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Patent 2190539 Summary

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(12) Patent Application: (11) CA 2190539
(54) English Title: MOBILE TERMINAL AND SYSTEM USING VARIABLE LENGTH ABBREVIATED SLOT FORMAT FOR REVERSE DIGITAL CONTROL CHANNEL
(54) French Title: TERMINAL MOBILE ET SYSTEME UTILISANT UN FORMAT D'INTERVALLE DE TEMPS ABREGE DE LONGUEUR VARIABLE POUR VOIE DE RETOUR A COMMANDE NUMERIQUE
Status: Deemed Abandoned and Beyond the Period of Reinstatement - Pending Response to Notice of Disregarded Communication
Bibliographic Data
(51) International Patent Classification (IPC):
  • H04W 48/16 (2009.01)
(72) Inventors :
  • ALANARA, SEPPO (Finland)
  • MORING, HELENA (Finland)
(73) Owners :
  • NOKIA MOBILE PHONES LIMITED
(71) Applicants :
  • NOKIA MOBILE PHONES LIMITED (Finland)
(74) Agent: MARKS & CLERK
(74) Associate agent:
(45) Issued:
(22) Filed Date: 1996-11-18
(41) Open to Public Inspection: 1997-06-16
Availability of licence: N/A
Dedicated to the Public: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data:
Application No. Country/Territory Date
08/575,426 (United States of America) 1995-12-15

Abstracts

English Abstract


A method is disclosed for operating a user terminal (10),
such as a cellular radiotelephone, of a type that is
bidirectionally coupled to a network (32) through an RF
interface. The method includes a first step of receiving a
message from the network, at least a portion of the message
indicating a size of a cell within which the user terminal
is located. A second step of the method transmits a message
to the network, the message being transmitted so as to
include a guard time period that has a duration that is set
by the mobile terminal a function of the indicated size of
the cell. In a preferred embodiment of the invention the
message received from the network is an Access Parameters
message. The message transmitted to the network is an
Abbreviated Burst, transmitted on a Random Access Channel
(RACH), and includes at least one data portion. A number of
bits transmitted during the data portion of the message is
made inversely proportional to the duration of the guard
time period. By example, the number of bits transmitted
during the data portion varies within a range of about 200
to about 242. A digital cellular radio communications
system that operates in accordance with the variable
Abbreviated Burst is also disclosed. A further method of
the invention adaptively adjusts the guard time period as
a function of a distance between the user terminal and a
base station.


Claims

Note: Claims are shown in the official language in which they were submitted.


16
CLAIMS
What is claimed is:
1. A method for operating a user terminal of a type
that is bidirectionally coupled to a network through a
wireless interface, comprising the steps of:
receiving a message from the network, at least a
portion of the message indicating a size of a cell
within which the user terminal is located; and
transmitting a message to the network, the message
being transmitted so as to include a guard time period
that has a duration that is set by the mobile terminal
a function of the indicated size of the cell.
2. A method as set forth in claim 1, wherein the
message received from the network is an Access Parameters
message.
3. A method as set forth in claim 1, wherein the
message transmitted to the network includes at least one
data portion, and wherein a number of bits transmitted
during the data portion of the message is inversely
proportional to the duration of the guard time period.
4. A method as set forth in claim 3, wherein the
number of bits transmitted during the data portion varies
within a range of about 200 to about 242.
5. A method for operating a digital cellular mobile
station that is bidirectionally coupled to a base station
through radio channels, comprising the steps of:
receiving an Access Parameters message from the base

17
station, at least a portion of the Access Parameters
message specifying as a function of a number of bits
a duration of a guard time for use when transmitting
an Abbreviated Burst message on a Random Access
Channel from the mobile station to the base station:
storing the specified duration of the guard time in a
memory of the mobile station;
transmitting an Abbreviated Burst message from the
mobile station to the base station, the Abbreviated
Burst message comprising a plurality of data bits; and
terminating the transmission of the data portion
during the Abbreviated Burst message at a time that is
a function of the stored specified duration of the
guard time wherein a number of data bits transmitted
during the data portion of the Abbreviated Burst
message is a function of the stored specified duration
of the guard time.
6. A method as set forth in claim 5, wherein the
number of bits transmitted during the data portion varies
from about 200 to about 242.
7. A method as set forth in claim 5, wherein the
portion of the Access Parameters message that specifies
the duration of the guard time is comprised of four bits,
and specifies the duration of the guard time as being from
one symbol to 15 symbols.
8. A method as set forth in claim 7, wherein one
symbol is comprised of two bits.
9. A method as set forth in claim 5, wherein the
portion of the Access Parameters message that specifies the

