The Evolution of TDMA to 3G & 4G Wireless Systems

  The Evolution of TDMA to 3G & 4G Wireless Systems.ppt (Size: 4.2 MB / Downloads: 0)
AT&T Wireless Services
TDMA
European GSM over 250 million
North American TDMA ~ 50 million
Japanese PDC ~ 50 million
CDMA
North American CDMA ~ 60 million (including S. Korea)
TDMA parameters
30 KHz channels (like analog & CDPD)
20 msec speech frames
24.3 kbaud symbol rate
3 time-slots/users
7.4 kbps ACELP speech coding
1/2-rate channel coding on important bits interleaved over 2 bursts in 40 msec
Differential pi/4-QPSK modulation
EDGE TechnologyEnhanced Data-rates for Global Evolution
Evolutionary path to 3G services for GSM and TDMA operators
Builds on General Packet Radio Service (GPRS) air interface and networks
Phase 1 (Release’99 & 2002 deployment) supports best effort packet data at speeds up to about 384 kbps
Phase 2 (Release’2000 & 2003 deployment) will add Voice over IP capability
GPRS Airlink
General Packet Radio Service (GPRS)
Same GMSK modulation as GSM
4 channel coding modes
Packet-mode supporting up to about 144 kbps
Flexible time slot allocation (1-8)
Radio resources shared dynamically between speech and data services
Independent uplink and downlink resource allocation
EDGE Airlink
Extends GPRS packet data with adaptive modulation/coding
2x spectral efficiency of GPRS for best effort data
8-PSK/GMSK at 271 ksps in 200 KHz RF channels supports 8.8 to 59.2 kbps per time slot
Supports peak rates over 384 kbps
Requires linear amplifiers with < 3 dB peak to average power ratio using linearized GMSK pulses
Initial deployment with less than 2x 1 MHz using 1/3 reuse with EDGE Compact as a complementary data service
GPRS Networks
consists of packet wireless access network and IP-based backbone
shares mobility databases with circuit voice services and adds new packet switching nodes (SGSN & GGSN)
will support GPRS, EDGE & WCDMA airlinks
provides an access to packet data networks
Internet
X.25
provides services to different mobile classes ranging from 1-slot to 8-slot capable
radio resources shared dynamically between speech and data services
Compact vs Classic
Classic
4/12 reuse
continuous downlinks on first 12 carriers
2.4 MHz x2 minimum spectrum
Compact
1/3 reuse in space
frame synchronized base stations
reuse of 4 in time for control channels
partial loading for traffic channels
discontinuous downlinks
600 KHz x2 minimum spectrum
EDGE Evolution
Best effort IP packet data on EDGE
Voice over IP on EDGE circuit bearers
Network based intelligent resource assignment
Smart antennas & adaptive antennas
Downlink speeds at several Mbps based on wideband OFDM and/or multiple virtual channels
VoIP over EDGE Bearer Performance
Focused on GMSK full-rate & 8PSK half-rate EDGE channels with dedicated MAC & random frequency hopping for 7.4 kbps voice coding
AT&T Labs-Research Work on 4G
Smart antennas
Multiple-Input-Multiple-Output Systems
Space-Time Coding
Dynamic Packet Assignment
Wideband OFDM
MIMO Radio Channel Measurements
Multiple antennas at both the base station and terminal can significantly increase data rates with sufficient multipath
Ability to separate signals from closely spaced antennas has been demonstrated indoors and in AT&T-Lucent IS-136 field trial
Lucent has demonstrated 26 bps/Hz in 30 kHz channel with 8 Tx and 12 Rx antennas indoors
AT&T has performed measurements on 4 Tx by 4 Rx antenna configurations in full mobile & outdoor to indoor environments
Multiple Input Multiple Output Wireless
RX diversity - HF, terrestrial microwave, cellular….
TX frequency offset diversity & simulcasting for paging - 70’s
Adaptive array processing in military systems
TX diversity - 80’s
frequency offset (channel decoding combining)
delay (equalizer combining)
Optimum combining for cellular (multipath channels) - 80’s
Space-division multiple access - 80’s & 90’s
angle-of-arrival based
multi-path based (supports co-location & multi-channels per user)
MIMO - 80’s & 90’s
Multiple spatial channels using adaptive antenna arrays
BLAST - successive interference cancellation combined with coding
Space-Time coding
Multiple Antennas increase System Capacity
MIMO (BLAST & space-time coding) techniques increase bit rate and/or quality on a page link by creating multiple channels and/or enhancing diversity
Switched/steered beam antennas for base stations and interference suppression/adaptive antennas for terminals reduce interference, increasing system capacity
High peak-to-average power levels
Preservation of orthogonality in severe multi-path
Efficient FFT based receiver structures
Enables efficient TX and RX diversity
Adaptive antenna arrays without joint equalization
Support for adaptive modulation by subcarrier
Frequency diversity
Robust against narrow-band interference
Efficient for simulcasting
Variable/dynamic bandwidth
Used for highest speed applications
Supports dynamic packet access
Summary: Key Features of 4G W-OFDM
IP packet data centric
Support for streaming, simulcasting & generic data
Peak downlink rates of 5 to 10 Mbps
Full macro-cellular/metropolitan coverage
Asymmetric with 3G uplinks (EDGE)
Variable bandwidth - 1 to 5 MHz
Adaptive modulation/coding
Smart/adaptive antennas supported
MIMO/BLAST/space-time coding modes
Frame synchronized base stations using GPS
Network assisted dynamic packet assignment