 Private branch exchange and line exchange method |
| It is therefore an object of the present invention to effectively utilize an extension terminal ... |
|
| System for monitoring carriers of peripheral zones |
| Accordingly, the present invention, in consideration of the above-mentioned problem, has as its ... |
|
| Electronic gating control for manual telephone switchboard |
| These and other objects of the present invention are accomplished by the present invention which ... |
|
| Telecommunication system comprising subscriber connection units having independent routing ability |
| The present invention provides a subscriber connection unit having independent routing ability for ... |
|
| Communication network call traffic manager |
| OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention is now described with ... |
|
| Handover in a mobile communication system having a multilayer radio coverage |
| OF THE INVENTION The present invention can be applied in any cellular mobile communication system. ... |
|
| Method for an admission control function for a wireless data network |
| OF THE PREFERRED EMBODIMENT In networks in general, and in wireless data networks in particular, ... |
|
| Method and apparatus for maintaining connectivity of nodes in a wireless local area network |
| It is therefore an object of the present invention to provide a wireless local area network (LAN) ... |
|
| Dual mode subscriber unit for short range, high rate and long range, lower rate data communications |
| Wireless LANs are generally private networks, that is they are installed, owned, and maintained by ... |
|
|
Adaptive antenna for use in same frequency networks
| Details |
Inventors: Proctor, Jr., James A.; Gainey, Kenneth M.;
Assignee: Tantivy Communications, Inc. (Melbourne, FL)
Primary Examiner: Phan; Dao
Assistant Examiner:
Attorney, Agent or Firm: Hamilton, Brook, Smith & Reynolds, P.C.
An antenna apparatus which can increase capacity in a cellular communication system. The antenna operates in conjunction with a mobile subscriber unit and provides a plurality of antenna elements, each coupled to a respective programmable phase shifter. The phase of each antenna element is programmed for optimum reception during, for example, an idle mode which receives a pilot signal. The antenna array creates a beamformer for signals to be transmitted from the mobile subscriber unit, and a directional receiving array to more optimally detect and receive signals transmitted from the base station. By directionally receiving and transmitting signals, multipath fading is greatly reduced as well as intercell interference. Various techniques for determining the proper phase of each antenna element are accommodated. |
|
DETAILED DESCRIPTION Problems of the Prior Art Various problems are inherent in prior art antennas used on mobile subscriber units in wireless communications systems.
One such problem is called multipath fading.
In multipath fading, a radio frequency signal transmitted from a sender (either base station or mobile subscriber unit) may encounter interference on route to an intended receiver.
The signal may, for example, be reflected from objects such as buildings that are not in the direct path of transmission, but that redirect a reflected version of the original signal to the receiver.
In such instances, the receiver receives two versions of the same radio signal; the original version and a reflected version.
Since each received signal is at the same frequency but the reflected signal may be out of phase with the original due to reflection and a longer transmission path, the original and reflected signals may tend to cancel each other out.
This results in fading or dropouts in the received signal, hence the term multipath fading.
Single element antennas are highly susceptible to multipath fading.
A single element antenna has no way of determining the direction from which a transmitted signal is sent and cannot be tuned or attenuated to more accurately detect and receive a signal in any particular direction.
The dual element antenna described in the aforementioned reference is also susceptible to multipath fading, due to the symmetrical nature of the hemispherical lobes formed by the antenna pattern when the phase shifter is activated.
Since the lobes created in the antenna pattern are more or less symmetrical and opposite from one another, a signal reflected in a reverse direction from its origin can be received with as much power as the original signal that is directly received.
That is, if the original signal reflects from an object beyond or behind the intended receiver (with respect to the sender) and reflects back at the intended receiver from the opposite direction as the directly received signal, a phase difference in the two signals can create a multipath fading situation
|
|
Caller ID 
