Title of Invention

A METHOD AND RADIO BASE STATION FOR REDUCING SHARED DOWNLINK RADIO CHANNEL INTERFERENCE BY TRANSMITTING TO MUTIPLE MOBILES USING MULTIPLE ANTENNA BEAMS

Abstract A radio base station includes multiple antennas associated with a cell. Multiple mobile radios are selected (12) to receive transmissions over a shared radio channel (10) during a predetermined time interval. Information is transmitted over the shared radio channel to multiple mobile radios in the cell during the predetermined time interval using multiple antenna beams (14). As a result, interference from the transmission appears as white additive Gaussian noise in time and in space in the cell. A "flashlight effect" caused by a single beam transmission over the shared channel during a predetermined time interval that would normally detrimentally impact mobile channel quality detection is avoided. Other methods for avoiding the flashlight effect are described.
Full Text BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to cellular radio communications, and more
particularly, to downlink radio transmission where multiple antennas are employed at the
radio base station.
Shared downlink radio channels, like the high speed-downlink shared
channel (HS-DSCH) employed in third generation, wideband code division multiple
access (WCDMA) systems, offer high data transmission rates, reduced round-trip delays,
and high capacity, at least with respect to a typical transport channel. The HS-DSCH
supports higher order modulation to achieve higher user and system throughput, fast link
adaptation that takes into account the instantaneous quality of the radio propagation
environment and adapts the coding and modulation scheme accordingly, and hybrid-ARQ
with soft combining to decrease retransmissions and thereby reduce delay.
HS-DSCH mobile radio users periodically measure the instantaneous radio
channel quality of a pilot channel broadcast by a radio base station, which is called Node
B in the WCDMA specification. The mobile users periodically report a channel quality
Indicator (CQI) based upon the measured radio channel transmission. The base station
responsible for handling the HS-DSCH uses the CQI to assign an appropriate coding and
modulation scheme. It may also use the CQI to decide which mobile radio should be
scheduled to receive downlink transmission over the HS-DSCH. Various scheduling
strategies can be used for transmitting over the high speed shared channel.
There is an inherent time delay between the time instant when a mobile
user reports the CQI and the time instant that the base station schedules transmission over
the high speed shared channel to a mobile user. During this time delay, the interference
may change dramatically for reasons described below. If the difference between the
reported channel quality and the actual channel quality at the time of scheduling is large,
the selected coding and modulation scheme may not be sufficiently robust to ensure
transmission with a low enough error rate. If the data is received in error, the mobile radio
requests retransmission which degrades system performance.
This difference between a reported CQI and the actual CQI at the scheduled
HS-DSCH transmission is particularly problematic in adaptive antenna systems. An
adaptive antenna system can change its beam characteristics in response to changes in the
network. An antenna beam is any signal transmission deliberately covering only part of a
cell. A cell is a coverage area of the base station. Because the base station can detect the
direction of a mobile station, it can transmit dedicated information in an antenna beam
towards the desired mobile station. By directing the signal just toward its recipient, the
interference in the network can be substantially reduced. Adaptive antennas can
significantly increase the data capacity in a cellular radio network.
The discrepancy between the reported channel quality and the
instantaneous channel quality caused by scheduling different mobile users to receive
transmissions over a shared radio channel may be traced in large part to a "flashlight
effect." The flashlight effect will be described in conjunction with Figures 1, 2, 3, and
Figure 1 illustrates a base station with three cells or sectors. In the upper, left-hand sector
cell, the base station transmits a sector antenna beam which covers most of that sector cell.
An adaptive antenna array in the right-most sector cell transmits five, relatively narrow
antenna beams 1-5. Most antenna patterns contain a main lobe and several minor lobes
commonly known as side lobes. The term "beam" refers to the main lobe. Eight mobile
radios, (a mobile radio is referred to in WCDMA as a user equipment (UE)), are shown in
or close to the right-most sector cell and are identified as U1-U8.
Figure 2 illustrates an example situation where mobile radio U3 is
scheduled for a current time instant to receive information over the high-speed downlink
shared channel with maximum power. This is illustrated by the main and side lobes of
beam B2 being represented in a bold solid line, with the remaining four beams Bl, B3, B4,
B5 carrying little or no power during this scheduled time period. By the end of the
scheduled time period, all mobile radios, including the scheduled mobile radio U3, report
