Adapting WLAN MAC Parameters to Enhance VoIP Call Capacity

Size: px
Start display at page:

Download "Adapting WLAN MAC Parameters to Enhance VoIP Call Capacity"

Transcription

1 Adapting WLAN MAC Parameters to Enhance VoIP Call Capacity Gráinne Hanley, Seán Murphy and Liam Murphy Dept. of Computer Science, University College Dublin Belfield, Dublin 4, Ireland ABSTRACT This work describes a detailed simulation-based study of the performance of an IEEE 82.11e Medium Access Control (MAC) layer over an IEEE 82.11g Physical (PHY) layer. The study focuses on the number of simultaneous bidirectional G.711 Voice over IP (VoIP) calls that can be supported by a Wireless Local Area Network (WLAN) using the Extended Rate PHY - Orthogonal Frequency Division Modulation (ERP-OFDM) mode of 82.11g. A new scheme for adapting the WLAN MAC parameters is proposed in this work. The new scheme dynamically adapts the Contention Window (CW) based on the retransmission rate of the system. In addition, an adaptive Transmission Opportunity (TXOP) mechanism aids in balancing the uplink and downlink traffic levels and so provides the equality in uplink and downlink performance that is required for bidirectional VoIP traffic. The proposed scheme can thus maintain acceptable levels of QoS for higher call capacities, increasing the overall VoIP capacity of the system. Categories and Subject Descriptors: C.2.1 [Network Architecture and Design]: Wireless communication General Terms: Performance. Keywords: Wireless LAN, VoIP, Medium Access Control, Quality of Service, Parameter Adaptation. 1. INTRODUCTION Quality of Service of VoIPoW systems is currently an area receiving much interest in both the research community and the marketplace. The real-time nature of VoIP means that it imposes strict loss and delay bounds on the network. Since IEEE based WLANs have difficulty meeting such strict loss and delay constraints, a key question relates to how best to configure the parameters of the WLAN to deliver the best performance. In this work, an approach to adapting the WLAN parameters for bidirectional VoIP is proposed. Unlike other schemes that have been proposed, this integrated approach c ACM, 25. This is the author s version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version will appear in the conference below. To appear in MSWiM 5, October 1 13, 25, Montreal, Quebec, Canada. c ACM, 25. enables two of the key WLAN performance parameters to be adapted simultaneously in order to deliver the best performance for VoIP traffic. The approach is based on measuring two quantities at the AP - the amount of retransmissions in the system and the uplink and downlink throughput - and adapting the key WLAN parameters appropriately. The simulations studied here use an IEEE 82.11e MAC layer in association with an IEEE 82.11g PHY layer. The focus here is on the 82.11e distributed mode of operation, called Enhanced Distributed Channel Access (EDCA). Choi et al. described this scheme in detail in [9] with some emphasis on the packet bursting mechanism often referred to as Contention Free Bursting (CFB) which was incorporated into the IEEE 82.11e MAC in order to enhance the system performance. The focus of this study is a WLAN carrying purely VoIP packets. Such traffic is transmitted using the highest priority Access Category (AC) in 82.11e. IEEE 82.11g is an extension of the IEEE and 82.11b PHY standards for the 2.4GHz ISM band. The standard outlines 4 transmission schemes but only the ERP- OFDM mode is considered in this work, as it is the only mandatory mode that provides data rates of up to 54Mb/s. This paper is structured as follows. Section 2 outlines some of the published work related to this study. In Section 3, the simulation setup is described in detail. A discussion of the proposed adaptive scheme and the results are presented and discussed in Section 4. Finally, the paper is concluded in Section RELATED WORK There has been much activity in the area of WLAN performance analysis in the last few years. The most relevant related works are highlighted here. Bianchi did seminal work in this area by developing the first analytical model [2] to compute the saturation throughput of the Distributed Coordination Function (DCF) scheme. He highlighted the dependence of system performance on the number of nodes in the system and the size of the minimum CW issues that are very relevant in the scenario studied here. Other related research has focused on approaches to adapting system parameters. For instance, work carried out by Aad et al. [1], showed that the standard CW mechanism was quite inefficient. Their results demonstrated that since the number of contending stations often remains reasonably stable, resetting the CW to the minimum value after a successful transmission leads to an increase in collisions

2 and thus delays. Hence, they proposed a scheme that involves a more gradual decrease in the CW value after a successful transmission. These ideas influenced the approach described here as it consists of a CW which does not change so rapidly. One other aspect of WLAN behaviour which is important in this work is that of the disparity between uplink and downlink performance. This was reported by Casetti & Chiasserini in [4], but their work was related to the IEEE 82.11e MAC over the IEEE 82.11b PHY layer. They suggested a combined AIFS and CW strategy, rather than the use of TXOP adjustments, to help alleviate the disparity. Pong and Moors [1] demonstrated the advantage of using TXOPs in achieving higher network capacity; use of TXOP is a key aspect of the scheme proposed here. 3. THE SIMULATION SCENARIO For this work, a simulation model of IEEE 82.11e using the EDCA scheme and including the CFB mechanism, was used. It was developed by the TKN group in the Technical University of Berlin, as an extension of the Network Simulator package, NS-2. Using this model, a series of simulations were performed in order to determine the performance of VoIP in an 82.11e/82.11g system. The standard values for both the 82.11e EDCA scheme and the 82.11g ERP- OFDM PHY parameters were used. The maximum mandatory data rate of 24Mb/s was used throughout the simulations and in accordance with the 82.11g standard the short Physical Layer Convergence Protocol (PLCP) preamble and short PLCP header were transmitted at Mb/s. In these simulations, the wireless nodes were arranged with an AP in the network, which formed a connection between every node in the wireless domain and a single node in the wired domain (see Fig. 1). This AP was connected to the wired network by a high capacity link with negligible delay, which was dimensioned such that it could easily carry all the traffic and hence no loss occurred on this link. Figure 1: Network Topology The simulations were configured such that each node used bidirectional traffic sources, so as to model VoIP traffic. This was represented as Constant Bit-Rate (CBR) traffic, transmitted using User Datagram Protocol (UDP). These sources were parameterised to model G.711 voice at 4kb/s with 2ms voice payload. The G.711 scheme was chosen as it is still commonly used, due to its simplicity, despite the availability of schemes with better compression. A VoIP data payload size of 1 bytes was generated every 2ms, to which the 2 byte IP header, the 12 byte Real-time Transport Protocol (RTP) header and the 8 byte UDP header were added. This resulted in 8kb/s of traffic being sent in each direction between each node and the AP. This VoIP traffic was always transmitted using the highest priority AC of 82.11e in accordance with the standard. There are two more important delay-related points which must be made. Firstly, due to the delay bounded nature of VoIP traffic, packets which experience excessively high delays, will be dropped at the receiver as they will arrive too late to be of use. The ITU-T recommends in the G.114 standard that end-to-end delay should be kept below 15ms, so as to maintain acceptable call quality [7]. Hence, throughout this work 15ms was considered to be the maximum acceptable delay for unidirectional VoIP. The second point relates to internet delay. In early 1998, Kostas et al. [8] chose worst case delays of 1ms. Given the technology improvements which have taken place, a 7ms internet delay budget value has been chosen here. The above points can be used to arrive at a delay budget for the WLAN. Of the 15ms total delay budget, 7ms can be allocated to internet delay and 3ms is required for the voice encoding, decoding and packetisation processes. The leaves 5ms for access delays. Assuming WLAN connectivity on both ends of the connection, a delay budget of 25ms can be allocated to each WLAN. 4. OVERVIEW OF PROPOSED SCHEME The proposed scheme consists of two main parts, a CW adaptation and a TXOP adaptation, with both of these parameters being adjusted every 25 packets. The scheme is quite centralised in that appropriate values for the TXOP and CW are determined at the AP and communicated to each of the nodes in the system. The aim of the CW adaptation in the proposed scheme is to determine an appropriate CW size which strikes the right balance between loss associated with small CW sizes and delay associated with larger CWs. Using this approach, collisions and retransmissions can be kept to a level which is appropriate for the traffic on the system. The proposed scheme differs from the standard scheme in that the wireless nodes do not adapt the CW themselves. Specifically, they do not increase their CW range if they experience an unsuccessful transmission. Rather, they maintain a fixed value for the CW, which is called ĈW for clarity, until the AP advises them to update their window size. If a transmission is unsuccessful, a random backoff time is again selected from the range [1, ĈW +1]. If there are many retransmissions, however, the AP will rather quickly determine a new value for ĈW which is appropriate for the network conditions. Another component of the scheme is the adaptation of the TXOP parameter. Adapting the TXOP parameter in an appropriate way can result in good control over the division of the available resources between uplink and downlink traffic - something that is important for symmetric VoIP traffic. The specific approach that was used in this work was to vary the TXOP used by the AP and to keep that of the wireless nodes fixed. This approach is reasonable as the uplink/downlink control is more sensitive to the ratio

