 |
|
|
When PCS was young (and my, how fast it has entered the troubled teen years!) it seemed that standards had faded in importance. At one time there were seven radio interface standards under consideration for use in the PCS band, and even now there are three major radio standards actually in use (GSM, CDMA and IS-136 TDMA) and two network standards (GSM and IS-41). The game appeared to be to put together a nationwide presence that would avoid the need for roaming and multi-technology phones. The dream of some was apparently a single-technology system where the lack of standards would not be a detriment, but a way of distinguishing your nationwide system from the competition, and a way to reduce churn.
Things have not turned out this way, and new carriers are beginning to refocus on standards. Even a nationwide carrier needs international roaming agreements, and with the huge number of licensed areas in the US, it is unlikely that any one carrier – not even AT&T Wireless – will ever cover the entire country. Taking into consideration the concepts of franchising and common branding and the need for common communication channels between carriers, the need for standards is even more obvious. Another point to consider is whether agreements between carriers will always be drawn within technological barriers. A CDMA carrier in the US may want to facilitate roaming with a TDMA carrier in South America, without the use of different technologies being a barrier to a business need.
Standards are important even within the operations of a single carrier. Many have multiple suppliers of infrastructure equipment, and the most cost effective way to facilitate interoperability is through standards. Whether it is communication between MSCs, or between an MSC and an HLR, or between an MSC and a base station, a protocol is required, and a standardized protocol has big benefits.
The most important standards in wireless are no longer the radio interface standards. As multi-mode phones become more practical, and as roaming becomes more important, it is the network interconnection that is of paramount importance. Without a network to carry information from the current serving system to the home system, none of the fancy features of new air interfaces can be supported. In the arena of network interfaces, there are, luckily, only two major competitors: GSM MAP and IS-41.
The fundamental philosophical differences between GSM MAP and IS-41 mean that there is actually a bigger gulf between GSM and IS-136 TDMA systems in the US than between IS-136 and CDMA – even though GSM and IS-136 both use TDMA technology. Only a basic level of compatibility is possible between systems that are connected to a GSM network and those connected to an IS-41 network. This will translate into limited capabilities for any GSM/AMPS phones that are developed to extend the reach of US GSM-based PCS systems. For example, while mobiles can handoff from IS-136 TDMA or IS-95 CDMA modes in either the PCS or cellular bands to AMPS in the cellular band, GSM phones are not able to handoff to any other technology – even if the phone itself supports that technology. This is because of the lack of interoperability between GSM MAP and IS-41. And because the methods of intersystem handoff are quite different, this limitation is unlikely to ever be overcome. Similar barr iers apply to feature control, short message service and authentication.
The need for standards in wireless is real, but a larger need is for standards between wireless systems and wireline systems. A good example is the Calling Party Pays feature. This is simple to describe (“you call, you pay”) and quite easy to implement in many countries. But in the US, due to the vast number of carriers of all types, it has huge hurdles to overcome. Surmounting these will require standardization and, beyond standardization, possibly even regulatory intervention to ensure that all carriers can communicate for the benefits of their subscribers.
The CTIA is currently developing a Calling Party Pays (CPP) service description in an attempt to stimulate the standardization that must occur. It is too early to define exactly what standards will be required, but they will certainly tie together systems that today operate completely independently. Think about the case of someone calling a Calling Party Pays mobile from a payphone. Currently, ‘smart’ payphones can determine the cost of a call by looking at the dialed digits. If a local NPA-NXX is dialed, the call might cost a quarter, no matter how long it takes. If another North American number is dialed, the call might be charged at 25¢ a minute, with other rates applying to international calls. But a Calling Party Pays local call perhaps should be rated at 25¢ a minute, passing the cost of airtime back to the caller. How can the payphone possibly know about this charge? How can it reimburse the wireless carrier with some of the money that is collected? The an swer is that it cannot, unless it has the ability to communicate with the outside world in real-time. It will need not just the ability to communicate with the local wireline switch that it is connected to, but also to the home system of the CPP subscriber, to ensure that the correct rate is charged and that revenue settlement occurs.
Local Number Portability (LNP) is another example of a service that will require enormous cooperation between carriers. When phone numbers are moved from one carrier to another, a method for communicating the service order is required, along with a central database that can be accessed to control the routing of calls. LNP will require all carriers in a local service area to communicate, directly or indirectly, regardless of differences between the types of equipment that they operate. The fact that LNP is a government-imposed mandate and CPP is an industry-desired feature is irrelevant – both require the ability to communicate in new ways.
CPP and LNP are just two examples of emerging services that will require unprecedented cooperation among diverse carriers. And not just cooperation, but often instantaneous cooperation at that, which will require a real-time computer protocol. The need for communication between virtually any pair of carriers will mandate industry standards. With the mind boggling number of carriers in the US and increasingly more types of carriers, the need for standards can only grow. Other countries that are trying to increase the amount of competition in wireline and wireless telecommunications will develop a similarly insatiable appetite for standards. As a telecom standards consultant, I can only applaud this trend and print more business cards.
© – Copyright