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CDMA Network reference Model. :

CDMA Network reference Model. Presented to: Presented by : Dr. SBL Sachan Nirbhay Kr. Singh 151607 ME-ECE(Modular)


CONTENTS About network reference model. Mobile Standards Different Generations CDMA Need for CDMA Technology Cdma One IS-95 Architecture IS 95 Vs 2G systems 3G Vision Migrating to 3G CDMA 2000 Architecture WCDMA TD-SCDMA CDMA network reference model

What is Network Reference Model:

What is Network Reference Model A network is a group of computers, printers and other devices that are connected together either with a cable or wireless media.

The network users share hardware or software over the network.:

The network users share hardware or software over the network.

A network reference model defines the functions of communication software in a generalized and structured manner which helps to carry out the network product development activities. :

A network reference model defines the functions of communication software in a generalized and structured manner which helps to carry out the network product development activities.


CDMA Network is the system meant to regulate CDMA technology. It includes all aspects and functionality starting from the base station, transmitting antenna, receiving antenna, to mobile switching centers MS  Mobile station; BST  Base station transceiver; MSC  Mobile switching center; BSC  Base station controller; PSTN  Public switched telephone network


IS-95 CDMA is an access method. IS-95 was the first ‘operating system’ to use CDMA Invented by Qualcomm Began production in 1995. At this point, this is still called 2G wireless. Known as a narrowband system. Being supplanted by CDMA2000 (WCDMA) and UMTS, fully 3G systems. They both use CDMA. Known as wideband systems.


MOBILE PHONE NETWORKS There are a number of different digital cellular technologies, including: Global System for Mobile Communications (GSM)  General Packet Radio Service (GPRS)  Code Division Multiple Access (CDMA)  Evolution-Data Optimized (EV-DO)  Enhanced Data Rates for GSM Evolution (EDGE or GSM EDGE)  3GSM  Digital Enhanced Cordless Telecommunications (DECT)  Digital AMPS (IS-136/TDMA)  Integrated Digital Enhanced Network (IDEN).


CDMA Interim Standard 95 (IS-95)  is the first CDMA-based digital cellular standard pioneered by Qualcomm. The brand name for IS-95 is  CDMA ONE . It is a 2G Mobile Telecommunications Standard that uses CDMA, a multiple access scheme for digital radio, to send voice, data and signaling data (such as a dialed telephone number) between mobile telephones and cell sites. CDMA or "code division multiple access" is a digital radio system that transmits streams of bits (PN codes). CDMA permits several radios to share the same frequencies.

International Standardization:

International Standardization ITU (International Telecommunication Union) Radio standards and spectrum IMT-2000 ITU’s umbrella name for 3G which stands for International Mobile Telecommunications 2000 National and regional standards bodies are collaborating in 3G partnership projects ARIB, TIA, TTA, TTC, CWTS. T1, ETSI - refer to reference slides at the end for names and links 3G Partnership Projects (3GPP & 3GPP2) Focused on evolution of access and core networks

IMT-2000 Radio Standards:

IMT-2000 Radio Standards IMT-SC* Single Carrier (UWC-136): EDGE GSM evolution (TDMA); 200 KHz channels; sometimes called “2.75G” IMT-MC* Multi Carrier CDMA: CDMA2000 Evolution of IS-95 CDMA, i.e. cdmaOne IMT-DS* Direct Spread CDMA: W-CDMA New from 3GPP; UTRAN FDD IMT-TC** Time Code CDMA New from 3GPP; UTRAN TDD New from China; TD-SCDMA IMT-FT** FDMA/TDMA (DECT legacy) * Paired spectrum; ** Unpaired spectrum

Mobile Standards Organizations:

Mobile Standards Organizations European Technical Standard Institute (Europe): http://www.etsi.org Telecommunication Industry Association (USA): http://www.tiaonline.org Standard Committee T1 (USA): http://www.t1.org China Wireless Telecommunication Standard (China): http://www.cwts.org The Association of Radio Industries and Businesses (Japan): http://www.arib.or.jp/arib/english/ The Telecommunication Technology Committee (Japan): http://www.ttc.or.jp/e/index.html The Telecommunication Technology Association (Korea): http://www.tta.or.kr/english/e_index.htm

First Generation:

First Generation Advanced Mobile Phone Service (AMPS) US trials 1978; deployed in Japan (’79) & US (’83) 800 MHz band — two 20 MHz bands TIA-553 Still widely used in US and many parts of the world Nordic Mobile Telephony (NMT) Sweden, Norway, Demark & Finland Launched 1981; now largely retired 450 MHz; later at 900 MHz (NMT900)


Cont.. Total Access Communications System (TACS) British design; similar to AMPS; deployed 1985 Some TACS-900 systems still in use in Europe

