CHAPTER 2 LITERATURE SURVEY

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1 CHAPTER 2 LITERATURE SURVEY 2.1 CURRENT STATUS OF RESEARCH 3G communication in mobile computing is a prominent area of research in today s scenario. It has gained significant impetus in the area of mobile communication to transfer multimedia data at very high speed without any delay and loss in data transfer. The researchers have been constantly working on various aspects of mobile communication like congestion control, QoS, routing, flow control, energy efficiency, security etc. with a lot more to be done in the major fields of congestion control in networks. The work done by various researchers in the field of congestion control and QoS have been summarized below:- 3G TS : UTRAN Overall Description [1] UMTS is 3GPP project. Fig. 2.1 depicts the basic architecture of universal mobile telecommunication system. Fig. 2.1 UMTS Architecture

2 LITERATURE SURVEY 60 Fig. 2.1 shown as main parts of UMTS architecture. Core network is connected to UTRAN wit Iu interface and UTRAN is connected to user equipment with Uu interface. UMTS is consists with core network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and user equipment (UE). The core network is connected with UTRAN via. Iu interface and UTRAN is connected with user equipment via Uu interface. Fig. 2.2 UTRAN Architecture UMTS Terrestrial Radio Access Network is main part of universal mobile telecommunication system network. UTRAN consists with a number of Radio network subsystem (RNS). These RNS is consists with radio network controller (RNC) and base station (Node B). RNC is connected with node B via Iub interface and RNC is connected with other RNC via Iur interface. Node B is directly connected to user equipment through wireless channel. Fig. 2.2 shows UTRAN architecture. A modification of TCP flow control for improving end to end TCP performance over networks with wireless links [2] TCP is end to end Transmission Control Protocol (TCP) and performance of TCP is one of the main significant matters in wireless networks. This paper performs the

3 LITERATURE SURVEY 61 improvement of end to end TCP performance via a TCP-aware link layer protocol known as Adaptive TCP (A-TCP). In this Adaptive TCP A-TCP agent is present. This A-TCP Agent is situated in each base station and presents a mobile host as it has a wired link with the base station. It means it work as a virtual host model. To implement virtual host model, the A-TCP agent provides three functions that are local retransmission, sender freezing and A-TCP flow control. A Survey on Congestion Control for Mobile Ad-Hoc Networks [3] Congestion control is major problem in MANETs (mobile ad-hoc networks). Various TCP congestion control mechanism is not efficient to maintain the specific properties of a shared wireless multihop channel as well. Wireless network have the properties of frequent changes in the network topology and its shared nature of the wireless channel that cause important challenges in wireless networks. Various research works proposed to reduce these challenges and difficulties in the wireless networks. This paper, perform an overview over existing proposals and explain various congestion control methods that uses in MANETs. Survey is performed to check the performance of various congestion control algorithms on different networks. Various networks play an important role in communication like Wi-Fi, WiMaX, UMTS, and WLAN etc. So which congestion control is performs better in all of these networks is checked. Congestion control is necessary for provide a smoother transfer of data from one node to another node. In mobile ad hoc networks congestion control is a major problem. In wireless communication, standard TCP congestion control protocol is unable to work with the wireless related losses such as wireless channel fading. In wireless scenarios frequent changes in the network topology can occur and the wireless channel is in shared nature that poses major challenges. Various modifications have been proposed to reduce these challenges.

4 LITERATURE SURVEY 62 Performance of Transport Protocols in Wireless Networks [4] This paper performs a survey of research on wireless network s transport protocols. This paper first reviews the proposals that improve transmission control protocol performance in wireless network and then perform a categorization of transport protocols in ad hoc networks. Transmission control protocol, as a standard transport protocol for internet, is performed well for wired network and works poorly in wireless networks. Transport protocol as a necessary part of the whole protocol hierarchy offers end to end communication between multiple communication hosts. In wired network TCP performs better because it is reliable and connection oriented protocol. But in wireless network is the TCP performs best or some wireless losses degrade the performance of TCP. As the area of wireless networks is increase and it indicates that wireless links are important in future internetworks. In whole protocol stack transport protocol as an important part. Transport protocol provides end to end communication between two or more communication hosts. A network is the collection of the devices and other communicating devices (computer, mobiles PDA s). Connect by the communicating channels capable to sharing information and others resources among themselves. As per requirement of the network all the services are used as the in the small network peer to peer connection required but in the large network Wide area network is used. TCP Performance Enhancement for UMTS Access Network [5] This paper maximizes the TCP performance over UMTS access network. UMTS network sends and receive multimedia data and it is affected by large delay bandwidth product. The main cause for the delay is the diversity technique at physical layer and latency from the link layer ARQ retransmissions. In between UMTS access network and Internet this paper proposes to place a split transmission control protocol proxy at gateway GPRS support nodes. Bandwidth delay product divides into two parts by the split proxy. Due to this splitting, two transmission control protocol connections with smaller bandwidth delay products generated and it reduces the delay in the network. Simulation results

