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1. Wireless Sensing Lab Module Instructors Manual Fred Schwaner Joel Castro Ali Abedi Casey Clark Copyright 2013 WiSe Net Lab ECE Dept UMaine Educational use of this document and associated source codes when citing the reference is permitted Any other use including but not limited to the commercial and or for profit use requires licensing permission from WiSe Net Lab Director Dr Ali Abedi ali abedi maine edu 1 Note to Instructors This exists as a supplemental version of the standard user manual which is also included with this product The purpose of this manual is to introduce you to the phenomenon of signal fading The MC 9090 that runs the software included with this manual is capable of transmitting a radio frequency electromagnetic signal Just like light sound and other types of signals electromagnetic signals fade Fading is dependent on many factors Among them are distance and obstacles This manual is to introduce you to these factors and discusses the hardware and software used to introduce these concepts to students 2 System Overview The electromagnetic signal transmitted by the MC9090 is used to communicate with what are called Radio Frequency Identification or RFID tags RFID tags are available in many shapes and sizes but all work approximately the same way The tags consist of an antenna a microchip and sometimes a small battery The antenna on the tag converts the power in th2. Availability ONLIME Tags Read E20034116802011293053533 E2O034116802011293S053535 E20034116802011293053534 E200341166802011293S0535s2 E2003411B680201129305353 EE Figure 9 Press and release the trigger Currently writing to My Documents 1 txt 8 Sour Note the status changes to BUSY and that the file l txt is currently being written Also note the tag IDs being shown in the table Back S RFID Reader ar qf 3 12 X RFID Reader Availability ONLIME Tags Read E20034116802011293053533 E20034116802011293053535 E20034116802011293053534 E2O03411660201129S0535s2 003411B80201129305353 Figure 10 After 10 seconds the device beeps Also the status changes back to READY and a message indicates file 1 txt has finished being written 1 txt now contains tag IDs from a 10 second scan Status READY Finished writing to Wey Documents 1 txt 7S RFID Reader ar i415 X RFID Reader Availability ONLINE Tags Read E20034116802011293053530 E20034116802011293053534 E20034116802011293053535 Ez20034116802011293053532 E20034116802011293053529 E20034116802011293053531 Figure 11 Press and hold the trigger Notice the tag list clears and begins to repopulate as tags are once again recorded After the device beeps af ter 10 seconds release the trigger The reader will continue to scan for tags until the next beep which will occur 10 sec onds after the first Status BUSY Currently w
3. ata plt files m 91 40 16 2 0 My Pictures Rainmeter desktop ini gt gt plt files C Users Guest Documents data 1 2 7 5 10 Figure 19 Workspace and Command Window after calling the function Note ans is saved in the workspace 14 The figure generated looks like the following Receved Packets at Different Distances of Packets Distance from Tag ft Figure 20 Plot of Received Packets versus Measured Distance 15 About Authors Dr Ali Abedi is Associate Professor of Electrical and Computer Engineering and Director of Wireless Sensor Networks WiSe Net Lab UMaine Orono He serves as Principal Investigator on this project Mr Fred Schwaner and Mr Joel Castro are graduate students at UMaine who helped in developing the code and manual for this lab module Mr Casey Clark is an undergraduate research assistant at UMaine who helped with preparation of this manual Dr Ali Abedi Fred Schwaner Joel Castro Casey Clark WISENET EECE MAINE EDU
4. dures are simply 1 Open MATLAB 2 Go to directory containing the file plt_files m 3 Type the command plt_files lt directory gt lt distances in order gt replacing lt directory gt and lt distances in order gt with respective values 4 and press Enter 10 MATLAB Example Let us use the following as an example e Tag files are stored in the directory C Users Guest Documents data e The plt_files m file is located in C Users Guest Documents e The distances for the experiment were 1 2 5 7 and 10 First we go to file location C Users Guest Documents using the cd command in MATLAB File Edit Debug Parallel Desktop Window Help c Es BS be w ry Fl ee ee wel Workspace Of X gt gt cd C Users Guest Documents RE Select data to plot fs gt gt Start Click and drag to move Command Window Figure 15 Using the cd command to get to the proper directory 12 You can use the ls command to check and see if the file is where it should be File Edit Debug Parallel Desktop Window Help d g Ba FE w ts gr mi E c CA Users Guest Documents gt gt cd C Users Guest Documents ire Select data to plot gt gt ls as cee Name My Music My Videos data plt files m My Pictures Rainmeter desktop ini Figure 16 Results of ls command The command to be typed would look like this File Edit Debug Parallel Desktop Window Hel
