The high quality PCS communications are enabled in environments where adjacent PCS service bands operate with out-of-band harmonics that would otherwise interfere with the system's operation. The highly bandwidth-efficient communications method combines a form of time division duplex (TDD), frequency division duplex (FDD), time division multiple access (TDMA), orthogonal frequency division multiplexing (OFDM), spatial diversity, and polarization diversity in various unique combinations. The method provides excellent fade resistance. The method enables changing a user's available bandwidth on demand by assigning additional TDMA slots during the user's session.

Method for frequency division duplex communications

A discrete multitone stacked-carrier spread spectrum communication method is based on frequency domain spreading including multiplication of a baseband signal by a set of superimposed, or stacked, complex sinusoid carrier waves. In a preferred embodiment, the spreading involves energizing the bins of a large Fast Fourier transform (FFT). This provides a considerable savings in computational complexity for moderate output FFT sizes. Point-to-multipoint and multipoint-to-multipoint (nodeless) network topologies are possible. A code-nulling method is included for interference cancellation and enhanced signal separation by exploiting the spectral diversity of the various sources. The basic method may be extended to include multielement antenna array nulling methods for interference cancellation and enhanced signal separation using spatial separation. Such methods permit directive and retrodirective transmission systems that adapt or can be adapted to the radio environment. Such systems are compatible with bandwidth-on-demand and higher-order modulation formats and use advanced adaptation algorithms. In a specific embodiment the spectral and spatial components of the adaptive weights are calculated in a unified operation based on the mathematical analogy between the spectral and spatial descriptions of the airlink.

Highly bandwidth efficient communications

Two or more antenna elements are arranged in the vertical direction to give vertical spatial adaptivity to a wireless discrete multitone spread spectrum communications system. The system is based on a combination of Discrete Multitone Spread Spectrum (DMT-SS) and multi-element adaptive antenna array technologies. This enables the automatic positioning of a beam in the vertical direction to position nulls where interferers are located on the same azimuth but are separated in elevation.

Vertical adaptive antenna array for a discrete multitone spread spectrum communications system

In an exemplary communication system, a multiplicity of mobile terminals are to share a communication link with a host processor communicating through base transceivers. The mobile terminals evaluate communication signals being transmitted to one or more of the mobile transceivers and according to the evaluation of such signals, each mobile terminal independently selects a relatively high data rate or a lower more conservative data rate for communication with the host processor. The mobile terminal enters a dormant state after a fixed period elapses during which the mobile unit is not engaged in communication with the base station. Periodically, the mobile terminal reenters active state in receive mode for a brief interval and if no polling signal or other message directed to the mobile terminal is present, the mobile terminal returns to dormant state. When a signal is directed to the mobile terminal, the mobile terminal remains in active receive mode until a fixed period after a communication session is completed and then returns to dormant/active cycling. A base station utilizing a dormant polling protocol transmits polling sequences to a plurality of remote transceivers during periods of heavy loading. During periods of low loading, the base station stops polling and enters into a dormant state, listening for communication request from the remote transceivers. Upon receiving such a request, the base station immediately responds by servicing the requesting remote transceiver. In this way, the base station provides optimized utilization of the communication channel during periods of heavy and light loading conditions.

Remote radio data communication system with data rate switching

Improved apparatus for a radio communication network having mobile transceiver units in communication with base transceiver units. The radio communication network is adaptive in that in order to compensate for the wide range of operating conditions, a set of variable network parameters are adapted for communication between transceivers in the network. These parameters may, for example, define optimized communication on the network under current network conditions. Examples of such parameters may include, without limitation: packet size, data rate, type of modulation, type or degree of error correction coding and spread spectrum communication parameters.

Radio frequency communication network having adaptive communication parameters

A nondiversity radio system provides compensation for multipath fading by means of continuous amplitude feedback. Intelligence is transmitted from one station by means of frequency modulation, while amplitude modulation is caused by the fading en route. At the other station the received amplitude envelope is fed back as part of a frequency modulated, return intelligence signal. The feedback envelope is used at the first station to amplitude modulate the subsequent transmission to precompensate for the anticipated fade and produce fade-free reception at the other station. The system is especially well suited for mobile radio telephone applications since fading can be eliminated at a relatively simple, single branch mobile station.

W Lee

Papers

Radio system with feedback for fading compensation