18
duration of the guard time is an optional portion, and
wherein if the optional portion is not transmitted as part
of the Access Parameters message the mobile station sets
the duration of the guard time at a default, maximum value.
10. A digital cellular communications system,
comprising a plurality of base stations each comprising at
least one transceiver and at least one antenna coupled to
said transceiver, each of said plurality of base stations
serving an associated cell having an area bounded by edges
measured from said at least one antenna, each of said base
stations being operable for transmitting an Access
Parameters message to mobile stations located within said
associated cell, at least a portion of the Access
Parameters message specifying a duration of a guard time
for use when transmitting an Abbreviated Burst message on
a Random Access Channel from each of the mobile stations to
the base station, the specified duration being a function
at least of the area of the associated cell.
11. A digital cellular communications system as set
forth in claim 10, wherein each of said plurality of mobile
stations is comprised of:
means for storing the specified duration of the guard
time;
means for transmitting an Abbreviated Burst message to
the base station, the Abbreviated Burst message
comprising a data portion having plurality of data
bits; and
means for terminating the transmission of the data
portion at a time that is function of the stored
specified duration of the guard time; wherein

19
a number of data bits transmitted during the data
portion of the Abbreviated Burst message is a function
of the stored specified duration of the guard time.
12. A digital cellular communications system as set
forth in claim 10, wherein the portion of the Access
Parameters message that specifies the duration of the guard
time is comprised of four bits, and specifies the duration
of the guard time as being from one symbol to 15 symbols.
13. A digital cellular communications system as set
forth in claim 12, wherein one symbol is comprised of two
bits.
14. A digital cellular communications system as set
forth in claim 10, wherein the portion of the Access
Parameters message that specifies the duration of the guard
time is an optional portion, and wherein if the optional
portion is not transmitted as part of the Access Parameters
message the mobile station sets the duration of the guard
time at a default, maximum value.
15. A method for operating a user terminal of a type
that is bidirectionally coupled to a network through a
wireless interface, comprising the steps of:
determining a distance between the user terminal and
a base station; and
transmitting a burst from the user terminal to the
base station, wherein the user terminal adjusts a
ratio of information carrying time to non-information
carrying time within the transmitted burst as a
function of the determined distance between the user
terminal and the base station.

16. A method as set forth in claim 15, wherein the
transmitted burst is transmitted over a digital random
access control channel.
17. A method as set forth in claim 15, wherein the
burst transmitted to the base station includes at least one
data portion and at least one guard time portion, wherein
a number of bits transmitted during the at least one data
portion is inversely proportional to a duration of a guard
time portion, and wherein the step of adjusting the ratio
includes a step of specifying, in the user terminal, the
duration of the guard time portion.
18. A method as set forth in claim 17, wherein the
number of bits transmitted during the data portion varies
within a range of about 200 to about 242.
19. A method for operating a user terminal of a type
that is bidirectionally coupled to a cellular network
through a base station, comprising the steps of:
receiving a message from the base station, at least a
portion of the message indicating a size of a cell
within which the user terminal is located;
transmitting a first burst to the base station, the
first burst being transmitted so as to include a guard
time period that has a duration that is set by the
mobile terminal a function of the indicated size of
the cell:
registering with the network;
determining a distance between the user terminal and
the base station; and

21
transmitting a second burst from the user terminal to
the base station, the second burst being transmitted
so as to include a guard time period that has a
duration that is set by the mobile terminal as a
function of the determined distance between the user
terminal and the base station.
20. A method as set forth in claim 19, wherein the
first burst and the second burst transmitted to the base
station each include at least one data portion and at least
one guard time portion, and wherein a number of bits
transmitted during the at least one data portion of the
first and second bursts is inversely proportional to a
duration of the at least one guard time portion of each
burst.

Description

Note: Descriptions are shown in the official language in which they were submitted.


