Wcdma for umts radio access for third genergation mobile communacations phần 6 doc

The operator’s coverage probability requirement for the 8 kbps, 64 kbps and 384 kbps services was set, respectively, to 95 %, 80 % and 50 %, or better. The planning phase started with radio link budget estimation and site loca tion selections. In the next planning step the dominance areas for each cell were optimised. In this context the dominance is related only to the propagation conditions. Antenna tilting, bearing and site locations can be tuned to achieve clear dominance areas for the cells. Dominance area optimisation is crucial for interference and soft handover area and soft handover probability control. The improved soft/softer handover and interference performance is automatically seen in the improved network capacity. The plan consists of 19 three-sectore d macro sites, and the average site area is 7.6 km 2 . In the city area, the uplink loading limitation was set to 75 %, corresponding to a 6 dB noise rise. In case the loading was exceeded, the necessary number of mobile stations was randomly set to outage (or moved to another carrier) from the highly loaded cells. Table 8.15 shows the user distribution in the simulations and the other simulation parameters are listed in Table 8.16. In all three simulation cases the cell throughput in kbps and the coverage probability for each service were of interest. Furthermore, the soft handover probability and loading results were collected. Tables 8.17 and 8.18 show the simulation results for cell throughput Figure 8.18. The network scenario. The area measures 12 Â 12 km 2 and is covered with 19 sites, each with three sectors Radio Network Planning 211 and coverage probabilities. The maximum uplink loading was set to 75 % according to Table 8.16. Note that in Table 8.17 in some cells the loading is lower than 75 %, and, correspondingly, the throughput is also lower than the achievable maximum value. The reason is that there was not enough offered traffic in the area to fully load the cells. The loading in cell 5 was 75 %. Cell 5 is located in the lower right corner in Figure 8.18, and there is no other cell close to cell 5. Therefore, that cell can collect more traffic than the other cells. For example, cells 2 and 3 are in the middle of the area and there is not enough traffic to fully load the cells. Table 8.18 shows that mobile station speed has an impact on both throughput and coverage probability. When mobile stations are moving at 50 km/h, fewer can be served, the throughput is lower and the resulting loading is higher than when mobile stations are moving at 3 km/h. If the throughput values are normalised to correspond to the same loading value, the difference between the 3 km/h and 50 km/h cases is more than 20 %. The better capacity with the slower-moving mobile stations can be explained by the better E b =N 0 performance. The fast power control is able to follow the fading signal and the require d E b =N 0 target is reduced. The lower target value reduces the overall interference level and more users can be served in the network. Table 8.15. The user distribution Service in kbps Users per service 8 1735 64 250 384 15 Table 8.16. Parameters used in the simulator Uplink loading limit 75 % Base station maximum transmission power 20 W (43 dBm) Mobile station maximum transmission power 300 mW (¼ 25 dBm) Mobile station power control dynamic range 70 dB Slow (log-normal) fading correlation between base stations 50 % Standard deviation for the slow fading 6 dB Multipath channel profile ITU Vehicular A Mobile station speeds 3 km/h and 50 km/h Mobile/base station noise figures 7 dB/5 dB Soft handover addition window À6dB Pilot channel power 30 dBm Combined power for other common channels 30 dBm Downlink orthogonality 0.5 Activity factor speech/data 50 %/100 % Base station antennas 65  /17 dBi Mobile antennas speech/data Omni/1.5 dBi 212 WCDMA for UMTS Comparing coverage probability, the faster-moving mobile stations experience better quality than the slow-moving ones, because for the latter a headroom is needed in the mobile transmission power to be able to maintain the fast power control – see Section 8.2.1. The impact of the speed can be