U.S. patent application number 09/115095 was filed with the patent office on 2001-08-30 for immediate channel assignment in a wireless system.
Invention is credited to DATTA, PRABIR, HE, XIAOPING, JOSHI, CHANDRA, NOERPEL, ANTHONY.
Application Number | 20010018348 09/115095 |
Document ID | / |
Family ID | 21977639 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010018348 |
Kind Code |
A1 |
JOSHI, CHANDRA ; et
al. |
August 30, 2001 |
IMMEDIATE CHANNEL ASSIGNMENT IN A WIRELESS SYSTEM
Abstract
An approach for immediate channel assignment in a wireless
communications system involves receiving a channel request message
from a wireless transceiver, the channel request message including
a dialed party number; forming an immediate assignment message
including a channel assignment; transmitting the immediate
assignment message to the wireless transceiver; and establishing a
communications channel between the wireless transceiver and a
called party by establishing a channel between the wireless
transceiver and the called party.
Inventors: |
JOSHI, CHANDRA;
(GAITHERSBURG, MD) ; NOERPEL, ANTHONY;
(LOVETTSVILLE, VA) ; HE, XIAOPING; (GERMANTOWN,
MD) ; DATTA, PRABIR; (DELHI, IN) |
Correspondence
Address: |
Patent Docket Administration
Hughes Electronics Corporation
Bldg. 001, Mail Station A-109
P.O. Box 956
El Segundo
CA
90245-0956
US
|
Family ID: |
21977639 |
Appl. No.: |
09/115095 |
Filed: |
July 13, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60052443 |
Jul 14, 1997 |
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Current U.S.
Class: |
455/450 ;
455/455 |
Current CPC
Class: |
H04W 76/10 20180201;
H04W 72/0413 20130101; H04W 72/042 20130101; H04W 74/00 20130101;
H04B 7/19 20130101; H04W 80/00 20130101; Y02D 30/70 20200801; H04B
7/18582 20130101; H04W 28/14 20130101; H04W 84/06 20130101; Y02D
70/164 20180101; H04B 7/18517 20130101; H04B 7/2041 20130101; H04W
52/0216 20130101; H04B 7/18567 20130101; H04B 7/18539 20130101;
Y02D 70/20 20180101; Y02D 70/446 20180101; H04B 7/18543 20130101;
H04W 76/25 20180201; H04B 7/18571 20130101; H04W 52/0203 20130101;
H04B 7/1858 20130101; H04B 7/2125 20130101; H04B 7/18558
20130101 |
Class at
Publication: |
455/450 ;
455/455 |
International
Class: |
H04Q 007/20 |
Claims
What is claimed is:
1. A method for immediate channel assignment in a wireless
communications system comprising: receiving a channel request
message from a wireless transceiver; forming an immediate
assignment message including a channel assignment; transmitting the
immediate assignment message to the wireless transceiver; and
establishing a communications channel between the wireless
transceiver and a called party by establishing a channel between
the wireless transceiver and the called party.
2. The method of claim 1 wherein said receiving said channel
request comprises receiving at least a portion of a called party
number.
3. The method of claim 2 further comprising: determining whether
said at least a portion is a complete called party number;
transmitting to the wireless transceiver an immediate assignment
assignment message with an indication to initiate extended
assignment procedures; and receiving from the wireless transceiver
an extended channel request message comprising a complete called
party number.
4. The method of claim 2 further comprising: transmitting to the
wireless transceiver, through a first gateway, a location update
message directing the wireless transceiver to another gateway;
receiving from the wireless transceiver, through the other gateway,
a confirmation message.
5. The method of claim 4 further comprising: transmitting the
channel request message from wireless terminal; and initiating an
access timer in the wireless terminal in response to the
transmitting of the channel request message.
6. The method of claim 5 further comprising: repeating transmission
of said channel request message in the event a response is not
received by said wireless terminal before expiry of said access
timer.
7. The method of claim 5 wherein said transmitting of said
immediate assignment message to said wireless transceiver comprises
transmitting an immediate assignment message with a pause
indicator, and said method further comprises: receiving in said
wireless terminal said immediate assignment message with said pause
indicator; and initiating a pause timer in response to the
receiving of said immediate assignment message with said pause
indicator.
