Chapter -5 QUALITY OF SERVICE (QOS) PLATFORM DESIGN FOR REAL TIME MULTIMEDIA APPLICATIONS
Chapter 5 QUALITY OF SERVICE (QOS) PLATFORM DESIGN FOR REAL TIME MULTIMEDIA APPLICATIONS 5.1 Introduction For successful real time data transmission we have developed a layered architecture as a QoS platform and in our proposed architecture, Power and Delay Optimized AODV (PDO AODV) protocol has been designed in the network layer of Mobile Adhoc Network with the improved mechanism of optimizing delay and residual battery power during packet processing and forwarding in a conventional AODV protocol. In the proposed work, a new L-HCCA scheme has been proposed which works for channel access instead of Polling the stations for group applications (in HCCA) is explained in detail in next section and it is based on LLQ scheduling algorithm which performs better when supplies realtime group information to the PDO AODV (Power and Delay Based Optimized Adhoc On Demand Distance Vector Routing ) Protocol.We have given great importance to the existence of diversified packet types in our target network. So, it is necessary to filter delay sensitive packets from their generic counterparts such as beset effort packets for further processing. Selection of real time packets from the common traffic flow has been incorporated using a flow control module. Components of the proposed platform perform the functionalities of delay, power and jitter management in the channel during real-time data transmission. Specifically video file transfer has been taken during simulation in NetSim Ver 8.3. 5.2. The Proposed Design In our proposed architecture, Power and Delay Optimized AODV (PDO AODV) protocol has been designed in the network layer of Mobile Adhoc Network. It employs an improved mechanism for optimizing delay and residual battery power during packet processing and forwarding using a conventional AODV protocol. Fig.5.1 shows the flow diagram of our proposed Protocol in Network Layer.Fig.5.2 describes the flow chart of checking congested nodes. 79
Fig.5.1: Flow diagram of Proposed Architecture 80
Fig.5.2: Flowchart to check congested node Fig.5.3 shows the basic block diagram of the proposed QoS platform discussed above. Basically the proposed Optimized PDO AODV Protocol functions are having communicational co-ordination with new and improved proposed MAC Channel access mechanism at the Data link layer. The QoS flow is controlled and monitored by Prioritized QoS Flow Control Mechanism at the confluence of both the layers. Again an enhanced real time task scheduler is used which is an extensive proposal based on EDF (Earliest Deadline First). This real time scheduler which intelligently schedules the real time tasks efficiently manages all the events such that every real time tasks are completed within their required deadline. This helps to maintain the QoS in the platform by reducing congestion and minimizing end-to-end delay for real time applications. 81
Fig.5.3: Block Diagram of QoS Platform Architecture The IP (Internet Protocol) Controller controls the overall functionality of the Network layer with PDO AODV protocol management and MAC Controller orders the L- HCCA Channel Access Mechanism as per functionality explained in Fig.4.The following section briefly explains about components used at the relay nodes as part of our proposed QoS platform. 5.2.1 Routing Strategy In our proposed QoS framework, the Routing logic is implemented in the PDO AODV protocol. According to the protocol, the core routing engine at every station has three sub modules as described above and each of them execute smart routine during the transmission. Objective of our framework which is to transmit multimedia data transmission successfully, is achieved by using an intelligence based path finding and packet forwarding through suitable nodes so that the real time packets transmit with highest priority and with QoS satisfaction. Fig.6 shows the functional diagram at relay node for Quality of service Provision. 82
5.2.2 Admission control Policy This module checks availability of required resources during start of the communication at source. After the required resources are reserved for a particular real time flow, the transmission starts as per the QoS requirement. When the transmission time ends, the allocated resources are released. As we have designed the frame work for multimedia data flow, our application is delay and jitter sensitive. Our admission control policy works as per proposed algorithm in PDO AODV protocol for uniformity of jitter interval and minimized latency. Fig.5.4 Relay node modules in our QoS Framework 5.2.3 QoS Checking After resources are allocated, these modules checks the QoS satisfaction for the connection, by matching the validity of reservations made during channel creation. These QoS parameters are based on bandwidth, processing time, rate of processing, deadline and bounded delay. 5.2.4 Resource Reservation This module is responsible for physical assignment of required resources reserved for the connection. At the relay nodes this module has facility of re-negotiation and regeneration of resources to sustain the QoS connection. Resource Renegotiation/ Regeneration - According to change of QoS demand of the channel due to congestion or overloaded condition this module has provision of regeneration of QoS resources. Flow Control Policy - Internally the frame transfer policy using the required mechanism is used 83
