1、 TIA STANDARD TIA-728 Intersystem Link Protocol (ISLP) TIA-728 JANUARY 2002 Reaffirmed February 2007TELECOMMUNICATIONS INDUSTRY ASSOCIATION The Telecommunications Industry Association represents the communications sector of NOTICE TIA/EIA Engineering Standards and Publications are designed to serve
2、the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standar
3、ds and Publications shall not in any respect preclude any member or nonmember of TIA/EIA from manufacturing or selling products not conforming to such Standards and Publications, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than TIA/EIA membe
4、rs, whether the standard is to be used either domestically or internationally. Standards and Publications are adopted by TIA/EIA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, TIA/EIA does not assume any liability to any patent owner, nor does it a
5、ssume any obligation whatever to parties adopting the Standard or Publication. TIA STANDARDS TIA Standards contain information deemed to be of technical value to the industry, and are published at the request of the originating Committee without necessarily following the rigorous public review and r
6、esolution of comments which is a procedural part of the development of a TIA/EIA Standard. TIA Standards should be reviewed on an annual basis by the formulating Committee and a decision made on whether to proceed to develop a TIA/EIA Standard on this subject. TIA Standards must be cancelled by the
7、Committee and removed from the TIA/EIA Standards Catalog before the end of their third year of existence. Publication of this TIA Standard for trial use and comment has been approved by the Telecommunications Industry Association. Distribution of this TIA Standard for comment shall not continue beyo
8、nd 60 months from the date of publication. It is expected that following this 36 month period, this TIA Standard, revised as necessary, will be submitted to the American National Standards Institute for approval as an American National Standard. Suggestions for revision should be directed to: Standa
9、rds to copyright in the TIAs name any TIA standards publication even though it may include portions of this contribution; and at TIAs sole discretion to permit others to reproduce in whole or in part the resulting TIA standards publication. This document represents “working papers.” Therefore, the c
10、ontents cannot be viewed as reflecting the corporate policies or the views of the Telecommunications Industry Association or of any company. The Association, the companies and individuals involved, take no responsibility in the application of this document. Copyright 1998 Telecommunications Industry
11、 Association. All rights reserved. iTIA-728 iiTIA-728 Foreword This foreword is not part of IS-728 IS-728 specifies an Intersystem Link Protocol (ISLP) for circuit-mode data services. These data services include Asynchronous Data (ADS) and Group-3 Fax as specified in TIA/EIA/IS-99 and TIA/EIA/IS-135
12、. The ISLP adapts between air-interface data rates and higher-speed intersystem rates. The ISLP may be used between a serving system and an anchor system, possibly through one or more tandem systems (see ANSI/TIA/EIA-41.1 for details on “serving system“, “anchor system“, and “tandem system“). The IS
13、LP does not provide any error-checking or error-correcting services. Any intervening tandem system is only a physical-layer relay that transparently passes ISLP data without modification or significant delay. IS-728 was developed by TR45.2, the TIA Intersystem Operations Subcommittee. TIA welcomes s
14、uggestions for improvement of this standard. Please send suggestions to the following address: Telecommunications Industry Association 2500 Wilson Boulevard Suite 300 Arlington VA 22201-3836 iiiTIA-728 Revision History Version Comments 0 April 1997. ivTIA-728 Contents Foreword This foreword is not p
15、art of IS-728iii Revision History.iv Contents v List of Figures vi 1. Purpose and Scope 1 2. Terminology2 3. References.3 4. Overview.4 5. ISLP Structure.6 5.1 ISLP Service Data Units (SDUs)6 5.2 Zero Inserter and Zero Extractor.7 5.3 Framer.7 5.4 ISLP Protocol Data Units (PDU)7 5.5 Rate Synchronize
16、r.8 6. Enabling and Disabling Procedures 9 6.1 Enabling ISLP at Intersystem Handoff .9 6.2 Enabling ISLP at Service Change.10 6.3 Disabling ISLP11 vTIA-728 List of Figures Figure 4-1 Simplified Network Reference Model . 4 Figure 4-2 ISLP Communications Profile . 5 Figure 5-1 ISLP Processes and Signa
17、ls . . 6 Figure 5-2 ISLP Protocol Data Units (PDU) . 7 Figure 6-1 Simple Handoff Forward 9 viTIA-728 1. Purpose and Scope This document specifies an Intersystem Link Protocol (ISLP) for circuit-mode data services. These data services include Asynchronous Data (ADS) and Group-3 Fax as specified in IS
