Wireless Wide Area NetworksWireless Wide Area Networks3G/4G - mobile phones

Multiplexing

(collection of schemes to transmit multiple signals simultaneously)

FDM - Frequency-Division Multiplexing - analog, modulated to a fixed frequency band, channel.

TDM - Time-Division Multiplexing - same frequency in alternating time slices, each channel makes full use of the bandwidth, GSM and D-AMPS use TDM

CDM - Code-Division Multiplexing - makes better use of frequency than FDM and TDM. Signals are transmitted on the same frequency and same time, but have a unique code to identify itself. CDMA use CDM, of course.

Spread Spectrum

(signals in a wider band with low power density (power per frequency), appears as background noise to

others than the receiver. Used in CDMA and WLANs.) DSSS - direct-sequence spread spectrum - a chipping

sequence code (digital modulation) creates a chipping sequence (shorter signals than original bits) that is modulated with a carrier signal (radio modulation). 802.11b, CDMA uses DSSS.

FHSS - frequency-hopping spectrum - first modulates to narrowband signals, then a second modulation uses a hopping sequence of frequency to send the radio signal. Bluetooth uses FHSS.

OFDM - orthogonal-frequency-division multiplexing - uses multiple subcarriers in parallel to transmit data. The subcarriers are orthogonal in that they are modulated with their own data independently. It is used in ADSL, 802.11a/g wireleess LANs, and WiMax.

DSSS and FHSS can be multiplexed by CDM.

Cellular generations

(from the point of view of using multiplexing and spread spectrum)

First generation: FDMA (FDM Access), where each cell supports a number of channels of equal bandwidth, and each cellphone uses two channels (one up and another down).

Second generation in two groups: TDMA (TDM Access): GSM (Global System for Mobile)

and D-AMPS (IS-136). GSM is basically circuit-switching based, but GPRS (general packet radio service) was added to support data: SGSN (serving GPRS support node) and GSSN (gateway GPRS support node).

CDMA (CDM Access): CDMA comply with IS-95 (also known as cdmaOne). Uses DSSS combined with CDM. Designed by Qualcomm Inc, which holds IP over CDMA.

Cellular bands for AMPS (1G)

an analog cellular phone system using FDMA

AMPS reverse communication band

Second-generation cellular phone systems

D-AMPS (IS-136, is a digital cellular phone system using TDMA and FDMA)

GSM bands (digital cellular phone system using TDMA and FDMA)

GSM system (each voice channel is digitized and compressed to a 13kbps digital signal)

GSM frame and frequency bands

IS-95 forward transmission (digital cellular phone system using CDMA/DSSS and FDMA)

IS-95 reverse transmission

IMT-2000 radio interfaces (3G)

IMT (International Mobile Telecommunication)

GSM

GPRS&EDGE

GSM (3G)

3G data rate requirements 144 kbps at driving speed 384 kbps outside stationary speed 2Mbps for indoors speed

GSM + GPRS + EDGE achieve 3G GPRS added to allow dynamic use of

multiple channels and speeds up to 115 kbps (2.5 G)

EDGE (Enhanced Data Rates for Global Evolution) added to allow speeds up to 384 kbps

GSM uses SIM (subscriber identity module) cards to identify user, network, etc.

CDMA and GSM Evolution CDMA 2000

Delivered 3G speeds (CDMA-MC) CDMA voice and LTE data (1XEV-DO) VoLTE in progress

Verizon to end CDMA in 2021 GSM after Edge

UMTS (W-CDMA) LTE

LTE uses SIM Gained over 802.16 WiMax and Qualcomm’s Ultra Mobile

Broadband. LTE co-exists with other standards, allowing in theory

handoffs between cells supporting LTE and cells supporting UMTS, GSM/GPRS, 2G CDMA, CDMA-MC or 1XEV-DO

New generation: 4G

Introduced around 2010 Typical speed 3 Mbps to 5 Mbps: 10 times over

3G Designed to give at least 2 Mbps download

speeds to mobile customers Eventually, 100 Mbps to mobile users and 1 Gbps

to stationary users Designed to give at least 100 Mbps download

speeds to fixed customers Sufficient for high-definition video Runs over IP Wikipedia data rate comparison

4G Technologies

WiMAX (Worldwide Interoperability for Microwave Access) Based on 802.16 standard. WiMAX forum promotes it 802.16m will eventually provide 100 Mbps to mobile

users and 1 Gbps to stationary users. Clearwire was a pioneer in its deployment Bought by Sprint that will shut down WiMax in 2015

Long Term Evolution (LTE) The 4G technology that most cellular carriers have

adopted. Provide 14 Megabits speeds LTE Advanced will provide 100 Mbps to mobile users

and 1 Gbps to stationary users.

Differences between Wi-Fi and  3G

Convergence of Wi-Fi and cellular technologies

3G and 4G Mobile Smartphones and tablets Often can connect directly to an 802.11 WLAN for service Typically faster speeds than cellular for data Cellular companies like offloading flat-fee subscribers to the

WLAN Some Smart Phones Can Act as 802.11 Access Points Several 802.11users can share its capacity.

Cellular

Carrier

Cellular

Carrier

ISPISP

3G or

4G802.11

802.11

Mobile computing growth

Mobile computing technologies

Operating System 2013 Sales 2013 Market Share (%)

2012 Sales 2012 Market Share (%)

Android 758,719.90 78.4 451,621.00 66.4 iOS 150,785.90 15.6 130,133.20 19.1 Microsoft 30,842.90 3.2 16,940.70 2.5 BlackBerry 18,605.90 1.9 34,210.30 5.0 Other OS 8,821.20 0.9 47,203.00 6.9 Total 967,775.80 100 680,108.20 100

Worldwide Smartphone Sales to End Users by Operating System in 2013 (Thousands of Units)

Operating System

2013 Sales 2013 Market Share (%)

2012 Sales 2012 Market Share (%)

Android 120,961,445 61.9 53,341,250 45.8 iOS 70,400,159 36.0 61,465,632 52.8 Microsoft 4,031,802 2.1 1,162,435 1.0 Others 41,598 <0.1 379,000 0.3 Total 195,435,004 100 116,348,317 100

Worldwide Tablet Sales to End Users by Operating System, 2013 (Units)

Source: Gartner (2014) 

Mobile computing links (a few)

• My on-going series• UB OTS Lab App• Creating Android Apps• Creating iOS Apps• 16 essential Android apps for IT Professionals• The 25 Best iPhone Apps from PC Magazine• The 25 Best Android Apps   from PC Magazine• Engadget• C|Net news• Zdnet• PC World