~ 2~90539
MOBILE TERMINAL AND SYSTEM USING VARIABLE LENGTH
ABBREVIATED SLOT FORMAT FOR REVERSE
DIGITAL CONTROL CI~ANNEL
FIELD OF THE INVENTIQN:
This invention relates generally to radiotelephones and, in
particular, to mobile terminals such as those capable of
operation with a digital cellular network.
BACKGROUND OF TEl~ INVENTION;
It is known in the art of digital cellular radio
telecommunications, in particular in Time Division,
Mu1tiplQ Access (TDMA) systems, to use a random access
reverse radio channel between mobile stations or terminals
and a base station that 6erves a cell within which the
mobile ~-~rlr;n~l is located. The mobile terminal can
transmit a burst during a time slot of the random access
channel in order to make an access request to the system,
such as on a call origination by the mobile terminal. After
being accepted by the base station, the base station will
typically determine an amount of propagation delay
experienced by the mobile station's transmission, and will
transmit time alignment information for use by the mobile
terminal in adjusting its transmissiorl time so as to fit
within an assigned time slot. In this manner subsequent
bursts transmitted by the mobile terminal on a traffic
channel will not interfere with bursts transmitted by other
mobile stations in adjacent time slots of the traffic
channel. By example, a mobile terminal at an edge of the
cell will require a larger time alignment than another

2~90~39
Docket No.: NC 6852 2
mobile station that is located in close proximity to the
base station ' s receiving antenna .
Since the rec~uired amount of time alignment is not known
when the mobile station first transmits a burst on the
5 access channel, such access bursts may be defined to be
Shortened Bursts (e.g., as in IS-54) or Abbreviated Bursts
(as in IS-136). That is, by transmitting a burst having a
significant amount of guard time (i.e., a period wherein
the mobile terminal does not transmit) either at the
10 beginning and/or end of the shortened burst, the
probabilities of collisions with other bursts transmitted
on the random access channel by other mobile terminals is
reduced .
However, it can be appreciated that providing significant
15 predetermined amounts of guard time during the access burst
also correspondingly reduces the information carrying
capacity of the burst.
Furthermore, the predetermined amount of guard time may be
derived baseq on some worst case ( i . e., largest possible)
20 cell radius, whereas typical cells sizes are but a fraction
of such an anticipated largest cell radius. As such, the
predetermined amount of guard time may be excessive for
most cells.
25 O~C~S oF T~ E~TIQN:
It is thus a first object of this invention to provide an
improved digital cellular radio communications system
wherein an amount of guard time is made variable, thereby
enabling an increase in a data carrying capacity of a burst
30 transmitted from a mobile terminal to a base station.
It is a second obj ect of this invention to provide an

-
21~0~39
Docket No.: NC 6~352 3
improved digital cellular radio communications system
wherein an amount of guard time for a given cell is made a
function of the size of the given cell, thereby optimizing
within a slot a ratio of guard time to data transmission
5 time.
It is a further object of this invention to provide methods
and apparatus for informing a mobile terminal of a size of
a cell, so that the mobile terminal is enabled to transmit
a random access burst having a minimized guard time
10 duration and a maximized data transmission duration.
It is a still further object of this invention to provide
a cellular communications system wherein a mobile terminal
ad~usts a ratio of information carrying to non-information
carrying time within a burst, as a function of a distance
15 between the mobile ~Prmin 1l and the base station.
SUMMARY OF T~F TNV~NTION
The foregoing and other problems are overcome and the
objects of the invention are realized by methods and
apparatus in accordance with embodiments of this invention.
20 A first method of this invention is disclosed for operating
a user t~rm;n~l, such as a cellular radiotelephone, of a
type that is bidirectionally coupled to a network through
an RF interface. The method includes a first step of
receiving a message from the network, at least a portion of
25 the message indicating a size of a cell within which the
user terminal is located. A second step of the method
transmits a message to the network, the message being
transmitted so as to include a guard time period that has
a duration that is set by the mobile t~r~nin~l a function of
30 the indicated size of the cell. In a preferred embodiment
of the invention the message received erOm the network is
an Access Parameters message. The message transmitted to
.. . .....

