Abstract—Attractive features of time-hopping spread-spectrum multiple-access systems employing impulse signal technology are outlined, and emerging design issues are described. Performance of such communications systems in terms of achievable transmission rate and multiple-access capability are estimated for both analog and digital data modulation formats under ideal multiple-access channel conditions. Index Terms—Impulse radio, ultra-wide bandwidth. I. INTRODUCTION TO IMPULSE RADIO SYSTEMS THE TERM wideband, as applied to communication systems, can have different meanings. In conventional systems, “wideband ” implies a large modulation bandwidth and thus a high data transmission rate. In this paper, a spread-spectrum

Abstract — Impulse radio, a form of ultra-wide bandwidth (UWB) spread-spectrum signaling, has properties that make it a viable candidate for short-range communications in dense multipath environments. This letter describes the characteristics of impulse radio using a modulation format that can be supported by currently available impulse signal technology and gives analytical estimates of its multiple-access capability under ideal multiple-access channel conditions. Index Terms—Impulse radio, spread-spectrum multiple access, time hopping, ultra-wideband radio. I. A RATIONALE FOR IMPULSE RADIO IMPULSE RADIO communicates with baseband pulses of very short duration, typically on the order of a nanosecond, thereby spreading the energy of the radio signal very thinly from near dc to a few gigahertz. When this pulse is applied to

Abstract—This paper introduces an improved nonlinear parallel interference cancellation scheme for code-division multiple access (CDMA) that significantly reduces the degrading effect on the desired user of interference from the other users that share the channel. The implementation complexity of the scheme is linear in the number of users and operates on the fact that parallel processing simultaneously removes from each user a part of the interference produced by the remaining users accessing the channel the amount being proportional to their reliability. The parallel processing can be done in multiple stages. The proposed scheme uses tentative decision devices at the multiple stages to produce the most reliably estimated received data for generation and cancellation of user interference. Simulation results are given for a multitude of different situations, in particular, those cases for which the analysis is too complex. Index Terms — Communication theory, spread spectrum communicatons. I.

This paper proves large-system asymptotic normality of the output of a family of linear multiuser receivers that can be arbitrarily well approximated by polynomial receivers. This family of receivers encompasses the single-user matched filter, the decorrelator, the minimum mean square error (MMSE) receiver, the parallel interference cancelers, and many other linear receivers of interest. Both with and without the assumption of perfect power control, we show that the output decision statistic for each user converges to a Gaussian random variable in distribution as the number of users and the spreading factor both tend to infinity with their ratio fixed. Analysis reveals that the distribution conditioned on almost all spreading sequences converges to the same distribution, which is also the unconditional distribution. This normality principle allows the system performance, e.g., the multiuser efficiency, to be completely determined by the output signal-to-interference ratio (SIR) for large linear systems.

Abstract—A key goal for future personal communication systems is to integrate voice and data communications in the same wireless packet network. This paper deals with a time-division multiple-access (TDMA)-based wireless packet network which provides access to a base station (BS) over a common shortrange radio uplink channel for many spatially dispersed voice and data user terminals. Voice users obtain reservations for their talkspurts by means of a random access protocol. Speech activity detection is assumed for voice communications to temporarily allocate data transmissions slots unused by voice users during silence periods. A suitable polling protocol is assumed to allow data users to access the uplink channel. The network proposed demonstrates good performance both in terms of quality of voice communications which is independent of data transmissions and maximum data traffic load supported with bounded delay. A performance comparison with the packet-reservation multipleaccess (PRMA) protocol and more recent alternatives have also been performed to highlight the good behavior of the proposed protocol. Index Terms—Wireless packet network. I.

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