Spelling suggestions: "subject:"delay etworks"" "subject:"delay enetworks""
1 |
Performance trade-off analysis in bidirectional network beamforming.Zaeri Amirani, Mohammad 01 October 2011 (has links)
This research examines a two-way relay network consisting of two transceivers and
multiple parallel relays, which are equipped with single antennas and operate in a halfduplex
mode. In this system, the two transceivers prefer to exchange their information via
relays. It is assumed that the relays have the full instantaneous channel state information
(CSI) and relay the signals using the amplify-and-forward (AF) method.
The performance of two AF bi-directional network beamforming schemes, namely
multiple access broadcast channel (MABC) strategy and time division broadcast channel
(TDBC) protocol, under joint optimal power control and beamforming design are
studied and compared. To do so, we first design a TDBC-based bi-directional network
beamformers, through minimization of the total power consumed in the whole network
subject to quality of service (QoS) constraints, for the case with a direct link between
the two transceivers. The corresponding power minimization problem is carried out over
the transceiver transmit powers as well as relay beamforming weights, thus resulting in a
jointly optimal power allocation and beamforming approach. We devise optimal secondorder
cone programming based solutions as well as fast gradient-based solutions to these
problems.
Then these solutions are exploited to compare the performance of the underlying
TDBC-based approach to that of the MABC-based technique developed in [1]. This
comparison is important because the TDBC approach appears to have certain advantages
which can be exploited towards improving the performance of two-way network
beamforming. These advantages include the additional degree of freedom as well as the
possibility of benefitting from the availability of a direct link between the two transceivers.
Interestingly, in the absence of a direct link between the two transceivers, we show that
when the QoS constraints are imposed to meet certain given probabilities of un-coded error
(or, equivalently, to meet certain signal-to-noise ratio constraints), these two schemes
perform closely in terms of the minimum total transmit power. However, when the QoS
iv
constraints are used to guarantee certain given rates, the MABC-based scheme outperforms
the TDBC counterpart. In the case when a direct link exists between the two
transceivers, the TDBC-based approach can outperform the MABC-based method provided
that the direct link is strong enough. / UOIT
|
2 |
Design and Analysis of Coded Cooperation in Relay NetworksChu, Josephine 06 August 2010 (has links)
This dissertation deals with wireless communications using cooperating relay nodes.
Specifically, this dissertation relaxes two restrictive conditions ubiquitous in the current literature. First, the assumption that relay nodes can perform complex calculations is lifted. Demodulate-encode-forward (DEF) is a low-complexity relaying scheme where the relay is asked only to demodulate, not decode, a source transmission. The implementation of DEF and various methods that can be used with DEF to improve the performance while satisfying the hardware complexity limitations are detailed here. Second, we remove the assumption that the relays either transmit the complete source codeword or not transmit at all. When relays have limited resources, each relay may only be able to transmit part of the source codeword. Fractional cooperation, which allows nodes to transmit a fraction of the source codeword, is proposed and analyzed. Fractional cooperation is also very flexible because coordination between relaying nodes is not required.
A third contribution of this dissertation is the use of the union-Bhattacharyya bound
(UBB) to analyze relay networks. The bound has the significant advantage of accounting for the specifics of the system parameters and coding scheme used. The UBB is
shown here to provide an effective and efficient scheme for relay selection, performance prediction, and system design. It can also be used to distribute relay resources in order to optimize the total energy consumed and error rate performance. A sub-optimal distributed algorithm that can be used to solve the optimization problems is introduced.
|
3 |
Design and Analysis of Coded Cooperation in Relay NetworksChu, Josephine 06 August 2010 (has links)
This dissertation deals with wireless communications using cooperating relay nodes.
Specifically, this dissertation relaxes two restrictive conditions ubiquitous in the current literature. First, the assumption that relay nodes can perform complex calculations is lifted. Demodulate-encode-forward (DEF) is a low-complexity relaying scheme where the relay is asked only to demodulate, not decode, a source transmission. The implementation of DEF and various methods that can be used with DEF to improve the performance while satisfying the hardware complexity limitations are detailed here. Second, we remove the assumption that the relays either transmit the complete source codeword or not transmit at all. When relays have limited resources, each relay may only be able to transmit part of the source codeword. Fractional cooperation, which allows nodes to transmit a fraction of the source codeword, is proposed and analyzed. Fractional cooperation is also very flexible because coordination between relaying nodes is not required.
