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1、TSG-RAN Working Group 4 (Radio) meeting #37R4-051132Seoul, Korea, 7 11 November, 2005Source:EricssonTitle:How to apply SCME in RAN4Agenda item:7.1Document for:DiscussionIntroductionIn a contribution on Spatial Radio Channel Models to RAN4#36 in London 1, an extended SCM was proposed based on work in
2、 the WINNER project for systems beyond 3G. The model is called SCME (SCM Extension) and the contribution introduces the model for bandwidths up to 20MHz.Radio channel and propagation models have many applications in RAN4, both for defining system and link level scenario assumptions for simulations a
3、nd analysis, and to define receiver requirements in the specifications. This contribution looks at the different uses of channel models in RAN4 work and shows how SCME could be applied in that work.Use of channel models in RAN4 specifications today1. UE performance requirements (TS 25.101)The UE spe
4、cification TS25.101 1 has a large range of receiver requirements defined in clauses 8, 9 and 10 for both static and multipath fading propagation. These are used to define the link level requirements for DCH demodulation, power control, compressed mode, etc. There are also requirements for a number o
5、f other channels, including BCH, PCH, HS-DSCH and E-DCH related channels.Defining receiver requirements is mainly a way of making sure that receiver implementations are up to the standard required for good system performance. They are used both as reference points for simulations in developing and b
6、enchmarking receiver algorithms and as “conformance testing conditions” for UEs. For this reason, the propagation conditions need to be quite simple in structure and should have fixed rather than stochastic properties in order to reduce simulation and testing time.Several sets of propagation conditi
7、ons are defined over the different releases of the specification in Annex B of TS25.101 5: Case 1-8 propagation conditions define fixed tapped delay line models for different UE speeds. The models are not based on any “real-life measurement, but some are still “typical” propagation profiles with exp
8、onential decaying taps. The aim was originally to pick a number of points in the vast domain of propagation conditions that “test” the performance of a Rake receiver in terms of e.g high delay spread (Case 2) and high mobile speed (Case 3 and 6) Moving and Birth-Death propagation conditions are two
9、more “artificial” conditions specifically aimed at testing a Rake receiver in terms of catching stronger propagation rays of that have quickly changing delay (“moving” conditions) and rays that quickly appear and disappear (“birth-death” conditions). HSDPA performance propagation conditions were int
10、roduced for HS-DSCH and E-DCH related performance in Rel-5 and Rel-6, since it was felt by many that the conditions defined by Case 1-8 were too “artificial”. The HSDPA conditions are based on the ITUs Pedestrian A/B and Vehicular A models.2. BS performance requirements (TS 25.104)The BS specificati
11、on TS25.104 1 has a set of receiver requirements defined in clauses 8, similar in structure to the UE specification. Also here, propagation conditions need to be quite simple and should not have stochastic properties in order to reduce simulation and testing time.Originally, the same set of tapped d
12、elay line propagation conditions was defined as for the UE, but they have developed in a slightly different way. BS conditions are found in Annex B of TS25.104 6: Case 1-4 propagation conditions define fixed tapped delay line models for different UE speeds. They correspond to Cases 1-3 and 6 for the
13、 UE. Moving and Birth-Death propagation are the same as for the UE. E-DCH performance propagation are used for E-DCH performance in Rel-6 and are the same as the HSDPA conditions for the UE, based ITUs Pedestrian A/B and Vehicular A models.3. Radio Resource Management requirements (TS 25.133)There a
14、re also some UE test cases in the RRM specification TS25.133 7 that makes use of the fading propagation conditions. It is Case 1, 3 and 5 from the UE performance requirements in 5 that are re-used for test cases concerning reporting of neighbours and event triggered reporting.4. Channel models for d
15、eployment evaluation (TR 25.943)There was also a set of channel models for “deployment evaluation” developed in Rel-4, documented in TR25.943 8. The purpose was a set of channel models that were based on measurements and thus more “real life” than Cases 1-8.The models are based on the COST259 work 3
16、. The COST 259 models define parameters for a number of environments, where the parameters describe the distribution functions for each particular case. The COST259 model is in that sense stochastic, since channel realisations are generated through distribution functions. The 3GPP models in TR25.943
17、 8 are however a set of reduced complexity COST259 models based on the parameters from COST207 that define the propagation models used for GSM in GERAN: Typical Urban (TU), Rural Area (RA) and Hilly Terrain (HT). Each model is described with a set of fixed parameters and also with a fixed taped dela
18、y line profile with 10 or 20 taps. This enables shorter simulation or testing time in cases where the models are used for benchmarking or as a reference point in simulations.5. Channel models used in RF system scenarios (TR 25.942)For many of the specification points in the RAN4 specifications, cert
19、ain RF system scenarios were used to evaluate system performance and to define different receiver and transmitter requirements. These are collected in TR25.942 7. The scenarios define co-existence within the system and with other systems and are used for requirements such as ACLR, ACS, Blocking, FDD
20、/TDD co-existence, definition of BS classes, RRM, etc.Most RF system scenarios require a propagation model for the evaluation, but not necessarily defined with multipath fading. Propagation for macro, micro, pico and also mixed environments are defined in TR25.942 7. A few scenarios also define mult
21、ipath propagation model for the link level parameters to be included in the analysis.In a system evaluation, multipath-fading models with parameters defined as distributions can be useful, but has so far not been applied in TR25.942 7. Since there are so many stochastic parameters in such an analysi
