source: zahid ghadialy, 5g: an advanced introduction“ (slides)
TRANSCRIPT
1Source: Zahid Ghadialy, "5G: An Advanced Introduction“ (slides)
Background: Cellular network technologyOverview
1G: Analog voice (no global standard …)
2G: Digital voice (again … GSM vs. CDMA)
3G: Digital voice and data• Again ... UMTS (WCDMA) vs. CDMA2000 (both CDMA-based)
• and … 2.5G: EDGE (GSM-based)
4G: LTE, LTE-Advanced …• OFDM (OFDMA for downlink and SC-OFDM for uplink)
5G …
Trends Advanced networks (SDN, NVF), everything on cloud, immersive
experience, tele presence, massive connectivity, D2D, ...
More data, packet-based switching, shared channel, directional (spatial reuse), multi-antenna, etc.
Other goals: Seamless with other technologies, QoS for multimedia, etc.
2
BSCBTS
Base transceiver station (BTS)
Base station controller (BSC)
Mobile Switching Center (MSC)
Mobile subscribers
Base station system (BSS)
Legend
2G (voice) network architecture
MSC
Public
telephone
network
GatewayMSC
G
7-3Wireless and Mobile Networks
3G (voice+data) network architecture
radionetwork controller
MSC
SGSN
Public
telephone
network
GatewayMSC
G
Serving GPRS Support Node (SGSN)
Gateway GPRS Support Node (GGSN)
Public
Internet
GGSN
G
Key insight: new cellular data
network operates in parallel
(except at edge) with existing
cellular voice network
voice network unchanged in core
data network operates in parallel
7-4Wireless and Mobile Networks
radionetwork controller
MSC
SGSN
Public
telephone
network
GatewayMSC
G
Public
Internet
GGSN
G
radio access networkUniversal Terrestrial Radio
Access Network (UTRAN)
core networkGeneral Packet Radio Service
(GPRS) Core Network
public
Internet
radio interface(WCDMA, HSPA)
3G (voice+data) network architecture
7-5Wireless and Mobile Networks
Code Division Multiple Access (CDMA)
used in several wireless broadcast channels (cellular, satellite, etc) standards
unique “code” assigned to each user; i.e., code set partitioning
all users share same frequency, but each user has own “chipping” sequence (i.e., code) to encode data
encoded signal = (original data) X (chipping sequence)
decoding: inner-product of encoded signal and chipping sequence
allows multiple users to “coexist” and transmit simultaneously with minimal interference (if codes are “orthogonal”)
6
CDMA Encode/Decode
slot 1 slot 0
d1 = -1
1 1 1 1
1- 1- 1- 1-
Zi,m= di.cm
d0 = 1
1 1 1 1
1- 1- 1- 1-
1 1 1 1
1- 1- 1- 1-
1 1 11
1-1- 1- 1-
slot 0
channel
output
slot 1
channel
output
channel output Zi,m
sendercode
data
bits
slot 1 slot 0
d1 = -1
d0 = 1
1 1 1 1
1- 1- 1- 1-
1 1 1 1
1- 1- 1- 1-
1 1 1 1
1- 1- 1- 1-
1 1 11
1-1- 1- 1-
slot 0
channel
output
slot 1
channel
outputreceiver
code
received
input
Di = S Zi,m.cm
m=1
M
M
7
CDMA: two-sender interference
8
Practical chipping codes …
9
Orthogonal even under offset? No synchronization … Random sequence; high probability low cross-correlation
Different chip lengths? different rates, take advantage of silence, more calls
radionetwork controller
MSC
SGSN
Public
telephone
network
GatewayMSC
G
Public
Internet
G
3G versus 4G LTE network architecture
GGSN
radio access networkUniversal Terrestrial Radio
Access Network (UTRAN)
Evolved Packet Core
(EPC)
MME
Public
Internet
P-GW
G
S-GW
G
HSS
3G
4G-LTE
7-10Wireless and Mobile Networks
4G: differences from 3G
all IP core: IP packets tunneled (through core IP network) from base station to gateway
no separation between voice and data – all traffic carried over IP core to gateway
radio access networkUniversal Terrestrial Radio
Access Network (UTRAN)
Evolved Packet Core
(EPC)
Public
Internet
P-GW
G
S-GW
G
UE(user element)
eNodeB(base station)
Packet data networkGateway(P-GW)
Serving Gateway(S-GW)
data
MMEHSS
Mobility Management Entity (MME)
Home Subscriber Server(HSS)(like HLR+VLR)
7-11Wireless and Mobile Networks
Some example responsibilities eNodeB
Admission control and congestion control
Scheduling and allocation of resources to UEs
State transition: IDLE to CONNECTED
Control mobility in connected mode
Buffering of data during handover
MME Handle mobility + maintain context in IDLE mode
Bearer management for UE
S-GW Mobility anchor for data bearers
Buffer downlink data when UE in IDLE mode
P-GW Allocate IP for UE
Maps packets into different QoS-based bearers 12
Radio+Tunneling: UE – eNodeB – PGW
7-13Wireless and Mobile Networks
tunnellink-layer radio net
UEeNodeB
S-GWG
P-GWG
IP packet from UE encapsulated in GPRS Tunneling Protocol (GTP) message at ENodeB
GTP message encapsulated in UDP, then encapsulated in IP. large IP packet addressed to SGW
Quality of Service in LTE
QoS from eNodeB to SGW: min and max guaranteed bit rate
QoS in radio access network: one of 12 QCI values
7-14Wireless and Mobile Networks
LTE and LTE-Advanced
15
ITU, IMT-advanced, 3GPP, and LTE-Advanced ... All traffic is IP-based Base station called enhanced NodeB, eNodeB or eNB
UE
Internet
LTE and LTE-Advanced
16
ITU, IMT-advanced, 3GPP, and LTE-Advanced ... All traffic is IP-based Base station called enhanced NodeB, eNodeB or eNB
UE
InternetRN
LTE and LTE-Advanced
17
ITU, IMT-advanced, 3GPP, and LTE-Advanced ... All traffic is IP-based Base station called enhanced NodeB, eNodeB or eNB
RN
UE
Internet
Evolved packet core
MME HSS
SGW PGW
Data traffic
LTE and LTE-Advanced
18
Relays HetNets etc. Carrier aggregation Downlink (OFDMA) vs uplink (SC-OFDM)
RN
UE
Internet
Evolved packet core
MME HSS
SGW PGW
Data traffic
LTE downlink (OFDMA-based)
19
Data symbols are independently modulated and transmitted over a high number of closely spaced orthogonal subcarriers.
