CISCO 802.11ac White Paper 정리

출처: http://www.cisco.com/c/en/us/products/collateral/wireless/aironet-3600-series/white_paper_c11-713103.pdf

CISCO의 802.11ac 관련한 White Paper를 정리한 내용입니다

   

1. Executive Summary

• How to increase speed
  • More channel bonding 40 -> 80 ~ 160MHz
  • Denser modulation: 64qAM -> 256QAM
  • MIMO: 4x4 -> 8x8
• 5GHz Only Tech.

     

2. What is 802.11ac?

2.1 Drivers for 802.11ac

   

   

2.2 How does 802.11 Go So Fast?

   

• 
• Nothing is for free: it does consume more spectrum, and each time We're splitting the same transmit power over twice as many subcarriers, so the speed doubles, but the range for that doubled speed is slightly reduced (for an overall win).

   

2.3 How Do We Make 802.11ac Robust?

2.3.1 Technology Overview

• RTS/CTS
• Stronger Clear Channel Assessment (CCA)

   

2.3.2 Difference Between 802.11ac and 802.11n

   

2.3.3 Standard Based Beamforming

2.3.4 RTS/CTS with bandwidth indication

2.3.5 All A-MPDUs

2.3.6 Channelization and 80+80MHz

• Since the number of 160-MHz channels is tiny, 160 MHz is unsuited to typical enterprise use. In the home, every 160-MHz channel is subject to difficult radar detection regulatory requirements. Thus, 802.11ac also introduces a noncontiguous 80+80 MHz mode
• Unfortunately, an 80+80 MHz device is much more complicated than a 160-MHz device, since the 80+80 MHz device needs twice as many RF chains
• Primary channel alignment
  • Aligned
    • Virtual carrier sense works completely, yet all 20- and 40-MHz traffic (including broadcast, multicast, and data traffic to 802.11a/n devices) is sent in series. During these times, 40 or 60 MHz of bandwidth is unused.
    • if the clients are predominantly 802.11ac, this is generally the best approach in terms of throughput and airtime fairness.
  • Unaligned
    • if one AP's primary channel is assigned to the lower 40 MHz and another AP's channel is assigned to the upper 80 MHz, 20- and 40-MHz traffic can be parallelized (as shown in Figure 5). If clients are predominantly 802.11a/n, this is the better choice
    • When the whole 80 MHz is free, as measured by physical carrier sense and/or RTS/CTS with bandwidth indication, 80-MHz communication between 802.11ac devices is still allowed.

   

2.3.7 Rate at Range

• 

   

2.3.8 Regulatory Considerations

   

2.3.9 MU-MIMO

• Null steering을 위해서 지속적인 sounding이 필요함

     

2.3.10 802.11ac Project Authorization Request

   

3. When is 802.11ac Happening?

• 

     

4. How Does 802.11ac Affect Me?

4.1 Compatibility

   

4.2 When to Upgrade to 802.11ac?

   

4.3 Radio Resource Management and WIPS Effects

   

5. Summary