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TRANSCRIPT
Ivan Tam 2015
Wireless Network Infrastructure – An OverviewIVAN TAM
Fixed and Mobile Service Provider Architecture
InternetCoreService EdgeAggregationAccess
xDSL
Core RouterInternet Gateway
Transit Carrier Router
Internet Exchanges
• Access – provides cost/performance effective connectivity using copper, fiber to home and offices
• Aggregation –aggregate the traffic from various types of access terminating at CO/POP
• Service/edge – service management point where authentication, service quality, and service features are provided BNG ( Broadband Gateway)/VPN
PE (Provider Edge) or as MME, SGW and PGW in LTE
• AAA – where database of customers are stored and checked by service edge
• Value added service (VAS) –IPTV server, internet cache
• Core – national connectivity between data centers and service edge to each other and to the internet
• Transit – service provider interface with a number of transit carriers via own border routers. Transit carrier is responsible for routing traffic back and forth to destinations in the worls
Data Center
Central Office
Transit
Web site’s service provider
Web site’s hosting data center/ Cloud
Basestation
Backhaul
Fixed and Mobile Service Provider Architecture
InternetCoreService EdgeAggregationAccess
xDSL
Core RouterInternet Gateway
Transit Carrier Router
Internet Exchanges• AAA – where database of customers are stored and checked by service edge
• Value added service (VAS) –IPTV server, internet cache
Data Center
Central Office
Transit
Web site’s service provider
Web site’s hosting data center/ Cloud
Basestation
Backhaul
How does radio wave carries information?
How to track the location of user terminals?
How to mitigate interference between neighbor cells?
How does user terminal join the packet network?
How to ensure that user data can be transported to/from packet network as user moves ?
How to optimize on the amount of info over radio?
How to arbitrate the access of radio resource by user terminals?
How to maintain QOS of different traffic types?
Security and Authentication?
3GPP (3rd Generation Partnership Project) Releases – Technology Evolutions
UMTS (2000 – 2007) LTE + UMTS HSPA evolution LTE-Advanced 5G
Release 99 (2000)• UMTS (3G), 5Mhz• DL (384Kbps), UL (128Kbps)
Release 5,6 (2002-2004)• HSDPA with QAM 16(14Mbps), HSUPA
(5.7Mbps), IP architecture
Release 7 (2007)• HSPA+ with QAM64 DL (21Mbps),
QAM16 and 2x2MIMO (42Mbps)
Release 8 (2008)LTE – DL MIMO2x2 and 20Mhz (150Mbps), UL (75Mbps), all IP networkUMTS – 2xMIMO+QAM64 or Dual Carrier+QAM64 (42Mbps)
Release 9 (2009)LTE – Femto cell (HetNet)
UMTS – Dual Carrier multi-band with 2xMIMO DL + 64QAM (84Mbps)
Release 10 (2011)LTE Advanced – Carrier Aggregation (CA) , DL at 2x20Mbps (300Mbps)Self-Organizing Network (SON)Relaying – for cell without wireline backhaulHSPA+ Multicarrier (4)+2xMIMO+QAM64 (168Mbps)
Release 11 (2012)LTE Advanced – COMP, eICICHSPA – Multi-carriers (8) with 2xMIMO (336Mbps)
Release 12 (2012)M2MMobile RelayCA – 3 carrier DL, 2 carrier UL
UMTS2000-2007 – Mobile Broadband era• WCDMA using spread spectrum
technology over 5Mhz • Initially ATM transport but
moved to IP • Larger latency but reduced as
advanced to HSPA
LTE & HSPA2008-> Introduce LTE, full packet based and high bandwidth• OFDM – subcarrier scheduling, path
diversity, flexible at 1.4, 3, 5, 10,15,20Mhz
• Lower latency• Flat IP network• Voice over IP• Carrier aggregation (UMTS)
LTE Advanced2011-> Further optimization of LTE for performance• Small cells, hetnet• Inter-cell coordination on interference eICIC• Carrier aggregation (LTE)
3GPP Specifications and References
3GPP 36.2xx series – Physical Layer
36.3xx – Layer 2 and 3, 36.4xx S1 and X2 interfaces
36.1xx – Core performance requirements
36.5xx terminal conformance testing
http://www.3gpp.org/DynaReport/36-series.htm
4G Americas Industry trade organization with extensive technical and deployment reports
http://www.4gamericas.org/en/
Agenda
Spectrum and Transmission Technologies Wired and wireless media, modulation, signal propagation
LTE Overall Architecture and 3GPP
Physical transmission, UL and DL channel allocations
Attachment, mobility tracking and handover
Moving on to LTE-A LTE-A Further Optimizations and more cell sites collaboration
Virtualization and change in architecture
Heterogeneous network, WiFi, LTE over unlicensed spectrum
Current Development
Modulation (simplified) Signal is transmitted over medium by modulating a carrier wave
Amplitude, phase, and frequency or combination of these on the carrier
Simple phase shift-keying modulate the phase of the carrier, e.g, BPSK shift the carrier wave 180 degree when info change between 0 and 1
QPSK allows phase shift in 4 values, e.g., 45, 135, 225, and 315 degree, with four different patterns hence representing two bits symbol, i.e., 2 bits represents 4 values
QAM further mix phase shift together with amplitude change, giving more patterns, e.g., in QAM 16 the combination of phase shift and amplitude change give us 16 patterns, representing a 4 bit symbol, i.e., 4 values, 2 , QAM64 support 6 bits per symbol
The more patterns we try to get a wave to exhibit, the closer these patterns are in terms of phase and amplitude and harder for receiver to decide especially when received signal is poor resulting in transmission error
Hence QAM 64 is used when the channel condition is good, and QPSK is used when high reliability is required, i.e., higher Signal to Noise Ratio (SNR)
Baud Rate - The number of time we modulate a carrier per second
When a carrier wave is modulated at a Baud rate B, it will “occupy” a spectrum range of B centered around the carrier frequency
E.g., say f is the carrier frequency, then the spectrum used is : ((f+B/2) - (f-(B/2))
E.g., a 20Mhz bandwidth allocated to and operator at 2540-2560Mhz when modulated at QAM 16 is able to carry up to 80Mbps
Actually useful data rate is smaller due to error check coding, overhead of channel etc.
