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Performance Analysis and Evaluation of WiMedia UWB MAC protocols Masters Thesis Proposal Rukhsana Ruby University of Victoria

Performance Analysis and Evaluation of WiMedia UWB MAC protocols

Feb 01, 2016




Masters Thesis Proposal Rukhsana Ruby University of Victoria. Performance Analysis and Evaluation of WiMedia UWB MAC protocols. History of IPTV. IP/TV – First Internet Video product, 1995 An IPTV over DSL broadband by Kingston Communications, 1999 - PowerPoint PPT Presentation
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  • Performance Analysis and Evaluation of WiMedia UWB MAC protocols

    Masters Thesis ProposalRukhsana RubyUniversity of Victoria

  • History of IPTVIP/TV First Internet Video product, 1995An IPTV over DSL broadband by Kingston Communications, 1999IPTV service by AT&T, 2006 300 channels in 11 citiesNowadays Broadband connections are widespread Served more than 200 million households, 2005Will grow to 400 million by 2010

  • IPTV in-home distributionEthernet solution Rewiring is expensive and awkwardNo new-wires solution availability and achievable performance is uncertainWireless solution

  • OutlineExisting WLAN/WPAN Technologies UWB OverviewSummary of UWB ExperimentationMethodologyPerformance ResultsDiscussion of limitations of current workFuture Research

  • Existing WLAN TechnologiesSupport low data rate (11 to 54 Mbps)802.11b and 802.11a/g (Achieve less than 50% of actual data rate)Work in 2.4 and 5 Ghz frequency band. avg throughput of 802.11g 10 Mbps Contention based MAC802.15 family supports maximum 55 Mbps data rate in very short range (10 metre)

  • UWB OverviewUWB is a radio technologyUWB is regarded as the best technology for the high-speed wireless PAN. Why?High speed at short rangeUp to 480Mb/s currently. Ultimately support the speed at Gbit/s.In the range of 10 meters.Radio spectrum: 3.1 to 10.6 GHz (very large).Low energy consumption level

  • UWB MACTime is divided into super frames.256 MAS (Each MAS is 256us)Beacon Period (First 32 MAS)Contract and Expand ableData PeriodDRP and PCA (Like 802.11e)Acknowledgement PolicyNo, Block and Immediate Acknowledgement

  • Overview of EDCAFUser traffic is differentiatedMinimum contention window sizeRetry limitArbitration inter-frame spaceTXOP limitBackoff counter is decremented ahead of slot time no matter slot is busy or idleUser traffic is denoted by ACi {i = 1, 2, 3,4}

  • Discussion (UWB Experimentation)Tradeoff between TxRate and Retry LimitThroughput, Latency tradeoff between clustered and scattered reservation.Fig. Goodput vs. TxRate and Retry LimitFig. Throughput vs. Reservation Pattern

  • Renewal Reward TheoremOther stations transmissionTagged stations transmission

  • EDCAF AnalysisFig: Illustration of renewal cycleCCSFrame service time = (E[R] + E[B])*generic slot

  • EDCAF Analysis(Cont.)Expected number of backoff slotsExpected number of retransmissionsTransmission probabilityCollision probability of AC2 stationCollision probability of AC1 station

  • EDCAF Analysis(Cont.)Generic slot calculationFrame service time for AC1 station

  • EDCA Analysis (Cont.)Frame service time for low priority station are two partsNumber of generic slots in zone 2Pre-backoff waiting period

    First part of frame service time for AC2 stationEach pre-backoff waiting period lengthTotal pre-backoff waiting periodFrame service time for AC2 station

  • EDCAF Analysis (With DRP)No. of DRP faced by AC1 stationFrame service time for AC1 stationFrame service time for AC2 stationTQ is the summation of DATA tx time, ACK tx time, SIFS and guard time

  • Simulation MethodologySimulator ns-2Modified TKN implementation of 802.11e 802.11 physical layer to UWB Incorporate super frame structureInsert some hard drp in super frame

  • Simulation ScenarioAC2 stationAC1 stationBase stationRadius of circle: 20 metreTx range: 250 metreFreespace propagation modelData rate: 480 MbpsMAC layer Packet size with all overhead: 1500 bytesMin contention window for AC1: 7Min contention window for AC2: 15Retry limit: 7AIFS1: 2 slotsAIFS2: 4 slots

  • Saturated Simulation and Analysis Results (Without and with DRP)Fig. Frame service time without DRP Fig. Frame service time with DRP Beacon period: 1-32DRP: 100-132, 200-232

  • Unsaturated AnalysisPre-backoff waiting period per backoff segment for AC2Prob of no AC1 station transmits in zone 1Collision Prob of AC2 station Collision Prob of AC1 station

  • Unsaturated Simulation and Analysis Results (Without DRP)Fig. Frame service time without DRPFig. Frame service time without DRPNumber of stations: 10Offered Load: 0.00086 frames/slot

  • DiscussionDifficult to get the exact pre-backoff waiting period for AC2 station.Due to propagation delay perfect simulation result is not possible.Frame service time in the presence of DRP is also approximation.

