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ECE 5221 Personal Communication Systems

ECE 5221 Personal Communication Systems. Prepared by: Dr . Ivica Kostanic Lecture 22 – Basics of 3G - UMTS. Spring 2011. Why 3G? Phenomenal growth of 2G - lack of capacity Voice is becoming a commodity service Inadequacy of 2G networks for data services

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ECE 5221 Personal Communication Systems

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  1. ECE 5221 Personal Communication Systems Prepared by: Dr. Ivica Kostanic Lecture 22 – Basics of 3G - UMTS Spring 2011

  2. Why 3G? Phenomenal growth of 2G - lack of capacity Voice is becoming a commodity service Inadequacy of 2G networks for data services technically inadequate (available data rates, data QoS guarantees, integration with existing data networks, etc.) operationally inadequate (billing is location and time based) Industry mergers create diverse communication platforms - need for global convergence 3G networks are designed to address thedeficiencies of 2G 3G characteristics High capacity air interfaces (based on CDMA) Designed to handle data services Core network convergence Tighter integration with existing landline data networks Cellular networks of the third generation Most important 3G driving force: wireless data

  3. High mobility (vehicular) Macro cell 144 kbps High mobility (pedestrian) Macro or mini cell 384 kbps Low mobility Indoor coverage 2 Mbps Cell type Mega cell Macro cell Micro cell Pico cell Cell radius 100-500 km <= 35km <= 1km <=50m Operating environment Global Suburban Urban In-building Typical installation type Satellites Rooftops Lamp-post Inside a building Mobile speed [km/h] <=500 <100 <10 IMT-2000 Requirements • IMT-2000 is designed to work across many different environments and to provide multiple communication services • 3G work started in 1992 at the initiative of IMT IMT-2000 data rate requirements IMT-2000 HCS: Cell definitions

  4. Frequency allocation for the 3G • ITU recommendations • 1885-2025MHz UL • 2110-2200 MHz DL • In some areas portions of the ITU band already allocated • Additional US-AWS • 1710-1755MHz UL • 2110-2155MHz DL • Second generation bands - UMTS deployed as overlay on the existing technology • Additional allocations around 2.6GHz, 2.3GHz, and between 400MHz and 700MHz World wide allocations: http://www.worldtimezone.com/gsm.html

  5. 3G requirements Some differentiators between 3G and 2G • User throughputs up to 2Mbps • Variable bit rate that ca be offered on demand • Multiplexing services with different QoS requirement on the same link • Network delay that ca accommodate real time traffic • Quality requirements tat can be set from 10% FER to 10-6 BER • Coexistence and backward compatibility with 2G systems • Support of asymmetric UL and DL traffic • High spectrum efficiency • Standardization of major network interfaces

  6. Evolution of 3G • 3G continues to evolve • Standardized through 3GPP • 3G gracefully evolves into 4G – starting from R7 and R8 • Date rates • R99: 0.4Mbps UL, 0.4Mbps DL • R5: 0.4Mbps UL, 14Mbps DL • R6: 5.7Mbps UL, 14Mbps DL • R7: 11Mbps UL, 28Mbps DL • R8: 50Mbps UL on LTE, 42Mbps DL on HSPA and 160 Mbps on LTE Note: theoretical data rates are never seen in the field. They represent the highest throughputs supported by the system design Evolution of the UMTS (3G)

  7. Global cellular system evolution • 3GPP standards 85% of global subscription (almost 5B worldwide) • 3GPP2 about 10% of global subscription • Within 3GPP group – coexistence and compatibility of standards • Major carriers that deploy 3GPP2 technologies have announced their migration to LTE (3GPP) • As of 2011 • 200+ UMTS Networks • 300M subscribers Evolution map for cellular technologies

  8. 3G Services • 2G optimized for voice • 3G designed for service plurality • Flexibility of handling both CS and PS through same air interface • Management of different types of PS • Advanced capabilities required for service plurality • High data rates ( 2Mbps in R99 to 28.8Mbps in R7. Practically 1 to 2Mbps – frequently limited by cellular provider) • Low packet delay times (100ms in R5, 50ms in R6) • Seamless mobility for PS applications • QoS differentiation between PS • Simultaneous voice and data • Interworking with GSM/GPRS • 3G services may be • Person to person • Content to person • Business connectivity • Person to person – peer to peer services (voice or data) • Content to person – access of server based information • Business connectivity – use of WCDMA as a radio modem

