Guoqiang Mao

University of Sydney, Sydney, New South Wales, Australia

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Publications (111)70.52 Total impact

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    ABSTRACT: Two-tier femtocell networks are an efficient communication architecture that significantly improves throughput in indoor environments with low power consumption. Traditionally, a femtocell network is usually configured to be either completely open or completely closed in that its channels are either made available to all users or used by its own users only. This may limit network flexibility and performance. It is desirable for owners of femtocell base stations if a femtocell can partially open its channels for external-user access. In such scenarios, spectrum and energy efficiency becomes a critical issue in the design of femtocell network protocols and structure. In this paper, we conduct performance analysis for two-tier femtocell networks with partially open channels. In particular, we build a Markov chain to model the channel access in the femtocell network and then derive the performance metrics in terms of the blocking probabilities. Based on stationary state probabilities derived by Markov chain models, spectrum and energy efficiency is modeled and analyzed under different scenarios characterized by critical parameters, including number of femtocells in a macrocell, average number of users, and number of open channels in a femtocell. Numerical and Monte Carlo (MC) simulation results indicate that the number of open channels in a femtocell has an adverse impact on the spectrum and energy efficiency of two-tier femtocell networks. Results in this paper provide guidelines for trading off spectrum and energy efficiency of two-tier femtocell networks by configuring different numbers of open channels in a femtocell.
    IEEE Transactions on Vehicular Technology 01/2014; 63(3):1306-1319. · 2.06 Impact Factor
  • Guoqiang Mao, Brian DO Anderson
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    ABSTRACT: This paper investigates the capacity of a random network in which the nodes have a general spatial distribution. Our model assumes n nodes in a unit square, with a pair of nodes directly connected if and only if their Euclidean distance is smaller than or equal to a threshold, known as the transmission range. Each link has an identical capacity of W bits/s. The transmission range is the same for all nodes and can be any value so long as the resulting network is connected. A capacity upper bound is obtained for the above network, which is valid for both finite n and asymptotically infinite n. We further investigate the capacity upper bound and lower bound for the above network as n → ∞ and show that both bounds can be expressed as a product of four factors, which represents respectively the impact of node distribution, link capacity, number of source destination pairs and the transmission range. The bounds are tight in that the upper bound and lower bound differ by a constant multiplicative factor only. For the special case of networks with nodes distributed uniformly or following a homogeneous Poisson distribution, the bounds are of the same order as known results in the literature.
    IEEE Transactions on Wireless Communications 01/2014; 13(3):1678-1691. · 2.42 Impact Factor
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    ABSTRACT: Cooperative communication technologies can improve the system throughput energy efficiency and reliability in dynamic wireless networks. For practical multi-cell multi-antenna mobile cellular networks, co-channel interference is a critical issue affecting cooperative transmission (Co-Tx) performance. In this paper, we first derive a cooperative outage probability model and a cooperative block error rate (BLER) model incorporating a binary differential phase shift keying modulation for performance analysis in such cooperative cellular networks. Based on them, a cooperative energy efficiency model is proposed and analyzed under different Co-Tx scenarios, interference levels and wireless channel conditions. As demonstrated by numerical results, our analytical models show that Co-Tx is an effective approach to mitigate co-channel interference and improve the energy efficiency, BLER and overall outage probability performance in multi-cell multi-antenna cooperative cellular networks.
    The Computer Journal 08/2013; 56(8):1010-1019. · 0.76 Impact Factor
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    ABSTRACT: We study a new variant of consensus problems, termed `local average consensus', in networks of agents. We consider the task of using sensor networks to perform distributed measurement of a parameter which has both spatial (in this paper 1D) and temporal variations. Our idea is to maintain potentially useful local information regarding spatial variation, as contrasted with reaching a single, global consensus, as well as to mitigate the effect of measurement errors. We employ two schemes for computation of local average consensus: exponential weighting and uniform finite window. In both schemes, we design local average consensus algorithms to address first the case where the measured parameter has spatial variation but is constant in time, and then the case where the measured parameter has both spatial and temporal variations. Our designed algorithms are distributed, in that information is exchanged only among neighbors. Moreover, we analyze both spatial and temporal frequency responses and noise propagation associated with the algorithms. The tradeoffs of using local consensus, as compared to standard global consensus, include higher memory requirement and degraded noise performance. Arbitrary updating weights and random spacing between sensors are analyzed in the proposed algorithms.
