Annex 3 B. Determination of the Masks Discrimination and the Net Filter Discrimination in the Fixed Service

Transcription

1 Annex 3 B Determination of the Masks Discrimination and the Net ilter Discrimination in the ixed ervice

2 Annex 3B, page 2 of 12 The calculations of the masks discrimination and the net filter discrimination are ased on the relation of two powers. Because these powers are represented y areas, only the areas are taken into account for the determination of the masks discrimination and the net filter discrimination. 1. Masks Discrimination MD The Masks Discrimination (MD) expresses the reduction (in db) of the interference power caused y the filter shape of the transmitter spectrum density mask and the receiver selectivity mask. MD is calculated as follows : MD = 10 log (TX area/ overlapping area at co-channel) 1.1 calculation of the TX area An example of a transmitter spectrum density mask is given in igure 1. The mask can e split up into different elements. The areas of these elements are relative power portions to the transmitter power. The area within the entire mask represents the TX area. t 0,1 t 2.3 Attenuation (db) t 4,5 A B C D E f igure 1 lat elements have to e calculated using formula 2.1 with r i = 0 (see elow), slope elements have to e calculated using formula 2.2 with r i = 0 (see elow).

3 Annex 3B, page 3 of Calculation of the overlapping area at co channel An example of the overlapping area at co channel etween transmitter spectrum density mask and receiver selectivity mask is given in igure 2. Common frequency range at co channel r 0,1 =0 RX Atten. Calc. Point r i, t i r 2,3 r 4,5 t 0,1,2,3 =0 t 4 TX Atten. req. t 5 t 7 f 0 f 1 f 2 f 3 f 4 f 5 f 7 Overlapping area at co channel req. a 0,1 = 0 Atten. Calc. Point a i = t i + r i a 2,3 a 4 a 5 f 0 f 1 f 2 f 3 f 4 f 5 req. igure 2

4 Annex 3B, page 4 of 12 The common frequency range at co channel has to e split into flat and slope partial elements. lat element () is a partial element where oth masks are flat. lope element () is a partial element where at least in one partial element a slope is detected. lat elements have to e calculated using formula 2.1; slope elements have to e calculated using formula 2.2. The overlapping area is the sum of all partial elements calculated using formulas 2.1 and 2.2 in the common frequency range at co channel. 2. Net ilter Discrimination ND The Net ilter Discrimination (ND) expresses the reduction (in db) of the interference power if the transmitter and receiver frequencies are different. The ND value can e determined y measurement or y calculation. 2.1 Method ased on measurement The principle of the measurement method is to plot the test channel receiver input level required for a specified BER (e.g ) as a function of the signal (carrier) to interference ratio (C/I). The testing arrangement is in igure 3. PRB Gen. Transm. I Atten. Power meter PRB Transm. BER Atten. Receiver Gen. C meas. Dir. coupler igure 3 PRB: Pseudo Random Bitrate ignal By plotting two curves, one for co-channel interference and the other for the adjacent channel interference, the horizontal shift etween them at the specified receiver input level (see igure 4) is the ND.

5 Annex 3B, page 5 of 12 igure 4 Using the curves, the ND value can e determined from two points, one on each of the two curves, corresponding to a given carrier level, e.g. for the 3 db degradation points. 2.2 Method ased on calculation The ND is defined according to ETI TR as: ND = 10 log (Pc/Pa) Where: Pc is the total power received after co-channel R, I and ase and filtering. Pa is the total power received after offset R, I and ase and filtering. or calculation of the power ratio (Pc/Pa) in the common frequency case the overlapping area is considered only. or the calculation of Pc and Pa the same transmitter power is used and therefore the formula for ND can e ND = 10 log (overlapping area at co-channel / overlapping area at frequency offset) Pc is calculated taking the overlapping area of TX spectrum density mask and RX selectivity mask at same operational frequency

6 Annex 3B, page 6 of 12 An example of the overlapping area at co channel etween transmitter spectrum density mask and receiver selectivity mask is given in igure 5. Common frequency range at co channel r 0,1 =0 RX Atten. Calc. Point r i, t i r 2,3 r 4,5 t 0,1,2,3 =0 t 4 TX Atten. req. t 5 t 7 f 0 f 1 f 2 f 3 f 4 f 5 f 7 Overlapping area at co channel req. a 0,1 = 0 Atten. Calc. Point a i = t i + r i a 2,3 a 4 a 5 f 0 f 1 f 2 f 3 f 4 f 5 req. igure 5 The calculation method is ased on integration of the spectrum density of the transmitter spectrum density mask and the receiver selectivity mask in the common frequency range at co channel. The common frequency range at co channel has to e split into flat and slope partial elements. lat element () is a partial element where oth masks are flat, lope element () is an partial element where at least in one partial element a slope is detected.

7 Annex 3B, page 7 of 12 lat elements have to e calculated using formula 2.1, slope elements have to e calculated using formula 2.2. The overlapping area at co channel is the sum of all partial elements calculated using formulas 2.1 and 2.2 in the common frequency range of oth masks. Pa is calculated taking the overlapping area of TX spectrum density mask and RX selectivity mask with the frequency offset: The common frequency range is the part where oth masks are overlapping each other. An example of the common frequency range at frequency offset etween transmitter spectrum density mask and receiver selectivity mask is given in igure 6.