18、-99 2 and IS-135 4. The ISLP adapts between air-interface data rates and higher-speed intersystem rates. The ISLP may be used between a serving system and an anchor system, possibly through one or more tandem systems. This document comprises the following sections: 2 provides an overview. 3 specifie
19、s ISLP structure and processes. 4 specifies ISLP enabling and disabling procedures. 5 specifies terminology. 6 lists references. 1TIA-728 2. Terminology ADS Asynchronous Data Service BS Base Station IMSCCID Inter MSC Circuit Identification ISDN Integrated Services Digital Network ISLP Intersystem Li
20、nk Protocol IWF Interworking Function MAP Mobile Application Part MS Mobile Station MSC Mobile Switching Center PDU Protocol Data Unit PPP Point-to-Point ProtocolPSTN Public Switched Telephone Network RLP Radio Link Protocol SDU Service Data Unit TCP/IP Transport Control Protocol / Internet Protocol
21、 2TIA-728 3. References The following standards contain provisions that constitute provisions of this standard. At the time of publication, the editions indicated were valid. Standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate applying th
22、e most recent editions. ANSI and TIA maintain registers of their currently valid standards. 1. TIA/EIA Data Services, Telecommunications Industries Association, 1997. 2. TIA/EIA/IS-99. Data Services Option Standard for Wideband Spread Spectrum Digital Cellular System.,Telecommunications Industry Ass
23、ociation, 1995. 3. TIA/EIA/IS-130. 800 MHz Cellular Systems TDMA Radio Interface Radio Link Protocol 1, Telecommunications Industry Association, 1995. 4. TIA/EIA/IS-135. 800 MHz Cellular Systems TDMA Services Async Data and Fax, Telecommunications Industry Association, 1995. 5. ANSI/TIA/EIA-41. Cell
24、ular Radiotelecommunication Intersystem Operationss, Telecommunications Industry Association, 1997. 3TIA-728 4. Overview Figure 41 presents a simplified network reference model. This simplified model is based on the detailed network reference model in ANSI/TIA/EIA-41.1 5, with addition of the IWF at
25、 the anchor system. Figure 42 presents a communications profile showing the ISLP and its relationship to other layers. Figure 41 Simplified Network Reference Model MS UmBS MSCMSCMSC IWFPSTNE E AiServing System Tandem System Anchor SystemISDNDiBS Base Station ISDN Integrated Services Digital Network
26、IWF Interworking Function MS Mobile Station (may include a Mobile Termination) MSC Mobile Switching Center PSTN Public Switched Telephone Network AiMSC-to-PSTN interface DiMSC-to-ISDN interface E MSC-to-MSC interface UmBS-to-MS interface, also known as the air-interface Circuit-mode data services tr
27、ansport data, via the Um and E interfaces, between the MS in the serving system and the IWF in the anchor system. Circuit-mode data services also transport data, via the Ai interface or the Di interface, between the IWF and a data terminal in the PSTN or ISDN. 4TIA-728 Figure 42 ISLP Communications
28、Profile Higher LayersISLPBearer layerHigher layersISLPBearer layerServing System MSC/BS/MSAnchor System MSC and IWFTandem MSCThe ISLP transports circuit-mode data from the serving system, possibly via one or more tandem systems, to the anchor system where the interworking function (IWF) resides. At
29、the anchor system, the IWF provides interoperability between the protocols used over the serving systems air interface and protocols used by PSTN-based or ISDN-based data terminals (e.g., V-series modems). The IWF is placed at the anchor system, rather than the serving system, to prevent data loss a
30、nd PSTN or ISDN disconnects during intersystem handoffs or service changes. The ISLP does not provide any error-checking or error-correcting services. Any intervening tandem system is only a physical-layer relay that transparently passes ISLP data without modification or significant delay. The ISLP
31、provides the following services to the higher layers: Rate adaptation between air-interface data rates and higher-speed intersystem data rates. The ISLP requires the following services from the bearer layer: A 56 kbit/s clear channel. 5TIA-728 5. ISLP Structure The ISLP comprises the processes and s
32、ignals shown in Figure 51. The model in Figure 51 is not meant to unnecessarily constrain implementations any ISLP imple-mentation that, as a whole, behaves the same as the ISLP specified in this standard, by definition, complies with this standard. Figure 51 ISLP Processes and Signals Zero Inserter
33、 and Zero ExtractorFramerRate SynchronizerISLP SDUsISLP Modified SDUsISLP PDUsISLP Rate- Synchronized PDUsISLP SDUISLP Processes ISLP SignalsFlagHigher LayerPhysical LayerISLP SDUISLP Modified SDUISLP Modified SDUISLP Modified SDUISLP Modified SDUISLP PDUISLP Modified SDUISLP Modified SDU5.1 ISLP Se
34、rvice Data Units (SDUs) The ISLP shall receive ISLP SDUs from the higher-level protocol (e.g., RLP1 3 or TCP/IP/PPP). The ISLP shall also deliver ISLP SDUs to the higher-level protocol. The format and length of the ISLP SDUs shall be determined by the higher-layer protocol. The ISLP shall transmit I
