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A distributed power-control algorithm with active link protection (DPC/ALP) is studied in this paper. It maintains the quality of service of operational (active) links above given thresholds at all times (link quality protection). As network congestion builds up, established links sustain their quality, while incoming ones may be blocked and rejected. A suite of admission control algorithms, based on the DPC/ALP one, is also studied. They are distributed/autonomous and operate using local interference measurements.

Spread spectrum techniques and collision avoidance multiple access protocols are combined to form a new set of medium access protocols for mobile wireless ad hoc networks. The Request-to-Send and Clear-to-Send message dialogue solves the "hidden terminal" and the "exposed terminal" problems and speeds up the retransmission. The spreading code assignment avoids disruption of any ongoing transmission by an intruder. Simulation results confirm that a higher channel throughput is achieved by the new protocols even in a dense network. I. INTRODUCTION Designing an efficient and effective medium access control (MAC) protocol with collision avoidance capability in a mobile ad hoc network is a very challenging task because the network is self-organizing without the aid of wired backbone or centralized network control. The existing MAC protocols can be classified into ALOHA [1], carrier sense medium access (CSMA) [2], multiple access with collision avoidance (MACA) [3], MACAW [4], floor acquis...

Studies of ad hoc wireless networks are a relatively new field gaining more popularity for various new applications. In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, and signal fading effects. Although a lot of research has been conducted on MAC protocols, the various issues involved have mostly been presented in isolation of each other. We therefore make an attempt to present a comprehensive survey of major schemes, integrating various related issues and challenges with a view to providing a big-picture outlook to this vast area. We present a classification of MAC protocols and their brief description, based on their operating principles and underlying features. In conclusion, we present a brief summary of key ideas and a general direction for future work.

This thesis addresses the problems of managing the transmissions of stations in a spread-spectrum packet radio network so that the system can remain effective when scaled to millions of nodes concentrated in a metropolitan area. The principal difficulty in scaling a system of packet radio stations is interference from other stations in the system. Interference comes both from nearby stations and from distant stations. Each nearby interfering station is a particular problem, because a signal received from it may be as strong as or stronger than the desired signal from some other station. Far-off interfering stations are not individually a problem, since each of their signals will be weaker, but the combined effect may be the dominant source of interference. The thesis begins with an analysis of propagation and interference models. The overall noise level in the system (mainly caused by the many distant stations) is then analyzed, and found to remain manageable even as the system scales ...

In this paper, we study, via simple discrete mathematical models, the problems of data distribution and data collection in wireless sensor networks. The work that follows continues the work presented by the authors in [1] where the focus was on sensor networks equipped with unidirectional antenna elements. Here we shift our interest to networks equipped with omnidirectional antenna elements. In particular we show how the data distribution and collection tasks can be performed optimally (with respect to time) on tree networks and give the corresponding time performances of those strategies. We also present a strategy for general graph networks that performs within a factor of 3 of the optimal performance. Finally we compare the performance of a network equipped with omnidirectional antenna elements with one equipped with unidirectional antenna elements. We show the latter outperforms the former by 33% at most in tree networks. To that purpose we included relevant results on directional antenna sensor networks, partly obtained in [1].

In this paper, the effect of scheduling on the performance of CDMA wireless ad hoc networks is examined. In ad hoc networks, it is necessary to suppress transmissions by nodes around the desired receiver in order to achieve successful communication. This minimum separation, the guard zone, has important implications on carrier sensing and other MAC-level protocols. But previously, the guard zone has not been well understood. In this paper, the guard zone is investigated in CDMA ad hoc networks, with non-spread spectrum ad hoc networks being a special case where the spreading gain is unity. It is shown that the size of this exclusion zone has a large impact on the transmission capacity of ad hoc networks, and an optimal guard zone is found using stochastic geometry. These results provide useful insight in the design of contention resolution algorithms as compared to pure random access in ad hoc networks.

A new signal processing based collision resolution technique for random access wireless ad hoc networks is proposed in this paper. Without assuming the knowledge of propagation channels and signal waveforms, the proposed algorithm is capable of separating colliding packets by exploiting channel diversities and known symbols embedded in data packets. Compared with training-based methods, the proposed algorithm requires considerably fewer known symbols. This algorithm can be applied to various spread spectrum and narrowband systems along with existing medium access control protocols. Index Terms---Collision resolution, random access network, semi-blind approach. I. INTRODUCTION A. Packet Collision and Multiple Packet Reception in Random Access Networks I N A SLOTTED random access ad hoc network, all users share a common radio channel for immediate packet transmission. A packet collision occurs when more than one user transmits in the same slot. For conventional narrowband networks,...

This paper motivates the need for Multiple Path Transport #MPT# of video and image information in a multihop mobile radio network. The video and image information is encoded non-hierarchically into multiple descriptions #MDC# with the following objectives. The received picture quality should be acceptable even if only one description is received and every additionally received description contributes to enhanced picture quality.Typical applications will need a higher bandwidth#higher reliability connection than that provided by current mobile networks. For supporting these applications a mobile node may need to set up and use multiple paths to the desired destination, either simply because of the lackofraw bandwidth on a single channel or because of its poor error characteristics, which reduces its e#ective throughput. In the context of this work, the principal reasons for considering suchanarchitecture are providing high bandwidth and more robust end-to-end connections. We describe a protocol architecture that addresses this need and, with the help of simulations, we demonstrate the feasibilityofthis system and compare the performance of the MDC-MPT scheme to that of a hierarchical coding scheme.

Abstract—Data collection, i.e., the aggregation at the user location of information gathered by sensor nodes, is a fundamental function of sensory networks. Indeed, most sensor network applications rely on data collection capabilities, and consequently, an inefficient data collection process may adversely affect the performance of the network. In this paper, we study via simple discrete mathematical models, the time performance of the data collection and data distribution tasks in sensory networks. Specifically, we derive the minimum delay in collecting sensor data for networks of various topologies such as line, multiline, and tree and give corresponding optimal scheduling strategies. Furthermore, we bound the data collection time on general graph networks. Our analyses apply to networks equipped with directional or omnidirectional antennas and simple comparative results of the two systems are presented. Index Terms—Data collection, delay, sensory networks. I.