Title of Invention

"A BASE STATION IN A CELLULAR COMMUNICATION SYSTEM AND A METHOD OF RADIO INTERFACE ORGANIZATION"

Abstract The present invention relates to radio engineering, and more particularly to the method of radio interface organization and base station equipment in CDMA communication system, which provides continuous connection between mobile stations (MS) and base station (BS). The purpose of the invention is to increase the interference stability, enhance the communication system capacity, and improve the quality of the receive and transmit information for a larger number of simultaneously operating users. Increase of the interference stability, enhancement of the communication system capacity, and improvement of the receive and transmit information quality are achieved in the present invention through the fact that the location of base station transmit-receive antennas, orientation of their antenna patterns, and their power of electromagnetic radiation are selected so that maximum regular distribution of electromagnetic radiation power within a cell, minimal noise level for neighboring cells, and maximum regular distribution of mobile stations between coverage zones of different base station transmit-receive antennas are provided, the connection between mobile stations, located on the cell territory, and base station, serving the given cell via those base station transmit-receive antennas, in the electromagnetic radiation power coverage zone of which the corresponding mobile stations are located, is provided, handoff is provided via those base station transmit-receive antennas, in the service zone of which the corresponding mobile stations are located.
Full Text METHOD OF RADIO INTERFACE ORGANIZATION AND BASE
8TATIQN IN CELLULAR COMMUNICATION SYSTEM
Field of Invention
The present invention relates to radio engineering, and more
particularly to the method of radio interface organization and base station
equipment in CDMA communication system, which provide continuous
connection between mobile stations (MS) and base station (BS).
Description of the Related Art
A mobile cellular radio communication system should serve a
maximal number of simultaneously operating mobile stations with the
specified quality of transmit and receive information, i.e. provide the
maximal system capacity. At the same time, it is necessary to provide a
minimal level of mutual interference both between MS and cells. This can
be achieved, first, by reducing the power of BS and MS transmit-receive
antenna electromagnetic radiation to the minimum acceptable level and,
second, by optimal placing BS transmit-receive antennas and orientation
of their antenna patterns.
The book (see Ratynski M.V. Basics of Cellular Communication,
Library of Cellular Communication series, BEELINE Cellular
Communication, Moscow, Radio and Communication, 2000 (pp. 19-24,
55-57) contains a systematic overview of the basic aspects of modern
cellular communication, conventional description and schematic
presentation of a standard communication system, description and
illustration of the procedure of a mobile station handoff by base stations
when crossing cell borders.
Under conditions of limited bandwidth of operation frequencies
assigned to mobile communication systems, the number of users can be
increased through repeated use of operation frequencies, space and time
diversity of the radiated signals, and application of effective modulation
methods.
There is no universal solution to this task. In each specific case it
should be treated differently.
An invention has been proposed (see WO 98/12889 "Base Station
and Process of Powering a Cell of a Cellular Mobile Radio System", H 04
Q 7/36, H 04 B 7/06, published March 26, 1998), which describes the
method and device of radio interface organization in GSM system (Global
System for Mobile Communication).
There are two possible embodiments of this invention aimed to
increase overall system capacity:
according to the first embodiment, additional space diversity of BS
transmit-receive antennas is performed at the cell periphery;
according to the second embodiment, sectorization of BS transmitreceive
antenna, located in the cell center, is carried out.
According to the first embodiment of the solution, L BS transmitreceive
antennas are placed at the cell periphery. Communication
channels between BS and MS are formed, thus providing additional space
diversity of BS signal. When organizing radio interface between BS and
MS, time and frequency multiplexing is used.
To serve N simultaneously operating MS by all L BS transmitreceive
antennas, there should be N different carrier frequencies at all BS
transmit-receive antennas. From the description of the given invention it
follows that the number of carrier frequencies can be reduced through
their switching by planning the load of each channel of diversity reception
from BS to MS. The channel load depends on specific characteristics of
each cell. Depending on the channel load, the required number of BS
transmit-receive antennas is determined. BS channels are connected or
disconnected depending on the quality of signal transmission via BS-MS
connection on the whole, when the quality of signal transmission is
evaluated by all communication channels or by the quality of signal
transmission in separate channels. In case of inappropriate connection
quality, additional BS channels can be connected or the channels with the
worst transmission quality can be removed. Thus the economy of carrier
frequencies is achieved in order to provide connection with a larger
number of end users.
According to the second embodiment of the solution, BS contains
sector transmit-receive antennas located in the cell center. Sector
transmit-receive antennas form BS channels and are oriented in such a
way that the cell to which BS belongs is divided into sectors. In this case,
sectors of separate neighboring BS transmit-receive antennas are
overlapped in such a way that one MS could be connected to at least two
sector transmit-receive antennas.
Such cell division into sectors allows reducing mutual influence of
signals from neighboring sectors, thus reducing the amount of mutual
interference. It also allows using one and the same carrier frequency for
MS in different non-overlapping sectors.
To implement this algorithm, BS sector antennas are connected to
separate transceivers. Transceivers, in their turn, are connected to
switching device by means of which sector antenna channels are selected
through commutation and their switch, i.e. control, is carried out
depending on the load.
With this structure of cellular communication system, owing to BS
channel switching, the number of frequency channels in BS transmitreceive
sector antennas, involved in a communication session with a
specific MS, becomes reduced. BS transmit-receive sector antennas which
are not used in a communication session with a given MS become
disconnected and are used for other purposes, for example, connection
with other MS. Hence, the present technical solution provides cell
resource economy and increases system capacity by means of additionally
assigned frequency band.
However, placing BS transmit-receive antennas at the cell
periphery only, as proposed in the mentioned method, in real operation
conditions means the following disadvantages:
- irregular distribution of BS transmit-receive antenna
electromagnetic radiation power within a cell and occurrence of signal
shadow areas, the so called "dead zones", where no connection between
BS and MS is possible (see Microwave Mobile Communications. Edited
by William C. Jakes. Reissued in cooperation with the IEEE
Communications Society. Press NY, 1994, chapters 2, 7).
- low quality of connection between BS and MS in the zones of
depression of the electromagnetic radiation field strength, thus requiring
increased radiation power of BS and MS transmit-receive antennas;
- impossibility to provide the required, i.e. potential, cell capacity
in case of irregular MS distribution across the cell square.
The proposed sectorization of BS transmit-receive antenna
radiation, located in the cell center, with the specified radio interface
organization does not eliminate essential interference of BS and MS
signals from neighboring cells.
The structure of the cellular communication system and control
algorithm proposed in the above technical solution are not universal and
designed for GSM standard systems only.
CDMA base station equipment (see patent US N° 5,103,459
«System and Method for Generating Signal Waveforms in a CDMA
Cellular Telephone System», Fig. 2, Int. Cl.5 H 04 L 27/30) has been
proposed, which contains device for MS signal reception and device for
signal transmission. Device for MS signal reception consists of two
receive antennas intended for MS signal reception and two corresponding
analog-digital receivers, at least two searchers and three data receivers,
signal combining unit with a decoder, control processor, and digital data
transmission channel. Device for BS signals transmission contains
sequentially connected modulator, power control unit, summator,
transmitter power amplifier connected to pilot signal unit, and antenna for
information transmission in the reverse channel.
The mentioned device operates in the following way. A group
signal, which is a sum of mobile station signals, located within the service
zone of a given receive antenna, arrives at each BS receive antenna.
Group signal energy at the input of each BS receive antenna equals the
sum of signal energies from each of MS and is an average characteristic
of the communication channel. In the analog-digital receiver, these
signals are transformed into a digital form and supplied to the input of
searchers and data receivers. Searchers scan the uncertainty area and
detect MS signals. Having detected MS signal, searchers pass the
information to control processor. Control processor estimates the
information signals supplied from receivers and passes control signals to
data receivers. Data receivers process the received signal through control
signal and pass the processed signal to signal combining unit with
decoder. Signal combining unit with decoder performs operations of
diversity reception of signals from each specific MS, supplied from data
receivers, decodes them and passes to the user network.
Information signal from the user network, transformed considering
the reverse channel characteristics, via modulator, power control unit,
summator, and transmitter power amplifier is supplied to transmit
antenna.
However, the above device and its algorithm do not allow for
implementation of the required, i.e. potential, cell capacity in case of
irregular MS distribution across the cell square.
Finally, an invention has been proposed (see EP 0 817 406 "Mobile
Communication System with Improved Antenna Arrangement" Int. Cl.
H04B 7/26, H04Q7/36), with several embodiments of BS antenna system
organization in each cell. In this technical solution, BS contains a
multiplicity of transmit-receive antennas located along the cell border and
have directivity characteristics oriented to the cell center.
According to the first embodiment, each of the three BS transmitreceive
antennas has directivity characteristics oriented to cover 120
degree sectors of the cell square. BS transmit-receive antennas are located
along the cell border with the angle interval of 120 degrees.
BS transmit-receive antennas can also be located in another way.
One of them, the central BS transmit-receive antenna, has directivity
characteristic covering 60 degree sector of the cell square and the other
two BS transmit-receive antennas have directivity characteristics covering
120 degree sectors of the cell square and are located at the two sides of
the central antenna. All BS transmit-receive antennas are located along
the cell border with the angle intervals of 60 degrees.
According to the second embodiment of this antenna system, the
central BS transmit-receive antenna has directivity characteristic covering
120 degree sector of the cell square and each of the two BS transmitreceive
antennas at the two sides of the central BS transmit-receive
antenna has directivity characteristic covering 60 degree sectors of the
cell square. All BS transmit-receive antennas are located along the cell
border with the angle intervals of 60 degrees.
The preferred embodiment is when BS transmit-receive antennas
have directivity characteristics oriented to cover 120 degree sectors of the
cell square and are located with the intervals of 60 degrees along the cell
border and the undirected BS transmit-receive antenna is in the cell
center.
The given invention compared to the previous technical solution in
the second embodiment eases the difficulties of system frequency
resource utilization that arise due to the technique of organization of the
cellular communication system featuring BS sector combined circular
pattern transmit-receive antennas located in the cell center.
In the mentioned patent (see EP 0 817 406 "Mobile
Communication System with Improved Antenna Arrangement" Int. Cl.
H04B 7/26, H04Q7/36), along with the description of embodiments of BS
transmit-receive antenna organization in each cell, the issues of providing
regular cell square coverage by electromagnetic radiation power are
indirectly touched and certain structures of signal processing at BS and
MS are considered, (see Fig. 8 -20, pp. 15-21 Patent specification).
Let us consider, for example, Fig. 20 on p. 21 of the Patent
description. Fig. 20 shows the multifunction structure of BS. In the given
application, the device is presented on Fig. 1.
The device of Fig. 1 consists of:
BS transmit-receive antennas - l j - 1L,
Signal diversity unit 2,
Signal combining unit 3,
Channel estimation unit 4,
Receive signal processing and transmit signal forming unit 5,
Modulator amplifier 6,
Transmission diversity control unit 7.
This device operates in the following way. A group signal, which is
a sum of signals of mobile stations located within the service zone of a
given BS transmit-receive antenna, arrives at each BS transmit-receive
antenna l j - 1L. Group signal energy at the input of each BS transmitreceive
antenna li - IL equals the sum of signal energies from each of MS
and is an average characteristic of the communication channel. Via signal
diversity unit 2, these signals are supplied to channel estimation unit 4
and signal combining unit 3. Signal combining unit 3 performs an
operation of diversity signal reception from each specific MS which
arrives from signal diversity unit 2, in order to provide a resultant signal
at the input of receive signal processing and transmit signal forming unit
5 with a maximal signal-to-noise ratio. Unit 5 demodulates the input
signal and transmits it to the user network. Channel estimation unit 4
estimates the strength of the group signal in each of the channels received
by BS transmit-receive antennas l j - 1L. Quality reception at MS can be
achieved by correction of the signal transmitted from BS, according to the
received estimation of the communication channel state.
In particular, in TDD communication system, signals of the forward
and reverse communication channels are transmitted and received at one
and the same frequency. Hence, the forward and reverse channel
characteristics are the same. The process of BS transmitter signal
correction is as follows.
Information signal from the network is supplied via unit 5 to unit 6,
where the signal for transmission in the reverse channel is generated.
Then, the signal arrives at unit 7 which transforms it according to
the estimated state characteristics of communication channels that were
obtained as a result of estimation in unit 4. The output signal from unit
arrives via unit 2 at BS transmit-receive antennas li - 1L..
Regular space distribution of BS transmit-receive antennas along
the border only or along the border and in the cell center, as proposed in
the mentioned invention, in real operation conditions leads to the
following drawbacks:
irregular distribution of BS transmit-receive antenna
