Identifying Some Techno-Economic Criteria in PLC/BPL Applications and Commercialization Paul A Brown White Box Associates 30 Applerigg Kendal, Cumbria, LA9 6EA, UK E-mail: pab@whiteboxassociates.co.uk ABSTRACT developers need engineering expertise, investment and a detailed knowledge of EDNs as a means of providing a sustainable transmission The development of first-pass simplified medium for telecommunication services. business models for power line communication Investors do not necessarily possess engineering (PLC) systems is necessary in order to provide expertise and therefore they require the an early focus on the key technical and financial developer’s skill and knowledge. Similarly the criteria by which investment and the return on developers need financing in order to sustain investment (ROI) might be considered. For PLC development. So what kind of first-pass example, PC based spreadsheet modeling information might be useful to investors? If we provides a useful mathematical tool for assume that PLC / BPL is now at a stage of identifying sensitivities in the broadband power potential mass-deployment and R&D continues line (BPL) business cases by enabling rapid to enhance PLC systems development then, most comparisons between electrical distribution of all, we require to scope out the potential scale network (EDN) technical parameters, BPL of the ROI. equipment specifications, system features and customer expectations. It is important for both For example, investors need to know such things developers and investors to understand the as: technical challenges and business opportunities offered by PLC. • Is the PLC business case sensitive to equipment costs such as customer 1. INTRODUCTION premises equipment (CPE), repeaters, PC based spreadsheet modeling and graphical coupling devices etc? analysis provide a first-pass means of identifying • Is BPL system design sensitive to and comparing the sensitivities of both technical service transmission speeds e.g. 256, and financial input data such as EDN topography, 512 kb/s etc? channel characteristics, PLC system cost, • Does EMC regulation impact PLC / capability, capacity, quality of service (QoS) and BPL system design? potential penetration rates in order to support an • Is voice over Internet Protocol (VoIP) acceptable ROI. achievable over PLC systems? • What might be the anticipated churn In order to develop PLC systems there are a rate? number of fundamental requirements: • What are the potential PLC / BPL operational and marketing overheads? • A power line infrastructure i.e. EDN • Investor(s) in PLC R&D Whilst potential customers might, for example, • PLC developer(s) with the necessary focus on the following issues: expertise • Installation fee The power line is a pervasive element and is • Monthly, quarterly or annual service therefore not a problem. Investors need to feel charges confident that there is a viable and potentially • QoS parameters long term business opportunity in PLC. PLC
2. CONSIDER BPL NETWORK TOPOLOGY networks. It also illustrates how these networks further interconnect utilizing PLC overlays on In a first-pass BPL business plan it will be LV EDN, medium voltage (MV) EDN and necessary to make some assumptions about the incorporates fiber optic backhaul. These network topology. These assumptions are network combinations include metropolitan area needed in order to consider specific deployment networks (MANs) and the interfaces to Internet scenarios whilst still being general enough to be Service Providers (ISPs). This model is typical applied to a wide variety of network topologies. of most all of the major European BPL The PLC network is of necessity a hierarchy of deployments to date. networks. This global perspective of electricity and telecommunication transmission and Corporate Intranet Network Management distribution (T&D) infrastructure is illustrated in MAN LV S/Stn Figure 1 and is shown as a hierarchy of electricity distribution (wired) and PLC Repeater telecommunication transmission (fiber optic) Backbone Network LV S/Stn networks. PLC Concentrator LV transformer - substation LV EDNs ISP Gateway Fiber Optic MANs SDH Fibre Core LVEDN MVEDN Fig. 3: Fiber Optic MV and LV Networks 3. DATA INPUT VERSUS OUTPUT If we consider, for example, EMC issues which affect PLC system operation then we might choose to examine a range of relevant input parameters such as: the PLC equipment launch MV EDNs power spectral density (PSD), the average attenuation of the channel, the channel noise floor, and the minimum signal to noise ratio Fig. 1: PLC – Hierarchy of Networks (SNR) required for adequate operation of the PLC equipment. Research in Europe [1] has Figure 2 illustrates a section of typical UK low shown that with a nominal channel attenuation voltage (LV) underground (UG) EDN (ATT) of 0.4 dB/m (i.e. below 10 MHz), a flat interconnecting residential customer premises to noise floor PSD of -120 dBm/Hz and a minimum the local LV substation transformer. SNR of 15 dB the distance (D) covered by a single customer premises modem, or repeater, might be estimated as follows: D max = (PSD tx – PSD noise – SNR min ) = ATT dB/m = (- 50- (-120) – 15)m = 137.5 m (1) 0.4 If we now model the average LV transformer to building distance (e.g. by reference data gathered from the respective EDN) and assuming a best- fit Gaussian distribution, with an average Fig. 2: Section of a UK LV EDN Diagram distance of, for example, 100m and a standard deviation of say 50m. We might then use this Figure 3 shows an overall schematic view of the statistical distribution to estimate the cumulative network infrastructure including the integration statistical distribution of the distances between the buildings and the LV EDN transformer. of domestic (residential) customers, small businesses and corporate telecommunication From this initial output data we might choose to
further graph ‘Distance to the LV Transformer’ diagrammatic appoach to depict physical data against ‘Percentage of Buildings (customer sources. First by examining a particular network premises) served by a transformer. The element in isolation and then when integrated graphical results obtained for such an example with a number of similar elements such as might are illustrated in Figure 4. be found in practice. If we then examine the PLC network component in isolation and then integrated with other similar components and by applying a variety of, potentially, relevant mathematical formulas we might make comparisons between calculated and measured input / output parameters. This should enable validation of the most applicable formula whose calculated results align most accurately with the practical results obtained by measurement. For example, if we assume a single PLC cell as a first-pass model (i.e. a single element), as shown in Figure 5, then integrate this single cell with a Fig. 4: Reach Vs Percentage of Buildings number of similar cells, as we might expect in practice, we might then deduce the cumulative As can be seen from Figure 4 approximately effect of a number of such cells on the noise 80% of buildings are below the 137.5m threshold floor at a given distance [3]. and might therefore be overlayed with BPL without the need for a repeater. The PLC S/Stn Cell Now from Equation 1 and interpolating for a BPL launch PSD of -50dBm/Hz we can reach Electricity 137.5m, at maximum, from the substation Electricity & Telecomms PLT Basestation transformer without the need for repeaters. Therefore we already have some cost inference from our modeling i.e. there will be additional nMbit/s cost in providing and installing a repeater if it is UK typical UG Distributor 250m (multiplexed) 150 Customer Premises per S/Stn required to extend the reach to pass a further 20% of the customers premises and still comply Fig. 5: Single PLC Substation Cell with EMC requirements (i.e. launch PSD does not exceed -50dBm/Hz). Figure 6 shows the integration of a number of such PLC cells around a notional ‘quiet’ radio So now we have a simple example of EDN input site where the noise floor is, approximately, -15 data (i.e. parameters such as cable attenuation, dBm/Hz measured in a 9kHz bandwidth. launch PSD...etc) being formulated (Eq. 1) and the resulting data output in graphical form. Equation 1 requires only simple mathematical operations and can easily be applied in spreadsheet form (e.g. Excel) and we can therefore easily modify the input data in order to test sensitivities. 4. EMC – CUMULATIVE EFFECTS Practical EMC measurements of both the input and output parameters of PLC networks (i.e. launch PSD and radiated emission levels) and Fig. 6: Multiple PLC Substation Cells their subsequent comparison with calculated values are of considerable importance in PLC Now we can visualize the situation we might system development [2]. Therefore we might choose to compare the possible propagation consider some further aspects of using a modes, at or near the Earth’s surface, which
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