Danpu Liu

An energy-efficient virtual V-BLAST transmission scheme for cluster-based wireless sensor networks

Wireless sensor network is a promising technique in the near future, but energy-constrained characteristic of sensor nodes is one of the key issues that we must consider in designing. In this paper, a cluster-based virtual V-BLAST transmission scheme is proposed for energy-constrained wireless sensor networks. Compared to previous work, there are two new aspects in this scheme. Firstly, the proposed scheme makes use of multiple cluster heads simultaneous transmission instead of single one. Secondly, the receiver-side V-BLAST processing is incorporated into the original LEACH protocol. In addition, an analysis model based on energy consumption of the whole network is developed to find the optimum parameter for the scheme. Simulation results show that the proposed scheme is more energy-efficient when compared to the original LEACH protocol.

Fair Resource Allocation in OFDMA Two-Hop Cooperative Relaying Cellular Networks

This paper discusses on the fair resource allocation in OFDMA two-hop cooperative relaying cellular networks which consist of a single base station (BS), dedicated fixed relay stations (RSs) and user stations (USs). By assuming the relay strategy employed on each subcarrier is adaptively selected among direct transmission, amplify-and-forward (AF) and decode-and-forward (DF) according to different channel conditions, we formulate a fair subcarrier assignment, relay station and relay strategy selection problem with QoS constraints in terms of user’s minimum rate requirement. The formulated problem is a Binary Integer Programming (BIP) problem which is NP-complete, so a simple suboptimal algorithm is proposed to manage the network resources. Simulations demonstrate the proposed algorithm obtains near optimal solution with low complexity and achieves a good tradeoff between the overall system performance and the fairness among users.

A QoS-Aware Resource Allocation Scheme with Limited Feedback in Downlink OFDMA Systems

In orthogonal frequency division multiple access (OFDMA)-based systems, base station (BS) can adaptively adjust modulation and coding parameters according to channel quality indicator (CQI) fed back, therefore spectrum efficiency can be significantly improved. In this paper, based on the joint consideration of both quality of service (QoS) difference and spectrum efficiency, we have proposed a novel resource allocation algorithm and a modified top- M feedback scheme for OFDMA-based systems with limited CQI feedback. In order to meet the QoS requirements, users of different traffic types are assigned with different priorities. Simulation results have proved that the proposed allocation algorithm can fully sustain users requirements under reasonable traffic loads, and simultaneously the feedback load can be greatly reduced.

An energy aware distributed clustering routing protocol for energy harvesting wireless sensor networks

Energy harvesting wireless sensor networks (EH-WSNs) have been widely used in various areas in recent years. Unlike battery-powered wireless sensor networks, EH-WSNs are powered by energy harvested from ambience. This change calls for new designs on routing protocols in EH-WSNs. This paper proposes a novel energy-aware distributed clustering routing protocol for EH-WSNs, it takes the node current residual energy and the harvested energy in a short term prediction horizon into cluster heads election process of the distributed clustering routing. A neural network based solar energy prediction model is exploited to make the protocol energy-aware. Nodes with higher residual energy and stronger energy harvesting capabilities thus have higher probability of being cluster heads. The proposed routing algorithm is compared with LEACH (low-energy adaptive clustering hierarchy) in terms of the number of awake nodes and network throughput. Simulation results show that the proposed clustering routing has stronger ability to balance energy consumption among sensor nodes and increases the network throughput by about 30% over LEACH.

Proactive relay selection in distributed multi-source cooperative networks

This paper investigates proactive relay selection (PRS) in distributed cooperative networks with multiple potential relays and multiple source-destination pairs. A simple PRS scheme is proposed and its outage probability is analyzed. Compared with the reactive relay selection (RRS) scheme proposed in [6], our PRS scheme has a loss on the outage performance. However, its significance lies in three aspects: 1) It is fully decentralized; 2) It has less signalling overhead; 3) It saves the network energy consumption. This shows that our PRS scheme is specifically valuable to networks which do not allow centralized control and are energy constrained, such as ad hoc or sensor networks.

Asymptotic Expression for Transmission Capacity of Wireless Ad Hoc Networks

We study the transmission capacity of wireless Ad hoc networks in this paper. Transmission capacity can not be got the close-form for general cases except for some special cases. In this paper we provide a new solution to this problem. By using Taylor series, the asymptotic expression for transmission capacity is derived. Comparing the asymptotic with the exact expressions shows that, the asymptotic expression is a good approximation which is accurate enough when the outage constraint is close to zero.

An Improved Space-Time Decoder Under MIMO System

Optimum space-time convolution code, which provides maximum diversity and coding gain, are produced for cases with PSK modulation and various numbers of states and antennas. In this paper, we modify the conventional Viterbi algorithm used in space-time encoder under the MIMO system, and give the recursive metric equation. The modified Viterbi algorithm can be used in the receiver when the MIMO channel information is known a prior. The new approach provides an efficient method that allows a search for optimum path. Compared with the conventional decoding algorithm, the improved algorithm can be used in the every receiver respectively. It is shown that the improved algorithm is also an optimal algorithm, however, its metric convergence speed is faster than the standard Viterbi algorithm.