The WiMAX 802.16e Advantage An analysis of WiFi 802.11 a/b/g/n and WiMAX 802.16e technologies for license-exempt, outdoor broadband wireless applications. White Paper
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Objective WiMAX and WiFi are technologies utilized for outdoor wireless applications. Both technology standards have evolved throughout the years, offering wider coverage, higher throughput and better interference mitigation. The inherent characteristics of, and thus differentiators between WiMAX and WiFi, stem from the fact that WiMAX, as a technology, was originally designed for outdoor implementations, while WiFi was meant for indoor usage. This paper will discuss the history of these technologies and assess their differences and advantages. WiMAX and WiFi Technology Evolution IEEE 802.11 is a set of standards for Wireless Local Area Network (WLAN) communication in the 2.4, 3.6 and 5 GHz frequency bands. 802.11 Overview The 802.11 family includes over-the-air modulation techniques that use the same basic protocol. The most popular protocol versions, in terms of usage, are the 802.11b (released in October 1999) and 802.11g (released in June 2003), which are amendments to the original standard 802.11-1997 (the first wireless networking standard). The 802.11a standard (also released in October 1999) operates in 5 GHz. This carrier frequency is not as popular as the previous ones for access applications. The 802.11n group was formed in January 2004. The main objective was to achieve higher data rates in a multipath fading channel. 802.11n is a recent amendment which improves upon the previous 802.11 standards by adding Multiple-Input Multiple-Output (MIMO) and other new features. 802.11 technology performance results are commonly presented by the theoretical maximum net bit rate; quoted as 11 Mbps for 802.11b, 54 Mbps for 802.11a/g and 270 Mbps for 802.11n (MIMO 2X2 @ 40 MHz). The actual throughput is 25-50% of the theoretical rate in an indoor environment; and in an outdoor environment, the performance is significantly reduced (depending on the topology, deployment scenario LOS/ NLOS) The 802.11 indoor protocol performance also degrades as the number of users increase. IEEE 802.16, a series of broadband wireless standards, operates in licensed and license-exempt frequencies. The standard was originally designed to support Wide Area Networks (WAN), describing how wireline technologies such as Ethernet, ATM and IP are encapsulated on the air interface, and how data is classified. 3
802.16 Overview IEEE 802.16 standardizes the air interface and related functions associated with Broadband Wireless Access systems, a key feature of 802.16 is that it is a connection-oriented technology. The Subscriber Station (SS) cannot transmit data until it has been allocated a channel by the Base Station (BS). This allows 802.16e to provide strong support for Quality of Service (QoS) and the ability to support large number of users simultaneously while maintaining high service quality. The latest IEEE 802.16 standard is 802.16-2009, incorporating the IEEE 802.16e, which addresses mobile broadband wireless. This implemented a number of enhancements to 802.16-2004, including better support for QoS, the use of scalable OFDMA, MIMO antennas and HARQ support. This standard is also called Mobile WiMAX, as its enhanced technology supports inherent mobility, enabling the subscriber to transparently roam from one base station to another. The enhanced radio features that enable mobility support also significantly increase general performance especially in high interference conditions resulting in an optimum wireless broadband solution for fixed and nomadic license-exempt networks. Technical Differences WiFi 802.11 a/b/g/n WiMAX 802.16e Comments Technology Design Target Designed for (WLAN) mainly for indoor applications and small networks Designed for WAN, for outdoor applications and large networks to support fixed, nomadic and mobile applications Target Application Characteristics Indoor wireless 5 access Short distance Small network High capacity Outdoor wireless access Long distance Small/mid/large networks High capacity Mobile applications 4 (vehicular for 5 GHz) The 802.11 technology can support additional applications to those mentioned here; however the performance is significantly reduced when an application has requirements out of the scope of the technology design, e.g. large number of subscribers, long distance, etc. Channel BW 5/10/20/40 MHz 5/10/20 (2X10) MHz A 40 MHz channel has limited contribution in an outdoor license-exempt deployment. In most outdoor scenarios using a 40 MHz channel will cause performance degradation when compared to a 20 MHz channel due to increased interference exposure. 4
