Note: Descriptions are shown in the official language in which they were submitted.
~' \~ 9~3/20b64 z ~ ~ Pf.T1US93/0253~
-1-
~r~rwo~ ~rV~ ~PP~~~TUS Fog ~ ~A~ro ~~Ir~ro°rh
R~~~~T~R r~ ~ ~rorT~~ cElrr_ur~~~ s~~~r~'
co~r~r~r~'c~~°ro~ ~Y~T~~r
I°i~Id of the Inv~ntion
The present inv~ntion r~alates to cellular radio ~mmunication
systems and, more pa~icularty, to a method and apparatus for using
radio remate rap~ater m~chanisms in a digital c~Iluiar radio
~mmunication system.
Background of the Invention
~ 5 Cellular radio communication systems typically include a number
of central communication base sites. each central communication site
has a service area coverage for servicing mobile communication units
within the service area. The service areas typically are arranged such
that adjacent remote bas~ sit~ service coverage ar~as overlap in a
manner that provides a substantially continuous service region. The
substantially continuous s~rvice region provides uninterrupted service
by handing off mobile communication units from on~ base site serving a
service area to an adjacent base site serving another service area.
Communication between the central communication sites and
mobile communication units typically occurs on a pair of frequency
CA 02133111 1998-02-24
-2-
channels (i.e., transmit and receive frequenaes) assigned according to
a cellular communication system channel reuse plan. Upon activation,
a mobile communication unit searches a radio fn3quency spectrum for
control signal transmissions from a local central communication site.
The control signal transmissions from the local communication site are
found in a radio frequency broadcast control channel (BCCH). The
BCCH contains specific information needed by the mobile
communication unit in order to format and code radio communication
system access requests to the local central communication site. The
Group Special Mobile (GSM) Pan-European cellular communication
system, as specified in GSM n~commendations by Motorola available
from the European Telecommunication Standards Institute (ETSI), is an
example of a system using such a format including the BCCH.
On the BCCH many control transmissions are transmitted
including timing information, a local central communication site ID for
the central communication site which is transmitting the information,
format information for specifying the format of transmit access requests,
and may further include in some environments information identifying
frequencies on which to transmit such access requests. In addition, the
formatting information may further identify the communication system as
a time division multiple access (TDMA) system and may identify a time
slot in which to transmit an access request.
The mobile communication unit upon detecting and decoding
information received on a BCCH subsequently transmits an access
request to a local central communication site. The local central
communication site, upon receiving the access request from the mobile
communication unit subsequently responds by transmitting a signal
directed to the mobile communication unit which identifies a resource
which it can use for communication with the local central communication
site.
To limit noise in cellular communication systems due to
communication between other mobile communication units in other
nearby service areas serviced by other central communication sites as
well as increase the capacity of the cellular communication system,
reuse of the available, but limited number of communication resources
is done within a service region of the cellular communication system. To
CA 02133111 1998-02-24
-3-
ensure that the reuse of communication resources does not cause
unacceptable noise in the communication channel, central
communication sites which are allocated the same communication
resources are geographically separated. By having sufficient
geographic separation, the noise in the communication channel is
limited. However, the geographic separation needs to ensure an
adequate signal to noise ratio (negligible noise in the communication
channel) limits the capacity of the communication system because not
all of the available communication resources may be used in each
service area.
To enhance the efficiency of communication resource reuse and
to improve capacity of the cellular communication system, service areas
of central communication sites can be divided into sectors, wherein
each sector a percentage of the available communication resources,
(i.e., communication channels). By having the service area divided into
sectors, the required geographic separation may be reduced while
maintaining an adequate signal to noise ratio. For example, U.S. Patent
Number 4,128,740, assigned to Motorola, Inc. discloses a four cell
(service area) - six sector communication resource reuse pattern. As
disclosed, each cell is divided into six sectors and each sector contains
approximately 1/24th of the available communication resources. For
every four cell sites, the communication resource pattern is repeated.
This communication resource reuse pattern may be further reduced to a
1 cell site reuse pattern as disclosed in U.S. Patent No. 5,355,367
which was issued on October 11, 1994 and also assigned to Motorola, Inc. It
will be appreciated by those skilled in the art many other reuse patterns
exist
for use in cellular communication systems including but not limited to 3, 7,
21,
49, 63, 91 site reuse patterns.
