DOCSLIB.ORG

An Overview on Integrated Localization and Communication Towards 6G Zhiqiang Xiao and Yong Zeng, Member, IEEE

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
An Overview on Integrated Localization and Communication Towards 6G Zhiqiang Xiao and Yong Zeng, Member, IEEE 1 An Overview on Integrated Localization and Communication Towards 6G Zhiqiang Xiao and Yong Zeng, Member, IEEE Abstract—While the fifth generation (5G) cellular system is information of mobile terminals is expected to play an in- being deployed worldwide, researchers have started the investiga- creasingly important role in future wireless networks. While tion of the sixth generation (6G) mobile communication networks. the deployment of 5G networks is ongoing, researchers around Although the essential requirements and key usage scenarios of 6G are yet to be defined, it is believed that 6G should be the world have already started the investigation on the sixth able to provide intelligent and ubiquitous wireless connectivity generation (6G) mobile communication targeting for network with Terabits per second (Tbps) data rate and sub-millisecond 2030, with various visions proposed [2]–[7]. For example, it (sub-ms) latency over three-dimensional (3D) network coverage. was envisioned that 6G should achieve “ubiquitous wireless To achieve such goals, acquiring accurate location information intelligence” [5], for providing users smart context-aware of the mobile terminals is becoming extremely useful, not only for location-based services but also for improving wireless services through wireless connectivity anywhere in the world. communication performance in various ways such as channel This renders that acquiring the accurate real-time location estimation, beam alignment, medium access control, routing, information of users becomes more critical than ever before, and network optimization. On the other hand, the advancement with potentially centimeter-level localization accuracy for 6G. of communication technologies also brings new opportunities However, most current localization services provided by to greatly improve the localization performance, as exemplified by the anticipated centimeter-level localization accuracy in 6G global navigation satellites systems (GNSS), wireless local by ultra massive MIMO (multiple-input multiple-output) and area networks (WLAN) or cellular networks can at best millimeter wave (mmWave) technologies. In this regard, a unified achieve meter-level localization accuracy in clutter envi- study on integrated localization and communication (ILAC) is ronments. Such coarse localization services are difficult to necessary to unlock the full potential of wireless networks for the meet the centimeter-level localization accuracy requirements best utilization of network infrastructure and radio resources for dual purposes. While there are extensive literatures on wireless of many emerging applications. For example, the following localization or communications separately, the research on ILAC three promising usage scenarios of 5G-and-beyond networks, is still in its infancy. Therefore, this article aims to give a tutorial namely, intelligent interactive networks, smart city, and au- overview on ILAC towards 6G wireless networks. After a holistic tomatic factory, all highlight the critical role of accurate survey on wireless localization basics, we present the state-of- localization in future network design. the-art results on how wireless localization and communication a) Intelligent Interactive Networks: It is believed that the inter-play with each other in various network layers, together with the main architectures and techniques for localization and ultimate goal of communication networks is to promote the communication co-design in current two-dimensional (2D) and intelligent interactions across the world, in terms of people- future 3D networks with aerial-ground integration. Finally, we to-people, people-to-machine, and machine-to-machine. An outline some promising future research directions for ILAC. unprecedented proliferation of new internet-of-things (IoT) Index Terms—Wireless localization, integrated localization and services, like multisensory extended reality (XR) encompass- communication, cellular networks, B5G, 6G ing augmented/mixed/virtual reality (AR/MR/VR) [8], brain- computer interfaces (BCI) [3], as well as tele-presence and tele-control services [5], brings excellent opportunities to I. INTRODUCTION arXiv:2006.01535v1 [eess.SP] 2 Jun 2020 realize the goal of interaction with everything. To implement Starting from the second generation (2G), wireless local- such new applications, it is necessary to achieve the high ization has been included as a compulsory feature in the localization performance, as elaborated in the following. standardization and implementation of cellular networks, with • Multisensory XR: XR services will enable users to continuous enhancement on the localization accuracy over experience and interact with virtual and immersive en- each generation, e.g., from hundreds of meters accuracy in vironments through first-person view [8]. To enable truly 2G to tens of meters in the fourth generation (4G). For immersive XR applications, it must deploy XR systems the forthcoming fifth generation (5G) mobile networks, lo- through wireless networks, and thus the tracking accuracy calization is regarded as one of the key components, due to of XR devices is of paramount importance. For wireless its fundamental support for various location-based services, XR applications, a control center collects the tracking and the requirement on localization accuracy is up to sub- information of the XR devices, and sends data to those meter level [1]. The availability of accurate real-time location devices through