BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a radio
communication system, or more in particular to a communi-
cation system comprising a cell site (CS) not connected
to a switching system and a communication method.
Description of the Related Art
Radio communication systems for portable
telephone such as cellular systems and cordless telephone
systems are known, which comprise a cell site assigning
channels dynamically for connecting a plurality of per-
sonal stations (PS) through a radio channel and a line
switching network (switching system) for connecting a
plurality of cell sites to each other by radio channels
or cable lines.
JP-A-6-178345 discloses a technique in which a
standby radio channel is provided between CSs, and in the
case of a fault of the line between a CS and a switching
system, the communication is routed between the CSs
through the standby radio channel so that a network and a
PS are connected avoiding the fault point. This tech-
nique concerns a method of connecting a PS to a switching
system through two CSs, but no method is described for
connecting the switching system on the network side to
the PS.
A method for an automobile telephone system is
described in JP-A-5-68282, ir. which in the case of a line
fault between switching systems, a connection in speech
is routed using an adjacent CS, thereby circumscribing
the faulty point.
On the other hand, JP-A-4-196626 discloses a
technique in which a radio terminal routes signals in a
mobile communication system.
These techniques, which provide emergency
means in case of a system or a line fault, have a limit
in the number of applicable connections and applicable
status of connection.
In ordinary radio communication systems,
installation of a new CS requires the construction of a
cable transmission path for connecting the CS to a
switching system or the assignment of a new radio fre-
quency band to the CS for connecting the CS and the
switching system through a radio channel.
As a result, installation of a new CS is
expensive.
SUMMARY OF THE INVENTION
Accordingly, the object of the present inven-
tion is to provide a communiceition system in which a CS
can be installed at low cost.
In order to achieve the above-mentioned ob-
ject, according to one aspect of the invention, there is
provided a radio communication system comprising a plu-
rality of CSs including at least a first CS accommodated
in a communication network, at least a second CS not
included in the communication network, and at least a PS,
wherein the first and second CSs accommodate a plurality
of radio channels capable of being dynamically estab-
lished for a communication to be started with the PS or
with other CSs, and the second CS establishes a radio
channel for communication with the PS or other first or
second CS, and also a radio channel for communicating
with other first or second CS and relaying the communica-
tion between the two radio channels.
According to another aspect of the invention,
there is provided a radio communication system capable of
routing the communication between CSs using a radio
channel to be dynamically assigned for PSs. As a result,
a CS can be connected to an intended communication net-
work through at least one other CS accommodated in the
communication network. It is therefore not necessary to
install a cable transmission path for connecting the
communication network with CSs nor to assign a dedicated
radio frequency channel to a OS for connection with the
communication network.
The present invention is useful for adding a
CS temporarily in case of emergency or for adding a CS in
view of the difficulty of laying a transmission path to a
switching system.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram showing a configura-
tion of a radio communicatior system;
Fig. 2 is a diagram showing a communication
sequence at the time of location registration in a radio
communication system;
Fig. 3 is a diagram showing a communication
sequence at the time of call-out from a PS in a radio
communication system;
Fig. 4 is a diagram showing a communication
sequence at the time of call-in to a PS in a radio commu-
nication system;
Fig. 5 is a diagram showing an example config-
uration of a radio communication system;
Figs. 6A and 6B show example frame configura-
tions of a traffic channel for relaying by a CS.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present embodiment employs a radio commu-
nication system based on the personal handy phone system
according to RCR STD (Reseach & Development Center for
Radio Systems Standard) -28.
Generally, a radio communication system com-
prises a plurality of interconnected switching systems
(SW), a plurality of CSs associated with the respective
SWs, and a plurality of PSs connected to the respective
CSs.
Fig. 1 shows an example configuration of a
part of a radio communication system comprising a switch-
ing system SW 140, a CS2 103 connected to the SW, and a
CS1 102 not connected with the SW.
The SW 140 includes a data base 141 for loca-
tion registration. The CS1 102 is connected to CS2 103
and PS1 101 by radio channels 122, 121, respectively.
