huawei lte-r technical white paper - actfornet lte for rail... · huawei lte for rail technical...
TRANSCRIPT
Huawei LTE for Rail
Technical White Paper
Issue 01
Date 8/8/2014
HUAWEI TECHNOLOGIES CO., LTD.
ii
Copyright © 2014 Huawei Technologies Co., Ltd. All rights reserved.
No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd.
Trademarks and Permissions
and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd. All other
trademarks and trade names mentioned in this document are the property of their respective holders.
Notice
The purchased products, services and features are stipulated by the commercial contract made
between Huawei and the customer. All or partial products, services and features described in this
document may not be within the purchased scope or the usage scope. Unless otherwise agreed by
the contract, all statements, information, and recommendations in this document are provided “AS IS” without warranties, guarantees or representations of any kind, either express or implied.
The information in this document is subject to change without notice. Every effort has been made in
the preparation of this document to ensure accuracy of the contents, but all statements, information,
and recommendations in this document do not constitute the warranty of any kind, express or implied.
All logos and images displayed in this document are the sole property of their respective copyright holders. No endorsement, partnership, or affiliation is suggested or implied.
Huawei Technologies Co., Ltd.
Address: Huawei Industrial Base
Bantian, Longgang
Shenzhen 518129
People’s Republic of China
Website: http://www.huawei.com
Email: [email protected]
Contents
Contents .................................................................................................................................................................... i
Change History ........................................................................................................................................................ 2
1 Why Railways Need LTE .................................................................................................................................. 3
1.1 GSM-R EOL is near ........................................................................................................................................ 3
1.2 LTE is a powerful, suitable successor .................................................................................................. 4
1.2.1 Unified evolution of wireless technologies .................................................................................. 4
1.2.3 LTE has already been widely deployed......................................................................................... 4
1.3 LTE railway benefits ......................................................................................................................... 6
1.3.1 Supports existing GSM-R services ................................................................................................. 6
1.3.2 Improved end-to-end performance and reliability.......................................................... 7
1.3.3 LTE prevents interference .................................................................................................... 7
1.3.4 Strong security defense ......................................................................................................... 8
2 Critical Steps from GSM-R to LTE ...................................................................................................................... 11
2.1 Services — the heart of a migration strategy .................................................................................... 11
2.1.1 Refarm existing GSM-R spectrum for LTE use .............................................................. 12
2.1.2 New spectrum for LTE use ................................................................................................. 13
3 Infrastructure ................................................................................................................................................. 14
Abbreviations ......................................................................................................................................................... 17
Huawei LTE for Rail Technical White Paper
Page 2
Change History
Date Version Description Author
2014-06-24 V1.0 First edition Wenhua
Huawei LTE for Rail Technical White Paper
Page 3
1 Why Railways Need LTE
1.1 GSM-R EOL is near
Data-based communications are becoming faster — so fast, that carriers are
investing more in new technologies to improve their data throughput, to upgrade
wireless networks, and to apply more spectrum frequencies. A victim of these
continual upgrades is GSM, especially 2G GSM: investments in this technology
are shrinking and the 2G GSM spectrum has been re-purposed for 3G/4G.
What’s more, customers of aging 2G systems have been informed that 2G
voice quality will worsen, data transfer speeds will slow and, as a result, they
are being urged to switch to a 3G or 4G handset. Some carriers already have
set timetables for EOL of all GSM services. As a result, GSM will become a
risky investment for all industries, including railways: there will be less demand
for GSM chipsets, base stations, and handsets.
Luckily for railways, they have been paying close attention to the evolution of
new wireless techniques. In 2010, the International Union of Railways published
“The Future Railways Mobile Telecommunications Systems Study.” In 2013, the
European Railway Agency published a wireless system roadmap that gives a
clear direction for railways that have equipped their lines with thousands of
kilometers of GSM-R networks.
Huawei LTE for Rail Technical White Paper
Page 4
1.2 LTE is a powerful, suitable successor
1.2.1 Unified evolution of wireless technologies
Wireless technology is evolving to broadband and higher spectrum efficiency.
