U.S. patent number RE39,381 [Application Number 11/087,107] was granted by the patent office on 2006-11-07 for establishment of a connection between a base station and a mobile station using random access channels.
This patent grant is currently assigned to Nokia Corporation. Invention is credited to Seppo Granlund, Hannu Hakkinen, Seppo Hamalainen.
United States Patent |
RE39,381 |
Hakkinen , et al. |
November 7, 2006 |
Establishment of a connection between a base station and a mobile
station using random access channels
Abstract
A connection establishment method for establishing a random
access type connection using a random access channel, which is used
in a radio system having several subscriber terminal equipments (37
to 38) and base stations (33 to 36) where one or more transceiver
units (40 to 47) operate, and in which system connection
establishment between one of the subscriber terminal equipments (37
to 38) and the base station (33 to 36) is possible when the one
subscriber terminal equip nt (37 to 38) is situated in the coverage
area of one or more transceiver units (40 to 47) of the base
station, where the one subscriber terminal equipment (3 to 38)
evaluates the quality of the connections to be established.
Starting from a condition in which no connection is established
with the one subscriber terminal equipment, the one subscriber
terminal equipment (37 to 38) forms a random access type connection
to more than one base station transceiver unit (40 to 47) included
in one or more base stations (33 to 38).m
Inventors: |
Hakkinen; Hannu (Espoo,
FI), Granlund; Seppo (Helsinki, FI),
Hamalainen; Seppo (Beijing, CN) |
Assignee: |
Nokia Corporation (Espoo,
FI)
|
Family
ID: |
8545314 |
Appl.
No.: |
11/087,107 |
Filed: |
February 4, 1997 |
PCT
Filed: |
February 04, 1997 |
PCT No.: |
PCT/FI97/00064 |
371(c)(1),(2),(4) Date: |
December 09, 1998 |
PCT
Pub. No.: |
WO97/29596 |
PCT
Pub. Date: |
August 14, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
09117923 |
Dec 9, 1998 |
06539236 |
Mar 25, 2003 |
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Foreign Application Priority Data
Current U.S.
Class: |
455/525; 455/437;
455/442; 455/562.1; 455/444; 370/332 |
Current CPC
Class: |
H04W
74/0833 (20130101); H04B 7/022 (20130101); H04W
36/36 (20130101); H04W 48/20 (20130101); H04W
36/18 (20130101); H04W 52/40 (20130101); H04W
74/0866 (20130101) |
Current International
Class: |
H04B
7/00 (20060101); H04Q 7/20 (20060101) |
Field of
Search: |
;455/524-525,562.1,561,436-444,101,134-135,448-449,63.2,132
;370/329-336,342-343,347 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 288 904 |
|
Nov 1988 |
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EP |
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0 565 507 |
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Oct 1993 |
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EP |
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WO 91/07037 |
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May 1991 |
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WO |
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Primary Examiner: Ramos-Feliciano; Eliseo
Attorney, Agent or Firm: Pillsbury Winthrop Shaw Pittman
LLP
Claims
What is claimed is:
1. A connection establishment method including a random access
connection establishment using a random access channel, which is
used in a radio system having a plurality of subscriber terminal
equipment and base stations where at least one transceiver unit
operates, and in which system connection establishment between one
of the subscriber terminal equipment and at least one of the base
stations is possible when the one subscriber terminal equipment is
situated in a coverage area of at least one transceiver unit of the
at least one of the base stations, the method comprising:
evaluating, by the one subscriber terminal equipment, a quality of
connections related to a plurality of base station transceiver
units included in one of the at least one base stations; and
forming random access connections to a plurality of transceiver
units included in the at least one of the base stations before a
traffic channel connection between the at least one of the base
stations and the subscriber terminal equipment.
2. The method according to claim 1, further comprising: selecting,
by the subscriber terminal equipment before the actual connection
establishment to a transceiver unit, the plurality of transceiver
units to which the quality of the connection is the best when
establishing a connection.
3. The method according to claim 2, wherein the subscriber terminal
equipment, in a connection establishment request, sends to a base
station controller, via a transceiver unit providing the best
connection, information about the selected plurality of transceiver
units.
4. The method according to claim 3, wherein the base station
controller allows the selected plurality of transceiver units to
establish a connection with the subscriber terminal equipment.
5. The method according to claim 1, wherein evaluating, by the one
subscriber terminal equipment, a quality of connections to be
established includes measuring a result of a transmission power in
a pilot signal of the at least one of the base stations and a power
of a received pilot signal; and selecting the plurality of
transceiver units having a greatest power of the received pilot
signal in comparison with the transmitted power.
