CHAPTER 1 INTRODUCTION

Transcription

1 CHAPTER 1 INTRODUCTION 1.1 Wireless Networks A computer network using wireless data connections to connect different nodes is known as wireless network. Wireless networking is a method using which costly process of digging cables into buildings is avoided by enterprises and business installations. Administration of these wireless networks is done by radio waves and governs implementation at physical layer. Examples of wireless networks include cell phone networks, Wi-fi local networks and terrestrial microwave networks. Wireless networks have variety of interesting and important applications in business, telecommunication, defence, disaster management and real time control system. Wireless networks have provided flexibility for increasing workforce in such applications because of which number of wireless subscribers has increased rapidly during recent past. Wireless Communication technology have seen rapid advancements with increase in number of laptops, availability of wireless networks and urge of humans to work on the move. It has added tremendously to growth of wireless networks and has fuelled demand for more and more powerful networks. In early stages of its inception this technology was expensive and was reserved for specified purposes like military operations or mobile situations where cable networks were unable to reach. With the maturing of industry standards and deployment of lightweight wireless networking hardware across a broader market section, wireless technology has come of age Types of Wireless Networks Wireless PAN Wireless personal area networks (WPANs) interconnect devices within a person s reach. Infrared light and bluetooth connections used for connecting headset to laptop are examples of wireless personal area networks. Wireless PANs are very common now a days as almost all devices are shipped with Bluetooth or wi-fi connectors. 3

2 Wireless LAN Wireless local area network (WLAN) uses wireless distribution mechanisms to inter connect two or more devices over a short distance through an access point. Users can move around while connecting to network with help of spread spectrum or OFDM technologies. Wi-Fi is the more commonly used name for such networks. Wireless MAN Wireless metropolitan area networks connect multiple wireless LANs together and cover a larger geographical area. Recently IEEE has decided to standardize such types of networks and IEEE series of standard describes rules and mechanisms for implementation of such networks. Examples of such MANs are WiMAX and HiPERMAN. Wireless WAN Wireless wide area networks cover large areas as towns and cities. Point to Point microwave links are used to interconnect different access points using parabolic dishes. The whole system consists of access points, base station gateways and wireless bridging relays. WAN may be considered as integration of various MANs in point to multipoint or Mesh configuration. Wireless mesh network Different nodes in such networks are organized in a mesh topology. One node connected to outside world is termed as centralized base station and provides connectivity. All nodes have ability to communicate to its peers. All nodes in mesh networks can act as base station and can offer or steal bandwidth from neighbouring nodes if need arises. Cellular network These are radio networks in which fixed location transceiver provides coverage to designated geographical region known as cell. These cells use different set of frequencies so as to minimize interference among neighbours. Joining of these cells together enables cellular networks to cover large geographical areas and provide connectivity. This concept is being employed by mobile operators and enables different devices to communicate with each other using fixed transceivers. Mobility is also a feature of such networks in which users can move around different cells but can still connect to network. Global System for Mobile Communications (GSM), Personal Communications Service (PCS) and D-AMPS (Digital Advanced Mobile Phone Service) are different forms of cellular networks. 4

3 Global area network Global area network (GAN) comprises network that is used for connecting multiple wireless LANs and providing them mobile support. They cover a far wider range than wireless MAN and may be termed as wireless WANs, IEEE is an example of such networks. These networks operate in unlicensed bands below 3.5 GHz and can provide connectivity at higher speed of 250 km/h. Space network Space networks are networks used for communication between spacecraft, usually in the vicinity of Earth. NASA's Space Network is an example for such networks. 1.2 Broadband Wireless Access Networks Wireless broadband technology provides high-speed wireless Internet access or computer networking access over a wider area. As per IEEE standard , broadband means having instantaneous bandwidths of more than 1 MHz and supporting data rates greater than 1.5 Mbit/s. Wireless broadband refers to wireless technology that addresses last mile problem whereby remote places can be connected to an ISP or carrier s backbone network without leasing traditional cables or wires. It refers to wireless connectivity between one location to another utilized by enterprises, businesses, households and telecommuters. Technically wireless broadband is an extension of point-to-point wireless-lan bridging concept to deliver high-speed and high capacity pipe that can be used for Internet access services. The primary goal of wireless broadband is to connect LANs to internet and provide support for multiple services like data, voice and video. Wireless broadband is faster to market, and allows easy addition of new subscribers as it can work over prevailing resources and no further installations are required. Data rates supported by these networks are equivalent to some wired networks, such as that of asymmetric digital subscriber line (ADSL) or a cable modem. These networks are symmetric in terms of speed offered in uplink and downlink direction. Few wireless internet service providers provide download speeds of over 100 Mbit/s and range for most broadband wireless access (BWA) services is estimated at about 50 km from base station [theoretical]. It makes use of technologies like LMDS (Local Multipoint Distribution Service), MMDS 5

