1、 Rep. ITU-R M.2031 1 REPORT ITU-R M.2031 Compatibility between WCDMA 1800 downlink and GSM 1900 uplink (Question ITU-R 229/8) (2003) 1 Introduction 1.1 Introduction and outline of the Report This Report discusses the compatibility analysis of radio coexistence between wideband CDMA deployed in the 1
2、 800 MHz bands (WCDMA 1800) and GSM deployed in the PCS 1900 bands (GSM 1900) in adjacent bands and opposite duplex direction. The objective is to determine by means of deterministic calculations and Monte Carlo simulations the amount of guardband necessary to protect the two adjacent services again
3、st mutual interference. The deterministic calculations have been applied to the base station to base station (BS-BS) scenarios. Monte Carlo simulations have been used to investigate both the mobile station to mobile station (MS-MS) and BS-BS scenarios. This Report is arranged as follows: in 2, the a
4、ssumptions pertaining to the BS-BS interference scenario are recalled. 3 examines the impact of WCDMA 1800 BS interference on GSM 1900 uplinks by means of deterministic calculations, whereas 4 presents the Monte Carlo simulation results of the BS-BS and MS-MS scenarios. The Appendix summarizes the m
5、ethodology and assumptions specific to the Monte Carlo simulations. 1.2 Background The analysed phase 1 of personal communication system (PCS) evolution is characterised by the introduction of IMT-2000 technologies in the 1 710-1 755/1 800-1 845 MHz bands. The proposed allocation is considering a 5
6、MHz guardband between the WCDMA 1800 downlink band and the PCS 1900 uplink band, as highlighted in Fig. 1. Rap 2031-011 700 1 750 1 800 1 850 1 900 MHzPCS-Bphase 1MS TxBSTxPCSMS TxFIGURE 1Analysed phase 1 of PCS evolution2 Rep. ITU-R M.2031 This Report considers interference from the WCDMA 1800 syst
7、em (specifications not yet finalized) to an existing GSM 1900 system when considering various spectrum arrangements in the bands 1 710-1 990 MHz, e.g. on the spectrum border at 1 850 MHz, denoted guardband (GB) as depicted in Fig. 2. Rap 2031-021 850 MHzFIGURE 2WCDMA 1800 dowlink and GSM 1900 uplink
8、GSMGBWCDMAAs an example, we are addressing here the GSM 1900 system but there are also other technologies in the PCS bands, such as IS-95 and TDMA (IS-136) where similar potential interference exists. This sharing situation will occur if portions of both the WCDMA 1800 and the PCS 1900 bands are all
9、ocated in the same geographical area. This causes potential mobile MS-MS as well as BS-BS interference. The deterministic calculations (worst case analysis) and the Monte Carlo simulations are two methodologies that complement each other. While deterministic calculations consider worst-case values f
10、or the systems parameters, statistical approaches like Monte Carlo simulations give access to an estimate of the probability with which this worst case will occur. The Monte Carlo methodology applied to the analysis of radio systems coexistence is now widely approved and recommended by the Electroni
11、c Communication Committee (ECC)1, Report ITU-R SM.2028 and third generation partnership project (3GPP)2. The 3GPP-based Monte Carlo methodology has been used to analyse the guardband needed between the WCDMA 1800 and PCS 1900 bands. Simulation results pertaining to the macro-cellular environment are
12、 reported and discussed in this document. The simulation methodology and assumptions are described in details in Appendix 1. 2 Assumptions for the BS-BS scenario Table 1 aims at summarizing the assumptions adopted for the study. An objective of this section is also to clarify the relationship that e
