192620010 Mobile & Wireless Networking Lecture 5: Cellular - PowerPoint PPT Presentation

192620010 Mobile & Wireless Networking Lecture 5: Cellular Systems (UMTS / LTE) (1/2) [Schiller, Section 4.4] Geert Heijenk Mobile and Wireless Networking 2013 / 2014

Outline of Lecture 5 Cellular Systems (UMTS / LTE) (1/2) q Evolution of cellular systems q GSM l GSM Network Architecture l GSM radio interface l GPRS l EDGE q 3G UMTS l UMTS Network Architecture l Wideband CDMA 2 Mobile and Wireless Networking 2013 / 2014

Evolution of cellular systems Source: Agilent Technologies, 2012 3 Mobile and Wireless Networking 2013 / 2014

GSM Architecture OMC, EIR, AUC HLR GMSC fixed network NSS with OSS VLR MSC MSC VLR BSC BSC RSS 4 Mobile and Wireless Networking 2013 / 2014

GSM Radio Interface: TDMA/FDMA 935-960 MHz 124 channels (200 kHz) downlink 890-915 MHz 124 channels (200 kHz) uplink higher GSM frame structures time GSM TDMA frame 1 2 3 4 5 6 7 8 4.615 ms GSM time-slot (normal burst) guard guard tail user data S Training S user data tail space space 3 bits 57 bits 1 26 bits 1 57 bits 3 546.5 µ s 577 µ s Mobile and Wireless Networking 2013 / 2014

GPRS (General Packet Radio Service) q packet switching q using free slots only if data packets ready to send q (~reservation Aloha) Class slots Receiving slots Sending Maximum q Few changes to base station number of slots (software) 1 1 1 2 q New core network architecture 2 2 1 3 (router-based) 3 2 2 3 5 2 2 4 8 4 1 5 10 4 2 5 12 4 4 5 1 slot 2 slots 3 slots 4 slots 5 slots 6 slots 7 slots 8 slots Coding scheme CS-1 9.05 18.2 27.15 36.2 45.25 54.3 63.35 72.4 CS-2 13.4 26.8 40.2 53.6 67 80.4 93.8 107.2 CS-3 15.6 31.2 46.8 62.4 78 93.6 109.2 124.8 CS-4 21.4 42.8 64.2 85.6 107 128.4 149.8 171.2 6 Mobile and Wireless Networking 2013 / 2014

GPRS architecture and interfaces SGSN G n PDN BSS SGSN GGSN MS U m G b G n G i HLR/ MSC GR VLR EIR 7 Mobile and Wireless Networking 2013 / 2014

EDGE EDGE (Enhanced Data rates for GSM Evolution): q New modulation technique: 8PSK instead of GMSK (bitrate x3) q Can be combined with GPRS q Adaptive Modulation and Coding q Incremental Redundancy (Hybrid ARQ) q New BS hardware 8 Mobile and Wireless Networking 2013 / 2014

Outline of Lecture 5 Cellular Systems (UMTS / LTE) (1/2) q Evolution of cellular systems q GSM l GSM Network Architecture l GSM radio interface l GPRS l EDGE q 3G UMTS l UMTS Network Architecture l Wideband CDMA 9 Mobile and Wireless Networking 2013 / 2014

UMTS architecture (original release (R99)) UTRAN (UMTS Terrestrial Radio Access Network) q Cell level mobility q Radio Network Subsystem (RNS) q Encapsulation of all radio specific tasks UE (User Equipment) CN (Core Network) q Inter system handover q Location management if there is no dedicated connection between UE and UTRAN U u I u UE UTRAN CN 10 Mobile and Wireless Networking 2013 / 2014

UTRAN architecture RNS RNC: Radio Network Controller RNS: Radio Network Subsystem I ub UE 1 Node B I u RNC CN UE 2 Node B Node B UTRAN comprises several RNSs Node B can support FDD or UE 3 TDD or both I ur RNC is responsible for handover Node B decisions requiring I ub signalingto the UE Node B Cell offers FDD or TDD RNC Node B Node B RNS 11 Mobile and Wireless Networking 2013 / 2014

Core network: architecture VLR BSS A bis I u BTS BSC MSC GMSC PSTN Node B BTS I u CS AuC EIR HLR GR Node B I ub Node B RNC SGSN GGSN G i G n Node B Node B I u PS CN RNS 12 Mobile and Wireless Networking 2013 / 2014

UMTS Protocol Architecture - User Plane App App TCP TCP IP IP IP GTP-U PDCP GTP-U PDCP GTP-U L2 L2 UDP UDP UDP UDP RLC RLC MAC MAC IP IP IP IP FP FP L1 L1 PHY L2 L2 L2 L2 L2 PHY L2 L1 L1 L1 L1 L1 L1 UE SGSN Node B RNC GGSN Host Gi Iub Uu IuPS Gn Other Legend: UMTS UMTS Transport Network Internet 13 Mobile and Wireless Networking 2013 / 2014

UMTS Protocol Architecture – Control Plane UMM/SM UMM/SM RANAP RRC RRC RANAP SCCP SCCP RLC RLC Signalling MAC Signalling MAC Bearer Bearer NBAP NBAP PHY L2 L2 L2 PHY L2 L1 L1 L1 L1 UE SGSN Node B RNC Iub Uu IuPS Legend: UMTS UMTS Transport Network 14 Mobile and Wireless Networking 2013 / 2014

