Microsoft Spot Market 2

Project Background

The Client

Problem Statement

Requirements Gathering

Persona

Storyboards

Operating Systems

In terms of operating systems, we researched operating systems that mobile phones normally use. Therefore, we have reached the conclusion that the platforms most normally used are Android, iOS and Windows Phone. In order to target all of these platforms at the same time, without needing to develop individually for each of them, we decided to use Xamarin as a framework (at the suggestion of our client as well). Moreover, the previous Spot Market project was also done in Xamarin so it is important for us to work in the same environment.

Programming Languages

In order to be able to develop for Xamarin, we needed to learn C# and accommodate to the framework's syntax. Therefore, at the suggestion of Yun Fu, we have studied a book called "Xamarin Cross-platform Application Development - Second Edition" by Jonathan Peppers. We have successfully studied and understood the requirements for the project by trying out the examples in the book.

Libraries and APIs

In order to make the project we required beacons. The ones we decided to get were Estimote beacons. Not only were they compatible with a library called AltSpace which tries to unify all beacons under one easy-to-control library, but also they have their own API. For both of these we researched the documentation in order to understand how they work. Finally, we decided to use the Estimote SDK as it allowed us more control over the beacons and better means of reading the signal.

Indoor positioning system

Indoor positioning system is a system that locates objects or people inside indoors using radio waves, magnetic fields, acoustic signals, or other sensory information collected by mobile devices. There are several commercial systems on the market, but there is no standard for the system.

Indoor positioning system uses different technologies, including distance measurement to nearby nodes with known positions (e.g. WiFi access points), magnetic positioning, dead reckoning. They constantly locate mobile devices and tags for devices to get sensed.

Despite a range of technologies we could choose from, the client specifically recommended beacons. As a result, our research was mainly focus on the bluetooth technology of beacons.

Bluetooth Technology

Bluetooth is a technology used to enable smart devices to communicate with each other wirelessly. Its design allows it to consume very low power as well as is based on low-cost transceiver microchips. Approximately, bluetooth communicates using radio waves with frequencies within the 2.4 GHz ISM frequency band. ISM frequency band is a frequency band that has been specifically reserved for industrial, scientific and medical devices by international agreement. The specification of bluetooth was internationally devised in 1994 and is now managed by the Bluetooth Special Interest Group (SIG). The technology can be split into three main categories according to its range. The listed range can vary from location to location, since the signals tend to be affected by propagation effects especially in an indoor environment. Type 3 is regarded ideal for indoor positioning system due to its relatively short range. However, most bluetooth devices are available in a form of the second class.

Such device can connect to up to seven other devices at the same time by setting up an ad-hoc network. Such networks may be set up automatically where the initiating device acts as a master to all other devices. A technique referred to as spread-spectrum frequency hopping is a method used by bluetooth to avoid any interferences among devices. With this method, a device will send out one of 79 randomly chosen frequencies, switching from one to another frequency 1600 times per second. As a result, it is highly unlikely that two devices will transmit signals on the same frequency and hence minimises the risk of interference.

In practice, a device must perform an inquiry to discover other devices which are in its range before a network can be set up. This process can take up to 11 seconds in one go. Subsequently, any discovered devices will send back information about itself like their names and addresses. The network can then be set up between devices that are within the master device’s range.

Beacons

Beacons or bluetooth beacons in the specific case are small radio transmitters that send out signals in a radius of 10-30 meters. The signals will get picked up by the user’s device via bluetooth. Given that the location of the beacon is known, the application then uses the signals previously received by the device to work out the accurate location of the user within the store. The project is largely based on the integration of beacons where great challenges lie.

Mathematical Modelling

Location will be worked out numerically by estimating signal propagation and calculating angles or distance. Inverse trigonometry will then be used to determine location of an object. In general, there are three main methods used in this, fingerprinting, triangulation and trilateration. Only the latter method, however, will be covered since it is the method that the client wanted us to implement in.

Trilateration

Because the user U is at a distance d1 from beacon B1, we know that the user is placed on the circle with the center marked by the B1’s position and with the radius d1.

(xu-xb1)^2+(yu-yb1)^2=d1^2

Where:

xu=x coordinate of U

yu=y coordinate of U

xb1=x coordinate of B1

yb1=y coordinate of B1

Similarly, U is also placed on the circle with the center in B2 and with the radius d2, so the user should be at one of the 2 intersections of these 2 circles. We now have a system of 2 quadratic equations, with 2 unknown variables (xu and yu):

(xu-xb1)^2+(yu-yb1)^2=d1^2

(xu-xb2)^2+(yu-yb2)^2=d2^2

Where:

xu=x coordinate of U

yu=y coordinate of U

xb1=x coordinate of B1

yb1=y coordinate of B1

xb2=x coordinate of B2

yb2=y coordinate of B2

This system has 2 possible solutions. We can use the distance between U and B3 to find the right solution (at which intersection U is).

References

http://tam.unige.ch/assets/documents/masters/bekkelien/Bekkelien_Master_Thesis.pdf

http://uk.businessinsider.com/beacons-and-ibeacons-create-a-new-market-2013-12

http://www.qrg.northwestern.edu/projects/vss/docs/navigation/1-what-is-triangulation.html

https://senion.com/indoor-positioning-system/

Interact with the prototype by clicking on the screen

Unit Testing

To ensure we were heading in the right direction and therefore the functionality required by the client was feasible, we had to carry out a number of tests at the end of each cycle. Since there were many different aspects to the software, we decided to apply unit testing to the project. By following the practice of unit testing, we isolated each component into the smallest units before carrying out a testing on each individual unit to ensure its correctness. We came up with a table of all units of the project (which can be seen on our project website) in which was used as the guidance when testing.