4 6 (Multichannel multipoint distribution service) and ISM (Industrial scientific and medical) radio bands for providing wireless access. IEEE was first standard developed for such technology which is popularly known as WiMAX. WiMAX is type of MAN expected to deliver broadband access services to residential and enterprise customers in a city with speed much higher than wi-fi. The next section throws some light on IEEE standard and correlation of its various layers with OSI model. 1.3 to IEEE and WiMAX Wireless and mobile communications have changed communication systems over past decades. IEEE is a series of Wireless Broadband standards written by the Institute of Electrical and Electronics Engineers (IEEE). IEEE Standards Board established a working group in 1999 to develop standards for broadband for Wireless Metropolitan Area Networks and made this workgroup a unit of IEEE 802 Local and Metropolitan Area Network standards committee (LMSC). IEEE is an internationally accepted standard [1][2] which is designed to provide 30 to 40 megabit-persecond data rates, with 2011 update providing up to 1 Gbit/s for fixed stations which is better than conventional cable modem and DSL connections. It supports connection oriented media access control (MAC) layer that utilizes a grant-request mechanism to allow data exchange which in turn enhances use of radio resources. WiMAX technology provides support for wide variety of protocols such as ATM, IPv4, Ethernet etc. and can function on both licensed and non licensed frequencies. The standard has high-speed wireless packet-based radio connectivity with strong privacy and key management protocol. It uses flexible authentication architecture for providing multiple subscriber credentials. It is as an IP-based wireless broadband technology that can be incorporated into both wide-area third-generation (3G) mobile, wireless and wire-line networks. As a capable broadband wireless technology, WiMAX has various advantages such as quality of service, security, high data rates, scalability and mobility. This next-generation wireless technology is specially designed to enable high-speed, mobile Internet access to wide array of devices. It delivers low-cost, open networks solution for efficient transmission with QoS (Quality of Service) support at Media Access Control (MAC) layer for guaranteeing multimedia transmissions. WiMAX facilitates various service providers to come across various challenges that they encounter due to

5 IEEE standard b g a a e Date ratified 1999/9 2003/6 1999/9 2001/ /1 2005/ Access Type LAN MAN WAN Mobility support Portable Fixed Portable Pedestrian speed (<150kmph) Vehicular speed (<250 kph) Channel conditions NLOS LOS NLOS NLOS NLOS Max cell range 100m 50m 50m 2-5 km 7-10 km(max 50km ) 2-5 km 20 km Spectrum License Exempt License Exempt License Exempt License and License exempt Licensed Frequency Band 2.4 GHz 2.4 GHz 5 GHz GHz 2-11 GHz 2-6 GHz <3.5 GHz Max Data rate 11 Mbps 54 Mbps 54 Mbps Mbps Upto 75 Mbps Upto 15 Mbps > 4 Mbps Channel Bandwidth 20 MHz 20,25,28 MHz MHz MHz MHz Spectrum Efficiency 0.55 (bps/hz) 2.7 (bps/hz) 2.7 (bps/hz) 4.8 (bps/hz) 3.75 (bps/hz) ~3 (bps/hz) >1 (bps/hz) Modulation QPSK BPSK, QPSK, 16-,16- QAM BPSK, QPSK, 16-,16- QAM QPSK, 16QAM and 64QAM OFDM 256 carriers plus QPSK 16 QAM, 64QAM and OFDMA 2048 carrier OFDMA QoS support e introduces QoS functionality Yes Yes Mesh Vendor Proprietary No Yes Yes No Access Protocol CSMA/CA Request Grant Request Grant Request Grant Request Grant Table 1.1:- Comparison of WiMAX with other wireless technologies 7

