Title of Invention

"METHOD AND APPARATUS FOR ALLOCATING A PILOT SIGNAL ADAPTED TO THE CHANNEL CHARACTERISTICS"

Abstract ^c, A set of different pilot structures are designed for use in different environments and/or different user behaviours that are expected to occur in a cell. The radio conditions for a user are estimated. Each user is then assigned an area (108A-E) in resource space for its communication, which has a suitable pilot configuration. In one embodiment, the entire resource space is provided with different pilot structures in different parts (110A-D) In advance and allocation of resources to the users are then performed in order to match estimated radio conditions to the provided pilot structure. In another embodiment, allocation is performed first, and then the actual pilot structure is adapted within the allocated resource space area to suit the environmental conditions.
Full Text TECHNICAL FIELD
The present invention relates generally to wireless multi-carrier
communications systems and in particular to resource allocation and pilot
signals of such systems.
BACKGROUND
In most wireless systems, e.g. GSM (Global System for Mobile
communications), WCDMA (Wideband Code Division Multiple Access), WLAN
(Wireless Local Area Network), special well known training sequences or pilot
signals are transmitted so that the receiver can estimate the channel
parameters sufficiently well for detection of any data signal, not previously
known by the receiver. Several methods exist to do this, some use user
specific pilots and some use common pilots or combinations. Some pilots are
code spread and overlaid with user data, others have dedicated timefrequency
slots when pilots are transmitted. In any case, some part of the
available radio resources must be allocated for pilots resulting hi overhead
that cannot be used for data.
In single-carrier systems, such as e.g. described in US 6,452,936, pilot data
can be provided in certain time slots within a transmission frame. A shorter
time interval between successive pilot data gives a more accurate channel
estimation, but decreases instead the transmission rate. In US 6,452,936, a
particular code of the CDMA system is allocated to a user. A pilot density of a
frame structure is continuously selected dependent on channel estimation
information.
A multi-canier approach has been proposed hi wireless communications
systems, in which a data stream typically is separated into a series of parallel
data streams, each of which is modulated and simultaneously transmitted
with a different frequency. An example of a multi-carrier system is an OFDM
(Orthogonal Frequency Division Multiplexing) system. This allows a relative
size of transmitted symbols relative to a multipath delay to be much larger
which reduces intersymbol interference. Such a cellular multi-user, multicarrier
wireless communications system thus allows a particular user to
utilise more than one carrier simultaneously. The allocation of one or several
carriers depends typically on quality of service consideration, such as
requested transmission rate. Generally, in a multi-carrier, multi-user
system, the resource space is used in a flexible manner to give each user the
best possible quality at each time. The principles and requirements for
providing channel estimations become in this way more complex than in a
single-carrier system, since a continuously use of a single communication
resource is not ensured. In a cellular multi-user, multi-carrier wireless
communications system, the base station must accommodate many users
that each experiences different channel characteristics due to fading in both
time and frequency. Furthermore, different users travel at different speeds
and thus experience different Doppler shifts.
Today, there are a few multi-carrier systems in use. However, they are not
particularly designed for the difficult, ever changing, hard-to-predict multiuser
environments that are envisioned for future wireless systems.
For example, the systems for DVB /DAB (Digital Video Broadcasting/Digital
Audio Broadcasting) are broadcast systems that cannot take into account
the need for individual users. Such systems must design their pilot structure
according to the worst-case scenario so that detection becomes possible even
under the worst possible conditions. Such a pilot structure gives rise to a
substantial pilot overhead, and is indeed necessary in these worst-case
scenarios. However, whenever the situation is better than the worst case,
which typically is the case most of the time, the pilot structure is
unnecessarily extensive, giving an unnecessary pilot overhead for most
users. The pilot overhead can indeed be substantial. This reduces data
capacity in the own cell and furthermore increases the interference to the
neighbouring cells (so called 'pilot pollution").
Another example of a multi-carrier system is WLAN (i.e. IEEE 802. lla, IEEE
802. Hg). Such a system is designed for a limited geographical area in which
the users are stationary or slowly moving. The design is not intended for
conditions in which the user is moving quickly or for handling mobility in a
multi-cellular environment.
In the published US patent application 2003/0215021, a communications
system is disclosed, in which channel characteristics are determined by
analysing a signal received over a (sub)-carrier. The determined
characteristics are then used to divide the sub-carriers into groups of similar
fading characteristics. Each group is then allocated a pilot sub-carrier.. The
determined pilot allocation scheme is then used for future transmissions
across the sub-carrier. This system compensates for differences in fading
characteristics over the carrier bandwidth, but has a disadvantage in that it
is assumed that a sub-carrier is continuously used for one single user. A
user has to have access to a large number of sub-carriers in order to make
such a pilot allocation efficient. Furthermore, entire sub-carriers are
allocated as pilot sub-carriers, which occupies a large part of the available
resource space, contributing to the pilot pollution.
SUMMARY
The rpfrfri problems with existing solutions are that pilot structures are
either not at all suitable for considerably changing radio conditions or that
they are designed for worst cases which in turn results in vast pilot overhead
and "pilot pollution".
An objective of the present invention is to provide methods and devices for
multi-user multi-carrier wireless communications system, which are capable
to provide all users with sufficient pilots without causing unnecessary pilot
overhead and pilot pollution. A further objective of the present invention is to
provide such methods and devices, which are easy to implement within
present and planned wireless systems.
The above objectives are achieved by methods and devices according to the
enclosed patent claims. In general words, a set of different pilot structures
are designed for use in different environments and/or different general radio
characteristics that are expected to occur in the cell. The radio conditions for
a user are estimated, either from direct measurements or from knowledge
about the cell characteristics, possibly combined with position information.
Each user is then assigned an area in resource space for its communication,
which has a suitable pilot configuration, hi one embodiment, the entire
resource space is provided with different pilot structures in different parts in
advance and allocation of resources to the users are then performed in order
to match estimated radio conditions to the provided pilot structure. In
another embodiment, allocation is performed first, and then the actual pilot
structure is adapted within the allocated resource space area to suit the
environmental conditions. For best performance, depending on such things
as frequency selectivity, time selectivity (e.g. time dispersion and Doppler
shift), and path loss the amount of pilot energy should be adapted and the
'distance' between pilots in the time-frequency domain needs to be changed.
The radio resource space can have different dimensions. In multi-carrier
systems, frequency is one dimension. Other dimensions that could be utilised
within the present invention are time, code, antenna and/or spatial
dimensions. One or several of these dimensions span the radio resource
space, in which the present invention is applied.
By adapting the pilot structure to the environment or set of environments
likely to occur in the cell and allocating these pilots to the users most likely
to benefit from them, an overall efficiency is achieved. The amount of pilot
overhead is then connected to the actual environments being accommodated.
Difficult environments require more overhead than simpler ones and hence
pilot pollution is reduced on the average.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with further objects and advantages thereof; may
best be understood by making reference to the following description taken
together with the accompanying drawings, in which:
FIG. 1 is a schematic illustration of a multi-user wireless communication
system;
FIGS. 2A and 2B are Illustrations of pilot structures in time-frequency
space, and the allocation of different users to subspaces;
FIG. 3A illustrates a radio resource space having a code dimension;
FIG. SB is an illustration of a pilot structure in the frequency-code subspace;
FIG. 4 is a flow diagram illustrating an embodiment of a method
according to the present invention;
FIGS. 5A, 5B and 6 are diagrams illustrating pilot structures in timefrequency
space, and the allocation of different users to subspaces according
to embodiments of the present invention;
FIGS. 7A and 7B are flow diagrams illustrating other embodiments of a
method according to the present invention;
FIG. 8 is a flow diagram illustrating a part of a further embodiment of a
method according to the present invention;
FIGS. 9A to 9C are block diagrams of downlink radio management
devices of network nodes according to embodiments of the present invention;
FIG. 10 is a block diagram of uplink radio management devices of
network nodes according to embodiments of the present invention;
FIG. 11 is a diagram illustrating pilot structures in tune-frequency space
having different intensities, and the allocation of different users to subspaces
according to an embodiment of the present invention; and
FIGS. 12 and 13 are diagrams illustrating limited data descriptions of
regular pilot structure.
DETAILED DESCRIPTION
In the following description, OFDM (Orthogonal Frequency Division
Multiplexing) systems are used for exemplifying the present invention.
However, the present invention can also be applied to other multi-carrier
•wireless communications systems.
In the present disclosure, "pilots" refer to signals known by a receiver and
therefore used for estimation purposes. "Data" refers to signals not
previously known by the receiver, typically user data, control signals or
broadcast information.
Fig. 1 illustrates a multi-user multi-carrier wireless communications system
1O, in this particular embodiment intended to be an OFDM system. Nonexclusive
examples of other communications systems, in which the present
invention is advantageously applicable, are 1FDMA (Interleaved Frequency
Division Multiple Access) systems, non-orthogonal or bi-orthogonal multicarrier
systems. A base station or access point 20 communicates with two
mobile stations or user equipments 30A, SOB. There is a downlink connection
22A between the access point 2O and the user equipment 30A and an uplink
connection 24A between the same nodes. Likewise, there is a downlink
connection 22B between the access point 20 and the user equipment SOB
and an uplink connection 24B between the same nodes. User equipment 30A
is located at a relatively large distance from the access point 20, but the
speed 32A (illustrated as an arrow) of the user equipment SOA is small. User
equipment 30b is located closer to the access point 20, but has a high speed
32B (also illustrated as an arrow). The user equipment SOA may have a
relatively high need for repetitive pilots in the frequency dimension, since the
propagation conditions for the different carriers may differ considerably over
the bandwidth in case of multi-path propagation with large delay spread.
However, the radio conditions are probably quite slowly varying with time
due to tiie small speed of user equipment SOA The user equipment SOB is
close to the access point, and a pilot on one frequency can probably be used
for channel estimations for many neighbouring carriers. However, the radio
conditions are probably changing rapidly in time, whereby frequent pilots in
time dimension are required.
Fig. 2A is a diagram of a time-frequency space. This can represent a limited
portion of the entire available radio resource space 10O in these two
dimensions. Data is transmitted in quantities limited in time and frequency.
These data quantities correspond to the small squares 104 in the diagram.
Selected ones 102 of these data quantities contain pilot data and are
illustrated in the diagram with hatching. The pilot structure is in this
embodiment dispersed over the time-frequency space relatively uniformly.
With this distribution, one data quantity out of 11 is occupied by pilot data.
The useful data transmission rate is thereby reduced by 1/11. The users of
the user equipments 30A and 30B (Fig. 1) have allocated radio resources
within the available radio resource space 100. User equipment 30A is
allocated the resource sub-space indicated by 108A, while user equipment
30B is allocated the resource sub-space indicated by 108B. Both users are
experiencing the same pilot density and the uniform distribution between the
frequency and time dimensions.
User 30B moves fast. The time between two consecutive pilot messages in
time dimension is 11 time slots, and even if information from neighbouring
frequencies are used for channel estimation in the meantime, at least 4 time
slots will pass between two consecutive updates. The speed of user 30B is so
high that this pilot structure is not sufficient for an acceptable quality of
service.
However, arranging the pilot structure as in Fig. 2B will change the
situation. Here, there is a new update in time dimension every second time
slot, which well supports the fast moving user equipment. Despite this
increased density in time direction, the total amount of pilot data quantities
is reduced somewhat. Now only one data quantity out of 12 comprises a pilot.
The overhead has decreased from 1/11 to 1/12 (about 9%).
However, user equipment 30A now achieves problems. This user equipment
3OA moves slowly and is of limited use of the frequent updating in time.
However, it has need for more closely located pilots in frequency dimension
instead. The pilot structure of Fig. 2B becomes very unsuitable for user
equipment 3OA.
So far, only two dimensions, time and frequency, have been discussed. Fig.
3A illustrates a radio resource space in three dimensions, time, frequency
and code, hi such a system, each data quantity will instead correspond to a
small cube 1O4. Generalisation can be performed to higher order spaces,
comprising e.g. antenna or space dimensions. In general, any radio resource
space in at least two dimensions, of which one is frequency, can be used with
the present invention.
Fig. 3B illustrates a pilot pattern in a frequency-code space for a specified
time. In this example 16 different codes are available and also 16 different
frequencies. The illustrated pilot pattern leads to that the pilots are
transmitted on all frequencies during the specified time duration, however,
spread out in the code dimension. One code in each frequency is occupied by
a pilot, whereas the remaining 15 codes are used for data transmission.
As mentioned briefly above, more generally the antenna or spatial
dimensions could also be part of the resource space. One example is that
different frequency bands are allocated to different beams of a multi-sector or
fixed beam site. In this case, the spatial dimension is part of the description
since different pilot patterns may be deployed for the different beams that
overlap in the spatial domain. With the grouping of resources in terms of
antenna sectors or beams the pilots allocated to different users can change
dynamically when the user for example moves between sectors and the
sectors have different frequency bands allocated to them. In such cases,
antenna or spatial dimension can also be used as additional dimensions in a
total resource space.
The flow diagram of Fig. 4 illustrates the main steps of an embodiment of a
method according to the present invention. The procedure starts in step 200.
In step 202, a number of pilot configurations are provided, which are
believed to suit different radio conditions appearing in the cell in question. At
least two such pilot configurations are available, i.e. they can be handled by
both sides of the transmission connection. At least one of the pilot
configurations comprises sub-carriers having both pilot resources and data
resources, i.e. resources allocated for any data not previously known by the
receiver, such as user data, control signals or broadcast information, hi order
to accommodate efficiency requests from e.g. slow-moving terminals. The
transmitter manages the sending of pilots according to this configurations
and the receiver is capable of performing channel estimation based on the at
least two pilot configurations. In step 204, an estimation of the radio
conditions at the receiver is obtained. This estimation can be provided in
many different ways. The actual radio conditions can be measured and
evaluated. Another possibility is to assume an_j?stimate from knowledge
about the characteristics in the cell, and possibly based on e.g. location
and/ or speed of the receiver relative the transmitter.
In step 206, a user is allocated resources in resource space, which have a
pilot configuration that is matched to the estimated radio conditions. This
matching can be performed in different manners, described more in detail
