Raymond Hall Yip Louie

Practical physical layer network coding for two-way relay channels: performance analysis and comparison

This paper investigates the performance of practical physical-layer network coding (PNC) schemes for two-way relay channels. We first consider a network consisting of two source nodes and a single relay node, which is used to aid communication between the two source nodes. For this scenario, we investigate transmission over two, three or four time slots. We show that the two time slot PNC scheme offers a higher maximum sum-rate, but a lower sum-bit error rate (BER) than the four time slot transmission scheme for a number of practical scenarios. We also show that the three time slot PNC scheme offers a good compromise between the two and four time slot transmission schemes, and also achieves the best maximum sum-rate and/or sum-BER in certain practical scenarios. To facilitate comparison, we derive new closed-form expressions for the outage probability, maximum sum-rate and sum-BER. We also consider an opportunistic relaying scheme for a network with multiple relay nodes, where a single relay is chosen to maximize either the maximum sum-rate or minimize the sum-BER. Our results indicate that the opportunistic relaying scheme can significantly improve system performance, compared to a single relay network.

Performance analysis of beamforming in two hop amplify and forward relay networks with antenna correlation

The performance of beamforming with antenna correlation in a two hop amplify and forward (AF) multiple input multiple-output (MIMO) relay network is analyzed. This network consists of a single relay which is used to amplify and forward the signal from the source to the destination. The source and destination are both equipped with multiple antennas, which are correlated in space, while the relay has a single antenna. In this paper, we derive new closed form expressions for the outage probability and probability density function of the received signal-to-noise ratio (SNR) at the destination. We also present exact symbol error rate expressions for the two hop AF MIMO relay network, and show that the full spatial diversity order can be achieved. Our results also indicate that spatial correlation is detrimental to the outage probability and symbol error rate at high SNR, and beneficial at low SNR.

Performance Analysis of Beamforming in Two Hop Amplify and Forward Relay Networks

The performance of beamforming in a two hop amplify and forward (AF) relay network is analyzed. This network consists of a single relay which is used to amplify and forward the signal from the source to the destination. The source and destination are both equipped with multiple antennas while the relay has a single antenna. In this paper, we derive closed form expressions for the outage probability and probability density function of the received SNR. We also present exact symbol error rate expressions for the two hop AF relay network and show that full spatial diversity order, which corresponds to the minimum number of antennas at the source and destination, can be achieved. Our analytical results are confirmed through comparison with Monte Carlo simulations.

Two hop amplify-and-forward transmission in mixed rayleigh and rician fading channels

The performance of a two hop amplify-and-forward relay system, where the source-relay and the relay-destination channels experience Rayleigh and Rician fading respectively, is investigated. We derive exact and lower bound expressions for the outage probability and average bit error probability, where the bounds become tight at high signal-to-noise ratios (SNR). Our results are verified through comparison with Monte Carlo simulations, where we also illustrate the positive impact of the Rician factor on the system performance.

Relay Selection With Network Coding in Two-Way Relay Channels

In this paper, we consider the design of joint network coding (NC) and relay selection (RS) in two-way relay channels. In the proposed schemes, two users first sequentially broadcast their respective information to all the relays. We propose two RS schemes: 1) a single RS with NC and 2) a dual RS with NC. For both schemes, the selected relays perform NC on the received signals sent from the two users and forward them to both users. The proposed schemes are analyzed, and the exact bit-error-rate (BER) expressions are derived and verified through Monte Carlo simulations. It is shown that the dual RS with NC outperforms other considered RS schemes in two-way relay channels. The results also reveal that the proposed RS-NC schemes provide a selection gain compared with an NC scheme with no RS and an NC gain relative to a conventional RS scheme with no NC.