8. The method of claim 7 further comprising: repeating transmission
of said channel request message in the event a response is not
received by said wireless terminal before expiry of said pause
timer.
9. A system for immediate channel assignment comprising: a wireless
communications system comprising: a gateway receiving a channel
request message from a wireless transceiver, the channel request
message including at least a portion of a called party number,
forming an immediate assignment message including a channel
assignment, transmitting the immediate assignment message to the
wireless transceiver, and establishing a communications channel
between the wireless transceiver and a called party; the wireless
transceiver transmitting to the gateway, the channel request
message including the dialed party number, receiving the immediate
assignment message from the gateway, and establishing the
communications channel between the wireless transceiver and a
called party; and a satellite link passing communications between
the gateway and the wireless transceiver through the satellite.
10. The system of claim 9 wherein said gateway includes: means for
determining whether said at least a portion is a complete called
party number; means for transmitting to the wireless transceiver an
immediate assignment message with an indication to initiate
extended assignment procedures; and means for receiving from the
wireless transceiver an extended channel request message comprising
a complete called party number.
Description
[0001] This application claims priority to U.S. Provisional patent
application Ser. No. 60/052,443, of ______, et al.; filed Jul. 14,
1997, for ______, incorporated herein by reference.
[0002] This patent document relates to a common air interface
described in a series of patent documents filed concurrently
herewith. Related patent documents are: U.S. patent application
Ser. No. 09/______, filed Jul. 13, 1998, of Soleimani, et al.; for
SIGNALING MAINTENANCE FOR DISCONTINUOUS INFORMATION COMMUNICATIONS,
now U.S. Pat. No. ______; U.S. patent application Ser. No.
09/______, filed Jul. 13, 1998, of Joshi, et al.; for SYSTEM AND
METHOD FOR IMPLEMENTING TERMINAL TO TERMINAL CONNECTIONS VIA A
GEOSYCHRONOUS EARTH ORBIT SATELLITE, now U.S. Pat. No. ______; U.S.
patent application Ser. No. 09/______, filed Jul. 13, 1998, of
Roos, et al.; for MOBILE SATELLITE SYSTEM HAVING AN IMPROVED
SIGNALING CHANNEL, now U.S. Pat. No. ______; U.S. patent
application Ser. No. 09/______, filed Jul. 13, 1998, of Noerpel, et
al.; for SPOT BEAM SELECTION IN A MOBILE SATELLITE COMMUNICATION
SYSTEM, now U.S. Pat. No. ______; U.S. patent application Ser. No.
09/______, filed Jul. 13, 1998, of Noerpel, et al.; for PAGING
RECEPTION ASSURANCE IN A MULTIPLY REGISTERED WIRELESS TRANSCEIVER,
now U.S. Pat. No. ______; U.S. patent application Ser. No.
09/______, filed Jul. 13, 1998, of Joshi, et al.; for ERROR AND
FLOW CONTROL IN A SATELLITE COMMUNICATIONS SYSTEM, now U.S. Pat.
No. ______; and U.S. patent application Ser. No. 09/______, filed
Jul. 13, 1998, of Roos, et al.; for SYNCHRONIZATION OF A MOBILE
SATELLITE SYSTEM WITH SATELLITE SWITCHING, now U.S. Pat. No.
______, all of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to channel assignment in a
wireless communications system, and more particularly to immediate
channel assignment in a wireless communications system. Even more
particularly, the present invention relates to channel assignment,
or connection resolution and gateway assignment at an early time in
a signalling phase of a wireless call.
[0004] Wireless communications have increased mobility,
reachability and efficiency in modern society. Most wireless
communications systems are land based systems known as cellular
telephony systems. Cellular telephony systems are based on
terrestrial base stations that together form a network of cells
within which communications between subscriber units and the base
stations are conducted.
[0005] In remote locations, however, or in locations in which a
particular subscriber unit or wireless transceiver is not
authorized to communicate, a wireless transceiver can have little
or no value to its user.
[0006] One solution to the geographic limitations imposed by
terrestrial cellular systems is the satellite based system. In
these systems, a few satellites cover wide areas of the globe with
wireless transceivers operating anywhere within these areas
communicating directly with the corresponding satellites.
