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AsiaFI Winter Camp 2008, Seoul Korea Tran Minh Trung Information & Communications University

A Multi-Channel TDMA MAC protocol for supporting QoS of multimedia traffic over multihop Wireless Mesh Networks. AsiaFI Winter Camp 2008, Seoul Korea Tran Minh Trung Information & Communications University Wireless Internet Networks Lab 2008/02/20. Outlines. 1. Introduction WMN Overview

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AsiaFI Winter Camp 2008, Seoul Korea Tran Minh Trung Information & Communications University

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  1. A Multi-Channel TDMA MAC protocol for supporting QoS of multimedia traffic over multihop Wireless Mesh Networks AsiaFI Winter Camp 2008, Seoul Korea Tran Minh Trung Information & Communications University Wireless Internet Networks Lab 2008/02/20

  2. Outlines • 1. Introduction • WMN Overview • Problem statements & motivation • Related works • 2. Key ideas • Separation of data and Voice/Video • Manage recourse for multimedia in two dimensions • 3. Proposed solutions & primary results • 4. Conclusion & Future plan

  3. Introduction >WMN Overview (1)What is WMN ? • Mesh components: • Mesh Routers (access points) • Clients (PDA, laptop, …) • Mesh Gateways to Internet • Traffic • Voice, video, data • Most traffic is from mesh clients to gateways. • Other is between mesh client • Communication • Wireless: between mesh routers, mesh clients • Wired: connect gateway to Internet B E A C D Figure 1: Wireless Mesh Network Voice call from a mesh client to a mesh client Video traffic from a mesh client to a mesh client Voice call from a mesh client to a mesh client

  4. Introduction >WMN Overview (2)Why WMN ? • Enables rapid deployment • Easy to provide coverage • Eliminate cost of wired backhaul • Self-healing, resilient, extensible

  5. Introduction >WMN Overview (3)WMN applications & challenges • Applications • Emergency service • Multiplayer games • Multimedia service (Voice/Video) • …. • Key challenges • The performance of WMN is significant reduced when • The number of hop is increased • The number of contenders is high

  6. Introduction > Problem statement & Motivations (1)Problem statement & motivations • Problem statement: How to design a MAC protocol which can provide QoS for multimedia traffic (voice/video) over WMN? • Motivations: • Multimedia is an important service of WMN • It is challenge to support QoS for it in WMN • A successful solution can help last mile service providers deploy the multimedia service with low cost and high quality (IPTV, voice calls…)

  7. Throughput Number of nodes Introduction > Related works (1) QoS of multimedia traffic over wireless multi-hop networks • Problems that can affect the QoS of Voice/Video over WMN • Self-interference [T.M.Trung et al. 2006] • Interference between data links and multimedia links (Co-existing problem) • Interference between multimedia links • High packet over head [D. Niculescu et al. 2005] • G7209a: Payload/Packet ~ 10% Figure 2: System throughput - # contenders Figure 3: Packet overhead

  8. 2 2 1 1 Ch-1 Ch-1 3 4 3 4 Ch-1 Ch-2 User bandwidth = B/2 User bandwidth = B Introduction > Related works (2) Approaches for improving QoS & capacity B = bandwidth of a channel • Reduce self- interference • Multi-channel MACs (MCMPs) • Reduce packet overhead • Header compression • Packets aggregations Figure 4: Single channel vs. Multi-channel capacity Ref: [Akyildiz et al. 2005]

  9. Introduction > Related works (3) MCMPs’ performance • McMAC [W.So et al. 2007] scales well with an increasing number of channels while the single rendezvous protocols do not Figure 5: Throughput vs. no. of channels. Avg. packet size is 1Kbyte (left) or 10Kbytes (right) Ref: [J.Mo et al. 2004]

  10. Introduction > Related works (4) Problem of McMAC • Voice capacity is significant reduced when the data traffic load is increased Figure 6. Voice capacity of McMAC in the case of 802.11b (left), 802.11a (right) setting Ref. [T.M.Trung et al. 2007]

  11. Key Ideas Channels • Separation of data and Voice/Video • To avoid the conflict between data links and multimedia links • Manage resources for multimedia links in two dimensions: time slots and channels • Better utilize channel resource • Reduce the conflict between multimedia link EXPRESS BUSES Normal cars Time slots Figure 7. Separation of data and voice/video Figure 8. Two dimensions resources for multimedia traffic

