Location-Based Information Push as a Short Message Service
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 ROC
firstname.lastname@example.org email@example.com firstname.lastname@example.org
“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
In 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
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 Review
2.1 GSM Architecture
GSM 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)
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.
Figure 2.Mobile subscriber data in the HLR
(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.
Figure 3.Mobile subscriber data in the VLR
(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 Notification
There are many kinds of location-based services available, among them is the
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
Figure 4.High-level model of location-based notification
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), depending on how
the SMLC is connected. (Jonathan et al., 2002)
Le Lg Ls Lb
LCS Gateway MSC/ Serving
Client MLC VLR MLC
Figure 5.Logical Architecture for GSM Location Services
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 technique
There 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).
Table 1. The characteristic analysis of mobile positioning technique
Technology Cell-ID TOA/TDOA E-OTD/OTDOA A-GPS
Positioning Network- Network- terminal- hybrid-
based based based based based
Proximity 200~2000m 50~200 m 50~150m 5~50m
Start the machine
time 1~3 seconds 3~6 seconds 5~8 seconds 10~40 seconds
Start the machine fast
End The software GPS machine; GPS network、GPS
demand of fine tuning Connected time RNC、LMU equipment receiver、IP-
the office synchronism Based network
Demand of none none Location software, GPS receive module,
end user Logical processing location software
Network GSM/GPRS GSM/GPRS E-OTD－GSM/GPRS GSM/GPRS
system WCDMA WCDMA OTDOA－WCDMA WCDMA
CDMA2000 CDMA2000 CDMA2000
Suitable Location service Location service, Location service, Location service,
services Tracking service Tracking 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
Figure 6.Cell-ID positioning method of network-based
2.4 Short Message Service
Short 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
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
3 System Analysis and Design
We propose an architecture for this system in this chapter.
3.1 System Analysis
According 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
Figure 7 shows a general idea of systematic maintenance.
Figure 7. Systematic maintenance
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
3.2 Procedure of system
When 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.
Search MS of the
of MS in given area
Save failure data No Yes Save success
in log file data in log file
Figure 8.Flow chart for System
4 Implementation of the Location-Based Information Push System
4.1 System architecture
For 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.
Systematic platform Short message sender Mobile subscribers
System Message Deliver
Figure 9.Architecture of 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 interface
Figure 10 shows the three parts of the system interface that are the windows for
delivering short messages, selecting area and LBS database query.
messages Selecting area
LBS Database query windows
Figure 10. System main components
The window for LBS database query is used to select mobile subscribers in given 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.
Figure 11. A message of warning emergent earth fall
Nowadays, 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.
Cell-loc Location Technologies. <http://www.cell-loc.com/how_tech.html>
GSM 03.71: “Digital cellular telecommunications system (Phase 2+); Location
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.