seen, especially if the bit rates used are high, because for low bit rates the coverage is better due to a larger processing gain. The coverage is tested in this planning tool by using a test mobile after the uplink iterations have converged. It is assumed that this test mobile does not affect the loading in the network. This example case demonstrates the impact of the user profile, i.e. the serv ice used and the mobile station speed, on network performance. It is shown that the lower mobile station speed provides better capacity: the number of mobile stations served and the cell throughput are higher in the 3 km/h case than in the 50 km/h case. Comparing coverage probability, the impact of the mobile station speed is different. The higher speed reduces the required fast Table 8.17. The cell throughput, loading and soft handover (SHO) overhead. UL ¼ uplink, DL ¼ downlink Basic loading: mobile speed 3 km/h, served users: 1805 —————————————————————————————————————————— Cell ID Throughput UL (kbps) Throughput DL (kbps) UL loading SHO overhead cell 1 728.00 720.00 0.50 0.34 cell 2 208.70 216.00 0.26 0.50 cell 3 231.20 192.00 0.24 0.35 cell 4 721.60 760.00 0.43 0.17 cell 5 1508.80 1132.52 0.75 0.22 cell 6 762.67 800.00 0.53 0.30 MEAN (all cells) 519.20 508.85 0.37 0.39 Basic loading: mobile speed 50 km/h, served users: 1777 Cell ID Throughput UL (kbps) Throughput DL (kbps) UL loading SHO overhead cell 1 672.00 710.67 0.58 0.29 cell 2 208.70 216.00 0.33 0.50 cell 3 226.67 192.00 0.29 0.35 cell 4 721.60 760.00 0.50 0.12 cell 5 1101.60 629.14 0.74 0.29 cell 6 772.68 800.00 0.60 0.27 MEAN 531.04 506.62 0.45 0.39 Basic loading: mobile speed 50 km/h and 3 km/h, served users: 1802 Cell ID Throughput UL (kbps) Throughput DL (kbps) UL loading SHO overhead cell 1 728.00 720.00 0.51 0.34 cell 2 208.70 216.00 0.29 0.50 cell 3 240.00 200.00 0.25 0.33 cell 4 730.55 760.00 0.44 0.20 cell 5 1162.52 780.92 0.67 0.33 cell 6 772.68 800.00 0.55 0.32 MEAN 525.04 513.63 0.40 0.39 Radio Network Planning 213 fading margin and thus the coverage probability is improved when the mobile station speed is increased. 8.3.4 Network Optimisation Network optimisation is a process to improve the overall network quality as experienced by the mobile subscribers and to ensure that network resources are used efficiently. Optimisa- tion includes: 1. Performance measurements. 2. Analysis of the measurement results. 3. Updates in the network configuration and parameters. The optimisation process is shown in Figure 8.19. A clear picture of the current network performance is needed for the performance optimisation. Typical mea surement tools are shown in Figure 8.20. The measurements can be obtained from the test mobile and from the radio network elements. The WCDMA mobile can provide relevant measurement data, e.g. uplink transmission power, soft handover rate and probabilities, CPICH E c =N 0 and downlink BLER. Also, scanners can be used to provide some of the downlink measurements, like CPICH measurements for the neighbourlist optimisation. Table 8.18. The coverage probability results Test mobile speed: Basic loading: mobile —————————————— speed 3 km/h 3 km/h 50 km/h 8 kbps 96.6 % 97.7 % 64 kbps 84.6 % 88.9 % 384 kbps 66.9 % 71.4 % Test mobile speed: Basic loading: mobile —————————————— speed 50 km/h 3 km/h 50 km/h 8 kbps 95.5 % 97.1 % 64 kbps 82.4 % 87.2 % 384 kbps 63.0 % 67.2 % Test mobile speed: Basic loading: mobile 3 —————————————— and 50 km/h 3 km/h 50 km/h 8 kbps 96.0 % 97.5 % 64 kbps 83.9 % 88.3 % 384 kbps 65.7 % 70.2 % 214 WCDMA for UMTS The radio network can typically provide connection level and cell level measurements. Examples of the connection measurements include uplink BLER and downlink transmission power. The connection level measurements both from the mobile and from the network are important to get the network running and provide the required quality for the end users. The cell level measurements become more important in the capacity optimisation phase. The cell Performance analysis Networks tuning Key Performance Indicators (KPI) Update of parameters, site configurations etc. Performance measurements Figure 8.19. Network optimisation process Figure 8.20. Network performance measurements Radio Network