Wireless Communications and Networks

1
Wireless Communications Engineering
Lecture 12 3G Systems Prof. Mingbo Xiao Dec.
23, 2004
2
Limits of 2G Cellular Systems

• 2G systems are highly successful, but
• Capacity of the system saturated
• Transmit speed is too slow (9.6 Kbps or 14.4
  Kbps) to support multimedia services
• Symmetric transmission so not suitable for
  Internet traffic
• Main service is voice, but voice service is
  becoming less profitable

3
Voice versus Data over Cellular
4
Internet Access from GSM
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Enhanced Data for GSM Evolution (EDGE)

• Common factor for GSM and IS-136 uses their
  existing spectrum bands
• Support both packet- and circuit-switched
  services
• Eight-phase-shift (8 PSK) modulation
• Every time slot can support up to 48 Kbps
• The highest speed is up to 384 Kbps
• 40 times of GSM and 3 times of GPRS

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Packet-Switched Data in GPRS
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Packet and circuit-switch in GPRS
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Protocol Architecture
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Protocol Architecture (cont.)

• Physical layer
• RFL (Physical RF Layer) modulation,
  demodulation
• PLL (Physical Link Layer) error control,
  congestion detect
• Data link layer
• MAC (Medium Access Control) slotted ALOHA
• RLC (Radio Link Control) error correction
• LLC (Logical Link Control) always connected

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Protocol Architecture (cont.)

• GPRS supports interworking of MSs with X.25-,
  IP-based networks by encapsulation and
  decapsulation
• Between SGSN and MS, further encapsulation is
  performed by SNDCP (SubNetwork-Dependent
  Convergence Protocols)
• including multiplexing, compression,
  segmentation
• The MAC is derived from a slotted reservation
  ALOHA protocol, and operate between MS and BTS

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Goals of 3G Systems

• More services
• Web browsing
• VoD
• Video phone call
• Mobile computation
• Improved quality
• Higher rates 2.048 Mbps for low speed users, 384
  Kbps for modest speed users and 144 Kbps for high
  speed users
• More reliable and larger capacity
• Compatible with 2G systems
• More flexible
• Support both circuit-switching and
  packet-switching
• Work in hierarchical mode with pico-/micro-/macro-
  cells
• Support asymmetric services

19
Interest to 3G Applications

• Western
  Eastern USA
  Europe
  Europe
• Emails 4.5 4.7 4.3 City
  maps/directions 4.3 4.2 4.2 Latest news
  4.0 4.4 4.0 Authorize/enable payment
  3.4 3.8 3.0 Banking/trading online 3.5 3.4
  3.2 Downloading music 3.1 3.4 3.2
  Shopping/reservation 3.0 3.1 2.9
  Animated images 2.4 2.7 2.6 Chat rooms,
  forums 2.3 2.9 2.2 Interactive games 2.0
  2.2 2.4 Games for money 1.8 1.8 1.8
• (Means based upon a six-point interest scale,
  where 6 indicates high interest and 1 indicates
  low interest.)

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Upgrade Paths to 3G
2G
IS-136PDC
GSM
IS-95
2.5G
GPRS
HSCSD
IS-95B
EDGE
3G
cdma200-1xRTT
W-CDMA
EDGE
cdma2000-1xEV,DV,DO
TD-SCDMA
cdma200-3xRTT
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WCDMA Network
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Network Elements

• BTS Base Transceiving Station
• BSC Base Station Controller
• MSC Mobile Switching Center
• GMSC Gateway MSC
• RNC Radio Network Controller
• MS Mobile Station
• HLR Home Location Register
• VLR Visitor Location Register
• EIR Equipment Identity Register
• AUC Authentication Center
• OMC Operation and Maintenance Center
• SGSN Serving GPRS Support Node
• GGSN Gateway GPRS Support Node
• GR GPRS register

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Interface

• Iu Interface between the RNC and the Core
  Network (MSC or SGSN).      - Iucs Iu circuit
  switched (voice from/to MSC)      - Iups Iu
  packet switched (data from/to SGSN)
• Iub Interface between the RNC and the Node B.
• Iur Interface between two RNCs.
• Gn Interface between SGSN and GGSN
• Gi Interface between GGSN and external packet
  data network