wireless links. Therefore, the accuracy of device tracking and the delay of signal measurements Z. Xiao and Y. Zeng are with the National Mobile Communications will significantly affect the XR information transmission Research Laboratory, Southeast University, Nanjing 210096, China. Y. Zeng is also with the Purple Mountain Laboratories, Nanjing 211111, China (e-mail: and hence impact the user experience. For instance, an zhiqiang [email protected], yong [email protected]). inaccurate head-tracking may cause cybersickness, like 2 nausea, disorientation, headaches, and eye strain [9]. In Different from outdoor scenarios, one critical issue of in- general, for XR services, depending on the usage scenar- door localization is the severe non-light-of-sight (NLoS) ios, the requirement for localization accuracy ranges from signal propagation that may significantly degrade the 1 centimeter (cm) to 10 cm, and the time delay should localization accuracy [11], [12]. Meanwhile, the privacy be typically less than 20 milliseconds (ms) [8]. protection of location information is another critical issue • Wireless BCI (WBCI): The forthcoming 5G and future for public indoor localization services [5]. One of the key 6G networks bring new opportunities to tailor commu- problems is to identify what kind of location information nication networks into the versatile networks integrated needs to be protected. For example, for some public with human-centric communication, wireless sensing, and devices, their location information should be accessible remote control [3], where people will be enabled to to all user devices, while that for user personal devices interact with their surrounding environment using various or some kernel public devices needs to be protected. IoT devices connected through the WBCI technology. It • Smart Transportation: The research on smart trans- opens the door for people to control their neighboring IoT portation is still ongoing, with several standards proposed, devices through their brain implants, gestures, empathic like dedicated short-range communications (DSRC) [13] as well as haptic messages [8]. Such a breathtaking tech- and vehicle-to-everything (V2X) [14]. The autonomous nology requires the communication services of extremely driving [15] and vehicle-to-vehicle (V2V) communica- high data rate, ultra-low latency, and high reliability, as tions [16] are envisioned as two attractive developing well as the localization support of high accuracy, e.g., trends of smart transportation, both of which call for centimeter-level accuracy. In addition, the cooperative advanced localization technologies. For autonomous driv- localization among IoT devices is also quite important ing, the 3D mapping for the real-time scenarios is critical, for WBCI. which requires the accurate relative distances between • Tele-presentation and Tele-control: With the advance- the vehicle and obstacles to construct the environment ment of various supporting technologies including high- model. The V2V communications also need accurate resolution imaging and sensing, wearable displays, mo- localization to improve the communication performance. bile robots and drones, it is expected that the technologies Compared with other use cases, for smart transportation, of tele-presentation and tele-control will become reality the localization systems should be designed not only for in the near future [5]. For tele-presentation, a remote high accuracy, but also for wide coverage, as well as for environment can be represented through real-time envi- robustness in highly mobile scenarios. ronment capturing, information transmission, and three- c) Automatic Factory: The development of connected dimensional (3D) holographic rendering, which makes robotics and autonomous systems (CRAS) like autonomous the accurate location information critical for 3D mapping. robotics, drone-delivery systems, etc., promotes the progress Furthermore, people may operate the remote IoT devices of automatic factory [3], such as smart storage, autonomous through
Load more

Recommended publications
  • Data Networks
    Second Ed ition Data Networks DIMITRI BERTSEKAS Massachusetts Institute of Technology ROBERT GALLAGER Massachusetts Institute ofTechnology PRENTICE HALL, Englewood Cliffs, New Jersey 07632 2 Node A Node B Time at B --------- Packet 0 Point-to-Point Protocols and Links 2.1 INTRODUCTION This chapter first provides an introduction to the physical communication links that constitute the building blocks of data networks. The major focus of the chapter is then data link control (i.e., the point-to-point protocols needed to control the passage of data over a communication link). Finally, a number of point-to-point protocols at the network, transport, and physical layers are discussed. There are many similarities between the point-to-point protocols at these different layers, and it is desirable to discuss them together before addressing the more complex network-wide protocols for routing, flow control, and multiaccess control. The treatment of physical links in Section 2.2 is a brief introduction to a very large topic. The reason for the brevity is not that the subject lacks importance or inherent interest, but rather, that a thorough understanding requires a background in linear system theory, random processes, and modem communication theory. In this section we pro­ vide a sufficient overview for those lacking this background and provide a review and perspective for those with more background. 37 38 Point-to-Point Protocols and Links Chap. 2 In dealing with the physical layer in Section 2.2, we discuss both the actual com­ munication channels used by the network and whatever interface modules are required at the ends of the channels to transmit and receive digital data (see Fig 2.1).
