The document discusses network architectures for resilient emergency communications combining aerial and terrestrial base stations. It proposes two new use cases and requirements: 1) Isolated EUTRAN operation on aerial platforms to allow public safety users to communicate via an aerial base station with wireless backhaul when outside normal coverage. 2) Isolated EUTRAN operation with conventional public system support to allow different types of public safety devices like LTE and TETRA terminals to communicate within a single base station coverage area.

1. 3GPP TSG-SA WG1 Meeting #64 S1-135024
San Francisco, USA, 11th – 15th November 2013 (revision of S1-13xxxx)
Title: Use Cases and Requirements for Isolated EUTRAN Operation
Agenda Item: 9.2 FS_REOPS: Resilient E-UTRAN operation for Public Safety
Source: III
Contact: Lucas Yi-Hsueh Tsai (lucas@iii.org.tw)
Introduction
When an emergency, disaster or any tremendous unexpected events occurs, communications
infrastructure play an essential role. In many critical incident related scenarios, the terrestrial
infrastructure might be seriously compromised and cannot guarantee reliable communications for
rescue teams. A network architecture combining aerial and terrestrial base station with wireless
backhaul links can provide rapidly deployable, resilient and flexible mobile networks, comprising
innovative components, advanced functionalities for broadband applications. It can ensure the
continued ability to communicate between Public Safety officers on the ground, even though they
may be moving in and out of LTE network coverage or out of network coverage completely, will be
of the utmost importance.
Figure 1 depicts a network architecture combining aerial and terrestrial base station with wireless
backhaul links [10].
Figure 1 Aerial and Terrestrial Platform (Source: [10])

2. The system is consisted by 3 main levels of action: [8][10]
a) Emergency Operation Center (EOC): the strategic level where the response is planned
b) Mobile Command Post (MCP): the tactical level and base of operations on field
- Aerial Base Stations (AeNB): embedded in Low Altitude Platforms (LAPs) providing
high data rates and coverage over large areas
- Terrestrial Base Stations (TeNB): interoperable with conventional public safety systems
(such as TETRA) and sensor networks, enabling dedicated coverage
c) First Responders (FRs): the operational level
- Advanced multimode professional terminals (MMUE) enabling direct mode
communications (LTE D2D) when outside of MCP coverage
For non-public safety usage, Figure 2 depicts an experimental network architecture supporting direct
Air-to-Ground Communication.
Figure 2 Direct Air-to-Ground Communication [8]
Legacy coexistence and migration strategies
The legacy coexistence is for the LTE network to interwork with conventional public system such as
TETRA/P25 voice and low data-rate services (ex. short message). This interworking enables
interoperability and also provides the necessary migration path from conventional public system
with an LTE overlay to a mission-critical LTE network running all mission critical services. TCCA
has developed a vision for Critical Communications Networks evolution leveraging multiple radio

3. access networks and standardized applications for a step-by-step migration toward an LTE mission
critical network, as shown in Figure 3 [7].
TETRA,
TETRAPOL,
etc. PMR/LMR
networks
Non Mission
Critical data
(commercial
LTE)
Mission
Critical Data
(Private LTE)
Mission
Critical Voice
(Private LTE)
Single sign-on services (security) Communications
services - including PMR/LMR applications
Subscriber & group management, group calls, etc.
Cloud - based Applications including
Control Room Applications
1 2 3 4
TIME / STAGE
Mission Critical voice
services Until LTE
readiness & maturity
Upgrade Learn Build Migrate
Strategic: requires
spectrum for private LTE
Using commercial
3G/4G carriers
Figure 3 Evolution vision for critical users [7]
Discussion
In mobile command post, an AeNB with the temporal connection such as microwave, aerial E-
UTRA backhaul link or satellite link provides the radio network coverage for nearby public safety
UEs. However, the current TR 22.897 [6] did not have any use case and requirement for aerial E-
UTRA access/backhaul link and conventional public system capability support, such as TERTA [7].
In this contribution, we propose two new use cases and requirements for Public Safety to support
aerial E-UTRA access/backhaul link and conventional public system capability support.