6 growing customer demands [5][6] since it has capability to flawlessly interoperate across different network types. It also gives network operators economy of scale and flexibility enabling them to address each market differently and efficiently. In comparison to wi-fi, which in most cases is limited to a few hundred feet range WiMAX can provide BWA over several miles. A comparison of WiMAX with its counterpart wi-fi and IEEE which is another upcoming standard for WAN networks is presented in Table 1.1 which justifies that WiMAX is a real competitor to be front runner as latest BWA technology. Although family of standards is officially called Wireless MAN in IEEE, it has been commercialized under the name "WiMAX" (from "Worldwide Interoperability for Microwave Access") by WiMAX Forum [4]. WiMAX forum is a non profit organization with telecom operators and equipment manufacturers as its members that looks after development in field of WiMAX and makes specifications for design of equipments. It issues WiMAX Forum certified label to products of equipment manufacturers developed in compliance with IEEE standard. WiMAX forum defines three functional areas for itself: air interface specifications that define specifications for Physical and MAC layer focussing on first and second layer of OSI model; network specifications that define compliance of equipments to OSI model upper layers. These are developed by WiMAX forum and IEEE does not provide any guidelines for it. Third functional area is roaming specifications dealing with Roaming Business Framework. IEEE has standardized only air-interface for WiMAX consisting of physical layer and Media Access control layer. Functionality for upper layers is developed within WIMAX forum in collaboration with equipment manufacturers. Figure 1.1 explains layered architecture of WiMAX and its resemblance to OSI model. Physical Layer WiMAX physical layer provides support for orthogonal frequency division multiplexing to enable high-speed data, video, and multimedia communications. OFDM is currently utilized by variety of commercial broadband systems, including DSL, Wi-Fi, Digital Video Broadcast- Handheld (DVB-H), and Media FLO(Forward link only) besides WiMAX. IEEE uses scalable OFDMA to carry data, supporting channel bandwidths between 1.25 MHz and 20 MHz, with up to 2048 sub-carriers. It supports adaptive modulation and coding which means that in 8

7 good channel conditions efficiency of 64 QAM is employed while in poor channel conditions robustness of BPSK coding is used. 16 QAM and QPSK will be employed in relatively normal conditions. PHY also provides support for Multiple-in Multiple-out (MIMO) antenna techniques Fig. 1.1:- WiMAX layers with OSI reference Model that provides good non-line-of-sight propagation characteristics. IEEE also provides support for hybrid automatic repeat request (HARQ) for good error correction performance [7]. IEEE MAC IEEE MAC is divided into three distinct components: service-specific convergence sub-layer (CS), common-part sub-layer, and security sub-layer. Convergence sublayer acts as interface between MAC layer and network layer of network and its job is to receive data packets or MAC service data units from higher layer. CS performs operations like header compression and address mapping. Packet operations like fragmentation and concatenation of MAC SDUs into MAC PDU (Physical Data Units) that are independent of any specific layer are performed by common-part sub-layer of MAC. It is also responsible for Quality of Service control, ARQ (automatic repeat request) and transmission of MAC PDUs. Functions like 9

8 encryption and authorization are being handled by security sub-layer. It provides authentication support by using secure key exchange and uses protocols like Advanced Encryption Standard (AES) or Data Encryption Standard (DES) for providing encryption support during data transfer. MAC layer is also responsible for functions like power saving and performing handover[8] Advancements in IEEE standard In the mid-1990 s many telecommunication companies initiated the idea to promote use of fixed broadband networks for providing Internet connectivity to businesses and individuals. This technology would operate as a versatile system for corporate or institutional backhaul distribution with a challenge to fight with leading Internet carriers. Initial advancement in standard started when scientists and engineers experienced requirement of having wireless internet access and other broadband services that works suitably well in rural areas or in areas where it is difficult to develop cost-effective wired infrastructure. The outcome of these findings led to formation of NII (National Information Infrastructure) bands of range 5-6 GHz and 30 GHz Local Multipoint Distribution Service (LMDS). A need was felt by wireless community to standardize networks operating in such range that eventually paved way for IEEE standard. Within the IEEE Computer Society, there exists standards Activity Board (SAB) looking after development of various standards. This board has multiple IEEE-802 LAN/MAN Standards Committees (LMSC) working under it. Their aim is to develop standards for Local Area Network (LAN) and Metropolitan Area Network (MAN) mainly concerning the lowest two layers of OSI Model. Within the LMSC, there are a number of Working Groups (WGs) and one Executive Committee (EC) to work among all WG chairs. One of LMSC Working Groups is the IEEE Working Group working on Broadband Wireless Access Standards, which is referred as IEEE WG. Projects within various working groups intend to result in standards that are published by the IEEE-SA (IEEE Standards Association) which is an activity area of IEEE focused on the development of internationally recognized consensus standards. PARs (Project Authorization Request) is written by Study Group (SG) which is further approved by IEEE-SA Standards Board(SASB). Once a PAR is approved by IEEE-SASB, than that particular SG is disbanded and a Sub-Group or Task Group (TG) within the WG is assigned role 10

