cdma technology optimization
Power Control Required in Reverse link cdma due to following reason. Maximum System Capacity is Achieved if: All Mobiles are Power Controlled to the Minimum Power for Acceptable Signal Quality in Reverse Link. As a Result, all Mobiles are Received at About Equal Power at the Base Station Independent of Their Location in reverse Link. … Read more
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 are possible. This is a six fold increase over CDMA2000 1X and is provided largely by the ability of 1xEV-DO to negotiate increased data rates … Read more
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 and Pilot. These are time division multiplexed. Traffic Channel – This channels uses Quadrature Phase Shift Keying (QPSK) modulation for data rates up to 1.2288 … Read more
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 of 1.2288 Mbps. When the voice coder moves to a lower date rate, the CDMA mobile bursts its output by only sending the appropriate number … Read more
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 same bit patterns as many times as needed to get back to the full rate of 9,600 bps. So, if the vocoder selects a frame … Read more
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 by 1.33 times for the 14400 bps case. It is then interleaved, a process that has no effect on the rate, but does introduce time … Read more
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 kbps) Each has Different Voice Quality: IS-96A – moderate quality EVCR – near toll quality CDG – toll quality All digital communication systems use various … Read more
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 is desirable in CDMA since the idea is to increase the occupied bandwidth (spread the data). The forward link uses a half-rate convolutional encoder to … Read more
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 data rate of approximately 13 kbps to digitized voice signals. After adding bits used to support the traffic channel, the final traffic channel data rate … Read more
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 (UTC). GPS and UTC difer by an integer number of seconds, specifically the number of leap second corrections added to UTC since January 6, 1980. … Read more