5 LITERATURE SURVEY 63 depict that, the transmission control protocol performance under high bit rate DCH channel scenario (e.g.256 kbps) significantly improves by the split TCP proxy. This paper shows that how the performance of TCP is optimized in wireless scenario especially in UMTS network. Improving TCP Performance over Mobile Networks [6] This paper shows how transmission control protocol (TCP) is well work with the packet losses in wired networks. The Packet losses in wired networks are mainly due to congestion in the network. By this the packets drop at any node in the network. It then defines mobility and the problems related with it. Regular TCP is not appropriate for mobile hosts and their wireless links by providing simulation results that demonstrate the effect of the high bit error rates of the wireless link on TCP performance. Problems developed by the mobility of hosts using a graph tracing packets between fixed and mobile hosts. This paper presents a survey of the research done to increase the performance of TCP over mobile wireless networks. Recently mobile ad hoc networks are more popular, it is the wireless network that is operate with any fixed infrastructure. A mobile ad hoc network is the vendor of mobile system forming an ad hoc network without any centralized structure. It is new art of network there all the node are the movable and not the cost effective. The popular IEEE and 802.1X protocols are introduced for the infrastructure-less network. IEEE WI-FI protocol is able to provide ad hoc network facility of low level, when there is no any access point is available. So here nodes are limited to send and receive data but don t route to anyone across the network. MANET s is an IEEE framework. It is the connected collection of wireless nodes where there is no any networking infrastructure in the form of the base station. In this network every node can act as a router. It provides the router of the other node. If here a node wants to share some data or information but the destination node not in the range of the source node so here other nodes are act as the router for the short time.

6 LITERATURE SURVEY 64 In Figure 2.3 show the mobile ad hoc network architecture in figure all the nodes are shared all data and information within the network range, in network mobile nodes may contains mobile phones, laptops and PDA s etc. Fig. 2.3 Mobile AdHoc Network (MANET) Transmission Control Protocol (TCP) is the most extensively used transport protocol for Internet. For future internetworks the mobile computers and their wireless communication links are important part of research. For wired circuits regular TCP is properly worked for packet loss. But for wireless links TCP not perform well. Mobility effects also discus in wireless scenario. Fig. 2.4 shows the network topology for mobility

7 LITERATURE SURVEY 65 Fig. 2.4 Network Topology This paper examines that how the performance of TCP can enhance in mobile networks because the TCP is most reliable and connection oriented protocol and it is the basic of communication model. VEGAS: Better Performance than Other TCP Congestion Control Algorithms on MANETs [7] This paper analyzed six different flavors of TCP Congestion Control Algorithms. Further this paper checked their performance i.e. congestion loss, packet delay on Mobile Ad-hoc Networks (MANET). This paper also shows the performance behavior of BIC, Cubic, TCP Compound, Vegas, Reno and Westwood congestion control algorithms. The evaluation of various TCP congestion algorithms is simulated through Network Simulator (NS2). The performance of these congestion control algorithms is analyzed with suitable metrics. This paper examines various TCP flavors that are present for wireless networks and checked which flavor is most suitable for MANETs. There is no any preexisting network in the mobile ad hoc network. The main challenge in the mobile ad hoc network is the design topology, architecture. Mobile ad hoc network is without ant centralized control in the network every node have own control and configure itself when any one node change the network topology or data transmission scenario. This is the dynamic change for the system scalability and performance. Mobile ad hoc network nodes are contains wireless transmitters and receivers using antennas, which may be highly directional, Omni directional or some other antennas. At given time the information transmits and receives coverage patterns, communication power level and co

8 LITERATURE SURVEY 66 channel interface level, a wireless connectivity in the form of random nodes graph of ad hoc network exist among the nodes. TCP provide flow and congestion control for reliable data transmission. In MANETs the mobile nodes are moved in unconstrained manner. TCP is not able to check network congestion or link down in network to initiate related congestion controls on the Mobile Ad-hoc Networks. The standard congestion control mechanisms of the TCP are unable to maintain the specific properties of a shared wireless multihop channel well. So the common changes of the network topology in MANETs and the shared nature of the wireless channel generate some critical issues. TCP over 2.5G and 3G wireless networks [8] TCP is used to transmit internet traffic. Different internet services i.e. www web browsing, electronic mail, and FTP are execute over TCP protocol. Mobile Internet also provides some existing applications and, consequently, TCP protocol also. In TCP flow control and retransmission mechanisms are the main problems over wireless interfaces. These problems develop mainly because the basic TCP suppose that all packet losses are due to network congestion, not by bit errors. When this assumption is joined with the rough flow control scheme of TCP, the performance of TCP transmissions over wireless networks can be sternly degraded. Fortunately, a number of TCP optimization methods are exists that can be used to improve the situation. In TCP, flow control and retransmission mechanisms, are the major problems over wireless links. These problems arise because the basic TCP mechanism shows that packet loss is performed due to network congestion, not by the bit errors. Due to these network situations the performance of wireless networks are sternly degraded. To reduce this congestion and optimize the performance of wireless network a number of TCP optimization methods can be used. There are various issues by using 2.5 generation and 3 generation wireless networks. These are as follows.

