现代通信新技术导论
第四章 大覆盖无线网络
Chapter 4 Wireless Networks with Large Coverage
电控学院 电子工程学科部
司鹏搏 综合楼825室
sipengbo@bjut.edu.cn
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现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
–
–
–
–
–
–
4.1.1 Introduction to LTE
4.1.2 Targets
4.1.3 Key features
4.1.4 Network architecture
4.1.5 Physical layer
4.1.6 Layer 2
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
2
现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
– 4.2.1 Introduction to WiMAX
– 4.2.2 System Architecture
– 4.2.3 Physical Layer Overview
– 4.2.4 MAC Layer Overview
– 4.2.5 WiBro
• 4.3 Wireless RAN
3
现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
– 4.3.1 Current spectrum allocation and utilization
– 4.3.2 Ideas and architecture of cognitive radio
– 4.3.3 Design issues of cognitive radio
– 4.3.4 IEEE 802.22
– 4.3.5 Proactive cognitive radio networks
4
现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
–
–
–
–
–
–
4.1.1 Introduction to LTE
4.1.2 Targets
4.1.3 Key features
4.1.4 Network architecture
4.1.5 Physical layer
4.1.6 Layer 2
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.1 Introduction to LTE
• The latest standard in the mobile network technology tree
– That previously realized the GSM/EDGE and UMTS/HSxPA network
technologies that now account for over 85% of all mobile subscribers.
• Ensure 3GPP’s competitive edge over other cellular technologies.
• The next step on a clearly-charted roadmap to so-called ‘4G’ mobile
systems
• Building on the technical foundations of the 3GPP family of cellular
systems
– Embracing GSM, GPRS and EDGE as well as WCDMA and now HSPA
(High Speed Packet Access)
• Offers a smooth evolutionary path to higher speeds and lower latency
• Enables an even richer, more compelling mobile service environment
– Coupled with more efficient use of operators’ finite spectrum assets
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.1 Introduction to LTE
• Video 1: Motorola LTE Test
• Video 2: Ericsson TD LTE Introduction
• Video 3: Verizon LTE Test
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.1 LTE Evolution
• Release 99 (2000): UMTS/WCDMA
• Release 5 (2002) : HSDPA
• Release 6 (2005) : HSUPA, MBMS (Multimedia
Broadcast/Multicast Services)
• Release 7 (2007) : DL MIMO, IMS (IP
Multimedia Subsystem), optimized real-time
services (VoIP, gaming, push-to-talk).
• Release 8(2009) :LTE (Long Term Evolution)
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.1 Motivations
• Need for higher data rates and greater spectral efficiency
– Can be achieved with HSDPA/HSUPA
– And/or new air interface defined by 3GPP LTE
• Need for Packet Switched optimized system
– Evolve UMTS towards packet only system
• Need for high quality of services
– Use of licensed frequencies to guarantee quality of services
– Always-on experience (reduce control plane latency significantly)
– Reduce round trip delay
• Need for cheaper infrastructure
– Simplify architecture, reduce number of network elements
9
现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
–
–
–
–
–
–
4.1.1 Introduction to LTE
4.1.2 Targets
4.1.3 Key features
4.1.4 Network architecture
4.1.5 Physical layer
4.1.6 Layer 2
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.2 LTE Targets
•
•
•
•
•
•
•
Significantly increased peak data rates
Increased cell edge bitrates
Improved spectrum efficiency
Improved latency
Scalable bandwidth
Reduced CAPEX and OPEX
Acceptable system and terminal complexity, cost and
power consumption
• Compatibility with earlier releases and with other systems
• Optimized for low mobile speed but supporting high
mobile speed
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.2 Specific Targets
• Data rate
– Goal
• Significantly increased peak data rates, scaled linearly according to spectrum
allocation
– Targets
• Instantaneous downlink peak data rate of 100Mbit/s in a 20MHz downlink spectrum
(i.e. 5 bit/s/Hz)
• Instantaneous uplink peak data rate of 50Mbit/s in a 20MHz uplink spectrum (i.e.
