Bulent Tavli

Broadcast capacity of wireless networks

We present an upper bound on the broadcast capacity of arbitrary ad hoc wireless networks. The throughput obtainable by each node for broadcasting to-all-of the other nodes in a network consisting of n nodes with- fixed transmission ranges and C bits per second channel capacity is bounded by O(C/n), which is equivalent to the upper bound for per node capacity of a fully connected single-hop network

TRACE: time reservation using adaptive control for energy efficiency

Time reservation using adaptive control for energy efficiency (TRACE) is a time frame based media access control (MAC) protocol designed primarily for energy-efficient reliable real-time voice packet broadcasting in a peer-to-peer, single-hop infrastructureless radio network. Such networks have many application areas for various scenarios that obey a strongly connected group mobility model, such as interactive group trips, small military or security units, and mobile groups of hearing impaired people. TRACE is a centralized MAC protocol that separates contention and data transmission, providing high throughput, bounded delay, and stability under a wide range of data traffic. Furthermore, TRACE uses dynamic scheduling of data transmissions and data summarization prior to data transmission to achieve energy efficiency, which is crucial for battery operated lightweight radios. In addition, energy dissipation is evenly distributed among the nodes by switching network controllers when the energy from the current controller is lower than other nodes in the network, and reliability is achieved through automatic controller backup features. TRACE can support multiple levels of quality-of-service, and minimum bandwidth and maximum delay for voice packets are guaranteed to be within certain bounds. In this paper, we describe TRACE in detail and evaluate its performance through computer simulations and theoretical analysis.

MH-TRACE: multihop time reservation using adaptive control for energy efficiency

Multihop time reservation using adaptive control for energy efficiency (MH-TRACE) is a distributed MAC protocol for energy efficient real-time packet broadcasting in a multihop radio network. In MH-TRACE, the network is dynamically partitioned into clusters without using any global information except global clock synchronization. The clustering algorithm is simple and robust enough to ensure that the gain from clustering is much higher than the clustering overhead, even in the presence of node mobility. In MH-TRACE, time is organized into superframes, which consist of several time frames. Each cluster chooses a frame for transmitting control packets and for the transmission of data from nodes in the cluster. However, each node in the network can receive all the desired packets in its receive range without any restriction based on the formed clusters. Each node learns about future data transmissions in its receive range from information summarization (IS) packets sent prior to data transmission by each transmitting node. Therefore, each node creates its own listening cluster and receives the packets it wants. By avoiding energy dissipation for receiving unwanted data packets or for waiting in idle mode, MH-TRACE guarantees the network to be highly energy efficient. Furthermore, since data transmission is contention free, the throughput of MH-TRACE is better than the throughput of CSMA type protocols under high traffic loads.

Energy and Spatial Reuse Efficient Network-Wide Real-Time Data Broadcasting in Mobile Ad Hoc Networks

In this paper, we present NB-TRACE, which is an energy-efficient network-wide voice broadcasting architecture for mobile ad hoc networks. In the NB-TRACE architecture, the network is organized into overlapping clusters through a distributed algorithm, where the clusterheads create a nonconnected dominating set. Channel access is regulated through a distributed TDMA scheme maintained by the clusterheads. The first group of packets of a broadcast session is broadcast through flooding, where each data rebroadcast is preceded by an acknowledgment to the upstream node. Nodes that do not get an acknowledgment for a predetermined time, except the clusterheads, cease to rebroadcast, which prunes the redundant retransmissions. The connected dominating set formed through this basic algorithm is broken in time due to node mobility. The network responds to the broken links through multiple mechanisms to ensure the maintenance of the connected dominating set. We compare NB-TRACE with four network layer broadcast routing algorithms (flooding, gossiping, counter-based broadcasting, and distance-based broadcasting) and three medium access control protocols (IEEE 802.11, SMAC, and MH-TRACE) through extensive ns-2 simulations. Our results show that NB-TRACE outperforms other network/MAC layer combinations in minimizing energy dissipation and optimizing spatial reuse, while producing competitive QoS performance

MC-TRACE: multicasting through time reservation using adaptive control for energy efficiency

In this paper, we present multicasting through time reservation using adaptive control for energy efficiency (MC-TRACE), which is an energy-efficient voice multicasting architecture for mobile ad hoc networks. MC-TRACE is a monolithic design, where the medium access control layer functionality and network layer functionality are performed by a single integrated layer. The basic design philosophy behind the networking part of the architecture is to establish and maintain a multicast tree within a mobile ad hoc network using broadcasting to establish the desired tree branches and pruning the redundant branches of the multicast tree based on feedback obtained from the multicast leaf nodes. Energy efficiency of the architecture is partially due to the medium access part, where the nodes can switch to sleep mode frequently; and partially due to the network layer part where the number of redundant data retransmissions and receptions are mostly eliminated. Furthermore, MC-TRACE achieves high spatial reuse efficiency by keeping the number of nodes taking part in multicasting operation minimal. We evaluated the performance of MC-TRACE through ns simulations and compared with flooding. Our results show that packet delivery ratio performance, energy efficiency and spatial reuse efficiency of MC-TRACE is superior to those of flooding