9 LITERATURE SURVEY 67 (1) High bit error rate TCP shows that all packet loss is performed due to the network congestion but not by the bit error rate in wired networks because in wired networks bit error is not a common measure. However, the wireless networks bit error rate (BER) is high because wireless transmission is unreliable due to interference from the environment. (2) Mobility Mobility is the impotent aspect in wireless communication. Wireless hosts frequently move while perform communication with each other. (3) Narrow bandwidth In wireless networks bandwidth is a limited resource. For 3G standards maximum bandwidth for circuit switching is 2M bits/s and it is used only in indoor. The bit rate for outdoor is around 384K bits/s. In wireless networks variation in the bandwidth is high. TCP OPTIMIZATION METHODS Parameter Optimization 1) MTU size MTU (Maximum Transfer Unit) is link layer parameters. The greater MTU permits TCP to increase the congestion window faster, because the window is counted in unit of segments. 2) Path MTU discovery Path MTU discovery permits a sender to determine the maximum end to end transmission unit for a certain routing path. 3) Advertised window size If the advertised window value is large, the sender might send many segments at once. That situation causing overflows in the last element before the slow link. TCP throughput is decreased by Packet losses. So the mobile receiver should not advertise a too large window if the wireless link is thin. But it is not always clear that, what will be the offered bandwidth of a wireless connection.

10 LITERATURE SURVEY 68 Flow related methods 1) Fast TCP In Fast-TCP mechanism when flow of acknowledgement is controlled then it can indirectly affect the dynamics of TCP behavior. Therefore, when at the forward path of the router the congestion is detected, the backward ACKs will be waiting so it reduce the congestion quickly and enhance the TCP throughput. Fig. 2.5 shows the fast TCP mechanism. Fig. 2.5 Fast TCP Mechanism 2) Window pacing, In the window pacing modification is performed in the advertised window of TCP acknowledgments if a network element gets congested. 3) Random early detection (RED), In RED algorithm, packets are dropped before it gets really congested. In RED average queue length is calculated. If the average queue length is greater that a maximum threshold, all incoming packets are dropped and if the average queue length is below a minimum threshold, all incoming packets are accepted. End system modifications 1) Early Congestion Notification (ECN) In ECN routers detect the congestion before the queue overflows. There is no limit to drop the packets if congestion occurs in network. If the congestion occurs in network

11 LITERATURE SURVEY 69 then routers set a Congestion Experienced (CE) bit in the header of packets. When the receiver receives the packet with a CE bit in header, it will send the notification in backward packet. By this notification sender minimize the current window and reduces the transmission rate, so the congestion should be minimize. 2) Selective Acknowledgment (SACK) When multiple packets are dropped from one window of data TCP may get poor performance. SACK improves the TCP efficiency when a number of packets are lost. By selective acknowledgments, the sender informed about the received segments successfully at receiver. So that the sender may only transmits the lost segments. In wireless environment SACK TCP is really useful where packets lost not only perform by congestion but also by transmission errors. 3) Increasing TCP's initial window RFC 2414 describes an upper bound of initial congestion window that is 4380 bytes is specified. This shows a change from RFC RFC 2001 shows that the congestion window must be initialized to only one segment. In the new RFC, at the beginning of the connection up to four segments can be sent. Snoop method Snoop method is similar with Split TCP methods. Since it does not break the TCP connection, it is an improvement over Split TCP because end to end semantics is preserved. In snoop method base station contain a snoop module and it looks every packet on all TCP connections. TCP Performance Enhancement over UMTS Network with RNC Feedback [9] In today s scenarios more and more users use the internet services. Traditional applications that is offered by World Wide Web is electronic mail and file transfer protocol (FTP) but many network users try to develop some new applications, such as video conference, tele-education, video on demand (VoD) and video telephone on the Internet. A best-effort network like internet gets congested under high network load. If the congestion occurs in the network, use of network resources is not being optimized. It

12 LITERATURE SURVEY 70 is also possible that when the network is congested, further any transmitted packets would be lost because of less network resources such as the buffer spaces at the routers. How a TCP sender control its sending rate. Both side of TCP connection consists of a send buffer, a receive buffer and several variables, such as RcvWindow, LastByteRead and so on. Each side of a connection TCP congestion control contains an extra variable, the congestion window (CWND). According to the congestion window size the sending rate of a sender is decided in the network. At the sender the amount of unacknowledged data may not exceed the minimum of CWND and RcvWND (receiver window). LastByteSent LastByteAcked MIN (CWND, RcvWND) TCP manages the rate of transmission of the packets and also the congestion occurrence in the network. The TCP throughput is as TCP Throughput = (W * MSS)/RTT Three major components of TCP congestion algorithm are: additive slow-start, increase and multiplicative decrease and reaction to timeout events. Slow Start When a new TCP connection is established, the CWND is initialized to 1 MSS and slowstart threshold (SSTHRESH). CWND= CWND+ MSS The exponential growth continues until loss events not occur. When loss event occur CWND is cut in half. Additive-Increase, Multiplicative-Decrease When congestion is not present in end-to-end path TCP sender additively increases its sending rate but when it detect packet loss in path or congestion in the path it multiplicatively decreases its sending rate. So TCP congestion control is often called as an additive-increase, multiplicative-decrease (AIMD) [CHIU D. M & JAIN R, 1989].