in this module and depending on the QoS channel if few frames could not be acknowledged properly then they will b re transmitted 5.2.5 Comparison with AQA AODV An improved QoS approach for reducing end to end delay in time sensitive data transmission has been presented in [123] known as AQA-AODV in which route formation takes place as per requirement of the application. An improved link and path based bandwidth calculation has been done here that provides information to the sender node regarding the state of the network, so that the required transmission rate may be changed by the source. Paper [124] presents ILP (Integer Linear Programming) based QoS architecture for optimization of MANET routing in term of QoS satisfaction in delay and bandwidth. Using such architecture they are not only able to reduce total energy consumption in the network but also there is prolonged network life time and better computational performance. We have compared our QoS Cross layer platform with the above two approaches and the comparison results are presented in the simulation section. 5.3 Improved Real Time Task Scheduler The Rate Monotonic Algorithm (RMA) is used as an improved mechanism to assign fixed priorities to real time applications with an intention to improve the possibility of parallel schedulable tasks. Simultaneous execution of real-time tasks without missing deadline of any task is possible by checking the schedulable status of a group of tasks at a time. According to this algorithm the priority of every task is assigned according to its time period, with an intention to provide higher priority to short time period tasks.[125 ].If the period of task t1 is shorter than the period of task t2, then as per RMA s rule, t1 has higher priority than t2. This criteria is checked for all the group members of the real-time applications in a group. So far, RMA is considered to be the finest fixed priority based algorithm [125 ]. 84
Fig. 5.5: Real Time Scheduling using RMA Sometimes after getting maximum CPU utilization, few processes do not achieve their deadlines. In such cases, altering priority levels works successfully depending on other prioritized deadline based real-time tasks in the group. The Real-time packet scheduling module controls multiple real time tasks generated in the same time period with different deadlines using event-driven scheduling method. In event driven scheduling, which is a preemptive type, a higher priority real time task can preempt a low priority task and can be executed to achieve its deadline. The QoS Flow Control Mechanism This Module controls and monitors proper flow of Qos parameters in the channel. Tasks such as Admission control Policy, QoS checking, Resource Reservation and Flow Control are the main function of this module which is described in the next section. 5.4 Real Time Task Scheduling Issues Minimization of Latency-During the period when any real time transmission or any real time application takes place, the system should response very quickly and serves it as quickly as possible. So, event latency refers to the amount of time elapses from the time when an event occurs to when it is serviced. Fig.4.6 shows the event latency and the performance of real time systems are affected by two types of latency, such as interrupt latency and dispatch latency. 85
Fig.5.6 Event Latency i. Interrupt latency As Fig 5.7 shows, it is the period of time from the interrupt arrives for real time processing in prioritized way to the time it is actually serviced. Fig.5.7 Interrupt Latency ii. Dispatch latency It is the amount of time required for the real time scheduler to stop one process and start another. 86
Fig.5.8: Dispatch Latency Dispatch latency can be minimized by allowing the real time transmission with dynamically preferred access to the processors of the nodes by utilizing preemptive kernels at the MANET nodes. As the figure above shows, the conflict phase has two constituents. First one is the preemption of any process running in the kernel, and second one is releasing the resources from low priority jobs such as normal packet transmission and assigns them to the real time multimedia data transmission. 5.5 Rate Monotonic Scheduling (RMS) Priority to the processes are assigned according to the inverse of the period of the real time applications. In this case the priority remains static. If the period is short in comparison to another application, then its priority will be higher, and another application with longer period will have lower priority. Suppose P1 and P2 are two real time applications transmitting over the internet. P1 with period 20 and deadline 50 nano seconds. P2 has period 35 and deadline 100 nano seconds. As per Rate Monotonic scheduling P1 will be assigned a higher priority than P2. 87
Fig.5.9: Real time process prioritization in Rate Monotonic Scheduling In fig. 5.9 above, the system remains idle from 75 to 100 nanoseconds of time, but the deadline of both applications are achieved without missing deadline. Fig.5.10 Missed deadlines with RMS As shown in Fig.5.10, Deadline for each process requires that it completes the processors burst by the start of its next period. If the task is scheduled in such a way that P2 has higher priority than P1, then as the figure below shows there will be missing deadlines. 5.6 Proposed RR-DSR Scheduling Algorithm In order to facilitate the successful transmission of real time applications in MANET, we have proposed an improved algorithm for real time scheduling called RR- 88