9 to prepare and develop successive draft documents that eventually lead to publication of document as a new standard. Each project approved within an existing group is referred to by assigned suffix letter(s) together with a leading P character (for Project) in its project number (e.g P802.16m). The origin of standard and its growth is discussed in this section. It is divided into four different stages covering entire life span of standard with different amendments and revisions made to it. Stage 1:- Origin of Standard and Initial years ( ) IEEE 802 Study Group established in 1998 on Broadband Wireless Access (BWA) created P project and approved specification for interoperable LMDS in LMDS obtained consideration of investors as it provided broadband internet with other entertainment services but it failed as there was not any uniform standard for its access. Then IEEE Working Group was erected by disbandment of this SG to manage a new project, P802.16, on Broadband Wireless Access Standards. This project used a single carrier for air interface in GHz and therefore was named Wireless MAC SC(single carrier). However it was renamed to P in 2000 so that consistency in numbering can be maintained with concurrent project, P , developed by Task Group 2. Project P aimed at developing new standard for air interface for 2-11 GHz was approved in 2000 and TG3 was constituted for its development. The project proposed three implementations for physical layer: WirelessMAN-SCa6 (Single Carrier), WirelessMAN-OFDM (Orthogonal Frequency Division Multiplexing) and WirelessMAN-OFDMA (Orthogonal Frequency Division Multiple Access). It was agreed to use a single MAC protocol running over different physical layer options therefore all air interface projects were intended to be brought under one standard namely A separate amendment was developed for each additional air interface specification. Therefore in 2001 following projects were renumbered:- P to P802.16, P to P802.16a and P to P802.16b. Two task groups TG3 and TG4 decided to work together on a single document for P802.16a and P802.16b in Goals of P802.16b were integrated in P802.16a and the former was withdrawn. Finally, IEEE Std was born in 2001 and was published in April

10 The standard was amended with IEEE c detailed system profiles for GHz and set of predefined parameters were included to provide interoperability support. It was the first amendment to IEEE Std and was aimed for wireless networks operating on licensed radio frequency bands. A second amendment to IEEE Std was made in form of IEEE Std a-2003 in Certain modifications to MAC were made and additional physical layer specifications for 2-11 GHz were included. This standard was not affected by rain attenuation and operated in NLOS (Non-Line-of-Sight) environment which led to reduction in installation of antennas. IEEE a supported mesh network modes of operation that broadens basic transmission range by passing single communication from one transceiver for providing guaranteed QoS to support voice and video messages. The following IEEE standards were applicable in 2003: IEEE Std : IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems IEEE Std c-2002: Amendment 1: Detailed System Profiles for 10-66GHz IEEE Std a-2003: Amendment 2: Medium Access Control Modifications and Additional Physical Layer Specifications for 2-11GHz Stage II:- First Major Revisions to Standard ( ) In 2002, a new study group named as Mobile Wireless MAN Study Group was established to pertain to issues of mobility. Group has to draft report on addition of mobility to existing standard by making number of subcarriers scalable with used bandwidth. This was implemented as project P802.16e as it was being handled by Task Group E. Project P802.16d was transformed into revision project P REVd so that all amendments could be accommodated into single revision. It led to approval of IEEE Std and IEEE and its two amendments were made obsolete. This standard offered OFDM (Orthogonal Frequency Division Multiplexing) with 256 carriers. It provides three different airinterfaces: a) WirelessMAN-SC2: single carrier modulation b) Wireless MAN-OFDM: OFDM modulation with a 256-point Fast Fourier Transform (FFT) with TDMA channel access. c) Wireless MAN-OFDMA: OFDM employed with a 2048-point FFT. It includes two-way authentication for security purposes and supports multihop mesh networking to enable 12

11 retransmission of packet from one node to another. Both time division duplex (TDD) and frequency division duplex (FDD) transmission were supported by this extension for conformance testing of a equipments. In 2004 a new study group named as Network Management Study Group was created. This group was responsible for development of Management Information Base for fixed service and Management plane procedures and services for fixed and mobile services. It resulted in creation of two projects P802.16f and P802.16g. The draft document proposed in P802.16f was approved as standard IEEE Std f in Sep This was first amendment made to IEEE Std and was published in Dec Progress made in project P802.16e which was started in 2002 eventually led to a new standard IEEE Std e-2005.This may be treated as second amendment to IEEE Std The standard was fully integrated with corrigendum IEEE Std /Cor1 before publication, which was result of draft document within P /Cor1. IEEE (IEEE e) was published in February 2006 by IEEE with frequency band of 2-6 GHz for mobility. It is also known as Mobile WiMAX. This technology adds support for mobile subscriber stations. It would also support communication for users moving at vehicular speeds because of its technological advances of high speed signal handoffs. The IEEE e has some clear advantages over as it provides support for multicast and broadcast service feature. It also supported enhanced techniques of Multiple-Input Multiple-Output (MIMO) and Adaptive Antenna System (AAS). Security features were also updated and new privacy sublayer was added. It also introduced power save modes for mobility supporting SS. The following were active standard available in beginning of 2008 IEEE Std : IEEE Standard for Local and Metropolitan Area networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems IEEE Std f-2005: Amendment 1: Management Information Base IEEE Std /Cor1-2005: Corrigendum1(not published separately, but jointly with IEEE Std e-2005) IEEE Std e-2005:Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands 13

