Department of Computer Science Institute for System Architecture, Chair for Computer Networks

Transcription

1 Department of Computer Science Institute for System Architecture, Chair for Computer Networks LTE, WiMAX and 4G Mobile Communication and Mobile Computing Prof. Dr. Alexander Schill

2 LTE: Characteristics LTE = Long Term Evolution European implementation of IMT (International Mobile Telecommunications) by ETSI (European Telecommunication Standards Institute) Packet oriented propagation only High data rates Up to 300 Mbit/s Downlink Up to 75 Mbit/s Uplink Flexible frequency assignment About 40 frequency ranges Varying frequency blocks (1.4, 3, 5, 10 and 20 MHz) small latency of 5ms between mobile phone and conventional telephone network optimized for travelling speeds of up to 15 km/h (but up to 500km/h possible with reduced quality) 2

3 LTE User Equipment (UE) Examples of LTE-enabled devices iphone, Samsung Galaxy LTE, Samsung LTE Stick Five device categories Category Peak data rate Mbit/s RF bandwidth DL UL MHz Modulation QPSK, 16QAM QPSK, 16QAM, 64QAM 2 Rx diversity Assumed in performance requirements 2x2 MIMO Not supported Mandatory 4x4 MIMO Not supported Mandatory 3

4 LTE: Frequency bands Germany (currently) 5 bands: 800 MHz, 900 MHz, 1800 MHz, 2000 MHz, 2600MHz Rural Areas 800 MHz Urban Areas 800 MHz 1800 MHz -> partially reassignment from GSM 2600 MHz for crowded areas in cities (train stations, shopping malls, etc.) USA: 700MHz, 1700MHz and 2100 MHz Europe: 800 MHz and others Bands of 700, 800, 1800 and 2600 MHz will potentially allow world wide roaming in the future 4

5 LTE: Examples of frequency bands frequency spectrum of the digital dividend: better building penetration & propagation features > higher range 790 MHz 862 MHz (72 Mhz) 5 MHz frequency block Duplex gap* 12 MHz 820 MHz 832 MHz * The Duplex gap is meant as a fallback position for wireless production technology. frequency spectrum of the IMT extension band: Enough blocks for 20 MHz bandwidth > Higher data rate 2500 MHz (190 Mhz) 2690 MHz 5 MHz frequency block 2570 MHz 10 x 5 MHz blocks uncoupled 2620 MHz 5

6 LTE Reference Architecture S6a HSS MME PCRF S1-MME S11 Gx UE enodeb S-GW P-GW LTE - Uu S1-U S5/S8 SGi PSTN eutran Core Network Evolved NodeB (enodeb): Radio Network Control, Base Stations Core network Serving Gateway (S-GW) Mobility Management Entity (MME) PDN (Packet Data Network) Gateway (P-GW) Home Subscriber Server (HSS) Policy Control and Charging Rules Function (PCRF) 6

7 Tasks of enodeb: Overview enodeb manages one or several cells Major tasks: IP header compression Encryption Radio resource management Connectivity to core network Bearer management UE mobility MME S-GW MME S-GW Core Network enodeb enodeb enodeb E-UTRAN comm. between enodebs signaling to MMEs bearer path 7

8 LTE: TDD and FDD subframe = 1 millisecond Uplink (UL) Downlink (DL) FDD Special Frame UpPTS Uplink (UL) Downlink (DL) TDD DwPTS Guard Period two versions of LTE provide solutions for coupled/uncoupled frequency blocks transmitted signals divided into subframes (time units of 1 ms) FDD (Frequency division duplex) -separated frequency blocks for UL/DL TDD (Time division duplex) one frequency block alternately used for UL/DL: - Downlink subframes, Uplink subframes and Special Frames Special Frame = one subframe for each switching from down to up link; contains DwPTS (Downlink Pilot Timeslot), GP (Guard Period avoids overlay of sent and received messages) and UpPTS (Uplink Pilot Timeslot) 8

9 LTE: Use of OFDM for Multiplexing LTE transmission is based on OFDM (Orthogonal frequency-division multiplexing) in OFDM data is distributed over a large number of closely spaced orthogonal subcarriers (two subcarriers are orthogonal if the maximum amplitude of one subcarrier is reached while the other subcarriers amplitude is zero) Subcarriers modulated with conventional modulation scheme (QAM) Improved spectrum efficiency and lower bandwidth demand Robust against interference because interference on subcarrier does not influence the whole frequency band (and combination with other schemes such as CDMA possible) But power consumption increases with the number of subcarriers due to overheads for coding and decoding OFDM with 3 subcarriers FDM with 3 subcarriers f f 9

