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1. Agenda – Day 1 • Network Planning in 3G • WCDMA Air-Interface • Power Budget Calculation • Load Calculation • Radio Network Dimensioning • Capacity & Coverage Improvement • Planning Support for 3G Roll-Out39 © NOKIA FILENAMs.PPT/ DATE / NN Power Budget Calculation - Objectives - At the end of this module you will be able to... •• List at least three WCDMA specific parameters List at least three WCDMA specific parameters in the link budget, which are not in GSM in the link budget, which are not in GSM •• Explain the meaning of Macro Diversity Gain Explain the meaning of Macro Diversity Gain (MDC) (MDC) •• Explain the meaning of Interference Margin Explain the meaning of Interference Margin •• Explain the meaning of Soft Handover Gain Explain the meaning of Soft Handover Gain •• Explain the meaning of Power Control Explain the meaning of Power Control Headroom Headroom40 © NOKIA FILENAMs.PPT/ DATE / NN
Power Budget Calculation Introduction • Power Budget is needed for path loss & cell range calculations • There are a few WCDMA-specific parameters in the power budget compared with GSM: • Processing gain • Load margin (interference) • Power control headroom • Soft handover gain • Limiting factors in the calculation • Mobile station transmit power in UL. • Total base station transmit power in DL. • When balancing the uplink and downlink service areas both links must be considered41 © NOKIA FILENAMs.PPT/ DATE / NN Power Budget Calculation Overview Result Output Losses BS Path- Load SHO MS MS/ Ec/I0 Process- MDC Eb/N0 power (Cable, Antenna loss (Interfe- Gain anten- body ing gain gain Combin-gain rence na loss (de- er,…) margin) gain spreading) Input Categories Hardware related System related Capacity related Application related42 © NOKIA FILENAMs.PPT/ DATE / NN
Power Budget Calculation ParametersLink budget Chip rate 3840.00 DL data rate 64.00 • Thermal Noise density [dBm/Hz] is defined as: UL Data rate UL Load 64.00 50% DL load 85% Thermal _ Noise _ Density = 10 * Log (kT )NRT 64kbit/s, 3km/h 2 ⇒ Where k is Boltzmans constant and T is the Uplink Downlink temperature in Kelvin ⇒ In normal conditions (290 K) the thermalRECEIVING END Node B UEThermal Noise Density dBm/Hz -173.98 -173.98Receiver Noise FigureReceiver Noise Density dB dBm/Hz 3.00 -170.98 8.00 -165.98 noise density is -173.98 dBm/HzNoise Power [NoW] dBm -105.14 -100.14Reguired Eb/NoSoft handover MDC gain dB dB 2.00 0.00 5.50 1.00 • Receiver noise figure [dB]Processing gain dB 17.78 17.78 ⇒ Equipment specific values which areInterference margin (NR) dB 3.01 8.24Required BTS Ec/Io [q] dB -12.77 -5.04 assumed to be 3dB at the BS and 8dB at theRequired Signal Power [S] dBm -117.91 -105.18Cable loss dB 2.00 0.00 MSBody loss dB 0.00 0.00Antenna gain RXSoft handover gain dBi dB 18.00 2.00 0.00 2.00 • Receiver Noise Density [dBm/Hz]Power control headroomIstropic power dB dBm 3.00 -132.91 0.00 -107.18 ⇒ Receiver noise density is the sum of theTRANSMITTING END UE Node B thermal noise density and the receiver noisePower per connection dBm 21.00 24.73 figure.Cable loss dB 0.00 2.00Body loss dB 0.00 0 ⇒ Thermal Noise density [dBm/Hz] + Receiver noise figure [dB] = Receiver Noise DensityAntenna gain TX dBi 0.00 18Peak EIRP dBm 21.00 40.73Isotropic path lossDL peak to average ratio dB dB 153.91 147.91 6.00 [dBm/Hz]Isotropic path loss to the cell border 153.9143 © NOKIA FILENAMs.PPT/ DATE / NN Power Budget Calculation Parameters • In order to calculate the Noise power of the receiver (minimum baseband signal strength at the receiver i.e. the receiver sensitivity for the non loaded network) the receiver noise density has to be scaled to the WCDMA carrier bandwidth ⇒receiver noise power [dBm] = Receiver Noise Density [dBm/Hz] + 10log10(3.84*106) =-170.98 + 65.84 = -105.14 dBm • Required Eb/N0 means that for some quality target (BLER) a certain average bit-energy divided by total noise+interference spectral density (Eb/N0) is required • the value depends on the service and the MS speed for which the link budget is to be calculated • Soft Handover MDC (macro diversity combining) gain, as a result of soft and softer handover • 40 % SHO overhead is used as average figure • approx. 30% of MSs are connected to 2 or more BSs at the same time. Furthermore, we can assume 20% is in 2-way SHO and 10% in 3-way SHO Consequently on average the softhandover overhead is 0.70x1 + 0.2x2 + 0.10x3 = 1.444 © NOKIA FILENAMs.PPT/ DATE / NN