QPSK
Q
I
QAM16 Q
I
1101 1111
1100 1110
0111 0101
0110 0100
0010 0000
0011 0001
1000 1010
1001 1011
0001
11 10
4
Information
Carrier
Phase modulation
Source: IDA Spectrum Management Handbook
Source: IDA, Singapore
3GPP LTE BandsLTE Band Uplink Band Downlink Band Duplex Mode Region
1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz FDD UMTS Core
2 1850 MHz – 1910 MHz 1930 MHz – 1990 MHz FDD US PCS
3 1710 MHz – 1785 MHz 1805 MHz – 1880 MHz FDD 1800
4 1710 MHz – 1755 MHz 2110 MHz – 2155 MHz FDD US AWS
5 824 MHz – 849 MHz 869 MHz – 894 MHz FDD US 850
6 830 MHz – 840 MHz 875 MHz – 885 MHz FDD Japan
7 2500 MHz – 2570 MHz 2620 MHz – 2690 MHz FDD 2600
8 880 MHz – 915 MHz 925 MHz – 960 MHz FDD GSM 900
9 1749.9 MHz – 1784.9 MHz 1844.9 MHz – 1879.9 MHz FDD Japan 1700
10 1710 MHz – 1770 MHz 2110 MHz – 2170 MHz FDD Extended AWS
11 1427.9 MHz – 1447.9 MHz 1475.9 MHz – 1495.9 MHz FDD Japan 1500
12 699 MHz – 716 MHz 729 MHz – 746 MHz FDD
13 777 MHz – 787 MHz 746 MHz – 756 MHz FDD
14 788 MHz – 798 MHz 758 MHz – 768 MHz FDD
17 704 MHz – 716 MHz 734 MHz – 746 MHz FDD
18 815 MHz – 830 MHz 860 MHz – 875 MHz FDD
19 830 MHz – 845 MHz 875 MHz – 890 MHz FDD
20 832 MHz – 862 MHz 791 MHz – 821 MHz FDD
21 1447.9 MHz – 1462.9 MHz 1495.9 MHz – 1510.9 MHz FDD
22 3410 MHz – 3490 MHz 3510 MHz – 3590 MHz FDD
23 2000 MHz – 2020 MHz 2180 MHz – 2200 MHz FDD
24 1626.5 MHz – 1660.5 MHz 1525 MHz – 1559 MHz FDD
25 1850 MHz – 1915 MHz 1930 MHz – 1995 MHz FDD
26 814 MHz – 849 MHz 859 MHz – 894 MHz FDD
27 807 MHz – 824 MHz 852 MHz – 869 MHz FDD
28 703 MHz – 748 MHz 758 MHz – 803 MHz FDD
29 Downlink Only 717 MHz – 728 MHz FDD
30 2305 MHz – 2315 MHz 2350 MHz – 2360 MHz FDD
31 452.5 MHz – 457.5 MHz 462.5 MHz – 467.5 MHz FDD
32 Downlink Only 1452 MHz – 1496 MHz FDD
33 1900 MHz – 1920 MHz 1900 MHz – 1920 MHz TDD UMTS Core (TDD)
34 2010 MHz – 2025 MHz 2010 MHz – 2025 MHz TDD UMTS Core (TDD)
35 1850 MHz – 1910 MHz 1850 MHz – 1910 MHz TDD
36 1930 MHz – 1990 MHz 1930 MHz – 1990 MHz TDD
37 1910 MHz – 1930 MHz 1910 MHz – 1930 MHz TDD
38 2570 MHz – 2620 MHz 2570 MHz – 2620 MHz TDD
39 1880 MHz – 1920 MHz 1880 MHz – 1920 MHz TDD China UMTS TDD
40 2300 MHz – 2400 MHz 2300 MHz – 2400 MHz TDD China TDD
41 2496 MHz – 2690 MHz 2496 MHz – 2690 MHz TDD
42 3400 MHz – 3600 MHz 3400 MHz – 3600 MHz TDD
43 3600 MHz – 3800 MHz 3600 MHz – 3800 MHz TDD
44 703 MHz – 803 MHz 703 MHz – 803 MHz TDD
LTE Band Uplink Band Downlink Band Duplex Mode Region
LTE Architecture
SGW PGW
HSS
OCS
S1-U
S1-U
S1-MME
S1-MME
S6a
Core Router
S5
Internet Gateway
MME
S11
SGW (Serving Gateway)- Mobility anchor
PGW (Packet Data Network Gateway)- Interface to external packet network
eNodeB
SGi
X2
MME (Mobility Management Entity)-
HSS – Home Subscriber Server
Packet Data Network (PDN)
S1 BearerRadio Bearer S5/S8 Bearer
EPS (Evolved Packet System) Bearer
Uu
• EPS bearer is a “tunnel” that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base
PCRF
Gx
Gy
OCS (Online charging system)
PCRF (Policy and Charging Rules Function)
S1 BearerRadio Bearer S5/S8 Bearer
LTE Architecture
SGW PGW
HSS
S1-U
S1-U
S1-MME
S1-MME
S6a
Core Router
S5
Internet Gateway
MME
S11
eNodeB
SGi
X2
Packet Data Network (PDN)
Radio Bearer S1 Bearer S5/S8 Bearer
EPS (Evolved Packet System) Bearer
Uu
• EPS bearer is a “tunnel” that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base
OCSHow does radio wave carries information?
How to track the location of user terminals?
How to mitigate interference between neighbor cells?
How does user terminal join the packet network?
How to ensure that user data can be transported to/from packet network as user moves ?
How to optimize on the amount of info over radio?
How to arbitrate the access of radio resource by user terminals?
How to maintain QOS of different traffic types?
Security and Authentication?
PCRF
LTE Architecture
SGW PGW
HSS
S1-U
S1-U
S1-MME
S1-MME
S6a
Core Router
S5
Internet Gateway
MME
S11
SGW (Serving Gateway)- Mobility anchor
