Jean-Paul M. G. Linnartz

Exact analysis of the outage probability in multiple-user mobile radio

A novel mathematical method is presented to express the outage probability for a desired radio signal received from a mobile transmitter in the presence of multiple interfering signals with combined log-normal and Rayleigh fading. In contrast to previously reported analyses, this exact method avoids approximation of the PDF of the received powers of the various signals. This is useful in determining the spectrum efficiency and performance of (interference-limited) radio networks for high-capacity cellular telephony, two-way paging, packet radio and other mobile data networks. >

Stability of mobile slotted ALOHA network with Rayleigh fading, shadowing, and near-far effect

Dynamic network behavior is investigated using the classical ALOHA queueing model extended to mobile channels. The focus is on the assessment of receiver capture probabilities, based on a general propagation model for mobile radio communications. Queueing of packets in a mobile slotted ALOHA network with Rayleigh fading, shadowing, and UHF groundwave propagation is studied, using a finite Markov chain model. It is shown that receiver capture, assisted by all three propagation mechanisms, reduces bistability of the network substantially compared to the retransmission strategy. Results are presented for a uniform spatial distribution of the packet traffic ordered to the ALOHA channel. The near-far effect is highlighted, since the total network performance and the spatial distribution of the attempted traffic interact. >

Near-far effects in land mobile random access networks with narrow-band Rayleigh fading channels

The near-far effect of random access protocols in mobile radio channels with receiver capture is investigated. To this end, the probability of successful reception of a packet from a terminal at a known distance from the central receiver is obtained taking into account Rayleigh fading, UHF propagation attenuation, and the statistics of contending packet traffic in radio nets employing slotted ALOHA, carrier sense multiple access (CSMA) or inhibit sense multiple access (ISMA) protocols. Various models of receiver capture are compared, namely packet error rates for synchronous detection in slow- and fast-fading channels, and the probability that the signal-to-interference ratio is above a required threshold. >

Effect of coding in digital microcellular personal communication systems with co-channel interference, fading, shadowing, and noise

An analytical model is developed for the performance of a microcellular radio network in the presence of cochannel interference and additive white Gaussian noise. The modulation schemes considered are binary phase-shift keyed (BPSK), binary frequency-shift keyed (BFSK), and quadrature phase-shift keyed (QPSK). The multiple-access channel is statistically modeled by one Rician-distributed desired signal and several uncorrelated Rayleigh plus log-normally shadowed interfering signals, propagating according to dual path loss law with a turning point. The performance is determined in terms of bit error rate (BER), outage probability, block error probability, crosstalk probability, and spectrum efficiency, considering both fast and slow multipath fading. The effect of error correction codes, consisting of blocks with equal number of bits, on the performance parameters is also studied. The computational results show that the propagation loss exponents, Rician factor, turning point, and cell size all plays a major role in the design of an efficient microcellular system. >

Performance of personal communication networks with error correction coding in microcellular channels

The performance of microcellular radio networks is investigated by evaluating the bit error rate (BER) for a Rician fading desired signal with BPSK/BFSK/QPSK modulation in the presence of Rayleigh fading co-channel interference, log-normal shadowing and additive white Gaussian noise. The influence of the normalised reuse distance and cluster size on the BER and spectrum utilisation is investigated. Also, the probability of successful reception of a block of bits is analyzed. In particular, the effect of error correction coding on the probability of success, considering fast and slow multipath fading is addressed.<<ETX>>

Site diversity in land-mobile cellular telephony network with discontinuous voice transmission

Cellular radio channels suffer from signal outages due to multipath fading and shadowing. Analytical expressions are given for the probability that the instantaneous C/I-ratio drops below a required protection ratio. A radio signal from a mobile subscriber exhibits outages at different base station sites with relatively low correlation. The quality of communication over a mobile telephone circuit can be improved by appropriately combining voice segments received at various base stations. The probability of dropping a voice segment for an end-to-end «up-link» circuit (mobile-to-PSTN) in an interference-limited cellular network with discontinuous voice transmission and macro diversity is evaluated mathematically. Asymptotic expressions of the signal outage probability for high average C/I-ratios are presented in closed form.

Near-far effect on slotted ALOHA channels with shadowing and capture

Signal statistics are modelled in an environment of shadowing and ground wave path loss. This propagation model is used to investigate the channel performance of a slotted ALOHA network. The results are presented as receiver capture probability vs. packet propagation distance, with the log-normal variance and the offered traffic as parameters. Log-normal spatial distributions and uniform distributions of users over the coverage area are compared. The former facilitate the analysis of mobile packet-radio channels with near-far effect and shadowing and can often approximate the latter type of distribution. It is shown that stability and throughput cannot be realistically studied by (quasi-) uniform distributions. The log-normal subscriber density with a spatial spread of 8.68 dB gives a viable alternative to the study of the heavily loaded collision-type multiple-access channel.<<ETX>>

Throughput of inhibit sense multiple access with propagation delays

A large number of terminals transmitting data packets over a common radio channel to a central base station is studied. In inhibit sense multiple access (ISMA), the base station broadcasts a busy signal when an incoming packet is being received, to inhibit other terminals from colliding transmissions. This busy signal arrives at each terminal with a propagation delay, proportional to the distance between the base station and the terminal. This leads to unfairness in the probability of successfully transmitting a data packet, since nearby terminals have more up-to-date information on the actual channel status than remote terminals. This unfairness is additional to the advantage that nearby terminals have because of the capture effect, which is also considered. The paper applies nonstationary Poisson processes to describe the random arrivals of data packets at the central receiver. It is shown that the probability of a successful attempt to transmit a packet decreases, approximately linearly with the distance between the transmitter and the central receiver. The total throughput is also assessed, and it is found that the assumption of a fixed propagation delay adopted in CSMA studies by others gives too optimistic results for ISMA. Moreover, the analysis suggests a subtle change of the fixed delay approximation that enhances its accuracy, without adding complexity. The effect of propagation delays in random access radio networks are of increasing importance, since newly developed systems are designed to transmit with increasingly high bit rates. >

Performance analysis of a slotted-ALOHA network using error correction and error detection coding with BPSK modulation

The performance of a slotted ALOHA-network in a slow Rayleigh-fading channel for mobile data communications is investigated considering error correction and detection coding with binary phase shift keying (BPSK) modulation. The performance is measured in terms of receiver error probability and throughput. An enhanced performance is obtained by using error correction coding. In spite of the use of error correction coding, a packet can be in error, i.e. the receiver erroneously detects a codeword that none of the terminals transmitted. Bounded distance decoding can be used effectively to reduce the packet error probability. A comparison of the performance is presented for a specific code with equal Hamming distance d/sub min/, exchanging between the error correcting and error detecting capability of that code. Also, the effects of signal carrier detection on receiver error probability and throughput are investigated.<<ETX>>

One dimensional cellular network with "spatial-ALOHA" protocol

We address the transmission of data packets from base stations to mobile terminals in a one-dimensional cellular network. The probability that a data packet successfully arrives at the destined mobile terminal highly depends on the activity of nearby co-channel base stations. Motivated by favorable results from earlier studies we consider a network in which all base stations use the same radio channel. Packets lost because of mutual interference are retransmitted with a random backoff mechanism. Recursive arguments are applied for the calculation of the mean time necessary for a base station to deliver the packet, provided that in an initial state all stations have packets to transmit. The average delivery time, maximized over all base station locations, is also analyzed. The relations obtained give some further insight into the behavior of a (highway) cellular data network.