5. e signal transmitted by the reader to electricity to power the microchip The microchip then sends an identification number back to the MC9090 by transmitting it on the tag s antenna Small batteries are sometimes used to help power the microchip because as you may find out the signal strength decreases in some situations making it more difficult to successfully read the tag 3 Fading Fading is the disruption of a signal due to environmental factors As the electromagnetic signal propagates its strength decays This is not unlike any other form of signal In fact we deal with this phenomenon every day whether we are aware of it or not When we speak to one another from longer distances we have to increase the volume of our voice The reason for this is that the strength of the sound coming from the other person decreases the farther the two people are apart The same effect can occur due to obstacles When there are obstacles in the way two things can happen Firstly the signal will degrade When people speak from different rooms of a house the sound is often muffled and quieter due to some of the sound s energy being absorbed by walls and floors Secondly the signal can bounce When sound reflects off multiple obstacles the path travelled by the signal often returns to the place of origin resulting in an echo This is similar to one heard by yelling in a large empty room 4 Experiments Different experiments describ
6. ed here are designed to experiment with the conditions that cause fading 4 1 Experience Packet Loss Due to Distance e Stand 50cm from the tag with the MC9090 Attempt to read the tag for a 10 seconds Repeat the previous step for distances of 100cm 150cm e Count the number of successful reads R at each location and plot them e Attempt to match an equation of the following type to your data points R Tet where d is distance in meters is a decay factor T is an adjustment variable and R is the number of tags read at each location WALL WALL TAG 7 d TAG 7 1 Ee K TN READER READER Figure 1 Distance Experiment 4 2 Experience Packet Loss Due to Obstacles e Place a tag on a wall Standing on the other side of the wall attempt the same experiment as above e How do the equations compare How do T and a differ from in the previous experiment e Attempt this with various types of walls and objects e Try placing objects between you and the tag but off to the side so the MC9090 still has a direct path to the tag READER READER Figure 2 Obstacle Experiment 4 3 Experience Packet Loss Due to Reflections e Place the tag on a tall movable object 1 meter from a wall e Stand facing the wall 50cm from the wall yet off to the side so that you are reflecting the signal off the wall to the tag Attempt to read the tag for 10 seconds e Repeat while m
7. he files input as a string and the distances used in the sampling as a vector The number of distances input must not exceed the number of files created during the test There can be more files than distances however This is allowed since the software for the RFID reader creates files before the user starts recording this means there will always be 1 extra but near empty file The function takes the directory with the files and begins to extract the tags from each file and then save the most common tag and the number of times it appears This is done since it is assumed the user was aiming directly at the desired tag and any other tags that might appear especially at further distances will be read less The function then takes these data values and sorts them in ascending order of distance For example distances 5 10 1 20 dataSet 100 20 200 2 becomes distances 1 5 10 20 dataSet 200 100 20 2 A figure is then generated as explained in the overview Note that the plot distances are in feet The code is written such that input values for distance are assumed to be in feet This can be changed in the plotting section of the code Please see the comments in the MATLAB function script for more details 9 4 Use of Function As a prerequisite make sure the user has the following e MATLAB 2009b or newer e Directory containing only files generated by RFID Reader e List of known test distances The proce