13 LITERATURE SURVEY 71 CWND= CWND+ MSS (MSS/CWND) Congestion avoidance (CA) is the linear increase phase of TCP s congestion control protocol. Fig. 2.6 shows the Additive-Increase, Multiplicative-Decrease. Fig. 2.6 TCP Additive Increase and Multiplicative Decrease Congestion Control Reaction to Timeout Events After a certain amount of time if an acknowledgement (ACK) is not received for a given segment, this time is known as retransmission time out (RTO) value. When a time out event occurs, a TCP sender switches to slow-start phase. TCP sender sets the CWND to one MSS and then increases the congestion window exponentially until CWND reaches SSTHRESH. Congestion avoidance phase is starts when CWND reaches to SSTHRESH, during this CA CWND moves linearly. Initial value of congestion window is equals 1MSS, initial value of SSTHRESH is large, i.e 64 Kbyes, and TCP sender begins in slow stat state, figure 2.7 shows slow start and congestion avoidance followed by a timeout.

14 LITERATURE SURVEY 72 Fig.2.7 TCP Congestion Control The TCP provide reliable and in order packet delivery. All major types of TCP uses congestion control algorithm. But the implementation of the fast retransmit and recovery mechanism is a different approach. This paper presents such a mechanism that notifies the TCP sender of any non congestion related losses by introducing a proxy at the RNC node of the universal mobile telecommunication system network. Only a minimum modification to the standard transmission control protocol is needed to achieve this. OPNET simulator is used in this study and the simulation results depicts that the proposed scheme significantly improves the TCP performance.

15 LITERATURE SURVEY 73 TCP Congestion Control over 3G Communication Systems: an Experimental Evaluation of New Reno, BIC and Westwood+ [10] In packet switched networks, main work of TCP is to react and evade network congestion. An extensive literature is exists, that concern with the behavior of congestion control algorithms. In various scenarios multiple congestion control algorithms have been suggested to increase the performances in specific scenarios. This research paper mainly focuses on the UMTS wireless scenario. Various measurements perform using three different TCP stacks. Congestion control algorithm standardized by IETF. Default congestion control algorithm that is adopted by the Linux operating system is TCP BIC and for Linux kernel TCP Westwood+ is also available. To increase the performance of wireless networks multiple congestion control algorithms is available. As the increasing nature of wireless network as per the need of users to use and deploy new network applications such as voice conferencing, video conferencing VoIP and all, it is important to check that which transmission control protocols is best for control the congestion. In variety of 3G networks the UMTS network provides wide area Internet wireless access with a high downlink speeds up to 384 kbps. UMTS is very much suitable for multimedia data and for Voice over IP (VoIP) applications. When lossy links are present in the routing path the efficiency of TCP as a transport protocol reduces. Radio Link Control (RLC) protocol in UMTS masks the lossy channel to its upper layers by using retransmissions. TCP Congestion Control Algorithms Performance in 3G networks with moving client [18] This article focuses on improving performance of the TCP/IP connection in specific condition - connection between the data server and client downloading data, using mobile (cellular) network as an Internet connection method, while driving. A way to affect mechanisms of transport layer, and achieve better performance, is method described as changing TCP s Congestion Control Algorithm (CCA), which is responsible for congestion window behaviour. Today s TCP flavours are presented. For experimental

16 LITERATURE SURVEY 74 research, topology is created, and test scenarios are being discussed. Methodology and tools are presented, as well as comparison of different CCA performance in realized test runs. Presented research leads to conclusion there is a field of study on cwnd behavior in 3G networks while using a family of congestion control algorithms designed for fast networks, since those get better results than CCAs designed for wireless networks. Performance Evaluation of TCP Tahoe, Reno, Reno with SACK, and NewReno Using OPNET Modeler [22] This paper shows the simulation of four TCP flavors Reno, Tahoe, New Reno and Reno with Selective Acknowledgment (SACK) by using OPNET Modeler, in several wireless and wired networks. By observing file download response time, congestion window size, goodput and throughput, this paper analyzes congestion window maintenance and recovery process for each TCP algorithm. In wireless networks with fading, signal attenuation and multipath, TCP Reno has shorter file download response time, larger congestion window size,, and higher goodput and throughput, than the remaining three TCP algorithms. In case of wired networks, TCP Reno with SACK shows the best overall performance. This paper, examine the performance of the different Transmission Control Protocol algorithms over wireless links with their packet losses. Various scenarios are created to check the performance of various TCP flavors in the network. For such a scenario, paper show that the performance of New Reno is of inferior quality than the performance of TCP Tahoe in many situations and even old Tahoe in a few situations. This is because the fast recovery method of New Reno is not efficient. Performance Evaluation of the Radio Link Control Protocol in 3G UMTS [23] Since today s data traffic is mainly based on Transmission Control/Internet Protocol (TCP/IP) suite. To support reliable upper layer protocols such as TCP, Universal mobile telecommunication system networks have employed a Radio Link Control protocol. For performing partial error recovery at the link layer Radio Link Control employs