2.5 bit/s/Hz)
• Cell range
– 5 km - optimal size
– 30km sizes with reasonable performance
– Up to 100 km cell sizes supported with acceptable performance
• Cell capacity
– Up to 200 active users per cell(5 MHz) (i.e., 200 active data clients)
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.2 Specific Targets
• Mobility
–
–
–
–
–
–
Be optimized for mobile speeds 0 to 15 km/h
Support, with high performance, speeds between 15 and 120 km/h
Maintain mobility at speeds between 120 and 350 km/h
And even up to 500 km/h depending on frequency band
Support voice and real-time services over entire speed range
With quality at least as good as UTRAN
• Latency
– User plane < 5ms
– Control plane < 50 ms
• Improved spectrum efficiency
• Cost-effective migration from Release 6 UTRA radio interface and
architecture
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.2 Specific Targets
• Spectrum flexibility
– E-UTRA to operate in 1.25, 1.6, 2.5, 5, 10, 15 and 20 MHz
allocations, allowing different possibilities for re-farming already
in use spectrum
– uplink and downlink…
– paired and unpaired
• Improved broadcasting
• IP-optimized
• Scalable bandwidth of 20MHz, 15MHz, 10MHz, 5MHz and
<5MHz
• Co-existence with legacy standards (users can transparently
start a call or transfer of data in an area using an LTE standard,
and, when there is no coverage, continue the operation without
any action on their part using GSM/GPRS or W-CDMA-based
UMTS)
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现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
–
–
–
–
–
–
4.1.1 Introduction to LTE
4.1.2 Targets
4.1.3 Key features
4.1.4 Network architecture
4.1.5 Physical layer
4.1.6 Layer 2
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.3 Key Features of LTE
• Multiple access scheme
– Downlink: OFDMA
– Uplink: Single Carrier FDMA (SC-FDMA)
•
Adaptive modulation and coding
– DL modulations: QPSK, 16QAM, and 64QAM
– UL modulations: QPSK and 16QAM
– Rel-6 Turbo code: Coding rate of 1/3, two 8-state constituent
encoders, and a contention- free internal interleaver.
• Bandwidth scalability for efficient operation in differently sized
allocated spectrum bands
• Possible support for operating as single frequency network (SFN)
to support MBMS
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.3 Key Features of LTE
• Multiple Antenna (MIMO) technology for enhanced data rate
and performance.
• ARQ within RLC sublayer and Hybrid ARQ within MAC
sublayer.
• Power control and link adaptation
• Implicit support for interference coordination
• Support for both FDD and TDD
• Channel dependent scheduling & link adaptation for enhanced
performance.
• Reduced radio-access-network nodes to reduce cost, protocolrelated processing time & call set-up time
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现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
–
–
–
–
–
–
4.1.1 Introduction to LTE
4.1.2 Targets
4.1.3 Key features
4.1.4 Network architecture
4.1.5 Physical layer
4.1.6 Layer 2
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.4 Network Architecture
R
C
HLR/AuC*
HSS*
EIR
MSC
GERAN
MT
TE
SMS-GMSC
SMS-IWMSC
SMS-SC
Um
Gb, Iu
Rx+ (Rx/Gq)
Gr
Gf
Gs
Gd
Iu
Gn
GGSN
Ga
Billing
System*
SGSN
UE
BM-SC
Gi
Gn/Gp
Uu
R
Gx+ (Go/Gx)
Gmb
Gc
SGSN
UTRAN
MT
TE
AF
PCRF
Ga
Gi
PDN
Mb
Gy
IMSMGW
Mb
MRFP
OCS*
Wi
CGF*
Gm
IMS
P-CSCF
CSCF
Mw
CDF
Wf Wf
Wd
3GPP AAA
Proxy
Intranet/
Internet
Wa
WLAN
UE
Wa
WLAN Access
Network
Ww
D/Gr
Dx
Cx
HLR/
AuC*
HSS*
SLF
Wx
Dw
3GPP AAA
Server
Wm
OCS*
**
Wo Wy
Wg
PDG
WAG
Wp
Wn
Wz
Wu
Traffic and signaling
Signaling
CGF*
Billing
System*
Note: * Elements duplicated for picture
layout purposes only, they belong to the
same logical entity in the architecture
baseline.
