Location-Based Information Push as a Short Message Service– Its Architecture, Design, and Applications

Jang-Ruey Tzeng1 Patrick S. Chen2 Wei-Hsuan Tsao3

Center for Strategies and Industrial Study(CSIS)Dept. of Information Management, Tatung University ,

No.40,Sec.3,Zhongshan N.Rd., Taipei City 10433,Taiwan ROCpetertzeng@gmail.com1 chenps@ttu.edu.tw2 mimo0722@hotmail.com3

ABSTRACT “Push” and “Pull” are two main kinds of information propagation. Nowadays, mobile communication environment, cellular phones are not only prevalence, but also become an important means for acquiring information. Due to the limited viewing windows and small bandwidth, most information presented to cellular phones is in the form of short message. In the present time, information broadcasting to newly entering mobile stations is technically feasible. But, mobile stations used to move from one BTS to another, making the location of a mobile station a difficult task. If we want to push information to specified mobile subscribers in a given area, we need to remodel the system, since it is a waste for the sender to send a message out of the given area, and it is also a disturbance for the receiver to receive an unwanted message. In order to determine whether a mobile station is in a given area, we have to search the entire location table, causing a huge system cost. Therefore, by way of using Cell-ID location technique that we suggest to construct and maintain a LBS database, registering all currently connected mobile stations in a specified area. The proposed system cannot only be used in commercial area such as for local retailers to send information to their customers, but also in public sectors such as for police to send warnings in emergent rescue.

Keyword: Short Message Service, Information Push, Location-Based Service, Cell-ID

1 IntroductionIn the recent years we have seen increased attention being given to Location-Based Service (LBS) in the mobile commerce application. LBS is a service in which only people in certain area will be given the information, but not out of the area. Perfect use of LBS could bring more convenience to people’s daily life.

“Push” and “pull” are two main kinds of information propagation. In pull ser vice,

customer takes the initiative to submit requests to the server, and the server responds

with information requested. It is a common way for people getting information from

the website. With push service, the sender sends information to the client according to

certain rules. For example, it can be the broadcast of radio or the sending of

advertising letter. In the present-day mobile communication environment, cellular

phones are widely used, becoming an important means for acquiring information, so

people often receive messages passively. Because mobile communication is

characterized by its narrow bandwidth and cellular phone is limited by its viewing

window, short message service is still regarded as the most widely used value-added

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application. Short message service is easy to handle; its cost is low; it is one of the

most welcome services in mobile commerce.

It is a common practice to push information to mobile stations, so we can acquire

instant information conveniently. Because the mobile stations are often moving from

a base station to another, it is a subject worthy of study how to push information to

specified mobile stations in a given area. Let us think over a scenario: a bakery would

like to sell out all its bread before it closes in two hours. So, we send promotion

information as a short message to notify the consumers near the bakery. Because some

customers may leave this area, it will be a waste to send a message out of this area. So

we have to improve the existing GSM technology, because mobile stations may stay

in this area, they may leave this area too.

It is a waste for the sender to send a message out of the given area, and it is also a

disturbance for the receiver to receive an unwanted message. How to facilitate an

adequate information push is the topic of this discussion, in which we do not intend to

modify the current system of GSM, but to adopt the mechanism of GSM LCS to set

up a notification system.

2 Literature Review2.1 GSM ArchitectureGSM was originally developed to provide a second-generation communication technology for Europe so that the same subscriber units could communicate throughout the continent. GSM first appeared in 1990 in Europe. It contains the essential “intelligent” functions for the support of personal mobility, especially with regard to user identification and authentication, and for the localization and administration of mobile users. (Stallings, 2005)

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Figure 1.GSM Architecture

In Figure 1, GSM system is divided mainly into Mobile station, Base station subsystem (BSS) and Network Subsystem (NS). Mobile stations (MS) are pieces of equipments which are used by mobile service subscribers for access to services. These consist of two components, one is Mobile Equipment (ME) and another one is Subscriber Identity Module (SIM). A base Station Subsystem (BSS) consists of a base station controller (BSC) and one or more base transceiver stations (BTS). Each BTS defines a single cell and it also includes a radio transceiver, a radio antenna and a link to a base station controller. A BSC may be collocated with a BTS or control many BTS units and hence multiple cells. The BSC reserves radio frequencies, manages the handoff of a mobile station from one BTS to another.