Planning 215 level measurements may include total received power and total transmitted power, the same parameters that are used by the radio resource management algorithms. The measurement tools can provide lots of results. In order to speed up the measurement analysis it is beneficial to define those measurement results that are considered the most important ones, Key Performance Indicators, KPIs. Examples of KPIs are total base station transmission power, soft handover overhead, drop call rate and packet data delay. The comparison of KPIs and desired target values indicates the problem areas in the network where the network tuni ng can be focused. The network tuning can include updates of RRM parameters, e.g. handover parameters, common channel powers or packet data parameters. The tuning can also include changes of antenna directions. It may be possible to adjust the antenna tilts remotely without any site visits. An example case is illustrated in Figure 8.21. If there is too much overlapping of the adjacent cells, the other cell interference is high and the system capacity is low. The effect of other cell interference is represented with the parameter other cell to own cell interference ratio, i, in the load equations of Section 8.2, see Equation (8.16). The importance of the other cell interference is illustrated in Figure 8.22: if the other cell interference can be decreased Figure 8.21. Network tuning with antenna tilts = ∑ N j =1 η DL u j Other cell interference ( E b / N 0 ) j W/R j If i can be reduced from 1.3 to 0.65, the number of users N can be increased 57 %. We assume a = 0.5. [(1−α)+ i ] Figure 8.22. Importance of other cell interference for WCDMA downlink capacity 216 WCDMA for UMTS by 50 %, the capacity can be increased by 57 %. The large overlapping can be seen from the high number of users in soft handover between these cells. With advanced Operations Support System (OSS) the network performance monitoring and optimisation can be automated. OSS can point out the performance problems, propose corrective actions and even make some tuning actions automatically. The network performance can be best observed when the network load is high. With low load some of the problems may not be visible. Therefore, we need to consider artificial load generation to emulate high loading in the network. A high uplink load can be generated by increasing the E b =N 0 target of the outer loop power control. In the normal operation the outer loop power control provides the required quality with minimum E b =N 0 . If we increase manually the E b =N 0 target, e.g. 10 dB higher than the normal operation point, that uplink connection will cause 10 times more interfer ence and converts 32 kbps connection into 320 kbps high bit rate connection from the interference point of view. The effect of higher E b =N 0 can be seen in the uplink load equation of Equation (8.12). The same approach can be applied in the downlink as well in Equation (8.16). Another load generation approach in downlink is to transmit dummy data in downlink with a few code channels, even if there are no mobiles receiving that data. That approach is called Orthogonal Channel Noise Source, OCNS. For more information on the radio network optimisation process please refer to [3], Chapter 8, and for advanced monitoring and network tuning see [3], Chapter 10. 8.4 GSM Co-planning Utilisation of existing base station sites is important in speeding up WCDMA deployment and in sharing sites and transmission costs with the existing second generation system. The feasibility of sharing sites depends on the relative coverage of the existing network compared to WCDMA. In this section we compare the relative upli nk coverage of existing GSM900 and GSM1800 full rate speech services and WCDMA speech and 64 kbps and 144 kbps data services. Table 8.19 shows the assumptions made and the results of the comparison of coverage. The maximum path loss of the WCDMA 144 kbps here is 3 dB greater than in Table 8.4. The difference comes because of a smaller interference margin, a lower base station receiver noise figure, and no cable loss. Note also that the soft handover gain is included in the fast fading margin in Table 8.19 and the mobil e station