Also, PS2 100 is connected to CS2 103 through a radio
channel 123. A radio channel having a quality higher
than a predetermined requirement is assigned dynamically
for these channel connection Taking interferences and
noises into consideration.
Now, explanation wiLl be made about a configu-
ration of CS1 and CS2.
As shown, CS1 102 not connected to SW 140 in-
cludes a radio frequency unit iRF) 113, a modem 114, a
multiplexer/demultiplexer (MUX/DEMUX) 115, a digital
signal processing unit (PROC) 116, a loop-back circuit
(LB) 117, a control unit 112 and a data base 111. The
radio frequency unit 113 and the modem 114 are for trans-
mitting and receiving the radio frequency signal. The
multiplexer/demultiplexer 115 is for multiplexing the
transmission signals corresponding to radio frequency
transmission channels and demultiplexing the received
signal into the respective radio channels. The digital
signal processing unit 116 is for extracting the control
information from the received signal and for inserting
the control information into the transmission signal.
The control unit 112 controls the insertion of the con-
trol signal in the digital signal processing unit 116 and
the returning of the signal from the loop-back circuit
117 in accordance with the control information extracted
in the digital signal processing unit 16, thereby realiz-
ing various sequences described later. The data base 111
holds the information on the lacation registered PSs and
the information for identifying other CSs.
CS2 103 connected to SW has substantially the
same configuration as CS1 102. In addition to the con-
figuration of CS1 102, however, CS1 103 has a network
interface circuit 138 for connecting to the SW 140.
Also, in the case where CS2 conducts no relay operation,
the loop-back circuit 117 may be omitted.
Assume, for example, that CS1 102 has received
a signal through a radio channel 121 assigned to PS1 101.
This received signal is sent through the radio frequency
unit 113, the modem 114, the multiplexer/demultiplexer
115 and the digital signal processing unit 116 to the
loop-back circuit 117. The signal transmitted from PS1
101 to the loop-back circuit 3 17 is returned toward the
transmission-side circuit of CS1 102. The signal thus
returned is processed in a digital signal processing unit
116, a multiplexer/demultiplexer 115, a modem 114 and a
radio frequency unit 113, and further transmitted to CS2
103 through a radio channel 122 set with CS2. In CS1
102, the return operation can realize the connection of
two radio channels.
In CS2 103, on the ether hand, the signal
received from CS1 102 through the radio channel 122 is
input to a loop-back circuit 117 through radio frequency
unit 113, a modem 114, a multiplexer/demultiplexer 115
and a digital signal processing unit 116. The loop-back
circuit 117 sends the signal to a network interface
circuit 138 without loop back. The network interface
circuit 138 transmits the signal from CS1 102 to a
switching system 140 through a channel set up with the
switching system 140 for the radio channel 122.
The signal from the switching system 140 to
PS1 101 is first sent to CS2 L03 through the line set
between the switching system L40 and the CS2 103. In CS2
103, the signal received from 3W at the network interface
circuit 138 is processed through the digital signal
processing unit 116, the multiplexer/demultiplexer 115,
the modem 113 and the radio frequency unit 113, eind
transmitted to CS1 102 through the radio channel 122 set
with CS1 102. In CS1 102, the: signal received through
the radio channel 122 is sent to the loop-back circuit
117 through the radio frequency unit 113, the modem 114,
the multiplexer/demultiplexer 115 and the digital signal
processing unit 116. The signal sent from CS2 103 to the
loop-back circuit 117 is returned to the transmission
circuit of CS1 102. The signal, thus returned is
processed in the digital signal, processing unit 116, the
multiplexer/demultiplexer 115, the modem 114 and the
radio frequency unit 113 on transmission side, and
transmitted to PS1 101 through the radio channel 121 set
with PS1 101.
According to this embodiment, a channel is
established between PS1 101 ar.d SW 140 through the inter-
mediary of CS1 102.
