Mobile Wireless Communications Tomorrow (cont.)

by Puneet Gupta

Individual Technology Evolution Paths

A variety of technologies/standards exist and therefore, so do the number of paths that can be taken. The table below briefly summarizes these standards.

GSM and TDMA To 3G

GSM and TDMA systems have more or less the same set of options for migrating to 3G. The path to 3G is not as simple in case of GSM/TDMA as is in the case of CDMA. The main evolutionary standards are GPRS, EDGE and, finally, W-CDMA. Vendors are positioning each of these standards as a step to the next, but operators are not so sure. For an operator moving from GSM to GPRS to EDGE and then to W-CDMA, he'll have to make investments 3 times which won't be pleasing to any operator. As [1] suggests, at this time, there seem to be four basic options that GSM and TDMA operators are considering:

• Install GPRS, then move straight to WCDMA;
• Install EDGE, then move straight to WCDMA;
• Install GPRS, then move to EDGE, then to WCDMA; or
• Install EDGE, skip move to WCDMA, and wait for the next generation (4G).

Source: The Yankee Group, 2000

CDMA To 3G

While GSM and TDMA operators have multiple choices ahead for progressing to the next-generation networks, CDMA operators have a single path that truly builds upon itself . Currently all North American CDMA networks are based on IS-95 (cdmaOne) which can be setup to provide data rates upto 14.4 kbps. The next step is to have a software upgrade from IS-95A to IS-95B which provides additional voice efficiencies giving additional capacity, and allows for up to 84-Kbps packet data. (We might not see 84kbps but instead 64kbps, initially.) While this migration does not need any additional hardware but as brought out by [1] most operators may decide not to move to IS-95B because of two reasons.

1. IS-95A in itself is relatively new and carriers have just launched their IS-95A data services.

2. By the time IS-95B becomes available, 1XRTT will be ready.

Source: The Yankee Group, 2000

What Are The Costs?

In the shorter term, TDMA and GSM have a much more cost-effective upgrade option by means of moving to GPRS to be in a position to provide data services. As mentioned earlier, an upgrade to GPRS doesn't require substantial investments and existing GSM/ TDMA service providers can upgrade to GPRS at around 28% cost of their initial 2G investments. The IS-95 upgrade path to 1xRTT is comparatively costly at around 40% investments on the existing 2G networks. It should also be noted that IS-95A in itself has also not been in existence for long. However, in the final run to truly 3G networks, GSM/TDMA operators may have to incur much higher investments as shown in the figure below. The cost equations for TDMA or GSM may vary depending on the exact path taken (EDGE or no EDGE or only EDGE). CDMA has the unique advantage of having the same air interface in 2G as in 3G (same underlying technology).

Therefore, it is very probable that most CDMA carriers in North America will move straight to 1XRTT. 1XRTT is the first step in moving to the full ITU/UMTS-defined 3G standard. It has many features that make it completely different from IS-95B. It will provide more than double the data speeds available from IS-95B (153 Kbps vs. 64 Kbps); but, more importantly, in the spectrum-constrained market of North America, 1X will almost double the voice capacity. Additionally, the software and chip boards necessary for 1X are also an essential step to continue the upgrade to 3XRTT, which is also called G3G-MC-3X, but is also more popularly known by the trade name of cdma2000 (307 Kbps). However, cdma2000 is expected to provide only moderate voice capacity gains over 1X, and as such, 1X is the primary concern of carriers for the immediate future. Besides 1X and 3X paths to the ITU/UMTS-sanctioned G3G standards, there is also the Qualcomm-defined offshoot of CDMA--High Data Rate (HDR). This standard, which is proprietary to Qualcomm, sets aside a standard 1.25-MHz CDMA carrier specifically for data, and offers rates of up to 2.4 Mbps in a mobile environment. Though this standard achieves the data rates required for 3G, it is not considered a 3G standard because it is a data-only standard and has not been opened up for the approval of any standards bodies.

Source: The Yankee Group, 2000

Next: Onward To 4G...