Note: Descriptions are shown in the official language in which they were submitted.
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Title:
ON-DEMAND CHANNBL ALLOCATION FOR PACKET DATA
TECHNICAL FIELD
The present invention relates to allocation of channel resources
in a radio communication system supporting transmission of packet
data. The invention also relates to a method of communicating
packet data in a cellular radio communications network.
STATE OF THE ART
In cellular radio communication systems, which are divided into a
number of cells, each of which cells being served by a base
station, and wherein a number of base stations groupwise are
served or controlled by a switching arrangement, generally known
as a mobile switching center, each cell generally contains a
broadcasting channel (BCCH) for broadcasting of channel structure
information on all the channels belonging to the cell. With
channel structure information is here meant which kinds of
channels exist, for what the channels are used etc.
In a cellular radio communication system supporting a so called
packet data service (PDS), which means communication of packet
data, the information broadcasted on the broadcast channel must
contain information about the existence of, and possibly also the
number of, packet data communication channels in the respective
cells. The packet data communication channels are here also
referred to as packet physical channels (PPCH). The usage of the
packet data service however varies strongly throughout the
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network, i.e. the cellular radio communication system. There are
for example cells in which the packet data service is used to a
high extent as well as there are other cells in which the packet
data service is used very sparsely.
In most cellular radio communication systems supporting
communication of packet data, each cell contains at least one
packet data communication channel, i.e. a channel which is
reserved for communication of packet data only. It is apparent,
that in those cells in which communication of packet data only
occurs to a very low degree, or very irregularly, it is
unsatisfactory from the frequency planning point of view to always
have at least one channel allocated for packet data communication
purposes, i.e. to have one or more channels which only are used to
a very limited extent or only occasionally in order to still
provide a satisfactory grade of service for the packet data
service. It is of course also disadvantageous from an economical
point of view that the available channel resources in a cell or in
a system in general are not used efficiently.
Thus, in a cellular system supporting communication of packet data
the cells have to be equipped with packet data communication
channels in order to meet the requirements as to the grade of
service as specified by the operator of the network. The number of
packet data communication channels in a given cell is completely
independent of the actual packet data traffic load at a given time
in a particular cell which means that one or more channels are
reserved or occupied for carrying packet data also when there in
fact is no packet data traffic at all or only to a very limited
extent.
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Dynamic allocation as such of channels is known from a number of
documents for different purposes, such as using the radio
resources to the best possible extent and to obtain maximum system
capacity at the same time as the power transmitted from mobile
stations is minimized. For example in US-A-5 491 837 a system is
shown in which measurements are performed on the mobile stations
in order to determine the quality on the link and channels are
allocated in dependence of the carrier to interference (C/I)-
ratio. However, the disclosure of this document does not take into
account any implementation of packet data communication in the
system.
SUMMARY OF THE INVENTION
What is needed is therefore a cellular radio communication system
supporting communication of packet data in which the available
channel resources in each, or at least a number of cells, are used
to a high or satisfactory extent irrespectively of whether the
packet data traffic is low or high, regular or irregular. A system
is also needed which enables a satisfactory frequency planning
enabling an efficient use of channel resources. A system is also
needed which provides a good grade of service as far as packet
data communication is concerned.
A method of allocating/deallocating channel resources in a
cellular radio communication system supporting communication of
packet data through which the above-mentioned advantages are
obtained is also needed.
Therefore a cellular radio communication system is provided which
comprises a number of base stations each of which serves a cell, a
number of switching arrangements, each of which in turn serving a
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number of base stations and a number of mobile stations. Traffic
channels are used for carrying speech and/or circuit switched data
and control channels are provided for carrying signalling
information or synchronization information. The communication
system furthermore supports communication of packet data. The
system comprises a number of resource management nodes for
managing channel resources, e.g. allocating/deallocating channel
resources, and in addition thereto a number of packet data
handling nodes are provided for handling the packet data services
in the system. At least in some of the cells, channel resources
are allocated for communication of packet data in dependence of
the demand to send packet data in the respective cells.
The resource management nodes as well as the packet data handling
nodes can be arranged in a number of different ways in the system.