DSR (Round-Robin with Deadline based Shortest Remaining Time), which fastens the real time data processing by the processors at the relay nodes when multiple real time packets to be forwarded or processed at the nodes. As shown in Fig. 5.8, this proposal is based on round robin and SRTF (Shortest Remaining Time First) scheduling algorithm. Our proposed algorithm can be explained with help of an example. Suppose there are four realtime applications p1, p2, p3 and p4 with deadlines p1(25), p2(28), p3(35) and p4(33). They are assigned a time slice of 2 nano second in round robin method initially. Fig.5.11 System Structure of Proposed RR-DSR Algorithm In order to facilitate the successful transmission of real time applications in MANET, we have proposed an improved algorithm for real time scheduling called RR- DSR (Round-Robin with Deadline based Shortest Remaining Time), which fastens the real time data processing by the processors at the relay nodes when multiple real time packets to be forwarded or processed at the nodes. As shown in Fig. 5.12, this proposal is based on round robin and SRTF (Shortest Remaining Time First) scheduling algorithm. Our proposed algorithm can be explained with help of an example. Suppose there are four real time applications p1, p2, p3 and p4 with deadlines p1(25), p2(28), p3(35) and p4(33). They are assigned a time slice of 2 nano second in round robin method initially. 89
Fig.5.12: Proposed RR-DSR Scheduling (Part 1) After 24 units of time, as shown in fig 5.13 there will be again priority checking based on shortest remaining deadline time. According to the algorithm, the new sequence of application processing will be p1(1),p2(3),p4(4) and p3(5), and all the applications can achieve their transmission within deadline. Fig.5.13: Proposed RR-DSR Scheduling (Part 2) 5.7 QoS Provision in Proposed Approach Over heterogeneous networks with multiple technologies, the objective of QoS satisfaction is to provide prioritized service with dedicated bandwidth, jitter and latency control as demanded by specified applications and minimization of data drop rate by avoiding starvation of other low prioritized tasks in other flows. QoS represents a specific client-oriented requirement serviced as a guarantee to the users. Therefore, in telecommunication service QoS offers better service to certain traffic over varieties of network. Our QoS framework satisfies the following criteria for real-time applications. 90
1) Throughput: Our QoS platform satisfies maximum throughput during online games, video file transmission with minor delay that does not affect the overall transmission and can be completed before the deadline. Online Games such as Popular Games Guild Wars and Counter Strike can be both played with 60 Kbps connection. 2) End-to-end delay: This delay is a major factor during online playing of games. The delay between any two commands issued by the player and the time whether it immediately executed on the screen matters during the game. For optimal performance, 50 ms or less in video games is permissible. This value again differs from game to game. 3) Jitter and Packet Loss Rate: Jitter is the delay variation between packets transmission during an application. Non-uniform jitter creates problem during an online game. Jitter problems causes irregular packet delivery, receiving packets late causing the playing of the game in a horrible state. If the packets are not received in time or received in wrong order, then the previous played information are lost 4) Delay: Delay in multimedia data transmission is due to processes involved in transfer of remote visualizations with video and image transformation techniques using some algorithms and the amount of data transfer. 5) Bandwidth: Speed of link or bandwidth plays important part during the transmission in the channel. A higher bandwidth ensures uniformity of jitter and better performance in multimedia applications. 91
Fig.5.14: Block diagram of our QoS Framework at source, relay node and destination Fig.5.14 describes the QoS framework at source, Relay nod and the destination node. Different modules of our designed QoS frame work perform important tasks to support end to end QoS satisfaction in a connection. These modules are designed as objects in the proposed framework during network setup. Functionalities performed by individual objects and connection between them is briefly discussed in the following section. 92
5.8 Components of the Proposed Framework 1) Routing Logic: In our proposed QoS framework, the Routing logic is implemented in the PDO AODV protocol. According to the protocol, the core routing engine at every station has three sub modules as described above and each of them execute smart routine during the transmission. Objective of our framework which is to transmit multimedia data transmission successfully, is achieved by using an intelligence based path finding and packet forwarding through suitable nodes so that the real time packets transmit with highest priority and with QoS satisfaction. 2) Admission control Policy: This module checks availability of required resources during start of the communication at source. After the required resources are reserved for a particular real time flow, the transmission starts as per the QoS requirement. When the transmission time ends, the allocated resources are released. As we have designed the frame work for multimedia data flow, our application is delay and jitter sensitive. Our admission control policy works as per proposed algorithm in PDO AODV protocol for uniformity of jitter interval and minimized latency. 3) QoS Checking: After resources are allocated, these modules checks the QoS satisfaction for the connection, by matching the validity of reservations made during channel creation. These QoS parameters are based on bandwidth, processing time, rate of processing, deadline and bounded delay. 4) Resource Reservation: This module is responsible for physical assignment of required resources reserved for the connection. At the relay nodes this module has facility of re-negotiation and regeneration of resources to sustain the QoS connection. 5) Resource Renegotiation/Regeneration: According to change of QoS demand of the channel due to congestion or overloaded condition this module has provision of regeneration of QoS resources. 6) Flow Control Policy: Internally the frame transfer policy using the required mechanism is used in this module and depending on the QoS channel if few frames could not be acknowledged properly then they will b re transmitted. 93