PGW (Packet Data Network Gateway)- Interface to external packet network
eNodeB
SGi
X2
MME (Mobility Management Entity)-
HSS – Home Subscriber Server
Packet Data Network (PDN)
Radio Bearer S1 Bearer S5/S8 Bearer
EPS (Evolved Packet System) Bearer
Uu
• EPS bearer is a “tunnel” that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base
Billing System
How to track the location of user terminals?
How to mitigate interference between neighbor cells?
How does user terminal join the packet network?
How to ensure that user data can be transported to/from packet network as user moves ?
How to optimize on the amount of info over radio?
How to arbitrate the access of radio resource by user terminals?
How to maintain QOS of different traffic types?
How does radio wave carries information?
?
?
Security and Authentication?
LTE – Physical Layer Range of spectrum bandwidth from 1.4Mhz, 3, 5, 10, 15, 20Mhz
Downlink (DL) via OFDM-A (Orthogonal Frequency Division Multi-Access) and Uplink (UL) DFTS-OFDM
OFDM-A divides spectrum into subcarriers of 15Khz
Info are divided and transmit in these subcarriers in parallel at each at lower rate rather than being modulated at very high rate using the whole bandwidth over single carrier
Each Subcarrier is structured in time domain as slot of 0.5ms with 7/6 symbols in each slot. Two slots forms a subframe (1ms)
A Resource block is 12 subcarriers (total 180Khz) for a duration of 1 slot (0.5ms)
Scheduler schedule resources in pairs of resource blocks, i.e., a subframe (1ms)
Different modulation schemes (QPSK, QAM16/64) can be used based on UE radio conditions
Much smaller symbol rate at 15khz rather than say full 20Mhz
Symbol duration 66.7us and 4.69us for CP (Cyclic Prefix)
CP “period” avoids symbol overlapping when signal are deflected during their propagation and resulting in multiple paths of different length
4.69us = 1.4km by speed of light, i.e., if a path of the first symbol is delayed less than 1.4km worth of distance then it will still not overlap with the data of the second symbol
Time Frames
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Subframe (1ms)Slot 0 Slot 1
One SymbolOne Resource Element
15Khz
Resource Block
6 R
eso
urc
e B
lock
s ~
1.1
MH
z1
00
Res
ou
rce
Blo
cks
~ 2
0M
hz
Resource Block
Resource Block
Resource Block
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Spectrum Bandwidth
1.4Mhz 3Mhz 5Mhz 10Mhz 15Mhz 20Mhz
No. of Resource Block
6 15 25 50 75 100
CP Symbol
• The CP of first symbol is longer at 5.2us• A longer CP option support larger cell (longer path) in expense of 6 symbols per slot
Larger Delay
UE 1
UE 2Resource Block
Resource BlockResource Block
UE 3
Inter-symbol Interference
LTE Control Data Channels Functional Overview Control information must be exchanged between basestations and UE For basestation to tell UE the control
parameters and how fields are formatted
For UE to be attached to the network to receiving service and tracked
For basestation to communicate resource allocations at DL and UL
Physical level control channels are critical and usually uses more robust QPSK (DL, UL) or even BPSK (UL)
Physical level shared channels carries control from upper layer and data, could use QPSK, QAM16 or QAM64 depending on the channel condition of the UEs sharing the channel
DL Control• Identify which UE transmits at which RB• UE power control• Acknowledge UL data• Grant to UE UL request
UL Control• Allow UEs to request for uplink transmission• UL Random access – allow unattached UE to establish initial radio link• CQI (Channel Quality Indication) – consist channel quality overall or specific UE selected set of
subcarriers. In addition PMI (Precoding matrix indicator) and RI (Rank Indicator) is reported when MIMO is used
DL Data• Voice, Video, Web
UL Data• Voice, Video, Web DL Broadcast
• Master information block
Power Cable Fiber
RRH (Remote Radio Head)
Antenna
Cabinet/ShelfBackup power
