Uplink Interferenece Measurement

Interferences detection on new network deployment

Document number: LTE/ENG/RF/ATT01 Document issue: 01.02 / EN Document status: Standard Date: 04/AUGUST/2010

Confidential document - Not to be circulated outside ALCATEL-LUCENT

Copyright© 2010 Alcatel-Lucent, All Rights Reserved

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Alcatel-Lucent confidential

LTE/ENG/RF/ATT01 * Standard 04/AUGUST/2010 Page 2/30

PUBLICATION HISTORY

14/MAY/2009

Issue 01.01 / EN, First release

A.ROULLIN

04/AUGUST/2010

Issue 01.02 / EN, Modification

A.ROULLIN




CONTENTS

1. INTRODUCTION............................................................................................................................5 1.1. SCOPE OF THIS DOCUMENT................................................................................................5 1.2. ASSOCIATED DOCUMENTS..................................................................................................5 1.3. GENERALITY: ....................................................................................................................5 1.4. PREAMBLE........................................................................................................................6

2. JAMMERS DESCRIPTION............................................................................................................7 2.1. POSSIBLE JAMMERS ..........................................................................................................7

2.1.1 Networks and others transmissions................................................................................7 2.1.2 The real jammers ............................................................................................................8 2.1.3 others miscelaneous jammers ........................................................................................8

2.2. JAMMERS CHARACTERISTICS .............................................................................................9 2.3. JAMMERS ANALYSIS.........................................................................................................10 2.4. HOW TO DECIDE IF INTERFERENCES ARE IMPACTING:.........................................................10

2.4.1 Reference of equipments behavior:..............................................................................10 2.4.2 Case of UMTS networks: ..............................................................................................11 2.4.3 Case of Intermodulation:...............................................................................................12

2.5. HOW TO DETECT INTERFERENCES:...................................................................................13 2.6. HOW TO LOCALIZE INTERFERENCES: ................................................................................13 2.7. HOW TO THWART INTERFERENCES ...................................................................................14 2.8. THE EQUIPMENTS USED...................................................................................................15

2.8.1 Analog measurement with spectrum analyzer..............................................................15 2.8.2 Analog receiver .............................................................................................................17 Multi-technologies Receivers .......................................................................................................17 2.8.3 Antennas used ..............................................................................................................18 2.8.4 Others equipments needed ..........................................................................................18

2.9. RADIO MONITORING MEANS FOR NOISE LEVEL CONTROL. ...................................................19 2.10. GENERAL CONCLUSIONS ..................................................................................................19

3. THE INTERFERENCES DETECTION.........................................................................................20 3.1. PRE-REQUISITES .............................................................................................................20 3.2. THE RECOMMANDED TOOLS.............................................................................................20 3.3. THE GLOBAL PROCESS ....................................................................................................21

3.3.1 Process presentation ....................................................................................................21 3.3.2 Measurement configuration ..........................................................................................22 3.3.3 Measurement Panel......................................................................................................24 3.3.4 Example of results: .......................................................................................................26

4. MEASUREMENT QUALITY ........................................................................................................27

5. POST PROCESSING ..................................................................................................................27

6. RESULTS ANALYSIS .................................................................................................................27




7. DELIVERABLES..........................................................................................................................28

8. ACRONYMS GLOSSARY ...........................................................................................................29




1. INTRODUCTION

Jammed areas could present various kinds of trouble on new network. Interferences can limit the coverage and create difficulties to communicate clearly. This document is a help for Alcatel-Lucent Teams working on various projects such as Trial, early deployment or mass market deployment. It presents the jammer tracking and detection.

1.1. SCOPE OF THIS DOCUMENT

The scope of this document is a support to find possible interferences in several areas. It offers some ways and the associated equipments used to perform the measurements, detect the jammers and propose some solution to the customer.

1.2. ASSOCIATED DOCUMENTS

R1: OPI-O-RF-0039 - Detection of spurious signals in the UMTS Uplink band.

R2: OPI-O-RF-047 V2 - On site interferences debugging guidelines

1.3. GENERALITY:

To deploy wireless network, we need to consider the global requirement for the best network efficiency. Wireless network could be divided in two parts :

- The radio layer (essentially represented by the coverage of expected used area). This radio coverage ensured for certain frequencies must give the guaranty to ensure the transport and the quality necessary to deliver the exchanged information.

- The radio network. It must ensure, by well know and innovative concepts and features, enhanced transfer of information in accordance with certain parameters of throughput and quality.

Radio layer is characterised by the efficiency of its coverage. This one must be optimized to offer a minimum of power to guaranty the main parameters of synchronization and attach on network, the UE reception, and the mobility between sites without outage.