  • Future ResearchExtend the model to allow heterogeneous traffic.Send video over UWB, find performance metrics and improvement scope.Distributed algorithm for DRP allocation

  • Thank You! Questions?

    The term IPTV first appeared in 1995 with the founding of Percept Software. Precept designed and built an internet video product named "IP/TV". Kingston Communications, a regional telecommunications operator in UK, launched KIT (Kingston Interactive Television), an IPTV over DSL broadband interactive TV service in September 1999 after conducting various TV and VoD trials. In 2006, AT&T launched its U-Verse IPTV service. AT&T offered over 300 channels in 11 cities with more to be added in 2007 and beyond. In the past, this technology has been restricted by low broadband penetration. IPTV has grown at dramatic pace to more than 200 million households worldwide by the year 2005 due to the availability of broadband access. It will grow to more than 400 million by 2010

    There are several solution for IPTV in-room access. One is ethernet solution, however rewiring turns out to be very expensive, and running cables along corners or outside houses is also very awkward. There are several no new-wires solutions and many industries have come up with some technologies to transport ethernet frames over existing household cable, phone and power wires, but their achievable performance and availability is still uncertain.So far wireless solution is assumed as the best. Existing wireless technologies support very low data rate. For example 802.11b can support raw data rate up to 11Mps and 802.11a/g up to 54 Mbps. Apparently we can say these data rate is sufficient for high quality video streaming. However physical and mac layer overhead through these technologies we can only achieve 50% of data rate. IEEE 802.11 devices work in the same 2.4 and 5 GHz unlicensed frequency bands as other home devices such as cordless phones and microwave ovens which causes interference and reduces SNR further. It is found that average throughput of 802.11g devices is around 10 Mbps. Contention based MAC also reduces achievable throughput due to channel idle and collision times. The reasons why UWB is regarded as the best technology is due to its high data rate. It works 3.1 to 10.6 GHz frequency range to accommodate more device groups and thus supports such huge raw data rate. Since UWB devices consume very low power, uwb has very little interference with other devices.Time is divided into super frames, each super frame is 65.536 ms and is divided into 256 MAS where each MAS is 256 us. Super frame is again divided into beacon period and Data transmission period. Beacon period is usually first 32 MAS, however its contract and expand able.Two kinds of data transmission is possible during data transmission period of super frame. DRP period allows user exclusive hold of the channel, and it has also some variations; hard drp and soft drp. Another kind of data transmission of UWB PCA is just like EDCA. Three kinds of acknowledgement are supported in UWB MAC; No acknowledgement (receiver does not acknowledge sender if it receives data successfully), block (receiver send acknowledgement after receiving certain number of data), immediate acknowledgement (receiver sends ack just after receiving the data pkt) There are two tradeoffs we have got from our experimentation. A higher TxRate implies higher packet loss ratio at the same received SNR, and a higher retry limit can reduce packet loss but may reduce goodput. with a clustered reservation, there are fewer turnarounds in a superframe, which leads to less guard time and higher channel utilization. On the other hand, for the same number of reserved slots, a clustered reservation will increase serviceinterval, which potentially increases access latency. Therefore, in order to increase throughput and reduce latency,we have to strike a balance between scattered and clustered reservations, particularly for video traffic.A level 1 renewal cycle X is defined as the period between the end of a channel busy event to the end of the next one. From the viewpoint of the tagged station, a level 1 cycle is of X1 if the busy channel is caused by transmission from other stations and it will be of type X2 if its own transmission causes the channel busy. A level-2 renewal cycle Y is from the end of an X2 cycle to the end of the next X2 cycle. A level-2 cycle can be of type Y1, in which transmission results in a collision, or of type Y2, in which the transmission succeeds. A level-3 renewal cycle Z is from the end of a Y2 cycle to the end of the next Y2 cycle. The successful transmission of a frame in Z cycle can be viewed as the reward for the level-3 renewal cycle.

    The top figure shows the high level view of tagged stations renewal cycle before a successful transmission. It follows geometric distribution due to collision probability. Below two figures show how backoff counter is decremented without interruption and when it is interrupted by other stations transmission. Left side of below shows tagged station chooses backoff counter 3 and therefore it passes 3 backoff slots before transmission. Right side of below figure shows how backoff counter is decremented when it is interrupted by other stations transmission. Initially it chooses backoff counter 3 and eventually it goes for two backoff and fixed slot. So we can say no matter how many times backoff counter is interrupted , no. of slots it need to pass is same as it chose initially. Therefore we can say frame service time is the summation of number of retransmission and number of backoff slots multiplied with generic slot. Above figure shows how pre-backoff waiting period is calculated. Pre-backoff period happens when al least one AC1 station transmits in zone1, ac2 station does not get chance to decrement its backoff counter. It follows a geometric distribution with the probability no ac1 station transmits in zone 1. In unsaturated case all the equations will be changed. However the approach is same as saturated case. Since in unsaturated case there is always no packet in queue we have introduced another term rho which is the fraction of frame service time and frame inter-arrival time. Therefore we can say tx probability in a particular slot is rho multiplied with tau. In this case we have to solve six equations instead of 4 equations.