After allocating a communication resource for use by the mobile
communication unit, the local central communication site typically
allocates a transceiver typically located at the local central
communication site to service any subsequent communication with the
mobile communication unit on the assigned communication channel
resource. The transceiver of the central communication site will
subsequently route the communications of the mobile communication
unit to a target communication unit. The target communication unit
maybe either another mobile communication unit within the same
WO 93/20664 - PC1'1US93/0253~:
_4_
servsce area, a mobile communication unit in another service ar~a, or a
subscriber on the public switched telephone network (PSTN).
hligh density cellular communication systems with sufficient
spectrum can serve a large number of users in an urban environment by
using microcells which service a small geographic area. However, in
lower user density like rural or suburban areas, higher signal
propagation losses and high infrastructure costs severely limit the
economic viability of such communication systems. Since providing
service coverage to rural, suburban and urban environments alike is
crucial in establishing a complete cellular service, the need for a less
costly means of deploying a cellular communication system is large.
Another consideration is chat due to increasing competition for
frequency spectrum, the service Overage areas of central
communication sites may have to be reduced to allow for frequency
reuse in a relatively close proximity. Reducing the service coverage
area of a central communication site, on the other hand, increases the
number of cantle! communication sites necessary to cover a given.
geographic area. Therefore, it is desirable to minimize the cost of the
individual central communication sites equipment so that the overall
cost of the cellular corr~munication system can be r~duced.
Summary of the Invention
The present invention overcomes the above-mentioned
communication system cost problems by effectively trading radio
frequency spectrum, which is typically abundant in low communication
traffic density areas, for a less expensive way to serve a larger
geographic area. in addition, the present invention can be used in
microcellular applications as a substitute for wireline connections
between cell site controllers provided sufficient radio spectrum is
available. The present invention provides a digital cellular radio
communication system having a remote repeater and a central
~mmunication site. The central communication site transmits and
receives signals in a first radio channel assigned according to a cellular
communication system channel reuse plan, transmits signals to and
receives signals from a cellular communication network unit, and
digitally processes received signals for subsequent transmission in the
~~33~1~.
. .O 93/20664 PCT/US93/02535
-5-
first radio channel or to the cellular communication network unit. The
remote repeater (i.e., remote communication sit~), which is substantially
remotely located from the central communication site, receives a signal
in either the first radio channel or a second radio channel assigned
aocorcling to the cellular communication system channel reuse plan,
channel shifts the received signal betw~en the first and the second radio
channels, and transmits the shifted signal in the other of the first and the
second radio channels.
As a result of this configuration of the ~mmunication system, the
hardware and software needs of the remote communication sites are
less than the central communication sites because the remote
communication site does not need to have a mechanism for
communicating with the cellular communication network unit or a
mechanism for digitally processing received signals. Therefor~, the
monetary cost of a the remote communication sites is reduced and as
such the overall cost of the communication system can be recJuced by
using these less expensive r~mote communication sites in conjunction
with central communication sites in low communication traffic density
areas.
brief Description of the Drawings
FIGs. 1-1, 1-2 are diagrams showing preferred embodiment
digital cellular radio communication systems.
FI(~s. 2-1, 2-2 are diagrams showing preferred embodiment
central communication sites.
FIGS. 3-1, 3-2 are diagrams showing preferred embodiment
remote communication sites.
FIGS. ~-1, 4-2 show flowcharts of how a signal travels from a
cellular communication network unit to a mobile communication unit in
each tareferred embodiment digital cellular radio communication system.
Flfas. 5-1, 5-2 show flowcharts of how a signal travels from a
mobile communication unit to a cellular communication network unit in
each preferred embodiment digital cellular radio communication system.
Detailed Description
WO 93/20664 PCT1US9310253~<;.
311. _s_
Referring now to FIG. 1-1, a preferred embodiment digital cellular
radio communication system 100 having r~mote repeaters 102 is ,
shown. The communication system 100 includes at least one central
communication site 104. The central communication site 104 contains
an antenna tower 106 and a site equipm~nt storage .unit 108. As
shown in FIG. 2-1, the site equipment storage unit 108 preferably
includes a transceiver mechanism 110; communication unit 114, and a
processor apparatus 112.
The transceiver mechanism 110 is op~rably connected to the
antenna tower 106 to which an antenna 116 is preferably mounted so
that the transceiver 110 can transmit and receive signals in a first radio
channel through antenna 116. Antenna 116 may be an omn6-
directional antenna, sectorized antenna array, or a narrow beam
antenna. It will be appreciated by those skilled in the art that the best
type of antennae varies depending on the particular installation
environments. In the preferred embodiment antenna 116 is ~n omni-
directional antenna. In addition, it will be well understood by those
skilled in the art that a radio channel refers to a pair of charmei bands
used for a communication link by two communication devices. For the
following discussion this pair of channel bands will be designated from
the perspective of the central communication s'tte 104. More precisely,
the portion of the first radio channel used for transmitting messages to
the central communication site 104 will be designated as the inbound
portion of the first channel. Similarly, the portion of the first radio
channel used for transmitting messages from the central communication
site 104 will be designated as the outbound portion of the first channel.