Assume that CS2 10? has received a signal
through the radio channel 123 assigned to PS2 100. In
CS2 103, the signal received through the radio channel
123 is applied to the loop-back circuit 117 through the
radio frequency unit 113, the modem 114, the
multiplexer/demultiplexer 115 and the digital signal
processing unit 116. The loop-back circuit 117 sends the
signal to the network interfere circuit 138 through the
switching system 140 without Loop-back. The network
interface circuit 138 transmits the signal from PS2 100
to SW 140 through the channel set with the SW 140 for the
radio channel 123.
The signal from SW 140 to PS2 100, on the
other hand, is first sent to 3S2 103 through the line set
between SW 140 and CS2 103. In CS2 103, the signal
received from the switching system by the interface
circuit 138 is processed in the digital signal processing
unit 116, the multiplexer/demultiplexer 115, the modem
114 and the radio frequency jnit 113, and further trans-
mitted to PS2 100 through the radio channel 123.
In this way, a channel is established between
SW 140 and PS2 100 through a single CS as in the prior
art.
A method of signal loop-back, i.e., a method
of relay for CS1 will be described in detail. A link
channel is established througn the same procedure as
normal channel other than the relay. After the link
channel is set, however, a service channel is routed by
one of the following-described two ways. Figs. 6A and 6B
show a frame configuration of a traffic channel (TCH)
used for the respective methods.
One method consists; in returning the received
signal directly in the loop-back circuit 117 and trans-
mitting it through the radio frequency unit 113. In this
case, the digital signal processing unit 116 determines
on a signal type, i.e., whetheir the signal is to be
relayed to other radio stations (or performs the; process
for returning a rejection signal in the case whesre the
signal cannot be relayed). in the case where the signal
is the one to be relayed, a channel selector in the digi-
tal signal processing unit i:.5 does not perform the frame
termination process but the !. oop-back circuit 117 direct-
ly returns the signal for transmission. The transmitting
end of the digital signal processing unit 116 performs
nothing but to insert the local station ID in the frame.
As a result, an area for writing an overhead signal (for
channel control) for the next transmission channel is
required to be prepared in the signal frame (Fig. 6A).
In Fig 6A, the information t^ be relayed is contained in
the slots of Control Info A, B, C and so forth. The
circuit at the transmitting end writes these control
signals, sets a radio channel with the next radio station
and, upon complete setting of the channel, starts the
communication. This method secures the area of the
overhead signal for a plurality of relay channels and may
reduce the area usable for the>. frame assigned to the
traffic information. Nevertheless, the process in the
radio stations relaying the signal is simplified.
A second method is such that after the re-
ceived signal is terminated at the digital signal pro-
cessing unit 116, each component of the received signal
is returned to the transmitting end by the loop-back
circuit 117 and the frame is reconstructed at the trans-
mitting end of the digital signal processing unit 116.
According to this method, the control information area of
the received frame is rewritten according to the channel
relayed. The new channel connection information between
radio stations such as a newly-connected radio station ID
is added to the control information. Consequently, the
control information can occupy only one slot, and there-
fore a larger area can be secured for assignment to the
traffic information. The frame reconstruction increases
the processing burden of the (7.5, but the frame can trans-
mit more information (Fig. 6B).
According to this embodiment, PS1 101, PS2
100, CS1 102 and CS2 103 register their locations in the
nearby CSs before starting communication, i.e., before
assignment of a radio channel The location is regis-
tered when the power supply of the PSs and CSs is turned
on.
First, the operation of location registration
will be explained.
In Fig. 1, PS1 101 registers the location in
CS1 102, PS2 100 in CS2 103, ZS1 102 in CS2 103, and CS2
103 in CS 102.
The data base 111 of each CS is registered
with the information on the PSs and the CSs located in
the cell covered by the particular CS. The data base 141
of the switching system 140, on the other hand, holds all
the identifiers and the location information (the infor-
mation on the cell in which a 3S or a PS is located) of
the CSs and PSs belonging to the particular switching
system.