further below. The procedure stops in step 299. Anyone skilled in the art
realises that step 202 preferably is performed once, and the provided pilot
structures can then be used for any future allocation of users, or reallocation
of existing users.
A few examples, using OFDM as an example system, will be used to visualise
the effect of the present invention. The basic setup in Fig. 5A is assumed as
follows. During a certain time period and seen over all frequency resources.
the available radio resources constitute a grid of basic resources that can be
used for data, control signaling or pilot signals or other signals as discussed
earlier. The resolution in frequency dimension is one OFDM carrier and in
time it is one OFDM symbol. Pilot symbols are as above depicted with
hatched boxes.
The transmitter side, in this example assumed to be the base station,
determines a number of different pilot patterns and assigns these pilot
patterns to different parts of the entire radio resource space. The pilot
patterns may for example be periodically recurring with some period or
pseudo-randomly designed. This means that different parts of the radio
resource space have a denser or at least differing pilot pattern than other
parts. Bach pilot pattern is intended to accommodate users experiencing
different channel characteristics.
This is illustrated in Fig. 5A. The entire radio resource space illustrated is
divided into four rectangular parts, 110A-D. The resource space part 110A
has a pilot pattern, having a dense occurrence in time dimension (every
second OFDM symbol at certain carriers), but a more dispersed behaviour in
the frequency dimension (only every sixth OFDM carrier). The resource space
part HOB has a very diluted pilot pattern, having only one pilot in 36
resource units, evenly spread in time and frequency dimensions. The
resource space part HOC is the opposite of part 11QA, with a dense pilot
pattern in frequency dimension, but sparse in time dimension. Finally,
resource space part HOD has a very dense pilot structure in both
dimensions, comprising a pilot symbol in every fourth resource unit.
According to one embodiment of the invention, the users are now allocated to
the different parts of the radio resource space dependent on their estimated
radio conditions. In other words, whenever a certain user has certain
demands, the user is assigned resources in the resource space where pilots
with the appropriate density can be utilised for channel estimation. In the
situation in Fig. 5A, there are pilot structures suitable for typically four
combinations of Doppler and delay^pread. In part 110A, the pilot structure
is intended for a large Doppler and low delay spread. In part HOB, the pilot
structure is intended for a low Doppler and low delay spread. In part HOC,
the pilot structure is intended for a low Doppler and high delay spread. In
part HOD, the pilot structure is intended for a high Doppler and nigh delay
spread.
A first user, having radio conditions demanding a high density of pilots in
both dimensions is allocated to the resource sub-space 1O8A within the part
HOD. A second user, only having need for dense pilot in the time dimension
is allocated resources in a resource sub-space 108B within the part HOA. A
third user with very favourable radio conditions is allocated to a resource
sub-space 1O8C in part HOB. Finally, two more users, having high demands
on pilot density are given resources in two sub-spaces 108D and 108E,
respectively in part HOD. One realises that each user has achieved a pilot
pattern that is suited to its individual needs. It is beneficial, e.g. to assign
resources for mobiles with certain fast varying channel or Doppler conditions
in the dense parts of the pilot pattern and users with more slowly varying
conditions in the less dense parts.
Note that the base station does not need to transmit all pilots at all times.
Only pilots that in fact can be utilised by any user needs to be transmitted. If
a pilot resource at time of transmission cannot be utilised by any data
symbol that some user need to detect with the help of said pilot, then the
pilot need not be transmitted. In such a way, the overall pilot pollution is
reduced, and so is the average transmission power.
In Fig. 5B, a further embodiment of the present invention is illustrated.
Assume the same situation as was present in Fig. 5A. Three users are
occupying all resources in the densest part HOD. If yet another user with
need for a very dense pilot configuration appears, the pre-defined pilot
configuration plan of Fig. 5A becomes insufficient. However, the new user
can be allocated to a free resource sub-space 108F, preferably in connection
with the part HOD. This sub-space 108F had originally a pilot pattern
according to part HOC, but when allocating the user, the pilot pattern is
adjusted to match the demands put by the never user. In such a way, the
original pre-determined division into different parts in the resource space
can be adapted to the actual need. However, if a good initial configuration is
used, most cases are covered and the frequency of adjustments is low.
Now, return to the situation of Fig. 5A. If the user having the allocation of
sub-space 108E slows down, the estimated radio conditions change, and the
need for pilots is reduced. The user can then be reallocated to another subspace
of the resource space, having a more suitable pilot configuration for
the new estimated radio conditions, e.g. to part HOC. An alternative is to
keep the allocated sub-space but instead change the pilot pattern to a more
suitable one for the new conditions.
The ideas of adjusting or adapting the pilot configuration when needed can
also be brought to the extreme end, where no pilot pattern at all is preconfigured
for the different parts of the resource space. Instead, there is
always an adjustment of pilot pattern for all users. This is schematically
illustrated in Fig. 6. Here, a first user was assigned a sub-space 108A,
without associated pre-defined pilot pattern. The pilot pattern was then
adjusted according to the actual needs as concluded from the estimated
radio conditions. In this case a dense pattern was selected. A second user
was allocated to sub-space 108B and subsequently, a suitable pilot pattern
was selected for this sub-space. In such a way, all the sub-spaces 108A-F
were associated with pilot configurations suitable for each individual need.
Sub-spaces not allocated to any user do not comprise any pilots in such an
approach. A user with certain estimated properties is thus allocated to use
certain resources and the pilot pattern is designed accordingly. The result is
the same as the previous embodiments, pilot patterns and user
characteristics are matched.
The above embodiments can also be expressed in flow diagrams. In Fig. 7A, a
flow diagram corresponding to the situation in Fig. 5A is illustrated. The
resource space is in step 203 provided with at least two different predetermined
pilot configurations at different parts of the resource space. Step
204 is unchanged compared to Fig. 4. In step 207, the matching of the radio
conditions and pilot structures is performed by selecting a suitable resource
space.
The situation in Fig. 5B is illustrated by the flow diagram of Fig. 7B. Also
here, pre-defined pilot configurations are associated with different parts of
the resource space in step 203. hi step 205, it is determined whether there is
any available resources in parts that are suitable for the particular
estimated radio conditions for the user to be allocated. If there are resources
with suitable pilot structures available, the procedure continues to step 207,
as in Fig. 7A. If no resource space with appropriate pilot structure is
available, any free resource space is allocated in step 209, however,
preferably in the vicinity of the part having a suitable pilot pattern. In step
210, the pilot configuration is adapted within the selected resource subspace
to match the estimated radio conditions.
The embodiment illustrated in Fig. 6 can similarly be illustrated by the part
flow diagram of Fig. 8. Here, the step 206 in Fig. 4 is described in more detail.
In step 208, an area is selected as a resource sub-space for the user. In step
210, the pilot configuration in the selected area is adapted to the need
connected to the estimated radio conditions of the user. Note the similarities
between Fig. 7B and Fig. 8.
The present invention can be implemented for wireless communication
between any nodes in a communications system. Such nodes can be e.g. user
equipment, mobile station, base station, access point or relay. In the
examples below, the most straightforward situation with communication
between a base station and a user equipment will be discussed as an
example. The scope of the claims should, however, not be affected by this
example.
Multi-carrier communication is typically most applied in downlink
connections. In Fig. 9A, a wireless communications system according to an
embodiment of the present invention is illustrated. A base station 2O
communicates with a mobile terminal 30 via an uplink 24 and a downlink 22
connection. In the downlink communication, the ideas of the present
invention are implemented. The base station 20 comprises a downlink control
unit 25, which is enlarged in the lower part of Fig. 9A. The downlink control
unit 25 is responsible for allocating resources for communication on the
downlink 22 between the base station 20 and the mobile terminal 30 and
comprises in turn a pilot manager 26 and a radio condition processor 28.
Similarly, the mobile terminal or user equipment 3O also comprises a
downlink control unit 35, also enlarged in the lower part of Fig. 9A. The
downlink control unit 35 comprises a channel estimator 36 and a
measurement unit 38 for radio conditions.
The radio conditions measurement unit 38 measures the actual radio
conditions at the user equipment 3O. Such measurements can comprise
Doppler shift and signal strength as well as power delay profile, channel
impulse response, time and frequency selectivity measurements and
interference levels. The results of the measurements are transferred to the
radio conditions processor 28 of the base station 20, preferably by the uplink
communication link 24. The radio conditions processor 28 evaluates the
measured conditions and translates it to estimated radio conditions for the
user equipment 30. In other words, the radio conditions processor 28 obtains
data associated with estimated radio conditions for the user equipment
In a basic version, the estimated radio conditions could e.g. comprise two
flags, one indicating low or high Doppler shift and one indicating small or
large delay spread. When having a radio resource space in frequency and
time dimensions, quantities associated with coherence bandwidth and
coherence time, respectively, are of interest. The estimated radio conditions
are forwarded to the pilot manager 26, which performs the actual selection
and/or adjustment of resource sub-spaces. The pilot manager 26 thus
provides access to the use of the different pilot configurations. When predefined
pilot patterns are used, the pilot manager selects in which part of the
multi-carrier space the allocated resource sub-space win be placed. Without
pre-defined patterns in different parts of the multi-carrier space, the pilot
manager 26 comprises functionalities for selecting a multi-carrier sub-space
for allocation and functionalities to adapt the pilot pattern of that selected
sub-space according to the estimated radio conditions. When the pilot
manager has decided what pilot pattern to apply, the user equipment 3O has
to be informed about the selection, in order to be able to perform the right
channel estimation upon reception of the data. The pilot manager 26 thus
comprises means for transferring suitable data to the channel estimator
In Fig. 9B, another embodiment is illustrated, where the base station 2O has
the entire responsibility for the selection of pilot structure. The downlink
control unit 25 here also comprises a position estimator 29. The position
estimator 29 provides an estimation of the position of the user equipment 3O
and preferably also the velocity. This can be performed in any manner, e.g.
according to prior art methods, and is not further discussed here. The
position is forwarded to the radio condition processor 28. The radio condition
processor 28 has access to knowledge about the different environments
within the cell. A cell could e.g. cover a first area having generally slowly
moving user equipments, and a second area, were the average speed is
considerably higher. The position estimation could reveal the location of the
user equipment, i.e. if it is situated in the high- or low-speed area. From
such information, the radio condition processor 28 can conclude what radio
conditions that should be assumed for the user equipment. Such estimation
then forms the base on which the pilot pattern is selected.
hi Fig. 9C, yet another embodiment is illustrated. In this embodiment, the
user equipment 30 makes more efforts in the procedure to find suitable pilot
structures. The downlink control unit 35 here additionally comprises a radio
conditions processor 39. This means that both the measurements and the
evaluation of the measurements are performed in the user equipment
The estimated radio conditions are reported to the base station 2O, e.g. in the
form of data representing coherence bandwidth and coherence time,
respectively. Alternatively, the radio conditions processor 39 can also select
an appropriate pilot pattern and transmit a request to use such a pattern to
the base station 20. The base station 20 can in such a case either follow the
recommendation or overrule it and make an own decision.
Fig. 10 illustrates one possible configuration for uplink communication. The
base station 20 comprises an uplink control unit 45, in turn comprising a
radio conditions measurement unit 21, a radio conditions processor 28 and a
pilot manager 26. The operations of the units are similar to the ones in the
downlink case, but adapted for uplink communication instead, i.e. it is the
radio conditions of the received signals from the user equipment 30 that are
of importance. The pilot manager 26 decides which pilot pattern that is
appropriate to apply, and transmits a request to an uplink control unit 55 in
the user equipment 30. In a basic version, the uplink control unit 55 simply
applies the proposed pilot pattern on its uplink traffic. The uplink control
unit 35 of the base station 20 also comprises a channel estimator 27 in order
to be able to detect the data sent on the uplink. This channel estimator 27 is
also informed about the pilot structure to use.
Fig. 11 illustrates yet another embodiment of the present invention, in which
one makes use of the possibilities to vary the intensity to reduce pilot
pollution. In parts llOAand HOD, an or some of the pilot data is marked to
be transmitted with a lower (or zero) intensity. If a user equipment using the
pilot signals fc; close to the base station, the transmission power does not
have to be equally high to obtain a reasonable channel estimation compared
with user equipments situated further away from the base station. In such a
way, it is also possible to vary the pilot intensity throughout the resource
space. Such intensity configurations can as above be performed either in
advance or as adjustment procedures.
The pilot symbols can also be transmitted with different power for different
classes of users and depending on path loss. The power levels can either be
dynamically varying between zero and a given number Pmaa or be defined in
advance. Note that a power level equal to zero is equivalent to no pilots for
this slot, enabling the use of this slot for other purposes, such as data. If the
power is dynamically varying, the power levels have to be signalled to the
receiver for appropriate treatment.
When there are several possible pilot patterns to use in a system, the
receiver has to be informed about which one is actually used. If a numbered
set of pre-determined pilot patterns are used, the identification number of
the pilot pattern is sufficient. However, more elaborate systems can use
different pilot patterns for different cells and the numbering of patterns can
be difficult to manage. In such a case, a solution is to transfer a complete
description of the pilot pattern to be used. For regular pilot patterns, the
amount of data that is needed to uniquely define the patterns is quite
limited.
In Fig. 12, a pilot pattern is illustrated within a resource sub-space hi
frequency and time dimensions. The resource sub-space is reported anyway,
and is typically defined by frequency and time "coordinates" and the number
of frequency DF and time DT slots that are comprised in the sub-space. The
pilot pattern is then easily characterised by only three vectors in the (twodimensional)
resource space. A first vector VO defines the "distance" in
frequency and time, respectively, between a well-defined position in the subspace,
e.g. the lower left corner as illustrated in the picture, and any pilot
data within the pattern. A second vector VI defines a "relative distance"
between the two closest pilots in the pattern. A third vector V2 defines a
"relative distance" between the second closest pilots, that is not aligned with
the first vector VI. By knowing only these vectors, the entire pilot pattern
can easily be calculated.
Also somewhat more complicated patterns can be fit into a similar model. In
Fig. 13, a pattern having two neighbour pilots distributed in pairs over the
resource space. In order to describe this pattern, only one extra vector is
needed, the relative vector between the two pilots in each pair. Anyone
skilled in the art realises that with a very limited number of data, rather
complex pilot patterns can easily be defined.
It wfll be understood by those skilled in the art that various modifications
and changes may be made to the present invention without departure from
the scope thereof, which is defined by the appended claims.







