4G Wireless Networks 4G Wireless Networks Need for Improved Loss - - PowerPoint PPT Presentation

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4G Wireless Networks 4G Wireless Networks Need for Improved Loss - - PowerPoint PPT Presentation

Jun 08, 2023 262 likes •432 views

4G Wireless Networks 4G Wireless Networks Need for Improved Loss Tolerance K. K. Ramakrishnan AT&T L b R AT&T Labs Research, NJ h NJ Thanks to: Robert Miller(AT&T), Vijay Subramanian and Shiv Kalyanaraman (RPI) Adaptive W

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SLIDE 1

4G Wireless Networks 4G Wireless Networks

Need for Improved Loss Tolerance

  • K. K. Ramakrishnan

AT&T L b R h NJ AT&T Labs Research, NJ

Thanks to: Robert Miller(AT&T), Vijay Subramanian and Shiv Kalyanaraman (RPI)

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SLIDE 2

Adaptive W ireless: Goal is to Make W ireless As Good As W ired

Adaptive modulation and coding exploits previously Adaptive modulation and coding exploits previously inaccessable capacity enabling higher rates

Shannon Limit

Multiple Antennas and Space Time Coding

4G Technologies e g

Adaptive Modulation Space-Time Coding Combined with Better Cell Propagation Predictability Provide “Wire-Like” Performance

User Rate

Technologies e.g. MI MO, Small-Cells (802.11n)

Adaptive Modulation and Error Correction Coding Provide Higher Throughputs if Propagation Allows

Potential I mprovement (3G, 802.16) 2.5G Systems Signal to Noise Ratio

Fixed modulation and coding provides the same rate to all users, even if their links could Users in this region could get some connectivity rather than no service

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provide higher rates than no service

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SLIDE 3

Reach-Data rate Tradeoff

100

Higher Rate, Lower-Speed Mobility

Peak

10

4G H/S Wireless LAN

2.4 & 5 GHz Unlicensed

  • nd/User

UWB

1

Peak Data Rate 4G Wireless NAN

2.4 & 5 GHz

ts per Seco

Wider Area, Higher Speed Mobility

3G/802.16 Wireless

Various Bands

3G/MAN Fixed or Pedestrian Megabit 3G/MAN Mobile

1

Bluetooth

PANs

Zigbee

Higher-Speed Mobility

2.5G Mobile/Pedestrian

.1

2.4GHz and UWB

Zigbee (Europe)

2/2.5G Wireless

800 MHz, 2 GHz

Zigbee (US)

10 feet 100 feet 1 mile 10 miles

Reach

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SLIDE 4

Cell Coverage Area Trends

Maritime Mobile

  • Increased Bandwidth Demand/User
  • Battery/Dissipation Device Constraints
  • Moore’s Law Radios
  • Increased Edge Intelligence

100 Watts

Mobile HF Radio Service (~300 mi)

1,000,000

1G

g g

  • Distributed Control Techniques

10 Watts 100,000

2G Cellular Expanded S Macrocellular Systems (~8 mi)

10,000 mi2 700 mi2

Mobile/ Portable Maximum Power Output

1 Watt 10,000

Cell Radius (Feet)

Service (~4 mi) Metroliner Train Telephone ( 15 mi) MJ-MK Mobile Telephone (~60 mi)

The 2G “Sweet Spot” The 3G/WiMax “Sweet Spot”

Output

100 mW 1,000

(Feet)

30 mW

.01 mi2 (~15 mi) PCS Microcells ( 0 5 2 i) 2.5G Microcells (~2 mi)

1950 1960 1970 Y

100

1980 1990 2000 2010

(~0.5 -2 mi) WNAN/LAN Nanocells (~.06 -.2mi)

The 4G “Sweet Spot”

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Year

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SLIDE 5

Architecting a 2G-3G-4G Wireless “Network I nfrastructure”

AT&T VoIP Infrastructure

BE PSTN

Gateway

AT&T Common BB Backbone

BE BE IS-41 TDM BE Voice

BB Access Network Cellular Network

MSC MSC

BS

Home 4G 4G Hot Zones Enterprise 4G

BS BS BS BS BS

Municipal Network

Home 4G 4G Hot Zones Enterprise 4G Page 5

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SLIDE 6

How Might A W ireless Deploym ent Look?