radiation power within a cell and decrease in connection quality between
BS and MS;
occurrence of signal shadow areas, the so called "dead
zones", where no connection between BS and MS is possible;
low quality of connection between BS and MS in the zones
of depression of the electromagnetic radiation field strength, thus
requiring increased electromagnetic radiation power of BS and MS
transmit-receive antennas;
impossibility to provide the required, i.e. potential, cell
capacity in case of irregular MS distribution across the cell square.
The above drawbacks are clearly illustrated on Fig. 2A, 2B, and 2C.
Consider them in more detail.
Fig. 2A shows 3D graphic presentation of coverage of cell square
by the electromagnetic radiation power of BS transmit-receive antennas,
which was obtained through computer simulation, with BS transmitreceive
antennas placed along the border and in the cell center, when BS
transmit-receive antennas have directivity characteristics oriented to cover
120 degree sectors of the cell square and are located along the cell border
with the intervals of 60 degrees, the undirected BS transmit-receive
antenna placed in the cell center.
Fig. 2B shows section projections of equal levels of
electromagnetic radiation power to the horizontal plane for the threedimensional
object shown on Fig. 2A.
Fig. 2C shows section projections of equal levels of
electromagnetic radiation power to the horizontal plane for the threedimensional
object shown on Fig. 2A. Conditionally, the case is
demonstrated where in a cell the "dead zone" D occurs generated by a
block of high buildings, constructed, for example, in a form of a "closed
rectangle". On Fig. 2C this zone is shadowed. MS located in this zone is
inaccessible for communication even to the nearest BS transmit-receive
antennas AI, A4, A5, and A6.
Accepted denotations on Fig. 2A and Fig. 2B:
AI -BS transmit-receive antenna placed in the cell center,
A2 - A7 - BS transmit-receive antennas located along the cell
border,
Accepted denotations on Fig. 2C:
AI - BS transmit-receive antenna placed in the cell center,
A2 - A7 - BS transmit-receive antennas located along the cell
border,
D - "dead zone".
From Figures 2A, 2B, and 2C it can be seen that with such location
of BS transmit-receive antennas, the cell square coverage by
electromagnetic radiation power is irregular, due to which additional
problems of signal reception in "dead zones" may arise.
Simulation of this method has shown that, in the ideal case, where
the environment of radio-wave distribution is isotropic and there are no
signal shadow areas, the irregularity of cell square coverage by
electromagnetic radiation power becomes substantially reduced compared
to the conventional transmit-receive antenna location in the cell center.
Improved distribution of electromagnetic radiation power is especially
evident from the vertical sections of the three-dimensional image of Fig.
2A. The vertical sections of Fig. 2A are shown on Fig. 3 A, 3B, and 3C.
Consider Fig. 3A that illustrates distribution of BS transmit-receive
antenna electromagnetic radiation power in the vertical section passing
through BS transmit-receive antennas A2 - AI - A5.
Fig. 3A shows:
by dotted line - distribution of electromagnetic radiation power P0
in a cell, with the conventional BS transmit-receive antenna location in
the cell center, where Preq. - minimal power level of electromagnetic
radiation, determined by the corresponding standards for radio
communication and required to provide quality connection with MS
within cell borders;
by curves a, b, c - distribution of electromagnetic radiation power
in a cell from BS transmit-receive antennas, from A2 - AI - A5
respectively;
by curve d - resultant value of the electromagnetic radiation power
distribution curve in a cell from BS transmit-receive antennas;
R - cell radius.
Consider Fig. 3B, which illustrates distribution of BS transmitreceive
antenna electromagnetic radiation power in the vertical section
passing through BS transmit-receive antennas A2 - AI - A5) in case of a
"dead zone" D, generated by a block of high buildings, constructed, for
example, in a form of a "closed rectangle".
Fig. 3 B shows:
by dotted line - minimal power level of the electromagnetic
radiation Preq. determined by the corresponding standards for radio
communication and required to provide quality connection with MS
within cell borders;
by curve d - resultant distribution of electromagnetic radiation
power in a cell from BS transmit-receive antennas, when the "dead zone"
D is absent;
by curve d' - resultant distribution of electromagnetic radiation
power in a cell from BS transmit-receive antennas, in case of "dead zone"
D occurence.
Consider Fig. 3C that illustrates distribution of electromagnetic
radiation power of MS transmit-receive antenna in the vertical section,
passing through BS transmit-receive antennas A2 - AI - A5> for the cases
when MS is located in the "dead zone" D and when the "dead zone" is
absent.
Fig. 3C shows:
by dotted line - minimal power level of the electromagnetic
radiation Preq., determined by the corresponding standards for radio
communication and required to provide quality connection with MS
within cell borders;
by curve «f» - distribution of electromagnetic radiation power of
MS transmit-receive antenna, in case the "dead zone" D is absent,
by curve «e» - distribution of electromagnetic radiation power of
MS transmit-receive antenna in case MS is within the "dead zone" D.
From the resultant curve d on Fig. 3A, it can be seen that, within a
cell, the total power level of electromagnetic radiation of BS transmitreceive
antennas located along the border and in the cell center, compared
to the conventional central placing, has reduced, though substantial
irregularity has remained.
From the resultant curves «d» and «d'» on Fig. 3B, it can be seen
that in the "dead zone" D the total power level of electromagnetic
radiation of BS transmit-receive antennas reduces sharply thus rendering
the connection between BS and the user located within this zone
impossible.
From the resultant curves «f» and «e» on Fig. 3C, it can be seen
that the power level of electromagnetic radiation of MS transmit-receive
antenna, located within the "dead zone" D, reduces sharply outside this
zone thus rendering the connection between MS and nearest BS transmitreceive
antennas AI, A5 impossible.
Therefore, with the proposed in the patent (see EP 0 817 406
"Mobile Communication System with Improved Antenna Arrangement"
Int. Cl. H04B 7/26, H04Q7/36) geometry of placing BS transmit-receive
antenna system, intended to provide connection between BS and MS,
located within the "dead zone" D, the power of electromagnetic radiation
must be substantially increased, both from BS transmit-receive antennas
and MS transmit-receive antennas. This leads to irrational use of BS and
MS resources and increases the noise level for other users.
Note that all the above described examples of covering the cell
square by the power of electromagnetic radiation of BS transmit-receive
antennas do not solve one more important problem. This problem is
connected with irregular MS distribution across the cell square, which can
occur both occasionally and predictably. To such zones of MS irregular
distribution across the cell square belong the areas of increased MS
concentration, further referred to as "1C". These are public places, for
example, stadiums, exhibitions, trade fairs, shopping centers, railway
stations and airports, busy motorways and so on.
Beside the geographical position of these areas in a cell, the seasonday
activity of mobile stations in these areas can be predicted rather
accurately.
High user concentration on limited squares leads to BS overload in
these cell zones, whereas the optimal mode of resource use is achieved
through regular load of BS transmit-receive antennas.
Fig. 4 shows possible embodiment of MS placing across the cell
square, in case in real conditions the mode of BS overload occurs.
For example, as proposed in the mentioned invention (see EP 0 817
406 "Mobile Communication System with Improved Antenna
Arrangement" Int. Cl. H04B 7/26, H04Q7/36), the cell square is divided
into seven service zones, where BS transmit-receive antennas AI - A7, are
placed, and the whole square is covered by the power of electromagnetic
radiation.
Each of BS transmit-receive antennas has limited resources for MS
quality service, for example, 35 MS.
Fig 4 shows that at some point of time in each of the seven service
zones there is, for example, the following number of simultaneously
operating MS, denotated by the corresponding numbers:
in the service zone of BS transmit-receive antenna AI - 35 MS,
in the service zone of BS transmit-receive antenna A2 -10 MS,
in the service zone of BS transmit-receive antenna AS - 30 MS,
in the service zone of BS transmit-receive antenna A4 - 7 MS,
in the service zone of BS transmit-receive antenna A5 - 25 MS,
in the service zone of BS transmit-receive antenna A6 - 20 MS,
in the service zone of BS transmit-receive antenna A7 - 50 MS.
In the service zone of BS transmit-receive antenna A7> 30 out of 50
MS are located on a limited predictable square of increased concentration
"1C". Due to the resource deficiency, BS transmit-receive antenna A7 can
serve no more than thirty-five MS. Hence, fifteen out of fifty mobile
stations will be denied service.
Therefore, such method and device should be created that would
allow serving maximal number of simultaneously operating mobile
stations with specified quality of information transmission and reception,
i.e. would provide maximal system capacity.
Summary of the Invention
The goal of the present invention is to create the method of radio
interface organization and base station for a cellular communication
system that improve communication system capacity and receive and
transmit information quality for a larger number of simultaneously
operating users.
The object is attained by the method of cellular communication
system radio interface organization consisting in that a territory served by
a communication system is divided into cells adjacent to one another, a
base station and a multiplicity of transmit-receive antennas are placed in
every cell, connection between transmit-receive antennas and a cell base
station is provided, handoff during a mobile station travel across cells is
provided, according to the claimed invention:
location of base station transmit-receive antennas, orientation of
antenna patterns, and power of their electromagnetic radiation are selected
so that the maximum regular distribution of electromagnetic radiation
power within a cell and minimal noise level for neighboring cells are
provided on the one hand, and, on the other one, the maximum regular
distribution of mobile stations is achieved between coverage zones of
different base station transmit-receive antennas,
connection is provided between the mobile stations within a cell
area and the base station that serves this cell via those base station
transmit-receive antennas in whose electromagnetic radiation power
coverage zone the corresponding mobile stations are placed,
handoff during a mobile station travel across cells is provided via
those base station transmit-receive antennas, in the service zone of which
the corresponding mobile stations are located.
While organizing a cellular communications system radio interface
it is preferable to provide, for example, orthogonality of the signals
radiated by different base station transmit-receive antennas, and soft
handoff within a cell during a mobile station travel from the service zone
these groups of base station transmit-receive antennas to the service zone
those groups of base station transmit-receive antennas.
The groups are understood to be a set of BS transmit-receive
antennas through which connection with MS is conducted within a given
interval.
The goal of the invention is further attained through the following.
Cellular communication system base station comprising L transmitreceive
antennas, signal diversity unit, MS signal path combining unit,
channel estimation unit, receive signal processing and transmit signal
forming unit, modulator amplifier, and signal transmission diversity
control unit; the inputs of transmit-receive antennas are at the same time
the device signal inputs and their outputs are connected to the
corresponding first inputs of signal diversity unit, the outputs of signal
diversity unit are connected to the first inputs of mobile station signal
path combining unit, the first outputs of which are connected to the first
inputs of receive signal processing and transmit signal forming unit, the
first outputs of which are the outputs of the device, second inputs of
receive signal processing and transmit signal forming unit are the inputs
of the user signal, second inputs of receive signal processing and transmit
signal forming unit are connected to the inputs of modulator amplifier, the
outputs of which are connected to the first inputs of signal transmission
diversity control unit, the second inputs of which are connected to the
outputs of channel estimation unit, the outputs of signal transmission
diversity control unit are connected to the second inputs of signal
diversity unit, the outputs of which are connected to transmit-receive
antennas, is added with the following:
signal path search unit, conducting search of all mobile station
signal paths,
control processor, forming control signals at the first outputs setting
the form and phase of the pseudorandom sequence for all mobile station
signal paths, at the second outputs the control signals of reference signal
selection for detected signal paths of mobile stations, at the third outputs -
control signals of reference signal selection of detected mobile station
signal paths, corrected considering time delays,
the first inputs of signal path search unit are combined with the first
inputs of mobile station signal path combining unit and connected to the
outputs of signal diversity unit, the outputs of signal path search unit are
connected to the inputs of the control processor, the first outputs of which
are connected to the second inputs of signal path search unit, the second
outputs of control processor are connected to the second inputs of mobile
station signal path combining unit, the third outputs of the control
processor are connected to the first inputs of channel estimation unit, the
second inputs of which are connected to the second outputs of mobile
station signal path combining unit.
The newly proposed sequence of method operations allows for the
following:
serve maximal number of simultaneously operating mobile stations
with specified quality of information transmission and reception; this
being achieved through the maximum regular distribution of
electromagnetic radiation power within a cell and minimal noise level to
neighboring cells, on the one hand, and the maximum regular distribution
of mobile stations between coverage zones of different base station
transmit-receive antennas, on the other one,
provide high-quality communication between mobile stations
within a cell area and the base station serving this cell; this being
achieved through providing communication established via those base
station transmit-receive antennas, in whose electromagnetic radiation
power coverage zone the corresponding mobile stations are located,
efficiently conduct handoff during a mobile station travel across
cells; handoff being carried out via those base station transmit-receive
antennas, in whose service zone the corresponding mobile stations are
located,
provide minimal noise level to neighboring cells; this being
achieved through orientation of electromagnetic radiation inwardly within
a cell for BS transmit-receive antennas, located in the proximity of a cell
border and selection of BS transmit-receive antenna patterns, located in
"dead zones" and areas of increased MS concentration "1C", and
redistribution of electromagnetic radiation power between BS transmitreceive
antennas, which reduces the total power level of electromagnetic
radiation to the minimum acceptable one.