3 between the AP TXOP and that of the wireless nodes than the specific values that are used. The following section explains the development of the scheme in greater detail. This is followed by a discussion of the choice of appropriate parameters for the scheme and how they were selected. 4.1 Detailed Description of Proposed Scheme There are three important aspects to the scheme - determining the level of retransmissions on the system, defining how ĈW is adjusted and defining how the TXOP parameter is adjusted. Each of these is discussed in the subsections below Determining the Level of Retransmissions in the System An Exponentially Weighted Moving Average (EWMA) estimator, as defined in equation 1, was used to determine the level of retransmissions in the system. y(k) is the moving average estimator of the level of retransmissions on the system and x(k) is the number of transmissions packet k has undergone before it was successfully received at the AP. α is the parameter that determine how much memory the EWMA estimator has. In this case a value of.98 was used: this choice of α means that the weight of those samples which are not in the previous 25 samples is minimal. y(k) = [α y(k 1)] + [(1 α) x(k)] (1) In order to estimate the retransmission level on the system, it was necessary to know the number of attempted transmissions required by each packet before it was successfully received. Here, it was assumed that this information can be obtained from each packet. A small change to the standard can facilitate this. More specifically, an extra field can be added to the MAC header in which the sender inserts the transmission attempt number of each packet CW Adaptation The CW was adapted as follows. After every 25 packets, the AP compared the estimated level of retransmissions with a reference parameter. If the estimate fell below the reference parameter, the CW was decreased and if it was in excess of the reference parameter, the CW was increased. The following approach, then, was used to adjust the value of ĈW. if (y(k) > γ) then (ĈW (k) = (ĈW (k 1) + κ inc)) where γ is the reference parameter and κ inc is the parameter that controls how much ĈW is incremented by. Similarly, ĈW is decremented if the estimate of the level of retransmissions is greater than γ using the rule if((ĉw (k) > 7) && (y(k) < γ)) then (ĈW (k) = (ĈW (k 1) κ dec)) Note that there is a lower bound of 7 on the value of ĈW as is the case in the standard ERP-OFDM scheme. Appropriate values for the increment and decrement parameters, κ inc and κ dec were unclear and some simulations were performed to arrive at suitable values. These are described below TXOP Adaptation In this scenario, given the use of the G.711 codec and a data payload of 2ms, the time taken to transmit a single packet was approximately 15µs. This value takes into account the delay for data transmission, a SIFS delay, the delay for the acknowledgment and the delay for the OFDM signal extension. The time required for the data transmission consists of time spent transmitting the data payload, MAC header, RTP header, UDP header, IP header and PLCP header and preamble. So as to accommodate multiple such transmissions with ease, TXOP adjustments were made in multiples of 155µs. As all connections go through the AP, it is clear that the AP requires more access to the medium than the other nodes in the system. By assigning a larger TXOP value to the AP, it can transmit more packets once it gains medium access, resulting in greater use of the medium by the AP. In order to determine an appropriate TXOP size for the AP, counts of both the ACKs successfully received from the wireless nodes and the packets successfully received at the AP were. After every 25 packets received at the AP, these two counts were compared. If more data packets were received than ACKs, it was an indication that the uplink was performing better than the downlink. At such times the maximum TXOP for the AP was increased by 155µs to enable the AP to transmit more in the downlink. Conversely, if more ACKs were received than packets, then the maximum TXOP for the AP was decreased by 155µs. No upper bound was put on the TXOP value used by the AP. In this manner, the system was able to adapt to changing traffic levels in order to maintain similar uplink and downlink performance levels. Many simulations were carried out in order to determine a reasonable value for the maximum TXOP used by the wireless nodes. Results showed that a maximum TXOP value of 185µs demonstrated improved performance. This represents a maximum of approximately 7 packets being sent in each burst by the wireless nodes. This value was chosen for the experiments below. 4.2 Determination of Appropriate System Parameters Two important sets of system parameters must be defined for the above approach to operate. Firstly, the reference parameter, γ must be defined. The meaning of this parameter and a description of experiments performed to arrive at a suitable value for this parameter is given in the subsection below. The other parameters that need to be defined are the increment and decrement parameters, κ inc and κ dec. Experiments were performed to determine appropriate values for these parameters - these are described in the following subsection Determination of γ Several series of simulations were performed in order to determine an appropriate level for γ. For these initial experiments κinc and κ dec were set to 1. In this instance the interpretation of γ is reasonably clear - it is a target operat-

4 ing point for the system in terms of the fraction of retransmissions on the system. Different values of γ were compared on the basis of goodput, loss and delay. γ values of 2%, 5%, 1%, 15%, 2% and 25% were examined. The scheme which provided the highest goodput and call capacity whilst maintaining delay and loss within recommended boundaries was chosen. Results for the different γ values showed that the 2% and 5% levels exhibited significantly lower goodput than the other retransmission levels and for this reason they were ruled out as possible operating points. % Packets % 7 15% 2% 25% Figure 2: Percentage of Packets Within 25ms Uplink Delay Budget The other potential γ levels were then compared (see Fig. 2) on the basis of the call capacity each scheme could handle before packet delays exceeded a 25ms uplink delay budget. From these results it can be seen that both the 1% and the 15% levels began to show increased delay prior to the other schemes. This occurs as these levels of retransmissions can only be realised if the values of ĈW are large, resulting in large backoff delays and ultimately, unacceptably large delays. Of the 2% and 25% retransmission rates, both schemes seemed to give reasonably good performance. As there was little difference between these two target values in terms of both goodput and delay, either would be equally suitable; the 2% value was chosen Determination of κ inc and κ dec Experiments using different values for κ inc and κ dec were performed for γ = 2%. The results were compared on the basis of both loss and delay. A scheme which reacted to increases in retransmission levels with large increases in ĈW and then single step decreases, seemed to perform the best. A scheme which incremented in steps of 7 and decremented in steps of 1 was ultimately chosen. It is worth noting that this choice of κ inc and κ dec meant that the system no longer oscillated around γ, i.e. γ was no longer a target operating point which the system continually attempted to converge to. Further, the levels of retransmissions on the system were always lower than γ when this approach was used, as the system had a tendency to use a larger ĈW. As this choice of κinc and κ dec resulted in better performance, they were selected for the experiments below, even though the interpretation of γ was less clear. 4.3 Results and Discussion In order to assess the performance of the adaptive scheme, it was compared with the original scheme. However, for the traffic patterns under consideration here, the small maximum CW value from the standard is inappropriate. Therefore, a series of simulations were performed with the maximum CW value of the standard scheme increased to different multiples of its original value. Thus, the maximum CW values chosen for analysis were 3, 127, 255 and Goodput All five scenarios are found to give quite a similar goodput level (see Fig. 3). Although the adaptive scheme performs slightly better than the other schemes. However, the difference is very marginal, especially in comparison with the schemes using the larger maximum CW values. The schemes with smaller maximum CW values are seen to perform slightly worse, which indicates that the maximum CW value in these cases is bounded at a value that results in significant collisions on the medium. Mb/s Figure 3: Original Loss Comparison of Adaptive Goodput with ETSI studies [5] indicate that a packet loss rate of 5% is at the quality threshold of fair quality voice. The results in Fig. 4 show that all of the schemes result in acceptable uplink loss. However, there is a difference between the loss levels obtained under the different schemes. The adaptive scheme clearly performs better than the other schemes with negligible loss for the call levels studied. Loss Rate Figure 4: Uplink Loss Comparison In addition, the downlink loss in all the schemes (see Fig. 5), was found to be low in general. Downlink loss rates did not even reach 2.5% in any of the scenarios studied. Although the adaptive scheme demonstrated the highest downlink loss rates at times, the aggregate loss rate (uplink+downlink) for the adaptive scheme is still significantly lower than that of the other schemes. Also, it is well below the loss threshold of 5%.

