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Urban Area NLOS Backhaul StudyEffect of EIRP on Backhaul Performance & Cost

November 20, 2014

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Summary of Backhaul Study

Overview– Simulation study was conducted analyzing the effects of EIRP on cost

and performance of NLOS wireless backhaul in an urban environmentSimulation environment– Urban application of small cells, Washington, DC, example– 2.2 km x 1 km area served by 24 small cells for capacity injection,

installed at street-level– Goal: provide 100 Mbps Committed Information Rate (CIR) backhaul to

each small cell using NLOS wireless links operating in the 3.5 GHz band– Utilize existing high-bandwidth Points of Presence (PoP’s) (i.e.

Macrocell sites on building rooftops) for NLOS aggregation points fortransport to the core network

Analysis tools– Ray tracing propagation model using AWE Communications software

(AWE)– 3D geo-data of downtown DC area

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Setup SelectionSmall Cell locations selected to provide a good statistical profile taking into accountvarious constraints:

– Availability of suitable location (i.e., location of lamp posts, signs, or other suitable mountingstructures)

– Inter-cell interference management between small cells and with macrocells– Coverage holes – these are most challenging NLOS locations in relation to macrocells

Adjacent streets have coverage issues in urban environmentsIndoor coverage using outdoor small cell

NLOS hub locations for backhaul aggregation assumed to be macrocell sites– Backhaul hubs are often set up at macrocells due to availability of fiber PoP’s

Preferred rooftop hub locations assumed (building corners) that may not be available in realityThat is, an actual NLOS link profile might be worse than assumed

According to several studies (including ITU documents), the probability of achieving LOSfrom a rooftop to street-level in an urban environment is <20%

– At a radius of ~400m Outlined rectangle includes approximately 8 macrocells– Operators estimate anywhere between 4 and 8 small cells per macrocell Between 30 to 60 small

cells could be deployed in the areaWe selected a lighter scenario:

– 24 small cells, of which 22 are NLOS– This is a reasonable number of NLOS locations in a mix of 35-40 small cells (NLOS and LOS )– Assumed NLOS locations are realistic and present a statistically accurate representation of an

average situation

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DowntownWashington, DC6 Macrocells, 24 Small Cells

Macrocell Small Cells

site1site2

site3 site4site5

site6

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2224 m

1000 m

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DowntownWashington, DC (3D Building View)6 Macrocells, 24 Small Cells

Macrocell Small Cells

site1site2 site3 site4

site5

site6

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A1: Backhaul Network Topology12 Hubs, 24 Remote Backhaul Modules (RBMs)

Macrocell Small Cells

site1site2

site3 site4site5

site6

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2224 m

1000 m

Hub1

Hub2

Hub3

Hub4

Hub5

Hub6

Hub7

Hub8

Hub9

Hub10

Hub11

Hub12

Remote Backhaul Antenna Boresight Direction

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A1: Backhaul Network TopologyPoint-to-Multipoint 12 Hubs, 24 RBMsSite Hub Height

(m)Azimuth(degree)

Downtilt(degree)

ServingRBMs

Distance(m) Link

11 40 193 15

1 190 LOS2 336 NLOS

2 40 345 123 246 NLOS4 368 NLOS

23 46 190 13

5 240 NLOS6 446 NLOS

4 46 342 187 150 LOS8 294 NLOS

35 46 202 22

9 154 NLOS10 372 NLOS

6 46 335 2411 200 NLOS12 304 NLOS

47 48 162 24

13 262 NLOS14 392 NLOS

8 48 23 2215 174 NLOS16 287 NLOS

59 33 170 18

17 348 NLOS18 400 NLOS

10 33 25 2519 118 NLOS20 230 NLOS

611 39 158 27

21 132 NLOS22 208 NLOS

12 39 20 2523 239 NLOS24 334 NLOS

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Simulation Setup

AWE Intelligent Ray Tracing modelWashington, DC map: 5m x 5m resolutionHub antenna: 16 dBi; Remote antenna: 16 dBi– Note: The proposed rules allow a maximum EIRP of 30 dBm/10 megahertz and a

maximum conducted power of 24 dBm/10 megahertz – there is no maximumantenna gain so long as the system complies with these parameters. See FNPRM¶ 74; Proposed Rule § 96.38.