To guaranty that, we need to verify the radio link permanence and eliminate any source of interferences that can create service degradation.

To realize that we need to eliminate hole of coverage and large coverage overlap by an efficient Radio Design and the RF optimization (essentially tilt adjustment). In second hand interferences study must be realized to eliminate or reduce greatly main risk of defects and limitation inside this coverage. Several kinds and sources of interferences must be controlled during the design and installation of new network.




In certain cases, when the required targeted KPI are not reached and without parameters problems, it could be necessary to control if some interferences are appeared. This case is more sensitive due to existing network deployed and operated.

However, often it is possible to realize some on site verification to search them.

1.4. PREAMBLE

The jamming detection or frequency clearance analysis is a part of deployment process. Due to the difficulty to separate jammers and regular network transmission this activity must be conduct early during the Design phase and always before any deployment and on air transmission. Sometime, it conducts to require the Governmental Regulator Office to modify or clear the allocated frequency band. Sometimes, due to necessary coexistence, it conducts to introduce some complementary protections such as filters on our equipments.

For the case of site sharing or very dense network (Dense urban area or area with high concentration of subscribers as hot spots), the interferences must be analyzed early as possible to eliminate the risks due to these situations. Note: Be careful, often, if interferences are quickly known, it is possible to find solution through Design or installation phase. After that only some work around could be finding with less efficiency.




2. JAMMERS DESCRIPTION

In first approach the way is to have an idea of what could be the possible Jammer. When this description is put on the paper it is easier to organize the research on field.

2.1. POSSIBLE JAMMERS

Depending on frequency range used different kinds of jammers could be found. Through our worldwide intervention we can divide the jammers in three categories.

1. Networks and others transmissions inside the allocated frequency range,

2. Jamming due to adjacent transmissions,

3. Spurious, intermodulation and others miscellaneous jammers.

2.1.1 NETWORKS AND OTHERS TRANSMISSIONS

In this category we can found different types of jammers.

• Main jammers are similar networks in boundaries of your deployment area. Or others networks where the frequency range used presents an overlap with your networks (This case appears often in South America where North American and European systems are used equally on close or same areas. Even if the detection is easy, these networks can’t be removed and the cohabitation is always difficult and required high filtering performances or even impossible.

• Some military transmission could be integrated in this type of jammers. Often after regulator request they move on others frequencies or the allocated band is moved.

• The jamming due to high level of transmission in adjacent channel: Available frequencies are rare. New networks can use reallocated old frequency ranges. Due to difficult frequency range positioning it appears that some network receiver bands are more or less close to radio transmission. It could be the case, by example, when terrestrial TV transmission channels are re-allocated for new system. Adjacent channel interferences or blocking could appear.

• Point to point transmissions: They could be old Transmission link used in lower frequency and neglected today or specific actual transmission link used for backbone of others networks. Normally, in this case the jammed area must be narrow and selective. However if our equipment is directly inside the point to point line, the interferences level could be high.




2.1.2 THE REAL JAMMERS

Real Jammers could be local or more general.

Local jammers are created everywhere by low informed peoples or public organisms such as movie theaters, restaurants or others shows to forbid peoples to use mobile phones. These jammers appeared during end of nineties are often not selective and the transmit power can go up to 40 Watts (values given on supplier datasheets).

They are in direct selling on the Web.

Unauthorized transmission: Other possibility is to find real forbidden RF transmissions; this case appears essentially when government regulator has poor means or no real control of the frequency bands.

2.1.3 OTHERS MISCELANEOUS JAMMERS

The Spurious: They appear essentially when sites are shared (unwanted transmission from other base stations or transmission equipments defaults) effects are clearly local. Normally spurious are covered by the equipments standardization, but in some cases particularly if the equipment is old some spurious can be found on non allocated frequency band when the old product was created.

Intermodulations are generated on non linear components (such as band soldering, bad connection or ground defaults) by mix of two different frequencies. The jammer signal could be narrow or wide depend on mixed transmission types. Odd third order intermodulations are the most serious.

External jamming due to urban noise: This jamming is often due to non filtered electrical motor. That is traduced by real RSSI increasing inside the reception band.

The jamming due to antenna cross azimuth: When two networks are closely positioned in frequency, some problem can appear when the both networks antennas are face to face. If the distance between them is limited, the RSSI presents in Rx band could be increasing.

Others: In Europe certain mall and shopping centers use radio frequency features to control public entrance and doors. But this technology is less used today. However some years ago it was a problem with GSM introduction.




2.2. JAMMERS CHARACTERISTICS

Jammers are characterized by:

The frequency: It could be in our allocated frequency range or in direct adjacent channels.

