Modern Wireless Communication Systems

zaahir salam

Overview

Wireless communication networks was concept of 1960s and 1970s and become much more popular in 1990’s.

Radio Spectrum licenses for personal communication service(PCS) in the 1800-2000 MHz frequency bands.

The rapid growth in cellular telephone subscribers has demonstrated conclusively that wireless communications are:

Robust

Viable voice and data transport mechanism.

Next generations are being designed to facilitate high speed data communications traffic in addition to voice calls.

New standards and technology are being implemented to replace fiber optic or copper lines.

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Used as a replacement for wires within the homes, buildings, and office

settings through the development of wireless local area networks

(WLANs).

Bluetooth modem standard promises to replace troublesome appliance

communication cords with invisible wireless connections within a personal

workspace.

The WLAN’s and Bluetooth use low power levels and generally do not

require a license for spectrum use.

They are used as data networks within buildings without a license.

Networks that don't require a licensed spectrum for there use

First Generation Wireless Systems (1G)

First-generation wireless technology is based on analog signals.

Mostly relied on FDMA/FDD and analog FM.

Are very limited in capacity and did not extend across geographic areas

Systems using 1G :

AMPS, TACS, and NMT

Working of 1G

In this, mobile device sends the waves to a base station where they are

processed to determine the signal’s next destination Once the destination is

determined, the signal is reconstructed as accurately as possible

The analog signal received by the end user may closely resemble the

original transmission but rarely duplicate it.

Noticeable differences in quality and form occur due to:

recreation errors.

Signal destruction .

translation and interference problems .

2 Generation wireless systems Developed in Europe and the US to provide better voice quality, higher capacity

as well as lower power consumption.

2G services are frequently referred as Personal Communications Service or PCSin the US.

Offer support for simple non-voice services like SMS (simple messagingservice).

Difficult roaming between countries using different systems.

Cannot meet subscriber demands for new, faster non-voice services on themove.

Its standards use digital modulation formats and TDMA/FDD and CDMA/FDDmultiple access techniques.

2 G Continued……… The Standards include 3 TDMA standards and 1 CDMA:

•A) Global System Mobile(GSM)

It supports 8 time slotted users for each 200kHz radio channel

• B) Interim Standard 136(IS-126)

It supports 3 time slotted users for each 30KHz radio channel.

• C) Pacific Digital Cellular

It is similar to IS-136 with more than 50 million users

• D) CDMA one

It supports upto 64 users that are orthogonology coded and

transmitted on each 1.25MHz channel.

Modern cellular systems are also being installed to provide fixed

telephone service to residences and businesses in developing nations- this

is particularly cost effective for providing plain old telephone

service(POTS)

2G technologies offer a three times increase in spectrum efficiency .

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Worldwide subscriber base as a function of cellular technology in late 2001

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1st GA GSM IS-136 &PDC IS-95 CDMA

Cdma2000-1xEV,DV,DO

Cdma2000-3xRTT

IS-9 IS-136 & PDC

GPRS

HSCSDIS-95B

EDGE

Cdma200-1xRTT

3GPP2HSCSD

HSCSD

HSCSD3GPP

2G

3G

2.5G

Various upgrade paths for 2G technologies

GSM

What is 2.5G Wireless? It was an effort to retrofit the 2G standards for compatibility with increased

throughput data rates that are required to support modern internet applications.

This standard allows existing 2G equipment to be modified and supplemented with new base station add-ons and subscriber unit software updates to support:

High data rate transmission .

E-mail traffic

Mobile commerce

Location based mobile services.

This technology also support new web browsing format language , called wireless Applications Protocol (WAP).

WAP allows standard web pages to be viewed in a compressed format specifically designed for small, portable hand held devices.

• HSCSD (High speed circuit switched data ) for 2.5G GSM

• It simply requires the service provider to implement a software change at

existing GSM base station.

• is a circuit switched technique that allows a single mobile subscriber to use

consecutive user time slots in the GSM standard .

• HSCSD relaxes the error control coding algorithms

• increases the available application data rate to 14,440bps as compared to

9,600bps in GSM specification.

• by using up to 4 consecutive time slots it is able to provide a raw

transmission rate of up to 57.6kbps to individual users.

• GPRS (General Packet Radio Service) for 2.5G GSM and IS-136

• It is a packet based data network which is well suited for:

» Non-real time internet usage

• It supports multi-user network sharing individual radio channels and time

slots.

• In this all 8time slots of a GSM radio channel are dedicated to GPRS by

which an individual user is able to achieve as much as 171.2kbps.

• EDGE(Enhanced data rates for GSM)

• It is a more advanced upgrade to GSM standard.

• It requires addition of new hardware and software at existing base stations.

• It introduces a new digital modulation format, 8-PSK(octal phase shift keying) which is used in addition to GSM’s standard GMSK modulation.

• IS-95B for 2.5G CDMA

» CDMA has a single upgrade path for eventual 3G operation.

» It supports medium data rate (MDR) service by allowing a dedicated user to command up to 8 different users walsh codes simultaneously and in parallel for an instantaneous throughput of 115.2 kbps per user.

