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The communications technology journal since 1924
Non-line-of-sight microwave
backhaul for small cells 12
Software-defined ...
“The object of this magazine is to
spread information concerning
the work and activities of this and
associated enterprise...
The communicat ons techno ogy journal since 1924
Non line of sight microwave
backhaul for small cells 12
Software defined ...
Delivering content
with LTE Broadcast
Ericsson has demonstrated LTE Broadcast with evolved Multimedia Broadcast
Multicast ...
solution. The concept has been built on
eMBMS technology and based on a set
the radio-channel quality and overall
Broadcast is implemented as an
extension to the existin...
broadcast area, provided they have the
right subscription level and an MBMS-
capable device, can receive broadcast-
eMBMS-enabled applications with-
underlying transport,control,orradio-
files through eMBMSs using MBMS file
By ...
Michael Slssingar
is an Ericsson senior
specialist in service
delivery architectures and
holds a post-graduate
diploma and...
Nine decades
of innovation
Automatic exchanges to smart networks
The history of our technology is deeply entrenched in tha...
Non-line-of-sight microwave
backhaul for small cells
The evolution to denser radio-access networks with small cells in clu...
technologies to meet coverage and
capacity requirements. Despite this, a
number of studies on NLOS transmis-
Here, the margin is defined as the
difference between received power
er threshold for ...
The 28GHz system can sustain full
throughput at much deeper NLOS
than the 5.8GHz system, which is to be
expected as it has...
shown in Figure 5A. The circle and tri-
Measurements were carried o...
full duplex throughput along the main
street canyon and in the neighboring
Jonas Hansryd
joined Ericsson
Research in 2008 and is
currently managing the
microwave high-speed
and electronics group. H...
Toward the end of this decade, Ericsson trialed a crossbar
networking: the service
provider perspective
An architecture based on SDN techniques gives operators grea...
of the data plane (including SGW, PGW
and M-MGW) and the control plane
(including MME and MSC-S) was intro-
duced. Now SDN...
vides the necessary support for applica-
tions and tenants to trigger automatic
Ericsson and Telstra have jointly devel-
oped a service-chaining prototype that
leverages SDN technologies to enhance
carefully. Dynamic service-chaining
can optimize the use of extensive high-
touch services ...
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
Ericsson Review: special 90th anniversary edition
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Ericsson Review: special 90th anniversary edition


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Ericsson employees have been sharing their expertise in our technology journal for nine decades now. Celebrating 90 years in publication, Ericsson Review is one of the longest-running technical journals, providing insights on significant developments in telecoms technology. With a global understanding of the telecom industry, our experts aim to share their knowledge of building high-performance networks for the Networked Society and how current research is shaping the future and addressing the constantly changing challenges.

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Ericsson Review: special 90th anniversary edition

  1. 1. The communications technology journal since 1924 Non-line-of-sight microwave backhaul for small cells 12 Software-defined networking: the service provider perspective 20 HSPA evolution: for future mobile- broadband needs 26 Next generation OSS/BSS architecture 38 Carrier Wi-Fi: the next generation 48 Nine decades of innovation 11, 19 & 47 Next generation video compression 33 Delivering content with LTE Broadcast 4 901924-2014
  2. 2. “The object of this magazine is to spread information concerning the work and activities of this and associated enterprises, and to furnish a connecting link between these latter and the head firm.” These lines are taken from the introduction to The L. M. Ericsson Review – Tidskrift för Allmänna Telefonaktiebolaget L. M. Ericsson – when the first issue of the new journal was published in 1924. In his historical article to celebrate this journal’s 50th anniversary (1974), Sigvard Eklund, former editor of Ericsson Review (1943-1972), wrote the following words: “Apart from an article on ‘the devel- opment and present size of the LM Ericsson Group,’ there was a 10-page description of the company’s auto- matic 500-line selector system, illus- trated by a few photographs of the recently opened automatic exchange in Rotterdam, one of the first major exchange equipments to be delivered up to that time.” In the 40 years since then – and the 90 years since this journal first started promoting technology – the world we live in has been transformed by tech- nology to such a degree that I some- times find it difficult to recognize the old one. I would like nothing more than to be able to give you a glimpse of what we will be writing about 90 years from now… what will the 22nd century bring? What generation of technology will have been reached by then, what business models will we use, how will we pay for things, and what sort of devices will we connect with? These are just some of my ques- tions, and I wonder even if they will be relevant; maybe we won’t even use devices, as connectivity will simply exist in everything. Even if I don’t have an open window on the next centu- ry, the research and development we carry out at Ericsson today is aimed at the next generation, which promises Ulf Ewaldsson Chief Technology Officer Head of Group Function Technology at Ericsson Celebrating 90 years of technology insights to continue along the current path of evolution: to be data driven, video heavy and influenced by the gaming world. The articles in this edition address a wide range of telecommunication issues, but they all have one thing in common and that is performance. Getting data through the network fast and efficiently so that the best user experience can be delivered to sub- scribers is a recurring theme no mat- ter what part of network architecture is being discussed. From future OSS/ BSS architecture to integrated Wi-Fi and to packets stuffed with data, the message is clear… the faster the net- work can serve one subscriber, the faster it can move on to the next. One thing I am convinced about, however, is convergence. And not just in terms of fixed and mobile, but everywhere. Industries and technolo- gies are merging. The lines between TV, the internet, and telecommuni- cation will not exist for much longer. Education, work and family life are all coming together and the key is individualism. With a connection, every individ- ual on the planet has the potential to take control over their life. The tradi- tional models of work and education are being challenged. Connectivity is providing individuals with more choices, greater flexibility and the abil- ity to mix things up in a way that suits them, their budget, their lifestyle and their goals. We are not there yet, and there are many pieces that need to be in place, but right now we are lay- ing the foundation for the Networked Society. Mobile subscriptions are set to rise to 9.3 billion and mobile data traf- fic to grow by 45 percent (CAGR) by 2019. The opportunities are becoming available for more people, and connec- tivity is becoming a way of life. This edition is a celebration of 90 years of technology innovation. I hope you enjoy it. The most frequent users interact with their smartphone more than 150 times a day, or an average of every seven minutes during the daytime.* Editorial *Ericsson Mobility Report, November 2013 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014
  3. 3. The communicat ons techno ogy journal since 1924 Non line of sight microwave backhaul for small cells 12 Software defined networking the service provider perspective 20 HSPA evolution for future mobile broadband needs 26 Next generation OSS/BSS architecture 38 Carrier Wi Fi the next generation 48 Nine decades of innovation 11 19 & 47 Next generation video compression 33 Delivering content with LTE Broadcast 4 901924-20 4 CONTENTS 90TH ANNIVERSARY 2014 a collection of articles from 2013 4 Delivering content with LTE Broadcast The data volume in mobile networks is booming – mostly due to the success of smartphones and tablets. LTE Broadcast is one way of providing new and existing services in areas that can at times be device dense, such as stadiums and crowded city centers. Built on LTE technology, LTE Broadcast extends the LTE/EPC with an efficient point-to-multipoint distribution feature that can serve many devices with the same content at the same time. This article was originally published on February 11, 2013. 11, 19 47 Nine decades of innovation Automatic exchanges to smart networks. 12 Non-line-of-sight microwave backhaul for small cells The evolution to denser radio-access networks with small cells in cluttered urban environments has introduced new challenges for microwave backhaul. A direct line of sight does not always exist between nodes, and this creates a need for near- and non-line-of-sight (NLOS) microwave backhaul. This article was originally published on February 22, 2013. 20 Software-defined networking: the service provider perspective An architecture based on software-defined networking (SDN) techniques gives operators greater freedom to balance operational and business parameters, such as network resilience, service performance and QoE against opex and capex. With its beginnings in data-center technology, SDN has developed to the point where it can offer significant opportunities to service providers. This article was originally published on February 21, 2013. 26 HSPA evolution for future mobile-broadband needs As HSPA evolution continues to address the needs of changing user behavior, new techniques develop and become standardized. This article covers some of the more interesting techniques and concepts under study that will provide network operators with the flexibility, capacity and coverage needed to carry voice and data into the future, ensuring HSPA evolution and good user experience. This article was originally published on August 28, 2013. 33 Next generation video compression Requiring only half the bitrate of its predecessor, the new standard – HEVC or H.265 – will significantly reduce the need for bandwidth and expensive, limited spectrum. HEVC (H.265) will enable the launch of new video services and in particular ultra-HD television (UHDTV). This article was originally published on April 24, 2013. 38 Next generation OSS/BSS architecture When two large companies merge, it often takes a while – years in some cases – before processes get redesigned to span all departments, and the new organization settles into a lean and profitable machine. And the same is true of OSS/BSS. These systems have been designed for two different purposes: to keep the network operational and to keep it profitable. But today’s demanding networks need the functions of both of these systems to work together, and to work across the varying life cycles of products and services. This article was originally published on November 25, 2013. 48 Carrier Wi-Fi: the next generation Putting the network in control over whether or not a device should switch to and from Wi-Fi, and when it should switch, will make it easier for operators to provide a harmonized mobile broadband experience and optimize resource utilization in heterogeneous networks. This article was originally published on December 20, 2013. To bring you the best of Ericsson’s research world, our employees have been writing articles for Ericsson Review – our communications technology journal – since 1924. Today, Ericsson Review articles have a two-to-five year perspective and our objective is to provide you with up-to-date insights on how things are shaping up for the Networked Society. Address : Ericsson SE-164 83 Stockholm, Sweden Phone: +46 8 719 00 00 Publishing: Ericsson Review articles and additional material are pub ished on www Use the RSS feed to stay informed of the latest updates. Articles are also available on the Ericsson Technology Insights app for Android and Apple tablets. The ink for your device is on the Ericsson Review website:www. If you are viewing this digitally, you can: download from Google Play or download from the App Store Publisher: U f Ewaldsson Editorial board: Håkan Andersson, Hans Antvik, Ulrika Bergström, Joakim Cerwall, Deirdre P. Doyle, Dan Fahrman, Anita Frisell, Jonas Högberg, U f Jönsson, Magnus Karlsson, Cenk Kirbas, Sara Kullman, Kristin Lindqvist, Börje Lundwall, Hans Mickelsson, U f Olsson, Patrik Regårdh, Patrik Roséen and Gunnar Thrysin Editor: Deirdre P. Doyle deirdre.doyle@jgcommunication se Chief subeditor: Birgitte van den Muyzenberg Contributors: John Ambrose, Håkan Andersson, Paul Eade, Ian Nicholson, Gunnar Thrysin and Peter Öhman Art director and layout: Jessica Wiklund and Carola Pilarz Illustrations: Claes-Göran Andersson Printer: Edita Bobergs, Stockholm ISSN: 0014-0171 Volume: 91, 2014 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014
