U.S. patent application number 14/330664 was filed with the patent office on 2014-10-30 for method and devices for communicating over a radio channel.
The applicant listed for this patent is Telefonaktiebolaget L M Ericsson (publ). Invention is credited to Richard Abrahamsson, David Astely, Robert Baldemair.
Application Number | 20140321352 14/330664 |
Document ID | / |
Family ID | 39830049 |
Filed Date | 2014-10-30 |
United States Patent
Application |
20140321352 |
Kind Code |
A1 |
Baldemair; Robert ; et
al. |
October 30, 2014 |
Method and Devices for Communicating Over a Radio Channel
Abstract
The invention relates to methods and communication devices for
transmitting data on a radio channel comprising the steps of
determining a first preamble format to be used in a cell of the
second communication device, determining a basic cyclic shift value
from a set of basic cyclic shift values, the set is selected based
on the preamble format, and transmitting data comprising indication
of the determined first preamble format and a basic cyclic shift
value pointer indicating the basic cyclic shift value in the set of
basic cyclic shift values.
Inventors: |
Baldemair; Robert; (Solna,
SE) ; Abrahamsson; Richard; (Knivsta, SE) ;
Astely; David; (Bromma, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget L M Ericsson (publ) |
Stockholm |
|
SE |
|
|
Family ID: |
39830049 |
Appl. No.: |
14/330664 |
Filed: |
July 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12742750 |
May 13, 2010 |
8781484 |
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PCT/SE2008/050826 |
Jul 2, 2008 |
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14330664 |
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61013788 |
Dec 14, 2007 |
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Current U.S.
Class: |
370/312 ;
370/336 |
Current CPC
Class: |
H04W 74/002 20130101;
H04W 74/006 20130101; H04W 72/042 20130101; H04L 7/043 20130101;
H04W 72/005 20130101; H04L 7/041 20130101; H04W 74/0833
20130101 |
Class at
Publication: |
370/312 ;
370/336 |
International
Class: |
H04W 74/00 20060101
H04W074/00; H04W 72/00 20060101 H04W072/00; H04W 72/04 20060101
H04W072/04 |
Claims
1. A method in a base station for transmitting data on a radio
channel comprising the steps of: determining a first preamble
format to be used in a cell of the base station, the method is
characterized in determining a basic cyclic shift value from a set
of basic cyclic shift values, the set to use is indicated by the
preamble format, and transmitting data comprising indication of the
determined first preamble format and a basic cyclic shift value
pointer indicating the basic cyclic shift value in the set of basic
cyclic shift values.
2. A method according to claim 1, wherein the step of determining
the basic cyclic shift value comprises to select a basic cyclic
shift value from the set of basic cyclic shift values, and wherein
the set is one set of at least two sets of basic cyclic shift
values, wherein each set is related to different preamble
formats.
3. A method according to claim 1, wherein the steps of determining
the first preamble format and the basic cyclic shift value is based
on the size of the cell.
4. A method according to claim 1, wherein each preamble format
corresponds to a set of basic cyclic shift values.
5. A method according to claim 1, wherein the data is transmitted
on a broadcast channel.
6. A base station comprising a control unit arranged to determine a
first preamble format to be used in a cell of the base station and
to determine a basic cyclic shift value from a set of basic cyclic
shift values, wherein the set to use is indicated by the first
preamble format and the base station further comprises a
transmitting arrangement adapted to transmit data comprising
indication of the determined first preamble format and a basic
cyclic shift value pointer indicating the basic cyclic shift value
in the set of basic cyclic shift values.
7. A base station according to claim 6, further comprising a
receiving arrangement adapted to receive random access data from a
user equipment, wherein the control unit is arranged to process the
received data.
8. A base station according to claim 6, further comprising a
memory, wherein the control unit is arranged to select the basic
cyclic shift value in the set of basic cyclic shift values, the set
being one of at least two sets stored in the memory, wherein each
set is related to different preamble formats.
9. A base station according to claim 6, wherein the transmitting
arrangement is adapted to transmit data on a broadcast channel.
10. A method in a user equipment for processing a signal comprising
the steps of: receiving data from a base station on a radio
channel, the data comprises an indication of preamble format and a
basic cyclic shift value pointer indicating the basic cyclic shift
value to be used in a random access procedure, determining the
preamble format from the received data, and selecting a basic
cyclic shift value in a set of basic cyclic shift values, the set
to use is indicated by the preamble format, based on the basic
cyclic shift value pointer.