Therefore, the newly proposed sequence of method operations improved communication system capacity.
BS quality signal reception from mobile stations is impossible without search for signals and their estimation. At BS, MS signal search and estimation mode should be provided, consequently in the filed base station equipment signal search unit and control processor, which adjusts the process of MS signal reception and transmission considering the radio channel characteristics, are introduced.
It is said in the description of the mentioned patent (see EP 0 817 406 "Mobile Communication System with Improved Antenna Arrangement" Int. CI. H04B 7/26, H04Q7/36), that BS (Fig. 1) comprises search unit and control processor. However, even if we assume that MS signal path combining unit and channel estimation unit comprise search units and control processors, it means that each of these units comprises at least one search unit and control processor, which makes the device more complex.
Moreover, the absence of links between signal combining unit 3 and channel estimation unit 4 (Fig. 1) shows that in the mentioned device operation in the receive channel and transmit channel is not coordinated. It means that MS signal detection and channel estimation take place separately in each of these channels, which can lead to degradation of MS signal reception and transmission quality.
Introduction of signal path search unit, searching for all mobile station signal paths, and control processor which adjusts the process of MS signal reception and transmission considering the radio channel characteristics in the claimed device allows BS quality reception and transmission of MS signals.-

Statement of the Invention
According to the present invention there is provided a base station for a
cellular communication system, the base station comprising L transmit-receive
antennas, a signal diversity unit, a mobile station signal path combining unit, a
. channel estimation unit, a receive signal processing and transmit signal forming
unit, a modulator amplifier, and a signal transmission diversity control unit,
wherein the inputs of the transmit-receive antennas are base station signal inputs and their outputs are connected to the corresponding first inputs of the signal diversity unit, the outputs of the signal diversity unit are connected to the first inputs of the mobile station signal path combining unit, the first outputs of which are connected to the first inputs of the receive signal processing and transmit signal forming unit, the first outputs of which are the outputs of the base station, second inputs of the receive signal processing and transmit signal forming unit are the inputs of the user signal.second outputs of receive signal processing and transmit signal forming unit are connected to the inputs of the modulator amplifier, the outputs of which are connected to the first inputs of the signal transmission diversity control unit, the second inputs of which are connected to the outputs of the channel estimation unit, the outputs of the signal transmission diversity control unit are connected to the second inputs of the signal diversity unit, the outputs of which are connected to the transmit-receive antennas,
a signal path search unit for searching all mobile station signal paths; and,
a control process for forming at the first outputs control signals, which assign the form and phase of the pseudo random sequence for all mobile station signal paths, at the second outputs control signals of reference signal selection for the detected mobile station signal paths, and at the third outputs control signals of reference signal selection for the detected mobile station signal paths, corrected considering time delays,
wherein the first inputs of the signal path search unit are combined with first inputs of the mobile station signal path combining unit and connected to the output of the signal diversity unit, the outputs of the signal path search unit are connected to the inputs of the control processor, the first outputs of which are connected to the second inputs of the signal path search unit, the second outputs of the control processor are connected to the second inputs of the mobile station signal path combining unit, the third outputs of the control processor are connected to the first inputs of the channel estimation unit, the second inputs of which are connected to the second outputs of the mobile station signal path combining unit.
Brief Description of the Drawings
Detailed examples of embodiment are set forth below when taken in conjunction with the drawings.
Fig. 1 is a block diagram of the device, at which the present method is implemented.
Fig. 2A is a three-dimensional representation of cell square coverage by electromagnetic radiation power of BS transmit-receive antennas, which was obtained through computer simulation when placing