Power Budget Calculation Uplink Soft Handover MDC Gain Soft HO Combining Downlink (including softer combining gain for theSofter HO other branch)Combining• In UL the MDC gain is 0 dB (on average) • In UL the MDC gain is calculated over all the connections (the ones in SHO and the ones not in SHO). Since there is only one transmitter in UL the MDC gain is negligible. • soft handover combining is done at RNC level (selection combining) • softer handover combining is done at the BTS (maximal ratio combining)• In DL there the combining gain is about 1dB • In DL the MDC gain calculated over all the connections (with and without SHO) is having value of around 1dB. • MS maximal ratio combining is used 45 © NOKIA FILENAMs.PPT/ DATE / NN Power Budget Calculation Soft Handover Gain• Soft handover gain is the gain against shadow fading. This is roughly the gain of a handover algorithm, in which the best BTS can always be chosen (based on minimal transmit power of MS) against a hard handover algorithm based on geometrical distance. • In reality the SHO gain is a function of required coverage probability and the standard deviation of the signal for the environment. • The gain is also dependent on whether the user is outdoors, where the likelihood of multiple servers is high, or indoors where the radio channel tends to be dominated by a much smaller number of serving cells. • For indoors users the recommendation is to use smaller SHO gain value. • SHO gain is measured as the gain in required Eb/No relative to that of single link and it is averaged over all the radio links in the SHO area.• Soft handover gain of 2 dB has been used average figure RNC 46 © NOKIA FILENAMs.PPT/ DATE / NN
Power Budget Calculation Parameters• Processing gain is the gain that can be obtained from the spreading the signal (required service bitrate) over the wide 3.84*106 Chips band. 10 ⋅ Log 3840 ⋅⋅10 = 24 .98 dB 3 10 10 3 12 .2 ⇒For 12.2 kbit service the processing gain is ⇒the processing gain is calculated by using the L2 user datarate in the denominator, not the actual radio interface rate matched symbol rate• Interference margin is calculated from the UL/DL loading (η) values. This parameter shows how much the Node B "sensitivity" is decreased due to the network load (subscribers in the network) − 10 ⋅ Log 10 (1 − η ) [dB ] ⇒Interference margin =• Required Ec/I0 is the required (in order to meet the baseband Eb/N0 criteria) RF C/I ⇒Required Ec/I0 = required Eb/N0 - softhandover MDC gain - processing gain + interference margin• Required Signal power is the required lowest signal strength that is needed for that particular service and load. ⇒Required signal power = receiver noise power + required Ec/I047 © NOKIA FILENAMs.PPT/ DATE / NN Power Budget Calculation Processing Gain because of the processing gain Power Density the spread signal can be below the thermal noise level Processing Gain Eb/No= + 4 dB Eb/No= + 2 dB Eb/No= + 1 dB Required Signal Power Noise level (ex. -105 dBm) -9 dB NRT 384 kbps +10 dB - 16 dB RT 64 kbps +18 dB - 21 dB Voice 12.2 kbps +25 dB48 © NOKIA FILENAMs.PPT/ DATE / NN
Power Budget Calculation Parameters• Power control headroom is the parameter to describe the margin against fast fading. This parameter is needed because at the cell edge the mobile does not have enough power to follow the fast fading dips. This is especially important for the slow moving mobiles! MS moving towards the cell edge 25 20 B 15 d 10 0 0.5 1 1.5 2 2.5 3 3.5 4 20 10 m B d 0 Mobile transmission -10 0 0.5 1 1.5 2 2.5 3 3.5 4 power starts hitting 1.5 its maximum value 1 0.5 0 Received quality -0.5 degrades, more 0 0.5 1 1.5 2 2.5 3 3.5 4 15 frame errors B d 10 Eb/N0 target 5 increases fast 0 0.5 1 1.5 2 2.5 3 3.5 4 S ec onds• Isotropic power is the minimum needed power for certain service in order to fulfill the Eb/No requirement for that service • Isotropic power=required signal power + cable loss + body loss - antenna gain - soft handover gain + power