Results 1 - 10
of
11
Dynamics of networks selection in heterogeneous wireless networks: An evolutionary game approach
- IEEE Transactions on Vehicular Technology
, 2009
"... Abstract—Enabling users to connect to the best available network, dynamic network selection scheme is important for sat-isfying various quality of service (QoS) requirements, achieving seamless mobility and load balancing in heterogeneous wireless networks. In this paper, we formulate the network se ..."
Abstract
-
Cited by 33 (1 self)
- Add to MetaCart
(Show Context)
Abstract—Enabling users to connect to the best available network, dynamic network selection scheme is important for sat-isfying various quality of service (QoS) requirements, achieving seamless mobility and load balancing in heterogeneous wireless networks. In this paper, we formulate the network selection problem in heterogeneous wireless networks with incomplete information as a Bayesian game. In general, the preference (i.e., utility) of a mobile user is private information. Therefore, each user has to make the decision of network selection optimally given only the partial information of the preferences of other users. To study the dynamics of such network selection, the Bayesian best response dynamics and aggregate best response dynamics are applied. Bayesian Nash equilibrium is considered to be the solution of this game, and there is a one-to-one mapping between the Bayesian Nash equilibrium and the equilibrium distribution of the aggregate dynamics. The numerical results show the global convergence of the aggregate best response dynamics for this Bayesian network selection game. This ensures that even with incomplete information, the equilibrium of network selection decisions of mobile users can be reached.
Aggregation With Fragment Retransmission for Very High-Speed WLANs
, 2009
"... In upcoming very high-speed wireless LANs (WLANs), the physical (PHY) layer rate may reach 600 Mbps. To achieve high efficiency at the medium access control (MAC) layer, we identify fundamental properties that must be satisfied by any CSMA-/CA-based MAC layers and develop a novel scheme called aggr ..."
Abstract
-
Cited by 31 (9 self)
- Add to MetaCart
(Show Context)
In upcoming very high-speed wireless LANs (WLANs), the physical (PHY) layer rate may reach 600 Mbps. To achieve high efficiency at the medium access control (MAC) layer, we identify fundamental properties that must be satisfied by any CSMA-/CA-based MAC layers and develop a novel scheme called aggregation with fragment retransmission (AFR) that exhibits these properties. In the AFR scheme, multiple packets are aggregated into and transmitted in a single large frame. If errors happen during the transmission, only the corrupted fragments of the large frame are retransmitted. An analytic model is developed to evaluate the throughput and delay performance of AFR over noisy channels and to compare AFR with similar schemes in the literature. Optimal frame and fragment sizes are calculated using this model. Transmission delays are minimized by using a zero-waiting mechanism where frames are transmitted immediately once the MAC wins a transmission opportunity. We prove that zero-waiting can achieve maximum throughput. As a complement to the theoretical analysis, we investigate the impact of AFR on the performance of realistic application traffic with diverse requirements by simulations. We have implemented the AFR scheme in the NS-2 simulator and present detailed results for TCP, VoIP, and HDTV traffic. The AFR scheme described was developed as part of the IEEE 802.11n working group work. The analysis presented here is general enough to be extended to proposed schemes in the upcoming 802.11n standard. Trends indicated in this paper should extend to any well-designed aggregation schemes.
Performance Analysis of the IEEE 802.11e Block ACK Scheme in a Noisy Channel
- Proceedings of IEEE International Conference on Broadband Networks (IEEE BROADNETS
, 2005
"... Abstract — A Block ACK (BTA) scheme has been proposed in IEEE 802.11e to improve medium access control (MAC) layer performance. It is also a promising technique for next-generation high-speed Wireless LANs (WLANs) such as IEEE 802.11n. We present a theoretical model to evaluate MAC saturation throug ..."