  4. 4. Delivering content with LTE Broadcast Ericsson has demonstrated LTE Broadcast with evolved Multimedia Broadcast Multicast Services at a number of international trade shows. These demos have shown the solution’s potential to create new business models for telcos and ensure consistent QoS, even in very densely populated places like sports venues. respondents stated they would watch more TV if the content was provided on their mobile device, and 61 percent saidtheywouldswitchoperatortogain accesstomobile-TVservices.Themajor- ity of respondents said content they would find interesting to watch while on the move includes local news and weather information, movies, national news,sitcomsandsports. To meet this growing demand for mobile TV, operators are rapidly updat- ing their offerings, continuously add- ing new services and content to live and on-demand streams – increasing the volume of information transport- ed. Naturally, this causes network utili- zation to rise, requiring more efficient ways to deliver content, while network dimensioningbecomesallthemorecru- cial,andnewbusinessmodelsareneed- edtomaintainARPU. Given the direction in which the industryisclearlymoving,Ericssonhas developed an end-to-end LTE Broadcast the broadcast streams within the SFN that are of interest. In this way, devices downloadonlyrelevantdata–notevery- thingwithintheareatothenjustthrow unwanted data away. This ensures that devicesworkinabattery-efficientway. Businessincentives The coextending evolution of mobile technologies and devices has made it possible for people to consume video using handheld equipment without compromising their experience. Based onanEricssonConsumerLabstudy1 ,the most recent Ericsson Mobility Report2 , statesthatvideoisthebiggestcontribu- tor to mobile-traffic volumes, account- ing for more than 50 percent. And the growth of traffic is expected to contin- ue,increasing12-foldby2018. According to another study, carried out by Mobile Content Venture3 , more than half of US consumers would con- siderviewingprogramsontheirsmart- phones and tablets – 68 percent of THORSTEN LOHMAR, MICHAEL SLSSINGAR, VERA KENEHAN AND STIG PUUSTINEN BOX A Terms and abbreviations AL-FEC Application Layer FEC API application program interface ARPU average revenue per user BLER Block Error Rate BM-SC Broadcast Multicast Service Center CDN content distribution network eMBMS evolved MBMS eNB eNodeB EPC Evolved Packet Core EPS Evolved Packet System FDD frequency division duplex FEC forward error correction FIFA Fédération Internationale de Football Association FLUTE file delivery over unidirectional transport HEVC High Efficiency Video Coding IMB integrated mobile broadcast ISD inter-site distance ISI inter-symbol interference M2M machine-to-machine MBMS Multimedia Broadcast Multicast Service MBMS-GW MBMS-gateway MBSFN Multimedia Broadcast over an SFN MCE Multicell Coordination Entity MME Mobility Management Entity MPEG Moving Picture Experts Group MPEG- MPEG-Dynamic Adaptive DASH Streaming over HTTP NBC National Broadcasting Company OFDM orthogonal frequency division multiplexing PGW packet data network gateway SDK software development kit SFN single-frequency network SGW service gateway SNR signal-to-noise ratio TDD time division duplex UDP User Datagram Protocol UE user equipment The solution is built on LTE technology, extending the LTE/ EPC with an efficient point-to- multipoint distribution feature that can serve many eMBMS- capable LTE devices with the same content at the same time. It can be used to boost capacity for live and on-demand content so that well-liked websites, breaking news or popular on-demand video clips can be broadcast – off- loading the network and providing users with a superior experience. Single-frequency network (SFN) tech- nology is used to distribute broadcast streamsintowell-definedareas–where allcontributingcellssendthesamedata duringexactlythesameradiotimeslots. The size of the coverage area of an LTE SFN can vary greatly, from just a few cells serving a stadium, to many cells delivering content to an entire coun- try. eMBMS-enabled devices can select 4 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 Capture your audience
  5. 5. solution. The concept has been built on eMBMS technology and based on a set ofusecasesthatcanbedividedintotwo maincategories deliveryoflivepremiumcontent;and unicastoff-loading(forexample,local devicecaching). Premiumcontent Despite the diversity of available con- tentandanobviousshiftbysubscribers towardson-demandviewing,watching certaineventsandprogramslivecontin- uestoappealtolargeaudiences. London 2012 is a good example of an event that enjoyed widespread live- viewing appeal. Ratings place the NBC coverage of the games as some of the most watched TV in US history; almost half of the online video streams were delivered to tablets or smartphones, and revenue expectations were far sur- passed. Some use cases for premium contentfollow. Regional and local This use case covers regional and local interestevents,suchasconcerts,sports fixtures or breaking news. Such as the Super Bowl, FIFA World Cup matches, aswellaselectionsandroyalweddings. Givensuitablecontentsecurityanddig- ital-rights handling, this use case can beenhancedtoallowuserstostoreand replay the event on-demand from their deviceforacertainperiodoftime. Venue casting This use case covers specific locations such as shopping malls, museums, air- ports, university campuses and amuse- ment parks. In this case, the operating enterprise may wish to broadcast con- tent to users, which can vary from breaking news of national interest to very specific information such as special offers available at the mall, ­additional information about the main artistofanartexhibition,ordepartures and­arrivalsinformationattheairport. Forallofthesepremium-contentuse cases, operators can deliver services on a nationwide basis as well as ­locally. The duration of a broadcast and the size of the geographical area where it is available can be managed dynami- cally, depending on the nature and rel- evance of the content. By using unicast forblendedservices,broadcastservices can be complemented with interactiv- ity – opening up new ways to generate revenuefromcontent. Atasoccermatch,forexample,these value-added services could include ­video streams carrying footage from additionalcameraangles,diverseaudio coverage and live results of related matches taking place at the same time inotherstadiums. Unicastoff-loading MBMSsaretraditionallyassociatedwith the delivery of live, linear TV, although this technology also supports file deliv- ery. Exploiting this and the caching capability available in both mobile and fixed devices creates new possibilities forarangeofusecases. Popular content Operators can choose to deliver popu- lar TV and video clips to the local cache of a user’s device at their convenience. Based on content popularity and busy- hour-trafficdistribution,operatorscan deliver content when network load is low. Content shared on popular vid- eo streaming sites, as well as the con- tent provided by national and cable TV channels can all be pre-loaded to mobiledevicesthroughbroadcast–sig- nificantlyreducingtheoverallnetwork capacityrequiredtodeliverfrequently- consumedvideostreams. News Daily clips and subscription content suchasamagazinecanbepre-delivered to the cache of a subscriber’s preferred deviceforthatcontent. Software upgrades Upgrades to application software and operating systems are usually released over the network to large numbers of subscribers at the same time. This tra- ditional way of performing an upgrade can be a burden on the network. By using LTE Broadcast instead, upgrades can be distributed as packages to a multitude of devices at little expense in terms of required resources – an approach that is particularly advanta- geous if the broadcast can be delivered duringoff-peakhours. X % Broadcast FIGURE 1 Broadcast versus unicast Y%,Y% Y%, Y% Y%, Y% Unicast Table 1: Broadcast versus unicast Broadcast One data channel per content Limited data channels, unlimited number of users Resource allocation viewer independent Unicast One data channel per user Unlimited channels, limited number of users Resources allocated when needed 5 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014
  6. 6. the radio-channel quality and overall trafficvolumeswithinthecell. Broadcast is implemented as an extension to the existing EPS architec- ture(seeFigure 7andBox B).Ericsson’s LTE Broadcast system is mainly a soft- wareupgradeappliedtoexistingnodes. The concept was designed according to 3GPP MBMS 23.246 for E-UTRAN and to coexist with unicast-data and voice services. LTE Broadcast gives operators the flexibility to tailor the way content is deliveredtosuittheircapabilities. Servicedynamics This supports live streaming and file- delivery use cases. Different service combinations may be delivered simul- taneouslyoverthesamebearer. Timedynamics LTE Broadcast activation triggers the allocation of radio resources on a needs basis.Asessionmaybeactiveforashort time say several minutes or for longer periods: several days in some cases. Whenthesessionisnolongeractive,the assignedradioandsystemresourcescan bereallocatedforusebyotherservices. Locationdynamics LTEBroadcastcanbeactivatedforsmall geographical locations, such as stadi- ums and city centers, or for large areas, covering say an entire city or region. As long as there is sufficient capacity in the network, multiple broadcast ses- sionscanbeactivesimultaneously. Resourceallocationdynamics This involves the free allocation of resources for LTE Broadcast. Up to 60 percent of the FDD radio resources and upto50percentforTDDcanbeassigned toabroadcasttransmission. Principlesoftheradiointerface The LTE radio interface is based on OFDM in the downlink, where the fre- quency selective wideband channel is subdivided into narrowband chan- nels orthogonal to each other. In time domain, a 10ms radio frame consists of subframes of 1ms each; where a sub- frame is the smallest unit with full fre- quencydomainthatcanbeallocatedto abroadcasttransmission. With eMBMS, all users within the M2M and B2B Over the coming decade, machine-to- machine (M2M) data traffic and the internet of things will create more connectivity demands on the network and create the need for diverse types of eMBMS LTE-enabled devices. LTE Broadcasttechnologysupportsefficient one-to-many transfer of machine data inanyfileformat,whichcanbeusedfor M2Musecases,off-loadingthenetwork and providing the essential machine connectivityandcontrol. Ericssonvalueproposition TheconceptofEricsson’sLTEBroadcast solution enables unicast and broadcast service blending, aiming to help meet the challenges created by rising mobile usageandthegrowthofvideotrafficin LTE networks. The solution covers the entirechainfromliveencoder,through delivery via point-to-multipoint trans- porttodevices. Particular focus has been placed on the specification and implementation ofthedevice,startingwiththephysical chipsetaswellastransportcontrolmid- dleware–essentialenablersforthecre- ationanddeploymentofeMBMSs. Implementing live streaming with MPEG-DASH4 isatechnologychoicethat supports the common use of a player on devices and a live encoder head-end system for both unicast and broadcast – reducing operating costs and maxi- mizing infrastructure usage. As out- lined later in this article, extensive simulation, lab testing and field trials have been conducted with the aim of characterizing the spectral efficiency of eMBMSs in deployed networks with mixedtrafficprofiles. Theresultsshowthatlivevideobroad- cast with commercially acceptable lev- els of video and audio degradation is achievable. For video broadcasting to smartphones and tablets, compression using the H.2645 standard is feasible, with HEVC6 coming sometime in the nearfuture. Systemarchitecture Broadcast and unicast radio channels coexist in the same cell and share the available capacity. The subset of avail- ableradioresourcescantemporarilybe assignedtoabroadcastradiochannel. Mobile-communicationsystemssuch asLTEaretraditionallydesignedforuni- cast communication, with a separate radio channel serving each device. The resourcesallocatedtothedevicedepend onthedataraterequiredbytheservice, Sector edge multipath gain Maximum usable set of subframes Radio frame = 10ms Subframe = 1ms bandwidth 0 1 2 3 4 5 6 7 8 9 0 1 t Cell C1 C1 C2 Cell C2 FIGURE 2 SFN principles 6 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 Capture your audience
