Telecommunications – Radiotelephone system – Auxiliary data signaling
Reexamination Certificate
1999-02-05
2001-04-24
Urban, Edward F. (Department: 2683)
Telecommunications
Radiotelephone system
Auxiliary data signaling
C455S433000, C455S412100, C455S458000
Reexamination Certificate
active
06223045
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to a method of delivering Short Message Service (SMS) messages to a mobile station via a satellite air interface radio link in a radio telecommunications network.
2. Description of Related Art
FIG. 1
is a simplified block diagram of an existing satellite system based on a Global System for Mobile Communications (GSM) radio telecommunications network
10
illustrating the network nodes involved in delivering SMS messages to a mobile station
13
. A satellite link is shown to include a satellite gateway
11
, a communication satellite
12
, and the MS
13
which may be partially shielded within a structure
14
. Within the gateway
11
, a Mobile Switching Center/Visitor Location Register (MSC/VLR)
15
is connected to a Base Station Subsystem (BSS)
16
via an A-interface
17
. The BSS is modified for use with satellites, and is connected to a Radio Frequency Terminal (RFT)
18
via, for instance, a modified Abis interface
19
. The RFT
18
includes an antenna system for tracking and communicating with the satellite
12
. The satellite
12
provides an air interface link from the gateway
11
to the MS
13
. A feeder link
21
(from the gateway
11
to the satellite
12
) typically operates in the Ku-band. A downlink
22
(from the satellite to the MS) typically operates in the Ku-band or L-band. Different bands have different propagation characteristics depending, for instance, on rain attenuation. There is some attenuation of the signal on all bands if the mobile station antenna is not deployed, or if the mobile station
13
is located inside a building.
The network
10
also includes a SMS Service Center (SMS-SC)
23
, a Short Message Gateway Mobile Switching Center (SM-GMSC)
24
, a Home Location Register (HLR)
25
, and a Short Message Interworking Mobile Switching Center (SM-IWMSC)
26
to handle outgoing messages from the network
10
.
The air interface link includes a plurality of logical channels such as traffic channels, broadcast channels, dedicated control channels, and various associated channels. In the normal GSM architecture, there is also a single paging channel which accommodates various paging methods using different algorithms such as, for example, global paging, repeated paging, and so forth. Paging over a satellite link, however, poses additional problems which are not typically encountered by paging systems in cellular telecommunications networks. When paging over a satellite link, there is increased attenuation of the signal due to the distance the signal must travel, water vapor in the air, and various power limits imposed on the satellite transceiver. By the time the paging signal reaches the ground, it is likely that the signal will not penetrate walls or other obstructions such as wet foliage.
To address this problem in the past, satellite networks have typically either utilized a higher power level on the satellite, or a separate logical channel has been defined which utilizes different channel coding. Utilizing higher power on the satellite is a problem because satellites are typically power-constrained. The available power on the satellite is one of the major constraints on its throughput, and high power cannot be used for every page because this would decrease the amount of total traffic that the satellite can handle. Therefore, higher power levels are generally utilized sparingly. If a separate logically channel is defined and utilized for paging, it creates other problems because this method is less effective than raising the power level, and less information can be carried by the paging signal since additional coding must be used on the channel.
Satellite paging systems also suffer from reliability problems caused, once again, by the attenuation of the signal and the inability to page the mobile station when the mobile station is in a disadvantaged mode (i.e., the mobile station is in a shielded location and/or the mobile station antenna is not raised). This can lead to lost messages or, if the network takes corrective action as described below, the same message may be delivered more than once.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a method of paging mobile stations in a satellite radio telecommunications network which uses high power paging only when needed, and conserves satellite power by using lower power at other times. In addition, it would be advantageous for such a paging system to reliably deliver SMS messages to the paged mobile station without delivering the same message more than once. The present invention provides such a method.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a method of sending a short data message to a mobile station operating in a radio telecommunications network. The network includes a mobile switching center/visitor location register (MSC/VLR) serving the mobile station. The method includes the steps of sending the message from a message service center to a paging server associated with the MSC/VLR, storing a copy of the message in the paging server, sending the message from the paging server to the MSC/VLR, and delivering the message from the MSC/VLR to the mobile station via an air interface radio link. The paging server may be co-located with the MSC/VLR or may communicate with it using a communication protocol such as Mobile Application Part (MAP).
In another aspect, the present invention is a method of sending a short data message to a mobile station operating in a radio telecommunications network having a mobile switching center/visitor location register (MSC/VLR) serving the mobile station. The method includes the steps of sending the message from a message service center to a paging server associated with the MSC/VLR, storing a copy of the message in the paging server, sending the message from the paging server to the MSC/VLR, and making a first attempt to deliver the message from the MSC/VLR to the mobile station via an air interface radio link. This is followed by sending the message a second time from the message service center to the paging server, determining in the paging server whether the message received the second time has already been sent to the MSC/VLR, and discarding by the paging server, the message received the second m 1Utime upon determining that the message has already been sent to the MSC/VLR.
In yet another aspect, the present invention is a paging server in a radio telecommunications network having a Short Message Service (SMS) service center, a mobile switching center/visitor location register (MSC/VLR) which serves a mobile station, and an air interface radio link between the MSC/VLR and the mobile station. The paging server includes means for receiving from the SMS service center a SMS message directed to the mobile station, and a memory for storing the received SMS message. An interface between the paging server and the MSC/VLR includes means for sending the received SMS message to the MSC/VLR, and means for receiving messages from the MSC/VLR indicating whether the SMS message was successfully delivered to the mobile station. The paging server also includes means for comparing received SMS messages with SMS messages already stored in the memory, and means for discarding received SMS messages that are already stored in the memory.
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patent: 5590396 (1996-12-01), Henry
patent: 5628051 (1997-05-01), Salin
patent: 5719918 (1998-02-01), Serbetciouglu et al.
patent: 5884170 (1999-03-01), Valentine et al.
patent: 5943399 (1999-08-01), Bannister et al.
patent: 5966663 (1999-10-01), Gleason
patent: 6014429 (2000-01-01), LaPorta et al.
patent: 6057782 (2000-05-01), Koenig
Davidson Lee
Valentine Eric
Ericsson Inc.
Jackson Blane J.
Navarro Arthur I.
Urban Edward F.
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