Lina Zheng

Link-Utility-Based Cooperative MAC Protocol for Wireless Multi-Hop Networks

In this paper, we propose a novel link-utility-based cooperative MAC (LC-MAC) protocol for wireless multi-hop networks. By fully utilizing the broadcast nature of wireless multi-hop networks, the node that has overheard data packets in the previous hop may become a partner of the transmitter in the current hop. As diversity gain can be achieved by virtual antenna array formed by transmitter and partner, one-phase cooperative transmission is introduced to improve the throughput. In LC-MAC, based on the instantaneous channel measurements, each node tries to maximize its own link-utility (indicator of a nodes ability to cooperate) by jointly adjusting transmission rate and power. Subsequently, distributed backoff procedure is activated to select the best node that has the maximum link-utility. The optimal transmission type, rate and power are uniquely determined by the best node. Since only local information is required, LC-MAC is a completely distributed protocol. Finally, extensive simulations are performed to investigate the impact of scenario and protocol parameters on the performance of LC-MAC. Numerical results show that LC-MAC significantly outperforms the cooperative relay-based rate adaptation (CRBAR) scheme and the receiver-based rate adaptation (RBAR) scheme in terms of throughput and energy efficiency.

Approximate SEP Analysis for DF Cooperative Networks With Opportunistic Relaying

We analyze the symbol error probability (SEP) performance of cooperative diversity networks with opportunistic decode-and-forward (ODF) relaying. Assuming that channels suffer from independent nonidentical Rayleigh fading and symbols are M-PSK modulated, the approximate closed-form SEP expressions are derived for opportunistic relaying with adaptive and fixed DF protocols, respectively. Simulations are carried out to validate the theoretical analysis. Results show that the derived approximate SEP is tight particularly at medium and high SNR.

Cooperative Spectrum Sharing With Wireless Energy Harvesting in Cognitive Radio Networks

We study cooperative spectrum sharing in cognitive radio networks with wireless energy harvesting (EH), where all the primary and secondary users are overlaid on the 2-D plane. Each primary user (PU) should harvest energy from the wireless signal sent by its access point (AP), whereas all the APs and the secondary users have stable power supply. To improve EH efficiency, an EH zone is applied around each PU, where the secondary transmitter (ST) with the shortest distance toward the PU is selected to transfer the wireless energy. Using the harvested energy, the PU can transmit its data over the reverse link to the AP, but the data transmission is more likely to fail due to the weak transmission power and the severe path loss. In this case, a cooperative region is applied between each PU and its corresponding AP, where a suitable ST with the best channel quality toward the AP is selected to forward the primary data. The performance requirement of the primary system can be easily satisfied with ST cooperation, and thus, a fraction of bandwidth can be released to the secondary-data transmission. The optimization problem is formulated to maximize the area throughput of the secondary system under the performance constraint of the primary system. By analyzing system performance using the stochastic geometry theory, we propose an algorithm to optimally allocate the bandwidth and time resources to facilitate both the EH and data transmission. Performance results are presented to validate our theoretical analysis and show the impacts of various system settings.

Performance Analysis of SNR-Based Hybrid Decode-Amplify-Forward Cooperative Diversity Networks over Rayleigh Fading Channels

Cooperative diversity has recently been proposed as a promising technology to achieve spatial diversity in wireless networks. In this paper, we analyze the performance of SNR-based hybrid decode-amplify-forward (HDAF) relaying cooperative diversity networks over independent non-identical flat Rayleigh fading channels with maximum ratio combining (MRC) technique. Closed-form expressions for the outage and bit error probability of the HDAF relaying scheme are derived. Computer simulations are carried out to illustrate and validate the correctness of analytical results. Besides, the impacts of the SNR threshold and relay location on the performances of outage and bit error probability are investigated.

Lifetime Maximization via a New Cooperative MAC Protocol in Wireless Sensor Networks

Lifetime extension is a key design issue for wireless sensor networks (WSN) with battery-operated nodes. Compared with direct transmission, transmission power can be significantly reduced by cooperative communication, because it can effectively mitigate multi-path fading by introducing space diversity. In this paper, BER analysis for M-PSK and M-QAM modulation in non-cooperative and cooperative situations is firstly presented. Then power is optimally allocated to source and relay nodes with the objective of minimizing the total transmission power under the average BER constraint. Based on these works, a new distributed cooperative MAC protocol is proposed to improve the lifetime of WSN. In this protocol, both channel state information (CSI) and residual energy information (REI) of sensor nodes are considered to choose the cooperative nodes. Simulation results show that when the access point (AP) is above a certain height, the proposed cooperative protocol can significantly prolong network lifetime compared with non-cooperative MAC protocols.