6. The method according to claim 1, wherein evaluating, by the one
subscriber terminal equipment, a quality of connections to be
established includes measuring a result of downlink interference,
and selecting the plurality of transceiver units operating on lower
connection transmission power.
7. A subscriber terminal equipment to establish a random access
connection using a random access channel in a radio system and a
plurality of base station; each one of the plurality of base
stations including at least one transceiver unit, the connection
between the subscriber terminal equipment and at least one of the
plurality of base stations is possible when the subscriber terminal
equipment is in a coverage area of one or more of the plurality of
transceiver units; the subscriber terminal equipment comprises: an
evaluator to monitor the quality of the connections between the
subscriber terminal equipment and a plurality of transceiver unit
included in one of the plurality of base stations; and a controller
to control random access connections establishment to the plurality
of transceiver units included in at least one of the plurality of
base stations before a traffic channel connection between the at
lest one of the plurality of base stations and the subscriber
terminal equipment.
8. The subscriber terminal equipment according to claim 7, further
comprising a selector to select the plurality of transceiver units
having a best quality of connection; and the controller is arranged
to control the subscriber terminal equipment in such a manner that
the subscriber terminal equipment is arranged to send information
about the selected plurality of transceiver units to a base station
controller on the random access channel.
9. The subscriber terminal equipment according to claim 7, wherein
the evaluator is arranged to monitor a quality of the connection by
measuring a result of a transmission power in a pilot signal of the
at least one of the plurality of base stations and a power of a
received pilot signal and the selector is arranged to select the
plurality of transceiver units having a greatest power of the
received pilot signal in comparison with the transmitted power.
10. The subscriber terminal equipment according to claim 7, wherein
the evaluator is arranged to monitor a quality of the connection by
measuring a result of downlink interference, and the selector is
arranged to select the plurality of transceiver units operating on
lower transmission power.
11. A radio system comprising: a subscriber terminal equipment and
a plurality of base stations having a plurality of base station
transceiver units; the subscriber terminal equipment is arranged to
send a random access connection establishment request via a random
access channel wherein a radio system connection between the
subscriber terminal equipment and at least one of the plurality of
base stations is possible when the subscriber terminal equipment is
in a coverage area of one or more base station transceiver units of
the plurality of base stations, the subscriber terminal equipment
including an evaluator to monitor the quality of the connections
between the subscriber terminal equipment and a plurality of base
station transceiver units associated with one of the base stations;
and to control the establishment of random access connections
between the subscriber terminal equipment and a plurality of base
station transceiver units included in at least one of the plurality
of base stations before a traffic channel connection between the at
least one of the plurality of base stations and the subscriber
terminal equipment.
12. The radio system according to claim 11, wherein the subscriber
terminal equipment is arranged to select, on the basis of the
quality of the connection, the plurality of base station
transceiver units having the best quality of the connection and to
send information about the selected plurality of base station
transceiver units to a base station controller on the random access
channel via a base station transceiver unit providing the best
connection, wherein the base station controller allows the selected
plurality of base station transceiver units to be used for the
connections required by the subscriber terminal equipment.
13. The radio system according to claim 11, wherein the subscriber
terminal equipment is arranged to evaluate the quality of the
connection by measuring a result of a transmission power in a pilot
signal of the plurality of base station transceiver units and a
power of a received pilot signal and wherein the subscriber
terminal equipment is arranged to select the plurality of base
station transceiver units having the greatest power of the received
pilot signal in comparison with the transmitted power.
14. The radio system according to claim 11, wherein the subscriber
terminal equipment is arranged to evaluate the quality of the
connection by measuring a result of downlink interference, and
wherein the subscriber terminal equipment is arranged to select the
plurality of base station transceiver units operating on lower
transmission power.
15. The radio system according to claim 11, wherein the plurality
of base station transceiver units are arranged to receive the
connection establishment request of the subscriber terminal
equipment.
16. The radio system according to claim 11, wherein the subscriber
terminal equipment is arranged to be synchronized with the
connection establishment request.
17. A connection establishment method including a random access
connection establishment using a random access channel, which is
used in a radio system having a plurality of subscriber terminal
equipment and base stations where at least one transceiver unit
operates, and in which system connection establishment between one
of the subscriber terminal equipment and at least one of the base
stations is possible when the one subscriber terminal equipment is
situated in a coverage area of at least one transceiver unit of the
at least one of the base stations, the method comprising:
evaluating, by the one subscriber terminal equipment, a quality of
connections related to a plurality of base station transceiver
units included in one base station of the plurality of base
stations; forming a random access connection to a first transceiver
unit included in a base station; forming at least one random access
connection to at least one other transceiver unit included in a
base station; and each of the random access connections being
established to one transceiver unit and all of the random access
connections being formed before a traffic channel connection
between the at least one of the transceiver units and the
subscriber terminal equipment.