    [Show full text]
  • High-Level Data Link Control
    ELEC3030 (EL336) Computer Networks S Chen High-Level Data Link Control • This class of data link layer protocols includes High-level Data Link Control (HDLC), Link Access Procedure Balanced (LAPB) for X.25, Link Access Procedure for D-channel (LAPD) for ISDN, and Logic Link Control (LLC) for FDDI • The frame format is: Flag Address Control Data FCS Flag Note that address and control bits 8 8 8 variable 16 8 can be extended to 16 bits, so bit position 12 3 4 5 6 7 8 N(S)=send sequence number N(R)=receive sequence number that sequence number is 7-bit Information: 0 N(S) P/F N(R) S=supervisory function bits P/F • Frame flag: 01111110, so bit Supervisory: 1 0 S N(R) M=unumbered function bits stuffing is used Unumbered: 1 1 M P/F M P/F=poll/final bit • Address: For multipoint operation, it is used to identify the terminal that transmits or receives the frame and, in point-to-point link, it is used to distinguish Commands from Responses (2nd bit for C/R: 0/1). The address is now extended to 16 bits (1st bit indicates long/short 16/8 bits) • Checksum: FCS contains the remainder of a 16-bit CRC calculation of the frame. It may be extended to 32 bits, using a 32-bit CRC • Control: Three types of frames, I, S and U frames. The old protocol uses a sliding window with 3-bit sequence number and the maximum window size is N = 7. The control field is now extended to 16 bits with 7-bit sequence number 60 ELEC3030 (EL336) Computer Networks S Chen HDLC (continue) • I-frames: carry user data.
    [Show full text]
  • International Civil Aviation Organization
    Guidance for the Implementation of National IP Networks INTERNATIONAL CIVIL AVIATION ORGANIZATION PROJECT RLA/06/901 GUIDANCE FOR THE IMPLEMENTATION OF NATIONAL DIGITAL NETWORKS THAT USE THE IP PROTOCOL, TO SUPPORT CURRENT AND FUTURE AERONAUTICAL APPLICATIONS Project RLA/06/901 Page 1 Guidance for the Implementation of National IP Networks The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of ICAO concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimination of its frontiers or boundaries. Project RLA/06/901 Page 2 Guidance for the Implementation of National IP Networks TABLE OF CONTENTS i. Table of Contents..................................................................................................................... 3 ii. Background.............................................................................................................................. 4 General Decision-Making Considerations ............................................................................... 5 Business ......................................................................................................................... 5 Industrial Support........................................................................................................... 5 Security Policies............................................................................................................. 5 Implementation .............................................................................................................
    [Show full text]
  • Chapter 5 Peer-To-Peer Protocols and Data Link Layer
    Chapter 5 Peer-to-Peer Protocols and Data Link Layer PART I: Peer-to-Peer Protocols Peer-to-Peer Protocols and Service Models ARQ Protocols and Reliable Data Transfer Flow Control Timing Recovery TCP Reliable Stream Service & Flow Control Chapter 5 Peer-to-Peer Protocols and Data Link Layer PART II: Data Link Controls Framing Point-to-Point Protocol High-Level Data Link Control Link Sharing Using Statistical Multiplexing Chapter Overview z Peer-to-Peer protocols: many protocols involve the interaction between two peers z Service Models are discussed & examples given z Detailed discussion of ARQ provides example of development of peer-to-peer protocols z Flow control, TCP reliable stream, and timing recovery z Data Link Layer z Framing z PPP & HDLC protocols z Statistical multiplexing for link sharing Chapter 5 Peer-to-Peer Protocols and Data Link Layer Peer-to-Peer Protocols and Service Models Peer-to-Peer Protocols zzz zzz z Peer-to-Peer processes execute layer-n protocol to provide service to n + 1 peer process n + 1 peer process layer-(n+1) z Layer-(n+1) peer calls SDU SDU layer-n and passes PDU Service Data Units n peer process n peer process (SDUs) for transfer z Layer-n peers exchange Protocol Data Units (PDUs) to effect transfer n – 1 peer process n – 1 peer process z Layer-n delivers SDUs to destination layer-(n+1) peer zzz zzz Service Models z The service model specifies the information transfer service layer-n provides to layer-(n+1) z The most important distinction is whether the service is: z Connection-oriented z Connectionless z Service model possible features: z Arbitrary message size or structure z Sequencing and Reliability z Timing, Pacing, and Flow control z Multiplexing z Privacy, integrity, and authentication Connection-Oriented Transfer Service z Connection Establishment z Connection must be established between layer-(n+1) peers z Layer-n protocol must: Set initial parameters, e.g.