8 Annex 3B, page 8 of 12 Common frequency range with frequency offset Tx Atten. t i f t 4,5,6,7 Calc. Point r i, t i Rx Atten. r i t 2,3,9,10 t 0,1,11,12 r 0,1,2 r 3 = flat area element = slope area element req. r 5, 6,7 r 8 r 9,10,11,12 f 0 f 1 f 2 f 3 f 4 f 5 f 6 f 7 f 8 f 9 f 10 f 11 f 12 req. Overlapping area with frequency offset Calc. Point a i = t i + r i a 4 a 2 a 5,6,7 a 3 a 8 a 0,1 a 9,10 a 11,12 f 0 f 1 f 2 f 3 f 4 f 5 f 6 f 7 f 8 f 9 f 10 f 11 f 12 req. igure 6 The calculation method is ased on integration of the spectrum density of the transmitter spectrum density mask and the receiver selectivity mask in the common frequency range.

9 Annex 3B, page 9 of 12 The common frequency range has to e split into flat and slope partial elements. lat element () is a partial element where oth masks are flat, lope element () is an partial element where at least in one partial element a slope is detected. lat elements have to e calculated using formula 2.1, slope elements have to e calculated using formula 2.2. The overlapping area is the sum of all partial elements calculated using formulas 2.1 and 2.2 in the common frequency range of oth masks. lat element areas () can e calculated according to following formula: = f c (2.1) where: for the element f c = f i+1 - f i = t i + r i = t i+1 + r i+1 with f i+1 > f i where: f i+1 f i f c sum of the attenuation of the transmitter ( t i ) and receiver ( r i ) masks at the eginning or at the end of an element (db), frequency at the end of the element (MHz), frequency at the eginning of the element (MHz), andwidth of the element (MHz), partial elements areas under the spectrum masks in the common frequency range. lope element areas () can e calculated according to following formula: a f c = ln(10) a 10 * only if a is different to 0. (2.2)* or the element a = (t i + r i )/f c f c = f i+1 - f i = t i+1 + r i+1 with f i+1 > f i If the two corresponding elements of the masks represent inverted inclinations, the parameter a may turns to 0. When a=0, the formula (2.1) shall e applied. where: t i r i f i f c sum of the attenuation of the transmitter (t i ) and receiver (r i ) masks at the end of an element (db), transmitter mask attenuation at the eginning of an element (db), receiver selectivity mask attenuation at the eginning of the element (db), frequency at the eginning of the element (MHz), andwidth of the element (MHz),

10 Annex 3B, page 10 of 12 partial elements areas under the spectrum masks in the common frequency range. t i+1 r i+1 f i+1 transmitter mask attenuation at the end of the element (db), receiver selectivity mask attenuation at the end of the element (db), frequency at the end of the element (MHz), = f c (2.1) where: for the element f c = f f i i +1 = t i + ri where: sum of the attenuation of the transmitter ( t i ) and receiver ( r i ) masks at the eginning of an element (db), f i f c frequency at the eginning and at the end of the element (MHz), andwidth of the element (MHz), partial elements areas under the spectrum masks in the common frequency range. lope element areas () can e calculated according to following formula: a f c = ln(10) a 10 (2.2) for the element t a = ti 1 + ri ri f c i 1 f c = f i f i 1 = i t i 1 + r 1 where: t i r i f i f c sum of the attenuation of the transmitter and receiver masks at the eginning of an element (db), transmitter mask attenuation at the eginning and at the end of an element (db), receiver selectivity mask attenuation at the eginning and at the end of the element (db), frequency at the eginning and at the end of the element (MHz), andwidth of the element (MHz),

11 Annex 3B, page 11 of 12 partial elements areas under the spectrum masks in the common frequency range. 3. Necessary data for the calculation of MD and ND 3.1 Transmitter spectrum density mask or the calculation, the real spectrum density mask shall e used and descried in Paragraph If this mask is not availale, the relevant ETI transmitter mask shall e used. 3.2 Receiver selectivity mask or the calculation, the real receiver selectivity mask shall e used and descried in Paragraph If this mask is not availale, the relevant ETI transmitter mask of the accompanying transmitter can e used as receiver selectivity mask. 3.3 Necessary data for the data exchange procedure Up to six points ut at least two points of each, the transmitter spectrum density mask and the receiver selectivity mask, have to e provided (see igure 7). Each point is defined y its frequency (MHz) and its attenuation (db). The first point (which is not a part of the data exchange procedure) is automatically defined as 0 MHz and 0 db. The last point must e set for the attenuation of 40 db The ND values for the first adjacent channel, named ND 1 (+ 1 channel spacing), and the second adjacent channel, named ND 2 (+ 2 channels spacing), shall e derived from measured data, if availale. In order to use ND1 and ND2 values, the following conditions must e fulfilled: the interferer and interfered equipment must e produced y the same supplier, and have the same identification; the interferer and interfered frequencies must elong to the same frequency plan; the capacities (Mit/s) of the interferer and interfered equipment must e the same.

12 Annex 3B, page 12 of 12 Transmitter spectrum density mask Receiver selectivity mask Attenuation (db) >40 requency (MHz) igure 7