Multiplex communications – Communication over free space – Combining or distributing information via time channels
Patent
1996-07-01
1999-08-24
Olms, Douglas W.
Multiplex communications
Communication over free space
Combining or distributing information via time channels
370341, 455 121, 455552, 455557, H04B 7185
Patent
active
059433337
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a radio communications device and particularly but not exclusively to handoff between two dissimilar systems to which the device is communicating.
BACKGROUND OF THE INVENTION
Various digital communication networks exist worldwide and provide various services for registered user devices. In many areas different networks overlap and service to more than one network is possible.
Multi-mode devices have been proposed which are able select and register with one from a number of networks, depending on the availability of the networks in question.
A problem with this arrangement is that a multi-mode device having a single transmitter/receiver would not be able co-establish and co-register on two networks simultaneously without losing data. Therefore an already established call on one network must be terminated before the device can switch to the other network, i.e. the call must be relinquished.
It would be possible to build a device with two receivers, so as to monitor and receive from two networks simultaneously, thus preserving an established call and switching it from one network to another. However, a device with two receivers would be expensive and significantly larger in size than a single receiver terminal. Similarly it would be possible to provide two transmitters for maintaining a call on one network and establishing a call on the second network during a handover period before dropping the call on the first network. This too would be expensive.
This invention seeks to provide a radio communications device and method in which the above mentioned disadvantages are mitigated.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention a radio communications device is provided, arranged to communicate time divided signals over first and second time discontinuous systems having first and second frame structures respectively, comprising: switching means for switching between communicating signals over the first system during time periods of the first frame structure and communicating signals over the second system during time periods of the second frame structure, such that over a given period of time the device simultaneously communicates time divided signals over the first and second systems.
Preferably the device further comprises control means for causing the switching means to switch between communicating signals according to a contention scheme, wherein the contention scheme manages the activities of the device during simultaneous communication such that any contention between the communicating signals over the first and second systems is resolved.
The contention scheme preferably manages the switching means such that contention is resolved between transmission communication signals and reception communication signals when the device is not capable of transmitting and receiving simultaneously.
Preferably the device is arranged to receive first and second time divided signals from the first and second systems, such that over a given period of time the device simultaneously receives time divided signals from the first and second systems.
The device is preferably arranged to transmit first and second time divided signals to the first and second systems, such that over a given period of time the device simultaneously transmits time divided signals to the first and second systems.
Preferably the management of the communication includes substantially reducing and eliminating any data loss.
According to a second aspect of the invention a method of handoff from a first time discontinuous system to a second time discontinuous system by a radio communications device is provided, comprising the steps of, establishing a call with a remote user via the first time discontinuous system; establishing communication with the second time discontinuous system while continuing the call via the first time discontinuous system according to a contention scheme, handing off from the first to the second time discontinuous system whilst maintaining the call
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Gibbs Jonathan Alastair
Robinson William Neil
Van Den Heuvel Anthony P
Whinnett Nicholas William
Coffing James A.
Hom Shick
Lukasik Susan L.
Motorola
Olms Douglas W.
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