It will be appreciated by those skilled in the art that the first radio
channel may be any one of several types of radio channels including,
but not limited to, code division channels (e.g., direct sequence and
frequency hopping spread spectrum channels), time division channels
(e.g., GSf~ll-based channels), and frequency division channels. For
simplicity, the remainder of the detailed description will be described
using frequency divided channels. The preferred embodiment
transceiver mechanism 110 preferably is capable of transmitting a
signal in the outbound portion of the first radio channel and is capable of
receiving a signal in the inbound portion of the first radio channel.
~~.3~111
..O 931206(4 i'CT/US93/02535
_7_
The communication unit 114 preferably is operably connected to
a cellular communication network unit 120 such that the unit 120 can
transmit signals to and receive signals from the network unit 120. The
communication network unit 114 may be a base communication site
controller, another central communication site or a communication
system switch (e.g., PSThI switch).
Processor apparatus 112 is operatively coupled to the
transceiver mechanism 110 and the communication unit 114 such that
the processor 112 can digitally process a signal received by either the
transceiver 110 or the communication unit 114 and subsequently
provide the processed signal to the device which did not send the signal
to the processor 192 (i.e., either the transceiver 110 or the
communication unit 914).
The communication system 100 also includes at least one
remote communication site 102 which is substantially remotely located
from the central communication site 104. The remote communication
s'tte 102 contains an antenna tower 122 and a site equipment storage
unit 124. As shown in FIG. 3-1, the site equipment storage unit 124
preferably includes a first transceiver mechanism 126, a channel
shifting device 126, and a second transceiver mechanism 130.
The first transceiver mechanism 126 is operably connected to the
antenna tower 122 to which an antenna 132 is preferably mounted so
that the transceiver 126 can transmit and receive signals in the first
radio channel through antenna 132. ~4ntenna 132, like antenna 916,
may be an omni-directions! antenna, sec.°torized antenna array, or a
narrow beam antenna. In the preferred embodiment antenna 132 is a
narrow beam antenna configured such that a signal transmitted from
antenna 132 will appear to the central communication Site 104 to be
from a mobile communication unit 136 within cell 1 and configured such
that a signal transmitted by antenna 116 can be received at remote
communication site 902. The use of the narrow beam (i.e., directional
antenna) on an antenna tower 922 will typically result in a high quality
radio link (possible even line of sight) befinreen the central 104 and the
remote 102 communication sites. The preferred embodiment first
transceiver mechanism 126 preferably is capable of transmitting a
signal in the inbound portion of the first radio channel and is capable of
receiving a signal in the outbound portion of the first radio channel.
WO 931206~A~~ ~ ~ ~ ~ PCT/US93/0253~.,": ~e
The second transceiver mechanism 130 is operably connected
to the antenna tower 122 to which an antenna 134 is preferably
mounted so that the transceiver 130 can transmit and receive signals in .
a second radio channel through antenna 134. Antenna 134, like
antenna 116, may be an omni-directional antenna, sectorized antenna
array, or a narrow beam antenna. In the preferred embodiment antenna
134 is an omni-directional antenna configured such that a signal
transmitted from antenna 134 can be received by a mobile
communication unit 138 within cell 2 and configured such that a signal
transmitted by mobile communication unit 138 can be received at
remote communication site 102. In addition, it will be well understood
by those skilled in the art that the second radio channel, like the first
radio channel, has a pair of channel bands designated from the
perspective of the remote communication site 102. More precisely, the
~ 5 portion of the second radio channel used for transmitting messages to
the remote communication site 102 will be designated as the inbound
portion of the second channel. ~imilarty, the portion of the second radio
channel used for transmitting messages from the remote communication
site 102 will be designated as the outbound portion of the second
channel. Also, like the first radio channel, the discussion will focus on
frequency divided channels even though other types of radio channels
may be used without departed from the scope and spirit of the present
invention. The preferred embodiment second transceiver mechanism
130 preferably is capable of transmitting a signal in the outbound
portion of the second radio channel and is capable of receiving a signal
in the inbound portion of the second radio channel.