  7. 7. broadcast area, provided they have the right subscription level and an MBMS- capable device, can receive broadcast- edcontent.Bysettingupasinglebearer over the radio interface, operators can distribute a data stream to an unlimit- ednumberofusers. Although it is possible to deliver broadcasts within a single cell, the con- cept becomes truly interesting with SFN, the principles of which are illus- tratedinthelowerpartofFigure 2. Broadcast data is sent over synchro- nized SFN – tightly synchronized, identical transmissions from multiple cells, using the same set of subframes and modulation and coding schemes, appear to the device as a transmission from a single large cell over a time-dis- persivechannel.Thisimprovesreceived signalqualityandspectralefficiency(as shown in Figure 2). For a more detailed description, refer to LTE/LTE-Advanced forMobileBroadband7 . Themaximalusablesetofsubframes is shown in the top left of the diagram, andthenodesaretime-synchronizedto ahighprecision. By using long data-symbol duration in OFDM, it is possible to mitigate the effect of inter-symbol interference (ISI) caused by delayed signals. For addi- tional protection against propagation delays LTE/OFDM uses a guard interval – delayed signals arriving during the guard interval do not cause ISI and so the data rate can be maintained. For SFN,unlikeunicast,signalsarrivefrom many geographically separate sources andcanincurlargedelayspread. Consequently, one of the factors lim- itingMBMScapacityisself-interference from signals from transmitters with a delay that is greater than the guard interval (low transmitter density). To overcome this, a long cyclic prefix is added to MBSFN-reserved subframes to allow for the time difference in the receiver and corresponds to an ISD of approximately5km. Architecture The eMBMS architecture, shown in Figure  3, is designed to handle trans- missionrequirementsefficiently. The Broadcast Multicast Service Center (BM-SC) is a new network ele- ment at the heart of the LTE Broadcast- distribution tree. Generic files or MPEG-DASH live video streams are carried as content across the BM-SC and made available for broadcast. The BM-SC adds resilience to the broadcast by using AL-FEC – which adds redun- dancy to the stream so that receivers canrecoverpacketlosses–andsupports the 3GPP-associated delivery proce- dures. These procedures include uni- castbasefilerepair–allowingreceivers to fetch the remaining parts of a file through unicast from the BM-SC and reception reporting, so operators can collect QoE reports and make session- qualitymeasurements. Anothernewnetworkelementisthe MBMS-GW,whichprovidesthegateway functionbetweentheradioandservice networks.Itforwardsstreamsfromthe BM-SC to all eNBs participating in the SFN transmission. IP multicast is used on the M1 interface between the gate- wayandtheeNBs,sothatthepacketrep- licationfunctionofexistingrouterscan be used efficiently. The gateway routes MBMS session control signaling to the MMEs serving the area. The MMEs in turn replicate, filter and forward ses- sioncontrolmessagestotheeNBspartic- ipatinginthespecificbroadcastsession. The eNBs provide functionality for configuration of SFN areas, as well as broadcasting MBMS user data and MBMS-related control signaling on the radio interface to all devices. Note, the eNB contains the 3GPP Multicell CoordinationEntity(MCE)function. eMBMS LTE-enabled devices are an essential part of the ecosystem. LTE capabilities are becoming inte- grated into more and more types of devices and may be implemented on devices other than phones and tablets such as embedded platforms for M2M communications. TheUEplatformisdividedintothree mainblocks(seeFigure  4): thelowerblockincorporatestheLTE radiolayers,whicharetypically implementedintheLTEchipset, supportingunicastaswellasbroadcast; themiddlewareblockhandlestheFLUTE protocol8 ,AL-FECdecoding,unicastfile repairandotherfunctions.Itincludes transportcontrolfunctions,suchas servicescheduling,aswellasacachefor post-broadcastfileprocessing;and thetopplatformblockexposesAPIsto themiddlewareandconnectivitylayer methods. Application development is enabled through an SDK, which provides the platform APIs. The SDK enables developers to create and test Unicast S1-U S11 Sm SGi SGmb SGi-mb M3 / S1-MME M1 S/PDN-GW BM-SC MBMS-GW eNB eNB eNB MME Content Control User data FIGURE 3 Architecture – with only eMBMS components shown 7 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014
  8. 8. eMBMS-enabled applications with- outrequiringdetailedknowledgeofthe underlying transport,control,orradio- bearertechnology. Spectralefficiency According to 3GPP specifications, eMBMSs and unicast services should be provisioned on a shared frequency. Consequently,whileabroadcastservice is active, radio-interface resources can beborrowedfromunicastcapacity. Spectral efficiency can be defined as the possible information rate trans- mitted over a given bandwidth with a defined loss rate. The information loss rate depends on the modulation and coding scheme used for physical trans- missions and the protection offered by AL-FEC. This definition of spectral effi- ciency includes packet overheads, such asAL-FECredundancy. Thesimulationresultsfromanevalu- ationofspectralefficiencyareshownin Figure  5.Theresultsassociatedwitha broadcast transmission depend on the ISD in a link budget – signal-to-noise ratio (SNR) – limited deployment. Two urban environments were simulated: indoorscenarioswith20dBpenetration loss and in-car scenarios with 6dB loss assuming95percentcoverageprobabil- ityinallcases. The failure criterion used was 10-3 BLER (corresponding to a packet loss of four packets per hour) and simulations were run with and without AL-FEC. An ideal Raptor code with FEC covering 2s persourceblockwasusedinthisevalu- ation.Thepayloadforeachsourceblock consisted of 50 packets with each IP packetspanningtwotransportblocks. TheMBSFNsimulationarea­-included 19 sites, each with three sectors. The results show that MBMS spectral effi- ciencyofabout1-3bps/Hz(indoor/in-car) couldbeachievedforacellularISDofup to2km.Thesimulationresultsandaddi- tional testing show that FEC improves videoqualityandsavescapacity. FromthegraphsinFigure 5,itispos- sible to conclude that when ISD is less than 1km, spectral efficiency is great- erthan2.5b/s/Hz.Byallocatingonesub- frameforMBMStransmissionin20MHz spectrum, corresponding to 10 percent ofcapacity,theachievabledatarateisin therangeof5Mbps.  Livevideoandfiledelivery ThetwomaineMBMSusecasesarelive streaming and on-request file delivery. Live streaming supports services for real-time video and audio broadcast- ing,andon-requestfiledeliveryenables services such as unicast off-load (local device caching), software updates and M2M file loading. In fact, any arbitrary fileorsequenceoffilescanbedistribut- edovereMBMSs. The target broadcast area for these usecasesmaybeanydesiredsize–some scenarios require a small broadcast area,suchasavenueorashoppingmall, and other cases require much larger areas,evenuptonationwidecoverage. Ericsson has selected MPEG-DASH for live streaming delivery over eMBMSs. This solution slices the live stream into a sequence of media segments, which are then delivered through the system asindependentfiles. Typically, HTTP is used to fetch these —— 0 1 2 3 4 5 6 7 8 9 0 0.5 1.0 1.5 2.0 2.5 3.0 ISD (km) Spectral efficiency (b/s/Hz) w/o AL-FEC AL-rBLER=1e-3 AL-rBLER=1e-5 indoor; - - - in-car FIGURE 5 Evaluating spectral efficiency SGmb SGi-mb BM-SC Platform APIs eMBMS middleware LTE chipset (L1, L2, L3) User equipment SDK App download LTE Broadcast and unicast network Content FIGURE 4 UE and SDK in eMBMS ecosystem BOX B   Standards­ The standard­ ization of MBMS started in 3GPP with Rel-6, which supported GERAN and UTRAN access networks. Over time, 3GPP has improved the access network support by, for example, defining the integrated mobile broad­ cast (IMB) solution, which uses UTRAN TDD bands to offer up to 512kbps per content channel. Support for E-UTRAN access (LTE) was added to 3GPP Rel-9 as part of the eMBMS standardization activity. 8 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 Capture your audience
  9. 9. files.IntheeMBMScase,onequalityrep- resentationisdeliveredasasequenceof files through eMBMSs using MBMS file delivery. By using MPEG-DASH with eMBMSs, the same live encoder and common clients can be used for unicast and broadcast offerings. This solution also supports using the same system proto- col stack for both live streaming and file-deliveryimplementation. The IETF FLUTE protocol8 allows dis- tribution of files over unidirectional links using UDP. Most service-layer fea- tures can be used for both streaming andfiledelivery;transmissionreliabili- tycanbeincreasedusingAL-FECinboth cases.Filedeliverycanalsomakeuseof theunicastfile-repairfeature–allowing UEs to fetch any missing file segments. However, this feature is not intended forusewithservicesthathavereal-time requirements,suchaslivestreaming. With FLUTE, delivery and eMBMS sessions are used, where the duration of a delivery session may span one or more eMBMS sessions. The broadcast is active for the entire eMBMS session, during which UEs can receive content. The relationship between delivery ses- sions and eMBMS sessions is shown in Figure  6. Service announcement is used to inform devices about delivery sessionsandalsoabouteMBMSsessions usingascheduledescription.UEsdonot need to monitor the radio interface for eMBMSsessionscontinuously. InFigure 6,the scheduledescription instructs the UE to expect an eMBMS sessionbetweent2 andt3 andbetweent6 andt7.BeforetheUEexpectsaneMBMS session, it is already active on the radio interface (t1 t2). When it comes to file- delivery services, it is preferred that devices should search for sessions prior to expected transmission time on the radio, to ensure that they do not miss thestartofatransmission. TheexampleinFigure 6couldrepre- sent a service, such as downloading an applicationthatallowsuserstoactivate, receive and interact with the broadcast usingunicastservicesfromaphone,tab- letortelevision. From the point of view of the user andtheUEmiddleware,thetwobroad- castsbelongtothesameMBMSuserser- vice,whichpresentsacompleteoffering includingactivationanddeactivation. Conclusions The data volume in mobile networks is booming mostly due to the success of smartphonesandtablets. LTE Broadcast is one way of provid- ing new and existing services in areas that can at times be device dense, such as stadiums and crowded city centers. Single-frequency network technology Service announcement informs the UE about the schedule t2 to t3 UEs expects to receive data of that FLUTE session t6 to t7 UEs expects to receive data of that FLUTE session Service announcement informs the UE about the schedule eMBMS session Service announcement Delivery session (FLUTE) eMBMS session t1 t2 t3 t4 t5 t6 t7 t8 Time FIGURE 6 Example of two scheduled broadcasts is used to distribute the content over theairinterface. LTE Broadcast provides operators with techniques to deliver consistent service quality, even in highly crowded areas. Such techniques for delivering content efficiently are valuable as they free up capacity, which can be used for otherservicesandvoicetraffic. App FR/RR (HTTP) HTTP SGiS5/S8 S1-U S11 S1-MME M3 M1 SmUu SGmb SGi-mb UE eNB MBMS-GW SGW PGW BM-SC Application server CDN/ live encoder MME FIGURE 7 eMBMS architecture 9 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014