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WCDMA Protocol Architecture
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WCDMA Channels
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Logical Channel

• Broadcast Control Channel (BCCH), Downlink (DL),
  carries system and cell specific information
• Paging Control Channel (PCCH), DL
• Dedicated Control Channel (DCCH), UL/DL
• Common Control Channel (CCCH), UL/DL
• Dedicated Traffic Channel (DTCH) for
  point-to-point data transmission in the uplink
  and downlink, UL/DL
• Common Traffic Channel (CTCH), Unidirectional
  (one to many)

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Transport Channels

• Dedicated Transport Channel (DCH), UL/DL, mapped
  to DCCH and DTCH
• Broadcast Channel (BCH), DL, mapped to BCCH
• Forward Access Channel (FACH) for massages from
  the base station to the mobile in one cell, DL,
  mapped to BCCH, CCCH, CTCH, DCCH and DTCH
• Paging Channel (PCH) for messages to the mobiles
  in the paging area, DL, mapped to PCCH
• Random Access Channel (RACH), UL, mapped to CCCH,
  DCCH and DTCH
• Uplink Common Packet Channel (CPCH), UL, mapped
  to DCCH and DTCH
• Downlink Shared Channel (DSCH), DL, mapped to
  DCCH and DTCH

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Physical Channels

• Dedicated Transport Channel (DCH), UL/DL, mapped
  to DCCH and DTCH
• Broadcast Channel (BCH), DL, mapped to BCCH
• Forward Access Channel (FACH) for massages from
  the base station to the mobile in one cell, DL,
  mapped to BCCH, CCCH, CTCH, DCCH and DTCH
• Paging Channel (PCH) for messages to the mobiles
  in the paging area, DL, mapped to PCCH
• Random Access Channel (RACH), UL, mapped to CCCH,
  DCCH and DTCH
• Uplink Common Packet Channel (CPCH), UL, mapped
  to DCCH and DTCH
• Downlink Shared Channel (DSCH), DL, mapped to
  DCCH and DTCH

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Channel Multiplexing
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IQ/code multiplexing with complex spreading
circuit
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WCDMA Parameters
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cdma2000 Overview

• Introduction
• cdma2000 Architecture
• Physical Layer
• Forward Links
• Reverse Links
• Data Link Layer
• Link Access Control sublayer
• Media Access Control sublayer
• Data Service in cdma2000
• Packet data service
• High-speed circuit data service
• Conclusions
• References

33
Introduction

• Backward compatibility to TIA/EIA-95-B
• Supports TIA/EIA-95-B signaling and services
• Spreading bandwidths compatible with IS-95-B
  deployments
• Supports cdma2000 to IS-95/IS-95-B hard handoff
• Minimal changes to IS-41 and IS-634
• Protects operator investment in existing cdmaOne
  networks
• Provides simple and cost-effective migration to
  3G services
• Overlay upgrade to TIA/EIA-95-B
• Supports backward compatible common channels
• Forward Link orthogonality maintained between
  cdma2000 mobiles and IS-95-A/B mobiles

34
Introduction (cont.)

• Support of IMT-2000 data rates
• Vehicular 144 kbps (supported by 1X systems)
• Pedestrian 384 kbps (supported by 3X systems)
• Indoor 2 Mbps
• Advanced Medium Access Control (MAC)
• Support different quality of service for a wide
  range of advanced services concurrently
• Simultaneous voice/data support for multi-service
• QoS support for multimedia applications
• Significantly improved mobile stand-by time
• Spot beam and smart antenna coverage

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cdma2000 Architecture
36
Physical Layer

• The Radio Configurations (RCs) specify the data
  rates, channel encoding, and modulation
  parameters supported on the traffic channel
• For Spreading Rates (SRs) 1 and 3, there are 6
  RCs for the reverse link and 9 RCs for the
  forward link
• RCs 1 and 2 are specified to provide backward
  compatibility with TIA/EIA-95-B
• There are 6 reverse and 11 forward physical
  channels in cdma2000