5 Loss Rate Figure 5: Downlink Loss Comparison Delay The percentage of packets that arrive within a delay budget of 25ms are now compared for all five schemes. It was found that the number of packets received within the delay budget on the downlink remain acceptable, at more than 99%, in all five cases for the call levels studied. In contrast, delays on the uplink (see Fig. ) rise sharply at or before 49 calls in the schemes using maximum CW values of 3 and 127. This is as a result of the traffic levels on the system, as in this situation the higher maximum CW values cause a decrease in the level of retransmissions. This results in a higher percentage of packets being received within the specified delay budget. % Pkts Figure : Uplink Packets Within Delay Budget of 25ms At 48 calls the 255 CW scheme already shows 4.4% of packets exceeding the uplink delay budget and the 511 CW scheme shows 3.7% of packets exceeding this budget. However, the adaptive scheme shows that less than 3% of packets exceed the uplink budget until after the 52 call point, thus showing its superior ability to adjust to network conditions. This shows that an additional 4 calls can be accommodated when using the adaptive scheme according to this uplink delay budget. When higher uplink delay budgets were used, similar results were obtained. Results show that delays in the other schemes reach higher levels much more quickly, whereas the adaptive scheme demonstrates a more gradual increase in both loss and delays, something which is quite desirable in WLAN systems. 5. CONCLUSION & FUTURE WORK A mechanism for jointly adapting the contention window and TXOP parameter on the basis of successful and unsuccessful transmissions is outlined. The mechanism dynamically adapts these MAC parameters so as to maintain acceptable performance levels for higher call capacities. The dynamic nature of this scheme takes into account the current conditions of the WLAN and adapts the parameters accordingly. Comparisons using a series of simulations using the standard 82.11e/82.11g scheme but using different maximum CW values were discussed in detail. Results show that the adaptive scheme dynamically adjusts the contention window and TXOP to give similar goodput to variants of the standard scheme with increased CW but with lower delays and loss due to the effect of both the TXOP and the ĈW being adjusted in parallel. Thus, the adaptive scheme can consistently provide a higher VoIP call capacity, for the studied scenarios. Future work involves examining the operation of the proposed scheme in conjunction with the other QoS classes outlined in the IEEE 82.11e MAC. An examination of the scheme operating at the different data rates available to IEEE 82.11g, as well as with a range of VoIP codecs, is also to be performed. Finally, a modified version of the scheme is planned, which dynamically adapts on the basis of goodput levels rather than retransmission rates. Acknowledgements The support of the Informatics Research initiative of Enterprise Ireland is gratefully acknowledged.. REFERENCES [1] I. Aad, Q. Ni, C. Castelluccia and T. Turletti, Enhancing IEEE Performance With Slow CW Decrease, IEEE 82.11e working group document /74r, Nov. 22 [2] G. Bianchi, Performance Analysis of the IEEE Distributed Coordination Function, IEEE Journal on Selected Areas in Communications, 18(3): , Mar. 2 [3] G. Bianchi, IEEE Saturation Throughput Analysis, IEEE Communications Letters, 2(12), Dec [4] C. Casetti and C.F. Chiasserini, Improving Fairness And Throughput For Voice Traffic In 82.11e EDCA, Proc. of IEEE PIMRC 4, Barcelona, Spain, Sep. 24 [5] ETSI TR V2.1.1 (22-2) Technical Report Telecommunications and Internet Protocol Harmonization Over Networks (TIPHON) Release 3; Part [] D. Gu and J. Zhang, A New Measurement-Based Admission Control Method for IEEE Wireless Local Area Networks, Proc. of IEEE PIMRC, pp , Sep. 23 [7] ITU-T Recommendation G.114: One Way Transmission Time, May 23. [8] T. J. Kostas, M. S. Borella, I. Sidhu, G. M. Schuster, J. Grabiec and J. Mahler, Real-Time Voice Over Packet-Switched Networks, IEEE Networks, 12(1):18-27, Jan./Feb [9] S. Choi and J.del Prado Pavon, 82.11g CP: A Solution for IEEE 82.11g and 82.11b Inter-Working, Proc. of VTC-Spring 3, Jeju, Korea, Apr. 23. [1] D. Pong and T. Moors, Using Transmission Opportunities and Judicious Parameter Selection in Enhancing Real-Time Applications over Wireless LANs, Proc. of ATNAC 3, Dec. 23

Adaptive DCF of MAC for VoIP services using IEEE 802.11 networks

Adaptive DCF of MAC for VoIP services using IEEE 802.11 networks Adaptive DCF of MAC for VoIP services using IEEE 802.11 networks 1 Mr. Praveen S Patil, 2 Mr. Rabinarayan Panda, 3 Mr. Sunil Kumar R D 1,2,3 Asst. Professor, Department of MCA, The Oxford College of Engineering,

More information

then, we require that, in order to support the offered load, (1)

then, we require that, in order to support the offered load, (1) Capacity of an IEEE 802.11b Wireless LAN supporting VoIP To appear in Proc. IEEE Int. Conference on Communications (ICC) 2004 David P. Hole and Fouad A. Tobagi Dept. of Electrical Engineering, Stanford

More information

Establishing How Many VoIP Calls a Wireless LAN Can Support Without Performance Degradation

Establishing How Many VoIP Calls a Wireless LAN Can Support Without Performance Degradation Establishing How Many VoIP Calls a Wireless LAN Can Support Without Performance Degradation ABSTRACT Ángel Cuevas Rumín Universidad Carlos III de Madrid Department of Telematic Engineering Ph.D Student

More information

Introduction VOIP in an 802.11 Network VOIP 3

Introduction VOIP in an 802.11 Network VOIP 3 Solutions to Performance Problems in VOIP over 802.11 Wireless LAN Wei Wang, Soung C. Liew Presented By Syed Zaidi 1 Outline Introduction VOIP background Problems faced in 802.11 Low VOIP capacity in 802.11

More information

Optimization of VoIP over 802.11e EDCA based on synchronized time

Optimization of VoIP over 802.11e EDCA based on synchronized time Optimization of VoIP over 802.11e EDCA based on synchronized time Padraig O Flaithearta, Dr. Hugh Melvin Discipline of Information Technology, College of Engineering and Informatics, National University

More information

VoIP in 802.11. Mika Nupponen. S-72.333 Postgraduate Course in Radio Communications 06/04/2004 1