Cell 1
Cell 2
Cell 3Base Station Hotel-> C-RAN (Centralized RAN)-> vRAN (Virtualized RAN)
Pico cell radio head
RRH
Coaxial Cable
Mobile Radio Access Network Deployment
CPRI/Fiber
Backhaul
DL Control and Data121110
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Subframe (1ms)Slot 0 Slot 1
15Khz
Resource Block
Resource Block
User A
User B
User C
Control Channels, e.g., PDCCH, PHICH occupy the first 1, 2 or 3 symbols of the subframe. Resource allocation to UE is done by PDCCH identifying it using RNTI (Radio Network Temporary Identifier) which is assigned to UE by eNB
Reference Signal (RS) pattern – known cell/antenna specific pattern for UE to asses channel quality, RS from different antenna locates differently in resource block to avoid inter-antenna RS interference
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(H)ARQ = (Hybrid) Automatic Repeat Request
User IP Packets
LTE Stack
RLC(Radio Link Control)
MAC(Medium Access Control)
PHY
PDCP(Packet Data
Convergence Protocol)
RRC(Radio Resource Control)
Segmentation/ConcatenationIn-sequence DeliveryRLC establishment
H-ARQPriority handlingMapping between logical to transport channel
Ciphering, in-sequence deliveryHeader compressionIntegrity protection for control plane
Paging, Radio Bearer ControlMobility functions (handover)UE measurement controlRRC connection set up
PBCH(Physical Broadcast Channel – Master
information Block for UE access, QPSK)
PDSCH(Physical Downlink Shared Channel,
QPSK, QAM16/64)
PDCCH(Physical Downlink Control Channel –
downlink allocation, uplink grant, power
control, QPSK)
PHICH(Physical Hybrid-
ARQ Indicator Channel – Data
acknowledgement, QPSK)
Physical level control channels
(Paging Control Channel –
paging for UE)PCCH
(Broadcast Control
Channel)BCCH
(Common Control Channel – for initial
control with UE before RRC attach)
CCCH
(Dedicated Traffic Channel –
bidirectional user data for one UE )
DTCH
(Dedicated Control Channel – for
control to UE after RRC attach)
DCCH
(Multicast Traffic Channel – multicast
user data )MTCH
(Multicast Control
Channel)MCCH
DL-SCH(Downlink Shared Channel – shared among logical channels carry both control and data, decide dynamic resource allocation, modulation, coding, support beamforming, sleep cycle)
BCH(Broadcast Control
Channel)
PCH(Paging Channel – support UE power saving, page to
cell coverage area)
PCFICH(Physical Control
Frame Indictor for location of the
PDCCH)
Transport Channels -Define transport characteristics like modulation, coding, antenna mapping MCH
PMCH
Logical Channels -
MAC LayerRLC
(Radio Link Control)
MAC(Medium Access Control)
PHY
PDCP(Packet Data
Convergence Protocol)
Transport Channels
RRC(Radio Resource Control)
eNodeBUE
NAS NAS
MME
User IP Packets
Maintaining connection with core, mobility managementNon Stratum Access Non Stratum Access
Logical channels
PDCP Header
RLC Header
PDCP Header
MAC Header
Transport Block
Scrambling, Modulation, Layering Mapping, Antenna Mapping
Uplink Control and Data
PUSCH(Physical Uplink Shared
Channel, QPSK, QAM16/64 )
PUCCH(Physical uplink Control
Channel – Quality feedback, scheduling
request, H-ARQ for DL, BPSK, QPSK)
(Common Control Channel – for initial
random access before attach)
CCCH
UL-SCH(Uplink Shared Channel – shared among UEs
carry both control and data, dynamic resource allocation, modulation, coding)
Control Downlink - format of frames, allocation of downstream and upstream subscarriers/slot,
acknowledgement of data received, paging for mobile terminals, reference pattern
Uplink – random access for attachment, bandwidth request, feedback on downlink channel quality
Data – both downlink and uplink
Transport Channels -Define transport characteristics like modulation, coding, antenna mapping
RACH(Random Access Channel – for initial
attachment from uplink)
PRACH(Physical Random Access Channel –
generates preambles for UE identification and provide random access)
