There is an interesting paper in IEEE Wireless Comms Magazine 2008, " ENABLING MULTISERVICE ON 3G AND BEYOND: CHALLENGES AND FUTURE DIRECTIONS" and a gist of that article could also obtained from this presentation by one of its authors. - MultiService: The UE should be able to perform multiple services simultaneously. Though this is possible to quite an extent in the present phones, there are still limitations and few allowed combinations that will have to be changed
- MultiNetwork: These MultiServices should not be restricted to a single network at any time. A user could be having a voice call using HSPA+ network while he is watching youtube clips using 802.11n.
- MultiMode: For these MultiServices on MultiNetworks, the users will have to use MultiMode terminals with n different kinds protocol stacks. So the terminal would support WLAN, UMTS, HSPA+, LTE, 802.21, WiMAX, Bluetooth, DVB-H, etc. (sorry if missed something else)
This Multinetwork environment providing Multiservice with Multimode terminals is also referred to as Hetrogeneous Wireless Network or HWN.The real challenge which has not yet been present on the current terminals is that these multiple technologies not only independently provides services to a user, but also interacts with others in a collaborative manner to provide a given QoS guarantees. This will probably require revolutionary design change from the existing approach of multiple protocol stacks each independent of each other.
Another big challenging problem to solve would be automatic handovers horizontally and vertically. A horizontal handover migrates a connection between two homogeneous networks. A vertical handover deals with the migration between heterogeneous networks (e.g., from cellular to WLAN). The terminal will need to have intelligence to handover a particular service horizontally or vertically independent of other services. The terminal will also have to take into account the delay and the loss associated with the handover.
This is all very interesting concept but the complexity and challenges will mean that this wont see light before 2016 or rather 2020.
Agree that the protocol stack design should allow for many radios as network I/O, while having a single IP stack above them in the kernel, and another IP stack (possibly) in user mode. There are issues with the CS / non-data services of radios but for the mobile Internet device running mostly IP, a more UNIX like arrangement would make great sense.
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Michael G. Williams
Also wanted to mention that 802.21 can provide an excellent internal API for signaling between layers in a multiradio handset. It could be said that the addition of mobility to network devices showed us the need for signaling interfaces between the protocol layers, without violating the layering. I initiated some work with the JSR community to try ind get synergy with .21 and Java apps too, since protocol layers at 7+ can sometimes benefit from quicker notification of changes going on for their streams.
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Michael G. Williams