VoIP in 802.11. Mika Nupponen. S-72.333 Postgraduate Course in Radio Communications 06/04/2004 1 VoIP in 802.11 Mika Nupponen S-72.333 Postgraduate Course in Radio Communications 06/04/2004 1 Contents Introduction VoIP & WLAN Admission Control for VoIP Traffic in WLAN Voice services in IEEE 802.11

More information

An Experimental Study of Throughput for UDP and VoIP Traffic in IEEE 802.11b Networks

An Experimental Study of Throughput for UDP and VoIP Traffic in IEEE 802.11b Networks An Experimental Study of Throughput for UDP and VoIP Traffic in IEEE 82.11b Networks Sachin Garg sgarg@avaya.com Avaya Labs Research Basking Ridge, NJ USA Martin Kappes mkappes@avaya.com Avaya Labs Research

More information

II. IEEE802.11e EDCA OVERVIEW

II. IEEE802.11e EDCA OVERVIEW The 18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC'7) CACITY IMPROVEMENT OF WIRELESS LAN VOIP USING DISTRIBUTED TRANSMISSION SCHEDULING Kei Igarashi,

More information

Fast Retransmission Mechanism for VoIP in IEEE 802.11e wireless LANs

Fast Retransmission Mechanism for VoIP in IEEE 802.11e wireless LANs Fast Mechanism for VoIP in IEEE 802.11e wireless LANs Gyung-Ho Hwang and Dong-Ho Cho Division of Electrical Engineering, Department of Electrical Engineering and Computer Science, KAIST, 373-1 Guseong-dong

More information

An End-to-End Measurement-Based Admission Control Policy for VoIP over Wireless Networks

An End-to-End Measurement-Based Admission Control Policy for VoIP over Wireless Networks An End-to-End Measurement-Based Admission Control Policy for VoIP over Wireless Networks Ala Khalifeh Department of EECS University of California, Irvine [akhalife]@uci.edu Abstract in this paper, we present

More information

IEEE 802.11E ENHANCEMENT FOR VOICE SERVICE

IEEE 802.11E ENHANCEMENT FOR VOICE SERVICE V OICE OVER WIRELESS LOCAL AREA N ETWORK IEEE 802.11E ENHANCEMENT FOR VOICE SERVICE PING WANG, HAI JIANG, AND WEIHUA ZHUANG, UNIVERSITY OF WATERLOO Wired network IP phone Gateway router Access point Motivated

More information

Can I add a VoIP call?

Can I add a VoIP call? Can I add a VoIP call? Sachin Garg Avaya Labs Basking Ridge, NJ 07920 Email: sgarg@avaya.com Martin Kappes Avaya Labs Basking Ridge, NJ 07920 Email: mkappes@avaya.com Abstract In this paper, we study the

More information

PROVIDING STATISTICAL QOS GUARANTEE FOR VOICE OVER IP IN THE IEEE 802.11 WIRELESS LANS

PROVIDING STATISTICAL QOS GUARANTEE FOR VOICE OVER IP IN THE IEEE 802.11 WIRELESS LANS V OICE OVER WIRELESS LOCAL AREA N ETWORK PROVIDING STATISTICAL QOS GUARANTEE FOR VOICE OVER IP IN THE IEEE 82.11 WIRELESS LANS HONGQIANG ZHAI, JIANFENG WANG, AND YUGUANG FANG, UNIVERSITY OF FLORIDA The

More information

Analysis of QoS parameters of VOIP calls over Wireless Local Area Networks

Analysis of QoS parameters of VOIP calls over Wireless Local Area Networks Analysis of QoS parameters of VOIP calls over Wireless Local Area Networks Ayman Wazwaz, Computer Engineering Department, Palestine Polytechnic University, Hebron, Palestine, aymanw@ppu.edu Duaa sweity

More information

Express Forwarding : A Distributed QoS MAC Protocol for Wireless Mesh

Express Forwarding : A Distributed QoS MAC Protocol for Wireless Mesh Express Forwarding : A Distributed QoS MAC Protocol for Wireless Mesh, Ph.D. benveniste@ieee.org Mesh 2008, Cap Esterel, France 1 Abstract Abundant hidden node collisions and correlated channel access

More information

A TCP-like Adaptive Contention Window Scheme for WLAN

A TCP-like Adaptive Contention Window Scheme for WLAN A TCP-like Adaptive Contention Window Scheme for WLAN Qixiang Pang, Soung Chang Liew, Jack Y. B. Lee, Department of Information Engineering The Chinese University of Hong Kong Hong Kong S.-H. Gary Chan

More information

Enhanced TXOP scheme for efficiency improvement of WLAN IEEE 802.11e

Enhanced TXOP scheme for efficiency improvement of WLAN IEEE 802.11e Enhanced TXOP scheme for efficiency improvement of WLAN IEEE 802.11e Jakub Majkowski, Ferran Casadevall Palacio Dept. of Signal Theory and Communications Universitat Politècnica de Catalunya (UPC) C/ Jordi

More information

Attenuation (amplitude of the wave loses strength thereby the signal power) Refraction Reflection Shadowing Scattering Diffraction

Attenuation (amplitude of the wave loses strength thereby the signal power) Refraction Reflection Shadowing Scattering Diffraction Wireless Physical Layer Q1. Is it possible to transmit a digital signal, e.g., coded as square wave as used inside a computer, using radio transmission without any loss? Why? It is not possible to transmit

More information

AN ANALYSIS OF DELAY OF SMALL IP PACKETS IN CELLULAR DATA NETWORKS

AN ANALYSIS OF DELAY OF SMALL IP PACKETS IN CELLULAR DATA NETWORKS AN ANALYSIS OF DELAY OF SMALL IP PACKETS IN CELLULAR DATA NETWORKS Hubert GRAJA, Philip PERRY and John MURPHY Performance Engineering Laboratory, School of Electronic Engineering, Dublin City University,

More information

Enhancement of VoIP over IEEE 802.11 WLANs by Adapting Transmitting Interval

Enhancement of VoIP over IEEE 802.11 WLANs by Adapting Transmitting Interval Enhancement of VoIP over IEEE 82.11 WLANs by Adapting Transmitting Interval Zhuo Chen, Lingyun Wang, and Xinbing Wang School of Electronic, Information and Electrical Engineering Shanghai Jiao Tong University

More information

Enhancement of VoIP over IEEE 802.11 WLAN via Dual Queue Strategy

Enhancement of VoIP over IEEE 802.11 WLAN via Dual Queue Strategy Enhancement of VoIP over IEEE 802.11 WLAN via Dual Queue Strategy + Multimedia & Wireless Networking Laboratory School of Electrical Engineering Seoul National University jgyu@mwnl.snu.ac.kr, schoi@snu.ac.kr

More information

TCP in Wireless Networks

TCP in Wireless Networks Outline Lecture 10 TCP Performance and QoS in Wireless s TCP Performance in wireless networks TCP performance in asymmetric networks WAP Kurose-Ross: Chapter 3, 6.8 On-line: TCP over Wireless Systems Problems

More information

HO Policies for Combined WLAN/UMTS Networks

HO Policies for Combined WLAN/UMTS Networks HO Policies for Combined WLAN/UMTS Networks Sven Wiethölter Telecommunication Networks Group TU Berlin Telecommunication Networks Group Technische Universität Berlin Project Overview Project partners Goal:

More information

Enhancing WLAN MAC Protocol performance using Differentiated VOIP and Data Services Strategy

Enhancing WLAN MAC Protocol performance using Differentiated VOIP and Data Services Strategy IJCSNS International Journal of Computer Science and Network Security, VOL.9 No.12, December 2009 89 Enhancing WLAN MAC Protocol performance using Differentiated VOIP and Data Services Strategy S.Vijay