4. Reference
[1] S1-122149, “Network Operation Using an eNB-RN with a Broken S1 Interface”
[2] S1-124017, “Mobility Consideration for Public Safety”
[3] S1-124022, “Public Safety Use Cases with UAV”
[4] S1-134049, “Resilient E-UTRAN Operation: deriving the problem statement”
[5] S1-134051, “A review of 3GPP activities in the area of Resilient E-UTRAN Operation”
[6] S1-134118, “Study on Isolated E-UTRAN Operation for Public Safety (Release 13)”
[7] “Mission Critical Mobile Broadband: Practical standardisation & roadmap considerations”
(http://lteworld.org/whitepaper/mission-critical-mobile-broadband-practical-standardisation-
roadmap-considerations/)
[8] “Direct Air-to-Ground Communication – Broadband for Planes (DA2GC – B4P)”
(http://www.cept.org/Documents/fm-50/4735/FM50_12_INFO-005_Attcht_DA2GC-
B4P_Trial_Fl-ight_Presentation.pdf)
[9] E-SPONDER, FP7 Program (http://www.e-sponder.eu/)
[10] ABSOLUTE, FP7 Program (http://www.absolute-project.eu/)
Proposal
The following update of the TR 22.897 V0.1.0 is proposed for section 5:
*** First Change ***
5.x Isolated EUTRAN Operation on Aerial Platform
5.x.1 Description
This use cases describes the case that UEs can establish and maintain user traffic sessions via an aerial E-UTRA access
link with other UEs within the coverage of an Aerial eNB (AeNB) with wireless backhaul link (aerial E-UTRA link or
satellite link) but outside the terrestrial E-UTRAN coverage.
5.x.2 Pre-conditions
An AeNB with wireless backhaul link is mounted in an aerial mobile command post (AMCP) to offer Public Safety UEs
network access service.
The AMCP deployed in the incident area to ensure the continued ability to communicate between Public Safety officers
on the ground.
Officer A and Officer B use Public Safety UE’s, where Officer A’s and Officer B’s UEs are within the coverage of the
AeNB.
Officer A and Officer B have activated aerial E-UTRA access capability on their UE’s such that they can communicate
with other Public Safety UEs via the AeNB.

5. 5.x.3 Service flows
The AeNB is connected to Evolved Packet Core (EPC) via aerial E-UTRA link.
Officer A wants to communicate with Officer B, afterward, both Office A’s and Officer B’s UEs establish an aerial E-
UTRA access link with the AeNB and communicate to each other.
The aerial E-UTRA link between the AeNB and EPC is temporary unavailable, afterward, the AeNB is connected to
EPC via satellite link.
5.x.4 Post-conditions
Officer A’s and Officer B’s UEs continue their existing communications via the AeNB with satellite link.
The AeNB restore its connection with EPC via the aerial E-UTRA link when the link is available.
5.x.5 Requirements
Subject to operator policy, the 3GPP system shall be capable of supporting aerial E-UTRA access link between Public
Safety UE and Aerial eNB.
Subject to operator policy, the 3GPP system shall be capable of supporting aerial E-UTRA backhaul link between an
Aerial eNB and EPC.
Potential requirements that might impact RAN for aerial backhaul and access link includes:
1. aerial-link channel model,
2. ability to communicate with Aerial eNB at high speed,
3. ability to communicate with Aerial eNB at up to high altitude,
4. long range cells for Aerial eNB with high gain antenna, and
5. temperature ranges may be more extreme.
Subject to operator policy, an Aerial eNB shall be capable of maintaining existing E-UTRA communications while the
Aerial eNB reconnected to EPC via its redundant backhaul link.
*** End of First Change ***
*** Second Change ***
5.y Isolated EUTRAN Operation with Conventional Public System Support
5.y.1 Description
This use cases describes the case that conventional Public Safety UEs, such as TERTA terminals, can be able to
communicate with other E-UTRAN Public Safety UEs within the coverage of a Public Safety eNB with conventional
public system capability support, such as TERTA.
5.y.2 Pre-conditions
An eNB with both E-UTRA and TERTA access capabilities is mounted in a mobile command post (MCP) to offer
conventional Public Safety UEs network access service.

6. The MCP deployed in the incident area to ensure the continued ability to communicate between Public Safety officers on
the ground.
Officer A and Officer B use E-UTRAN Public Safety UE’s, while Officer C and Officer D use TERTA UE’s, where
Officer A’s, Officer B’s, Officer C’s and Officer D’s UEs are within the coverage of the eNB.
5.y.3 Service flows
Officer A wants to communicate with Officer B, Officer C, and Officer D simultaneously.
Office A’s and Officer B’s UEs establish an E-UTRAN communication link with the eNB.
Office C’s and Officer D’s UEs establish a TERTA communication link with the eNB.
5.y.4 Post-conditions
Officer A, Officer B, Officer C and Officer D are communicate to each other.
5.y.5 Requirements
Subject to operator policy, the 3GPP system, i.e. E-UTRAN, shall be capable of interworking with conventional public
system, such as TERTA.
Subject to operator policy, the 3GPP system shall be capable of establishing communication link between conventional
Public Safety UEs (such as TERTA terminals) and E-UTRAN Public Safety UEs.
Note: When the backhaul link of conventional public system is down, supporting continue operating for conventional
public system is out of scope.
*** End of Second Change ***