Operational Audit Check (OAC) is part of Cell Site Analaysis (CSA)

 

 

There is a news aticle on News96.5.com about a mast (US cell tower) that caught figure during an install/maintenance work (http://www.news965.com/news/news/local/cell-phone-tower-burning-could-fall/nZYBg/). The article provides us with a useful reminder when conducting cell site analysis (CSA) to remember to conduct an operational audit check (OAC) and request confirmation that the target mast and the density of support radio coverage masts in the immediate area were all operational at the material time. This should be requested as soon as practicalable to do so.

Invariably, an event (e.g. a serious crime) requires instant action and requires, if relevant, knowing the cell coverage at the scene of crime (SoC) and the coverage in surrounding areas (e.g. identifying potential get away routes). It could impact the investigation if an OAC is not conducted regarding the density of surrounding masts and it later comes to light a mast was out of commission for a period and other masts in trh surrounding area had their coverage increased.

In some cases, it may not be possible at short notice to draught-in coverage from other masts and a radio black spot may occur. This, too, is in important to anticipate and be considered when analysing call records, road networks and the density of masts (thus coverage) upon the landscape. Moreover, if the out of commission mast is at a central location of a road network or town/city, consider also the base stations delivering small cell/micro cell coverage. Many of these base stations have their antennas tilted. There are two types of tilt commonly available: electrical and mechanical. Electrical tilt enables the network to remotely alter the tilt angle of the antennas. Mechanical tilt requires an engineer to visit site and mechanically alter the antenna tilt. Here again, not considering these points could mean an investigation can include arriving at erroneous conclusions that may be uncovered later on.

My experience of performing OAC for particular cases can vary from the experience of others. I am not able to say why information I have found was available was not accessible to other experts/investigators. It seems to me that an illustration of the information that supports the above comments I made should be demonstrated. I have hidden some cell site/mast details from the data served in a particular case, that of site name, address and NGR, as this relevation is not necessary to specifically identity the cell site/mast details in that particular case. However, it is assumed that site name, address and NGR are standard details that form part of the request of the information sought from a particular operator.

Below is further reading material I hope you will find helpful, which I have produced here at the blog in the past, and that the events/actions mentioned in them might provide further support or clarity to you about the issues discussed above or during an investigation.

LTE, Test Trials and Cell Site Analysis
http://trewmte.blogspot.co.uk/2012/10/lte-test-trials-and-cell-site-analysis.html

CSA - R&TTE Directive
http://trewmte.blogspot.co.uk/2012/06/csa-r-directive.html

GSM Mast Installations (Density)
http://trewmte.blogspot.co.uk/2008/06/gsm-mast-installations-density.html

Basic Terrain Plot, GPS & CSA
http://trewmte.blogspot.co.uk/2011/11/basic-terrain-plot-gps-csa.html

CSA: From Ockham's (Occam's) Razor to Checking Masts
http://trewmte.blogspot.co.uk/2008/11/csa-from-ockhams-occams-razor-to.html

Cell Site Analysis (CSA) Images
http://trewmte.blogspot.co.uk/2009/08/cell-site-analysis-csa-images.html

Cell Site Analysis (CSA) Images Part 2
http://trewmte.blogspot.co.uk/2009/08/cell-site-analysis-csa-images-part-2.html

Cell Site Analysis (CSA) Images
http://trewmte.blogspot.co.uk/2009/08/cell-site-analysis-csa-images.html

Mobile Phones and Fringe Coverage
http://trewmte.blogspot.com/2008/11/mobile-phones-and-fringe-coverage.html

Evolving Cell Site Analysis (CSA)
http://trewmte.blogspot.co.uk/2011/05/evolving-cell-site-analysis-csa.html

Mini Course in Cell Site Identification (Pt3.s2)
http://trewmte.blogspot.co.uk/2012/04/mini-course-in-cell-site-identification.html

Mini Course in Cell Site Identification (Pt3.s1)
http://www.trewmte.blogspot.co.uk/2012/01/mini-course-in-cell-site-identification.html

Mini Course in Cell Site Identification (Pt2)
http://trewmte.blogspot.com/2011/12/mini-course-in-cell-site-identification_31.html

Mini Course in Cell Site Identification (Pt1)
http://trewmte.blogspot.com/2011/12/mini-course-in-cell-site-identification.html

Mini Course in Cell Site Identification (Pt3.s2)

Mini Course in Cell Site Identification (Pt3.s2)

Links to previous discussions in these Mini Course modules:

Mini Course in Cell Site Identification (Pt3.s1)
http://www.trewmte.blogspot.co.uk/2012/01/mini-course-in-cell-site-identification.html

Mini Course in Cell Site Identification (Pt2)
http://trewmte.blogspot.com/2011/12/mini-course-in-cell-site-identification_31.html

Mini Course in Cell Site Identification (Pt1)
http://trewmte.blogspot.com/2011/12/mini-course-in-cell-site-identification.html

In this module the discussion follows on, for section 3.2, identifying further locations where research material maybe obtained to assist cell site identitifcation (CSI). Previously in Pt3 s1 the observations identified where information can be obtained from a local authority or council planning department. The 'reality' of such information being existence and available to any enquiror occurs due to statutory provisions and public employees employed to provide such information and provide such identification that is accessible because of the charges made within national and local taxes. Presumably this might be the same situation in other countries.

