1. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING Real-Time Performance Monitoring and Evaluation of an 802.11 Wireless LAN – Wireless Research API (WRAPI) Anand Balachandran Charles Hudak Geoffrey M. Voelker

2. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 2 Motivation 2. Network administrators and applications need to monitor the wireless LAN for site survey, nature of RF environment, load balancing decisions, etc. 1. Users in a wireless LAN benefit from an understanding of the RF network weather – recd. signal strengths, operating power, RF channel, SSID etc. Interne t Access Points

3. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 3 Outline Motivation Existing Mechanisms WRAPI – purpose Features Methodology Demo of WRAPI Future Work

4. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 4 Existing Mechanisms WLAN monitors (e.g. OriNoCo Client Manager) »Vendor Specific »Expose different interfaces »Not all vendors support the same OIDs (object identifiers) Firmware Implementations »Proprietary – written by the hardware vendors »Code is not made available

5. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 5 So, What is WRAPI? Wireless Research API (WRAPI) »A software library that allows applications running in user- space on mobiles hosts (and APs) to query/set information in the network they are attached to. WRAPI: »Is hardware-agnostic WLAN monitoring tool (supports all 802.11b compliant hardware) »Is Programmable!! »Exposes all IEEE 802.11 WLAN objects »Currently runs on Windows XP »Can be ported to WinCE (Pocket PC 2002)

6. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 6 WRAPI – Features WRAPI provides an interface to applications to monitor the WLAN in real time Supports 25 WLAN OIDs (see table for a sample) OIDs are either read-only, read-write, or write-only IEEE 802.11 OIDQuerySet Service Set Identifier (SSID) Yes Base Service Set Identifier – BSSId (AP MAC Addr.) YesNo BSSId List Scan (scan channels NoYes Received Signal StrengthYesNo

7. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 7 IEEE 802.11 Network Objects typedef struct OID_802_11_BSSID { ULONGLength; NDIS_802_11_MAC_ADDRESSMacAddress; UCHARReserved[2]; NDIS_802_11_SSIDSsid; ULONGPrivacy; NDIS_802_11_RSSIRssi; NDIS_802_11_NETWORK_TYPENetworkTypeInUse; NDIS_802_11_CONFIGURATIONConfiguration; NDIS_802_11_NETWORK_INFRASTRUCTUREInfrastructureMode; NDIS_802_11_RATESSupportedRates; } NDIS_WLAN_BSSID, *PNDIS_WLAN_BSSID;

8. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 8 Methodology The NDIS Stack DeviceIoControl()

9. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 9 Methodology (2) Flow of Logic in the WRAPI DLL: Gets a handle to the NDISUIO Protocol Driver Enumerate Devices Bind NDISUIO to the device Query/Set the parameter using WIN32 DeviceIoControl() API

10. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 10 WRAPI – Demo

11. 7/14/2015 Center for Wireless COMMUNICATIONS COMPUTER SCIENCE and ENGINEERING 11 Future Work Traces and scripts available at: http://ramp.ucsd.edu/pawn/wrapi/ We are using WRAPI To build the signal map of a location-determination system To implement inter-AP load balancing algorithms that take into account individual user workloads