Mobility Challenges in Urban 5G Networks TECHNOLOGIES CO., LTD. Mobility Challenges in Urban 5G Networks ... velocity is increased, but still LTE CSI latencies are not enough for large

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Mobility Challenges in

Urban 5G Networks

TAKE-5 Workshop 16.12.2016

Editor Email: [email protected]

Version: V1.0(20161216)

mailto:Gelabert/[email protected]

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential 2

How does 5G radio interface differentiate

from WiFi? Through MTC and mobility!

The other use cases are handled by WiFi evolution

A lot of unlicensed spectrum

Low-cost technology that is continuously developing

MIMO, higher frequencies, quite good spectral efficiency

Because of the way WiFi uses spectrum

Difficult to achieve low latency and reliability for machine-type-

communication (MTC)

Can only handle pedestrian speeds

Vehicular speeds require predictable access to the channel,

not possible in listen-before-talk system


Connected car & bus is a critical

differentiator for 5G

Vehicular users are indoor users ->

primary consumers of Internet content

5G target 300 Mbps per user in dense

urban (NGMN White Paper)

Self-driving cars with UHD displays

Busses with advanced displays for

individual users

Data glasses and other UI technologies

Pedestrians are less interested in

high-volume content


High mean user rate and urban

mobility are a difficult combination

Massive MIMO (MMIMO) is an

efficient way to provide additional

capacity for low-speed users

MMIMO has challenges with

moving cars in urban

environments (rich multipath)

The problem: acquisition of rapidly

changing channel state information ->

has to revert to DOA estimation and

pencil beams -> fails in dense urban

∂ (Δφ) / ∂t


Macro MMIMO Simulation Results

MMIMO/Zero Forcing provides

promising results when stationary

users are served

With more than 30 beams formed per

TTI zero forcing starts to collapse

due to limited macro cell TX power

budget for available degrees of

freedom

CSI age aware scheduling keeps

some data going through when

velocity is increased, but still LTE CSI

latencies are not enough for large

amount of mobile users


Adding small cells in ad-hoc manner will

not solve the mobility problem either

Hotspot small cells cannot handle

vehicular users

Massive buffering -> high latency

(tens of seconds)

Not sufficient capacity for ~300

Mbps per user or ~3 Gbps per bus

(average)

Unreliable handover to hot spot

Need continuos small cell layer

(continuous UDN or C-UDN)


>50 Mbps for every car with UDN


Street-light deployment with MMIMO

backhaul – the lowest-cost UDN option?

Advantages

Power cabling

available

No visual footprint

Smart streetlighting

control

Efficient site

acquisition


The new proactive mobility scheme:

Proactive tracking based on UL beacons

More efficient than BS pilots for UDN

ANd3

UNdANd2ANd1

AMC

Tx Beacon

decode & measure Beacon

Sync signal

process BeMeas

update control

link for UNd

UPN

User Plane Data

Control Plane Signalling L1/L2/L3

report BeMeas

PK arrival

for UNdPK indicator

for UNd

Sync to

”strongest” ANd

Rx DL control

channel (MIB &SIB)

Rx DL control

channel

PK indicator for

UNd + allocation


User-centric, network controlled

UE tracking based on UL beacons

ANd1.2

ANd2.3

ANd1.3

ANd1.1

ANd1.5

ANd2.4

ANd2.1

ANd2.2

UNd1

@time t1

ANd2.8

ANd1.6

ANd2.7

ANd2.6ANd2.5

UNd2

@time t2

UNd2

@time t1

AMC1

Controlling

ANd1.x

UNd1

@time t2

Trajectory UNd1

ANd1.4

Boundaries of UNd1 UL beacon transmission

range at two different time instants using

signature sequence S1

Trajectory UNd2

ANd2.9

ANd2.10

AMC2

Controlling

ANd2.x

Boundary of UNd2 UL beacon transmission

range at time instant t2 using signature

sequence S2

Boundaries of UNd2 UL beacon transmission

range at time instant t1 using signature

sequence S1

DL Ctrl

channel C1

DL Ctrl

channel C1

S1

S1

S1

S2

DL Ctrl

channel C1

DL Ctrl

channel C2

Advantages

• Minimize signaling (no HO

signaling no multi-cell

paging)

• Remove UE cell

measurements

• Enables proactive

mobility, critical for UDN

• Accurate low-power UE

positioning as a bonus


5G -> 5.5G: Mobility for mm-wave

access Discovery and

tracking in multi-

user mm-wave

environment is a

big challenge with

no good

solutions

proposed

Let cm-wave

positioning

technology solve

the problem

Multiplecm-wave

positioning

beams (wide)

mm-wave

access beam

(narrow)

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Power efficient ”always-reachable”• Due to short frames with low idle mode latency UDN 5G outperforms LTE in Idle mode power

consumption• Short frames enable fast synchronization and low latency beacon allocation procedure• + possible HW improvements: modem ramp-up/down procedures can be further simplified reducing

the HW latencies• Figure below shows that in the UDN 5G modem is able to utilise sleep states more often than LTE modem

• E.g. with 50 ms activity cycle in UDN (DORA) the modem is in deep sleep ~90% of the time whereas LTE modem is not able to reach deep sleep

Parameters DORA 5G LTE

1.Sleep power 20 20 mW2. Baseband power 350 350 mW

3. Active total power (RF+BB) 770 770 mW

4. Time needed for beaconing (sync.+DL control+beacon)

1 (~6 frames) ms

5. Minimum deep sleep latency6 (w HW impr.)/

26 (wo HW impr.)50 ms

6. Minimum light sleep latency1.3 (w HW impr.)/3 (wo HW impr.)

10 ms

Modem

Pow

er

Consu

mpti

on

t1.

2.

3.

4.

6.

5.


Macro Massive MIMO Simulations

3.5 GHz center frequency

200 MHz bandwidth, TDD

20x20 planar MMIMO array, 53m height

46 dBm per 20 MHz carrier TX power budget

1000 users per km2

1 antenna per user

Velocity: 0, 0-3, 3-10, 10-50 km/h

CSI for precoding obtained from SRS

SRS measurement age aware scheduling

METIS Madrid grid

METIS 3D ray tracing channel model


DORA 5G Madrid Grid test scenario

3.5 GHz center frequency

200 MHz unpaired TDD carrier

43 Ands, 5m height

0 dBm TX power budget per ANd

1000 users per km2

25 antenna circular arrays

1 antenna per user

Velocity: 0, 3-10, 10-50 km/h

METIS Madrid grid

METIS 3D ray tracing channel

model

Documents

Mobility Challenges in Urban 5G Networks TECHNOLOGIES CO., LTD. Mobility Challenges in Urban 5G Networks ... velocity is increased, but still LTE CSI latencies are not enough for large