5.9 Comparison with other similar QoS Architecture In paper [123] a better QoS approach for reducing end to end delay in time sensitive data transmission has been presented known as AQA-AODV in which route formation takes place as per requirement of the application. An improved link and path based bandwidth calculation has been done here that provides information to the sender node regarding the state of the network, so that the required transmission rate may be changed by the source. Paper [124] presents ILP (Integer Linear Programming) based QoS architecture for optimization of MANET routing in term of QoS satisfaction in delay and bandwidth. Using such architecture they are not only able to reduce total energy consumption in the network but also there is prolonged network life time and better computational performance. We have compared our QoS Cross layer platform with the above two approaches and the comparison results are presented in the simulation section. 5.10 Simulation of Qos Platform with Real Time Scheduler Design NetSim is a discrete event simulator which has finite state machine modeling strategy and a useful simulation tool for designing of both wired and wireless networks with wide variety of network and research applications. It provides depth and flexibility of simulating various types of applications. This has facility of almost all supported standard protocols in MANET with source code in C language, assimilated animation with outlining and correcting error provision. Its MAC layer is demonstrated as per IEEE 802.15.4 layering slotted CSMA / CA, unslotted CSMA / CA with Super frame transmission scheme and Beacon transmission utility. Table 5.1 shows the simulation parameters used. 94
Table 5.1: Simulation Parameters Parameter Name Parameter Value Channel Type Wireless Channel Radio Propagation Model Two Ray Ground Network Interface Type Wireless Phy Type of Traffic V B R Simulation Time 2 Minutes MAC Type Mac/802_11 Max Speed 50 m/s Network Size 1600 x 1600 Mobile Nodes 120 Packet Size 512 Kb Interface queue Type Queue/Droptail Protocol PDO AODV with QoS Simulator NETSIM The following section describes the simulation results with graphs and comparative analysis of our approach with other efficient approaches. We have simulated the network performance by sending a video file vid.mp4 of size 400MB using our proposed QoS architecture and again using the same file in a normal network without QoS, and presented the simulation results in the following section. Fig. 5.15: Jitter Analysis of two video files 95
We have transmitted two video files during our simulation. The simulation was carried out for 2 minutes. The graph in fig 5.15 reveals the fact that a video file transmitted using our proposed PDO AODV Protocol with QoS architecture send packets with uniform jitter. As the figure shows that different segments of the file are reached with equal latency one after the other so that there is no video streaming problem and the video data which is a real time application reaches successfully at its destination with all specified Quality of Service specification. Fig.5.16: Bandwidth Analysis of two video files. Fig 5.16 shows the comparison of bandwidth in which two video files were sent. Video file 1 was transmitted in our QoS platform which exhibits almost uniform bandwidth while transmission throughout the channel with minor deviation satisfying QoS criteria whereas video file 2 when transmitted without our platform in normal channel using AODV protocol reveals high deflection of bandwidth as shown in the graph in fig. 5.16. Fig.5.17: Delay comparison of video file transmission 96
Fig.5.17 shows the graphical analysis of a video file vid.mp4 when transmitted with and without our QoS architecture. We can observe that there is sufficient reduction in average delay of video file transmission in the conventional AODV concept that our proposed improved QoS architecture. Fig 5.18: Comparison of Avg. Power consumption Fig.5.18 is an output graph when a video file vid.mp4 was transmitted using both approaches. In the QoS approach with PDO AODV it shows comparatively less power consumption in comparison to the approach without using QoS architecture. Fig.5.19 Comparison of Network Life time As discussed above, we have compared our approach with two other important cross layer approaches similar with our approach, but they have used different technique for efficient multimedia transmission. Fig.5.19 shows that when network life time was 97
compared between the said three QoS methods, our approach has higher network life time than other two platforms. Fig 5.20: Comparison of Packet Delivery Ratio Similarly when compared for packet delivery ratio(pdr), Fig 5.20 clearly shows that our PDO AODV based QoS platform outperforms than the other two ILP based [124] and AQA-AODV based [123] QoS architectures. 5.11 Summary In this research paper we have presented a cross layer architecture for supporting quality of service provision in real-time application specifically for multimedia video data transmission. The issues of non-uniform jitter and video streaming problem due to delay at multiple stations have been discussed and eliminated up to a great extent by introducing intelligent and power efficient logic at the smart modules of network layer and data link layer as well as with effective communication between them. There is a also a guard module for controlling the QoS flow in the channel, which increases reliability of multimedia transmission over the network. Simulation result shows better performance of our QoS platform when compared with other similar approach. 98