[0007] In conventional wireless access communications, whether
cellular, fixed wireless, personal communications services or
satellite-based, a random access channel is an access window in
which the wireless transceiver transmits a short channel request
message of only a few bits. This message is received by a
respective network and used only for contention resolution and
timing synchronization. Since most wireless systems do not support
optimal routing to other gateways, this protocol is satisfactory in
such systems. For systems, however, like satellite systems, with
optimal routing, implementing this approach results in a call setup
time penalty of more than, for example, five seconds.
SUMMARY OF THE INVENTION
[0008] The present invention advantageously addresses the needs
above as well as other needs by providing an approach to immediate
channel assignment in a wireless communication system.
[0009] In one embodiment, the present invention can be
characterized as a method for immediate channel assignment in a
wireless communications system. The method has steps of receiving a
channel request message from a wireless transceiver, the channel
request message including a dialed party number; forming an
immediate assignment message including a channel assignment;
transmitting the immediate assignment message to the wireless
transceiver; and establishing a communications channel between the
wireless transceiver and a called party by establishing a channel
between the wireless transceiver and the called party.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The above and other aspects, features and advantages of the
present invention will be more apparent from the following more
particular description thereof, presented in conjunction with the
following drawings wherein:
[0011] FIG. 1 is schematic diagram illustrating a satellite system
with which teachings of the present invention can be employed;
[0012] FIG. 2 is a signal diagram showing various signals sent
between various hardware and software subsystems in order to effect
channel assignment in the satellite system of FIG. 1 ;
[0013] FIG. 3 is a signal diagram showing various signals sent
between various hardware and software subsystems in order to effect
an extended immediate assignment in the satellite system of FIG. 1;
and
[0014] FIG. 4 is another signal diagram showing signals sent
between various hardware and software subsystems in order to effect
extended immediate channel assignment in the satellite system of
FIG. 1.
[0015] Corresponding reference characters indicate corresponding
components throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] The following description of the presently contemplated best
mode of practicing the invention is not to be taken in a limiting
sense, but is made merely for the purpose of describing the general
principles of the invention. The scope of the invention should be
determined with reference to the claims.
[0017] Referring first to FIG. 1, a block diagram is shown of a
satellite system 10 comprising a wireless transceiver 12, a
satellite link 14, a gateway/network 16 and a public switched
telephone network 18 (PSTN).
[0018] In order to perform optimal routing for mobile originated
calls in the satellite system, as early as possible in a call
signalling flow, a channel request message, transmitted in a random
access channel (RACH), may contain, as an example, up to 15 dialed
digits of a called party's telephone number. These 15 dialed digits
are used by the gateway/network to connect through the public
switched telephone network 18 to the called parties location. Thus,
the channel request message transmitted in the random access
control channel contains enough information to route a call from
the wireless transceiver 12 through the gateway/network 16 into the
public switched telephone network 18, by assigning the wireless
transceiver to an appropriate call channel immediately upon receipt
of the channel request message in the random access control
channel.
[0019] This approach represents a novel use of the random access
control channel, which is normally used only for contention
resolution.
[0020] Two additional aspects of the present embodiment include
adaptation of a new timer, referred to herein as a pause timer,
which is employed in a channel assignment process; and an extended
immediate assignment protocol for those cases in which a called
parties number consists of more than 15 digits, or whatever number
has been defined in the channel request message format for the
communications system within which the teachings of the present
embodiment are employed.
[0021] To further expand on the above discussion, the channel
request message is transmitted within the random access control
channel, as with prior art systems, however, in accordance with
prior art systems, this message is normally a very short burst
containing a larger than normal synch word and about eight bits of
a random code. The larger synch word helps the network synchronize
and demodulate the burst, while the eight random bits are echoed
back to the wireless transceiver. The random bits are there to
resolve contention in the case of two or more wireless transceivers
transmitting bursts in the random access control channel
simultaneously. In this way the wireless transceivers (assuming
there are two or more wireless transceivers transmitting bursts in
the random access control channel simultaneously) are able to
determine to which wireless transceiver the immediate assignment
message is directed. In accordance with the present embodiment, the
gateway/network 14 also sends back an immediate assignment message
assigning the wireless transceiver 12 to a traffic channel.