At one point, competition was stiff between WiMAX and LTE over which technology would
“win” the wireless broadband competition, but questions about WiMAX’s evolution path
and its low commercial use has put LTE in the lead. What’s more, LTE belongs to the
3GPP family, which ensures smooth migration to future technologies such as LTE-A,
LTE-B and 5G.
1.2.3 LTE has already been widely deployed
LTE is a mature technology that is widely deployed for commercial use(please refer to
http://en.wikipedia.org/wiki/LTE_(telecommunication) to see the commercial deployment
of LTE), which has reduced LTE equipment and handset costs. That is good news for
railways.
In fact, LTE is being used for railways right now. In China, for example, the Shuohuang
railway line is a 594 km-long coal freight line with 34 stations and 33 sections. Huawei has
Huawei LTE for Rail Technical White Paper
Page 5
deployed a TDD 1.8G LTE network that provides services such as group call over LTE,
synchronization of multiple locomotives, data transmission, and video surveillance on
moving trains. To ensure reliability, the network uses a double radio layer and redundant
control nodes. The use of LTE has helped increase Shuohuang’s coal-hauling capacity
from 200 million tons to 350 million tons.
Huawei LTE for Rail Technical White Paper
Page 6
1.3 LTE railway benefits
1.3.1 Supports existing GSM-R services
GSM-R LTE for Rail
Huawei LTE for Rail Technical White Paper
Page 7
European Train
Control System
(ETCS)
Circuit Switched Data Packet Switched Data
PTP Call Circuit Switched Voice
Call SIP-based Voice Call
PTT Call VGCS/VBS eMBMS-based LTE Group
Communication
Emergency Call VGCS eMBMS-based LTE Group
Communication
Priority eMLPP QCI, ARP
Functional
Addressing SCP SCP
Location-
Dependent
Addressing
SCP SCP
Access Matrix SCP SCP
1.3.2 Improved end-to-end performance and reliability
Existing GSM-R services are expected to improve their performance while migrating to
the flat, all-IP LTE infrastructure, especially services related to E2E delay.
Another benefit from the LTE architecture is the reduction of NEs, which has, as a result,
reduced the number of potential failures. Other features, like the MME pool, further
improve network reliability.
1.3.3 LTE prevents interference
LTE uses OFDM sub-carrier scheduling to detect frequency interference. This is a leading
reference signal design that quickly and accurately detects interference by tracing channel
changes on time and frequency domains. In addition, the simultaneous response of
multiple LTE terminals helps speed the response to interference.
Huawei LTE for Rail Technical White Paper
Page 8
To avoid interference, LTE provides a complete mechanism for coding, re-transmission,
and IRC. This microsecond-level scheduling mechanism ensures that the LTE network
schedules resources in a timely and dynamic manner. When detecting interference, or
cross-talk, the sub-carrier with the highest C/I ratio will be allocated. LTE also provides
AMC, which will dynamically adjust the modulation and coding method according to the
RSRP and SINR, which further increase LTE’s interference prevention capability.
To control interference inside the network, LTE provides a complete power control
mechanism. Moreover, algorithms such as ICIC and CoMP further improve LTE’s
capability to control interference. Depending on the measures employed, LTE can still
provide some bandwidth to provide services with QoS guarantees when encountering
interference.
1.3.4 Strong security defense
Security is an important feature of LTE networks. Measures are taken on User Identity
Confidentiality, Entity Authentication, User Equipment (UE) Authentication, Confidentiality
and Integrity for Signaling and User Data, Non-Access Stratum (NAS) Security, etc.
User Identity Confidentiality
MME allocates a globally unique temporary identity to user equipment, which the
EPS uses to avoid frequent exchange of the UE’s permanent IMSI over the radio
access link.
Entity Authentication
An EPS Authentication and Key Agreement (AKA) procedure is used to provide
mutual authentication between the user and the network, and agreement on the NAS
Key Access Security Management Entity (KASME). KASME forms the basis for
generating Access Stratum (AS) and NAS ciphering and integrity keys. The keys are
used for radio resource control in the access stratum, and for user plane and NAS
Huawei LTE for Rail Technical White Paper
Page 9
signaling protection.