Cooperative Spectrum Sharing in Cognitive Radio Networks With Multiple Antennas

In this paper, we consider a cognitive radio network consisting of a primary transmitter-primary receiver pair, and a secondary base station-secondary receiver pair. To improve the performance of both the primary and secondary pair, we propose an overlay spectrum sharing scheme where the primary user (PU) leases half of its time slots to the secondary user (SU) in exchange for the SU cooperatively relaying the PUs data using the amplify and forward scheme. The proposed scheme will involve the design of antenna weights and power allocation to meet a certain error or rate design criterion for both the PU and SU. To analyze the performance of the proposed scheme, we derive new closed form expressions for the rate and bit error rate for arbitrary signal-to-noise ratio (SNR). In addition, we carry out an asymptotic analysis in the high SNR regime to obtain the diversity order. These expressions, along with numerical analysis, reveal that the proposed cooperative overlay scheme can achieve significant performance gains, for both the PU and the SU, compared to a conventional noncooperative underlay scheme, which gives both users the incentive to cooperate.

Autonomous Demand Side Management Based on Energy Consumption Scheduling and Instantaneous Load Billing: An Aggregative Game Approach

In this paper, we investigate a practical demand side management scenario where the selfish consumers compete to minimize their individual energy cost through scheduling their future energy consumption profiles. We adopt an instantaneous load billing scheme to effectively convince the consumers to shift their peak-time consumption and to fairly charge the consumers for their energy consumption. For the considered DSM scenario, an aggregative game is first formulated to model the strategic behaviors of the selfish consumers. By resorting to the variational inequality theory, we analyze the conditions for the existence and uniqueness of the Nash equilibrium (NE) of the formulated game. Subsequently, for the scenario where there is a central unit calculating and sending the real-time aggregated load to all consumers, we develop a one timescale distributed iterative proximal-point algorithm with provable convergence to achieve the NE of the formulated game. Finally, considering the alternative situation where the central unit does not exist, but the consumers are connected and they would like to share their estimated information with others, we present a distributed synchronous agreement-based algorithm and a distributed asynchronous gossip-based algorithm, by which the consumers can achieve the NE of the formulated game through exchanging information with their immediate neighbors.

Open-Loop Spatial Multiplexing and Diversity Communications in Ad Hoc Networks

This paper investigates the performance of open-loop multi-antenna point-to-point links in ad hoc networks with slotted ALOHA medium access control (MAC). We consider spatial multiplexing transmission with linear maximum ratio combining and zero forcing receivers, as well as orthogonal space time block coded transmission. New closed-form expressions are derived for the outage probability, throughput and transmission capacity. Our results demonstrate that both the best performing scheme and the optimum number of transmit antennas depend on different network parameters, such as the node intensity and the signal-to-interference-and-noise ratio operating value. We then compare the performance to a network consisting of single-antenna devices and an idealized fully centrally coordinated MAC. These results show that multi-antenna schemes with a simple decentralized slotted ALOHA MAC can outperform even idealized single-antenna networks in various practical scenarios.

Zero Forcing in General Two-Hop Relay Networks

In this paper, we investigate four different two-hop amplify and forward relay networks, which differ on the processing capabilities at the source, relay, and destination nodes. We derive new exact outage probability expressions where zero-forcing processing is performed at the following four areas: (1) source and relay; (2) relay; (3) relay and destination; and (4) destination nodes only. We show that, depending on the particular scheme, adding source, relay, and/or destination nodes can be either beneficial or detrimental to the outage probability. We confirm our results through comparison with Monte Carlo simulations.

Maximum sum-rate of MIMO multiuser scheduling with linear receivers

We analyze scheduling algorithms for multiuser communication systems with users having multiple antennas and linear receivers. When there is no feedback of channel information, we consider a common round robin scheduling algorithm, and derive new exact and high signal-to-noise ratio (SNR) maximum sum-rate results for the maximum ratio combining (MRC) and minimum mean squared error (MMSE) receivers. We also present new analysis of MRC, zero forcing (ZF) and MMSE receivers in the low SNR regime. When there are limited feedback capabilities in the system, we consider a common practical scheduling scheme based on signal-to-interference- and-noise ratio (SINR) feedback at the transmitter. We derive new accurate approximations for the maximum sum-rate, for the cases of MRC, ZF and MMSE receivers. We also derive maximum sum-rate scaling laws, which reveal that the maximum sum-rate of all three linear receivers converge to the same value for a large number of users, but at different rates.