12 IEEE Std g-2007: Amendment 3: Management Plane Procedures and Services Stage III:- Second Revision and New Amendments ( ) As P /Cor2 was merged into P802.16Rev2, IEEE working group decided to merge draft of P802.16i within Network Management Task Group into draft of P802.16Rev2 within Maintenance Task group in It led to with drawl of project P802.16i in In Jan. 2008, an Adhoc group 16jm was instated to study issues regarding repercussions of j and relay support on architecture of m. This AdHoc Group delivered its final report in 2008 as a contribution to Task Group m. IEEE later in 2009 approved new revision of IEEE Std known as IEEE Std IEEE Std that was previously responsible for making IEEE Std and its amendments (IEEE Std c-2002 and IEEE Std a-2003) obsolete was now facing its own exit and was ready to be replaced by new standard IEEE Std Support of single carrier physical layer for 2-11 GHz frequencies no longer interested vendors, eventually leading to removal of WirelessMAN-SCa and inclusion of WirelessMAN- SC, Wireless MANOFDM and Wireless MAN-OFDMA. In 2009, IEEE SASB approved IEEE Std j-2009 on basis of draft for project developed by Relay Task Group. Newly approved standard IEEE got its first revision immediately on its inception as IEEE Std and IEEE Std j was published by IEEE on Jun Working Group had approved creation of an AdHoc Committee on Network Robustness and Reliability (NRR) in 2008 aiming to promote robustness and reliability. The committee proposed creation of IEEE GRIDMAN Study Group on Greater Reliability In Disrupted Metropolitan Area Networks in GRIDMAN Study Group proposed an amendment to IEEE Std on Higher Reliability Networks, which was approved in 2010 by IEEE-SASB as project P802.16n. GRIDMAN Task Group started work for drafting standard on project P802.16n and proposed extension of specifications for Wireless-MAN OFDMA and enhancement of MAC protocol. Work on license exempt TG was started in 2004 but no progress was made in this project even after four years of its inception which is the maximum life time period for any project assessment report. Two extensions were already granted to it and it was facing closure. However 14

13 this licence exempt work group was able to develop project P802.16h and IEEE SASB approved it as standard h-2010 in This was the second amendment made to IEEE Std In order to investigate future network challenges and possibilities, a new Project planning group was formed in November This Project Planning AdHoc group began drafting a machine-to-machine (M2M) Communications study report in 2010 and IEEE Project planning committee was formed on the basis of this group. IEEE Project Planning Committee proposed an amendment to existing IEEE Std on enhancements for machine to machine (M2M) communications, which was accepted by IEEE-SASB as project P802.16p. This amendment supports low power operations, small burst transmissions and was built on features in project P802.16m. Draft for project P802.16m by task group m was completed in 2011 as IEEE Std m Following standards were available at end of Stage III. IEEE Std : IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Broadband Wireless Access Systems IEEE Std j-2009: Amendment 1: Multihop Relay Specification IEEE Std h-2010: Amendment 2: Improved Coexistence Mechanisms for License- Exempt Operation IEEE Std m-2011: Amendment 3: Advanced Air Interface Stage IV:- Current Standard and Ongoing Projects The growth of IEEE standard and its various amendments is shown as timeline diagram in figure 1.2. The figure shows development of various projects and evolution of standard on year wise time scale. Table 1.2 also summarizes progress of standard, in addition to active standard. Table also describes superseded standards and projects that are at draft level. Currently as on today (10 th March 2014) following standards are active Active Standards IEEE : Revision of IEEE Std , including IEEE Std h, IEEE Std j, and IEEE Std m (but excluding the Wireless MAN- Advanced radio interface, which was moved to IEEE Std ) approved by IEEE-SA Standards Board on and published August