Available modulation schemes for E-UTRA downlink: QPSK, 16QAM, and 64QAM (with 2, 4 , and 6 bits/symbol, respectively)
OFDM signal is generated using Inverse Fast Fourier Transform (IFFT) digital signal processingƒ
Figure from:3GPP TR 25.892; Feasibility Study for Orthogonal Frequency Division Multiplexing (OFDM) for UTRAN enhancement (Release 6)
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Time domain structure: 10 ms frame consisting of 10 subframes of length 1 ms Each subframe consists of 2 slots of length 0.5 ms Each slot consists of 7 OFDM symbols (6 symbols in case
of extended CP)
ƒ Resource element (RE) One subcarrier during one OFDM symbol
ƒ Resource block (RB) 12 subcarriers during one slot (180 kHz × 0.5 ms)
Figure from: S. Parkvall, “LTE – The Global Standard for Mobile Broadband”, presentation, Ericsson Research
21
Scheduling decisions done in the base station Scheduling algorithm is a vendor-specific, but
typically takes into account Radio link quality situation of different users Overall interference situation Quality of Service requirements Service priorities, etc.
Uplink
22
Downlink vs uplink
23
Parallel transmission on large number of narrowband subcarriers
Avoids own-cell interference
Robust to time dispersion ƒ Bad power-amplifier
efficiency
Single carrier properties Better battery lifetime at
phones/sender (reduced power-amplifier power)
More complexity at receiver (equalizer needed)
Lower throughput
Multi-antenna (*slide from Ericsson)
24
Beamforming
25
Advantages: - Beam towards user- Strong receive signal- Save transmit power (by sending
same signal at lower power)- Less interference
Multi-antenna examples
26
Spatial diversity - Different antennas see “outages” at
different times- Multiple paths to receiver - Path lengths d1 and d2- Multi-path fading: Small movements
make big difference …- “Outage” with probability p- M independent antennas send same
signal: at least on success 1-pM.
Spatial multiplexing
Determine the time delay to locations of users and adjust phase accordingly …
27
y = H s + n
s’ = H-1 y
Note:
- H based on channel
estimation (fading) using
known reference of pilot
signal
- Stability depends on
condition number of H
- Want cond(H) close to 1
- Decomposition methods,
rather than pure inversion
Evolved Multimedia Broadcast/Multicast Service (eMBMS) in LTE-advanced
28
Evolved Multimedia Broadcast/Multicast Service (eMBMS) in LTE-advanced
Separation of control plane and data plane
29
Image from: Lecompte and Gabin, Evolved Multimedia Broadcast/Multicast Service (eMBMS) in LTE-Advanced: Overview and Rel-11 Enhancements, IEEE Communications Magazine, Nov. 2012.
Evolved Multimedia Broadcast/Multicast Service (eMBMS) in LTE-advanced
MBMSFN and use of services areas
30
Image from: Lecompte and Gabin, Evolved Multimedia Broadcast/Multicast Service (eMBMS) in LTE-Advanced: Overview and Rel-11 Enhancements, IEEE Communications Magazine, Nov. 2012.
Some words about 5G
Advanced network (e.g., SDN, NVF, context-aware, content-aware ...)
Millimeter waves (open up new high-frequency spectrum)
Multi-RAT (Radio Access Technology)
Small cells (mini-base stations, e.g., every 250m)
Massive MIMO (100s of ports)
Beamforming (efficient per-device delivery routes)
Full duplex (on same frequency)
Advanced D2D
… 31
Use-case-driven requirements …
32Source: Zahid Ghadialy, "5G: An Advanced Introduction“ (slides)
Use-case-driven requirements …
33Source: Zahid Ghadialy, "5G: An Advanced Introduction“ (slides)
High data rates
High densityUltra reliable +
Low latency
… wish list …
34Source: Zahid Ghadialy, "5G: An Advanced Introduction“ (slides)
5G goals/targets/requirements ...
35Source: Zahid Ghadialy, "5G: An Advanced Introduction“ (slides)
More slides …
36
Overview
37Image: http://www.ltehandbooks.com/2015/09/lte-radio-interface-ofdmofdmasc-fdma.html
Functional split of major LTE components
holds idle UE infoQoS enforcement
handles idle/active UE transitionspages UEsets up eNodeB-PGW tunnel (aka bearer)
7-38Wireless and Mobile Networks