41 research outputs found
Relay Selection for Bidirectional AF Relay Network with Outdated CSI
Most previous researches on bidirectional relay selection (RS) typically
assume perfect channel state information (CSI). However, outdated CSI, caused
by the the time-variation of channel, cannot be ignored in the practical
system, and it will deteriorate the performance. In this paper, the effect of
outdated CSI on the performance of bidirectional amplify-and-forward RS is
investigated. The optimal single RS scheme in minimizing the symbol error rate
(SER) is revised by incorporating the outdated channels. The analytical
expressions of end-to-end signal to noise ratio (SNR) and symbol error rate
(SER) are derived in a closed-form, along with the asymptotic SER expression in
high SNR. All the analytical expressions are verified by the Monte-Carlo
simulations. The analytical and the simulation results reveal that once CSI is
outdated, the diversity order degrades to one from full diversity. Furthermore,
a multiple RS scheme is proposed and verified that this scheme is a feasible
solution to compensate the diversity loss caused by outdated CSI.Comment: accepted by IEEE Transactions on Vehicular Technolog
Relay Selection Considering Successive Packets Transmission in Cooperative Communication Networks
Relay selection has been regarded as an effective method to improve the performance of cooperative communication system. However, frequent operation of relay selection can bring enormous control message overhead and thereby decrease the performance of cooperative communication. To reduce the relay selection frequency, in this paper, we propose a relay selection scheme to choose the best relay with considering successive packets transmission. In this scheme, according to the length of data packet, data transmission rate and the estimated channel state information (CSI), the best relay is selected to maximize the number of successive packets transmission under the condition that the given symbol-error-rate (SER) is kept. Finally, numerical results show that the proposed relay selection scheme can support the operation of successive packets transmission in cooperative wireless networks and that the maximum number of successive packets transmission is affected by the different network parameters, i.e., data transmission rate, packet length and Doppler frequency at one relay node
Performance Analysis of Best Relaying Protocol Selection with Interferences at Relays
In this paper, we investigate the performance of selecting the best protocol between amplify and forward (AF) and decode and forward (DF) in multiple relay networks with multiple interferences at relays. In the selection scheme, the best protocol between AF and DF is selected depending on the comparisons of signal-to-interference and noise ratio (SINR) for all source-relay links. All relays measure the received SINR to decide forwarding signal or not. When SINR is above a certain threshold then DF is used otherwise AF is used. Particularly, we develop an accurate mathematical model for best relaying protocol by considering the effect of interferences to our scheme. Firstly, we derive the asymptotic closed form expression for the symbol error rate (SER) for the system under study. Also we derive an upper and lower bound of symbol error rate and show how they were tight with exact SER. Furthermore an approximate expression for the outage probability is derived. Numerical results are finally presented to validate the theoretical analysis with a different number of relays
Hybrid satellite–terrestrial networks toward 6G : key technologies and open issues
Future wireless networks will be required to provide more wireless services at higher data rates and with global coverage. However, existing homogeneous wireless networks, such as cellular and satellite networks, may not be able to meet such requirements individually, especially in remote terrain, including seas and mountains. One possible solution is to use diversified wireless networks that can exploit the inter-connectivity between satellites, aerial base stations (BSs), and terrestrial BSs over inter-connected space, ground, and aerial networks. Hence, enabling wireless communication in one integrated network has attracted both the industry and the research fraternities. In this work, we provide a comprehensive survey of the most recent work on hybrid satellite–terrestrial networks (HSTNs), focusing on system architecture, performance analysis, design optimization, and secure communication schemes for different cooperative and cognitive HSTN network architectures. Different key technologies are compared. Based on this comparison, several open issues for future research are discussed
Adaptive Relay-Selection In Decode-And-Forward Cooperative Systems
In the past few years adaptive decode-and-forward cooperative diversity systems have been studied intensively in literature. Many schemes and protocols have been proposed to enhance the performance of the cooperative systems while trying to alleviate its drawbacks. One of the recent schemes that had been shown to give high improvements in performance is the best-relay selection scheme. In the best-relay selection scheme only one relaying nodes among the relays available in the system is selected to forward the source\u27s message to the destination. The best relay is selected as the relay node that can achieve the highest end-to-end signal-to-noise ratio (snr) at the destination node. Performance improvements have been reported as compared to regular fixed decode-and-forward relaying in which all relays are required to forward the source\u27s message to the destination in terms of spectral efficiency and diversity order. In this thesis, we use simulations to show the improvement in the outage performance of the best-relay selection scheme
Performance study of an underlay cognitive radio network in the presence of co-channel interference
PhD ThesisMassive innovation in all aspects of the wireless communication network
has been witnessed over the last few decades. The demand for data
throughput is continuously growing, as such, the current regulations for
allocating frequency spectrum are not able to respond to this exponential growth. Cognitive radio (CR), has been proposed as a solution to
this problem. One of the possible scenarios of the implementation of CR
is underlay cognitive radio. In this thesis the performance of an underlay cognitive radio network (UCRN) in the presence of the co-channel
interference (CCI) is assessed.
