doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 1 W-CHAMB Wireless CHannel Oriented Ad-hoc Multi-hop Broadband A new MAC for better support of Mesh networks with QoS Rui Zhao, Bernhard Walke, Guido R. Hiertz ComNets Chair of Communication Networks RWTH Aachen University Aachen Germany

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 2 Outline Overview of W-CHAMB Better Multi-hop Support QoS Support of W-CHAMB Synchronization of W-CHAMB Summary Simulation Result

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 3 Overview of W-CHAMB TDMA based Channel-oriented Fully distributed MAC protocol Possible PHY –IEEE a/g –OFDMA –MC-CDMA Full scale QoS guarantee –Prioritized access (DiffServ) Multi-hop operation Energy (E) signals –Access-E-Signal Prioritized access to wireless medium –Busy-E-Signal Calm down hidden stations Control transmission direction Adaptive multi-slot option –Control of capacity of Traffic Channel (TCH) –Increase of channel utilization Large-scale ad-hoc Mesh networks

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 4 W-CHAMB Protocol Stack Radio Resource Control (RRC) –Call Admission Control (CAC) –Dynamic Frequency Selection (DFS) –Power Control (PC) –Link Adaptation (LA) Media Access Control (MAC) –Multiple access to wireless medium –TDMA channels with dynamic TDD mode –Hidden station elimination (busy tone) –TDMA Traffic Channel (TCH) to connect neighbored Mesh points –Priority handling of packet data flows per Mesh point –Multiplex packets to TCHs under DiffServ Radio Link Control (RLC) –Un-/acknowledged data

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 5 Important Notice! All PHY parameters are examples only All durations are example values No assumption on PHY to be used is made Here:.11a OFDM like realistic PHY assumed

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 6 MAC Frame and Energy Signals Access Channel (ACH) Traffic Channel (TCH) Energy signal Channel (ECH) Single Value Busy-E-Signal (SVB) –Signal TCH occupied to hidden stations Double Value Busy-E-Signal (DVB) –Signal TCH occupied & Reverse (TDD) transmission requested ACH TCH1 … TCHn … ACH1-n 45us x n ECH 1-n 6us x n 6us x (n +m) + 28us Priori- tization Phase Contention Phase Transmission Phase nm28us Access-E-signal 1us2us 1us 6us Tx Off Tx On GuardSignal 1us 2us 6us Tx Off Tx On Guard Signal 1us2us 1us 6us Tx Off Tx On GuardSignal Single Value Busy-E- Signal (SVB) Double Value Busy-E- Signal (DVB)

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 7 Access Channel (ACH) ACH-Prioritization Phase –QoS-related contention –n binary Access-E-signals ACH-Contention Phase –Contention with m binary Access-E-signals –Higher success probability of an access packet –m depends on network size ACH-Transmission Phase –Transmission of request- packet –Network control data 6us x (n +m) + 28us Prioritization Phase Contention Phase Transmission Phase nm28us

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 8 Access Method (similar to HiperLAN/1) Mesh Points generate number [0;2 n -1] –According to QoS requirement Check number bit by bit –If 1, send E-signal –If 0, listen –If Mesh point hears E-signal, it defers from contention Winners of prioritization phase contend again –Draw random number from [0;2 m -1] Winner sends request packet (or other) via ACH Prioritized Access Method

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 9 Contention Sub-phase in ACH Guarantee single winner –In almost every contention –Even in high density mesh Failed Mesh Points –Initiate new contention in next frame –Use bigger contention number Increase chance to win Achieve fairness among Mesh points –With control algorithms of TCH Support bottle-neck Mesh Points (Mesh AP, portal) –Get bigger contention number Win more access trials More transmission chances 6us x (n +m) + 28us Prioritizati on Phase Contention Phase Transmission Phase nm28us

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 10 Transmission Sender Receiver Forward Transmission Send packet data via the reserved TCH(s). (Data might be station`s own or relay data) Signal SVB on the corresponding ECH(s) Send packet data via the reserved TCH(s) Signal DVB on the ECHs to request reverse TDD transmission Send packet data via the reserved TCH(s) in alternate direction Signal SVB(DVB) on the corresponding ECH(s) Reverse Transmission (On Demand TDD) Check available channels Send a request packet on ACH containing proposed TCHs and QoS description Accept the request by signaling SVB on ECH(s) corresponding to the selected TCH(s) Connection Setup Check available channels A TCH is defined on a per hop basis only.

