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The frame structure as a possible solution to enable the proposed link adaptation and selection in an OFDMA-TDD based cellular wireless relay network where the users are within the coverage of the BS and the RS.
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We propose a link adaptation and selection method for the links constituting an orthogonal frequency division multiplexing (OFDM) based wireless relay network. The proposed link adaptation and selection method selects the forwarding, modulation, and channel coding schemes providing the highest end-to-end throughput and decides whether to use the re...
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Context 1
... DF s,j ), thr(γ SR,j ), P c (γ DF s,j ), and P c (γ RS,j ) are read from the lookup table (11). Then, the end-to- end throughput for each scheme is calculated based on the de- rived equations in Section II-B. Finally the transmission scheme and the AMC modes providing the highest end-to-end through- put is determined for each sub-channel. In Fig. 6, a frame struc- ture is presented as a possible solution to enable the proposed link adaptation and selection in an OFDM(A)-TDD based cellu- lar wireless relay network where the users are within the cover- age area of the BS and some of them are in the coverage area of both the BS and the RS. Before data transmissions start, the BS ...
Context 2
... The BS needs to receive this infor- mation as well and hence it has to switch from the receive mode 5 Note that the BS and RS can also transmit their preambles simultaneously. to the transmit mode before data transmissions start. This neces- sitates a guard interval. Finally, transmissions with the selected schemes start in the second phase. In Fig. 6, cooperative-MISO based relaying is used. In the first and second phase, data trans- mission at each sub-channel take place which is designated for a given MS. For cooperative-MISO based relaying, the duration of the first phase can be adjusted based on the average SINR in the S → R ...
Context 3
... We consider a total of 2048 sub- carriers 6 with a system bandwidth of 22.4 MHz [18]. The sys- tem operates at a carrier frequency of 2.5 GHz. Frames have a 5 ms duration. 44 out of 48 OFDM symbols in a given frame are reserved for data transmission where 24 of them are reserved for downlink transmissions [18]. The frame structure depicted in Fig. 6 is considered. The downlink subframe is divided into two phases where each phase can have a duration of 12-OFDM sym- bols. We use a multi-path wireless channel model for S → D and R → D links with an rms delay spread of 0.231 μs [23]. A subcarrier spacing of 22.4 MHz/2048 = 10.94 kHz is as- sumed. This corresponds to a 90% coherence ...
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Citations
... This erroneous link decision is non-negligible in the end-to-end error performance between S and D nodes. In order to alleviate the associated performance loss, channel-aware demodulators and link adaptive relaying solutions have been proposed [72]- [76]. In [72], an end-to-end link adaptation and selection method is presented with efficient adaptive modulation and coding scenarios for wireless relay channels. ...
... In order to alleviate the associated performance loss, channel-aware demodulators and link adaptive relaying solutions have been proposed [72]- [76]. In [72], an end-to-end link adaptation and selection method is presented with efficient adaptive modulation and coding scenarios for wireless relay channels. In [73], transmit power adaptation is used to obtain the optimum spectral efficiency while switching between half and full duplex modes at the relay. ...
Network Coding (NC) can significantly help increase the efficient use of network resources. However, directly applying NC to wireless networks is not an effective design solution. Wireless channels are prone to bit errors due to fading, possibly generating erroneous decisions at the relay nodes while applying NC. Furthermore, the broadcast nature of wireless channels may provide a direct communication link between source and destination nodes. In order to combat fading channel impairments, and also to exploit the inherent spatial diversity provided through the direct link, network coded cooperation (NCC) techniques should be incorporated to the NC systems for wireless networks. This tutorial provides an overview of the state-of-the-art in the NCC systems, combining the powerful tools of NC and cooperative communication, in order to increase data transmission rates and robustness of multiple source wireless networks.
... The Relay station is a base station that requires line of sight (LOS) connectivity with another relay station or a base station. Relay station is not connected to the wired back-haul as shown in fig. 2. [3] Broadband wireless networks which are mostly in place these days rely on LOS communication. As WiMAX is being targeted for providing higher data rates at large distances, so the coverage and the throughput of WiMAX should be better. ...
... In the second phase, all the selected RSs forward the decoded data to the BS simultaneously, while the user remains silent. Consider a general case that K RSs are selected to relay for the mobile user, assuming that the maximal ratio combining (MRC) is applied at the BS, then the post-processing SINR at the destination is [26] γ DF ...