It will be appreciated by those skilled in the art that the
functionality of transceivers 126 and 130 could be incorporated into a
single transceiver mechanism. similarly, function performed by antenna
132 and 134 could be provided by a single antenna. These two
possible combinations of elements in remote communication site 102
could be readily implemented if TDMA or CDM~1 type radio channels
werre used such that two or more time slots of a time frame or two or
more code divided channels i0 a wide band signal burst could be
transmitted or received by a single set of devices.
The channel shifting device 128 shifts the received signal
between the first and the second radio channels. The channel shifting
,
.~JO 93/20664 PCT/US93/U2535
_g_
device 128 shifts a r~ceived signal in the inbound portion of th~ second
radio channel to the inbound portion of the first radio channel. Likewise,
the channel shifting d~vice 128 shifts a r~ceiv~d signal in th~ outbound
portion of the first radio channel to the outbound portion of the second
radio channel. The channel shifting d~vice 128 may also include an
automatic gain control circuitry for adjusting the gain of the received
signal to a predetermined power level. This gain control circuitry would
insure that a signal transmitted by the first and/or the second transceiver
mechanism 12fi, 130 would have adequate signal power. Thus, when
mobile communication unit 138 is near the remote communication site
704, th~ transmitted signal pow~r could be attenuated. In addition,
when mobile communication unit 138 is far from the remote
~mmunication site 104, the t~nsmitted signal power could tie
increased.
tt will be appreciated by those skilled in the art that substantial
cost savings in the cellular communication system infrastructure can be
achieved through the use of th~se pref~rr~d embodiment rerrsote
communication sites 102. This cost savings is due in part to the
elimination of processor 112 and ~mmunication unit 114 as well as
the associated connections to a c~Ilular communication network unit
120.
The communication system 100 also includes mobile
communication unit 136 or 138 which is substantially remotely located
from the central communication site 104 and substantially remotely
located from the remote communication site 102. 'The mobile
communication unit 138,138 contains transceiver mechanism. The
transceiver mechanism preferably is operably configured transmit and
receive signals in the first and the second radio channels. The
preferred embodiment mobile unit transceiver mechanism preferably is
capable of receiving a signal in the outbound portion of either the first or
the second radio channels, determining in which radio channels the
signal was received, and transmifiting a signal in the inbound portion of
the determined radio channel. Thus, the mobile transceiver can directly
communicate with the first transceiver 110 of the central communication
site 104 and the second 130 transceiver of the remote communication
site 102.
WO 93/206 ~ PCT1US93/0253w:: ~
3~~,.1 _, o_
~1
One particularly important aspect of using remote communication
sites (e.g., site '102) which frequency shift and repeat a signal
transmitted by a central communication site (e.g., site 104) is ,
communication channel reuse.
The specific first and second radio channels preferably are assigned
according to a cellular communication system channel reuse plan
based upon a channel reuse pattern (e.g., 3-site, 4-site, 7-sits, 21-site,
49-s'tte, 63-site or 91-site channel reuse patterns). Depending on the
particular channel reuse plan used, the radio channel assigned to the
first radio channel may be substantially similar to the radio channel
assigned to the second radio channel. Also, the radio channel assigned
to the first radio channel may be substantially different from the radio
channel assigned to the second radio channel.
Each central communication site 104 can be configured to
extend communication traffic control to remote communication sites in
each of the surrounding cells (i.e., cell 2-c~11 ~). D~pending upon the
particular channel reuse plan used, the ravio channel assigned to the
first radio channel (associated with the central communication s~~ 104)
may be substantially similar to or different from the radio channel
assigned to the second radio channel (associated with the remote
communication site 102) and may be substantially similar to or different
from the radio channel assigned to the other second radio channels
(associated with the other remote communication sites found in cells 3,
4, 5, 6, and 7 which are also served by the central communication site
104).
For example, each served remote site may operate with respect
to a second radio charnel which is assigned acxording to the cellular
communication system channel reuse plan and is substantially different
from the first radio channel and is substantially different from the second
radio channel assigned to each other remote communication site.
Further, each served remote site may operate with respect to a
second radio channel which is assigned acxording to the cellular
communication system channel reuse plan and is substantially different
from the first radio channel and is substantially similar to the second
radio channel assigned to each other remote communication site.
Furthermore, each remote site may operate with respect to a
second radio channel which is assigned according to the cellular
~~.3~111
vJ0 93/20664 ~ PC'~'1US93/02535
communication system channel reuse plan and is substantially similar to
the first radio channel and is substantially similar t~ the second radio
channel assigned to each other r~mot~ communication site.
