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EVDO reverse Link

Here I write about EVDO (HSD) reverse channel in short or summarize defination. The EVDO channels for the reverse connection have a similar structure as for CDMA2000. The reverse link for 1xEV-DO has a structure similar to that for CDMA2000. In EV-DO all signalling is performed on the data channel and this means that there … Read more

Propagation Path

Radio wave can be propagated from the transmitting antenna to the receiving antenna in many ways: perpendicular incidence wave or ground refraction wave, diffraction wave, troposphere reflection wave, ionosphere reflection wave, as shown in the diagram. As for radio wave, the most simple propagation mode between the transmitter and the receiver is free space propagation. … Read more

CDMA System Time

For both mobiles and base station in direct sequence CDMA must be synchronized. In the IS-95A system, synchronization is based on the Global Positioning Satellite system time. The CDMA system time is the time reference used by all IS-95 / IS-2000 and IS-856 systems. It is synchronous to UTC time (Universal Coordinated Time) except for … Read more

Forward Traffic Channel of CDMA

Forward Traffic Channel is used to Transmit Data and Signaling Information. Symbol repetition makes symbol streams at different rates adapted to those at the rate of 19.2k. The original symbol stream at  the rate of 19.2Kbps will not be repeated, 9.6Kbps symbol stream will be repeated once, 4.8Kbps symbol stream will be repeated twice…. Then, … Read more

Spread Spectrum Concept

Dsss – Direct sequence spread spectrum DSSS – Direct Sequence Spread Spectrum is a spread spectrum technology in which original data is expand using PN code randomly to reduce noise and this also provide high security to data as is scrambled data. Spread spectrum technology spread spectrum technology used in CDMA and Cdma is a … Read more

How To Set Pilot Search Window Sizes in CDMA ?

When the handset first powers up, it does an exhaustive search for the best pilot. No windows are used in this process. On the paging channel, the handset learns the window sizes SRCH_WIN_A, N, R and uses them when looking for neighbors both in idle mode and during calls. When a strong neighbor is requested … Read more

Advantages of CDMA Handoff

It is “soft”, meaning that communication is not interrupted by the handoff. This is sometimes called “make before break.” This means fewer dropped calls for users and higher customer satisfaction for operators. The handoff is not abrupt, but rather it is a prolonged call state during which there is communication via two or more base … Read more

Location Area Identity (LAI) and Global Cell Identity (GCI) in CDMA

Location Area Identity (LAI)  PAGING message is broadcast within a local area, the size of which depends on traffic, paging bearer capability, signaling flow , etc. Format:  MCC+MNC+LAC  MCC:  Mobile Country Code, 3 digits. MNC:  Mobile Network Code, 2 digits. LAC:  Location Area Code, a 2-byte-long hexadecimal BCD code. 0000 cannot be used with FFFE. … Read more

How to Reverse Access Channel Work in CDMA?

Reverse Access Channel used by MS Initiate Communication or Respond to Paging Channel. A reverse channel is first spread with WALSH to 307.2Kbps and then becomes 1.2288Mcps after long code modulation. The long code here not only spreads spectrum, but implements the function of channelization.  “Data burst randomizer” means discarding repeated chips during the transmission … Read more

How Sync Channel work in CDMA?

A long code is used for scrambling. However, a long code has too long a period, which cannot be wholly used for scrambling. We can only sample some chips of a long code at some point of time and use them as the sequences of scrambling. This requires that a mobile station should know the following … Read more