18. A subscriber terminal equipment to establish a random access
connection using a random access channel in a radio system and a
plurality of base stations; each one of the plurality of base
stations including at least one transceiver unit, the connection
between the subscriber terminal equipment and at least one of the
plurality of base stations is possible when the subscriber terminal
equipment is in a coverage area of one or more of the plurality of
transceiver units; the subscriber terminal equipment comprises: an
evaluator to monitor the quality of the connections between the
subscriber terminal equipment and a plurality of transceiver units
associated with one base station of the plurality of base stations;
and a controller; to control a random access connection
establishment to a first transceiver unit included in a base
station; to control a further random access connection
establishment to at least one other transceiver unit included in a
base station, and each of the random access connections being
established to one transceiver unit and all of the random access
connections being formed before a traffic channel connection
between the at least one of the transceiver units and the
subscriber terminal equipment.
19. A connection establishment method in a radio system including a
random access connection establishment using a random access
channel, which is used in a radio system having a plurality of
subscriber terminal equipment and base stations where at least one
transceiver unit operates, and in which system connection
establishment between one of the subscriber terminal equipment and
one of the base stations is possible when the one subscriber
terminal equipment is situated in a coverage area of at least one
transceiver unit of the one base station, the method comprising:
evaluating, by the subscriber terminal equipment, quality of
connections related to a plurality of base station transceiver
units included in the at least one base station; transmitting, on a
random access channel, a connection establishment request relating
to the base station transceiver units included in the at least one
base station to which the quality of connections is evaluated; and
forming random access connections between the subscriber terminal
and at least some of the base station transceiver units in the
connection establishment request by responding, by the base station
transceiver units in the connection establishment request, to the
connection establishment request on paging channels of the base
station transceiver units.
20. A connection establishment method in a radio system including a
random access connection establishment using a random access
channel, which is used in a radio system having a plurality of
subscriber terminal equipment and base stations where at least one
transceiver unit operates, and in which system connection
establishment between one of the subscriber terminal equipment and
one of the base stations is possible when the one subscriber
terminal equipment is situated in a coverage area of at least one
transceiver unit of the one base station, the method comprising:
evaluating, by the subscriber terminal equipment, quality of
connections related to a plurality of base station transceiver
units included in the at least one base station; selecting, by the
subscriber terminal equipment, a base station transceiver unit with
the connection of the best quality; transmitting, by the subscriber
terminal equipment on a random access channel, a connection
establishment request message to the base station transceiver unit
with the connection of the best quality, the connection
establishment request message comprising information on the quality
of evaluated connections; and transmitting, by the base station
transceiver unit with the connection of the best quality, a channel
assignment message to .[.file.]. the subscriber terminal
equipment.
21. The method of claim 19 or 20, forming traffic channel
connections to the base station transceiver units in the connection
establishment request.
22. Subscriber terminal equipment configured to establish a random
access connection in a radio system using a random access channel
in a radio system and a plurality of base stations, each one of the
base stations including a plurality of transceiver units, the
connection between the subscriber terminal equipment and at least
one of the plurality of the base stations being possible when the
subscriber terminal equipment is in a coverage area of one or more
of the plurality of base station transceiver units, the subscriber
terminal equipment comprising an evaluator to monitor the quality
of the connections between the subscriber terminal equipment and
the plurality of transceiver units, and the subscriber terminal
being configured to transmit, on a random access channel, a
connection establishment request relating to the base station
transceiver units included in the at least one base station to
which the quality of connections is evaluated, the subscriber
terminal also being configured to form random access connections
between the subscriber terminal and at least some of the base
station transceiver units in the connection establishment request
when the base station transceiver units in the connection
establishment request respond to the connection establishment
request on paging channels.
23. Subscriber terminal equipment terminal equipment configured to
establish a random access connection in a radio system using a
random access channel in a radio system and a plurality of base
stations, each one of the base stations including a plurality of
transceiver units, the connection between the subscriber terminal
equipment and at least one of the plurality of the base stations
being possible when the subscriber terminal equipment is in a
coverage area of one or more of the plurality of base station
transceiver units, the subscriber terminal equipment comprising an
evaluator to monitor the quality of the connections between the
subscriber terminal equipment and the plurality of transceiver
units, and the subscriber terminal being configured to select a
base station transceiver unit with the connection of the best
quality and the subscriber terminal also being configured to
transmit, on a random access channel, a connection establishment
request message to the base station transceiver unit with the
connection of the best quality, the connection establishment
request message including information on the quality of evaluated
connections, .Iadd.the subscriber terminal being configured to
receive a channel assignment message as response from .Iaddend.the
base station transceiver unit with the connection of the best
quality being configured to respond by transmitting a channel
assignment message to the subscriber terminal equipment.