RBM height = 4 - 6mFrequency = 3.6 GHzBandwidth sharing– Point-to-point (PTP): the entire bandwidth is allocated to a single RBM– Point-to-multipoint (PTMP): the entire bandwidth is equally shared

among RBMsEIRP = +43 dBm/20MHz & +33 dBm/20MHz analyzed

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Example Ray Tracing: Site 1Serving RBMs = 1,2,3,4

RBM2

RBM3 RBM4

RBM1

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A1: Link Performance ResultsCIR = 100 Mbps

RBM CIRsatisfaction

1 Yes2 Yes3 Yes4 Yes5 Yes6 Yes7 Yes8 Yes9 Yes10 Yes11 Yes12 Yes13 Yes14 Yes15 Yes16 Yes17 Yes18 Yes19 Yes20 Yes21 Yes22 Yes23 Yes24 Yes

EIRP = +43 dBmRBM CIR

satisfaction1 Yes2 No3 No4 No5 No6 No7 Yes8 No9 No10 No11 No12 No13 No14 No15 No16 No17 No18 No19 No20 No21 No22 No23 No24 No

EIRP = +33 dBm

Only RBMs 1 and 7 satisfyCIR with EIRP = +33 dBm

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A2: Backhaul Network Topology (9 additional Hubs)Total = 21 Hubs (12+9), 24 RBMs

Macrocell Small Cells

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2224 m

1000 m

Hub1

Hub2

Hub3

Hub4

Hub5

Hub6

Hub7

Hub8

Hub9

Hub10

Hub11

Hub12

Hub13

Hub14 Hub15

Hub16

Hub17 Hub18

Hub19 Hub20

Hub21

site1site2 site3 site4

site5

site6

site7

site8

site9

site10

site11

site12

Remote Backhaul Antenna Boresight Direction

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A2: Backhaul Network TopologyTotal 21 Hubs, 24 RBMs

Site Hub Mode Height(m)

Pointing(degree)

Downtilt(degree)

ServingRBMs

Distance(m) Link

11 PTP 40 193 15 1 190 LOS2 PTP 40 345 12 3 246 NLOS

23 PTP 46 190 13 5 240 NLOS4 PTP 46 342 18 7 150 LOS

35 PTP 46 202 22 9 154 NLOS6 PTP 46 335 24 11 200 NLOS

47 PTP 48 162 24 13 262 NLOS8 PTP 48 23 22 15 174 NLOS

59 PTP 33 170 18 17 348 NLOS10 PTP 33 25 25 19 118 NLOS

611 PTP 39 158 27 21 132 NLOS12 PTP 39 20 25 23 239 NLOS

7 13 PTMP 33 220 202 200 NLOS

6 120 LOS

814 PTP 56 250 25 4 233 LOS

15 PTMP 56 112 188 135 NLOS

12 472 NLOS9 16 PTP 29 48 22 10 188 LOS

1017 PTP 32 246 22 16 176 LOS

18 PTMP 32 103 1520 94 LOS

24 388 NLOS

1119 PTP 25 317 24 14 148 LOS20 PTP 25 55 18 18 186 NLOS

12 21 PTP 39 125 28 22 240 LOS

PTP = Point-to-pointPTMP = Point-to-multi-point

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Example Ray Tracing: Site 7, 11Hub 13 (RBM 2,6), Hub 19 (RBM 14), Hub 20 (RBM 18)

RBM2

RBM6

RBM14 RBM18

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A2: Link Performance ResultsCIR = 100 Mbps: EIRP = +33 dBm

RBM CIRsatisfaction

1 Yes2 Yes3 Yes4 Yes5 Yes6 Yes7 Yes8 Yes9 Yes10 Yes11 Yes12 Yes13 Yes14 Yes15 Yes16 Yes17 Yes18 Yes19 Yes20 Yes21 Yes22 Yes23 Yes24 Yes

