| 1. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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Dynamic Buffer Management Scheme Based on Rate Estimation in Packet-Switched Networks
- 2002
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Ingår i: Computer Networks. - : Elsevier. - 1389-1286 .- 1872-7069. ; 39:6, s. 769-787
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Tidskriftsartikel (refereegranskat)abstract
- While traffic volume of real-time applications is rapidly increasing, current routers do not guarantee minimum QoS values of fairness and drop packets in random fashion. If routers provide a minimum QoS, resulting less delays, more fairness, and smoother sending rates, TCP-friendly rate control (TFRC) can be adopted for real-time applications. We propose a dynamic buffer management scheme that meets the requirements described above, and can be applied to TCP flow and to data flow for transfer of real-time applications. The proposed scheme consists of a virtual threshold function, an accurate and stable per-flow rate estimation, a per-flow exponential drop probability, and a dropping strategy that guarantees fairness when there are many flows. Moreover, we introduce a practical definition of active flows to reduce the overhead coming from maintaining per-flow states. We discuss how proposed scheme motivates real-time applications to adopt TFRC.
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| 2. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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Multiple Quality Control : A New Framework for QoS Control in Forward Link of 1xEV-DV Systems
- 2002
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Ingår i: IEEE 55TH VEHICULAR TECHNOLOGY CONFERENCE, VTC SPRING 2002, VOLS 1-4, PROCEEDINGS. - : IEEE. - 0780374843 ; , s. 1165-1169
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Konferensbidrag (refereegranskat)abstract
- One of main issues in 1xEV-DV systems is how to support and satisfy various QoS requirements of data services and voice service simultaneously. Another main issue in 1xEV-DV systems is how to increase throughput of data services without sacrificing voice service's QoS requirements. The main motivation for our proposed architecture, MQC (Multiple Quality Control), is to use per-stream buffers in physical layer and to fully utilize air resource. The problem of existing architecture is that PDUs from only one stream can be transmitted and those PDUs may not fill out the allocated time slots. In contrast to existing architecture, MQC can multiplex several streams into one PLP(Physical Layer Packet) because MQC utilizes per-service buffers in physical layer. We also introduce a multiplexing scheme that minimizes queueing delays of realtime traffic and maximizes cell throughputs.
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| 3. |
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| 4. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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Capacity of Interference-Limited Ad Hoc Networks with Infrastructure Support
- 2006
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Ingår i: IEEE Communications Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1089-7798 .- 1558-2558. ; 10:1, s. 16-18
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we consider the capacity of ad hoc networks with infrastructure support. Although Grossglauser-Tse mobile network model enables Θ(1) per-node throughput scaling, the mobility assumption may be too unrealistic to be accepted in some practical situations. One of the key observations we acquired is that the infrastructure support plays the same role played by the mobility in the Grossglauser-Tse model. We show that nodes can utilize the randomly located infrastructure support instead of mobility when nodes are nearly static. In this case, we show that the per-node throughput of Θ(1) is still achievable when the number of access points grows linearly with respect to the number of nodes.
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| 5. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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Fundamentals of the Backoff Process in 802.11 : Dichotomy of the Aggregation
- 2015
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Ingår i: IEEE Transactions on Information Theory. - : IEEE Press. - 0018-9448 .- 1557-9654. ; 61:4, s. 1687-1701
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Tidskriftsartikel (refereegranskat)abstract
- This paper discovers fundamental principles of the backoff process that governs the performance of IEEE 802.11. A simplistic principle founded upon regular variation theory is that the backoff time has a truncated Pareto-type tail distribution with an exponent of $ { (log gamma !)/log m}$ ( $boldsymbol {m}$ is the multiplicative factor and $ {gamma }$ is the collision probability). This reveals that the per-node backoff process is heavy-tailed in the strict sense for $ { gamma > 1/m^{2}}$ , and paves the way for the following unifying result. The state-of-the-art theory on the superposition of the heavy-tailed processes is applied to establish a dichotomy exhibited by the aggregate backoff process, putting emphasis on the importance of time-scales on which we view the backoff processes. While the aggregation on normal time-scales leads to a Poisson process, it is approximated by a new limiting process possessing long-range dependence (LRD) on coarse time-scales. This dichotomy turns out to be instrumental in formulating short-term fairness, extending existing formulas to arbitrary population, and to elucidate the absence of LRD in practical situations. A refined wavelet analysis is conducted to strengthen this argument.
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| 6. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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Infrastructure Support Increases the Capacity of Ad Hoc Wireless Networks
- 2005
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Ingår i: VTC2005-FALL: 2005 IEEE 62ND VEHICULAR TECHNOLOGY CONFERENCE, 1-4, PROCEEDINGS. - : IEEE Press. - 0780391527 ; , s. 2663-2668
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Konferensbidrag (refereegranskat)abstract
- In ad hoc wireless networks, one of the hottest research directions has been to increase the throughput capacity scaling with respect to the number of nodes n. Gupta and Kumar (2000) introduced a fixed random network model and showed that the throughput per source-destination pair is Theta(1/root nlogn) when the network is coordinated by a centralized entity. Grossglauser and Tse (2001) introduced a mobile random network model and showed that a source-destination pair acquires a constant throughput of Theta(1) assuming that delays incurred by mobile nodes with low mobility are tolerable.In this paper, we consider the capacity of ad hoc wireless networks with infrastructure support. Although Grossglauser-Tse mobile network model enables Theta(1) per-node throughput scaling, the mobility assumption may be too unrealistic to be accepted in some practical situations. One of the key observations we acquired is that the infrastructure support plays the same role played by the mobility in the Grossglauser-Tse model. We show that nodes can utilize the randomly located infrastructure support instead of mobility when nodes are nearly static. In this case, we show that the per-node throughput of Theta(1) is still achievable when the number of access points grows linearly with respect to the number of nodes. Furthermore., we show that there is additional per-node throughput improvement of Theta(1) when nodes are mobile.
