P1015 FREEHANDS "Fibre and Radio Enhanced integration in Heterogeneous Access Networks for Delivery of broadband Services"

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1 Technical Information P1015 FREEHANDS "Fibre and Radio Enhanced integration in Heterogeneous Access Networks for Delivery of broadband Services" Requirements for Radio Systems supporting Broadband services in An Heterogeneous Access Network Authors: M. Spini (editor), V. Palestini (CSELT/Telecom Italia) C. Pantjiaros, Z. Ioannou (Cyprus Telecommunications Authority) P. Jaffre (France Telecom) J. Tkac, (Slovak Telekom) Abstract This Technical Information report has been produced within the EURESCOM, P1015 FREEHANDS project. It is intended to provide information regarding the need for integration of Broadband Radio in a Full Services Access Network (FSAN) and to outline the requirements for doing so. EDIN Project P1015 For full publication November 2000

2 Disclaimer This document contains material which is the copyright of certain EURESCOM PARTICIPANTS, and may not be reproduced or copied without permission. All PARTICIPANTS have agreed to full publication of this document. The commercial use of any information contained in this document may require a license from the proprietor of that information. Neither the PARTICIPANTS nor EURESCOM warrant that the information contained in the report is capable of use, or that use of the information is free from risk, and accept no liability for loss or damage suffered by any person using this information.

3 EURESCOM Technical Information page 1(14) Table of contents Table of contents...1 Abbreviations Introduction Network aspects Architecture System configuration Optical Line Termination Optical Network Unit Optical Distribution Network BRAN System Configuration Functional Blocks ONU functional block Optical Line Termination functional block Optical Distribution Network functional block Broadband Wireless Access functional block Functional Reference Model for Radio in FSAN Platform Transmission delay requirement Requirement on the VP handling capability Dynamic bandwidth allocation (DBA) ATM requirements Traffic control requirements Interfaces Network Performance Network Management Proposal EURESCOM Participants in Project P1015 EDIN

4 page 2 (14) EURESCOM Technical Information Abbreviations ABR CLP CBR DBA DLC EFCI EPD FEC ISDN MAC NMS NPC ONU OLT PPD PVC SVC CRS TS ODN SNI UNI NNI ATM FTTx UPC UBR VBR Available Bit Rate Cell Loss Priority Constant Bit Rate Dynamic Bandwidth Allocation Digital link Control Explicit Forward Congestion Indication Early Packet Discard Forward Error Correction Integrated Service Digital Network Medium Access Control Network Management System Network Parameter Control Optical Network Unit Optical Line Termination Partial Packet Discard Permanent Virtual Connection Switched Virtual Connection Central Radio Station Terminal Station Optical Distribution Network Service Node Interface User Network Interface Node Network Interface Asynchronous Transfer Mode Fiber To The (x=b - Bulding, Cab - cabinet) Usage Parameter Control Unspecified Bit Rate Variable Bit Rate EDIN EURESCOM Participants in Project P1015