We Claim:
1. Method for wireless communication in a multi-user, multi-carrier communications system (10), using a multi-carrier resource space (100) of least two dimensions, of which one is frequency, said multi-carrier communications systems(lO) allowing a data stream to be separated in to a series of parallel data streams, each of which is modulated and simultaneously transmitted with a different frequency, comprising the steps of:
allocating a first resource sub-space (108A-F) of entire said multicarrier resource space (100) for communication between a first node (20, 30; 30A-B) and a second node (20, 30; 30A-B);
said first resource sub-space (108A-F) having resources of more than one carrier; and
obtaining data associated with estimated radio conditions for communication between a first node (20, 30; 30A-B) and a second node (20, 30; 30A-B);
allocating a second resource sub-space (108A-F) of entire said multi-carrier resource space (100) for communication between the first node (20, 30; 30A-B) and a third node (20, 30; 30A-B);
said second resource sub-space (108A-F) having resources of more than one carrier, and
obtaining data associated with estimated radio conditions for communication between the first node (20, 30; 30A-B) and the third node (20,30; 30A-B),
characterized by,
providing access to the use of at least two pilot resource configurations, intended for different estimated node radio conditions,
whereby the first resource sub-space (108A-F) is associated a pilot resource configuration, being in agreement with pilot need for the estimated radio conditions for the second node (20, 30; 30A-B) and the second resource sub-space (108A-F) is associated a pilot resource configuration, being in agreement with pilot need for the estimated radio conditions for the third node (20, 30; 30A-B), and

