3 CDMA Link Buget

Internal Use Only▲ <ZTE Confidential> Internal Use Only▲ CDMA Link Budget Presented Presented by: by: Author Author CDMA CDMADivision Division ZTE ZTECorporation Corporation Mobile: Mobile: E-mail: E-mail: <ZTE Confidential> Internal Use Only▲ Outline Basic conception of link budget Reverse link budget in CDMA 2000 1X Forward link budget in CDMA 2000 1X <ZTE Confidential> Internal Use Only▲ OUTLINE Basic concept of link budget Reverse link budget in CDMA2000 Forward link budget in CDMA2000 <ZTE Confidential> Internal Use Only▲ What is Link Budget Under condition of ensuring the service quality, confirm the Maximum Allowable Path Loss of the propagation environment between BTS and terminals. Hata Hata Cost231 Cost231 Correction Correction model model … … To predict coverage radius using link budget Figure out numbers of sectors to meet coverage requirement <ZTE Confidential> building Internal Use Only▲ The constitution of wireless link Transmitter Transmission line antenna ” Transmit Power ” Loss of transmission line ” Gain ” Path loss ” Margin ” Gain antenna Transmission line Receiver <ZTE Confidential> ” Loss of transmission line ” sensitivity Internal Use Only▲ Link Budget Model mobile Feeder loss Antenna gain Path loss margin Antenna gain Feeder loss BTS Down link Up link Margin Margin Fademargin margin Fade Interferencemargin margin Interference Penetrationloss… loss… Penetration <ZTE Confidential> Internal Use Only▲ Transmitter TransmitEIRP(dBm) = TansmitPower (dBm) + AntennaGainOfTansmitter (dBi ) − feeder (orBody ) Loss (dB ) <ZTE Confidential> Internal Use Only▲ Receiver ReceiverSensitivity (dBm) = InterferenceNoise(dBm / Hz ) + ( Eb / No)req(dB) + DataRate(dB − Hz ) <ZTE Confidential> Internal Use Only▲ Penetration Loss Building loss Car loss Main mechanism： diffraction, refraction Calculation method： statistic Typical value of Building Penetration Loss ? ? <ZTE Confidential> ? Dense urban 25 dB Urban 20 dB Sub urban 15 dB Rural 6 dB Open land 0 dB Internal Use Only▲ Fade margin Probability density <ZTE Confidential> 0.675σ=5.4 dΒ Normal Distribution RSSI - 105 dBm σ=8dB -99.6dBm Accumulated normal probability distributing 100% 90% 80% 75% 70% 60% 50% 40% 30% 20% 0.675σ 10% 0% -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 Area Assuming that at least 75% of edge area (90% in cell) can reliably receive signal strength more than -105dBm. Standard Deviation is generally 8 dB. From the table we can find that 75% Probability corresponds to 0.675σ 0.675 x 8 = 5.4 dB -105 + 5.4 = -99.6 dBm Therefore, The designed middle value should be -99.6 dBm [ ]dx Deviation to middle value signal strength M Px 0 = P [ x ≥ x 0 ] = ∫ ∞ x0 75% 90% 1 σ 2π exp −( x−m )2 2σ 2 3 Internal Use Only▲ OUTLINE Basic concept of link budget Reverse link budget inCDMA2000 Forward link budget inCDMA2000 <ZTE Confidential> 内部公开▲ CDMA 2000 1X System 800M Reverse link budget <本文中的所有信息归中兴通讯股份有限公司所有，未经允许，不得外传> Internal Use Only▲ Explanation for link budget (1) service rate Use to show the voice service and data service system can support, at present, Radio Configuration in CDMA2000 1X is RC3, so in reverse link ,it can support 9.6kbps，19.2kbps，38.4kbps，76.8kbps，153.6kbps. MS EIRP CDMA terminal’s maximum TX power is 0.2W, 23dBm MS antenna gain CDMA mobile’s antenna gain is 0 dB，and fixed terminal (in door or out doot) has its relative gain. Body loss Most of the time body loss is 3 dB，IF it is fixed terminal or data service，we could consider that mobile a little far from body, and body loss can be 0dB. <ZTE Confidential> Internal Use Only▲ Explanation for link budget (2) common antenna gain 450M 800M 1.9G <ZTE Confidential> Polarization Horizon beamwidth Vertical beamwidth Gain Dual 65 17 15.5dBi Single 360 10 10dBi Single 65 10 17dBi Single 90 10 15.5dBi Single 360 8 11dBi Dual 65 7 18dBi Dual 90 6.5 16.5dBi Single 360 7 11dBi Single Internal Use Only▲ Explanation for link budget (3) BS feeder loss When the length from BTS to antenna is less than 15m, usually only 1/2 inch Antenna Jumper cable is required. Meanwhile there is only jumper cable loss. If 7/8 inch feeder cable is also used, we needs to take 7/8 inch feeder loss into 1/2“Jumper Grounding Clip consideration. When cable is longer than 80m, we consider it’s too long, it’s better to use 5/4 inch or other big size feeder. 