Investigating QoS Support in WiMAX Over Metro-Ethernet Backhaul

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1 Investigating QoS Support in WiMAX Over Metro-Ethernet Backhaul 1 S.D. Sepehr, 2 N. Movahhedinia, 3 A Baraani 1 sdseepehr@gmail.com, 2 naserm@eng.ui.ac.ir, 3 ahmadb@eng.ui.ac.ir Computer Eng. Dept., Faculty of Eng., University of Isfahan, Isfahan, Iran Abstract- Regarding the necessity of internet and also increasing demand for various services, WiMAX network with high bandwidth and suitable speed of transfer can be considered as a solution for public access. This technology with production in considerable volumes from fixed to portable versions shows notable progress in wireless connectivity. Capability of Quality of Service (QoS) support provides user satisfaction in real-time and interactive services over WiMax networks. The purpose of this study is to investigate WiMAX network performance over a Metro-Ethernet backhaul. As in WiMAX network the QoS is of due importance, the investigation of the possibility of transfer and maintenance of this quality is considered. A method for WiMAX and Metro- Ethernet fusion is suggested and its performance is evaluated by simulation. Keywords: WiMAX network, Metro-Ethernet, Quality of Service 1. Introduction Computer networks are developing very quickly either in architecture or in network applications which require proper level of quality of service. To that extent, the examination of network s QoS has been investigated and discussed by researchers. IEEE protocol is another step in industry to present a new generation of wireless networks with metropolitan extension. This protocol is introduced by Air Interface for fixed broadband wireless access system standard and is distinguished with the commercial name of WiMAX. In the modern wireless commutation systems designing products with high flexibility and benefit is considered to have low cost implementation and consuming power and optimal speed and transfer rate [2, 5, 10]. Originally suited for local area networks, Ethernet services are topologically divided into two groups, linear Ethernet (point to point) and Ethernet network (point to multi point). Those services can also be categorized based on provided bandwidth to be in the form of individual services or common services among several users. As the geographical size of the Ethernet over fiber optics is increased to several hundred of kilometepers and its speed is raised to multi Giga-bit per second, Ethernet has turned into a suitable choice for Metropolitan Area Networks. Moreover OoS is provided in such networks by the means of VLAN technology to guarantee the bandwidth and delay requirements for heterogeneous services. In this paper considering Metro-Ethernet as the backhaul for WiMAX in a metro-network, a method of integration between these two technologies is proposed and the performance of the total system is evaluated by simulating typical networks [4]. This paper is organized as follows. Section 2 is allocated to the concepts and operation of WiMAX network and Metro-Ethernet history. The suggested idea for the representation of Metro-Ethernet to implement QoS in WiMAX networks, evaluating the operation of the suggested idea and the simulation of that network is presented in section 3. Conclusion is presented in section Overview of WiMAX and Metro- Ethernet With the recent growth of the telecommunication networks, increasing Quality of service is importance. The need to communicate with information world and also remove the limitation of time and place has been the concern of computer science experts and especially internet engineers for a long time standards for metropolitan network is the last solution to answer these requirements. WiMAX with 50 kilometer frequency and access speed of 70 mbps is developing ASL technology. The weak point of broadband technology is that they are not able to cover all areas because it is no possible to use wires in all areas. WiMAX technology provides wireless access to the broadband for the common and business users [9, 11]. The main structure of the network which is supported by standard is consisted of central stations named bus station(bs) and subscriber station(ss) that receives network /12/$ IEEE 36 Downloaded from

