Search

A cooperative spectrum-sensing technique in cognitive radio (CR) networks based on the data fusion of various chaotic stochastic resonance (CSR) energy detectors is proposed in this paper. Due to noisy uncertainty in unpredictable wireless communication environments, detection performance of conventional energy detection cannot be guaranteed. By introducing the CSR system with various CSR noise types, and with the data fusion on these CSR-based energy detectors, the detection probability can be improved under the same constant false-alarm rate (CFAR), particularly under low signal-to-noise ratio (SNR) circumstances. Theoretical analyses and computer simulation results verify the effectiveness of the proposed novel cooperative spectrum-sensing approach under serious wireless conditions. [ABSTRACT FROM PUBLISHER]

This paper considers transmission schemes in multiaccess relay networks (MARNs) where J single-antenna sources send independent information to one N-antenna destination through one M-antenna relay. For complexity considerations, we propose a linear framework, where the relay linearly transforms its received signals to generate the forwarded signals without decoding and the destination uses its multiantennas to fully decouple signals from different sources before decoding, by which the decoding complexity is linear in the number of sources. To achieve a high symbol rate, we first propose a scheme called ConcurrentS\rightarrowR\rightarrowD-IC_D in which all sources' information streams are concurrently transmitted in both the source-relay link and the relay-destination link. In this scheme, distributed space-time coding (DSTC) is applied at the relay, which satisfies the linear constraint. DSTC also allows the destination to conduct the zero-forcing interference cancellation (IC) scheme originally proposed for multiantenna systems to fully decouple signals from different sources. Our analysis shows that the symbol rate of ConcurrentS\rightarrowR\rightarrowD-IC_D is 1/2 symbols/source/channel use and the diversity gain of the scheme is upperbounded by M-J+1. To achieve a higher diversity gain, we propose another scheme called ConcurrentR\rightarrowD-IC_D in which the sources time-share the source-relay link. The relay coherently combines the signals on its antennas to maximize the signal-to-noise ratio (SNR) of each source, then concurrently forwards all sources' information. The destination performs zero-forcing IC. It is shown through both analysis and simulation that when N\geq 2J-1, ConcurrentR\rightarrowD-IC_D achieves the same maximum diversity gain as the full TDMA scheme in which information streams from each source are assigned to orthogonal channels in both links, but with a higher symbol rate. [ABSTRACT FROM AUTHOR]

A typical multicast network consists of a single tree, in which only a few internal nodes contribute most resources and are involved in performing the multicast functionality. This leads to an uneven and inefficient utilization of network resources. The problem is more pronounced in mobile ad hoc networks (MANET5), where network resources are limited. One solution is to split the multicast content over a number of trees. This provides several paths for the multicast content and would involve more nodes in implementing multicast functionality. Although this approach improves network utilization, overall multicast latency increases. This paper presents a distributed algorithm to construct multiple edge, sharing trees (MESTs) for small group multicast. MESTs balance the resource allocation and delay constraints by choosing to overlap certain edges that have low weight. Simulation results show that MESTs can generate multicast networks that have low delays and fair resource utilization. MESTs are designed to work with any form of multicast in both wired and wireless networks. [ABSTRACT FROM AUTHOR]

In this paper, we consider wireless networks with directional antennas using slotted ALOHA medium access control. The channel model incorporates the effects of propagation loss and shadowing with Rayleigh fading. By deriving the cumulative distribution function of the signal-to-interference-and-noise ratio (SINR) of a certain link in the network, the outage probability of the link is analyzed. In particular, the analysis works for the arbitrary beam patterns of the directional antennas used in the networks. Moreover, we propose a new parameter, i.e., the array interference factor, which can characterize the average performance of an arbitrary beam pattern in random wireless networks. This provides an efficient way for designers to evaluate the system performance under different beam patterns. The network throughput and the transport capacity of a random wireless net- work with directional antennas are also analyzed. It is shown that the network transport capacity is of the same order as the square root of the node density, which conforms with the well-known capacity of wireless networks. The analysis is useful for designers to optimize the system performance of wireless networks with directional antennas. [ABSTRACT FROM AUTHOR]

In this paper, we investigate efficient wireless data access algorithms in mobile hotspots. We introduce a proxy cache (PC) and propose PC-based poll-each-read (P-PER) and PC-based callback (P-CB) data access algorithms to reduce the transmission cost over wireless links in mobile hotspots. An analytical model is developed, and extensive simulations are conducted to demonstrate the performance of P-PER and P-CB. It is shown that P-PER and P-CB can improve cache hit performance and significantly reduce transmission cost. A tradeoff between P-PER and P-CB suggests the need to use a hybrid proxy-based approach to attain optimal performance of wireless data access in mobile hotspots. [ABSTRACT FROM AUTHOR]