1/2“Jumper Lightening Arrester Cabinet <ZTE Confidential> 7/8“Cable Grounding Clip Internal Use Only▲ Explanation for link budget (4) Eb/N0 Eb/N0 is demodulation SNR which reverse link requires when system is unload In practical system, the Eb/N0 required is different in different frequency band, different wireless environment, different terminal characteristic, different RC, different frame error rate. Minimum Performance testing standard provides Eb/N0 at a high FER and a low FER, If Eb/N0 of other FER is required，figure it out by linear interpolation. The table below is from standard: Case Band Classes 0, 2, 3, 5, 7, and 9 B 5 <ZTE Confidential> Data Rate (bps) 9600 4800 2400 1200 9600 4800 2400 1200 FER Limits (%) At Lower Eb/N0 At Upper Eb/N0 2.8% @ 5.9 dB 7.6 @ 5.9 dB 23.0 @ 5.9 dB 22.0 @ 5.9 dB 3.5 @ 5.5 dB 5.5 @ 5.5 dB 7.5 @ 5.5 dB 9.0 @ 5.5 dB 0.3 @ 6.5 dB 2.2 @ 6.5 dB 12.0 @ 6.5 dB 14.0 @ 6.5 dB 0.3 @ 6.1 dB 0.9 @ 6.1 dB 2.5 @ 6.1 dB 4.5 @ 6.1 dB Internal Use Only▲ Explanation for link budget (5) Interference Margin This value is related to System Loading. The formula is interfernce margin = -10log10 (1 − systemload ) In CDMA 2000 1X system, generally loading factor is 75% <ZTE Confidential> Internal Use Only▲ Explanation for link budget (6) soft hand-off gain Soft hand-off provides forward traffic channel multi-path diversity at the edge of BS, improves channel’s ability of anti-fading, decreases mobile’s Tx power, thereby decreases mobiles' interference to system, and extra gain to reverse link coverage. In CDMA system, soft hand-off gain’s concrete value is related to correlation coefficient ρof two propagation path, normal fading variance σ, edge coverage rate Prel. Prel ρ σ=8dB Soft hand-off gain(dB) <ZTE Confidential> 0.75 0.5 3.7 0.9 0.5 4.09 0.95 0.5 4.2 0.98 0.5 4.67 Internal Use Only▲ Explanation for link budget (7) Edge Coverage probability of serving area There are relationship between edge coverage probability and area coverage probability. The concrete relationship is as follows: In the chart the left y-axis is the area coverage probability, right y-axis is edge coverage probability, and x-axis is the standard deviation/ index of path loss. example path loss index: n=4 (complex propagation environment), standard deviation=8dB, edge coverage rate=75%, corresponding area coverage probability will be 94%; path loss index n=2 (free space), standard deviation=8dB,edge coverage rate=75%, corresponding area coverage probability will be 91%. <ZTE Confidential> Internal Use Only▲ Explanation for link budget (8) Antenna Height ÜGenerally antenna height is lower in dense urban area with large capacity, to reduce pilot pollution and interference to other cells. ÜIn open area with the capacity distributes dispersible, antenna height will be higher, and cover lager area. ÜRecommended Antenna height values are as follows: dense urban: 30m, urban: 40m,suburban and rural: 50m. <ZTE Confidential> Internal Use Only▲ Explanation for link budget (9) antenna height ÜIn same environment, the faster the speed of data rate is, the smaller the coverage radius 1X system can provide is. ÜComparing with voice service, high speed data service’s coverage radius is smaller, but generally the capacity is key restricted factor, especially in urban environment. So BTS’s actual coverage radius is smaller than coverage prediction, and