The width of the jammer: Some of them are narrow, some others are wide some others have specific signature. Sometime due to the width of signal it could be comparable to noise.

The power level: Power level of jammers could be more or less important. It traduces distance and type of the jammer. On large area, the level variation could be used to detect specific jammer type.

Permanence of the signal: The signal presence is an important parameter. Two kinds of signals could be found. The permanent signal traduces broadcasted information or transmission link (Radio & TV broadcast, GSM BCCH, UMTS CPICH, others semaphore beacons…). Intermittent transmission could be representative of PMR or military signal, traffic channels or others specifics transmission.

Bursted signals are in the cross of the two others. They are more difficult to display but they have serious effect on our communication.

Channel occupancy must be controlled to have good view of possible interferences issues.

In parallel, we can split the jammers in two main groups.

External jammers: They are jammers from type I or II. These jammers must be detected before the deployment on air of the new network. After that, they can create interferences but they are merged inside the network signal and could be difficult to find.

The on site interferences: linked to the site used these on sites interferences or local interferences must be studied locally and could be analyzed when some troubles appear. It is often the case for type III interferences.




2.3. JAMMERS ANALYSIS

To detect jammers or interferences the only way is to perform radiomonitoring on high points (the more free space as possible). We can use sites or futures sites, hills that overhang the deployment area or others founded high points.

On network deployment, first detection approach must be omnidirectional. If interferences are found to affine the study directive antenna should be used to investigate.

If location is necessary to help the customer specific process and tools must be used. (Please refer to this specific activity).

Be careful, detection is on our responsibility, localization could be offered as additional services for customer or regulator. Frequency clearance and frequency change is on regulator responsibility after customer requirement.

Special case: For the trials, often sites are imposed and due to the time schedule it could be more interesting to realize this activity through the real final antenna lines. However this activity must be realized before transmission.

2.4. HOW TO DECIDE IF INTERFERENCES ARE IMPACTING:

2.4.1 REFERENCE OF EQUIPMENTS BEHAVIOR:

How to decide if pollution or interferences are contraining or not on our network. Our equipments are often protected against certain level of pollution. If the interferences have low level or are seen as pseudo noise (RSSI increase) it is necessary to see if it is acceptable or not. For that, we need to refer to the equipment characteristics and the limit of degradation acceptable.

The curve of interferences impacts could give an idea about that. They show, for two kinds of equipments, the degradation introduced by presence of narrow band interferers.

The parameters taken in account during this whole study were:

- The level of power of the interferer

- The frequency spacing from the channel center frequency

- The spectrum width of interferer (narrow, wide)




Example of RRH Rx desensitization due to interferences level received at Rx connector.

2.4.2 CASE OF UMTS NETWORKS:

On this paragraph we present an example of degradation calculation on WCDMA (UMTS) network.

To create an issue on UMTS BTS receiver band, interferences must be inside the used band (or channel). If the unwanted signal is narrow band, to disturb a spreaded signal the jammer must be higher than UMTS value using the formula below. Due to cross-correlation of the code signal with a narrow band signal will spread the power of the narrowband signal, reducing the interfering power in the information bandwidth.

If interferences appear on Uplink UMTS channel, the maximum accepted of cell degradation must be ≤ to 0.5 dB. To be compliant with that, the level of an interferer should not be higher than –113.4 dBm once spread over 3.84 MHz.

Then, for the BTS, the narrow band signal should not be higher than:

–113.4 dBm+10*(log(3.84MHz/B MHz)).

If Narrow band is 20KHz wide The acceptable limit is under -91dBm For signal with bandwidth = 200 KHz The acceptable limit is under -101 dBm

(*) These values given for the BTS can be similar with an offset of sensitivity for the mobile disturbed by a Jammer.

On narrow band communication as PMR or GSM system the maximum of interferences acceptable inside reception channel is given by the C/I ratio target.




2.4.3 CASE OF INTERMODULATION:

Sometime, on site interferences appear due to site sharing and mix of available frequencies. This is the intermodulation. To find if the IM product risk exists, it is recommended to control the frequencies used on site. If some couple of frequencies can generate IM product, the best way is to change one of these frequencies to eliminate the risk. If not possible, attention must be given on installation and engineering rules to limit the risk of appearance of these interferences.

Bellow some analysis are presented to see if IM products due to frequencies mix can fall inside the reception bandwidths used on site. These curves are extracted from our Intermodulation studies.

For wide bands networks 3rd, 5th and 7th order of Intermodulation must be taken into account.

Intermodulation products

View of IM produced by 2 wide band signals.

Possibility to create IM inside UMTS Uplink band by mix of UMTS downlink channels. (Cositing with others UMTS operators.




