Long Term Evolution

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This white paper provides information about 4 G LTE Architecture and Details.

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Long Term Evolution

  1. 1. October 2012 | | Preet Kanwar Rekhi, Sukhvinder Malik, Rahul Atri White Paper Long Term Evolution (LTE): The Mobile Broadband Technology 1. Introduction Contents 1. Introduction This paper is purely a technical paper and provides an overview of 2. Driving Factor of Long Term Evolution (LTE), the leading technologies for next- Technology generation mobile broadband. 3. Evolution: 1G AMPS to 4G LTE The information presented here will help readers to understand the 4. Key Features of LTE Evolution of Telecommunication, LTE technology, Key benefits 5. LTE Network which make LTE so popular, Network Architecture and Architecture connectivity of LTE System to other 3GPP and Non 3 GPP legacy 6. LTE Access Network networks. 7. LTE Core Network 8. Interworking with 3GPP and Non 3GPP2. Driving Factor of Technology Networks 9. ConclusionDriving the evolution of wireless broadband technology is user’s 10. Referencesincreasing expectations for speed, bandwidth, and global access.Users want more information, such as business and consumerapplications, and entertainment available through their mobile devices,but with greater speeds.For wireless carriers to achieve greater speeds and pervasiveconnectedness, their networks need to start behaving more like landlineIP-based networks. This line of thinking represents a fundamental shiftin perspective—from mobile services to broadband connections—forusers and service providers alike to enter the fourth-generation (4G). 1.wireless network.
  2. 2. Unlike earlier wireless standards, 4G technology is based on TCP/IP, the core protocol of the Internet. TCP/IP enables wireless networks to deliver higher-level services, such as video and multimedia, while supporting the devices and applications of the future. This point of time, there are two technologies which can provides such user experience IEEE’s WiMAX and 3GPP LTE. Service providers are choosing LTE over WiMAX as the technological foundation for 4G wireless broadband network. The service provider believes that make LTE offers a number of significant technological and business advantages over WiMAX that make it a superior networking standard. Wireless users want to be have maximum speed as possible with advanced User devices that provide a similar immersive experience as found in today’s wired networks—whether it’s downloading or uploading large files, video, gaming, downloading music, or social networking. These are the reasons, which make Long Term Evolution as a Driving Technology. 3. Evolution: 1G AMPS to 4G LTE The various communications systems looking in the past revolutionized the3GPP and 3 GPP2 way people Communicate, joining together communications and mobility. Evolution of wireless access technologies is about to reach its fourth generation (4G). Looking past, wireless access technologies have followedThe 3GPP and 3GPP2 both different evolutionary paths aimed at unified target: performance andOrganisation works for encompassingthe Radio, Core Network and Service efficiency in high mobile environment.architecture standardization. The first generation (1G) AMPS has fulfilled the basic mobile voice, whileThe 3rd Generation Partnership the second generation (2G) GSM (3GPP), CDMA one (3GPP2) hasProject (3GPP) is a standardization introduced capacity and coverage. This is followed by the third generationbody which makes standards and (3G), UMTS, WCDMA (3GPP) and EV-DO (3GPP2) which has quest forspecification that can be usedglobally. 3GPP has given the data at higher speeds to open the gates for truly “mobile broadband”specifications for GSM, GPRS, experience, which will be further realized by the fourth generation (4G).EDGE, UMTS, HSPA, LTE and LTE-A.The 3rd Generation PartnershipProject 2 (3GPP2) is astandardization group for CDMA.3GPP has given specification forCDMA one, CDMA 2000, EV-DOA&B and UMB. The Fourth generation (4G) LTE will provide access to wide range of telecommunication services, including advanced mobile services, supported by mobile and fixed networks, which are increasingly packet based, along with a support for low to high mobility applications and wide range of data rates, in accordance with service demands in multiuser environment. . 2 Figure1