13、xists between the carrier-to-carrier spacing and the guardband parameters. 1CEPT ECC Report 68, downloadable from ERO website http:/www.ero.dk/. 2RF System Scenarios 3GPP TR 25.942 v2.3.1. Rep. ITU-R M.2031 3 TABLE 1 Assumptions for the deterministic calculations and the Monte Carlo simulations Figu
14、re 3 presents the WCDMA carrier-to-GSM carrier spacing when no guardband is introduced between the WCDMA and the GSM allocations. As a consequence there is the following linear relationship between carrier-to-carrier spacing and guardband: Guardband = Carrier-to-carrier spacing (MHz) 2.8 MHz Rap 203
15、1-03FIGURE 3For 5 MHz allocated bandwidth - carrier-to-carrier spacing is 2.8 MHz*5 MHz channel3.84 MHz WCDMA200 kHz rasterClosest blocker2.8 MHz2.4 MHz2.6 MHz400 kHzGSMBand edge* Carrier to carrier spacing for UMTS-1800 Motorola 3GPP TSG RAN WG4 R4-1800AH 0112 1800/1900 ad hoc meeting, Seattle, Uni
16、ted States of America, 2-3 May 2001. 3UTRA (BS) FDD; Radio Transmission and Reception 3GPP TS 25.104 v3.4.0. 4Results of UMTS1800/GSM Co-existence Simulations (Uplink) 3GPP TSG RAN WG4 Ericsson TSG R4 No. 15 (01) 0344 February 2001. This contains the UMTS 1800 simulation assumptions agreed within 3G
17、PP RAN WG4. Deterministic calculations Monte Carlo simulations WCDMA 1800 BS transmitter power (dBm) 43 43 60 dB (carrier-to-carrier spacing = 5 MHz)363,7 dB (guardband = 5 MHz)3WCDMA 1800 BS adjacent channel leakage ratio (ACLR) 72 dB (carrier-to-carrier spacing =10 MHz)381 dB (guardband = 10 MHz)3
18、WCDMA 1800 BS transmitter antenna gain (dBi) 14 114GSM 1900 BS receiver antenna gain (dBi) 12 114GSM 1900 base transceiver station (BTS) sensitivity (dBm) 104 1074GSM receiver power (dBm) 101 Not deterministic simulated C/I target (GSM 1900 uplink) (dB) 9 64BS-BS propagation model Dual-slope line-of
19、-sight LoS (see 3) Free space (see Appendix 1) 4 Rep. ITU-R M.2031 3 Deterministic calculations The following study highlights the potential interference from the WCDMA downlink transmission to the GSM uplink reception in a base-to-base constellation when considering a rooftop installation scenario.
20、 In this section, only the WCDMA out-of-band transmission is considered, i.e. the WCDMA BS transmitter is suggested to be the limiting factor to the performance. It is noted that similar studies are also required in the opposite direction involving the terminals. BSs are supposed to be located withi
21、n LoS, and consequently, the dual-slope LoS propagation model is used. Assuming a carrier frequency of about 2 GHz, the path loss is calculated as: +=breakbreakbreakLoSdddddddLfor)(log40)(log205.381for)(log205.38101010With an effective BS height over the reflecting surface of 6 m (BS height = 30 m,
22、average building height = 24 m), the breakpoint, dbreak, is 960 m (dbreak= 4 htx hrx/). 3.1 Adjacent channel interference The adjacent channel interference (ACI) is calculated as: convBWLGGACLRPACIxrAxtAxt_,+= dBm where: Ptx: WCDMA BS output power ACLR : adjacent channel leakage power ratio GA,txand
23、 GA,rx: transmitter and receiver antenna gain respectively L : path loss BW_conv : bandwidth conversion factor. 3.2 Minimum coupling loss Given a maximum value of the adjacent channel interference, ACImax, we can calculate the minimum required path loss, Lmin, denoted as the minimum coupling loss (M
24、CL). maxxrAxtAxtminACIconvBWGGACLRPL += _,dB 3.3 Minimum separation distance The minimum required path loss is then transferred to a minimum separation distance (MSD) by means of the propagation model. Assuming that the ACI must not exceed the noise floor at the sensitivity level, ACImaxcan be set t
25、o: GSMxrmaxICSACI = dBm where: Srx: GSM sensitivity level :GSMICrequired GSM C/I. Rep. ITU-R M.2031 5 Given the parameter values below, the minimum required path loss and separation distance could be found in Table 2. Ptx= 43 dBm ACLR = 46/58 dB for 5/10 MHz carrier separation ( f ) GA,tx= 14 dB GA,