power class is here assumed to be 21 dBm. Table 8.19 shows that the maximum path loss of the 144 kbps data service is the same as for speech service of GSM1800. Therefore, a 144 kbps WCDMA data service can be provided when using GSM1800 sites, with the same coverage probability as GSM1800 speech. If GSM900 sites are used for WCDMA and 64 kbps full coverage is needed, a 3 dB coverage improvement is needed in WCDMA. Section 12.2.1 analyses the uplink coverage of WCDMA and presents a number of solutions for improving WCDMA coverage to match GSM site density. The comparison in Table 8.19 assumes that GSM900 sites are planned as coverage-limited. In densely populated areas, however, GSM900 cells are typically smaller to provide enough capacity, and WCDMA co-siting is feasible. The downlink coverage of WCDMA is discussed in Sect ion 12.2.2 and is shown to be better than the uplink coverage. Therefore, it is possible to provide full downlink coverage for bit rates 144 to 384 kbps using GSM1800 sites. Radio Network Planning 217 Any comparison of the coverage of WCDMA and GSM depends on the exact receiver sensitivity values and on system parameters such as handover parameters and frequency hopping. The aim of this exercise is to compare the coverage of the GSM base station systems that have been deployed up to the present with WCDMA coverage in the initial deployment phase during 2002. The sensitivity of the latest GSM base stations is better than the one assumed in Table 8.19. Since the coverage of WCDMA typically is satisfactory when reusing GSM sites, GSM site reuse is the preferred solution in practice. Let us consider next the practical co-siting of the system. Co-sited WCDMA and GSM systems can share the antenna when a dual band or wideband antenna is used. The antenna needs to cover both the GSM band and UMTS band. GSM and WCDMA signals are combined with a diplexer to the common antenna feeder. The shared antenna solution is attractive from the site solution point of view but it limits the flexibility in optimising the antenna directions of GSM and WCDM A independently. Another co-siting solution is to use separate antennas for the two networks. That solution gives full flexibility in optimising the networks separately. These two solutions are shown in Figure 8.23. The co-siting of GSM and WCDMA is taken into account in 3GPP performance requirements and the interference between the systems can be avoided. Table 8.19. Typical maximum path losses with existing GSM and with WCDMA GSM900/ GSM1800/ WCDMA/ WCDMA/ WCDMA/ speech speech speech 64 kbps 144 kbps Mobile transmission power 33 dBm 30 dBm 21 dBm 21 dBm 21 dBm Receiver sensitivity 1 À110 dBm À110 dBm À125 dBm À120 dBm À117 dBm Interference margin 2 1.0 dB 0.0 dB 2.0 dB 2.0 dB 2.0 dB Fast fading margin 3 2.0 dB 2.0 dB 2.0 dB 2.0 dB 2.0 dB Base station antenna gain 4 16.0 dBi 18.0 dBi 18.0 dBi 1 8.0 dBi 18.0 dBi Body loss 5 3.0 dB 3.0 dB 3.0 dB — — Mobile antenna gain 6 0.0 dBi 0.0 dBi 0.0 dBi 2.0 dBi 2.0 dBi Relative gain from lower 7.0 dB 1.0 dB — — — frequency compared to UMTS frequency 7 Maximum path loss 160.0 dB 154.0 dB 157.0 dB 157.0 dB 154.0 dB 1 WCDMA sensitivity assumes 4.0 dB base station noise figure and E b =N 0 of 4.0 dB for 12.2 kbps speech, 2.0 dB for 64 kbps and 1.5 dB for 144 kbps data. For the E b =N 0 values see Section 12.5. GSM sensitivity is assumed to be À110 dBm with receive antenna diversity. 2 The WCDMA interference margin corresponds to 37 % loading of the pole capacity: see Figure 8.3. An interference margin of 1.0 dB is reserved for GSM900 because the small amount of spectrum in 900 MHz does not allow large reuse factors. 3 The fast fading margin for WCDMA includes the macro diversity gain against fast fading. 4 The antenna gain assumes three-sector configuration in both GSM and WCDMA. 5 The body loss accounts for the loss when the terminal is close to the user’s head. 6 A 2.0 dBi antenna gain is assumed for the data terminal. 