whereby at least one of the first resource sub-space (108A-F) and the second resource sub-space (108A-F) having a carrier having both pilot resources and data resources within said first resource sub-space (108A-F) or said second resource sub-space (108A-F), respectively.
2. The method as claimed in claim 1, wherein the entire multi-carrier resource space (100) being divided into parts(110 A-D) having different pilot resource configurations, whereby the steps of allocating comprises the step of selecting the first resource sub-space (108A-F) and the second resource sub-space (108A-F) in respective parts having a pilot resource configuration suitable for the estimated radio conditions for the second node(20, 30; 30A-B) and the third node (20, 30; 30A-B), respectively.
3. The method as claimed in claim 2, wherein the step of selecting the first resource sub-space (108A-F) and the second resource sub-space (108A-F), comprises the steps of selecting if no resource space part (110A-D) having a pilot resource configuration suitable for the estimated radio conditions for the second node (20, 30; 30A-B) or the third node (20, 30; 30A-B), respectively, is available, an arbitrary first multi-carrier resource sub-space; and adapting the pilot resource configuration within the first multi-carrier resource sub-space to suit the estimated radio conditions for the second node (20, 30; 30A-B) or the third node (20, 30; 30A-B), respectively.
4. The method as claimed in claim 1, wherein providing access to the use of at least two pilot resource configurations comprises the steps of: -
selecting the first multi-carrier resource sub-space;
selecting the second multi-carrier resource sub-space; and
adapting the pilot resource configuration within the first and second multi- carrier resource sub-space to suit the estimated radio conditions for the second node (20, 30; 30A-B) and the third node (20, 30; 30A-B)respectively, after the step of selecting.
5. The method as claimed in any of the claims 1 to 4, wherein the multi- carrier
resource space (100) has a time dimension.

