1 / 44

coordinated multi-flows: how to make wireless network coding work in cellular systems

coordinated multi-flows: how to make wireless network coding work in cellular systems . Petar Popovski Aalborg University, Denmark Elisabeth de Carvalho Chan D. T. Thai, Fan Sun, Huaping Liu, Henning Thomsen . relays in wireless cellular systems. coverage extension

alicia
Download Presentation

coordinated multi-flows: how to make wireless network coding work in cellular systems

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. coordinated multi-flows:how to make wireless network coding work in cellular systems Petar Popovski Aalborg University, Denmark Elisabeth de Carvalho Chan D. T. Thai, Fan Sun, Huaping Liu, Henning Thomsen

  2. relays in wireless cellular systems • coverage extension • spectral efficiency impaired due to half-duplex operation • still not an architectural mainstream

  3. two way relaying • (wireless) network coding of multiple flows • reclaims the spectral efficiency • however • a lot of attention to a specific traffic pattern

  4. is this only a trick for a specific traffic combination or something that can be applied more widely?

  5. the two underlying principlesjoint transmission of multiple communication flowsintentional interference that can be canceled by side information

  6. the two principles in action self interference cancellation base station joint transmission relay interference cancellation self interference cancellation 2 time slots terminal

  7. standard cellular architecture • downlink and uplink are decoupled • counterarguments • CSI exchange, flexible TDD switching, etc. • however, this is time sharing • no “true” interaction among the flows

  8. better than time sharing

  9. our approachfind building blocks that use the principles of wireless network codingconsider system model with two-way communication at each device combine the building blocks to serve all the flows in the system

  10. an example problem definition relay relay relay

  11. new building blocks coordinated direct and relay(CDR) links

  12. CDR links example 1 1 relayed user: downlink traffic 1 direct user: uplink traffic relay T2 T1

  13. direct and relay linksreference approach relay T2 3 time slots T1

  14. CDR 1approach that uses the two principles self interference cancellation relay T2 2 time slots T1

  15. CDRexample 2 relay T2 T1

  16. CDR 2the two principles again relay T2 2 time slots T1

  17. two other CDR traffic patternsCDR 3 and CDR 4 DL UL DL UL relay T2 relay T2 T1

  18. four-way traffic relay T2 what is the best way to serve these four flows using all the building blocks that we are aware about? T1

  19. at least two possible schemes compared to

  20. each scheme uses time sharing

  21. 4D rate region Max achievable rate in first scheme Max achievable rate in composite scheme

  22. we can do even better Ref schemes CDR schemes

  23. … and even better, combining all that we know

  24. the optimization problemfor a given set of communication flowsfind the optimal time sharing among all the possible transmission schemesto determine the achievable rate region.

  25. 2D projections of the rate region • define an downlink-uplink ratio • reflects practical constraints • web browsing 5:1 • gaming and calls 1:1

  26. rate region

  27. another building block four-way relaying

  28. traffic configuration • 2 terminals far from base station, served by relay • uplink and downlink traffic • assumption • the relays are antipodal within the cell, no interference between them

  29. our reference: two-way relaying 4 transmission phases

  30. a better flow coupling:two transmission phases first transmission phase second transmission phase how do we achieve this?

  31. four-way relaying:the first transmission phase broadcast phase multiple access multiple access broadcast using superposition coding

  32. four-way relaying:the second transmission phase multipleaccess broadcast broadcast broadcast signal from BS broadcast signal from BS multiple access

  33. Four way relaying 4WR 2WR + 2WR

  34. this can be generalized in multiple ways …

  35. four-wayrelaying with multiple antennas how to distribute efficiently the degrees of freedom 2M antennas at the base station M antennas at the relay and users Phase 1 Phase 2 8 Degrees of Freedomper transmission

  36. reference schemes 4Degrees of Freedomper transmission 8 Degrees of Freedomper transmission

  37. precoders ZF precoder to separate 4 streams Precoding matrix Precoding matrix

  38. precoders

  39. optimization

  40. performance with multiple antennas

  41. main consequence building blocksdefine new optimization problem for two-way terminals

  42. the example revisited relay relay relay

  43. concluding remarks • benefits of wireless network coding beyond the canonical two-way relaying • wireless backhauling becomes viable • new transmission schemesthat act as building blocksand enlarge the optimization space • consequences for the architectural approachand overall system design

  44. what else do we do • massive M2M communications http://massm2m.lab.es.aau.dk/ • cognitive radio • very reliable communication protocols

More Related