WiMAX: Technology for Broadband Wireless Access
16.2 Comparison Between WiMAX and WiFi
A start can be made by saying that comparing WiMAX and WiFi is comparing two different frameworks. WiMAX has much longer distances and may (or will) also include mobility between cells. In fact, WiFi and WiMAX are complementary, specifically if WiMAX is used for the backhauling of WiFi (see Chapter 1).
There is also a difference in the chronology. WiFi is a WLAN, based on the IEEE 802.11 standard, published in 1997, and the 802.11b variant, published in 1999. WiMAX is a BWA system, including mobility, based on the IEEE 802.16-2004 standard [1], published in 2004, and the 802.16e variant [2], published in February 2006 (in addition to other 802.16 amendments). Hence, if we consider the standard or the products, there is a difference of about six years between the two. In Table 16.1, some comparison elements between WiFi and WiMAX and proposed.
| WiFi/802.11 WLAN | 802.16/WiMAX | |
|---|---|---|
| Data rate (PHY Layer, optimistic) | 54Mb/s /20MHz channel | 26.2 Mb/s/7 MHz channel |
| QoS management | Best Effort, unless for the seldome (until now) implemented 802.11 variant | Five classes of QoS |
| Multiple access | CSMA/CA (MAC Layer common to 802.11, 802.11a, 802.11b and 802.11g); TDD | TDMA: TDD and FDD. Sophisticated bandwidth reservation mechanisms |
| Range | Order of magnitude: 100m | 20 km (outdoor CPE), 10 km (indoor CPE) |
| Frequency bands | Unlicensed | Unlicensed and licensed |
| Typical use | WLAN | Fixed wireless access, portability, mobility, etc. |
Some precision must be given for the data rate. The one expressed in Table 16.1 is the PHYsical data rate, i.e. the data rate of coded bits. The highest data rate mode is displayed in the table. For all these packet-type transmissions, there is no fixed value for a data layer data rate value due to retransmission, link adaptation, variable header sizes, etc. Standardisation efforts are going on in order to have a higher data rate for IEEE 802.11/WiFi, specifically with the 802.11 n variant.
WiMAX has a much better performance than WiFi (range, QoS management, spectrum use efficiency, etc.) but this comes at the price of a higher cost in frequencies and in equipment complexity (and then cost). Consequently, it is definitely not certain that WiMAX could one day soon replace WiFi for some applications.
[1]IEEE 802.16-2004, IEEE Standard for Local and Metropolitan Area Networks, Air Interface for Fixed Broadband Wireless Access Systems, October 2004.
[2]IEEE 802.16e, IEEE Standard for Local and Metropolitan Area Networks, Air Interface for Fixed Broadband Wireless Access Systems, Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and Corrigendum 1, February 2006 (Approved: 7 December 2005).
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