    08/2013;
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    Guoqiang Mao, Zihuai Lin, Xiaohu Ge, Yang Yang
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    ABSTRACT: Extensive research has been done on studying the capacity of wireless multi-hop networks. These efforts have led to many sophisticated and customized analytical studies on the capacity of particular networks. While most of the analyses are intellectually challenging, they lack universal properties that can be extended to study the capacity of a different network. In this paper, we sift through various capacity-impacting parameters and present a simple relationship that can be used to estimate the capacity of both static and mobile networks. Specifically, we show that the network capacity is determined by the average number of simultaneous transmissions, the link capacity and the average number of transmissions required to deliver a packet to its destination. Our result is valid for both finite networks and asymptotically infinite networks. We then use this result to explain and better understand the insights of some existing results on the capacity of static networks, mobile networks and hybrid networks and the multicast capacity. The capacity analysis using the aforementioned relationship often becomes simpler. The relationship can be used as a powerful tool to estimate the capacity of different networks. Our work makes important contributions towards developing a generic methodology for network capacity analysis that is applicable to a variety of different scenarios.
    IEEE Transactions on Wireless Communications 06/2013; · 2.42 Impact Factor
  • ACM Transactions on Sensor Networks 01/2013; · 1.44 Impact Factor
  • Seh Chun Ng, Guoqiang Mao, B.D.O. Anderson
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    ABSTRACT: In this paper we investigate the critical node density required to ensure that an arbitrary node in a large-scale wireless multi-hop network is connected (via multi-hop path) to infinitely many other nodes with a positive probability. Specifically we consider a wireless multi-hop network where nodes are distributed in ℝ2 (d = 2, 3) following a homogeneous Poisson point process. The establishment of a direct connection between any two nodes is independent of connections between other pairs of nodes and its probability satisfies some intuitively reasonable conditions, viz. rotational and translational invariance, nonincreasing monotonicity, and integral boundedness. Under the above random connection model we first obtain analytically the upper and lower bounds for the critical density. Then we compare the new bounds with other existing bounds in the literature under the unit disk model and the log-normal model which are special cases of the random connection model. The comparison shows that our bounds are either close to or tighter than the known ones. To the best of our knowledge, this is the first result for the random connection model in both 2D and 3D networks. The result is of practical use for designing large-scale wireless multihop networks such as wireless sensor networks.
    IEEE Transactions on Wireless Communications 01/2013; 12(4):1512-1523. · 2.42 Impact Factor
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    ABSTRACT: To enhance spectral efficiency, full frequency reuse has been adopted in advanced cellular communication networks, which, however, generates severe intercell cochannel interference and degrades the achievable rate at mobile terminals, particularly for those located near cell boundaries. Therefore, it is of great importance and interest for network operators and service providers to evaluate and understand the impact of locationdependent intercell cochannel interference on the achievable data rate in cellular networks. In this paper, considering a realistic spatial distribution of user locations, we first derive and analyze the probability density function (pdf) of the intercell power interference factor, which represents path loss of the adjacent cell signals, for the classic linear Wyner model. The closed-form result of the maximum achievable rate in cellular uplink channels is also derived under the Nakagami- m fading model. Based on these new results, an upper bound of the uplink maximum achievable rate with location-dependent intercell signal interference factors is calculated. Furthermore, the rate is analyzed in a running-train scenario for the application of the linear Wyner model. Numerical results show that user locations have strong impact on the maximum achievable rate per cell.
    IEEE Transactions on Vehicular Technology 01/2013; 62(9):4615-4628. · 2.06 Impact Factor
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    ABSTRACT: In this paper, we propose a distributed network coding (DNC) scheme based on the Raptor codes for wireless sensor networks (WSNs), where a group of sensor nodes, acting as source nodes, communicate with a single sink through some other sensor nodes, serving as relay nodes, in a multi-hop fashion. At the sink, a graph-based Raptor code is formed on the fly. After receiving a sufficient number of encoded packets, the sink begins to decode. The main contributions of this paper are the derivation of a bit error rate (BER) lower bound for the LT-based DNC scheme over Rayleigh fading channels under maximum-likelihood (ML) decoding, and the derivations of upper and lower BER bounds for the proposed Raptor-based DNC scheme on the basis of the derived BER bound of LT codes.