** is a reference point currently missing
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.4 Network Architecture
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.4 System Architecture Evolution (SAE)
• SAE is the evolution of the GPRS Core Network, with some
differences
• The main principles and objectives of the LTE-SAE architecture
include
– A common anchor point and gateway (GW) node for all access
technologies
– IP-based protocols on all interfaces
– Simplified network architecture
– All IP network
– All services are via Packet Switched domain
– Support mobility between heterogeneous RATs, including legacy
systems as GPRS, but also non-3GPP systems (say WiMAX)
– Support for multiple, heterogeneous RATs, including legacy
systems as GPRS, but also non-3GPP systems (say WiMAX)
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.4 System Architecture Evolution (SAE)
GERAN
Gb
GPRS Core
Iu
SGSN
PCRF
Rx+
UTRAN
S7
S3
S4
S6
HSS
Op.
S5a
S1
Evolved RAN
S5b
MME
3GPP
UPE
Anchor
IP
SGi
SAE
Anchor
(IMS,
PSS,
S2b
IASA
Serv.
etc…)
S2a
Evolved
Packet Core
Trusted non 3GPP IP
Access
ePDG
WLAN
3GPP IP
Access
WLAN
Access NW
22
现代通信新技术导论 第四章 大覆盖无线网络
4.1.4 Evolved Packet Core (EPC)
•
MME (Mobility Management Entity):
–
•
UPE (User Plane Entity):
–
•
Manages and stores UE context, ciphering, mobility anchor, packet routing and
forwarding, initiation of paging
3GPP anchor:
–
•
Manages and stores the UE control plane context, generates temporary ID, provides UE
authentication, authorization, mobility management
Mobility anchor between 2G/3G and LTE
SAE anchor:
–
Mobility anchor between 3GPP and non 3GPP (I-WLAN, etc)
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4.1.4 E-UTRAN Architecture
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4.1.4 User-Plane Protocol Stack
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4.1.4 Control-Plane Protocol Stack
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现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
–
–
–
–
–
–
4.1.1 Introduction to LTE
4.1.2 Targets
4.1.3 Key features
4.1.4 Network architecture
4.1.5 Physical layer
4.1.6 Layer 2
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.5 Physical Layer
Layer 3
Layer 1
Control / Measurements
Layer 2
Radio Resource Control (RRC)
Logical channels
Medium
(MAC)
Access
Control
Transport channels
Physical layer
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.5 Physical Layer
• The Layer 1 can adapt to various spectrum allocations
• Downlink physical channels:
– Physical Downlink Shared Channel (PDSCH)
– Physical Downlink Control Channel (PDCCH)
– Common Control Physical Channel (CCPCH)
• Uplink physical channels:
– Physical Uplink Shared Channel (PUSCH)
– Physical Uplink Control Channel (PUCCH)
• Downlink modulation schemes
– QPSK, 16QAM and 64QAM
• Uplink modulation schemes
– QPSK and 16QAM
• Broadcast channel modulation scheme
– QPSK
29
现代通信新技术导论 第四章 大覆盖无线网络
4.1.5 Downlink Physical Layer
• OFDM
– Meets the LTE requirement for spectrum flexibility and enables
cost-efficient solutions for very wide carriers with high peak rates
– Uses a large number of narrow sub-carriers for multi-carrier
transmission
– Can be seen as a time-frequency grid. In the frequency domain
– Δf = 15kHz, OFDM symbol duration time = 1/Δf + cyclic prefix
• Downlink physical layer procedures
–
–
–
–
Cell search and synchronization
Scheduling
Link Adaptation
Hybrid ARQ (Automatic Repeat Request)
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.5 Physical Layer
• Channel coding: Turbo coding
– Coding rate R = 1/3
– Two 8-state constitute encoders
– A contention-free quadratic permutation polynomial (QPP) turbo
code internal interleaver
– Trellis termination is used
• Block segments
– Maximized information block size: 6144 bits
– Error detection is supported by the use of 24 bit CRC
• Signals are defined as
– Reference signals
– Primary and secondary synchronization signals / random access
preambles
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4.1.5 Uplink Physical Layer
• SC-FDMA
– Single Carrier Frequency Division Multiple Access
– Because of the drawback of OFDM: very high Peak to Average Power
Ratio (PAPR)
– Solves this problem by grouping together the resource blocks
• That reduces the need for linearity
• And reduces PAPR
