In mobile ad hoc networks (MANETs) there is no centralized supervision over the network operations. In such networks, it is imperative to have protocols that are implemented locally in a distributed manner. To achieve high network performance utilizing only the wireless channels a distributed transmission‐scheduling medium‐access control (MAC) protocol is desirable. This type of protocol can guarantee a certain level of quality of service (QOS) and works well in congested networks. However, the transmission schedules are often decided in advance and if a node does not have a packet to transmit in its assigned slot then the slot is unused. We propose a protocol called recovering minislots transmission scheduling (RMTS) that salvages these unused transmission slots that would have otherwise been wasted. We show that the proposed protocol produces significant improvements in network performance over traditional transmission‐scheduling approaches.

We study the resource allocation and management issues related to heterogeneous wireless systems made up of several Radio Access Technologies (RATs) that collectively provide a unified wireless network to a diverse set of users through co-ordination managed by a centralized Global Resource Controller (GRC). We assume that the user devices are multi-modal, which makes it possible for each device to use the Access Point (AP)/Base Station (BS) of any available RAT at any given time. Through detailed protocol level simulations performed in ns-2, we show an increase in spectral efficiency of up to 99.2% and an increase in instantaneous fairness of up to 28.5% for two greedy sort-based user device-to-AP/BS association algorithms implemented at the GRC compared to a distributed solution where each user makes his/her own association decision.

We consider an ad hoc network consisting of frequency-agile radios that have the ability to change their carrier frequency and transmission rate over a wide range of possibilities. The radios in this type of network are permitted to utilize multiple nonoverlapping channels, and each channel differs significantly in its characteristics, such as achievable data rate, communication range, and traffic load. We introduce a new channel-access protocol for this type of network such that the selection of a traffic channel for a data packet transmission considers characteristics of the channels such as data rate, range, and load. We show that by accounting for these channel characteristics, our protocol is able to maintain high network-layer performance in a wide range of scenarios compared to a channel-access protocol that assumes homogeneous channels (when in fact the channels are heterogeneous), and channel-access protocols that only consider the data rate associated with a particular traffic channel.

New distributed protocols for channel access and adaptive spreading are described and evaluated for use in direct-sequence spread-spectrum packet radio networks that have no central controllers, access points, or base stations. The protocols rely on demodulator statistics to provide the information needed for efficient sharing of the frequency band and compensation for changes in the communications environment in a network of half-duplex radios for which simultaneous two-way communications is not possible.

In a mobile ad hoc network using broadcast transmission scheduling, a terminal that is ready to join the network must first determine the current state of the transmission-scheduling protocol. In order to transmit and receive packets without interference, the new terminal needs to notify other terminals of its presence and exchange information with them so that it can form a collision-free broadcast transmission schedule. A new distributed protocol is described that allows a new terminal to acquire sufficient information about the terminals in its local neighborhood so that it can efficiently integrate itself into the existing transmission schedule. The protocol is also designed to enable a group of terminals to form a new transmission schedule if one does not already exist. We show that a large group of terminals can quickly form a new and efficient collision-free transmission schedule

This paper presents a load-based transmission scheduling (LoBaTS) protocol for wireless ad hoc networks. Since terminals in these networks may be required to forward unequal amounts of traffic, a transmission scheduling protocol which assigns equal transmission capacity to all terminals may result in traffic bottlenecks as traffic load increases. The LoBaTS protocol allows terminals to alter their existing transmission schedules so that those terminals which are required to forward more traffic can reserve additional transmission slots, thereby alleviating traffic bottlenecks. The LoBaTS protocol is designed to avoid creation of new traffic bottlenecks, maintain collision-free broadcast transmissions, and execute with minimal disruption to the network. In addition, it requires only local information to operate, making it suitable for implementation in a distributed-control environment. Simulations utilizing a variety of test networks and traffic conditions show that the LoBaTS protocol greatly improves end-to-end packet delay, throughput, and completion rate when compared to a transmission schedule which does not account for traffic load.

A new protocol is presented for routing multimedia traffic in an energy-efficient manner in a frequency-hop, store-and-forward, packet radio network. The FH network employs an adaptive-transmission protocol integrated with a distributed, energy-aware routing protocol, based on least-resistance routing. Adaptive transmission gives rise to alternative paths through the network with different energy requirements. The adaptive routing and transmission protocols are designed to exploit the differences in the energy consumption of different routes and the service requirements of the different types of traffic. Results are provided that show that our energy-efficient routing protocol provides good service to the different types of media while conserving energy.

We study an algorithm, originally defined by Lyui (1991), for assigning collision-free broadcast transmissions for packet radio networks. The method has a number of advantages - it is distributed, fair, permits each terminal to calculate a different frame size, requires only a limited exchange of information, and does not require a contention-based channel-access protocol. These properties make the assignment algorithm particularly useful for dynamic ad hoc networks because the transmission assignments can be easily and quickly adapted to local changes in the topology. An improved description of Lyui's algorithm is given and new simulation results are presented to demonstrate the properties of the transmission assignments for a variety of large networks.

