La Federación de Amigos de los Museos en España

This section identifies some of the frequently asked questions (FAQs) that arise from using the Access model.

Q1. I can't edit a certain cell - why ?

A1. The sheet is protected, and the only cells that the user is supposed to edit are those that are unprotected - all of these are colour coded as described in the Styles section above.

Q2. I can't see the formula in a certain cell. Why ? how can I view it ?

A2. The sheet is protected. To unprotect the sheet, use the Excel command Tools - Protection - Unprotect Sheet.

Q3. Some columns / rows are hidden… how can I view them ?

A3. The model uses Data Grouping to allow collapsed / expanded views of the data. To alter the view you need to Unprotect the sheet (Tools / Protection / Unprotect Sheet), then change the Grouping by clicking on the + or – symbol for the relevant columns or rows

Q4. Some of the results are shown as errors eg #VALUE or #N/A. Why ?

A4. Some of the input data fields (or combinations of such data) are not valid. The most common examples are: text values input instead of numerical values; or zero values input for fields that should be non-zero.

Q5: What is the difference between Input Data (shaded yellow) and Input Parameters (shaded green/blue) ?

5_{The exception is that there is one user-defined function, AvD(distance, radius) that is used to calculate the}

average distance between the points inside a circle (representing eg customer sites), of a given radius, and a fixed point (representing eg a PDP, RSS, or SDP) at a given distance from the centre of the circle.

A5: Input Parameters are generally data that should only be changed if you understand the consequences in full. Eg it may change the meaning of other data, or it may act as the dimensions of a number of arrays. Always validate any changes to Input Parameters by using the Audit Tools (visible via Tools - Auditing - Show Auditing Toolbar) to explore all dependent cells and confirm that the consequences of the change are valid.

Q6: The model is showing some error message(s) in bold red text - is there a bug? Can I ignore them?

A6: These messages are built into the model to check the validity of the input data and the intermediate results. They indicate problems with the data rather than bugs in the model. Read the message(s) and decide the best course of action to take. If the highlighted cell or the message is in red or starts with the word "Error", then it needs to be addressed; If it is coloured orange, or starts with "Warning" or "NB" then it may be perfectly acceptable to ignore it. (NB such error messages may also appear in the other models.)

Q7: Some of the cells in the output sheets are showing as #VALUE or #N/A - what is going on?

A7: The most likely cause of this is that some of the input data is of the wrong type, eg Excel has interpreted your input as text when it should be numeric.

Q8: I want to derive some other key results from the Access model, besides those passed to Consolidation. How can I do this?

A8: Generally this would require development of the model; however, before doing so, have a look at the relevant calculations to see what data is already available.

It may be possible to start a new workbook and link it to the data in the Access model, and do the further analysis there.

For example:

• there are also some useful results calculated in the sheet "C_Resources_Used", giving results by geotype and by zone.

• Table 1.2 in the sheet O_to_Consolidat ion gives a summary of costs below the scorched node broken down into about 20 major cost categories.

Q9: How can I optimise the Access network?

A9: The main opportunity for reducing the cost by optimisation (as opposed to reducing costs or reducing the capacity of the network) is by varying the design of the copper part of the Access network. This is done in Table 5 in the sheet I_Zones_Data. For each zone in the sample, you can vary the following:

• Inside the Tatort (main urban area for the zone):

− size of PDPs and of SDPs. The suggested approach is to aim for a ratio, going up from NTP towards RSS, of successive nodes serving 10x to 30x the number of customers served by the nodes in the next layer down; hence some zones may have three layers in their access network (RSS-PDP, PDP- SDP, and SDP-NTP) whilst others have two layers, or (where there are very few lines in the zone) even only one layer. This approach is only a suggestion and the user should experiment with different solutions. The true optimum will

depend on the geographical parameters for each sample zone and on the cost-volume relationships for both cable sizes and for distribution points. − strategy for locating the PDPs and SDPs - close to the RSS (minimise total

pair-km) or close to the customer (minimise total cable km). The suggested approach is to use a location parameter in the range 0.25 to 0.5, but it is worth experimenting with values in the range 0 to 1 and occasionally higher.

− if the RSS is outside the Tatort – decide whether to connect the Tatort, using one large “Super-PDP” serving the Tatort as a satellite from the RSS. If using a “Super-PDP”, you can vary the strategy for locating it.

• Outside the Tatort:

− Same set of parameters – all of which can be set independently of those for the network inside the Tatort - except that there is no “Super-PDP”.

Q10: I have changed the details of the 25 sample switch zones - eg weightings, and numbers of lines in each zone - but the cost of the copper network has not changed much. Why?

A10: The model uses the figures that you input for the total number of copper lines

(NTPs), and the total area of the country, as a control total. These are input in Tables 1.1 and 1.2 and 5 of the worksheet I_Access_Services. If the weighted sum of the results for the sample zones gives too few lines and too small an area, the model adjusts the data for the zones in the sample, to correct for this bias.

Q11: The copper cable and node calculations give errors and warning messages for a number of zones - does this matter?

A11: These messages are provided to help spot errors and inconsistencies in the input data. Anything flagged in red or describing an Error should be investigated and resolved, Anything flagged in orange or described as a Warningshould be noted, and avoided if it can be done easily or it time allows, but the condition is not in itself a problem.