35、SLP SDU bits in the order in which they are received. For ISLP implementations that carry RLP1 traffic, a one-to-one relationship shall be maintained between an RLP1 frame and an ISLP SDU. IS-130 specifies an RLP1 frame size of 27 octets. 6TIA-728 For ISLP implementations that support CDMA data serv
36、ices, the SDU relays octets that are received from higher-level protocols. The maximum number of octets carried in an ISLP SDU shall be 1508 octets. 5.2 Zero Inserter and Zero Extractor ISLP SDU bit sequences that contain more than five consecutive 1s shall be modified since these sequences could be
37、 misinterpreted as flags. ISLP Modified SDUs may be of any length, but shall not contain any sequence of more than 5 consecutive 1s. At the transmitting end, the zero inserter shall insert a 0 immediately following every sequence of five consecutive 1s (regardless of character boundaries). It shall
38、output the resulting ISLP Modified SDU to the framer. At the receiving end (following flag removal), the zero extractor shall remove a 0 immediately following a string of five consecutive 1s. It shall pass the resulting ISLP SDU to the higher-level protocol. Zero-bit insertion is transparent to the
39、end user and any intermediate tandem system. 5.3 Framer ISLP PDUs are delimited by flag sequences (see 5.4). At the transmitting end, the framer shall insert flags at the beginning and end of every ISLP Modified SDU. It shall pass the resulting ISLP PDUs to the rate synchronizer. At the receiving en
40、d, the framer shall remove the flags at the beginning and end of every ISLP PDU. It shall pass the resulting ISLP Modified SDUs to the zero extractor. 5.4 ISLP Protocol Data Units (PDU) ISLP PDUs, also known as ISLP Frames, shall have the structure shown below: Figure 5-2 ISLP Protocol Data Units (P
41、DU) ISLP Modified SDU FF8 8Variable length F, the flag sequence, serves as a frame delimiter and as interframe fill. It shall be the 8-bit pattern 01111110 (0x7E). ISLP Modified SDUs may be of any length. 7TIA-728 5.5 Rate Synchronizer Repeating flags shall be used as interframe fill to adapt the ai
42、r-interface data rate to the intersystem-facility data rate. At the transmitting end, the Rate Synchronizer shall perform the following functions, as needed: The Rate Synchronizer may delete flags between two adjacent ISLP PDUs, as long as at least one remains. The Rate Synchronizer shall synchroniz
43、e the ISLP output data rate to the physical-layer transmission rate by continually inserting flags between ISLP PDUs. No flags shall be inserted within an ISLP PDU. Two consecutive flags shall not share a single interior 0 bit. The Rate Synchronizer shall output ISLP Rate-Synchronized PDUs to the ph
44、ysical layer at the physical-layer transmission rate. At the receiving end, the Rate Synchronizer shall perform the following functions, as needed: The Rate Synchronizer shall add one flag between any adjacent ISLP Modified SDUs separated by a single flag. The Rate Synchronizer shall delete interfra
45、me flags, i.e., those flags in excess of beginning flag and ending flag for each ISLP PDU.The rate synchronizer shall output ISLP PDUs to the Framer. 8TIA-728 6. Enabling and Disabling Procedures The ISLP may be enabled or disabled on an intersystem trunk. When the ISLP is enabled by an MSC at one e
46、nd of a trunk, the MSC may begin sending ISLP Rate-Synchronized PDUs as described in 5.5. The ISLP may be enabled under any of the following contexts: Intersystem handoff. In-call service change to a circuit-mode data service. The ISLP may be disabled under the following contexts: Call release. Inte
47、rsystem handoff (e.g. handoffback or handofftothird). In-call service change to a service that does not require the ISLP (e.g., voice). The following sections describe in greater detail the signaling sequences and procedures for the ISLP. 6.1 Enabling ISLP at Intersystem Handoff ANSI/TIA/EIA-41.2 sp
48、ecifies the following MAP operations and invoke sequences for intersystem handoff, and intersystem call setup: FacilitiesDirective2 (FACDIR2) HandoffBack2 (HANDBACK2) HandoffToThird2 (HANDTHIRD2) InterSystemSetUp (ISSETUP) Figure 61 illustrates, for a simple handoff forward, when the ISLP should be
49、enabled during the specified intersystem handoff sequences. HandoffToThird2 only indirectly enables or disables the ISLP. The HandoffToThird2 results in FacilitiesDirective2 which enables the ISLP as shown in Figure 6-1. 9TIA-728 Figure 61 Simple Handoff Forward Anchor and ServingSystemTarget SystemServed Mobile StationMSC IWFMSC MSCall in progressFACDIR2facdir2handoff orderMS arrives on channelMSONCHCircuit and ISLPabcdefga. A circuit-mode data call is in progress. b. The Serving System seizes a circui