~ 2190~3g
Docket No.: NC 6~352 4
the network includes at least one data portion. A number of
bits transmitted during the data portion of the message is
made inversely proportional to the duration of the guard
time period. By example, the number of bits transmitted
5 during the data portion varies within a range of about 200
to about 2 4 2 .
Further in accordance with this invention there is
disclosed a digital cellular communications system having
a plurality of base stations each of which includes at
10 least one transceiver and at least one antenna coupled to
the transceiver. Each of the plurality of base stations
serves an associated cell having an area bounded by edges
measured from the at least one antenna. Each of the base
stations is operable for transmitting an Access Parameters
15 message to mobile stations located within the associated
cell, at least a portion of the Access Parameters message
specifying a duration of a guard time for use when
transmitting an Abbreviated Burst message on a Random
Access Channel from each of the mobile stations to the base
20 station. The specified duration of the guard time is a
functiDn at least of the area of the associated cell.
Each of the plurality of mobile stations includes a memory
for storing the specified duration of the guard time; a
transmitter for transmitting an Abbreviated Burst message
25 to the base station, the Abbreviated Burst message
comprising a plurality of data bits: and a controller for
terminating the transmission of the Abbreviated Burst
message at a time corresponding to the stored specified
duration of the guard time. In accordance with the teaching
30 of this invention the number of data bits transmitted
during the data portion of the Abbreviated Burst messaye is
a function of the stored specLfied duration of the guard
time .

~ ~19~539
Docket No.: NC 68S2 5
In a presently preferred embodiment of this invention the
portion of the Access Parameters message that specifies
the duration of the guard time is comprised of four bits,
and specifies the duration of the guard time as being from
5 one symbol to 15 symbols.
Further in accordance with the presently preferred
embodiment of this invention, the portion of the Access
Parameters message that specifies the duration of the guard
time is an optional portion and, if the optional portion is
10 not transmitted as part of the Acces~ Parameters message,
the mobile station sets the duration of the guard time at
a default, maximum value.
A further method of this invention is disclosed for
operating a mobile tPrm;n~l of a type that is
15 bidirectionally coupled to a network through an RF
interface. The method includes a first step of determining
a distance between the mobile terminal and a base station;
and a second step of transmitting a message from the mobile
tPrminAl to the base station, wherein the mobile t~rm;nAl
20 ad~usts a ratio of information carrying to non-information
carrying time within a burst, as a function of a distance
between the mobile t~rm;nAl and the base station. ~3y
example, the mobile terminal sets a duration of a guard
time period as a function of the determined distance to the
25 base station. As in the embodiment described above, the
number of bits transmitted during the data portion of the
message is made inversely proportional to the duration of
the guard time period, and may vary within a range of, by
example, about 200 to about 242.
RRTF:F' DE~SCRTPTION OP TEIF DRA~TN ~
The above set forth and other features of the invention are
made more apparent in the ensuing Detailed Description of

. ~. 21~0~39
Docket No.: NC 6852 6
the Invention when read in conj unction with the attached
D~awings, wherein:
Fig. 1 is a block diagram of a mobile t~rm;nAl that is
constructed and operated in accordance with this invention;
5 Fig. 2 is an elevational view of the mobile terminAl shown
in Fig. 1, and which further illustrates a cellular
communication system to which the mobile t~rminAl i5
bidirectionally coupled through wireless RF links;
Fig. 3A is diagram illustrating a prior art "normal" slot
10 format for a digital control channel (DCCH~ transmitted
from a mobile station to a base station, such as that
specified in Fig. 4-2 of IS-136.1;
Fig. 3B is diagram illustrating a prior art abbreviated
slot format for the DCCH transmitted from the mobile
15 station to the base station, such as that specified in Fig.
4-3 of I5-136.1; and
Fig. 3C is diagram illustrating a variable abbreviated slot
format for the DCC~I in accordance with this invention.
Dl~rrATr ~n Dr~ pTpTIoN OF ~ r~ TNV~NTION
20 Reference is made to Figs. 1 and 2 for illustrating a user
tPrrninAl or mobile station or mobile tPrminAl 10, in
particular a cellular radiotelephone, that is suitable for
practiclng this invention. The mobile t~rminAl 10 includes
an antenna 12 for transmitting signals to and for receiving
25 signals from a base site or base station 30. The base
station 3 0 includes at least one transceiver and antenna
30a and forms a part of a cellular network comprising a BMI
32 that includes a Mobile switching Center (MSC) 34. The
MSC 34 provides a connection to landline trunks when the