Abstract
-
Cited by 10 (2 self)
- Add to MetaCart
(Show Context)
Abstract — A Block ACK (BTA) scheme has been proposed in IEEE 802.11e to improve medium access control (MAC) layer performance. It is also a promising technique for next-generation high-speed Wireless LANs (WLANs) such as IEEE 802.11n. We present a theoretical model to evaluate MAC saturation throughput of this scheme. This model takes into account the effects of both collisions and transmission errors in a noisy channel. The accuracy of this model is validated by NS-2 simulations. Index Terms — IEEE 802.11, IEEE 802.11e, wireless LAN, medium access control, Block ACK, saturation throughput
Phy aided mac: A new paradigm
- INFOCOM 2009. The 28th Conference on Computer Communications. IEEE
, 2009
"... Abstract—Network protocols have traditionally been designed using a layered method in part because it is easier to implement some portions of network protocols in software and other portions must be implemented in hardware for performance reasons. These different implementation techniques enforce la ..."
Abstract
-
Cited by 6 (4 self)
- Add to MetaCart
(Show Context)
Abstract—Network protocols have traditionally been designed using a layered method in part because it is easier to implement some portions of network protocols in software and other portions must be implemented in hardware for performance reasons. These different implementation techniques enforce layer boundaries. In this paper, we show that with the advent of software defined radios, it becomes possible to blur those layer boundaries and produce higher performance network protocols as a result. In this paper we exploit a programmable physical layer and simultaneous transmission to have clients signal whether they have packets to send. By detecting the high energy at the simultaneous transmission, the AP gets the following information: a) which stations have packets to send and b) whether the traffic load is high, medium or low. Again, using the programmable physical layer, the AP schedules clients efficiently while wasting little of the spectrum on signaling overhead. The proposed protocol is a) fast, since no packet transmission is required for polling responses and all clients respond concurrently; b) reliable, as the poll response is contention free and c) scalable. We demonstrate the feasibility of implementing such a system using a FPGA based prototype software defined radio platform. We then show how the MAC protocol can scale using the QualNet network simulator and compare the performance to a contention based protocol. I.
Security Overhead and Performance for Aggregation with Fragment Retransmission (AFR) in Very High-Speed Wireless 802.11 LANs
- IEEE Trans. Wireless Communications
, 2010
"... Abstract—In this paper, we study the overhead introduced by the advanced encryption standard cipher in the context of wireless LANs, specifically at the medium access control layer, as described in the 802.11 standard developed by the 802.11n task group. The advanced encryption standard is incorpora ..."
Abstract
-
Cited by 3 (1 self)
- Add to MetaCart
Abstract—In this paper, we study the overhead introduced by the advanced encryption standard cipher in the context of wireless LANs, specifically at the medium access control layer, as described in the 802.11 standard developed by the 802.11n task group. The advanced encryption standard is incorporated into existing aggregation schemes for 802.11 wireless LANs in order to achieve secure transmission of frames. We compute the maximum throughput, optimal frame, and fragment sizes which can be achieved in this context and compare them to the optimal values when encryption is not used. We evaluate the delay performance of such a scheme in the context of encryption and study asymptotic properties of the medium access control layer efficiency, expected frame size, and throughput. Index Terms—802.11, AES, fragmentation, security overhead, 802.11n.
Performance Comparison of Uplink WLANs with Single-user and Multi-user MIMO Schemes
"... Abstract — In this paper, we compare the performance of wireless local area networks (WLANs) with single-user MIMO (SU-MIMO) and multi-user MIMO (MU-MIMO) in terms of collision probability, average throughput, and delay. In the SU-MIMO scheme, multiple antennas are used for transmitting multiple dat ..."