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 11 Busy-E-Signal (6μs) –Does not contain user related information –Preamble not needed TCHs defined on disjoint time slots Busy-E-Signal to Calm Down Hidden Stations STA1 STA8 STA4 STA2 STA3 STA5 STA6 STA7 TCH3 ECH3 TCH4 ECH4

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 12 Capacity Increase: Release of a TCH After Specified Hang-on Time TCH freed by a Mesh Point –No packet in TCH buffer –Hang-on time expired Dependent on type of service Higher service level = longer hang-on time Longer value lower transmission delay –Packet-oriented behavior Example for hang-on time equal to 2 MAC frames

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 13 Dynamic Adjustment of Number of TCH for a Connection Mesh points contend for more TCHs if QoS cannot be satisfied Release TCH after hang- on time –Service specific Here –Hang-on time = 1 MAC frame –Max TCHs = 3 TCHs Efficient resource use even for rt-VBR

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 14 PDU Trains for better Efficiency PDU trains –Achieve higher efficiency –>2 adjacent TCHs used from source to same destination ACH ECHs TCH ACHECHs TCHs ACHECHsTCHs PDU 4.7µs 45µs Tx power on AGCAGC SYNSYN 36µs4.3µs Tx power off PDU 4.7µs 90µs Tx power on AGCAGC SYNSYN 81µs 4.3µs Tx power off PDU 27µs PDU 4.7µs Tx power on AGCAGC SYNSYN 126µs 4.3µs Tx power off PDU 135µs PDU 31.5µs

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 15 Medium Access Fully Decentralized No central control Mesh Points connect to neighbor pico-nets Any Mesh point is centre of a pico-net Power control/save mode depend on Mesh point Routing modes: –Bridge/router based –MANET Mesh points care for TCHs to neighbors

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 16 Traffic Schemes for Bottle-necks Bottle-necks (BNs), Mesh APs or portals –More in & out traffic than average –Powerful computational ability & plenty power supply & large memory –In right location Schemes for transmission between BNs –Several continuous TCHs reserved According to load Longer hang-on time values –Multiplexing of different traffic streams into reserved TCHs Expedited forwarding (EF) PHB (Per-Hop Behaviors) (DiffServ) [6] ACHECHsTCHs Hang-on times (unit: MAC frames) 1084 Prrmium Silver Bronze Gold TCHs BN STA

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 17 Better Multi-hop Support Transmission range Interference range Sensing range CTS RTS IEEE ACH-Req has knowledge about existing transmission W-CHAMB TCHs ECHs TCHs Transmitting in parallel in different TCHs Ongoing transmission between Mesh point 4 & 5 Mesh point 1 attempts to initiate a transmission to 2 (Instability, see [4])

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 18 QoS Support Efficient prioritized access –Up to 16 levels TCH Valid transmission time (VTT) –Associated with QoS type –Higher Qos level=higher value –Statistical interruption of lower level transmission TCH Hangon time –Depends on priority –Controls traffic performance (longer value lower transmission delay) Multi-slots capability for higher throughput QoS guarantee under heavy load –Due to channel-oriented structure No probing packets for CAC (Call Admission Control) –Observe TCHs & ECHs

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 19 Synchronization of W-CHAMB [5] Periodic Beacons –Every Mesh Point participates in generation –Analysis by recipients –In full ad-hoc operations mode –Able to support large scale networks –Support multi-hop operation –Support Mesh Point mobility Clock shift compensation algorithm –Combat clock drifts –Accuracy for one-hop network = 0.4±0.1 µs

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 20 W-CHAMB Summary Channel-Oriented On top of any existent or future PHY layer Decentral Control Scheme Flexible Multi-Hop (Mesh) Support Perfect Ad-Hoc Mesh Networking Sophisticated QoS Guarantee Support of large number of Mesh points in ad-hoc Mesh

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 21 References [1]. B. Xu, B. Walke, W-CHAMB: A Wireless Channel-oriented Ad-hoc Multihop Broadband Network – Comparison with IEEE In Proc. European Wireless99, Munich, Germany, October pp [2]. B. Xu, B. Walke, Protocols and Algorithms supporting QoS in an Ad-hoc Wireless ATM Multihop Network, in Proc. EPMCC99, pp , Paris, France, Mar [3]. M. Lott and B. Walke, Performance of theWireless Ad hoc Network W- CHAMB, in Proc. European Wireless (EW99), (Munich, Germany), Oct [4]. S. Xu and T. Saadawi – Does the IEEE MAC Protocol Work Well in Multihop Wireless Ad Hoc Networks? IEEE Communications Magazine, June 2001, pp [5]. R. Zhao, and B. Walke: A Synchronization Scheme for the Wireless Channel-oriented Ad-hoc Multi-hop Broadband System (W-CHAMB). In Wireless World Research Forum, Zurich, Switzerland, July 2003 [6]. RFC 2598, An Expedited Forwarding PHB, June 1999

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 22 Simulation MAP MAP1 MAP2 MAP5MAP4 MAP6 MAP3 STA1 STA2 STA3 STA4 STA5 STA6 1 hop 2 hop2 A two hop scenario MAP:Mesh AP STA:Station Comparing maximum through- put, & W-CHAMB –PHY: a (OFDM) –Packet size = 9 symbols W-CHAMB QPSK¾, 16QAM¾, 64QAM¾ QPSK¾, 16QAM¾, 64QAM¾ W-CHAMB MAC –Number of TCH & ECH 16 –TCH 45µs –Energy signal 6µs –ACH (6*4+8*4+28)µs = 100µs

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 23 Maximum Throughput

doc.: IEEE /0991r0 Submission September 2004 Rui Zhao, ComNets, RWTH Aachen UniversitySlide 24 Thanks for your attention