(Dedicated Control Channel – for control to UE after attach)
DCCH
(Dedicated Traffic Channel – user data for
one UE )DTCH
MIMO – Multi-Input Multi-Output MIMO
Defined by convention as MxN in one direction
M means the number of transmitter and N is the number of receiver
Up to 4 antennas FDD and 8 antennas in TDD
Assume all UE support two receivers
MIMO make use of multiple antenna to achieve robustness of channel or higher capacity
Make use of multipath condition
SINR (Signal to Noise Ratio) When UE is in low SINR(Signal to Noise ratio)
E.g., cell edge, transmit diversity or beamforming provide benefits
High SINR environment SU MiMO or MU-MIMO can be used provide there are spatial diversity on
the paths (low correlation)
Close loop – feedback from UE Useful when UE not in high speed mobility
Transmit Diversity- Single data stream is coded differently on
two antennas for transmission, don’t assume feedback on channel quality
- Improve data reception at cell edge ( mainly for control channels) but not higher rate
Multi-user MU-MIMO- Multiple UE transmit at the same time with same
subcarriers- Rely on spatial diversity to achieve minimal
interference, double the throughput
Beam Forming- Improve coverage- Weighted phase and magnitude of individual
antennas, work with interference- Require known channel state information,
terminal estimate overall beamformed channel- Easier for TDD as downlink channel is same as
uplink channel
1 Transmission layer is based on rank which is the number of linearly independent path (spatial layer) between M antenna and N receivers based on feedback from UE2 Layers <= # Antennas, layers are split to antenna, single layer result in beamforming
SU-MIMO Spatial Diversity- Multiple data streams to antennas for simultaneous
transmission known as layers, Higher peak rate, layers <= number of antennas
- rate- Open or close loop feedback to precoder
1,2
Enhance cell edge performance
Enhance peak performance
LTE Cell CapacityLet’s find the theoretical downstream throughput of 20Mhz DL with 2x MIMO spatial diversity
- RB is 180Khz with 12 subcarriers at 7 symbols at 0.5ms slot, 1 subframe has 2 slots
- For 20Mhz channel, number of RB is : 100
- Assume optimistically that QAM 64 is used, which carries 6 bit per symbol
- Bandwidth per subframe = 100 RB x 12 subcarriers x 2 slots x 7 symbols x 6 bit per symbol
= 100800bits per ms
- Bandwidth per second = 100Mbps
- Factor in 25% overhead -> 75Mbps
- Assume 2x2 MIMO with spatial diversity => 75x2Mbps = 150Mbps
- Assume 4x4 MIMO with spatial diversity => 75x4Mbps = 300Mbps
• UE further away• Signal is weaker• QPSK used for robustness• Smaller Throughput
• UE nearby• Signal received well• QAM64 used • Higher Throughput
Basestation
In Reality, the actual capacity of a cell depends on:• Noise condition, Interference from other cells, location of the UEs within the cell• The modulation and coding scheme (MCS) of a channel is dependent on the feedback CQI
(Channel Quality Indicator) from the UEs that it serves
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Subframe (1ms)Slot 0 Slot 1
One SymbolOne Resource Element
15Khz
Resource Block
6 R
eso
urc
e B
lock
s ~
1.1
MH
z1
00
Res
ou
rce
Blo
cks
~ 2
0M
hz
Resource Block
Resource Block
Resource Block
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UE 1
UE 2Resource Block
Resource BlockResource Block
UE 3
LTE Architecture
SGW PGW
HSS
S1-U
S1-U
S1-MME
S1-MME
S6a
Core Router
S5
Internet Gateway
MME
S11
SGW (Serving Gateway)- Mobility anchor
PGW (Packet Data Network Gateway)- Interface to external packet network
eNodeB
SGi
X2
MME (Mobility Management Entity)-
HSS – Home Subscriber Server
Packet Data Network (PDN)
Radio Bearer S1 Bearer S5/S8 Bearer
EPS (Evolved Packet System) Bearer
Uu
• EPS bearer is a “tunnel” that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base
Billing System
How to track the location of user terminals?