to the base station their current or instantaneous detected channel quality indicator (CQI)
based on the quality of reception of the base station's pilot signal. The base station
transmits information to the next-scheduled mobile radio over the HS-DSCH channel at
maximum power during the next scheduling time period.
In the example shown in Figure 3, the next-scheduled mobile radio is U5
because at the time the scheduling decision was made, U5 had the highest CQI. Beam 3
B3, which encompasses mobile U5, is selected based on beam quality information
detected at the base station. At the time instant shown Figure 2, mobile radio U5 is at a
"null" between the main lobe of beam B2 and a side lobe of beam B2. That null means U5
experiences low interference from the beam B2 transmission. On the other hand, mobile
radio U4, which is relatively close to mobile radio U5, reports a much lower CQI because
the main lobe of beam B2 creates a high interference at U4 on the order of 15 dB. Since
mobile U4 is relatively close to the scheduled mobile U3, it is "blasted" by beam B2 and
therefore reports a dramatically lower CQI than mobile U5. Yet, in the absence of the
beam B2, the reported CQI from both mobiles U4 and U5 would be approximately the
same. These kinds of "blasts" cause the flashlight effect.
The flashlight effect can be further illustrated using the example
transmission scheduling table shown in Figure 4. Here six mobiles U1-U6 report detected
channel quality indicators (CQI) for each transmission time interval (TIT) TTI1-TTI7.
The highest CQI for each TTI is underlined, and the scheduled mobile user for each TTI is
circled. In this example, it takes two TTIs for the mobile user with the highest CQI to be
scheduled for transmission over the HS-DSCH channel.
The table illustrates that the scheduled mobile radio does not always have
the highest CQI during its scheduled TTI. For example, mobile U1 is scheduled to receive
a transmission during TTI 5. Mobile U2, which is served by the same beam B1 as mobile
Ul, reports a very low CQI of 5 during TTI 5 because it is being temporarily "blasted" by
the beam B1 transmission to mobile user U1. As a result, mobile U6 reports the highest
CQI and is scheduled for TTI 7. Absent the flashlight effect of transmitting to mobile Ul
during TTI 5, mobile U2 would have reported a much higher CQI. Indeed, after the
flashlight effect of the beam B1 transmission during TH's 5 and 6 subsides, mobile U2
reports a channel quality of 20, which is higher than the CQI of 18 reported by the
scheduled mobile U6. The rapid and dramatic CQI increase from 4 to 20 for mobile U2
between TTI 6 and TTI 7 demonstrates the flashlight effect of beam B1 on mobile U2.
This dramatic and rapid change of reported CQI from one scheduled time interval to the
next is the flashlight effect.
In summary, the flashlight effect is intense interference detected by a
mobile causing that mobile to report a low CQI for a short time period which results from
the mobile being "flashed" by a brief downlink transmission to another scheduled mobile.
The flashlight effect is a serious problem in fixed multi-beam systems, adaptive antenna
systems, and transmit diversity systems.
The flashlight effect is overcome by selecting multiple mobile radios to
receive a transmission over a shared radio channel during^ predetermined transmission
time Interval. Information is transmitted over the shared radio channel to the multiple
mobflelradios using multiple antenna beams so that interference from the transmission
appears as white additive Gaussian noise in time and in space in the cell. The "flashlight
effect" caused by a single beam transmission over the shared channel that would
detrimentally impact a mobile radio's detection of channel quality is avoided.
Mobile radios detect the channel quality of a pilot or other broadcast signal
transmitted in the cell and report to the radio network. Shared channel transmissions are
scheduled to multiple mobile radios for each time interval based on the received reports.
One mobile radio is selected for transmission for each antenna beam based on the received
reports. The information is transmitted over the shared channel using each antenna beam
to each of the selected mobile radios during the predetermined time interval.
The shared radio channel radio resources are allocated to the multiple
mobile radios using a resource allocation scheme. An optimal coding and modulation
scheme is preferably selected for each scheduled mobile radio to achieve an acceptable
error rate. Example resource allocation schemes include dividing the shared radio channel
resources evenly between each selected mobile radio. The resource allocation scheme
may divide the shared radio channel resources in proportion to each of the mobile radio's
reported detected channel quality, e.g., in accordance with a "water pouring" distribution
algorithm. Alternatively, the shared channel resources may be divided using a non-linear
relationship between two or more of the following: amount of channel resources,
throughput, quality of service, and detected channel quality. That relationship may be
stored in a lookup table for easy application. If a change is detected in radio channel