Finally, each remote site may operate with r~spect to a s~cond
radio channel which is assigned according to the cellular
communication system channel reuse plan and is substantially similar to
the first radio channel and is substantially different from the second
radio channel assigned'to each other remote communication site.
By way of example, FIG. 4-1 shows flowchart describing how a
signal preferably travels from the cellular communication network unit
120 to mabile communication unit 138. The process begins 200 at a
cellular communication network unit 120 when a signal is sent to a
central communication site 104. The central ~mmunication site 104
receives 202 the signal from the cellular communication network unit
120. The central communication site 102 digitally processes 204 the
received signal. In addition, a first radio channel is assignee! 206
wording to a cellular communication system channel reuse plan to the
central communication site 104. This first radio channel has inbound
and outbound radio channel portions. The central communication site
104 transmits 208 the processed signal in the outbound portion of the
first radio channel. Subsequently, a remote communication site 102,
which is substantially remotely Docated from the central ~mmunication
site 104, receives 210 the transmitted signal in the outbound portion of
the first radio channel. In addition, a second radio channel is assigned
212 according to the cellular cr~mmunication system channel reuse
plan to the remote communication site 102. This second radio channel
also has inbound and outbound radio channel portions. Subsequently,
the received signal is channel shifted 214 from the first radio channel to
the second radio channel at the remote communication site 102. The
gain of the shifted signal is adjusted 215 to a predetermined power
level. Then, the remote communication site 102 transmits 216 the
shifted signal in the outbound portion of the second radio channel.
Finally, the shifted signal is received 218 in the outbound portion of the
second radio channel at a mobile communication unit 138 which ends
220 the process.
By way of example, FIG. 5-1 shows flowchart describing how a
signal preferably travels from mobile communication unit 138 to the
WO 93/206 PC'I'1US93/0~535v: .. '°
133~.~.1
-12-
cellular communication network unit 120. The process begins 230 at a
mobile communication unit 138. A first radio channel is assigned 232
acxording to a cellular communication system channel reuse plan to a .
central communication site 104. The first radio channel has inbound
and outbound radio channel portions. A second radio channel is
assigned 234 according to the cetiular communication system channel
reuse plan to a remote communication site 102 which is substantially
r~motely located from the ce~rai communication site 104. The send
radio channel has inbound and outbound radio charmei portions. The
mobile communication unit 138 transmits 236 a signal in the inbound
portion of the second radio channel. The remote communication site
102 receives 238 the signal in the inbound portion of the second radio
channel. Subsequently, the received signs! is channel shifted 240 from
the second radio channel to the first radio channel at the remote
communication site 102. The gain of the shifted signal is adjusted 242
to a predetermined power level. Then, the remote communication site
102 transmits 244 the shifted signal in the inbound portion of the first
radio channel. The central communication site 104 receives 246 the
transmitted signal in the inbound portion of the fsrst radio channel. The
received signal is digitally processed 248 at the central ~mmunication
site 104. Finally, the processed signs! is transmitted 250 from the
central communication site 104 to a cellular communication network
unit 120 which ends 252 the process.
referring now to FICa. 1-2, an alternative preferred embodiment
digital cellular radio communication system 100 having remote
repeaters 102 is shown. The communication system 100 includes at
least one central communication site 104. The ~ntra! communication
site 104 contains an antenna tower 106 and a site equipment storage
unit 108. As shown in Flfa. 2~2, the site equipment storage unit 108
preferably includes a transceiver mechanism 110, transceiver
mechanism 111, communication unit 114, and a processor apparatus
112.
The transceiver mechanism 110 is operably connected to the
antenna tower 106 to which an antenna 118 is preferably mounted so
that the transceiver 110 can transmit and receive signals in a first radio
channel through antenna 118. Antenna 118 may be an omni
directional antenna, sectorized antenna array, or a narrow beam
~JO 93/20664 _ ~ i 3 3 ~.1 ~ p~'/US93/0253;
-13_
antenna. It will be appr~aated by thos~ skilled in the art that the best
type of antennae varies depending on the particular installation
environments. In the preferred embodiment antenna 1 i8 is an omni-
directionat antenna. In adelition, it will be well understood by those
skilled in the art that a radio charmei refers to a pair of channel bands
used for a communication link by two communication devices. For the
following discussion this pair of channel bands will be designated from
the perspective of the central communication site 1 ~. llAore precisely,
the portion of the first radio channel used for transmitting messages to
~ 0 the central communication site 1046 will be designated as the inbound
portion of the first channel. Similarly, the portion of the first radio
channel used for transmitting messages from the central communication
site 1114 will be designated as the outbound portion of the fir;~t channel.