For example, according to one embodiment, the resource management
nodes are associated with the switching arrangements which for
example are so called mobile switching centers (MSCs). In an
alternative embodiment, however, the.resource management nodes are
arranged separately from the switching arrangements throughout the
system. Of course any combination thereof is possible, meaning
that some resource management nodes may be arranged separately
from the switching arrangements whereas other resource management
nodes are associated with switching arrangements. Further still
the packet data handling nodes may be associated with the
switching arrangements or they may be arranged separately from the
switching arrangements. Still further some of the packet data
handling nodes may be associated with switching arrangements
whereas others are not. Yet further the packet data handling nodes
may be arranged separately from the resource.management nodes or
they may be associated with them. In principle any combination is
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possible. In general each cell comprises a broadcast channel for
broadcasting information about the channel structure of all
channels in the respective cell. A mobile station entering a cell
or starting up a packet data session in a cell is via the
5 broadcasting channel informed about whether the cell supports
packet data communication or not. According to the invention, a
mobile station entering a cell, or starting a packet data session
in a cell which has no channel allocated for packet data
communication, issues a request to the management node responsible
for the cell, for a packet data channel resource. If there is an
available traffic channel, such is reallocated as a packet data
communication channel. Particularly the mobile station includes
means for sending a message requesting a resource for packet data
transmission on a signalling control channel to the relevant
resource management node. The message may for example be contained
in a set-up message and the resource management node receiving the
request includes means for ordering the base station serving the
cell to search for an available traffic channel. If an available
traffic channel is found, the base station blocks the channel for
traffic communication i.e. speech or circuit data communication
and dedicates it temporarily for packet data communication.
Particularly the (a) signalling control channel of the cell is
used by the resource management node for sending an information
message to the mobile station containing the information that a
channel has been allocated for packet data communication. The
mobile station having received such information, transmits a
request for registration with the packet data handling node of the
packet data communication channel and the mobile station then uses
the reallocated channel for sending/receiving packet data. The
resource management node also includes means for sending a message
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to the mobile station over the signalling control channel if no
available traffic channel is found. The mobile station then
terminates the packet data session.
In a preferred embodiment, a channel allocated for packet data
communication depending on demand, or in other words a reallocated
traffic channel, is deallocated for carrying traffic (e. g. speech)
after a predetermined period of time of non-usage of the channel
for transmission of packet data by/to any mobile station in the
cell. Further still, a channel allocated as a packet data
communication channel depending on demand, is deallocated to
function as a traffic channel if a priority call request (i.e. a
priority speech/circuit data call request) is received in the
resource management node.
In a preferred embodiment means are provided for establishing the
amount of packet data communication in a number of cells and
demand-controlled allocation of traffic channels as packet data
communication channels is implemented if the amount of packet data
communication exceeds a given value. In an exemplary
implementation of the invention, in cells in which the packet data
communication load is high, one or more channels are constantly
allocated as packet data communication channels whereas in cells
in which a predetermined value for the amount of packet data
communication is not exceeded, demand controlled allocation of
channels for packet data communication is implemented. Of course,
in a cell one or a number of channel resources may be constantly
allocated for packet data communication whereas additional
channels may be allocated on demand if the load is so high that
the channels constantly reserved for packet. data communications
are overloaded. In a particular embodiment means are also provided
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for keeping control of the time during which a channel resource,
reallocated for packet data communication on demand, is used to a
given extent. If it is used more or less constantly for at least a
given a period of time, the channel may be allocated as a constant
packet data communication channel.