    IEEE Transactions on Communications 01/2013; 61(10):4357-4368. · 1.75 Impact Factor
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    ABSTRACT: Wireless communications between devices can be lossy owing to a number of issues, such as channel fading, interference or mobility of devices. In some scenarios, the lossy characteristic of wireless communications can be random hence better characterized from a stochastic perspective. In view of this, lossy wireless networks have been studied recently, where the transmission between each pair of nodes is successful with a certain probability. This paper investigates the reliability of broadcast in lossy networks, where the reliability is measured by the probability that every node in the network receives the packets of every other node. To improve the reliability, nodes can cooperate with each other using network coding techniques. In this paper, a neighbor network coding scheme is proposed and network reliability under this coding scheme is investigated analytically. This paper shows that reliability of networks can be improved considerably by using the proposed neighbor coding scheme. Further, closed-form upper and lower bounds on the network reliability are presented. Moreover, an optimal neighbor coding scheme that maximizes the reliability of a given network is discussed.
    Communications Workshops (ICC), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: Trilateration-based localization techniques have been widely used in sensor networks due to their computational efficiency and distributedness. However in sparse networks or in the boundary area of networks, trilateration-based techniques often fail to localize all localizable nodes. Bilateration-based techniques emerge as a generalization of trilateration techniques to a broader class of networks. Compared with trilaterationbased techniques, the main benefit of bilateration-based schemes is that they can localize a higher percentage of nodes while still maintaining the low computational complexity and distributedness properties. One potential drawback of bilaterationbased schemes is that the number of estimated possible positions (hence the memory required to store these positions) may grow exponentially with the number of nodes in the network. Despite the empirical observations reported in the literature that such exponential growth is a rare event, there is a lack of rigorous analysis quantifying the complexity of bilaterationbased schemes. In this paper, we tackle the challenge by first characterizing a broad subclass of the set of critical sub-networks within which the number of possible estimated positions grows exponentially with the size of these sub-networks. Then using mathematical techniques from percolation theory, we prove that, in random geometric networks, with very high probability the size of these critical sub-networks, which constitute the worst case for bilateration-based localization, is bounded. Therefore the complexity of bilateration-based localization technique does not grow exponentially with the size of the entire network. The significance of this result is to analytically demonstrate that bilateration-based techniques not only localize a higher fraction of nodes than their trilateration counterpart, but also they can be implemented in a very efficient (low computational cost) manner.
    Wireless Communications and Networking Conference (WCNC2013), Proceedings of IEEE; 01/2013
  • Chao Zhai, Wei Zhang, Guoqiang Mao
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    ABSTRACT: In this paper, we propose a cooperative spectrum sharing scheme between cellular network downlink and mobile ad-hoc network based on the analysis using stochastic geometry theory. The licensed spectrum belongs to the cellular network and the strong interference at cell-edge becomes a bottleneck to guarantee the quality of service requirement. In this case, the secondary ad-hoc users can assist the transmission between the base station and cell-edge mobile users in exchange for spectrum usage. Through maximizing the transmission capacity of secondary system under the constraint of throughput improvement of primary system, an optimal spectrum allocation can be obtained. Numerical and simulation results are provided to validate the analysis and verify the efficiency of the proposed scheme.
    Acoustics, Speech and Signal Processing (ICASSP), 2013 IEEE International Conference on; 01/2013
  • Zijie Zhang, Guoqiang Mao, B.D.O. Anderson
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    ABSTRACT: Broadcast in mobile ad-hoc networks is a challenging and resource demanding task, due to the effects of dynamic network topology and channel randomness. In this paper, we consider 2D wireless ad-hoc networks where nodes are randomly distributed and move following a random direction mobility model. A piece of information is broadcast from an arbitrary node. Based on an in-depth analysis into the popular Susceptible-Infectious-Recovered (SIR) epidemic routing algorithm for mobile ad-hoc networks, an energy and spectrum efficient broadcast scheme is proposed, which is able to adapt to fast-changing network topology and channel randomness. Analytical results are provided to characterize the performance of the proposed scheme, including the fraction of nodes that can receive the information and the delay of information propagation. The accuracy of analytical results is verified using simulations.
