1、 ETSI TR 102 269 V1.1.1 (2003-12)Technical Report PowerLine Telecommunications (PLT);Hidden Node review and statistical analysisETSI ETSI TR 102 269 V1.1.1 (2003-12) 2 Reference DTR/PLT-00011 Keywords analysis, hidden node, transmission ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FR
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7、ts Members and of the 3GPP Organizational Partners. ETSI ETSI TR 102 269 V1.1.1 (2003-12) 3 Contents Intellectual Property Rights4 Foreword.4 Introduction 4 1 Scope 5 2 References 5 3 Abbreviations and symbols 5 3.1 Abbreviations .5 3.2 Symbols5 4 Measurement method and measurement locations.6 5 Exa
8、mple test results6 6 Principles of statistical evaluation of noise- and TTL-data8 7 Statistical evaluation of noise measurements.9 8 Statistical evaluation of measured TTL11 9 Dependencies from national particularities concerning installation- and earthing techniques in Germany, The Netherlands and
9、Spain19 History 20 ETSI ETSI TR 102 269 V1.1.1 (2003-12) 4 Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members,
10、and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/webapp.etsi.org/IPR/home.asp).
11、 Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the presen
12、t document. Foreword This Technical Report (TR) has been produced by ETSI Technical Committee PowerLine Telecommunications (PLT). Introduction In order to study and compare characteristics of the LVDN network in different countries a STF (Special Task Force) was set-up. The present document is one o
13、f the four TRs which present the result of the work of the STF (TR 102 258 5, TR 102 259 6 and TR 102 270 3). The present document takes into account matters like earthing variations, country variations, operator differences, phasing and distribution topologies, domestic, industrial housing types al
14、ong with local network loading. The measurement set-up, the measurements as such, the used software the site reports and parts of the analysis are common for all the TRs and is collected in the TR 103 270 3. ETSI ETSI TR 102 269 V1.1.1 (2003-12) 5 1 Scope The present document shows results from Tran
15、sverse Transfer Loss (TTL) measurements performed in Germany, The Netherlands and Spain. It investigates the distribution of the TTL-values in respect to the carrier-frequency, to the relative location of the sockets, to the phase conditions between the sockets and to the national LVDN-particulariti
16、es (wiring technology, earthing etc). These data are basic for the development of realistic hidden node models required for the development and/or the test of MAC-protocols as well as for the assessment of the performance in presence of hidden nodes. 2 References For the purposes of this Technical R
17、eport (TR) the following references apply: 1 ITU-T Recommendation G.117: “Transmission aspects of unbalance about earth“. 2 IEEE Transactions on Electromagnetic Compatibility (Vol 41, No. 1, pp 3-14): “A probe for the measurement of electrical unbalance of networks and devices“, Ian P. Macfarlane. 3
18、 ETSI TR 102 270: “PowerLine Telecommunication (PLT); Basic LVDN measurement data“. 4 ETSI TR 102 175: “PowerLine Telecommunications (PLT); Channel characterization and measurement methods“. 5 ETSI TR 102 258: “PowerLine Telecommunications (PLT); LCL review and statistical analysis“. 6 ETSI TR 102 2
19、59: “PowerLine Telecommunications (PLT); EMI review and statistical analysis“. 3 Abbreviations and symbols 3.1 Abbreviations For the purposes of the present document, the following abbreviations apply: BALUN BALanced to UNbalanced transformer EDP Electronic Data Processing LCL Longitudinal Conversio
20、n Loss LVDN Low Voltage Distribution Network OFDM Orthogonal Frequency Division Multiplexing STF Special Task Force ToR Terms of Reference (see note) TTL Transverse Transfer Loss NOTE: For Specialist Task Force 222 (MB). 3.2 Symbols For the purposes of the present document, the following symbols app
21、ly: a frequency space for which noise or TTL is below a specified value k specified threshold, frequencies are usable when the TTL or noise are below k ETSI ETSI TR 102 269 V1.1.1 (2003-12) 6 4 Measurement method and measurement locations For the analysis of hidden node problems, the signal strength
