1. Field of Invention
The present invention relates to an improved wireless communications system. More particularly, the preferred embodiment of the invention concerns a multiple mode communications system, including special handsets designed to operate with standard analog or digital protocols when within the coverage of a standard cellular radiotelephone network, and to automatically switch to an enhanced cordless mode that operates with unique protocols when within the coverage area provided by independent, low power xe2x80x9cpicoxe2x80x9d cells that are connected to the wireline telephone network. Pico cells are provided at customer selected locations to cooperate with a framework of overlay cells that operate independently of the cells of the cellular network.
This overlay cell framework allows the service provider to exercise complete control over the operation of each special handset and the pico cell system by means of service control units and host stations. The standard cellular system can be further enhanced by the addition of zone identifier overhead messages which are ignored by standard handsets but interpreted by the special handsets to inform those customers continuously of the special handset""s current operating mode.
2. Description of Related Art
There has long been a recognized need for ubiquitous telecommunications services wherein each customer is assigned a personal service number and provided with suitable equipment which will permit the customer to have two-way communication capability (i.e., the ability to make and receive calls) regardless of the customer""s changing location.
Systems that extend beyond traditional wireline telephone service have been developed in order to more closely achieve this capability from a technical perspective. For example, recent innovations in paging, standard cordless within the home telephone service, cellular telephone service and personal communications systems are well known. The designs of such systems all comprise efforts to cost effectively satisfy the need for ultimate ubiquitous service. However, each system has well recognized technical and cost disadvantages which cause it to fall short of providing ubiquitous telecommunications service.
Accordingly, a need still exists for an improved communications system that comes closer to providing ubiquitous communications service to customers than existing systems.
The following U.S. Patents assigned to the assignee of the present invention were issued to Robert G. Zicker et. al. and are related to this invention to the extent that they relate generally to improvements in telecommunications systems or service:
Therefore, it is an object of this invention to provide an improved telecommunications system which more completely meets customer needs for low cost, ubiquitous telecommunications service.
It is another object of the invention to provide an improved telecommunications system, designed to include a standard cellular network, and which further includes a network of overlay cells that operate independently of the cells of the cellular network.
It is a further object of the invention to provide, in such a system, a multi-channel pico station at each customer location that, in turn, supports multiple portable telephone handsets, with each handset being capable of operating in a wireless or pico mode when within the customer premises, and in a standard cellular mode when away from the customer premises and yet within the cellular coverage area.
It is yet a further object of the invention to provide such an improved telecommunications system wherein call forwarding capability is provided in conjunction with distinctive ring so that a customer with a portable personal handset selected to operate in one of the dual modes can receive and readily identify incoming calls, directed to the assigned cellular customer number, through the unselected or inactive mode of the system.
It is yet another object of the invention to provide automatic registration and control of such a dual mode portable handset, without customer action, and with the customer being provided with a display advising the status or mode which the handset is set to operate in at any time, so that the customer can make informed, cost-effective decisions as to call placement.
It is another object of the invention to provide in a dual mode system using one radio per handset, a mode of operation based upon a unique, though cellular compatible, protocol that permits easy dynamic channel allocation and occupancy.
It is another object of the invention to provide an alternate line option capability which permits selective allocation of call traffic between the customer premises and the cellular network.
These objects and other features and advantages of the invention are attained in a telecommunications system that is designed to operate in conjunction with a standard cellular network having multiple cell sites of either analog or digital configuration and embodying standard geographical coverage. The system also includes a comparable network of overlay cells that operate independently of the standard cell sites of the cellular network. Alternatively, the system could be used within a radiotelephone network of other character, such as an SMR network, for example.
Preferably, each overlay cell provides radio communication coverage to a geographical area that corresponds generally to the cellular site area, but on a set of reserved cellular frequencies that are selected with the maximum possible separation with respect to the assigned cellular network signaling frequencies, so as to be non-interfering.
To cooperate with the overlay cells a base station, referred to hereinafter as a pico station, is provided at each customer site. Each pico station is designed to support up to six improved portable handsets which function in dual modes. In a first mode each handset functions as a normal portable network or cellular telephone, when it is physically removed from the proximity of the pico station. A second wireless mode of operation is described herein for the handsets of the system which has been referred to herein as enhanced cordless on the first iterations and will be referred to as the pico mode in subsequent usage. The enhanced cordless mode of this invention differs from the operation of standard cordless telephones in several respects. This system employs a unique burst mode s communication control protocol between the handsets and the pico station which is not found in standard cordless operation. This protocol is compatible with cellular standards to permit dual mode operation which would not be possible with standard cordless. Moreover, the standard cordless frequency arrangement is obviously different from cellular frequencies used in this system. Other differences will become apparent from the description that follows, which result in operational improvements in the service offered.
The use of the unique protocol of this system permits remote activation and control using the 10 k bit Manchester encoded data pathway inherent in cellular telephone hardware. Therefore, when dose to the pico station, the handset operates as a cordless telephone supported by the pico station via a connection to the house PSTN wiring.
In the preferred mode, call delivery is provided through a link that may also include an alternate line option module connected between the pico station and the PSTN. With that arrangement, service can be provided through direct access from the pico station to the public switched telephone network, or alternatively, service from the pico station can be selectively redirected back to the cellular network by the radio of the alternate line option module. A significant advantage of the system arises from the capability of allocating selected portions of call traffic between these two paths, in order to accommodate call capacity and varying call demand. This permits deployment of the system in areas with limited cellular capacity, without necessitating rationing of service.
Service control units and a host station are provided to facilitate set up and control of the portable handsets and pico stations using remote programming techniques which were not previously practical.
Each handset includes components comparable to that of a standard analog cellular telephone having one radio transceiver. In addition, the handset has added software to permit it to operate in the pico mode, in cooperation with the pico station located at the customer premises. As an alternative to analog technology, the modified handsets can embody compatible digital technology, again with the same necessary additions or modifications to support pico operation.
After initial set-up, each handset employs a process to identify when it is in the general neighborhood of its authorizing pico station. Only then will the handset seek out its authorizing pico station by periodically transmitting a signal to determine if it is within acceptable communication range. If the pico station receives an acceptable level handset signal, it responds and exchanges registration information with the handset to establish or register the handset in the pico mode.
The handset then sends a message to the cellular system upon which it also operates, directing that all incoming calls subsequently attempted on the cellular network be forwarded to this authorizing pico station telephone number (this may be the customer home PSTN number). Finally, the handset is switched to the pico mode and sends a response control message to the pico station indicating that it is xe2x80x9chomexe2x80x9d and in service. At that time, a message on the handset display indicates to the user that the handset is in the pico mode, as opposed to the cellular mode.
When in the pico mode, the system operates at a lower power level on selected, reserved cellular channels with the same basic technical standards as analog AMPS type cellular systems. During this mode, the pico station can and does function as a telecommunications base station with no hand-off capability.
Up to six handsets may be registered with the pico station. In the preferred embodiment only one handset may transmit at any one time. However, the system supports the capability for other handsets to join calls in progress. The handset to pico station link is accomplished at very low power levels during call activity, which results in low battery drain.
The pico station is connected directly to home telephone wiring for call delivery, but is always controlled via a radio frequency link to a service control unit and an overlay host station located within the network area. When the handset is carried out of range of the pico station in an operating state, it automatically switches back to the cellular mode and cancels any existing call forwarding.
It should be noted that operation of the special handsets and overlay network of the invention is transparent to, and will not interfere with, standard cellular network operations.