A set of adaptive protocols for mobile wireless frequency-hop spread-spectrum communication networks is described. The primary elements of the protocol suite are the adaptive-transmission protocol, the adaptive-routing protocol, and the adaptive-forwarding protocol. Together, these protocols control the transmission of packets on each link in the network and the routing of packets through the network. Each protocol interacts with the other protocols and with elements of the physical layer in order to obtain information about the energy requirements and interference conditions of the alternative routes. The protocols adapt their responses to the observed changes in these energy requirements and interference conditions. No measurements of the signal-to-noise ratio or the received power are required by the adaptive protocols.

The terminals in a mobile store-and-forward wireless network must be able to react quickly to changes in propagation conditions and interference levels on the links in a network. Routing updates are often very slow in responding to changes in link quality, especially for the links that are not utilized frequently. The adaptive-forwarding protocol can assist the routing protocol by forcing some transmissions on less frequently utilized links, thereby updating the information about the states of these links. We say that alt-forwarding occurs for a given packet if that packet was originally scheduled for transmission on one link but the adaptive-forwarding protocol elects to transmit the packet on a different link. By forcing a packet on an alternative link, we allow the adaptive-transmission protocol to update the transmission parameters for the link, and we cause the adaptive-routing protocol to deliver the packet along a secondary route. The feedback gathered by utilizing an alternative link helps the networking protocols respond to dynamic conditions and discover more energy-efficient routes. We show that by designing the criteria for selecting an alternative link to account for the status of the link and the likelihood that the link leads to an efficient route, there is a significant increase in the energy efficiency of the network.

The performance of an energy-efficient adaptive routing protocol is evaluated for a frequency-hop (FH) store-and-forward wireless network that must operate in the presence of partial-band interference. The routing protocol is based on least-resistance routing with a metric that accounts for link quality and energy consumption. The distributed routing protocol is integrated with the adaptive transmission and channel-access protocols. The performance of this protocol suite is demonstrated for a distributed FH network by use of a network simulation that includes multiple sources of partial-band interference. We find that the combination of energy-efficient routing and adaptive transmission improves the information throughput and energy efficiency of the network.

A new method is described for routing multimedia traffic in a frequency-hop (FH) store-and-forward packet radio network. The method is illustrated for traffic of two types, each type having its own throughput, delay, and error-rate requirements. A typical application is the routing of voice and data packets in a distributed multiple-hop network. In such an application, voice packets cannot tolerate much delay, but they are allowed to contain a small number of frame erasures while data packets must be delivered error-free even if a moderate delay is required to do so. The fully distributed routing protocol presented in the paper takes into account the type of service required for each type of traffic, and it adapts to the interference as seen by the FH radio receivers in the network. Our approach to multimedia routing is based on least-resistance routing with different link and path resistance metrics for different message types. Each of the resistance metrics for a link reflects the ability of the link to provide the service required by the one of the message types. This includes, but is not limited to, a measure of the likelihood of successful reception by the FH radio receiver for that link. The route selection for a particular type of packet depends on the resistances of the links along the routes from that packet's source to its destination. In general, different routes may be selected for different types of packets. The primary conclusion of this paper is that the quality of service increases for each of the two types of multimedia traffic if the routing protocol accounts for the type of message that is being relayed.

Reliable data distribution within spread-spectrum packet radio networks requires high performance from the network protocols. This paper describes research in forwarding and routing protocols that are designed specifically for slow-frequency hop (SFH) packet radio networks in which some of the radios are subjected to excessive interference. It is shown that information extracted from the decoder can be used to aid the network protocols. New metrics are introduced that use this information to give a quantitative assessment of the interference environment experienced by the receiver in an SFH radio. Forwarding protocols are developed that can react quickly to local sources of interference, and the metrics that are introduced permit the routing algorithm to react to changes in the interference conditions in the network.>

Adaptive protocols that specify the ways in which a radio is permitted to modify its normal forwarding procedures based on information obtained locally in the network are considered. A computer program has been developed to simulate a frequency-hop (FH) packet radio network with partial-band jamming and interference due to other FH and narrowband radios. The radios in the network use time-slotted, receiver-directed, FH spread-spectrum signaling. Results on throughput, delay, and end-to-end probability of success are presented, and comparisons between different forwarding protocols are given for a static network topology with both static and mobile network jamming.>

Research in adaptive, decentralized routing for frequency-hop packet radio networks with mobile partial-band jamming. A routing technique called least-resistance routing (LRR) is developed, and various versions of this routing method are examined. LRR uses a quantitative assessment of the interference environment experienced by a radio's receiver to determine a resistance value for that radio. Two components for the interference environment are considered: transmissions from other radios and partial-band jamming. The resistances for each of the radios in a particular path are combined to form the path resistance, and packets are forwarded on the path with the smallest resistance. Comparisons are made between different versions of LRR and between LRR and previously developed adaptive routing techniques. It is found that LRR is an effective way for dealing with mobile jamming in a frequency-hop packet radio network. Significant increases in throughput and end-to-end probability of success are obtained with LRR.>