  9. Person to Person: CS Voice • UMTS uses AMR (Adaptive Multi Rate vocoder) • Rates 12.2 (EFR), 10.2, 7.40, 6.70, 5.90, 5.15, 4.75 kbps • Rates controlled by RAN and may be changed every 20ms through in band signaling • Two modes: • AMR-NB, Fs = 8k, BW – (200,3400) Hz • AMR-WB, Fs = 16K, BW – (50, 7000) Hz • AMR is Algebraic Code Excited Linear Predictive vocoder • Advanced features • Voice activity detection (VAD) • Background noise evaluation (comfort noise) through SID (silence descriptor frame) • Discontinuous transmission (DTX) • Frame substitution (error concealment) • Performance requirement – AMR can tolerate 1% of FER without perceivable quality degradation • Rate control may be used by RAN to • Increase capacity during high loading • Extend the coverage in low signal areas • For further capacity increase – newer networks may use AMR with source adaptation

  10. Person to person: Wideband AMR • Introduced in Release 5 • Wideband – Fs = 16KHz • Wider bandwidth (50,7000)Hz • Better voice quality • Adopted by ITU-T for landline telecom • Future landline and wireless system would use same coder • No transcoding • AMR-WB shows excellent MOS • Better than AMR-NB (for the same rate) • Better than 64kbps PCM • Robust in noisy environment • Improvements are result of • Higher sampling frequency – better for capturing the frequency content of consonants • Increased processing (more sophisticated voice analysis algorithms) MOS comparison between AMR-NB and AMR-WB

  11. Person to Person: Other • Video telephony – supported as of Release 5 as CS switched service(ITU-T H324M) • Packet switched services • SMS Messaging • MMS Messaging • Audio messaging (very cost effective, one minute AM is only 35kB) • Instant messaging • Mobile email • Video sharing • Push to talk cellular • VoIP • Multi-player games • PS person to person services – large revenue potential for operators • PS applications – very diverse QoS requirements

  12. Content to person service • Web Browsing • Accounts for more than 50% of mobile data usage • Progressive download • Podcasting – users upload audio and video content for free download by other web users • Social media • Audio and video streaming • Becoming increasingly popular • Less complicated from digital content rights that downloadable media • Less demanding from the mobile memory standpoint • Content download • Application, ring tone, MP3,… • Download may vary from few kilo bytes to few megabytes • All content to person services are highly asymmetric in traffic demand.

  13. RAN architecture

  14. UMTS Network Architecture • Standardized interfaces • Air interface (Uu) • UTRAN-CN interface (Iu) • Interface standardization – allow different vendors for UE, RAN and CN • 3G Network • User equipment (phones, data cards) • UMTS Terrestrial Radio Network (UTRAN) • Core Network (CN) • Relative to 2G • Revolution on the UE and UTRAN • Evolution on CN Major components of 3G network

  15. UMTS domains Domain based view of UMTS network • Network units are combined into functional blocks called domains • There are six domains • Interfaces between domains are standardized • Grouping of communication task – stratum • Access stratum – communication between User Equipment (UE) and Radio Access Network (RAN) • Non-access stratum – communication between USIM and ME, or between UE and CN

  16. Circuit versus packet switching • Packet Switched (PS) • Data stream subdivide into blocks (packets) • Packets have address of the destination • Packet released into communication network and routed independent of each other • Receiver assembles the packets • Better suited for data traffic due to • Efficient resource utilization • Robustness • Circuit Switched (CS) • Communication path set at the beginning • Path maintained throughout entire communication session • Permanent path – no addressing/routing required • Used in voice telephony • Not appropriate for data communication due to poor utilization of resources CS communication PS communication UMTS accommodates both CS and PS

  17. UMTS architecture • W-CDMA air interface for UMTS radio Access • Reuse of the Existing GSM network architecture • UMTS terrestrial network built on ATM Acronyms: Node B = Base Station SGSN = Service GPRS Node GGSN = Gateway GPRS Node MSC = Mobile Switching Center VLR = Visitor Location Registry HLR = Home Location Registry Note: from the radio planning and optimization perspective the most important is Uu interface Open Interfaces: Uu – W-CDMA air interface Iub – Node B to RNC Iur – between RNC Iu – between UTRAN and CN

  18. Circuit switched portion of the UMTS • Circuit switched portion of the UMTS CN is evolution of GSM • Iu interface towards CN is Iu-CS • Same elements but upgraded interfaces • Consists of switches (MSC, GMSC) and appropriate databases (HLR and VLR) • MSC – Mobile Switching Center • GMSC- Gateway MSC (end network switch) • VLR – Visitor Location Registry • HLR – Home location Registry

  19. Packet data portion of the UMTS • Packet data portion of the UMTS CN is evolution of GPRS • Iu interface towards PD core is Iu-PS • Same elements but upgraded interfaces • Consist of SGSN and GGSN nodes and appropriate interfaces • For service management, GGSN and SGSN nodes are connected to HLR • SGSN (Serving GPRS Support Node) – router for PS data and local administration of user data service • GGSN (Gateway GPRS Support Node) – edge router that connects to external PS networks