11. A method according to claim 10, wherein the method further
comprises a step of setting up the user equipment in an operational
mode to perform a random access procedure using the determined
preamble format and a preamble sequence that is cyclically shifted
using a cyclic shift value that is based upon the determined basic
cyclic shift value.
12. A method according to claim 10, wherein the step of selecting
the basic cyclic shift value comprises to select a basic cyclic
shift value from a set of basic cyclic shift values of at least two
sets of basic cyclic shift values, wherein the set to select from
is based on the determined preamble format.
13. A method according to claim 10, wherein each preamble format
corresponds to a set of basic cyclic shift values.
14. A method according to claim 10, wherein the set of basic cyclic
shift values is a table of basic cyclic shift values and the
received data comprises bits indicating the basic cyclic shift
value, wherein the bits are the basic cyclic shift value pointer in
the table and the preamble format indicates which table to use.
15. A method according to claim 10, wherein the random access
procedure comprises a preamble containing a guard time and/or a
cyclic prefix, wherein the cyclic prefix and/or the guard time is
determined as a function of the basic cyclic shift value.
16. A method according to claim 10, wherein the data is received on
a broadcast channel.
17. A user equipment comprising a receiving arrangement adapted to
receive data comprising a basic cyclic shift value pointer
indicating a basic cyclic shift value and an indication of a first
preamble format from base station on a radio channel, wherein a
control unit is arranged to determine a preamble format to be used
in a random access procedure from the indication in the received
data and to select a basic cyclic shift value in a set of basic
cyclic shift values based on the basic cyclic shift value pointer,
wherein the set to use is indicated by the preamble format.
18. A user equipment according to claim 17, wherein the control
unit is further arranged to perform a random access procedure using
the determined preamble format and a preamble sequence that is
cyclically shifted in accordance with the selected basic cyclic
shift value.
19. A user equipment according to claim 18, further comprising a
transmitting arrangement adapted to transmit the preamble sequence
to the base station.
20. A user equipment according to claim 17, further comprising a
memory, wherein the control unit is arranged to select the basic
cyclic shift value in the set of basic cyclic shift values, the set
being one of at least two sets stored in the memory, wherein each
set is related to different preamble formats.
21. A user equipment according to claim 17, wherein the receiving
arrangement is adapted to receive data on a broadcast channel.
Description
TECHNICAL FIELD
[0001] The invention relates to methods and communication devices
in a communication network, in particular, for
transmitting/receiving data on a radio channel.
BACKGROUND
[0002] In modern cellular radio systems: the radio network has a
strict control on the behavior of a user equipment. Uplink
transmission parameters like frequency, timing, and power are
regulated via downlink control signaling from a base station to the
user equipment, UE.
[0003] At power-on or after a long standby time, the UE is not
synchronized in the uplink. The UE may derive from the downlink
(control) signals an uplink frequency and power estimate. However,
a timing estimate is difficult to make since the round-trip
propagation delay between the base station and the UE is unknown.
So even if UE uplink timing is synchronized to the downlink, it may
arrive too late at the base station receiver because of the
propagation delays. Therefore, before commencing traffic, the UE
has to carry out a Random Access (RA) procedure to the network.
After the RA, base station can estimate the timing misalignment of
the UE uplink and send a correction message. During the RA, uplink
parameters like timing and power are not very accurate. This poses
extra challenges to the dimensioning of a RA procedure.
[0004] Usually, a Physical Random Access Channel (PRACH) is
provided for the UE to request access to the network. An access
burst is used which contains a preamble with a specific sequence
with good autocorrelation properties. The PRACH can be orthogonal
to the traffic channels. For example, in GSM a special PRACH slot
is defined.
[0005] Because multiple UEs may request access at the same time,
collisions may occur between requesting UES. Therefore, multiple RA
preambles have been defined for Evolved UTRAN (E-UTRAN), also
called for LTE, Long Term Evolution. A UE performing RA picks
randomly a preamble out of a pool and transmits it. The preamble
represents a random UE ID which is used by the base station when
granting the UE access to the network. The base station receiver
may resolve RA attempts performed with different preambles and send
a response message to each UE using the corresponding random UE
IDs. In case that multiple UEs simultaneously use the same preamble
a collision occurs and most likely the RA attempts are not
successful since the base station cannot distinguish between the
two users with a different random UE ID. In LTE, EUTRAN, sixty four
preambles are provided in each cell. Preambles assigned to adjacent
cells are typically different to insure that a RA in one cell does
not trigger any RA events in a neighboring cell. Information that
must be broadcasted is therefore the set of preambles that can be
used for RA in the current cell.