A third contribution of this dissertation is the use of the union-Bhattacharyya bound
(UBB) to analyze relay networks. The bound has the significant advantage of accounting for the specifics of the system parameters and coding scheme used. The UBB is
shown here to provide an effective and efficient scheme for relay selection, performance prediction, and system design. It can also be used to distribute relay resources in order to optimize the total energy consumed and error rate performance. A sub-optimal distributed algorithm that can be used to solve the optimization problems is introduced.
|
4 |
Fundamental Aspects of Cooperative Interference ManagementDo, Hieu January 2013 (has links)
Today and future wireless networks are facing one of their greatest limiting factors:interference. This is due to the unprecedented increase in the number of connecteddevices. Therefore, in order to meet the ever increasing demand for data rate andquality of services, more advanced techniques than what we have today are requiredto deal with interference. This thesis takes a step towards interference managementin multiuser wireless systems by means of relaying and cooperation. We study fourfundamental building blocks in network information theory, propose new codingschemes, and derive limits on the capacity regions. The first problem we consider is the one-sided interference channel with bidirectional and rate-limited receiver cooperation. We propose a coding scheme that tailors two versions of superposition coding with classical relaying protocols. Theproposed scheme unifies and recovers previous results for the unidirectional coop-eration, yet in simpler forms. Analytical and numerical results confirm the benefitsof cooperation and illuminate the ideas behind the coding strategy. The second problem generalizes the first one by allowing the existence of bothcrossover links in the channel. We propose a coding scheme for this channel byextending noisy network coding to encompass rate-splitting at the encoders. Theachievable rate region is shown to be the same as a region achieved by explicitbinning. As a corollary, we prove that noisy network coding achieves the capacityregion of the Gaussian channel within 1 bit, under strong interference. Our resultis among the first to show constant-gap optimality of noisy network coding for amultiple-unicast problem, and to demonstrate equivalence in terms of achievablerates of two different coding approaches for a noisy interference network. We follow up by introducing a dedicated relay into the interference channelwhich simultaneously helps both receivers. For this third problem, the interferencechannel with a relay, we propose new coding schemes based on layered codes for long- and short-message quantize-forward techniques. The short-message schemesshow improvements in the achievable rates compared to other known coding tech-niques, especially when the channel is asymmetric, while relaxing the excessive delayissue of the long-message scheme. The analysis also reveals the trade-off betweenachievable rates, encoding and decoding delays, and complexity. In the fourth problem, we propose a new model for cooperative communication,the interfering relay channels, which consists of two neighboring relay channelsinducing interference to each other. Each relay, by utilizing a finite-capacity andnoise-free link to its own receiver, helps the receiver decode the desired message.We characterize the exact and approximate capacity region and sum-capacity forvarious classes of channels. The established results generalize and unify severalknown results for the relay and interference channels.The methods and results shown in this thesis aim at providing insight intopotential techniques for cooperative interference management in real-world systems. / <p>QC 20131001</p>
|
5 |
Channel estimation and training sequence design in one-way and two-way relay networksWang, Gongpu Unknown Date
No description available.
|
6 |
Asynchronous bi-directional relay-assisted communication networksVahidnia, Reza 01 February 2014 (has links)
We consider an asynchronous bi-directional relay network, consisting of two singleantenna
transceivers and multiple single-antenna relays, where the transceiver-relay
paths are subject to different relaying and/or propagation delays. Such a network can
be viewed as a multipath channel which can cause inter-symbol-interference (ISI) in
the signals received by the two transceivers. Hence, we model such a communication
scheme as a frequency selective multipath channel which produces ISI at the two
transceivers, when the data rates are relatively high. We study both multi- and
single-carrier communication schemes in such networks.
In a multi-carrier communication scheme, to tackle ISI, the transceivers employ
an orthogonal frequency division multiplexing (OFDM) scheme to diagonalize the
end-to-end channel. The relays use simple amplify-and-forward relaying, thereby
materializing a distributed beamformer. For such a scheme, we propose two different
algorithms, based on the max-min fair design approach, to calculate the subcarrier
power loading at the transceivers as well as the relay beamforming weights.
In a single-carrier communication, assuming a block transmission/reception scheme,
block channel equalization is used at the both transceivers to combat the inter-blockinterference
(IBI). Assuming a limited total transmit power budget, we minimize
the total mean squared error (MSE) of the estimated received signals at the both
transceivers by optimally obtaining the transceivers??? powers and the relay beamforming
weight vector as well as the block channel equalizers at the two transceivers.
|
7 |
Optimal Node Placement in Wireless Multiple Relay NetworksWang, Suhuan 18 August 2008 (has links)
This thesis explores the optimal node placement for linear Gaussian multiple relay
networks of an arbitrary size and with one source-destination pair. Consider
the the
low attenuation regime (path loss exponent less than 3/2). Under the condition that the
minimum achievable rate from source to destination is maintained, we derive upper
bounds of node placement with the incoherent and coherent coding schemes, and examine
the optimal power assignment related to the node placement with the coherent
coding scheme. We prove that the farthest distance between two adjacent nodes is
bounded even for an infinite total number of relay nodes, and closed-form formulas
of the bounds are derived for both the coding schemes. Furthermore, the distance
from the source to the destination is of the same order as the total number of nodes,
given the path loss exponent greater than one half under the incoherent coding scheme and the path loss exponent greater than 1
with coherent relaying with interference subtraction coding scheme. Conditioned on
a conjecture based on the simulation results, we also provide heuristic upper bounds,
which are a little tighter than the strictly proved bounds. The bounds provided in
this thesis can serve as a helpful guideline for the relay extension problem in practical
network implementation.
