1 / 31

SMACK: Smart ACKnowledgment Scheme for Broadcast Messages in Wireless Networks

SMACK: Smart ACKnowledgment Scheme for Broadcast Messages in Wireless Networks . Aveek Dutta , Dola Saha , Dirk Grunwald , Douglas Sicker, University of Colorado. Premise.

garvey
Download Presentation

SMACK: Smart ACKnowledgment Scheme for Broadcast Messages in Wireless Networks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SMACK: Smart ACKnowledgment Scheme for Broadcast Messages in Wireless Networks AveekDutta, DolaSaha, Dirk Grunwald, Douglas Sicker, University of Colorado

  2. Premise • wireless protocols can exploit simultaneous transmission to reduce the cost of reliable multicast/broadcast transmission by orders of magnitude

  3. Background • OFDM is a modulation mechanism that allows for multi-user communication through orthogonal channels

  4. Background • OFDM is a modulation mechanism that allows for multi-user communication through orthogonal channels simultaneous transmission and reception

  5. Protocol Summary • Each node is assigned a unique “membership id”

  6. Protocol Summary • Each node is assigned a unique “membership id” • An AP sends the broadcast message

  7. Protocol Summary • Each node is assigned a unique “membership id” • An AP sends the broadcast message • Clients decode the broadcasted message (if possible)

  8. Protocol Summary • Each node is assigned a unique “membership id” • An AP sends the broadcast message • Clients decode the broadcasted message (if possible) • Client uses assigned subcarrier specified by “membership id” to send back an ACK

  9. Protocol Summary • Each node is assigned a unique “membership id” • An AP sends the broadcast message • Clients decode the broadcasted message (if possible) • Client uses assigned subcarrier specified by “membership id” to send back an ACK • AP receives composite signal of all subcarriers and demodulates the individual ACK’s

  10. How does the AP know when a station is transmitting a tone? • Checks if average received signal strength (RSS) is above some constant threshold

  11. Varying Signal Power • Want: One single threshold to detect clients in the network • Problem: signal powers from clients may vary widely • Solution: adjusting the transmission power of clients such that received power from all clients are within a tolerable range • Existing channel assessment techniques done in CDMA

  12. Interference

  13. Timing Concerns • All subcarriers must be present with sufficient energy within the FFT window. • near-far effect • different processing power of the client nodes

  14. Experimental Setup • Using SDR platform with an OFDM transceiver using a Virtex-IV FPGA • Used 2.484GHz as the carrier frequency for the experiment

  15. Results • Can use simple FT to detect multiple tone transmission no matter how dense the subcarrier spacing is • This protocol is feasible using reconfigurable radio to meet the timing constraint

  16. Exp #1 Evenly Spaced Subcarriers Exp #2 Closely Spaced Subcarriers Exp #3 Contiguous Subcarriers

  17. Evenly spaced subcarriers [-26, -16, -6, +6, +11, +16)

  18. Closely spaced subcarriers [+6, +8, +10, +12, +14, +16)

  19. Contiguous subcarriers[+8, +9, +10, +11, +12, +13]

  20. Results • Can use simple FT to detect multiple tone transmission no matter how dense the subcarrier spacing is • This protocol is feasible using reconfigurable radio to meet the timing constraint

  21. Complete System with 1 broadcaster and 2 responders at +12 and -12

  22. Conclusion • Adaptability of SMACK to any higher level group communication and signaling protocols as long as they require simple “yes/no” answers • Reducing Redundant Rebroadcast • Parallel Polling

More Related