24. The subscriber terminal equipment of claim 26 and 27 wherein
the subscriber terminal is configured to form traffic channel
connections to the base station transceiver units in the connection
establishment request.
25. A radio system comprising: a subscriber terminal equipment; and
a plurality of base stations having a plurality of base station
transceiver units, wherein, the subscriber terminal equipment is
configured to send a random access connection establishment request
via a random access channel and a radio system connection between
the subscriber terminal equipment and at least one of the base
stations is possible when the subscriber terminal equipment is in a
coverage area of one or more transceiver units of that base
station, the subscriber terminal equipment includes an evaluator to
monitor the quality of the connections between the subscriber
terminal equipment and the plurality of transceiver units and the
subscriber terminal is configured to transmit, on a random access
channel, a connection establishment request relating to the base
station transceiver units included in the at least one base station
to which the quality of connections is evaluated, the subscriber
terminal, and wherein, at least some of the base station
transceiver units in the connection establishment request are
configured to form random access connections with each other by
responding, by the base station transceiver units in the connection
establishment request, to the connection establishment request on
paging channels of the base station transceiver units.
26. A radio system comprising: a subscriber terminal equipment; and
a plurality of base stations each having a plurality of base
station transceiver units, wherein, the subscriber terminal
equipment is configured to send a random access connection
establishment request via a random access channel, a radio system
connection between the subscriber terminal equipment and at least
.Iadd.one .Iaddend.of the base stations is possible when the
subscriber terminal equipment is in a coverage area of one or more
transceiver units of that base station, the subscriber terminal
equipment includes an evaluator to monitor the quality of the
connections between the subscriber terminal equipment and the
plurality of transceiver units, the subscriber terminal is also
configured to select a base station transceiver unit with the
connection of the best quality and also to transmit, on a random
access channel, a connection establishment request message to the
base station transceiver unit with the connection of the best
quality, the connection establishment request message comprising
information on the quality of evaluated connections, and wherein
the base station transceiver unit with the connection of the best
quality is configured to respond by transmitting a channel
assignment message to the subscriber terminal equipment.
27. The CDMA radio system of claim 25 or 26, wherein the subscriber
terminal and the base station units in the connection establishment
request are configured to form traffic channel connections with
each other.
Description
This application is the national phase of international application
PCT/F197/00064, filed Feb. 4, 1997 which designated the U.S.
FIELD OF THE INVENTION
The invention relates to a connection establishment method
comprising a random access type connection establishment using a
random access channel, which is used in a radio system comprising
several subscriber terminal equipments and base stations where one
or more transceiver units operate, and in which system the
connection establishment between the subscriber terminal equipment
and the base station is possible when the subscriber terminal
equipment is situated in the coverage area of one or more
transceiver units of the base station, in which area the subscriber
terminal equipment evaluates the quality of the connections to be
established.
The invention further relates to a subscriber terminal equipment
which is arranged to establish a random access type connection by
using a random access channel in a radio system comprising several
subscriber terminal equipments and base stations which comprise one
or more transceiver units, and in which system the connection
between the subscriber terminal equipment and the base station is
possible when the subscriber terminal equipment is situated in the
coverage area of one or more base station transceiver units, where
the subscriber terminal equipment comprises an evaluation means for
monitoring the quality of the connections to be established.
The invention also relates to a radio system comprising several
subscriber terminal equipments and base stations which comprise one
or more transceiver units and where the subscriber terminal
equipment is arranged to send a random access type connection
establishment request via a random access channel and in which
system the connection between the subscriber terminal equipment and
the base station is possible when the subscriber terminal equipment
is situated in the coverage area of one more transceiver units of
the base station, in which area the subscriber terminal equipment
comprises and evaluation means for monitoring the quality of the
connections to be established.