  3. 3. The Fourth generation (4G) LTE will provide access to wide range Of telecommunication services, including advanced mobile services, supported by mobile and fixed networks, which are increasingly packet based, along with a support for low to high mobility applications and wide range of data rates, in accordance with service demands in multiuser environment.. 4. Key Features of LTE The 4 G Long Term Evolution has following key feature which make this technology superior than other technologies. 1. Peak Through put: - Peak download rates up to 300 Mbps and upload rates up to 75.Mbps depending on the user equipment category (with 4x4 antennas using 20 MHz of spectrum). 2. Low Latency: - Low data transfer latencies (sub-5ms LTE Key Features latency for small IP packets in optimal conditions), Summary lower latencies for handover and connection setup time than with previous radio access technologies. Feature Detail 3. Mobility Support:-Improved support for mobility, exemplified by support for terminals moving at up to Peak DL 300 Mbps 350 km/h (220 mph) or 500 km/h (310 mph) depending Throughputs UL 75 Mbps with on the frequency band. 4*4 MIMO Latency Control-plane 100ms 4. Access Technologies:-OFDMA for the downlink, SC- User-Plane -5ms FDMA for the uplink to conserve power. Access DL- OFDMA 5. Duplexing Support:-Support for both FDD and TDD UL-SC-FDMA communication systems as well as half-duplex FDD Duplexing FDD and TDD with the same radio access technology Bandwidth 1.4,3,5,10,15 and 20 6. Flexible Bandwidths:- 1.4 MHz, 3 MHz, 5 MHz, MHz 10 MHz, 15 MHz and 20 MHz Cell size 5 Km to 100 Km 7. Large Cell Size Support:-Support for cell sizes from tens of metres radius (femto and Pico cells) up to 100 km radius macro cells. In the lower frequency bands to be used in rural areas, 5 km is the optimal cell size, 30 km having reasonable performance, and up to 100 km cell sizes supported. 8. Simplified architecture: LTE architecture is FLAT IP Based. The access side of LTE is composed only of eNodeB. Support for inter- operation and co-existence with legacy standards like GSM/EDGE, UMTS and CDMA2000. Users initiate a call or transfer of data in an area using an LTE standard and, should coverage be unavailable, continue the operation without any action on their part using GSM/GPRS or W-CDMA-based UMTS or even 3GPP2 networks such as CDMA One or CDMA2000. 3
  4. 4. 5. LTE Network Architecture Long Term Evolution (LTE) has been designed to support only packet-switched services. It aims to provide seamless Internet Protocol (IP) connectivity between User Equipment (UE) and the packet data network (PDN), without any disruption to the end user’s applications during mobility The term “Long Term Evolution” encompasses the evolution of the Universal Mobile Telecommunications System (UMTS) radio access through the Evolved UTRAN (E-UTRAN) It is accompanied by an evolution of the non-radio (Core Network) aspects under the term “System Architecture Evolution” (SAE), which includes the Evolved Packet Core (EPC) network. The E-UTRAN and EPC together comprise the Evolved Packet System (EPS) and shown in below figure 2.Long Term Evolution(LTE) Network Nodes  LTE RAN is called E- UTRA network.  LTE core Network is called Evolved Packet Core (EPC).  Both E-UTRA and EPC makes Evolved Packet System (EPS).LTE Network has two parts at highlevel  Radio Access part having just one node eNodeB  Core Network part having many nodes like  Mobility Management Entity (MME)  Serving Gateway (SGW)  Packet Data Network Gateway (PGW) Figure 2  Home subscriber Sever (HSS) At a high level, the network is comprised of the Core Network  Policy Control & (EPC) and the access network E-UTRAN. The Core Network Charging Rule Function consists of many logical nodes. (PCRF) The access network is made up of essentially just one node, the evolved NodeB (eNodeB), through which Connects UE to the network. Each of these network elements is interconnected by means of interfaces that are standardized in order to allow multi-vendor interoperability. This gives the possibility to source different network elements 4 from different vendors
