CDMABy Justin Joshua Jesudass

F.Y.B.sc.IT-017

Introduction

• Code Division Multiple access (CDMA)• CDMA is a channel access method used

by various radio communication technologies.

• Time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it by frequency.

• CDMA is a form of spread-spectrum signaling, since the modulated coded signal has a much higher data bandwidth than the data being communicated.

• The technology of CDMA was used in 1957,By Leonid Kupriyanovich in Moscow .

• An experimental model of a wearable automatic mobile phone, called LK-1

• LK-1 has a weight of 3 kg, 20-30 km operating distance, and 20-30 hours of battery life.

CDMA Architecture

• Mobile Station• Base Station (BS)• Base Station Controller (BSC)• Mobile Switching Center (MSC)• Home Location Register (HLR)• Visitor Location Register (VLR)• Authentication Center (AC)• Operation and Administration (OAM)

Mobile Station

• The CDMA mobile station communicates with other parts of the system through the base-station system.

• Mobile phones handsets.

Base Station (BS)

• The base station (BS) handles the radio interface to the mobile station.

• The base station (BS) handles the radio interface to the mobile station.

Base Station Controller (BSC)

• The BSC provides the control functions and physical links between the MSC.

• It provides functions such as handover, cell configuration data and control of RF power levels in base transceiver stations.

• A number of BSCs are served by a MSC.

Mobile Switching Center (MSC)

• The MSC performs the telephony switching functions of the system.

• It also performs such functions as toll ticketing, network interfacing, common channel signaling, and others.

Home location Register (HRL)

• The HLR database is used for storage and management of subscriptions.

• The home location register stores permanent data about subscribers, including a subscriber's service profile, location information, and activity status.

Visitor Location Register (VLR)

• The home location register stores permanent data about subscribers, including a subscriber's service profile, location information, and activity status.

• It reduces the need for interrogation of the home location register (HLR).

Authentication Center (AC)

• The AC provides authentication and encryption parameters that verify the user's identity and ensure the confidentiality of each call.

• The authentication center (AC) also protects network operators from fraud.

Operation and Administration (OAM)

• The OAM is the functional entity from which the network operator monitors and controls the system.

• OAM offer support for centralized, regional, and local operational and maintenance activities that are required for a CDMA network.

Steps in CDMA modulation

• CDMA is a spread spectrum multiple access technique. A spread spectrum technique spreads the bandwidth of the data uniformly for the same transmitted power.

• In CDMA a locally generated code runs at a much higher rate than the data to be transmitted.

• The figure shows how a spread spectrum signal is generated. The data signal with pulse duration of Tb is XOR’ed with the code signal with pulse duration of Tc.

• The bandwidth of the data signal is 1 / Tb and the bandwidth of the spread spectrum signal is 1 / Tc. Since Tc is much smaller than Tb.

• The ratio Tb / Tc is called the spreading factor or processing gain and determines to a certain extent the upper limit of the total number of users supported

USES

• One of the early applications for code division multiplexing is in GPS.

• The Qualcomm standard IS-2000, known as CDMA2000. like Globalstar satellite phone network.

• CDMA has been used in the OmniTRACS satellite system for transportation logistics.

• In CDMA signal security is high.

Difference between CDMA and GSM

• The Multiplexing method used in the airial communication i.e. from Mobile Tower to your mobile and vice versa.

• CDMA mobile communication takes place with a "code" communicating between them and the other end if one is knowing that code then only it can listen to the data being transmitt ed i.e. the communication is in the coded form.

• CDMA handsets do not use SIM cards. • The handset is assigned a number from

the telecom operator and gets incorporated in itself

• CDMA handsets have RSN number which gets linked to a specific number assigned by operator.

Collaborative CDMA

• A novel collaborative multi-user transmission and detection scheme called Collaborative CDMA.

• The authors show that it is possible to achieve this increase at a low complexity and high bit error rate performance in flat fading channels, which is a major research challenge for overloaded CDMA systems.

• The new collaborative multi-user receiver consists of two stages:

• group multi-user detection (MUD) stage to suppress the MAI between the groups and a low complexity maximum-likelihood detection stage to recover jointly the co-spread users’ data using minimum Euclidean distance measure and users’ channel gain coefficients.

Bibliography

• htt p://www.argospress.com/Resources/cdma/cdmarchit.htm

• htt p://in.answers.yahoo.com/questi on/index?qid=1006050901222

• htt p://en.wikipedia.org/wiki/Code_division_multi ple_access

• htt p://www.diff en.com/diff erence/CDMA_vs_GSM

• htt p://www.youtube.com/watch?feature=player_embedded&v=r-l2p7RFaK8#!