EV-DO forward link in short
The forward link possesses many features that are specific to EV-DO, having been optimised for data transmission, particularly in the downlink direction. Average continuous rates of 600 kbps per sector…
Tag: cdma
cdma technology optimization
Forward link EVDO channels in Detail
A number of channels are transmitted in the forward direction to enable signalling, data and other capabilities to be handled. These channels include the Traffic channel, MAC channel, Control channel…
Mobile Power Bursting in CDMA
Each 20 millisecond frame in EIA/TIA-95-B CDMA is divided into sixteen “power control groups”. When the mobile transmits, each power control group contains 1536 data symbols (chips) at a rate…
Base Station Variable Rate Vocoder
The base station uses a slightly different scheme when the vocoder moves to lower rates. First, EIA/TIA-95-B CDMA base stations do not pulse their transmissions. Rather, base stations repeat the…
How Forward Link Traffic Channel Physical Layer in CDMA
Voice data at 9600 bps or 14400 bps (full rate) is first passed through a convolutional encoder, which doubles the data rate for the 9600 bps case or increases it…
CDMA Vocoders how and why
Vocoders Convert Voice to/from Analog Using Data Compression There are Three CDMA Vocoders: IS-96A Variable Rate (8 kbps maximum) CDG Variable Rate (13 kbps maximum) EVRC Variable Rate (improved 8…
How Frame Formats in CDMA
Once the analog voice is compressed by one of the vocoder processes, some additional data is added to produce a frame. Each frame in CDMA is 20 milliseconds regardless of…
How Forward Error Protection in CDMA
Uses Half-Rate Convolutional Encoder Outputs Two Bits of Encoded Data for Every Input Bit Unlike many digital cellular systems, CDMA provides powerful error correction to all voice data bits. This…
How Traffic Channel Forward Link Modifications in CDMA
In an effort to provide CDMA with even greater voice quality, the CDG (CDMA Development Group) has proposed and implemented a new vocoder. This new vocoder uses and improved, higher…
How Long Code Generation and Scrambling in CDMA
All base stations digital transmissions are referenced to a common CDMA system-wide time scale that uses the GPS time scale, which is traceable to and synchronous with Universal Coordianted Time…
Closed Loop Power Control Puncturing in CDMA
Once the data has been scrambled with the user specific long code, the closed loop power control data is then punctured into the data stream. Remember that the power control…
why the data needs to be scrambled again at the same rate
After all of the coding used so far in the forward channel, you’re probably wondering why the data needs to be scrambled again at the same rate. If all cells…