26、rx= 12 dB Srx= 104 dBm C/IGSM= 9 dB BW_conv = 5 MHz/200 kHz = 14 dB. TABLE 2 Minimum required path loss and separation distance between WCDMA 1800 and GSM 1900 BSs 4 Monte Carlo simulations 4.1 BS-BS scenario 4.1.1 BSs co-siting Monte Carlo simulations have been run using the 3GPP assumed BS-BS MCL
27、value of 30 dB (including antenna gains2) and a level of unwanted emission from the WCDMA BS compliant with current 3GPP specifications3. Fig. 4 shows that WCDMA BS interference is causing more than 90% outage on the GSM uplink for a 5 MHz guardband. This degradation can be limited by taking into ac
28、count more realistic values for the following parameters: The BS-BS minimum coupling loss. The WCDMA BS unwanted emissions level. The guardband value between the WCDMA 1800 and PCS 1900 bands. The geographical shift of interfering BSs is also investigated ( 4.1.2). f / guardband (MHz) 5/2.2 10/7.2 M
29、inimum path loss, Lmin(dB) 122 110 MSD (m) 3 790 1 900 6 Rep. ITU-R M.2031 4.1.1.1 BS-BS minimum coupling loss impact on GSM outage The influence of the minimum coupling loss between the WCDMA and GSM BSs antennas on the GSM capacity loss has been investigated. Since the MCL value of 30 dB specified
30、 in 3GPP TS 25.104 is a worst-case value, higher MCL values have been considered in this study5. Results for MCL of 40, 50 and 60 dB are presented in Fig. 4. It is found that when considering a guardband of 5 MHz, GSM capacity loss can be reduced down to around 6% by applying a MCL value of 60 dB. R
31、ap 2031-041009080706050403020100FIGURE 4GSM outage for 3GPP unwanted emission level*MCL = 30 dBMCL = 40 dBMCL = 50 dBMCL = 60 dB2.5 7.551015GSMBSoutagelevel (%)Guardband (MHz)* See footnote3.4.1.1.2 WCDMA BS unwanted emissions impact on GSM outage The same set of Monte Carlo simulations have been ru
32、n under the assumption of a lower WCDMA BS unwanted emission level (margins of 10 dB and 20 dB have been added to the 3GPP unwanted emission level to take into account additional filtering at the WCDMA BS transmitter for frequency offset greater than 7.8 MHz). Outage figures for MCL values of 30 dB
33、(3GPP specifications), 40 dB and 50 dB are presented in Fig. 5 (10 dB margin) and in Fig. 6 (20 dB margin). The results show that for a guardband of 5 MHz between the GSM and WCDMA bands in opposite duplex direction, GSM outage level is less than 5% for the 10 dB margin and for MCL higher or equal t
34、o 50 dB. When considering the 20 dB margin case, an MCL value of 40 dB is sufficient to reduce GSM system outage below 5%. 5Antenna-to-antenna Isolation Measurements 3GPP TSG RAN WG4 Allgon TSG R4 No. 8 (99)631 October 1999. Rep. ITU-R M.2031 7 Rap 2031-051009080706050403020100FIGURE 5GSM outage for
35、 WCDMA BS unwanted emission level 10 dB lower than 3GPP specifications for frequency offsetsgreater than 7.8 MHz*MCL = 30 dBMCL = 40 dBMCL = 50 dB2.5 7.551GSM BS outage(%)Guardband (MHz)* See footnote3.Figures 5 and 6 when compared to Fig. 4 show that MCL and additional filtering at the WCDMA BS hav
36、e an equivalent quantitative impact on the GSM system outage in uplink, so that a trade-off between these two mitigating factors is possible. Rap 2031-0680706050403020100FIGURE 6GSM outage for WCDMA BS unwanted emission level 20 dB lower than 3GPP specifications for frequency offsetsgreater than 7.8
37、 MHz*MCL = 30 dBMCL = 40 dBMCL = 50 dB2.5 7.551GSM BS outage(%)Guardband (MHz)* See footnote3.8 Rep. ITU-R M.2031 4.1.1.3 Power levels statistics This section proposes to further investigate the BS-BS scenario in co-siting by analysing the GSM BTS received power statistics. The victim GSM uplink sig
