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Mobile Communications: Long Term Evolution Part 1 Motivation for LTE Evolution of the standards Requirements and targets Competing standards Frequency.

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Presentation on theme: "Mobile Communications: Long Term Evolution Part 1 Motivation for LTE Evolution of the standards Requirements and targets Competing standards Frequency."— Presentation transcript:

1 Mobile Communications: Long Term Evolution Part 1 Motivation for LTE Evolution of the standards Requirements and targets Competing standards Frequency bands System architecture Part 2 LTE enabling technologies – OFDM – MIMO – SC-FDMA

2 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Motivation for LTE For consumers –Fast data access (several megabytes in just some seconds) –Flexible media access (access to any media content from everywhere) –Real time services (streaming, VoIP, videoconferencing, etc.) For network operators –Flexibility (scalable bandwidth from 1.25MHz to 20MHz) –Efficiency (more standard voice customers, more data, more services) –Cost savings (cheaper infrastructure, migration to an All-IP-Network) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 2

3 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II IMT-2000 to IMT-Advanced (source: ITU-R M. 1645) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 3

4 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Cellular wireless system evolution Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 4

5 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Evolution of UMTS towards packet only system First version of LTE is documented in 3GPP specifications Rel-8 Former specifications of LTE are known as E-UTRA and E-UTRAN Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 5

6 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Requirements and targets (source: TR and ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 6 Peak data rate Latency C-Plane latency: less than 100ms camped-to-active transition and less than 50ms dormant-to-active transition (excluding DL and paging delay) U-Plane latency: less than 5ms in upload condition Capacity at least 200 active users per cell for spectrum allocations up to 5 MHz at least 400 users for higher spectrum allocations

7 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Requirements and targets (source: TR ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 7 Average user throughput per MHz and spectrum efficiency DL: 3 to 4 times Release 6 HSDPA. UL: 2 to 3 times Release 6 Enhanced Uplink Mobility Optimized for low mobile speed at 0 – 15km/h Support 15 – 120km/h with high performance 120 – 350km/h main mobility (500km/h depending on frequency band) Coverage Up to 5km: meet targets for throughput, spectrum efficiency and mobility Up to 30km: support full mobility, slight degradations of throughput and more significant degradation of spectrum efficiency are acceptable Further enhanced MBMS Improved cell edge performance Defined interruption time when changing between different streams

8 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Requirements and targets (source: TR ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 8 Deployment Scenarios Standalone (no interworking with UTRAN/GERAN) Integrated (existing UTRAN and/or GERAN in same geographical area) Spectrum flexibility Support for spectrum allocations of different size (1.25 (1.4?) – 20MHz) Support for diverse spectrum arrangements Spectrum deployment Co-existence and co-location with GERAN/3G and between operators on adjacent channels Co-existence and interworking with 3GPP RAT Interruption time during handover between E-UTRAN and 3GPP-RAN (real-time service < 300msec, non real-time service < 500msec)

9 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Requirements and targets (source: TR ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 9 Architecture and migration Single E-UTRAN architecture (packet based) Simplified and minimized number of interfaces Minimized delay variation (jitter) Radio resource management requirements Enhanced end-to-end QoS Support efficient transmission and operation of higher layer protocols over the radio interface (e.g. IP header compression) Support of load sharing and policy management across different Radio Access Technologies Complexity Minimized number of options No redundant mandatory features Optimized terminal complexity and power consumption

10 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Parameters in context (source: Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 10

11 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page Complementary Access Systems Switching between the layers need to be transparent to the user Some existing standards and technologies for the different layers Source ITU-R M.1645 IEEE GPP LTE IEEE Bluetooth* IEEE IEEE UWBmmWave IEEE GPP2 UMB/ IEEE

12 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Competing 3.9G standards Different organizations - different standards? –3GPP: LTE –3GPP2: UMB (discontinued) –IEEE and WiMAX Forum: Mobile WiMAX (IEEE e) All have similar goals –Improved spectral efficiency –Wide bandwidth –Very high data rates Goals shall be achieved primarily by –Higher-order modulation schemes –Multi-antenna technology –Simplified network architecture Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 12