Therefore a method of controlling the allocation of channel
resources in a cellular radio communication system is also
provided. The coverage area of the radio communication system is
divided into a number of cells and it supports packet data
communication. Traffic channels are used for carrying speech
and/or circuit switched data in a conventional manner as well as
control channels are used for signalling and/or synchronization
information. According to the method, at least in some of the
cells, channels used for carrying traffic/circuit switched data
are reallocated for communicating packet data in dependence of the
demand in the respective cell. The method preferably includes the
steps of: broadcasting information from a resource management node
to all mobile stations in the cell about the actual channel
structure in the cell, ordering the base station serving the cell
to search for and to block a traffic channel when a packet data
communication channel is requested by a mobile station entering or
being in the cell, intending to start up a packet data session,
i.e. sending and/or receiving packet data, requesting the base
station to start up the channel for packet data communication and,
providing information to the mobile station about the channel
reallocated for packet data communication and performing a
registration with the packet data handling node. Particularly the
method also includes the step of transmitting information from the
resource management node managing the cell to a mobile station
requesting a packet data transmission resource if no traffic
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channel is found which is available for re-allocation as a packet
data communication channel. The mobile stations then terminates
the packet data communication session. In an exemplary embodiment
the method further includes the steps of collecting information
about the time period during which the packet data communication
channel has not been used, and deallocating a packet data
communication channel allocated upon request or depending on
demand as a traffic channel if a predetermined time period is
exceeded. Particularly the method includes the step of
deallocating at least a packet data communication channel
allocated on request or depending on demand to communicate speech
and/for circuit data, i.e. as a traffic channel, if a priority
speech/circuit data call request for a traffic channel, is received
in the resource management node and no free traffic channel is
found.
Further still, for deallocating a packet data transmission channel
the method particularly includes the steps of: sending a
deallocation request from the data handling node to the resource
management node, sending a request to block the packet data
communication channel from the resource management node to the
base station, transmitting a response from the base station to the
resource management node, blocking the packet data communication
channel, and sending a traffic channel start-up request from the
resource management node to the base station and using the
deallocated channel for speech/circuit data communication on
request.
It is an advantage of the invention that the channels in a network
will be used in a more efficient manner than in hitherto known
systems and that the channel functionality will change dynamically
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depending on the traffic load situation, on the demand for packet
data communication resources etc.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will in the following be further described in a non-
limiting way and with the reference to the accompanying drawings
in which:
Fig. 1 very schematically illustrates the structure of a
cellular communication system in which resource
management nodes and packet data nodes are associated
with the switching arrangements,
Fig. 2 is a figure similar to that of Fig. 1 disclosing an
embodiment in which the resource management nodes and
packet data handling nodes are arranged in different
manners,
Fig. 3 illustrates a mobile station moving through a number of
cells,
Fig. 4 schematically illustrates starting-up of a packet data
communication channel on demand for a mobile station
entering a cell,
Fig. 5 is a figure similar to Fig. 4 in which a mobile station
starts up a packet data session in a cell,
Fig. 6 schematically illustrates deallocation of a packet data
communication channel due to .non-usage for a
predetermined period of time,
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Fig. 7 schematically illustrates deallocation of a packet data
communication channel due to reception of a priority
call,
5
Fig. 8 shows a flow diagram describing re-allocation of a
traffic channel as a packet data communication channel
on demand,
10 Fig. 9 is a simplified flow diagram describing deallocation of
a packet data communication channel due to non-usage,
and
Fig. 10 is a flow diagram illustrating deallocation of a packet
data communication channel due to a priority call
request.
DETAILED DESCRIPTION OF THE INVENTION
Fig. 1 is a very schematical illustration of a cellular
communication system. With each cell a base station is associated,
here base stations BS1, BS2,... serving the particular cell in
which it is arranged. A number of switching arrangements, here
particularly illustrated as mobile switching centers M-RD1, M-RD2,
are provided, each of which serves a number of base stations. Each
MSC is connected via wire links to the base stations it serves,
for example M-RD1 is responsible for base stations BS3, BS4, BS9,
BS10, BS11, BS17, BS18 whereas M-RD2 controls base stations BS6,
BS7, BS12, BS13, BS14, BS20, BS21 etc. For reasons of simplicity
only two switching arrangements are illustrated in the figure. It
should be obvious to anyone skilled in the art that the particular
cell structure, the number of cells and the number of base
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stations controlled by one switching arrangement can differ a lot
and the invention is not limited to any particular structure or
similar.
A number of resource management nodes are provided for handling
the allocation/deallocation of radio resources in the network. In
the example as illustrated in Fig. 1 the resource management nodes
and the data handling nodes are associated with the respective
switching arrangements M-RDl, M-RD2.
In Fig. 2 a cellular communication system similar to that of Fig.
