microwave capacity%5f understanding techniques to improve throughput

1

UNDERSTANDING TECHNIQUES TO IMPROVE THROUGHPUT

AVIAT TECHNOLOGY SERIES

MICROWAVE CAPACITY

“I canna change the laws o’ physics captain”

Strategies for Increasing Microwave Capacities

1. More Spectrum

(More Hz)

2. More Spectral Efficiency

(More Bits per Hz)

3. More “Effective” Throughput

(More Data per Bit)

Technique

Multiple channels with link aggregation (incl CCDP)

ACM

Technique

Higher modulations (512/1024 QAM, ACM)

FEC redundancy

Technique

Header optimization / suppression

Payload compression

Asymmetrical RF

NOVEMBER 2011 AVIAT NETWORKS | 3

Poll Question: Your Understanding of Microwave Capacity?

1. High. I understand the concepts and how to apply them

2. Medium. I understand the concepts, unclear how to apply

to my network

3. Low. I lack some understanding on concepts/technologies

4. Very low. I am completely confused

NOVEMBER 2011 4 AVIAT NETWORKS |

Focus =

RF Link

Aggregation

Multi-Channel Requires Link Aggregation: 2 Approaches


Ethernet Links Radio Links or Polarizations (CCDP)

LAG 802.1ax

Layer 1 Link Aggregation (L1LA)

Designed

for this

Supports

this

Custom solution

for RF links

Radio/RF Link: Aggregation Options


LAG 802.1ax L1LA

Approach Packet-by-Packet Byte-by-Byte

Number of links Yes (up to 2 RF links)

Yes (up to 4 RF links)

Load balancing Effectiveness

Medium High

Easy capacity expansion Yes Yes

Latency High Low

Adaptive to RF No Yes

Radio Links

Link Aggregation Recommendations and Conclusions

1. To enable N+0 radio links (which is the most important

problem to solve since radio capacity is constrained), L1LA

is the ideal solution

2. Only use LAG on Ethernet links for > 2 Ethernet ports

(higher layer protection and load balancing schemes work

best)


Higher Order Modulation Schemes – 1024QAM

• Improves bits/Hz efficiency within the same channel size

• 24% throughput improvement over 256 QAM

• Disadvantages in fixed operation:

• Lower system gain (Tx power and Rx threshold), leading to shorter hops or larger antennas

• Increased sensitivity to interference can reduce link density

• Increased phase noise and linearity requirements increases radio design complexity and cost

• Should be deployed in conjunction with ACM

• First commercially available systems on the market in 12-18 months


FEC Redundancy

• Forward Error Correction is employed as standard on all digital

microwave systems

• Enables virtually error free performance right up to Rx threshold

• Involves adding additional overhead bits (~10%), to enable bit errors to

be detected and corrected at the receiver

• FEC can be:

• Stronger – more bits enables more errors corrected – better system gain, but at the

expense of lower throughput

• Weaker – less bits enables higher throughput, but poorer system (Rx) performance

• Actual implementation can vary. Some vendors (eg: Aviat) offer both


ACM Capacity Improvement: Example 1

• Requirement:

• Capacity: 150 Mbps

• Availability: 99.999%

• Path Length: 15.3 miles

• ACM Benefits

• 23 Mbps more capacity

for most of time

• 15% more data sent

• ~4 minutes more

uptime per year

• Same antenna, same

frequency, same

channel, etc

10 NOVEMBER 2011 AVIAT NETWORKS |

ACM Design (6 GHz, 6' Antennas)

Uptime Time in Modulation (min)

Capacity (Mbps)

Total Bytes Per Year (TB)

256QAM 99.9975% 525,587 178 701.66

64QAM 99.9991% 9 144 0.01

16QAM 99.9995% 2 94 0.00

QPSK 99.9999% 2 46 0.00

out of service 1 0

Total 525,600 701.67

Fixed Modulation Design (6 GHz, 6' Antennas)


Capacity (Mbps)


128QAM 99.9990% 525,595 155 611

out of service 5 0

Total 525,600 611

ACM Capacity Improvement: Example 2

• Requirement:

• Capacity: 50 Mbps

• Availability: 99.999%

• Path Length: 10.15 miles

• ACM Benefits

• 213 Mbps more

capacity for most of time

• 500% more data sent

• 28 sec more uptime per

year

• Smaller antenna =

$4,800 per year cost

savings

11 NOVEMBER 2011 AVIAT NETWORKS |

ACM Design (18 GHz, 2' Antenna)


Capacity (Mbps)


256QAM 99.5613% 523,294 263 1,032

64QAM 99.7784% 1,141 155 1.33

16QAM 99.9299% 796 100 0.60

QPSK 99.9995% 366 50 0.14

out of service 3 0

Total 525,600 1,034

Fixed Modulation Design (11 GHz, 4' Antennas)


Capacity (Mbps)


64QAM 99.9994% 525,597 50 181

out of service 3 0

Total 525,600 181

ACM gives more capacity, at lower cost

Poll Question: What’s stopping you from deploying ACM?