Technical Differences WiFi 802.11 a/b/g/n WiMAX 802.16e Comments Maximum Capacity 802.11a: 54 Mbps (20 MHz) 802.11b: 11 Mbps (20 MHz) 802.11g: 54 Mbps (20 MHz) 802.11n: 130 Mbps (20 MHz) 270 Mbps (40 MHz) 802.16e: *45 Mbps (10+10 MHz) MIMO A *80 Mbps (10+10 MHz) MIMO B *BreezeMAX Extreme 3650/5000 This is not an apple to apple comparison 802.11 statistics quote the modem rate while 802.16e statistics quote user data rate 802.11n presents theoretical modem rate 802.16e incorporates more features for handling interference mitigation which reduce the total available 802.16e bit rate. The 802.16e actual bit rate is actually expected to be higher than 802.11n in most deployments scenarios due to its superior interference mitigation In general, 802.11n quotes refer to indoor performance, while 802.16e to outdoor deployments. 40 MHz cannot be implemented in most outdoor deployments due to license-exempt interference Coverage Related Features MIMO A: only in 802.11n MIMO A HARQ CTC The 802.16e link budget is better in 5 db compared to 802.11n, thus wider coverage is supported OFDM OFDMA The 802.16e OFDMA support handles NLOS in a more efficient manner and enables wider coverage when compared to 802.11 5
Technical Differences WiFi 802.11 a/b/g/n WiMAX 802.16e Comments Interference Mitigation MIMO A: only in 802.11n, and not implemented on most chipsets available (as they are designed for indoor) OFDM Overcoming short range multipath FFT 64 (3.2µsec), Guard Interval 0.8µsec MIMO A OFDMA Overcoming long range multipath FFT 1024 (90µsec), Guard Interval 11µsec HARQ Scheduled protocol OFDMA provides each user best performance according to the link quality (location and propagation characteristics), thus overcoming fading and interference challenges based on each user while maintaining its maximal performance As 802.16e is targeted for outdoor deployments it supports 13 times multipath distance comparing to 802.11n HARQ is a state-of-the-art error detection and correction method that significantly improves the link performance and reliability The 802.16e scheduled protocol significantly increases interference resistance compared to the 802.11 CSMA protocol QoS Limited to AP s local QoS WMM/WME 4 access categories: voice, video, best effort, and background Limited MIR/CIR support Network-wide advanced QoS Connection-oriented Centralized control Scheduled protocol 5 QoS classes: UGS, ertps, rtps, nrtps, BE CIR/MIR support The 802.16e QoS is a network wide mechanism taking into consideration the load and prioritization in the entire network The 802.11 QoS mechanism is local to the AP and to the subscribers connected to it. The QoS mechanism considers the complete network The 02.16e QoS performance is expected to perform better in an outdoor license-exempt deployment challenged by high traffic, mixed applications and interference 6
Technical Differences WiFi 802.11 a/b/g/n WiMAX 802.16e Comments Number of Subscribers Limited High In an 802.11 network, aggregated throughput is expected to be decreased as more subscribers are added due to packet collisions In an 802.16e network traffic is centrally managed and scheduled. Adding more subscribers does not degrade the total aggregated throughput Conclusion 802.16e and 802.11n are examples of two leading wireless technologies evolving and improving with the addition of new features and enhanced radio techniques. The core technology and its original target applications greatly influence the performance that can be achieved in different scenarios. 802.11n, which was originally designed for indoor applications, offers higher potential bit rate. The benefit of this high bit rate can be achieved only in small, indoor wireless networks. Performance is expected to be significantly reduced in a large, outdoor deployment. 802.16e was originally designed for large, outdoor deployments by reserving more bandwidth to overcome the outdoor challenges. Its superior radio techniques and QoS mechanism enable maintaining high performance and better control of network traffic. Theoretically 802.11n may present higher performance than 802.16e, but actual deployments indicate that high throughput can only be achieved in an indoor deployment or in limited scenarios of outdoor deployments. In standard and complex outdoor deployments, 802.16e technology is designed to provide better performance utilizing its enhanced radio and QoS capabilities that were originally designed for the more challenging, outdoor deployments. 7
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