In any case of a change which may occur in the
contents of the data base 111., each CS informs the
switching system and requests the switching system to
update the data base 141 in the switching system.. Each
CS can accept the registration of a plurality of other
CSs connectable with it.
The sequence of the location registration is
shown in Fig. 2.
In Fig. 2, numerals 311 to 323 designate the
sequence of location registration of PS1 101 in CS1 102.
Numerals 331 to 350 designate "he sequence of location
registration of CS1 102 in CS2 103, and the sequence of
location registration of CS1 102 in CS2 103.
As shown, in the sequence of location regis-
tration of PS1 101 in CS1 102, PS1 101 transmits a link
channel establishment request using a channel on a spe-
cific time slot on the frequency channel called a logical
control channel (311). Upon receipt of a link channel
assignment notifying the assignment of a link channel
from CS1 102 through the logic control channel, PS 101
exchanges a sync burst (313) with a CS (CS1 102 in this
case) which has transmitted trie particular link channel
assignment, using the assigned link channel, thereby
setting up the synchronization for transmission and
receipt on the link channel.
Once the synchronization of transmission and
receipt is set up for the link channel, PS1 101 transmits
a SABM requesting the set-up of a multi-frame link to CS1
102 using this link channel (314). Upon receipt of a UA
as a response to the SABM from CS1 102 (315), PS1 101
sends a request for location registration to CS1 102
using the multi-frame link (3.5). In response to this
request, a request is sent from CS1 102 for the authenti-
cation information to authenticate the PS (317). Then,
the authentication information is sent to CS1 102 as an
authentication response (318). Upon normal completion of
authentication of CS1 102 and upon receipt of the loca-
tion registration acceptance informing that the location
registration has been accepted (319) with a DISC in-
structing to disconnect the multi-frame link (320), PS1
101 sends a UA (321) to CS1 102 as a response to the
DISC. Upon receipt of an instruction (322) to disconnect
the radio channel, the disconnection completion of the
radio channel is notified thereby to release the radio
channel (323).
The sequence 331 to 340 of location registra-
tion of CS2 103 in CS1 102 and the sequence 343 to 350 of
location registration of CS1 102 in CS2 103 are also per-
formed in the same manner as the sequence of location
registration of PS1 101 in CS1 102. In the former case,
however, the radio channel and the multi-frame link that
have already been set up are used for the location regis-
tration of both CS 1 102 and CS 103. A predetermined au-
thentication information assigned to a CS is used as the
authentication information for the particular CS.
Also, though not shown, the sequence of loca-
tion registration of PS2 100 in CS2 103 is performed in
the same manner as the sequence of location registration
of PS1 101 in CS1 102.
Upon the location registration completion of
PS1 101, CS1 102 and CS1 102 in this way, the identifica-
tion information and authentication information of the
PSs and other CSs registered i n each CS are stored in the
data base 111 of the CS. Also, each time of a new loca-
tion registration therein, each CS1 102 and CS2 103
notifies the SW 140 of the change of the location regis-
tration. In Fig. 1, CS1 102 notifies SW 140 through CS2
that PS1 101 and CS2 103 are registered therein, and CS2
103 notifies SW 140 that CS1 102 and PS2 100 are regis-
tered therein. The transmission of location information
between CSs uses an arbitrary traffic channel or a dedi-
cated channel as in the case of normal data. SW 140
accumulates the contents of the location registration
notified from each CS in the data base 141 thereof. The
sequence of connection and ccnmunication to the switching
system from each CS is similar to the calling sequence of
CS in the calling sequence from PS described below.
First, explanation will be made about the
sequence of a call from PS1 101.
The sequence of a call from PS1 101 to other
PS connected to SW (network) 140 is shown in Fig. 3.