  10. 10. Michael Slssingar is an Ericsson senior specialist in service delivery architectures and holds a post-graduate diploma and master’s in computing and software engineering. He has held many senior engineering roles at Ericsson, mainly in the media-delivery field, and has contributed to the Ericsson IPTV and Mobile TV delivery solutions. In the field of MBMS, Slssingar initially specialized in WCDMA MBMS, where he helped develop the Ericsson Content Delivery System. More recently, he has worked with LTE eMBMS broadcast, where he has a strong interest in the service layer BM- SC node, UE middleware and metadata provisioning areas. Thorsten Lohmar joined Ericsson in Germany in 1998 and worked in different Ericsson Research units for several years. He worked on a variety of topics related to mobile- communication systems and led research projects specifically in the area of multimedia technologies. On the development front, he is focusing on the technical coordination of eMBMSs with an end-to-end perspective. He is currently working as a senior specialist for end-to-end video delivery, principally in mobile networks. Lohmar holds a Ph.D. in electrical engineering from RWTH Aachen University, Germany. 1. Ericsson, 2012, Ericsson ConsumerLab report, TV and video – changing the game, available at: http:// consumerlab-tv-video-changing-the-game.pdf 2. Ericsson, November 2012, Ericsson Mobility Report, On the pulse of the Networked Society, available at: http://www. november-2012.pdf 3. Mobile Content Venture, June 2012, Dyle Mobile TV Data Report, available at: DyleReport.pdf 4. ISO/IEC 23009-1:2012, Information technology – Dynamic adaptive streaming over HTTP (DASH) — Part 1: Media presentation description and segment formats, available at: catalogue_detail.htm?csnumber=57623 5. ITU-T H.264 Advanced video coding for generic audiovisual services, available at: 6. ITU-T H.265 / ISO/IEC 23008-2 HEVC, available at: aspx?AAPSeqNo=2741 7. Erik Dahlman, Stefan Parkvall, Johan Sköld, 2011, LTE/LTE-Advanced for Mobile Broadband, available at: lte-lte-advanced-for-mobile-broadband/ dahlman/978-0-12-385489-6 8. IETF RFC 3926, FLUTE – File delivery over unidirectional transport, T. Paila, et al., October 2004, available at: http:// References Vera Kenehan is a strategic product manager within LTE Radio and has worked with several generations of radio-access technologies, including LTE, WCDMA and PDC. She was largely involved in the initial standardization of LTE, including eMBMS. For the past two years, she has been working on the MBMS product as well as promoting and bringing eMBMS to the market. She holds a master’s in telecom engineering from the University of Belgrade, Serbia. Stig Puustinen is a senior project manager at System Management within Business Unit Networks, where he is currently running an LTE/ EPC systems project involving extensive eMBMSs work. He joined Ericsson in 1991, and has since held a variety of project- and program- management roles. He was involved in the early releases of GSM, the first introduction of WCDMA/HSPA and the first release of LTE/EPC. 10 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 Capture your audience
  11. 11. Nine decades of innovation Automatic exchanges to smart networks The history of our technology is deeply entrenched in that of the telecoms industry. War, international terrorism, and developments in other industries such as railways and the morerecentdigitalrevolutionhaveshapedourplayingfield. Our technical expertise is not just based on theory; it is about how to apply the right technology to create commer- cially viable products. Standards – and the ability to create and evolve them – have helped us and our industry become globalprovidersofinteroperablesolutions–acornerstoneof theNetworkedSociety. Overthepastninedecades,theworldhasprobablychanged more than ever before. Here are a few highlights from Ericsson’s history and some of the world events that have playedtheirpartintheevolutionoftelecoms. In 1924, Ericsson launched its automatic 500-point sys- tem. Highlighted in the very first issue of Ericsson Review, this revolutionary switching system was demonstrated at the Gothenburg Exhibition of 1923. In hindsight, it sounds curious that attendees could ‘watch’ the switching process, whichatthetimewasmechanical.Bythe1930s,Ericssonhad deliveredabout100systemswithatotalofmorethan350,000 lines. Sales of the system continued to rise over the coming decades, not declining significantly until the 1970s. By 1974, 4.8 million lines using this system were in operation in pub- lictelephonestations. The very first 500-point system was put into service at the Norra Vasa exchange in Stockholm, and was still in operation 60 years later. At the time of installation in 1924, Televerket–theSwedishgovernmentagencyfortelecommu- nications (1853-1993) – had four different systems to choose from,includingacrossbarsystemalsodevelopedbyEricsson. Televerket’s choice was a decisive one for the future develop- mentofEricsson. In the 1920s and 1930s, the opening of a new telephone exchange was a major event for small towns and villages. Official opening ceremonies were often carried out by the localmayor,tothebackdropofabrassbandandrefreshments providedforthelocalsbytheoperatorandthevendor. Inthe1930s,Ericssonintroducedaphotoelectricannounc- ing machine – a simple device that could deliver short prere- corded messages. This offloaded the work of operators and hadtheability to deliver longerannouncements,suchasthe speakingclockand–laterinthedecade–automaticweather forecasts. The first device for weather forecasts was put into service in Stockholm on June 1, 1936 and was the first of its kind in the world. It wasn’t until two decades later that they werereplacedwithnewertechnologies. Inthe1940s,Ericssonintroducedaninformationmanage- mentstructurecalledtheABCSystem.Ericssonstillusesthis system to classify and manage its information and products. Continuedon page19... ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 11 Re:view The Roaring Twenties In 1924, in the very first issue of Ericsson Review, the editor stated that the objective of the magazine was to take up points of design and construction, which had not yet reached final standardization, for discussion. The cover article featured Ericsson’s presence at the Gothenburg Exhibition (1923), where a giant replica of our standard table set telephone housed a complete Ericsson exchange for 500 lines, to which a few telephones were connected. Visitors could make calls and watch the switching process, through the plate-glass windows. Depression and modernism The cover of issue 2, 1934 shows the ‘photo-electric talking machine for automatic time indication.’ This issue included an account of a carrier system supplied by Ericsson to the Indian Radio and Communications Company. In the spirit of modernism, this issue included a number of articles relating to the use of clocks and timing mechanisms in industry. An article on party lines discussed the problem of connecting several telephone instruments to one line. This was of particular interest at the time, as exchanges in rural districts were being automated and party lines were in need of some degree of modification. One of the main concerns was how to use party lines without altering the subscriber equipment. The war years Ericsson Review was not published in English between 1940 and 1944 due to the ongoing world war. Apart from the fact that the paper situation necessitated a reduction both of quantity and quality of printing paper, the journal was issued as usual in its Swedish edition during the war years. In 1945, a collection of some of the articles published during the war in Swedish were printed in a composite English language edition. Ericsson Review, issues 1 2, 1924. Ericsson Review, issue 2, 1934.
  12. 12. Non-line-of-sight microwave backhaul for small cells The evolution to denser radio-access networks with small cells in cluttered urban environments has introduced new challenges for microwave backhaul. A direct line of sight does not always exist between nodes, and this creates a need for near- and non-line-of-sight microwave backhaul. solution that is also effective for small- cellbackhaul(seeFigure 1). Network architects aim to dimen- sion backhaul networks to support peak cell-capacity3 – which today can reach 100Mbps and above. However, in reality, there is a trade-off among cost, capacity and coverage resulting in a backhaul solution that, at a minimum, can support expected busy-hour traffic with enough margin to account for sta- tistical variation and future growth: in practicearound50Mbpswith availabil- ity requirements typically relaxed to 99-99.9percent.Suchavailabilitylevels requirefademarginsoftheorderofjust afewdecibelsforshort-linkdistances. For small-cell backhaul simplicity andlicensingcostareimportantissues. Light licensing or technology-neutral block licensing are attractive alterna- tives to other approaches such as link licensing, as they provide flexibility4 . Using unlicensed frequency bands can be a tempting option, but may result in unpredictableinterferenceanddegrad­ ed network performance. The risk associated with unlicensed use of the 57-64GHz band is lower than that asso- ciated with the 5.8GHz band, owing to higheratmosphericattenuation,sparse initial deployment, and the possibility of using compact antennas with nar- row beams, which effectively reduces interference. Providingcoverageinlocationswith- outaclearlineofsightisafamiliarpart of the daily life of mobile-broadband and Wi-Fi networks. However, maybe because such locations are common- place, a number of widespread myths and misunderstandings surrounding NLOS microwave backhaul exist – for example, that NLOS microwave back- haulneedssub-6GHzfrequencies,wide- beam antennas and OFDM-based radio Complementingthemacro-celllayerby addingsmallcellstotheRANintroduc- es new challenges for backhaul. Small- cell outdoor sites tend to be mounted 3-6m above ground level on street fix- tures and building facades, with an inter-sitedistanceof50-300m.Asalarge number of small cells are necessary to support a superior and uniform user experience across the RAN2 , small-cell backhaulsolutionsneedtobemorecost- effective, scalable, and easy to install than traditional macro backhaul tech- nologies. Well-known backhaul tech- nologies such as spectral-efficient LOS microwave, fiber and copper are being tailored to meet this need. However, owing to their position below roof height, a substantial number of small cellsinurbansettingsdonothaveaccess toawiredbackhaul,orclearlineofsight to either a macro cell or a remote fiber backhaulpointofpresence. The challenges posed by locations withoutaclearlineofsightarenotnew to microwave-backhaul engineers, who use several established methods to overcome them. In mountainous terrain, for example, passive reflectors and repeaters are sometimes deployed. However, this approach is less desir- able for cost-sensitive small-cell back- haul,asitincreasesthenumberofsites. In urban areas, daisy chaining is often usedtoreachsitesintrickylocations–a JONAS HANSRYD, JONAS EDSTAM, BENGT-ERIK OLSSON AND CHRISTINA LARSSON BOX A Terms and abbreviations FDD frequency division duplexing LOS line-of-sight MIMO multiple-input, multiple-output NLOS non-line-of-sight OFDM orthogonal frequency division multiplexing RAN radio-access network TDD time division duplexing Using non-line-of-sight (NLOS) propagation is a proven approach when it comes to building RANs However, deploying high-performance microwave backhaul in places where there is no direct line of sight brings new challenges for network architects. The traditional belief in the telecom industry is that sub-6GHz bands are required to ensure performance for such environments. This article puts that belief to the test, providing general principles, key system parameters and simple engineering guidelines for deploying microwave backhaul using frequency bands above 20GHz. Trials demonstrate that such high-frequency systems can outperform those using sub- 6GHz bands – even in locations with no direct line of sight. Point-to-point microwave is a cost-­ efficient technology for flexible and rapid backhaul deployment in most locations. It is the dominant backhaul medium for mobile networks, and is expected to maintain this position as mobile broadband evolves; with micro- wave technology that is capable of pro- vidingbackhaulcapacityoftheorderof severalgigabits-per-second1 . 12 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 Dispelling the NLOS myths