How to mitigate interference between neighbor cells?
How does user terminal join the packet network?
How to ensure that user data can be transported to/from packet network as user moves ?
How to optimize on the amount of info over radio?
How to arbitrate the access of radio resource by user terminals?
How to maintain QOS of different traffic types?
How does radio wave carries information?
?
?
?
Security and Authentication?
?
UE Attachment Procedure
PCRF
Internet Gateway
eNodeB
4. eNodeB relay attach request to MME, add its own ID, PDN connection Request
5a. Authentication Request for the UE using IMSI. HSS assembles AUTH vector send to MME
6. Location update, HSS
8. MME request SGW create session, EPS bearer id, IMSI PGW address with APN, QOS
7. HSS reply with APN, QOS profile include AMBR (aggregated bit rate), QCI, PGW address with assigned static IP if specified
9. SGW request PGW Create session, default EPS bearer id,S5 SGW TEID APN, QOS profile
11. PGW reply with assigned IP and authorized QOS profile, S5 PGW TEID
12. SGW response to MME and pass S1 SGW TEID for eNodeB to create S1-U bearer
13. a)Attach request accept with GUTI, TA list, b) request default bearer from eNodeBto UE, c) initial context request to EnodeB with AMR, QCI, S1 SGW TEID
15. eNodeB and UE exchange messages on a) attach accept (NAS) with the assigned IP, TA list, GUTI, and b) reconfigure the RRC to activate default bearer
16b. eNodeB response initial context, include eNodeB TEID of S1-U bearer
1a. UE receives cell identify and master information block (MIB) with up and downlink control channel config via broadcast channel. 1b. Via the PDCCH, SIB is obtained which identify random access channel (PRACH) frequency and offset to make initial contact with eNB
EPS (Evolved Packet System) Bearer
17. MME sends update bearer request to SGW with S1 eNB TEID
Packet Data Network (PDN)
2) UE performs random access secure uplink resource and setup RRC with eNB, obtain C-RNTI the UE identifier within the cell,
3). UE sent attach request including IMSI to MME
5b) MME sends AUTH vector for UE to verify, UE send response to MME for further checking
UE eNB MME
HSS
PGWSGW
S11 S5
14. UE and eNB set up security and encryption for RRC message and user data
Radio Bearer S1 Bearer S5/S8 Bearer
Step 10/11Step 11,12,14,15Step 14
16a. eNodeB sends Attach complete to MME
(1). UE cell identification, synchronize physical layer parameters(2,3). UE set up Radio link with eNB and request for attachment (NAS) to the mobile network with MME(5) . MME checks with HSS to get authentication vector and mutual authentication with UE(6,7). MME updates the HSS on location and gets the profile of the UE, including APN, PGW address, QOS Profile etc.(8-12) MME set ups EPS bearer by first setting up the S11 and S5 bearer, it request SGW to create session with UE parameters from HSS. SGW and PGW set up the S5 bearer, PGW allocates IP address and check profile with PCRF. PGW response to SGW which then response to MME for bearer setup(13) MME verify bandwidth profile, set up bearer toward eNB and UE, sends request to eNB(14) eNB establish secure communication over radio with UE(15-17) UE and eNB set up the radio bearer, acknowledge the set up to MME, MME finalize the S1 bearer with SBW using info from eNB
IMSI – International Mobile Subscriber Identification consists of MCC (Mobile Country code, MNC (Mobile Network Code), MSIN (Mobile Subscriber Identification Number)TEID (Tunnel Endpoint ID) – is end point identification for GTP (GPRS Tunnel Protocol) tunnel implementing bearersQCI (QOS Class Identifier)APN (Access Point Name) – identifies PDN/service to be connectedGUTI – Globally Unique Temporary ID, MME’s identifiers for a UETA List – list of tracking areas within which UE don’t need to update MME
10 PGW checks with PCRF on policy using UE IP, IMSI, APN, QOS Profile. PCRF response with rules to be enforced in PGW
Tracking Area
TA-1
TA-2
TA-3TA-4
TA-5
Cells are grouped into individual tracking area (TA), a number of tracking areas (up to 15) put under a tracking area list
MME keeps track of a UE in terms of its current TA list, TA list is also given to UE when it register with the MME
UE updates the MME when it moves to a TA not in its TA list via an action called TAU (update) trade off on size of TA, TAL and TAU frequency)
When downstream data comes for an idle UE, the MME send a paging to cells on the TA in the UE’s TA list
Cell “page” for UEs using “paging occasions” on (PDSCH) and defined by (PDCCH)
A sleeping UE wakes up periodically and listen to paging, the period is called default paging cycle cycle length (DRX discontinuous receive cycle) trades response time against UE battery consumption