14 Fig. 1.2:- Timeline showing development of standard IEEE

15 Active Standards Amendments made Pre-Draft Stage Superseded standards IEEE Revision of IEEE ,including h,802.16j,16m IEEE As amended by IEEE a, b IEEE k-2007 Bridging of IEEE IEEE Std (reaffirmed for 5 years) IEEE Std /conformance IEEE m-2011 (Amendment to IEEE ) Advanced Air Interface IEEE h-2010 (Amendment to IEEE ) Improved Coexistence Mechanism for license exempt operation IEEE j-2009 (Amendment to IEEE ) Multi-hop Air Interface for Broadband Wireless Access Systems IEEE g (Amendment to IEEE ) Management plane Procedures and Services IEEE f-2005 (Amendment to IEEE ) Management Information Base Project P802.16q Multi-tier Amendment(to be an Amendment to IEEE Std ) Project r Small Cell backhaul with Ethernet(to be an Amendment to IEEE Std ) Project P Mobile Broadband Network Performance Measurement ( to be an independent standard) Table 1.2:- Summary of IEEE standards IEEE Std Amended by IEEE j-2009,802.16h- 2010,802.16m-2011 IEEE Std Amended by IEEE g-2007,802.16f- 2005,802.16e-2005, IEEE /Cor1/2005 IEEE Std Amended by a- 2003(NLOS: 2-11GHz) c-2002 IEEE LOS:10-66 GHz IEEE Std p (First Amendment to IEEE Std ): Enhancements to support Machine-to-Machine Applications Approved by IEEE-SA Standards Board on 30 September 2012 and published in October IEEE Std n (Second Amendment to IEEE Std ): Higher Reliability Networks Approved by IEEE-SA Standards Board and published in June2013. IEEE : WirelessMAN-Advanced Air Interface for Broadband Wireless Access Systems; published 07 September IEEE Std (Reaffirmed for five years, ) 17

16 IEEE Std /Conformance IEEE Std k-2007: Bridging of IEEE Quality of Service Provisioning in WiMAX IEEE was developed keeping in view variety of traffic models in mind and is supposed to accommodate both real and non-real type traffic applications simultaneously. It must be able to satisfy quality of service requirements for these applications. IEEE has variety of QoS mechanism at PHY layer like TDD, FDD, FEC, FFT and OFDM that helps to achieve desired QoS levels. The main feature of QoS provisioning that distinguishes it from other wireless standards (i.e and 3G), is that each packet is associated with a service flow which makes for connection oriented MAC protocol. Transmissions between BS and SS occur on basis of unidirectional connections. Each connection is identified by 16-bit number known as connection ID (CID) and is mapped to a service flow which is identified by 24-bit identifier known as SFID. CID is mapped to SFID only when service flow is either active or admitted. A service flow specifies quality of service requirements that govern transmission of protocol data units (PDUs) on that connection. A QoS parameter set is associated with each service flow. Type of QoS parameter set determines status granted to service flow by Authorization Module (admitted or active). An external set of QoS parameters can also be provisioned to MAC without Authorization Module. There are three types of defined QoS parameter sets ProvisionedQoSParameterSet :- set of external QoS parameters provided to MAC, for example by Network Management system, AdmittedQoSParameterSet: set of QoS parameters for which resources are reserved by BS or SS and consist of flows that have been admitted by BS. Active QoSParameterSet: It contains parameters that reflect actual service being offered to service flow. Service flows may be created, changed or deleted using Dynamic Service Addition (DSA), DS change (DSC), and DS delete (DSD) MAC management messages, respectively which mean that they can be dynamically managed. A classification process is defined by IEEE to facilitate delivery of MAP SDU(service data unit) with appropriate QoS constraints. This process 18

17 maps MAC SDU to its corresponding connection and further to service flow for that connection. It is performed by classifiers consisting of a set of protocol-specific matching criteria. Each user application is checked for service to be offered and a specific scheduling service is attributed to handle this flow. Based on this, a new service flow is created but set of QoS parameters for that scheduling service shall be specified before its creation. Uplink flows in addition to a scheduling service, are mapped to one of these request/grant scheduling types: unsolicited grant service (UGS), real-time polling service (rtps), extended real-time polling service (ertps), non real-time polling service (nrtps), and best effort (BE). Each scheduling service is designed to meet QoS requirements of a specific applications category and has priorities of its own. Standard specifies more priority to real time scheduling services like UGS, ertps and rtps as compared to non-real type service classes. Table 1.3 lists mandatory service flow QoS parameters that needs to be specified for various scheduling service types. Type of Service Bandwidth Request Uplink Scheduling Min reserved traffic rate UGS rtps nrtps BE ertps CBR flows Not required fixed number of time slots in a frame Real-time VBR flows Not Defined Require better than best effort service Contentionfree (Unicast Polling) Contentionfree contention Not Defined Best effort service Real time variable size flows with guaranteed data rate Table 1.3:- Mandatory QoS parameters for different scheduling service types for IEEE or All types Not defined Yes Yes Yes -- Yes Max latency Yes Yes Yes Tolerated jitter Yes Yes Traffic priority --- Yes Yes --- Yes Example VoIP MPEG video FTP HTTP, SMTP Polling and Uplink allocation Not defined VoIP with silence suppression 19

