Deployment Method for Real-Time Wireless Network Optimizer in CDMA Network

Transcription

1 Deloymen Mehod for Real-Time Wireless Nework Oimizer in CDMA Nework Chi-Young Rhee, ang-jin Park, Yong-Hee Lee, Bum Kwon, and Jae-Hwang Yu Nework Engineering Develomen Team Nework R&D Cener, K Telecom {rhee, sjark, cola, bkwon, jhyu}@skelecom.com Absrac: CDMA Nework has develoed from 2G o CDMA X and 1xEV-DO, and made a raid rogress o WCDMA. In accordance wih i, wireless nework oimizaion mehod is also develoing. Basic mehod for oimizaion is o measure field daa manually using field ools. Beer soluion is o gaher measured daa and nework daa ogeher and analyze hem afer combining hem. Bu his soluion also has limiaion, since i gahers daa offline and he analyzing rocess is manual and reeiive, so we can hink of more sysemaic oimizaion mehod by develoing a real-ime and on-line wireless nework oimizaion sysem. A firs, he sysem inerfaces wih oher oeraing ools auomaically by on-line o sore and manage wireless nework daa in a cenral daabase. Then, i analyzes he erformance and efficiency of wireless nework using his daabase. The analysis resul is used o resen base saion s saus and soluions o he nework roblems such as inerference, high noise level, ec. This aer inroduces a sysem for wireless nework erformance oimizaion, called Oimizer, ha does nework daa inerface, KPI (Key Performance Indicaor) monioring, saisical analysis, wireless nework analysis. 1. Inroducion Afer CDMA nework has become in commercial use for mobile communicaion service, field engineers gaher and analyze measured field daa, nework daa, and RF daa Tx Power, Rx Power, waveform of Tx and Rx, ec. indeendenly. o, he engineers can figure ou only arial soluions for wireless nework oimizaion. Now, we can hink of an oeraing ool o overcome he roblems of reeiive rocess of exising oimizaion mehod. I is a wireless nework oimizing sysem ha analyzes field, nework, and RF daa simulaneously and builds a knowledge daabase ha sores oimizaion know-how. The sysem has 1) real-ime auomaic wireless nework daa gahering funcion, 2) wireless nework erformance and efficiency deerioraion deecing funcion, 3) saisical analysis funcions using ime series, correlaion, clusering, mining, ec., and 4) funcions o give oimizing soluions o enhance he erformance and efficiency of wireless nework. In his aer, we inroduce a framework of erformance oimizaion and is alicaion sraegy, which can imrove he erformance of CDMA wireless nework in a cenralized and auomaed manner. 2. ysem Conce 2.1. Oimizaion rocedure [Figure 1] shows wireless nework oimizaion flow. Firs, i gahers raw daa such as nework daa, measured field daa, RF daa eriodically. Then, i moniors nework erformance and efficiency o deec base saions ha deeriorae wireless nework qualiy. And finally, i resens erformance oimizaion soluions using 1) sysem level analysis, 2) wireless link level analysis, 3) saisical analysis, and 4) knowledge daabase ysem Archiecure Wireless nework oimizaion sysem, called Oimizer, consiss of Iner-working erver, Analysis erver, Daabase(DB) erver, and Web erver.[figure 2] Iner-working erver inerfaces wih exernal servers, which sores nework daa or RF daa using secial roocol for each server, gahers raw daa eriodically, and convers he daa ino aroriae forma o sore in he Daabase erver. Analysis erver uses gahered raw daa from DB erver o generae wireless nework analysis resul. DB erver sores and manages all he daa generaed by Iner-working erver and Analysis erver. Web erver roduces analysis resul web ages for he field engineers. [Figure 1] Oimizaion Process Flow

