Showing posts with label WiFi. Show all posts
Showing posts with label WiFi. Show all posts
Sunday, March 22, 2015
CSA Wi-Fi Testing
Tuesday, August 19, 2014
CSA - Site Survey Method4/Cell Types
Cell types
GSM reports, as far back as 20 years ago, distinguished three kinds of cells as the growth in GSM installations massively increased following popularity as a preferred digital cellular network: large cells, small (mini) cells and micro cells. The main difference between these kind of cells lay in the cell range, the antenna installation site, and the propagation model applying to each of them. Moreover, these cells could be overlayed one on top of another to provide coverage for varying traffic conditions and illustrated in the previous discussion http://cellsiteanalysis.blogspot.co.uk/2014/07/csa-site-survey-methodmobility-models.html.
CSA has been subjected to understanding cell layer tiering involvement in a particular geographical area and what impact the finding of tiering might have determined from radio test measurement results, and what impact the results might infer for a particular investigation. In the previous discussion on Mobility Models it highlighted a simple issue: why walk tests are important to mimic the pedestrian's experience of obtaining mobile services. Germane and relevant, whilst the mobile networks are highly intelligent networks and use memory and memoryless in their propagation models, CSA examiners, students and experts cannot apply intelligent algorithms in the manual function of their work when conducting site surveys. It is, therefore, necessary to distinguish processes and procedures hidden within the intelligent network functionality that provide us (CSA examiners, students and experts) with knowledge that helps us gain skills and experience in the performance of the work we do.
So we know "walk tests" are unavoidable (thus inescapable) forming part of the methodology we should apply, where relevant, during site surveys. Whilst this requirement is a basic simple binary style approach to CSA that doesn't mean to suggest mobile networks aren't sophiscated, convoluted, NASA style complex system because mobile networks are very much the latter. These grass root levels are important to CSA. For instance a GSM mobile network may use Cell Selection Procedures C1 and C2. The network can use components from C2 (cell reselection) to identify coverage for a slow moving mobile (e.g. pedestrian/walk test) which can be used to understand the microcell coverage. Drive testing equally needs to be represented for the benefits it provides for CSA.
Above, three tiers of cell coverage have been illustrated. Microcells are distnguished as a cell type because predominantly this type of cell in GSM (or CDMA for that matter) is usually represented as localised coverage to a small area. Pedestrian is seen as relevant to it. However, vehicular mobile usage is largely predicted within the network as "fast moving". Let us take the case of the getaway car speeding away from the scene of crime. Would it not seem strange to you to find the target's mobile phone call records identifying a number of Microcell IDs designed to cope with long dwell time in an area associated with slow mobile movements (e.g.5~10mph) compared with Macrocell umbrella coverage designed to handle accelerated speeds (e.g. 30~70mph). Why would the getaway car be driving so slowly after a crime, unless the *bogey wanted to be caught red-handed and why s/he commited the crime in the first place just to be arrested? On first blush of the call record evidence it wouldn't make sense.
*The term bogey has been adopted from the military theatre of war identification procedure representing an un-identified (unknown criminal) target, whereas a bandit is an identified (known criminal) target. In criminal investigations the latter can also suggest surveillance in progress on the target's activities.
But drive testing can throw up unexpected issues. CSA demands keeping an open mind and, as previously mentioned at my blogs, CSA examiner, student and expert should be "not only be environmentally aware, but equally be environmentally astute." A case I dealt with in the North of England concerned a series of smash-n-grabs at wholesale and retail outlets. From my radio tests I suggested the radio evidence did not follow the getaway route the police required that I test. CSA involves noticing factors that could impede or record a particular route. In this case a speed camera that was in lock-n-load (active) to capture speeding vehicles was located at an early stage on the suggested getaway route. When I asked did the speed camera record a speeding violation, the response came back "no", yet the ascertion by the police was the getaway vehicle was speeding. However, the radio test measurement survey along the complete route did not entirely match the cell IDs in the call records either as some of the cell IDs were for slower mobile traffic and cells covering a middle layer coverage area and the use of these cells suggested the mobile dwell time was not travelling outside a certain geographical area. Eventually, a more senior detective suggested a route that veered away from the first route getaway route. My attention was drawn to an area inbetween local buildings, a mud track leading to a field and a nearby cemetary and housing estate. Infact the bogeys turned out to be previously known bandits and the entire operation of the smash-n-grabs was orchestrated from a house on the estate sited perfectly for comings and goings for the many crimes but quite hard to detect. CSA played an effective part to support other evidence and intel.
