Quality of Service in WiMAX Based Broadband Wireless Networks - Essay Example

Quality of service in WiMAX Based Broadband Wireless Netwoks Worldwide Interoperability for Microwave Access (WiMAX), is a new wireless standard for large WAN/MAN networks. It offers better opportunities and a different set of challenges in deployment and QoS. With increasing demand of higher data transfer rates in wireless networks, WiMAX based broadband wireless networks has drawn greater attention of research community worldwide. WiMAX Forum a leading industry consortium and IEEE working groups are working in collaboration of research community to overcome current infrastructure, QoS and implementation issues that are restriction the adoption of WiMAX technology. WiMAX technology promises a better, more robust and cost effective alternative to existing wireless networking technologies and traditional wire-based broadband Internet connections. Introduction IEEE 802.16/WiMAX-based broadband and mobile wireless access is expected to be a significant component in the next generation (e.g., beyond 3G, 4G) wireless systems (Hossain 1). There is a clear shift from telephony to data transfer in wireless networks. In this scenario WiMAX technologies and solutions are poised to play a major role in broadband Internet access and other form of connectivity. The technology is in its early development phase and there is a widespread research and consultation is going on this field. The issues of quality of service (QoS) are becoming more demanding with the growing demand of the rich media of smartphones and high end gadgets. Users are now more concerned with the QoS of the services with increasing capacity and reach of wireless technologies. IEEE 802.16/WiMAX standard, which incorporates several advanced radio transmission technologies such as orthogonal-frequency division multiplexing (OFDM), adaptive modulation and coding, and adaptive forward error correction (FEC), is designed to provide broadband wireless capability using a well-defined quality-of-service (QoS) framework. Though, the adoption of technology is still very limited due to cost and infrastructure restrictions, researchers contest that with a wide-scale adoption and production of WiMAX compliant solutions, it can provide a cost effective connectivity solution to locations where it currently is neither feasible nor affordable (Richardson, Ryan 1). This paper will discuss the current evolutions going on in the field of WiMAX technologies and issues related to quality of service issues in WiMAX Based Broadband Wireless Netwoks along with its, its forms, and the status of its standardization. A specification of the selected topic and the motivation behind this selection WiMAX and WiMAX-based broadband wireless network offer an alternative to existing wireless and mobile communication technologies. Due to mounting demand for higher bandwidth and better QoS, WiMAX technology has became a subject of intense research and debate among researchers and academicians. In this context the selection of the topic "Quality of Service in WiMAX-Based Broadband Wireless Networks" as a subject of this paper is quite contemporary and may act as a part of ongoing debate over the technology. Existing protocols and solutions IEEE's 802 LAN/MAN Standards Committee is almost anonymous with a wireless standards body. IEEE 802.11 set of standards developed by this committee provide a basis for wireless local area network (WLAN) communications. The IEEE 802 LAN/MAN Standards Committee established a working group in 1999 for the development of standards specific to Broadband Wireless Access. IEEE 802.16 Working Group on Broadband Wireless Access Standards, as it is known, is responsible for laying down formal standard specifications for broadband wireless MAN/WAN networks. Since the first 802.16 standard was approved in December 2001, three working groups have been involved for developing standards; the group IEEE 802.16.1 is responsible for creating standards for air interfaces in range of 10 to 66 GHz, known as Local Multipoint Distribution Service, group IEEE 802.16.2 is working on coexistence of broadband wireless access systems and IEEE 802.16.3 is involved with the development in the field of air interfaces for licensed frequencies of 2 to 11 GHz, also known as 802.16a. IEEE's 802 LAN/MAN Standards Committee has outlined several standards that govern wireless networking technologies: IEEE 802.16-2004 - IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems. IEEE 802.16.2-2004 IEEE Recommended Practice for Local and metropolitan area networks -- Coexistence of Fixed Broadband Wireless Access Systems. IEEE 802.16Conformance01-2003 IEEE Standard for Conformance to IEEE 802.16 Part 1: Protocol Implementation Conformance Statement (PICS) Proforma for 10-66 GHz WirelessMAN-SC Air Interface. IEEE 802.16Conformance02-2003 IEEE Standard Conformance to IEEE Std 802.16 Part 2: Test Suite Structure and Test Purposes for 10-66 GHz WirelessMAN-SC Air Interface. IEEE 802.16Conformance03-2004 IEEE Standard Conformance to IEEE Std 802.16 Part 3: Radio Conformance Tests (RCT) for 10-66 GHz WirelessMAN-SC Air Interface. IEEE 802.16Conformance04-2006 IEEE Standard Conformance04-2006 Part 4: Protocol Implementation Conformance Statement (PICS) Proforma for Frequencies below 11 GHz. IEEE 802.16e-2005 IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems Amendment for Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands. IEEE 802.16f-2005 IEEE Standard for Local and Metropolitan Area Networks - Part 16: Air Interface for Fixed Broadband Wireless Access Systems--Amendment 1--Management Information Base. IEEE 802.16g-2007 IEEE