More information

Modeling and Simulation of Quality of Service in VoIP Wireless LAN

Modeling and Simulation of Quality of Service in VoIP Wireless LAN Journal of Computing and Information Technology - CIT 16, 2008, 2, 131 142 doi:10.2498/cit.1001022 131 Modeling and Simulation of Quality of Service in VoIP Wireless LAN A. Al-Naamany, H. Bourdoucen and

More information

VoIP Session Capacity Expansion with Packet Transmission Suppression Control in Wireless LAN

VoIP Session Capacity Expansion with Packet Transmission Suppression Control in Wireless LAN 1144 PAPER Special Section on Internet Technology and its Architecture for Ambient Information Systems VoIP Session Capacity Expansion with Packet Transmission Suppression Control in Wireless LAN Yasufumi

More information

DUE to the high performance versus price ratio, IEEE

DUE to the high performance versus price ratio, IEEE Improving WLAN VoIP Capacity Through Service Differentiation Deyun Gao, Member, IEEE, Jianfei Cai, Senior Member, IEEE, Chuan Heng Foh, Member, IEEE, Chiew-Tong Lau, Member, IEEE, and King Ngi Ngan, Fellow,

More information

Handover Management based on the Number of Retries for VoIP on WLANs

Handover Management based on the Number of Retries for VoIP on WLANs Handover Management based on the Number of Retries for VoIP on WLANs Shigeru Kashihara Yuji Oie Department of Computer Science and Electronics, Kyushu Institute of Technology Kawazu 68-4, Iizuka, 82-852

More information

Extended-rtPS Algorithm for VoIP Services in IEEE 802.16 systems

Extended-rtPS Algorithm for VoIP Services in IEEE 802.16 systems Extended-rtPS Algorithm for VoIP Services in IEEE 802.16 systems Howon Lee, Taesoo Kwon and Dong-Ho Cho Department of Electrical Engineering and Computer Science Korea Advanced Institute of Science and

More information

No Ack in IEEE 802.11e Single-Hop Ad-Hoc VoIP Networks

No Ack in IEEE 802.11e Single-Hop Ad-Hoc VoIP Networks No Ack in IEEE 802.11e Single-Hop Ad-Hoc VoIP Networks Jaume Barceló, Boris Bellalta, Anna Sfairopoulou, Cristina Cano, Miquel Oliver Abstract This paper analyzes the impact of the No Ack policy in VoIP

More information

Philippe Klein. avb-phkl-802-11-qos-overview-0811-1

Philippe Klein. avb-phkl-802-11-qos-overview-0811-1 802.11 QoS Overview Philippe Klein IEEE Plenary Meeting Nov 08 Dallas, TX avb-phkl-802-11-qos-overview-0811-1 Disclaimer This presentation is not a highly detailed technical presentation but a crash course

More information

CSMA/CA. Information Networks p. 1

CSMA/CA. Information Networks p. 1 Information Networks p. 1 CSMA/CA IEEE 802.11 standard for WLAN defines a distributed coordination function (DCF) for sharing access to the medium based on the CSMA/CA protocol Collision detection is not

More information

VoIP codec adaptation algorithm in multirate 802.11 WLANs : distributed vs centralized performance comparison

VoIP codec adaptation algorithm in multirate 802.11 WLANs : distributed vs centralized performance comparison VoIP codec adaptation algorithm in multirate 82.11 WLANs : distributed vs centralized performance comparison Anna Sfairopoulou, Carlos Macián, Boris Bellalta Network Technologies and Strategies (NeTS)

More information

RESOURCE ALLOCATION FOR INTERACTIVE TRAFFIC CLASS OVER GPRS

RESOURCE ALLOCATION FOR INTERACTIVE TRAFFIC CLASS OVER GPRS RESOURCE ALLOCATION FOR INTERACTIVE TRAFFIC CLASS OVER GPRS Edward Nowicki and John Murphy 1 ABSTRACT The General Packet Radio Service (GPRS) is a new bearer service for GSM that greatly simplify wireless

More information

IEEE 802.11e WLANs / WMM. S.Rajesh (rajeshsweb@gmail.com) AU-KBC Research Centre, BroVis Wireless Networks, smartbridges Pte Ltd.

IEEE 802.11e WLANs / WMM. S.Rajesh (rajeshsweb@gmail.com) AU-KBC Research Centre, BroVis Wireless Networks, smartbridges Pte Ltd. IEEE 802.11e WLANs / WMM S.Rajesh (rajeshsweb@gmail.com) AU-KBC Research Centre, BroVis Wireless Networks, smartbridges Pte Ltd. Outline A short review of 802.11 MAC Drawbacks of 802.11 MAC Application

More information

Admission Control for VoIP Traffic in IEEE 802.11 Networks

Admission Control for VoIP Traffic in IEEE 802.11 Networks Admission Control for VoIP Traffic in IEEE 802.11 Networks Sachin Garg Avaya Labs Basking Ridge, NJ 07920 Email: sgarg@avaya.com Martin Kappes Avaya Labs Basking Ridge, NJ 07920 Email: mkappes@avaya.com

More information

ENSC 427: Communication Networks. Analysis of Voice over IP performance on Wi-Fi networks

ENSC 427: Communication Networks. Analysis of Voice over IP performance on Wi-Fi networks ENSC 427: Communication Networks Spring 2010 OPNET Final Project Analysis of Voice over IP performance on Wi-Fi networks Group 14 members: Farzad Abasi (faa6@sfu.ca) Ehsan Arman (eaa14@sfu.ca) http://www.sfu.ca/~faa6

More information

Multicast Polling and Efficient VoIP Connections in IEEE 802.16 Networks

Multicast Polling and Efficient VoIP Connections in IEEE 802.16 Networks Multicast Polling and Efficient VoIP Connections in IEEE 82.16 Networks Olli Alanen Telecommunication Laboratory Department of Mathematical Information Technology University of Jyv-askyl-a, FINLAND olli.alanen@jyu.fi

More information

Performance Evaluation of VoIP Services using Different CODECs over a UMTS Network

Performance Evaluation of VoIP Services using Different CODECs over a UMTS Network Performance Evaluation of VoIP Services using Different CODECs over a UMTS Network Jianguo Cao School of Electrical and Computer Engineering RMIT University Melbourne, VIC 3000 Australia Email: j.cao@student.rmit.edu.au

More information

Aspects of Coexistence Between WiFi and HSDPA

Aspects of Coexistence Between WiFi and HSDPA (Cross-layer design and network planning for B3G systems) Aspects of Coexistence Between WiFi and HSDPA Orlando Cabral Valdemar Monteiro 2005, it - instituto de telecomunicações. Todos os direitos reservados.

More information

Supporting VoIP in IEEE802.11 Distributed WLANs

Supporting VoIP in IEEE802.11 Distributed WLANs Supporting VoIP in IEEE802.11 Distributed WLANs Zuo Liu Supervisor: Dr. Nick Filer July 2012 1 Voice VoIP Applications Constant Streaming Traffic Packetize interval usually 10-30 ms 8 160 bytes each packet

More information

A Multiplex-Multicast Scheme that Improves System Capacity of Voice-over-IP on Wireless LAN by 100% *

A Multiplex-Multicast Scheme that Improves System Capacity of Voice-over-IP on Wireless LAN by 100% * A Multiplex-Multicast Scheme that Improves System Capacity of Voice-over-IP on Wireless LAN by 100% * Wei Wang, Soung C. Liew, Qixiang Pang Department of Information Engineering The Chinese University

More information

ANALYSIS OF VOICE OVER IP DURING VERTICAL HANDOVERS IN HETEROGENEOUS WIRELESS AND MOBILE NETWORKS

ANALYSIS OF VOICE OVER IP DURING VERTICAL HANDOVERS IN HETEROGENEOUS WIRELESS AND MOBILE NETWORKS ANALYSIS OF VOICE OVER IP DURING VERTICAL HANDOVERS IN HETEROGENEOUS WIRELESS AND MOBILE NETWORKS Kire Jakimoski Ss. Cyril and Methodius University, Faculty of Electrical Engineering and Information Technologies

