• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
 

Smart Antennas

on

  • 3,064 views

 

Statistics

Views

Total Views
3,064
Views on SlideShare
3,060
Embed Views
4

Actions

Likes
0
Downloads
56
Comments
0

3 Embeds 4

http://www.linkedin.com 2
http://www.slideshare.net 1
https://www.linkedin.com 1

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Smart Antennas Smart Antennas Presentation Transcript

    • Performance of Smart Antennas and PCF Vinayak Nandikal Courtesy: Nokia Research Center
    • Introduction
      • IEEE802.11 will be an important method for providing high rate low mobility data services
      • While existing capacity may seem high, particularly for IEEE802.11a, the enterprise environment may experience capacity limits
      • Antenna technologies offer a means to boast IEEE802.11 capacity without changing the existing PHYs
    • What is a SMART Antenna? Antenna that adjusts its beam pattern based upon the channel and interference between AP and STA AP STA STA
    • Approach to Model Performance
      • Measure channel using a channel sounder to determine
        • Multipath power profile as a function of time
        • Signal-to-interference ratio
      • Simulate PHY to obtain PER information as a function of channel measurements and the number of packets delivered as a function of time
      • Use PER, number of packets delivered by the PHY as a function of time and models of real-time traffic to examine delay and throughput using a PHY with and without smart antennas
      • PCF is used for delivery of audio and video packets
    • PHY Simulation Parameters
    • PHY Channel Sounder Approach
      • 127 chip pn sequence is transmitted at 5.3 GHz with a bandpass bandwidth of 30 MHz
      • A 32 element array with 0.5 wavelength space is used to downconvert the transmitted pn sequence
      • Snap shots of the delay spread are written to memory and stored on a hard disk
      For further information see: Jarmo Kivinen, Timo O. Korhonen, Pauli Aikio, Ralf Gruber, Pertti Vainikainen, and Sven-Gustav Häggman, IEEE Transactions on Instrumentation and Measurement, vol. 48, no. 1, pp. 39-44, 1999.
    • Smart Antenna Operation (5GHz) Uplink Operation Downlink Operation RF A/D FFT RF A/D FFT RF A/D FFT Antenna Combining Weight Calculation Decoding STA STA OFDM Symbol Index Subcarrier D/A RF D/A RF D/A RF IFFT IFFT IFFT Antenna Weighting Coding & Modulation STA STA
    • Channel Correlation
      • The figure to the right shows the correlation coefficient for different measurement environments
      • For smart antenna operation, the AP needs the ability to probe the channel between any STA and AP
      Note: Ruholahti and Heikkiläntie are Nokia office buildings 0 50 100 150 200 250 300 350 400 450 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1 time [ms] amplitude correlation coefficient average over TX positions Ruoholahti Heikkiläntie Airport Airport 2
    • MAC Simulation Parameters
    • Traffic Model:
      • All traffic measured in data-units/slot-time
        • 1 data-unit takes 1 slot-time for transmission
        • Max traffic in network = 1.0
      • Audio and video traffic originates from “calls” made by the user
      • Calls are Poisson distributed; once placed, each call generates periodic packet traffic
      • Mean inter-call-arrival-time controls load on the network
    • Traffic Model (cont.):
      • Real-time traffic load =
      apkt_sz : audio packet size vpkt_sz : video packet size int_call_arvl_time : mean intercall arrival time (8:1 ratio between audio and video calls) int_apkt_arvl_time, int_vpkt_arvl_time : arrival time between audio packets and video packets respectively acalls, vcalls : number of audio anc video calls respectively
    • Throughput & Latency Curves: Audio Packets Packets/Seconds Packets/Second Normalized Througput PCF Latencies 0 0.5 1 1.5 2 2.5 x 10 4 10 -4 10 -3 10 -2 10 -1 No SDMA 3-channel SDMA DCF:PCF = 1:1 Audio Packets 0 0.5 1 1.5 2 2.5 x 10 4 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 No SDMA 3-channel SDMA DCF:PCF = 1:1 Audio Packets
    • Throughput & Latency Curves: Audio Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies 0 1 2 3 4 x 10 4 10 -4 10 -3 10 -2 10 -1 No SDMA 3-channel SDMA DCF:PCF = 1:3 Audio Packets 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 No SDMA 3-channel SDMA DCF:PCF = 1:3 Aduio Packets
    • Throughput & Latency Curves: Video Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies 0 100 200 300 400 500 10 -4 10 -3 10 -2 10 -1 No SDMA 3-channel SDMA DCF:PCF = 1:1 Video Packets 0 100 200 300 400 500 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 No SDMA 3-channel SDMA DCF:PCF = 1:1 Video Packets
    • Throughput & Latency Curves: Video Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies 0 200 400 600 800 10 -4 10 -3 10 -2 10 -1 No SDMA 3-channel SDMA DCF:PCF = 1:3 Video Packets 0 100 200 300 400 500 600 700 800 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 No SDMA 3-channel SDMA DCF:PCF = 1:3 Video Packets
    • New Control Frame Subtypes for Smart Antennas
      • AP to STA
        • A message requesting the STA to transmit a preamble (null frame) for channel estimation
        • Channel Id Request
      • STA to AP
        • A response to the above request
        • Channel Id Response
      Duration RA TA FCS Message Fields Frame Control
    • Remove Polling Dependence
      • The existing standards reads,
      • "During each CFP, the PC shall issue polls to a subset of the STAs on the polling list in order by ascending AID value".
    • Conclusions
      • Particularly in a large enterprise environment, smart antennas can help boast capacity
        • Wireless office replacement for "wired" Ethernet
        • Public service networks such as airports
      • Changes to the existing MAC are minor to enable antenna technologies in IEEE802.11a networks
      • SDMA is not for all WLANS
        • Multiple antennas cost additional money for the AP that may not be required in homes and small businesses