6. The method as claimed in any of the claims 1 to 5, wherein the multi- carrier resource space (100) has a code dimension.
7. The method as claimed in any of the claims 1 to 6, wherein the multi- carrier resource space (100) has a spatial dimension.
8. The method as claimed in any of the claims 1 to 7, wherein the step of obtaining in turn comprises the step of estimating a set of estimated radio conditions.
9. The method as claimed in claim 8, wherein the set of estimated radio conditions comprises at least Doppler conditions and coherence time conditions.
10. The method as claimed in claim 8 or 9, wherein the set of estimated radio conditions comprises at least delay spread conditions and coherence bandwidth conditions.
11. The method as claimed in any of the claims 8 to 10, wherein the step of estimating are based on position and/or velocity information concerning the second node (20, 30; 30A-B) and the third node (20, 30; 30A-B), respectively..
12. The method as claimed in any of the claims 1 to 11, wherein the step of obtaining comprises the step of receiving instructions and/or suggestions about preferred pilot resource configuration.
13. The method as claimed in any of the claims 1 to 12, wherein the first node (20, 30; 30A-B) is selected from the group of user equipment, mobile station, base station, access point (20) and relay.
14. The method as claimed in any of the claims 1 to 13, wherein at least one of the second node (20, 30; 30A-B) and the third node (20, 30; 30A-B) is selected from the group of user equipment, mobile station, base station, access point (20) and relay.

