1、 Rep. ITU-R M.2045 1 REPORT ITU-R M.2045 Mitigating techniques to address coexistence between IMT-2000 time division duplex and frequency division duplex radio interface technologies within the frequency range 2 500-2 690 MHz operating in adjacent bands and in the same geographical area (2004) 1 Sco
2、pe This Report considers techniques to improve compatibility between IMT-2000 time division duplex (TDD) and frequency division duplex (FDD) radio interface technologies operating in adjacent frequency bands and in the same geographic area. Report ITU-R M.2030 analyzed and presented results of the c
3、onsequences of adjacent channel interference on FDD and TDD compatibility within the 2 500-2 690 MHz band, for a range of scenarios. It identified several scenarios where co-existence between TDD and FDD networks was problematic due to base station to base station (BS-to-BS) or mobile station to mob
4、ile station (MS-to-MS) interference. This Report considers techniques, within specified classifications, to mitigate this interference, and hence to improve coexistence between TDD and FDD mobile networks in adjacent frequency bands and in the same geographic area. In so doing, this Report describes
5、 the degree of improvement they offer. The analysis in this Report considers the following IMT-2000 radio interfaces operating within the 2 500-2 690 MHz band: FDD: IMT-2000 CDMA Direct Spread: (WCDMA or UTRA FDD) TDD: IMT-2000 CDMA TDD: (UTRA TDD) with its two modes: high chip rate (HCR, 3.84 Mchip
6、/s) TDD and low chip rate (LCR, 1.28 Mchip/s) TDD, known also as TD-SCDMA. However, the mitigation techniques described in this Report may be also more generally applicable to other frequency bands and to other TDD and FDD radio interfaces. The mitigation techniques described in this Report address
7、the issues identified in Report ITU-R M.2030 and use assumptions consistent with those made in Report ITU-R M.2030. When these assumptions do not hold for a particular deployment the improvement obtained may be more or less. This study is not fully exhaustive and there may be other techniques not an
8、alysed and reported herein that may assist in achieving compatible deployment of TDD and FDD systems in adjacent frequency bands. 2 Introduction and summary Previous studies have found that significant interference can be experienced in some base station to base station (BS-to-BS) scenarios (whether
9、 they be co-located or operate in the same geographical area) as well as in mobile station to mobile station (MS-to-MS) scenarios, where outages would impact user service levels. These studies have considered time division duplex (TDD) and frequency division duplex (FDD) systems operating on adjacen
10、t frequencies within the 2.5 GHz band using representative parameters for each scenario, in which no specific measures had been deployed to mitigate this interference. These studies are described in Report ITU-R M.2030 - Coexistence between IMT-2000 time division duplex and frequency division duplex
11、 terrestrial 2 Rep. ITU-R M.2045 radio interface technologies around 2600 MHz operating in adjacent bands and in the same geographical area. This Report identifies a number of techniques that may be applied to mitigate interference between TDD and FDD systems operating on adjacent frequencies. It id
12、entifies the applicability of these techniques to the scenarios identified in Report ITU-R M.2030 where interference might occur, and analyses the potential benefits of the techniques. The evaluation criteria used in this Report are the same as those presented in Report ITU-R M.2030, e.g. required s
13、eparation distances and/or isolation requirements or supported cell range, capacity loss and probability of interference. The Report also indicates the manner in which any particular mitigation technique can be applied, who would apply it (e.g. the vendor or operator), and whether or not coordinated
14、 action is required in both the TDD and FDD networks. The successful deployment of TDD and FDD systems in adjacent bands may require the use of one or more of these mitigation techniques to resolve the BS-BS or MS-MS interference scenarios that may be relevant. This Report also identifies potential
15、constraints that any mitigation technique may impose on deployment and what effect, if any, they may have on system complexity and/or network performance. Some of the characteristics of operational IMT-2000 networks within the 2 500-2 690 MHz frequency range are likely to differ from the assumptions
16、 made in the analysis of this Report and in Report ITU-R M.2030. This Report provides information to assist in assessing and optimizing, for the scenarios identified in Report ITU-R M.2030, the trade-off between the benefits of each mitigation technique and its drawbacks, versus the use of guardband
17、s and/or increased geographic cell separation. This Report identifies a set of interference mitigation techniques that are useful in facilitating coexistence between TDD and FDD systems. Each technique described will mitigate interference problems but may not entirely eliminate the problem. It is li