... The derivation of F m (γ) is given in Appendix A. For convenience of analysis, we consider the data transmission from a source to a destination through both direct link and relay links as achieved on an equivalent virtual link. For the DF based relay transmission, the choice of adaptive modulation and coding (AMC) mode only depends on the post-processing SINR at the corresponding destination [26], which is calculated from (1). Given γ DF p , we can obtain the maximum achievable rate 3 (MAR) of the virtual link, which is denoted by r * . ...
Although extensive research has been carried out on the issue of how to optimally select relays in wireless relay networks, relay selection for mobile users is still a challenging problem because of the requirement that the dynamic selection should adapt to user mobility. Moreover, because the selected relays consume their energy on relaying data for the users, it is required that the users have to pay for this relay service. The price of selecting relays will affect the users' decisions. Assuming that different relays can belong to different service providers, we consider the situation that the service providers can strategically set the prices of their relays to maximize their profits. In this paper, we jointly study the dynamic relay selection for mobile users and profit maximization for service providers. Also, we design a Stackelberg-game hierarchical framework to obtain the solution. At the lower level, we investigate the relay selection problem for the mobile users under given prices of selecting the relays. It is formulated as a Markov decision process problem with the objective to minimize the mobile user's long-term average cost (which consists of the payment to the relay service and the cost due to packet loss), and solved by applying the linear programming technique. At the upper level, we study the game of setting relay prices for the service providers, with the knowledge that the mobile users will make relay selections based on their given prices. Nash equilibrium is obtained as the solution. Our results can help to provide a guidance for service providers to compete for providing relay services. Copyright © 2012 John Wiley & Sons, Ltd.
... Orthogonal frequency division multiplexing (OFDM) which has been used in the fourth generation of wireless networks can effectively combats to this drawback. Similar to other strategy, OFDM technique has been investigated for the cooperative networks in literature which generally cover topics such as performance analysis of single antenna OFDM cooperative systems with relay selection [14, 15], subcarrier mapping in variable gain VG AF relaying system with no direct communication between the source and destination [16], link adaptation and selection method for the links constituting an OFDM based wireless relay network [17], and subcarrier-pair based resource allocation for cooperative multiple relays OFDM [18]. It is notable www.ietdl.org ...
In this study, the performance of a multi-carrier (MC) multi-relay system with multi-antenna at source and destination nodes is investigated based on Alamouti space-time block coding (STBC) and amplify-and-forward (AF) cooperative diversity protocol with different schemes. In particular, transmission of each STBC in the system is initiated by signal broadcasting from the source node to the destination node and all the relay nodes. Depending on the cooperative scheme, one or more relays, applying AF protocol, transmit the signal to the destination. Applying maximum ratio combination technique to both the direct and the relayed subcarriers at the destination, the outage probability bounds are analytically derived for various schemes of relaying. Simulation results confirm the validity of the derived bounds, and show that the cooperative MC-multiple-input-multiple-output channel yields a notable outage performance with an acceptable capacity, especially in the average best relay selection scheme, which exploits the limited feedback.
... The RS does not have any connection with backhaul as it connects with nearest BS to enhance throughput, coverage and capacity. The position of the RS is also an important issue for placement in the area where signal to noise ratio (SNR) is high and link budget is good [6,8]. ...
The relay station (RS) is widely used in major wireless technologies such as WiMAX and long term evolution (LTE) which provides cost effective services to the operators and end users in order to provide guaranteed Quality of Service (QoS). The existing research in IEEE802.16m to cover a base station (BS) territory in rural areas using four RSs in order to provide the services to mobile users beyond the range of BS has proven to be a costly solution. In this paper, how to use the available spectral resources as efficiently as possible to minimize the delay and improve throughput for end users with high demanding applications such as voice and video with decreased deployment cost of RS has been investigated. A novel solution has been proposed for cost effective deployment of three RSs in IEEE802.16m using adaptive modulation and coding (AMC) scheme, cell sectoring and directional antenna. The simulation results show that enhanced performance can be achieved by using less number of RS in the same BS territory without compromising the QoS and throughput of the WiMAX2 Network.