    Communications (ICC), 2013 IEEE International Conference on; 01/2013
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    Guoqiang Mao
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    ABSTRACT: Studying the capacity of wireless multi-hop networks is an important problem and extensive research has been done in the area. In this letter, we sift through various capacity-impacting parameters and show that the capacity of both static and mobile networks is fundamentally determined by the average number of simultaneous transmissions, the link capacity and the average number of transmissions required to deliver a packet to its destination. We then use this result to explain and help to better understand existing results on the capacities of static networks, mobile networks and hybrid networks and the multicast capacity.
    07/2012;
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    Guoqiang Mao, Brian Do Anderson
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    ABSTRACT: This paper provides a necessary and sufficient condition for a random network with nodes Poissonly distributed on a unit square and a pair of nodes directly connected following a generic random connection model to be asymptotically almost surely connected. The results established in this paper expand recent results obtained for connectivity of random geometric graphs from the unit disk model and the fewer results from the log-normal model to the more generic and more practical random connection model.
    IEEE Transactions on Information Theory 04/2012; · 2.62 Impact Factor
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    ABSTRACT: Infrastructure-based vehicular networks (consisting of a group of Base Stations (BSs) along the road) will be widely deployed to support Wireless Access in Vehicular Environment (WAVE) and a series of safety and non-safety related applications and services for vehicles on the road. As an important measure of user satisfaction level, uplink connectivity probability is defined as the probability that messages from vehicles can be received by the infrastructure (i.e., BSs) through multi-hop paths. While on the system side, downlink connectivity probability is defined as the probability that messages can be broadcasted from BSs to all vehicles through multi-hop paths, which indicates service coverage performance of a vehicular network. This paper proposes an analytical model to predict both uplink and downlink connectivity probabilities. Our analytical results, validated by simulations and experiments, reveal the trade-off between these two key performance metrics and the important system parameters, such as BS and vehicle densities, radio coverage (or transmission power), and maximum number of hops. This insightful knowledge enables vehicular network engineers and operators to effectively achieve high user satisfaction and good service coverage, with necessary deployment of BSs along the road according to traffic density, user requirements and service types.
    IEEE Journal on Selected Areas in Communications 01/2012; 30(4):740-747. · 3.12 Impact Factor
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    Lixiang Xiong, Lavy Libman, Guoqiang Mao
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    ABSTRACT: Cooperative communication techniques offer significant performance benefits over traditional methods that do not exploit the broadcast nature of wireless transmissions. Such techniques generally require advance coordination among the participating nodes to discover available neighbors and negotiate the cooperation strategy. However, the associated discovery and negotiation overheads may negate much of the cooperation benefit in mobile networks with highly dynamic or unstable topologies (e.g. vehicular networks). This paper discusses uncoordinated cooperation strategies, where each node overhearing a packet decides independently whether to retransmit it, without any coordination with the transmitter, intended receiver, or other neighbors in the vicinity. We formulate and solve the problem of finding the optimal uncoordinated retransmission probability at every location as a function of only a priori statistical information about the local environment, namely the node density and radio propagation model. We show that the solution consists of an optimal cooperation region which we provide a constructive method to compute explicitly. Our numerical evaluation demonstrates that uncoordinated cooperation offers a low-overhead viable alternative, especially in high-noise (or low-power) and high node density scenarios.