17 LITERATURE SURVEY 75 sophisticated retransmission schemes, thus it is hiding transmission errors from upper layers. For every segment loss TCP will treat it as a notification of congestion. The above mentioned technique can diminish the possibilities of a wrong invocation of the TCP congestion control mechanism, which results in performance degradation. IP Traffic Control on UMTS Terminal Equipment [24] The paper shows the architecture of universal mobile telecommunication system terminal equipment. It is optimized for IP based communications and explains the traffic control mechanisms needed to support the developing 3G services. This paper depicts some results of the research work done in the European IST project Advanced Radio Resource Management for Wireless Services (ARROWS). This research project intends to provide Quality of Service (QoS) management solutions and advanced Radio Resource Management (RRM) for the support of integrated services within the context of Universal Terrestrial Radio Access (UTRA). The research project addresses asymmetrical traffic, multimedia services and packet access all based on IP. Optimization of Application QoS Protocols for 3G/4G Mobile Networks [25] In third generation and fourth generation mobile network, one of the central issues is to design and analyze the importance of Quality of Service provisioning. In terms of equipment design, available network resources, and Quality of Service performances, mobile multimedia applications have high demands. The range of new applications i.e. high definition video telephony, TV program distribution, medical applications, teleengineering, location based services etc. installed in mobile networks. Number of research activities in this area has been oriented to the network, different areas of system, middleware support for Quality of Service and transport. On the other side, for implementing an overall adaptive application Quality of Service support there is a lack of proposed architectures and protocols. To obtain optimal Quality of Service performance there is a need to create an adaptive application Quality of Service protocol suit. This is the challenging task for research activities.

18 LITERATURE SURVEY 76 Mobility Management: From GPRS to UMTS [26] This paper shows mobility management for the third generation (3G) mobile networks. This paper focuses the growth from General Packet Radio Service (GPRS) to Universal Mobile Telecommunication System (UMTS). In this development, the radio access network UTRAN has been commenced and radio-related management function is shifted from the core network to UTRAN. Mobility management is needed when user move from one area to another. Due to this mobility, it is checked that the call drop rate is minimize and effective handover of call from one cell to another is processed. Simulation-based study of TCP flow control mechanisms using OPNET Modeler [30] This paper gives an overview of TCP flow control mechanisms. Various TCP flow control mechanisms are used to control the flow of data in the network. For different TCP flavors, algorithms like Slow Start, Congestion Avoidance, Fast Retransmit and Fast Recovery are the basics of congestion control. Tahoe, Reno and New Reno are various TCP flavors that use by these congestion control algorithms. Simulation based comparisons of Tahoe, Reno, and SACK TCP [31] This paper performs the simulations to investigate the advantages of adding selective repeat and selective acknowledgments (SACK) to TCP. This paper makes a comparison in between TCP Tahoe and Reno TCP. These are the two major known reference implementations for transmission control protocol, with two modified versions of Rent TCP. The first version is New Rent TCP. Rent TCP is a modified version of transmission control protocol without SACK that avoids some of Rent TCP's performance problems when multiple packets are dropped from a window of data. The second version is SACK TCP, a conservative extension of Rent TCP modified to use the SACK option being proposed in the Internet Engineering Task Force (IETF).

19 LITERATURE SURVEY 77 Modeling wireless links for transport protocols [32] This paper assesses simulation models for WLAN, satellite links and cellular utilized to propose the design of transport protocols. This paper also considers the communication between transport and wireless links. This paper shows the evaluation and design of transport protocols. The design of transport protocols can be enhanced by using simply obtainable wireless links models. UMTS access network architecture for multimedia services [33] This paper shows scheduling mechanism. This scheduling mechanism is presented within proposed universal mobile telecommunication system access network architecture, employed to done quality of service experiment. Wide band code division multiple access is the most important candidate for the air interface technology of universal mobile telecommunication system, which will comprise both a terrestrial part (T-UMTS) and a satellite part (S-UMTS). In WCDMA, to provide quality of service provisioning for multimedia traffic dynamic resource scheduling is proposed as a framework. Performance Analysis for GPRS with Prioritized and Non-Prioritized Mobility Management Procedures [34] In the evolution of 3G network general packet radio service is the part of this evolution. This research paper examines the effect of user mobility on packet transmission in general packet radio service. To study the end to end behavior of data transmission a simulator was developed among a mobile client and a fixed server through general packet radio service and internet. Impact of hybrid queuing disciplines on the VoIP traffic delay [36] The paper shows various queuing disciplines and their effect on the VoIP traffic delay within the network. Three queuing methods are used to perform network simulation that are custom queuing (CQ) with CBWFQ, priority queuing (PQ) with class-based weighted fair queuing (CBWFQ) and weighted fair queuing (WFQ) with CBWFQ. The comparison

