Spreading from a Frequency-Domain View

• Traditional technologies try to squeeze signal into minimum required bandwidth
• CDMA uses larger bandwidth but uses resulting processing gain to increase capacity
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How Does CDMA Work? Introduction to Basic Principles

Claude Shannon:

The Einstein of Information Theory

• The core idea that makes CDMA possible was first explained by Claude Shannon, a Bell Labs research mathematician
• Shannon's work relates amount of information carried, channel bandwidth, signal-to-noise-ratio, and detection error probability. It shows the theoretical upper limit attainable

SHANNON’S CAPACITY EQUATIONC= Bωlog2[1 + ]S N Bω= bandwidth in HertzC = channel capacity in bits/secondS = signal powerN = noise power.

In 1948 Claude Shannon published his landmark paper on information theory, A Mathematical Theory of Communication. He observed that "the fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point." His paper so clearly established the foundations of information theory that his framework and terminology are standard today.Shannon died Feb. 24, 2001, at age 84.

February, 2005 Technical Introduction to CDMA

Optimizing in Two Worlds

Circuit-Switched Voice Traffic

• Some operators are implementing 1xRTT mainly to gain capacity for additional voice traffic
• Their optimization techniques remain about the same as for 2G voice networks today - Keep network adequately dimensioned – Control RF environment – Monitor and manage capacity utilization
  

IP Data Traffic

• Operators adding IP traffic to upgraded voice networks
• Conventional optimization techniques are still appropriate for general
  

RF environment and circuit-switched network performance

• New IP and QoS issues require a new optimization focus for the blended total network - IP performance depends on both IP and RF factors - IP and Voice performance involve competitive tradeoffs

The Big Picture Optimization Issues CDMA 1xRTT

1xRTT services may include both traditional circuit-switched voice and new fast IP data connections

• A User's link is in multiple jeopardy, both radio and packet worlds

Radio environment portion

• Problems: FER, drops, access failures, capacity woes
• Causes: mainly in the RF world, because of mainly RF problems
  

Packet environment

• Problems: Setup failures, dropped connections, low throughput
• Causes: could be IP-related, or could be RF related
  

Optimization Issues
Network Design and Configuration

• Coverage holes, excessive coverage overlap

Call Processing Problems due to Misconfiguration

• Neighbor Lists
• Search Windows
• Power control parameters
  

Physical Problems/Hardware Problems

• Mismatched multicarrier sector coverage

Capacity Issues

• Forward and Reverse Power Control Overload
• Physical resource congestion : Channel elements, packet pipes - IP network congestion
  

Managing A New Dimension: circuit-switched and IP traffic blend

• QoS-related competitive issues

PERFORMANCE MONITORING OR GROWTH MANAGEMENT

PERFORMANCE MONITORING

benchmark existing performance : dropcall % , access failure % , traffic levels.
identify problem cells and clusters : weigh cells and clusters against one another.
look for signs of overload : TCE or walsh minutes - excessive ? soft handoff excessive ?
required number of channel elements - excessive?
forward power overload : originations , handoff blocked
Traffic trending and projection : track busy hour traffic on each sector ; predict exhaustion.
develope plant for expansion, multiple carriers.

Optimization Requirements

• performance optimization requires several things :

1. a stable system
2. performance expectation and performance goals
3. a good understanding of CDMA2000 : general RF technology , transmitter and receiver basics CDMA signal characteristics ; a) the different CDMA channels and what they do. b) how mobile and base station power are regulated during a call. c) the basic steps of how a call is set up, how handoffs happen, etc. d) how noise and interfering signals affect the call.
4. a good data measurement / analysis capability

• improving performance in one area should not degrade performance in some other area.