Telecommunications – Radiotelephone system – Special service
Reexamination Certificate
1998-06-23
2002-05-21
Urban, Edward F. (Department: 2683)
Telecommunications
Radiotelephone system
Special service
C455S517000, C370S346000
Reexamination Certificate
active
06393273
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a method of and a system for determining if a base station is capable of receiving messages in automatic retransmission request (ARQ) format.
BACKGROUND OF THE INVENTION
With reference to
FIG. 1
, it is known in the art to have a mobile station
20
in radio communication with a base station
22
, which is connected to and in communication with a public switched telephone network
24
. Radio communication between the mobile station
20
and the base station
22
is represented by a double-headed arrow
26
.
In particular, the mobile station
20
and the base station
22
communicate on various radio frequencies, also referred to in the art as channels. The channels are usually classified as being either traffic channels or control channels. The traffic channels are used to bear information during the conversation state of a call. The control channels are used for the exchange of information between the mobile station
20
and the base station
22
relating, for example, to call setup (i.e. initiating a communications session between the mobile station
20
and the base station
22
on a traffic channel).
To send a voice or data message from the mobile station
20
to the base station
22
, the mobile station
20
first sends a traffic channel (origination) request message on a control channel to the base station
22
to request access to one of the traffic channels associated therewith. In response, the base station
22
sends a traffic channel assignment message to the mobile station
20
on a control channel containing a designation of the traffic channel which is allocated to the mobile station
20
. (These steps are referred to as “launching” the communication). The mobile station
20
then uses the allocated traffic channel to transmit a voice or data message from the mobile station
20
to the base station
22
.
It is also known in the art that there are two general types of radio communication systems, analog and digital, with control and traffic channels on an analog system being referred to as analog control and traffic channels, and with control and traffic channels on a digital system being referred to as digital control and traffic channels. The two types of systems differ in that a message on the traffic channel of a digital system is digitized, i.e. the message is divided up into small segments which are then transmitted and reassembled upon receipt to form the message.
For example, if the traffic channel is a digital traffic channel, then a message to be communicated between the mobile station
20
and the base station
22
is divided into a number of segments, referred to as frames. At the present time, the individual frames are transmitted one at a time in one of a plurality of time slots into which the traffic channel is divided in the time domain. Typically, a digital traffic channel is presently divided into three time slots.
When the base station
22
receives a message on a digital traffic channel, the base station
22
will initially wait to assemble all of the frames received from the mobile station
20
, and then attempt to reconstruct the message. If one or more of the frames are lost in transmission between the mobile station
20
and the base station
22
, however, the base station
22
will be unable to reconstruct the message, and the message is lost. The frames may be lost, for example, because of electromagnetic noise on the traffic channel, noise being practically impossible to absolutely filter out of all radio communications.
It is therefore known in the art to format the message to be transmitted on a digital traffic channel in what is known as automatic retransmission request (ARQ) format. In ARQ format, each of the frames of the message is given a frame number. As a consequence, the base station
22
can determine whether all of the frames of the message have been received from the mobile station
20
. If one or more frames of the message are missing, i.e. have not been received by the base station
22
, the base station
22
can send an ARQ status frame to the mobile station
20
asking for retransmission of those specific frames which were not received by the base station
22
. In this fashion, the loss of one or more frames in the transmission of a message from the mobile station
20
to the base station
22
does not result in the loss of the entire message.
Unfortunately, not all base stations are equipped to receive messages from a mobile station in ARQ format. Consequently, it is necessary for a mobile station, such as the mobile station
20
, to determine whether the base station, for example the base station
22
, is ARQ capable.
It is therefore known in the art for a mobile station, such as the mobile station
20
, to prepare a capability update request which is transmitted to the base station
22
. The base station
22
then responds with a capability update response, from which the mobile station
20
can determine the ARQ capability of the base station
22
.
This prior art method is explained in greater detail with reference to
FIGS. 1 and 2
. A mobile station
20
used in the prior art method described above may have an antenna
28
, a transmitter/receiver
30
, a microprocessor
32
, a memory
34
, an input/output assembly
36
, and a bus
38
. The bus
38
can be used to transfer information between the transmitter/receiver
30
, the microprocessor
32
, the memory
34
, and the input/output assembly
36
. In addition, the base station
22
has an antenna
39
which is used to receive messages from the mobile station
20
.
As is shown in
FIG. 2
, upon receiving a message at a block
40
, a program operating in the microprocessor
32
formats a capability update request at a block
42
. The program controls the microprocessor
32
to transmit the capability update request via the transmitter/receiver
30
and the antenna
28
to the base station
22
at a block
44
.
The mobile station
20
then waits for a capability update response to be sent from the base station
22
to the mobile station
20
at a block
46
. Once the capability update response has been received by the mobile station
20
, the program controls the microprocessor
32
to read the response and to determine therefrom whether the base station
22
is ARQ capable at a block
48
.
If the base station
22
is ARQ capable, then the program controls the microprocessor
32
to format the message received at the block
40
in ARQ format at a block
50
. The program then controls the microprocessor
32
to control the transmitter/receiver
30
to send the message formatted in ARQ to the base station
22
at a block
52
. The program ends at a block
54
.
If the microprocessor
32
determines at the block
48
that the base station
22
is not ARQ capable, then at block
56
the program controls the microprocessor
32
to format the message received at the block
40
in non-ARQ format. The microprocessor
32
then controls the transmitter/receiver
30
at a block
58
to transmit the message in non-ARQ format to the base station
22
. The program then ends at the block
54
.
One disadvantage of the prior art method is the time required for the mobile station
20
to format the capability update request and for the base station
22
to format the capability update response. The preparation of the request and the response can cause a delay in communication between the mobile station
20
and the base station
22
which is typically viewed by users of mobile stations
20
as undesirable.
Another disadvantage of the prior art method is that while the request typically takes only a single frame, the response usually requires two frames. As a consequence, the process of determining the ARQ capability of a base station requires three links, one uplink and two downlinks. The additional downlink required adds time to the overall method.
Alternatively, provided the communication between the mobile station
20
and the base station
22
is launched using a digital control channel, the mobile station
20
may be ab
Anderson Keith William
Hicks Scott Gordon
Ericsson Inc.
Myers Bigel & Sibley & Sajovec
Urban Edward F.
LandOfFree
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