Lianghui Ding

Lifetime maximization routing with network coding in wireless multihop networks

In this paper, we consider the lifetime maximization routing with network coding in wireless multihop networks. We first show that lifetime maximization with network coding is different from pure routing, throughput maximization with network coding and energy minimization with network coding. Then we formulate lifetime maximization problems in three different cases of (i) no network coding, (ii) two-way network coding, and (iii) overhearing network coding. To solve these problems, we use flow augmenting routing (FA) for the first case, and then extend the FA with network coding (FANC) by using energy minimized one-hop network coding. After that, we investigate the influence of parameters of FANC, evaluate the performance of FANC with two-way and overhearing network coding schemes and compare it with that without network coding under two different power control models, namely, protocol and physical ones. The results show that the lifetime can be improved significantly by using network coding, and the performance gain of network coding decreases with the increase of flow asymmetry and the power control ability.

Capacity Analysis of Selection Cooperation in Wireless Ad-Hoc Networks

In this letter, we analyze the transmission capacity of selection cooperation (SC) in wireless ad-hoc networks. We first derive the distribution of decoded relay set which follows inhomogeneous Poisson point process (PPP) and then present the closed-form expressions for the outage probability and transmission capacity. Furthermore, we propose an upper bound of source node density given an outage probability constraint and find an optimal transmitter density at which the transmission capacity reaches its maximum. Numerical results show that the performance gain provided by SC can be optimally adjusted by selecting appropriate node density. It is also shown that SC further expands advantage at severer large-scale fading.

Weight adjust algorithm in indoor fingerprint localization

Wireless signal RSSI (Received Signal Strength Indication) is widely used in indoor localization. However, due to severe multipath effect in indoor environment, RSSI measured by the user equipment varies in a large range. Inaccurate RSSI measurement yields large localization error and decreases the performance of indoor localization and navigation. Through extensive tests, we prove that the variance of RSSI in indoor environment does not keep the same all the time, while varies with the mean of RSSI. In this paper, we analyze the relationship between the mean value and variance of RSSI, and propose a novel Weighted Distance Fingerprint (WDF) algorithm, which assigns different weights to different RSSI measurements based on its variance. We apply the proposed WDF algorithm in our indoor localization testbed, and evaluation result shows that WDF reach a 0.8m to 2m improvement on the average localization error.

Cost-Delay Trade off of Network Coding in Asymmetric Two-Way Relay Networks

In this paper, we analyze and evaluate the cost-delay trade off of opportunistic network coding in a two-way relay network with asymmetric arrival rates. We first formulate the variance of the queue into a Markov chain and derive the transition probability and the stationary distribution. Then we analyze the average power cost and delay, formulate the optimal power-delay trade off, and propose a heuristic discrete solution. After that, we present numerical results on the performance of the discrete solution.

Dedicated Return Channel for ATSC 3.0

To support emerging interactive services, a consensus to include an optional, in-band dedicated return channel (DRC) for the next-generation terrestrial broadcast system (ATSC3.0) has been reached. This paper introduces the design of DRC as well as several implementation concerns. First, the network architecture, link budget, and radiation feature of DRC are described in detail. Then the requirements and detailed design of both the physical layer and the MAC layer of DRC are presented respectively. Meanwhile, the performance of DRC is evaluated and comparisons with typical techniques are carried out in terms of bit error rate, access probability, resource utilization, etc. Furthermore, the cooperation between downlink broadcast and DRC is analyzed.

Multi-hop time synchronization for Underwater Acoustic Networks

Time synchronization plays an important role in UANs, which need fine-grained coordination among nodes. Precise time synchronization is also needed for a variety of other coordinate tasks in UANs such as data fusion, TDMA scheduling, localization, power-saving and so on. Recently, time synchronization protocol for point-to-point with high propagation delay has been proposed, while time synchronization for multi-hop UANs is still an open issue. In this paper, we propose a multi-hop time synchronization scheme for Underwater Acoustic Networks (MSUAN). MSUAN includes three stages. In the first stage, we assign each node a level by establishing a path to the reference node. During the second phase, nodes realize synchronization by receiving synchronization packets both from its parent node and neighboring nodes. The third stage re-synchronizes nodes because the clock may drift away without synchronization for long time. Mathematical analysis of MSUANs synchronization error shows that the more time-stamps we get, the more accurate skew we will get. At the end, we use OPNET to simulate MSUAN, and the simulation result under pyramid topology shows that even the hop accumulates to 8, for MSUAN, the average offset error is maintained at about 58us and the average skew error is below 2ppm.

