Date post: | 25-Dec-2015 |
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Objective
At the end of the module the participant will be able to:
• Describe UMTS network and Radio Access Network.
• Explain aspects of UMTS Release 99 air interface.
• Briefly introduce HSPA system and key elements of HSPA.
Content
• UMTS evolution and HSPA
• UMTS Release 99 environment– Network
– Air Interface
• HSDPA introduction and advantages
• HSUPA introduction and advantages
HSPA or HSxPA
Consists of:
• HSDPA = High Speed Downlink Packet Access– Introduced in Release 5
– Up to 14.4 Mbps in downlink
• HSUPA = High Speed Uplink Packet Access– Introduced in Release 6
– Up to 5.76 Mbps in uplink
Future enhancements to HSPA will lead to even higher data rates.
Rel 99 ( = Rel 3)
Rel 4 Rel 5 Rel 98 (EGPRS)
RAN
CORE
UTRANQoS
HSDPA
VoIPMGW
QoSIMS
Rel 6
HSUPA
Evolution of UMTS
UMTS Release 99 Environment
Core Network: Same as GSM/GPRS/EDGE
Radio Access Network:
• User Equipment (UE) = Mobile phone + USIM
• Node B – Base station supporting WCDMA
• Radio Network Controller (RNC) – Controller in 3G RAN
Unlike 2G, Iur interface exists between neighbor RNCs.
UMTS Network
Circuit-switchedand IN network
Internet
IntranetISP
Node B Node BB
3G access
network
Packet-switchednetwork
Management System
Node BIur
IuCS
IuPSIub
E
Gn Gi
RNC
GGSN
GMSC PSTN
IN
RNC
MSC
SGSN
3G Core network
UE
Uu
HLR
UMTS Release 99 Air Interface
• Large 5 MHz bandwidth.
• FDD: Simultaneous transmit and receive using different band.
• CDMA– Spreading: creating signal through unique user code to create multiple
bandwidth.
– Despreading: reobtaining original signal by correlating signal with user code.
Frequency Time PN code
FDMATDMACDMA
frequency f
time t
power
TS 1TS 2
TS 3
TDMA
frequency f
time t
power
1 2 3
FDMA
frequency f
time t
power
123
CDMAMultiplexmethod
BS & MS with commonknow-how regarding:
P
P P
For coordinating limited frequency resources to different users
-1
User data:100
0 01
T Bit
Spreading code:0110
+1
+1
-1
+1
-1
Coded signal T chip
t
t
t
SF = 4
0 0 0 0 0 01 1 1 1 1 1
0 0 0 01 1 1 11 10 0
Spreading
CodeGenerator
WidebandModulation
CarrierGenerator
De-Spreading
CodeGenerator
De-Modulation
RB
AirInterface
RB
RC
Timesynchronization
RB: Bit RateRC: Chip RatefT: Carrier frequency
RCfT
bits chips symbol
Transmitter Receiver
Cch,1,0 = (1)c
(c , c)
(c , -c)
SF = 1 SF = 2 SF = 4 SF = 8
Cch ,2,0 = (1,1)
Cch ,2,1 = (1,-1)
Cch ,4,0 = (1,1,1,1)
Cch ,4,1 = (1,1,-1,-1)
Cch ,4,2 = (1,-1,1,-1)
Cch ,4,3 = (1,-1,-1,1)
Cch ,8,0 = (1 , 1 , 1 , 1 , 1 , 1 , 1 , 1)
Cch ,8,1 = (1 , 1 , 1 , 1 , -1 , -1 , -1 , -1)
Cch , 8,2 = (1 , 1 , -1 , -1 , 1 , 1 , -1 ,-1)
Cch ,8,3 = (1 , 1 , -1 , -1 , -1 , -1 , 1 , 1)
Cch , 8,4 = (1 , -1 , 1 , -1 , 1 , -1 , 1 , -1)
Cch ,8,5 = (1 , -1 , 1 , -1 , -1 , 1 , -1 , 1)
Cch ,8,6 = (1 , -1 , -1 , 1 , 1 , -1 , -1 , 1)
Cch ,8,7 = (1 , -1 , -1 , 1 , -1 , 1 , 1 , -1)
Code Tree in UMTS Air Interface
Role of Channelization and Scrambling Code in Downlink Direction
• Channelization codes distinguish user within a cell.