2.5. HOW TO DETECT INTERFERENCES:

To detect interferences and jammers on one area, Omni directional antenna is necessary. For best efficiency this antenna must be used on area without mask effect.

That determines why RF interferences detections are always realized on high points, top of building or top of pylon. Due to surrounded masks effects, if these activities are realized on ground level, the result is very often “clear frequency range” but this result is always false.

This activity realized before deployment or at minimum before network transmission must ensure the clearance of the frequency range allocated to the customer. It must integrate on each side a guard band equivalent to one channel.

To integrate the more as possible all the possibility of interferences appearance this activity must be conducted during long time. Due to schedule, organization and management, often this activity is performed on whole day. Result must be recorded in specific report given to the customer.

Results must show the shape of interferers and there occurrence (channel occupancy).

If required, it could be necessary to localize or to have an idea of about the location of the found interferers. In this case antenna used and measurement duration must be adapted.

2.6. HOW TO LOCALIZE INTERFERENCES:

To localize jammer the main way is to cross several measurements used to search main direction of arrival. To determine the jammer transmission place at minimum two directions are necessary. Depending on measurement fineness and distance between the two measurements points, the jammer could be close to the crossed direction lines. If more than two direction lines are available for the same jammer, we can refine the result.

To make good jamming test on big urban area, 6 to 8 measurements points are necessary. For rural area that could be equivalent or more (depending on the covered surface).

These sites must be chosen through the complete area with a well-done distribution.




2.7. HOW TO THWART INTERFERENCES

Two cases must be studied. If real jammers are found, the way is to request government regulator to clear the allocated frequency range or to change it.

If interferences are not really unauthorized transmissions, the first way is to qualify and quantify them.

Several solutions are possible to thwart the interferences and their effects. They depend on interferences types, characteristics and pollution level. The first levels of solutions are some specifics hardware and software enhancement to return more robustness on our system it is better than some years ago but not sufficient. Some external solution could be added.

External solution panel can play on :

Antenna choice (types and characteristics as radiation patterns, tilt variation, port isolation, side lobe suppression or front to back ratio enhancement).

Antenna positioning (height, azimuth, masking, relative decoupling…).

Filtering (multiplexors, rejection filters, cositing filters…).

At least, if it is impossible to limit enough the pollution the last way is to request the local government regulator for frequency range change or to abandon the network project.

Thwart jammer in our band: Filtering is not possible. Sometimes, solution could be found by antennas repositioning or allocated frequency range cleaning or moving. The solution depends on the jamming level.

Thwart jammer positioned in adjacent channel or out of band: Filtering is possible. It depends on level that must be filtered and the width of frequency available to realize this filtering. Interferences qualification is key. Some others additional solution could be considered as antenna positioning or at least frequency range moving.

Thwart spurious or intermodulation: Spurious and intermodulation are local jammers. Issue and solution must be found on site. Antenna choice and positioning could help greatly to eliminate spurious impact. Particularly the antenna decoupling, that could be used with respect of open angle in azimuth (divergence of azimuth) . Intermodulation is more constraining. That necessitates specific study to find aggressor, victim and coupling way. If interferences seems like intermodulation, that is easy to verify it. With the reference of frequencies used on site it is enough to calculate the product of mix o find victim and aggressor. 3rd order products are the more impacting for narrow band. For wide band order 5 and 7 must be controlled. Interferences qualification and quantification are Keys.

Thwart interferences caused by urban noise: It is impossible to filter or plays on antenna choice to limit these risks. The only way is to play on antenna positioning if roof top is used. In all cases, these interferences must be finely studied and the equipments used should be modified (Hard or soft) to taken into account of this issue.




2.8. THE EQUIPMENTS USED

To detect the jammers 2 kinds of measurements are possible. The first one is purely analog. The second one uses the digital receiver facilities. To cover the both 2 kind of equipments should be used.

The best way is to use autonomous equipments (without AC power supply). These equipments must be able to record the results (in standalone or with a PC support).

2.8.1 ANALOG MEASUREMENT WITH SPECTRUM ANALYZER

The Spectrum analyzer is the best tool to make analog measurement with a direct real view of the result. It offers the possibility to qualify the level of channel power, adjacent power and to control the type of interferences that appear. Different kind of measurements could be used as averaged measurement, maxhold measurement, single measurement, channel power measurements, and on certain tools the possibility to have channels or band occupancy. Sometime on averaged mode minimum and maximum of power could be displayed. Bursted or intermittent transmission could be easily highlighted. Some A.S. have spectrogram analyzer function. Specially dedicated to this activity, this function offers numerous possibilities of configuration and exploitation (MS2721B or MT822xA).

To enhance the noise floor level it could be possible to use internal or external pre-amplifier. That increases the tool capacity to show low level interferences.