~ 219~39
Docket No.: NC 6852 7
mobile t.ormin~l 10 is registered with the network. The base
station 30 serves a particular geographical area, referred
to as a cell 1, that is typically centered on the antenna
30a. Other base stations (not shown) serve adjacent cells
5 (e.g., cell 2, cell 3, etc.). Each of the other base
stations (not shown) are also connected to the MSC 34. The
cells are shown as having a regular shape, although in
practice the shape of the individual cells is typically not
so regular, and overlap between adjacent cells is common.
10 The mobile t~rm;n;ll 10 includes a modulator (MOD) 14A, a
transmitter 14, a receiver 16, a demodulator (DEMOD) 16A,
and a controller 18 that provides signals to and receives
signals from the transmitter 14 and receiver 16,
respectively. These signals include si~nAl 1 ing information
15 in accordance with the air interface standard of the
applicable cellular system, and also user speech and/or
user generated data. The air interface standard is assumed
for this invention to include a capability for a t~rminAl
to request a particular channel type (e. g., analog or
20 digital), and a capability to transfer data over a channel
between the t~rminAl and the network.
A user interf ace includes a conventionaL speaker 17, a
conventional microphone 19, a display 20, and a user input
device, typically a keypad 22, all of which are coupled to
25 the controller 18. The keypad 22 includes the conventional
numeric (0 9) and related keys (#, *) 22a, and also other
keys 22b used for operating the mobile tPrmin~l 10. These
other keys 22b include, by example, a SEND key, various
menu scrolling and soft keys, and a P~R key.
30 The mobile t~rmin;ll 10 also includes various memories,
shown collectively as the memory 24, wherein are stored a
plurality of constants and variables that are used by the
controller 18 during the operation of the mobile torminAl.
_ _ _ _ _, . .. . ... _ . . .. . , , _ . _ _ _ _ _ ,

1 9053~
Docicet No.: NC 6852 8
For example, the memory 24 stores the values of various
cellular system parameters and the number assignment module
(NAM). An operating program for controlling the operation
of controller 18 is also stored in the memory 24 (typically
in a ROM device). The memory 24 also stores data, including
user messages, that are received from the BMI 32 prior to
the display of the messages to the user. The mobile
t~rminAl 10 also includes a battery 26 for powering the
various circuits that are required to operate the ~Prmin~l.
lo It should be understood that the mobile terminal 10 can be
a vehicle mounted or a handheld device. It should further
be appreciated that the mobile t~rminAl 10 can be capable
of operating with one or more air interface standards,
modulation types, and access types. By example, the mobile
tPrminAl may be capable of operating in accordance with a
frequency modulated (FM), frequency division multiple
access (FDMA) transmission and reception standard, such as
one known as EIA/TIA-553. The t~rm;nAl may also be capable
of operating with any of a number of other analog or
digital standards, such as GSM, EIA/TIA 627 (DAMPS), IS-136
(DDAMPS), and IS-95 (CDMA). Narrow-band AMPS (NAMPS), as
well as TACS, mobile terminals may also benefit from the
teaching of this invention. It should thus be clear that
the tPA~ hin~ of this invention is not to be construed to be
limited to any one particular type of mobile tPrm;nAl or
air interface standard.
The operating program in the memory 24 includes routines to
respond to control messages received from the base station
3 O, and to compose and transmit messages to the base
station 30. In a presently preferred embodiment of this
invention the mobile tPrm;nAl 10 is compatible with a
standard }cnown as IS-136 and revisions thereof. IS-136
specifies the use of a Digital Control Channel (DCCH),
which is a collection of logical -hAnnPl ~ conveyed over
_ . _ . . , _ _ _ , _ . .

