1、 STDmCEPT ERC REPORT 31-EMGL 1994 M 232b4L4 0015395 T55 ERC REPORT 31 European Radiocommunications Committee (ERC) ., within the European Conference of Postal and Telecommunications Administrations (CEPT) COMPATIBILITY BETWEEN DECT AND DCS18 Brussels, June 1994 STDeCEPT ERC REPORT 31-ENGL 1994 H 232
2、b414 0035396 591 H ERC REPORT 31 Page 1 1. SUMMARY Practical as well as theoretical papers have been considered during this compatibility study. The following recommendations are seen (together) as a means of reducing potential interference: - Increased frequency separation between carriers in adjac
3、ent systems. - Improve blocking requirements of DECT receiver equipments (particuiarly for telepoint implementations) at offsets greater than twice the channel bandwidth. - Investigate possible escape mechanisms (for both systems), to avoid local interference problems and the consequent reduction in
4、 capacity. Such mechanisms could include: Dynamic channel selection (for DEO Intra-cell handover Careful location of the BCCH (control) channels. fieqrncy hopping - Note should be made of proposed solutions detailed in ETSI PT10(92)083, Version 01.02. - Introduction of an additional 4 watt MS power
5、class within the parameters indicated by SMG, will have only a marginal effect on the compatibility situation. 2. INTRODUCTION This paper examines the potential compatibility problems between two digital radiocommunications systems which are planned to operate around 1800 MHz. These systems are DECT
6、 (Digital European Cordless Telephone), and DCS1800 (Digital Communications System or Public Communications Network - FCN), As a result of both theoretical work, based on ETSI specifications and practical measurements carried out under laboratory controlled conditions, the isolation requirements for
7、 different interference mechanisms were determined. These were expressed in dBs and translated into separation distances using the agreed propagation models. Owing to the various configurations identified for typical DECT applications. Several interference scenarios were analyzed to identify those t
8、hat exhibited significant interference ranges. The following three interference mechanisms were identified as being the most problematic; Blocking Of DECT from DCS1800be DECT out of band emission interfering with DCS1800mobile Blocking of DCSI8OOmobi1e fromDECT The following measure are seen (togeth
9、er) as being a means of reducing the compatibility problems. Changing the Frequency Separation Between the two Systems Based on the existing specifications and the assumptions made in section 5, a frequency separation would significantly reduce the incompatibility between the systems. At present app
10、roximately 2.2 MHz is achieved, 1.8 MHz within the DECT band, and 400 kHz within the DCS1800 band when channel number 885 is not used. The minimum frequency separation required between DCS1800 and DECT carriers, to significantly alleviate the problem without changing the standards is 5 MHz. If this
11、is implemented, the separation distanes required in most instances are deemed acceptable. However, individual operational problems occurring in the following specific cases will need to be addressed: (a) In we 1, model A, DECT installations in the upper parts of high buildings facing a DCS1800 BS sh
12、ould plan for extra wanted signal, and therefore reduced coverage, if the distance between installations is 40 m STDmCEPT ERC REPORT 31-ENGL 1994 = 232b419 0015397 828 ERC REPORT 31 Page 2 (b) in case 3, DECT telepoint base stations using 12 dBi antenna gain should, if the distance is less than 60 m
13、 to a DCS1800 BS, require 10 dB extra blocking (61780 MHz) or plan for 10 dB extra wanted signal. A 5 MHz separation between the highest carrier frequency of DCS1800 (1876.6 MHz: ARFCN 869) and the lowest carrier frequency of DECT (1881.792 MHz) requires 16 x DCS1800 channels to be stedised, effecti
14、vely 3.1 MHz of spectrum. A similar procedure could be envisaged in the upper adjacent band. Changing the Standards Without a guard band the minimum frequency separation between DCS1800 and DECT carriers is 2.2 MHz. This is in the 2nd adjacent channel of the DECT system. The compatibility problem co
15、uld be reduced by improving the minimum blocking performance and the adjacent channel selectivity of the DECT receiver. However, the amount of improvement required in this parameter alone to achieve a reasonable separation distance seems unrealisable in practice. The feasibility of improving the DEC
16、T specification increases as the frequency separation increases. DCS1800 mobile receivers will also be affected (as in case 2), where there are out of band emissions from a DECT transmitter Wig on the DCS1800 receive kequency. The out of band emissions from DECT are not high, and the amount of impro
17、vement in this parameter alone required to achieve a reasonable separation distance seems unreaiisable in practice. It can be seen from figure 2 that improving the DCS1800 mobile blocking specification will not alleviate the problem with cases 2 and 5 which are limited by the DECT out of band emissi