Furthermore, the gateway/network 16 measures the difference in time
between actual receipt of the channel request message and a
targeted time in which the wireless transceiver 12 intended the
message be received by the gateway/network 16. This time is
reported back to the wireless transceiver 12 along with a channel
assignment in an immediate assignment message so that the wireless
transceiver 12 can connect its corrected time of transmissions so
as to be synchronized with the gateway/network.
[0022] The wireless transceiver 12 executes a procedure referred to
herein as a random access procedure whereby, in the case of
collisions, the wireless transceiver 12 retransmits the channel
request message. The wireless transceiver 12 starts a timer when it
launches the channel request message, and if it does not receive a
response from the gateway/network 16 before the timer expires, the
wireless transceiver 12 assumes that the first transmission was not
properly received by the gateway/network 16, either because of a
fade or because of a collision with another wireless transceiver's
20 channel request, or for some other reason. The wireless
transceiver 12 then calculates another transmission time within the
random access control channel, with a random element to avoid
repeated collisions and retransmits the random access message.
[0023] Ideally the retransmission timer should be short so that the
channel request is not overly delayed. In conventional systems,
this timer is normally only a little bit longer than a roundtrip
propagation delay in the satellite system, plus some modest
processing time allowance.
[0024] In accordance with the present embodiment, the
gateway/network 16 also sends back an immediate assignment message
assigning the wireless transceiver 12 to a traffic channel. In
accordance with the present approach to the immediate assignment of
channels, the channel request message, in addition to all the
normal functions it is performing, i.e., contention resolution and
timing correction, also transmit to the gateway/network 16
information needed by the network to route the call optimally. In
accordance with the present embodiment, the gateway/network 14 also
sends back an immediate assignment message assigning the wireless
transceiver 12 to a traffic channel.
[0025] In the case of wireless transceiver 12 originated calls,
this means that the channel request message can contain the dialed
digits or the called party number. The gateway/network 16, upon
receipt of this burst in the random access channel, analyzes the
dialed digits and determines a best gateway through which to route
the calls so that the network facilities used to connect the call
are minimized.
[0026] In contrast, in a conventional approach, the wireless
transceiver 12 is assigned to a channel at the current gateway, and
proceeds with call establishment signalling. This entails
establishing a data link layer connection, radio resource layer
connection and finally a mobility management connection. During
this time the wireless transceiver 12 is authenticated and cipher
mode is established. The wireless transceiver 12 then transmits a
setup message that contains the call party number as an information
message. This information message is conveyed directly to a switch
for digit analysis. It is at this point that the gateway/network
recognizes that the call may need to be routed to another gateway.
At least five or more seconds may have elapsed under this approach
before the gateway selection process takes place. Unfortunately, if
a wireless transceiver is to be reconnected to another gateway,
this entire process must be repeated adding to the call setup
delay.
[0027] Advantageously, the approach of the present embodiment
allows the network to receive the dialed digits early and perform
gateway selection before the data link layer is established and
other signalling procedures take place. While this procedure
greatly reduces call setup time, the digital analysis and gateway
selection time take a variable amount of time, depending on the
number of the called party and the contents of the channel request
message. For example, the called party may be a wire line (or land
line) telephone associated with the public switched telephone
network 18, which is immediately connected to the gateway receiving
the channel request message. In this case, the digit analysis
proceeds rapidly and the immediate assignment message can be
dispatched very quickly. In contrast, if the called party is
another wireless transceiver, and this other wireless transceiver
is roaming, the home location register (HLR) of the roaming
wireless transceiver must be queried and other network signalling
may need to take place in order to locate the called party before
an optimal gateway can be selected and the link appropriately
routed. The gateway selection time thus may vary from a few tens of
milliseconds to several seconds.
[0028] Thus, a contention resolution timer must be set for a
maximum time in order to avoid cases where it prematurely expires,
causing the wireless transceiver 12 to transmit more random access
control channel bursts unnecessarily. An affect of these
unnecessary retransmissions of random access channel bursts would
be to cause congestion on the random access control channel. To
avoid this problem, the present embodiment employs a new channel
request timer referred to herein as a pause timer. The use of the
pause timer is illustrated in FIG. 2.
[0029] Referring next to FIG. 2, a timing diagram is shown of
message traffic between the wireless terminal 12 and the
gateway/network 16 operating in accordance with one embodiment of
the present invention. As shown, a channel request message 30 is
sent with a called party number as discussed above.