Protocols for local data delivery in wireless microsensor networks

Sensor networks are becoming increasingly important as tools for monitoring remote environments. As sensors are typically battery-operated, it is important to efficiently use the limited energy of the nodes to extend the lifetime of the sensor network. Two factors can greatly influence the performance of protocols for these networks: the data delivery model, which describes how the end user wants to access the data; and the network dynamics, which include sensor mobility as well as changes in sensor data rates throughout the lifetime of the network. In this paper, we look at several media access control protocols for sending data from sensors to a local data collector. Comparing these protocols shows that there is an inherent tradeoff in energy efficiency with adaptability of the protocol.

Energy efficiency and error resilience in coordinated and non-coordinated medium access control protocols

Energy efficiency of a MAC protocol is one of the most important performance metrics, especially in mobile ad hoc networks, where the energy sources are limited. Two key factors in achieving energy efficiency for a MAC protocol are coordination among the nodes and schedule-based channel access. In order to achieve a sufficient level of coordination among the nodes, and hence to achieve energy efficiency, the exchange of control information via control packets is vital. As such, coordinated MAC protocols, which regulate channel access through scheduling, have been shown to achieve very high energy efficiencies when compared to non-coordinated MAC protocols, which do not employ scheduling. However, due to their increased vulnerability to channel errors, the performance of coordinated MAC protocols is affected more by the channel bit error rate (BER) than non-coordinated MAC protocols, which lack such control packets. In this paper, we investigate the energy efficiency and resilience against channel errors for coordinated and non-coordinated MAC protocols. Our results reveal that it is possible to achieve better system performance with coordinated MAC protocols even in lossy channels, provided that the BER level is not extremely high.

The effects of channel errors on coordinated and non-coordinated medium access control protocols

In this paper, we investigate the effects of channel noise on the performance of coordinated and non-coordinated MAC protocols. Comparative evaluations of these protocols under a perfect channel assumption have shown that coordinated MAC protocols, which regulate channel access locally, outperform non-coordinated channel access schemes in terms of energy efficiency and throughput. However, coordinated MAC protocols are more vulnerable than non-coordinated MAC protocols to channel noise due to their dependence on the robustness of the control traffic. In order to observe the degradation in performance of a coordinated MAC protocol (MH-TRACE), we investigate the impact of losing control packets. Furthermore, the performance in terms of throughput, delay, and energy efficiency of both coordinated (MH-TRACE) and non-coordinated (IEEE 802.11) MAC protocols is explored using a general error model that takes into account the length of the packets. Our results show that despite its higher level of vulnerability, the coordinated MAC protocols performance is superior to the performance of the non-coordinated MAC protocol even when error rates are high.

NB-TRACE: network-wide broadcasting through time reservation using adaptive control for energy efficiency

We present network-wide broadcasting through time reservation using adaptive control for energy efficiency (NB-TRACE), which is an energy-efficient network-wide voice broadcasting architecture for mobile ad hoc networks. In the NB-TRACE architecture, the network is organized into overlapping clusters, where the clusterheads create a non-connected dominating set. Channel access is regulated through a locally maintained distributed TDMA scheme. The first group of packets of a broadcast session is broadcast through blind flooding. Each data rebroadcast includes an implicit acknowledgement to the upstream node. Nodes that do not get acknowledgement for a predetermined time, except the clusterheads, cease to rebroadcast, which prunes redundant retransmissions. The distributed connected dominating set formed through this basic algorithm is broken in time due to node mobility. The network responds to the broken links through passive and active clusterhead data transmission monitoring to ensure the maintenance of the connected dominating set. We compare NB-TRACE with flooding and gossiping using MH-TRACE, IEEE 802.11, and SMAC medium access control protocols through ns-2 simulations. Our results show that NB-TRACE outperforms other network/MAC layer combinations in terms of energy efficiency, packet delivery ratio, jitter, and number of rebroadcasts.

An analysis of coordinated and non-coordinated medium access control protocols under channel noise

In this paper, we present an analysis of the effects of channel noise on the performance of coordinated and non-coordinated MAC protocols. In order to observe the degradation in the performance of a coordinated MAC protocol (MH-TRACE) with increasing BER level, we created an analytical model to estimate MH-TRACES performance. This analytical model is validated through simulation experiments. Our results show that despite its higher level of vulnerability, the coordinated MAC protocols performance loss is comparable to the performance loss of the non-coordinated MAC protocol (IEEE 802.11) for low to mid BER levels (i.e., BER <10-4). On the other hand, for extremely high BER levels (i.e., BER ges10-4) the performance loss of the coordinated MAC protocol is comparatively higher than the performance loss of the non-coordinated MAC protocol due to its dependence on control traffic, which is also affected by the BER level