18、ons. Reducing System Capacities The dynamic channel selection of DECT will avoid blocking from DCS1800 but this will result in a capacity reduction for DECT. Similarly DCS1800 mobiles can avoid interference from DECT if the control channels for DCS1800 CCH carriers) are allocated more than 3.5 MHz f
19、rom the DECT band edge, and the options of frequency hopping and possibly inira-cell hand over is employed. An assessment of the economic and practical implications of improving the performance standards for DECT and DCS1800 described above will require work to be done by ETSI. 3. BACKGROUND DECT is
20、 the term used for the Digital European Cordless Telecommunications system located between 1880 and 1900 MHz. The DECT specification (ETSI prETS 300175-2) provides for ten wide band channels with centre frequencies defined by fc=1897.344 MHz-c.1728 kHz, where c= 0,1,.,., 9. DCS1800 is the standard d
21、eveloped by ETSI for Digital Cellular Systems for use between 1710 to 1785 MHz (Mobile Transmit) and 1805 to 1880 MHz (Base Station Transmit). Different parts of the hd can be allocated for DCS services on a nationai basis. Radiocommunications systems operating in adjacent bands may adversely effect
22、 each other due to the presence of a number of potential interference mechanisms e.g.: receiver blocking, spurious responses, transmitter spurious emissions, intermodulation products generated within the transmitter, intermodulation products generated within the receiver. The basic methodology adopt
23、ed for addressing the perceived problems associated with the DECT-DCS1800 adjacent band allocations, was to look at: theoretical values (laid down in the system specifications), STD-CEPT ERC REPORT 3L-ENGL 1994 2326434 0015396 764 w ERC REPORT 31 Page 3 practical values (obtained from tests on real
24、equipment). The maximum permissible level of received interference power, can be related to the following equipment performance parameters defined within the system standards, including: Co-channel, adjacent channel, blocking, intermodulation. this, in conjunction with knowledge of the following: in
25、terfering transmitters power, level of spurious emissions, antenna configurations, .can be used to derive the required isolation for interference free operation. Practical measurement of a receivers ability to reject interfering signals (intrinsic immunity) can also be used in this analysis. The req
26、uired isolation can then be translated into an interference range, through the application of an appropriate propagation model. This, will then yield a number of interference ranges relating to the different interference mechanisms, frequency separations. transmitter powers and receiver sensitivitie
27、s. Sine short range propagation at 1800 MHz depends on the local environment, many different propagation models were considered. pinally, six propagation models were selected to represent the propagation conditions appropriate to the five different interference scenarios. The interference ranges for
28、 different scenarios may range fi-om metres to kilometres. The probability of each interference scenario occurring depends on a number of factors. Some scenarios will be much more likely to OCCUT than others. It is the highly probable scenarios that exhibit significant interference ranges that are o
29、f major concern and have been identified and addressed in this paper. The r.f. aspects of the DCS1800 specification (ETSI GSM 05.05-DCS) are based upon the GSM 900 specification. The carrier frequencies are defined by fi( = 1710.2 + 0.2(n-512) MHz, 512 In I 885; fu(n) = f) + 95 MHz. A pictorial over
30、view of the major interference scenarios (Pigure i). propagation models and interference ranges are given in section 4. SCENARIOS of this report. 4. SCENARIOS The following five major interference scenarios were identified as giving cause for concern regards compatibility between DECT and DCS1800; C
31、ase Interferer Victim 1 DCS1800 base outdoors DECT base indoors 2 DECT base indoors DCS 1800 mobile indoors 3 DCS1800 base outdoors DECT base outdoors 4 DCS1800 base outdoors DECT mobile outdoors 5 DECT base outdoors DCS1800 mobile outdoors For each scenario an appropriate propagation model was chos
32、en, see below. STD*CEPT ERC REPORT 31-ENGL 1994 9 232b414 0015399 bTO m ERC REPORT 31 Page4 Case 1 the DCS1800 base station (antenna) is assumed to be located on a roof top. To take account of ail of the possible locations of the DEL“ base station (within a multi-level building), many different prop
33、agation models were considered. Three models were agreed as appropriate, A, B, and C see below and overview diagram. Line of site. In the worst situation, the DECT receiver may be located within line of sight to the DCS1800 base station. “Model - A“ is assumed to be appropriate. Oblique. In this gen