To optimize the analysis Radio bandwidth and video bandwidth must be adapted.

The span must be adapted to the requested analysis. In general manner, a large span must be used in first approach to see direct frequency environment.

For the measurements of interference level the way is to use two kind of narrow spans:

1° - Allocated frequency range or channels plus two adjacent channels by side.

2° - Allocated frequency range or channels plus one adjacent channel by side.

To ensure and qualify the measurements quality two kind of accessories would be available:

- A cositing filter (adapted on our uplink frequency band)

- A set of load and attenuators to control measurement quality.

- Directive coupler to visualize functioning in real time (Optional).

In several country, like USA, it exist a large offer of renting equipments if necessary.




Example of equipment available:

ANRITSU Handheld Spectrum analyzer – Anritsu has a large offer for field RF tools. The adapted Spectrum Analyzer is the MS2721B. Designed for the field, It is very portable and has a included pre-amplifier and battery pack.

ADVANTEST Spectrum analyzer – Advantest offers a large range of Spectrum Analyzer with several field equipments. These equipments are available with battery pack in option to work without AC power. (Ulis series are correct products as U4341 or U3641…) The 3641 offer also some direct measurements on adjacent channel and interferences.

AGILENT TECHNOLOGIES Analyzer: - Agilent proposes several classes of Spectrum analyzers. The most efficient for field measurements are the N1996A or E44xxB ESA series. However, it seems that the N1996A has no software to transfer the traces to a PC. The ESA series can be connected to a PC with the Intuitlink software available for free on the Agilent website.

HP Spectrum Analyzer: - The more popular Spectrum Analyzer from HP is the series HP 85XX. The 856x is oriented Labs and the series 859x is oriented field such as 8590 – 8591 or 8592. These equipments, not dedicated, are ageing but correct to cover this kind of activity.

RHODE & SCHWARZ FSH 3 field spectrum analyzer.

The R&S model option 23 have Preamplifier and tracking generator to allow performing main measurements. It is possible to store trace inside internal memory and to transfer it by RS232 or to control remotely the tool by RS 232C (option K1) cable loss & VSWR measurement are possible with option Z2-K2 and DTF is possible with additional option B1. This tool is oriented field measurement and present low size and robust protection. For interference location it could be coupled with active cardioids’ antenna HE200. Another option allows converting the FSH3 (or 6) in receiver mode to for radio monitoring application.




2.8.2 ANALOG RECEIVER

Some analog receivers are able to realize these measurements with good efficiency including interferences power level (peak, average and mini), bandwidth or channel occupancy or noise floor characterization. The main parameters of they products are the sensitivity, the selectivity, the measurement dynamic and the speed of measurement. Good EMC protection is also necessary to work in disturbed area. These receivers are more dedicated than spectrum analyzer for this kind of activity.

These receivers must be piloted by PC through measurement and processing software. They allow listening to one frequency, a frequency range and some dedicated sections of one large frequency range. Real time analysis is possible through the PC software and its graphic interface.

Two kinds of products could be used:

• The purely analog receiver using classical frequency generation. Less efficient for the speed due to fine frequency positioning they have often excellent radio characteristics. (Example Chase GPR series or Rohde & Schwarz ESVD).

• Analog receiver using pre-positioning by DSP use. Faster to measure, these equipments must have high level of protection against EMC. It is the case for Willtek Griffin or Rhode & Schwarz EB 200. These receivers are more efficient to realize bandwidth or channel occupancy.

Generally, they use Pilot PC to configure, manage and store the measurements. Only one set of measurement is necessary to control interferences. This set could be more or less long. For example Jammers detection on deployment area necessitates several measured site with duration of 24 h by site. Noise level control necessitate only fifteen minutes of measurement.

MULTI-TECHNOLOGIES RECEIVERS

In addition of analog tracking it is possible to investigate more deeply the problem.

For this kind of measures the best way is to use a digital receiver able to work in standalone without any PC.

In this case The Anritsu MT822xA are good products, especially when interferences are the problem. In fact they integrate spectrum analyzer (equivalent to Anritsu MS2721B) and a multi-techno receiver for complementary measurements. Specific interferences analysis mode would be used including waterfall spectrogram to enhance the field measurements.




Another usable product is the YBT 250 from Tektronix. It has the capacity to realize specific and adapted measurement to investigate when the level of reception is high. Its concept is also organized around spectrum analyzer base, but the performances are lower than with the 8222A.

Others limitation, if the interferences level is too low it is more difficult to use it and it presents not possibility to use it in a moving car.

Be careful, this equipment could be rented and used but it is discontinued and can’t be bought.

