Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-11-17
2004-08-03
Gelin, Jean (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S075000
Reexamination Certificate
active
06771966
ABSTRACT:
TECHNICAL FIELD
This invention relates to deployment of radio systems and more particularly to systems and methods providing for the placement of transmitter/receiver paths to provide links at desired locations while minimizing interference.
BACKGROUND
In the past, high frequency high bandwidth wireless communication has been provided through the use of point-to-point radio systems, such as point-to-point microwave radio transmitters and receivers providing line of sight communications. Portions of the microwave spectrum of frequencies are made available for use in such point-to-point systems. High frequencies, such as the above mentioned microwave spectrum of frequencies, are generally desirable in providing high bandwidth communication because of their ability to provide large bandwidth in a relatively narrow portion, or channel, of the spectrum.
Presently, one desiring to establish point-to-point communications references a record of all the sites currently established using such microwave communications, and determines where a new link may be established which does not interfere with or receive interference from these established links. This has generally been acceptable where link deployment is scattered. However, the above described technique for deployment is not well suited for mass deployment of such radio links, such as is useful in the metropolitan area wireless networks shown and described in the above referenced patent application entitled COMMERCIAL NETWORK TOPOLOGIES UTILIZING POINT TO POINT RADIOS. Accordingly, other solutions must be utilized for mass deployment of radio systems. One such solution is shown and described in the above referenced patent application entitled SYSTEM AND METHOD FOR ESTABLISHING A POINT TO POINT RADIO SYSTEM. This solution allows for the mass deployment of radio systems through the regulated positioning and orientation of the communication nodes.
Before wireless high frequency communication service can be provided on a mass basis in an area there should exist a deployment technique that can support the planned service in order to provide for the desired location of links without restricting the ability to locate other links where necessary or desired. In order to provide for a dense deployment pattern, such a technique should be able to deploy a large number of radio links established where the antenna gain is at its maximum, i.e., two way radio communication established through main beams of both transmitting and receiving antennas, in a given area such that the individual radio links do not significantly interfere with one another.
There are a number of parameters that determine the magnitude of such interference, such as the antenna gain in the path of the interference, the “hop” distance between interfering and interfered systems, polarization isolation and frequency channel separation. For example, interference is at its worst when the interfering transmitting main beam is directed towards the interfered receiving main beam, somewhat less when the interfering main beam is directed toward the interfered receiving sidelobe, and even less when the interfering transmitting sidelobe is directed toward the interfered receiving sidelobe. Additionally, the interference decreases the farther apart, i.e., the greater the “hop” distance between the interfering and the interfered.
A good example of a radio frequency deployment scheme is the cell structure currently in use for cellular wireless service, which may be utilized in fixed location point-to-multipoint systems, which utilizes frequency reuse techniques. The cellular structure provides a model to show that the interference is controllable by frequency reuse and sectorization. Typically, in a cellular network, each set of frequencies is reused in every seventh cell, with each cell divided into three sectors, thereby defining a cellular frequency reuse pattern.
Cellular networks are broadcast based such that a transmitter sends out signals into a designated area and any properly tuned receiver within that area can pick up the signals. However, where radios work at high frequencies, such as point-to-point microwave systems typically operating above 18 GHz, the wavelengths are short so that for effective communication the transmitter and receiver are preferably pointing essentially directly at each other, i.e., line of sight. Such narrow beam transmission implies that the transmitters and receivers are all in fixed positions with respect to each other where their density is not great. Thus, in contrast to cellular systems, there is generally no need in these high frequency systems to “blanket” a given area with transmitted signals. This line of sight characteristic has allowed prior point-to-point systems to be constructed without much regard to each other.
However, interference between discrete systems will result when a particular receiver is within the radiation pattern of more than one transmitter. Accordingly, as the demand for high bandwidth communication systems increases the ability to establish links, deployed according to the above described technique, experiencing interference at or below desired levels becomes increasingly difficult. For example, existing links may be positioned and oriented such that an additional link from a particular location, such as an additional office building to be provided service, may not be able to be established due to unavoidable interference from existing links deployed without regard to any other links. Such a technique is not conducive to the implementation of densely deployed radios.
Further, as the number of desired nodes and network complexity increases, the complexity of the interference between nodes expands exponentially. Existing planning tools are unable to effectively and in a timely manner handle interference computations for such large sets of possible node combinations and permutations.
Thus, a need exists in the art for a system and method for developing a radio frequency deployment plan for transmitter/receiver pairs so as to minimize interference while providing for establishing links at desired sites. This system and method should identify the radio frequency plan efficiently. Further a need exists for the location of the desired sites to be freely located within a service region.
A further need exists for such a system and method in which not all of the communication links need be deployed at any time, but which will accommodate growth in any direction throughout the deployment region.
A further need exists for a system and method in which multiple combinations and permutations forming a network of sites are considered, analyzed and an optimized topology is identified.
A further need exists for such a system and method to consider environmental factors in its development of the radio frequency plan.
SUMMARY OF THE INVENTION
These and other objects, features and technical advantages are achieved by a system and method which provide a technique by which radio links may be densely deployed with minimized interference by making link determinations based on analysis of acceptable link combinations. According to a preferred embodiment of the present invention, multiple levels of link analysis are performed to determine an optimum network link configuration.
Preferably, the set of possible links connecting the various nodes of an RF network are first analyzed to identify the subset of practicably realizable links, i.e., those links which are within effective range, within line of sight and having an acceptable path loss in view of system gains. Interference analysis is then performed between sets of links so as to identify mutually independent and mutually exclusive links, i.e., links that do not exclude other links and those that impede the inclusion of other links. Mutually exclusive links are eliminated from the feasible set which is then subject to further selection and optimization to arrive at a preferred network topology.
Alternately, a first high order link analysis is performed, such as by a master radio frequency (RF) pl
Carriercomm, Inc.
Fulbright & Jaworski LLP
Gelin Jean
LandOfFree
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