However, umbrella macrocell coverage in a geographical location can be used to support high speed getaways e.g. where CCTV has recorded or an eyewitness had seen the getaway vehicle speeding through dense urban area. Given the speed of the vehicle the network would be detecting the mobile's short dwell time in that area. The omission of use of overlayed microcells providing limited area coverage is a suggestion of fast moving traffic. The use of a macrocell would not be out of place supporting the notion of a fast moving mobile. This can be stated in relation to the density of non-used microcells and their cell boundarys compared to macrocell cell boundaries and, of course, any location updates, time, velocity etc.
Since 2010 Cells types have rapidly moved on with a split between voice/data and data-only cells transforming the way CSA is and will be conducted in the future. For instance, there are increases in carriers (2G frequencies allocation migrating (re-use) to 3G frequencies allocation) Moreover, with LTE linking with WiFi/WLAN etc there are enormous advantages and dis-advantages that have crept into CSA site survey methodology.
The impact of these changes requires improved comprehension about the various cells and as higher frequencies are used or are brought into use cell coverage gets smaller. This fact is a benefit because the approximated location of the mobile is improved and significantly improves where smaller cells are relevant. It may not be GPS accuracy but there seems no reason why it could not meet justification under an e.g. Daubert test. Furthermore, it doesn't means CSA should jettison early styles of CSA site survey method which will remain relevant for some years to come. But CSA will become even more localised creating a specialism in InnerCity CSA (ICCSA) compared with rural CSA. A beneficary of ICCSA knowledge will be the neuromancer cybercrime arena utilising our forensic and investigative skills to comprehend the technicality behind a suspected crime defined by the outcome from particular usage of technology.
Site survey methods do not have to be overly complicated, merely identify the radio technology at given points and by using a structured appraisal, distinguishing each wireless carrier available at particular geographical locations, to show the relevance to an investigaion or crime scene.
Rel-5 (Release 5)
Rel-6 (Release 6)
Rel-7 (Release 7)
Rel-8 (Release 8)
Rel-9 (Release 9)
Rel-10 (Release 10)
Rel-11 (Release 11)
Rel-12 (Release 12)
GSM reports, as far back as 20 years ago, distinguished three kinds of cells as the growth in GSM installations massively increased following popularity as a preferred digital cellular network: large cells, small (mini) cells and micro cells. The main difference between these kind of cells lay in the cell range, the antenna installation site, and the propagation model applying to each of them. Moreover, these cells could be overlayed one on top of another to provide coverage for varying traffic conditions and illustrated in the previous discussion http://cellsiteanalysis.blogspot.co.uk/2014/07/csa-site-survey-methodmobility-models.html.
CSA has been subjected to understanding cell layer tiering involvement in a particular geographical area and what impact the finding of tiering might have determined from radio test measurement results, and what impact the results might infer for a particular investigation. In the previous discussion on Mobility Models it highlighted a simple issue: why walk tests are important to mimic the pedestrian's experience of obtaining mobile services. Germane and relevant, whilst the mobile networks are highly intelligent networks and use memory and memoryless in their propagation models, CSA examiners, students and experts cannot apply intelligent algorithms in the manual function of their work when conducting site surveys. It is, therefore, necessary to distinguish processes and procedures hidden within the intelligent network functionality that provide us (CSA examiners, students and experts) with knowledge that helps us gain skills and experience in the performance of the work we do.
So we know "walk tests" are unavoidable (thus inescapable) forming part of the methodology we should apply, where relevant, during site surveys. Whilst this requirement is a basic simple binary style approach to CSA that doesn't mean to suggest mobile networks aren't sophiscated, convoluted, NASA style complex system because mobile networks are very much the latter. These grass root levels are important to CSA. For instance a GSM mobile network may use Cell Selection Procedures C1 and C2. The network can use components from C2 (cell reselection) to identify coverage for a slow moving mobile (e.g. pedestrian/walk test) which can be used to understand the microcell coverage. Drive testing equally needs to be represented for the benefits it provides for CSA.
