CDMA2000 Network Optimization Fundamentals

Salam…
In this post, I wanna share with you about CDMA2000 Optimization Procedure. Hope you’ll enjoy it! ^_^
Wireless network Optimization can be devided in to three layers:

• Device Layer
• Network Layer
• Resource Utilization Layer

We can conduct some methods to examine problems on those layers, i.e.,

• Drive tests and Analysis
• Signaling Tracking
• OMC analysis
• Synthesis

Let’s we go in to deep to each layer above,

1. Device Layer
• Antenna and Feeder Cable Fault
• Transmission Fault
• GPS Fault
• Wireless Configuration
• Office Direction Problem
• Termination Problem
2. Network Layer
• Solving Dropped Call Problem with Drive Test and Analysis Method
• Solving Problem with OMC Analysis Method
• Improving Coverage with Synthess Method
3. Resource Utilization Layer
• Network Block Optimization
4.  

CDMA Performance Indicators
RF Performance indicators captured by drive-test activity. It show the CDMA RF environment to guide Optimization and Troubleshooting in air interface. Some parameters indicate uplink conditions, some downlink, and some both. These parameters collected at the subscriber side, so it’s easy to capture using commercial handset equipment without BSC’s assist.
Basic knowledge about CDMA spread spectrum signal characteristics such as: channel definitions, power control system, call processing flow, signal behaviour in noise and interference, and RF units ( transmitter and receiver) are needed, to analyse the parameters below.

• FER (Frame Error Rate) -> an excellent call quality summay statistic, it’s the end result of the whole transmission link
• reverse channel -> realized on the Base Station
• forward channel -> realized at handset
• if FER is good, any other problems aren’t having much effect
• if FER is bad, we have to check other indicators to analyze the network problem, because FER is just the end-result of the problem
• Mobile Receiver Power (Rx)-> Received Power at the handset (dBm). It should be noted that Received Power is Important, but it’s exact value isn’t critical.
• High Rx value (-35 dBm or higher) could cause overload condition in Amplifier sensitivity, intermod and code distortion on received CDMA signals.
• Low Rx value (-105 dBm or weaker would leave too much noise in the signal after de-spreading, resulting symbol errors, bit errors, bad FER and other problems.
• Ec/Io -> We can’t just use the handset’s power level to guide handoffs because it represents the total power measurement from all sectors reaching the handset. To measure the the signal level of each sector individually, we have to use each sector’s pilot (Walsh 0) as a test signal to guide handoffs.
• Ec/Io is a parameter, represents pilot cleannesses.
• foretells the readability of the associated traffic channels to guide soft handoffs decision
• derived from: ratio of good to bad energy seen by search correlator at the desired PN offset -> Ec/Io(forward) = Pilot Energy / (Paging + Synch + Traffic) Energy. Can be degraded by strong RF from other Cells, Sectors (imperfect PN orthogonality could cause -20 dB degradation) and also by noise.
• in Light condition (without traffic) Ec/Io = 3 dB, in Heavy loaded Ec/Io = -7 dB
• in a clean Situation which theres a sector dominant, Ec/Io just as good as it was when transmitted. But in “Pilot Pollution” condition, mobile hears a ’soup’ made up of all the overlapped sectors signal. So Io is the sum of all the signal received by MS, and Eo is the energy of desired sector’s Pilot signal. The Large Io will overrides the weak Ec -> Ec/Io is too Low!
• Handset Transmitter power (TxPO)
• TxPO is the actual RF power output of the handset transmitter(max= 23 dBm), including combined of open loop power control and closed loop power control (TxGA)
• this is the simple formula : TxPO = -(Rx dBm) - C + TxGA ( C= +73 for 800 MHz systems, and C=+76 for 1900 MHz systems) to reach balance link.

Sumber : http://pram.web.id/blog/2008/03/31/cdma2000-network-optimization-fundamentals