conditions, the look-up table is preferably updated.
In the situation where the radio communications system is a CDMA-based
system and radio channel resources include scrambling codes, with each scrambling code
having an associated channelization code tree, an example resource allocation scheme
includes allocating one scrambling code to the shared radio channel. One or more
different channelization codes associated with that scrambling code are allocated to each
antenna beam during each predetermined time interval. Alternatively, a different
scrambling code may be allocated for each antenna beam during each predetermined time
interval.
The flashlight effect may be avoided by carefully planning in space and/or
in time which beam is used for transmission. Another technique for avoiding the
flashlight effect employs a beam transmission sequence order. Multiple mobile radios
may be selected to receive a transmission over a shared radio channel using a beam
transmission sequence order. Mobile users belonging to a selected beam may be
scheduled. The beam selection is decided using a beam sequence number. Information is
transmitted over the shared radio channel to each of the mobile radios in the cell following
the beam transmission sequence order. Beam switching in accordance with the beam
transmission sequence order occurs over multiple transmission time intervals so that
interference from the transmission appears as white noise in time and in space.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a cellular communications system with a base station
serving three sector cells;
Figure 2 illustrates antenna beam patterns for an HS-DSCH transmission
during one time interval;
Figure 3 illustrates an antenna beam pattern for transmission over an HS-
DSCH channel during a subsequent transmission time interval;
Figure 4 is a transmission time interval table during which CQI's reported
by mobile radios are used to illustrate an example of the flashlight effect;
Figure 5 is a flowchart diagram illustrating procedures for implementing
one example embodiment of the present invention;
Figure 6 is a graph illustrating an example of multiple beam transmission
per transmission time interval over a shared radio channel;
Figure 7 illustrates an example, non-limiting radio communication system
in which the present invention may be advantageously employed;
Figure 8 is a flow chart illustrating procedures involved in certain aspects
of the present invention as applied to the example system shown in Figure 7;
Figure 9 illustrates an adaptive lookup table that may be employed in the
base station illustrated in Figure 7; and
Figures 10A-10C are graphs illustrating performance of a multi-beam
transmission over the HS-DSCH.
DETAILED DESCRIPTION
The following description, for purposes of explanation and not limitation, sets forth
specific details, such as particular components, electronic circuitry, techniques, etc., in
order to provide an understanding of the present invention. But it will be apparent to one
skilled in the art that the present invention may be practiced in other embodiments that
depart from these specific details. In other instances, detailed descriptions of well-known
methods, devices, and techniques, etc., are omitted so as not to obscure the description
with unnecessary detail. Individual function blocks are shown in one or more figures.
Those skilled in the art will appreciate that functions may be implemented using discrete
components or multi-function hardware. Processing functions may be implemented using
a programmed microprocessor or general-purpose computer, using an application specific
integrated circuit (ASIC), and/or using one or more digital signal processors (DSPs).
A shared channel scheduling procedure (block 10) is illustrated in flow
chart form in Figure 5. One non-limiting example of a shared radio channel is the high-
speed downlink shared channel (HS-DSCH) described above. Of course, neither this
description nor the invention is limited to the HS-DSCH. Multiple mobile radios are
selected to receive transmissions over the shared radio channel for a predetermined
transmission time interval (block 12). One mobile radio is selected to receive transmission
over the shared channel per each antenna beam. Transmissions over the shared radio
channel to the selected mobile radios use multiple antenna beams during that transmission
time interval so that the interference caused by that shared channel transmission appears as
white noise in space and time (block 14). In a preferred example embodiment, the noise is
rendered white additive Gaussian noise. Stated differently, the multiple beam-to-multiple
radio transmission over the shared channel ensures that intra-cell (and consequently inter-
cell) interference appears spatially and temporally as white. But there is a trade-off
between how many simultaneous shared-channel mobile users may be scheduled for
transmission and overall system throughput. Thus, it is preferable to allocate the system
resources, (e.g., power, codes, coding and modulation schemes, etc.), in an optimal way.
Example resource allocation schemes are described later.
Figure 6 illustrates the multiple antenna beam transmission in one