2 [Figure 2] ysem Archiecure 3. On-line inerface To oimize he erformance of wireless nework, field engineers have been gahering daa from various measuring ools or managemen sysems searaely, and analyzed he daa manually. Bu, Oimizer inerfaces wih all he ools and sysems by on-line inerfacing rocess of Iner-working erver, and hen builds a cenral daabase called Oimizer DB. I inegraes diverse oeraional daa, so he searae analysis rocess which was deenden uon he oeraing ools in he as, can be combined ino one sysem, he Oimizer Inerfacing Tyes Iner-working erver has o minimize he load of he oher servers, so he way of on-line daa gahering rocess deends on he erformance of he inerfacing counerar. There are various yes of inerface in Oimizer. Tex log file gahering Remoe command inerface Remoe DB query Afer gahering he raw daa by one of hese ways, Iner-working erver convers he daa ino aroriae forma o sore in he Oimizer DB Daa Tyes Here are some of he daa yes used by he Oimizer. BM(Base aion Managemen ysem) daa Oimizer uses BM log files for erformance, configuraion, and sysem faul daa. I eriodically connecs o BM o ge he log files, and arses he raw daa ino he daabase forma. RF daa RF daa, which is measured from base saions, conains Tx ower, Rx ower, and waveform of Tx and Rx ower. These are mainly measured by auomaic command inerface. Oimizer usually akes saisical value of he RF daa. Measured field daa I conains daa ha can be measured by field ools. And mos of he measured daa has is daa sorage server, so we can connec o he DB of he sorage servers and do remoe query o rerieve measured field daa. 4. KPI Monioring Afer gahering wireless nework daa, analysis rocess of each base saion sars. KPI (Key Performance Indicaor) monioring, which is he firs ar of he rocess, deecs erformance and efficiency deerioraion of each base saion. This monioring rocess filers low-erformance base saions, which should be oimized in he firs lace. We can ge sandard values of each erformance indicaor ha are offered by saisical analysis of wireless nework, and use hem o selec base saions ha does no saisfy he erformance hreshold. For erformance monioring, we use curren saus and rend of originaion/erminaion call success rae, call comleion rae, call dro rae, and oher saisical raffic daa. For efficiency monioring, we analyze handoff overhead, Q-Facor (raffic balance rae beween secors), channel elemen usage, FA (Frequency Assignmen) usage, cell loading, ec. Also, average value of erformance indicaor of MC or BC can be used in non-arameric analysis. Using hese daa, Oimizer filers and riggers base saions ha deeriorae wireless nework s qualiy.

3 5. Wireless Nework Analysis Oimizer analyzes and diagnoses base saions ha are filered by KPI monioring. [Figure 3] shows he wireless nework analysis rocess ysem Level Analysis The mos criical roblems can be found a sysem level firs. Faul Message Analysis Oimizer inegraes frequen criical faul messages caused by he nework sysem s sofware, and deermines he main cause by faul reasons. Alarm Analysis Oimizer reors alarm messages caused by he nework sysem s hardware. This includes sysem alarm, LPA/LNA alarm, reeaer alarm, ec. Parameer Analysis Oimizer deecs abnormal arameer seing, and reors i o he field engineers Wireless Link Level Analysis Forward Link Forward link analysis handles overhead ower for ilo, sync, and aging and Tx ower for oal ransmiing ower including raffic. Here are samle funcions ha are analyzed on forward link. Traffic, handoff, and overhead ower s raio of Tx ower Tx ower rend of 24 hours[figure 4], 20 days, and 60 days[figure 5] Power usage er Erlang Average FPG (Forward Power Gain) and Over FPC (Forward Power Conrol) values are also used o deec abnormal ower saus. To deec abnormal handoff saus and coverage efficiency, we analyze handoff aem from/o he low-erformance base saion[figure 6], acive PN coun, Ec/Io, C/I, RI, ec. [Figure 4] 24-Hour-Trend of Tx Power [Figure 5] 60-Day-Trend of Tx Power [Figure 6] Handoff Analysis [Figure 3] Wireless Nework Analysis Process

4 5.3. Wireless Link Level Analysis Reverse Link Based on Rx level measured from base saions, N o W(hermal noise), I o (own cell inerference), I oc (oher cell inerference), and cell loading are obained and used in reverse link analysis.[figure 7] Here is a samle rocess o derive own cell inerference, I o. Firs, we calculae E b /N by hese equaions. From measured RF value, we can ge oal Rx level R. And by monioring RF value of idle hour (minimum call aem hour), N o W can be derived, so we can ge I o and I oc. As we calculae I o and I oc, engineering arameer of reverse link such as frequency reuse facor and cell loading can be derived o use in he reverse link analysis rocess of Oimizer. [Figure 8] shows 60-day-rend of cell loading. E b R N R W (1) E N b R R W G R (2) E b /N ignal Energy er Bi divided by Noise ecral Densiy Average Rx Level of one mobile saion R Bi Rae R Toal Rx Level of a base saion W CDMA Chi Rae G Processing Gain If required E b/n of he cell is K, E b K N Req by (2), we ge equaion for like his. K ( R ) G o, we can ge oal Rx level of he cell (I o ) using. Io (Own Cell Inerference) Ioc (Oher Cell Inerference) ( G + K) KR KR G + K I 0 N Unknown Inerference N h or No (Thermal Noise) N u Number of users er cell Inerference from Own Cell Users Inerference from Neighbor Cell Users [Figure 7] Base saion s Rx ignal u Reeaer Noise, Non CDMA ignal ( TV Booser, Miliary ysem, ec), Abnormal Mobile aion kt -173dBm/Hz (k:bolzmann Consan, T:Absolue Temeraure) [Figure 8] 60-Day-Trend of Cell Loading 5.4. aisical Analysis To suor sysem level analysis and wireless nework analysis, saisical analysis rocess is also imoran in Oimizer. Correlaion To figure ou he main facor of erformance deerioraion, we use mulivariae analysis, such as logisic regression. This analysis rocess akes all facors wireless nework erformance indicaor, saisical daa, nework sysem saus or faul, arameer, ec. Then, i calculaes he relaionshi beween wireless nework erformance and he facors o figure ou which facor effecs he mos. Also, daa mining echnique, such as decision ree, is used o deermine facors ha can classify high-erformance or low-erformance base saions. caer Plo Afer deecing main facors of erformance deerioraion by correlaion analysis, we use scaer lo o deermine he oin where he erformance declinaion sars. [Figure 9] is a samle scaer lo of C/I and call connecion rae in 1xEV-DO nework. In his case, call connecion rae kees declining a he oin of -1, so C/I -1 is he deerioraion oin of call connecion rae. Trend To forecas wireless nework erformance, saisical rend is used. o, he rend grah of wireless nework erformance indicaor and correlaed facor is a ar of saisical analysis. [Figure 10] is a samle rend grah of originaion Erlang wih acual value and is forecas resul. We use Winer s Addiive moohing Model, which is one of he mos racical mehod for rend analysis.