As shown, first, PS1 101 is assigned with a
link channel from CS1 102 in the same manner as in the
location registration described above (511 to 514). Once
a link channel is assigned, a multi-frame link is set on
the particular link channel in the same manner as in the
location registration described above (515, 516).. A call
set-up message is transmitted to CS1 102 using the
multi-frame link (517). Upon receipt of a call set-up
acceptance indicating the acceptance of the call set-up
(518), the radio management information is sent to CS1
102 (519). CS1 102 determines: the contents set-up for
the radio channel (service channel) to be set using this
radio management information. Also, CS1 102 transmits
the radio management information acceptance to PS1 101
(520). PS1 101, upon receipt of the radio management
information acceptance, transmits an authentication
request signal (521). Upon receipt of an authentication
response indicating the authentication from CS1 102
(522), DISC (523) and UA (524 are exchanged to discon-
nect the multi-frame link. In this process, a radio
channel (service channel) is set up between PS1 101 and
CS1 102.
Upon the authentication completion of PS1 101,
CS1 102 is assigned with a link channel from CS2 103 in
the same manner as in the case of location registration
described above (551 to 554). Upon assignment of a link
channel, as in the location registration described above,
a multi-frame link is set on the particular link channel
(555, 556). Using the multi-frame link thus set, the
call setting message already received from PS1 101 is
sent to CS2 103 (557). Upon receipt of a call setting
acceptance indicating the acceptance of a call set-up
(558), the radio management information is sent to CS2
103 (559). CS2 103 returns the radio management informa-
tion acceptance to CS1 102 (560). CS1 102, upon the re-
ceipt of the radio management information acceptance,
sends an authentication request signal (561) for authen-
tication, and upon the receipt of an authentication re-
sponse indicating the authentication from CS2 103 (562),
DISC and UA are exchanged to disconnect the multi-frame
link (563, 564). Now, a radic channel (service channel)
is setup between CS1 102 and CS2 103. CS1 102 connects
the radio channel with PS1 101 to the radio channel with
CS2 103.
Upon the authentication completion of CS1 102,
CS2 103 transmits a call set-up received from CS1 102 to
"the switching system 140 using an unoccupied one of the
channels with SW 140. Upon receipt of the call set-up
acceptance from SW 140, the channel with SW 140 is con-
nected to the radio channel with CS1 102.
CS1 102 then receives the paging signal and
response sent from the switching system through CS2 103
(565, 566). Once the channel with the called party PS is
established by the call set-up transmitted from PS1 101
through CS2 103 and SW 140 (5567), CS1 102 transmits a
paging signal (525) and RBT ;ring-back tone) (526) and
response (527 ) to PS1 101.
Now, the channel oetween PS1 101 and the
called PS becomes in-communlcation state (528, 568).
Explanation will be made about a call origi-
nated from PS2 100.
In the call origination sequence in this case,
the call origination sequence of PS2 100 registered in
CS2 103 conforms to that from PS2 100 through CS2 103
when CS1 102 in Fig. 3 is replaced by PS2 100.
Now, explanation will be made about the case
in which PS1 101 is called from a PS connected to the
switching system (network) 140.
The sequence in this case is shown in Fig. 4.
In this case, CS2 103 accepts an incoming call
and call set-up message from SW 140 through the channel
with SW 140. The set-up message of SW 140 includes, in
addition to the identifier of PS1 101, all the identifi-
ers up to PS1 101 in the order of call routing. The
switching system 140 selects the shortest route on the
basis of the location information of each CS notified
earlier from each CS and accumulated in the data base
114, and includes in the call set-up message the identi-
fiers of the CSs in the route up to the called party PS.
Upon acceptance of the call set-up message in-
cluding the identifiers of CSL 102 and PS1 101, CS2 103
transmits a incoming call message to CS1 102 using the
logical control channel described above in the presence
of an unoccupied channel, if any (411).
CS1 102 that has received the incoming call
message sets up a link channel, with CS2 103 (412 to 415),
and sets up a multi-frame link (416, 417). Subsequently,
as shown, messages such as paging, response, acknowl-
edgment response are exchangeci in addition to messages
for incoming call response, call set-up, call set-up
acceptance, radio information and authentication (418 to
427). Then, the multi-frame link is released (427, 428).