  13. 13. technologies to meet coverage and capacity requirements. Despite this, a number of studies on NLOS transmis- sionusingfrequencybandsabove6GHz, for example, have been carried out for fixed wireless access5 and for mobile access6 . Coldrey et al. showed that it is realistic to reach 90 percent of the sites in a small-cell backhaul deploy- ment with a throughput greater than 100Mbps using a paired 50MHz chan- nelat24GHz7 . NLOSprinciples AsillustratedinFigure 1,allNLOSprop- agation scenarios make use of one or moreofthefollowingeffects: diffraction; reflection;and penetration. Allwaveschangewhentheyencounter an obstacle. When an ­electromagnetic wave hits the edge of a building, dif- fraction occurs – a phenomenon often described as the bending of the signal. Inreality,theenergyofthewaveisscat- tered in the plane perpendicular to the edge of the building. The energy loss – which can be considerable – is propor- tionaltoboththesharpnessofthebend andthefrequencyofthewave8 . Reflection,andinparticularrandom multipath reflection, is a phenomenon that is essential for mobile broadband usingwide-beamantennas.Single-path reflectionusingnarrow-beamantennas is, however, more difficult to engineer owing to the need to find an object that can provide the necessary angle of inci- dencetopropagateasdesired. Penetrationoccurswhenradiowaves pass through an object that completely or partially blocks the line of sight. It is a common belief that path loss result- ing from penetration is highly depen- dent on frequency, which in turn rules out the use of this effect at higher fre- quencies.However,studieshaveshown that in reality path loss due to penetra- tion is only slightly dependent on fre- quency,andthatinfactitisthetypeand thicknessoftheobjectitselfthatcreates theimpactonthroughput9,10 .Forexam- ple, thin, non-metallic objects – such as sparse foliage (as shown in Figure 1) – addarelativelysmallpathloss,evenfor highfrequencies. Deployment guidelines can be defined given a correct understanding and application of these three propaga- tion effects, giving network engineers simple rules to estimate performance foranyscenario. Systemproperties A simplified NLOS link budget can be obtainedbyaddinganNLOSpathatten- uation term (ΔLNLOS) to the traditional LOSlinkbudget,asshowninEquation 1. Equation1 PRX=PTX +GTX +GRX -92-20log(d)-20log(f)-LF -ΔLNLOS Here, PRX and PTX are the received and transmittedpower(dBm–ratioofpow- er in decibels to 1 milliwatt); GTX and GRX areantennagain(indecibelsisotro- pic–dBi)forthetransmitterandreceiv- er respectively; d is the link distance (in kilometers); f is the frequency (in gigahertz); LF is any fading loss (in deci- bels); and ΔLNLOS is the additional loss (in decibels) resulting from the deploy- ment of NLOS-propagation effects. Not shown in this equation is the theoreti- calfrequencydependencyoftheanten- na gain, which for a fixed antenna size will increase as 20log(f) and as a conse- quence, the received signal – PRX – will actually increase as 20log(f) when car- rier frequency is increased for a fixed antenna size. This relationship indi- catestheadvantageofusinghigherfre- quenciesforapplicationswhereasmall antenna form factor is of importance –asisthecaseforsmall-cellbackhaul. To determine the importance of NLOS-system properties, Ericsson car- riedoutmeasurementtestsontwocom- merciallyavailablemicrowavebackhaul systems in different frequency bands (described in Table 1). The first system used the unlicensed 5.8GHz band with a typical link configuration for applica- tionsinthisband.Theairinterfaceused up to 64QAM modulation in a 40MHz- wide TDD channel with a 2x2 MIMO (cross-polarized) configuration pro- viding full duplex peak throughput of 100Mbps (200Mbps aggregate). The sec- ond system, a MINI-LINK PT2010, used a typical configuration for the licensed 28GHz band, based on FDD, 56MHz channel spacing and single-carrier technology with up to 512QAM modu- lation, providing full duplex through- put of 400Mbps (800Mbps aggregate). To adjust the throughput based on the quality of the received signal, both FIGURE 1 Microwave backhaul scenarios for small-cell deployment Daisy chain Penetration Reflection Diffraction Fiber Table 1: Test system specifications SYSTEM TECHNOLOGY CHANNEL SPACING ANTENNA GAIN OUTPUT POWER PEAK THROUGHPUT 5.8GHz TDD/OFDM 64QAM 40MHz 17dBi 19dBm 100Mbps 28GHz FDD/single carrier 512QAM 56MHz 38dBi 19dBm 400Mbps 13 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014
  14. 14. Here, the margin is defined as the difference between received power (accordingtoEquation1)andthereceiv- er threshold for a particular modula- tion level (throughput) – in line of sight conditions without fading (Lf = 0). If ΔLNLOS caused by any NLOS effect can bepredicted,thecurvesinFigure 2can be used to estimate throughput. The advantagesofusinghigherfrequencies areclear:withcomparableantennasiz- es,thelinkmarginisabout20dBhigher atapeakrateof400Mbpsforthe28GHz system compared with the 5.8GHz sys- tematapeakrateof100Mbps. Measurements Diffraction It is commonly believed that the dif- fractionlossesoccurringatfrequencies above 6GHz are prohibitively high, and consequently,deployingasystemusing thiseffectforNLOSpropagationatsuch frequencies is not feasible. However, even if the absolute loss can be relative- ly high, 40dB and 34dB for the 28GHz and 5.8GHz systems respectively (with a diffraction angle of 30 degrees), the relative difference is only 6dB8 – much lessthanthedifferenceingainforcom- parable antenna sizes even when tak- ing into account the higher free-space lossforthe28GHzsystem(seeFigure 2). Figures 3A and 3B show the set- up and measured results of a scenario designedtotestdiffraction.Afirstradio was positioned on the roof of an office building (marked in Figure 3A with a whitecircle).Asecondradiowasmount- ed on a mobile lift, placed 11m behind a 13m-high parking garage. The effect onthesignalpowerreceivedbythesec- ondradiowasmeasuredbyloweringthe mobile lift. Figure 3B shows the mea- sured received signal-power versus dis- tance below the line of sight for both test systems, as well as the theoretical receivedpowercalculatedusingtheide- alknife-edgemodel8 .Bothradiostrans- mitted 19dBm output power, but due to the 21dBi lower antenna gain for the 5.8GHz system, the received signal for this radio was 20dB weaker after NLOS propagationthanthe28GHzsystem. The measured results compare well againsttheresultsbasedonthetheoreti- calmodel,althoughanoffsetofacouple ofdecibelsisexperiencedbythe28GHz system–asmalldeviationthatisexpect- edduetothesimplicityofthemodel. To summarize, diffraction losses can be estimated using the knife-edge ­model8 . However, due to the model’s simplicity, losses calculated by it are slightly underestimated. This can be compensated for in the planning pro- cess by simply adding a few extra deci- belstothelossmargin. systems used adaptive modulation. Physicalantennasizesweresimilar,but duetothefrequencydependencyofthe antenna gain and the parabolic type used in the 28GHz system, it offered a gain of 38dBi while the flat antenna of the5.8GHzsystemreached17dBi. Link margin versus throughput and hop distance is shown in Figure 2. Link distance (m) Link margin (dB) 80 70 60 50 40 30 20 10 50 100 150 200 250 300 350 400 450 500 28GHz 5.8GHz 90Mbps 185Mbps 280Mbps 10Mbps 60Mbps 80Mbps 100Mbps 400Mbps FIGURE 2 Link margin as a function of throughput and distance 14 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 Dispelling the NLOS myths FIGURE 3A Test site for NLOS backhaul – diffraction 150m © 2013 BLOM © 2013 Microsoft Corporation
  15. 15. The 28GHz system can sustain full throughput at much deeper NLOS than the 5.8GHz system, which is to be expected as it has a higher link mar- gin. Full throughput – 400Mbps – was achieved at 28GHz up to 6m below the line of sight, equivalent to a 30-degree diffractionangle,whilethe5.8GHzsys- tem dropped to under 50Mbps at 3m below the line of sight. The link mar- ginisthesinglemostimportantsystem parameterforNLOSpropagationand,as expected, the 28GHz system performs in reality better in a diffraction scenar- io than a 5.8GHz system with compara- bleantennasize. Reflection The performance characteristics of the 5.8GHz and 28GHz systems were mea- sured in a single-reflection scenario in an area dominated by metal and brick facades – shown in Figure 4A. The firstradiowaslocatedontheroofofthe office building (marked with a white circle),18mabovegroundlevel;andthe second on the wall of the same build- ing, 5m above ground, facing the street canyon.Thebrickfacadeofthebuilding on the other side of the street from the second radio was used as the reflecting object,resultinginatotalpathlengthof about100m.Thereflectionlosswillvary with the angle of incidence, which in thiscasewasapproximately15degrees, resulting in a ΔLNLOS of 24dB for the 28GHz system and 16dB for the 5.8GHz system–figuresthatareinlinewithear- lier studies11 . Reflection loss is strongly dependentonthematerialofthereflect- ing object, and for comparison purpos- esΔLNLOS foraneighboringmetalfacade was measured to be about 5dB for both systemswithsimilarangleofincidence. To summarize, it is possible to ­cover areas that are difficult to reach using multiple reflections in principle. However, taking advantage of more thantworeflectionsisinpracticeprob- lematic – due to limited link margins and the difficulty of finding suitably aligned reflection surfaces. ΔLNLOS pre- dictions for a single-facade reflection in the measured area can be expect- ed to vary between 5dB and 25dB at 28GHz and between 5dB and 20dB at 5.8GHz. The throughput for both sys- tems measured over 16 hours is shown inFigure 4B. The 28GHz system shows a stable throughput of 400Mbps, while the throughputforthe5.8GHzsystem,with a much wider antenna beam, dropped from 100Mbps to below 70Mbps. These variations are to be expected owing to the fact that the wider beam expe- riences a stronger multipath. OFDM is an effective mitigation technolo- gy that combats fading, which will, at severe multipath fading, result in a graceful degradation of throughput – as illustrated. However, the narrow ­antenna lobe at 28GHz, in combina- tionwiththeadvancedequalizerofthe high-­performance MINI-LINK radio, effectively suppresses any multipath degradation, enabling the use of a sin- gle-carrier QAM technology for NLOS conditions – even up to 512QAM and 56MHzchannelbandwidths. FIGURE 3B Throughput and received power – diffraction FIGURE 4A Test site for NLOS backhaul – reflection 100m Distance below line of sight (m) Throughput (Mbps) Received power (dBm) 700 600 500 400 300 200 100 0 -10 -20 -30 -40 -50 -60 -70 -80 –2 0 2 4 6 8 10 Received power 28GHz Received power 5.8GHz Theoretical power 28GHz Theoretical power 5.8GHz Throughput 28GHz Throughput 5.8GHz 15 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 © 2012 TerraItaly © 2013 Microsoft Corporation Pictometry Bird’sEye © 2012 Pictometry International Corp.
