Showing papers on "Wireless published in 1987"

Universal Digital Portable Communications: A System Perspective

Abstract: In our highly mobile society, the provision of voice and data communications to a person away from his/her wireline telephone has become a major communications frontier. The early penetration of this frontier has been based on very limited portable communications approaches, e.g., cordless telephones, mobile radio telephones, and radio paging. Each of these approaches only partially satisfies portable communications needs. This paper describes an approach to providing universal digital portable communications integrated into telephone networks. A system configuration employing time-division multiple-access radio link architecture and frequency reuse is described. Issues affecting radio link transmission rates and radio system coverage are discussed. Characteristics and parameters of a possible system to supplement the wire (or fiber) loop are indicated.

Correction to "Design and Experimental Results for a Direct-Sequence Spread-Spectrum Radio Using Differential Phase-Shift Keying Modulation for Indoor, Wireless Communications"

Abstract: We report on our design and measurements that have been made for a direct-sequence spread-spectrum radio using differential phase-shift keying modulation for a wireless PBX. We describe the design and implementation of a transmitter and a receiver using a surface acoustic wave (SAW) filter matching the spread-spectrum code of a user. The receiver performance is within 1 dB of the theoretical performance of a differential phase-shift keying (DPSK) receiver in the presence of additive white Gaussian noise. We also show receiver performance in a multipath fading indoor environment with multipath fade notches of up to 50 dB depth. The indoor channel multipath fading can be overcome by using an equal gain diversity combiner which is suitable when DPSK modulation is used. We confirm that the indoor mean power level attenuation follows the inverse fourth power of the distance. Also, we investigate the multiple-access capability of the system by introducing an interfering transmitter with a different spread-spectrum code sequence.

System applications for wireless indoor communications

Abstract: Buildings present a hostile environment for radio communications, with in-building radio propagation difficult to predict and continuously changing. W ireless indoor communications can be used in a bride range of applications to provide for user mobility, easy setup, and reconfiguration of terminals, telephones, and so forth. Such applications can be divided $#to two classes: (1) Narrowband applications, such as paging or wireless PBX systems for voice and low rate data and (2) Wideband applications, such as a wireless local area network capable of handling data rates u p to several Megabits per second. Buildings, however, present a hostile environment for radio communications, with in-building radio propagation difficult to predict and continuously changing. Problems include multipath and shadow fading, which reduce the coverage region, and dispersion due to delay spread, which limits the maximum data rate. Furthermore, in buildings with multiple users, interference among users can be a serious problem, and the available spectrum might be much less than that required to handle all potential users. In this article we describe various antenna diversity techniques, including selection, maximal ratio and optimum combining, and show how diversity, in combination with other techniques, can be used to overcome these problems. One such technique is resource sharing, which recognizes that, at any moment, only ;I small fraction of all users are experiencing transmission difficulties, and assigns extra system resources (for example, bandwidth or time slots) as needed to protect those users.\" We first briefly describe the indoor radio environment and show why diversity can be effective. We then describe techniques for narrowband applications , such as wireless PBX's, that can be used to increase the coverage region, eliminate interference problems, and permit frequency reuse within the same coverage region, thereby dramatically increasing system capacity. Finally, we describe techniques for wide-band applications, such as wireless local area networks , that can be used to increase both the maximum data rate and the coverage region. With indoor radio communication, there is rarely a line of sight between the transmitter and receiver, and multiple signal propagation paths exist. The signals from these paths combine both constructively and destructively at the receiver to produce multipath fading. For narrowband transmission, where the propagation delays associated with the various paths are extremely small compared to the inverse of the signal bandwidth, the channel can be considered as a Rayleigh fading channel with frequency flat fading [ 141. This Rayleigh fading …

Cordless telephone system

Abstract: A cordless telephone system is provided including a base communication unit and portable communication units. The base communication unit is connected to a number of telephone lines, and has the same number of radio transceivers as the telephone lines. Each of the portable communication units is connected to a respective one of the transceivers of the base communication unit by a cordless communication link. In operation, each of the portable communication units is intermittently rendered operative at a particular timing and a predetermined period which are designated by a first signal. The first signal is produced in the base communication unit, and is based on the number of portable communication units turned ON. The particular timing and predetermined period are changed in response to a second signal which is produced in the base communication unit, and which is based on the number of portable communication units turned ON, and on the number of wireless communication units being used.

