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LTE BACKHAUL REQUIREMENTS

A REALITY CHECK

P E T E R C R O Y, S E N I O R N E T W O R K A R C H I T E C T, AV I AT N E T W O R K S

LTE Cell: Single User Throughput Estimates

• IP packet throughput rates vary with RF channel bandwidth and user distance from cell center

• Majority of handsets in a cell/sector are located within medium & far distance from the cell center (>90% of cell coverage area)

Data Rate Down/Up [Mbps] vs. Distance from Cell Center

Channel Bandwidth Close Medium Far

5Mhz 17 / 5.6 11 / 3.7 5.6 / 1.8

(FDD typical) 10MHz 43 / 14.4 28 / 9.5 14 / 4.8

20MHz 85 / 28 56 / 18 28 / 9.5

High LTE data speeds require exclusive use of radio cell!

JANUARY 13TH, 20112 AVIAT NETWORKS |

Estimating LTE Cell Backhaul Capacity

• Typical macro cell tower hosts 3 LTE radio sectors• Site backhaul capacity with overbooking factor (OBF) between 3 and 5• Capacity includes 15% dynamic range margin for QoS• Figures are already LTE high-end estimates, higher capacities through

reducing overbooking factor to 1 from 3

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Cell backhaul capacity [Mbps] vs. deployment areaChannel

BandwidthDense Urban

(close range throughput)Sub-urban

(medium range throughput)Rural

(medium range throughput)

5Mhz 20 (OBF 3) 13 (OBF 3) 8 (OBF 5)

(FDD typical) 10MHz 50 (OBF 3) 33 (OBF 3) 20 (OBF 5)

20MHz 100 (OBF 3) 65 (OBF 3) 40 (OBF5)

LTE backhaul realistically 10’s, not 100’s of Mbps

Backhaul Capacity Trend: 10MHz LTE ChannelCapacity[Mbps]

100

75

50

4x4 MIMO, 64QAM

2x2 MIMO, 64QAM

No MIMO, 64QAM

LTE theoretical max. radiothroughput (Layer 1)

LTE launch Service uptake,New data plans

New 2x2 hand-sets, more sites

4x4 upgrade,Service uptake

30

40

60

0

LTE single sector backhaul capacity requirement

Time

JANUARY 13TH, 20114 AVIAT NETWORKS |

Backhaul Topology Comparison for LTE

LTE Backhaul Topology

FeatureDaisy chain Hub &

SpokeTree/Tiered

Mesh/Ring

Capacity distribution

Achieve required network availability

Provide LTE cell-to-cell connectivity (X2)

Network cost factor

Future proof factor

Mesh or Ring topology best for LTE backhaul network

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Backhaul Capacity Example: Ring Architecture

• Six cell backhaul in dense urban area @50Mbps• Multiple site packet capacity not simply sum of cell capacities• Network recovers from any single link failure

To/fromcore network

50Mbps

50Mbps70Mbps

50Mbps70Mbps

100Mbps

150Mbps

Additional ring sites only add incremental capacity!

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The LTE Hype Cycle

JANUARY 13TH, 20117 AVIAT NETWORKS |

LTE

YOU ARE HERE!

Gartner Hype Cycle, 1995

3G

LTE Capacity Conclusions

• LTE backhaul capacity needs are regularly over-stated

• Capacity is fixed per site and only determined by base station technology

• The backhaul limit for a site will likely be ~150 Mbit/sfor a 10MHz LTE radio channel

• Only way to add more network capacity: - Add more cell sites, upgrade to MIMO or increase the LTE channel

bandwidth

• Ring/Mesh topologies are best suited to cope with the high capacity requirements

JANUARY 13TH, 20118 AVIAT NETWORKS |

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S T U A RT L I T T L E , D I R E C TO R O F M A R K E T I N G , AV I AT N E T W O R K S

HOW LICENSED MICROWAVE MEETS THE BACKHAUL CAPACITY NEEDS OF LTE

Uncertainty can lead to bad backhaul choices

• Backhaul discussion often in terms of hundreds of megabits or even gigabits of capacity

• Just one in four mobile operators have said that they understood the requirements for LTE backhaul

• This uncertainty could drive over-investment for backhaul capacity that is not needed within the foreseeable future

JANUARY 13TH, 201110 AVIAT NETWORKS |

LTE Cell-Site Capacity

JANUARY 13TH, 201111 AVIAT NETWORKS |

Time

Capacity

Zone of Capacity Growth Maximum Cell-site Capacity

Maximum Cell-site Capacity (100-200Mbit/s)

Maximum Microwave Capacity Room for future capacity growth

You can’t outstrip MW capacity to a cell-site - physics won’t allow it!

Cell-site Capacity Curve

1 Gbit/s

Why pay for capacity you may never need?

• The total cost of building or leasing fiber to the cell-site far exceeds that of a typical microwave connection

• Over-building capacity with fiber will waste an enormous amount of network investments

JANUARY 13TH, 201112 AVIAT NETWORKS |

The 3 Most Important Backhaul Decision Factors

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Microwave is cheaper than fiber (in nearly all cases)

Microwave far exceeds LTE cell

site capacity demands

Each link needs to be evaluated to understand microwave and fiber costs and capacities…

OR RISK

Microwave connected cell sites often have greater uptime than

fiber sites

CAPACITY COST RELIABILITY

Microwave Capacity Expansion Options

• Native Ethernet transport• Adaptive Modulation• Adaptive Coding• Ethernet Frame suppression and compression

• Capacity-doubling through co-channel operation with XPIC

JANUARY 13TH, 201114 AVIAT NETWORKS |

Microwave techniques for high capacity

300Mbit/s

350Mbit/s

400Mbit/s

450Mbit/s

500Mbit/s

550Mbit/s

600Mbit/s

311 Mbit/s

360 Mbit/s

380 Mbit/s

470 Mbit/s

550 Mbit/s

+16%

+6%

+24%

+17%

2xOC3/STM1

Native Ethernet Throughput

Add Light Coding

Add IFG & Preamble Suppression

Add MAC Header Compression

JANUARY 13TH, 201115 AVIAT NETWORKS |

*Throughput figures are based upon maximum modulation in a 56/80 MHz channel for 64 byte frame sizes. Capacity will be less for smaller channels and/or larger frame sizes.

Co-Channel link capacity doubling

300Mbit/s

400Mbit/s

500Mbit/s

600Mbit/s

700Mbit/s

800Mbit/s

900Mbit/s

1100 Mbit/s

1000Mbit/s

1100Mbit/s

1200Mbit/s

+100%

Add Co-Channel Operation with XPIC

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Getting even more wireless capacity

• Diverse path network topologies (rings/mesh)

• Lightly licensed and license free 60-90 GHz Millimeter wave bands

• Payload compression• Higher order modulation

schemes >256QAM• Multi-carrier operation• Multiple-in/Multiple-out (MIMO)

techniques

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Don’t let fiber break the bank!

JANUARY 13TH, 201118 AVIAT NETWORKS |

• Fiber is not the only answer for operators deploying HSPA+ & LTE

• Operators need to balance realistic capacity expectations with total cost

• Microwave transport meets the foreseeable capacity needs for mobile backhaul for several years to come

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