38、nal and the interfering WCDMA BS signal levels have been computed from the simulations by considering various scenarios (varying the MCL, the additional filtering and the cell size). Their statistics are presented in this section. The objective was to further investigate the influence of the antenna
39、 isolation (modelled by the MCL parameter) and the WCDMA BTS additional filtering. An understanding of these distributions will also help the comprehension of the role played by the GSM power control mechanism in the mitigation of the WCDMA interference. GSM only (no WCDMA interference; cell radius
40、= 577 m) Figures 7 and 8 respectively show the distribution of GSM wanted power level and intra-system interference power received at the GSM BTS. The narrow distribution obtained for the intra-system interference power in Fig. 8 shows that the GSM system achieves an intra-system interference level
41、between 114 dBm and 110 dBm for more than 85% of the uplinks. Rap 2031-072015105025120 112 104 96 88 80 72 64 56 48 40FIGURE 7GSM received signal strength when GSM network is isolatedWanted signals received power (dBm)GSM links(%)Figure 7 shows that when the GSM power control loop has terminated, al
42、l the GSM uplinks are experiencing received power higher than 102 dBm, which is 5 dB above sensitivity. Even when isolated from the WCDMA interference, the GSM system is interference-limited (intra-system interference). Rep. ITU-R M.2031 9 Rap 2031-08706050403020100120 112 104 96 88 80 72 64 56 48 4
43、0FIGURE 8GSM intra-system interference when GSM network is isolatedWCDMA interferences received power (dBm)GSMlinks(%)WCDMA interference (MCL = 30 dB including antenna gains; ACLR7.8 MHz = 63.7 dB; cell radius = 577 m) When applying the WCDMA interference, inter-system interference caused by the emi
44、ssion of the WCDMA BSs is added to the GSM intra-system interference (see Fig. 10). When considering MCL and ACLR values as per current 3GPP specifications, Monte Carlo simulations show that for more than 99% of the GSM uplinks, wanted GSM signal is received at higher power than 80 dBm (i.e. 27 dB a
45、bove sensitivity), as can be seen in Fig. 9. Given these results, the worst case for that scenario would be to consider a wanted received power of 80 dBm since less than 1% of the GSM links have a wanted received power lower or equal to 80 dBm. This case occurs for the GSM users that are the furthes
46、t from their BS. In that case, all the GSM MS transmission powers are equal or almost equal to the maximum transmit power (i.e. 30 dBm), meaning that the GSM power control loop is saturated due to the high interference levels coming from the WCDMA BSs. In this particular case, GSM outage reaches an
47、unacceptable level of 90%. Rap 2031-0914121086420120 110 100 90 80 70 60 50 40 30 20FIGURE 9GSM received signal strength for GSM protection as per current requirementsWanted signals received power (dBm)GSMlinks(%)10 Rep. ITU-R M.2031 Rap 2031-104035302520151050120 112 104 96 88 80 72 64 56 48 40FIGU
48、RE 10WCDMA interference for GSM protection as per current requirementsWCDMA interferences received power (dBm)GSM links(%)It can also be noted that the distribution of the interference power in Fig. 10 is a narrow distribution. This validates the deterministic calculation approach for the determinat
49、ion of the WCDMA BS interference on the GSM BSs6. On the contrary, the distribution of the wanted GSM signal is wider in power range, which implies that the received wanted power assumption used within the deterministic calculations need to be validated carefully by comparing it with the actual power distribution. In that particular case, it is shown that a worst received wanted signal strength chosen 27 dB above the sensitivity level will occ