[0006] One or multiple RA preambles are derived from a single
Zadoff-Chu sequence--in the following also denoted root sequence by
cyclic shifting: Due to the ideal auto correlation function of
Zadoff-Chu sequence, multiple mutually orthogonal sequences may be
derived from a single root sequence by cyclic shifting one root
sequence multiple times the maximum allowed round trip time plus
delay spread in time-domain. Since each cyclic shift amount must be
at least as large as the maximum round trip time in the cell plus
delay spread the number of preamble that can be derived from a
single root sequence is cell size dependent and decreases with cell
size. In order to support operation in cells with different sizes
LTE defines sixteen basic cyclic shift lengths supporting cell
sizes from approximately 1.5 km up to approximately 100 km. The
value that is used in the current cell is broadcasted.
[0007] Not only the length of the basic cyclic shift should be
larger than the maximum round trip time plus delay spread, also the
cyclic prefix and the guard period--which account for the timing
uncertainty in unsynchronized RA--should be larger than the maximum
round trip time plus delay spread. LTE FDD, Frequency Division
Duplex, currently defines four different RA preamble formats with
three different cyclic prefix/guard period length supporting cell
sizes of 15 km, 30 km, and 100 km.
[0008] The cell size that is supported with a certain RA
configuration is therefore limited by
1) the length of the cyclic prefix/guard period and 2) the length
of the basic cyclic shift.
[0009] In addition to these limitations of course also received
energy is crucial, some of the RA preamble formats are therefore
longer to increase the energy received in the base station.
[0010] Currently only one set of basic cyclic shift lengths/values
is defined, independent which cyclic prefix/guard period or RA
preamble format is used. For example, a preamble format with 100 is
cyclic prefix/guard period supports cell sizes up to 15 km. In this
case all basic cyclic shift lengths that support larger cell sizes
cannot be efficiently used since a supported cell size is limited
by the cyclic prefix and/or the size of the guard time and a basic
cyclic shift that is longer than the cyclic prefix is an
unnecessary over dimensioning.
SUMMARY
[0011] It is an object of embodiments to increase the number of
different preambles to be used in a random access process.
[0012] Embodiments relate to a method in a second communication
device for transmitting data on a radio channel. The method
comprises the steps of determining a first preamble format to be
used in a cell of the second communication device and determining a
basic cyclic shift value from a set of basic cyclic shift values.
The set is selected based on the preamble format. The method
further comprises the step of transmitting data comprising
indication of the determined first preamble format and a basic
cyclic shift value pointer indicating the basic cyclic shift value
in the set of basic cyclic shift values.
[0013] Because of the very short duration of the additional RA
preamble in, for example, LTE TDD, an additional table of basic
cyclic shifty lengths is introduced and the preamble format is used
as selector which set of basic cyclic shift lengths to use. Since
the preamble format needs anyway be signaled no additional
signaling is required with this method.
[0014] Embodiments further relate to a second communication device
comprising a control unit arranged to determine a first preamble
format to be used in a cell of the second communication device and
to determine a basic cyclic shift value from a set of basic cyclic
shift values. The set relates to the preamble format. The second
communication device further comprises a transmitting arrangement
adapted to transmit data comprising indication of the determined
first preamble format and a basic cyclic shift value pointer
indicating the basic cyclic shift value.
[0015] Furthermore, embodiments relate to a method in a first
communication device for processing a signal. The method comprises
the steps of receiving data from a second communication device on a
radio channel and determining a preamble format from the received
data. The data comprises an indication of preamble format and a
basic cyclic shift value pointer. The method further comprises the
step of selecting a basic cyclic shift value in a set of basic
cyclic shift values based on the determined preamble format and the
basic cyclic shift value pointer indicating the basic cyclic shift
value.
[0016] In addition, embodiments disclose a first communication
device comprising a receiving arrangement adapted to receive data
from a second communication device on a radio channel. The data
comprises a basic cyclic shift value pointer indicating a basic
cyclic shift value and an indication of a first preamble format.