  12. Challenges • How to separate data and voice/video? • How to allocate channels slots? • How to make reservations? • How to decide: • the number of channels for voice/video? • the length of frames? • the number of slots in each frame? • …

  13. Proposed solutions Solution’s descriptions • Separation of Data and Voice/Video • Mechanisms & Architecture • Two dimensions resource allocation • Distributed channel slots allocation protocol for single collision domain (VMcMAC) • Centralize channel slots allocation protocol for multiple collision domain (McTMAC) • Primary evaluations results

  14. Proposed solutions > Separation (1)Separation of Data and Voice/Video • Out of n channels, up to N channels can be reserved for Voice/Video Traffic • Data: Use an Efficient Multichannel MAC such as McMAC • Voice/Video: Propose a Reservation based Multi-Channel TDMA MAC (McTMAC) Reserved Channel Reserved Channel Data Channel Data Channel Data Channel Figure 9: Channels reservation for voice/video

  15. Proposed solutions > Separation (2) Separation architecture • Packets arrived at link layer are forwarded to two types of interface queue • IFQM for multimedia • IFQD for data • Each type of IFQ is associated with different MAC protocols • IFQM associated with proposed McTMAC • IFQD associated with McMAC Routing Link layer object IFQD IFQM McTMAC McMAC PHY Figure 6: Separation architecture Reserved Channels Non reserved channel

  16. Proposed solutions > Distributed channel slots allocation (VMcMAC) (1)Multimedia Traffic with TDMA Manner • Voice/video source generate packets periodically • Each voice node occupied a time slots and transmit packets with fixed interval. • Other nodes can overhearing the Voice/video packets from other nodes to figure out free time slots

  17. Proposed solutions > Distributed channel slots allocation (VMcMAC) (2) Time slot structure 1 2 3 4 1 2 3 4 • Time is divided into big time unit (BTU) • TBTU <= Delay threshold • Big time unit is further divided into K small time unit (STU). Each STU is long enough to carry a bi-direction voice frame. 8/24/2014 17

  18. Proposed solutions > Distributed channel slots allocation (VMcMAC) (3) Distributed slots allocation steps • Step1: Sender scan for free slots (overhearing for a while on VC) • Step2: Switch to reviver channel to send call request • Step3: Switch back to VC channel to exchange packets Figure 10: Voice call procedure 8/24/2014 18

  19. Proposed solutions > Distributed channel slots allocation (VMcMAC) (4) Pos. & Cons of distributed approach • Pos. • Do not need a centralize coordinator • No need global synchronization • Cons. • Just proposed for single collision domain • Difficult to deploy in multihop environment • Difficult to keep fairness between links • Proposed an extended version with centralize based for multi-hop Wireless Mesh Networks

  20. Main Ideas (2) > Centralize channel slots allocation (McTMAC) (1) TDMA delay over multihop • Time slots should be assigned in a specific order • The former link should be allocated before the latter link • Perform spatial reuse to reduce the size of big time slots • Links can use the same time slots if they are allocated on different channel Ref. [P. Djukic et al. 2007] e1 e2 e3 e4 e5 e6 e1 e2 e3 e4 e5 e6 e1 e2 e3 e4 e5 e6 3T 0 T 2T Figure 11. TDMA delay over multi hop Round trip time > 2T e1 e3 e5 e6 e4 e2 e1 e3 e5 e6 e4 e2 e1 e3 e5 e6 e4 e2 3T 0 T 2T Round trip time = 2T

  21. Main Ideas (2) > Centralize channel slots allocation (McTMAC) (2) Time slots assignment rule • WMN Backbone is Infrastructure based • WMN can be represented by a tree based topology with root is a gateway • Rule 1: Time slots are assigned base on the hop count from root nodes B E A C E T1 T2 D B D T2 T3 T3 T3 A C Figure 12: VMcMAC procedure and performance

  22. Main Ideas (2) > Centralize channel slots allocation (McTMAC) (3) Channel assignment rule • Rule 2: • The links in explicit conflict graph can use the same time slot if they are allocated on different channels • Example: CB and AD • This rule help us to minimize the number of required slots or reduced TDMA frame size Figure 14: Explicit conflict graph Figure 15: An Example

