Klein S. Gilhousen

On the capacity of a cellular CDMA system

It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

Variable rate vocoder

A method of speech signal compression, by variable rate coding of frames of digitized speech samples, comprising the steps of: determining a level of speech activity for a frame of digitized speech samples; selecting an encoding rate from a set of rates based upon said determined level of speech activity for said frame; coding said frame according to a coding format of a set of coding formats for said selected rate wherein each rate has a corresponding different coding format and wherein each coding format provides for a different plurality of parameter signals representing said digitized speech samples in accordance with a speech model; and generating for said frame a data packet of said parameter signals.

Soft handoff extends CDMA cell coverage and increases reverse link capacity

The effect of handoff techniques on cell coverage and reverse link capacity is investigated for a spread spectrum CDMA system. It is shown that soft handoff increases both parameters significantly relative to conventional hard handoff. >

On the system design aspects of code division multiple access (CDMA) applied to digital cellular and personal communications networks

A breadboard CDMA digital cellular system was developed by QUALCOMM and demonstrated in San Diego in November 1989. In February 1990, an extensive technical field trial was carried out in midtown Manhattan with NYNEX Mobile. For the purposes of carrying out the CDMA trials and demonstrations, a total of three cell-site and two mobile prototype units were built. In each case, the demonstration system utilized two actual cell sites and one mobile and included A/B comparisons with the commercial analog system. The fundamental features of CDMA, such as power control and soft handoff, were tested and proven in a variety of field conditions. The authors describe the CDMA signal and waveform design, the CDMA system design, CDMA power control, and additional features of CDMA.<<ETX>>

Increased capacity using CDMA for mobile satellite communication

The performance of a spread-spectrum CDMA (code-division multiple access) system in a mobile satellite environment is analyzed. Comparisons to single-channel-per-carrier FDMA systems are presented which show that the CDMA approach provides greater capacity. Results from computer simulations, laboratory tests, and field tests of a prototype modem are also presented. The tests results show excellent performance of the modem in the mobile environment and also the feasibility of the spread-spectrum approach to satellite mobile communications. >

Soft Handoff Extends CDMA Cell Coverage and Increase Reverse Link Capacity

We present a simple model for analyzing the soft handoff, and hard handoff performance as well as quantitative performance improvement measures for the capacity of the reverse links. The results will be based on a propagation model that represents the μth power of the distance (average path loss) and the log-normal component representing the shadowing losses.

OmniTRACS: a commercial Ku-band mobile satellite terminal and its applicability to military mobile terminals

The technical characteristics of the OmniTRACS system are described. This system is the first operational mobile Ku-band satellite communications system and provides two-way message and position determination service to mobile terminals using existing Ku-band satellites. Interference to and from the system is minimized by the use of spread-spectrum techniques, together with low-power, low-data-rate transmissions. The applicability of this technology to implement a military mobile terminal operating over existing SHF satellites is also presented. Features discussed include the return- and forward-link modulating signals, the return-link power density, and the mobile-terminal hardware.<<ETX>>

The CDMA Digital Cellular System An ASIC Overview

The Code Division Multiple Access (CDMA) protocol has been proposed along with other standards to compete for the next genera t i on of ce l lu la r telecommunications. This paper will describe the CDMA system, give an overview of some of the basic principles of the system, and how that system has been partitioned into custom ASICs.