Gerald Paul Labedz

Wideband channel measurements at 900 MHz

The paper describes RF channel measurements conducted in a mixed urban-suburban region of Bellevue, Washington using a BPSK DS-SS sounder with a bandwidth of 20 MHz (10 Mc/s) operating in the 915 MHz ISM band. The survey was used to study delay spread characteristics in a 1.23 MHz wide channel. The fast-fading envelope distribution of resolvable rays was found to vary between Rayleigh and Rician-distributed at 1.23 MHz bandwidth. At a higher bandwidth of 20 MHz the distribution was approximately Rician with a K-factor of 8-12 dB. It was estimated that a 4-finger, 2-port non-coherent IS-95 base station would make use of the second finger pair approximately 60% of the time. The differential delay between 1st and 2nd finger assignments was usually less than 8 /spl mu/s, and there was little observable variation in the delay of the first-arriving multipath component between channel soundings spaced at 3 s intervals.

AMPS cell transmitter interference to CDMA mobile receiver

There exists significant interference from an AMPS base transmitter to a CDMA mobile receiver. This interference is severe when the CDMA mobile gets close to a same-system noncolocated AMPS site or close to other-system AMPS site. We investigate the interference of AMPS cell site to a CDMA mobile subscriber unit in 1:3 colocated AMPS and CDMA deployment (or other pattern). A quantitative evaluation of the interference was carried out including the side-band noise and an exact evaluation of third order intermodulation. The paper covers same system interference as well as other system interference.

Predicting real-world performance for key parameters in a CDMA cellular system

A computer model based on theoretical and simulation work is described. This model takes as input radio characterization, propagation information, system configuration and parameter settings. The system model produces a plethora of time-continuous system performance information for each subscriber, cell and location in the system. The model was tested by attempting to predict key operational parameters, e.g. subscriber station receive and transmit power under full dynamic power control, in a field test carried out in Bellevue WA. The model was able to predict the time-continuous location-specific values of key parameters of the monitored equipment with small mean error. Additionally, simulation results for a single cell with multiple users is presented and compared with theory and other reported field results, again with excellent agreement.

Network and radio receiver simulation studies of the Pan-European digital cellular system .

Two GSM (Groupe Special Mobile) network simulation tools, TRANSIM and GSMRCVR, are discussed. The first has been effectively used to predict call-type traffic delays and processor performance and can also be used to configure mobile switching centers. Extensive simulations have been performed on the radio reception performance for GSM. Coding gains have been established for the basic coding/interleaving scheme. This scheme appears to break down at slower speeds and requires hopping over a number of frequencies to correct. Results have been found to be quite sensitive to the channel model used.<<ETX>>

A new time-based outage criterion for the forward and reverse links of DS-CDMA cellular systems

Previous work on outage criteria and cell admission policies in direct sequence CDMA cellular systems has focused on the reverse, or subscriber-to-base link. Such criteria generally are based on noise at the receiver. We show that a simple received noise rise estimate is not sufficient to declare a blocking or outage situation. We resolve the problem by proposing a new outage calculation which includes both a time sequential factor and simultaneous consideration of the forward link. The outage criterion is based on the inability of the physical transmitting device to produce enough power to generate the subjectively required error rate over some time continuous period. We show how the calculation can be applied to any distribution of subscribers, and cells, and any propagation environment. The outage is calculated not just statistically but can also be located in a realistic environment.