Reducing Operator Carbon Footprint with RAN Sharing - Case Study
During recent years RAN (Radio Access Network) Sharing has become more popular when mobile operators increasingly see a need for infrastructure consolidation to combat declining profit margins. In RAN sharing both the passive site infrastructure and the active telecom equipment are shared to maximize cost savings. The operators still keep some level of independence through their separate core networks and services platforms.
RAN Sharing is driven by Operators’ need to reduce network and operational cost, to share investments in new technology and to reduce time to market for new services. But RAN Sharing also brings significant environmental benefits. Through reductions in network energy consumption, carbon emissions are dramatically reduced.
To illustrate this, Sustainable Approach carried out a case study covering a shared 3G RAN in Europe. The shared RAN consists of 3-sector sites, each site having one of four NodeB configurations installed. The RAN is connected to the two operators’ core networks using the Multi Operator Core Network (MOCN) feature. Offered service level is Dual Cell HSPA. Typical power consumption per NodeB configuration is shown in the below picture:
As can be seen as much as 50% of the NodeB power consumption is independent of traffic load. Typical consumption for transmission, RNCs, IP routers and site cooling was added. The consumption in these elements has limited dependence on traffic load compared to the NodeB and was therefore assumed to be constant.
We collected one week’s hourly traffic data from each NodeB in the shared RAN. Combining this information with data on installed configurations made it possible to estimate the NodeB load hour by hour by comparing the measured throughput with the load level triggering congestion.
The data traffic contribution from each Operator's subscribers will be different from site to site and from time to time due to different traffic distributions and usage patterns. When plotting the sites ranked after data throughput in a diagram, we see that the traffic in some sites is dominated by one of the operators whereas other sites have a more even split of traffic. If we plot the same type of diagram but with only one Operator’s traffic we see an almost identical slope when we reorder the sites according to throughput for only that Operator, see simulation for a small number of sites below:
Assuming each Operator provides 50% of the total traffic on aggregated network level, the corresponding hourly load and configurations for a standalone RAN could thus be estimated by halving the hourly throughput values and applying the same upgrade thresholds as for the shared RAN.
These calculations provided NodeB configuration and load hour by hour during the week in question for each site in the shared and standalone RANs respectively. Total weekly power consumption could be calculated using the curves in the above power consumption diagram. When scaling up the results to a full year we could conclude that the shared RAN consumes 20,8 GWh whereas one standalone RAN consumes 18,4 GWh. This means that the shared RAN provides a 43% reduction in total energy consumption when compared to the two Operators running their own separate RANs.
The resulting environmental and cost benefits of RAN sharing are significant. The reduced energy consumption translates into a saving of almost 700 Euro per site and year (electricity cost 0,12 Euro per kWh assumed). The corresponding reduction in CO2 emissions is 7 871 tonnes per year if the electricity used is produced in coal power plants (emission factor 483 g CO2 per kWh assumed).
This case study clearly demonstrates the environmental and cost benefits of the reduction in electricity consumption made possible with RAN sharing. Further reductions are possible, in the same way as for the standalone network, through implementation of various power saving features offered by the system vendors. RAN sharing is one key element in making the ICT industry more sustainable.