The network subsystem (NS) provides a link between the cellular network and the public switched telecommunications networks (PSTN). The NS controls handoffs between cells in different BSS, authenticates users and validates their accounts, and includes functions for enabling worldwide roaming of mobile users. The central element of the NS is the mobile switching center (MSC). It has four databases:(1) Home Location Register (HLR) database: The HLR stores information, both

permanent and temporary, about each of the subscribers that ‘belongs’ to it. It stores IMSI, MSISDN, MSRN, Subscriber information, LMSI etc. Figure 2.

(2) Visitor Location Register (VLR) database: One important, temporary piece of information is the location of the subscriber, and this location is determined by the VLR into which the subscriber is entered. The visitor location register maintains information about subscribers that are currently physically in the area covered by the switching center. It also stores some information, which is IMSI, MSRN, TMSI, LAI, MSISDN, etc.

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Figure 2.Mobile subscriber data in the HLR

(3) Authentication Center (AuC) database: The database is used for authentication activities of the system.

(4) Equipment Identity Register (EIR) database: The EIR plays a role in security which keeps track of the type of equipment that exists at the mobile station.

We can know that signals are conveyed through each base station. This study is based on mobile subscribers of GSM system, because base stations were densely set up with high coverage in Taiwan.

2.2 Location-Based NotificationThere are many kinds of location-based services available, among them is the notification system:1. The ability to precisely locate subscribers according several positioning techniques.2. Precisely defined and arbitrarily located notification areas.3. The ability to detect entrance to a notification area within a short time period, such

as one minute or less.4. The ability to track each and every wireless subscriber at an interval that will

satisfy requirement.

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Figure 3.Mobile subscriber data in the VLR

In Figure 4, “subscribers” are the set of subscribers to whom notifications may be sent. The Notification Initiator begins the process by sending a subscriber ID to the Position Determination function, which computes the position of the given subscriber using the wireless carrier’s position-determining technology. “Notification Area” is the set of geographic areas that have been created by clients of the location-based notification service. Proximity Detection determines whether a subscriber is in a notification area. The Preferences Filter blocks notifications from being sent to subscribers when their preferences indicate they do not want notifications from a particular client. Notification Composition composes a notification to be sent to a subscriber, based on what the client specified, and the Notification Delivery system actually delivers the notification. For example, this may be the carrier’s SMS system.

We adopt the standard of GSM 03.71 which is the digital cellular telecommunications

system (phase 2+); Location Services (LCS); Functional Description; Stage2.” It is

mainly a standard for GSM in LCS (Figure 5). It shows the logical architecture

defined by GSM for its LCS (Location Services) network feature. The LCS Client

sends a LCS Service Request to the Gateway Mobile Location Center (GMLC),

supplying the subscriber’s IMSI (International Mobile Subscriber Identifier) or

MSISDN (Mobile Station ISDN Number) to obtain the position of a mobile

subscriber. The GMLC needs to know which MSC is currently serving the subscriber,

and so obtains this information from the Home Location Register (HLR). The request

is then forwarded to the appropriate MSC. The MSC forwards the request to the

Serving MLC, either directly or through the BSS (Base Station Subsystem),

LocationDetermination

NotificationInitiator

PreferencesFilter

NotificationComposition

Subscribers

ClientSpecifications

NotificationAreas

NotificationDelivery

ProximityDetection

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Figure 4.High-level model of location-based notification

depending on how the SMLC is connected. (Jonathan et al., 2002)

There are two points of the GSM LCS architecture that we should mention: one is designed to serve location requests for individual subscribers, and another is designed around the requirement that applications have no prior knowledge of a subscriber’s location, but know only subscriber’s IMSI or MSISDN. We fallowed this architecture in GSM LCS.

