Distributed Cooperative Routing Algorithm for Multi-Hop Multi-Relay Wireless Networks

ASADUZZAMAN,KONG, Hyung-Yun The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.4

<P>Motivated by the recent research in crosslayer design of cooperative wireless network, we propose a distributed cooperative routing algorithm for a multihop multi-relay wireless network to achieve selection diversity. We propose two algorithms, rate optimal path selection and outage optimal path selection, to satisfy the different requirements of the systems. Both algorithms work on distributed processing without requiring any centralized controller. Simulations are conducted to evaluate the performance of the proposal. The results of the simulations show that the proposed routing algorithms significantly improve the end-to-end data rate and outage performance compared with noncooperative routing protocols.</P>

Interference Tolerant Based CR System with Imperfect Channel State Information at the CR-Transmitter

Asaduzzaman,Hyung-Yun Kong 한국전자파학회JEES 2011 Journal of Electromagnetic Engineering and Science Vol.11 No.2

In interference tolerance based spectrum sharing systems, primary receivers (PRs) are protected by a predefined peak or average interference power constraint. To implement such systems, cognitive radio (CR) transmitters are required to adjust their transmit power so that the interference power received at the PR receivers is kept below the threshold value. Hence, a CR-transmitter requires knowledge of its channel and the primary receiver in order to allocate the transmit power. In practice, it is impossible or very difficult for a CR transmitter to have perfect knowledge of this channel state information (CSI). In this paper, we investigate the impact of imperfect knowledge of this CSI on the performances of both a primary and cognitive radio network. For fixed transmit power, average interference power (AIP) constraint can be maintained through knowledge of the channel distribution information. To maintain the peak interference power (PIP) constraint, on the other hand, the CR-transmitter requires the instantaneous CSI of its channel with the primary receiver. First, we show that, compared to the PIP constraint with perfect CSI, the AIP constraint is advantageous for primary users but not for CR users. Then, we consider a PIP constraint with imperfect CSI at the CR-transmitter. We show that inaccuracy in CSI reduces the interference at the PR-receivers that is caused by the CR-transmitter. Consequently the proposed schemes improve the capacity of the primary links. Contrarily, the capacities of the CR links significantly degrade due to the inaccuracy in CSI.

Performance Analysis of Coded Cooperation Protocol with Reactive and Proactive Relay Selection

Asaduzzaman,Hyung-Yun Kong 한국전자파학회JEES 2011 Journal of Electromagnetic Engineering and Science Vol.11 No.2

Coded cooperation that integrates channel coding in cooperative transmission has gained a great deal of interest in wireless relay networks. The performance analysis of coded cooperation protocol with multiple relays is investigated in this paper. We show that the diversity order achieved by the coded cooperation in a multi-relay wireless network is not only dependent on the number of cooperating relays but is also dependent on the code-rate of the system. We derive the code-rate bound, which is required to achieve the full diversity gain of the order of cooperating nodes. The code-rate required to achieve full diversity is a linearly decreasing function of the number of available relays in the network. We show that the instantaneous channel state information (CSI)-based relay selection can effectively alleviate this code-rate bound. Analysis shows that the coded cooperation with instantaneous CSI-based relay selection can achieve the full diversity, for an arbitrary number of relays, with a fixed code-rate. Finally, we develop tight upper bounds for the bit error rate (BER) and frame error rate (FER) of the relay selection based on coded cooperation under a Rayleigh fading environment. The analytical upper bounds are verified with simulation results.

Code Combining Cooperative Diversity in Long-haul Transmission of Cluster based Wireless Sensor Networks

( Asaduzzaman ),( Hyung Yun Kong ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.7

A simple modification of well known Low Energy Adaptive Clustering Hierarchy (LEACH) protocol is proposed to exploit cooperative diversity. Instead of selecting a single cluster-head, we propose M cluster-heads in each cluster to obtain a diversity of order M. The cluster-heads gather data from all the sensor nodes within the cluster using same technique as LEACH. Cluster-heads transmit gathered data cooperatively towards the destination or higher order cluster-head. We propose a code combining based cooperative diversity protocol which is similar to coded cooperation that maximizes the performance of the proposed cooperative LEACH protocol. The implementation of the proposed cooperative strategy is analyzed. We develop the upper bounds on bit error rate (BER) and frame error rate (FER) for our proposal. Space time block codes (STBC) are also a suitable candidate for our proposal. In this paper, we argue that the STBC performs worse than the code combining cooperation.

