what is power congestion and Code Congestion ? there is nothing called power congestion,instead it is reffered as near far problem i.e in cdma cdma user in cell edge needs more power than user near by BS so by open and closed loop pc wcdma system makes sure the mobile gets minimum m inimum amoun of power needed to maintain connection therefore limits ul interference and hence can serve more users because interference is propotional to capacity. code allocation is dynaically managed by rnc by use of rrm .
Power Blocking & CE blocking Power Blocking:Blocking :- When an UE start call setup process it sends 4 succesive aceess preamble's(+-1 db) to Node B on the feedback of open loop power control which is basiclly used to overcome near-far effect. If after 4 successive access preambles Node B doesnt aknowlade to mobile than it comes under power blocking. Another power blocking is happen's happen's due to Noise floor rise above the thresold value 6-7 db typically. typically. The feedback system for this is closed loop power c ontrol. Channel Element Blocking:Blocking :- It's direcetly related to the insufficient resources to mature a call. There is one channel card called CCU which contains 128 CE's for perticular carrier of the Node B.
1. DL Powerr congestion: normally this happens when no room for DL Power common channel available due to some possible reasons: High amount of traffic, noise floor, inacurate CPICH power settings, too low Power Admission settings, inaccurate attenuation of Feeder/j umper leading to lowering down the Maximum DL Power Capability supplied by node B. As you might know, we have 3 different allocation of power: Common channel + DCH Traffic (75%), SHO margin (10 - 15%) and HS portion (10 - 15% or remaining portion). 2. DL Channelization code: it's related to the fact that no Channelizaion code that y ou normally derived from Code Tree alghoritme available for traffic. The factors affecting this: setting of DL Code Admission (normally 85% for traffic, comon chanel, SHO and 15% for HS), amount of traffic, HS DPA parameter settings including HSUPA / EUL and Spreading Factors settings. Identically, if a cell is having problem with DL Code insufficiency due to traffic or usage, there have been indication that the Scrambling code serving to that particular spot / area is used up. So you can play around with coverage control, SHO intersection shift, adding more Scrambling Code (by means of adding more Best server to that spot), etc...
Uplink load can be due internal and external reasons; -external interference; control the neighbouring cells, measure the interference at related frequency -internal interference; check antenna/feeder/tma configuration, check the eulownload and eulmawrotcoverage parameters, check the uplink trafic load (number of eul 2ms users), check mobility parameters There are many ways you can solve the code congestion problem. One way is to r educe the no of codes for HSDPA. The other technique is that during high congestion some services are not allowed and become barred. Like PS384 services can be stopped so that the codes are available for other services. One way of reducing Code Congestion is to decrease the no of codes used by HSDPA. HSDPA uses upto 15 codes. Decreasing the no of codes will increase the availability of codes for other services namely CS services but the downside of it is t hat the user throughput is decreased.
What is difference between congestion and Blocking? Congestion = time when all resources are occupied (no free TCH available) Blocking = rejected (blocked) attempts over all attempts in %. Also there is different formulas for TCH blocking. For example in subscriber perceived TCH Blocking all successful directed retries to another cell are removed from the nominator. Blocking dives you the non served calls congestion gives the time when no resource are available (it is possible that nobody needs them so no blocks) there is a possiblity to have high blocking and low c ongestion - this means that you have a peak of the attempts. Congestion is time based (i.e at particular time say IN Busy Hour) and blocking is resource based (can be any time due to some issues like H/w, no TCH available)
If congestion is spread among different hours and days, and on the same NodeB, the fo llowing parameters can be used to decrease the usage of UL CEs UlMidRateThd (DCCC): Uplink Mid Bit Rate Threshold. UlDcccRateThd (DCCC): Uplink Bit Rate Threshold for DCCC. UlFullCvrRate (DCCC): Uplink Full Coverage Bit Rate. UlGBR (USERGBR): Uplink GBR for BE service. UlRateDnAdjLevel (DCCC): set to 3_Rates can be reduced to 2_Rates. UlRateUpAdjLevel (DCCC): set to 2_Rates can be increased to 3_Rates. Other Option: Decrease the Max Bit Rate
Shift R99 traffic HSPA Reduce Initial bit Rate from 64 to 32kbs Enable the DCCC Algorithm Enable cell & Node B credit LDR with first action as beratereduction & if your network is having multiple frequencies then 2nd action as inter frequency load ho. Change HSUPAINITIALRATE from D64 to D32. Change UL & DL GBR to D32 by command SET UUSERGBR.
