U.S. patent application number 14/597805 was filed with the patent office on 2015-05-21 for discontinuous transmission cdma system.
This patent application is currently assigned to Core Wireless Licensing S.A.R.L.. The applicant listed for this patent is Kalle Ahmavaara, Fabio Longoni. Invention is credited to Kalle Ahmavaara, Fabio Longoni.
Application Number | 20150139216 14/597805 |
Document ID | / |
Family ID | 10851728 |
Filed Date | 2015-05-21 |
United States Patent
Application |
20150139216 |
Kind Code |
A1 |
Longoni; Fabio ; et
al. |
May 21, 2015 |
Discontinuous Transmission CDMA System
Abstract
A method of transmitting in a second mode at least one data
frame from a first node to a second node. Determining if there is
data to be transmitted and if there is no data to be transmitted
then transmitting from said first node to said second node no frame
in the second mode. The first node receiving an indication that the
first node should use a first mode and transmitting an
acknowledgement in response to the indication. Switching from the
second mode to the first mode and transmitting in the first mode at
least one data frame from the first node to the second node. Then,
further determining if there is data to be transmitted and if there
is no data to be transmitted then transmitting from said first node
to said second node at least one empty frame in the first mode.
Inventors: |
Longoni; Fabio; (Espoo,
FI) ; Ahmavaara; Kalle; (Helsinki, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Longoni; Fabio
Ahmavaara; Kalle |
Espoo
Helsinki |
|
FI
FI |
|
|
Assignee: |
Core Wireless Licensing
S.A.R.L.
Plano
TX
|
Family ID: |
10851728 |
Appl. No.: |
14/597805 |
Filed: |
January 15, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13484690 |
May 31, 2012 |
|
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14597805 |
|
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|
09959034 |
Jan 8, 2002 |
8233442 |
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PCT/EP00/03453 |
Apr 17, 2000 |
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13484690 |
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Current U.S.
Class: |
370/342 |
Current CPC
Class: |
H04W 72/04 20130101;
H04B 7/216 20130101; H04B 7/204 20130101; H04W 76/28 20180201 |
Class at
Publication: |
370/342 |
International
Class: |
H04W 76/04 20060101
H04W076/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 1999 |
GB |
9908805.6 |
Apr 27, 1999 |
GB |
9909689.3 |
Claims
1. (canceled)
2. A method comprising: transmitting in a first mode at least one
data frame from a first node to a second node; determining if there
is data to be transmitted , wherein if there is no data to be
transmitted, transmitting from said first node to said second node
at least one empty frame in the first mode; receiving, at the first
node, an indication that the first node should use a second mode;
transmitting, from the first node, an acknowledgement in response
to the indication; switching, at the first node, from the first
mode to the second mode in response to the receiving of the
indication; transmitting, in the second mode, at least one data
frame from the first node to the second node; and determining if
there is data to be transmitted , wherein if there is no data to be
transmitted, transmitting from said first node to said second node
no frame in the second mode.
3. The method of according to claim 2 wherein the indication is
different for the first mode and the second mode.
4. The method according to claim 2, wherein the first node switches
to the second mode from the first mode after the acknowledgement
has been sent.
5. A method comprising: transmitting in a second mode at least one
data frame from a first node to a second node; determining if there
is data to be transmitted , wherein if there is no data to be
transmitted, transmitting from said first node to said second node
no frame in the second mode; receiving, at the first node, an
indication that the first node should use a first mode;
transmitting, from the first node, an acknowledgement in response
to the indication; switching, at the first node, from the second
mode to the first mode in response to the receiving of the
indication; transmitting in the first mode at least one data frame
from the first node to the second node; and determining if there is
data to be transmitted , wherein if there is no data to be
transmitted, transmitting from said first node to said second node
at least one empty frame in the first mode.
6. The method according to claim 5, wherein the indication is
different for the first mode and the second mode.
7. The method according to claim 5, wherein the first node switches
to the first mode from the second mode after the acknowledgement
has been sent.
8. An apparatus comprising: a memory to store data; a processor
coupled to the memory, the processor configured to: transmit in a
first mode at least one data frame from a first node to a second
node; determine if there is data to be transmitted , wherein if
there is no data to be transmitted, transmitting from said first
node to said second node at least one empty frame in the first
mode; receive, at the first node, an indication that the first node
should use a second mode; transmit, from the first node, an
acknowledgement in responsive to the indication; switch, at the
first node, from the first mode to the second mode; transmit in the
second mode at least one data frame from a first node to a second
node; and determine if there is no data to be transmitted , wherein
if there is no data to be transmitted, transmitting from said first
node to said second node no frame in the second mode.