8. later recommended e Windows Mobile 6 Professional Software Development Kit e Microsoft Activesync Note Activesync and the Mobile 6 Professional SDK are available for free from Microsoft 6 2 Installing the Software The code is written in C and can be opened using Microsoft Visual Studio The SenseME Mobile solution file sln is in the code s root directory Visual Studio lists the files used in the project on the right hand side by default The main function is located in Program cs The two windows in the program each have a designer file and a code file The designer file simply describes the physical setup of the window The code file runs the features of the window Visual Studio also provides methods to compile build and install the program onto the MC9090 In order to install or deploy the solution to the MC9090 one must have Microsoft Activesync installed on their computer Activesync allows communication between the MC9090 and the computer to allow transfer of files Visual Studio should install the executable in the My Devices gt My Program directory of the MC9090 The code is available for download at the WiSe Net website 6 3 How To Use This program is designed to be very simple to use Upon start a simple How To procedure is shown to the user describing very simply how to use the software as shown in Figure 4 r Welcome Er 2 56 X RFID Logger Device MOTOROLA M900 How fo use Sim
9. location of the file just written The text file written by the program includes the tag IDs of all the tags read during the interval The files are written into My Documents Naming convention is 1 txt for the first reading interval 2 txt for the second reading interval so on When the user wishes to quit the program they may press Back in the lower left corner returning them to the welcome screen 7 Related Reference Material e MC9090 G Regulatory Guide e MC9090 G RFID Integrator Guide 8 Illustrated Sample How To Procedure rS File Explorer a 3 01 X senseme mobile test Name amp DeviceReader 11 7 11 25468 enseME Mob 5 5 05 40 0K Figure 6 From My Device Program Files senseme mobile test open the SenseME Mobile Test file ra Welcome a 3 02 X RFID Logger Device MOTOROLA M900 How fo use Simply press the trigger to read RFID tags The reader will scan For RFID tags in 10 second intervals The unit will beep after 10 seconds indicating the reader switching back to a Ready state As tags are read their IDs will appear on the screen as well as be written to a text File located in My Documents Figure 7 At the welcome screen press Begin in the lower right rS RFID Reader a 23 05 X RFID Reader Availability ONLIME Tags Read Status READY e Figure 8 At the RFID Reader screen 7S RFID Reader Er qf 308 X RFID Reader
10. otting NOTE You can use the use the Ac tiveSync or Storage Device mode when connecting the MC9090 to a PC to copy the files created over to a PC for running the MATLAB code later 9 MATLAB Code 9 1 Requirements e MATLAB 2009b or newer e Directory containing only files generated by RFID Reader e List of known test distances 9 1 1 Note on Compatibility This MATLAB function was written for MATLAB 2009b and is guarenteed to work as described for that and newer versions which are for the most part backwards compatible It may also run in older versions of MATLAB but has not been verified This code uses only the base compo nents installed with MATLAB and most PC s should be capable of running a base version of MATLAB No special requirements are necessary for the PC specifications ouside the minimum requirements for MATLAB itself 9 2 Overview This function reads the set of files containing the RFID tags read in by the MC9090 RFID reader and plots the number of read tags for each distance This requires the directory where the files generated by the MC9090 code are located at and a list of the distances that the test was conducted at The ordered list of tags counted at each distance is created in the workspace and a figure is plotted where the x and y axis represents the distance and number of packets received respectively 9 3 Function Properties As mentioned in the Overview the function uses the directory of t
11. oving the tag backwards from the wall Record and plot WALL WALL aN ZN bS Pa NG D N N J aa Q Q SX READER READER ra Figure 3 Reflection Experiment 5 MC9090 Hardware 5 1 Requirements e Motorola MC9090 RFID Reader e Connector cable for communication with PC 5 2 Overview The hardware used is a Motorola MC9090 Z RFID handheld device This is a Windows Mobile device with IEEE 802 11a b g support allowing wireless networking with other computers and wireless internet routers The unit is controlled by an Intel XScale Bulverde PX A270 processor running at 624 MHz This provides ample speed for applications and data management The RFID reader built into the device has an output power of 4 watts EIRP and can read tags up to 10 feet away The unit s field of view is a 70 degree cone from the nose of the device The MC9090 Z RFID is widely available for purchase from a simple internet search The tags used are EPC Gen 2 RFID tags These tags are highly compatible with most readers as they were standardized to simplify a wide range of varying protocols used in early RFID systems As a result they are very easy to work with easy to find and cheap to purchase For our development purposes we used ALN 9634 from Alien Technologies as they offered good angular sensitivity and were readily available 6 C Software 6 1 Requirements e Microsoft Windows XP or newer e Microsoft Visual Studio 2008 or
