Location-based Services Enhancement Using Zone- Based Update ...

Location-based Services Enhancement Using ZoneBased Update Mechanism S. Almasri, E. Sedoyeka, M. Alnabhan and Z. Hunaiti Faculty of Science and Technology,Anglia Ruskin University University, Bishop Hall, Chelmsford, United Kingdom s.almasri@anglia .ac.uk Abstract- Location Based Services (LBS) have become popular in the last few years, enabling users easy access to useful information while they travel from one place to another. This paper focuses on evaluating a zone-based approach, which can be implemented in LBS to enhance the efficiency and cut any unnecessary cost associated with updating process. The new strategy is based on dividing the Geographical Information System (GIS) database into a set of geographical entities, which allow the LBS update management system to upload the only, needed information required by the users according to their location. In this way, several advantages can be achieved including; saving the bandwidth of the mobile network, minimising the mobile device power consumption, better utilisation of the mobile device memories; both physical and virtual (cashing) memories, decreasing the time required to perform query and minimising the overhead in the mobile network. This paper presents an evaluation experiment which has been carried out to demonstrate the impact of a zone-based strategy to improve the performance of the LBS systems.

I.

battery lifespan is between 3 to 8 hours (maximum load). Hence, it is essential to reduce the services’ loading time so as to save the battery life. Secondly, the mobile device memory is still small compared to personal computers and laptops. For example, the size of RAM for (HP iPAQ Pocket PC hx2100) is 64 MB. In order to improve this memory utilisation, the requested information provided by LBS should be minimized efficiently. This process can directly contribute to reduce the overhead and latency of the mobile network.

INTRODUCTION

The LBS systems combine the physical location information of the user with intelligent computer systems [2]. As shown in Fig. 1, a typical LBS system consists of Global Positioning System (GPS) and Geographical Information System (GIS) connected via a wireless connection. The GIS is a computer system for capturing, managing, integrating, manipulating, analyzing, and displaying data which is spatially referenced to Earth [4]. LBS offer many opportunities. For the mobile user, some examples of LBS systems are; requesting the nearest business or service, such as an ATM or restaurant and receiving alerts, such as notification of a nearest gas station or warning of traffic jam. LBS systems support individual and public route planning, tracking individuals, computer gaming, information and emergency services. Accordingly, LBS represent a new source of revenue opportunity. Reports from Allied Business Intelligence Research show that the worldwide market for LBS reached $40 billion in 2006 [6]. Users can exploit the LBS by using a mobile device (e.g. Personal Digital Assistant (PDA), Mobile phones ) to send a request for information to the LBS server, which replies in form of speech, pictures, text, map of directions etc. [2]. Such devices experience several drawbacks: Firstly, the power consumption caused by short lifespan of the mobile battery. The average PDA

ISBN: 1-9025-6016-7 © 2007 PGNet

Fig. 1. General Architecture for LBS systems

This paper presents a Zone-Based Update Mechanism to customize the size of data sent from server to the end user in order to enhance the overall LBS systems performance. II.

ZONE-BASED UPDATE MECHANISM

The key elements for developing efficient LBS systems are to provide services for end users in real time, satisfying their needs and considering the following [7]: • processing (including local storage and battery power), • bandwidth allocation and connection link performance and • GPS positioning accuracy. This paper investigates the first two points (processing and bandwidth). It is assumed that the LBS systems consider using a zone-based mechanism to provide necessary GIS information to the end user according to their location and needs. Each user has his own profile identifying his requirements and needs [1]. Generally, the end users through a GPS device send their

position information to a location server where the location based services is performed, then the LBS server provides access to the end user to load a customised amount of information depending on the received position and user profile. The proposed zone-based mechanism includes the following main procedures: • Dividing the GIS data base information into different zones efficiently based on the latitude and longitude coordinates depending on the user location. •

The mechanism divides the data base until it reaches the minimum amount of information according to the user request and profile.

•

Providing the user with only a satisfied zone of information, for example, a map showing only his location with a limited radius; reducing the effects of presenting the entire map to the user such as more delay time, bandwidth utilisation, power consumption and memory wastage.

•

The system will also consider the available bandwidth, connection status and end user capabilities according to feedback information.

In order to measure the performance and efficiency of the above procedures, the proposed approach was applied on a GIS map in Chelmsford City map as shown in Fig. 2. For simplicity in this paper, only the map was considered, without any video, voice or other database information.

Fig. 3. Chelmsford Map Zone A in four new Geographical Zones

Generally, performing the zone-based mechanism will improve the QoS and overall performance of LBS systems in terms of connection quality, power and cost save and finally user’s satisfaction, the main advantages are summarised as follows; •

Improving the LBS Server performance: The server can process more queries for more users efficiently.

•

Reducing the network bandwidth utilisation: The amount of data will be monitored and reduced efficiently according to the bandwidth capabilities, in which only necessary information will be presented to the end user.

•

Minimizing the mobile device power consumption: The end user will receive a reduced amount of information, therefore processing time of and memory usage will be reduced.

The following section presents the experiment work that was used to evaluate and test the performance of the proposed zonebased mechanism, the conducted results has proven the efficiency of the proposed mechanism in different scenarios. III.

Fig. 2. Master map of Chelmsford

Initially the above map was divided into four zones depending on the LBS user’s location (Zone A, B, C and D) as shown in figure 2. Further division processes were performed on zone A as shown in figure 3 until it reached the appropriate map zone that the user would load and display. As mentioned earlier, the LBS end user will display only the map representing his zone location without any extra map information.

