Showing papers on "Cognitive radio published in 1988"

Wireless intraoffice networks

Abstract: An overview of the existing and growing demands for wireless office information networks is provided, and the existing research activities are assessed in some detail The radio frequency (RF) and infrared (IR) communication technologies are examined as candidates for wireless intraoffice communications The available bandwidths, according to federal regulations and characteristics of the channel for RF communications, are given Digital narrow-band and wideband spread-spectrum RF communications are assessed in terms of supportable data rate or number of simultaneous users in one cell of a cellular architecture in an office environment Various limitations of IR communications are discussed and existing systems and architectures are reviewed

Distributed algorithm for efficient and interference-free broadcasting in radio networks

Abstract: The authors consider multihop, mobile, packet radio networks that need to determine broadcasting transmission schedules in a distributed way with the goal of avoiding interference and achieving reasonable efficiency. Several centralized scheduling schemes have been proposed in the literature, while very few and mostly ad hoc distributed schemes have been considered that generally suffer from serious weaknesses. The authors propose a distributed scheme for scheduling broadcasts that involves very limited overhead and has very good efficiency performance. >

Radio telecontrol system and method for operating the system

Abstract: A method for operating a radio telecontrol system for transmitting control commands to a machine, having a multi-channel transmitter and multi-channel receiver for frequency-modulated signals is characterised in that, when the reception of these radio signals is disturbed or absent, the radio channels in the receiver are automatically switched to an in each case other one of the existing channels until one of these further channels corresponds to a channel newly selected at the transmitter and the radio signals of this transmitter are received again undisturbed.

Control channel setting system for cordless key telephone system

Abstract: PURPOSE: To prevent interference of a control channel and to realize the device with a simple circuit by radiating a radio wave through a control channel with a prescribed time difference between stationary radio equipments when simultaneous data transmission exists. CONSTITUTION: A radio transmission reception circuit 46 sends and receives a transmission signal and a control signal through the forming of a radio line with a mobile radio telephone set 41 under the control of a control circuit 45. Which of a control channel of 2CH is used is designated to the stationary radio equipments 39a-39n from the circuit 45 to the circuit 46 and the designation is set through the setting of an extension number by an extension circuit 40 simultaneously. When a data is sent from a master set 32 and its control signal is a common control signal requiring radio communication to mobile radio telephone sets 41a-41n as a call of an external line incoming call, for example, the radiation timing of a radio wave is controlled according to the order number such that it is retarded by each of utilizing time (3sec) of the control channel. COPYRIGHT: (C)1990,JPO&Japio

Method for transmitting radio signals and transmission system for carrying out the method

Abstract: The method is used in the transmission of radio signals from radio users who cannot get into direct radio contact with one another, by means of a radio transmission system with radiating cables, which are electrically coupled only for the duration of a radio signal transmission either in a forward or backward direction, where the radio transmission system remains operational even following a break in a cable.

Call system for mobile radio equipment

Abstract: PURPOSE: To reduce the frequency of occurrence of a failure of a call and to improve the servicability to the user by setting a radio line with a stationary radio equipment of other radio zone if the setting of line with a stationary radio equipment of a radio zone is failed in the case of making a call while storing at least two radio zones. CONSTITUTION: A mobile radio equipment 3a is located at a location where radio zones 51, 52 are overlapped and stores the radio zones 51, 52 as the radio zones to which the mobile radio equipment belongs. In this case, when the mobile radio equipment 3a makes a call, e.g., a stationary radio equipment 41 is selected and the mobile radio equipment sends a call signal 1a including an identification signal of the stationary radio equipment 41. The stationary radio equipment 41 receiving the signal 41a sends a channel designation signal. Thus, if a designated speech channel is busy, the mobile radio equipment 3a sends a call signal 1b including an identification signal of other stationary radio equipment 42 after a prescribed time (t) elapses. Thus, the frequency of the occurrence of a failed call is reduced and the servicability to the user is improved. COPYRIGHT: (C)1990,JPO&Japio

Teleterminal system (mobile data communication)

Abstract: A teleterminal system is described that has been designed in response to the needs of mobile data communication. The system provides services by radio packet transmission with multichannel access techniques in small radio zones. The system features efficient frequency spectrum use, large subscriber capacity, and a small and light data terminal, and integrates radio transmission with packet switching and computer communication. Both automatic repeat request (ARQ) and authentication are adopted in the radio link. The system is virtually error free and is provided with a countermeasure against unauthorized invasion. A pilot system has been developed and experimentation was done for investigation and confirmation on a system design. More than an 80% coverage of service area is obtained in each zone to satisfy a BER of 1*10/sup -3/. >

Propagation modelling for cellular RF system planning

Abstract: Radio communication systems only operate satisfactorily if adequate signal strength is received by all communicating parties and if the level of interference is low enough not to degrade reception. Site location and frequency planning are therefore crucial factors in the design of any radio communication system. The author briefly describes the propagation and coverage estimation (PACE) system developed for and used by Racal to help plan the VODAFONE cellular radio system.

Limits of Radio Communication — Collaborative Transmission Over Cellular Radio Channels

Abstract: Communication by the radiation of electromagnetic waves — radiocommunication — is potentially the simplest and most flexible means of transmitting information over distances of more than a few metres. A transmitter, a receiver, and two antennas is all that is needed. Its flexibility lies in that it is wireless — pun intended! — especially if either the transmitter, or the receiver (or both) are mobile, when radio is the only feasible means of communication. But this very convenience and flexibility also makes radio the interesting and challenging field of endeavour that it is in practice. The difficulty is the all-pervasive transmission medium. Radio waves can propagate — as air-waves, space-waves, and so on — to many places where they are unwanted, whereas “wire” communication is guided (normally) only to where it is required. More subtly, the purpose of communication is to put people in contact, by means of suitable connecting arrangements and protocols. This element of organisation is built in to wire communications, if only because of the need to provide a transmission medium between all those who may wish to communicate; often it has been overlooked or neglected in the case of radiocommunication.

Digital mobile communications switching

Abstract: Digital switching controls for integrated-services digital mobile radio communications are discussed. The digital radio networks controls radio terminals by way of the radio multiaccess subscriber line. The network also handles tracking switching for call setup and handover for voice and data communications. The basic concepts of the signal reference model, layer configuration, and protocol structure of the user/network interface are described. >

Experimental direct-sequence spread-spectrum digital mobile radio transmission

Abstract: This paper is concerned with the conception and the realization of a direct-sequence spread-spectrum digital mobile radio transmission at 910 MHz. The system has been used either as a spread-spectrum communication modem or as a wideband channel sounder. The performance measurements, carried out in the laboratory, reveal a good theory and experiment agreement and they clearly show various advantages of spread spectrum techniques. The radio propagation conducted measurements have shown the temporal and spatial behaviours of the urban mobile radio channel. The measurement results may be used for a statistical modeling of the channel which in turn could lead to the transmission quality improvement.