Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
2002-10-25
2004-01-20
Cumming, William (Department: 2684)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
Reexamination Certificate
active
06681118
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a digital wireless communication system. In particular, the invention relates to cordless telephones and cellular networks.
BACKGROUND
A common type of wireless communication is the communication which occurs between a cordless telephone handset and its associated base unit within a limited distance range around the user's home or business. Cordless telephones typically operate over a radio frequency (RF) portion of the spectrum set aside for general public use. Also, the power of the cordless phone signal is lower than other communication signals, because the signal needs to only be transmitted between the cordless handset and the associated base unit within the home or business of the user. Therefore, there is no user license from the Federal Communications Commission (FCC) required to operate a cordless telephone. Ultimately the communication is carried from the associated base unit along a landline on the public telephone network to the connecting party; therefore the cost of the telephone call is regulated by the LEC which owns the public switched telephone network (PSTN).
Another method of wireless communication is a regional cellular communication network which is operated by a cellular operator to enable the transmission of voice and data from a mobile station to a cellular base station over a specific band of frequencies, e.g., 824-849 MHz and 869-894 MHz, under license by the FCC. The bands are generally broken up into transmission channels and reception channels which each employ different bands of frequencies in the cellular spectrum. Cellular transmissions from the base station to the mobile station occupies the spectrum between 824 and 849 MHz with each transmission channel occupying about 30 KHz Cellular reception from the mobile stations to the base stations generally occupy the spectrum between 869 and 894 MHz with each reception channel occupying about 30 KHz. As is well known to those of ordinary skill in the art, each of the transmission and reception bands are divided between two cellular service providers in each market and are referred to as “A” and “B” bands. Thus, each provider operates four hundred and sixteen pairs of transmission and reception frequency channels on which to provide service. Twenty-one of the four hundred and sixteen frequency channels pairs are ordinarily used as control channels to send control signals from the base station to the mobile station, thus only three hundred and ninety-five channels are actually available to transmit calls between the cellular base station and mobile station. The cellular service provider enlists subscribers who are authorized to communicate via the regional cellular network. Each subscriber must purchase a mobile station or handset which is capable of communication with the regional cellular network. The handset, at the time of manufacture, is assigned an electronic serial number (ESN). The ESN is generally stored in the permanent memory, such as an EEPROM, in the handset. The subscriber registers the mobile station with the regional cellular network and the mobile station is assigned a mobile identification number (MIN) by which the mobile station can be accessed. As the price of mobile stations decreases and the cost of air time decreases, the number of users that subscribe to regional cellular networks is increasing.
Recently, handsets have been disclosed which are capable of switching between communication with a cellular network and with an RF cordless telephone until Once the handset is in the proximity of the cordless telephone unit, the telephone unit is capable of receiving calls from both the public switched telephone network (via the RF cordless telephone unit) and the regional cellular network. Since the cellular and RF cordless communication systems utilize different frequency bands for communication, a handset that can communicate with both cellular and RF cordless base stations requires some significant additional hardware and software. In practice, a handset that can communicate with both types of base stations requires one transceiver that can communicate with cordless frequencies and one transceiver that can communicate with cellular frequencies as well as separate interface hardware between each transceiver and the main handset controlling hardware. Further, the main handset controlling hardware must be able to recognize and communicate with the different communications protocols required to communicate with the RF cordless telephone base station and with the cellular networks. The additional hardware required to communicate with both base stations increases the size and the weight of the handset. Further, the additional hardware increases the cost of the handset in a highly price-competitive market.
SUMMARY
The preferred embodiment of the present invention comprises a cordless cellular base system. A cordless cellular base station is capable of communicating with a cellular network compatible mobile unit, also referred to as a mobile station herein. The cordless cellular base station, also referred to as a subregional basestation, is preferably connected to a landline on a public switched telephone network and is assigned a landline number or phone number. The mobile station is registered with a cellular network and is assigned a mobile identification number. Advantageously, the mobile station is capable of communication with both a conventional regional cellular base station and to the cordless cellular base station utilizing the same cellular frequency range and communications protocol. When the mobile station is communicating with the cellular network, it is referred to as being in the regional cellular service mode. When the mobile station is communicating with the cordless cellular base station, it is referred to as being in cordless cellular telephone landline service mode.
The mobile station of the present invention advantageously communicates with the cordless cellular base station and with the regional cellular base stations of the cellular network utilizing the same frequency range and the same communications protocol. In a preferred embodiment, the communications protocol that is utilized is compliant with the IS-136, parts one and two, air interface standard which is hereby incorporated by reference in its entirety. The IS-136, parts one and two, standard is available from the Telecommunications Industry Association (TIA), Engineering Dept., 2001 Pennsylvania Avenue, N.W., Washington, D.C. 20006. This standard provides in part for TDMA (time division multiple access) digital communications and is well known to those of skill in the art The IS-136 standard is designed to ensure compatibility between cellular mobile telecommunication systems so that a mobile station can obtain service in any cellular system manufactured in accordance with the standard. Since the mobile station communicates with the cordless cellular base station and with the regional cellular base stations of the cellular network utilizing the same frequency range and the same communications protocol, the mobile station may be manufactured using similar hardware, such as a digital transceiver, and similar software to communicate with both the cordless cellular base station and the cellular network. Therefore, the overall size and the weight of the mobile station is not increased compared to conventional cellular telephones which are compatible with the IS-136 standard. Further, by reducing the amount of additional hardware and additional software necessary, the cost of the mobile station of the preferred embodiment is not much higher than conventional IS-136 compliant mobile stations. The cordless cellular base station is able to communicate with the mobile station and act as a conduit between the mobile station and the public switched telephone network. Further, despite the fact the mobile station is IS-136 compliant and can communicate with both analog and digital regional cells, the mobile station preferably communicates with the cordless cellular ba
Bamburak Michael D.
Glass David R.
Jarett Keith
Kibria Masud
Lawrence Christopher G.
AT&T Wireless Services Inc.
Cumming William
Perkins Coie LLP
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