MC-CDMA and the moves towards 4G networks and services
CDMA technology is a continuing driving force behind wireless networks around the globe and according to the CDMA Development Group (CDG), there were 431 million CDMA subscribers and 91million CDMA 2000 1x subscribers worldwide by the end of the year 2007.
According to 3GPP2, there are 280 operators globally that use the CDMA 2000 family of standards.
Systems beyond 3G such as WiMAX and 3GPP LTE which are based on OFDM have already been established. However, some systems such as Evolved HSPA, EV-DO Rev B and UMB are based on CDMA. The CDMA Development Group claims that a variety of technologies will drive competition which is healthier for the market. It is therefore believed that 4G may not be connected to a specific technology and will be a multitude of different access technologies that will complement each other providing a seamless experience to the user regardless of location. On the other hand, major European vendors believe that the 3GPP and 3GPP2 paths could coincide at the LTE point (2010-2011) and that after this time the same technology will be used by carriers that have been using 3GPP and 3GPP2 standards. It is also worth noting that the major backer of CDMA technologies Qualcomm believes that there is no reason why CDMA could not be used for even higher data rates such as those defined by the ITU for 4G, if a 4x4 MIMO configuration is implemented and the bandwidth is leveraged.
Most operators seem to prefer to see a transition to a new generation take place gradually. This is because, in addition to considerations of cost, operators prefer to reduce their risks, by rolling out new technologies and network architectures incrementally to gain a better understanding of the technology and the market response. It is believed that there will be many operators who will regard the HSPA+ and EV-DO Rev B path as an easier and safer way into higher data rates. Furthermore, an upgrade to HSPA+ is generally considered cheaper than a move to LTE since LTE is based on OFDM and a number of new components will be required.
It is therefore expected that by the year 2017, mobile OFDM solutions such as LTE, UMB and mobile WiMAX will only account for 6.4% of the global number of cellular subscribers. These initial deployments will primarily occur in densely populated areas as the spectrum is likely to remain underutilised.
This suggests that CDMA (both CDMA 2000 and WCDMA) will continue to dominate the cellular market for years to come. Therefore advanced 4G coverage is likely to take up to 20 years to happen. It is expected that at least till then CDMA and OFDM technologies will coexist. CDMA may also be used for even higher data rates as VSF (variable spread frequency)-OFCDM a technique similar to MC-CDMA has been used by NTT DoCoMo in various 4G field trials conducted by the company.
Источник: Report Linker
Заметили неточность или опечатку в тексте? Выделите её мышкой и нажмите: Ctrl + Enter. Спасибо!