WIFI Comparison With Wimax

WiMAX is different from WiFi in many respects. The WiFi MAC layer uses contention access. This causes users to compete for data throughput to the access point. WiFi also has problems with distance, interference, and throughput and that is why triple play (voice, data, video) technologies cannot be hosted on traditional WiFi. In contrast, 802.16 uses a scheduling algorithm. This algorithm allows the user to only compete once for the access point. This gives WiMAX inherent advantages in throughput, latency, spectral efficiency, and advanced antenna support.

Companies developing radical innovations may adopt different stances not only based on the strategic interests of the company but also by taking into other considerations such as the market and its needs and requirements, as well as other products it may carry.

When comparing WiFi and WiMAX, one is comparing their substitutability and complementary to existing technologies and how different companies have and will view them. WiMAX and WiFi can offer some potentially significant cost savings for mobile network operators by providing an alternate means to backhaul BS traffic from cell site to the BS controllers. Mobile network operators typically utilize some type of wired infrastructure that they must buy from an incumbent operator. A WiFi or WiMAX mesh can offer a much more cost-effective backhaul capability for BSs in metropolitan environments.

Using WiFi and WiMAX open broadband wireless standards and implementing mobile computing, governments and partners can quickly and cost-effectively deploy broadband to areas not currently served, with little or no disruption to existing infrastructures. Standards-compliant WLANs and proprietary WiFi mesh infrastructures are being installed rapidly and widely throughout the world. Standards-compliant WiMAX products can provide NLOS backhaul solutions for these local networks and WiMAX subscriber stations can currently provide Internet access to customers such as schools and other educational institutions and campuses.

The results of the comparison show that mobile WiMAX has better performance in all the areas listed above (where it shares performance enhancing features with EVDO and HSDPA/HSPA). Furthermore, the technologies on which mobile WiMAX is based result in lower equipment complexity and simpler mobility management due to the all-IP core network. They also provide mobile WiMAX systems with many other advantages over CDMA-based systems such as

• Tolerance to multipath and self-interference
• Scalable channel bandwidth
• Orthogonal UL multiple access
• Support for spectrally-efficient TDD
• Frequency-selective scheduling
• Fractional frequency reuse
• Improved variable QoS
• Advanced antenna technology

1XEVDO Comparison With Wimax

This standard is developed by the third generation partnership project 2 (3GPP2), the body responsible for CDMA and EVDO. 1xEVDO is an enhanced version of CDMA2000-1x. There are four versions that have been released, namely, Rev. 0, Rev. A, Rev. B, and Rev. C.

1xEVDO is a high-speed data only specification for 1.25 MHz frequency division duplex (FDD) channels with a peak downlink (DL) data rate of 2.4 Mbps.

Improvements to CDMA2000-1x in the 1xEVDO Rev. 0 specification include:

• DL channel is changed from code division multiplexing (CDM) to time division multiplexing (TDM) to allow full transmission power to a single user.
• DL power control is replaced by closed-loop DL rate adaptation.
• Adaptive modulation and coding (AMC).
• HARQ.
• Fast DL scheduling.
• Soft handoff is replaced by a more bandwidth efficient “virtual” soft handoff.

1xEVDO Rev. 0, however, was designed to support only packet data services and not conversational services. In 1xEVDO Rev. A and EVDO Rev. C (also dubbed DORC), additional enhancements were added to the 1xEVDO specification. They include the following:

• DL: Smaller packet sizes, higher DL peak data rate (up to 3.1 Mbps), and multiplexing packets from multiple users in the MAC layer.
• Uplink (UL): Support of HARQ, AMC, higher peak rates of 1.8 Mbps, and smaller frame size

These enhancements in both the UL and DL of 1xEVDO Rev. A allow it to support conversational services.

COMPARISON WITH COMPETING TECHNOLOGIES

At some point current 2G and 3G network operators will migrate to a 4G network technology. Mobile WiMAX is likely to face competition from 3G and 4G technology enhancements. They include the code division multiple access (CDMA) variants CDMA2000 and wideband-CDMA (WCDMA) and their enhancements which are 1x evolution data optimized (1xEVDO) and HSDPA, respectively. Unlike in the early days of the CDMA vs. GSM competition, this higher generation competition will be quite different and fruitful because for these new generations networks; the applications are separated and do not depend on each other. 4G networks will go far beyond 2G and 3G by mainly improving three parameters:

• Interface technology: 4G standards will make a radical change and will use OFDM [9]. The new modulation itself will not automatically bring an increase in speed but very much simplifies the following two enhancements:
• Channel bandwidth: 4G systems will use a bandwidth of up to 20 MHz, i.e., the channel offers four times more bandwidth than channels of current systems. As 20 MHz channels might not be available everywhere, most 4G systems will be scalable, e.g., in steps of 1.25 MHz. It can therefore be expected that 4G channel sizes will range from 5 to 20 MHz.
• MIMO: The idea of MIMO is to use the multipath phenomena. Although this behavior is often not desired, MIMO makes active use of it by using several antennas at the sender and receiver side, which allows the exchange of multiple data streams, each over a single individual wave front. Two or even four antennas are foreseen to be used in a device. How well this works is still to be determined in practice but it is likely that MIMO can increase throughput by a factor of two in urban environments.

Increasing channel size and using MIMO will increase throughput by about 8–10 times. Thus speeds of 40 Mbps per sector of a cell are thus possible. Using a commonly accepted evaluation methodology for 3G systems, mobile WiMAX has been simulated against the 3G enhancements [23]. These simulations have shown that

• Mobile WiMAX peak data rates are up to 5x better than 3G+ technologies.
• Mobile WiMAX spectral efficiency is 3x better than any 3G+ technology.
• Lower equipment cost for WiMAX due to certified products (compare with WiFi).
• WiMAX requires new infrastructure while high-speed packet access (HSPA) rides on UMTS.
• Roughly the same coverage (average ~5 km).
• Roughly the same performance (average ~2 Mbps per user).
• HSDPA launched in 2006 while HSUPA will come in 2008.
• WiMAX standard set end of 2005 and first products in 2006.
• HSPA has a higher acceptance with mobile operator.