7 The attenuation in 900 MHz is assumed to be 7.0 dB lower than in UMTS band and in GSM1800 band 1.0 dB lower than in UMTS band. 218 WCDMA for UMTS 8.5 Inter-operator Interference 8.5.1 Introduction In this section, the effect of adjacent channel interference between two operators on adjacent frequencies is studied. Adjacent channel interference needs to be considered, because it will affect all wideba nd systems where large guard bands are not possible, and WCDMA is no exception. If the adjacent frequencies are isolated in the frequency domain by large guard bands, spectrum is wasted due to the large system bandwidth. Tight spectrum mask requirements for a transmitter and high selectivity requirements for a receiver, in the mobile station and in the base station, would guarantee low adjacent channel interference. However, these requirements have a large impact, especially on the implementation of a small WCDMA mobile station. Adjacent Channel Interference power Ratio (ACIR) is defined as the ratio of the transmission power to the power measured after a receiver filter in the adjacent channel(s). Both the transmitted and the received power are measured with a filter that has a Root- Raised Cosine filter response with roll-off of 0.22 and a bandwidth equal to the chip rate [11]. The adjacent channel interference is caused by transmitter non-idealities and imperfect receiver filtering. In both uplink and downlink, the adjacent channel performance is limited by the performance of the mobile. In the uplink the main source of adjacent channel interference is the non-linear power amplifier in the mobile station, which introduces adjacent channel leakage power. In the downlink the limiting factor for adjacent channel interference is the receiver selectivity of the WCDMA terminal. The requirements for adjacent channel performance are shown in Table 8.20. GSM base station Dual band antenna for GSM and UMTS band WCDMA base station GSM base station UMTS band WCDMA base station GSM band Diplexer Figure 8.23. Co-siting of GSM and WCDMA Radio Network Planning 219 Such an interfer ence scenario, where the adjacent channel interference could affect network performance, is illustr ated in Figure 8.24. Operator 1’s mobile is connected to a far-away base station and is at the same time located clos e to Operator 2’s base station on the adjacent frequency. The mobile will receive interference from Operator 2’s base station which may – in the worst case – block the reception of its own weak signal. In the following sectio ns the effect of the adjacent channel interference in this interference scenario is analysed by worst-case calculations and by system simulations. It will be shown that the worst-case calculations give very bad results but also that the worst-case scenario is extremely unlikely to happen in real networks. Therefore, simulations are also used to study this interference scenario. Finally, conclusions are drawn regarding adjacent channel interference and implications for network planning are discussed. 8.5.2 Uplink vs. Downlink Effects While the mobile in Figure 8.24 receives interference, it will also cause interference in uplink to Operator 2’s base station. In this section we analyse the differences between uplink and downlink in the worst-case scenario. The worst -case adjacent channel interference occurs when a mobile in uplink and a base station in downlink are transmitting on full power, and the mobile is located very close to a base station that is receiving on the adjacent carrier. Table 8.20. Requirements for adjacent channel performance [11] Frequency separation Required attenuation Adjacent carrier (5 MHz separation) 33 dB both uplink and downlink Second adjacent carrier (10 MHz separation) 43 dB in uplink, 40 dB in downlink (estimated from in-band blocking) Operator 1 Operator 1 Operator 2 Weak signal Operator 1 Operator 2 Interference frequency 5 MHz 5 MHz Adjacent channel interference Figure 8.24. Adjacent channel interference in downlink 220 WCDMA for UMTS [...]... applicable in the third generation WCDMA air interface, where various bit rates have to be supported simultaneously Typical locations of the RRM algorithms in a WCDMA network are shown in Figure 9.1 WCDMA for UMTS, third edition Edited by Harri Holma and Antti Toskala # 2004 John Wiley & Sons, Ltd ISBN: 0-470-870 96- 6 WCDMA for UMTS 232 Figure 9.1 Typical locations of RRM algorithms in a WCDMA network 9.2... core band The frequency variants are listed in Table 8. 26 Table 8. 