An Improved Selection Cooperation Scheme for Decode-and-Forward Relaying

In this letter, an improved selection cooperation (ISC) scheme for decode-and-forward relaying is proposed based on selection cooperation (SC) strategy. Assuming that channels suffer from independent non-identical Rayleigh fading, we derive closed-form expression for the exact symbol error rate (SER) of ISC scheme. The result holds for arbitrary number of relays and refers to both M-PSK and M-QAM modulations. Simulations are carried out to validate the theoretical analysis. Results show that the proposed ISC scheme outperforms SC for all the cases we investigate.

Maximise lifetime of wireless sensor networks via a distributed cooperative routing algorithm

Combining cooperative diversity, truncated automatic repeat request scheme and distributed energy-aware routing strategy, a novel cooperative routing algorithm adopting decode-and-forward fashion is proposed to maximise the lifetime of wireless sensor networks from the cross-layer design perspective. In this algorithm, the transmission power is optimally allocated while satisfying the per-link symbol error rate or the end-to-end throughput requirement. The average total consumed power weighted by the normalised remaining energy of every participating node is used as the link cost to avoid the overuse of certain nodes with extremely little energy. With the use of the traditional distributed shortest path algorithm, the best route that includes a cascade of single-relay building blocks is constructed with polynomial complexity. In contrast to the non-cooperative routing schemes, this cooperative routing algorithm can significantly prolong the network lifetime and improve the energy efficiency by reducing the total network residual energy. Copyright

Two-Transmitter Two-Receiver Cooperative MAC Protocol: Cross-Layer Design and Performance Analysis

Cooperative diversity is a promising and practical technique for realizing spatial diversity through a virtual antenna array formed by multiple distributed antennas of different nodes. In this paper, we propose and evaluate a novel cooperative cross-layer medium access control (CC-MAC) protocol, which combines space-time coding and adaptive modulation at the physical layer and employs truncated automatic repeat request (ARQ) at the data-link layer. The transmitters partner is selected in the previous hop, and the receiver invites a partner to participate in data reception in the current hop, and in this situation, a two-transmitter two-receiver model is constructed. Because distributed space-time coding is applied at the transmitting set (transmitter and its partner), cooperative diversity and coding gain can be obtained. Based on the instantaneous channel state measured at the receiver, an adaptive modulation scheme is adopted to improve the link throughput at the physical layer. In addition, the truncated ARQ scheme is employed to further enhance the throughput performance at the data-link layer. Furthermore, under different system models with or without the truncated ARQ scheme, performances of the average packet error rate (PER) and symbol error rate (SER) with multiple phase shift keying (M-PSK) modulation and multiple quadrature amplitude modulation (M-QAM) over Rayleigh fading channel are analyzed. Simulation results verify the correctness of the performance analysis and show that CC-MAC can significantly improve system throughput and energy efficiency compared with other transmission schemes.

Exact capacity analysis of multi-relay multiuser cooperative networks based on two-step selection

SUMMARY This paper advocates the capacity analysis of an amplify-and-forward cooperative communication system model in multi-relay multiuser networks. A two-step selection scheme is adopted, and both relay and user selection are based on the outdated channel state information. Exact expression of channel capacity for independent, but not necessarily identically distributed, Rayleigh fading channels is derived. Finally, simulations are carried out to verify the correctness of theoretical analysis and illustrate the effect of parameters on the performance. Results show that although the performance of our scheme is inferior to the optimal joint selection scheme, it is still a practical scheme because its complexity is much lower than that of the optimal scheme. Copyright

Performance of opportunistic relaying with truncated ARQ over Nakagami-m fading channels

On the basis of the decode-and-forward protocol, the opportunistic relaying scheme selects the best relay out of the N available relays with the correct data copy of the source. The best relay forwards the data of source to the destination in the second time slot. While in the truncated automatic repeat request scheme, the relay will cooperatively do the data transmission only when the original signal is erroneously received by the destination. Through combining these two conceptions, the system throughput can be improved without sacrificing the space diversity. The performance of traditional noncooperative and such cooperative schemes with M-ary phase-shift keying and M-ary quadrature amplitude modulation symbols over Nakagami-m fading channels is analysed in terms of packet error rate, symbol error rate and throughput. In addition, we suppose that the destination either combines the previous and retransmitted packets using maximal ratio combining technique or simply (SIM) discards the previous wrong packet and uses the current packet alone (SIM). Monte Carlo simulations are included to verify the accuracy of analytical results. Copyright