10 LTE: Specific enhancements of OFDM LTE uses specific enhancements of OFDM with a focus on efficient simultaneous access of multiple users: OFDMA (Orthogonal frequency-division multiple access) for Down Link subsets of subcarriers are assigned to individual users, so simultaneous (lower data rate) transmissions are enabled for several concurrent users on the same subcarrier SC-FDMA (Single Carrier FDMA) for Up Link multiple access on the same carrier realized by insertion of user-specific coefficients by the sender before Fourier transformation, and respective decoding by the receiver (roughly comparable to CDMA). More energy-efficient for battery-driven mobile devices. 10

11 LTE Bearer Application/service layer UL- TFT UL-TFT RB- ID <- - > S1- TEID S1- TEID <- - > S5/S8- TEID DL-TFT DL-TFT UE enodeb S- GW P- GW Radio bearer S1 bearer S5/S8 bearer Different QoS requirements of applications (VoIP, browsing, file download) are mapped to bearers Bearers cross multiple interfaces, each part is individually mapped to lower layer bearer with own bearer id Each node manages binding between bearer ids Packet filters (Traffic Flow Templates (TFT)) assign IP packets to bearers (e.g. based on IP header information and TCP port numbers) 11

12 Standardized QoS class identifier for LTE QCI Resource Type Priority Packet Delay Budget(ms) Packet Error Loss Rate Example Service 1 GBR Conversational voice 2 GBR Conversational video (live streaming) 3 GBR Non- conversational video (buffered streaming) 4 GBR Real- time gaming 5 Non- GBR IMS signaling 6 Non- GBR Voice, video (live streaming), interactive gaming 7 Non- GBR Video (buffered streaming) 8 Non- GBR TCP- based (for example, WWW, e- mail), chat, FTP, p2p file sharing, progressive video and others 9 Non- GBR GBR guarantied bit rate, IMS IP Multimedia Subsystem 12

13 LTE Interworking UTRAN (GSM, UMTS) 3G-SGSN S3 S4 MME S1-MME S11 UE E-UTRAN S-GW P-GW LTE - Uu S1-U S5/S8 non-3gpp networks (CDMA2000, WiMAX, ) Interworking and mobility with other networks and older standards enabled via Service Gateway (S-GW) 13

14 LTE Advanced Improved performance Data rate up to 1 GBit/s End-to-end delay ms Enhancements Carrier aggregation up to 5 * 20 MHz -> 100MHz Possible in contiguous and non-contiguous spectrum allocations Multiple Input, Multiple Output (MIMO) Up to 4 LTE antennas in LTE devices to use MIMO also for Uplink Base stations can be equipped with up to 8 antennas Support for relay node base stations Additional intermediate base stations Improve signal quality at cell borders Support of low power nodes for pico cells for crowded areas 14

15 WiMAX / IEEE WiMAX: Worldwide Interoperability for Microwave Access, standardized by IEEE and WiMAX-Forum (large industry consortium) IEEE FBWA (Fixed Broadband Wireless Access) initially was an alternative for broadband cable services like DSL; frequency range: GHz, in assumption of LOS (line of sight) Enhancement IEEE a; frequency band: 2-11 GHz, NLOS (non line of sight) Enhancement IEEE e: MBWA (Mobile Broadband Wireless Access); frequency band: 2-6 GHz, NLOS Enhancement IEEE m: Mobile High Speed Communication; projected for up to 1 Gbit/s 15

16 WiMAX/IEEE : overview Standard a e m Spectrum, GHz LOS-condition LOS NLOS NLOS NLOS Bit rate, MBit/s up to 75 up to 100 up to 1000 (theoretical) Range, km up to 5 up to 50 (cellular) Channel bandwith, MHz 20, 25 and 28 Variable: 1, ,5-20 1,5-20 Modulation QPSK, 16QAM, 64QAM OFDM, QPSK, 16QAM, 64QAM OFDM, QPSK, 16QAM, 64QAM OFDM, QPSK, 16QAM, 64QAM, 128QAM (N)LOS (Non) Line-of-Sight 16

17 WiMAX: Frequencies worldwide For Germany especially: 3,41-3,452 GHz and 3,51-3,552 GHz 17

18 WiMAX: Modulation WiMAX: strong dependency of applicable modulation technique on effective channel capacity, spectrum efficiency, range, signalnoise-ratio: BPSK Binary Phase Shift Keying QPSK Quadrature Phase Shift Keying 16QAM Quadrature Amplitude Modulation 64QAM Quadrature Amplitude Modulation (typical example distribution (percentage) of users in different coverage areas) 18