  5. 5. 6. LTE Access NetworkThe access network of LTE simply consists of a network ofeNodeBs. For normal user traffic (as opposed to broadcast), there isno centralized controller in E-UTRAN; hence the E-UTRANarchitecture is said to be flat.The eNodeBs are normally interconnected with each other bymeans of an interface known as “X2” and to the EPC by means ofthe S1 interface The protocols that run between the eNodeBs andthe UE are known as the “AS protocols.” LTE Access Network  eNodeB Communicate to each other via X2 inter face  E-UTRA Network Communicate to Core Network via S1 interface.  S1 interface also called S1 Flex. Access Network Functions  Radio Resource Management  Header Compression Figure 3  Security  Connectivity to Core NetworkThe Access Network is responsible for all radio-related functionssuch as • Radio resource management (RRM) – This covers all functions related to the radio bearers, such as radio bearer control, radio admission control, radio mobility control, scheduling and dynamic allocation of resources to UEs in both uplink and Downlink. • Header Compression – This helps to ensure efficient use of the radio interface by compressing the IP packet headers that could otherwise represent a significant overhead, especially services using small packets such as VoIP. • Security – All data sent over the radio interface is encrypted. • Connectivity to the EPC – This consists of the signalling toward MME and the bearer path toward the S-GW.All of these functions reside in the eNodeBs, each of which can beresponsible for managing multiple cells, Unlike some of theprevious 2G and 3G technologies, LTE integrates the radiocontroller function (RNC) into the eNodeB, allows tight interactionbetween the different protocol layers of the radio access network 5(RAN), thus reducing latency and improving efficiency
  6. 6. LTE does not support soft handover .Due to lack of centralized controller node, the network must transfer all information related to a UE i.e. the UE context, together with any buffered data, from one eNodeB to another as the UE moves which is transferred over X2 interface. S1 interface connect eNodeB to Core Network and this also called S1-flex because it can be interconnect to multiple Core networks. It means an eNodeB may thus be served by multiple MME/SGWs. The set of MME/S-GW nodes that serves a common area is called an MME/S-GW pool, and the area covered by such a pool of MME/S-GWs is called a pool area. Pool Area concept allows UEs in the cell or cells controlled by one eNodeB to be shared between multiple CN nodes, thereby providing a possibility for load sharing and also eliminating single points of failure for the CN nodesLong Term Evolution 7. LTE Core Network(LTE) Core Network The core network in LTE is called Evolved Packet Core (EPC) which is responsible for the overall control of the UE andLTE Core Network is called EPC establishment of the bearersLogical Nodes of EPC are: The main logical nodes of the EPC are:• PDN Gateway (P-GW) • PDN Gateway (P-GW)• Serving Gateway (S-GW) • Serving Gateway (S-GW)• Mobility Management Entity • Mobility Management Entity (MME) (MME) • Home Subscriber Server (HSS)• Home Subscriber Server • Policy Control and Charging Rules Function (PCRF) (HSS)• Policy Control and Charging The figure below shows the interconnection of Access and Core Rules Function (PCRF) Network. Figure 4 6
  7. 7. P-GW-is Public Data Network (PDN) Gateway .It is responsiblefor IP allocationfor the UE, as well as QoS enforcement and flow-based charging according to rules from the PCRF.It also does filtering of downlink packets into the different QoS-based bearers on the basis of traffic flow template (TFT). It alsoserves as the mobility anchor for interworking with non-3GPPtechnologies such as CDMA2000 and WiMAX® networks.S-GW- is serving gateway. All user IP packets are transferredthrough the Serving Gateway, which serves as the local mobilityanchor for the data bearers when the UE moves between eNodeBsThe S-GW also performs some administrative functions in thevisited network such as collecting information for charging (forexample, the volume of data sent to or received from the user)It also serves as the mobility anchor for inter working with other Long Term Evolution Core3GPP technologies such as general packet radio service (GPRS)and UMTS Network PGW responsible for IP allocationMME is Mobility management Entity. It is a control node that to UE, QoS