` 2~0~39
Docket No.: NC 6852 9
radio channels using 7r/4-DQPSK modulation. The DCCH is used
to convey control information and short user data messages
between the base and mobile stations by way of TD~rA frames
having 1944 bits (972 symbols) and a duration of 40
5 milliseconds. Each frame consists of six equally sized time
slots, each having 324 bits (162 symbols).
Referring now to Fig. 3A there is illustrated a normal slot
format for the mobile station to base station (reverse)
transmission on the DCCH. ~oving from the beginning of the
10 slot to the end of the slot, the slot consists of a six bit
duration guard time field (G) where the mobile station
maintains a carrier off condition, a six bit duration ramp
time field (R) where the mobile station's transmitter power
is ramped up, a 16 bit preamble field (PREA~), a 28 bit
lS synchronization field (SYNC), a first 122 bit data field
(DATA), a 24 bit additional synchronization field (SYNC~),
and a second 122 bit data field (DATA).
Fig. 3B illustrates an abbreviated slot format, also
referred to herein as an Abbreviated Burst, for the mobile
20 station to base station (reverse) transmission on the DCCH.
The abbreviated slot also consists of a total 324 bits (162
symbols), and differs only in the definition of the final
122 bits corresponding to the second data field in the
normal slot format of Fig. 3A. In the abbreviated slot
25 format of Fig. 3B the data field is defined instead to have
a duration of 78 bits, and the remaining 44 bits (22
symbols in duration) are defined as a second ramp field (R)
of six bit duration (where the mobile station's transmitter
power is ramped down), and a 38 bit abbreviated guard field
30 (AG) where mobile station maintains a carrier off
condition .
The abbreviated slot format of Fig. 3B is used when the
mobile station 10 is transmitting a Random Access burst to
, . ....... _ .. _ ,,, , , _ _ _ _ _ _ _

` 2190539
Docket No.: NC 6852 10
the base station 30 (referred to as the Random Access
Control Channel (RACH) ) . As is specifled in paragraph 5. 2
and 5.2.1 of IS-136, the BMI informs the mobile station
whether to use a normal length burst (as in Fig. 3A) during
5 a mobile station access procedure, or whether the
abbreviated length burst (as in Fig. 3B) is to be used. It
can be appreciated that the inclusion of the R and AG
f ields at the end of the abbreviated slot prevents
collisions between random access bursts transmitted from
10 mobile stations at varying distances from the base station.
It is noted that the mobile station to base station DCCH
abbreviated slot format shown in Fig. 3B is identical to
that specified for the digital traffic channel (DTC)
shortened burst (IS-136.2).
15 However, even for the DTC the actual coverage radius of a
cell is determined by time alignment process limitations,
which reduces the effective radius of the cell to
approximately 30 bits (200 km). Therefore, to get equal
actual coverage on both the DTC and DCCH the Abbreviated
20 Burst length could be modified to 214 bits, which provides
10~ bits after channel coding. With this change there is
no penalty to the actual serving distance (on both the DTC
and DCCH). It should be noted that the serving distance,
even after this change, is an unrealistic 210 km = 130
25 miles, whereas a cell considered to be large has a radius
of but 50 km. To further enhance the RACH thL~ u~ even
longer Abbreviated Burst lengths can be used. The operative
area is from 214 bits up to 244 bits.
In accordance with a first erlbodiment of this invention,
30 variability of the operational distance (e.g., effective
cell radius) is made possible by providing an information
element or parameter in an Access Parameters message that
is transmitted from the BMI 32 to the mobile station 10.

3~
Docket No.: NC 6852 11
One suitable format for the Access Parameters is shown in
paragraph 6.4.1.1.1.2 of IS-136.1. In the preferred
embodiment of this invention the information element
specifies the length of the AG field, and may be referred
5 to as an AG Length field or parameter. A 4-bit field in the
Access Parameters message is sufficient for this purpose,
since there is no need to control the full 44 bit = 22
symbol length. This is because the operative area of the
DTC is only 30 bits 5 15 symbols. However, the teaching of
10 this invention is not limited for use with only a 4-bit
field for this purpose.
The optional AG Length f ield in the Access Parameters
message may be encoded as follows: 0001= AG length = 1
symbol (2 bits)...1111 = AG length = 15 symbols (30 bits).
15 In the absence of this optional information element in the
Access Parameters message, the conventional Abbreviated
Burst length (Fig. 3B) may be used by the mobile terminal
10. However, if the optional information element is present
in the Access Parameters message, the mobile torm;n~l 10
20 receives this parameter and stores same in the memory 24,
and is thus enabled to use the additional time, normally
reserved for implementing R and AG fields, for the
transmission of additional data bits.
Referring now to Fig. 3C, it is shown that in the variable
25 Abbreviated Burst in accordance with this invention the
second R field is effectively eliminated, the length of the
AG field is made variable between, by example, 2 and 44
bits, thus making the length of the second data field
variable between 78 and 120 bits, with the total number of
30 bits of the second data and AG fields always equaling 122
bits to preserve compatibility with the specified slot
format. When the AG field is 44 bits the data field is 78
bits, and is thus identical to the conventional format
shown in Fig. 3B. When the AG field is specified to be only
_ _ _ _ _ , . . . . .. _ . .... , . . .. , . , , _ _ , ,