UE Authentication
UE authentication is initiated by the serving MME through EPS NAS procedures. An
EMM authentication request is sent to the user equipment with authentication
parameters (RAND, AUTN) and the NAS Key Set Identifier (known as eKSI or
KSIASME).
The user equipment responds to the MME with an authentication response, including
a response upon successful processing of the authentication challenge data. The
MME then must validate RES; the intermediate KASME is determined after
successful completion of the current EPS AKA, as agreed upon by the UE and MME.
Confidentiality and Integrity for signaling and user data
As we have seen, to ensure confidentiality and integrity protection for signaling and
user data in the EPS, two levels of security associations exist: the AS and NAS.
AS security
Carried out for RRC and user plane data and belongs to the scope of user equipment
(such as handsets) and eNodeB.
The PDCP layer on the user equipment and eNodeB side is responsible for ciphering
and integrity protection.
RRC messages are integrity-protected and ciphered but U-Plane data is only
ciphered.
NAS security
Carried out for NAS messages and within the scope of UE and MME. In this case,
NAS message communication between UE and MME are integrity protected and
ciphered with an extra NAS security header.
Ciphering mechanisms can be used to provide signaling and user data confidentiality
between the UE and the EPS, while integrity and replay mechanisms can be used to
provide signaling and user data integrity. The related algorithms are:
Huawei LTE for Rail Technical White Paper
Page 10
Integrity
• “0000” EIA0 Null Integrity Protection algorithm
• “0001”128-EIA1 SNOW 3G
• “0010” 128-EIA2 AES
Ciphering
• “0000” EEA0 Null ciphering algorithm
• “0001” 128-EEA1 SNOW 3G-based algorithm
• “0010” 128-EEA2 AES-based algorithm
Huawei LTE for Rail Technical White Paper
Page 11
2 Critical Steps from GSM-R to LTE
2.1 Services — the heart of a migration strategy
Railway services carried by wireless networks are at the heart of the migration strategy of
GSM-R to LTE. Railway wireless services can be classified into two categories: critical
and common. Critical services refer to those in direct connection with train movement, for
example, train-to-ground voice calls. Common services refer to those with no relation to
train movement, for example, train arrival announcements on displays in the train station.
Since critical services play a far more important role than common services, the service
migration strategy may look like this:
Step 1:
LTE usually is first introduced into railways by common, or even assistant services. This
Huawei LTE for Rail Technical White Paper
Page 12
step relieves the stress on GSM-R of more and more data-based services. With the high
spectrum efficiency of LTE, new services can be added to existing common services. This
will benefit railway personnel, who can gain experience with LTE networking, O&M, etc.,
and be ready for its further application.
Step 2:
After step 1, railway managers and personnel will have grown confident in the ability of
LTE to carry critical services. However, migrating critical services should be done
gradually, in order to ensure consistency and reliability. GSM-R will serve as the backup
system.
Step 3:
At this stage, LTE will have proved to be a trustworthy system. Meanwhile, GSM-R
maintainability will become worse as the EOL of GSM technology gets closer, and the
poor spectrum efficiency of GSM-R will become less acceptable. Step 3 is the obvious
time to decommission and dispose of the GSM-R system.
2.1.1 Refarm existing GSM-R spectrum for LTE use
For a railway that already has a 7M spectrum for GSM-R networking, a “refarming”
strategy is recommended during the evolution to LTE.
Step 1. LTE for common services, GSM-R for critical services
First, refarm the 3M frequency for LTE FDD to fulfill the service requirement in Step1 of
the service migration process described in 2.1. This spectrum allocation is suggested for
the following reasons:
Huawei LTE for Rail Technical White Paper
Page 13
1. 3M is a standardized LTE bandwidth defined in 3GPP, and can provide a
throughput of 12.4 Mbit/s (downlink), 3.4 Mbit/s (uplink) under normal conditions*,
which are enough for transporting common railway services.
2. Railways have abundant experience with the 4M spectrum in GSM-R operations.
*The data rates above assume: eNodeB 2T2R, LTE terminal 1T2R, cell radius 2.5 km,
tower height 45m.
