1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Q.1731 SERIES Q: SWITCHING AND SIGNALLING Signalling requirements and protocols for IMT-2000 (06/2000) Radio-technology independent requirements for IMT-2000 layer 2 radio interface ITU-T Recommendation Q.173
2、1 (Formerly CCITT Recommendation) ITU-T Q-SERIES RECOMMENDATIONS SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN SPECIFICATIONS OF SIGNALLING SYSTEMS No. 4 AND No. 5 SP
3、ECIFICATIONS OF SIGNALLING SYSTEM No. 6 SPECIFICATIONS OF SIGNALLING SYSTEM RI SPECIFICATIONS OF SIGNALLING SYSTEM R2 DIGITAL EXCHANGES INTERWORKING OF SIGNALLING SYSTEMS SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 PUBLIC LAND MOBILE NETWORK INTERWORKING WITH
4、 SATELLITE MOBILE SYSTEMS INTELLIGENT NETWORK CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS Q.1-Q.3 Q.4-Q. 59 Q.60-Q.99 Q.100-Q.119 Q. 120-Q.249 Q.250-Q.309 Q.310-Q.399 Q.400-Q.499 Q.500-Q.599 Q.600-Q.699 Q.700-Q.849 Q.850-Q.999 Q. 1000-Q. 1 O99 Q.1100-Q.1199 Q. 1200-Q. 1699 SIGNALLING REQUIREMENTS A
5、ND PROTOCOLS FOR IMT-2000 Q.1700-Q.1799 BROADBAND ISDN Q.2000-Q.2999 For further details, please rer to ITD-T List of Recommendations. ITU-T RECOMMENDATION 4.1731 RADIO-TECHNOLOGY INDEPENDENT REQUIREMENTS FOR IMT-2000 LAYER 2 RADIO INTERFACE Summary This Recommendation defines requirements for commo
6、n services, functions and primitives for the radio-technology independent parts of the Layer 2 of the IMT-2000 radio interface, to ensure maximum commonality between IMT-2000 family members. Source ITU-T Recommendation Q. 173 1 was prepared by ITU-T Study Group 1 1 (1997-2000) and was approved under
7、 the WTSC Resolution No. 1 procedure on 15 June 2000. Keywords ACK, acknowledgement, aggregation, ARQ, assured mode, control plane, data link layer, fragmentation, function, IMT-2000, L2, LAC, Layer 2, layer, link access control, LLC, logical link control, mapping, NAK, octet stream, PDU, piggybacki
8、ng, primitive, protocol instance, QoS, reassembly, SAP, SDU, segmentation, service, sublayer, transparent mode, unassured mode, user plane. Recommendation 4.1731 (06/2000) 1 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunicatio
9、ns. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommun
10、ication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC
11、 Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication admin
12、istration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or
13、 applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be require
14、d to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. o ITU 2000 All rights reserved. No part of this publication may be reproduced or utilized in any form or by
15、any means, electronic or mechanical, including photocopying and microfilm, without permission in writing fi-om the ITU. 11 Recommendation 4.1731 (06/2000) CONTENTS 1 2 3 4 5 5.1 5.2 5.3 6 7 7.1 7.2 8 8.1 8.2 9 9.1 9.2 Scope . References . Definitions Abbreviations Services . General requirements Con
16、trol Plane Services 5.2.1 Reserved 5.2.2 Delivery Modes . 5.3.1 General requirements . 5.3.2 Delivery Modes . User Plane Services . Functions . Primitives Control Plane Primitives . 7.1.1 Primitives at the Upper Boundary . 7.1.2 Primitives at the Lower Boundary . User Plane Primitives 7.2.1 Primitiv
17、es at the Upper Boundary . 7.2.2 Primitives at the Lower Boundary . . Interactions with Layer Management Services provided to Layer Management Primitives Logical channels . Logical channel designation Examples . Recommendation 4.1731 (06/2000) 1 1 1 3 9 11 12 12 14 15 15 18 19 19 19 20 20 21 . 111 R
18、ecommendation 4.1731 RADIO-TECHNOLOGY INDEPENDENT REQUIREMENTS FOR IMT-2000 LAYER 2 RADIO INTERFACE (Geneva, 2000) 1 Scope The scope of this Recommendation is the definition of common services, functions and primitives for the radio-technology independent parts of the Layer 2 of the IMT-2000 radio i
19、nterface, to ensure maximum commonality between IMT-2000 family members, consistent with ITU-T Recommendation Q. 17 1 1 i. The exact division of functionality between various sublayers of Layer 2 (sometimes referred to as LAC and MAC), as well as the exact placement of functionality of the layers an
20、d the sublayers in physical components of the radio access networks is considered to be IMT-2000 family member and/or implementation dependent, and is, thus, not addressed in this Recommendation. Specifically, this Recommendation is concerned with: 1) Defining specifications and requirements for Lay