9. The apparatus of according claim 8 wherein the indication is
different for the first mode and the second mode.
10. The apparatus according to claim 8, wherein the first node
switches to the second mode from the first mode after the
acknowledgement has been sent.
11. The apparatus according to claim 8 wherein the indication
indicates the mode is not to be changed.
12. The apparatus according to claim 11 where the first node
continues to operate in the first mode.
13. The apparatus according to claim 8 wherein the processor is
further configured to: receive a second indication, wherein the
second indication indicates switching from the second mode to the
first mode; determine data is available to be sent; and transmit
the data from the first node to the second node.
14. An apparatus comprising: a memory for storing data; a processor
coupled to the memory, wherein the processor is configured to:
transmit in a second mode at least one data frame from a first node
to a second node; determine if there is data to be transmitted ,
wherein if there is no data to be transmitted, transmitting from
said first node to said second node no frame in the second mode;
receive, at the first node, an indication that the first node
should use a first mode; transmit, from the first node, an
acknowledgement in response to the indication; switch, at the first
node, from the second mode to the first mode in response to the
receiving of the indication; transmit in the first mode at least
one data frame from the first node to the second node; and
determine if there is data to be transmitted , wherein if there is
no data to be transmitted, transmitting from said first node to
said second node at least one empty frame in the first mode.
15. The apparatus of according claim 14 wherein the indication is
different for the first mode and the second mode.
16. The apparatus according to claim 14, wherein the first node
switches to the first mode from the second mode after the
acknowledgement has been sent.
17. The apparatus according to claim 14 wherein the indication
indicates the mode is not to be changed.
18. The apparatus according to claim 17 where the first node
continues to operate in the second mode.
19. The apparatus according to claim 14 wherein the processor is
further configured to: receive a second indication, wherein the
second indication indicates switching from the second mode to the
first mode; determine data is available to be sent; and transmit
the data from the first node to the second node.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
13/484,690 filed on May 31, 2012, which is a continuation of
application Ser. No. 09/959,034 filed Jan. 8, 2002, now U.S. Pat.
No. 8,233,442 issued May 31, 2012, which was the National Stage of
International Application No. PCT/EP00/03453 filed Apr. 17, 2000,
which claims the benefit of United Kingdom Application No.
9908805.6 filed Apr. 16, 1999 and United Kingdom Application No.
9909689.3 filed Apr. 27, 1999. Each of the above referenced
applications are hereby incorporated by reference in their
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of transmitting
and in particular but not exclusively to a method of transmitting
in a wireless telecommunications network.
BACKGROUND OF THE INVENTION
[0003] The use of code division multiple access (CDMA) is being
proposed for the next generation of cellular telecommunication
networks. Additionally, code division multiple access is also being
used in the IS-95 Standard in the USA. CDMA is a direct sequence
spread spectrum technique. In a wireless cellular network using
CDMA, the mobile terminals in one cell associated with a first base
station will use the same frequency as mobile stations in an
adjacent cell associated with a second base station. The different
mobile stations can be distinguished by the respective base
stations as each mobile station will be using a different spreading
code.
[0004] In U.S. Pat. No. 5,101,501 a CDMA system is described which
uses "soft" handoff. With soft handoff, a mobile station is capable
of communicating with more than one base station at the same time.
This will typically occur when the mobile station is close to the
boundary defined between two cells. The signals sent by the mobile
stations will be received and processed by both of the base
stations. Likewise, the mobile station will receive the same signal
from the two base stations. The signals from the two base stations
may be combined. The combined signal may provide better quality
than any of the individual signals received by the mobile
station.
[0005] Thus, one mobile station can listen to two or more base
stations simultaneously. It is therefore important that the
information received by the mobile stations from the different base
station be identical. If different information is received from the
different base stations, the mobile station will have no way of
determining which is the correct information and which information
can be ignored. Additionally it will not be possible to combine the
signals from the different base stations to provide a meaningful
combined signal.
[0006] Generally, different information will be received by the
mobile station because an error in transmission has occurred and
one of the expected transmissions from one or more of the base
stations is not transmitted by the base station. The base station
may not receive any information to be transmitted to the mobile
station for two reasons. Firstly there has been an error in the
information received by the base station. Secondly, there is in
fact no information to be received. The lack of information may be
due to, for example a pause in conversation or because the
transmission is a discontinuous transmission. It is therefore
necessary to determine whether the lack of received information is
intentional or whether it is due to an error.
