Emad S. Hassan

Performance evaluation of OFDM and single-carrier systems using frequency domain equalization and phase modulation

In this paper, we study the performance of the continuous phase modulation (CPM)-based orthogonal frequency division multiplexing (CPM-OFDM) system. Also, we propose a CPM-based single-carrier frequency domain equalization (CPM-SC-FDE) structure for broadband wireless communication systems. The proposed structure combines the advantages of the low complexity of SC-FDE, in addition to exploiting the channel frequency diversity and the power efficiency of CPM. Both the CPM-OFDM system and the proposed system are implemented with FDE to avoid the complexity of the equalization. Two types of frequency domain equalizers are considered and compared for performance evaluation of both systems; the zero forcing (ZF) equalizer and the minimum mean square error (MMSE) equalizer. Simulation experiments are performed for a variety of multipath fading channels. Simulation results show that the performance of the CPM-based systems with multipath fading is better than their performance with single path fading. The performance over a multipath channel is at least 5 and 12 dB better than the performance over a single path channel, for the CPM-OFDM system and the proposed CPM-SC-FDE system, respectively. The results also show that, when CPM is utilized in SC-FDE systems, they can outperform CPM-OFDM systems by about 5 dB. Copyright

Peak-to-average power ratio reduction in space-time block coded multi-input multi-output orthogonal frequency division multiplexing systems using a small overhead selective mapping scheme

The selective mapping (SLM) scheme is one of the most popular peak-to-average power ratio (PAPR) reduction techniques proposed for multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. One of the major disadvantages of this scheme is the need for the transmission of side information (SI) bits to enable the receiver to recover the transmitted data. The authors present a small overhead SLM (s-SLM) scheme for space-time block coded (STBC) MIMO-OFDM systems. This proposed scheme improves the system bandwidth efficiency and achieves a significantly lower bit error rate (BER) than the individual SLM (i-SLM) and direct SLM (d-SLM) schemes. In addition, approximate expressions for the complementary cumulative distribution function (CCDF) of the PAPR and the average BER of the proposed s-SLM scheme are derived. The simulation results show that the proposed s-SLM scheme improves the detection probability of the SI bits and hence gives a better performance than the i-SLM and the d-SLM schemes.

Chaotic interleaving scheme for single- and multi-carrier modulation techniques implementing continuous phase modulation

Abstract In this paper, we present a chaotic interleaving scheme for both the Continuous Phase Modulation (CPM) based Orthogonal Frequency Division Multiplexing (CPM-OFDM) and CPM-based Single-Carrier Frequency-Domain Equalization (CPM-SC-FDE) systems. Chaotic interleaving is used to generate permuted versions from the sample sequences to be transmitted with low correlation among their samples, and hence a better Bit Error Rate (BER) performance can be achieved. The proposed CPM-OFDM and CPM-SC-FDE systems with chaotic interleaving combine the advantages of the frequency diversity and the high power efficiency of the CPM-based systems and the performance improvements due to chaotic interleaving. The BER performance of the both systems with and without chaotic interleaving is evaluated by computer simulations. Also, a comparison between chaotic interleaving and block interleaving is performed. Simulation results show that, the proposed chaotic interleaving scheme can greatly improve the performance of the CPM-OFDM system and the CPM-SC-FDE system. Furthermore, the results show that the chaotic interleaving scheme outperforms the traditional block interleaving scheme in both systems. The results also show that the use of chaotic interleaving with CPM-OFDM and CPM-SC-FDE systems provides a good trade-off between system performance and bandwidth efficiency.

A Chaotic Interleaving Scheme for the Continuous Phase Modulation Based Single-Carrier Frequency-Domain Equalization System

In this paper, we propose a chaotic interleaving scheme for the continuous phase modulation based single-carrier frequency-domain equalization (CPM-SC-FDE) system. Chaotic interleaving is used in this scheme to generate permuted versions from the sample sequences to be transmitted, with low correlation among their samples, and hence a better bit error rate (BER) performance can be obtained. The proposed CPM-SC-FDE system with chaotic interleaving combines the advantages of the frequency diversity, the low complexity, and the high power efficiency of the CPM-SC-FDE system and the performance improvements due to chaotic interleaving. The BER performance of the CPM-SC-FDE system with and without chaotic interleaving is evaluated by computer simulations. Also, a comparison between the proposed chaotic interleaving and the conventional block interleaving is performed. Simulation results show that, the proposed chaotic interleaving scheme can greatly improve the performance of the CPM-SC-FDE system. Furthermore, the results show that this scheme outperforms the conventional block interleaving scheme in the CPM-SC-FDE system. The results also show that, the proposed CPM-SC-FDE system with chaotic interleaving provides a good trade-off between system performance and bandwidth efficiency.

A New Relay and Jammer Selection Schemes for Secure One-Way Cooperative Networks

This paper presents different relay and jammer selection schemes for one-way cooperative networks to increase the security against malicious eavesdroppers. We consider a single source-destination cooperative network with multiple intermediate nodes and one or more eavesdroppers. The selection in the proposed schemes is made with the presence of direct links and the assumption that the broadcast phase is unsecured. The proposed schemes select three intermediate nodes. The first selected node operates in the conventional relay mode and assists the source to deliver its data to the corresponding destination via a Decode-and-Forward strategy. The second and third selected nodes are used in different communication phases as jammers to create intentional interference at the eavesdroppers’ nodes. Moreover, a hybrid scheme which switches between jamming and non-jamming modes is introduced in this paper. The proposed schemes are analyzed in terms of ergodic secrecy capacity and secrecy outage probability. Extensive analysis and a set of simulation results are presented to demonstrate the effectiveness of the different schemes presented in this work. The obtained results show that the proposed schemes with jamming outperform the conventional non-jamming schemes and the hybrid switching scheme further improves the secrecy capacity. The impact of changing both the eavesdroppers and the relays location on ergodic secrecy capacity and secrecy outage probability is also discussed. Finally, the impact of the presence of multiple eavesdroppers is studied in this paper.