transmission time interval. Of eight mobile users U1-U8, five are selected to receive
transmissions from the five beams B1-B5 during a transmission time interval over the
shared radio channel. The transmission from beam Bl is directed to mobile U2; the
transmission from beam B2 is directed to mobile U3; the transmission from beam B3 is
directed mobile U5; the transmission from beam B4 is directed to mobile U6; and the
transmission from beam B5 is directed to mobile U8.
The present invention may be advantageously applied to the example, non-
limiting radio communication system 20 shown in Figure 7. A control network node 24
couples a base station 22 to other nodes and networks. In a wideband-CDMA context,
such a network control node may be, for example, a radio network controller (RNC). Base
station 22 includes a supervisory controller 28 for controlling the overall operation of the
base station. A channel quality controller 36 collects channel quality information provided
from various mobile stations 26. For example, the channel quality controller 36 may
receive channel quality indicators (CQI's) from mobile stations. One or more transmit
data buffers 38 store data for transmission over a shared radio channel to multiple mobile
stations. A transmission scheduler 30 selects mobiles to receive transmissions that have a
maximum CQI for each beam. The scheduler 30 also monitors the availability of shared
radio channel resources 32 and maintains an adaptive lookup table 34. The lookup table
34 may be used in one non-limiting example to determine how shared radio channel
resources may be allocated to each selected mobile for each transmission time interval.
Signal processing and radio transceiving circuitry 40, a beam forming network 42, and an
antenna array 44 are employed to transmit multiple antenna beams to the selected mobile
users for each transmission time interval.
A mobile station 26 (sometimes referred to as a user equipment (UE) in the
wide-band CDMA context) includes a supervisory controller 46 for controlling the overall
operation of the mobile. It also includes a channel quality detector 48 used to detect the
quality of the base station pilot channel and provide channel quality information back to
the base station via the signal processing and transceiving circuitry 50. One example
method is for the mobile station to measure the signal-to-noise ratio (SNR) of the received
base station pilot. Knowing the average power allocated to a high speed-downlink shared
packet channel (HS-DSCH), the mobile deduces the signal to noise ratio of the HS-DSCH.
That HS-DSCH SNR is converted to a CQI value which is reported to the base station
every transmission time interval.
The channel quality controller 36 groups received CGI reports from all
shared channel mobile users into a number of groups corresponding to the number of
antenna beams transmitting over the shared radio channel. This channel quality
information is provided by channel quality controller 36 to the scheduler 30 which
identifies the mobile radios to receive transmissions over each of the antenna beams
transmitting over the shared radio channel. In one non-limiting example, the scheduler 30
selects for each transmission time interval (TTI) the mobile user having the highest CQI
for each beam group. The shared channel transmissions to each selected mobile via its
corresponding antenna beam occur in this non-limiting example two TTI's after the CQI's
are reported.
The scheduler 30 also monitors the available channel resources 32 and
employs some type of resource allocation method for allocating resources for each antenna
beam transmission for each transmission time interval. One possible method is "round
robin" scheduling where resources are scheduled sequentially. A round robin algorithm
can be applied per beam. Users are regrouped per set with each set corresponding to a
specific beam. The round robin scheduler is applied to each set so that mobile users in
each set are scheduled in a time-multiplexed fashion. Another example scheduling
method is to divide the shared channel radio resources evenly between the selected
multiple mobile radios.
Yet another example shared channel resource allocation scheme is to divide
the shared radio channel resources in proportion to each mobile radio's reported detected
channel quality. A well-known "water filling" algorithm may be used to implement this
particular allocation scheme. Still further, the resources may be divided using a non-linear
relationship between two or more parameters such as the following: channels, power,
throughput, quality of service, detected channel quality, etc. Regardless of the resource
allocation scheme employed, an optimal coding and modulation scheme is preferably also
selected for each scheduled mobile radio in order to achieve an acceptable error rate.
Using a wideband-CDMA system as an example context for resource
allocation, the radio channel resources include scrambling codes. Each scrambling code
has an associated channelization code tree. One example shared channel resource
allocation scheme allocates a single scrambling code to the shared radio channel. One or
more different channelization codes from the single scrambling code tree are allocated to
each antenna beam for use during the predetermined transmission time interval.