2 service from BSs. Base station is joined to the network s core by a fiber optic or microwave point to point communication. 2.1 Protocol stack media access layer in standards The protocol structure of MAC layer consisted of three sublayers. The explanation of the task of each of them is presented below. 1- Convergence sublayer: The highest sublayer with the task of recording the received traffic from the user which is located in the upper layer of MAC (such as network s layer packets from a route detector or a bridge) to the connections based on the quality of service. 2- Common part sublayer: The main part of MAC operation happens in this sublayer. Generally the task of this syblayer is to manage the connections based on the services, allocating bandwidth to these connections, creating access layer packets and also all the activities related to the entrance of a subscriber to a network supported by a base station and communication alongside creating and exchanging all the managerial messages. 3- Security maintenance sublayer: This sublayer s task is to identify, modify the code s key, code and decode the received and sent messages. In this protocol, the access layer uses the common media in two different ways to transfer data, which are point to multi point (PMP) and mesh. Mesh method is more general than PMP and their difference is that PMP transfer data traffic just between BS and other subscribers (SS) but in Mesh method like AD-hoc networks, data traffic exists among subscriber stations (SS) too. Therefore, subscriber stations are also able to manage and time the sending of data among themselves [7]. Standardization of the basis of QoS in WiMAX network considers some details about the current s type of supported services. As wireless environments are full of environmental noise, power weakening barriers, radio signal reflecting surfaces and phase distortion factors, suitable wires should be used to connect access points (AP) and external network. Therefore, a reliable basis such as Metro-Ethernet should be used to connect APs or BS. In the next step, as the WiMAX vast wireless network is used, the distance between the nodes is geographically long and the structure of SS is accessible in control sublayer; therefore, third layer switches or MLS are used to benefit from virtual local networks or VLAN. In the last step, each of the VLANs should prioritize their packets and based on the priority send the related packet. To guarantee the quality of service in WiMAX wireless network, there is a need to define and enforce the mechanisms of forming the traffic, timing, queuing and prioritizing the data traffic. The packets hierarchical timing model for the UL state in WiMAX network is introduced in two ways: soft QoS and hard QoS. nrtps traffic and rtps traffic are considered as a part of soft service quality group because the bandwidth between maximum and minimum is the amount of bandwidth for each required connection. UGS traffic is considered as a part of hard QoS because the maximum bandwidth which is accessible for each connection is required. With timing BE traffic by BS, the model can distribute bandwidth between BE and other traffic exploitation classes and guarantee fairness in supported in QoS [12, 13]. 2.2 Metro-Ethernet Ethernet is a developed, beneficial and wellknown technology and its media are accessible in most of communication and data devices. The media compatible with this standard are accessible for 10,100, 1000 Mbps speeds and the standard related to the speed of 10Gbps has approved. Metropolitan Ethernet networks are able to increase the network s capacity economically and have benefited from a wide level of services simply, flexibly and measurably. A metropolitan network based on Ethernet is generally called Metropolitan Ethernet network and some of service providers have made it possible to use Ethernet in the metropolitan for widespread networks. Suitable qualification of Metro-Ethernet network such as transferring through available station and providing quality of service has encouraged developers to use this network as the basis of wireless network in Metropolitan dimension. Most of these networks have extended in Metropolitan in past years with high expenses and limited flexibility. The idea of developing a low expense and simple Ethernet from a local network to a metro network that makes it possible to use the available networks in the Metropolitan as the basis of Ethernet transfers, has created interests to make networks called Metro-Ethernet. Also, the basis of providing quality of service is created in these networks. 2.3 WiMAX network with Metro-Ethernet /12/$ IEEE 37