• Each cell has the same channelization code tree – two users in different cells can have the same channelization code assigned.
• Therefore the different cells must be characterized by a Scrambling code.
Code 3
Code 3Code 2
Code 1
Code 2
Code 1
Code Comparison between Uplink and Downlink
Uplink Downlink
Scrambling Codes User separation Cell separation
Channelisation CodesData and control channels
from same UEUsers within a cell
Available
Channelisation Codes
FDD
4, 8, 16, 32, 64, 128, 2564, 8, 16, 32, 64, 128, 256,
512
Spreading Code Channelisation Code x Scrambling Code
In the uplink direction the user signals are not synchronised due to time delay.
In case of different time delays Channelization Codes are not orthogonal any more.
Scrambling Codes: High autocorrelation if synchronized, almost zero correlation between different codes even if unsynchronized.
Chann. Code = (1,-1,-1,1)
Chann. Code = (1,1,-1,-1)
T=0
1 1 -1 -1 1 1 -1 -1 1 1 -1 -1
1 -1 -1 1 1 -1 -1 1 1 -1 -1 1
Delay
t
Role of Scrambling Code in Uplink Direction
Reserved forsignaling
2 voiceconnections
7 dataconnections
3.4 kbps
SF=64
SF=8
SF=16
SF=32
SF=4
12.2 kbps
384 kbps
SF=128
SF=256
144 kbps
64 kbps
OVSF Code Tree Usage
2560 chipsTimeslot TS
2/3 ms
Frame TS#0 TS#i TS#14••• •••
10 ms
f#1 f#i f#72••• •••Superframe
720 ms
1/3,840,000 s 0.2604 s
Chip Shortest information unit in CDMA
(of the spreading code)
Periodic repetition ofcontrol information (e.g. TPC)
Shortest transmission durationand data rate adaption
Counting period for:• Definition of physical channels• Handover to GSM (120 ms frame)
Chip, Timeslot, Frame, Superframe
HSDPA
• Introduced in Release 5.• Can coexist with non-HSDPA in the same cell.• Improve downlink direction. Uplink still relies on Rel '99.
Advantages:• Higher data rate: up to 14.4 Mbps with practical rate 10.8
Mbps.• Reduce latency:
– especially with TCP Slow Start and Congestion Avoidance.– Retransmission and HARQ in Node B.
• Spectral efficiency: TTI=2ms schedule of shared channels.
TCP Window Size
8,760
congestion occurs
receiver’s window seize
cwnd
slow start threshold, start value = 65535
slow start threshold, readjusted value
readjustment
of slow start
thresholdthird phase:
congestion voidance,
linear growth
second phase:
slow start,
eponential growthfirst phase:
slow start,
exponential growth
Rel‘99 DCH
RNC RNC
Packet
Node B
Packet
Retransmission
L1 ACK / NACK
RLC ACK / NACK
Retransmission
Retransmission Cycle in HSDPA
Rel‘5 HS-DSCH
HSDPA Scheduling
10 msDedicated DCH
SharedHS-DSCH Big shared pipe
Time
Code
HSDPA
wasted bandwidth!
2 ms
inefficient usage!
Rel '99
HSUPA
• Introduced in Release 6.
• Improve uplink direction. Rely on HSDPA in downlink.
Advantages:
• Higher data rate: up to 5.76 Mbps with practical rate 1.44 Mbps in first version.
• Reduce latency: retransmission request by Node B.
• Increased coverage and capacity: efficient handling of uplink interference problem.