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Figure 3Typical usage of communications standards.access to terminals (laptops, VCRs, and soon). Figure 3 illustrates the end-user's personalarea network (PAN). Via HIPER-LAN/2, users gain access to their network—for instance, to the Internet, an intranet, oranother HIPERLAN/2-capable device. Bycontrast, Bluetooth technology is mainlyused for linking individual communicationdevices within the personal area network.System overviewThe HIPERLAN/2 standard specifies aradio-access network that can be used witha variety of core networks. This is made possiblethanks to• a flexible architecture that defines corenetwork independent physical (PHY) anddata-link-control (DLC) layers; and• a set of convergence layers that facilitateaccess to various core networks (Figure 4).Several convergence layers have been or arecurrently being defined for interworkingwith• Internet protocol (IP) transport networks(Ethernet and the point-to-point protocol,PPP);• asynchronous transfer mode-based (ATM)networks;• third-generation core networks; and• networks that use IEEE 1394 (Firewire)protocols and applications.The data units that are transmitted withinthese core networks can differ in length,type, and content. A specific convergencelayer in HIPERLAN/2 segments data unitsinto fixed-length HIPERLAN/2 DLC userservice data units (U-SDU) that are transmittedto their destination by means of DLCand PHY data-transport services.The HIPERLAN/2 standard supports ter-Figure 4Architecture of the HIPERLAN/2 protocols.110 Ericsson Review No. 2, 2000
minal mobility at velocities of up to 10 m/s.In addition, it provides a means of handlingdifferent interference and propagation environments,with the aim of• maintaining the communications link atlow signal-to-interference ratios;• maintaining quality of service; and• finding a suitable trade-off between communicationsrange and data rate.The air interface of the HIPERLAN/2 standardis based on time-division duplex(TDD) and dynamic time-division multipleaccess (TDMA). HIPERLAN/2 is a flexibleplatform on which a variety of business andhome multimedia applications can be basedto provide bit rates of up to 54 Mbit/s. In atypical business application scenario, a mobileterminal receives services over a fixedcorporate or public network infrastructure.In addition to quality of service, the networkprovides mobile terminals with security andmobility management services when theymove between networks—for example,when terminals move between local area andwide area networks or between corporateand public networks. In a home applicationscenario, low-cost and flexible networkingis supported to interconnect wireless digitalconsumer devices.HIPERLAN/2 relies on cellular networkingtopology combined with ad hoc networkingcapability. It supports two basicmodes of operation: centralized mode (CM)and direct mode (DM).The centralized mode of operation appliesto the cellular networking topology whereeach radio cell is controlled by an accesspoint (AP) that covers a certain geographicalarea. In this mode, mobile terminalscommunicate with one another or with thecore network through the access point. Thecentralized mode of operation is mainly usedin indoor and outdoor business applicationswhere the area to be covered is larger than aradio cell.The direct mode of operation applies tothe ad hoc networking topology of privatehome environments and where the entireserving area is covered by one radio cell. Inthis mode, mobile terminals in a single-cellhome network can exchange data directlywith one another. The access point controlsthe assignment of radio resources to the mobileterminals.Convergence layerThe convergence layer (CL) has two mainfunctions: it adapts service requests fromhigher layers to the service offered by theFigure 5General structure of the convergence layer.DLC, and it converts higher-layer packets offixed or variable length into a fixed-lengthservice data unit (SDU) that is used withinthe DLC.The convergence layer thus maps incomingdata onto different bearers of the DLC.For example, if we assume that Ethernetquality of service is supported via IEEE802.lp, then the priority indicated in theadditional tag field stipulates the type oftraffic to be carried in the packet. 10 The convergencelayer maps different traffic typesinto different classes and consequently ontodifferent radio bearers.There are two types of convergence layer:• a cell-based convergence layer, whichhandles higher layers with fixed-lengthpackets—for instance, ATM-based corenetworks; and• a packet-based convergence layer, whichhandles higher layers with variablelengthpackets—for instance, Ethernet.Separate service-specific convergence sublayers(SSCS) have been defined to make theappropriate service adaptation for Ethernet,IEEE 1394, PPP, and the universal mobiletelecommunications system (UMTS). Figure5 depicts the basic structure of each typeof convergence layer.The padding, segmentation and reassemblefunction of the fixed-length DLC servicedata units is a key feature that makes it pos-Ericsson Review No. 2, 2000 111
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Ericsson 2/2000REVIEWTHE TELECOMMUN
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ContributorsIn this issueLuis Barri
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Ericsson Review is also published o
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Evolving from cdmaOne to third-gene
Page 10 and 11: Figure 2Operators Harmonization Agr
Page 12 and 13: more features, and greater reliabil
Page 14 and 15: Figure 7Ericsson's third-generation
Page 16 and 17: Figure 11Ericsson's timeline for ev
Page 18 and 19: Third-generation TDMAChristofer Lin
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Page 24 and 25: Figure 5Curves illustrating maximum
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Page 28 and 29: erage can be achieved in existing c
Page 30 and 31: Business solutions for mobile e-com
Page 32 and 33: Figure 2Comparison of traditional a
Page 34 and 35: BOX B, THE E-COMMERCE TIMELINE1999E
Page 36 and 37: Figure 6Mobile e-Pay end-user servi
Page 38 and 39: Figure 8Access features with push-a
Page 40 and 41: AuthenticationTo verify that end-us
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Page 44 and 45: Figure 2The footprint of the RBS 22
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Page 48 and 49: BOX B, SYMMETRIC KEY SYSTEMSGood sy
Page 50 and 51: Figure 4Construction of an ESP-prot
Page 52 and 53: Figure 7An X.500 database structure
Page 54 and 55: Figure 9GPRS VPN scenarios.Figure 1
Page 56 and 57: TRADEMARKSRC4 and RC4 are registere
Page 58 and 59: HIPERLAN type 2 for broadband wirel
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Page 64 and 65: TABLE 1PHYSICAL LAYER MODES OF HIPE
Page 66 and 67: Queen City WaterfrontEMERGING PROJE
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Page 70: Previous issuesNo. 1,2000IPv6—The
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