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Wireless Services engineering

Services

Questions that require answers

1. What is the service that we want to create?

2. Who do we create it for?

3. What kind of devices they are having?

4. What kind of communication capabilities the user devices have?

5. Do we need to create client program for user device?

6. What kind of communication model should be used?

7. What is required from the user and how can we help on it?

8. What to optimise in the servise

Communication models

  • Request-reply
    • Client requests data and server provides the data requested
    • The most common model
    • Latency affects heavily
  • Push
    • Server sends data to clients without requests
    • Can be intrusive
    • Who can push data to mobile device?
      • Push validation, whitelists
      • OMA Push Proxy Gateway (OMA PPG)
    • Is the communication capability always on at user device?
      • e.g. Bluetooth communication capability is turned of by default
  • Publish-subscribe
    • Client subscribes itself to server
      • When ever subscribed data in server changes it is pushed to the client
    • Advantages over request reply
      • The bandwidth requirements are reduced.
        • The server program only sends data changes for a specic point to those clients that have registered for exceptions on that point.
      • Reduces latency problems
        • Client program is no longer constantly asking for new data.
        • The data is not delayed by polling cycles
  • How to handle subscriptions
    • Server side
      • Lost connection means unsubscribe?
      • Timers
    • Client:
      • Automated resubscriptions
      • When to give up?
  • Retransmission?
  • Limitations to the amount of subscribees?
  • Allow anonymity to subscribees?
  • Presence based services
  • Peer-to-Peer communications
    • The communicating applications (devices) are equal
      • Either one can initiate the connection
      • Data transmission can go in both ways
      • End-to-end security
      • How to handle dierencies in device capabilities
        • Division of calculation
  • ComLab Peerhood
    • Peer-to-peer neighborhood
    • Provides information about devices and their applications that are in the communication range
    • Supports multiple communications technologies
    • Provides capability to switch from one communication technology to another seemlessly.

Ad hoc communications

  • Spontaneous temporary connections
  • All the communicating devices can be mobile
    • Application cannot rely that the connections remain functional.
  • Routing is problematic
  • Load balancing
    • Movement of nodes may cause extra burden to others.

Client

  • Is there need to create one?
    • Can the service be used with an existing application
      • Microbrowser … Instant messaging client
  • UI
    • What kind of interaction has to be supported
    • How many hardware platforms have to be supported
  • Data storage
    • Do you need to store data at the device
    • Can data be stored and hw much there is space?

The user aspects

  • What is required from the user?
    • Creation of connection
      • Is the wireless connection creation simple enough?
    • Interaction with the service?
  • Transparent service
    • The service access and running does not require any user action
      • e.g Information walls
    • Where to draw the line on automation?
  • How can we help the user to use the service
    • Personalisation
      • What is too much automation?
    • Configuration
      • Can the user know what the selections done are?
    • Context awareness
      • Location
      • Time
      • Role

Optimisation

  • What to optimize?
    • Minimize data transfer?
    • Minimize pakcet amount?
    • Minimize client processor use?
    • Security vs. usability
  • Selections depend on the requirements of the service and the user.

Wireless possibilities

  • Mobility
  • Presence and availability
    • Mobile device is most of the time with user
  • Location
    • Use of user location to customise the service
  • Context aware application
Last modified: 2013/07/01 14:42