Q Qing Wang

Cyclic additional optical true time delay for microwave beam steering with spectral filtering

Optical true time delay (OTTD) is an attractive way to realize microwave beam steering (MBS) due to its inherent features of broadband, low-loss, and compactness. In this Letter, we propose a novel OTTD approach named cyclic additional optical true time delay (CAO-TTD). It applies additional integer delays of the microwave carrier frequency to achieve spectral filtering but without disturbing the spatial filtering (beam steering). Based on such concept, a broadband MBS scheme for high-capacity wireless communication is proposed, which allows the tuning of both spectral filtering and spatial filtering. The experimental results match well with the theoretical analysis.

Angle-of-Arrival Measurement of a Microwave Signal Using Parallel Optical Delay Detector

A novel parallel optical delay detector is proposed for angle-of-arrival (AOA) measurement of a microwave signal with accuracy monitoring. A theoretical model is built up to analyze the proposed system, including measurement accuracy monitoring. The measurements of AOA are then experimentally investigated with monitored measurement accuracy.

Phase modulation parallel optical delay detector for microwave angle-of-arrival measurement with accuracy monitored

A novel phase modulation parallel optical delay detector is proposed for microwave angle-of-arrival measurement with accuracy monitored by using only one dual-electrode Mach-Zehnder modulator. A theoretical model is built up to analyze the proposed system including measurement accuracy monitoring. The spatial delay measurement is translated into the phase shift between two replicas of a microwave signal. Thanks to the accuracy monitoring, the phase shifts from 5° to 165° are measured with less than 3.1° measurement error.

Green hybrid Fi-Wi LAN

Enterprise WLANs encompassing supernumerary Access Points (APs) are being used to provide capacity to indoor environments. The approach of over dimensioned deployment of APs to meet the capacity needs of users at critical time points are advocated without little concern towards the important issue of power wastage. For a sustainable greener environment the issue of power saving in such enterprise WLANs has to be integrated in our present day design. Hybrid Fiber-Wireless (Fi-Wi) LAN is envisioned as the evolution of enterprise WLAN which can help us enormously to reduce the power wastage while meeting the demands of the indoor users. In this paper, we propose a hybrid Fi-Wi LAN architecture based On Demand Strategy which results in massive power saving (approximately 60%) by switching of APs or Cell Access Nodes (CANs) based on user demand estimation while maintaining coverage throughout the whole cell area.

Cell switching mechanisms for access point sharing in WLAN over radio-over-fiber systems

Radio-over-fiber (RoF) technology is a promising candidate to provide high data rates and ubiquitous coverage by distributing small cells over the service area. For wireless LAN (WLAN) application in RoF systems, an access points (AP) can be shared among multiple small cells. The medium access mechanisms in the distributed coordination function (DCF) under this context encounter some issues due to the carrier sensing failure between the nodes in different cells. For alleviating this problem and also supporting flexible AP sharing, two switching mechanisms are discussed. One employs a time division scheme for sharing the APs and the other a selective reception of uplink frames among the associated cells. Both approaches are shown to be effective. The proposed mechanisms do not require changes in the existing protocols on both the client side and AP side. And they are complementary to each other due to their different switching principles.

Microwave beam steering with tunable spectral filtering using cyclic additional optical true time delay

A novel broadband microwave beam steering scheme for high capacity wireless communication is proposed with tunable spectral filtering using cyclic additional optical true time delay. The experimental results match well with the theoretical analysis.