BS transmit-receive antennas along the border and in the cell center, when
BS transmit-receive antennas have the directivity characteristics oriented
to cover 120 degree sectors of the cell square and are located with
intervals of 60 degrees along the cell border, and the undirected BS
transmit-receive antenna is in the cell center.
Fig. 2B is an illustration of section projections of equal levels of
electromagnetic radiation power to the horizontal plane for a threedimensional
object shown on Fig. 2A.
Fig. 2C is section projections of equal levels of electromagnetic
radiation power to the horizontal plane for a three-dimensional object
shown on Fig. 2A; conditionally a case is demonstrated where in a cell a
"dead zone" D occurs generated by a complex of tall buildings,
constructed, for example, in a form of "closed rectangle".
Fig. 3A is a distribution of BS transmit-receive antenna power of
electromagnetic radiation in the vertical section passing through BS
transmit-receive antennas A2 -Ai - A5.
Fig. 3B is a distribution of BS transmit-receive antenna power of
electromagnetic radiation in the vertical section passing through BS
transmit-receive antennas A2 - AI - A5) in case of a "dead zone" D
generated by a complex of tall buildings, constructed, for example, in a
form of "closed rectangle".
Fig. 3C is a distribution of MS transmit-receive antenna power of
electromagnetic radiation in the vertical section passing through BS
transmit-receive antennas A2 - A\ - AS for the cases when MS is in the
"dead zone" D and when the "dead zone" is absent.
Fig. 4 is an example of MS placing across the cell square, as
described in the known invention, leading to BS overload, when BS
transmit-receive antennas are located in the center and along the border
for the ideal cell form.
Fig. 5A is an embodiment of the filed method for the ideal cell
form, when BS transmit-receive antennas are located along the border, in
the cell center and, additionally, in the local minima of electromagnetic
radiation power.
Fig. 5B is a vertical section of BS transmit-receive antenna power
of electromagnetic radiation distribution, passing through BS transmitreceive
antennas A2 - AI - A5, when BS transmit-receive antennas are
located along the cell border, in the cell center and, additionally to them,
BS transmit-receive antennas A8 - An are located in the local minima of
electromagnetic radiation power, i.e. as shown on Fig. 5A.
maximum regular distribution of electromagnetic radiation power
within a cell and minimal noise level for neighboring cells is provided,
and, on the other hand, maximum regular distribution of mobile stations
between coverage zones of different base station transmit-receive
antennas is provided
Fig. 6A is an embodiment of the filed method, when BS transmitreceive
antenna placing and their antenna pattern orientation are
performed so that, on the one hand, maximum regular distribution of
electromagnetic radiation power within a cell and minimal noise level for
neighboring cells are provided, and on the other hand, maximum regular
distribution of mobile stations between coverage zones of different BS
transmit-receive antennas is provided considering the specific area and
the current situation in a cell at some point of time.
Fig. 6B is a vertical section of BS transmit-receive antenna power
of electromagnetic radiation distribution, passing through BS transmitreceive
antennas A7 - A9 - A2 - A4. Fig. 6B clarifies the principle of
overcoming A7 transmit-receive antenna overload when switching A9
transmit-receive antenna, serving the area of increased concentration
"1C".
Fig. 7 is a block diagram of the claimed base station of the cellular
communication system.
Fig. 8 is a search unit used in the claimed device, shown as an
example of embodiment.
Detailed Description of the Preferred Embodiments
The claimed base station of the cellular communication system,
shown on Fig. 7, contains L transmit-receive antennas li — 1L, unit 2 of
signal diversity, unit 3 of MS signal path combining, unit 4 of channel
estimation, unit 5 of receive signal processing and transmit signal
forming, modulator amplifier 6, and unit 7 of signal transmission diversity
control, the inputs of transmit-receive antennas \\ - 1L are at the same
time the device signal inputs and their outputs are connected to the
corresponding first inputs of signal diversity unit 2, the outputs of signal
diversity unit 2 are connected to the first inputs of mobile station signal
path combining unit 3, the first outputs of which are connected to the first
inputs of receive signal processing and transmit signal forming unit 5, the
first outputs of receive signal processing and transmit signal forming unit
5 are the outputs of the device, the second inputs of which are the inputs
of the user signal, second inputs of receive signal processing and transmit
signal forming unit 5 are connected to the inputs of modulator amplifier 6,
the outputs of which are connected to first inputs of signal transmission
diversity control unit 7, the second inputs of which are connected to the
outputs of channel estimation unit 4, the outputs of signal transmission
diversity control unit 7 are connected to the second inputs of signal
diversity unit 2, the outputs of which are connected to transmit-receive
antennas li - IL, according to the invention, the device contains
additionally signal path search unit 8, conducting search of all mobile
station signal paths, and control processor 9, forming at the first outputs
control signals, which assign the form and phase of the pseudorandom
sequence for all mobile station signal paths, at the second outputs -
control signals of reference signal selection for detected signal paths of
mobile stations, at the third outputs - control signals of reference signal
selection of detected mobile station signal paths, corrected considering
time delays, the first inputs of signal path search unit 8 are combined with
first inputs of mobile station signal path combining unit 3 and connected
to the outputs of signal diversity unit 2, the outputs of signal path search
unit 8 are connected to the inputs of control processor 9, the first inputs of
which are connected to the second inputs of signal path search unit 8,
second outputs of control processor 9 are connected to the second inputs
of mobile station signal path combining unit 3, the third outputs of control
processor 9 are connected to the first inputs of channel estimation unit 4,
the second inputs of which are connected to the second outputs of mobile
station signal path combining unit 3.
Fig. 7 shows an embodiment of MS signal path combining unit 3
for use in the claimed device. Unit 3 consists of L nodes of MS antenna
signal path combining 10i - 10L and node of antenna signal combining
11, the inputs of nodes 10] - 10L of L antenna MS signal path combining
form the first inputs of unit 3, second inputs of nodes 10i - 10L of L
antenna MS signal path combining form second inputs of unit 3, L outputs
of nodes 10i - 10Lof L antenna MS signal path combining are connected
to L inputs of antenna signal combining node 11 and form second outputs
of unit 3, outputs of node 11 of antenna signal combining form first
outputs of unit 3.
Fig. 8 shows an embodiment of signal path search unit 8, which
contains K search channels \2\ — 12^, each search channel contains
correlator 13, pseudorandom sequence generator (PRSG) 14 and
threshold comparison node 15, the first inputs of correlator 13 are at the
same time the first inputs of the search channel, second input of correlator
13 is connected to output of PRSG 14, the input of which is the second
input of the search channel, the output of correlator 13 is connected to the
input of threshold comparison node 15, the output of which forms the
output of the search channel. The first inputs of all search channel
correlators \2\ - 12k are combined and form first inputs of search unit 8,
the inputs of PRSG 14 of all search channels 12j - 12k form the second
inputs of search unit 8, the outputs of threshold comparison nodes 15 of
all search channels \2\ - 12k form the outputs of search unit 8.
The method of radio interface organization in the cellular
communication system according to the present invention is described
below with references to the foresaid device and Fig. 5A, 5B, 6A, 6B, 7,
and 8.
The territory served by the communication system is divided into
neighboring cells.
BS and a multiplicity of transmit-receive antennas are placed in
each cell.
Location of BS transmit-receive antennas, orientation of antenna
patterns, and the power of electromagnetic radiation are selected so that,
on the one hand, maximum regular distribution of electromagnetic
radiation power within a cell and minimal noise level for neighboring
cells are provided, and on the other hand, maximum regular distribution
of mobile stations between coverage zones of different base station
transmit-receive antennas is provided.
Connection of transmit-receive antennas with the cell base station
is provided.
Connection between mobile stations located on the cell territory
and the base station, serving the given cell via those base station transmitreceive
antennas, in the electromagnetic radiation power coverage zone of
which the corresponding mobile stations are located, is provided. Then,
for example, signal orthogonality, radiated by different BS transmitreceive
antennas, is provided.
Handoff during a mobile station travel between cells is provided
via those base station transmit-receive antennas, in the service zone of
which the corresponding mobile stations are located. Then soft handoff
within a cell should be provided during a mobile station travel from the
zone of serving some groups of base station transmit-receive antennas to
the zone of serving other groups of BS transmit-receive antennas.
Consider Fig. 5A, that illustrates conditionally an exemplary
organization of radio interface in the cellular communication system by
the filed method for ideal conditions and ideal cell form, when BS
transmit-receive antennas are located along the border, in the cell center,
and in the local minima of electromagnetic radiation power, orientation of
their antenna patterns is conducted so that maximum regular distribution
of electromagnetic radiation power within a cell and minimal noise level
for neighboring cells are provided.
Fig. 5A shows:
BS transmit-receive antenna AI is, for example, in the cell center,
BS transmit-receive antennas A2 - A7 are along the cell border,
BS transmit-receive antennas A8- - AJ3' - are in the local minima of
the electromagnetic radiation power.
The distinctive feature of this exemplary BS transmit-receive
antenna location in relation to the proposed technical solution (see EP 0
817 406 "Mobile Communication System with Improved Antenna
Arrangement" Int. Cl. H04B 7/26, H04Q7/36) is that BS transmit-receive
antennas are located in the local minima of the electromagnetic radiation
power distribution (whereas in the proposed technical solution - in the
center and along the cell border). The proposed approach reduces
interference between MS and between neighboring cells and improves
MS connection quality, owing to signal diversity reception.
Note that the given exemplary embodiment of the claimed method,
shown on Fig. 5A, can be used in practice in real conditions, both for the
case of symmetrical location of BS transmit-receive antennas in local
minima and for the case of unsymmetrical location of transmit-receive
antennas in local minima.
Fig. 5B illustrates the advantage of the filed method compared to
the known invention and shows how the distribution of BS transmitreceive
antenna power of electromagnetic radiation changes, when BS
transmit-receive antennas A8 - AJ3 are additionally placed in local minima
of electromagnetic radiation power. The curve of BS transmit-receive
antenna magnetic radiation power distribution is shown in the same
vertical section as in the known invention (Fig. 3A), i.e. in the section
passing through BS transmit-receive antennas A2- Aj - A5
On Fig. 5B it is denoted:
by dotted line - distribution of electromagnetic radiation power P0
in a cell with conventional BS transmit-receive antenna location in the
cell center, where Preq. - minimal level of electromagnetic radiation
power, determined by the corresponding standards for radio
communication, necessary to provide quality connection with MS within
a cell;
curves a, b, c, e, f illustrate distribution of electromagnetic radiation
power from BS transmit-receive antennas A2 - A! - A5, AIQ - AH, and A8
-An;
curve d - resultant distribution of electromagnetic radiation power;
R - cell radius.
From the resultant curve of electromagnetic radiation power
distribution d, it can be seen that the irregularity of electromagnetic
radiation power distribution (compared to the known invention (see Fig.
3A) is removed by placing BS transmit-receive antennas in local minima.
At the same time, further reducing the power level radiated by BS
transmit-receive antennas, due to its redistribution between BS transmitreceive
antennas.
Consider in detail Fig. 6A, showing an example of the claimed
method preferred embodiment, when BS transmit-receive antenna
location, orientation of their antenna patterns, and their power of
electromagnetic radiation are selected so that, on the one hand, maximum
regular distribution of electromagnetic radiation power within a cell and
minimal noise level for neighboring cells are provided, and, on the other
hand, maximum regular distribution of mobile stations between coverage
zones of different base station transmit-receive antennas is provided. This
example of BS transmit-receive antennas location considers specific
geographic conditions of the territory, where the radio interface of the
cellular communication system is organized and the conditions of BS
transmit-receive antennas interaction with mobile stations. In addition,
"dead zones" and areas of increased mobile station concentration across
the cell square should be taken into account.
There is one more important fact in favor of such BS transmitreceive
antenna location within a cell. In urban environment, even
radiation of nondirectional antennas is anisotropic by azimuth (see
William C.Y. Lee Mobile Cellular Telecommunications, Analog and
Digital Systems (Second edition) New York, 1995, NY10011). The whole
cell square, including shadow areas, becomes covered by electromagnetic
radiation power extremely irregularly and asymmetrically. Therefore, it is
impossible to achieve regular electromagnetic radiation power coverage
of the cell square by any of the proposed ordered set of BS transmitreceive
antennas in real conditions.
During organization of the cellular communication system radio
interface the assigned area is analyzed, which is never geometrically
proper in real conditions. Therefore, the cell borders will be arbitrary and
will depend on the specific geographic and radio communication
environment.
For example, the assigned cell square is divided into eight service
zones, where BS transmit-receive antennas AI - A8 providing regular
distribution of electromagnetic radiation power across the cell square are
located, BS transmit-receive antenna A9 is located in the area of increased
mobile station concentration (denoted "1C"), and BS transmit-receive
antenna Aj0 is in the "dead zone".
BS transmit-receive antennas are placed in the following way:
BS transmit-receive antenna Aj - in the center or near the cell
center,
BS transmit-receive antennas A2, A3 A4, A5, A6, A7 H A8 - near the
cell border,
BS transmit-receive antenna A9 - in the area of increased MS
concentration "1C",
BS transmit-receive antenna AIQ - in the "dead zone".
By numbers in the rectangles the number of MS simultaneously
served by the corresponding BS transmit-receive antennas is shown.
The shadowed area located in the service zone of transmit-receive
antenna A7 is an area of increased MS concentration "1C".
The shadowed area located in the service zone of transmit-receive
antenna A5 is a "dead zone".
Dotted line connecting points Z and Z\t denotes the route of MS
travel from the zone of serving some groups of transmit-receive antennas
to the zone of serving other groups of BS transmit-receive antennas,
where Z - initial point, Z\ - end point of MS travel route,
On the left, there shown a diagram of MS service zones by BS
transmit-receive antennas during MS travel from point Z to point Zi.
The shown shadowed area, located in the service zone of transmitreceive
antenna AIQ, is a "dead zone" generated, for example, due to the
land lowering, i.e. ravine, or tall buildings of the type "closed rectangle",
or other reasons. Therefore, an additional BS transmit-receive antenna A!0
is located in the "dead zone" (for example, as shown on Fig. 6A). Then
the orientation, power of electromagnetic radiation, and antenna pattern of
BS transmit-receive antenna AIO are selected considering the summed
radiation power of the neighboring antennas (Ai, A4 and A5).
The shown shadowed area, located in the service zone of transmitreceive
antenna A7, is an area of increased MS concentration "1C". This
problem is connected with irregular MS concentration across the cell
square, which can occur both occasionally and predictably during mobile
station movement. To such areas of concentration belong, for example,
public places, stadiums, exhibitions, trade fairs, shopping centers, railway
stations, airports, busy motorways and so on. Beside the geographical
position of these areas in a cell, the season-day activity of mobile stations
in these areas can be predicted rather accurately
High concentration of simultaneously operating MS on limited