... Coverage extension (i.e., filling coverage holes due to shadowing and overcoming low signal-to-interference-plus-noise ratio at cell edges) has been also investigated in mobile relaying [7]. Cooperative relaying has attracted a lot of attention as an effective technique [9], [10] to improve end-to-end throughput, since it can perform like MIMO (multiple input multiple output) techniques even without multiple antennas which require additional costs at a terminal. In [8], the authors developed an analytical model for the two-hop mobile relay to capture the relationship between the capacity and the probability of out-of-coverage. ...
... Although many studies have been focused on the improvement of capacity and coverage of cellular networks by relaying [3]- [5], [7]- [10], very few attempts have been made for a comprehensive analysis of relaying effect on the capacity and fairness trade-off relationship, i.e., increasing one objective may deteriorate the other. ...
... The relay node is used to improve the data rate between the BS and MS. To calculate the data rate of a triangular link, we adopt a conventional two-phase time division method as in [10]. In the first phase, a source transmits data to a relay, and a relay transmits data to the destination in the second phase. ...
Due to the tradeoff between capacity and fairness in a wide variety of networks, increasing one objective may deteriorate the other. This paper investigates the possibility of improving capacity and fairness at the same time, specifically in two-hop cellular networks. First, we prove that an achievable capacity region can be enlarged by using relay, i.e., the capacity and fairness tradeoff relationship is alleviated. To achieve the Pareto-efficient boundary of this enlarged capacity region, an appropriate scheduling algorithm should be developed. Thus, second, we propose a generalized opportunistic scheduling algorithm for relaying mode that can improve both capacity and fairness. Furthermore, we propose a heuristic algorithm with low complexity and signaling overhead for relaying mode. Extensive simulations under various configurations demonstrate that the proposed algorithm not only increases the throughput of each user but also effectively alleviates unfairness among users.
... Traditionally, adaptive resource allocation schemes in cooperative communication were designed based on system performance metrics such as end-to-end throughput [65], cooperative diversity [66], bit error rate [67], and capacity [68]. The optimization of such metrics does not take into account the power consumption of the network. ...
Demand for high data rates is increasing rapidly for the future wireless
generations, due to the requirement of ubiquitous coverage for wireless broadband
services. More base stations are needed to deliver these services, in order
to cope with the increased capacity demand and inherent unreliable nature of
wireless medium. However, this would directly correspond to high infrastructure
cost and energy consumption in cellular networks. Nowadays, high power
consumption in the network is becoming a matter of concern for the operators,
both from environmental and economic point of view.
Cooperative communications, which is regarded as a virtual multi-inputmulti-
output (MIMO) channel, can be very efficient in combating fadingmultipath
channels and improve coverage with low complexity and cost. With its
distributed structure, cooperative communications can also contribute to the
energy efficiency of wireless systems and green radio communications of the
future. Using network coding at the top of cooperative communication, utilizes
the network resources more efficiently.
Here we look at the case of large scale use of low cost relays as a way
of making the links reliable, that directly corresponds to reduction in transmission
power at the nodes. A lot of research work has focused on highlighting
the gains achieved by using network coding in cooperative transmissions.
However, there are certain areas that are not fully explored yet. For instance,
the kind of detection scheme used at the receiver and its impact on the link
performance has not been addressed. The thesis looks at the performance
comparison of different detection schemes and also proposes how to group
users at the relay to ensure mutual benefit for the cooperating users. Using
constellation selection at the nodes, the augmented space formed at the receiver
is exploited for making the links more reliable. The network and the
channel coding schemes are represented as a single product code, that allows
us to exploit the redundancy present in these schemes efficiently and powerful
coding schemes can also be designed to improve the link performance.
Heterogeneous network deployments and adaptive powermanagement has
been used in order to reduce the overall energy consumption in a cellular network.
However, the distributed structure of nodes deployed in the network,
is not exploited in this regard. Here we have highlighted the significance of
cooperative relaying schemes in reducing the overall energy consumption in
a cellular network. The role of different transmission and adaptive resource
allocation strategies in downlink scenarios have been investigated in this regard.
It has been observed that the adaptive relaying schemes can significantly
reduce the total energy consumption as compared to the conventional relaying
schemes. Moreover, network coding in these adaptive relaying schemes, helps
in minimizing the energy consumption further. The balance between the number
of base stations and the relays that minimizes the energy consumption, for
each relaying scheme is also investigated.