2.3 Cell-ID positioning techniqueThere are various kinds of action-oriented technology available, three of them are utilized extensively at present. The first one is network-based positioning technique. It utilizes the signal send out by mobile subscribers, determines their locations in the base station or the network system server that publishes the position of the mobile subscribers, such as Cell-ID and TOA/TDOA. The second one is terminal-based positioning technique which utilizes signals sent out by base station to a mobile subscriber, and the mobile station calculates its position relative to the mobile station, such as E-OTD/OTDOA. The third is a hybrid-based technique. The location is determined by the mobile station and mobile network together (Table 1). .

GatewayMLC

MSC/VLR

ServingMLC BSS

HLRM

S

Le Lg

Lh

Ls Lb

RRLP

Figure 5.Logical Architecture for GSM Location Services

LCSClient

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Table 1. The characteristic analysis of mobile positioning techniqueTechnolog

y

Cell-ID TOA/TDOA E-OTD/OTDOA A-GPS

Positioning

based

Network-

based

Network-

based

terminal-

based

hybrid-

based

Proximity

positioning

200~2000m 50~200 m 50~150m 5~50m

Positioning

time 1~3 seconds 3~6 seconds 5~8 seconds

Start the machine

slowly

10~40 seconds

Start the machine

fast

1~30 seconds

End

demand of

the office

The software

fine tuning

GPS machine;

Connected time

synchronism

RNC、LMU

equipment

GPS network、GPS

receiver、IP-

Based network

Demand of

end user

none none Location software,

Logical processing

GPS receive module,

location software

Network

system

GSM/GPRS

WCDMA

CDMA2000

GSM/GPRS

WCDMA

CDMA2000

E-OTD－GSM/GPRS

OTDOA－WCDMA

GSM/GPRS

WCDMA

CDMA2000

Suitable

services

Location service Location

service,

Tracking service

Location service,

Tracking service

Location service,

Tracking service

Data resource: MIC of Institute for Information Industry, 2006/08

Cell-ID is the basic reference for mobile positioning techniques; COO (Cell of Origin) positioning technique is also based on Cell-ID. Cell of Origin (COO) is a mobile positioning technique for finding a caller's cell (the basic geographical coverage unit of a cellular telephone system) location. It may be used by emergency services or commercial use. COO is the only positioning technique that is widely used in wireless networks and is used for Phase one of 911 service in the US. It considers the location of the base station to be the location of the caller. This is not very accurate, but may be useful in rural locations and in the cities. In the Figure 6 we show the COO positioning method.

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2.4 Short Message ServiceShort Message Service (SMS) is a mobile data service that allows alphanumeric

messaging between mobile phones and other equipment such as voice mail systems

and email. SMS is a store-and-forward system. Messages are sent to a Short Message

Service Center (SMSC) from various devices such as another mobile phone or via

email. The SMSC interacts with the mobile network to determine the availability of a

user and the user's location to receive a short message. SMS first appeared in GSM in

about 1991. Although with the advent of 3G, SMS is still based on the existing GSM

architecture.In this study, we adopt the short message service to deliver message to mobile subscribers in a given area. We utilize Cell-ID positioning technique to implement the system.

3 System Analysis and DesignWe propose an architecture for this system in this chapter.3.1 System AnalysisAccording to the literature cited above, the study sets up a structure based on GSM LCS. Following this structure, we compose the format of short message and Cell-ID positioning technique, to establish real time location-based information push service. The basic design of the system is:(1) Select an area, in which we want to push information. (2) Search mobile subscribers according to client’s request.(3) Register the state when a mobile subscriber enters this area, and deliver the data

back to MSC/VLR database.(4) Register the state when a mobile subscriber leaves this area, and update

MSC/VLR database.Figure 7 shows a general idea of systematic maintenance.