37
Forward Links Features

• Supports chip rates of N x 1.2288 Mcps,
  N1,3,6,9,12
• N 1
• similar to IS-95B, but QPSK modulation and fast
  closed-loop power control are used
• N gt 1
• Multicarrier
• Direct spread

38
Multicarrier and Direct Spread
39
Key Characteristics of Forward Links

• Channels are orthogonal and use variable-length
  Walsh codes.
• QPSK modulation is used before spreading to
  increase the number of usable Walsh codes.
• Forward Error Correction (FEC) is used
• Convolutional codes (k9) are used for voice and
  data.
• Turbo codes (k4) are used for high data rate on
  SCHs
• Supports nonorthogonal forward link
  channelization
• These are used when running out of orthogonal
  space (insufficient number of Walsh codes)
• Quasiorthogonal functions are generated by
  masking existing Walsh functions

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Key Characteristic of Forward Links (cont.)

• Synchronous forward links
• Forward link transmit diversity
• Fast-forward power control (closed loop) 800
  times per second

41
Key Characteristics of Reverse Links

• Continuous waveform
• Minimizes interference to biomedical devices
• Enables the interleaving to be performed over the
  entire frame
• Orthogonal channels with different-length Walsh
  sequences
• Higher data rate channels -gt shorter Walsh
  sequences
• Rate matching
• Puncturing
• Symbol repetition
• Sequence repetition

42
Key Characteristics of Reverse Link (cont.)

• Independent data channels
• Enables the system to be optimized for multiple
  simultaneous services
• The channels are separately coded and interleaved
  and may have different transmit power level and
  FER set points.
• Reverse power control
• Open loop
• Closed loop
• Outer loop

43
Key Characteristics of Reverse Link (cont.)

• Separate dedicated control channels
• Allows for a flexible dedicated control channel
  structure that does not impact the other pilot
  and physical channel frame structures.
• Forward error correction
• Convolutional codes (k9) are used for voice and
  data
• Parallel turbo codes (k4) are used for high data
  rates on supplemental channels
• Fast-reverse power control
• 800 times per second

44
Data Link Layer

• Subdivided into two sublayers
• Link Access Control (LAC) sublayer
• Manages point-to-point communication channels
  between peer upper layer entities
• Provides framework to support a wide range of
  different end-to-end reliable link layer
  protocols
• Media Access Control (MAC) sublayer
• MAC control state
• Best-effort delivery
• Multiplexing and QoS control

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Data Link Layer MAC Control States
46
Data Services in cdma2000

• (1) Packet data services
• Support a large number of mobile stations using
  packet data services
• Dedicated channels for packet service users are
  allocated on demand and released immediately
  after the end of the activity period
• Short data bursts can be transmitted over a
  common traffic channel
• Using Mobile IP to support wireless packet data
  networking capability

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Data Services in cdma2000
48
Data Services in cdma2000

• (2) High-speed circuit data service
• Dedicated traffic and control channels are
  typically assigned to the MS for extended periods
  of time during the circuit service sessions
• Some delay-sensitive services such as video
  applications require a dedicated channel for the
  duration of the call

49
???TD-SCDMA

• Time Division-Synchronous Code Division Multiple
  Access
• (?????????????)
• ?ITU??????????????????????,??
• ??CWTS?3GPP?????
• ????????????????????,?UTRA-FDD
• ??????
• ??CDMA?TDMA?FDMA??????????????????
• ????????????????
• ?????????????????????CDMA?????
• ?????????????????????????????

50
TD-SCDMA ?????
??(..)

• ??????
• ?????????????
• ??????????
• ??????????
• ???????????
• ?????
• ?????
• ...

51
???? (Smart Antenna)

• Antenna array
• BB digital data Processing
• Providing a beamformed
• pattern for each user
• Fast beamforming to follow
• the moving user

????????????
52
???? (Smart Antenna)

• ?????
• ????? ????
• ????? 120o ??
• ?????????????????
• ??????
• ????,????????????????????
• ???

???
???
????
????
53
???? (S.A.)???

• ?????? ...
• ?????????
• ??????????????????????