21、er 2 in terms of: services offered by Layer 2 to the upper layers and Layer Management; functions performed by Layer 2 to deliver those services. Defining interfaces between Layer 2 and the adjacent layers, consisting of: service access points (SAPS) where the identified services are offered; primit
22、ives and their associated parameters. Identimng the functionality in the Control Plane and the User Plane, as well as the interactions with Layer Management. 2) 3) All the requirements are subject to market needs and may be met in phases. 2 References The following ITU-T Recommendations and other re
23、ferences contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged
24、to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. i ITU-T Recommendation Q. 17 1 1 (1 999), Network functional model for IMT-2000. 3 Definitions This
25、 Recommendation defines the following terms: 3.1 automatic repeat request (ARQ): Technique for providing reliable delivery of signals between communicating stations, involving autonomous retransmissions of the signals and transmission of acknowledgments until implicit or explicit confirmation of del
26、ivery is received. 3.2 function: An operational modality employed in the offering of a service. Recommendation 4.1731 (06/2000) 1 3.3 information stream: The totality of data generated and transported, in time, and associated with a specific logical communication session. 3.4 layer 1: Layer 1 (Physi
27、cal Layer) provides for the transmission and reception of radio signals between the radio access network and the mobile terminal. 3.5 layer 2: Layer 2 (Data Link Layer) provides for the correct transport and delivery of signalling messages and user data generated by Layer 3 (see below). In some impl
28、ementations, Layer 2 may be seen as divided into an upper Link Access Control (LAC) sublayer and a lower Medium Access Control (MAC) sublayer. Layer 2 makes use of the services provided by Layer 1. 3.6 layer 3: Layer 3 originates and terminates signalling messages and user data according to the sema
29、ntics and timing of the communication protocol between the radio access network and the mobile terminal. Layer 3 makes use of the services provided by Layer 2. 3.7 layering: A method of organization for communication protocols in which the sent or received information is transferred in pipeline fash
30、ion, within each station, in well-defined, encapsulated data units between coordinated processing entities (“layers“). A layer is defined in terms of its communication protocol to the peer layer in the other station and the services it offers to the next higher layer in its own station. 3.8 logical
31、channel: A communication path between stations, described in terms of the intended use of, and access to the transferred data, and direction of transfer. A logical channel can be “mapped“ to/rom one or more physical channels. 3.9 mapping: In this context, technique for forming associations between l
32、ogical and physical channels. 3.10 message: Signalling data unit being transferred between the radio access network (RAN) and the mobile terminal (MT). 3.11 octet stream: An information stream where data is organized in semantically meaningful fixed-size data units (octets) which are generated in a
33、certain order and possibly, at a given rate. The octets can be assembled in blocks prior to transmission and have to be delivered in the same order and possibly, at the same rate, upon reception. 3.12 physical channel: A communication path between stations, described in terms of the RF characteristi
34、cs such as coding, power control policies, etc. 3.13 piggybacking: ARQ efficiency technique, where information related to the acknowledgment of a prior transmitted PDU is carried together with a data PDU sent in the opposite direction, thus saving the transmission of a separate PDU containing only t
35、he acknowledgement information. 3.14 primitive: An atomic, well-defined method of transferring data and control information between two adjacent layers and sublayers. Conventionally represented as a function invocation with the data andor control information as parameters. 3.15 protocol data unit: E
