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. 1. AVIAT ADVANCED MICROWAVE TECHNOLOGY SEMINARIMPROVING MICROWAVE CAPACITYU 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. 2. microwave is just a big pipe you get out what you put in
  3. 3. “I canna change the laws o’ physics captain”
  4. 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 capacity4 AVIAT NETWORKS | APRIL 2012
  5. 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. 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. 7. get a bigger pipe!How Bigger get more data through the pipe?Get acan you Pipe!7 AVIAT NETWORKS | NOVEMBER 2011
  8. 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 MHz8 AVIAT NETWORKS | APRIL 2012
  9. 9. use more efficient schemesHow Bigger get more data through the pipe?Get acan you Pipe! to pack more data into the pipe9 AVIAT NETWORKS | NOVEMBER 2011
  10. 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. 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 8QAM11 AVIAT NETWORKS | APRIL 2012
  12. 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+312 AVIAT NETWORKS | APRIL 2012
  13. 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. 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. 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. 16. use more than one pipeUse more than one pipe16 AVIAT NETWORKS | NOVEMBER 2011
  17. 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/Router17 AVIAT NETWORKS | APRIL 2012
  18. 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/Router18 AVIAT NETWORKS | APRIL 2012
  19. 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 links19 AVIAT NETWORKS | APRIL 2012
  20. 20. only send the dataOnly send the data that you need through the pipe that you need20 AVIAT NETWORKS | NOVEMBER 2011 through the pipe
  21. 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 operation21 AVIAT NETWORKS | APRIL 2012
  22. 22. Ethernet Frame Header Optimization •  Inter-frame Gap and Preamble Removal •  MAC Header Compression !22 AVIAT NETWORKS | APRIL 2012
  23. 23. Throughput Improvement23 AVIAT NETWORKS | APRIL 2012
  24. 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. 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 size25 AVIAT NETWORKS | APRIL 2012
  26. 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 industry26 AVIAT NETWORKS | APRIL 2012
  27. 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. 28. IN CONCLUSION
  29. 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 254429 AVIAT NETWORKS | APRIL 2012
  30. 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 36030 AVIAT NETWORKS | APRIL 2012
  31. 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 * + Latency31 AVIAT NETWORKS | APRIL 2012
  32. 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
  33. 33. AVIATNETWORKS.COM

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