If there is any unoccupied radio channel that can be used
for connection to PS 1 101, the radio channel (service
channel) is set up with CS1 103. On the basis of the
identifier of PS1 101 included in the call set-up re-
ceived from CS2 103, CS1 102 transmits a incoming call
message to PS1 101 (451).
Then, PS1 101 that has received the incoming
call message, sets up a link channel with CS1 102 (452 to
455), and sets up a multi-frame link (456, 457). Subse-
quently, as shown, messages such as a paging, response
and acknowledgment response are exchanged in addition to
messages for incoming call response, call set-up; call
set-up acceptance, radio information and authentication
(458 to 467), thus setting up 3 radio channel (service
channel) with CS1 102. Fig. 4 shows the case in which
the user of PS1 101 is placed the handset off-hook in
accordance with a call.
On the other hand, ZS1 102 connects the radio
channel assigned to PS1 101 and the radio channel with
CS2 103.
Thus, a channel is established between the
call of PS1 101 and the called party so that the channel
between them becomes in-communication status (470, 431).
Now, explanation will be made about the case
in which PS2 100 is called frcm a PS connected to SW
(network) 140.
The sequence in this case conforms with the
call-incoming sequence to PS2 100 through CS2 103 when
CS1 102 of Fig. 3 replaced by PS2 100. This sequence,
however, corresponds to the case in which the user of PS1
101 is placed the handset off-hook in accordance with a
call.
Explanation was made above about a radio
communication system according to this embodiment.
According to this embodiment, as shown in Fig.
5, a radio communication system can be realized which
comprises at least one CS 204 connected to a switching
system 200, a plurality of CSs 201 to 203 connected to CS
204 by means of a dynamic radio channel assignment and
other CS, and a plurality of PSs connected by means of a
dynamic radio channel assignment to each CS. In this
radio communication system, each radio channel is dynami-
cally assigned with the connection between a CS and a PS
or the connection between CSs. In the shown case, the
location of CS 202 is registered in CS 201, and those of
CSs 201, 203 in CS 204. PSs 211, 212, 213 with the
locations thereof registered in CS 202, therefore, are
connected to SW 200 through CSs 202, 201, 204, while PS
214 with the location thereof registered in CS 203 is
connected to SW 200 through CSs 203, 204.
As described above, according to this embodi-
ment, a radio channel of a CS ased also for accommodating
a PS is utilized only when required to relay between CSs.
In this way, a CS not directly connected to the switching
system is connected to the switching system. A separate
transmission path to SW, therefore, is not required for
each CS.
Also, a CS registers; the. location thereof in
other CSs communicable by a radio channel. Specifically,
according to this embodiment, the same protocol used
between a PS and a CS which are granted mobility is used
also between CSs. Therefore, a protocol processing
section or the like is not required in the CS configura-
tion for relay between CSs.
Some modifications will be explained.
In the above-mentioned radio communication
system, calls may be classified into an emergency call, a
priority call and other types of call, so that a radio
channel is always secured between CSs for emergency and
priority calls. In securing :such a radio channel, two
CSs negotiate each other to determine a radio channel
used for emergency or priority call when one of them
registers the location thereof in the other CS, which
radio channel is not assigned for other than emergency
and priority calls.
By doing so, even a system in which a radio
channel is dynamically assigned can guarantee the; use of
the radio communication system according to the invention
for emergency and priority cai;.s.
Also, a link channel, may be fixedly installed
between CSs. This can be realized by making an arrange-
ment in such a way that the link channel used for loca-
tion registration from one CS to another is fixedly
utilized as a link channel between them. In such a case,
the process of setting a link channel can be saved at the
time of originating call or incoming call described in
the above embodiments.
Also, a memory for storing data temporarily
may be arranged in the CS, and a call exclusive for data
transmission may be handled in the following-described
manner. A radio channel is established between PS and CS
or between CS and CS independently in the order of data
transmission. The data transmitted through a channel
first established is stored in the memory of CS. Upon
establishment of the next channel, the data is read out
of the memory and transmitted.