squares leads to BS overload in these cell zones. At the same time,
optimal mode of resource use is achieved through regular load of BS
transmit-receive antennas.
Each of BS transmit-receive antennas AI - A8has limited resources
for quality service of simultaneously operating MS, for example, 35 MS.
At some point of time, in each of the eight service zones there is,
for example, the following number of MS denoted by the corresponding
numbers:
in the service zone of BS transmit-receive antenna AI - 35 MS,
in the service zone of BS transmit-receive antenna A2 -10 MS,
in the service zone of BS transmit-receive antenna A3 - 30 MS,
in the service zone of BS transmit-receive antenna A4 - 7 MS,
in the service zone of BS transmit-receive antenna A5 - 25 MS,
in the service zone of BS transmit-receive antenna A6 - 20 MS,
in the service zone of BS transmit-receive antenna A7 - 50 MS, including
thirty MS located on the limited predictable square of increased
concentration "1C",
in the service zone of BS transmit-receive antenna A8 - 15 MS.
A predictable situation has occurred, when BS transmit-receive
antenna A7 can serve no more than thirty-five simultaneously operating
MS. Therefore, in the zone of increased concentration "1C" BS transmitreceive
antenna A9 should be placed in advance. In the current situation
this BS transmit-receive antenna A9 will provide quality and prompt
service of thirty simultaneously operating MS, located in the zone of
increased concentration "1C".
The electromagnetic radiation parameters of BS transmit-receive
antenna A9 are selected so that it serves mobile stations within the area of
increased concentration "1C" only.
The algorithm of overload overcome is based on the automatical
load redistribution between BS transmit-receive antenna A7 and BS
transmit-receive antenna A9.
The electromagnetic radiation power of BS transmit-receive
antenna A9 is selected so that, in the mode of soft handoff during a mobile
station travel to the zone "1C", the service of a mobile station would
switch from BS transmit-receive antenna A7 to BS transmit-receive
antenna A9.
During radio interface organization in the cellular communication
system the connection between mobile stations located on the cell
territory, and base station serving the given cell should be conducted via
those BS transmit-receive antennas, in the service zones of which the
corresponding mobile stations are located; then, for example,
orthogonality of signals radiated by different BS transmit-receive
antennas should be provided.
To provide orthogonality of signals radiated from different BS
transmit-receive antennas is required for separate processing of one and
the same signal arrived from different sources of electromagnetic
radiation, radiating antennas and reflecting objects.
The signal radiated from each BS transmit-receive antenna is a
group signal. By the group signal we understand a sum of signals
assigned for all mobile stations operating in the service zone of BS
transmit-receive antennas in the given point of time, i.e. for each MS its
own signal is assigned, which is orthogonal to all the rest signals of the
group signal.
During reception of a mobile station signal the orthogonality of
group signal identical components from different BS transmit-receive
antennas can be provided through space diversity of BS transmit-receive
antennas.
On the other hand, since each BS transmit-receive antenna is served
by a separate base station transceiver, synchronized in time with all the
rest ones, the orthogonality of signals from different BS transmit-receive
antennas can be provided through additional signal coding, by means of
relative time and frequency diversity of groups signals, as well as by other
means.
The necessary condition for normal operation of modern cellular
communication systems is provision of communication session continuity
during MS travel from the one BS service zone to another BS service
zone.
The procedure of a user channel (traffic channel) switch from
serving by one base station to another during mobile station movement is
conventionally called handoff. There are varieties of handoff, such as, for
example, "hard" handoff and "soft" handoff. "Hard" handoff is
characteristic of the first generation of cellular communication systems
and picocellular systems, in which MS receives information, first, from
one BS, then, moving to another cell, switches to another BS serving the
given cell, i.e. in the reception mode MS works with one BS only (see
Y.A. Gromakov. "Standards and Systems of Cellular Radio
Communication", ECO - TRENDS, Moscow, 1998, p. 68).
Modern digital radio communication systems with channel code
division are characterized by "soft" handoff, when a mobile station is able
to conduct parallel reception of information signal simultaneously from
more than one base station, for example, in accordance with standard IS-
95, (see Standard of mobile and base station compatibility for two-mode
cellular wideband systems with specter extension TIA/EIA/IS-95-A, May
1995. Telecommunication Industry Association). The standard IS-95
provides for the "soft" handoff procedure, both during MS movement
from one cell to another, and during movement within a cell from one cell
area to another.
Consider an exemplary embodiment of the claimed method, when
"soft" handoff is provided during a mobile station movement from the
zone of serving some groups of BS transmit-receive antennas to the zone
of serving other groups of BS transmit-receive antennas.
On Fig. 6A by the dotted line connecting points Z and Z\, MS
travel route from the zone of serving some groups of BS transmit-receive
antennas to the zone of serving other groups of BS transmit-receive
antennas, where Z - initial point, Z\ - end point of MS travel route. On the
left, there shown a diagram of MS service zones by BS transmit-receive
antennas during MS travel from point Z to point Zi.
In the view of electromagnetic radiation power distribution from
BS transmit-receive antennas within a cell, all MS in the cell are in equal
conditions. However, depending on a specific MS location in a cell, the
contribution to its summed input useful signal from different BS transmitreceive
antennas is inequal in power.
Assume that MS is at the initial point Z, in the service zone of one
BS transmit-receive antenna A8. As MS moves along the cell territory
towards the point Z\, it conducts connection with other BS transmitreceive
antennas or groups of BS transmit-receive antennas, as shown on
the diagram on Fig. 6A on the left. At the end point Z\t which is located in
the service zone of BS transmit-receive antenna A6, MS can receive
signals from BS transmit-receive antenna A6. In this case, it should be
mentioned that, MS passing through the increased concentration area
"1C", is served by transmit-receive antenna A9, located in this area.
In other words, one or more out of Z BS transmit-receive antennas
with the best conditions of signal propagation participate in a
communication session with a specific MS, where L - total number of BS
transmit-receive antennas in a cell. These transmit-receive antennas,
participating in a communication session, change during MS travel. The
change of a transmit-receive antenna is conducted based on the results of
measuring MS levels of pilot signals, radiated by neighboring transmitreceive
antennas, and analysis of the transmitted results of measurements
at BS, or based on the results of analysis of signal levels received by
neighboring BS transmit-receive antennas from the given MS. The
decision about transmit-receive antenna change is made at BS. Thus, BS
transmit-receive antennas in a cell are selected automatically and "soft"
handoff is conducted within a cell.
Soft handoff during MS travel from one cell to another is
conducted similarly, though the decision about transmit-receive antenna
change during MS movement from one cell to another is made by BS
controller.
Consider Fig. 6B, where vertical section of BS transmit-receive
antenna electromagnetic radiation power distribution is shown, passing
through BS transmit-receive antennas A7 - AI. Fig. 6B clarifies the
principle of overcoming transmit-receive antenna A7 overload when
switching transmit-receive antenna A9, serving the area of increased
concentration "1C".
Accepted denotations on Fig. 6B:
curve a illustrates distribution of electromagnetic radiation power
of BS transmit-receive antenna A7;
curve b - distribution of electromagnetic radiation power of BS
transmit-receive antenna AI,
curve c - distribution of electromagnetic radiation power of BS
transmit-receive antenna A4,
curve d - .distribution of electromagnetic radiation power of BS
transmit-receive antenna A9,
Curves a, b, c, and d show how electromagnetic radiation power of
BS transmit-receive antenna A9, serving the area "1C", exceeds the
summed electromagnetic radiation power of BS transmit-receive antennas
A7, AI, and A4 in this area. Therefore, as a result of soft handoff all MS
located in the area "1C" will be served by BS transmit-receive antenna A9
only. Thus, BS transmit-receive antenna A7 will be downloaded.
Consider the structure of signal processing at BS, according to the
claimed invention (Fig. 7).
BS transmit-receive antennas li - 1L are placed considering
specific environment (VCJIOBHH MCCTHOCTH), where a cell is located, but
necessarily so that, on the one hand, maximum regular distribution of
electromagnetic radiation power within a cell and minimal noise level for
neighboring cells are provided, and, on the other hand, maximum regular
distribution of mobile stations between coverage zones of different base
station transmit-receive antennas is provided, considering "dead zones"
and areas of increased MS concentration "1C".
To make it clear how the claimed invention is implemented,
exemplary embodiments of unit 3 (Fig. 7) and unit 8 (Fig. 8) are shown.
At each BS transmit-receive antenna l! - 1L, a group signal is
supplied, which is a sum of signals from mobile stations located in the
service zone of the given BS transmit-receive antenna.
The group signal at each base station transmit-receive antenna is
formed by summing all signal paths of all mobile stations located in the
service zone of this base station transmit-receive antenna in the given cell.
I.e. electromagnetic field of each mobile station signal path induces its
power in a base station transmit-receive antenna, and the summed power
corresponds to the group signal which is a sum of signals from all mobile
stations that arrived at the given base station transmit-receive antenna.
The group signal of BS transmit-receive antennas li - 1L is
supplied to the first inputs of signal diversity unit 2.
Operation of signal diversity unit 2 can be organized in different
ways. In the forward and reverse channels, unit 2 provides duplex device
connection, for example, through frequency signal diversity. Unit 2 can
act as a duplexer, since inputs and outputs of unit 2 are connected to the
corresponding transmit-receive antennas, and base station transmitreceive
antennas provide for signal reception and transmission, i.e.
provide duplex communication.
The output signals from unit 2 are supplied to the first inputs of MS
signal path combining unit 3 and signal path search unit 8.
Signal path search unit 8, scanning the uncertainty area by the time
delay, detects a signal of each MS which can consist of several paths, in
the group signals of each BS transmit-receive antenna lr 1L.
Fig. 8 shows an example, when MS signal path search unit 8
conducts scanning of uncertainty area, for example, in parallel, i.e.
simultaneously in K search channels \2\- 12k. In each channel search of
signal paths of all MS, forming the input group signal, are searched.
In signal path search unit 8, signal paths of specific mobile stations
are isolated and their parameters - time delays - are estimated. Time
delays of expected mobile station signals are estimated in signal path
search unit 8, and time delays of signal paths during its schematic
processing are specified in technical documentation.
In signal path search unit 8, by the control signals from control
processor 9, supplied to PRSG 14j - 14K, in search channels 12r 12k,
signals are formed which assign the form and phase of PRS for all MS
signal paths. The output signals from PRSG 14i - 14K arrive at the second
inputs of correlators 13p 13k. At the first inputs of correlators 13r 13k
MS group signal is supplied. In search channels 12r 12k) in correlators,
correlations of MS input signal paths are calculated with the output
signals of PRSG 14j - 14K, the results are compared in threshold
comparison nodes 15i - 15K- Based on the comparison results, obtained in
nodes 15i - \5^. of all search channels 12r 12k> the decision about MS
signal path detection.
The output signals from MS signal path search unit 8 (Fig. 7) are
supplied to the first inputs of control processor 9.
Control processor 9 is made on microcomputer. It has a program, in
accordance with which the algorithm of all mobile station signal path
processing is performed. According to the program, control processor 9
forms reference signals for all detected MS signal paths, considering the
form and phase of PRS, and supplies them to MS signal path combining
unit 3 at MS signal path combining nodes 10t - 10L via each transmitreceive
antenna.
In nodes \Q\ - 10L> MS signal paths are combined via each BS
transmit-receive antenna li - 1L> considering the form and phase of MS
signal paths. The detected mobile station signal paths are combined by the
following algorithm. For example, / -th transmit-receive antenna receives
one path of the first mobile station, two signal paths of &-th mobile
station, 4 paths - /-th mobile station. In z'-th node of mobile station signal
path combining 10;, for each mobile station the signal paths of this mobile
station are summed, considering time delays. At the output of node 10; a
summed signal for each mobile station is formed, which is in our example
a sum of signal paths:
for the first mobile station - one signal path,
for k-th mobile station - summed value of two signal paths,
for /- th mobile station - summed value of four signal paths.
Similarly, in each mobile station signal path combining node signal
paths are combined for each mobile station (i.e. those signal paths are
combined that are detected by unit 8 at the given transmit-receive
antenna).
The output signals from nodes 10i - 10L are supplied to the second
inputs of channel estimation unit 4 and antenna signal combining node
11. In unit 11 MS signal paths are combined via all BS transmit-receive
antennas l j - 1L, forming a summed output signal which is supplied to
receive signal processing and transmit signal forming unit 5.
Unit 5 demodulates the input signal and transmits it to the user
network.
Signal from the user network, addressed to specific MS, arrives
through the second inputs of unit 5 to unit 6, where signal for
transmission in reverse channel is generated.
Unit 4 estimates the signal paths of specific MS, isolated by control
processor 9, and forms control command of signal transmission diversity,
which is transmitted to the second inputs of signal transmission diversity
control unit 7.
Unit 7, in accordance with the received from unit 4 control
command of signal transmission diversity, transforms the signal, supplied
from modulator amplifier 6, according to the estimated characteristics of
communication channel state, i.e. in unit 7 by the signal from control
processor 9 the best channels of MS signal path propagation are selected
and the level of transmitted signal is corrected for MS message
transmission.
The output signal from unit 7 for each MS arrives at unit 2 via
selected channels of transmission to the corresponding BS transmitreceive
antennas.
Thus, application of the invention allows serving maximal number
of simultaneously operating mobile stations with specified transmission
and reception quality, i.e. providing maximal system capacity. This can be
achieved through maximum regular distribution of electromagnetic
radiation power within a cell, minimal noise level for neighboring cells,
and maximum regular distribution of mobile stations between coverage
zones of different base station transmit-receive antennas.
Minimal noise level for neighboring cells is achieved through
orientation of electromagnetic radiation inwards the cell for BS transmitreceive
antennas, located near the cell border, and selection of BS
transmit-receive antenna patterns, located in "dead zones" and zones of
increased MS concentration "1C", as well as through electromagnetic
radiation power redistribution between BS transmit-receive antennas,
which allows reducing the total level of electromagnetic radiation power
to the minimum acceptable. As a result of regular coverage by BS
electromagnetic radiation power across the cell square, the required MS
electromagnetic radiation power becomes reduced, which also assists in
reducing mutual interference within a cell and improving the
communication system capacity.
Using the claimed base station in conjunction with the claimed
method of cellular communication system radio interface organization
allows increasing interference stability, and thus increasing the capacity
of this communication system, which is achieved through signal search at
the time uncertainty interval, receive channel quality estimation for each
MS and selection of the best channels for transmitting messages for MS
with the corresponding correction of the transmit signal level.
Industrial Applicability
The method of radio interface organization and cellular
communication system base station are designed for use in CDMA
telecommunication systems.