Standard for Local and Metropolitan Area Networks - Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems - Amendment 3: Management Plane Procedures and Services. IEEE 802.16k-2007 IEEE Standard for Media Access Control (MAC) Bridges Amendment 2: Bridging of IEEE 802.16. WiMax infrastructure provides protocol support for various existing interface technologies such as Ethernet, TDM, ATM, IP, and VLAN. 802.16 infrastructure is made up of three physical layers namely Orthogonal Frequency Division Multiplexing (OFDM), Single carrier (SC) and Orthogonal Frequency Division Multiplexing Access (OFDMA). Media access controller (MAC) an another major component of WiMAX infrastructure offers a flexible uplink and downlink capacity to adjust according to link conditions to terminals and accommodate major protocols for a enhanced quality of services. Fig: WiMAX Infrastructure MAC plays a major role in ensuring the quality of services. It uses a variable protocol data unit which provides a better tradeoff between quality and robustness of wireless services. MAC is designed to provide native support to all popular current and future data transport protocols and interfaces. Different versions of 802.16 standards, as listed above, developed over time seeks to provide better compatibility between existing protocols and solutions. The dynamic nature of MAC provides a better load balancing and QoS during periodic activities such as scheduling, packing, fragmentation and ARQ. According to the WiMAX Forum, "The fundamental premise of the IEEE 802.16 MAC architecture is QoS. It defines Service Flows which can map to DiffServ code points or MPLS flow labels that enable end-to-end IP-based QoS. Additionally, subchannelization and MAP-based signaling schemes provide a flexible mechanism for optimal scheduling of space, frequency, and time resources over the air interface on a frame-by-frame basis. With high data rate and flexible scheduling, the QoS can be better enforced. As opposed to priority-based QoS schemes, this approach enables support for guaranteed service levels including committed and peak information rates, latency, and jitter for varied types of traffic on a customer-by-customer basis". Packet size in Wireless data transmission varies according to requirements of different services. Some of services are require more accuracy than others whereas some services focuses more on the latency factor the error factor. WiMAX overcomes these issues by Protocol Data Unit (PDUs); it assigns variable length PDUs to data packets when data leaves the physical layer of protocol stack that reduces signaling overhead in the PHY layer. The use of variable length of PDUs is referred as adaptive modulation and gives a clear edge the WiMAX over other existing wireless technologies. Similarly, MAC uses adaptive modulation of Service Data Units (SDUs) to reduce packet bottlenecks during signaling. WiMAX supports both Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD) technologies for data transmission. FDD which requires two separate cannels to send and receive data is most commonly used technique for cellular networks whereas TDD provides a dynamic and symmetric transmission of data across a single channel. This multiple duplexing support provides WiMAX a flexible deployment options and WiMAX vendors can work on the products that appeal a large section of industrial and personal users. WiMAX Solutions WiMAX based broadband wireless networks and solutions can be used as a: Alternative to cable and DSL for last mile back haul broadband access. An interface between existing networking technologies such as Wi-Fi hotspots, IP based packet networks, and mobile technologies such as GSM and CDMA. Alternative to Wi-Fi and other networks to provide data and telecommunications services. WiMAX QoS Issues QoS in WiMAX based broadband wireless netwoks is a complicated and difficult issue due to several factors such as unpredictable radio link and evolving interfacing to existing TCP/IP protocols. QoS over any wired or wireless network constitute of bandwidth, latency, jitter and reliability factors. WiMAX has fixed and wireless access applications and interfaces both wireless access technologies such as 3G and WiFi along with fixed-line technologies such as DSL and fiber. Major QoS issues with WiMAX based broadband wireless networks are discussed below: Bandwidth: Bandwidth is a major issue from end-user perspective. It is first parameter that a bandwidth hungry end-user look for to satisfy their high data demand on the move. With invent of hi-end gadgets such as iPhone that acts as a mini computer, higher access rate is becoming a prerequisite for selecting a networking technology. The bandwidth factor is dependent on the physical layer of link between an end-user and a service base station. It is also proportional to number of total users connected to a base station. A higher bandwidth can suppress other QoS issues of latency and jitter. Moreover other issues come in light only during the service whereas bandwidth is a major criterion for selecting a technology. WiMAX technology is touted to support a bandwidth of about 70 Mb/s over 31 miles which give it a clear superiority over other networking technologies such as Wi-Fi but as of current developments it only can support either a coverage of around 30 miles or a max bandwidth of 70 Mb/s. in fact a WiMAX network can deliver 70 Mb/s of data rate for a short range, as the range increases the data rate goes down. Further, in a metropolitan area bandwidth can be further depleted due to sharing in a large user base. Latency : It is delay in receiving a packet by user after the transmission is initiated be a base station. Latency has been a major issue for VoIP services and solutions. It depends upon the nature of physical layer, various QOS protocols and how packets are queued. 