On the Capacities of Spectrum-Sharing Systems with Transmit Diversity

Asaduzzaman,Hyung-Yun Kong 한국전자파학회JEES 2010 Journal of Electromagnetic Engineering and Science Vol.10 No.3

Motivated by recent works on spectrum-sharing systems, this paper investigates the effects of transmit diversity on the peak interference power limited cognitive radio(CR) networks. In particular, we derive the ergodic and outage capacities of a spectrum-sharing system with multiple transmit-antennas. To derive the capacities, peak interference power constraint is imposed to protect the primary receiver. In a CR transmitter and receiver pair with multiple antennas at the transmitter side, the allowable transmit power is distributed over the transmit-antennas to achieve transmit diversity at the receiver. We investigate the effect of this power distribution when a peak interference power constraint is imposed to protect the primary receiver. We show that the transmit diversity does not improve the ergodic capacity compared to the single-antenna system. On the other hand, the transmit diversity significantly improves the outage capacity. For example, two transmit-antennas improve the outage capacity 10 times compared to the singleantenna with a 0 ㏈ interference constraint.

Opportunistic Relaying Based Spectrum Leasing for Cognitive Radio Networks

Asaduzzaman,Hyung Yun Kong,Insoo Koo 한국통신학회 2011 Journal of communications and networks Vol.13 No.1

Spectrum leasing for cognitive radio (CR) networks is an effective way to improve the spectrum utilization. This paper presents an opportunistic relaying based spectrum leasing for CR networks where the primary users lease their frequency band to the cognitive users. The cognitive users act as relays for the primary users to improve the channel capacity, and this improved capacity is used for the transmission of secondary users’ data. We show that the cognitive users can use a significant portion of the communication resource of primary networks while maintaining a fixed target data rate for the primary users. Moreover, the primary network is also benefited by the cooperating cognitive users in terms of outage probability. Information theoretic analysis and simulation results are presented to evaluate the performances of both primary and cognitive networks.

Coded diversity for cooperative MISO based wireless sensor networks

Asaduzzaman,Hyung Kong IEEE 2009 IEEE communications letters Vol.13 No.7

<P>Motivated by the recent works on cooperative MIMO, this letter presents a coded diversity based cooperative protocol for wireless sensor networks. In densely deployed sensor networks, nearby nodes form a cluster of virtual antenna array to provide independent fading paths. The source node encodes the information bits with any channel code and forwards a portion of the codeword towards the cooperating nodes. The source and the cooperating nodes transmit different portion of the codeword to achieve a coded diversity at destination. Analysis and simulation show that our proposal can achieve full diversity when code rate is below a certain threshold.</P>

사용자간 잡음 채널을 위한 부호화 협력통신

( Asaduzzaman ),공형윤 ( Hyung-yun Kong ),이동운 ( Dong-un Lee ) 한국정보처리학회 2006 한국정보처리학회 학술대회논문집 Vol.13 No.2

A new frame structure for Cooperative Coding when the interuser channel is vulnerable with fading and AWGN is proposed in this paper. We consider the similar two frame structure proposed in recent works of coded cooperation scheme with an additional acknowledgement bit after transmission of first frame towards both the cooperative partner and destination (Base station or access point). On the basis of the acknowledgement signal each user transmits its own, partner orcombined own and partners second frame. We proposed a new technique for this combination when one user cooperates and another does not due to the noisy interuser channel.

Automatic Request for Cooperation (ARC) and Relay Selection for Wireless Networks

ASADUZZAMAN,KONG, Hyung-Yun The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.3

<P>Recently, there has been growing interest in the design of wireless cooperative protocol to achieve higher diversity-multiplexing tradeoff among single antenna devices. We propose an automatic request for cooperation (ARC) scheme for wireless networks which can achieve higher order diversity by selecting the best relay. In this scheme, a source transmits a data packet towards a destination and a group of relays. The destination tries to decode the information from the source and if the detection is correct the process will stop. Otherwise, the destination transmits an ARC towards the relays. We utilize this ARC signal for selecting the best relay from the set of relays that have successfully decoded the source packet. The selected relay generates and transmits redundant information for the source packet. The destination combines the two packets received from the source and the best relay to improve the reliability of the packet. We analyze the packet error rate, spectral efficiency and diversity-multiplexing tradeoff of our proposal and compare them with some existing protocols. Analysis shows that our proposal can achieve higher diversity multiplexing tradeoff than conventional cooperative protocols.</P>

Code Combining Based Cooperative LEACH Protocol for Wireless Sensor Networks

ASADUZZAMAN,KONG, Hyung-Yun The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.6

<P>This letter proposes a simple modification of LEACH protocol to exploit its multi-hop scenario for user cooperation. Instead of a single cluster-head we propose <I>M</I> cluster-heads in each cluster to obtain the diversity of order <I>M</I>. All cluster-heads gather data from all sensor nodes within the cluster using the same technique as LEACH. Cluster-heads transmit gathered data cooperatively towards the destination or higher order cluster-head. We propose a code combining based cooperative protocol. We also develop the upper bounds on frame error rate (FER) for our proposal. Simulation and analysis show that our proposal can significantly prolong the system lifetime.</P>