22、s and the noise levels of different connection points to the LVDN must be known. The noise levels were measured symmetrically with the LCL-measurement adapter according to Macfarlane 2. The differential mode design impedance of the adapter is Z = 100 . Measurement locations were selected in order to
23、 get results from different countries, from different types of installations and from buildings of different use. All measurements were performed during day-time with household appliances, EDP-equipment and production machinery normally connected to the mains. For the estimation of the signal streng
24、th available at a receiver location the output level of the transmitter and the attenuation of the network between transmitter and receiver location must be known. The output level is a specific modem design parameter and is therefore a priori unknown. The attenuation is a characteristic of the netw
25、ork and can be measured by Transverse Transfer Loss (TTL) according to ITU-T Recommendation G.711 1. Details of the measurement method and connection to the LVDN can be seen in TR 102 270 3. A modem designer will be able to determine the influence of hidden nodes by including the data presented in t
26、he present document into his system analysis, e.g. by calculating the data throughput both real and for the limit case of Shannon. Since the present document must be independent of any specific modem design, further evaluation of the data cannot be provided. The present document is limited on the an
27、alysis of noise floor- and attenuation- measurements. 5 Example test results In general, both noise floor and TTL are strongly dependent on frequency and measurement location. Therefore a statistical evaluation must be performed in order not to consider simply the absolute worst case or any other in
28、tuitively chosen conditions. The system parameters shall be chosen in such a way, that a defined percentage of the LVDN-sockets show equal or better results than the assumed limit case. Figure 1 shows typical results of noise measurements at two plugs at different measurement locations (red: Germany
29、, green: Spain). Figure 2 shows TTL at the same locations. Comparison of the different noise and TTL plots show that no specific behaviour can be observed regarding the country or the installation types (earthing variations). Therefore it is not necessary to distinguish between principle country- an
30、d installation-types for noise measurements. For the statistical evaluation of TTL two groups and two subgroups have been defined: a) Transmitter and receiver located in the same flat or the same (small) house: 1) Transmitter and receiver connected to same LVDN-phase. 2) Transmitter and receiver con
31、nected to different LVDN-phases. b) Transmitter and receiver located in different flats or houses in the neighbourhood. ETSI ETSI TR 102 269 V1.1.1 (2003-12) 7 0102030405060700 5 10 15 20 25 30U indB(V)f in MHzNOTE: - - - - - - -: The Netherlands _: Spain Figure 1: Example noise floor-measurements 1
32、0152025303540455055600 5 10 15 20 25 30TTLindBf in MHzNOTE: - - - - - - -: The Netherlands _: Spain Figure 2: Example TTL-measurements In total 69 noise floor measurements, 519 group A-TTL measurements and 124 group B-TTL measurements were performed. Each noise measurement consists of 291 single fre
33、quency points and each TTL measurement consists of 59 single frequency points. Typical variations of the noise floor and TTL at a given measurement site are shown by figure 3, where all results measured in one flat are plotted in a single diagram. ETSI ETSI TR 102 269 V1.1.1 (2003-12) 8 010203040506
34、070800 5 10 15 20 25 30f / MHzNoise floor in dB(V)01020304050607080900 5 10 15 20 25 30ATT /dBf / MHzNOTE: Gartenstrasse, Stuttgart, Germany. Figure 3: Variation of noise floor and TTL at a single measurement site 6 Principles of statistical evaluation of noise- and TTL-data For a general view all f
35、requency plots were statistically evaluated. The empirical cumulative probability (using threshold k) was calculated and the contour lines for the probabilities of 20 %, 50 % and 80 % were chosen in figures 5 to 8. From such plot it is difficult to derive hidden node criteria for a specific modem de