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SLIDE 7

The Muni Network Concept Gets “Legs”

The number of municipalities operating The number of municipalities operating, installing, or planning Wi-Fi networks is growing rapidly, driven by…

  • User acceptance/use of Wi-Fi
  • User acceptance/use of Wi-Fi
  • Large number of devices already

equipped (instant customer base)

  • Availability of low-cost networking
  • Availability of low-cost networking

systems (including mesh)

  • Ability to transport Ethernet-like

throughputs

  • Desire to project “Cybercity” image
  • “Digital Divide” amelioration
  • Improvement in public service
  • Improvement in public service

communications capabilities

  • Leverage existing municipal

infrastructure and fiber

  • Revenue opportunities/new

business models

  • Ability to raise bond capital for

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infrastructure

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SLIDE 8

3G / Metro Area Wireless H b (PTMP Fi d S i t B i MDU

Fiber, 4G, and Multi-Tier Wireless: A NanoNet

Hub (PTMP Fixed Service to Businesses, MDUs, EcoPoles w/ o fiber availability) Fiber Ring City Fiber Local PON Fiber PON Eco- Pole AP LAN Wi d Fiber Hub PON Hub Fiber PON NAN Eco- Pole AP I ndoor Cell Window Bridge EcoPole Cell EcoPole AP

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SLIDE 9

“NanoNet” I ndoor Coverage Using “Window Bridging”

3G / Metro Area Wireless H b (PTMP Fi d S i t B i MDU Hub (PTMP Fixed Service to Businesses, MDUs, EcoPoles w/ o fiber availability) Fiber Ring City Fiber Local PON Fiber PON Fiber Hub PON Hub NAN Eco- Pole AP Fiber PON Eco- Pole AP Wi d LAN Cell Window Bridge I ndoor Cell

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SLIDE 10

Solving Outdoor-to-I ndoor Penetration: The Window Bridge

Page 10

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SLIDE 11

Motivation for our w ork on LT-TCP

  • Dense wireless deployments in urban areas/ high

rises will cause disruptions/ burst errors due to interference

  • Protocols need to be loss tolerant and provide

l b l reliability – Especially as we move to multi-hop wireless i t environments

  • Divide the burden of reliability between link and

transport layers transport layers

  • Keep Residual Loss Rate low; Delay small; Link

and Transport Layer Goodput high and Transport Layer Goodput high

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SLIDE 12

TCP-SACK Perform ance under Lossy Conditions

  • Sharp drop-off in performance with PER (degrades beyond an error

rate of 5% PER)

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  • Performance is poorer as combination of PER and RTT grows
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SLIDE 13

Goals for our Enhancem ents to TCP

  • Dynam ic Range:

y a c a ge – Can we extend the dynamic range of TCP into high loss regimes? – Can TCP perform close to the theoretical capacity achievable under high loss rates?

  • Congestion Response:

– How should TCP respond to notifications due to congestion.. – … but not respond to packet erasures that do not signal congestion? congestion?

  • Mix of Reliability Mechanism s:

– What mechanisms should be used to extend the operating point of TCP into loss rates from 0% - 50 % packet loss rate? TCP into loss rates from 0% 50 % packet loss rate? – How can Forward Error Correction (FEC) help? – How should the FEC be split between sending it proactively (insuring the data in anticipation of loss) and reactively (sending FEC i t l )? FEC in response to a loss)?

  • Tim eout Avoidance:

– Timeouts: Useful as a fall-back mechanism but wasteful otherwise especially under high loss rates especially under high loss rates. – How can we add mechanisms to minimize timeouts?

  • Our Enhancem ents to TCP: Loss Tolerant-TCP ( LT-TCP)

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SLIDE 14

LT-TCP Perform ance

  • Performance of LT-TCP is much better compared to that of TCP-SACK

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  • LT-TCP degrades gracefully (nearly linear degradation with loss rate)
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SLIDE 15

Transport layer perform ance w ith loss tolerance across layers

  • Combining Loss Tolerance at the Transport layer with Link layer

enhancements allows us to strike a balance in providing the appropriate loss tolerance over a wide range of losses

  • Limiting ARQ at link layer to manage latency
  • Manageable link level residual loss rate
  • Reasonable Goodput even under extreme conditions

High Loss Rates: High Loss Rates: both LL both LL-

  • HARQ+LT

HARQ+LT-

  • TCP needed

TCP needed to get better performance to get better performance Low Loss Rates: Low Loss Rates: just LL just LL-

  • HARQ (link) helps

HARQ (link) helps to get better performance to get better performance

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