1 is schematically illustrated. In this embodiment, however, the
switching arrangements, here called MSCl and MSC2 since they have
the functionality of ordinary switching arrangements, .respectively
are arranged in cells 10 and 13 whereas additional switching
arrangements MSC3, MSC4 and MR-1 are arranged in cells 37, 40 and
63 respectively. However, in this embodiment a resource management
node RRMN-1 is separately located in cell 26 and it manages the
cells belonging to MSC1, MSC2 and MSC4. A data handling node PDN
is provided in cell 23 and it handles the packet data service in
cells controlled by MSC1, MSC2 and MSC3. In cell 63 a switching
arrangement, MR-1 is provided with which a resource management
node is associated which controls at least the cells belonging to
MSC4. In cell 60 a combined PDN/RRMN is provided. For reasons of
clarity, the base stations are indicated in some of the cells.
This embodiment is illustrated to show that in one and the same
network packet data nodes as well as radio resource management
nodes either can be associated with switching arrangements or not
and in that more than one alternative can be used in one and the
same system.
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In Fig. 3 cells C1', C2',...,C7' of a cellular communication
system axe illustrated. In each cell C1', C2',...,C7' a base
station BS1', BS2',...,BS7' is arranged. In the illustrated
embodiment it is supposed that the switching arrangement, here a
mobile switching center MSC is associated with the resource
management node RRMN and the packet data node PDN, i.e. included
in one and the same entity 10. Mobile station MS1 moves around in
the network for example through cells C5', C6', C7', C4'. The user
of MS1 uses the packet data service and it is a requirement of the
user that the packet data service is not interrupted in case the
user enters a cell not supporting the packet data service, i.e. a
cell having no channel allocated as a physical packet channel
PPCH. Here it is supposed that cells C5', C7' and C4' along the
route of MS1 all have a channel allocated as a physical packet
channel PPCH and it is irrelevant whether in any or more of these
cells such a packet data communicating channel has been allocated
on demand or whether it is constantly allocated as a packet data
communicating channel. However, cell C6' does not support the
packet data service, i.e. no channel is allocated for packet data
2o communicating purposes at the time being. For example the user of
MS1 starts the packet data session in cell C5' , which includes a
physical packet data channel. When MS1 enters cell C6', through
the broadcast information sent out on the broadcasting channel
(BCCH) MS1 is made aware of the fact that C6' does not contain a
PPCH. MS1 then requests the network, i.e. the radio resource
management node RRMN for a PPCH, i.e. MS1 requests the starting up
of a PPCH by using a traffic channel TCH available for
reallocation in C6'. The procedure when a mobile station is
informed that there is no PPCH in a cell in which the user needs
to use the packet data service will be further described with
reference to Fig. 4.
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Fig. 4 schematically illustrates the messages and the information
sent between the mobile station MS, the base station BS, the
packet data node PDN and the radio resource management node RRMN
in a system according to the invention in which at least a
particular cell uses allocation of packet data communication
channels, also called packet physical channel PPCH, on demand.
When for example a mobile station MS detects that it needs tc
perform a channel re-selection for example due to poor radic
coverage on the .currently used packet physical channel PPCH, the
MS starts listening to the broadcasting channels BCCH of the
neighbouring cells. The MS selects the strongest BCCH. Of course
the MS may also select some other HCCH, if there are some
particular reasons therefore; this is irrelevant for the
functioning of the present inventive concept. The broadcast
information is sent out over the broadcast channels of the
respective cells by the resource management node RRMN.
