Delivering Location Sensitive Advertisements Using Wi-Fi Networks Ranveer Chandra, Jitu Padhye, Lenin Ravindranath, Alec Wolman Microsoft Research

Motivation Explosive growth in Wi-Fi Networks in the last few years Delivery of Advertisements over the Internet has become a huge market as well Ads are targeted – relevant to the user Location Sensitive Advertisements will be a very important market in the near future Google has announced Free WiFi Access in San Francisco MSN has introduced “Locate Me” feature

Scenario Users with WiFi-equipped devices in a market/mall - Devices could be PDAs, laptops or phones. Users receive ads from nearby stores, restaurants on their devices - Filter Ads based on preference of the user

Example Ad: CoffeeDay at 13rd Cross Ad: Hi-Style: 30% off on any purchase of 1000 rupees or more What all is close to me? CoffeeDay Hi-Style (30% off…) Is there an apparel store? Hi-Style (30% off…)

Existing Approaches Client establish connection with an Access Point Client may also send Info about its Location Download Ads “Pull” model of Ad Delivery Download Ads Establish Connection

Goal Send Ad Text over WiFi Networks Make it visible to all clients in the vicinity Advertisement Ad

Wi-Fi Protocol - Beacons Access Point Beacon Packets Network Name SSID: NYCWireless Network Name SSID: T-Mobile Networks Found Connected

Our Idea Send Ad Text as part of Beacon packets that announce Wi-Fi networks Modify certain fields in the Beacon to carry Ads A software at the Client extracts Ad Text from the Beacons seen “Push” Model of Ad Delivery Location Sensitive: Only the Clients in the vicinity of the AP receive their Ads

AdCenter AP at CoffeeDay WiFi Beacon Within 250 m of CoffeeDay CoffeeDay close to me.. Hmm! I love Hot Choc! Go to CoffeeDay Coffee DayDrink of the day is Hot Chocolate Client running our software

Advantages Beacons are not encrypted Advertising a network using a beacon does not mean that you have to let clients “connect” to the network Clients receive beacons (hence ads) even when they are not connected to any network Clients receive beacons from other networks even when they are connected to a particular network Can update Ad text to include dynamic information  Number of tickets left  Daily specials in a restaurant  Stock quotes

Approaches to Send Ads Field carrying AdSizeMechanismProsCons SSID Network Name 32 bytes  Break ad into fragments  Send in successive Beacons  Client reassembles Ad from multiple beacons When Ad sent in BSSID/ BIE SSID is “AdCenter” - User level client software - Works with non- windows clients - Low Bandwidth - Spam BSSID Unique Identifier 6 bytes - User level client software - Prevent Spam Lowest Bandwidth BIE Vendor Specific Information 256 bytes - Higher Ad Bandwidth - Prevent Spam Kernel modifications at clients 3 approaches, each with its own pros and cons

Implementation Details – AP Access Points Provide Interface to Specify Ads Fragment Long Ads Overload in Beacons sent Modify Access Points Modify AP Driver Software Access Points Wireless Card with modified Driver Send beacons constructed at User Level Effective for broadcasting Ads Approaches

Implementation Details - Client Software at Client Query Beacon fields Reassemble Ads Display to user User Preferences No driver modification at the client required Connected to Google Network Still receive Ads from MSN Ad Client need not be connected to a network Client can even be connected to a competitive network

Security Sending Fake Ads JavaWorld near Coffee Day sends “Coffee Day is closed for a day” Replay Attacks JavaWorld replays an Ad sent by Coffee Day at an earlier date Unique ID includes a cryptographically secure signature, verifiable by client-side software Only display ads that pass the test The secure ID can be provided by MSN Encrypt Ad and time of validity with MSN private key Decrypt at the client with MSN’s public key

Preferences AdCenter AP at a Shopping mall WiFi Beacons Coffee Day Drink of the day is Hot Chocolate T-MobileInternet at 20Rs Preferences: See only ISPs Preferences: See all Ads

Advertisements ShopISPDynamic Info

Features - ISP Selection More details about the ISP without connecting to them Dollars per hour Supported Rates Number of users connected etc User connects to the ISP of his choice

Features - MapPoint AP Sends Lat Long

Design - Access Point Ad Constructor Append Ad with Custom Details Type ISP Details Location Info Fragmenter Divide long Ads into Fragments Append Unique ID Sequence Number More Frag Bit Beacon Constructor Construct valid Beacon With Ad Fragment in SSID/BSSID/BIE

Design - Client Ad Parser Parse Ad Extract Type ISP Details Location Info Ad Filter Filter Ad based User Preference Ad Type Driver Interface Query Beacon Fields SSID, BSSID – XP All fields – Vista/ Modified Clients Reassembly Construct Ad from Fragments