~19~39
. ~.
Docket No.: NC 6852 12
2 bits (minimum), the second data field is made equal to
120 bits (maximum), and the total number of data bits of
the abbreviated slot becomes only two less (i.e., 242) than
the total number of data bits shown in Fig. 3A for the
5 normal DCCH slot. As can be appreciated, this latter case
adds an additional 42 bits (21 symbols) to the information
carrying capacity of the Abbreviated Burst on the RAC~I.
It should be noted that, when using only a few bits for the
AG field, it is assumed that the mobile station 10 is
10 capable of ramping down the transmitter 14 in a short
period of time. In modern mobile stations this is generally
the case.
The Abbreviated Burst length information in the Access
Parameters message is preferably sent in a broadcast mode
15 to all mobile stations within the coverage area of a given
cell, and is intended to inform those mobile stations
intending to access the BMI of the access parameters in
effect within the cell. The receipt of the Abbreviated
Burst AG Length information element in the Access
20 Parameters message thus also conveys to the mobile station
an indication of the approximate size of the cell. That is,
the radius of the cell can be considered to be directly
proportional to the number of bits allocated for the AG or,
alternatively, to be inversely proportional to the number
25 of bits allocated for the second data field.
By example, in a very large cell, i.e., one having a
significant propagation delay the edge of the cell to the
base station 30, the number of bits allocated for the AG is
made large to minimize collisions with RAC}I Abbreviated
30 Bursts sent by mobile stations at the periphery of the
cell. Conversely, in a small cell having short propagation
delays from the edge of the cell to the base station 30,
the number of bits allocated for the AG can be reduced
. , . ... .. . _ _ _ _ _ . . . .

2190539
Docket No.: NC 6852 13
without increasing the probability of collisions occurring
with RACH Abbreviated Bursts sent by mobile stations at the
periphery of the cell.
Furthermore, it should be realized that the additional data
5 capacity made possible in the variable Abbreviated Burst of
Fig. 3C can reduce the number of messages that a given
mobile station 10 is required to transmit to the base
station. For example, a short origination message (e.g.,
6even digits plus TMSI, no optional fields, no concatenated
10 serial number, and authentication) may be sent in but one
variable Abbreviated Burst on the RACH, instead of
requiring two conventional Abbreviated Bursts where the
second data field is limited to 7~3 bits. The use of but one
RACH Abbreviated Burst to make the origination request
15 corresponds, in this case, to a channel payload increase of
100~. This increases the overall capacity of the system,
and furthermore reduces the power consumption of the
battery 26. Statistically, over a large number of cells of
varying sizes, the use of the variable Abbreviated Burst of
2 o this invention is estimated to provide at least an
approximate 20% increase in performance.
The application of the teaching of this invention also
provides further benefits to the BMI 32, as it makes the
reception of the variable Abbreviated Burst on the RACH, on
25 any radio channel, to be more compatible with the normal
traffic channel slot which may be present on the same radio
channel .
The value of the AG Length parameter for the Access
Parameters message can be determined at the time that the
30 cell i6 first installed, based at least one the radius of
the cell, and then stored in the BMI 32. Subsequent
"tunin~" of the value of the AG Length parameter can be
accomplished after cell goes into operation, the tuning
. . , , . _ _ _

~ 2~90.~39
Docket No.: NC 6852 14
being based on operational experience.
It should therefore be appreciated that the value of the AG
Length field can be different in ad~acent cells, such as
those shown in Fig. 2, and that a mobile torminRl can thus
5 operate with a different duration abbreviated guard time
(AG) when, by example, the mobile tPrminRl originates a
call in each of the different cells.
In a further embodiment of this invention the abbreviated
burst length is made dependent upon the location of the
10 mobile torm;nRl 10 within the cell. In this case the mobile
terminal 10 determines its location in the cell using known
locating methods, such as by utilizing time alignment
measurements from the ~uLL~1u~lding base stations. The base
station 30 can also determine the distance to thc mobile
15 torminAl 10, using known techniques, and then transmit the
detPrminod distance using appropriate distance units (e.g.,
km, propagation delay, symbols, etc.) The mobile tPrminAl
lo then ad~usts the size of the AG field in accordance with
the distance to the base station so as to optimize the
20 data-carrying capacity of the uplink slot. In this case the
physical size of the cell is not the key parameter, but
instead the actual distance between the mobile torminAl 10
and the base station 30 controls the duration of the guard
time at the end of the slot. As the mobile tprminAl 10
25 moves within the slot the duration of the guard time can be
periodically adjusted as required.
In practice it may be preferable that the mobile tPmm;nRl
lo should initially use the first method of this invention,
wherein the AG Length f ield is employed to set the length
30 of the AG, Rnd then later (after the mobile tPrminRl 10 has
registered in the network) to employ the second method
wherein the mobile terminal's location is used to define an
optimal length for the AG.

