5G Mobile Radio

FrontHaul Test and Assurance

John Govert

EUCNC 2016

Architecture Overview

• There is an on-going discussion in working groups about unification of Fronthaul and Backhaul

network infrastructure. Main drivers are:

-- Reduce Bandwidth CPRI is unsustainable….

-- Enable Resource Pooling (Cloud Infrastructure, RAN sharing) Huge Cost and Performance

Driver

• Ethernet will also cover Fronthaul networks.

• However time requirements of Fronthaul networks are stringent, so

Ethernet has to do some homework TSN (time sensitive networks)

© 2016 Viavi Solutions, Inc. | Viavi Confidential and Proprietary Information 3 R. Bechstein 22.06.2016

OAM, RRM

RRC

PDCP, RLC

MAC

PHY

RF

5 Gbps - 200us (CPRI)

200 Mbps 1ms

150 Mbps 5-10ms

L1

L2

L3 Lit ETH, BW ~ traffic, delay tolerant

CPRI, limited distance (15km)

ETH

over

Fiber

Rates indicate peak throughput on a single 20MHz LTE carrier (2Tx, 2Rx)

Existing

transport

Fiber-based,

but scalable

150 Mbps 20ms

0.5 - 1 Gbps 1ms

L3 Split

PDCP / RLC

Split

L2 Split

L1-FEC

Split HARQ

Loop

(3ms)

Front-Haul Split – TSN Implications

Key Is Time Sensitive Ethernet

4

What is

Time Sensitive Ethernet (TSN)?

© 2016 Viavi Solutions, Inc. | Viavi Confidential and Proprietary Information 5 R. Bechstein 22.06.2016

Old wine in new bottles?

Back when almost flawless streaming QoS was required ...

-- we had land-line circuit-switched telecom networks,

-- connections were based on “circuits” (nailed-up paths from end to end with deterministic characteristics).

The internet changed this model to “connections”

-- highly adaptive, very robust, but timing is very sloppy

-- use the sloppy timing budget as a way to get the data through (retries, adaptive routing, etc)

Now the sloppy timing is facing real world, real time requirements/applications

-- Industrial automation, vehicle control, tactile internet require low latency packet forwarding

-- Mobile Radio Fronthaul has stringent delay, continuous throughput and synchronization

demands (e.g. CPRI, HARQ loop, carrier frequency accuracy). This is a must for a

working mobile radio network infrastructure.

Time-Sensitive Networking (TSN) is the answer to these demands and returns to “circuits”

-- but we call them “streams” with defined QoS characteristics (e.g. max. latency)

-- but still this shall seamlessly interoperate with existing models of “the internet”

How do we do this?

-- Provide a network-wide precision clock reference for scheduling

-- Limit network delays to a well-known (and hopefully small) value

-- Keep non-time-sensitive traffic from messing things up

To achieve this, we need to fix the low-level plumbing (transport layer) …..

In case of networks based on Ethernet, we use IEEE 802.1Q Time-Sensitive Networking.

© 2016 Viavi Solutions, Inc. | Viavi Confidential and Proprietary Information 6 R. Bechstein 22.06.2016

What is a Time Sensitive Network – A New Ethernet!

The primary TSN projects include:

Time synchronization of TSN components

802.1AS (based on IEEE 1588)

Schedule, Queue & Forward time-sensitive streams

802.1Qav credit-based shapers, new P802.1Qbu

frame preemption, P802.1Qbv time-aware queuing,

P802.1Qch cyclic queueing, P802.1Qci input gating and

P802.1CB seamless redundancy.

Registration & Reservation of time-sensitive Streams

802.1Qat – a distributed “stream reservation protocol”,

extended in new P802.1Qcc to support preemption,

scheduling, centralized control, and interaction with

higher layer IETF services

Overall system architecture for Mobile Fronthaul

802.1CM:

a) The VLAN Bridge specification in IEEE Std 802.1Q.

b) Interspersing express traffic specification in IEEE 802.3br.

c) Frame preemption specification IEEE Std 802.1Qbu.

d) The time synchronization standard IEEE Std 1588, or one

of its suitable profiles.

e) The MAC and PHY standards specified for the various LAN

MAC/PHY technologies, such as IEEE 802.3, IEEE 802.11.

.

The above listed needs test functionality

beyond what is currently implemented

in our instruments!

7

TSN UnitTesting

© 2016 Viavi Solutions, Inc. | Viavi Confidential and Proprietary Information 8 R. Bechstein 22.06.2016

Lab - Testing Frame Preemption, Queuing and Scheduling

DUT

Dual Port 10/100G Test Unit

Performed tests:

Preemption: Data integrity/frame loss under varying frame size conditions

Queuing: Correct routing of express vs standard packets based on priority/VLAN

Scheduling: Correct timeslot assignment of packet based on SyncE/PTP synchronization. Basic PDV

General parameters: packet delays, packet timing (slot based histogram)

Check dependency of key parameters on load variation (background traffic) or impairments (timing)

Port 2

Traffic

Analysis

Port 1

Traffic

Generation

© 2016 Viavi Solutions, Inc. | Viavi Confidential and Proprietary Information 9 R. Bechstein 22.06.2016

Testing Next Generation Fonthaul Interfaces (NGFI)

DUT

Dual Port 10/100G

Performed tests:

Basic protocol functionality/connectivity

Link Delays

Loss of frames

Verification of end to end connectivity/protocol/timing in NGFI (fronthaul link)

SyncE performance testing

NGFI Device

NGFI

sink

NGFI

source

10

Network Test and SON

Sample SON reconfiguration options

SON fronthaul levers

Change functional split

As split point moves IQ to PDCP defined bandwidth requirement decreases

Minimum latency requirement increases

Split may differ in UL and DL and between different RU

Latency provision

Different co-operative modes require stricter latency requirements

Fronthaul path configuration

SON reconfiguration options

A. Impose/remove latency guarantee on existing path to support CoMP vs other traffic

B. Switch Ethernet path to

equalise hops & distribute traffic to facilitate latency to support CoMP vs other traffic

Circumvent node failure

C. Activate small cells and switch-off SON to release resources (bandwidth and latency) for small cells

D. Change functional split point to reduce bandwidth requirement or, conversely, to exploit available bandwidth

© 2016 Viavi Solutions, Inc. | Viavi Confidential and Proprietary Information This technology roadmap is for informational purposes only and does not create an

obligation for Viav to deliver any of the features or products. Due to our rapidly changing technology environment, JDSU cannot commit to a specific item or

date and reserves the right to make changes to the roadmap at any time.

BU RU

BU RU

A.

B.

Potential set-up for next steps towards D3.3 and WP5

Section 6 in ToC of D3.2

100GE+ trunks, low cost optics

Point-to-point or few node rings (up to 20km)

TSN

Co

ntr

ol &

Ser

vice

Ass

ura

nce

Allows investigation of different split options and Eth scenarios

WEB GUI System manager + SON

Next-Generation Central Office

Legacy BBU(s) CPRI

TSN Eth-Switch

Mod Split BBUs (int.)

CPRIoEth

IAF Prototype Platform

Eth

Eth

Mod Split BBUs (ext.)

TSN Eth-Agg MEC option (ADVA)

CPRIoEth

up to 10G

Legacy RRH

up to 10GE

up to 10GE

Mod Split OAI RRH (Kent)

Mod Split 60GHz RRH (HHI)

Next-Generation Cell Site

Pluggable Probes

Fronthaul

cloud

Built-in probes

Radio performance & configuration

“OMC“

SDN