Above, three tiers of cell coverage have been illustrated. Microcells are distnguished as a cell type because predominantly this type of cell in GSM (or CDMA for that matter) is usually represented as localised coverage to a small area. Pedestrian is seen as relevant to it. However, vehicular mobile usage is largely predicted within the network as "fast moving". Let us take the case of the getaway car speeding away from the scene of crime. Would it not seem strange to you to find the target's mobile phone call records identifying a number of Microcell IDs designed to cope with long dwell time in an area associated with slow mobile movements (e.g.5~10mph) compared with Macrocell umbrella coverage designed to handle accelerated speeds (e.g. 30~70mph). Why would the getaway car be driving so slowly after a crime, unless the *bogey wanted to be caught red-handed and why s/he commited the crime in the first place just to be arrested? On first blush of the call record evidence it wouldn't make sense.
*The term bogey has been adopted from the military theatre of war identification procedure representing an un-identified (unknown criminal) target, whereas a bandit is an identified (known criminal) target. In criminal investigations the latter can also suggest surveillance in progress on the target's activities.
But drive testing can throw up unexpected issues. CSA demands keeping an open mind and, as previously mentioned at my blogs, CSA examiner, student and expert should be "not only be environmentally aware, but equally be environmentally astute." A case I dealt with in the North of England concerned a series of smash-n-grabs at wholesale and retail outlets. From my radio tests I suggested the radio evidence did not follow the getaway route the police required that I test. CSA involves noticing factors that could impede or record a particular route. In this case a speed camera that was in lock-n-load (active) to capture speeding vehicles was located at an early stage on the suggested getaway route. When I asked did the speed camera record a speeding violation, the response came back "no", yet the ascertion by the police was the getaway vehicle was speeding. However, the radio test measurement survey along the complete route did not entirely match the cell IDs in the call records either as some of the cell IDs were for slower mobile traffic and cells covering a middle layer coverage area and the use of these cells suggested the mobile dwell time was not travelling outside a certain geographical area. Eventually, a more senior detective suggested a route that veered away from the first route getaway route. My attention was drawn to an area inbetween local buildings, a mud track leading to a field and a nearby cemetary and housing estate. Infact the bogeys turned out to be previously known bandits and the entire operation of the smash-n-grabs was orchestrated from a house on the estate sited perfectly for comings and goings for the many crimes but quite hard to detect. CSA played an effective part to support other evidence and intel.
However, umbrella macrocell coverage in a geographical location can be used to support high speed getaways e.g. where CCTV has recorded or an eyewitness had seen the getaway vehicle speeding through dense urban area. Given the speed of the vehicle the network would be detecting the mobile's short dwell time in that area. The omission of use of overlayed microcells providing limited area coverage is a suggestion of fast moving traffic. The use of a macrocell would not be out of place supporting the notion of a fast moving mobile. This can be stated in relation to the density of non-used microcells and their cell boundarys compared to macrocell cell boundaries and, of course, any location updates, time, velocity etc.
Since 2010 Cells types have rapidly moved on with a split between voice/data and data-only cells transforming the way CSA is and will be conducted in the future. For instance, there are increases in carriers (2G frequencies allocation migrating (re-use) to 3G frequencies allocation) Moreover, with LTE linking with WiFi/WLAN etc there are enormous advantages and dis-advantages that have crept into CSA site survey methodology.
The impact of these changes requires improved comprehension about the various cells and as higher frequencies are used or are brought into use cell coverage gets smaller. This fact is a benefit because the approximated location of the mobile is improved and significantly improves where smaller cells are relevant. It may not be GPS accuracy but there seems no reason why it could not meet justification under an e.g. Daubert test. Furthermore, it doesn't means CSA should jettison early styles of CSA site survey method which will remain relevant for some years to come. But CSA will become even more localised creating a specialism in InnerCity CSA (ICCSA) compared with rural CSA. A beneficary of ICCSA knowledge will be the neuromancer cybercrime arena utilising our forensic and investigative skills to comprehend the technicality behind a suspected crime defined by the outcome from particular usage of technology.
Site survey methods do not have to be overly complicated, merely identify the radio technology at given points and by using a structured appraisal, distinguishing each wireless carrier available at particular geographical locations, to show the relevance to an investigaion or crime scene.