The first communication device further comprises a control unit
arranged to determine a preamble format to be used in a random
access procedure from the indication in the received data and to
select a basic cyclic shift value in a set of basic cyclic shift
values based on the basic cyclic shift value pointer. The set of
basic cyclic shift values is related to the determined preamble
format.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Embodiments will now be described in more detail in relation
to the enclosed drawings, in which:
[0018] FIG. 1 shows a schematic overview of a first and second
communication device communicating,
[0019] FIG. 2 shows a schematic flow chart of determining a basic
cyclic shift value,
[0020] FIGS. 3a-3b show tables of basic cyclic shift values for
different preamble formats,
[0021] FIG. 4 shows schematically how a user equipment determines
when to transmit a RA preamble,
[0022] FIG. 5 shows a combined signalling and method diagram
between a user equipment a NodeB,
[0023] FIG. 6 shows a schematic flow chart of a method in a second
communication device,
[0024] FIG. 7 shows a schematic overview of a second communication
device,
[0025] FIG. 8 shows a schematic flow chart of a method in a first
communication device, and
[0026] FIG. 9 shows a schematic overview of a first communication
device.
DETAILED DESCRIPTION OF EMBODIMENTS
[0027] Embodiments of the present solution will be described more
fully hereinafter with reference to the accompanying drawings, in
which embodiments of the solution are shown. This solution may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
solution to those skilled in the art. Like numbers refer to like
elements throughout.
[0028] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" "comprising," "includes" and/or
"including" when used herein, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, elements, components, and/or
groups thereof.
[0029] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms used
herein should be interpreted as having a meaning that is consistent
with their meaning in the context of this specification and the
relevant art and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0030] The present solution is described below with reference to
block diagrams and/or flowchart illustrations of methods, apparatus
(systems) and/or computer program products according to embodiments
of the invention. It is understood that several blocks of the block
diagrams and/or flowchart illustrations, and combinations of blocks
in the block diagrams and/or flowchart illustrations, can be
implemented by computer program instructions. These computer
program instructions may be provided to a processor of a general
purpose computer, special purpose computer, and/or other
programmable data processing apparatus to produce a machine, such
that the instructions, which execute via the processor of the
computer and/or other programmable data processing apparatus,
create means for implementing the functions/acts specified in the
block diagrams and/or flowchart block or blocks.
[0031] These computer program instructions may also be stored in a
computer-readable memory that can direct a computer or other
programmable data processing apparatus to function in a particular
manner, such that the instructions stored in the computer-readable
memory produce an article of manufacture including instructions
which implement the function/act specified in the block diagrams
and/or flowchart block or blocks.
[0032] The computer program instructions may also be loaded onto a
computer or other programmable data processing apparatus to cause a
series of operational steps to be performed on the computer or
other programmable apparatus to produce a computer-implemented
process such that the instructions which execute on the computer or
other programmable apparatus provide steps for implementing the
functions/acts specified in the block diagrams and/or flowchart
block or blocks.
[0033] Accordingly, the present invention may be embodied in
hardware and/or in software (including firmware, resident software,
micro-code, etc.). Furthermore, the present invention may take the
form of a computer program product on a computer-usable or
computer-readable storage medium having computer-usable or
computer-readable program code embodied in the medium for use by or
in connection with an instruction execution system. In the context
of this document, a computer-usable or computer-readable medium may
be any medium that can contain, store, communicate, propagate, or
transport the program for use by or in connection with the
instruction execution system, apparatus, or device.
[0034] The computer-usable or computer-readable medium may be, for
example but not limited to, an electronic, magnetic, optical,
electromagnetic, infrared, or semiconductor system, apparatus,
device, or propagation medium. More specific examples (a
non-exhaustive list) of the computer-readable medium would include
the following: an electrical connection having one or more wires, a
portable computer diskette, a random access memory (RAM), a
read-only memory (ROM), an erasable programmable read-only memory
(EPROM or Flash memory), an optical fiber, and a portable compact
disc read-only memory (CD-ROM). Note that the computer-usable or
computer-readable medium could even be paper or another suitable
medium upon which the program is printed, as the program can be
electronically captured, via, for instance, optical scanning of the
paper or other medium, then compiled, interpreted, or otherwise
processed in a suitable manner, if necessary, and then stored in a
computer memory.
[0035] As used herein a communication device may be a wireless
communications device, in the context of the invention, the
wireless communication device may e.g. be a node in a network such
as a base station, UE or the like. User equipment may be a mobile
phone, a PDA (Personal Digital Assistant), any other type of
portable computer such as laptop computer or the like.