5 EURESCOM Technical Information page 3(14) 1 Introduction EURESCOM project P1015 FREEHANDS started in March 2000 and will conclude in October It aims at investigating the integration of broadband radio systems with ATM PON, to achieve the flexible and rapid delivery of broadband services over an heterogeneous access network. The main contributors to this project are: British Telecommunications plc, Cyprus Telecommunications Authority (CYTA), Deutsche Telekom AG, France Telecom, CSELT/Telecom Italia, Telenor AS, Portugal Telecom S.A. and Slovak Telekom. The scope of this document is to propose generic and interworking requirements for broadband radio systems used in an heterogenous access network. In particular the scenario in which a radio system is interconnected with an APON system in an FTTx architecture, as defined in ITU-T Rec. G.983.1, is discussed, taking into account the complexity and the variety of requirements which should be covered, e.g. ATM, traffic management, OAM, DLC, MAC etc. Further contributions will be provided later as and when relevant results are obtained in the project. 2 Network aspects The variety of customer needs and mutations in telecommunication scenarios are imposing to Telcos the highest level of flexibility. Therefore new approaches, like those based on wireless-optical technologies need to be investigated. Integration of wireless and optical technologies will result in an access network, where the customer perception of the services provided is media independent, but the flexibility allows network operators the deployment of the most suitable technology taking into account all constrains. In order to have such a flexibility both from the network and service points of view the general requirements for wireless and optical technology should be identical. Furthermore, the interconnection of the two systems should be possible. The two systems should also be interchangeable used in the same portion of the network they should provide similar network and service performance. 2.1 Architecture The generic architecture of an access network is defined by ITU-T Rec. G.902, whilst the reference configuration for an optical distribution network is stemming from the ITU-T Rec.G.982. Since the FREEHANDS Project is devoted to the study of integration of broadband wireless systems within an APON FTTx framework, the reference architectures presented in the following are referring to such a scenario. In particular HIPERACCESS systems can be used within the access network as stand-alone systems directly connecting the user to the core network, as shown in Figure 1, or in an heterogeneous access network for deeper penetration to provide the last mile drop, as depicted in Figure 2. The Terminal Station (TS) provides the user side interface between the broadband access network and the user terminals, i.e. the UNI interface, connected through the air interface to a Central Radio Station (CRS) that provides the network side interface of the access network, i.e. the SNI interface. The Optical Network Unit (ONU), Optical Line Termination (OLT) and the Optical Distribution Network (ODN) are the usual elements of the FTTx architecture as defined by the ITU-T Rec. G The reference point (R) represents the interface between ONU and CRS. This interface between the CRS and the ONU should be an ATM interface, since the FTTx system is ATM-based. With reference to the general configuration as shown in the HIPERACCESS system Overview Report the UNI interface corresponds to interface W.3, while the interface W.2 corresponds to the SNI, or to Reference point (R) EURESCOM Participants in Project P1015 EDIN

6 page 4 (14) EURESCOM Technical Information U S E R S I D E TS 1 TS n Air CRS SNI Core Network UNI Figure 1: Radio P-MP architecture NT 1 ONU 1 U S E R NT n Copper ONU n { ODN λ 1 λ 1 OLT Core Network S I D E (r) Reference point ATM UNI/NNI STM-1 or ATMF 25.6 SNI TS 1 Air CRS UNI TS n 2.2 System configuration Optical Line Termination Figure 2 : Architecture for interconnection at ATM level. The Optical Line Termination (OLT) connects the PON over an SNI interface to service nodes. The OLT is responsible for managing all the PON specific aspects of the ATM transport system. The ONU and OLT provide transparent ATM transport service over the PON between the UNIs/NNIs (Reference point R) and the SNI Optical Network Unit The Optical Network Unit (ONU) interfaces over the IF PON to the OLT, and to the UNI/NNI. Together with the OLT, the ONU is responsible for providing transparent ATM transport service between the NNI/UNI and the SNI. In this architecture, the ATM transport protocols at an IF PON are described as consisting of Physical Media Dependent layer, Transmission Convergence layer, and ATM layer. This architecture is only intended to address the transport of ATM, further detail is contained in Recommendation I.732. The Physical Media Dependent layer would include the modulation schemes for both the upstream and downstream channels (they may be different). It may be possible for the specification to allow for more than one type of Physical Media Dependent layer in a single direction. The Transmission Convergence layer will be responsible for managing the distributed access to the upstream PON EDIN EURESCOM Participants in Project P1015

