3GPP UMTS and WCDMA Releases & Features
Release 99 – Specified the first UMTS 3G networks, incorporating a CDMA air interface.
Release 4 – Introduced mainly the CS Core Network split feature plus other minor enhancements.
Release 5 – Introduced mainly IMS, HSDPA (allowing broadband services on the Downlink), and other
minor enhancements.
Release 6 – Integrated operation with Wireless LAN networks and added HSUPA (enables broadband
uploads and services), MBMS, and enhancements to IMS such as Push-to-Talk over Cellular (PoC), video
conferencing, messaging, etc.
Release 7 – Significant progress made in 2006 and 2007 toward completion of this release. Most documents
are under revision control. Introduced, among other features, enhancements to High-Speed Packet Access
(HSPA+), QoS, and improvements to real-time applications like VoIP.
Release 8 – In progress (expected 2009). Introducing, among others, E-UTRA (also called LTE, based on
OFDMA), All-IP Network (also called SAE), and Femto cells operation. Release 8 constitutes a re-factoring
of UMTS as an entirely IP based fourth-generation network. 3GPP RAN approved the LTE Physical Layer
specifications in September 2007. The specifications are 36.201–36.214 and are on the 3GPP site at
http://www.3gpp.org/ftp/Specs/html-info/36-series.htm.
Each release incorporates hundreds of individual standards documents, each of which may have gone
through many revisions. Current 3GPP standards incorporate the latest revision of the GSM standards.
Standards documents are available for free on the 3GPP Web site. These standards cover the radio
component (Air Interface) and the Core Network, as well as billing information and speech coding down to
source code level. Cryptographic aspects (authentication, confidentiality) are also specified in detail. More
details about the 3GPP releases content can be found at http://www.3gpp.org/specs/releases-contents.htm
and http://www.3gpp.org/Management/WorkPlan.htm.
LTE and EPS Terminology
• Long Term Evolution (LTE): Evolution of 3GPP UMTS
Terrestrial Radio Access (E-UTRA) technology
• Evolved Packet System (EPS): Evolution of the
complete 3GPP UMTS Radio Access, Packet Core and
its integration into legacy 3GPP/non-3GPP networks.
It includes:
– Radio Access Network – Evolved UTRA Network (E-UTRAN)
– System architecture – Evolved Packet Core (EPC)
• This course uses the terms LTE and E-UTRA
interchangeably.
E-UTRA Design Performance Targets
• Scalable transmission bandwidth (up to 20 MHz)
• Improved Spectrum Efficiency
– Downlink (DL) spectrum efficiency should be 2-4 times Release 6 HSDPA.
Downlink target assumes 2x2 MIMO for E-UTRA and single TX antenna with Type 1
receiver HSDPA.
– Uplink (UL) spectrum efficiency should be 2-3 times Release 6 HSUPA.
Uplink target assumes 1 TX antenna and 2 RX antennas for both E-UTRA and
Release 6 HSUPA.
• Coverage
– Good performance up to 5 km
– Slight degradation from 5 km to 30 km (up to 100 km not precluded)
• Mobility
– Optimized for low mobile speed (< 15 kph)
– Maintained mobility support up—to 350 kph (or even up to 500 km/h)
• Advanced TX schemes and multiple-antenna technologies
• Inter-working with existing 3G and non-3GPP systems
– Interruption time of real-time or non-real-time service handover between
E-UTRAN and UTRAN/GERAN shall be less than 300 or 500 ms.
User Throughput and Spectrum Efficiency Requirements
Detailed throughput requirements:
Downlink:
– 5%-tile Downlink user throughput per MHz 2-3 times Release 6 HSDPA
– Average Downlink user throughput per MHz 3-4 times Release 6 HSDPA
– Downlink spectrum efficiency should be 3-4 times Release 6 HSDPA
– Downlink performance targets assume 2 transmit and 2 receive antennas for E-UTRA, and 1 transmit and
enhanced Type 1 receiver for Release 6 HSDPA
– Downlink user throughput should scale with spectrum allocation
Uplink:
– 5%-tile Uplink user throughput per MHz 2-3 times Release 6 HSUPA
– Average Uplink user throughput per MHz 2-3 times Release 6 HSUPA
– Uplink spectrum efficiency should be 2-3 times Release 6 HSDPA
– Uplink performance targets assume 1 transmit and 2 receive antennas for both E-UTRA and Release 6
HSDPA
– Uplink user throughput should scale with spectrum allocation and mobile maximum transmit power
E-UTRA is expected to outperform Release 6 HSPA by a factor of 2-4 in user throughput and spectrum efficiency.
This assumes a maximum cell range up to 5 km. For cell ranges up to 30 km, slight degradations are expected for the
achieved performance for the user throughput targets and more significant degradation for the spectrum efficiency
targets. However, cell ranges up to 100 km should not be precluded by the specifications.
3GPP Network Architecture Evolution
Faster RRM response for CDS
Reduced packet latencies
Network Architecture Evolution (decentralization process)
From a centric RNC-Based RRM (stupid Base Stations and smarter RNCs)
To a decentralized Base Station-based RRM (smarter Base Stations, less smart RNCs)
From user packet data forwarding to GGSN through RNC (intermediary RNCs)
To direct user packet data forwarding to GGSN (Direct Tunneling)
Enhanced Node B (eNB) Functions
• Radio Resource Management: – Radio Bearer Control
– Admission/congestion control
– Connection and mobility control
– UL/DL dynamic scheduling
• IP header compression and
encryption of user data
• Selection of an MME at UE
attachment (if necessary)
• Routing of User Plane data towards
S-GW
• Routing of paging messages from
MME towards UE
• Measurement and reporting
configuration
Reference 23.401
eNB (Evolved Node B) provides the E-UTRA User Plane (PDCP/RLC/MAC/PHY) and
Control Plane (RRC) protocol terminations towards the UE.
