2013 P3 offers its

service nationwide.

P3 communications experts have in-

tensive knowledge of nding sources of

interference in different environments

from dense urban environments as Man-

hattan to rural areas.

Additionally twice broadband interfer-

ence is seen (D1, D2). The spectrum was

taken during a drive test, so just from

the measurement data it is impossible to

see if the broadband interference existed

only for a short time period or if it was

caused by a weak local interferer that

was only visible while the measurement

vehicle was near.

Although the spectrum in the downlink

band is organized well, still problems can

arise from such a spectrum allocation:

Inadequate system setup (namely insuf-

cient antenna down tilt resulting range

overshooting) can cause interference in

places with a different band allocation.

Scanning Results

A useful visualization of the spectrum measurement is what is called a waterfall diagram, a graphical representation that shows

the color coded signal level over time. The graph below shows the downlink (left) and the uplink portion (right) of the PCS band.

Spectrum Measurements

Spectrum Clearance

698-798 MHz (LTE spectrum)

824849 MHz (850 MHz Uplink)

869894 MHz (850 MHz Downlink)

18501910 MHz (PCS Uplink)

19301990 MHz (PCS Downlink)

17101790 MHz (AWS Uplink)

21102170 MHz (AWS Downlink)

Three different systems coexist in theband:

a UMTS system (downlink center at1.9675 GHz, uplink center at 1.8875GHz), showing some downlink andoccasional uplink activity (A).

CDMA2000 systems which can be id-entied by bandwidths of 1.25 MHz (B)

a GSM system (C)


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Localization Procedure

The main objective of our interference

hunting service is to pinpoint the main

characteristics for any sources of inter-

ference, ideally including:

Location,

Address,

Spectrum footprint,

Geographic footprint of the

interference,

Power used, and

Ofcial site information (FCC).

We employ various direction nding sys-

tems and handheld devices in order to

cover most practical applications. This

includes outdoor far-ranging measure-

ments, urban near-eld drivetests and

portable indoor investigations. Localiza-

tion of interfering sources is based on

either triangulation or hunting activities.

In triangulation the position of an inter-

fering transmitter is estimated from the

combination of multiple bearing results

obtained at various measurement loca-

tions in the area where the interferer is

present. This method applies in particu-

lar for high power interferers like unau-

thorized transmitters or harmonics of

regular stations.

The term hunting in this context means

the continuous approaching of an inter-

fering source by following the bearing

results with respect to the surrounding

environment (street canyons, buildings,

forest, trees, etc.). With our experienced

measurement personnel it is possible to

localize the actual source and arrive at

its door sign within reasonable time. P3

communications supports the process of

shutting down the culprit.

Pre-LaunchA thorough spectrum audit before launch-

ing a service will ensure clear spectrum

for proper network operation. Although

the P3 communications service is identi-

fying the interference source in a timely

manner, the process of shutting down the

interfering transmitter may require legal

actions or other possibly time-consuming

steps. Additionally, localization of weak

interferers in downlink bands may re-

quire downtime of the interfered network

nodes. Pre-launch spectrum clearance

can prevent these disadvantages and is,

therefore, the preferable solution.

Post-Launch

Due to constant changes in the network

and the introduction and installation of

further wireless devices new sources of

interference will inevitably show up.

Those can be identied during proactive

spectrum audits or reactive and specic

interference hunting activities. In most

cases, the exibility of the deployed

measurement equipment and the exper-tise of the engineers in charge enables

P3 communications to identify the inter-

ference sources without the need for ser-

vice-impacting network downtime.

Often, the customer will have problems

with specic cell sites that show subopti-

mal performance. The deployed network

equipment may also allow for rst spec-

trum scans at the location of the cell site

and provides well understood KPIs (access

failures, call drops, etc.).

The P3 communications service will lever-

age these insights and expertise on the

customers side and will prevent any dou-

bled work during the project execution.

The P3 communications engineers will

closely cooperate with the customers

personnel and bring in the experience of

previous interference hunts. At the begin-

ning, they will ask the right questions to

limit the number of possible options what

type of interference source may cause the

observed problems. These preparations

ensure that no existing piece of informa-

tion is neglected and allow for more ef-cient measurements out in the eld.

Integrated approach

The background in the areas of network

benchmarking and optimization enables

P3 communications to also consider more

than only power measurements on the

physical layer. Taking into account higher

layer information available from the net-

work scanner allows for an integrated ap-

proach that is especially helpful in post-

launch scenarios.

In operational networks, bad signals, i.e.,

interference, and good signals, i.e., cus-

tomer calls or data transmissions, have to

be differentiated. However, interfering

signals may have a multitude of spectral

shapes and may look very similar to the

active network transmissions. Weak inter-

ferers may hardly be identied and wrong

conclusions may easily be drawn.