When the MS has selected a BCCH (i.e, a cell) and received the
information broadcasted over said HCCH, it is supposed that MS
detects that the particular cell does not have any channel
allocated as a PPCH. The MS then sends a message to the network,
i.e. to the resource management node RRMN, for a PPCH, requesting
that a PPCH is started up in the cell. Advantageously this message
is sent on the signalling control channel SCCH. This can be done
in different ways, for exampla through the use of a particular
message type used in the SETUP message. Alternatively a specified
feature activation code can be used in the SETUP message. The
SETUP message is a message initiating a call establishment. For
example for the PDC (Pacific Digital Communications) it is
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described in RCRSTD-27F (Personal Digital Cellular Communication
System),, ARIB Standard (Association of Radio Industries and
Business), issued April 30, 1991, last revised, revision F
February 18, 1997. The invention of course also relates to other
cellular communication systems, such as GSM (Global System for
Mobile Communications) with its GPRS (General Packet Radio
Service), (D)-AMPS, ADC etc. Also other alternatives are possible,
the essential being that a message is sent requesting the starting
up of a PPCH. When such a request or message is received in the
RRMN, the RRMN searches for a traffic channel TCH that is
available for re-allocation in the cell. If the RRMN founds such
an available TCH, that TCH is marked busy and RRMt~ sends a
blocking request to the base station BS of the cell , i . a . the BS
is requested to block the found TCH. When the BS has~blocked the
particular TCH, it sends a response to the RRMN informing RRMLV
that the particular TCH is blocked.
The RRMN then sends a request to the BS to start up a PPCH using
the same resource that was blocked for communication of
speech/circuit data, i.e. to reallocate the channel used as a
traffic channel to act as a PPCH instead. The BS then reports to
the RRMN that the PPCH has been started up in a start-up PPCH
response message. The RRMN then transmits a message to the mobile
station over the signalling control channel SCCH to inform the MS
that the PPCH is started and that it operates on a particular
channel having a particular channel structure, i.e. the MS is
informed about the channel identity and of the channel structure.
The RRMN, advantageously substantially simultaneously, changes the
broadcast information to include also information about the
existence of the newly started PPCH so that any other mobile
station entering, or intending to enter the cell, is informed
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about the existence of a PPCH in the cell. The MS then moves to
the PPCH and uses the PPCH for performing the normal packet
channel registration procedure which is done with the packet data
node PDN which issues a response message to the MS when the
5 registration has been completed.
If, however, the RRMN is not able to find an available traffic
channel, RRMN sends a message to the MS, e.g. through transmission
of an error code, to inform the MS that no channel can be
10 allocated as a PPCH in the particular cell. MS then terminates the
packet data service and the user is informed that the
communication with the network has been lost. Alternatively,
instead of terminating the packet data service, the MS might
instead listen to another broadcast channel ~of another
15 neighbouring cell and the same procedure as described above would
be repeated in that other cell.
In a preferred embodiment a PPCH allocated on demand, i.e. upon
request, in a cell, may be deallocated or reallocated so as to
reassume its original functionality on the occurence of certain
events or if some given requirements are met, i.e. a traffic
channel reallocated as a PPCH on demand, may again be deallocated
to function as a traffic channel. For example a time period may be
defined on a per cell basis, which time period may be
characteristic for a given cell or it may be the same for a number
of cells within a given area such as for example a so called
packet paging area which is the cell area covered by a PDN. Any
alternative is in principle possible, the main thing being that if
a predetermined time period has elapsed during which the channel
allocated as a PPCH has not been used for carrying packet data,
i . a . there are no MSs registered on this PPCH meaning that there
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are no MSs which, although not actually sending any packet data,
still are registered on the PPCH, it is deallocated. As soon as a
demand arises, i.e. a MS requests a PPCH, a traffic channel, if
available, is reallocated to function as a packet data
communication channel instead, giving a very flexible system in
which the channel resources are efficiently utilized. If for
example, at a given time, the demand for PPCHs was high in a cell
and more than one channels were allocated as PPCHs, and the demand
decreases, the deallocation procedure may be carried out stepwise
through deallocating one channel at a time even if the demand for
example has gone down so drastically that there actually is no
demand at all for a predetermined period of time, for example
taking into account the fact that the probability that the demand
goes up again in short may be high or for some other reason.
Alternatively, the deallocation of channels may of course be
coordinated so that if there is actually no demand at all for
PPCHs, all PPCHs of the cell may be deallocated substantially
simultaneously.
Another reason for deallocating a PPCH may be the reception of a
priority speech/circuit data call requiring a traffic channel. One
example.on a priority speech/circuit data call is an SOS-call from
another mobile station in the cell and if there are no free
traffic channels available. According to different embodiments
both or either reasons for deallocation of a PPCH may be
implemented in one or more cells of the system. It is also
possible to constantly allocate a PPCH allocated on demand as a
"constant" PPCH if the demand exceeds a given value or if it is
high during a predetermined time interval which advantageously is
quite long.
