1 / 18

Capacity Regions for Wireless AdHoc Networks

Capacity Regions for Wireless AdHoc Networks. The presentation is based on a paper: S. Toumpis and A. J. Goldsmith: Capacity Regions for Wireless Ad Hoc Networks , IEEE Transactions Wireless Communications , Vol. 2 No. 4, pp 736-748, July 2003 Presented by Antti Tölli

byron-nash
Télécharger la présentation

Capacity Regions for Wireless AdHoc 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. Capacity Regions for Wireless AdHoc Networks The presentation is based on a paper: S. Toumpis and A. J. Goldsmith: Capacity Regions for Wireless Ad Hoc Networks , IEEE Transactions Wireless Communications , Vol. 2 No. 4, pp 736-748, July 2003 Presented by Antti Tölli antti.tolli@ee.oulu.fi

  2. Outline • Introduction • System Model • Transmission Schemes and Schedules • Rate Matrices • Capacity regions • Results for Specific Configurations Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  3. Intro • Lower and upper bounds of capacity of AdHoc NWs defined for large number of nodes (Gupta&Kumar*, Grossglauser&Tse**) • Capacity regions for AdHoc NWs with any number of nodes defined in this article • Although, max achievable rates defined for specific tx protocols (maybe suboptimal) • Impact of power control, multihop routing, spatial reuse, successive interference cancellation, etc. studied • Special Challenges of Ad Hoc Networks • No infrastructure • Decentralized control (power, routing, data rates, etc) • Dynamic topology • Wireless channel impairments *P. Gupta and P. R. Kumar, “The capacity of wireless networks,” IEEE Trans. Inform. Theory, vol. 46, pp. 388–404, Mar. 2000. **M. Grossglauser and D. N. C. Tse, “Mobility Increases the Capacity of Ad Hoc Wireless Networks,” IEEE/ACM Trans. on Networking, vol. 10, no. 4, August 2002, pp. 477-486 Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  4. System Model, #1 • nodes : A1 … An • Each Ai • has transceiver with infinite buffer • maximal power output is Pi • canNOT simultaneously send and receive • may send data to any Aj (multihop routing possible) • occupy ALL bandwidth (W) while transmitting • NO broadcast Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  5. System Model, #2 • Channel Gains: G = {Gij}, f(distance, shadowing) • Noise: AWGN, H = [h1 ... hn] • Each node knows “everything”: G, H, P • t  J At is transmitting with power Pt • If Ai (i  J) transmits to Aj (j  J), • SINR: • data rate: Rij = f(gij) pre-agreed for performance; e.g., f(gij) =W log2(1+gij) Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  6. S1 S2 Transmission Schemes T-scheme S : Complete description of information flow betweeen different nodes in the network at a given time instant • all transmit-receive node pairs, and data rates • originating node of data • Example: Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  7. S1 T1 S2 T2 Time Division Scheduling • Network may alternate various schemes • Example • T1 = 0.5S1+0.5S2 or • T2 = 0.75S1+0.25S2 • Resulting info flow: Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  8. S1 S2 Rate Matrices, #1 • For given scheme S, R(S) is n×n matrix such that • Rij= ±r Ajreceives/send r bps originating at Ai Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  9. T1 T2 Rate Matrices, #2 • Time-division scheduling: Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  10. Transmission Protocols & Basic Rate Matrices • Transmission protocol: collection of rules that node must satisfy when transmitting • Transmit own info only, Transmit with max power, Can transmit simultaneously with other nodes, Interference treatment: noise (SIC not allowed) or SIC • Given a protocol, many Tx schemes are possible • Basic rate matrix: each Tx scheme has a rate matrix • The less restrictive Tx protocol, the larger the collection of rate matrices and vice versa Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  11. Capacity Region: Definition • Capacity region: Convex Hull of all basic rate matrices such that the weighted sums have NO negative off-diagonal elements • Describes the net flow of the info in the NW • Uniform Capacity, Cu= Rmax× n(n−1) with Rmaxlargest R given the matrix is in the capacity region: Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  12. Network Parameters • Nodes: 5 uniformly distributed in box [-10m , 10m]×[-10m , 10m] • Gij= K·Sij ·(d0/dij)a, K=10-6, d0 =10m, a=4 • Sij(shadowing) lognormal with µ= 0dB and s= 8 db • Pj= 0.1W ; hj= 10-11 W/Hz • Bandwidth: W = 106 Hz • rij=f(gij) =W log2(1+gij) Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  13. Capacity: Single-Hop Routing, No Spatial Reuse • Only one transmits at a time: # of schemes is Na= n(n−1)+1 • Associated rate matrices : (Ra)i , i= 1 … Na • uniform capacity : 0.83 Mbps • Slice of capacity region (see a) in p. 16) • Only nodes A1 and A3 send data • Straight line – no spatial reuse, transmission only between one source-destination point at any time Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  14. Capacity: Multi-Hop Routing, No Spatial Reuse • Only one transmits at a time • N nodes in the system, each has n-1 different possible receivers and n possible nodes to forward data • # of schemes is Nb= n2(n−1)n+1 • Uniform capacity : 2.85 Mbps (242% increase) • Slice of capacity region (see b in figure, p. 16) • Straight line again – no spatial reuse, transmission only between one source-destination point at any time • Significant capacity increase: multiple hops over favourable channels instead of transmitting directly over paths with small gains Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  15. Capacity: Multi-Hop Routing, with Spatial Reuse • Multiple active connections allowed at any time • # of schemes is • Uniform capacity : 3.58 Mbps (26% increase) • Slice of capacity region (see c in figure, p. 16) • No longer a straight line, NW can use spatial reuse to maintain multiple active transmissions (directly or over multihop) Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  16. Capacity Figures (a) Single-hop, No spatial reuse (b) Multihop, no spatial reuse (c) Multihop, spatial reuse (d) 2-level power cntrl added to (c) (e) Succs. interference cancellation Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  17. Fading and Mobility Increase Capacity • Time varying flat fading channel • Capacity increases as the # of fading states increases • a) % b) one fading state • c) 2 fading states • d) 10 fading states • e) 15 fading states M different fading states Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

  18. Conclusions • Mathematical framework developed for finding capacity regions for AdHoc/multihop NWs under time-division routing and given transmission protocol • Network performance shown to be improved by: • Multihop routing, spatial reuse and interference cancellation • Fading and node mobility Capacity Regions for Wireless Ad Hoc Networks, CWC @ Univ. of Oulu

More Related