the coverage radius that data service provides in 1X system can also approach the actual radius BS provides. >153.6 kbps distance subscribers >76.8 kbps >38.4 kbps >19.2 kbps >9.6 kbps <ZTE Confidential> Internal Use Only▲ Explanation for link budget (10) EVDO (RLS 0) Reverse link budget related ÜStructure of link budget table is the same as data service part of CDMA 1X ÜName of Parameters changed ÜMobile station :MS—>access terminal :AT ÜFrame error rate FER—>package error rate:PER ÜValue of parameters ÜDemodulating threshold Eb/No is different from CDMA 1X，but it is simuliar with CDMA 1X ÜBody loss is 0dB <ZTE Confidential> Internal Use Only▲ OUTLINE Basic concept of link budget Reverse link budget in CDMA2000 Forward link budget inCDMA2000 <ZTE Confidential> Internal Use Only▲ CDMA 2000 1X system 800M forward link budget <ZTE Confidential> Internal Use Only▲ Explanation (1) The maximum Tx power per traffic channel in one BTS ÜThis value is in direct ratio with rated transmit power of the BTS. ÜIn RC3 configuration, when system parameters are default. The maximum Tx power per traffic channel (voice) accounts for the total output 7.46%, approximate 31.47dBm, under the condition of two legs. ÜIn 8X and 16X data rate system, The upper limit of Supplemental channel’s Tx power accounts for total output power 25% ,approximate 36.99dBm. ÜIn 2X and 4X data rate, The upper limit of Supplemental channel’s Tx power accounts for total output power 19.9% ,approximate 36dBm. Ptotal = Ppil + Psync + N P Ppag + K traf Mα f Ptraf P pil Power of pilot channel N P sync Power of sych channel M P pag Power of paging channel P traf Power of traffic channnel K traf Forward link power control factor <ZTE Confidential> α p Channel number of active paging channel channel number of active traffic channel f Forward link voice activation factor Internal Use Only▲ Explanation (2) interference factor of other cells Forward link interference includes two parts: interference of local cell and of other cells. Because CDMA’s forward link channel is orthogonalized by Walsh code, in ideal situation, interference from local cell is 0, but multi-path results in incomplete orthogonalization of other channels, which increases interference, and it becomes the main interference gradually when mobile station is getting closer to Base station. The interference from other cells becomes the main interference gradually when mobile station is getting closer to the edge of cell, it is also the interference we calculated in forward link budget. <ZTE Confidential> Internal Use Only▲ A sample of EVDO forward link budget <ZTE Confidential> Internal Use Only▲ EVDO link budget explanation—Terminology Demodulation threshold—Required Îor/No for each antenna Ü Dual antennas terminal Ü Îor and No are both power spectrum density, custom usage for DO, it can be converted to Eb/Nt. Rx Diversity Gain Ü Under the same condition of download bitrates, target PER, the antenna’s demodulation threshold Îor/No required by dual antenna terminal is lower than that of signal antenna terminal. Ü According to ZTE shield room’s test result, the gain is approximately 5~6dB Package Error Rate—PER Multi-user Diversity Gain Ü The gain of forward throughput of sectors with multiple active users to those with single active user is correlate with forward dispatch algorithm. Ü According to outdoor testing result, the gain is 2dB <ZTE Confidential> Internal Use Only▲ EVDO link budget explanation—difference from 1X Items Link 1X EVDO Class of forward bitrates forward 9.6kbps~153.6kbps, 5 classes 38.4kbps~2.4Mbps, 9 classes Terminal types forward Single antenna Single & dual antenna Body loss Forward& reverse Demodulation threshold Forward & reverse Multi-uses diversity gain <ZTE Confidential> Forward 3dB voice 0dB data 0dB different no yes Internal Use Only▲ <ZTE Confidential>