WCDMA Congestion Control and Its Parameter What is Congestion Control? Congestion Control monitors the dynamic utilization of specific cell resources and insures that overload conditions do not occur. If overload conditions do occur, Congestion Control will immediately restrict Admission Control from granting additional resources. In addition, Congestion Control will attempt to resolve the congestion by either down switching, or terminating existing users. Once the congestion is corrected, the congestion resolution actions will cease, and Admission Control will be enabled. Parameter of congestion control: PwrAdm: Admission limit for admission on DL cell carrier power. PwrAdmOffset: Relative admission limit on DL cell carrier power. PwrOffset: Used by Congestion Control. PwrHyst: Hysteresis time setting for detection of congestion in the DL transmitted carrier power. iFCong: Threshold at which UL congestion is detected i n the cell. iFOffset: Offset that, together with parameter iFCong, determinesthe RTWP measurement level at which UL congestionis to be resolved. iFHyst: Hysteresis time setting for detection of congestion in theUL RTWP in a cell.
UMTS Capacity Planning To figure out the WCDMA network, we have to associate the several information. As WCDMA blockage can occur at several part also the multiple-service will consume different resource in the network. Furthermore the congestion in WCDMA is consisting of soft and hard blocking.To avoid the congestion and blockage of the service, we have to monitor the following resources
CE/Iub Dimensioning A channel element (CE) is defined as the baseband resources required in the NodeB to provide capacity for 12.2 k AMR voice, including 3.4 k DCCH. The HSUPA shares the CE resource with the R99 services.
Signaling and CCH not required CE
CE are pooled per NodeB for all cells
Low CE resource required for higher data rate
Advance algorithm improve the utilize efficiency of Iub transmission
Each service type will occupy different resources. Hence we should divide the traffic volume corresponding to each service type to understand the characteristic of the cell. – AMR – VP – PS R99 DL – PS R99 UL – HSDPA – HSUPA
CE resource is consisting of hardware and software. CE is the pool resource at NodeB level, all cells connected to NodeB will share the same CE resource. OVSF Code Resource OVSF Code is the limit resource of each cell. The expansion can’t be possible in a single cell. OVSF Code will be limited only DL direction. • Typical usage of OVSF code –AMR : SF128 – SF256 –VP : SF32 –PS R99 DL : SF8 – SF128 –HSDPA : SF16, Maximum is 15 * SF16 HSDPA Code usage is depended on Manual or Automatic assignment. More OVSF code manually assigned to HSDPA is less OVSF code left for R99. more OVSF Code Resource UL and DL Power Resource Even the UL power is not limit corresponding to each UE power, but the noise raise will trig the rejection due to Call Admission Control as well. Hence, the increment in UL load can cause service rejection and slow down the data service.
DL Power Limit is considered at RRU total power. Typical use of RRU power in True move is 20 and 40 watt.
In general, the common control channel will consume about 20% of total power.
The power consumption of each service will be different as well as the radio condition of each UE (e.g. distance, RSCP, Ec/Io)
HSDPA will use the remaining power left from R99 service.
• Iub is the pool resource at NodeB, each Radio Unit have to share same Iub resource. • Typical configuration bandwidth of Iub is 10, 16 and 20 Mbps, based on traffic. • True move deploys IP based Iub transmission. Total resource usage Total resource usage
2 states of service interruption from the picture • The user can’t get the service (rejection). • The user can’t get at the desire QoS (low throughput of data service) Total Power in a Cell Total Carrier Power (TCP) is one of limited resource depending upon Radio unit total power output that impact directly to cell capacity and performance. Although it’s the same Radio unit power, it may different in the capacity because of UE distributio n in a cell. To overview the power setting in a cell, we can check parameter setting of total power and CPICH power. CPICH Power – MaxPCPICHPower (~ 10% of total cell power) – Default = 33 or 36 dBm Total Power – MaxTxPower – Default = 43 or 46 dBm according to license CPICH power + common channel will consume around 20% of total cell power.
