Delivering Location Sensitive Advertisements Using Wi-Fi Networks

Ranveer Chandra, Jitu Padhye, Lenin Ravindranath, Alec WolmanMicrosoft 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?

CoffeeDayHi-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 Ad

Wi-Fi Protocol - Beacons

Access Point

Beacon Packets

Network NameSSID: NYCWireless

Network NameSSID: T-Mobile

Networks Found

Connected

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 APat CoffeeDay

WiFi Beacon

Within 250 m of CoffeeDay

CoffeeDay close to me..

Hmm!

I love Hot Choc! Go to CoffeeDay

Coffee Day Drink 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 Ad Size Mechanism Pros Cons

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 MSNAd

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 aShopping mall

WiFi Beacons

Coffee Day Drink of the day is Hot Chocolate

T-Mobile Internet at 20Rs

Preferences: See only ISPs

Preferences: See all Ads

Advertisements

Shop ISP Dynamic 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 PointAd ConstructorAppend Ad with Custom Details

Type ISP Details Location Info

FragmenterDivide long Ads into Fragments

Append Unique ID Sequence Number More Frag Bit

Beacon ConstructorConstruct valid Beacon

With Ad Fragment in SSID/BSSID/BIE

Design - Client

Ad ParserParse AdExtract

Type ISP Details Location Info

Ad FilterFilter Ad based

User Preference Ad Type

Driver InterfaceQuery Beacon FieldsSSID, BSSID – XPAll fields – Vista/ Modified Clients

ReassemblyConstruct Ad from Fragments

Revenue ModelsDeployment Scenarios

This is like.. How it works? Revenue Opportunities

APs at Stores Banner 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 Home Banners 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 AdsApproaches

3 approaches, each with its own pros and conso SSID field of beacons carry Ad Message

SSID field identifies the network such as MSFTWLANo 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 802.11 allows to add vendor specific information

Metrics used to compare: Ease of deployment, Spam, Bandwidth for ads

Approach 1Use 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 1Use SSID field

Pros User level client software is enough Works with non-Windows Clients

Cons Low Bandwidth Spam

Approach 2Use 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 3Add 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 Model Push 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:

<UniqueID>

- This identifies the specific advertisement <SeqNo>

- Fragment number <More Flag>

- Are there more fragments left to come <Text>

- 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 1APs 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 2APs 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 2APs in Public Places

AdCenter AP on Commuter Bus

Ad

Starbucks Coffee of the day is Mocha Java 10 sec

Tully’s 10% off on opening account 20 sec

Borders NYT Bestsellers 20% off 1 min

B&N Amazon sucks! 5 min

Amazon B&N really sucks! 10 min

+

Shown Every …

$$$ decides Ad Frequency

Revenue Model 3APs 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

FeaturesDistributing Coupons

Starbucks: Get 10% off a Hot Chocolate

Step 1: Coupon Distribution Step 2: Coupon Validation

Present coupon

Discounted Coffee

User does not have to connect to the Internet!