    IEEE Journal on Selected Areas in Communications 01/2012; 30:280-288. · 3.12 Impact Factor
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    Tao Yang, Guoqiang Mao, Wei Zhang
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    ABSTRACT: Wireless multi-hop networks are being increasingly used in military and civilian applications. Connectivity is a prerequisite in wireless multi-hop networks for providing many network functions. In a wireless network with many concurrent transmissions, signals transmitted at the same time will mutually interfere with each other. In this paper we consider the impact of interference on the connectivity of CSMA networks. Specifically, consider a network with n nodes uniformly and i.i.d. on a square [-\frac{\sqrt{n}}{2},\frac{\sqrt{n}}{2}]^{2} where a node can only transmit if the sensed power from any other active transmitter is below a threshold, i.e. subject to the carrier-sensing constraint, and the transmission is successful if and only if the SINR is greater than or equal to a predefined threshold. We provide a sufficient condition and a necessary condition, i.e. an upper bound and a lower bound on the transmission power, required for the above network to be asymptotically almost surely (a.a.s.)connected as n → ∞. The two bounds differ by a constant factor only as n → ∞. It is shown that the transmission power only needs to be increased by a constant factor to combat interference and maintain connectivity compared with that considering a unit disk model (UDM) without interference. This result is also in stark contrast with previous results considering the connectivity of ALOHA networks under the SINR model.
    IEEE Transactions on Wireless Communications 01/2012; 11(6):2266-2275. · 2.42 Impact Factor
  • Chao Zhai, Wei Zhang, Guoqiang Mao
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    ABSTRACT: In traditional cooperative communications, coordination is required among relay nodes to help data transmission through distributed signal transmission or coding techniques. For large cooperative networks, the overhead for coordination is huge and the synchronization among relays is very difficult. In this paper, we propose uncoordinated cooperative communication schemes in a large wireless network that do not need the coordination among relays while realizing cooperative diversity for the source-destination link. Without a central controller, all relays that are spatially randomly placed contend for the channel to relay the packet from the source to the destination in a distributed fashion. The competition for the channel access is governed by the retransmission probability that is independently calculated by the relays according to the location or channel quality information. Three schemes of uncoordinated cooperative communications are proposed to determine the retransmission probabilities of the potential relays based on the local distance, direction, and channel quality, referred to as distance based, sectorized, and local SNR based schemes, respectively. Success probabilities for the proposed uncoordinated schemes are analyzed. Numerical and simulation results show that the local SNR based scheme has the best performance and the distance based scheme outperforms the sectorized scheme.
    IEEE Transactions on Wireless Communications 01/2012; 11(9):3126-3135. · 2.42 Impact Factor
  • Tao Yang, Guoqiang Mao, Wei Zhang
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    ABSTRACT: Connectivity is one of the most fundamental properties of wireless multi-hop networks. In a wireless network with many concurrent transmissions, signals transmitted at the same time may mutually interfere with each other. In this paper we consider the impact of interference on the connectivity of CSMA networks using the SINR model. On the basis of our earlier work in which we give a sufficient condition, i.e. an upper bound, on the critical transmission power required for a CSMA network with a total of n nodes i.i.d. on a √n × √n square following a uniform distribution to be a.a.s. connected as n → ∞ under the SINR model, in this paper we continue to study the necessary condition for the above CSMA network to be a.a.s. connected. A lower bound is obtained on the critical transmission power required for the above CSMA network to be a.a.s. connected under any scheduling scheme satisfying the carrier-sensing constraint. The lower bound differs from the upper bound by a constant factor only. Compared with previous literature assuming a unit disk model, it is shown that the critical transmission power for a CSMA network under the SINR model to be a.a.s. connected is within a constant factor of that required for a network under the unit disk model, which does not consider the impact of interference, to be a.a.s. connected. That is, transmission power only needs to be increased by a constant factor to combat interference and maintain connectivity. This result is also in sharp contrast with previous results considering the connectivity of ALOHA networks under the SINR model.
    Personal Indoor and Mobile Radio Communications (PIMRC), 2012 IEEE 23rd International Symposium on; 01/2012

Publication Stats

1k Citations
70.52 Total Impact Points

Institutions

  • 2003–2013
    • University of Sydney
      • School of Electrical and Information Engineering
      Sydney, New South Wales, Australia
  • 2007–2012
    • National ICT Australia Ltd
      Sydney, New South Wales, Australia
    • Deakin University
      Geelong, Victoria, Australia
  • 2009
    • University of Vic
      Vic, Catalonia, Spain
    • University College London
      Londinium, England, United Kingdom
  • 2000–2002
    • Edith Cowan University
      • School of Engineering
      Perth, Western Australia, Australia