So what are the potentially inter-connected Cell types that fall within the scope of CSA large cell and small cell environments:
Macrocells
Minicells
Microcells
Metrocells
Picocells
Nanocells
Femtocells
WIMAX cells
WLAN cells
WiFi cells
etc
And in support of that environment it should not under-estimate the importance of devices capability from providing services and to accessing services. This mean from not simply the network, but the radio network e.g. BTS/(e)NodeB/H(e)NB etc to the enhanced (U)SIM and handset terminal. That requires knowning which Release (R) is relevant to the investigation:
R99 (Release 1999)
Rel-4 (Release 4)Rel-5 (Release 5)
Rel-6 (Release 6)
Rel-7 (Release 7)
Rel-8 (Release 8)
Rel-9 (Release 9)
Rel-10 (Release 10)
Rel-11 (Release 11)
Rel-12 (Release 12)
etc
Monday, May 05, 2014
New Book - RFPS (Radio Frequency Propagation Survey)
Joe Hoy from Forensic Analytics joins us this month at Cell Site Analysis blog to outline the purpose and content for his forthcoming book regarding RFPS (Radio Frequency Propagation Survey).
What is your background, Joe?
"I am a telecoms engineer and trainer with 27 years of industry experience. For the last 17 years I have concentrated on telecoms training, specialising in cellular technologies particularly, for the past few years, 4G LTE.
"I have also worked extensively as a forensic cell site analyst and expert witness, contributing to many high-profile cases for either the prosecution or the defence. I’ve undertaken the work of the RFPS surveyor, capturing measurements of cellular coverage at crime scenes and other locations and have also provided extensive training for cell site analysts and RFPS engineers.
What is your current employment?
"I now run a company called Forensic Analytics, we develop and supply software tools, such as our CSAS (Cell Site Analysis Suite) tool, to police forces and cell site analysis companies to aid them in processing call data records and RF survey results and also help them to effectively analyse, query, visualise and present that data. Traditionally, cell site analysis and their attendant forensic radio surveys were undertaken by external cell site experts, but there has been a growing trend, in the UK but also elsewhere, for law enforcement agencies to reduce the cost of forensic cell site investigations by taking some or all of the survey work ‘in house’.
Who are the potnetial readers of your book and why?
"Many police forces now employ their own radio surveyors who undertake radio surveys for them – although there are many experienced radio engineers included in this set, in many cases the people being employed to perform these tasks are investigators and do not come from a cellular radio engineering background. Their understanding of the background of the role can therefore be somewhat limited and their technical understanding of the operation of the networks they are surveying may benefit from additional enhancement.
"In light of this, I have been asked by John Wiley Sons, the technical book publisher, to write a book that outlines the theory and practice related to the RFPS (Radio Frequency Propagation Survey) discipline within the field of cell site analysis.
Can you provide CSA blog readers with a brief outline of the content of the book
"The first half of the book provides a reasonably simple but nonetheless detailed overview of radio theory, of basic cellular network principles and concepts and of the operation of cellular networks. The radio theory section provides an introduction to basic radio theory and offers simple explanations of the mathematical concepts that underlie radio measurements scales such as dB and dBm. The network types section is mainly focused on 3GPP network types – GSM, UMTS and LTE – but also provides an overview of the operation of other network types, such as 3GPP2 cdmaOne/CDMA2000/EV-DO, Chinese TD-SCDMA, WMIAX, WiFi, iDEN, TETRA and others.
"One of the main aims of the first half of the book is to introduce new surveyors to enough fundamental concepts to enable them to understand the meaning and significance of the measurements they will capture during surveys. It also provides details of the specific types of measurement that are captured for each network type and gives an idea of the typical range of values to be expected.
"The second half of the book focuses on forensic radio surveys; the various types of survey, the techniques employed for each survey type, the considerations and potential problems that can be encountered when surveying different types of network.
"This book is intended to be used as both a text book and as an aide memoire handbook by forensic radio survey engineers, particularly those working for official police agencies. It is not intended to act as a detailed technical reference for cell site experts or others who already understand these topics.
Which markets would benefit from your book?
