|Title of Invention||
"WIRELESS MULTIMODE COMMUNICATION DEVICE USING A SINGLE CLOCK SIGNAL AND METHOD OF OPERATING THE SAME"
|Abstract||A wireless communications network participant comprising: a plurality of communications subsystems, each subsystem being arranged to transmit and/or receive signals under a different telecommunications standard; means for generating a clock signal; and scheduling means for sending commands to at least one of the subsystems for its or their operation, the scheduling means deducing the timing of the commands relative to the clock signal.|
The invention relates to the field of wireless communications. For example, the invention is
applicable to the field of mobile telephony.
Technical specifications will differ from one wireless communications network to another. This
leads to the problem that a wireless communications device designed to work in one network
is unlikely to be compatible with other networks. One approach to ameliorating the
compatibility issue is to provide a standard operating scheme for adoption by designers and
manufacturers of wireless communications networks. For example, standards such as GSM.
AMPS, CDMAOne and UMTS exist in the mobile telephony field. In fact, the mobile
telephony field illustrates the situation where several incompatible standards coexist with
the result that the compatibility problem, although reduced, is not eliminated. For example, a
mobile telephone designed according to the AMPS standard will not work in a GSM network.
In practice, wireless communications networks do not have perfect coverage, i.e. there will be
places where a user will find it difficult or impossible to connect to his or her wireless
communications network. Even if another network provides adequate coverage to the
user's location, the user's device may be incompatible with the other network, as discussed
US2003/02144916 describes a multi-mode mobile communication device capable of communicating
with more than one mobile communication system simultaneously which has a timer for arbritrating
between transmit events of two communication systems.
EP1213830 relates to a multi-mode radio communications device using a common reference
oscillator which uses accumulator timers to achieve GSM and TDMA synchronisation requirements
without using additional reference PLLs.
One object of the present invention is to improve the chances of a user being able to
connect to a wireless communications network.
timing of the commands relative to the clock signal. Typically, these commands cause the
subsystem(s) to begin, modify or stop performing certain processes.
Thus, the invention provides a system which cooperate under several standards, thereby
facilitating connection by a user to a number of wireless communications networks, with
the result that the chances of a wireless communications device being used successfully are
Furthermore, the invention advantageously permits a single timing signal within the
wireless communications network participant to be used for interacting with networks
organised according to different standards so that separate timing signals do not need to be
generated for use with different standards. Moreover, where the wireless communications
network participant switches from interacting with a network organised according to one
standard to interacting with a network organised according to another standard, the use of a
single timing signal allows the switchover to be implemented efficiently as the timings
required under the different standards are reckoned relative to the same clock signal.
In one embodiment, the process of determining how the timing of operations of the
wireless communications network participant should be controlled relative to the timing
signal in order to permit the participant to interact with a target unit involves producing an
offset indicating a timing offset between a point in the timing signal and a corresponding
point in a notional timing signal formatted for communicating between the participant and
the target unit.
The wireless communications network participant may be, for example, a mobile
telephone. The target units interacting with the wireless communications device may be,
for example, basestations in a mobile telephony network., Two of the standards used by the
subsystems may be, for example, me UMTS and GSM standards.
By way of example only, certain embodiments of the invention will now be described with
reference to the accompanying figures, in which:
Figure 1 shows, schematically, a dual band mobile telephone interacting with a GSM
network and a UMTS network;
Figure 2 is a timing diagram illustrating the operation of the mobaile telephone of Figure 1;
Figure 3 shows, schematically, a modified version of the telephone of Figure 1.
Figure 1 shows a mobile telephone 10 which is capable of interacting with basestations,
such as 11 and 13, in a mobile telephone network 12 organised according to the UMTS
standard and in a mobile telephone network 14 organised according to the GSM standard.
The structure of the mobile telephone 10 is not shown in detail in Figure 1 which
schematically illustrates only the processes within the telephone that contribute towards the
As shown in Figure 1, the mobile telephone 10 comprises a GSM subsystem 16 for
performing the processing operations that are necessary when communicating with a GSM
network, such as network 14. The mobile telephone 10 also comprises a UMTS subsystem
18 for performing the processing operations that are necessary when communicating with a
UMTS network, such as network 12. Each of the processing subsystems 16 and 18 is
configured to generate signals for transmission from an antenna 20 of the telephone 10 and
also to process signals received by the telephone 10 through the antenna 20. The
subsystems 16 and 18 share some of the hardware of the telephone 10, including a clock
The scheduling and timing of tasks performed by the processing subsystems 16 and 18 are
controlled, ultimately, by a clock signal 23 provided by the clock 24. Clock 24 contains a
crystal oscillator for the purpose of generating the clock signal 23. The crystal oscillator is
arranged such that the clock signal 23 is at the frequency required by the UMTS subsystem
18 to perform UMTS tasks. Thus, when the telephone 10 is communicating with a UMTS
basestation, the UMTS subsystem 18 times and schedules UMTS tasks by using the clock
signal 23 directly.
