1、 Rec. ITU-R F.1669-1 1 RECOMMENDATION ITU-R F.1669-1*Interference criteria of fixed wireless systems operating in the 37-40 GHz and 40.5-42.5 GHz bands with respect to satellites in the geostationary orbit (Question ITU-R 127/9) (2004-2007) Scope Recommendation ITU R F.1669 provides the interference
2、 criteria to protect fixed wireless systems (FWSs) from interference produced by GSO satellites in the 38 and 40 GHz bands. It includes two sets of criteria for, on the one hand, some links in certain broadband wireless access applications and, on the other hand, all other FWSs. The ITU Radiocommuni
3、cation Assembly, considering a) that it is desirable to determine the protection criteria of fixed wireless systems (FWSs) operating in the 38 GHz (37-40 GHz) and 40 GHz (40.5-42.5 GHz) bands with respect to interference from geostationary-satellite (GSO) systems operating on a co-primary basis; b)
4、that in interference situations involving GSO space stations, fixed service (FS) systems are potentially exposed to high levels of interference for some geometric cases which could affect the performance or availability of these systems; c) that the FS link design in the 38 and 40 GHz bands is contr
5、olled by rain attenuation, which can be modelled using Recommendation ITU-R P.530; d) that in the 38 and 40 GHz bands, some administrations employ automatic transmit power control (ATPC) on some FS links and that such use will increase the susceptibility of these links especially with regard to shor
6、t-term interference; e) that some FS links employing small net fade margins may not be fully protected from interference from GSO satellite systems without unduly constraining those services; f) that typical FS links using ATPC will require tighter protection criteria than those needed for FS links
7、with large fade margin that do not use ATPC; g) that no pointing restrictions apply to FS systems in the 38 and 40 GHz bands, and that such restrictions are not practicable in view of the large-scale, cost-sensitive deployment, recognizing a) that the bands 37.5-40 GHz and 40.5-42.5 GHz are shared o
8、n a co-primary basis with the FSS, and that the ITU-R established Recommendation ITU-R SF.1573, on pfd levels that are required to protect the FS in these bands; *This Recommendation should be brought to the attention of Radiocommunication Study Groups 3, 4 and 7. 2 Rec. ITU-R F.1669-1 b) that the a
9、pplication of the criteria in this Recommendation is not intended to lead to a revision of Recommendation ITU-R SF.1573, noting a) that the representation of the interference produced by GSO satellites on a FS receiver versus the whole azimuth of this FS receiver presents, as shown in Fig. 2, two in
10、terference peaks for two particular FS azimuth for which, depending on the geometry of the FS link, the pointing direction of this link passes through the GSO arc, recommends 1 that the following interference criteria, defining an interference mask such as described in Fig. 1, should be used to prot
11、ect the fixed service systems from interference produced by GSO satellites from various services in the 37-40 GHz and the 40.5-42.5 GHz bands on a co-primary basis: 1.1 for fixed wireless systems in general: 1.1.1 the interference-to-noise ratio (I/N) at the input of the FS receiver should not excee
12、d 10 dB except within 15 separation from the azimuth where the FS antenna main beam intersects with the GSO arc (Notes 1 and 2); 1.1.2 for the FS azimuth within this 15 range, interference-to-noise ratio at the input of the FS receiver can be accepted up to +4 dB for the azimuth corresponding to the
13、 peaks (Notes 1 and 2); 1.2 for some links in certain BWA applications: 1.2.1 the interference-to-noise ratio (I/N) at the input of the FS receiver should not exceed 10 dB except within 5 separation from the azimuth where the FS antenna main beam intersects with the GSO arc (Notes 1 and 2); 1.2.2 fo
14、r the FS azimuth within this 5 range, interference-to-noise ratio at the input of the FS receiver can be accepted up to 0 dB for the azimuth corresponding to the peaks (Notes 1 and 2); 2 that the information contained in Annex 1 and its Appendices should be used as guidance for the use of this Recom
15、mendation. NOTE 1 These I/N levels are referenced to the total noise at the receiver input including system noise level (kTBF) and intra-service interference (see 5 in Annex 1). NOTE 2 The 15 or 5 azimuth range specified in recommends 1.1 and 1.2, respectively, are based on the application of a temp
16、oral approach methodology and elements of a specific rain cell model. Further refinement of this rain cell model or a new model may have some impact on these azimuth ranges and may lead to further development of this Recommendation. Rec. ITU-R F.1669-1 3 Annex 1 Derivation of FS protection criteria
17、in the 38 GHz and 40 GHz bands to be applied in the GSO sharing scenarios 1 Introduction The methodology presented in this Annex is based on the assumptions that the bit error performance in the 38 GHz and 40 GHz bands is dominated by rain fading. Therefore, in the situations where the interference