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The embodiment described with reference to Fig. 4 assumes that the
MS has done a first packet registration in a cell containing a
PPCH. In Fig. 5 the case is illustrated when a MS wants to
initiate a packet data session when it is in a cell having no
PPCH. With reference to Fig. 3 it is e.g. supposed that MS1 wants
to start up a packet data session when it is in C6'. The procedure
is substantially the same as the procedure described with
reference to Fig. 4, but instead of a packet channel registration
request a packet communication registration request is sent from
the MS to the PDN when a PPCH has been started up. The signal from
PDN to the MS will then, correspondingly, be a packet
communication registration response.
Fig. 6 schematically illustrates the sending of messages in the
case of deallocation of a PPCH because of non-usage during a
predetermined time interval.
In a preferred embodiment the detection of non-usage of an on-
demand allocated.PPCH for a predetermined time takes place in the
packet data node PDN. The PDN then marks the PPCH as inavailable
and transmits a message to the resource management node RRMN
containing a request to deallocate the PPCH. RRMN then sends a
blocking request to the BS to block the PPCH. The BS sends a
response message that the blocking of the PPCH has been completed
to the RRMN. The RRMN then also changes the broadcast information
in the concerned cell, i.e. the broadcast information will no
longer indicate support for PDS in the cell or alternatively it
will contain information about the level of PDS support in the
cell. This is not explicitly indicated in the figure. The RRMN
then sends a request to the base station to ;start up the channel
for carrying speech/circuit data i.e. to act as a TCH again. A
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response is transmitted from the BS to the RRMN. The channel
resource again allocated for traffic communication will then be
used by the RRMLV when needed.
Fig. 7 schematically discloses the sending of messages when a PPCH
is deallocated because of reception of a priority speech/circuit
data call, in the following in short called a priority call, in
the RRMN. It is then supposed that a priority call SET-UP message
is received in the RRMN. This means that the RRMN has to find a
free traffic channel TCH for said priority call. If the RRMN
establishes that there is no channel resource having the
functionality of a traffic channel available, the RRMN checks if
there is any traffic channel which has been reallocated as a
packet data communication channel, RRMN sends a blocking request
to the base station that the PPCH be blocked. When this has been
done, the BS sends a response to the RRMN. The RRMN at the same
time changes the broadcast information in the concerned cell in
the corresponding manner. The RRML~T then 'sends a start-up request
to the base station that the channel resource is to be re-started
to function as a traffic channel again. Thereupon a response is
provided from the BS to the RRML~1 which uses the TCH for the
priority call.
The re-allocation of a channel resource used for carrying traffic
as a physical packet data channel will now be described with
reference to the flow diagram of Fig. 8. An MS using PDS searches
and finds a new cell CN, 100, as discussed above. The MS then
receives information on the cell structure of the new cell CN over
the broadcasting channel of CN, 101. The mobile station examines
whether there is any (available) PPCH facility in CN, 102. If CN
actually does contain an available PPCH, MS uses that PPCH, 102A.
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If on the other hand MS establishes that there is no PPCH in CN
(or not sufficient capacity for packet data communication), MS
sends a request for a PPCH to RRMN, 103. RRMN then examines if any
free traffic channel TCH can be found, 104. If not, in this
particular case, the MS terminates its PDS session 104A. If, on
the other hand, a free TCH is found by RRMN, RRMN sends a request
to base station BS in CN to block the found channel resource for
traffic (i.e. speech or circuit data) communication, 105. It is
supposed that the found channel resource is denoted TCHl. The base
station then informs RRMN that TCH1 has been blocked, 106, for
speech/circuit data communication whereupon RRMN sends an order to
the base station to start-up the channel resource for packet data
communication as PPCHd (physical packet channel on demand) using
the channel resource previously used for traffic communication,
i.e. former TCH1, 107. The start-up of the PPCHd is then confirmed
by the base station through the sending of a response message to
the RRMN, 108, and RRMN sends information to the MS about PPCHd
and it also up-dates the broadcast information to include
information about the existence of PPCHd, 109. The mobile station
then requests PPCHd registration with the packet data node using
the PPCHd in a conventional manner, 110. The PPCHd request is then
confirmed by the packet data node by a packet channel registration
response on the PPCHd, 111.