[0030] After transmission of the channel request message 30 an
access timer T.sub.a3 is set. The access timer T.sub.a is a short
time period allowing only for propagation delay and some modest
processing time, such as in a similar timer employed in the prior
art. If the gateway/network 16 can analyze the called party number
rapidly because of the nature of the called party number, the
gateway/network 16 transmits an immediate assignment message 32
with the channel assignment, timing connection and random access
resolution well before the access timer T.sub.a expires. On the
other hand, if due to the nature of the called party number,
gateway selection for optimal routing cannot take place very
quickly, the immediate assignment message 32 resolves the random
access by correctly responding to the wireless transceiver on the
Access Grant Channel (AGCH), but instead of assigning a channel or
gateway, commands the wireless transceiver 12 to start a much
longer pause timer T.sub.p. This pause timer T.sub.p gives the
gateway/network 16 more time to perform gateway selection and
prevents the wireless transceiver 12 from needlessly clogging the
random access control channel with unnecessary messages. A second
immediate assignment message 34 is later sent with a gateway
selection information.
[0031] If a wireless transceiver's access timer T.sub.a does expire
before receipt of a first immediate assignment message, it is
because of collision, fading or some unusual cause. The wireless
transceiver 12 will initiate retransmission in this event.
[0032] Another aspect of the present embodiment is referred to
herein as the extended channel request procedure. A channel request
message cannot be set overly long to accommodate the number of
dialed digits, because of physical constraints, for example, the
limit of the satellite system may be about 15 digits. For cases
where the teachings of the present embodiment apply to other
satellite systems, this limit might be different, but the concepts
disclosed herein are equally applicable.
[0033] In a case where the called party number is larger than the
capacity of the channel request message for the satellite system to
which the present embodiment is applied, the wireless transceiver
12 transmits all of the digits of the called party number that will
fit into the channel request message. Because this number of digits
is not all of the digits in the called party number, the
gateway/network cannot be able to perform digit analysis and proper
gateway selection 32. In this case, the immediate assignment
message instructs the mobile to perform the extended channel
request procedure as described below.
[0034] On receipt of the immediate assignment message, with an
indication to initiate extended assignment procedures, because
fewer than all of the digits of the called party number were
transmitted in the initial channel request message 30, and an
assignment of an SSDCCH (Standalone Duplicate Control Channel) from
the network, the wireless transceiver initiates the extended
immediate assignment procedure as follows:
[0035] stop the access timer T.sub.a;
[0036] correct timing in the wireless transceiver according to
feedback received from the gateway/network in the immediate
assignment message 32;
[0037] send an extended channel request message 40 (with complete
information, including all the digits of the called party number)
on the assigned SDDCH after establishing the multiframe
transmission made or (See FIG. 3.);
[0038] start the access timer T.sub.a; and
[0039] start to listen on the downlink of the assigned SDCCH while
waiting for response from the gateway/network 16 or expiration of
the access timer T.sub.a.
[0040] The gateway/network 16 in accordance with the present
embodiment allocates a traffic channel to the wireless terminal 12
by sending in an extended immediate assignment message 42 in an
acknowledged mode on the assigned SDCCH, (as shown in FIG. 3).
[0041] Note that the gateway/network 16 sends back the extended
immediate assignment message 42 only when the information received
is not sufficient, i.e., when fewer than all the digits of the
called party number.
[0042] Referring to FIG. 4, if the extended immediate assignment
message contains an indication for a location update (LU) service
request, then the wireless terminal shall:
[0043] stop the access timer T.sub.a if it is ever started;
[0044] activate the new assigned channel;
[0045] compare the length of a layer three message with the size of
user information field of the assigned channel (the wireless
terminal transfer the layer three information to the data link (DL)
to initiate a link based on the channels assigned to it);
[0046] if the size of the assigned channel (user information field)
is equal or greater than the size of the layer three message, the
wireless terminal shall request that the DL to initiate a link
establishment by issuing a DL_EST_REQ primitive with the layer
three message, and on establishment of the link, the wireless
terminal shall issue a RR_EST_CNF 50 primitive in response to a
RR_EST_REQ to the mobility management (MM) for the establishment of
the wireless terminal connection; and
[0047] if the size of the assigned channel (user information field)
is less than the size of the layer three message then the wireless
terminal shall request the DL to initiate a link establishment
procedure by issuing the DL_EST_REQ 52 primitive with only unique
information such as mobile identify within it, and on establishment
of the link, the wireless terminal shall transfer the layer three
message to the DL with the DL_DATA_REQ 54 primitive and issue a
RR_EST_CNF 56 primitive in response to a RR_EST_REQ 58 to the MM
for establishment of the wireless terminal connection.
