Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1997-02-19
2002-03-19
Harrison, Jessica J. (Department: 3713)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S404000
Reexamination Certificate
active
06359871
ABSTRACT:
TECHNICAL FIELD
This invention relates to a cellular communication network and method which has particular utility in underground mines, but also application in industry and localised open environs.
BACKGROUND ART
The underground mining industry has long recognised the importance of radio communications for enhancing productivity and safety. Experiments on radio transmission in underground mines date back to as early as the 1920s. Most of these early experiments were aimed at through-the-rock radio communication between the surface and underground mine personnel. However, past experience has indicated that through-the-rock radio transmission is too sensitive to rock composition for it to be considered reliable.
Starting at the end of the 1960s through to the 1970s, extensive experimental and theoretical investigations on electromagnetic propagation in underground tunnels were carried out in Europe and USA. These studies led to a good understanding of the complex mechanisms involved in radio propagation in underground mine, road and railway tunnels as well as the developments of leaky feeders and mode converters for improving radio propagation along tunnels. Radio systems employing leaky coaxial cables are still widely used in underground mines. However, these systems are usually restricted to supporting only one or two voice channels and remain expensive for continually extending the communication distance required in conjunction with the ongoing extension of the mine in a normal mining area application.
In recent years, the sophistication of mechanical equipment used in modern underground mines has grown rapidly with advanced technology but the progress in underground communications remains almost stagnant. In addition to voice communication, modern underground mines require data communication for remote monitoring and control of machinery. In these cases, data communication is usually achieved with a separate wired system operating independently from the radio system for voice communication.
In most underground mines, voice communication is achieved via either line telephone or radio systems based on low-frequency inductive loop or high-frequency leaky feeder techniques. In an attempt to improve communication quality, in recent times there has been a focus on VHF and UHF leaky coaxial cable systems. A drawback with these systems, however, is that the higher cable attenuations encountered at these high frequencies mean that signal amplifications by intermediate repeaters are needed at approximately every 500 m to 1500 m. It follows that a good understanding of the complex operating mechanisms of leaky coaxial cable is essential for achieving the required system performance. Furthermore, these leaky systems require rewiring for each advance of the active mining area.
For remote monitoring and control purposes, it is common to use a separate data transmission system based on metallic cables, such as twisted pairs and coaxial cable, or more recently optical fibre cable. Manually operated data loggers are sometimes employed for data acquisition in smaller mines.
These existing systems remain very restrictive in terms of communication capacity, mobility, voice quality and flexibility in system reconfiguration and extension. Despite the high investment in installing, maintaining and operating an array of incompatible systems, the performance achieved has been less than satisfactory. Therefore it is believed that a significant cost advantage can be achieved by adopting an integrated system capable of handling both voice and data.
Having regard to surface communication networks, in recent times the cellular concept of radio coverage has become well established in the wide area cellular telephone field. Moreover, applications involving smaller cell sizes for servicing local areas in offices, factories and residential areas are beginning to be introduced. An example is the advanced Digital European Cordless Telecommunications system (DECT). In this system, fixed radio base stations are suitably located to provide radio coverage for particular zones of the service area. Usually, each base station is linked by a cable to a central control hub in a star configuration. For most of these surface applications, the links between the base stations and the central hub are short. As such, a star network is appropriate. However, a very different situation is encountered in underground mining, and hence conventional surface cellular communication networks cannot be employed.
Moreover, in an underground mining situation, the structural layout of an underground mine is typified by a series of tunnels and crossings which severely restrict radio transmission. Consequently, severe radio propagation losses are encountered along tunnels and around corners and crossings.
DISCLOSURE OF INVENTION
Accordingly, it is an object of the present invention to provide for a cellular communication network and method within an area, and parts and accessories thereof capable of handling both voice and data communications to provide improved operational efficiency and flexibility as well as reducing the cost otherwise needed for maintaining separate communication systems within said area.
It is a preferred object of the invention to provide reliable communications for multiple channels of two-way voice, monitoring data, control signals and compressed digital video signals within the network.
It is a further preferred object of the invention to provide a communication network which is capable of automatic tracking and locating of objects such as personnel and equipment within said area.
In accordance with a first aspect of the present invention, there is provided a communication network for an area including:
a plurality of cascaded base stations serially interconnected in a ring structure to form a network backbone;
one of said base stations at one end of said network backbone comprising a network controller for controlling the network;
a plurality of portables adapted for communication with any of said base stations by a common air interface;
a network protocol for communicating between said network controller and said base stations or between said base stations along said network backbone; and
a common air interface protocol for communicating between a said portable and a said base station;
wherein the other base stations function as slaves to said network controller, and
wherein each slave base station defines a discrete cell within which communication between a said portable disposed within said cell and said base station thereof, is able to be performed over said common air interface.
Such a network has particular utility in an underground mine, whereby the network not only enhances voice communication between mining personnel, but allows the use of distributed monitoring and control of both personnel and mining equipment. Furthermore, the communication network can be continually extended with the further progression of the mine, to provide for mine wide communications and thus provide an immediate warning to workers of dangerous situations and locations, thus improving the overall safety level of underground mines.
In accordance with a second aspect of the present invention, there is provided a base station for a communication network of the type defined in the preceding aspect of the invention, including one or more backbone controller means for communicating with the network backbone, a common air interface controller means for communicating with any of the portables within the cell of the base station, and a backplane means for controlledly interconnecting said backbone controller means, said common air interface controller means and said network backbone.
In accordance with a third aspect of the present invention, there is provided a network controller for a communication network of the type defined in the first aspect of the invention, including a communications microcontroller provided with a serial communication channel for operating the network controller and communicating with the network backbone, a mi
Barker David Antony
Chung Kah-Seng
Seale Richard Beaumont
Curtin University of Technology
Harrison Jessica J.
Nguyen Kim T.
Schwegman Lundberg Woessner & Kluth P.A.
LandOfFree
Cellular communications network does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cellular communications network, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cellular communications network will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2818127