UE checks the paging occasions for its own identification, if found, it sends service request to MMETAU
TA List TA List
MME
Handover via X2 Procedure
SGW
PGWInternet Gateway
Source eNB
Radio Bearer S1 Bearer S5/S8 Bearer
EPS (Evolved Packet System) Bearer
Step 9/10Step 11,12,14,15Step 13
1. UE sends Cell Measurement Report on source and neighbor eNB2. Source node identify better performance can be achieved if UE use a neighbor
eNB and initiate Switch Over Request to target node3. Target eNB checks resource to take in UE, send reply to Switch Over Request
together with target eNB own parameters4. Source eNB instructs UE to switch to target node with Radio Reconfigure Request
(RRC) with target eNB parameters5. Source eNB sends Transfer Status update to target eNB on transport status, relay
DL data to UE via X2 bearer to target node6. UE synch, attaches to target eNB running RRC confirm with target eNB7. Target eNB sends path switching request to MME8. MME sends Modify Bearer Request to SGW 9. S-1 bearer between SGW and target node is set, SGW ack Modify Bearer Request10. MME acknowledges the Modify Bearer Request to target node11. Target node instructs the source node to release the UE context
Packet Data Network (PDN)
1
5
6
3
MME
8 97
24
11
Original traffic between source node and UE
DL traffic forwarded by source node to target node and to UE after step 6
UL traffic from UE via target node after step 6
DL traffic from UE via target node after step 9
10
Target eNB
LTE Architecture
SGW PGW
HSS
S1-U
S1-U
S1-MME
S1-MME
S6a
Core Router
S5
Internet Gateway
MME
S11
SGW (Serving Gateway)- Mobility anchor
PGW (Packet Data Network Gateway)- Interface to external packet network
eNodeB
SGi
X2
MME (Mobility Management Entity)-
HSS – Home Subscriber Server
Packet Data Network (PDN)
Radio Bearer S1 Bearer S5/S8 Bearer
EPS (Evolved Packet System) Bearer
Uu
• EPS bearer is a “tunnel” that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base
Billing System
How to track the location of user terminals?
How to mitigate interference between neighbor cells?
How does user terminal join the packet network?
How to ensure that user data can be transported to/from packet network as user moves ?
How to optimize on the amount of info over radio?
How to arbitrate the access of radio resource by user terminals?
How to maintain QOS of different traffic types?
How does radio wave carries information?
?
Frequency Reuse
S1
S2
S3
S1
S2
S3
S1
S2
S3
f1
f2
f3 f3
f2
f1
Refers to how frequency band are used in cell deployment Reuse of 1 => the same frequency is used in all sector
Reuse of 3 => frequency band is reused every 3 sectors – lower utilization of whole band
Inter-cell Interference (ICI) occurs when a UE is in the edge of a sector and is subceptable to the interference of a neighbor cell
Reuse of 1 result in high ICI
A reuse 3 approach divides the frequency band among 3 sectors eliminate ICI but result in much lower cell capacity
SFR (Soft Frequency Reuse) divide the frequency into minor and major band. Major band is used all the way up to cell edge by using higher power, and minor band is used in the cell center at lower power. Major bands can be derived by dividing whole band into 3 non overlapping bands.
Full capacity is harnessed at the cell center with a reuse of 1
At the edge due to the division of frequency, the reuse is >1, e.g., 3
Furthermore band power can be adjusted to change the extend of reuse depending on the inter-cell condition and UEs requirements
minor band
major band
minor bandminor band
minor band
Reuse 3Reuse 1 Reuse ~1 with SFR
Heterogeneous NetworkQuality of Experience issues
◦ Coverage problems at cell edge or indoor, e.g., terrace house and deep in office buildings, poor voice quality
◦ Capacity problem at hotspot, low mobile broadband throughput and poor user experience
Build more macro cell◦ Site acquisition issue and macro cells start to interfere
with each others
Heterogeneous Network - Small cells of lower power
◦ Macro (40W), Micro, Pico/metro (5-10W), and Femto(100mw)
◦ Serves smaller area providing or increase the capacity in hotspot
◦ A small cell is connected via wireline broadband network to core via a small cell gateway or alternatively, it is a radio head and connects via optical fiber to nearby basestation for baseband processing
◦ UE locked onto a small cell when signal is above threshold, use further bias configuration to bias UE towards connecting with small cell, thus offloading the traffic from macro cell, thus extending the range
◦ Issue with interference from macro cell at the small cell edge
Coverage Issue
Capacity Issue at hotspot Coverage and Capacity Issue
Build more macro cell
Heterogeneous Network- Build smaller calls of lower power
Potential interference from macro
Femto cell dedicated to private user group e.g., home or office UE
