IMT-2000
• IMT-2000 stands for
IMT: International Mobile Communications
2000: the frequency range of 2000 MHz and the year 2000
• In total, 17 proposals for different IMT-2000 standards were submitted by
regional SDOs to ITU in 1998. 11 proposals for terrestrial systems and 6 for
mobile satellite systems (MSSs).
• All 3G standards have been developed by regional standard developing
organizations (SDOs).
• Evaluation of the proposals was completed in 1998, and negotiations to build a
consensus among different views were completed in mid 1999. All 17 proposals
have been accepted by ITU as IMT-2000 standards. The specification for the
1
Radio Transmission Technology (RTT) was released at the end of 1999.
IMT-2000
• The (IMT-2000), consists of 3 operating modes based on Code
Division Multiple Access (CDMA) technology.
• 3G CDMA modes are most commonly known as:
– CDMA2000,
– WCDMA (called UMTS) and
– TD-SCDMA
(Time Division-Synchronous Code Division Multiple Access)
2
High-Speed Packet Data Services
• 2 Mbps in fixed or in-building environments (very
short distances, in the order of metres)
• 384 kbps in pedestrian or urban environments
• 144 kbps in wide area mobile environments
• Variable data rates in large geographic area systems
(satellite)
3
4
Network Elements from UMTS
UMTS differs from GSM Phase 2+ (GSM +GPRS) mostly in the new
principles for the air interface transmission
WCDMA instead of TDMA/FDMA
Therefore a new RAN (Radio Access Network) called:
UTRAN (UMTS Terrestrial Radio Access Network)
must be introduced with UMTS
Only minor modifications are needed in the CN (Core Network) to
accommodate the change
5
UTRA: UMTS Terrestrial Radio Access
The most significant change in REL. ´99 was the “UTRAN”,
a W-CDMA radio interface for land-based communications.
UTRAN supports time (TDD) and frequency division duplex (FDD).
The TDD mode is optimized for public micro and pico cells and
unlicensed cordless applications.
The FDD mode is optimized for wide-area coverage, i.e. public
macro and micro cells.
Both modes offer flexible and dynamic data rates up to 2 Mbps.
6
UMTS architecture
UTRAN (UTRA NETWORK)
• Radio Network Subsystem (RNS)
UE (User Equipment)
CN (Core Network)
Uu
UE
Iu
UTRAN
CN
7
UTRAN
Two new network elements
are introduced in UTRAN
• RNC
• Node B
UTRAN is subdivided
into individual radio
network systems (RNSs),
where each RNS is
controlled by an RNC.
The RNC is connected to
a set of Node B elements,
each of which can serve
one or several cells.
8
UTRAN architecture
RNS
UE1
Node B
Iub
RNC: Radio Network Controller
RNS: Radio Network Subsystem
Iu
RNC
CN
UE2
Node B
UTRAN comprises several RNSs
UE3
Iur
Node B
Iub
Node B
RNC
Node B can support FDD or TDD
or both
RNC is responsible for handover
decisions requiring signaling to the
UE
Node B
Cell offers FDD or TDD
RNS
UTRAN functions
•
•
•
•
•
•
•
•
•
•
Admission control
Congestion control
Radio channel encryption
Handover
Radio network configuration
Channel quality measurements
Radio resource control
Data transmission over the radio interface
Outer loop power control (FDD and TDD)
Channel coding
10
Core network
The Core Network (CN) and the Interface Iu, are separated into two logical domains:
Circuit Switched Domain (CSD)
Packet Switched Domain (PSD)
• Circuit switched service incl. signaling
• Resource reservation at connection setup
• GSM components (MSC, GMSC, VLR)
• IuCS
• GPRS components (SGSN, GGSN)
• IuPS
VLR
BTS
Abis
BSS
BSC
Iu
MSC
GMSC
PSTN
Node
BTSB
IuCS
AuC
EIR
HLR
GR
Node B
Iub
Node B
RNC
SGSN
GGSN
Gn
Node B
RNS
IuPS
Gi
CN
Access method CDMA
•CDMA (Code Division Multiple Access)
– all terminals send on the same frequency probably at
the same time and can use the whole bandwidth of
the transmission channel
– each sender has a unique random number, the
sender XORs the signal with this pseudo random
number
– the receiver can “tune” into this signal if it knows the
pseudo random number, tuning is done via a
correlation function
Spreading and scrambling of user data
•
Constant chip rate of 3.84 Mchip/s
•
Different user data rates supported via different spreading factors
– higher data rate: less chips per bit and vice versa
•
User separation via unique, quasi orthogonal scrambling codes
– users are not separated via orthogonal spreading codes
– much simpler management of codes: each mobile can use the
same orthogonal spreading codes
data1
data2
data3
data4
data5
spr.