18、kely, that in order to obtain satisfactory performance several of the mitigation techniques will have to be applied simultaneously. The evaluation of the impact of a particular mitigation technique in this Report is done in the context of and benchmarked against the scenarios identified and describe
19、d in Report ITU-R M.2030. These scenarios may not always correspond to actual deployment scenarios in the field and care needs to be taken when extrapolating these results to different scenarios. Additionally, given the nature of RF propagation in the real-world the analysis relies heavily on simula
20、tion and statistical analysis rather than relying solely either on worst case or best case deterministic analysis. As well as mitigation techniques, this Report also describes mechanisms included in the IMT-2000 TDD and FDD specifications that also provide mitigation of interference. 3 Review of pre
21、vious related work Report ITU-R M.2030 addresses coexistence between IMT-2000 TDD and FDD radio interface technologies within the frequency range 2 500-2 690 MHz operating in adjacent bands and in the same geographical area. Specifically, the interference properties between IMT-2000 Direct Spread (W
22、CDMA or UTRA FDD) and IMT-2000 CDMA TDD (UTRA TDD) with its two modes high chip rate (HCR, 3.84 Mchip/s) TDD and low chip rate (LCR, 1.28 Mchip/s) TDD are studied. For the purposes of the analysis it is assumed that TDD and FDD systems at 2.5 GHz have similar characteristics to those of WCDMA and HC
23、R/LCR TDD as defined in 5, 6, 7 and 8. Report ITU-R M.2030 provides an analysis and presents results of the consequences of adjacent channel interference on FDD and TDD compatibility for a number of scenarios. That study is based on deterministic calculations for BS-BS scenarios leading to required
24、separation distance and/or Rep. ITU-R M.2045 3 isolation requirements or supported cell range. The interference from MSs into MSs and BSs is analysed both with deterministic and statistical calculations leading to capacity loss and/or probability of interference. The conclusions of the Report reflec
25、t only the studies made in that Report. Report ITU-R M.2030 does not address potential improvement brought about by mitigation techniques such as site engineering, equipment improvement, adaptive antenna, etc. These mitigation techniques are the subject of this Report. 4 Subjects considered in this
26、document 4.1 List of scenarios BS-to-BS, WCDMA-TDD Macro-to-macro line-of-sight (LoS) Macro-to-micro (vehicular) Micro-to-micro (LoS) Micro-to-micro (pedestrian) MS-to-MS. 4.2 List of mitigation techniques classes Methods related to specifications Equipment performance (supplier improving the equipm
27、ent performance) Site engineering on single site Deployment relationship between sites. 4.3 Parameters for IMT-2000 assumed in this Report The analysis in Report ITU-R M.2030 and in this Report has been based on the specifications for FDD and TDD as defined in 5, 6, 7 and 8. These specifications do
28、not include requirements for the frequency range 2 500-2 690 MHz. However for the analysis, the requirements for the frequency range 1 900-2 170 MHz have been assumed. It is possible that the requirements for the 2 500-2 690 MHz band for the parameters related to coexistence between FDD and TDD will
29、 be different to those for the frequency range 1 900-2 170 MHz, as the result of advances in technology and the impact of the higher operating frequency. 5 Mitigation techniques: A short description of their characteristics and improvement potential 5.1 Site placement 5.1.1 Brief description Site pl
30、acement as a mitigation technique is only applicable to the micro to macro scenarios that assumes rooftop and street level deployment respectively with a significant antenna height differential. As a result, the coupling between micro BSs that are close to a macro BS will be 4 Rep. ITU-R M.2045 redu
31、ced. The benefits are provided by the vertical antenna patterns of the macro and micro BS antennas. However, in non-LoS conditions the improvements may be reduced. 5.1.2 Integration into an IMT-2000 technology This is a deployment technique, which is technology independent. 5.1.3 Indication of who s
32、hould apply the technique The technique should be applied by the operator of the micro BS. 5.1.4 Implications and trade offs The technique is available due to the different placement characteristics (on rooftop vs. at street level) between the BS types. The full benefit is only available for each ne
33、arby macro BS (approximately within 50 m of the micro BS) and the amount of additional isolation would be expected to decrease for larger macro-micro BS separation. 5.2 Antenna separation 5.2.1 Brief description Coupling between two antennas located in the same site can be reduced by separating the