7 EURESCOM Technical Information page 5(14) resource across the multiple ONUs. This is a key protocol element and will directly affect the resulting ATM QoS. The ATM protocols should see no change in the way they operate over the PON. Within both the OLT and the ONU, the functions performed at the ATM layer at both an OLT and ONU would include cell relaying Optical Distribution Network The Optical Distribution Network provides the optical transmission means from the OLT towards the users and vice versa. It utilises passive optical components BRAN System Configuration The BRAN system is described in ETSI BRAN Technical reports. 2.3 Functional Blocks ONU functional block The ONU is active and decouples the PON network delivery mechanism from the distribution or drop (VDSL or Broadband Wireless Access). The ONU core consists of ODN interface, VDSL or possibly Wireless Access Ports, Transmission, Services and Customers Multiplexing (MUX)/demultiplexing functions and powering. 1) Optical Distribution Network interface The ODN interface handles the optoelectronic conversion process. The ODN interface extracts ATM cells from the downstream PON payload and inserts ATM cells into the upstream PON payload based on synchronization acquired from the downstream frame timing. 2) Multiplexing Multiplexer (MUX) multiplexes service interfaces to ODN interface. Only valid ATM cells can be passed through the MUX, so many VPs can share the assigned upstream bandwidth effectively. 3) Access Ports The VDSL Ports provide the line termination of the respective NTs which in turn provide the UNI interface at the customer side in the case of wired drops. For Wireless Broadband access the respective Ports may interface at either the ATM layer or below the ATM layer at the reference point R. The simpler case is that of interfacing at the ATM layer, however full integration below the ATM layer presents some advantages, including better management of end-to-end QoS and capacity resources. The Access Ports may handle inserting ATM cells into the upstream payload and extracting ATM cells from the downstream payload. 4) ONU powering The powering of the ONU may be implementation dependent Optical Line Termination functional block The OLT is connected to the switched networks via standardized interfaces (VB5.x, V5.x, NNI s). At the distribution side, it presents optical accesses according to the agreed requirements, in terms of bit rate, power budget, etc. The OLT consists of three parts: the service port function; ODN interface; and MUX for VP grooming. This combination is not intended to preclude the Virtual Channel (VC) layer function in the OLT. The VC layer function is for further study. 1) Service port function 2000 EURESCOM Participants in Project P1015 EDIN

8 page 6 (14) EURESCOM Technical Information The function interfaces to service nodes. The service port function may handle inserting ATM cells into the upstream SDH payload and extracting ATM cells from the downstream SDH payload. The function may be duplicated, then a protection switching function is necessary. 2) MUX The MUX provides VP connections between the service port function and the ODN interface and different VPs are assigned to different services at IF PON. Various information such as main contents, signaling, and OAM flows are exchanged by using VCs of the VP. 3) ODN interface The PON Line Terminal handles the optoelectronic conversion process. The ODN interface handles inserting ATM cells into the downstream PON payload and extracting ATM cells from the upstream PON payload Optical Distribution Network functional block In general, the Optical Distribution Network (ODN) provides the optical transmission medium for the physical connection of the ONUs to the OLTs. Individual ODNs may be combined and extended through the use of optical amplifiers (see Recommendation G.982) Broadband Wireless Access functional block Figure 3 shows the basic system arrangement, in which user terminal equipment connects via interface W.3 or UNI with an Access Termination (AT). User terminals may support one or more of a range of user services, according to the particular system specification. A system will normally deploy many Access Terminations. ATs communicate with the rest of the network over the Air Interface (W.1). Direct connection to local (core) networks occurs at the SNI or interface point W.2. The W.2 interface may also be connected to an NNI interface, such as the Reference point R shown in Figure 2. The W.2 interface occurs at Access Points (APs), comprising APTs (Access Point Transceivers), APCs (Access Point Controllers) and IWFs (Inter-Working Functions). The interface point W.2 may connect to one or more networks including the ATM and IP. LOCAL (CORE) NETWORKS TERMINALS W.3 AT W.1 APT APC IWF W.2 ATM, IP, UMTS AP etc. The Broadband Radio Access Network B.3 EMS Figure 3 - Basic arrangement of a HIPERACCESS Network 2.4 Functional Reference Model for Radio in FSAN Platform Figure 2 shows a BRAN system interconnected at the Reference point R with an FSAN platform. Figure 4 shows the protocol model of an FSAN platform composed by OLT, ONU, CRS and TS EDIN EURESCOM Participants in Project P1015

9 EURESCOM Technical Information page 7(14) based on I.321, Figure 5 shows the functional model based on I.731. This configuration can be considered as a first step before reaching a complete integration of the two systems below the ATM level. The DLC layer contains two sublayers: a Medium Access Control sublayer (MAC) and a Logical Link Control sublayer (LLC). The MAC sublayer implements a service policy that takes into account such factors as channel quality, number of terminal devices and medium sharing with other wireless subnetworks. The LLC sublayer maintains the quality of service on a virtual circuit basis. Depending on the type of service provided and channel quality, capacity and utilisation, the LLC layer may implement a variety of means including FEC, ARQ and flow pacing to optimise the service provided to the (DLC) user. Physical layer contains the functions dealing with modulation, coding, etc. The Wireless ATM Convergence Sublayer (WCS) is defined as a sublayer that generates no protocol but that provides the wireless DLC layer with the information it needs to perform its QoS management functions as required (e.g. the DLC could have parameters: VPI/VCI, cell loss priority, user data). The Layer Management Entity (LME) of the DLC layer is used to convey traffic contract information and performance requirements between the DLC layer and the higher, connection control functions EURESCOM Participants in Project P1015 EDIN

