CSA - Site Survey Method 2/ITU

The International Telecommunications Union (ITU) combines standards making capability and also has regulatory functions specific to mobile telecommunications. Therefore the ITU goes beyond standards making that may not create obligations in contrast with issuing regulatory measures that clearly do create regulation for it members who are signatories to the Convention.

 

 

Three important functions of the ITU are:

1) Regulation and Recommendations

Where there is an international aspect involved the ITU has the responsibility to manage the radio-frequency spectrum. The ITU allocates frequency bands to certain applications that would make use of the RF bands (see list below) e.g. Radio/Television Broadcast; Microwave Links; Radio-Astronomy; Mobile Telephony. The technical means and the physical nature of the frequency bands form the basis of the allocations. That is to say where a frequency band can be used and doesn't interfere with prescribed wide-ranging criteria; and the technical means exists or can be developed that enables the physical radio medium to be manipulated for use. Member states are bound to this allocation prepared by the ITU but assigning the frequencies to users is within the power and autonomy for each member state. ITU decisions are, in principle, binding to its members. The relevance behind that statement is that the ITU origins began to facilitate and enable subsequent amendments of the agreements to be agreed upon made at the Interntaional Telegrahy Convention of 1865. The principle of being bound only comes into effect when member states ( http://www.itu.int/online/mm/scripts/mm.list?_search=ITUstates&_languageid=1 ) ratify the text of an evolving Convention. Changes to any text in the Convention thereafter also need to be ratified. A member state ( http://www.itu.int/en/membership/Documents/signatories-pp10.pdf compare with http://www.itu.int/en/membership/Documents/signatories-pp06.pdf ) failing to ratify new text is not bound by it thus watering down the effects of any binding powers over national sovereignty.

Essentially, whilst understanding ITU's can make decisions when it comes to Band allocations we know that ITU does not hold regulatory functions when it comes to standards. When dealing with interntional bodies like ITU the term standard, as we commonly understand it, is more profound at the ITU's level. This is because international technical issues are being addressed. Were the standards to be made binding that could have political implications / ramifications regarding national sovereignty etc. However, a standard adopted by the ITU are called "recommendations". The recommendations carry a voluntary adoption by members states. The recommendations can though become directly or indirectly binding if it is incorporated into member states legislation where the legislation refers to a particular ITU recommendation. That would have a direct binding agreement. An indirect binding agreement could be where European legislation does not mention ITU recommendation per se but refers to CEPT or ETSI standards that become recorded that are in-turn derived from ITU recommendations. Were there to be an inextricable link requiring identical wording for CEPT/ESTI standard/ITU recommendation then that may amount to an indirect binding agreement with or to the ITU recommendation. It may be accepted that *CEPT/ETSI might be in the driving seat but isn't this nothing more than that old adage 'What is in a name? That which we call a rose by any other name would smell as sweet...(Romeo and Juliet)?'

* At an appropriate juncture in another discussion CEPT/ETSI will also be discussed.

2) Recommendations as Standards

ITU draws up standards (recommendations) and provides them to the telecommunications community that are relevant for telecommunications between countries.  There are numerous diverse tasks requiring standards under the umbrella and responsibility of the ITU that are prepared and developed by numerous advisory groups that are split into divisions.

As this discussion relates to CSA and identified recommendations listed here ( http://cellsiteanalysis.blogspot.co.uk/2014/07/csa-survey-method-2.html ) the detail below highlights the radio subject matter from the division ITU-R.

Radio:
http://www.itu.int/en/ITU-R/Pages/default.aspx
-- http://www.itu.int/pub/R-REG
--- http://www.itu.int/en/membership/Documents/WRC-12.pdf
--- http://www.itu.int/en/membership/Documents/signatories-wrc07.pdf
---- http://www.itu.int/pub/R-REC

Individual Recommendations for allocated bands
BO - Satellite delivery
BR - Recording for production, archival and play-out; film for television
BS - Broadcasting service (sound)
BT - Broadcasting service (television)
F - Fixed service
M - Mobile, radiodetermination, amateur and related satellite services
http://www.itu.int/rec/R-REC-M/e
P - Radiowave propagation
http://www.itu.int/rec/R-REC-P/e
RA - Radio astronomy
RS - Remote sensing systems
S - Fixed-satellite service
SA - Space applications and meteorology
SF - Frequency sharing and coordination between fixed-satellite and fixed service systems
SM - Spectrum management
SNG - Satellite news gathering
TF - Time signals and frequency standards emissions
V - Vocabulary and related subjects

Telecommunications
http://www.itu.int/en/ITU-T/Pages/default.aspx

Development
http://www.itu.int/en/ITU-D/Pages/default.aspx

Whether a member state has signed up to using the standards (recommendations) or not predominantly it is inescapable the technical information in the standards provides useful advice to countries and industry concerning: interconnection, access, terminal device standards, reference standards etc. Certainly in the areas of GSM, TDMA, CDMA, WCDMA/UMTS-UTRA etc many of those standards specific to these technologies constantly refer to ITU recommendations, thus further underpinning how useful ITU recmmendations are to use as references and guidance for cell site analysis.

3) Forums and Facilitors

Agreements between members require a commonality in understanding as to the reliability of international services available; thus technical services and commercial agreements need to be acceptable to both parties. ITU offers forums that help facilitate international agreements.