15. The method as claimed in any of the claims 1 to 14, wherein resources of the first and second resource sub-spaces are allocated for downlink communication (22; 22A-B).
16. The method as claimed in claim 15, wherein the steps of obtaining data associated with estimated radio conditions for the second node (20, 30; 30A-B) and the third node (20, 30; 30A-B) is performed in a base station or access point (20).
17. The method as claimed in claim 16, wherein data characterizing the first pilot resource configuration from the base station or access point (20) is transferred to the second node (20, 30; 30A-B) and data characterizing the second pilot resource configuration from the base station or access point (20) is transferred to the third node (20, 30; 30A-B).
18. The method as claimed in any of the claims 1 to 12, wherein resources of the first resource sub-space and the second resource sub-space are allocated for uplink communication (24; 24A-B).
19. The method as claimed in claim 18, wherein the steps of obtaining data associated with estimated radio conditions for the second node (30; 30A-B) and for the third node (30; 30A-B) are performed in a base station or access point (20), followed by the steps of transferring the data associated with estimated radio conditions for the second node (30; 30A-B) to the second node (30; 30A-B) and transferring the data associated with estimated radio conditions for the third node (30; 30A-B) to the third node (30; 30A-B).
20. The method as claimed in claim 18 wherein the step of obtaining data associated with estimated radio conditions for the second node (30; 30A-B) is performed in the second node (30; 30A-B) and the step of obtaining data associated with estimated radio conditions for the third node (30; 30A-B) is performed in the third node (30; 30A-B).

