A STUDY ON FAST AND SAFE WLAN COMMUNICATION PROTOCOL FOR FACTORY AUTOMATION CONTROL SYSTEMS Lam Duc Khai Contents 1 Introduction 1. ee 1⁄2 Research Objectives. Thesis Hierarchy Industrial Wireless Communication Overview 2.2 Wireless industrial networks for factory automation controls .2 Industrial Wireless Communication Technologles.3 Time Synchronization Protocols .1 NTP Synchronization Protocol.2 GPS Synchronization Protocol. PTP Synchronization Protocol.4 Summary 3 iWLAN Communication Protocol 35 3.2 Proposed iWLAN Protocol .1 | Proposed Transmission Protocol.2 Proposed MU PDMA DL Transmission Technique.
Performance Comparisons Under Non-Error Based Transmissions. 43 Control Duration Analysis Under Error Transmissions Based. 47 Control Duration Evaluation Under Error Transmissions Based .1 Control Duration AnalysisResults. Control Duration Simulation Results.
ee 58 iWLAN MAC Hardware Design 62 4. WLAN MAC Hardware Design 62 4.3 Proposed iWLAN MAC Hardware Design for Master.4 Proposed iWLAN MAC Hardware Design for Slave.5 Hardware Simulation Results. ee ees 72 PTP Time Synchronization Protocol for iWLAN System 74 5.2 Proposed PTP Protocol. Proposed Low Overhead PTP Message Exchanges .4 Time Synchronization Accuracy Evaluations.
ee 86 PTP Hardware Design for iWLAN System 89 6. ee 89 62 Master PTP Hardware Design .3 Slave PTP Hardware Design .4 Hardware Simulation Results. Ặ Q Q HQ ee 7 Conclusion and Future Work 7A Conclusion 2. 0 eeeee Bibliography iv List of Tables 11 Research objectives.
ee 12 21 Performance comparisons between BT, Zigbee and iPCF technologies .2 Time synchronization offset error comparisons.1 System configuration parameters.3 Performance comparisons under non-error transmissions based .4 Additional parameters for the performance evaluation under error transmis- sions based”. NF gma VOM.1 FPGA utilization of MAC hardware system .1 Transmission Overheads Comparison .1 Message_Type values. 2 ee 92 List of Figures 11 Industrial communication system. 10 21 Industrial wireless sensor network 16 2.2 Industrial wireless system for factory automation controls.
17 243 Wireless channel characteristics [6] .4 Bluetooth transmission protocol with SCO and ACL .5 Zigbee transmission protocol with superffame.11 PCF transmission protocol.7 PROFINET - iPCF protocol.8 Clock synchronization for industrial wireless system .9 NTP synchronization protocol 29 2.10 GPS synchronization protocol 31 211 PTP synchronization protocol 32 3.1 FA wireless communication system model.2 Proposed FAiWLAN Protocol.3 Transmission sequence operations of proposed FA iWLAN protocol .4 MU-MIMO SDMA DL technique .5 Sounding procedure in MU-MIMO SDMA DL technique .6 Proposed MU-PDMA DL technique.7 Proposed MU-PDMA DL frame format .8 DL and UL frame formats of Conv.9 DL and UL frame formats of Conv.10 DL and UL frame formats of Prop.11 Communication chain with transition probabilities of (WLAN system 49 3.12 Packet Error Rate (PER) simulation results for UL and DL of the proposed 3.13 Numerical results of control duration per SL for the proposed system at the probability threshold = 1, working duration = 1 year and different SNR values 2ee 3.14 Numerical results of control duration per SL for the proposed system at SNR = 17 dB, working duration = 1 year and different probability threshold 3.15 Numerical results of control duration per SL for the proposed system at SNR = 17 dB, working duration = 1 hour and different probability thresh- oldvalues 2.17 Control duration per SL comparison between Bit-based and Abstracted- based PHY modelsatNÑ=32.18 Control duration per SL simulation results at SNR=17.19 Control duration per SL simulation resultsatN=32.20 System Error Rate (SER) atN=32 .21 The probability of retransmission number (M) of the proposed system at different SNR values 2.1 WLAN MAC Hardware Design Architecture. iWLAN MAC Hardware Design ArchitectureofMS .4 DL-MPDU dataformat.5 SYNC-MPDU dataformat.6 UL-MPDU dataaformat.7 State machine for PM modules of MS 4.8 iWLAN MAC Hardware Design ArchitectureofSL.9 State machine for PM modulesofSL.10 MS-SL communication system for MAC hardware design verification .11 Transmission protocol simulation results of the MAC hardware implemen- tation between MS andSLI.12 Transmission protocol simulation results of the MAC hardware implemen- tation between MS and SL1-8, in case no transmission error .13 Transmission protocol simulation results of the MAC hardware implemen- tation