Firstly, the impact of CCI on the dual-hop cooperative UCRN is investigated over Rayleigh fading channels. In order to do this, the exact outage
probability (OP), average error probability (AEP) and the ergodic capacity (EC) are studied. In addition, simple and asymptotic expressions
for the OP and AEP are derived. Furthermore, the optimal power allocation is investigated to enhance the network performance. Moreover,
the performance of a multi-user scenario is studied by considering the
opportunistic SNR-based selection technique.
Secondly, the effect of both primary network interference and CCI on
the dual-hop UCRN over Rayleigh fading channels are studied. The
equivalent signal-to-interference-plus-noise ratio (SINR) for this network
scenario is obtained by considering multi-antenna schemes at all receiver
nodes. The different signal combinations at the receiver nodes are investigated and compared, such as selection combining (SC) and maximum
ratio combining (MRC) techniques. Then, the equivalent probability
density function (PDF) and cumulative distribution function (CDF) of
the network’s equivalent SINR are derived and discussed. Furthermore,
expressions for the exact OP, AEP, and EC are derived and reviewed.
In addition, asymptotic OP expressions are obtained for different case
scenarios to gain an insight into the network parameters.
Thirdly, multiple-input multiple-output (MIMO) UCRN is investigated
under the influence of primary transmitter interference and CCI over
Rayleigh fading channels. The transmit antenna selection and maximum
ratio combining (TAS/MRC) techniques are considered for examining
the performance of the secondary network. At first the equivalent SINR
for the system is derived, then the exact and approximate expressions
for the OP are derived and discussed.
Fourthly, considering Nakagami-m fading channels, the performance of
the UCRN is thoroughly studied with the consideration of the impact
of primary network interference and CCI. The equivalent SINR for the
secondary system is derived. Then, the system equivalent PDF and CDF
are derived and discussed. Furthermore, the OP and AEP performances
are investigated.
Finally, for the cases mentioned above, numerical examples in conjunction with MatLab Monte Carlo simulations are provided to validate the
derived results. The results show that CCI is one of the factors that
severely reduces the UCRN performance. This can be more observable
when the CCI power increases linearly with the transmission power of
the secondary transmitter nodes. Furthermore, it was found that in
a multi-user scenario the opportunistic SNR-based selection technique
consideration can improve the performance of the network. Moreover,
adaptive power allocation is found to give better results than equal power
allocation. In addition, cooperative communication can be considered to
be an effective way to combat the impact of transmission power limitation of the secondary network and interference power constraint. The
multi-antenna schemes are another important consideration for enhancing the overall performance. In fact, despite the interference from the
CCI and primary user sources, the multi-antennas scheme does not lose
its advantage in the UCRN performance improvementHigher Committee for Education Development in Iraq (HCED). I am also grateful to
the Ministry of Transportation and Communication, Kurdistan Regional
Government-Iraq