Congestion Indicators for EUL
Congestion Indicators for EUL Iub overload problems are solved by flow control for Enhanced Uplink highspeed data services. For EUL increased delay is measured internally and thedata flow from RB S in UL is throttled according to measurements recorded,therefore there is no congestion as such but rather the transmission rate of thedata is slowed down in the uplink direction when potential overload is detected.There are counters which can be used to monitor whe n the Iub tends towardscongestion for EUL service s. When that happens it should be considered toexpand the Iub capacity for EUL services.
3G-WCDMA (UMTS) March 14, 2009, 12:54 pm Filed under: Uncategorized | Tags: Uncategorized Artikel ini dikutip dari berbagai sumber
Apa itu 3G-WCDNA? Pada dasarnya 3G,WCDMA ataupun UMTS itu sama saja. UMTS ( Universal Mobile Telecommunications Service ) juga disebut “third-generation ( 3G ),” broadband, transmisi paket dasar text, suara ,gambar
dan multimedia dengan kecepatan data mencapai 2 Mbps yang akan menawarkan layanan ke mobile computer dan mobile phone. Didasarkan pada standar komunikasi Global System for Mobile communication ( GSM ), UMTS disahkan dengan standar utama perangkat dan mesin, standar ini direncanakan untuk pelanggan bergerak pada 2002. Setelah UMTS se penuhnya diimplementasikan, komputer dan telepon seluler dapat terhubung ke Internet ketika mereka di perjalanan, dan me ndapat layanan roaming serta kemampuan menget ahui dimana lokasi pelanggan. Pelanggan akan mendapat akses melalui hubungan terestrial wireless dan transmisi satelit. Sampai terealisasinya UMTS, pelanggan dapat memiliki peralatan multi mode yang terhubung ke teknologi yang sudah ada (seperti G SM 900 dan 1800). Saat ini, sistem telepon seluler sebagian besar adalah circuit-switched , dengan koneksi bergantung pada tersedianya circuit.. Hubungan packet-switched , menggunakan Internet Protocol , yang berarti hubungan sebenarnya selalu tersedia ke setiap titik dalam jar ingan.. Hal ini memberi kemungkinan untuk menciptakan layanan baru seperti metode tagihan alternatif (pay-per-bit, pay-per-session, flat rate, asymmetric bandwidth, dll ). Besarnya bandwidth dari UMTS juga memberi harapan untuk layanan video confrencing. UMTS berjanji untuk merealisasikan Virtual Home Environment, dengan proses roaming pelanggan dapat mempunyai layanan yang sama ketika berada dirumah atau di kantor, melalui kombinasi hubungan terrestrial dan satelit. Penelitian tentang teknologi UMTS, menggunakan peralatan prototipe advanced mobile phone / computing, telah perkenalkan pada tahun 1999 oleh Nortel Networks dan BT (British Telecommunications). Spektrum radiasi elektromagnetik untuk UMTS telah diidentifikasikan dengan band frekuensi 1885-2025 MHz untuk sistem IMT-2000, dan 1980 -2010 MHz dan 2170-2200 MHz untuk bagian satelit dari sistem UMTS.
Perkembangan Teknologi 3G
Pada gambar diatas menunjukkan pe rkembangan teknologi telekomunikasi di dunia. mulai dari teknologi atau telepon yang hanya bisa untuk layanan suara sampai bisa mengirim SMS (short messaging service) dan juga layanan multimedia lainnya dengan berbagai fitur seperti internet dan MMS (Multimedia Messaging Service). Layanan tersebut semakin berkembang sesuai dengan kebutuhan pelanggan yang menginginkan meningkatnya kecepatan transfer data yang semakin lama semakin bertambah cepat. Pada artikel ini kita akan memfokuskan pembahasan tentang 3G W-CDMA (UMTS). Wideband Code-
Division Multiple Access atau biasa ditulis Wideband-CDMA atauW-CDMA, merupakan teknologi generasi ketiga (3G) untuk GSM, biasa disebut jugaUMTS (Universal Mobile Telecommunication System). Teknologi ini tidak kompatibel dengan CDMA2000 atau sering disebut juga dengan CDMA saja. Pada perkembangannya sistem seluler CDMA mengalami perkembangan dari teknologi 2G ke 3G dengan banyaknya penambahan fitur-fitur yang mendukung kearahmultimedia mobile. Seperti pada bagan diatas. Ada beberapa persyaratan yang harus dipenuhi oleh teknologi generasi ke-3 yang m embedakannya dengan 2G : Radio network : 1. Mendukung kecepatan data rate sampai dengan 2 Mbps (multimedia). 2. Mendukung pengimplementasian yang operasional.