21. The method as claimed in claim 20, wherein data characterizing the first pilot resource configuration from the second node (30; 30A-B) is transferred to the first node (20, 30; 30A-B) and data characterizing the second pilot resource configuration from the third node (30; 30A-B) is transferred to the first node (20, 30; 30A-B).
22. The method as claimed in any of the claims 1 to 21, wherein transmitting pilots are refrained in areas of the entire multi-carrier resource space (100) not being allocated.
23. The method as claimed in any of the claims 1 to 22, wherein the wireless communication utilises OFDM.
24. The method as claimed in any of the claims 1 to 23, wherein the available at least two pilot resource configurations comprises different distribution patterns of pilot symbols in the multi-carrier resource space (100).
25. The method as claimed in claim 24, wherein the available at least two pilot resource configurations further comprises transmission of pilot symbols with differing intensity.
26. A first node (20, 30; 30A-B) of a multi-user, multi-carrier wireless communications system (10) using a multi-carrier resource space of least two dimensions, of which one is frequency, said first node being arranged for handling a data stream separated into a series of parallel data streams, each of which being modulated and simultaneously transmitted with a different frequency, the first node (20, 30; 30A-B) comprising:
means (25) for allocating a first resource sub-space (108A-F) of entire said multi-carrier resource space (100) for communication between the first node (20, 30; 30A-B) and a second node (20, 30; 30A-B);
said first resource sub-space (108A-F) having resources of more than one carrier;

means (28, 29, 38, 39) for obtaining data associated with estimated radio conditions for communication between the first node (20, 30; 30A-B) and the second node (20, 30; 30A-B);
means (25) for allocating a second resource sub-space (108A-F) of entire said multi-carrier resource space (100) for communication between the first node (20, 30; 30A-B) and a third node (20, 30; 30A-B);
said second resource sub-space (108A-F) having resources of more than one carrier;
means (28, 29, 38, 39) for obtaining data associated with estimated radio conditions for communication between the first node (20, 30; 30A-B) and the third node (20, 30; 30A-B)
characterized in that the first node (20, 30; 30A-B) have means (26) for providing access to the use of at least two pilot resource configurations, intended for different estimated node radio conditions,
whereby the first resource sub-space (108A-F) have a pilot resource configuration, being in agreement with pilot need for the estimated radio conditions for the second node (20, 30; 30A-B) and the second resource sub-space (108A-F) have a pilot resource configuration, being in agreement with pilot need for the estimated radio conditions for the third node (20, 30; 30A-B), and
whereby at least one of the first resource sub-space (108A-F) and the second resource sub-space (108A-F) comprises a carrier having both pilot resources and data resources within said first resource sub-space (108A-F) or said second resource sub-space (108A-F), respectively.
27. The node as claimed in claim 26, wherein the entire multi-carrier resource space (100) being divided into parts (1 IDA-D) having different pilot resource configurations, whereby the means (25) for allocating being arranged for selecting the first resource sub-space in a part having a pilot resource configuration suitable for the estimated radio conditions for the second node (20, 30; 30A-B) and for selecting the second resource sub-space in a part having a pilot resource configuration suitable for the estimated radio conditions for the third node (20, 30; 30A-B).

28. The node as claimed in claim 26, wherein the means (26) for providing
access comprises:
means (26) for selecting the first multi-carrier resource sub-space; means (26) for selecting the second multi-carrier resource sub-space; and means (26) for adapting the pilot resource configuration within the first multi-carrier resource sub-space to suit the estimated radio conditions for the second node (20, 30; 30A-B) and for adapting the pilot resource configuration within the second multi-carrier resource sub-space to suit the estimated radio conditions for the third node (20, 30; 30A-B), the means (26) for adapting being connected to an output of the means for selecting.
29. The node as claimed in any of the claims 26 to 28, wherein data characterizing the first pilot resource configuration from the first node (20, 30; 30A-B) is transferred by means for transferring to the second node (20, 30; 30A-B) and for transferring data characterizing the second pilot resource configuration from the first node (20, 30; 30A-B) to the third node (20, 30; 30A-B).
30. The node as claimed in any of the claims 26 to 29, wherein the means (28, 29, 38, 39) for obtaining data associated with estimated radio conditions for the second node (20, 30; 30A-B) in turn comprise a receiver for receiving instructions and/or suggestions about preferred pilot resource configuration from the second node (20, 30; 30A-B) and the third node (20, 30; 30A-B).
31. The node as claimed in any of the claims 26 to 30, wherein the node being arranged for OFDM.
32. The node as claimed in any of the claims 26 to 31, wherein the node being a node selected from the group of user equipment, mobile station, base station, access point (20) and relay.

