Improving Microwave Capacity
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We explain how to improve microwave radio capacity by understanding techniques that improve throughput.
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Improving Microwave Capacity
- 1. AVIAT ADVANCED MICROWAVE TECHNOLOGY SEMINAR IMPROVING MICROWAVE CAPACITY U N D E R S TA N D I N G T E C H N I Q U E S TO I M P R O V E T H R O U G H P U T 1
- 2. microwave is just a big pipe you get out what you put in
- 3. “I canna change the laws o’ physics captain”
- 4. How to Understand Vendor Capacity Claims? • It is getting increasingly harder to compare capacity claims from various vendors • Multiple techniques are being employed to boost throughput figures • We will attempt to explain the various techniques and how they impact capacity 4 AVIAT NETWORKS | APRIL 2012
- 5. How can you get more data through the pipe? how do you get more data through the pipe? 5 AVIAT NETWORKS | NOVEMBER 2011
- 6. Strategies for Increasing Microwave Capacities More Spectral More Spectrum More “Effec5ve” Efficiency (More Hz) Throughput (More Bits per Hz) (More Data per Bit) Technique Technique Technique Higher Modula6on Levels Wider Channels Header Op6miza6on/ Suppression/Compression Adap6ve Modula6on Mul6ple channels with link aggrega6on (incl. CCDP) Payload Compression Reduced FEC Redundancy Asymmetric Opera6on 6 AVIAT NETWORKS | APRIL 2012
- 7. get a bigger pipe! How Bigger get more data through the pipe? Get acan you Pipe! 7 AVIAT NETWORKS | NOVEMBER 2011
- 8. Use Wider Channels 6 GHz 70-90 GHz 11 GHz 30 MHz 40 MHz 5 GHz 60 GHz 18 GHz 250 MHz 80 MHz 23 GHz 50 MHz 8 AVIAT NETWORKS | APRIL 2012
- 9. use more efficient schemes How Bigger get more data through the pipe? Get acan you Pipe! to pack more data into the pipe 9 AVIAT NETWORKS | NOVEMBER 2011
- 10. Increasing Modulation Level þ Improves bits/Hz efficiency within the Modula6on Bits/Symbol Incremental same channel size Level (QAM) Bits/s/Hz Capacity Gain ☒ Diminishing capacity improvement with 4 (QPSK) 2 -‐ every higher modulation step 8 3 50% ☒ Much lower system gain - shorter hops, 16 4 33% larger antennas 32 5 25% ☒ Much higher sensitivity to interference – 64 6 20% difficult link coordination, reduced link density 128 7 17% ☒ Increased phase noise and linearity – 256 8 14% increased design complexity cost 512 9 13% þ Should be deployed with ACM to offset 1024 10 11% lower system gain 2048 11 10% 10 AVIAT NETWORKS | APRIL 2012
- 11. Higher Modulation = More Capacity, but… 10% 45 110 Carrier to Interference Ratio (C/I), dB 15% 40 105 Capacity Increase 20% 35 100 System Gain, dB 25% 30 95 30% 25 90 35% 20 85 40% 15 80 45% 10 75 50% 5 70 55% 0 65 1024QAM 2048QAM 16QAM 32QAM 64QAM 128QAM 256QAM 512QAM 8QAM 11 AVIAT NETWORKS | APRIL 2012
- 12. Applying Adaptive Modulation • AM/ACM allows higher order modulations to be employed, but mitigate the adverse effects • Modulation rate/capacity adapts to increase system gain when needed • Fixed modulation links can be upgraded to ACM to: 1. Increase link capacity 2. Decrease antenna size, and so tower rental costs 3. Increase link availability 4. Or, a combination of 1+2+3 12 AVIAT NETWORKS | APRIL 2012
- 13. Forward Error Correction (FEC) Typical Radio Frame NMS PAYLOAD FEC FEC bytes enable radio to Bytes reserved for radio correct a limited number of link and network bit errors, increasing management informa6on receiver performance 13 AVIAT NETWORKS | APRIL 2012
- 14. Forward Error Correction Typical Radio Frame NMS PAYLOAD FEC ‘Light’ FEC NMS PAYLOAD FEC Less FEC Increased Payload = = Decreased Higher Throughput System Gain 14 AVIAT NETWORKS | APRIL 2012
- 15. ‘Strong’ Forward Error Correction Typical Radio Frame NMS PAYLOAD FEC ‘Light’ FEC Decreased Payload More FEC = NMS PAYLOAD FEC = Lower Throughput Beaer System Gain ‘Strong’ FEC NMS PAYLOAD FEC 15 AVIAT NETWORKS | APRIL 2012
- 16. use more than one pipe Use more than one pipe 16 AVIAT NETWORKS | NOVEMBER 2011
- 17. Link Aggregation using IEEE 802.1AX • The most common legacy link aggregation approach (originally defined in IEEE 802.3ad) • 802.1AX cannot dynamically redistribute traffic load for optimal utilization of available links Designed Supports for this this P1 P3 DPP1 RAC 60 RAC 60 DPP1 P3 P1 Module Module P2 P4 DAC GE3 DAC GE3 P4 P2 4+0 Link P3 P5 DPP2 RAC 60 RAC 60 DPP2 P5 P3 CCDP/XPIC LAG or P4 P3 DPP1 RAC 60 ACAP RAC 60 DPP1 P3 P4 Module Module P5 P4 DAC GE3 DAC GE3 P4 P5 P6 P5 DPP2 RAC 60 RAC 60 DPP2 P5 P6 Switch/Router Eclipse INU/INUe Eclipse INU/INUe Switch/Router 17 AVIAT NETWORKS | APRIL 2012