CDMA Evolution

•Voice Data

up to 14.4

Kbps

•Voice Data

up to 115

Kbps

•2x increases in

voice capacity

upto 307 kbps*

packet data on a

single (1.25 MHz)

carrier

•First 3G system

for any

technology

worldwide

•Optimized, very

high-speed data

(Phase 1)

•Up to 2.4Mbps*

packet data on a

single (1.25 MHz)

carrier.

•Integrated voice

and data (Phase 2); up to 3.09 Mbps

3G Wireless Systems They are new generation of systems that offer high bandwidth and support

digital voice along with multimedia and global roaming.

Globally, different systems are being used, so, to migrate to globally acceptable systems, numerous standardization activities were carried out and three systems emerged: W-CDMA, CDMA2000, and TD-SCDMA

W-CDMA (Wideband Code-Division Multiple Access)

Standard derived from Code-Division Multiple Access (CDMA), is officially known as IMT-2000 direct spread. W-CDMA is a 3G mobile wireless technology that promises much higher data speeds to mobile and portable wireless devices than commonly offered in today's market.

It can support mobile/portable voice, images, data, and video communications at up to 2 Mbps (local area access) or 384 Kbps (wide area access). The input signals are digitized and transmitted in coded, spread-spectrum mode over a broad range of frequencies. A 5 MHz-wide carrier is used, compared with 200 kHz-wide carrier for narrowband CDMA.

TD-SCDMA (time division synchronous code division multiple access) Supporting data transmission at speeds up to 2 Mbps, TD-SCDMA

combines support for both circuit-switched data, such as speech or video, and also packet-switched data from the Internet. The standard combines time division multiple access (TDMA) with an adaptive, synchronous-mode code division multiple access (CDMA) component.

cdma2000 The name cdma2000 actually denotes a family of standards that

represent the successive, evolutionary stages of the underlying technology. These are, in order of evolution:CDMA2000 1xRTTCDMA2000 1xEV-DO: Release 0, Revision A, Revision BCDMA2000 1xEV-DO Revision C or Ultra Mobile Broadband (UMB)CDMA2000 1xEVDV

In the above nomenclature, EVDO is short for Evolution - Data Optimized and EVDV, for Evolution - Data and Voice.

3G System Capabilities Capabilities to support circuit and packet data at high bit rates:

•144 kilobits/second or higher in mobility (vehicular) traffic

•384 kilobits/second for pedestrian traffic

•2 Megabits/second or higher for indoor traffic

Common Billing/User Profiles

Sharing of usage/rate information between service providers

Standardized call detail recording

Standardized user profiles

Capability to determine geographic position of mobiles and report it to

both the network and the mobile terminal

Interoperability and roaming

3G System Capabilities ….

Capability to determine geographic position of mobiles and report it to both the network and the mobile terminal

Support of Multimedia Services/Capabilities

Fixed and variable rate bit traffic

Bandwidth on demand

Asymmetric data rates in the forward and reverse links

Multimedia mail store and forward

Broadband access up to 2 Megabits/second

Communication services

•Video telephony

•Video conference

•Personal location (GPS)

Education

•Virtual schools

•On-line science lab

•On-line library

•On-line language labs

•Training

Applications Using 3G

Business services

• Mobile office

•Narrowcast business TV

•Virtual workgroups

•Expertise on tap

Entertainment

•Audio on demand

•Games

•Video clips

•Virtual sightseeing

1G 2G 3G

System Analogue Digital Digital

Major Systems AMPS,NMT,TACS GSM,CDMA,TDMAWCDMA,CDMA2000,

TD-SCDMA

Application VoiceVoice + little Circuit

switch-data

Voice + Packet-

switch-data

Local Subscriber Less than 500k About 5.9 MillionMore than 5Million

(estimated)

SpeedDepends on

Analogue Signal9.6kbps to 14.4kbps

144kbps for mobile to

2Mbps for stationary

Properties

Unstable,

incomplete coverage

and poor sound

quality

More secure data

services available,

broader coverage,

more stable, allow

more users, better

sound quality

Multimedia data,

positioning capability,

connection to

internet, always

connected

Comparison of Generations

Key Parameters of 3G and 4G Systems3G 4G

Frequency

Band1.8 - 2.5 GHz 2 - 8 GHz

Bandwidth 5 - 20 MHz 5 - 20 MHz

Data RateUp to 2 Mbps (384

Kbps deployed)Up to 20 Mbps

AccessW - CDMA / CDMA

2000 / TD -SCDMA

MC - CDMA or OFDMA

(TDMA)

Switching Circuit / Packet Packet

Mobile top

speeds200 Km/h 200 Km/h

Technologies that use Non licensed Spectrum

• Bluetooth is a new short-range wireless technology designed to enable

wireless communication between diverse devices.

• A local area network (LAN) is a group of computers and associated devices

that share a common communications line or wireless link. Typically,

connected devices share the resources of a single processor or server within

a small geographic area (for example, within an office building)

REFERENCES

• Modern wireless communication by rappaport

• Internet

• 3G wireless ppt. by keith doughlas