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| 7. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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Joint Network-wide Opportunistic Scheduling and Power Control in Multi-cell Networks
- 2007
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Ingår i: 2007 IEEE INTERNATIONAL SYMPOSIUM ON A WORLD OF WIRELESS, MOBILE AND MULTIMEDIA NETWORKS, VOL 1. - : IEEE Press. - 9781424409938 ; , s. 1-12
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Konferensbidrag (refereegranskat)abstract
- We present a unified analytical framework that maximizes generalized utilities of a wireless network by network-wide opportunistic scheduling and power control. That is, base stations in the network jointly decide mobile stations to be served at the same time as the transmission powers of base stations are coordinated to mitigate the mutually interfering effect. Although the maximization at the first glance appears to be a mixed, twofold and nonlinear optimization requiring excessive computational complexity, we show that the maximization can be transformed into a pure binary optimization with much lower complexity. To be exact, it is proven that binary power control of base stations is necessary and sufficient for maximizing the network-wide utilities under a physical layer regime where the channel capacity is linear in the signal-to-interference-noise ratio. To further reduce the complexity of the problem, a distributed heuristic algorithm is proposed that performs much better than existing opportunistic algorithms. Through extensive simulations, it becomes clear that network-wide opportunistic scheduling and power control is most suitable for fairness-oriented networks and underloaded networks.
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| 8. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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Joint Network-wide Opportunistic Scheduling and Power Control in Multi-cell Networks
- 2009
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Ingår i: IEEE Transactions on Wireless Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1536-1276 .- 1558-2248. ; 8:3, s. 1520-1531
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Tidskriftsartikel (refereegranskat)abstract
- We present a unified analytical framework that maximizes generalized utilities of a wireless network by network-wide opportunistic scheduling and power control. That is, base stations in the network jointly decide mobile stations to be served at the same time as the transmission powers of base stations are coordinated to mitigate the mutually interfering effect. Although the maximization at the first glance appears to be a mixed, twofold and nonlinear optimization requiring excessive computational complexity, we show that the maximization can be transformed into a pure binary optimization with much lower complexity. To be exact, it is proven that binary power control of base stations is necessary and sufficient for maximizing the network-wide utilities under a physical layer regime where the channel capacity is linear in the signal-to-interference-noise ratio. To further reduce the complexity of the problem, a distributed heuristic algorithm is proposed that performs much better than existing opportunistic algorithms. Through extensive simulations, it becomes clear that network-wide opportunistic scheduling and power control is most suitable for fairness-oriented networks and under loaded networks. We believe that our work will serve as a cornerstone for network-wide scheduling approaches from theoretical and practical standpoints.
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| 9. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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On the Asymptotic Validity of the Decoupling Assumption for Analyzing 802.11 MAC Protocol
- 2012
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Ingår i: IEEE Transactions on Information Theory. - : IEEE Press. - 0018-9448 .- 1557-9654. ; 58:11, s. 6879-6893
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Tidskriftsartikel (refereegranskat)abstract
- Performance evaluation of the 802.11 MAC protocol is classically based on the decoupling assumption, which hypothesizes that the backoff processes at different nodes are independent. This decoupling assumption results from mean field convergence and is generally true in transient regime in the asymptotic sense (when the number of wireless nodes tends to infinity), but, contrary to widespread belief, may not necessarily hold in stationary regime. The issue is often related with the existence and uniqueness of a solution to a fixed point equation; however, it was also recently shown that this condition is not sufficient; in contrast, a sufficient condition is a global stability property of the associated ordinary differential equation. In this paper, we give a simple condition that establishes the asymptotic validity of the decoupling assumption for the homogeneous case (all nodes have the same parameters). We also discuss the heterogeneous and the differentiated service cases and formulate a new ordinary differential equation. We show that the uniqueness of a solution to the associated fixed point equation is not sufficient; we exhibit one case where the fixed point equation has a unique solution but the decoupling assumption is not valid in the asymptotic sense in stationary regime.
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| 10. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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On the Payoff Mechanisms in Peer-Assisted Services With Multiple Content Providers : Rationality and Fairness
- 2014
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Ingår i: IEEE/ACM Transactions on Networking. - : IEEE Press. - 1063-6692 .- 1558-2566. ; 22:3, s. 731-744
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies an incentive structure for cooperation and its stability in peer-assisted services when there exist multiple content providers, using a coalition game-theoretic approach. We first consider a generalized coalition structure consisting of multiple providers with many assisting peers, where peers assist providers to reduce the operational cost in content distribution. To distribute the profit from cost reduction to players (i.e, providers and peers), we then establish a generalized formula for individual payoffs when a "Shapley-like" payoff mechanism is adopted. We show that the grand coalition is unstable, even when the operational cost functions are concave, which is in sharp contrast to the recently studied case of a single provider where the grand coalition is stable. We also show that irrespective of stability of the grand coalition, there always exist coalition structures that are not convergent to the grand coalition under a dynamic among coalition structures. Our results give us an incontestable fact that a provider does not tend to cooperate with other providers in peer-assisted services and is separated from them. Three facets of the noncooperative (selfish) providers are illustrated: 1) underpaid peers; 2) service monopoly; and 3) oscillatory coalition structure. Lastly, we propose a stable payoff mechanism that improves fairness of profit sharing by regulating the selfishness of the players as well as grants the content providers a limited right of realistic bargaining. Our study opens many new questions such as realistic and efficient incentive structures and the tradeoffs between fairness and individual providers' competition in peer-assisted services.
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