Tuesday, August 23, 2011


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.
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