PRISMA Telecom Testing Srl | Private & Confidential | Vers. 1.6 LTE-Handover on High Speed Trains: In-lab experimental study on the current and future solutions A.Parichehreh, P.Marini, Luca Dell’Anna, Umberto Spagnolini 2016.10.19 IWPC Workshop Evolving the Internet of Things Turin, October 18-20, 2016
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Two-tier Architecture for on-board wreless connectivity
Experimental Result
In-Lab Exerimental Setup
Conclusion
Confidential – Version 1.6
Introduction to HST On-board Internet Service
Page 3
• Satellite Communication • Low bandwidth and high latency • Disconnections across tunnels • Cost of communication
• GSM-R • signaling of train and
ground station • 114 kbit/second for GPRS
• HSPA/HSPA+ • 3G technology based on CDMA • 14 Mbps in DL and 5.76 Mbps in UL.
• LTE/LTE-A • 4G technology based on TDMA/FDMA • 100Mbps peak data rate in high mobility scenario (>350km/h).
HST with speed up to 500 km/h
• Challenges • Varying channel and Doppler Shift • Penetration loss • Frequent handovers • Resource limitations
High speed train (HST) is becoming one of the preferred mid-range
transportation and the on-board Internet service is a must for train operators.
Confidential – Version 1.6
Problem definition of Handover (HO) in mobility system
Low mobility scenario train setting (e.g., v=70km/h = 20m/s, carriage length=25m) • Arrival time of carriage i+1 is larger than the HO time of carriage i • All HO related to one carriage is concluded before the next carriage
Page 4
Cell border
HO latency
RS
RP
[dB
m]
Ms
Mn
H
Os
On
TTT
A3 E
vent
Meas. R
eport
Confidential – Version 1.6
Problem definition of Handover (HO) in mobility system
High mobility scenario train setting (e.g., v = 350km/h = 97m/s, carriage length=25m) • Arrival time of carriage i+1 is smaller than the HO time of carriage i
Page 5
Handovers (HOs) of multiple UEs (20-60UE/carriage) and carriages (8-10carriage/train) must be done within a short time to guarantee QoE over the RACH signaling with heavy signaling overload. Basic idea and motivation:
• To study and verify the performance of different manufacturer for this special challenging scenario
Cell border
HO latency Depend on the HST speed/load
RS
RP
[dB
m]
Ms
Mn
H
Os
On
TTT
A3 E
vent
Meas. R
eport
Confidential – Version 1.6
Amplify and Forward (AF)-LTE Relaying
Page 6
Radio Relay
Technology General Description Advantages/Disadvantages
Type-1
Layer-1 relay
(analog repeater)
AF relay
AF of on-board UEs (transparent relay)
with full-duplex capability.
+
• Simple and inexpensive
• Minimum impact on the LTE standard
(already defined in LTE Rel.8)
• Suitable solution when carriage are shielded
-
• Noise and inter-cell interference amplification
• Frequent HOs, the same as baseline scenario (with direct link between UEs and
ground eNB)
LTE Relay LTE Relay
HO region L
TE
serv
ice
rate
Moving direction
Confidential – Version 1.6
Decode and Forward (DF)-LTE Relaying
Page 7
Radio Relay
Technology General Description Advantages/Disadvantages
Type-2:
Moving Relay Node
(MRN)
Acting with the same functionalities of a
base station, non-transparent for on-
board UEs.
DF half-duplex relay.
+
• Noise and inter-cell interference mitigation capability
• Group HOs and Tracking Area Updates (TAU)
-
• Requires its own PCID and non-transparent to UEs
• UEs need mobility management for joining to MRN
• Extra resource allocation overhead for LTE backhaul link between Donner evolved
NodeB (DeNB) and MRN (Un), and MRN and UEs (Uu).
• Needs further modifications on LTE specification (LTE Rel.12)
MRN MRN
HO region L
TE
serv
ice
rate
Moving direction
Uu
Un
Uu
Confidential – Version 1.6
UeSIM Architecture
Page 8
• Protocol processor and IP traffic generator. Processes the lower protocol layers for LTE/WCDMA/GSM (MAC, RLC, PDCP)
• Simulation control and Control Plane processing
• Optimized implementation of RRC/NAS
• SDR Unit provides multi-standard baseband processing and includes the RF interface • The same SDR Unit can be configured to work with any 3GPP radio access technology and any frequency band: GSM, UMTS, LTE/FDD, LTE/TDD
SDR Units S1 eNodeB
cell 1
GbE
PE-Wireshark AirMosaic
GUI
eLSU
GbE Test Manager
Workstation
eNodeB
cell 2
eNodeB
cell 3
S1
S1
ePC
Core Network
Logging workstation
tracing from Radio to
Application Layer
User Workstation controlling
test scenario, mobility,
application, radio conditions
Confidential – Version 1.6
TCP measurement of the ensemble of on-board UEs
Page 9
UE 1
UE N
eN
B
Core
ne
two
rk
UE N
UE 1
UE 2 UE 2
Onboard
UE
s
Internet
Services
D=1km
0
0
0
0
0
Moving direction v=300kmph
a)
b)
c)
d)
e)
UE 1
UE 2
UE N
eNB1→ eNB2
eNB2→ eNB3
eNBK-1→ eNBK
eNB1 eNB2 eNB3 eNBK
PHY
UE N
PHY
MAC
MAC
MAC
MAC
MAC
MAC
UE 1
UE 2
UE N
UE 1
UE 2
PHY level
settings
BB Interf eNodeB
cable
Mu
ltiu
ser
traff
ic
gen
era
tor
(vid
eo,
HT
TP
, F
TP
)
eNodeB
Cell k
Cell k+1
Simulated group of UEs via UeSIM LTE eNB & core network