The data transmission call may be distin-
guished by the flag in the call setting together with
emergency and priority calls.
Each CS can have the. location information of a
plurality of other CSs. At tne same time, the order of
priority can be incorporated in the information.
Each CS may set up a radio channel with other
CSs according to this order of. priority. Specifically,
a CS selects other CSs in the order of priority, and
tries to set up a radio channel with a CS ranking next in
the order of priority until a radio channel can be set up
with a CS selected after accessing prior CSs having no
unoccupied lines.
The present invention is applicable not only
to cordless telephone systems like PHS but also to a
radio communication systems such as cellular telephone
systems and also WLL (Wireless Local Loop) systems with
equal effect.
' CLAIMS': „ „ _
1. A radio communication system comprising;
at least a switching system;
at least a first CS (Cell Site) connected to
said switching system;
at least a second CS not connected to said
switching system; and
a plurality of PSs ;Personal Station);
wherein said first CS includes means for
accommodating a plurality of radio channels that can
dynamically establish the comnunication channel to con-
nect with said PSs and said second CS, and
said second CS includes means for accommodat-
ing a plurality of radio channels that can dynamically
establish the communication channel to connect with said
PSs, said first CS and other second CSs, and for relaying
the radio channels.
2. A radio communication system according to
Claim 1,
wherein said first C3 registers in said
switching system the location information of said PSs and
said second CS connected by reidio channels,
said second CS registers the location informa-
tion of said PSs, said first OS and said other second CSs
connected by radio channels, in said switching system
through said first CS, and
said PSs connected -:d said second CS by radio
channels are connected to said switching system through
said first CS.
3. A radio communication system according to
Claim 2,
wherein said switching system determines the
route between said switching system and said second CS
according to said registered location information when
called party PS is connected to said second CS.
4. A radio communication system according to
Claim 1,
wherein at least a dedicated radio channel is
installed between said first CS and said second CS or
between said second CSs.
5. A radio communication system according to
Claim 1,
wherein said radio communication is conducted
according to RCR STD-28.
6. A radio communication system according to
Claim 2,
wherein said second CS includes means for
storing identifiers of said f. irst CS and said other
second CSs connectable by a r. adio channel and the order
of priority of connection among said CSs, and said second
CS tries to establish a radio channel with other CSs in
accordance with the order of stored priority.
7. A radio communication system according to
Claim 4,
wherein calls are classified into an emergency
call, a priority call, other call, and
said first and second CSs assign said dedicat-
ed radio channel to an emergency call and a priority
call.
8. A radio communication system according to
Claim 1,
wherein said second CS includes means for
storing temporarily data exchanged with said PSs, and
when one channel is established, said second CS receives
the exchanged data, stores them therein temporarily until
the other channel is established, and reads and transmits
the data from said memory means after establishing the
other channel.
9. A radio communication system according to
Claim 3,
wherein said switching system sets the deter-
mined route between the switching system and said second
CS in the call set-up message.
10. In a radio communication system including at
least a switching system, at least a first CS connected
to the switching system and a plurality of PSs, a method
for accommodating at least a second CS not connected to
said switching system, comprising the steps of:
providing said second CS with the function of
routing a plurality of radio channels between said PSs,
said first CS and said other second CSs;
registering in saia switching system the loca-
tion information of said PSs and said second CS connected
to said first CS by a radio channel by said first CS; and
registering the location information of said
PSs, said first CS and said otner second CS connected to
said second CS by a radio channel, in said switching
system through said first CS connected by a radio channel
by said second CS;
wherein said PSs connected to said second CS
by a radio channel are connected to said switching system
through said first CS.

A radio communication system comprises at
least a switching system, at least a first CS (Cell Site)
connected to the switching system, at least a second CS
not connected to the switching system, and a plurality of
PSs (Personal Station). The first CS accommodates a plurality
of radio channels that can be dynamically established
between the PSs and the second CS. The second CS
accommodates a plurality of radio channels that can be
dynamically established between the PSs, the first CS and
other second CS, and has the function of relaying the
radio channels.