3GPP
Network Architecture
Radio Access Technologies
UMTS vs. LTE: a comparison overview
Unik4230: Mobile Communications
Khai Vuong
May 16, 2011
Discussion
3GPP
Network Architecture
Radio Access Technologies
Agenda
3GPP
Network Architecture
UMTS
LTE
Radio Access Technologies
WCDMA
OFDMA
Discussion
Discussion
3GPP
Network Architecture
Radio Access Technologies
3GPP Standards (I)
Discussion
1
3GPP: 3rd Generation Partnership Project
Version
Release 98
Release 99
Released
1998
2000 Q1
Release 4
2001 Q2
Release 5
Release 6
2002 Q1
2004 Q4
1
Info
specified pre-3G GSM network
specified the first version of UMTS, incorporating a CDMA air interface
aka. Release 2000, added all-IP Core
Network
introduced IMS and HSDPA
integrated operation with Wireless LAN
networks and added HSUPA, MBMS,
enhancements to IMS
http://en.wikipedia.org/wiki/3GPP
3GPP
Network Architecture
Radio Access Technologies
3GPP Standards (II)
Version
Release 7
Released
2007 Q4
Release 8
2008 Q4
Release 9
2009 Q4
Release 10
2011 Q1
2
Discussion
2
Info
decreasing latency,
improvements
to QoS and real-time applications,
HSPA+ , NFC, EDGE Evolution.
First LTE release.
All-IP Network
(SAE), new OFDMA, FDE and MIMO
based radio interface.
SAES Enhancements, Wimax and
LTE/UMTS Interoperability
LTE advanced
http://en.wikipedia.org/wiki/3GPP
3GPP
Network Architecture
Radio Access Technologies
3GPP data evolution
3
Huawei Technologies Co., Ltd. 2009
3
Discussion
3GPP
Network Architecture
Radio Access Technologies
User experience
Type of services
Web surfing
Download 5MB music
Download 750MB movie
Download HD video
Video telephony
Corporate VPN, Intranet
Mobile TV
On-demand TV
Video-based mobile advertising
...
UMTS
8 seconds
3 minutes
6.5 hours
∼2-3 days
√
√
√
Table: Data services4
4
Huawei Technologies Co., Ltd. 2009
LTE
immediately
1 second
2.5 minutes
∼15 minutes
√
√
√
√
√
√
Discussion
3GPP
Network Architecture
Radio Access Technologies
Services for telecommunication systems
1. Teleservice: Information that transfered between end users,
e.g speech service, messaging, emergency calls.
2. Bearer service: Different QoS classes for various type of
traffic:
•
•
•
•
Conversasional: voice, video, telephony, video gaming
Streaming: multimedia, video on-demand, webcast
Interactive: web browsing, network gaming, database access
Background: email, SMS, downloading
Discussion
3GPP
Network Architecture
Radio Access Technologies
UMTS objectives
1. improvement in data performance, multimedia services and
access to the Internet
2. new radio interface WCDMA
3. Core Network: connection function
Discussion
3GPP
Network Architecture
Radio Access Technologies
Discussion
Core Network for UMTS
•
•
MSC:Mobile switching center, switch the CS transactions
•
SGSN: Serving GPRS Support Node, similar to MSC/VLR but this is for PS
traffic.
•
GGSN: Gateway GPRS Support Node, similar to GMSC but it serves for the PS
traffic.
GMSC: Gateway MSC: a switch that connects the UMTS PLMN to the external
CS networks.
3GPP
Network Architecture
Radio Access Technologies
LTE’s objectives
Discussion
5
1. higher data rates in both downlink and uplink transmission
2. reduce packet latency, more responsive user experience
3. flat architecture: IP-based, open interfaces, simplified network
4. flexible radio planning and high spectral efficiency
5. reduce delivery costs for rich communications
6. long-term revenue stability and growth
7. coexistence alongside circuit switched networks
5
UMTS Forum 2008
3GPP
Network Architecture
Radio Access Technologies
Why LTE?6
GSM
EDGE
WCDMA
HSPA
LTE
Non-3GPP technologies
Figure: Flexible upgrade path
Figure: Reduce pris per MB to
remain profitable
6
Nokia Siemens Networks
Discussion
3GPP
Network Architecture
Radio Access Technologies
UMTS vs. LTE Architecture
Figure: Network architecture, simplified
LTE: simplified IP flat architecture
•
•
•
7
BSC/RNC disappeared, functions transfer to eNodeB
All eNodeB connect directly through X2 interface
PS service only, voice over IP.
