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Unit 6 CDMA Technology

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Unit - 6 CDMA Technology
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Unit - 6 CDMA Technology

System overview Code division multiple access (CDMA) 1989 Qualcomm IS-95 Also called wideband spread spectrum 3G cellular Time Division Synchronous CDMA [TD-CDMA] Multicarrier CDMA [MC-CDMA] Wideband CDMA [W-CDMA]

CDMA2000

Evolution of 3G CDMA

Approved for IMT-2000 3G standards (International Mobile Telecommunications)

Backward compatible with TIA/EIA-95-B (Telecommunication industry association) (Electronic Industries Alliance)

Data services up to 2 mbps Multimedia, advanced radio technologies 2 versions cdma2000 1xEV : 2.4 mbps EV: Evolution; provides higher speeds implemented in two phases

cdma2000 1xEV-DV: 3 mbps EV-DV: Evolution data and voice only Integrates voice and data on the same carrier

Evolution of 3G CDMA First form of CDMA was IS-95 Dual mode of operation in 800 MHz Compatible with AMPS and CDMA

Additional features in IS-95A describes Wideband 1.25 GHz Power controls, registration, handoff, voice service procedures Compatibility

Cdmaone - group of all CDMA technologies

CDMAone Network componentsWireless Priority Service Center (WPSC) *FC+DN Visitor Location Register (VLR) Home Location Register (HLR)/Authentication Center (AC)

Mobile Station (MS)

Base Station (BS)

MSC Inter-Working Function (IWF) PSTN/ ISDN

FC Feature Code DN - Directory Number Signaling

Mobile Switching Center (MSC) Wireless Intelligent Network

Signaling and User Data

CDMA Basics Based on wideband spread spectrum digital techniques Separation of signals in time and frequency domain Transmission on same frequency at same time

Signals are spread over entire bandwidth Encoded and broadcasted Other than the intended receiver discard the signal as if it is noise Receiver demodulates the signal if it is above the threshold SNR

Multiple Access

FDMA FDMA - frequency division multiple access spectrum divided into narrowband channels each user given a channel for use transmission confined to signal power within channel selective filters used used at both ends to distinguish other channels reuse distance must be far away

TDMA TDMA - Time division multiple access spectrum divided into timeslots each user given a timeslot for use transmission confined to the time slot BTS and MS require synchronization Increases spectral efficiency at expense of each user's total data rate

CDMA CDMA - Code division multiple access Each mobile has continuous use of entire spectral allocation Spreads its transmitted energy out over the entire bandwidth of allocation Uses unique code for each transmitted signal MS and BTS are able to distinguish between signals transmitted simultaneously over the same frequency allocation CDMA can be combined with TDMA and FDMA to increase capacity

Comparison of access technology

CDMA Example

CDMA Basics For CDMA standard carrier and channel are differentiated carrier carrier frequency may be divided by means of codes into 64 different channels

channel cannel carry information related to a separate and distinct conversation or data connection in digital form

In TDMA carrier is divided into timeslots and each timeslot serves as channel

CDMA Advantages/Disadvantages Advantages Increased cellular communications security. Simultaneous conversations. Smaller phones Low power requirements and little cell-to-cell coordination needed by operators. Extended reach - beneficial to rural users situated far from cells.

Disadvantages CDMA is relatively new, and the network is not as mature as GSM CDMA cannot offer international roaming, a large GSM advantage

3G Wireless Systems & Standards3G Wireless Standards & SystemsCDMA- Code Division Multiple Access UMTS- Universal Mobile CDMA 2000 (Successor of IS-95) Telecommunications System RTT- Radio Transmission Technology

UMTS

FDD W-CDMA 1xRTT 3xRTT

TDD W-CDMA

FDD- Frequency Division Duplex TDD- Time Division Duplex

1x EVDO

1x EVDV

EV- Evolution DO- Data Only DV- Data and Voice.

CDMA Frequency bands Cellular bands Uplink - 824 MHz to 849 MHz Downlink - 869 MHz to 894 MHz 20 MHz separation Only some of the frequencies will be used

1900 MHz PCS Band 1200 Channels 60 KHz channel spacing 80 MHz separation

CDMA Frequency bandsTransmitter CSMA PCS Channel Number N Center frequency for CDMA Channel MHZ TDMA PCS Channel Number N TDMA PCS Channel Frequency (MHz)

Mobile station Base Station

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