tt will be appreciated by those skilled in the art that the first radio
channel may be any one of several types of radio channels including,
but not limited to, code division channels (e.g., direct sRquence and
frequency hopping spread spectrum channels), time division channels
~e.g., CSM-based channels), and frequency division channels. For
simplicity, the r~mainder of the detailed description will b~ described
using frequency divided channels. The preferred embodiment
transceiver mechanism 110 preferably is capable of transmitting a
signal in the outbound portion of the first radio channel and is capable of
receiving a signal in the inbound portion of the first radio channel.
The transceiver mechanism 111 (hereinafter cross-transceiver
111) is operabiy connected to the antenna tower 1~6 to which an
antenna 116 is preferably mounted so that the cross-transceiver 111
can transmit and receive signals in a second radio channel through
antenna 116. Antenna 116 may be an omni-directional antenna,
sectoriZed antenna array, or a narrow beam antenna. In the preferred
embodiment antenna 116 is an omni-dir~ctional antenna. In addition,
the portion of the second radio channel used for transmitting messages
to the central communication site 1~4 will be designated as the inbound
portion of the second channel. Similarly, the portion of the seoand radio
channel used for transmitting messages from the central communication
site 104 will be designated as the outbound portion of the second
channel. The preferred embodiment cross-transceiver mechanism 111
pr~ferably is capable of transmitting a signal in the inbound portion of
WO 93/206b4 PCTlUS93/0253~: :;:;~~~
. ~.:a:3 ~ ~.1 _, ~_
the first radio channel and is capable of riving a signal in the
outbound portion of the first radio channel.
The use of two omni-directional ant~nna on an antenna tower
106 will typically result in som~ mutual interfer~nce. Thus, th~ two
antenna 116, 118 must be mounted on the ant~nna tow~r 106 at
cliff~ring heights and additional filt~ring in th~ transceivers 110, 111
may be needed to achi~ve a high quality radio links.
The communication unit 11~ preferably is operably connected to
a cellular communication network unit 120 such that th~ unit 120 can
transmit signals to and r~c~ive signals from the network unit 120. The
~mmunication n~twork unit 114 may be a base communication site
control)er, another c~ntral communication site or a communication
system switch (e.g., PST~I swi~,ch).
Processor apparatus 112 is op~rativgly coup)~d to the
transceiver mechanism 110, the cross-transc~iver mechanism 111 and
the~communication unit 114 such that th~ processor 112 can digitally
process a signal received by either the transc~iver 110, the cross-.
transc~iver 111, or the communication unit 1i4 and subsequ~ntly
provide the process~d signal to one of th~ devic~s which did not s~nd
the signal to the processor 112 (i.e., eith~r the transc~iver 110, cross-
transceiver 111, or the communication unit 114).
The communication system 100 also includes at least one
remote communication site 102 which is substantially remotely located
from the central communication site 104. The r~mot~ communication
site 102 contains an antenna tower 122 .and a site equipment storage
unit 124. As shown in I=ICa. 3-2, the site equipm~nt storage unit 124
preferably includes a first transc~iver mechanism i26, a channel
shifting d~vice i28, and a s~cond transc~iver mechanism 130.
The first transceiver mechanism 7 26 is operably connected to the
antenna tower 122 to which an antenna 132 is pr~ferably mounted so
that the transc~iver 126 can transmit and receive signals in the first
radio channel through antenna 132. Ant~nna 132, like antenna 116,
may b~ an omni-directional antenna, sectorized antenna array, or a
narrow beam antenna. In the preferred embodiment ant~nna 132 is an
omni-directional antenna configunad such that a signal transmitted from
antenna 132 will appear to the centre! communication site 104 to be
from another central communication unit within cell 1 and configured
PAC I'/US93/02S3a
'rv0 93!20664
-15-
such that a signal transmitted by antenna 116 can be received at
remote communication site 102. The preferred embodiment first
transceiver m~chanism 126 preferably is capable of transmitting a
signal in the outbound portion of the first radio channel and is capable of
receiving a signal in the inbound portion of the first radio channel.