18、from GSO satellites arrives at azimuths close to the azimuth of the main-beam axis of the FS receiving antenna, both the desired and the interfering signal will be subjected to fading. As a consequence, the unfaded interference power may be higher than that which would be permissible if the interfer
19、ence power was constant. This unfaded interference power is determined by requiring that the controlling bit error performance criterion be met for the same percentage of time regardless of whether any correlation exists between the fading of the desired and interfering power. 2 FS fade margins In t
20、he 38 GHz and 40 GHz bands, and since link lengths are likely to be shorter than 2 km, an FS fade margin of 14 dB was considered representative of conventional links since it was assumed that a majority of such links have a fade margin (or net fade margin1) higher than this value. It has to be noted
21、 that this 14 dB fade margin, when considering systems using ATPC, corresponds to a link with a higher margin (e.g. = 14 dB net fade margin +10 dB ATPC range). On the other hand, it was also noted that in certain BWA applications, a fade margin of 10 dB is used for some short links and that these li
22、nks would consequently require a lower I/N value. In support of the consideration of these margins, Table 2 which is based on Recommendation ITU-R P.530, gives the required rain margin for link lengths up to 1.6 km at five different rain rates for both vertical and horizontal polarization. However,
23、it has to be noted that the 14 dB or the 10 dB rain fade margin in these 38 and 40 GHz bands are justified on calculations using Recommendation ITU-R P.530 which does not provide values of fade margin referenced to an error performance measure but gives absolute attenuation values (rain fading) for
24、a given percentage of time. In addition, according to Recommendation ITU-R F.1498, for a link designed for a 99.999% availability and in particular BWA systems which are assumed to compete with fibre, the fade margin may refer to the BER 1 106or severely errored seconds (SESs) level. It was also agr
25、eed that the design of the FS link should take into account a 1 dB allowance for interference from the FS which hence increases the reference noise power to 1 dB above the system noise power. In addition, it was also considered that, due to technical reasons (minimum practicable power, available ant
26、enna sizes, fixed transmit power for hub stations, ), the FS links in the 38 and 40 GHz bands, and in particular point-to-multipoint systems, are likely to present an “extra design margin” compared to the rain margin. At the minimum, for point-to-point links, the value of this “extra design margin”
27、depends on the level of granularity of the power setting, the possible attenuators as well as the antenna gain that would allow the FS designer to adjust the receiver level as close as possible to the theoretical level. Even though it has not been taken into account in the 1For an FS link using ATPC
28、, the net fade margin = total fade margin ATPC range. 4 Rec. ITU-R F.1669-1 definition of the reference total margin of the FS link, it was agreed to consider it as an additional confidence factor in the derivation of the protection criteria. On the basis of the agreed assumptions that the fade marg
29、ins, MF, for errored seconds (ESs) and SESs are respectively 3 dB lower and 1 dB higher than the fade margin referenced to the BER 1 106level which is 2 dB lower than the fade margin referenced to the BER 1 103level, Table 1 summarizes the different values of fade margins corresponding to a MF= 14 d
30、B and 10 dB referenced to the SES level. TABLE 1 Correspondence of rain fade margin and error performance objectives 14 dB rain margin 10 dB rain margin ES (dB) 10 6 BER 1 106(dB) 13 9 SES (dB) 14 10 BER 1 103(dB) 15 11 3 Derivation of the I/N mask The derivation of the I/N mask to be applied to FSS
31、 GSO satellites has been based on the assessment of two different factors: the impact on the FS of interference and in particular, in the main beam of the FS antenna in rainy conditions, of the composite interference resulting of faded and unfaded portions of the interference (see Appendix 2 to Anne
32、x 1); the correlation between the rain attenuation on the signal and interference in the main beam of the FS antenna in order to determine angle X from the main beam at which this level of correlation can be assumed correlated with a certain level of confidence (see Appendix 3 to Annex 1). 4 I/N cri
33、teria mask Based on the elements in 3, Fig. 1 describes the I/N masks that represents the azimuth related protection criteria of the FS presenting a maximum I/N for the peak interference that relate to the case where the FS receiver is pointing through the GSO arc and an azimuth range for which the