3 There are some ways to adjust WiMAX network traffic on Metro-Ethernet such as EVC, 802.1P and VLAN Each of which are explained briefly below. MEF association has introduced some of the new Metro-Ethernet services based on the network architecture. Customer s equipment are joined to their Metro-Ethernet network by Ethernet port. The task of this connection to network which is called UNI is to define physical limitation of service provider s tasks and customer s tasks. Inside metro network, the connection between UNIs is provided by Ethernet virtual connection. Switch processor can be arranged and formed in a way that separate some nodes from the stations and treat them like several independent LAN: a collection of virtual LANs that their connected stations reflect organizational structure not geographical structure P standard is enforced in access control sublayer in connected layer. Eight classes are defined in this standard. In 802.1P, if packets with higher priority exist in line, packets with lower quality won t be sent P doesn t support admission control but it can simply allocate priority to all packets P header consists three bits for prioritization which allows packets to be categorized in different traffic classes [3]. 3. Simulation and Analysis Regarding the fact that the most important part of each study is allocated to results, this section will examine the results of this study. 3.1 simulation results In the simulated scenario, three subnets with different number of nodes were used within WiMAX network with Metro-Ethernet backhaul. The connection between subnets is done by third layer switches, VLAN and 802.1P and 802.1Q standards are used to prioritize the traffic. In order to provide high security, speed and QoS guarantee in WiMAX network, the connection of service providers and the relationship between APs with Metro-Ethernet basis is considered in this study. Traffic generation rate among packets is considered so these packets always have some packets to send. In this simulation, the number of produced packets is 50 bucket per hour and production time of buckets is 120 seconds. The transferred packets use UDP, RTP and IP protocols. Delay, reliability and throughput parameters are used for sound service (6), Best effort (0) and traffic background. In this scenario, assume each node has the same PHY mode that is OFDMA 20MHZ. Table 1. Simulation parameters Number of subnet 3 Number of subscriber node 200 Subscriber node transmission 0.50 power(w) Number of base station node 24 base station node transmission 0.70 power(w) Packet size 4096bit Simulation time 15minute Cell radius(km) 2.00 Node placement Random, Grid 3.2 The evaluation of QoS in the suggested scenario The suggested network in this study is evaluated based on these aspects: 1. jitter 2. delay 3. network s load Jitter In order to investigate the jitter parameter in QoS evaluation of suggested scenario, the average of the delay of passing packets between mobile nodes and then deviation rate and are calculated. Jitter is defined as the criteria deviation of packets delay or the amount of packets delay fluctuation around the average amount which is the balance or imbalance of packets delay in packets arrival. One of the factors of QoS is jitter. With less jitter, the system will have a better operation. As showed in figure, in WiMAX network with Metro- Ethernet basis and prioritizing passing traffic with 802.1P standard, the jitter amount will decrease. As sound is sensitive to jitter, in suggested scenario, the WiMAX network operation with Metro-Ethernet basis in sound transfer is evaluated /12/$ IEEE 38

4 Figure 2. Proposed model for evaluating End-to-End Delay Figure 1. Evaluating jitter in WiMAX End-to-End Delay Delay is measured as the average of total time that lasts until one packet after production in source is delivered to final receiver in destination. Delay parameter is achieved by the following combination. In order to calculate the amount of the delay of passing packets between nodes in WiMAX network with Metro-Ethernet basis, the delay of all the three states should be considered. Figure 3 shows all the three delays for the sending of packets between two packets in the network. Delay ete = Delay SS_BS1 +Delay BS!_BS2 +Delay BS2_SS The propagation delay: it is the limited speed of signal propagates. The speed of transfer and propagation packets is higher in Metro-Ethernet networks because of their wired basis. As in satellite and wireless state, this delay is maximum so in the simulated scenario of WiMAX network, propagation delay among APs is extremely decreased due to using a Metro-Ethernet basis. The queuing delay: the delay due to packets inside buffers router until it s the time of their sending on exit line. The switching delay: it is the required time for searching the destination address inside switching table, orientating and finding the suitable exit channel for packet. As MLS switches are used in simulated scenario and these switches both support VLAN and have a high speed, switching delay is decreased in comparison to standard state. The