Transcript General Application - My FIT (my.fit.edu)

Wireless Data Communication Networks
Lecture 21: GSM evolution
Florida Institute of Technology
ECE Department
Outline
Evolution of GSM into a packet data network
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ECE Department
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GSM Evolution path
GSM – migrates towards packet data
networks with broadband access air
interface
Driver behind the migration –
change in the use model for
GSM networks
Florida Institute of Technology
ECE Department
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Cellular data networks – throughput comparison
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ECE Department
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GPRS Network Architecture
 GPRS introduces new entities to support data packet transmissions
 New entities are PCU, GSN, Border Gateway, and GPRS register
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ECE Department
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GSM/GPRS – put together
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ECE Department
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GPRS/EDGE – MCS and throughputs
 GPRS and EDGE introduce multiple Modulation and
Coding Schemes (MCS)
 MCS allows different data rates through the GSM time
slot
 Selection of MCS depends on channel condition and
capability of mobile
 GPRS and EDGE allow for multiple slot aggregation
 Slot aggregation allows increase in data rate offered to
the user
GPRS MCS
 EDGE introduces new modulation scheme – 8-PSK
EDGE MCS
Note: EDGE supports both GMSK and 8PSK
PHY throughput
for different MCS
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ECE Department
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UMTS architecture
Node B
User
Subscriber
Identity
Module
(USIM)
Radio
Network
Controller
RNC
Node B
Cu
Mobile
Equipment
(ME)
MSC/
VLR
Circuit
Switched
Network
HLR
Node B
Node B
 W-CDMA air interface for
UMTS radio Access
 Air interface is based on
CDMA access
 Reuse of the existing
GSM network architecture
Iur
Iub
User Equipment
(UE)
 Iub fully standardized
Radio
Network
Controller
RNC
SGSN
GGSN
Packet Data
Network
 The core network allows
both GSM and UMTS
radio access
Core Network
(CN)
UMTS Terrestial Radio
(UTRAN)
Acronyms:
GMSC/
VLR
Uu
Iu
Node B = Base Station
SGSN = Service GPRS Node
Open Interfaces:
GGSN = Gateway GPRS Node
Uu – W-CDMA air interface
MSC = Mobile Switching Center
Iub – Node B to RNC
VLR = Visitor Location Registry
Iur – between RNC
HLR = Home Location Registry
Iu – between UTRAN and CN
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ECE Department
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UMTS Radio Interface
•
•
•
•
•
Air interface determines the performance of a cellular
system
W-CDMA – revolutionary change from GSM’s TDMA
scheme
Advanced radio resource management – required by
diverse 3G applications
Summary of W-CDMA properties
Property
Value
Access scheme
DS-CDMA with FDD and asynchronous operation
Bandwidth
5MHz
Chip rate
3.84 Mc/second
Spreading
Variable: UL 1-512 (power of 2), DL(1-256)
Single code user rates
15,30,60,120,240,480, 960 kb/sec
UL (after coding)
Up to 6 code aggregation
Single code user rates
15,30,60,120,240,480, 960, 1920 kb/sec
DL(after coding)
Up to 3 code aggregations
Frame Length
10ms
Power control
Open loop and closed loop with 1500 commands/sec
Detection
Coherent on both UL and DL
Diversity support
DL TX Diversity, DL and UL RAKE receiver reception,
UL space diversity
Multi-rate spreading
W-CDMA is interference limited
• Provides soft capacity and
•
Coverage, capacity, quality tradeoffs
Power spectrum
density
W-CDMA Scheme
f2
W-CDMA
Channel
UL – Uplink, DL - Downlink
f1
10 ms
10 ms
10 ms
time
frame
frequency
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ECE Department
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Long Term Evolution (LTE)
 LTE – 4 G technology
 Changes in both radio access and core
 Radio access is OFDM based (1.4-20MHz)
 Core is packet only; Voice as VoIP
 Simplified core – all IP
 eNodeB responsible for RRM
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ECE Department
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Review
 List successor technologies to GSM
 How is voice handled in GSM (as CS
or as PS)
 Which technology promises higher
data rates: EDGE or HSPA?
 What type of access scheme is used
in UMTS?
 What type of access scheme is used
in LTE?
 Does LTE core network contain
switches?
 How is voice handled in LTE?
 Explain the concept of adaptive MCS
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ECE Department
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