BACKGROUND OF THE INVENTION
A typical cellular radio system, such as the CDMA system (Code
Division Multiple Access), comprises a set of subscriber terminal
equipments and base stations. When a subscriber terminal equipment
has no connection on a normal traffic channel, it monitors paging
channels of the base station when necessary, sends messages on an
access channel to the base station. The paging channel and the
access channel provide an organization channel. When a connection
is established in the cellular radio system between a subscriber
terminal equipment and a base station, either the subscriber
terminal equipment or the base station sends a connection
establishment request on the organization channel. A specific
Random Access Channel (RACH), which is a channel of a subscriber
terminal equipment is typically used as an access channel in the
CDMA cellular radio system for establishing a connection from among
all the possible access channels and from among the phases
available for the phase of a pseudo-noise code. When a radio
connection is to be established, the terminal equipments send a
connection establishment message via an access channel to the base
station which forwards it to the system where traffic channel
resources are allocated to the connection. When the base station
requests a traffic channel connection, it sends via a paging
channel a request to the subscriber terminal equipment which
responses to the paging by requesting a traffic channel for its use
via the access channel.
In the CDMA system, each base station sends continuously a pilot
signal so that there is a specific pilot signal in different
sectors or beams of the base station because each sector and beam
has a specific base station transceiver unit. It is previously
known to use a pilot signal for identifying a base station, a beam
or sector of the base station. A pilot signal is a spread-coded
signal without data modulation which signal each base station sends
continuously to its coverage area. The terminal equipment may
identify the base station transceiver units by the pilot signal
because the phases of the spreading codes in the pilot signal
differ from one another. The subscriber terminal equipments
continuously carry out measurings of pilot signals, and subscriber
terminal equipments establish an active group of the base station
transceiver units providing the best connections, the base station
transceiver units in the group being utilized when establishing new
connections.
Each base station also sends on a sync channel. A signal of the
sync channel may be demodulated and detected whenever the pilot
signal can be identified. Information is transmitted on the sync
channel about the base station, about the power and the phase of
the pilot signal and about the size of uplink interferences.
In addition to a circuit-switched connection, the base station and
the subscriber terminal equipment may communicate over a
packet-mode connection which is used in the PRMA system (Packet
Reservation Multiple Access). In that case the channel needed for
transmitting the signal is only reserved for the duration of the
signal and it is released immediately when the signal is
discontinuous or when it ends or has a break. If the signal is sent
discontinuously, the channel has to reserved again after each
break.
In prior art solutions, when a subscriber terminal is establishing
a connection with a base station on the access channel, the
connection is only to one base station, sector or beam of the base
station. Access channel and paging channel connections are used
especially when establishing a traffic channel connection, in which
case when the connection establishment is successful, the traffic
channel will, at least at first, have a connection to only one base
station, sector or beam of the base station. This raises a need to
increase considerably the transmission power of the subscriber
terminal equipment and/or the base station and carry out fast an
updating of the active group, whereby interference level and the
amount of signaling will increase. Furthermore, during a
packet-mode transmission it is difficult to carry out soft handover
the middle of the packet although the quality of the connection
during the transmission would change to be favourable for
handover.
BRIEF DESCRIPTION OF THE INVENTION
The object of the present invention is to accomplish a solution
which will diminish interferences relating especially to the
initial stage of the connection and enable the use of
macrodiversity also for a packet-mode connection.
This is achieved with a method as shown in the preamble which is
characterized in that the subscriber terminal equipment forms a
random access type connection to more than one base station
transceiver unit included in one or more base stations.
The subscriber terminal equipment of the invention is characterized
in that the subscriber terminal equipment comprises a control means
for controlling a random access type connection establishment to
more than one base station transceiver included in one or more
basic stations.
The radio system of the invention is characterized in that the
radio system comprises subscriber terminal equipment which is
arranged to control a random access type connection establishment
between the base station and the subscriber terminal equipment so
that it is possible for the subscriber terminal equipment to
establish a connection to more than one base station transceiver
unit included in one or more base stations.
Considerable advantages are attained with the solution of the
invention. By using the method of the invention, macrodiversity
state will be assumed from the beginning of connection
establishment. In that case the updating of the active group is
required less and at the beginning of the connection, a lower
transmission power can be used than in prior art solutions. In this
way the need for signaling will be reduced and the capacity of the
system will increase.
In a packet-mode data transmission, macrodiversity state will also
be assumed directly, the state continuing for the duration of the
whole packet in which case the quality of the provided connection
will worsen less probably during the packet. The use of
macrodiversity on a packet-mode connection is possible only by a
method according to the invention because it is difficult to carry
out soft handover during a packet.
In the SDMA technique (Space Division Multiple Access) the
transmission and reception of the base station takes place in
narrow beams, each of which has a specific base station transceiver
unit. In that case the best connection is enabled with the method
of the invention.