    [Show full text]
  • Infrastructure Layers Dr
    Infrastructure Internet perspective Change in point of view Internet standards do not discuss Data Link + Physical Layers Hardware developers define standards Infrastructure Internet Layer Model Internet application Application Layers Expects Internet services from OS Internet Aware Local + remote ports Transport Service requirements Network End-to-end IP routing + forwarding Data Link Layer — hardware management Not Internet Infrastructure Physical Layer — hardware Aware Computer Networks — Hadassah College — Fall 2015 Infrastructure Layers Dr. Martin Land 1 Computer Networks — Hadassah College — Fall 2015 Infrastructure Layers Dr. Martin Land 2 Infrastructure Infrastructure Engineering perspective Economic perspective Infrastructure layers Enormous investment in existing equipment Bottom-up design physical bits Global network of hardware nodes + transmission lines Physical layer (PHY) Developed to provide many services Internet (IP-based unreliable connectionless) just one service Defines physical transmission of bits Exploits a physical technology Most developed before Internet Telegraph — 1794 Data Link layer (DL) defines management of Physical Layer Telephone — 1876 How to make physical technology do what we want Teletype modem — 1943 Infrastructure management Digital telephone — 1962 Delivering data messages — 10% of effort Internet opened to public — 1992 Making hardware work correctly — 90% of effort Hardware updates OAM = Operations+Administration+Maintenance Replacement of manufactured hardware Application assumes infrastructure
    [Show full text]
  • Analysis and Application of Frame Relay Dongyue Cheng,Guoyou Han,Yuanguo Pan Information Engineering College, Xining University of Technology, Qinghai, China
    Journal of Networking and Telecomunications （2018） Original Research Article Analysis and Application of Frame Relay Dongyue Cheng,Guoyou Han,Yuanguo Pan Information Engineering College, Xining University of Technology, Qinghai, China ABSTRACT Frame relay is developed from integrated services digital network, in 1984, recommended as the International Telegraph and telephone Consultative Committee (CCITT) standard, in addition, TIS the United States authorized by the American National Standards Institute Standards Committee also made some preliminary work on frame relay. Due to the optical fi ber network of the bit error rate (less than 10^-9) than early telephone network error rate (10^- 4~10^-5) is much lower, therefore can reduce some X.25 procedures, which can reduce processing time and improve network throughput. Frame relay is produced in this environment. Is provided by the frame relay data link layer and physical layer specifi cation, any higher-layer protocols are independent of the frame relay Protocol, therefore, greatly simplifies the implementation of frame relay. Frame Relay LAN interconnection is one of the main application, especially when the LAN interconnection over a wide area network, using frame relay can refl ect the low network delay, the advantages of low cost, high bandwidth utilization. Frame relay is an advanced WAN technologies is a form of group communication, except that it will be between X.25 packet switches in the network, error recovery, to prevent the obstruction of the process was simplifi ed. KEYWORDS: Frame Relay throughput WAN technology packet communication 1. Overview Frame relay is a provider of connectivity and the ability to support multiple protocols, multiple applications of WAN technology for communication between multiple locations, which defi nes the process that sends data in public data networks, belonging to high-performance, high-speed data connectivity technologies.