• And improves coverage and the cell-edge performance
• Uplink Physical Layer Procedures
–
–
–
–
–
Random access
Uplink scheduling
Uplink link adaptation
Uplink timing control
Hybrid ARQ
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.5 Frame Structure
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.5 Generic Frame Structure
Available Downlink Bandwidth is Divided into Physical Resource Blocks
LTE Reference Signals
are Interspersed Among
Resource Elements
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现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
–
–
–
–
–
–
4.1.1 Introduction to LTE
4.1.2 Targets
4.1.3 Key features
4.1.4 Network architecture
4.1.5 Physical layer
4.1.6 Layer 2
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.6 DL and UL Layer 2
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4.1.6 MAC and RLC of Layer 2
• MAC (media access control) protocol
– Handles uplink and downlink scheduling and HARQ signaling
– Performs mapping between logical and transport channels
• RLC (radio link control) protocol
– Focuses on lossless transmission of data
– In-sequence delivery of data
– Provides 3 different reliability modes for data transport. They are
• Acknowledged Mode (AM)-appropriate for non-RT (NRT) services such
as file downloads
• Unacknowledged Mode (UM)-suitable for transport of Real Time (RT)
services because such services are delay sensitive and cannot wait for
retransmissions
• Transparent Mode (TM)-used when the PDU sizes are known a priori such
as for broadcasting system information
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.6 PDCP and RRC of Layer 2
• PDCP (packet data convergence protocol)
– handles the header compression and security
functions of the radio interface
• RRC (radio resource control) protocol
– Handles radio bearer setup
– Active mode mobility management
– Broadcasts of system information, while the NAS
protocols deal with idle mode mobility management
and service setup
38
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4.1.6 Transport Channels
• In order to reduce complexity of the LTE protocol
architecture, the number of transport channels has been
reduced
• Downlink transport channels are
–
–
–
–
Broadcast Channel (BCH)
Downlink Shared Channel (DL-SCH)
Paging Channel (PCH)
Multicast Channel (MCH)
• Uplink transport channels are:
– Uplink Shared Channel (UL-SCH)
– Random Access Channel (RACH)
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现代通信新技术导论 第四章 大覆盖无线网络
4.1.6 Logical Channels
• Control channels are
–
–
–
–
–
Broadcast Control Channel (BCCH)
Paging Control Channel (PCCH)
Common Control Channel (CCCH)
Multicast Control Channel (MCCH)
Dedicated Control Channel (DCCH)
Mapping between uplink
logical and transport channels
• Traffic channels are
– Dedicated Traffic Channel (DTCH)
– Multicast Traffic Channel (MTCH)
Mapping between downlink
logical and transport channels
40
现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
– 4.2.1 Introduction to WiMAX
– 4.2.2 System Architecture
– 4.2.3 Physical Layer Overview
– 4.2.4 MAC Layer Overview
– 4.2.5WiBro
• 4.3 Wireless RAN
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现代通信新技术导论 第四章 大覆盖无线网络
4.2.1 Introduction to WiMAX
• Worldwide Interoperability for Microwave Access
– A certification mark for products that pass conformity
and interoperability tests for the IEEE 802.16 standards
– Last mile access
– Run by WiMAX Forum
• 400+ member in 120+ countries, including Alcatel, AT&T, BT,
Fujitsu, Nokia, Motorola, Intel, SAMSUNG, LG, Huawei,
ZTE …
– NLOS/LOS, high spectrum efficiency, high data rate,
QoS, flexible spectrum utilization
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4.2.1 Applications of 802.16
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4.2.1 History of WiMAX
802.16
(Dec 2001)
• Original fixed wireless broadband air Interface
for 10 – 66 GHz: Line-of-sight only, Point-toMulti-Point applications
802.16c
(2002)
802.16 Amendment
WiMAX System Profiles
10 - 66 GHz
802.16a
(Jan 2003)
802.16REVd
(802.16-2004)
(Oct 2004)
802.16e
(802.16-2005)
(Dec 2005)
• Extension for 2-11 GHz: Targeted for nonline-of-sight, Point-to-Multi-Point
applications like “last mile” broadband access
• Adds WiMAX System Profiles and Errata for
2-11 GHz
• MAC/PHY Enhancements to support
subscribers moving at vehicular speeds