[0007] It has been suggested by the inventor that empty frames of
data can be sent to the base station in two different ways. These
two ways do not constitute prior art. Firstly, the transmission is
suspended. In other words, the base station will be sent nothing.
This has the advantage that the processing resources at the base
station are saved as well as in other network elements. The load at
the interface between the base station and the network controller,
which is sending the information to the base station, is reduced.
However this method has the disadvantage that it is not possible to
distinguish between a transmission error and the fact that there is
no data. This leads to two problems.
[0008] Firstly, failures in the interface between the base station
and the network controller are not detected by the base station in
the case of information being sent from the network controller to
the base station or by the network controller in the case of
information being sent from the base station to the network
controller.
[0009] Secondly, if a data frame is not received, due to an error,
by a base station, that data frame cannot be transmitted by the
base station to the mobile station. If the mobile station is in
soft handoff, that is communicating with more than one base station
at a time, the mobile station will receive different data streams
from the base stations due to the error. This may lead to errors in
the mobile station when it attempts to combine the different data
streams.
[0010] The second method for dealing with empty frames of data is
for the base station to be sent empty frames of data. This makes it
possible to distinguish between errors and the fact that there is
no information. However, this method does have the disadvantage
that additional processing capacity is required at the base station
and other network elements. Additionally, the load at the interface
between the base station and the network controller is
increased.
[0011] Similar problems can also occur in the uplink
directions.
SUMMARY OF THE INVENTION
[0012] It is an aim of embodiments of the present invention to
provide a method of dealing with the absence of information or data
which addresses the disadvantages of the known methods.
[0013] According to one aspect of the present invention, there is
provided a method of transmitting from a first node to a second
node, the method comprising the steps of transmitting in a first
mode at least one data frame from the first node to the second
node; and determining if there is no data to be transmitted and if
there is no data to be transmitted transmitting at least one empty
frame in the first mode; and switching to a second mode in which no
transmission is made in the absence of data to be transmitted at
least some of the time.
[0014] The first and second nodes may be any suitable elements in a
telecommunications network.
[0015] According to a second aspect of the present invention there
is provided a method of receiving transmissions from a first node
at a second node, the transmission has a first mode in which if
there is no data to be transmitted, empty frames are transmitted
and a second mode in which if there is no data to be transmitted
nothing is transmitted, the method comprising the steps of:
receiving transmissions from the first node, wherein if the
transmissions have a first mode and a frame is not received an
error is determined to have occurred.
[0016] According to a third aspect of the present invention there
is provided a first node for transmitting data to a second node,
wherein the first node comprises transmitting means for
transmitting data to the second node, the transmitting means have a
first mode of operation in which data is transmitted in data frames
and if there is no data to be transmitted empty frames are
transmitted and a second mode of operation in which if there is no
data no frames are transmitted.
[0017] According to a fourth aspect of the present invention, there
is provided a second node for receiving transmissions from a first
node at a second node, the transmissions have a first mode in which
if there is no data to be transmitted, empty frames are transmitted
and a second mode in which if there is no data to be transmitted
nothing is transmitted, the second node comprising means for
receiving transmissions from the first node, and determining means
for determining that if the transmissions have a first mode and a
frame is not received, an error has occurred.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For a better understanding of the present invention and as
to how the same may be carried into effect, reference will now be
made by way of example to the accompanying drawings in which:
[0019] FIG. 1 shows a schematic diagram of part of a cellular
telecommunications network incorporating base transceiver stations
and mobile stations;
[0020] FIG. 2 shows part of the network of FIG. 1 in more detail;
and
[0021] FIG. 3 illustrates the normal and silent modes used by the
base stations of FIG. 1.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0022] Reference will first be made to FIG. 1 in which three cells
2 of a cellular telecommunications network are shown. Each cell 2
is served by a respective base transceiver station (BTS) 4. Each
base transceiver station 4 is arranged to transmit signals to and
receive signals from the mobile stations 6 located in the cell
associated with the given base transceiver station 4. Likewise,
each mobile station 6 is able to transmit signals to and receive
signals from the respective base transceiver station 4.
[0023] The cellular telecommunications network shown in FIG. 1 uses
a code division multiple access technique. Accordingly, at least
some of the mobile stations will be in communication with more than
one base station at the same time. This, however, will be described
in more detail hereinafter.
[0024] Reference is now made to FIG. 2. As can be seen from this
figure, the base stations are connected to a SRNC (serving radio
network controller) 20. Data blocks are transmitted between the
SRNC 20 and the base stations 28 and 30 using a frame protocol FP.
A data frame contains data which is to be transmitted in one
interleaving period and a transport format indicator TFI. The
interleaving period is the period over which data is interleaved.