20 LITERATURE SURVEY 78 is performed between each hybrid method with basic method. Fig.2.8 shows the weighted fair queuing.. Fig.2.8 Weighted fair queuing For example, the custom queuing method is compared with the CQ-CBWFQ method, and so on. OPNET Modeler simulation tool is used to test all the hybrid queuing disciplines. The simulation shows that how various queuing combinations affect VoIP traffic quality, with regard to Ethernet jitter and delay. Fig.2.9 shows the hybrid queuing discipline. Fig.2.9 Hybrid Queuing Discipline The paper presents shows various queuing methods and their impact on the multimedia data regarding delay and jitter within the network. Queuing methods is used to increase the performance of the network and to reduce the delay. Number of queuing algorithms is such that priority queuing (PQ) with class-based weighted fair queuing (CBWFQ), custom queuing (CQ) with CBWFQ and weighted fair queuing (WFQ) with CBWFQ in wired networks used to minimize the delay and jitter in wired network.

21 LITERATURE SURVEY 79 Comparative Analysis of Scheduling Algorithms for UMTS Traffic in Case of DiffServ Network Congestion [37] For providing end to end Quality of Service (QoS) interworking between Universal Mobile Telecommunication System (UMTS) and other external networks is important and critical. To provide the QoS in all-ip mobile networks, especially in broadband multimedia services, Differentiated Services (DiffServ) technology used in UMTS network. Fig.2.10 UMTS Network architecture for QoS conceptual model Low Latency Queuing (LLQ) scheduler is proposed in this paper. The main aim of the research paper is to provide mapping of voice and video telephony in two different QoS classes and virtual queues. Fig depicts the universal mobile telecommunication system network architecture for QoS conceptual model. Ubiquitous Wireless Connectivity across Cellular and Wireless Local Area Networks [38] This paper recommends an end to end mobility management solution. While going across such heterogeneous access networks this solution enables mobile users to sustain

22 LITERATURE SURVEY 80 seamless connectivity. By using of mobile devices that is equipped with dual network interfaces, continuous network connectivity is obtained. Capability to switch data transmission among these interfaces depends upon the accessibility of the network. This paper present and discuss the design of such a dual- mode radio access device and intend a simple inter-technology handoff technique. Various simulation experiments are performed on OPNET simulator. Performance Evaluation of Queuing Disciplines for Multi-Class Traffic Using OPNET Simulator [39] Various queuing disciplines is implemented in a hypothetical network topology. Multiclass traffic is flow in the network routers. Various queuing disciplines such as first in first out (FIFO), Priority queuing (PQ), weighted fair queuing (WFQ) and deficit weighted round robin (DWRR) is implemented for multi-class traffic. Finally analyze the performance of all queuing disciplines using a simulation tool OPNET. In today s scenario a rapid growth of network and internetworking is increasing exponentially. Various services are needed as per the user demands are also appears on the screen. Various network parameters are used to evaluate the network performance and it is needed in various parts of the network as per the applications. Some applications are delay sensitive while other are not. In real time applications delay is an important parameter rather than throughput but there are some applications where delay is not an important parameter, these applications are more concern about throughput. A number of queuing disciplines are proposed to guarantee fairness among various competing requests at a service point and get best performance. FCFS, Round Robin, Priority Queues, Fair Queuing, WFQ, WRR, DWRR etc. There are number of queuing disciplines that perform best. This paper shows a hypothetical network topology based on multi class traffic approach. These queuing approaches used to reduce delay and jitter in network.

23 LITERATURE SURVEY 81 Evaluation and Comparison of Soft and Hard Handovers in Universal Mobile Telecommunication (UMTS) Networks [40] This paper focused on soft and hard handover techniques in UMTS networks and conducted a comparison among soft and hard handover s performance. The project divided into two scenarios: soft handover and hard handover. Soft handover produces better results in terms of uplink transmission power and enables the mobiles to perform the handover at lower power levels. Soft handover benefit from a concept called "soft handover gain" and the network can lower the quality block error ratio (BLER) below the requested level, then the transmission power can be kept at lower levels during soft handover while still providing the same quality to higher layer. HSUPA Transport Network Congestion Control [41] This paper suggests a high speed up link packet access transport network flow control algorithm that works with congestion conditions in network proficiently and supports QoS differentiation. Transport network congestion is detected in the Radio Network Controller (RNC). About transport network congestion, radio network controller notifies the base station by relying on the standardized control frame. In case of transport network congestion, base station part of the high speed up link packet access flow control instructs the air interface scheduler to decrease the bitrate of the flow to remove congestion. The performance analysis give attention to transport network limited scenarios. An overview and comparison of analytical TCP models [42] This paper presented an overview of TCP dynamics and modeling environment and it surveyed a number of analytical models compared the models with respect to assumptions, approaches, and validation methods. Number of TCP models is compared and performance is checked for getting best model in all.