Alternatively, multiple different scrambling codes may be allocated for each beam during
the predetermined transmission time interval. Using multiple scrambling codes as
compared to a single scrambling code for the shared radio channel resources increases the
intra-cell interference, but also ensures stable spatial and temporal interference patterns in
the cell without degrading the system throughput. In this way, the flashlight effect is
mitigated, and system performance is considerably improved.
As mentioned above, a nonlinear relationship may be used to divide the
shared channel resources. An example follows. If the signal-to-noise ratio (SNR)
decreases by 50% due to poor channel conditions, the number of channelization codes or
scrambling codes needed to compensate varies depending on the current quality of service
requirements. For a higher quality of service, the number of codes may need to increase
by 75% to offset the 50% decrease in channel condition. Figure 9 shows an example
where a nonlinear relationship is defined using an adaptive lookup table 34. The CQI's
reported from the mobile stations, the available shared channel resources, and one or more
measurements are received as an inputs. Example measurements may include, for
example, mobile user location, mobile speed, throughput, etc. The throughput is a
function of the number of channelization codes or scrambling codes allocated to a
particular mobile user, but it also depends upon the current radio channel conditions. The
output of the adaptive lookup table 34 includes a power P^, a modulation and coding
scheme MSC, and scrambling and channelization codes C. The lookup table 34 is
preferably constructed to associate the received CQI with the least amount of system
resources to ensure a high throughput.
Preferably, the lookup table 34 is dynamically updated to match the current
radio channel conditions. One method for deriving an optimal lookup table is based on
"reinforcement learning" where for each action taken, e.g., a code allocation, an award is
given. Reinforcement learning populates the lookup table by maximizing a numerical
reward signal. At a high level, a reinforcement learning controller faces a problem and
must learn the behavior of the system through trial and error interactions with the dynamic
environment in order to maximize performance. One way is to use statistical techniques
including information feedback and dynamic programming methods to estimate the utility
of taking certain actions in that environment. The controller knows its current state and
performs a number of actions in each state, e.g., deciding the MCS number, power level,
etc.
Reference is made to the HS-DSCH scheduling routine (block 60) shown in
flowchart form in Figure 8. CQI's determined by various mobiles for a base station
downlink signal, e.g., pilot signal, are collected by the base station (block 62). The
channel quality controller 36 groups the CQI's by antenna beam (block 64). Based upon
the CQI, and perhaps other information available at the base station, (e.g., mean user bit
rate), the scheduler 30 selects one mobile per beam for transmission over the HS-DSCH
during a subsequent TTI (block 66). As explained above, one scheduling technique selects
the mobile station per beam with the highest reported CQI. The scheduler 30 allocates
HS-DSCH radio channel resources for this each interval beam transmission using a
resource allocation procedure. Example allocation procedures include: dividing the
resources equally amongst the beams, allocating resources in proportion to reported CQI,
and allocating using a non-linear relationship (block 68). For any resource allocation
procedure, it is desirable to select an optimal modulation and coding scheme (MSC) (if
one can be selected) to ensure an acceptable error rate at the mobile (block 70).
Figures 10A-10C illustrate the frame or block error rate (FER) versus the
signal-to-interference-plus-noise ratio (SINR) for various allocated codes (12, 6, and 3)
and for different numbers of data bits per TO (here the TO is 2ms). These data bits are
indicated in the figure legends. TFRC in these figures corresponds to CQI. The figures
show the nonlinear relation between the SINR, FER, and the data rate. A disadvantage
with using six or three codes instead of 12 codes is the loss of granularity of the switching
points of different TFRCs. In fact within a given range of SINR, fewer choices of TFRC
are offered.
The inventors performed simulations using two different types of radio
propagation models to test the performance of the invention in one implementation (i.e., a
closed loop mode I transmit diversity). One channel model called a "pedestrian A"
channel with relatively little scattering and reflection. The other channel model called an
"urban" channel contains considerably more scattering and reflection. Assuming a
reference or comparison point a single sector beam to transmit to one "best" mobile user,
the simulated implementation for the invention achieved a 50% capacity gain for the
pedestrian channel and approximately a 15% capacity gain for the typical urban channel.
Unfortunately, splitting the resources amongst multiple beams during one