The transport format indicator TFI provides information as to the
format of the data frame such as the size of the data block, the
interleaving period and the like.
[0025] Each UE (user equipment for example mobile stations or the
like) has an independent transport connection which means that each
frame contains the data and current transport format indicator TFI
of one bearer only. Typically a call will have more than one
bearer, for example a signalling bearer and a data or voice bearer.
For downlink communications (from the SRNC 20 to the base station
direction), all the data blocks of users having the same user
equipment are multiplexed onto a single radio link. The manner in
which the multiplexing is done will depend on the transport format
indicator TFI of each frame which indicates the amount of data in
each frame for the bearers. A transport format combination
information TFCI field of the radio frame provided in a dedicated
physical control channel DPCCH will indicate the manner in which
the multiplexing is carried out. The transport format combination
information TFCI field will indicate the transport format indicator
TFI for each of the bearers whose data is multiplexed in the radio
frame or frames in the dedicated physical data channel DPDCH. In
the case of soft handoff where a mobile station is in communication
with more than one mobile station at a time, the dedicated physical
data channels DPDCH from each of the base stations communicating
with the mobile station in question will be the same as will the
rate information RI fields in all the radio links.
[0026] The format described hereinbefore is part of the currently
proposed UMTS (universal mobile telephone service) standard. It
should be appreciated that any other standard can alternatively be
used.
[0027] In the following, it is assumed for simplicity that there is
only one bearer per transport channel and the SRNC does not carry
out any multiplexing. The transport format information can have a
particular value which indicates that the frame does not contain
any data. For simplicity it is assumed that the particular value is
zero although the particular value can be any other value.
[0028] The SRNC 20 shown in FIG. 2 has first and second medium
access controllers MAC 24 which receive the data from respective
bearers. For simplicity, the medium access controllers 24 are each
shown as receiving information from one bearer only. The medium
access controllers can receive information from more than one
bearer and carry out the multiplexing function described
hereinbefore.
[0029] The medium access controller 24 receives an input from a
first bearer Bearer 1 and a second bearer, Bearer 2 and outputs a
first transport channel 1 and a second transport channel 2. The
input from Bearer 1 maps to the first transport channel 1 and the
input from Bearer 2 maps to the second transport channel 2. The
transport channels are input to respective macrodiversity combiners
26. The macrodiversity combiners 26 output the transport channels
to each base station which is in communication with the mobile
station for which the transport channel is intended. In the example
shown in FIG. 2, the first transport channel 1 is output to first
and second base stations 28 and 30 as is the second transport
channel 2. Thus the first and second base stations are each
arranged to transmit the same channels to a single mobile
station.
[0030] The mode of operation for transmission of information
between the SRNC 20 and base stations will now be described with
reference to FIG. 3. Two modes are defined. The first mode is the
normal mode and the second mode is the silent mode. The data which
is to be sent to the mobile station is interspersed with periods
where there is no data. This may occur during pauses in a
conversation between two parties. Alternatively, in the case of non
speech data, the data may be discontinuous.
[0031] In the normal mode A of operation, on the transmit side, the
SRNC 20 transmits a frame F for every interleaving period. As shown
in FIG. 3, frames F1 and F2 contain data. If no data is present,
frames F3, F4 and F5 which are empty frames E are sent. After N
consecutively received empty frames E, the frame protocol
connection is switched to the silent mode S. N can have any
suitable value such as 1, 2 or 3 or any other suitable value.
[0032] In the silent mode S, on the transmit side, the SRNC 20 is
prevented from transmitting any frame if there is no data in the
frame. The SRNC may transmit K empty frames F6 at the beginning of
the silent mode S to ensure that the base station has switched to
the silent mode; also if up to K of the N empty frames previously
sent have been lost during the transmission. After M consecutive
frames F7 and F8 including data are transmitted, the frame protocol
connection is switched to the normal mode A again. K may be 0 or 1
or any other suitable number. M can be 1, 2, 3 or any other
suitable number.
[0033] In the normal mode A, on the receive side, if a frame is not
received in an interleaving period, the base station generates an
interface failure alarm and decides whether to transmit the radio
frame without the data or to not transmit the frame at all . After
the base station has received N empty frames, the frame protocol
connection is switched to the silent mode S.
[0034] In the silent mode S, on the receive side, if a frame is not
received in one interleaving period, the base station considers the
bearer to be in an inactive state and sets the transport format
indicator TFI to zero. After M consecutive data frames with data
have been received, the frame control layer connection is switched
to the normal mode A.
