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DSC leveraging uplink RTS/CTS control

This paper investigates the performance of DSC (Distributed Switched Channel) in dense scenarios and proposes the use of RTS/CTS (Request-to-Send/Clear-to-Send) control to mitigate drawbacks and improve performance gains. The impact of frame size on RTS-enabled DSC stations is studied using NS-3 simulation environment.

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DSC leveraging uplink RTS/CTS control

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  1. DSC leveraging uplink RTS/CTS control Authors:

  2. Outline • Context • Simulation Environment: NS-3 • Simulation scenario and assumptions • RTS/CTS threshold setting • Impact of frame size on DSC+RTS • Conclusions • References • Appendix M. Shahwaiz Afaqui (UPC)

  3. IEEE 802.11ax enabled devices are expected to maintain and reduce energy consumed per successful information bit. • However, different amendments that are proposed to increase the efficient operation of PHY and MAC layer would work against the aforementioned requirement. • Since interference management is of paramount importance in dense deployments, IEEE 802.11ax aspires to intelligently utilize RTS/CTS method based on observed channel conditions on per node basis. • In [1], the authors highlight the possible mechanism through which an AP can control the RTS/CTS policy for the associated stations. • It has been shown in our previous presentations [2-3] that the use of DSC can increase per-user throughput in dense scenarios over the cost of increase in Frame Error Rate (FER) due to increased number of hidden nodes. • In this submission we, • investigate the performance of DSC, • By utilizing intelligent RTS/CTS control method as means to mitigate the drawbacks associated with DSC and to improve performance gains. • recommend method to select threshold to enable RTS/CTS on each node. • study the impact of frame size on RTS enabled DSC stations. 1. Context M. Shahwaiz Afaqui (UPC)

  4. NS-3 • Allows the study of protocols and network performance of large-scale systems in a controlled and scalable environment. • Main characteristics, • Discrete event simulator • Packet level simulator (layer 2 and above) • Layered architecture • Free and open source • Frequent updates ( latest version ns 3.23- release date 14-05-2015) • Large number of protocol implementations and models available, • TCP, UDP • IPV4, IPV6, static routing • IEEE 802.11 and variants, WiMAX, LTE • IEEE 802 physical layer • Mobility models and routing protocols • Ability to design indoor, outdoor or hybrid networks • etc. 2. Simulation Environment: NS-3 M. Shahwaiz Afaqui (UPC)

  5. Limitations of NS3 • Simplified abstraction of PHY layer • MPDU aggregation is not yet mature and thus not used within these simulations. • IEEE 802.11ac model has not yet been developed and current results focus on IEEE 802.11n. 2. Simulation Environment: NS-3 M. Shahwaiz Afaqui (UPC)

  6. Topology • multi-floor residential building, • 5 stories • 2×10 apartments per story. • Apartment size: 10m×10m×3m. • 1 AP placed randomly in each apartment at 1.5m height. • channelselected randomly for each cell. • Three channel scheme (1, 6, 11) 1/3 of the cells share the same channel • 5 STAs placed randomly around their respective AP. 3. Simulation scenarios and assumptions M. Shahwaiz Afaqui (UPC)

  7. Frequency band: focused on 2.4GHz , • Intended to investigate the impact of DSC in a band that is more restricted in dense environments. • Traffic: UDP CBR uplink transmission in saturation conditions is considered, • Worst case in terms of contention. • Pathloss model: Hybrid Building Propagation loss model [12], • obtained through a combination of several well known pathloss including indoor (through walls, floors) and outdoor (urban, suburban, open). • We simulated specific scenarios (with same STA and AP positions) with and without utilizing the DSC and RTS/CTS control method. • Additional simulation details are provided in the appendix. 3. Simulation scenarios and assumptions M. Shahwaiz Afaqui (UPC)

  8. FER of nodes used to enable and disable RTS/CTS control from the AP. • i.e. if FER of a node is greater than RTSThrehold→ enable RTS/CTS for that node. • Formula: RTSThreshold= N x AvgFER • Improvement over DSC-enabled network for longest frame (MCS0 with maximum MSDU size of 2302bytes) : 4. RTS/CTS threshold setting • ~14% improvement in throughput over DSC when RTSThrehold = 0.6 x AvgFER • N = 0.6 used in all the following experiments. M. Shahwaiz Afaqui (UPC)

  9. From previous slide, intelligent use uplink RTS/CTS control can have multifold benefits. • To build on the proposed argument, different frame sizes are used (i.e. 1000, 1600 and 2302Bytes) for comparative evaluation with RTS enabled DSC nodes (RTSDSC) with, • IEEE802.11n network with RTS disabled DSC nodes (NORTSDSC) • IEEE802.11n network with RTS disabled non-DSC nodes (NORTSNODSC) 5. Impact of frame size on DSC+RTS • Up to 55% improvement in throughput (longest frame duration). • RTS control adds to benefits of DSC. • Maximum FER improvements are achieved for small frame size. M. Shahwaiz Afaqui (UPC)

  10. More efficient DSC is achieved when combined with uplink RTS/CTS control, as proposed in [1]. • One of the major drawbacks of DSC scheme was the increase in FER due to hidden nodes  RTS enabled DSC network can mitigate the aforementioned problem. • We propose to intelligently enable RTS/CTS, • The AP knows uplink FER of all associated STAs • AP decides which STA uses RTS/CTS based on: • Threshold FER derived from average FER in the cell (RTSThreshold = 1.4 x AvgFER) • Frame size (excessive overhead for small packets) 6. Conclusions M. Shahwaiz Afaqui (UPC)

  11. [1] Sigurd Schelstraete, IEEE 802.11-15-0059, Uplink RTS/CTS Control. [2] Eduard Garcia-Villegas , IEEE 802.11-15-0027, Simulation-based evaluation of DSC in residential scenario. [3] Eduard Garcia-Villegas, IEEE 802.11-15-0371, Proposal and simulation based evaluation of DSC-AP Algorithm 7. References M. Shahwaiz Afaqui (UPC)

  12. PHY parameters Simulation assumptions M. Shahwaiz Afaqui (UPC)

  13. MAC parameters • Simulation parameters M. Shahwaiz Afaqui (UPC)

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