Regulator
In the UK we have the 'communications' (previously known as the 'telecommunications') regulator called OFCOM (Office of Communications). It is the duty, accordng to EU directive, UK statute and regulation that the regulator provides accessible information that is current and up-to-date. One of the tools that an examiner will use is OFCOM's sitefinder service. There is a caveat to the information available from this service, which states (http://www.sitefinder.ofcom.org.uk/):

"Sitefinder was set up as a result of recommendations of the Stewart Report in 2000. It is a voluntary scheme under which mobile network operators make information available on the location and operating characteristics of individual base stations, so that people who wish to inform themselves about this can do so.

"Ofcom hosts the Sitefinder tool on behalf of Government, which can be searched for the location and details of mobile phone base station sites around specific locations. The data within Sitefinder is owned by the mobile network operators, who supply it on a voluntary basis. A request made under the Freedom of Information Act 2000, for Ofcom to make available the information contained within Sitefinder, is subject to an ongoing legal process. Meanwhile, the mobile network operators (except Everything Everywhere) continue to provide voluntary updates which are made every 3 months or so.

The Sitefinder tool therefore remains available and reasonably current (except for Everything Everywhere sites); meanwhile Ofcom will not release the underlying database pending the outcome of the legal process.

Ofcom cannot accept liability for any inaccuracies or omissions in the data provided within Sitefinder, or its currency."

The OFCOM service does provide useful information about cell sites and an examiner would be quite foolish to ignore it, but as equally foolish to believe this is the only source of information, independent from actual enquiries to the mobile network operator and so on.  By way of illustration, I was able to show that information from the local council identified that historcially a base station (cell site) had moved from its original installation (relevant to a particular investigation), which was not revealed by using the OFCOM service. This revelation is further support for an examiner being not only being aware but, equally, being astute.

Examples of the discovery process from the OFCOM sitefinder website is a glimpse at the density of cell sites in a given area:

The relevance of  density of cell site was discussed here -  http://trewmte.blogspot.co.uk/2008/06/gsm-mast-installations-density.html

Moreover, the sitefinder site also provdes details that have been registered by an operator about a particular mast:

Mobile Network Operator
However, the discovery process doesn't stop there but additionally investigation to a particular mobile network operator's website and searching for coverage in a particular geographical area is as equally important to have performed that task. For this reason I have for quite sometime provided links to UK mobile network operators' websites so that examiners can make investigative searches of a particular operator's site regarding coverage relevant for a particular geographical area.

International Marketplace
It is also relevant to be aware that mobile communications also includes 'Roaming' calls and discovery in other countries. The narrative in the aforementioned would largely be wasted without some reference sources and below I have listed a few website in order to bring an international understanding to this discussion:

US cell sites
http://www.cellreception.com/

Austria
http://www.senderkataster.at/

France
http://www.cartoradio.fr/netenmap.php?cmd=zoomfull

Malta
https://www.mca.org.mt

Netherlands
http://www.antennebureau.nl/

Sweden PTT
http://www.pts.se/en-gb/Radio/

GSMA Roaming and Coverage Maps
And for coverage aspects relevant to roaming an examiner can also visit the GSMA website to see what can be revealed about cell site identification and its coverage before conducting site surveys etc:

http://maps.mobileworldlive.com/

In this module it hasn't provided the definitive elements cell site identification (CSI), but it does provide observations for examiners to explore the options about details about a cell site (Mast) and also coverage from it. This may also reveal where the latter can provide important material, such as to define aspects about coverage, which may not have been revealed in documents / information presented by the other side.

As a refresher, readers of this mini course in cell site identification may recall at the very off I set out factors that impact on propagation from a mast and an interpretation of the possible function and responsibility of a mast and thus the natural and obligatory requirement for an exmainer to discover as much about the cell site (mast) as possible. The relevant parts produced thus far have intended to show that even before the examiner peruses call records / mast details obtained for a particular case, the examiner cannot simply take those details on face value and must make strenuous effects to understand that cell site identification is not merely about a cell ID, LAC, postocde, NGR, etc but additionally information about defined coverage that should assist the examiner prepare for site surveys etc. Furthermore, to assess the information provided by the other side to identify or isolate omissions in it/them which, once revealed, may provide an entirely different fact or influence about the evidence the other side had failed to present.

