Get Here about CDMA technology and How CDMA Works, CDMA Solution and CDMA RF Optimization.
When we talk, we pause between syllables and words. CDMA takes advantage of these pauses in speech activity. Analog to digital conversion The voice signal is converted to a digital signal using PCM. Variable rate vocoder The vocoder (Voice Coder) is used to compress the digital signal from the Codec (Code/Decode). The vocoder, used in … Read more
The Global Positioning System (GPS) is a radio-navigation system that employs RF transmitters in 24 satellites. The satellite configuration when completed will guarantee that a GPS receiver located anywhere on earth can receive RF signals from at least four satellites 24 hours a day (with unobstructed visibility). For commercial use, each satellite transmits unique bi-phase … Read more
Downtilting is the method of effectively adjusting the vertical radiation pattern of the antenna to increase the amount of power radiated downwards. Downtilting can be used to increase the amount of coverage close to the site where “nulls” (holes) may exist due to the effective height of the antenna. Downtilting can also be used to … Read more
Voltage Standing Wave Ratio Voltage Standing Wave Ratio (VSWR) is another parameter used to describe an antenna performance. It deals with the impedance match of the antenna feed point to the feed or transmission line. The antenna input impedance establishes a load on the transmission line as well as on the radio link transmitter and … Read more
Antenna beamwidth is measured in degrees between the half power points (3 dB) of the major lobe of the antenna, Beamwidth can be expressed in terms of azimuth (horizontal or H-plane) and elevation (vertical or E-plane). The predominant type of antenna configuration within urban areas at PCS frequencies will be three sectored. This implies that … Read more
CDMA forward channel carrier power varies greatly depending on how many traffic channels are in use, the characteristics of the users voices, the Forward Power Control settings as requested by each subscriber unit in use, and the power allocated for overhead functions (Pilot, Page and Sync). An approximation of the CDMA forward channel carrier power … Read more
Eb/No corresponds to energy per bit over interference plus noise density for a given target FER (typical FER target is 1%). In digital communications, it is customary to designate one-sided noise density with No. In CDMA, interference is dominated by the noise generated due to other users in the system. Here No, is refers to … Read more
Soft handoff is the term that is normally associated with the fact that a CDMA system makes a connection to a target cell prior to releasing (breaking) from the source site, commonly referred to as “make-before-break”. A hard handoff, associated with AMPS, GSM, or USDC, requires that the signal strength from the target cell be … Read more
In determining RF coverage in CDMA systems, the effect of interference generated from the serving cell as well as the neighboring cells must be considered, this is in contrast to the RF coverage analysis for AMPS cells where interference mainly affects the frequency assignment but not the coverage. The interference margin is dependent upon the … Read more
There are various parameters and terms which come into play when discussing PN offsets and their function in CDMA. System Time All base station digital transmissions are referenced to a common CDMA system-wide time scale that uses the Global Positioning System (GPS) time scale, which is traceable to and synchronous with Universal Coordinated Time (UTC). … Read more