1、STD-CEPT ERC REPORT 21-ENGL 1993 I 232b414 OOLSLbO 974 h ERC REPORT 21 ?L. L.; - . ?-l. v.-.-. European Radiocommunications Committee (ERC) within the European Conference of Postai and Telecommunications Administrations (CEFT) ? w - ._._ COMPATIBILITY BETWEEN ERMES AND PMR SYSTEMS Montreux, October
2、1993 STD.CEPT ERC REPORT 21-ENGL 1993 m 232b414 OOLSLbL 00 II Copyright 1994 the European Conference of Postai and Teiecommunications Administrations (CEPT) ERC =PORT 21 Page 1 COMPATIBILITY BETWEEN ERMES AND PMR SYSTEMS SUMMARY Several papers detailing the results of practical measurements have bee
3、n considered, all of these indicate that a significant and complex compatibility problem exists. In summary the practical and theoretical studies confirmed the following problem areas: i) Significant interference between ERMES and PMR base station receivers caused by adjacent channel interference, s
4、purious emissions and blocking; ii) iii) Isolation of up to 90 dl3 may be required between adjacent systems in densely populated areas; Cost will be incurred by both PMR and ERMES operators; iv) Good site engineering practice will be required at all sites where ERMES and PMR base stations are ce sit
5、ed. STD-CEPT ERC REPORT SL-ENGL 3993 M 232b434 0035363 683 a ERC REPORT 21 Page 2 1. INTRODUCTION This paper examines the potential compatibility problems between ERMES (European Radio Message System), and PMR systems operating around 170 MHZ. As a result of both theoretical work, based on ETSI spec
6、ifications, and practical work carried out under laboratory controlled conditions, the isolation requirements for different interference mechanisms were determined. These were expressed in dBs and translated into separation distances using appropriate propagation models. 2. BACKGROUND ERMES is the P
7、an European Paging System and as such will be implemented across Europe. It is understood however that the implementation is likely to be different in various member states. Radiocommunications systems operating in adjacent bands may adversely effect each other due to the presence of a number of pot
8、ential interference mechanisms e.g. receiver blocking, receiver spurious responses, transmitter spurious emissions or the generation of intermodulation products within the transmitter or receiver. Concerns have been expressed regarding the actual performance of PMR equipments, however laboratory tes
9、ts have shown that they were well within specification. It has also been noted that there is a band of frequencies from the second adjacent channel to 1 MHz from the wanted channel where PMR receiver performance is undefined, limited testing however has revealed that extrapolation would appear to be
10、 appropriate. It is felt however that the actual performance should be specified. The minimum isolation required between ERMES and PMR systems, for correct operation, can be calculated from knowledge of the equipments performance (obtained from the systems specifications, or actual tests carried out
11、 on equipments), and the transmitter power, receiver sensitivity and antenna gains etc. This minimum isolation can then be translated into an interference distance through the application of an appropriate propagation model for different interference scenarios. This will yield a number of interferen
12、ce distances relating to the different interference mechanisms, frequency separations, transmitter powers and receiver sensitivities etc. The interference distances for different scenarios may range from metres to kilometres, although some scenarios will of course be more likely to occur than others
13、. The interference scenarios considered as being significant are as shown below in order of perceived importance: i) ii) iii) iv) v) vi) ERMES base station to PMR base station; ERMES base station to PMR mobile station; PMR base station (50 m) to ERMES mobile station; PMR base station (30m) to ERMES
14、mobile station; PMR mobile station to ERMES mobile station; ERMES base station to ERMES mobile station. The probability of interference occurring within each scenario has not been addressed. 3. STUDY AND RESULTS The theoretical field strength produced by the transmitter is: E = ERP + 2010g f + 79.36
15、, where E is the field strength in dBpV/m, EFW f is the effective radiated power in dBm is the frequency in MHZ. STD-CEPT ERC REPORT 21-ENGL 1993 .I 232b4L4 0015Lb4 51T I ERC REPORT 21 Page 3 At the frequency 169.5 MHZ, the results would then be as shown below: ERMES base station dBp.V/m 178 (250) 1
16、74 (100) 168 (25) PMR base station dBpV/m 171 (SO) 164 (10) PMRmobile station dBpV/m 168 (25) 154 (1) Note : figures in round brackets are system ERP in Watts. System parameters With derived values are shown below: ERMES” s44) Max allowed Cwhannel interference fs (dBpV/m) 44 Receiver sensitivity (dB
17、pV/m) 25 Minimum fs to be protected (dE%p.V/m) Co-channel protection (dB) 10 Adjacent channel power (dBc) -70 ” “ selectivity (dB) 60 Spurious response immunity (dBpV/m) 76) Blocking ratio (dB) i591 Blocking threshold (dBpV/m) 84” EIRP of spurious emission (pW) 0.25 Spurious response rejection (dB)