    [Show full text]
  • Les Mécanismes De Fiabilisation (Protocoles ARQ) Et Leur Adaptation Dans Les Réseaux Radiomobiles De 3G Robert Bestak
    Les mécanismes de fiabilisation (protocoles ARQ) et leur adaptation dans les réseaux radiomobiles de 3G Robert Bestak To cite this version: Robert Bestak. Les mécanismes de fiabilisation (protocoles ARQ) et leur adaptation dans les réseaux radiomobiles de 3G. Traitement du signal et de l’image [eess.SP]. Télécom ParisTech, 2003. Français. tel-00005738 HAL Id: tel-00005738 https://pastel.archives-ouvertes.fr/tel-00005738 Submitted on 5 Apr 2004 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Thèse présentée pour obtenir le grade de docteur de l’Ecole Nationale Supérieure des Télécommunic ations Spécialité : Informatique et Réseaux Robert BESTAK Les mécanismes de fiabilisation (protocoles ARQ) et leur adaptation dans les réseaux radiomobiles de 3G Soutenue le 18 décembre 2003 devant le jury composé de Xavier LAGRANGE Président Khaldoun AL AGHA Rapporteurs Laurent TOUTAIN Philippe MARTINS Examinateurs Boris SIMAK Jérôme BROUET Invités Rémy ROGACKI Philippe GODLEWSKI Directeur de thèse A mes parents v Remerciements Tout d’abord, je tiens à remercier mon directeur de thèse le professeur Philippe Godlewski. Ses conseils et ses critiques constructives m’ont beaucoup apporté tout au long de ces années. Je lui suis très reconnaissant pour sa patience et ses efforts à me guider durant ma formation scientifique.
    [Show full text]
  • UNIT II DATA-LINK LAYER & MEDIA ACCESS Introduction – Link-Layer
    UNIT II DATA-LINK LAYER & MEDIA ACCESS Introduction – Link-Layer Addressing – DLC Services – Data-Link Layer Protocols – HDLC – PPP - Media Access Control - Wired LANs: Ethernet - Wireless LANs – Introduction – IEEE 802.11, Bluetooth – Connecting Devices. 2.1 Introduction What is DLL (Data Link Layer)? The Data Link Layer is the second layer in the OSI model, above the Physical Layer, which ensures that the error free data is transferred between the adjacent nodes in the network. It breaks the datagram passed down by above layers and converts them into frames ready for transfer. This is called Framing. It provides two main functionalities Reliable data transfer service between two peer network layers Flow Control mechanism which regulates the flow of frames such that data congestion is not there at slow receivers due to fast senders. 2.2 LINK-LAYER ADDRESSING In a connectionless internetwork such as the Internet we cannot make a datagram reach its destination using only IP addresses. The reason is that each datagram in the Internet, from the same source host to the same destination host, may take a different path. The source and destination IP addresses define the two ends but cannot define which links the datagram should pass through. Three Types of addresses Some link-layer protocols define three types of addresses: unicast, multicast, and broadcast. Unicast Address Each host or each interface of a router is assigned a unicast address. Unicasting means one-to-one communication. A frame with a unicast address destination is destined only for one entity in the link. A3:34:45:11:92:F1 Multicast Address Some link-layer protocols define multicast addresses.
    [Show full text]
  • Trillium 3G Wireless Software White Paper | Radisys
    White Paper | Feburary 2010 Trillium 3G Wireless Software By Ravi Raj Bhat, Vice President of Engineering This white paper presents an overview of technology trends in the wireless CONTENTS market, a historical overview of the evolving wireless technologies. The paper also presents Radisys’ Trillium software solutions which 3G Wireless Market Drivers pg. 1 enable wireless communications and Internet infrastructure equipment Existing Mobile Networks pg. 2 manufacturers to develop 3G network elements for quick and efficient deployment. Next Generation Mobile Networks pg. 2 Third Generation (3G) Wireless Networks pg. 4 3G Wireless Market Drivers Interworking with 2G and 2G+ Wireless Telecommunications service providers and network operators have embraced Networks pg.6 third generation (3G) wireless standards in order to address emerging user demands and to provide new services. The concept of 3G wireless technology Comparison of 2G and 3G Mobile Networks pg. 7 represents a shift from voice-centric services to multimedia-oriented (voice, Trillium 3G Wireless Solutions pg. 8 data, video, fax) services. In addition, heavy demand for remote access to personalized data is fueling development of applications, such as the Wireless Application Protocol (WAP) and multimedia management, to complement the 3G protocols. Complementary standards, such as Bluetooth, will enable interoperability between a mobile terminal (phone, PDA etc.) and other electronic devices, such as a laptop/desktop and peripherals, providing added convenience to the consumer and allowing for the synchronization and uploading of information at all times. The third generation of mobile communications greatly enhances the implementation of sophisticated wireless applications. Users will be able to utilize personal, location-based wireless information and interactive services.