36、ncapsulated data being sentlreceived by a layer rom the peer layer on the other station. 3.16 protocol instance: Set of state variables, fully describing the status of a communication session at any moment in time, and associated with the transmissionheception of a specific information stream. Multi
37、ple information stream may use the same protocol, but each will receive its own “instance“. 3.17 protocol stack: Conceptual model of the layered architecture for communication protocols (see Layering) in which layers within a station are represented in the order of their numeric designation and requ
38、iring that transferred data be processed sequentially by each layer, in the order of their representation. Graphically, the “stack“ is drawn vertically, with the layer having the lowest numeric designation at the base. 2 Recommendation 4.1731 (06/2000) 3.18 service: A semantically meaningful, consis
39、tently performed, well-defined functionality unit, offered by an entity at the interface with another entity, to be performed on data units exchanged between the entities. 3.19 service data unit: Data being transferred to/fiom a layer fiodto the layer immediately “above“ it, in the protocol stack. U
40、nless stated otherwise, in this Recommendation, SDU refers to the Layer 3 service data unit being transferred to/fiom Layer 2. 3.20 service access point (SAP): Conceptual place at the interface between two adjacent layers where services are provided to the upper layer and data and protocol informati
41、on is exchanged between layers. 3.21 sublayer: A protocol layer of finer granularity, within another protocol layer or sublayer. Layer 2 may be seen as having a LAC sublayer and a MAC sublayer. In turn, those sublayers may have several sublayers of their own. 3.22 upper layers: General reference to
42、Layer 3 and the layers above it. 4 Abbreviations This Recommendation uses the following abbreviations: ACK ARQ FCS LAC L1 L2 L3 MAC MT NAK PDU QOS RAN SAP SDU 5 5.1 1) 2) (Positive) Acknowledgement Automatic Repeat Request Frame Check Sequence Link Access Control Layer 1 Layer 2 Layer 3 Medium Acces
43、s Control Mobile terminal Negative Acknowledgement Protocol Data Unit Quality of Service Radio Access Network Service Access Point Service Data Unit Services General requirements EfJiciency In providing services to Layer 3 and Layer Management, Layer 2 should make efficient use of resources, especia
44、lly radio resources. Support for multiple protocol instances Layer 2 should be able to support multiple information streams, independent of each other, by assigning a different instance of the Layer 2 protocol engine to each stream. Recommendation 4.1731 (06/2000) 3 3) Prioritization among diferent
45、information streams Layer 2 should be able to prioritize the order of transmission among SDUs fiom different information streams. Priority may be based on the type of the traffic in the information stream, e.g. voice, data, signalling, etc. 5.2 Control Plane Services 5.2.1 Reserved 5.2.2 Delivery Mo
46、des Layer 2 shall provide the following modes of delivery of C-plane SDUs on a per SDU basis: o Assured Delivery. o Unassured Delivery. The transmitting Layer 3 entity indicates to Layer 2 the delivery mode to be used for each SDU. 5.2.2.1 Assured Delivery Mode When providing Assured Delivery servic
47、e, Layer 2 shall satisfy the following requirements: 1) Guaranteed delivery Layer 2 shall deliver every SDU submitted to it by Layer 3 for delivery to its peer. If Layer 2 is unable to deliver an SDU to the peer, it shall notify the transmitting Layer 3 entity and/or Layer Management of the failure,
48、 if so requested. 2) Error-free delivery Layer 2 shall deliver to the receiving Layer 3 entity only those SDUs that are fiee of transmission errors. 3) Unique delivery Layer 2 shall deliver each SDU to the receiving Layer 3 entity only once. When providing Assured Delivery service, Layer 2 should de
49、liver SDUs according to the indication fiom the transmitting Layer 3, either In-sequence or Immediate, as follows: 4) In-sequence delivery Layer 2 shall deliver SDUs to the receiving Layer 3 entity in the same order as the transmitting Layer 3 entity submits them to Layer 2. 5) Immediate delivery Layer 2 shall deliver an SDU to the Layer 3 receiving entity as soon as it arrives at the receiver. Thus, the order of delivery of SDUs to the receiving Layer 3 entity may be different rom the order in which they were submitted by the transmitting Layer 3 entity, e.g. due to retransmis