In this context, the expertise of the ex-

perienced P3 communications engineers is

key to efcient and reliable service provi-

Localization Procedure & Shutdown

Pre or Post-LaunchNaturally, one prefers to clear any interference in a spectrum band before launching the service using that spectrum. However, new

interference sources may come up and the spectrum should closely be monitored during service operation.

P3 communications provides bespoke solutions for both scenarios:

Spectrum clearance services in a pre-launch stage and interference hunting for all post-launch cases.

The impact of interference on the performance of a base station depends on the usage type of the affected frequency band.

Uplink interference impacts the overall performance of one or several base stations. The interference must be received by the

base station to impact its performance. Uplink interference problems can be investigated during regular network operation de-

pending on UL trafc volume. Downlink interference impacts only a certain geographical area of one or more base stations. Any

downlink interference has an impact on the user inside of the interfered area. Downlink interference can only be measured in a

pre-launch phase without impacting network operation.


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sion. The status data of the live network

provides additional side information to

guide the interference hunt and to pre-

vent the engineers from mixing good and

bad signals.

Due to the broad communication engi-

neering knowledge P3 communications

considers all pieces of information that

give hints for identifying the interference

source also during regular network opera-

tion in a post-launch scenario.

What to do about it?

P3 communications measurement and interference hunting results are intended to provide sufcient information to initiate

the necessary steps or legal actions in order to get rid of an interfering signal. Owner and address data might be used to con-

tact the responsible party directly, the information on frequency, position, call sign, site ID in combination with the elaboratedmeasurement results can be passed to FCC for further actions. As far as possible P3 communications will support the process to

shut-down interference sources or P3 communications engineers switch of the sources themselves.

The measurement results obtained will not only be used by the customer, but the customer may also want to present it to third

parties (e.g. as legal proof). P3 communications is aware of the absolute necessity to deliver highest quality measurement results.

In order to guarantee reliability and ac-

curacy, P3 communications sends well-

trained measurement experts to the eld

and is using equipment from the worldsbest measurement equipment manufac-

turers. For the scanning and interference

hunting, P3 communications has selected

equipment made by Rohde & Schwarz

which is also in use with many govern-

ment agencies.

Each piece of measurement equipment is

connected to a PC or laptop, such that

the data measured is stored continuous-

ly. The measurement expert is monitor-

ing the spectrum continuously. This way,

whenever an interferer is found he can

start the bearing immediately, therebyincreasing the chance to also nd sources

of interference that transmit only over

a short time span. GPS data is recorded

continuously and a correlation between

measurement result and position can be

established.

Using a spectrum scanner that is

capable of demodulating signals,

P3 communications has the means to in-

vestigate signal sources more deeply. In

case of AM/FM modulated audio signals

being part of the interference, the audio

signal can directly be listened to.With the modular setup of the

P3 communications measurement system

it is also possible for the measurement

expert to unplug the spectrum scanner

(typically a handheld Rohde & Schwarz

PR100), connect a handheld narrow beam

antenna to it, and to trace the interfer-

ing transmitter down to the last yard,

even inside buildings.

Measurement Equipment

Interference Hunting - Indoor

Portable Receiver PR 100 Spectrum and spectrogram (waterfall) display

LAN interface for remote control and data

output

Ergonomic and rugged design for portable use

Portable operation using a highly directive

antenna for direction nding

Map-based direction nding supported using

multiple measurements taken at different

locations

Interference Hunting Outdoor

Data

GPS

RF

RFElectronic Compass,

Antenna Element

Control

Digital Directional Finder DDF255 Direction nding of signals with almost any

modulation

Wide-aperture behavior above 300 MHz

Very short signals of 10 ms detectable

High accuracy and sensitivity

Bandwidth setting independent of receiver

AC supply or battery operation

Simultaneous operation of all DF antennas

(HF and VHF/UHF) without replacing antennas

Network and Spectrum Scanning

Data

GPS

Band 1

Filter

Amplier

Band 2

Spectrum Analyzer TSMW Input frequency range from 30 MHz to 6 GHz

Two independent RF and signal processing

paths, each with a bandwidth of 20 MHz

Spectrum measurements with RF power scan

option

Parallel measurements in GSM, WCDMA, LTE,

CDMA, Tetra, WiMAX

High accuracy and sensitivity

Integrated GPS with PPS

P3 communications, Inc, 412 Mt. Kemble Ave, Suite G2, Morristown, 07960 NJ, USA

phone +1 973 984 6050, [email protected]

Headquarters:

Morristown (NJ, USA), Aachen (GER), Belgrade (SRB), Sydney (AUS)

Documents

P3CI_InterferenceHunting2013