Image courtesy: UMTS Forum 2008
7
Discussion
3GPP
Network Architecture
Radio Access Technologies
LTE’s interfaces: S1 and X2
Discussion
8
• X2: connects eNodeB
• MME (Mobility
Management Entity):
distribution of paging
message to eNodeB
• UPE (User Plan Entity): IP
• S1: self-optimizing network
8
Image courtesy: developer.att.com
header compression,
encryption of user data
stream, termimating and
switching of U-plane
3GPP
Network Architecture
Radio Access Technologies
Wideband CDMA
Figure: Access technique for UMTS
9
Huawei Technologies Co., Ltd. 2009
9
Discussion
3GPP
Network Architecture
Radio Access Technologies
Discussion
CDMA: Principles
• each user is assigned a spreading code for encoding it’s data
• Receiver knows the code of user, it can decode the received
signal, recover the original data
• Bandwidth of coded data signal much larger than original
data signal due to the encoding process spreads the spectrum
of the origianl signal, based on spread-spectrum modulation
3GPP
Network Architecture
Radio Access Technologies
WCDMA in UMTS [4]
• Direct Sequence CDMA system, with chip-rate 3.84 Mc/s
• Combined with FDMA: every carrier is allocated 5 MHz
frequency band so that many operators can provide services
without interference each other.
• Codes: scrambling and channelization
Channelization: seperates
traffic to and from different
users, called Orthogonal
Variable Spreading Factor
(OVSF) which varies from 1
to 128
Scrambling codes: not
increase bandwidth, but is
used for distinguishing
terminals in uplink and
sectors (cells) in downlink
Discussion
3GPP
Network Architecture
Radio Access Technologies
LTE’s downlink: OFDMA
OFDM: Multiple access scheme,
allows simultaneous connections
to/from multiple mobile
terminals
Users share different subcarriers,
either consecutive or distributed
manner.
Discussion
3GPP
Network Architecture
Radio Access Technologies
Discussion
LTE’s uplink: Single Carrier-FDMA
•
SC-FDMA: hybrid modulation
scheme that combines the low
PAPR techniques of single-carrier
transmission systems, such as GSM
and CDMA, with the multi-path
resistance and flexible frequency
allocation of OFDMA
•
Data symbols in the time domain
are converted to the frequency
domain using a discrete Fourier
transform (DFT)
•
Cyclic Prefix (CP) is added, a serial
sequence of symbols is modulated
and transmitted instead of parallel
OFDM-scheme
Figure: Structure for UL and DL in
LTE [5]
•
On receiver’s side, an extra N-point
IDFT is applied to reconstruct the
original symbols.
An advantage of SC-FDMA compares to
OFDMA is low Peak to Power Average
Ratio (PAPR), that helps increasing
battery life.
3GPP
Network Architecture
Radio Access Technologies
Discussion
References
Ville Eerola, LTE Network Architecture Evolution, Lecture
note in T-109.5410 Technology Management in the
Telecommunications Industry, Helsinski University of
Technology, 2010.
UMTS Forum, Toward Global Mobile Broadband, retreived
May 16, 2011from
www.umts-forum.org/component/option,com.../Itemid,12/
M. Neruda and R. Bestak, Evolution of 3GPP Core Network,
IWSSIP 2008.
Lecture notes in UniK 4230, UiO, Lecture9-10.pdf
OFDM(A) for wireless communications, Telenor R&I R 7/2008
3GPP
Network Architecture
Radio Access Technologies
A brief comparision
Requirements
Spectral Efficiency
Peak Data Rate
Sector Capacity
No. of Tranceivers/Cell
RTT User Plane
Call setup time
Mobility
Bandwidth
10
UMTS
0.2bit/s/Hz
2 Mbit/s
1 Mbit/s
30
50 ms
2s
250 km/h
5 MHz
Discussion
10
LTE
1.57bit/s/Hz
170 Mbit/s
31.4 Mbit/s
1
5 ms
50 ms
350 km/h
scalable up to 20 MHz
UMTS/HSPA to LTE Migration, Motorola Inc. 2009
3GPP
Network Architecture
Radio Access Technologies
Discussion
Point to discuss, focus on this topic, futher questions?
Discussion