1. Mid-term Project Presentation Eli Bendersky Igor Oks

2. The project  Driver for a 802.11 wireless LAN network card.

3. Project goals  Experience with Windows CE development for handheld computers.  Understanding the internals of a wireless network card driver.  Serve as a starting-point for future projects based on communication using the 802.11 protocol.  Setting up a functional WLAN environment

4. Background

5. Wireless LAN  A Local Area Network, for office, home, school etc.  Wireless connection: No need for network wires, sockets, etc.  Fast  Prices dropping

6. How does WLAN work

7. What was done so far ?

8. A development environment was set up  HW: Desktop PC and a hand-held PC (iPac) with a 802.11 network card. Access point to the network.  SW: Windows CE Platform SDK, Microsoft Visual C++ for Embedded applications. Source code of a sample driver.

9. A thorough understanding of the 802.11 standard  Operates on the Physical & Data Link network layers  Consists of an Access points and client(s) (can also operate on peer- to-peer level)

10. 802.11 – Physical Layer  Frequency: 2,400 Mhz – 2,483 Mhz  Speed: 1-2 Mbps  There are two common methods:  DSSS (Direct Sequence Spread Spectrum) – uses Phase Shift Keying (PSK) modulation.  FHSS (Frequency Hopping Spread Spectrum) – uses FSK (Frequency Shift Keying)

11. FHSS  The 2.4 Ghz band is divided to 79 channels of 1 Mhz  Sender and receiver agree on a channel switching scheme  Maximum speed is 2 Mbps

12. DSSS  The 2.4 Ghz band is divided into 14 partly-overlapping channels  Data is sent over a single channel without switching

13. 802.11 – Data Link Layer  LLC – Similar to other 802 networks (such as Ethernet)  MAC – Uses CSMA/CA (Carrier Sense, Multiple Access / Collision Avoidance)

14. Driver implementation  Using the Windows CE DDK (Driver Development Kit)  Following NDIS (Network Driver Interface Specification)  Latest NDIS version is 5.0

15. Understanding NDIS 5.0  NDIS – interface by which one or more LAN adapters communicate  The 802.11 network card driver uses NDIS  Primary purpose: define a standard API for Network Interface Cards

16. The driver  Directly manages a network interface card and provides an interface to higher level drivers.  Miniport – wrapped by NDIS on both the higher and the lower levels  Calls lower-level NDIS functions  Provides functions to upper levels. For example: DriverEntry

17. DriverEntry  Called by the system to load the driver  Creates an association between the driver and the NDIS Library  Registers driver version number and entry points with NDIS

18. Heaps of source code  Given a sample driver (from Intel)  Going through the code, understanding the flow  Recognizing lower-level and higher- level interface calls

19. To be done …

20. Understanding the driver  A lot of source code to go through !

21. Making things work  Compiling the driver (with MS VC++ Embedded)  Loading the driver onto the iPac

22. Establish Communication  Establish communication from the iPac to an access point using our driver  Remote debugging to watch over the process

23. If that succeeds …  Communication via 802.11 works !  Think about applications  Extensive documentation

24. Schedule  21.1.02 – Complete our understanding of the driver and the underlying protocols.  31.1.02 - Debugging  14.2.02 – Making the driver work on the iPac with a 802.11 network card  3.3.02 – Final presentation & report