A QoE-Driven Encoder Adaptation Scheme for Multi-User Video Streaming in Wireless Networks

Video streaming over networks has grown rapidly in recent years. Increasing focus has gradually turned from quality of service awareness to end viewer’s quality of experience (QoE) awareness. For multi-user video streaming services, videos are encoded and transmitted through a bandwidth-limited wireless networks. Therefore, proper encoder settings for videos are required to satisfy the total channel rate constraint. In this paper, a QoE-driven High Efficiency Video Coding (HEVC) encoder adaptation scheme is proposed, aiming to maximize QoE of all the users for wireless networks. First, the influence of HEVC encoder on video streaming is investigated to generate an encoder parameter model. Then, the effect of network impairment together with HEVC encoder is taken into account to derive a subjective QoE prediction model. Afterward, we formulate a QoE-maximized encoder adaptation with total channel rate constraint into an optimization problem based on the obtained encoder parameter model and the subjective QoE model. The problem is solved and incorporated into an online encoder adaptation scheme. Compared with conventional rate allocation methods, the proposed QoE-driven encoder adaptation scheme achieves significant QoE gains independent of wireless network channel rate and video content. Simulation results demonstrate that the proposed encoder adaptation scheme can improve the QoE by 31.4% with fixed number of users or increase the number of satisfied users by 35.5% with variable number of users.

Subjective QoE based HEVC encoder adaptation scheme for multi-user video streaming

Video streaming over networks has grown rapidly in recent years. Increasing focus has gradually turned from Quality of Service (QoS) awareness to user Quality of Experience (QoE) awareness. In this paper, we propose a subjective QoE model based HEVC encoder adaptation scheme for multi-user video streaming. Firstly, the impact of HEVC encoder on video streams is investigated with different configurations to generate an encoder parameter model. Secondly, considering loss-prone channels, the effect of network impairment factor together with HEVC encoder is taken into account to derive a subjective QoE prediction model. Thirdly, an encoder parameter adaptation scheme is modeled as an optimization problem based on the subjective QoE model and encoder parameter model, aiming at maximizing user satisfaction with constraint bandwidth. To validate the performance of our proposed scheme, a set of simulations are carried out. Compared with fixed encoder parameter method, our proposal achieves maximal end users MOS and supports the weighted encoder adaptation according to the user priority.

Incorporating TCP Acknowledgements in MAC Layer in IEEE 802.11 Multihop Ad Hoc Networks

The poor performance of TCP in multihop ad hoc networks is mainly attributed to the inefficient interaction among different protocol layers in previous literature, while the heavy load caused by end-to-end TCP acknowledgements (ACKs) with limited information is usually ignored. In this paper, we propose a novel incorporating ACK transfer scheme, IACK, to alleviate its impact. In IACK, TCP acknowledgements are incorporated in the control packets at the MAC layer and are transferred hop by hop from the sink node to the source node. To meet the requirement of IACK, we enhance the packet queuing policy at the routing layer, and propose a new rate-based TCP transfer scheme, TCP-AP+. Then, we implement IACK in ns-2, evaluate it over comprehensive scenarios and compare it with TCP-AP and TCP-Newreno. Simulation results show that IACK improves both the TCP throughput and goodput significantly.

Balanced uplink scheduling for dedicated return channel of future broadcast TV

To satisfy interaction between users and service providers (SP) in lots of rural areas without enough communication infrastructure, a dedicated return channel for the terrestrial digital TV is demanded. Therefore, we propose a specification on Dedicated Return Channel (DRC) based on SC-OFDMA technique for future broadcast, and promote it to Advanced Television Systems Committee (ATSC). To efficiently utilize the wireless resources of the uplink channel and support large number of users and wide coverage areas, scheduling among multiple users is the most important part. In this paper, we propose a balanced uplink scheduling (BUS) algorithm in order to meet Quality of service (QoS) requirements of large amount of users and make full use of user diversity, frequency diversity and time diversity at the same time.