44
现代通信新技术导论 第四章 大覆盖无线网络
Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
– 4.2.1 Introduction to WiMAX
– 4.2.2 System Architecture
– 4.2.3 Physical Layer Overview
– 4.2.4 MAC Layer Overview
– 4.2.5 WiBro
• 4.3 Wireless RAN
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4.2.2 WiMAX Architecture
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4.2.2 WiMAX Architecture
SDU: Service Date Unit
SAP: Service Access Point
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4.2.2 Scope of 802.16 Standards
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Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
– 4.2.1 Introduction to WiMAX
– 4.2.2 System Architecture
– 4.2.3 Physical Layer Overview
– 4.2.4 MAC Layer Overview
– 4.2.5 WiBro
• 4.3 Wireless RAN
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现代通信新技术导论 第四章 大覆盖无线网络
4.2.3 Physical Layer Summary
Designation
Applicability
MAC
Duplexing
Wireless MAN-SC
10-66 GHz
Licensed
Basic
Wireless MAN-SC
2-11 GHz Licensed
Basic, (ARQ), (STC), TDD, FDD
(AAS)
2-11 GHz Licensed
Basic, (ARQ), (STC), TDD, FDD
(AAS)
2-11 GHz Licenseexempt
Basic, (ARQ), (STC), TDD
(DFS), (MSH), (AAS)
2-11 GHz Licensed
Basic, (ARQ), (STC), TDD, FDD
(AAS)
2-11 GHz Licenseexempt
Basic, (ARQ), (STC), TDD
(DFS), (MSH), (AAS)
Wireless MAN-OFDM
Wireless MANOFDMA
TDD, FDD, HFDD
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4.2.3 Channel Characteristics
• 10-66 GHz
– Very weak multipath components (LOS is required)
– Rain attenuation is a major issue
– Single-carrier PHY
• 2-11 GHz
– Multipath
– NLOS
– Single and multi-carrier PHYs
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4.2.3 Time Division Duplexing (TDD)
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4.2.3 General Downlink Frame Structure
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4.2.3 General Uplink Frame Structure
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4.2.3 OFDMA TDD Frame Structure
•
•
DL-MAP and
UL-MAP indicate
the current frame
structure
BS periodically
broadcasts
Downlink
Channel
Descriptor (DCD)
and Uplink
Channel
Descriptor (UCD)
messages to
indicate burst
profiles
(modulation and
FEC schemes)
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现代通信新技术导论 第四章 大覆盖无线网络
4.2.3 Frame Structure
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4.2.3 Network Entry Process
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4.2.3 SDU and PDU
• Service Data Unit
(SDU)
– Data units
exchanged between
adjacent layers
• Protocol Data Unit
(PDU)
– Data units
exchanged between
peer entities
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4.2.3 Connections
• 802.16/WiMAX is connection oriented
• For each direction, a connection is identified
with a 16 bit CID
• Each CID is associated with a Service Flow
ID (SFID) that determines the QoS
parameters for that CID
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4.2.3 PDU Transmission
Packing
Fragmentation
MAC PDUs
Concatenation
Brust
Shortening
MAC PDUs
Preamble
FEC Block
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4.2.3 QoS Mechanism
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Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
– 4.2.1 Introduction to WiMAX
– 4.2.2 System Architecture
– 4.2.3 Physical Layer Overview
– 4.2.4 MAC Layer Overview
– 4.2.5 WiBro
• 4.3 Wireless RAN
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4.2.4 Generic MAC Frame
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4.2.4 Generic Bandwidth Request
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4.2.4 Management Messages
• Management messages are broadcast or sent
on three CIDs in each direction: Basic,
Primary, and Secondary
–
–
–
–
–
–
Uplink Channel Descriptor
Downlink Channel Descriptor
UL-MAP
DL-MAP
DSA-REQ
DSA-RSP
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4.2.4 Key Management Messages
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4.2.4 Key Management Messages
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4.2.4 Scheduling Types and QoS
Scheduling Type
Parameters
Unsolicited Grant Service
(UGS)
Non-real-time Polling
Service (nrtPS)
Max Sustained Traffic Rate,
Maximum Latency,
Tolerated Jitter
Max Sustained Traffic Rate, Min
Reserved Traffic Rate,
Committed Burst Size,
Maximum Latency, etc.