36、sign, since these diagrams hide the spikes occurring on every measurement location. Therefore two other criteria were defined as shown in figure 4. TTLkfLargest WindowSecond WindowFigure 4: Definition of characteristic measures for hidden node analysis (TTL as example) Criteria applicable for modems
37、 with OFDM and similar broadband modulation schemes are the part of the frequencies, for which noise and TTL are below specified threshold k. It is calculated as the ratio between the frequencies marked in green in figure 4 and the whole investigated frequency range (1 MHz to 30 MHz). ETSI ETSI TR 1
38、02 269 V1.1.1 (2003-12) 9 rangefrequencywholekTTLorNoisespacefrequencya_)_(_%100= Another criteria applicable for modems which need a continuous frequency band is the size of the largest window (referred to as “size of window“), where noise and TTL are below specified threshold k. To consider modems
39、 needing two channels (up and downstream) an additional quantity (referred to as “sum of window size“), the sum of the sizes of the two largest windows is defined. Due to the fact that noise was measured in a frequency raster of 100 kHz and with a bandwidth of 10 kHz and that TTL was measured in a f
40、requency raster of 500 kHz it is possible that very narrow spikes are missed. 7 Statistical evaluation of noise measurements The general frequency-dependence of the noise floor can be seen in figure 5, where the cumulative probability is plotted on the noise-frequency plane as contour plot. The shor
41、t wave broadcast-bands are well visible. 0 5 10 15 20 25 30f in MHz0510152025303540U in dB(V)NOTE: from above: 80 % (green), 50 % (blue), 20 % (violet) cumulative probability. Figure 5: Noise floor in dependence of frequency for all sites The largest continuous window is evaluated in figure 6. ETSI
42、ETSI TR 102 269 V1.1.1 (2003-12) 100204060801000 5 10 15 20 25 30cumulativeprobability in%size of window in MHz100806040200certainty in%NOTE: from top to down: k = 10 dB(V) (red), 20 dB(V) (green), 30 dB(V) (blue), 40 dB(V) (violet). Figure 6: Size of largest continuous window, for which noise k Fig
43、ure 6 should be read in the following way: With a certainty of 0 % (never) a continuous frequency window of 29 MHz is available when a noise threshold k of 20 dB(V) (green curve) is assumed. This also describes the top right corner in figure 6. With a certainty of 80 % a continuous frequency window
44、of 12 MHz or more is available when a noise threshold k of 30 dB(V) is assumed. When a modem needs two channels and therefore requires two free frequency windows, figure 7 will give the analogous information. 0204060801000 5 10 15 20 25 30cumulative probability in %sum of window size in MHz100806040
45、200certainty in%NOTE: from top to down: k = 10 dB(V) (red), 20 dB(V) (green), 30 dB(V) (blue), 40 dB(V) (violet). Figure 7: Sum of the size of largest two continuous windows, for which noise k ETSI ETSI TR 102 269 V1.1.1 (2003-12) 11Figure 7 shall be interpreted in the same way than figure 6. E.g. w
46、ith a certainty of 80 % two continuous frequency windows with a total size of 17 MHz or more are available when a noise threshold k of 30 dB(V) is permissible. The probability distribution of the sum of frequencies, for which noise is below a specified value k, is shown in figure 8. Figure 8 can be
47、interpreted in the following ways: In 50 % of all measurement locations 45 % of the frequency range (1 MHz to 30 MHz) have a noise below 10 dB(V). If a higher degree of certainty is required (e.g. 80 %) we can read: In 20 % of all measurement locations 70 % of the frequency range (1 MHz to 30 MHz) h
48、ave a noise below 20 dB(V). For a modem design the noise may be considered in the following way: If a modem design needs a noise, which is less than 10dB(V), the maximum usable frequency range is 20 % (5,8 MHz) with a certainty of 80 %. 0204060801000 10 20 30 40 50 60 70 80 90 100cumulativeprobabili
49、tyin%a in %0 5 10 15 20 25 29 Usable frequency room in MHz100806040200certainty in%NOTE: from above: k = 10 dB(V) (red), 20 dB(V) (green), 30 dB(V) (blue), 40 dB(V) (violet). Figure 8: Cumulative probability for the sum of frequencies with a noise below k 8 Statistical evaluation of measured TTL The general dependence of TTL on frequency can be seen in figures 9 to 12, where the cumulative probabilities are plotted on the TTL-frequency plane as contour plot. ETSI ETSI TR 102 269 V1.1.1 (2003-12) 120 5 10 15