  16. 16. shown in Figure 5A. The circle and tri- anglesymbolsindicatewheretheradio beamsexitthefoliage. Measurements were carried out under rainy and windy weather con- ditions, resulting in variations of the NLOSpathattenuation,asshowninthe received signal spectra for the 28GHz radio link in Figure 5B. Under LOS con- ditions the amplitude spectrum enve- lope reached -50dBm. Consequently, the excess path loss for the single-tree (sparsefoliage)scenariovariedbetween 0 and 6dB when measured for 5 min- utes. In the double-tree (dense foliage) case excess path loss varied from 8dB Penetration As with the case for NLOS reflection, the path loss resulting from penetra- tion is highly dependent on the mate- rial of the object blocking the line of sight. The performance of both test systems was measured in a scenario showninFigures 5Aand5B.Thesend- ing and receiving radios were located 150m apart, with one tall sparse tree and a shorter, denser tree blocking the line of sight. The radio placed on the mobile lift was positioned to measure the radio beam first after penetration of the sparse foliage and then lowered to measure the more dense foliage, as up to more than 28dB. A complementa- ry experiment showing similar excess pathlosswascarriedoutat5.8GHz. To summarize, contrary to popular belief,a28GHzsystemcanbeusedwith excellent performance results using theeffectofNLOSpenetrationthrough sparsegreenery. Deploymentguidelines So far, this article has covered the key system properties for NLOS propaga- tion – diffraction, reflection and pene- tration–dispellingthemyththatthese effectscanbeusedonlywithsub-6GHz frequencies.Thenextstepistoapplythe theory and the test results to an ­actual deployment scenario for microwave backhaul. Table 2showstheindicativethrough- put for each NLOS scenario, using the measuredlossfromtheexamplesabove togetherwiththegraphsinFigure2. A trial site, shown in Figure 6, was selectedtomeasurethecoverageforan NLOS backhaul deployment ­scenario. Four- to six-story office buildings with a mixture of brick, glass and metal facadesdominatethetrialarea.Thehub node was placed 13m above ground on the corner of a parking garage at the south end of the trial area. By using the measuredlossinthediffraction,reflec- tion and penetration from the tests as a rule of thumb, an indicative through- put for each NLOS scenario has been taken from Figure 2 and summarized inTable 2. ThecoloredareasinFigure6showthe line of sight conditions for the trial site: the green areas show where pure LOS exists;theyellowareasindicatetheuse of single-path reflection; the blue areas indicate diffraction; and the red areas show where double reflection is need- ed. Areas without color indicate either that no throughput is expected or that they are outside the region defined for measurement. Measurements were made within the region delineated by the dashed white lines. Referring to Table 2, it is expected that the 5.8GHz system will meet small-cell backhaul requirements (50Mbps throughput) within a 250m radius of the hub; and the28GHzsystemshouldprovidemore than 100Mbps full duplex throughput up to 500m from the hub. To test the actual performance, a receiver node Time (hours) Throughput (Mbps) 120 380 400 420 100 80 60 0 2 4 6 8 10 12 14 16 28GHz 5.8GHz FIGURE 4B Throughput over time – single reflection = sparse foliage = dense foliage FIGURE 5A Test site for NLOS backhaul – penetration 16 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 Dispelling the NLOS myths
  17. 17. wasplaced3mabovegroundmeasuring full duplex throughput along the main street canyon and in the neighboring streets.Onaccountofthewideantenna lobeofthe5.8GHzsystem,realignment wasnotneededforthehubantennafor measurement purposes. For the 28GHz system, realignment of the narrow antennabeamwasneededateachmea- surement point – a fairly simple proce- dureevenunderNLOSconditions. The actual values observed at each measurement point exceeded or matchedthepredictedperformancelev- els in Table 2. Due to the lack of correct- lyalignedreflectionsurfaces,providing backhaul coverage using the double- reflection technique (the red areas of the trial area in Figure 6) was only pos- sible for a limited set of measurements. Multipath propagation, including the reflection effects created by vehi- cles moving along the street canyon, was significant for the 5.8GHz system, but resulted only in slightly reduced throughput in some of the more diffi- cultscenariosforthe28GHzsystem. Summary In traditional LOS solutions, high sys- temgainisusedtosupporttargetedlink distance and mitigate fading caused by rain. For short-distance solutions, this gain may be used to compensate for NLOS propagation losses instead. Sub- 6GHz frequency bands are proven for traditional NLOS usage, and as shown in this article, using these bands is a viable solution for small-cell backhaul. However, contrary to common belief, but in line with theory, MINI-LINK microwave backhaul in bands above 20GHz will outperform sub-6GHz sys- temsundermostNLOSconditions. The key system parameter enabling the use of high-frequency bands is the muchhigherantennagainforthesame antenna size. With just a few simple engineering guidelines, it is possible to plan NLOS backhaul deployments that provide high network performance. And so, in the vast amount of dedicat- ed spectrum available above 20GHz, microwave backhaul is not only capa- ble of providing fiber-like multi-gigabit capacity, but also supports high perfor- mancebackhaulforsmallcells,evenin locations where there is no direct line ofsight. Table 2: Indicative bitrate performance for different NLOS key scenarios LOS SINGLE REFLECTION DOUBLE REFLECTION DIFFRACTION* PENETRATION*** 5.8GHz 0-100m 100Mbps 100Mbps 10Mbps** 80Mbps 100Mbps 100-250m 100Mbps 80Mbps 10Mbps** 60Mbps 100Mbps 250-500m 100Mbps 60Mbps 10Mbps** 10Mbps** 80Mbps 28GHz 0-100m 400Mbps 400Mbps 280Mbps** 400Mbps 400Mbps 100-250m 400Mbps 400Mbps 185Mbps** 400Mbps 400Mbps 250-500m 400Mbps 400Mbps 185Mbps** 280Mbps 400Mbps *30-degree diffraction angle; **not recommended for small-cell backhaul; ***sparse foliage or similar FIGURE 5B Channel amplitude response – penetration Frequency (GHz) Received power (dBm) –40 –50 –60 –70 –80 ~6dB fluctuation Maximum power over 5 minutes Minimum power over 5 minutes 29.32 29.34 29.36 29.38 29.40 29.42 Sparse foliage Frequency (GHz) Received power (dBm) –40 –50 –60 –70 –80 20dB fluctuation Maximum power over 5 minutes Minimum power over 5 minutes 29.32 29.34 29.36 29.38 29.40 29.42 Dense foliage Resolution bandwidth: 50kHz FIGURE 6 NLOS backhaul trial area 17 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 500m 100m 250m © 2013 BLOM © 2013 Microsoft Corporation Legend line-of-sight double reflection single reflection diffraction
  18. 18. Jonas Hansryd joined Ericsson Research in 2008 and is currently managing the microwave high-speed and electronics group. He holds a Ph.D. in electrical engineering from the Chalmers University of Technology, Gothenburg, Sweden and was a visiting researcher at Cornell University, Ithaca, US, from 2003-2004. Jonas Edstam joined Ericsson in 1995 and is currently head of technology strategies at Product Line Microwave and Mobile Backhaul. He is an expert in microwave radio-transmission networks focusing on the strategic evolution of packet-based mobile backhaul and RAN. He holds a Ph.D. in applied solid-state physics from Chalmers University of Technology, Gothenburg, Sweden. 1. Ericsson, 2011, Ericsson Review, Microwave capacity evolution, available at: review/Microwave-Capacity-Evolution.pdf 2. Ericsson, 2012, White Paper, It all comes back to backhaul, available at: whitepapers/WP-Heterogeneous-Networks-Backhaul.pdf 3. NGMN Alliance, June 2012, White Paper, Small Cell Backhaul Requirements, available at: http://www.ngmn. org/uploads/media/NGMN_Whitepaper_Small_Cell_ Backhaul_Requirements.pdf 4. Electronic Communications Committee (ECC), 2012, Report 173, Fixed service in Europe – current use and future trends post, available at: official/pdf/ECCRep173.PDF 5. Seidel, S.Y.; Arnold, H.W.; 1995, Propagation measurements at 28 GHz to investigate the performance of local multipoint distribution service (LMDS), available at: http://ieeexplore. 6. Rappaport, T.S.; Yijun Qiao; Tamir, J.I.; Murdock, J.N.; Ben-Dor, E.; 2012, Cellular broadband millimeter wave propagation and angle of arrival for adaptive beam steering systems (invited paper), available at: org/xpl/articleDetails.jsp?arnumber=6175397 7. Coldrey, M.; Koorapaty, H.; Berg, J.-E.; Ghebretensaé, Z.; Hansryd, J.; Derneryd, A.; Falahati, S.; 2012, Small-cell wireless backhauling: a non-line-of-sight approach for point- to-point microwave links, available at: http://ieeexplore. 8. ITU, 2012, Recommendation ITU-R P.526, Propagation by diffraction, available at: rec/R-REC-P.526-12-201202-I 9. Anderson, C.R.; Rappaport, T.S.; 2004, In-building wideband partition loss measurements at 2.5 and 60 GHz, available at: jsp?arnumber=1296643 10. Okamoto, H.; Kitao, K.; Ichitsubo, S.; 2009, Outdoor-to- Indoor Propagation Loss Prediction in 800-MHz to 8-GHz Band for an Urban Area, available at: org/xpl/articleDetails.jsp?arnumber=4555266 11. Dillard, C.L.; Gallagher, T.M.; Bostian, C.W.; Sweeney, D.G.; 2003, 28GHz scattering by brick and limestone walls, available at: jsp?arnumber=1220086 References Christina Larsson joined Ericsson Research in 2010. Her current focus area is microwave backhaul solutions. She holds a Ph.D. in electrical engineering from Chalmers University of Technology, Gothenburg, Sweden, and was a post-doctoral researcher at the University of St. Andrews, St. Andrews, UK, from 2004-2006. Bengt-Erik Olsson joined Ericsson Research in 2007 to work on ultra-high-speed optical communication systems. Recently he switched interest to wireless-technology research, and is currently working on NLOS backhaul applications for microwave links. He holds a Ph.D. in optoelectronics from Chalmers University of Technology, Gothenburg, Sweden. The authors gratefully acknowledge the colleagues who have contributed to this article: Jan-Erik Berg, Mikael Coldrey, Anders Derneryd, Ulrika Engström, Sorour Falahati, Fredrik Harrysson, Mikael Höök, Björn Johannisson, Lars Manholm and Git Sellin Acknowledgements 18 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 Dispelling the NLOS myths
  19. 19. Toward the end of this decade, Ericsson trialed a crossbar system,30yearsaftertheseswitcheswerefirstputintoprac- ticaloperation. TheSecondWorldWarhadaprofoundeffectonpeopleand business. Widespread misery, rations and a shortage of raw materials naturally led many companies to diversify their operations.Butoverall,theslowdowningrowthandreduced levelofinformationexchangeamongresearchersledtoadip indevelopment.Worldaveragetelephonedensityin1930was 2 per 100 capita; by 1950 this figure had risen to 3, and in the twodecadesfollowingthat,subscriberdensitymorethandou- bled–reachingatotalof7in1970. In preparation for the 1952 Summer Olympics, Ericsson installed its first commercial crossbar system in Helsinki, Finland, in 1950. The decision to move to crossbar switching cameaboutduringthewarasEricssonwasdevelopingsmall- er exchanges for rural communities and enterprises. This technology, however, presented new challenges in terms of trafficengineeringanddimensioninginparticular.Inhisthe- sis on a study of congestion in link systems, lifelong Ericsson employee Christian Jacobæus presented a way to calculate traffic capacity that was subsequently trialed and became a worldwidestandard. Computing was the next wave of technology to be adopt- ed by the telecoms industry. Parts of Ericsson’s AKE range of telephone exchanges were computer controlled, the key fea- turebeingaStoredProgramControlled(SPC)element,which managed the switches and operated in real time. The initial commercial deployments in 1968 were the first computer- controlledexchangesoutsidetheUS. By the end of the 1960s, however, it had become clear that something different was needed. Something that was more flexible – a modular system that could be expanded to accommodate new technologies and services without the need for fundamental system changes: something that was future-proof. The downturn of the global economy following the oil cri- sisinthe1970sagainledtoseveraltoughyearsforindustryin general.ForEricsson,aboostcamewhentheSaudiMinistryof TelecommunicationschoseEricssonAXEexchangesinwhat wastobethebiggestcontractinthehistoryoftelecomsatthat time. This digital exchange introduced modular design and becameoneoftheworld’smostsuccessfulswitchingsystems. In 1984, Ericsson Review published a special ‘F’ edition dedicated to fiber optic. This issue covered every aspect of fiber optics from cable manufacture to installation, applica- tionsanddevicetechnology.Ericsson’stransmissionexpertise goes right back to the late 1920s when it began manufactur- ingloadingcoils,earlysignsofEricsson’sethostoprovidethe telecomsindustrywithawiderrangeofproductsandservices. Continuedon page47... Nine decades of innovation Automatic exchanges to smart networks ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 19 Re:view Recovery and prosperity   In 1954, the cover article of Ericsson Review issue 1 looked at the traffic reliability of the crossbar system, which Ericsson delivered to the Helsinki Telephone Corporation in 1950. The cover illustrates the interior of the Helsinki exchange for PBX subscribers. The final testing of the system was carried out in the latter half of 1953 and gave a fault rate of 0.090 percent based on 20,000 test connections. This result was deemed to be highly satisfactory, as the exchange was very heavily loaded during peak periods. Flower power and revolution The cover of issue 3 in 1968 portrayed printed circuit cards in the transfer unit of Ericsson’s Stored Program Controlled (SPC) AKE exchange system. The photograph is from the automatic exchange installed in Tumba (a suburb of Stockholm). SPC exchanges were a milestone in the development of telephony, as they made it easier to trace faults, and thus reduce maintenace costs. The major concerns at the time were capacity and cost of memory. Oil and energy crises The second issue of 1976 presented the AXE 10 switching system. The range of articles in this issue highlighted the shift in technology focus. Telecoms was becoming much more than wires, switches, exchanges and transmission. Hardware architecture and design were now being intimately combined with software structure to provide services, efficient traffic handling, management systems and scalability. Ericsson Review, issue 1, 1954. Ericsson Review, issue 3, 1968. Ericsson Review, issue 2, 1976.