[0036] The wireless network between the communication devices may
be any network such as an IEEE 802.11 type WLAN, a WiMAX, a
HiperLAN, a Bluetooth LAN, or a cellular mobile communications
network such as a GPRS network, a third generation WCDMA network,
or E-UTRAN. Given the rapid development in communications, there
will of course also be future type wireless communications networks
with which the present invention may be embodied, but the actual
design and function of the network is not of primary concern for
the solution.
[0037] In FIG. 1 a schematic overview of a first communication
device 10 communicating with a second communication device 20 is
shown. The communication is performed over a first interface 31
such as an air interface or the like. In the illustrated example,
the first communication device 10 is a user equipment, such as a
mobile phone, a PDA or the like and the second communication device
20 is a base station, such as an eNobeB, NodeB, RBS or the
like.
[0038] The second communication device 20 sets up and transmits
random access, RA, configurations in order for the first
communication device 10 to perform a random access process. The RA
configuration comprises preamble format, basic cyclic shift length
and the like.
[0039] A high granularity of basic cyclic shift lengths is
desirable since it maximizes the number of preambles that can be
derived from a single root sequence.
[0040] Requiring less root sequences in a cell is preferable since
1) different root sequences are not orthogonal creating
interference and 2) the detection of multiple root sequences
increases complexity.
[0041] The size of the guard time is to be chosen in accordance
with the cell radius. Choosing it too large will increase
complexity and overhead, whereas choosing it too small will limit
the cell range.
[0042] LTE defines a 4 bit signaling to indicate which basic
cyclic, shift length is used in the cell in the following we call
the information conveyed by these 4 bits the basic cyclic shift
value pointer. This pointer may address entries in sets consisting
of 16 values.
[0043] It is now proposed to define multiple sets of basic cyclic
shift values. With the current signaling each of these tables may
have 16 or less entries. The interpretation which set of basic
cyclic shift values to use is given by the RA preamble format or
the length of the cyclic prefix. Since the RA preamble format is
anyway signaled this does not increase signaling amount.
[0044] Further, for LTE TDD, Time Division Duplex, in other
embodiments, the size of the guard time may be derived, for
example, by determining the RA transmission timing, from the basic
cyclic shift value as well as the preamble format.
[0045] Reusing the same basic cyclic lengths as for the other
preambles--which are designed for substantially larger cells--leads
to more root sequences in a cell. This implies higher interference
and detection complexity.
[0046] LTE currently defines a single set of basic cyclic shift
values with maximum cell sizes, ignoring for simplicity delay
spread but just considering round trip time, of [1.9 2.1 2.6 3.1
3.7 4.6 5.4 6.6 8.4 10.9 13.3 17.0 23.9 39.9 59.9 120.0] km.
[0047] Expressed in time these shifts are [12.4 14.3 17.2 21.0 24.8
30.5 36.2 43.9 56.3 72.5 88.7 113.5 159.2 266.0 399.5 0] .mu.s.
[0048] On the other side LTE defines three cyclic prefix/guard
period lengths supporting cell sizes of 15 km, 30 km: and 100
km.
[0049] Since only one set of basic cyclic shift values is defined
the same set is used independent of the preamble format and its
associated cell size limit. This implies for preamble formats with
15 km cell size support that only 11 of the available 16 basic
cyclic shift values can be used efficiently. For the preamble
format with 30 km cell size support 13 values can be used
efficiently.
[0050] Using the available 4 bits signaling a higher granularity of
basic cyclic shift lengths could be achieved if three different
tables would exist, one with the largest basic cyclic shift length
supporting 15 km, one with the largest basic cyclic shift length
supporting 30 km, and the existing table with cell size support of
up to 100 km.
[0051] In LTE TDD a new preamble is introduced that spans
substantially shorter time duration, currently considered values
are 133 .mu.s or 200 .mu.s. Because of this very short duration
this preamble is only applicable--due to link budget--for very
small cell sizes up to at the most a few km with main target cell
sizes, probably around 1 km. Because of the limited link budget it
is furthermore important to create as many as possible orthogonal
preambles, i.e. by cyclic shifting from a single root sequence.
With the currently specified basic cyclic shift values the shortest
basic cyclic shift is 12 .mu.s. From a single root sequence
(assuming a preamble length of 133 .mu.s) only 133 .mu.s/12
.mu.s=11 preambles can be derived. In total 64/11=6 root sequences
are needed to create 64 preambles where most of them are not
orthogonal.