13 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Comparison of the competitors (source: Technical overview of 3GPP LTE by Hyung G. Myung in May 2008) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 13

14 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II E-UTRA operating bands (source: TS ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 14 FDD LTE frequency bands -Paired bands for simultaneous transmission on UL and DL -Separation reduces the impact of signals to the receiver performance TDD LTE frequency bands -Unpaired because UL and DL share the same frequency but time separated Overlapping frequency bands -(roaming) UE needs to detect whether to use TDD or FDD on a particular band

15 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Additional information (source: Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 15

16 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Frequency division in Germany (source: ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 16

17 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II LTE network coverage in Germany (December 2011) E-Plus-Group (intended network expansion) Source: netzausbau.redaktionsserv ice-eplus-gruppe.de/4g- datennetz.php Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 17 Telekom Deutschland Source: mobile.de/funkversorgung/inland/0, 12418,15400-_,00.html) Vodafone Source: lte.de/zum- onlineshop/netzabdeckun g/vodafone-lte- netzabdeckung.htm) Telefónica O 2 Germany (no map provided)

18 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II 2G and 3G cellular network today (source: TR ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 18 The 3GPP project System Architecture Evolution (SAE) shall simplify this complex architecture by defining an all-IP network called the Evolved Packet Core (EPC). The EPC is required for specific features of LTE The EPC supports LTE, UTRAN, GERAN and non- 3GPP radio access networks such as cdma2000,

19 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Logical high level architecture (source: TR ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 19 Mobility Management Entity (MME) manages and stores the UE control plane context, generates temporary Id, UE authentication, authorisation of TA/PLMN, mobility management User Plane Entity (UPE) manages and stores UE context, DL UP termination in LTE_IDLE, ciphering, mobility anchor, packet routing and forwarding, initiation of paging 3GPP anchor is the mobility anchor between 2G/3G and LTE access systems SAE anchor is the mobility anchor between 3GPP and non 3GPP access systems (WLAN, WiMAX, etc.)

20 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Interfaces (source: TS ) S1: –S1-MME is reference point between E-UTRAN and MME –S1-U is reference point between E-UTRAN and Serving GW for per bearer U-Plane tunneling and inter eNB path switching during handover S2: mobility support between WLAN 3GPP IP access or non 3GPP access S3: user and bearer information exchange for inter 3GPP access system mobility S4: control and mobility support between GPRS Core and Inter AS Anchor S5: user plane tunneling and tunnel management between Serving GW and PDN GW S6: transfer of subscription and authentication data for user access to the evolved system S7:Transfer of (QoS) policy and charging rules from PCRF Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 20

21 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II The evolution of UTRAN Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 21

22 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 22 System architecture of LTE-Rel8 (source: TR ) eNB provides E-UTRA U-Plane and C-Plane protocol terminations towards the UE X2 connects eNBs as mesh network, enabling direct communication between the elements and eliminating the need to tunnel data back and forth through a (RNC) S1 connects E-UTRAN to EPC (eNBs are connected to MME and S-GW elements through a many-to-many relationship)

23 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Overview of the functional split (source: TR ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 23 Yellow boxes depict the logical nodes white boxes depict the functional entities of the control plane blue boxes depict the radio protocol layers

24 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Functions of the eNodeB (source: TR ) Radio resource management IP header compression and encryption Selection of MME at UE attachment Routing of user plane data towards S-GW Scheduling and transmission of paging messages and broadcast information Measurement and measurement reporting configuration for mobility and scheduling Scheduling and transmission of ETWS messages Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 24

25 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Functions of the MME (source: TR ) Non-access stratum (NAS) signaling and NAS signaling security Access stratum (AS) security control Inter CN node signalling for mobility between 3GPP access networks Idle mode UE Reachability Tracking Area list management (for UE in idle and active mode) PDN GW and Serving GW selection MME selection for handovers with MME change SGSN selection for handovers to 2G or 3G 3GPP access networks Roaming Authentication Bearer management functions including dedicated bearer establishment Support for ETWS message transmission Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 25