Committed Information Rate,
Maximum Information Rate
Best Effort (BE)
Maximum Information Rate
Real-Time Polling Service
(rtPS)
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4.2.4 Scheduling Classes
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4.2.4 Advanced 802.16 Features
• Multiple Input and Multiple Output (MIMO)
– MIMO channel capacity is given by
C = B log2 det(I + SNR.HH*T/N)
where H is MxN channel matrix with M and N are receive
and transmit antennas, resp.
• Hybrid-ARQ
– For faster ARQ, combines error correction and detection
and makes use of previously received versions of a frame
• Adaptive Antenna System (AAS)
– Enables directed beams between BS and SSs
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Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
– 4.2.1 Introduction to WiMAX
– 4.2.2 System Architecture
– 4.2.3 Physical Layer Overview
– 4.2.4 MAC Layer Overview
– 4.2.5 WiBro
• 4.3 Wireless RAN
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4.2.5 WiBro (Wireless Broadband)
• WiBro is an early large-scale deployment of
802.16 in South Korea (Dec 2005)
• Demonstrates 802.16 performance as
compared to 3G/4G cellular alternatives
• 3 operators have been licensed by the
government (each spending ~$1B)
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Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
– 4.3.1 Current spectrum allocation and utilization
– 4.3.2 Ideas and architecture of cognitive radio
– 4.3.3 Design issues of cognitive radio
– 4.3.4 IEEE 802.22
– 4.3.5 Proactive cognitive radio networks
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4.3.1 The Problem of current Spectrum Allocation
• Current “Static” Spectrum Allocation Strategy is Wasteful
– Huge opportunities exist in time, frequency, and space
– Apparent spectrum scarcity
Maximum Amplitudes
Heavy Use
Heavy Use
Amplidue (dBm)
Less than 6% Occupancy
Sparse Use
Medium Use
Frequency (MHz)
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Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
– 4.3.1 Current spectrum allocation and utilization
– 4.3.2 Ideas and architecture of cognitive radio
– 4.3.3 Design issues of cognitive radio
– 4.3.4 IEEE 802.22
– 4.3.5 Proactive cognitive radio networks
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4.3.2 Opportunistic Spectrum Access
• Basic Idea:
Opportunistic Spectrum
Access
– sense the spectrum you
want to transmit in
– look for “holes” or
“opportunities” in time
and frequency
– transmit so that you
don’t interfere with the
licensees
Power
Frequency
Time
Spectrum in use by Primary user
Spectrum Hole
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4.3.2 Cognitive Radio Architecture
CU
CU
CU
PU
CU
CU
PU
CU
CU
CU
PU
CU
CU
CU
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4.3.2 Cognitive Radio Research

Spectrum Policy

Economics
 Regulation
 Legal
 Business


Theory and Algorithms

Cooperative Communications
 Information & Coding Theory
 Statistical Signal Processing
 Game Theory & Microeconomics
Hardware/Software Platforms & Prototyping

Programmable agile radios
 GNU platforms
 Cognitive Radio Network Testbeds
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4.3.2 Motivations
• Static allocation of spectrum is inefficient
– Slow, expensive process that cannot keep up with technology
• Spectrum allocation rules that encourage innovation &
efficiency
– Free markets for spectrum, more unlicensed bands, new services,
etc.
• Anecdotal evidence of WLAN spectrum congestion
– Unlicensed systems need to scale and manage user “QoS”
• Density of wireless devices will continue to increase
– ~10x with home gadgets, ~100x with sensors/pervasive computing
• Interoperability between proliferating radio standards
– Programmable radios that can form cooperating networks across
multiple PHY’s
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4.3.2 Definition and Cycle
• An enhancement on the traditional software radio concept
wherein the radio is aware of its environment and its capabilities,
is able to independently alter its physical layer behavior, and is
capable of following complex adaptation strategies.