19 Medium Access TDMA (Time Division Multiple Access) Each communication channel gets fixed slot for data transmission DAMA (Demand Assigned Multiple Access) 2 Phases: Reservation: every station tries to acquire slot for each transmission phase (collision possible) Data transmission: within reserved slot guaranteed collision free transmission Duplex connection FDD (Frequency Division Duplex): simultaneous use of different frequencies TDD (Time Division Duplex): Switching between upand downlink on the same frequency 19

20 WiMAX: Cellular backbone Network e.g Gigabit Ethernet PHY OFDM- PHY UMTS cell WiMAX cell Point to Point Backbone Point to Multipoint 20

21 Network topologies 1) Last Mile (point to point) or 2) Point to Multipoint network Base Station (BS) is the central point for the Mobile Stations (MS) Sending in Downlink-direction: Broad-, Multi-, Unicast Connection of a MS to BS is characterized via Channel ID (CID), Channel id gives the possibility for the BS to receive multicast messages Network MS/BS BS MS MS/BS MS MS MS 21

22 Network topologies 3) Mesh network MS can communicate directly Mesh BS: connected with a network outside the mesh other differentiation neighbor: direct connection to a node neighborhood: all other neighbors extended neighborhood: remote neighborhoods Network Mesh MS Mesh MS Mesh MS Mesh BS Mesh MS Mesh MS Mesh MS 22

23 MBWA (Mobile Broadband Wireless Access); Working Group originated from goal: Specification of PHY and MAC for Packet-based MBWA- System Should close the gap between WLAN and slower but highly mobile networks (UMTS) But never reached operational state, so practically not relevant anymore Summary: Overall judgement of WiMAX - Interesting approach especially for last mile in remote neighborhoods with weakly developed infrastructure - However, even in such areas, 3G and 4G are emerging, and also due to lack of flexible and affordable end devices, WiMAX is strongly declining 23

24 Technology comparison UMTS/HSPA/HSPA+ WiMAX MBWA LTE (advanced) Mobility Handover, Roaming Handover, Roaming, Mobile IP --- Max Speed 300 km/h 120 km/h 300 km/h 500 km/h Switching type circuit and packet Packet switching Peak data rates Down Link 2/14,4/28 Mbit/s (5MHz channel) Cell sizes pico(1) -, micro (2) -, macro (3) -cells QoS End-to-end QoS Different classes 365 Mbit/s (2x 20MHz channel, variations) variable End-to-end QoS Different classes pico (1) -, micro (2) -, macro (3) -cells End-to-end QoS Mbit/s ( MHz channel) pico (1) -, micro (2) -, macro (3) -cells End-to-end QoS Different classes Scalability variable data rate ~ Multiple users per BS Air Interface CDMA adaptive Modulation MIMO OFDM(A), adaptive Modulation MIMO OFDM Adaptive Modulation OFDM, SC-FDMA adaptive Modulation MIMO Security AES AES, X.509 AES 3G Security (1) <100m, (2) ~500m, (3) >1km 24

25 4G Characteristics: Summary high mobility Ú Handover, Roaming, velocity up to more than 300 km/h switching technique Ú pure packet switching integrated multi-media-services Ú VoIP, TVoIP, VoD, Streaming high data rate (up to 1Gbit/s) Ú even at high mobility should be like DSL Size of cell Ú variable and scalable QoS Ú prioritization of specific multimedia data scalability Ú available and reliable with many users air interface Ú OFDM (better spectrum efficiency) security Ú up to date standards (e.g. AES) Extension / integration of UMTS, LTE and WLAN approaches 25

26 Technology comparison 3G to 4G LTE (3G) LTE Advanced (4G) Peak data rate Down Link (DL) Peak data rate Up Link (UL) Transmission bandwidth DL Transmission bandwidth UL Coverage Scalable bandwidths Scalability Capacity 300 Mbit/s 1 Gbit/s 75 Mbit/s 500 Mbit/s 20 Mhz (max.) 100 Mhz 20 Mhz (max.) 40 Mhz (requirements as defined by ITU) Full performance up to 5km 1.4, 3, 5, 10 and 20 MHz MHz variable data rate Multiple users per BS 200 active participants per cell at 5 MHz Same as LTE requirement. Should be optimized or deployed in pico cell / micro cell environments. variable data rate Multiple users per BS 3 times higher than that in LTE 26

27 Summary: Data rates and mobility High-speed /Wide-area Mobility Medium-speed /Urban area Walking /Local area 2G Standing /Indoors Source: Bitrate, MBit/s 27

28 Some further readings Eds.: Sesia, S., Toufik, I., Baker, M.: LTE The UMTS Long Term Evolution From Theory to Practice, Whiley, 2009 LTE: WiMAX technology: IEEE web sites for and : grouper.ieee.org/groups/802/16/ and /802/20 28