The second transce'rvar mechanism 130 is oparabiy connected
to the antenna tower 122 to which an antenna 1 ~ is preferably
mounted so that the transceiver 130 can transmit and receive signals in
a second radio channel through antenna 134. Antenna 134, like
antenna 116, may ba an omni-directional antenna, sectoriz~d antenna
array, or a narrow beam antenna. In the preferred embodiment antenna
134 is an omni-directional antenna configur~d such that a signal
transmitted from antenna 134 can be received by a mobile
communication unit 138 within cell 2 and configured such that a signal
transmitted by mobile communication unit 138 can ba received at
remote communication site 102. The pr~farr~d embodiment second
transceiver mechanism 130 pr~ferably is c;apabia of transmitting a
signal in the outbound portion of the second radio channel and is
capable of receiving a signal in the inbound portion of the second radio
channel.
Tha use of two omni-directional antenna 132, 134 on an
antenna tower 122 will typically result in some mutual interference.
Thus, the two antenna 132, 134 must ba mounted on the antenna
tower 122 at differing heights and additional filtering in the transceivers
126,130 may ba needed to achieve a high quality radio links.
It will ba appreciated by those skilled in the art that the
functionality of transceivers 126 and 130 could be incorporated into a
single transceiver mechanism. Similarly, function performed by antenna
132 and 134 could be provided by a single antenna. Theca two
possible combinations of elements in remote communication site 102
could ba readily implemented if TDMA or CDMA type radio channels
were used such that two or more time slots of a time frame or two or
more code divided channels in a wide band signal burst could be
transmitted or received by a single sat of devices.
The channel shifting device 128 shifts the received signal
between the first and the second radio channels. The channel shifting
device 128 shifts a received signal in the inbound portion of the first
WO 93/20664 P~:T/U~93J0253a ~jY
-i 6-
radio channel to the outbound portion of the send radio channel.
Likewise, the channel shifting device 128 shifts a received
signal in the
inbound portion of the second radio channel to the outbound
portion of
the first radio channel. The channel shifting device 128 may
also
indude .an automatic gain control drcuitry for adjusting the
gain of the
received signal to a predetermined power level. This gain control
circuitry would insure that a signal transmitted by the first
and/or the
second transceiver mechanism 1.26, 130 would have adequate
signal
power. Thus, when mobile communication unit 738 is near the
remote
communication site 104, the transmitted signal power could
be
attenuated. in addition, when mobile communication unit 138
is far
from the remote communication site 104, the transmitted signal
power
could be increased.
It will be appreciated by those skilled in the art that substantial
cost savings in the cellular communication system infrastructure
can be
achieved through the use of these preferred embodim~:~t remote
communication sites 102. This gist savings is due in part to
the
elimination of processor 112 and communication unit 11~ as
well as
the associated connections to a cellular ~mmunication network
unit
120.
The communication system 100 also indudes mobile
communication unit 136 or 138 which is substantially remotely located
from the central communication site 104 and substantially remotely
located from the remote communication site 102. The mobile
communication unit 136,138 contains transceiver mechanism. The
transceiver mechanism pr~ferably is operabiy ~nfigur~d transmit and
r~ceive signals in the first and the second radio channels. The pr~ferred
embodiment mobile unit transceiver mechanism preferably is capable of
receiving a signal in the outbound portion of either the first or the second
radio channels, determining in which radio channels the signal was
received, and transmitting a signal in the inbound portion of the
determined radio channel. Thus, the mobile transceiver can directly
communicate with the first transceiver 110 of the central communication
site 104 and the first 126 and the second 130 transceiver of the remote
communication site 102.
One particularly important aspect of using remote communication
sites (e.g., site 102) which frequency shift and repeat a signal
~133.~1.~
WO 93/20664 PCT/U~93/0253;
_17_
transmitted by a central communication site (e.g., site 104) is
communication channel revs~<
the speafic first and second radio channels preferably are assigned
according to a cellular communication system channel reuse plan
based upon a channel reuse pattern (e.g., 3-sit~, 4-site, 7-site, 21-site,
49-site, 63-site or 91-site channel reuse patterns). Depending on the
particular channel reuse plan used, the radio channel assigned to the
first radio channel may be substantially similar to the radio channel
assigned to the second radio channel. Also, the radio channel assigned
to the first radio channel may be substantially different from the radio
channel assigned to the send radio channel.
Each central communication sit~ 104 can be configured to
extend cammunication traffic ~ntrol to remote communication sites in
each of the surrounding cells (i.e., cell 2-III 7). D~pending upon the
particular channel reuse plan used, the radio channel assigned to the
first radio channel (associated with the central communication site 104)
may be substantially similar to or different from the radio channel
assigned to the second radio channel (associated with the remote
communication site 102) and may be substantially similar to or different
from the radio channel assigned to the other send radio channels
(associated with the other remote communication sites found in cells 3,
4, 5, 6, and 7 which are also served by the central communication site
104).
