1 / 33

Wireless Channel Emulation

Wireless Channel Emulation. Mehmood Ismail Tily Sabiha Hasan. INTRODUCTION. Introduction. The aim of the project is to design and emulate the effects of wireless propagation on transmitted signals. Specifically targeting the effects of wireless communication amongst multiple motes.

darryl-oneal
Download Presentation

Wireless Channel Emulation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Wireless Channel Emulation Mehmood Ismail Tily Sabiha Hasan

  2. INTRODUCTION

  3. Introduction • The aim of the project is to design and emulate the effects of wireless propagation on transmitted signals. • Specifically targeting the effects of wireless communication amongst multiple motes.

  4. Who will benefit? • designers working on wireless nodes can benefit from the device. • models the channel characteristics taking into account various external conditions .

  5. THEORY

  6. Theory: The transmitter can be viewed as launching a waveform that propagates in a spherical fashion outward from the transmitter. A transmitted signal represented by x(t)= √2cos(2 π fct) appears at the receiver side as y(t) = Lp √2cos((2 π fct-ζp))

  7. Attenuation and Phase Shift: Where, Lp is the loss of free space propagation due to the power of the signal being spread across a bigger spherical wave, and it grows with distance. ζp is the time delay in the radio wave propagation due to the speed of light and results in a phase shift which is given by, Φp = -2 πd/λc d = distance between transmitter and receiver. λc = wavelength of the electromagnetic wave.

  8. NOISE Output INPUT ∑ Noise Model: • We used the Additive White Gaussian Model to model the noise in the wireless channel. • The mean of the distribution for noise is zero.

  9. Multipath Propagation: • Radio Signal undergoes defraction and Scattering due to objects in the physical environment, thus taking multiple paths from the transmitter to the receiver. The resulting signal at the receiver antenna is the superposition of the effects of each multipath signal.

  10. Multipath Propagation Model: This resulting signal at the receiver side can be modeled as mp Y(t) = ∑Hnx(t- ζn) + W(t) n=1 • mp is thenumber of distinct multipaths in a particular channel • Hn is the multipath multiplicative distortion ζn is thetime delay for the nth multipath • W(t) is additive white guassian noise

  11. Multipath Propagation Cont: • The amplitude of this multiplicative term is due to the distance between the transmitter and the receiver, the type of media the radio waves propagate through, and the surfaces of scattering objects. • The phase, which is also a function of the factors is given by θn - 2 πdn/λ • dn is the distance traveled by from the transmit antenna to receive antenna by the nth multipath

  12. SCENARIO

  13. Signals at the Receiver of a Mote Micro- controller TRANSMITTER RECEIVER Channel Model Micro- controller TRANSMITTER RECEIVER Micro- controller TRANSMITTER RECEIVER RECEIVER TRANSMITTER Micro- controller

  14. DESIGN

  15. Model Implementation: • Modules • Handshaking with Controller • Transmitter • Receiver

  16. TOP LEVEL IMPLEMENTATION TRANSMITTER C-PROGRAM RESET dn L CLK TRANSMITTER A11, θ11 DATA PIO HANDSHAKING MODULE A12,θ12 ENABLE RECEIVER PCLK PDATA DATA A21, θ21 RECEIVER DCLK A32, θ32 DIO A22, θ22 RECEIVER A31, θ31 RECEIVER TRANSMITTER TRANSMITTER

  17. RESET Clock PIO HANDSHAKING MODULE ENABLE PCLK DATA PDATA DATA DCLK DIO Handshaking Module: • Transmission: • Generates clock for the microcontroller. • On every positive edge of clock, transmit data from DIO to the transmitter and enable the transmitter. • Reception: • On every clock pulse, transfer data from receiver module to DIO • Change of mode: • Modes of radio are controlled by micro-contorller. • To set transmission/reception mode, microcontroller asserts PALE and send address of the register on PDATA. • First 7 bits are address, 8th bit determines read or write operation and 8 bits are data. • Register 00 (bit7) contains the mode information.

  18. RESET Clock Dn, L Data from Handshaking A11 Transmitter A12 Enable from Handshaking A21 A22 A31 A32 θ11 θ12 θ21 θ22 θ31 θ32 Transmitter: • When Reset = 0 • Wait for enable from handshaking module. • When enabled, will latch data on the positive edge of clock. • Depending upon the input, will calculate θs and send θs and As to other motes • When Reset = 1 • Send request signal to the serial port of the computer. • From next clock pulse, start latching data from serial port. • MSB is sent first

  19. Clock Reset RECEIVER A11 A12 Data out A21 A22 A31 A32 θ11 θ12 θ21 θ22 θ31 θ32 Receiver: • When Reset = 0 • Latch the values of As and θs. • Calculate x = ∑Aicosθi and y = ∑Aisinθi • sin θ and cosθ are calculated by using lookup tables. • Noise is incorporated by adding random numbers to x and y. • Signs of x and y determine the data. • If x and y have same signs • Data out = 1 • Else • Data out = 0 • When Reset = 1 • Set noise count = 0

  20. C-Program: • C program is used to get values from computer • Calculate k and θ and to ensure their bounds • Serial Port • Waits for request from the FPGA • As soon as it gets request signal, starts transmitting the data • Sends MSB first • Data is sent in the order of k and θ of a particular data path

  21. Parameters with Justification: • Expression: • Kect + θ + noise • K: • 1 bit sign, 10 bit integer part, 5 bit fraction part • Downloaded from computer • θ : • 1 bit sign, 5 bit integer part, 5 bit fraction part • Downloaded from computer • c: • Constant • C = 2πfox with x = 1 / (4*fdata_rate)

  22. Parameters with Justification: • C = 2πfox with x = ¼*fdata_rate • Fdata_rate = 76.8KHz • f0 = +/- 152.3 KHz • One of the values in the radio • Provided a periodic ct with integer t. • θ: • = 2πd/ λc • bounded in the range [- π, π] • Made sure by the C-program

  23. Parameters with Justification: • Distance: • Range from 1m to 31m with granularity of 1m • C program will calculate the value of k and θ on the basis of the distance. It checks the range of the distance too.

  24. Parameters with Justification: • Decision at receiver: • Decision is based on the phase of the summation of all signals • Negative => 0, Positive => 1 • The phase is found by tan-1 (y/x) • However, the value of phase is not needed. • Thus, by just looking at the sign of y/x, the sign of tan-1 (y/x) can be determined

  25. Parameters with Justification: • Number representation: • Fixed point number representation is used. 5 bits are used for the fractional part, providing granularity of 1/32 • 2s compliment is used to represent signed number.

  26. DEMO/ SIMULATIONS

  27. CONCLUSION

  28. Our Progress: • Working modules with individual verification ready • Due to lack of time, Integration is not done

  29. Limitations: • Time • Initial Xilinx software support

  30. Extension to the Project: • Integration • Optimization • Extrapolate the current model for larger number of Motes, longer distances and more Multipaths

  31. Acknowledgements • Gautam Kulkarni • Vijay Raghunathan

  32. References: • Modeling of Space-Time Wireless Channels. By M.Fitz • Wireless Propagation – Lecture series from Wireless Communication Systems • www.xbow.com • www.chipcon.com • www.atmel.com • http://webs.cs.berkeley.edu/tos/ • www.infomit.com • www.taltech.com

  33. QUESTIONS?

More Related