code1
spr.
code2
spr.
code3
spr.
code1
spr.
code4
scrambling
code1
sender1
scrambling
code2
sender2
Length
1
Ri
Length
1
Ri  Rc
1
Ri
Rc
SPREADING FACTOR
1
Rc
DS-CDMA= Direct Sequence Code Division Multiple Access
3.84 Mchip/s
CDMA in theory
•
•
•
•
Sender A
– sends Ad = 1, key Ak = 010011 (assign: „0“= -1, „1“= +1)
– sending signal As = Ad * Ak = (-1, +1, -1, -1, +1, +1)
Sender B
– sends Bd = 0, key Bk = 110101 (assign: „0“= -1, „1“= +1)
– sending signal Bs = Bd * Bk = (-1, -1, +1, -1, +1, -1)
Both signals superimpose in space
– interference neglected (noise etc.)
– As + Bs = (-2, 0, 0, -2, +2, 0)
Receiver wants to receive signal from sender A
– apply key Ak bitwise (inner product)
Ae = (-2, 0, 0, -2, +2, 0)  Ak
(-2, 0, 0, -2, +2, 0)  (-1, +1, -1, -1, +1, +1)= 2 + 0 + 0 + 2 + 2 + 0 = 6
• result greater than 0, therefore, original bit was „1“
– receiving B
Be = (-2, 0, 0, -2, 2, 0)  Bk
( -2, 0, 0,- 2,- 2, 0)  (1, 1, -1, +1, -1, +1) = -6, i.e. „0“
CDMA on signal level I
data A
1
0
1
Ad
key A
key
sequence A
data  key
0 1 0 1 0 0 1 0 0 0 1 0 1 1 0 0 1 1 Ak
1 0 1 0 1 1 1 0 0 0 1 0 0 0 1 1 0 0
signal A
Here the binary ”0” is assigned a positive value,
The binary ”1” a negative value!
Real systems use much longer keys resulting in a larger distance
between single code words in code space.
As
CDMA on signal level II
signal A
+1
-1
1
data B
key B
key
sequence B
+1
-1
+2
0
As + Bs
0
0
Bd
0 0 0 1 1 0 1 0 1 0 0 0 0 1 0 1 1 1 Bk
1 1 1 0 0 1 1 0 1 0 0 0 0 1 0 1 1 1
data  key
signal B
As
-2
Bs
CDMA on signal level III
data A
1
0
1
1
0
1
+2
As + Bs
0
-2
1
Ak
-1
+2
(As + Bs)
* Ak
0
-2
integrator
output
comparator
output
Ad
CDMA on signal level IV
data B
1
0
0
1
0
0
As + Bs
Bk
(As + Bs)
* Bk
integrator
output
comparator
output
Bd
CDMA on signal level V
+2
As + Bs
0
-2
wrong
key K
+2
(As + Bs)
0
*K
-2
integrator
output
comparator
output
(0)
(0)
?
OSVF coding
Ortogonal Variable Spreading Factor Codes
1,1,1,1,1,1,1,1
...
1,1,1,1
Recursive rule
1,1,1,1,-1,-1,-1,-1
1,1
1,1,-1,-1,1,1,-1,-1
X,X
1,1,-1,-1,-1,-1,1,1
1
X
...
1,1,-1,-1
1,-1,1,-1,1,-1,1,-1
X,-X
...