18 UGS is designed to support real-time applications that generate fixed-size data packets at periodic intervals, such as T1/E1 and voice over IP (VoIP) without voice activity detection (VAD). Bandwidth is not requested by UGS connections. BS computes amount of bandwidth to be allocated to UGS on the basis of minimum reserved traffic rate specified in service flow of that connection after fixed time intervals. rtps is designed to provide support for real-time applications generating variable-size data packets at periodic intervals, such as MPEG video. Bandwidth requirements for rtps must be specified to BS and every rtps connection is allocated bandwidth by BS periodically. SS may use this bandwidth for sending data or for requesting more bandwidth. This corresponds to polling bandwidth-request mechanism. WiMAX supports three types of polling: unicast polling, multicast polling and broadcast polling. rtps connections can use unicast polling only. Extended rtps was introduced by IEEE e-2005 standard to support real-time service flows that generate variable size data packets on a periodic basis, such as Voice over IP services with silence suppression. It is defined to use bandwidth allocation advantages of UGS class and variable size allocations of rtps class. BS is supposed to make unicast grants in an unsolicited manner like for UGS class which saves latency of bandwidth request. Other advantage of using ertps is that allocations can be of variable size like rtps. The default size of allocation is equal to current value of Maximum Sustained Traffic Rate specified by connection however size of allocation can be changed on request by SS. nrtps is designed to support delay-tolerant applications which require a minimum amount of bandwidth such as FTP. Polling is allowed for nrtps connections but individual polling is not allowed. Multicast and broadcast polling is allowed for nrtps connections which must not necessarily be periodic but must be regular. BE is designed for applications that do not have any specific bandwidth or delay requirement, such as web traffic HTTP and SMTP traffic. Poling of all forms is allowed for BE. BE connections have least priority and normally residual bandwidth is allocated to these connections. 1.5 Objectives of Research Every ongoing activity is aimed at certain goals. The present study is aimed at achievement of under mentioned objectives 20

19 1. To study growth of IEEE standard and various Quality of Service, scheduling and bandwidth allocation aspects of IEEE networks. 2. Study of various soft computing techniques as applicable to solve scheduling problem in IEEE networks. 3. Proposal and implementation of scheduling framework for IEEE networks. 4. Improve overall performance of network by providing desired QoS levels and imparting fairness to different types of flows in IEEE networks. 5. Comparison of proposed and already existing algorithms based upon some network performance parameters like throughput, jitter, delay etc. 1.6 Significance of Research WiMAX is expected to provide high-bandwidth connectivity with guaranteed quality-ofservice to mobile users in a seamless manner; however, this desired functionality demands efficient and quick schedulers for seamless distribution of resources. The process of resource allocation in network like WiMAX is very challenging because of severe competition among its peers and fading channel conditions. Development of effective schedulers is heart of providing guaranteed quality of service to various applications. Significance of research proposed in this study can be viewed from three perspectives:- End user, Industry and Academia. End-user Significance:-Man being a social animal is always hungry for interaction and communication. Growth of rich multi-media applications and availability of smart phones has raised human appetite for more and more resources. Present schedulers are not able to adapt themselves to changing user requirements. This proposal is an attempt to provide a scheduling mechanism that adapts itself to changing requirements of real time traffic. The overall communication among different end users will increase and end users will be benefitted with increased data rates. Quality of videos and voice transmitted on network will increase thereby facilitating various applications like TV and medical imaging. Industrial Significance:- Recognizing strong co-relation between broadband proliferation and increased economic activity and experience of burgeoning wireless market, government has recently make BWA auctions in 2008 to accelerate BB adoption in India. Industry and country are awaiting to see which wireless technology will be adopted to provide cost effective, robust, 21

