26 research outputs found
On the performance of STDMA Link Scheduling and Switched Beamforming Antennas in Wireless Mesh Networks
Projecte final de carrera realitzat en col.laboració amb King's College LondonWireless Mesh Networks (WMNs) aim to revolutionize Internet connectivity due to
its high throughput, cost-e ectiveness and ease deployment by providing last mile
connectivity and/or backhaul support to di erent cellular networks. In order not to
jeopardize their successful deployment, several key issues must be investigated and
overcome to fully realize its potential. For WMNs that utilize Spatial Reuse TDMA
as the medium access control, link scheduling still requires further enhancements.
The rst main contribution of this thesis is a fast randomized parallel link swap
based packing (RSP) algorithm for timeslot allocation in a spatial time division multiple
access (STDMA) wireless mesh network. The proposed randomized algorithm
extends several greedy scheduling algorithms that utilize the physical interference
model by applying a local search that leads to a substantial improvement in the
spatial timeslot reuse. Numerical simulations reveal that compared to previously
scheduling schemes the proposed randomized algorithm can achieve a performance
gain of up to 11%. A signi cant bene t of the proposed scheme is that the computations
can be parallelized and therefore can e ciently utilize commoditized and
emerging multi-core and/or multi-CPU processors.
Furthermore, the use of selectable multi-beam directional antennas in WMNs,
such as beam switched phase array antennas, can assist to signi cantly enhance
the overall reuse of timeslots by reducing interference levels across the network and
thereby increasing the spectral e ciency of the system. To perform though a switch
on the antenna beam it may require up to 0.25 ms in practical deployed networks,
while at the same time very frequent beam switchings can a ect frame acquisition
and overall reliability of the deployed mesh network.
The second key contribution of this thesis is a set of algorithms that minimize the
overall number of required beam switchings in the mesh network without penalizing
the spatial reuse of timeslots, i.e., keeping the same overall frame length in the
network. Numerical investigations reveal that the proposed set of algorithms can
reduce the number of beam switchings by almost 90% without a ecting the frame
length of the network
On the performance of STDMA Link Scheduling and Switched Beamforming Antennas in Wireless Mesh Networks
Projecte final de carrera realitzat en col.laboració amb King's College LondonWireless Mesh Networks (WMNs) aim to revolutionize Internet connectivity due to
its high throughput, cost-e ectiveness and ease deployment by providing last mile
connectivity and/or backhaul support to di erent cellular networks. In order not to
jeopardize their successful deployment, several key issues must be investigated and
overcome to fully realize its potential. For WMNs that utilize Spatial Reuse TDMA
as the medium access control, link scheduling still requires further enhancements.
The rst main contribution of this thesis is a fast randomized parallel link swap
based packing (RSP) algorithm for timeslot allocation in a spatial time division multiple
access (STDMA) wireless mesh network. The proposed randomized algorithm
extends several greedy scheduling algorithms that utilize the physical interference
model by applying a local search that leads to a substantial improvement in the
spatial timeslot reuse. Numerical simulations reveal that compared to previously
scheduling schemes the proposed randomized algorithm can achieve a performance
gain of up to 11%. A signi cant bene t of the proposed scheme is that the computations
can be parallelized and therefore can e ciently utilize commoditized and
emerging multi-core and/or multi-CPU processors.
Furthermore, the use of selectable multi-beam directional antennas in WMNs,
such as beam switched phase array antennas, can assist to signi cantly enhance
the overall reuse of timeslots by reducing interference levels across the network and
thereby increasing the spectral e ciency of the system. To perform though a switch
on the antenna beam it may require up to 0.25 ms in practical deployed networks,
while at the same time very frequent beam switchings can a ect frame acquisition
and overall reliability of the deployed mesh network.
The second key contribution of this thesis is a set of algorithms that minimize the
overall number of required beam switchings in the mesh network without penalizing
the spatial reuse of timeslots, i.e., keeping the same overall frame length in the
network. Numerical investigations reveal that the proposed set of algorithms can
reduce the number of beam switchings by almost 90% without a ecting the frame
length of the network
Improving the resource utilization in Wireless Mesh Networks based on Spatial -TDMA
Projecte final de carrera realitzat en col.laboració amb King's College LondonWireless Mesh Networks are expected to gain signi cant importance in the telecom-
munication market in the near future. Nevertheless, some critical factors menace
them not to achieve their expected features. In this thesis we focus our research on
the improvement of their performance. To face the multiple access issue we consider
the utilization of Spatial Time Division Multiple Access (STDMA). STDMA bene ts
from the spatial distribution of nodes allowing the reuse of timeslots by users su -
ciently far apart. This feature permits a better utilization of the spectrum, but arises
an NP-complete optimization problem consisting in distributing e ciently links into
timeslots. In the rst part of the thesis, we will address the link scheduling problem
and we will propose two heuristics to try to improve the overall performance of the
system. In the second part of the thesis, we will deal with directional antennas,
and in particular, with switched beam antennas. Several works have demonstrated
the signi cant bene ts of switched beam antennas applied to WMNs. This kind of
antennas are formed by several xed beam patterns that are switched according to
the communications requirements. Switching among patterns cause, though, a con-
sumption of energy and a lose of time to stabilize the patterns. A set of algorithms
to reduce the switchings without deteriorating the frame length achieved with the scheduling algorithms will be presente
Achilles : Design of a high capacity mesh network with directional antennas
Master'sMASTER OF ENGINEERIN
Cross-layer schemes for performance optimization in wireless networks
Wireless networks are undergoing rapid progress and inspiring numerous applications. As the application of wireless networks becomes broader, they are expected to not only provide ubiquitous connectivity, but also support end users with certain service guarantees.
End-to-end delay is an important Quality of Service (QoS) metric in multihop wireless networks. This dissertation addresses how to minimize end-to-end delay through joint optimization of network layer routing and link layer scheduling. Two cross-layer schemes, a loosely coupled cross-layer scheme and a tightly coupled cross-layer scheme, are proposed. The two cross-layer schemes involve interference modeling in multihop wireless networks with omnidirectional antenna. In addition, based on the interference model, multicast schedules are optimized to minimize the total end-to-end delay.
Throughput is another important QoS metric in wireless networks. This dissertation addresses how to leverage the spatial multiplexing function of MIMO links to improve wireless network throughput. Wireless interference modeling of a half-duplex MIMO node is presented. Based on the interference model, routing, spatial multiplexing, and scheduling are jointly considered in one optimization model. The throughput optimization problem is first addressed in constant bit rate networks and then in variable bit rate networks. In a variable data rate network, transmitters can use adaptive coding and modulation schemes to change their data rates so that the data rates are supported by the Signal to Noise and Interference Ratio (SINR). The problem of achieving maximum throughput in a millimeter-wave wireless personal area network is studied --Abstract, page iv