2.8.3 ANTENNAS USED

To realize the field activities, the antennas used can be different function of the need. In general manner, Omni directional antenna is used to investigate on the presence or not of jammers, but is not appropriate to find main jammed direction.

To find more precisely the jammer the only way is to use directive antenna. This antenna must be really directive (40° or less are necessary in horizontal aperture). An other parameter that must be taken into account, it is the front to back ratio. More the antenna F/B ratio is important better is the antenna selectivity. In order cardioid antenna is the best product. If it is impossible to find this antenna adapted to the tested frequency range, Yagi antenna is the good compromise product. At least, standard directive antenna could be used but with more difficulty and less efficiency.

2.8.4 OTHERS EQUIPMENTS NEEDED

To finalize this chapter don’t forget that, often, we need others complementary equipments such as attenuators (3dB, 6 or 10 dB) these attenuator should be used in case of doubt of intermodulation or receiver dazzle.

RF cable: It ensures the link between antenna and Spectrum analyzer. It must be flexible with N connectors (a set of N adaptors M/M and F/F can also be used).

Pre-Amplifier: This external pre-amplifier is used if the tool dynamic is not sufficient to see jammers at low level or noise increasing. Be careful badly used it could generate wrong results.

Filters or diplexers: These features allow to limit out of band blocking or saturation.

Directive coupler helps to measure with necessary protection the forwarded power. (Emission masks study).

Set of various loads & adaptors: these equipments could be used to connect the measurement tool everywhere that we need.




Set of survey: four main tools compose it. The main are the camera and the compass to describe environment and azimuth used during the measurements if necessary. Decameter is used to have roof distance, antenna and building height. Binocular could be necessary to search surrounded informations.

2.9. RADIO MONITORING MEANS FOR NOISE LEVEL CONTROL.

Another kind of measurement could be assimilated to the jammer detection to find local on site interferences such as noise level increasing or local intermodulation products appearance. This measurement is performed after on site installation and often when the site is shared with others equipments. Difficult to implement when RRH are used (difficulty to connect the measurement system on Rx port) this measurement allows to verify that the site noise floor is not disturbed by its on site radio environment. When RRH is used duplexer must be introduced inside antenna link at RRH connector to protect the tools. Dedicated process is available see R1.

2.10. GENERAL CONCLUSIONS

Jamming issue occurs generally close to the cell edge due to received power limitation. That decreases the cell size and introduces holes of coverage and reduces or disturbs the communication on air interface. If the level of interferences is too high communication could be impossible. Interferences management necessitates qualifying and quantifying the interferences the most upstream as possible.

In any case, when interferences issues appear the only and first activity is to study them. This operation is ‘key’ to find solution to thwart or limit the problem.

To see any interference the only places to investigate are in free space. That imposes to realize this activity with the antenna on roof top, top of hill or on pylon. Any measurement on ground is doomed to failure.

This activity consists to listen to the controlled frequency range. It is why this activity must be realized in upstream of deployment. Otherwise it is close to impossible to find something.

Due to the interferences risk on network efficiency, this mandatory activity was integrated inside the deployment process upstream to the design and in all case before any transmission.




3. THE INTERFERENCES DETECTION

To detect the jammers RF engineer should have adapted process and equipments. This section describes the whole means for this activity.

3.1. PRE-REQUISITES

To launch interferences measurement campaign, some pre-requisite are necessary. These information are the following:

- Customer frequency range allocation (F start, F stop, Number of channel, channel width).

- Measurement sites availability (For deployments on main city 6 to 7 sites are necessary. For Trial, 2 sites are necessary).

- Site access, including possibility to take pictures of site and surrounding.

- Tools and adapted filter availability on tested frequency ranges.

- Tool set availability and efficiency.

3.2. THE RECOMMANDED TOOLS

To realize this activity, the recommended tools are:

Anristu spectrum analyzer handheld: this tool is present on various field analyzers as MT822xA, MS2721B, S331E or 332E... Configuration performance and associated kinds of measurements possibilities are the same.

RF cable: It must have 20 or 25m length to be compliant with any installation without limitation. Its loss must be well known or measured on site at used frequency.

Antennas: Omnidirectional and optional directive antennas must be adapted with the frequency range used.

The telescopic mast: It would be in well condition and must have safety guide for installation.

Post processing tool: the tool used for post processing is Master Software Tool provided by Anritsu. This tool is free of charge and given with the used handheld. It allows presenting the results on various configurations (Time occupancy, frequency occupancy, waterfall or 3D).

Two survey equipments can complete the tool set. The digital camera is mandatory in all field activities to present and prove anything and a compass is necessary to control the azimuths.

Complementary tools: Pre-amplifiers and filters would be available on site to thwart the possible measurement’s risks and limitations.