10 page 8 (14) EURESCOM Technical Information Service layer (e.g. IP, E1,..) Service layer (e.g. IP, E1,..) ATM layer Adaptation Adaptation ATM layer PHY layer PHY layer ATM PHY PON transmision PON PHY PON transmision PON PHY ATM PHY User equipment UNI TE BTS Reference point (R) ONU IF PON OLT SNI Figure SEQARABIC4 : Radio P-MP system integrated into a FSAN platform EDIN EURESCOM Participants in Project P1015

11 EURESCOM Technical Information page 11(14),3Ã/D\HU,3ÃPDSSLQJÃLQÃ$70ÃVXFKÃDV 5)&Ã333ÃSURWRFRO $$/Ã/D\HU $$/ $$/ 9&Ã/D\HU 9&/B7 9&/B7 9&/B7 939& $ 939& $ 939& $ 93B7 93B7 93B7 93Ã/D\HU 93/B7 93/B7 93/B $ 7393 $ 7393 $ 73B7 73B7 73B7 $70ÃRYHUÃ670RU 9&ÃRUÃ9&Ã6'+ 321 $GDSWDLRQ 0XOWLSOH[ VHFWLRQÃ6' UDQVPLVVLRQ 5HJHQHUDWRU VHFWLRQÃ6'+ &RQYHUJHQFH OD\HU Ã'/&Ã0$&U 2'1 $70Ã670Ã11,,QWHUIDFH 3K\VLFDO 2SWLFDO 3K\VLFDO UDGLR ÃEDVH7 3K\VLFDO HOHFWULFDO $70Ã81,Ã(,QWHUIDFH Figure 5 : Functional model of a radio system connected to an ONU Transmission delay requirement The transmission delay for the POTS services has been specified as less than 1.5 ms in ITU-T G.982. The same provisional values are assumed here (if applicable to the other services). The transmission delay in a radio P-MP system is due to the following facts: propagation delay decoding latency frame duration MAC scheduler efficiency. The propagation delay is negligible (20µs with respect to the 1.5 ms transmission delay) because we are considering signals propagating at m/s for a distance of up to 5 km EURESCOM Participants in Project P1015 EDIN

12 page 12 (14) EURESCOM Technical Information The decoding latency is also negligible, because the FEC coding scheme operates on small blocks ( bit). Some problems could rise only if concatenated codes with long interleaving or long iterative decoding algorithm (Turbo codes) are employed. The frame duration and the efficiency of the MAC scheduler, that works on a frame by frame basis, are mainly responsible for the transmission delay. The first one determines the period of repetition of the scheduling algorithm and of the bandwidth resource grant to different services. In actual LMDS systems and in the BRAN Hiperaccess specification the frame length is around 1 ms (exactly 1 ms in Hiperaccess). The main reason for this choice is to have the best trade-off between small overhead (long frame) and small delay (short frame). With this frame length (1 ms) it s quite difficult for a scheduler to achieve a transmission delay less than 1.5 ms because any ATM cell should be transmitted within the frame next to its arrival time for all the services. In any case, for the time being, this figure (1.5 ms) could be kept as a reference requirement for transmission delay Requirement on the VP handling capability The VP field is coded on 12 bits (4096 handled VPI) at the SNI interface and at the ODN level whereas it is coded on 8 bits (256 possible VPI only) at the reference point R between ONU and CRS. Therefore the number of base stations (CRS) connected to an ONU and the range of valid VPI for a given radio P-MP connection should be organized so that there exists some compatibility between the available capacity on each ONU branch of the ATM optical access network and the number of permanent virtual connections required for each CRS. The possibility that several PVC can be established for a given terminal station TS should also be taken into consideration. For that reason, the availability of the ATMF (25.6 Mb/s) interface as interface in addition to E1 and IEEE at the output of the Terminal Station TS should also be considered Dynamic bandwidth allocation (DBA) In the considered case of integration and interconnection at the ATM level, the DBA functions of both juxtaposed systems (ATM optical and ATM radio) may operate with their own specifics, according to their own capacities. The Admission Control of the Connections is carried out at the ATM level with respect to their traffic contract (refer to paragraph 3.2). 2.5 ATM requirements Traffic control requirements In the same way as the optical ATM part of the system, the radio ATM part of the interconnected network as presented in Figure 2 should be able to handle the different ATM transfer capabilities defined in ITU-T I.371 (also referred to by the acronyms CBR, VBR, ABR and UBR) and related to the classes of QoS defined in ITU-T I.356. In order to be in a position to assess the traffic priorities, the Hiperaccess system should therefore ensure the functions of UPC/NPC (Usage Parameter Control/Network Parameter Control) defined in ITU-T I.371 based on: the cell loss priority (CLP) bit: the UPC/NPC functions may discard, tag or pass the cells according the traffic contract and the value of the CLP bit the explicit forward congestion indication (EFCI) in order to induce a decrease of the cell rate at the customer equipment EDIN EURESCOM Participants in Project P1015