The clock signal 23 conforms to the UMTS standard so it cannot be used directly in the
control of GSM operation of the mobile telephone 10 because the GSM standard demands
a clock signal at a different frequency. To allow GSM tasks to be performed with the
correct timing, the telephone 10 contains a scheduler 22 that interacts with the clock signal
23. The scheduler 22 uses the clock signal 23 as a reference signal to calculate the
moments when certain actions must be begun or stopped by the GSM subsystem 16. Based
on the calculated event timings, the scheduler can send commands to the GSM subsystem
16 to cause GSM tasks to be carried out at the correct times. Thus, the GSM tasks are not
controlled directly by a master clock signal but on the contrary the GSM subsystem 16
receives commands to perform the required GSM tasks at the correct times.
The operation of the subsystems 16 and 18 and the scheduler will now be described with
reference to Figure 2.
Figure 2 illustrates the clock signal 23 extending forward in time from an arbitrary origin
tO. Figure 2 illustrates a situation where the mobile telephone 10 can acquire signals from
four basestations in its vicinity. Two of these basestations form part of a UMTS network
and are labelled UMTS#1 and UMTS#2. The other two of these basestations form part of a
GSM network and are labelled GSM#1 and GSM#2.
For the purposes of this example, it is assumed that the mobile telephone 10 is initially
operating in the UMTS mode and that it first establishes a link to UMTS#2. The UMTS
core 18 determines that the boundary of the frame structure of the signals from basestation
UMTS#2 occurs at time t3. Therefore, the UMTS subsystem 18 records offset C indicating
the position of t3 relative to tO so that the UMTS subsystem 18 has a record of the frame
structure of the signals of basestation UMTS#2. At some subsequent time, if the mobile
telephone is required to interact with basestation UMTS#2, the appropriate UMTS task can
be scheduled to commence at the appropriate time by taking offset C into account. In a
similar way, the UMTS subsystem 18 can acquire signals from basestation UMTS#1 and
determine an offset A indicating the position t1 of the boundary of the frame structure of
the signals from the basestation UMTS#1 relative to the arbitrary origin tO of clock signal
23. Likewise, the GSM subsystem 16 can acquire signals from basestations GSM#1 and
GSM#2 and process them under cornmands from the scheduler 22 to determine offsets B
and D indicating the boundaries t2 and t4 of the frame structures of the signals from
GSM#1 and GSM#2 respectively relative to the arbitrary origin tO of the clock signal 23.
When linked to basestation UMTS#2, the telephone 10 will monitor the other basestations
UMTS#1, GSM#1 and GSM#2 in the vicinity. Primarily, this monitoring is done to
determine whether better communications can be achieved (e.g. with fewer errors) by using
a communications link to a different basestation.
Figure 3 shows a modified version 10a of the telephone of Figure 1. In Figure 3, the clock
signal is abstracted from the telecommunications standards used by the subsystems 16 and
18 and a modified scheduler 22a uses the clock signal to deduce event timings for
controlling both the UMTS subsystem 18 and the GSM subsystem 16. The clock signal 23
must be of sufficiently high frequency so that it can accurately time its issuing of
commands to the UMTS and GSM subsystems within the timing error tolerances of those
standards. In this example, the clock 24 produces a signal at 19.2 MHz, which simplifies
the calculation of event times by the scheduler 22a because it is 5 times the UMTS chip
rate and 86 times the 200 kHz radio channel spacing used in GSM.
1. A wireless communications network participant comprising :
A plurality of communications subsystems, each subsystem being arranged to
transmit and/or receive signals under a different telecommunications standard;
Means for generating a clock signal; and
scheduling means for sending commands to at least one of the subsystems for
its or their operation, the scheduling means deducing the timing of the
commands relative to the clock signal.
2. A participant as claimed in claim 1, wherein several subsystems each receive
commands from the scheduler on the basis of the clock signal.
3. A participant as claimed in claim 1, wherein the clock signal is matched to at
least one of the subsystems and the or each matched subsystem is arranged to
utilise the clock signal without the intermediary of the scheduling means.
4. A participant for a wireless communications network, the participant being
substancially as hereinbefore described with reference to Figures 1 and 2 or to
Figures 2 and 3.
"WIRELESS MULTIMODE COMMUNICATION DEVICE USING A
SINGLE CLOCK SIGNAL AND METHOD OF OPERATING THE SAME"
A wireless communications network participant comprising: a plurality of
communications subsystems, each subsystem being arranged to transmit and/or
receive signals under a different telecommunications standard; means for
generating a clock signal; and scheduling means for sending commands to at
least one of the subsystems for its or their operation, the scheduling means
deducing the timing of the commands relative to the clock signal.
|Indian Patent Application Number||2217/KOLNP/2006|
|PG Journal Number||33/2013|
|Date of Filing||07-Aug-2006|
|Name of Patentee||MSTARFRANCE SAS|
|Applicant Address||13 RUE CAMILLE DESMOULINS, 92441 ISSY LES MOULINEAUX, FRANCE|
|PCT International Classification Number||H04Q 7/32|
|PCT International Application Number||PCT/GB2005/000500|
|PCT International Filing date||2005-02-10|