EXPERIMENTAL SETUP

A simplified set-up of LBS system was established as shown in figure 4; the system was configured to real-life scenarios. The main aim was to perform experiments to measure the effects of reducing the map size efficiently using the zone-based services. The experiment focused on evaluating the zone-based update mechanism’s impact on the two main parts of the LBS system: •

Mobile link performance (Delay, Bandwidth utilisation).

•

Mobile device performance (Battery, Memory utilisation).

Figure 4 presents the network architecture used during the conducted experiment.

The second task was to measure the delay between the mobile device and the LBS server. As shown in figure 6, this test was repeated in four different scenarios: •

Idle HSDPA link.

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Loading the master map on the mobile device via HSDPA link.

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Idle WLAN.

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Loading the master map on the mobile device via WLAN connection.

Fig. 4. Network Architected for experimental scenarios

The live experimental scenarios were implemented using a Toshiba Equium laptop that represents the mobile end user. During the experiments two main connections were used to perform the tests in different scenarios: Firstly, the end user was connected to the T-Mobile network through a Web’n’walk PCMCIA data card to establish a live HSDPA (3.5G) wireless connection. T-Mobile Web’n’walk data card supports a theoretical speed of up to 1.8 Mbps. In the second scenario the end user was connected to a Wireless Local Area Network (WLAN) at Anglia Ruskin University network infrastructure (IEEE 802.11b) which is connected to the internet using JANET (a network connecting different educational institutions in the UK) with a speed of up to 100 Mbps [5]. An ordinance survey master map of Chelmsford city shown in figure 2 was uploaded to the LBS server. This server is accessed via the internet. During the experiments, Ping command was used to send Internet Control Message Protocol (ICMP) to the server to asses the link performance in idle and busy status (Downloading and Uploading). ICMPs packets were used to calculate the Round Trip Delay Time (RTT), in order to estimate the delay experienced in the connection link. Moreover, the time, power and memory utilisation during loading the master map and the zone maps were measured in order to check the difference between the regular system and the Zone-based system. IV. RESULTS

Fig. 6. RTT for HSDPA and WLAN connections.

The third task was to measure the discharge rate of the laptop battery, which was accomplished through monitoring the battery in two cases: • •

Idle mode (no heavy application is running) Downloading mode (downloading the map)

The discharge rate for each case is shown in figure 7.

The first task of this experiment was to measure the time taken to download each file (full map, zone map) using the two types of connections (3.5G and WLAN), the results obtained from this task are shown in figure 5.

Fig. 7. End user Power Discharge Rate V.

Fig. 5. Loading time in HSDPA and WLAN networks

DISCUSSION

In this section the impact of zone based strategy on LBS components will be discussed.

A. Mobile network performance As shown in figure 6, the time taken to download the whole map in both scenarios (HSDPA and WLAN) was approximately four times the time taken to download the zone map. In the HSDPA connection the master map needs 256.83 seconds to be loaded completely on the user's device while the zone map requires only 62.56 seconds. Also in the WLAN connection the total time needed to load the master map was 183.78 seconds while the zone map took only 46.88 seconds to be loaded. Therefore, the congestion can be reduced. Hence, the performance of the mobile network has been directly affected since the time of accessing the network was reduced using the zone-based update mechanism. Moreover, the delay was high when the user was accessing the network (map downloading). Using zone-based update mechanism to reduce the amount of the data transferred between the server and the mobile device has reduced the demand on the mobile network bandwidth and contributed to the reduction of the cost of accessing the mobile network by the end user. As a result of using small size map, the overhead on the network has been reduced significantly.

B. Mobile device performance Evidently, from the results obtained the use of zone-based mechanism can directly affect the performance of the mobile device. This can be seen through comparing the power consumption in each case (whole map and zone-based). The calculated total discharge rate from the whole and small maps can be seen in figure 8.

mechanism allows the user to benefit from LBS server and use the rest of the memory for other applications. Moreover, dealing with a smaller sized database can help in responding to the user’s query quicker.

VI. CONCLUSION AND FURTHER WORK This paper presented the outcome from experimental work conducted to evaluate the impact of using the zone-based update mechanism in LBS performance. The results obtained from this work have shown that the mechanism can directly contribute in enhancing the overall performance of LBS systems, particularly, network link performance and user mobile device. In addition, such mechanism can also minimise unnecessary cost which might be added due to uploading redundant information by the end users. These experiments were carried out using a simplified LBS set-up, however, further experiments need to be carried out to fully evaluate and test the mechanism.

ACKNOWLEDGMENT This research work is supported by Intergraph Ltd, the world’s pioneers of spatial information management software, under Registered Research Laboratory (RRL) program. Maps are supported by Ordnance Survey. The authors wish to thank Mr Ralph Diment (Intergraph UK) and Mr Chris Philips (Ordnance Survey) for their help and support. REFERENCES [1]

[2] [3] [4] [5] [6] [7]

Fig. 8. Total Calculated Discharge rates

As shown in figure 8, the use of the zone-based mechanism can allow the mobile device battery to last longer, which can be beneficial in case the end user cannot recharge the mobile device in emergency situations. Another benefit is better utilization and management of the storage space. This is important when the mobile device storage capability is limited. Zone-based

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