26 WCDMA frequency variants Frequency variant Uplink [MHz] Downlink [MHz] Band I / UMTS core band 1920–1980 2110–2170 Band II / WCDMA1 900 Band III / WCDMA1 800 1850–1910 1710–1785 1930–1990 1805–1880 Band IV / WCDMA1 700 Band V / WCDMA8 50 1710–1755 824–849 2110–2155 869 –894 Band VI / WCDMA8 00 830–840 875–885 Countries Europe, Asia, some... fast power control cannot compensate for the fading WCDMA for UMTS 2 36 Table 9.3 Simulated power rises Multipath channel ITU Pedestrian A, antenna diversity assumed UE speed (km/h) 3 10 20 50 140 Average power rise (dB) 2.1 2.0 1 .6 0.8 0.2 More information about the uplink power control modelling can be found in [1] Why is the power rise important for WCDMA system performance? In the downlink, the air... effect of the interference; WCDMA for UMTS 2 26  reduce the downlink instantaneous packet data bit rate to provide more processing gain to tolerate more interference;  reduce the downlink AMR voice bit rate to provide more processing gain 8 .6 8 .6. 1 WCDMA Frequency Variants Introduction The 3GPP WCDMA standard covers a number of other frequency variants in addition to the UMTS core band The frequency... Uplink’, Proceedings of VTC’99, Houston, Texas, May 1999, pp 1 266 – 1270 ¨ [2] Ojanpera, T and Prasad, R., Wideband CDMA for Third Generation Mobile Communications, Artech House, 1998 [3] Laiho, J., Wacker, A and Novosad, T., Radio Network Planning and Optimisation for UMTS, John Wiley & Sons, 2001 [4] Saunders, S., Antennas and Propagation for Wireless Communication Systems, John Wiley & Sons, 1999 ¨... cell 2 Figure 9. 16 General scheme of the WCDMA soft handover algorithm WCDMA for UMTS 2 46  If Pilot_Ec /I0 < Best_ Pilot_Ec /I0 À Reporting_range À Hysteresis_event1B for a period of ÁT, then the cell is removed from the active set This event is called Event 1B or Radio Link Removal  If the active set is full and Best_candidate_Pilot_Ec /I0 > Worst_Old_Pilot_Ec /I0 þ Hysteresis_event1C for a period of... requirements are defined for the Bands II, III, IV, V, where other technologies exist on the same band 2.7 MHz GSM WCDMA 30 dB attenuation with WCDMA mobile selectivity Figure 8.30 Attenuation from GSM signal 2.7 MHz from WCDMA derived from narrowband blocking requirements WCDMA for UMTS 228  The mobile reference sensitivity requirement is relaxed by 2–3 dB from À117 dBm to À115/À114 dBm to allow high enough... Laiho-Steffens, J., Sipila, K and Heiska, K., ‘The Impact of the Base Station Sectorisation on WCDMA Radio Network Performance’, Proceedings of VTC’99, Amsterdam, The Netherlands, September 1999, pp 261 1– 261 5 ¨ [6] Sipila, K., Honkasalo, Z., Laiho-Steffens, J and Wacker, A., ‘Estimation of Capacity and Required Transmission Power of WCDMA Downlink Based on a Downlink Pole Equation’, Proceedings of VTC2000, Spring... Simulator for Studying WCDMA Radio Network Planning Issues’, Proceedings of VTC’99, Houston, Texas, May 1999, pp 24 36 2440 [10] Nokia NetActTM Planner, http://www.nokia.com/networks/services/netact/netact_planner/ [11] 3GPP Technical Specification 25.101, UE Radio Transmission and Reception (FDD) [12] 3GPP Technical Report 25.942, RF System Scenarios [13] Holma, H and Velez, F ‘Performance of WCDMA1 900... find the locations where the interference could cause problems We show an example for WCDMA voice service in downlink with the following assumptions:  The required Ec =I0 for WCDMA voice ¼ Eb =N0 – processing gain ¼ À18 dB from Table 8.24  The maximum transmission power per WCDMA connection is assumed to be 33 dBm  WCDMA mobile selectivity is 33 dB  The base stations’ transmit power is 43 dBm The maximum . 2 26. 67 192.00 0.29 0.35 cell 4 721 .60 760 .00 0.50 0.12 cell 5 1101 .60 62 9.14 0.74 0.29 cell 6 772 .68 800.00 0 .60 0.27 MEAN 531.04 5 06. 62 0.45 0.39 Basic loading: mobile speed 50 km/h and 3 km/h,. 84 .6 % 88.9 % 384 kbps 66 .9 % 71.4 % Test mobile speed: Basic loading: mobile —————————————— speed 50 km/h 3 km/h 50 km/h 8 kbps 95.5 % 97.1 % 64 kbps 82.4 % 87.2 % 384 kbps 63 .0 % 67 .2 % Test mobile. 2 208.70 2 16. 00 0.29 0.50 cell 3 240.00 200.00 0.25 0.33 cell 4 730.55 760 .00 0.44 0.20 cell 5 1 162 .52 780.92 0 .67 0.33 cell 6 772 .68 800.00 0.55 0.32 MEAN 525.04 513 .63 0.40 0.39 Radio Network