3.3. THE GLOBAL PROCESS

3.3.1 PROCESS PRESENTATION

The process to make interferences measurement is very simple to follow.

- Make a small surrounding survey including whole 360° panoramic view and 2 or 3 pictures of installation, to show that no mask is in the direct antenna environment.

- Install the antenna (in case of antennas available on site, use them)

Omni directional to find interferences

Directive (Yagi, cardioids) for direction determination.

Site antenna with good tilt and azimuth to evaluate cell perturbation.

- Connect and control RF cable (Loss, VSWR)

- Connect and configure the measurement tool.

Spectrum analyzer (frequency range, VBW, RBW, sample collection mode (average, peak or Maxhold)) if spectrum analyzer has spectrogram function use and configure it.

- Collect the data and complementary information and pictures.

RF data must be highlighted by pictures of antennas and feeders, global Cell panoramic view and site information as presented on example below.

- Store all the results.

- Post processing: Replay the result to found the jammer and organize them to create the report.

- Write activity report.

However, if the global process is simple measurement are not easy due to Radio environment, possible perturbations and quality & efficiency control.




3.3.2 MEASUREMENT CONFIGURATION

Two main configurations should be used if no equipments are installed. This is the best way to search interferers.

If definitive antennas are mounted, after risk evaluation it is possible to use these antennas to control the level of interferences that coming from jammer in our network uplink band.

Interferences or jammers research configuration

Measurement on high point (roof top, pylon, hill) research in free space and in all direction. Used for interferences detection.

Antennas used

Interferences or jammers localization configuration. Measurement on high point and free space. Research of main direction of signal arrival. Characterization of signal power level. Antenna must be facing to higher signal level(front the main arrival direction).

dB22

CHASE

GRFM

dB22

CHASE

GRFM




Case of installed site configuration:

If the site is already installed, final antenna’s lines could be used. In this case the measurement organization should be the following.

Equipment used could be analog receiver and PC or Spectrum analyzer with PC or able to store results.

Configuration on installed antenna: Connection is realized at feeder connector. If RET is used, it is possible to modify the tilt, if PC with adapted configuration software and dedicated power supply are plugged on antenna line through AISG BiasT.

Example of live configuration on antenna line using TMA.

The next picture shows an example of organization for measurements on installed antenna. Fixed on pylon and using TMA.

On left side required information are presented and value must be wrote inside the radiomonitoring report. On right side equipments set is described.

Be careful if interferer is strong, blocking or saturation could affect the TMA function.




3.3.3 MEASUREMENT PANEL

This part of document gives an overview of different measurements available to analyze the interferences. The choice of several kind of measurements is often necessary to Find interferers and to validate some assumption to thwart them.

In general manners, allocated frequency range and adjacent channels must be controlled. If necessary a wider view can give complementary information.

- Preamplifier and filter or attenuator should be used if necessary.

- If necessary, TMA and/or RET system should be fed by external power supply on BiasT (AISG or not depend the need).

Information on configuration of tested line and pictures of these measurements configuration must be added inside the report.

Measurements with spectrum analyzer:

- Frequency range (Span) centered on our middle of allocated band, It must including the adjacent channels or at minimum a guard band equivalent of 5 MHz on each side.

- RBW and VBW must be adapted to the measurement often they are compromise between speed and spectrum analyzer sensitivity.

Real time measurement: It is the standard approach. Offer instantaneous view of band occupancy. Used for first approach.

Drawbacks: Feeble readability, undefined noise floor. Poor view of bursted signal.

Maxhold view: Allow to aggregate bursted signal through the time until possibility to find transmission signature (TDD). Minimum measurement duration must be around 15mn.

Drawback: Impossible to have real occupancy ratio, interferer level is optimistic (too high).

Averaged view: Give often min, max and average of interferer power level. Best for interferences analysis.

Drawbacks: modify transmission signature and limit jammer identification.

Channel power measurement: For wide or composite interferences signals only way to have the real channel power.

Spectrogram measurement: Allow to have channel pollution through the time (Channel Occupancy). Could be used remotely.

Drawback: Depending on spectrogram measurement configuration it could be hardly to read and to understand. Signal signature can’t be seen.




Adjacent channels measurements: Depending on possibilities we have, it is possible to perform two main kinds of adjacent channel measurements. The first one called ACLR for Adjacent Channel Leakage Ratio. The second one more flexible is called ACPR for Adjacent Channel Power Ratio.

ACLR is defined as the ratio of the amount of leakage power inside the adjacent channel compared to the total of transmit power inside the tested channel. ACLR could be studied for first or second adjacent channel. The results values are given directly in dBc (dB relative to the controlled carrier). ACLR measurements, available on various tools, are often optimized for best efficiency.

