Adaptive relaying protocol multiple-input multiple-output orthogonal frequency division multiplexing systems

In wireless broadband communications, orthogonal frequency division multiplexing (OFDM) has been adopted as a promising technique to mitigate multi-path fading and provide high spectral efficiency. In addition, cooperative communication can explore spatial diversity where several users or nodes share their resources and cooperate through distributed transmission. The concatenation of the OFDM technique with relaying systems can enhance the overall performance in terms of spectral efficiency and improve robustness against the detrimental effects of fading. Hybrid relay selection is proposed to overcome the drawbacks of conventional forwarding schemes. However, exciting hybrid relay protocols may suffer some limitations when used for transmission over frequency-selective channels. The combination of cooperative protocols with OFDM systems has been extensively utilized in current wireless networks, and have become a promising solution for future high data rate broadband communication systems including 3D video transmission. This thesis covers two areas of high data rate networks. In the first part, several techniques using cooperative OFDM systems are presented including relay selection, space time block codes, resource allocation and adaptive bit and power allocation to introduce diversity. Four (4) selective OFDM relaying schemes are studied over wireless networks; selective OFDM; selective OFDMA; selective block OFDM and selective unequal block OFDM. The closed-form expression of these schemes is derived. By exploiting the broadcast nature, it is demonstrated that spatial diversity can be improved. The upper bound of outage probability for the protocols is derived. A new strategy for hybrid relay selection is proposed to improve the system performance by removing the sub-carriers that experience deep fading. The per subcarrier basis selection is considered with respect to the predefined threshold signal-to-noise ratio. The closed-form expressions of the proposed protocol in terms of bit error probability and outage probability are derived and compared with conventional hybrid relay selection. Adaptive bit and power allocation is also discussed to improve the system performance. Distributed space frequency coding applied to hybrid relay selection to obtain full spatial and full data rate transmission is explored. Two strategies, single cluster and multiple clusters, are considered for the Alamouti code at the destination by using a hybrid relay protocol. The power allocation with and without sub-carrier pairing is also investigated to mitigate the effect of multipath error propagation in frequency-selective channels. The second part of this thesis investigates the application of cooperative OFDM systems to high data rate transmission. Recently, there has been growing attention paid to 3D video transmission over broadband wireless channels. Two strategies for relay selection hybrid relay selection and first best second best are proposed to implement unequal error protection in the physical layer over error prone channels. The closed-form expressions of bit error probability and outage probability for both strategies are examined. The peak signal-to-noise ratio is presented to show the quality of reconstruction of the left and right views

Error probability of OFDM-based hybrid relay protocols over wideband fading channels

Orthogonal frequency division multiplexing (OFDM) based relay architecture is a promising technique in modern wireless communication systems. In frequency-selective channels, different sub-carriers experience different fades. Data transmitted on the sub-carriers which experience deep fade will have a high probability of getting lost at the destination. In this paper, we propose a multicarrier-adaptive hybrid relay protocol (MC-AHRP) over frequency-selective channels to overcome this problem. In the proposed protocol, the subcarrier performs an amplify-and-forward (AF) scheme when the instantaneous SNR of the source-relay link exceeds a preset threshold value, or it utilizes the adaptive decode-and-forward (ADF) scheme as the alternative. For any subcarrier of the ADF scheme that fails to be decoded, the destination selects the respective subcarrier from the direct transmission path instead. The performance of the proposed scheme is analyzed in terms of bit error probability (BEP). Simulation and numerical results show that a significant performance gain can be achieved

Cooperative relay selection based UEP scheme for 3D video transmission over Rayleigh fading channel

In this paper, we propose an unequal error protection (UEP)scheme for 3 dimensional (3D) video transmission based on dual AF-DF relay selection protocol. In the proposed Scheme, we consider an Amplify-and-Forward (AF) and Decodeand-Forward (DF) cooperative diversity together with the unique properties of video plus depth format to improve 3D transmission over wireless networks. We assume that the relays have the ability to perfect error-checking and the source encoded each frame of 3D video data and classify it into two sequences. The former one is the color sequence which is relayed in high reliable scheme by using perfect DF relay and the latter is depth sequence which is transmitted through AF relay. Results show that the proposed scheme improved the quality of color and depth data by exploiting the relay selection diversity, where the color data has better performance than depth data due to channel reliability

Distributed space-frequency coding for OFDM-based hybrid relay selection

Cooperative communication in conjunction with orthogonal frequency division multiplexing (OFDM) has recently emerged as a promising technique with the potential to dominate future generations of broadband wireless communications systems. In this paper, we propose an OFDM modulation scheme combined with distributed space-frequency codes (DSFC) based upon a hybrid relay selection protocol. The DSFC process is not required for the amplify-and-forward (AF) relays to reduce the system complexity. Simulation results show that a substantial improvement in bit error rate (BER) performance can be achieved in comparison with conventional relaying protocols. Full rate transmission and diversity order is attainable by this proposed system

Performance Analysis of Cooperative NOMA for Different Power Allocation Strategies