[0048] If the extended immediate assignment message 42 contains an
indication of location update (LU) request, then the wireless
terminal shall:
[0049] stop the access timer T.sub.a;
[0050] activate the new assigned channel;
[0051] force the mobility management (MM) layer to institute a
location update procedure (it sends an RR_EST_CNF primitive 50 to
indicate establishment of the RR connection and indicate to the MM
the identity of the AT (IMSI). If it is unknown in the visitor
location register (VLR), RR (radio resource) sending release
indication to mobility management, by sending the RR_DATA_IND
primitive 60 and RR_REL_IND primitive 62, and the RR_DATA_IND
primitive 60 carries a CM service reject message (with a reject
cause value of 4 IMSI is unknown in visitor location register), and
the RR_REL_IND primitive 62 indicates normal release. Then,
mobility management asks to establish RR link to perform location
updating procedure.
[0052] RR receives an RR_EST_REQ primitive 58 with a layer three
message (location update request);
[0053] RR compares the length of the layer three message with the
size of the user information field of the assigned channel, and the
wireless transceiver shall transfer the layer three information to
the data link (DL) along with the type of channel assigned to
it;
[0054] if the size of the assigned channel (user information) is
equal or greater than the size of the layer three message, the
wireless transceiver shall request the DL to initiate a link
establishment procedure by issuing a DL_EST_REQ primitive 52 with a
layer three message, and on establishment of link the wireless
transceiver shall issue a RR_EST_CNF 56 primitive in response to
the RR_EST_REQ 58 to the MM for the establishment of the wireless
transceiver connection;
[0055] if the size of the assigned channel (user information) is
less than the size of the layer three message, the wireless
transceiver shall request the DL to initiate a link establishment
procedure by issuing a DL_EST_REQ 52 primitive with only unique
information such as a mobile identity, and on establishment of the
link the wireless transceiver will transfer the layer three message
to the DL with a DL_DATA_REQ primitive 54 and issue a RR_EST_CNF
primitive 56 in response to the RR_EST_REQ 58 to the MM for the
establishment of the wireless transceiver connection.
[0056] In case the gateway/network fails (access is denied, or no
channel) to assign the channel, the gateway/network sends an
extended immediate assignment reject message (not shown) to the
wireless transceiver. On receipt of the extended immediate
assignment reject message, the wireless transceiver stops the
access timer.
[0057] The wireless transceiver stops sending the extended channel
request messages, returns to the auto mode, and indicates to the MM
layer a failure to establish a wireless transceiver connection by
using a RR_REL_IND primitive in response to a RR_EST_REQ primitive
58, and starts to listen for messages broadcast, for example, in
the paging channel of the broadcast control channel, by the
gateway/network.
[0058] If the access timer T.sub.a expires without receiving a
correct response from the gateway/network, the wireless terminal
repeats transmission of the extended channel request message.
[0059] The wireless terminal maintains a count of the total number
of transmission steps made during execution of the extended
immediate assignment procedure (retries). When the value of a retry
counter exceeds a counter broadcast over the broadcast control
channel, the wireless transceiver reports failure to establish a
link to a layer 3 by sending an RR_DL_IND primitive and returns to
idle mode.
[0060] Table I shows a message format for an exemplary extended
channel request message.