13 EURESCOM Technical Information page 13(14) For the need of the system management, the recording of some ATM statistics is useful. This information should be in compliance with the recommendation included in the document ETSI EN v1.1.1 ( ), paragraph Interfaces The main baseband interfaces at any reference point are those defined in Table 1. UNI (W.3) SNI Reference point (R) - Ethernet 10BaseT VB5.1 ATMF 25M - ATMF25,6 - E1 (fractional/not fractional) E1 ATM (G.804) VB ATM UNI V5.1 V ATM NNI ISDN BRA/PRA (I.430, I.431) - POTS Table 1: Baseband interface The correspondence between interfaces and reference points W.3 and W.2 are the following: 1. UNI Å W.3 2. SNI Å W.2 3. Reference point (R) Å W Network Performance The FTTx system is ATM based, so the broadband radio systems should also be ATM based. Moreover, in order to guarantee the same Service Level Agreement requirements for services provided over FTTx and over radio systems all ATM requirements should be satisfied. The list of ITU-T Recommendations specifying ATM requirements is illustrated in Table 2. Recommendation Focus ITU-T I Parameters for ATM cell transfer performance - QOS classes ITU-T I ATM cell structure - ATM service primitives - GFC class ITU-T I ATM adaptation layer (AAL) requirements ITU-T I functions and parameters for traffic and congestion control 2.8 Network Management Table 2: List of relevant ITU-T Recommendations The network element management requirements by functional category can be defined by five categories, according to M These are: a) Configuration Management b) Performance Management c) Fault Management d) Security Management 2000 EURESCOM Participants in Project P1015 EDIN

14 page 14 (14) EURESCOM Technical Information e) Accounting Management The functions required to operate and maintain the physical layer and ATM layer aspects of the B-ISDN for permanent, semi-permanent, reserved and on-demand virtual connections are defined by ITU-T Rec. I.610. Maintenance of the ATM layer at segment or end-to-end levels covering VP and VC respectively is implemented by means of dedicated OAM cells.recommendation ITU-T I.610 specifies the purpose and the realisation (using different OAM cell types) of the following functions: 1. Fault management, using AIS, RDI, CC and LB cells. 2. Performance management, using FPM and BR cells. 3. Activation/deactivation of PM and/or CC, using activation/deactivation cells. 4. System management cells for use by end-systems only. The management information flows through the Q3 interface. To enable integration of broadband radio with ATM PON (ITU-T G.983.1), it is necessary to study the requirements for managing the system end-to-end. Some useful requirements that will be considered for the integration are those arising within ITU-T G.983.2, specifying the ONU/ONT Management and Control Interfaces to enable multi-vendor interoperability between the OLT and the ONU enlarging the scope to include the CRS. In order to reduce the cost of terminal equipment, however, a minimum set of OAM functions may be supported. The definition of this reduced set is for further study. 3 Proposal The present document describes generic and interworking requirements for broadband radio systems supporting ATM connections. We propose to add or use all relevant texts presented here when revising the current System Overview standard. Furthermore, this text is brought to the attention of ETSI BRAN for consideration in developing Hiperaccess specifications. Finally, EURESCOM project FREEHANDS intends to support standardisation with further contributions in the future. EDIN EURESCOM Participants in Project P1015