More information

Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc

Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc (International Journal of Computer Science & Management Studies) Vol. 17, Issue 01 Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc Dr. Khalid Hamid Bilal Khartoum, Sudan dr.khalidbilal@hotmail.com

More information

CROSS-LAYER SOLUTIONS TO PERFORMANCE PROBLEMS IN VOIP OVER WLANS

CROSS-LAYER SOLUTIONS TO PERFORMANCE PROBLEMS IN VOIP OVER WLANS 4th European Signal Processing Conference (EUSIPCO 26), Florence, Italy, September 4-8, 26, copyright by EURASIP CROSS-LAYER SOLUTIONS TO PERFORMANCE PROBLEMS IN VOIP OVER WLANS F. Maguolo, F. De Pellegrini,

More information

PLUS-DAC: A Distributed Admission Control Scheme for IEEE 802.11e WLANs

PLUS-DAC: A Distributed Admission Control Scheme for IEEE 802.11e WLANs -DAC: A Distributed Admission Control Scheme for IEEE 8.e WLANs Kiran Kumar Gavini, Varsha Apte and Sridhar Iyer Kanwal Rekhi School of Information Technology Indian Institute of Technology Bombay, Powai,

More information

Performance Comparison of Dual Queue and EDCA for VoIP over IEEE 802.11 WLAN

Performance Comparison of Dual Queue and EDCA for VoIP over IEEE 802.11 WLAN Performance Comparison of Dual Queue and for VoIP over IEEE 8. WLAN Jeonggyun Yu and Sunghyun Choi Multimedia & Wireless Networking Laboratory (MWNL), School of Electrical Engineering, Seoul National University,

More information

Adaptive Coding and Packet Rates for TCP-Friendly VoIP Flows

Adaptive Coding and Packet Rates for TCP-Friendly VoIP Flows Adaptive Coding and Packet Rates for TCP-Friendly VoIP Flows C. Mahlo, C. Hoene, A. Rostami, A. Wolisz Technical University of Berlin, TKN, Sekr. FT 5-2 Einsteinufer 25, 10587 Berlin, Germany. Emails:

More information

FORTH-ICS / TR-375 March 2006. Experimental Evaluation of QoS Features in WiFi Multimedia (WMM)

FORTH-ICS / TR-375 March 2006. Experimental Evaluation of QoS Features in WiFi Multimedia (WMM) FORTH-ICS / TR-375 March 26 Experimental Evaluation of QoS Features in WiFi Multimedia (WMM) Vasilios A. Siris 1 and George Stamatakis 1 Abstract We investigate the operation and performance of WMM (WiFi

More information

A study of Skype over IEEE 802.16 networks: voice quality and bandwidth usage

A study of Skype over IEEE 802.16 networks: voice quality and bandwidth usage Iowa State University Digital Repository @ Iowa State University Graduate Theses and Dissertations Graduate College 2011 A study of Skype over IEEE 802.16 networks: voice quality and bandwidth usage Kuan-yu

More information

Virtual PCF: Improving VoIP over WLAN performance with legacy clients

Virtual PCF: Improving VoIP over WLAN performance with legacy clients Virtual PCF: Improving VoIP over WLAN performance with legacy clients by Usman Ismail A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master

More information

Performance evaluation of QoS in wireless networks using IEEE 802.11e

Performance evaluation of QoS in wireless networks using IEEE 802.11e Performance evaluation of QoS in wireless networks using IEEE 802.11e Laio B. Vilas Boas, Pedro M. C. Massolino, Rafael T. Possignolo, Cintia B. Margi and Regina M. Silveira Abstract The increase demand

More information

Throughput Analysis of WEP Security in Ad Hoc Sensor Networks

Throughput Analysis of WEP Security in Ad Hoc Sensor Networks Throughput Analysis of WEP Security in Ad Hoc Sensor Networks Mohammad Saleh and Iyad Al Khatib iitc Stockholm, Sweden {mohsaleh, iyad}@iitc.se ABSTRACT This paper presents a performance investigation

More information

Advanced Wireless LAN VoIP Technology

Advanced Wireless LAN VoIP Technology Wireless LAN VoIP QoS Advanced Wireless LAN VoIP Technology A technical overview is given of an optimal access point selection method and an autonomous distributed scheduling MAC method that take QoS into

More information

WLAN QoS : 802.11e. Merle Frédéric

WLAN QoS : 802.11e. Merle Frédéric WLAN QoS : 802.11e Merle Frédéric Summary Introduction What is QoS? Why do we need QoS in wireless LAN nowadays? 802.11e MAC Protocol Enhanced Distributed Channel Access (EDCA) Presentation How does it

More information

IEEE 802.11 Ad Hoc Networks: Performance Measurements

IEEE 802.11 Ad Hoc Networks: Performance Measurements IEEE 8. Ad Hoc Networks: Performance Measurements G. Anastasi Dept. of Information Engineering University of Pisa Via Diotisalvi - 56 Pisa, Italy Email: g.anastasi@iet.unipi.it E. Borgia, M. Conti, E.

More information

Capacity Evaluation of VoIP in IEEE 802.11e WLAN Environment

Capacity Evaluation of VoIP in IEEE 802.11e WLAN Environment Capacity Evaluation of VoIP in IEEE 802.11e WLAN Environment Abdelbasset Trad, Farukh Munir INIA, Planete Project 4 oute des Lucioles, BP-93 06902 Sophia-Antipolis, France Email: {atrad, mfmunir}@sophia.inria.fr

More information

Bluetooth voice and data performance in 802.11 DS WLAN environment

Bluetooth voice and data performance in 802.11 DS WLAN environment 1 (1) Bluetooth voice and data performance in 802.11 DS WLAN environment Abstract In this document, the impact of a 20dBm 802.11 Direct-Sequence WLAN system on a 0dBm Bluetooth link is studied. A typical

More information

PERFORMANCE OF THE GPRS RLC/MAC PROTOCOLS WITH VOIP TRAFFIC

PERFORMANCE OF THE GPRS RLC/MAC PROTOCOLS WITH VOIP TRAFFIC PERFORMANCE OF THE GPRS RLC/MAC PROTOCOLS WITH VOIP TRAFFIC Boris Bellalta 1, Miquel Oliver 1, David Rincón 2 1 Universitat Pompeu Fabra, Psg. Circumval lació 8, 83 - Barcelona, Spain, boris.bellalta,

More information

A Cross Layer Solution for VoIP over IEEE802.11

A Cross Layer Solution for VoIP over IEEE802.11 A Cross Layer Solution for VoIP over IEEE82. F. De Pellegrini, F. Maguolo, A. Zanella and M. Zorzi. depe,maguolof,zanella,zorzi @dei.unipd.it.it Department of Information Engineering, University of Padova,

More information

Asia-Pacific Advanced Network

Asia-Pacific Advanced Network Frame aggregations in the wireless LANs: A review paper Presented by: Anwar Saif Asia-Pacific Advanced Network Wireless communication 2009 Abstract The overhead induced by the IEEE 802.11 PHY and MAC layer

More information

Department of Computer Science Columbia University

Department of Computer Science Columbia University Towards the Quality of Service for VoIP traffic in IEEE 82.11 Wireless Networks Sangho Shin Henning Schulzrinne Email: sangho, hgs@cs.columbia.edu Department of Computer Science Columbia University 28

More information

Railway Freight Dispatching Telephone System Based on VoIP in Wireless Networks

Railway Freight Dispatching Telephone System Based on VoIP in Wireless Networks International Conference on Computer, Communications and Information Technology (CCIT 2014) Railway Freight Dispatching Telephone System Based on VoIP in Wireless Networks Jun Xiao1, Feng Liu1, 2 1 2 School