The preferred embodiments of the method of the invention will also
appear from the appended dependent claims, the preferred
embodiments of the subscriber terminal equipment of the invention
will appear from the appended dependent claims relating to the
subscriber terminal equipment and the preferred embodiments of the
radio system of the invention will appear from the appended
dependent claims relating to the radio system.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
In the following, the invention will be explained in more detail
with reference to the examples of the accompanying drawings,
where
FIG. 1 illustrates the subscriber terminal equipment of the
invention, and
FIG. 2 illustrates the radio system of the invention.
DETAILED DESCRIPTION OF THE INVENTION
In the following, the invention will be explained in more detail by
examining its operation in a CDMA cellular radio system without
restricting it thereto. The invention is also suitable for use in a
time division GSM (Global System for Mobile communication) system
and/or SDMA and PRMA systems.
FIG. 1 illustrates the subscriber terminal equipment of the
invention in its essential parts. The subscriber terminal equipment
comprises a receiver part A and a transmitter part B. The receiver
part A comprises an antenna 10, radio frequency parts 11, an A/D
converter 12, a demodulator 13, a signal quality evaluation means
14, selection means 15, a channel decoder 16, a source decoder 17
and a loud speaker 18. The transmitter part B comprises a
microphone 20, a source encoder 21, a channel encoder 22, a
modulator 23, a D/A converter 24, radio frequency parts 25 and an
antenna 26.
The base station transceiver is in main parts similar to the
subscriber terminal equipment without a loud speaker and a
microphone. However, the base station transceiver generally
comprises several reception antennas for space diversity reception.
Because of this, the signals of different antennas are also
combined by diversity combination means.
The reception part A operates in the following way. A radio
frequency analogous signal received by the radio frequency parts 11
from the antenna 10 is transferred to an intermediate frequency and
filtered. The signal filtered by the A/D converter 12 is converted
into a digital signal. The demodulator 13 comprises an incoherent
demodulator which restores a broadband, spread-coded pseudo-noise
signal to a narrowband data signal, and an orthogonal demodulator
which determines the bits of the received data signal usually on
the basis of correlation. Various diversity combinations are also
carried out in the demodulator 13 if such diversity combinations
are used in the receiver part A. An estimate, such as a signal
noise estimate, is provided by the signal quality evaluation means
14. The selection means 15 selects the base station transceiver
unit candidates with the best connections for a future connection.
The channel decoder 16 typically decodes a convolution-coded signal
and its operation is based on a Viterbi algorithm, for example.
Further, the channel decoder 16 generally comprises means for
decrypting and de-interleaving a pre-processed signal. The source
decoder 17 generally decodes an RELP-coded signal (Residually
Exited Linear Predictive code) received from the channel decoder
16, and D/A converts and at the end amplifies the signal into a
form suitable for the loud speaker 18.
The transmitter part B operates in the following way. The
microphone 20 receives an audio signal and sends an electronic
response to the source encoder 21 which A/D-converts and RELP-codes
it, for example. The digital signal from the source encoder 21
proceeds to the channel encoder 22 which typically
convolution-codes the signal. Additionally, the channel encoder 22
typically encrypts the signal and interleaves the bits or bit
groups of the signal. The convolution-coded narrowband signal is
pseudo-noise encoded into a broadband spread spectrum signal in a
modulator 23. After this, the spread spectrum signal is converted
into an analogous signal by the D/A converter and the analogous
signal is converted into a radio frequency signal in radio
frequency parts 25 and sent via the antenna 26 in accordance with
prior art.
A control means 19 controls the function of both the receiver part
A and the transmitter part B. The means 13 to 17, 19, and 21 to 23
and the functions contained therein are implemented in prior art
solutions by a signal handling processor and/or as an ASIC circuit.
The antennas 10 and 26 are transmitter and receiver antennas of
prior art radio systems. The microphone 20, the load speaker 18,
the radio frequency parts 11 and 24 and the A/D converter 12 and
the D/A converter 24 are also prior art parts, used in prior art
radio systems.
FIG. 2 illustrates a schematic view of the radio system to be
explained in the following on the basis of the CDMA technique
without restricting the invention thereto. Two base station
controllers 31 and 32 are connected to a mobile services switching
centre 30 by digital transmission links, the base station
controllers monitoring, for example, the number of the connections
and deduce from that which of the connections proposed by a
subscriber terminal equipment 37 are possible. Base stations 33 and
34, and correspondingly, base stations 35 and 36 are further
connected to the base station controllers 31 and 32 by digital
transmission links. Subscriber terminal equipments 37 and 38 have a
connection to the base station 33 to 36. Each base station
controller and the base stations associated with it form a base
station system. The coverage area of one base station typically
forms one cell. Each of the base stations 33 to 36 has available a
finite number of operating radio channels where pilot, sync, paging
and traffic signals, for example, are transmitted. Each base
station 33 to 36 comprises one or more transceiver units 40 to 47.
