Mid-term Project Presentation Eli Bendersky Igor Oks

The project  Driver for a wireless LAN network card.

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 protocol.  Setting up a functional WLAN environment

Background

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

How does WLAN work

What was done so far ?

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

A thorough understanding of the 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)

– 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)

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

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

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

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

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

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

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

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

To be done …

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

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

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

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

Schedule  – Complete our understanding of the driver and the underlying protocols.  Debugging  – Making the driver work on the iPac with a network card  – Final presentation & report