between MS and SL 1-8, in case UL transmission error of SLL.1 Conventional PTP frame exchanges .2 Improve PTP frame exchanges. iWLAN communication with adapted PTP message exchanges .4 PTP message exchanges oniWLAN protocol.5 iWLAN transmission with aggregated PTP frame formats.6 iWLAN hardware system with adapted PTP protocol .7 Offset Error of the conventional PTP protocol.8 Offset Error of the proposed PTP approach.9 Histogram of Offset Error of the conventional PTP protocol.10 Histogram of Offset Error of the proposed PTP approach .1 MAC and PTP ArchitectureofMS.2 PTP Hardware DesignofMS. Sync+Delay Response message format .4 Follow_Up message format 92 6.5 Delay Request message Íormat.ẶẶẶẶ Ốc 93 67 MAC and PTP ArchitectureofSTA .8 PTP Hardware DesignofSL .10 MS-SL communication system for PTP hardware design verification.11 Synchronization protocol simulation results of the PTP hardware imple- mentation between MS and SL 1, in case no transmission error .12 Synchronization protocol simulation results of the PTP hardware imple- mentation between MS and SL 1, in case UL transmission error of SL1.
100 viii List of Abbreviations AC Access Categories ACL Asynchronous Connectionless AIFS Arbitration Interframe Space AP Access Point BER Bit Error Rate BFRP Beamforming Report Poll BPSK Binary Phase Shift Keying BT Bluetooth CAP Contention Access Period CB Compressed Beamforming CBC-MAC Cipher Block Chaining Message Authentication Code cc CRC Check CCA Clear Channel Access CFP Contention Free Period CG CRC Generation CP-Poll Contention Free Poll cP Contention Period CRC Cyclic Redundancy Check CSIT Channel State Information at Transmitter CSMA/CA Carrier Sense Multiple Access with Collision Avoidance CTI Crosstalk Interference CW Contention Window DCCS Distributed Computer Control System DCF Distributed Coordination Function DIFS DCF Interframe Space DL Downlink DSSS Direct-Sequence Spread Spectrum EDCA Enhanced Distributed Channel Access FA Factory Automation FDMA Frequency Division Multiple Access FH Frequency-Hopping FHSS Frequency-Hopping Spread Spectrum. FSM Finite State Machine G-FSK Gaussian Frequency Shift Keying GPS Global Positioning System GTS Guaranteed Time Slot HC Header Check HCCA HCF Controlled Channel Access HCF Hybrid Coordination Function HG Header Generation LAN Local Area Network MAC Media Access Control MIMO Multiple Inputs and Multiple Outputs MPDU MAC Protocol Data Unit MS Master MSDU MAC Service Data Units MU Multi-User NDP Null Data Packet NDPA Null Data Packet Announcement NTP Network Time Protocol OFDM Orthogonal Frequency Division Multiplexing OQPSK Offset Quadrature Phase Shift Keying PC Personal Computer PCF Point Coordination Function PDMA Packet Division Multiple Access PHY Physical Layer PIFS PCF Interframe Space PIN Personal Identification Number PLC Programmable Logic Controller 2 PLCP Legacy Physical Layer Convergence Protocol PPDU PLCP Protocol Data Unit PR PLCP Reception PT PLCP Transmission PTP Precision Time Protocol QAM Quadrature Amplitude Modulation QPSK Quadrature Phase Shift Keying QoS Quality of Service RC4 Rivest Cipher 4 Rx Reception SCO Synchronous connection oriented SDMA Space Division Multiple Access SER System Error Rate SFH Sub-Frame Header SFT Super Frame Structure SIFS Short Interframe Space SIL Safety Integrity Level SL Slave SNR Signal-to-Noise Ratio SYNC Synchronization TDD Time Division Duplex TDMA Time Division Multiple Access TXOP Transmit Opportunities Tx Transmission UL Uplink WEP Wired Equivalent Privacy WLAN Wireless Local Area Network WPA Wi-Fi Protected Access WSN Wireless Sensor Network iPCF industrial PCF iRB industrial Robot iWLAN industrial WLAN List of Symbols a Clock drift factor Dụ›s Communication path delay from the MS to SL Dsom Communication path delay from the SL to MS cMS CLK Frequency of the MS clock SL CLK Frequency of the SL clock Sosfeet Frequency difference between SL and MS clocks k Number of control duration within the working duration Number of retransmissions Current number of retransmission Number of SLs in the communication system Number of errors occurring during the m'" retransmission Number of SLs, which need to communicate with MS Number of errors occurring when MS communicates with n, SLs Number of SLs to which MS transmits the DL frames Number of SLs which transmits the UL frames to MS Number of SLs which fail to receive the DL frames Number of SLs which successfully receive the DL frames Number of SLs which