ACPR measurement could be analog to the previous one but all the parameters must be set. This kind of measurement could be used when the radio parameter of system are not really known.

Measurement with analog receiver:

Analog receiver can made directly or remotely different kind of measurement. All the data are stored and analysis must be during post processing.

Channel occupancy: Give view of occupancy ratio on channel. (If the channel is wide often measurement must be a frequency scan post processed).

Drawback: scan duration could be too important for real results efficiency.

Frequency scan: It could be on various independent frequencies, a frequency range or some segment of frequency range. Result understanding is function of post processing.

Drawback: if the range is important the scanning duration could be long and band occupancy couldn’t be deduced.




3.3.4 EXAMPLE OF RESULTS:

Results with Analog receiver (Chase system - SMS) : Occupancy band

Results with Spectrum Analyzer : Occupancy band continuous view and averaged view

Results with MT 822xA : Maxhold Occupancy band and Spectrogram measurement.

Results with MT 822xA : ACLR measurement and Spectrum ACPR measurement




4. MEASUREMENT QUALITY

This kind of field activity could be constraining for the future deployment. As others pre-qualification, it must be controlled to eliminate any doubt due to the measurements, post-processing or final interpretation.

For the results quality and warranty the equipments need to have a calibration report under validity (minus one year old). During long measurement campaign all main equipments must be verified weekly to eliminate the risk to redo the whole campaign due to broken equipments (antennas, cables, receiver or spectrum analyzer).

During measurement, several kinds of error risks are possible. That could be trouble due to out of band saturation, bad antenna positioning or surrounding clearance, problem generated by the measurement system itself... For each of these troubles, field operator should have to verify anything before to record the analysis.

Due to very fast radio environment change, the results period of validity for jamming test can’t exceed one year. In fact, in gives guaranty that the frequency clearance was effective (or not) before network deployment and use.

5. POST PROCESSING

The field phase measurements could be conduct to search and identify the possible interferences. If necessary the following activities could be added: detection of the estimated location and verification of some assumptions to solution or limit the problem.

After the field phase, the way is to post-process the results to shape the information. To realize this, if Anritsu recommended tools are used, the way is to use master software tool (MST).

6. RESULTS ANALYSIS

Global analysis is essentially performed to control the results views and to associate each pertinent information in accordance with the localization and others information. If necessary it could introduce to search some solutions for the customer.

Without the fact to store all the collected data (more efficient for analysis but sometime difficult in the field), analysis is limited.

If jammers appear it should be interesting to locate and quantify them and to give the information to the customer. The post processing phase should be to associate results, pictures and complementary information.

(*) For remembering, customer is the only parties who have the authority to ask government regulator to clean the frequency range or to ask for new frequency band.




7. DELIVERABLES

Inside the synthesis report, all information, pictures and measurement captures should be organized to explain the issue and if necessary to describe possible available solution (leaned on complementary realized measurements).

Deliverable must contain:

- The formal report,

- The measurements data (raw and post processed data)

Scanning on frequency band, channel power measurements, adjacent channel measurements…

- Informed Panoramic view (Cell by cell or informed 360°)

- Equipments configuration (parameters and pictures)

- Mandatory complementary information (Antenna line characteristics, antenna positioning).




8. ACRONYMS GLOSSARY

ACLR Adjacent Channel Leakage Ratio.

ACPR Adjacent Channel Power Ratio.

AISG Antenna Interface Standards Group.

BCCH Broadcast Control Channel

CPICH Common Pilot Channel

dB Decibel (Define quantity of energy on logarithm scale).

F. Start Frequency Start (spectrum analyzer use).

F. Stop Frequency Stop (spectrum analyzer use).

F/B ratio Front to Back ratio ratio between energy transmit front an antenna and behind it.

FDD Frequency Division Duplexing (Duplexing method for radio transmission ).

GSM Global System for Mobile communication also called 2G for 2nd generation

KPI Key Point In,dicator

MHz MegaHertz .

MST Master Software Tools (Tool delivered by Anritsu)

PC Personal Computer.

PMR Private Mobile Radio.

RBW Resolution Bandwidth (measurement window for radio analysis).

RET Remote Electrical Tilt

RF Radio Frequency

RRH Remote Radio Head

RSSI Received Signal Strength Indicator

Rx Receiver

SMS Signal Monitoring Software

TDD Time Division Duplexing (Duplexing method for radio transmission ).

TMA Top of mast Amplifier

Tx Transmitter

UMTS Universal Mobile Telecommunications System (3rd generation)

VBW Video Bandwidth (measurement Video filter of spectrum analyser).

VSWR Voltage Standing Wave Ratio




END OF DOCUMENT

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