Second Generation — 2G:

Second Generation — 2G Digital systems Technology to increase capacity Speech compression; digital signal processing Utilize “Intelligent Network” concepts Add new services There are a wide diversity of 2G systems IS-54/ IS-136 North American TDMA; PDC (Japan) IS-95 CDMA ( CDMAOne ) GSM

Need for CDMA Technology:

Need for CDMA Technology Higher capacity Improved performance in multipath by diversity Lower mobile transmit power = longer battery life Power control Variable transmission rate with voice activity detection Allows soft handoff Sectorization gain High peak data rates can be accommodated Combats other-user interference = lower reuse factors


CDMA???? Both an access method and air-interface Rest of the network is very similar Radio resource management, mobility management, security are similar Power control and handoffs are different Uses DSSS and ECC Frequency reuse factor is 1 Three CDMA systems IS-95 2G CDMA2000 W-CDMA

CDMA Analogy:

CDMA Analogy 10 people in a room. 5 speak English, 2 speak Spanish, 2 speak Chinese, and 1 speaks Russian. Everyone is talking at relatively the same time over the same medium – the air. Who can listen to whom and why? Who can’t you understand? Who can’t speak to anyone else?

CDMA Standards - IS-95:

CDMA Standards - IS-95 IS-95 deployed in the 800 MHz cellular band Evolution fixes bugs and adds data IS-95A provides data rates up to 14.4 kbps IS-95B provides rates up to 64 kbps (2.5G) Both A and B are compatible with J-STD-08 All variants designed for TIA IS-41 core networks (ANSI 41) CDMA was first commercialized by its founder A.J Verterbi at Qualcomm in 1995.

CDMA Standards - IS-95A:

CDMA Standards - IS-95A IS-95A is the CDMA-based second generation (2G) standard for mobile communication. The following are the key aspects of this standard: Support for data rates of upto 14.4 kbps IS-95A has been used exclusively for circuit-switched voice Convolutional Channel coding used Modulation technique used is BPSK

CDMA Standards - IS-95B:

CDMA Standards - IS-95B IS-95B is the evolved version of IS-95A and is designated as 2.5G. IS-95B maintains the Physical Layer of IS-95A, but due to an enhanced MAC layer, is capable of providing for higher speed data services. The following are the key aspects of the standard: Theoretical data rates of upto 115 kbps, with generally experienced rates of 64 kbps


Cont.. Additional Walsh codes and PN sequence masks, which enable a mobile user to be assigned up to eight forward or reverse code channels simultaneously, thus enabling a higher data rate Code channels, which are transmitted at full data rates during a data burst Convolutional Channel coding Binary Phase Shift Keying (BPSK) as the Modulation technique used

IS-95 CDMA Features-(1):

IS-95 CDMA Features-(1) Bandwidth Recycling Enhancing the system capacity due to the increase of reuse efficiency. Achieving higher bandwidth efficiency (interference limited) and simplifying the system planning. Achieving flexibility due to the bandwidth on demand. Power Control Reducing the interference and increasing the talk time of mobile station by using the efficient power control scheme. Soft handoffs Contributing to the achievement of the diversity and reduce the chance of loss of link midway through the conversation.

IS-95 CDMA Features-(2):

IS-95 CDMA Features-(2) Diversity Taking advantage of multiple levels of diversity: frequency diversity (spreading), spatial diversity (multiple antennas), path diversity (rake receiver) and time diversity (block interleaver), all of which reduce the interference and improve speech quality. Variable Rate Vocoder Offering high speed coding and reducing background noise and system interference based on the detection of the voice activity. Coding Technique Enhancing the privacy and security.

IS-95 Vs 2G Phone Systems:

IS-95 Vs 2G Phone Systems

Frequency Allocation GSM Vs CDMA:

Frequency Allocation GSM Vs CDMA

Spread Spectrum:

Spread Spectrum A modulation system in which the modulated (spread spectrum) signal bandwidth is much greater than the message signal bandwidth. The spectral spreading is performed by a code that is independent of the message signal. The same code is used at receiver to de spread the received signal and to recover the message signal.