For example, each s~rved remot~ site may operate with respect
to a second radio channel which is assigned according to the cellular
communication system channel reuse plan and is suhstantially different
from the first radio channel arx~l is substantially different from the second
radio channel assigned to each other remote communication site.
Further, each sereed remote site may operate with respect to a
second radio channel which is assigned according to the cellular
communication system channel reuse plan and is substantially different
from the first radio channel and is substantially similar to the second
radio channel assigned to each other remote communication sits.
Furthermore, each remote site may operate with respect to a
second radio channel which is assigned according to the cellular
communication system channel reuse plan and is substantially similar to
iV0 93/20664 PCT/U593/0253~~ v-
-18-
,,
the first radio channel and is substantially similar to the second radio
channel assigned to each other remote communication site.
Finally, each remote site may operate with respect to a second
radio channel which is assigned a~rding to the cellular
communication system channel reuse plan and is substantially similar to
the first radio channel and is substantially different from the second
radio channel assigned to each other r~mot~ communication site.
~y way of example, FIG. 4-2 shows flowchart describing how a
signal preferably travels from the cellular communication network unit
120 to mobile communication unit 138. The process begins 200 at a
cellular communication network unit 120 when a signal is sent to a
central communication site 104. The central communication site i04
receives 202 the signal from the cellular communication nat,worfc unit
120. The central communication site 102 digitally procasse~s 204 the
received signal: In addition, a first radio channel is assigned 206
according to a ceii~.°lar communication system channel reuse plan to
the
central communication site 104. This first radio channel has inbound
and outbound radio channel portions. Tha central ~mmunication site
104 transmits 208' the processed signal in the inbound portion of the
first radio channel. Subsequently, a remote communication site 102,
which is substantially remotely located from the central communication
site 104, receives 210' the transmitted signal in the inbound portion of
the first radio channel. in addition, a sat~nd radio channel is assigned
212 according to the cellular ~mmunic~~tion system channel reuse
plan to the remote communication site 102. This second radio channel
also has inbound and outbound radio channel portions. Subsequently,
the received signal is channel shifted 21~ from the first radio channel to
the second radio channel at the remote communication site 102. The
gain of the shifted signal is adjusted 218 to a predetermined power
level. Then, the remote communication site 102 transmits 216 the
shifted signal in the outbound portion of the second radio channel.
Finally, the shifted signal is received 218 in the outbound portion of the
second radio channel at a mobile communication unit 138 which ends
220 the process.
By way of example, FIG. 5-2 shows flowchart describing how a
signal preferably travels from mobile communication unit '938 to the
cellular communication network unit 120. The process begins 230 at a
~1~3~.1~.
WO 93/20664 ~ PCTlUS93102535
_19_
mobile communication unit 138. A first radio channel is assigned 232
aoconding to a cellular communication system channel reuse plan to a
central communication site 104. The first radio channel has inbound
and outbound radio channel portions. A second radio channel is
assigned 234 according to the cellular communication system channel
reuse plan to a remote communication site 102 which is substa~tiaNy
remotely located from the central communication site 104. The saaond
radio channel has inbound and outbound radio channel portions. The
mobile communication unit 138 transmits 236 a signal in the inbound
portion of the second radio channel. The remote communication site
102 receives 238 the signal in the inbound portion of the second radio
channel. Subsequently, the received signal is channel shifted 240 from
the second radio channel to the first radio channel at the remote
communication site 102. The gain of the shifted signal is adjusted 242
to a predetermined power level. Then, the remote communication site
102 transmits 244' the shifted signal in the outbound portion of the first
radio channel. The central communication site 104 receives 246' the
transmitted signal in the outbound portion of the first radio channel. The
received signal is digitally processed 248 at the central communication
site 104. Finally, the processed signal is transmitted 250 from the
central communication site 104 to a celtular communication network
unit 120 which ends 252 the process.
Although the invention has been described and illustrated with a
certain degree of particularity, it is understood that the present
disclosure of embodiments has been made by way of example only and
that numerous changes in the arrangement and combination of parts as
well as steps may be resorted to by those skilled in the art without
departing from the spirit and scope of the invention as claimed.
Although the invention has been described and illustrated with a
certain degree of particularity, it is understood that the present
disclosure of embodiments has bean made by way of example only and
that numerous changes in the arrangement and combination of parts as
well as steps may be resorted to by those skilled in the art without
departing from the spirit and scope of the invention as claimed.
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