delay between two mobile nodes in two different cells requires the evaluation of the three following steps: The delay between source nodes to source AP. The delay between APs. The delay between AP in destination to destination node. Figure 3. Evaluating End-to-End Delay in WiMAX Network s load Increasing the number of mobile packets (users) in each cell not only decrease each station s share from channel s useful capacity and Metro-Ethernet but also decrease the network s useful capacity because of the increase in overhead queuing and timing operation. Also, the number of users in each cell affects the amount of AP s load in each cell. The amount of each AP s load is extremely changing due to wireless nature of WiMAX network and mobile nature of stations. Each AP s load in WiMAX depends on parameters such as AP s sending rate, the type of station s practical programs, the amount of delay, jitter, bandwidth and rate of packets loss. In order to evaluate the amount of network s load, the bandwidth of mobile nodes should be calculated. In order to compute each station s useful share from bandwidth, the following parameters should be considered: /12/$ IEEE 39

5 In each cell, at most several stations are connected to that cell s AP and receive service. How much is the frequency of traffic production in each practical program (average). Whether the sum of station s produced traffic is more than network s useful capacity. The type of operations (profile) that available users in a cell use. In simulated scenario of WiMAX network with Metro-Ethernet basis, mobile nodes in each cell or even in each subnet are considered changeable in order to examine different factors and their changes Conclusion Figure 4. Evaluating network s load In this paper, we proposed a method of implementation for WiMAX network over Metro-Ethernet backhaul to decrease the amount of jitter, end-to-end delay and network s load in such system. To model the packet transfer between two BSs, we used Markov chain. Our simulations show noticeable advantages for the integration of the MLS switch, IEEE 802.1P which is proposed in this paper. 5. Reference wimax_vlan_markov-standard_wimax-des-1: Wireless Subnet_5.Base Station_4.WiMAX.Load (packets/sec) wimax_vlan_markov-markov_vlan_wimax-d 1: Wireless Subnet_5.Base Station_4.WiMAX.Lo (packets/sec) [1] Sunil Kr. Singh, A. K. (2011). Architectural Performance of WiMAX over WiFi with Reliable QoS over Wireless Communication. International Journal Advanced Networking and Applications Volume: 03, Issue: 01, [2] C. Eklund, e. a. (2002). IEEE Standard : A Technical Overview of the Wireless MAN Air Interface for Broadband Wireless Access. IEEE Commun. Mag., vol. 40, no. 6, [3] Hossain, D. N. (2007). Integration of WiMAX and WiFi: Optimal Pricing for Bandwidth Sharing. IEEE Commun. Mag., vol. 45,, [4] Kamal Gakhar, A. G. (2006). IROISE: A New QoS Architecture for IEEE and IEEE e Interworking. in Proc. of IEEE International Conference on Broadband Networks, [5] M.Cao, W. Q. (2005). Modelling and performance analysis of the distributed scheduler in IEEE mesh mode. Proceedings of the 6th ACM international symposium on Mobile ad hoc networking and computing, Urbana-Champaign, IL, USA, [6] Q. Liu, S. Z. (2005). Queuing With Adaptive Modulation and Coding Over Wireless Links: Cross-Layer Analysis and Design. IEEE Transactions on Wireless Communications, Vol. 4, No. 3, [7] Qiang Ni, e. a. (2007). Investigation of Bandwidth Request Mechanisms under Point-to-Multipoint Mode of WiMAX Networks. IEEE Commun. Mag.vol. 45, no, [8] S. Ghazal, Y. A.-A. (2008). Applying a Self-Configuring Admission Control Algorithm in a New QoS Architecture for IEEE Networks. in Proceedings of IEEE Symposium on Computers and Communications (ISCC), [9] So-In, C. J.-T. (2010). Generalized Weighted Fairness and its support in Deficit Round Robin with Fragmentation in IEEE WiMAX. The 2nd International Conference on computer and Automation Engineering (ICCAE), Singapore, Vol. 1, [10] So-In, C. J.-T. (2009). Scheduling in IEEE e Mobile WiMAX Networks:Key Issues and a Survey. IEEE Journal on Selected Areas in Communications (JSAC), Vol. 27, No. 2, [11] Sunil Kr. Singh, A. K. (2011). Architectural Performance of WiMAX over WiFi with Reliable QoS over Wireless Communication. International Journal /12/$ IEEE 40

6 Advanced Networking and Applications Volume: 03, Issue: 01, [12] Wei Nie, H. W. (2011). Packet Scheduling with QoS and Fairness for Downlink Traffic in WiMAX Networks. Journal of Information Processing Systems, Vol.7, No.2, Y. YU V. Genc, S. M. (2008). IEEE j Relay- Based Wireless Access Networks: an Overview. IEEEWireless Communications /12/$ IEEE 41