- 18. Layer 1 Link Aggregation (L1 LA) • Unique and Aviat patented radio link aggregation scheme designed to address limitations of the traditional 802.1AX approach • Uniform load balancing even for ACM links and carriers of different capacities • High utilization and low added overhead • Carrier-grade convergence and recovery from individual link failures (<50 msec) Layer 2 (802.1AX) Domain L1LA Domain P1 P3 DPP1 RAC 60 RAC 60 DPP1 P3 P1 Module Module P2 P4 DAC GE3 DAC GE3 P4 P2 LAG LAG P3 P5 DPP2 RAC 60 RAC 60 DPP2 P5 P3 4+0 Link P4 P3 DPP1 RAC 60 RAC 60 DPP1 P3 P4 Module Module Stacking P5 P4 DAC GE3 DAC GE3 P4 P5 P6 P5 DPP2 RAC 60 RAC 60 DPP2 P5 P6 Switch/Router Eclipse INU/INUe Eclipse INU/INUe Switch/Router 18 AVIAT NETWORKS | APRIL 2012
- 19. Comparing Link Aggregation Options LAG 802.1AX L1 LA Load balancing Effec6veness Medium High Easy capacity expansion Yes Yes Latency High Low Adap6ve to RF No Yes L1LA is the ideal solution for N+0 links 19 AVIAT NETWORKS | APRIL 2012
- 20. only send the data Only send the data that you need through the pipe that you need 20 AVIAT NETWORKS | NOVEMBER 2011 through the pipe
- 21. Using Ethernet Optimization • Using common Ethernet optimization and compression techniques: • Ethernet Frame Suppression • MAC Header Compression • Multi-Layer Header Compression • Payload Compression • Send only needed data over the radio link. Suppress or compress everything else • Asymmetric link operation 21 AVIAT NETWORKS | APRIL 2012
- 22. Ethernet Frame Header Optimization • Inter-frame Gap and Preamble Removal • MAC Header Compression ! 22 AVIAT NETWORKS | APRIL 2012
- 23. Throughput Improvement 23 AVIAT NETWORKS | APRIL 2012
- 24. Header Suppression Throughput Improvement IFG & Preamble Standard Frame IFG & Preamble Frame & MAC header Size Frame Frame Frame Mbps Mbps Increase Mbps Increase Space Space Space 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% 24 AVIAT NETWORKS | APRIL 2012
- 25. Multi-Layer Header Compression • AKA ‘Packet Throughput Boost’, ‘Enhanced Packet Compression’ ‘Layer 1/2/3/4 Header Compression’ or ‘Deep Ethernet header compression’ • Adds compression of IPv4/v6 header address bytes • Still highly dependent upon payload traffic type and frame size 25 AVIAT NETWORKS | APRIL 2012
- 26. Payload Compression • Some microwave vendors are employing common compression techniques • Pros • Replaces strings of repeated patterns of data • Promises dramatic throughput improvement (2.5x), with no additional spectrum requirement • Cons • Improvement is not guaranteed nor predictable, since it is highly dependent on the traffic mix • Increased link latency • Most data traffic is already compressed • Typical real-world improvement is minimal (~4%) • Payload compression has not been generally adopted in the industry 26 AVIAT NETWORKS | APRIL 2012
- 27. Asymmetric Link Operation • Proposal to configure links with lower capacity upstream than downstream • Assumes downstream traffic is much higher volume than upstream, and that backhaul links can be similarly dimensioned • Claimed benefits are higher downstream speeds and frequency savings (upstream) 27 AVIAT NETWORKS | APRIL 2012
- 28. IN CONCLUSION
- 29. Beware common tactics to inflate throughput • Present throughput figures based upon 64 byte frame When it comes to sizes only Microwave Capacity • Assume that up to 100% (or a large proportion) of traffic is compressible • Assume availability of very wide channels (80 MHz) • Assume 2+0 co-channel operation on the same frequency assignment (using XPIC) • Present half-duplex throughput figures • Include non-payload overhead (NMS, FEC) • Assume gains from other unproven techniques Test, using an industry standard benchmark - RFC 2544 29 AVIAT NETWORKS | APRIL 2012
- 30. Best Case Throughput – 80 MHz channel 1024QAM Throughput figures are stated in Mbit/s and are approximate for a Payload 2500 single 80MHz RF channel and 256QAM (unless otherwise stated) Compression ‘Guaranteed’ throughput 2000 Maximum ‘Best Efforts’ throughput 2+0 64 byte frame size, ideal traffic profile XPIC 1040 IFG+PA MAC HC 900 Strong Suppression 720 720* Airlink FEC 450 520 * + Latency 340 360 360 360 30 AVIAT NETWORKS | APRIL 2012
- 31. Realistic Throughput – 30 MHz channel Throughput figures are stated in Mbit/s and are approximate for a single 30MHz RF channel and 256QAM (unless otherwise stated) ‘Guaranteed’ throughput Maximum throughput For 260 bytes average frame sizes, and 1024QAM typical traffic profile Payload 2+0 Compression 544 XPIC +25% IFG+PA MAC HC 418 435 +4% 475 Strong Suppression Airlink FEC 201 +6% 209 +4% 380 380* 180 190 190 190 * + Latency 31 AVIAT NETWORKS | APRIL 2012
- 32. Capacity Improvements – Hype and Availability Hype Factor Availability Higher Modula6on Medium 6-‐12 months Strong FEC Low Now ACM Low Now Aggregated Mul6-‐Channel Low Now Traffic Op6miza6on High Now Payload Compression High Now Asymmetrical Opera6on High ?? 32 AVIAT NETWORKS | APRIL 2012