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Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
– 4.3.1 Current spectrum allocation and utilization
– 4.3.2 Ideas and architecture of cognitive radio
– 4.3.3 Design issues of cognitive radio
– 4.3.4 IEEE 802.22
– 4.3.5 Proactive cognitive radio networks
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4.3.3 Towards Cognitive Radio Networks
• Research themes that have emerged from mobile ad hoc and/or
sensor networks research:
– Hierarchical Network Architecture wins
• Capacity scaling, energy efficiency, increases lifetimes, facilitates discovery
– Cooperation wins
• Achievable rates via information theoretic relay and broadcast channels
– “Global” awareness and coordination wins
• Space, time and frequency awareness and coordination beyond local
measurements
– Efficient operation requires radios that can
•
•
•
•
Cooperate
Collaborate
Discover
Self-Organize into hierarchical networks
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4.3.3 Towards Cognitive Radio Networks
• Fundamental research and algorithms – based on
– Information and Coding Theory
• Relay cooperation, User Cooperation, Coding techniques for
cooperation, Collaborative MIMO techniques
– Signal Processing
• Collaborative signal processing, Signal design for spectrum
sharing, Interference avoidance, Distributed sensing algorithms
– Game Theory
• Spectrum warfare, Microeconomics and pricing based schemes for
spectrum sharing, negotiation and coexistence, Coalition
formation, Incentive mechanisms for cooperation
– MAC and Networking Algorithms
• Discovery protocols, Etiquette protocols, Self-organization
protocols, Multihop routing
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4.3.3 Cognitive Radio: Design Space
Unlicensed band +
simple coord protocols
Protocol
Complexity
(degree of
coordination)
Ad-hoc,
Multi-hop
Collaboration
Internet
Server-based
Spectrum
Etiquette
“cognitive radio”
schemes
Radio-level
Spectrum
Etiquette
Protocol
Unlicensed
Band
with DCA
(e.g. 802.11x)
Internet
Spectrum
Leasing
Reactive
Rate/Power
Control
Static
Assignment
Agile
Wideband
Radios
“Open Access”
+ smart radios
UWB,
Spread
Spectrum
Hardware Complexity
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4.3.3 Design Issues
• Primary (licensed) and Secondary (unlicensed) users
• Basic requirement
– To ensure secondary users take advantage of the unused
spectrum without adversely affecting primary users
• Challenges
–
–
–
–
Potentially oblivious primary users
Imperfect “channel state information” may cause collisions
Network dynamics (mobility, traffic)
Distributed solutions desirable
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4.3.3 Basic Components of Cognitive Radio
• Observation process
– Measurement and noise reduction mechanisms
– Passive or Active
– Interference temperature, collision probability, traffic load, etc
• Learning process
– Extracting useful information from collected data
– Supervised and unsupervised/reinforcement
• Planning and decision making process
– Using knowledge obtained from learning to schedule and prepare
for the next transmission
• Action
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4.3.3 Approaches in Cognitive Radio
• Estimation techniques
– For the observation process
– Obtain multiple information, channel state, traffic load,
neighborhood information, etc
• Game theory
– To understand competitive situations in which rational decision
makers interact to achieve their objectives
– Nash equilibrium——all the players are satisfied with their
received payoffs
• Evolutionary computing
– Based on evolution of biological life in the real world
– Genetic algorithm
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4.3.3 Approaches in Cognitive Radio
• Fuzzy logic
– Imprecise, noisy, and incomplete input information
• Markov decision process
– And POMDP
• Pricing theory
– Resource allocation: auction
• Theory of social science
– Modeled by a society of independent decision makers in which the
radio devices are aware of the society
• Reinforcement learning
– Learning by interacting with the environment.