The eNBs are logically interconnected with each other by means of the X2 interface.
The eNBs are also connected by means of the S1 interface to the EPC (Evolved Packet Core), more specifically to the MME (Mobility Management Entity) by means of the S1-MME and to the Serving Gateway (S-GW) by means of the S1-U.
The S1 interface supports a many-to-many relation between MMEs / Serving Gateways and eNBs.
Serving Gateway (S-GW) & P-GW Functions
S-GW
handover
• Mobility anchoring for inter-3GPP mobility
• E-UTRAN Idle Mode Downlink packet buffering and
initiation of network triggered service requests
• Lawful interception
• Packet routing and forwarding
• Transport level packet marking in the UL and DL
• UL and DL charging per UE, PDN, and QCI
• Termination of U-plane packets
• Switching of U-plane for support of UE
mobility
P-GW
• Per-user based packet filtering
• Lawful interception
• UE IP address allocation
• DL rate enforcement based on AMBR
For more details, see
3GPP TS 23.401
MME Functions
• NAS signaling and its security
• AS Security Control
• Inter CN node signaling for mobility
between 3GPP access networks
• Idle mode UE Reachability (including
control and execution of paging
retransmission)
• Tracking Area List Management (idle and
active)
• PDN GW and Serving GW selection
• MME selection for handovers with MME
change
• Idle state mobility control
• SGSN selection for 3GPP handovers
• Roaming and Authentication
• EPS bearer management
For more details, see
3GPP TS 23.401
E-UTRAN Protocol Stack: User Plane
References:
• LTE-Uu: 36.201 (Physical Layer), 36.321 (MAC), 36.322 (RLC), 36.323 (PDCP)
• S1: 36.411 (Physical Layer), 36.414 (S1- Data Transport)
• X2: 36.421 (Physical Layer); 36.424 (X2 – Data Transport)
Transport Layer reference for the S1 and X2 Interfaces:
IP in E-UTRAN
- Used in user and control planes
- IP in E-UTRAN shall also support:
1. NDS/IP (Network Domain Security for IP): Sets up Confidentiality and Integrity for data exchange
between network entities
2. Diffserv (Differentiated Services): Enhancements of the IP protocol for QoS
References:
RFC2475, An Architecture for Differentiated Services
GTP (GPRS Tunneling Protocol) in E-UTRAN
- GTP goes over UDP/IP transport protocol stack
- No flow or error control or any mechanism to guarantee the data delivery of S1-U interface
- As a reminder in 3G, GTP is used over the Iu-PS interface (connection between RNC and SGSN)
E-UTRAN Protocol Stack: Control Plane
References:• LTE-Uu: 36.331 (RRC)
• S1: 36.412 (Signaling Transport),
36.413 (Application Protocol)
• X2: 36.422 (Signaling Transport),
36.423 (Application Protocol)
• IETF RFC 2960 (Stream Control
Transmission Protocol)
About the SCTP (Stream Control Transmission Protocol):
- It is a reliable connection-oriented transport protocol similar to TCP
- As TCP, SCTP implements Congestion and flow control, detection of data corruption and loss/duplication of packets
- SCTP connection needs to be set up connection between peers before actual data transmission (as TCP)
- From functional perspective, there are some key new features in SCTP:
1. Multi-streaming - 2. Multi-homing - 3. Message Level Framing
1. Multi-streaming:
- In SCTP protocol, a stream is a unidirectional sequence of user data delivered to upper layers
- With Multi-streaming, SCTP allows to set up several independent streams between two peers. With this feature, if transmission error occur in
one stream, it does not affect the other streams.
- This feature is important for signaling transfers between two nodes of UTRAN where, for instance, the delivery order of each user signaling
flow can be preserved, but hey can be delivered independently.
- TCP, however, in some instances can also use multiple parallel streams. Example of this is the downloading of web-pages with multiple
multimedia objects.
2. Multi-homing
- Allows SCTP endpoint to be reached through multiple network addresses
- In case of error in one of the address, the retransmitted packets may be sent to an alternate address providing redundancy operation
3. Message level Framing
- SCTP works at message level whereas TCP is octet based framing and does not preserve transmitted data structure
- In SCTP, messages are transmitted as whole set of bytes if the maximum SCTP length is not reached
- This is an advantage for E-UTRAN signaling transport
Reference Documents:
RFC2960 Stream Control Transmission Protocol
EPS Architecture
3GPP TS 23.401 V8.2.0 (2008-06)
Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS)
enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access
(Release 8).
PCRF is the policy and charging control element. PCRF functions are described in more detail in
TS 23.203 [6].
In a non-roaming scenario, there is only a single PCRF in the HPLMN associated with one
UE’s IP-CAN session. The PCRF terminates the RX interface and the Gx interface.
In a roaming scenario with local breakout of traffic, there may be two PCRFs associated
with one UE’s IP-CAN session:
– H-PCRF that resides within the H-PLMN
– V-PCRF that resides within the V-PLMN