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We derive the diversity order of some multiple antenna multi-user cancellation and detection schemes. The common property of these detection methods is the usage of Alamouti and quasi-orthogonal space-time block codes. For detecting J users each having N transmit antennas, these schemes require only J antennas at the receiver. Our analysis shows that when having M receive antennas, the array-processing schemes provide the diversity order of N (M − J + 1). In addition, our results prove that regardless of the number of users or receive antennas, when using maximum-likelihood decoding we get the full transmit and receive diversities, i.e. N M , similar to the no-interference scenario.

Abstract-We investigate the connectivity of fading wireless ad-hoc networks with a pair of novel connectivity metrics. Our first metric looks at the problem of connectivity relying on the outage capacity of MIMO channels. Our second metric relies on a probabilistic treatment of the symbol error rates for such channels. We relate both capacity and symbol error rates to the characteristics of the underlying communication system such as antenna configuration, modulation, coding, and signal strength measured in terms of Signal-to-Interference-Noise-Ratio (SIN R). For each metric of connectivity, we also provide a simplified treatment in the case of ergodic fading channels. In each case, we assume a pair of nodes are connected if their bi-directional measure of connectivity is better than a given threshold. Our analysis relies on the central limit theorem to approximate the distribution of the combined undesired signal affecting each link of an ad-hoc network as Gaussian. Supported by our simulation results, our analysis shows that (1) a measure of connectivity purely based on signal strength is not capable of accurately capturing the connectivity phenomenon, and (2) employing multiple antenna mobile nodes improves the connectivity of fading ad-hoc networks.

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Received signal strength has been widely used as the main criterion of connectivity between wireless nodes. We investigate the connectivity of fading wireless ad-hoc networks with a novel connectivity metric. Our metric of connectivity considers realistic effects of the characteristics of the utilized wireless nodes such as modulation and symbol error rate. We assume a pair of nodes are connected if the bi-directional symbol error rate on their direct connecting link is below a given threshold. Our treatment of the problem relies on a probabilistic approach describing the quantities of interest in the form of random variables. Our simulation results over sample ad-hoc topologies support the fact that depending on the characteristics of the wireless nodes, different connectivity results may be observed for the same signal strength.

We study the problem of connectivity in MIMO fading ad-hoc networks. Based on a probabilistic analysis of achievable capacity on individual links of a random topology, we introduce a novel connectivity metric for wireless ad-hoc networks. We assume a pair of nodes are connected if their bi-directional capacity is more than a given threshold. Our metric is more sophisticated compared to previously proposed metrics of connectivity as it captures the effects of time-varying fading channel, power, and multiple antennas. Our results show that employing mobile nodes with multiple antennas enhances the connectivity of fading wireless ad-hoc networks.

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