Lower power pico cell
Metro/Pico cell serves public UE in a hotspot area
Macro cell still provides overall coverage
Wireline broadband
Optical fiber
LTE-A - eICICeICIC (Enhanced Inter-cell Interference coordination)
◦ UE at pico/metro cell edge tends to suffer from interference from macro cell
◦ Interference onto the pico cell can be reduced if the macro cell refrain from using the subframesthat pico cell is using on it’s edge UE/s
◦ Pico cells exchange load info with macro cell which takes account of own load and Macro cell identify which resource blocks not to be used, called ABS (Almost Blank subframe)
◦ Pico cells near to the macro cell can allocate the same subframe corresponding to the ABS for UEs at the edge as there will be less interference from macro
◦ Synchronization between the pico and macro as both must now aligned on ABS subframe
Macro cell determines the ABS based on load of Pico and Macro cell
Macro eICICScheduling
Pico submit load and Macro cell informs ABS pattern
Corresponding subframe assigned to UE at Pico cell edge
LTE-A – CACA – Carrier Aggregation
- Operators often have license to multiple frequency blocks, may be in the same band or different band
- Being able to allocate them to UEs together increase peak rate of UEs, and potentially increase utilization efficiency
- Up to 5 carriers (component carriers) to transmit data down or upstream, currently up to 3 is defined
- Component carriers can be in same band or different band◦ e.g., GSM refarming, and newly acquired 2.6Ghz band
- Primary frequency known as PCell is responsible for signaling such as mobility management and allocate one more secondary frequency known as SCell to UE
- Algorithm runs in basestation to decide whether to activate CA configuration of UE depending on availability of resource and UE demand, deactivate when not needed to save UE power
- Multiple scenarios◦ Low band + high band -> low band provides coverage and high
band provides capacity
◦ FDD+TDD -> FDD at macro provides coverage and TDD as RRH provides additional capacity
◦ Macro+small cell using different frequency – macro provides coverage and small cell provides capacity
Intra-band contiguous
Intra-band non-contiguous
Inter-band non-contiguous
f1 - pCell
f2 - sCell
Pico/TDD RRH
macro
f1 - pCell
f2 - sCell
Low band + Highband
Pico+ Macro or FDD + TDD
LTE-Advanced - COMP COMP (Coordinated Multipoint Transmission)
Coordinates among a set of transmission (Tx) or receiving points (Rx) which can be intra or inter site to provide better performance at the cell edge by mitigating interference
Two major approaches – Coordinated Scheduling/Coordinated Beamforming achieving interference avoidance, Joint Processing/Joint Transmission or Joint Processing/Dynamic Point selection (DPS) where multiple Txs transmit to the cell sites
RRH_1RRH_2
JT – both Tx in a Frequency time resource
DCS – one Tx transmit at a time
eNodeB_2
Data stream to both Tx
Only the serving cell receive data stream and transmit other Tx points are coordinated at the scheduling or beamforming to reduce interference.
Serving cell transmission
Coordinated Scheduling/BeamformingJoint Processing – Joint Transmission/Dynamic Cell selection
UE Category
UE Category DL SpatialMIMO Layer
UL Spatial MIMO Layer
QAM 64DL
QAM 64UL
RF Bandwidth
DL Peak Rate
UL Peak Rate
Category 1 Optional No Yes No 20Mhz 10 5
Category 2 2x2 No Yes No 20Mhz 50 25
Category 3 2x2 No Yes No 20Mhz 100 50
Category 4 2x2 No Yes No 20Mhz 150 50
Category 5 4x4 No Yes Yes 20Mhz 300 75
Category 6 2x2 or 4x4 No Yes No 40Mhz 300 50
Category 7 2x2 or 4x4 2x2 Yes No 40Mhz 300 100
Category 8 8x8 4x4 Yes Yes 100Mhz 3000 1500
LTE-
Ad
van
ced
Car
rier
Agg
rega
tio
n
Up to Release 10
Further DevelopmentLTE in Unlicensed band (LTE-U)
◦ Licensed Assisted Access (LAA-LTE) where LTE runs on unlicensed band, 5GHz being considered
◦ Licensed band macro serve as primary cell for signaling and basic service, use local cell with unlicensed band as supplementary either only on downlink or with uplink as well, based on CA (carrier aggregation)
◦ 3GPP Release 13 work items
LTE and WiFi Aggregation (LWA)◦ Part of LTE traffic is “tunneled” via WiFI (hence still using WiFi medium access, AP etc.)
◦ LTE traffic at licensed band and those tunneled via WiFi is combined at the local eNB e.g., small cell
◦ Better coexistence of WiFi as there is no LTE RAN in the unlicensed band, no hardware change in UE
◦ 3GPP Release 13 work items
Machine to Machine communications, IOT (Internet of Things)◦ Still very loosely defined
◦ Huge number of devices at low bandwidth, sleep and communicate
◦ Reduce complexity on UE to reduce power, e.g., reduce bandwidth capability, transmission mode
◦ Support for longer distance