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The introduction of the general packet radio service marks the start of a new era in personal communications. The author looks at the technology and its implications for users and operators.

A new noncoherent parallel matched-filter (MF) acquisition scheme with reference filter (RF) is proposed for a direct-sequence spread-spectrum/multiple-access packet radio system. It is shown that a parallel MF-RF achieves higher packet throughput than a serial MFRF and a parallel MF without an RF.

The performance of a packet data buffer in a CDMA2000 radio access network supporting voice preference over packet data (VPOP) is investigated. Through numerical analysis the relationship between the packet data buffer size and the voice call holding time is investigated.

Expressions are derived for the asymptotic throughput bounds for both slotted and nonslotted, nonpersistent ICMA assuming coherent addition of interfering signals in environments of pure Rayleigh fading, and Rayleigh fading combined with distance-dependent path loss. The asymptotic lower throughput bounds are shown to be nonzero in value in the presence of capture. Hence, the ICMA protocol under such conditions of fading and capture is stable.

A complementary approach is presented for obtaining the link adaptation (LA) switching thresholds defining the regions (CIR ranges) where each coding scheme is most suitable. The approach is based on multiple replications providing an indication of the accuracy of the threshold. GPRS (General Packet Radio Services) and different operating environments are studied.

Traditionally, multihop wireless networks focus on datagram and mobility services. The packet radio network (PRNET), for example, was a very important contribution in that it provided a conceptually simple, distributed, reliable, totally asynchronous solution to the problem. PRNET handled datagram traffic reasonably well, but did not offer efficient multimedia support. Several multimedia, multihop (M/sup 3/) wireless network architectures have been developed, which assume some form of synchronous, time division infrastructure. The synchronous time frame leads to efficient multimedia support implementations. However, it introduces more complexity and is less robust in the face of mobility and channel fading. The author examines the impact of synchronisation on wireless M/sup 3/ network performance. First, he introduces MACA/PR, an asynchronous network based on the collision avoidance MAC scheme employed in the IEEE 802.11 standard. Then, he evaluates and compares several wireless packet networks ranging from the total asynchronous PRNET to the synchronised cluster TDMA network. He examines the tradeoffs between time synchronisation and performance in various traffic and mobility environments.

A threshold decision for code acquisition in direct-sequence spread-spectrum packet radio systems is described. It is shown that this scheme achieves lower false alarm probability than the acquisition scheme based on the Neyman-Pearson criterion, giving comparable performance for the detection probability.

The throughput performance of a broadcast DS/SSMA packet radio network using adaptive error control is investigated. Simulated results for the network throughput against offered load are presented and show that adaptive error control significantly increases the throughput performance at all offered loads.

The author presents a multiple-capture model for the centralised spread-spectrum (SS) packet radio systems in which each user is assigned common direct-sequence (DS) spreading code for packet transmission. Basic equations for the multiple-capture probability and throughput performance are derived at the central receiver. At the link-level, two key design parameters in common spreading code systems are evaluated, namely, the expected number of packets captured at the receiver and the allowable number of simultaneous transmissions that are supportable at a specified data bit-error rate and probability of packet capture. Using the block oriented systems simulator (BOSS), simulations were carried out for the central receivers with coherent, differential, and envelope header detection, and results from the simulations are compared with theoretical evaluations of the multiple-capture probability. It is shown, for a threshold approximation to the probability of data packet success, that the multiple-capture model significantly improves system throughput.

A multiple-frequency channel is proposed to enhance the capacity of slotted ALOHA radio networks. The throughput is derived considering each packet being frequency assigned randomly in an uncorrelated shadowing and fading channel. Poisson and binomial distributions are assumed for the packet arrival models for an infinite and a finite number of users, respectively.

The author addresses a multiple header detection issue for the centralised spread-spectrum packet radio system with common directsequence/ binary phase-shift-keying (DS/BPSK) modulation. Chernoff bounds on the false alarm and missed detection probabilities of the header are derived and computed for a specific class of spreading codes and header sequences. Using these performance bounds, the author compares the header sequences and finds a good one which can be received with small probability of false alarm and high probability of correct detection. He also determines a proper randomisation time to minimise the two bounds for given system parameters, and then calculates the allowable number of transmitting radios subject to a constraint on the bounds for this randomisation time.

To relieve the contention in packet initiations in CDMA packet radio networks, a novel protocol, the busy code broadcasting and sensing protocol, is proposed, and its steady-state throughput-delay performance upper bounds are numerically analysed. The results reveal that a high throughput of about 0.47 (when the normalised channel trafficr = 1) and a stable performance of the network can be achieved by busy code broadcasting and sensing to avoid possible packet conflicts in the CDMA packet radio channel. The hidden terminal problem which exists in carrier sense multiple access is avoided in the proposed protocol. The study also shows that the new protocol can use CDMA spreading codes more efficiently than can other conventional spreading code protocols.