20 22 wide availability and scalable BB solution to Indian market. WiMAX emerges as the quintessential answer to these issues given its superior performance and lower costs as compared to other similar technologies like 3G, LTE etc. It is an ideal choice for telecommunication companies for providing high speed wireless connectivity at affordable prices as it reduces per MB cost for deployment since it can operate on already available infrastructure. Design of good schedulers will help industry to manufacture devices that can handle more number of users applications per cell and help them to raise their revenues. Academic Significance:- Resources in wireless network are always famine and schedulers available today do not react to changing requirements of users. Application of soft computing techniques will help to design adaptive schedulers and will attract budding researchers from other domains like Artificial Intelligence to look for further research in this direction. The intra domain gap will be reduced with involvement of more researchers on to a common platform. Currently WiMAX has been offered as subject in some reputed universities around the world and IIT Kharagpur in India. Study of explorations in field of WiMAX are important from that view point also as students will be able to work on an upcoming technology that will be very recently adopted by industry. 1.7 Research Contributions Authors of the study hope to contribute at number of places that will be helpful for researchers adopting this field. Progress of standard, various amendments made to it since its inception by IEEE has been studied and documented. A review as well as categorization of various schedulers currently available in literature has been done and published. Analysis and comparison of recent and promising scheduling proposals under PMP mode is also made. It can help budding researchers to start with basic understanding of scheduling problem and available scheduling solutions. Soft computing techniques have been explored for applicability to scheduling problem. Use of soft computing techniques will attract and invite researchers for more inter disciplinary work. A new approach based on fuzzy logic for scheduling is proposed which can be utilized by industry to optimize working of schedulers and manufacture devices that are able to satisfy user requirements more efficiently. The approach has been simulated in Qualnet 5.2 simulator that required making modifications to source code. The complete process of simulation and how changes to schedulers have been made

21 is documented in this study. Qualnet being a proprietary of Scalable Technologies Ltd, USA has limited or negligible help available as compared to other simulators like ns2, MATLAB etc. There has not been a single paper describing how to add own scheduling component to existing Qualnet libraries. The process elaborated in this study will act as ladder for researchers to understand and implement features related to IEEE network in Qualnet. 1.8 Chapter Summary and Thesis Organization has introduced topic of wireless and broadband networks. IEEE is series of standards developed by IEEE for wireless broadband metropolitan area networks. WiMAX is more common name for such networks developed and popularised by WiMAX forum. Comparison of WiMAX with other similar technologies has been discussed. History of development of various IEEE projects and standards over the years of its inception is described at stretch with listing of currently active and superseded standards. This chapter has also elaborated as how WiMAX provides quality of service support to various applications by mapping different user applications to five types of scheduling services namely UGS, ertps, rtps, nrtps and BE. These scheduling services are allocated bandwidth by base station based on their requirements however allocation mechanism is not specified by standard. The chapter has also listed out objectives which this study has tried to achieve. Significance from end user, industry and academic prospective has been discussed. The major research areas where this research can contribute are also specified in this chapter. The rest of thesis is organized as follows:- Chapter 2 covers exploration of literature available in the field of WiMAX scheduling. It begins with introduction to process of resource allocation and role of scheduler in WiMAX. Literature available in field of scheduling has been discussed by classifying available techniques into five different categories. These categories have been defined by authors on basis of their working principles and type of service classes served by them. Chapter 3 sums up availability of gaps in already explored studies of Chapter 2 and lists out areas where further explorations can be made. Problem statement has been documented and research methodology adopted to solve this problem is also discussed. This chapter helps to confine scope of problem from a wider 23

22 problem area to a narrower domain. Limitations under which current study is implemented are also listed. Chapter 4 describes design of scheduling framework used for solving scheduling problem in IEEE networks. It provides elaborations as how fuzzy logic has been used to provide dynamism to make traditional weighted fair queuing algorithm adaptive. Working of WFQ and enhancements made to working of WFQ using fuzzy logic is described. The framework is proposed to work as component of base station and works as 3 variable input and single variable output system. Process of bandwidth allocation to various flows and transmission of data packets to various destinations is elaborated. Chapter 5 explains development of the proposed framework of fuzzy adaptive system in Qulanet simulator. Available facilities and architecture of simulator are discussed followed by detailed elaboration of process of incorporating a new scheduler for WiMAX networks. Detailed steps for embedding fuzzy logic in Qualnet environment are explained. Chapter ends by discussions on network setup used and how various experiments are designed for verification and analysis of proposed approach. Chapter 6 portraits results obtained by executing various designed experiments and chats about inferences obtained from these results. Performance of developed scheduler in terms of various performance metrics is measured and explanation for variations in results is presented. Comparison of proposed approach with traditional established approaches like WRR, WFQ and EDF is also done in this chapter. Chapter 7 summarizes the overall progress of study and provides with a brief conclusion of work done. Achievement of various objectives is condensed. Future directions of research originating from current research work are also briefed. 24