Fig. 9 is a schematical flow diagram describing the deallocation
of a channel resource from having the functionality of carrying
packet data to speech/circuit data communication. It is here
supposed that a time period of non-usage of the on-demand-
allocated PPCHd, after which deallocation is to take place, has
been given. This information is contained in storing and
processing means in the packet data node PDN. Thus, in PDN the
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time period of non-usage of PPCHd is surveilled, 201, and it is
examined if the time period of non-usage of PPCHd exceeds a
predetermined threshold value Ttr, 202. If the time period has not
been exceeded, the channel resource remains allocated as PPCHd,
5 202A. If, however, the time period is exceeded, a deallocation
request is sent from PDN to RRMN, 203, requesting that the channel
resource be no more used for packet data communication. Upon
receiving such a deallocation request from PDN, RRN~1 sends a
blocking request to BS, 204, that BS should block the channel
10 resource allocated on demand for communication of packet data. BS
then performs a blocking operation and sends a blocking
confirmation message to RRNIN, 205, that PPCHd has been blocked.
RRN1~1 sends a start-up request to BS that the channel resource be
used for apeech/circuit data communication again ~ as traffic
15 channel TCH, 206. The TCH start-up is confirmed by the base
station through a message sent to the RRNInT, 207, and RRN~T up-dates
the broadcasting information correspondingly, 208. If there is a
request for a traffic channel TCH, 209, TCH will be used for
speech/circuit data, 209A. If on the other hand there is no actual
20 request for the traffic channel resource, TCH remains available
for traffic communication unless a new PDS-request is received in
RRMN, 210. Of course, if such a request is received in RRN~1 and
there are also other traffic channels available, or free, also
another traffic channel may be selected for re-allocation as a
PPCH on demand.
Fig. 10 is a schematical flow diagram describing the procedure
when a priority speech/circuit data call set-up request is
received in RRN~1, 301. Upon reception of such a request, RRNR~
performs a search for a free traffic channel, 302. If a free
traffic channel is found, 303, the found traffic channel is used
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21
for the priority call, 303A. If, however, no free traffic channel
is found, RRMN examines if there is any PPCH in the concerned
cell, 304. If there is no PPCH in the cell, any traffic channel
may be reallocated for the priority call set-up 304A using any
appropriate technique. How this is done is not relevant for the
functioning of the present invention. If however a PPCH is
contained in the cell, RRN~T requests the base station to block the
PPCHd allocated on demand, 305. (If there are more than one PPCH
one of them is selected acording to same given criteria; generally
if a particular PPCH is not actually used, or used only to a very
limited extent, that PPCH is selected. Different selection
criteria may be given. ) After blocking has been performed, it is
confirmed by the base station, 306, and the broadcast information
is up-dated by RRNIrT, 307. RRNR~T then requests the base station to
start-up a traffic channel using the channel resource that had
been used for packet data communication, 308. The start-up of the
traffic channel is confirmed by the base station, 309, in a
message sent to RRI~, and the traffic channel is used for the
priority call, 310. It should however be clear that the
deallocation procedure, as described with reference to Figure 9
and Figure 10, does not have to be limited to channel resources
allocated for packet data communication on demand but it could
also be implemented on channel resources "constantly" allocated as
packet physical channels. Alternatively the deallocation
procedure, as far as channels constantly allocated as PPCH:s are
concerned, only is implemented in the case of priority calls when
neither any free traffic channel nor any on-demand allocated PPCH
can be found.
It is an advantage of the invention that a flexible use of
available channels is enabled and in that channel resources can be
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22
utilized very efficiently. It is also an advantage of the
invention that the functionality can be implemented in cells in a
network in which the normal packet data service traffic normally
is very low, but the operator of the network still wants to have a
coverage of the packet data service which is substantially 100.
Through implementing the inventive concept the frequency planning
will be optimized due to the fact that free traffic channels can
be temporarily used for packet data communication. The invention
is not limited to the illustrated embodiments but it can be varied
freely within the scope of the appended claims.
