2,112 research outputs found
An Upper Bound on Multi-hop Transmission Capacity with Dynamic Routing Selection
This paper develops upper bounds on the end-to-end transmission capacity of
multi-hop wireless networks. Potential source-destination paths are dynamically
selected from a pool of randomly located relays, from which a closed-form lower
bound on the outage probability is derived in terms of the expected number of
potential paths. This is in turn used to provide an upper bound on the number
of successful transmissions that can occur per unit area, which is known as the
transmission capacity. The upper bound results from assuming independence among
the potential paths, and can be viewed as the maximum diversity case. A useful
aspect of the upper bound is its simple form for an arbitrary-sized network,
which allows insights into how the number of hops and other network parameters
affect spatial throughput in the non-asymptotic regime. The outage probability
analysis is then extended to account for retransmissions with a maximum number
of allowed attempts. In contrast to prevailing wisdom, we show that
predetermined routing (such as nearest-neighbor) is suboptimal, since more hops
are not useful once the network is interference-limited. Our results also make
clear that randomness in the location of relay sets and dynamically varying
channel states is helpful in obtaining higher aggregate throughput, and that
dynamic route selection should be used to exploit path diversity.Comment: 14 pages, 5 figures, accepted to IEEE Transactions on Information
Theory, 201
Relay selection in mobile multihop relay network
Mobile Multihop Relay (MMR) network is an attractive and low-cost solution for expanding service coverage and enhancing throughput of the conventional single hop network. However, mobility of Mobile Station (MS) in MMR network might lead to performance degradation in terms of Quality of Service (QoS). Selecting an appropriate Relay Station (RS) that can support data transmission for high mobility MS to enhance QoS is one of the challenges in MMR network. The main goal of the work is to develop and enhance relay selection mechanisms that can assure continuous connectivity while ensuring QoS in MMR network using NCTUns simulation tools. The approach is to develop and enhance relay selection that allows cooperative data transmission in transparent relay that guarantees continuous connectivity. The proposed relay selection defined as Co-ReSL depends on weightage of SNR, α and weightage of Link Expiration Time (LET), β. The QoS performances of the proposed relay selections are in terms of throughput and average end-to-end (ETE) delay. The findings for Co-ReSL shows that at heavy traffic load, throughput increases up to 5.7% and average ETE delay reduces by 7.5% compared to Movement Aware Greedy Forwarding (MAGF) due to cooperative data transmission in selective links. The proposed relay selection mechanisms can be applied in any high mobility multi-tier cellular network
Capacity Enhancement in 60 GHz Based D2D Networks by Relay Selection and Scheduling
Millimeter-wave or 60 GHz communication is a promising technology that enables data rates in multigigabits. However, its tremendous propagation loss and signal blockage may severely affect the network throughput. In current data-centric device-to-device (D2D) communication networks, the devices with intended data communications usually lay in close proximity, unlike the case in voice-centric networks. So the network can be visualized as a naturally formed groups of devices. In this paper, we jointly consider resource scheduling and relay selection to improve network capacity in 60 GHz based D2D networks. Two types of transmission scenarios are considered in wireless personal area networks (WPANs), intra and intergroup. A distributed receiver based relay selection scheme is proposed for intragroup transmission, while a distance based relay selection scheme is proposed for intergroup transmission. The outage analysis of our proposed relay selection scheme is provided along with the numerical results. We then propose a concurrent transmission scheduling algorithm based on vertex coloring technique. The proposed scheduling algorithm employs time and space division in mmWave WPANs. Using vertex multicoloring, we allow transmitter-receiver (Tx-Rx) communication pairs to span over more colors, enabling better time slot utilization. We evaluate our scheduling algorithm in single-hop and multihop scenarios and discover that it outperforms other schemes by significantly improving network throughput
Multihop Diversity in Wideband OFDM Systems: The Impact of Spatial Reuse and Frequency Selectivity
The goal of this paper is to establish which practical routing schemes for
wireless networks are most suitable for wideband systems in the power-limited
regime, which is, for example, a practically relevant mode of operation for the
analysis of ultrawideband (UWB) mesh networks. For this purpose, we study the
tradeoff between energy efficiency and spectral efficiency (known as the
power-bandwidth tradeoff) in a wideband linear multihop network in which
transmissions employ orthogonal frequency-division multiplexing (OFDM)
modulation and are affected by quasi-static, frequency-selective fading.
Considering open-loop (fixed-rate) and closed-loop (rate-adaptive) multihop
relaying techniques, we characterize the impact of routing with spatial reuse
on the statistical properties of the end-to-end conditional mutual information
(conditioned on the specific values of the channel fading parameters and
therefore treated as a random variable) and on the energy and spectral
efficiency measures of the wideband regime. Our analysis particularly deals
with the convergence of these end-to-end performance measures in the case of
large number of hops, i.e., the phenomenon first observed in \cite{Oyman06b}
and named as ``multihop diversity''. Our results demonstrate the realizability
of the multihop diversity advantages in the case of routing with spatial reuse
for wideband OFDM systems under wireless channel effects such as path-loss and
quasi-static frequency-selective multipath fading.Comment: 6 pages, to be published in Proc. 2008 IEEE International Symposium
on Spread Spectrum Techniques and Applications (IEEE ISSSTA'08), Bologna,
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