Final thoughts

The intention of this mini-overview about ITU recommendations was to demonstrate the value they offer given that they have weight due to the requirement of reliability to assist commonality and provide useful guidance for member states for that purpose. When dealing with CSA we are usually not involved at the member state level but at the operational performance of radio communications and services at the local level of which the ITU recommendations can and do provide useful reference material for reports and useful knowledge, skill and experience when conducting in the field surveys.

GSM Radio Test Measurements

GSM Radio Test Measurements

Radio Test Measurements 1

The screen image (Radio Test Measurements 1) represents the output results of radio coverage detected at the receiver (mobile telephone) and represent a single static view of that coverage at one instance. During cell site analysis there will be many screens obtained but for the purposes of this discussion this single screen image will do the job. Firstly, the reader will need to comprehend, at least, an interpretation that can be given to the identifiers in the screen image above.

TOP ROW
1. Chan: this indicator refers to the Broadcast Control Channel number.
2. RxLv: this indicator refers to the received strength of signal at the test handset measured in deciBel milliwatts, (dBm), where dBm is the notion for the measurement of power of the received radio signal e.g -75dBm.
3. C1: this is a quality indicator (path loss criterion) and is used for cell selection and cell reselection. The parameters are determined from the signal strength, the minimum received power levels for initiation of signals between the mobile and network, the maximum transmit power for accessing the network and the power of the mobile phone itself.
4. C2: this is an indicator used only for cell reselection optimisation and identifies parameters to aid the mobile phone in its cell reselection process.

LEFT COLUMN
5. 'ACT' denotes the strongest, thus dominant, serving cell coverage at that location providing the best quality associated with the BCCH number (Chan). Meaning the mobile telephone has completed the cell selection/reselection processes for normal service and has chosen a cell from which it plans to receive all available services (known as "camping on a cell").
6. 'NC2-NC6' denotes other cells available in an area that may equally offer service, but that the mobile phone has not camped upon them. However, the mobile network is aware that the mobile phone has choices available to it. Displayed beside the NCs are the cells, identified by their respective Broadcast Control Channel (BCCH) numbers.

OBSERVATIONS

If it is accepted that Chan (Channel) identifies the BCCH frequencies of the radio coverage that the receiver (mobile telephone) has detected in the ether (or as Professor Clerk-Maxwell (1886) so put it "ethereal wind" when describing electro-magnetic energy in the air ) then the consideration of the RxLv (signal strength) and C1 and C2 can then be considered.

Signal Strength

The maximum received signal strength at the receiver is understood to be -40dBm for GSM (see e.g GSM 11.10 etc) and commonly -40dBm is said to be at or very close to the transmitter. However, when looking at Radio Test Measurement 1 for ACT and NC1 we see Chan 81 and 87 detected at the receiver with signal strength -27dBm and -37dBm respectively. This raises the suggestion of saturation by the transmitter's coverage determined at the receiver, where the receiver is located on the ground. So what could be the reason for this?

One suggestion might be the sensitivity at the receiver is out of spec. For this instance it would be wrong. When I conduct cell site analysis I have five (5) mobile telephones with me set in network engineering mode in order to account for a faulty handset and other anomolies and for the purposes to determine when several mobile telephones are switched ON and side by side whether they would detect and camp on the same cell (GSM terminology for radio coverage from a particular Mast) or other cells. For the radio test measurements in this case all five (5) were switched ON and all detected Chan 81 with signal strength ranging from -27dBm / -30dBm.

So if it is accepted that the mobile telephones collectively are not revealing false-positives, what other occurrence might cause this to occur. To determine this matter readers may wish to investigate by way of the GSM Standards to comprehend the standard for upper and lower limits of signal strength and review the requirements for BTS (Base Transceiver Station) transmission power etc.

It may equally be helpful to mention at this point that the signal strengths for NC2 (- 44dBm), NC3 (-67dBm), NC4 (-68dBm), NC5 (-69dBm) and NC6 (-70dBm) are very respectable levels of signal strength being that they are of high quality. When I refer to high quality I am of course referring to the term as used by the objective GSM Standard GSM03.22. It contains a useful reference when considering the quality of signal strength (RxLv) recorded in radio test measurements that a mobile network "shall be understood to be received with high quality signal if the signal level is above ‑85 dBm".

Moreover, GSM05.08 identfies the threshold RXLEV (same as RxLv) on the downlink for handover process to commence. Typical range -103 to -73 dBm. Thus NC2 to NC6 received signal strength at the receiver, being above -73dBm, could one conclude from that were the mobile telephone to have camped on either one of NC2 to NC6 the network is unlikely to handover the mobile to another cell in the list? My observation to any reader would be investigate the GSM Standards in order to consider all the elements in order to produce a more rounded opinion on this matter.

C1/C2

Cell selection and cell reselection are rather complex and convoluted matters to discuss in this short discussion thread. My observation to the reader would be to look at C1/C2 and see whether at first instance the threshold results are identical or different? What does it mean if they are not identical? Also look closely to see if cells are indicated as not available for selection or reselection - denoted in Radio Test Measurement 1 as -99. Why would a cell not be selected and/or reselected? Is it due to poor signal strength; the mobile telephone has calculated its own power capability as low; or is it detecting interference etc?

The above is just a fraction of the information that needs to be considered during and following cell site analysis and from the little I have extrapolated above means that a casual approach to radio test measurements and cell site analysis can result in erroneous conclusions being drawn.

For more on Cell Site Analysis, see Cell Site Analysis Part 1.