More information

Measuring the Performance of VoIP over Wireless LAN

Measuring the Performance of VoIP over Wireless LAN Measuring the Performance of VoIP over Wireless LAN Keshav Neupane, Student Victor Kulgachev, Student Department of Computer Science Northern Kentucky University Highland Heights, KY, USA, 41099 neupanek1@nku.edu

More information

Seamless Congestion Control over Wired and Wireless IEEE 802.11 Networks

Seamless Congestion Control over Wired and Wireless IEEE 802.11 Networks Seamless Congestion Control over Wired and Wireless IEEE 802.11 Networks Vasilios A. Siris and Despina Triantafyllidou Institute of Computer Science (ICS) Foundation for Research and Technology - Hellas

More information

Analysis and Enhancement of QoS in Cognitive Radio Network for Efficient VoIP Performance

Analysis and Enhancement of QoS in Cognitive Radio Network for Efficient VoIP Performance Analysis and Enhancement of QoS in Cognitive Radio Network for Efficient VoIP Performance Tamal Chakraborty 1, Atri Mukhopadhyay 2 1 Dept. of Electronics and Telecommunication Engineering 2 School of Mobile

More information

VoIP over Wireless Opportunities and Challenges

VoIP over Wireless Opportunities and Challenges Prof. Dr. P. Tran-Gia VoIP over Wireless Opportunities and Challenges Universität Würzburg Lehrstuhl für verteilte Systeme H.323 RTP Codec Voice-over-IP over Wireless (VoIPoW) UDP IMS G723.1 SIP G729 HSDPA

More information

QoS-aware MPDU Aggregation of IEEE 802.11n WLANs for VoIP Services

QoS-aware MPDU Aggregation of IEEE 802.11n WLANs for VoIP Services QoS-aware MPDU Aggregation of IEEE 802.11n WLANs for VoIP Services Shinnazar Seytnazarov and Young-Tak Kim Department of Information and Communication Engineering, Graduate School, Yeungnam University

More information

QUALITY EVALUATION OF VOIP SERVICE OVER IEEE 802.11 WIRELESS LAN. Andrea Barbaresi, Massimo Colonna, Andrea Mantovani and Giovanna Zarba

QUALITY EVALUATION OF VOIP SERVICE OVER IEEE 802.11 WIRELESS LAN. Andrea Barbaresi, Massimo Colonna, Andrea Mantovani and Giovanna Zarba QUALITY EVALUATION OF VOIP SERVICE OVER IEEE 802.11 WIRELESS LAN Andrea Barbaresi, Massimo Colonna, Andrea Mantovani and Giovanna Zarba Telecom Italia, via G. Reiss Romoli 27, I-1018 Torino (TO), Italy

More information

Improving the Performance of TCP Using Window Adjustment Procedure and Bandwidth Estimation

Improving the Performance of TCP Using Window Adjustment Procedure and Bandwidth Estimation Improving the Performance of TCP Using Window Adjustment Procedure and Bandwidth Estimation R.Navaneethakrishnan Assistant Professor (SG) Bharathiyar College of Engineering and Technology, Karaikal, India.

More information

Measuring Data and VoIP Traffic in WiMAX Networks

Measuring Data and VoIP Traffic in WiMAX Networks JOURNAL OF TELECOMMUNICATIONS, VOLUME 2, ISSUE 1, APRIL 2010 Measuring Data and VoIP Traffic in WiMAX Networks 1 Iwan Adhicandra Abstract Due to its large coverage area, low cost of deployment and high

More information

VoIP on WLAN, QoS issues and VoIP specifics

VoIP on WLAN, QoS issues and VoIP specifics ETSI STQ Workshop Compensating for Packet Loss in Real-Time Applications, Feb 2003 VoIP on WLAN, QoS issues and VoIP specifics Alan Duric Sen. Systems Architect SIP/email: alan.duric@globalipsound.com

More information

ECE 358: Computer Networks. Homework #3. Chapter 5 and 6 Review Questions 1

ECE 358: Computer Networks. Homework #3. Chapter 5 and 6 Review Questions 1 ECE 358: Computer Networks Homework #3 Chapter 5 and 6 Review Questions 1 Chapter 5: The Link Layer P26. Let's consider the operation of a learning switch in the context of a network in which 6 nodes labeled

More information

Lecture 17: 802.11 Wireless Networking"

Lecture 17: 802.11 Wireless Networking Lecture 17: 802.11 Wireless Networking" CSE 222A: Computer Communication Networks Alex C. Snoeren Thanks: Lili Qiu, Nitin Vaidya Lecture 17 Overview" Project discussion Intro to 802.11 WiFi Jigsaw discussion

More information

Solutions to Performance Problems in VoIP over 802.11 Wireless LAN 1

Solutions to Performance Problems in VoIP over 802.11 Wireless LAN 1 1 Solutions to Performance Problems in VoIP over 802.11 Wireless LAN 1 Wei Wang, Soung C. Liew Department of Information Engineering The Chinese University of Hong Kong Victor O. K. Li Department of Electrical

More information

International Journal of Advance Engineering and Research Development. QoS Analysis of VOIP Traffic over WiMAX

International Journal of Advance Engineering and Research Development. QoS Analysis of VOIP Traffic over WiMAX Scientific Journal of Impact Factor(SJIF): 3.134 International Journal of Advance Engineering and Research Development Volume 2,Issue 5, May -2015 QoS Analysis of VOIP Traffic over WiMAX Saira Banu 1,

More information

Responses by TG1 (2000-09-14) included

Responses by TG1 (2000-09-14) included 20 00-09-14 I EEE 802.16.1-00/04 Comparison between TG3 Functional Requirements Document and TG1 proposed MAC Prepared by TG3 (2000-09-14) Comments in black Responses by TG1 (2000-09-14) included Green

More information

QOS PROTECTION FOR IEEE 802.11E IN WLAN WITH SHARED EDCA AND DCF ACCESS

QOS PROTECTION FOR IEEE 802.11E IN WLAN WITH SHARED EDCA AND DCF ACCESS QOS PROTECTION FOR IEEE 802.11E IN WLAN WITH SHARED EDCA AND DCF ACCESS Jakub Majkowski, Ferran Casadevall Palacio Dept. of Signal Theory and Communications Universitat Politècnica de Catalunya (UPC) C/

More information

Gauging VoIP call quality from 802.11 WLAN resource usage

Gauging VoIP call quality from 802.11 WLAN resource usage Gauging VoIP call quality from 82.11 WLAN resource usage Miroslaw Narbutt and Mark Davis Communications Network Research Institute School of Electronic and Communications Engineering Dublin Institute of

More information

Transport Layer Protocols

Transport Layer Protocols Transport Layer Protocols Version. Transport layer performs two main tasks for the application layer by using the network layer. It provides end to end communication between two applications, and implements

More information

An Efficient Transmission Scheme for Short Message Service in IEEE 802.16 Systems

An Efficient Transmission Scheme for Short Message Service in IEEE 802.16 Systems An Efficient Transmission Scheme for Short Message Service in IEEE 802.16 Systems Sung-Min Oh* and Jae-Hyun Kim* *Ajou University, School of Electrical and Computer Engineering smallb01@ajou.ac.kr and

More information

Seamless Handover of Streamed Video over UDP between Wireless LANs

Seamless Handover of Streamed Video over UDP between Wireless LANs Seamless Handover of Streamed Video over UDP between Wireless LANs Ger Cunningham, Seán Murphy, Liam Murphy Department of Computer Science University College Dublin Dublin, Ireland {ger.munningham,liam.murphy@ucd.ie,

More information

Rohit Sharma SUSCET, Tangori, Mohali, Punjab, India

Rohit Sharma SUSCET, Tangori, Mohali, Punjab, India ISSN : 2229-4333(Print) ISSN : 976-8491(Online) Simulator to Analyze QoS for /a/g standards Rohit Sharma SUSCET, Tangori, Mohali, Punjab, India E-mail : rohit9299@yahoo.com IJCST Vo l. 1, Is s u e 2, De

More information

Wireless Mesh Networks Impact on Voice over Internet Protocol. Mohammad Tariq Meeran PhD Student Institute of Informatics, Tallinn University

Wireless Mesh Networks Impact on Voice over Internet Protocol. Mohammad Tariq Meeran PhD Student Institute of Informatics, Tallinn University Wireless Mesh Networks Impact on Voice over Internet Protocol Mohammad Tariq Meeran PhD Student Institute of Informatics, Tallinn University Email: meeran@tlu.ee February 2014 What is wireless mesh networks?