802.16 based wireless networks offer a latency of about 5 ms. Jitter: Jitter is the variation of latency of different packets. Techniques such as packet buffering are generally used to minimize the jittering during transmission that is packets are stored in a buffer when they arrive at users' end and users use these packets when a certain predefined number of packets are collected. Jitter control is more important for voice communication than data. WiMAX infrastructure tightly controls this latency and jitter on links used for voice, while appropriately adjusting for various other types of data (Tucker). Reliability: It is measure of the successfully delivered packets over total packet transmission. Reliability of wireless network has always been a subject of wide research and debate among researchers and academics. The issue is that wireless networks have an inherent unreliability because of the vicissitudes of radiowave propagation - especially to mobile terminals with small antennas and low powers in cluttered environments such as urban areas. So packet loss and numbers of packets errors will be higher in wireless networks than for fixed-line networks (Dawood 6). Automatic Repeat Request (ARQ) feature in WiMAX MAC helps in ensuring communication reliability. It resend missing or corrupt frames before the upper layers are aware of the error condition, making the network more efficient (Tucker). Comparison and Criticism of the Advantages and the Shortcuts of the Solutions Proposed By the Literature WiMAX and WIMAX-based wireless networks have attracted immense interest from researchers and scholars. While most of the research paper univocally highlighted the advantages of WiMAX technology others have been skeptical about the capabilities and deploy-ability of WiMAX solutions. Several alternative solutions have been proposed to overcome shortcomings and limitations of the technology. Gierowski, Woniak, and Nowicki in their research paper "A hybrid-mesh solution for coverage issues in WiMAX metropolitan area networks" highlighted the design and implementation difficulties concerning network coverage discovered in a test-bed implementation of WiMAX and the presence of unexpected "white spots" in the WiMAX coverage, which are not inherently characteristic of the WiMAX concept. They have suggested a reconfigurable mesh organization of WiMAX base stations to overcome the the existing problem. Though the proposed mesh architecture is very promising, a fully functional mesh mode requires a significant number of additional, advanced mechanisms, and is still in a very early stage of research and development. Mo Shakouri, vice president of marketing for the WiMAX Forum explains, "[b]y adding mobility to WiMAX, it would be a unique capability to complement DSL and compete with DSL" (Luna 2005, p. 3). As Shakouri further notes, WiMAX will compete with cable/DSL by providing mobility in addition to a high-speed connection (Luna 2005, p. 3). According to researchers, WiMAX cannot truly compete for 3G data services unless a company like Sprint Nextel ends up using WiMAX equipment and immediately builds a nationwide infrastructure for it (Richardson & Ryan 29). Richardson and Ryan further adds that WiMAX may be a 4G technology because its modulation techniques make more efficient use of radio spectrum; as a result, higher data rates are possible than with any of the 3G technologies. Conclusion and recommendations WiMAX technology and based solutions such as broadband wireless networks are still in its early stage of development. Though there are certain concerns about the deployability of WiMAX-based wireless networks, it offers a reliable and robust alternative to existing networking technologies such as Wi-Fi. More research and development in this field can help in developing this technology for potential uses in for flung areas where regular wired access to broadband Internet services is not possible. A large scale adoption of the technology may bring down the cost of WiMAX compliant products and services which is considered by many as a major roadblock for the WiMAX. It may also compete with existing technologies 3G or 4G for providing a higher data transfer rates better QoS. Works Cited Does WiMAX have quality of service (QOS) capability 25 Dec 2008 . Dawood, M. Theoretical Research about: WiMAX & QoS. May 2007. Gierowski K., Woniak, J. and Nowicki, K. A hybrid-mesh solution for coverage issues in WiMAX metropolitan area networks. Journal of Telecommunication and Information Technology. Jan 2008. Hossain, E. IEEE802.16/WiMAX-Based Broadband Wireless Networks: Protocol Engineering, Applications, and Services. Fifth Annual Conference on Communication Networks and Services Research (2007): 1-4. IEEE 802.16 Broadband Wireless Metropolitan Area Netwrok (WirelessMAN). IEEE Standards Association. 25 Dec 2008 < http://standards.ieee.org/getieee802/802.16.html>. Luna, Lynette (2005), "Wireless Quadruple Play: Prime Time for WiMAX" Telephony, 246 (20), in Ebsco Host [database-online], Academic Search Premier, (accessed November 10, 2005). Richardson M. and Ryan P. WiMAX: Opportunity or Hype Proceedings of the Fourth Annual ITERA Conference, ITERA 2006. Murray State University Center for Telecommunications Systems Management. Tucker, E. Why WiMAX for Voice: Can Voice be the Killer App for WiMAX 25 Dec 2008 . WiMAX Protocol. 25 Dec 2008 < http://www.tutorial-reports.com/wireless/wimax/protocol.php>. WiMAX Forum home page. 25 Dec 2008 http://www.wimaxforum.org/home/. Read More