[RM Ch 3] Energy efficiency updates

As discussed at RM calls, I have edited this section, changed the order and added more info, and references to NGA.

doc/ref_model/chapters/chapter03.rst

@@ -1982,40 +1982,21 @@ In virtualized environments AF_XDP could be used as interface between guest Kern
 Energy efficiency
 -----------------
 
-The energy efficiency should be an overall requirement for both the cloud infrastructure itself and the workloads
-hosted by this infrastructure. It is defined as "the relation between the useful output and energy consumption" by
-`ITU-T L.1330 <https://www.itu.int/rec/T-REC-L.1330>`__ :cite:p:`itutl1330` for telecommunication networks and
-`ETSI EN 303 471 <https://portal.etsi.org/webapp/workprogram/Report_WorkItem.asp?WKI_ID=50095>`__ :cite:p:`etsien303sp471` for NFV,
-the useful output being a metric which represents the capacity provided by the service whose energy efficiency is
-assessed.
-
-As an example, the useful output of a traffic forwarding function can be the data volume forwarded (e.g., measured
+Energy efficiency should be an overall requirement for the cloud infrastructure itself, the workloads
+hosted by this infrastructure, and the interface layer between them. 
+
+For telecommunication networks, energy efficiency is defined by `ITU-T L.1330 <https://www.itu.int/rec/T-REC-L.1330>`__ :cite:p:`itutl1330`
+as "the relation between the useful output and energy consumption", the useful output being a metric which represents the capacity provided by the service whose energy efficiency is
+assessed. As an example, the useful output of a traffic forwarding function can be the data volume forwarded (e.g., measured
 in Byte) and the assessment of its energy efficiency is then based on the ratio between this volume and the energy
 consumed for processing it (e.g., measured in Watt.hour) :
-Energy Efficicency (B/Wh) = Traffic Volume / Consumed Energy
+Energy Efficicency (B/Wh) = Traffic Volume / Consumed Energy.
 
-The method for assessing energy efficiency depends on the service targeted and the objectives. For NFV, ETSI proposes
-a method for production environment in `ETSI EN 303 471
-<https://portal.etsi.org/webapp/workprogram/Report_WorkItem.asp?WKI_ID=50095>`__ :cite:p:`etsien303sp471` and another one for laboratory one
-in `ETSI ES 203 539 <https://portal.etsi.org/webapp/workprogram/Report_WorkItem.asp?WKI_ID=47210>`__ :cite:p:`etsies203sp539` (which is
-a common work with ITU-T which published as `ITU-T L.1361 <https://www.itu.int/rec/T-REC-L.1361>`__ :cite:p:`itutl1361`).
-
-Whatever the method and the service, it requires the cloud infrastructure to provide some **energy consumption metrics**
-for different parts of the infrastructure hardware (server, CPU etc.) as included in
-:ref:`chapters/chapter04:internal performance measurement capabilities`.
-These metrics can be an amount of consumed energy (measured in Joule or Watt.hour) or a real-time power utilisation
-(measured in Watt or Joule/second) as proposed by `DMTF Redfish DSP0268 2022.2
-<https://www.dmtf.org/sites/default/files/standards/documents/DSP0268_2022.2.pdf>`__ :cite:p:`dmtfredfish` which specifies metrics
-EnergykWh and PowerWatts for this purpose.
-
-Some relevant information regarding NFV energy efficiency can also be found in `Open RAN Technical Priority - Focus
-on Energy Efficiency (March 2022) <https://www.o-ran.org/ecosystem-resources>`__ :cite:p:`oranenergyeff` and `QuEST Forum - NFV
-Workload Efficiency Whitepaper (October 2016)
-<https://tl9000.org/resources/documents/NFV%20Workload%20Efficiency%20Whitepaper.pdf>`__ :cite:p:`questnfvwlenergyeff`.
+As elaborated in the Next Generation Alliance's whitepaper `NGA Green G <https://nextgalliance.org/white_papers/green-g-the-path-towards-sustainable-6g/#:~:text=Green%20G%3A%20The%20Path%20Toward%20Sustainable%206G%20shows%20how%20the,while%20accelerating%20progress%20toward%206G>`__ :cite:p:`ngagreeng`,
+with the global migration from 4G to 5G, one can observe the rise in data center power consumption with the parallel reduction in the energy consumption of core network 
+elements. This observation emphasizes the importance of the energy efficiency on the infrastructure and workload levels, and on the interface layer between them. 
 
 Examples of opportunities for the energy demand and cost reductions for the telecommunications operators are classified below.
-Only the first group, which is related to the optimisation on the workload to infrastructure interface level, is relevant for 
-this Reference Model.
 
 - Optimisation based on workload load demand, enhanced by AI-based smart monitoring
   - Smart sleep and shutdowns of elements of infrastructure
@@ -2034,3 +2015,26 @@ this Reference Model.
   - Sustainable energy generation
   - Procurement of green energy
   - Fuel usage optimisation
+
+In this Reference Model, the focus is on the first group, which is related to the optimisation on the workload to infrastructure interface level.
+
+The method for assessing energy efficiency depends on the service targeted and the objectives. For NFV, ETSI proposes
+a method for production environment in `ETSI EN 303 471
+<https://portal.etsi.org/webapp/workprogram/Report_WorkItem.asp?WKI_ID=50095>`__ :cite:p:`etsien303sp471` and another one for laboratory one
+in `ETSI ES 203 539 <https://portal.etsi.org/webapp/workprogram/Report_WorkItem.asp?WKI_ID=47210>`__ :cite:p:`etsies203sp539` (which is
+a common work with ITU-T which published as `ITU-T L.1361 <https://www.itu.int/rec/T-REC-L.1361>`__ :cite:p:`itutl1361`).
+
+Whatever the method and the service, it requires the cloud infrastructure to provide some **energy consumption metrics**
+for different parts of the infrastructure hardware (server, CPU etc.) as included in
+:ref:`chapters/chapter04:internal performance measurement capabilities`.
+These metrics can be an amount of consumed energy (measured in Joule or Watt.hour) or a real-time power utilisation
+(measured in Watt or Joule/second) as proposed by `DMTF Redfish DSP0268 2022.2
+<https://www.dmtf.org/sites/default/files/standards/documents/DSP0268_2022.2.pdf>`__ :cite:p:`dmtfredfish` which specifies metrics
+EnergykWh and PowerWatts for this purpose.
+
+Some relevant information regarding NFV energy efficiency can also be found in `Open RAN Technical Priority - Focus
+on Energy Efficiency (March 2022) <https://www.o-ran.org/ecosystem-resources>`__ :cite:p:`oranenergyeff` and `QuEST Forum - NFV
+Workload Efficiency Whitepaper (October 2016)
+<https://tl9000.org/resources/documents/NFV%20Workload%20Efficiency%20Whitepaper.pdf>`__ :cite:p:`questnfvwlenergyeff`.
+
+