Antennas. DIRC: Increasing Indoor Wireless Capacity Using Directional. Antennas. Problems with Omnidirectional Antennas

Transcription

1 ntennas IR: Increasing Indoor Wireless apacity Using irectional ntennas Xi Liu, nmol Sheth, Michael Kaminsky, Konstantina Papagiannaki, Srinivasan Seshan, and Peter Steenkiste Omnidirectional Equal power in all directions Produces interference to other nearby devices irectional irected signal power Experiences scattering and multipath effects in indoor environments Problems with Omnidirectional ntennas Omnidirectional Easily achieve link throughput with only a single link.but what about more devices? irectional Provides spatial isolation but what is the correct orientation to direct antenna? irectional ntennas and Importance of Environment ifferent gains based on direction Increase or decrease signal strength by up to 20d ffected by RF reflectors like: Metallic cabinets Walls oors irect LOS (Outdoor) locked LOS (Indoor) 1

2 Importance of ntenna Orientation Select orientation to maximize power at receiver? arefully select orientation to maximize total benefits onflict Graph for irectional ntennas onflict Graph that two Ps cannot use at Vertices (i,j,k) means P I,,,, onflict Graph for irectional ntennas onflict Graph that two Ps cannot use at Vertices (i,j,k) means P I,,,,,, onflict Graph for irectional ntennas onflict Graph that two Ps cannot use at Vertices (i,j,k) means P I,,,,,,,, 2

3 Selecting est Orientation onflict Graph that two Ps cannot use at Vertices (i,j,k) means P I,,,,,,,, Greedy pproach to uild onflict Graph onflict Graph that two Ps cannot use at Vertices (i,j,k) means P I irect Measurements Record orientations from different Ps that conflict Takes prohibitively long to discover conflict graph SINR onflict Graph SINR onflict Graph SINR Measurements SINR Measurements SINR is a good predictor of successful/failure transmission Edge can be efficiently computed by subtracting the received and transmitted SINR SINR = RSS (,, ) RSS (,, ) SINR is a good predictor of successful/failure transmission Edge can be efficiently computed by subtracting the received and transmitted SINR Each P scans individually in all directions recording other P scans. 3

4 Scheduling given onflict Graph Given that scheduling is NP hard, use a heuristic to approximate: 1. Order transmission based on FIFO 2. Iterative antenna orientation search 1. Fix all antennas 2. Vary orientation of a single antenna to maximize network capacity 3. Loop ealing with ynamicity Periodically or bad performance forces rescan to update conflict graph Period is determined by choosing a reasonable time such that the overhead is < 5% network capacity TM based M protocol synchronizes uplink and downlink traffic for Ps, clients, and controller annot transmit to new client until probes are performed so delay transmit until rescan oes this improve performance? How does it react to dynamics? Improve UP performance by 65% over other approaches and 100% over omnidirectional antennas oth transmit without interference Motion only affects own throughput Link2 arrives forcing rescan Rescans djust well to traffic changes 4

5 Pros: Thoughts etter utilize shared medium etter understanding of interference ons: entralized ontroller Rescans ynamic Environments 5