Cooperative None Orthogonal Multiple Access (C-NOMA) is a promising approach for 5G and beyond communication networks. Users will benefit from the full bandwidth of the channel without time constraints. NOMA’s features are incomplete without efficient power allocation that ensures power distribution among users fairly. Integrating power management (allocation) with Cooperative-NOMA (C-NOMA) may improve the system metrics. In addition, a physical layer security (PLS) is added to make the process of sending and receiving safe, and the system works in an integrated manner, preventing any interrupting or eavesdropping inside or outside the network. This paper demonstrates the user and channel performance of C-NOMA with Amplify-and-forward (AF) and Decode-and-forward (DF) approaches. The analysis is performed by varying the power allocation techniques to derive the best system configurations. The simulation results confirmed the analytic findings and showed that the proposed system outperforms orthogonal multiple access (OMA), conventional NOMA, and conventional cooperative NOMA, enhancing the performance metrics in terms of throughput, sum rate, and outage probability. The bit-error-rate (BER) of the far user can be identical to that of the near user if power allocation is properly set. All techniques excelled except for the fixed power allocation, which had the same BER. The Channel capacity and outage probability were also considered. A slight variation in the channel capacity in all the experiments for different numbers of users was found. The generalized power allocation for AF and DF models had the optimum channel capacity close to 14 bps/Hz. Moreover, far users always had a higher outage probability than near users and channels, and generalized power allocation was the highest outage probability technique when the transmit power was close to (4 dB)

Joint subcarrier pairing and resource allocation for adaptive hybrid relay protocol in OFDM systems

Orthogonal frequency division multiplexing (OFDM) has been adopted as a promising technique to mitigate multi-path fading and provides high spectral efficiency in broadband communications. In this paper, we investigate resource allocation and sub-carrier permutation in OFDM-based hybrid relay protocol over frequency-selective channels. Selective multicarrier-adaptive hybrid relay protocol (MC-AHRP), involves the sub-carrier utilizing an amplify-and-forward (AF) scheme when the instantaneous signal-to-noise ratio (SNR) is larger than threshold value and an adaptive decode-and-forward (ADF) scheme when the instantaneous SNR is less than threshold value. The proposed protocol exploits the benefits of adaptive hybrid relay protocol, OFDM, resource allocation, and sub-carrier permutation to provide a substantial enhancement in the system performance. The simulation results show that when the protocol performs resource allocation (RA) and sub-carrier permutation (SP) can provide an excellent improvement in the capacity of the system. It also demonstrate that the proposed protocol can achieve a significant improvement in throughput compared with conventional protocols

Power allocation of distributed space-frequency coding for OFDM-based hybrid relay selection

Cooperative communications in conjunction with orthogonal frequency division multiplexing (OFDM) has recently emerged as a promising technique to mitigate multi-path fading and provides high spectral efficiency in broadband wireless communications systems. In this paper, we investigate resource allocation of an OFDM modulation scheme combined with distributed space-frequency codes (DSFC) based upon a hybrid relay selection protocol. The optimum problem is divided into two suboptimal problems. The first one is to optimize the power allocation between the source and relay nodes under a sum power constraint. Then the relay power is optimized for the selected relay nodes according to the channel power gain of the second time slot. Simulation results show that a substantial improvement in terms of bit error rate (BER) and capacity performance can be achieved in comparison with conventional relaying protocols

Outage probability of unequal block-based OFDM amplify-and-forward relay protocol over wideband channels

In this paper, we consider a dual-hop multiplerelay network with orthogonal frequency division multiplexing (OFDM) based Amplify-and-Forward (AF) relay protocol over frequency-selective channels. In practice, subcarriers suffered that suffer deep fade in one relay may have good channels available for another relay. Therefore, each relay can support a different number of subcarriers. We propose an unequal blockbased OFDM-AF relaying scheme. In our scheme, an OFDM symbol is divided into unequal blocks of subcarriers at its destination. The destination assigns each relay a corresponding number of subcarriers depending on the signal-to-noise ratio (SNR) of the signals. We derive a closed form expression of the probability of outage and this gives the general expression for our protocol and selective OFDM, OFDMA, and block-OFDM schemes. results show that the scheme achieves a better performance for a given number of blocks than the selective block-OFDM protocol

Best relays selection method for error-resilient 3-D video transmission

In color-plus-depth map three-dimensional (3-D) video representation, color and depth map sequences exhibit different error sensitivities to the overall quality. Recognizing that, in this paper, we propose to exploit the relay cooperation benefits to achieve unequal error protection (UEP) for better quality 3-D video transmission. Specifically, we propose to apply the first best amplify-and-forward (AF) relay for transmitting color information with high priority (HP) while the second best AF relay is employed for the depth information with low priority (LP). In particular, we drive closed-form expressions for the bit error probability (BEP). Simulation results of the BEP are presented to demonstrate the proposed UEP scheme in terms of the received 3-D video quality

Analysis, Modeling, and Design of a Reliable Wide Area Network Case Study for Tikrit University Intranet

This work presents the analysis and modeling of communication network used for data transmission with multi-protocols in campus network. The designed network is based on the geographical location of communication nodes. (Colleges and centers). Network optimal backbone is first designed by Kruskal algorithm. It will be subject to reliability improvement by links addition. Tie-sets method is used to evaluate the network reliability. Communication nodes are modeled using local area network (LAN), server, links, router, switch, and Firewall. Intranet will be used as communication backbone mainly to connect different communication nodes with the Principal Communication Center (PCC) where the System Server (SS) is located. The connection of Intranet to the Internet is mad via the front-end system server (SS). Tikrit University Intranet (TUI) is taking as case study in the present research. Tikrit University sites are grouped into master communication nodes. Each node is composed from several colleges, centers, and administrative sections