12. p T G Ba Fe wj gp ry CA Users Guest Documents Workspace O 7 X gt gt cd C Users Guest Documents RE Select data to plot gt gt 1s anna My Music My Videos data plt files m My Pictures Rainmeter desktop ini 7 je gt gt plt files C Users Guest Documents data 1 2 7 5 10 al Figure 17 Example Command 13 An alternative can be to use the input the directory with the files as a relative path where represents the current directory In this case the directory can be entered as seen in the next image File Edit Debug Parallel Desktop Window Help oa 2B mm E C Users Guest Documents Workspace A oe re gt gt cd C Users Guest Documents R Select data to plot gt gt ls My Music My Videos data plt files m My Pictures Rainmeter desktop ini fe gt gt plt_files data 1 2 7 5 10 Figure 18 Alternative method of directory entry is underlined It is important to remember that the distance vector is in the order that the tags were collected in If they are not the plot may become distorted and out of the correct order The result can be seen as printed to the screen and added to the workspace MATLAB 7 9 0 R2009b File Edit Debug Parallel Desktop Window Help i GS 2B ry E C Users Guest Documents P Workspace Um gt gt cd C Dsers Guest Documents R Select data to plot hi gt gt Ls Mame Value My Music My Videos d
13. ply press the trigger to read RFID tags The reader will scan For RFID tags in 10 second intervals The unit will beep after 10 seconds indicating the reader switching back to a Ready state As tags are read their IDs will appear on the screen as well as be written to a text File located in My Documents Figure 4 Welcome Screen From this screen the user may either press Quit in the lower left corner or Begin in the lower right This button leads to the RFID reading screen At the RFID screen seen in Figure 5 the user may begin reading tags A table of recently read tags is displayed and the RFID reader status which can be either Busy or Ready is printed at the bottom of the screen rS RFID Reader ar 256 X RFID Reader Availability ONLINE Tags Read Status READY Figure 5 RFID Reader Screen To read tags simply press the trigger button on the MC9090 The reader status will change to Busy and below that a message will be displayed indicating the name of a text file being written with all the tags read The RFID reader scans for tags in intervals of 10 seconds At the end of 10 seconds the reader will beep If the trigger is still pressed the user will continue reading in 10 second intervals and beeping until the trigger is released and its current 10 second interval is over When the reader switches back to Ready mode the message below the status indicator contains the
14. riting to Wey Documents 2 txt TET r RFID Reader Er 4 16 X RFID Reader Availability ONLINE Tags Read E20034116802011293053530 E200341166802011293053534 E20034116802011293053535 E20034116802011293S053532 E200341166802011293053529 E2003411B80201129305353 Status READY Finished writing to Wy Documents 2 txt Figure 12 Reader is finished scanning for tags 2 txt now contains tag IDs from a 20 second scan na File Explorer ar i4 57 X My Documents ale LI My Music m My Pictures LJ My Ringtones Personal _ Templates Figure 13 Press Back and then BE 5 5 05 3156 Quit In My Documents there are BE 5 5 05 2116 now three text files 1 txt 2 txt and 3 5 5 05 3B 3 txt The first two files contain the tag IDs read during the two read in tervals respectively The third file is empty and was created by the program after the completion of the second read interval in preparation for a third read cycle rS Word Mobile Er WE 4 45 ok E2003411B80201129S055530 E2003411B80201129S055534 E2003411B802011293S055535 EF2003411BS0201129s055530 EF2003411BS0201129s055532 EF2003411BS0201129S055530 E2003411BS0201129S055529 E2003411B80201129S055531 10 Figure 14 Opening file 2 txt displays a file counter at the top of the page as well as a list of the tags read These files can then be read into the MAT LAB function for analysis and pl
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