I CLAIM:
1. The base station of the cellular communication system, containing L transmit-receive antennas, signal diversity unit, MS signal path combining unit, channel estimation unit, receive signal processing and transmit signal forming unit, modulator amplifier, and signal transmission diversity control unit, when the inputs of transmit-receive antennas are the device signal inputs and their outputs are connected to the corresponding first inputs of signal diversity unit, the outputs of signal diversity unit are connected to the first inputs of mobile station signal path combining unit, the first outputs of which are connected to the first inputs of receive signal processing and transmit signal forming unit, the first outputs of which are the outputs of the device, second inputs of receive signal processing and transmit signal forming unit are the inputs of the user signal, second inputs of receive signal processing and transmit signal forming unit are connected to the inputs of modulator amplifier, the outputs of which are connected to die first inputs of signal transmission diversity control unit, the second inputs of which are connected to the outputs of channel estimation unit, the outputs of signal transmission diversity control unit are connected to the second inputs of signal diversity unit, the outputs of which are connected to transmit-receive antennas,
characterized by the introduction of signal path search unit, searching all mobile station signal paths,
wherein control processor, forming at the first outputs control signals, which assign the form and phase of the pseudo random sequence for all mobile station signal paths, at the second outputs - control signals of reference signal selection for the detected mobile station signal paths, at the third outputs - control signals of reference signal selection for the detected mobile station signal paths, corrected considering time delays,
wherein the first inputs of signal path search unit are combined with unit first inputs of mobile station signal path combining unit and connected to the output of signal diversity unit, the outputs of signal path search unit are connected to the inputs of control processor,
wherein the first outputs of the control processor are connected to the second inputs of signal path search unit, the second outputs of control processor are connected to the second inputs of mobile station signal path combining unit, the third outputs of control processor are connected to the first inputs of channel estimation unit, and
wherein the second inputs of the channel estimation unit are connected to the second outputs of mobile station signal path combining unit.