Mini Course in Cell Site Identification (Pt3.s1)

Mini Course in Cell Site Identification (Pt3.s1)

Mini Course in Cell Site Identification (Pt1)
http://trewmte.blogspot.com/2011/12/mini-course-in-cell-site-identification.html

Mini Course in Cell Site Identification (Pt2)
http://trewmte.blogspot.com/2011/12/mini-course-in-cell-site-identification_31.html

In Part 1 and Part 2 of this mini course on cell site identification certain themes have been illustrated. For Part 1 four images were presented with the intention to provide the reader with a starting point. That starting point related to identifying various ways in which the Mast, a.k.a. BTS etc provided ‘the’ pivotal link that enabled a mobile station (MS) to communicate with the mobile network in order to send and receive communications(voice/text) and obtain other services. Identification of various factors that are needed was also illustrated; nothing in-depth, of course, just bullet points hinting at matters to be considered. Behind each of the bullet points there hides a huge range of material such that each bullet point deserves its own chapter in a book, e.g. purely on cell site identification issues alone.

I do not have the luxury to produce all the material I have because this is only a free mini course with an intention to prompt the examiner, investigator and/or expert into appreciating the importance of a mast. That is to say, merely going to site, taking a photo of a mast and performing a selection of ‘motionless’ or ‘drive tests’ doesn’t even begin to cover the important science and art of cell site identification, let alone cell site analysis, let alone cell site identification.     

In Part 2 the discussion moved on to demonstrating a selection of images of masts defined by the effect of the propagation they produce and how environmental condition impacts against propagation due to the siting of the mast. But as the course is about cell site identification and not radio propagation, I set out to challenge the reader with examples of whether the reader’s understanding of the images could be altered. Why did I do that? For exactly the point I made above in the last paragraph. Taking a photo of a mast said to have produced ‘the’ coverage used by a particular MS, but omitting definition and technical detail about a mast, is certainly not cell site identification.  Moreover, failing to comprehend the arrangements of the way in which a mast is installed, position and setup in order to deliver radio coverage can impact down the line.

One example, if one looks at the image Fig. D. The mast has been sited in the centre of the roof. A depiction of radio coverage has been enunciated by the use of blue-scale colour and an explanation of a probable outcome of coverage forecast from that particular install. Additional commentary was given to challenge the reader to consider that minimal acquisition of information about a mast may not be satisfactory for cell site identification when analysis is made following radio test measurement and the results may raise questions about coverage because of a lack of understanding, at first instance, about the mast install.

For Part 3 the theme continues with further consideration about masts, but from the viewpoint of ways to identify and investigate the technical install of and at the mast. In order to give this part of the topic some airing Part 3 will be separated in to three sections (3.1, 3.2 and 3.3) so illustrate places where discovery can be made.

The earlier images shown in Part 2 illustrated various types of masts regarding their location/positioning but no detail of the technical install was given, so the examiner, investigator and/or expert has to look to options available to obtain details of a mast’s technical install. A word of caution about cell site identification details received about a mast, especially in criminal proceedings, the discovery of information (data etc) served can be very limited.   There can be numerous reasons for this and rather than e.g. an investigating police officer accepting information presented under the camouflage caveat of information s/he is entitled to receive or entitled to request under “proportionality”, a good copper with a nose for policing wont allow his/her horizons to be limited by that.

Section 3.1 - The Council Planning Department
This line of enquiry may be a shock that it is mentioned at all and for consideration first, but it is being given promenance precisely for those reasons. The amount of times I recall being informed by one party or another that the limited information provided to me by them is all I can have as that is all that is available I found quite astounding. Put simply, it is mendacious (whether intentional or not) to claim 'limitation' about the avalability of the details about a mast, particularly where the operator, depending upon which country is relevant, has obligations to main details about a particular mast in some cases upto six months after a mast has been decommissioned. Moreover, archives of mast installs can go back much longer than that. Any proposed install (mast) that has the intention to be used to provide radio coverage to a geographical location requires proper scrutiny regarding the operator's mission statement, environmental impact, interference with or to other services and health and safety etc prior to its approval to install. There are some exceptions where planning may not be required for external operator masts, but that doesn't mean that the planning department is unaware about a mast's detail. 

Submitted plans for a proposed install or an existing install are available locally. There is a large range of information available, and to whet your appetite below is a selection of technical detail I have choosen that you can find out from your local planning office:

A photo of the Mast (this one is b/w because that is how it was submitted to the planning department)


Because some masts are occupied by more than one operator's equipment the elevation and detail of a mast's height and the height of each operator's equipment on it is important to know.


Additionally, for the antenna array it is important to comprehend the mechanical arrangement of the antenna and the delivery of intended coverage to the e.g. azimuth


In preparation for comprehending site survey and radio test measurements you may also think it important to understand the detail of True North/Magnetic North and other bearings given for the arrangements at the mast's core.

So the range of information provided from this source should be treated as important in the fact finding process and form a natural and integral part of the cell site identification (CSI) investigation.