  23. Main Ideas (2) > Centralize channel slots allocation (McTMAC) (4) Feasible timeslot and channel assignment algorithm (FTCA) • Input: G(V,E), Gc(Vc,Ec), GI(VI,EI), Roots, nC • Output: Assignment matrix (AM) • Initialization • nT=0: Number of time slots • cC: Current channel • ct: Current time slots • nRoots: Next roots • For each (roots) • Check(Gc,root) • For each link • If links share the same end nodes • nT=nT+1 //Time slot ordering • Assign [cC,t(nT)] to link(i) • Else // spatial reuse checking • Check (Gc) • For each cC • If cC(j),t(nT)is free then • assign [cC(j),t(nT)] to link(i) //Reuse slot t(nT) • cC=cC(j) • Else • nT=nT+1 // • Assign t(nT) to link(i) • End if • End if • End for • End check • Return (link(i),nT,cT) • End for

  24. Main Ideas (2) > Centralize channel slots allocation (McTMAC) (5) Min delay path selection • Example • Path 1: A,B,C,D • D1 = T1 + T2 + T3 + T4 + T1 = 5 Time slots • Path 2: A,E,F • D2 = T2 + T3 + T4 = 3 Time slots • Min_delay = Min(D1, D2) = D2 • Selected path is [A,B,C,D] • Evaluation formula: • Let • ts : the length of a time slots (us) • Pn : the order (position) of time slot ( T3: Pn = 3) • s: the number of hops Figure 15: Min delay path Selection: [A,B,C,D]

  25. Primary results • Time slot and channel allocation performance • FTCA • AFTCA (Without Rule 1) • Greedy (Without Rule 2) • Voice capacity of McTMAC with • FTCA • AFTCA • Greedy • Comparing with McMAC

  26. Primary results > Time slot and channel allocation performance (1) Simulation scenario 1 • Simulation scenario • Generate A random WMNs with number of node various (20,40,80) • Select a root node randomly • Run FTCA with the input is • Generate WMNs grap G(C,V) • Number of channel =2 • Goals: • Check the performance of time slot and channel allocation algorithm • Evaluation items • Number of required time slots (Frame size in slots) • Delay (in slots) Figure 12: A random WMNs topology with 40 nodes

  27. Primary results > Time slot and channel allocation performance (2)Results: Number of time slots and delay • We compare the performance of FTCA with greedy algorithm • The simulation results show that: • FTCA has smallest delay while reduce the frame size upto 45% to compare with greedy algorithm FTCA Greedy AFTCA FTCA Greedy AFTCA Figure 13:# of required time slots Figure 14:# Min delay

  28. Primary results > Time slot and channel allocation performance (3)Results: Spatial reuse status Spatial reuse status Figure 15: Spatial reuse status on each channel in case of using Greedy algorithm Figure 16: Spatial reuse status on each channel in case of using FTCA

  29. Primary results > McTMAC performance (1) Simulation scenario • Simulation scenario • Generate A WMNs with 10 nodes and one gate way (fig. 17) • PHY:802.11a, 11 available channels • Number of channel reserved for voice traffic: 2 • Data traffic • Flow Arrivals: unidirectional flows between node pairs follow an On-off model. • Packet Arrivals: i.i.d. packet arrivals during each time slot when a flow is ON. • Load: N_pairs * avg_flow_dur * p_arrival * avg_pkt_len / num_chans(0 <= Load <= 1) • Voice traffic • Each mesh router has the same number of CBR flows. Each flow is bidirectional and goes to internet gateway nodes. • Voice traffic pattern generation is based on a simple periodic packet arrival model at each mesh node. • In this simulation we use codec is G729a with packet interval is 20ms. Figure 17: A WMN with 10 nodes and 1 internet gateways

  30. Primary results > McTMAC performance(1) Voice performance metric • Acceptable quality level: • R-Score >70 • Delay < 150ms • Lost <2% • Current evaluation focusing on delay Ref. [R.Cole et al. 2001]

  31. Simulation results Delay AFTCA Delay CDF Seconds Voice capacity Number of voice calls

  32. Conclusions • Introduce a Multi-Channel TDMA MAC protocol to support QoS for multimedia traffic over multihop WMN • Distributed approach • Centralize approach • The simulation results show VMcMAC and McTMAC outperform McMAC. The voice capacity is increased significantly with up to 3 times by using McTMAC.