Unit testing allowed us to work with small components of software, so if there are problems we could detect and fix them without overly affecting the other units. Moreover, this provided some kind of documentation of the software, in which the team members could use as a tool to revisit unit’s features and ways to use them. This could also be useful for the client as well; he could use it to gain a better understanding of what each unit does.

However, the testing did present certain downfalls as well. It was a difficult decision for the team members to make on what component could be represented as a unit. Also, the testing required the team to constantly update the table as the client’s requirements varied.

Despite certain disadvantages, every team member agreed that this was unit testing was the best approach in terms of testing. It allowed us to work with smaller components of the system which in effect massively reduced the complexity that might have arose otherwise.

In order to do unit testing in Xamarin, we used xUnit, a framework which contains various ways of doing unit testing.

User Acceptance Testing

As we didn't previously work with Xamarin before and our project was important to be tested by multiple users, we decided to also use User Acceptance Testing as a means of testing. This can be divided into two groups: beta based on prototype we used to gather information from student colleagues and client feedback we continously received during the development process.

We made a beta that had limited functionality in order to easily gather information about errors. We asked our users to send feedback to us in order to improve the apps until the final submission. Overall, we tested our app with around 10 users and managed to identify a few number of bugs in the retailer app.

Moreover, during the development process we also gathered feedback from the client. Whenever we implemented something new, we showed our client at the next meeting we had. This was very useful as our client came with suggestions that made us realize other functionalities that we could implement and that were trivial in some cases. For example, our retailer app didn't allow users to add maps that used shapes other than rectangles. Our client suggested that a store might be triangular or circle-shaped. Thus, we implemented the zone detector to find zones that use different shapes.

Overall, the User Acceptance Testing helped us gather erros and suggestions for features from our users and client. We considered using a library to automate the testing in this case, called Xamarin.UITest, but ultimately we think getting feedback directly from users was more beneficial.

Compatibility Testing

One issue when developing for Android is the various number of mobile devices that use this operating system. There can be phones with different phone sizes or different Android Versions. Moreover, some phones even have their own UI software installed on top of Android. This results in a conflict in how a developed app looks like when deploying to multiple phones. For example, if, when developing, we use a small screen size(let's say 4") to make the UI, when we deploy to a larger screen (say 5"), the content will not scale automatically and will looks really small in comparison to the screen size developed for.

The best solution is to create UI screens for all screen ratios. Thus, each phone will acquire the components it needs for its own size.

We managed to test compatibility between phones using Xamarin Test Cloud. Xamarin Test Cloud is a powerful tool which lets an user to deploy his app to the cloud, where it is installed on multiple phones. Our client, Tim Gregson, mentioned that Xamarin Test Cloud actually uses real phones and not simulations of them. This is really useful as you can see how your application behaves on different phone sizes.

At first, our application did not look good and actually worked only for 4" screens. We managed to solve this easily, but it took some time to redesign the front end again for all versions. While we didn't have enough time to scale the content for tablets, we managed to make the app scalable for phones with screen sizes between 4"-6" which, ultimately, should be enough as most of the phone nowadays fit in this profile.

One more small issue that showed up while doing Compatibility Testing was the app not installing on some of the phones. We concluded that this is perfectly normal as we targetted Android SDK Level 16 as a minimum in order to make use of several newer features in Android. This means that a phone will need a minimum Android version of 4.1 (Android JellyBean).

Incomplete Features and Bugs:

Beacons tend to display wrong distance due to them not being accurate enough (bug)

User can be shown outside the map due to previous issue (bug)

Information below the map is currently useless as we do not do anything with it(incomplete feature)

Critical Evaluation

Future Work

Development Schedule

Software Development Methodologies: Extreme Programming

As part of COMP204P and COMP205P, each student group is assigned a client who requires the team to develop a specific piece of software. We got assigned Tim Gregson from Microsoft who wanted us to continue working on the Spot Market engine from last year. The client’s requirements for our team were very simplified and open-ended; he initially wanted us to develop a software which utilises an indoor positioning system. The team realised that in order to develop a high-quality software productively in such circumstance, flexibility and effective communications were at heart of the project. We then went on the explore many different software development methodologies and extreme programming (XP) seemed to be the most promising one.

The fact that we only need to submit the project once means that we will not be able to retrieve the project to make any further improvements if the client is not satisfied with certain features. This then required us to apply short development cycles to the project rather than a long one. We kept the client updated of every cycle through regular meetings (around once every two weeks), bi-weekly reports and the project’s website. We informed the client of everything that was going on in terms of functionality, tools used and progress. This had allowed him to effectively and conveniently communicate any desires he may have regarding to project.

Also, we started off the project with a simple solution to the client’s request believing that extra features can be added in later stages which is the concept encouraged by XP. Goals for every cycle were set aimed at specific functionality. In the post-feedback development cycles, we then made modifications accordingly. Unit testing was used as mean to validate results for each cycle.

By following the practice of extreme programming, the client was allowed to make changes of requirements along the way at any stage of the project he may wish. Moreover, we worked very hard to ensure that we were within the client’s reach; we regularly kept the client up-to-date with every progress made in each development cycle through website and documentation.