TO lowers the peak bit rate because the transmit power per beam largely impacts the
achievable bit rate. The highest peak bit rate is achieved by allocating all transmit power
resources to one beam in a cell. However, as already described above, a single beam
allocation-without careful planning-causes the flashlight effect. But by carefully
planning in space and/or in time which beam is used for transmission, the flashlight effect
may be avoided.
For example, each cell can be allocated a beam transmission sequence
order using a list that gives the order of beams to be used for transmission. Mobile users
belonging to this beam may be scheduled. The beam selection is decided using a beam
sequence number. For example, in Figure 2, assuming that beam 1 is the left-most beam
and beam 5 the right-most beam seen from the base station, a simple beam transmission
list could be {B1, B2, B3, B4, B5}. The beams are switched more slowly, e.g., not every
TTI but rather over multiple TTIs. If there are HS-DSCH cells geographically opposite to
each other, it is desirable to have the beam sequences be as orthogonal as possible to lower
the probability of transmitting simultaneously on the opposite beam belonging to different
cells. It is also desirable to avoid synchronization in the network in order to decrease the
frequency of beam switching (e.g., occurs with a slower time interval than a TTI (e.g., a
multiple of 2ms)). This results in a more reliable/stable CQI measurement. This beam
transmission sequencing approach mitigates the flashlight effect by switching beams more
slowly than usual so that the interference stays constant over several intervals. At the
same time, this beam sequencing approach permits high peak bit rates and provides
improved overall system performance.
The present invention includes any spatial and/or temporal interference
management scheme that eliminates the flashlight effect. By selecting an optimal resource
allocation procedure, higher downlink system throughput and overall system performance
are substantially improved. Smoother interference variations are introduced artificially in
the network to ensure a stable network and much easier interference prediction. The
invention may be applied to various antenna techniques such as beam-forming, transmit
diversity, etc.
The invention has been described in connection with what is presently
considered to be the most practical and preferred embodiments. The invention is not
limited to the disclosed embodiments. The invention is applicable whenever multiple
antenna beams are employed for a transmission over a radio channel including diversity
transmission schemes. The invention can by applied to other various advanced antenna
techniques, for instance, steered beams, closed loop transmit diversity, and situations
where the mobile station instructs the base station on a beam weight to be used. Indeed,
the present invention may be employed with transmission schemes in which signals are
sent with different polarizations. The invention covers various modifications and
equivalent arrangements included within the scope of the appended claims.
WE CLAIM :
1. A method for use in a radio communications system (20) with a radio base
Station (22) that includes multiple antennas (44) associated with a cell,
characterized by
receiving reports from mobile radios of a detected channel quality of a pilot signal
transmitted in the cell;
scheduling for each transmission time interval based on the received reports
selected multiple mobile radios (26) in the cell for transmitting information over a shared
radio channel, HS-DSCH, during a predetermined transmission time interval using
multiple antenna beams such that interference from the transmission is equally distributed
over the entire frequency spectrum range and in space.
2. The method in claim 1, further comprising :
selecting one of the mobile radios to receive a transmission from one of the
antenna beams based on the received reports, and
transmitting the information over the HS-DSCH using each antenna beam to each
selected mobile radio during the predetermined share time interval.
3. The method in claim 1, further comprising:
splitting shared radio channel resources among the multiple mobile radios
using a resource allocation scheme.
4. The method in claim 3, wherein the radio communications system is a CDMA-
based system where radio channel resources include scrambling codes, each scrambling
code having an associated channelization code tree, and wherein the resource allocation
scheme allocates a scrambling code to the shared radio channel and allocating one or more
different channelization codes associated with the shared radio channel scrambling code to
each antenna beam during the predetermined transmission time interval.
5. The method in claim 3, wherein the radio communications system is a CDMA-
based system where radio channel resources include scrambling codes, each scrambling
code having an associated channelization code tree, and wherein the resource allocation
scheme allocates a different scrambling code for each antenna beam during the
predetermined transmission time interval.
6. The method in claim 3, wherein the resource allocation scheme divides the
shared radio channel resources evenly between the multiple mobile radios.