Revenue Models Deployment Scenarios This is like..How it works?Revenue Opportunities APs at StoresBanner put up by a business in its own space - MSN sells APs - Owners broadcast Ads - Sale of Hardware - Sale of Software - Free/Paid WiFi Access APs in Public Places Billboards placed in prominent public places (malls or trains) - Merchants bid to have their Ads delivered - Controlled by MSN Servers - Charge of messages sent (depending on length, frequency etc) - Wi-Fi Access APs at HomeBanners placed on side of a residential building on a busy street - Give away free APs with broadband connection - Customers allow MSN to send Ads - Nearby Merchants bid to have their Ads delivered - Charge based on length, frequency etc

Backup Slides

Sending Ads Approaches 3 approaches, each with its own pros and cons o SSID field of beacons carry Ad Message  SSID field identifies the network such as MSFTWLAN o BSSID in beacons carry Ads  BSSID are 6 byte unique identifiers of an AP and can be set to any value o InfoElement blob (BIE) in beacon packets carries Ad messages  allows to add vendor specific information Metrics used to compare: Ease of deployment, Spam, Bandwidth for ads

Approach 1 Use SSID field SSID is network name with 32 byte limit Mechanism: Break ad message into chunks < 32bytes each Successive beacons carry next chunk of ad message Client software assembles the ad message Beacon 1: Beacon 2: Starbucks: Coffee of the da y is Mocha Java

Approach 1 Use SSID field Pros User level client software is enough Works with non-Windows Clients Cons Low Bandwidth Spam

Approach 2 Use BSSID field Encode ad in BSSID Only 6 bytes per beacon packet All ads have same SSID, say “AdCenter” Client assembles ad message from multiple beacons Pros User level client software Works with non-Windows clients Prevent Spam Cons Lowest Bandwidth

Approach 3 Add InfoElement Blob Modify AP driver to add 256 byte ad message - Send larger ad messages in multiple blobs/beacons Client driver modified to pass IE blob to user level - Driver changes not required for Vista Native WiFi cards Pros Higher ad bandwidth Prevent Spam Cons Kernel modifications at clients Limited support for non-Windows clients

Push vs Pull Model Pull ModelPush Model Client explicitly associates with an AP and downloads Ads Client need not associate with any AP to receive Ads Client may also transmit information to the system about its location Client does not transmit any information Receive Ads only from the network connected Receive Ads even when connected to competitive network Higher Bandwidth for downloading Ads (54 Mbps) Lower Bandwidth (200 Kbps) Ads can be highly customized for individual users Users set preferences to filter Ads Raises concerns about privacy issues (client transmits identity and location) Does not cause any privacy issues

Sending Long Ad Messages Fragment the Message and send in successive beacon Each message is of the form: - This identifies the specific advertisement - Fragment number - Are there more fragments left to come - Text of this fragment User-level software on client reassembles all fragments, and presents the advertisement to user

Preventing Spam All ads use the same SSID E.g. “AdCenter” This is the only extra network seen by users who do not run special client software Ad text is sent as beacon option Decoded and displayed by MSN-specific client software User creates a profile on their device to filter ad messages I do not want to see ads for shoes, but want to see ads for electronics

Revenue Model 1 APs at Stores Banner put up by a business in its own space MSN sells special APs and associated software to business Owners broadcast appropriate Ads APs can provide Wi-Fi Access MSN can manage them this Wi-Fi Access Revenue Opportunities Sale of Hardware Sale of the Associated Software Periodic Subscription to keep the cryptographic keys updates Managing the AP to provide free/paid Wi-Fi Access

Revenue Model 2 APs in Public Places Billboards placed in prominent public spaces (malls or train stations or buses) MSN either rents are owns these “billboards” Merchants bid to have their ads delivered via these APs Controlled by MSN Servers Can also support free or paid WiFi Access Revenue Opportunities MSN charge for messages sent (depending on length, frequency etc) Provide Wi-Fi Access and charge

Revenue Model 2 APs in Public Places AdCenter AP on Commuter Bus Ad StarbucksCoffee of the day is Mocha Java10 sec Tully’s10% off on opening account20 sec BordersNYT Bestsellers 20% off1 min B&NAmazon sucks!5 min AmazonB&N really sucks!10 min + Shown Every … $$$ decides Ad Frequency

Revenue Model 3 APs at home Banners placed on side of a residential building on a busy street Form partnership with a broadband provider (Comcast) Give away Free APs to Customers Customers allow MSN to remotely program these APs to send Ads Revenue Nearby merchants bid to have their Ads Fee Structure depends on length, frequency etc

Features Distributing Coupons Starbucks: Get 10% off a Hot Chocolate Step 1: Coupon DistributionStep 2: Coupon Validation Present coupon Discounted Coffee User does not have to connect to the Internet!