• ???????
• ???????????
• ??????
• ????????
• ???????
• ???????(????)
• ????????????
• ??????,??????

• ??????? ...
• ?????????
• ???????????????,????CDMA?????????

54

???? (J.D.)

• CDMA???????(M.A.I.)???????????????
• ???????????????60?
• ???CDMA?????????MAI??????
• J.D.????MAI??????

• ??????
• ??????
• ??????????
• ????????
• ??????
• ???????(???)????????????????
• ?????????,???????????

55
????????????

• ?????????
• ??????,??CDMA????
• ??????????EIRP
• ????????????
• ????????
• ?????(????)
• ???????????????,???????????????? ?????????
• ?TD-SCDMA???????,?????????????,???? ????

56
?????? (DCA)

• ?TDD???CDMA???,???????
• ??? ??
• ?? - ??
• ?? - ??
• ?? - ??
• ????????
• ????????????,???????????????
• ???????,???????????
• ?? 1)?????? 2)?????

57
??????

• ??
• ?????????????
• ??????
• ??
• CDMA????,
• ???????,
• ??CDMA??
• ????,????

58
?????

????????

• ????? ...
• ?1.6MHz??????
• 2Mbps?????

• ??????
• ??????
• ???????

59
????

• MS?BS0??
• BS0????????
• ???????????????????
• MS????,????
• BS?MS??????
• ????????
• MS???????????????
• ????
• ??
• ??????,??????,??????

BS2
MS
BS1
BS0
60
???? (TDD)

TD-SCDMA ???

• ?????????, ???????????????
• ????????,??????,??????
• ???????????,?????????,????????????
• ??????????,?????,????

??
61
?????
????????

• ???????????
• ???????????????
• ??????????
• ???????

• ??????
• ?????????
• ???

62
TD-SCDMA???

• ?????1.28Mcps(WCDMA?1/3),???1.6MHz
• ?????????CDMA????
• ??????????
• ???3GPP??????????????????
• ??????????
• ?????????
• ????0-200?/?
• ??????1-3dB
• ??????1/8????
• ???????

63
TD-SCDMA????????
TD-SCDMA??? ??????/????? TS0????? TS1????? ??????
GP, DwPTS, UpPTS ?????????????????UL/DL??
64
??(TS)??

• ????704 Chips??,??675us
• ????????????,????????352 Chips??
• ????(Midamble)?144 Chips??
• 16 Chips???
• ????????

65
TD-SCDMA?????????

• ??????
• ???????????
• ???????????
• BCH/DwPTS????????,??????,????
• ???????
• ????????????,???????

66
TD-SCDMA??????

• ??????????????,????????
• ??????TDD??
• ??????????
• ???????????
• ????????,????????
• ???,?????????????
• TD-SCDMA????????????

67
TDD ???????

• ??????????????
• ?????????????,???????
• ?????????????,?????????,
• ??????????,???FDD????????
• ???
• TD-SCDMA????????????

68
TD-SCDMA????????????
?? ????????????????/MHz/?? ??
?????????????/MHz/??
GSM IS95 CDMA2000 WCDMA
TD-SCDMA ?????? 7
1 1 1
1 ?????(MHz) 0.4 2.5
2.5 10
1.6 ?????????? 8 20 30
60 24 ?????(??)
2.8 8 12
6 15 ???????? -
- 2.5Mbps 4Mbps
2Mbps ?????(??, Mbps/MHz/cell) 1.0
0.4 1.25
69
IMT-2000 ??????

• Main tech discussed in ITU WP8F
• (Ref. ITU Doc. 8F/TEMP/65-E, Oct. 2000, Geneva)
• Smart Antenna (????)
• Not only for TDD(as TD-SCDMA), but also for FDD,
  it may lead to change physical layer design in
  FDD
• Software Defined Radio(???????)
• Simplifying hardware
• Multi-mode UE for worldwide roaming
• High speed down-link package data transmission
• Using the concept in TDD Higher modulation
  scheme (16QAM)----HDR in some time slots in FDD
• ??TD-SCDMA ?? 3G ??????