  20. User equipment • User Equipment consists of: • Mobile Equipment (ME) - hardware providing the adjustment of user data to the Uu interface • UMTS Subscriber Module (USIM) - Evolution of GSM’s SIM. Detaches the user identity from a given communication hardware • UMTS specifies a number of UE implementation types: single mode FDD, single mode TDD, dual mode FDD/TDD, dual mode TDD/GSM and triple mode FDD/TDD/GSM • Majority UMTS mobile are dual mode UMTS/HSPA and GSM/GPRS/EDGE • UE is • Node B counterpart (processing of radio signals) • RNC counterpart (radio resource management, mobility management, encryption) • CN counterpart (service request, bearer negotiation, authentication) UE in a form of phone UMTS/HSPA data card

  21. UTRAN consists of Node B (Base station) Hosts radio TX/RXs Provides layer 1 functionality Communicates to RNC over open Iubinterface Due to processing speed requirements some radio resource management functions moved from RNC to Node B Radio Network Controller (RNC) Evolution of GSM’s BSC Central node of UTRAN Provides support for mobility (soft handover) and RRM (power control) Direct link between RNC (Iur interface) All interfaces in UTRAN are open - facilitates market entrance of single component equipment manufacturers UMTS terrestrial radio (UTRAN)

  22. RNC responsibilities • Call admission control – RNC accesses the network loading for call admission management • Radio resource management – allocation of channels, power control, priority control. • Radio bearer setup and release • Code allocation – management of spreading codes • Power control of mobiles and Node B. Most critical slow power control on the UL • Packet scheduling – RNC schedules packet over Uu based on available resources and negotiated QoS • Handover management – RNC manages both soft and hard handovers in UMTS. Determines conditions and executes required signaling. • Encryption - Data arriving from fixed networks are encrypted for over the air transmission • O&M – RNC collects a wealth of performance data. These data are used for network management, optimization and troubleshooting

  23. Handover in UMTS • Three basic types of handover • Soft handover • Softer handover • Hard handover • Soft handover (make before break) • UE communicates with up to three different sectors from Node-Bs • On downlink: Data are split at the RNC and send to all involved sectors. For CS – same data sent from all involved Node-Bs. • On the uplink: Data received from Node B’s forwarded to RNC who assembles the uplink • Softer handover • UE communicates with different sectors of the same Node B • Hard handover • From UMTS to GPS • Between different UMTS carriers • Advantages of soft/softer handovers • Improved reliability due to macro-diversity • Reduced interference on both UL and downlink

  24. RAN view of handover • Intra Node B / Intra RNC (hard or soft) • Same Node B, same RNC • Inter Node B / Intra RNC (hard or soft) • Different Node B, same RNC • Inter Node B / Inter RNC (hard or soft) • Different Node B, different RNC • Intra Node B / Inter RNC • Same Node B, different RNC • Serving RNC is changed • Handover internal to RAN (no over the air signaling) • Inter MSC handover (hard) • Different Node B, different RNC, different MSC • Inter-system handover (hard) • Hanover between UMTS and GSM • Inter-Segment-Handover • Handover from terrestrial to satellite (*) (*) still being developed • Each handover has associated signaling • To reduce latency – Iur interface allows direct signaling between RNC’s Note: from UE standpoint: 1-way, 2-way or 3-way handover.

  25. Location management in UMTS • To route calls, network must know the location of the mobile • Network is subdivided into Location Areas, with specific LA Indexes (LAI) • Current mobile LAI is stored and updated in HLR • When mobile is called the page is send through all the cells carrying mobile’s current LAI • Size of LAI area balances • Paging overhead • LAI update frequency • LA sizes are different for CS and PS sides of the network • CS – larger areas • PS – smaller areas • Location area for PS – Routing Area (RA) Note: boundaries between LA, RA and URA do not overlap

  26. Migration towards pure IP core • Evolution of UMTS core is towards all IP network • In LTE, there is no CS domain. Voice is handled through VoIP • Advantages: • Simpler and modern network design • Integrated network for both CS and PS • Utilizes cheap and readily available routing technology (both software and hardware) • Easy integration with Internet • Easy provisioning of new services • Disadvantages • Complex migration of 2G networks • Security issues • QoS provisioning for time critical services HSS – Home Subscriber Server (evolution of HLR) R-SGW – Roaming Signaling Gateway (transforms CS signaling into internal Internet signaling) MGW – Media Gateway (transforms internal VoIP to PSTN)

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