[0035] The parameters M, N and K may be:
[0036] 1. predetermined, for example fixed in a standard used by
the network;
[0037] 2. Iub/Iur (Iub is the interface between the SRNC and the
base station while Iur is the interface between two radio network
controllers) interface protocol configurable parameters, that is
the parameters can be set at each interface as required; and
[0038] 3. signalled from the SRNC to base stations every time a new
branch or bearer is set. The parameters may be reconfigurable as
required.
[0039] Control frames which do not contain data but instead contain
control information such as power control and synchronisation
information are sent in both the normal mode and the silent mode.
Control frames may not be present in either or both of these
modes.
[0040] Reference will now be made to a second embodiment of the
present invention which uses explicit signalling in order to switch
from the normal mode to the silent mode. In this second embodiment,
the base station will not automatically switch to the silent mode
when a predetermined number of consecutive empty frames have been
received. However, the transmission of a predetermined number of
empty frames when in the normal mode can be used as an indication
that the silent mode should be used. Of course, any other suitable
measure can be used to determine that a switch should be made
between the normal and the silent mode.
[0041] Once a determination has been made that the base station
should stop using the normal mode and start using the silent mode,
the radio network controller will include in the next frame sent to
the base station a mode bit indicative of this determination. This
mode bit may have a given value for the silent mode and the other
value for the normal mode. Alternatively, one value of the bit
indicates that the mode should change either from the normal to the
silent mode or from the silent mode to the normal mode. The other
value of the bit would indicate that the mode is not to be
changed.
[0042] When the base station receives the frame transmitted by the
radio network controller, it checks the mode bit. If this bit
indicates that the mode is to change from the normal mode to the
silent mode, the base station changes its mode and sends an
acknowledgement confirming that the base station has understood
that the mode is changed. Once the radio network controller has
received the acknowledgement from the base station, the radio
network controller will use the silent mode.
[0043] Changes from the silent mode to the normal mode can be
achieved in the same way as in the first embodiment. However, it is
also possible to alter the mode from the silent to normal mode in
the following. When it is determined that the base station is to
receive using the normal mode, the radio network controller will
alter the mode bit in the next frame sent to the base station, to
indicate that the mode should change to the normal mode. If a data
frame is being sent to the base station, the mode bit will be
altered in that frame. If no data frame is being sent to the base
station due to an absence of data, the radio network controller
will send an empty frame with the mode bit set accordingly.
[0044] The base station will send an acknowledgement indicating
that it has received the frame and has noted that the mode is
changed to the normal mode. When the radio network controller
receives the acknowledgement, the radio network controller will
then use the normal mode.
[0045] It is possible to use this second method to notify the base
station by sending in advance information that the mode will change
after a predetermined number of frames or the like.
[0046] The method used by the first embodiment has the advantage
that the frame structure does not need to be altered. A second
advantage of the first method is that two way communication does
not have to be set up if one party, for example, the radio network
controller is sending data to the base station and the base station
is not sending any data to the radio network controller. The second
method is advantageous in that both parties are certain as to which
mode of operation is being used.
[0047] The acknowledgement sent by the base station to the radio
network controller may use a mode bit in the frame, as described
hereinbefore in relation to the frames sent from the radio network
controller to the base station. Thus the acknowledgement may
comprise the mode bit in the frame sent by the base station to the
radio network changing to reflect the new mode. Either of the
options for the mode bit described hereinbefore may be used.
[0048] It should be appreciated that although the transmissions
from the SRNC to the base station are described as using the normal
and silent mode of operation, this mode of operation can
alternatively or additionally be used for transmissions from the
base station to the SRNC. The values of the parameters used in the
downlink and uplink directions may differ. Embodiments of the
present invention may be applied to the communications between any
two nodes of a telecommunications network, wired or wireless.
[0049] It should be appreciated that although embodiments of the
present invention are particularly advantageous when used in a soft
handoff or similar context, that is when a mobile station is in
communication with more than one base station at the same time,
embodiments of the present invention can also advantageously be
used where the mobile station is in communication with one base
station at a time. In an alternative embodiment of the present
invention, the normal and silent mode of operation may only be used
when the mobile station is in communication with more than one base
station at a time. A different mode of operation may be used when
the mobile station is in communication with only one base station.
The different mode of operation may be one which incorporates one
of the previously known methods for dealing with empty frames.
[0050] Whilst preferred embodiments have been described in the
context of a code division multiple access system, embodiments of
the present invention can be used with any other spread spectrum
technique or any other suitable access technique such as time
division multiple access, frequency division multiple and space
division multiple access as well as hybrids thereof.
* * * * *