Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2000-05-18
2001-12-04
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C455S432300
Reexamination Certificate
active
06326926
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to communication systems, and in particular to a method of operating a wireless LAN and a short-range wireless connection in the same frequency range.
BACKGROUND OF THE INVENTION
The use of cellular communication systems having mobile devices which communicate with a hardwired network, such as a local area network (LAN) or a wide area network (WAN), has become widespread. Retail stores and warehouse, for example, may user cellular communications systems with mobile data terminals to track inventory and replenish stock. The transportation industry may use such systems at large outdoor storage facilities to keep an accurate account of incoming and outgoing shipments. In manufacturing facilities, such systems are useful for tracking parts, completed products and defects. Such systems are also utilized for cellular telephone communications to allow users with wireless telephones to roam across large geographical regions while retaining telephonic access. Paging networks also may utilize cellular communications systems which enable a user carrying a pocket sized pager to be paged anywhere within a geographic region.
A typical cellular communications system includes a number of fixed access points (also known as base stations) interconnected by a cable medium often referred to as a system backbone. Also included in many cellular communications systems are intermediate access points which are not directly connected to the system backbone but otherwise perform many of the same functions as the fixed access points. Intermediate access points, often referred to as wireless access points or base stations, increase the area within which access points connected to the system backbone can communicate with mobile devices.
Associated with each access point is a geographic cell. The cell is a geographic area in which an access point has sufficient signal strength to transmit data and receive data from a mobile device such as a data terminal or telephone with an acceptable error rate. Typically, access points will be positioned along the backbones such that the combined cell area coverage from each access point provides full coverage of a building or site.
Mobile devices such as telephones, pagers, personal digital assistants (PDA's), data terminals etc. are designed to be carried throughout the system from cell to cell. Each mobile device is capable of communicating with the system backbone via wireless communication between the mobile device and an access point to which the mobile device is registered. As the mobile device roams from one cell to another, the mobile device will typically deregister with the access point of the previous cell and register with the access point associated with the new cell. In order to provide sufficient cell area coverage, access points (or the antennas associated with each access point) within the cellular communications system typically are distributed at separate physical locations throughout an entire building or set of buildings.
Recently a standard for wireless local area networks (WLANs) known as the IEEE 802.11 standard has been adopted and has gained acceptance among the industrial, scientific and medical communities. The IEEE 802.11 standard for WLANs is a standard for systems that operate in the 2,400-2,483.5 MHz industrial, scientific and medical (ISM) band. The ISM band is available worldwide and allows unlicensed operation of spread spectrum systems. The IEEE 802.11 RF transmissions use multiple signaling schemes (modulations) at different data rates to deliver a single data packet between wireless systems. The latest IEEE 802.11 wireless LAN uses a band of frequencies near 2.4 Ghz for direct sequence spread spectrum transmissions. Another recently adopted short-range standard has evolved known as the Bluetooth standard (see www.bluetooth.com). The Bluetooth standard is a low-cost short range wireless connection which uses much of the same range of frequencies for its frequency-hopping spread spectrum transmissions as the IEEE 802.11 standard. In some applications, it is appropriate to use systems employing IEEE 802.11 concurrently with other systems using the Bluetooth standard. Consequently, there is expected to be considerable interference between the two systems. Early theoretical studies show widespread use of Bluetooth standard reducing the band-width of a co-located 802.11 LAN by as much as 20-50%. It is also possible for 802.11 transmissions to interfere with Bluetooth.
Schemes proposed for mitigating the interference of 802.11 and Bluetooth generally involve adding intelligence to the networks so that they will sense each other and avoid collisions as much as possible. This is workable but complicated. Such methods will slow initial deployment of IEEE 802.11 and Bluetooth together, and add to the cost of maintenance.
Accordingly, there is a strong need in the art for a system and method that overcomes the aforementioned problems.
SUMMARY OF THE INVENTION
In many 802.11 wireless LAN installations, the access points or base stations are placed high above communication terminals in order to maximize the coverage range of each access point and minimize the number of access points (AP's) required. The ceilings of warehouses and large retail stores are typical AP locations. On the other hand, communication terminals that use the Bluetooth standard to communicate are typically located at approximately tabletop level or at the height of the terminal communicating to the Bluetooth devices. Due to the locations of the AP's conforming to the IEEE 802.11 standard and the locations of the AP's conforming to the Bluetooth standard, the antennas for IEEE 802.11 and Bluetooth in a terminal (mobile or stationary) that communicates via either or both using IEEE 802.11 and Bluetooth may be designed with directional properties that minimize interference between the two systems.
The antenna for the 802.11 wireless LAN (WLAN) can have a pattern of radiation or sensitivity that is approximately in the shape of an inverted cone. The antenna for the Bluetooth connection can have a pattern of radiation or sensitivity that is approximately in the shape of a disk with a shallow cone-shaped depression in the top. With this antenna arrangement, Bluetooth enabled devices located in a given floorspace at about the same height will “see” each other for Bluetooth communication. But these Bluetooth links will not “see” interfering IEEE 802.11 transmissions. Similarly, IEEE 802.11 enabled devices will communicate with one another via the AP's above them. However, they will not “see” the interfering Bluetooth transmissions. `It is to be appreciated that the two antenna radiation patterns may be used separately in any device or terminal, or they may be used together in the same device or terminal.
Maintaining the orientation of the antenna patterns with respect to the ground is straightforward when the terminal or device is stationary, but a mobile terminal presents a bit more problem. The antennas of a mobile device can be mounted in such a way as to track the orientation of the ground. This may be achieved by mounting the antenna in a double gimbal arrangement, suspending the antenna in a fluid, or perhaps, by control means. For example, by providing a ground tracking system coupled a control component, the orientation of the antenna can be maintained regardless of the orientation of the mobile terminal. However, if a mobile terminal is always held in approximately the same orientation with respect to the ground when it is operating, then special orientation mechanisms may not be necessary.
The present invention provides for a system and method for providing a first antenna arrangement tuned to communicate within a first radiation pattern and a second antenna arrangement tuned to communicate within a second radiation pattern. In a preferred aspect of the invention, the first radiation path has an inverted conical shape and the second radiation path has a disk shape. The first radiation path is
Rozmus J. Michael
Shoobridge Richard Allen
Amin & Turocy LLP
Clinger James
Phan Tho
Telxon Corporation
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