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Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
– 4.3.1 Current spectrum allocation and utilization
– 4.3.2 Ideas and architecture of cognitive radio
– 4.3.3 Design issues of cognitive radio
– 4.3.4 IEEE 802.22
– 4.3.5 Proactive cognitive radio networks
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4.3.4 IEEE 802.22 Networks
• Wireless Regional Area Network
– To provide broadband Internet connectivity in rural and
remote areas
– To operate in the licensed VHF and UHF bands used for TV
services
• Since many TV channels in these frequency spectra are largely
unused in many regions
–
–
–
–
Coverage: WWAN > WRAN (100km) > WMAN
Flexibility and adaptability
Must not disturb the primary users
Measure the CSI, select and schedule the spectrum band,
and adjust the modulation/coding scheme and transmission
power
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Main Contents
• 4.1 Wireless WAN (3G LTE)
• 4.2 Wireless MAN (WiMAX)
• 4.3 Wireless RAN
– 4.3.1 Current spectrum allocation and utilization
– 4.3.2 Ideas and architecture of cognitive radio
– 4.3.3 Design issues of cognitive radio
– 4.3.4 IEEE 802.22
– 4.3.5 Proactive cognitive radio networks
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4.3.5 Proactive Cognitive Radio
• Regular assumption/rule
– CR users are not introducing interference to primary users
• However, as the users devices are becoming more and
more
– Smart
– Complicated
• The regular assumption may not exist anymore
– They have their own objective, with proactive actions
– The devices may intend to interfere primary users
– Or accidentally
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4.3.5 In Regular CR Networks
• The motivation of the secondary users: Obtain more
reward
– Obey the rule: Anything good?
– Intend to interfere: Find more opportunities to transmit
– Interfere accidentally: Due to the ill behaviors due to
the reduction of money spent on device
upgrading/maintenance
• The motivation of the primary users: Obtain more
reward
– Ask for very high spectrum rent
– Provide low-level services
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4.3.5 In Regular CR Networks
• The behaviors will result in
– Secondary users
• Always try to interfere if no spectrum hole is found
• Bad behavior without intention due to the SW/HW bugs
– Primary users
• Annoyed by the interference from the unknown source
• Collect heavy rent to compensate the lost due to the
interference
– The networks
• Full of interference and complaints
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4.3.5 Solution to the Problems
• Primary users
– Objective: Maximize the reward obtained
• Maximize the total spectrum rent
• Maximize the fine collected
• Minimize the cost of system upgrading/maintenance
– To achieve the objective: Balance
• Attracting more SUs
• Requesting higher rent/fine
– Actions
• Establish the regulation/rule/law
– Define the bad behaviors
– Define and optimize the punishment to the bad behaviors
• Collect the spectrum rent and the fine
• Be equipped with the bad behavior detection devices
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4.3.5 Solution to the Problems
• Secondary users
– Objective: Maximize the reward obtained
• Maximize the data transmission
• Minimize the cost of renting/fine/system upgrading and maintenance
– To achieve the objective:
• Choose the best PU to associate with
• Optimize the transmission actions and parameters
– Actions
•
•
•
•
•
Transmit with fingerprint information (obliged)
Detect the available PU networks
Choose the PU network that could provide the most reward
Detect the channel state information
Decide the transmission action and parameter
– Transmit or not
– Modulation and coding scheme, data rate, transmission power, signal shape, …
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4.3.5 Comparison of Human Society and Proactive CR
• Human Society
–
–
–
–
–
–
With laws, rules and regulations
With police, jails and punishment
With benefits (salary, promotion, reward, award, etc)
With evidence of criminals, clues at least
With cooperation and competition
With some freedom of choosing the government (immigrants)
• Proactive CR Network
–
–
–
–
–
–
With spectrum access regulations
With PUs who are watching over the SUs, spectrum jails and fine
With objectives (maximize the reward obtained)
With fingerprint information included in the transmission signals
With cooperation and competition
With some freedom of choosing the PUs (if more than one PUs available)
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A Brief Review
• Wireless Wide Area Networks
– Cellular networks 1G-2G-2.5G-2.75G-3G-3.5G-3.9G
– LTE: Targets and the evolved architecture
– Physical layer and Layer 2
• Wireless Metropolitan Networks
– WiMAX, IEEE 802.16, especially 16d and 16e
– System architecture
– Physical layer and MAC layer
• Wireless Regional Networks
–
–
–
–
–
Cognitive radio
Dynamic spectrum management
Cycle
Design Issues
Proactive CR networks
99