1,-1,1,-1
1,-1,1,-1,-1,1,-1,1
SF=n
1,-1
SF=2n
1,-1,-1,1,1,-1,-1,1
...
1,-1,-1,1
1,-1,-1,1,-1,1,1,-1
SF=1
SF=2
SF=4
SF=8
Support of mobility:
macro diversity
• Multicasting of data via
several physical
channels
– Enables soft handover
– FDD mode only
• Uplink
UE
Node B
– simultaneous reception
of UE data at several
Node Bs
Node B
RNC
CN
• Downlink
– Simultaneous
transmission of data via
different cells
Transmit Power Control is essential
Near – far problem
despreading
MS
MS
Node B
Power control
despreading
MS
Transmit
Power Control
MS
Minimize
the Tx power
Node B
More
secure
Increase
the system capacity
Frequency Allocation
FDMA / TDMA
f2
f2
f1
f3
f2
f1
f3
f2
f1
f3
f2
f1
f3
f2
CDMA
f1
f3
f2
f1
f3
A case of 3 cell repetitions
f1
f1
f3
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
f1
Same frequency in all cells.
27
UMTS protocol stacks (user plane)
UE Uu UTRAN IuCS 3G
MSC
apps. &
protocols
Circuit
switched
RLC
MAC
RLC
MAC
radio
radio
UE
Packet
switched
apps. &
protocols
IP, PPP,
…
PDCP
SAR
SAR
AAL2
AAL2
ATM
ATM
Uu UTRAN
IuPS
3G
SGSN
IP tunnel
Gn 3G
GGSN
IP, PPP,
…
GTP
RLC
RLC
GTP
UDP/IP
MAC
MAC
AAL5
AAL5
L2
L2
radio
radio
ATM
ATM
L1
L1
PDCP
GTP
UDP/IP UDP/IP
GTP
UDP/IP
EDGE
Enhanced Data rates for GSM Evolution
• ECSD - Enhanced CSD
(Circuit Switched Data)
• EGPRS - Enhanced GPRS
• For higher data rates
• New coding and modulation schemes
• The base stations need to be up dated
• EGPRS up to 384 kbps (48 kbps per time slot)
• ECSD 28.8 kbps
29
Modulation
30
The Beauty Contest
Ten companies asked for one out of four licences
Licences were given to
• Vodaphone
• Tele2
• Hi3G
• Orange
The incumbent, Telia, was not given a licence!!!
31
UMTS in Sweden
The licensees have to cover 8 860 000 inhabitants.
Two joint ventures:
Svenska UMTS nät - Tele2 and Telia
Telia and Tele2 have established a joint venture, Svenska UMTS nät,
with a common 3G network.
3GIS – Telenor and 3*
To meet the regulatory requirements, Telenor and 3 has build individual
networks, and each has to cover 30% of the population.
Telenor and 3 have established a joint venture, 3G Infrastructure Services
(3GIS) with a common shared network. This network covers
approximately 70% of the population.
32
Björkdahl & Bohlin
Network coverage
Theoretically it is possible to cover 8 860 000 inhabitants by covering
20 400 km² of Sweden’s surface area. (Swedish total area is 411 000 km².)
Theoretical level corresponds to a coverage of 5% of the Swedish area.
In practice, it seems reasonable that the operators will aim for a total
coverage of around 170 000 km². This corresponds to a coverage of 41%
of the Swedish surface area.
The operators will be able to cover all urban areas and 84% of the
inhabitants by covering around 11 000 km². This corresponds to a
coverage of 2.7% of the Swedish surface area.
33
Investment for an average operator
Comparing
Germany, United Kingdom and Sweden
The table shows the average 3G investment per capita per year, including
applicable license fees, in Sweden, Germany and the UK for an average
operator in each country, for the entire license duration.
7.5 USD
6.2 USD
3.8 USD
1 USD = 8 SEK
34
Summary of main findings
•The average 3G network investment per operator is
estimated to be SEK 6.1 billion.
•The total 3G network investment in Sweden is estimated
to be SEK 24 billion.
•If the Swedish joint ventures co-operate in rural areas the
total 3G network investment is estimated to be SEK 19
billion.
35
End of Chapter
36