Introduction To 3G/4G: WCDMA Basic Theory
Introduction To 3G/4G: WCDMA Basic Theory
Introduction To 3G/4G: WCDMA Basic Theory
Introduction to 3G/4G
1. EVOLUTION OF MOBILE COMMUNICATIONS 1G
Analog cellular Voice AMPS TACS 9.6 Kbps 80
2G
Digital cellular Voice /data CDMA GSM 64 Kbps 1992 1XRtt GPRS 144 Kbps 1999 2001
3G
Digital cellular Voice / high speed data CDMA2000 / WCDMA 2 Mbps 2004
4G
Hybrid IP based Voice / very high speed data HSDPA / HSUPA >10 Mbps Not yet deployed
AMPS: Advanced Mobile Phone System TACS: Total Access Communication System GPRS: General Packet Radio Services
1G 1st Generation: Analog Cellular 1) Feature: frequency division multiple access (FDMA) analog signal narrow band 2) Main mode: AMPS TACS NMT 3) Limitations: hard to develop digital bearer services cannot adopt to digitization of fixed networks low frequency efficiency cannot meet larger capacity requirements easy to be eavesdropped 2G 2nd Generation: Digital Cellular 1) Feature: time division multiple access (TDMA); narrow code division multiple access (N-CDMA) digital signal, narrow band strong anti-interference capability
2) Main mode: GSM D-AMPS N-CDMA 3) Limitations: Narrow bandwidth unable to provide various broadband information services such as high speed data services. 3G 3rd Generation: Digital Cellular IMT 2000 1) Feature:
code division multiple access (CDMA) digital signal broadband integrated service system integrating all current mobile telephone system functions providing multiple services large capacity
2) Meaning of 2000: frequency spectrum around 2000MHz data rate up to 2000kbps putting into business about 2000 3) Main mode: WCDMA CDMA2000 TD-SCDMA 4G 4th Generation: Hybrid IP Based Mobile Network 1) Feature:
3G Mobile Voice and Data Service, Broadband Access, Video Call > 10 Mbps Data Rate In principle will allow high-quality smooth video transmission HSDPA / HSUPA
2. 3G VOCABULARIES
3G systems are referred to as Universal Mobile Telecommunications System (UMTS) in Europe and International Mobile Telecommunications 2000 (IMT2000) worldwide. UMTS - Universal Mobile Telecommunications System
WCDMA = Wideband CDMA IMT-2000 = International Mobile Telecommunications 2000 3GPP = 3rd Generation Partnership Program
MS = Mobile Station (WCDMA) BTS = Base Transceiver Station (WCDMA) RNC = Radio Network Controller 3G-SGSN = 3G Serving GPRS Support Node GGSN = Gateway GPRS Support Node SCP = Service Control Point HLR = Home Location Register MSC = Mobile Switching Centre GMSC = Gateway MSC UTRAN = UMTS Terrestrial Radio Access Networ
3. NUMBERS
UMTS Working frequency: 2GHz Bandwidth: 5MHz Chip rate: 3.84Mcps Frame length: 10 ms 3G Bit Rates 64 - 144 kbits/s, Rural outdoor 384 kbits/s, Urban 2 Mbits/s, Indoor, low range outdoor
4. ADVANTAGES OF WCDMA
Wideband Code Division Multiple Access Uses direct sequence spread-spectrum technology to transmit a number of independent conversations across 5MHz segments of the radio spectrum.
FDM A
Pow Frequency
Time
Large capacity WCDMA uses different user use same frequency at the same time, but with different spreading code Large Coverage Almost 2 times than GSM, save money for operator
Example: To cover 1000 km2 : GSM will need 200 BTS WCDMA will only need 50 BTS ** Attention: exact result need Link Budget
TDM A
Pow Frequency Time
CDM A
Pow Frequency Time
High privacy and hard to eavesdropped Use soft handoff: decrease drop-call rate o WCDMA: make before break--- soft handoff o Other systems: make after break--- hard handoff Perfect Power Control and voice activation This makes the UE power low, which is healthy for the human body.
Traditional technologies try to squeeze the signal into the minimum required bandwidth Direct-Sequence Spread spectrum systems mix their input data with a fast spreading sequence and transmit a wideband signal The spreading sequence is independently regenerated at the receiver and mixed with the incoming wideband signal to recover the original data
SPREAD-SPECTRUM SYSTEM
Wideband Signal
Slow Information Sent TX RX Slow Information Recovered
Spread Spectrum Technique employs a transmission bandwidth that is several orders of magnitude greater than the minimum required signal bandwidth.
Sender combines data with a fast spreading sequence, transmits spread data stream Power is Spread Over a Larger Bandwidth; Many code channels are individually spread and then added together to create a composite signal
Receiver intercepts the stream, uses same spreading sequence to extract original data
6. COVERAGE
WCDMA performance is determined by such factors as Number of users Transmission rate Mobile rate Wireless environment o indoors o outdoors The sizes of cell depend on such factors as: Local radio conditions (local interference) Traffic in neighbouring cells (distanced interference) Cell Radius decrease according to the increase number of users
Up to 10 mile range without wires Broadband speeds without cable or T1 Handles last mile access in remote areas Affordable technology
Two corresponding WiMAX standards: IEEE 802.16-2004 for fixed point-to-point and point-to-multipoint wireless access. It's akin to a faster, airborne version of Digital Subscriber Line (DSL) or cable-modem services and became the industry's first NLOS BWA standard last June. IEEE 802.16e for mobile wireless access from laptops and handhelds. It's analogous to a faster version of third-generation telecommunications technology. WiMAX proponent Intel Corp. has promised 802.16e-enabled laptops by early 2007. WiMAX Applications:
Residential and SOHO High Speed Internet Access Small and Medium Business Wi-fi Hot Spot Backhaul