24 LITERATURE SURVEY 82 UMTS-to-IP QoS Mapping for Voice and Video Telephony Services [43] It is crucial to maintain mapping of Quality of service between UMTS services and IP transport to maintain end-to-end delay for UMTS technology. These two technologies are differ in QoS classifications so a straightforward mapping is not possible. The recent proposals within the 3GPP show unpredictable and undesirable performance for certain services. To provide guaranteed QoS for multimedia services, a number of QoS provisioning mechanisms is incorporated in UMTS technology. Integrated services (IntServ) and differentiated services (DiffServ) are used. Internet Engineering Task Force (IETF) introduced IntServ mechanism first. This IntServ mechanism is based on a per flow reservation by using Resource Reservation Protocol (RSVP). For an IP-based network six abstract QoS classes is used. That is from A to F, in which A class is being highest priority and F is lowest. In practice, this paper use a typical DiffServ architecture, and in this case the abstract quality of service classes can be implemented and matched to the different DiffServ classes (EF, AF1, AF2, AF3, AF4, and BE). For low-loss service and low-latency expedited forwarding (EF) class is used, and for relative QoS services assured forwarding (AF) classes are used. Modified Tahoe TCP for Wireless Networks Using OPNET Simulator [44] This paper performs a modification to the Transmission Control Protocol s Tahoe flavor that is used in Wireless networks. It explains that when TCP Tahoe algorithm is slightly modified, it can perform well to wireless links, while continuing its benefits on the wired networks at the same time. This is very advantageous feature as the conventional transmission control protocol in most cases opposes to the requirements of the wireless links of the network. This paper performs some modification in TCP Tahoe to increase the performance of wireless networks and reduces the delay in the network. By this enhancement the packet loss should be minimized and increase the efficiency of network.

25 LITERATURE SURVEY 83 Performance Evaluation of Quality of VoIP in WiMAX and UMTS [45] This paper performs simulation study to assess the quality of service performance of WiMAX and universal mobile telecommunication system network for maintaining VoIP traffic. Simulation modules are designed in OPNET for WiMAX and universal mobile telecommunication system network. Extensive simulations are taken out to evaluate and analyze different essential performance metrics such as end to end delay, MOS, packet delay variation and jitter. Simulation results depict that WiMAX scores better then the UMTS with a satisfactory margin and WiMAX is the good technology to support VoIP applications as compared with UMTS. Currently there is great use of WiMAX and universal mobile telecommunication system networks and the possible to integration of these two networks. So it is required to study their quality of service differences and plausible methods to determine the differences between their quality of service models. The focus of next generation wireless networks is to converge different Radio Access Technologies. There is increasing demand for voice and video applications over internet. So voice and video applications over IP networks are growing quickly. To provide the requirement of high quality of VoIP at any time and from anywhere, it is essential to design suitable quality of service model. UMTS simulation module Fig shows the UMTS simulation model. The UMTS simulation module mainly consists by User Equipment (UE), UMTS Terrestrial Radio Access Network (UTRAN) and Core Network (CN). Core network perform switching, routing and all network management functions. The UTRAN is consists by base station (Node B) and Radio Network Controller (RNC). User equipment can be laptop, desktop, mobile handset or any device that can connect to the UMTS network.

26 LITERATURE SURVEY 84 Fig.2.11 UMTS simulation Module Congestion Control in WCDMA with Respect to Different Service Classes [46] This paper discuss that during congestion, how different service classes can be differentiated. In 3G communication different multimedia classes is used to provide various services to users. This differentiation gives better quality of service provisioning for the multimedia users according to their service requirements. When choosing the best congestion indicator, it seems to effectively reduce the congestion and increase the quality of service. It also provides efficient utilization of the radio resources. User want a improved quality of service with minimize data loss and delay. Radio resource management functions are provided by two protocol layers that is radio resource control and medium access control layer in the Universal Mobile Telecommunications System (UMTS). RRC layer perform all the congestion control functions. So that to control the congestion strong interaction is required between the radio interface protocol layers. UTRAN consists by: a) WCDMA channel: UMTS uses the WCDMA for transmission of data.