|
8 |
Optimal Node Placement in Wireless Multiple Relay NetworksWang, Suhuan 18 August 2008 (has links)
This thesis explores the optimal node placement for linear Gaussian multiple relay
networks of an arbitrary size and with one source-destination pair. Consider
the the
low attenuation regime (path loss exponent less than 3/2). Under the condition that the
minimum achievable rate from source to destination is maintained, we derive upper
bounds of node placement with the incoherent and coherent coding schemes, and examine
the optimal power assignment related to the node placement with the coherent
coding scheme. We prove that the farthest distance between two adjacent nodes is
bounded even for an infinite total number of relay nodes, and closed-form formulas
of the bounds are derived for both the coding schemes. Furthermore, the distance
from the source to the destination is of the same order as the total number of nodes,
given the path loss exponent greater than one half under the incoherent coding scheme and the path loss exponent greater than 1
with coherent relaying with interference subtraction coding scheme. Conditioned on
a conjecture based on the simulation results, we also provide heuristic upper bounds,
which are a little tighter than the strictly proved bounds. The bounds provided in
this thesis can serve as a helpful guideline for the relay extension problem in practical
network implementation.
|
9 |
Adaptive OFDM Cooperative SystemsAmin, Osama Mohammed Hussein 06 December 2010 (has links)
Cooperative communication is a promising technique for wireless communication systems where wireless nodes cooperate together in transmitting their information. Such communication transmission technique, which realizes the multiple antenna arrays in a distributed manner over multiple wireless nodes, succeeds in extending the network coverage, increasing throughput, improving both link reliability and spectral efficiency.
Available channel state information at the transmitting nodes can be used to design adaptive transmission schemes for improving the overall system performance. Throughout our work, we adaptively change loaded power and/or bit to the Orthogonal Frequency Division Multiplexing (OFDM) symbol in order to minimize bit error rate or maximize the throughput.
In the first part of this dissertation, we consider single-relay OFDM system with amplify-and-forward relaying. We propose three algorithms to minimize the bit error rate under total power constraint and fixed transmission rate. These algorithms are optimal power loading, optimal bit loading and optimal bit and power loading. Through Monte Carlo simulations we study the proposed system performance and discuss the effect of relay location and channel estimation. This study shows that the proposed algorithms result in exploiting the multi-path diversity and achieving extra coding gain.
In the second part, we extend the problem to a multi-relay OFDM network but with decode-and-forward relaying. We propose an adaptive power loading algorithm to minimize the bit error rate under total power constraint based on two relay selection strategies. The proposed system leads to achieve both multi-path and cooperative spatial diversity using maximal-ratio combiner for the detection.
In the last part, we consider also multi-relay network but with amplify and forward relaying. We optimize the bit loading coefficients to maximize the throughput under target bit error rate constraint. The proposed algorithm is considered more practical since it takes into consideration the channel estimation quality. The considered adaptive system has less complexity compared with other adaptive systems through reducing the feedback amount. Furthermore, the full network channel state information is needed only at the destination.
|
10 |
Adaptive OFDM Cooperative SystemsAmin, Osama Mohammed Hussein 06 December 2010 (has links)
Cooperative communication is a promising technique for wireless communication systems where wireless nodes cooperate together in transmitting their information. Such communication transmission technique, which realizes the multiple antenna arrays in a distributed manner over multiple wireless nodes, succeeds in extending the network coverage, increasing throughput, improving both link reliability and spectral efficiency.
Available channel state information at the transmitting nodes can be used to design adaptive transmission schemes for improving the overall system performance. Throughout our work, we adaptively change loaded power and/or bit to the Orthogonal Frequency Division Multiplexing (OFDM) symbol in order to minimize bit error rate or maximize the throughput.
In the first part of this dissertation, we consider single-relay OFDM system with amplify-and-forward relaying. We propose three algorithms to minimize the bit error rate under total power constraint and fixed transmission rate. These algorithms are optimal power loading, optimal bit loading and optimal bit and power loading. Through Monte Carlo simulations we study the proposed system performance and discuss the effect of relay location and channel estimation. This study shows that the proposed algorithms result in exploiting the multi-path diversity and achieving extra coding gain.
In the second part, we extend the problem to a multi-relay OFDM network but with decode-and-forward relaying. We propose an adaptive power loading algorithm to minimize the bit error rate under total power constraint based on two relay selection strategies. The proposed system leads to achieve both multi-path and cooperative spatial diversity using maximal-ratio combiner for the detection.
In the last part, we consider also multi-relay network but with amplify and forward relaying. We optimize the bit loading coefficients to maximize the throughput under target bit error rate constraint. The proposed algorithm is considered more practical since it takes into consideration the channel estimation quality. The considered adaptive system has less complexity compared with other adaptive systems through reducing the feedback amount. Furthermore, the full network channel state information is needed only at the destination.
|
Page generated in 0.0498 seconds