control headroom49 © NOKIA FILENAMs.PPT/ DATE / NN Power Budget Calculation Parameters • Power per connection is the parameter to define the maximum TX power for the MS and the needed power (for that service) from the Node B. • Body loss: this parameter describes the additional loss in power budget. The loss can is usually used for speech services where the mobile antenna is often shadowed by the users head. For data services the body loss can be set to 0dB due to that the when having data service on the mobile is usually held in hand. • Antenna gain TX (and RX): For MS having data services some gain can be used (2dBi) ?? • Peak EIRP: is the maximum transmitted power after the antenna. • Peak EIRP = power per connection - cable losses - body loss + antenna gain50 © NOKIA FILENAMs.PPT/ DATE / NN
Power Budget Calculation Parameters • Isotropic path loss: Maximum pathloss between the transmitting and receiving antenna is calculated for UL and DL separately. • Isotropic path loss: Peak EIRP - isotropic power • DL peak to average ratio (IPL correction factor): this parameter describes the ratio between the maximum pathloss and the average pathloss. Due to that the subscribers are usually not located (all) at the cell edge but they are distributed through the whole cell coverage area, this parameter is needed. Worst case scenario - Reality - mobiles distributed (usually not evenly) all the mobiles at the cell edge over the cell coverage area51 © NOKIA FILENAMs.PPT/ DATE / NN Power Budget Calculation Power Budget Examples Speech 64 kbits/s 128 kbits/sPlanner needs Uplink Downlink Uplink Downlink Uplink Downlinkto enter these RECEIVING END Thermal Noise Density dBm/Hz Node B UE -173.98 -173.98 Node B -173.98 UE -173.98 Node B UE -173.98 -173.98WCDMA BTS Receiver Noise Figure dB 3.00 8.00 3.00 8.00 3.00 8.00parameters BTS Receiver Noise Density dBm/Hz BTS Noise Power [NoW] dBm -170.98 -105.14 -165.98 -100.14 -170.98 -105.14 -165.98 -100.14 -170.98 -165.98 -105.14 -100.14 Reguired Eb/No dB 4.00 6.50 2.00 5.50 1.50 5.00 Soft handover MDC gain dB 0.00 1.00 0.00 1.00 0.00 1.00 Processing gain dB 24.98 24.98 17.78 17.78 14.26 14.77 Interference margin (NR) dB 3.01 6.99 3.01 6.99 3.01 6.99 Required BTS Ec/Io [q] dB -17.97 -12.49 -12.77 -6.29 -9.75 -3.78 Required Signal Power [S] dBm -123.11 -112.63 -117.91 -106.43 -114.89 -103.92 Cable loss dB 2.00 0.00 2.00 0.00 2.00 0.00 Body loss dB 0.00 3.00 0.00 0.00 0.00 0.00 Antenna gain RX dBi 18.00 0.00 18.00 0.00 18.00 0.00 Soft handover gain dB 2.00 2.00 2.00 2.00 2.00 2.00 Power control headroom dB 3.00 0.00 3.00 0.00 3.00 0.00 Isotropic power dBm -138.11 -111.63 -132.91 -108.43 -129.89 -105.92 TRANSMITTING END UE Node B UE Node B UE Node B Power per connection dBm 21.00 22.48 21.00 23.48 21.00 28.97 Cable loss dB 0.00 2.00 0.00 2.00 0.00 2.00 Body loss dB 3.00 0 0.00 0 0.00 0 Antenna gain TX dBi 0.00 18 0.00 18 0.00 18 Peak EIRP dBm 18.00 38.48 21.00 39.48 21.00 44.97 Isotropic path loss dB 156.11 150.11 153.91 147.91 150.89 150.89 DL peak to average ratio dB 6.00 6.00 0.00 Isotropic path loss 156.11 153.91 150.8952 © NOKIA FILENAMs.PPT/ DATE / NN
Power Budget Calculation Coverage Area CELL SIZE 12.2kbits 64kbits 128 kbits • In WCDMA cellular networks the Antenna height Node B 30.00 30.00 30.00 coverage area of cells overlap and the Antenna height UE Correction factor 1.50 0.00 1.50 0.00 1.50 0.00 mobile stations is able to connect to more than just serving cell. Outdoor location prob. 95% 95% 95% Outdoor standard deviation 7.00 5.00 5.00 • This will increase the location Slow fading margin Outdoor cell size 7.27 2.27 4.51 2.36 4.51 1.93 probability against the isolated cell. Indoor location prob. 95% 95% 95% • If we can reduce the LP from 96% to BPL 18.00 18.00 18.00 90% we can reduce the Slow Fading Indoor standard deviation 12.00 12.00 12.00 Slow fading margin 14.64 14.64 14.64 Margin and thus reduce the number of Intdoor cell size 0.43 0.37 0.31 Node B of about 38%, in theory. In car location prob. 95% 95% 95% Car PL 5.00 5.00 5.00 In car standard deviation 8.00 8.00 8.00 Slow fading margin 8.70 8.70 8.70 In car cell size 1.49 1.29 1.0653 © NOKIA FILENAMs.PPT/ DATE / NN
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