7. The method in claim 3, wherein the resource allocation scheme divides the
shared radio channel resources in proportion to each mobile radio's reported detected
channel quality.
8. The method in claim 3, wherein the resource allocation scheme divides the
shared channel resources using a non-linear relationship between two or more of the
following: amount of channel resources, throughput, quality of service, and detected
channel quality.
9. The method in claim 8, wherein the non-linear relationship is stored in a look-up
table.
10. The method in claim 9, further comprising
detecting a change in radio channel conditions, and updating the look-up table based on
changed radio channel conditions.
11. The method in claim 1, wherein the mobile radios are selected using a beam
transmission sequence order, the method further comprising:
transmitting information over the shared radio channel using one beam to one or
more mobile radios following the beam transmission sequence order for multiple
predetermined time intervals, and
performing beam switching in accordance with the beam transmission sequence
order after multiple transmission time intervals.
12. The method in claim 11, further comprising:
receiving reports from mobile radios of a detected channel quality of a pilot signal
transmitted in the cell, and scheduling transmissions to one of the mobile radios over the
HS-DSCH for more than one transmission time interval in accordance with the beam
transmission sequence based on the received reports.
13. A radio base station (22) for use in a radio communications system (10),
comprising multiple antennas (44) associated with a cell for generating multiple antenna
beams, each beam covering only a portion of the cell, and one or more transmit buffers
(38),characterised in:
a channel quality controller (30) for receiving reports from mobile radios of a
detected channel quality of a pilot signal transmitted in the cell;
a channel scheduler (30) for scheduling transmissions for each transmission time
interval based on the received reports selected multiple radios over a shared radio channel,
HS-DSCH, during a predetermined transmission time interval; and
transceiving circuitry (40) for transmitting information stored in one or more
transmission buffers over the shared radio channel via the adaptive antenna array to the
multiple mobile radios in the cell during the same predetermined transmission time
interval using multiple antenna beams to spread out the interference caused by the
transmission.
14. The radio base station in claim 13, wherein the scheduler is configured to select
one of the mobile radios to receive a transmission from one of the antenna beams based on
the received reports, and wherein the transceiving circuitry is configured to transmit the
information over the HS-DSCH using each antenna beam to each selected mobile radio
during the predetermined transmission time interval.
15. The radio base station in claim 13, wherein the scheduler is configured to split
the radio resources of the shared radio channel among the multiple mobile radios using a
resource allocation scheme.
16. The radio base station in claim 15, wherein the radio communications system is
a CDMA-based system here radio channel resources include scrambling codes, each
scrambling code having an associated channelization code tree, and wherein the resource
allocation scheme includes allocating a scrambling code to the shared radio channel and
allocating one or more different channelization codes associated with the shared radio
channel scrambling code to each antenna beam during the predetermined transmission
time interval.
17. The radio base station in claim 15, wherein the radio communications system is
a CDMA-based system where radio channel resources include scrambling codes, each
scrambling code having an associated channelization code tree, and wherein the resource
allocation scheme includes transmission allocating a different scrambling code for each
antenna beam during the predetermined time interval.
18. The radio base station in claim 15, wherein the resource allocation scheme
includes dividing the shared radio channel resources evenly between the multiple mobile
radios.
19. The radio base station in claim 15, wherein the resource allocation scheme
includes dividing the shared radio channel resources in proportion to each mobile radio's
reported detected channel quality.
20. The radio base station in claim 15, wherein the resource allocation scheme
includes dividing the shared channel resources using a non-linear relationship between two
or more of the following: amount of channel resources, throughput, quality of service, and
detected channel quality.
21. The radio base station in claim 20, wherein the non-linear relationship is stored
in a look-up table.
22. The radio base station in claim 21, wherein the scheduler is configured to
detect a change in radio channel conditions, and update the look-up table based on
changed radio channel conditions.
23. The radio base station in claim 13, wherein the multiple antennas include an
adaptive antenna array.
24. The radio base station in clairn 13, wherein the multiple antennas include
transmit diversity antennas.
Dated this 20th day of April 2006.


