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Access Layer

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Yang Du – 1st expert on this subject based on the ideXlab platform

  • Analysis of Performance of Unsaturated Slotted IEEE 802.15.4 Medium Access Layer
    , 2020
    Co-Authors: Shuai Fang, Qiang Xu, Lu Rong, Yang Du

    Abstract:

    In this paper, we analyze the uplink performance of unsaturated slotted IEEE 802.15.4 medium Access Layer using the Markov chain model and the theory of M/G/1 queues. We flnd that retransmission due to collision of packets plays a very important role in under- standing the mechanisms of the slotted CSMA-CA algorithm, with its occurance indicating the conventional assumption about independent carrier sensing is no longer valid. The impact of some important system parameters and operational conflgurations on system performance is in- vestigated. The validity of our model is demonstrated by very good agreements between our model results and Network Simulator 2 (ns-2) simulations for all cases over a wide range of tra-c load, beacon order and number of ∞ows. Park etal. (1) modelled IEEE 802.15.4 slotted CSMA-CA under saturation conditions. Pollin etal. (2) also considered saturated cases, then modelled unsaturated tra-c by adding flxed number of delay slots. Since IEEE 802.15.4 has been designed for low-data rate applications, an analysis based on unsaturated tra-c is more desirable. Misic etal. modelled both uplink and downlink yet their results seem to diverge signiflcantly from their simulation results (3,4). Yet collision was ignored in (2), because it was assumed that collided packets were not retransmitted. In (3) although collision was mentioned, yet it was touched brie∞y without su-cient treatment for such performance-determining factor. Not only collision increases energy consumption and latency, when retransmission due to collision is performed, it has a fundamental implication on the analytical model as well. In addition, the efiect of delay line should be adequately assessed. A delay line refers to the situation when a node is about to enter the Clear Channel Assessment (CCA) state, it flnds that the remaining time of the current superframe is not long enough for two successful CCA and transmission of the packet, and in turn holds the CCAs to the beginning of next superframe after beacon. This detail was ignored in (2). Although it was considered in (3), its efiect on key system performance descriptors such as the probability of collision was not clearly identiflable. A careful treatment of the aforementioned issues provides the motivation for the current work. The analytical tools we resort to are the Markov chain model and the theory of M/G/1 queues. The validity of our model is demonstrated by very good agreements between our model results and ns-2 simulationss for all cases over a wide range of tra-c load, beacon order and number of ∞ows. In this paper, we use m for macMaxCSMACABackofis, and n for aMaxFrameRetries for nota- tional convenience. Let us deflne fi to be the probability of sensing channel busy during the flrst CCA slot; and fl to be the probability of sensing channel busy during the second CCA slot; and ∞ to be the probability to collide among nodes during transmission; and ? to be the probability to sense channel within an arbitrary slot; and – to be the probability for a queue to be empty after an empty slot; and ” to be the probability to enter delay line after backofi countdown; and … to be the probability that queue is empty immediately after packet departure; and s(t) to be the stochastic process that represents either of the listed states | backofi, CCA, sending packet, waiting for acknowledge, receiving acknowledge, and queue being empty; and b(t) to be the stochastic process that counts discrete difierent backofi stages and sensing channel stages; and c(t) to be the counting stochastic process. The process (s(t); b(t); c(t)) is used to deflne the state of a node, where the state can be any state in Fig. 1. We also denote by L(s; b; c) the length of state xs;b;c in times of backofi period. Lcca, Lpkt, Lack, Lwt, Ldly, and Lcap stand for duration of double CCAs, transmission and receiving an ACK, waiting for ACK, length of delay line, and length of CAP, respectively. We consider a cluster with N identical nodes. For a single node, we present our discrete-time Markov model for the 802.15.4 slotted CSMA-CA mechanism under unsaturated tra-c conditions in Fig. 1 in which all states are formed in (s(t); b(t); c(t)).

  • Performance analysis of unsaturated slotted IEEE 802.15.4 medium Access Layer
    IET International Communication Conference on Wireless Mobile and Computing (CCWMC 2009), 2009
    Co-Authors: Wei Wang, Qiang Xu, Shuai Fang, Honglin Hu, Lu Rong, Yang Du

    Abstract:

    In this paper, we analyze the uplink performance of unsaturated slotted IEEE 802.15.4 medium Access Layer using the Markov chain model and the theory of M/G/1 queues. In our treatment the emphasis is paid to retransmission due to collision of packets, since it plays a very important role in the behavior of the slotted CSMA-CA algorithm. The validity of the proposed model is demonstrated by good agreements between the model results and Network Simulator 2 (ns-2) simulations.