[0052] It is therefore important to have another set of basic
cyclic shift values adopted for these very small cell sizes. The
transmitted 4 bits indicating the basic cyclic shift value are now
a pointer in the table, which table to use is indicated by the
preamble format.
[0053] Even though LTE currently defines a common basic cyclic
shift value table for the four longer preambles the same principle
could of course also be applied here and define multiple tables and
use the preamble format to indicate which table to use. The current
basic cyclic shift value signaling (4 bits) can address entries in
a 16 element long table, however, additional tables may of course
be shorter if not all 16 values are needed.
[0054] FIG. 2 shows a schematic illustration how to determine the
basic cyclic shift length, denoted as basic cyclic shift value BCSV
out of preamble format indicator PFI and basic cyclic shift value
pointer BCSVP. The PFI indicates a basic cyclic shift set BCSS, a
table, out of a plurality of sets, for example, for formats 0-3 a
first table and a second table for format 4. The basic cyclic shift
value BCSV is then determined based on the indicated table and the
BCSVP.
[0055] In FIG. 3a, a table of basic cyclic shift values for
preamble formats 0-3 is shown. In the first column 50 the Ncs
configuration is indicated and in the second column 52 basic cyclic
shift values BCSV are indicated.
[0056] In FIG. 3b, a table of basic cyclic shift values for
preamble format 4 is shown. In the first column 54 the Ncs
configuration is indicated and in the second column 56 basic cyclic
shift values BCSV are indicated. As seen, the BCSV are much smaller
than in column 52 resulting in increased number of cyclic shifts of
a root sequence.
[0057] Further, the size of the basic cyclic shift is chosen with
respect to the expected cell size, and as mentioned above, also the
size of the cyclic prefix as well as the size of the guard time
needs to be chosen in accordance with the cell size, in
embodiments, the size of the guard time and/or cyclic prefix
associated with the preamble is then chosen as a function of the
basic cyclic shift as well as the preamble format.
[0058] In FIG. 4, it is shown that a UE determines the transmission
of the RA preamble based only on the downlink TSU is a time
defining a guard period GP at the switch from DL to UL and
transmission timing Tst is a time window defining the time when the
UE starts RACH transmission after DL has ended. In the upper case
Tst=TDU. In the lower case, the Tst is reduced with function of the
basic cyclic shift value f(Ncs).
[0059] Ter is the length of receiving window of an eNodeB. In the
upper case, Ter may be up to Tpre+GT0, wherein Tpre is a time for a
preamble length and GT0 is an initial guard time at the eNodeB. In
the lower casem, the Ter is extended with a function of the basic
shift value f(Ncs).
[0060] At the bottom, the UE determines the preamble transmission
timing Tst also as a function of the size of the basic cyclic shift
value. The larger the basic cyclic shift value, the earlier the
terminal starts transmitting the RA preamble, and as a consequence
the guard time increases.
[0061] One way to increase the guard time is to let the UE to start
transmission of the RA preamble as a function of the basic cyclic
shift value. The longer the basic cyclic shift, the earlier the UE
starts the transmission of the RA preamble. One example is when the
RA is to be received after a DL period. Recall that for TDD, there
is a guard period GP at the transition from DL to UL, and even
though there may be interference from, for example, base stations
during the guard period GP, the last part of the guard period can
be used to receive part of the RA burst. Thus, part of the guard
period GP can be reused as guard time for RA reception Ter. In such
a case, however, interference may allow only a small part of the
guard period to be used, and this then limits how large the guard
time can be made, and this in turn limits the size of the supported
cells. The size of the guard time, or equivalently the transmission
timing Tst of the RA preamble, is then determined as a function of
the basic cyclic shift signaled to the terminal
[0062] What FIG. 4 shows/assumes is that there is other UL data to
be received, for example from UL shared channel transmissions that
starts right after the eNodeb receiver window Ter. Note that the
receiver window Ter has a length equal to the preamble length Tore
and guard time GT0 which accounts for the unknown Round-Trip Time
RTT. Hence, the "dotted preamble" illustrates the received signal
at the eNodeB for the case that the RTT to the UE is zero. The
unfilled part+the dotted preamble represent the total window in
which a preamble could be received. IF the RTT equals the GT, then
the signal received by the eNodeB is aligned at the end of the
eNodeB receiver window.