22、s, simulation time is not affected very much by also making the multipath fading stochastic.Application of SCME in E-UTRA specificationsThe spatial channel model described in TR25.996 2 and its extension to the wider bandwidth SCME proposed in 1 can be useful for E-UTRA, since MIMO and other advance
23、d antenna concepts are a fundamental part of E-UTRA. But as shown in the previous section of this paper, simpler models that do not have stochastic parameters are the ones most suited for most aspects of the RAN4 work, especially for performance requirements. Still, we would also like to define perf
24、ormance requirements for MIMO. Another goal for the work on E-UTRA should be to use a consistent set of models throughout the RAN work, avoiding divergence into several sets of incompatible models.In a recent conference paper on the SCME 4 fixed tapped delay line models based on the SCME are demonst
25、rated, including also fixed angular parameters. They are derived taking one set of values from the parameter distributions, in a way similar to the reduced complexity models defined for UTRA in TR25.943 8. The following parameters from the SCME can be fixed: Relative path power Relative path delay P
26、ath angle of arrival Path angle of departureIt is possible to keep some model parameters fixed and use others to derive “secondary” parameters in further simplified models. The fixed angular parameters can e.g. be used to derive correlation values between antennas in a multiple-antenna diversity cas
27、e if a default antenna pattern is assumed. For a single link the model would “collapse” into a simple tapped delay line model with a single set of tap delay and relative power values.We can thus envision a set of multipath models with different levels of “simplification”, all based on the same SCME:
28、(A) Full SCME model (as presented in 1)(B) Tapped delay-line SCME model with fixed angular parameters (example in table 5 of 4)(C) Tapped delay-line model for multiple antennas with correlation parameters derived from fixed angular parameters and an assumed antenna pattern.(D) “Simple” tapped delay-
29、line model for single linkFor models (C) and (D), the Doppler spectrum can be derived from the angular parameters or a Classical Doppler spectrum can be assumed.E-UTRA will require propagation models to at least the same extent as UTRA. Below are given examples of how the SCME model could be applied
30、 in the different E-UTRA specifications:1. UE performance requirementsFor single link performance requirements, a simple delay line model (D) is sufficient. For UEs with receiver antenna diversity, modelling of correlation can be done using model (C). For MIMO performance requirement with multiple a
31、ntennas, a multi-antenna model (C) with correlation parameters is required.2. BS performance requirementsThe situation is quite similar in terms of models for BS requirements. For single link, model (D) can be used. For receiver diversity, MIMO etc, a model with correlation parameters like (C) is ne
32、eded.3. Radio Resource Management requirementsRRM requirements may be relevant for single link and possibly Rx antenna diversity. Model (D) and (C) will be sufficient for those cases.4. Channel models for deployment evaluationIf a consistent set of models derived from SCME can be defined and are wid
33、ely accepted, there will be no need for special models for “deployment evaluation”.5. Channel models used in RF system scenariosCo-existence within and between systems must work without special antenna solution and all requirements have to be general. Link level results should therefore be consisten
34、tly defined with a simple tapped delay line model (D). Note that SCME can also be used to model path loss and site-to-site correlation (but not sector-to-sector).6. System studiesFor comparative evaluation of different L1 schemes like MIMO, beam forming and closed loop Tx diversity, full models (A)
35、on link level will be needed. As an alternative, in order to make simulation results more easily comparable between companies and to reduce simulation time, the simplified model (B) can be used.Open issuesThere are some open issues with applying SCME as a general model for RAN4 specifications. Some
36、that need special consideration are: The model scenarios do presently not cover outdoor-to-indoor or indoor-to-indoor, new scenarios and model parameters are needed. For the UE, the interface from antennas to antenna connector not tested, instead an assumed antenna pattern is applied to determine th
37、e fixed model parameters. How is the test part A vs. test port B problem handled for the BS? Requirements at the antenna connector cannot easily be made equivalent to requirements at test port B. The two last bullets are more related to testing, but they also have an impact on how the channel model
38、is defined in case of multiple antennas.ConclusionSCME as a proposed propagation model for E-UTRA can have many applications in the RAN4 specifications. It is shown in this paper that for receiver requirements in general, simplified versions of SCME can be sufficient. SCME can in this way provide a
39、consistent set of models with varying complexity for use throughout the RAN work on E-UTRA, avoiding divergence into several sets of incompatible models.References1“Spatial Radio Channel Models for Systems Beyond 3G”, R4-050854, Source: Elektrobit, Nokia, Siemens, Philips, Alcatel, Telefonica, Lucen
40、t, Ericsson.23GPP TR 25.996 V6.1.0 (2003-09), “Spatial channel model for Multiple Input Multiple Output (MIMO) simulations (Release 6)”.3L.M. Correia, ed., Wireless flexible personalized communications - COST 259: European co-operation in mobile radio research, John Wiley & Sons 2001.4“An Interim Ch
41、annel Model for Beyond-3G Systems Extending the 3GPP Spatial Channel Model (SCM)”, Daniel S. Baum et al, Proc. IEEE VTC05, Stockholm, Sweden, May 2005.53GPP TS 25.101 V7.1.0 (2005-09), “User Equipment (UE) radio transmission and reception (FDD) (Release 7)”.63GPP TS 25.104 V7.1.0 (2005-09), “Base St
42、ation (BS) radio transmission and reception (FDD) (Release 7)”.73GPP TS 25.133 V7.1.0 (2005-09), “Requirements for support of radio resource management (FDD) (Release 7)”.83GPP TR 25.942 V6.4.0 (2005-03), “Radio Frequency (RF) system scenarios (Release 6)”.93GPP TR 25.943 V6.0.0 (2004-12), “Deployment aspects (Release 6)”.