Now all RBMs satisfy CIR with EIRP = +33dBm

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Summary

Comparison of total number of hubs serving 24 small cells to satisfyrequired CIR = 100 Mbps

Based on this simulation example, to achieve same CIR, a lower EIRP limitrequires 75% higher number of NLOS Hub radios.However, this is not the complete story!– Fiber PoP’s are at defined locations (i.e., at macrocell locations)– To create additional PoP’s requires:

Fiber extensions: microwave or other requires additional links to bring capacity to new sitesAdditional rooftop approvals, leasing arrangements, power

Factoring in costs of intermediate hops results in ~200 % Total Costof Ownership (TCO) increase – including hardware (i.e. backhaulequipment), site rentals, and maintenance – which breaks thesmall cell business case

EIRP = +43 dBm EIRP = +33 dBm

Total hubs 12 21

New PoP’s - 6

Additional PTP radios - 12

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Backup Slides

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RBM Orientation InvestigationExample: RBM 9

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Example: RBM93D Building View

Hub associate = Hub 5 (Site 3)Direct distance from hub = 154 mLink = NLOS

RBM9 pole

Hub5

Site3

RBM9

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Example: RBM9Different Angle Orientation

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0o

45o

90o

135o

180o225o

270o

315o

Angle orientationrespect to the north

Hub5

RBM 9 is served by Hub 5.

The ray tracing shows the propagation signal goes along the canyonfrom the west to the RBM.

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Example: RBM9 Link Performance ResultsDifferent Angle Orientation

RBM9: 43 dBm EIRPAngle orientation respect to the north (degree)

0 45 90 135 180 225 270 315

CIR satisfaction No No No No No No Yes No

Topology A1

RBM9: 33 dBm EIRPAngle orientation respect to the north (degree)

0 45 90 135 180 225 270 315

CIR satisfaction No No No No No No Yes No

Topology A2

270o is the optimal orientation for RBM9 meeting CIR target

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3D Building View and RBM PoleExamples: RBM 3, 15

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Examples: RBM 3,15

Hub2Site1

RBM3

RBM3 pole

RBM15 pole

Hub8Site4

RBM15

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Ray Tracing

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Ray Tracing Propagation ModelShort Description

Wireless channel wave propagation is generally characterized by a multi-path propagation.Ray tracing is modeled by a multi-path propagation and so provides ahighly accurate model to predict– Power delay profile (channel impulse response)– Delay spread– Angle of Departure (AoD) and Angle of Arrival (AoA)Each path of ray tracing model is determined based on a deterministicwave propagation process (interactions) from transmitter to receiverincluding reflection, diffraction and shadowing.The path loss of each path is calculated independently which contains Txgain, Rx gain and loss due the interactions. Then signal strength considersall propagation paths = the summation of the path loss of all paths.

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Ray Tracing: Site 2Serving RBMs = 5, 6, 7, 8

RBM5

RBM6

RBM8RBM7

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Ray Tracing: Site 3Serving RBMs = 9, 10, 11, 12

RBM9

RBM10

RBM11

RBM12

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Ray Tracing: Site 4Serving RBMs = 13, 14, 15, 16

RBM13

RBM14

RBM15RBM16

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Ray Tracing: Site 5Serving RBMs = 17, 18, 19, 20

RBM17

RBM18

RBM19RBM20

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Ray Tracing: Site 6Serving RBMs = 21, 22, 23, 24

RBM21RBM22

RBM23 RBM24

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Ray Tracing: Site 8, 9Hub 14 (RBM 4), Hub 15 (RBM 8, 12), Hub 16 (RBM 10)

RBM4RBM8

RBM12

RBM10

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Ray Tracing: Site 10, 12Hub 17 (RBM 16), Hub 18 (RBM 20,24), Hub 21 (RBM 22)

RBM16RBM20

RBM24

RBM22