... In [12], it can be seen that when relay node can correctly decode the packets from source, the cooperative relay transmissions are used, which in turn causes throughput loss. In [13], end-to-end link adaptation and link selection methods have been developed for a single user in an Orthogonal Frequency Division Multiplexing (OFDM) Time Division Duplex (TDD) based wireless relay network. The emerging IEEE 802.16j standard may allow without relay transmissions in the second phase. ...
Cooperative diversity is a technique in which various radio terminals relay
signals for each other. Cooperative diversity results when cooperative
communications is used primarily to leverage the spatial diversity available
among distributed radios. In this paper different cooperative diversity schemes
and their applications in various wireless networks are discussed. In this
paper the impact of cooperative diversity on the energy consumption and
lifetime of sensor network and the impact of cooperation in cognitive radio are
discussed. Here, user scheduling and radio resource allocation techniques are
also discussed which are developed in order to efficiently integrate various
cooperative diversity schemes for the emerging IEEE 802.16j based systems.
... The AMC is also of great interest in satellite communications and is adopted in the DVB-S2 standard [10]- [12]. The idea of applying AMC to a wireless relay network is investigated in [13] and [14]. ...
... Transmission during outage is counted as the only source of error as capacity achieving codes are assumed that resolve errors due to channel noise. In [14], an OFDM based wireless M. Mardani relay network is considered and aiming at optimizing the end-to-end instantaneous throughput, a joint relaying scheme (without ARQ) and AMC mode selection algorithm is proposed, where the solutions are provided in the form of lookup tables. ...
... In order to solve (P3), a simple numerical search method is devised as follows. We first select the rate pair ሺܴ ଵ , ܴ ଵ ሻ as an initial solution, and increase the transmission rates of source and relay successively to find the possible rate pairs which satisfy the PLR constraint in (14). ...
In a cooperative relay network, a relay (R) node may facilitate data transmission to the destination (D) node when the latter node cannot correctly decode the source (S) node data. This paper considers such a system model and presents a cross-layer approach to jointly design adaptive modulation and coding (AMC) at the physical layer and the truncated cooperative automatic repeat request (C-ARQ) protocol at the data-link layer for quality-of-service (QoS)-constrained applications. The average spectral efficiency and packet loss rate of the joint C-ARQ and AMC scheme are first derived in closed form. Aiming to maximize the system spectral efficiency, AMC schemes for the S-D and R-D links are optimized, whereas a prescribed packet-loss-rate constraint is satisfied. As an interesting application, joint link adaptation and blockage mitigation in land mobile satellite communications (LMSC) with temporally correlated channels is then investigated. In LMSC, the S node data can be delivered to the D node when the S-D is in the outage, therefore provisioning the QoS requirements. For applications without instantaneous feedback, an optimized rate selection scheme based on the channel statistics is also devised. Detailed and insightful numerical results are presented, which indicate the superior performance of the proposed joint AMC and C-ARQ schemes over their optimized joint AMC and traditional ARQ counterparts.
... There may be cases when a relay might not be even required. Therefore, the main focus of our paper had been the selection of best relay from a pool of potential candidates of optimum relay which would utilize intelligent forwarding protocol [8]. The relay selection process is a sophisticated chain of procedures that is done based on the channel state information (CSI) received from the relay stations and mobile stations [9]. ...
... The operational integrity of the ART algorithm relies heavily on the instantaneous CSI received of the network. It has been proved in [8,13] that this approach is highly efficient in maximizing the overall link capacity. The ART algorithm typically runs on existing common forwarding schemes mentioned on [3,9]. ...
... The ART algorithm typically runs on existing common forwarding schemes mentioned on [3,9]. The equations (1) to (8) for each of the schemes below have been taken from [3], where the complete derivations can also be found. ...
The use of relay nodes in future wireless networks significantly enhances the system capacity and achieves spatial diversity; however, relaying in degraded channel conditions may not be favorable. Hence, relay selection is a major area for research. This paper aims to optimize the channel capacity of a relay network by choosing an optimal relay, following hybrid forwarding protocol, based on adaptive selection. The main contribution of this paper is the Adaptive Relay Table (ART) algorithm, which intelligently utilizes the instantaneous channel state information (CSI) for the selection. Several characteristics are established to replicate a realistic scenario.