More information

... neither PCF nor CA used in practice

... neither PCF nor CA used in practice IEEE 802.11 MAC CSMA/CA with exponential backoff almost like CSMA/CD drop CD CSMA with explicit ACK frame added optional feature: CA (collision avoidance) Two modes for MAC operation: Distributed coordination

More information

An Overview of Wireless LAN Standards IEEE 802.11 and IEEE 802.11e

An Overview of Wireless LAN Standards IEEE 802.11 and IEEE 802.11e An Overview of Wireless LAN Standards IEEE 802.11 and IEEE 802.11e Jahanzeb Farooq, Bilal Rauf Department of Computing Science Umeå University Sweden Jahanzeb Farooq, 2006 (tipputhegreat@hotmail.com) Chapter

More information

Aggregation of VoIP Streams in a 3G Mobile Network: A Teletraffic Perspective

Aggregation of VoIP Streams in a 3G Mobile Network: A Teletraffic Perspective Aggregation of VoIP Streams in a 3G Mobile Network: A Teletraffic Perspective Olufemi Komolafe Agilent Laboratories, South Queensferry, EH30 9TG, UK, o.komolafe@ieee.org Robert Gardner Agilent Laboratories,

More information

Mobile Communications Exercise: Satellite Systems and Wireless LANs. Georg von Zengen, IBR, TU Braunschweig, www.ibr.cs.tu-bs.de

Mobile Communications Exercise: Satellite Systems and Wireless LANs. Georg von Zengen, IBR, TU Braunschweig, www.ibr.cs.tu-bs.de Mobile Communications Exercise: Satellite Systems and Wireless LANs N 1 Please define the terms inclination and elevation using the following two figures. How do these parameters influence the usefulness

More information

Performance analysis and simulation in wireless mesh networks

Performance analysis and simulation in wireless mesh networks Performance analysis and simulation in wireless mesh networks Roberto Cusani, Tiziano Inzerilli, Giacomo Di Stasio University of Rome Sapienza INFOCOM Dept. Via Eudossiana 8, 84 Rome, Italy Abstract Wireless

More information

VOIP on Wireless LAN: A Comprehensive Review

VOIP on Wireless LAN: A Comprehensive Review VOIP on Wireless LAN: A Comprehensive Review Sana Munir [1], Imran Ahmad [2] [1] Center for Advanced Studies in Engineering,Islamabad, PAKISTAN [2] NWFP University Of Engineering and Technology, Peshawar,

More information

ALL-IP CELLULAR NETWORK ARCHITECTURE FOR EFFICIENT RESOURCE MANAGEMENT

ALL-IP CELLULAR NETWORK ARCHITECTURE FOR EFFICIENT RESOURCE MANAGEMENT ALL-IP CELLULAR NETWORK ARCHITECTURE FOR EFFICIENT RESOURCE MANAGEMENT Young-June Choi, Kwang Bok Lee and Saewoong Bahk School of Electrical Engineering and Computer Science, INMC Seoul National University

More information

802.11 standard. Acknowledgement: Slides borrowed from Richard Y. Yang @ Yale

802.11 standard. Acknowledgement: Slides borrowed from Richard Y. Yang @ Yale 802.11 standard Acknowledgement: Slides borrowed from Richard Y. Yang @ Yale IEEE 802.11 Requirements Design for small coverage (e.g. office, home) Low/no mobility High data-rate applications Ability to

More information

ANALYSIS OF LONG DISTANCE 3-WAY CONFERENCE CALLING WITH VOIP

ANALYSIS OF LONG DISTANCE 3-WAY CONFERENCE CALLING WITH VOIP ENSC 427: Communication Networks ANALYSIS OF LONG DISTANCE 3-WAY CONFERENCE CALLING WITH VOIP Spring 2010 Final Project Group #6: Gurpal Singh Sandhu Sasan Naderi Claret Ramos (gss7@sfu.ca) (sna14@sfu.ca)

More information

Video Transmission over Wireless LAN. Hang Liu Hang.liu@thomson.net

Video Transmission over Wireless LAN. Hang Liu Hang.liu@thomson.net Video Transmission over Wireless LAN Hang Liu Hang.liu@thomson.net Page 1 Introduction! Introduction! Wi-Fi Multimedia and IEEE 802.11e for QoS Enhancement! Error Control Techniques Page 2 Introduction!

More information

Voice Service Support over Cognitive Radio Networks

Voice Service Support over Cognitive Radio Networks Voice Service Support over Cognitive Radio Networks Ping Wang, Dusit Niyato, and Hai Jiang Centre For Multimedia And Network Technology (CeMNeT), School of Computer Engineering, Nanyang Technological University,

More information

Performance Evaluation of Wired and Wireless Local Area Networks

Performance Evaluation of Wired and Wireless Local Area Networks International Journal of Engineering Research and Development ISSN: 2278-067X, Volume 1, Issue 11 (July 2012), PP.43-48 www.ijerd.com Performance Evaluation of Wired and Wireless Local Area Networks Prof.

More information

Wi-Fi Capacity Analysis for 802.11ac and 802.11n: Theory & Practice

Wi-Fi Capacity Analysis for 802.11ac and 802.11n: Theory & Practice Wi-Fi Capacity Analysis for 802.11ac and 802.11n: Theory & Practice By Timo Vanhatupa, Ph.D. Senior Research Scientist at Ekahau Contents Introduction Why capacity matters with Wi-Fi... 3 Part 1: Modeling

More information

CS6956: Wireless and Mobile Networks Lecture Notes: 2/11/2015. IEEE 802.11 Wireless Local Area Networks (WLANs)

CS6956: Wireless and Mobile Networks Lecture Notes: 2/11/2015. IEEE 802.11 Wireless Local Area Networks (WLANs) CS6956: Wireless and Mobile Networks Lecture Notes: //05 IEEE 80. Wireless Local Area Networks (WLANs) CSMA/CD Carrier Sense Multi Access/Collision Detection detects collision and retransmits, no acknowledgement,

More information

Analysis and Simulation of VoIP LAN vs. WAN WLAN vs. WWAN

Analysis and Simulation of VoIP LAN vs. WAN WLAN vs. WWAN ENSC 427 Communication Networks Final Project Report Spring 2014 Analysis and Simulation of VoIP Team #: 2 Kadkhodayan Anita (akadkhod@sfu.ca, 301129632) Majdi Yalda (ymajdi@sfu.ca, 301137361) Namvar Darya

More information

EETS 8316 Wireless Networks Fall 2013

EETS 8316 Wireless Networks Fall 2013 EETS 8316 Wireless Networks Fall 2013 Lecture: WiFi Discovery, Powersave, and Beaconing http://lyle.smu.edu/~skangude/eets8316.html Shantanu Kangude skangude@lyle.smu.edu Discovery and Beaconing Discovery?

More information