1840328
Split-channel pipelined packet scheduling for wireless networks
To reduce medium access control (MAC) overhead and improve channel utilization, there has been extensive research on dynamically adjusting the channel access behavior of a contending station based on channel feedback information. This paper explores an alternative approach, named pipelined packet scheduling, to reduce the MAC overhead. MAC overheads can be divided into bandwidth-dependent and bandwidth-independent components and these overheads can both be reduced by using split-channel pipelining mechanisms, as demonstrated in this paper. In the past, pipelining mechanisms have not been well studied. This paper introduces two total pipelining schemes that attempt to fully pipeline contention resolution with data transmission. Further, the paper identifies shortcomings of total pipelining in the wireless environment and proposes a partial pipelining approach to overcome these shortcomings. Simulation results show that substantial performance improvement in channel utilization, average packet access delay, and access energy cost can be achieved with a properly designed scheme.
1110384
Priority scheduling in wireless ad hoc networks
Ad hoc networks formed without the aid of any established infrastructure are typically multi-hop networks. Location dependent contention and "hidden terminal" problem make priority scheduling in multi-hop networks significantly different from that in wireless LANs. Most of the prior work related to priority scheduling addresses issues in wireless LANs. In this paper, priority scheduling in multi-hop networks is discussed. We propose a scheme using two narrow-band busy tone signals to ensure medium access for high priority source stations. The simulation results demonstrate the effectiveness of the proposed scheme.
16121262
On physical carrier sensing in wireless ad hoc networks
The aggregate throughput of a wireless ad hoc network depends on the channel capacity, channel utilization (i.e., the fraction of channel capacity used for generating good put), and the concurrent transmissions allowed in the network. While channel utilization is determined by MAC overhead, physical carrier sense has been used as an effective way to avoid interference and exploit spatial reuse. Prior research has attempted to identify the optimal carrier sense range that can maximize the aggregate throughput. However, the impact of MAC overhead has been ignored. In this paper, we use both an analytical model and simulation results to show that MAC overhead has significant impact on the choice of optimal carrier sense range. If MAC overhead is not taken into account properly in determining the optimal carrier sense range, the aggregate throughput can suffer a significant loss.
31254944
Priority Scheduling in Wireless Ad Hoc Networks
Ad hoc networks formed without the aid of any established infrastructure are typically multi-hop networks. Location dependent contention and hidden terminal problem make priority scheduling in multi-hop networks significantly different from that in wireless LANs. Most of the prior work related to priority scheduling addresses issues in wireless LANs. In this paper, priority scheduling in multi-hop networks is discussed. We propose a scheme using two narrow-band busy tone signals to ensure medium access for high priority source stations. The simulation results demonstrate the effectiveness of the proposed scheme.
1833949
DSCR: a wireless MAC protocol using implicit pipelining
In wireless networks, the collision cost is much higher than wired networks since a station cannot detect collision until a transmission is over and the expected acknowledgment does not come back. Therefore, more efficient contention resolution algorithms are desired for wireless networks to reduce the collision probability among contending stations. IEEE 802.11 defines a distributed random access MAC protocol named DCF (Distributed Coordination Function), which uses binary exponential backoff (BEB) algorithm to resolve channel contention. In DCF, a station wanting to access the channel generates a random backoff counter uniformly distributed over the interval [0, CW] (CW represents contention window). This backoff counter corresponds to the number of idle slots this station has to wait before its transmission. The contention window, CW, is exponentially increased by a factor of 2 each time when a collision happens, and reset to the minimum value upon successful transmission. An appropriate choice of CW can optimize the performance of 802.11. However, the optimum value of CW changes with the network size and 802.11 operates far from this optimum point. In particular, in a heavily contended network, the collision probability increases significantly, degrading the performance of 802.11. To improve the performance of IEEE 802.11, [1] proposes that each station continuously observes channel activities and estimates the number of contending stations, hence, dynamically tune the value of CW to the optimum point. [2] also proposes a fast collision resolution algorithm, in which the winning station occupies the channel for a certain period of time to reduce the collision probability. However, both of these two schemes are designed for wireless LANs, where all stations are within each other’s transmission range. This paper proposes a MAC protocol, named DSCR (Dual Stage Contention Resolution), uses “pipelined” two stage contention resolution algorithm to reduce collision probability and achieve better channel utilization than 802.11 in both wireless LANs and ad hoc networks. In our prior work, we developed two explicit pipelining schemes, which use a separate control channel (either to transmit RTS/CTS or to send busy tone) to pipeline contention resolution with data transmission [4]. In contrast, DSCR performs implicit pipelining in that no separate control channel is required.
1335433
A wakeup scheme for sensor networks: achieving balance between energy saving and end-to-end delay
Energy saving is a critical task for sensor networks with limited energy supply. Wakeup schemes that turn off sensors' radio when communication is not necessary have great potential in energy saving. However, existing wakeup schemes encounter critical tradeoffs between energy saving and wakeup latency, and little attention has been paid to reducing the packet end-to-end delay while preserving the energy saving capability. We argue that a long delay can be detrimental for large sensor networks. We propose a wakeup scheme that helps to achieve the balance between energy saving and end-to-end delay. The conditions under which the proposed scheme can show improvement are identified.
8765654
Virtual Reality Tools for Internet-Based Robotic Teleoperation
This paper describes the general system and software architecture for the Internet-based robotic teleoperation system using virtual reality tools. The existing technology and application are discussed in this paper. An example is also presented based on the general architecture. Finally, the conclusion and future research direction are given.
34097947
Multiobjective second-order symmetric duality with F
We suggest a pair of second-order symmetric dual programs in multiobjective nonlinear programming. For these second-order symmetric dual programs, we prove the weak, strong and converse duality theorems under F-convexity conditions.
5734078
A DoS-limiting network architecture
We present the design and evaluation of TVA, a network architecture that limits the impact of Denial of Service (DoS) floods from the outset. Our work builds on earlier work on capabilities in which senders obtain short-term authorizations from receivers that they stamp on their packets. We address the full range of possible attacks against communication between pairs of hosts, including spoofed packet floods, network and host bottlenecks, and router state exhaustion. We use simulation to show that attack traffic can only degrade legitimate traffic to a limited extent, significantly outperforming previously proposed DoS solutions. We use a modified Linux kernel implementation to argue that our design can run on gigabit links using only inexpensive off-the-shelf hardware. Our design is also suitable for transition into practice, providing incremental benefit for incremental deployment.
14514560
Cone spline approximation via fat conic spline fitting
Fat conic section and fat conic spline are defined. With well established properties of fat conic splines, the problem of approximating a ruled surface by a tangent smooth cone spline can then be changed as the problem of fitting a plane fat curve by a fat conic spline. Moreover, the fitting error between the ruled surface and the cone spline can be estimated explicitly via fat conic spline fitting. An efficient fitting algorithm is also proposed for fat conic spline fitting with controllable tolerances. Several examples about approximation of general developable surfaces or other types of ruled surfaces by cone spline surfaces are presented.
8264127
Convex composite multi-objective nonsmooth programming
This paper examines nonsmooth constrained multi-objective optimization problems where the objective function and the constraints are compositions of convex functions, and locally Lipschitz and Gâteaux differentiable functions. Lagrangian necessary conditions, and new sufficient optimality conditions for efficient and properly efficient solutions are presented. Multi-objective duality results are given for convex composite problems which are not necessarily convex programming problems. Applications of the results to new and some special classes of nonlinear programming problems are discussed. A scalarization result and a characterization of the set of all properly efficient solutions for convex composite problems are also discussed under appropriate conditions.