  33. Current status • Extending VMcMAC for mesh (McTMAC) • Get some primary simulation results • Published F-MAC, VMcMAC T.M.Trung , J. Mo “VMcMAC: A multi-channel MAC protocol for voice over wireless Ad-hoc networks,”, IEEE Communications Letters, vol. 11, no. 5, May 2007. T.M.Trung , J. Mo, and S.-L. Kim, “A Flow-Based Media Access Control (F-MAC) for Wireless Ad-Hoc Networks”, IEICE Transactions on Communications, Vol. E89-B (3), p.756-763, 2006.

  34. Plan • Solve the existing problems of McTMAC • Check with video traffic • Formulate the relation between: system demand, small time slots size, time frame size, number of available channels and the number of channel reserved for multimedia traffic • Deal with channel variation • Implement in a real testbed system or perform mathematical analysis

  35. References • [T.M.Trung et al. 2007] T.M.Trung , J. Mo “VMcMAC: A multi-channel MAC protocol for voice over wireless Ad-hoc networks,”, IEEE Communications Letters, vol. 11, no. 5, May 2007. • [T.M.Trung et al. 2006] T.M.Trung , J. Mo, and S.-L. Kim, “A Flow-Based Media Access Control (F-MAC) for Wireless Ad-Hoc Networks”, IEICE Transactions on Communications, Vol. E89-B (3), p.756-763, 2006. • [J.Mo et al. 2005] J. Mo, H. W. So, and J. Walrand, “Comparison of Multichannel MAC protocols for Wireless Networks,” In Proc. of ACM/IEEE MSWIM 2005. • [H. W. So et al. 2005] H. W. So, and J. Walrand, “McMAC: A Multi-Channel MAC Proposal for Ad-Hoc Wireless Networks,” Technical Report, 2005. • [P. Djukic et al. 2007] P. Djukic and S. Valaee, “Link scheduling for minimum delay in spatial re-use TDMA,” in Proceedings of INFOCOM, 2007 • [ X.Zhang et al. 2007] X.Zhang, J.Hong, L.Zhang, X.Shan, Li, V.O.K., "CC-TDMA: Coloring- and Coding-Based Multi-Channel TDMA Scheduling for Wireless Ad Hoc Networks", WCNC 2007 • [R.Draves et al. 2004] Richard Draves, JitendraPadhye, and Brian Zill, “Routing in Multi-Radio, Multi-Hop Wireless Mesh Networks,” in ACM Mobicom, 2004. • [A.Raniwala et al. 2004] AshishRaniwala, KartikGopalan, and Tzi-ckerChiueh, “Centralized Channel Assignment and Routing Algorithms for Multi-Channel Wireless Mesh Networks,” Mobile Computing and Communications Review, vol. 8, no. 2, pp. 50–65, April 2004. • [J.So et al. 2004] Jungmin So and Nitin H. Vaidya, “Multi-channel MAC for Ad Hoc Networks: Handling Multi-Channel Hidden Terminals using a Single Transceiver,” in Mobihoc, 2004. • [P.Bahl et al. 2004] ParamvirBahl, Ranveer Chandra, and John Dunagan, “SSCH: Slotted Seeded Channel Hopping for Capacity Improvement in IEEE 802.11 Ad-Hoc Wireless Networks,” in ACM Mobicom, 2004. • [P. Kyasanur et al. 2005] PradeepKyasanur and Nitin H. Vaidya, “Routing and Interface Assignment in Multi-Channel Multi-Interface Wireless Networks, WCNC 2005 • [J. Shi et al. 2006] J. Shi, T. Salonidis, and E. Knightly “Starvation Mitigation Through Multi-Channel Coordination in CSMA based Wireless Networks,, ” MobiHoc 2006, • [C. Chereddi et al. 2006] ChandrakanthChereddi, PradeepKyasanur, and Nitin H. Vaidya, “Design and Implementation of a Multi-Channel Multi-Interface Network”, REALMAN 2006 • [A.Raniwala et al. 2005] A.Raniwala, Chiueh, “Architecture and Algorithms for an IEEE 802.11-based Multi-channel Wireless Mesh Network”, IEEE Infocom 2005; • [J. So et al. 2004] J. So and N. H. Vaidya, “Multi-channel MAC for Ad Hoc Networks: Handling Multi-Channel Hidden Terminals using a Single Transceiver,” in Mobihoc, 2004. • [RG98] ITU-T Recommendation G.114. General Characteristics of International Telephone Connections and International Telephone Circuits: One-Way Transmission Time, Feb. 1998.

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