Their base station antennas may be antenna systems by means of
which it is possible for different receiver units of the base
station to link to different beams. Diversity antennas can also be
used. In addition to the transceiver units 40 to 47, the base
stations 33 to 36 comprise peripheral equipment 50 comprising prior
art means and power supplies associated with signal transmission,
for example.
The method of the invention is now examined more closely by
employing FIGS. 1 and 2. It is assumed first that the need for
establishing a connection between the subscriber terminal equipment
and the base station appears at the subscriber terminal equipment
37. When the subscriber terminal equipment 37 initiates connection
establishment, it sends on the access channel (RACH) a transmission
request or more generally a connection establishment request
relating to several base station transceiver units to one base
station 33 from which the request is forwarded to the base station
controller 31. In the solution of the invention, several base
stations, for example base stations 33 to 35, respond on their
paging channel to the connection establishment request or the
response connection operates via several base stations or beams or
sectors of the base stations. The base station transceiver unit 40
to 47 attends to the transmission and reception operation and the
connection in the direction of the beam or sector of the base
stations 33 to 36. Thus in the solution of the invention the
connection between the subscriber terminal equipment 37 and the
base stations 33 to 36 is established in the random access way to
more than one base station transceiver unit 40 to 42 included in
one or more base stations 33 to 34. After the connection has been
established, if a traffic channel connection is needed, the
subscriber terminal equipment 37 has a ready traffic channel
connection to several base station transceiver units 40 to 42.
A typical connection establishment, which also uses traffic
channels, takes place in the CDMA system as in the following Table
1:
TABLE-US-00001 TABLE 1 Connection establishment Subscriber terminal
equipment Channel used Base station [Receives a call Paging channel
Sends a call] Sends a request Access channel Receives a request
Receives a Ch Ass M Paging channel Sends a Ch Ass M Communication
on the traffic channel
In Table 1 the events are in chronological order so that the time
axis may be imagined to travel from top to bottom. On the uppermost
line the base station calls the subscriber terminal equipment on a
paging channel. The subscriber terminal equipment responds to this
request on its access channel and requests a connection to several
base station transceiver units, which is shown on the second line
in Table 1. The base station responds to the request by sending a
Channel Assignment Message (Ch Ass M), after which the base station
and the subscriber terminal equipment communicate on the normal
traffic channel. The first line in Table 1 is in brackets because
when the subscriber terminal equipment contacts the base station,
Table 1 should be read without its first line. That is, the
subscriber terminal equipment then sends a connection request to
the base station, which is shown on the second line of the table.
After this the base station responds in the same way as in the
previous case and it results in a traffic channel connection.
Before the subscriber terminal equipment 37 sends a connection
establishment request, the subscriber terminal equipment 37 selects
preferably from the base station transceivers 40 to 47 the ones
where the quality of the connection is presumably the best and to
which it would be preferably in connection. In this way the
subscriber terminal equipment sends information about the base
station transceiver units 40 to 45 it has selected on the access
channel to the base station controller 30 via the base station
transceiver unit providing the best connection, which may be the
base station transceiver unit 41. In the preferred embodiment of
the invention, the base station controller 31 allows all or at
least some of the base station transceiver units 40 to 45 selected
by the subscriber terminal equipment, and the allowed base station
transceiver units, such as 40 to 42, respond to the subscriber
terminal equipment on their paging channel and thus establish
preferably a macrodiversity connection of soft random access type
with the subscriber terminal equipment 37. The reason why the base
station controller 31 may restrict the number of the base station
transceiver units may the heavy loading of the system at that
moment, which loading the base station controller 31 wishes to
restrict when allocating new channels.
In an alternative procedure, the subscriber terminal equipment 37
also sends a transmission request to several base station
transceivers 40 to 42. This may be based on the use of one random
access channel or on that the base station transceiver 40 to 42
comprises a receiver for random access channels of several cells.
This procedure may have several purposes. At its simplest,
connection establishment is initiated along with several base
station transceivers 40 to 42 but the actual connection will be
established with only one transceiver. The connection has been
established with the best connection at that moment. In a more
advanced alternative, the connection establishment message may also
proceed via several base station transceivers. In the third
alternative the message proceeds along one route but the other base
station transceivers are synchronized with the connection request
of the subscriber terminal equipment without being able to
interpret the message correctly. This will also accelerate the
generation of the actual macrodiversity connection.