3. Efisiensi penggunaan spectrum dan kapasitas. Core network : 1. Packet data network dan IP mobility. 2. Global roaming. 3. Quality of Services (QoS). Secara garis besar service pada UMTS terdapat empat kelas: a.
conversational class
b.
streaming class
c.
interactive class
d.
background class 1. Integrasi dengan system 2G yang sudah ada.
Pada Wideband CDMA terdapat sistem Direct-Sequence Code Division Multiple Access (DS-CDMA) pita lebar, yaitu bit informasi dari pelanggan tersebar melalui bandwith yang lebar dengan cara multiply data pelanggan dengan chip yang dibentuk dari CDMAspreading codes. W-CDMA merupakan focus primer oleh standard 3GPP. Beberapa hal yang dimiliki oleh teknologi W-CDMA: 1. Kapasitas inisialisasi yang tinggi dan dukungan terhadap pengembangan teknologi di masa mendatang baik dari segi coverage maupun kapasitas, seperti penggunaan smart antenna dan advanced receiver structures karena adanya sistem MUD. 2. W-CDMA menawarkan layanan untuk packet switched dan circuit switched . Mendukung layanan yang simultan pada tiap mobile terminal karena setiap terminal W-CDMA dapat mengakses beberapa layanan yang berbeda pada saat yang bersamaan. 3. Dapat diaplikasikan pada lingkungan interferensi yang tinggi. 4. Menyediakan kapasitas yang lebih besar daripada sistem FDMA, TDMA, maupun Narrowband CDMA. 5. Kerahasiaan yang tinggi. 6. Penggunaan spektrum radio yang efisien 7. Akses layanan yang cepat.
Perbandingan GSM dengan UMTS
Pada GSM terdapat istilah kanal. Dimana satu kanal memiliki delapan times slot dan masing-masing times slot hanya boleh diduduki satu orang user untuk jenis service apa pun. Sedangkan dalam WCDMA, dikenal dengan istilah CE(Channel Element). Konsep CE ini berbeda dengan Ts. Berikut tabel penggunaan CE untuk masing-masing service yang berbeda:
RAB
CE/UL
CE/DL
SF/UL
SF/DL
AMR speech
1
1
4
128
CS 64
4
2
16
32
PS 64/128
4
4
16
16
PS 64/384
4
8
16
8
PS 64 for HSDPA
4
NA
16
256
PS 384 for HSDPA
16
NA
256
GSM/GPRS à UMTS Summary of change New
WCDMA Air interface (UE-Node B)RAN interfaces Iub (Node B-RNC), Iur (RNC- RNC) CN Interface – Iu (MSC-RNC & SGSN_RNC)
Modification
MSC and SGSN for Iu Interface
No Changes
Circuit Core Network (HLR/AuC)Packet core network (GGSN)
Setelah mempelajari GSM dan GPRS, maka untuk berevolusi ke UMTS-WCDMA kita memerlukan beberapa modifikasi sesuai tabel di atas. Ada beberapa elemen network yang baru, yang fungsinya adalah :
1.
Node B
Fungsinya mirip seperti BTS pada GSM, berfungsi melakukan proses pada layer 1 ( layer fisik ), seperti : channel coding, interleaving, rate adaptation, spreading, dan beberapa bagian dari operasi Radio Resource Management (RRM) misalnya inner loop power control.
2.
Radio Network Controller ( RNC )
Fungsinya mirip seperti BSC pada GSM. RNC be rhubungan satu sama lainnya dengan interface Iur, sedangkan RNC dengan node B berhubungan dengan interface Iub. Tugas RNC adalah mengontrol beberapa node B, bertanggung jawab pada load dan congestion control, dan hampir semua proses RRM terjadi di sini (layer 3 : RRC), handover,outer loop power control.
3.
Core Network (CN)
CN dibagi atas 2 bagian, untuk memproses layanan Circuit Switc hed (CS) dan Packet Switched (PS). Dimana terjadi integrasi antara CN dari system G SM untuk layanan CS dan CN dari GPRS untuk layanan PS. Ada beberapa penyesuaian tentunya menyangkut software, dan services.