Outline of Lecture 5 Cellular Systems (UMTS / LTE) (1/2) q Evolution of cellular systems q GSM l GSM Network Architecture l GSM radio interface l GPRS l EDGE q 3G UMTS l UMTS Network Architecture l Wideband CDMA 15 Mobile and Wireless Networking 2013 / 2014

Wideband CDMA Direct Sequence CDMA, also Transport channels known as Wideband CDMA Channel Channel Chip rate 3.84 Mc/s coding coding Carrier spacing 5 MHz Multiplexing Physical-layer procedures Transport-channel Mapping to physical channels and processing measurements Physical channels Spreading Spreading 3.84 Mc/s Modulation Modulation ≈ 5 MHz 16 Mobile and Wireless Networking 2013 / 2014

How do we spread the data? The operation of spreading in a CDMA system is divided into two separate parts q Spreading code = Scrambling code + Channelization code Scrambling q Separates different mobiles (in uplink) and different cells/sectors (in downlink) Channelization q Separates different physical channels that are transmitted on the same scrambling code q The purpose of channelization is most evident in the downlink 17 Mobile and Wireless Networking 2013 / 2014

Spreading and scrambling of user data Constant chipping rate of 3.84 Mchip/s Different user data rates supported via different spreading factors q higher data rate: less chips per bit and vice versa User separation via unique, quasi orthogonal scrambling codes q users are not separated via orthogonal spreading codes q much simpler management of codes: each station can use the same orthogonal spreading codes q precise synchronisation not necessary as the scrambling codes stay quasi- orthogonal data 1 data 2 data 3 data 4 data 5 spr. spr. spr. spr. spr. code 1 code 2 code 3 code 1 code 4 scrambling scrambling code 1 code 2 sender 1 sender 2 18 Mobile and Wireless Networking 2013 / 2014

Orthogonal Variable Spreading Factor (OVSF) coding 1,1,1,1,1,1,1,1 1,1,1,1 ... 1,1,1,1,-1,-1,-1,-1 1,1 1,1,-1,-1,1,1,-1,-1 ... 1,1,-1,-1 X,X 1,1,-1,-1,-1,-1,1,1 1 X 1,-1,1,-1,1,-1,1,-1 X,-X ... 1,-1,1,-1 1,-1,1,-1,-1,1,-1,1 1,-1 SF=n SF=2n 1,-1,-1,1,1,-1,-1,1 ... 1,-1,-1,1 1,-1,-1,1,-1,1,1,-1 SF=1 SF=2 SF=4 SF=8 19 Mobile and Wireless Networking 2013 / 2014

UMTS FDD frame structure W-CDMA • 1920-1980 MHz uplink Radio frame � • 2110-2170 MHz downlink • chipping rate: 10 ms � 0 � 1 � 2 � ... � 12 � 13 � 14 � 3.840 Mchip/s • soft handover Time slot � • QPSK 666.7 µs � uplink DPCCH � Pilot � TFCI � FBI � TPC � • complex power control (1500 power control 2560 chips, 10 bits � cycles/s) • spreading: UL: 4-256; 666.7 µs � Data � uplink DPDCH � DL:4-512 2560 chips, 10*2 k-1 bits (k = 1...7) � 666.7 µs � Data 1 � TPC � TFCI � Data 2 � Pilot � downlink DPCH � FBI: Feedback Information TPC: Transmit Power Control DPDCH � DPCCH � DPDCH � DPCCH � TFCI: Transport Format Combination Indicator 2560 chips, 10*2 k bits (k = 0...7) � DPCCH: Dedicated Physical Control Channel DPDCH: Dedicated Physical Data Channel DPCH: Dedicated Physical Channel Slot structure NOT for user separation but synchronisation for periodic functions! 20 Mobile and Wireless Networking 2013 / 2014

Bit rates and Spreading Factors Channel bit rate [kbps] User bit rate (bef. coding) [kbps] k Spreading Uplink Downlink Uplink Downlink factor 0 512 N/A 15 kbps N/A 6 kbps 1 256 15 kbps 30 kbps 15 kbps 24 kbps 2 128 30 kbps 60 kbps 30 kbps 51 kbps 3 64 60 kbps 120 kbps 60 kbps 90 kbps 4 32 120 kbps 240 kbps 120 kbps 210 kbps 5 16 240 kbps 480 kbps 240 kbps 432 kbps 6 8 480 kbps 960 kbps 480 kbps 912 kbps 7 4 960 kbps 1920 kbps 960 kbps 1872 kbps 21 Mobile and Wireless Networking 2013 / 2014

Fading Path loss – fading due to distance q 1/distance α ( α between 3 and 4) Long term (slow) fading – caused by shadowing q Log-normal Short term (fast) fading – caused by multipath propagation q Rayleigh fading amplitude Signal level (dB) Path loss Long term fading Short term fading Distance (log) 22 Mobile and Wireless Networking 2013 / 2014

Purpose of Power Control Goal q mobile station transmitted power is controlled such that all users in the cell experience the same SIR (Signal to Interference Ratio) at the base station receiver Open Loop (initial power setting) q compensate for pathloss and slow fading q uses downlink pilot channel Closed Loop (fast power control) q compensates also for fast fading q needs dedicated downlink control channel for power control commands 23 Mobile and Wireless Networking 2013 / 2014

Dynamic Range of Power Control P C P I Worst case: P C (dB) – P I (dB) = – 80 dB ! Interferers are rejected by the processing gain: R chip 10 6 G = = = 100 → 20 dB R bit 10 4 C ⇒ = – 80 + 20 = – 60 dB ! I Power control with a large dynamic range is essential! 24 Mobile and Wireless Networking 2013 / 2014