The subscriber terminal equipment 37, as the other subscriber
terminal equipments of the system, evaluates the quality of the
connection by utilizing the measuring result of the transmission
power of the pilot signal of the base stations 33 to 36 and the
power of the received pilot signal. Further, the measuring result
of the downlink interference will have an effect on the quality of
the connection. On the basis of at least one of the above measuring
results of the quality of the connection, the subscriber terminal
equipment 37 selects from the base station transceiver units 40 to
47 the ones where the quality of the connection is the best.
The base stations 33 to 36 generally send a base station specific
pilot signal and data on the transmission power of the pilot signal
and the size of the uplink interference I.sub.uplink on their sync
channel. The subscriber terminal equipments 37 and 38 measure the
strength of the received pilot signal and the size of the downlink
interference I.sub.downlink. If the transmission power of the all
the pilot signals is the same, in the preferred embodiment of the
invention the selection means 15 of the subscriber terminal
equipment 37 selects the base station transceiver units where the
received power of the pilot signal is the strongest. If the pilot
signals are sent on different power, the power of the transmitted
and received pilot signal is compared to one another and it will
result in a connection distance attenuation L which can be
indicated as a formula in the following way: ##EQU00001## where
P.sub.TXpilot is the power of the transmitted pilot signal and
P.sub.RXpilot is the power of the received pilot signal. In the
preferred embodiment of the invention, the value L is used for
selecting base station transceiver units. Thus the connection
evaluation means 14 forms a parameter L representing connection
distance attenuation and on the basis of this, the selection means
15 select the candidates for the connection from the base station
transceiver units.
By considering also the required signal interference ratio
SIR.sub.req in both uplink and downlink directions, the required
transmission power may be calculated for both the subscriber
terminal equipment P.sub.MS and the base station transceiver unit
P.sub.STS. The required signal interference ratio SIR.sub.req for
the subscriber terminal equipment is ##EQU00002## from which it is
obtained as the transmission power P.sub.MS of the subscriber
terminal equipment P.sub.MS=SIR.sub.reqI.sub.uplinkL The required
signal interference ration SIR.sub.req for the base station
transceiver unit is ##EQU00003## from which it is obtained the
required transmission power P.sub.BTS of the base station
transceiver unit in the same way as in the case of the subscriber
terminal equipment P.sub.BTS=SIR.sub.reqI.sub.downlinkL The
solution of the invention uses parameters L, P.sub.MS and P.sub.BTS
in a random access type algorithm. By means of a random access type
algorithm, the selection means 15 of the subscriber terminal
equipment selects the base station transceivers for which the
connection distance attenuation L is smaller than some
predetermined value and the transmission power of both the base
station transceiver unit and the subscriber terminal equipment is
preferably smaller. The power of the received signals is preferably
measured before spread-coded signals are assembled, that is, from a
broadband signal. The reception power of the pilot signal is
measured by assembling a pseudo-noise signal of the pilot signal by
means of a correlator.
In the following it is assumed that the need for establishing a
connection between the subscriber terminal equipment and the base
station arises at the base station, at the base station 35, for
example. In this case the base station 35 sends on its paging
channel a connection establishment request to the subscriber
terminal equipment, which may be 38 in this case. The subscriber
terminal equipment 38 responds to this request on its access
channel and informs the base station controller 31 in its response
signal of the base station transceiver units with which it is ready
to establish a connection. From this point onwards the connection
is established according to the invention similarly as when the
subscriber terminal equipment 37 initiates connection
establishment.
When operating in system based on FDMA (Frequency Division Multiple
Access) or TDMA (Time Division Multiple Access), the solution of
the invention is possible when using the same access channel to a
random access type connection for several base station transceiver
units. For example, a pilot signal is not sent in the GSM system,
wherefore macrodiversity has to be generated without any previously
evaluated quality information of the connection, or some other
signal has to be used instead of the pilot signal for evaluating
the quality of the connection. Instead of a pilot signal, it is
possible to use a BCCH signal which the base station transceiver
unit sends on a BCCH channel (Broadcast Control Channel).
In a system using PRMA technique, data transmission takes place in
packet mode. The connection establishment method is similar to the
CDMA system described above. By using the solution of the invention
also in packet-mode data transmission, several base station
transceiver units can be used and macrodiversity will be attained,
whereby changes in the quality of the connection are less
significant than when in connection to only one base station or
base station transceiver unit.
Although the invention has been explained above with reference to
the examples of the appended drawings, it is evident that the
invention is not restricted thereto, but it can be modified in
various ways within the scope of the inventive idea disclosed in
the accompanying claims.
* * * * *