Multiplex communications – Communication over free space – Repeater
Reexamination Certificate
2000-04-13
2004-06-29
Yao, Kwang Bin (Department: 2667)
Multiplex communications
Communication over free space
Repeater
Reexamination Certificate
active
06757263
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to communication networks. More specifically, the present invention relates to communication networks in which repeating subscriber units are interconnected through wireless communication links.
BACKGROUND OF THE INVENTION
While wireless communication provides numerous advantages for mobile applications, wireless communication has been conventionally viewed as less suitable where ends of a communication path are stationary. Wireless communication suffers from numerous challenges, including a need to use and reuse a minimum amount of assigned radio frequency spectrum as efficiently as possible, a need to prevent and tolerate interference, a need to tolerate multipath, fades and other RF signal difficulties, and often a need to consume a greater amount of power compared to wireline communications to convey signals a given distance. Accordingly, when ends of a communication path are stationary, cables or wires which physically attach to communication devices at the ends (i.e., wireline communications) of the communication path have conventionally been viewed as a desirable solution to the numerous wireless communication challenges.
But wireline communication has its own set of challenges to overcome. For example, a tremendous amount of time and expense may be involved in running cables between various locations. Accordingly, high bandwidth RF communication systems have been proposed for the wireless distribution of communications, and particularly broadband communications, between stationary locations. Typically, such systems propose operation at S-band and higher frequencies where the signal propagation path tends to follow a line-of-sight. At these higher frequencies, communication signals suffer from severe attenuation or obstruction by geographical features, such as hills and mountains, man-made structures, foliage, and/or rain. Operation at such higher frequencies enables the communication of high data rates because larger amounts of the electromagnetic spectrum are available for use. In addition, highly directional, small antennas may be cheaply manufactured for operation at such higher frequencies, and interference is managed and frequency reuse enhanced by operating at low power using such highly directional antennas.
High bandwidth RF communication networks with repeating subscriber units have been proposed as a solution to the challenges of line-of-sight wireless communications. Subscriber units are the communication devices located at the premises of customers or subscribers of the network. Through subscriber units, the subscribers transmit and receive data, which may be in the form of video, audio, voice, computer, or other data. By configuring subscriber units to also function as repeaters, the range and coverage of the network may be expanded. Subscriber units which may not be able to engage in high frequency wireless communications with a base station due to some signal obstruction between the subscriber's premises and the base station may still be able to engage in wireless communications with a neighbor subscriber unit. When the neighbor subscriber unit functions as a repeater, those communications may be repeated to the base station or to another repeating subscriber unit that will forward the communications to a base station.
One problem experienced by proposed wireless communication networks which rely on repeating subscriber units is reliance on a centralized, cellular-like, network architecture. In such a centralized system, network data traffic for each subscriber unit passes through a base station in whose jurisdiction the subscriber unit is located. This causes the traffic to become concentrated as it nears the base station. Traffic bottlenecks may develop because repeating subscriber units located near the base station are required to handle a large percentage of the traffic which passes through the base. At the same time, repeating subscriber units located at the edge of a base station's cell are required to handle very little traffic beyond that which terminates at the subscriber unit. Moreover, direct subscriber unit to subscriber unit communications which bypass the base are not permitted under the centralized architecture. Consequently, further inefficiencies in traffic distribution throughout the network result.
Furthermore, in a centralized system routing decisions (i.e., determinations about how to route communications through various repeating subscriber units between a base station and a terminating subscriber unit) tend to be made at the base station. However, the base station does not have knowledge of conditions currently experienced by various repeating subscriber units from moment to moment. Thus, the base station repeatedly sends probe messages through its domain to gain the knowledge needed to make routing decisions. The use of such probe messages is undesirable because probe messages consume system resources which might otherwise be used to convey subscriber payload data. Moreover, data determined from probe messages tends to become stale quickly, and routing decisions based on such messages tends to be outdated unless a lot of system resources are dedicated to probing.
Another problem experienced by proposed wireless communication networks which rely on repeating subscriber units is a reliance on connection-oriented or circuit switched traffic distribution. In a connection-oriented system, network resources are allocated from end-to-end of a “call” throughout the duration of a call from call setup to call tear down. This type of traffic distribution is particularly inefficient in networks which rely on repeating subscriber units because most of the networks traffic distribution resources are not actively used for a large percentage of the duration of the call. Connection-oriented switching also poses a packing problem because routing or packing a large item, such as an entire end-to-end call path, in a given network or space is a more difficult task than routing or packing several smaller items in the same network or space.
The problems suffered by wireless networks that rely on repeating subscriber units are compounded when both centralized control and connection-oriented switching are used.
Another problem with proposed wireless communication networks which rely on repeating_subscriber units is that they are not well suited to interoperate with common network standards such as the interval protocol suit (TCP/IP). This results in poor performance, or the need for expensive custom protocols, or both.
Therefore, what is needed is an improved repeating wireless subscriber unit which is useable in a wireless communication network and which efficiently utilizes resources so that the repeating subscriber units and wireless network may be kept as simple, reliable, and inexpensive as possible. It should also be well suited for operating in a network that provides an efficient underlying infrastructure upon which standard network protocols and services can be operated.
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Bogacz Frank J.
Botsch Bradley J.
Motorola Inc.
Yao Kwang Bin
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