1. Uncertain value, not convinced of benefits

2. Unclear of FCC’s position

3. Unclear how to design/implement it

4. Existing equipment lacks ACM support

5. Nothing, already deploying/deployed


Ethernet Traffic Optimization


• Inter-frame Gap and

Preamble Removal

• 20 bytes at the

beginning of each

frame

• Payload Header

Compression

• Removes known or

restorable information

from MAC and/or IP

header

• Payload Compression

• Identifies repetitive

patterns in the payload

and compresses them

Benefit of Header Compression


Frame Size

Standard Frame

IFG & Preamble IFG & Preamble &

MAC header

Frame Space

Mbps Frame Space

Mbps Increase Frame Space

Mbps Increase

64 84 76.2 68 94.1 24% 58 110.3 45%

128 148 86.5 132 97.0 12% 122 104.9 21%

260 280 92.9 264 98.5 6% 254 102.4 10%

512 522 96.2 516 99.2 3% 506 101.2 5%

1518 1538 98.7 1522 99.7 1% 1512 100.4 2%

Payload Compression

• Employing common compression techniques to replace

strings of repeated patterns of data

• Pros

• Promises dramatic throughput improvement (2.5x), with minimal

additional cost or spectrum requirements

• Cons

• Improvement is not guaranteed nor predictable, since it is highly

dependent on the traffic mix

• Compression works better for uncompressed VoIP and partially filled

TDM

• No benefit for traffic that is already compressed

• Typical real-world improvement is minimal (~4%)

• Other potential issues with compression, eg: increased link latency

• Conclusion – don’t expect to see payload compression

adopted widely in the industry


Asymmetric Link Operation

• Involves the concept of ‘spectrum borrowing’

• Moving spectrum from the uplink of an adjacent link to increase downlink spectrum bandwidth

• Advantages

• Useful for networks with asymmetrical traffic flows

• Disadvantages

• FCC Common Carrier bands are symmetric only

• Introducing asymmetrical operation into existing bands will be almost impossible

• Requires complicated and lengthy regulatory approval



f1 f2

DL

f1’ f2’ UL f3 f4 UL

f3’ f4’

DL

Before - Symmetric Microwave Network

2x10MHz = 20MHz channel


f1 f2

DL

f1’ f2’ UL f3 f4 UL

f2’ f3’

DL

Asymmetric Microwave Network, after Spectrum Borrowing

3x10MHz = 30MHz channel f4’ f3

Congratulations….

you’ve increased your

microwave capacity

• You can now meet

capacity demands of

your end applications

• You can now

implement lower cost

network designs


Obvious

Not so obvious

Capacity Comparison by Architecture (no ACM)


Hub – Spoke Ring

Sites 6 6

Links 5 (1+1) 6

Antennas 10 12

Average Antenna Size 5.2 2.3

Reliability (per link) 99.999% 99.95% (average)

Capacity (per link) 50Mbps 200Mbps

CAPEX $176k $119k

Yearly Tower Lease $77k $48k

5 Year TCO $676k $478k

How do some vendors inflate throughput?

• Present throughput figures based upon 64 byte

frame sizes only

• Assume that up to 100% of payload traffic is

compressible

• Assume availability of wide channels (80 MHz)

• Assume co-channel operation (2x RF carriers)

on the same frequency assignment (using XPIC)

• Present half-duplex throughput figures

• Assume gains from other unproven techniques


When it comes to

Microwave Capacity

To be sure, use an industry standard benchmarking test, like RFC 2544

Best Case Throughput – 80 MHz channel


340

Airlink Strong

FEC

360

IFG+PA

Suppression

450

MAC HC

520

2+0

XPIC

1040

Payload

Compression

2000

1024QAM

2500

360 360

720 720* 900

‘Guaranteed’ throughput

Maximum ‘Best Efforts’ throughput 64 byte frame size, ideal traffic profile

Throughput figures are stated in Mbit/s and are approximate for a

single 80MHz RF channel and 256QAM (unless otherwise stated)

* + Latency

Realistic Throughput – 30 MHz channel


180

Airlink Strong

FEC

190

IFG+PA

Suppression

201

MAC HC

209

2+0

XPIC

418

Payload

Compression

435

1024QAM

544

190 190

380 380*

475

‘Guaranteed’ throughput

Maximum throughput For 260 bytes average frame sizes, and

typical traffic profile

Throughput figures are stated in Mbit/s and are approximate for a

single 30MHz RF channel and 256QAM (unless otherwise stated)

* + Latency

+4%

+6% +4%

+25%

Microwave Capacity Improvements – Hype and Availability


Hype Factor Availability

Multi-Carrier Low Now

Higher Modulation Medium 12-18 months

Strong FEC Low Now

ACM Low Now

Traffic Optimization Medium Now

Payload Compression High Now

Asymmetrical Operation High >3 years

Ring Networks Low Now

Aviat Advanced Microwave Technology Seminar

Email:

[email protected]

November 8, 9 2011

Aviat HQ

Santa Clara, CA

Day 1 Network migration - TDM to IP Carrier Ethernet Transport & MPLS LTE requirements on backhaul Ethernet radio capacity analysis Network Timing and Synchronization

Day 2 ACM Microwave Strong Security Microwave antenna tech update Outsourced network operations

NOVEMBER 2011 AVIAT NETWORKS | 25

Poll Question: Next Webinar Topic

1. Microwave Security

2. Ethernet OAM

3. Ethernet Protection and Redundancy

4. Q&A with Dick Laine (no slides)

5. Microwave Q&A (no slides)


THANK YOU

microwave capacity%5f understanding techniques to improve throughput

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