34、eral situation, more complicated propagation conditions apply. “Model B“ is assumed to be appropriate. Ground level. When the DECT base station is located at ground level, “Model C“ is assumed to be appropriate. Case 2 When both the DCS1800 base station and the DEC mobile station are located within
35、the same building, “Model - D“ is assumed to be appropriate. Case3and4 When the DCS1800 base station (antenna) is located at roof level and the DECT base or mobile station is located in the street, “Model E“ is assumed to be appropriate. Case 5 When the DECT base station and the DCS 1800 mobile stat
36、ion are located in the street, “Model F“ is assumed to be appropriate. FIGURE 1 OVERVIEW OF MAJOR SCENARIOS DECT M.S. +24 dBr +7I DECT B.S I DECT B.S +24 dBi k ERC REPORT 31 Page 5 U DCS . M.S. DECT B.S. STD-CEPT ERC REPORT 31-ENGL 1334 2326414 0015401 089 ERC REPORT 31 Page 6 5. PROPAGATION MODELS
37、“Model A“ This model assumes free space propagation for ail distances, plus an additional 15 dB to account for building attenuation. This can be expressed with the following equations: lb=53+ 20logd “Model B“ This model assumes free space propagation for distances below 10 m and a 4th power law for
38、greater distances, plus an addition 15 dE3 to account for building attenuation. This can be expressed with the following equations: Lb=53+2010gd, dlh “Model C“ The COST obstruction model is described in doc FMlO/SE7(92)22. An extension is made by linear extrapolation for distances below the range of
39、 the model. 15 dB has been added to account for building attenuation. The following Lb=83+201ogd, Ol Om “Model E“ The COST obstruction model is described in doc FMlO/SE7(92)22. An extension is made by linear extrapolation for distances below the range of the model. The following equations can be use
40、d: Lb =46.6+ 301ogd, 130 6 MHz ftom carrier Spurious emissions, Af 5 MHz from carrier TABLE 1 TABLE 2 Receiver IM ERC REPORT 31 Page 8 MECHANISM- REVERSE PATH Out-of-band emissions Spurious emissions Receiver IM Blocking Case 2 (Model D). ISOLATION RANGE (metres) (dBs) Model D 35 3 MHz from carrier
41、TABLE 4 ERC REPORT 31 Page 9 REVERSE PATH Out-of-band emissions Spurious emissions Receiver IM Blockirig Case 3 (Model E). (dBs) Model E 84 6 96 25 1 o5 71 52 c1 TABLE 5 unous emssions, TABLE 6 STDoCEPT ERC REPORT 31i-ENGL 1974 W 232b414 0015405 724 W MECHANISM- FORWARD PATH Out-of-band emissions, A
42、f 5 MHz from carrier I Spurious emissions, Af30 MHz from band edge Receiver IM 83 68 Af 3 MHz fiom carrier Spurious emissions, 74 34 Blocking, 67 20 Blocking, 60 12 TABLE 10 60 I 12 STD-CEPT ERC REPORT 31-ENGL 1994 = 232b414 0015407 5T7 W ERC REPORT 31 Page 12 Observations. The following comments ca
43、n be made regarding the different interference mechanisms: Spurious emissions: The required isolation values due to spurious emissions are generdly higher than those for out-of-band emissions. These levels should be treated as a mask rather than a continuous noise floor. The spurious signals will ap
44、pear at a few specific frequencies, and therefore these problems could be solved by the Dynamic Channel Selection in DECT and by intra-cell handover in DCS18. Receiver intermodulation: In general the most likely interference resulting from unwanted intermodulation effects in receivers is the third o
45、rder product, described by: A flM=2fl-f2=flkAf The implications of this are that no 3rd order products will appear in the DECT band due to DCS18 mobile transmissions, and that the 3rd order products due to DECT transmissions are limited to the upper 20 MHz of the DCS1800 mobile receive band. SinCe t
46、he probability of DI interfaence is low, these problems could also be solved by intra-cell handover in DCS18 and by the Dynamic Channel Selection in DECT. NOTE: A recent propagation experiment has indicated that in one installation case, similar to cases 3 and 4, the propagation loss was less than p
47、redicted by the propagation model hiel E). STDmCEPT ERC REPORT 31-ENGL 1774 232b414 0015408 433 JCRC REPORT31 Page 13 6. RESULTS - PRACTICAL STUDY Practical tests made on some preproduction DECT equipment tends to indicate that; - DECT equipment on the market is likely to have better blocking perfor
48、mance than the minimum requirement except for the few MHz closest to the DECT carrier. Close to the band edge, adjacent channel selectivity detennines the blocking performance. This conclusion is supported by tests made by two manufacturers. - in one of these tests the blocking level was registered
49、as the point at which a listener could discern interference to the link. The other test was made using a BER of 10- to determine the blocking level. 3 - - DCS1800 interferer will not be worse than a CW interferer except, possibly, within a few MHz from the DECT carrier. 7. CONCLUSIONS Based upon the findings of the theoretical studies and the results of some limited practical blocking measurements, it is concluded that the following topics shouid be considered together as a means of reducing the potential compatibility problems: Arrangements for an increased frequency separat