[0063] The maximum RTT is thereby increased since the receive
window Ter becomes larger.
[0064] In FIG. 5, an example of a combined signalling and method
diagram for a user equipment UE 10 performing a random access
procedure to a NodeB 20 is shown.
[0065] In step S10, the NobeB 10 determines a first preamble format
to be used in a cell of the NodeB. The determination may be based
on the cell size, the load on the network and/or the like.
Furthermore, a basic cyclic shift length is determined from a table
of basic cyclic shift values. The table is related to the
determined first preamble format. The NodeB has consequently at
least two tables to select from.
[0066] In step S20, the NodeB transmits data on a broadcast channel
over the cell of the NodeB. The data comprises an indication of the
determined preamble format and a basic cyclic shift value pointer
pointing to the determined basic cyclic shift value in the selected
table.
[0067] In step S30, the UE receives the data on the broadcast
channel, decodes the data and retrieves the preamble format to use
as well as the basic cyclic shift value pointer. The UE then
determines basic cyclic shift value to use by reading the element
indicated by the basic cyclic shift value pointer in the table
related to the preamble format.
[0068] The UE then performs a random access procedure by using the
preamble format and the basic cyclic shift value forming a random
access request with a preamble sequence cyclically shifted
according to the basic cyclic shift value.
[0069] In step S40, the random access request is transmitted to the
NodeB.
[0070] In step S50, the random access request is received at the
NodeB and the preamble sequence is processed in order to identify
the UE to be able to respond to the UE.
[0071] In FIG. 5, a schematic flow chart of a method in a second
communication device is shown.
[0072] In step 34, the second communication device determines
preamble format to use based on, for example, size of a cell of the
second communication device and the like.
[0073] In step 34, the second communication device determines a
basic cyclic shift length/value from a set of basic cyclic shift
values: the set is selected based on the preamble format. The
preamble format has a corresponding table of basic cyclic shift
values stored on the second communication device, and the basic
cyclic shift value is determined from a table corresponding to the
preamble format. The basic cyclic shift value is determined based
on, for example, cell size and/or the like.
[0074] In embodiments, the set selected is one set of at least two
sets of basic cyclic shift values, each set relates to at least one
preamble format.
[0075] Each set of basic cyclic shift values nosy correspond to a
preamble format.
[0076] Data is created comprising an indication of the preamble
format and a basic cyclic shift value pointer indicating the
determined basic cyclic shift value in the set of basic cyclic
shift values.
[0077] In step 36, the second communication device transmits the
data over a radio channel over the cell. The radio channel may be a
broadcast channel or the like.
[0078] During operation the second communication device may receive
random access requests of the preamble format with a cyclically
shifted root sequence according to the basic cyclic shift
value.
[0079] In order to perform the method a second communication device
is provided. The second communication device may be base station,
such as a NodeB, eNodeB, RBS, combined RBS/RNC or the like.
[0080] In FIG. 7, a schematic overview of a second communication
device 20 is shown.
[0081] The second communication device 20 comprises a control unit
CPU 201 arranged to determine a first preamble format to be used in
a cell of the second communication device 20 and to determine a
basic cyclic shift value from a set of basic cyclic shift values,
the set relates to the preamble format. The control unit 201 may be
arranged to determine the first preamble format and the basic
cyclic shift value based on the size of the cell, load on the
network/cell and/or the like.
[0082] In some embodiments, each preamble format corresponds to a
set of basic cyclic shift values.
[0083] The second communication device 20 further comprises a
transmitting arrangement 205 adapted to transmit data comprising
indication of the determined first preamble format and a basic
cyclic shift value pointer indicating the basic cyclic shift length
in the set of basic cyclic shift values. The data is transmitted
over a radio channel, such as a broadcast channel or the like.
[0084] The second communication device 20 may further comprise a
receiving arrangement 203 adapted to receive data from different
communication devices, for example, a first communication device
transmitting a random access request comprising a preamble sequence
of the determined preamble format and cyclically shifted according
to the basic cyclic shift value.
[0085] In the illustrated example, the second communication device
20 comprises a memory unit 207 arranged to have application/s
installed thereon that when executed on the control unit 201 makes
the control unit 201 to perform the method steps. Furthermore, the
memory unit 207 may in some embodiments have data stored, such as
tables of basic cyclic shift values and the like, thereon. The
control unit 201 may then be arranged to select the basic cyclic
shift value in the set of basic cyclic shift values, the set being
one of at least two sets stored in the memory 207, wherein each set
is related to different preamble formats.