1 EXTENDED CHANNEL REQUEST Information Format Element Type Presence
Length Reference Protocol V M 1/2 Discriminator Skip V M 1/2
Indicator Message Type V M 1 Type of V M 1/2 Number Numbering V M
1/2 Plan ID Priority V M 1/2 Service V M 2 1/2 Provider ID Re-Try V
M 1/2 Counter Number LV M 12 Digits AT Power V M 1/2 Class Rest
Octect V M 5
[0061]
2 Information Format Element Type Presence Length Reference
Protocol V M 1/2 Discriminator Skip V M 1/2 Indicator Message Type
V M 1 AT Info Flag V M 1 Channel V M 4 Description Timing V M 2
Correction Power V M 1 Correction Frequency V M 1 Correction Rest
Octect V M 13
[0062]
3 EXTENDED IMMEDIATE ASSIGNMENT REJECT Information Format Element
Type Presence Length Reference Protocol V M 1/2 Discriminator Skip
Indicator V M 1/2 Message Type V M 1 Cause V M 1 Rest Octect V M
21
[0063] In accordance with the present embodiment, several
variations of the above procedures are available. ATCH/3 may be
sent back to the AT on an immediate assignment. TCH/3 is used to
send in the extended channel request by the AT. This would normally
be sent over two or three segments, since the segment size for
TCH/3 is at most 7 bytes. The benefit of this approach is that a
deallocation message is not required for the TCH/3 given on the
immediate assignment since it can be used for non-signalling
traffic.
[0064] SDCCH/4 represent four users that share one physical channel
(same carrier with same time slot allocation) and may be sent back
to the AT on the immediate assignment. In this case a SDCCH
(standalone dedicated control channel) is used to send the extended
channel request by the AT. The advantage of this approach is that
this will most likely not be sent over just one segment, since
segment size of SDCCH/4 is about 28 bytes, in accordance with the
embodiment described herein. However, ATCH/3 is most likely sent
back in the extended immediate assignment since all network
operation (e.g., the gateway selection) was performed. This is
similar to the regular immediate assignment described above.
[0065] One solution is to let the GSS retain information on the
DCCH (dedicated control channel), and when the GSS receives
confirmation that the TCH/3 is being used, it sends a deallocate
SDCCH message through the TCH. In the GSS, this event is triggered
by receiving a CM service request message from the AT.
[0066] Another solution is the GSS to keep a timer, such that when
the timer expires the SDCCH is deallocated.
[0067] The preferred solution is the GSS to keep a timer for
deallocation of the SDCCH, because it is simple to implement (GSS
already implements a timer, no changes are required to the TCS), it
eliminates indirection of new message, and works well for optimal
routing (no gateways involved in a call setup).
[0068] The entire procedure can be simplified by sending the
additional information and channel request message with a larger
size random access channel burst. This burst requires only a change
of the physic level and avoids all complexities.
[0069] Except in the TT call immediate assignment procedure, the
AT(O) sends channel requests on the random access control channel
with the called party number, and waits for the immediate
assignment on the access grant channel (AGCH) of the corresponding,
control channel (CCCH).
[0070] On the gateway/network site, on receipt of the channel
request message, the TCS(O) determines whether or not the called
party number is a satellite transceiver or cellular number or a
public switch telephone network number by analyzing the received
called party number. In case the called party number is either a
satellite system number or a cellular system number, the TCS(O)
sends an immediate assignment message with a pause indication to
AT(O). The TCS(O) interrogates the called party HLR (satellite
gateway/network HLR) to determine the current location of the
called AT(T), i.e., the MSC IT of the AT(T).
[0071] The TCS(O) validates and assigns resources to the GSC(OL).
The GSC(OL) activates the resources and acknowledges the TCS(O).
The TCS(O), on receipt of acknowledgement of the resources,
computes timing, frequency, and power correction for the AT(O) and
assigns the allocated traffic channel to the AT(O) by sending the
immediate assignment (pause=false) the corresponding common control
channel with an indication of a CM service request procedure. The
GSC(OL) gets a spare TCH and a reserve TTCH channel and uses them
at the time of single hop connection. At the GS(O), the TCS(O)
assigns the resources and transfers the "call reference ID" to the
select GSC(OL) to identify the originating side of the TtT call.
The AT(O), on receipt of the immediate assignment (pause=false)
message activates the assigned channel and indicates a link
establishment procedure on the assigned (TCH) channel. In this
procedure, the AT(O) sends a set of asynchronous balance mode
(SABM) message, and the GSC(OL) sends an unnumbered acknowledgement
(UA) message in response to the SABM message. Successful completion
of the link establishment, the wireless terminal connection is
known to be established between the AT(O) and the GS(O).
[0072] While the invention herein disclosed has been described by
means of specific embodiments and applications thereof, numerous
modifications and variations could be made thereto by those skilled
in the art without departing from the scope of the invention set
forth in the claims.
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