radio communication failure

[serworacle]

Hi everyone, this is the topic I'm looking for.
In jeppessen, as everyone knows, It says


INSTRUMENT METEOROLOGICAL CONDITIONS

A controlled flight experiencing communication failure in IMC, or where it does not appear feasible to continue in VMC shall:

1. set transponder to code 7600;
   
2. maintain for a period of 7 minutes the last assigned speed and level or the minimum flight altitude, if the minimum flight altitude is higher than the assigned level. The period of 7 minutes commences:
   1. if operating on a route without compulsory reporting points or if instructions have been received to omit position reports:
      • – at the time the last assigned level or minimum flight altitude is reached, or
        
      • – at the time the transponder is set to Code 7600, whichever is later, or
        
   2. if operating on a route with compulsory reporting points and no instruction to omit position report has been received:
      • – at the time the last assigned level or minimum flight altitude is reached, or
        
      • – at the previously reported pilot estimate for the compulsory reporting point, or
        
      • – at the time of a failed position report over a compulsory reporting point, whichever is later;
        
        3.thereafter, adjust level and speed in accordance with the filed flight plan;
        
        4.if being radar vectored or proceeding offset according to RNAV without a specified limit, proceed in the most direct manner possible to rejoin the current flight plan route no later than the next significant point, taking into consideration the applicable minimum flight altitude;
        
        5. proceed according to the current flight plan route to the appropriate designated navigation aid serving the destination airport and, when required to ensure compliance with para 6 below, hold over this aid until commencement of descent;
        
        6. commence descent from the navigational aid specified in para 5 above at, or as close as possible to, the expected approach time last received and acknowledged or, if no expected approach time has been received and acknowledged, at or as close as possible to, the estimated time of arrival resulting in the current flight plan;
        
        7. complete a normal instrument approach procedure as specified for the designated navigation aid, and
        
        8.land, if possible, within 30 minutes after the estimated time of arrival specified in para 6 above or the last acknowledged expected approach time, whichever is later

for example, if we fly at fl 360 on route to Porto from Athens and and fly according to the flight plan, when do we start to descent.
it doesn't seem logic to me keeping 360 until over nav aid or fix then descent. Or should we descent when top of descent come? This is more logic because like it says we proceed with the flight plan and also ATC knows when we descent with squawk 7600.
My teacher and I have an argument on this subject and he says we can't descent like that.
Actually I am looking for cleaner explanations(official documents) than jeppessen does for descending having radio failure on IMC to change his .

I hope you can help me.

Thanks in advance.