2. The method of radio interface organization in a cellular communication system as
claimed in claim 1, consisting in that the territory served by the communication system, is
divided into neighboring cells, a base station and a multiplicity of transmit-receive
antennas are placed in each cell, handoff is provided during a mobile station movement
from one cell to another, wherein the location of base station transmit-receive antennas,
orientation of antenna patterns, and their electromagnetic radiation power are selected so
that maximum regular distribution of electromagnetic radiation power within a cell,
minimal noise level for neighboring cells, and maximum regular distribution of
mobile stations between coverage zones of different base station transmit-receive antennas are provided, connection between mobile stations, located on the cell territory, and base station, serving the given cell via those base station transmit-receive antennas, in the electromagnetic radiation power coverage zone of which the corresponding mobile stations are located is provided, handoff is provided via those base station transmit-receive antennas, in the service zone of which die corresponding mobile stations are located.
3.. Method as claimed in claim 2, wherein the orthogonality of signals radiated by different base station transmit-receive antennas is provided.
4. Method as claimed in claim 2, wherein the soft handoff is provided during a mobile station movement from the zone of serving some groups of base station transmit-receive antennas to the zone of serving other groups of base station transmit-receive antennas.
5. The method of radio interface organization in a cellular communication system, substantially as hereinbefore described with reference to the accompanying drawings.
6. The base station of the cellular communication system, substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

