Multiple-input Multiple-output Ad-hoc Network Research Articles

Outage probability analysis of multiple input multiple output ad‐hoc networks with random topology

Outage probability performance of multiple-input multiple-output (MIMO) ad-hoc network with quantised beamforming and finite rate feedback is analysed with the assumption that the nodes are uniformly distributed with random topology. In quantised beamforming, each receiver sends the label of the best beamforming vector obtained from the codebook to the transmitter through a finite rate limited feedback. The code book is shared between the desired users to prevent decoding of other user's information in a MIMO ad-hoc network. In such a practical environment, feedback links can only convey finite number of bits, from which transmit beamformer designs are investigated using either the outage probability or average signal to interference ratio as the figure of merit. In this study, a mathematical analysis for the estimation of the interference power statistics and the corresponding outage probability in MIMO wireless ad-hoc networks with random position of interference nodes is carried out. In lieu of validating the obtained simulation results, theoretical results have also been compared.

Distributed MIMO Ad-hoc Networks: Link Scheduling, Power Allocation, and Cooperative Beamforming

For next-generation network topologies, the distributed wireless ad-hoc network is one of the most challenging issues because of the inherent node intelligence decision. Nevertheless, due to the randomness of node distribution, it is difficult to achieve high efficiency without signaling to neighboring nodes to coordinate random interference among the nodes, which, in turn, leads to high computational overhead in general. In this paper, we propose a framework of distributed multiple-input- multiple-output (MIMO) ad-hoc networks to improve link capacity while achieving computational simplicity without interworking with other links in a fully distributed manner. To achieve this goal, we align three main resource management algorithms, i.e., the distributed link-scheduling algorithm (DLSA), the distributed power allocation algorithm (DPAA), and the distributed cooperative beamforming algorithm (DCBA). In the simulation results, performance has proven to be promising in terms of the average sum rate, compared with that of other conventional schemes.

Outage probability analysis for multiple input–multiple output ad-hoc network with quantised beamforming

In this study, exact closed-form expressions are derived for sum throughput/capacity and outage probability for multiple input–multiple output (MIMO) ad-hoc network with quantised beamforming and finite-rate feedback. In quantised beamforming, each receiver sends the label of the best beamforming vector obtained from the codebook to the transmitter through a finite rate limited feedback. The code book is shared between each transmitter–receiver pair to prevent decoding of other user's information in a MIMO ad-hoc network comprising of K simultaneous communicating transceiver pairs with each receiver employing single-user detection. In such a practical environment, feedback links can only convey a finite number of bits, from which transmit beamformer designs are investigated using either the outage probability or average signal to interference noise ratio (SINR) as the figure of merit. Hence, by deriving closed-form expressions for outage probability and network sum throughput interesting insights in the high-SINR regimes are provided. In lieu of validating the obtained simulation results, the theoretical results have also been compared.

Integrated Cooperative Opportunistic Packet Forwarding and Distributed Error Control in MIMO Ad Hoc Networks

In this paper, we address the problem of packet forwarding in multi-hop wireless networks of nodes equipped with multiple antennas. Through the use of MIMO (multiple-input multiple-output) technology, the physical layer is able to superimpose multiple concurrent information flows, thereby increasing the communications parallelism in the network. We propose a cooperative cross-layer scheme that integrates distributed incremental redundancy hybrid automatic retransmission request (HARQ) error control with routing in order to increase the efficiency of the transmissions and decrease the interference load in the network. In the proposed scheme, next hop relays are opportunistically selected during the HARQ process in order to avoid overloaded receivers and guarantee the geographical advancement of the packets. Thus, cooperation is used to both strengthen weak links and select the path to the destination. Numerical results are presented for a specific instantiation where a layered space-time multiuser detection (LASTMUD) transmitter-receiver architecture with spread-spectrum signals is implemented at the physical layer and packets are encoded with a linear erasure code (LEC).

Experimental evaluation of game theoretic power allocation in MIMO ad-hoc networks

Multiple input multiple output (MIMO) communication systems in an ad-hoc network can provide high spectral efficiency. Several resource allocation methods have been presented and experimentally demonstrated to improve performance in a resource limited environment. Recently, a game theoretic method has been published with promising results. The goal of this paper is to present simulation and experimental results for this game theoretic technique.

An Optimization Framework for Demand-based Fair Stream Allocation in MIMO Ad Hoc Networks

In this paper, we investigate the problem of scheduling flows for fair stream allocation (or, stream scheduling) in ad hoc networks in which the transmitter and receiver use multiple antennas called Multiple Input Multiple Output (MIMO) technology. Our main contributions include: i) the concept of stream allocation to flows based on their traffic demands or class, ii) stream allocation to flows in the network utilizing single user or multiuser MIMO communication, iii) achieving the proportional fairness of the stream allocation in the minimum possible schedule length, and iv) performance comparison of the stream scheduling in the network for single user and multiuser communication and the tradeoff involved therein. We first formulate demand-based fair stream allocation as an integer linear programming (ILP) problem whose solution is a schedule that is guaranteed to be contention-free. We then solve this ILP in conjunction with binary search to find a minimum length contention-free schedule that achieves the fairness goals. We show that an implementation of our algorithm for a number of sample topologies in fact yields minimum length schedules that achieve the fairness goals. We then give performance comparison results that show the benefit of multiuser MIMO links over single user links at higher traffic workloads in the network. Finally, we also give a greedy heuristic for stream scheduling and compare its performance with the ILP-based algorithm in terms of the fairness goals achieved in a given schedule length.

MAC/PHY Cross-Layer Design of MIMO Ad Hoc Networks with Layered Multiuser Detection

In this paper, we present a novel MAC approach for ad hoc networks in which Multiple Input-Multiple Output (MIMO) techniques are used at the physical level (PHY). The use of MIMO in PHY point-to-point as well as multiuser communications has been extensively studied in the recent literature. Here we go one step further, extending the approach to also include protocol design for decentralized and infrastructureless ad hoc networks. First, we study the impact of MIMO on packet transmission in an ad hoc network setting. Then, following a crossiquestlayer design paradigm, we deploy a distributed access control protocol and characterize its performance, with the aim to improve spatial reuse and convey more information on a single ad hoc link. We also explore the interaction between the Medium Access Control (MAC) and PHY layers, and use this knowledge to implement proper policies for distributed traffic control and robustness against interference. Important tradeoffs that arise when managing radio resources are highlighted, and extensive simulation results are presented and discussed.