34、I/N decreases from this maximum down to 10 dB. Rec. ITU-R F.1669-1 5 For fixed wireless systems (FWSs) in general, for which a 14 dB fade margin has been agreed as being representative, the maximum I/N and azimuth range have been determined to be respectively +4 dB and 15. For some links in certain
35、BWA applications that use a fade margin of 10 dB, these parameters have been determined to be respectively 0 dB and 5. 5 Noise level reference The I/N masks as described in 4 above refer to the total noise level which includes an agreed 1 dB intra-service interference allowance. It means that N = k
36、T B F + 1 dB. 6 Rec. ITU-R F.1669-1 Appendix 1 to Annex 1 TABLE 2 Rain fade margins for 99.999% availability Fade margin at 39.3 GHz, horizontal polarization (dB) Fade margin at 39.3 GHz, vertical polarization (dB) Rain rate (mm/h) (Zone) Rain rate (mm/h) (Zone) Link distance (km) 12 (B) 22 (E) 42 (
37、K) 63 (M) 95 (N) 12 (B) 22 (E) 42 (K) 63 (M) 95(1)(N)0.1 0.8 1.3 2.5 3.6 5.2 0.6 1.1 2.1 3 3.0 0.2 1.5 2.7 4.9 7.1 16.4 1.3 2.3 4.2 6 5.9 0.3 2.2 4 7.3 10.6 15.4 1.9 3.4 6.2 9 8.8 0.4 3 5.3 9.6 14 20.3 2.6 4.5 8.2 11.9 11.6 0.5 3.7 6.5 12 17.4 25.1 3.2 5.6 10.2 14.7 14.3 0.6 4.4 7.8 14.3 20.7 29.8 3
38、.8 6.7 12.2 17.6 17.0 0.7 5.2 9.1 16.6 24 34.3 4.5 7.8 14.2 20.3 19.6 0.8 5.9 10.4 18.9 27.2 38.8 5.1 8.9 16.1 23 22.2 0.9 6.6 11.6 21 30.4 43.2 5.7 10.0 18.0 25.8 24.7 1.0 7.3 12.8 23.3 33.6 47.5 6.3 11.0 19.9 28.5 27.1 1.1 8 14.1 25.5 36.7 51.7 6.9 12.1 21.8 31 29.5 1.2 8.7 15.3 27.7 39.8 55.8 7.5
39、 13.1 23.7 33.7 31.9 1.3 9.4 16.5 29.9 42.8 59.8 8.1 14.2 25.5 36.2 34.1 1.4 10.1 17.7 32 45.8 63.8 8.7 15.2 27.3 38.8 36.4 1.5 10.8 18.9 34.1 48.7 67.6 9.3 16.2 29.1 41.3 38.6 1.6 11.4 20.1 36.2 51.6 71.4 9.9 17.3 30.9 43.7 40.8 (1)Fade margins for the case of 95 mm/h rain rate for vertical polariz
40、ation were calculated under the assumption that the latitude is less than 30 (which impacts the calculation in accordance with Recommendation ITU-R P.530). Rec. ITU-R F.1669-1 7 Appendix 2 to Annex 1 Impact of interference on FS systems 1 Introduction In general, a link will be designed to exactly m
41、eet only one performance criteria. If this criterion is the controlling criterion, the link will also meet the other criteria. For example, if a link is designed to meet the severely errored second ratio (SESR) criteria of ITU-T Recommendation G.826 or G.828 under the assumption of constant received
42、 interference power, the ES criterion must be met at a rain attenuation smaller by four dB. Since the percentage of time allowed for errored seconds may be 10 or 20 times as great as for SES, the ES criterion will be met if the SES criterion is met. For perfectly correlated fading of interfering and
43、 desired signals, it can be shown that this four dB increase in C/N + I corresponds to a decrease in rain attenuation of about 4.7 dB. Hence, it is likely that the SESR criteria is the controlling criteria and that this is the only criterion that needs to be satisfied. Thus, the case where the inter
44、ference fading is perfectly correlated with the fading of the desired signal can be handled quite simply. The acceptable level of interference in the absence of fading for this case is merely higher than the permissible interference for the constant (uncorrelated) interference case by the fade margi
45、n. In accordance with Recommendation ITU-R F.758, the I/N is 10 dB in these frequency bands for the case of constant (uncorrelated) interference. In accordance with Recommendation ITU-R F.1094, the reference noise should be the total allocated noise consisting of the receiving system noise augmented
46、 by an allocated increment due to interference from the fixed service, an increment for interference from unwanted emissions and the additional increment due to interference from co-primary services. Hence the ratio of interference to total reference noise, I/Nref, is 10 dB, and the ratio of interfe
47、rence to the system noise, I/N0, is 9 dB. For the case where the fading of the inter-service interference is perfectly correlated with the fading of the desired signal, the same interference power (I/N0= 9 dB ) must be present when the signal is faded by the fade margin of MFdB; otherwise the desire
48、d performance will not be achieved. Consequently, the ratio of the unfaded interference power to system noise power for the case of perfectly correlated fading is MF 9 dB. Figure 2 provides an illustration of the unfaded interference produced by a fully populated GSO arc. The two peaks where the int
49、erference level is high correspond to the azimuth at which a single satellite is in the main beam of the antenna of an FS station. 8 Rec. ITU-R F.1669-1 For these two particular azimuths the interference propagation path may be co-linear with the propagation path of the desired signal and the fading would be perfectly correlated at these azimuths. As the azimuth moves from these peak values the fading on the two paths is only partially correlated and the permissible interference reduces from MF9 dB to 9 dB. Such a reduction is illustr