[0086] The memory unit 207 may be a single unit or a number of
memory units.
[0087] Furthermore, the second communication device 20 may comprise
an interface 209 for communicating with a network.
[0088] In FIG. 8, a schematic flow chart of a method in a first
communication device is shown.
[0089] In step 42, the first communication device receives data on
a radio channel, such as a broadcast channel or the like, from a
second communication device indicating a preamble format and
comprising a basic cyclic shift value pointer.
[0090] The first communication device decodes the data and
retrieves, for example, the preamble format and the basic cyclic
shift value pointer.
[0091] In step 44, the first communication device selects a set of
basic cyclic shift values based on the preamble format. The first
communication device may have a plurality of tables related to
different preamble formats. In an example, the first communication
device has a first table of basic cyclic shift values for preamble
formats 0-3 and a second table of basic cyclic shift values for
preamble format 4, wherein the set to select from is based on the
determined preamble format.
[0092] In some embodiments, each preamble format corresponds to a
set of basic cyclic shift values.
[0093] The received data may comprise bits indicating the basic
cyclic shift length, wherein the bits are the basic cyclic shift
value pointer in the table and the preamble format indicates which
table to use.
[0094] In step 46, the first communication device determines a
basic cyclic shift value to use based on the basic cyclic shift
value pointer in the selected set.
[0095] In optional step 48, the first communication device is set
up in an operational rode and in order to access a network the
first communication device performs a random access procedure using
the basic cyclic shift value and the preamble format. Hence, a
random access request is generated of the preamble format with a
cyclically shifted root sequence according to the basic cyclic
shift value and transmitted to the second communication device
requesting access to the network.
[0096] The random access procedure may comprise a preamble
containing a guard time and/or a cyclic prefix, wherein the cyclic
prefix and/or the guard time is determined as a function of the
basic cyclic shift value.
[0097] In order to perform the method steps a first communication
device is provided. The first communication device may be a user
equipment, such as a mobile phone, a PDA, or the like.
[0098] In FIG. 9 a schematic overview of a first communication
device 11 is shown.
[0099] The first communication device 1 comprises a receiving
arrangement 103 adapted to receive data over a radio channel, such
as a broadcast channel or the like, from a second communication
device. The data comprises an indication of a first preamble format
to use and a basic cyclic shift value pointer indicating the basic
cyclic shift value in a set of basic cyclic shift values to use.
The first communication device 10 further comprises a control unit
101 arranged to decode the data to obtain the indication of
preamble format and the basic cyclic shift value pointer. The
preamble format is used to select a set of at least two sets and
the basic cyclic shift pointer is used to determine the basic
cyclic shift value. The first communication device 10 is then set
up in an operational mode adjusted to use the preamble format and
the basic cyclic shift value.
[0100] The control unit 101 may in some embodiments additionally be
arranged to perform a random access process in order to access a
network. In the random access process the control unit 101 uses the
preamble format and the basic cyclic shift value and transmits the
connection request using a transmitting arrangement 105. Hence, the
request is of the preamble format with a cyclically shifted root
sequence according to the basic cyclic shift value.
[0101] The first communication device 10 may in some embodiments
further contain a memory arrangement 107, comprising a single
memory unit or a number of memory units. Applications, arranged to
be executed on the control unit 101 to perform the method steps,
may be stored on the memory arrangement 107 as well as RA
configurations data, such as, preamble format, basic cyclic shift
values and the like. Furthermore, the memory unit 107 may in some
embodiments have data stored, such as tables of basic cyclic shift
values and the like, thereon. The control unit (101) may then be
arranged to select the basic cyclic shift value in the set of basic
cyclic shift values based on the basic cyclic shift value pointer,
the set being one of at least two sets stored in the memory (207),
wherein each set is related to different preamble formats.
[0102] It should be understood that the receiving and transmitting
arrangements in the communication devices may be separated devices
or a combined device such as a transceiving unit.
[0103] In the drawings and specification, there have been disclosed
exemplary embodiments of the invention. However, many variations
and modifications can be made to these embodiments without
substantially departing from the principles of the present
invention. Accordingly, although specific terms are employed, they
are used in a generic and descriptive sense only and not for
purposes of limitation, the scope of the invention being defined by
the following claims.
* * * * *