Efficient Image Transmission with Multi-Carrier CDMA

This paper presents a new approach for efficient image transmission over Multi-Carrier Code Division Multiple Access (MC-CDMA) systems using chaotic interleaving. The chaotic interleaving scheme based on Baker map is applied on the image data prior to transmission. The proposed approach transmits images over wireless channels, efficiently, without posing significant constraints on the wireless communication system bandwidth and noise. The performance of the proposed approach is further improved by applying Frequency-Domain Equalization (FDE) at the receiver. Two types of frequency-domain equalizers are considered and compared for performance evaluation of the proposed MC-CDMA system; the Zero-Forcing equalizer and the Linear Minimum Mean Square Error (LMMSE) equalizer. Several experiments are carried out to test the performance of the image transmission with different sizes over the proposed MC-CDMA system. Simulation results show that image transmission over wireless channels using the proposed chaotic interleaving approach is much more immune to noise and fading. Moreover this chaotic interleaving process adds a degree of encryption to the transmitted data. The results also show a noticeable performance improvement in terms of the Root Mean Square Error and Peak Signal-to-Noise Ratio values when applying FDE in the proposed approach, especially with the LMMSE equalizer.

Energy-efficient hybrid opportunistic cooperative protocol for single-carrier frequency division multiple access-based networks

In this study, a new energy-efficient hybrid opportunistic cooperative (HOC) transmission protocol is proposed for single-carrier frequency division multiple access (SC-FDMA)-based cooperative networks. The author considers a single source- destination pair and multiple relays network. The proposed protocol improves the energy efficiency of SC-FDMA- based networks by selecting the most energy-efficient cooperative transmission protocol from a set of available protocols according to the current channel state information. The protocols considered in the development of the HOC protocol are amplify-and-forward, decode-and-forward, compress-and-forward and estimate-and-forward. Computer simulation is done over four different scenarios of channel conditions. The obtained results show that the proposed HOC protocol significantly improves the delay-limited capacity and minimises the outage probability of SC-FDMA-based cooperative networks. The results also show that the minimum required average total power in the proposed HOC protocol is less than that of opportunistic decode-and-forward by 0.55 dB.

New interleaving scheme for CE-OFDM systems using chaotic maps

Continuous phase modulation (CPM) is an attractive scheme for wireless communications because of its constant envelope (CE) and its ability to improve the diversity of the multipath channel. In this paper we propose a new interleaving scheme for the CPM based orthogonal frequency-division multiplexing (CE-OFDM) system, namely chaotic interleaving. The proposed system combines the key characteristics of CE-OFDM and the chaotic maps. Thus, this new system gets the advantages of power efficiency of CE-OFDM and the performance improvement of the chaotic interleaving. The proposed system comprises frequency domain equalization (FDE) to obtain high diversity gains over frequency selective multipath fading channels. The bit error rate (BER) performance of the CE-OFDM system with and without chaotic interleaving is evaluated by computer simulations. The simulation results show that, the CE-OFDM system based on the new interleaving scheme provides a better performance of about 2.3 dB improvements in SNR than the conventional CE-OFDM system.

Cooperative hybrid self-healing scheme for secure and data reliability in unattended wireless sensor networks

Unattended wireless sensor networks (UWSNs) are operated in hostile environments without constant supervision by a trusted sink; so it faces the risk of compromising by adversaries (ADVs). In this study, proposed is a cooperative hybrid self-healing randomised distributed (CHSHRD) scheme, a new mechanism to enhance the confidentiality of the data collected by UWSNs. The proposed scheme employs both proactive and reactive peers to ensure both backward secrecy and data reliability. It helps the unattended sensors to self-heal and restore their backward secrecy by asking for help from the best qualified neighbours to generate a new secret key to regain their secrecy. The sick sensors also use the best qualified neighbours to distribute the data parts among them to protect the data from eavesdropping and this will enhance the data reliability. In this study, they also present a powerful, realistic and agile ADV model and show how CHSHRD scheme can result in sensor regaining secrecy and achieving high data reliability, despite the adversary efforts to the contrary. The evaluation of the proposed scheme relies on both theoretical probabilistic results and simulation results that compare the proposed scheme to other protection schemes. The results show that this hybrid scheme provides better protection than other schemes that use either proactive or reactive peers.

A continuous phase modulation single-carrier wireless system with frequency domain equalization

This paper presents a continuous phase modulation (CPM) based single-carrier frequency-domain equalization (CPM-SC-FDE) structure for broadband wireless communication systems. The proposed structure combines the advantages of the frequency diversity and low complexity of SC-FDE and the energy efficiency of CPM. Simulation results show that, the proposed CPM-SC-FDE structure provides a better performance than conventional SC-FDE and the CPM based orthogonal frequency division multiplexing (OFDM) systems, by exploiting the channel frequency diversity, efficiently. A properly chosen modulation index can achieve an efficient utilization of the multipath diversity, while maintaining high bandwidth efficiency. The performance analysis of the proposed structure is also presented in the paper.