  20. 20. Software-defined networking: the service provider perspective An architecture based on SDN techniques gives operators greater freedom to balance operational and business parameters, such as network resilience, service performance and QoE against opex and capex. every year1 . One of the root causes of network complexity lies in the tradi- tional way technology has developed. The design of network elements, such as routers and switches, has tradition- allybeenclosed;theytendtohavetheir own management systems with verti- callyintegratedforwardingandcontrol components, and often use proprietary interfaces and features. The goal of network management is, however, to ensurethattheentirenetworkbehaves as desired – an objective that is much more important than the capabilities of any single network element. In fact, implementing end-to-end networking isanimportantmissionformostopera- tors, and having to configure individu- al network elements simply creates an unwantedoverhead. Network-wideprogrammability–the capabilitytochangethebehaviorofthe network as a whole – greatly simplifies the management of networks. And the purposeofSDNisexactlythat:tobeable to modify the behavior of entire net- worksinacontrolledmanner. The tradition of slow innovation in networking needs to be broken if net- worksaretomeettheincreaseddemand for transport and processing capaci- ty. By integrating recent technological advances and introducing network- wide abstractions, SDN does just that. Itisanevolutionarystepinnetworking. Telephony has undergone similar architectural transitions in the past. One such evolution took place when a clearseparationbetweenthefunctions Ericsson’sapproachtoSDNgoesbeyond the data center addressing issues in the service-provider environment. In short Ericsson’s approach is Service Provider SDN. The concept aims to extend virtu- alization and OpenFlow – an emerging protocol for communication between the control and data planes in an SDN architecture–withthreeadditionalkey enablers: integrated network control; orchestrated network and cloud man- agement;andserviceexposure. There is no denying that networks are becoming increasingly complex. More and more functionality is being integrated into each network element, and more and more network elements are needed to support evolving service requirements–especiallytosupportris- ing capacity needs, which are doubling ATTILA TAKACS, ELISA BELLAGAMBA, AND JOE WILKE The traditional way of describing network architecture and how a network behaves is through the fixed designs and behaviors of its various elements. The concept of software-defined networking (SDN) describes networks and how they behave in a more flexible way – through software tools that describe network elements in terms of programmable network states. The concept is based on split archi- tecture, which separates forwarding functions from control functions. This decoupling removes some of the com- plexity from network management, providing operators with greater flexi- bilitytomakechanges. BOX A Terms and abbreviations API application programming interface ARPU average revenue per user CLI command-line interface DPI deep packet inspection GMPLS generalized multi-protocol label switching L2 Layer 2 L3 Layer 3 L2-L4 Layers 2-4 M-MGW Mobile Media Gateway MME Mobility Management Entity MSC-S Mobile Switching Center Server NAT Network Address Translation NMS network management system ONF Open Networking Foundation OSS/BSS operations and business support systems PE provider edge device PGW Packet Data Network Gateway RG residential gateway RWA routing and wavelength assignment SDN software-defined networking SGW Service Gateway SLA Service Level Agreement VHG virtual home gateway VoIP voice over IP WAN wide area network 20 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 New network abstraction layers
  21. 21. of the data plane (including SGW, PGW and M-MGW) and the control plane (including MME and MSC-S) was intro- duced. Now SDN has brought the con- ceptofsplitarchitecturetonetworking. As the business case proves, over the next two to five years, SDN technology willbedeployedinnetworksworldwide. Atthesame time,theneed to maintain traditional operational principles and ensure interoperability between SDN and more traditional networking com- ponents will remain. In the future, SDN will help operators to manage scale,reducecostsandcreate­additional ­revenuestreams. Standardization The goal of the Open Networking Foundation (ONF), which was estab- lished in 2011, is to expedite the stan- dardization of the key SDN interfaces. Today, the work being conducted by ONF focuses on the continued evolu- tionoftheOpenFlowprotocol.ONFhas recently established the Architecture andFrameworkWorkingGroup,whose goal is to specify the overall architec- ture of SDN. The work carried out by this group will guide future standard- izationeffortsbasedonstrategicusecas- es, requirements for data centers and carrier networks, the main interfac- es, and their roles in the architecture. Ericsson is actively driving the work of thisgroup,cooperatingwithotherorga- nizations to promote the evolution of OpenFlow and support an open-source implementation of the most recent specifications. Otherstandardizationorganizations, most notably the IETF, have recently begun to extend their specifications to support SDN principles. In IETF, the Interface to the Routing System (i2rs) WG and the recent activity of the Path Computation Element (PCE) WG will result in standardized ways to improve flexibilityinchanginghowIP/MPLSnet- worksbehave.Thisisachievedthrough the introduction of new interfaces to distributed protocols running in the network,andmechanismstoadaptnet- work behavior dynamically to applica- tionrequirements. Inadditiontostandardizationorgani- zationsamultitudeofactivecommuni- tiesandopen-sourceinitiatives,suchas OpenStack, are getting involved in the specificationofvariousSDNtools,work- ingonmaturingthenetworkingaspect ofvirtualization. Architecturalvision Split architecture – the decoupling of control functions from the physical devicestheygovern–isfundamentalto theconceptofSDN.Insplit-architecture networks, the process of forwarding in thedataplaneisseparatedfromthecon- troller that governs forwarding in the control plane. In this way, data-plane and control-plane functions can be designed, dimensioned and optimized separately, allowing capabilities from theunderlyinghardwaretobeexposed independently. This ability to separate control and forwardingsimplifiesthedevelopment and deployment of new mechanisms, and network behavior becomes easi- er to manage, reprogram and extend. Deploying a split architecture, howev- er, does not remove the need for high- availability software and hardware components, as networks continue to meet stringent carrier requirements. However, the decoupling approach to architecture will help rationalize the network, making it easier to intro- duce new functions and capabilities. The ultimate goal of the SDN architec- ture is to allow services and applica- tions to issue requests to the network dynamically, avoiding or reducing the need for human intervention to create newservices.This,comparedtotoday’s practices,willreducethetimetomarket ofnewservicesandapplications. The OpenFlow protocol2 is support- ing the separation of data and control planes and allowing the path of pack- etsthroughthenetworktobesoftware determined. This protocol provides a simple abstraction view of networking equipment to the control layer. Split architecture makes virtualization of networking resources easier, and the controlplanecanprovidevirtualviews ofthenetworkfordifferentapplications andtenants. Ericsson has worked together with service providers to understand their needs for SDN both in terms of reduc- ing costs and creating new revenue opportunities. Based on these discus- sions,Ericssonhasexpandedtheindus- try definition of SDN and customized it tofittheneedsofoperators. Ericsson’s hybrid approach – Service Provider SDN – extends industry def- initions including virtualization and OpenFlow with three additional key enablers: integratednetworkcontrol; orchestratednetworkandcloud management;and serviceexposure. Service exposure Northbound APIs to allow networks to respond dynamically to application/service requirements Integrated network control Control of entire network from radio to edge to core to data center for superior performance Orchestrated network and cloud management Unified legacy and advanced network, cloud management system and OSS/BSS to implement SDN in step-by-step upgrade Service provider needs: Service Provider SDN • Accelerated service innovation • Advanced public/hybrid enterprise and consumer cloud services • Improved QoE • Opex reduction through centralized management • Capex control FIGURE 1 Service Provider SDN – components and promise 21 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014
  22. 22. intothisunifiedorchestrationlayerpro- vides the necessary support for applica- tions and tenants to trigger automatic changes in the network, ensuring opti- malQoSandguaranteeingSLAs. Unified and centralized orchestra- tionplatformsgreatlysimplifythepro- cess of configuring, provisioning and managing complex service networks. Instead of having to tweak hundreds of distributed control nodes using fairly complexCLIprogramming,operations staff can use simple intuitive program- ming interfaces to quickly adjust net- work configurations and create new services. By accelerating the process of service innovation, Service Provider SDNwillleadtoincreasedmarketshare and service ARPU, creating significant revenue growth and possibly reducing annualchurnrates. A high-level network architecture that supports the Service Provider SDN vision is illustrated in Figure   2. Service-providernetworkswillcombine distributed control plane nodes (tradi- tionalroutersandappliances),anddata- plane elements that are governed by centralized elements – SDN controllers – in the control plane. Consequently, tomakeservice-providernetworkspro- grammable, distributed and central- izedcontrol-planecomponentsmustbe exposed to a unified orchestration plat- form. In addition, the key elements of theorchestrationplatformandthecon- trolplaneneedtobeexposedtonetwork andsubscriberapplications/services. Applicationexamples Themajorusecasesorapplicationsof SDN in service-provider networks are summarizedinFigure 3.Oftheseappli- cations, the data center was the first to makeuseofSDN.Ericsson’sapproachto this is described in several articles pub- lishedinEricssonBusinessReview3 and inEricssonReview4,5 . SDN can be applied in the aggrega- tion network to support sophisticated virtualization and to simplify the con- figuration and operation of this net- work segment. Ericsson has developed a proof-of-concept system in coopera- tionwithTier1operatorstoevaluatethe applicability of SDN to aggregation net- works. This work has been carried out as part of the European Commission’s SeventhFrameworkProgramme6 . Integratednetworkcontrol Service providers will use SDN across thenetworkfromaccess,toedgetocore and all the way into the data center. With integrated network control, oper- ators can use their network features, includingQoS,edgefunctionsandreal- time activity indicators to deliver supe- rioruserexperience. Orchestratednetwork andcloudmanagement ServiceProviderSDNwillintegrateand unifylegacynetworkmanagementsys- tems with new control systems as well as with OSS/BSS. The platform for