18、1511 Spurious emissions fs (dBpV/m) (169.5 MHz) 861 PMR* 20 20 8 I21 -70 70 70 84 0.25 1901 1 o41 t861 1) 2) 3) 4) 5) The ERMES parameters are taken from ETS 300 133. The PMR parameters are taken from ETS 300 086. Values within square brackets are derived from the ETS parameters. This is the field s
19、trength outdoors. The margin above the receiver sensitivity is necessary to ensure good reception indoors. These values are assumed to be measured with the wanted signal level at the receiver sensitivity (25 dB pV/m). When the wanted signal level is 54 dBpV/m the spurious response immunity is assume
20、d to be 54 + 51 = 105 dBp.V/m and the blocking threshold 54 + 59 = 113 dBpV/m. In all of the following isolation calculations, the receiver antenna gain is assumed to be O dBi Isolation due to Adjacent Channel The required isolation between ERMES and PMR when they are operated in adjacent channels i
21、s determined by the greatest of two values: i) ii) the required isolation due to the adjacent channel power of the transmitter and, the required isolation due to the adjacent channel selectivity of the receiver. These values are shown below: ERMES TRANSMITTER - PMR RECEIVER (250 (1OOW) (25w) i) (dB)
22、 96 92 86 ii) (dB) 88 84 78 PMR TRANSMITTER - ERMES RECEIVER (50W (25W) (low) (1w) i) (dB) 57 54 50 40 ii) (dB) 57 54 50 40 ERC REPORT 21 Page 4 ERMES TRANSMITTER - ERMES RECEIVER (250w) (100W) (25w) i) (dB) 64 60 54 ii) (dB) 64 60 54 Isolation due to Spurious Responses The spurious response immunit
23、y applies to any frequency at which a response is obtained. The required isolation due to spurious responses is calculated as the difference between the radiated field strength and the spurious response immunity and is given below. ERMES TRANSMITTER - PMR RECEIVER (250w) (loow) (25w) (a) 88 84 78 PM
24、R TRANSMITTER - ERMES RECEIVER (50W) (25W) (low) (1w) (B) 66 63 59 49 ERMES TRANSMITTER - ERMES RECEIVER (250w) (100W) (25W (W 73 69 63 Isolation due to Blocking The blocking specifications apply for frequency separations between 1 and 10 MHz. The required isolation due to blocking is calculated as
25、the difference between the radiated field strength and the blocking threshold. The values are shown below. ERMES TRANSMITTER - PMR RECEIVER (250w) (100W) (25w) (dB1 74 70 64 PMR TRANSMITTER - ERMES RECEIVER (50w) (25W (low) (1w) (dB) 58 55 51 41 ERMES TRANSMITTER - ERMES RECEIVER (250 (1OOW) (25w) (
26、W 65 61 55 Isolation due to Spurious Emissions The required isolation due to spurious emissions is calculated as the difference between the field strength of a spurious emission and the maximum allowed cc-channel interference power. The values are shown below. Transmitters ERMES PMR ERMES Receivers
27、PMR ERMES ERMES (dB1 74 42 42 ERC REPORT 21 Page 5 Isolation due to Intermodulation As a result of a separate study it is evident that there is a potential compatibility problem between ERMES and PMR in high band as a result of intermodulation products. This stems from the high transmit power of the
28、 ERMES equipment and its proximity to the PMR equipment. If ERMES transmissions are able to mix with PMR base transmissions, there is the possibility of intermodulation products falling in the base receive band. These products could be at a level sufficient to cause Uiterference to PMR services. Pro
29、pagation Models Interference from an ERMES base station to a PMR base station. In this case the free space formula is used. It is recognised that this model probably will underestimate the propagation loss for long distances ( 5 - 10 km), but since the acceptable distances are much shorter than that
30、 the model can still be used. Interference from an ERMESPMR base station to a PMR/ERMES mobile station. In these cases the HATA model is used when this gives a greater propagation loss than free space propagation. For other (shorter) distances the free space model is used. Interference from a PMR mo
31、bile station to an ERMES mobile station. For propagation between two mobiles the free space formula is used for distances up to 15 meters, and the plane earth model is used for greater distances. For urban areas, the same model with an additional attenuation B = 9 dB due to urban clutter is used. Se
32、paration distances Separation distances, in metres, are given overleaf. These are the distances that would be required to achieve the desired isolation in the absence of any additional measures such as filtering. STD.CEPT ERC REPORT ZL-ENGL 1993 232b41Li 0015167 229 m ERC REPORT 21 Page 6 Adjacent c
33、hannel Spurious responses Blocking Spurious emissions Adjacent channel Spurious responses Blocking Spurious emissions Adjacent channel Spurious responses Blocking Spurious emissions Adjacent channel Spurious responses Blocking Spurious emissions Adjacent channel Spurious responses Blocking Spurious
