Wireless Wide Area Networks 3 G4 G mobile
Wireless Wide Area Networks 3 G/4 G - mobile phones
Multiplexing (collection of schemes to transmit multiple signals simultaneously) n n n 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. ) n n 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. 11 b, 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. 11 a/g wireleess LANs, and Wi. Max. DSSS and FHSS can be multiplexed by CDM.
Cellular generations (from the point of view of using multiplexing and spread spectrum) n n 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: n n TDMA (TDM Access): GSM (Global System for Mobile) and DAMPS (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 cdma. One). Uses DSSS combined with CDM. Designed by Qualcomm Inc, which holds IP over CDMA.
Cellular bands for AMPS (1 G) 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 13 kbps 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 (3 G) GSM GPRS&EDGE IMT (International Mobile Telecommunication)
GSM (3 G) n n 3 G data rate requirements n 144 kbps at driving speed n 384 kbps outside stationary speed n 2 Mbps for indoors speed GSM + GPRS + EDGE achieve 3 G n GPRS added to allow dynamic use of multiple channels and speeds up to 115 kbps (2. 5 G) n EDGE (Enhanced Data Rates for Global Evolution) added to allow speeds up to 384 kbps n GSM uses SIM (subscriber identity module) cards to identify user, network, etc.
CDMA and GSM Evolution n CDMA 2000 n Delivered 3 G speeds (CDMA-MC) CDMA voice and LTE data (1 XEV-DO) Vo. LTE in progress n Verizon to end CDMA in 2021 n n n GSM after Edge n n n UMTS (W-CDMA) LTE uses SIM n n Gained over 802. 16 Wi. Max 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, 2 G CDMA, CDMA-MC or 1 XEV-DO
New generation: 4 G n n n n Introduced around 2010 Typical speed 3 Mbps to 5 Mbps: 10 times over 3 G 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
4 G Technologies n Wi. MAX (Worldwide Interoperability for Microwave Access) n n n Based on 802. 16 standard. Wi. MAX forum promotes it 802. 16 m 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 Wi. Max in 2015 Long Term Evolution (LTE) n n n The 4 G 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 3 G
Convergence of Wi-Fi and cellular technologies n 3 G and 4 G Mobile Smartphones and tablets n n n 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. 11 users can share its capacity. ISP Cellular Carrier 3 G or 4 G 802. 11
Mobile computing growth
Mobile computing technologies Worldwide Smartphone Sales to End Users by Operating System in 2013 (Thousands of Units) 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 i. OS Apps • 16 essential Android apps for IT Professionals • The 25 Best i. Phone Apps from PC Magazine • The 25 Best Android Apps from PC Magazine • Engadget • C|Net news • Zdnet • PC World
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