inte- grated orchestration supports end-to- end network solutions ranging from access over aggregation to edge func- tions as well as the data centers used to delivertelcoandenterpriseapplications andservices. Serviceexposure Northbound APIs expose the orches- tration platform to key network and subscriber applications and services. Together, the APIs and platforms allow application developers to maximize networkcapabilitieswithoutrequiring intimate knowledge of their topology orfunctions. By expanding the perspective of SDN to include these three elements, ser- vice providers can evolve their exist- ing network to the new architecture to improvetheexperienceoftheircustom- ers.ImplementingServiceProviderSDN shouldremovethedumbpipelabelgiv- ing operators an advantage over com- petitorsthatdonotownnetworks. Networkvirtualization One of the benefits of Service Provider SDN, especially from a network-­ spanning perspective is network vir- tualization. Through virtualization, logical abstractions of a network can be exposed instead of a direct repre- sentation of the physical network. Virtualizationallowslogicaltopologies tobecreated,aswellasprovidingaway toabstracthardwareandsoftwarecom- ponents from the underlying network elements, thereby separating control from forwarding capabilities and sup- portingthecentralizationofcontrol. Unified orchestration platforms sup- portnetworkprogrammingatthehigh- est layer as programming instructions flow through the control hierarchy – potentiallyallthewaydowntogranular changesinflowpathsattheforwarding plane level. Adding northbound APIs Application Control Forwarding Application Control Forwarding (v) Control plane APIs (such as OpenFlow) Tenants SDN controller Forwarding Forwarding Integrated systems Routers Physical Forwarding elements Ericsson NMS and cloud management system Virtual Software Hardware Application FIGURE 2 Service Provider SDN – architectural vision 22 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 New network abstraction layers
  23. 23. Ericsson and Telstra have jointly devel- oped a service-chaining prototype that leverages SDN technologies to enhance granularity and dynamicity of service creation. It also highlights how SDN can simplify network provisioning and improveresourceutilizationefficiency. Packet-opticalintegrationisapopular topicofdebate,outofwhichseveraldif- ferent approaches are emerging. Split architecture provides a simple way to coordinatepacketandopticalnetwork- ing;andsoSDN,enhancedwithfeatures suchasroutingandwavelengthassign- ment (RWA) and optical impairments management will be a natural fit for packet-opticalintegration. Ericsson has started to develop solu- tions to virtualize the home gateway. Virtualization reduces the complexity of the home gateway by moving most of the sophisticated functions into the network and, as a result, operators can prolongthehomegatewayrefreshment cycle, cut maintenance costs and accel- eratetimetomarketfornewservices. Virtualizationofaggregationnetworks The characteristics shared by aggrega- tionandmobile-backhaulnetworksare a large number of nodes and relative- ly static tunnels – that provide traffic grooming for many flows. These net- worksarealsoknownfortheirstringent requirements with regard to reliabil- ity and short recovery times. Besides L2 technologies IP and IP/MPLS is mak- ing an entrance as a generic backhaul solution. From an operational point of view, despite the availability of the dis- tributed control plane technology, this networksegmentisusuallyconfigured statically through a centralized man- agement system, with a point of touch to every network element. This makes the introduction of a centralized SDN controllerstraightforwardforbackhaul solutions. Acontrolelementhostedonatelecom- grade server platform or on an edge router provides the operator with an interface that has the same look and feel as a single traditional router. The differencebetweenoperatinganaggre- gation SDN network and a traditional network lies in the number of touch points required to provision and oper- ate the domain. In the case of SDN, only a few points are needed to control the connectivity for the entire net- work. Consider, for example, an access/­ aggregation domain with hundreds or even thousands of nodes running dis- tributed IGP routing protocols and the LabelDistributionProtocol(LDP)tocon- figure MPLS forwarding. In this case, SDNprinciplescanbeappliedtosimpli- fy and increase the scalability of provi- sioningandoperatingofsuchanetwork by pulling together the configuration of the whole network into just a few controlpoints. Thecontrolelementtreatstheunder- lying forwarding elements as remote linecardsofthesamesystemand,more specifically, controls their flow entries through the OpenFlow protocol. With this approach, any kind of connectivi- tymodelisfeasibleregardlessofwheth- er the forwarding node is L2 or L3 as, from a pure forwarding point of view, the same model is used in both flows. At the same time, network resilience at the transport level can be implement- ed by adding protection mechanisms to the data path. The SDN controller can pre-compute and pre-install back- up routes and then protection switch- ingishandledbythenetworkelements for fast failover. Alternatively, the SDN controller can reroute around failures, in case multiple failures occur, or in scenariosthathavelessstringentrecov- eryrequirements. Fromtheoutside,theentirenetwork segment appears to be one big PE rout- erand,forthisreason,neighboringnet- work elements of the SDN-controlled area cannot tell the difference (from a protocolpointofview)betweenitanda traditional network. The network con- troller handles the interfacing process with legacy systems for connection set- up.Additionalinformationonthispoint can be found in a presentation on the VirtualNetworkSystem7 . Dynamicservice-chaining Forinlineservices,suchasDPI,firewalls (FWs),andNetworkAddressTranslation (NAT), operators use different middle- boxesorappliancestomanagesubscrib- er traffic. Inline services can be hosted on dedicated physical hardware, or on virtual machines. Service chaining is required to route certain subscriber trafficthroughmorethanonesuchser- vice.Therearestillnoprotocolsortools available for operators to perform flex- ible,dynamictrafficsteering.Solutions currently available are either static or their flexibility is significantly limited byscalabilityinefficiencies. Given the rate of traffic growth, con- tinued investment in capacity for Virtualization of aggregation network Virtual home gateway Policy-based service chaining Packet and optical integration Network support for cloud Cloud/data centerMobile Residental Business FIGURE 3 Application examples 23 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014
  24. 24. inlineservicesneedstobemanaged carefully. Dynamic service-chaining can optimize the use of extensive high- touch services by selectively steering traffic through specific services or bypassing them completely which, in turn,canresultincapexsavingsowing totheavoidanceofover-dimensioning. Greater control over traffic and the use of subscriber-based selection of inline services can lead to the cre- ation of new offerings and new ways to monetize networks. Dynamic service steering enables operators to offer sub- scribersaccesstoproductssuchasvirus scanning, firewalls and content filters throughanautomaticselectionandsub- scribeportal. This concept of dynamic service chaining is built on SDN principles. Ericsson’s proof-of-concept system uses alogicallycentralizedOpenFlow-based controllertomanagebothswitchesand middleboxes. As well as the traditional 5-tuple, service chains can be differen- tiated on subscriber behavior, applica- tion, and the required service. Service paths are unidirectional; that is, differ- ent service paths can be specified for upstreamanddownstreamtraffic. Traffic steering has two phases. The first classifies incoming packets and assigns a service path to them based on predefined policies. Packets are then forwardedtothenextservice,basedon the current position in their assigned service path. No repeating classifica- tion is required; hence the solution is scalable. TheSDNcontrollersetsupandrecon- figures service chains flexibly to an extent that is not possible with today’s solutions.Thedynamicreconfiguration ofservicechainsneedsamechanismto handle notifications sent from middle- boxestothecontroller.Forexample,the DPI engine notifies the controller that it has recognized a video flow. These notifications may be communicated using the extensibility features of the OpenFlow1.xprotocol. Figure  4 summarizes service-­ chaining principles. The Virtual Network System (VNS) is a domain of the network where the control plane is centralizedwhichexcludessomeofthe traditionalcontrolagents.AsimpleAPI, such as OpenFlow, can be used to con- troltheforwardingfunctionalityofthe network,andtheVNScancreatenorth- bound interfaces and APIs to support creationofnewfeatures,suchasservice chaining, which allows traffic flows to besteereddynamicallythroughservic- esorpartsthereofbyprogrammingfor- wardingelements. The services provided by the net- work may reside on devices located in different parts of the network, as well as within an edge router – for example, on the service cards of Ericsson’s Smart ServicesRouter(SSR).Servicechainsare programmedintothenetworkbasedon acombinationofinformationelements fromthedifferentlayers(L2-L4andpos- siblyhigher).Basedonoperatorpolicies, variousservicescanbeappliedtotraffic flowsinthenetwork. Forexample,trafficmaypassthrough DPI and FW functions, as illustrated by the red flow in Figure 4. However, once the type of the flow has been deter- mined by the DPI function, the opera- tor may decide to modify the services applied to it. For example, if the flow is aninternetvideostream,itmaynolon- ger need to pass the FW service, reduc- ing load on it. Furthermore, after the servicetypehasbeendetected,thesub- sequent packets of the same flow may no longer need to pass the DPI service either;hencethepathoftheflowcanbe updated – as indicated by the blue flow inFigure4. Packet-opticalintegration The increased programmability that SDN enables creates an opportunity to address the challenges presented by packet optical networking. SDN can simplify multi-layer coordination and optimizeresourceallocationateachlay- er by redirecting traffic (such as VoIP, video and web) based on the specific requirementsofthetrafficandthebest servinglayer. Instead of a layered set of separated media coordinated in a static manner, SDNcouldtransformthepacket-optical infrastructure to be more fluid, with a unified recovery approach and an allo- cation scheme based on real-time link utilization and traffic composition. The ONF still has some work to do to adapt OpenFlow to cope with optical constraints. To speed up packet-optical inte- gration, a hybrid architecture can be deployed where OpenFlow drives the packetdomain,andtheopticaldomain remains under the control of GMPLS. This approach utilizes the extensive optical capabilities of GMPLS and, therefore, instead working to extend OpenFlow with optical capabilities, it allowsustofocusontheactualintegra- tion of optical and packet domains and applicationsthatutilizetheflexibilityof aunifiedSDNcontroller. FIGURE 4 Service-chaining principles Virtual Network System domain FW DPI NAT FW DPI SSR SDN switch Flow before Flow after SDN switch SDN switch 24 ERICSSON REVIEW • 90TH ANNIVERSARY • 2014 New network abstraction layers