Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-12-01
2004-06-08
Chin, Vivian (Department: 2682)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S560000, C455S003010, C455S445000, C379S207110, C379S220010
Reexamination Certificate
active
06748239
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to communications methods and apparatus, and more particularly, to methods and apparatus for communicating facsimiles and data. Wireless communications systems are commonly employed to provide voice and data communications to subscribers. For example, analog cellular radiotelephone systems, such as those designated AMPS, ETACS, NMT-450, and NMT-900, have long been deployed successfully throughout the world. Digital cellular radiotelephone systems such as those conforming to the North American standard IS-54 and the European standard GSM have been in service since the early 1990's. More recently, a wide variety of wireless digital services broadly labeled as PCS (Personal Communications Services) have been introduced, including advanced digital cellular systems conforming to standards such as IS-136 and IS-95, lower-power systems such as DECT (Digital Enhanced Cordless Telephone) and data communications services such as CDPD (Cellular Digital Packet Data). These and other systems are described in
The Mobile Communications Handbook
, edited by Gibson and published by CRC Press (1996).
FIG. 1
illustrates a typical terrestrial cellular radiotelephone communication system
20
. The cellular radiotelephone system
20
may include one or more radiotelephones (mobile terminals)
22
, communicating with a plurality of cells
24
served by base stations
26
and a mobile switching center or mobile telephone switching office (MTSO)
28
. Although only three cells
24
are shown in
FIG. 1
, a typical cellular network may include hundreds of cells, may include more than one MTSO, and may serve thousands of radiotelephones.
The cells
24
generally serve as nodes in the communication system
20
, from which links are established between radiotelephones
22
and the MTSO
28
, by way of the base stations
26
serving the cells
24
. Each cell
24
will have allocated to it one or more dedicated control channels and one or more traffic channels. A control channel is a dedicated channel used for transmitting cell identification and paging information. The traffic channels carry the voice and data information. Through the cellular network
20
, a duplex radio communication link may be effected between two mobile terminals
22
or between a mobile terminal
22
and a landline telephone user
32
or another wireless communication network through a public switched telephone network (PSTN)
34
. The function of a base station
26
is to handle radio communication between a cell
24
and mobile terminals
22
. In this capacity, a base station
26
functions as a relay station for data and voice signals.
Recently, wireless communications systems have seen an increasing demand for services other than voice, including facsimile and data transmission associated with features such as internet access. Each of these services typically has different performance requirements. For example, facsimile systems are widely used to transmit images, typically of documents, from one location to another. Conventionally, a document is scanned by a “fax machine” to convert it into facsimile data which is then transmitted over a communications channel, typically a voice channel on the PSTN. The document is then reconstructed into hard copy from the transmitted facsimile data by a similar facsimile machine located at the other end of the communications channel.
Standard communications protocols have been developed for transmission of facsimile data. Older analog protocols, such as CCITT Group 1 and Group 2, are now generally obsolete. The digital CCITT Group 3 protocol, widely used by conventional office and home facsimile machines, uses digital modems transmitting digital facsimile data at speeds up to 9600 baud over conventional PSTN telephone lines. The Group 3 protocol includes handshaking and signal quality evaluation features which enable facsimile machines to step down the communication baud rate if the communications channel exhibits poor quality. A CCITT Group 4 protocol has also been established to provide less error-prone communication between facsimile machines over public data networks other than the PSTN.
Because of the increased mobility it offers, cellular radiotelephone technology is increasingly supplanting or being used in addition to the PSTN for many facsimile and data communications applications. Mobile cellular radiotelephones are now a common sight in businesses, home, and automotive environments. Personal computers have also been adapted for use with cellular radiotelephone communications systems, exchanging the wireline modem for a similar device acting over a cellular radiotelephone voice or data channel. In addition, wireless terminal devices have been introduced, referred to as Single Line Terminals (SLT), which provide an RJ-type interface typically associated with a PSTN to the user while utilizing a wireless communication link to the destination device for a call or, alternatively, to a PSTN which services the destination device.
One obstacle to implementation of facsimile communications over cellular radiotelephone communications systems is the generally lower bandwidth, lower signal quality, and higher communications costs which may be associated with cellular radiotelephone channels in comparison to conventional PSTN channels. One approach to providing more reliable radio transmission of facsimile data using packet data protocols with checking and retransmission features is described in U.S. Pat. No. 5,282,238 to Berland. An approach to sending faxes over analog cellular networks is described in U.S. Pat. No. 5,752,199 to Scott. Each of these approaches proposes ways to improve performance of facsimile transmission when a wireless channel is provided for this purpose.
The IS-136 communication standard, which provides for both analog and digital communication support, specifically supports Group 3 type facsimile transmissions. Under the IS-136 standard, a mobile terminal requesting communication access typically provides the communication network a service code. The service code may, for example, request analog speech, digital speech, analog or digital speech with a specified preference, asynchronous data or Group 3 type facsimile services from the IS-136 network. On receipt of a Group 3 facsimile service code, under the IS-136 standard, the communication system determines if a digital traffic channel is available.
Unfortunately, the PSTN in most locations does not support the transmission of a service code. Therefore, a problem is encountered with transmissions of data or facsimiles where the transmission path includes use of the PSTN to couple two wireless communication networks using service codes, such as two IS-136 systems. One proposed solution utilizes two stage dialing to provide a pilot number for transmission over the PSTN to communicate service code information. An example of two stage dialing is illustrated in FIG.
2
.
As shown in the schematic illustration of
FIG. 2
, two stage dialing is provided for call setup because PSTN signaling typically does not support delivery of the service code which is, for example, on the IS-136 protocol, mandatory. Accordingly, the source device attempting to establish a channel to communicate data or a facsimile image
200
first transmits a pilot number to a wireless device such as the SLT
210
. The pilot number carries service code information for the over air protocol, (such as IS-136,) as it is coherently related to the available service codes (i.e., a one to one unique correspondence is provided between pilot numbers and service codes supported by the over air protocol).
The single line terminal
210
receives the pilot number, determines the appropriate service code for the over air protocol and provides both the pilot number and the service code to the mobile switching center
28
. The mobile switching center
28
provides a dial tone to the FAX/PC device
200
through the SLT
210
. In other words, after receipt of the service code and pilot number from the SLT
210
Chin Vivian
Ericsson Inc.
Myers Bigel & Sibley & Sajovec
Yun Eugene
LandOfFree
Methods and systems for communicating service codes over a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods and systems for communicating service codes over a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods and systems for communicating service codes over a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3364350