enforcement andprocesses the signalling between the UE and the CN. The main making TFT and also serves mobility anchor for interworkingfunctions supported by the MME can be classified as: with non 3GPP technologies like Functions related to bearer management – This includes the CDMA 2000. establishment, maintenance and release of the bearers and is handled by the session management layer in the NAS protocol. SGW transfer all IP packets to and Functions related to connection management – This includes fro. Its serves as local mobility the establishment of the connection and security between the anchor for interworking with 3GPP network and UE and is handled by the connection or mobility technology like GSM, GPRS and management layer in the NAS protocol layer. UMTS. MME is a control node for processing the signaling between theHSS- is Home Subscriber Server. It contains user’s subscription UE and Core Network. The protocoldata such as the EPS-subscribed QoS profile and any access used between the UE and Corerestrictions for roaming. It also holds information about the PDNs Network is NAS protocol.to which the user can connect. HSS contains user’s subscriptionsIt also holds dynamic information such as the identity of the MME data and information about the PDNto which the user is currently attached or registered. The HSS also to which user can connect. It isintegrate the authentication center (AUC), which generates similar to HLR in GSM.authentication and security keys PCRF is responsible for policy control decision making and PCEF function. It provides QoSPCRF-is Policy Control and Charging Rules Function authorization (QCI and Bit rate).It is responsible for policy control decision-making, as well as forcontrolling the flow-based charging functionalities in the PolicyControl Enforcement Function (PCEF), which resides in the P-GWThe PCRF provides the QoS authorization (QCI and bit rates) thatdecides how a certain data flow will be treated in the PCEF andensures that this is in accordance with the user’s subscriptionprofile. 7
  8. 8. 8. Interworking with 3GPP and Non 3GPP Networks LTE also supports inter working and mobility (handover) with networks using other Radio Access Technologies such as GSM, UMTS, CDMA2000 and WiMAX The S-GW acts as the mobility anchor for inter working with other 3GPP technologies such as GSM and UMTS P-GW serves as an anchor allowing seamless mobility to non-3GPP networks such as CDMA2000 or WiMAX. The P-GW may also support a Proxy Mobile Internet Protocol (PMIP)-based interface Long Term Evolution (LTE) interworking with other technologies SGW is responsible for 3GPP Inter- RAT GSM, GPRS and UMTS technologies interworking PGW is responsible for Non 3GPP Inter RAT CDMA and WiMAX Technologies interworking. Figure 5 8Architecture 9. Conclusion In this paper, we described the Network architecture and performance objectives of the next generation access-network technology being developed by 3GPP. 3GPP LTE technology is with the envisaged throughput and latency targets and emphasis on simplicity, spectrum flexibility, added capacity and lower cost per bit, LTE is destined to provide greatly improved user experience, delivery of new revenue generating exciting mobile services and will remain a strong competitor to other wireless technologies in the next decade for both developed and emerging markets. 8
  9. 9. Authors 10. References 1. Wikipedia.com 2. www.3gpp.org 3. 3GPP standard 36.300 , Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall Description 4. LTE, The UMTS long Terms Evolution: From Theory to PractiseSukhvinder MalikLTE Testing EngineerRahul Atri, LTERadio Access Network Engineer Disclaimer: Authors state that this whitepaper has been compiled meticulously and to the best of theirPreet Kanwar Singh Rekhi knowledge as of the date of publication. The information contained herein the white paperLTE Testing Engineer is for information purposes only and is intended only to transfer knowledge about the respective topic and not to earn any kind of profit. Every effort has been made to ensure the information in this paper is accurate. Authors 9 does not accept any responsibility or liability whatsoever for any error of fact, omission, interpretation or opinion that may be present, however it may have occurred

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