fail to transmit the UL frames to MS k-combination from a set of n elements Timing difference between SL and MS clocks Packet error rate of UL transmission Packet error rate of DL transmission Probability that the system errors occur after Ta Probability that no system errors occur after 7,„ Probability that the system errors occur after Tyg Probability that no system errors occur after 7;„„ PI year Probability that the system errors occur after | year py Probability that the system errors occur after M recommunications pi Expected threshold of probability of the system errors Nal Mie Probability that z„„ errors occur when n,, SLs transmit the UL frames to MS P, Hung Probability that n, errors occur when MS communicates with n, SLs pm ” Probability that the errors occur after m re-communications Twa Working duration Tea Control duration Tyne SYNC frame transmission duration cam Communication duration Trecom Re-communication duration Tsigs SIFS duration Ta DL frame transmission duration Tut UL frame transmission duration T sounding Sounding duration Tsr Control duration per SL Theaders PHY and MAC headers transmission overhead Theacon Beacon transmission duration Tefend CF-End tranmsission duration Tpigs PIFS duration Duration of the total m re-communications Tm recom Tạ Control duration after m re-communications 1s Stamped time at MS after transmitting the Sync frame 8L Timing at SL when MS stamps íŠ th Stamped time at SL after receiving the Sync frame MS fod Stamped time at MS after transmitting the Follow_Up frame SL ft đ Stamped time at SL after receiving the Follow-Up frame LÊN Stamped time at SL after transmitting the Delay_Request frame MS 1 Stamped time at SL after receiving the Delay_Request frame u Number of SLs on the DL frame Summary In recent years, wireless technology has emerged as a promising alternative for industrial communications because it can provide the flexibility needed for mobile robot settings. Because of the recognizable advantages of the mobilities, reducing cabling, installation, maintenance and reconfiguration costs and the danger of breaking cables in the harsh envi- ronments, wireless communications have been promoted for industrial and factory automa- tion (FA). For the communication protocol, there are several communication techniques employed in industrial wireless sensor network, such as Bluetooth, Zigbee.
Recently, the IEEE 802.11 wireless local area network (WLAN) technique has also been attracted by the industrial communication applications. However, due to the non-deterministic, i. non-scheduled, and low speed of these techniques, they are not applicable for the industrial communication in FA control systems. For the time synchronization protocol of the industrial wireless communication in FA control systems, the accuracy of time synchronization protocol is extremely critical to guar- antee that the clocks of all stations in the wireless communication network are identical to preserve the proper function of the communication protocol.
If the clocks of these sta- tions are not synchronized, the transmission errors may occur, then the operations of whole control system could be unreliable. From the current synchronization techniques, such as Network Time Protocol (NTP), Precision Time Protocol (PTP) and Global Positioning System (GPS), we have found that the PTP technique can provide adequate accuracy with low cost and non - line of sight requirement for the industrial wireless communication in FA control systems. However, the accuracy of the conventional PTP technique still suffers from two effects, that are the clock drifts of crystal oscillators and the asymmetric delays between downlink (DL) and uplink (UL) paths. Therefore, the accuracy of PTP can be improved if these effects are considered.
In addition, the conventional PTP synchroniza- tion with four message exchanges makes it not applicable for the fast industrial WLAN (WLAN) communication system. From the demands of fast, safe and reliable wireless communications for industrial FA control systems, in this thesis we have attempted to present our proposed iWLAN commu- nication system to meet those demands. The thesis includes two main topics. In the first topic, in order to enhance the throughput of the conventional communication protocols meanwhile the deterministic communications are still guaranteed, we propose a novel iWLAN media access control (MAC) communication protocol for FA control sys- tem.