Nixon Mtonyole – 2nd expert on this subject based on the ideXlab platform

  • Software Based Traffic Separation at the Access Layer
    , 2020
    Co-Authors: Yona Andegelile, Nixon Mtonyole

    Abstract:

    Access Network is the subscriber part of the telecommunications network or the network connecting the subscribers to the Internet Service Providers (ISP) [1]. In many countries including Tanzania Access network is still predominantly made up of the copper cable based or other point to point wireless connections. This has kept the network in large proportions passive, inflexible and relatively unreliable [2]. This traditional network has long been tailored to the services generally provided i.e. voice, leased lines, Internet, corporate data and video conference, sometimes each provided by separate equipment and networks. This paper presents the study on approaches used by ISP in Tanzania to separate traffic in the Access network. The paper also presents the effective way of traffic separation, whereby multiple hardware used to separate traffic currently has been replaced with single hardware. The traffic separation technique is based on creating logical links (software based) for each traffic type inside single physical link, providing a differentiated QoS support for each type of traffic according to its individual QoS requirements.

  • Voice Quality Analysis for Software based Traffic Separation at the Access Layer of Hierarchical Design Model
    International Journal of Computer Applications, 2014
    Co-Authors: Nixon Mtonyole, Yona Andegelile

    Abstract:

    In many countries including Tanzania Access network is still predominantly made up of the copper cable or point to point wireless connections. This has kept the network in large proportions passive, inflexible and relatively unreliable. Software based traffic separation at the Access Layer is a technique that is used to reduce the number of physical links to customer premises. This paper performs quality analysis for voice transmitted through such links (i.e. logical links) and it is observed that there is no major difference as to when dedicated physical links are used. General Terms Voice quality, Traffic separation, Hierarchical design model

F Catthoor – 3rd expert on this subject based on the ideXlab platform

  • performance analysis of slotted carrier sense ieee 802 15 4 medium Access Layer
    IEEE Transactions on Wireless Communications, 2008
    Co-Authors: Sofie Pollin, Mustafa Ergen, Sinem Coleri Ergen, Bruno Bougard, Der L Perre, Ingrid Moerman, Ahmad Bahai, Pravin Varaiya, F Catthoor

    Abstract:

    Advances in low-power and low-cost sensor networks have led to solutions mature enough for use in a broad range of applications varying from health monitoring to building surveillance. The development of those applications has been stimulated by the finalization of the IEEE 802.15.4 standard, which defines the medium Access control (MAC) and physical Layer for sensor networks. One of the MAC schemes proposed is slotted carrier sense multiple Access with collision avoidance (CSMA/CA), and this paper analyzes whether this scheme meets the design constraints of those low-power and low-cost sensor networks. The paper provides a detailed analytical evaluation of its performance in a star topology network, for uplink and acknowledged uplink traffic. Both saturated and unsaturated periodic traffic scenarios are considered. The form of the analysis is similar to that of Bianchi for IEEE 802.11 DCF only in the use of a per user Markov model to capture the state of each user at each moment in time. The key assumptions to enable this important simplification and the coupling of the per user Markov models are however different, as a result of the very different designs of the 802.15.4 and 802.11 carrier sensing mechanisms. The performance predicted by the analytical model is very close to that obtained by simulation. Throughput and energy consumption analysis is then performed by using the model for a range of scenarios. Some design guidelines are derived to set the 802.15.4 parameters as function of the network requirements.

  • wlc10 5 performance analysis of slotted carrier sense ieee 802 15 4 medium Access Layer
    Global Communications Conference, 2006
    Co-Authors: Sofie Pollin, F Catthoor, Mustafa Ergen, Sinem Coleri Ergen, Bruno Bougard, Ingrid Moerman, Ahmad Bahai, L Van Der Perre, Pravin Varaiya

    Abstract:

    The IEEE 802.15.4 standard defines the medium Access control (MAC) and physical Layer for sensor networks. One of the MAC schemes proposed is slotted carrier sense multiple Access with collision avoidance (CSMA/CA), and this paper analyzes whether this scheme meets the design constraints of low-power and low-cost sensor networks. The paper provides a detailed analytical evaluation of its performance in a star topology network for both saturated and unsaturated periodic traffic.The form of the analysis is similar to that of Bianchi for IEEE 802.11 DCF only in the use of a per user Markov model to capture the state of each user at each moment in time. The key assumptions to enable this important simplification and the coupling of the per user Markov models are however different, as a result of the very different designs of the 802.15.4 and 802.11 carrier sensing mechanisms. The performance predicted by the analytical model is very close to that obtained by simulation. Throughput and energy consumption analysis is then performed and design guidelines are derived.