Step 2. LTE for all services, GSM-R for backup
To fulfill the service requirement in Step 2 of the service migration process described in
2.1, 2 Mbit/s additional spectrum will be allocated for LTE to provide critical services, while
GSM-R will use 2 Mbit/s of the spectrum to act as the backup network to provide basic
critical services during an emergency.
Step 3. LTE for Rail
For the final decommissioning and disposal of the GSM-R system, LTE will get an
additional 1.4 Mbit/s for its network.
2.1.2 New spectrum for LTE use
For railways limited by the GSM-R 4M spectrum for networking, it is recommended to
apply for additional LTE spectrum.
Step 1. LTE for common services, GSM-R for critical services
Huawei LTE for Rail Technical White Paper
Page 14
Step 2. LTE for all services, GSM-R for backup
The newly applied spectrum is dedicated for LTE use to fulfill the service requirement in
Steps1 and 2 of the service migration process described in 2.1. The original 4 Mbit/s is
always allocated for GSM-R use.
Step 3. LTE for Rail
For the final decommissioning and disposal of the GSM-R system, LTE will get an
additional 3 Mbit/s for its network.
3 Infrastructure
Step 1. LTE for common services, GSM-R for critical services
Huawei LTE for Rail Technical White Paper
Page 15
Huawei’s core network has integrated the function of the GSM-R circuit switched and
packet switched cores with the function of the LTE packet switched core and VoLTE. Only
a license is needed to enable the evolved packet core function.
Huawei’s BTS3900 is an SDR base station. Only one existing RF module needs to be
configured from GSM to LTE mode when the spectrum refarming strategy is applied. By
adding LTE BBU boards into an existing BBU that simultaneously provides a base station
to support GSM-R, the LTE network will be ready. To avoid redesigning a GSM-R network,
a dedicated antenna should be deployed for LTE.
LTE requires IP transmission between the EPC and the base station. The IP transmission
function in Huawei’s MSTP equipment can be activated without any hardware changes. At
this point, LTE services can be provided over LTE terminals such as handsets.
Step 2. LTE for all services, GSM-R for backup
In this step, LTE needs to provide critical services. Huawei’s core network and BTS3900
need to be updated to support VoLTE, and the ETCS RBC needs to be updated to
support the IP interface. Meanwhile, EDOR needs to support the LTE air interface. In this
way, ETCS can be transmitted over LTE. In addition, cab radios and handsets need to
support VoLTE to coordinate with the core network for voice services.
Huawei LTE for Rail Technical White Paper
Page 16
Step 3. LTE for Rail
In conclusion, when the decommissioning and disposal of GSM-R systems finally occurs,
all GSM-R functions/equipment/terminals will canceled, together with TDM transmission.
Huawei LTE for Rail Technical White Paper
Page 17
Abbreviations
AMC Adaptive Modulation and Coding
ARP Allocation and Retention Priority
AS Access Stratum
BBU Baseband Unit
C/I Carrier/Interference
CoMP Coordinated Multi-Point
CPE Customer Premises Equipment
CS Circuit Switched
EDOR European Data Only Radio
EOL End Of Life
EPC Evolved Packet Core
EPS Evolved Packet System
ETCS European Train Control System
FDD Frequency-Division Duplexing
GSM-R GSM for Railway
ICIC Inter-Cell Interference Coordination
IRC Interference Rejection Combining
LCD Liquid Crystal Display
LTE Long-Term Evolution
MME Mobility Management Entity
MSTP Multi-Service Transfer Platform
NAS Non-Access Stratum
Huawei LTE for Rail Technical White Paper
Page 18
OFDM Orthogonal Frequency-Division Multiplexing
PS Packet Switched
PTP Point-to-Point
PTT Push-To-Talk
QCI QoS Class Identifier
QoS Quality of Service
RBC Radio Block Center
RF Radio Frequency
RSRP Reference Signal Received Power
SCP Service Control Point
SDR Software-Defined Radio
SINR Signal to Interference plus Noise Ratio
TDD Time-Division Duplexing
TDM Time-Division Multiplexing
UE User Equipment
VBS Voice Broadcast Service
VGCS Voice Group Call Service
VoLTE Voice over LTE