Advantages of Spread Spectrum:

Advantages of Spread Spectrum It is Secure, difficult to intercept A large number of codes can support a large number of users As a large bandwidth is used the system is less prone to distortion Resistant to jamming Asynchronous multiple access technology

Types Of Spread Spectrum:

Types Of Spread Spectrum Direct Sequence Spread Spectrum Frequency Hoping Hybrid System

CDMA Forward Link:

CDMA Forward Link The forward link uses the same frequency spectrum as AMPS (824-849 Mhz) . Each carrier 1.25MHz Four types of logical channel Pilot, Synchronization, 7 Paging, and 55 Traffic channels Channels are separated using different spreading codes

CDMA Reverse Channel:

CDMA Reverse Channel Fundamentally different from the forward channels Uses OQPSK for power efficiency QPSK demodulation is easy 869-894 MHz range. No spreading of the data using orthogonal codes Same orthogonal codes are used for WAVEFORM encoding Two types of logical channels: Access channels Reverse traffic channels


QPSK is the modulation scheme Orthogonal Walsh codes are used (64 total) After orthogonal codes, they are further spread by short PN spreading codes Short PN spreading codes are M sequences generated by LFSRs of length 15 with a period of 32768 chips.

3G Vision:

3G Vision Universal global roaming Multimedia (voice, data & video) Increased data rates 384 kbps while moving 2 Mbps when stationary at specific locations Increased capacity (more spectrally efficient) IP architecture

IS 95 to CDMA 2000 3G Evolution :

IS 95 to CDMA 2000 3G Evolution


CDMA2000 Evolution from original Qualcomm CDMA Better migration story from 2G to 3G cdmaOne operators don’t need additional spectrum 1xEVD0 promises higher data rates than UMTS, i.e. W-CDMA Better spectral efficiency CDMA2000 core network less mature cdmaOne interfaces were vendor-specific


W-CDMA Wideband CDMA Standard for Universal Mobile Telephone Service (UMTS) Committed standard for Europe and likely migration path for other GSM operators Leverages GSM’s dominant position Requires substantial new spectrum 5 MHz each way (symmetric) Legally mandated in Europe and elsewhere Sales of new spectrum completed in Europe

Need For WCDMA:

Need For WCDMA WCDMA is a step further in the CDMA technology. Uses a 5 MHz wide radio signal and chip rate of 3.84 Mcps , which is about three times higher than the chip rate of CDMA2000 (1.22 Mcps ) QPSK Modulation Migration from 3G to 4G Higher spectrum efficiency

W-CDMA Vs cdma2000:

W-CDMA Vs cdma2000


TD-SCDMA Time division duplex (TDD) Chinese development - deployed in China Good match for asymmetrical traffic! Single spectral band (1.6 MHz) possible Costs relatively low Handset smaller and may cost less Power consumption lower TDD has the highest spectrum efficiency Power amplifiers must be very linear Relatively hard to meet specifications 35MHz for downlink and uplink

Rake Receiver:

Rake Receiver Mobile station receives multiple attenuated and delayed replicas of the original signal (multipath diversity channels). Two multipath signals are resolvable only if their relative delay exceeds the chip period Tc Amplitudes and phases of multipath components are found by correlating the received waveform with multiple delayed versions of the signal (delay = nTc). Searcher performs the above task for up to 3 different multipath signals. 3 parallel demodulators (RAKE fingers) isolate the multipath components and the RAKE receiver combines them.

Summary :

Summary Different mobile standard organization ITU, IMT 2000, TIA, IS CDMA IS 95 , IS95A,IS95B Codes –Walsh,Autocorrelation, PN Rake Receiver Forward and Reverse Link CDMA 2000 WCDMA

Network Reference Model and Security Aspects:

Network Reference Model and Security Aspects The network and signaling requirements for CDMA cellular systems IS-95 also use the augmentation and privacy procedures Which are used in the D-AMPS SYSTEMS. This model is here


The functions assigned to each of the entities: BS ,MSC ,HLR,VLR,AC, EIR,etc. Essentially support the same function as in GSM


At the time of subscription: 1- MS is programmed with Mobile identification number(MIN) 2-Electronics serial number (ESN) 3-Cellular authentication and voice encryption (CAVE) algorithm


Subscriber uses the terminal keypad to enter the 64-bit A key into the MS , and its correct entry is verified by the security software within the MS. The A key also resides HLR/AC IN THE SUSCRIBER HOME NETWORK


HLR/AC asks the MS To generate the secret shared data(SSD) By sending RANDSSD parameter to MS. The MS utilizes the RANDSSD, the A key, and the ESN As input to the CAVE algorithm to generate SSD


To authenticate a roaming subscriber autonomously , The SSD is passed from the HLR/AC of the home network of serving VLR, Along with the subscriber specific data (MIN/ESN).


The VLR broadcasts a global challenge At frequent intervals in the form of 32-bit random number (RAND), Which can be used by any terminal served by VLR To generate necessary authentication result.


An unauthorized interception of the SSD During its transport from HLR to the VLR May result in the impersonation of the user and Fraudulent use of network


Confidentiality for the users in terms of their identity and location is an important security aspect in mobile network, Where the user identity may be transported over an unencrypted radio channel during initial registration or call set up. In GSM it is handled by TM


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