Measurement-based methods for the reassignment of a call to a time-slot with less cochannel interference on a time-division multiple access (TDMA) radio link are described and evaluated using discrete-event simulation. Portable radio access, transfer triggering, and time-slot selection are simulated using an integrated radio and traffic model. It was found that link quality can be maintained with a low transfer rate, even under heavy traffic load. Performance was robust with respect to trigger measurement error. Hysteresis reduced the transfer rate without noticeably affecting quality.< >
A computer-simulation study of user access in a universal digital portable communications system is described. An access algorithm consisting of relative power channel-ranking followed by data error detection is evaluated and compared to an optimal reference in a co-channel interference environment. For typical propagation conditions and radio configurations, it was found that an access algorithm based on the ranking of system channels by relative power provides a viable means of channel selection for the portable radio. It was found that the multiple-block data error check improved transmission quality in a co-channel interference environment, approaching the optimum with respect to the 99% statistical reliability criterion.< >
In the portable and mobile information age, the services delivered to the user will be primarily determined by the user. The radio and wireless network technologies used to deliver these services should enable them, not limit them. Thus, it is necessary to understand the demands of wireless products, applications, and services from a top-down, layered point of view. The objective of the paper is to discuss how to usefully model the performance of wireless applications and their protocols without having to construct models so detailed in a layer by layer sense as to be impractical.
A computer simulation study of user access in a universal digital portable communications system is described. The performance of a portable radio access algorithm is evaluated in a cochannel interference environment. For typical propagation conditions, the ranking of channels by relative power provides a viable means of channel selection with respect to optimal performance.< >
Computer simulations of portable radio access were made to compare access performance using two dissimilar path loss models. One model corresponds to a residential environment, where customers are served by external radio ports (fixed radios). The other model was published by Ericsson Radio Systems from measurements in one office building. The results of the study quantify the impact of the contrasting service assumptions on the spectral allocation required for reliable portable radiotelephone service. Simulation results show that these quite different path loss models produced radically different predicted performance in cochannel interference-limited operation. In the residual environment, with a path loss exponent of 4 and a log-normal standard deviation of 10-dB for shadowing, a reuse factor of at least 25 is required for a 10-dB uplink SIR (signal to cochannel interference ratio) at the first percentile. With Ericsson's in-building model, a reuse factor of 4 with 30-m interport spacing or a reuse factor of 2 with 45-m interport spacing results in equal quality and reliability.< >
The problem of assigning a time slot to a user in a frequency-reuse time-division multiplexed digital portable radio system is considered. Time-slot assignment algorithms are studied using a discrete-event stochastic computer simulation that models many concurrent two-way radio links. Three time-slot assignment algorithms were modeled: random selection of an idle time slot, selection of the idle time slot with the least interference power, and selection of the idle time slot with the largest signal-to-interference ratio not exceeding a given threshold. It is shown that under heavy traffic loads, measurement-based assignment of time slots yields improvements in transmission quality of 8 dB (local mean) to 15 dB (instantaneous) over random assignment for 99% of the users. As a result, the amount of radio spectrum needed is halved according to local mean performance.< >
The author gives results of a simulation study of the uplink and downlink transmission quality of portable-radio-based multiple access in a frequency-reuse radio system. In addition to shadow and Rayleigh fading, the positional variability of portable users, differences in uplink and downlink interference, and independence of multipath fading for the uplink and downlink are modeled. The study has shown that portable-radio-based multiple access can provide acceptable two-way transmission quality in an interference-limited environment. This assumes a simple and economical fixed-port configuration based on one TDM/TDMA (time-division multiplexing/time-division multiple-access) channel assigned to each port in a regular reuse pattern operating independently in terms of control and signal processing. It is shown that this approach provides a cost-effective design for the fixed radio port grid.< >
Measurement-based methods for the reassignment of a call to another time-slot with less cochannel interference on a time-division multiple access (TDMA) radio link are described and evaluated using a discrete-event simulation. Portable radio access, transfer triggering, and time-slot selection are modeled using an integrated radio and traffic call model. Results showed that link quality can be maintained with a low transfer rate, even under busy conditions. Regeneration of transfers was minimal. Performance was robust with respect to trigger measurement error, whereas the dynamic range of transmission quality measurement was found to be more critical in maintaining quality. Hysteresis reduced the rate of time-slot transfer while only minimally affecting quality.< >
The use of narrow beam directional antennas in wireless messaging has the potential of improving the transmission quality, increasing base station capacity, and reducing the number of base stations needed to provide a service for portable radio users. Directional antenna beams increase the protection to cochannel interference. The performance of a three-sector, twelve beam antenna system is compared with an omnidirectional and a conventional three-sector antenna configuration via computer simulation.
Network databases will be essential to support wide area connectivity between personal communications services (PCS) users for a variety of data management functions ranging from user mobility to communications security. The authors present a model for real-time database query and update processes associated with user mobility, registration/deregistration activity and call delivery. The mean and probability distribution of database transaction volume are then estimated both analytically and by Monte Carlo simulations. The authors' results indicate that for PCS in a regional calling area, the real-time query rate is an order of magnitude higher than the near-term load of intelligent network databases, and in addition, a substantial amount of real-time updates is required.< >
'%3e%3ccircle r='20' fill='%23008'/%3e%3ccircle r='17.5' fill='%23fff'/%3e%3ccircle r='3.5' fill='%23008'/%3e%3cg id='d'%3e%3cg id='c'%3e%3cg id='b'%3e%3cg id='a' fill='%23008'%3e%3ccircle r='.875' transform='rotate(7.5 -8.75 133.5)'/%3e%3cpath d='M0 17.5.6 7 0 2l-.6 5L0 17.5z'/%3e%3c/g%3e%3cuse xlink:href='%23a' transform='rotate(15)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(30)'/%3e%3c/g%3e%3cuse xlink:href='%23c' transform='rotate(60)'/%3e%3c/g%3e%3cuse xlink:href='%23d' transform='rotate(120)'/%3e%3cuse xlink:href='%23d' transform='rotate(-120)'/%3e%3c/g%3e%3c/svg%3e)