LTE for critical communications
APCO Broadband Summit 2014
Andreas Roessler
Technology Manager North America
[email protected]
Rohde&Schwarz USA, Inc.
Thanks to Wim – A short reflect to the previous talk
How to ensure VoLTE performance, incl. audio quality, battery life?
R&S®UPV Audio Analyzer
LTE network …incl.
emulation, e.g. IMS …incl. audio
codec (e.g.
Band 14 …incl.
AMR-WB/NB)
DRX
…incl. IP
impairments
R&S®CMW500 Wideband Radio
Communication Tester
RF link
R&S®NGMO2 Power Supply
To/from
head jack
Measure current drain
May 2014
LTE for critical communications
2
Commercial vs. critical communication
ı Standards for commercial and critical communications have been separate.
Commercial cellular: vast success, economy of scale, high speed (broadband)
enables multimedia, network capacity.
not optimized for critical communications, no strong coverage obligations.
Critical communications: robust, group operation, priority control, direct mode.
Expensive due to limited volume, slower evolution than commercial cellular
Cellular
Industry
LTE enhancements
ı Commitment to LTE by authorities,
industry organizations.
Source: LTE Standards for Public Safety – 3GPP view , Balazs Bertenyi. Chairman 3GPP TSG SA at Critical Communications World, May 2013
May 2014
LTE for critical communications
3
Public Safety in LTE
Study Item, Work Item
3GPP Rel.
Status
Reference
Public Safety Broadband High Power User
Equipment (HPUE) for Band 14 for Region 2
11
finished
RP-120362
RP-130949
Study on Proximity-based Services (ProSe)
12
finished
TR 22.803
Group Communication
System Enablers for LTE
12
ongoing
Proximity-based Services (ProSe)
12
ongoing
Study on LTE Device to Device
Proximity Services, Radio aspects
12
finished
TR 36.843
Study on Group Communication
12
finished
TR 36.868
Study on Isolated E-UTRAN operation for public safety
13
ongoing
TR 22.897
Mission Critical Push-To-Talk over LTE
13
ongoing
TS 22.179
Isolated E-UTRAN operation for public safety
13
Ongoing
TS 22.278
Proposal: Study on inclusion of Terrestrial
Beacon Systems (TBS) in LTE
???
Postponed
RP-140446
TS 22.468
TS 23.468
TS 22.278
TS 23.303
Source: http://www.3gpp.org/ftp/Information/WORK_PLAN/Description_Releases/LTE%20for%20Public%20Safety%20(authority-to-authority)%20communications_20140316.zip
May 2014
LTE for critical communications
4
High-Power User Equipment (HPUE) demonstration
at Mobile World Congress 2014 Barcelona/SPAIN
+
Commercial:
+23 dBm
+
HPUE:
+31 dBm
R&S®CMW500 Wideband Radio Communication Tester
May 2014
LTE for critical communications
6.2.2_1
Maximum Output Power for HPUE
6.2.3_1
Maximum Power Reduction (MPR) for HPUE
6.2.4_1
Additional Maximum Power Reduction (A-MPR) for HPUE
6.2.5_1
Configured UE transmitted Output Power for HPUE
6.3.5_1.1
Power Control Absolute power tolerance for HPUE
6.3.5_1.2
Power Control Relative power tolerance for HPUE
6.3.5_1.3
Aggregate power control tolerance for HPUE
6.6.2.3_1
Adjacent Channel Leakage power Ratio for HPUE
5
Proximity Services / Device-to-Device communication
Underlying problem: Current communication flow in LTE
UE #1
eNodeB
UE #2
E-UTRAN
May 2014
eNodeB
LTE for critical communications
EPC
UE – User Equipment (LTE-capable terminal)
eNode B – evolved Node B (LTE base station)
EUTRAN – Evolved UMTS Terrestrial Radio Access Network
EPC – Evolved Packet Core (core network)
EPS – Evolved Packet System (= EUTRAN + EPC)
6
Way forward: ProSE / D2D
Communication steps
Align receiver window and
frequency correction when
detecting D2D channels.
Synchronization
Power efficient mechanism for
two (or multiple) UE’s in
proximity to detect each other
Discovery
Communication
Align transmitter timing
and parameters when
transmitting D2D channels.
May 2014
e.g. Group Call (VoIP)
LTE for critical communications
7
General challenges: Physical Channel Design for
ProSe / D2D
ı Is D2D link based on today’s LTE physical channel design?
ı If yes, Downlink or Uplink (OFDMA vs. SC-FDMA)?
Today’s working assumption in 3GPP: reuse of uplink structure / spectrum.
ı How are the resources scheduled? What about MCS/TBS selection?
ı HARQ: How is feedback managed? Is there any feedback at all?
ı Power, power control?
ı Interference coordination/handling?
ı Method of multiplexing between D2D link and Uu (= LTE air interface)?
May 2014
LTE for critical communications
8
Synchronization is prerequisite
Different synchronization sources are possible dependent on scenario
Synchronization
Cluster Head (SCH)
eNodeB
D2DSS
Cluster 1
D2DSS
Cell 1
?
Where to synch too?
Cluster 2
Cell 2
Synchronization
Cluster Head (SCH)
eNodeB
Source: R1-135803 Synchronization Procedures for D2D Discovery and Communication, Ericsson [Nov.2013]
May 2014
LTE for critical communications
9
Definition of ProSE discovery and communication
ı ProSE discovery.
Under control by the network operator, authorized on a “per UE” and/or “per UE per
application” basis. Network controls the resources used for discovery.
ProSE discovery is not necessarily followed by ProSE communication.
ı ProSE communication.
Enables communication path between two or more ProSE-enabled UE’s.
The network may switch between an EPC and ProSE communication path; an EPC and
ProSE communication path could also be active at the same time.
For specific public safety use case:
ProSE communication can start w/o discovery if UE’s are in communication range.
Authorization by operator required. Public Safety ProSE-enable UE’s need to be able to
participate in group and broadcast communication regardless if they are served by NW.
ProSE communication also supports ProSE UE-to-NW relay.
Single mechanism for 1:1, 1:M communication both for in- and out-of-coverage.
Source: 3GPP TS 22.278 V12.3.0 Service requirements for Evolved Packet System (EPS) (June 2013)
May 2014
LTE for critical communications
10
Example: device discovery
Source: Qualcomm proposal (one of many contributions)
ı Discovery Resources: LTE uplink spectrum is used i.e. 64 ms every 20 s using
44 RB.
Direct Discovery Resources (DRID)
64 ms
20 s
LTE Uplink
Subframe = 1 ms
………..…..….
………..…..….
0
1
…..…….….
…..…….….
…..…….….
…..…….….
…..…….….
…..…….….
…..…….….
…..…….….
…..…….….
10 MHz (50 RB)
…….………….
43
………..…..….
0
1
t=0
………..…..….
63
0
1
t=1
Apply Hopping sequence
………..…..….
63
*)
May 2014
LTE for critical communications
0
1
t = 63
63
Source: LTE Direct Overview, Sajith Balraj, Qualcomm Research
11
D2D communication link
ı Application focus: (Group) voice call (VoIP).
See Traffic Model in TR 36.843, section A.2.1.3
ı Proposal: simplified design similar to TETRA DMO.
Reuse PUSCH architecture as much as possible.
MCS is fixed (e.g. QPSK, RC= ½).
No physical layer feedback (focus on broadcast communication).
Blind HARQ retransmission to improve reliability.
May 2014
LTE for critical communications
12
“If youThank
want to go
fast,for
go alone.
you
If youyour
want toattention!
go far, go together!”
African proverb