26 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Functions of the S-GW (source: TR ) Local mobility anchor point for inter eNB handovers Mobility anchoring for inter 3GPP mobility E-UTRAN idle mode DL packet buffering and initiation of network triggered service request procedure Lawful interception Packet routing and forwarding Transport level packet marking in the uplink and the downlink Accounting on user and QCI granularity for inter-operator charging UL and DL charging per UE, PDN and QCI Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 26

27 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Functions of the P-GW (source: TR ) Per-user-based packet filtering Lawful interception UE IP address allocation Transport level packet marking in the downlink UL and DL service level charging, ating and rate enforcement DL rate enforcement based on APN-AMBR Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 27

28 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Erweiterungen an dieser Stelle für das nächste Semester Protocol Stack –C-Plane –U-Plane Attach Procedure Detach Procedure Mobile Terminating Call Mobile Originating Call Handover Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 28

29 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Identities of the UE International Mobile Subscriber Identity (IMSI) –unique permanent identity of the SIM card, stored in HSS –used as little as possible when UE is communicating with the network Temporary Mobile Subscriber Identity (TMSI) –Alias used instead of IMSI –temporary ID, allocated by the MME during the attach procedure Radio Network Temporary ID (RNTI) –To identify the UE on the radio –Handed out by eNodeB, when UE establishes radio contact with eNodeB Access Point Name (APN) –IP address, allocated by PDN-Gateway as soon as UE is powered on Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 29

30 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Attach procedure Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 30 1.UE contacts eNB it hears the strongest 2.eNB will then select an MME for the UE 3.MME will select a serving gateway 4.S-GW selects a PDN-GW which provides an IP to the UE (PDN-GW is selected from the APN parameter provided by the enduser or the operator)

31 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II LTE enabling technologies Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 31 Orthogonal Frequency Division Multiple Access (OFDMA) Single Carrier FDMA (SC-FDMA) Multiple Input Multiple Output (MIMO) …

32 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II OFDM Available spectrum is divided into multiple narrowband parallel channels (subcarriers) Information is transmitted on the subcarriers at a reduced signal rate Frequency responses of the subcarriers are overlapping and orthogonal Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 32 f f Single carrier Multi carrier W W / N

33 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II OFDM (source: F. Khan, LTE for 4G Mobile Broadband, ISBN ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 33 Example shows 5 OFDM subcarriers –Each subcarrier is modulated by a data symbol –The OFDM symbol is formed by adding the modulated subcarrier signals –Here all subcarriers are modulated by data symbols 1s Resulting OFDM symbol signal has much larger signal amplitutde variations than the individual subcarriers –This characteristic of OFDM signal leads to larger signal peakness +

34 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II OFDM (source: F. Khan, LTE for 4G Mobile Broadband, ISBN ) Application of rectangular pulse in OFDM results in a sinc- square shape power spectral density This allows minimal subcarrier separation with overlapping spectra where signal peak for a given subcarrier corresponds to spectrum nulls for the remaining subcarriers Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 34

35 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Cyclic prefix (source: F. Khan, LTE for 4G Mobile Broadband, ISBN ) Orthogonality of OFDM subcarriers can be lost when the signal passes through a time-dispersive radio channel due to inter-OFDM symbol interference (multipath propagation) A cyclic prefix extension of the OFDM signal can be performed to avoid this interference Cyclic prefix length is generally chosen to accomodate the maximum delay spread of the wireless channel Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 35

36 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II OFDM signal representation (source: TR ) Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 36

37 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II OFDMA (source: Orthogonal Frequency Division Multiple Access (OFDMA) is a DL multi carrier transmission scheme for E-UTRA FDD and TDD modes based on conventional OFDM Incorporates elements of time division multiple access (TDMA) to avoid narrowband fading and interference OFDMA allows subsets of the subcarriers to be allocated dynamically among the different users on the channel (Frequency selective scheduling) Result is a more robust system with increased capacity Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 37

38 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II OFDM vs. OFDMA Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 38 Data is modulated over sub-carriers and time slots Enables high data rate in a wireless channel Each subscriber can get different quantity of data Enables optimal balance of data forwarding between subscribers

