Energy consumption of telecommunication access networks

6.2 VDSL2-Vectoring 6.2.1 Access network The model region consists of 25,311 subscribers and 212 street cabinets (see Figure 14), which are assigned to six central offices. By updating all 212 existing street cabinets and central offices with VDSL2-Vectoring DSLAMs, the minimum data rate of 50 Mbit/s can be provided to 21,403 subscribers. On the other hand, at 3,908 subscribers the minimum data rate of 50 Mbit/s will not be reached. That corresponds to approximately 15% of total subscribers. Results for the model region in total (100% homes connected) Number of connection points Avg. number of connection points per street cabinet Number of subscribers Avg. number of subscribers per street cabinet Street cabinets existing 212 14,096 66 21,403 101 Street cabinets new 326 2,659 8 3,908 12 Street cabinets total 538 16,755 31 25,311 47 Figure 14: Table of subscribers and connection points per street cabinet – existing and new ones. One of the main reasons that these 3,908 connections cannot be supplied is that the cable lines between the street cabinet and the connection point are too long. To solve this problem, new street cabinets closer to the subscriber have to be built. To estimate the number of additional street cabinets, new locations for the additional street cabinets were determined by georeferential analysis, which generates amaximumof subscribers per street cabinet within a certain radius. This analysis leads to 326 additional street cabinets. The average number of subscribers per street cabinet drops from 101 to only 12. As a result, the financial and technical expenses per subscriber increase significantly. This is illustrated again in Figure 15. In this figure, all street cabinets of the model region are assigned to a DSLAM size class, which reflects the maximum number of subscribers per DSLAM. 361 of the 538 street cabinets (approximately 67%) use a DSLAMwith 48 ports. The average number of subscribers in this DSLAM size class is approximately 12 and significantly smaller than the possible 48 subscribers. That is not very efficient. In the higher DSLAM size classes the average number of subscribers per street cabinet is much closer to the maximum per DSLAM than in the 48 port class. Subscribers per DSLAM by DSLAM size (100% homes connected) Max ports per DSLAM Number of street cabinets Number of connection points Number of subscribers Avg. number of subscribers per street cabinet 48 361 3,031 4,368 12 96 68 3,376 4,996 73 144 61 4,961 7,320 120 192 36 3,789 5,977 166 >192 12 1,598 2,650 221 Total 538 16,755 25,311 47 Figure 15: DSLAM size classes and numbers of assigned subscribers per DSLAM street cabinet. Overall, Figure 15 shows the challenges of a rural VDSL2-Vectoring expansion – long cable lines and only few customers in a given area. 19