Modem suited for wireless communication channel use

Abstract: The modem of this invention overcomes problems associated with use in a wireless radio frequency communications channel. This modem provides a data carrier detection (DCD) function for associated data terminal equipment even though a transmission carrier or tone is not used. Provision is also made for communicating with data terminal equipment operating at a substantially lower data rate than the modem data rate without requiring a reduction in the modem data rate.

Wireless handset for a telephone set

Abstract: A handset is provided with a microphone, a speaker, as well as a wireless transmitter and a wireless receiver, so that voice signals or voice waves can be transmitted and received. A wireless main unit is provided between the handset andthe telephone main unit, the wireless main unit having a signal transmission line, a wireless transmitter and a wireless receiver, so that the signals can be transmitted and received between the telephone set and the handset. When the handset is connected to the wireless main unit through a cord, the voice signals are transmitted to or received from the telepone set through the signal transmission line of the wireless main unit. When the cord of the handset is disconected from the wireless main unit, the handset and the wireless main unit are coupled together in a wireless system by wireless transmitters and wireless receivers provided in the handset and in the wireless main unit. Therefore, the telephone set can be used as an ordinary one or as a wireless one within a predetermined range.

In‐house wireless optical digital SSMA

Abstract: With the recent development of the office automation, portable in-house terminals for data communication have attracted attention. For this purpose, wireless transmission by optical link is considered promising, since it does not require the installation of signal lines. The past discussions and experiments, however, considered only the one-to-one or one-to-many communications, but many-to-many, i.e., multiple connections were not considered. This paper aims at the application of the spread-spectrum system to the wireless optical communication link to realize the multiple connections, and derives the basic theoretical expressions for the receiver characteristics. More precisely, the modulation scheme is selected taking the restriction into consideration, which is inherent to the inhouse wireless optical link. Then, the receiver error rate and the multiple connection characteristics of the proposed modulation scheme have been theoretically derived, providing the basis for the system design. Finally, a qualitative discussion is made on the construction and operation of the synchronous system for the proposed modulation scheme.

Movable sound input system

Abstract: PURPOSE:To remarkably expand the moving range of a worker carrying a conventinal analog radio equipment, by combining a wireless modem, the analog radio equipment, and a movable sound input device. CONSTITUTION:Analog radio equipments(WL)2 and 3 are provided, and a microphone 1 is connected to the radio equipment 2 on one side. And the radio equipment 3 on the other side is connected to a portable type sound input device(SR)4. A wireless modem(WM)5 is connected to the portable type sound input device 4. The worker performs the input of sound from the portable sound input device 4 within the applied range of the radio equipments 2 and 3, carrying the portable sound input device within the range of the wireless modems 5 and 6. The price of the wireless modem is cheaper down to 1/10 of a work range expanding measure using conventional antenna, and analog amplifier, and as a result, it is possible to construct a system economically.

Call channel allocating method

Abstract: PURPOSE:To effectively control the flexible allocation of a channel, by allocating the number of wireless channels corresponding to the number of moving machines existing within a wireless zone CONSTITUTION:For a common control channel used between a radio base station and a mobile station, a multioffice simultaneous/sequential transmission system is used The moving machine transmits the registration signal of a zone where its own party exists, to the radio base station after attaching a selected radio base station number, using the up channel of the common control channel All of the call channels, or a part of them, available at the radio base station, are managed and controlled mainly by a control station In this way, the number of the channels available at the radio base station, can be allocated corresponding to the number of the moving machines per zone

Radio telephone equipment

Abstract: PURPOSE: To prevent an important call loss in a communication by previously setting a subscriber class for indicating the class for respective radio telephone sets and forming the speech channel of the radio telephone set according to the subscriber class at the time of the transmission or the incomming call of the radio telephone set. CONSTITUTION: Plural wireless connection equipment CE for executing a wireless communication with the radio telephone set RTEL disposed in a radio zone disposed in the respectively different wireless zones Z 1 ∼Z n , a subscriber file 115b in which the subscriber class for indicating the class for every radio telephone set RTEL is previously stored and a means forming a speech path with the radio telephone set RTEL through the wireless connection equipment CE according to the subscriber class are provided. Thereby, since the subscriber class can limit and form the low speech path of the radio telephone set, the call loss of the imporatant communication can be prevented. COPYRIGHT: (C)1988,JPO&Japio