Communications: radio wave antennas – Antennas – Mesh – woven – braided or multiple strip
Reexamination Certificate
1998-08-25
2001-06-12
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Mesh, woven, braided or multiple strip
C343S844000, C343S893000, C455S422100
Reexamination Certificate
active
06246380
ABSTRACT:
BACKGROUND OF THE INVENTION
Before wireless high frequency point-to-point communication service can be provided on a mass basis in an area there must exist a deployment scheme that can support the planned service. Such a scheme must be able to deploy a large number of radio links, i.e., two way radio communication established through main beams of both transmitting and receiving antennas where the antenna gain is at its maximum 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, polarization isolation and frequency channel separation. For example, interference is worst case where 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. Likewise, orthogonal polarization and frequency separation provide radiation in transmitting to receiving interference.
A good example of a deployment scheme is the cell structure currently in use for cellular wireless service. The cellular cell 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.
Cellular networks are broadcast based such that a transmitter sends out signals into a designated area and any receiver within that area can pick up the signals, if properly tuned. Point-to-point radios work at a frequency, typically above 18 GHZ, where the wavelengths are short so that for effective communication the transmitter and receiver must be pointing essentially directly at each other, i.e., line of site. 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 no need in point-to-point systems to “blanket” a given area with transmitted signals. This line of sight requirement has allowed point-to-point systems to be constructed without regard to each other. However, as the demand for point-to-point systems increases (because of their inherent higher data carrying capacity), interference between discrete systems will result when a particular receiver is within the radiation pattern of more than one transmitter.
Thus, a need exists in the art for a system and method for developing a deployment pattern for transmitter/receiver pairs so as to minimize interference while maximizing the frequency reuse pattern.
A further need exists for such a deployment system which can be replicated from location to location.
A further need exists for such a system in which not all of the transmitter/receiver pairs need be deployed at any time, but which will accommodate growth in any direction throughout the deployment region on a pre-approved basis.
A need exists for a deployment standard for high frequency radio transmission systems which will allow any transmitter/receiver pair to be added by any user at certain calculable points within a geographic region while still maintaining maximum effective coverage within that region.
SUMMARY OF THE INVENTION
These and other objects, features and technical advantages are achieved by a system and method in which a network node deployment structure is utilized to improve the mutual interference associated with densely deployed radio systems as well as to provide a small exclusion zone for any single link. Accordingly, a lattice matrix structure is used to control interference between transmitter/receiver pairs. In the ideal case, the lattice nodes would be multi-level, i.e., at alternating heights, perhaps on top of tall and medium height buildings respectively. Therefore, the preferred embodiment of the present invention provides dense radio deployment where nodes are disposed such that interference is present to all, is through antenna sidelobes only, thus significantly improving mutual interference.
In the preferred embodiment of the present invention, the angle &agr; is the angle in the horizontal plane between adjacent antenna nodes on different planes (the high (H) plane and the low (L) plane) and the angle &bgr; is the angle in the elevation or vertical plane between adjacent antenna nodes on different planes. The angle &agr; may be equal to angle &bgr; to reduce the complexity of implementing the lattice structure of the present invention while providing interference avoidance. Ideally, both angles are smaller than 5 degrees.
A key factor in increasing radio link density is to place radio links as closely together as possible, including the exclusion (radiation) zone of the transmitting antenna. The primary method for accomplishing the desired link density is to insure that the main beam of any transmitting radio antenna does not point directly at (or send its radiation pattern to) any receiving radio antenna other than the desired receiving antenna. Other factors, which are important in the placement transmitting and receiving radio antennas, are antenna polarization isolation and antenna sidelobe control.
The 3-dimensional lattice structure has the capability of keeping interfering radio links from pointing directly at one another. Thus, it is a technical advantage of this invention that the horizontal and vertical angles between antennas can be pre-calculated so as to allow for maximum density and minimum interference.
It is a further technical advantage of this invention that the angles, both horizontal and vertical, can be adjusted to accommodate various geometric constraints while still serving to maximize the coverage within a given geographic zone.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
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Wong Don
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