34、antennas vertically, horizontally or back-to-back by a few metres. For network planning purposes the widely accepted figure of the coupling loss for co-located antennas that are not coordinated is 30 dB. Higher values of coupling loss are achievable where the three types of separations described abo
35、ve are available (see 5.2.2). The improvement is achievable using the antenna patterns only, without the use of any additional screening or absorption material. 5.2.2 Integration into an IMT-2000 technology This is a deployment technique, which is technology independent. 5.2.3 Indication of who shou
36、ld apply the technique Coordination is needed between the two networks deployed in the cell site and operating in adjacent frequencies. 5.2.4 Implications and trade-offs The location for mounting antennas is subject to practical site engineering considerations such as space availability, lease agree
37、ments, coaxial runs, zoning laws etc. It will not be possible to maintain the appropriate separation distance between antennas at all of the co-located BSs. Therefore, the gains will not be fully realizable at all locations throughout the network. Issues like target area coverage, inter-system inter
38、ference, frequency reuse pattern also need to be taken into account for antenna placement. 5.3 Antenna polarization 5.3.1 Brief description It is possible to get additional isolation between two linearly polarized BS antennas by having them orthogonally polarized to each other. As an example, using
39、vertical polarization on one antenna and horizontal polarization on the other can reduce the degree of coupling between the two. The Rep. ITU-R M.2045 5 coupling effect is quantified in terms of an antenna characteristic know as cross polar discrimination (XPD). One possible scenario for implementin
40、g this technique would be the case of two BS antennas at close proximity, potentially in LoS of each other. While the underlying path loss could be insufficient to provide enough isolation for adjacent or alternate channel operation, additional isolation due to the use of a polarization orthogonal t
41、o that of the interferer could potentially solve the problem. It should be noted that the amount of isolation through XPD of the antennas is likely to be achievable when the two antennas are in the worst-case scenario configuration; i.e., main-beam coupling in LoS, where isolation is needed most. 5.
42、3.2 Integration into an IMT-2000 technology This is a deployment technique, which is technology independent. 5.3.3 Indication of who should apply the technique A coordinated decision needs to be made for the two networks operating in adjacent frequencies. 5.3.4 Implications and trade-offs This techn
43、ique cannot be used if either network uses polarization diversity. 5.4 Adaptive antennas 5.4.1 Brief description Adaptive antennas may be defined as “an array of antennas that is able to change its antenna pattern dynamically to adjust to noise, interference and multipath” 9. Adaptive antennas are u
44、sed to enhance received signals and may also be used to form beams for transmission. The direct benefit from the use of adaptive antennas on the coexistence, however, is due to the fact that the RF energy radiated by antenna arrays is both lower than that from conventional antennas for the same e.i.
45、r.p. and focused in limited, specific regions of a cell rather than wide sectors. 5.4.2 Integration into an IMT-2000 technology Adaptive antennas are included in the TD-SCDMA IMT-2000 standard and can also be applied to other IMT-2000 technologies. 5.4.3 Indication of who should apply the technique
46、This technique may be integrated into the BS hardware and software or could be added on to an otherwise conventional BS. For the integrated case, the BS would have had to have been developed with the use of adaptive antenna arrays and spatial processing as an integral system capability. Otherwise, i
47、t will require the joint support of both the BS and the adaptive antenna system vendors. 5.4.4 Implications and trade-offs The typical reason for the deployment of systems using adaptive antennas is to increase the network capacity and coverage thus making better use of available spectrum. Adaptive
48、antennas can also be used to perform null steering, which is not analysed in this Report, to reduce a BSs susceptibility to interference from other systems BSs. In either case, using adaptive antennas to address coexistence problems is likely to limit the availability of the capacity and coverage be
49、nefits they typically provide. 6 Rep. ITU-R M.2045 5.5 Transmitter/receiver improvements 5.5.1 Brief description For BS-to-BS interference, filtering or linearization or both can be used to reduce the unwanted emissions from one BS to another thus reducing the interference at the victim BS. In a similar manner, receiver filtering may reduce the in-band interference to the victim BS. When the overall interference is reduced, BSs could operate closer to each other, or allowed higher Tx power or both while maintaining a desired interference level. 5.5.2 Integrati