Proses Perencanaan Core Network 1. Network Analysis Pada tahap network analysis, dilakukan pengumpulan data pelanggan, informasi demografi, jumlah pelanggan, informasi topografi, dan data trafik. Data dari jaringan eksisting memberikan informasi tentang jumlah site dan trafik yang yang sebaiknya di-generate. Trafik total berasal dari trafik yang berasal dari jaringan itu sendiri maupun dari jaringan luar. Distribusi trafik ini akan sangat membantu dalam perencanaan dan optimasi jaringan core. Data pelanggan akan dijadikan input dalam tahap dimensioning.
2. Network Dimensioning Dimensioning merupakan tahap perencanaan jaringan yang bertujuan untuk menghitung kebutuhan jaringan sehingga didapatkan jaringan yang efektif dilihat dari segi biaya, segi teknikal, dan juga performansi. Dimensioning akan meliputi network element dannetwork interface.
3. Detail Planning Detail planning pada core network secara umum terdiri dari signalling plan, routing plans,numbering dan charging plan. Informasi yang dikumpulkan pada tahap network analysisakan sangat berguna pada tahap ini. Output utama dari detailed core network planadalah : a. Routing plan
Jenis routing sebenarnya sudah diputuskan pada tahap analysis dan dimensioning.Pada tahap ini routing harus ditetapkan termasuk destination, sub-destination, circuit group, dan lain-lain yang menyangkut routing. b. Signalling plan
Pada tahap ini didefinisikan signalling point, signalling end point, signalling transfer point, signalling point code. Penentuan jumlah signaling link dan signalling link set juga harus diselesaikan. c. Numbering
Pada tahap ini harus diselesaikan numbering group yang digunakan oleh setiapswitched . Untuk mempermudah proses numbering group biasanya didasarkan pada lokasi geografi. Di bawah ini adalah gambar call processing secara garis besar untuk sistem UMTS-WCDMA yang biasanya disebut koneksi RRC.
Ada yang membedakan antara WCDMA pada UMTS dibandingkan dengan teknologi lainnya yaitu cdma2000, walaupun keduanya berdasarkan pada metode CDMA.
UMTS
CDMA 200
Spreading Rate
3.84 Mcps
1.2288 Mcps
Bandwidth
5 MHz
1.25 MHz
Synchronation Between Cell
Asynchronous
Synchronous
Direct Spread configuration
Direct Spread (1x)Multi-csrrier (3x
Sites Configuration
forward link) Convolutional Turbo(Parameter
Convolutional Turbo(Parameter
flexible)
fixed in the standard)
modulation
QPSK in both direcions
QPSK in forwardBPSK in reverse
Frame size
10 msec for physical layer10,20,40 5 (for signaling),10,20,40 and 80
Chanel Coding
and 80 msec for transport layer
msec physical layer
Modes
FDD and TDD mode
Only FDD mode
Transmit Diversity scheme
Time switched transmit
Orthogonal transmit
diversitySpace time block coded
diversitySpace time spreading
transmit diversity
Channelization codes
Orthogonal variableSpreading
Walsh codes (same as OVSF)
factor (OVSF) codes from 4-256
codes from 4-128 bits
bits
Source identification code for
512 unique scrambling codes each One PN code (32,768 bits)512
sector
identifying a sector (38,400 bits)
unique offset are generated using PN offset 42
Source identification code for
Unique scrambling codes assigned One long PN code (2 bits).
mobiles
by sector
Unique offset are generated based on ESN. Not assigned by sector
Arsitektur UMTS
Landasan utama dari arsitektur core network untuk UMTS berdasar pada jaringan GSM dengan GPRS. Core network terbagi manjadi dua bagian, yaitu: a) circuit switched domain.
b) Packet switched domain.
Dari uraian di atas dapat kita lihat bahwa CDMA sebagai metode akses jamak (multiple access) dapat digunakan sebagai air interface pada banyak system komunikasi seluler maupun satelit. CDMA dalam
perkembangannya diharapkan menjadi air interface bagi system komunikasi yang lebih handal misalnya 4G dan seterusnya. Karena dengan teknologi W-CDMA ini dapat mengkases ke internet, ini sangat mengkhawatirkan para orang tua karena dengan mudahnya kita dapat mengakses situs-situs dewasa yang me njamur dalam jaringan internet, sayangnya belum ada program yang dapat memblock hadirnya situs tersebut, kecuali dengan pengawasan ketat terhadap anak-anak.