Abstract
-
Cited by 1 (1 self)
- Add to MetaCart
Abstract — In this paper, we compare the performance of wireless local area networks (WLANs) with single-user MIMO (SU-MIMO) and multi-user MIMO (MU-MIMO) in terms of collision probability, average throughput, and delay. In the SU-MIMO scheme, multiple antennas are used for transmitting multiple data streams of a single user and this MIMO technique increases link capacity at physical (PHY) layer. In the MU-MIMO scheme, however, multiple antennas at different users are used for transmitting data streams of multiple users. The MU-MIMO scheme reduces the collision probability at medium access control (MAC) layer and increases the link capacity. Both MIMO schemes yield different collision, throughput, and delay performance at the MAC layer of WLANs. Numerical results show that the MU-MIMO scheme yields lower colli-sion probability and shorter delay performance than the SU-MIMO scheme. Furthermore, the SU-MIMO scheme yields better throughput performance for high SNR values and a small number of contending stations. In other cases, the MU-MIMO scheme yields better throughput performance. I.
Advisory Committee:
, 2008
"... Performance evaluation of computer networks is primarily done using packet-level simulation because analytical methods typically cannot adequately capture the combination of state-dependent control mechanisms (such as TCP congestion control) and stochastic behavior exhibited by networks. However, pa ..."
Abstract
- Add to MetaCart
(Show Context)
Performance evaluation of computer networks is primarily done using packet-level simulation because analytical methods typically cannot adequately capture the combination of state-dependent control mechanisms (such as TCP congestion control) and stochastic behavior exhibited by networks. However, packet-level simulation becomes prohibitively expensive as link speeds, workloads, and net-work size increase. Timestepped Stochastic Simulation (TSS) is a novel technique that overcomes the scalability problems of packet-level simulation by generating a sample path of the system state S(t) at time t = ; 2; , rather than at each packet transmission. In each timestep [t; t+], the distribution Pr ( S(t+) jS(t)) is obtained analytically, and S(t + ) is sampled from it. This dissertation presents TSS for shared links, specically, 802.11 WLAN links. Our method computes sample paths of instantaneous goodput (successful transmissions per timestep) Ni(t) for all stations i in a WLAN over timesteps of length . For accurate modeling of higher layer protocols, should be lesser than their control timescales (e.g., TCP's round-trip time). At typical values of (e.g, 50ms), Ni(t)'s are correlated across timesteps (e.g., a station with high contention window has low goodput for several timesteps) as well as across stations (since they share the same media). To model these correlations, we obtain, jointly with the Ni(t)'s, sample paths of the WLAN's state, which consists of a contention window and a backo counter at each station. Comparisons with packet level simulations show that TSS is accurate and provides up to two orders of magnitude improvement in simulation runtime.
Out-of-Band Signaling Scheme for High Speed
"... Abstract — In recent years, the physical layer data rate pro-vided by 802.11 Wireless LANs has dramatically increased thanks to significant advances in the modulation and coding techniques employed. However, previous studies show that the 802.11 MAC operation, namely the Distributed Coordination Fun ..."
Abstract
- Add to MetaCart
(Show Context)
Abstract — In recent years, the physical layer data rate pro-vided by 802.11 Wireless LANs has dramatically increased thanks to significant advances in the modulation and coding techniques employed. However, previous studies show that the 802.11 MAC operation, namely the Distributed Coordination Function (DCF), represents a limiting factor: the throughput efficiency drops as the channel bit rate increases, and a throughput upper limit does indeed exist when the channel bit rate goes to infinite high. These findings indicate that the performance of the DCF protocol will not be efficiently improved by merely increasing the channel bit rate. This paper shows that the DCF performance may significantly benefit from the adoption of two separate physical carriers: one devised to manage the channel access contention, and another devised to deliver information data. We propose a scheme, referred to as Out-of-Band Signaling (OBS), designed to reuse (and remain backward compatible with) the existing 802.11 medium access control (MAC) specification. Performance evaluation of OBS is carried out through analytical techniques validated via extensive simulation, for both saturation and statistical traffic conditions. Numerical results show that OBS improves the throughput/delay performance, and provides better bandwidth usage compared with the in-band signaling technique employed by DCF. Index Terms — Wireless LAN, IEEE 802.11, computer network performance.