A radio base station includes multiple antennas associated with a cell. Multiple mobile
radios are selected (12) to receive transmissions over a shared radio channel (10) during a
predetermined time interval. Information is transmitted over the shared radio channel to
multiple mobile radios in the cell during the predetermined time interval using multiple
antenna beams (14). As a result, interference from the transmission appears as white
additive Gaussian noise in time and in space in the cell. A "flashlight effect" caused by a
single beam transmission over the shared channel during a predetermined time interval
that would normally detrimentally impact mobile channel quality detection is avoided.
Other methods for avoiding the flashlight effect are described.

Documents:

01007-kolnp-2006 correspondence.pdf

01007-kolnp-2006 form-18.pdf

01007-kolnp-2006-abstract.pdf

01007-kolnp-2006-asignment.pdf

01007-kolnp-2006-claims.pdf

01007-kolnp-2006-correspondence other.pdf

01007-kolnp-2006-correspondence others-1.1.pdf

01007-kolnp-2006-correspondence-1.1.pdf

01007-kolnp-2006-description (complete).pdf

01007-kolnp-2006-drawings.pdf

01007-kolnp-2006-form-1.pdf

01007-kolnp-2006-form-2.pdf

01007-kolnp-2006-form-3.pdf

01007-kolnp-2006-form-5.pdf

01007-kolnp-2006-international publication.pdf

01007-kolnp-2006-pct form.pdf

01007-kolnp-2006-priority document.pdf

1007-KOLNP-2006-(30-08-2011)-CORRESPONDENCE.pdf

1007-KOLNP-2006-(30-08-2011)-OTHERS.pdf

1007-KOLNP-2006-ABSTRACT_1.0.pdf

1007-KOLNP-2006-ABSTRACT_1.1.pdf

1007-KOLNP-2006-AMENDED PAGES.pdf

1007-kolnp-2006-assignment.pdf

1007-KOLNP-2006-CANCELLED DOCUMENTS.pdf

1007-KOLNP-2006-CLAIMS.pdf

1007-KOLNP-2006-CORRESPONDENCE 1.1.pdf

1007-KOLNP-2006-CORRESPONDENCE 1.2.pdf

1007-KOLNP-2006-CORRESPONDENCE 1.3.pdf

1007-KOLNP-2006-CORRESPONDENCE 1.4.pdf

1007-KOLNP-2006-CORRESPONDENCE-1.1.pdf

1007-kolnp-2006-correspondence1.5.pdf

1007-KOLNP-2006-DESCRIPTION COMPLETE.pdf

1007-KOLNP-2006-DRAWINGS.pdf

1007-kolnp-2006-examination report.pdf

1007-KOLNP-2006-FORM 1.1.1.pdf

1007-KOLNP-2006-FORM 1.pdf

1007-kolnp-2006-form 18.pdf

1007-KOLNP-2006-FORM 2.1.2.pdf

1007-KOLNP-2006-FORM 2_1.0.pdf

1007-KOLNP-2006-FORM 2_1.1.pdf

1007-kolnp-2006-form 3.pdf

1007-kolnp-2006-form 5.pdf

1007-KOLNP-2006-FORM-27.pdf

1007-kolnp-2006-gpa.pdf

1007-kolnp-2006-granted-abstract.pdf

1007-kolnp-2006-granted-claims.pdf

1007-kolnp-2006-granted-description (complete).pdf

1007-kolnp-2006-granted-drawings.pdf

1007-kolnp-2006-granted-form 1.pdf

1007-kolnp-2006-granted-form 2.pdf

1007-kolnp-2006-granted-specification.pdf

1007-KOLNP-2006-OTHERS 1.1.pdf

1007-KOLNP-2006-OTHERS.pdf

1007-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

1007-kolnp-2006-reply to examination report1.1.pdf

abstract-01007-kolnp-2006.jpg


Patent Number 248764
Indian Patent Application Number 1007/KOLNP/2006
PG Journal Number 34/2011
Publication Date 26-Aug-2011
Grant Date 22-Aug-2011
Date of Filing 20-Apr-2006
Name of Patentee TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Applicant Address TORSHAMNSGATAN 23, S-164 83 STOCKHOLM
Inventors:
# Inventor's Name Inventor's Address
1 See attached documents See attached documents
PCT International Classification Number H04Q 7/36
PCT International Application Number PCT/SE2004/001218
PCT International Filing date 2004-08-20
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/668,363 2003-09-24 U.S.A.