39 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II SC-FDMA (source: Single Carrier – Frequency Division Multiple Access (SC-FDMA) is UL transmission scheme for LTE with structure and performance similar to OFDMA It combines the low Peak-to-Average Ratio (PAR) techniques of single-carrier transmission systems (GSM and CDMA), with the multi-path resistance and flexible frequency allocation of OFDMA Brief description: –Convert data symbols from time to frequency domain via DFT –Map data symbols to desired location in overall channel bandwidth before they are converted back to time domain via IFFT –Inserted cyclic prefix Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 39

40 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II OFDMA vs. SC-FDMA Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 40

41 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II SC-FDMA signal generation (source: Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 41 Create time domain waveform (IQ representation) of SC-FDMA symbol Represent the symbol in frequency domain via DFT –DFT sampling frequency is chosen such that the time-domain waveform of one SC-FDMA symbol is fully represented by M=4 DFT bins spaced 15 kHz apart, with each bin representing one subcarrier in which amplitude and phase are held constant for 66.7 μs Shift the symbol to the desired part of the overall channel bandwidth

42 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II MIMO (source: Multiple antenna schemes that help to achieve higher spectral efficiency (throughput ) and link reliability (data quality) Key idea: Tx sends multiple data streams on multiple antennas and each stream goes through different paths to reach each Rx antenna The different paths taken by the same stream to reach multiple Rx allow canceling errors using superior signal processing techniques MIMO also achieves spatial multiplexing to distinguish among different symbols on the same frequency Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 42

43 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II MIMO formats Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 43 Use spatial (antenna) diversity to transmit high quality data Use spatial multiplexing to transmit many data Multipath propagation causes destructive interference (fading) –Affects SNR and error rate of the channel MIMO utilizes the different paths to improve –the robustness of the channel use multiple antennas to send the same signal on different paths signals on the different paths will be affected in different ways probability that all signals will be affected simultaneously is reduced –the throughput use the additional paths as additional channels for data transmission

44 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II The different antenna schemes (source: SISO – Single Input Single Output –No diversity, no additional processing –(+) simple, (-) channel performance is limited, (-) impact of interference and fading is significant SIMO – Single Input Multiple Output –Receive diversity (smart antennas) –Types: switched diversity and maximum ratio combining –(+) simple implementation, (+) reduces effects of fading, (-) processing needs to be done in Tx and Rx Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 44

45 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II MISO –Transmission diversity –Rx can receive optimum signal –(+) multiple antennas and redundancy coding / processing is moved from Rx to Tx, (+) size, cost and battery consumption of the UE Full MIMO –more than one antenna on both sides (Tx and Rx) –Channel coding to separate data from different paths –(+) can improve robustness and throughput of the channel, (-) additional cost for processing and antennas Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 45 The different antenna schemes (source:

46 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Shannons Law (source: MIMO spatial multiplexing provides additional data capacity Achieved by using multiple paths as additional data channels Shannons Law defines maximum data rate on a radio channel Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 46

47 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II MIMO spatial multiplexing (source: Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 47 MIMO systems utilize a matrix mathematical approach Transmit a number of n data streams t from n antennas Each path has different channel properties h Properties are processed to enable Rx to be able to differentiate between the different data streams

48 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II MIMO spatial multiplexing (source: Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 48 r n is the signal received at antenna n To recover transmitted data stream t n –Estimate individual channel transfer characteristic h ij to determine the channel transfer matrix [H] –Multiply received vector with inverse of the transfer matrix [H] [T] = [H] -1 x [R]

49 Chair Systems Monday, 20. October 2008 winter term 2008 – Mobile Communication Systems II Thursday, 15 May 2014 winter term 2010/11 – Mobile Communication Systems II Page 49 Enabling Technologies for LTE- Advanced Peak Data Rate improvement –DL 4x4 : LTE baseline 2x2 –UL 2x4 : LTE baseline 1x2 –8 Tx antennas at eNode-B including 8x8 MIMO spatial multiplexing is also considered Sector/cell throughput improvement –Advanced Downlink MU-MIMO: 8 Tx beam-forming –Uplink SU-MIMO –Hybrid OFDMA and SC-FDMA in uplink –Multi-stream MIMO SFN broadcast –Superposition of unicast and broadcast traffic Cell edge performance improvement –Multi-hop relay – coverage extension –Multi-cell MIMO (Network MIMO) – toward a cell without cell edge?


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