    [Show full text]
  • Switched Communication Networks
    Module 4 Switched Communication Networks Version 2 CSE IIT, Kharagpur Lesson 4 X.25 Version 2 CSE IIT, Kharagpur Special Instructional Objective On completion of this lesson, the student will be able to: • State the key features of X.25 • Explain the frame format of X.25 • Specify the function of the Packet layer of X.25 • State the limitations of X.25 4.4.1 Introduction In the early 1970's there were many data communication networks (also known as Public Networks), which were owned by private companies, organizations and governments agencies. Since those public networks were quite different internally, and the interconnection of networks was growing very fast, there was a need for a common network interface protocol. In 1976 X.25 was recommended as the desired protocol by the International Consultative Committee for Telegraphy and Telephony (CCITT) called the International Telecommunication Union (ITU) since 1993. X.25 is a standard for WAN communications that defines how connections between user devices and network devices are established and maintained. X.25 is designed to operate effectively regardless of the type of systems connected to the network. It is typically used in the packet-switched networks (PSNs) of common carriers, such as the telephone companies. Subscribers are charged based on their use of the network. 4.4.2 X.25 Devices and Protocol Operation X.25 network devices fall into three general categories: data terminal equipment (DTE), data circuit-terminating equipment (DCE), and packet-switching exchange (PSE) as shown in Fig. 4.4.1. Data terminal equipment (DTE) devices are end systems that communicate across the X.25 network.
    [Show full text]
  • Frame Relay/ATM PVC Service Interworking Implementation Agreement FRF.8.1
    Frame Relay/ATM PVC Service Interworking Implementation Agreement FRF. 8.1 Frame Relay Forum Technical Committee February, 2000 Note: The user’s attention is called to the possibility that implementation of the frame relay implementation agreement contained herein may require the use of inventions covered by patent rights held by third parties. By publication of this frame relay implementation agreement the Frame Relay Forum makes no representation that the implementation of the specification will not infringe on any third party rights. The Frame Relay Forum take no position with respect to any claim that has been or may be asserted by any third party, the validity of any patent rights related to any such claims, or the extent to which a license to use any such rights may not be available. Editor: Doug O'Leary Bell Atlantic For more information contact: The Frame Relay Forum Suite 307 39355 California Street Fremont, CA 94538 USA Phone: +1 (510) 608-5920 FAX: +1 (510) 608-5917 E-Mail: [email protected] WWW: http://www.frforum.com Copyright © Frame Relay Forum 2000. All Rights Reserved. This document and translations of it may be copied and furnished to others, and works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Frame Relay Forum, except as needed for the purpose of developing Frame Relay standards (in which case the procedures for copyrights defined by the Frame Relay Forum must be followed), or as required to translate it into languages other than English.
    [Show full text]
  • X.25 Packet Switching Protocol Advanced Protocols
    X.25 Packet Switching Protocol Advanced Protocols X.25 Overview In the childhood of data transmission, analogue first public data networks and for many years in- line quality was poor so the need for a reliable and dustries like banking and air lines relied heavily on safe packet switching protocol was evident. Also their X.25 networks. Today the protocol has lost its network devices at that time did not possess the importance, but derivatives are still used, e.g. in complex features which in today´s devices are tak- GPRS, in amateur radio as AX.25 and in the aero- en for granted. This lead in 1976 to the creation of nautical networks. the fairly complicated X.25 protocol used on the Fig. 1 X.25 protocol stack Fig. 2 X.25 WAN and devices X.25 Architecture The illustration below shows the X.25 protocol lay- In an X.25 network a DTE (Data Transmission ers compared to the standard OSI Reference Mod- Equipment) connects to another DTE via DCEs el. The physical layer consists of the various electri- (Data Circuit-terminating Equipment) and interme- cal interfaces which allow a device to connect to diary packet switches (PSEs). Communication takes the network or directly to another device. place on logical channels, either as Switched Virtual At the data link layer the LAPB (Link Access Proto- Circuits, which are set up at the beginning of a call col - Balanced) is an implementation of the ISO and maintained for the duration of this call, much HDLC (High-level Data Link Control) bit-oriented similar to a telephone call, or a Permanent Virtual protocol.
    [Show full text]