34、emissions Adjacent channel Spurious responses Blocking Spurious emissions U 5 64 327 126 126 U 64 118 68 14 ERMES BASE to PMR BASE (2.50) (100) 8913 5623 3548 2239 708 447 708 708 ERMES BASE to PMR MOBILE (250) (100) S O U s O U 885 2855 430 634 2174 286 513 1656 249 391 1261 166 198 638 96 150 447
35、64 198 638 126 198 638 126 PMR BASE (Som) to ERMES MOBILE (50) (10) U s O U S 40 62 100 25 39 73 115 282 45 71 42 66 112 26 41 14 18 18 14 18 PMR BASE (30m) to ERMES MOBILE (50) (10) U s O U S 37 57 100 23 36 66 103 282 42 65 39 61 112 25 38 14 18 I8 14 18 PMR MOBILE to ERMES MOBILE (25) (1) B=9 B=O
36、 B=9 20 33 5 33 56 14 21 35 6 6 17 6 ERMES BASE to ERMES MOBILE (250) (100) s O U S O U 100 224 49 76 141 32 185 596 90 141 400 60 107 251 52 82 158 35 18 18 14 18 18 14 (25) 2818 1122 224 708 (25) S 448 260 1 O0 198 O 45 126 50 18 O 45 126 50 I8 B=O 14 25 16 17 (25) s 51 93 54 18 O 1445 838 224 638
37、 O 71 200 79 18 U = urban area S = suburban area O = open area. ERC REPORT 21 Page 7 4. PRACTICAL TESTS PMR Receivers The measured performance of the PMR receivers with regard to sensitivity, adjacent channel and blocking was better than the specification required. Comparison of the unwanted signal
38、levels required to produce identical reductions in SINAD in the laboratory showed that, apart from the adjacent channel, there was negligible difference between the degradation caused by a PMR, or an ERMES, interferer. The close-in unwanted signal rejection performance of the two PMR receivers teste
39、d was quite different. One rejected unwanted (PMR) signals 25 kHz away as effectively as it did those 1 MHz away, the second receiver achieved this level of rejection when the unwanted (PMR) signals were in excess of 100 kHz away. Comparing the results of the laboratory tests conducted using a simul
40、ated ERMES signal, and those obtained in the field using an operational NEC PBJlOV ERMES transmitter, indicates that broadband noise from an ERMES transmitter falling in the wanted channel will be the dominant interference mechanism with the better PMR receivers. It should be noted however, that the
41、 broadband noise from the ERMES transmitter was not excessive and that similar, or higher, (relative) levels of broadband noise may be emitted from PMR transmitters. Apart from identifying the need to consider the effects of broadband transmitter noise, the results of the practical tests support the
42、 theoretical calculations contained in this document. ERMES Transmitter Measurements were conducted on a pre production ERMES transmitter under laboratory conditions. The adjacent channel power was found to be better than that specified and furthermore the broadband noise was lower than that anticip
43、ated (typically -90 dBc in a 12% kHz bandwidth). 5. OBSERVATIONS The calculated separation distances, necessary for ERMES transmitters to operate in the adjacent channel to a PMR base station receiver, without causing interference is several kilometres. Even with frequency separations in excess of 1
44、 MHz, receiver blocking (ERMES and PMR) may cause compatibility problems at distances of several hundred metres. Both PMR and ERMES specifications have an area, from the second adjacent channel to 1 MHz from the wanted channel, where the receiver performance is undefined. Actual performance in this
45、area will be of crucial importance to the magnitude of the compatibility problem. The magnitude of the compatibility problem is likely to be greatest where the PMR base station sites are concentrated (where market demand is greatest). i.e. cities, main conurbations and transport centres. The measure
46、s necessary to provide solutions to the compatibility problems are expected to cause unforeseen economic costs to operators and users of the PMR and ERMES services. The most significant compatibility problem is that of the ERMES transmitter affecting PMR base station receivers. Other interference sc
47、enarios may also cause compatibility problems, but to a lesser extent. To avoid worsening interference problems good site engineering practice at least to the level of MPT 1331 (UK) or ETR 58 will be required at all sites where ERMES and PMR base stations are Co-sited. ERC REPORT 21 Page 8 6. CONCLU
48、SIONS in my countries the ERMES channels are surrounded by PMR channels with base stations for both systems co- sited in urban areas. This work confirms that if ERMES is introduced without adequate precautions, a significant interference problem will exist. A number of techniques have been suggested
49、 to improve the situation, and all of these techniques will be required at some sites. The solutions will be costly in many cases, and the mix of solutions will need to take into account the economics of both PMR and ERMES. Various options to improve the situation are listed below in no particular order: Ensuring adequate (spatial / vertical) separation Providing frequency separation. Provide filtering. Controlling power levels. Tightening the specification(s). None of the above options should be considered in isolation. Notes: Provide fiilering. Cavity filters (specXcaily Q-C
