The deserving popularity of the Internet as an entertainment and information source has fueled an insatiable demand for faster, more flexible, and more dynamic communications inter-networks. Communications inter-networks are now used to transport all types of data including text, graphics, audio, video, and others. There are two kinds of communications inter-networks: wired and wireless.
In general, wireless inter-networks may be more preferable over wired inter-networks because of the low installation costs as well as the protracted installation time required. A wireless communication inter-networks consists of sub-networks (e.g., Local Area Networks (LANs)) that communicate together through the use of gateways (a.k.a. routers) over wired wideband links. Each sub-network is designed to provide coverage to a predetermined local geographical area and consists of a central station (a.k.a. hub) and a number of subscriber units located within that local area. The central station and the subscriber units are linked together through wireless Radio Frequencies (RF) narrow band links. Narrow band links, instead of wideband links, are used in sub-networks because of costs and practicality reasons.
In short, in a wireless communication sub-network, the central station serves as a relay station for communications between local subscriber units. The central stations also serve as relay stations for long-distance communications between sub-networks. Due to limitation in wireless communication resources (e.g., frequency, time, power, transmission loss, and others), different methods have been developed to more efficiently make use of these resources. Some of the methods include Frequency Division Duplex (FDD), Frequency Division Multiple Access (FDMA), Time Division Duplex (TDD), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and others. Generally, the above methods involve either frequency sharing or time-sharing.
Presently, to allow for full duplex wireless communications, (i.e., transmit and receive simultaneously) separate transmit and receive frequency bands are used. However, to prevent interference and leakage between the transmit and receive frequency bands, a frequency gap is normally introduced between the transmit and receive frequency bands. Such frequency gap is known as the middle frequency band. The middle frequency band may be as wide as 10 MHz which is a sizeable unused amount of a precious communications resource. Such unused frequency band is even more significant given the small bandwidth of the narrow band links between the subscriber units to the central station in a sub-network.
More importantly, as mentioned earlier, current demands dictate that all types of data including text, audio data, and video data be provided over communication inter-networks. This presents a difficult challenge given the fixed bandwidth of the narrow band links used in sub-networks. While such fixed bandwidth are adequate for the average application which is likely to involve voice data (e.g., telephones) and may require a bandwidth of approximately 64 Kbps, they are extremely inadequate for applications involving high data transfer rates such as video conference or Internet video download which may require a bandwidth of as high as several Mbps. Because the bandwidth of the narrow band links is fixed, they can not readily and practically be reconfigured to accommodate these applications.
U.S. Pat. No. 5,005,169 issued Apr. 2, 1991 to Bronder et al. (hereinafter Bronder et al.) discloses a communications system for sending information over the guardbands. The system under Bronder et al. describes how a spread spectrum modulated information carrying signal is inserted in the guard bands that exist in the conventional Frequency Division Multiplexing (FDM) structure. In other words, Bronder et al. describes a system that uses the CDMA method. The guard band defined here is a small narrow frequency band (25 kHz) between two adjacent information carrying bands. However, it is well-known that the distance coverage that CDMA provides is rather limited.
U.S. Pat. No. 5,267,233 issued Nov. 30, 1993 to Bauerschmidt (hereinafter Bauerschmidt) describes a communication system that combines a FDM structure with a Time Division Duplex (TDD) structure. The Bauerschmidt system uses a voice detector to switch off the receiver so that data bits for transmission can be transmitted on the same time slot of the same channel. However, such TDD structure is at best a half-duplex communication technique. Accordingly, the Bauerschmidt system does not provide full duplex communications.
Thus, a need exists for a dynamic full duplex wireless communication system, apparatus, and method that implements widely accepted communication methods, makes efficient use of the allocated frequency band in transferring text, audio, and video data, and has large distance coverage.