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Bit Multiplexed Real Time Network –

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Presentation on theme: "Bit Multiplexed Real Time Network –"— Presentation transcript:

1 Bit Multiplexed Real Time Network –
A Novel Approach to Real-Time Networking Introduction Design Implementation Future Work Paul Richardson Mukul Gadde University of Michigan-Dearborn 1/17/2019 NDIA-IVS 2003

2 Real-Time Networks A network in which messages have explicit or implicit time constraints Correct operations defined in terms of both reliable and timely delivery of data Some Data is Critical Data – Untimely Delivery can Result in Damage or Injury 1/17/2019 NDIA-IVS 2003

3 Temporal Components of a Message’s Transmission
(1) Local Host Delay from Buffering (2) Transmission Time – Number of Bits  Bit Period (3) Signal Propagation Delay – Determined by Geographic Distance (4) Network Delay – From Contention Between Nodes NIC Application tsend treceive tnet tlocal tTX tprop 1/17/2019 NDIA-IVS 2003

4 Guaranteed Message Time Constraints - Classical Approach
For Each Message  Determine Worst Case Response Time (WCRT) If WCRT < Deadline  Message will be on Time, else it can be Late WCRT = tprop + tTX + tlocal + tnet Propagation Delay: constant, often negligible Transmission Time: constant per frame size - can easily be determined typically tTX << Deadline Local Delay: Depends Only on Local Traffic – Determined Independently Network Delay: Depends on All Network Traffic – Most Unpredictable of all Temporal Components 1/17/2019 NDIA-IVS 2003

5 WCRT = tprop + tTX + tlocal
Objectives of Bit Multiplexing Eliminate Network Delay Component Removes Network Wide Timing Dependencies Eliminates Trade-Off Between Frame Sizes Reduce Variance in WCRT – More Efficient Simple Design – Easy to Implement Using FPGAs WCRT = tprop + tTX + tlocal tnet eliminated tlocal will increase by a factor of n for n nodes 1/17/2019 NDIA-IVS 2003

6 What is Bit Multiplexing? The Network is Shared on a BIT
boundary – not on the FRAME boundary Each node is assigned a time slot to transmit a bit Frames are rebuilt from recovered bits idle bit patterns are sent during idle time to maintain synchronization NIC Application tnet tsend treceive tlocal tprop tbit 1/17/2019 NDIA-IVS 2003

7 Result - Each Node Perceives its Own Dedicated Physical Channel
Ideally - Aggregate Data Rate Remains the Same In Most Cases – WCRT will be Lower Application Application Application NIC NIC NIC 1/17/2019 NDIA-IVS 2003

8 Primary Modules of a Node Synchronization Module
Transmitter Module (Tx) Receiver Module (Rx) Synch Counter Transmitter Receiver transmit buffer receive buffer transmission medium 1/17/2019 NDIA-IVS 2003

9 Synch Module – Manchester Codes
Counter Transmitter Receiver reset 30 counter enable edge detector 32clk slot counter RX enable, TX disable or TX enable, RX disable A B C Module Initialization power up register configuration Counter determines current “slot” enables signals for Tx and Rx 1/17/2019 NDIA-IVS 2003

10 Transmit Module Node C slot counter 0 0 1 16 counter enable TX C A B C
Synch Counter Transmitter Receiver A B C 30 counter edge detector 32clk slot counter enable TX C transmit frame buffer 1 16 counter 1/17/2019 NDIA-IVS 2003

11 Receive Module Node A select slot counter 0 0 1 8 counter enable RX B
Synch Counter Transmitter Receiver A B C 30 counter edge detector 32clk slot counter receive frame buffers 1 slot B slot C select enable RX B 8 counter destination address encoded in frame 1/17/2019 NDIA-IVS 2003

12 Implementation – Proof of Principal
Using VHDL and 3 Xilinx XC4010E/XL Boards 7000 Gates Used for Each Node (10,000 Maximum) 4 Input/Output Channels Used (160 Maximum) Transmit Data: Static Characters from RAM Buffer Receive Data: Displayed on 7-Segment Displays Aggregate 600KHz Signal Rate  300Kbps Data Rate Individual Node Rate = 100Kbps NODE A TX RX NODE B NODE C 1/17/2019 NDIA-IVS 2003

13 Next Phase: interconnect computers via PCI
Follow on work Next Phase: interconnect computers via PCI receive data – save to RAM & display to CRT send data files, images, etc Increase data rate (10-100Mbps) Add Fault Tolerance – Sustain Network Faults Increase Scalability – Add/Remove Nodes 1/17/2019 NDIA-IVS 2003

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