5 [Figure 9] caer Plo of C/I and Call Connecion Rae [Figure 10] Erlang Trend 6. Diagnosis and oluions Low-erformance base saions, which are filered by KPI monioring rocess, go hrough sysem level analysis, wireless link level analysis, and saisical analysis. And finally, hey go ino he diagnosis rocess for soluions o imrove he erformance. Oimizer has knowledge daabase of CDMA heory and oeraional know-how, which describes he case-bycase soluions for he wireless nework roblems, ha has been colleced since he nework consrucion. o, diagnosis rocess uses his knowledge daabase for each case of erformance deerioraion cause, o ge he soluions ha he field engineers can aly. Oionally, field engineers can do drive es or hardware insecion, before or afer hey aly he soluion, if hey hink i s necessary. [Figure 11] shows he whole rocess. 7. Conclusion Nework field engineers had o gaher daa and analyze i searaely from nework managemen sysem, reeaer managemen sysem, field measuring ools, ec. for wireless nework erformance oimizaion. This was manual, reeiive, and imeconsuming job. Also, he analysis resul was deenden uon he analyzer s skill. This aer inroduced wireless nework erformance oimizaion sysem o overcome hese roblems of he as. Oimizer 1) collecs and inegraes oeraional daa from all he oher ools by on-line, 2) moniors erformance of each base saion based on he gahered daa, 3) analyzes he wireless nework erformance indicaor o deermine he cause of erformance deerioraion, and 4) gives case-by-case soluions by he analysis resul and knowledge daabase which sores CDMA heory and oeraional know-how. K Telecom has been using his sysem, and here has been a dramaic change in erformance oimizaion rocess. As i became more sysemaic, non-skillful field engineers could deec and analyze he nework romly as exer engineers do, so we could maximize he efficiency of oeraion and oimizaion rocess of wireless nework. Fuure work is o enhance he diagnosis rocess as we iemize more soluions for each erformance deerioraion case, and evolve i ino an exer sysem. REFERENCE [1] Vijay K. Garg, "I-95 and CDMA2000 : Cellular/PC ysems", Prenice Hall PTR, [2] Y. H. Lee, "Parameer Decision for Oimal Wireless Nework Oimizer Real-Time Monioring and Analysis Reques Performance Monioring aisical Daa Analysis Correlaion/Trend Analysis Aly Alying oluions Field Engineer Oion Drive Tes Oion H/W Insecion ysem Faul Analysis RF ALM, Waveform Insecion oluions Parameer Insecion Forward Link Analysis Reverse Link Analysis Analysis Resul Inegraion Knowledge DB [Figure 11] Analysis and Diagnosis Flow

6 Handoff Gain in CDMA2000 ysem", PIMRC2002 Vol.5, [3] J.. Lee, Leonard E. Miller, "CDMA ysem Engineering Handbook", Arech House Publishers, 1998 [4] K. I. Kim, "Handbook of CDMA ysem Design Engineering and Oimizaion", Prenice Hall PTR, [5]. J. Lee,. J. Park, Y. H. Lee, C. Y. Ahn, B. C. hin, B. C. Ahn, and J. T. Ihm, "Radio Nework Oimizaion Mehod wih aisical Analysis in CDMA2000 1X ysem", PTC Conference, [6]. J. Park, W. W. Kim, B. Kwon, "Analysis of Effec of Wireless Nework by Reeaer in CDMA ysem", IEEE VTC ring, 2001 [7] A. M.Vierbi, A. J. Vierbi, "Erlang Caaciy of a Power Conrolled CDMA ysem" IEEE Journal on eleced Areas in Communicaions, Augus, 1993.