27 LITERATURE SURVEY 85 b) UMTS Radio Access Bearers: UTRAN offer radio access bearers to provide data service. A bearer transport is offered between the core network and mobile equipment. To support the quality of service requirements these services configured in UTRAN very flexibly. Four quality of service classes are defined in UMTS that are: Conversational Class Streaming Class Interactive Class Background Class c) UTRAN Radio Interface Protocols : The UTRAN radio interface is layered in three protocol layers: Physical layer Data link layer Network layer The relationship is shown in Fig Fig.2.12 Radio Interface protocol configuration

28 LITERATURE SURVEY 86 End-to-end UMTS Network Performance Modeling [48] This paper represents detailed end to end simulation model of a UMTS network. This network was developed to contain network architecture, application traffic characteristics, protocol features, and network element details. The model has been used to identify system bottlenecks, evaluate architectural alternatives and validate performance requirements. The main conclusion is that end to end application-level performance must be designed in at all phases of the development process. This paper also describes a user plane simulation model of an end to end reference connection through a UMTS network. The tool models all protocol layers from the physical through the application layer and models details of the packet handling characteristics of each network element along the path. Congestion avoidance and control [54] This paper shows the basic idea for congestion avoidance and to control the congestion in the network. For this purpose various algorithms are used that is: (i) Round trip time variance estimation (ii) Exponential retransmit timer backoff (iii) Slow start (iv) More aggressive receiver acknowledgement policy (v) Dynamic window sizing on congestion (vi) Karn's clamped retransmit backoff (vii) Fast retransmit Analysis of TCP performance over mobile ad hoc networks [57] This paper examines the outcomes of link failure on TCP performance due to node mobility in ad-hoc networks. An intended and closed simulation performs and results obtained from these simulations show that when nodes move throughput of TCP reduces significantly.tcp is not able differentiate between link failure and congestion. Following fig shows the TCP flow control.

29 LITERATURE SURVEY 87 TCP Flow Control : Fig.2.13 TCP flow control TCP Round Trip Time and Timeout: Estimated RTT = (1-x) Estimated RTT + x Sample RTT This average is an exponential weighted moving average. There is an influence of given sample decreases exponentially fast. A typical value for x is Timeout = Estimated RTT + 4 Deviation Deviation = (1-x) Deviation + x Sample RTT Estimated RTT TCP packet control for wireless networks [58] This paper proposes various packet control algorithms. On intermediate routers packet control algorithms are deployed. These packet control algorithms increase the performance of TCP in wireless networks with long sudden packet delays and packet delay variations.

30 LITERATURE SURVEY 88 Modeling and Simulation of Queuing Scheduling Disciplines on Packet Delivery for Next Generation Internet Streaming Applications [59] This paper performs analysis for various queuing disciplines for next generation streaming applications. There are four queuing disciplines are explained first and then a practical implementation is perform by using OPNET simulator. Different queuing scheduling disciplines used to control that according to network congestion which packets get dropped or transmitted. If a high priority packet dropped then it is s degradation in network throughput. So to provide a reliable communication system Quality of Service (QoS) plays an essential role. Following figures 2.14 shows priority queuing. Fig.2.14 Priority Queuing Fig shows the Weighted Fair Queuing with respect to input traffic by using a scheduler. Fig.2.15 Weighted Fair Queuing

31 LITERATURE SURVEY 89 Fig.2.16 Weighted Round Robin Fig.2.16 shows the Weighted Round Robin queuing. A priority weight is given to each queue and with respect to this assigned weight the queue is processed. Fig shows the modified weighted round robin technique.

32 LITERATURE SURVEY 90 Fig.2.17 Modified Weighted Round Robin UMTS Model user guide [60] Universal mobile telecommunication system model guide provide the specific documentation on UMTS network. How UMTS network is modeled in OPNET modeler is described in this documentation. There are few UMTS modeling topics are described as under. (1) General Model Description: This is the first step give the model description. According to the UMTS network an equivalent model is described in OPNET

33 LITERATURE SURVEY 91 shown in fig. After modeling UMTS network various network parameters are evaluated. That is end to end service quality, throughput, drop rate, end to end delay and delay jitter. Fig shows the representation of UMTS in OPNET modeler. Fig.2.18 UMTS in OPNET modeler Model Features and Limitations: This shows the UMTS model features and its limitations. Creating a UMTS Network Topology: For creating the UMTS model UMTS specialized model library is available that contain UMTS and UMTS_AdV object palettes to model the UMTS network. Following fig.2.19 Show the object palette. Fig.2.19 UMTS object Palette

34 LITERATURE SURVEY 92 Following Fig.2.20 show the simple UMTS network for raw traffic within the UMTS network in OPNET model Fig.2.20 Simple UMTS network Model Attributes: For each and every node in UMTS network some attributes are set to model the UMTS network. For various UMTS network entities various parameters are set that is used to model the different parameters of UMTS network. Attributes is set for User equipment, Node B, RNC, SGSN, GGSN etc. If UMTS network is connected to server via GGSN then attributes is also set for server. Simulation Attributes: Simulation attributes are set to perform the simulation over UMTS network. UMTS Statistics: For simulation various statistics is collected to view the result. Different statistics is collected at various parts of network. The statistics is as node statistics and global statistics. Node statistics is collected for different nodes of UMTS network such as user equipment, Node-B, RNC, SGSN and GGSN. Global statistics is collected for network level.