2190539
Docket No.: NC 6852 15 - -=
As such, this second method includes a first step of
de~rm;n~n~ a distance between the mobile t~rrqin il and a
base station; and a second step of tran5mitting a message ::
from the mobile t~rm;n 11 to the base station, wherein the
5 mobile terminal adjusts a ratio of information carrying
time to non-information carrying time within a burst, as a
function of a distance between the mobile ~rmin~l and the
base station. By example, the mobile t~rmin~l sets a
duration of a guard time period as a function of the
10 determ; n~d distance to the base station. As in the
embodiment described above, the number of bits transmitted
during the data portion of the message is made inversely
proportional to the duration of the guard time period, and
may vary within a range of, by example, about 200 to about
242.
Although described above in the context of the specific
slot formats, bit lengths, and fields shown in Figs. 3A-3C,
it should be realized that these are exemplary, and should
not be construed in a limiting sense. By example, the G and
20 AG fields could be reversed in the slot. Furthermore, t-he
use of a second synchronization ~SYNC~) is not required for
the operation of the invention. Also by example, the
preamble field is not required, especially if the base
station is constructed 50 as not to require an equalizer.
25 Thus, while the invention has been particularly shown and
described with respect to preferred embodiments thereof, it
will be understood by those skilled in the art that changes
in form and details may be made therein without departing
from the scope and spirit of the invention.

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

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Event History

Description Date
Inactive: IPC from PCS 2022-09-10
Inactive: IPC expired 2009-01-01
Inactive: IPC expired 2009-01-01
Inactive: IPC expired 2009-01-01
Inactive: IPC expired 2009-01-01
Inactive: IPC from MCD 2006-03-12
Inactive: IPC from MCD 2006-03-12
Application Not Reinstated by Deadline 2002-11-18
Inactive: Dead - RFE never made 2002-11-18
Deemed Abandoned - Failure to Respond to Maintenance Fee Notice 2002-11-18
Inactive: Abandon-RFE+Late fee unpaid-Correspondence sent 2001-11-19
Application Published (Open to Public Inspection) 1997-06-16

Abandonment History

Abandonment Date Reason Reinstatement Date
2002-11-18

Maintenance Fee

The last payment was received on 2001-10-23

Note : If the full payment has not been received on or before the date indicated, a further fee may be required which may be one of the following

  • the reinstatement fee;
  • the late payment fee; or
  • additional fee to reverse deemed expiry.

Patent fees are adjusted on the 1st of January every year. The amounts above are the current amounts if received by December 31 of the current year.
Please refer to the CIPO Patent Fees web page to see all current fee amounts.

Fee History

Fee Type Anniversary Year Due Date Paid Date
MF (application, 2nd anniv.) - standard 02 1998-11-18 1998-10-21
MF (application, 3rd anniv.) - standard 03 1999-11-18 1999-10-26
MF (application, 4th anniv.) - standard 04 2000-11-20 2000-10-18
MF (application, 5th anniv.) - standard 05 2001-11-19 2001-10-23
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
NOKIA MOBILE PHONES LIMITED
Past Owners on Record
HELENA MORING
SEPPO ALANARA
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Representative drawing 1997-08-18 1 23
Description 1997-04-14 15 654
Abstract 1997-04-14 1 39
Claims 1997-04-14 6 194
Drawings 1997-04-14 3 51
Reminder of maintenance fee due 1998-07-20 1 116
Reminder - Request for Examination 2001-07-18 1 118
Courtesy - Abandonment Letter (Request for Examination) 2001-12-30 1 172
Courtesy - Abandonment Letter (Maintenance Fee) 2002-12-15 1 176
PCT Correspondence 2001-08-07 1 24