Spatial Interference Cancelation for Mobile Ad Hoc Networks: Perfect CSI

Interference between nodes directly limits the capacity of mobile ad hoc networks. This paper focuses on spatial interference cancelation with perfect channel state information (CSI), and analyzes the corresponding network capacity. Specifically, by using multiple antennas, zero-forcing beamforming is applied at each receiver for canceling the strongest interferers. Given spatial interference cancelation, the network transmission capacity is analyzed in this paper, which is defined as the maximum transmitting node density under constraints on outage and the signal-to-interference-noise ratio. Assuming the Poisson distribution for the locations of network nodes and spatially i.i.d. Rayleigh fading channels, mathematical tools from stochastic geometry are applied for deriving scaling laws for transmission capacity. Specifically, for small target outage probability, transmission capacity is proved to increase following a power law, where the exponent is the inverse of the size of antenna array or larger depending on the pass loss exponent. As shown by simulations, spatial interference cancelation increases transmission capacity by an order of magnitude or more even if only one extra antenna is added to each node.Comment: 6 pages; submitted to IEEE Globecom 200

Enhanced congestion control in TCP for solving hidden terminal problems in ad hoc wireless networks

This paper studies TCP performance over multihop wireless ad hoc networks that use the IEEE 802.11 protocol as the access method. The aim is to improve the TCP fairness while keeping the algorithm as simple as possible, since in previous works the algorithm designs were more complicated. We propose a simple approach to improve fairness based on scheduling (pacing) new packets according to the transmission interval formed from scaled round-trip time (RTT) and congestion window. Our simulation shows that, given specific scale parameter x, TCP achieves high fairness and throughput via improved spatial channel reuse, if it operates in a certain range of the transmission interval

Spatial reuse through adaptive interference cancellation in multi-antenna wireless networks

Abstract — Efficient medium access control in wireless networks has been a challenging task. While the IEEE 802.11 standard coordinates contention effectively, it severely limits the number of concurrent communications. This results in reduced throughput and efficiency. Recent research has focused on employing multiple antennas to increase throughput in a multipath environment by enabling multiple streams between a transmitreceive pair. In this paper we show that exploiting multiuser diversity to enable concurrent communications has certain advantages over multiple streaming. We propose a medium access control (MAC) protocol that uses adaptive interference cancellation with multiple antennas to increase network throughput and to provide better fairness, while requiring minimal change to the widely-deployed 802.11 MAC structure. I