5,662 research outputs found
Enhancing IEEE 802.11MAC in congested environments
IEEE 802.11 is currently the most deployed wireless local area networking standard. It uses carrier sense multiple access with collision avoidance (CSMA/CA) to resolve contention between nodes. Contention windows (CW) change dynamically to adapt to the contention level: Upon each collision, a node doubles its CW to reduce further collision risks. Upon a successful transmission, the CW is reset, assuming that the contention level has dropped. However, the contention level is more likely to change slowly, and resetting the CW causes new collisions and retransmissions before the CW reaches the optimal value again. This wastes bandwidth and increases delays. In this paper we analyze simple slow CW decrease functions and compare their performances to the legacy standard. We use simulations and mathematical modeling to show their considerable improvements at all contention levels and transient phases, especially in highly congested environments
DTMsim - DTM channel simulation in ns
Dynamic Transfer Mode (DTM) is a ring based MAN technology that
provides a channel abstraction with a dynamically adjustable capacity.
TCP is a reliable end to end transport protocol capable of adjusting
its rate. The primary goal of this work is investigate the coupling
of dynamically allocating bandwidth to TCP flows with the affect this
has on the congestion control mechanism of TCP. In particular we
wanted to find scenerios where this scheme does not work, where either
all the link capacity is allocated to TCP or congestion collapse
occurs and no capacity is allocated to TCP. We have created a
simulation environment using ns-2 to investigate TCP over networks
which have a variable capacity link. We begin with a single TCP Tahoe
flow over a fixed bandwidth link and progressively add more complexity
to understand the behaviour of dynamically adjusting link capacity to
TCP and vice versa
Goodbye, ALOHA!
©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The vision of the Internet of Things (IoT) to interconnect and Internet-connect everyday people, objects, and machines poses new challenges in the design of wireless communication networks. The design of medium access control (MAC) protocols has been traditionally an intense area of research due to their high impact on the overall performance of wireless communications. The majority of research activities in this field deal with different variations of protocols somehow based on ALOHA, either with or without listen before talk, i.e., carrier sensing multiple access. These protocols operate well under low traffic loads and low number of simultaneous devices. However, they suffer from congestion as the traffic load and the number of devices increase. For this reason, unless revisited, the MAC layer can become a bottleneck for the success of the IoT. In this paper, we provide an overview of the existing MAC solutions for the IoT, describing current limitations and envisioned challenges for the near future. Motivated by those, we identify a family of simple algorithms based on distributed queueing (DQ), which can operate for an infinite number of devices generating any traffic load and pattern. A description of the DQ mechanism is provided and most relevant existing studies of DQ applied in different scenarios are described in this paper. In addition, we provide a novel performance evaluation of DQ when applied for the IoT. Finally, a description of the very first demo of DQ for its use in the IoT is also included in this paper.Peer ReviewedPostprint (author's final draft
TCP-Aware Backpressure Routing and Scheduling
In this work, we explore the performance of backpressure routing and
scheduling for TCP flows over wireless networks. TCP and backpressure are not
compatible due to a mismatch between the congestion control mechanism of TCP
and the queue size based routing and scheduling of the backpressure framework.
We propose a TCP-aware backpressure routing and scheduling that takes into
account the behavior of TCP flows. TCP-aware backpressure (i) provides
throughput optimality guarantees in the Lyapunov optimization framework, (ii)
gracefully combines TCP and backpressure without making any changes to the TCP
protocol, (iii) improves the throughput of TCP flows significantly, and (iv)
provides fairness across competing TCP flows
Active Queue Management for Fair Resource Allocation in Wireless Networks
This paper investigates the interaction between end-to-end flow control and MAC-layer scheduling on wireless links. We consider a wireless network with multiple users receiving information from a common access point; each user suffers fading, and a scheduler allocates the channel based on channel quality,but subject to fairness and latency considerations. We show that the fairness property of the scheduler is compromised by the transport layer flow control of TCP New Reno. We provide a receiver-side control algorithm, CLAMP, that remedies this situation. CLAMP works at a receiver to control a TCP sender by setting the TCP receiver's advertised window limit, and this allows the scheduler to allocate bandwidth fairly between the users
Application Protocols enabling Internet of Remote Things via Random Access Satellite Channels
Nowadays, Machine-to-Machine (M2M) and Internet of Things (IoT) traffic rate
is increasing at a fast pace. The use of satellites is expected to play a large
role in delivering such a traffic. In this work, we investigate the use of two
of the most common M2M/IoT protocols stacks on a satellite Random Access (RA)
channel, based on DVB-RCS2 standard. The metric under consideration is the
completion time, in order to identify the protocol stack that can provide the
best performance level
X-TCP: A Cross Layer Approach for TCP Uplink Flows in mmWave Networks
Millimeter wave frequencies will likely be part of the fifth generation of
mobile networks and of the 3GPP New Radio (NR) standard. MmWave communication
indeed provides a very large bandwidth, thus an increased cell throughput, but
how to exploit these resources at the higher layers is still an open research
question. A very relevant issue is the high variability of the channel, caused
by the blockage from obstacles and the human body. This affects the design of
congestion control mechanisms at the transport layer, and state-of-the-art TCP
schemes such as TCP CUBIC present suboptimal performance. In this paper, we
present a cross layer approach for uplink flows that adjusts the congestion
window of TCP at the mobile equipment side using an estimation of the available
data rate at the mmWave physical layer, based on the actual resource allocation
and on the Signal to Interference plus Noise Ratio. We show that this approach
reduces the latency, avoiding to fill the buffers in the cellular stack, and
has a quicker recovery time after RTO events than several other TCP congestion
control algorithms.Comment: 6 pages, 5 figures, accepted for presentation at the 2017 16th Annual
Mediterranean Ad Hoc Networking Workshop (MED-HOC-NET
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