33. The node as claimed in any of the claims 26 to 32, wherein the second node (20, 30; 30A-B) is selected from the group of user equipment, mobile station, base station, access point (20) and relay.
34. Wireless communications system (10), being a multi-user, multicarrier wireless communications system (10) using a multi-carrier resource space of least two dimensions, of which one is frequency, said wireless communications system (10) being arranged for handling a data stream separated into a series of parallel data streams, each of which being modulated and simultaneously transmitted with a different frequency, comprising at least one node as claimed in any of the claims 26 to 33.
35. User equipment (30) being arranged to handle connection to a multiuser, multi-carrier wireless communications system (10) using a multi-carrier resource space (100) of least two dimensions, of which one is frequency, said user equipment being further arranged for handling a data stream to be separated into a series of parallel data streams, each of which is modulated and simultaneously transmitted with a different frequency, comprising:
means (35) for communication between the user equipment (30) and a node (20, 30; 30A-B) utilizing a first resource sub-space (108A-F) of entire said multi-carrier resource space (100);
said first resource sub-space (108A A-F) having resources of more than one carrier.
characterised in that
the first resource sub-space (108A-F) comprises a first pilot resource configuration, out of a set of at least two different pilot resource configurations,
whereby the first pilot resource configuration being in agreement with pilot need for estimated, radio conditions for the user equipment (30); and
whereby the first resource sub-space (108A-F) comprises a carrier having both pilot resources and data resources within said first resource subspace (108A-F).
36. The user equipment as claimed in claim 35, wherein data characterizing the
first pilot resource configuration from the node (20, 30; 30A-B) is received by a receiver,

the receiver being connected to a means (36) for channel estimation, whereby the means for channel estimation is arranged to perform channel estimation based on the received data characterizing the first pilot resource configuration.

Documents:

4001-DELNP-2006-Abstract-(27-04-2009).pdf

4001-delnp-2006-abstract.pdf

4001-DELNP-2006-Claims-(27-04-2009).pdf

4001-delnp-2006-claims.pdf

4001-DELNP-2006-Correspondence-Others (17-12-2009).pdf

4001-delnp-2006-Correspondence-Others-(18-02-2010).pdf

4001-DELNP-2006-Correspondence-Others-(18-03-2010).pdf

4001-DELNP-2006-Correspondence-Others-(20-04-2010).pdf

4001-delnp-2006-Correspondence-Others-(26-05-2010).pdf

4001-DELNP-2006-Correspondence-Others-(27-04-2009).pdf

4001-DELNP-2006-Correspondence-Others-(28-06-2010).pdf

4001-DELNP-2006-Correspondence-Others-(31-12-2008).pdf

4001-delnp-2006-correspondence-others-1.pdf

4001-delnp-2006-correspondence-others.pdf

4001-delnp-2006-description (complete).pdf

4001-delnp-2006-drawings.pdf

4001-delnp-2006-form-1.pdf

4001-delnp-2006-form-18.pdf

4001-delnp-2006-form-2.pdf

4001-delnp-2006-form-26.pdf

4001-DELNP-2006-Form-3-(27-04-2009).pdf

4001-delnp-2006-form-3.pdf

4001-delnp-2006-form-5.pdf

4001-delnp-2006-pct-101.pdf

4001-delnp-2006-pct-105.pdf

4001-delnp-2006-pct-210.pdf

4001-delnp-2006-pct-301.pdf

4001-delnp-2006-pct-304.pdf

4001-delnp-2006-pct-306.pdf

4001-delnp-2006-pct-409.pdf

abstract.jpg


Patent Number 242281
Indian Patent Application Number 4001/DELNP/2006
PG Journal Number 35/2010
Publication Date 27-Aug-2010
Grant Date 20-Aug-2010
Date of Filing 12-Jul-2006
Name of Patentee TELEFONAKTIEBOLAGET LM ERICSSON (PUBL), a Swedish Company of SE-164 83 Stockholm, Sweden
Applicant Address SE-164 83 STOCKHOLM (SE)
Inventors:
# Inventor's Name Inventor's Address
1 NYSTRÖM, Johan, a Swedish citizen KRONOBERGSGATAN, 22, S-112 33 STOCKHOLM, SWEDEN
2 SIGNELL, Svante, a Swedish citizen ANGSULLSVAGEN 170, S-162 46 VALLINGBY, SWEDEN
3 DAHLMAN, Erik, a Swedish citizen TACKJARNSVAGEN 12, S-168 68 BROMMA, SWEDEN
4 KLANG, GÖRAN, a Swedish citizen BERGKANTSVAGEN 12, S-122 32 ENSKEDE, SWEDEN
5 FRENGER, Pal, a Swedish citizen EKÄNGEN MASÅRP, SE-582 75 LINKÖPING, SWEDEN
PCT International Classification Number H04Q 7/38
PCT International Application Number PCT/EP2004/053192
PCT International Filing date 2004-12-01
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 03104661.8 2003-12-12 EUROPEAN UNION