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Figure 6.Cell-ID positioning method of network-based

A mobile subscriber will register to the mobile station when it enters this base station, and the data will be stored in VLR database. So, we only need to know the Cell-ID of each base station in a given area when we search. We also know the cellular number of mobile subscribers in this given area. We have to protect the privacy of the subscribers.

3.2 Procedure of systemWhen requested by the client to push information, the system will look up the database in a given base station. Based on Cell-ID, the each base station will search all mobile subscribers in its area. It will get a list of mobile subscribers that are of the interest of the client. Success or failure in sending will also be recorded for future billing. Figure 8 shows the system flow.

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Figure 7. Systematic maintenance

4 Implementation of the Location-Based Information Push System

4.1 System architectureFor mobile subscribers often move from one area to another. This will be registered

automatically. The data will be stored in VLR database, VLR will forward the data to

HLR to update the position information. Simultaneously, it can obtain the subscriber's

basic data from HLR, and then store back to VLR database.

Architecture of the system is decomposed into System platform, Short Message

Sender and Mobile Subscribers. System Platform contains a LBS database and system

interface, and there is an interface to the short message sender. Figure 9 shows

architecture for the system.

Start

End

Search MS of the database

Deliver

Select area

Acquire subscribers of MS in given area

Save success data in log file

Save failure data in log file

No Yes

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Figure 8.Flow chart for System

The main concept of the system is to obtain subscribers’ cellular numbers from LBS to deliver when we want to push short message to specified mobile subscribers. Mobile subscribers who are not in this area will not receive any message, so the senders who are unwilling to waste the expenses on delivering short message.

4.2 System interfaceFigure 10 shows the three parts of the system interface that are the windows for

delivering short messages, selecting area and LBS database query.

The window for LBS database query is used to select mobile subscribers in given

System Interface

LBS Database

Short MessagePlatform

.............

Deliver

Systematic platform

Query

Short message sender Mobile subscribers

Figure 9.Architecture of System

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Delivering short messages Selecting area

LBS Database query windows

Figure 10. System main components

area. We first query the wanted area and then select one or more base stations in this

given area, so we can know which mobile subscribers are in the base stations of given

area. According to Cell-IDs of the base stations, so we can select the mobile

subscribers’ cellular phone numbers we want. Finally, the window for delivering short

message is an interface to input message and to click to deliver. The mobile

subscribers will receive a message we pushed.

This system has many applications, not only in commercial area such as for local

retailers to send information to their customers, but also in public sectors such as for

police to send warnings in emergent rescue. Figure 11 shows a case for the mobile

subscribers in given area to receive a message of earth fall.

5 ConclusionNowadays, short message services are widely used, but many of them are not

targeted, causing a waste of money. The mechanism introduced in this research is effective in solving this problem.

Many applications are conceivable, for example, retailer transmits instant news to specific customers, investment firms publish real-time stock market tendency, etc. In public sectors, government departments take precautions against natural calamities, or police agencies evacuate people in flooded area.

In the future, we will put the system into connection with telecommunication industry. We would like to see how well it works in real environment. We will test the overall efficiency of system and investigate the time needed for sending a short message online. Whether the message sent to the customers is well-accepted is also worthy of studying.

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Cell-loc Location Technologies. <http://www.cell-loc.com/how_tech.html>

GSM 03.71: “Digital cellular telecommunications system (Phase 2+); Location

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Figure 11. A message of warning emergent earth fall

Services (LCS); Functional Description; Stage 2”.

Ivana Podnar, Manfred Hau Content to Mobile Users, The 22nd International

Conference on Distributed Computing Systems Workshop.

Jonathan P. Munson, Vineet K. Gupta, Location-based notification as a general-

purpose service, International Workshop on Mobile Commerce archive

Proceedings of the 2nd international workshop on Mobile commerce, pp.40-44

William Stallings,Wireless Communications& Networks, Pearson Prentice Hall

Emiliano Trevisani, Andrea Vitaletti, Cell-ID location technique, limits and benefits:

an experimental study.

Eberspaecher, Joerg，「GSM switching, services, and protocols」，Wiley,2001.

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