Packet conflicts in an asynchronous distributed CDMA packet radio network is a main cause of throughput inefficiency and network instability. To reduce the packet conflicts due to random packet initiations in the network an alternative collision-avoiding CDMA protocol, the receiver-based (R) spreading code sensing protocol, is proposed and its performance is numerically analysed. The results reveal that, by using the code-sensing technique in the conventional receiver-based spreading code protocol, the throughput-delay performance and the stability of the network can be dramatically improved. The results are also compared with those of other CDMA spreading code protocols without code sensing. A two-dimensional time-continuous Markov chain model for the R code sensing protocol is developed to evaluate its steady-state performance.

The authors propose an ‘integrated packet reservation multiple access’ (IPRMA) protocol for transmitting both speech and data information. While speech users are allowed contend for reservation slots on a frame-by-frame basis, data users may reserve multiple slots across a frame to increase throughput. The protocol includes a priority mechanism which ensures that speech users have greater access to idle slots since speech packets have a more demanding delay constraint. The proposed scheme is shown to provide equitable access to channel resources for both types of users yielding improvements in overall system performance while significantly increasing data throughput compared to a system without data packet reservation.

The throughput of packet radio channels is analysed using the interference model in Rician fading environment and capture effect. Three types of packet protocols are considered, namely: (i) slotted ALOHA; (ii) unslotted nonpersistent inhibit sense multiple access (np-ISMA); and (iii) slotted nonpersistent ISMA. The test signal is always considered as Rician distributed and the interfering signal is modelled by either uncorrelated Rician or uncorrelated Rayleigh distributed. Numerical results are presented, indicating the effect of propagation impairments on channel capacity (i.e. maximum throughput). The results are of importance for mobile data networks, wireless office communications and other packet systems with contention-limited performance.

In using a CSMA (carrier-sense multi-access) protocol in a packet radio network, one cannot ignore the probability that the environment is so noisy that the channel state is misdetected. Similarly, with a BTMA (busy-tone multi-access) protocol, one must take into account the probability of misdetecting the busy or idle state of the channel. The authors focus on these problems and try to evaluate the throughput performance in p-persistent access schemes, using an iterative approximation method. Furthermore, a new protocol is suggested, which can effectively cope with the imperfect sensing property to achieve an improved throughput by sensing the channel in several consecutive slots.

A new wide-area data network is described. The network employs packet switching techniques within a multi-access, narrowband cellular radio environment and provides a flexible alternative to copper wire telecommunications for short data message applications. Following a discussion of the network requirements, the paper describes the key design areas in terms of a layered model. A new data link layer protocol called dynamic slotted reservation Aloha is introduced. This protocol is optimised for the bidirectional communication of packets containing around 1000 bits of application data. The practical implementation is presented briefly before a number of the major applications are discussed. >

Calculation of the throughput of a carrier sense multiple access (CSMA) packet radio network with capture over slow Rayleigh-fading channels is presented. The effects of capture on the throughput of the system are related to the modulation and coding technique of the transmission system, the general distribution of terminals in the area and the length of the transmitted packets. BPSK modulation and BCH coding are considered.

A software simulator for a mobile packet radio system is described. Bitwise coherent addition of interfering DPSKpackets can be expected, resulting in a smaller throughput than achieved with incoherent addition, but higher than in a nonfading channel.

The slotted ALOHA protocol is modified to accommodate stations with multiple directional antennas in a multihop packet radio network environment. The one-hop throughput is derived for both the Poisson station distribution and the deterministic lattice station distribution. Numerical results show that the throughput values are very close for the two distributions. If the number of stations in the transmission circle is fairly large, say 50, the throughput gain using directional antennas could be as large as the number of directional antennas used.

The throughput of a slotted-ALOHA radio channel with lognormal shadowing has been derived. Uncorrelated packet shadowing is shown to assist receiver capture, so that the throughput always exceeds the throughput obtained in both ‘ideal’ channels and channels with pure Rayleigh fading.

This paper proposes a multi-media packet protocol for realizing packetized data, voice, and video communications in a packet switched network. Requirements for such multi-media packet communications services are greatly manifold, ranging from low to high speed, low to high grade service quality or simple to sophisticated service facilities, depending on the communications media.The proposed protocol provides high-speed transmission function with priority rules, transmission error correcting functions and packet transit delay indicating functions for voice and video communications, in addition to the X. 25 protocol functions for data commmunications. Also, a newlylayered structure for this protocol is presented, in which functional overlaps among layers are eliminated and common functions used by every medium are arranged into lower layers.

The probability of establishing a connection of a given length through a network of randomly distributed packet radio stations with a given number of hops is calculated. The required density of stations to ensure that this probability is high is found, as is the expected number of hops for a given path length.

Statistical multiple access is analysed for a number of independent transmitter-receiver pairs exchanging data packets over a shared mobile-radio channel. Rayleigh fading ‘softens’ the channel, resulting in less packet contentions and higher traffic capacity than for the standard Aloha channel.

Frame synchronisation sequences with the smallest possible correlation sidelobes are determined by exhaustive search for the case when the frame synchronisation word is preceded by specific bit synchronisation patterns. For a given length these new sequences have significantly lower sidelobes than the optimum autocorrelation sequences.