2140-delnp-2004-abstract.pdf

2140-DELNP-2004-Claims-(30-11-2007).pdf

2140-delnp-2004-claims.pdf

2140-DELNP-2004-Correspondence-Others-(07-07-2008).pdf

2140-delnp-2004-correspondence-others-(11-07-2008).pdf

2140-DELNP-2004-Correspondence-Others-(30-11-2007).pdf

2140-delnp-2004-correspondence-others.pdf

2140-delnp-2004-description (complete)-10-07-2008.pdf

2140-delnp-2004-description (complete).pdf

2140-delnp-2004-drawings.pdf

2140-delnp-2004-form-1.pdf

2140-delnp-2004-form-18.pdf

2140-DELNP-2004-Form-2-(30-11-2007).pdf

2140-delnp-2004-form-2.pdf

2140-delnp-2004-form-26.pdf

2140-DELNP-2004-Form-3-(30-11-2007).pdf

2140-delnp-2004-form-3.pdf

2140-delnp-2004-form-5.pdf

2140-delnp-2004-pct-210.pdf

2140-DELNP-2004-Petition-137-(30-11-2007).pdf

2140-DELNP-2005-Abstract-(10-07-2008).pdf

2140-DELNP-2005-Claims-(10-07-2008).pdf

2140-DELNP-2005-Correspondence-Others-(10-07-2008).pdf

2140-DELNP-2005-Form-1-(10-07-2008).pdf

2140-DELNP-2005-Form-2-(10-07-2008).pdf

2140-DELNP-2005-GPA-(10-07-2008).pdf

abstract.jpg


Patent Number 222128
Indian Patent Application Number 2140/DELNP/2004
PG Journal Number 32/2008
Publication Date 08-Aug-2008
Grant Date 23-Jul-2008
Date of Filing 23-Jul-2004
Name of Patentee GARMONOV ALEXANDR VASILIEVICH
Applicant Address 394062, VORONEZH, UL.L.SHEVTSOVOI, D.5/1, KV.6, RUSSIA.
Inventors:
# Inventor's Name Inventor's Address
1 GARMONOV ALEXANDER VASILIEVICH 394062 VORONEZH, UL.L.SHEVTSOVOI,D.5/1, KV,6,RUSSIA
2 DRUGOV MIKHAIL LGOREVICH 394062 VORONEZH, UL. OSTUZHEVA, D.46, KV.56, RUSSIA
3 SERGIENKO ALEXANDR IVANOVICH 394051, VORONEZH, UL., PESHESTRELETSKAYA, D. 151, KV. 38, RUSSIA
PCT International Classification Number H04B 7/26
PCT International Application Number PCT/RU02/00043
PCT International Filing date 2002-02-12
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA