Content for TR 45.902 Word version: 18.0.0
0 Introduction
1 Scope
2 References
3 Definitions, symbols and abbreviations
4 Motivation
5 Requirements
...
...
0 Introduction p. 5
A new type of physical layer is proposed for the GSM/EDGE Radio Access Network (GERAN): the flexible layer one (FLO). The main advantage of FLO is that the configuration of the physical layer (e.g. channel coding and interleaving) is specified at call setup. This means that the support of new services such as IP Multimedia Subsystem (IMS) services can be handled smoothly without having to specify new coding schemes in each release.
Through several enhancements such as reduced granularity and flexible interleaving, the radio bearers offered by FLO would not only fulfil the IMS requirements in terms of flexibility and performance, but also greatly improve the link level performance of real-time IMS services compared to GERAN Release 5.
The objective of this TR is to provide an overview of FLO, its architecture and study the impacts it has on the GERAN radio protocol stack.
1 Scope p. 6
The present document provides an overview of the flexible layer one, its architecture and studies the impacts it has on the GERAN radio protocol stack.
The present document specifies functions, procedures and information which apply to GERAN Iu mode. However, functionality related to GERAN Iu mode is neither maintained nor enhanced.
2 References p. 6
The following documents contain provisions, which, through reference in this text, constitute provisions of the present document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TS 22.101: "Service Principles".
[3]
TS 22.228: "Service requirements for the IP Multimedia Core Network Subsystem".
[4]
TS 23.107: "QoS Concept and Architecture".
[5]
TS 23.228: "IP Multimedia Subsystem".
[6]
TS 25.201: "Physical layer - General description".
[7]
TS 25.212: "Multiplexing and channel coding (FDD)".
[8]
TS 25.331: "RRC Protocol Specification".
[9]
TS 35.201: "Specification of the 3GPP Confidentiality and Integrity Algorithms".
[10]
TS 44.018: "Radio Resource Control protocol".
[11]
TS 44.118: Release 11 "Radio Resource Control protocol, Iu mode".
[12]
TS 44.060: "Radio Link Control/Medium Access Control protocol".
[13]
TS 44.160: Release 11 "Radio Link Control/Medium Access Control protocol, Iu mode".
[14]
TS 45.002: "Multiplexing and multiple access on the radio path".
[15]
TS 45.003: "Channel Coding".
[16]
TS 45.005: "Radio transmission and reception".
3 Definitions, symbols and abbreviations p. 6
3.1 Definitions p. 6
For the purposes of the present document, the following terms and definitions apply.
Active Transport Channel:
a transport channel is active during a TTI if it carries a transport block.
Dynamic attributes:
for one transport channel, the values of the dynamic attributes are different among transport formats. They are configured by Layer 3 and can change on a TTI basis under the control of the MAC sublayer.
Empty Transport Format:
a transport format such that no transport block is carried over the transport channel (i.e. the transport channel is inactive).
Empty Transport Format Combination:
a transport format combination that is made up only of empty transport formats.
Inactive Transport Channel:
a transport channel is inactive during a TTI if it does not carry a transport block (i.e. the transport block size is zero).
Radio Frame:
The result of applying rate matching to a transport block along with its associated CRC that have first been channel encoded.
Radio Packet:
The set of one or more radio frames together with the applicable coded TFCI that form the volume of payload that can be transmitted on a basic physical subchannel for any given TTI.
Semi-static attributes:
for one transport channel, the values of the semi-static attributes are common to all transport formats. They are configured by Layer 3 and can only be changed by Layer 3 signalling.
Transport Block:
block exchanged on a transport channel between the physical layer and the MAC sublayer.
Transport Channel:
SAP between the physical layer and the MAC sublayer.
Transport Format:
configuration of a transport channel, including for instance channel coding, CRC size, etc.
Transport Format Combination:
allowed combination of transport format(s) of the different transport channels that are multiplexed together on a basic physical subchannel.
Transport Format Combination Indicator:
layer one header that indicates the transport format combination that has been selected for each radio packet.
Transport Format Combination Set:
set of allowed transport format combinations on a basic physical subchannel.
Transport Format Indicator:
index identifying a particular transport format within the transport format set.
Transport Format Set:
set of all transport formats defined for a particular transport channel.
Transmission Time Interval:
rate at which transport blocks are exchanged between the physical layer and the MAC sublayer on a transport channel.
3.2 Abbreviations p. 7
For the purposes of the present document, the following abbreviations apply:
ADCH
Associated Dedicated CHannel
CCTrCH
Coded Composite Transport CHannel
CDCH
Control-plane Dedicated CHannel
CTFC
Calculated Transport Format Combinations
DCH
Dedicated CHannel
FLO
Flexible Layer One
GERAN
GSM/EDGE Radio Access Network
IMS
IP Multimedia Subsystem
MAC
Medium Access Control
QoS
Quality of Service
PDU
Protocol Data Unit
RAN
Radio Access Network
RLC
Radio Link Control
RRC
Radio Resource Control
RT
Real Time
SDU
Service Data Unit
SAP
Service Access Point
TB
Transport Block
TBF
Temporary Block Flow
TF
Transport Format
TFI
Temporary block Flow Identity
TFS
Transport Format Set
TFIN
Transport Format INdicator
TFC
Transport Format Combination
TFCI
Transport Format Combination Indicator
TFCS
Transport Format Combination Set
TrCH
Transport Channel
TTI
Transmission Time Interval
UDCH
User-plane Dedicated CHannel
UTRAN
Universal Terrestrial Radio Access Network
Other abbreviations used in the present document are listed in TR 21.905.
4 Motivation p. 8
The need for a flexible layer one for the Release 6 of GERAN is driven by the introduction of IMS services. For an efficient support of IMS services, requirements are set on the radio bearer service of the RAN (see TS 22.101, TS 22.228, TS 23.228 and TS 23.107):
- the radio bearers should be flexible enough to efficiently deploy any IP multimedia applications;
- the radio bearers should allow the transport of several flows in parallel (e.g. text and video);
- the radio bearers should satisfy the user in a spectral efficient manner;
- the radio bearer should support the UMTS QoS concept and architecture.
5 Requirements p. 8
The flexible layer one should:
- fulfil most of the IMS requirements in terms of radio bearer service attributes;
- support the multiplexing of parallel flows on to a basic physical subchannel;
- provide an optimisation of spectral efficiency through the support of different interleaving depths, unequal error protection/detection, reduced channel coding rate granularity and support of 8PSK and GMSK modulations;
- provide an efficient support of real time IMS services;
- be applicable to both modes of operation: A/Gb mode and Iu mode;
- minimize the impacts on the radio protocols;
- minimize the overhead introduced by the radio protocol stack;
- not introduce an unfeasible number of test configurations;
- be future proof;
- within reason, be compatible with legacy transceiver implementations.