"There is a growing market for cell site analysis in general. The UK has largely pioneered this area of forensic activity and has an experienced and mature market but the market in other parts of the world is still developing. Many countries use cell site techniques but base their conclusions purely on the proximity of a cell to a significant location. This isn’t ‘proof’ in an empirical sense and this type of cell site evidence is subject to challenge and dismissal in court. As cell site markets and techniques mature in other countries there will be a need for proper RFPS evidence and therefore, I hope, a growing market for the information provided in this book.
When will your book be available and how do readers get hold of a copy?
"The book is due to be published by Wiley in the Autumn, but for further details please contact me at joe.hoy@forensicanalytics.co.uk. For details of our CSAS tool go to www.forensicanalytics.co.uk."
What is your background, Joe?
"I am a telecoms engineer and trainer with 27 years of industry experience. For the last 17 years I have concentrated on telecoms training, specialising in cellular technologies particularly, for the past few years, 4G LTE.
"I have also worked extensively as a forensic cell site analyst and expert witness, contributing to many high-profile cases for either the prosecution or the defence. I’ve undertaken the work of the RFPS surveyor, capturing measurements of cellular coverage at crime scenes and other locations and have also provided extensive training for cell site analysts and RFPS engineers.
What is your current employment?
"I now run a company called Forensic Analytics, we develop and supply software tools, such as our CSAS (Cell Site Analysis Suite) tool, to police forces and cell site analysis companies to aid them in processing call data records and RF survey results and also help them to effectively analyse, query, visualise and present that data. Traditionally, cell site analysis and their attendant forensic radio surveys were undertaken by external cell site experts, but there has been a growing trend, in the UK but also elsewhere, for law enforcement agencies to reduce the cost of forensic cell site investigations by taking some or all of the survey work ‘in house’.
Who are the potnetial readers of your book and why?
"Many police forces now employ their own radio surveyors who undertake radio surveys for them – although there are many experienced radio engineers included in this set, in many cases the people being employed to perform these tasks are investigators and do not come from a cellular radio engineering background. Their understanding of the background of the role can therefore be somewhat limited and their technical understanding of the operation of the networks they are surveying may benefit from additional enhancement.
"In light of this, I have been asked by John Wiley Sons, the technical book publisher, to write a book that outlines the theory and practice related to the RFPS (Radio Frequency Propagation Survey) discipline within the field of cell site analysis.
Can you provide CSA blog readers with a brief outline of the content of the book
"The first half of the book provides a reasonably simple but nonetheless detailed overview of radio theory, of basic cellular network principles and concepts and of the operation of cellular networks. The radio theory section provides an introduction to basic radio theory and offers simple explanations of the mathematical concepts that underlie radio measurements scales such as dB and dBm. The network types section is mainly focused on 3GPP network types – GSM, UMTS and LTE – but also provides an overview of the operation of other network types, such as 3GPP2 cdmaOne/CDMA2000/EV-DO, Chinese TD-SCDMA, WMIAX, WiFi, iDEN, TETRA and others.
"One of the main aims of the first half of the book is to introduce new surveyors to enough fundamental concepts to enable them to understand the meaning and significance of the measurements they will capture during surveys. It also provides details of the specific types of measurement that are captured for each network type and gives an idea of the typical range of values to be expected.
"The second half of the book focuses on forensic radio surveys; the various types of survey, the techniques employed for each survey type, the considerations and potential problems that can be encountered when surveying different types of network.
"This book is intended to be used as both a text book and as an aide memoire handbook by forensic radio survey engineers, particularly those working for official police agencies. It is not intended to act as a detailed technical reference for cell site experts or others who already understand these topics.
Which markets would benefit from your book?
"There is a growing market for cell site analysis in general. The UK has largely pioneered this area of forensic activity and has an experienced and mature market but the market in other parts of the world is still developing. Many countries use cell site techniques but base their conclusions purely on the proximity of a cell to a significant location. This isn’t ‘proof’ in an empirical sense and this type of cell site evidence is subject to challenge and dismissal in court. As cell site markets and techniques mature in other countries there will be a need for proper RFPS evidence and therefore, I hope, a growing market for the information provided in this book.
When will your book be available and how do readers get hold of a copy?
"The book is due to be published by Wiley in the Autumn, but for further details please contact me at joe.hoy@forensicanalytics.co.uk. For details of our CSAS tool go to www.forensicanalytics.co.uk."
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