Coalition game-theory-based congestion control in Hybrid Fi-Wi indoor network

As more bandwidth hogging applications like video streaming or video conferencing are entering the telecom market, indoor networks need to be more efficient, failure-resilient and flexible. WiFi have predominantly been the most ubiquitous indoor wireless technology. WiFi Access Points (APs) are placed progressively in indoor locations resulting in highly congested ISM spectrum bands. Thus users are experience diminishing data rates. Hybrid Fiber-Wireless (Fi-Wi) architecture are pursued as the way forward for such large indoor networks. Fi-Wi provides a future proof backbone for supporting multiple wireless technologies indoor via a centralized controlled architecture. A residential gateway namely Home Communication Controller (HCC) hosts all APs and serve as the brain of the indoor network. Cell Access Nodes (CANs) located inside each room distributes the radio signals and are connected to the HCC (i.e. APs) using different optical wavelengths. The flexibility of the architecture makes it possible to switch the connection of APs with a different set of CANs periodically in order to reduce the congestion level of the whole network. Game theory is regarded as a major mathematical tool in formulating such congestion control problems. In this work we formulate the problem of congestion control using coalition game theory and propose a centralized assignment algorithm to dynamically assign CANs to APs. We prove that the assignment algorithm terminates in a stable partition which attains optimal grand aggregate utility for the network. The simulation results project a maximum decrease of 45% congestion level with 200 non-uniformly distributed users in the network.

A throughput fair SLNR scheduling algorithm for hybrid Fi-Wi indoor downlink MU-MIMO

Indoor downlink communication contributes to a large part of the data traffic generated in todays world. Enormous high data rate supporting devices are entering todays market. They demand for high rate wireless indoor coverage for their uninterrupted service. The main challenge lies in working with the existing wireless technologies while providing a future proof centralized optical fiber indoor backhaul for efficient indoor coverage. Fiber to the room paradigm is gaining a lot of attention in this regard. For supporting high data rates indoor, multiuser MIMO (MU-MIMO) is definitely a prominent choice. While quality of service serves as the most attractive feature that should be ensured among the mobile terminals (MTs). In this work we propose a throughput fair successive signal to leakage and noise ratio (SLNR) precoding algorithm for such a fiber-wireless (Fi-Wi) MU-MIMO indoor. The network capacity and individual MT data rate for our proposed scheme are compared against the greedy SLNR scheme and a random selection based SLNR precoding scheme. The Jains fairness index value for our scheme is shown to achieve maximal fairness.

Multiuser — MIMO for capacity gain in Fi-Wi hybrid networks

Fiber to the Rooms paradigm is gaining a lot of attention recently. In this paradigm, the last mile wireless (viz., IEEE 802.11×) connectivity, backed by optical fiber infrastructure, supports uncompressed high data rate while rendering seamless mobility and higher frequency reuse. To provide cost effective solution, Access Points (AP) in each room are replaced by distributed antennas. A centralized home communication controller provides AP functionality. WiFi inherently suffers from the problem of hidden nodes (HN). This problem persists even in the Fiber-Wireless (Fi-Wi) hybrid world causing degradation of throughput. In this paper we propose a Multi-User Multiple Input Multiple Output (MU-MIMO) uplink technique using both spatial and optical wavelength multiplexing. This scheme can increase the data rate significantly through diversity gain or spatial multiplexing. The proposed scheme is compared against an eminent joint decoding technique called Successive Interference Cancellation (SIC) adapted for operability in Fi-Wi indoor environment. The main contribution is that we propose an unique MU-MIMO uplink technique for Fi-Wi Hybrid indoor environment which address the problem of HN. We evaluate the performance of our proposed MU-MIMO technique based on ergodic capacity and probability of bit error.

Energy efficient Fi-Wi LAN with performance optimization

In the IEEE 802.11 standard meager effort has been invested towards devising greener WLAN communication. Especially with the massive deployment of Enterprise WLAN in indoor networks a lot of access points (APs) are densely packed for increasing the capacity offered. But most of the APs deployed are idle for a larger period of time in a day. This paper proposes to use a centralized controlled distributed antenna systems employing Radio over Fiber (RoF) techniques for efficiently managing energy resources in the network. The main contribution of the paper is that we propose power managed load balanced (PMLB) algorithm which minimizes the total power consumption of the overall network while appeasing the user demand and also provides load balancing across the APs for a better network performance.